Abstract: Operating fluid pressure is supplied to a fluid motor past a modulating operating fluid pressure and a work pressure so as to control the work pressure.

Abstract: An improved machine for use in determining the fatigue life for elastomeric specimens. The machine is characterized by a plurality of juxtaposed test stations, specimen support means located at each of the test stations for supporting a plurality of specimens of elastomeric material and means for subjecting the specimens at each of said stations to sinusoidal strain at a strain rate unique with respect to the strain rate at which the specimens at each of the other stations is subjected to sinusoidal strain.

Abstract: A predetermined amount of segregation is introduced into a molten sample of a composite that exhibits the Soret effect, such amount approximating the amount of segregation resulting from directional solidification of the sample. The molten sample is then directionally solidified starting at the end opposite the end richer in the constituent that would migrate toward the cooler part of a liquid solution of the composite maintained in a temperature gradient. Since solidification commences at the end deficient in such constituent, its migration toward the interface between the solid and liquid during the solidification will compensate for the deficiency yielding a more homogeneous product.

Abstract: An opto-mechanical subsystem for supporting a laser structure which minimizes changes in the alignment of the laser optics in response to temperature variations. Both optical and mechanical structural components of the system are formed of the same material, preferably beryllium, which is selected for high mechanical strength and good thermal conducting qualities. All mechanical and optical components are mounted and assembled to provide thorough thermal coupling throughout the subsystem to prevent the development of temperature gradients.

Abstract: A system for measuring fluid velocity in a turbulently flowing fluid including a sensing apparatus for dynamically sensing the mainstream and two orthogonal cross velocity components of the fluid and a transducer operative to provide three electrical output signals representative of the velocity components in the mainstream and in the cross directions. Signal processors can be utilized to derive the Reynolds stress wave and the Reynolds stress.

Abstract: Apparatus for directly measuring the quantity .sqroot..rho.ck of a test specimen such as a wind tunnel model where .rho. is the density, c is the specific heat and k is the thermal conductivity of the specimen. The test specimen and a reference specimen are simultaneously subjected to the heat from a heat source. A thermocouple is attached to the reference specimen for producing a first electrical analog signal proportional to the heat rate Q that the test specimen is subjected to and an infrared radiometer that is aimed at the test specimen produces a second electrical analog signal proportional to the surface temperature T of the test specimen. An analog-to-digital converter converts the first and second electrical analog signals to digital signals. These digital signals are applied to a computer for determining the quantity .sqroot..rho.ck by computing the quantity ##EQU1## WHERE T.sub.

Abstract: The present invention provides an apparatus for phase separating a gas-liquid mixture as might exist in a sub-critical cryogenic helium vessel for cooling a superconducting magnet at low gravity such as in planetary orbit, permitting conservation of the liquid and extended service life of the superconducting magnet.

Abstract: An open loop digital frequency multiplier with a multiplied output synchonized to low frequency clock pulses. The system includes a multi-stage digital counter which provides a pulse output as a function of an integer divisor. The integer divisor and the timing or counting cycle of the counter are interrelated to the frequency of a clock input. The counting cycle is controlled by a one-shot multivibrator which, in turn, is driven by a reference frequency input.

Abstract: A method and apparatus for stabilizing the amplitude and repetition rate of mode-locked Nd:YAG laser pulses by controlling the laser length through a feedback loop is described. The end mirror of the laser is mounted on a piezoelectric crystal which is dithered at a low frequency. A portion of fundamental 1.06 micrometer laser radiation is converted into its second harmonic frequency and the average power of the second harmonic frequency is detected by an integrating detector. The amount of the power of the second harmonic frequency depends on the match between the optical length of the laser cavity and the mode-lock frequency. The length is controlled by a feedback loop which phase compares the output of the second harmonic detector to the piezoelectric crystal dither signal.

Abstract: A hot wire anemometer probe that includes a ceramic body supporting two conductive rods therein in parallel spaced apart relation. The body has a narrow edge surface from which the rods protrude. A probe wire welded to the rods and extending along the edge surface and ceramic adhesive for securing the probe wire to the surface so that the probe wire is rigid. A method for fabricating the probe wherein the body is molded and precisely shaped by machining techniques before the probe wires are installed.

Abstract: An acoustic surface wave oscillator is constructed from a semiconductor-piezoelectric acoustic surface wave amplifier by providing appropriate perturbations at the piezoelectric boundary. The perturbations cause Bragg order reflections that maintain acoustic-wave oscillation under certain conditions of gain and feedback.

Abstract: An optical heterodyne receiver comprises a system of reflectors forming a folded Gregorian configuration for collecting a signal beam, and an optical detector located at the focus of the system. The reflectors comprise a paraboloidal primary reflector and an ellipsoidal secondary reflector facing each other on an optical axis with the focus of the secondary reflector coinciding with the focus of the primary reflector. An auxiliary laser generates a local oscillator beam that is combined with the signal beam after the signal beam emerges from the exit pupil (which is also the aperture stop) of the system, and the resultant is impinged on the detector. A pair of image motion compensators is located as close to the exit pupil as possible for aligning off-axis inputs to the detector. The compensators also ensure that off-axis as well as on-axis inputs are substantially coaxial with the local oscillator beam, thereby maximizing signal detector efficiency.

