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Ground-Water Recharge Through Active Sand Dunes in Northwestern Nevada
Most water-resouree investigations in semiarid basins of the Great Basin in western North America conclude that groundwater recharge from direct precipitation on the valley floor is negligible. However, many of these basins contain large areas covered by unvegetated, active sand dunes that may act as conduits for ground-water recharge. The potential for this previously undocumented recharge was investigated in an
David L. Berger
Groundwater recharge in natural dune systems and agricultural ecosystems in the Thar Desert region, Rajasthan, India
NASA Astrophysics Data System (ADS)
Water and nutrient availability for crop production are critical issues in (semi)arid regions. Unsaturated-zone Cl tracer data and nutrient (NO3 and PO4) concentrations were used to quantify recharge rates using the Cl mass balance approach and nutrient availability in the Thar Desert, Rajasthan, India. Soil cores were collected in dune/interdune settings in the arid Thar Desert (near Jaisalmer) and in rain-fed (nonirrigated) and irrigated cropland in the semiarid desert margin (near Jaipur). Recharge rates were also simulated using unsaturated zone modeling. Recharge rates in sparsely vegetated dune/interdune settings in the Jaisalmer study area are 2.7-5.6 mm/year (2-3% of precipitation, 165 mm/year). In contrast, recharge rates in rain-fed agriculture in the Jaipur study area are 61-94 mm/year (10-16% of precipitation, 600 mm/year). Minimum recharge rates under current freshwater irrigated sites are 50-120 mm/year (8-20% of precipitation). Nitrate concentrations are low at most sites. Similarity in recharge rates based on SO4 with those based on Cl is attributed to a meteoric origin of SO4 and generally conservative chemical behavior in these sandy soils. Modeling results increased confidence in tracer-based recharge estimates. Recharge rates under rain-fed agriculture indicate that irrigation of 20-40% of cultivated land with 300 mm/year should be sustainable.
Scanlon, Bridget R.; Mukherjee, Abhijit; Gates, John; Reedy, Robert C.; Sinha, Amarendra K.
Spatial and Temporal Variability of Groundwater Recharge in Changing Semiarid Dune Environments
NASA Astrophysics Data System (ADS)
Groundwater recharge (GWR) is one of the major factors controlling water resources in semiarid and arid regions. This time-space-dependent flux is needed for groundwater modeling, analysis of climate change impacts, and water resources management. Typically, climate changes are studied on multi-decadal to centennial time scales, but travel times of soil moisture across the vadose zone vary broadly and may exceed multi-centennial periods in semiarid and arid environments. For given climatic conditions on the land surface, we evaluate travel times in the vadose zone and compare with times scales of climate change studies. This comparison defines the land surface areas contributing to GWR changes where travel times are shorter than times scales of climate change studies. In areas with travel times longer than climate change time scales, GWR remains unchanged over the considered period of water resources management. Such analysis allows for separation of the effect of land surface topography and vadose zone thickness from that of spatial and temporal variations in climate. Our simple travel time estimates are based on the velocity of a pressure pulse from the land surface, equivalent to a kinematic wave approximation of Richards' equation. The underlying assumptions of a unit hydraulic head gradient and relatively small magnitude of changes to upper boundary flux, caused by slow climate changes, are supported by observations in the High Plains aquifer region, USA. The input data include DEMs of land surface and groundwater table elevations, future projections of hydroclimatic variables, precipitation and evapotranspiration (WCRP-CMIP3 with hydrology VIC model outputs), and estimates of hydraulic conductivity from pedotransfer functions. Future GWR rates are estimated in four steps: GIS analysis of vadose zone thickness using difference in DEMs; evaluation of deep drainage rates based on difference between precipitation and evapotranspiration rates (PRISM and MODIS, respectively); calculation of travel times of moisture across the vadose zone and GIS mapping; and inference of time-referenced GWR map. This methodology is applicable to semiarid and arid regions, where overland flow can be neglected and actual evapotranspiration and precipitation data for current and future conditions are available. A study of the Nebraska Sand Hills, USA, the largest vegetated dune field in the Western Hemisphere of area 58,000 km2, provides analysis of spatial and temporal aspects of GWR with consideration of future climate changes.
Zlotnik, Vitaly; Rossman, Nathan; Rowe, Clinton; Szilagyi, Jozsef
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] Context image for PIA03634 Dunes This dune field is located on the floor of a crater located southeast of Mutch Crater. Image information: VIS instrument. Latitude 3.1S, Longitude 307.5E. 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Evaluating the recharge mechanism of the Lower Kuiseb Dune area using mixing cell modeling and residence time data
NASA Astrophysics Data System (ADS)
SummaryA mixing cell approach was extended by a method incorporating mean cell residence times derived from 14C to further constrain and validate the modeling results. This extended approach was used to model the groundwater system of the Lower Kuiseb Dune area in Namibia. The Kuiseb river is a 560 km long ephemeral river that crosses the Namib Desert from east to west. Transmission losses from the riverbed during flood events are an important source of groundwater recharge to the underlying aquifer system. The Lower Kuiseb area is located in a hyper arid region with annual precipitation less than 25 mm/yr. Hydrochemical data from 13 wells in the area were used in the mixing cell model (MCM). End members were identified as sources for the groundwater found in the Lower Kuiseb, including inflow from the crystalline basement plateau north of the Kuiseb as well as floodwater from the Kuiseb river. A conceptual groundwater recharge and flow model was developed, and then inverse mixing cell modeling was carried out using hydrochemical tracers. This approach generally allows for several possible solutions. After completing the inverse modeling, a forward mixing cell model was developed by varying the mean residence time of each cell to fit calculated 14C data to the measured 14C data. This new approach joins previously developed methods solely based on conservative mixing or residence time optimization. Based on the results of the model the fraction of floodwater in different sections of the Lower Kuiseb groundwater systems was calculated, ranging from 61% to 98.2%. In addition to floodwater, groundwater inflow from the crystalline basement north of the Kuiseb was shown to contribute to the Lower Kuiseb aquifer, accounting for salinization during periods without flooding.
Klaus, Julian; K�lls, Christoph; Dahan, Ofer
NSDL National Science Digital Library
Most will agree that nothing is more relaxing that lying or walking on a beach. While unwinding, have you ever wondered what caused those big mounds of sand that you crossed to get there? This topic in depth addresses this issue, featuring Web sites that discuss sand dune processes and formations. Some of the Web sites also discuss research, mining, and protection activities taking place in areas with sand dune.The Environment Bay of Plenty in New Zealand has an online brochure (1) dealing with the coastal processes that form sand dunes and beaches. From this site, users can obtain a general understanding of how dunes change with time. Ted Brambleby developed the second site (2) for the Marine Education Society of Australasia, Inc. This site gives a great overview of the functions and formations of dunes as well as describing their unique beauty and strategies on how to care for the dunes. Produced by Nova Scotia Museum of Natural History, the third site (3) is an online pamphlet discussing the physical features and locations of sand dunes in Nova Scotia. Visitors can also read about the ecosystem supported by these dynamic features. The forth site (4), created by John Mangimeli for the National Park Service, is a review of the scientific research completed throughout the years dealing with the geology of sand dunes. Visitors will find a more in-depth discussion about sand movement, sand accumulation, and sand dune features. The fifth site is a scientific paper (5 ) written by R.L. Van Dam, et al. Studying the long term evolution of the Parengarenga Sandspit, these researchers used ground penetrating radar (GPR) "to (1) explore the possibilities for mapping lateral continuity of the coffee rock, (2) study the sedimentary architecture and stratigraphy of the solitary dunes, and (3) reconstruct the wind regime on the sandspit." The next two sites discuss the threats to sand dunes and activities taking place to protect them. The Lake Michigan Federation addresses the issues of mining (6). Visitors can learn about alternatives to mining dune sand and the ecological values of dunes. The Department of Environmental Quality in Michigan created a site (7) that provides users with statistical information dealing with the amount of sand harvested, the regulations of mining, and maps of critical dune areas. After learning about the formation, processes, threats, and protections efforts; the last site (8), created by Eva Hornecker with the University of Bremen, will allow users to get a real sense of the beauty of the sand dunes. The site features a collage of spectacular images of the Great Sand Dunes in the San Luis Valley.
Enright, Rachel
NSDL National Science Digital Library
This activity was developed during the workshop, Teaching Climate Change: Insight from Large Lakes, held in June 2012. Dune Geomorphology by Anthony (Tony) Layzell, University of Kansas Main Campus J. Elmo ...
NASA Technical Reports Server (NTRS)
[figure removed for brevity, see original site]Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form. Our final look at the north polar erg was taken at 80 degrees North latitude during Northern summer. This image is of lower resolution than the previous images, but covers a much larger area. The dunes have very little remaining frost cover. Note the large extent of coverage, and the different dune forms. Image information: VIS instrument. Latitude 80.8, Longitude 184.6 East (175.4 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
NASA Technical Reports Server (NTRS)27 July 2004 Frost-covered dunes develop spots and streaks as they begin to defrost in springtime. This April 2004 Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a suite of north polar dunes in the early stages of the defrosting process. At the time the image was acquired, Mars was only 1 month into the northern spring season. The picture is located near 75.9oN, 266.0oW, and is illuminated by sunlight from the lower left. The image covers an area about 3 km (1.9 mi) wide.
NASA Technical Reports Server (NTRS)10 October 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows ripples on the surface of a dune in a crater west of Sinus Meridiani near 2.5oN, 9.3oW. Most martian dune surfaces do not show ripples at the scale of MOC images---a higher resolution (better than 15 cm/pixel) view would be needed. These ripples are probably not typical sand ripples; they may be coarser-grained granule ripples (usually made up, in part, of grains 1-4 millimeters in size). The light-toned features in the image are wind-eroded outcrops of sedimentary rock. The image covers an area about 1.5 km (0.9 mi) wide. Sunlight illuminates the scene from the upper left.
National Technical Information Service (NTIS)
Shows the 700-foot high dunes in their endless cycle of building and decaying, and explains in lay terms the geologic reasons for the dunes. Primary audience: visitors to Great Sand Dunes National Monument.
Utilization of oxygen-18 and deuterium in stem flow for the identification of transpiration sources: soil water versus groundwater in sand dune terrain
Forestation and reforestation in an arid sand dune terrain raise the issue as to what extent they affect the local groundwater system: that is, the effects of transpiration versus groundwater recharge. In general, sand dunes are considered to be the most efficient zone for groundwater recharge in deserts. This is especially true for arid zones with a limited amount of
Dark Dunes Over-riding Bright Dunes
NASA Technical Reports Server (NTRS)Some martian sand dunes may be more active than others. In this picture, wind has caused the dark and somewhat crescent-shaped dunes to advance toward the lower left. While their movement cannot actually be seen in this April 1998snapshot, the location of their steepest slopes--their slip faces--on their southwestern sides indicates the direction of movement. Oddly, these dark dunes have moved across and partly cover sets of smaller, bright ridges that also formed by wind action.This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image illustrates an intriguing martian 'find.' Strangely, the two dune types have different shapes and a different relative brightness. There are two explanations for the relationship seen here, and neither can be distinguished as 'the answer'--(1) it is possible that the brighter dunes are old and cemented, and represent some ancient wind activity, whereas the dark dunes are modern and are marching across the older, 'fossilized' dune forms, or (2) the bright dunes are composed of grains that are much larger or more dense than those that compose the dark dunes. In the latter scenario, the bright dunes move more slowly and are over-taken by the dark dunes because their grains are harder to transport. An interpretation involving larger or denser grains is consistent with the small size and even-spacing of the bright dunes, as well, but usually on Earth such features occur on the surfaces of larger, finer-grained dunes, not under them. The actual composition of either the bright or dark materials are unknown. This example is located on the floor of an impact crater in western Arabia Terra at 10.7oN, 351.0oW. The picture is illuminated from the right.
Hydrogeology and hydrochemistry of dunes and wetlands along the southern shore of Lake Michigan, Indiana
The dunes and the wetlands along the southern shore of Lake Michigan are underlain by a complex aquifer system composed of unconsolidated glacial, lacustrine, and eolian deposits. Surficial dune, beach, and glacial lacustrine sands compose an extensive surficial aquifer. The underlying drift contains three major confined sand aquifers. Potentiometric and hydrochemical data are consistent with a conceptual model in which regional and intermediate flow systems, recharged in end moraines south of the dune-beach complexes, discharge into Lake Michigan and the Great Marsh by upward leakage through unconsolidated sediments. Local flow systems in the surficial aquifer, recharged in the major dune-beach complexes, discharge into streams, ditches, and ponded areas in the adjacent interdunal wetlands. Shallow ground water discharges directly into Lake Michigan only north of a water-table divide that underlies the dune-beach complex along the shoreline. The position of ground-water seepage faces is affected by transient water-table mounds observed in the dune-beach complexes at the margins of wetlands. Substantial recharge to the dune complexes probably occurs near these dune-wetland margins. In the dune-beach complexes and intradunal wetlands, the shallow ground and wetland waters are dilute calcium bicarbonate and calcium bicarbonate sulfate types. More mineralized bicarbonate water types having variable proportions of calcium, magnesium, and sodium are found in interior parts of the Great Marsh because this area is probably a discharge zone for the regional and intermediate flow systems.
Shedlock, Robert J.; Cohen, D. A.; Imbrigiotta, T. E.; Thompson, T. A.
NASA Technical Reports Server (NTRS)
6 January 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes in southern Galle Crater, east of Argyre Planitia. The sand that comprises these dunes, like other dunes on Mars, is dark, but at the time this picture was acquired during early southern summer, the dunes were covered with a coating of bright dust. Occasional, passing dust devils or wind gusts created the dark streaks seen on a few of the dunes. The dunes are located near 51.9oS, 31.2oW. The image covers an area 3 km (1.9 mi) wide; sunlight illuminates the scene from the upper left.
NASA Technical Reports Server (NTRS)05 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows large, low albedo (dark) sand dunes in Kaiser Crater near 47.2oS, 340.4oW. The dunes are--ever so slowly--moving east to west (right to left) as sand avalanches down the steeper, slip face slopes of each. Avalanching sand in the Kaiser dune field has left deep scars on these slopes, suggesting that the sand is not loose but is instead weakly cemented. The image covers an area approximately 3 km (1.9 mi) wide and is illuminated by sunlight from the upper left.
NASA Technical Reports Server (NTRS)
MGS MOC Release No. MOC2-354, 8 May 2003In this Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image, wind has streaked a field of defrosting sand dunes in Chasma Boreale in the martian north polar region. Dune slip faces--the steep slope formed by avalanching sand on each dune--and the dark streaks indicate that wind transports sediment from the lower left toward the upper right. The picture covers an area about 3 km (1.9 mi) wide near 84.6oN, 358.5oW. Sunlight illuminates the scene from the lower left.
NASA Technical Reports Server (NTRS)
MGS MOC Release No. MOC2-495, 26 September 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows windblown sand dunes in Chasma Boreale, a wide trough in the north polar region of Mars. The dunes are shown here in their summertime configuration; that is, they are not covered with seasonal frost. The dunes are dark because the grains that make up these sandy landforms consist of dark minerals and/or fragments of dark-toned rock. The steepest slopes on these dunes, their slipfaces, point toward the top/upper left (northwest), indicating that winds blow the sand from the lower right (southeast). This picture is located near 84.7oN, 359.3oW, and covers an area 3 km (1.9 mi) across. Sunlight illuminates the scene from the lower left.
NASA Technical Reports Server (NTRS)
[figure removed for brevity, see original site]Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form. This VIS image was taken at 81 degrees North latitude during Northern spring. In this region, the dunes are isolated from each other. The dunes are just starting to emerge from the winter frost covering appearing dark with bright crests. These dunes are located on top of ice. Image information: VIS instrument. Latitude 82.1, Longitude 191.3 East (168.7 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Sand dunes as migrating strings.
We develop a reduced complexity model for three-dimensional sand dunes, based on a simplified description of the longitudinal and lateral sand transport. The spatiotemporal evolution of a dune migrating over a nonerodible bed under unidirectional wind is reduced to the dynamics of its crest line, providing a simple framework for the investigation of three-dimensional dunes, such as barchan and transverse dunes. Within this model, we derive analytical solutions for barchan dunes and investigate the stability of a rectilinear transverse dune against lateral fluctuations. We show, in particular, that the latter is unstable only if the lateral transport on the dune slip face prevails over that on the upwind face. We also predict the wavelength and the characteristic time that control the subsequent evolution of an unstable transverse dune into a wavy ridge and the ultimate fragmentation into barchan dunes. PMID:23767529
Guignier, L; Niiya, H; Nishimori, H; Lague, D; Valance, A
NASA Technical Reports Server (NTRS)
[figure removed for brevity, see original site]Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form. Our final dune image shows a small dune field inside an unnamed crater south of Nili Fossae. Image information: VIS instrument. Latitude 20.6, Longitude 79 East (281 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
NASA Technical Reports Server (NTRS)
[figure removed for brevity, see original site]Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form. A common location for dune fields on Mars is in the basin of large craters. This dune field is located in Holden Crater at 25 degrees South atitude. Image information: VIS instrument. Latitude -25.5, Longitude 326.8 East (33.2 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Seasonal changes observed on the surface of Mars can in part be attributed to the transport of geological materials by wind. Images obtained by orbiting spacecraft in the 1970s showed large wind-formed features such as dunes, and revealed regional time-varying albedos that could be attributed to the effects of dust erosion and deposition. But the resolution of these images was insufficient to identify different types and sources of aeolian materials, nor could they reveal aeolian deposits other than large dunes or extensive surface coverings that were redistributed by dust storms. Here we present images of Mars with up to 50 times better resolution. These images show that martian dunes include at least two distinct components, the brighter of which we interpret to be composed of relatively soft minerals, possibly sulphates. We also find large areas of the martian surface that have several metres or more of aeolian mantle lacking obvious bedforms.
Thomas, P. C.; Malin, M. C.; Carr, M. H.; Danielson, G. E.; Davies, M. E.; Hartmann, W. K.; Ingersoll, A. P.; James, P. B.; McEwen, A. S.; Soderblom, L. A.; Veverka, J.
NASA Technical Reports Server (NTRS)
[figure removed for brevity, see original site]Our topic for the weeks of April 4 and April 11 is dunes on Mars. We will look at the north polar sand sea and at isolated dune fields at lower latitudes. Sand seas on Earth are often called 'ergs,' an Arabic name for dune field. A sand sea differs from a dune field in two ways: 1) a sand sea has a large regional extent, and 2) the individual dunes are large in size and complex in form. This VIS image shows a dune field within Nili Patera, the northern caldera of a large volcanic complex in Syrtis Major. Image information: VIS instrument. Latitude 9, Longitude 67 East (293 West). 19 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
The Algodones Dunes, California
NSDL National Science Digital Library
The Center for Biological Diversity blends "conservation biology with litigation, policy advocacy, and an innovative strategic vision" in efforts to protect endangered species and wild places, focusing on the western US. This Web site contains a slide show of images from the Algodones Dunes, California's largest dune system. The fourteen slides show images of the area's natural history and environmental threats, such as effects from off-road vehicles. Each slide is accompanied by a brief description. While not overly informative, this Web site offers visitors a quick overview look at this unique natural area.
NASA Technical Reports Server (NTRS)23 August 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows sand dunes in the martian north polar region in mid-spring, July 2004. In summer, the dunes will be dark. As they defrost, dark spots form on their surfaces. This image is located near 82.8oN, 219.6oW. The image covers an area about 3 km (1.9 mi) across and sunlight illuminates the scene from the lower left.
NASA Technical Reports Server (NTRS)
MGS MOC Release No. MOC2-390, 13 June 2003This is a Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) view of frost-covered sand dunes in Chasma Boreale in the early northern spring season. Dark spots, some of them with bright halos of re-precipitated frost, have formed as the dunes begin to defrost. Most of the frost is carbon dioxide which freezes out of the atmosphere during the cold martian polar winters. This picture is located near 84.7oN, 358.8oW, and is illuminated from the lower left.
NSDL National Science Digital Library
The Bureau of Land Management presents the current news, projects, and the geologic and cultural history of the Imperial Sand Dunes at this website. Users can easily search through an abundance of remarkable images of dunes as well as other Californian landscapes. The website offers links to the current rules, regulations, and management plans. Individuals, who will be traveling to the area, can find the weather forecast, an events calendar, and information on volunteering. Visitors can locate archives of Federal Register Notices as well as news releases.
Planetary science: Titan's sticky dunes?
Titan's surface is covered by vast fields of linear dunes, probably composed of organic sand-sized particles. The study of linear dunes in China suggests that sediment cohesiveness can be as important as wind direction in the creation of these dune forms.
Jani Radebaugh
Dynamics of intertidal gravel dunes
This paper examines the dynamics of intertidal gravel dunes subjected to high-energy unsteady and reversing tidal currents in the Severn Estuary, UK. The dunes were composed of shale particles with median grain size, D50, around 4 mm and had mean heights and wavelengths of 60 cm and 7 m, respectively. Acoustic instruments were deployed above a dune to measure the
Jon J. Williams; Paul A. Carling; Paul S. Bell
The general object of this invention is to provide an improved rechargeable lithium cell. A more specific object of the invention is to provide a rechargeable lithium cell having an improved low temperature performance and rate capability. It has now been found that the aformentioned objects can be attained using lithium as the anode, a solution of a lithium salt
M. Salomon; E. J. Plichta
National Technical Information Service (NTIS)
The flora, vegetation, and microenvironment of beach and dune are sufficiently different to warrant their separate treatment in this chapter. Beach is defined here as the expanse of sandy substrate between mean tide and the foredune or, in the absence of ...
M. G. Barbour A. F. Johnson
NASA Technical Reports Server (NTRS)5 September 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a field of dark, windblown sand dunes in the Noachis Terra region near 45.2oS, 321.4oW. The image covers an area approximately 3 km (1.9 mi) across. Sunlight illuminates this scene from the upper left.
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] This image, located near 30E and 47.5S, displays sand dunes within Proctor Crater. These dunes are composed of basaltic sand that has collected in the bottom of the crater. The topographic depression of the crater forms a sand trap that prevents the sand from escaping. Dune fields are common in the bottoms of craters on Mars and appear as dark splotches that lean up against the downwind walls of the craters. Dunes are useful for studying both the geology and meteorology of Mars. The sand forms by erosion of larger rocks, but it is unclear when and where this erosion took place on Mars or how such large volumes of sand could be formed. The dunes also indicate the local wind directions by their morphology. In this case, there are few clear slipfaces that would indicate the downwind direction. The crests of the dunes also typically run north-south in the image. This dune form indicates that there are probably two prevailing wind directions that run east and west (left to right and right to left).Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Dunes reveal Titan's recent history
NASA Astrophysics Data System (ADS)
Large fields of linear dunes are abundant on Titan, covering nearly 20% of the surface. They are among the youngest features and represent interactions between near-surface winds and sediment. This interaction may vary from area to area creating unique populations of eolian features identified by dune field parameters such as crest-to-crest spacing, dune width and orientation. These parameters respond to changes in near-surface conditions over periods of time ranging from minutes to many thousands of years depending on dune size and the duration of the changes. While pattern analysis of dune field parameters on Earth and, in this study, Titan reveals much about current climatic conditions, such as wind regimes and wetter vs. drier areas, many inferences about past conditions can also be made. Initial pattern analysis of linear dunes on Titan reveals a single population of linear dunes representing a large percentage of all observed dunes. This single population is the result of two leading possibilities: Either there has been only one long period of dune building, leading to very old cores that have been built upon over long periods of time, perhaps punctuated with few or many intervals of non-deposition; or the current conditions of dune building have persisted long enough to completely erase any evidence of previous conditions. We have not yet worked through all the input parameters to adjust Earth's time scales to Titan's, and thus it is not yet possible to give a precise age for Titan's dunes. However, if these large linear dunes are similar to Earth's large linear dunes, they may represent at least several thousand years of dune building.
Savage, Christopher J.; Radebaugh, Jani
Dune formation under bimodal winds
The study of dune morphology represents a valuable tool in the investigation of planetary wind systems�the primary factor controlling the dune shape is the wind directionality. However, our understanding of dune formation is still limited to the simplest situation of unidirectional winds: There is no model that solves the equations of sand transport under the most common situation of seasonally varying wind directions. Here we present the calculation of sand transport under bimodal winds using a dune model that is extended to account for more than one wind direction. Our calculations show that dunes align longitudinally to the resultant wind trend if the angle ?w between the wind directions is larger than 90�. Under high sand availability, linear seif dunes are obtained, the intriguing meandering shape of which is found to be controlled by the dune height and by the time the wind lasts at each one of the two wind directions. Unusual dune shapes including the �wedge dunes� observed on Mars appear within a wide spectrum of bimodal dune morphologies under low sand availability.
Parteli, Eric J. R.; Duran, Orencio; Tsoar, Haim; Schwammle, Veit; Herrmann, Hans J.
NASA Technical Reports Server (NTRS)9 February 2005 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark sand dunes overlying an eroded, layered substrate in Chasma Boreale, amid the materials of the martian north polar cap. Location near: 84.5oN, 358.3oW Image width: 3.0 km (1.9 mi) Illumination from: lower left Season: Northern Summer
Artificial recharge of groundwater
The vast underground reservoirs formed by aquifers constitute invaluable water supply sources as well as water storage facilities. Because natural replenishment of the supply occurs very slowly, continued excessive exploitation of it causes groundwater levels to decline with time. If not corrected this leads to an eventual depletion of a valuable natural resource. To prevent mining and groundwater pollution, the artificial recharge of groundwater basins is becoming increasingly important in groundwater management as a way to increase this natural supply of water. Artificial recharge can reduce, stop, and even reverse declining levels of groundwater. In addition, it can protect underground freshwater in coastal aquifers against salt-water intrusion from the ocean, and can be used to store surface and reclaimed water for future use. This book is a treatise of the artificial recharge of groundwater, with particular emphasis on recharge with reclaimed municipal wastewater.
Asano, T.
NASA Technical Reports Server (NTRS)Except for small wind ripples on their surfaces, normal, active sand dunes have very smooth slopes. However, some dunes found in the Herschel Basin of Terra Cimmeria (around 15oS, 228oW) have very rough, grooved surfaces instead. These grooves indicate that the dune surfaces for some reason are cemented--i.e., the sand is not loose--and that wind has actually had to scour the sand to remove it and transport it away from these dunes. What has caused these dunes to become cemented is unknown, and dunes like this are extremely rare on Mars (they have only been seen in Herschel Basin, thus far). This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image was acquired on May 5, 1999, and is illuminated from the upper left.
NASA Astrophysics Data System (ADS)
Currently, there is no comprehensive, global, digital database for dune deposits on Mars. The advent of a series of successful Mars missions, coupled with advances in technology enabling a significant increase in instrument resolution, have provided a large compilation of data covering a wide range of wavelengths for the Martian surface. Given the recent availability of high-resolution data and detailed surficial information returned from orbital and rover missions, it is critical that we update the Mars global information base by creating a digital database of dune deposits that includes this new influx of data. As of spring 2004, the Thermal Emission Imaging System (THEMIS) infrared (IR) coverage of the surface of Mars was 98% for nighttime and 75% for daytime acquired images, forming a data set of global coverage at a resolution not previously possible. The combination of high-resolution and global coverage makes the THEMIS IR data set the logical choice for a planet wide inventory of dune deposits. Data sets of a global scale like those of Mars Orbiter Laser Altimeter (MOLA) and Thermal Emission Spectrometer (TES) will enable rapid and contiguous comparisons with the dune database. Other imagery like that of Mars Orbiter Camera (MOC) will provide very high-resolution, localized visual data for accurate interpretations of morphological characterizations. The dune database will provide researchers with an extensive, comprehensive and stable database for use in a wide-array of global studies. The database will also offer researchers a centralized depository for updating physical parameters with newly validated findings. The initial construction of the database is based upon dune forms or deposits identified, classified and digitized using only THEMIS IR images. These digitized polygons are converted from THEMIS image coordinates to ARCMAP aerographical coordinates, allowing delineation of areal extent of the deposits and preserving relevant THEMIS image information such as Ls, local time, and sun azimuth/angle. The ARCMAP polygons will also retain reference to all THEMIS IR images used in their construction. Where available, THEMIS VIS and/or MOC images will be used to confirm, modify or refine original classifications. In addition to providing an improved resolution for features below the IR image threshold, this secondary examination will also provide a list of cross-referenced THEMIS VIS and MOC images for future investigations. Physical parameters such as wind direction based on slip-face geometry, dune wavelength, elevation, and volume of the deposits will be incorporated into the database on a priority-based schedule. In addition to THEMIS VIS and MOC images, supplemental data sets, such as TES and others, will be used where available to further refine and/or validate existing data on global wind patterns, sediment transport, sources and sinks, and stratigraphic units.
Hayward, R. K.; Titus, T. N.; Mullins, K. F.; Fenton, L. K.; Bourke, M.; Christensen, P. R.
Sand Dunes: A Phenomenon Of Wind
NSDL National Science Digital Library
This webpage from Wayne's Word provides information about the origin of sand dunes, forms of life present there, and the sounds produced by "booming" dunes. Numerous dunes in the United States are described and pictured.
NASA Technical Reports Server (NTRS)
MGS MOC Release No. MOC2-517, 18 October 2003Frost covers dark sand dunes in this springtime view from Chasma Boreale in the martian north polar region. Dark spots indicate areas where the cold, carbon dioxide frost has begun to sublime away. This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image is located near 84.7oN, 359.3oW and covers an area 3 km (1.9 mi) wide. The scene is illuminated by sunlight from the lower left.
Predicting vegetation-stabilized dune field morphology
NASA Astrophysics Data System (ADS)
The morphology of vegetation-stabilized dune fields on the North American Great Plains (NAGP) mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare, with the exception of transverse and barchan mega-dunes in the Nebraska Sand Hills. We present a hypothesis from a numerical dune field model explaining the vegetation-stabilized morphology of dunes under unidirectional wind. Simulations with a range of initial dune morphologies (closely-spaced transverse to disperse barchans) indicate that stabilized morphology is determined by the ratio of slipface deposition rate to deposition tolerance of vegetation. Slipface deposition rate is related to dune height, flux, and celerity. With a fixed depositional tolerance, large, slow-moving dunes have low slipface deposition rates and �freeze� in place once vegetation is introduced. Relatively small, fast dunes have high slipface deposition rates and evolve into parabolic dunes, often colliding during stabilization. Our hypothesis could explain differences in stabilized morphology across the NAGP and elsewhere.
Barchyn, Thomas E.; Hugenholtz, Chris H.
NASA Technical Reports Server (NTRS)
This approximate true-color image taken by the Mars Exploration Rover Spirit's panoramic camera shows the windblown waves of soil that characterize the rocky surface of Gusev Crater, Mars. Scientists were puzzled about whether these geologic features were 'ripples' or 'dunes.' Ripples are shaped by gentle winds that deposit coarse grains on the tops or crests of the waves. Dunes are carved by faster winds and contain a more uniform distribution of material. Images taken of these features by the rover's microscopic imager on the 41st martian sol, or day, of the rover's mission revealed their identity to be ripples. This information helps scientists better understand the winds that shape the landscape of Mars. This image was taken early in Spirit's mission.[figure removed for brevity, see original site] Click on image for larger view [Image credit: NASA/JPL/ASU] This diagram illustrates how windblown sediments travel. There are three basic types of particles that undergo different motions depending on their size. These particles are dust, sand and coarse sand, and their sizes approximate flour, sugar, and ball bearings, respectively. Sand particles move along the 'saltation' path, hitting the surface downwind. When the sand hits the surface, it sends dust into the atmosphere and gives coarse sand a little shove. Mars Exploration Rover scientists are studying the distribution of material on the surface of Mars to better understand how winds shaped the landscape.
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] Context image for PIA03192 Holden Crater Dunes These dunes occur on the floor of Holden Crater. Image information: VIS instrument. Latitude 25.8S, Longitude 326.5E. 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] Context image for PIA03637 Galle Cr. Dunes These dunes are located on the floor of Galle Crater. Image information: VIS instrument. Latitude 51.5S, Longitude 329.0E. 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] Context image for PIA03039 Dunes in Darwin Crater The dunes and sand deposits in this image are located on the floor of Darwin Crater. Image information: VIS instrument. Latitude 57.4S, Longitude 340.2E. 17 meter/pixel resolution. Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time. NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Coastal Dunes: Primer for Dune Management with Models of Dune Response to Storm Frequencies.
National Technical Information Service (NTIS)
Coastal dunes are natural features of the coastal landscape. They exist in conjunction with the beach and are part of the sand sharing system that actively exchanges sand between the dune, the beach, and the offshore bars. In areas of adequate sand supply...
N. P. Psuty E. Rohr
The general object of this invention is to provide an improved rechargeable lithium cell. A more specific object of the invention is to provide a rechargeable lithium cell having an improved low-temperature performance and rate capability. It has now been found that the aformentioned objects can be attained using lithium as the anode, a solution of a lithium salt such as LiF/sub 6/ or LiA1C/sup 14/ in a mixed organic solvent as the electrolyte and a lithium intercalating cathode.
Salomon, M.; Plichta, E.J.
Sea turtle nesting presents a potential pathway to subsidize nutrient-poor dune ecosystems, which provide the nesting habitat for sea turtles. To assess whether this positive feedback between dune plants and turtle nests exists, we measured N concentration and d15N values in dune soils, leaves from a common dune plant (sea oats (Uniola paniculata)), and addled eggs of loggerhead (Caretta caretta)
Laura B. Hannan; James D. Roth; Llewellyn M. Ehrhart; John F. Weishampel
The internal structure of the Mega-dunes in the Badainjaran desert revealed by ground penetrating radar and its implications to arid hydrology
NASA Astrophysics Data System (ADS)
Badainjaran desert in northwestern China has the world's highest stationary sand dunes, which are up to 500 m tall. Despite the prevailing dry and windy weather conditions the mega dunes were relatively moist underneath a dry surface layer of about 20 cm. It is very common to see a lake directly at the foot of the leeward side of a mega dune. Using 50- and 100-MHz antenna we conducted ground penetrating radar (GPR) surveys on both the windward and leeward of three mega dunes in southeastern Badainjaran desert. The GPR surveys clearly revealed the existence of numerous, almost evenly spaced calcareous cement and travertine features at shallow depth on the windward side of the mega dunes. The leeward tilted orientation of these calcareous cement and travertine features will be likely inducing more infiltration toward the leeward thus getting more recharge to the lake than the windward side. This trend may be one key factors to keep the lake exist in a very arid environment with high evaporation rate. The GPR profile also clearly depicted the shape of the water table beneath the mega dunes. The water table is gradually elevated outward from the lake, implies that the lake is possibly recharged by both precipitation from the vadose zone and the free water recharge from beneath the water table. A preliminary precipitation-evaporation-yield analysis based on our observation indicates that the lakes we studied may be survival if no further reduction of precipitation in this desert area.
Qian, R.; Li, J.; Liu, L.
Lithium rechargeable envelope cells
NASA Astrophysics Data System (ADS)
Prototype lithium manganese oxide rechargeable cells have been made in an envelope format, which is particularly suitable for scaling up to large batteries. Materials have been tested in laboratory cells. The synthesis of lithium manganese oxide has been investigated and cathode components for cells have been fabricated. Cycling results are reported.
Gilmour, A.; Giwa, C. O.; Lee, J. C.; Ritchie, A. G.
Lithium rechargeable envelope cells
Prototype lithium manganese oxide rechargeable cells have been made in an envelope format, which is particularly suitable for scaling up to large batteries. Materials have been tested in laboratory cells. The synthesis of lithium manganese oxide has been investigated and cathode components for cells have been fabricated. Cycling results are reported.
A. Gilmour; C. O. Giwa; J. C. Lee; A. G. Ritchie
NASA Technical Reports Server (NTRS)21 July 2006 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows a small portion of the floor of Kaiser Crater in the Noachis Terra region, Mars. The terrain in the upper (northern) half of the image is covered by large windblown ripples and a few smoother-surfaced sand dunes. The dominant winds responsible for these features blew from the west/southwest (left/lower left). Location near: 47.2oS, 341.3oW Image width: 3 km (1.9 mi) Illumination from: upper left Season: Southern Winter
NASA Technical Reports Server (NTRS)
11 February 2004 This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image shows dark-toned sand dunes in a crater in eastern Noachis Terra. Most big martian dunes tend to be dark, as opposed to the more familiar light-toned dunes of Earth. This difference is a product of the composition of the dunes; on Earth, most dunes contain abundant quartz. Quartz is usually clear (transparent), though quartz sand grains that have been kicked around by wind usually develop a white, frosty surface. On Mars, the sand is mostly made up of the darker minerals that comprise iron- and magnesium-rich volcanic rocks--i.e., like the black sand beaches found on volcanic islands like Hawaii. Examples of dark sand dunes on Earth are found in central Washington state and Iceland, among other places. This picture is located near 49.0oS, 326.3oW. Sunlight illuminates this scene from the upper left; the image covers an area 3 km (1.9 mi) wide.
Radiation measurements inside the Contact Decon Maintenance Cell (CDMC) in the Defense Waste Processing Facility (DWPF) at the Savannah River Site (SRS) are required to determine stay times for personnel. A system to remotely recharge the transmitter of an Electronic Personnel Dosimeter (EPD) and bail assembly to transport the EPD within the CDMC was developed by the Savannah River National Laboratory (SRNL) to address this need.
Vrettos, N; Athneal Marzolf, A; Scott Bowser, S
Rechargeable Magnesium Power Cells
NASA Technical Reports Server (NTRS)
Rechargeable power cells based on magnesium anodes developed as safer alternatives to high-energy-density cells like those based on lithium and sodium anodes. At cost of some reduction in energy density, magnesium-based cells safer because less susceptible to catastrophic meltdown followed by flames and venting of toxic fumes. Other advantages include ease of handling, machining, and disposal, and relatively low cost.
Koch, Victor R.; Nanjundiah, Chenniah; Orsini, Michael
The sedimentary structure of linear sand dunes
Linear sand dunes--dunes that extend parallel to each other rather than in star-like or crescentic forms--are the most abundant type of desert sand dune. But because their development and their internal structure are poorly understood, they are rarely recognized in the rock record. Models of linear dune development have not been able to take into account the sub-surface structure of existing dunes, but have relied instead either on the extrapolation of short-term measurements of winds and sediment transport or on observations of near-surface internal sedimentary structures. From such studies, it has not been clear if linear dunes can migrate laterally. Here we present images produced by ground penetrating radar showing the three-dimensional sedimentary structure of a linear dune in the Namib sand sea, where some of the world's largest linear dunes are situated. These profiles show clear evidence for lateral migration in a linear dune. Moreover, the migration of a sinuous crest-line along the dune produces divergent sets of cross-stratification, which can become stacked as the dune height increases, and large linear dunes can support superimposed dunes that produce stacked sets of trough cross-stratification. These clear structural signatures of linear dunes should facilitate their recognition in geological records. PMID:10894538
Bristow; Bailey; Lancaster
Groundwater recharge in urban areas
NASA Astrophysics Data System (ADS)
The two interlinked networks of hydrological pathways in urban areas are described with particular reference to the links with groundwater. As well as reducing direct recharge, urbanization creates new pathways and sources of water for recharge, including leaking water mains, sewers, septic tanks and soakaways. The net effect is often to increase recharge to pre-urbanization rates, or higher in dry climates and cities with high densities and large imported water supplies.
Lerner, David N.
Predicting vegetation-stabilized dune morphology
NASA Astrophysics Data System (ADS)
The morphology of vegetation-stabilized dune fields on the North American Great Plains mostly comprises parabolic dunes; stabilized barchan and transverse dunes are rare. One notable exception is the Nebraska Sand Hills (NSH), where massive grass-covered barchan and transverse dunes bear proof of former desert-like conditions. We present a hypothesis from a numerical dune field model to explain the vegetation-stabilized morphology of dunes. The model incorporates a growth curve that preferentially grows vegetation in regions of sediment deposition with a sharp drop in growth at the peak depositional tolerance of vegetation, qualitatively matching biological response to erosion and deposition. Simulations on a range of pre-stabilization dune morphologies, from large closely-spaced transverse dunes to small dispersed barchans, indicate that the stabilized morphology is largely determined by the ratio of slipface deposition rate to peak depositional tolerance of vegetation. Conceptually, slipface deposition rate is related to dune height and celerity. By keeping depositional tolerance constant (representing a constant vegetation type and climate) the model shows that large slow-moving dunes have low slipface deposition rates and essentially 'freeze' in place once vegetation is introduced, retaining their pre-vegetation morphology. Small fast-moving dunes have higher slipface deposition rates and evolve into parabolic dunes. We hypothesize that, when barchan and transverse dunes are subjected to a stabilizing climate shift that increases vegetation growth rate, they retain their pre-stabilization morphology if deposition rates are below the depositional tolerance of stabilizing vegetation, otherwise they become parabolic dunes. This could explain why NSH dunes are stabilized in barchan and transverse morphologies while elsewhere on the Great Plains dune fields are dominated by smaller parabolic dunes.
Barchyn, T.; Hugenholtz, C.
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] The large sand sheets and dunes observed in this THEMIS image are located near the north pole of Mars. Changes in surface albedo across the image are likely due to variable thicknesses of dark sand that cover lighter surfaces. Layering of units is observed near the top of the image and is evidence to changing conditions throughout the geologic history of Mars.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.Image information: VIS instrument. Latitude 37.1, Longitude 15.3 East (19.1 West). 19 meter/pixel resolution.
Heat transport in the vicinity of an artificial recharge site
NASA Astrophysics Data System (ADS)
Since July 2002, the Intermunicipal Water Company of the Veurne region (IWVA) artificially recharges fresh water in the dunes of the western Belgian coastal plain by means of two recharge ponds. This recharge water is produced from secondary treated waste water effluent by the combination of ultra filtration and reverse osmosis. Extraction wells (112) are located north and south of the ponds. The artificial recharge project loops the water cycle: extracted water goes to the users and their waste water is purified and re-used. Therefore, it is an example of sustainable water management in coastal aquifers. Groundwater flow of this recharge site has been examined in the past by the use of a tracer test, hydrochemistry (environmental isotopes, conservative tracers) and groundwater flow modelling. Temperature, however, forms a relatively easy measurement which can add to or confirm the knowledge of the groundwater flow. Temperature time series (temperature as function of time) were measured at different levels in a number of wells located between the recharge ponds and the extraction wells, and in one well south of the recharge and extraction area. Secondly, temperature logs (temperature as function of depth) were measured in these wells at different times over the course of 2 years. Finally, the temperature of the recharged and extracted water is constantly monitored by the water company. The temperature of the recharge water shows a yearly fluctuation, ranging from 25 �C during summer to slightly above 0 �C during the winter. The temperature of the extracted water (combination of water extracted in all the wells) ranges between 17 �C during summer and 10 �C during winter. Minima and maxima in the extracted water are observed between 76 and 110 days (mean of 90 days and standard deviation of 13.5 days) later in the extracted water with respect to the recharged water. Measurements show that the difference in time when maxima and minima are observed in an observation well with reference to the ponds increases with depth (for instance from 28 days 4.1 m below surface to 154 days 10 m below surface for an observation well at 10 m from the ponds). This confirms previous flow modelling which showed that groundwater flows relatively rapidly laterally from the recharge ponds towards the extraction wells. Additionally, part of the recharge water flows in a deeper flow cycle towards the extraction wells. Residence times in this deeper flow cycle are evidently larger than in the direct lateral flow cycle from the ponds towards the wells. This explains the increase with depth. The 154 days (with respect to a mean time of 90 days) points to the fact that the extracted water contains a large spectrum of residence times with mean of 90 days for the heat transport, as was also derived by the flow modelling previously
Vandenbohede, Alexander; van Houtte, Emmanuel; Lebbe, Luc
High Power Rechargeable Thermal Battery.
National Technical Information Service (NTIS)
Report developed under STTR contract; a proof of concept for a portable, rechargeable thermal battery (RTB). Including a superinsulated case, a lightweight (10 lb) RTB can provide 250W for 2-6h at 140 Wh/kg with days of activation between recharging. It c...
T. D. Kaun
Rechargeable batteries with aqueous electrolytes
In recent years, rechargeable batteries (RB�s) have found important new applications in rapidly expanding markets, such as portable computers (laptops), telecommunication equipment (handies), camcorders and tools. The interest in electric vehicles has continued to stimulate research on RB�s having improved specific energy. Attention has been focussed on nonaqueous battery systems, in particular on lithium batteries. Small rechargeable lithium batteries, available
Fritz Beck; Paul R�etschi
NASA Technical Reports Server (NTRS)The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) took this image of the southeastern edge of a large dune field within Nili Patera, an irregularly shaped volcanic caldera that is about 65 kilometers (40 miles) in diameter. The image was acquired at 1333 UTC (8:33 a.m. EST) on Feb. 1, 2007, near 8.8 degrees north latitude, 67.3 degrees east longitude. CRISM's image was taken in 544 colors covering 0.36-3.92 micrometers, and shows features as small as 20 meters (66 feet) across. The region covered by the image is just over 10 kilometers (6 miles) wide at its narrowest point. The top image was constructed from three visible wavelengths that correspond to what our eyes would see; the colors are stretched to bring out subtle color contrast. The bottom image is a spectral map constructed using three infrared wavelengths that usually highlight compositional variations. Areas with high concentrations of iron- and magnesium-rich igneous minerals appear red. The entire dune field, covering about 500 square kilometers, resides mainly in the southwest quadrant of the caldera, occupying approximately 15% of its floor. Some of the dune forms seen here are 'barchans' -- individual, crescent shaped dunes that form when winds come primarily from one direction, resulting in one slipface. The orientation of the slipfaces indicates that primary winds were coming from the east-northeast. Using images from Mars Global Surveyor's narrow-angle camera, researchers measured approximately 400 slipfaces throughout the dune field and calculated an average azimuth of 245 degrees. Some of the barchans have elongated horns, suggesting that they experienced a slight secondary wind, or that the primary wind direction varied a little. When sufficient sand is available, barchans will coalesce, losing their individual crescentic shape. The resulting dune form, referred to as barchanoid, describes the vast majority of dunes in this image. In the lower left portion of the image, where the dune pattern is most regular, the distance from dune crest to dune crest is about 400 meters (437 yards). The relationship shown here, with barchans at the margin of a barchanoid dune field, is common on Mars. CRISM's mission: Find the spectral fingerprints of aqueous and hydrothermal deposits and map the geology, composition and stratigraphy of surface features. The instrument will also watch the seasonal variations in Martian dust and ice aerosols, and water content in surface materials -- leading to new understanding of the climate. The Compact Reconnaissance Imaging Spectrometer for Mars (CRISM) is one of six science instruments on NASA's Mars Reconnaissance Orbiter. Led by The Johns Hopkins University Applied Physics Laboratory, the CRISM team includes expertise from universities, government agencies and small businesses in the United States and abroad.
Environmental Impact Research Program. Environmental Considerations for Dune-Stabilization Projects.
National Technical Information Service (NTIS)
Contents--History of Human Efforts to Stabilize Coastal Dunes; Report Objectives; Role of Dunes in Shore Processes; Overtopping, Sand Reservoir; Natural Dune Systems: Vegetation of Natural Dunes; Description of Man-Made Dune Systems: Dune-Building Techniq...
