A memory element structure in a programmable logic device (PLD) reduces power consumption by placing the memory element in a power save mode when the memory element is unused in a user design implemented in the PLD. An exemplary structure includes a multiplexer driving a memory element. A multiplexer control circuit controls the multiplexer, and also drives a clock control circuit for the memory element. When the memory element is used by a user design implemented in the PLD, one of the data inputs is selected to drive the memory element. The controlled functions occur normally in the memory element. When the memory element is not used by the user design, none of the data inputs is selected, an input control signal is intercepted by the clock control circuit, and the controlled functions do not occur in the memory element, reducing the power consumption of the unused memory element.

Programmable logic devices (PLDs) are a well-known type of integrated circuit that can be programmed to perform specified logic functions. One type of PLD, the field programmable gate array (FPGA), typically includes an array of programmable tiles. These programmable tiles can include, for example, input/output blocks (IOBs), configurable logic blocks (CLBs), dedicated random access memory blocks (BRAM), multipliers, digital signal processing blocks (DSPs), processors, clock managers, delay lock loops (DLLs), and so forth.
Each programmable tile typically includes both programmable interconnect and programmable logic. The programmable interconnect typically includes a large number of interconnect lines of varying lengths interconnected by programmable interconnect points (PIPs). The programmable logic implements the logic of a user design using programmable elements that can include, for example, function generators, registers, arithmetic logic, and so forth.
The programmable interconnect and programmable logic are typically programmed by loading a stream of configuration data into internal configuration memory cells that define how the programmable elements are configured. The configuration data can be read from memory (e.g., from an external PROM) or written into the FPGA by an external device. The collective states of the individual memory cells then determine the function of the FPGA.
Another type of PLD is the Complex Programmable Logic Device, or CPLD. A CPLD includes two or more "function blocks" connected together and to input/output (I/O) resources by an interconnect switch matrix. Each function block of the CPLD includes a two-level AND/OR structure similar to those used in Programmable Logic Arrays (PLAs) and Programmable Array Logic (PAL) devices. In CPLDs, configuration data is typically stored on-chip in non-volatile memory. In some CPLDs, configuration data is stored on-chip in non-volatile memory, then downloaded to volatile memory as part of an initial configuration sequence.
For all of these programmable logic devices (PLDs), the functionality of the device is controlled by data bits provided to the device for that purpose. The data bits can be stored in volatile memory (e.g., static memory cells, as in FPGAs and some CPLDs), in non-volatile memory (e.g., FLASH memory, as in some CPLDs), or in any other type of memory cell.
Other PLDs are programmed by applying a processing layer, such as a metal layer, that programmably interconnects the various elements on the device. These PLDs are known as mask programmable devices. PLDs can also be implemented in other ways, e.g., using fuse or antifuse technology. The terms "PLD" and "programmable logic device" include but are not limited to these exemplary devices, as well as encompassing devices that are only partially programmable. For example, one type of PLD includes a combination of hard-coded transistor logic and a programmable switch fabric that programmably interconnects the hard-coded transistor logic.
An FPGA configurable logic block (CLB) typically includes one or more groups of related lookup tables and memory elements. The lookup tables (LUTs) are related to one another in that the LUT output signals are coupled to a common carry chain, and the memory elements are typically also related in that each can be optionally driven by the output signal from one of the LUTs. Such a group of logic is commonly known as a "slice". For example, FIGS. 6A and 6B of U.S. Pat. No. 5,914,616 each illustrate one slice from the well-known Virtex™ FPGA currently available from Xilinx, Inc. (U.S. Pat. No. 5,914,616 is hereby incorporated herein by reference in its entirety.) Together, these two slices make up one CLB of the Virtex FPGA.
In order to reduce the number of transistors required to implement a slice, the memory elements within a slice typically share common control signals, e.g., clock, clock enable, set, and/or reset signals. Because the user logic implemented in a slice is often related, the logic targeted to memory elements within one slice can typically share common control signals without significant loss of implementation efficiency.
FIG. 1 shows how memory elements share control signals in a known FPGA, the Virtex-II Pro™ FPGA from Xilinx, Inc. (FIG. 1 is derived from a figure on page 51 of the "Virtex-II Pro Platform FPGA Handbook", published Oct. 14, 2002 and available from Xilinx, Inc., 2100 Logic Dr., San Jose, Calif., which page is hereby incorporated herein by reference.) In the Virtex-II Pro PFGA, each slice includes two memory elements, each configurable as either a latch or a flip-flop. As shown in FIG. 1, memory elements FFX and FFY in each slice share common clock (CK), clock enable (CkE), and S/R (set/reset) signals.
More specifically, memory element FFX has a data input terminal Dt driven by a data input multiplexer 102, which selects between data input DX and a bypass data input BX (optionally inverted by programmable multiplexer 115). Memory element FFY has a data input terminal D driven by a data input multiplexer 101, which selects between data input DY and a bypass data input BY (optionally inverted by programmable multiplexer 111). The clock enable (CkE) input terminal of each memory element FFX, FFY is driven by a clock enable signal CE optionally inverted by multiplexer 112. The clock (CK) input terminal of each memory element FFX, FFY is driven by a clock signal CLK optionally inverted by multiplexer 113. The set/reset (S/R) input terminal of each memory element FFX, FFY is driven by a set/reset signal SR optionally inverted by multiplexer 114. The reverse set/reset (REV) input terminal of each memory element FFX, FFY is optionally driven (as controlled by programmable switches 122, 121, respectively) by the bypass signal BY optionally inverted by multiplexer 111.
In the Virtex-II Pro slice, some programmable attributes for the memory elements apply to both memory elements in the slice, while others are individually controllable for each memory element. For example, the following attributes are specific to each flip-flop: INIT0 (initialize to a low value); INIT1 (initialize to a high value); SRHIGH (signal S/R sets the value in the memory element; signal REV resets the value); and SRLOW (signal S/R resets the value in the memory element; signal REV sets the value). However, if synchronous functionality is selected for the slice, this selection applies to both memory elements. Similarly, a selection of asynchronous functionality applies to both memory elements.
Power consumption is an important consideration for PLD systems designers. Particularly with today's larger PLDs, power consumption can be such a critical issue that it can dictate the choice of whether or not a given PLD can be used to implement a particular user design. Therefore, it is desirable to find methods of reducing power consumption in PLDs. Because many available PLDs include thousands of programmable memory elements, programmable memory elements having reduced power consumption could provide a significant power savings over currently available circuits.

Programmable memory element with power save mode in a programmable logic device


A liquefied gas tank includes an inner tank (2) that stores liquefied gas and is disposed so as to be capable of self-standing on a floor surface (F), and an outer tank (3) that is covered over the inner tank (2) and is supported by an upper face portion (2a) of the inner tank (2). The outer tank (3) is configured to be capable of sliding on the upper face portion (2a) of the inner tank (2) in response to expansion and contraction in the horizontal direction of the inner tank (2), and to be capable of moving in response to expansion and contraction in the vertical direction of the inner tank (2). A ceiling portion (3a) of the outer tank (3) that is placed on the upper face portion (2a) of the inner tank (2) is not fixed to the upper face portion (2a) of the inner tank (2), and the inner tank (2) and the outer tank (3) are configured to be capable of sliding in the horizontal direction relative to each other. The outer tank (3) includes an expansion and contraction mechanism portion (33) that is disposed along the lower outer circumference thereof.

Conventionally, a transport ship (tanker), a floating storage unit, an above-ground storage facility, an underground storage facility and the like are used for transportation or storage of cryogenic liquids such as LNG (liquefied natural gas) and LPG (liquefied petroleum gas) (for example, see Patent Literature 1 and Patent Literature 2).
In Patent Literature 1, a liquefied gas carrying vessel is disclosed that includes an outer tank that constitutes the hull of a ship, and a tank (inner tank) that is disposed in a self-standing state inside the outer tank. In Patent Literature 2, an above-ground LNG tank is disclosed that includes an outer tank that is disposed on the ground and an inner tank that is disposed in a self-standing state inside the outer tank. By adopting a configuration in which an inner tank that stores liquid cargo is independent from an outer tank in this manner, the inner tank can be protected from the external environment while allowing expansion and contraction (thermal expansion and thermal contraction) of the inner tank that accompanies changes in the temperature of the liquid cargo.


Apparatus for reducing the mass and the responsive inertia of a bearing cartridge for a disc drive actuator assembly, the bearing cartridge including a stationary shaft, a bearing assembly and a bearing sleeve. The bearing assembly is disposed between, and rigidly attached to, the stationary shaft and the bearing sleeve, to facilitate radial movement of the bearing sleeve relative to the stationary shaft. The disc drive actuator assembly has an actuator rigidly attached to, and supported by, the bearing cartridge. The bearing assembly has an inner race rigidly attached to the stationary shaft, and an outer race rollingly engaging a plurality of roller bearings disposed between the inner and outer races. The outer race has a chamfered edge in a plane between a reference vertical axis and a reference horizontal axis, and the bearing sleeve has an internal taper matingly joining the chamfered edge to provide a miter joint therebetween.

