Abstract: A process is provided for fabricating MODFET's in group III nitride compound semiconductors. The process precedes isolation of the MODFET structure with the use of e-beam lithography to define very narrow (e.g., .about.0.25 micrometer) gates which enhance transistor microwave cut-off frequency. Because these compound semiconductors resist chemical etchants, isolation is accomplished by etching with reactive ions to form an isolation mesa having a vertical mesa sidewall. To improve breakdown, the mesa sidewall is covered with a passivation layer prior to deposition of a gate feed that contacts the gate. To reduce parasitic gate capacitance, the gate feed is spaced from a narrow edge of the transistor's two-dimensional electron gas.

Abstract: A pollutant destruction system connects a capacitive corona discharge chamber in a self-resonant circuit with an inductive element. Intermittent energizing signals are furnished from a power supply to induce corona discharges within the chamber, with the resonant circuit responding to the energizing signals by initiating additional corona discharges between energizing signals in a highly energy efficient operation. One or more discharge chambers can be provided in the resonant circuit, with each discharge chamber comprising a dielectric enclosure with a distributed electrode outside and an elongate electrode inside the enclosure. The inner electrode can extend either along the chamber axis, or along the inner chamber wall for better support and heat dissipation.

Abstract: An apparatus and method of processing a planar HEMT or FET semiconductor device is disclosed. An ohmic metalization is patterned on a semiconductor surface then lifted-off. A plurality of process control monitors are isolated, preferably using a wet etch process. The process control monitors preferably include transmission line patterns (TLMs) and etch field effect transistors The TLMs measure the contact resistance during the ohmic alloy process, and the etch field effect transistors monitor the drain current during the gate-recess step. The ohmic metalizations are then alloyed, and a gate is written using an electron beam. The semiconductor device is isolated, followed by application of an overlay which connects all resulting planar device connecting pads.

Abstract: An iterative time frequency algorithm filters noisy wide band/nonstationary signals by projecting the noisy signal into the TF domain, masking the TF response, computing the inverse TF transform to extract a filtered signal, and repeating these steps until the projection lies within the mask. As a result, the TF domain properties of the extracted signal are substantially equal to the desired TF domain properties. Furthermore, the iterative approach is computationally simple because it avoids inverting matrices. The TF transform and its inverse must be selected such that the iterative algorithm is guaranteed to converge. Candidate transform pairs can be tested on known data, and if the TF transforms converge to the desired TF properties, the candidate pair can be selected. Alternately, the candidate pairs can be tested against a sufficient convergence condition, and if they satisfy the condition within an acceptable tolerance, they can be selected with confidence.

Abstract: A new photorefractive material comprises BaTiO.sub.3 double-doped with two dopant species, both of which have at least two valence states, with one of the dopant species (e.g., cerium) having an ionization level that is near the middle of the barium titanate bandgap and the other dopant species (e.g., rhodium) having an ionization level that is closer to the valence band edge of barium titanate, such that both dopant species are sensitive to visible light, but only one dopant species (the one closer to the valence band edge) is sensitive to infrared radiation. The double-doped BaTiO.sub.3 provides a unique combination of photorefractive properties, thereby improving its performance as a holographic storage medium. The double-doped barium titanate crystal is employed as a holographic recording element. The double-doped barium titanate crystal has a dark storage time at room temperature of several years or more and may be nondestructively read out at an infrared wavelength.

Abstract: A speech processing and analysis apparatus and method for generating a time-frequency distribution of a speech signal combines a set of spectrograms with varying window lengths and orientations to provide a parameter-less time-frequency distribution having good joint time and frequency resolution at all angular orientations. The analysis window of a spectrogram is rotated relative to the frequency components of the signal by preprocessing using a Fractional Fourier Transform to form rotated window spectrograms. In particular, to form the rotated window spectrogram, the signal is initially pre-processed using a Fractional Fourier Transform of angle .alpha., the spectrogram time-frequency distribution of the pre-processed signal is then computed using analysis window h(t) and then rotated by angle -.alpha..

