A gas operated part forming die apparatus has compact high tonnage presses which are operated by high pressure gas generated within chambers and controlled to operate high pressure pistons and dies for compressing particulate material into dense formed parts. Combustion chambers are filled with pressurized mixtures of combustible gases and diluents. Elongated chambers have insulating walls and spaced electrodes. Some contain liquid or particulate ablatable materials or ablatable liners. Others extend fuzes between the electrodes and are filled with pressurized gases. Gas is removed from the particulate material. Die cavities may be precompressed during filing of chambers with pressurized gas. Igniting the combustible gases or creating arcs between the electrodes produces rapidly expanding high pressure resultant gases for driving pistons and movable dies and rapidly compressing die cavities. Pressures in the chambers are contained, or pistons are restrained until releasing and driving the pistons. Large area pistons drive smaller movable dies.

1. Field of the Invention
This invention relates in general to the field of powder metallurgy and in particular to an improved and less expensive method and apparatus for generating controllable pressure pulses (both in the shock regime and in a rapid, but shock-free, regime in the same device) for the purpose of consolidating (compacting) powders to a contiguous rigid form, primarily for the purpose of producing material samples and manufactured parts. In this field, the emphasis is generally on producing higher quality and better performing parts, which generally means parts with higher density, strength and ductility, and doing so at lower cost.
2. Description of Related Art
Powder metallurgy (P/M) offers possibilities for the design of materials into near net shape which exhibit a wide range of unique and novel properties. In principle, there is no limitation on the production of a material with any desired composition by such methods. However, the high cost of powder metallurgy technology must compete with other low cost manufacturing methods.
Below, we first describe two specific market areas (soft and hard magnetic materials) of some commercial interest as an example of the need. Other markets for other materials are of equal interest. The dynamic compaction of conventional powders using the described invention as a low cost high tonnage compact press is expected to have high value in the part manufacturing industry. Then we describe present powder consolidation technology and dynamic powder consolidation techniques and their limitations.
Soft Magnetic Materials
The world-wide magnetic materials market is a multi-billion dollar industry, and soft magnetic materials comprise a significant fraction of this market. Soft magnetic materials play a key role in a number of applications, especially with respect to electric power applications. Some of these applications include electric motors, distribution transformers, and generators.
Soft magnetic materials find applications in electrical, electronics, and computer systems that characterize modern society. Soft magnetic materials play a key role in power distribution, make possible the conversion between electrical and mechanical energy, underlie microwave communication, and provide both the transducers and the active storage material for data storage in information systems. As the properties of these materials are continuously being improved, many new applications are likely to emerge.
The critical properties necessary in designing optimum soft magnetic materials include a high saturation magnetization, low coercivity, low hysteresis loss, high permeability, low magnetostriction, low eddy current losses, high Curie temperature, low temperature dependence of the magnetic properties, and cost. In practice, the available materials must compromise some of these properties in favor of others. For example, permalloys (Fe—Ni-based alloys) have a tremendously high permeability and very low coercivity, but the saturation magnetization is only approximately 60 percent of the value for α-Fe.
Many of the requisite properties are intrinsic, such as a high saturation magnetization and magnetostriction. These properties are tailored through the specific design of the alloy. Other properties are influenced by extrinsic factors, most notably by microstructural features. The magnetic properties strongly influenced by the microstructure are those involving domain wall motion. For example, the eddy current losses arise because soft magnetic materials generally operate in alternating fields. The losses arise primarily because of difficulties in reversing the magnetization state of the material. This, in turn, is controlled by domain wall motion; if domain wall motion is inhibited, the losses are greater. Microstructural features such as precipitates and localized strain fields from dislocations and impurity atoms provide pinning sites for domain walls. The eddy current losses also increase as the size of the magnetic regions increases and as the resistivity decreases. Thus, the eddy current losses can be reduced by reducing the coercivity and the scale of the microstructure and by decreasing the electrical resistivity.
The coercivity is affected by both intrinsic and extrinsic factors. Intrinsically, the coercivity is controlled by the specific anisotropy of the crystal lattice (magnetocrystalline anisotropy). While cubic crystals possess the lowest anisotropy, there is variability between different cubic materials. For example, the anisotropy constant (the parameter that describes the degree of anisotropy) differs by almost an order of magnitude between Fe and Ni. As with other intrinsic properties, the anisotropy can be altered through alloy design.
The primary extrinsic influence on the coercivity is the microstructure. The microstructure, in fact, influences the entire shape of the hysteresis loop. Some examples of microstructural features that influence the coercivity by affecting domain wall motion include defect density, including dislocations and point defects (e.g., impurity atoms). Therefore, it is critical to control microstructural features in order to produce more efficient soft magnetic materials.
One microstructural feature that greatly impacts the coercivity is the structural correlation length (D). In crystalline materials, the structural correlation length is equal to the grain size, while in amorphous materials it is essentially the distances over which short range order exists. As grain sizes decrease from the millimeter size range to approximately 0.1 μm, there is a corresponding increase in coercivity proportional to 1/D. However, when the structural correlation length approaches the ferromagnetic exchange length, which is on the order of the domain wall width, the coercivity begins to decrease. With a continuing decrease in the structural correlation length, the coercivity was observed to decrease with a D6 dependence. This dramatic decrease in coercivity has been attributed to the averaging of local anisotropies by the exchange interactions, with the net effect of eliminating (or significantly reducing) the influence of magnetocrystalline anisotropy on the magnetization process.
The strong dependence of coercivity on the structural correlation length has prompted a significant amount of research in the areas of nanocrystalline and amorphous alloys, where D ranges from 0.5 to 50 nm. Amorphous alloys typically consist of Fe— or Co-based alloys with additions of Si and B, which enhance the glass formability, and other alloying additions to control, for example, the magnetostriction. Currently, nanocrystalline microstructures are formed by the crystallization of specific amorphous alloys, with the resulting microstructure consisting of 10 to 15 nm crystallites surrounded by an amorphous matrix. The primary advantage of amorphous and nanocrystalline alloys is the reduction of the anisotropy and, in the case of nanocrystalline materials, magnetostriction. Amorphous metals have been used in place of grain-oriented Si steels in transformer applications, which provided a reduction of 75 percent in eddy current losses because of reduced coercivity and magnetostriction. However, the saturation magnetization is significantly reduced, with values ranging from 10 to 15 kG for current amorphous and nanocrystalline alloys (compared to 21.5 kG for α-Fe). The lower saturation values result from the dilution of the Fe or Co alloys with elements that enhance glass formability or alter other intrinsic properties. Future advances in soft magnetic materials will be made by increasing the saturation magnetization while retaining the advantageous properties of amorphous and nanocrystalline microstructures.
Generally, nanocrystalline and amorphous materials are produced in particulate form by atomization or melt spinning techniques. Practically, the consolidation of nanocrystalline and amorphous particulate into useful engineering devices provides many unique challenges. Most densification techniques rely on elevated temperatures to promote densification. However, exposure to elevated temperatures significantly degrades the hard-won microstructural features through crystallization and grain growth. Other techniques utilize binders, allowing low temperature consolidation. Using binders, however, dilutes the amount of magnetic material in the final part to, at most, 70 percent by volume, resulting in a lower saturation magnetization by volume in the final engineering component.
Dynamic consolidation techniques allow densification to full density without prolonged exposures to elevated temperatures and the concomitant degradation of the microstructures. Dynamic consolidation techniques utilize shock waves of sufficient strength to generate interparticle welding and melting, with temperature excursions essentially eliminated. Shock waves generated by, for example, explosives or projectiles have been utilized to densify rapidly solidified particulate materials in a wide variety of alloy systems, including magnetic materials. Most dynamic consolidation techniques, however, are not amenable for large-scale production techniques. Novel techniques to generate sufficient shock waves must be developed in order to fully realize the benefits of dynamic consolidation on a practical level.
Dynamic consolidation techniques are desirable to consolidate soft magnetic nanocrystalline and amorphous materials. Dynamic consolidation will allow full densification without deleterious effects on the microstructure. Thus, the benefits of nanocrystalline and amorphous microstructures on the magnetic properties can be retained in the final engineering component.
Hard Magnetic Materials
Permanent magnet materials significantly affect a wide spectrum of industries, with applications in such diverse areas as microelectronics, the automobile industry, medical devices, and power generation. Applications in permanent magnet motors alone require some 920 tons of fully dense and 770 tons of bonded Nd—Fe—B magnets annually. Currently, the permanent magnet industry is a $4.05 billion industry, with projections reaching $10 billion for 2005.
Hard magnetic materials find applications in the automotive, aerospace, and telecommunication industries. For their size and weight rare earth magnets, such as NdFeB, have a higher energy density than other hard magnets. These magnets are used in compact powerful electric motors for computer disk drives and fly-by-wire aircraft. They also find applications as high precision actuators used to focus the laser in a compact disk player and in miniature loud-speakers of personal stereos. Automotive applications include starters, small motors, alternators, sensors, meters, and electric and hybrid vehicle propulsion systems. These magnets are made from powdered metal by forming to shape under pressure and sintered.
Two materials comprise almost 90 percent of the hard magnetic market: ferrites (58 percent) and Nd—Fe—B (31 percent). With only modest magnetic properties, with a maximum energy product of approximately 5 MGOe, the principal advantage of ferrite is its inexpensiveness, especially in terms of raw materials cost. It is used in applications where size and weight are not design considerations. When magnetic strength is more paramount than cost, Nd—Fe—B magnets are favored. The energy product of isotropic Nd—Fe—B magnets range from 7-8 MGOe for bonded magnets to 15 MGOe for fully dense hot pressed magnets. The energy product of anisotropic Nd—Fe—B magnets range from 45 MGOe for commercially available products to 54.4 MGOe for magnets produced on a laboratory scale.
