Pixel-selected ray tracing

An acceleration method based on an idea that T. Whitted (Commun. ACM, vol.23, no.6 pp.343-349, June 1980) presented on ray tracing is discussed. He proposed making antialiased images by hierarchical adaptive oversampling. The present authors use hierarchical adaptive undersampling to reduce the number of pixels whose intensity must be calculated by ray tracing. To implement pixel-selected ray tracing (PSRT), homogeneous regions in images must first be found. Generally, adaptive undersampling can result in some image-quality defects, because small objects and parts of thin or wedge-shaped objects may disappear when they are located between the initially sampled pixels. PSRT has an improved algorithm that uses pixels with the correct object information from among the sampled pixels to find pixels with erroneous color and correct them. Moreover, PRST uses ray-object intersection trees for precise classification of the homogeneity of regions and for fast intensity calculation in homogeneous regions. Experimental results are presented. They show that PSRT is two to nine times faster than standard ray tracing     

Interfacial Reactions between Sapphire and Silver—Copper—Titanium Thin Film Filler Metal

Wetting and brazing studies of sputtering-deposited, submicrometer thin film filler metal in an Ag—Cu—Ti/Al₂O₃ system were performed. The interfacial reaction layer between the filler metal and Al₂O₃ was investigated. It is possible to make a brazing joint even with a reaction layer of less than 100 nm thickness. Different types of interfacial reaction layers were observed when the Ti content in the filler metal was varied. The Cu—Ti—O system compounds were observed in the samples with high wetting capabilities, but not in the sample with low wetting characteristics. It was found that these compounds are substances that promote effective brazing.     

Evaluation of absorption of micro-droplets on paper for creation of paper-based microstructures

This study clarifies the absorption behavior of micro-droplets of water on treated paper to support the design of functional microstructures, such as electronics and micro-fluid channels, on paper. The period of time between when a micro-droplet of water ejected from an ink-jet head lands on the paper’s surface and its complete disappearance by absorption was defined as the micro-sizing degree (MSD), and an MSD measurement method was established. The MSD was evaluated using microscopic high-speed video images of the side view recorded every millisecond. Several grades of commercially available ink-jet paper media and laboratory sheets having different levels of water repellency prepared from a pulp and a sizing agent were examined. The MSD of commercial ink-jet papers, which are known to absorb water very quickly, was 3–6 ms. Weakly sized laboratory sheets exhibited a lower MSD of 2–3 ms. The absorption behavior was analyzed in terms of the capillary pressure with and without the Laplace pressure; the theoretical and experimental results agreed moderately well. The results indicated that the Laplace pressure cannot be neglected in the analysis. The MSD of a wet surface where a preceding micro-droplet had already landed was higher than that on a dry or partially wet surface, presumably because water remains inside pores for an unexpectedly long time.     

Oxygen-permselectivity in new type polyorganosiloxanes with carboxyl group on the side chain

Summary Oxygen-permselectivity through polyorganosiloxanes with carboxyl group on the side chain is discussed in terms of the differences between the O₂, N₂ diffusion coefficients or their solubility coefficients. The oxygen-selectivity increases from 2 to 5 with the increase in the carboxyl component of the side chain. Especially the selectivity in the diffusion coefficient is found to more contribute to the oxygenpermselectivity in comparison with that of the solubility coefficient. But the permeation coefficient decreases with the permselectivity.This work was partially supported by a Grand-in-Aid from the Ministry of Education, Science and Culture, Japan.     

Environmental effect on mechanical properties of recrystallized L12-type Ni3(Si,Ti) intermetallics

The environmental effect on the mechanical properties of boron-doped and undoped Ni₃(Si, Ti) polycrystals was investigated by tensile testing in air from room temperature to 1073 K, and the results were compared with those obtained previously by tensile testing in vacuum. The environmental effect for the Ni₃(Si, Ti) alloys was significant at ambient temperatures whereas that for the boron-doped Ni₃(Si, Ti) alloys was considerable at elevated temperatures. When these samples at associated temperatures were tensile tested in air and also at low strain rate, intergranular fracture was dominant. It was suggested that the environmental embrittlements at low and high temperatures were due to hydrogen and oxygen absorbed from the air, respectively, and were caused by the weakening of the grain-boundary cohesion. It was proposed that boron competing with hydrogen, for site occupation or for its effectiveness at grain boundaries, has the effect of suppressing hydrogen embrittlement, whereas it was suggested that the low-melting phases, consisting of boron and oxygen (and/or constituent atoms), may be responsible for the ductility loss in the boron-doped Ni₃(Si, Ti) alloys.