A method for creating an output vector Z(n-1:0) from a first vector X(n-1:0) and a second vector Y(n-1:0). The second vector Y(n-1:0) is a complement of the first vector X(n-1:0). The method subdivides X into a lower-order subvector XL(m-1:0) and a higher-order subvector XH(n-1:m). If a first 1 exists in position k in XL, then Z(k) is set to 0 and all other bits in Z(m-1:0) are set to 1. If a first 1 does not exist in XL, then all bits in Z(m-1:0) are set to 1. The method also determines if a 1 exists in XL. If a 1 exists in XL, then Z(n-1:m) is masked.

This invention relates in general to computer algorithms and an apparatus for rapidly performing same. More particularly, this invention relates to a method and an apparatus for creating an output vector from a first vector and a second vector, the second vector being a complement of the first vector. This method is particularly useful for rapidly finding the first 1 in a long vector.
As is well known in the art, binary numbers are the native tongue of computers. The transistor, the basic building block of most modern microprocessors, can create binary information: a 1 if current passes through, or a 0 if current doesn't. From these 1s and 0s, which are called bits, a computer can create any number, provided it has enough transistors grouped together to hold the 1s and 0s required. A group of 1s and 0s is commonly known as a vector. For example, a vector X(n-1:0) has n storage locations numbered from 0 to n-1. The first bit in the vector X(n-1:0) is X(0) while the last bit is X(n-1). When referring to an entire vector X(n-1:0), a short-hand notation X is often used by those skilled in the art.
Consider a vector X' having a length n of 8 and equal to 01101110. The rightmost bit X'(0), in this case 0, is the least significant bit. The left most bit X'(7), in this case 0, is the most significant bit. If it is desired to find the first 1 in X', one could first look at the least significant bit, X'(0). Because X'(0) is 0, one could then look at the next higher-order bit, X'(1). In this case, X'(1) is 1. Thus, X'(1) is "the first 1 found in X'." While in this simple example the first 1 in X' was found in a relatively small number of steps, much more complicated examples would require many additional time-consuming steps.
It may be desired to represent the first 1 found in X in another vector Z'. In this case, Z' could be set equal to 1111101 where the 0 in Z'(1) indicates the position of the first 1 found in X'.
In modern microprocessors, it may be necessary to find the first 1 in a long vector. For example, a resource scheduler or a resource allocator may need to find the first 1 in a vector X(n-1:0) that represents the availability of n resources. A 1 in such a vector, which will be referred to as a resource vector, may represent that a particular resource is available, while a 0 may represent that the resource is busy. These resources may include floating point registers and general registers for out-of-order instruction execution. Because of the large number of resources in modern microprocessors, the length n of a resource vector may be as great as 64. It is likely that future microprocessors will have even more resources and will utilize even larger resource vectors.
It may also be necessary to find the first 1 in a long vector when aligning complex instruction set computer (CISC) instructions. An instruction alignment unit may search a long vector that marks the end bytes of CISC instructions. Thus, the location of the end byte of a particular CISC instruction may be found by finding the first 1 in that long vector.
Because of the ever-increasing clock speeds of modern microprocessors, certain microprocessor functions, such as scheduling and allocating resources, need to be performed more rapidly than ever before. Such functions are preferably performed in less than a single microprocessor clock cycle.
Conventional methods for finding the first 1 in a long vector utilize AND gates. As is known in the art, an AND gate is a multiple-input-single-output device which realizes the logical function AND. These conventional methods require multiple levels of AND gates, i.e., the output of a first AND gate is coupled to an input of a second AND gate and so on. Each level of AND gates induces a delay equal to the switching speed of the AND gate. Modern AND gates have extremely fast switching speeds. However, the multiple levels of AND gates required for finding the first 1 in a long vector using conventional methods do not allow scheduling or allocating resources in a single clock cycle of a modern microprocessor. This deficiency is also due in part to the fact that AND gates are relatively slow when implemented in domino logic.
Domino logic is known by those skilled in the art as a modification of conventional clocked CMOS logic. Domino logic allows a single clock to pre-charge and evaluate a cascaded set of dynamic logic blocks. In a cascaded set of logic blocks, each stage evaluates and causes the next stage to evaluate--in the same way a line of dominos fall. Any number of logic stages may be cascaded, provided that the sequence can evaluate within the evaluate clock phase.
Another conventional method for finding the first 1 in a vector does not involve the use of AND gates. FIG. 1 shows a diagram of a prior art Find First One Block. This block contains a plurality of domino OR gates. As shown in FIG. 1, vector X(n-1:0) is input into the block. Likewise, vector Y(n-1:0) is input into the block. Y is the complement of X. For binary numbers, the complement of 1 is 0. Similarly, the complement of 0 is 1. For example, if a vector X' has a length n of 8 and is set equal to 01101110, then the complement of X' is 10010001. The output of the block is vector Z.
In this prior art method, Y(0) is directly coupled to Z(0). For k equals 1 to n-1, X(k-1:0) and Y(k) are input into a k+1 input OR gate. The output of each k+1 input OR gate is output into Z(k).
While this prior art method can find the first 1 more rapidly than the above described method using AND gates, it could not efficiently find the first 1 in long vectors. As can be seen in FIG. 1, there is a large fanout of X(0) because it is connected to n-1 OR gates. Large fanouts typically increase the load capacitance and slow down the previous driving gate in the domino chain. In addition, as the number of inputs into an OR gate increases, the diffusion capacitance increases and the output speed decreases. Finally, the surface area required to implement this prior art block is large due to the significant transistor count. The large surface area increases device costs. Further, the large surface area increases delays and slows down the block. As is known by those skilled in the art, delays due to wire lengths are becoming comparable to more dominant gate delays as process geometries shrink.
Thus, a need exists for a method and apparatus for efficiently finding the first 1 in a long vector within a single microprocessor clock cycle.

Method and apparatus for creating an output vector from an input vector


A normally-off cascode power switch circuit is disclosed fabricated in wide bandgap semiconductor material such as silicon carbide or gallium nitride and which is capable of conducting current in the forward and reverse direction under the influence of a positive gate bias. The switch includes cascoded junction field effect transistors (JFETs) that enable increased gain, and hence blocking voltage, while minimizing specific on-resistance.

1. Field of the Invention
This invention relates generally to semiconductor power switches and more particularly to a normally-off cascode power switch fabricated in wide bandgap semiconductor material, such as silicon carbide or gallium nitride.
2. Description of the Prior Art
Semiconductor power switches are generally well known in the art and comprise many types of circuit configurations, one of which is the cascode power switch. One such power switch is known to include a normally-on (depletion mode) conducting junction gated transistor (e.g., the junction field effect transistor (JFET), static induction transistor (SIT), or metal semiconductor field effect transistor (MESFET)) as the high-voltage device connected in cascode circuit relationship with a normally-off (enhancement mode) non-conducting metal oxide semiconductor field effect transistor (MOSFET) as the low-voltage device. The normally-off low voltage device is designed to block approximately 20V to 50V, thus providing sufficient reverse gate-source bias on the high voltage normally-on device to promote current pinch-off. An arrangement using a normally-off silicon MOSFET as a control device, however, cannot operate at relatively high operating temperatures, for example in the range of 125° C. which greatly restricts the design parameters in systems such as modern high power motor drivers, directed energy weapon systems and power supply switching and conversion systems.


An approach for determining a representation of a physical object, the representation indicating at least one of a color, a texture, and a pattern associated with the object, comparing the representation to one or more reference representations on a basis of at least one of the color, the texture, and the pattern, selecting one of the plurality of reference representations based on the comparison; and determining one or more physical items associated with the one reference representation, is presented.

With the consumer adoption of mobile devices, such as cellular telephones, laptop computers, personal digital assistants, and the like, these devices have provided an avenue for solving challenges facing consumers. Device manufacturers and service providers are continually seeking applications and services to meet these challenges. With advancements in the manufacturing processes of physical items, such as consumer products, consumers are offered a wider selection of choices concerning characteristics of the products (e.g., color, texture, pattern, and the like). Often, differences between characteristics can be so subtle as to be indiscernible by the average consumer. Moreover, different vendors of consumer products often have their own unique system for identifying the various characteristics, making matching between vendors of consumer products on the basis of the characteristic more difficult. By way of example, paint vendors often have their own naming system for the various paints they produce, and matching paints between vendors is often based on merely a visual, side-by-side inspection of the paints. Where one of the paints has already been applied to an object, such as a bedroom wall, it is often more difficult to make the comparison.
Based on the foregoing, there is a need for an approach to develop applications and services for mobile devices with respect to discerning characteristics of items.

Method and system for item selection based on characteristic matching


A tension leg platform in deep water over an underwater wellhead system supports an upstanding pig riser. The riser ID is smaller than the shoreline ID delivering produced oil to shore. The shoreline is pigged by a tapered nose pig inserted into the bell nipple at the top, open end to enable pig passage down the riser compressing the pig body. The body is formed of N discs and N foam donut spacers to clean the shoreline ID.