Abstract: A pollutant destruction system connects a capacitive corona discharge chamber in a self-resonant circuit with an inductive element. Intermittent energizing signals are furnished from a power supply to induce corona discharges within the chamber, with the resonant circuit responding to the energizing signals by initiating additional corona discharges between energizing signals in a highly energy efficient operation. One or more discharge chambers can be provided in the resonant circuit, with each discharge chamber comprising a dielectric enclosure with a distributed electrode outside and an elongate electrode inside the enclosure. The inner electrode can extend either along the chamber axis, or along the inner chamber wall for better support and heat dissipation.

Abstract: An improved pattern recognition system. The invention operates on a plurality of feature vectors from a single class of data samples. The inventive system estimates a pruning radius for the feature vectors in the single class of data samples and generates a replacement class therefrom based on the estimated pruning radius. This pruning radius is used to train a classifier which in turn facilitates the recognition of a data pattern in raw data. In a specific implementation, the pruning radius is adapted based on current results from the classifier. The invention satisfies the need in the art by providing an automated technique for training classifiers for nonstationary data classes which is not limited by the need for more than one class of data.

Abstract: A system for redistributing a television signal to a multiplicity of receiver units within a multiple dwelling unit (MDU) includes a main receiving antenna which receives a broadband television signal and a translation device that translates the broadband television signal into a different carrier frequency band. One or more broadcasting antennas, located at advantageous sites within the MDU, transmit the translated television signal along one or more walls of the MDU to be received by antennas associated with one or more individual receiver units. Each receiver unit demodulates the received television signal and provides a user-specified channel to a television set for display.

Abstract: A workpiece is heated by first forming an ionized gas plasma around the workpiece. A positive potential is applied to the workpiece to accelerate electrons from the plasma into the workpiece. The workpiece is uniformly surface heated by the energy directed into the workpiece by the electrons. The workpiece is cooled by providing a flow of a pressurized liquid material such as carbon dioxide having a triple point. The liquid material is expanded through a nozzle to form solid particles that contact the surface of the workpiece and remove heat from it by subliming.

Abstract: Near on-demand delivery of digital signals is accomplished by first dividing the signals into sequences of N numbered fragments, where the length of each fragment is equal to the broadcast time interval. The fragments are broadcast so that the first fragment is repeated every broadcast time interval, the second fragment is repeated every two time intervals, and so forth until the Nth fragment is repeated at least every Nth time interval. A fractal channel packing algorithm is preferably used to sequence the fragments over a plurality of channels to reduce the variability in peak bandwidth caused by fragmentation. The fragments are locally downloaded and stored during successive time intervals in response to a subscriber's request so that the first fragment is available within one time interval from the request, and the higher numbered fragments are available within their respective periods. The fragments are read out in order and integrated to seamlessly deliver the requested signal.

Abstract: The present invention presents an electrostatic discharge and power surge protected circuit board (10) and method for providing an electrostatic discharge and power surge protected circuit board. The protected circuit board (10) includes temperature sensitive conducting material (14) and semiconductor circuit components (12). The temperature sensitive conducting material (14) has a critical current density, provides a high impedance when the critical current density is exceeded, and preferably comprises a high temperature superconductor. Preferably, the temperature sensitive conducting material (14) and the semiconductor circuit components (12) are coupled in series. In a method aspect of the present invention, an electrostatic discharge protected circuit board (10) is provided by providing a current carrying mechanism (16) on the circuit board (10), and coupling the current carrying mechanism (16) to temperature sensitive conducting material (14).

Abstract: A cold-cathode, crossed field switch has a magnet system which generates a magnetic field that is radially-oriented about a switch axis and a planar electrode system which generates an axially-oriented electric field. These structures facilitate a switch whose capacitance, inductance and fabrication costs are all reduced from that of conventional cold-cathode, crossed-field switches. Magnets of the magnet system are arranged in two concentric annular rings with their north and south poles aligned either axially or radially. The planar electrode system includes a cathode, a source grid, a control grid and an anode which are arranged in a substantially parallel relationship.

Abstract: In a pollutant destruction apparatus employing one or more corona discharge reactors, an automatic control system controls power generation characteristics for corona discharge reactions according to factors such as the types and the amounts of pollutants in an exhaust gas, maximum allowable emissions, engine operating characteristics, drive control characteristics and intelligent vehicle highway system inputs, to achieve improved treatment of the pollutants.

