Research plan for divertor simulation making use of a large tandem mirror device

We are planning to start a study of divertor simulation under the closely resemble to actual fusion plasma environment making use of the advantage of open magnetic field configuration and to contribute the solution for realizing the divertor in ITER as a future research plan of Plasma Research Center of the University of Tsukuba. In the research plan, the concepts of two divertor devices are introduced. One has an axi-symmetric divertor configuration with the separatrix which is similar to toroidal divertor of torus systems and the other is a high heat flux divertor simulator by using an end-mirror exit of the existing tandem mirror device. Development of magnetic field configuration for ensuring the MHD stability is under way and a designed example is investigated under the optimal condition for plasma production. Consideration of plasma heating scheme using Fokker-Planck simulation code was successfully performed at both axi-symmetric divertor and end-mirror regions. Preparative experiments using calorimeter, Mach probe and high-speed camera have been started at the end-mirror region and the heat flux density of the level in 1-10 MW m⁻² was achieved in standard hot-ion mode plasma-confining experiments, which gives a clear prospect of generating the required heat flux density for divertor studies.     

Boiling Heat Transfer and Pressure Drop of a Refrigerant Flowing Vertically Upward in Small Rectangular and Triangular Tubes

In the present study, experiments were performed to examine the characteristics of flow boiling heat transfer and pressure drop of a refrigerant R410A flowing vertically upward in small copper rectangular and triangular tubes with hydraulic diameters of 1.04 and 0.88 mm, respectively, for the development of a high-performance heat exchanger using small tubes or minichannels for air-conditioning systems. Their characteristics were clarified by comparing the previous experimental data of the small circular tube (1.00 mm internal diameter). In the rectangular and triangular tubes, the pressure drop was found to be slightly lower and the heat transfer was much better than in the circular tube.     

Three-stage growth of Cu–In–Se polycrystalline thin films by chemical spray pyrolysis

Structural, optical and electrical properties of polycrystalline Cu–In–Se films, such as CuInSe₂ and ordered vacancy compounds (OVC), prepared by three-stage process of sequential chemical spray pyrolysis (CSP) of In–Se (first stage), Cu–Se (second stage) and In–Se (third stage) solutions have been studied in terms of substrate temperature at the second stage (T_S2). The films grown at T_S2420 °C exhibited larger grains in comparison with the Cu–In–Se films grown by the usual CSP method. Optical gap energy was approximately 1.06 eV for 360 °CT_S2420 °C, but increased dramatically from 1.06 to 1.35 eV when the T_S2 rose from 420 to 500 °C. Conductivity type was p-type for T_S2<420 °C, but n-type for T_S2>420 °C.     

How Reliable is the Plasticity Index for Estimating the Liquefaction Potential of Clayey Sands?

This paper examines the validity of the plasticity index (PI) as a criterion for estimating the liquefaction potential of clayey soils under cyclic loading. The results of undrained cyclic stress-controlled ring-shear tests on artificial mixtures of sand with different clays saturated with water indicated that an increase in PI decreased the soil potential to liquefy, and soil with PI>15 seemed to be nonliquefiable, a finding that is in agreement with the results of other researchers. However, in this study some deviations from this relation were found when a bentonite–sand mixture was treated with solutions of different ions, thus bringing into question the effectiveness of PI as a measure of the liquefaction potential of clayey soil having a certain pore water chemistry.     

Floating-point number LISP

A floating-point-number-oriented LISP has been developed. Though it performs type checking on every numeric operation, it runs as fast as Fortran for simple differential-equation problems. This paper describes the implementation, provides some measurements of its efficiency, and discusses the feasibility of this type of implementation.     

Curing behaviour and mechanical properties of dicarboxylated telechelic poly(ε-caprolactone)s/styrene–(epoxidized butadiene)–styrene triblock copolymer reactive blends

End-carboxylated telechelic poly(ε-caprolactone)s (XPCLs) with different molecular weights were blended into a triblock copolymer of styrene–(epoxidized butadiene)–styrene (ESBS) to investigate the curing behaviour and the mechanical properties of the XPCL/ESBS binary reactive blend. It was found that the time–torque cure curve showed a significant torque increase after a very short induction period, in which the degree of the torque increase depended on the molecular weight of XPCL. This indicates that substantial crosslinking reaction takes place between the XPCLs and the epoxidized polybutadiene of the ESBS. Stress–strain curves of the blends after cure depended on the molecular weight of XPCL and the blend ratio. The XPCL/ESBS blends had sufficient thermal stability to show elastomeric behaviour at elevated temperature above the glass transition of the styrene domains of ESBS because of formation of crosslinking points between unlike polymer components by the reactive blending. © 1999 Society of Chemical Industry     

Influence of Asymmetrical Waveform on Low-Cycle Fatigue Life of Micro Solder Joint

The effects of waveform symmetry on the low-cycle fatigue life of the Sn-3.0Ag-0.5Cu alloy have been investigated, using micro solder joint specimens with approximately the same volume of solder as is used in actual products. Focusing on crack initiation life, fatigue tests on Sn-Ag-Cu micro solder joints using asymmetrical triangular waveforms revealed no significant reduction in fatigue life. A slight reduction in fatigue life at low strain ranges caused by an increase in the fatigue ductility exponent, which is the result of a weakening microstructure due to loads applied at high temperature for long testing time, was observed. This was due to the fact that grain boundary damage, which has been reported in large-size specimens subjected to asymmetrical triangular waveforms, does not occur in Sn-Ag-Cu micro size solder joints with only a small number of crystal grain boundaries.     

Development of technique for observing pores in hardened cement paste

Mercury intrusion porosimetry is a widely used technique to determine the pore size distribution in porous materials. However, this technique does not provide information about the shapes and locations of pores. A new technique is developed, in which gallium (Ga) is used as an alternative intrusion liquid because of its property of being solid at normal room temperature (melting point: 29.8 °C). This permits the examination of pores using image analysis. The technique is applied to hardened cement paste. The distribution of solid Ga is observed through an electron probe microanalyzer (EPMA), and the shapes and locations of pores in cement paste are discussed.