Pipeline pigs are extremely helpful in the operation of pipelines. Ordinarily, pipelines extend cross country, typically placed on the surface, but sometimes they extend under bodies of water. They can cross rivers and lakes. It's not uncommon for pipelines to pass under several bodies of water. In offshore circumstances, pipelines extend from production platforms perhaps 50 to 100 miles out in the Gulf of Mexico. Typically, the water is relatively shallow. In many places, the water is only about 100 feet deep even when the production platform is many miles offshore. In those instances, the platforms are fixed structures supported on the bottom. In deeper waters, platform erection costs become prohibitive. While two or three large platforms have been erected or perhaps have proceeded to the planning stage, it appears that the maximum limit for stationary construction of a platform is about 1,200 feet of water. Such platforms are extraordinarily expensive in that they require the frame structure as large as any of the tall buildings in the U.S. They are erected on shore and towed to an offshore location. They are deployed only when the production platform is known to be above a very prolific and highly productive field. A better approach now is the use of a tension leg platform. A tension leg platform involves a platform which is made with adequate buoyancy that it will float and hold the working deck properly above the wave action. It is held in place by cables which extend to the bottom and are anchored at the bottom. The buoyant body is held on flexible lines which are maintained in tension. It resembles a buoy which is anchored by multiple anchor lines extending to the bottom. This reduces markedly the amount of structural steel and the assembly required to assemble that structure into a supportive rigid framework. The tension legs are deployed around the platform and are anchored at the bottom.
The typical platform installed at offshore locations supports a complex amount of equipment on the deck for actual production. Indeed, the production platform may also temporarily support a drilling rig while the last of several wells are drilled. Ordinarily, a platform will not be installed unless several wells are serviced from the platform. While the number can be varied, it is not uncommon to terminate 30 to 50 wells serviced from a single platform. Many of the wells are deviated so that they actually reach bottom depth at desired locations scattered over a producing formation so that optimum production can be obtained. All the wells are therefore connected to the platform and are operated from the platform. Wellhead equipment (such as the Christmas tree) and surface gathering lines associated with land wells are not always placed on the production platform. It is desirable that wellhead equipment be located at the mudline. Typically, the wells incorporate conductor pipes to a mat or template which supports the casing and pipe strings. The many wells are terminated at the wellhead equipment located underwater. Producing wells are connected with a manifold to deliver the produced fluid and that in turn is directed into a flow line from the underwater template toward shore.
To make the example specific, assume that 40 completed wells terminate at the underwater template. Each well is provided with appropriate wellhead equipment. Wellhead valves direct their flow into a gathering line. Assume that the gathering line is a 16 inch line located in 1,000 feet of water. The gathering line delivers, under pressure, the produced oil which is pumped into the gathering line and flows to a shore location where the line emerges from the ocean. Assume that the gathering line is 200 miles long. The 200 miles of gathering line is exposed to cumulative collection of materials from the flowing oil. The materials in the gathering line often will coat the inside of the gathering line. Pipe coating is primarily dependent on the nature of the production and the temperature of the production fluids. If, for instance, the production fluids are extremely hot when produced, they will be cooled significantly in transit along the 200 mile gathering line. As cooling occurs, heavier molecules tend to coat on the pipe. It is possible that the inside diameter of the pipe will be markedly reduced by the cooling of the produced well fluids.
Sometimes, a producing well will produce small or great quantities of water which is laden with insoluble constituents. Again, the nature of the constituents will vary widely. It is however possible that they also will go out of solution and thereby plate the inside wall of the pipe. It is not uncommon for the gathering line to require cleaning periodically. Cleaning of the gathering line requires insertion of a pipeline pig into the gathering line. The pig is forced by the fluid flow from the underwater wellhead to the far end of the gathering line where it emerges onshore. In this particular instance, the gathering line must be pigged so that optimum production can be continued. If pigging is neglected, it is conceivable that the gathering line will become smaller and smaller in effective flow volume. Ultimately, serious problems can arise when the gathering line is severely plugged. It is not uncommon for the hardened materials which collect against the wall to reduce effective cross-sectional flow area by 50%. Because of that, pigging is absolutely essential to clean the line. A pig launcher is ordinarily used for lines onshore. In this instance, the pig launcher is not normally installed underwater. A vertical riser pipe is used for the pig launcher. The vertical riser must stand taller than the depth of water in which the wells are located. If the wellhead equipment is located at a depth of 1,000 feet, then the riser pipe must be 1,000 feet in height, and must have sufficient additional height so that the open end will not take any water. It is necessary to extend the pipe about 60 feet taller than the normal depth of the ocean. This vertical riser is 1,060 feet in height. This vertical gathering line riser is unwieldy. It must be stabilized laterally. Otherwise, ocean currents will force it to the side. It is sufficiently unstable in light of its relative height that it would otherwise topple. It is, however, tied to the platform above. This will add stability at the upper end so that the riser pipe will not fall over or be deflected by ocean currents or wave action.
With jack-up drilling rigs, no problem arises because the weight of the drilling rig is supported on the ocean bottom. With fixed platforms, weight does not pose a problem either because the weight is supported on the legs. With a tension leg platform, weight becomes a problem if it is excessive. In this particular instance, the gathering line riser poses a problem because it is heavy and it connects with the platform at one edge.
Again, the offset point of connection would not be a problem with a fixed platform. Here, the point of connection becomes a problem because that amount of weight at one side tends to tilt the platform because it is a floating platform. Because the platform is floating, both the weight and offset connection of the riser becomes a serious problem.
One way to overcome this is to reduce the diameter of the riser. Another weight reduction is to reduce the wall thickness. Wall thickness, however, is mandated by the depth of the water. If production is large, then a larger diameter gathering line is serviced by a larger diameter riser.
The present disclosure sets forth an improved system for gathering line pigging where the pig must be inserted through a vertical riser of several hundred feet in height. It sets forth a pig construction which is passed downwardly through the riser and then finally into the gathering line. If the vertical riser is reduced in diameter and wall thickness, a substantial reduction in weight occurs. In turn, a reduction in diameter of the riser requires a different pig construction. Therefore, another aspect of the present disclosure sets forth a different type pig. In particular, this pig is constructed to work with a bell receptacle or nipple at the top end of the riser. The pig is dropped into the riser, and lands in the bell. By gravity, it is caused to fall into the riser. Ultimately, it turns to the horizontal into the gathering line. The pig is used time and again until it is finally worn out.
The present disclosure thus describes both a riser pipe construction and a pig construction so that the pipe is made as light as possible, the pig is readily inserted, and yet the pig is permitted to shrink and then expand for actual transit through the producing line.

Method and apparatus for launching a pig in a vertical riser pipe


A solid state imaging system has at least one CMOS imager with first and second series of pixels in which the pixels of one series are offset, i.e., staggered, in respect to the pixels of the other series. Multiple imagers can be arrayed end to end, with jumper wires connecting the pixel output conductors or each so that the pixels feed into a common output amplifier for each series, to minimize chip to chip offset voltages. The pixels may be diagonally offset from one another, and a color imager can be constructed in which color ribbon filters are arranged diagonally across the imaging area. This arrangement minimizes color cross talk.

This invention concerns solid state imagers and image capture systems, and in particular is directed to an improved configuration of the pixels into offset or staggered arrangements of two or more series of pixels. The invention is more particularly concerned with a configuration that employs two or more imager chips butted end-to-end, and which avoids undesirable gain variations from chip to chip. The invention is desirably carried out using low-power CMOS imager technology and offset series of pixels.
Solid state image sensors are used in a wide variety of applications, and there has been much interest in pursuing low-cost, high-resolution, high-reliability image sensors for such applications. CMOS imager technology is advantageous because of the requirement for a only a single power supply voltage, its ruggedness, and its inherent low power consumption. There has been great interest in achieving extremely high resolution also, which requires increased pixel density.
Scanning systems are used for a variety of image capture applications, such as web inspection and document copying and archiving. Conventionally, scanners of this type have utilized either Contact image Sensor (CIS) modules or CCDs to capture the image information. In such scanning systems, CCD imagers are limited in size to only a fraction of the width of the object being scanned, such as a photograph or text. This size limitation arises because of charge transfer difficulties over large distances, i.e., over distances comparable to the width of a page. This requires focusing the image of the document to reduce it down to the size of the imager. While it might be desirable to join a number of CCD imagers end to end to create in effect a single long image capture device, there are many drawbacks that make that impractical.
FIG. 1 illustrates a prior-art scanner arrangement or scanning system 10 which employs a CCD solid state imager 12. A focusing lens system 14 is positioned to focus onto the CCD imager 12 a reduced image of the object, e.g., a sheet of text 16, which is to be scanned. Mirrors (not shown here) may be employed in many practical scanner arrangements. An output buffer 18 is coupled to the CCD imager 12 and is employed via a flexible cable to drive an application-specific integrated circuit (ASIC) 22. An input buffer 20 is also coupled to the CCD imager 12 and is used to interface the captured image data, digitized by an analog-to-digital converter (A/D), to the host computer, networks, or other peripheral devices such as printers or modems, or in some cases all or some portion of a Multi-Function Peripheral (MFP) with image processing functions, motor control, light control, sheet feeder, and user interface ASIC device(s). A desktop system also contains a motor and a light source to move the imager underneath the document 16 to be scanned. Various different light sources such as fluorescent tubes and LEDs, and various different drive motors, such as stepping motors and synchronous motors can be employed. These are well known and not shown here, but would be understood to be included in the scanner system. The CCD imagers have many drawbacks and limitations, such as speed limitations, which arise due to charge transfer efficiency limitations, as well as a high power consumption, and a severely limited capability for integration of other functions onto the pixel array. In addition, in CCD imagers the pixels must be read out in a fixed sequence, which does not permit pixel information to be skipped.
A conventional CIS-based scanning system 30 is illustrated in FIG. 2. In this system, there are a plurality of CIS modules 32(1) to 32(N) joined end to end. The CIS modules 32(1)–32(N) are located in tight proximity to each other to construct a long contiguous array of sensors as wide as the image being captured. An optical coupler 34 is positioned to face the object 36 to be scanned and to focus an image of it onto the array of CIS modules. Because the array of modules 32(1)–32(N) need to be as wide as the object 36 to be scanned, the array has to be quite large. Accurate placement of the CIS modules 32(1)–32(N), which is necessary to pick up the entire image without gaps or jumps across the width of the object, makes the construction of the CIS-based system rather expensive. Also, the various individual CIS sensors each have individual voltage offsets that have to be corrected, and this also adds to the complexity of the system.
An active column sensor (ACS) architecture has recently been developed, as disclosed in Pace et al. U.S. Pat. No. 6,084,229, which permits a CMOS image sensor to be constructed as a single-chip video camera with a performance equal to or better than that which may be achieved by CCD or CID imagers. ACS imagers enjoy very low fixed pattern noise. The principles as disclosed and illustrated in the Pace et al. patent can be advantageously incorporated into imagers employed in scanning applications, and that patent is incorporated herein by reference.