Requisite intrinsic properties necessary for high strength permanent magnets include a high saturation magnetization, large magnetocrystalline anisotropy, and a reasonably high Curie temperature. In addition, the properties of any real material are strongly influenced by extrinsic factors, most notably the microstructure. Such factors as the microstructural scale, phase content and grain morphology and orientation strongly influence a material's properties. These factors also greatly influence the magnetic properties, especially the scale of the microstructure. Superior properties arise when the grain size is below a critical limit known as the single domain limit. When the grain size is larger than the single domain limit, multiple domains are present in each grain. This multiple domain state leads to relatively easy demagnetization and poor hard magnetic properties. When the grain size is below the single domain limit, demagnetization is much more difficult, leading to excellent hard magnetic properties. The single domain limit is related to specific intrinsic magnetic properties, including the anisotropy constant and the saturation magnetization. For Nd—Fe—B magnets, the single domain limit is approximately 300 nm.
For isotropic permanent magnets, it is imperative that the grain size be below the single domain limit. Because of this requirement of a fine grain size, non-equilibrium processing techniques are required. Currently, the commercially preferred technique to generate a fine-scale microstructure is melt spinning. Depending on the processing parameters, melt spinning generates a microstructure that ranges from fine, equiaxed grains on the order of 20 to 30 nm to an amorphous structure that crystallizes during consolidation. It is critical to retain as fine a microstructure as possible upon further processing to optimize the magnetic properties.
Monolithic Nd—Fe—B permanent magnets useful in applications are produced by the consolidation of comminuted melt spun ribbon. Isotropic Nd—Fe—B permanent magnets, with energy products of approximately 12-15 MGOe, are consolidated by conventional hot pressing techniques. However, during the relatively prolonged times at elevated temperatures, grain growth occurs, resulting in deleterious effects on the magnetic properties. Anisotropic magnets are produced by die upset processing of the hot pressed magnets. Die upsetting results in crystallographic alignment through preferred grain growth. The high degree of crystallographic alignment results in higher energy products. However, the additional exposure to elevated temperatures during die upsetting further degrades the microstructure. The degradation in the microstructure and the limited crystallographic alignment achievable limits commercially available energy products to 45 MGOe, only 70 percent of the theoretical maximum of 64 MGOe.
On a laboratory scale, efforts have been made to retain the beneficial microstructural features produced during melt spinning. This has been accomplished through consolidation by shock and explosive compaction. These dynamic consolidation processes result in extremely short exposure to elevated temperatures, allowing the fine microstructures generated during melt spinning to be retained. The dynamically consolidated magnets retained the magnetic properties and microstructures of the initial melt spun ribbon. In addition, die upsetting of shock-consolidated amorphous ribbon resulted in an anisotropic fine-grained monoliths with an energy product of 54.4 MGOe (85 percent of the theoretical maximum).
The laboratory-scale tests illustrate the benefits of retaining a fine microstructure in the final consolidated magnet. However, scale-up of the previously mentioned dynamic consolidation techniques provide unique challenges. The development of other dynamic consolidation processes that limit the material's exposure to elevated temperatures while providing consolidation to near full density will provide a route to materials with improved magnetic properties. In addition, the development of processes that retain fine microstructures during consolidation would provide an avenue to commercially produce magnets utilizing novel magnetic materials that absolutely rely on a nanocrystalline microstructure, such as the recently discovered nanocomposite or spring-type magnets.
Non-magnetic Powders
The dynamic compaction of conventional powders (ferrous and non-ferrous) using the described invention as a low cost high tonnage compact press is expected to have high value in the part manufacturing industry because of higher green density and green strength in the resulting parts at faster compaction rates. According to the trade association, Metal Powder Industries Federation (MPIF), the P/M (powder metallurgy) parts and products industry in North America has estimated sales of over $2 billion. It is comprised of 150 companies that make conventional P/M parts and products from iron and copper-base powders; and about 50 companies that make specialty P/M products such as superalloys, tool steels, porous products, friction materials, strip for electronic applications, tungsten carbide cutting tools and wear parts, rapidly solidified powder products, and metal injection molding (MIM) parts and tool steels. P/M is international in scope with growing industries in all of the major industrialized countries. The value of U.S. metal powder shipments (includes paste and flake) was $1.9 billion in 1996. Annual worldwide metal powder production exceeds one million tons.
MPIF estimates the MIM North American market to exceed $100 M and to grow at an annual rate of 20 to 25%. There was an estimated 25 to 40 companies in North America manufacturing MIM products either as job shops or in plant departments. This growth rate is fueled by strong auto production and an increase in PM parts applications in auto engines and transmissions. The advanced particulate materials sector of the PM industry has a bright future, especially PM high speed tool steels, PM superalloys and composites, MIM and spray formed parts, materials, and fibers. PM parts and products made from advanced particulate materials will find new applications in automotive, aircraft engine, electronic packaging, computer peripheral equipment and medical markets. Looking ahead, PM nickel-based superalloys and advanced composites are being considered for the NASA high speed civilian transport plane. According to MPIF, the PM parts industry will outpace metalworking due to increases in applications for PM components, longer term growth of the industry will continue to gain metalworking market share, and the use of PM parts in industrial markets especially automotive is now widely recognized for contributing significantly to cost and performance competitiveness.
An example of advanced materials, is the intermetallic compound TiAl, possessing the ordered (γ-fct) structure, has attractive and unique properties for extended high temperature applications. Parts made of aluminides (TiAl, Ti3Al, NiAl, NbAl3, etc.) and other intermetallic compounds have potential for applications requiring light weight and high-temperature strength and oxidation resistance. Intermetallic compound powders made by rapid solidification processing (RSP) are brittle and hard, making it difficult to consolidate these powders by conventional techniques. The high temperature exposures for long times, involved in the conventional techniques, causes excessive grain growth and phase transformation of the initially RSP microstructure. Therefore, to ensure ductility and other desired mechanical properties these parts need to be formed by consolidation of the RSP powders. Also, room-temperature brittleness is a problem with conventional intermetallics. The challenge, then, is to develop powder consolidation techniques that do not adversely affect any enhancements due to RSP. Intermetallics are also used as matrices in composite materials. Here, the goal is consolidation without incurring excessive reactions between matrix and reinforcement.
Present Powder Consolidation Technology and its Limitations
Conventional Powder Consolidation Techniques
Several conventional consolidation techniques and their variants for particulate materials exist. These include die pressing, cold (CIP) or hot isostatic pressing (HIP), reactive sintering, powder injection molding, ceramic consolidation, and electroconsolidation which produce consolidated products.
Conventional powder compaction is performed by die pressing. The die provides the cavity into which the powder is pressed and gives lateral constraint to the powder. An external feed shoe vibrates the powder into the die. An upper and a lower punch are used for most compaction. Both punches are loaded to generate stress within the powder to produce the part. There are several modes of pressing and thus several types of presses including hydraulic, mechanical, rotary, isostatic, anvil, etc. These are all very large, noisy, complex, and expensive systems. The limitations of conventional die pressing include limited green density, limited green strength, green density gradients, need for binders and binder removal (a slow and expensive process), and shrinkage of parts during sintering.
CIP is used for complex shapes involving undercuts or large length to diameter ratios. A flexible mold is filled with powder and pressurized isostatically using a fluid such as oil or water. CIP is typically performed at pressures below 350 MPa (megapascals) although pressures up to 1400 MPa have been achieved. While higher green densities with less density gradients are reached at a given pressure when compared to die pressing, most of the other limitations of die pressing exist in CIP.
In HIP, a gas-tight can is used to contain the powder. Volatile contaminants are removed by heating and vacuum degassing. The can is then sealed and pressed in an internally heated pressure vessel. Argon gas at high pressure is used to transfer heat and pressure isotropically to the compact, leading to densification. After HIP, the can is stripped from the densified compact. This is a low strain rate process because the stress rise is slow. The long time exposures at high temperatures lead to grain growth and loss of the initial fine and rapidly solidified microstructures.
Several variants of reactive sintering have been employed to consolidate metallic and intermetallic materials. The basis of all reactive sintering processes is the formation of a liquid phase as a result of an exothermic reaction between elemental powders present in the mixture. The liquid phase accelerates consolidation and is consumed during the process. The reaction may proceed with no pressure (reactive sintering), with isostatic pressure (reactive hot isostatic pressing, RHIP) or unidirectional pressure (reactive hot pressing, RHP). As an example, the typical process steps for NiAl-20 volume % TiB2 composite are as follows:                1) Ni and Al (along with TiB2) are mixed to stoichiometric proportions.        2) Compacts are pressed to a green density of approximately 70% of theoretical.        3) Compacts are vacuum encapsulated in 304 stainless steel.        4) Encapsulated compacts are pressed at 1200° C. and 172 MPa for 1 hour.
A disadvantage with reactive sintering is the difficulties associated with HIP, which often accompanies or succeeds reactive processing, such as the need for ductile canning materials that do not react with the powders and the need to seal cans carefully. The expenses associated with welding HIP cans and expense of reactive metals such as Ti and Nb overcomes the low costs associated with reactive sintering step.
Powder injection molding involves extrusion of a mixture of powders, any reinforcements, and a binder through a die. The extrusion should be performed above the softening temperature of the binder. After extrusion the binder is removed (thermally or by wicking action) and the compact is consolidated to approximately full density by HIP. Fully dense Al2O3-reinforced composites of NiAl and MoSi2 have been produced successfully by this method. This process offers the possibility of producing complex P/M parts. However, the principal disadvantages are the difficulty of complete binder removal and the inability to produce continuous fiber-reinforced composites.
