Abstract: A method and an apparatus are provided for measuring the pressure of a gas within a sealed vessel. A sonic transducer is used to apply an oscillating force to the surface of the vessel. The frequency of the ultrasonic wave is swept through a range which causes resonant vibration of the gas in the vessel. A receiving transducer measures the amplitude of the resultant vibration at the vessel surface and reveals the resonant frequency of the gas as peaks in the amplitude of the sweep. The resonant frequency obtained depends upon the composition of the gas, its pressure and temperature, and the shape of the confining vessel. These relationships can be predetermined empirically so that the pressure inside the vessel can be calculated when the composition of the gas, its temperature, and shape of the confining vessel are known. The output of the receiver is fed into a computer which is programmed to calculate the pressure based upon these predetermined relationships which are stored in the computer.

Abstract: A liquid accumulator (28) for use in a substantially zero gravity environment which utilizes the surface tension of a liquid to form a meniscus which acts as a gas-liquid interface providing a barrier to the passage or entrainment of a gas into the liquid. The apparatus includes a plurality of tubes (36) for capillary containment of a liquid, a grid member (34) provided with a plurality of holes (one of each tube) for receiving therein in sealing engagement an end of the tube. An opposite end of each of the tubes contains a gas. The apparatus further includes a housing (30) extending circumferentially about the grid member and defining a liquid zone (38) on the side of said grid member opposite said tubes located within the liquid zone and extending partially into each of the tubes is a body of liquid which forms a meniscus (42) in each of the tubes. Fluid communication is provided between the liquid zone of the apparatus and a source of liquid subject to thermal expansion and contraction.

Abstract: A method for efficiently producing a multicolored laser beam. The second harmonic of a 1.06 micron wavelength laser beam is produced from a YAG laser. The second harmonic has a wavelength equal to 0.53 micron. The second and third harmonics of a 1.32 micron wavelength laser beam are simultaneously produced from a second YAG laser. The second harmoic has a wavelength equal to 0.66 micron and the third harmonic has a wavelength equal to 0.44 micron. The produced harmonics from the previous steps are combined to form a multicolored laser beam.

Abstract: The dynamic viscosity of a viscous medium is measured by positioning an acoustic transducer in the temperature and pressure environment of the medium and spaced from the medium, then measuring a first resonant frequency and bandwidth for acoustic shear wave propagation within the transducer. The transducer is then positioned in surface contact with the medium, and a second resonant frequency and bandwidth are measured. The viscosity of the medium is calculated from the difference between the first and second resonant frequencies and bandwidths. The step of measuring a first resonant frequency and bandwidth involves applying a first input signal to the transducer to generate acoustic shear waves within the transducer, measuring the frequency and amplitude of the output signal produced by the transducer in response to the acoustic shear waves, and repeating the steps of applying and measuring for a range of first input signal frequencies to determine a first resonant frequency and bandwidth for the transducer.

Abstract: A flat panel matrix display pixel structure emulates raster scan cathode ray tube shadow mask resolution. A display generator connected to anti-aliasing and/or dot flair circuitry activates the display. A selected pixel is fully activated and surrouding pixels are activated at a lower luminance level. As a function of the pitch of a shadow mask cathode ray tube the pixel density and the horizontal and vertical pixel spacing are derived for a monochrome matrix display, and the pixel density and the horizontal and vertical triad spacing are derived for a color matrix display panel.

Abstract: A nonlinear adaptive filter has an input and an output, and includes an adjustable linear filter and nonlinear filter connected serially between the input and output. The parameters for the adjustable linear filter are derived from signals on the adaptive filter output and from signals on the adaptive filter input. Preferably, the adjustable linear filter is coupled between the adaptive filter input and the nonlinear filter. A parameter computer for adjusting the parameters of the adjustable linear filter includes an input coupled to the output of the nonlinear filter, a processor for processing a signal received from the output of the nonlinear filter, and apparatus for applying the processed output signal to the parameters of the adjustable linear filter. A linear filter for shaping the spectrum of a signal received from the output of the nonlinear filter is preferably coupled between the nonlinear filter output and the parameter computer.

Abstract: A method of cleaning a fuel assembly contaminated with a radioactive alkali metal in which the fuel assembly is subjected to heating with an inert gas followed by being placed under vacuum and finally cooled with an inert gas; the latter two steps being performed in repetitive cycles.

Abstract: There is disclosed a technique for providing resynchronization for message reception in digital transmission systems, and particularly in digital frequency hopping systems employing data framing techniques. In the transmission of framed data using known digital techniques for frequency hopping systems, synchronization is provided in frames preceding the message frames transmitting digital data. In addition, resynchronization information is transmitted in subsequent frames which are interspersed with data frames including the message data. A predetermined number of frames is set to provide all the resynchronization information so that once those frames have been detected, a receiver will have acquired resynchronization during message transmission. This technique allows improved signal acquisition by providing an opportunity following the first conventional synchronization frame to acquire synchronization or to reacquire synchronization during message transmission.

Abstract: An improved hollow electrode 10 and hollow electrode working tip 14 for a gas tunsten arc welding apparatus is disclosed. The hollow electrode face is formed as a lune-shaped radial surface 16 having two tapered intersecting cone-shaped angled surfaces 18. The improved electrode working tip provides a controllable stable arc resulting in an improved weld.

