Abstract: Systems and methods for tracking objects in a field of view are disclosed. In one embodiment a method may include capturing, via a camera, a real-world object in the field of view; generating a first object data associating the real-world object with a first position of the real-world object in a real-world environment at a first time; generating a virtual object representative of the real-world object depicting the real-world object in the first position at the first time; generating a second object data associating the real-world object with a second position of the real-world object in the real-world environment at a second time, determining a displacement value of the real-world object between the first position and the second position, modifying the virtual object to include an indication that the real-world object has been displaced when the displacement value is greater than a threshold value.

Abstract: The invention includes systems and methods for melting materials to make glass and other materials subject to electric melting that improve the capacity of the melters and/or the melt quality and/or the melting costs and/or the life of tank melters. These systems and methods use one or more of boosting with one or more streams of super hot melt coming from one or more boosting melters, cooling one or more components of one or more of the melters normally cooled using water with a high temperature cooling fluid or fluid suspension and protecting the normally high wear areas of refractory linings by covering those high wear areas with one or more strips of a corrosion and oxidation resistant metal or alloy useful above 2400 degrees F.

Abstract: Provided are a silicon purification apparatus that uses a ring-shaped thermal-insulating lid, which can be replaced while heating a crucible, as a thermal-insulating means for keeping the surface of a silicon melt at a high temperature, and has a simple structure and is easy to produce, said silicon purification apparatus being capable of continuously processing several tens of portions of charged silicon with the crucible heated as is; a silicon purification method that makes use of the silicon purification apparatus; and a purification method.

Abstract: An apparatus for melting and refining a silica-based glass composition includes a vertical first reaction chamber having an input adjacent to a lower end for receiving glass-forming components. The glass-forming components are heated to elevated temperature during upward flow through the vertical first reaction chamber to form a glass precursor melt adjacent to an upper end of the vertical first reaction chamber. A vertical second reaction chamber has an input adjacent to an upper end and an output adjacent to a lower end for delivering glass melt. A cross passage connects the upper end of the vertical first reaction chamber to the upper end of the vertical second reaction chamber such that the precursor melt flows from the vertical first reaction chamber through the cross passage and then through the vertical second reaction chamber to homogenize the precursor melt.

Abstract: The present invention discloses an integrated glass including opposite outer and inner surfaces and a solid sculpted area formed either on the outer surface or the inner surface. The solid sculpted area includes a number of concave shapes or convex shapes which can be used to form letters, numbers or patterns for user decorating or identifying. Besides, a mold for fabricating the integrated glass, a method for making the integrated glass, and a touch sensor device with such integrated glass are also disclosed by the present invention.

Abstract: A system for making clipped thermoplastic yarns or filaments, such as chipped glass yarns, including at least a die co-operating with at least a cutting machine located in extension of each other. A mechanism sizes the yarns and/or filaments coming from the die. The system further includes at least one return mechanism and a floor. Further, a mechanism displaces and positions the cutting machine in at least two positions, the first position being beneath the floor and the second position being above the floor. A first opening is provided in the floor through which the cutting machine is moved.

Abstract: The invention relates to a method for changing glass compositions in continuously operated melting installations which has a significantly shortened melt changeover time and therefore lower costs and in which the glass quality is not adversely affected.

Abstract: Apparatus (26) and a method for forming heated glass sheets in a heated chamber (22) of a housing (20) includes an upper mold support assembly (28) for supporting an upper mold (38) within the heated chamber for cyclical vertical movement between upper and lower positions. A lower mold shuttle (50) supports a lower mold (36) for cyclical movement between an idle position horizontally spaced from the upper mold and a use position below the lower mold. The apparatus also includes a lower mold support assembly (60) to which the lower mold is cyclically transferred from the lower mold shuttle (50) to provide support thereof while permitting horizontal alignment with the upper mold upon each cycle of downward movement to form a heated glass sheet between the molds. The lower mold shuttle (50) is supported by vertically movable rollers (70) to provide the transfer between the lower mold shuttle and the lower mold support assembly (60).