P. L. Knutson K. Finkelstein
'Endurance Crater's' Dazzling Dunes (false-color)
NASA Technical Reports Server (NTRS)As NASA's Mars Exploration Rover Opportunity creeps farther into 'Endurance Crater,' the dune field on the crater floor appears even more dramatic. This false-color image taken by the rover's panoramic camera shows that the dune crests have accumulated more dust than the flanks of the dunes and the flat surfaces between them. Also evident is a 'blue' tint on the flat surfaces as compared to the dune flanks. This results from the presence of the hematite-containing spherules ('blueberries') that accumulate on the flat surfaces. Sinuous tendrils of sand less than 1 meter (3.3 feet) high extend from the main dune field toward the rover. Scientists hope to send the rover down to one of these tendrils in an effort to learn more about the characteristics of the dunes. Dunes are a common feature across the surface of Mars, and knowledge gleaned from investigating the Endurance dunes close-up may apply to similar dunes elsewhere. Before the rover heads down to the dunes, rover drivers must first establish whether the slippery slope that leads to them is firm enough to ensure a successful drive back out of the crater. Otherwise, such hazards might make the dune field a true sand trap.
Fluidic, with the help of ARPA-E funding, has developed and deployed the world's first proven high cycle life metal air battery. Metal air technology, often used in smaller scale devices like hearing aids, has the lowest cost per electron of any rechargeable battery storage in existence. Deploying these batteries for grid reliability is competitive with pumped hydro installations while having the advantages of a small footprint. Fluidic's battery technology allows utilities and other end users to store intermittent energy generated from solar and wind, as well as maintain reliable electrical delivery during power outages. The batteries are manufactured in the US and currently deployed to customers in emerging markets for cell tower reliability. As they continue to add customers, they've gained experience and real world data that will soon be leveraged for US grid reliability.
Friesen, Cody
Mars global digital dune database: MC-30
The Mars Global Digital Dune Database (MGD3) provides data and describes the methodology used in creating the global database of moderate- to large-size dune fields on Mars. The database is being released in a series of U.S. Geological Survey Open-File Reports. The first report (Hayward and others, 2007) included dune fields from lat 65� N. to 65� S. (http://pubs.usgs.gov/of/2007/1158/). The second report (Hayward and others, 2010) included dune fields from lat 60� N. to 90� N. (http://pubs.usgs.gov/of/2010/1170/). This report encompasses ~75,000 km2 of mapped dune fields from lat 60� to 90� S. The dune fields included in this global database were initially located using Mars Odyssey Thermal Emission Imaging System (THEMIS) Infrared (IR) images. In the previous two reports, some dune fields may have been unintentionally excluded for two reasons: (1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or (2) resolution of THEMIS IR coverage (100 m/pixel) certainly caused us to exclude smaller dune fields. In this report, mapping is more complete. The Arizona State University THEMIS daytime IR mosaic provided complete IR coverage, and it is unlikely that we missed any large dune fields in the South Pole (SP) region. In addition, the increased availability of higher resolution images resulted in the inclusion of more small (~1 km2) sand dune fields and sand patches. To maintain consistency with the previous releases, we have identified the sand features that would not have been included in earlier releases. While the moderate to large dune fields in MGD3 are likely to constitute the largest compilation of sediment on the planet, we acknowledge that our database excludes numerous small dune fields and some moderate to large dune fields as well. Please note that the absence of mapped dune fields does not mean that dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS), Mars Orbiter Camera (MOC) narrow angle, Mars Express High Resolution Stereo Camera, or Mars Reconnaissance Orbiter Context Camera and High Resolution Imaging Science Experiment images allowed, we classified dunes and included some dune slipface measurements, which were derived from gross dune morphology and represent the approximate prevailing wind direction at the last time of significant dune modification. It was beyond the scope of this report to look at the detail needed to discern subtle dune modification. It was also beyond the scope of this report to measure all slipfaces. We attempted to include enough slipface measurements to represent the general circulation (as implied by gross dune morphology) and to give a sense of the complex nature of aeolian activity on Mars. The absence of slipface measurements in a given direction should not be taken as evidence that winds in that direction did not occur. When a dune field was located within a crater, the azimuth from crater centroid to dune field centroid was calculated, as another possible indicator of wind direction. Output from a general circulation model is also included. In addition to polygons locating dune fields, the database includes ~700 of the THEMIS VIS and MOC images that were used to build the database.
Hayward, R. K.; Fenton, L. K.; Titus, T. N.; Colaprete, A.; Christensen, P. R.
Groundwater recharge: A hydrogeologic thought
The ensuing paper imparts vital information on an important component of the hydrologic cycle: recharge. Water flows through\\u000a the porous media and forms a definite flow pattern that can be depicted in an elaborate manner through the micro level studies\\u000a at the small watershed level. The estimation of recharge is indispensable for the groundwater budgeting studies. The advantages\\u000a and disadvantages
A. K. Taqveem
Daily cycles of summer sea breezes produce distinctive cyclic foreset deposits in dune sands of the Texas and Oregon coasts. In both areas the winds are strong enough to transport sand only during part of the day, reach a peak during the afternoon, and vary little in direction during the period of sand transport. Cyclicity in the foreset deposits is made evident by variations in the type of sedimentary structure, the texture, and the heavy-mineral content of the sand. Some of the cyclic deposits are made up entirely of one basic type of structure, in which the character of the structure varies cyclically; for example, the angle of climb in a climbing-wind-ripple structure may vary cyclically. Other cyclic deposits are characterized by alternations of two or more structural types. Variations in the concentration of fine-grained heavy minerals, which account for the most striking cyclicity, arise mainly because of segregation on wind-rippled depositional surfaces: where the ripples climb at low angles, the coarsegrained light minerals, which accumulate preferentially on ripple crests, tend to be excluded from the local deposit. Daily cyclic deposits are thickest and best developed on small dunes and are least recognizable near the bases of large dunes. ?? 1988.
Hunter, R. E.; Richmond, B. M.
Stability of transverse dunes against perturbations: A theoretical study using dune skeleton model
NASA Astrophysics Data System (ADS)
The dune skeleton model is a reduced model to describe the formation process and dynamics of characteristic types of dunes emerging under unidirectional steady wind. Using this model, we study the dependency of the morphodynamics of transverse dunes on the initial random perturbations and the lateral field size. It was found that (i) an increase of the lateral field size destabilizes the transverse dune to cause deformation of a barchan, (ii) the initial random perturbations decay with time by the power function until a certain time; thereafter, the dune shapes change into three phases according to the amount of sand and sand diffusion coefficient, and (iii) the duration time, until the transverse dune is broken, increases exponentially with increasing the amount of sand and sand diffusion coefficient. Moreover, under the condition without the sand supply from windward ground, the destabilization of transverse dune in this model qualitatively corresponds to the subaqueous dunes in water tank experiments.
Niiya, Hirofumi; Awazu, Akinori; Nishimori, Hiraku
Investigation of Reversing Sand Dunes at the Bruneau Dunes, Idaho, as Analogs for Features on Mars
NASA Astrophysics Data System (ADS)
The Bruneau Dunes in south-central Idaho include several large reversing sand dunes located within a cut-off meander of the Snake River. These dunes include the largest single-structured sand dune present in North America. Wind records from the Remote Automated Weather Station (RAWS) installation at the Mountain Home Air Force Base, which is ~21 km NW of the Bruneau Dunes, have proved to be very helpful in assessing the regional wind patterns at this section of the western Snake River Plains province; a bimodal wind regime is present, with seasonal changes of strong (sand-moving) winds blowing from either the northwest or the southeast. During April of 2011, we obtained ten precision topographic surveys across the southernmost reversing dune using a Differential Global Positioning System (DGPS). The DGPS data document the shape of the dune going from a low, broad sand ridge at the southern distal end of the dune to the symmetrically shaped 112-m-high central portion of the dune, where both flanks of the dune consist of active slopes near the angle of repose. These data will be useful in evaluating the reversing dune hypothesis proposed for enigmatic features on Mars called Transverse Aeolian Ridges (TARs), which could have formed either as large mega-ripples or small sand dunes. The symmetric profiles across TARs with heights greater than 1 m are more consistent with measured profiles of reversing sand dunes than with measured profiles of mega-ripples (whose surfaces are coated by large particles ranging from coarse sand to gravel, moved by saltation-induced creep). Using DGPS to monitor changes in the three-dimensional location of the crests of the reversing dunes at the Bruneau Dunes should provide a means for estimating the likely timescale for changes of TAR crests if the Martian features are indeed formed in the same manner as reversing sand dunes on Earth.
Zimbelman, J. R.; Scheidt, S. P.
Functional materials for rechargeable batteries.
There is an ever-growing demand for rechargeable batteries with reversible and efficient electrochemical energy storage and conversion. Rechargeable batteries cover applications in many fields, which include portable electronic consumer devices, electric vehicles, and large-scale electricity storage in smart or intelligent grids. The performance of rechargeable batteries depends essentially on the thermodynamics and kinetics of the electrochemical reactions involved in the components (i.e., the anode, cathode, electrolyte, and separator) of the cells. During the past decade, extensive efforts have been dedicated to developing advanced batteries with large capacity, high energy and power density, high safety, long cycle life, fast response, and low cost. Here, recent progress in functional materials applied in the currently prevailing rechargeable lithium-ion, nickel-metal hydride, lead acid, vanadium redox flow, and sodium-sulfur batteries is reviewed. The focus is on research activities toward the ionic, atomic, or molecular diffusion and transport; electron transfer; surface/interface structure optimization; the regulation of the electrochemical reactions; and the key materials and devices for rechargeable batteries. PMID:21394791
Cheng, Fangyi; Liang, Jing; Tao, Zhanliang; Chen, Jun
Hematite Outlier and Sand Dunes
NASA Technical Reports Server (NTRS)[figure removed for brevity, see original site] Released 4 December 2003This image shows a crater just south of the edge of the famous hematite-bearing surface, which is visible in the context image as a smooth area to the north. The crater has two features of immediate note. The first is a layered mound in the north part of the crater floor. This mound contains hematite, and it is an outlying remnant of the greater deposits to the north that have otherwise completely disappeared in this crater. The second feature is a dune field in the center of the crater floor, with dark dunes indicating winds from the northwest. The dunes grade into a dark sand sheet with no coherent structure, indicating that the sand layer thins out to the south and east.Image information: VIS instrument. Latitude -4.4, Longitude 357.3 East (2.7 West). 19 meter/pixel resolution.Note: this THEMIS visual image has not been radiometrically nor geometrically calibrated for this preliminary release. An empirical correction has been performed to remove instrumental effects. A linear shift has been applied in the cross-track and down-track direction to approximate spacecraft and planetary motion. Fully calibrated and geometrically projected images will be released through the Planetary Data System in accordance with Project policies at a later time.NASA's Jet Propulsion Laboratory manages the 2001 Mars Odyssey mission for NASA's Office of Space Science, Washington, D.C. The Thermal Emission Imaging System (THEMIS) was developed by Arizona State University, Tempe, in collaboration with Raytheon Santa Barbara Remote Sensing. The THEMIS investigation is led by Dr. Philip Christensen at Arizona State University. Lockheed Martin Astronautics, Denver, is the prime contractor for the Odyssey project, and developed and built the orbiter. Mission operations are conducted jointly from Lockheed Martin and from JPL, a division of the California Institute of Technology in Pasadena.
Defrosting North Polar Dune Field
NASA Technical Reports Server (NTRS)
MGS MOC Release No. MOC2-331, 15 April 2003This Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC) image captures frost-covered north polar sand dunes in springtime as they are beginning to defrost. Dark spots and streaks indicate areas where frozen carbon dioxide has started to be removed by sublimation and wind. The picture covers an area 3 km (1.9 mi) wide near 76.3oN, 264.9oW. Sunlight illuminates the scene from the lower left.
On the dynamics of cartoon dunes
NASA Astrophysics Data System (ADS)
The spatio-temporal evolution of a downsized model for a barchan dune is investigated experimentally in a narrow water flow channel. We observe a rapid transition from the initial configuration to a steady-state dune with constant mass, shape, velocity, and packing fraction. The development towards the dune attractor is shown on the basis of four different starting configurations. The shape of the attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward (upstream) side, crest, brink, and steep lee (downstream) side. The migration velocity is reciprocal to the length of the dune and reciprocal to the square root of the value of its mass. The velocity scaling and the shape of the barchan dune is independent of the particle diameter. For small dunes we find significant deviations from a fixed height-length aspect ratio. Moreover, a particle tracking method reveals that the migration speed of the model dune is one order of magnitude slower than that of the individual particles. In particular, the erosion rate consists of comparable contributions from low energy (creeping) and high energy (saltating) particles. Finally, it is shown that the velocity field of the saltating particles is comparable to the velocity field of the driving fluid.
Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.
Artificial recharge of groundwater: hydrogeology and engineering
.�� Artificial recharge of groundwater is achieved by putting surface water in basins, furrows, ditches, or other facilities\\u000a where it infiltrates into the soil and moves downward to recharge aquifers. Artificial recharge is increasingly used for short-\\u000a or long-term underground storage, where it has several advantages over surface storage, and in water reuse. Artificial recharge\\u000a requires permeable surface soils. Where
Herman Bouwer
Rechargeable nickel-zinc batteries
NASA Technical Reports Server (NTRS)
Device proves superiority in having two and one half to three times the energy content of popular lead-zinc or nickel-cadmium batteries. Application to electric utility vehicles improved acceleration rate and nearly doubled driving range between rechargings. Unit contributes substantially toward realization of practical urban electrical automobiles.
Soltis, D. G.
High energy lithium rechargeable cells
Methyl formate solutions are noted to be attractive in rechargeable Li cell applications due to their high conductivities and outstanding electrochemical stability; their primary limitation has been their inability to efficiently cycle Li. By doping methyl formate solutions with CO2, however, Li cycling efficiencies of the order of 98 percent have been achieved. A combination of transition metal oxide insertion-type
Walter B. Ebner; John A. Simmons; David L. Chua
Conceptual models of the evolution of transgressive dune field systems
NASA Astrophysics Data System (ADS)
This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, 'tree islands' and 'bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to 'restore' some perceived loss of ecosystem or dune functioning.
Hesp, Patrick A.
Conceptual models of the evolution of transgressive dune field systems
NASA Astrophysics Data System (ADS)
This paper examines the evolutionary paths of some transgressive dune fields that have formed on different coasts of the world, and presents some initial conceptual models of system dynamics for transgressive dune sheets and dune fields. Various evolutionary pathways are conceptualized based on a visual examination of dune fields from around the world. On coasts with high sediment supply, dune sheets and dune fields tend to accumulate as large scale barrier systems with little colonization of vegetation in arid-hyper to arid climate regimes, and as multiple, active discrete phases of dune field and deflation plain couplets in temperate to tropical environments. Active dune fields tend to be singular entities on coasts with low to moderate sediment supply. Landscape complexity and vegetation richness and diversity increases as dune fields evolve from simple active sheets and dunes to single and multiple deflation plains and basins, precipitation ridges, nebkha fields and a host of other dune types associated with vegetation (e.g. trailing ridges, slacks, remnant knobs, gegenwalle ridges and dune track ridges, �tree islands' and �bush pockets'). Three principal scenarios of transgressive dune sheet and dune field development are discussed, including dune sheets or dune fields evolving directly from the backshore, development following foredune and/or dune field erosion, and development from the breakdown or merging of parabolic dunes. Various stages of evolution are outlined for each scenario. Knowledge of evolutionary patterns and stages in coastal dune fields is very limited and caution is urged in attempts to reverse, change and/or modify dune fields to �restore' some perceived loss of ecosystem or dune functioning.
A. Hesp, Patrick
Mars Global Digital Dune Database; MC-1
The Mars Global Digital Dune Database presents data and describes the methodology used in creating the global database of moderate- to large-size dune fields on Mars. The database is being released in a series of U.S. Geological Survey (USGS) Open-File Reports. The first release (Hayward and others, 2007) included dune fields from 65 degrees N to 65 degrees S (http://pubs.usgs.gov/of/2007/1158/). The current release encompasses ~ 845,000 km2 of mapped dune fields from 65 degrees N to 90 degrees N latitude. Dune fields between 65 degrees S and 90 degrees S will be released in a future USGS Open-File Report. Although we have attempted to include all dune fields, some have likely been excluded for two reasons: (1) incomplete THEMIS IR (daytime) coverage may have caused us to exclude some moderate- to large-size dune fields or (2) resolution of THEMIS IR coverage (100m/pixel) certainly caused us to exclude smaller dune fields. The smallest dune fields in the database are ~ 1 km2 in area. While the moderate to large dune fields are likely to constitute the largest compilation of sediment on the planet, smaller stores of sediment of dunes are likely to be found elsewhere via higher resolution data. Thus, it should be noted that our database excludes all small dune fields and some moderate to large dune fields as well. Therefore, the absence of mapped dune fields does not mean that such dune fields do not exist and is not intended to imply a lack of saltating sand in other areas. Where availability and quality of THEMIS visible (VIS), Mars Orbiter Camera narrow angle (MOC NA), or Mars Reconnaissance Orbiter (MRO) Context Camera (CTX) images allowed, we classified dunes and included some dune slipface measurements, which were derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. It was beyond the scope of this report to look at the detail needed to discern subtle dune modification. It was also beyond the scope of this report to measure all slipfaces. We attempted to include enough slipface measurements to represent the general circulation (as implied by gross dune morphology) and to give a sense of the complex nature of aeolian activity on Mars. The absence of slipface measurements in a given direction should not be taken as evidence that winds in that direction did not occur. When a dune field was located within a crater, the azimuth from crater centroid to dune field centroid was calculated, as another possible indicator of wind direction. Output from a general circulation model (GCM) is also included. In addition to polygons locating dune fields, the database includes THEMIS visible (VIS) and Mars Orbiter Camera Narrow Angle (MOC NA) images that were used to build the database. The database is presented in a variety of formats. It is presented as an ArcReader project which can be opened using the free ArcReader software. The latest version of ArcReader can be downloaded at http://www.esri.com/software/arcgis/arcreader/download.html. The database is also presented in an ArcMap project. The ArcMap project allows fuller use of the data, but requires ESRI ArcMap(Registered) software. A fuller description of the projects can be found in the NP_Dunes_ReadMe file (NP_Dunes_ReadMe folder_ and the NP_Dunes_ReadMe_GIS file (NP_Documentation folder). For users who prefer to create their own projects, the data are available in ESRI shapefile and geodatabase formats, as well as the open Geography Markup Language (GML) format. A printable map of the dunes and craters in the database is available as a Portable Document Format (PDF) document. The map is also included as a JPEG file. (NP_Documentation folder) Documentation files are available in PDF and ASCII (.txt) files. Tables are available in both Excel and ASCII (.txt)
Hayward, R. K.; Fenton, L. K.; Tanaka, K. L.; Titus, T. N.; Colaprete, A.; Christensen, P.R.
Rapid improvement of grey dunes after shallow sod cutting
Grey dunes are an important habitat in Dutch coastal sand dunes, harbouring various Red Data Book flora and fauna species. However, during the last decades, dune grasslands belonging to this habitat have suffered from severe grass encroachment due to prolonged stabilisation, atmospheric pollution, and rabbit decline. In the Amsterdam Water supply Dunes shallow sod cutting was ap- plied in 2002
Mark van Til; Annemieke Kooijman
Reproducibility and utility of dune luminescence chronologies
NASA Astrophysics Data System (ADS)
Optically stimulated luminescence (OSL) dating of dune deposits has increasingly been used as a tool to investigate the response of aeolian systems to environmental change. Amalgamation of individual dune accumulation chronologies has been employed in order to distinguish regional from local geomorphic responses to change. However, advances in dating have produced chronologies of increasing complexity. In particular, questions regarding the interpretation of dune ages have been raised, including over the most appropriate method to evaluate the significance of suites of OSL ages when local 'noisy' and discontinuous records are combined. In this paper, these issues are reviewed and the reproducibility of dune chronologies is assessed. OSL ages from two cores sampled from the same dune in the northeast Rub' al Khali, United Arab Emirates, are presented and compared, alongside an analysis of previously published dune ages dated to within the last 30 ka. Distinct periods of aeolian activity and preservation are identified, which can be tied to regional climatic and environmental changes. This case study is used to address fundamental questions that are persistently asked of dune dating studies, including the appropriate spatial scale over which to infer environmental and climatic change based on dune chronologies, whether chronological hiatuses can be interpreted, how to most appropriately combine and display datasets, and the relationship between geomorphic and palaeoclimatic signals. Chronological profiles reflect localised responses to environmental variability and climatic forcing, and amalgamation of datasets, with consideration of sampling resolution, is required; otherwise local factors are always likely to dominate. Using net accumulation rates to display ages may provide an informative approach of analysing and presenting dune OSL chronologies less susceptible to biases resulting from insufficient sampling resolution.
Leighton, Carly L.; Thomas, David S. G.; Bailey, Richard M.
Reestablishing Naturally Functioning Dunes on Developed Coasts.
/ The potential for reestablishing dune habitat is investigated in municipalities in New Jersey, USA, where natural coastal landforms and biota have been eliminated or reduced in extent. Dunes are classified using width, relationship to natural and cultural features, and changes through time, and they are assessed for their value as naturally functioning landforms in developed municipalities. The relationship between size and longevity that exists under natural conditions is altered by human activity. Small dunes on privately owned lots can survive as long as larger dunes in natural areas that are located farther inland, and foredunes repaired using sand fences and earth-moving equipment can survive where they could not under natural conditions.Common beach management practices reduce the ecological values of coastal dunes. Mechanical beach cleaning eliminates incipient dunes, habitat for nesting birds, seed sources for pioneer dune colonizers and food for fauna, and artificially small, stabilized foredunes reduce the variability in microenvironments necessary for biodiversity. Recent initiatives for reducing coastal hazards, protecting nesting birds, and encouraging nature-based tourism provide incentive for the development of a restoration program for beaches and dunes that is compatible with human use. Suggested changes in management practice include restricting or rerouting pedestrian traffic, altering beach-cleaning procedures, using symbolic fences to allow for aeolian transport while preventing trampling of dunes, and eliminating or severely restricting exotic species. Landforms will be more natural in function and appearance but will be more dynamic, smaller and in a different position from those in natural areas. Research needs are specified for ecological, geomorphological, and attitudinal studies to support and inform restoration planning. PMID:10552101
Nordstrom; Lampe; Vandemark
Scaling coastal dune elevation changes across storm-impact regimes
NASA Astrophysics Data System (ADS)
Extreme storms drive change in coastal areas, including destruction of dune systems that protect coastal populations. Data from four extreme storms impacting four geomorphically diverse barrier islands are used to quantify dune elevation change. This change is compared to storm characteristics to identify variability in dune response, improve understanding of morphological interactions, and provide estimates of scaling parameters applicable for future prediction. Locations where total water levels did not exceed the dune crest experienced elevation change of less than 10%. Regions where wave-induced water levels exceeded the dune crest exhibited a positive linear relationship between the height of water over the dune and the dune elevation change. In contrast, a negative relationship was observed when surge exceeded the dune crest. Results indicate that maximum dune elevation, and therefore future vulnerability, may be more impacted from lower total water levels where waves drive sediment over the dune rather than surge-dominated flooding events.
Long, Joseph W.; de Bakker, Anouk T. M.; Plant, Nathaniel G.
Hydrogeochemical transport modeling of the infiltration of tertiary treated wastewater in a dune area, Belgium
NASA Astrophysics Data System (ADS)
Managed artificial recharge (MAR) is a well-established practice for augmentation of depleted groundwater resources or for environmental benefit. At the St-Andr� MAR site in the Belgian dune area, groundwater resources are optimised through re-use of highly treated wastewater by means of infiltration ponds. The very high quality of the infiltration water sets this system apart from other MAR systems. The low total dissolved solid (TDS) content in the infiltration water (less than 50 mg/L) compared to the dune aquifer (500 mg/L) triggers a number of reactions, increasing the TDS through soil-aquifer passage. Multi-component reactive transport modelling was applied to analyse the geochemical processes that occur. Carbonate dissolution is the main process increasing the TDS of the infiltration water. Oxic aquifer conditions prevail between the infiltration ponds and the extraction wells. This is driven by the high flow velocities, leaving no time to consume O2 between the ponds and extraction wells. Cation exchange is important when infiltration water is replaced by native dune water or when significant changes in infiltration-water quality occur. The seasonal variation of O2 and temperature in the infiltration water are the main drivers for seasonal changes in the concentration of all major ions.
Vandenbohede, Alexander; Wallis, Ilka; Van Houtte, Emmanuel; Van Ranst, Eric
Longitudinal dunes on Mars: Relation to current wind regimes
NASA Technical Reports Server (NTRS)
Longitudinal dunes are extremely rare on Mars, but constitute a substantial fraction of terrestrial desert dunes. We report finding isolated examples of longitudinal dunes on Mars and relate their occurrence to expected sand transport regimes. Terrestrial longitudinal dunes form in bimodal and multimodal transport regimes. General circulation models and streak data indicate that bimodal and multimodal transport of sand should be very rare on Mars. Thus the dearth of longitudinal dunes on Mars is consistent with their apparent formation conditions on Earth.
Lee, Pascal; Thomas, Peter C.
'Sharks Teeth' -- Sand Dunes in Proctor Crater
NASA Technical Reports Server (NTRS)Sometimes, pictures received from Mars Global Surveyor's Mars Orbiter Camera (MOC) are 'just plain pretty.' This image, taken in early September 2000, shows a group of sand dunes at the edge of a much larger field of dark-toned dunes in Proctor Crater. Located at 47.9oS, 330.4oW, in the 170 km (106 mile) diameter crater named for 19th Century British astronomer Richard A. Proctor (1837-1888), the dunes shown here are created by winds blowing largely from the east/northeast. A plethora of smaller, brighter ripples covers the substrate between the dunes. Sunlight illuminates them from the upper left.
Directional Underwater Noise Estimates - the Dunes Model.
National Technical Information Service (NTIS)
The modelling of the directionality of underwater noise due to wind-generated noise sources and shipping is presented. The formulations are incorporated in the Directional Underwater Noise Estimates - DUNES model. It provides estimates of omnidirectional,...
A. S. Burgess, D. J. Kewley, R. W. Bannister
Geometric aeolian dune crest migration model
NASA Astrophysics Data System (ADS)
We present a geometric aeolian dune crest model that provides a predictive linkage between local lee face sediment deposition and wholesale landform change. The model is driven using an initial condition of 3D dune crest data obtained from a time series of airborne LIDAR surveys of White Sands, NM, and wind observations from nearby Holloman AFB. Transient dune migration is modeled by volume filling of a simple theoretical dune geometry with sediment flux derived using shear velocity dependent transport (Bagnold, 1941) modified by a new incidence angle dependent lee face sediment deposition function styled after Rubin and Hunter (1985). Model calibration is achieved using an azimuthal wind direction correction and threshold values for shear velocity dependent sediment transport. Agreement between observations and model results are presented using a l2 norm representing a global error estimate.
Swanson, T.; Mohrig, D. C.; Kocurek, G.; Pedersen, A.
Priorities for Future Research on Planetary Dunes
NASA Astrophysics Data System (ADS)
Planetary Dunes Workshop: A Record of Climate Change; Alamogordo, New Mexico, 28 April to 2 May 2008; Landforms and deposits created by the dynamic interactions between granular material and airflow (eolian processes) occur on several planetary bodies, including Earth, Mars, Titan, and Venus. To address many of the outstanding questions within planetary dune research, a workshop was organized by the U.S. Geological Survey, the Planetary Science Institute, the Desert Research Institute, and the Search for Extraterrestrial Intelligence Institute and was sponsored by the Lunar and Planetary Institute and the Jet Propulsion Laboratory. The workshop brought together researchers from diverse backgrounds, ranging from image analysis and modeling to terrestrial analog studies. The group of approximately 45 international researchers had intense discussions in an attempt to identify the most promising approaches to understanding planetary dune systems. On the basis of these discussions, the group identified the following 10 priorities for future planetary dune research.
Titus, Timothy N.; Lancaster, Nick; Hayward, Rose; Fenton, Lori; Bourke, Mary
High energy lithium rechargeable cells
NASA Astrophysics Data System (ADS)
Methyl formate solutions are noted to be attractive in rechargeable Li cell applications due to their high conductivities and outstanding electrochemical stability; their primary limitation has been their inability to efficiently cycle Li. By doping methyl formate solutions with CO2, however, Li cycling efficiencies of the order of 98 percent have been achieved. A combination of transition metal oxide insertion-type cathode materials with the methyl formate electrolyte solutions and advanced cathode processing techniques, two promising rechargeable Li technologies have been defined: Li/V2O5, which has demonstrated 250 discharge cycles with little degradation in capacity, and Li/Li(x)CoO2, with excellent low temperature performance.
Ebner, Walter B.; Simmons, John A.; Chua, David L.
Invasive plants on disturbed Korean sand dunes
NASA Astrophysics Data System (ADS)
The sand dunes in coastal regions of South Korea are important ecosystems because of their small size, the rare species found in this habitat, and the beautiful landscapes they create. This study investigated the current vegetative status of sand dunes on three representative coasts of the Korean peninsula, and on the coasts of Cheju Island, and assessed the conditions caused by invasive plants. The relationships between the degree of invasion and 14 environmental variables were studied. Plots of sand dunes along line transects perpendicular to the coastal lines were established to estimate vegetative species coverage. TWINSPAN (Two-Way Indicator Species Analysis), CCA (Canonical Correspondence Analysis), and DCCA (Detrended Canonical Correspondence Analysis) were performed to classify communities on sand dunes and assess species composition variation. Carex kobomugi, Elymus mollis, and Vitex rotundifolia were found to be the dominant species plotted on the east, the west, and the peripheral coasts of Cheju Island, respectively. Vegetation on the south coast was totally extinct. The 19 communities, including representative C. kobomugi, C. kobomugi- Ixeris repens, C. kobomugi- Oenothera biennis, E. mollis, Lolium multiflorum- Calystegia soldanella, and V. rotundifolia- C. kobomugi, were all classified according to TWINSPAN. Oenothera biennis and L. multiflorum were exotics observed within these native communities. CCA showed that invasive native and exotic species distribution was segregated significantly, according to disturbance level, exotic species number, gravel, sand and silt contents, as well as vegetation size. It further revealed that human disturbance can strongly favor the settlement of invasive and exotic species. Restoration options to reduce exotic plants in the South Korean sand dune areas were found to be the introduction of native plant species from one sand dune into other sand dune areas, prohibition of building and the introduction of exotic soils, and conservation of surrounding sand dune areas.
Kim, Kee Dae
The particle size of Martian aeolian dunes
NASA Technical Reports Server (NTRS)
The effective particle size of unconsolidated materials on the Martian surface can be determined from thermal inertia, due to a pore size dependence of thermal conductivity at Martian atmospheric pressures. Because dunes consist of a narrow range of well-sorted, unconsolidated particles, they provide for a test of the relationship between particle size and thermal inertia calculated from midinfrared emission data for the Martian surface. Two independent approaches are used. First, thermal inertia data indicate that Martian dunes have an average particle size of about 500 +/-100 microns, or medium to coarse sand. Second, expected dune particle sizes are determined from grain trajectory calculations and the particle size transition from suspension to saltation. On earth, the transition occurs for a grain when the ratio of the terminal fall velocity to the wind friction speed, u*(t) is near unity; for grains at u*(t) this occurs at about 52 microns. Terrrestrial dune sands have a mean of 250 microns and are composed entirely of grains greater than 52 microns. The corresponding Martian transition grain size is about 210 microns, suggesting that Martian dunes should be significantly coarser than terrestrial dunes. Grain saltation path length as a function of particle size also shows that, under Martian conditions, larger grains than on earth will become suspended. Both approaches indicate that Martian dune sand should be coarser than terrestrial dune sand. These results closely match the grain sizes determined from thermal inertia models, providing the first direct test of the validity of these models for actual Martian surface materials.
Edgett, Kenneth S.; Christensen, Philip R.
Survey of rechargeable battery technology
We have reviewed rechargeable battery technology options for a specialized application in unmanned high altitude aircraft. Consideration was given to all rechargeable battery technologies that are available commercially or might be available in the foreseeable future. The LLNL application was found to impose very demanding performance requirements which cannot be met by existing commercially available battery technologies. The most demanding requirement is for high energy density. The technology that comes closest to providing the LLNL requirements is silver-zinc, although the technology exhibits significant shortfalls in energy density, charge rate capability and cyclability. There is no battery technology available ``off-the-shelf` today that can satisfy the LLNL performance requirements. All rechargeable battery technologies with the possibility of approaching/meeting the energy density requirements were reviewed. Vendor interviews were carried out for all relevant technologies. A large number of rechargeable battery systems have been developed over the years, though a much smaller number have achieved commercial success and general availability. The theoretical energy densities for these systems are summarized. It should be noted that a generally useful ``rule-of-thumb`` is that the ratio of packaged to theoretical energy density has proven to be less than 30%, and generally less than 25%. Data developed for this project confirm the usefulness of the general rule. However, data shown for the silver-zinc (AgZn) system show a greater conversion of theoretical to practical energy density than would be expected due to the very large cell sizes considered and the unusually high density of the active materials.
Not Available
Intercalation dynamics in rechargeable batteries
NASA Astrophysics Data System (ADS)
We consider the ion intercalation of rechargeable battery electrode particles during charging (or discharging). We have developed a general phase-field model which incorporates entropic, enthalpic and elastic effects within the particle as well as the nonlinear chemical reactions at the particle- electrolyte interface. It is shown through linear stability analysis and numerical simulations that particle size and elastic effects will decrease or even eliminate both the spinodal region and the miscibility gap in the phase diagram.
Stanton, Liam; Bazant, Martin
Mean sediment residence time in barchan dunes
NASA Astrophysics Data System (ADS)
When a barchan dune migrates, the sediment trapped on its lee side is later mobilized when exposed on the stoss side. Then sand grains may undergo many dune turnover cycles before their ejection along the horns, but the amount of time a sand grain contributes to the dune morphodynamics remains unknown. To estimate such a residence time, we analyze sediment particle motions in steady state barchans by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than the convergent sediment fluxes associated with avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchans. Then, for different flow strengths and dune sizes, we find that the mean residence time of sediment particles in barchans is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan morphodynamics. Finally, we initiate a discussion about sediment transport and memory in the presence of bed forms using the advantages of the particle tracking technique.
Zhang, D.; Yang, X.; Rozier, O.; Narteau, C.
Mars Global Digital Dune Database (MGD3): Global dune distribution and wind pattern observations
The Mars Global Digital Dune Database (MGD3) is complete and now extends from 90�N to 90�S latitude. The recently released south pole (SP) portion (MC-30) of MGD3 adds ?60,000 km2 of medium to large-size dark dune fields and ?15,000 km2 of sand deposits and smaller dune fields to the previously released equatorial (EQ, ?70,000 km2), and north pole (NP, ?845,000 km2) portions of the database, bringing the global total to ?975,000 km2. Nearly all NP dunes are part of large sand seas, while the majority of EQ and SP dune fields are individual dune fields located in craters. Despite the differences between Mars and Earth, their dune and dune field morphologies are strikingly similar. Bullseye dune fields, named for their concentric ring pattern, are the exception, possibly owing their distinctive appearance to winds that are unique to the crater environment. Ground-based wind directions are derived from slipface (SF) orientation and dune centroid azimuth (DCA), a measure of the relative location of a dune field inside a crater. SF and DCA often preserve evidence of different wind directions, suggesting the importance of local, topographically influenced winds. In general however, ground-based wind directions are broadly consistent with expected global patterns, such as polar easterlies. Intriguingly, between 40�S and 80�S latitude both SF and DCA preserve their strongest, though different, dominant wind direction, with transport toward the west and east for SF-derived winds and toward the north and west for DCA-derived winds.
Hayward, Rosalyn; Fenton, Lori; Titus, Timothy N.
A bibliography of dunes: Earth, Mars, and Venus
NASA Technical Reports Server (NTRS)
Dunes are important depositional landforms and sedimentary environments on Earth and Mars, and may be important on Venus. The similarity of dune forms on Earth and Mars, together with the dynamic similarity of aeolian processes on the terrestrial planets indicates that it is appropriate to interpret dune forms and processes on Mars and Venus by using analog studies. However, the literature on dune studies is large and scattered. The aim of this bibliography is to assist investigators by providing a literature resource on techniques which have proved successful in elucidating dune characteristics and processes on Earth, Mars, and Venus. This bibliography documents the many investigations of dunes undertaken in the last century. It concentrates on studies of inland dunes in both hot and cold desert regions on Earth and includes investigations of coastal dunes only if they discuss matters of general significance for dune sediments, processes, or morphology.
Lancaster, N.
Modeling emergent large-scale structures of barchan dune fields
NASA Astrophysics Data System (ADS)
In nature, barchan dunes typically exist as members of larger fields that display striking, enigmatic structures that cannot be readily explained by examining the dynamics at the scale of single dunes, or by appealing to patterns in external forcing. To explore the possibility that observed structures emerge spontaneously as a collective result of many dunes interacting with each other, we built a numerical model that treats barchans as discrete entities that interact with one another according to simplified rules derived from theoretical and numerical work, and from field observations: Dunes exchange sand through the fluxes that leak from the downwind side of each dune and are captured on their upstream sides; when dunes become sufficiently large, small dunes are born on their downwind sides ('calving'); and when dunes collide directly enough, they merge. Results show that these relatively simple interactions provide potential explanations for a range of field-scale phenomena including isolated patches of dunes and heterogeneous arrangements of similarly sized dunes in denser fields. The results also suggest that (1) dune field characteristics depend on the sand flux fed into the upwind boundary, although (2) moving downwind, the system approaches a common attracting state in which the memory of the upwind conditions vanishes. This work supports the hypothesis that calving exerts a first order control on field-scale phenomena; it prevents individual dunes from growing without bound, as single-dune analyses suggest, and allows the formation of roughly realistic, persistent dune field patterns.
Worman, S. L.; Murray, A.; Littlewood, R. C.; Andreotti, B.; Claudin, P.
Transverse dune trailing ridges and vegetation succession
NASA Astrophysics Data System (ADS)
We describe the evolution of, and vegetation succession on, a previously undescribed landform: transverse dune trailing ridges at El Farall�n transgressive dunefield in the state of Veracruz, Mexico. Three-dimensional clinometer/compass and tape topographic surveys were conducted in conjunction with 1 m 2 contiguous percent cover and presence/absence vegetation survey transects at eight locations across two adjacent trailing ridges. At the study site, and elsewhere, the transverse dune trailing ridges are formed by vegetation colonization of the lateral margins of active transverse, barchanoidal transverse, and akl� or network dunes. For simplicity, all trailing ridges formed from these dune types are referred to as transverse dune trailing ridges. Because there are several transverse dunes in the dunefield, multiple trailing ridges can be formed at one time. Two adjacent trailing ridges were examined. The shortest length ridge was 70 m long, and evolving from a 2.5 m-high transverse dune, while the longer ridge was 140 m long, and evolving from an 8 m-high dune. Trailing ridge length is a proxy measure of ridge age, since the longer the ridge, the greater the length of time since initial formation. With increasing age or distance upwind, species diversity increased, as well as species horizontal extent and percent cover. In turn, the degree of bare sand decreased. Overall, the data indicate a successional trend in the vegetation presence and cover with increasing age upwind. Those species most tolerant to burial ( Croton and Palafoxia) begin the process of trailing ridge formation. Ipomoea and Canavalia are less tolerant to burial and also are typically the next colonizing species. Trachypogon does not tolerate sand burial or deposition very well and only appears after significant stabilization has taken place. The ridges display a moderately defined successional sequence in plant colonization and percentage cover with time (and upwind distance). They are significant geomorphologically as a unique landform in transgressive dunefields, and also because they may be the only remaining indication of transverse dune presence, and net dune migration direction once the dunefield is stabilized and in a final evolutionary state.
Hesp, Patrick A.; �Marisa' Martinez, M. L.
Rechargeable lithium battery technology - A survey
NASA Technical Reports Server (NTRS)
The technology of the rechargeable lithium battery is discussed with special attention given to the types of rechargeable lithium cells and to their expected performance and advantages. Consideration is also given to the organic-electrolyte and polymeric-electrolyte cells and to molten salt lithium cells, as well as to technical issues, such as the cycle life, charge control, rate capability, cell size, and safety. The role of the rechargeable lithium cell in future NASA applications is discussed.
Halpert, Gerald; Surampudi, Subbarao
Choosing appropriate techniques for quantifying groundwater recharge
.�� Various techniques are available to quantify recharge; however, choosing appropriate techniques is often difficult. Important\\u000a considerations in choosing a technique include space\\/time scales, range, and reliability of recharge estimates based on different\\u000a techniques; other factors may limit the application of particular techniques. The goal of the recharge study is important\\u000a because it may dictate the required space\\/time scales of
Bridget R. Scanlon; Richard W. Healy; Peter G. Cook
Sand dunes of Taklimakan deset obtained from satellite data
NASA Astrophysics Data System (ADS)
Making use of shadows effects in the images of SPOT/HRV, JERS-1/OPS, ASTER/VNIR/SWIR/TIR, LANDSAT-7/ETM+ and TERRA/MODIS an attempt is made to derive some geometrical features of sand dunes at Taklimakan Desert in China. It is found that the prevailing orientation of the sand dunes well coincides with the prevailing strong winds. In the northeastern part of the desert the spacing between the well developed large sand dunes is from 1.5 to 3 kms. It is also found that the small sand dunes are superimposed on the large sand dunes and the average of the spacing between small sand dunes is approximately 200 meters. It is interesting to notice that one order of smaller scale transversal sand dunes exists in the perpendicular direction of large longitudinal sand dunes. The height of sand dunes estimated from LANDSAT-7 image is approximately 50 meters. On the other hand the small sand dunes of fine sand exist in the southwestern part of the desert and the spacing between small sand dunes is from 150 to 200 meters. The height of small sand dunes estimated from SPOT image is approximately 20 meters. As mentioned above, it is shown that the image data obtained from various satellites is fairly useful for clarifying sand dunes features in the desert.
Tsuchiya, K.; Oguro, Y.
Dunes on Titan observed by Cassini Radar
Thousands of longitudinal dunes have recently been discovered by the Titan Radar Mapper on the surface of Titan. These are found mainly within ??30?? of the equator in optically-, near-infrared-, and radar-dark regions, indicating a strong proportion of organics, and cover well over 5% of Titan's surface. Their longitudinal duneform, interactions with topography, and correlation with other aeolian forms indicate a single, dominant wind direction aligned with the dune axis plus lesser, off-axis or seasonally alternating winds. Global compilations of dune orientations reveal the mean wind direction is dominantly eastwards, with regional and local variations where winds are diverted around topographically high features, such as mountain blocks or broad landforms. Global winds may carry sediments from high latitude regions to equatorial regions, where relatively drier conditions prevail, and the particles are reworked into dunes, perhaps on timescales of thousands to tens of thousands of years. On Titan, adequate sediment supply, sufficient wind, and the absence of sediment carriage and trapping by fluids are the dominant factors in the presence of dunes. ?? 2007 Elsevier Inc. All rights reserved.
Radebaugh, J.; Lorenz, R. D.; Lunine, J. I.; Wall, S. D.; Boubin, G.; Reffet, E.; Kirk, R. L.; Lopes, R. M.; Stofan, E. R.; Soderblom, L.; Allison, M.; Janssen, M.; Paillou, P.; Callahan, P.; Spencer, C.; the, Cassini, Radar, Team
Barchan dune mobility in Mauritania related to dune and interdune sand fluxes
NASA Astrophysics Data System (ADS)
We present a 1 year study of 50 dunes in a small field of barchan dunes in Mauritania. We documented the morphological evolution of the dunes and their migration rates and measured at 10 min intervals the interdune sand transport, the wind strength, and its direction for the same interval of time. The dune heights H0 range between 2 and 5 m, and their celerity c is found to be well approximated by the standard migration law: c = Q0/H0, with Q0 ? 50 m3/m yr. From both the interdune sand flux and the migration rate of the dunes we were able to estimate the spatially averaged sand flux at the dune crest as well as the bulk sand flux associated with the mass of sand transported by the dune. We found that the sand flux at the crest was about 3 times greater than the interdune mass transport rate, whereas the bulk sand flux was surprisingly of the same order as the interdune flux. Moreover, we analyzed carefully the interdune sand transport data, which can be well described by the Sorensen law. The cumulative mass of sand transported during moderate wind events within 1 year was much greater than that transported during strong wind events.
Ould Ahmedou, D.; Ould Mahfoudh, A.; Dupont, P.; Ould El Moctar, A.; Valance, A.; Rasmussen, K. R.
Sand dune dynamics and climate change: A modeling approach
NASA Astrophysics Data System (ADS)
We provide several examples for the coexistence of active and fixed sand dunes under similar climatic conditions, namely, with respect to wind power and precipitation rate. A model is developed for dune vegetation cover that includes wind power, precipitation rate, and anthropogenic effects, such as grazing and wood gathering. The model reproduces the observed dune's bistability and shows that under intense human pressure and prolonged droughts the fixed dunes may turn active. Moreover, the model shows that the dune reactivation process is almost irreversible, as a fixed dune will become active only under the action of very strong winds and can then return to the fixed state only when wind power decreases far below the levels under which the initial dune maintained its stability. Similar hysteretic behavior of dune mobility is predicted by the model with respect to changing precipitation and human pressure parameters.
Yizhaq, H.; Ashkenazy, Y.; Tsoar, H.
NASA Astrophysics Data System (ADS)
Morphological changes during more than 100 years have been investigated for a cliff-top dune complex at Rubjerg at the Danish North Sea coast. Here the lower 50 m of the cliff front is composed of Pleistocene steeply inclined floes of silt and clay with coarse sand in between which gives it a saw-tooth appearance. On top of this the dunes are found for several kilometres along the coastline. Due to erosion by the North Sea the cliff has retreated about 120 m between approximately 1880 and 1970 as indicated from two national surveys, and recent GPS-surveys indicate that erosion is continuing at a similar rate. Nevertheless the cliff top dune complex has survived, but its morphology has undergone some changed. The old maps indicate that around 1880 the dune complex was composed of several up to about 20 m high dunes streamlined in the East-West direction which is parallel to the prevailing wind direction. When protective planting started during the first half of the 20th Century the cliff top dunes gradually merged together forming a narrow, tall ridge parallel to the shore line with the highest part reaching about 90 m near 1970. In 1993 the highest points along the ridge was almost 95 m high, but then the protective planting was considerably reduced and recent annual GPS-surveys indicate that the dunes respond quickly to this by changing their morphology towards the original appearance. It is remarkable that despite the mass wasting caused by the constant erosion of the cliff front the dunes have remained more or less intact. Theoretical studies of hill flow indicate given the proper geometry of the cliff then suspension of even coarse grains can be a very effective agent for carrying sand from the exposed parts of the cliff front to and beyond the cliff-top. Mostly the sand grains are deposited within some hundred meters downwind of the cliff dune while silt is often carried more than 10 km inland. Field observations indicate that where the dislodged floes and beds of coarse sand are missing the cliff is steep and dunes are absent at the cliff top. On the other hand when floes are present then some parts of the cliff are less steep and where sand is abundant cliff top dunes seem to be abundant, too. In order to investigate how flow conditions at the cliff front responds to its geometry, scale models of the cliff front approximately 1:10, but with different steepness have been tested in a boundary layer wind tunnel. All runs have been made with proper roughness scaling and besides a variation in their longitudinal profiles some variation in their transverse profiles has also been tested. The surface-near flow has been mapped with high resolution 2-D laser-Doppler profiling, and one of the important aims is to demonstrate the interaction between sediment and geological structure on one side and flow and dune state on the other side. A particular aim is to investigate if and how the separation bubble may have a profound control on mobilization and transport of sediment.
Rasmussen, K. R.