Modern hard disc drives comprise one or more rigid discs that are coated with a magnetizable medium and mounted on the hub of a spindle motor for rotation at a constant high speed. Information is stored on the discs in a plurality of concentric circular tracks by an array of transducers ("heads") mounted to a radial actuator for movement of the heads relative to the discs.
Typically, such radial actuators employ a voice coil motor to position the heads with respect to the disc surfaces. The heads are mounted via flexures at the ends of a plurality of arms which project radially outward from an actuator body. The actuator body pivots about a shaft mounted to the disc drive housing at a position closely adjacent the outer extreme of the discs. The pivot shaft is parallel with the axis of rotation of the spindle motor and the discs, so that the heads move in a plane parallel with the surfaces of the discs.
The actuator voice coil motor includes a coil mounted on the side of the actuator body opposite the head arms so as to be immersed in the magnetic field of a magnetic circuit comprising one or more permanent magnets and magnetically permeable pole pieces. When controlled DC current is passed through the coil, an electromagnetic field is set up which interacts with the magnetic field of the magnetic circuit to cause the coil to move in accordance with the well-known Lorentz relationship. As the coil moves, the actuator body pivots about the pivot shaft and the heads move across the disc surfaces.
Control of the position of the heads is typically achieved with a closed loop servo system such as disclosed in U.S. Pat. No. 5,262,907 entitled HARD DISC DRIVE WITH IMPROVED SERVO SYSTEM issued Nov. 16, 1993 to Duffy et al. (Duffy '907), and assigned to the assignee of the present invention. A typical servo system utilizes servo information (written to the discs during the disc drive manufacturing process) to detect and control the position of the heads through the generation of a position error signal (PES) which is indicative of the position of the head with respect to a selected track. The PES is generated by the servo system by comparing the relative signal strengths of burst signals generated from precisely located magnetized servo fields in the servo information on the disc surface.
During track following in which a selected head is caused to follow a selected track, a servo processor compares the value of the PES to a desired value indicative of the desired position of the head to the selected track and issues a digital correction signal to the power amplifier, which in turn provides an analog current to the actuator coil to adjust the position of the head with respect to the track. During a seek operation in which a selected head is moved from an initial track to a destination track, relatively large currents are applied to the coil to initially accelerate and then decelerate the head towards the destination track. The velocity of the head is repeatedly measured and the current applied to the coil is adjusted in accordance with the difference between the actual velocity of the head and a velocity profile.
As will be recognized, a continuing trend in the industry is to provide characteristics at an ever decreasing cost. To this end, efforts are continually being undertaken to improve disc drive data storage and transfer rates, including increases in the rotational speeds of the discs, increases in track densities and increases in the radial velocities of the heads during seek operations. However, a problem that has been experienced with increases in the radial velocities attained by heads during seeks is the relative mass of the bearing cartridge which produces a limiting inertia force in opposition to the desired movement of the heads.
One way of decreasing the inertial effect is to decrease the mass of the bearing cartridge. Decreasing the mass, however, tends to weaken the structural integrity of the bearing cartridge and thus adversely affect the rotational support and stability of the actuator arm. In order to maintain the necessary stiffness for adequate support of the actuator arm, any mass reduction must be compensated for by an improved structural response of the bearing cartridge construction. Simplicity of manufacture and assembly are also important factors that cannot be sacrificed to any great extent for merely a reduction in mass.
Accordingly, there is a continual need for improvements in bearing cartridge construction that are both operationally effective and inexpensively implemented.


A kit for producing a modular prosthesis is provided, the kit including a first prosthesis member having a cavity such as a bore formed in it, and a clamp releasably clamped in the cavity. The clamp, which may be a rod having an axial bore through a portion of its length, is subjected to an external stimulus such as a stretching force to cause the diameter of the clamp to be reduced enough so that the clamp is received in the cavity. As the stimulus is withdrawn, the clamp returns toward its initial configuration, and in so doing, expands against the walls of the cavity. A second prosthesis member may be configured to receive a portion of the first member such that expansion of the clamp in the cavity of the first member concurrently causes that member to expand into contact with the second member to clamp the members together.

Prostheses for replacement of joints commonly involve two parts having mutually articulating surfaces, and structure for mounting the parts to bone. To duplicate closely the structure and function of natural joints, the prostheses parts must be carefully shaped and sized, and must be properly oriented by the surgeon with respect to each other and with respect to the anatomy of the patient.
To achieve good surgical results, a surgeon should have as much freedom as possible during the surgical implantation procedure to vary the shape, size and orientation of prosthesis parts. Mainly for this reason, efforts have been made to provide prostheses that are modular in form so that various elements of a prosthesis can be individually selected and the prosthesis can be assembled and oriented according to the anatomical needs of the patient.
Modular prostheses for the hip joint are shown, for example, in Boleski et al., U.S. Pat No. 5,080,685, Gianezio et al., U.S. Pat. No. 4,520,511, Demane et al., U.S. Pat. No. 4,995,883, Luman, U.S. Pat. No. 5,002,578 and Rhenter et al., U.S. Pat. No. 4,693,724. Such prostheses for the most part involve a substantial number of parts that are held together in one configuration or another by means of mounting screws which operate to draw together tapered connections of the parts. Although some freedom of selection is provided by previous modular prostheses, the use of threaded mounting screws and tapered connections can lead to loosening of the parts and to other problems. Physical and chemical corrosion can become substantial problems due to weakening of the prosthesis and to biologic responses to corrosion debris and byproducts. See Jacobs, J. J. et al., Biological Activity of Particulate Chromium-Phosphate Corrosion Products, Collected Papers of the 21st Annual Meeting of the Society for Biomaterials, Mar. 18-22, 1995, p. 398, and Urban, Robert M., et al., Corrosion Products From Modular-Head Femoral Stems of Different Designs and Material Couples, Collected Papers of the 21st Annual Meeting of the Society for Biomaterials, Mar. 18-22, 1995, p. 326. Fretting corrosion caused by relative motion between adjoining surfaces leads to the production of debris which in turn may lead to accelerated wear between normally articulating joint parts of a prosthesis and to osteolysis. When gaps occur between adjacent surfaces of prosthesis parts, oxidation of the surfaces may lead to formation of an acidic environment and hence to chemical attack of the surfaces (commonly referred to as crevice corrosion).
It would be desirable to provide a modular prosthesis kit having elements that can be freely chosen and oriented by the surgeon in the operating arena and that can be strongly and firmly fastened to one another without the need for screw fasteners or tapered connections that are drawn together.


A storage and delivery device for a cryogenic liquid that includes a vessel assembly and a delivery line assembly. The vessel assembly has a liquid space and a vapor space. The delivery line assembly has a liquid line, a vapor line, and a delivery line. The liquid line is in fluid communication with the liquid space. The vapor line is in fluid communication with the vapor space. The liquid line has a flow control device located thereon and structured to control the flow of fluid through the liquid line. The liquid line flow control device is structured to close the liquid line when the vessel assembly is at a predetermined pressure.

