Load balancing strategies for a parallel ray-tracing system based on constant subdivision

Static and dynamic load balancing strategies for a multiprocessor system for a ray tracing algorithm based on constant subdivision are presented. An object space is divided into regular cubes (subspaces), whose boundary planes are perpendicular to the coordinate axes, and these are allocated to the processors in the system. Here, load balancing among the processors is the most important problem. Firstly, in a category of static load balancing, strategies for mapping the subspaces into the processors are evaluated by simulation. Moreover, we propose a hierarchical multiprocessor system in order to realize dynamic load balancing with the static one. Its architecture can overcome the limitation of the static load balancing in a large scale multiprocessor system.     

Stable range of copper molybdenum sulfide CuxMo6S8−y and measurement of the superconducting critical temperature Tc

Copper molybdenum sulfides CuxMo₆S_8?y with rhomobhedral structure have been prepared by vacuum seal technique at 1000°C. The nonstoichiometric range of copper x varies between 2.0 and 4.0, and that of sulfur (8?y) varies between 7.75 and 8.00. The compositional dependence of the lattice parameters a_R and α_R, and that of the super-conducting critical temperature Tc have been examined. Both a_R and α_R remarkably increase with increment of copper content but they are almost independent of sulfur content. Tc is about 10K at both x = 2.0 and 2.5, and about 6K and 7K at x = 3.0 and 3.5, respectively but it varies only a little with variation of sulfur content. Copper content may affect Tc but the compositional change in sulfur has very little effect on Tc.     

Tribological Characteristics of α-Alumina in High-Temperature Water

The effects of temperature, sliding speed, and contact load on the tribological behavior of an α-alumina ceramic sliding on the same material in water were investigated in the range from room temperature to 300°C under the corresponding saturated vapor pressures. The specific wear rate increased remarkably at elevated temperatures. The primary wear mechanisms in high-temperature water are considered to be microfracture, promoted by the solution of grain boundary layers, and stress corrosion cracking. A film containing γ-alumina particulates appeared on the worn surface with increasing sliding speed and increasing contact load in 300°C water.     

After-ripening of fruits adjusted by ethylene-generating agents

A simple way of after-ripening for pears and kiwi fruits was studied using ethylene-generating agents and films for packaging. A method that requires no special facility or apparatus. For the generation of ethylene, two agents were used with different gas-generating characteristics (A, zeolite; B, powder ethanol with catalyser), and the fruits were packaged either in a 20-kg harvesting container or a unit pack of 3.5 kg each. In the combination of agent A and the harvesting container, pears were treated with ethylene for 2 days (C₂H₄, 3250 or 1700 ppm), and kiwi fruits for one day (C₂H₄. 2050 or 750 ppm). Thus the treated fruits were ripened faster than those untreated, i.e. about 10 days earlier for the pears and 40–50 days earlier for the kiwi fruits. Using Agent B, kiwi fruits were stored/packaged in EVA30 and PE30 films (C₂H₄, 350 or 30 ppm). The fruits were ripened in several days, but gas damage was evident in the PE30 packagings. In addition, changes in fruit respiration were studied, and the effects of treatment with ethylene also were confirmed from the physiological point of view.     

The neutron irradiation effect on mechanical properties of HIP joint material

Dispersion strengthened copper (DSCu) and stainless steel are the candidate material for the heat sink and the structural material of the ITER shielding blanket and these materials are joined by hot isostatic pressing (HIP). In this study, the neutron irradiation effect on mechanical properties of HIP joint material was examined by tensile and impact tests using specimens with irradiation damage of about 1.5 dpa. The results of tensile tests show that tensile strength of HIP joint material was about the same as that of DSCu base material, and this trend did not change after neutron irradiation. On the other hand, the impact value of HIP joint material was smaller than that of DSCu base material because of the diffusion of main elements at joint boundary. It was shown that embrittlement by the neutron irradiation effect is smaller than that of the effect by HIP joint.     

A PWM rectifier/inverter system capable of suppressing both harmonics and EMI

This paper proposes a new PWM rectifier/inverter system that is capable of suppressing not only supply harmonic currents but also electromagnetic interference (EMI). The conversion system consists of a PWM rectifier and inverter, and an active common‐noise canceler (ACC) which has been proposed by the authors. The ACC developed for this system is characterized by the sophisticated connection of a common mode transformer which can compensate for common mode voltages produced by both the PWM rectifier and inverter. As a result, the size of the common mode transformer can be reduced to one‐third, compared with the previously proposed ACC. A prototype PWM rectifier/inverter system (2.2 kW) has been implemented and tested. Some experimental results show reduction characteristics of the supply harmonic current and EMI. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 59–68, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10062     

Fibrous polyaniline as positive active material in lithium secondary batteries

Fibrous polyaniline (f-PANI) has displayed a maximum discharge capacity of 164 A h kg⁻¹, a low rate of self-discharge, and a long life as a positive active material in a secondary lithium battery.     

Significant effect of thermal stresses on fatigue crack propagation properties

Fatigue crack propagation properties of low-alloy ferritic steel were investigated using 50-mm-wide compact-type (CT) specimens and 200-mm-wide center-cracked-type (CCT) specimens at room temperature and 300°C. Most of the stress ratios were nearly equal to zero. Significant differences in fatigue crack propagation rate in the CCT specimen, which was heated to the test temperature only locally near the crack plane, were compared with the rates for the CT specimen which was enclosed completely by a furnace. It was found that the differences were related to the compressive stresses arising from the thermal gradients.

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Résumé On étudie les propriétés de propagation des fissures de fatigue dans un acier ferritique faiblement allié à l'aide d'éprouvettes de traction compactes CT longues de 50 mm et d'éprouvettes de traction à fissure centrale (CCT) longues de 200 mm, à température ambiante et à 300°C. Dans la plupart des cas, les rapports de contraintes R sont égaux à zéro. On constate et on compose des différences importantes de vitesses de propagation en fatigue sur les éprouvettes CCT où le chauffage jusqu'à température d'essai est appliqué localement au voisinage du plan de la fissure, par rapport aux vitesses de propagation constatées sur les éprouvettes CT complètement insérées dans un four. On trouve que ces différences sont liées aux contraintes de compression associées aux gradiants thermiques.

     

Diffication of high affinity fatty acid receptors in rat myocardial sarcolemmal membranes

High affinity receptors for fatty acid were purified from rat cardiac sarcolemmal membrane using gel filtration, DEAE-cellulose chromatography and affinity chromatography. The purified protein was homogeneous on polyacrylamide gel electrophoresis with the molecular weight of 60 kDa. Binding studies revealed the presence of a single class of high affinity binding sites with an apparent dissociation constant of 1.0 μM and a maximal binding capacity of 12.1 pmol/μg protein.     

Decomposition of chlorofluorocarbons in the presence of water over zeolite catalyst

The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. More than 40% of the conversion of CFC was observed on HY zeolite, H-mordenite, H-ZSM-5, γ-Al₂O₃, and SiO₂TiO₂ catalysts, and the selectivity to CO and CO₂ was nearly 100% except on γ-Al₂O₃. Although the H-mordenite had the highest activity among the tested catalysts, it was gradually deactivated during the reaction due to the elimination of Al atoms from the zeolite framework. A good relationship was found between the reactivity on H-mordenite and the bond energy of CCl in compounds of CCl₄, CCl₃F, CCl₂F₂, and CClF₃, suggesting that the rate controlling step was the cleavage of the CCl bond.