Abstract: A process for sealing of niobium-ceramic through-wall assemblies for ceramic or metal vessels for high temperature and high pressure or vacuum applications, for example an electrical feedthrough and sealable fill opening in an alumina arc tube for a high intensity discharge (HID) lamp. The process produces a fritless hermetic seal while maintaining the ductility of the niobium components. The niobium-ceramic through-wall assembly includes an axially bored alumina or yttria sealing means having a ductile niobium throughpiece close fitted to and extending through the bore. The throughpiece is preferably essentially pure niobium, but may contain up to about 2% zirconium. The assembly is fired at about 1400.degree.-2000.degree. C. in a pure oxygen- and hydrogen-free (<5 ppm each) inert, preferably flowing, atmosphere or vacuum for a time sufficient to form a hermetic seal between the throughpiece and the sealing means. The fired assembly is then cooled to below 250.degree. C.

Abstract: A semiconductor mesa structure is covered with a photoresist material in a localized flooding manner such that the photoresist material is thinner on the top of the mesas and also at the upper most portion of the sidewalls than at the base of the mesa and the intervening channel. The photoresist is then exposed through a mask in a manner so that when developed, the photoresist from the mesa top and upper most portion of the sidewall can be removed. When the photoresist is exposed to the actinic radiaction, the thinner photoresist is adequately exposed more rapidly than the thicker portion nearer the bottom of the mesa, if the mask does not adequately shield the actinic radiation from reaching it. Thus the alignment tolerance is greater than if the photoresist were of uniform thickness.

Abstract: A dense cermet article including about 80-95% by volume of a granular hard phase and about 5-20% by volume of a metal phase. The granular hard phase consists essentially of a ceramic material selected from the hard refractory carbides, nitrides, carbonitrides, oxycarbides, oxynitrides, carboxynitrides, and borides of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, boron, and mixtures thereof. The metal phase consists essentially of a combination of nickel and aluminum having a weight ratio of nickel to aluminum of from about 90:10 to about 70:30 and 0-5% by weight of an additive selected from the group consisting of titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, cobalt, boron, or carbon, or combinations thereof. In the preferred metal phase, an amount of about 15-80% by volume of the metal phase component exhibits a Ni.sub.3 Al ordered crystal structure.

Abstract: A phosphor having a continuous protective bi-layer coating of alumina surrounding silica surrounding the phosphor particles is disclosed. The method of making a bi-layer coating on phosphor particles is also disclosed. The first layer surrounding the phosphor is silica. The second layer surrounding the phosphor is alumina. The bi-layer phosphor is useful in fluorescent lamps providing improved maintenance and brightness. The bi-layer phosphor can also be used in high color rendition lamps employing blends of phosphors.

Abstract: A method for making essentially crack free large cross section ceramic articles by injection molding techniques comprises the use of from about 0.1 v/o to about 10 v/o fibers with the ceramic injection molding formulation followed by the injection molding, binder removal and densification steps to form an essentially crack free densified large cross section ceramic article. The fibers are softened prior to the onset of densification and incorporated into the ceramic intergranular phase. This process eliminates the component distortion during densification which would have occurred if the fibers remained in the component.

Abstract: The present disclosure describes a method for determining the condensate location within an HID lamp. The method involves monitoring current and voltage waveforms during the glow phase of lamp starting. If the voltage drop during the glow phase is low with a corresponding high current, then the volatile component of the lamp fill has condensed on the electrodes during the previous cool down period. If the voltage drop is high and current is low then most of the condensate has localized on the arc tube wall. An automated detection apparatus is used to carry out the measurements to determine condensate location.

Abstract: A method and apparatus for mixing ceramic powder and binder to form an injection molding formulation is disclosed. A container made of wear resistant plastic such as polytetrafluoroethylene, nylon or polyetheretherketone having an inner surface which forms a mixing cavity is used. A mixing ball having a radius of curvature less than the radius of curvature of the inner surface is added to the mixing cavity along with the ceramic powder and binder. The container is heated and shaken to form an injection molding formulation. In one embodiment the mixing ball is made of an outer plastic shell surrounding an inner metallic core. In an alternate embodiment, the mixing ball is made of the ceramic material being compounded.