1. Field of the Invention
This invention relates to a cryogenic fluid storage system and, more specifically, to a cryogenic fluid storage system having a check valve on the vapor line at a location between the vapor space and the use device.
2. Background Information
Cryogenic liquids, such as liquid natural gas (LNG), nitrogen, oxygen, CO2, hydrogen and the like, are substances that normally exist as gasses, but are liquids at cold temperatures. Special vessels and systems must be used to store and transfer cryogenic liquids because of difficulty in maintaining the extremely cold temperatures. Such vessels typically include a double walled vessel having a vacuum in the annular space. While the vacuum provides an effective insulation, the insulation is not perfect and, as such, heat penetrates the vessel. When heat is added to the cryogenic liquid, a portion of the liquid returns to the gaseous state. The gas within the vessel increases the internal pressure. The build up in pressure may even occur when liquid is being removed from the vessel and being delivered to a use device, such as an engine. Eventually, to prevent over pressurization of the vessel, the gas must be removed from the vessel. It is desirable, however, to not waste the gas by venting the gas to the atmosphere. That is, if possible, it is desirable to use the vented gas in the use device.
For example, where the cryogenic liquid is LNG, the use device is typically an engine. The following description shall use the example of LNG and an engine, but it is understood that the system described herein is applicable to any cryogenic liquid and any use device. The fuel system for the engine includes the cryogenic vessel, a delivery line extending from the cryogenic vessel to the engine, a vaporizer on the delivery line and an economizer circuit. Within the cryogenic liquid vessel are a liquid space and a gas, or vapor, space. The delivery line includes a portion adjacent to the vessel that, in normal operation, contains the cryogenic liquid, hereinafter, the "liquid line." The liquid line is in fluid communication with the cryogenic vessel liquid space. The economizer circuit, or vapor line, is in fluid communication with both the cryogenic vessel vapor space and the liquid line. Down stream of this joint between the liquid line and the vapor line, the delivery line may contain liquid, gas, or a combination of liquid and gas. Because the engine uses the natural gas in a gaseous state, a vaporizer may be located upstream of the engine.
In normal operation, if the vessel does not have a sufficient pressure, a small quantity of cryogenic liquid may be removed from the liquid space, passed through a vaporizer where it is converted to gas, and returned to the vapor space of the cryogenic liquid vessel. Alternatively, when the engine is not running, any excess cryogenic liquid from within the delivery line is allowed to evaporate and is returned to the vapor space through the vapor line of the economizer circuit. This gas pressurizes the cryogenic liquid vessel so that, when the engine is running, the pressure within the vessel causes the cryogenic liquid to exit the vessel to be delivered to the engine. Once the vessel is pressurized the delivery line may be opened to deliver LNG to the vaporizer or engine. Within the vessel, the vapor and the cryogenic liquid are at the same pressure. However, due to the additional pressure created by the weight of the cryogenic liquid, there is a slightly higher pressure acting on the liquid line. Thus, the path of least resistance to fluid flow is through the liquid portion of the delivery line and, when both the economizer circuit and the delivery line are open, fluid will flow from the liquid space within the vessel. Alternatively, the economizer circuit vapor line may include a regulator structured to close when the pressure in the vessel is below a set limit. This ensures that the liquid line is the path of least resistance.
As noted above, heat causes the cryogenic liquid within the cryogenic liquid vessel to be converted to gas and may cause an undesired increase in pressure. That is, the vessel may become over-pressurized. In this situation, gas must be removed from the vapor space to prevent a catastrophic failure of the vessel. One method of removing gas is to simply vent the gas to the atmosphere. This, of course, results in wasted gas. To prevent the venting of gas to the atmosphere when the cryogenic vessel is over-pressurized, gas may be removed from the vapor space within the cryogenic vessel and delivered to the engine. While a direct connection between the cryogenic vessel vapor space and the engine is possible, more typically, the gas is withdrawn through the economizer circuit. That is, because the economizer circuit is in fluid communication with the delivery line, high pressure gas may be transferred through the vapor line to the delivery line and then to the end use. Thus, when the pressure within the vessel exceeds a set limit, the regulator on the economizer circuit vapor line opens allowing gas to flow from the vapor space to the delivery line. However, because the pressure in the vapor line and the liquid space is, essentially, equal, and because the vapor line is also connected to the liquid line, there must be a device on the liquid line to increase the back pressure so that the vapor line is the path of least resistance for the fluid flow. Typically, flow of the cryogenic liquid within the liquid line is reduced by a pressure relief valve, or a restricted orifice, structured to create a back pressure in the liquid line. This additional back pressure ensures that, when the economizer circuit vapor line regulator is open, the vapor line is the path of least resistance and gas within the vapor space is expelled through the economizer circuit to be delivered to the engine, thereby reducing the pressure within the cryogenic vessel. See, e.g., U.S. Pat. No. 5,421,161.
The disadvantage of this system is that the flow of cryogenic liquid is not stopped when the regulator is open. That is, even in an over-pressurization situation, the pressure relief valve or a restricted orifice allows liquid to move through the delivery line. Because the use device is receiving fluid from both the vessel liquid space and vapor space, the speed of pressure reduction is slower than if the use device was receiving fluid from the vapor space only.
There is, therefore a need for a cryogenic liquid storage vessel structured to rapidly reduce the internal pressure while delivering the gas from the vapor space to the use device.
There is a further need for a cryogenic liquid storage vessel structured to rapidly reduce the internal pressure in the cryogenic liquid storage vessel that stops the flow of cryogenic liquid through the delivery line while gas from the vapor space is being delivered to the use device.

Pressure management system for liquefied natural gas vehicle fuel tanks


One or more techniques and/or systems are disclosed for efficiently organizing one or more images in a display. The display may comprise one or more display lines, such as display rows or display columns. Images can be selected sequentially from an image database and scaled to fill into a display line, at least until a selected image does not fit. If the selected image does not fit, a cropping amount can be determined for the images in the display line, including the image that does not fit, and the images can be proportionally cropped accordingly. The cropping amount can comprise merely enough display space to accommodate a cropped version of the image that does not fit into the display line. The cropped version of the image can then be filled into the display line, and, if available, a next display line can similarly be populated.

In computing environments, images can be retrieved from an image database and displayed on a variety of display screens, such as computer monitors, handheld devices, and others. Further, images can be displayed in a variety of formats. Commonly, when an image database comprises a collection of images a plurality of thumbnail versions of the images can be displayed on a screen together. A "thumbnail view" may be a visualization of a collection of photos, such as from a folder, in which a large number or all of the photos are visible on the display and remaining photos can be observed by a simple scrolling action. Often, when a user wishes to view images from the image database, which can contain a few or thousands of images, they continually browse a displayed selection (e.g., scroll through) until they find a desired image or images. Additionally, images can be comprised of different sizes, aspect ratios, and layouts; and a user may be able to specify a size of a thumbnail version for preferred viewing on a display. Image layouts for a display can vary depending on an image size, image aspect ratio, and/or a layout design for displaying images.


The invention relates to the use of low levels of glycols and short chain diols to control air void formation in any polymerization reaction having carbonyl-containing monomers, and preferably carboxylic acid ester monomers, at a level of at least 10% of total monomer, where the monomer has a peak polymerization exotherm temperature of greater than the boiling point of the monomer. The glycols and short chain diols are used in the polymization mixture at levels of 0.5 to 10 weight percent, based on the carboxylic acid ester-containing monomer. It is believed the glycols and short chain diols hydrogen bond with the —(C═O)O— containing monomer to increase the monomer boiling point, and decrease or even eliminate the formation of air voids due to monomer boiling. The invention is especially useful in polymerization of methyl methacrylate polymers and copolymers, either neat, or as a polymer composite system.

The polymerization of carbonyl-containing vinyl monomers is an exothermic reaction. If the temperature of the reaction mixture exceeds the boiling point of the monomer(s), the monomer boils, resulting in undesirable bubble formation. In a viscous polymer system, the trapped bubbles remain in the solidified polymer product after polymerization as air voids. These air voids are defects that influence the mechanical properties of the cured polymer and compromise its long-term stability and aesthetics. This problem becomes more severe as the final articles become thicker, where heat transfer is more limited and the exotherm temperature gets higher. For a methyl methacrylate monomer system, exotherm temperature higher than 100° C. cause the formation of air voids.
Traditional methods for controlling the polymerization exotherm of carbonyl-containing monomer, such as PMMA and PMMA composites, involve conducting the polymerization in a mold surrounded by a cooling bath. Other strategies involve chemical methods such as the use of inhibitors and chain transfer agents. Although these chemical strategies can successfully reduce the exotherm temperature and lower air void formation, they interfere with the chemistry of polymerization by trapping the polymer radicals, which increases the cure time and reduce the molecular weight of the resulting polymer, causing a negative effect on polymer mechanical properties. There is a need for better strategies to mitigate the effect of the polymerization exotherm and lower or even eliminate air void formation in the cured polymer, while causing minimal or no impact on the cure kinetics and molecular weight of polymer. One system that is especially in need of such strategies is the polymerization of methyl methacrylate (MMA) into polymethyl methacrylate (PMMA) and its copolymers.
Surprisingly it has been found that the addition of low levels of one or more glycols and short chain diols in a MMA liquid resin system will reduce and even eliminate air void formation in the polymerized PMMA. The same effect is expected in any bulk polymerization involving carbonyl-containing monomers. While not being bound by any particular theory, it is believed that the addition of low levels of glycols and short chain diols, act as hydrogen bond donors, increases the boiling point of MMA, likely by forming hydrogen bonds with the MMA monomer. By increasing the boiling point of MMA above the temperature of the polymerization exotherm, air void formation can be eliminated. Depending on the chemical structure of the glycols and short chain diols, the low level of the additive in the composition has little or no effect on the cure kinetics and molecular weight of the PMMA product.
While the application will focus on (meth)acrylic monomers, and in particular on final polymers containing greater than 51 weight percent of methyl methacrylate, the principles and technical solution described would be expected to work efficiently in any polymerization involving at least 10% of carbonyl-containing monomers. The same mechanism achieving the same technical effect of controlling or eliminating air voids would be expected.

Air void control composition for carbonyl-containing monomer polymerization


An accumulation-mode power MOSFET includes a trenched gate that is formed in a semiconductor material of a first conductivity type. A region of second conductivity type is formed in the substrate (which may include an epitaxial layer) and a PN junction formed by the region of second conductivity type is connected in parallel with the current path through the accumulation-mode MOSFET. The diode is designed to have a breakdown voltage was causes the diode to break down before the oxide layer surrounding the gate can be ruptured or otherwise damaged when the MOSFET is in an off condition.

