Further design considerations for unevacuated horizontal multi-layer insulation systems

Two design criteria for unevacuated horizontal multi-layer insulation systems, with equal spacings of the intermediate plates yielding the minimum heat transfer rate, are described.     

Growth and led evaluation ofN-type conductive lec gaas co-doped with in and si

Dislocation-free and low dislocation densityn-type conductive GaAs crystals, 50 mm in diameter, were grown by the In and Si co-doping LEC technique. Two-dimensional LED arrays were fabricated on substrates obtained from these crystals by the MOCVD technique and the influence of the In doping on the LED characteristics was examined. The light output power of LEDs fabricated on co-doped substrate with an In concentration of 1 ×10²⁰atoms/cm³ are low and are non-uniformly distributed, as compared with the boat-grown substrate, even though the co-doped substrate is dislocation-free. However, the LED properties of a substrate with an In concentration of 2 × 10¹⁸atoms/cm³ are the same as those of a boat-grown substrate. The light output power of the LEDs becomes higher as the In concentration in the substrate decreased.     

Arsenic behavior in paddy fields during the cycle of flooded and non-flooded periods

The behavior of As in paddy fields is of great interest considering high As contents of groundwater in several Asian countries where rice is the main staple. We determined the concentrations of Fe, Mn, and As in soil, soil water, and groundwater samples collected at different depths down to 2 m in an experimental paddy field in Japan during the cycle of flooded and non-flooded periods. In addition, we measured the oxidation states of Fe, Mn, and As in situ in soil samples using X-ray absorption near-edge structure (XANES) and conducted sequential extraction of the soil samples. The results show that Fe (hydr)oxide hosts As in soil. Arsenic in irrigation waters is incorporated in Fe (hydr)oxide in soil during the non-flooded period, and the As is quickly released from soil to water during the flooded period because of reductive dissolution of the Fe (hydr)oxide phase and reduction of As from As(V) to As(III). The enhancement of As dissolution by the reduction of As is supported by high As/Fe ratios of soil water during the flooded period and our laboratory experiments where As(III) concentrations and As(III)/As(V) ratios in submerged soil were monitored. Our work, primarily based on data from an actual paddy field, suggests that rice plants are enriched in As because the rice grows in flooded paddy fields when mobile As(III) is released to soil water.     

Study of the Effect of Fluorine Atom(s) on Fluoromethylated Imines in the Tandem Mannich–Michael-type Reaction

Differences in chemical behavior between non-fluorinated and fluorinated methylimines in the tandem Mannich–Michael-type reaction are described based on NMR and computational studies.     

A METHOD FOR THE PREPARATION OF RAW POWDER FOR THE TANTALUM CAPACITOR: INFLUENCE OF PARTICLE SIZE AND BINDER CONTENT

Raw powder for use in the tantalum solid electrolytic capacitor was prepared by different processes, that is, the wet method (currently used conversion method) and the dry method (the proposed method). The properties of prepared powder from the dry method were compared with those of the wet method. The present report has focused on the relationship between the conditions of binder preparation and the properties of the prepared powder, such as the particle size distribution, angle of repose, and the tap density, respectively. Furthermore, the utility of the dry method was investigated.

Based on the results, it has been clarified that the properties of powder prepared by the dry method differ from those of the wet method. In the case of the dry method, it is suggested that the mechanism of preparation of the fine binder (PMMA powder) differs from that of the coarse binder. Furthermore, based on the experimental results, it has been suggested that the dry method could be used as the preparation method of the raw powder used in the tantalum solid electrolytic capacitor.     

An automatic Euler solver using the unstructured upwind method

A fully-automatic grid generator and an unstructured upwind method for the Euler equations are developed in order to achieve automation in flow computations. The unstructured grid is generated using two techniques: a geometry-adaptive refinement; and a solution-adaptive refinement. The former introduces information about the flowfield geometry into the grid, and the latter introduces the fluid physics. A combination of these two techniques enables the generation of a grid in a fully-automatic manner. Flowfields are solved by an unstructured upwind solver, which is an extension of the flux-vector splitting method of Van Leer for use on arbitrary-shaped unstructured meshes. This robust flow solver with the automatic grid generator can be a useful CFD tool for routine engineering work. The method is applied to external and internal flow problems to demonstrate its capability.     

Snow Entrainment Coefficient Estimated by Field Observations and Wind Tunnel Experiments

The boundary condition for concentration of snow particles at the bed is necessary to calculate snowdrifts by a numerical analysis model. The flux type or the gradient type boundary conditions are reasonable. An idea of an entrainment coefficient of snow particle at the snow surface is useful. The values of the coefficient are considered to be a function of the density and viscosity of the working fluid and the properties of snow particles. In this paper, the values of the coefficient are estimated based on the k–ε turbulence model and the distribution of snow particle flux observed at the Mizuho Station, Antarctica in 2000, assuming the steady, fully developed flow over a flat snow surface. The snow entrainment coefficient is two or three orders smaller than the sand entrainment coefficient in a river. The reason is that the specific weight of snow particles in air is much larger than that of sand particles in water.     

Polymer-electrolyte water electrolysis

The electricity for the electrolyzer is supplied by a variable electricity supply unit that simulates actual outputs of both series and parallel combinations of solar cells exposed to various solar intensities. An amorphous-silicon solar cell is used as a sensor for the unit The operation was continued for more than 600 days without trouble. The case of direct connection of the solar cell and polymer electrolyte (PE) water electrolyzer is simulated: the test results show that more than 95% of the peak electricity power of the solar battery can be utilized for the electrolyzer over various solar radiation conditions.     

Environmental protection: researches in National Institute of Radiological Sciences

Some studies for radiological protection of the environment have been made at the National Institute of Radiological Sciences (NIRS). Transfer of radionuclides and related elements has been investigated for dose estimation of non-human biota. A parameter database and radionuclide transfer models have been also developed for the Japanese environments. Dose (rate)-effect relationships for survival, growth and reproduction have been investigated in conifers, Arabidopsis, fungi, earthworms, springtails, algae, duckweeds, daphnia and medaka. Also genome-wide gene expression analysis has been carried out by high coverage expression profiling (HiCEP). Effects on aquatic microbial communities have been studied in experimental ecosystem models, i.e., microcosms. Some effects were detected at a dose rate of 1 Gy day(-1) and were likely to arise from interspecies interactions. The results obtained at NIRS have been used in development of frameworks for environmental protection by some international bodies, and will contribute to environmental protection in Japan and other Asian countries.     

Theoretical Estimation of Changes in Plane Elastic Waves due to Cylindrical Inclusions

Changes in amplitude and phase shifts in plane elastic waves were theoretically estimated when they propagated through an elastic body containing cylindrical inclusions. Based on the integral equation suggested by Lavrov et al., these changes were calculated in the case when only one cylindrical inclusion was located in the body and the propagating waves have a single frequency. These calculations were expanded to more practical case when multiple cylindrical inclusions aligned in the body and the waves have some frequency band. The changes in amplitude and phase shifts calculated were associated to the changes in apparent sonic velocity and attenuation coefficient due to a structural change in the material. This theoretical approach contributes to a quantitative damage evaluation based upon structural changes in various materials by measuring the acoustical parameters such as apparent sonic velocity and attenuation coefficient.