Abstract: A semiconductor laser having a high modulation bandwidth is made by utilizing an InGaAsP cap layer and an InGaAsP active layer of different crystal structure. Channels are anisotropically etched through the cap, cladding and active layers and partially through the buffer layer. The active and cap layers a laterally etched and a semi-insulating material is overlaid the sidewalls. A further etching leaves a thin wall of the semi-insulating material surrounding the active layer. 1.3 .mu.m InGaAsP lasers with 3 dB bandwidths of 24 GHz and intrinsic resonance frequencies in excess of 22 GHz have been successfully fabricated. This is the highest bandwidth ever reported for a semiconductor laser, and the highest resonance frequency for InGaAsP lasers. Excellent modulation efficiencies are observed to high frequencies.

Abstract: Apparatus and method for determining the identity and concentration of one or more components in a test atmosphere having a known concentration of oxygen. A solid electrolyte oxygen sensor is used, having a first solid electrolyte wall in contact with, and interposed between, a first electrode and a second electrode and a second solid electrolyte wall in contact with, and interposed between a third electrode and a fourth electrode. The second and fourth electrodes are in communication with the test atmosphere. A partition wall separates the first and third electrodes forming a first chamber bounded by the first wall and the partition wall and a second chamber bounded by the partition wall and the second wall. Diffusion limiting means inhibit gas-flow of the gas from the test atmosphere to the first chamber and from the first chamber to the second chamber.

Abstract: A process is disclosed for coating phosphors with hydrolyzed alkylaluminum. The hydrolyzed alkylaluminum coating renders the phosphors insensitive to atmospheric moisture. the coating process involves vaporizing an aluminum-containing precursor such as trimethylaluminum or triethylaluminum in an inert gas stream and passing this through a fluidized bed containing the phosphor particles. Water vapor is also passed through the fluidized bed and the water and aluminum precursor react on the surface of the phosphor particles to form hydrolyzed trimethylaluminum or other alkylaluminum. The hydrolyzed trimethylaluminum or other alkylaluminum phosphors are particularly useful in electroluminescent lamps.

Abstract: A process for making a densified silicon nitride article utilizing polysilanes or polysilazanes as a binder is described. The process involves blending of a silicon nitride composition with a polysilane or a polysilazane to form a mixture. The mixture is molded into an article. The article is then pyrolyzed in a non-oxidizing atmosphere and at a temperature sufficient to form a pyrolyzed article comprising amorphous silicon nitride and silicon carbide. The article is then sintered at a temperature equal to or greater than 1400.degree. C. to form a densified silicon nitride article.

Abstract: The present invention describes a technique for sample preparation and analysis of ceramics and oxides. The technique involves mixing the ceramic or oxide powder with a conducting powder such as gallium, indium or silver and adding a small amount of dopant. The dopant comprises approximately 5-30% by weight of the sample and is selected from the group comprising thoria, yttria or ytterbia. It is theorized that the addition of the dopant provides a source of electrons that stabilizes the plasma in the glow discharge mass spectrometer which allows for impurity analysis in the part-per-million range.

Abstract: Composite articles, cutting tools and wear parts are prepared by densification of a mixture comprising whiskers, fibers, or particles of hard refractory transition metal carbides, nitrides or carbonitrides uniformly distributed in a titanium diboride matrix. Optionally, other dispersoids may also be incorporated. The preferred composite article or cutting tool has a fracture toughness equal to or greater than about 2.5 MN.multidot.m.sup.1/2. Methods of preparation and use are also disclosed.

Abstract: Heteroepitaxial semiconductor structures of, for example, GaAs on InP or Si. The epitaxially grown GaAs is in the form of individual spaced-apart islands having maximum dimensions in the plane of the surface of the substrate of no greater than 10 micrometers. In islands of this size stress in the plane of the epitaxially grown layers due to mismatch of the coefficients of thermal expansion of the substrate and epitaxially grown materials is insignificant.