Accumulation mode field-effect transistors, sometimes referred to as "ACCUFETs", are trench-type MOSFETs which contain no body region and hence no PN junctions. The region between the trenched gates, sometimes called a "mesa", is made relatively narrow (e.g., 0.5 to 4.0 .mu.m wide), and the gate material (typically polysilicon) is doped in such a way that it has a work function which depletes the entire mesa region, much like a junction field-effect-transistor (JFET). The current path extends between a "source" at the top of the mesa and a "drain" at the bottom of the substrate. The trenches are normally formed entirely in an epitaxial layer which is grown on top of the substrate.
A cross-sectional view of a typical ACCUFET 10 is illustrated in FIG. 1. Trenched gates 11 are etched in a silicon material 12, which includes an N-epitaxial layer 13 grown on an N+ substrate 14. Trenched gates 11 define two cells 10A and 10B. An N+ source 15 is formed at the top of the mesa between gates 11. A metal layer 16 is formed over the source regions, and a power source 17 and a load 18 are connected between the N+ source 15 and the N+ substrate 14, which acts as the drain.
ACCUFET 10 is turned off when the gate voltage is equal to the source voltage (i.e., V.sub.gs =0). If V.sub.gs is increased, the depletion regions surrounding the gates (shown by the dashed lines) contract and open a current path between the source and the drain. With further increasing V.sub.gs the depletion regions continue to contract until eventually accumulation regions are formed adjacent the trenches, enhancing channel conduction and further lowering the on-resistance of the device.
This sequence of events is illustrated in FIGS. 2A, 2B and 2C, FIG. 2A showing ACCUFET 10 in the off condition, FIG. 2B showing ACCUFET 10 turned partially on, and FIG. 2C showing ACCUFET 10 turned fully, with the accumulation regions being designated by the numeral 19. In FIGS. 2B and 2C the arrows represent the flow of electrons from the source to the drain.
Additional information concerning ACCUFETs is given in U.S. Pat. No. 4,903,189 to Ngo et al.; B. J. Baliga et al., "The Accumulation-Mode Field-Effect Transistor: A New Ultralow On-Resistance MOSFET", IEEE Electron Device Letters, Vol. 13, No. 8, August 1992, pp. 427-429; and T. Syau et al., "Comparison of Ultralow Specific On-Resistance UMOSFET Structures: The ACCUFET, EXTFET, INVFET, and Conventional UMOSFET's", IEEE Electron Device Letters, Vol. 41, No. 5, May 1994, pp. 800-808, each of which is incorporated herein by reference in its entirety.
ACCUFETs can be fabricated with a very high cell density and a very low on-resistance. Despite these advantages, ACCUFETs have not so far achieved widespread use in the field of power semiconductor devices for several reasons. One of the principal reasons is their inability to withstand high voltages when they are in an off condition.
This problem is illustrated in FIGS. 3A and 3B, which show oxide layers 11A bordering gates 11. FIG. 3A shows ACCUFET 10 connected to an inductive load 30. The symbols t.sub.0, t.sub.1, t.sub.2, t.sub.3 and t.sub.4 represent sequential times in the process of turning off ACCUFET 10. The dashed lines in FIG. 3A represent the edges of the spreading depletion region at times t.sub.0, t.sub.1, t.sub.2, t.sub.3 and t.sub.4. FIG. 3B illustrates the strength of the electric field in the gate oxide layer 11A and epitaxial layer 13 at times t.sub.0, t.sub.1, t.sub.2, t.sub.3 and t.sub.4. As shown, as V.sub.gs begins to decrease at time t.sub.0, the electric field resides in the gate oxide layer 11A and a portion of epitaxial layer 13. At times t.sub.1 and t.sub.2, the strength of the field in the gate oxide layer 11A has increased somewhat, but a portion of the increase is absorbed by the epitaxial layer 13. At time t.sub.2, however, the electric field has reached the interface between epitaxial layer 13 and N+ substrate 14. Since N+ substrate 14 is heavily doped, it cannot support an electric field to any significant extent, and thus all further increases in the field must be taken up in the limited space of gate oxide layer 11A and epitaxial layer 13. This means that the electric field in the gate oxide layer 11A begins to increase at a faster rate with decreases in V.sub.gs. Unless limited in some way, the increases may eventually rupture gate oxide layer 11A, and in FIG. 3B this is shown as occurring at time t.sub.4. When the gate oxide layer has been ruptured, the device is generally destroyed beyond repair.
Since many loads (such as load 30) include an inductive component, voltage spikes inevitably occur in the power lines as the loads are switched on and off. The inability of ACCUFETs to withstand these voltage spikes has seriously limited their use in the power MOSFET field.
Push-pull halfbridge circuit 40, shown in FIG. 4A, illustrates the problem that occurs when using ACCUFETs with an inductive load. Halfbridge circuit 40 includes a high-side ACCUFET 41 and a low-side ACCUFET 42, which drive a coil 43 in a motor, for example. ACCUFETs 41 and 42 are connected in series between a battery voltage V.sub.batt and ground. FIG. 4B shows the voltages (V.sub.GS) across the gate oxides of the ACCUFETs 41 and 42 and the voltage V.sub.o at the output of the halfbridge circuit. Assume that at a starting point, V.sub.o is low, meaning that high-side ACCUFET 41 is off and low-side ACCUFET 42 is on. With ACCUFET 42 on, generally some current will be flowing through ACCUFET 42 and coil 43. In this situation the gate of ACCUFET 42 is tied to V.sub.batt and the gate of ACCUFET 41 is tied to a voltage equal to V.sub.o, so that the V.sub.GS in ACCUFET 41 is zero.
In order to switch V.sub.o from low to high, low-side ACCUFET 42 is turned off and then high-side ACCUFET 41 is turned on. Both ACCUFETs cannot be on at the same time, however, or a direct current path from V.sub.batt to ground would be created, leading to a large current and most likely the destruction of both devices. Thus, at time T.sub.1 in FIG. 4B, ACCUFET 42 is turned off by switching its gate voltage from V.sub.batt to ground. However, current flowing through coil 43 resists an abrupt cutoff, and V.sub.o therefore increases rapidly to a level greater than V.sub.batt, as shown by the top curve in FIG. 4B. V.sub.o will increase until ACCUFET 42 either breaks down or is destroyed. Meanwhile, the V.sub.GS in ACCUFET 41 falls rapidly at an equal rate (its source being biased more positively than its gate). It is highly likely that in this situation the gate oxide of ACCUFET 41 will rupture before ACCUFET 42 begins to conduct and thereby attempt to clamp the output voltage V.sub.o.
A scenario similar to that shown in FIGS. 4A-4B will occur in virtually any situation in which an ACCUFET is used to switch currents through an inductive load.
Accordingly, there is a real need for a device which has the superior cell density and on-resistance characteristics of an ACCUFET yet is able to switch an inductive load or survive voltage spikes of limited energy in a reliable manner particularly without damaging the trench gate.

Voltage-clamped power accumulation-mode MOSFET


A method of producing a fuel cell separator in which dry granules of a composition for a fuel cell separator mainly containing a conductive material, a binder, and an additive are produced by mixing raw materials including at least the conductive material, the binder, and the additive, granulating the resultant mixture to obtain granules, and drying the granules. The dry granules may be further sized. Then the granules are packed in a mold and hot-press molded. The granules have a residual volatile matter content in a range of 4 weight-% or less, and an average particle size in a range of 200 to 700 xcexcm (60 to 160 xcexcm for the sized granules) and a specific particle size distribution.