Scanning imager employing multiple chips with staggered pixels


A special purpose cuvette assembly with features that create a small, restricted volume to minimize bulk movements of liquid and that minimize backscattering of light. The special-purpose cuvette assembly enables recording of Brownian movements of nanoparticles in a liquid when it is placed in a suitable optical device comprising a light sheet and an optical microscope attached to a video camera that is oriented perpendicular to the light-sheet plane.

Nanoparticles are ubiquitous and by far the most abundant particle-like entities in natural environments on Earth and are widespread across many applications associated with human activities. There are many types of naturally occurring nanoparticles and man-made (engineered) nanoparticles. Nanoparticles occur in air, aquatic environments, rain water, drinking water, bio-fluids, pharmaceuticals, drug delivery and therapeutic products, and a broad range of many industrial products. Nanoparticles usually occur within polydisperse assemblages which are characterized by co-occurrence of differently-sized particles.
Given the widespread usage of nanoparticles, the ability to control and accurately characterize their properties may be useful to many applications. Conventional methods for measuring nanoparticle properties include Nanoparticle Tracking Analysis, which uses a microscope and video camera to analyze frames of the recorded videos to track images of light reflected or scattered by the nanoparticles undergoing Brownian motion. The instrument to perform such analysis is usually comprised of a small cell, or cuvette, that enables illumination of a liquid with a very precisely defined, narrow light sheet and observation of scattered light from the nanoparticles, usually at a 90-degree angle to the light sheet, hence the cuvette must contain at least two surfaces with minimal light attenuation properties (for example optical glass). Such cuvettes are widely used in all types of optical measurements in various laboratory instruments, are easily available and have standardized internal dimensions, in the case of the prototype 10 mm×10 mm×45 mm.
Ideally there should be no bulk movement of the liquid when the videos are being recorded so the only particle motion is pure Brownian motion. However, due to the low thermal conductivity of glass and because of potentially considerable energy transmitted from the illuminating beam to the liquid and wall of cuvette by absorption, one can observe thermally generated micro flow of the liquid regardless of the volume of liquid in a traditional cuvette. Other sources of micro flows are possible, for example, movements of the table on which the instrument is mounted that cause vibrations of the table or evaporation of the sample liquid that cools its surface. Flow can also be induced by stirring the liquid in the cuvette, or by pumping liquids in and out of the cuvette. In these and other induced flow cases, it is always desirable to arrest the flow as quickly as possible for effective and timely particle analysis. Algorithms are available to detect and remove effects of such bulk liquid movement, however, these algorithms have limitations and more accurate results are always achieved in the absence of bulk liquid movement.
Another desirable situation for optimal detection and processing of scattered light from nanoparticles in liquids is to minimize or eliminate backscattering of light from the wall of the cuvette that is opposite to the wall where light enters the cuvette (the back wall). Such backscattering of the incoming light beam typically broadens the illuminated region (thickening of light sheet), thus creating images that could be partially out of focus of the microscope (fuzzy images) which are not suitable for precise particle tracking. Backscattering-induced broadening has an inherently inconsistent impact on the width of the light sheet, and as such also causes variability in particle concentration measurements since the width of the light sheet effects the volume of sample that is being analyzed in each measurement. Secondarily deleterious light scattering effects from other reflective surfaces in the cuvette should also be minimized through use of light absorbing materials or coatings (such as black paint).
Another important consideration is compatibility with existing components that accurately hold the cuvette in place relative to the light sheet, control its temperature and enable stirring and or pumping of the liquid. Such stirring and/or pumping facilitates examination of multiple fresh aliquots from the same sample within the cuvette and is easily achieved with a magnetic stirring bar at the bottom of the cuvette which is driven by an external rotating magnet, or with an external pump.
What is needed, therefore, is an improved system that can minimize movement of the liquid while also eliminating backscatter of the light within the observation region of the cuvette.

Special purpose cuvette assembly and method for optical microscopy of nanoparticles in liquids


A power transmission device for an electrically driven vehicle basically includes a power transmission mechanism, a sliding contact brush, a brush case cover, and a brush protective jig. The power transmission mechanism includes a case element, an axle element and a power transmission element. The sliding contact brush is mounted on an axle end of the axle element. The brush case cover is selectively mounted to the case element to enclose the axle end of the axle element in the case element. The brush protective jig is mounted to cover the brush contact when mounting the sliding contact brush to the axle end. The brush protective jig is dimensioned to contact the brush case cover and to prevent the brush case cover from being mounted to the case element while the brush protective jig is in an attached state that covers the brush contact.

1. Field of the Invention
The present invention relates to a power transmission device for an electrically driven vehicle, such as electric vehicle, and a manufacturing method therefore, in which a countermeasure is taken to suppress high-frequency noise from an inverter.
2. Background Information
In an electrically driven vehicle having an electric motor that provided at least as driving source for travel, it is known that a high-frequency noise (also referred to as "radio noise") from an inverter as a source of generation, which controls the motor is emitted to the outside with the motor drive system used as antenna, thereby adversely affecting the radio receiver.
As countermeasure, such a conventional device is known where a slide brush which is electrically connected to a vehicle body is mounted to a motor shaft driven by an inverter at a location opposite to a power transmission mechanism with respect to a rotor (for example, see Japanese Laid-Open Patent Application Publication No. 2006-320129).

Power transmission device for electrically driven vehicle and manufacturing method therefore


A partition in lattice form forms a plurality of housing sections. A plurality of circuit blocks including a semiconductor block and a terminal base block are electrically connected one to another in a state of being housed in the housing sections to form a power semiconductor circuit. The semiconductor block is formed by covering an IGBT with an insulating material. A collector of the IGBT is connected to an electrode through a metal plate. The electrode is led out from an inner portion of the insulating material to a side surface of the insulating material. A terminal base block includes a power terminal to which an external power wiring for supplying electric power to the IGBT is electrically connected, and a screw hole into which a screw for fixing the power wiring is inserted.

An ordinary drive circuit of power IGBTs is of a bridge structure such as a 2-in-1 structure in which IGBTs and an FWDs are mounted on the upper arm side and the lower arm side. However, drive circuits to which any ordinary half-bridge circuits cannot be applied, e.g., drive circuits for SR motors not using a rare-earth magnet or the like are being put to practical use (see, for example, Patent Literature 1). Also, a technique to form a semiconductor circuit by disposing block members with electrical circuits between sectional members disposed in lattice form has been proposed (see, for example, Patent Literature 2).


Treadmills are generally discussed herein with specific discussion to Omni-directional treadmills that incorporate powered offset casters to move a belt in the X, Y, and theta directions. The belt is positioned over a frame and the frame includes a plurality of rollers for allowing the belt to turn about the frame. The powered offset casters can be mounted under the belt or on top of the belt and are controlled by a control system, which controls the translational motion and rotational motion of the belt.

An Omni-directional treadmill (ODT) that allows a user to traverse in the X, Y, and theta directions has been described as the Holy Grail for virtual reality systems. Among other things, the ODT can function as a walking simulator when used in combination with virtual reality environments for activities such as gaming, military simulations, or evacuation simulations. Other examples of where an ODT may be used include laboratories for human motion studies, in perceptual studies for psychology experiments, in a gym as indoor exercise equipment, as language immersion systems, and as conveyors for manufacturing, just to provide some examples.
The company Virtual Space Devices, Inc. has an existing commercial ODT product. However, the available model only allows the user to move in two directions. The Virtual Space ODT uses a regular treadmill that includes 3400 rollers in the lateral direction to allow the user to slip sideways, and to move in two directions. However, the Virtual Space ODT is very complicated, noisy, and does not allow for natural movements. For example, the sideways motion feels icy, and the user has to wear a harness in case he or she slips.
The Virtual Reality Laboratory at University of Tsukuba developed an ODT called the Torus treadmill. The Torus treadmill uses a torus-shaped surface to build the locomotion interface. This treadmill consists of ten normal belt conveyers, which are connected side by side and driven in a perpendicular direction to simulate an infinite surface. The position of the walker is fixed in the real world by computer-controlled motion of the conveyers. This product requires many motors, and the motion of the user must be sensed using a vision system.
The US Army is funding the development of a locomotion simulator called the OmniTrek™, which allows motion in two directions as well as stair climbing. It is a complex device that involves two servo controlled robot arms to catch the user's feet. Another ODT is the Sarcos Treadport™, which was developed in 1995 and is based on the standard one-directional treadmill. The user of the Sacros Treadport™ must be monitored and constrained by a mechanical attachment to the user's waist. The user can walk, jog, and kneel, and the incline of the treadmill can be adjusted to simulate hills. However, the physical movement is constrained to one direction.
Other inventions include a giant sphere to walk inside, a walking surface consisting of hundreds of miniature balls, an air-walker, a treadmill that rotates, and walking slippers. However, the current systems all have at least one or more shortcomings that include: restrictive motion, being limited to upright motion, noisy, complicated, requires a tracking system, and, during acceleration transitions, having a tendency of causing the user to slip or fall.
Preferably, an ODT needs a surface that reacts to movement in any direction so that the user remains in a small set area. As discussed above, some ODTs incorporate rollers in the sideways or transverse direction to allow the user to slip back to the center of the ODT. However, the disadvantage with this design is that the slippery motion does not allow the user to walk freely. The ODT with rollers also tends to leave the user with the feeling of stepping and then sliding, not a natural walking motion.
Accordingly, there is a need for an ODT that is simple to operate, that provides smooth accelerations and transitions, that is relatively quiet, and that can control the damping or stiffness in any planar direction. Furthermore, there is a need for a method of making the ODT with all the advantages discussed.