Abstract: A random digital signal generator circuit responsive to a clock signal from a block signal source for outputting a sequential series of logic signals. The circuit comprises a clocked flip-flop that provides a signal at its output terminal that has a value corresponding to the state of its input signal until a subsequent clock signal is received. An array of oscillator signal generators is provided with each oscillator signal generator operating at a different frequency. An EXCLUSIVE-OR network means having an array of input terminals has each input terminal of the EXCLUSIVE-OR network coupled to the output terminal of a corresponding oscillator signal generator. The EXCLUSIVE-OR network provides a random output signal at its output terminal. The EXCLUSIVE-OR network means output terminal is coupled to the flip-flop input terminal. The flip-flop responds to each the clock signal to sample the state of the random output signal from the EXCLUSIVE-OR network.

Abstract: A nonlinear optical matrix multiplier includes a nonlinear optical medium with a first optical input beam impinging on the medium, the transverse spatial intensity of the first input beam being modulated by a first two dimensional matrix. A second optical input beam impinges on the medium, with the transverse spatial intensity of the second input beam being modulated by a second two dimensional matrix. An optical probe beam impinges on the medium, the first input beam, the second input beam, and the probe beam being oriented with respect to one another and with respect to the medium such that the beams interact within the medium by means of four-wave mixing. A diffracted output beam emerges from the medium, with the transverse spatial intensity of the output beam modulated by the product of the first and second matrices.

Abstract: A circuit for charging a capacitive load such as a data or address bus in a VLSI circuit includes a voltage source input, a PFET switch connected between the voltage source input and the capacitive load or bus, and a voltage regulator connected to the capacitive load and to the gate of the PFET switch to cause the switch to conduct during a predetermined time only if the voltage on the capacitive load is less than a predetermined voltage, and to disconnect the capacitive load from the voltage source input when the voltage on the capacitive load reaches or exceeds that predetermined voltage level. The voltage regulator may include a first inverter having its input connected to the bus and a second inverter having an input connected to the output of the first inverter and having an output connected to the control input of the switch. The first inverter is constructed to output a low level when the voltage on the first inverter input is at or above the designated predetermined voltage.

Abstract: A compact, lightweight thruster assembly (10) is provided consisting of a dual armature piston assembly (24). A single solenoid coil (46) operates either or both armatures (26), (34) depending on the level of applied current to effect either of two levels of predetermined impulse emitting from the thruster nozzle (20).

Abstract: A deployment system for controlling unfolding kinematics of radiator panels 26 of a space power system. The deployment system includes a plurality of forming mandrels 30 associated with a housing 38 of opposing generally triangular plates 40. Within the housing, a drive wheel 52 and two additional guide wheels 50 interact with the mandrels to effect predetermined deflection and deployment of the multiple radiator panels.

Abstract: FM signals are demodulated with lower distortion and expenditure of less computing time by digitizing the signals using an A/D converter of predetermined sample frequency and down-converting the signals to their base band quadrature components. The quadrature components are delayed by one sample period, and the complex cross-product of current quadrature components and the delayed quadrature components from the immediately preceding A/D sample period is taken. The arctangent of the resulting cross-product is taken by calculating the ratio of the imaginary and real components thereof to produce a value which is representative of the original modulating signal.

Abstract: An amplifier signal limiter is disclosed which has the operational capability of tracking slowly varying signal components while precluding errant transient outputs, and has a programmable limit range which is independently controllable for broader or narrower allowable outputs.

Abstract: A solid state dc switch for switching power from the positive terminal of a ground referenced dc voltage source to the terminal of a ground referenced load. The solid state switch has a divide-by-two circuit means responsive to a clock signal and to a control signal first state for providing first and second symmetrical output signals at a frequency of one-half the frequency of said clock frequency. It also has a transformer drive and rectifier means for providing an isolated dc signal. An isolated switching means is included which is responsive to the high state of an isolated dc signal, having a transistor switch having a collector, an emitter and a base, the collector being coupled to a positive terminal of a ground referenced voltage source. The emitter is coupled to the return of the ground referenced load. The base is coupled to an isolated dc signal.

Abstract: A method of adjusting the threshold voltages of field effect transistors fabricated on a III-V compound semi-insulating wafer includes the steps of measuring the threshold voltages of the transistor, directing an ion beam at the wafer to selectively damage the channels of the transistors, thereby shifting the threshold voltages to an interim value, and annealing the wafer at a temperature and for a time sufficient to stabilize the threshold voltages at a predetermined optimum value determined by the intensity and duration of the ion beam implantation. The III-V compound semi-insulating wafer may be GaAs. The ion beam may be supplied as protons accelerated to approximately 320 KeV with a concentration of between approximately 10.sup.11 and 10.sup.13 protons/cm.sup.-2. The wafer may be annealed at a temperature from approximately 100.degree. C. to approximately 300.degree. C. (for approximately one half hour at 300.degree. C.

Abstract: An apparatus and method for enhancing the efficiency of a free electron laser, (10). A plurality of electrodes, (28) are imbedded in an electrically insulating vacuum tube, (18) enclosing the electron beam, (14) and its copropagating electromagnetic wave. A variable computer controlled high voltage d.c. power supply, (29) is connected to the electrodes, (28) for energizing the electrodes, (28) at saturation indicated by detectors, (30) thereby converting d.c. electric potential to electromagnetic radiation without gain degradation.

Abstract: The specification discloses a meteor burst communication system including at least two spaced apart master stations, in association with a plurality of groups of remote stations spaced at locations remote from the master stations, with each group being associated with one of the master stations. Each of the master stations incudes a radio transmitter for transmitting probing digital radio signals having address portions which are directed from the master station for reflection from meteor trails to the remote stations associated with the master station. Circuitry is provided to vary the length of the address portions transmitted by the master station in dependence upon desired signal-to-noise and timing considerations. Each of the remote stations includes a radio receiver for receiving the reflected probing digital radio signals from the master stations. Each of the remote stations also includes at least one sensor of physical characteristics such as snow depth, rain fall or the like.