The present invention relates to a method of producing a fuel cell separator, a fuel cell separator, and a polymer electrolyte fuel cell. In particular, the present invention relates to a method of producing a fuel cell separator at a reduced rate of occurrence of molding failures, accordingly, at a high efficiency, a high quality fuel cell separator produced by the method, and a polymer electrolyte fuel cell including a plurality of unit cells whose separators are partly or entirely composed of the fuel cell separators, which cell has a high gas sealing characteristic and an excellent impact resistance, and is particularly suitable as a movable power supply for automobiles, small-sized marine vessels, etc.
A fuel cell, particularly, a polymer electrolyte fuel cell, is configured as a cell stack formed by juxtaposing unit cells of the number of several tens to several hundreds, wherein each of the unit cells includes, as shown in FIG. 1, a pair of fuel cell separators 1 each having on its right and left side surfaces a plurality of ribs 1a, and a polymer electrolyte membrane 2 and two gas diffusion electrodes 3 interposed between these separators 1.
As shown in FIG. 2, the fuel cell separator 1 has a unique shape having the plurality of ribs 1a projecting from the right and left side surfaces of a thin plate-like body, wherein passages (grooves) 4 for supplying and discharging a fuel gas such as hydrogen or oxygen are formed between the ribs 1a on each side of the separator 1 and the corresponding electrode 3. Accordingly, the separator 1 is required to have a high elasticity, an excellent dimensional accuracy, and a desirable gas non-permeability, and the unit cell (fuel cell) is required to have a high gas sealing characteristic capable of preventing a leak of a fuel gas, and an excellent impact resistance, particularly, when the fuel cell is used as a movable power supply for automobiles, etc.
Such a fuel cell separator has been produced by various methods, for example, a method (1) of forming a plate-like body from phenol resin, polyimide resin, or furan resin by molding, hardening and baking the resin of the plate-like body, and forming ribs by machining; a method (2) of impregnating a dense carbon shaped into a plate-like body with a thermosetting resin, and forming ribs by machining; a method (3) of impregnating carbon fiber unwoven fabrics with a conductive paint prepared by adding a solvent and a conductive filler to a thermosetting resin such as epoxy resin or phenol resin, and laminate-molding the resultant fabrics into the shape of a fuel cell separator; and a method (4) of kneading a carbon powder having a particle size of 100 mesh or less with phenol resin, and hot-press molding the kneaded material into the shape of a fuel cell separator.
Each of the methods (1) and (2), however, has problems that since the ribs are formed by machining, the cost is correspondingly raised as well as the number of steps is increased, and that the separator, if it is of a thin type, is liable to be cracked during machining or assembly of a fuel cell.
The method (3) has a problem that the ribs, that is, the grooves of the separator cannot be accurately formed by laminate-pressing because of non-flexibility of the unwoven fabrics.
The method (4) has a problem that since the mixture of the carbon material and the resin is molded, if the content of the carbon material as a conductive filler is made large for improving the conductivity, the moldability and the mechanical strength are degraded, and if the content of the binder resin is made large for improving the moldability and the mechanical strength, the conductivity is lowered because of the small content of the carbon material.
By the way, since a voltage outputted from each unit cell of a fuel cell is low, the fuel cell is required to have an array of unit cells of the number of several tens to several hundreds for ensuring a practical output ( less than several hundreds kW). Therefore, to uniformly arrange a large number of unit cells in parallel, it is required to establish a technique of producing fuel cell separators, each of which is formed into a uniform shape with no deformation and no partial unevenness in thickness, on a large scale with a high yield without occurrence of molding failures such as chips, cavities, and the like.
The conventional method of producing a fuel cell separator mainly containing a thermosetting resin such as phenol resin and graphite, however, cannot satisfy the above-described requirement. The reason for this is as follows. The conventional method generally involves packing a compound in a separator mold having a specific shape, and hot-press molding the compound for 5 to 10 min at a temperature of 150 to 160xc2x0 C. and a pressure of 10 to 50 MPa. Such a method has a problem, from the viewpoint of uniformly producing fuel cell separators with a high quality, that since the compound contains a large amount of graphite for imparting a necessary conductivity, the flowability of the compound is poor and accordingly it is difficult to uniformly pack the compound in the separator mold, to cause a large number of molding failures. The conventional method has another problem that molding failures may occur due to a gas generated at the time of hot-press molding.
An object of the present invention is to provide a method of producing a fuel cell separator at a reduced rate of occurrence of molding failures, accordingly, at a high efficiency, a fuel cell separator produced by the method and having a high dimensional stability, an excellent gas non-permeability, and a uniform quality, and a polymer electrolyte fuel cell including a plurality of unit cells whose separators are partly or entirely composed of the fuel cell separators, which cell has a high gas sealing characteristic and an excellent impact resistance, and is particularly suitable as a movable power supply for automobiles, small-sized marine vessels, etc.
To achieve the above object, the present inventor has examined to improve a method of producing a fuel cell separator. The production method includes the steps of producing dry granules of a composition for a fuel cell separator mainly containing a conductive material, a binder, and an additive by mixing raw materials of the composition, granulating the mixture, and drying the granules; and packing the dry granules in a mold, and hot-press molding the dry granules. With respect to such a method, the present inventor has found that, to produce a high quality fuel cell separator at a high production yield, it is effective to adjust an average particle size and particle size distribution of the dry granules in respective specific ranges and to reduce a residual volatile matter content of the dry granules.
The findings by the present inventor will be described in detail with reference to FIG. 3. FIG. 3 is a graph showing a particle size distribution of dry granules of a composition for a fuel cell separator, produced by mixing, granulating and drying. In this graph, a curve (B) shows a sharp particle size distribution of a granule sample A, and a curve (A) shows a gentle particle size distribution of a granule sample B. In the case of packing each of the granule samples A and B in a separator mold, even if the average particle size of the granule sample A is equal to that of the granule sample B, the degree of occurrence of voids of the granule sample A is larger than that of the granule sample B, and therefore, it is difficult to uniformly pack the granule sample A as compared with the granule sample B. That is to say, it has been found that the use of granules having a suitable average particle size and having a wide particle size distribution, or the use of fine granules most of which have particle sizes smaller than 500 xcexcm, produced by sizing the granules obtained by mixing, granulating and drying, is effective to improve the flowability and the packing rate of the granules and hence to suppress the occurrence of molding failures. Further, it has been found that the reduction in a residual volatile matter content of the granules is effective to make the generation of gas at the time of molding as small as possible and hence to suppress the occurrence of molding failures.
As a result of further examination of the production method on the basis of the above-described knowledge, the present inventor has found the following fact. Namely, granules having a residual volatile matter content of 4 parts by mass or less, an average particle size in a range of 200 to 700 xcexcm, and a particle size distribution (5 to 30% of particles: 5 xcexcmxe2x89xa6D (particle size)  less than 100 xcexcm, 10 to 40% of particles: 100 xcexcmxe2x89xa6D less than 300 xcexcm, 10 to 50% of particles: 300 xcexcmxe2x89xa6D less than 500 xcexcm, and balance: 500 xcexcmxe2x89xa6D less than 1000 xcexcm) are obtained by adding and mixing the additive to and with the conductive material, to obtain a sub-mixture, adding the binder to the sub-mixture in an amount of 5 to 30 parts by mass on the basis of 100 parts by mass of the conductive material and simultaneously adding a solvent to the sub-mixture in an amount of 20 parts by mass or less on the basis of 100 parts by mass of the conductive material, and wet-mixing the sub-mixture with the binder and the solvent; or fine granules most of which have sizes in a range of less than 500 xcexcm are obtained by further sizing the granules obtained by the above production method. The present inventor has further found that, by the use of the above granules or fine granules, it is possible to significantly improve the flowability and the packing rate of the granules and hence to uniformly pack the granules or fine granules in a separator mold having a significantly complicated groove structure, and to significantly reduce the generation of gas at the time of molding, and therefore, it is possible to produce a fuel cell separator having a high dimensional stability and a high quality at a very low rate of occurrence of molding failures such as chips or cavities.
The present inventor has also examined to improve a polymer electrolyte fuel cell, and found that a polymer electrolyte fuel cell which has an excellent gas sealing characteristic and a high impact resistance, and which is particularly suitable as a movable power supply for automobiles, small-sized marine vessel, etc. is obtained by using, as part or all of separators of unit cells of the fuel cell, the above-described fuel cell separators having an excellent gas non-permeability and a high quality without occurrence of molding failures.
Accordingly, a first aspect of the present invention, there is provided a method of producing a fuel cell separator, including the steps of: producing dry granules of a composition for a fuel cell separator mainly containing a conductive material, a binder, and an additive by mixing raw materials including at least the conductive material, the binder, and the additive, granulating the resultant mixture to obtain granules, and drying the granules; and packing the dry granules in a mold, and hot-press molding the dry granules packed in the mold; wherein a residual volatile matter content of the dry granules is in a range of 4 wt % or less; an average particle size of the dry granules is in a range of 200 to 700 xcexcm; and a particle size distribution of the dry granules is as follows:
According to a second aspect of the present invention, there is provided a method of producing a fuel cell separator, including the steps of: producing sized dry granules of a composition for a fuel cell separator mainly containing a conductive material, a binder, and an additive by mixing raw materials including at least the conductive material, the binder, and the additive, granulating the resultant mixture to obtain granules, drying the granules, and sizing the dry granules; and packing the sized dry granules in a mold, and hot-press molding the sized dry granules packed in the mold; wherein a residual volatile matter content of the sized dry granules is in a range of 4 wt % or less; an average particle size of the sized dry granules is in a range of 60 to 160 xcexcm; and a particle size distribution of the sized dry granules is as follows:
According to a third aspect of the present invention, there is provided a method of producing a fuel cell separator, including the steps of: producing dry granules of a composition for a fuel cell separator mainly containing a conductive material, a binder, and an additive by mixing raw materials including at least the conductive material, the binder, and the additive, granulating the resultant mixture to obtain granules, and drying the granules; and packing the dry granules in a mold, and hot-press molding the dry granules packed in the mold; wherein the step of mixing raw materials including at least the conductive material, the binder, and the additive comprises the steps of: adding and mixing the additive to and with the conductive material, to obtain a sub-mixture; adding the binder to the sub-mixture in an amount of 5 to 30 parts by mass on the basis of 100 parts by mass of the conductive material and simultaneously adding a solvent to the sub-mixture in an amount of 20 parts by mass or less on the basis of 100 parts by mass of the conductive material; and wet-mixing the sub-mixture with the binder and the solvent.
According to a fourth aspect of the present invention, there is provided a fuel cell separator produced by any one of the production methods according to the first, second, and third aspects of the present invention, wherein a gas permeability of the separator, measured by a method B specified under JIS K7126, is in a range of 30 cc/m2xc2x724 hrxc2x7atm or less.
According to a fifth aspect of the present invention, there is provided a polymer electrolyte fuel cell including: a plurality of unit cells juxtaposed, each of which has a pair of electrodes disposed with a polymer electrolyte membrane put therebetween, and a pair of separators disposed with the electrodes put therebetween and shaped to form gas supply/discharge passages between the separators and the electrodes; wherein the fuel cell separators according to the fourth aspect of the present invention are used as part or all of the separators in the fuel cell.

Method of producing fuel cell separator, fuel cell separator, and polymer electrolyte fuel cell


Conductive compositions which are useful as thermally conductive compositions and may also be useful as electrically conductive compositions are provided. The compositions include a conductive particle constituent in combination with a sintering aid which can, for example be a compound of the same metal in the nanometal, an organo-metallic, a metalorganic salt, mercaptan and/or resinate. In some embodiments the conductive particles include a small amount of nanoscale (<200 nm) particles. The compositions exhibit increased thermal conductivity.