A process for liquefying natural gas in conjunction with producing a liquid stream containing predominantly hydrocarbons heavier than methane is disclosed. In the process, the natural gas stream to be liquefied is partially cooled, expanded to an intermediate pressure, and supplied to a distillation column. The bottom product from this distillation column preferentially contains the majority of any hydrocarbons heavier than methane that would otherwise reduce the purity of the liquefied natural gas. The residual gas stream from the distillation column is compressed to a higher intermediate pressure, cooled under pressure to condense it, and then expanded to low pressure to form the liquefied natural gas stream.

This invention relates to a process for processing natural gas or other methane-rich gas streams to produce a liquefied natural gas (LNG) stream that has a high methane purity and a liquid stream containing predominantly hydrocarbons heavier than methane. The applicants claim the benefits under Title 35, United States Code, Section 119(e) of prior U.S. provisional application Ser. No. 60/296,848 which was filed on Jun. 8, 2001.
Natural gas is typically recovered from wells drilled into underground reservoirs. It usually has a major proportion of methane, i.e., methane comprises at least 50 mole percent of the gas. Depending on the particular underground reservoir, the natural gas also contains relatively lesser amounts of heavier hydrocarbons such as ethane, propane, butanes, pentanes and the like, as well as water, hydrogen, nitrogen, carbon dioxide, and other gases.
Most natural gas is handled in gaseous form. The most common means for transporting natural gas from the wellhead to gas processing plants and thence to the natural gas consumers is in high pressure gas transmission pipelines. In a number of circumstances, however, it has been found necessary and/or desirable to liquefy the natural gas either for transport or for use. In remote locations, for instance, there is often no pipeline infrastructure that would allow for convenient transportation of the natural gas to market. In such cases, the much lower specific volume of LNG relative to natural gas in the gaseous state can greatly reduce transportation costs by allowing delivery of the LNG using cargo ships and transport trucks.
Another circumstance that favors the liquefaction of natural gas is for its use as a motor vehicle fuel. In large metropolitan areas, there are fleets of buses, taxi cabs, and trucks that could be powered by LNG if there were an economic source of LNG available. Such LNG-fueled vehicles produce considerably less air pollution due to the clean-burning nature of natural gas when compared to similar vehicles powered by gasoline and diesel engines which combust higher molecular weight hydrocarbons. In addition, if the LNG is of high purity (i.e., with a methane purity of 95 mole percent or higher), the amount of carbon dioxide (a "greenhouse gas") produced is considerably less due to the lower carbon:hydrogen ratio for methane compared to all other hydrocarbon fuels.
The present invention is generally concerned with the liquefaction of natural gas while producing as a co-product a liquid stream consisting primarily of hydrocarbons heavier than methane, such as natural gas liquids (NGL) composed of ethane, propane, butanes, and heavier hydrocarbon components, liquefied petroleum gas (LPG) composed of propane, butanes, and heavier hydrocarbon components, or condensate composed of butanes and heavier hydrocarbon components. Producing the co-product liquid stream has two important benefits: the LNG produced has a high methane purity, and the co-product liquid is a valuable product that may be used for many other purposes. A typical analysis of a natural gas stream to be processed in accordance with this invention would be, in approximate mole percent, 84.2% methane, 7.9% ethane and other C2 components, 4.9% propane and other C3 components, 1.0% iso-butane, 1.1% normal butane, 0.8% pentanes plus, with the balance made up of nitrogen and carbon dioxide. Sulfur containing gases are also sometimes present.
There are a number of methods known for liquefying natural gas. For instance, see Finn, Adrian J., Grant L. Johnson, and Terry R. Tomlinson, "LNG Technology for Offshore and Mid-Scale Plants", Proceedings of the Seventy-Ninth Annual Convention of the Gas Processors Association, pp. 429–450, Atlanta, Ga., Mar. 13–15, 2000 and Kikkawa, Yoshitsugi, Masaaki Ohishi, and Noriyoshi Nozawa, "Optimize the Power System of Baseload LNG Plant", Proceedings of the Eightieth Annual Convention of the Gas Processors Association, San Antonio, Tex., Mar. 12–14, 2001 for surveys of a number of such processes. U.S. Pat. Nos. 4,445,917; 4,525,185; 4,545,795; 4,755,200; 5,291,736; 5,363,655; 5,365,740; 5,600,969; 5,615,561; 5,651,269; 5,755,114; 5,893,274; 6,014,869; 6,062,041; 6,119,479; 6,125,653; 6,250,105 B1; 6,269,655 B1; 6,272,882 B1; 6,308,531 B1; 6,324,867 B1; and 6,347,532 B1 also describe relevant processes. These methods generally include steps in which the natural gas is purified (by removing water and troublesome compounds such as carbon dioxide and sulfur compounds), cooled, condensed, and expanded. Cooling and condensation of the natural gas can be accomplished in many different manners. "Cascade refrigeration" employs heat exchange of the natural gas with several refrigerants having successively lower boiling points, such as propane, ethane, and methane. As an alternative, this heat exchange can be accomplished using a single refrigerant by evaporating the refrigerant at several different pressure levels. "Multi-component refrigeration" employs heat exchange of the natural gas with one or more refrigerant fluids composed of several refrigerant components in lieu of multiple single-component refrigerants. Expansion of the natural gas can be accomplished both isenthalpically (using Joule-Thomson expansion, for instance) and isentropically (using a work-expansion turbine, for instance).
Regardless of the method used to liquefy the natural gas stream, it is common to require removal of a significant fraction of the hydrocarbons heavier than methane before the methane-rich stream is liquefied. The reasons for this hydrocarbon removal step are numerous, including the need to control the heating value of the LNG stream, and the value of these heavier hydrocarbon components as products in their own right. Unfortunately, little attention has been focused heretofore on the efficiency of the hydrocarbon removal step.
In accordance with the present invention, it has been found that careful integration of the hydrocarbon removal step into the LNG liquefaction process can produce both LNG and a separate heavier hydrocarbon liquid product using significantly less energy than prior art processes. The present invention, although applicable at lower pressures, is particularly advantageous when processing feed gases in the range of 400 to 1500 psia [2,758 to 10,342 kPa(a)] or higher.
In the following explanation of the above figures, tables are provided summarizing flow rates calculated for representative process conditions. In the tables appearing herein, the values for flow rates (in moles per hour) have been rounded to the nearest whole number for convenience. The total stream rates shown in the tables include all non-hydrocarbon components and hence are generally larger than the sum of the stream flow rates for the hydrocarbon components. Temperatures indicated are approximate values rounded to the nearest degree. It should also be noted that the process design calculations performed for the purpose of comparing the processes depicted in the figures are based on the assumption of no heat leak from (or to) the surroundings to (or from) the process. The quality of commercially available insulating materials makes this a very reasonable assumption and one that is typically made by those skilled in the art.
For convenience, process parameters are reported in both the traditional British units and in the units of the International System of Units (SI). The molar flow rates given in the tables may be interpreted as either pound moles per hour or kilogram moles per hour. The energy consumptions reported as horsepower (HP) and/or thousand British Thermal Units per hour (MBTU/Hr) correspond to the stated molar flow rates in pound moles per hour. The energy consumptions reported as kilowatts (kW) correspond to the stated molar flow rates in kilogram moles per hour. The production rates reported as pounds per hour (Lb/Hr) correspond to the stated molar flow rates in pound moles per hour. The production rates reported as kilograms per hour (kg/Hr) correspond to the stated molar flow rates in kilogram moles per hour.


A bicycle light system has front and rear (white and red) lights with mounting brackets to secure on a bicycle helmet. A rechargeable battery is contained in the rear light casing, with an electrical cord extending between the front and rear light casings. The front light casing has controls for both front and rear lights, which can include different power levels and preferably a flash mode for the front light. 360° visibility preferably is provided via the front light, which projects colored light, such as amber, toward the sides. In a preferred embodiment the battery is rechargeable using a micro USB connection, a serial bus configuration widely used for cell phones, so that the battery will ordinarily be rechargeable via a cell phone recharging cable or a connection to a computer. Helmet mountings for the front and rear light casings have a quick-release feature enabling the lights to be easily and quickly removed from the helmet, such as for recharging.