The Ceracon (for "CERAmic CONsolidation") process uses a granular ceramic material as the pressure-transmitting medium (PTM) as opposed to the gas used in HIP. A preform of the material to be consolidated is preheated and immersed in the hot ceramic PTM. Pressures as high as 1.24 GPa (180×103 psi) are applied to the preform via the PTM for 30 to 60 seconds. The uniaxial pressure applied to the PTM bed is transmitted to the preform as quasi-isostatic pressure, and consolidation of the part takes place in 30 to 60 seconds. Both the Ceracon and HIP processes operate in the plastic-yielding range and it is possible with the Ceracon process to produce full densification almost exclusively by plastic yielding, which is essentially instantaneous. The high consolidation pressure available, in the Ceracon process, permits the temperature to which the material is exposed to be relatively low (compared with HIP and hot pressing) and the exposure times to be short. This allows full densification of the material while maintaining the fine microstructure. In composite materials interfacial reactions between the matrix and reinforcement phases are minimized or eliminated. Critical parameters of the process include part temperature, PTM temperature, applied pressure, strain rate, preheat time and temperature, and hold time at temperature.
The electroconsolidation process uses graphitic-carbon particles, having controlled electrical properties, as both the PTM and as an electrical resistor for simultaneous heating and consolidation of powder preforms in a modified hot-pressing facility. This technique is being evaluated for rapid pressure-assisted densification, to near-net shape, of metal and ceramic powder preforms, whisker-reinforced ceramic composites, and other materials that require, or could benefit from, pressure-assisted consolidation at very high temperatures. Electroconsolidation is a member of the family of "soft" tooling, pseudo-HIP, or containerless-HIP consolidation processes that use a particulate "pseudo-fluid" as the PTM. A cold preform is heated to the consolidation temperature by resistive heating of the surrounding medium, within the die, simultaneously with the application of the compaction pressure. This "inside-out" method of preform heating is particularly advantageous for densifying nonoxide ceramics and other materials that require very high temperatures for consolidation to near theoretical density. Such temperatures are difficult to achieve by other powder-vehicle compaction methods that require transfer of either a preheated preform or the heated medium into the compaction vessel. In development work, a 50-t (55 ton, 490 kN) and a 100-t (110 ton, 980 kN) presses were adapted for electroconsolidation.
Electroconsolidation was demonstrated to compact SiC preforms to near-theoretical density. The cold compacted preforms were oven dried, baked, and then heat treated at 1500° C.
Electroconsolidation followed, using a compaction pressure of 28 MPa (4000 psi) and a nitrogen atmosphere. At power levels above 20 kW rapid densification was obtained; densities of 90+% and 95% of theoretical were obtained in less than 2 minutes and 4 minutes respectively. Parts were rapidly heated by the conductive medium to about 2000° C. (3630° F.). Advantages of the process, compared with conventional hot pressing and HIP, include: rapid cycle times (minutes versus hours), high temperature capability (to 3000° C., 5430° F.), controlled atmosphere capability (inert or active gases), and the ability to densify complex shapes without "canning". Because densification is rapid, this process has the potential for inhibiting grain growth, resulting in fine-grain parts having the improved mechanical properties associated with this fine microstructure. In addition, high-vacuum or high-pressure pumps are not needed, and the ability to adapt existing hot-pressing systems can help keep equipment costs down.
Materials Modification, Inc., (MMI) has developed and patented a powder consolidation technique called Plasma Pressure Compaction (U.S. Pat. Nos. 6,187,087; 6,183,690; 6,001,304; 5,989,487). This is based on the plasma activated sintering (PAS) technique published by several investigators. In the PAS process, densification is achieved by a combination of resistance heating with pressure application and plasma generation among the powder particles. The time for high temperature and pressure application is short, of the order of minutes rather than hours, to reach full densification. Difficult to sinter materials such as covalent ceramics, oxygen sensitive intermetallic compounds, and superconductors have been consolidated by PAS. MMI's Plasma Pressure Compaction technique claims to consolidate submicron and nanomaterials (metals, intermetallics, and quasiceramics) at reduced consolidation time, lower oxygen content in the final part, higher density (tungsten to 97% and rhenium to 96% dense), and reduced processing temperature.
Dynamic Powder Consolidation Techniques
In addition to the above conventional techniques and their variants, there are dynamic consolidation techniques which use explosives, impact, and pulsed magnetic forces to yield full densities. Dynamic (shock) consolidation and synthesis of materials have been used to a considerable degree in research activity on materials development. Shock-wave consolidation of powders was used for the first time in the 1950's to produce high density parts from materials used in aerospace and atomic energy applications. Dynamic consolidation has the potential to meet the challenges to consolidation of advanced materials such as intermetallic monolithic and composite materials, and become a cost effective technique for fabrication of intermetallic-based parts.
Conventional powder-consolidation methods, such as sintering and HIP, typically involve long times at high temperatures, and rely on solid-state diffusion. Dynamic consolidation typically involves high-pressure shock waves that travel at several kilometers per second through the sample. These shock waves are generated in the sample by various methods including detonating explosives to accelerate a "flyer plate" into the powder sample or using a gun to fire a projectile into the sample. Larger samples generally can be produced with explosives, while use of a projectile generally allows better control and measurement of experimental parameters such as impact velocity. Processing is generally achieved by discharge of a single high-energy pulse through a pressurized powder blend. Applied pressures range from 210 to 420 MPa and the specific energy inputs varied between 3200 and 4800 kJ/kg. Consolidation occurs by diffusion through a thin layer of liquid that is temporarily created between particles. As the shock wave passes through the powder, it gives up most of its energy at particle boundaries, possibly because of interparticle friction. Partial melting occurs near these boundaries, and the liquid rapidly solidifies by heat conduction into the relatively cool particle interiors. Dynamic consolidation can therefore be considered a "cold" method. Details of the actual consolidation mechanism depend on the powder and processing conditions. For example, solid-state bonding of particles sometimes occurs without partial melting, and melting may be caused by adiabatic heating generated by plastic deformation of particles, rather than by interparticle friction. Scientists at Rockwell International have dynamically consolidated rapidly solidified γ-Ti-48Al powder using explosive-launched stainless steel flyer plates. This dynamic consolidation resulted in a nonequilibrium single-phase alpha-2 (DO19) structure. When the same powder is hot pressed, the equilibrium lamellar mixture of 85 to 90 volume % γ and 10 to 15 volume % α-2 phases result. Rockwell scientists also dynamically consolidated SiC/Ti—Al—Nb composites resulting in a uniform dispersion of the SiC fibers in the aluminide matrix with a safe and very thin (50 nm) fiber/matrix reaction zone. The same composite when hot pressed resulted in a thick (more than 1 micrometer) fiber/matrix reaction zone that is deleterious to the fracture properties of the composite.
Potential advantages of dynamic consolidation, as identified by previous investigators, include:                Nonequilibrium microstructures produced in rapidly solidified powders can be retained in the compact. Consolidation occurs so rapidly that there is not enough time to re-establish equilibrium.        For the same reason above, composite materials can be fabricated with very thin reaction zones between matrix and reinforcement. This minimizes the formation of brittle reaction products that can degrade composite fracture properties.        Many powders that are extremely difficult or impossible to form by other methods can be dynamically consolidated. For example, some powders are so brittle that conventional isostatic pressing may cause excessive particle fractures.        Dynamic consolidation has the potential for fabricating net-shape parts.        Although most samples produced to date have been small (centimeter size), the process can, in principle, be scaled up to produce large (meter size) compacts.
Even though dynamic consolidation can offer significant inherent advantages and versatility in forming both metallic- and intermetallic-based monolithic and composite materials, it is important to recognize that the method is still very much in the development stage, and major problems need to be addressed. For example, methods of precisely controlling process parameters and obtaining uniform samples must be developed. Cracking is another problem that must be solved. When the powder-consolidating shock wave reaches a free surface, it transforms into a relief wave that can fracture the sample. Also, the rarity of kinetic energy storage machines and the small sizes of samples produced to date make it difficult to predict whether kinetic energy discharge is a commercially viable way to consolidate powders.
The techniques discussed above are in various stages of R&D and prototype development.
Other alternative approaches for dynamic consolidation of powders are being pursued. For example, dynamic magnetic compaction (DMC) described in U.S. Pat. Nos. 5,405,574 and 5,611,139 is a process which claims to consolidate powders into full density parts in less than a millisecond. In this process, high currents are passed through a compactor coil, at the center of which is a powder container. The current in the coil generates a magnetic field, which in turn applies magnetic pressure up to 1400 MPa (200 ksi) to the powder (300 MPa is typically achieved), in two orthogonal directions. The pressure consolidates powders such as high-strength steels, titanium-nickel intermetallics, tungsten alloys, and superconductor ceramics. The process claims to consolidate powders at room or elevated temperatures in any controlled atmosphere, and claims that the forces can be controlled with precision. So far, the process has been used to compact small sized shapes (rods and bars 2 to 20 cm long and up to 2 cm thick); although it is claimed that there is no fundamental size limitation. One limitation of DMC is the general need for post sintering, under a reducing atmosphere such as hydrogen, or HIP to complete grain bonding. At the DMC pressures typically achievable (300 MPa) grain bonding is generally not complete. Note that the quoted peak pressure of 1400 MPa apparently leads to damage to the coil, and a consequently limited lifetime. Making survivable coils which can operate repetitively at pressures above 5-6 kbar is difficult.
All known techniques, both static and dynamic, are in general not cost effective compared to conventional wrought processing techniques and none of the dynamic techniques have generated any significant commercial activity. Therefore, cost effective consolidation techniques are needed which can produce near theoretical densities (i.e. nearly 100%), can enable sintering at lower temperatures to obtain preferred microstructures, and can allow fabrication of conventional die presses of small size and lower expense.

