Abstract: An improved self-powered vehicle detector (SPVD) uses a two-axis magnetomr to sense a vehicle's magnetic signature and then telemeter vehicle presence information to a roadside receiver. The SPVD system includes digital nulling loops to cancel D.C. offset changes in the magnetometic output, a multi-tone code transmitter to transmit vehicle presence and SPVD condition signal, and an omnidirectional microstrip antenna to simplify installation and maintenance of the SPVD.

Abstract: A variable temperature method for the preparation of single and multiple epitaxial layers of single-phase (e.g., face-centered cubic), ternary lead chalcogenide alloys (e.g., lead cadmium sulfide, [Pb.sub.1-w Cd.sub.w ].sub.a [S].sub.1-a wherein w varies between zero and fifteen hundredths, inclusive, and a=0.500.+-.0.003), deposited upon substrates of barium fluoride, BaF.sub.2, maintained in near thermodynamic equilibrium with concurrently sublimated lead alloy and chalcogenide sources. During preparation, the temperature of the substrate is varied, thereby providing an epilayer with graded composition and predetermined electrical and optical properties along the direction of growth. This growth technique can be used to produce infrared lenses, narrowband detectors, and double heterojunction lasers.

Abstract: A compact, directional antenna element for achieving narrow beamwidths and ide bandwidths. The element is formed from a polyrod having a high dielectric constant embedded in a wave guide made of a second medium having a dielectric constant slightly lower than that of the rod.

Abstract: The shear absorption of a viscoelastic material is determined by directing acoustical energy at the viscoelastic material and sampling the backscattered signals that result when compressional waves propagate through the material and are scattered by either a fluid-filled or evacuated cavity contained therein. The backscattered signals are converted to a resonance amplitude versus frequency domain and the shear absorption of the viscoelastic material is determined from the frequency and the half-width of the resonance peaks.

Abstract: An apparatus and method for determining the material properties characterizing a fluid contained in a cavity inside a solid comprises analyzing the resonances in the amplitude of elastic waves scattered by the cavity. Specifically, the resonance positions and their widths are used to determine the sound speed and the density of the cavity filler. The sound speed is found from the spacing between two consecutive overtones of any mode, which asymptotically becomes uniform for the higher-index overtones. The density is obtained from the width of any high order resonance and accordingly, all the information about the material composition of the filler is contained, and can be extracted, from the high-frequency asymptotic region.

Abstract: A system for digitally quantizing, at high resolution, relatively small vations of an analog input signal. Initially, a reference level signal having a preselected value close to the average magnitude of the analog signal being quantized is compared with the analog input signal. The difference between these two signals is amplified and then analog to digital converted. By an iterative process, the reference level is adjusted as necessary to closely track the gross magnitude level of the analog input signal. Analog to digital conversion is applied only to the small difference signal, thereby allowing quantization to occur with high resolution. The system automatically keeps track of gross signal excursions so that the magnitude of the quantized signals is also available to the user.

Abstract: An electronic breathing mixture control system which senses and controls oxygen component partial pressure of an underwater breathing mixture. Three oxygen sensors disposed within a mix chamber generate voltages proportional to the oxygen partial pressure in the mixture. These voltages are processed and compared with reference voltages using digital logic circuitry. The resulting processed signals control two light emitting diodes warning the user of improper oxygen partial pressure and in addition control a switch that actuates an oxygen valve which either restricts oxygen flow to the mix chamber or allows more oxygen to flow therein.

Abstract: Disclosed is a frequency shift key demodulator for the coherent detection of both mark and space tones. Cross coupled phase locked loops lock onto and track the difference in frequency between translated mark and space tones. An additional set of cross coupled phase locked loops locks onto and tracks overall frequency drift of the mark and space tones. Signals are generated within the first set of cross coupled loops allowing for coherent detection thereby permitting detection during signal to noise ratios of less than one. Loop bandwidths can be independently controlled and are independent of the data rate thus permitting wide system flexibility.

Abstract: In an acoustic homing torpedo having a transducer section mounted forward the nose shell, an elastomeric, acoustically transparent sleeve is installed over the torpedo nose section and extends aft of the discontinuity at the transducer/nose section interface, thereby reducing the torpedo self-noise generated by cavitation occurring at the discontinuity.