The present invention relates to thermally enhanced adhesive pastes particularly well suited for bonding high density, microcircuit electronic components to substrates.
The attachment of high density, microcircuit components onto substrates, such as silicon dies onto ceramic sheet, has been an important aspect of the electronics industry for many years. Generally, it is known to use a die attach paste which is deposited between the die and substrate. Typically, the die attach paste includes a filler, an adhesive and a carrier. The filler is selected to impart to the finished bonding layer desired conductive, resistive or dielectric properties. The adhesive is chosen to create a strong bond between the die and substrate. The carrier maintains all the components in a fluid, uniform mixture, which allows the paste to be applied easily to the die-substrate interface. It also has suitable volatility to migrate from between the die and substrate following heat treatment of the assembly. After the paste is deposited and the die and substrate are assembled, the assembly is typically heated to fuse the adhesive and drive off the carrier. Upon cooling, the die is firmly attached to the substrate.
The power density of active components continues to rise, creating an increasing demand of higher thermally conductive adhesives to attach these components. These demands have previously been met by technologies described in the prior art, including U.S. Pat. Nos. 6,111,005 and 6,140,402. These patents describe a technology involving the use of powdered organic polymer resins, suspended in a non-solvent along with highly thermally conductive filler. The type of powered resin was varied depending on the application. For large area component attachments where the Coefficient of Thermal Expansion (CTE) mismatch to the substrate was also large, low modulus thermoplastic polymers were incorporated to handle the shear stress generated at the bondline of the adhesive. For smaller area components where the expansion mismatch to the substrate was lower, thermoset or combinations of thermoplastic and thermoset polymer powders were employed in the adhesive composition with the filler. The use of the higher modulus polymers also increased the thermal conductivity.
U.S. Pat. No. 6,265,471 describes an even higher thermal conductivity technology where the highly conductive filler is suspended in a liquid epoxy resin which is dissolved in a fugitive solvent. This technology increased the thermal conductivity over the prior technology described in U.S. Pat. Nos. 6,111,005 and 6,140,402. Unfortunately, the elastic modulus of the thermosetting liquid resin system was relatively high when cured or cross-linked. Consequently, the application of this technology was limited to small area component attach and or substrates that were closely matched in CTE to the component, usually a semiconductor die. The prior art described in the technologies described above clearly shows a linear relationship between the modulus and the thermal conductivity of the adhesive. Low modulus adhesives, described in U.S. Pat. Nos. 6,111,005 and 6,140,402, were lower in thermal conductivity, whereas the higher modulus adhesives described in U.S. Pat. No. 6,265,471 were higher in thermal conductivity. As higher function semiconductor devices grew in size and power, the need also grew for an adhesive with both high thermal conductivity and low modulus, such adhesives were needed to absorb the bondline shear stresses caused by the thermal expansion mismatch between the die and the high expansion, high thermally conductive substrates. One large application in the marketplace is the attachment of large area, flip chip microprocessor devices to a high expansion, high thermally conductive heat spreader. Both high conductivity and low modulus properties are needed for this application. Heretofore, the series of adhesives described in U.S. Pat. Nos. 6,111,005, 6,140,402 and 6,265,471 were used in this application. However, the microprocessor devices increased in power density and thus the demand increased for adhesives having even better thermal properties with low elastic modulus.


The improved housing coupling mechanism includes a first housing such as a motor housing having a first end in abutting relationship to a second housing such as a pump housing. The first housing includes a plurality of slots arranged about the housing perimeter and in a spaced relationship one to another and from the first end of the housing. The second housing includes a plurality of bosses, each boss being configured for coupling an attachment means thereto. Each attachment means includes a fastener (such as a bolt or threaded shaft) and an accompanying plate positionable to be in engagement with one of the slots in the first housing. Each fastener is positionally adjustable in a continuum, thereby providing a force to couple the first housing to the second housing. Coupling is accomplished when each attachment means is adjusted to provide a clamping force between its plate and the slot engaged by the plate. The improved mechanism simplifies and cost-reduces certain components and permits quick and easy assembly and disassembly of the housings.

Coupling mechanisms are commonly used to join pipe sections, motor housings or the like. Desirable characteristics and features of such mechanisms, often found lacking in prior work in this field, include low manufactured cost, mechanically secure coupling and ease of assembly and disassembly. Other desirable features include a minimal number of parts, a degree of "forgiveness" with respect to variations in certain manufacturing tolerances and the ability to couple structures of equal or disparate sizes.
One type of coupling mechanism is shown in U.S. Pat. No. 198,508 and includes a pipe section with an integral collar and a mating flange with a collar and a pair of rotatable turnbuckles mounted on the collar. When the flange and the mating pipe section are coupled together, the eccentric turnbuckle heads engage the pipe collar. A disadvantage of this arrangement is that the pipe section must have a collar affixed thereto and this adds to manufactured cost. Another, more serious disadvantage is that the eccentric heads can engage the pipe collar in only one position for each 360.degree. rotation of the turnbuckle. Unless machining tolerances are very tightly controlled, the eccentric heads will only loosely engage the pipe collar. Even if such tolerances are exceptionally well controlled, there is no tolerance "forgiveness" as wear occurs on the heads and/or the collar engaged by them.
Another type of coupling mechanism is shown in U.S. Pat. No. 2,867,454. The pipe coupling shown therein is used to join two sections of pipe of equal diameter and equal wall thickness and uses a plurality of keys, each of which engages a notch in the pipe wall. While the coupling shown therein undoubtedly has great mechanical strength, it requires two hubs and two flanges (together with bolts and keys) to achieve secure coupling. Such multiplicity of parts adds to manufactured cost and complexity. In addition, the securing nuts and other component parts must be entirely removed in order to disassemble the coupling.
Yet another form of coupling mechanism is shown in U.S Pat. No. 3,797,949. The described device uses a bolted key and notch for securing a pin within a machine structure. While the mechanism shown therein does not clamp the illustrated parts together in abutting relationship (and in fact is incapable of doing so), it does secure them to prevent relative movement. In addition, the bolt must be entirely removed in order to fully separate the two parts.
Another known type of coupling assembly is found on certain types of motor-driven water pumps. In such units, the electric motor typically has a generally cylindrical housing with either a square or round "bell housing" or flared mounting flange of enlarged dimension. Bolts or other fasteners are used to couple this flange to a mating pad on the pump housing. The inclusion of the flange on the motor housing adds significantly to the housing cost. In addition, such units can be separated (for motor or pump servicing, for example), only by completely removing all of the bolts which couple the pump housing and the motor housing to one another.
A housing coupling mechanism which permits simplification of housing configuration, which permits quick disassembly of the coupled units without the necessity of complete bolt removal, which is "forgiving" of certain dimensional variations and which has a reduced manufactured cost would be an important advance in the art.


The disclosure relates to an apparatus for determining a quality score (MOS) for an audio signal sample, the apparatus comprising: an extractor configured to extract a feature vector from the audio signal sample, wherein the feature vector comprises a plurality of feature values and wherein each feature value is associated to a different feature of the feature vector; a pre-processor configured to pre-process a feature value of the feature vector based on a cumulative distribution function associated to the feature represented by the feature value to obtain a pre-processed feature value; and a processor configured to implement a neural network and to determine the quality score (MOS) for the audio signal sample based on the pre-processed feature value and a set of neural network parameters for the neural network associated to the cumulative distribution function.

Network operators providing services involving speech, such as telephony services, want to assure that the perceived quality of such services meet certain speech quality requirements. The most reliable method for assessing speech quality is the so-called subjective assessment, where a panel of human subjects is asked to listen to transmitted speech signals and score their quality, as illustrated in FIG. 1a.
One of the most widely used listening tests is the absolute category rating (ACR) method, described in the International Telecommunication Union (ITU-T) Recommendation P.800. In this test, several subjects are asked to rate the quality of a number of short speech sentences processed by the system under test using a five-point scale (5: excellent, 4: good, 3: fair, 2: poor, and 1: bad). The average rating is commonly referred to as the "Mean Opinion Score (MOS)", Depending on the test results, network operators can assess the user experience of their services and, if necessary, improve the quality thereof.
However, as subjective speech quality tests are generally very laborious and time-consuming, objective speech quality tests have been introduced, which allow assessing speech quality in an automatic manner and which aim to deliver estimated MOS values that are highly correlated with the MOSs obtained from subjective listening experiments. Essentially, in objective speech quality tests the listener panel required in subjective speech quality tests is replaced by a computational algorithm. Such a computational algorithm implemented as part of an objective speech quality test, generally, requires some kind of prior training, e.g. machine learning, on the basis of a database of speech training samples.
Generally, known objective speech quality tests are based on a model, which can be classified according to the following main categories: (i) intrusive or non-intrusive models and (ii) parametric or waveform models.
In an intrusive model both a processed, usually degraded speech signal and the original reference speech signal are available for the objective speech quality test. Often, however, for instance in real-time scenarios, only the processed speech signal is available for the objective speech quality test, which is referred to as a non-intrusive model. FIGS. 1b and 1c show a schematic illustration of an intrusive model and a non-intrusive model, respectively.
The goal of a parametric model is to estimate speech quality on the basis of some analytical form (e.g., polynomial function) of the feature set and using as input a codec pattern, coding rate, packet loss rate or the like. The parametric model usually has a low computational complexity and is widely used in network planning. However, there is often a substantial gap between the quality estimated by a parametric model and the "perceptual" quality, e.g. the quality perceived by a user.
In comparison to the parametric model, the waveform model tries to estimate the quality based signal processing. More specifically, the waveform model may extract the feature vector on the basis of some psychoacoustic principles. As a result, the output of the waveform model mostly outperforms the output provided by a parametric model with respect to "perceptual" quality, but the complexity of a waveform model is generally much higher than that of a parametric model.
The following major industrial standards have been defined in this field: ITU-T P.863, which is based on an intrusive waveform model, ITU-T P.563, which is based on a non-intrusive waveform model, and e-model, which is based on a parametric model.
In light of the above there is a need for further improvements of devices and methods for evaluating speech quality of audio signal samples on the basis of a neural network and/or machine learning.

