Abstract: An electromagnetic transducer is provided which transmits and receives ultrasonic waves from a metallic part predominately in only one direction. At least two rows of permanent magnets are placed adjacent each other in a side-by-side relation. The N-S axes of the magnets are substantially parallel and adjacent magnets in each row have opposite polarity so that two periodic magnetic fields are created. The adjacent magnets are off-set by one-fourth period. Coils wrapped around each row of magnets are driven in phase quadrature in order to generate a unidirectional elastic wave in the metallic part. In another embodiment, sets of three rows of magnets are offset by one-sixth period and driven in 60.degree. phase shift.

Abstract: A predominately .alpha.-phase titanium base alloy having good high temperature creep strength. The alloy has about 8% aluminum to promote a strengthening .alpha..sub.2 precipitate, and about 5% columbium to ductilize the .alpha..sub.2 precipitate. Additionally, the alloy has about 5% zirconium, up to 0.5% silicon, up to 2% tin, and up to about 1.5% molybdenum.

Abstract: A solar cell is constructed by coating an n-type conductivity semiconductor with a thin layer of bromine doped, polymeric sulfur-nitride, (SNBr.sub.0.4).sub.x. Metal deposits are provided on both materials for making electrical contact to the cell. In a preferred embodiment, the semiconductor is silicon. In a second preferred embodiment, the semiconductor is GaAs on an n.sup.+ -type conductivity GaAs substrate.

Abstract: The flowmeter is basically a curved rotameter, having a tapered conduit which is curved in the vertical plane. Inlet and outlet plenum chambers are provided for passing the fluid through the curved rotameter. A ball is positioned within the curved rotameter so that it can move up the conduit under the influence of the stream of fluid. A differential pressure sensor (which may be mounted on a partition separating the plenum chambers) determines the pressure differential between both sides of the ball. This pressure differential is an indication of the rate of flow of fluid through the meter. In a preferred embodiment, two conduits with opposed curves are used to compensate for variations in vertical alignment of the flowmeter.

Abstract: A method is provided for imparting a fine grain structure to aluminum alloys which have precipitating constituents. The alloy is first heated to a solid solution temperature to dissolve the precipitating constituents in the alloy. The alloy is then cooled, preferably by water quenching, to below the solution temperature and then overaged to form precipitates by heating it above the precipitation hardening temperature for the alloy but below its solution treating temperature. Strain energy is introduced into the alloy by plastically deforming it in a temperature range of 380.degree. F. to 450.degree. F. to reduce its cross-sectional area a total of 40% minimum, at least 25% of the reduction in area being accomplished in a single continuous deformation operation. The alloy is then subsequently held at a recrystallization temperature so that new grains are nucleated by the overaged precipitates and the development of these grains results in a fine grain structure.

Abstract: A cell is provided which utilizes the electrochemical permeation technique to determine the hydrogen content of a metal. The working face of the cell has an opening into a cavity within the cell. A sponge for holding electrolyte fits in the cavity and an anode extends into the cavity. A contact is provided on the working face for contacting the metal being measured. When the cell is held against the metal being measured by the magnet which encloses the cell, a current caused by the oxidation of hydrogen permeating from the metal flows between the anode and the contact electrode. A circuit is provided to measure this hydrogen oxidation current and to calculate the hydrogen content based upon diffusion equations. A seal formed around the opening prevents leakage of electrolyte during the measurement and defines the area being measured.

Abstract: Disclosed is an electromagnetic acoustic transducer for generating and detecting an elliptically polarized ultrasonic wave in an electrically conductive material. The transducer includes a row of uniformly sized, adjacent, alternately oriented permanent magnets, which establish a periodic magnetic field. Coaxially wound around the row is a first coil for inducing an alternating current perpendicular to the field and perpendicular to the periodic direction, while a second coil is wound around the coil orthogonal to the first coil to induce an alternating current perpendicular to the field and parallel to the periodic direction. An ultrasonic ellipsometer includes such a dual coil transmitting transducer for generating an elliptically polarized wave and a dual coil receiving transducer for detecting the wave after it has propagated through an electrically conductive medium.

Abstract: A plurality of metal deposits are formed on the insulated surface of a semiconductive material to create an array of capacitive photodetectors. A plurality of metal columns connect the metal deposit of each photodetector to a corresponding metal deposit on the insulated surface of a silicon charge-coupled device (CCD). In this manner, the voltage signal generated in each photodetector is capacitively coupled to the charge-coupled device. The metal deposit on the CCD forms a gate for a fill/spill circuit which provides the input to the charge-coupled device. In a preferred embodiment, a bi-polar fill/spill circuit is used to provide an input to the CCD which is proportional to the change in voltage of a photodetector during a predetermined clocking period.

Abstract: A method and an apparatus are provided for ultrasonically inspecting a cylindrical object. The object is placed between the poles of a magnet to create a circumferential magnetic field in the object. A group of electromagnetic transducers (EMAT's) are placed adjacent the material so that the transducers scan the entire object when it is rotated. When an RF signal is applied to the transducers, elastic waves are generated in the material. These elastic waves reflect from defects in the material and these reflections are received by the transducers.

