A method of an open loop characterization of an electrostatic MEMS based resonator with a varying gap, the method including: converting, via a trans-impedance amplifier circuit, an output current signal of the resonator into a voltage; multiplying the output current signal converted into the voltage, by means of a multiplier circuit, with an AC signal or with a different signal at a frequency of the resonator and carrying a second harmonic signal to a main tone; and measuring a frequency response of a signal cleared of frequencies apart from the main tone using a network analyzer.

MEMS resonators are used in many military, biomedical and various end user applications. Accelerometers and gyroscopes, thermometers, and mass sensors with nanogram sensitivity are the most known applications that make use of resonator structures. In all of these applications, detection of the resonance frequency is crucially important. Moreover, when the quality factor is high, the small changes in resonance frequency are perceived more easily and the phase noise during close circuit oscillation gets lower.
MEMS resonators can simply be modeled with a spring, a mass and a damper (FIG. 1). When this system is actuated (driven) by a force, it moves. Maximum movement is observed when the actuation frequency is equal to the resonance frequency. In FIG. 2, a varying gap electrostatic MEMS resonator is illustrated. A typical electrostatic resonator comprises a drive electrode, a sense electrode and a DC polarization electrode.
If the movable proof mass that is polarized with DC voltage is actuated with AC drive voltage, it starts moving with the effect of electrostatic force (Electrostatic Drive). The gap changes because of the movement, leading to capacitance change that causes the generation of AC current at the sensing electrode. This current is defined as the output current.
The maximum output current is observed when the input voltage frequency is equal to the mechanical resonance frequency. The forces that are formed in varying gap resonators comprise different harmonic elements; however, the effect of higher harmonic components are not reflected into movement due to the band-pass structure of the resonator. As the relationship between the capacitance change and the change in the gap during the conversion of the motion into a current is not linear, the output current comprises other harmonic elements apart from drive frequency (main tone).
In the other studies in the literature, other harmonic elements in the output current have been neglected and only main tone has been used for the characterization of a resonator. However, the parasitic capacitance between the drive electrode and the sensing electrode (and the parasitic resistance formed in some cases) leads to the observation of parasitic currents in the main tone. The parasitic currents, that are also called feedthrough currents, may be limiting in some cases during the characterization of electrostatic MEMS resonators. Especially in applications requiring stiffer springs, as the voltage-current gain is reduced, the output current is dominated by the feedthrough current. For example in real-time measurements carried out in liquid mediums (fluid, gas etc.), the damping effect of the liquid(s) reduces the output whereas the fault currents may be more dominant.
While performing resonance characterization of a typical resonator, first, a frequency sweep is carried out when the electrostatic resonator is active. Following this, the DC bias of the resonator is turned off and another frequency sweep is carried out again at the same frequency ranges. The results of both characterizations can be subtracted from each other in a computer environment and the real resonance characteristics can be obtained. However, this method does not enable real-time characterization.
In order to enable real time resonance characterization, the feedthrough current should be eliminated from the system. Moreover, the closed loop oscillation is not possible without eliminating feedthrough current. To eliminate the feedthrough current, various methods have been proposed in the literature. In the first method, an active and a passive resonator are used. The passive and active resonators are driven with 180° phase different signals and thereby out-of-phase feedthrough currents are generated. When these currents are added at the sense electrode, ideally the feedthrough currents are eliminated. However, it is not possible to provide ideal elimination conditions. First, the phase difference between the generated signals needs to be exactly 180°. Moreover, the multiplication of the signal amplitudes and parasitic capacitances of the signals need to be as close to each other. When the two conditions are not completely satisfied, the feedthrough current cannot be completely eliminated. Another elimination method is a method where resonators with differential output currents are used. In this method, two out-of-phase currents of the same resonator is differentiated and mutual parasitic currents are eliminated. In the case that parasitic capacitances are mismatched, the signals obtained from the two outputs need to be multiplied by different gains and then they are subtracted from each other. If the gains of the signals are not properly adjusted, the feedthrough current cannot be completely eliminated. In addition, the differential method brings about an extra (application specific) resonator design cost.
The quality factor (Q) is an important parameter for accomplishing real time resonance characterization using the present methods based on the main tone signal. The high quality factor means that the gain at the resonance frequency is higher than gains in other frequencies. This makes it easier to detect the resonance frequency during open circuit resonance characterization and for closed loop oscillation. Especially the quality factors of resonators that operate in a fluid medium (liquid or gas) can be low because of the suppression of the output current by parasitic feedthrough currents due to the damping effect. In such applications, it may not always be possible to accomplish real time resonance characterization by using the present methods. Moreover, the quality factors of silicon MEMS resonators that operate under vacuum is limited by the quantum limit of silicon. According to this, There is a maximum value of the frequency-quality factor multiplication of the system (Q*f).
When the present applications of the known state of the art are taken into consideration, it can be seen that there exist no application having the same features of the proposed second harmonic reading based characterization/drive method that reduces the feedthrough current and increases the quality factor in electrostatic MEMS resonators. The reduction of the quality factor in high damping coefficient mediums and the repression of the resonator current due to the feedthrough current can be compensated by means of this invention.

Characterization and driving method based on the second harmonic, which is enhancing the quality factor and reducing the feedthrough current in varying gap electrostatic MEMS resonators


This disclosure is related to devices, systems, and techniques for determining an acceleration. For example, an accelerometer system includes a proof mass, a pole piece connected to the proof mass, and a coil disposed around the pole piece and connected to the proof mass, where the coil is rectangular in shape. Additionally, the accelerometer system includes circuitry configured to deliver an electrical signal to the coil in order to maintain the proof mass at a null position and determine an electrical current value corresponding to the electrical signal. Additionally, the circuit is configured to identify, based on the electrical current value, an acceleration of the accelerometer system.

Accelerometers function by detecting a displacement of a proof mass under inertial forces. Some accelerometers include a capacitive pick-off system. For example, electrically conductive material (e.g., a capacitor plate) may be deposited on the upper surface of the proof mass, and similar electrically conductive material may be deposited on the lower surface of the proof mass. An acceleration or force applied along the sensitive axis of the accelerometer causes the proof mass to deflect either upwardly or downwardly causing the distance (e.g., a capacitive gap) between the pick-off capacitance plates and upper and lower non-moving members to vary. This variance in the capacitive gap causes a change in the capacitance of the capacitive elements, which is representative of the displacement of the proof mass along the sensitive axis. The change in the capacitance may be used as a displacement signal, which may be applied to a servo system that includes one or more electromagnets (e.g., a force-rebalancing coil) to return the proof mass to a null or at-rest position.

Accelerometer including rectangular coil and rectangular pole piece


Coal friendly, non-toxic, green fracturing compositions, methods of preparing fracturing compositions and methods of use in various fracturing applications are described. The compositions are characterized as non-toxic compositions enabling effective use of the fracturing compositions in coal bed methane (CBM) formations and particularly shallow CBM formations. The compositions include a liquid component (water-based component) and a gas component in proportions that can support a proppant under turbulent conditions and that promote the formation of a mist.