Dynamic consolidation of powders using a pulsed energy source


The present invention relates to a water movement device comprising a flexible wall (1) placed in water close to the surface, substantially vertically in a static rest state, made up of optionally perforated (5) massive unit blocks (4) assembled to one another in strings by cables (2, 3) on which said blocks (1) are threaded or on which said blocks are crimped, said cables comprising: a series of cables (2) disposed vertically (ZZ′) side by side, parallel to one another, and a second series of cables (3) disposed horizontally (XX′) one above another and in parallel, and said vertical cables (2) being suspended or tensioned at their top ends and/or respectively tensioned or moored at their bottom ends, and said blocks including empty orifices (5) passing through them between the front and rear faces (1-1, 1-2) of said wall (1), and/or empty spaces (7) between said blocks, such that said orifices (5) and/or empty spaces between said blocks (7), if any, confer overall porosity on said wall lying in the range 5% to 75%, preferably 20% to 45%, of the area of the vertical section of said wall.

1. Field of the Invention
The present invention relates to a device constituting a wall, partition, or curtain for damping water movement(s) and intended more particularly for damping the slipstreams induced by the propellers of ships, and also chop and swell of small amplitude. It is intended more particularly to be installed vertically within pontoons on piles, more precisely under said pontoons and between the supporting piles in port installations.
2. Discussion of Related Art
A port is a space in which ships maneuver, with the help of their thrusters (propellers and/or bow thrusters in particular), in particular for docking or for leaving the quayside where they were moored. Such thrusters deliver slipstreams that can propagate over long distances and that can give rise to scouring that is limited or eliminated by anti-scouring devices that are generally placed at the bottoms of structures or in sensitive zones. Such thruster slipstreams can also lead to discomfort or difficulties in docking for certain boats situated nearby.
The movement of ships also gives rise to waves of short period, thus also interfering with boats, in particular yachting or fishing boats, in the same manner as chop generated by local winds.
In port environments, it is generally desirable to create protected zones in which the surface of the water remains calm, and numerous techniques have already been developed for creating such sheltered zones, and mention can be made of uninterrupted breakwaters, interrupted breakwaters, Jarlan type rigid perforated walls, and caisson walls. With all those techniques, the idea is either to reflect a wave, causing it merely to head back out to sea, or else to dissipate the intrinsic energy in the mass of moving water, either by transforming it directly into heat within the mass of water (uninterrupted or partial breakwaters), or by recovering the energy so as to transform it into electricity (tidal amplitude chambers), or indeed by creating phase shifts within the waves as occurs with caisson walls.
All of those systems present great effectiveness in absorbing strong swell and more particularly short swell. However, they are in general works of considerable mass since they need to withstand very large forces and to do so over durations exceeding 30 years to 50 years or even more.
The solution that consists in "waterproofing" quays of the type that are built on piles is not always desirable (even ignoring the extra cost), since that leads to unwanted reflections having the effect of increasing roughness, in particular at the end of a dock or along a straight quay, thereby reducing the comfort and the workability of berths along the quay.
With the exception of uninterrupted breakwaters that create a total screen, interrupted breakwaters, and caisson walls are not very effective in damping waves of long wavelength and chop generated by turbulent currents around the piles or created by ships' propellers while the ships are approaching their mooring points on a pontoon.
Patent WO 02/26019 describes a device that seeks to dissipate wave energy, the device comprising an array of floating modules of plastics material assembled together by a system of flexible rubber hinges, both in the vertical direction and in the horizontal direction, forming a system that is relatively complex and expensive to make, and also relatively fragile.
The complexity of the device described in WO 02/26019 comes from the particular shape of the modules defining particular openings, and from the shape of the assembly elements outside said modules.
In addition, the flexibility of the hinge system of WO 02/26019 constituted by resilient rubber assembly elements external to the various floating modules gives that device as a whole excessive mobility, leading to phenomena of wear and limited lifetime.


Compositions having antimicrobial activity contain surface functionalized particles comprising an inorganic copper salt which has low water solubility. These types of inorganic salts may also be introduced in porous particles to yield antimicrobial compositions. The compositions may optionally comprise additional antimicrobial agents, salts with high water solubility, organic acids, salts of organic acids and their esters. The compositions may be added to various fluids used in the petroleum extraction industry, or used as coatings on components used in this industry. These antimicrobial materials may be used for reducing both anaerobic and aerobic bacteria and are also useful for reducing corrosion of ferrous components caused by anaerobic bacteria. Although such compositions may be used for any antimicrobial application, and some of the other important uses of these compositions are in wound care, personal care and waste processing.

The antimicrobial effect of various metals and their salts has been known for centuries. Its germicidal effects increased its value in utensils and as jewelry. The exact process of silver's germicidal effect is still not entirely understood, although theories exist. One of these is the "oligodynamic effect," which qualitatively explains the effect on some microorganisms, but cannot explain antiviral effects. Silver is widely used in topical gels and impregnated into bandages because of its wide-spectrum antimicrobial activity.
The oligodynamic effect is demonstrated by other metals, specifically gold, silver, copper, zinc, and bismuth. Copper is one such metal. Copper has long been used as a biostatic surface to line the bottoms of ships to protect against barnacles and mussels. It was originally used in pure form, but has since been superseded by brass and other alloys due to their lower cost and higher durability. Bacteria will not grow on a copper surface because it is biostatic. Copper alloys have become important netting materials in the aquaculture industry for the fact that they are antimicrobial and prevent biofouling and have strong structural and corrosion-resistant properties in marine environments. Organic compounds of copper are useful for preventing fouling of ships' hulls. Copper alloy touch surfaces have recently been investigated as antimicrobial surfaces in hospitals for decreasing transmission of nosocomial infections.
Numerous scientific investigations have focused on the role of the metal form of copper, and have concluded that multiple mechanisms may be possible for copper's antimicrobial effect, including increased production of reactive oxidation species such as singlet oxygen and hydroxide radicals, covalent binding of copper metal to reactive sites in enzymes and co-factors, interference with lipid bilayer transport proteins, and interaction of copper ions with moieties of microorganisms analogous to what have been proposed for silver ions.

This patent is subject to a terminal disclaimer.

Antimicrobial compositions for use in products for petroleum extraction, personal care, wound care and other applications


A fish bite indicator system includes a flag post having a flag attached to the post by a removable collar. The post is further attached to an elbow member by a coil. The elbow member is attachable to a pole of a fishing rod. The coil urges the post into a perpendicular orientation with respect to the pole. A retention assembly is provided for holding the post in a parallel orientation when in a set position. The fishing line passes through the retention assembly such that sufficient pull on the fishing line disengages the retention assembly such that the post returns to the perpendicular orientation. The fish bite indicating system is also usable without the retention assembly by retaining the post using the handle of a spinning reel. The elbow member is adjustably attachable to the pole using a bolt and nut holding a pair of rubber washers around the pole. A pair of metal washers are positioned around the rubber washers, one of the metal washers having a bent portion urging one of the rubber washers around the pole such that the pole is secured between the rubber washers.

1. Field of the Invention
The present invention relates to fishing bite indicators and more particularly pertains to a new fish bite indicator system for indicating the bite of a fish when fishing.
2. Description of the Prior Art
The use of fishing bite indicators is known in the prior art. More specifically, fishing bite indicators heretofore devised and utilized are known to consist basically of familiar, expected and obvious structural configurations, notwithstanding the myriad of designs encompassed by the crowded prior art which have been developed for the fulfillment of countless objectives and requirements.
Known prior art fishing bite indicators include U.S. Pat. Nos. 3,646,698; 4,146,988; 5,152,093; 3,727,342; 4,573,281; 3,962,812; PCT Patent WO 94/15458; and PCT Patent WO 97/40666.
While these devices fulfill their respective, particular objectives and requirements, the aforementioned patents do not disclose a new fish bite indicator system. The inventive device includes a spring biased flag pole and retention assembly for holding the flag in a set position prior to the bite of a fish.
In these respects, the fish bite indicator system according to the present invention substantially departs from the conventional concepts and designs of the prior art, and in so doing provides an apparatus primarily developed for indicating the bite of a fish when fishing.