Indirect Interaction of Barchan Dunes by Inter-dune Sand Flow
NASA Astrophysics Data System (ADS)
The most impressive sand structure seen in desert is crescent sand dunes called barchan. Barchan dune has two horns and sand flow release from the tips of them. Seeing aerial photos of deserts, we recognize that barchan dunes tend to align in a characteristic pattern, that is, the horn of one barchan pointing to the center of leeward barchan. As a result, barchans form a convoy with a geese-flying like triangular pattern or align in an slanted line. The pattern has been observed also for barchans found on Mars, and thus there should be some universal mechanism underlying it. Also barchan dunes are highly mobile; human-made structures such as roads or pipelines in their way are sometimes buried in sand. It has been a long-standing problem how we can control this unstoppable march of barchan dunes. There are some interaction such as collision and inter-dune sand flow in marching barchan dunes. Here we investigated interaction dynamics of barchan dunes focusing on the effect of indirect interactions mediated by an inter-dune sand flow using computer simulations. We showed that a barchan is driven laterally by a sand stream to right below the point source of sand.Principal mechanism of this motion is a fast mixing of sand in a barchan that keeps the symmetric shape unchanged.We thereby propose a possibility of controlling the motion of a barchan using a sand stream. In addition,the very same mechanism produces an indirect interaction between barchans mediated by sand stream and can induce the self-organization of the geese-flying like pattern.
Katsuki, A.
North Carolina Groundwater Recharge Rates, from Heath, R.C., 1994, Ground-water recharge in North Carolina: North Carolina State University, as prepared for the NC Department of Environment, Health and Natural Resources (NC DEHNR) Division of Enviromental Management Groundwater S...
Reflections on Dry-Zone Recharge
NASA Astrophysics Data System (ADS)
Quantifying recharge in regions of low precipitation remains a challenging task. The design of permanent nuclear-waste isolation at Yucca Mountain, Nevada, the design of arid-site landfill covers and the pumping of groundwater in desert cities, like Las Vegas, are examples where accurate recharge estimates are needed because they affect billion-dollar decisions. Recharge cannot be measured directly and must rely on estimation methods of various kinds including chemical tracers, thermal profiling, lysimetry, and water-balance modeling. Chemical methods, like chloride-mass-balance can significantly underestimate actual recharge rates and water-balance models are generally limited by large uncertainties. Studies at the U. S. Department of Energy's Hanford Site in Washington State, USA illustrate how estimates of recharge rates have changed over time and how these estimates can affect waste management decisions. Lysimetry has provided reliable estimates of recharge for a wide range of surface condittions. Lysimetric observations of reduced recharge, resulting from advective drying of coarse rock piles, suggest a way to avoid costly recharge protection using titanium shields at Yucca Mountain. The Pacific Northwest National Laboratory is funded by the U. S. Department of Energy under contract DE-AC05-76-RL01830.
Gee, G. W.
Transformer Recharging with Alpha Channeling in Tokamaks
Transformer recharging with lower hybrid waves in tokamaks can give low average auxiliary power if the resistivity is kept high enough during the radio frequency (rf) recharging stage. At the same time, operation in the hot ion mode via alpha channeling increases the effective fusion reactivity. This paper will address the extent to which these two large cost saving steps are compatible. __________________________________________________
N.J. Fisch
Improved Carbon Anodes For Rechargeable Lithium Cells
NASA Technical Reports Server (NTRS)
Carbon anodes for rechargeable lithium cells improved by choosing binder contents and fabrication conditions to achieve maximum porosity, uniform loading, and maximum reversible lithium capacity. Stacking electrodes under pressure during assembly of cells increases cyclability of lithium. Rechargeable, high-energy-density lithium cells containing improved carbon anodes find use in spacecraft, military, communications, automotive, and other demanding applications.
Huang, Chen-Kuo; Surampudi, Subbarao; Attia, Alan; Halpert, Gerald
Lithium Cells Accept Hundreds Of Recharges
NASA Technical Reports Server (NTRS)
New mixed-solvent electrolyte increases number of times room-temperature lithium cell discharged and recharged. Conductivity 70 percent higher. Useful in such other room-temperature rechargeable lithium cells as lithium/niobium triselenide and lithium molybdenum disulfide systems.
Shen, David H.; Surampudi, Subbarao; Deligiannis, Fotios; Halpert, Gerald
Active Martian S. Hemisphere Dune Gullies
NASA Astrophysics Data System (ADS)
Martian gullies on steep slopes have been the focus of much controversy in recent years, as scientists seek to understand how they develop and what they imply about the martian environment. In this study, we examine classic gullies (composed of an alcove/channel and apron) on martian dunes in the southern hemisphere which have been active during the last 4.5 martian years. We completed a general survey of MOC, CTX, and HiRISE images, and found dune gullies from 40-70S, poleward of crater gullies. We also identified periods of gully activity -- measurable changes in gully morphology and/or geomorphic signatures of recent apron deposition. Changes in 17 gullies, within 6 dune fields (latitude 45-52S), all appear to occur during the early southern spring, implying the existence of a seasonal control. These observations and timeframes are consistent with the appearance of fresh-appearing deposits in classic non-dune gullies, implying a related evolution process [1]. We hypothesize that current dune gullies� evolution is related to seasonal accumulation of CO2 frost -- possibly by initiating shear flow by loading the surface [2] and/or increasing the fluidity of dry granular flow [3]. [1] Dundas, et al. (2009, this conference). [2] Ishii and Sasaki (2004) LPSC XXXV, abstract 1556. [3] Hugenholtz (2008) Icarus, 197:65-72. Spacecraft images showing changes in debris apron at large dune gully (49.49S, 34.86E), since 2002. In MOC E12/01043 (top image, 2002, Ls306 My 25), bright bedforms were visible at the foot of the debris apron. Those bedforms were partially covered in HiRISE PSP_006648_1300 (middle image, 2007, Ls9 My 29) and almost completely covered in HiRISE ESP_013478_1300 (bottom image, 2009, Ls283 My 29). To see the full-resolution HiRISE images, visit http://hirise.lpl.arizona.edu.
Diniega, S.; Byrne, S.; Dundas, C. M.; McEwen, A.
Linking restoration ecology with coastal dune restoration
NASA Astrophysics Data System (ADS)
Restoration and preservation of coastal dunes is urgently needed because of the increasingly rapid loss and degradation of these ecosystems because of many human activities. These activities alter natural processes and coastal dynamics, eliminate topographic variability, fragment, degrade or eliminate habitats, reduce diversity and threaten endemic species. The actions of coastal dune restoration that are already taking place span contrasting activities that range from revegetating and stabilizing the mobile substrate, to removing plant cover and increasing substrate mobility. Our goal was to review how the relative progress of the actions of coastal dune restoration has been assessed, according to the ecosystem attributes outlined by the Society of Ecological Restoration: namely, integrity, health and sustainability and that are derived from the ecological theory of succession. We reviewed the peer reviewed literature published since 1988 that is listed in the ISI Web of Science journals as well as additional references, such as key books. We exclusively focused on large coastal dune systems (such as transgressive and parabolic dunefields) located on natural or seminatural coasts. We found 150 articles that included "coastal dune", "restoration" and "revegetation" in areas such as title, keywords and abstract. From these, 67 dealt specifically with coastal dune restoration. Most of the studies were performed in the USA, The Netherlands and South Africa, during the last two decades. Restoration success has been assessed directly and indirectly by measuring one or a few ecosystem variables. Some ecosystem attributes have been monitored more frequently (ecosystem integrity) than others (ecosystem health and sustainability). Finally, it is important to consider that ecological succession is a desirable approach in restoration actions. Natural dynamics and disturbances should be considered as part of the restored system, to improve ecosystem integrity, health and sustainability.
Lithgow, D.; Mart�nez, M. L.; Gallego-Fern�ndez, J. B.; Hesp, P. A.; Flores, P.; Gachuz, S.; Rodr�guez-Revelo, N.; Jim�nez-Orocio, O.; Mendoza-Gonz�lez, G.; �lvarez-Molina, L. L.
Mobile dunes and eroding salt marshes
NASA Astrophysics Data System (ADS)
The paper deals with general outlines of salt marsh and dune vegetation in the Ellenbogen and Listland area on Sylt (Schleswig-Holstein, FRG). The composition of current salt marsh vegetation is considered to be mainly the result of a long-lasting process of tidal inundation, grazing, and a permanent influence of groundwater seepage from the surrounding dunes. The lower salt marsh communities have shown constancy for 67 years, due to the effect of heavy grazing. The mid-upper salt marsh communities demonstrated a succession from a Puccinellia maritima-dominated community of the lower marsh to a Juncus gerardii-dominated community of the mid-upper salt marsh, which may be due to the transport of sand � over a short time � on the surface of the marsh. The area covered by plant communities of annuals below Mean High Water (MHW) seemed to diminish. Salt marsh soils, especially of the mid-upper marsh, indicate sandy layers resulting from sand drift of the dunes. Dry and wet successional series of the dunes in the Listland/Ellenbogen area both show grassy stages shifting to dwarf shrubs as final stages. White primary dunes can only be found on the accreting shoreline of the Ellenbogen, which is also grazed by sheep; vegetation cover therefore remains dominated by grasses, mosses and lichens. Three mobile dunes (as the most prominent features of this landscape) have been left unaffected by seeding and planting by local authorities. Grazing is considered to be an inadequate tool in nature conservation as long as natural processes are to prevail in the landscape as major determinants.
Neuhaus, R.
Geology Fieldnotes: Great Sand Dunes National Monument Colorado
NSDL National Science Digital Library
This article describes the geology of Great Sand Dunes National Monument. The monument is in southern Colorado and contains North America's tallest dunes, which rise over 750 feet high against the Sangre de Cristo Mountains. Great Sand Dunes, containing 30 square miles of dunes, became a national monument in 1932. Features include links to maps, photographs and visitor information as well as a selection of links to related topics.
Mars Global Digital Dune Database and initial science results
NASA Astrophysics Data System (ADS)
A new Mars Global Digital Dune Database (MGD3) constructed using Thermal Emission Imaging System (THEMIS) infrared (IR) images provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields (area >1 km2) that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of Mars. MGD3 extends from 65�N to 65�S latitude and includes ~550 dune fields, covering ~70,000 km2, with an estimated total volume of ~3,600 km3. This area, when combined with polar dune estimates, suggests moderate- to large-size dune field coverage on Mars may total ~800,000 km2, ~6 times less than the total areal estimate of ~5,000,000 km2 for terrestrial dunes. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera narrow-angle (MOC NA) images allow, we classify dunes and include dune slipface measurements, which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid (referred to as dune centroid azimuth) is calculated and can provide an accurate method for tracking dune migration within smooth-floored craters. These indicators of wind direction are compared to output from a general circulation model (GCM). Dune centroid azimuth values generally correlate to regional wind patterns. Slipface orientations are less well correlated, suggesting that local topographic effects may play a larger role in dune orientation than regional winds.
Hayward, Rosalyn K.; Mullins, Kevin F.; Fenton, Lori K.; Hare, Trent M.; Titus, Timothy N.; Bourke, Mary C.; Colaprete, Anthony; Christensen, Philip R.
Mars global digital dune database and initial science results
A new Mars Global Digital Dune Database (MGD3) constructed using Thermal Emission Imaging System (THEMIS) infrared (IR) images provides a comprehensive and quantitative view of the geographic distribution of moderate- to large-size dune fields (area >1 kM2) that will help researchers to understand global climatic and sedimentary processes that have shaped the surface of Mars. MGD3 extends from 65??N to 65??S latitude and includes ???550 dune fields, covering ???70,000 km2, with an estimated total volume of ???3,600 km3. This area, when combined with polar dune estimates, suggests moderate- to large-size dune field coverage on Mars may total ???800,000 km2, ???6 times less than the total areal estimate of ???5,000,000 km2 for terrestrial dunes. Where availability and quality of THEMIS visible (VIS) or Mars Orbiter Camera. narrow-angle (MOC NA) images allow, we classify dunes and include dune slipface measurements, which are derived from gross dune morphology and represent the prevailing wind direction at the last time of significant dune modification. For dunes located within craters, the azimuth from crater centroid to dune field centroid (referred to as dune centroid azimuth) is calculated and can provide an accurate method for tracking dune migration within smooth-floored craters. These indicators of wind direction are compared to output from a general circulation model (GCM). Dune centroid azimuth values generally correlate to regional wind patterns. Slipface orientations are less well correlated, suggesting that local topographic effects may play a larger role in dune orientation than regional winds. Copyright 2007 by the American Geophysical Union.
Hayward, R. K.; Mullins, K. F.; Fenton, L. K.; Hare, T. M.; Titus, T. N.; Bourke, M. C.; Colaprete, A.; Christensen, P. R.
Polar margin dunes and winds on Mars
NASA Technical Reports Server (NTRS)
The approximately concentric arrangement of layered deposits and dune fields at the two Martian poles may reflect a nearly steady state dispersal of material from the polar deposits. Data on effective surface winds from high resolution Viking Images combined with theory of local winds suggest that the northern dunes are in part confined to a latitude band by winds generated by their own low albedo. Dispersal of the dark sand from the southern polar region is not subject to this kind of feedback because the irregular topography prevents areal accumulations sufficiently extensive to produce winds.
Thomas, Peter C.; Gierasch, Peter
Plant communities on sand dunes of the Navajo nation
Ongoing drought in the southwestern US has produced more sand dunes that potentially impact natural vegetation as they move across the landscape. I studied the plant communities of five dunes over two years near Tuba City, AZ to address the following hypotheses: (1) dunes intensify the physiological stress on desert plants, so that the density and diversity of plants on
Leanna Begay
Sand dune dynamics and climate change: A modeling approach
We provide several examples for the coexistence of active and fixed sand dunes under similar climatic conditions, namely, with respect to wind power and precipitation rate. A model is developed for dune vegetation cover that includes wind power, precipitation rate, and anthropogenic effects, such as grazing and wood gathering. The model reproduces the observed dune's bistability and shows that under
H. Yizhaq; Y. Ashkenazy; H. Tsoar
Ecology of Pacific Northwest Coastal Sand Dunes: A Community Profile.
National Technical Information Service (NTIS)
Sand dunes occur in 33 localities along the 950 km of North American Pacific coast between the Straits of Juan de Fuca (49 degrees N) and Cape Mendocino (40 degrees). The dune landscape is a mosaic of dune forms. These forms are the basic morphological un...
A. M. Wiedemann
``Raked'' linear dunes in the Kumtagh Desert, China
NASA Astrophysics Data System (ADS)
Linear dunes are extensive in sand seas and dune fields around the world, but they take a range of forms due to the complex factors that control their development. "Raked" linear dunes, composed of primary ridges and subsidiary ridges that lie almost perpendicular to the primary ridges, were recently identified in the northern part of China's Kumtagh Desert. The primary ridges are typical linear dunes, but the subsidiary ridges display vestiges of barchan dunes. The subsidiary ridges are sufficiently short that they do not greatly affect the general appearance of the linear dunes. However, the raked linear dunes in the Kumtagh Desert have several unique characteristics that distinguish them from typical linear dunes. These dunes develop in an environment that is deficient in available sediment, and under a wind regime typical of linear dunes: an environment with a high wind energy and a directional variability index (RDP/DP) around 0.5. The raked linear dunes appear to have evolved from barchans following a modified form of Tsoar's (1984) model. Barchans formed under a northern wind regime were modified by an eastern wind regime oriented at an oblique angle to the barchans. The strengths of the two wind regimes are similar. Under these conditions, the barchans became reoriented, with the limbs farthest from the eastern winds extending to form subsidiary ridges and the limbs closest to the eastern winds forming the primary ridges, which appear to form mainly from dune collisions.
Dong, Zhibao; Wei, Zhenhai; Qian, Guangqiang; Zhang, Zhengcai; Luo, Wanyin; Hu, Guangyin
A free cellular model of dune dynamics: Application to El Fangar spit dune system (Ebro Delta, Spain)
NASA Astrophysics Data System (ADS)
Currently, dune field surveying is employed to assess dune net volume changes and their accretion and erosion patterns. In dune fields with complex sediment sources and sink interactions such as El Fangar Spit (Ebro Delta, Spain), it is difficult to establish the sediment input and output with only net volume changes estimated by dune field surveying. This work presents a free dune dynamic cellular model that incorporates algorithms that introduce wind data into the erosion and transport processes. The model can be applied to dune systems with variable wind regime. A calibration methodology based on the morphological reproduction of the observed dune field evolution is proposed. The model and the calibration methodology is applied to a region of El Fangar dune system surveyed with DGPS on 15th and 18th April 2012. The difference between the final measured dune state and the best morphological reproduction obtained with the model is employed to estimate the sediment flux. This operation yields an output sand flux of 98.8 m3 and an input of 292.6 m3. This algorithm could have a great impact on the study of complex dune systems where the dunes act as sinks and sources of beach sediments and in the characterization of the beach�dune interactions.
Barrio-Parra, Fernando; Rodr�guez-Santalla, Inmaculada
Development of spatially diverse and complex dune-field patterns: Gran Desierto Dune Field, Sonora, Mexico
The pattern of dunes within the Gran Desierto of Sonora, Mexico, is both spatially diverse and complex. Identification of the pattern components from remote-sensing images, combined with statistical analysis of their measured parameters demonstrate that the composite pattern consists of separate populations of simple dune patterns. Age-bracketing by optically stimulated luminescence (OSL) indicates that the simple patterns represent relatively short-lived aeolian constructional events since ???25 ka. The simple dune patterns consist of: (i) late Pleistocene relict linear dunes; (ii) degraded crescentic dunes formed at ???12 ka; (iii) early Holocene western crescentic dunes; (iv) eastern crescentic dunes emplaced at ???7 ka; and (v) star dunes formed during the last 3 ka. Recognition of the simple patterns and their ages allows for the geomorphic backstripping of the composite pattern. Palaeowind reconstructions, based upon the rule of gross bedform-normal transport, are largely in agreement with regional proxy data. The sediment state over time for the Gran Desierto is one in which the sediment supply for aeolian constructional events is derived from previously stored sediment (Ancestral Colorado River sediment), and contemporaneous influx from the lower Colorado River valley and coastal influx from the Bahia del Adair inlet. Aeolian constructional events are triggered by climatic shifts to greater aridity, changes in the wind regime, and the development of a sediment supply. The rate of geomorphic change within the Gran Desierto is significantly greater than the rate of subsidence and burial of the accumulation surface upon which it rests. ?? 2006 The Authors. Journal compilation 2006 International Association of Sedimentologists.
Beveridge, C.; Kocurek, G.; Ewing, R. C.; Lancaster, N.; Morthekai, P.; Singhvi, A. K.; Mahan, S. A.
The invention relates to a rechargeable lithium-ion cell, a method for its manufacture, and its application. The cell is distinguished by the fact that it has a metallic housing (21) which is electrically insulated internally by two half shells (15), which cover electrode plates (8) and main output tabs (7) and are composed of a non-conductive material, where the metallic housing is electrically insulated externally by means of an insulation coating. The cell also has a bursting membrane (4) which, in its normal position, is located above the electrolyte level of the cell (1). In addition, the cell has a twisting protection (6) which extends over the entire surface of the cover (2) and provides centering and assembly functions for the electrode package, which comprises the electrode plates (8).
Bechtold, Dieter (Bad Vilbel, DE); Bartke, Dietrich (Kelkheim, DE); Kramer, Peter (Konigstein, DE); Kretzschmar, Reiner (Kelkheim, DE); Vollbert, Jurgen (Hattersheim, DE)
Lithium ion rechargeable systems studies
Lithium ion systems, although relatively new, have attracted much interest worldwide. Their high energy density, long cycle life and relative safety, compared with metallic lithium rechargeable systems, make them prime candidates for powering portable electronic equipment. Although lithium ion cells are presently used in a few consumer devices, e.g., portable phones, camcorders, and laptop computers, there is room for considerable improvement in their performance. Specific areas that need to be addressed include: (1) carbon anode--increase reversible capacity, and minimize passivation; (2) cathode--extend cycle life, improve rate capability, and increase capacity. There are several programs ongoing at Sandia National Laboratories which are investigating means of achieving the stated objectives in these specific areas. This paper will review these programs.
Levy, S.C.; Lasasse, R.R.; Cygan, R.T.; Voigt, J.A.
Particle dynamics of a cartoon dune
NASA Astrophysics Data System (ADS)
The spatio-temporal evolution of a downsized model for a desert dune is observed experimentally in a narrow water flow channel. A particle tracking method reveals that the migration speed of the model dune is one order of magnitude smaller than that of individual grains. In particular, the erosion rate consists of comparable contributions from creeping (low-energy) and saltating (high-energy) particles. The saltation flow rate is slightly larger, whereas the number of saltating particles is one order of magnitude lower than that of the creeping ones. The velocity field of the saltating particles is comparable to the velocity field of the driving fluid. It can be observed that the spatial profile of the shear stress reaches its maximum value upstream of the crest, while its minimum lies at the downstream foot of the dune. The particle tracking method reveals that the deposition of entrained particles occurs primarily in the region between these two extrema of the shear stress. Moreover, it is demonstrated that the initial triangular heap evolves to a steady state with constant mass, shape, velocity and packing fraction after one turnover time has elapsed. Within that time the mean distance between particles initially in contact reaches a value of approximately one quarter of the dune basis length.
Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.
Geomorphology of coastal sand dunes, Baldwin County, Alabama
Alabama's coastal eolian deposits are primarily vegetated dunes that are exemplified by sand ridges with flat to undulating upper surfaces and continuous irregular crests. Dune fields occur along Morgan peninsula between the foredune line and Little Lagoon and the Mobile Bay area. These dune fields consist primarily of one or more continuous ridges that parallel the coast and are generally vegetaed to grassy. Washover of the beach and backshore during Hurricane Frederic (1979) and subsequent smaller scale storms resulted in significant erosion of many of Alabama's dune fields. The primary dunes or foredunes are beginning to recover from the effects of these storms; however, numerous breaks in the primary dune line are present. Sand dunes in coastal Alabama provide protection against storm-generated waves and washover. The foredunes are protected by adherence to a Coastal Construction Control Line (CCCL) or construction setback line identified by markers along coastal Baldwin County.
Bearden, Bennett, L.; Hummell, Richard, L.; Mink, Robert, M.
Changes of Bulgarian Coastal Dune Landscape under Anthropogenic Impact
NASA Astrophysics Data System (ADS)
At one time large sand dune formations were widely distributed along the Bulgarian coast. However, due to increased urbanization in the coastal zone, the areas of total dune landscape has been constantly reduced. Dunes presently comprise only 10% of the entire 412 km long coastline of Bulgaria: they embrace a total length of 38.57 km and a total area of 8.78 km2 Important tasks in dune protection are identification of landscape changes for a certain period of time and accurate delineation of sand dune areas. The present research traces sand dune changes along the Bulgarian Black Sea coast over a 27 year period (1983-2010). This period includes also the time of expanded tourist boom and overbuilding of the coastal zone, and respectively presents the largest dune changes and reductions. Based on the landscape change analyst in GIS environment the study also aims to explore the importance of different natural and human factors in driving the observed dune alterations and destruction. To detect and assess dune changes during the last 3 decades, we used data for sand dunes derived from several sources at different time periods in order to compare changes in shoreline positions, dune contours and areas: i) Topographic maps in 1:5,000 scale from 1983; ii) Modern Very High Resolution orthophotographs from 2006 and 2010; iii) QuickBird Very High Resolution satellite images from 2009; iv) Statistical information for population and tourist infrastructure is also used to consider the influence of human pressure and hotel developments on the dune dynamics. In addition, for more detailed description and visualization of main dune types, digital photos have been taken at many parts of the Bulgarian coast. The study was performed in GIS environment. Based on the results obtained the dunes along the Bulgarian coast were divided into three main groups with relation to the general factors responsible for their alterations: i) Dunes that have decreased in result of shoreline retreat and erosion of the beach itself. Typically dunes are located behind sand beaches and they are part of the beach-dune systems. Such type of dune reduction could be driven by combination of many factors, both natural ones (such as severe storms, erosion, heavy rains or flooding) and human impacts (large number of installed coast-protection structures along the coast, which interrupt the sediment transport, create new sedimentary deficit and generate erosion). During the recent years most of the Bulgarian beaches have progressively eroded and their areas have significantly been decreased. ii) Dunes that have been reduced/damaged and lost due to expanded tourist and housing infrastructures/developments and due to afforestaion activities. The principal sources of human impacts on sand dunes in Bulgaria are rapid coastal urbanization over the recent years (i.e., hotel and residential constructions, roads, parking structures, and other related infrastructure), unregulated camping and "temporary" constructions on the dunes, a lax regulatory environment that tolerates the re-zoning of protected sand dunes to "agricultural" areas. At most recreational sites there were wide coastal dunes, which however have been destroyed during tourist constructions. Such are dunes at the most famous Bulgarian sea resorts of Golden Sands and Sunny Beach in the areas of Varna and Nessebar. As a consequence, major areas along the Bulgarian coast were completely urbanized by hotels and other infrastructures and large sand dune systems were damaged. iii) Dunes located at still undeveloped coastal sections: yet they are naturally preserved and unthreatened by human pressure boom. These are just a few dune sites: at the northernmost portion of the Bulgarian coast (in the area of Durankulak), at the central part in the region of the largest Bulgarian river, Kamchia River, and along the southernmost coastline (in the area of Veleka River). Although sand dunes in Bulgaria are protected areas and national reserves they have been exposed to large anthropogenic pressure in particu
Palazov, A.; Young, R.; Stancheva, M.; Stanchev, H.
Dune fields on Mars: Recorders of a climate change?
NASA Astrophysics Data System (ADS)
Dunes have similar morphologies on the Earth and Mars. The main differences between Martian and terrestrial dunes are their size, which is larger on Mars, and their duration of formation, which is longer on Mars. As the characteristic time of Martian dunes is in the same order as that of the Martian climatic oscillations, Martian dunes could be recorders of past winds regimes and past climates. In order to test this hypothesis, we performed a morphological study of 550 dune fields with high resolution images and we inferred the directions of the dune formative winds from the orientation of the dune slip faces. Our study shows that 310 dune fields record one to four distinct wind directions with some geometric patterns that do not exist on the Earth such as barchans built by opposite wind directions coexisting in the same dune field. Our study demonstrates that the inferred formative wind directions are only partially in agreement with the current wind-patterns predicted by General Circulation Models (GCM). Several possible causes for the misalignment between dunes and GCM outputs are discussed: these include the local variation of the global circulation due to local topographic effects or the possibility that these dunes could be in a transient geometry or fossil. Such bedforms are considered indeed to be not in equilibrium with the present-day atmospheric conditions. This latter hypothesis is supported by the presence, in some ergs, of closely spaced dunes showing nearly opposite slip face orientations. Therefore, we propose that Martian dune fields are constituted, in some cases, by active and fossil dunes and therefore have the potential to preserve information on paleoclimates over extensive periods.
Gardin, Emilie; Allemand, Pascal; Quantin, Cathy; Silvestro, Simone; Delacourt, Christophe
New Mechanically Rechargeable Zinc-Air Batteries.
National Technical Information Service (NTIS)
This report describes the design, development and testing of new mechanically rechargeable zinc-air batteries. Following research and development of a low cost silver-mercury cathode catalyst, prototype battery tests were conducted. Cycle life tests at 3....
J. Giltner
Revised North Carolina Groundwater Recharge Rates, from Heath, R.C., 1994, unpublished map: North Carolina State University, as modified by the NC Department of Environment and Natural Resources (DENR) Division of Water Quality (DWQ) Groundwater Section, (polygons)...
Integrating residence time data in mixing cell modeling - Application to the Lower Kuiseb Dune area
NASA Astrophysics Data System (ADS)
With few exceptions, only limited hydrologic data are available in regions with the highest scarcity of water. Especially in basins with limited data on hydrogeological structure, it is difficult to accurately characterize groundwater flow systems and their recharge sources. Therefore, estimation of available water resources in drylands requires methods that are based on existing data and on information that can be obtained with affordable efforts. Even in desert regions chemical and isotope data are often available or can be obtained quickly. In this study a mixing cell approach was extended by a method incorporating mean cell residence times derived from 14C to further constrain and validate the modeling results. This extended approach was used to model the groundwater system of the Lower Kuiseb Dune area in Namibia. The Kuiseb is a 560 km long ephemeral river crossing the Namib Desert from east to west. Transmission losses from the riverbed during flood events are an important source of groundwater recharge to the underlying aquifer system. Hydrochemical data from 13 wells in the area were used. End members were identified as sources for groundwater found in the Lower Kuiseb, including inflow from the crystalline basement plateau north of the Kuiseb as well as floodwater from the Kuiseb River. A conceptual groundwater recharge and flow model was developed, and then inverse mixing cell modelling was carried out using hydrochemical tracers. This approach generally allows for several possible solutions and leads to model equifinality. After completing the inverse modeling, a forward mixing cell model was developed by varying the mean residence time of each cell to fit calculated 14C data to the measured 14C data. With the additional use of 14C in the mixing approach the number solutions could be narrowed down for most of the different cells. As a important result it was possible to calculate the fractions of floodwater in the different cells of the aquifer beneath the Kuiseb. The floodwater fraction was shown to be between 85.2% and 98.2% for the upper aquifer cells and between 61.0% and 75.2% for the lower aquifer cells. This results show also that there is an important amount of recharge by sources except floodwater. This new approach joins previously developed methods solely based on conservative mixing or residence time optimization. Is very useful in reducing equifinality in the mixing cell modelling and gave important and new insights in the sources of groundwater recharge in the Lower Kuiseb aquifer system.
Klaus, J.; Kuells, C.
Issues and challenges facing rechargeable lithium batteries
Technological improvements in rechargeable solid-state batteries are being driven by an ever-increasing demand for portable electronic devices. Lithium-ion batteries are the systems of choice, offering high energy density, flexible and lightweight design, and longer lifespan than comparable battery technologies. We present a brief historical review of the development of lithium-based rechargeable batteries, highlight ongoing research strategies, and discuss the challenges
J.-M. Tarascon; M. Armand
Lithium rechargeable cell with a polymer cathode
Thin films of electropolymerized poly 3-methylthiophene (PMT) were used as a rechargeable cathode in Li(SO2)3AlCl4 electrolyte. Capacity was superior to porous carbon electrodes of like thickness. Pulse power levels of 2 W cm-2 were achieved, and high rate constant current pulses of four-second duration were reproducible over cycles. Cells could be recharged at potentials below 4.0 V, minimizing the formation
Charles W. Walker Jr.
Proposed artificial recharge studies in northern Qatar
The aquifer system in northern Qatar comprises a water-table aquifer in the Rus Formation which is separated by an aquitard from a partially confined aquifer in the top of the overlying Umm er Radhuma Formation. These two aquifers are composed of limestone and dolomite of Eocene and Paleocene age and contain a fragile lens of freshwater which is heavily exploited as a source of water for agricultural irrigation. Net withdrawals are greatly in excess of total recharge, and quality of ground water is declining. Use of desalinated seawater for artificial recharge has been proposed for the area. Artificial recharge, on a large scale, could stabilize the decline in ground-water quality while allowing increased withdrawals for irrigation. The proposal appears technically feasible. Recharge should be by injection to the Umm er Radhuma aquifer whose average transmissivity is about 2,000 meters squared per day (as compared to an average of about 200 meters squared per day for the Rus aquifer). Implementation of artificial recharge should be preceded by a hydrogeologic appraisal. These studies should include test drilling, conventional aquifer tests, and recharge-recovery tests at four sites in northern Qatar. (USGS)
Kimrey, J. O.
Global map of Titan's dune fields
NASA Astrophysics Data System (ADS)
Introduction Methane is the second major constituent of Titan's atmosphere; but it should be totally removed at least in ten million years by photochemistry in the stratosphere and condensation in the troposphere [1]. The first process produces hydrocarbons which form the haze and can condensate onto the surface. The second process causes methane rains on the surface, which carve channels networks. The loss of methane is possibly balanced by outgassing during cryovolcanic event [2]. But hydrocarbons grains deposited onto the surface cannot be recycled. They may be stored in the dunes [3], which were first seen by SAR (Synthetic Aperture Radar) [4]. We focus our study on the mapping of the dune fields in order to determine their global distribution. The aim is to constrain the amount of hydrocarbon material existing in the dunes, and to relate it to the duration of the methane cycle. Data from the Visual and Infrared Mapping Spectrometer (VIMS) and RADAR instruments onboard Cassini spacecraft can be used to map Titan's surface. Infrared images, which are mainly sensitive to composition and grain size, are very complementary to the microwave measurements which depend mainly on roughness and topography. We used spectral criteria after empirical correction of aerosols to map the distribution of heterogeneous units on Titan [5]. These units are compared with SAR images in overlapping regions. Titan's surface mosaics with VIMS VIMS probes the first ten of microns of the ground in seven narrow atmospheric windows in the 0.88 to 5.11 ?m wavelength range. We built infrared mosaics with cubes sorted by spatial resolution, by keeping cubes corresponding to favorable observing conditions (incidence, emergence, phase and time exposure). Band ratios were computed and combined in false color composite images (red as 1.59/1.27-?m, green as 2.03/1.27-?m and blue as 1.27/1.08-?m). Band ratios are useful to minimize the effect of illuminating conditions and albedo variations [6]. Mosaics of Titan's surface were created using images acquired during 42 flybys from Ta (October 26th 2004) to T42 (March 25th 2008). These images have been integrated into a Geographic Information System (GIS). Global maps of band ratios appear fuzzy at high latitudes due to a low spatial resolution and to the presence of haze and clouds. The unfavorable observing geometry, with high incidence angles, induces a very strong scattering by the aerosols in these regions. On the contrary, equatorial and mid-latitudes regions have been covered at a medium resolution, in better observing conditions. In our color composites, most of Titan surface appears either in brown units, bluish units or bright units. We observed that brown units cover 18% of the whole Titan's surface and are found in equatorial regions. Dark blue units cover roughly 2% of Titan's surface. They are systematically associated with bright terrains and are never found isolated within brown units (Fig. 1a). Dune patterns were first observed in the infrared with VIMS during the closest approach at T4 and T20 flybys [7, 8]. The detailed study of dune fields by [8] shows that dune patterns are found mainly in brown units and interdunes can account for the observed spectral variability. Dunes with Radar SAR dataset We also use the RADAR data in SAR mode, mainly sensitive to roughness, surface topography and dielectric constant variations. It is independent of solar light conditions and of the presence of clouds. We retrieved the radar swaths from Ta to T25 (February 22nd 2007) flybys from the PDS website and reprojected the data using the ISIS2 software. The spatial resolution of the SAR images allows the direct imaging of the dunes. Most of Titan's dunes appear longitudinal and resemble terrestrial dunes, such as the ones found in Namibia [4]. Detailed morphologic analysis was performed in [9], who inferred a dominant wind eastward to account for their formation. Two kinds of dunes have been observed: sand seas and small dunes in low sand supply zones. Most of the aeolian sand deposits are found in sand
Le Corre, L.; Le Mou�lic, S.; Sotin, C.; Barnes, J. W.; Brown, R. H.; Baines, K.; Buratti, B.; Clark, R.; Nicholson, P.
Avalanche grainflow on a simulated aeolian dune
NASA Astrophysics Data System (ADS)
Avalanches maintain the slipface of aeolian dunes, which alters their airflow characteristics and sediment dynamics, and results in the development of grainflow cross-bedding. We report on a series of experiments in which avalanches were observed on a 1:1 replica of a small (1.2 m brink height) transverse dune in the Dune Simulation Wind Tunnel under wind velocities of 8-11 m s-1. Changes in slipface topography were observed photographically and measured utilizing a 3-D laser scanner with 1 mm2 spatial resolution. Avalanches in noncohesive sands were observed to progress through scarp recession from the point of initiation and continue until the slope angle is reduced. Changes in local slope confirm that the steep, pre-avalanche mean slope relaxes to a uniform value equal to the angle of repose of the test sand (32�) over all involved portions of the slipface. Avalanche volumes are measured, and demonstrate that avalanche magnitude is independent of wind speed over the range of velocities observed. This independence provides the potential to significantly simplify the modeling of grainflow as a function of only the total cross brink sediment transport.
Sutton, S. L. F.; McKenna Neuman, C.; Nickling, W.
Twentieth century dune migration at the Great Sand Dunes National Park and Preserve, Colorado, relation to drought variability
NASA Astrophysics Data System (ADS)
The Great Sand Dunes National Park and Preserve in southern Colorado contains a large dune mass banked against the Sangre de Cristo Mountains. The dune mass is bounded for hundreds of kilometers by a vegetated low-relief sand sheet with abundant active parabolic and barchanoid dunes. The clear morphology of these dunes, formed by winds mostly from the southwest, and the unambiguous identification of these forms in remotely sensed images provide straightforward targets to assess temporal changes in dune position. A digital database of georeferenced remote sensing images from 1936 to 1999 is used to quantify parabolic and barchan dune migration rates and surface reflectance, an indicator of vegetation cover, with evolving drought conditions in the twentieth century. The total net migration of 13 parabolic dunes in 63 years is 0.31 to 0.66 km, whereas 11 barchan dunes moved an average of 0.12 to 0.47 km. Compared to intervening wet year, there is at least a three-fold increase in average parabolic dune migration, during well-documented droughts in the 1930s, 1950s, and 1990s with a concomitant reduction in vegetation cover and surface water resources. The landscape response to the most recent drought in the late twentieth century is documented by an average parabolic dune migration rate of 30 m/year, which is a six-fold acceleration over prior wet years, and similar to dune response during the 1930s. A nonlinear threshold for parabolic dune migration is indicated with lower quartile Palmer Drought Severity Index values of < - 2, which corresponds to at least a 25% reduction in summer and autumn precipitation.
Mar�n, L.; Forman, S. L.; Valdez, A.; Bunch, F.
Crescentic dunes on the inner continental shelf off northern California
These dunes appear to be migrating obliquely to the regional shelf gradient; a preferred offshore direction of tranpsort is indicated by the extended southern wings of many dunes. Over longer time periods (decades), the seaward transport of fine to medium sand in the crescentic dunes is probably an important way by which sand escapes the shallow part of the continental shelf in this region and mixes with the muddy deposits of the central shelf. -from Authors
Cacchione, D. A.; Field, M. E.; Drake, D. E.; Tate, G. B.
Dune migration in a steep, coarse-bedded stream
In the North Fork Toutle River at Kid Valley, Washington, weak correlation between flow depth and the standard deviation of bed elevation was noted. Dunes were often superposed on larger bed forms with wave periods between 10 and 30 min. Gradual changes in waveform height and periodicity occurred over several hours during storm runoff. Rates of migration for typical dunes were estimated to be 3 cm s-1, and dune wavelengths were estimated to be 6 to 7 m. -from Author
Dinehart, R. L.
Preliminary study of Kelso Dunes using AVIRIS, TM, and AIRSAR
NASA Technical Reports Server (NTRS)
Remote sensing of sand dunes helps in the understanding of aeolian process and provides important information about the regional geologic history, environmental change, and desertification. Remotely sensed data combined with field studies are valuable in studying dune morphology, regional aeolian dynamics, and aeolian depositional history. In particular, active and inactive sands of the Kelso Dunes have been studied using landsat TM and AIRSAR. In this report, we describe the use of AVIRIS data to study the Kelso dunes and to compare the AVIRIS information with that from TM and AIRSAR.
Xu, Pung; Blumberg, Dan G.; Greeley, Ronald
A Comparative Analysis of Barchan Dunes in the Intra-Crater Dune Fields and the North Polar Sand Sea
NASA Technical Reports Server (NTRS)
Martian sand dunes have the potential to contribute data on geological history through a study of their form. Recognition of the characteristics of both recent and ancient dunes is the first step towards understanding the present as well as past aeolian systems, and by proxy, climatic conditions on Mars. Dunes studied in detail in Viking 1 and 2 Orbiter images have been classified as barchan, barchanoid, transverse, and complex. Regionally, they are concentrated in four locations: The North and South Polar regions, in intra crater dune fields and in troughs and valleys. Here we present the results of a morphometric analysis of barchan dunes in two of these locations: the North Polar Sand Sea (NPSS) and intra-crater dunes.
Bourke, M. C.; Balme, M.; Zimbelman, J.
Estimated recharge rates at the Hanford Site
The Ground-Water Surveillance Project monitors the distribution of contaminants in ground water at the Hanford Site for the U.S. Department of Energy. A subtask called {open_quotes}Water Budget at Hanford{close_quotes} was initiated in FY 1994. The objective of this subtask was to produce a defensible map of estimated recharge rates across the Hanford Site. Methods that have been used to estimate recharge rates at the Hanford Site include measurements (of drainage, water contents, and tracers) and computer modeling. For the simulations of 12 soil-vegetation combinations, the annual rates varied from 0.05 mm/yr for the Ephrata sandy loam with bunchgrass to 85.2 mm/yr for the same soil without vegetation. Water content data from the Grass Site in the 300 Area indicated that annual rates varied from 3.0 to 143.5 mm/yr during an 8-year period. The annual volume of estimated recharge was calculated to be 8.47 {times} 10{sup 9} L for the potential future Hanford Site (i.e., the portion of the current Site bounded by Highway 240 and the Columbia River). This total volume is similar to earlier estimates of natural recharge and is 2 to 10x higher than estimates of runoff and ground-water flow from higher elevations. Not only is the volume of natural recharge significant in comparison to other ground-water inputs, the distribution of estimated recharge is highly skewed to the disturbed sandy soils (i.e., the 200 Areas, where most contaminants originate). The lack of good estimates of the means and variances of the supporting data (i.e., the soil map, the vegetation/land use map, the model parameters) translates into large uncertainties in the recharge estimates. When combined, the significant quantity of estimated recharge, its high sensitivity to disturbance, and the unquantified uncertainty of the data and model parameters suggest that the defensibility of the recharge estimates should be improved.
Fayer, M.J.; Walters, T.B.
Transient, spatially varied groundwater recharge modeling
NASA Astrophysics Data System (ADS)
The objective of this work is to integrate field data and modeling tools in producing temporally and spatially varying groundwater recharge in a pilot watershed in North Okanagan, Canada. The recharge modeling is undertaken by using the Richards equation based finite element code (HYDRUS-1D), ArcGIS�, ROSETTA, in situ observations of soil temperature and soil moisture, and a long-term gridded climate data. The public version of HYDUS-1D and another version with detailed freezing and thawing module are first used to simulate soil temperature, snow pack, and soil moisture over a one year experimental period. Statistical analysis of the results show both versions of HYDRUS-1D reproduce observed variables to the same degree. After evaluating model performance using field data and ROSETTA derived soil hydraulic parameters, the HYDRUS-1D code is coupled with ArcGIS� to produce spatially and temporally varying recharge maps throughout the Deep Creek watershed. Temporal and spatial analysis of 25 years daily recharge results at various representative points across the study watershed reveal significant temporal and spatial variations; average recharge estimated at 77.8 � 50.8 mm/year. Previous studies in the Okanagan Basin used Hydrologic Evaluation of Landfill Performance without any attempt of model performance evaluation, notwithstanding its inherent limitations. Thus, climate change impact results from this previous study and similar others, such as Jyrkama and Sykes (2007), need to be interpreted with caution.
Assefa, Kibreab Amare; Woodbury, Allan D.
76 FR 68503 - Ungulate Management Plan/Environmental Impact Statement, Great Sand Dunes National Park and...
Federal Register 2010, 2011, 2012, 2013
...Environmental Impact Statement, Great Sand Dunes National Park and Preserve, CO AGENCY...for the Ungulate Management Plan, Great Sand Dunes National Park and Preserve...for the Ungulate Management Plan, Great Sand Dunes National Park and Preserve,...
36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.
Code of Federal Regulations, 2010 CFR
...The Community Development District; The Dune District; The Seashore District. 28...The Community Development District; The Dune District; The Seashore District. ...District, the Seashore District, and the Dune District. (b) The Community...
76 FR 10915 - Minor Boundary Revision at Indiana Dunes National Lakeshore
Federal Register 2010, 2011, 2012, 2013
...Service Minor Boundary Revision at Indiana Dunes National Lakeshore AGENCY: National Park...9(c)(1), the boundary of Indiana Dunes National Lakeshore in the State of Indiana...depicted on a map entitled ``Indiana Dunes National Lakeshore, Proposed...
36 CFR 28.3 - Boundaries: The Community Development District; The Dune District; The Seashore District.
Code of Federal Regulations, 2010 CFR
...The Community Development District; The Dune District; The Seashore District. 28...The Community Development District; The Dune District; The Seashore District. ...District, the Seashore District, and the Dune District. (b) The Community...
77 FR 11061 - Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the Dunes Sagebrush...
Federal Register 2010, 2011, 2012, 2013
...Plants; Proposed Endangered Status for the Dunes Sagebrush Lizard AGENCY: Fish and Wildlife...2010, proposed endangered status for the dunes sagebrush lizard (Sceloporus arenicolus...a signed conservation agreement for the dunes sagebrush lizard in Texas. We are...
Precision topography of a reversing sand dune at Bruneau Dunes, Idaho, as an analog for Transverse Aeolian Ridges on Mars
NASA Astrophysics Data System (ADS)
Ten high precision topographic profiles across a reversing dune were created from a differential global position system (DGPS). The shapes of the profiles reveal a progression from immature to transitional to mature characteristics moving up the dune. When scaled by the basal width along each profile, shape characteristics can be compared for profiles whose horizontal scales differ by orders of magnitude. The comparison of width-scaled Bruneau Dunes profiles to similarly scaled profiles of Transverse Aeolian Ridges (TARs) on Mars indicates that many TARs are likely similar to transitional or mature reversing sand dunes.
Zimbelman, James R.; Scheidt, Stephen P.
Rechargeable alkaline manganese dioxide/zinc batteries
NASA Astrophysics Data System (ADS)
The rechargeable alkaline manganese dioxide/zinc MnO 2/Zn) system, long established commercial as a primay battery, has reached a high level of performance as a secondary battery system. The operating principles are presented and the technological achievements are surveyed by referencing the recent publications and patent literature. A review is also given of the improvements obtained with newly formulated cathodes and anodes and specially designed batteries. Supported by modelling of the cathode and anode processes and by statistical evidence during cycling of parallel/series-connected modules, the envisioned performance of the next generation of these batteries is described. The possibility of extending the practical use of the improved rechargeable MnO 2/Zn system beyond the field of small electronics into the area of power tools, and even to kW-sized power sources, is demonstrated. Finally, the commercial development in comparison with other rechargeable battery systems is examined.
Kordesh, K.; Weissenbacher, M.
Aeolian Processes of the Pismo-Oceano Dune Complex, California
NASA Astrophysics Data System (ADS)
The Pismo Dunes are located approximately 250 km northwest of Los Angeles and consist of 90 km2 of transverse, parabolic and paleodunes. The Pismo Dunes are one of the largest dune complexes on the west coast and are the largest remaining south of San Francisco Bay, but despite their size, relatively few process morphology studies have focused on their form and history. Specifically, the dune field includes 12 km2 of actively migrating transverse dune ridges advancing onshore in three distinct phases separated by small depressions easily indentified using a LiDAR-generated elevation model. An early field investigation by Tchakerian (1983) revealed a uniform increase in slip face heights and crestline wavelengths inland with no apparent change in grain size. Measurement of recent aerial imagery shows variable migration rates throughout the dunes and wavelengths between 30 and 100 m closest to the beach, in the second ridge between 50 and 140 m, and from 70 to 250 m furthest inland. During El Ni�o and La Ni�a periods, westerly winds advance onshore nearly perpendicular to the crestlines, fueling episodic migration of the dune field. It is hypothesized that particularly strong ENSO periods may have led to the development of distinct dune phases with separating depressions and the development of defects along the dune crest. Defects associated with the wakes of incipient vegetation and inter-dune depressions are conspicuous and widespread, though localized and variable through time and space. Aerial imagery taken in September 1994 shows a wider, more even distribution of defects across the dune field than currently visible. The signal is, however, complicated by the closure of the dune field to oversand vehicles in 1982. The closure of much of the complex to vehicular traffic in 1982 may play a role, as Tchakerian's crestline wavelength measurements were far smaller than those obtained for this study while maintaining a likewise increase between phases. At a decadal scale, excessive vehicular traffic may have impeded the transition of emergent, defect-ridden dune forms into mature transverse ridges. Despite the astounding lack to studies focusing on the Pismo Dunes, the complex presents multiple opportunities for inquiry regarding climatic control on dune field evolution, defect law and complex landform pattern development, and long-term anthropogenic alteration of coastal process morphology.