As is well known in the hydrocarbon industry, many wells require "stimulation" in order to promote the recovery of methane from the coal bed methane (CBM) production zone of the well. CBM is also known as NGC (natural gas from coal), CBG (coal bed gas) and CSM (coal seam methane).
One of these stimulation techniques is known as "fracturing" in which a fracturing fluid composition is pumped under high pressure into the well together with a proppant such that new fractures are created and passageways within the CBM production zone are held open with the proppant. Upon relaxation of pressure, the combination of the new fractures and proppant having been forced into those fractures increases the ability of methane to flow to the wellbore from the CBM production zone.
There are a significant number of fracturing techniques and fluid/proppant compositions that promote the formation of fractures in the CBM production zone and the delivery of proppants within those fractures. The most commonly employed methodologies seek to create and utilize fracturing fluid compositions having a high viscosity that can support proppant materials so that the proppant materials can be effectively carried within the fracturing fluid. In other words, a viscous fluid will support a proppant within the fluid in order that the proppant can be carried a greater distance within the fracture, or in some circumstances, carried at all. In addition, fracturing fluids are commonly designed such that upon relaxation of viscosity (or other techniques) and over time (typically 90 minutes or so), the fluid viscosity drops and the proppant is "dropped" in the formation and the supporting fluid flows back to the wellbore. The proppant, when positioned in the fracture seeks to improve the permeability of the CBM production zone in order that methane will more readily flow to the well. An effective fracturing operation can increase the flow rate of methane to the well by at least one order of magnitude. Many wells won't produce long term in an economic manner without being stimulated by methods such as fracturing.
Fracturing fluid compositions are generally characterized by the primary constituents within the composition. The most commonly used fracturing fluids are water-based or hydrocarbon-based fluids, defined on the basis of water or a hydrocarbon being the primary constituent of the specific composition. Each fracturing fluid composition is generally chosen on the basis of the subterranean formation characteristics and economics. In general, a production zone that produces in situ formation water is usually economically stimulated with a water-based system. For CBM formations, which are commonly water producing before they produce methane, an economic water-based fluid is a common choice whereas hydrocarbon based fluids are not used very often.
In the case of water-based fluids, in order to increase the viscosity of water, various "viscosifying" additives may be added to the water-based fluid at the surface such that the viscosity of the water-based fluid is substantially increased thereby enabling it to support proppant. As is known, these water-based fluids may include other additives such as alcohols, KCl and/or other additives to impart various properties to the fluid as known to those skilled in the art. The most commonly used viscosifying additives are polymeric sugars that are used to create linear gels having moderate viscosities. These linear gels may be further combined with cross-linking agents that will create cross-linked gels having high viscosities.
CBM formations generally naturally fracture with a primary set of natural fractures (face cleats) located perpendicular to a secondary set of natural fractures (butt cleats). In the past 20 years, many CBM wells were stimulated with cross-linked water-based fracturing fluids and foam fracturing fluids. However currently, unconventional reservoirs, including CBM formations, are generally pumped with low viscosity fluids such as slick (friction reduced) water and nitrified (up to 53% quality) slick water fracture compositions. Where traditional high viscosity fluids typically encourage a bi-wing fracture (two single fractures extending out from opposing sides of the well bore) by plugging secondary (usually orthogonal) fractures, low viscosity fluids generally are less likely to plug secondary fractures, thus forming a wide intersecting fracture network instead.
In the case of CBM production zones, there are generally two basic types: dry CBM production zones and wet (water containing) CBM production zones. In both cases, methane typically exists in two possible forms within the production zone. The first form is a free gas (gaseous state) where methane gas exists in the porosity of the formation, which is mostly in the natural fractures. The second form of methane is adsorbed onto the surface of the coal in equilibrium with reservoir pressure. If reservoir pressure increases, more free gas adsorbs onto the coal surface. If reservoir pressure decreases, more methane desorbs off of the coal surface to become free gas.
Stimulating production of a CBM production zone generally depends on the basic type of production zone (dry or water containing). If the CBM production zone is dry, the methane will generally desorb off the coal surfaces and flow to the well as a gas if the pressure of the well is lowered through well operations at the surface. If the CBM production zone is water containing, the reservoir pressure generally needs to be reduced through a process called dewatering. Dewatering is a well operation where water is pumped from the well to reduce pressure in the reservoir until methane starts to desorb off of the coal surface. As more water is removed from the reservoir, more methane desorbs from the coal surfaces at a faster rate. This process typically continues until poor economics of the well develop, due in part to eventually declining rates of methane production. Dewatering rates traditionally have been high, in the order of 30 m3/day, where current dewatering rates can be limited to maximum as low as 3 m3/day to maintain created and natural fracture permeability by not causing fractures to close.
During a typical fracturing operation, the fracturing fluid (without any proppant) is initially pumped into the well at a sufficiently high pressure and flow rate to fracture the formation, or in the case of CBM formations, to also dilate and/or re-open pre-existing natural fractures. After fracturing has been initiated, a proppant is generally added to the fracturing fluid, and the combined fracturing fluid and proppant is forced into the fractures in the CBM production zone. When pressure is released and over time (typically 90 minutes), the viscosity of the fracturing fluid drops such that the proppant separates or drops out of the fracturing fluid within the formation, and the "de-viscosified" fracturing fluid flows back to the well where it is removed.
One major problem in this type of fracturing is the large volumes of water required and the attendant issues relating to the disposal of the water that has been pumped downhole and ultimately recovered from the well as a coal particle or otherwise contaminated fluid. Naturally fractured formations in the past few years have responded quite well to slick water based fractures, however, these types of fractures can use extremely high volumes of water, generally 2 to 3 orders of magnitude higher than traditional fracturing methods in CBM production zones. For example, where a normally sized foam frac typically used 30 m3 of water in a CBM well 10 years ago, a slick water fracture with current technology can require 3,000 m3 of water. In the case that the well has a dry CBM production zone, often having very low reservoir pressures, injecting extremely large volumes of water can counteract the benefit of forming a wide intersecting fracture network. In the case that the well has a wet CBM production zone, some current dewatering practices have rates that can be as low as 3 m3/day and that can extend the lengths of time by months or years for steady methane production due to adding a large volume of fracturing water to the large volumes of reservoir water that already needs to be removed. As a result, in some cases the industry has required a reduction in water use while still maintaining a wide network of fractures by moving away from pure water-based fracturing fluids in favor of those technologies that utilize a high proportion of gas (usually nitrogen or supercritical carbon dioxide) as the fracturing fluid.
Generally, the use of a high proportion of gas in a fracturing fluid has several advantages, including minimized formation damage, reduced fluid supply costs and reduced disposal costs of fluid recovered from the well. For example, whereas water may increase the time required to dewater a CBM production zone to start flowing significant amounts of methane, high gas compositions may minimize such effects and will otherwise migrate from the formation more readily, and encourage larger amounts of fracturing water to flow back immediately after the fracturing operations. Gas injected and thus recovered from a well can simply be released to the atmosphere thereby obviating the need for decontamination and disposal of a substantial proportion of the materials recovered from the well.
With high ratio gas fracturing compositions, the characteristics of the compositions can be similarly controlled or affected by the use of additives. Generally, gas fracturing compositions can be characterized as a pure gas fracturing composition (typically a fluid comprising around 100% CO2 or nitrogen) or energized, foamed and emulsied fluids (typically a fracturing composition comprising less than about 85% CO2 or nitrogen by volume).
A pure 100% gas fracturing composition will have minimal viscosity and instead will rely on high turbulence to transport proppant as it is pumped into the CBM production zone. Unfortunately, while such techniques are effective in limited batch operations, the need for expensive, highly specialized, pressurized pumping, mixing and containment equipment substantially increases the cost of an effective fracturing operation. For example, a fracturing operation that can only utilize a batch process is generally limited in size to the volumetric capacity of a single pumping and containment unit. As it is economically impractical to employ multiple units at a single fracturing operation, the result is that very high volume gas fracturing operations can only be effectively employed in relatively limited circumstances. For example, a pure gas fracturing operation would typically be limited to pumping 300-32,000 kg of sand (proppant) into a well and is limited to the type of proppant that can be used in some circumstances. Common 100% gas fracturing compositions, such as liquid carbon dioxide or gelled propane, are inherently not preferred for CBM wells due to the chemical adsorption, methane desorption interference or damage that can occur on the surfaces of the coal to affect the long term production ability of the CBM production zone.
In the case of some shallow, dry and severely under-pressured CBM production zones, the reservoir often has high permeability, often due to being naturally fractured. During the drilling, casing and cementing process, the CBM production zone may be damaged or plugged such that perforations alone can't adequately communicate the well with the reservoir. A pure gas fracturing technique without proppant may be used to break through the damaged area and/or unplug the blocked area that prevents the methane flowing into the well from the CBM production zone. For example, high rate nitrogen is injected into a shallow coal bed methane CBM production zone at a rate of 1000 to 1500 scm/min for a volume of 3000 to 5000 scm (just a few minutes total operation) to unplug the damage and allow the CBM production zone to flow into the well. Due to economical requirements, comingling CBM production with conventional production from normally pressured sandstone or other lithologies is required. In the case that these conventional production zones are stimulated with proppant and fluids, as is often practiced, cross-flow can occur where gases and fluids from any one production zone may flow into any other production zone due to reservoir pressure differences either in a short time or long time after the stimulation. Where the conventional zones commonly have higher pressures than the under-pressured coal zones, there are inherently higher risks. Often it is desired that the fracturing compositions and methods used in the conventional zones be chemically compatible and prevent damage to the CBM zones if they are exposed or otherwise meet any environmental and non-toxic requirements.
In the case of some shallow, dry and severely under-pressured CBM production zones, the reservoir may have lower permeability than economically acceptable if high rate nitrogen stimulations are performed. In the case of most lower permeability production zones, a proppant fracture creating highly permeable paths for methane to flow to the well from the reservoir is required. Due to the low reservoir pressure, any normal amount of fracturing fluid may hydrostatically cause a water block which could prevent methane production as the reservoir pressure would be increased as well as a second phase being introduced to a pure gas system causing relative permeability reduction effects to methane flow.
The use of non-energized, energized, foamed and emulsied fluids for fracturing are generally not limited to batch operations as fluid mixing and pumping equipment for such fluids is generally not at the same scale in terms of the complexity and cost of equipment that is required for pure gas operations. In other words, the mixing and pumping equipment for a non-energized/energized/foamed/emulsied fluid fracturing operation is substantially less expensive and importantly, can produce effectively large continuous volumes of fracturing fluid mixed with proppant. That is, while a 100% gas fracturing operation may be able to deliver up to 32,000 kg of proppant to a formation, a non-energized/energized/foamed/emulsied fluid fracturing operation may be able to deliver in excess of 10 times that amount.