Buffer lines and corresponding buffer tags and buffer valid/dirty registers in conjunction with buffer control circuit are provided to a DMA controller enabling the DMA controller to conditionally pre-fetch data from memory while data being read are transferred from the DMA controller to the I/O device during read operations and to conditionally write data back to memory while data being written are transferred from the I/O device to the DMA controller during write operations, thereby improving asynchronous read/write throughputs. Read requests, random as well as sequential, are satisfied with pre-fetched data if they are validly stored. Write requests, random as well as sequential, are deferred, batched and optimized. The improved throughput is achieved in a manner completely transparent to system software.

1. Field of the Invention
The present invention is related to the field of computer systems. More particularly, the present invention is a method and direct memory access controller for asynchronously reading/writing data from/to a memory with improved throughput.
2. Art Background
Traditionally, data transfers between memory and an input-output (I/O) device of a computer system are accomplished in one of three ways:
1. Programmed I/O. In this case, all data transfers between the memory and the I/O device is completely controlled by the central processing unit (CPU), or more precisely, by a program executed by the CPU.
2. Interrupt I/O. In this case, all data transfers between the memory and the I/O device are initiated by the I/O devices through interrupts. In response, the CPU suspends whatever it is currently doing and attends to the needs of the I/O device.
3. Direct Memory Access (DMA). In this case, all data transfers between the memory and the I/O device are accomplished without involving the CPU.
The DMA approach provides a much faster way of moving data between the memory and the I/O device. Typically, a direct memory access controller is employed. The DMA controller, the CPU, the memory and the I/O device are all coupled to a system bus. Upon request of the I/O device, the DMA controller suppresses the CPU, takes control of the system bus and causes data to be transferred between the memory and the I/O device. The DMA controller is not involved in the actual transfer of the data. By duplicating the internal logic of the DMA controller, a DMA controller may support multiple I/O devices.
Alternatively, the I/O device may be coupled to the DMA controller instead of the system bus. In that case, after taking control of the system bus, the DMA controller causes data to be transferred from the memory (I/O device) to itself and then re-transmits the data to the I/O device (memory). By involving the DMA controller in the actual data transfer, the DMA controller gains the ability to interpret or process the data being transferred. However, the DMA controller pays for the added ability by sacrificing performance.
Typically, the data are transferred on a first-in first-out (FIFO) basis. The memory (I/O device) waits while the data are being re-transmitted from the DMA controller to the I/O device (memory). While some DMA controllers allow the next data transfer from the memory (I/O device) to parallel the re-transmission of the prior data to the I/O device (memory), the next data must be sequential to the prior data.
As will be discussed, the present invention overcomes the disadvantages of the prior art, and provides a method and a DMA controller for asynchronously reading/writing data from/to a memory with improved throughput. The method and the DMA controller achieve the improved throughput in a manner that is completely transparent to the system software.

Method and direct memory access controller for asynchronously reading/writing data from/to a memory with improved throughput


A magnetoresistive effect element of a tunnel junction type includes a magnetic multi-layered film (1), ferromagnetic film (3) and intervening insulating film (2) such that a current flows between the magnetic multi-layered film and the ferromagnetic film, tunneling through the insulating film. The magnetic multi-layered film includes a first ferromagnetic layer, second ferromagnetic layer and anti-ferromagnetic layer inserted between the first and second ferromagnetic layers.

This invention relates to a magnetoresistive effect element, magnetic memory and magnetic head, and more particularly to those having a ferromagnetic tunnel junction structure and capable of maintaining high sensitivity to an external magnetic field even when miniaturized in device size.
Magnetoresistive effect elements are under expectation toward practical use in a wide field of application including magnetic detector elements such as magnetic heads, magnetic memory devices, etc.
For example, there is a proposal of magnetic random access memory using a magnetic element exhibiting giant magnetoresistance effect as a solid magnetic storage device. Especially, magnetic memory using "ferromagnetic tunnel junction" is remarked as a magnetic element.
Ferromagnetic tunnel junction is mainly made of a three-layered film of first ferromagnetic layer/insulating film/second ferromagnetic layer, and a current flows, tunneling through the insulating film. In this case, the junction resistance value varies proportionally to the cosine of the relative angle between magnetization directions of the first and second ferromagnetic layers. Therefore, resistance value becomes minimum when the magnetization directions of the first and second ferromagnetic layers are parallel, and becomes maximum when they are anti-parallel. This is called tunneling magnetic resistance (TMR) effect. For example, in the literature, Appl. Phys. Lett., Vol. 77, p 283 (2000), it is reported that changes of resistance value by TMR effect reaches as high as 49.7% at the room temperature.
In a magnetic memory including a ferromagnetic tunnel junction as a memory cell, magnetization of one of ferromagnetic layers is fixed as a "reference layer", and the other ferromagnetic layer is used as a "recording layer". In this cell, by assigning parallel and anti-parallel magnetic orientations of the reference layer and the recording layer to binary information "0" and "1", information can be stored.
For writing information, magnetization of the recording layer is reversed by a magnetic field generated by supplying a current to a write line provided for the cell, and by detecting a resistance change by TMR effect. A number of such memory elements are aligned to form a large-capacity memory device.
Its actual configuration is made up by placing a switching transistor for each cell and combining peripheral circuits similarly to DRAM (dynamic random access memory), for example. There is also a proposal of a system incorporating ferromagnetic tunnel junctions in combination with diodes at crossing positions of word lines and bit lines (U.S. Pat. No. 5,640,343 and U.S. Pat. No. 5,650,958).
For higher integration of magnetic memory elements using ferromagnetic tunnel junctions as memory cells, the size of each memory cell becomes smaller, and the size of the ferromagnetic element forming the cell inevitably becomes smaller. There is the same situation in magnetic recording systems when the recording density is enhanced and the recording bit size is decreased.
In general, as the ferromagnetic element becomes smaller, its coercive force increases. Since the intensity of the coercive force gives criteria for judging the magnitude of the switching magnetic field required for reversal of magnetization, its increase directly means an increase of the switching magnetic field. Therefore, upon writing bit information, a larger current must be supplied to the write line, and it invites undesirable results such as an increase of power consumption, shortening the wiring lifetime, etc. Therefore, it is an important issue for practical application of high-integrated magnetic memory to reduce the coercive force of the ferromagnetic element used as the memory cell of magnetic memory.
To overcome this problem, it has been proposed to use, as a "recording layer", a structure including multi-layered film of at least two ferromagnetic layers and a nonmagnetic layer interposed between them and including anti-ferromagnetic coupling between those ferromagnetic layers (Japanese Patent Laid-Open Publication No. H9-25162, Japanese Patent Application No. H11-263741 and U.S. Pat. No. 5,953,248).
In this case, two ferromagnetic layers included in the "recording layer" are different in magnetic moment and thickness, and their magnetic orientations are opposite under anti-ferromagnetic coupling. Therefore, they effectively cancel each other's magnetization, and the entirety of the recording layer can be regarded equivalent to a ferromagnetic element having small magnetization in the easy axis direction. If a magnetic field is applied in the opposite direction from orientation of the small magnetization in the easy axis direction the recording layer has, magnetization of each ferromagnetic layer reverses while holding the anti-ferromagnetic coupling. Therefore, because of the closed magnetic line of force, influences of the demagnetizing field are small, and the switching magnetic field of the recording layer is determined by the coercive force of each ferromagnetic layer. As a result, even a small switching magnetic field enables magnetic reversal.
In case that no layer-to-layer coupling exists between the magnetic layers (J=0), there is an interaction by magnetostatic coupling by the leak magnetic field from the magnetic layers. In this case, however, it is known that the switching magnetic field decreases similarly to a case where such coupling exists (24th Japan Applied Magnetics Academy Scientific Lecture 12aB-3, 12aB-7, 24th Japan Applied Magnetics Academy Scientific Lecture Summary p. 26, 27).
However, in case that only magnetostatic coupling exists without no layer-to-layer coupling between magnetic layers, the magnetic structure made by the above-explained magnetization is unstable. Additionally, the squareness in the hysteresis curve or the magnetoresistance curve is small, and it is difficult to obtain a large magnetoresistance ratio. Therefore, it is not preferable for use as a magnetoresistive.
As explained above, reducing the switching magnetic field necessary for magnetic reversal of the "recording layer" is an indispensable factor for realization of a high-density magnetic recording system or magnetic memory, and it has been proposed to use a multi-layered film including anti-ferromagnetic coupling through a nonmagnetic metal layer.
However, as already recognized, in a minute ferromagnetic element in a minute magnetoresistive effect element as used in a high-density magnetic recording system or high-integrated magnetic memory, when the width of its shorter axis is miniaturized to the level of several microns through sub microns, a magnetic structure different from a central portion of the magnetic element is generated in perimeter portions of the magnetized region due to influences of an "demagnetizing field". Such a magnetic structure in perimeters is called "edge domain" (see, for example, J. App. Phys., 81, p. 5471 (1977)).
FIGS. 18A and 18B are schematic diagrams showing magnetic structures having such edge domains, respectively. In any of the magnetic structures shown in FIGS. 18A and 18B, magnetization M1 is generated in a direction in accordance with the magnetic anisotropy in a central portion of the magnetized region. In opposite end portions, however, magnetizations M2 through M5 are generated in directions different from that of the central portion. In this explanation, the domain structure shown in FIG. 18A is called "S-type structure", and the domain structure shown in FIG. 18B is called "C-type structure".
In a minute magnetic element used in a high-density magnetic recording system or high-integrated magnetic memory, the edge domain generated in its end portions exert strong influences, and changes of the magnetic structure pattern upon magnetic reversal becomes complicate. As a result, the coercive force increases, and the switching magnetic field undesirably increases.
As a method for minimizing such complicate changes of the magnetic structure, there is a proposal to fix the edge domain (U.S. Pat. No. 5,748,524, Japanese Patent Laid-Open 2000-100153). This method can certainly control behaviors upon magnetic reversal, but cannot substantially reduce the switching magnetic field. Additionally, his method needs an additional structure for fixing the edge domain, and it is not suitable for higher-density applications.

