Abstract: In an improvement over conventional finite element techniques, an oblate spheroidal infinite element is used for the modeling of acoustic fields in exterior, fluid-filled domains surrounding a structure. This oblate infinite element is based on a multipole expansion that describes, to arbitrary accuracy, any scattered and/or radiated field exterior to an oblate spheroid of any eccentricity. The oblate infinite elment is readily incorporated in any structural or acoustical finite element code.

Abstract: In an improvement over conventional finite element techniques, a prolate spheroidal infinite element is used for the modeling of acoustic fields in exterior, fluid-filled domains surrounding a structure. This prolate infinite element is based on a multipole expansion that describes, to arbitrary accuracy, any scattered and/or radiated field exterior to a prolate spheroid of any eccentricity. The prolate infinite elment is readily incorporated in any structural or acoustical finite element code. Structural acoustic modeling with the element is several orders of magnitude faster than modeling, at comparable accuracy, with the well-known and widely used boundary element method, at least for large-scale problems involving tens of thousands of degrees of freedom.

Abstract: A signal processor for, e.g., a telephonic communication system interconnecting a near location and at least one far location includes an echo canceller for suppressing the re-transmission of received signals. The operation of the echo canceller is controlled according to whether the near location is transmitting or receiving, and whether the far location is transmitting or receiving. The signal processor includes means for detecting doubletalk, and for controlling the echo canceller in response to the detection of doubletalk, such that doubletalk is permitted. In one method of operation, a delay is applied to the inputs to the echo canceller from the near and far ends, such that each of these signals is used for determining the operating state of the echo canceller before being used to operate an adaptive filter of the echo canceller. In another method of operation, doubletalk detection is carried out, in part, by evaluating the performance of an auxiliary adaptive filter.

Abstract: In order for neural network technology to make useful determinations of the identity of letters and numbers that are processed in real time at a postal service sorting center, it is necessary for the neural network to "learn" to recognize accurately the many shapes and sizes in which each letter or number are formed on the address surface of the envelope by postal service users. It has been realized that accuracy in the recognition of many letters and numbers is not appreciably sacrificed if the neural network is instructed to identify those characteristics of each letter or number which are in the category "invariant." Then, rather than requiring the neural network to recognize all gradations of shape, location, size, etc. of the identified invariant characteristic, a generalized and bounded description of the invariant segments is used which requires far less inputting of sample data and less processing of information relating to an unknown letter or number.

Abstract: Articles being graphical input patterns are sorted by a pattern-recognition machine that includes a data base of prototype patterns, each labeled with its respective class. The sorting method includes stops of storing input patterns in the pattern-recognition machine and classifying the stored input patterns. The classification is performed by calculating at least two distance functions between input patterns and prototype patterns. The distance functions belong to a hierarchy of distance functions that vary in the degree to which they are computationally intensive, and concomitantly, in their accuracy. Overall computational requirements are reduced by using less computationally intensive distance functions to preliminary filter out those prototype patterns that are farthest from the input pattern.

Abstract: An optical filter is adapted for selectively transmitting electromagnetic radiation within a wavelength passband bounded by a pair of stop bands of relatively low transmissivity. The filter includes at least one Bragg grating formed in a waveguiding optical medium. The Bragg grating has at least one wavelength band of relatively low transmissivity. This low-transmissivity band corresponds to at least a portion of one of the stop bands of the filter.

Abstract: A method is described for selectively modifying the refractive index of an optically transmissive body having an optical propagation axis. According to this method, polarized, actinic radiation is impinged on at least a portion of the body. In contrast to methods of the prior art, the actinic radiation is at least 60% polarized with a polarization direction parallel to a plane containing the propagation axis.

Abstract: A semiconductor optoelectronic device which can be used to perform the logical INVERTER or NOR operation. The device includes a surface-emitting laser 200 electrically coupled to a heterojunction phototransistor 240. When the total illumination intensity at the phototransistor is below a given threshold, the laser is in a lasing state; when the total illumination exceeds the threshold, the laser is in a non-lasing state. The phototransistor is operated at bias voltages below the threshold for avalanche effects.

Abstract: A second-order differential (SOD) microphone includes a first-order differential (FOD) microphone element installed in a housing. A pair of front sound conduits extend from respective ports to a chamber on the front side of the microphone diaphragm, and a pair of rear sound conduits extend from respective ports to a chamber on the rear side of the microphone diaphragm. The two front ports and the two rear ports are all substantially collinear along a minor axis, with the rear ports intermediate the front ports or the front ports intermediate the rear ports. The respective acoustic transfer functions from each port to the microphone diaphragm are equivalent. The microphone response is approximately proportional to the second spatial derivative, along the minor axis, of a sample acoustic pressure field.

