Monte Carlo calculations on vector supercomputers using GMVP

A multigroup general purpose Monte Carlo code GMVP has been developed. The vectorization algorithm is based on a stack-driven zone selection method. GMVP can treat repeated rectangular and hexagonal lattices together with combinatorial geometry which is quite useful to achieve a high gain by vectorization. The performance of the code was evaluated by solving various types of problems. In addition, the continuous energy code is under development and the performance is compare with conventional codes. The code was installed on other four different supercomputers to investigate portability and computer dependence of code performance.     

Robust control of a two-axis,magnetic suspension,flexible-beam system based on H∞ optimization theory

This paper deals with how to use H^∞ optimization theory for the controller design of a two-axis magnetic suspension, flexible-beam system, which is a simplified model for a flexible magnetic bearing system. Both simulation and experimental results show that the designed system not only has good performance in robustness to the plant's parametric uncertainty and the unmodelled dynamics in the beam's vibration modes, mode shapes, etc., but also has good performance in response characteristics.     

On a Multichannel Queueing System with Ordered Entry and Heterogeneous Servers

A multichannel queueing system with ordered entry and no waiting line is considered under the assumption of Poisson arrival and negative exponential service with a different rate in each channel. For the system with two or three heterogeneous servers, the best servers' arrangement is established by interchanging the order of servers to decrease the overflow probability and thereby increase the number of items serviced per unit time. The system considered is a simplified model for a production system with a closed loop conveyor.     

Thermal and chemical properties of TiO2-SiO2 porous glass-ceramics

The thermal and chemical stability of porous glass-ceramics of the TiO₂-SiO₂ system have been investigated. Porous glass-ceramics containing both anatase and rutile had thermal expansion coefficients of 40 to 55 x 10^–7 K^–1 in the range 0 to 700° C. They remained porous up to 1000° C, while the pores of high-silica porous glass of Vycor type collapsed completely at that temperature. The high thermal stability of the porous glass-ceramics may be attributed to a high viscosity due to dispersed crystallites of anatase and rutile in the skeleton. Most of the anatase in the skeleton was transformed to rutile by heat treatment at 900° C, but some of it remained untransformed even after 6 h. Surface -OH groups identified by IR spectroscopy were removed by dehydration polycondensation with heating up to 900° C. The porous glass-ceramics were quite durable to alkali solution compared with high-silica porous glass. The excellent durability of these porous glass-ceramics was attributed to the large amount of TiO₂ contained in the skeletal structure.     

A boundary integral approach in the geoelectrical cavity prospecting

The Fredholm integral equation of the second kind with respect to electrical potential is derived associated with the cavity concealed within the earth. In this approach, the positioning constant to be attached to the governing equation for the fundamental solution is of great significance, and we formulate the positioning constant at an unsmooth point on the boundary interface through the spherical geometry. It is shown that the numerical solutions are in sufficient agreement with the experimental data.     

Polymer-stabilized liquid crystal blue phases

Blue phases are types of liquid crystal phases that appear in a temperature range between a chiral nematic phase and an isotropic liquid phase. Because blue phases have a three-dimensional cubic structure with lattice periods of several hundred nanometres, they exhibit selective Bragg reflections in the range of visible light corresponding to the cubic lattice. From the viewpoint of applications, although blue phases are of interest for fast light modulators or tunable photonic crystals, the very narrow temperature range, usually less than a few kelvin, within which blue phases exist has always been a problem. Here we show the stabilization of blue phases over a temperature range of more than 60 K including room temperature (260-326 K). Furthermore, we demonstrate an electro-optical switching with a response time of the order of 10(-4) s for the stabilized blue phases at room temperature.     

Characterization of factors that transform linoleic acid into di- and trihydroxyoctadecenoic acids in mash

The qualities of beer are deteriorated by the presence of either di- or trihydroxyoctadecenoic acids, which reduce the beer 'head' and produce an astringent flavor. In this study we found that native extracts of malt mash transformed linoleic acid into di- and trihydroxyoctadecenoic acids, but this transforming activity and lipoxygenase activity were inactivated by heating the mash at 70 degrees C for 30 min. Recombinant barley lipoxygenase 1 was not able to transform linoleic acid into di- and trihydroxyoctadecenoic acids. The transforming activity of mash extract heated at 70 degrees C for 30 min could be restored by the addition of recombinant barley lipoxygenase 1; in contrast, the activity of boiled mash extract was not substantially restored by the recombinant enzyme. These results indicate that di- and trihydroxyoctadecenoic acids are generated from linoleic acid by both lipoxygenase and a heat-stable enzymatic factor present in the mash.     

Accumulation of L-cystathionine by an Escherichia coli mutant deficient in cystathionine beta-lyase

An Escherichia coli mutant deficient in cystathionine beta-lyase was found to accumulate a substance detectable by ninhydrin reaction and chloride platinic acid reaction in its cells (rarely in the culture supernatant) when cultured with a limited amount (50-200 microg/ml) of L-methionine to support the growth. The product was released by freezing treatment and isolated by ion-exchange chromatography (cation exchange resin: Daiaion SK1B). It was identified as L-cystathionine by liquid chromatography-mass spectrometry, 13C- and 1H-nuclear magnetic resonance analyses and high-performance liquid chromatography (as its 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranosyl isothiocyanate derivative).