Abstract: A method of passively aligning optical receiving elements such as fibers to the active elements of a light generating chip includes the steps of forming two front and one side pedestal structures on the surface of a substrate body, defining a vertical sidewall of the chip to form a mating channel having an edge at a predetermined distance from the first active element, mounting the chip epi-side down on the substrate surface, and positioning the fibers in fiber-receiving channels to that a center line of each fiber is aligned to a center line of a respective active element. When mounted, the front face of the chip is abutting the contact surfaces of the two front pedestals, and the defined sidewall of the mating channel is abutting the contact surface of the side pedestal. The passive alignment procedure is also effective in aligning a single fiber to a single active element.

Abstract: An electrodeless lamp may be formed with a capsule having a radiant energy transmissive material defining an approximately cylindrical enclosed volume having an external length less than 20.0 millimeters, and an outer diameter less than 8.0 millimeters. The enclosed volume is filled with a lamp fill excitable by a high frequency electromagnetic field to produce radiant energy. The small size capsule produces a particularly efficient, orientation tolerant arc discharge. The arc is then highly stable as to position, yielding a good optical source to design for. The temperature gradient is small, thereby yielding little thermal stress on the capsule. An electrodeless HID headlamp system may be formed with the efficient capsule from a radio frequency source operating from a the power supply of a typical automobile. The headlamp system includes a high frequency power source, a transmission line, a coupler, an excitable lamp fill captured in a lamp capsule, a reflector and a lens.

Abstract: A monolithically integrated optical preamplifier comprises an amplifying region, an optical detection region for detecting amplified light, and an optically transparent and electrically insulating isolation region interposed between the amplifying and optical detection regions. The amplifying region achieves reduced facet reflectivity by being designed to have a large spot size, single-traverse mode waveguide amplifier oriented at an angle with respect to a crystal plane through the preamplifier. The isolation region is preferably an air gap.

Abstract: An adaptive vector quantization scheme suitable for packet video adapts to the varying characteristics of the actual images sequence being compressed. A large code book is divided into two sections, having higher and lower priority, representing common characteristics and specific characteristics of images. Each new image to be coded is first compared to the common characteristics section of the code book. If a match of acceptable quality is not found, then it is compared to the specific characteristics section. The best match of the two sections is utilized. Entries in the two sections are reorganized and/or exchanged as a function of the usage of the code vectors therein. The rate and extent of adaptation is dictated by the update interval and the desired level of quality, respectively, without requiring any transmission of the vectors themselves or the side information.

Abstract: In fabricating a junction field effect transistor, specifically a static induction transistor, an epitaxial layer of high resistivity N-type silicon is grown on a substrate of low resistivity silicon. The surface of the epitaxial layer is marked in a pattern to expose a plurality of elongated surface areas. The wafer is subjected to reactive ion etchings in SiCl.sub.4 and Cl.sub.2 and subsequently in Cl.sub.2 to form parallel grooves with rounded intersection between the wide walls and bottoms of the grooves. Ridges of silicon are interposed between grooves. A layer of silicon oxide is grown on all the silicon surfaces. The grooves are filled with deposited silicon oxide and silicon oxide is removed to form a planar surface with the upper surfaces of the ridges.

Abstract: A vector quantization based image compression technique which exploits inter-block correlation and layered addressing structure to form variable block sizes. Without introducing any quality degradation, when compared to the traditional vector quantization algorithms, the invention described herein significantly increases the compression and reduces the bit rate. The concept of inter-block correlation is utilized to form variable size blocks, which are then coded using a hierarchical coding model. The method is based on starting off from a small basic block which is allowed to grow to a maximum of a preset block size as long as certain conditions are met. The basic idea of growing the block is based on the renormalization group theory in physics. The algorithm utilizes only one pixel code book for the basic block size and several address code books for the layer block sizes to encode an image. S/N ratio in excess of 30 dB at bit rates lower than 0.2 bpp are easily obtained.