Diamond synthesis from CO-H2 mixed gas plasma

Particulate or film-like diamond was prepared on silicon substrates from CO-H₂ mixed gas using a microwave plasma technique. The growth rate of diamond without graphite and amorphous carbon, as measured by Raman spectroscopy, was 9m h^–1 for particles and 4mh^–1 for flims. These values were larger than those in other source gas systems, such as CH₄-H₂, CH₄-H₂-H₂O and CH₃OH-H₂. The good formation rate and high quality of diamond in the CO-H₂ system was attributed to acceleration of methyl radical formation by the reaction of excited CO and H₂ molecules and removal of by-product graphite by OH radicals in the plasma.     

Measurements of neutronic characteristics of rectangular and cylindrical coupled hydrogen moderators

Extensive simulation calculations were performed in the design studies of the coupled hydrogen moderator for the pulsed spallation neutron source of the Japan Proton Accelerator Research Facility (J-PARC). It was indicated that a para-hydrogen moderator had an intensity-enhanced region at the fringe part, and that pulse shapes emitted from a cylindrical para-hydrogen moderator gave higher pulse-peak intensities with narrower pulse widths than those from a rectangular one without penalizing the time-integrated intensities. To validate the peculiar distribution and advantages in pulse shapes experimentally, some measurements were performed at the neutron source of the Hokkaido University electron linear accelerator facility. It was observed that the neutron intensity was enhanced at edges of the para-hydrogen moderators, whereas it decreased at the same part of the ortho-rich-hydrogen moderator, where the dimension of those moderators was 50 mm in thickness and 120 mm in width and height. The spatial distribution and pulse shapes were also measured for a cylindrical coupled para-hydrogen moderator that has the same dimensions as for the coupled moderator employed for J-PARC. The measured results from the cylindrical moderator were consistent with the results obtained in the design studies for the moderator for J-PARC.     

Epitaxial growth of lithium niobate film using metalorganic chemical vapor deposition

Lithium niobate films grown epitaxially on sapphire substrate were prepared using a thermal chemical vapor deposition method from the metalorganic compounds Li(C₁₁H₁₉O₂) and Nb(OC₂H₅)₅. The range of operating conditions for obtaining pure epitaxially grown LiNbO₃ without other oxides is within that for obtaining pure polycrystalline LiNbO₃ grown on silicon substrate. On analyzing the composition of the epitaxially grown LiNbO₃ film, the composition of the film was similar to that of the LiNbO₃ solid solution in the phase diagram of the Li-Nb composite oxide obtained for crystal growth from a molten solution.     

Feasible high-performance uninterruptible power supply incorporating current-mode controlled two-quadrant chopper-fed battery link

This paper presents a single-phase input-output common bus line uninterruptible power supply (UPS) circuit topology using a six-in-one insulated gate bipolar transistor (IGBT) module which incorporates a bidirectional chopper-linked battery bank with specific current-mode control strategy. The steady-state operating principle of this UPS topology and its new control strategy are described, together with conventional UPS. The experimental results of the cost-effective and high-performance small-scale UPS topology with a two-quadrant chopper-fed battery link are illustrated for the developed 3 kV A UPS and discussed, in comparison with conventional UPS topologies, from a practical point of view.     

Saturation and Polarization Characteristics of 1.56 μm Optical Probe Pulses in a LTG-GaAs Photoconductive Antenna Terahertz Detector

The characteristics of low temperature-grown GaAs photoconductive antenna (PCA) terahertz detectors probed by 1.56 μm laser pulses are investigated. The influence of TM and TE polarized probe, as well as the saturation characteristics are studied for 2 μm- and 5 μm-gap PCA’s. Different polarization characteristics at low probe powers and at the saturation regimes were observed. Results are explained in terms of the polarization-dependent photocarrier distribution at the PCA gap arising from tight focusing. This work also demonstrates using a 1.56 μm probe for a GaAs PCA to achieve ~60 dB SNR; matching its performance characteristics for above-bandgap probes.     

Rapid separation and counting of viable microbial cells in food by nonculture method with bioplorer, a focusing-free microscopic apparatus with a novel cell separation unit

A nonculture method utilizing a novel apparatus, the bioplorer, was developed. The bioplorer is composed of an efficient cell separation unit, a focusing-free microscopic device, and an image analysis program. A meat or vegetable suspension is poured into the cell separation funnel, and insoluble matter in the sample suspension is trapped by prefilters. Microbial cells passing through the two prefilters are then trapped by the membrane filter (pore size, 0.4 microm). Trapped cells are double-stained with 4',6'-diamidino-2-phenylindole and propidium iodide, and the membrane filter is removed and set on the focusing-free microscope. A fluorescent image is then recorded. Total numbers of viable and dead cells on the membrane filter can thus be determined automatically. One assay can be performed within 10 min, which is much faster than the culture method. The results obtained with both the nonculture method and the culture method for meat and vegetable samples were highly correlated (r = 0.953 to 0.998). This method is feasible for the practical purpose of food safety control.     

Preparation and characterization of nanoscale aromatic polyamide particles

Aromatic polyamide particles were prepared by reacting m-phthalyl chloride and 4,4′-diaminodiphenyl ether in a dioxane solution with high water content using a precipitation polymerization method. These nanoscale particles were spherical with a narrow size distribution. The morphologies and characteristic features of the polyamide products obtained depended strongly on the water content of this polymerization system. The characteristic features of the polyamide products were correlated with the amount of HCl (generated during polycondensation) complexed with polyamide products. Water was essential for the formation of spherical particles and played an important role in determining the polarity of the reaction solution. Further, water removed HCl from this condensation reaction system and played an important role as a reaction accelerator.     

Thermal Properties of Al-50%Si Alloys

AS FOR Al-Si alloy,this alloy with the characteristicsuch as excellent in a low coefficient of thermalexpansion(CTE),high-heat-conductivity,and wearresistance is used for the piston material of the engine,the heat radiation material,and electronic application1'2.The CTE of the Al-Si alloy decreases further withincreasing Si content because the CTE of Si is low3.The strength and wear resistance of Al-Si alloydecrease with increasing Si content because eutectic Siis coarse grain size an…