Abstract: A process for creating segments out of an arbitrary string of handwritten alphanumeric script is described, in which the contours of the image are defined by the path a ball or pointer follows when allowed to roll from the top and bottom of an image, down or up either side. From the contours, the initial image cut points are determined. The pointer is provided with a capability to measure ink density in the nearby pixels. A grey scale threshold control is provided which operates in conjunction with the pointer as it rolls or moves, to define ink density above the threshold as a white pixel wherein no image content is present; and ink density below the threshold as a black pixel wherein image content is present.

Abstract: Acoustic surveillance of objects and human traffic in a spatial zone of a financial transaction device is used to detect movement within the zone. Several specific types of detected movement defined as abnormal trigger an alert to a remote monitoring station. The alerts are automatically prioritized using rule-based criteria. Enhanced surveillance of the alert site by audio links as well as site alert history information are provided.

Abstract: Signal energy in an installed optical fiber is extracted without using a physical connector, by an improved process in which the fiber is bent to within a prescribed range of angles, then controllably heated, and thereafter controllably cooled. The resulting structure exhibits relatively low permanent stress. A fiber end conventionally placed at the bend point receives unusually useful amounts of optical signal which can be routed to optical branch circuits in, for example, a building or a LAN.

Abstract: A second-order differential (SOD) microphone includes a first-order differential (FOD) microphone element installed in a housing. A pair of front sound conduits extend from respective ports to a chamber on the front side of the microphone diaphragm, and a pair of rear sound conduits extend from respective ports to a chamber on the rear side of the microphone diaphragm. The two front ports and the two rear ports are all substantially collinear along a minor axis, with the rear ports intermediate the front ports or the front ports intermediate the rear ports. The respective acoustic transfer functions from each port to the microphone diaphragm are equivalent. The microphone response is approximately proportional to the second spatial derivative, along the minor axis, of a sampled acoustic pressure field.

Abstract: This disclosure describes a method for producing high-performance layered-element electrostrictive or piezoelectric actuators, and the resulting product. The process calls for steps that minimize decreases of the stack stiffness which usually characterize layered wafer actuators. These include making the wafers flat and parallel, using a referred wafer metalization process that does not affect wafer surface roughness, and using stock-bonding epoxies with viscosities which readily permit the bonding agent to "wick" into the interface areas of the wafer/electrode stacks thereby to minimize the bond agent thickness.

Abstract: Apparatus performs active, dynamic balancing of a rotating machine by shifting the spatial distribution of an inertial liquid within a body that co-rotates with the rotating shaft of the machine. The body includes chambers, substantially disposed at equal angular intervals, for containing the inertial liquid. The chambers communicate through a channel lying at or beyond the outermost radial position of the outward ends of the chambers. A motive element or elements are provided for impelling the inertial liquid through the channel. The chambers, channel, and motive elements form a sealable system.

Abstract: A radio or telephone handset configured with the usual transmitter and receiver ends and connecting handle is designed to have physical characteristics well adapted in its acoustic characteristics to complement noise cancellation circuitry. The receiver speaker is mounted in the receiver cap, and the cap is built with a domed, apertured earpiece extending from the exterior surface of said receiver cap. The dome fits into a user's outer ear, thereby to aid in positioning said handset on a user's ear. Openings radially placed on said receiver cap exterior surface and surrounding said earpiece, define an acoustic grill through which signal from said receiver speaker is passed substantially directly to said user's ear canal. Noise absorbing material is placed at strategic locations within the handset interior.

Abstract: Apparatus and processes are described for the automatic recognition of alphanumeric images. A set of cuts are made to the image which include incorrect segmentations. The resulting "cells" comprising in their totality the created segments of the image are then analyzed to determine which cells are legal neighbors and which are not. All cells which are legal neighbors are then presented as connected nodes. A pruning of nodes which are related to certain predetermined image cuts is effected. Each set of remaining connected nodes is then presented to a recognizer which identifies the image and assigns a specified probability to the output. Many cells which are not legal neighbors are thereby not presented to the recognizer, thus saving substantially on computations per recognized image.

Abstract: An optical filter is adapted for selectively transmitting electromagnetic radiation within a wavelength passband bounded by a pair of stop bands of relatively low transmissivity. The filter includes at least one Bragg grating formed in a waveguiding optical medium. The Bragg grating has at least one wavelength band of relatively low transmissivity. This low-transmissivity band corresponds to at least a portion of one of the stop bands of the filter.

Abstract: Improved microphone performance is achieved by configuring a second-order derivative microphone assembly in such a way that radially divergent near-field input produces a microphone response proportional to a first-order spatial derivative of the acoustic pressure field.

Abstract: A method for making gate dielectrics for MOS devices includes first forming a silicon oxynitride layer, and then forming a silicon dioxide layer that underlies the oxynitride layer. The oxynitride layer functions as a membrane for controlled diffusion of oxygen to the oxidation region of the silicon substrate.