Abstract: A fluid administration system for the operation of a cylinder and piston assembly for actuating mechanisms, mainly glassware forming and handling mechanisms, allowing rapid changing thereof, comprising: a passage network practiced at the cylinder cap, connected to the fluid admission and discharging passages of the centering ring, at the cylinder and at the support frame; and speed controlling valves, at the passage network of the cylinder cap, to control the velocity of discharging of fluid from the cylinder and piston assembly in its ascending and descending runs.

Abstract: A method and a machine for the production of hollow glassware articles, by the blow-and-blow, press-and-blow, press-and-blow paste mold and direct-press processes in a glassware forming machine including single or multiple machine sections each having single or multiple-cavity, comprising: forming a parison in an inverted orientation, into a blank mold and a first transferable and open-able neck ring mold held by an inverting apparatus having a first and a second diametrically opposed arms, each arm holding a transferable and open-able neck ring mold; inverting the parison held by the first transferable and open-able neck ring mold, by rotating the first arm 180° to an upright orientation at an intermediate station, while the second arm with a second transferable and open-able neck ring mold is simultaneously placed at the parison forming station; transferring the first transferable and open-able neck ring mold holding the parison in an upright orientation, from the intermediate station, to a blow mold st

Abstract: An article of relatively pure silica, and a furnace and method of producing the article. The article is produced by collecting molten silica particles in a refractory furnace in which at least a portion of the refractory has been exposed to a halogen-containing gas to react with contaminating metal ions in the refractory.

Abstract: A press bending station (12) for heated glass sheets includes a lower wheel bed (36) having a lower support (38) and wheel assemblies (40) with detachable connections (46) to a drive mechanism (48) of the lower support to provide rotational driving of a wheel (44) of each wheel assembly. An actuator (62) provides relative vertical movement that lifts a heated glass sheet received by the wheel bed (36) to provide press bending thereof between a lower press ring (52) and an upper press mold (58). The wheel bed (36) can have a curved shape or a flat shape. Connection and detachment of the wheel assemblies (40) facilitates switching from one production job to the next.

Abstract: A press bending station (12) for heated glass sheets includes a lower wheel bed (36) having a lower support (38) and wheel assemblies (40) with detachable connections (46) to a drive mechanism (48) of the lower support to provide rotational driving of a wheel (44) of each wheel assembly. An actuator (62) provides relative vertical movement that lifts a heated glass sheet received by the wheel bed (36) to provide press bending thereof between a lower press ring (52) and an upper press mold (58). The wheel bed (36) can have a curved shape or a flat shape. Connection and detachment of the wheel assemblies (40) facilitates switching from one production job to the next.

Abstract: A system and method of cooling glassware molds by directing liquid coolant to the blank or blow mold halves of a glassware forming machine through an enclosed pivotal rotary union-type structure. A coolant manifold is carried by each pivotal mold arm, and communicates with coolant inlet and outlet ports at the lower end of each mold part. The manifold is connected by a floating shaft seal and a rotary union assembly and a crank arm to a coolant source and coolant return in the section box of the associated machine section. Each pivotal connection—i.e., between the section box and the crank arm, between the crank arm and the rotary union assembly, and between the rotary union assembly and the floating shaft seal—comprises a bi-directional rotary union for feeding liquid coolant to the manifold and mold parts, and returning coolant from the manifold and mold parts.

Abstract: An I.S. machine is disclosed which has at least one section having a mold station wherein a glass forming operation is performed within a mold which includes an opposed pair of mold halves each of which has a blank diameter which can vary within a selected range and a planar surface to be clampingly engaged with the planar surface of the other mold half at a mold centerline. The section has a mold open and closed mechanism which includes a pair of opposed displaceable mold holders for holding one or a plurality of opposed pairs of mold halves, and a drive assembly for displacing the mold holders from a selected open position, the location of which is a direct function of the dimension of the blank diameter of the mold halves supported on the mold holders, to a closed position.