This invention concerns lighting for bicycles, and especially a compact set of front and rear lights to be mounted on the bicycle rider's helmet.
Bicycle riders have had a wide array of different options for night lighting, both to illuminate the path ahead and to warn those behind in vehicles or on other bicycles, using a red rear-facing light. These have included handlebar-mounted front lights, including high-powered lights connected to battery packs secured to bicycle frame bars, lower-powered head lamps that mount on handlebars with batteries contained in the light housing, and some lights provided for mounting on the rider's helmet. These helmet lights include bike lights marketed by Exposure Lights of West Sussex, England, under the name Joystick, and these have a helmet mounting for securing the flashlight-shaped light housing, containing a rechargeable battery, to the top center of a helmet. This is done with a bracket mounting configured to extend through a top center vent of the helmet with two opposed disc-like elements then screwed to draw them together to clamp onto the helmet. The flashlight casing has a rear port into which a connector can be secured to conduct power through a cord to a red rear light if desired. The red rear light is provided with a short cable and a VELCRO strap to secure directly to the helmet. These lights positioned at a high point on top of the rider's helmet put considerable weight at a high location, tending to make the helmet feel top heavy. The rider can feel the high center of gravity on the helmet, especially from the weight of batteries in the flashlight housing. In addition, this top projection on the helmet is subject to being damaged and knocked off the helmet by objects such as tree branches. Switch control of the light is not convenient when riding. Further, in a helmet with a center rib, as is most typical currently (rather than a center vent), the Exposure Light must be off-center because it must be positioned over a vent.
There is a need for an efficient, compact and lightweight helmet-mounted lighting system for bicycle riders, in which front and rear lights are mounted in low positions in the helmet, controls for light settings are conveniently accessible, and removal of the lights from the helmet is quick and efficient without requiring disconnection of mounting brackets.


Fiber optic connection assemblies that may include hybrid adapters and connector assemblies are generally described. The hybrid adapter may be configured to connect a first connector type and a second connector type, the first connector type being different from the second connector type. For example, the first connector type may be a micro connector and the second connector type may be an LC connector. A connector assembly may be configured as a micro connector having a tension element configured to facilitate optimized optical performance by spring loading the ferrules while maintaining a small form factor.

Fiber optics have become the standard cabling medium used by data centers to meet the growing needs for data volume, transmission speeds, and low losses. An optical fiber connector is a mechanical device disposed at an end of an optical fiber that acts as a connector of optical paths, for example, when optical fibers are joined together. An optical fiber connector may be coupled with an adapter to connect an optical fiber cable to other optical fiber cables or devices. An adapter may generally include a housing having at least one port that is configured to receive and hold a connector to facilitate the optical connection of one connector to another connector or device. For example, an LC adapter is typically configured to receive one or more standard sized LC connectors.
Hybrid adapters are configured to join different types of optical fiber connectors. At least one disadvantage of traditional hybrid adapters is that they are configured to couple two full size connectors causing the adapter ends to be bulky and, therefore, to take up too much space on both sides of the adapter. This is a major shortcoming in most hybrid adapter applications where when one end of the adapter is intended to be disposed inside a small module, as both the corresponding adapter end and the connector occupy too much space within the module.
Certain conventional hybrid adapters have been designed to accommodate coupling a standard full size optical fiber connector with a simplified optical fiber connector. A simplified optical fiber connector is merely a ferrule that may or may not have a metallic flange assembled onto the ferrule used to terminate the end of an optical fiber. At least one disadvantage of such hybrid adapters is that the simplified connector is held rigidly inside the adapter. However, for best optical performance, both ferrules in a mated pair should be floating, and subject to spring pressures that push the end faces of a pair of mated ferrules together. Unlike standard size optical fiber connectors that include an extension spring pre-loaded behind the ferrule which allow the ferrule to float, a simplified optical fiber connector may not include a spring behind the ferrule. Thus, the simplified optical fiber ferrule will be held rigidly inside one end of the adapter and the connection formed by the hybrid adapter will be subject to degraded performance.
Accordingly, there is a need for hybrid optical fiber adapters that occupy less space than conventional hybrid adapters, while enabling better optical performance by providing spring or spring-like pressure that allows the ferrules to float.

Optical fiber micro connector and connector assembly


A Denial of Service (DoS) mitigation scheme increases the ability of a call processing server to fend off DoS attacks. The DoS mitigation scheme identifies a probability for dropping or denying a call request according to the current load on the call processing server. The probability is then weighted according to certain characteristics of the call request. For example, a call request from a previously authenticated source may be given a different weight than a request from an unauthenticated source. The weighted probability is then compared with a randomly generated number and the call request accepted or rejected according to the comparison.

A call processing server in an Internet Protocol (IP) network needs to survive Denial of Service (DoS) attacks while still completing and processing phone calls. A DoS attack refers to some sort of condition that causes the call processing server to inappropriately deny or drop a legitimate call request due to overload with unauthorized requests. For example, a DoS attack may consist of one or more unauthorized sources flooding the call processing server with call requests.
In one specific example, a Session Initiated Protocol (SIP) server mediates SIP sessions for setting up IP phone calls. The SIP session includes call signaling that may request the initiation or termination of a phone call, request something from the SIP server after the call is already established, or make a request to the SIP server unrelated to any call. The SIP server may deny the request if the source of the SIP signaling is unauthorized to make the call or if the source has requested too many call connections.
A substantial amount of resources may be consumed by the call processing server for authenticating and authorizing call requests. If the call processing server is flooded with these unauthorized call requests (DoS attack), the call processing server can become congested and not process other authorized call requests.
Schemes currently exist for addressing congestion in network processing devices. For example, Random Early Detection (RED) is a high-speed congestion avoidance mechanism that responds to network congestion by dropping packets at a selected rate. The RED scheme starts dropping packets before the network device becomes overloaded. This allows a sender of TCP/IP traffic to back-off from a current transmission rate averting a persistent congestion condition.
A Weighted Random Early Detection (WRED) scheme provides a more intelligent classification of the TCP/IP traffic than RED. For example, certain sources of traffic can be assigned a higher priority that other sources of network traffic. This allows packets to be dropped from particular sources that may flood the network processing device.
RED and WRED have in prior art been applied at the packet level in intermediate switching and routing devices. Neither are directly applicable to handling requests in servers, nor to the function of mitigating denial of service attacks.

Method and apparatus for performing denial of service for call requests


The present disclosure relates to an ultrasonic device for real-time and nondestructive assessment of extracellular matrix stiffness, and the method of making and using the novel ultrasonic device.

This section introduces aspects that may help facilitate a better understanding of the disclosure. Accordingly, these statements are to be read in this light and are not to be understood as admissions about what is or is not prior art.
Structural support for cells in almost all organs in the body is provided by the extracellular matrix (ECM). Cells are embedded in the interstitial matrix, with the portion closest to the cells called the pericellular matrix. Optimum performance of the ECM is vital for appropriate regulation of cell proliferation, migration, differentiation, survival, homeostasis and morphogenesis. Collagen type I and II elastin and fibronectin are the main proteins of interstitial ECM. In healthy ECM an unstressed network of collagen and elastin is the main contributor to release applied tensile stress to the structure of matrix, thus keeping it as soft as necessary for enhanced and facilitated cell movement in the tissue. One of the age-related diseases associated with ECM alterations is cancer. In this disease, collagen crosslinking is promoted by the amine oxidase enzymes, lipoxygenases (LOX) secreted by tumor cells. This phenomenon results in ECM stiffening over time and ultimately, cancer progression. Increased matrix stiffness linked to higher production of collagen I, for instance, has been associated with increased risk of breast cancer, suggesting that ECM modifications also participate in the earliest stage of cancer development. Investigating ECM stiffening for research purposes requires accurate modelling techniques of the structure of ECM in vitro to be able to quantitatively measure stiffness over time in cell culture and thus, identify parameters capable of modulating stiffness and their effect on cell phenotype.
Classical 2D cell culture techniques are incapable of accurately modelling the ECM environment in vitro; therefore, different approaches have been developed such as hydrogels with or without biological components of the ECM. Hydrogels are composed of a water-swollen crosslinked polymer that is hydrophilic and biocompatible. Their stiffness is typically measured by assessing proportional deformation of the material in response to an applied force, which is a quantitative expression as the material's Young's (elastic) modulus. For example, soft materials have a very low elastic modulus, meaning that they deform easily with applied stress; while, with the same amount of stress, high elastic modulus materials undergo less deformation.
Overall, the techniques that have been developed for quantification of the mechanical properties of hydrogels can be categorized into destructive or nondestructive methods. Some of the destructive techniques include extensiometry, compression test and indentation test. In the extensiometry approach, a tensile load is applied to a hydrogel sample shaped as a strip or ring where elongation of the material under applied stress is recorded to extract the stress-strain curve. The elastic modulus is calculated as the slope of the linear region of the curve. In a compression test, a flat hydrogel sample (usually disc form) is placed between two plates and compressed. The magnitude of the applied pressure and the hydrogel compressive deformation are measured and converted to a stress-strain curve where the slope of the curve is the elastic modulus. One of the limitations of the compression test, despite the simplicity of sample preparation, is the difficulty in applying pressure to the surface of the hydrogel specimen evenly. Indentation-based approaches have also been used to quantify the elastic modulus of hydrogels in macro, meso and microscales. For instance, the mesoscale indentation technique involves measuring the indentation depth of a ball indenter of 0.5-1 mm in diameter with the use of a confocal microscope. In this technique, the elastic modulus of the hydrogel is measured by placing a micron-size metal bead with a known weight onto the hydrogel surface and measuring the indentation with respect to a reference focal point. The measurement resolution can also be enhanced by using confocal laser fluorescence microscopy with real-time image processing for increased noninvasive and accurate assessment of indentation depth. Optical-coherence-tomography (OCT) based-spherical indentation is another noninvasive indentation-based technique where the indentation depth of a spherical indenter into a hydrogel sample is measured by OCT, an interferometric-noninvasive imaging technique. In this approach, Hertz contact theory is used to extract the load-deformation relation. However, despite the high sensitivity and performance demonstrated by such imaging-based techniques, they still face several drawbacks such as high probability of damaging the hydrogel with cells due to requirement of placing external weight on the specimen. As opposed to the aforementioned optical imaging methods, Ultrasound Elastography imaging (UEI) is a promising nondestructive technique that enables evaluation of the tissue stiffness indirectly by measuring the speed of the shear ultrasound wave propagating in the region of interest, which can be categorized as static/quasistatic elastography and shear wave elastography. Since its first development in 1990s, UEI has seen major development and has been refined as a powerful noninvasive technique for diagnosis and staging of various life-threatening diseases (including breast cancer, prostate cancer, and Alzheimer's disease). Although, many efforts have been made to utilize UEI technologies for stiffness assessment for in vitro tissue culture, they have several drawbacks including requirement of costly equipment, need for skilled/trained ultrasonic imaging personnel, as well as inability to perform continuous measurements. These limitations make UEI impractical for on-chip applications, where cost, simplicity and adaptability to high throughput screening with real-time measurement capability is essential.
Therefore, there is an unmet need for a novel device for real-time and nondestructive assessment of extracellular matrix stiffness.


