Abstract: An adaptive record ranking method for full text information retrieval, which quantifies the relevance of retrieved records to query terms occurring in said record. The method utilizes a multilevel weighting technique which permits user input to affect record weighting at each level of the ranking process. The method utilizes weighted attributes of properties of terms occurring in the records of the data base and compensates for the distance between adjacent words of complex terms. The method has been implemented on large full text data bases and the resulting rankings achieve a relatively high level of precision in ranking the relevance of retrieved records to a user query.

Abstract: A wireless communication device using a verification protocol for verifying the identification of the wireless device by a wireless network control station in the presence of eavesdroppers is disclosed. Upon receiving a call request from a wireless device claiming a particular identity, the wireless network control station sends a mask consisting of binary digits in a random order. The wireless device is expected to respond to this mask with a reply that is consistent with both the password contained in the device and the mask. Specifically, the bits of both the password and the mask are "ANDed" and the result transmitted to the wireless network control station as the reply.

Abstract: Apparatus and method for determining the concentration of NOx in a gas mixture. The gas mixture is supplied to two electrodes at which different NOx decomposition conditions are present. The electrodes may be of different materials or sizes or may be positioned in different gas enclosure environments. The NOx decomposes at different rates at the two electrodes and an emf is thus produced between the electrodes. The concentration of NOx in the gas mixture is determined from the measured emf.

Abstract: A method of fabricating a semiconductor heterostructure includes the growth of a quantum well active region that is highly lattice-mismatched relative to a substrate. A buffer layer having a thickness above a critical value is grown on the substrate whereby the stress due to a lattice constant mismatch between the buffer layer and substrate is relieved through the formation of misfit dislocations. A strained superlattice structure is grown on the buffer layer in order to terminate any upwardly-propagating dislocations. An unstrained barrier layer is subsequently grown on the superlattice structure. The fabrication method concludes with the growth of a quantum well structure on the unstrained layer wherein a lattice constant mismatch between the quantum well structure and the unstrained barrier layer is smaller than the lattice constant mismatch between the quantum well structure and the substrate.

Abstract: Optical communication methods and apparatus are disclosed for transmitting two or more optical signals with different optical carrier frequencies on a single optical fiber with high spectral efficiency. Each optical carrier is typically modulated with multiple modulated subcarriers. In one embodiment, an optical phase modulator provides cancellation of second order intermodulation products in each optical signal, thereby permitting the optical carrier frequencies to be spaced by 2f.sub.max, where f.sub.max is the maximum modulation frequency. In another embodiment, a single sideband optical phase modulator provides cancellation of second order intermodulation products and one signal sideband, thereby permitting the optical carrier frequencies to be spaced by f.sub.max.

Abstract: A semiconductor optical amplifier with a high speed photodetector acting as an optical tap is disclosed. The device functions simultaneously as an in-line optical amplifier and as a high-speed photodetector tap. An in-line an optical amplifier is combined with a waveguiding, high speed (low capacitance) reverse-biased photodetector that absorbs only a percentage of the amplified signal, allowing the remainder to pass through without distortion.

Abstract: A filtering system is disclosed for receiving and bandpass filtering free space optical signals. The filtering system includes a plurality of optical fibers for accepting an optical signal. The fibers are implanted in an embedding material, having an index of refraction which is less than the optical fiber, for collimating the optical signal. The signal is further passed through a narrow, bandpass filter before detection by a photodetector device. In an alternative embodiment, the optical fibers are enclosed in a cladding, having a surface roughness at the interface of the cladding and the fiber, for enhancing the collimation of the optical signal.

Abstract: A superconducting copper oxide based wire exhibiting improved critical current density and method. A superconductor powder and a binder melt are mixed at a solids loading of at least 90% by weight. The binder is an ester wax with no more than about 0.25 weight percent extrusion-aiding additives. The ester wax has the general formula RCOOR' with R and R' being hydrocarbon chains of at least 6 carbons. The ester wax melting point is 40.degree.-100.degree. C.; its melt viscosity is 94-2000 centipoise. The mixture is shaped and heated in an oxidizing atmosphere at up to 120.degree. C./hr to 500.degree.-600.degree. C., and held at that temperature for a time sufficient to remove the binder and achieve a wire density of at least 50% of theoretical. The green wire is heated at 50.degree.-130.degree. C./hr to at least 920.degree. C., and held at 920.degree.-990.degree. C. to achieve 90% of theoretical density, then annealed in oxygen. The wire may be textured during the heating process or by seeding.

Abstract: An optoelectronic device is disclosed utilizing a semiconductor laser amplifier that provides for simultaneous detection, amplification, and modulation of an input optical signal. In one embodiment, an electronic transmitter and receiver are coupled to the semiconductor laser amplifier through an RF circulator. In an alternative embodiment, the electronic transmitter and receiver are coupled to the semiconductor laser amplifier through an RF power splitter with frequency or phase discriminating circuitry.