Abstract: The invention provides a method to transform large quantities of waste glass into useful ceramic products by a low-cost manufacturing process. The major steps of the method consist of dry preparation of glass powder, granulation with a non-aqueous organic binder system, dry pressing with adequate green strength, and firing at low temperatures. Water and clay are not required in the processing, which eliminates problems that were encountered in the past. Only one firing step is needed with a low peak firing temperature of about 750° C. The method conserves energy and natural resources compared to clay-based traditional ceramic manufacturing. High-quality impervious ceramic products with only a small amount of porosity can be produced by the invention.

Abstract: A mold half for mounting on a mold holder of a mold open and close mechanism of an I.S. machine. The mold holder includes an insert having a central locating lug on the top thereof and an annular front face. The insert also has an annular upwardly projecting rib, on either side of the lug, the outer surface thereof defining the top portion of the annular front face and inner surface thereof defining the front wall of corresponding annular groove segments. The mold half comprises a blank diameter portion, which can have a dimension within a predetermined dimensional range, to be located adjacent the annular front face of the insert proximate the lug and a two segment annular flange projecting outwardly from the blank diameter portion to be located on either side of the lug. Each of the annular flange segments includes a downwardly projecting annular lip segment for insertion into a corresponding annular groove segment on the insert.

Abstract: A common cage assembly for a mold for a glassware machine having a mold support member. The assembly further includes a first cage member and a second cage member. Each of the cage members is movably mounted adjacent to the mold support member. Each of the cage members has a mold receiving surface.

Abstract: A mold opening and closing mechanism for a section of an I.S. machine includes a mold carrier assembly and horizontal axially extending shafts. A housing supports these shafts for axial displacement and includes first and second vertically extending ducts which terminate at their tops with a sleeve. A manifold assembly includes a manifold including a plenum which overlies each of the mold halves. A spacer secured beneath said frame and having vertically extending holes communicates with the downwardly opening exit of the plenum for delivering cooling air from the plenum to the vertical cooling air passages of the mold halves. The manifold includes a pair of horizontally extending cylindrical inlet holes A pair of cylindrical tubes are received by the cylindrical holes and first and second elbows connect a second end of each of the cylindrical tubes to the sleeves so that cooling air from the ducts will be delivered to the pair of tubes.

Abstract: An I.S. Machine for making glass bottles, having a plurality of sections, each having a blank station for forming a parison. Each section has a section frame having a top surface, and a plunger mechanism including at least one plunger canister having a lower cylinder and an upper flange. A horizontal mounting plate having a top surface and vertical openings for receiving the lower cylinder of each of the plunger canisters is fixedly secured on the top surface of the section frame. The section frame top surface has vertical openings for receiving the lower cylinders of each of the plunger canisters and the flange of the plunger mechanism is secured to the top surface of the mounting plate.

Abstract: A method and system are described for controlling the delivery of vapor from a bubbler containing a supply of liquid through which a carrier gas is bubbled and from which bubbler vapors are delivered in a vapor stream entrained with the carrier gas. In general, the present invention involves utilizing the pressure of the vapor leaving the bubbler as the specific characteristic monitored and controlled to ensure that the concentration level of carrier gas to vapor is maintained at the desired level throughout the manufacturing process.The present invention involves introducing a concentration detector within the flow path of the bubbler vapors from the bubbler and having the output of the concentration detector input to a concentration controller. The concentration controller compares the concentration value received from the concentration detector to a desired concentration value determined for the system.

Abstract: Methods and apparatus for manufacturing silica crucibles 9 containing few, if any, white point defects. The white point defects are reduced by decreasing the amount of silica vapor condensing on electrodes 4,5,6 used in the manufacturing process. The silica vapor condensation is decreased by providing a flow of a protective or non-reactive gas or gas mixture through protective devices 11,12,13, over portions of the electrodes where the silica vapor would otherwise condense.