Devices and methods for evaluating speech quality


A method and system for selecting a mobile station active set based, at least in part, on the geographic location of the mobile station. A base station or other entity monitors the mobile station's location. When the location changes, the base station refers to a predefined sector-coverage database to identify as the active set one or more sectors that each encompass the mobile station's location. If more than one sector encompasses the location, the base station may further select as the active set a subset of one or more sectors to which the mobile station is closest.

1. Field of the Invention
The present invention relates to wireless telecommunications and, more particularly, to methods and systems for determining which sector or sectors in a cellular wireless network should serve a given mobile station. The invention conveniently uses the location of the mobile station as a basis to select one or more sectors that should be considered members of the mobile station's "active" set of sectors.
2. Description of Related Art
Cellular wireless is an increasingly popular means of personal communication in the modern world. People are using cellular wireless networks for the exchange of voice and data over cellular telephones, Personal Digital Assistants ("PDAs"), cellular telephone modems, and other devices. In principle, a user can seek information over the Internet or call anyone over a Public Switched Telephone Network ("PSTN") from any place inside the coverage area of the cellular wireless network.
In a typical cellular wireless system, an area is divided geographically into a number of cell sites, each defined by a radio frequency ("RF") radiation pattern from a respective base transceiver station ("BTS") antenna. The BTS antennae in the cells are in turn coupled to a base station controller ("BSC"), which is then coupled to a telecommunications switch or gateway, such as a mobile switching center ("MSC") for instance. The MSC or gateway may then be coupled to a telecommunications network such as the PSTN (public switched telephone network) or the Internet.
When a mobile station (such as a cellular telephone, pager, or appropriately equipped portable computer, for instance) is positioned in a cell, the mobile station communicates via an RF air interface with the BTS antenna of the cell. Consequently, a communication path is established between the mobile station and the telecommunications network, via the air interface, the BTS, the BSC and the MSC.
With the explosive growth in demand for wireless communications, the level of call traffic in most cell sites has increased drastically over recent years. To help manage the call traffic, most cells in a wireless network are usually further divided geographically into a number of sectors (which can be visualized ideally as pie pieces), each defined respectively by radiation patterns from directional antenna components of the respective BTS, or by respective BTS antennae.
In a Code Division Multiple Access ("CDMA") wireless network, each cell employs one or more carrier frequencies, and each sector is distinguished from adjacent physical sectors by a pseudo-random number offset ("PN offset"). Further, each sector can concurrently communicate on multiple different channels, distinguished by "Walsh codes". When a mobile station operates in a given sector, communications between the mobile station and the BTS of the sector are carried on a given frequency and are encoded by the sector's PN offset and a given Walsh code.
According to industry standard IS-2000 (published in March 2000 as TIA/EIA/IS-2000-A) and IS-95, a mobile station can communicate with a number of "active" sectors at a time. Depending on the system, the number of active sectors can be up to three or six (currently). The mobile station receives largely the same signal from each of the active sectors and, on a frame-by-frame basis, selects the best signal to use.
A mobile station maintains in its memory a list of the sectors in its "active" set. In addition, it maintains in its memory a list of "candidate" sectors (up to six), which are those sectors that are not yet in the active set but that have sufficient signal strength that the mobile station could demodulate signals from those sectors. Further, the mobile maintains a list of "neighbor" sectors, which are those sectors not in the active set or candidate set but are in close vicinity to the mobile station. All other possible sectors are members of a "remaining" set.
In existing systems, to facilitate a determination of which sectors should be in the mobile station's "active" set, all base stations emit a pilot channel signal, typically at a power level higher than other downlink signals. A mobile station then constantly measures the strength (Ec/Io, i.e., energy versus spectral density) of each pilot that it receives and notifies a primary base station (a base station currently serving the mobile station) when pilot strength falls above or below designated thresholds. The base station, in turn, provides the mobile station with an updated list of active pilots.
More particularly, according to IS-2000, the base station initially provides the mobile station with a Handoff Direction Message (HDM), which indicates (i) the PN offsets of the sectors in the active set and (ii) the following handoff parameters that relate to pilot signal strength:                T_ADD: Threshold pilot strength for addition to the active set (e.g., −14 dB)        T_COMP: Difference in signal strength from an active set pilot (e.g., 2 dB)        T_DROP: Threshold pilot strength for removal from the active set (e.g., −16 dB)        T_TDROP: Time for which an active set pilot falls below T_DROP to justify removal from the active set (e.g., 2 seconds)Additionally, the base station initially provides the mobile station with a Neighbor List Update Message (NLUM), which identifies the "neighbor" sectors for the current active set.
The mobile station then monitors all of the pilot signals that it receives, and the mobile station determines if any neighbor pilot exceeds T_ADD by T_COMP. If so, the mobile station adds the pilot to its "candidate" set and sends a Pilot Strength Measurement Message (PSMM) to the base station, indicating the estimated Ec/Io, for the pilot. Depending on current capacity and other issues, the base station may then send an HDM to the mobile station, listing the pilot as a new member of the active set. Upon receipt of the HDM, the mobile station then adds the pilot to its active set as instructed, and the mobile station sends a Handoff Completion Message (HCM) to the base station, acknowledging the instruction, and providing a list of the pilots (PN offsets) in its active set.
Similarly, if the mobile station detects that the signal strength of a pilot in its active set drops below T_DROP, the mobile station starts a handoff drop timer. If T_TDROP passes, the mobile station then sends a PSMM to the base station, indicating the Ec/Io and drop timer. The base station may then respond by sending an HDM to the mobile station, without the pilot in the active set. The mobile station would then receive the HDM and responsively move the pilot to its neighbor set and send an HCM to the base station.

Method and system for establishing mobile station active set based on mobile station location


A welding chamber having a laminar-vortex inert gas flow is disclosed. The welding chamber comprises a transparent dome that covers an open top side of a rigid generally rectanguloid enclosure. The dome includes a one-way vent for discharging ambient air from within the chamber while preventing the introduction of ambient air into the chamber. The enclosure includes a bottom and side walls that are joined at smooth, curved edges, and at least one side wall of the enclosure includes portholes with gloves for manually accessing the interior of the chamber while the dome is in a closed position. At least one gas distribution tube, a plurality of gas inlets and laminar-flow tunnels are included. In use, an inert gas is introduced into the distribution tube that substantially encircles the top of the enclosure. The inert gas is directed downward through the laminar flow tunnels, attached to the side walls of the enclosure, where the gas exits each tunnel with a laminar flow and is directed by the radiused bottom corners of the enclosure from a vertical flow to a horizontal flow across the bottom of the enclosure. As such, the inert gas creates a slow-moving counter-clockwise vortex pattern. In this manner, heavier-than-air argon gas fills the enclosure, displacing ambient air within the chamber, which is forced to rise and exit the chamber through a check valve vent in the top of the dome.

Many exotic metals, such as titanium, cannot be welded in the presence of air without producing a weak and discolored weld. An inert gas such as argon or helium may be used to displace the air surrounding the weld, thereby solving the problem. A popular solution is to place the workpieces to be welded into a welding chamber that has been designed to purge the air and replace it with inert gas.
There are currently on the market several types of welding chambers suitable for welding exotic metals in an inert-gas atmosphere. Each provides access to workpieces and a welding torch with plastic gloves through portholes in the side of the chamber. Each has a system for introducing the inert gas to the interior of the chamber. Each provides a vent in the chamber to expel air.
A "beach-ball" type of welding chamber is made from flexible clear-plastic pieces fastened together in the shape of a flat-bottomed beach ball. U.S. Pat. No. 5,685,771 to Kleppen on Nov. 11, 1997 is an example of such a device. This type of device is usually mounted to a round work table. Workpieces to be welded may be inserted and removed through a zipper in the plastic. A major problem with the beach-ball type of chamber is its susceptibility to damage from a hot torch, from weld spatter, or from sharp-edged workpieces, any of which may cause holes that allow the escape of inert gas or the entry of air. Costly downtime is the result until the damaged area is patched. Secondly, rips in the plastic may occur in the creases caused by repeated inflations and deflations. Thirdly, pockets of air residing the in the folds of such a chamber when deflated can mix with incoming inert gas, increasing the time required to fully purge such a chamber. Lastly, it is difficult to clean such a soft plastic chamber without it becoming scratched, which impedes viewing therethrough during subsequent operation by a user.
A "glove-box" or "sand-blaster" type of chamber is a steel box with gloved portholes in front and a clear plastic viewing window above the portholes. Workpieces are inserted and removed through a door in the top or side of the box. One problem with this type of device is its limited visibility through what is typically a small window. Secondly, if the door is located on the top of the chamber, it is difficult to add or remove workpieces, if the door is on the side of the chamber, inert gas is lost when the chamber is opened. Thirdly, the inside square edges and corners can trap pockets of air, increasing purge time and making cleaning relatively difficult.
A "bell-jar" type of chamber consists of a rigid plastic dome resting on a heavy steel table. A substantial counter-weight arrangement is necessary to help left the heavy dome. Porthole gloves are mounted through the plastic dome. This 50-year-old design is attributed to the aerospace industry in the early years of titanium welding and has little or no prior art. Workpieces are placed on or removed from the table by lifting the dome, resulting in a complete loss of gas. Although an optional access chamber may be built into the side of the dome to allow small workpieces to be inserted or removed from the chamber without lifting the dome, such as access chamber requires a separate purge system from the main bell-jar chamber. Often called the "Cadillac" of welding chambers, this type of device has several drawbacks. First is the expense, as many companies find such a device cost-prohibitive. Secondly is the often impractical weight of such a device. A forklift truck is typically necessary to move such a device. Thirdly, the right-angle juncture of the dome and the table leaves pockets of air. The device uses a diffuser to slow the entry of gas to prevent any turbulence, thereby inhibiting any scrubbing action of residual pockets of air within the device, resulting in longer purge times.
Accordingly, there is a need for an affordable welding chamber that allows for unfettered access to 100% of the chamber while still minimizing the escape of heavier-than-air gas from the chamber when a workpiece is removed or introduced to the chamber. Such a needed device would thereby conserve the inert gas that fills the chamber during welding operations. Further, such a needed device would provide a full 100% visibility of the inside of the chamber when a user is operating the device, such as through use of a pair of glove ports. Such a needed device would facilitate electrical grounding of any metal workpieces for arc welding thereof. Still further, such a needed device would be relatively light weight, easy and compact to store, easy to clean and free from any sharp projections or corners either inside the chamber or on the exterior surface thereof. Still further, the gas inside the chamber of such a needed device could be quickly purge if desired, minimizing turn-around time between welding sessions requiring a different gas inside the chamber. The present invention accomplishes these objectives. Further objects and advantages will become apparent from a consideration of the ensuing description and drawings.