The characteristics of energized, foamed and emulsied fluids are briefly outlined below as known to those skilled in the art.
An energized fluid will generally have less than 53% (volume %) gas together with a conventional gelled water phase. An energized fluid is further characterized by a continuous fluid phase with gas bubbles that are not concentrated enough to interact with each other to increase viscosity. For example, the overall viscosity of an energized fluid comprised of a linear gel and nitrogen gas may be in the range of 20 cP which is a "mid-point" between the viscosity of a typical linear-gel water phase (30 cP) and a nitrogen gas phase (0.01 cP). For a cross-linked gel, the viscosity range may be 150-1000 cP (typically 100-800 cP when mixed with gas). However, in the case of high viscosity fluids, such as cross-linked gel, the desired wide fracturing network is not as likely to occur during fracturing, and in most cases the cross-linking agent is toxic. As is known, and in the context of this description, viscosity values measured in centipoise (cP) are dependent on shear rate. In this specification, all viscosity values are referenced to a shear rate of 170 sec−1.
Foams will generally have greater than 53 vol % gas but less than about 85 vol % gas with the remainder being a gelled water phase. Foams are characterized as having a continuous fluid film between adjacent gas bubbles where the gas bubbles are concentrated enough to interact with each other to increase viscosity. Foams require the addition of foaming agents that promote stability of the gas bubbles. The viscosity of a foam will typically be in the range of 200-300 cP which may be 10 times greater than the viscosity of the gelled water phase (20-30 cP) and many times greater than the viscosity of the gas phase (0.01-0.1 cP). However, the greater viscosities may decrease the desired effect of forming a wide intersecting fracture network relative to lower viscosity systems absent of foamer. As known to those skilled in the art, most foaming agents will interfere or otherwise have a damaging effect with respect to the desorption process of methane from the coal faces in the production zone. In addition, most foaming agents do not pass relevant toxicity tests.
A carbon-dioxide emulsion, also known as a carbon-dioxide foam, is where the internal phase is a carbon-dioxide supercritical fluid and is characterized by having a second liquid film (i.e. the water-based phase) between adjacent liquid droplets. Emulsions will generally form when the supercritical fluid concentration is greater than 53 vol % and less than about 85 vol %. Emulsions require the addition of foaming agents to promote stability. The viscosity of an emulsion may also be 10 times greater than the individual viscosities of the separate gelled water phase and supercritical gas phase. Again, the higher viscosity emulsion will discourage the creation of wide intersecting fracture networks, which is desired in unconventional reservoirs. Furthermore, 100% carbon dioxide gas phases may damage CBM production zones by preferentially adsorbing on coal faces compared to methane such that permeability decreases (may be up to a 4 fold decrease) due to swelling decreasing the porosity and openness of the natural fractures.
Finally, when the gas concentration is increased above about 85% (typically 90-97%), the stability of a typical emulsion or a foam will decrease, such that the emulsion or foam will "flip" such that the gas phase becomes continuous, and the water phase is dispersed with the gas phase as small droplets or in larger slugs. This is commonly referred to as a "mist". The viscosity of a mist will generally revert to a "mid-point" of viscosity close to that of the gas (i.e. approximately 1-3 orders of magnitude lower than that of an emulsion) with the result being that the ability to support proppant based on viscosity is lost. As a result, fracturing compositions generally avoid the formation of mists and instead favor stabilizing foams and otherwise maximizing viscosities.
However, the tendency of developing a wide intersecting fracture network may increase when using a mist, while the volume of water needed is drastically reduced, and therefore less total potentially toxic materials are required to be added to the fracturing water to be injected into the production zone as the range of permeation may be greater.
Fracturing fluid compositions are inherently "toxic" as result of their make-up and specifically as a result of constituent compounds such as cross-linking agents, viscosifying additives, and any number of low cost additives of various functions that make up a fracturing fluid composition. As a result, there is a significant concern in the event of the fluids coming into contact with groundwater in either a short or longer time frame, and the associated concern that any contaminated fluids would be subsequently consumed by humans or animals. The deepest depth that easily processed and consumable groundwater is found is referred to as the base of ground water in which all deeper sources are saline and thus not fit for human or animal consumption. In CBM production zones, the water contained may either be fresh or saline.
When a fracturing operation is conducted in deep wells (i.e. generally greater than 200 m depth or below the base of groundwater regulations and protection), the toxicity is generally not an issue as the fracturing fluid is diluted by virtue of the migration distance to the groundwater as well as the low vertical permeability and ability of the fracturing fluid to migrate vertically at all through the matrix production zones, including CBM zones, due to cap rocks.
In the case of many shallow formations, operational economics are achieved by completing and stimulating multiple non-economic dry CBM production zones to form a marginal to good overall economic well with commingled production from all CBM zones. All zones could be stimulated at once by injecting down the well through casing only, but coiled tubing is often used to isolate the stimulation of individual zones with the flow back of the fracturing fluids commingled up the casing. When commingled deep (>200 m deep or deeper than base of groundwater) and shallow (<200 m deep or shallower than base of groundwater) CBM production zones are cleaned up and produced together up the casing, fracturing fluids can flow from any one CBM production zone out of the well or into another CBM production zone temporarily based on simple pressure differential. The result is that all CBM production zones in the well are at risk for being exposed to all fracturing fluids pumped into all CBM production zones. This effect, although not usually directly measured in the commingled stimulated well, can be risk assessed through regional bottom hole pressure measurements from offset wells with the same production zones to establish typical reservoir pressures.
However, in shallow wells, toxicity can be a significant problem as the fracturing operation may be conducted in relatively close proximity to groundwater such that the groundwater can be contaminated. For example, in Alberta, Canada, there has been a recent trend to develop shallow gas (commonly CBM) reservoirs less than 200 meters deep (or otherwise above the base of groundwater) using high fracture volumes, pump rates and pressures during such shallow fracturing operations.
In response to these concerns, regulatory agencies such as the Energy Resources Conservation Board (ERCB) (Alberta, Canada) are developing regulations to address these trends to ensure that the effects of these trends do not result in environmental contamination at or away from the well. For example, these regulations are considering imposing on companies conducting fracturing operations some or all of the following, including an effective assessment demonstrating that a complete review was conducted and all potential impacts were mitigated in the designed fracture program. Such an assessment is suggested to include the fracturing program design, including proposed pumping rates, volumes, pressures, and fluids; a determination of the maximum propagation expected for all fracture treatments to be conducted; identification and depth of offset oilfield and water wells within 200 m of the proposed shallow fracturing operations; verification of cement integrity through available public data of all oilfield wells within a 200 m radius of the well to be fractured; and landholder notification of water wells within 200 m of the proposed fracturing operations. These particular policies were introduced during recent times due to the high level of development of shallow, dry CBM wells that are drilled very close to one another.
Other conditions include restrictions for fracturing near a water well, in proximity to bedrock and limitations concerning pumping volumes during a nitrogen fracture. In particular, the use of non-toxic fracture fluids is required. This applies to many of the shallow, dry CBM wells.
In general, "green" or otherwise non-toxic, environmentally friendly fracturing compositions are preferred by society and regulatory agencies from industry. With any well operations including fracturing, there are small environmental risks from surface handling of materials before injection into the well or from recovering the fluids from the well after the frac. In general, preferences and requirements for the fracturing industry are requesting and in the future will require more non-toxic, green or environmentally friendly products. Society and government are particularly demanding when the perception that fresh water sources are at risk through well injection or during times of drought. Moreover, nitrogen condensed from the atmosphere that can be substituted for fresh water to inject into coal wells, reduces demand for fresh water sources leaving them for domestic use. The greater amount that inert nitrogen can be substituted for fresh water use, the more preferential the fracturing composition in turns of its effect on the environment.
The "toxicity" of many fluids is quantified by various protocols acceptable to a jurisdiction for testing the toxicity of a composition in the environment. Different areas or applications may use different protocols. For example, the Environmental Protection Agency (EPA) utilizes different testing protocols for testing soil contamination in different applications.
One set of standards that is generally accepted as a rigorous and meaningful test is the Microtox™ testing protocols for testing the toxicity of compositions in soil. Under the Microtox™ protocols, the viability of known bacterial cultures is measured within a sample to produce a numeric result as well as a "pass/fail" indication.
More specifically, the Microtox™ test is based on monitoring changes in the level of light emission from a marine bioluminescent bacterium, Vibrio fischeri NRRL-B-11177, when challenged with a toxic substance or sample containing toxic materials.
The test is performed by rehydrating freeze dried cultures of the organism, supplied as the Microtox™ reagent and determining the initial light output of homogenized bacterial suspensions. Aliquots of osmotically adjusted sample and sample dilutions are added to the bacterial suspension, and light measurements are made at specific intervals (generally at 5 or 15 minutes) after exposure to test samples. The diluent control (blank) is used to correct time-dependant change in light output.
The Microtox™ test endpoint is measured as the effective or inhibitory concentration of a test sample that reduces light emission by a specific amount under defined conditions of time and temperature. Normally, this is expressed as an ECSO(15) or ICSO(15) which is the effective concentration or inhibitory concentration of a sample that reduces light emission of the test organism by 50% over a 15 minute test period at 15°C.
The EC50 or IC50 is calculated by log linear plotting of Concentration (C) vs percent Light Decrease (percent A), or more precisely by plotting Gamma Q (which is the corrected ratio of the amount of light lost to the amount of light remaining) versus Concentration on a log-log graph. Either a hand calculator or computer program data reduction systems may be used to calculate Gamma and the corresponding EC50 or ICSO values.
As noted above, CBM production zones are unique in how they store and release methane gas, and, in turn, CBM has unique damage mechanisms. Production of methane from CBM wells is a growing unconventional contribution to the gas supply for North America. Further, CBM is damaged by many gelling agents, clay control agents, surfactants, breakers, cross-linking agents, and other chemicals. The chemical damage generally causes a reduction in the rate that methane can desorb from coal. Some gases like liquid carbon dioxide and potentially propane can adsorb onto coal to such a large extent that the coal swells and causes a permeability reduction through reduction of natural fracture porosity and cross-sectional flow area.
Accordingly, there has been a need for the development of non-toxic fracturing fluid compositions that will meet acceptable standards for "non-toxicity" and that generally address the increasing needs for environmentally friendly, green consumable materials used by many industries. There has also been a need to use CBM friendly chemistry that reduces coal damage and otherwise maximizes production. In addition, there are society and government issues to reduce fresh water use, which is addressed by this invention by substituting water with inert nitrogen gas.