Abstract: A method for producing a high purity synthetic quartz powder, characterized by using a tetramethoxysilane having a trimethoxymethylsilane content of at most 0.3 wt %, and converting it to a synthetic quartz by a sol-gel method.

Abstract: The invention is used to manufacture an inhomogeneous medium whose porosity and permeability undergo rapid transitions from one point to another of its volume, by juxtaposing different materials without creating a barrier. Such a transition is made by juxtaposing a first material and a second material with a different porosity to the first. One of them can be a rock sample such as sandstone for example, the other can be a composite material obtained by agglomerating pyrex powder for example, the whole being heated according to a specific temperature cycle up to a temperature (TR) lower than the melting point of the two materials but sufficient to achieve partial melting of one of the materials at the interface with the other material, but without formation of a continuous or discontinuous capillary barrier between them, or an interzone with preferred passage for fluids. Thus, different composite materials can be juxtaposed to constitute the inhomogeneous medium.

Abstract: Apparatus (32) and a method for heated mold changing at a forming station (24) in a heated chamber (22) where heated glass sheets are cyclically formed. A switching station (318) is located adjacent the forming station (24). An unloading station (320) and a mold preheating station (322) are each located adjacent the switching station. An unloading cart (324) is initially movable from the loading station (320) to the switching station (318) and then to the forming station (24) to receive one or more heated molds from the forming station and is subsequently moved from the forming station back through the switching station to the unloading station to permit unloading of each heated mold. A loading cart supports a second mold or a pair of molds for heating within the mold preheating station (322) and is movable from the mold preheating station to the switching station (318) and then to the forming station for mold loading.

Abstract: A number of unique processes are disclosed for manufacture of sintered high-purity quartz glass products in which a shaped silica body or preform is made from an aqueous slurry of micronized silica particles by gel casting, slip casting or electrophoretic deposition. The silica particles may comprise a major portion by weight of crystalline silica. In one embodiment of the invention the sintered quartz glass is transparent, substantially bubble-free and suitable for scientific or optical uses. In another embodiment the porous silica preform is fired in steam to increase the hydroxyl content and then nitrided in a nitrogen-hydrogen reducing atmosphere. A minute amount of chemically-combined nitrogen in the high-purity quartz glass is sufficient to provide a tremendous improvement in physical properties and an incredible increase in the resistance to devitrification.

Abstract: The invention concerns a process for preparing glass, more specifically glass powder or glass films, together with a process for conditioning the raw materials intended for preparing glass characterized in that raw materials are converted to freely flowing powder suitable for feeding to a plasma torch in which the powder is converted to glass.

Abstract: Plural layers of metallic particle layers in which metallic particles having morphological anisotropy are dispersed and dielectric layers are alternately stacked on at least one pricipal surface of a substrate having transparency to form a polarizing layer. The content of the group 0 elements in the polarizing layer is kept not higher than 1.5.times.10.sup.20 molecules/cm.sup.3.

Abstract: Disclosed is a quartz glass product of enhanced opacity manufactured by fusion of silica particles, the opacity being enhanced by the reaction of an organosilicon additive in the course of the fusion process. A method of enhancing the opacity of a quart glass product by fusing silica particles in the presence of an organosilicon additive is also disclosed.

Abstract: An apparatus and method for the preferably continuous manufacture of foamed material using a furnace are provided. A two-part mold mechanism is provided that includes an upper portion and a lower portion that are each endless loops and cooperate with one another to form a closed mold within the furnace. The upper and lower portions can each comprise a plurality of transverse mold members that can be easily replaced or exchanged during operation of the apparatus. A feed mechanism is provided for introducing material that is to be foamed to the mold mechanism upstream of the furnace. Scrapers or the like can be provided downstream of the furnace to aid in separating and supporting foamed material from the mold mechanism.

