Formation Reaction of ZrO2 Scatterers in ZrF4-Based Fluoride Fibers

This paper clarifies the formation reaction of ZrO₂ crystals which appear as extrinsic scatterers in fluoride fibers. EPMA analysis indicates that BaO exists at grain boundaries of BaF₂ purified by sublimation. BaO reacts with ZrF₄ to form ZrO₂ at 600°C during a glass-melting process. The ZrO₂ formation reaction is influenced by H₂O. Ba(OH)₂, which is formed by the reaction between BaO and water vapor, melts at 370° to 420°C and reacts with ZrF₄ to form ZrO₂ at 450° to 520°C. When low-oxide-content BaF₂ is used for fiber preparation, scatterers significantly decrease.     

Controlled Crystallization of Amorphous Si3N4by Ti and CI Additives

Thin films of amorphous Si₃N₄ were prepared by the rf-sputtering method, and the effects of titanium and chlorine additives on its crystallization were examined. When Ti-doped amorphous Si₃N₄ was heated, TiN precipitated at >1100°C; the TiN precipitates promoted the conversion of amorphous Si₃N₄ to β-Si₃N₄. Chlorine led to preferential conversion of amorphous Si₃N₄ to α-Si₃N₄.     

Development of High‐Power Density Interleaved dc/dc Converter with SiC Devices

We developed an interleaved dc/dc converter with SiC devices. We applied full‐SiC modules including MOSFETs and SBDs to the interleaved dc/dc converter to achieve a high‐power density. An SiC has a high temperature resistance, which facilitates an improvement in high‐frequency drives. We achieved a high‐power density by utilizing this high temperature resistance. We also fabricated a prototype and tested it with loads up to 65 kW.     

PRESENT STATUS OF POWDER TECHNOLOGY EDUCATIONAL PROGRAMS AND RESEARCHES IN JAPAN

Tables to indicate the present status of powder technology educational programs in Japan are presented on the basis of a questionnaire style investigation by the Society of Powder Technology, Japan. Research activities in universities and research institutes are also included in the tables.

The activities of both the Society of Powder Technology and the Association of Powder Process Industry and Engineering in Japan are also introduced by explaining their organizations and annual events.     

Spectral Variation of SKβ Emission with Sulfur Content in As-S Glasses

The bonding and chemical state of sulfur in binary As-S glasses were investigated by determining the S Kβ spectra with a vacuum 2-crystal X-ray spectrometer equipped with Ge(ll1) crystal analyzers. For glasses with sulfur contents <60 at.%, the spectra were similar to those of realgar (crystalline As₄S₄) and orpiment (crystalline As₂S₃); the profile of the SKβ spectrum did not change when half the sulfur was replaced by selenium. For sulfur contents > 60 at.%, the spectra became progressively similar to that of elemental sulfur with increasing sulfur content. It was found that S-S bonding occurs in the high-sulfur glasses.     

FLOW PATTERNS THROUGH TUBE BUNDLES AND PARTICULATE FOULING ONTO CYLINDERS

ABSTRACT

The shear-stress distributions around cylinders in tube bundles were measured by means of the limiting current method and the flow inside the bundle was also visualized. In the case of the staggered bundle, the shear-stress distributions had two peaks by the effect of the jet streams generated at the front row spacing and the adjacent cylinder. While in the bundle with in-line arrangement, the front stagnant point was shifted about 30° downward and the traverse streams among the rows were observed. This traverse streams caused asymmetry of the shear-stress distributions with respect to the main flow axis.

These results were discussed in connection with the fouling experiments investigated in dusty air. Particle deposition around cylinders could be qualitatively predicted from the shear-stress distributions, namely particles tend to deposit at positions where are less shear-stress in both tube arrangements. The size of particle deposited on the wake zone was coarser than that near the stagnant point behind the third row in both arrangements.     

An Origami Playing Simulator in the Virtual Space

A virtual manipulation system for origami (paper folding) is described. A piece of paper defined in a computer can be deformed interactively by picking and moving a corner vertex of a paper face on a graphic screen using a mouse. Three kinds of folding operations and a curving operation transform the paper into a three-dimensional figure made of flat or curved surfaces. The roundness of the curved surfaces is calculated in real-time by minimizing an elastic energy function. The simulated paper has traditional Japanese decoration applied as a texture to give a more realistic appearance. It is rendered with shading in real-time.     

Influence of Temperature and Humidity on Dynamic Fatigue of Optical Fibers

The influence of temperature and humidity on dynamic fatigue characteristics of silicone resin-coated optical glass fibers is examined. Dynamic fatigue is shown to result from subcritical crack growth. Test results verify that subcritical crack growth during dynamic loading is a thermally activated process and that the effect of humidity on crack growth is a function of water vapor pressure.     

Crack Growth in Silica Glass Under Dynamic Loading

A dynamic loading test at a slow strain rate was made to examine the stable crack-growth process in silica glass under several environmental conditions. The temperature and humidity influence on the crack-growth process was investigated in detail. Test results show that the transition from region I to region II occurs at a constant stress intensity factor, K , independent of temperature and humidity. The transition K value was determined to be 0.61 MPa.m^1/2. Furthermore, it is clear that the crack-growth rate is dependent on K , even in region II.     

Preparation of Submicrometer A12O3 Powder by Gas-Phase Oxidation of Tris (acetylacetonato) aluminum (111)

Fine A1₂O₃ powder was prepared by the gas-phase oxidation of aluminum acetyl-acetonate. The reaction products were amorphous material at 600° and 800°C, γ-Al₂O₃ at 1000° and 1200°C, and δ-Al₂O₃ at 1400°C. The powders consisted of spherical particles from 10 to 80 nm in diameter; particle size increased with increasing reaction temperature and concentration of chelate in the gas.