Barrineau, C. P.; Tchakerian, V.; Houser, C.
Morphodynamic implications of flow around interacting barchan dunes
NASA Astrophysics Data System (ADS)
Barchan dunes are three-dimensional topographic features characterized by a crescentic shape. These bedforms are ubiquitous on Earth's surface and are also observed on Mars. Barchan dunes are predominantly found in regions of sediment starvation and unidirectional flow. The barchans-dune migration rates for a given wind speed are a function of their respective volume. A barchan dune field is composed of a widely distributed dune size, which provides the potential for barchan dunes to approach and amalgamate. The mechanisms governing dune-dune interaction, collision and merging remain poorly understood for such complex three-dimensional bedforms due to the complexity of their shape and the high number of geometrical configurations that can occur. In order to quantify the flow structure produced by interacting barchan dunes, particle-image Velocimetry (PIV) is coupled with a refractive-index-matching (RIM) approach, facilitating full optical access to the obstructed regions of flow and eliminates reflections from the liquid-solid boundaries, allowing near-wall data to be collected. Transparent barchan dune models with different volumes are arranged in tandem, immersed in a turbulent flow and rendered invisible through accurate matching of the index of refraction of the solid and fluid phases. The approach applied herein facilitates flow-field measurements in both streamwise-wall-normal planes at varying spanwise positions and streamwise-spanwise planes at varying elevations. Ensemble-averaged flow fields and Reynolds stresses were obtained for different barchan dune spacings and compared to the reference case of an isolated barchan. Additionally, proper orthogonal decomposition (POD) analysis was employed to shed light as to the energetic attributes of the shear-layer interactions. The morphodynamic implications of these results are discussed. Shear-layer interactions between adjacent bedforms, stoss-side erosion and downstream separation of new bedforms from the upstream horn are found to be key aspects of the interaction process.
Tang, Z.; Blois, G.; Best, J.; Jiang, N.; Christensen, K. T.
Riverine Eolian Dunes in Uruguay: OSL Ages and Paleoenvironmental Significance
NASA Astrophysics Data System (ADS)
Relict parabolic dunes occur along Rio Negro and Rio Tacuaremb� in Uruguay under the current humid temperate climate. These dunes offer important terrestrial evidence of drier conditions in the past and may provide foresight about landscape consequences of future climate change. The ages of these dunes previously had not been measured by any absolute dating technique. Two dune fields were selected for optically stimulated luminescence (OSL) dating using the single aliquot regeneration method, including four samples along Rio Negro near Pueblo de la Arena and three samples along Rio Tacuaremb� near Ansina. Results indicate that the dunes were active during the late Pleistocene, with five of the OSL ages in the 22 ka to 12 ka range. One OSL age at the Ansina dune field returned an age of 6 ka, indicating the possibility of limited dune reactivation during the Holocene. There is clear evidence of historical dune activation (e.g. buried fences) at both the Rio Negro and Rio Tacuaremb� sites; one OSL sample from Rio Negro dunes confirms an historical age of 107 years BP. However, human land disturbance rather than climatic factors may explain the historical reactivation. Late Pleistocene dune activity in central Uruguay indicates much drier and windier paleoclimate (at least seasonally) than present, and correlates well with eolian activity in more arid parts of South America in western Argentina. Age and paleoenvironment of the riverine dunes in Uruguay are remarkably similar to those of the southeastern United States (USA), indicating similar patterns of paleoclimate in both hemispheres. Such similarities help to resolve the spatial patterns of global scale climate change.
Leigh, D. S.; Suarez, R.; Brook, G. A.
Relating climate and sand transport to incipient dune development.
NASA Astrophysics Data System (ADS)
Sea levels are continuously rising, increasing the risk of flooding and coastal erosion in low-elevation countries, such as the Netherlands. Coastal dunes are seen as a flexible and natural type of coastal defence, that is able to keep pace with rising water levels. Until now most research has focussed on dynamics and maintenance of established dunes, largely ignoring two critical transitions in early dune development: the transition from bare beach to vegetated incipient dune and that from incipient dune to established foredune. This knowledge is essential to enable more accurate prediction and even stimulation of new dune formation through sand nourishment. We explored the relative contributions of climate and sand transport to incipient dune development combining a 30 year time-series of aerial photographs (1979 - 2010) of the natural Wadden Island coast with high-resolution monitoring data of sand volume changes and climatic parameters. We selected 20 strips of 2.5 km in length along the coast of the Wadden Islands, with a 2 km buffer between them to avoid autocorrelation. For each of these strips of coast we assessed the changes in presence and area of incipient dunes over periods of 5-6 years. Change in fore dune volume and beach width were derived from high resolution beach elevation data. Seawater level and climate data were derived from a nearby meteorological station Preliminary analysis of the first half of the dataset showed that incipient dune area was positively related to beach width, but negatively to storm intensity. In our poster we will present the whole dataset and discuss the implications of our results for future dune development and anthropogenic sand nourishment schemes.
van Puijenbroek, Marinka; Limpens, Juul; Gleichman, Maurits; Berendse, Frank
All Inorganic Ambient Temperature Rechargeable Lithium Battery: Final Report.
National Technical Information Service (NTIS)
Having the advantages of high energy density and good charge retention, rechargeable lithium batteries have been of interest to many companies and research organizations within the last 15 years. Various lithium rechargeable systems with different positiv...
H. C. Kuo A. N. Dey C. Schlaikjer D. Foster M. Kallianidis
REFLEAK: NIST Leak/Recharge Simulation Program for Refrigerant Mixtures
National Institute of Standards and Technology Data Gateway
SRD 73 NIST REFLEAK: NIST Leak/Recharge Simulation Program for Refrigerant Mixtures (PC database for purchase)�� REFLEAK estimates composition changes of zeotropic mixtures in leak and recharge processes.
Electrolyte Additive for Lithium Rechargeable Organic Electrolyte Battery.
National Technical Information Service (NTIS)
The invention relates in general to a rechargeable lithium organic electrolyte battery and, in particular, to an electrolyte additive for such a battery that provides overcharge protection. Rechargeable lithium-organic electrolyte batteries are being deve...
W. K. Behl D. T. Chin
Electrode materials for aqueous rechargeable lithium batteries
In this review, we describe briefly the historical development of aqueous rechargeable lithium batteries, the advantages and\\u000a challenges associated with the use of aqueous electrolytes in lithium rechargeable battery with an emphasis on the electrochemical\\u000a performance of various electrode materials. The following materials have been studied as cathode materials: LiMn2O4, MnO2, LiNiO2, LiCoO2, LiMnPO4, LiFePO4, and anatase TiO2. Addition of
H. Manjunatha; G. S. Suresh; T. V. Venkatesha
Solar recharging system for hearing aid cells.
We present a solar recharging system for nickel-cadmium cells of interest in areas where batteries for hearing aids are difficult to obtain. The charger has sun cells at the top. Luminous energy is converted into electrical energy, during the day and also at night if there is moonlight. The cost of the charger and hearing aid is very low at 35 US$. The use of solar recharging for hearing aids would be useful in alleviating the problems of deafness in parts of developing countries where there is no electricity. PMID:7964140
G�mez Estancona, N; Tena, A G; Torca, J; Urruticoechea, L; Mu�iz, L; Aristimu�o, D; Unanue, J M; Torca, J; Urruticoechea, A
Lithium-manganese oxide rechargeable battery
A new type of rechargeable battery in which lithium ions shuttle between a lithium-manganese oxide electrode and a carbon electrode was unveiled recently by chemists from Bell Communications Research (Bellcore), Red Bank, N.J. The new battery--still experimental--is safer, longer lasting, and potentially cheaper to manufacture than other lithium-ion batteries. In addition, it provides three times the energy of nickel-cadmium cells, the most popular type of rechargeable battery. Bellcore scientists believe the new battery could replace nickel-cadmium and small lead-acid batteries in many applications.
Dagani, R.
Improved Separators For Rechargeable Lithium Cells
NASA Technical Reports Server (NTRS)
Improved pairs of separators proposed for use in rechargeable lithium cells operating at ambient temperature. Block growth of lithium dendrites and help prevent short circuits. Each cell contains one separator made of microporous polypropylene placed next to anode, and one separator made of microporous polytetrafluoroethylene (PTFE) next to cathode. Separators increase cycle lives of secondary lithium cells. Cells to which concept applicable those of Li/TiS(2), Li/NbSe(3), Li/CoO(2), Li/MoS(2), Li/VO(x), and Li/MnO(2) chemical systems. Advantageous in spacecraft, military, communications, automotive, and other applications in which high energy density and rechargeability needed.
Shen, David; Surampudi, Subbarao; Huang, Chen-Kuo; Halpert, Gerald
Karst and artificial recharge: Theoretical and practical problems. A preliminary approach to artificial recharge assessment
NASA Astrophysics Data System (ADS)
SummaryManaged Aquifer Recharge (MAR) is an emerging sustainable technique that has already generated successful results and is expected to solve many water resource problems, especially in semi-arid and arid zones. It is of great interest for karst aquifers that currently supply 20-25% of the world's potable water, particularly in Mediterranean countries. However, the high heterogeneity in karst aquifers is too complex to be able to locate and describe them simply via field observations. Hence, as compared to projects in porous media, MAR is still marginal in karst aquifers. Accordingly, the present work presents a conceptual methodology for Aquifer Rechargeability Assessment in Karst - referred to as ARAK. The methodology was developed noting that artificial recharge in karst aquifers is considered an improbable challenge to solve since karst conduits may drain off recharge water without any significant storage, or recharge water may not be able to infiltrate. The aim of the ARAK method is to determine the ability of a given karst aquifer to be artificially recharged and managed, and the best sites for implementing artificial recharge from the surface. ARAK is based on multi-criteria indexation analysis modeled on karst vulnerability assessment methods. ARAK depends on four independent criteria, i.e. Epikarst, Rock, Infiltration and Karst. After dividing the karst domain into grids, these criteria are indexed using geological and topographic maps refined by field observations. ARAK applies a linear formula that computes the intrinsic rechargeability index based on the indexed map for every criterion, coupled with its attributed weighting rate. This index indicates the aptitude for recharging a given karst aquifer, as determined by studying its probability first on a regional scale for the whole karst aquifer, and then by characterizing the most favorable sites. Subsequently, for the selected sites, a technical and economic feasibility factor is applied, weighted by the difficulties that could occur when trying to undertake a recharge operation at a selected site from the surface. Each site is finally rated by its rechargeability index - the product of two factors, the intrinsic rechargeability and the feasibility index. ARAK was applied to the region of Damour, Lebanon, on the Mediterranean coast where uncontrolled exploitation of public and private wells led to its partial salinization by seawater. A MAR system in Damour region represents an interesting solution to cope with salinization and the insufficiency of the resource.
Daher, Walid; Pistre, S�verin; Kneppers, Angeline; Bakalowicz, Michel; Najem, Wajdi
The role of vegetation in shaping dune morphology
NASA Astrophysics Data System (ADS)
Aeolian dunes naturally emerge under strong winds and sufficient sand supply. They represent the most dynamical feature of the arid and/or coastal landscape and their evolution has the potential to either increase desertification or reduce coastal vulnerability to storms. Although large-scale dune morphology mainly depends on the wind regime and sand availability, vegetation plays an important role in semiarid and/or coastal areas. It is well known that under certain conditions vegetation is able to stabilize dunes, driving a morphological transformation from un-vegetated mobile crescent dunes to static vegetated "parabolic" dunes, de facto paralyzing desertification and initiating land recovery. Furthermore, vegetation is also the primary ingredient in the formation of coastal foredunes, which determine vulnerability to storms, as low dunes are prone to storm-induced erosion and overwash. In both cases, the coupling of biological and geomorphic (physical) processes, in particular vegetation growth and sand transport, governs the evolution of morphology. These processes were implemented in a computational model as part of a previous effort. It was shown that, for a migrating dune, this coupling leads to a negative feedback for dune motion, where an ever denser vegetation implies ever lesser sand transport. The model also predicted the existence of a "mobility index", defined by the vegetation growth rate to sand erosion rate ratio, that fully characterizes the morphological outcome: for indices above a certain threshold biological processes are dominant and dune motion slows after being covered by plants; for lower indices, the physical processes are the dominant ones and the dune remains mobile while vegetation is buried or rooted out. Here, we extend this model to better understand the formation of coastal dunes. We include new physical elements such as the shoreline and water table, as well as different grass species and potential competition among them. Consistent with field observations, we find that basic dune morphology is primarily determined by grass species, with linear or hummocky dunes being built by some species, while others may prevent dune formation. We also find that the evolution of coastal dune morphology is controlled by at least two bio-geomorphic couplings: (1) between vegetation growth and sand transport, which leads to a positive feedback for dune growth, as certain beach grasses maximize growth under sand accretion, which means that an ever denser vegetation implies an ever higher accretion rate; and (2) between vegetation growth and shoreline position through the sand influx. While the first coupling is responsible for dune formation, the second one determines when dunes stop growing and thus controls final dune size. This is particularly relevant for accreting/eroding coastlines where we find that dune size, and thus coastal protection, is maximized for relatively small accretion rates while larger accretion rates lead to formation of a new, smaller dune ridge at the beach.
Duran Vinent, O.; Moore, L. J.; Young, D.
DUNES survey observational results (Eiroa+, 2013)
NASA Astrophysics Data System (ADS)
The on-line tabular material contains a complete description of the DUNES objects, providing absolute parameters of the stars, the photometry used to build their spectral energy distributions, the Herschel/PACS fluxes, the photospheric predictions at the PACS wavelengths, the significance of the potential excesses and additional information concerning the stars with extended emission, the offsets of the stellar positions as measured in the optical and in the PACS100 images, the AORs (Astronomical Observation Request number) of the observations and the on-source integration times. (11 data files).
Eiroa, C.; Marshall, J. P.; Mora, A.; Montesinos, B.; Absil, O.; Augereau, J.-C.; Bayo, A.; Bryden, G.; Danchi, W.; Del Burgo, C.; Ertel, S.; Fridlund, M.; Heras, A. M.; Krivov, A. V.; Launhardt, R.; Liseau, R.; Loehne, T.; Maldonado, J.; Pilbratt, G. L.; Roberge, A.; Rodmann, J.; Sanz-Forcada, J.; Solano, E.; Stapelfeldt, K.; Thebault, P.; Wolf, S.; Ardila, D.; Arevalo, M.; Beichmann, C.; Faramaz, V.; Gonzalez-Garcia, B. M.; Gutierrez, R.; Lebreton, J.; Martinez-Arnaiz, R.; Meeus, G.; Montes, D.; Olofsson, G.; Su, K. Y. L.; White, G. J.; Barrado, D.; Fukagawa, M.; Gruen, E.; Kamp, I.; Lorente, R.; Morbidelli, A.; Mueller, S.; Mutschke, H.; Nakagawa, T.; Ribas, I.; Walker, H.
Tour of Park Geology: Sand Dunes
NSDL National Science Digital Library
This Park Geology site provides links to tours of individual National Parks, Monuments, and Recreation Areas with sand dunes. Where appropriate for each park, links are provided to maps, photographs, geologic research, related links, visitor information, and teacher features (resources for teaching geology with National Park examples). The list includes places such as Death Valley and Mojave National Preserve, along with less well-known areas such as the Pictured Rocks National Lakeshore in Michigan and the Wright Brothers National Memorial in North Carolina.
Sound-producing dune and beach sands
NASA Technical Reports Server (NTRS)
Acoustic and seismic outputs of booming sands and singing (squeaking) sands in response to shearing are investigated, with samples of silent sands studied for controls. A vertical-axis geophone buried at shallow depth and an air microphone were used in the studies. The frequency spectra of the acoustic and seismic responses, propagation delays, comparison of acoustic and seismic traces, grain size and grain surface texture, particle morphology, coherent behavior of grains in assemblages, and relation to prevalent local winds were studied. Mechanisms are still obscure and disputed; slumping and avalanches were induced artificially in some studies. Existence of booming dune phenomena on Mars or on the moon is conjectured.
Lindsay, J. F.; Criswell, D. R.; Criswell, T. L.; Criswell, B. S.
Regional Estimation of Total Recharge to Ground Water in Nebraska
Naturally occurring long-term mean annual recharge to ground water in Nebraska was estimated by a novel water-balance approach. This approach uses geographic information systems (GIS) layers of land cover, elevation of land and ground water surfaces, base recharge, and the recharge potential in combination with monthly climatic data. Long-term mean recharge > 140 rnm per year was estimated in eastern
Jozsef Szilagyi; F. Edwin Harvey; Jerry F. Ayers
Evidence for community structure and habitat partitioning in coastal dune stiletto flies at the Guadalupe-Nipomo dunes system, California
This study provides empirical evidence for habitat selection by North American species of stiletto flies (Diptera: Therevidae), based on local distributions of adults and immatures, and the first hypothesis of community assemblages proposed for a stiletto fly community. Sites at three localities within the Guadalupe-Nipomo dune system were sampled for stiletto flies in 1997 and 2001 by sifting sand, malaise trapping, and hand netting. Nine species were collected from four ecological zones and three intermediate ecological zones: Acrosathe novella (Coquillett), Brachylinga baccata (Loew), Nebritus powelli (Webb and Irwin), Ozodiceromyia sp., Pherocera sp., Tabudamima melanophleba (Loew), Thereva comata Loew, Thereva elizabethae Holston and Irwin, and Thereva fucata Loew. Species associations of adults and larvae with habitats and ecological zones were consistent among sites, suggesting that local distributions of coastal dune stiletto fly species are influenced by differences in habitat selection. In habitats dominated by the arroyo willow,Salix lasiolepsis, stiletto fly larvae of three species were collected in local sympatry, demonstrating that S. lasiolepsis stands along stabilized dune ridges can provide an intermediate ecological zone linking active dune and riparian habitat in the Guadalupe-Nipomo dune system. Sites dominated by European beach grass, Ammophilia arenaria, blue gum, Eucalyptus globulus, and Monterey cypress, Cupressus macrocarpa, are considered unsuitable for stiletto flies, which emphasizes the importance of terrestrial habitats with native vegetation for stiletto fly species. The local distributions of stiletto fly species at the Guadalupe-Nipomo dune system allow the community to be divided into three assemblages; active dune, pioneer scrub, and scrub-riparian. These assemblages may be applicable to other coastal dune stiletto fly communities, and may have particular relevance to stiletto fly species collected in European coastal dunes. The results from this study provide a descriptive framework for studies testing habitat selection in coastal dune stiletto fly species and inform conservation of threatened dune insects.
Holston, Kevin C.
Dunes, Boxcars, and Ball Jars: Mining the Great Lakes Shores
NSDL National Science Digital Library
Spreadsheets Across the Curriculum module/Geology of National Parks course. Students estimate the volume of sand in Hoosier Slide, a large dome-shaped dune quarried away in the 1920s from what is now Indiana Dunes National Lakeshore. They also estimate the number of boxcars to carry the sand, and the number of Ball jars produced from it.
Module by: Tiffany Roberts, University of South Florida Cover Page by: Len Vacher and Denise Davis, University of South Florida
Particle tracking and mean residence time in barchan dunes
NASA Astrophysics Data System (ADS)
We analyze sediment particles motions in steady-state barchan dunes by tracking individual cells of a 3-D cellular automaton dune model. The overall sediment flux may be decomposed into advective and dispersive fluxes to estimate the relative contribution of the underlying physical processes to the barchan dune shape. The net lateral sediment transport from the center to the horns indicates that dispersion on the stoss slope is more efficient than avalanches on the lee slope. The combined effect of these two antagonistic dispersive processes restricts the lateral mixing of sediment particles in the central region of barchan dunes. Then, for different flow strength and dune size, we find that the mean residence time of sediment particles in barchan dunes is equal to the surface of the central longitudinal dune slices divided by the input sand flux. We infer that this central slice contains most of the relevant information about barchan dune morphodynamics. Finally, we initiate a discussion about sediment transport and memory in presence of bedforms using the advantages of the particle tracking technique.
Zhang, Deguo; Narteau, Clement; Rozier, Olivier
Holocene eolian activity in the Minot dune field, North Dakota
Stabilized eolian sand is common over much of the Great Plains region of the United States and Canada, including a subhumid area of ??? 1500 km2 near Minot, North Dakota. Eolian landforms consist of sand sheets and northwest-trending parabolic dunes. Dunes and sand sheets in the Minot field are presently stabilized by a cover of prairie grasses or oak woodland. Stratigraphic studies and accelerator mass spectrometry radiocarbon dating of paleosols indicate at least two periods of eolian sand movement in the late Holocene. Pedologic data suggest that all of the dune field has experienced late Holocene dune activity, though not all parts of the dune field may have been active simultaneously. Similar immobile element (Ti, Zr, La, Ce) concentrations support the interpretation that eolian sands are derived from local glaciofluvial and glaciolacustrine sediments. However, glaciolacustrine and glaciofluvial source sediments have high Ca concentrations from carbonate minerals, whereas dune sands are depleted in Ca. Because noneolian-derived soils in the area are calcareous, these data indicate that the Minot dune field may have had extended periods of activity in the Holocene, such that eolian abrasion removed soft carbonate minerals. The southwest-facing parts of some presently stabilized dunes were active during the 1930s drought, but were revegetated during the wetter years of the 1940s. These observations indicate that severe droughts accompanied by high temperatures are the most likely cause of Holocene eolian activity.
Muhs, D. R.; Stafford, Jr. , T. W.; Been, J.; Mahan, S. A.; Burdett, J.; Skipp, G.; Rowland, Z. M.
The coastal dunes belong to the most important ecosystems in the Netherlands, but they have also suffered from prolonged desiccation, changes in land use, diminished coastal dynamics, and acidification. Environmental management is applied to counteract the deterioration of threatened dune vegetation and to maintain biodiversity. An efficient and reliable monitoring system is neces- sary to investigate autonomous vegetation development and
Mark van Til; Annemieke Bijlmer
36 CFR 7.88 - Indiana Dunes National Lakeshore.
Code of Federal Regulations, 2010 CFR
...Property 1 2010-07-01 2010-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...
36 CFR 7.88 - Indiana Dunes National Lakeshore.
Code of Federal Regulations, 2010 CFR
...Property 1 2009-07-01 2009-07-01 false Indiana Dunes National Lakeshore. 7.88 Section 7.88 Parks, Forests...REGULATIONS, AREAS OF THE NATIONAL PARK SYSTEM § 7.88 Indiana Dunes National Lakeshore. (a) Fishing. Unless...
36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.
Code of Federal Regulations, 2010 CFR
... 1 2009-07-01 2009-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests...AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless flight. The...
36 CFR 7.80 - Sleeping Bear Dunes National Lakeshore.
Code of Federal Regulations, 2010 CFR
... 1 2010-07-01 2010-07-01 false Sleeping Bear Dunes National Lakeshore. 7.80 Section 7.80 Parks, Forests...AREAS OF THE NATIONAL PARK SYSTEM § 7.80 Sleeping Bear Dunes National Lakeshore. (a) Powerless flight. The...
Global synthesis of groundwater recharge in semiarid and arid regions
Global synthesis of the findings from �140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique
Bridget R. Scanlon; Kelley E. Keese; Alan L. Flint; Lorraine E. Flint; Cheikh B. Gaye; W. Michael Edmunds; Ian Simmers
Global synthesis of groundwater recharge in semiarid and arid regions
Global synthesis of the findings from 140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique
Bridget R. Scanlon; Kelley E. Keese; Alan L. Flint; Lorraine E. Flint; Cheikh B. Gaye; W. Michael Edmunds; Ian Simmers
Natural vs. artificial groundwater recharge, quantification through inverse modeling
NASA Astrophysics Data System (ADS)
Estimating the change in groundwater recharge from an introduced artificial recharge system is important in order to evaluate future water availability. This paper presents an inverse modeling approach to quantify the recharge contribution from both an ephemeral river channel and an introduced artificial recharge system based on floodwater spreading in arid Iran. The study used the MODFLOW-2000 to estimate recharge for both steady- and unsteady-state conditions. The model was calibrated and verified based on the observed hydraulic head in observation wells and model precision, uncertainty, and model sensitivity were analyzed in all modeling steps. The results showed that in a normal year without extreme events, the floodwater spreading system is the main contributor to recharge with 80% and the ephemeral river channel with 20% of total recharge in the studied area. Uncertainty analysis revealed that the river channel recharge estimation represents relatively more uncertainty in comparison to the artificial recharge zones. The model is also less sensitive to the river channel. The results show that by expanding the artificial recharge system, the recharge volume can be increased even for small flood events, while the recharge through the river channel increases only for major flood events.
Hashemi, H.; Berndtsson, R.; Kompani-Zare, M.; Persson, M.
Natural vs. artificial groundwater recharge, quantification through inverse modeling
NASA Astrophysics Data System (ADS)
Estimating the change in groundwater recharge from an introduced artificial recharge system is important in order to evaluate future water availability. This paper presents an inverse modeling approach to quantify the recharge contribution from both an ephemeral river channel and an introduced artificial recharge system based on floodwater spreading in arid Iran. The study used the MODFLOW-2000 to estimate recharge for both steady and unsteady-state conditions. The model was calibrated and verified based on the observed hydraulic head in observation wells and model precision, uncertainty, and model sensitivity were analyzed in all modeling steps. The results showed that in a normal year without extreme events the floodwater spreading system is the main contributor to recharge with 80% and the ephemeral river channel with 20% of total recharge in the studied area. Uncertainty analysis revealed that the river channel recharge estimation represents relatively more uncertainty in comparison to the artificial recharge zones. The model is also less sensitive to the river channel. The results show that by expanding the artificial recharge system the recharge volume can be increased even for small flood events while the recharge through the river channel increases only for major flood events.
Hashemi, H.; Berndtsson, R.; Kompani-Zare, M.; Persson, M.
Estimating recharge rates with analytic element models and parameter estimation
Quantifying the spatial and temporal distribution of recharge is usually a prerequisite for effective ground water flow modeling. In this study, an analytic element (AE) code (GFLOW) was used with a nonlinear parameter estimation code (UCODE) to quantify the spatial and temporal distribution of recharge using measured base flows as calibration targets. The ease and flexibility of AE model construction and evaluation make this approach well suited for recharge estimation. An AE flow model of an undeveloped watershed in northern Wisconsin was optimized to match median annual base flows at four stream gages for 1996 to 2000 to demonstrate the approach. Initial optimizations that assumed a constant distributed recharge rate provided good matches (within 5%) to most of the annual base flow estimates, but discrepancies of >12% at certain gages suggested that a single value of recharge for the entire watershed is inappropriate. Subsequent optimizations that allowed for spatially distributed recharge zones based on the distribution of vegetation types improved the fit and confirmed that vegetation can influence spatial recharge variability in this watershed. Temporally, the annual recharge values varied >2.5-fold between 1996 and 2000 during which there was an observed 1.7-fold difference in annual precipitation, underscoring the influence of nonclimatic factors on interannual recharge variability for regional flow modeling. The final recharge values compared favorably with more labor-intensive field measurements of recharge and results from studies, supporting the utility of using linked AE-parameter estimation codes for recharge estimation. Copyright ?? 2005 The Author(s).
Dripps, W. R.; Hunt, R. J.; Anderson, M. P.
Sensitivity Analysis of Dune Height Measurements Along Cross-shore Profiles Using a Novel Method for Dune Ridge Extraction
NASA Astrophysics Data System (ADS)
In barrier islands where communities are subjected to hazards including storm surge and high wave height, coastal dunes offer the first line of defense to property and vital infrastructure. When dunes are over-washed, substantial damage, including complete destruction of buildings and roads can occur. For this reason, dunes are an integral aspect of coastal hazard management. As new, more efficient mapping and analysis technologies evolve, currently used methodologies should be regularly be reexamined in order to ensure the development of the most effective coastal management strategies. Currently, topographical parameters, such as dune height, are usually measured along evenly spaced, shore-perpendicular beach profiles. In previous studies, profile spacing has varied from 20m to over 500m, however, it has been shown that dune height can vary substantially over tens of meters. Profile spacing is a compromise between the resources needed to perform high-resolution measurements and ensuring the capture of meaningful dune features. While it is often clear how the choice of profile spacing will affect the resources needed to perform the analysis, it is often unclear how spacing affects the ability to capture significant dune variation and prevent omission of a narrow dune breach that can open the way for significant flooding. In this study, the structure of alongshore variation in dune height is investigated. The studied dune ridge is located in the Outer Banks, North Carolina, USA and stretches 18km from south of Oregon Inlet (75:31:19W, 35:46:03N) to Rodanthe (75:27:56W, 35:36:31N). The dune ridge is extracted from a 0.5m resolution Digital Elevation Model (DEM) that was interpolated from airborne lidar data using regularized spline with tension. The lidar data was collected in March 2008 by the National Oceanic and Atmospheric Administration. A dune ridge is usually identified as the highest elevation along a shore-perpendicular profile or where ocean-facing slope meets landward-facing slope. In this study, a novel approach for dune ridge extraction is proposed. First, two alongshore end-points of the studied dune ridge are identified using a standard, profile-based method. Then, the dune ridge is traced as the least cost path connecting the two end-points on a cost surface that represents the cumulative penalty for tracing a low elevation path. The cost surface is derived from elevation (i.e., elevation is equal to the cologarithm of the cost). The extracted dune ridge is then sampled at the DEM resolution of 0.5m and analysis of dune ridge height is performed. Statistics on variation in dune height are computed to help understand the sensitivity of dune height measurements to profile spacing and placement. Preliminary results suggest that dune height becomes nearly uncorrelated within 50m and ranges on average nearly a half meter within a five meter window suggesting that dune height measurements are sensitive to profile placement.
Hardin, E.; Mitasova, H.; Overton, M.
Where to dig for gold? - Density segregation inside migrating dunes
NASA Astrophysics Data System (ADS)
If a fluid streams over an extended area of sand, the grains will self-organize by forming complex structures like ripples or dunes. Below the surface, the inner structure of a dune is determined by the individual fate of the particles. In general, agitated granular matter is known to show de-mixing whenever particles differ in size or density, and indeed size segregation is a well-known feature for dunes, called reverse grading. Here we report results of a recent experimental investigation with two particle species differing not in size but in density. Our experimental setup consists of a stadium-shaped flow channel which is filled with water. Measurements are made with a CCD-camera, placed in front of the straight part, recording side views of the dunes migrating downstream. From an initially prepared triangular heap a rapid relaxation to a steady-state solution is observed with constant mass, shape, and velocity. This attractor exhibits all characteristic features of barchan dunes found in nature, namely a gently inclined windward side, crest, brink, and steep lee face. In addition, if the dune consists of a bi-dense mixture of particles, the heavier particles accumulate at the top of migrating dunes whereas light particles are buried at its bottom. This insight into the sedimentology of dunes composed of different types of sand has, loosely speaking, the implication, that in a dune mixed of gold and sand, gold nuggets are likely to be found at the top of the dune, close to the surface at its crest.
Groh, Christopher; Rehberg, Ingo; Kruelle, Christof A.
How to estimate bidirectional wind conditions using isolated sand dunes
NASA Astrophysics Data System (ADS)
Sand dunes are shaped by the effect of wind on sand particles. While sand dunes under unidirectional wind have been used for indicators of the dominant wind direction, it has been difficult to use sand dunes formed by more complex wind conditions (e.g. bidirectional wind regime)to estimate the wind conditions. We focused on isolated sand dunes as a candidate of the indicator of bidirectional wind conditions because continuous dunes (longitudinal dunes) could not show the directions and durations of two flows when the amounts of the sand transported in two wind directions were not even. We conducted flume experiments that generated periodically bidirectional and oblique flows, and found that dune topographies were controlled by two elements under these conditions. The most important factor was the angle between the two flow directions, which determined both the nature of change in the crest line following the change in flow direction and the resultant topography. The second factor was the event duration ratio of the two flows, which influenced the curvature of the crest line. We propose a new phase diagram of the morphological development of isolated dunes under bidirectional flow conditions driven by differences in flow angle and duration. Our phase diagram could distinquish flow conditions of all types of sand topographies, while the exiting diagram using RDP/DP could not. And our diagram have higher angular resolution than that using continuous dunes. Moreover, the estimation of bidirectional wind regime using our phase diagram agree with data from a natural dune field in the Western Sahara where the wind regime is well understood.
Taniguchi, K.; Endo, N.
Rechargeable Lithium-Inorganic Electrolyte Cell.
National Technical Information Service (NTIS)
The overall objective of the present contract research is to develop and improve performance of Li/SO2Cl2 rechargeable cells with particular emphasis on: safety, discharge capacity, and cycle life. In order to achieve these objectives our approach is to i...
S. Hossain P. Harris R. McDonald C. Todino R. Witter
Prototype systems for rechargeable magnesium batteries
The thermodynamic properties of magnesium make it a natural choice for use as an anode material in rechargeable batteries, because it may provide a considerably higher energy density than the commonly used lead-acid and nickel-cadmium systems. Moreover, in contrast to lead and cadmium, magnesium is inexpensive, environmentally friendly and safe to handle. But the development of Mg batteries has been
D. Aurbach; Z. Lu; A. Schechter; Y. Gofer; H. Gizbar; R. Turgeman; Y. Cohen; M. Moshkovich; E. Levi
Recharging "Hot-Melt" Adhesive Film
NASA Technical Reports Server (NTRS)
Technique for recharging surface with "hot-melt" film makes use of one sided, high-temperature, pressure-sensitive adhesive tape. Purpose of the one-sided tape is to hold hot-melt charge in place until fused to surface. After adhesive has fused to surface and cooled, tape is removed, leaving adhesive on surface.
Progar, D. J.
Lithium electronic environments in rechargeable battery electrodes
This work investigates the electronic environments of lithium in the electrodes of rechargeable batteries. The use of electron energy-loss spectroscopy (EELS) in conjunction with transmission electron microscopy (TEM) is a novel approach, which when coupled with conventional electrochemical experiments, yield a thorough picture of the electrode interior. Relatively few EELS experiments have been preformed on lithium compounds owing to their
Adrian Hightower
Prototype Rechargeable Lithium Batteries. Phase 1.
National Technical Information Service (NTIS)
This report details the work performed on Phase I of an overall two-phase program. The aim of Phase I is to select a room-temperature lithium (Li) rechargeable couple that offers high energy density (60-90 Wh/1b), good rate capability (C/6-C/1), and low t...
W. B. Ebner H. W. Lin
Mechanically Rechargeable Zinc-Air Battery.
National Technical Information Service (NTIS)
The mechanically rechargeable zinc-air battery is a new power source that has an energy density in the order of 100 watthours per pound, twice that of the closest competing battery system. The many advantageous characteristics of this battery have encoura...
D. Linden
Characteristics of carbon-lithium rechargeable batteries
Carbon-lithium rechargeable batteries are composed of an activated carbon positive electrode, a lithium-occluded alloy negative electrode, and an organic electrolyte. The discharge curve obtainable from batteries of this type exhibits the slightly inclining linearity of a capacitor. Potential applications are envisioned in computer memory backup power sources and maintenance-free power source applications involving solar cell arrays.
K. Momose; H. Hayakawa; N. Koshiba; T. Ikehata
High reliability lithium rechargeable batteries for specialties
Since their development in the late 1980s, lithium rechargeable batteries have enjoyed rapid growth and wide use as a commodity battery known for its higher energy density storage and lightweight convenience. These same attributes are emerging as a strong platform in power source development for the medical and aerospace sectors with highly customized applications and narrowly defined criteria. Accordingly, this
H. Tsukamoto
Anode for rechargeable ambient temperature lithium cells
NASA Technical Reports Server (NTRS)
An ambient room temperature, high density, rechargeable lithium battery includes a Li(x)Mg2Si negative anode which intercalates lithium to form a single crystalline phase when x is up to 1.0 and an amorphous phase when x is from 1 to 2.0. The electrode has good reversibility and mechanical strength after cycling.
Huang, Chen-Kuo (inventor); Surampudi, Subbarao (inventor); Attia, Alan I. (inventor); Halpert, Gerald (inventor)
Anode for Rechargeable Ambient Temperature Lithium Cells.
National Technical Information Service (NTIS)
An ambient room temperature, high density, rechargeable lithium battery includes a Li(x)Mg2Si negative anode which intercalates lithium to form a single crystalline phase when x is up to 1.0 and an amorphous phase when x is from 1 to 2.0. The electrode ha...
C. Huang S. Surampudi A. I. Attia G. Halpert
High temperature rechargeable molten salt cell
This patent describes a high temperature rechargeable molten salt cell. It comprises: a member of the group consisting of lithium, lithium aluminum alloy, lithium silicon alloy, sodium, potassium, calcium, magnesium, an alkali metal, a group II A element, a group II A alloy and composite mixtures thereof, as the anode, a chemical compound of the composition XYS� wherein X is
E. J. Plichta; W. K. Behl
Recharging Our Sense of Idealism: Concluding Thoughts
ERIC Educational Resources Information Center
In this article, the authors aim to recharge one's sense of idealism. They argue that idealism is the Vitamin C that sustains one's commitment to implementing humanistic principles and social justice practices in the work of counselors and educators. The idealism that characterizes counselors and educators who are humanistic and social justice�
D'Andrea, Michael; Dollarhide, Colette T.
Channels on Dunes in Russell Crater
NASA Technical Reports Server (NTRS)Hundreds of enigmatic small channels are seen to carve into the slopes of these dark sand dunes lying within Russell Crater on Mars. These features were previously identified as gullies in images from the Mars Orbiter Camera (MOC) on Mars Global Surveyor, but the higher resolution HiRISE image brings out many new details and mysteries. The channels extend from near the top of the dunes to their bases, indicating that some fluid material carved into the sand. The channels commonly begin as smaller tributaries joined together, suggesting several sources of fluid. Distinct dark spots are located near where the channels seem to originate. Several channels appear to originate at alcoves. Several of these channels have sinuous middle reaches while others are straighter. Further down slope, some channel edges appear elevated above the surrounding terrain, particularly in the lower reaches. The channels seem to terminate abruptly, with no deposition of material, unlike at the bases of some other gullies on Mars that are not on dunes. One hypothesis for the origin of the channels, which has previously been proposed by the MOC team, is that CO2 (or maybe H2O) frost is deposited on the dunes in shadows or at night. Some frost may also be incorporated into the internal parts of the dunes due to natural avalanching. When the frost is eventually heated by sunlight, rapid sublimation triggers an avalanche of fluidized sand, forming a gully. HiRISE will continue to target small channel features such as these and may return to search for any changes over time. Image PSP_001440_1255 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on November 16, 2006. The complete image is centered at -54.2 degrees latitude, 12.9 degrees East longitude. The range to the target site was 251.4 km (157.1 miles). At this distance the image scale is 50.3 cm/pixel (with 2 x 2 binning) so objects 151 cm across are resolved. The image shown here has been map-projected to 50 cm/pixel and north is up. The image was taken at a local Mars time of 3:41 PM and the scene is illuminated from the west with a solar incidence angle of 85 degrees, thus the sun was about 5 degrees above the horizon. At a solar longitude of 136.3 degrees, the season on Mars is Northern Summer. NASA's Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Mars Reconnaissance Orbiter for NASA's Science Mission Directorate, Washington. Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. The High Resolution Imaging Science Experiment is operated by the University of Arizona, Tucson, and the instrument was built by Ball Aerospace and Technology Corp., Boulder, Colo.
Late Pleistocene dune activity in the central Great Plains, USA
NASA Astrophysics Data System (ADS)
Stabilized dunes of the central Great Plains, especially the megabarchans and large barchanoid ridges of the Nebraska Sand Hills, provide dramatic evidence of late Quaternary environmental change. Episodic Holocene dune activity in this region is now well-documented, but Late Pleistocene dune mobility has remained poorly documented, despite early interpretations of the Sand Hills dunes as Pleistocene relicts. New optically stimulated luminescence (OSL) ages from drill cores and outcrops provide evidence of Late Pleistocene dune activity at sites distributed across the central Great Plains. In addition, Late Pleistocene eolian sands deposited at 20-25 ka are interbedded with loess south of the Sand Hills. Several of the large dunes sampled in the Sand Hills clearly contain a substantial core of Late Pleistocene sand; thus, they had developed by the Late Pleistocene and were fully mobile at that time, although substantial sand deposition and extensive longitudinal dune construction occurred during the Holocene. Many of the Late Pleistocene OSL ages fall between 17 and 14 ka, but it is likely that these ages represent only the later part of a longer period of dune construction and migration. At several sites, significant Late Pleistocene or Holocene large-dune migration also probably occurred after the time represented by the Pleistocene OSL ages. Sedimentary structures in Late Pleistocene eolian sand and the forms of large dunes potentially constructed in the Late Pleistocene both indicate sand transport dominated by northerly to westerly winds, consistent with Late Pleistocene loess transport directions. Numerical modeling of the climate of the Last Glacial Maximum has often yielded mean monthly surface winds southwest of the Laurentide Ice Sheet that are consistent with this geologic evidence, despite strengthened anticyclonic circulation over the ice sheet. Mobility of large dunes during the Late Pleistocene on the central Great Plains may have been the result of cold, short growing seasons with relatively low precipitation and low atmospheric CO 2 that increased plant moisture stress, limiting the ability of vegetation to stabilize active dune sand. The apparent coexistence of large mobile dunes with boreal forest taxa suggests a Late Pleistocene environment with few modern analogs.
Mason, J. A.; Swinehart, J. B.; Hanson, P. R.; Loope, D. B.; Goble, R. J.; Miao, X.; Schmeisser, R. L.
Flow Fields Over Unsteady Three Dimensional Dunes
NASA Astrophysics Data System (ADS)
The flow field over dunes has been extensively measured in laboratory conditions and there is general understanding on the nature of the flow over dunes formed under equilibrium flow conditions. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly responding and reorganizing to these unsteady flows, over a range of both spatial and temporal scales. This is primarily through adjustment of bed forms (including ripples, dunes and bar forms) which then subsequently alter the flow field. This paper investigates, through the application of a numerical model, the influence of these roughness elements on the overall flow and the increase in flow resistance. A series of experiments were undertaken in a flume, 16m long and 2m wide, where a fine sand (D50 of 239?m) mobile bed was water worked under a range of unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms. During the experiments flow was measured with acoustic Doppler velocimeters, (aDv's). On four occasions the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models. This data provide the necessary boundary conditions and validation data for a Large Eddy Simulation (LES) model, which provided a three dimensional time dependent prediction of flow over the four static beds. The numerical predicted flow is analyzed through a series of approaches, and included: i) standard Reynolds decomposition to the flow fields; ii) Eulerian coherent structure detection methods based on the invariants of the velocity gradient tensor; iii) Lagrangian coherent structure identification methods based upon direct Lyapunov exponents (DLE). The results show that superimposed bed forms can cause changes in the nature of the classical separated flow region in particularly the number of locations where vortices are shed and the point of flow reattachment, which may be important for sediment entrainment and sediment transport dynamics during bed form adjustment. Finally, the flow predictions enable a reassessment of the drag caused by the superimposed bed forms generated by unsteady flow.
Hardy, R. J.; Reesink, A.; Parsons, D. R.; Ashworth, P. J.; Best, J.
Effects of sand fences on coastal dune vegetation distribution
NASA Astrophysics Data System (ADS)
Sand fences are important human adjustments modifying the morphology of developed shores. The effects of sand fences on sediment transport and deposition in their initial stages have been well studied, but little is known about the effect of deteriorated sand fences that have become partially buried low scale barriers within the dune, potentially benefiting vegetation growth by protecting it from onshore stress. Data on vegetation, topography and fence characteristics were gathered at three dune sites in Ocean City, New Jersey on September 2007 and March 2008 to evaluate the effect of fences within the dune on vegetation distribution. Variables include: distance landward of dune toe, degree of sheltering from onshore stressors, net change in surface elevation (deposition or erosion), vegetation diversity and density, presence of remnant fence, and distance landward of fence. Results for the studied environment reveal that 1) vegetation diversity or density does not increase near remnant fences because most remnants are lower than average vegetation height and can not provide shelter; but 2) vegetation distribution is related to topographic variables, such as degree of sheltering, that are most likely the result of sand accretion caused by fence deployment. Fence deployment that prioritizes the creation of topographically diverse dunes within a restricted space may increase the diversity and density of the vegetation, and the resilience and value of developed dunes. Managers should consider the benefits of using sand fences on appropriately wide beaches to create a protective dune that is also diverse, functional and better able to adapt to change.
Grafals-Soto, Rosana
Vegetation controls on the maximum size of coastal dunes.
Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the coevolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady-state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand "dune-building" species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the timescale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches. Higher waves associated with dissipative beaches increase the disturbance of strand species, which shifts foredune formation landward and thus leads to larger foredunes. In this scenario, plants play a much more active role in modifying their habitat and altering coastal vulnerability than previously thought. PMID:24101481
Dur�n, Orencio; Moore, Laura J
Vegetation controls on the maximum size of coastal dunes
NASA Astrophysics Data System (ADS)
Coastal dunes, in particular foredunes, support a resilient ecosystem and reduce coastal vulnerability to storms. In contrast to dry desert dunes, coastal dunes arise from interactions between biological and physical processes. Ecologists have traditionally addressed coastal ecosystems by assuming that they adapt to preexisting dune topography, whereas geomorphologists have studied the properties of foredunes primarily in connection to physical, not biological, factors. Here, we study foredune development using an ecomorphodynamic model that resolves the co-evolution of topography and vegetation in response to both physical and ecological factors. We find that foredune growth is eventually limited by a negative feedback between wind flow and topography. As a consequence, steady state foredunes are scale invariant, which allows us to derive scaling relations for maximum foredune height and formation time. These relations suggest that plant zonation (in particular for strand `dune-building' species) is the primary factor controlling the maximum size of foredunes and therefore the amount of sand stored in a coastal dune system. We also find that aeolian sand supply to the dunes determines the time scale of foredune formation. These results offer a potential explanation for the empirical relation between beach type and foredune size, in which large (small) foredunes are found on dissipative (reflective) beaches: higher waves associated with dissipative beaches increase the disturbance of strand species which shifts foredune formation landwards and thus leads to larger foredunes.
Duran Vinent, Orencio; Moore, Laura J.
Groundwater dynamics converted to a groundwater classification as a tool for nature development programs in the dunes
NASA Astrophysics Data System (ADS)
Within the European Union, Habitat Directives are developed with the aim of restoration and preservation of endangered species. The level of biodiversity in coastal dune systems is generally very high compared to other natural ecosystems, but suffers from deterioration. Groundwater extraction and urbanisation are the main reasons for the decrease in biodiversity. Many restoration actions are being carried out and are focusing on the restoration of groundwater level with the aim of re-establishing rare species. These actions have different degrees of success. The evaluation of the actions is mainly based on the appearance of red list species. The groundwater classes, developed in the Netherlands, are used for the evaluation of opportunities for vegetation, while the natural variability of the groundwater level and quality are under-estimated. Vegetation is used as a seepage indicator. The existing classification is not valid in the Belgian dunes, as the vegetation observed in the study area is not in correspondence with this classification. Therefore, a new classification is needed. The new classification is based on the variability of the groundwater level on a long term with integration of ecological factors. Based on the new classification, the importance of seasonal and inter-yearly fluctuations of the water table can be deduced. Inter-yearly fluctuations are more important in recharge areas while seasonal fluctuations are dominant in discharge areas. The new classification opens opportunities for relating vegetation and groundwater dynamics.