Magnetic memory having a ferromagnetic tunneling junction


Features are disclosed for providing items from an item store to an item store consumer. An item store organizer can request an item store from an item redemption system based on item store parameters. The item store organizer can receive a single use token from the item redemption system to provide initial access to the item store. The item redemption system can validate the item store consumer based on the single use token. The item redemption system can further validate redemption requests from the item store consumer based on the item store parameters. The item redemption system can fulfill the redemption request based on payment information of the item store organizer and shipping information of the item store consumer. The item redemption system can transmit redemption information to the item store organizer based on fulfilling the redemption request.

Retailers and merchants involved in commerce often provide items for purchase by a consumer via an electronic store, made available via a website or mobile application ("mobile app"). A consumer can often select an item to purchase (e.g., redeem) from a number of items made available by the store. For example, the electronic store may offer a selection of items, such as food, electronics, books, household goods, services, etc. Items can be purchased using payment information stored in the consumer's account with the electronic store or through a third party payment service, and the items can be shipped to the consumer using shipping information stored in the consumer's account. For example, a consumer may purchase a clothing item or book from an electronic store using the consumer's credit card information stored in the consumer's account with the electronic store, and the operator of the electronic store or another fulfillment provider may ship the item to a physical address of the consumer stored in the consumer's account. If the consumer is purchasing an item from the electronic store that is requested or required by their employer, or another entity with which they are associated, and the employer is to provide for payment, the consumer must either use the payment information of the employer (such as a company credit card) stored in the consumer's account (and submit an expense report), or use their own payment information stored in the consumer's account (and seek reimbursement). Alternatively, the employer may select and pre-purchase items from an electronic merchant that it wishes to distribute to employees. The employer may purchase the items with payment information stored in the employer's account with the electronic merchant, and the items may be shipped to the employer using employer shipment information stored in the employer's account. Alternatively, the employer can provide shipping information to the electronic merchant for each employee so that the items may be shipped directly to the employees. The employer typically purchases items based on actual or estimated employee demand, and if shipping the items directly to employees, the employer typically obtains the information from internal records. However, accurately predicting or determining the number of employees who will actually desire or require an item, and accurately maintaining a database of employee addresses, is difficult to do using existing approaches and technology.

Redeeming items from an item store using information from multiple accounts


The invention is a method for modeling the effects of interactions between wells on the watercuts in effluents produced by one or more wells through a zone of an underground hydrocarbon reservoir under development, swept by a fluid under pressure injected through one or more injection wells or swept by water from an aquiferous zone, in order to optimize the reservoir production. The method includes selecting a set of significant data from measurements taken from sweep fluid injection records and from records relative to the effluents produced by a series of wells of the zone, and setting up, by means of iterations, an optimized linear model connecting the variations with time of these watercuts with the variations with time of the significant data. The invention is useful to optimize the petroleum production of a reservoir.

1. Field of the Invention
The present invention relates to a method for modeling the effects of interactions between wells on the watercut in effluents produced by an underground hydrocarbon reservoir under development, swept by a fluid under pressure, in order to optimize the reservoir production.
2. Description of the Prior Art
The production of water is a major problem in petroleum production. Operators can be confronted with situations where the watercut in the production of a well is very high whereas the in-place oil recovery ratio remains low, which clearly shows the ineffectiveness of a sweeping operation. They can be led to cease producing from the well concerned, with all the economic consequences entailed through lack of solutions allowing these water inflows to be controlled. It is within the scope of the production of stratified reservoirs swept by water, for example, that complex evolutions of this watercut can sometimes be observed.
It is well-known to treat locally a well where water inflows occur, by plugging the well zones producing water by injecting cement, polymers, gels, etc, and using packers in order to delimit the zones to be treated while the products are set. This technique is difficult to implement because the critical zones first have to be properly defined. Servicing operations are heavy and expensive, with no economic justification for wells that are often at the limit of profitability.
In order to contain great water inflows, it is also well-known to subject the reservoir to global treatments, for example by injecting polymers therein, the rate of success thereof remaining low and notably difficult to predict.
Reservoirs generally have very complex physics. Consider the case of a well crossing a certain number i of reservoir levels considered to be hydraulically independent in proportion to the environment of the well (i=2 in the case of FIG. 1). Under the effect of a draw-off with, for example, a flow rate Q imposed by a pump, the bottomhole pressure is expressed by the relations as follows: ##EQU1## where Pi is the pressure prevailing in bed i. The overall flow rate Q of the well is made up of the sum of the contributions Qi of all the beds i, each contribution depending on the productivity index IP.sub.i of the bed considered and on the pressure difference P.sub.1 -P.sub.wf applied. The watercut fw of the well results from an average of the watercuts fwi of each bed, weighted by the contribution thereof to the overall flow rate of the well.
The expression Qi=IPi (Pi-Pwf) shows that any variation Pi of the pressure Pi of a bed leads to a variation Qi of the flow rate Qi of the bed and, if the watercuts of the beds are different, to a variation of the watercut of the well according to the changes in the relative contributions of each bed to the overall production of the well. The variation Pi of the pressure of a bed can notably be due to a variation of the injection or production rates of the neighbouring wells. Besides, when the pressures in the various beds are substantially different, a variation of the production pressure P leads to a distribution variation of the flow rates (.alpha.i).
Furthermore, in cases where the pressures Pi of the various beds are substantially different, any change in the stress imposed on the well: flow rate Q of the pump or pressure P.sub.wf in the well, will lead to a variation of the watercut, an increase or a decrease according to the relative distributions of the saturations and of the pressures of each bed.

Modeling of interactions between wells based on produced watercut


An acoustic emission system for seismic surveying at sea, for the purpose of emitting a soundwave in a given direction, the system comprising firstly a plurality of immersed sources mechanically connected to at least one float means and secondly a control circuit for controlling said sources and comprising a plurality of delay means suitable for applying respective phase delays to each of the sources, said delays being defined by a nominal phase law associated with said given emission direction. According to the invention, the system also includes at least two attitude sensors providing signals representative of the absolute position of at least two of said sources to correction means of said control circuit, said correction means providing each of said delay means with a signal for correcting the nominal phase law and representative of variations in the relative positions of the sources. This system has application to geological prospecting by seismic surveying at sea.

Geological exploration of the sea bed is generally performed by means of ship towing acoustic emission systems such as the system specified above, which systems emit soundwaves in different directions towards the bed to be explored. The soundwaves are then reflected by the formations under the sea bed and they are detected by transducers disposed along cables, known as "streamers", and likewise towed by the prospecting ship. By analyzing the reflected waves relative to the waves emitted by the sources, information is obtained on the structure, the nature, and the composition of the sea bed being studied.
The sources used in acoustic emission systems for seismic surveying at sea often constitute subassemblies forming a regular array in one to three dimensions. To emit a wave in a given direction, emission from the sources is controlled in application of a phase law that governs the phase delays to be applied to the sources. A nominal phase law is defined for an ideal configuration of the sources in which the water surface is planar and completely calm. For example, under such conditions in order to emit a wave in the vertical direction perpendicular to the surface of the water, the nominal phase law is uniform in that all of the sources emit simultaneously. In contrast, a soundwave of given inclination can be obtained by offsetting emissions from consecutive sources relative to one another by a phase delay that is a function of the looked-for inclination, it being understood that the emission direction is the direction in which the waves emitted by all of the sources interfere constructively.
In practice, real prospecting conditions are significantly different from the above-mentioned ideal configuration for which the nominal phase law is defined. In particular, the surface of the sea often has short range instabilities such as waves whose space frequency is equal to or greater than the distance between two consecutive sources within a subassembly under consideration. Such surface instabilities give rise to the sources moving with pendulum motion and without correlation between one another, thereby having the effect of varying the depth of each source as a function of time. The positions of the sources relative to the surface are thus affected, with the consequence that the nominal phase law no longer corresponds to the real configuration of the sources. The nominal phase law must therefore be corrected in real time. To do this, each source may be fitted with a pressure gauge for example, thereby providing a measure at each instant of the exact depth of each source relative to the surface, thereby making it possible to establish the relative positions between the sources. The necessary corrections to the phase law so as to take into account instabilities of this type are then deduced therefrom.
A method using such depth measurement, i.e. a depth of water measured piezometrically and corresponding to the effective towing depth of each source, is described in GB-2 148 001.
However, that known correction method is not usable when the water surface although calm, i.e. not having large waves, nevertheless presents undulations of large space period due to the phenomenon of swell. Under such circumstances, the sources remain relatively steady relative to the surface and the pressure gauges of the sources do not record any variations in pressure and thus in depth. Consequently, the nominal phase law is not corrected even though the sources are not in the corresponding ideal configuration.
Thus, the technical problem to be solved by the present invention is that of providing an acoustic emission system for seismic surveying at sea and as defined in the introduction, which system should make it possible to correct the nominal phase law of emission from the sources with respect to low frequency movements of the water surface.