Abstract: A method is provided for the manufacture of SiO.sub.2 granular material. Silicic acid is dispersed in a liquid to form a dispersion. The dispersion is stirred in a stirring tank with formation of a homogeneous liquid phase. The homogeneous liquid phase is maintained by stirring at a substantially constant rate until the granular mass develops, when the solids content of the dispersion is within the range of 65 to 80 weight percent. Moisture is gradually extracted to form a granular mass which is dried and sintered.

Abstract: Opaque quartz glass is provided which contains gas bubbles uniformly dispersed therein and is excellent in high-temperature viscosity and heat-insulating property. The opaque quartz glass has a defined apparent density, contains bubbles having a defined average bubble diameter in a defined amount, has a defined total bubble sectional area, generally exhibits a defined linear transmittance at a thickness of 1 mm or larger to projected light of a defined wavelength and contains nitrogen in a defined concentration. The opaque quartz glass is produced by a process comprising packing into a mold a powdery source material of powdery silica having a defined average particle diameter and powdery silicon nitride dispersed therein in a defined amount, heating the powdery source material to one of two first defined temperature ranges (both under vacuum) and further heating the source material up to a second temperature higher than the melting point and not higher than 1900.degree. C.

Abstract: A plunger base module for a selected number of vertically extending cylindrical plunger canisters each having a bottom surface and including a set of service conduits including plunger up, plunger down, and counterblow/vacuum or cooling, with each of the service conduits in a plunger canister having a selectively located inlet port communicating with the bottom surface of the plunger canister. The plunger base module includes a permanent plunger distribution base having a top surface and a plurality of sets of service conduits, each set including plunger up, plunger down, and counterblow/vacuum or cooling. Each plunger distribution base service conduit has an outlet port communicating with the top surface. A removable transition plate has a bottom surface for engaging the top surface of the plunger distribution base and a top surface.

Abstract: Fused silica boules (19) having improved off-axis homogeneity are produced by controlling the air flow around the boule (19) during its formation. The boule is formed in a containment vessel (13) which collects soot from a plurality of burners (14). The containment vessel (13) rotates and oscillates relative to the burners (14) as the boule (19) is formed. Surrounding the containment vessel (13) is an air flow wall (130) which oscillates with the containment vessel (13). The air flow wall (130) is spaced from the containment vessel (13) by a gap (175) through which air flows during boule formation. The dimensions of this gap (175) remain constant as the boule is formed. Surrounding the air flow wall (130) is a stationary wall (160). The stationary wall (160) is spaced from the air flow wall (130) by a gap (165) whose dimensions change as the boule is formed. A motion accommodating seal (155) blocks air flow in this gap (165).

Abstract: Quartz powder is fed into a rotating mold to form a crucible-like quartz powder layer body with the help of centrifugal force in the mold. The layer is melted by heating through the inner surface with an arc discharge to manufacture an outer crucible member. A hollow cylindrical inner crucible member having a beveled lower edge is welded to the outer crucible member while a temperature of the inner surface portion of the outer crucible member remains at 1400.degree. C. or higher by a remaining heat.

Abstract: The invention relates to a single crystal pulling apparatus comprising; an outer crucible 11 positioned inside a chamber (gas tight container) 2, for storing a semiconductor melt 21, and an inner crucible 30 comprising a cylindrical partition body, mounted inside the outer crucible 11 to form a double crucible, and wherein a single crystal of semiconductor 26 is pulled from the semiconductor melt 21 stored inside the inner crucible 30. With this arrangement, the inner crucible 30 is made from quartz and comprises an inside layer A, an outside layer C, and an intermediate layer B which lies between the inside layer A and the outside layer C, and the intermediate layer B is made from quartz with a larger gas bubble content than the quartz which makes up the inside layer A and the outside layer C of the inner crucible 30.