This patent is subject to a terminal disclaimer.

Green coal bed methane fracturing fluid compositions, methods of preparation and methods of use


A method for searching in a large-scale database of images for images that are visually similar to query images is provided using a processor to perform the following steps: computing visual features for the database images; constructing an Image Anchor Graph that contains a plurality of anchors corresponding to a subset of images in the database, according to the computed visual features; computing visual features for the query images; and retrieving database images similar to one or more user query images using a ranking algorithm that uses the anchors in the Image Anchor Graph according to the computed visual features of both the query images and the database images on the Image Anchor Graph.

Nowadays, image search has become an indispensable feature of web search engines, including GOGGLE, YAHOO!, BING, and ASK. However, most of these image search engines are not effective enough because image signals are too complicated to handle. Due to the remarkable success of text retrieval for searching web pages, these search engines return images solely based on the surrounding text associated with such images on the web pages. So far, no visual cue or image content is used during such a search process.
Since text-based image search yields unsatisfactory search results due to the difficulty in automatically associating the visual content of images with descriptive text, the current practice instead relies on analyzing visual similarities among the images. This general area is referred to as Content-Based Image Retrieval (CBIR), which has been actively studied for the past two decades. The key component of current CBIR systems deals with computing pairwise visual similarities between images from which a global ordering is derived by way of well-established ranking methods such as PageRank (see Y. Jing and S. Baluja, "VisualRank: Applying PageRank to large-scale image search," IEEE Transactions on Pattern Analysis and Machine Intelligence, volume 30, issue 11, pp. 1877-1890, 2008.) and Manifold Rank (see D. Zhou, J. Weston, A. Gretton, O. Bousquet, and B. Scholkopf, "Ranking on data manifolds," in Advances in Neural Information Processing Systems (NIPS), volume 16, 2004.). Unfortunately, at the web scale that involves tens of thousands to millions of images, pairwise similarity computation becomes prohibitively expensive in terms of both computer memory and time costs.
Fast nearest neighbor search is increasingly vital to many large-scale tasks such as image search, and existing state-of-the-art search techniques mainly focus on how to approximate the search results achieved by the Euclidean distance. Given the fact that low-dimensional intrinsic manifolds can exist among a massive number of images, it is more effective to search images along the underlying manifold structures. The manifold ranking method provides ranking scores to all training samples with respect to a particular query by leveraging a neighborhood graph to reveal the data manifolds. However, such a method cannot scale up to very large databases where a rapid and accurate search engine is required.
There is, therefore, a need to develop an efficient and effective ranking method to handle large-scale image search.