Martens, Kristine; Van Camp, Marc; Van Damme, Dirk; Walraevens, Kristine
Slow Progress in Dune (Right Rear Wheel)
NASA Technical Reports Server (NTRS)The right rear wheel of NASA's Mars Exploration Rover Opportunity makes slow but steady progress through soft dune material in this movie clip of frames taken by the rover's rear hazard identification camera over a period of several days. The wheel is largely hidden by a cable bundle. The sequence starts on Opportunity's 460th martian day, or sol (May 10, 2005) and ends 11 days later. In eight drives during that period, Opportunity advanced a total of 26 centimeters (10 inches) while spinning its wheels enough to have driven 46 meters (151 feet) if there were no slippage. The motion appears to speed up near the end of the clip, but that is an artifact of individual frames being taken less frequently.
Monitoring Cave Recharge in the Edwards Aquifer Recharge Zone for Natural and Simulated Rainfall Events
NASA Astrophysics Data System (ADS)
Across semi-arid regions of the world, woody plant encroachment is widespread with potential implications for groundwater recharge and streamflow. In an effort to better understand the interactions between woody plants and recharge, we are monitoring drip rates in shallow caves in the Edwards Aquifer recharge zone of Central Texas. The surface is covered by a dense stand of ashe juniper (Juniperus ashei). In addition to stemflow, throughfall, and surface runoff was monitored for both natural precipitation events as well as simulated rainfall. Interception and throughfall are measured using a grid of rain gauges and throughfall collectors. Surface runoff measurements were quantified with a 15.24 centimeter H- flume instrumented with an ultrasonic water level sensor. Drip collectors constructed inside the cave collect recharge entering the cave from the ceiling. Large scale rainfall simulation equipment onsite allows us to "re-create" these naturally occurring rainfall events and compare the resulting data with that from the original event. Performing these types of tests allows us to learn important information about the cave footprint's ability to transmit recharge waters into the cave. During a simulation, water is applied directly to the cave footprint and not to the entire hillslope as in a natural rain event. We found that recharge for the natural and simulated events were similar. In each case, recharge makes up less than 5% of the water budget, in spite of the fact that there was little, if any, surface runoff. The working hypothesis is that most of the rainfall is routed off the hillslope as lateral subsurface flow.
Gregory, L.; Veni, G.; Shade, B.; Wilcox, B. P.; Munster, C. L.; Owens, M. K.
Lithium rechargeable cell with a polymer cathode
NASA Astrophysics Data System (ADS)
Thin films of electropolymerized poly 3-methylthiophene (PMT) were used as a rechargeable cathode in Li(SO2)3AlCl4 electrolyte. Capacity was superior to porous carbon electrodes of like thickness. Pulse power levels of 2 W cm-2 were achieved, and high rate constant current pulses of four-second duration were reproducible over cycles. Cells could be recharged at potentials below 4.0 V, minimizing the formation of chlorine and thereby diminishing the capacity for corrosion. For a primary cell, greater discharge capacity was obtained with thionyl chloride and sulfuryl chloride electrolytes. Since PMT becomes electrically insulating in the reduced state, this could be used as a built-in safety feature to avert the hazards associated with abuse over-discharge.
Walker, Charles W., Jr.
Rechargeable Infection-responsive Antifungal Denture Materials
Candida-associated denture stomatitis (CADS) is a significant clinical concern. We developed rechargeable infection-responsive antifungal denture materials for potentially managing the disease. Polymethacrylic acid (PMAA) was covalently bound onto diurethane dimethacrylate denture resins in the curing step. The PMAA resins bound cationic antifungal drugs such as miconazole and chlorhexidine digluconate (CG) through ionic interactions. The anticandidal activities of the drug-containing PMAA-resin discs were sustained for a prolonged period of time (weeks and months). Drug release was much faster at acidic conditions (pH 5) than at pH 7. Drugs bound to the denture materials could be �washed out� by treatment with EDTA, and the drug-depleted resins could be recharged with the same or a different class of anticandidal drugs. These results suggest clinical potential of the newly developed antifungal denture materials in the management of CADS and other infectious conditions.
Cao, Z.; Sun, X.; Yeh, C.-K.; Sun, Y.
Rechargeable infection-responsive antifungal denture materials.
Candida-associated denture stomatitis (CADS) is a significant clinical concern. We developed rechargeable infection-responsive antifungal denture materials for potentially managing the disease. Polymethacrylic acid (PMAA) was covalently bound onto diurethane dimethacrylate denture resins in the curing step. The PMAA resins bound cationic antifungal drugs such as miconazole and chlorhexidine digluconate (CG) through ionic interactions. The anticandidal activities of the drug-containing PMAA-resin discs were sustained for a prolonged period of time (weeks and months). Drug release was much faster at acidic conditions (pH 5) than at pH 7. Drugs bound to the denture materials could be "washed out" by treatment with EDTA, and the drug-depleted resins could be recharged with the same or a different class of anticandidal drugs. These results suggest clinical potential of the newly developed antifungal denture materials in the management of CADS and other infectious conditions. PMID:20940361
Cao, Z; Sun, X; Yeh, C-K; Sun, Y
New mechanically rechargeable zinc-air batteries
This report describes the design, development and testing of new mechanically rechargeable zinc-air batteries. Following research and development of a low cost silver-mercury cathode catalyst, prototype battery tests were conducted. Cycle life tests at 3.5 amperes indicated satisfactory performance through at least 26 cycles when this test was terminated for the final hardware build. The cathode bi-cell design utilized the
J. Giltner
Dynamically compacted rechargeable ceramic lithium batteries
A rechargeable ceramic battery is made of a LixMn2O4 (x = 1.1) cathode, a graphite anode and a BPO4:yLi2O (y ?- 0.035) solid electrolyte by dynamic compaction. This battery system has a theoretical open-circuit potential of 4.2 V and a high energy density, which makes it interesting for application in electric vehicles.
M. J. G. Jak; E. M. Kelder; M. Stuivinga; J. Schoonman
Rechargeable alkaline zinc\\/ferricyanide battery
Technical and economic feasibility of the alkaline zinc\\/ferricy anide rechargeable battery for utility load leveling applications was assessed. This battery meets the requirements for this application with cell voltages of 1.94 V on charge and 1.78 V on discharge. Mean energy efficiency is 84% at 760 and 86% at 1110 4 hour cycles in full cell and redox half cell
G. B. Adams; R. P. Hollandsworth; B. D. Webber
High specific power lithium polymer rechargeable battery
PolyPlus Battery Company (PPBC) is developing an advanced lithium polymer rechargeable battery based on its proprietary positive electrode. This battery offers high steady-state (>250 W\\/kg) and peak power densities (3000 W\\/kg), in a low cost and environmentally benign format. This PolyPlus lithium polymer battery also delivers high specific energy. The first generation battery has a energy density of 100 Wh\\/kg
May-Ying Chu; Lutgard De Jonghe; Steven Visco
Rechargeable lithium batteries with aqueous electrolytes
Rechargeable lithium-ion batteries that use an aqueous electrolyte have been developed. Cells with LiMn{sub 2}O{sub 4} and VO{sub 2}(B) as electrodes and 5 M LiNO{sub 3} in water as the electrolyte provide a fundamentally safe and cost-effective technology that can compete with nickel-cadmium and lead-acid batteries on the basis of stored energy per unit of weight.14 refs., 4 figs.
Li, Wu; Dahn, J.R. [Simon Fraser Univ., Burnaby, British Columbia (Canada); Wainwright, D.S. [Moli Energy (1990) Limited, Maple Ridge, British Columbia (Canada)
Design and simulation of lithium rechargeable batteries
Lithium -based rechargeable batteries that utilize insertion electrodes are being considered for electric-vehicle applications because of their high energy density and inherent reversibility. General mathematical models are developed that apply to a wide range of lithium-based systems, including the recently commercialized lithium-ion cell. The modeling approach is macroscopic, using porous electrode theory to treat the composite insertion electrodes and concentrated
Capacity degradation of lithium rechargeable batteries
Li rechargeable cells made with structural arrangement Li\\/membrane\\/LixV2O5 were examined under different charge states using ac impedance, environmental scanning electron microscope (ESEM), transmission electron microscope (TEM) and the high-resolution nuclear magnetic resonance (NMR). These states include charged, discharged, and over cycled. The lowest internal resistance was obtained from the cell at charged state; the resistance increased when the cell was
J. P. Zheng; P. L. Moss; R. Fu; Z. Ma; Y. Xin; G. Au; E. J. Plichta
Rechargeable lithium batteries with aqueous electrolytes.
Rechargeable lithium-ion batteries that use an aqueous electrolyte have been developed. Cells with LiMn(2)O(4) and VO(2)(B) as electrodes and 5 M LiNO(3) in water as the electrolyte provide a fundamentally safe and cost-effective technology that can compete with nickelcadmium and lead-acid batteries on the basis of stored energy per unit of weight. PMID:17744893
Li, W; Dahn, J R; Wainwright, D S
Charge control investigation of rechargeable lithium cells
NASA Technical Reports Server (NTRS)
An ambient temperature rechargeable Li-TiS2 cell was cycled under conditions which simulate aerospace applications. A novel charge/discharge state-of-charge control scheme was used, together with tapered current charging, to overcome deleterious effects associated with end-of-charge and end-of-discharge voltages. The study indicates that Li-TiS2 cells hold promise for eventual synchronous satellite-type applications. Problem areas associated with performance degradation and reconditioning effects are identified.
Otzinger, B.; Somoano, R.
Charge control investigation of rechargeable lithium cells
An ambient temperature rechargeable Li-TiS2 cell was cycled under conditions which simulate aerospace applications. A novel charge\\/discharge state-of-charge control scheme was used, together with tapered current charging, to overcome deleterious effects associated with end-of-charge and end-of-discharge voltages. The study indicates that Li-TiS2 cells hold promise for eventual synchronous satellite-type applications. Problem areas associated with performance degradation and reconditioning effects are
B. Otzinger; R. Somoano
Advanced rechargeable lithium sulfur dioxide cell
The electrochemical performance and safety of the rechargeable lithium sulfur dioxide system has been investigated in laboratory cells and in high rate D cells. Small design and active materials were optimized to that cathode utilization of 1.6Ah\\/grams of carbon and 0.19Ah\\/cm3 of cathode were achieved with 100-200 cycles. Discharge and charge of cells at temperatures down to -30 C were
R. C. McDonald; P. Harris; F. Goebel; S. Hossain; R. Vierra
Inorganic rechargeable non-aqueous cell
A totally inorganic non-aqueous rechargeable cell having an alkali or alkaline earth metal anode such as of lithium, a sulfur dioxide containing electrolyte and a discharging metal halide cathode, such as of CuCl.sub.2, CuBr.sub.2 and the like with said metal halide being substantially totally insoluble in SO.sub.2 and admixed with a conductive carbon material.
Bowden, William L. (Nashua, NH); Dey, Arabinda N. (Needham, MA)
Rechargeable Infection-responsive Antifungal Denture Materials
Candida-associated denture stomatitis (CADS) is a significant clinical concern. We developed rechargeable infection-responsive antifungal denture materials for potentially managing the disease. Polymethacrylic acid (PMAA) was covalently bound onto diurethane dimethacrylate denture resins in the curing step. The PMAA resins bound cationic antifungal drugs such as miconazole and chlorhexidine digluconate (CG) through ionic interactions. The anticandidal activities of the drug-containing PMAA-resin
Z. Cao; X. Sun; C.-K. Yeh; Y. Sun
Nanomaterials for lithium-ion rechargeable batteries.
In lithium-ion batteries, nanocrystalline intermetallic alloys, nanosized composite materials, carbon nanotubes, and nanosized transition-metal oxides are all promising new anode materials, while nanosized LiCoO2, LiFePO4, LiMn2O4, and LiMn2O4 show higher capacity and better cycle life as cathode materials than their usual larger-particle equivalents. The addition of nanosized metal-oxide powders to polymer electrolyte improves the performance of the polymer electrolyte for all solid-state lithium rechargeable batteries. To meet the challenge of global warming, a new generation of lithium rechargeable batteries with excellent safety, reliability, and cycling life is needed, i.e., not only for applications in consumer electronics, but especially for clean energy storage and for use in hybrid electric vehicles and aerospace. Nanomaterials and nanotechnologies can lead to a new generation of lithium secondary batteries. The aim of this paper is to review the recent developments on nanomaterials and nanotechniques used for anode, cathode, and electrolyte materials, the impact of nanomaterials on the performance of lithium batteries, and the modes of action of the nanomaterials in lithium rechargeable batteries. PMID:16573064
Liu, Hua Kun; Wang, Guo Xiu; Guo, Zaiping; Wang, Jiazhao; Konstantinov, Kosta
Ground water recharge from Lake Chad
Lake Chad is a shallow, closed basin lake located in Sub-Sharan Africa. It has the largest drainage basin of any lake in the world, and is also very old, being formed by tectonic processes during the Cretaceous. These features should combine to form a saline lake, but the open waters of Lake Chad are reasonably fresh, having a total dissolved solids concentration of about 320 mg/1. This apparent discrepancy can be explained by noting that recharge of the unconfined aquifer to the SW in Nigeria by ground water infiltration through the lakebed can remove significant quantities of water and dissolved solutes from the lake. The authors have measured and calculated ground water infiltration and velocities by several techniques. Direct, volumetric measurements of ground water recharge seepage give velocities on the order of .28-8.8 x 10/sup -3/ m/day. Tracer monitoring in a borehole dilution test yielded ground water velocities of 3.6 m/day to the SW (away from the lake). Hydraulic conductivities approx. .004-.6 m/day were determined by falling head measurements. Finally, using static water levels, the potentiometric surface within approx. 80 km of the southwest portion of Lake Chad yields water table gradients of 1.0-1.7 x 10/sup -4/ away from the lake. These results confirm that surface water and solute inflow to Lake Chad is removed by recharge to the unconfined aquifer in Nigeria.
Isiorho, S.; Matisoff, G.; McCall, P.L.
Ideal Microhabitats on Mars: The Astrobiological Potential of Polar Dunes
NASA Astrophysics Data System (ADS)
Astrobiological potential of polar Dark Dunes: they may hold less oxidants, trap water-ice, mm layer of them shields UV radiation, allows light income for photosynthesis. Water uptake in nighttime, temperature in daytime is favorable for metabolism.
G�nti, T.; P�cs, T.; B�rczi, Sz.; Horv�th, A.; Kereszturi, A.; Sik, A.; Szathm�ry, E.
Plant regeneration from embryogenic suspension cultures of dune reed
Embryogenic callus, derived from mature seeds of dune reed (Phragmites communisTrinius) was used to establish suspension culture. Green shoot-forming type and albino shoot-forming type embryogenic callus of dune reed were selected carefully by the difference of shape and color of callus growing under light and mechanically dispersed before suspending in liquid MS medium supplemented with 1.0 mg l-12,4-D. They were
W. Wang; S. X. Cui; C. L. Zhang
Rip currents, mega-cusps, and eroding dunes
Dune erosion is shown to occur at the embayment of beach mega-cusps O(200??m alongshore) that are associated with rip currents. The beach is the narrowest at the embayment of the mega-cusps allowing the swash of large storm waves coincident with high tides to reach the toe of the dune, to undercut the dune and to cause dune erosion. Field measurements of dune, beach, and rip current morphology are acquired along an 18??km shoreline in southern Monterey Bay, California. This section of the bay consists of a sandy shoreline backed by extensive dunes, rising to heights exceeding 40??m. There is a large increase in wave height going from small wave heights in the shadow of a headland, to the center of the bay where convergence of waves owing to refraction over the Monterey Bay submarine canyon results in larger wave heights. The large alongshore gradient in wave height results in a concomitant alongshore gradient in morphodynamic scale. The strongly refracted waves and narrow bay aperture result in near normal wave incidence, resulting in well-developed, persistent rip currents along the entire shoreline. The alongshore variations of the cuspate shoreline are found significantly correlated with the alongshore variations in rip spacing at 95% confidence. The alongshore variations of the volume of dune erosion are found significantly correlated with alongshore variations of the cuspate shoreline at 95% confidence. Therefore, it is concluded the mega-cusps are associated with rip currents and that the location of dune erosion is associated with the embayment of the mega-cusp. ?? 2007 Elsevier B.V. All rights reserved.
Thornton, E. B.; MacMahan, J.; Sallenger, Jr. , A. H.
Habitat change in a perched dune system along Lake Superior
Episodes of habitat change, driven by changes in levels of the Great Lakes, must be considered when assessing human effects upon coastal vegetation and rare species. Paleoecological studies, baseline inventories, and long-term monitoring programs within the Grand Sable Dunes, a perched-dune system along Lake Superior, provide a window on vegetation change at different spatial and temporal scales and also provide an illustrative case study.
Loope, Walter L.; McEachern, A. Kathryn
Documentation of Recent Surface Winds on Martian Sand Dunes
NASA Astrophysics Data System (ADS)
Images from the High Resolution Imaging Science Experiment (HiRISE) are of sufficient resolution to record wind ripple patterns on the surfaces of sand dunes present across the surface of Mars. We are in the early stages of an investigation to map the ripple orientations preserved on Martian sand dunes, in order to evaluate the recent wind flow over the dunes, and compare that wind flow pattern to the winds documented over terrestrial sand dunes. HiRISE image ESP_025645_1455 covers a sand dune field on the floor of a 20-km-diameter unnamed impact crater in the Terra Cimmeria region of the southern highlands, east of the Hellas impact basin. This image is centered at 34.23 S latitude, 138.437 E longitude with 25 cm/pixel resolution, and was taken on Jan 25 of 2012 during northern spring (Ls = 57.4). Using ArcGIS, lines were drawn across three ripples perpendicular to the ripple crests, avoiding places where complex ripple patterns suggest more than one recent wind direction. The length of the lines provides a measure of ripple wavelength, and the line orientation gives azimuth (with a 180 degree absolute ambiguity). The barchan-like shape of some dunes, including occasional slip faces, suggest sand driving winds were from the southwest, although dune asymmetries indicate the wind regime likely was much more complex than a unimodal wind. Measurements of ripple orientations are being collected from dune locations across the planet, which should provide new constraints for the modeling of recent Martian winds. This work was supported by NASA MDAP grant NNX12AJ38G.
Zimbelman, J. R.; Johnson, M. B.
Pathomimie de l'enfant: ? propos d'une observation
La pathomimie cutan�e se d�finit comme une maladie factice, provoqu�e dans un etat de conscience claire par le patient lui-m�me, au niveau du rev�tement cutan�o-muqueux et/ou des phan�res. Rare chez l'enfant, il s'agit d'une manifestation psychopathologique potentiellement grave et souvent difficile � prendre en charge. Nous rapportons le cas d'une fillette de 10 ans pr�sentant une pathomimie sous forme de l�sions excori�es multiples du visage.
Abilkassem, Rachid; Dini, Nezha; Ourai, Hakim; Kmari, Mohamed; Agadr, Aomar
Internal Structure of a Star Dune Imaged Using Ground-Penetrating Radar
NASA Astrophysics Data System (ADS)
The Coral Pink Sand Dunes, located in far southwestern Kane County,Utah, is the site of an onging investigation into factors influencing dune field development. This elongate dune field (11 km by ~1.2 km) includes bedforms ranging along a continuum from stabilized sand sheets and vegetated parabolic dune forms to fully active transverse dunes and barchanoid ridges. This paper presents the results of our ground-penetrating radar (GPR) reconnaissance transects across a small star dune in the south central (active) portion of the dune field. GPR data (100 MHz, 1.0-meter offset, 0.5-meter step) were collected from four transects bracketing the star dune and provide radar imagery of the sedimentary structure of four arms of the dune and underlying bedrock. Processing of the GPR data consisted of a few steps, including dewowing and bandpass filtering, migration, and topographic correction. Results from data migration were mixed but overall did not appear to improve the imagery. Interpretations are made primarily from the unmigrated data cross-checked against the migrated dataset. Depth to bedrock ranges from 0 meters in the surrounding interdune serirs to 25 meters under the star dune crest. The shallow nature of the dune sands and a lack of major cross-stratification revealed in the cross sections suggest these dunes are still accumulating sand and respond quickly to changes in wind direction. The orientation of the foresets in the peak and main transverse dune arm imply the dune is presently responding to a southwesterly windflow. Southeasterward dipping foresets in three smaller (minor) arms longitudinal to the transverse dune possibly reflect modification of windflow around the main dune body. Comparison of aerial photography of the area from 1955 and 1960 with that of 1997 indicate the star dune formed through capture of another, smaller dune that merged from the southwest. The SE dipping foresets in the minor arms appear to reflect this capture, and so preserve both dune movement as well as windflow modification.
Wilkins, D. E.; Ford, R. L.; Clement, W. P.
Simulation model of erosion and deposition on a barchan dune
NASA Technical Reports Server (NTRS)
Erosion and deposition over a barchan dune near the Salton Sea, California, are modeled by bookkeeping the quantity of sand in saltation following streamlines of transport. Field observations of near surface wind velocity and direction plus supplemental measurements of the velocity distribution over a scale model of the dune are combined as input to Bagnold type sand transport formulas corrected for slope effects. A unidirectional wind is assumed. The resulting patterns of erosion and deposition compare closely with those observed in the field and those predicted by the assumption of equilibrium (downwind translation of the dune without change in size or geometry). Discrepancies between the simulated results and the observed or predicted erosional patterns appear to be largely due to natural fluctuations in the wind direction. The shape of barchan dunes is a function of grain size, velocity, degree of saturation of the oncoming flow, and the variability in the direction of the oncoming wind. The size of the barchans may be controlled by natural atmospheric scales, by the age of the dunes, or by the upwind roughness. The upwind roughness can be controlled by fixed elements or by sand in the saltation. In the latter case, dune scale is determined by grain size and wind velocity.
Howard, A. D.; Morton, J. B.; Gal-El-hak, M.; Pierce, D. B.
Regional estimation of total recharge to ground water in Nebraska.
Naturally occurring long-term mean annual recharge to ground water in Nebraska was estimated by a novel water-balance approach. This approach uses geographic information systems (GIS) layers of land cover, elevation of land and ground water surfaces, base recharge, and the recharge potential in combination with monthly climatic data. Long-term mean recharge > 140 mm per year was estimated in eastern Nebraska, having the highest annual precipitation rates within the state, along the Elkhorn, Platte, Missouri, and Big Nemaha River valleys where ground water is very close to the surface. Similarly high recharge values were obtained for the Sand Hills sections of the North and Middle Loup, as well as Cedar River and Beaver Creek valleys due to high infiltration rates of the sandy soil in the area. The westernmost and southwesternmost parts of the state were estimated to typically receive < 30 mm of recharge a year. PMID:15726925
Szilagyi, Jozsef; Harvey, F Edwin; Ayers, Jerry F
Modelling overbank flood recharge at a continental scale
NASA Astrophysics Data System (ADS)
Accounting for groundwater recharge from overbank flooding is required to reduce uncertainty and error in river-loss terms and groundwater sustainable-yield calculations. However, continental- and global-scale models of surface water-groundwater interactions rarely include an explicit process to account for overbank flood recharge (OFR). This paper upscales previously derived analytical equations to a continental scale using national soil atlas data and satellite imagery of flood inundation, resulting in recharge maps for seven hydrologically distinct Australian catchments. Recharge for three of the catchments was validated against independent recharge estimates from bore hydrograph responses and one catchment was additionally validated against point-scale recharge modelling and catchment-scale change in groundwater storage. Flood recharge was predicted for four of the seven catchments modelled, but there was also unexplained recharge present from the satellite's flood inundation mapping data. At a catchment scale, recharge from overbank flooding was somewhat under-predicted using the analytical equations, but there was good confidence in the spatial patterns of flood recharge produced. Due to the scale of the input data, there were no significant relationships found when compared at a point scale. Satellite-derived flood inundation data and uncertainty in soil maps were the key limitations to the accuracy of the modelled recharge. Use of this method to model OFR was found to be appropriate at a catchment to continental scale, given appropriate data sources. The proportion of OFR was found to be at least 4% of total change in groundwater storage in one of the catchments for the period modelled, and at least 15% of the riparian recharge. Accounting for OFR is an important, but often overlooked, requirement for closing water balances in both the surface water and groundwater domains.
Doble, R.; Crosbie, R.; Peeters, L.; Joehnk, K.; Ticehurst, C.
Shale recharge and production behavior of geopressured reservoirs
The reservoir simulator MUSHRM was used to study the conditions under which significant shale recharge may be expected. The calculations presented herein show that shale recharge is a strong function of the vertical shale permeability but is not greatly influenced by the shale compressibility. Significant shale recharge will occur only if the vertical shale permeability is at least of the order of 0.01 ..mu..d.
Garg, S.K.
Rechargeable zinc-air battery technology implementations in portable electronics
AER Energy's rechargeable zinc-air battery technology has the unique set of characteristics to provide long battery run-time for portable electronics. With more energy per pound and high energy content cells, rechargeable zinc-air can provide sufficient energy in a lightweight battery that is practical to build. Improvements made in the past year make AER Energy's rechargeable zinc-air even more flexible and
T. Cutler
Making Li-air batteries rechargeable: material challenges
A Li-air battery could potentially provide three to five times higher energy density/specific energy than conventional batteries, thus enable the driving range of an electric vehicle comparable to a gasoline vehicle. However, making Li-air batteries rechargeable presents significant challenges, mostly related with materials. Herein, we discuss the key factors that influence the rechargeability of Li-air batteries with a focus on nonaqueous system. The status and materials challenges for nonaqueous rechargeable Li-air batteries are reviewed. These include electrolytes, cathode (electocatalysts), lithium metal anodes, and oxygen-selective membranes (oxygen supply from air). The perspective of rechargeable Li-air batteries is provided.
Shao, Yuyan; Ding, Fei; Xiao, Jie; Zhang, Jian; Xu, Wu; Park, Seh Kyu; Zhang, Jiguang; Wang, Yong; Liu, Jun
A review of groundwater recharge under irrigated agriculture in Australia
NASA Astrophysics Data System (ADS)
Quantification of recharge under irrigated agriculture is one of the most important but difficult tasks. It is the least understood component in groundwater studies because of its large variability in space and time and the difficulty of direct measurement. Better management of groundwater resources is only possible if we can accurately determine all fluxes going into and out of a groundwater system. One of the major challenges facing irrigated agriculture in Australia, and the world, is to reduce uncertainty in estimating or measuring the recharge flux. Reducing uncertainty in groundwater recharge under irrigated agriculture is a pre-requisite for effective, efficient and sustainable groundwater resource management especially in dry areas where groundwater usage is often the key to economic development. An accurate quantification of groundwater recharge under irrigated systems is also crucial because of its potential impacts on soil profile salinity, groundwater levels and groundwater quality. This paper aims to identify the main recharge control parameters thorough a review of past field and modelling recharge studies in Australia. We find that the main recharge control parameters under irrigated agriculture are soil type, irrigation management, watertable depth, land cover or plant water uptake, soil surface conditions, and soil, irrigation water and groundwater chemistry. The most commonly used recharge estimation approaches include chloride mass balance, water budget equation, lysimeters, Darcy's law and numerical models. Main sources and magnitude of uncertainty in recharge estimates associated with these approaches are discussed.
Riasat, Ali; Mallants, Dirk; Walker, Glen; Silberstein, Richard
Seismicity induced by seasonal ground-water recharge at Mt
Abstract Groundwater recharge at Mt. Hood, Oregon, is dominated by spring snow melt which provides a natural large- amplitude,and narrow-width,pore-fluid pressure signal. Time delays between,this seasonal groundwater,recharge,and seismicity triggered by groundwater,recharge,can thus be used to estimate large-scale hydraulic,diffusivities and,the state of stress in the crust. We approximate,seasonal,variations in groundwater,recharge,with discharge in runoff- dominated streams at high elevations. We interpolate the
M. Saar; M. Manga
Large Eddy Simulation of Flow and Sediment Transport over Dunes
NASA Astrophysics Data System (ADS)
Understanding the nature of flow over bedforms has a great importance in fluvial and coastal environments. For example, a bedform is one source of energy dissipation in water waves outside the surf zone in coastal environments. In rivers, the migration of dunes often affects the stability of the river bed and banks. In general, when a fluid flows over a sediment bed, the sediment transport generated by the interaction of the flow field with the bed results in the periodic deformation of the bed in the form of dunes. Dunes generally reach an equilibrium shape, and slowly propagate in the direction of the flow, as sand is lifted in the high shear regions, and redeposited in the separated flow areas. Different numerical approaches have been used in the past to study the flow and sediment transport over bedforms. In most research works, Reynolds Averaged Navier Stokes (RANS) equations are employed to study fluid motions over ripples and dunes. However, evidences suggests that these models can not represent key turbulent quantities in unsteady boundary layers. The use of Large Eddy Simulation (LES) can resolve a much larger range of smaller scales than RANS. Moreover, unsteady simulations using LES give vital turbulent quantities which can help to study fluid motion and sediment transport over dunes. For this steady, we use a three-dimensional, non-hydrostatic model, OpenFOAM. It is a freely available tool which has different solvers to simulate specific problems in engineering and fluid mechanics. Our objective is to examine the flow and sediment transport from numerical stand point for bed geometries that are typical of fixed dunes. At the first step, we performed Large Eddy Simulation of the flow over dune geometries based on the experimental data of Nelson et al. (1993). The instantaneous flow field is investigated with special emphasis on the occurrence of coherent structures. To assess the effect of bed geometries on near bed turbulence, we considered different dune geometries based on dune height and wave length. We will also examine the role of near bed turbulence on sediment transport over dunes. For validation, profiles of velocities, turbulent intensities, and sediment transport calculated by the numerical model will be compared with available experimental measurements.
Agegnehu, G.; Smith, H. D.
Organic electrolyte for use in a lithium rechargeable electrochemical cell and lithium rechargeable electrochemical cell including said organic electrolyte
This invention relates in general to use of an organic electrolyte in a lithium rechargeable electrochemical cell and to a lithium rechargeable electrochemical cell including said electrolyte; and, in particular, to the use of 1 to 2 mol/dm/sup 3/ LiAsF/sub 6/ in dimethylcarbonate (DMC) or 1 to 2 mol/dm/sup 3/ LiAsF/sub 6/ in (DMC) mixtures with methyl formate (MF) in which the mass percent of the (DMC) can vary from 25 to 100 mass percent as the electrolyte in a lithium rechargeable electrochemical cell, and to a lithium rechargeable electrochemical cell including said electrolyte.
Plichta, E.J.; Slane, S.M.; Salomon, M.
Reply to ``Comment on `Minimal size of a barchan dune' ''
NASA Astrophysics Data System (ADS)
We reply to the preceding comment by Andreotti and Claudin [Phys. Rev. E 76, 063301 (2007)] on our paper [Phys. Rev. E 75, 011301 (2007)]. We show that the equations of the dune model used in our calculations are self-consistent and effectively lead to a dependence of the minimal dune size on the wind speed through the saturation length. Furthermore, we show that Meridiani Planum ripples are probably not a good reference to estimate the grain size of Martian dune sands: the soil in the ripple troughs at the landing site is covered with nonerodible elements (�blueberries�), which increase the minimal threshold for saltation by a factor of 2.0. We conclude that, in the absence of large fragments as the ones found at the landing site, basaltic grains of diameter d=500�100?m that compose the large, typical dark Martian dunes [K. S. Edgett and P. R. Christensen, J. Geophys. Res. 96, 22765 (1991)] probably saltate during the strongest storms on Mars. We also show that the wind friction speed u??3.0m/s that we found from the calculations of Martian dunes is within the values of maximum wind speeds that occur during Martian storms a few times a decade [R. E. Arvidson , Science 222, 463 (1983); H. J. Moore, J. Geophys. Res. 90, 163 (1985); R. Sullivan , Nature (London) 436, 58 (2005); D. J. Jerolmack , J. Geophys. Res. 111, E12S02 (2006)]. In this manner, the dune model predicts that Martian dunes can be formed under present Martian conditions, with no need to assume other conditions of wind and atmosphere that could have prevailed in the past.
Parteli, E. J. R.; Dur�n, O.; Herrmann, H. J.
Is Titan's dune orientation controlled by tropical methane storms?
NASA Astrophysics Data System (ADS)
Titan's equatorial regions are covered by eastward oriented linear dunes. This direction is opposite to mean surface winds simulated by Global Climate Models (GCMs) at these latitudes, oriented westward as trade winds on Earth [1, 2]. Here, we propose that Titan's dune orientation is actually determined by equinoctial tropical methane storms. Using meso-scale simulations of convective methane clouds [3, 4] with a GCM wind profile featuring the super-rotation [5, 6], we show that Titan's storms should produce fast eastward gust fronts above the surface (see Figure 1). Such gusts dominate the aeolian transport. Using GCM wind roses and analogies with terrestrial dune fields as the Rub' al-Khali desert, we show that under these conditions Titan's dune growth occurs eastward (see Figure 2). Moreover, we explain other features of Titan's dunes (i.e. divergence from the equator, size and spacing). This analysis therefore reveals an unexpected coupling between super-rotation, tropical storms and dune formation on Titan, and has implications for the understanding of terrestrial dunes. References: [1] Lorenz et al. (2006) Science [2] Lorenz & Radebaugh (2009) Geophysical Research Letter [3] Barth & Rafkin (2007) Geophysical Research Letter [4] Barth & Rafkin (2010) Icarus [5] Charnay & Lebonnois (2012) Nature Geoscience [6] Lebonnois et al. (2012) Icarus Development of a methane storm with formation of a gust front. Colorbar corresponds to the mixing ratio of condensed methane (in g/kg) Resultant drift direction obtained by combining the GCM sand flux roses with the impact of one gust front every equinox at any location.
Charnay, B.; Barth, E. L.; Rafkin, S. C.; Narteau, C.; Lebonnois, S.; Rodriguez, S.
Experimental survey of rechargeable alkaline zinc electrodes
NASA Astrophysics Data System (ADS)
Rechargeable alkaline zinc-air cells and zinc-manganese dioxide cells need zinc electrodes working for at least 100 cycles under anode limiting conditions. The discharge of the manganese dioxide cathode especially must be limited to a definite fraction (1/3) of its available capacity to obtain a good cycle life. This study proposes a new test cell for investigations on pasted alkaline zinc powder electrodes. When, following experimentation, the value of the construction was established, a series of different electrode mixtures was cycled. It was found that 100 full discharges could be obtained with a zinc utilization of about 30 percent in the final cycles.
Binder, L.; Odar, W.
Characterization of AA size lithium rechargeable cells
Testing of AA size rechargeable cells for underwater vehicle and other naval applications is complete for AT&T's lithium\\/niobium triselenide (Li\\/NbSe3) and Moli Energy's lithium\\/molybdenum disulfide (Li\\/MoS2) and in progress on Moli Energy's lithium\\/manganese dioxide (Li\\/MnO2) and W. R. Grace's lithium\\/titanium disulfide (Li\\/TiS2). Cell cycling was performed at various discharge rates, temperatures, and depths of discharge. At 25 C and 1
T. C. Murphy; D. M. Cason-Smith; S. D. James; P. H. Smith
Thin-film rechargeable lithium batteries
Thin-film rechargeable lithium batteries using ceramic electrolyte and cathode materials have been fabricated by physical deposition techniques. The lithium phosphorous oxynitride electrolyte has exceptional electrochemical stability and a good lithium conductivity. The lithium insertion reaction of several different intercalation materials, amorphous V{sub 2}O{sub 5}, amorphous LiMn{sub 2}O{sub 4}, and crystalline LiMn{sub 2}O{sub 4} films, have been investigated using the completed cathode/electrolyte/lithium thin-film battery.
Dudney, N.J.; Bates, J.B.; Lubben, D. [Oak Ridge National Lab., TN (United States). Solid State Div.
Characterization of AA size lithium rechargeable cells
Testing of AA size rechargeable cells for underwater vehicle and other naval applications is complete for AT&T's lithium\\/niobium triselenide (Li\\/NbSe3) and Moli Energy's lithium\\/molybdenum disulfide (Li\\/MoS2) and is in progress on Moli Energy's lithium\\/manganese dioxide (Li\\/MnO2) and W.R. Grace's lithium\\/titanium disulfide (Li\\/TiS2). Cell cycling was performed at various discharge rates, temperatures, and depths of discharge. At 25�C and 1 mA\\/cm2
T. C. Murphy; D. M. Cason-Smith; S. D. James; P. H. Smith
Low temperature studies on rechargeable lithium cells
Rechargeable lithium cells using intercalating cathodes of TiS2, a-MoS3, and mixed a-MoS3\\/TiS2 were studied at temperatures from 25 to -40 C. On the basis of conductivity investigations, LiAsF6 and LiAlCl4 electrolytes were selected for use in a binary solvent containing 24.4 mass percent 4-butyrolactone in 1,2-dimethoxyethane. The Li\\/TiS2 and Li\\/a-MoS3-TiS2 cells cycled well at 2 mA\\/sq cm down to -30
E. J. Plichta; M. Salomon
Differing Abundances of Gypsum in the Primary and Secondary Dunes of the Martian Dune Field Olympia Undae
NASA Astrophysics Data System (ADS)
We report on a compositional study in Olympia Undae, located around the polar cap of Mars. Gypsum has been detected throughout the sand sea but with a decline in abundance westward (Langevin et al., 2005). Dune crests are the regions of highest apparent gypsum concentration in CRISM images. Olympia Undae consists of primary dunes formed transverse to circumpolar easterly winds and secondary dunes which lie almost orthogonal to the primary dunes (Ewing et al. 2010). METHODS: We examined a number of CRISM and HiRISE images across the dune field. We focused our preliminary study on FRT0000C31A and FRT0000C2FC, which exhibited the best spectral signatures. Gypsum was identified in CRISM images by its unique 1.45/1.49/1.54 ?m triplet, ~1.94-1.95 ?m band, 2.22/2.27 ?m doublet and 2.49 ?m band with a 2.42 ?m shoulder. Spectra were acquired from regions of interest (ROIs) created along the crests of primary dunes and the low-relief crests of the secondary dunes (Fig. 1). FINDINGS: CRISM spectra of primary and secondary dune crest ROIs from FRT0000C2FC are compared with a gypsum-rich unit in FRT0000CA5C (Fig. 2). The I/F of gypsum-bearing regions is much darker than pure gypsum indicating a mixture composition containing darker components. The depth of the ~1.95 ?m hydration band is ~20-30% stronger for primary dune crests relative to the secondaries, which suggests a similar relationship among the gypsum abundance of these features, assuming similar components and grain sizes. Semi-quantitative analyses are underway to measure this in more detail. Continuing studies are planned with additional images as well. Figure 1 A map-projected view of CRISM image FRT0000C2FC with ROI locations for the primary (P) and secondary (S) dune crests marked. Figure 2 CRISM I/F spectra of gypsum-bearing units in Olympia Undae compared with laboratory reflectance spectra of minerals.
Szumila, I. T.; Bishop, J. L.; Fenton, L. K.; Brown, A. J.
Sediment and microbial fouling of experimental groundwater recharge trenches
NASA Astrophysics Data System (ADS)
A common method of recharging groundwater is by the use of injection wells and/or recharge trenches. With time the recharge capacities of the wells/trenches progressively decline. Deposition of suspended fines in the recharge water and growth of microorganisms in the aquifer are common causes of this decline. This paper presents an investigation of the relative significance of these two factors under controlled laboratory conditions. Large-scale physical models of recharge trenches were conducted in the laboratory to monitor the decline with time of the recharge capacity under controlled conditions. The physical models consisted of four hydraulically separate cells in which six different experiments were conducted. In three of the experiments microorganism were added as an inoculant. A nutrient and carbon fine solution was constantly injected into the influent stream entering through the inflow pipe. Both carbon fines and microorganisms caused plugging of the model recharge trenches in the laboratory. However, initialy the microbes appeared to have a beneficial effect by hindering the transport of the carbon fines from the gravel pack in the trench. Later the microbes contributed to the plugging of the gravel pack. A significant correlation was determined between the extent of carbon fine deposition and microbial growth. In the experiment using a biodegradable slurry, microbial growth did not affect the recharge capacity of the trench. One laboratory experiment involved the introduction of silt as a source of sediment fines to the model recharge trench. This experiment simulated conditions often found in the field when no carbon fine adsoprtion system is used and natural surface water is recharged into aquifer. This research will be useful in understanding the relative importance of factors contributing to the decline of recharge capacity observed in the field.
Warner, James W.; Gates, Timothy K.; Namvargolian, Reza; Miller, Paul; Comes, Gregory
Challenges of Artificial Recharge at the Chain of Lakes
NASA Astrophysics Data System (ADS)
A series of gravel quarry lakes, A through I (i.e. Chain of Lakes) in Alameda County, California are planned to convert to off-channel spreading lakes for artificial groundwater recharge. An operational plan is needed for the near-term improvements that would allow safe and efficient operations of Lake H and Lake I recently acquired for artificial recharge operations. Water source for the groundwater recharge comes from State Water Project (SWP) water releases at the South Bay Aqueduct turnout. The released water flows approximately nine miles in Arroyo Mocho Creek to the planned diversion facility. The recharge system includes multiple water delivery components and recharge components. Reliability of SWP water delivery is a water supply constraint to the recharge system. Hydraulic capacities of each delivery component and recharge capacities of each recharge component are physical constraints to the development of the operational plan. Policy issues identified in the Mitigated Negative Declaration which contains mitigation measures addressing potential impacts of fisheries and erosion are regulatory constraints to the operational plan development. Our approach that addresses technical challenges and policy issues in the development of the operational plan includes i) determination of lake recharge under observed conditions using water budget method; ii) development and calibration of a ground water flow model using MODFLOW; iii) estimation of lake recharge capacity for a range of lake levels using the calibrated ground water flow model; iv) analysis of clogging layer effects on recharge capacity; and v) development and application of operations models for the stream delivery system and the lake system.
Zeng, X.
Analysis of links between groundwater recharge and discharge areas and wetland plant communities distribution in Middle Biebrza Basin, Poland
NASA Astrophysics Data System (ADS)
Natural evolution of wetlands is strongly dependent on groundwater dynamics, soil aeration and climate. These environmental factors determine the constant development of wetland plant communities and peat forming processes. Depending on spatial distribution of groundwater flow systems and recharge and discharge conditions, shallow groundwater can also be influenced by phreatophytic plants. Such feedback plays an important role in wetland development, especially when landuse or climate changes occur. Thus, understanding the links between dynamics of biotopic and biocenotic relations is crucial for wetland management aimed at the comprehensive set of conservation strategies. Main aim of this study was to review links between valuable wetland plant communities and the groundwater recharge/discharge conditions of particular habitats of Middle Biebrza Basin, Poland. The study area consists of various types of wetland landscapes, of which the dominant are fens. Organogenic top layer is intersected locally by sandy dunes and glaci-fluvial residual plateaus. The northern boundary of the study area is covered with an outwash plateau. A three-dimensional regional groundwater flow model was set up to quantify groundwater system and flow paths. Model calibration involved measured heads of the unconfined organogenic top layer and the underlaying, confined sandy aquifer. Measured thickness of unsaturated zone as well as physical parameters of organogenic layer were taken into account in interpretation of shallow groundwater dynamics. Recharge to groundwater was spatially distributed in accordance to analysis of measured precipitation-groundwater level relationships. Cell-by-cell flow analysis and groundwater exfiltration analysis were applied to map groundwater recharge and discharge areas within the modelled area. Results of groundwater modelling were validated with phytosociologic research combined with remote-sensing based spatial analysis of wetland habitats distribution. Results indicated spatial distibution of water balance components of different wetland habitats. In areas of fen plant communities, modelled intensity of vertical upward groundwater flow to the top layer is significantly higher than in ombrotrophic habitats. Research indicated, that spatial patterns of groundwater recharge/discharge intensity is strongly linked to areal distribution of water quality dependent phreatophytic plant communities. In certain areas, simulated drainage conditions increased the thickness of the unsaturated zone, which explains a crucial response of wetland evolution in the last centuries: redirection of groundwater flow towards artificial canals resulted in diminished throughflow in organogenic layer, which causes accumulation of acidic rain water and - consequently - development of ombrotrophic habitats.
Grygoruk, Mateusz; Batelaan, Okke; Okruszko, Tomasz; Kotowski, Wiktor; Rycharski, Marek; Chormanski, Jaroslaw; Miroslaw-Swiatek, Dorota
The Mediterranean Coastal Dunes in Egypt: An Endangered Landscape
NASA Astrophysics Data System (ADS)
The Mediterranean coast in Egypt extends almost 900 km, the major part of which is bordered by sand dunes of different natures and types. Along the coastline between Alexandria and El-Alamein, a distance of some 100 km, the sand dunes represent a particular landscape with special characteristics and features, and consequently plants with particular attributes. In this area, the belt of sand dunes has developed immediately south of the shore and these dunes may rise up to 10 m in height and extend about 0�5-1�5 km inland from the shore. These dunes are famous as a habitat for the fig (Ficus carica L.) cultivation depending on the irregular rainfall. They also represent a landing station and a cross-road for birds such as quail migrating from Europe in the north. In the past, summer resort areas were confined to limited areas with few people, these same areas support the growth of some important plant species, for example, sand binders, medicinal and range plants. For more than two decades, there has been considerable socio-economic change and an open-door policy in the economy of the country has been adopted. One of the consequences of this change is that a great part of the coastal dune belt west of Alexandria till El-Alamein, has been subjected to destruction, due to the continuous construction of summer resort villages. These were built at a distance of about 100 m of the shoreline, extending 400-600 m inland and a breadth of 400 m or more along the shoreline. The area already covered by the dunes is now almost occupied by new buildings, gardens and other infrastructure. The consequences of these human activities are numerous and include impacts on the soil, water resources, the flora and the fauna, migrating birds, trends of the indigenous people, and the cultural environment. The present paper gives a concise environmental setting of the dune belt before the advent of the new activities, and the socio-economic and political attitudes which threaten the dunes. The ecological consequences of the recent human activities and recommendations are presented.
Batanouny, K. H.
Dune field reactivation from blowouts: Sevier Desert, UT, USA
NASA Astrophysics Data System (ADS)
Dune field reactivation (a shift from vegetated to unvegetated state) has important economic, social, and environmental implications. In some settings reactivation is desired to preserve environmental values, but in arid regions reactivation is typically a form of land degradation. Little is known about reactivation due to a lack of published records, making modeling and prediction difficult. Here we detail dune reactivations from blowout expansion in the Sevier Desert, Utah, USA. We use historical aerial photographs and satellite imagery to track the transition from stable, vegetated dunes to actively migrating sediment in 3 locations. We outline a reactivation sequence: (i) disturbance breaches vegetation and exposes sediment, then (ii) creates a blowout with a deposition apron that (iii) advances downwind with a slipface or as a sand sheet. Most deposition aprons are not colonized by vegetation and are actively migrating. To explore causes we examine local sand flux, climate data, and stream flow. Based on available data the best explanation we can provide is that some combination of anthropogenic disturbance and climate may be responsible for the reactivations. Together, these examples provide a rare glimpse of dune field reactivation from blowouts, revealing the timescales, behaviour, and morphodynamics of devegetating dune fields.
Barchyn, Thomas E.; Hugenholtz, Chris H.
Near surface airflow modelling over dunes in Proctor Crater, Mars
NASA Astrophysics Data System (ADS)
Multiple dune forms inside Martian craters is evident on much of the recent Hi-Rise imagery available. Typically, multiple length scales are present with progressively smaller bedform features superimposed on larger dunes. This has produced complex but regular topographical aeolian-driven patterns. Understanding the airflow conditions over and around these features will help in our understanding of the formational patterns and orientation of the aeolian bedforms relative to localised wind flow forcing. Here we use computational fluid dynamics modelling and present preliminary findings within Mars' Proctor Crater over a dune area measuring 4.5km x 5.0km running with a computational cell resolution of 5m x 5m. A range of wind speed and directions are investigated and results are compared to bedform orientation, length scale and migration of ripples evident from recent HiRise imagery. Results reveal a distinctive relationship between steered airflow and localised bedform orientation, mapping orthogonally onto the crestal ridges present. This work has important implications for evolutionary reconstruction of aeolian dunes within craters on Mars and helps lend further support to studies examining recent activity of Martian dune migration.