An inverse discrete cosine transform processor for transforming a video signal from frequency domain signals into spatial domain signals. A bus converter receives DCT coefficient data from parallel processing paths and converts the DCT coefficient data to even and odd processing paths. Partial IDCT processors convert, in parallel, the coefficient data from the even and off processing paths to produce intermediate coefficient values by performing a one dimensional transform. The intermediate coefficient values are transposed in a transpose RAM to produce transposed intermediate coefficient values which are subsequently separated into even and odd processing paths and converted in parallel to produce pixel values by performing a one dimensional transform.

In the United States a standard has been proposed for digitally encoded high definition television signals. A portion of this standard is essentially the same as the MPEG-2 standard, proposed by the Moving Picture Experts Group (MPEG) of the International Organization for Standardization (ISO). The standard is described in a International Standard (IS) publication entitled, "Information Technology--Generic Coding of Moving Pictures and Associated Audio, Recommendation H.626", ISO/IEC 13818-2, IS, 11/94 which is available from the ISO and which is hereby incorporated by reference for its teaching on the MPEG-2 digital video coding standard.
The MPEG-2 standard is actually several different standards. In MPEG-2 several different profiles are defined, each corresponding to a different level of complexity of the encoded image. For each profile, different levels are defined, each level corresponding to a different image resolution. One of the MPEG-2 standards, known as Main Profile, Main Level is intended for coding video signals conforming to existing television standards (i.e., NTSC and PAL). Another standard, known as Main Profile, High Level is intended for coding high-definition television images. Images encoded according to the Main Profile, High Level standard may have as many as 1,152 active lines per image frame and 1,920 pixels per line.
The Main Profile, Main Level standard, on the other hand, defines a maximum picture size of 720 pixels per line and 567 lines per frame. At a frame rate of 30 frames per second, signals encoded according to this standard have a data rate of 720 * 567 * 30 or 12,247,200 pixels per second. By contrast, images encoded according to the Main Profile, High Level standard have a maximum data rate of 1,152 * 1,920 * 30 or 66,355,200 pixels per second. This data rate is more than five times the data rate of image data encoded according to the Main Profile Main Level standard. The standard proposed for HDTV encoding in the United States is a subset of this standard, having as many as 1,080 lines per frame, 1,920 pixels per line and a maximum frame rate, for this frame size, of 30 frames per second. The maximum data rate for this proposed standard is still far greater than the maximum data rate for the Main Profile, Main Level standard.
The MPEG-2 standard defines a complex syntax which contains a mixture of data and control information. Some of this control information is used to enable the signals having several different formats to be covered by the standard. These formats define images, having differing numbers of picture elements (pixels) per line, differing numbers of lines per frame or field and differing numbers of frames or fields per second. In addition, the basic syntax of the MPEG-2 Main Profile defines the compressed MPEG-2 bit stream representing a sequence of images in six layers, the sequence layer, the group of pictures layer, the picture layer, the slice layer, the macroblock layer, and the block layer. Each of these layers is introduced with control information. Finally, other control information, also known as side information, (e.g. frame type, macroblock pattern, image motion vectors, coefficient zig-zag patterns and dequantization information) are interspersed throughout the coded bit stream.
To effectively receive the digital images, a decoder must process the video signal information rapidly. To be optimally effective, the coding systems should be relatively inexpensive and yet have sufficient power to decode these digital signals in real time.
Using existing techniques, a decoder may be implemented using a single processor having a complex design and operating at a high data rate to perform this function. This high data rate, however, would require very expensive circuitry, which would be contrary to the implementation of a decoder in a consumer television receiver in which cost is a major factor.
Another alternative is to use a decoder employing parallel processing. Using parallel processing reduces the cost of the circuitry while maintaining the high data rates. FIG. 13 shows one such system. The decoder in FIG. 13 includes two parallel processing paths A and B. First, the input bit-stream is applied to router circuitry 5. Router circuitry 5 directs the bit-stream into different logically defined processing paths A and B. each path processing macroblocks from a respectively different slice of an MPEG-2 encoded image. Variable Length Decoders (VLD) 10a and 10b decode the separated data streams to generate blocks of quantized discrete cosine transform (DCT) coefficient values. These blocks of values are applied to respective inverse zig-zag scan memories 15a and 15b to perform the inverse scan. The inverse quantizers 20a and 20b perform an inverse quantization of the quantized DCT values provided by inverse zig-zag scan memories 15a and 15b. The DCT coefficient values are provided to inverse discrete cosine transform (IDCT) circuits 25a and 25b. The output data of IDCT circuits 25a and 25b are blocks of pixel values or differential pixel values.
Each of the IDCT circuits 25a and 25b performs a 2-dimensional IDCT operation on the DCT coefficient values. An Inverse Discrete Cosine Transformation (IDCT) is performed, as discussed above, to reconstruct the original picture elements or pixels. An 8-point 1-D IDCT is shown equation (1): ##EQU1## where xn (n=0, 1, 2, . . . ,7) is the result of the matrix multiplication, Xn is a input coefficient value, and a, b, c, d, e, f, g are constants in the IDCT matrix. Intermediate coefficient values are produced using equations (2): ##EQU2## Each IDCT circuit implements the 1-D IDCT of equations (1) and (2) twice. The values Xn provided to the first 1-D are DCT coefficient values and the output value produced xn is an intermediate coefficient value. The input value Xn to the second 1-D IDCT are the transposed intermediate coefficient values xn from the first 1-D IDCT. The output values xn of the second 1-D IDCT are pixel values. Equation (1) includes matrix multiplication to calculate an inner product.
One method of calculating the inner product is distributed arithmetic. Distributed arithmetic is a bit-serial computational operation that forms an inner product of a pair of vectors. Distributed arithmetic has been used in the past to perform DCTs and IDCTs as shown in Maruyama, VLSI Architecture and Implementation of a Multi-Function Forward/Inverse Discrete Cosine Transform Processor, Visual Communications and Image Processing '90, Vol. 1360, pp. 410-417, and TWO-DIMENSIONAL DISCRETE COSINE TRANSFORM PROCESSOR, U.S. Pat. No. 4,791,598, (hereinafter the '598 patent) issued to Liou et al., each incorporated herein by reference for their teachings on distributed arithmetic to perform DCTs and IDCTs.
Distributed arithmetic is a bit-serial method where individual bits of the input values are used to address a Look-up Table (LUT) stored in, for example, a Read Only Memory (ROM). In general, this can be extended to a digit-serial method using Z bits per input value. The number Z is often referred to as the number of bits-at-a-time (baat). The LUT must be large enough to accommodate an input vector of length N with Z bits per input. One LUT could be used having an address of N * Z bits, however, this leads to a large LUT. The preferred embodiment of the present invention described herein uses Z LUT's each having an address of N-1 bits. The address reduction from N to N-1 exploits the fact that the absolute value of data is mirrored from the top half to the bottom half of a LUT having N address bits when offset binary is used to generate the LUT. The precomputed values in the LUT are inner products of the constant IDCT matrix in equation (1) and a single bit from each of N input values. These pre-computed values are then summed in a digit-serial manner to produce the complete inner product values.
In the decoder of FIG. 13, the IDCT circuits 25a and 25b can be implemented using IDCT processors that employ distributed arithmetic techniques. The disadvantage to the approach is that the pipeline is not kept full in the first 1-D IDCT section of both 25a and 25b. Eight 12-bit parallel input words are required to perform the inner product in FIG. 13. In distributed arithmetic, the word width in bits is divided by the number of input words to get the ideal number of bits-at-a-time (baat). In this case twelve divided by eight is 1.5. This number must be rounded up to 2 for actual implementation. The clock period required for the distributed arithmetic is calculated by dividing the word width in bits by the number of baat. The result of 12 divided by 2 is 6 clock periods. The eight input words require eight clock periods. Therefore, the pipeline is idle for 2 clock periods. In other words, resources in the first 1-D IDCT section of both 25a and 25b are not used for 2 out of 8 clocks. Although the processing speed of the decoder is maintained using the dual processing paths, the cost of the decoder is increased using the duplicate IDCT circuits.
The '598 patent illustrates an alternative method in a two-dimensional DCT processor which transforms pixels to DCT coefficients using distributed arithmetic. The '598 uses distributed arithmetic to simultaneously compute the inner product of an entire row or column of a matrix. The DCT processor includes a Nx1 column DCT processor which includes N circuits that compute the elements of the column transformation concurrently. The elements of the column transformation are stored in a transposition memory. Then, after being transposed, a Nx1 row processor transforms the output of the transposition memory. The '598 patent is not provided with pixel data from parallel paths and, thus, does not produce DCT coefficients from parallel processing paths. The '598 patent separates the pixels from a single processing path to transform that data in parallel. Consequently, the pixel data is processed at the rate it is received.