Abstract: A fiber optic amplifier is disclosed utilizing a doped fiber to provide amplification through stimulated emission. The doped fiber is simultaneously pumped by multiple pump lasers generating optical waves of differing wavelengths. The optical waves from the lasers are combined using a wavelength division multiplexer before introduction into the doped fiber. The use of multiple pump lasers decreases the power requirements of each laser, reduces the cost of the amplifier, and increases reliability without compromising the gain of the amplifier.

Abstract: The present invention describes an apparatus and method for shutting off an electrodeless lamp such that it can be restarted instantaneously at any time. The method involves reducing the applied microwave power in a controlled way the moment the lamp is turned off. The reduction of power is accomplished by modulating the microwave power with an ever decreasing duty factor or a decrease of analog power. This reduction in power results continually in reduced light output and lamp cooling while maintaining partial ionization of the lamp fill. Circuitry to accomplish this is also presented.

Abstract: A broadband space switch matrix constructed from a plurality of NAND gates arranged into a set of cascaded stages to form a tree-switch multiplexing configuration. A plurality of input digital signals are applied to input ports coupled to the NAND gates in the first stage. A selected one of the input signals emerges as an output signal from an output port coupled to a single NAND gate in the last stage. Each NAND gate has a select line for receiving control signals. The switching path for the selected input signal is established by placing the sequence of NAND gates defined by the selected switching path in a state of conduction whereby only the selected input signal propagates through the switch. This is effected by forcing to a HIGH state the particular NAND gates in each stage whose outputs are coupled to the same NAND gate in the following stage along with the output of the NAND gate in the current stage which is in the chosen path.

Abstract: Electrical ohmic contacts are made to a matrix of silicon having conductive rods embedded therein without making contact to any of the rods. Those rods which extend to the surface in the selected area of the matrix to be contacted are etched to form holes. The holes are filled with insulating polycrystalline silicon. The region of the selected area is heavily doped, and an ohmic contact member is made thereto. The underlying rods are spaced from the ohmic contact member and the heavily-doped region by intervening polycrystalline silicon.

Abstract: A method for secure exchange of password information between a requester node and a server node using a verification protocol for confirming the identification of the requester node by the server in the presence of eavesdroppers is disclosed. By adjusting the parameters of the protocol the possibility that an intercepter of the exchanges can impersonate a requester node after receiving a specified number of exchanges may be engineered to satisfy security objectives.

Abstract: This invention disclosure describes the application of a polarization insensitive acoustically-tuned optical filter used in a multichannel WDM system to equalize variations in the power level of the WDM channels. The invention also describes a simple means for providing a low frequency control system which enables the equalizer to determine the signal levels of N optical carriers prior to equalizing the signals.

Abstract: Heteroepitaxial semiconductor structures of, for example, GaAs on InP or Si. The epitaxially grown GaAs is in the form of individual spaced-apart islands having maximum dimensions in the plane of the surface of the substrate of no greater than 10 micrometers. In islands of this size stress in the plane of the epitaxially grown layers due to mismatch of the coefficients of thermal expansion of the substrate and epitaxially grown materials is insignificant.

Abstract: In a data communication system, apparatus provides a clock signal having a frequency of twice the frequency of a first clock signal. A time delay circuit delays the first clock signal by a time delay to provide a delayed first clock signal. An exclusive OR circuit is coupled to the first clock signal and the delayed first clock signal. The output of the exclusive OR is a second clock signal having a frequency twice the frequency of the first clock signal.

Abstract: A waferboard assembly incorporates mechanical registration features into a substrate platform to facilitate the passive alignment of lasers integrated on a chip to fibers in integral contact with the substrate. The waferboard includes two front pedestal structures and one side pedestal structure, and two vertical post structures within a mounting region defined by the pedestal structures. The laser chip is mounted on the vertical post structures, and placed in concurrent abutting contact with the pedestal structures. The waferboard is fabricated by etching the substrate to form the front and side pedestal structures, and etching the substrate to define the grooves. In order to form the post structures, a polyimide material is deposited on the substrate using an appropriate mask.

Abstract: A digital video encoder encodes a video frame into a differential video frame for transmission over a packet switched network. The video encoder includes an inter-frame encoder, an intra-frame encoder, and an encoding selector for selecting between the inter-frame and intra-frame encoder depending on the relative motion between the video frame being encoded and the previous video frame.A composite frame combiner provides a composite intra/inter-frame encoded difference frame having one set of pixels encoded by the inter-frame encoder, and another set of pixels encoded by the intra-frame encoder. The set of intra-frame encoded pixels includes at least one square or rectangular pixel block, a vertical strip of pixel blocks, and a horizontal strip of pixel blocks.Difference frames are encoded into separable data sets representing video information within a particular range of image resolution.

Abstract: Apparatus for improving the coupling efficiency of a laser to a single mode fiber by means of an intermediate waveguide is disclosed. For uniform waveguides maximum improvement results when waveguide's mode field radii MFR is designed as the geometrical mean of the MFR of the laser and the MFR of the fiber. The apparatus can be extended to multi-stage couplers. Each successive stage is designed to have a spot size which is the geometric mean of the section before and after. With only a small number of stages significant improvement in coupling efficiency can be realized.