Jackson, Derek; Bourke, Mary; Smyth, Thomas
A constitutive relationship between mean and local eolian dune migration
NASA Astrophysics Data System (ADS)
How can eolian dune fields achieve alignment to a wind regime if every sediment transporting wind event displaces curved bedform crests unequally? Gross bedform-normal transport and alignment is a kinematic model that describes how bedforms are oriented and migrate in response to a dominant and subordinate sediment-transport vector. The local bedform normal model describes how eolian dune crests deform non-uniformly in response to a singular sediment-transporting wind event. Bedform crest alignment to sediment transporting wind events is the conceptual underpinning that predicts what fraction of the sediment flux goes into bedform migration in both models. By embracing this geometric commonality we reconcile the two models. The new kinematic model yields a constitutive relationship between mean and local dune crest orientation and kinematics for a statistically steady wind regime. The new kinematic model is applied to calculate mean and directional variation in sediment flux at the White Sands dune field, NM, using meteorological data. The model results are compared to observed dune migration and orientation imaged in a time series of DEMs built from a time series of airborne LiDAR surveys.
Swanson, T.; Mohrig, D. C.; Kocurek, G.
Does current precipitation play a role in the recharge of groundwater in the deserts of northern China?
NASA Astrophysics Data System (ADS)
Arid and semi-arid areas account for more than one third of the Chinese landmass and are distributed over elevations ranging from 155 m below sea level to over 5000 m above sea level. The most typical landscapes of this vast and diverse region are sand seas in arid and sandy lands in the semiarid zones. The widely cited value about mean annual evaporation in the deserts of northern China is between ca. 1400 to 3000 mm / year in general and between 3000 and 3800 mm / year in dune fields. Under such a framework modern precipitation would be meaningless to the recharge of groundwater. Our new estimate, based on the weather data from the last four decades, suggests, however, there is a clear overestimate of the evaporation rate in the earlier data. In a sand sea like the Badain Jaran Desert in the western Inner Mongolia, our calculation using a modified Penman equation shows that the mean annual evaporation is ca. 1000 mm from lakes and ca. 100 mm from the land surface. Our estimate is consistent with a new analysis showing that only ca. 10% of chloride in the soluble salts of aeolian sands in western Inner Mongolia comes directly from rainfall while 90% of chloride in these salts is deposited directly by dust accumulation (dry deposition). Limited, short-term experiment with large evaporation ponds supports our new estimate also. Provided that the new estimate tells the truth, we can further conclude that the current precipitation - ca. 100 mm in the southeast of the Badain Jaran Desert - plays a significant role in the recharge of the groundwater that directly feeds a large number of "small" desert lakes in this region. The existence of measurable tritium in the shallow ground water samples from the margins of these desert lakes reconfirms the importance of modern precipitation in the recharge of groundwater as well.
Yang, Xiaoping
Reliability of Rechargeable Batteries in a Photovoltaic Power Supply System
We investigate the reliability If a rechargeable battery acting as the energy storage component in a photovoltaic power supply system. A model system was constructed for this that includes the solar resource, the photovoltaic power supp Iy system, the rechargeable battery and a load. The solar resource and the system load are modeled as SI ochastic processes. The photovoltaic system
P. Barney; R. G. Jungst; D. Ingersoll; C. OGorman; T. L. Paez; A. Urbina
Determining the recharge mode of Sahelian aquifers using water isotopes
It is proposed that the drainage network plays an important role in the recharge process of the fractured aquifers in the African Precambrian shield and that the fractured aquifer system is likely to be hydraulically continuous; this contrasts with most previous studies, which suggested direct recharge by rainwater percolation. Two areas were selected in Niger for the study of the
Pierre Girard; Claude Hillaire-Marcel; Marie Solange Oga
Downstream of downtown: urban wastewater as groundwater recharge
Wastewater infiltration is often a major component of overall recharge to aquifers around urban areas, especially in more arid climates. Despite this, such recharge still represents only an incidental (or even accidental) byproduct of various current practices of sewage effluent handling and wastewater reuse. This topic is reviewed through reference to certain areas of detailed field research, with pragmatic approaches
S. S. D. Foster; P. J. Chilton
Electrochemically active polymers for rechargeable batteries
Electrochemical energy storage systems (batteries) have a tremendous role in technical applications. In this review the authors examine the prospects of electroactive polymers in view of the properties required for such batteries. Conducting organic polymers are considered here in the light of their rugged chemical environment: organic solvents, acids, and alkalis. The goal of the present article is to provide, first of all in tabular form, a survey of electroactive polymers in view of potential applications in rechargeable batteries. It reviews the preparative methods and the electrochemical performance of polymers as rechargeable battery electrodes. The theoretical values of specific charge of the polymers are comparable to those of metal oxide electrodes, but are not as high as those of most of the metal electrodes normally used in batteries. Therefore, it is an advantage in conventional battery designs to use the conducting polymer as a positive electrode material in combination with a negative electrode such as Li, Na, Mg, Zn, MeH{sub x}, etc. 504 refs.
Novak, P.; Haas, O. [Paul Scherrer Inst., Villigen PSI (Switzerland). Electrochemistry Section] [Paul Scherrer Inst., Villigen PSI (Switzerland). Electrochemistry Section; Santhanam, K.S.V. [Tata Inst. of Fundamental Research, Mumbai (India)] [Tata Inst. of Fundamental Research, Mumbai (India); Mueller, K.
Global synthesis of groundwater recharge in semiarid and arid regions
Global synthesis of the findings from ???140 recharge study areas in semiarid and arid regions provides important information on recharge rates, controls, and processes, which are critical for sustainable water development. Water resource evaluation, dryland salinity assessment (Australia), and radioactive waste disposal (US) are among the primary goals of many of these recharge studies. The chloride mass balance (CMB) technique is widely used to estimate recharge. Average recharge rates estimated over large areas (40-374000 km2) range from 0.2 to 35 mm year-1, representing 0.1-5% of long-term average annual precipitation. Extreme local variability in recharge, with rates up to ???720 m year-1, results from focussed recharge beneath ephemeral streams and lakes and preferential flow mostly in fractured systems. System response to climate variability and land use/land cover (LU/LC) changes is archived in unsaturated zone tracer profiles and in groundwater level fluctuations. Inter-annual climate variability related to El Nin??o Southern Oscillation (ENSO) results in up to three times higher recharge in regions within the SW US during periods of frequent El Nin??os (1977-1998) relative to periods dominated by La Nin??as (1941-1957). Enhanced recharge related to ENSO is also documented in Argentina. Climate variability at decadal to century scales recorded in chloride profiles in Africa results in recharge rates of 30 mm year-1 during the Sahel drought (1970-1986) to 150 mm year-1 during non-drought periods. Variations in climate at millennial scales in the SW US changed systems from recharge during the Pleistocene glacial period (??? 10 000 years ago) to discharge during the Holocene semiarid period. LU/LC changes such as deforestation in Australia increased recharge up to about 2 orders of magnitude. Changes from natural grassland and shrublands to dryland (rain-fed) agriculture altered systems from discharge (evapotranspiration, ET) to recharge in the SW US. The impact of LU change was much greater than climate variability in Niger (Africa), where replacement of savanna by crops increased recharge by about an order of magnitude even during severe droughts. Sensitivity of recharge to LU/LC changes suggests that recharge may be controlled through management of LU. In irrigated areas, recharge varies from 10 to 485 mm year-1, representing 1-25% of irrigation plus precipitation. However, irrigation pumpage in groundwater-fed irrigated areas greatly exceeds recharge rates, resulting in groundwater mining. Increased recharge related to cultivation has mobilized salts that accumulated in the unsaturated zone over millennia, resulting in widespread groundwater and surface water contamination, particularly in Australia. The synthesis of recharge rates provided in this study contains valuable information for developing sustainable groundwater resource programmes within the context of climate variability and LU/LC change. Copyright ?? 2006 John Wiley & Sons, Ltd.
Scanlon, B. R.; Keese, K. E.; Flint, A. L.; Flint, L. E.; Gaye, C. B.; Edmunds, W. M.; Simmers, I.
44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.
Code of Federal Regulations, 2013 CFR
...Evaluation of sand dunes in mapping coastal flood hazard areas. 65.11 Section 65...INSURANCE AND HAZARD MITIGATION National Flood Insurance Program IDENTIFICATION...Evaluation of sand dunes in mapping coastal flood hazard areas. (a) General...
44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.
Code of Federal Regulations, 2010 CFR
... false Evaluation of sand dunes in mapping coastal flood hazard areas. 65...Insurance Program IDENTIFICATION AND MAPPING OF SPECIAL HAZARD AREAS § 65.11 Evaluation of sand dunes in mapping coastal flood hazard areas....
44 CFR 65.11 - Evaluation of sand dunes in mapping coastal flood hazard areas.
Code of Federal Regulations, 2010 CFR
... false Evaluation of sand dunes in mapping coastal flood hazard areas. 65...Insurance Program IDENTIFICATION AND MAPPING OF SPECIAL HAZARD AREAS § 65.11 Evaluation of sand dunes in mapping coastal flood hazard areas....
Groundwater Recharge Rate and Zone Structure Estimation Using PSOLVER Algorithm.
The quantification of groundwater recharge is an important but challenging task in groundwater flow modeling because recharge varies spatially and temporally. The goal of this study is to present an innovative methodology to estimate groundwater recharge rates and zone structures for regional groundwater flow models. Here, the unknown recharge field is partitioned into a number of zones using Voronoi Tessellation (VT). The identified zone structure with the recharge rates is associated through a simulation-optimization model that couples MODFLOW-2000 and the hybrid PSOLVER optimization algorithm. Applicability of this procedure is tested on a previously developed groundwater flow model of the Tahtal? Watershed. Successive zone structure solutions are obtained in an additive manner and penalty functions are used in the procedure to obtain realistic and plausible solutions. One of these functions constrains the optimization by forcing the sum of recharge rates for the grid cells that coincide with the Tahtal? Watershed area to be equal to the areal recharge rate determined in the previous modeling by a separate precipitation-runoff model. As a result, a six-zone structure is selected as the best zone structure that represents the areal recharge distribution. Comparison to results of a previous model for the same study area reveals that the proposed procedure significantly improves model performance with respect to calibration statistics. The proposed identification procedure can be thought of as an effective way to determine the recharge zone structure for groundwater flow models, in particular for situations where tangible information about groundwater recharge distribution does not exist. PMID:23746002
Ayvaz, M Tamer; El�i, Alper
Determining the recharge mode of Sahelian aquifers using water isotopes
NASA Astrophysics Data System (ADS)
It is proposed that the drainage network plays an important role in the recharge process of the fractured aquifers in the African Precambrian shield and that the fractured aquifer system is likely to be hydraulically continuous; this contrasts with most previous studies, which suggested direct recharge by rainwater percolation. Two areas were selected in Niger for the study of the aquifer recharge process using isotopic analyses of water ( 2H, 18O, 3H). The first area, centred on the village of Kobio, is the 21-km 2 drainage basin of the Lomona intermittent stream, some 60 km southwest of Niamey (the capital city of Niger). The second area, in the vicinity of Niamey, represents a portion of the Niger basin, draining a surface area many orders of magnitude larger than the Lomona basin. The mean 18O composition of water from all wells in the Kobio aquifer provides evidence for recharge by evaporated water. This is confirmed by the concomitant increase of 18O content with rising static water levels as recharge proceeded. Tritium data suggest progressive aging of the Kobio aquifer water in the flow direction inferred from static water levels, with a down-gradient depletion of 18O composition, suggesting that `enriched' recharge water is progressively mixed with `depleted' aquifer water. Recharge by a reach of the Lomona is proposed to explain these results. In the Niamey area wells, the 18O time series clearly define an injection of evaporated water from the surface into the fractured aquifer. This recharging plume of evaporated water most likely originates from the Niger River. Thus, isotope data for two drainage basins of very different sizes indicate that aquifers are recharged by water from the rivers and that the flow regime of surface waters controls the recharge process.
Girard, Pierre; Hillaire-Marcel, Claude; Oga, Marie Solange
Temperature and humidity measurements within desert barchan sand dunes, relation to dune aeolian mobility and microbial growth
NASA Astrophysics Data System (ADS)
We present diurnal variations of temperature and humidity profiles below the surface of hyper-arid aeolian crescent-shaped "barchan" dunes in Qatar and Mauritania, measured using a thermal probe and a new ultra-sensitive capacitance instrument that we developed for this purpose. We also report long-term measurements from a probe sunk on the downwind avalanche face of a mobile Qatar barchan, recording temperature and humidity until it emerged on the upwind slope 15 months later. We interpret the data by modeling heat and moisture transfer at the surface in terms of measured net surface radiation, wind, and atmospheric conditions. We demonstrate the presence of microbes on sand grains within these mobile dunes using microscopic observations, fluorescence counts, metagenomic sequencing, and C12/C13 isotope analysis of carbon dioxide sampled below the surface. By determining how water activity grows with moisture adsorbed on these sands, we delimit regions within the dune where our instruments recorded humidity conducive to microbial growth. Finally, we compare the mobility of two adjacent Mauritania barchans having distinct surface grain size, shape, and depth humidity profiles. Armored by large grains on its surface, the smaller dune was more oblong. As a result, it lacked flow recirculation in its wake, trapped less aeolian sand downwind, and was much less mobile than its smaller size would suggest. This slower mobility led to greater humidity and cohesion at depth than the larger dune exposed to the same atmospheric and wind conditions.
Louge, Michel; Hay, Anthony; Richer, Renee; Valance, Alexandre; Ould el Moctar, Ahmed; Xu, Jin; Abdul-Majid, Sara
Spring Time View of North Polar Sand Dunes
NASA Technical Reports Server (NTRS)
Spring has come to the martian northern hemisphere. The northern spring season began in mid-July 1998. With the arrival of spring comes the annual shrinkage of the north polar frost cap. Sunlight is now falling on the north polar cap, and all of the carbon dioxide frost and snow that accumulated during winter has been sublimating--going directly from solid to gas--and the surface beneath the frost is being revealed.The MOC image shown above, 45205, was obtained during the 452nd orbit of Mars Global Surveyor at 3:10 p.m. PDT on July 26, 1998. The image is located near latitude 76.87oN, longitude 253.81oW, and it shows a close-up view of martian sand dunes. These dunes were not visible to MOC until the last week of July. Just a few months earlier, the dunes were likely covered with frost, obscured by thick clouds, and cloaked by the darkness of the martian polar winter. Indeed, small patches of bright frost were still present when the picture was taken (e.g., the bright patches on the west (left) side of each crescentic dune in (left image).As the above picture illustrates, the camera on board Mars Global Surveyor (MOC) continued to take exciting new views of the martian surface throughout July 1998. As the month progressed, the ground track-- the area visible to the camera--migrated farther north. Simultaneously, sunlight began falling on the north polar regions, making it possible to take some pictures at far northern latitudes. However, these regions have been tricky to photograph because of thick clouds and hazes. The image shown here, for example, is relatively bland gray (has relatively low contrast) because of clouds.As first seen by the Viking 2 Orbiter in 1976, a vast 'sea' of sand dunes surrounds the north polar cap. The dunes imaged by MOC (above) are classic forms known as barchan dunes--the small, crescent-shaped hills (see left image above)-- and transverse dunes--ridges that resemble coalesced barchans (shown in right image above). These dunes are similar in size and shape to familiar sand dunes found in desert regions on Earth. These two varieties form from winds that persistently come from a single direction (in this case, from the southwest).Over the next several months, the sky above these dunes will clear. Northern Summer will arrive near the end of January 1999, and Mars Global Surveyor should have an excellent view of this region when it begins its mapping mission in late March 1999. Because it is in a polar orbit, Mars Global Surveyor will have many opportunities to revisit the north polar dunes in 1999. The images in 1999 will have resolutions around 1.5 meters (5 feet) per pixel--a substantial improvement even over the pictures shown here.
Martian linear dunes : observation and modelling from the LMD GCM data base
NASA Astrophysics Data System (ADS)
Dunes are common on Earth and Mars and have similar geometries on both planets. Martian dunes are larger than terrestrial one and are shaped by winds less efficient than terrestrial winds. Martian dunes move thus much more slowly than terrestrial dunes. Their characteristic time could be similar to the characteristic time of climate change on Mars. Their geometry could thus reflect past climate conditions. Linear dunes are a family of elongated dunes shaped by at least 2 winds that blow at an obtuse angle alternatively along the year. Contrary to simple dunes as barkhanes, it is therefore difficult to invert the shape of these dunes in term of wind direction and intensity. It is thus difficult to demonstrate if their geometry is coherent or not with the current wind regimes. We mapped 10 dune fields located inside impact craters of the southern hemisphere of Mars. Five fields are composed of barkhanes and 5 by linear dunes. For each dune field location, we extracted the annual wind velocity at 20m above the surface at a temporal resolution of 1 hour every 30 martian days from the Mars Climate Database of the LMD (www-mars.lmd.jussieu.fr/). The annual wind rose was calculated for each dune field. The sand flux along the year was also computed assuming a classical law of transport with threshold. Assuming that the avalanche face of barkhanes is perpendicular to the sand flux direction, we predicted the orientation of the avalanche face for each barkhane fields. These results are coherent with the observations. Assuming that linear dunes are aligned along the average sand flux direction, we predicted the orientation of the linear dunes and compared them to the observations. In 4 cases, the predicted dune orientation is consistent with observations. In one case, there is a strong discrepancy between the predicted and observed orientation that could indicate that this linear dune field is fossil.
allemand, pascal; Quiquerez, Am�lie; Quantin, Cathy
Windblown Dunes on the Floor of Herschel Impact Basin
NASA Technical Reports Server (NTRS)
Herschel Basin, one of many meteor impact craters on Mars, has some dark material on its floor that appeared from earlier spacecraft missions to have been blown and/or deposited by wind. Herschel Basin was imaged at low resolution by the Mariner 9 and Viking orbiters ((A) above) in the 1970s, and again by the Phobos 2 orbiter in 1989.On June 14, 1998, Mars Global Surveyor's Mars Orbiter Camera revealed that part of the dark surface on the floor of Herschel Basin consists of a field of sand dunes ((B) above). These dunes have a distinct crescent-like shape characteristic of dunes on Earth called barchan dunes. They result from winds that blow from a single dominant direction.In the case of Herschel Basin, the dunes indicate that the strongest winds blow approximately north-to-south. The crescent horns on the ends of some of the dunes in this image are elongated. This condition indicates that the dominant winds do not always blow in exactly the same direction-- sometimes the winds blow from the northeast, sometimes from the northwest, and sometimes from the north. The local topography probably influences the wind direction--and hence dune shape--because this dune field is located on a narrow, low plain between a high crater rim to the east, and a narrow mountain range-- the inner ring of the Herschel impact basin--to the west (see image (A)).MOC image 36507 was obtained on Mars Global Surveyor's 365th orbit around 10:51 a.m. PDT on June 14, 1998. This subframe is centered around 14.27oS, 231.68oW.Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
Climate variability effects on urban recharge beneath low impact development
NASA Astrophysics Data System (ADS)
Groundwater resources in urban and coastal environments are highly vulnerable to human pressures and climate variability and change, and many communities face water shortages and need to find alternative water supplies. Therefore, understanding how low impact development (LID) site planning and integrated/best management practices (BMPs) affect recharge rates and volumes is important because of the increasing use of LID and BMP to reduce stormwater runoff and improve surface-water quality. Often considered a secondary management benefit, many BMPs may also enhance recharge to local aquifers; however these hypothesized benefits have not been thoroughly tested or quantified. In this study, we quantify stormwater capture and recharge enhancement beneath a BMP infiltration trench of the LID research network at San Francisco State University, San Francisco, California. Stormwater capture and retention was analyzed using the SCS TR-55 curve number method and in-situ infiltration rates to assess LID storage. Recharge was quantified using vadose zone monitoring equipment, a detailed water budget analysis, and a Hydrus-2D model. Additionally, the effects of historical and predicted future precipitation on recharge rates were examined using precipitation from the Geophysical Fluid Dynamic Laboratory (GFDL) A1F1 climate scenario. Observed recharge rates beneath the infiltration trench range from 1,600 to 3,700 mm/year and are an order of magnitude greater than recharge beneath an irrigated grass lawn and a natural setting. The Hydrus-2D model results indicate increased recharge under the GFDL A1F1 scenario compared with historical and GFDL modeled 20th century rates because of the higher frequency of large precipitation events that induce runoff into the infiltration trench. However, under a simulated A1F1 El Ni�o year, recharge calculated by a water budget does not increase compared with current El Ni�o recharge rates. In comparison, simulated recharge rates were considerably lower beneath the grass lawn for historical and future precipitation years. This work highlights the potential management strategy of using LID to capture excess runoff during El Ni�o years that can be recharged and stored as groundwater. An additional benefit of LID in coastal aquifer systems is the ability to capture and redirect precipitation from runoff to recharge that may help mitigate the negative effects from groundwater pumping and sea-water intrusion.
Newcomer, M. E.; Gurdak, J. J.
76 FR 57074 - Transfer of Administrative Jurisdiction at or Near Great Sand Dunes National Park
Federal Register 2010, 2011, 2012, 2013
...Administrative Jurisdiction at or Near Great Sand Dunes National Park AGENCY: National Park...lands acquired for the benefit of Great Sand Dunes National Park, Baca National Wildlife...interests in land for the benefit of Great Sand Dunes National Park, Baca National...
Vegetation and ghost crabs in coastal dunes as indicators of putative stressors from tourism
Coastal dunes provide important ecosystem services and are susceptible to human disturbance such as vehicle traffic and human trampling. Notwithstanding, on several Australian beaches dunes serves as camping areas, where camping sites are located on the primary dunes landwards of the foredunes. Because these activities have the potential to impact on the biota of the foredunes directly adjoining the camping
Thomas A. Schlacher; Rudolf de Jager; Tara Nielsen
The role of streamline curvature in sand dune dynamics: evidence from field and wind tunnel measurements
Field measurements on an unvegetated, 10 m high barchan dune in Oman are compared with measurements over a 1:200 scale fixed model in a wind tunnel. Both the field and wind tunnel data demonstrate similar patterns of wind and shear velocity over the dune, confirming significant flow deceleration upwind of and at the toe of the dune, acceleration of flow
Giles F. S. Wiggs; Ian Livingstone; Andrew Warren
Responses of dune mosses to experimental burial by sand under natural and greenhouse conditions
Sand movement is a predominant feature of mobile coastal and lake-shoreline sand dunes. Plants growing in these environments are able to withstand and survive periods of burial by sand. Although mosses are important dune stabilizers in temperate dunes, there are few studies focused on their response to burial by sand. In this study we examined the effects of burial by
M. Luisa Mart�nez; M. A. Maun
Compressive strength and hydration with age of cement pastes containing dune sand powder
This experimental work has focused on studying the possibility of using dune sand powder (DSP) as a part mass addition to Portland cement. Studying the effect of addition dune sand powder on development of compressive strength and hydration with age of cement pastes as a function of water\\/binder ratio, was varied, on the one hand, the percentage of the dune
Salim Guettala; Bouzidi Mezghiche
An analytical model to predict dune erosion due to wave impact
An analytical model is developed to calculate recession distance and eroded volume for coastal dunes during severe storms. The transport relationship used in the model is based on wave impact theory, where individual swash waves hitting the dune face induce the erosion. Combining this relationship with the sediment volume conservation equation describes the response of the dune to high waves
Magnus Larson; Li Erikson; Hans Hanson
Southern high latitude dune fields on Mars: Morphology, aeolian inactivity, and climate change
In a study area spanning the martian surface poleward of 50?? S., 1190 dune fields have been identified, mapped, and categorized based on dune field morphology. Dune fields in the study area span ??? 116400km2, leading to a global dune field coverage estimate of ???904000km2, far less than that found on Earth. Based on distinct morphological features, the dune fields were grouped into six different classes that vary in interpreted aeolian activity level from potentially active to relatively inactive and eroding. The six dune field classes occur in specific latitude zones, with a sequence of reduced activity and degradation progressing poleward. In particular, the first signs of stabilization appear at ???60?? S., which broadly corresponds to the edge of high concentrations of water-equivalent hydrogen content (observed by the Neutron Spectrometer) that have been interpreted as ground ice. This near-surface ground ice likely acts to reduce sand availability in the present climate state on Mars, stabilizing high latitude dunes and allowing erosional processes to change their morphology. As a result, climatic changes in the content of near-surface ground ice are likely to influence the level of dune activity. Spatial variation of dune field classes with longitude is significant, suggesting that local conditions play a major role in determining dune field activity level. Dune fields on the south polar layered terrain, for example, appear either potentially active or inactive, indicating that at least two generations of dune building have occurred on this surface. Many dune fields show signs of degradation mixed with crisp-brinked dunes, also suggesting that more than one generation of dune building has occurred since they originally formed. Dune fields superposed on early and late Amazonian surfaces provide potential upper age limits of ???100My on the south polar layered deposits and ???3Ga elsewhere at high latitudes. No craters are present on any identifiable dune fields, which can provide a lower age limit through crater counting: assuming all relatively stabilized dune fields represent a single noncontiguous surface of uniform age, their estimated crater retention age is ??10000years. An average-sized uncratered dune field (94km2) has a crater retention age ??8My. This apparent youth suggests that present-day climate conditions are responsible for the observed degradation and reduced level of aeolian activity. A lack of observed transport pathways and the absence of large dune fields in the largest basins (Hellas and Argyre Planitiae) are consistent with the previously proposed idea that dune sands are not typically transported far from their source regions on Mars. ?? 2009 Elsevier B.V.
Fenton, L. K.; Hayward, R. K.
Rechargeable metal hydrides for spacecraft application
NASA Technical Reports Server (NTRS)
Storing hydrogen on board the Space Station presents both safety and logistics problems. Conventional storage using pressurized bottles requires large masses, pressures, and volumes to handle the hydrogen to be used in experiments in the U.S. Laboratory Module and residual hydrogen generated by the ECLSS. Rechargeable metal hydrides may be competitive with conventional storage techniques. The basic theory of hydride behavior is presented and the engineering properties of LaNi5 are discussed to gain a clear understanding of the potential of metal hydrides for handling spacecraft hydrogen resources. Applications to Space Station and the safety of metal hydrides are presented and compared to conventional hydride storage. This comparison indicates that metal hydrides may be safer and require lower pressures, less volume, and less mass to store an equivalent mass of hydrogen.
Perry, J. L.
Oxygen electrodes for rechargeable alkaline fuel cells
NASA Technical Reports Server (NTRS)
Electrocatalysts and supports for the positive electrode of moderate temperature single unit rechargeable alkaline fuel cells were investigated and developed. The electrocatalysts are defined as the material with a higher activity for the oxygen electrode reaction than the support. Advanced development will require that the materials be prepared in high surface area forms, and may also entail integration of various candidate materials. Eight candidate support materials and seven electrocatalysts were investigated. Of the 8 support, 3 materials meet the preliminary requirements in terms of electrical conductivity and stability. Emphasis is now on preparing in high surface area form and testing under more severe corrosion stress conditions. Of the 7 electrocatalysts prepared and evaluated, at least 5 materials remain as potential candidates. The major emphasis remains on preparation, physical characterization and electrochemical performance testing.
Swette, Larry; Giner, Jose
Spinel electrodes for rechargeable lithium batteries.
This paper gives a historical account of the development of spinel electrodes for rechargeable lithium batteries. Research in the late 1970's and early 1980's on high-temperature . Li/Fe{sub 3}O{sub 4} cells led to the evaluation of lithium spinels Li[B{sub 2}]X{sub 4} at room temperature (B = metal cation). This work highlighted the importance of the [B{sub 2}]X{sub 4}spinel framework as a host electrode structure and the ability to tailor the cell voltage by selection of different B cations. Examples of lithium-ion cells that operate with spinel anode/spinel cathode couples are provided. Particular attention is paid to spinels within the solid solution system Li{sub 1+x}Mn{sub 2-x}O{sub 4} (0 {le} x {le} 0.33).
Thackeray, M. M.
Polymer Energy Rechargeable System (PERS) Development Program
NASA Technical Reports Server (NTRS)
The National Aeronautics and Space Administration (NASA) and the Air Force Research Laboratory (AFRL) have recently established a collaborative effort to support the development of polymer-based, lithium-based cell chemistries and battery technologies to address the next generation of aerospace applications and mission needs. The overall objective of this development program, which is referred to as PERS, Polymer Energy Rechargeable System, is to establish a world-class technology capability and U.S. leadership in polymer-based battery technology for aerospace applications. Programmatically, the PERS initiative will exploit both interagency collaborations to address common technology and engineering issues and the active participation of academia and private industry. The initial program phases will focus on R&D activities to address the critical technical issues and challenges at the cell level.
Baldwin, Richard S.; Manzo, Michelle A.; Dalton, Penni J.; Marsh, Richard A.; Surampudi, Rao
Thin-film rechargeable lithium batteries
Small thin-film rechargeable cells have been fabricated with a lithium phosphorus oxyniuide electrolyte, Li metal anode, and Li{sub 1-x}Mn{sub 2}O{sub 4} as the cathode film. The cathode films were fabricated by several different techniques resulting in both crystalline and amorphous films. These were compared by observing the cell discharge behavior. Estimates have been made for the scale-up of such a thin-film battery to meet the specifications for the electric vehicle application. The specific energy, energy density, and cycle life are expected to meet the USABC mid-term criteria. However, the areas of the thin-films needed to fabricate such a cell are very large. The required areas could be greatly reduced by operating the battery at temperatures near 100{degrees}C or by enhancing the lithium ion transport rate in the cathode material.
Dudney, N.J.; Bates, J.B.; Lubben, D.
Polymer Energy Rechargeable System Battery Being Developed
NASA Technical Reports Server (NTRS)
Long description. Illustrations of discotic liquid crystals, rod-coil polymers, lithium-ion conducting channel dilithium phthalocyanine (Li2Pc) from top and side, novel star polyethylene oxide structures, composite polyethylene oxide materials (showing polyethylene oxide + lithium salt, carbon atoms and oxygen atoms), homopolyrotaxanes, and diblock copolymers In fiscal year 2000, NASA established a program to develop the next generation, lithium-based, polymer electrolyte batteries for aerospace applications. The goal of this program, known as Polymer Energy Rechargeable Systems (PERS), is to develop a space-qualified, advanced battery system embodying polymer electrolyte and lithium-based electrode technologies and to establish world-class domestic manufacturing capabilities for advanced batteries with improved performance characteristics that address NASA s future aerospace battery requirements.
Manzo, Michelle A.
Advanced rechargeable sodium batteries with novel cathodes
NASA Technical Reports Server (NTRS)
Various high energy density rechargeable batteries are being considered for future space applications. Of these, the sodium sulfur battery is one of the leading candidates. The primary advantage is the high energy density (760 Wh/kg theoretical). Energy densities in excess of 180 Wh/kg have been realized in practical batteries. More recently, cathodes other than sulfur are being evaluated. Researchers at JPL are evaluating various new cathode materials for use in high energy density sodium batteries for advanced space applications. The approach is to carry out basic electrochemical studies of these materials in a sodium cell configuration in order to understand their fundamental behaviors. Thus far studies have focused on alternate metal chlorides such as CuCl2 and organic cathode materials such as tetracyanoethylene (TCNE).
Distefano, S.; Ratnakumar, B. V.; Bankston, C. P.
Rechargeable thin-film lithium batteries
Rechargeable thin-film batteries consisting of lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have recently been developed. The batteries, which are typically less than 6-{mu}m thick, can be fabricated to any specified size, large or small, onto a variety of substrates including ceramics, semiconductors, and plastics. The cells that have been investigated include Li-TiS{sub 2}, Li-V{sub 2}O{sub 5}, and Li-Li{sub x}Mn{sub 2}O{sub 4}, with open circuit voltages at full charge of about 2.5, 3.6, and 4.2, respectively. The development of these batteries would not have been possible without the discovery of a new thin-film lithium electrolyte, lithium phosphorus oxynitride, that is stable in contact with metallic lithium at these potentials. Deposited by rf magnetron sputtering of Li{sub 3}PO{sub 4} in N{sub 2}, this material has a typical composition of Li{sub 2.9}PO{sub 3.3}N{sub 0.46} and a conductivity at 25{degrees}C of 2 {mu}S/cm. The maximum practical current density obtained from the thin-film cells is limited to about 100 {mu}A/cm{sup 2} due to a low diffusivity of Li{sup +} ions in the cathodes. In this work, the authors present a short review of their work on rechargeable thin-film lithium batteries.
Bates, J.B.; Gruzalski, G.R.; Dudney, N.J.; Luck, C.F.; Yu, Xiaohua
Quantifying the modern recharge of the "fossil" Sahara aquifers
NASA Astrophysics Data System (ADS)
The North-Western Sahara Aquifer System (NWSAS), one of the world's largest groundwater systems, shows an overall piezometric decline associated with increasing withdrawals. Estimating the recharge rate in such a semiarid system is challenging but crucial for sustainable water development. In this paper, the recharge of the NWSAS is estimated using a regional water budget based on GRACE terrestrial water storage monthly records, soil moisture from the GLDAS (a land data system that assimilates hydrological information), and groundwater pumping rates. A cumulated natural recharge rate of 1.40 � 0.90 km3 yr-1is estimated for the two main aquifers. Our results suggest a renewal rate of about 40% which partly contradicts the premise that recharge in this area should be very low or even null. Aquifer depletion inferred from our analysis is consistent with observed piezometric head decline in the two main aquifers in the region. Annual recharge variations were also estimated and vary between 0 and 4.40 km3 yr-1for the period 2003-2010. These values correspond to a recharge between 0 and 6.75 mm yr-1 on the 650,000 km2of outcropping areas of the aquifers, which is consistent with the expected weak and sporadic recharge in this semiarid environment. These variations are also in line with annual rainfall variation with a lag time of about 1 year.
Gon�Alv�S, J.; Petersen, J.; Deschamps, P.; Hamelin, B.; Baba-Sy, O.
Echo Meadows Project Winter Artificial Recharge.
This report discusses the findings of the Echo Meadows Project (BPA Project 2001-015-00). The main purpose of this project is to artificially recharge an alluvial aquifer, WITH water from Umatilla River during the winter high flow period. In turn, this recharged aquifer will discharge an increased flow of cool groundwater back to the river, thereby improving Umatilla River water quality and temperature. A considerable side benefit is that the Umatilla River should improve as a habitat for migration, spanning, and rearing of anadromous and resident fish. The scope of this project is to provide critical baseline information about the Echo Meadows and the associated reach of the Umatilla River. Key elements of information that has been gathered include: (1) Annual and seasonal groundwater levels in the aquifer with an emphasis on the irrigation season, (2) Groundwater hydraulic properties, particularly hydraulic conductivity and specific yield, and (3) Groundwater and Umatilla River water quality including temperature, nutrients and other indicator parameters. One of the major purposes of this data gathering was to develop input to a groundwater model of the area. The purpose of the model is to estimate our ability to recharge this aquifer using water that is only available outside of the irrigation season (December through the end of February) and to estimate the timing of groundwater return flow back to the river. We have found through the data collection and modeling efforts that this reach of the river had historically returned as much as 45 cubic feet per second (cfs) of water to the Umatilla River during the summer and early fall. However, this return flow was reduced to as low as 10 cfs primarily due to reduced quantities of irrigation application, gain in irrigation efficiencies and increased groundwater pumping. Our modeling indicated that it is possible to restore these critical return flows using applied water outside of the irrigation season. We further found that this water can be timed to return to the river during the desired time of the year (summer to early fall). This is because the river stage, which remains relatively high until this time, drops during the irrigation season-thereby releasing the stored groundwater and increasing river flows. A significant side benefit is that these enhanced groundwater return flows will be clean and cold, particularly as compared to the Umatilla River. We also believe that this same type of application of water could be done and the resulting stream flows could be realized in other watersheds throughout the Pacific Northwest. This means that it is critical to compare the results from this baseline report to the full implementation of the project in the next phase. As previously stated, this report only discusses the results of data gathered during the baseline phase of this project. We have attempted to make the data that has been gathered accessible with the enclosed databases and spreadsheets. We provide computer links in this report to the databases so that interested parties can fully evaluate the data that has been gathered. However, we cannot emphasize too strongly that the real value of this project is to implement the phases to come, compare the results of these future phases to this baseline and develop the science and strategies to successfully implement this concept to other rivers in the Pacific Northwest. The results from our verified and calibrated groundwater model matches the observed groundwater data and trends collected during the baseline phase. The modeling results indicate that the return flows may increase to their historic values with the addition of 1 acre-ft/acre of recharge water to the groundwater system (about 9,600 acre-feet total). What this means is that through continued recharge project, you can double to quadruple the annual baseflow of the Umatilla River during the low summer and fall flow periods as compared to the present base-flow. The cool and high quality recharge water is a significant beneficial impact to the river system.
Ziari, Fred
Spatial and temporal distribution of groundwater recharge in northern Nigeria
NASA Astrophysics Data System (ADS)
Moisture samples obtained from unsaturated-zone profiles in sands from northern Nigeria were used to obtain recharge estimates using the chloride (Cl) mass-balance method and to produce records of past recharge and climatic events. Recharge rates range from 14-49 mm/year, on the basis of unsaturated-zone Cl values and rainfall chemistry measured over eight years at three local stations. The unsaturated-zone results also provide a record of the changing recharge and climatic events of the past 80 years; this record compares quite well with modelling results using precipitation data from Maiduguri, especially for the late 20th-century period of drought. The best fit for the model is made, however, by using a lower mean rainfall Cl (0.65 mg/l) than that obtained from the mean of the field results (1.77 mg/l Cl). This result implies that the measured rainfall Cl probably overestimates the depositional flux of Cl, although the lower value is comparable to the minimum of the measured rainfall Cl values (0.6 mg/l Cl). Recharge estimates made using these lower Cl values range from 16-30 mm/year. The spatial variability was then determined using results from 360 regional shallow wells over 18,000 km2. Using the revised rainfall estimate, the Cl balance indicates a value of 43 mm for the regional recharge, suggesting that either additional preferential flow is taking place over and above that from the vadose one, or that the regional recharge represents inputs from earlier wetter periods. These recharge estimates compare favourably with those from hydraulic modelling in the same area and suggest that the recharge rates are much higher than values previously published for this area. High nitrate (NO3) concentrations (NO3-N>Cl) preserved under aerobic conditions in the vadose zone reflect secondary enrichment from N-fixing vegetation, as occurs elsewhere in the Sahel.
Edmunds, W. M.; Fellman, E.; Goni, I. B.; Prudhomme, C.
Discussion. Cemented horizon in subarctic Alaskan sand dunes.
Exception is taken to the conclusions (M.A. 84M/4465) concerning the distribution, age and origin of the cementing materials of carbonate crusts in the eaeolian sand deposits of the dune field in the central Kobuk Valley. (Following abstract)-M.S.
Galloway, J. P.; Koster, E. A.; Hamilton, T. D.
Simulation of barchan dynamics with inter-dune sand streams
NASA Astrophysics Data System (ADS)
A group of barchans, crescent sand dunes, exhibit a characteristic flying-geese pattern in deserts on Earth and Mars. This pattern implies that an indirect interaction between barchans, mediated by an inter-dune sand stream, which is released from one barchan's horns and caught by another barchan, plays an important role in the dynamics of barchan fields. We used numerical simulations of a recently proposed cell model to investigate the effects of inter-dune sand streams on barchan fields. We found that a sand stream from a point source moves a downstream barchan laterally until the head of the barchan is finally situated behind the stream. This final configuration was shown to be stable by a linear stability analysis. These results indicate that flying-geese patterns are formed by the lateral motion of barchans mediated by inter-dune sand streams. By using simulations we also found a barchan mono-corridor generation effect, which is another effect of sand streams from point sources.
Katsuki, Atsunari; Kikuchi, Macoto
Feasibility of using sand dunes as archives of old air
Large unaltered samples of the atmosphere coveting the past century would complement the history of atmospheric gases obtained from bubbles in ice cores, en- abling measurement of geochemically important species such as 02, 14CH4, and 4CO. Sand dunes are a porous media with interstitial air in diffusive contact with the atmo- sphere, somewhat analogous to the unconsolidated layer of firn
Jeffrey P. Severinghaus; Ralph F. Keeling; Benjamin R. Miller; Ray F. Weiss; Bruce Deck; Wallace S. Broecker
Analysis of Coastal Dunes: A Remote Sensing and Statistical Approach.
ERIC Educational Resources Information Center
Remote sensing analysis and statistical methods were used to analyze the coastal dunes of Plum Island, Massachusetts. The research methodology used provides an example of a student project for remote sensing, geomorphology, or spatial analysis courses at the university level. (RM)
Jones, J. Richard
Luminescence studies of dunes from North-Eastern Tasmania
Northern Tasmania has a geographically extensive cover of Quaternary aeolian features and although the morphology and stratigraphy of many of these have been studied it is difficult to assign a reliable chronology because of the lack of material suitable for radiocarbon dating. The dunes are primarily composed of quartz and hence are ideally suited for the application of luminescence dating.
G. A. T. Duller; P. Augustinus
Fly over of Mars Mesa, Tounge, Dunes, Sasquatch Crater
NSDL National Science Digital Library
This site from NASA's Scientific Visualization Studio features fly overs of Mesa, Tounge, Dunes, and Sasquatch Crater. Data for topography is based on the Mars Orbiting Laser Altimeter (MOLA) with Viking data used for color. Vertical exaggeration is about 300 times.
Studio, Nasa/goddard S.; Nasa
The Influence of Physical & Biological Cohesion on Dune Development
NASA Astrophysics Data System (ADS)
Existing predictions for dune bedforms are based on simplified physical parameters, with assumptions that sediment consists only of cohesionless sand. They do not include the complexities of mud: physical cohesion is imparted by cohesive clays and biological cohesion is created by the presence of organisms which, among other things, generate extra-cellular polymers (EPS). Using controlled experiments we show the profound influence on the size, development and equilibrium morphology of dune bedforms of both physical and biological cohesion. Experiments were completed at the Total Environment Simulator facility at Hull University, UK in a 10 x 2 m channel. A flat sediment bed was laid to 0.15 m depth. A unidirectional flow of 0.25 m depth was passed over the sediment for 10 h. In Phase 1 eight different sand:clay mixes were examined, where clay content was 18.0 - 2.1%. In Phase 2, the same mixtures were used with additions of EPS. A velocity of 0.8 m s-1 was used throughout, corresponding to the dune regime for the selected sand. Bedform development was monitored via ultrasonic ranging transducers, sediment cores and water samples. Phase 1 showed substantial differences in bedform type with clay content, with size inversely related to clay content, e.g. Run 1 (18.0% clay) generated 2D ripples; Run 7 (2.1% clay) generated 3D dunes. Transitional forms, included dunes with superimposed ripples, were present between these extremes. In Phase 2, EPS contents equivalent to only 1/30th of 1% by mass prevented the development of bedforms. Bedforms were generated in sediments with 1/20th and 1/10th of 1%, with an inverse relationship between bedform size and EPS content. Comparison of Phase 1 and Phase 2 runs with equal sand:mud ratios reveals that EPS acts to severely inhibit bedform development compared with the mud-only case. We can conclude that (1) the ripple-dune transition can occur under constant flow conditions, i.e. clay content may dictate bedform type, that (2) EPS can severely constrain the development of bedforms, at masses two orders of magnitude smaller than mud, ultimately preventing their development in conditions that would yield dunes in non-cohesive sands and that (3) biological cohesion appears to be greater than physical cohesion at ratios found in natural estuaries. We can conclude that, if the effects of physical and biological cohesion are not included when they are present, predictive models describing bedform growth, morphological equilibrium and migration will be inaccurate and in many cases misleading.
Schindler, Robert; Parsons, Daniel; Ye, Leiping; Baas, Jaco; Hope, Julie; Manning, Andy; Malarkey, Jonathan; Aspden, Rebecca; Lichtman, Dougal; Thorne, Peter; Peakall, Jeff; Patterson, David; Davies, Alan; Bass, Sarah; O'Boyle, Louise
Seismic Evidence for a Resonance Layer in Booming Sand Dunes
NASA Astrophysics Data System (ADS)
"Booming sand dunes" are large desert dunes that emit a loud droning, low-frequency sound during an avalanche of sand on the leeward face of a dune. The monotone sound (70-105 Hz) may continue for up to a minute after initiation, even after all visible motion has ceased. The source of the booming sound has long been a mystery and no accepted scientific explanation has been proposed yet. Seismic refraction experiments conducted with a closely-spaced 48 channel system show a shallow (< 10 m) subsurface layering inside the dune with significant velocity contrasts between the individual layers. The seismic body wave velocities in the top three layers of sand (240 m/s, 360 m/s and 460 m/s) are very close to the acoustic velocity in air (355 m/s) while at the same time the surface waves are highly attenuated. The seismic velocity changes cannot be explained by increasing confined pressure but must be provided by a seasonally changing physical structure. From the seismic survey it is further noted that the layering narrows towards the foothill. During the sustained boom, the frequency rises slightly (from 85 Hertz to 95 Hertz) as the source due to the avalanche proceeds downwards. This observation was deduced from analyzing the booming emission on all 48 geophones in conjunction with a high-quality air microphone. The multi-layer internal structure of the dune provides a resonance cavity that amplifies particular frequencies and creates the loud booming sound. The resonance and its interaction with the air is modeled with finite- difference simulations.
Vriend, N. M.; Hunt, M. L.; Clayton, R. W.
Morphology and distribution of common 'sand' dunes on Mars - Comparison with the earth
NASA Technical Reports Server (NTRS)
A comparative study of Martian and terrestrial dunes was made based on Viking Orbiter pictures and aerial pictures of terrestrial deserts. The morphological similarity between the Martian dunes and terrestrial crescentic dunes implies that the dynamics of dune formation are similar on the two planets, despite Martian constraints on dune formation that include much higher velocity winds required to move 'sand' in saltation, the possible inhibition of sand movement by absorbed water vapor, the seasonal 'snow' cover in the north circumpolar erg, and a probably sparse sand supply. The absence of longitudinal dunes and the restriction of massive crescentic dunes to a few sites on Mars suggests that Mars may have a long eolian history in which much of the sand suitable for saltation has already been transported to the north polar erg and crater floor fields.
Breed, C. S.; Grolier, M. J.; Mccauley, J. F.
Soil Water Balance and Recharge Monitoring at the Hanford Site � FY 2010 Status Report
This report summarizes the recharge data collected in FY 2010 at five locations on the Hanford Site in southeastern Washington State. Average monthly precipitation and temperature conditions in FY 2010 were near normal and did not present an opportunity for increased recharge. The recharge monitoring data confirmed those conditions, showing normal behavior in water content, matric head, and recharge rates. Also provided in this report is a strategy for recharge estimation for the next 5 years.
Fayer, Michael J.; Saunders, Danielle L.; Herrington, Ricky S.; Felmy, Diana
A comparison of seed banks across a sand dune successional gradient at Lake Michigan dunes (Indiana, USA)
In habitats where disturbance is frequent, seed banks are important for the regeneration of vegetation. Sand dune systems are dynamic habitats in which sand movement provides intermittent disturbance. As succession proceeds from bare sand to forest, the disturbance decreases. At Indiana Dunes National Lakeshore, we examined the seed banks of three habitat types across a successional gradient: foredunes, secondary dunes, and oak savanna. There were differences among the types of species that germinated from each of the habitats. The mean seed bank density increased across the successional gradient by habitat, from 376 to 433 to 968 seeds m-2, but with foredune and secondary dune seed bank densities being significantly lower than the savanna seed bank density. The number of seeds germinated was significantly correlated with soil organic carbon, demonstrating for this primary successional sequence that seed density increases with stage and age. The seed bank had much lower species richness than that of the aboveground vegetation across all habitats. Among sites within a habitat type, the similarity of species germinated from the seed banks was very low, illustrating the variability of the seed bank even in similar habitat types. These results suggest that restoration of these habitats cannot rely on seed banks alone. ?? 2008 Springer Science+Business Media B.V.