Inverse discrete cosine transform processor using parallel processing

Matsushita Electric Corporation of America


A method is provided for securing first and second splined members together, such as a midship tube shaft to an end fitting in a driveshaft assembly, to prevent relative axial movement from occurring therebetween. Initially, a first splined member is provided that includes an outer surface having a recess and a plurality of external splines provided thereon. Also, a second splined member is provided that includes an inner surface a plurality of internal splines provided thereon. The inner surface of the second splined member is disposed about the outer surface of the first splined member such that the plurality of internal splines cooperate with the plurality of external splines. Then, a portion of the second splined member is deformed into the recess of the first splined member to secure the first and second splined members together, while preventing relative axial movement from occurring therebetween.

This invention relates in general to a method of securing first and second splined members together, such as is done when manufacturing a driveshaft assembly for use in a drive train system. In particular, this invention relates to an improved method of securing an end fitting to a midship tube shaft in such a driveshaft assembly to prevent relative axial movement from occurring therebetween.
Drive train systems are widely used for generating power from a source and for transferring such power from the source to a driven mechanism. Frequently, the source generates rotational power, and such rotational power is transferred from the source to a rotatably driven mechanism. For example, in most land vehicles in use today, an engine/transmission assembly generates rotational power, and such rotational power is transferred from an output shaft of the engine/transmission assembly through a driveshaft assembly to an input shaft of an axle assembly so as to rotatably drive the wheels of the vehicle. To accomplish this, a typical driveshaft assembly includes a hollow cylindrical driveshaft tube having a pair of end fittings, such as a pair of tube yokes, secured to the front and rear ends thereof. The front end fitting forms a portion of a front universal joint that connects the output shaft of the engine/transmission assembly to the front end of the driveshaft tube. Similarly, the rear end fitting forms a portion of a rear universal joint that connects the rear end of the driveshaft tube to the input shaft of the axle assembly. The front and rear universal joints provide a rotational driving connection from the output shaft of the engine/transmission assembly through the driveshaft tube to the input shaft of the axle assembly, while accommodating a limited amount of angular misalignment between the rotational axes of these three shafts.
In some instances, the driveshaft assembly is formed from a hollow cylindrical driveshaft tube having a midship tube shaft secured thereto. The midship tube shaft includes a first end that is adapted to be secured to an end of the driveshaft tube and a second end portion having an externally splined portion provided thereon. The first end of the midship tube shaft is typically connected to the end of the driveshaft tube by welding. A center bearing assembly can be mounted on a central portion of the midship tube shaft located between the first and second end portions. An end yoke can be connected to the second end portion of the midship tube shaft. The end yoke has an internally splined sleeve portion that cooperates with the externally splined second end portion of the midship tube shaft so as to be fixed for rotation therewith.
In some applications, it is desirable to prevent relative axial movement from occurring between the midship tube shaft and the end yoke, notwithstanding the splined connection therebetween. To accomplish this, it is known to provide an external thread on the tip of the second end portion of the midship tube shaft. The threaded tip of the second end portion of the midship tube shaft extends through an opening formed through the end yoke. Then, a nut is threaded onto the threaded tip of the second end portion of the midship tube shaft to retain the end yoke thereon and to prevent relative axial movement from occurring therebetween. Although this structure has been effective, it has been found to be somewhat complicated, expensive, and space consuming. Alternatively, it is known to weld the end yoke directly to the second end portion of the midship tube shaft. However, the use of welding can be undesirable for a variety of reasons. Thus, it would be desirable to provide an improved method of securing an end fitting to a midship tube shaft to prevent relative axial movement therebetween in such a driveshaft assembly.

Method of securing first and second splined members together


A flat display panel (MPDP) of the emissive plasma pixel element type for scanned television image reproduction is disclosed yielding bright, efficient and rugged displays for TV applications by use of MEMS and VLSI technology for fabrication. The invention takes a commplete system approach towards designing a high efficiency television display of the mini type for portable applications. A main objective of the present invention is to overcome problems inherent in X-Y matrix scanning of the picture elements in a flat display screen. A simplified addressing method eliminates the need for conventional X-Y matrix addressing of 1200 conductors. By means of the invention a gaseous electric discharge causes a visible light pixel to move progressively and recurrently along a series of adjacent electrodes by application of voltage impulses so as to achieve interlaced scanning. Improved construction technology to achieve very small pixel elements is a feature of the inventive struture. This is particularly advantegeous for HDTV applications where pixel sizes need to be small (20 urn) for a MPDP. Another major advantage of the contruction is that sealed cavities allows morre than one atmosphere gas pressure providing substatially improved light emission. This significantly improves the brightness of MPDP displays and enables improved projection displays as well a useful scanned high intensity micro-lamp rear lighting illumination for conventional LED flat screen display device.