Method for searching a database using query images and an image anchor graph-based ranking algorithm


The present invention provides culture mediums that are useful for the expression of ADAMTS proteins, such as ADAMTS13. Methods for the expression and purification of ADAMTS proteins are also provided. In some embodiments, the mediums and methods of the invention are useful for the expression of ADAMTS proteins having high specific activities. Also provided are ADAMTS, e.g., ADAMTS13, protein compositions with high specific activities, which are expressed and purified according to the methods provided herein.

The ADAMTS (a disintegrin and metalloproteinase with thrombospondin type I motifs) proteins are a family of metalloproteinases containing a number of conserved domains, including a zinc-dependant catalytic domain, a cystein-rich domain, a disintegrin-like domain, and at least one, and in most cases multiple, thrombospondin type I repeats (for review, see Nicholson et al., BMC Evol Biol. 2005 Feb. 4; 5(1):11). These proteins, which are evolutionarily related to the ADAM and MMP families of metalloproteinases (Jones G C, Curr Pharm Biotechnol. 2006 February; 7(1):25-31), are secreted enzymes that have been linked to a number of diseases and conditions including thrombotic thrombocytopenic purpura (TTP) (Moake J L, Semin Hematol. 2004 January; 41(1):4-14), connective tissue disorders, cancers, inflammation (Nicholson et al.), and severe Plasmodium falciparum malaria (Larkin et al., PLoS Pathog. 2009 March; 5(3):e1000349). Because of these associations, the ADAMTS enzymes have been recognized as potential therapeutic targets for a number of pathologies (Jones G C, Curr Pharm Biotechnol. 2006 February; 7(1):25-31). Accordingly, methods of producing large yields of ADAMTS proteins having high specific activities, which are free of contaminants such as viruses, BSE, and pathogens like Mycoplasma bacteria, are needed.
For cultivation of cells, particularly eukaryotic cells, and more specifically mammalian cells, there is a constant need to use special culture media providing nutrient substances that are required for efficient growth of cells and for the production of biological products, especially biopharmaceuticals, such as, for example, recombinant proteins, antibodies, viruses, viral antigens, and virus-like particles. For the efficient production of said biological products, it is important to achieve an optimal cell density as well as an increase of the protein expression itself in order to obtain maximal product yield.
Cell culture media formulations have been supplemented with a range of additives, including undefined components like fetal calf serum (FCS), several animal derived proteins and/or protein hydrolysates of bovine origin as well as protein hydrolysates derived from plants or yeast.
In general, serum or serum-derived substances, such as, e.g., albumin, transferrin or insulin, may comprise unwanted agents that can contaminate the cell cultures and the biological products obtained thereof. Furthermore, human serum derived additives have to be tested for all known viruses, including hepatitis viruses and HIV which can be transmitted via serum. Moreover, bovine serum and products derived thereof bear the risk of BSE contamination. In addition, all serum-derived products can be contaminated by unknown substances. When using serum or protein additives derived from human or animal sources in cell culture, there are numerous problems (e.g., the varying quality in composition of different batches and the risk of contamination with mycoplasma, viruses or BSE), particularly if the cells are used in the manufacture of drugs or vaccines for human administration.
Therefore, many attempts have been made to provide efficient host systems and cultivation conditions, which do not require serum or other animal protein compounds.
Such serum-free media have been developed on the basis of protein extracts derived from plants or yeast. For example, soy hydrolysates are known to be useful for fermentation processes and can enhance the growth of many fastidious organisms, yeasts and fungi. WO 96/26266 describes that papaic digests of soy meal are a source of carbohydrate and nitrogen and many of the components can be used in tissue culture. Franek et al. (Biotechnology Progress (2000) 16, 688-692) describe growth and productivity promoting effects of defined soy and wheat hydrolysate peptide fractions.
WO 96/15231 discloses a serum-free medium composed of a synthetic minimal essential medium and a yeast extract for the propagation of vertebrate cells and a virus production process. A medium formulation composed of a basal cell culture medium comprising a rice peptide and an extract of yeast and an enzymatic digest thereof, and/or a plant lipid for growth of animal cells is disclosed in WO 98/15614. A medium comprising purified soy hydrolysate for the cultivation of recombinant cells is disclosed in WO 01/23527. WO 00/03000 discloses a medium that comprises a soy hydrolysate and a yeast extract, but also requires the presence of recombinant forms of animal proteins, such as growth factors.
EP-A-0 481 791 describes a biochemically defined culture medium for culturing engineered CHO cells, which is free from protein, lipid and carbohydrate isolated from an animal source, further comprising a recombinant insulin or insulin analogue, 1% to 0.025% w/v papain digested soy peptone and putrescine. WO 98/08934 describes a serum-free eukaryotic cell culture comprising hydrolyzed soy peptides (1-1000 mg/L), 0.01 to 1 mg/L putrescine and a variety of animal-derived components, including albumin, fetuin, various hormones and other proteins. In this context, it should be noted that putrescine is also known to be comprised in standard media like DMEM/Ham's F12 in a concentration of 0.08 mg/L.
The plant and/or yeast hydrolysates, however, are undefined mixtures of oligopeptides and other unknown components and contaminants. Moreover, the quality of commercially available lots of hydrolysates varies extremely. As a result, there are large variations in the production of recombinant proteins or viral products (a variation of up to a factor of three) as a function of the lots of hydrolysates used ("lot-to-lot variation"). This drawback affects the proliferation of the cells as well as the protein expression of each cell. US 2007/0212770 describes various animal protein-free and oligopeptide-free, chemically defined culture mediums that are useful for the large-scale production of recombinant protein biopharmaceuticals.
One ADAMTS family member, ADAMTS13, cleaves von Willebrand factor (vWF) between residues Tyr 1605 and Met 1606, a function responsible for the degradation of large vWF multimers in vivo. Loss of ADAMTS13 activity has been linked to a number of conditions, such as TTP (Moake J L, Semin Hematol. 2004 January; 41(1):4-14), acute and chronic inflammation (Chauhan et al., J Exp Med. 2008 Sep. 1; 205(9):2065-74), and most recently, severe Plasmodium falciparum malaria (Larkin et al., PLoS Pathog. 2009 March; 5(3):e1000349).
Thrombotic thrombocytopenic purpura (TTP) is a disorder characterized by thrombotic microangiopathy, thrombocytopenia and microvascular thrombosis that can cause various degrees of tissue ischemia and infarction. Clinically, TTP patients are diagnosed by symptoms such as thrombocytopenia, schistocytes (fragments of erythrocytes) and elevated levels of lactate dehydrogenase (Moake J L. Thrombotic microangiopathies. N Engl J Med. 2002; 347:589-600; Moake J L. von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. Semin Hematol. 2004; 41:4-14; Sadler J E, Moake J L, Miyata T, George J N. Recent advances in thrombotic thrombocytopenic purpura. Hematology (Am Soc Hematol Educ Program). 2004: 407-423; Sadler J E. New concepts in von Willebrand disease. Annu Rev Med. 2005; 56:173-191).
In 1982, Moake et al. found unusually large von Willebrand factor (UL-vWF) multimers in the plasma of the patients with chronic relapsing TTP (Moake J L, Rudy C K, Troll J H, Weinstein M J, Colannino N M, Azocar J, Seder R H, Hong S L, Deykin D. Unusually large plasma factor VIII:von Willebrand factor multimers in chronic relapsing thrombotic thrombocytopenic purpura. N Engl J Med. 1982; 307:1432-1435). The link between UL-vWF and TTP gained support with independent findings by Furlan et al. and Tsai and Lian that most patients suffering from TTP are deficient in a plasma metalloprotease, now known to be ADAMTS13, that cleaves vWF (Furlan M, Robles R, Solenthaler M, Wassmer M, Sandoz P, Laemmle B. Deficient activity of von Willebrand factor-cleaving protease in chronic relapsing thrombotic thrombocytopenic purpura. Blood. 1997; 89:3097-3103; Tsai H M, Sussman, I I, Ginsburg D, Lankhof H, Sixma J J, Nagel R L. Proteolytic cleavage of recombinant type 2A von Willebrand factor mutants R834W and R834Q: inhibition by doxycycline and by monoclonal antibody VP-1. Blood. 1997; 89:1954-1962; Tsai H M, Lian E C. Antibodies to von Willebrand factor-cleaving protease in acute thrombotic thrombocytopenic purpura. N Engl J Med. 1998; 339:1585-1594).
The ADAMTS13 protease is a 190 kDa glycosylated protein produced predominantly by the liver (Levy G G, Nichols W C, Lian E C, Foroud T, McClintick J N, McGee B M, Yang A Y, Siemieniak D R, Stark K R, Gruppo R, Sarode R, Shurin S B, Chandrasekaran V, Stabler S P, Sabio H, Bouhassira E E, Upshaw J D, Jr., Ginsburg D, Tsai H M. Mutations in a member of the ADAMTS gene family cause thrombotic thrombocytopenic purpura. Nature. 2001; 413:488-494; Fujikawa K, Suzuki H, McMullen B, Chung D. Purification of human von Willebrand factor-cleaving protease and its identification as a new member of the metalloproteinase family. Blood. 2001; 98:1662-1666; Zheng X, Chung D, Takayama T K, Majerus E M, Sadler J E, Fujikawa K. Structure of von Willebrand factor-cleaving protease (ADAMTS13), a metalloprotease involved in thrombotic thrombocytopenic purpura. J Biol Chem. 2001; 276:41059-41063; Soejima K, Mimura N, Hirashima M, Maeda H, Hamamoto T, Nakagaki T, Nozaki C. A novel human metalloprotease synthesized in the liver and secreted into the blood: possibly, the von Willebrand factor-cleaving protease; J Biochem (Tokyo). 2001; 130:475-480; Gerritsen H E, Robles R, Lammle B, Furlan M. Partial amino acid sequence of purified von Willebrand factor-cleaving protease. Blood. 2001; 98:1654-1661).
Mutations in the ADAMTS13 gene have been shown to cause TTP (Levy G G, Nichols W C, Lian E C, Foroud T, McClintick J N, McGee B M, Yang A Y, Siemieniak D R, Stark K R, Gruppo R, Sarode R, Shurin S B, Chandrasekaran V, Stabler S P, Sabio H, Bouhassira E E, Upshaw J D, Jr., Ginsburg D, Tsai H M. Mutations in a member of the ADAMTS gene family cause thrombotic thrombocytopenic purpura. Nature. 2001; 413:488-494). Idiopathic TTP, often caused by autoantibodies inhibiting ADAMTS-13 activity, is a more common disorder that occurs in adults and older children and can recur at regular intervals in 11% to 36% of patients (Tsai H M, Lian E C. Antibodies to von Willebrand factor-cleaving protease in acute thrombotic thrombocytopenic purpura. N Engl J Med. 1998; 339:1585-1594; Furlan M, Lammle B. Deficiency of von Willebrand factor-cleaving protease in familial and acquired thrombotic thrombocytopenic purpura. Baillieres Clin Haematol. 1998; 11:509-514).
Non neutralizing autoantibodies could also inhibit ADAMTS13 activity by inducing clearance from circulation (Scheiflinger F, Knobl P, Trattner B, Plaimauer B, Mohr G, Dockal M, Dorner F, Rieger M. Nonneutralizing IgM and IgG antibodies to von Willebrand factor-cleaving protease (ADAMTS-13) in a patient with thrombotic thrombocytopenic purpura. Blood. 2003; 102:3241-3243). Plasma ADAMTS13 activity in healthy adults ranges from 50% to 178% (Moake J L. Thrombotic thrombocytopenic purpura and the hemolytic uremic syndrome. Arch Pathol Lab Med. 2002; 126:1430-1433). In most patients with familial or acquired TTP, plasma ADAMTS13 activity is absent or less than 5% of normal activity. Without treatment, the mortality rate for TTP exceeds 90%, but plasma therapy has reduced mortality to about 20% (Moake J L. Thrombotic thrombocytopenic purpura and the hemolytic uremic syndrome. Arch Pathol Lab Med. 2002; 126:1430-1433).
vWF synthesized in megakaryocytes and endothelial cells is stored in platelet α-granules and Weibel-Palade bodies, respectively, as ultra large vWF (UL-vWF) (Moake J L, Rudy C K, Troll J H, Weinstein M J, Colannino N M, Azocar J, Seder R H, Hong S L, Deykin D. Unusually large plasma factor VIII:von Willebrand factor multimers in chronic relapsing thrombotic thrombocytopenic purpura. N Engl J Med. 1982; 307:1432-1435; Wagner D D, Olmsted J B, Marder V J. Immunolocalization of von Willebrand protein in Weibel-Palade bodies of human endothelial cells. J Cell Biol. 1982; 95:355-360; Wagner D D, Bonfanti R. von Willebrand factor and the endothelium. Mayo Clin Proc. 1991; 66:621-627; Sporn L A, Marder V J, Wagner D D. von Willebrand factor released from Weibel-Palade bodies binds more avidly to extracellular matrix than that secreted constitutively. Blood. 1987; 69:1531-1534; Tsai H M, Nagel R L, Hatcher V B, Sussman, I I. Endothelial cell-derived high molecular weight von Willebrand factor is converted into the plasma multimer pattern by granulocyte proteases. Biochem Biophys Res Commun. 1989; 158:980-985; Tsai H M, Nagel R L, Hatcher V B, Sussman, I I. Multimeric composition of endothelial cell-derived von Willebrand factor. Blood. 1989; 73:2074-2076). Once secreted from endothelial cells, these UL-vWF multimers are cleaved by ADAMTS13 in circulation into a series of smaller multimers at specific cleavage sites within the vWF molecule (Tsai H M, Nagel R L, Hatcher V B, Sussman, I I. Endothelial cell-derived high molecular weight von Willebrand factor is converted into the plasma multimer pattern by granulocyte proteases. Biochem Biophys Res Commun. 1989; 158:980-985; Dent J A, Galbusera M, Ruggeri Z M. Heterogeneity of plasma von Willebrand factor multimers resulting from proteolysis of the constituent subunit. J Clin Invest. 1991; 88:774-782; Furlan M, Robles R, Affolter D, Meyer D, Baillod P, Lammle B. Triplet structure of von Willebrand factor reflects proteolytic degradation of high molecular weight multimers. Proc Natl Acad Sci USA. 1993; 90:7503-7507).
ADAMTS13 cleaves at the Tyr842-Met843 bond in the central A2 domain of the mature vWF subunit and requires zinc or calcium for activity (Dent J A, Berkowitz S D, Ware J, Kasper C K, Ruggeri Z M. Identification of a cleavage site directing the immunochemical detection of molecular abnormalities in type IIA von Willebrand factor. Proc Natl Acad Sci USA. 1990; 87:6306-6310). vWF exists in "ball-of-yarn" and filamentous form as seen by electron microscopy (Slayter H, Loscalzo J, Bockenstedt P, Handin R I. Native conformation of human von Willebrand protein. Analysis by electron microscopy and quasi-elastic light scattering. J Biol. Chem. 1985; 260:8559-8563). Furthermore, atomic force microscopy confirms that vWF exits in a globular conformation under static conditions and an unfolded filamentous state after exposure to shear stress (Siedlecki C A, Lestini B J, Kottke-Marchant K K, Eppell S J, Wilson D L, Marchant R E. Shear-dependent changes in the three-dimensional structure of human von Willebrand factor. Blood. 1996; 88:2939-2950). This could occur also in vivo when one end of the vWF filament is anchored to a surface.
Thrombi of TTP patients consist of little fibrin and mainly of vWF and platelets, suggesting vWF-mediated platelet aggregation as a cause of thrombosis (Asada Y, Sumiyoshi A, Hayashi T, Suzumiya J, Kaketani K. Immunohistochemistry of vascular lesion in thrombotic thrombocytopenic purpura, with special reference to factor VIII related antigen. Thromb Res. 1985; 38:469-479). Patients with relapsing TTP have ultra-large multimers in the plasma. The UL-vWF multimers accumulate over time because the persistence of the inhibitor (Anti-ADAMTS13 Ab) decreases ADAMTS13 activity. The UL-vWF multimers are hyperactive and unfold as a result of shear stress causing platelet aggregation, resulting in intravascular thrombosis (Tsai H M. Von Willebrand factor, ADAMTS13, and thrombotic thrombocytopenic purpura. J Mol Med. 2002; 80:639-647; Tsai H M. Deficiency of ADAMTS-13 in thrombotic and thrombocytopenic purpura. J Thromb Haemost. 2003; 1:2038-2040; discussion 2040-2035).
It is believed that the presence of hyper-reactive UL-vWF multimers in the plasma due to ADAMTS13 deficiency could be associated with an increased risk of arterial thrombosis linked to coronary heart disease.
As ADAMTS proteins have been implicated in a number of diseases and conditions, there is a need in the art for methods of large scale production of recombinant ADAMTS proteins having high specific activities, which are suitable for pharmaceutical formulation and administration. The present invention provides methods which satisfy these and other needs in the art for the production and purification of ADAMTS proteins.