Leicht-Young, S. A.; Pavlovic, N. B.; Grundel, R.; Frohnapple, K. J.
The North Carolina Department of Environment and Natural Resources, Division of Water Quality and Groundwater Section, in cooperation with the NC Center for Geographic Information and Analysis, developed the Groundwater Recharge/Discharge digital data to enhance planning, siting ...
Waste Water Recharge and Dispersion in Porous Media.
National Technical Information Service (NTIS)
The recharge and disposal of treated and untreated waste waters in aquifers results in a mixing of these waters with the natural groundwater. The distribution and boundaries of the ensuing mixture are determined by dispersion and diffusion. This study inc...
J. A. Hoopes D. R. F. Harleman
Reliability of Rechargeable Batteries in a Photovoltaic Power Supply System.
National Technical Information Service (NTIS)
We investigate the reliability If a rechargeable battery acting as the energy storage component in a photovoltaic power supply system. A model system was constructed for this that includes the solar resource, the photovoltaic power supp Iy system, the rec...
P. Barney R. G. Jungst C. O'Gorman T. L. Paez A. Urbina
New Mechanically Rechargeable Zinc/Air Battery Design.
National Technical Information Service (NTIS)
Performance characteristics of the Yardney 20 AH Zinc/Air mechanically rechargeable systems are discussed in the light of the high power output requirements of the Technical Guidelines. Several design changes and improvements were incorporated into the bi...
R. F. Chireau R. G. Gunther
Improved zinc electrode and rechargeable zinc-air battery
The invention comprises an improved rechargeable zinc-air cell\\/battery having recirculating alkaline electrolyte and a zinc electrode comprising a porous foam support material which carries the active zinc electrode material. 5 figs.
P. N. Jr
Improved zinc electrode and rechargeable zinc-air battery
The invention comprises an improved rechargeable zinc-air cell/battery having recirculating alkaline electrolyte and a zinc electrode comprising a porous foam support material which carries the active zinc electrode material. 5 figs.
Ross, P.N. Jr.
This study describes and demonstrates two alternate methods for evaluating the relative costs and benefits of artificial groundwater recharge using percolation ponds. The first analysis considers the benefits to be the reduction of pumping lifts and land subsidence; the second considers benefits as the alternative costs of a comparable surface delivery system. Example computations are carried out for an existing artificial recharge program in Santa Clara Valley in California. A computer groundwater model is used to estimate both the average long term and the drought period effects of artificial recharge in the study area. Results indicate that the costs of artificial recharge are considerably smaller than the alternative costs of an equivalent surface system. Refs.
Reichard, Eric, G.; Bredehoeft, John, D.
Materials issues in lithium ion rechargeable battery technology.
National Technical Information Service (NTIS)
Lithium ion rechargeable batteries are predicted to replace Ni/Cd as the workhorse consumer battery. The pace of development of this battery system is determined in large part by the availability of materials and the understanding of interfacial reactions...
D. H. Doughty
Transition Metal Compounds as Cathodic Materials in Rechargeable Lithium Cells.
National Technical Information Service (NTIS)
A comparison was made between rechargeable lithium batteries, based on lithium intercalation or lithium interstitial compounds of transition metal chalcogenides or oxides, and nickel-cadmium batteries. Several chalcogenides and oxides show promise as cath...
H. F. Hunger J. E. Ellison
Status of the Development of Rechargeable Lithium Cells.
National Technical Information Service (NTIS)
The progress in the development of the ambient temperature lithium - titanium disulfide rechargeable cell under development at the Jet Propulsion Laboratory is described in this paper. Originally aimed at achieving a specific energy of 100 Wh/kg, 'AA' cel...
G. Halpert S. Surampudi D. Shen C. Huang S. Narayanan
Reliability of Rechargeable Batteries in a Photovoltaic Power Supply System
We investigate the reliability If a rechargeable battery acting as the energy storage component in a photovoltaic power supply system. A model system was constructed for this that includes the solar resource, the photovoltaic power supp Iy system, the rechargeable battery and a load. The solar resource and the system load are modeled as SI ochastic processes. The photovoltaic system and the rechargeable battery are modeled deterministically, imd an artificial neural network is incorporated into the model of the rechargeable battery to simulate dartage that occurs during deep discharge cycles. The equations governing system behavior are solved simultaneously in the Monte Carlo framework and a fwst passage problem is solved to assess system reliability.
Barney, P.; Jungst, R.G., Ingersoll, D.; O'Gorman, C.; Paez, T.L.; Urbina, A.
Bipolar rechargeable lithium battery for high power applications
NASA Technical Reports Server (NTRS)
Viewgraphs of a discussion on bipolar rechargeable lithium battery for high power applications are presented. Topics covered include cell chemistry, electrolytes, reaction mechanisms, cycling behavior, cycle life, and cell assembly.
Hossain, Sohrab; Kozlowski, G.; Goebel, F.
Graphite fiber as a positive electrode of rechargeable lithium cells
Graphite compounds have gained interest as possible positive electrodes for rechargeable lithium cells. Their charge-discharge characteristics have been studied in organic electrolytic solutions such as sulfolane dimethylsulfite, and propylene carbonate.
Matsuda, Y.; Katsuma, H.; Morita, M.
Cryogenic Transport of High-Pressure-System Recharge Gas
NASA Technical Reports Server (NTRS)
A method of relatively safe, compact, efficient recharging of a high-pressure room-temperature gas supply has been proposed. In this method, the gas would be liquefied at the source for transport as a cryogenic fluid at or slightly above atmospheric pressure. Upon reaching the destination, a simple heating/expansion process would be used to (1) convert the transported cryogenic fluid to the room-temperature, high-pressure gaseous form in which it is intended to be utilized and (2) transfer the resulting gas to the storage tank of the system to be recharged. In conventional practice for recharging high-pressure-gas systems, gases are transported at room temperature in high-pressure tanks. For recharging a given system to a specified pressure, a transport tank must contain the recharge gas at a much higher pressure. At the destination, the transport tank is connected to the system storage tank to be recharged, and the pressures in the transport tank and the system storage tank are allowed to equalize. One major disadvantage of the conventional approach is that the high transport pressure poses a hazard. Another disadvantage is the waste of a significant amount of recharge gas. Because the transport tank is disconnected from the system storage tank when it is at the specified system recharge pressure, the transport tank still contains a significant amount of recharge gas (typically on the order of half of the amount transported) that cannot be used. In the proposed method, the cryogenic fluid would be transported in a suitably thermally insulated tank that would be capable of withstanding the recharge pressure of the destination tank. The tank would be equipped with quick-disconnect fluid-transfer fittings and with a low-power electric heater (which would not be used during transport). In preparation for transport, a relief valve would be attached via one of the quick-disconnect fittings (see figure). During transport, the interior of the tank would be kept at a near-ambient pressure far below the recharge pressure. As leakage of heat into the tank caused vaporization of the cryogenic fluid, the resulting gas would be vented through the relief valve, which would be set to maintain the pressure in the tank at the transport value. Inasmuch as the density of a cryogenic fluid at atmospheric pressure greatly exceeds that of the corresponding gas in a practical high-pressure tank at room temperature, a tank for transporting a given mass of gas according to the proposed method could be smaller (and, hence, less massive) than is a tank needed for transporting the same mass of gas according to the conventional method.
Ungar, Eugene K,; Ruemmele, Warren P.; Bohannon, Carl
Estimating ground-water recharge from streamflow records
The purpose of this paper is to estimate ground-water recharge based on the investigation of the balance between ground-water recharge and discharge from streamflow hydrographs. Two methods of hydrograph analysis are employed in a case study of Cho-Shui River basin, Taiwan. The first is the recession-curve-displacement method, which assumes the linearity of the master recession curve while the profile of
Wei-Ping Chen; Cheng-Haw Lee
Delineating volcanic aquifer recharge areas using geochemical and isotopic tools
Relative recharge areas are evaluated using geochemical and isotopic tools, and inverse modeling. Geochemistry and water quality\\u000a in springs discharging from a volcanic aquifer system in Guatemala are related to relative recharge area elevations and land\\u000a use. Plagioclase feldspar and olivine react with volcanically derived CO2 to produce Ca-montmorillonite, chalcedony and goethite in the groundwater. Alkalinity, Mg, Ca, Na, and
Brendan M. Mulligan; M. Cathryn Ryan; Tom�s Padilla C�mbara
An approach for predicting groundwater recharge in mountainous watersheds
NASA Astrophysics Data System (ADS)
SummaryPredicting groundwater supply for an entire watershed in mountainous terrain required an approach that considered a wide range in data availability between valley bottom and headwater areas, large change in elevation, and steep topography. The methodology utilized the MIKE-SHE numerical code to simulate overland flow, actual evapotranspiration and recharge for data-rich areas, and a simpler, seasonal water budget for data-limited areas. Recharge estimates were combined to form spatially variable recharge boundary conditions for a larger-scale groundwater flow model of the entire mountainous watershed. Research focused on the BX Creek watershed, located in the north Okanagan Basin in British Columbia, one of Canada's fastest growing and most water-limited regions. Groundwater recharge was found to vary from 0 to 20 mm/yr at lower elevations, and from 20 to 50 mm/yr at higher elevations. Simulation of the whole flow system illustrated that 58% of the groundwater flux from upland areas occurs through a relatively narrow alluvial fan aquifer that extends to the valley bottom, and the remaining recharge is nearly equally divided between groundwater flow through the mountain block (20%) and direct recharge (22%). Geochemical data from domestic water wells within the watershed suggest that water in the alluvial aquifer and bedrock are generally similar (i.e., common origin); however, stable isotope data indicate that groundwater in the alluvial aquifer may be derived from snowmelt recharge at a different time and elevation than snowmelt recharge to the bedrock. The combination of modelling results and complimentary geochemical and isotopic analyses of surface water and groundwater, provide an adequate first-order approximation of groundwater flow in the watershed.
Smerdon, B. D.; Allen, D. M.; Grasby, S. E.; Berg, M. A.
Zinc electrode and rechargeable zinc-air battery
This patent describes an improved zinc electrode for a rechargeable zinc-air battery comprising an outer frame and a porous foam electrode support within the frame which is treated prior to the deposition of zinc thereon to inhibit the formation of zinc dendrites on the external surface thereof. The outer frame is provided with passageways for circulating an alkaline electrolyte through the treated zinc-coated porous foam. A novel rechargeable zinc-air battery system is also disclosed.
Ross, P.N. Jr.
Electrochemical behavior of hydrated molybdenum oxides in rechargeable lithium batteries
Oxide-hydrates of molybdenum (OHM) are investigated as 3-volt cathode materials for rechargeable lithium batteries. These\\u000a materials with different water content showed a much better performance than that of MoO3 as cathode of the rechargeable lithium battery. We report the electrochemical characteristics of Li\\/\\/OHM batteries using\\u000a the oxides and oxide-hydrates of molybdenum which were synthesized from molybdic acid. The oxide has
B. Yebka; C. Julien; G. A. Nazri
Inorganic electrolyte Li\\/CuCl2 rechargeable cell
A rechargeable lithium battery using a cathode of copper(II) chloride and an electrolyte consisting of LiAlCl4.3SO2 has been developed. The efficiency of lithium plating was evaluated in lithium-limited prototype cells. Cathode rechargeability was evaluated in cathode-limited prototypes, and system energy density was demonstrated by use of a wound D cell. The use of an electrolyte system which reacts reversibly with
A. N. Dey; W. L. Bowden; H. C. Kuo; M. L. Gopikanth; C. Schlaikjer; D. Foster
Rechargeable Li\\/V2O5 D cell development
The authors report on practical ambient temperature rechargeable lithium cells and batteries using V2O5. V2 O5 has interesting characteristics as a positive for lithium rechargeable cells. The material can be used to a 2.8 V discharge cutoff (upper plateau) or to 2 V. The development of practical D size cells for both uses is discussed, and capacity retention date and
R. J. Staniewicz; A. Romero; M. Broussely; J. M. Bodet; J. Labat
Estimating aquifer channel recharge using optical data interpretation.
Recharge through intermittent and ephemeral stream channels is believed to be a primary aquifer recharge process in arid and semiarid environments. The intermittent nature of precipitation and flow events in these channels, and their often remote locations, makes direct flow and loss measurements difficult and expensive. Airborne and satellite optical images were interpreted to evaluate aquifer recharge due to stream losses on the Frio River in south-central Texas. Losses in the Frio River are believed to be a major contributor of recharge to the Edwards Aquifer. The results of this work indicate that interpretation of readily available remote sensing optical images can offer important insights into the spatial distribution of aquifer recharge from losing streams. In cases where upstream gauging data are available, simple visual analysis of the length of the flowing reach downstream from the gauging station can be used to estimate channel losses. In the case of the Frio River, the rate of channel loss estimated from the length of the flowing reach at low flows was about half of the loss rate calculated from in-stream gain-loss measurements. Analysis based on water-surface width and channel slope indicated that losses were mainly in a reach downstream of the mapped recharge zone. The analysis based on water-surface width, however, did not indicate that this method could yield accurate estimates of actual flow in pool and riffle streams, such as the Frio River and similar rivers draining the Edwards Plateau. PMID:21434908
Walter, Gary R; Necsoiu, Marius; McGinnis, Ronald
Seasonal variation in natural recharge of coastal aquifers
NASA Astrophysics Data System (ADS)
Many coastal zones around the world have irregular precipitation throughout the year. This results in discontinuous natural recharge of coastal aquifers, which affects the size of freshwater lenses present in sandy deposits. Temperature data for the period 1960-1990 from LocClim (local climate estimator) and those obtained from the Intergovernmental Panel on Climate Change (IPCC) SRES A1b scenario for 2070-2100, have been used to calculate the potential evapotranspiration with the Thornthwaite method. Potential recharge (difference between precipitation and potential evapotranspiration) was defined at 12 locations: Ameland (The Netherlands), Auckland and Wellington (New Zealand); Hong Kong (China); Ravenna (Italy), Mekong (Vietnam), Mumbai (India), New Jersey (USA), Nile Delta (Egypt), Kobe and Tokyo (Japan), and Singapore. The influence of variable/discontinuous recharge on the size of freshwater lenses was simulated with the SEAWAT model. The discrepancy between models with continuous and with discontinuous recharge is relatively small in areas where the total annual recharge is low (258-616 mm/year); but in places with Monsoon-dominated climate (e.g. Mumbai, with recharge up to 1,686 mm/year), the difference in freshwater-lens thickness between the discontinuous and the continuous model is larger (up to 5 m) and thus important to consider in numerical models that estimate freshwater availability.
Mollema, Pauline N.; Antonellini, Marco
Laboratory Analyses Of Basaltic Dunes In The Ka'u Desert Of Hawaii And Implications For Understanding Dark Dunes On Mars
NASA Astrophysics Data System (ADS)
Dark dunes are the dominant aeolian bedforms on Mars and consist of ancient volcanic ashes and reworked basaltic lavas. Basaltic dunes are rare on Earth and only occur in limited areas, such Hawaii. Because the Hawaiian dunes are composed of reworked basaltic sediments transported by eolian processes, they are a promising subject matter of analogy studies. Samples of dark dune sands, ash, and tephra collected in Hawaii's Ka'u Desert were collected during field trips in summer 2009 and 2010. They were analyzed by a variety of laboratory methods, including spectral, microscope, and microprobe investigations, in order examine their detailed mineralogical composition and constitution. We then compared the results to the eolian dunes on Mars. Sand samples were collected from three different dark dunes in Ka'u Desert: a large, vegetated, parabolic dune, a falling dune, and a large climbing dune. Tephra from the phreatic eruption that began in March 2008 was collected over a two year period using sample collectors placed at different locations downwind of Kilauea caldera. Analyses of these samples allow us to determining the initial composition, grain shape, and grain size of probable source materials. The visible and near-infrared reflectance spectra of the samples were acquired for the 0.5 to 2.5�m range. The overall spectral shape of the dune sand samples indicates a mineralogical correlation between Martian and terrestrial dune sands indicating a similar volcanic origin of the sediments. The spectra of the Hawaiian samples reveal some aqueous alteration, which is probably related to hydrated amorphous silica. Initial microscope and microprobe analyses reveal a high amount of volcanic glass and rock fragments in the samples, followed by olivine, feldspars, and pyroxene. Vitric particles that dominate the majority of the dune samples indicate in situ material accumulation following larger phreatic eruptions. The top coarse-grained layer of the climbing dune comprises a higher amount of rock fragments, indicating that these sands originate from reworked lava and were deposited in a subsequent dune formation phase (see also Craddock et al., this conference). We will present the comparison of Martian, terrestrial and library spectra, determine grain shape and grain size, and propose possible sediment sources, transport mechanisms, and development of the dune material.
Tirsch, D.; Craddock, R. A.; Nanson, G.; Tooth, S.; Langhans, M.
Spectral analysis of dark dunes sands of Ka'u Desert (Hawaii) with regard to their applicability as terrestrial analogs to Martian dunes
NASA Astrophysics Data System (ADS)
Dark basaltic dunes represent the majority of Martian eolian bedforms. However, on Earth there are only few places where basaltic dunes can be found. Is has been suggested that the Marian dunes sands are volcanic in origin because their mineralogical composition consists of pyroxene and olivine. The dark dunes in Ka'u Desert on the Big Island of Hawaii are located on the western flank of Kilauea volcano. The dark sands are derived from volcanic ash and reworked pyroclastic material. Thus, the Hawaiian dark sand dunes could be an adequate analog to Martian dunes, particularly for testing the hypothesis of volcanic origin and to determine basic spectral characteristics that may be associated with differences in grain size and chemistry indicative of maturity and transport distances. Samples of different dark dunes in Ka'u Desert were collected during a field trip in summer 2009. We measured the samples with an ASD field spectrometer in a laboratory. We compared the terrestrial spectra with typical OMEGA and CRISM near-infrared spectra of different Martian dark dune fields. The overall spectral shape of the terrestrial spectra reflects a basaltic composition of the sands fairly similar to that of Martian dunes, dominated by olivine. These rock-forming minerals form as the lava cools, and are commonly found in basaltic volcanic ash. The correlation in mineralogical composition of terrestrial and Martian dunes hints to a similar origin of the dark sands on Mars and Earth. Since some terrestrial spectra show a beginning aqueous alteration of the dark sands these samples could be used to analyse alteration features of Martian dark dunes.
Tirsch, Daniela; Jaumann, Ralf; Craddock, Robert A.
Rechargeable Magnesium Batteries: Low-Cost Rechargeable Magnesium Batteries with High Energy Density
BEEST Project: Pellion Technologies is developing rechargeable magnesium batteries that would enable an EV to travel 3 times farther than it could using Li-ion batteries. Prototype magnesium batteries demonstrate excellent electrochemical behavior; delivering thousands of charge cycles with very little fade. Nevertheless, these prototypes have always stored too little energy to be commercially viable. Pellion Technologies is working to overcome this challenge by rapidly screening potential storage materials using proprietary, high-throughput computer models. To date, 12,000 materials have been identified and analyzed. The resulting best materials have been electrochemically tested, yielding several very promising candidates.
Rechargeable wireless EMG sensor for prosthetic control.
Surface electrodes in modern myoelectric prosthetics are often embedded in the prosthesis socket and make contact with the skin. These electrodes detect and amplify muscle action potentials from voluntary contractions of the muscle in the residual limb and are used to control the prosthetic's movement and function. There are a number of performance-related deficiencies associated with external electrodes including the maintenance of sufficient electromyogram (EMG) signal amplitude, extraneous noise acquisition, and proper electrode interface maintenance that are expected to be improved or eliminated using the proposed implanted sensors. This research seeks to investigate the design components for replacing external electrodes with fully-implantable myoelectric sensors that include a wireless interface to the prosthetic limbs. This implanted technology will allow prosthetic limb manufacturers to provide products with increased performance, capability, and patient-comfort. The EMG signals from the intramuscular recording electrode are amplified and wirelessly transmitted to a receiver in the prosthetic limb. Power to the implant is maintained using a rechargeable battery and an inductive energy transfer link from the prosthetic. A full experimental system was developed to demonstrate that a wireless biopotential sensor can be designed that meets the requirements of size, power, and performance for implantation. PMID:21095801
Lichter, P A; Lange, E H; Riehle, T H; Anderson, S M; Hedin, D S
Wearable textile battery rechargeable by solar energy.
Wearable electronics represent a significant paradigm shift in consumer electronics since they eliminate the necessity for separate carriage of devices. In particular, integration of flexible electronic devices with clothes, glasses, watches, and skin will bring new opportunities beyond what can be imagined by current inflexible counterparts. Although considerable progresses have been seen for wearable electronics, lithium rechargeable batteries, the power sources of the devices, do not keep pace with such progresses due to tenuous mechanical stabilities, causing them to remain as the limiting elements in the entire technology. Herein, we revisit the key components of the battery (current collector, binder, and separator) and replace them with the materials that support robust mechanical endurance of the battery. The final full-cells in the forms of clothes and watchstraps exhibited comparable electrochemical performance to those of conventional metal foil-based cells even under severe folding-unfolding motions simulating actual wearing conditions. Furthermore, the wearable textile battery was integrated with flexible and lightweight solar cells on the battery pouch to enable convenient solar-charging capabilities. PMID:24164580
Lee, Yong-Hee; Kim, Joo-Seong; Noh, Jonghyeon; Lee, Inhwa; Kim, Hyeong Jun; Choi, Sunghun; Seo, Jeongmin; Jeon, Seokwoo; Kim, Taek-Soo; Lee, Jung-Yong; Choi, Jang Wook
Rechargeable thin-film lithium batteries
Rechargeable thin-film batteries consisting of lithium metal anodes, an amorphous inorganic electrolyte, and cathodes of lithium intercalation compounds have been fabricated and characterized. These include Li-TiS{sub 2}, Li-V{sub 2}O{sub 5}, and Li-Li{sub x}Mn{sub 2}O{sub 4} cells with open circuit voltages at full charge of about 2.5 V, 3.7 V, and 4.2 V, respectively. The realization of these robust cells, which can be cycled thousands of times, was possible because of the stability of the amorphous lithium electrolyte, lithium phosphorus oxynitride. This material has a typical composition of Li{sub 2.9}PO{sub 3.3}N{sub 0.46}and a conductivity at 25 C of 2 {mu}S/cm. The thin-film cells have been cycled at 100% depth of discharge using current densities of 5 to 100 {mu}A/cm{sup 2}. Over most of the charge-discharge range, the internal resistance appears to be dominated by the cathode, and the major source of the resistance is the diffusion of Li{sup +} ions from the electrolyte into the cathode. Chemical diffusion coefficients were determined from ac impedance measurements.
Bates, J.B.; Gruzalski, G.R.; Dudney, N.J.; Luck, C.F.; Yu, X.
Electrolyte for laminated polymer lithium rechargeable battery
NASA Astrophysics Data System (ADS)
Proposed thin film battery is comprised of a polymer-lithium ion cell material with barrier-layer packaging and mechanical reinforcing layers. A semi-solid/ solid electrolyte and a mesoporous polymer separator are sandwiched in between of anode and cathode. A composite film with a carbon nanotube (CNT) network serves as the anode and a mesoporous transitional metal oxide LixCoO2 as the cathode, where porous metal sheets serve as the current collector. The CNT network fabrics have high in-plane tensile strength. LiCoO2 is used as the cathode, because the Co atoms do not migrate to Li layers, so that cathode does not generate flammable gases during charging that create safety problems. Merit of this study is using the porous metal sheet, which is flexible, lightweight, low electric resistance, high strength and strong stability in alkaline solution. This paper presented development of electrolyte for laminated polymer lithium rechargeable battery. Two-type electrolytes, semi-solid and solid, were attempted; high ionic conductivity of Li ion electrolytes was achieved.
Xu, Chunye; Ma, Chao; Taya, Minoru
Organic electrolyte for use in a lithium rechargeable electrochemical cell and lithium rechargeable electrochemical cell including said organic electrolyte
This invention relates in general to use of an organic electrolyte in a lithium rechargeable electrochemical cell and to a lithium rechargeable electrochemical cell including said electrolyte; and, in particular, to the use of 1 to 2 mol\\/dm³ LiAsF� in dimethylcarbonate (DMC) or 1 to 2 mol\\/dm³ LiAsF� in (DMC) mixtures with methyl formate (MF) in which the mass percent
E. J. Plichta; S. M. Slane; M. Salomon
Sedimentological, Mineralogical and Geochemical Characterization of Sand Dunes in Saudi Arabia
NASA Astrophysics Data System (ADS)
Sedimentological, mineralogical, morphological and geochemical studies of sand dunes from ten locations in Saudi Arabia were conducted in order to determine the differences between them and to find out the provenance and tectonic setting of these sand dunes. Sixty seven samples were collected from different sand dunes types ranging in morphology from linear, barchans, parabolic to stars dunes. In overall, the sand dunes are fine to coarse grained mean grain size, moderately sorted, near symmetrical skewness with mesokurtic distribution characterized sand dunes in most locations. The sand dunes grains are subrounded in all locations except in the Red sea, Qassim, central Arabia and the eastern province which showed sub-angular grains. The main mineral compositions of studied aeolian sand dunes are quartz, feldspar, calcite, and mica. Quartz is the dominant mineral in locations with significant amount of feldspars and mica in Najran, Red sea and Central Arabia locations. Moreover, calcite is present in Sakaka and NW Empty Quarter (Jafurah). Basement related sand dunes in Najran, Central Arabia and Red sea locations are sub-mature in terms of their mineralogical maturity. Whereas, sand dunes in other locations are texturally mature except those from the Red sea which showed sub-mature sand. The sands are classified as quartz arenite, except in the basement related sand dunes in Najran, central Arabia and the Red sea are ranging from sub-arkose, sub-litharenite and lithraenite. Morphologically, parallel to sub-parallel sand ridges with NE-SW orientation occurred in east and north parts of Empty Quarter (Najran and Jafurah) and NW-SE orientation in Dahna and Nafud deserts in central and north regions of Saudi Arabia. Parabolic sand dunes characterized the Nafud desert (Hail, Sakaka, Tayma locations). Barchans and star sand dunes characterize the Empty Quarter (Jafurah). Major, trace, and rare earth elements studies were carried out to determine the composition, provenance and tectonic history of the sand dunes. Geochemical analysis indicated that most of sand dunes are quartz arenite type, except in the Red sea, basement related central Saudi Arabia and Najran areas, the sand dunes are sub-arkoses, sub-litharenite and litharenite. The concentration of major,trace and rare elements showed active continental margins as a tectonic setting of Red sea, basement related Najran and central Arabia sand dune. In contrast, passive continental margins for the other locations. The distribution of major, trace and rare earth elements showed similarity in chemical composition between basement related sand dunes in Red sea, Najran and central Arabia.
Benaafi, Mohammed; Abdullatif, Osman
Dunes and Microdunes on Venus: Why Were So Few Found in the Magellan Data?
NASA Technical Reports Server (NTRS)
A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle I images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel reflections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be the most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.
Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven
Dunes and microdunes on Venus: Why were so few found in the Magellan data?
NASA Technical Reports Server (NTRS)
A search through cycle 1, 2, and 3 Magellan radar data covering 98% of the surface of Venus revealed very few dunes. Only two possible dune fields and several areas that may contain microdunes smaller than the resolution of the images (75 m) were identified. The Aglaonice dune field was identified in the cycle 1 images by the specular returns characteristic of dune faces oriented perpendicular to the radar illumination. Cycle 1 and 2 data of the Fortuna-Meshkenet dune field indicate that there has been no noticeable movement of the dunes over an 8-month period. The dunes, which are oriented both parallel and perpendicular to the radar illumination, appear to be dark features on a brighter substrate. Bright and dark patches that were visible in either cycle 1 or 2 data, but not both, allowed identification of several regions in the southern part of Venus that may contain microdunes. The microdunes are associated with several parabolic crater deposits in the region and are probably similar to those formed in wind tunnel experiments under Venus-like conditions. Bragg scattering and/or subpixel relfections from the near-normal face on asymmetric microdunes may account for these bright and dark patches. Look-angle effects and the lack of sufficient sand-size particles seem to be most likely reasons so few dunes were identified in Magellan data. Insufficient wind speeds, thinness of sand cover, and difficulty in identifying isolated dunes may also be contributors to the scarcity of dunes.
Weitz, Catherine M.; Plaut, Jeffrey J.; Greeley, Ronald; Saunders, R. Steven
Dates in the desert: Interpreting over 600 luminescence ages from southern African desert dune systems
NASA Astrophysics Data System (ADS)
Over 600 published luminescence ages from southern Africa's extensive continental dunefields and isolated dunes provide a rich record of aeolian system dynamics during the late Quaternary. Included in the Chronologic Database of INQUA's Dunes Atlas project, the majority of records come from sites within linear dune-dominated Kalahari dunefields, with lesser representation of both other dunefields (Namib, West Coast) and dune types ( lunette, transverse, sand ramp). Records are analysed not only for the evidence they provide of Late Quaternary environmental changes over the last 190ka, but in terms of the analytical techniques used, data quality and data presentation, as these all impact on how dune luminescence ages have been, or should be, interpreted as a tool for palaeoenvironmental and dune development studies. Although the sub-continent has yielded a substantial body of dune ages, the spatial unevenness of sampling for dating inhibits our ability to fully interrogate southern Africa's aeolian history. However, we argue that this is not a situation that can simply be improved by adding more and more ages to the full set of records. It is essential to 1) appreciate the spatial differences in dune sensitivities to activation; 2) the relationships of dune activity to potential changes in hydrological and other activity controls, and 3) establish better tools and approaches for analysing a rich but presently environmentally ambiguous record of dune accumulation.
Thomas, David; Burrough, Sallie
Episodic Late Holocene dune movements on the sand-sheet area, Great Sand Dunes National Park and Preserve, San Luis Valley, Colorado, USA
NASA Astrophysics Data System (ADS)
The Great Sand Dunes National Park and Preserve (GSDNPP) in the San Luis Valley, Colorado, contains a variety of eolian landforms that reflect Holocene drought variability. The most spectacular is a dune mass banked against the Sangre de Cristo Mountains, which is fronted by an extensive sand sheet with stabilized parabolic dunes. Stratigraphic exposures of parabolic dunes and associated luminescence dating of quartz grains by single-aliquot regeneration (SAR) protocols indicate eolian deposition of unknown magnitude occurred ca. 1290-940, 715 � 80, 320 � 30, and 200-120 yr ago and in the 20th century. There are 11 drought intervals inferred from the tree-ring record in the past 1300 yr at GSDNPP potentially associated with dune movement, though only five eolian depositional events are currently recognized in the stratigraphic record. There is evidence for eolian transport associated with dune movement in the 13th century, which may coincide with the "Great Drought", a 26-yr-long dry interval identified in the tree ring record, and associated with migration of Anasazi people from the Four Corners areas to wetter areas in southern New Mexico. This nascent chronology indicates that the transport of eolian sand across San Luis Valley was episodic in the late Holocene with appreciable dune migration in the 8th, 10-13th, and 19th centuries, which ultimately nourished the dune mass against the Sangre de Cristo Mountains.
Forman, S. L.; Spaeth, M.; Mar�n, L.; Pierson, J.; G�mez, J.; Bunch, F.; Valdez, A.
Estimated Infiltration, Percolation, and Recharge Rates at the Rillito Creek Focused Recharge Investigation Site, Pima County, Arizona
A large fraction of ground water stored in the alluvial aquifers in the Southwest is recharged by water that percolates through ephemeral stream-channel deposits. The amount of water currently recharging many of these aquifers is insufficient to meet current and future demands. Improving the understanding of streambed infiltration and the subsequent redistribution of water within the unsaturated zone is fundamental to quantifying and forming an accurate description of streambed recharge. In addition, improved estimates of recharge from ephemeral-stream channels will reduce uncertainties in water-budget components used in current ground-water models. This chapter presents a summary of findings related to a focused recharge investigation along Rillito Creek in Tucson, Arizona. A variety of approaches used to estimate infiltration, percolation, and recharge fluxes are presented that provide a wide range of temporal- and spatial-scale measurements of recharge beneath Rillito Creek. The approaches discussed include analyses of (1) cores and cuttings for hydraulic and textural properties, (2) environmental tracers from the water extracted from the cores and cuttings, (3) seepage measurements made during sustained streamflow, (4) heat as a tracer and numerical simulations of the movement of heat through the streambed sediments, (5) water-content variations, (6) water-level responses to streamflow in piezometers within the stream channel, and (7) gravity changes in response to recharge events. Hydraulic properties of the materials underlying Rillito Creek were used to estimate long-term potential recharge rates. Seepage measurements and analyses of temperature and water content were used to estimate infiltration rates, and environmental tracers were used to estimate percolation rates through the thick unsaturated zone. The presence or lack of tritium in the water was used to determine whether or not water in the unsaturated zone infiltrated within the past 40 years. Analysis of water-level and temporal-gravity data were used to estimate recharge volumes. Data presented in this chapter were collected from 1999 though 2002. Precipitation and streamflow during this period were less than the long-term average; however, two periods of significant streamflow resulted in recharge?one in the summer of 1999 and the other in the fall/winter of 2000. Flux estimates of infiltration and recharge vary from less than 0.1 to 1.0 cubic meter per second per kilometer of streamflow. Recharge-flux estimates are larger than infiltration estimates. Larger recharge fluxes than infiltration fluxes are explained by the scale of measurements. Methods used to estimate recharge rates incorporate the largest volumetric and temporal scales and are likely to have fluxes from other nearby sources, such as unmeasured tributaries, whereas the methods used to estimate infiltration incorporate the smallest scales, reflecting infiltration rates at individual measurement sites.
Hoffmann, John P.; Blasch, Kyle W.; Pool, Don R.; Bailey, Matthew A.; Callegary, James B.
Fundamental Concepts of Recharge in the Desert Southwest
NASA Astrophysics Data System (ADS)
Recharge in arid basins does not occur in all years or at all locations. To address the temporal and spatial variability of recharge, one must (1) distinguish between recharge and net infiltration, (2) understand travel time in the unsaturated zone, and (3) comprehend the local- and basin-scale deterministic processes and surficial properties that control net infiltration. Net infiltration is the quantity of water that moves below the zone of surface evapotranspiration whereas recharge is the quantity or process of water entering the saturated zone. Under steady-state conditions, net infiltration becomes recharge unless diverted to an area of spring flow, generally by laterally extensive, low-permeability rock. The rate of net infiltration, thickness of unsaturated zone, and the effective porosity of the flow-pathway control travel time through the unsaturated zone. Net infiltration and recharge vary spatially owing to variations in surface microclimates, root zone and unconsolidated material thickness, faults and fractures, and thickness and hydrologic properties of geologic strata in the unsaturated zone. Although temporal fluctuations in net infiltration diminish with depth, resultant recharge is expected to vary on timescales of days to centuries making decadal-scale climate cycles significant to understanding recharge. Results of model simulations of recharge indicate that net infiltration occurs in less than 5 percent of the area of a typical southwest basin and only when the surface-water supply exceeds the storage capacity of the root zone and evapotranspiration over a fixed period of time. The critical components controlling net infiltration and recharge are precipitation, as rain or snow (and snow accumulation and melt); infiltration and water storage capacity of the overlying soil (within the zone of evapotranspiration); potential and actual evapotranspiration; and bedrock permeability. In the desert Southwest, potential evapotranspiration exceeds precipitation on a yearly basis. However, on shorter time scales and in certain areas of a basin, precipitation and (or) snowmelt exceed the infiltration capacity of the soil and becomes runoff or exceed the storage capacity of the soil and becomes runoff in shallow soils or percolates below the root zone in deeper soils. A method to simulate the spatial and temporal variability of net infiltration was developed using a deterministic water-balance model and extensive GIS coverages. The GIS coverages include a digital elevation model and maps of geology, soils, vegetation, precipitation, and air temperature. Other required surficial properties for the model, such as permeability, porosity, and water-retention functions, have been calculated from associated data sets. The deterministic model identifies the areas and climatic conditions that allow for excess water, quantifies the amount of water available either as runoff or in-place recharge, and allows inter-basin comparison of recharge mechanisms (i.e. mountain front, mountain block, ephemeral stream) and potential recharge for current, wetter, and drier climates. Travel time through the unsaturated zone can be estimated if unsaturated zone thickness and permeability data are available. The model, which uses a monthly time step, is being used to evaluate the role of decadal-scale climate cycles (El Ni�o/La Ni�a and the Pacific Decadal Oscillation) and recharge potential at a pixel scale (generally 30 - 90 meters) across the entire desert Southwest.
Flint, A. L.; Flint, L. E.; Blainey, J. B.; Hevesi, J. A.
Evidence for sensitivity of dune wetlands to groundwater nutrients.
Dune slacks are seasonal wetlands, high in biodiversity, which experience considerable within-year and between-year variations in water-table. They are subject to many pressures including climate change, land use change and eutrophication. Despite their biological importance and the threats facing them, the hydrological and nutrient parameters that influence their soil properties and biodiversity are poorly understood and there have been no empirical studies to date testing for biological effects in dune systems resulting from groundwater nutrients at low concentrations. In this study we examined the impact of groundwater nutrients on water chemistry, soil chemistry and vegetation composition of dune slacks at three distance classes (0-150m, 150-300m, 300-450m) away from known (off-site) nutrient sources at Aberffraw dunes in North Wales, whilst accounting for differences in water-table regime. Groundwater nitrate and dissolved inorganic nitrogen (DIN) and soil nitrate and nitrite all had significantly higher concentrations closest to the nutrient source. Multivariate analysis showed that although plant species composition within this site was primarily controlled by water table depth and water table fluctuation, nitrogen from groundwater also influenced species composition, independently of water table and soil development. A model containing all hydrological parameters explained 17% of the total species variance; an additional 7% was explained following the addition of NO3 to this model. Areas exposed to elevated, but still relatively low, groundwater nutrient concentrations (mean 0.204mg/L+/-0.091 of DIN) had greater abundance of nitrophilous species and fewer basipholous species than in areas with lower concentrations. This shows that clear biological impact occurs below previously suggested DIN thresholds of 0.20-0.40 (mg/L). PMID:24846404
Rhymes, Jennifer; Wallace, Hilary; Fenner, Nathalie; Jones, Laurence
Comment on ``Minimal size of a barchan dune''
NASA Astrophysics Data System (ADS)
It is now an accepted fact that the size at which dunes form from a flat sand bed as well as their �minimal size� scales on the flux saturation length. This length is by definition the relaxation length of the slowest mode toward equilibrium transport. The model presented by Parteli, Dur�n, and Herrmann [Phys. Rev. E 75, 011301 (2007)] predicts that the saturation length decreases to zero as the inverse of the wind shear stress far from the threshold. We first show that their model is not self-consistent: even under large wind, the relaxation rate is limited by grain inertia and thus cannot decrease to zero. A key argument presented by these authors comes from the discussion of the typical dune wavelength on Mars (650 m) on the basis of which they refute the scaling of the dune size with the drag length evidenced by Claudin and Andreotti [Earth Planet. Sci. Lett. 252, 30 (2006)]. They instead propose that Martian dunes, composed of large grains (500?m) , were formed in the past under very strong winds. We emphasize that this saltating grain size, estimated from thermal diffusion measurements, is far from straightforward. Moreover, the microscopic photographs taken by the rovers on Martian Aeolian bedforms show a grain size of 87�25?m together with hematite spherules at millimeter scale. As those so-called �blueberries� cannot be entrained more frequently than a few hours per century, we conclude that the saltating grains on Mars are the small ones, which gives a second strong argument against the model of Parteli
Andreotti, B.; Claudin, P.
Comment on "Minimal size of a barchan dune".
It is now an accepted fact that the size at which dunes form from a flat sand bed as well as their "minimal size" scales on the flux saturation length. This length is by definition the relaxation length of the slowest mode toward equilibrium transport. The model presented by Parteli, Dur�n, and Herrmann [Phys. Rev. E 75, 011301 (2007)] predicts that the saturation length decreases to zero as the inverse of the wind shear stress far from the threshold. We first show that their model is not self-consistent: even under large wind, the relaxation rate is limited by grain inertia and thus cannot decrease to zero. A key argument presented by these authors comes from the discussion of the typical dune wavelength on Mars (650 m) on the basis of which they refute the scaling of the dune size with the drag length evidenced by Claudin and Andreotti [Earth Planet. Sci. Lett. 252, 30 (2006)]. They instead propose that Martian dunes, composed of large grains (500 microm), were formed in the past under very strong winds. We emphasize that this saltating grain size, estimated from thermal diffusion measurements, is far from straightforward. Moreover, the microscopic photographs taken by the rovers on Martian Aeolian bedforms show a grain size of 87+/-25 microm together with hematite spherules at millimeter scale. As those so-called "blueberries" cannot be entrained more frequently than a few hours per century, we conclude that the saltating grains on Mars are the small ones, which gives a second strong argument against the model of Parteli. PMID:18233886
Andreotti, B; Claudin, P
Soins des patients atteints d�une mucoviscidose
R�sum�La mucoviscidose, la maladie p�diatrique autosomique h�r�ditaire la plus fr�quente, n�atteint plus uniquement des enfants, car son traitement moderne a permis aux patients de vivre plus longtemps avec une meilleure qualit� de vie. Voici plus de 16 ans, l�identification du g�ne responsable et de la mutation la plus fr�quente, ?F508, a suscit� l�espoir g�n�ral d�une gu�rison rapide de cette maladie.
Birgitta Strandvik
Coupling Stormwater Capture and Managed Aquifer Recharge
NASA Astrophysics Data System (ADS)
We are quantifying the performance of a system that couples stormwater capture and managed aquifer recharge (MAR). Our field site is a working ranch in the Pajaro Valley, central coastal California, where runoff from ~125 acres of farmed and grazed land is directed into a 2.5-acre infiltration basin. Stormwater captured for MAR at this site would otherwise be routed off the property and eventually into the ocean. We instrumented the site prior to the start of the 2013 water year (1 October 2012) to measure local precipitation, total inflow to the basin, and point-specific infiltration rates across the bottom of the basin using heat as a tracer. We also deployed sediment measurement and collection instruments to quantify the amount, texture, and biochemical nature of sediment accumulating in the basin, and to evaluate associated maintenance requirements for the system. The 2013 water year was relatively dry, with total precipitation less than 50% of the long-term average for this region; most of this precipitation occurred in December 2012. Water level and flow records indicate 17 distinct rain events that generated runoff, most early in the water year. The total inflow to the infiltration basin was 4.1 x 104 m3, equivalent to ~33 ac-ft. During a water year with average precipitation, it appears that this system could collect 80-100 ac-ft of runoff. There was up to 10 cm of sediment accumulation in some parts of the infiltration basin by the end of the rainy season. Sediment samples collected at the end of the season are being processed for analysis of sediment distribution and character. Thermal data are being analyzed to calculate spatial and temporal variations in infiltration rates across the basin. These data will be combined to assess the efficacy of coupling stormwater capture and MAR, and can guide future projects in this region of high groundwater demand and limited resources.
Beganskas, S.; Hill, C. L.; Fisher, A. T.; Los Huertos, M.
Interdisciplinary Research Produces Results in the Understanding of Planetary Dunes
NASA Astrophysics Data System (ADS)
Second International Planetary Dunes Workshop: Planetary Analogs�Integrating Models, Remote Sensing, and Field Data; Alamosa, Colorado, 18-21 May 2010; Dunes and other eolian bed forms are prominent on several planetary bodies in our solar system. Despite 4 decades of study, many questions remain regarding the composition, age, and origins of these features, as well as the climatic conditions under which they formed. Recently acquired data from orbiters and rovers, together with terrestrial analogs and numerical models, are providing new insights into Martian sand dunes, as well as eolian bed forms on other terrestrial planetary bodies (e.g., Titan). As a means of bringing together terrestrial and planetary researchers from diverse backgrounds with the goal of fostering collaborative interdisciplinary research, the U.S. Geological Survey (USGS), the Carl Sagan Center for the Study of Life in the Universe, the Desert Research Institute, and the U.S. National Park Service held a workshop in Colorado. The small group setting facilitated intensive discussion of problems and issues associated with eolian processes on Earth, Mars, and Titan.
Titus, Timothy N.; Hayward, Rosalyn Kay; Bourke, Mary C.
Artificial-Recharge Experiments and Operations on the Southern High Plains of Texas and New Mexico
Experiments using highly turbid water from playa lakes for injection into the Ogallala Formation have resulted in greatly decreased yield of the recharge wells, Recharge of ground or surface water of good quality has indicated, however, that injection through wells is an effective method of recharging the aquifer. Water that is slightly turbid can be successfully injected for a period of time, but generally results in constantly declining yields and capacity for recharge. Redevelopment through pumping and surging significantly prolongs the life of recharge wells under some conditions. Surface spreading is little practiced on the High Plains, but locally may be a feasible means of artificial recharge.
Brown, Richmond F.; Signor, Donald C.
Development and setting of the Alcudia Bay beach-dune system (Mallorca, Spain)
NASA Astrophysics Data System (ADS)
The beach-dune system of Alcudia Bay is located in the north of the island of Mallorca. The system includes both simple and compound parabolic dunes formed by N to NNE winds and is made up of two dune areas with different dynamics: 1) the northern area, where, despite the fact that the source of beach sediment is from the south, dunes are formed by northerly winds and develop a narrow and linear barrier which separates a marsh from the bay; and 2) the southern area, where complex parabolic dunes formed by north-northeasterly winds, prograde south-southwest landward extending several kilometers inland. The broad pattern of the dunefield size is limited to the southeast by a mountain range and to the west by the effects of a topographic corridor, oriented north-south, which channels the prevailing northerly wind, causing a southward dune progression and limiting the westward extension of the dunefield.
Servera, Jaume; Gelabert, Bernad�; Rodr�guez-Perea, Antonio
Fate of human viruses in groundwater recharge systems
The overall objective of this research program was to determine the ability of a well-managed tertiary effluent-recharge system to return virologically acceptable water to the groundwater aquifer. The study assessed the quality of waters renovated by indigenous recharge operations and investigated a number of virus-soil interrelationships. The elucidation of the interactions led to the establishment of basin operating criteria for optimizing virus removal. Raw influents, chlorinated tertiary effluents, and renovated wastewater from the aquifer directly beneath a uniquely designed recharge test basin were assayed on a weekly basis for the presence of human enteroviruses and coliform bacteria. High concentrations of viruses were routinely isolated from influents but were isolated only on four occasions from tertiary-treated sewage effluents. In spite of the high quality effluent being recharged, viruses were isolated from the groundwater observation well, indicating their ability to penetrate the unsaturated zone. Results of poliovirus seeding experiments carried out in the test basin clearly indicated the need to operate recharge basins at low (e.g. 1 cm/h) infiltration rates in areas having soil types similar to those found at the study site. The method selected for reducing the test basin infiltration rate involved clogging the basin surface with settled organic material from highly turbid effluent. Alternative methods for slowing infiltration rates are discussed in the text.
Vaughn, J.M.; Landry, E.F.
Estimating infiltration recharge using a response function model
NASA Astrophysics Data System (ADS)
Rainfall infiltration influences both the quantity and quality of groundwater systems. The knowledge of the process of infiltration recharge is of great importance to the management of groundwater systems and the hydraulically connected streams. In this study, a response function model is developed to estimate soil water flux at the water table or the process of infiltration recharge from rainfall and evaporation data. The gamma probability density function is modified to represent the travel time distribution of infiltrating water by rainfall events. The travel time distribution is used to determine the recharge process according to the effective infiltration of a rainfall event. The effective infiltration is the amount of soil water pushed down into groundwater by infiltrating water of a rainfall event and is evaluated based on the vadose-zone soil water balance. Superposition is employed to compute the recharge rate produced by a sequence of rainfall events. Estimations of soil water flux at different groundwater depths are compared with lysimetric observations in the field. Good agreements between the estimated and observed results confirm the reliability of the response function model for predicting infiltration recharge processes.