Abstract: A device for tensioning test specimens within an hermetically sealed chamber. The device is characterized by a support column adapted to be received within an insulated, hermetically sealable chamber, a plurality of anchor pins mounted on the column for releasibly connecting thereto a plurality of test specimens, a plurality of axially displaceable pull rods received by the column in coaxial alignment with the anchor pins, one end of each pull rod being provided with a coupling for connecting the pull rod to a test specimen, while the opposite end of the pull rod is extended through a cover plate and adapted to be connected with a remotely related linear actuator through a connecting link including a load cell for measuring stress as the pull rod is placed in tension by the actuator.

Abstract: A method for making a glass-to-metal seal. A domed metal enclosure having a machined seal ring is fitted to a glass post machined to a slight taper and to a desired surface finish. The metal part is then heated by induction in a vacuum. As the metal part heats and expands relative to the glass post, the metal seal ring, possessing a higher coefficient of expansion than the glass post, slides down the tapered post. Upon cooling, the seal ring crushes against the glass post forming the seal. The method results in a glass-to-metal seal possessing extremely good leak resistance, while the parts are kept clean and free of contaminants.

Abstract: A mechanical sequencer having a rotatable drive shaft. The drive shaft has a spline formed thereon. A freely rotatable shaft contains a plurality of rollers positioned thereon, the axis of the freely rotatable shaft having an axis parallel to and offset from the axis of the drive shaft. A drive fitting has an opening therein, the drive fitting being positioned on the drive shaft spline for rotating the fitting with the shaft. A finger is formed integral with the drive fitting for enabling the fitting to move the rollers and the freely rotatable shaft. A crank structure is positioned in a plane perpendicular to the axis of the drive shaft and the freely rotatable shaft. The crank structure has a drive shaft opening through which the drive shaft passes. The crank structure further contains a slot into which the freely rotatable shaft and one of the rollers extends for driving the crank structure during movement of the freely rotatable shaft. A sequencer housing has a track formed therein.

Abstract: The susceptibility of bacteria, particularly those derived from body fluids, to antimicrobial agents is determined in terms of an ATP index measured by culturing a bacterium in a growth medium, assaying the amount of ATP in a sample of the cultured bacterium by measuring the amount of luminescent light emitted when the bacterial ATP is reacted with a luciferase-luciferin mixture, subjecting the sample of the cultured bacterium to an antibiotic agent and assaying the amount of bacterial adenosine triphosphate after treatment with the antibiotic by measuring the luminescent light resulting from the reaction, whereby the ATP index is determined from the values obtained from the assay procedures.

Abstract: A multi-rate digital command system is disclosed which uses the composite signal of a .mu.-type ranging system as a subcarrier to transmit range codes and data from a station to a receiver where the range codes are sequentially phase modulated on a subcarrier of frequency f.sub.sc by one of its own subharmonics as follows:C.sub.i = f.sub.sc .sym. f.sub.sc /2.sup.iand data is phase modulated on a selected ranging component, C.sub.i, where i is a number selected from the sequence 1, 2 . . . n in which the ranging components are transmitted. A range cleanup loop in a spacecraft locks the phase of a locally generated reference component C.sub.i to a received ranging component C.sub.i and retransmits the component to a ground station. When the inverse phase, C.sub.i , of a ranging component is received and detected, the cleanup loop is modified to demodulate phase modulated command symbols while continuing tracking the same ranging component C.sub.i.

Abstract: A thermionic converter unit for use in a nuclear reactor to generate current, which can be constructed at low cost and which efficiently utilizes the nuclear fuel. The reactor utilizes an array of thermionic emitters whose peripheries are fluted so that a bulge of one emitter interfits the depression of another, to permit compact mounting, each emitter having several fuel passages located in the bulged portions for holding nuclear fuel and having a central collector passage for holding a thermionic collector. The emitters are constructed of rods of tungsten containing a small amount of thorium oxide, the thorium oxide not only improving the machinability of the tungsten but making it an efficient emitter.

Abstract: A method and apparatus for producing intense, coherent, monochromatic light from a low temperature plasma are disclosed. The apparatus includes a housing for confining a gas at subatmospheric pressure and including a set of reflectors defining an optical cavity. At least one anode and cathode are positioned within the gas. First control means control the voltage applied to the anode and second control means independently control the temperature of the cathode. The pressure of the gas is controlled by a third control means. An intense monochromatic output is achieved by confining the gas in the housing at a controlled pre-determined reduced pressure, independently controlling the temperature of the electron emitting cathode and applying a predetermined controlled low voltage to the anode. An intermediate mode current is drawn from the cathode and produces in the confined gas, a region having a high density of metastable atomic states leading to a population inversion.

Abstract: A notch filter for the selective attenuation of a narrow band of frequencies out of a larger band wherein a helical resonator is connected to an input circuit and an output circuit through discrete and equal capacitors, and a resistor is connected between the input and the output circuits.