Abstract: An I.S. Machine for making glass bottles, having a plurality of sections, each having a blank station for forming a parison. Each section has a section frame having a top surface, and a plunger mechanism including at least one plunger canister having a lower cylinder and an upper flange. A horizontal mounting plate having a top surface and vertical openings for receiving the lower cylinder of each of the plunger canisters is fixedly secured on the top surface of the section frame. The section frame top surface has vertical openings for receiving the lower cylinders of each of the plunger canisters and the flange of the plunger mechanism is secured to the top surface of the mounting plate.

Abstract: A shaped body of amorphous silicon dioxide, which has a chemical purity of at least 99.9% and a cristobalite content of at most 1% and which is impermeable to gas, is known. To provide shaped bodies of amorphous silicon dioxide which have a high precision, which can be small or large in size and of simple to complicated shape, which have a chemical purity of at least 99.9%, are impermeable to gas above wall thicknesses of 1 mm, which have a high cold flexural strength, low thermal conductivity and low radiation of heat, which are thermal shock resistant and can be exposed repeatedly or also long-term to temperatures in the range from 1000.degree. to 1300.degree. C. and which can be welded in a sharply delineated manner without spreading joins and which have a low spectral transmission from the ultraviolet to the middle infrared spectral region, the shaped body is opaque, contains pores, at a wall thickness of 1 mm has a direct spectral transmission which is virtually constant in the wavelength range from .

Abstract: A porous body containing a silicon component as a starting material of optical element is immersed in a solution containing hydrofluoric acid, taken out from the solution and immersed in a solution containing a metal alkoxide containing a first metal component except silicon or a derivative thereof so that the porous body contains the first metal component in such a concentration gradient that the concentration of the first metal component decreases from a periphery of the porous body toward a center of the porous body. Hydrofluoric acid breaks glass bonds of the porous body, so that the concentration of the first metal component can be securely distributed in a desired gradient. Drying and sintering of the porous body enables producing, for example, a glass having a metal component concentration concavely distributed in its radial direction which is excellent in chromatic aberration suppressing capability.

Abstract: A metal such as Au and a dielectric such as borosilicate glass are simultaneously sputtered to form a film on a glass substrate. Next, this film is heated to grow metal particulates. Next, the substrate is drawn on heating to give an anisotropy to the metal particulates and produce a polarizer. The metal particulates are spheroidal and are dispersed almost homogeneously in the dielectric.

Abstract: A plunger mechanism has a plunger canister module to be mounted on the top wall of a section frame of an I.S. machine. The module includes one, two, three or four plunger canisters each having a vertically extending cylinder having a locating diameter at the top and a mounting flange secured to the top of the vertically extending cylinder. The module also includes a horizontal mounting plate adapted to be mounted on the top wall of the section having a top surface and a number of holes, corresponding to the number of plunger canisters, extending vertically therethrough for matingly receiving the locating diameter of each of the plunger canisters.

Abstract: A method and apparatus for making formed glass structures. A glass frit containing material is deposited within a recessed pattern, hardened in the recessed pattern, and transferred to a substrate. The method and apparatus of the invention are particularly useful for forming barrier rib structures for use in plasma display panels.

Abstract: A plunger mechanism comprising a vertically extending cylindrical plunger canister having a bottom surface and including a plurality of service air conduits with each conduit having an inlet port communicating with the bottom surface. A plunger distribution plate below said plunger canister having a top surface and including a corresponding plurality of service air conduits which are to be connected to the plunger canister service air conduits with each plunger distribution plate conduit having an outlet port communicating with the top surface. At least one outlet port of the plurality of service air conduits in the plunger distribution plate which are to be connected to the plunger canister service air conduits being axially offset from the corresponding inlet port of the plunger canister. A transition plate intermediate the plunger canister and the plunger distribution plate having a bottom surface for engaging the top surface of the plunger distribution plate and a top surface.