Cell culture methods for expressing ADAMTS protein


During the structural analysis of a protein or peptide by tandem mass spectroscopy, a peptide ion derived from a protein that has already been measured and that is expressed in great quantities is avoided as a tandem mass spectroscopy target. A peptide derived from a minute amount of protein, which has heretofore been difficult to analyze, can be automatically determined as a tandem mass spectroscopy target within the real time of measurement. Data concerning a protein that has already been measured and a peptide derived from the protein is automatically stored in an internal database. The stored data is collated with measured data with high accuracy to determine an isotope peak. In this way, the process of selecting a peptide peak that has not been measured as the target for the next tandem analysis can be performed within the real time of measurement and a redundant measurement of peptides derived from the same protein can be avoided. The information contained in the MSn spectrum is effectively utilized in each step of the MSn involving a multi-stage dissociation and mass spectroscopy (MSn), so that the flows for the determination of the next analysis content and the selection of the parent ion for the MSn+1 analysis, for example, can be optimized within the real time of measurement and with high efficiency and accuracy. Thus, a target of concern to the user can be subjected to tandem mass spectroscopy without wasteful measurement.

1. Field of the Invention
The present invention relates to a mass spectroscopy spectrum analysis system using a mass spectrometer, and to a system for automatically determining an optimum flow of mass spectroscopy within a measurement time in order to identify the chemical structure of biopolymers, such as polypeptides or sugars, with high precision and efficiency.
2. Background Art
In a general mass spectroscopy, a sample as the object of measurement is ionized, and a variety of resultant ions are delivered to a mass spectrometer for measuring the ion intensity for each mass-to-charge ratio m/z, which is the ratio of the mass number m of ion to the valence z. As a result, a mass spectrum is obtained, which consists of a peak of the measured ion intensity (ion peak) for each mass-to-charge ratio m/z value. Such a mass spectroscopic analysis of the ionized sample in a first dissociation step is called MS1. In tandem mass spectrometer, in which multiple-stage isolation is possible, an ion peak having a specific mass-to-charge ratio m/z is selected (the selected ion species is called a parent ion) from the ion peaks detected by MS1, and the thus selected ion is dissociated and broken up by collision with gas molecules or the like. The resultant dissociated ion species is then subjected to mass spectroscopy, thereby obtaining a mass spectrum in a similar manner. The n-stage dissociation of the parent ion and the subjecting of the dissociated ion species to mass spectroscopy are referred to as MSn+1. Thus, in the tandem mass spectrometer, the parent ion is dissociated in multiple stages (1, 2, . . . , n stages), and the mass number of the ion species generated in each stage is analyzed (MS2, MS3, . . . , MSn+1).
(1) Most of the mass spectrometers capable of tandem analysis are equipped with a data-dependent function whereby, when selecting the parent ion for MS2 analysis from the ion peaks in MS1, the ion peaks are selected in decreasing intensities (such as the ion peaks in the top 10 strongest-intensities) as the parent ions, and then they are subjected to dissociation and mass spectroscopy (MS2).
(2) The ion-trapping type mass spectrometer manufactured by Finningan is equipped with a Dynamic Exclusion function whereby, when selecting a parent ion for MS2 analysis from the ion peaks in MS1, the ion species having a mass-to-charge ratio m/z value that is designated by the user in advance is excluded from the selection as a parent ion.
(3) Known examples relating to the determination of correspondence between a measured ion species and an ion species that has been measured include the following:
Patent Document 1: JP Patent Publication (Kokai) No. 2001-249114 A
Patent Document 2: JP Patent Publication (Kokai) No. 10-142196 A 1998
In Patent Document 1, a characteristic peak in the first-stage spectrum data and the spectrum data in the second stage of the corresponding ion species are stored in a database. In the subsequent measurements, spectrum data obtained by mass spectroscopy in the second stage of a sample as the object of measurement is compared with the second-stage spectrum data in the database in order to determine the degree of correspondence. Data components with the highest degree of correspondence is outputted as the comparison result.
In Patent Document 2, a measurement is continuously carried out during a multiple-stage dissociation measurement without conducting a sample injection process during measurement so that an ion intensity fluctuation due to injection between the MSn and MSn+1 data can be prevented. In this way, the need for the addition of a standard sample can be eliminated, thereby enabling an efficient quantitative analysis. The routine returns to MSn+1 or proceeds to the next MS1 measurement, depending on whether or not the data corresponds to the designated ion data that has been already collected in the MSn and MSn+1 data analysis.
Reviews of Modern Physics, Vol. 62 (1990), pp. 531-540, provides a basic description of an ion trap. A cross section of a basic configuration of the ion trap is shown in FIG. 15. The ion trap, which is a quadrupole ion trap, is made up of two end-cap electrodes and a single ring electrode. An RF voltage is applied to these electrodes such that a quadrupole electric field is formed at the center of these electrodes, thus enabling the trapping of gaseous ions three dimensionally. By continuously varying the RF voltage, the mass of the ions that are discharged can be controlled. A quadrupole pole is made up of four parallel poles. By applying a RF voltage to the electrodes, gaseous ions can be two dimensionally trapped at the center of the electrodes. By controlling the RF voltage that is applied, it becomes possible to discharge ions with a specific mass or, conversely, trap only those ions with a specific mass.
A tandem mass spectroscopy (MS/MS) can be conducted using a quadrupole ion trap, as described in the U.S. Pat. No. Re. 34000. In this apparatus, those ions for which no analysis is required are discharged prior to MS/MS. Namely, the removal of the ions for which no analysis is required is not conducted prior to the primary mass spectroscopy. A RF voltage that resonates with the ions is then applied in order to increase the kinetic energy. As a result of these operations, dissociated ions (fragment ions) are created by the collision induced dissociation (CID) with remaining molecules. By subjecting these fragment ions to mass spectroscopy (tandem mass spectroscopy), the mass of the fragment ions can be determined. In this case, it is necessary to initially conduct a mass spectroscopy without involving a CID (primary mass spectroscopy) in order to determine the ions as the object of a tandem mass spectroscopy (MS/MS, or a secondary mass spectroscopy). It is also possible to repeat a similar operation to further conduct a tandem mass spectroscopy (MSn) on a specific dissociated ion.
Recently, mass spectroscopic methods are often employed for an exhaustive analysis of proteins. Analytical Chemistry, Vol. 73 (2001), pp.5683-5690, describes examples of analysis called a shotgun analysis. In this technique, a peptide mixture prepared by subjection a protein to enzymatic digestion is separated using a liquid chromatograph, and a separated sample is then subjected to a tandem mass spectroscopy using a quadrupole ion-trap mass spectrometer. With reference to the determined mass of the ion and that of the fragment ion, a database of proteins or genes is searched in order to identify a protein. In case the types of the peptide mixture are too numerous, each peptide might not be completely separated in the liquid chromatograph, and a plurality of kinds of peptides might be simultaneously introduced into the mass spectrometer. This gives rise to the need for automatic tandem analysis called data-dependent analysis. Specifically, the band width of a separated sample separated in a liquid chromatograph is in the order of one minute, and the number of kinds of ions that can be subjected to tandem mass spectrometer at one time is limited to five. In many cases, the ions with greater ion intensities are preferentially subjected to tandem mass spectroscopy, although this depends on the setting of the data-dependent analysis.
A technical material for the quadrupole ion-trap mass spectrometer manufactured by ThermoFinnigan (www.thermo.com/eThermo/CMA/PDFs/Articles/articlesFile—10918.pdf) describes a dynamic exclusion function. Prior to the start of analysis, the masses of those ions to be excluded from tandem mass analysis are entered and then a list is prepared. By this operation, it becomes possible to exclude those ions put on the list as the objects of data-dependent analysis (tandem mass spectrometer). When this function is to be employed, a conventional mass spectroscopy is conducted first without involving the CID, and then the mass of the ions to be detected is determined. Next, priorities of the ions as the objects of tandem mass spectroscopy are determined in the detected ions, whereupon those ions put on the list are excluded from the objects of data-dependent analysis (tandem mass spectroscopy).


An electrical test circuit includes a bridge configuration having two paths between two nodes, a buffer, and a capacitor. An output of the buffer is coupled to one of the paths, the buffer is adapted to either provide a defined potential or a high impedance, the capacitor is connected to the output of the buffer, and a signal of a device under test is adapted to be coupled to another one of the paths. One of the nodes of the bridge configuration can be supplied with a first current, and the other one of the nodes of the bridge configuration can be supplied with a second current.

So-called active-load circuits are often used within test systems for terminating signals of a device under test with a programmable current. Such test circuits are present e.g. on a plug-in card of the test systems. Such plug-in cards, however, are usually only applicable for digital signals of the device under test, and if an analog signal of the device under test is to be tested, different plug-in cards have to be applied.

Electrical test circuit with active-load and output sampling capability


A disclosed method and device relate to defining a link aggregation group (LAG) media access control (MAC) address and assigning the LAG MAC address to two or more links to define a LAG. The LAG MAC address does not duplicate physical MAC addresses associated with the links in the LAG. Datagrams associated with the links in the LAG are routed based on the LAG MAC address.

A link aggregation (e.g., as set forth in IEEE 802.3ad) is a computer networking term which describes using multiple links (e.g., Ethernet network cables and/or ports in parallel) as one logical port to increase the link speed beyond the limits of any one single link. Other terms used for link aggregation may include Ethernet trunking, network interface card (NIC) teaming, port teaming, NIC bonding, and/or link aggregation group (LAG). LAG will be used hereinafter to refer to link aggregation.
LAG is an inexpensive way to set up a high-speed backbone network that may transfer more datagrams than any one single port or device can utilize. A "datagram(s)" may include any type or form of data, such as packet or non-packet data. LAG may permit several devices to communicate simultaneously at their full single-port speed, while not permitting any one single device to monopolize all available backbone capacity. Network datagrams may be dynamically distributed across ports so that administration of what datagrams actually flow across a given port may be taken care of automatically with the LAG.
LAGs also provide reliability. Should one of the multiple ports used in a LAG fail, network traffic (e.g., datagrams) may be dynamically redirected to flow across the remaining good ports in the LAG. The redirection may be triggered when a switch learns that a media access control (MAC) address has been automatically reassigned from one LAG port to another port in the same LAG. The switch may send the datagrams to the new LAG port, and the network may continue to operate with virtually no interruption in service.
A LAG protocol (LAP), such as the LAP set forth in IEEE 802.3ad, allows one or more links to be aggregated together to form a LAG. Once implemented, the LAG can be configured and reconfigured quickly and automatically with a low risk of duplication or rendering of frames.
Each communication interface is typically assigned a unique real MAC (RMAC) address to ensure that all devices in an Ethernet network have distinct addresses. A real MAC address is a hardware or physical address that uniquely identifies each device of a system. A real MAC address may be programmed by the device manufacturer. The communication interfaces (e.g., ports) of a LAG may have the same MAC address so that the LAG may behave as a single virtual link.
Typically, the real MAC address of one member (e.g., a port) of the LAG is chosen as the LAG MAC address for the group. Problems occur when the member whose MAC address is being used as the LAG MAC address wants to leave the LAG. Currently, the entire LAG has to be taken out of service so that the LAG can take on a new LAG MAC address.


The present invention provides an LED (Light Emitting Diode) illumination unit, an LED illumination device, and an LED illumination system with better visual effect. The LED illumination unit includes: a substrate, having a carrying surface with an x direction as a length direction and a y direction as a width direction and facing a z direction; a plurality of LED chips, supported by the carrying surface of the substrate; a casing, allowing the light emitted from the LED chips to penetrate and covering the LED chips; and a heat dissipation component, having a pair of outside surfaces being planar, and mounted with the substrate and the casing, wherein the pair of outside surfaces is configured opposite and parallel to each other in the y direction at an interval, and is longer than the substrate in the x direction.