1. Field of the Invention
This invention relates to display devices of the gas discharge type, generally classified under 315/169.4 of the U.S. Patent Classification System and light sources under H01J61/96 of IPC. In particular, the inventive concept concerns replacing conventional matrix addressing of the glow discharge pixels in gas plasma display panels with electrical pulse transfer of the localized glow discharge along a recurring path with the use of MEMS (Micro Electro Mechanical Systems) and VLSI (Very Large Scale Integration) technology for fabrication. By the scheme greatly simplified pixel addressing for television interlaced scanning is disclosed for a mini plasma display including low fabrication cost achieved by the advantages of MEMS and integrated circuit process technology.
2. Description of the Prior Art
Television Technology
In order for a flat screen to be useful for television it must be able to reproduce the functions of interlaced scanning of the conventional cathode ray tube. One main object of the invention is to duplicate the interlaced scanning requirements for television in a flat screen gas discharge display without the need for separately addressing each of the 1225 horizontal and vertical lines of a conventional matrix display. Another main object is to achieve low cost construction for a plasma screen of the miniature type by use of MEMS and integrated circuit fabrication technology
The invention disclosed must meet the following essential technical criteria for interlaced TV scanning:
The standard picture repetition rate is 30 frames per second to accommodate eye-brain persistence. Interlaced scanning of the CRT electron beam means that first the odd-numbered lines, namely, 1, 3, 5, 7, etc., and then the even-numbered lines, 2, 4, 6, 8, 10, etc. are traced. Accordingly, two fields constitute one frame or a field repetition rate of 60 fields per second. Since 525 horizontal lines is the US standard for television reception and the standard aspect ratio of picture width to height is 4 to 3, and if the spacing between the elements along a horizontal line is the same as that in a vertical direction, then the theoretical maximum number of elements along a horizontal line is 525×4/3, or 700. Since the total number of elements in a picture is equal to the product of the number of horizontal and vertical elements, the theoretical maximum pixel density is 525×700, or 367,500 pixels.
In order to produce a clear steady picture, the scanning operation must satisfy the following requirements: (1) Each frame must be divided into two fields, (2) the rate of forward travel of a horizontal line must be linear, (3) the return trace of a horizontal line must be at a much higher speed than the active trace and should be blanked out, (4) the length of each horizontal line must be the same, (5) the rate of vertical movement of the beam must also be linear, (6) the vertical return trace of the beam must be at much higher speed than the downward motion and should be blanked out, (7) the amount of vertical movement must be the same for each field and each frame, (8) the width of the beam should be equal to the width of one horizontal line, (9) the space between adjacent lines in any field should be equal to the thickness of one line, (10) the first field should trace the odd-numbered lines as 1, 3, 5, etc., until 262½ lines of the 525-line raster are completed, (11) the second field must trace its 262½ lines (2, 4, 6, etc.) in the spaces midway between the lines of the first field, (12) each odd-numbered field must fall in the same position as the preceding odd-numbered field, (13) each even-numbered field must fall in the same position as the preceding even-numbered field.
Transmission of a special synchronizing signal from the television transmitter controls the instant of starting and the length of scanning time for each horizontal line at the picture tube of the receiver and also the vertical motion of the scanning beam. At the end of each horizontal line scan a blanking pulse is provided called the horizontal blanking pulse. The duration of this pulse is 1.27 μsec before the end of the active trace of a line. The sum of both the active and retrace portions for the 525-line system is 63.5 μsec. The duration of the blanking pulses between horizontal lines is approximately 10 μsec. The pulse provided at the end of each field is called the vertical blanking pulse. The duration of the blanking pulses between successive fields is kept within the limits of 1167 and 1333 μsec.
The following functions must be performed during the blanking period associated with the vertical synchronizing pulse: (1) blanking out for a period of 20 to 22 horizontal lines; (2) returning the 'beam' from the bottom to the top of the raster; (3) returning the 'beam' to either the start of a line or the center of a line so that it will begin the succeeding field at the position required to produce interlaced scanning; (4) continuing the operation of the horizontal oscillator at its proper frequency during this blanking period so that the scanning beam will be at its required position when the blanking pulse ends.
For good television pictures, a video signal with a range of 30 to 4,500,000 cps is desired. The lower frequency values are required when a scene of uniform density or shading is to be transmitted, and the higher frequency values are required for transmission of scenes having a large number of areas of alternately light and dark shading.
X-Y Matrix Plasma Displays
The scanning method presently used in state-of-the-art flat screen displays is matrix or X-Y addressing. Gas discharge lamps operate by passing a high voltage through a low-pressure gas to generate ultraviolet light which then strikes associated phosphors. As these phosphors return to their natural state they emit red, green or blue visible light. Thus they operate like fluorescent lamps, with each pixel the equivalent of a tiny colored bulb. Since plasma display panels (PDPs) are emissive and use phosphor, like CRTs, they have excellent viewing angle and color performance. Plasma display panels (PDPs) are numerous tiny gas discharge lamps of the type described which are individually turned on by use of an X-Y matrix of electrodes. The intersection of a row and column of electrodes at the tiny gas discharge lamp defines a pixel, constituting a tiny source of light. When a voltage is applied to orthogonal electrodes, the gas in the channel becomes ionized and conducts current where the electrodes cross. Within the pixel a gas such as Xenon is converted to plasma form by the electrical voltage applied where the electrodes intersect. The plasma generally emits ultraviolet light activating associated phosphors to cause localized light emission.
Matrix-addressed plasma displays are generally fabricated by forming rows of channels etched into a glass substrate, which are filled with xenon, neon, helium, or combinations of inert gas, then sealed. The gas channels making up the rows of the array are fitted with two electrodes. The electrodes along the rows provide a priming voltage which provides partially ionized gas while perpendicular to the gas channel rows are electrode strips that supply the analog pixel data. Because ionized gas is needed to complete the charging circuit, the column data voltages only have an effect on the pixels in a row for which a plasma channel is partially ionized. Consequently, by electrical activation of separate rows and columns of conductors a picture element is defined at the 'cross-over'. A matrix plasma display, therefore, operates by addressing a large number of tiny discrete gas discharges in sequence to correspond with the requirements of television scanning. By charging the channel rows in sequence and sending data signals during the time the gas is switched on, the display is addressed row by row. This cumbersome addressing method results in considerable switching complexity.
Another problem with conventional plasma screens is that they have traditionally suffered from low contrast. This is caused by the need to 'prime' the cells, applying a constant low voltage to each pixel across a row. Without this priming, plasma cells would suffer the same poor response time of household fluorescent tubes, making them impractical. The pixels, which really should be switched off for proper image contrast, emit some light thus resulting in dull contrast. Kanazawa, et al., describe apparatus attempting to eliminate the reduced contrast and for driving the orthogonal electrodes required of a gas discharge matrix display in U.S. Pat. No. 6,034,482. Tsutomu et al., describe a driving system for matrix operated plasma displays in U.S. Pat. No. 5,995,069. Buzak in U.S. Pat. No. 5,077,553 describes a synchronously addressed driving system for matrix operated plasma display of the X-Y type whereby the orthogonal electrodes are addressed using buffer memory, sample and hold, CCD, or other data drivers schemes.
Since conventional TV consists of 525 horizontal lines at a 4×3 aspect ratio, about 367,500 picture elements must be activated in sequence by matrix addressing. This means that separate connections must be made to 525 rows and 700 columns in the display and their activation must be in accordance with TV scanning requirements. Consequently, X-Y matrix systems are limited by the picture element resolution required for good picture reproduction and by the number of connections required to synchronize addressing 1225 horizontal and vertical connectors. It would be desirable to provide elimination of the considerably complex driving circuitry of matrix driven plasma displays while achieving the interlaced scanning requirements of television. Baasch describes in U.S. Pat. No. 3,681,754 a moving sign plasma display device using multidirectional transfer of the plasma glow by means such as magnetoplasmadynamic propulsion. Gas discharge stepping devices utilizing the bistable nature of the ionization properties of gas discharges are described in U.S. Pat. No. 2,443,407 by Wales wherein 3Ø devices of this type allow transfer of the glow discharge electrode-to-electrode. Townsend in U.S. Pat. No. 2,575,370 describes a special electrode configuration that allows 2Ø operation whereby only two supply lines are required for glow transfer. Witmer describes use of these stepping mechanisms for addressing a flat screen gas discharge display in U.S. Pat. No. 3,532,809.
Liquid crystal displays (LCDD) are another type of flat display. Unlike gas discharge displays, devices of the LCD type have no inherent illumination and consequently they must be backlit. Usually the LCD panels are backlit by fluorescent tubes that snake through the back of the unit and this sometimes results in brighter lines in some parts of the display than others. It would be desirable if the problem of uniform bright backlighting could be solved with preferably a scanning pixel light source.
TV Recurring Raster Patterns
It is well known in the TV art that standards for TV reception and transmission require what is called interlaced scanning by a recurring raster pattern for presentation of a TV image. What this means essentially is that a television display must duplicate the original cathode ray tube scanning method wherein an electron beam scans the screen of the picture tube and the brilliance of the spot produced varies in accordance with the amplitude of the picture-information signal voltage being applied to the control grid of the CRT. If the scanning action at the picture tube in the receiver is in synchronism with the scanning action at the camera tube of the transmitter then the original scene at the transmitter will be reproduced at the receiver. These standard TV requirements are detailed in such books as Essentials of Television, McGraw-Hill, pgs. 20-30 and many others so they will not be detailed here. Raster scanning, as it is called in the industry, requires that any proposed display for TV must be compatible with these requirements, including matrix addressing as described above.
A feature of the invention herein described is that it does not use matrix addressing to meet the scan requirements of TV standards but transfers a gas discharge along gas cavity pixel elements row by row to meet TV raster scan requirements in a manner similar to the scanning method used in the original CRTs.
Microfabrication Technology—Preferential or Selective Etching
As well known in the Microfabrication art (See for example, Fundamentals of Microfabrication, Mark Madow, CRC Press, 2002; pgs 207-280) the fact that silicon can be made crystalline is of extreme usefulness. The art of micromachining is dependent upon crystal plane differences whereby anisotropic etchants "machine," desired structures in crystalline materials by etching much faster in one crystal plane direction than another. The different crystal planes of semiconductor crystalline materials like silicon have different mechanical and chemical properties for one reason because of differing atomic density. Because of these different properties an important useful characteristic of crystalline silicon is that special etches can be used, called preferential or selective etches (also called structural etches), that exhibit anisotropy. That is, the chosen etch can be made to more quickly etch silicon (or other crystalline semiconductors) in one crystalline direction than the other thereby producing significant difference in etch rate and thus allowing specific desired structures. When carried out properly, anisotropic etching results in geometric shapes bounded by the slowest etching crystallographic planes providing perfectly defined structures. A wide variety of etchants have been used for anisotropic etching of silicon, including alkaline aqueous solutions of KOH, NaOH, LiOH, CsOH, RbOH, NH, OH, and quaternary ammonium hydroxides, with the possible addition of alcohol. Alkaline organics such as ethylenediamine, choline (trimethyl-2-hydroxyethyl ammonium hydroxide), hydrazine and sodium silicates with additives such as pyrocatechol and pyrazine are employed as well. For example, KOH solutions when used to etch <100> crystalline silicon quickly etch the atomic planes in the [100] direction but very slowly etch in the much denser [111] direction resulting in a cavity shaped with precisely defined sides of 54.7 degree slope. Because the cavity is bottomed by crystal planes in the [111] direction the cavity bottom is very slowly etched and thus flat, specular, and mirror smooth. Since lateral mask geometries on planar photoengraved substrates can be controlled with an accuracy and reproducibility of 0.5 μm or better this coupled with the anisotropic nature of preferential etchants allows this accuracy to be translated into control of the vertical etch profile for a silicon cavity. Features of the microfabrication art are used in combination in the present invention to provide the numerous very precisely defined gas cavities required for a miniature plasma display.
Another very important fabrication method used in combination in the present invention to provide numerous very precisely defined gas cavities for a plasma display is MEMS etch-stop technology. The MEMS (Micro Electro Mechanical Systems) art (see The MEMS Handbook, Mohammad Gad-el-Hak, CRC Press, 2002, pgs. 72-73) uses etch-stop techniques based on the fact that anisotropic etchants, especially EDP (Ethylene Diamine Pyrocatechnol), very slowly attack boron-doped (p+) silicon layers compared to non-doped boron layers. Experiments show that the decrease in etch rate is nearly independent of the crystallographic orientation and the etch rate is proportional to the inverse fourth power of the boron concentration. Atomically, the etch rate observed within the etch stop region is determined by the number of electrons available in the conduction band at the silicon surface. This number is assumed to be inversely proportional to the number of holes and thus the boron concentration. It is known in the microfabrication art that the concentration of boron and the depth of a boron layer can be very closely controlled in silicon by use of such well known techniques as diffusion, epitaxial layering, or Si-to-Si bonding. For example, silicon of N-type doping or of light boron doping can be of accurate specific thickness atop an etch-stop layer of silicon of high boron doping. Thereby the top layer of silicon can be etched relatively quickly down to the boron doped layer whereat the etch rate greatly decreases or effectively stops providing a cavity of specular bottom. These desirable features are used in combination in the present invention to provide numerous very precisely defined gas cavities for a plasma display.
The invention herein uses in combination these MEMS and microfabrication techniques such as preferential etch and etch-stop methods to precisely determine the depth of a gas containment cavity whereby extremely accurate gas cavities can be uniformly fabricated. In combination such MEMS technology as anodic bonding of glass to silicon, preferential etching, etch-stop techniques, and preferential tungsten deposition, known in the MEMS art, are used in combination in the present disclosure to provide advantageous construction of a miniature plasma display device.


A motor drive for an electric motor receives high frequency AC current, and delivers this current through a converter which is operable to change the current delivered downstream to an inverter and an electric motor.

This application relates to a motor drive for an electric motor wherein a high frequency AC power is supplied to a converter which can change the current supplied downstream to an inverter and then to the motor.
Electric motors are utilized in various applications. In one recent improvement to aircraft turbine engines, a plurality of electric motors are driven off an accessory bus. These motors may include pumps for supplying oil, fuel and air to the engine, as an example.
For various reasons, it has recently been proposed to utilize a high frequency AC power bus to supply electrical power to these accessories. One such system is disclosed in U.S. patent application Ser. No. 11/859,055, filed on Sep. 21, 2007 and entitled "Generator for Gas Turbine Engine Having Main DC Bus Accessory AC Bus."
It is also known in the art to provide a converter to change a voltage delivered to an electric motor, wherein DC power is utilized.
However, there have been no AC buses which are provided with a converter for changing the current actually delivered to the motors.

Motor drive architecture for high frequency AC bus