Acoustic emission system for seismic surveying at sea


A head-coupled display device for use in presenting electronically generated visual images to a viewer. The device includes a headpiece worn by a viewer, and an image display screen mounted in the headpiece for presenting electronically generated images. A fresnel lens is positioned adjacent the screen for focusing images from the screen at a selected position for viewing as a virtual image. The lens has a set of concentric converging rings whose surface curvatures act to minimize rectilinear distortion of the virtual images perceived by the viewer over the entire field of view of the image.

Virtual reality systems are designed to present a user with computer-generated visual, and optionally, auditory cues which allow the user to experience a computer-simulated reality. At the same time, the user may be equipped with a motion-responsive glove or body suit which permits user interaction with the virtual reality information being presented. For example, the user may be able to touch and "move" an object in the visual field, or experience a changing auditory cue as the image of an object in the visual field is moved with respect to the user's ear.
One important application of virtual reality systems is in flight simulators, where visual flight information is provided to a trainee-user. Another is for actual in-flight guidance, where visual cues processed from infrared or radar signals are provided to one of the pilot's eyes. Other applications are emerging, for example in architecture, medicine, engineering, and entertainment, as real-time computer-graphics capabilities are developed.
One desired type of virtual reality system employs a head-mounted display (HMD) designed to be worn by a user, and capable of generating visual images which -are perceived as three-dimensional virtual images. Head-mounted displays for use in flight simulation systems have been proposed. For example, U.S. Pat. No. 4,048,653 describes a head-coupled visual display system which includes a head-mounted unit worn by the observer, and a image projection system for projecting left-eye and right-eye images onto left- and right-eye screens in the head-mounted unit, via an optical train. More recently, the present inventors have described a HMD in which visual images are generated by liquid-crystal display (LCD) screens in a head-mounted unit, and viewed by the observer as three-dimensional virtual images.
In general, it is desirable for an observer to experience a wide-angle virtual image, such that even the peripheral vision of the observer is engaged. One aspect in the design of a wide-angle visual system in an HMD is the requirement for a large-diameter lens having a relatively small focal length. Such lenses can be relatively bulky and expensive. Further, spherical aberration effects associated with spherical glass lenses can produce pronounced rectilinear distortion at the outer regions of the wide-angle image. Heretofore, although a variety of head-coupled image systems have been proposed, none of these has proven capable of achieving distortion-free wide-angle image presentation.


A method of compensating for initial signal interference exhibited by a differential transmission line includes the step of determining whether the differential transmission line has been at a first differential voltage state for at least a first predetermined time period. The method also includes the step of transmitting a first data bit across the differential transmission line by impressing a first differential voltage having a first magnitude upon the differential voltage line in order to drive the differential transmission line from the first differential voltage state to a second differential voltage state if the determining step determines that the differential transmission line has not been at the first differential voltage state for at least the first predetermined time period. Another step of the method includes transmitting the first data bit upon the differential transmission line by impressing upon the differential voltage line a second differential voltage having a second magnitude larger than the first magnitude in order to drive the differential transmission line from the first differential voltage state to a second differential voltage state if the determining step determines that the differential transmission line has been at the first differential voltage state for at least the first predetermined time period. Apparatus for compensating for initial signal interference exhibited by a differential transmission line are also disclosed.

The present invention relates generally to data transmission, and more particularly to a method and apparatus for compensating for initial signal interference exhibited by differential transmission lines.
A computer bus is generally a set of parallel conductors or transmission lines interconnecting two or more electrical devices for the purpose of data transfer. The SCSI bus is one popular type of interconnect bus designed for short distant data communication between computers and peripheral devices. In particular, the SCSI bus has been designed to interconnect independent devices such as disk drives, tape drives, scanners, and computers. Several SCSI versions have been developed and standardized, with newer versions being developed to keep pace with changing computer speeds and requirements. One of the newer standards is low voltage differential (LVD) SCSI, an improved version of differential SCSI.
LVD SCSI transfers data via low differential voltage signals (e.g. xc2x1400 mV differences) which enable higher data transfer rates and longer data transfer distances than the older single-ended SCSI standards. More specifically, an LVD SCSI bus includes several differential bus line each comprising two separate bus lines or transmission lines. In general, LVD controllers transmit a binary zero over a differential bus line of the LVD SCSI bus by developing a positive voltage difference between a first bus line and a second bus line of the differential bus line. Similarly, LVD controllers transmit a binary one over a differential bus of a LVD SCSI bus by developing a possitive voltage difference between the first bus line and the second bus line of the differential bus line.
Generally, LVD SCSI bus controllers utilize either current mode LVD drivers or voltage mode LVD drivers to develop the differential voltages between the bus lines of the differential bus lines. More specifically, known LVD SCSI bus controllers with current mode LVD drivers have always transmitted binary zeros by driving the differential bus line with a first current having a first magnitude and have always transmitted binary ones by driving the differential bus line with a second current having a second magnitude. Similarly, known LVD SCSI bus controllers having voltage mode LVD drivers have always transmitted binary zeros by driving the differential bus line with a first voltage having a first magnitude, and have always transmitted binary ones by driving the differential bus line with a second voltage having a second magnitude.
While at slower transfer speeds these known LVD SCSI controllers were able to transfer data across differential bus lines without significant data loss, it has been found that significant data loss now occurs when using these known LVD drivers at the faster transfer speeds such as transfer speeds dictated by the Fast40 and Fast80 SCSI protocols. The inventor has found the reason that significant data loss occurs using the known LVD SCSI controllers is that differential voltage developed upon a differential bus line by the LVD drivers of the known LVD SCSI controllers has a diminished magnitude at the receiving devices when data is transferred across the differential bus line after the differential bus line has been at an opposite differential voltage state for a precharge time period. As a result of failing to develop a differential voltage having a sufficient magnitude at the receiving device, LVD receivers of the receiving device commonly failed to accurately receive at least the first data bit and possible more data bits following the differential data line being at the opposite differential voltage for a precharge time period.
For example, a known LVD SCSI controller may consecutively transfer a series of binary zeros across a differential bus line by driving the differential bus line to a first differential voltage state (e.g. xc2x1400 mV) for each binary zero of the series. Then, the LVD SCSI controller may transfer a series of binary ones across the differential bus line by driving the differential bus line to a second differential voltage state (e.g. xe2x88x92400 mV). At slower transfer rates, LVD receivers accurately received the series of binary zeroes and the series of binary ones. However, at faster transfer rates, the LVD receivers often inaccurately received the first binary one of the series of ones at higher transfer speeds due to the differential voltage developed at the LVD receiver for the first binary one having a diminished magnitude (e.g. xe2x88x92300 mV). The above phenomena of a diminished differential amplitude being developed at the LVD receiver is referred to herein as initial signal interference (ISI).
A need therefore exists for a method and apparatus that compensate for initial signal interface exhibited by differential transmission lines in order to enable reliable data transfers at high transfer rates across differential transmission lines.
In accordance with one embodiment of the present invention, there is provided a method of compensating for initial signal interference exhibited by a differential transmission line. One step of the method includes determining whether the differential transmission line has been at a first differential voltage state for at least a first predetermined time period. Another step of the method includes transmitting a first data bit across the differential transmission line by driving the differential transmission line from the first differential voltage state to a second differential voltage state with a first current having a first magnitude if the determining step determines that the differential transmission line has not been at the first differential voltage state for at least the first predetermined time period. Yet another step of the method includes transmitting the first data bit upon the differential transmission line by driving the differential transmission line from the first differential voltage state to the second differential voltage state with a second current having a second magnitude that is larger than the first magnitude if the determining step determines that the differential transmission line has been at the first differential voltage state for at least the first predetermined time period.
Pursuant to another embodiment of the present invention, there is provided a method of compensating for initial signal interference exhibited by a differential transmission line. The method includes the step of determining whether the differential transmission line has been at a first differential voltage state for at least a first predetermined time period. The method also includes the step of transmitting a first data bit across the differential transmission line by impressing a first differential voltage having a first magnitude upon the differential voltage line in order to drive the differential transmission line from the first differential voltage state to a second differential voltage state if the determining step determines that the differential transmission line has not been at the first differential voltage state for at least the first predetermined time period. Another step of the method includes transmitting the first data bit upon the differential transmission line by impressing upon the differential voltage line a second differential voltage having a second magnitude larger than the first magnitude in order to drive the differential transmission line from the first differential voltage state to a second differential voltage state if the determining step determines that the differential transmission line has been at the first differential voltage state for at least the first predetermined time period.
Pursuant to another embodiment of the present invention, there is provided a differential bus controller that compensates for initial signal interface associated with data transfers across a differential bus comprising differential bus lines. The differential bus controller includes a controller and differential drivers. The controller is coupled to the differential bus lines and is operable to control data transfers across the differential bus. The controller is also operable to separately determine for each differential bus line whether the differential bus line has been at a first differential voltage state for at least a first predetermined time period. Moreover, the controller is operable to generate a separate control signal for each differential bus line which indicates whether the differential bus line has been at the first differential voltage state for at least the first predetermined time period.
The differential drivers of the differential bus controller are coupled to the differential bus lines. Each differential driver is operable to transmit a first data bit across the differential bus line by driving the differential voltage line from the first differential voltage state to a second differential voltage state with a first current having a first magnitude if the control signal generated by the controller for the respective differential bus line indicates that the respective differential bus line has not been at the first differential voltage state for at least the first predetermined time period. Moreover, each differential driver is operable to transmit the first data bit across the differential bus line by driving the differential voltage line from the first differential voltage state to the second differential voltage state with a second current having a second magnitude that is greater than the first magnitude if the control signal generated by the controller for the respective differential bus line indicates that the respective differential bus line has been at the first differential voltage state for at least the first predetermined time period.
It is an object of the present invention to provide an improved method and apparatus for transferring data across a differential transmission line.
It is also an object of the present invention to provide a new and useful method and apparatus for transferring data across a differential transmission line.
It is another object of the present invention to provide a method and apparatus for increasing the reliability of data transfers across a differential transmission line.
It is yet another object of the present invention to provide a method and apparatus for compensating for initial signal interference exhibited by differential transmission lines during data transfers.
The above and other objects, features, and advantages of the present invention will become apparent from the following description and the attached drawings.