The invention relates mainly to a rotary electrical machine comprising: a rotor (12); a device (51) for measurement of the angular position of the rotor (12); a stator (11) comprising: a body comprising a plurality of notches; a winding (24) comprising a plurality of phase windings, each having a winding input and a winding output; each phase winding being formed by a plurality of pins (45) inserted in the notches and forming a chignon (40); at least one connector (48) which connects two pins of a single winding; the connector (48) extending opposite the measurement element (52); the connector (48) comprising a portion which is situated radially between an outer periphery of the body (23) and a base of a notch.

In a known manner, rotary electrical machines comprise a stator and a rotor integral with a shaft. The rotor can be integral with a drive and/or driven shaft, and can belong to a rotary electrical machine in the form of an alternator, an electric motor, or a reversible machine which can operate in both modes.
The stator is fitted in a housing which is designed to rotate the shaft on bearings by means of rollers. The rotor comprises a body formed by a stack of sheets of plates maintained in the form of a set by means of an appropriate securing system. The rotor comprises poles, formed for example by permanent magnets accommodated in cavities provided in the magnetic mass of the rotor. Alternatively, in a so-called "projecting" poles architecture, the poles are formed by coils wound around arms of the rotor.
In addition, the stator comprises a body constituted by a stack of thin plates forming a crown, the inner face of which is provided with notches open towards the interior in order to receive phase windings. These windings pass through the notches in the stator body, and form a chignon on both sides of the stator body. The phase windings are obtained for example from a continuous wire covered with enamel, or from conductive elements in the form of pins which are connected to one another by welding. These windings are polyphase windings which are connected in the form of a star or a triangle, the outputs of which are connected to an electric control module.
Connectors form the electrical connection between two pins of a single phase winding. In certain configurations, a connector extends circumferentially opposite a measurement element which makes it possible to determine the angular position of the rotor of the machine. However, because of the current which passes through it, a connector of this type generates a magnetic field which disrupts the signals obtained from the measurement element.

Rotary electrical machine which minimizes electromagnetic disturbances sustained by measurement element


The present invention relates to an improved insulating sheet material and to cigarettes and other smoking articles which employ the insulating sheet material as one or more components thereof. The improved insulating material is particularly useful in smoking articles having a fuel element and a physically separate aerosol generating means, e.g. as an insulating member for insulating the fuel element. In general, the sheet material of the present invention is formable without the use of any organic binder and comprises an inorganic fibrous material such as calcium sulfate fibers, calcium sodium phosphate fibers, or mixtures thereof, and a relatively small amount of highly refined cellulose-based fibers such as wood pulp.

The present invention relates to an improved insulating sheet material and to cigarettes and other smoking articles which employ the insulating sheet material as one or more components thereof. The improved insulating material is particularly useful in smoking articles having a fuel element and a physically separate aerosol generating means, e.g. as an insulating member for insulating the fuel element. In general, the sheet material of the present invention is formable without the use of any organic binder and comprises an inorganic fibrous material such as calcium sulfate, calcium sodium phosphate, or mixtures thereof, and a relatively small amount of highly refined fibrillated cellulose-based fibers such as wood pulp.
Cigarettes, cigars and pipes are popular forms of tobacco smoking articles. Many smoking products and smoking articles have been proposed through the years as improvements upon, or as alternatives to, these popular forms of tobacco smoking articles, particularly cigarettes.
Many, for example, have proposed tobacco substitute smoking materials. See, e.g., U.S. Pat. No. 4,079,742 to Rainer et al. Two such materials, Cytrel and NSM, were introduced in Europe in the 1970's as partial tobacco replacements, but did not realize any long-term commercial success.
Many others gave proposed smoking articles, especially cigarette smoking articles, based on the generation of an aerosol or a vapor. See, for example, the background art cited in U.S. Pat. No. 4,714,082 to Banerjee et al.
Recently, in European Patent Publication Nos. 0174645 and 0212234, U.S. Pat. No. 4,714,082 to Banerjee et al. and U.S. Pat. No. 4,756,318 to Shannon et al., assigned to R. J. Reynolds Tobacco Co., there are described smoking articles, especially cigarette smoking articles, which are capable of providing the user with the pleasures associated with smoking, by heating but not burning tobacco and without delivering appreciable quantities of incomplete combustion or pyrolysis products. The improved insulating sheet material of the present invention is particularly suited for use with such articles.
Calcium sulfate, also commonly referred to as gypsum, has been used by artists and builders for thousands of years.
Recently, calcium sulfate has been produced in a fibrous form, primarily as a filler for reinforcement in thermoset and thermoplastic systems, such as polyesters, urethanes, epoxies, silicones, polypropylene, nylon, etc. In these systems calcium sulfate is used as a partial replacement for glass fibers and other reinforcing materials.
Another inorganic filler is calcium sodium phosphate. Like calcium sulfate, it too has been widely used in a variety of materials, primarily as a filler, such as for composites in organic polymeric materials. U.S. Pat. No. 4,346,028 to Griffith et al. discloses very thin, flexible calcium sodium phosphate fibers which are insoluble in water, and which are acid, alkali and temperature resistant. Described uses for such crystals/fibers include mats and felts, as reinforcing agents for cellulosic papers and fibers, as a substitute for asbestos in asbestos/cement mixtures, as an additive to oil-based and latex paints to change the drying properties of the paint, and to form laminates and composites with organic polymeric materials.
In U.S. Pat. No. 4,609,433 to Crutchfield et al., there is described the use of crystalline calcium M phosphate fibers as a replacement or substitute for asbestos in the manufacture of fibrous sheets. The sheet comprises the crystalline calcium M phosphate fibers (65-95% by weight), auxillary fibers such as wood pulp or synthetic fibers (1-15% by weight) having a Canadian freeness from about 300 ml to about 700 ml, and a water insoluble organic polymeric binder (5-30% by weight).
Japanese Patent Application Kokai No. 61-101438 describes a method of manufacturing gypsum paper with 50-96 parts by weight calcium sulfate, 2-20 parts by weight pulp, 2-30 parts by weight fibrous material, and 0.5-5 parts by weight fixing agent.

Smoking article with improved insulating material


A wrench includes a handle having an engaging end at one end of the handle and a sleeve is slidably mounted to the handle. A tension gauge is received in the handle and connected to an electronic display screen. The display screen is exposed to an outer surface of the handle and can be covered by the sleeve.

The present invention relates to a wrench includes a slidable sleeve on the handle of the wrench and a tension gauge received in the handle so as to display the value of torque on an electronic display screen.
A conventional wrench that can display the value of torque is shown in FIG. 7 and generally includes a handle 100 with an engaging end 200 at one end of the handle 100 and a spring (not shown) is received in the handle 100. The value of the torque that the wrench outputs is displayed by way of bending the spring. Nevertheless, the fatigue of the spring appears after being used for a period of time and the spring cannot reflects a correct value of the torque that the wrench outputs. Another conventional wrench is shown in FIG. 8 and includes an electronic display screen 300 on an outer surface of the handle. An inherent shortcoming of the wrench is that the exposed screen 300 restricts the space that the wrench can be used, and the screen 300 could be damaged by impact of subjects.
The present invention intends to provide a wrench that has a slidable sleeve which may cover the electronic screen so as to protect the screen.
In accordance with one aspect of the present invention, there is provided a wrench which comprises a handle having an engaging end at one end of the handle and a tension gauge is received in the handle and connected to an electronic display screen which is exposed to an outer surface of the handle. A sleeve is slidably mounted to the handle.
The present invention will become more obvious from the following description when taken in connection with the accompanying drawings which show, for purposes of illustration only, a preferred embodiment in accordance with the present invention.