1. Field of the Invention
The present invention relates to an LED (Light Emitting Diode) illumination unit, an LED illumination device, and an LED illumination system, including a plurality of LED chips and used for, for example, indoor ground illumination or wall surface illumination.
2. Description of the Related Art
FIG. 28 is a sectional view of an example of a conventional LED illumination device (for example, referring to Patent Document 1). An LED illumination device 90 shown in the figure includes a rectangular substrate 91, a plurality of LED chips 92 mounted on the substrate 91, a tube 93 accommodating the substrate 91, terminals 94, and a circuit 95 for turning the LED chips 92 on. A wiring, not shown in the drawings, connected to the LED chips 92 and the terminals 94 is formed on the substrate 91. The LED illumination device 90 is constructed such that the LED chips 92 can be enabled to emit light by plugging the terminals 94 into insert openings of a socket of general fluorescent lamp illumination equipment. As the LED chips 92 require low power consumption and have a long service life, improvements can be realized in aspects of cost and environment if the LED illumination device 90 is used to replace the fluorescent lamp. In addition, the fluorescent lamp illumination equipment for general use is illumination equipment mainly widely used for indoor general illumination, and for example, in Japan, refers to straight tubular fluorescent lamps specified in JIS (Japanese Industrial Standards) C7617 or annular fluorescent lamps specified in JIS C7618 using a 100 V power supply.
However, the conventional fluorescent lamp illumination equipment is constructed on the premise of presence of the terminals 94 at two ends and light emission in all directions. Therefore, if a plurality of LED illumination devices 90 is mounted on illumination equipment having a plurality of fluorescent lamps configured in series, non-illumination dark portions can be formed between neighboring LED illumination devices 90. Sometimes, the visual effect is poor. Or, when it is intended to illuminate a part of the wall surface, other parts than the part intended to be illuminated can also be illuminated if the LED illumination device 90 is used. As a result, for example, a light shield for covering half of the LED illumination device 90 needs to be disposed.    Patent Document 1: Japanese Laid-open Patent Publication No. H6-54103

LED illumination unit, LED illumination device, and LED illumination system


The present invention provides a multi-channel tunable filter and methods for making such a filter. In one embodiment, the filter comprises a bank of gratings or a continuously varying filter frequency imprinted into a filter material, such as Lithium Niobate or glass or polymer. An optical read-head comprising a pair of lenses is configured to pass light from within an optical fiber carrying multiple wavelengths through an appropriate grating to extract or drop a specific wavelength. To ensure continuous data transmission, the filter is tuned to a wavelength by configuring the read-head to move in a hitless manner. In one embodiment, the gratings are recorded by the interference of two beams. A first plane wave reflects off a first mirror stack and a second plane wave reflects off a second mirror stack. In another embodiment, the gratings are recorded by a phase masking method.

1. Field of the Invention
The present invention relates to fiber optics, lasers, and in particular the invention is directed to a multi-channel tunable filter.
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2. Background Art
Digital and analog information is often communicated using optical fibers. In some schemes, many signals, each with its own optical wavelength, are communicated on the same optical fiber. At some point, it is necessary to add or to extract a signal (i.e. a particular optical wavelength) from the optical fiber and this is accomplished with an optical add/drop filter. Various types of optical filters have been developed for use in telecommunications. Fixed wavelength optical filters are the most commonly used in today's networks to filter optical channels off a multiplexed stream of wavelengths. A problem with fixed wavelength filters is that they are limited to a single fixed optical wavelength. The increasing rate at which information is transferred makes the network increasingly difficult to manage. Network manageability can be simplified by selectively routing information at the wavelength level. This can be understood by a review of optical signal transmission schemes.
With the rapid emergence of the Internet, there is a great need to increase the volume of data that can be transmitted across a network of computing devices (commonly termed bandwidth). Initially, optical fiber networks carried only a single signal at a single wavelength. The bandwidth of optical fibers was increased by using a scheme known as wavelength division multiplexing (WDM).
The concept of WDM is to launch and retrieve multiple data channels in and out, respectively, of an optical fiber. Prior to the use of WDM, most optical fibers were used to unidirectionally carry only a single data channel at one wavelength. WDM divides a network's bandwidth into channels, with each channel assigned a particular channel wavelength. This allows multiple signals (each at a different wavelength) to be carried on the same transmission medium. For example, multiple optical channels can be used with fiber optic cable to transmit multiple signals on the same cable. The gain in the network bandwidth is given by the aggregation of multiple single channel bandwidth.
In most situations, the channels are merged (multiplexed) at a transmitting end and transmitted to a receiving end where they are separated (demultiplexed) into individual signals. In the existing systems, the transmitting and receiving ends must be tuned to the same wavelengths to be able to communicate. That is, the transmitting and receiving ends use a device such as an add/drop multiplexer to transmit/receive a fixed signal channel. In the case of fiber optic cable, an optical add/drop multiplexer can be used at nodes or at the receiving ends to generate a fixed wavelength (e.g., using lasers) and to receive a fixed wavelength. For example consider four channels 1, 2, 3 and 4. If the transmitting end is sending via channel 1, the receiving end must tune into the channel 1 wavelength as well to receive the data signal. When the transmitting end switches to channel 2, the receiving end must follow as well. Existing systems have as many as 2-128 signal channels.
In WDM, add/drop filters are needed to direct traffic in Long-Haul or Metropolitan networks. Current drop filter implementations lack flexibility. Some implementations have fixed wavelength drop filters. In these filters, each add/drop filter is fixed, meaning it is configured to extract and transmit only a specific wavelength within the optical fiber. This limits the flexibility for bandwidth allocation that WDM can provide.
In other filters where switching is allowed, the switching is often done in a non-hitless manner, meaning data is lost or interrupted during switching. Achieving hitless (non-blocking) wavelength switching is a challenge in drop filter design. In many critical applications the loss of data signal or interruption of service during wavelength switching is unacceptable. In these applications, the ability to hitlessly select a new wavelength without interruption of data flow is a requirement. However, many existing implementations of prior art tunable add/drop filters do not have this hitless property.
Typical examples of tunable optical filters include Fabry-Perot based tunable filters ("Fabry-Perot Tunable Filters Improve Optical Channel Analyzer Performance", Calvin Miller, Lawrence Pelz, Micron Optic Corp. and Siemens Corp.), ring resonator tunable filters ("Micro-ring Resonator Channel Dropping Filters", B. E Little, S. T Shu, H. A. Haus, J. Foresi, , J.-P Laine, Journal of Lightwave Technology, vol 15. No 6, 1997), Fiber Bragg grating (FBG) tunable filters ("Bragg grating Fast tunable filter for wavelength division multiplexing", A. Iocco, H. G Limberger, R. P Salathe, L. A. Everall, K. E. Chisholm, J. A R. Williams, I. Bennion), thin film tunable filters (www.santec.com ), Acousto-Optic tunable filter ("Ti:LiNbO3 Acousto-optic tunable filter (AOTF)", T. Nakazawa, S. Taniguchi, M. Seino, Fujitsu, Sci. Tech. J, 35, 1, pp 107-112, 1999), Mach-Zehnder interferometers and electro-optic tunable filters. A review of these type of tunable optical filters is presented in "Tunable Optical Filters for Dense WDM Networks", D. Sadot, E. Boimovich, IEEE communication magazine, December 1998, page 50-55.
Fabry-Perot (FP) and ring resonator (RR) filters are based on the same principle: light bounces back and forth between two high reflectivity mirrors or circulate multiple times in the ring. Tunability is achieved by changing the optical path between the mirrors (or in the ring). By tuning from one wavelength to another, all wavelengths in-between are being swept during tuning yielding a blocking tuning. Fiber Bragg gratings use a periodic perturbation of the refractive index of a material to selectively reflect a particular wavelength: tunability is achieved by changing the period of the perturbation by applying mechanical or thermal stress. This tuning mechanism is blocking as well.
Tunable thin film filters are made by deposition of multiple layers of varying thickness and index of refraction. Tunability is achieved by spatially varying the layer thickness. Acousto-optic filters rely on the modulation of the index of refraction by the interaction of a acoustical wave launched in the material with a transducer. Tunability is achieved by varying the frequency of the acoustical wave. Although such a tuning mechanism is non-blocking (hitless), these filter are relatively broad-band (>1 nm) and difficult to fabricate.

Method and apparatus for implementing a multi-channel tunable filter


A .pi./4 shift QPSK modulator includes a pre-processing part for subjecting an input transmitting code sequece to a pre-processing, a modulator part for selectively subjecting the transmitting code sequence received via the pre-processing part to a modulation in conformance with QPSK and a modulation in conformance with a .pi./4 shift QPSK, and an output part for outputting a modulated signal having a burst form based on an output of the modulator part depending on a burst signal having leading and trailing edges, where the pre-processing part carries out the pre-processing so that I-axis and Q-axis data supplied to the modulator part have the same symbol in succession at parts corresponding to the leading and trailing edges of the burst signal, so as to suppress generation of unwanted waves in the output part.