Compensating for initial signal interference exhibited by differential transmission lines


In one embodiment, a server is assigned a candidate secondary server role such that the dynamic network employs a “make-before-break” redundancy where redundant nodes proactively synchronize replicated data and state information with a standby secondary server prior to releasing the responsibilities of active primary and/or secondary server(s). The “make-before-break” redundancy ensures relatively high availability of dynamic networks and realized services.

Dynamic networks, such as those for emergency response, disaster recovery and/or military operations, require high availability and server redundancy. Simultaneously, these types of networks must also account for the higher probability of individual nodes or clusters of nodes entering and leaving the network due to normal operational scenarios and/or catastrophic failures. These network entries and network exits result in a higher occurrence of controlled and uncontrolled switchovers between redundant nodes in which the network is left unprotected and vulnerable. To reduce network vulnerability, the transient time during these switchovers for which the network is left unprotected should be reduced.

Methods for improved server redundancy in dynamic networks


An object-analysis system includes a sensor and a processor. The sensor detects the movement and positioning of a user's hands within a three-dimensional space. The processor is communicatively connected to the sensor, and receives the movement and positioning information from the sensor. The processor determines the dimensions of the object based on the detected movements and positioning of the user's hands substantially adjacent to opposing sides of the object.

Shipping companies typically charge customers for their services based on package size (i.e., volumetric weight) and/or weight (i.e., dead weight). When printing a shipping label for a package, a customer enters the size and/or weight of the package into a software application that bills the customer based on the information. Typically, customers get this size information by hand-measuring a package's dimensions (e.g., with a tape measure) and weighing the package on a scale. Hand-measurement of packages can be time-consuming and prone to errors. The customer may have difficulty positioning a tape measure on an irregularly-shaped package, for example. Alternatively, the customer may have difficulty reading a tape measure or may misread or erroneously record the dimension measurement. Problematically for the customer, when the shipping company later determines that the package is larger and/or heavier than reported by the customer, the shipping company may issue an additional charge to the customer. Additional bills may reduce customer satisfaction with the shipping experience, and, if the shipping customer is a retail company that has already passed along the shipping cost to an end customer, decrease the customer's earnings.
As such, a commercial need exists for systems that accurately and speedily collect a package's dimensions (e.g., length, width, height) for integration with billing systems to reduce errors in obtaining and transcribing that dimensional data.


Techniques and implementations for providing enhanced functionality for handling data in Internet browsers or other applications used for accessing data over a network, including providing thumbnail image displays of the current appearance of webpages referenced by URLs returned in a set of search results, providing thumbnail image displays of the webpages referenced by a list of favorite or bookmarked websites, providing thumbnail image displays of webpages which have been blocked from appearing on a user's screen, and providing thumbnail image displays of images which have been extracted from webpages and stored for potential future use.

The continued growth and popularity of the Internet and World Wide Web has resulted in the availability of a vast amount of information to users. This has lead to an ever increasing demand from users for ways to easily search for, identify and retain the particular information in which they are interested without being overwhelmed by data, both solicited and unsolicited, that the user is not interested in. Typically, a user looking for information on a particular subject will navigate their Internet browser to a webpage for a search engine such as those offered by Yahoo!® or Google®. At the webpage, the user enters a search query (e.g., keywords or other text related to the subject in which they are interested) into a text box on the webpage (see FIGS. 1A and 1B) and that search query is sent by their browser to the server for the search engine. The search engine server performs the search and sends a webpage containing the results back to the user's browser. These results typically include a listing of hyperlinks for the webpages produced by the search and possibly additional information such as an excerpt of the text on the page which relates to the keywords entered by the user for the search (see FIGS. 1C and 1D). The search engine may also provide the option of conducting a search for images that relate to the user's search query. When such a search is conducted, the search engine server sends the user's browser a webpage which includes a display of the images resulting from the search and hyperlinks to the webpages that the images are from (see FIGS. 1E and 1F).
Frequently, in order to support the operation of the search engine, the search results also include "sponsored links," which are typically hyperlinks to advertisers' webpages for products or services related to the search results. For example, a link to an advertiser's webpage may be displayed in conjunction with searches conducted on certain subjects or keywords chosen by the advertiser. The search engine provider is typically compensated by the advertiser when a user clicks on the advertiser's sponsored link to be directed to the advertiser's webpage. These sponsored links are typically "redirect links" which when clicked on, rather than directly sending the user to the advertiser's webpage, send a message from the user's browser back to the search engine server indicating that the redirect link has been clicked on by the user. The search engine server logs that the sponsored link has been clicked on (so that the advertiser can be billed for the "click-thru") and then sends a message back the user's browser, redirecting it to the advertiser's webpage.
Some search engines, such as Google®, and software companies, such as Microsoft®, have developed "toolbars" which are software programs that may be installed directly onto a user's computer to enable searching to be conducted without first navigating to the search engine's webpage. These toolbars generally operate with the user's browser and provide an additional toolbar at the top of the browser's application window which contains a text box for entering search queries and a number of buttons to provide the various search functions. When a user enters a search query and presses a "search" button, the toolbar sends the query to the search engine server which responds by sending back a webpage of search results just as if the user had entered a query through the search engine's webpage (see FIG. 1G).
Another search toolbar, by GIRAFA™, occupies a vertical area on the side of the browser space and operates with a variety of search engines. When a user submits a query, the webpage listing search results from the selected search engine is displayed in the main browser area and the GIRAFA™ search tool bar area displays a thumbnail image of the webpages of each of the search results. These thumbnail images are retrieved from a thumbnail index maintained on a GIRAFA™ server (see FIG. 1H). Apparently, the GIRAFA™ index of thumbnail images is periodically updated by "crawling" the web. GIRAFA™' s website provides an interface for individuals to submit URLs (Uniform Resource Locators) which GIRAFA™ will index and add to their central index of thumbnail images. As a result, when a user navigates to a webpage by clicking on the thumbnail image, the webpage may appear different than the thumbnail image because the thumbnail was taken at some indeterminate point in the past (see FIG. 1I).
Some search toolbars and browsers include a feature commonly referred to as a "pop-up blocker." "Pop-ups" are additional windows (frequently advertisements) that are opened on a user's computer screen (either on top of or beneath the current browser window) by code or instructions from the webpage that the user is currently viewing or has recently viewed. These pop-ups are usually not solicited by the user but are opened by a webpage to which the user has navigated for another purpose. A pop-up blocker prevents such windows from being opened on a user's screen without permission.
Currently, there are a number of drawbacks to the search toolbars presently in use. For example, while allowing a search to be launched from the toolbar area, the results of the search are shown as text in the webpage area, not in the toolbar. Also, the thumbnail screenshots presented by the Girafa toolbar may be misleading regarding the webpage's current appearance because the webpage may have been updated since Girafa last stored a thumbnail of it in its central index. Moreover, the actual web pages of the individual results are not loading on the user's computer; therefore slowing the process of reviewing the information available on those sites. Furthermore, although the pop-up blocker functionality of these toolbars may provide an audio or visual cue that a pop-up has been blocked (e.g., a beep or a flashing mouse cursor), the user cannot see what was actually blocked from appearing and cannot restore the blocked pop-up if the user realizes he did not want it blocked.

Enhanced graphical interfaces for displaying visual data