Abstract: A low-leakage, heterojunction photodiode for use as a detector sensitive to infrared radiation is provided. The diode structure comprises a PbTe substrate of n-type conductivity with an n-type epitaxial buffer layer on the substrate and an epitaxial active layer on the buffer layer. The buffer layer is either Pb.sub.(1-x) S.sub.x Te or Pb.sub.1-x Se.sub.x Te with the atomic fraction of S or Se, x, being greater than 0 but less than 0.1. The active layer is Pb.sub.1-y Sn.sub.y Te with the atomic fraction of Sn, y, being greater than 0 but less than 0.3. There is a p-n junction created in the active layer with the n side of the junction being adjacent the buffer layer. Metal is deposited on the substrate and on the active layer to provide electrical contact to the diode.

Abstract: A method and apparatus are provided for automatically controlling the strain rate during superplastic forming of a blank of material into a part. The method and apparatus produce a part in a minimum time by deforming the material in its optimum superplastic conditions. A relationship is determined between time and the pressure required to form the blank against the configured surface of a die at a strain rate which causes the blank to flow superplastically. The blank is positioned in the die and held at a temperature at which the material exhibits superplasticity. Pressure is automatically applied across the thickness of the blank in accordance with the previously determined relationship between time and pressure until the part is formed. The apparatus comprises conduits connected to a die and to a high pressure gas. Valves in the conduits regulate the pressure applied to the blank. A controller receives command signals from a programmer which is programmed with the desired time vs pressure relationship.

Abstract: Articles made from Si.sub.3 N.sub.4 ceramic alloy powders are protected during heating by loosely packing them in Si.sub.3 N.sub.4 before heating. Compacts made from Si.sub.3 N.sub.4 ceramic alloys are protected from both oxidation and from volatilization by the encompassing powder even though the furnace atmosphere is air.

Abstract: A method is disclosed for capless annealing compound semiconductors such as ion-implanted GaAs semiconductors. The surface of the semiconductor to be protected during annealing is placed in loose physical contact with an inert material such as powdered graphite. The assembly is placed in a controlled atmosphere and heated to the annealing temperature where it is maintained until annealed. The semiconductor is cooled and then removed from the controlled atmosphere and inert material. In one embodiment, a volatile one of the elements in the compound is introduced into the inert material.

Abstract: An improved input circuit is provided for an array of photo detectors. For each photo detector in the array, the circuit utilizes a first FET with a source for coupling to an output of a photo detector, a gate coupled to a first gate voltage, and a drain for coupling to an output circuit. The first gate voltage is provided by a feedback circuit which utilizes matched properties of adjacent FETs. In one embodiment, FETs are used in an open loop feedback circuit to reduce the input impedance seen by the photodiode at the source of the first FET. A similar objective is accomplished in another embodiment utilizing FETs in a closed loop feedback circuit. Further embodiments utilize FETs arranged as a differential amplifier with active loads to provide a low input impedance and a virtual ground at the source of the first FET.

Abstract: Electronically excited nitrogen fluoride is formed by reacting fluorine atoms with azide radicals according to the reaction:F+N.sub.3 .fwdarw.NF*+N.sub.2.in a preferred embodiment, the azide radical is provided by using HN.sub.3, and the atomic F is formed by discharging microwaves through either F.sub.2 or CF.sub.4, or by thermally decomposing F.sub.2.

Abstract: Semi-insulating GaAs material is qualified for ion implantation by taking a sample or samples from the material to be evaluated, polishing a surface of the sample, and chemically etching the surface to remove mechanical damage. The surface is bombarded with ions of an inert gas such as krypton, helium, argon, neon, or xenon. After bombardment, the sample is annealed and the sheet resistance is measured to determine if it meets a predetermined acceptable value.

Abstract: A working electrode is swept through a voltammetric cycle, including a metal plating range and a metal stripping range, for at least two baths of known plating quality and a bath whose quality is to be evaluated. The current utilized during the metal stripping range is correlated to the quality of the baths of known quality. The current utilized to strip the metal in the bath of unknown quality is compared to the correlation and its quality evaluated. In a preferred embodiment, an inert working electrode is swept by a function generator through the voltammetric cycle. A counter electrode immersed in the plating bath is coupled in series with the function generator and a coulometer to measure the charge during the metal stripping portion of the cycle.

Abstract: A magnet is used to create a static magnetic field adjacent to the surface of a conductive material. At least one conductor runs through the magnetic field. When a pulse of current flows through the conductor, an elastic wave is generated in the material. In a preferred embodiment, a row of individual permanent magnets is used to create a periodic magnetic field. One side of a coil is placed in the periodic magnetic field so that a sheet of current moves transverse to the magnetic field when a pulse of current flows through the coil. When the coil is oriented parallel to the row of magnets, a horizontal shear wave is generated in the material. When the coil is oriented transverse to the row of magnets, a Lamb wave is generated in the material.

Abstract: A sealing material for use in contact with animal tissue such as for sealing a stoma opening. The material is a thermoplastic elastomer made by mixing: (1) at least one part of a high molecular weight, nonvolatile oil with (2) a block copolymer having non-elastomeric thermoplastic end blocks and an elastomeric intermediate block which form separate phases. In one embodiment, the end blocks are polystyrene, the intermediate block is either butadiene or isoprene polymer, and the oil is a hydrocarbon oil. In another embodiment, the end blocks are polyalphamethylstyrene, the intermediate block is polydimethylsiloxane, and the oil is a silicone oil.