Abstract: Self leveling apparatus that includes a frame, a device that is to be leveled, and a leveling mechanism such as a double ring gimbal having an inner gimbal ring and an outer gimbal ring. The outer gimbal ring is secured to the frame and the inner gimbal ring is secured to the device and to the outer ring. The inner ring comprises a viscous or preloaded bearing that allows the device to swing around an inner ring axle to thereby level itself in that axis and prevent spurious movement of the device. The outer gimbal ring and inner gimbal ring are attached by outer axles that comprise a viscous or preloaded bearing that allow the inner gimbal ring to swing around the outer axles thereby level the inner gimbal ring in that axis and prevent spurious movement of the device. A disclosed embodiment of the invention includes a magnetometer sensor that is coupled to signal processing and telemetry electronics and a power source that are leveled to keep axes of the sensor oriented along horizontal and vertical axes.

Abstract: A method of operating a flywheel (10) includes the provision of a central shaft (12) defining an axis of rotation; providing a disk-shaped hub (22) joining drivingly with both the shaft and with a rim portion (34); and which hub portion has a shape when the flywheel is at rest which is of a shallow dihedral geometry. That is, the hub is cone-shaped when the flywheel is at rest. As the rotational speed of the flywheel is increased from the at-rest speed toward and then to a design operating speed for the flywheel, this hub progressively flattens out until it becomes flat and extends radially between the shaft and the hub at the design speed for the flywheel. Thus, the flattening of the hub with increasing rotational speed for the flywheel moves the rim portion axially in response to centrifugal force.

Abstract: A positive current source (PCS) for supplying common mode current. The PCS includes a pair of unity gain inverting single ended amplifiers that are connected in antiparallel across a pair of matched resistors. Alternately, the resistors can be connected across the inverting and non-inverting sides of a differential amplifier. A constant voltage is applied across the resistors to supply the common mode current (I.sub.cm) while maintaining a common mode resistance of R/2 and a differential mode resistance approaching infinity. The PCS has a common mode resistance which is small enough to maintain a stable common mode operating point with process variations providing minimal impact.

Abstract: A process for plating aluminum alloy substrates such as aluminum pistons with an iron-cobalt alloy comprising the steps of (a) plating on the aluminum alloy substrate a thin layer of nickel from an electroless nickel bath; and (b) plating on the nickel layer a layer of iron-cobalt alloy from an iron-cobalt electroplating bath. The iron-cobalt layer is not subject to the corrosion problems inherent in a substantially pure iron-plated coating nor the excessive hardness, costliness, and environmental concerns related to the use of nickel as the primary plated layer. The iron-cobalt electroplating bath is cost-effective and can be utilized in a totally closed loop plating system. The resulting iron-cobalt plated, aluminum alloy parts evidence good adhesion, wear, thermal conductivity, and corrosion-resistant properties.

Abstract: A plasma assisted chemical transport system for additive or subtractive shaping of a substrate surface employs a plasma head (30) that generates a plasma (34) and is caused to scan the surface of a workpiece (51) to provide selective shaping, either by etching or depositing material. Corrosive gases of the plasma are isolated to minimize corrosive effects on the drive mechanism (20) by encompassing the plasma head within a flexible bellows (64). Scanning is in a circular path of varying radius. Acceleration induced vibrations caused by programmed varying scan velocity are avoided by use of an oppositely rotation body (56) of equal torsional inertia. Effects of linear acceleration in the radial direction are effectively avoided by making rotational scan velocity many times greater than radial scan velocity.

Abstract: A vector trellis coded modulation scheme (VTCM) is accomplished by blocking input samples into a sequence of input vectors of length L, vector convolutional coding the input vectors to map K input vectors into N output vectors and modulating the output vectors into symbols from an expanded alphabet. In a first case, each output vector is modulated to a different symbol thereby improving coding gain while maintain bandwidth efficiency. In a second case, blocks of N output vectors are modulated to one symbol thereby improving bandwidth efficiency by a factor of N while maintain coding gain. A polyphase/multirate representation of the vector convolutional codes is preferably used to generated the vector convolutional codes. In general, a computer search can be employed to find the polyphase coefficients that define the set of vector convolutional codes. When the input and output vectors have the same length, known scalar-valued convolutional codes are blocked to generate the vector convolutional codes.