The present invention generally relates to modulators, and more particularly to a .pi./4 shift quadrature phase shift keying (QPSK) modulator which suppresses generation of unwanted waves which interfere other communications when making a burst transmission.
In a radio communication system using a phase modulation or amplitude phase modulation, there is a problem in that unwanted waves are generated at leading and trailing edges of the burst when transmitting the burst from the transmitting side using the time division multiplexing (TDM) and that the unwanted waves interfere other communications. Accordingly, a method of solving this problem was previously proposed in a Japanese Published Patent Application No.63-47179.
According to this previously proposed method, the phase at the leading and trailing edges of the burst is always shifted by 180.degree., that is, from .pi. to 0 or from 0 to .pi., in order to prevent the generation of the unwanted waves. As shown in FIG. 1 (a), a modulator input signal is changed from 0 to 1 at the leading edge and is changed from 0 to 1 at the trailing edge, for example, and a burst signal is turned ON/OFF at the transition point. The amplitude of the demodulator output signal is zero at the zero crossing thereof as shown in FIG. 1 (b), and thus, a considerable amount of the unwanted waves can be suppressed if the switching of the burst signal is made at the zero crossing.
However, according to the method of FIG. 1 (a), the unwanted waves remain in the burst spectrum for the 0/.pi. modulation as indicated by a dotted line in FIG. 2. Hence, bits are added as shown in FIG. 1 (c) so that the data signal does not change by two or more symbols at the leading and trailing edges of the burst signal. In this case, the bits "100" are added at the leading edge of the burst signal to turn the burst signal ON at the transition point from 1 to 0, and the bits "001" are added at the trailing edge of the burst signal to turn the burst signal OFF at the transition point from 0 to 1. By taking these measures, the spectrum of the unwanted waves shift towards the center frequency as indicated by a one-dot chain line in FIG. 2 and it is possible to further reduce the unwanted waves outside the band.
According to the above described method, it is necessary to add the bits which do not change by two or more symbols at the leading and trailing edges of the burst signal. A phase modulator generally uses a differential logic circuit, and such a differential logic circuit always generates an output which is inverted with respect to the previous bit when "1" is input and generates the same output as the previous bit when "0" is input. Hence, the same data can easily made to continue for two symbols by setting the input of the differential logic circuit to (0, 0). Recently, a .pi./4 shift QPSK have been developed to improve the characteristic of the phase modulation system against distortion. According to this .pi./4 shift QPSK, the signal point arrangement of the QPSK and the signal point arrangement which is shifted by .pi./4 from that of the QPSK are alternately used to carry out a 4-phase phase modulation. FIG. 3 shows an example of a general signal point arrangement of the .pi./4 shift QPSK. As shown in FIG. 3, a signal point arrangement indicated by a mark ".sup..cndot. " is used at a certain timing, and a signal point arrangement indicated by a mark "x" and shifted by .pi./4 from the certain timing is used at a next timing, and such signal point arrangements are alternately used in a repeated manner to carry out the 4-phase phase modulation. As a result, the characteristic of the phase modulation system against the distortion is improved. According to the .pi./4 shift QPSK, the signal point data take five values.
However, the above described method of suppressing the unwanted waves by making the same data continue for two or more symbols at the leading and trailing edges of the burst signal cannot be applied to the .pi./4 shift QPSK. In other words, because the signal point arrangement according to the .pi./4 shift QPSK is always shifted by .pi./4 at each timing, the same data cannot be made to continue for two or more symbols by merely making the input of the differential logic circuit (0, 0).
Therefore, there is a demand to realize a .pi./4 shift QPSK in which the unwanted waves can be suppressed as in the case of the above described method, while improving the characteristic of the phase modulation system against the distortion.

.pi./4 quadrature phase shift keying modulator


Disclosed is a battery module, which includes: a battery cell assembly having at least one battery cell; a module case configured to accommodate the battery cell assembly; and at least one injection hole provided in a bottom portion of the module case to inject a thermally conductive adhesive into the module case.

Secondary batteries which are highly applicable to various products and exhibit superior electrical properties such as high energy density, etc. are commonly used not only in portable devices but also in electric vehicles (EVs) or hybrid electric vehicles (HEVs) driven by electrical power sources. The secondary battery is drawing attentions as a new energy source for enhancing environment friendliness and energy efficiency in that the use of fossil fuels can be reduced greatly and no byproduct is generated during energy consumption.
Secondary batteries widely used at the preset include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel hydrogen batteries, nickel zinc batteries and the like. An operating voltage of the unit secondary battery cell, namely a unit battery cell, is about 2.5V to 4.5V. Therefore, if a higher output voltage is required, a plurality of battery cells may be connected in series to configure a battery pack. In addition, depending on the charge/discharge capacity required for the battery pack, a plurality of battery cells may be connected in parallel to configure a battery pack. Thus, the number of battery cells included in the battery pack may be variously set according to the required output voltage or the demanded charge/discharge capacity.
Meanwhile, when a plurality of battery cells are connected in series or in parallel to configure a battery pack, it is common to configure a battery module composed of at least one battery cell first, and then configure a battery pack by using at least one battery module and adding other components.
In the case of the conventional battery module, the technology for efficiently cooling the heat generated at the battery cells is becoming more and more important as the demanded battery capacity is increasing.
For the efficient cooling, in the conventional battery module, a thermally conductive adhesive is applied to the inside of a module case to stably fix a battery cell assembly including at least one battery cell in the module case and to improve thermal conductivity.
However, in the conventional battery module, when an injection hole for injecting the thermally conductive adhesive into the module case is formed, the battery cell assembly in the module case may be damaged due to burr or the like, or an injection nozzle for injecting the thermally conductive adhesive may not be accurately inserted into the injection hole, or the thermally conductive adhesive may leak out of the module case.

Battery module, battery pack including battery module, and vehicle including battery pack


The high cost of fuel injectors for use in small scale environments is avoided in a fuel injection nozzle structure including a simple tube 10 used as a fuel injecting tube and having a fuel injecting end 12 received in a reduced diameter outlet 18 from an axial air flow chamber 20 concentric therewith. A swirling air flow chamber 34 surrounds the axial air flow chamber 20 and includes an annular, axially facing outlet 36 concentric with a diverging exit 24 from the reduced diameter outlet 18.

Swirl flow in combustors has been shown to be advantageous because the high centrifugal forces generated during operation may be utilized to advantageously modify flame turbulence. However, in small scale apparatus, wherein fuel is frequently atomized by high velocity air as a result of the pressure drop across an air swirler, the resulting fuel droplets are rapidly accelerated up to the speed of the air and mixed with the air as a consequence of the extremely high centrifugal forces present. When employed with turbines, at low turbine speeds and at low air temperatures, much of the fuel fails to evaporate and impinges as small droplets on the wall of the combustor. Tough starting of a turbine engine at low rotational speeds is a result.
This difficulty may be alleviated by upsizing the combustor but where the turbine is to be employed in an airborne environment, which is frequently the case and even the cause of low temperature, size and mass problems are compounded.
Moreover, in small scale turbines employing small scale combustors, a low cost apparatus is a commercial necessity. The injectors employed must be downsized and consequently must be simple and inexpensive to form. This in turn frequently means that the size of the fuel droplets generated during atomization by such small injectors increases. The increased droplet size means, of course, greater mass and greater susceptibility to the action of centrifugal force resulting from swirl flow.
Furthermore, even when starting ability is not of primary concern, the premixing of fuel and air as mentioned previously tends to lower stability of the flame and frequently, gaseous phase smoke is produced at fuel rich conditions that are provided to improve flame stability. This in turn results in high flame radiation. The combustor walls necessarily must absorb such radiation and as a consequence, the cooling of the combustor walls becomes more difficult.
The present invention is directed to overcoming one or more of the above problems.


A film is extruded from plastic material by an extruder. The film is orientated after extrusion. Material is mixed into the plastic so that when the plastic film is stretched, cavitation bubbles are formed in the material particles mixed into the plastic. During the orientation, gas is arranged to the plastic film under high pressure so that the gas diffuses in the cavitation bubbles and causes overpressure in them. Thus, it is possible to make a thin foamed film with a foaming degree over 70%.

The invention relates to a method for making a plastic film, the method comprising extruding a plastic film and orientating it.
The invention also relates to an apparatus for making a plastic film, the apparatus comprising an extruder and at least one orientation device for orientating the extruded film.
The invention further relates to a plastic film which comprises bubbles with the maximum diameter of about 100 micrometers and the maximum height of about 10 micrometers.
Making a plastic film by extruding it and then orientating it is known e.g. from U.S. Pat. Nos. 3,244,781 and 3,891,374. It is, however, difficult to make thin and in particular thin foamed films using these solutions.
EP publication 0,182,764 discloses a thin polypropylene film which contains wide and flat disk-like bubbles, which are about 80 micrometers in length and about 50 micrometers in width. The film is produced by extruding material which has been foamed chemically or by means of gas and by orientating the extruded material biaxially. The result is a very versatile plastic film. However, the foaming degree of the film is less than 50%, which is why the properties of the film are not good enough for all purposes.
Furthermore, it is not possible to produce thin films of polymethylpentene or cyclic olefin copolymer using the prior art solutions.
The object of this invention is to provide a very good and thin foamed plastic film and a simple and reliable method and apparatus for making said plastic film.
The method of the invention is characterized in that before extrusion material is mixed into the plastic of the plastic film, cavitation bubbles are formed in the plastic film to be stretched due to the influence of the material, after extrusion the plastic film is orientated by stretching, and simultaneously with orientation pressurized gas is arranged to act on the plastic film so that the gas diffuses in the cavitation bubbles, and thus bubbles containing gas are formed in the plastic film.
The apparatus of the invention is characterized in that the apparatus comprises gas supply means arranged in one orientation device for feeding pressurized gas into the plastic film simultaneously with orientation by stretching so that the fed gas diffuses in the cavitation bubbles that are formed in the plastic film during stretching, and thus bubbles containing gas are formed in the plastic film.
The plastic film of the invention is characterized in that material is mixed into the plastic of the plastic film, cavitation bubbles are formed in the plastic film to be stretched due to the influence of the material, and the plastic film is subjected to stretching and to pressure of pressurized gas simultaneously with stretching so that the bubbles contain said gas, the foaming degree of the plastic film being over 70%.
The basic idea of the invention is that a film is extruded from plastic material by means of an extruder and material has been mixed into the plastic so that when the plastic is stretched, cavitation bubbles are formed in the material particles mixed into the plastic. The film is orientated by stretching and at the same time gas is fed into the film under high pressure so that the gas diffuses in the cavitation bubbles and causes overpressure in them. The idea of a preferred embodiment is that after the first orientation the plastic film is orientated by stretching it in the direction substantially perpendicular to the first orientation direction, and thus the overpressure is released in the cavitation bubbles and the bubbles expand.
An advantage of the invention is that very thin films with a foaming degree of about 70 to 90% can be provided in a relatively simple manner. An advantage of the high foaming degree is that the electric and mechanical properties of the film are very good. A further advantage is that the method and apparatus can be used for making a film for example of polymethylpentene or cyclic olefin copolymer.

Method and apparatus for making plastic film, and plastic film