Wu, Jinquan; Zhang, Renduo; Yang, Jinzhong
Lichens as indicators of a perturbation\\/stability gradient in the Asperillo dunes, SW spain
In the asperillo dune system, Southwest Spain, lichen vegetation covering the dune sand, has a low species diversity but is\\u000a an important component of the perennial vegetation, providing stability, nutrients, and moisture to the soil layer. The Asperillo\\u000a dunes harbour (1) natural ecosystems, (2) disturbed systems affected by forestry activities where the natural vegetation is\\u000a eliminated, and (3) pine forest
J. B. Gallego Fern�ndez; M. C. D�az Barradas
Defrosting Polar Dunes--Dark Spots and Wind Streaks
NASA Technical Reports Server (NTRS)The first time that the Mars Global Surveyor (MGS) Mars Orbiter Camera (MOC)team saw dark spots on defrosting dune surfaces was in August and September of 1998. At that time, it was the north polar seasonal frost cap that was subliming away (more recent images from 1999 have shown the south polar frosts). This picture (above) shows a small portion of the giant dune field that surrounds the north polar region, as it appeared on August 23, 1998. At the time, it was early northern spring and the dunes were still covered with winter frost. Dark spots had appeared on the north polar dunes, and many of them exhibited a radial or semi-radial pattern of dark streaks and streamers. At first, there was speculation that the streaks indicated that the defrosting process might somehow involve explosions! The dark spots seemed to resemble small craters with dark, radial ejecta. It seemed possible that frozen carbon dioxide trapped beneath water ice might somehow heat up, turn to gas, expand, and then 'explode' in either a small blast or at least a 'puff' of air similar to that which comes from the blowhole of a surfacing whale or seal. The image shown here changed the earlier impression. The dark spots and streaks do not result from explosions. The spots--though not well understood--represent the earliest stages of defrosting on the sand dunes. The streaks, instead of being caused by small explosions, are instead the result of wind. In this picture, the fine, dark streaks show essentially identical orientations from spot to spot (e.g., compare the spots seen in boxes (a) and (b)). Each ray of dark material must result from wind blowing from a particular direction--for example, all of the spots in this picture exhibit a ray that points toward the upper left corner of the image, and each of these rays indicates the same wind regime. Each spot also has a ray pointing toward the lower right and top/upper-right. These, too, must indicate periods when the wind was strong enough to move materials, consistently, in only one direction. The sand that makes up the north polar dunes is dark. Each spot and streak is composed of the dune sand. The bright surfaces are all covered with frost. This picture is located near 76.9oN, 271.2oW, in the north polar sand sea. Illumination is from the lower left. The 200 meter scale also indicates a distance of 656 feet. Malin Space Science Systems and the California Institute of Technology built the MOC using spare hardware from the Mars Observer mission. MSSS operates the camera from its facilities in San Diego, CA. The Jet Propulsion Laboratory's Mars Surveyor Operations Project operates the Mars Global Surveyor spacecraft with its industrial partner, Lockheed Martin Astronautics, from facilities in Pasadena, CA and Denver, CO.
An agent-based model of dune interactions produces the emergence of patterns in deserts
NASA Astrophysics Data System (ADS)
Crescent-shaped barchan dunes are highly mobile dunes which are ubiquitous on Earth and other solar system bodies. Although they are unstable when considered separately, they form large assemblies in deserts and spatially organize in narrow corridors that extend in the wind direction. Collision of barchans has been proposed as a mechanism to redistribute sand between dunes and prevent the formation of very large dunes. Here we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan fields. We tune the dune field density by changing the sand load/lost ratio and follow the transition between dilute fields, where barchans barely interact, and dense fields, where dune collisions control and stabilize the dune field. In this dense regime, barchans have a small, well-selected size and form flocks: the dune field self-organizes in narrow corridors of dunes, as it is observed in real dense barchan deserts.
G�Nois, Mathieu; Pont, Sylvain Courrech; Hersen, Pascal; Gr�Goire, Guillaume
An agent-based model of dune interactions produces the emergence of patterns in deserts
NASA Astrophysics Data System (ADS)
Crescent-shaped barchan dunes are highly mobile dunes which are ubiquitous on Earth and other solar system bodies. Although they are unstable when considered separately, they form large assemblies in deserts and spatially organize in narrow corridors that extend in the wind direction. Collision of barchans has been proposed as a mechanism to redistribute sand between dunes and prevent the formation of very large dunes. Here, we use an agent-based model with elementary rules of sand redistribution during collisions to access the full dynamics of very large barchan fields. We tune the dune field density by changing the sand load/lost ratio and follow the transition between dilute fields, where barchans barely interact, and dense fields, where dune collisions control and stabilize the dune field. In this dense regime, barchans have a small, well selected size and form flocks: the dune field self-organizes in narrow corridors of dunes, as it is observed in real dense barchan deserts. Simulated dense barchan field, with spatial structuring along the wind direction.
G�nois, M.; Courrech Du Pont, S.
Eolian dune types preserved in the Tensleep Sandstone (Pennsylvanian-Permian), north-central Wyoming
NASA Astrophysics Data System (ADS)
The Tensleep Sandstone is one component of an erg system that prograded southward out of north-central Wyoming from Middle Pennsylvanian to Early Permian time. Each erg advance was temporarily interrupted by regional marine transgression. Interpretation of dune types deposited in these ergs is developed from an analysis of the relative proportions of eolian stratification types comprising foreset strata, geometry and relationships of bounding surfaces, and paleodispersal patterns. Two basic morphologic dune types are inferred: simple dunes and compound crescentic dunes. The simple dunes are dominant and are subdivided into 1-2 km wavelength and 1.0 km saddle-spacing slightly crescentic, and 0.1-0.2 km wavelength straight-crested subtypes based on their first-order bounding surface geometries. Foresets are composed of grainfall and wind-ripple strata; avalanche strata are rare. The compound crescentic dunes had wavelengths of 0.5-1 km and saddle spacings of 0.8 km. Foresets are dominated by avalanche and wind-ripple strata. A morphodynamic classification of the dune types is inferred from considerations deduced from paleodispersal patterns and comparison with paleocirculation models. The simple dunes were demonstrably oblique to some elements of the wind field and less oblique to others. The compound crescentic dunes had a predominantly transverse configuration.
Kerr, Dennis R.; Dott, Robert H.
A second look at western Sinai seif dunes and their lateral migration
Tsoar et al. [Tsoar, H., Blumberg, D.G., Stoler, Y., 2004. Elongation and migration of sand dunes. Geomorphology 57, 293-302.] reported that seif dunes in the western Sinai Desert did not migrate laterally between 1973 and 1999. If the planform sinuosities of the dunes are removed by filtering, spatial averaging, or linear regression, however, it is evident that the dunes did, in fact, migrate laterally roughly 13??m during this 26-year period. The measured migration distance is 1-2 orders of magnitude greater than the rms co-registration error Tsoar et al. determined for the first and last air photos that were used to map the dunes. The western Sinai dunes provide another example demonstrating that linear dunes can migrate laterally, and they illustrate some of the difficulties in documenting systematic lateral motion. Lateral migration of a dune can be important geologically or geomorphologically, even where migration is too slow to detect from repeated topographic surveys. This article explains the wind conditions for the lateral migration of seif dunes in western Sinai and the possible wind occurrences that would not lead to such a migration.
Rubin, D. M.; Tsoar, H.; Blumberg, D. G.
An experimental study of turbulent flow over a low-angle dune
NASA Astrophysics Data System (ADS)
Many large, sand bed alluvial channels are dominated by dunes that possess low-angle lee sides, often <10�, which play a critical role in the transportation of sediment and generation of significant bed form roughness. Despite the fact that these low-angle dunes are very common in such channels many current models of dune flow dynamics are based on bed forms with an angle of repose slip face that generates a zone of permanent separated flow in the dune lee. Study of flow associated with low-angle dunes in the field is inherently difficult since it is usually both hard to measure very near the bed and hard to quantify the nature of turbulence over these bed forms. Results from a detailed scale model experimental study of flow over a low-angle dune, which is based on a prototype dune from the Fraser River, Canada, present a necessary link between flume and field studies and document the origins of macroturbulence associated with these bed forms. Two-dimensional laser Doppler anemometer measurements over a low-angle dune (maximum lower lee side slope = 14�) show that dune morphology exerts a dominant control on the turbulent flow, causing flow deceleration in the lower lee and development of an intermittent layer of shear at the interface with the higher velocity flow above. The scale model confirms that permanent flow separation does not occur over low-angle dunes but, instead, is replaced by a small region (here �7% of the dune wavelength in length) of intermittent flow reversal, which may be present for up to 4% of the time. Shear layers generated along this small zone of decelerated and/or separated flow in the lower lee have a much smaller velocity differential than is characteristic of shear layers generated by flow separation in the lee of angle of repose dunes. Turbulence production associated with low-angle dunes is dominated by eddies generated along this shear layer, which produce highly variable horizontal and vertical velocities and large Reynolds stresses in this region. These results show that macroturbulence associated with low-angle dunes is generated by intermittent separation or shear layer generation due to velocity gradients established in the zone of lee side flow expansion. Velocity profiles and maps of turbulence structure from the scale model are in reasonable agreement with field measurements from low-angle dunes in natural sand bed rivers. These results highlight the need to consider the temporal evolution and intermittency of shear layer behavior, often very near the bed, when interpreting the generation of macroturbulence and dispersal of sediment associated with low-angle dunes.
Best, Jim; Kostaschuk, Ray
Numerical study of turbulent flow over complex aeolian dune fields: The White Sands National Monument
NASA Astrophysics Data System (ADS)
The structure and dynamics of fully developed turbulent flows responding to aeolian dune fields are studied using large-eddy simulation with an immersed boundary method. An aspect of particular importance in these flows is the downwind migration of coherent motions associated with Kelvin-Helmholtz instabilities that originate at the dune crests. These instabilities are responsible for enhanced downward transport of high-momentum fluid via the so-called turbulent sweep mechanism. However, the presence of such structures and their role in determining the bulk characteristics of fully developed dune field sublayer aerodynamics have received relatively limited attention. Moreover, many existing studies address mostly symmetric or mildly asymmetric dune forms. The White Sands National Monument is a field of aeolian gypsum sand dunes located in the Tularosa Basin in southern New Mexico. Aeolian processes at the site result in a complex, anisotropic dune field. In the dune field sublayer, the flow statistics resemble a mixing layer: At approximately the dune crest height, vertical profiles of streamwise velocity exhibit an inflection and turbulent Reynolds stresses are maximum; below this, the streamwise and vertical velocity fluctuations are positively and negatively skewed, respectively. We evaluate the spatial structure of Kelvin-Helmholtz instabilities present in the dune field sublayer (shear length Ls and vortex spacing ?x) and show that ?x=mduneLs, where mdune?7.2 in the different sections considered (for turbulent mixing layers, 7 Anderson, William; Chamecki, Marcelo 2014-01-01
Anderson, William; Chamecki, Marcelo
Hydrogeology of Regional Valley Fill Aquifers with Mountain System Recharge
NASA Astrophysics Data System (ADS)
Groundwater in the North Okanagan was investigated using an integrated physical, geochemical and numerical approach. The North Okanagan Groundwater Characterization and Assessment (NOGWCA) project began with an investigation of the geology and hydrostratigraphy of the North Okanagan region. The Deep Creek and Fortune Creek watersheds were found to contain multiple valley-fill aquifers which are recharged via mountain system recharge (MSR) and direct recharge to unconfined aquifers in the valley bottom. Detailed hydrometric data indicates groundwater recharge within the alluvial fan of Fortune Creek, and discharge to surface water in the lower reaches of Deep Creek. Valley side recharge from the adjacent mountains generates artesian conditions in the valley center. Physical hydrogeological measurements and groundwater and surface water geochemistry were used to determine the overall groundwater flow regime, inter-aquifer exchange and surface-water groundwater interactions. Conservative elements and deuterium/oxygen isotopes were used in a mixing cell model (MCM) approach to assess groundwater flow between aquifers. Efforts to accurately quantify and understand MSR are hampered by sparse data on the geochemical character of bedrock aquifers. Watershed scale recharge estimates and water balances were derived from a regional integrated climate dataset coupled to FEFLOW simulations. The first stage modeled steady state conditions within the main valley center aquifer. Integrated surface water and groundwater modeling is to be carried out in the future. The groundwater flow modeling will contribute to subsequent water management decisions at the watershed scale. Climate change and economic change scenarios will be considered in the integrated surface water and groundwater modeling.
Ping, J.; Nichol, C.; Wei, A.
High (ground) water levels and dune development in central Australia: TL dates from gypsum and quartz dunes around Lake Lewis (Napperby), Northern Territory
NASA Astrophysics Data System (ADS)
An episode of high lake levels prior to the last maximum glaciation has been identified at many localities in wastern Australia. Similar events have been recognized at playa lakes in central Australia, where gypsum dunes along playa margins formed during one or more episodes of high groundwater discharge, with a large influx of calcium sulphate. At Lake Lewis, exposures at two islands show similar sediment sequences: three pedogenic gypcrete layers interbedded with aeolian quartz and gypsum sand horizons form three units within gypsum dunes up to 7 m high. The lowest unit has cliffed edges buried by the upper units, indicating a significant time break. Four TL dates (coarse-grained quartz) show that this lowest unit was deposited at or before 70-80 ka. The middle unit of mixed gypsum and quartz sand capped by gypcrete represents the major phase of gypsum dune formation, and 6 TL dates range from 33 to 46 ka with overlapping error bars. These are slightly younger but statistically similar to TL dates (from 39 to 59 ka) of the shoreline gypsum dune at Lake Amadeus in the same region. The top unit of the two islands, up to 1 m thick, has not yet been well dated. One date is inconsistent with the well dated middle layer below, possibly because of incomplete bleaching, and has been rejected. The other date (17 � 5 ka) is much younger which possibly indicates a minor and local reactivation of old gypsum sediments. At the lake margin, there are quartz dunes overlying the gypsum dunes, and a buried aeolian quartz sand layer occurs in a lake-margin terrace. These represent reactivation of the regional quartz dune field after the major gypsum dune formation. Two consistent TL dates (21 � 4 ka and 23 � 6 ka) indicate that regional dunes were active at about the time of the Last Glacial Maximum.
Chen, X. Y.; Chappell, J.; Murray, A. S.
Study plan for determining recharge rates at the Hanford Site using environmental tracers.
National Technical Information Service (NTIS)
This report presents a study plan for estimating recharge at the Hanford Site using environmental tracers. Past operations at the Hanford Site have led to both soil and groundwater contamination, and recharge is one of the primary mechanisms for transport...
E. M. Murphy J. E. Szercsody
77 FR 8325 - Sixth Meeting: RTCA Special Committee 225, Rechargeable Lithium Batteries and Battery Systems...
Federal Register 2010, 2011, 2012, 2013
...Committee 225, Rechargeable Lithium Batteries and Battery Systems, Small and Medium Size...Committee 225, Rechargeable Lithium Batteries and Battery Systems, Small...15 min). Results of EFB thermal runaway on flightdeck...
Transmission losses, infiltration and groundwater recharge through ephemeral and intermittent streambeds: A review of applied methods
NASA Astrophysics Data System (ADS)
Overview of methods to quantify recharge in ephemeral and intermittent streams.Provides temporal and spatial scales of recharge measured using each method.Identifies gaps in the literature and suggests future directions.
Shanafield, Margaret; Cook, Peter G.
Thin rechargeable batteries for CMOS SRAM memory protection
NASA Astrophysics Data System (ADS)
New rechargeable battery technology is described and compared with classical primary battery back-up of SRAM PC cards. Thin solid polymer electrolyte cells with the thickness of TSOP memory components (1 mm nominal, 1.1 mm max) and capacities of 14 mAh/sq cm can replace coin cells. The SRAM PC cards with permanently installed rechargeable cells and optional electrochromic low battery voltage indicators will free the periodic PC card user from having to 'feed' their PC cards with coin cells and will allow a quick visual check of stored cards for their battery voltage status.
Crouse, Dennis N.
Thin rechargeable batteries for CMOS SRAM memory protection
NASA Technical Reports Server (NTRS)
New rechargeable battery technology is described and compared with classical primary battery back-up of SRAM PC cards. Thin solid polymer electrolyte cells with the thickness of TSOP memory components (1 mm nominal, 1.1 mm max) and capacities of 14 mAh/sq cm can replace coin cells. The SRAM PC cards with permanently installed rechargeable cells and optional electrochromic low battery voltage indicators will free the periodic PC card user from having to 'feed' their PC cards with coin cells and will allow a quick visual check of stored cards for their battery voltage status.
Crouse, Dennis N.
Natural versus Urban dunes along the Emilia-Romagna coast, Northern Adriatic (Italy)
NASA Astrophysics Data System (ADS)
Beach-dune interaction models can be precious tools for land managers and policymakers. However, if the models are inaccurate, land use policies may be designed based on false pretences or assumptions leading to poor land management, long-term erosion and sustainability issues, and increased difficulties in maintaining the dynamic coastal systems. From the literature, it appears that even the most reliable beach-dunes interactions models are not applicable to all coastal systems (Short and Hesp, 1982; Psuty, 1988; Sherman and Bauer, 1993). The study aims to identify the morphological evolution of the Emilia-Romagna coastal dunes according to its natural and "human" characteristics and to classify groups of dunes with similar evolutionary patterns. The coastal area consists essentially of 130 km of low sandy coast, interrupted by vast lagoon areas, harbor jetties and numerous hard coastal defense structures that were built during the first half of the 20th century to protect the Emilia-Romagna coast against erosion. Today about 57% of the littoral is protected by hard defenses, which have modified the morphodynamic characteristics of the beach without inverting the negative coastal evolution's trend. From recent aerial photographs (2011), 62 coastal dunes have been identified and mapped. Furthermore, the dune analysis shows a variability of the "physical characteristics" of coastal-dune systems along the Emilia-Romagna coast. The dune height varies from 1 to 7 meters, the width of the beach and of the active dunes range respectively from 10 to 150 m and from 10 to 65 m. Three main factors may explain the variability of the "physical characteristics": 1- Firstly the frontal dunes may be of different states according to the classification of Hesp (2002) since they correspond to incipient foredunes, well-developed foredunes, blowouts, residual foredunes as well as reactivated relict foredunes, 2- This could also be related to a different orientation of the coastline and foredune's line to the dominant onshore winds and, 3- Human impacts may also explain this variability since most of the dune-beach systems of Emilia-Romagna are characterized by important anthropogenic features that do not adequately describe beach-foredune interactions. A factor analysis of the coastal dunes has allowed formulating hypotheses about their evolutionary trends according to the importance and interference of factors, both natural and anthropic, acting on the beach-dune system. Four groups of dunes have been identified corresponding to natural dunes, semi-anthropic dunes with major natural features, semi-anthropic dunes with major anthropic feature and "urban" dunes. Furthermore, while human activities impede the formation and development of new incipient dunes, other human activities favor the conservation and development of the human-altered foredunes. Hesp, P., 2002: Foredunes and blowouts: initiation, geomorphology and dynamics, Geomorphology, 245-268. Psuty, N. P. 1988. Sediment budget and dune/beach interaction. Journal of Coastal Research Special Issue 3: 1-4. Sherman, D. J., and B. O. Bauer. 1993. Dynamics of beach-dune systems. Progress in Physical Geography 17 (4): 413-447 Short, A. D., and P. A. Hesp. 1982. Wave, beach and dune interactions in South Eastern Australia. Marine Geology 48: 259-284.
Corbau, Corinne; Simeoni, Umberto
Tidal dunes versus tidal bars: The sedimentological and architectural characteristics of compound dunes in a tidal seaway, the lower Baronia Sandstone (Lower Eocene), Ager Basin, Spain
NASA Astrophysics Data System (ADS)
The Lower Eocene Baronia Formation in the Ager Basin is interpreted as a series of stacked compound dunes confined within a tectonically generated embayment or tidal seaway. This differs from the previous interpretation of lower Baronia sand bodies as tidal bars in the front of a delta. The key architectural building block of the succession, the deposit of a single compound dune, forms a 1-3 m-thick, upward coarsening succession that begins with highly bioturbated, muddy, very fine to fine grained sandstone that contains an open-marine Cruziana ichnofacies. This is overlain gradationally by ripple-laminated sandstone that is commonly bioturbated and contains mud drapes. The succession is capped by fine- to coarse-grained sandstones that contain both planar and trough cross-strata with unidirectional or bi-directional paleocurrent directions and occasional thin mud drapes on the foresets. The base of a compound dune is gradational where it migrated over muddy sandstone deposited between adjacent dunes, but is sharp and erosional where it migrated over the stoss side of a previous compound dune. The cross strata that formed by simple superimposed dunes dip in the same direction as the inclined master bedding planes within the compound dune, forming a forward-accretion architecture. This configuration is the fundamental reason why these sandbodies are interpreted as compound tidal dunes rather than as tidal bars, which, in contrast, generate lateral-accretion architecture. In the Baronia, fields of compound dunes generated tabular sandbodies 100s to 1000s of meters in extent parallel to the paleocurrent direction and up to 6 m thick that alternate vertically with highly bioturbated muddy sandstones (up to 10 m thick) that represent the low-energy fringes of the dune fields or periods of high sea level when current speeds decreased. Each cross-stratified sandstone sheet (compound-dune complexes) contains overlapping lenticular "shingles" formed by individual compound dunes, separated by 10-30 cm of bioturbated muddy sandstone, which migrated over each other in an offlapping, progradational fashion. Each compound-dune complex (the best reservoir rock) thins as it downlaps, at average rates of 3-4 m/km in a dip direction. These reservoir units can be comprised of discrete compartments, each formed by a single compound dune, that extend for 500-1000 m in the direction of the current, and are at least 350-600 m wide in a flow-transverse direction. Distinguishing between tidal bars and tidal dunes in an ancient tidal succession can be difficult because both can contain similar cross-bedded facies and have overlapping thicknesses; however, the internal architecture and sandbody orientations are different. Tidal bars have their long axis almost parallel both to the tidal current direction and to the strike of the lateral-accretion master surfaces. In inshore areas, they are bounded by channels and fine upward. Large compound tidal dunes, in contrast, have their crest oriented approximately normal to the tidal currents and contain a forward-accretion architecture. Coeval channels are uncommon within large, sub-tidal dune fields. The above distinctions are very important to reservoir description and modeling, because the long axis of the intra-reservoir compartments in the two cases will be 90� apart.
Olariu, Cornel; Steel, Ronald J.; Dalrymple, Robert W.; Gingras, Murray K.
Late Quaternary stratigraphy and geochronology of the western Killpecker Dunes, Wyoming, USA
New stratigraphic and geochronologic data from the Killpecker Dunes in southwestern Wyoming facilitate a more precise understanding of the dune field's history. Prior investigations suggested that evidence for late Pleistocene eolian activity in the dune field was lacking. However, luminescence ages from eolian sand of ???15,000 yr, as well as Folsom (12,950-11,950 cal yr B.P.) and Agate Basin (12,600-10,700 cal yr) artifacts overlying eolian sand, indicate the dune field existed at least during the latest Pleistocene, with initial eolian sedimentation probably occurring under a dry periglacial climate. The period between ???13,000 and 8900 cal yr B.P. was characterized by relatively slow eolian sedimentation concomitant with soil formation. Erosion occurred between ???8182 and 6600 cal yr B.P. on the upwind region of the dune field, followed by relative stability and soil formation between ???5900 and 2700 cal yr B.P. The first of at least two latest Holocene episodes of eolian sedimentation occurred between ???2000 and 1500 yr, followed by a brief (???500 yr) episode of soil formation; a second episode of sedimentation, occurring by at least ???700 yr, may coincide with a hypothesized Medieval warm period. Recent stabilization of the western Killpecker Dunes likely occurred during the Little Ice Age (???350-100 yr B.P.). The eolian chronology of the western Killpecker Dunes correlates reasonably well with those of other major dune fields in the Wyoming Basin, suggesting that dune field reactivation resulted primarily due to departures toward aridity during the late Quaternary. Similar to dune fields on the central Great Plains, dune fields in the Wyoming Basin have been active under a periglacial climate during the late Pleistocene, as well as under near-modern conditions during the latest Holocene. ?? 2003 University of Washington. All rights reserved.
Mayer, J. H.; Mahan, S. A.
The diversity of aeolian dune forms and their causes - examples from deserts in northern China
NASA Astrophysics Data System (ADS)
In one side the form and size of aeolian sand dunes vary greatly on Earth and it is difficult to project the future form of a particular dune's further development. In the other side the constitution of sand dunes should reflect patterns of interactions between various long-lasting geomorphological processes associated with local, regional and even global environmental conditions. Earlier studies on the dune forms have paid great attention to wind data, sand availability and vegetation coverage but they still cannot precisely explain the occurrence of large variations in dune forms in a single desert like those in northern China. Many dunes in the deserts of northern China are even difficult to be listed in the inventory of dune forms because they are "compound" or "dune chains" consisting of multiple dune generations. Here we present our ongoing investigation of geoenvironmental factors controlling the distributions of sand seas in northern China and the forms of dunes in individual large sand seas, particularly in the Badain Jaran Desert, western Inner Mongolia. Our methods include interpretation of remote sensing data and geomorphological mapping in the field. We conclude that not only aridity but also regional tectonics control the occurrence of large sand seas which occur mainly in endorheic basins with large amount of loose sediments brought in by rivers with head waters in the surrounding mountains. The form of a single dune in northern China may have the potential of recording changes of climate parameters like the directions and strengths of winds, and precipitation although it is strongly influenced by onsite bedrock and local hydrological processes.
Yang, Xiaoping; Zhang, Deguo; Li, Hongwei
Bed load and suspended load contributions to migrating sand dunes in equilibrium
NASA Astrophysics Data System (ADS)
dominate the bed of sand rivers and are of central importance in predicting flow roughness and water levels. The present study has focused on the details of flow and sediment dynamics along migrating sand dunes in equilibrium. Using a recently developed acoustic system (Acoustic Concentration and Velocity Profiler), new insights are obtained in the behavior of the bed and the suspended load transport along mobile dunes. Our data have illustrated that, due to the presence of a dense sediment layer close to the bed and migrating secondary bedforms over the stoss side of the dune toward the dune crest, the near-bed flow and sediment processes are significantly different from the near-bed flow and sediment dynamics measured over fixed dunes. It was observed that the shape of the total sediment transport distribution along dunes is mainly dominated by the bed load transport, although the bed load and the suspended load transport are of the same order of magnitude. This means that it was especially the bed load transport that is responsible for the continuous erosion and deposition of sediment along the migrating dunes. Whereas the bed load is entirely captured in the dune with zero transport at the flow reattachment point, a significant part of the suspended load is advected to the downstream dune depending on the flow conditions. For the two flow conditions measured, the bypass fraction was about 10% for flow with a Froude number (Fr) of 0.41 and 27% for flow with Froude number of 0.51. This means that respectively 90% (for the Fr = 0.41 flow) and 73% (for the Fr = 0.51 flow) of the total sediment load that arrived at the dune crests contributed to the migration of the dunes.
Naqshband, S.; Ribberink, J. S.; Hurther, D.; Hulscher, S. J. M. H.
A dimensionless number describing the effects of recharge and geometry on discharge from simple karstic aquifers
The responses of karstic aquifers to storms are often used to obtain information about aquifer geometry. In general, spring hydrographs are a function of both system geometry and recharge. However, the majority of prior work on storm pulses through karst has not studied the effect of recharge on spring hydrographs. To examine the relative importance of geometry and recharge, we
M. D. Covington; C. M. Wicks; M. O. Saar
Interdune areas of the back-island dune field, North Padre Island, Texas
NASA Astrophysics Data System (ADS)
The small, young (about 100 yrs) back-island dune field on north Padre Island, south Texas, consists of fairly persistant oblique dunes (up to 6 m high) with well-developed interdune areas that grade northwestward to small, ephemeral transverse and barchan dunes with interconnected "interdune" areas, thence sheet sand areas. The subhumid climate is marked by rain associated with frontal systems and tropical storms. Winds are seasonally bimodal�prevailing southeasterly are punctuated by northerly and northwesterly winds with the passage of frontal systems in winter. The entire dune field and individual oblique dunes show a net migration of about 15 m yr -1 to the northwest. The dunes however are on a seasonally reversing track, changing their slipface direction and migration direction with frontal systems. One year of monitoring shows sand transport in the dune-interdune system to be complex and cyclic. During the wind reversals of winter, dunes are very ineffecfive sand traps owing to loss of flow separation, and much sand is lost to the interdune areas. Interdune areas store sand during these wet winter months as a result of the wind reversals and higher moisture content. During the summer, the interdune areas deflate and the dunes build in size. The overall dune field deposit appears to consist of three laterally contiguous zones from southeast to northwest: (1) continuous, climbing oblique dune and interdune deposits; (2) discontinuous lenses of dune sand in overall "interdune layers"; and (3) a chaotic mixture of dune and horizontal deposits of the sheet sand areas. One year's mapping and trenching documents that interdune sedimentary structures are extremely variable laterally and vertically reflecting specific microenvironments within the interdune flat. Wet-surface features consist of current and wave ripples, channel fill, miniature deltas, wrinkle marks, mini-ripples, rills, algae and sand volcanoes. Abundant adhesion structures, rain-impacted ripples, brecciated surfaces and microtopography reflect damp-surface deposits. Dry-surface features are predominately wind ripples; others include small isolated barchan and shadow dunes, organic debris lag surfaces, deflation scours, beetle bioturbation, plant-root structures associated with shadow-dunes, and grainfall from the adjacent dunes. Interdune deposits account for about 40% of the total dune field deposits, which seems reasonable compared to some ancient examples. By virtue of occupying a relative "basin", interdune deposits are selectively preserved compared to dune deposits. In general, interdune sedimentation is enhanced by non-eolian depositional mechanisms, a high water table, early evaporatic cements, and a variable wind regime. The actual thicknesses of individual dune and interdune deposits are less on Padre than ancient examples, reflecting the relative scale of the bedforms. In many respects, sequences of sedimentary structure in Padre Island interdune deposits are typical of ancient, coastal interdune strata, but some marked departures occur. Adhesion structures, relatively rare in some ancient examples but abundant within Padre interdune deposits, seem favored by the small size of dune and interdune area, the climate and a variable wind regime. Penecontemporaneous deformation, absent in Padre interdune deposits but pronounced in some ancient examples, probably reflects dune size and the nature of the deposits. Wavy laminae in ancient interdune deposits probably result from many causes, but seem best represented by modern examples of evaporitic algal/bacterial-formed structures.
Hummel, Gary; Kocurek, Gary
How much liquid water was there on Martian dunes?
NASA Astrophysics Data System (ADS)
Presently, liquid water unlikely to be found on the surface of Mars because of atmospheric pressure/temperature conditions below water's triple-point. However, gullies discovered by Malin and Edgett (2000) suggest that significant amounts of liquid water has flowed on Mars in the recent past. These gullies are among the youngest features on Mars based on the scarcity of cratered gullies (Heldmann et al., 2007) and their superposition on relatively young formations such as dunes. Several hypotheses have been suggested for the formation of gullies: (i) runoff and debris flows with liquid water from groundwater aquifers (Heldmann and Mellon, 2004; Malin et al., 2000), (ii) snow-melt (Christensen, 2003; Dickson et al, 2007), (iii) liquid CO2 breakout (Musselwhite et al., 2001), (iv) melting of near-surface ground ice (< 1 m meter) at high obliquity (Costard et al., 2002), (v) geothermal-heated aquifers (Gaidos, 2001; Hartmann, 2001), (vi) the presence of brines (Knauth et al., 2000; Knauth and Burt, 2003). This study focuses on gully morphologies on the Russell megadune (54.5�S; 12.7�E) and in Kaiser crater (46.2�S; 19.1�E) using High Resolution Imaging Science Experiment (HiRISE) images and Digital Terrain Models (DTM). Gullies on terrestrial sand dunes are rare, and their presence on Mars, as well as their mechanical properties, and the quantity of fluid required for their formation currently remain misunderstood. Based on the scenario of ground ice melting in a periglacial environment, we propose to test the hypothesis that Martian gullies on dunes were triggered by the presence of liquid water. The calculated results for Martian gullies are consistent with terrestrial studies on debris flows. Based on a morphological description and on the estimated physical parameters, we propose a model for gully formation on Martian dunes. The melt water from near-surface ground ice is incorporated in the debris flow and water concentration increases during its propagation. The increase of water concentration in the debris flow can be explained by a progressive increase of water/ice content in the permafrost downslope. Consequently, the lack of a final deposit at the front of some gullies tends to demonstrate that the flow became relatively highly concentrated in liquid downstream and all the water could have been lost in the final stage of the flow. Here we quantify the quantity of liquid necessary to form such a morphology.
Gargani, J.; Jouannic, G.; Costard, F.; Ori, G. G.; Marmo, C.; Schmidt, F.; Lucas, A.; Busson, J.
Microbial Influences on Aeolian Sulfates; A Case Study of a Dune Field at White Sands National Monument, New Mexico
NASA Astrophysics Data System (ADS)
Similarly to martian sulfate-rich dunes, the White Sands National Monument exhibits partially different mineral signatures of dune crests and interdune areas. At the WSNM these differences are caused by diagenetic processes and by biological activity.
Glamoclija, M.; Steele, A.; Fogel, M. L.
Oxygen electrodes for rechargeable alkaline fuel cells, 3
NASA Technical Reports Server (NTRS)
The investigation and development of electrocatalysts and supports for the positive electrode of moderate temperature single unit rechargeable alkaline fuel cells is described. Focus is on chemical and electrochemical stability and O2 reduction/evolution activity of the electrode in question.
Swette, L.; Kackley, N.; Mccatty, S. A.
This is the second report in a series which describes the performance of Water Factory 21, a 0.66 cu m/s advanced wastewater treatment plant designed to reclaim secondary effluent from a municipal wastewater treatment plant so that it can be used for injection and recharge of a g...
Trench infiltration for managed aquifer recharge to permeable bedrock
Managed aquifer recharge to permeable bedrock is increasingly being utilized to enhance resources and maintain sustainable groundwater development practices. One such target is the Navajo Sandstone, an extensive regional aquifer located throughout the Colorado Plateau of the western United States. Spreading-basin and bank-filtration projects along the sandstone outcrop's western edge in southwestern Utah have recently been implemented to meet growth-related water demands. This paper reports on a new cost-effective surface-infiltration technique utilizing trenches for enhancing managed aquifer recharge to permeable bedrock. A 48-day infiltration trench experiment on outcropping Navajo Sandstone was conducted to evaluate this alternative surface-spreading artificial recharge method. Final infiltration rates through the bottom of the trench were about 0.5 m/day. These infiltration rates were an order of magnitude higher than rates from a previous surface-spreading experiment at the same site. The higher rates were likely caused by a combination of factors including the removal of lower permeability soil and surficial caliche deposits, access to open vertical sandstone fractures, a reduction in physical clogging associated with silt and biofilm layers, minimizing viscosity effects by maintaining isothermal conditions, minimizing chemical clogging caused by carbonate mineral precipitation associated with algal photosynthesis, and diminished gas clogging associated with trapped air and biogenic gases. This pilot study illustrates the viability of trench infiltration for enhancing surface spreading of managed aquifer recharge to permeable bedrock. ?? 2010.
Heilweil, V. M.; Watt, D. E.
New Mechanically Rechargeable Zinc/Air Battery Design.
National Technical Information Service (NTIS)
The report discusses a program of study, design and development leading to the fabrication of new high performance 20 amphere hour mechanically rechargeable zinc/air batteries capable of meeting the requirements listed in the U.S. Army Electronics Command...
R. F. Chireau
Zinc electrode and rechargeable zinc-air battery
An improved zinc electrode is disclosed for a rechargeable zinc-air battery comprising an outer frame and a porous foam electrode support within the frame which is treated prior to the deposition of zinc thereon to inhibit the formation of zinc dendrites on the external surface thereof. The outer frame is provided with passageways for circulating an alkaline electrolyte through the
Philip N
Rechargeable zinc air batteries market and technology overview
AER Energy Resources is an Atlanta based technology company that has developed a rechargeable zinc air battery system. The primary advantage of the AER Energy Advanced Technology Battery is that its energy density on a weight basis is three times that of nickel cadmium, nickel metal hydride and lead acid batteries, and fifty percent higher than lithium ion batteries. This
M. Schimpf
Zinc electrode and rechargeable zinc-air battery
This patent describes an improved zinc electrode for a rechargeable zinc-air battery comprising an outer frame and a porous foam electrode support within the frame which is treated prior to the deposition of zinc thereon to inhibit the formation of zinc dendrites on the external surface thereof. The outer frame is provided with passageways for circulating an alkaline electrolyte through
P. N. Jr
Recent advances in rechargeable zinc-air battery technology
AER Energy's battery development effort is focused on improving the zinc-air rechargeable battery system to serve the portable computer market. Therefore system attributes such as energy density, power, life, form factor, environmental impact and safety are areas of active investigation. The battery system consists of cells in series, an air manager housing and an electronic control system for battery charge
D. Sieminski
Rechargeable lithium battery anodes: alternatives to metallic lithium
This review is concerned with alternatives to metallic lithium for use in rechargeable lithium batteries. Emphasis is placed on the use of various materials and combinations of materials in different types of electrodes rather than on the properties of the materials themselves. The review includes carbon based electrodes, alloys, conducting polymers and transition metal compounds. Special consideration is given to
D. Fauteux; R. Koksbang
Rechargeable lithium batteries in the Navy-policy and protocol
Rechargeable lithium batteries are an emerging technology that is finding widespread use in a myriad of applications. These batteries are supplanting many others because of superior performance characteristics, including high energy density and improved cycle life. The newest model laptop computers, camcorders and cellular phones are using these systems to provide lighter products with longer battery life. Potential military-use scenarios
Julie A. Banner; Clinton S. Winchester
Hysteresis in Thin-Film Rechargeable Lithium Batteries.
National Technical Information Service (NTIS)
Discharge - charge cycling of thin-film rechargeable lithium batteries with an amorphous or nanocrystalline LiXMn2.Y04 cathode reveals evidence for a true hysteresis in the lithium insertion reaction. This is compared with an apparent hysteresis attribute...
J. B. Bates N. J. Dudney C. D. Evans F. X. Hart
Oxygen electrodes for rechargeable alkaline fuel cells-II
NASA Technical Reports Server (NTRS)
The primary objective of this program is the investigation and development of electrocatalysts and supports for the positive electrode of moderate temperature single-unit rechargeable alkaline fuel cells. Approximately six support materials and five catalyst materials have been identified to date for further development.
Swette, L.; Kackley, N.
Method of Increasing the Useful Life of Rechargeable Lithium Batteries.
National Technical Information Service (NTIS)
The cycle life of rechargeable lithium batteries is significantly prolonged by applying to the battery as a charging mode a current interrupted at intervals of 1 milliseconds to 9 seconds in a frequency range of about 0.1 to about 10 Hertz.
O. C. Wagner
Rechargeable Battery Management and Recycling: A Green Design Educational Module
Rechargeable battery use is expected to continue growing with the increasing prevalence of portable electronics, appliances, and tools. Batteries represent a large volume of toxic and hazardous materials in common use, and these materials must be managed to avoid or minimize dissipation into the environment. One type of battery widely used in portable applications is nickel-cadmium batteries (NiCds). This module
Rebecca Lankey; Francis McMichael
Preliminary Study of Rechargeable Lithium Cells for Space Applications.
National Technical Information Service (NTIS)
Research carried out on lithium rechargeable cells using on organic electrolyte and intercalation compounds is described. Metal oxides such as V2O5, MoO3, and MoV2O8 are investigated as possible cathode materials. V2O5 shows the most potential of the thre...
J. Labat J. Goualard
Characterization of Ether Electrolytes for Rechargeable Lithium Cells.
National Technical Information Service (NTIS)
2Methyl-tetrahydrofuran (2Me-THF)/LiAsF6 and several diethyl ether (DEE)/LiAsF6-based electrolytes have been characterized for their usefulness in rechargeable Li/TiS2 cells. This characterization has involved extended room temperature cell cycling at var...
K. M. Abraham J. L. Goldman D. L. Natwig
Electrolytic characteristics of fluoromethyl methyl carbonate for lithium rechargeable batteries
Monofluorinated solvents exert the polar effect on various properties. We have investigated the electrolytic properties of fluoromethyl methyl carbonate (FMMC, monofluorinated dimethyl carbonate) and its application to lithium rechargeable batteries. We describe the dependence of electrolytic conductivity on the temperature, the molar concentrations of three lithium salts, and the molar fractions of the binary solvents. The conductivities of the FMMC
Noritoshi Nanbu; Susumu Watanabe; Masahiro Takehara; Makoto Ue; Yukio Sasaki
Development of new safe electrode for lithium rechargeable battery
A new concept cathode was proposed to improve the safety of lithium rechargeable batteries. The cathode contains a positive temperature coefficient (PTC) compound that can drastically increase resistivity at more than a specified temperature (PTC properties). A PTC cathode containing the PTC compound was fabricated and its resistivity was evaluated. The resistivity of PTC cathodes increased by several tens at
Makiko Kise; Shoji Yoshioka; Kouji Hamano; Daigo Takemura; Takashi Nishimura; Hiroaki Urushibata; Hajimu Yoshiyasu
NbSe3 Cathodes For Li Rechargeable Cells
NASA Technical Reports Server (NTRS)
Report describes experimental studies involving preparation, characterization, and measurements of performance of NbSe3, intended for use as cathode material in lithium rechargeable electrochemical cells. Characteristics superior to those of other intercalating cathode materials, including high volumetric and gravimetric energy densities and ability to sustain discharges at high rates.
Bugga, Ratnakumar V.; Ni, Ching-Ion; Distefano, Salvador; Somoano, Robert B.; Bankston, C. Perry
Lithium rechargeable cell with a poly 3-methylthiophene cathode
A poly 3-methylthiophene (PMT) cathode showed excellent coulombic efficiency during cycling in a lithium rechargeable cell. An electrolyte containing dimethyl carbonate was used since it is stable at the high anodic potentials reached during cell charging. The polymer cathode tolerated modest overcharge and was able to continue cycling after a severe short-circuit with minimal loss of capacity.
Charles W. Walker Jr.; Steven M. Slane
Polypyrrole Electrodes as Cathodes in a Rechargeable Cell
A study on Li ion rechargeable cells fabricated with polypyrrole (PPy) conducting polymer cathodes is reported in this paper. The PPy was prepared by electropolymerization of pyrrole in the presence of large surfactant anion dodecylbenzene sulphonate. Polyacrylonitrile based solid polymer electrolytes containing lithium triflate and ethylene carbonate (EC) and propylene carbonate (PC) as plasticisers were used as the separators. Cycling
K. P. Vidanapathirana; M. A. Careem; S. Skaarup
Rechargeable LiNiO sub 2 \\/carbon cells
Rechargeable cells can be made using two different intercalation compounds, in which the chemical potential of the intercalant differs by several eV, for the electrodes. In this paper, the authors discuss the factors that play a role in the selection of appropriate lithium intercalation compounds for such cells. For ease of cell assembly the cathode should be stable in air
J. R. Dahn; U. von Saken; M. W. Juzkow; H. Al-Janaby
Rechargeable LiNiO2\\/carbon cells
Rechargeable cells can be made using two different intercalation compounds, in which the chemical potential of the intercalant differs by several eV, for the electrodes. The factors that play a role in the selection of appropriate lithium intercalation compounds for such cells are discussed. For the ease of cell assembly, the cathode should be stable in air when it is
J. R. Dahn; U. von Sacken; M. W. Juzkow; H. Al-Janaby
Materials issues in lithium ion rechargeable battery technology
Lithium ion rechargeable batteries are predicted to replace Ni\\/Cd as the workhorse consumer battery. The pace of development of this battery system is determined in large part by the availability of materials and the understanding of interfacial reactions between materials. Lithium ion technology is based on the use of two lithium intercalating electrodes. Carbon is the most commonly used anode
Materials issues in lithium ion rechargeable battery technology
Lithium ion rechargeable batteries are predicted to replace Ni\\/Cd as the workhorse consumer battery. The pace of development of this battery system is determined in large part by the availability of materials and the understanding of interfacial reactions between materials. Lithium ion technology is based on the use of two lithium intercalating electrodes. Carbon is the most commonly used anode
Status of the development of rechargeable lithium cells
The progress in the development of the ambient temperature lithium - titanium disulfide rechargeable cell under development at the Jet Propulsion Laboratory is described in this paper. Originally aimed at achieving a specific energy of 100 Wh\\/kg, 'AA' cells have demonstrated 125 Wh\\/kg at the C\\/3 discharge rate. The results of evaluating cell design parameters are discussed and cycling test
G. Halpert; S. Surampudi; D. Shen; C.-K. Huang; S. Narayanan; E. Vamos; D. Perrone
The Cedar Creek Wastewater Reclamation Plant (CCWRP) located in Nassau County, NY is a 0.24 cu m/s (5.5 mgd) advanced wastewater treatment (AWT) plant designed to produce a high quality effluent suitable for groundwater recharge. The CCWRP was constructed as a demonstration proje...
Vertical characterization of a gasoline release site at East Patchogue, New York showed that methyl tert-butyl ether (MTBE) and aromatic plumes "dived" as they passed beneath a sand pit. That this behavior was caused by aquifer recharge was shown by two pieces of evidence. Fir...
Lithium-Air Battery: Study of Rechargeability and Scalability.
National Technical Information Service (NTIS)
Lithium-air battery is anticipated as the battery with highest energy density among all existing rechargeable battery systems known now. Literature reports suggest that the theoretical energy density of Li-air battery is close to that of gasoline. Thus, i...
M. Nookala
Rechargeable batteries: advances since 1977. [Collection of US patents
This book is based on US patents (including DOE patents) issued since January 1978 that deal with rechargeable batteries. It both supplies detailed technical information and can be used as a guide to the patent literature. Subjects treated are as follows: lead-acid batteries (grids, electrodes, terminals and connectors, polyolefin separators, polyvinyl chloride separators, other polymeric separators, other separators, electrolytes, venting
A polymer electrolyte-based rechargeable lithium\\/oxygen battery
A novel rechargeable Li\\/O� battery is reported. It comprises a Li{sup +} conductive organic polymer electrolyte membrane sandwiched by a thin Li metal foil anode, and a thin carbon composite electrode on which oxygen, the electroactive cathode material, accessed from the environment, is reduced during discharge to generate electric power. It features an all solid state design in which electrode
K. M. Abraham; Z. Jiang
National Park Service nonnative plant control in the Indiana Dunes National Lakeshore
Invasive plants have become a growing threat to plant diversity and hydrology in the Indiana Dunes National Lakeshore. Invasive plants compete with native plants for nutrients and sunlight, and certain invasive species have been known to completely take over certain areas of wetlands, nearly destroying entire ecosystems. The Dunes Lakeshore contains over 1,400 plants species and is one of the
Jacob Halpin; Laurie Eberhardt; Laura Thompson
La valeur collective d'une r�duction du nombre des bless�s de la route
Le travail pr�sente dans ce rapport et celui effectue sur la valeur collective de la sauvegarde d'une vie humaine (Duval et al., 1993, 1996) s'inscrivent dans un cadre th�orique commun et rel�vent des m�mes hypoth�ses : estimer les valeurs collectives unitaires d'une r�duction du nombre des bless�s de la route respectivement graves et l�gers pr�sente quelques difficult�s : -la premi�re
H. Duval; C. Filou; F. Molenda