Abstract: A process for producing inorganic microspheres (solid spheres or hollow spheres), which comprises pulverizing a material by wet pulverization to an average particle size of at most 5 .mu.m to obtain a slurry of a pulverized powder material, spraying the slurry to form liquid droplets, and heating the liquid droplets to fuse or sinter the powder material to obtain inorganic microspheres.

Abstract: A composition for the formation of barrier ribs of a plasma display panel and a method for the formation of the barrier ribs are disclosed. The formation of barrier ribs is effected by applying either a composition comprising (A) a low-melting glass having a working point of not more than 560.degree. C.

Abstract: The present invention relates to a process of forming ceramic tiles having the appearance of tiles produced from clays. The process includes melting a material to form a glass melt, treating the glass melt to produce a solid glass product, grinding the solid glass product to produce glass particles having a particle size of less than 200 microns, mixing the glass particles with a first additive to form a glass powder mixture having a composition of 55 to 99 wt. % glass particles and 45-1 wt. % first additive, forming the glass powder mixture into tiles by dry pressing, where the tiles have a primary crystalline phase selected from the group consisting of nepheline, diopside, anorthite, wollastonite, melilite, merwinite, spinel, akermanite, gehlenite, crystalline phases based on iron substitutions in the crystalline phase, and mixtures thereof.

Abstract: A process for producing stained crystallized glass and its articles which is characterized in meeting production of various crystallized glass articles in small quantity. By this process, crystallized glass is obtained with patterns and colors alike to that of granites, marble, and other natural stones. The process of heat-treatment to a prepared batch compounded of crystallizable glass granules, color powder and water at a temperature higher than the softening point thereof results in fusion bonding of the glass granules. The color powder is compounded by inorganic pigment, suspension stabilizing agent, agglomerant, deflocculant agent, and crystallizable glass powder. The surface pattern is formed by grain boundary part of crystallizable glass granules, and part of the inorganic pigment in the color powder moving with the crystallizable glass powder.

Abstract: UV absorbing glass is prepared by mixing ultrafine colloidal cerium oxide with glass-forming substances during the fabrication of the glass. An aqueous colloidal dispersion containing 1-20 weight percent 10-20 nm cerium oxide particles, optionally including a binder, is admixed with silica sand, and the sand is dried, melted and cooled to give a relatively clear UV absorbing glass containing 0.3-2 weight percent cerium oxide.

Abstract: An alumina ceramic article and a method for preparing the article. The method comprises the steps of:(1) Compacting a mixture of a first concentration of particulate aluminum oxide sufficient to prevent retention of the zirconium oxide alloy particles in the surface in a predominantly tetragonal crystal structure and a second concentration of particulate zirconium oxide alloy. The zirconium oxide alloy is zirconium oxide and a secondary oxide selected from the group consisting of MgO, CaO, Y.sub.2 O.sub.3, Sc.sub.2 O.sub.3, CeO.sub.2, and rare earth oxides having a concentration of secondary oxide generally of about 0.5 to about 5 mole percent Y.sub.2 O.sub.3, from about 0.1 to about 1 mole percent MgO, from about 0.5 to about 15 mole percent CeO.sub.2, from about 0.5 to about 7.0 mole percent Sc.sub.2 O.sub.3, or from about 0.5 to about 5 mole percent CaO, relative to the total of the zirconium oxide alloy. The compacting results in the formation of a blank.

Abstract: A process for producing opaque silica glass in which a quartz raw material grain having a particle size of 10 to 350 .mu.m is filled into a heat resistant mold, the quartz raw material grain is heated in a non-oxidizing atmosphere from a room temperature up to a temperature lower by 50.degree. to 150.degree. C. than a temperature at which the above raw material grain is melted at a temperature-increase speed not exceeding 50.degree. C./minute, then, slowly heated up to a temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted at the speed of 10.degree. C./minute or less, and the heated quartz raw material grain is further maintained at the temperature higher by 10.degree. to 80.degree. C. than the temperature at which the quartz raw material grain is melted, followed by cooling down to the room temperature.