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991.
Masamitsu Watanabe Akira Hokazono Takao Handa Toshihiro Ichino Nobuo Kuwaki 《Corrosion Science》2006,48(11):3759-3766
Corrosion products that had been formed on copper and silver plates exposed in Miyake Island, where suffered a volcanic eruption in 2000, were analyzed by X-ray techniques to get better understanding of copper and silver corrosion in harsh environment. The exposure experiment was carried out from September 2004 to April 2005. Many kinds of patina were found on copper such as cuprite (Cu2O), posnjakite (Cu4SO4(OH)6 · H2O), brochantite (Cu4SO4(OH)6), antlerite (Cu3SO4(OH)4), and geerite (Cu8S5). For silver, silver chloride (AgCl) and silver sulfide (Ag2S) were formed. Although the volcanic activity had greatly subsided, the atmospheric corrosion of copper and silver plates exposed on Miyake Island was mainly affected by volcanic gases, wet-dry cycles in the environment, and sea-salt aerosols. 相似文献
992.
Akira Kobayashi 《Surface & coatings technology》1997,90(3):555-202
The high hardness zirconia (ZrO2) coatings could be obtained at an atmospheric pressure by using a gas tunnel type plasma spraying. The characteristics of these high hardness ZrO2 coatings were investigated. The Vickers hardness of the ZrO2 coating at a short spraying distance was very high; a high hardness of more than Hv=1200 was achieved at the surface side of the coating. The microstructure of the obtained high hardness ZrO2 coating was also investigated by the microscopic method. And the characteristics of the high hardness ZrO2 coating was discussed in comparison with that of the coating formed by the conventional type plasma spraying. It was clarified that the ZrO2 coating of the gas tunnel type was not only much harder but also less porous than that of the conventional type. 相似文献
993.
Gd65Fe20Al15, Gd65Fe15Al20 and Gd70Fe15Al15 bulk amorphous alloys were produced by copper mold casting method with the maximum diameters of 2, 1 and 1 mm, respectively. The crystallization temperature (Tx) and melting temperature (Tm) of the Gd65Fe20Al15 bulk amorphous alloy are 808 and 943 K, respectively. Accordingly, the temperature interval of Tm and Tx, ΔTm (=Tm − Tx), is as small as 135 K and the reduced crystallization temperature (Tx/Tm) is as high as 0.86. The small ΔTm and high Tx/Tm values are presumed to be the origin for the achievement of the high amorphous-forming ability of the Gd–Fe–Al bulk amorphous alloy. The Gd65Fe20Al15, Gd65Fe15Al20 and Gd70Fe15Al15 bulk amorphous cylinders with a diameter of 1 mm exhibit superparamagnetism at room temperature, while the amorphous ribbon shows the paramagnetism at room temperature. Finally, the mechanical properties of Gd65Fe20Al15 bulk amorphous alloys are investigated. 相似文献
994.
The forced-convection-cooling performance of a fin array is dependent on its pressure-loss characteristics as well as on the pressure-discharge characteristics of fans/pumps driving the working fluid. From this point of view, the overall performance of the forced-convection fin array has been analyzed, considering these characteristics and introducing a new dimensionless parameter F, which governs the overall performance. Based on the results, optimum design methods for forced-convection-cooling fin arrays in practical use are proposed. © 1998 Scripta Technica, Heat Trans Jpn Res, 26(8): 515–527, 1997 相似文献
995.
Takaaki Bohno Akira Tomioka Shinichi Nose Masayuki Konno Toshio Uede Tadakazu Imayoshi Hidemi Hayashi Katsuya Tsutsumi Fujio Irie 《Electrical Engineering in Japan》1997,120(1):23-32
We are developing high-temperature-superconductor (HTS) current loads for a 1-MW/1-kWh modular SMES system. In the modular SMES system, a pair of current leads would be installed in each module so that the heat load to the low-temperature end through the leads is minimized. Design study of the lead configuration including the safety lead and its thermal characteristics is presented herein. The safety lead composed of stainless steel is placed in parallel to the bulk HTS. A test unit for verification of safe operation has been developed and the simulated bulk HTS quench test has been demonstrated. The maximum temperature of the safety lead reached 200 K and the terminal voltage of the safety lead was only 1.2 V in the case of a 1000-A quench test. This temperature rise was well below the designed value. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120(1): 23–32, 1997 相似文献
996.
Variable frequency inverter with sinusoidal voltage outputs using rotating coordinate transformation
Hirotami Nakano Masayuki Jibiki Akira Nabae Yositsugu Okamura 《Electrical Engineering in Japan》1997,118(4):94-102
An ideal inverter should have sinusoidal voltage and current outputs. Generally, output voltages of a voltage-source PWM inverter contain high-level switching frequency harmonies due to the PWM operation, while output currents are kept nearly sinusoidal. High-level harmonics contained in output voltages of a voltage-source inverter cause acoustic noises, iron losses and electromagnetic interferences. An LC filter was used to suppress the switching frequency harmonics; however, there is a danger of resonance in the LC filter. Accordingly, to remove harmonics of the LC filter resonance frequency, the authors add a voltage feedback loop. A conventional system can operate without difficulty within 50 Hz. However, with accompanying increases in the output frequency, output voltages are largely delayed and reduced by a high-pass filter inserted in the feedback loop. These problems are caused by a high-pass filter inserted in the feedback loop. Accompanied by the inverter output frequency, a high-pass filter cannot remove the fundamental component perfectly. As a result, a small fundamental component is fed back, which causes a delay and decrease in output voltage. This paper proposes the application of coordinate transformation to a high-pass filter inserted in the feedback loop. As a result, the proposed system realizes an ideal filter which can suppress fundamental frequency components perfectly, and improves the characteristics of the inverter with sinusoidal voltage outputs greatly. Theoretical analyses, simulations and experiments showed satisfactory results. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 118 (4): 94–102, 1997 相似文献
997.
The authors have previously presented a control scheme for synchronous reluctance motors in which the motor current is controlled to keep the MMF (magnetomotive force) phase angle constant, and have shown that a simpler control scheme is possible by using an N-speed synchro for a 2N pole motor. However, conventional brushless synchros are expensive and bulky due to the intricate construction, where a rotary transformer supplies current to the exciting winding on the rotor core. The authors have therefore developed a novel VR (variable reluctance) synchro without the rotary transformer. This paper describes the theory of the novel VR synchro and presents measured waveforms of the output voltages of a prototype VR four-speed synchro. In addition, a variable speed drive system for eight-pole reluctance motors which uses the new control scheme is introduced. In this system, the VR synchro is directly connected to the motor shaft, whose output voltages are demodulated and directly used as the current phase command for the inverter current supplied to the motor. Experimental results show a satisfactory speed response for four-quadrant drive. © 1997 Scripta Technica, Inc. Electr Eng Jpn, 120 (3): 54–63, 1997 相似文献
998.
Naohira Maeda Kunio Okimura Akira Shibata Kouzou Tsuchida Eiji Saji 《Electrical Engineering in Japan》1997,121(4):11-17
SiO2 films were prepared by plasma-enhanced chemical vapor deposition (PECVD) using tetraethoxysilane (TEOS) and N2O. The Si(SINGLE BOND)OH concentrations in the films deposited at a low temperature (200 °C) were found to be below the detection limit of Fourier-transform infrared spectroscopy (FTIR) with an RF power of more than 80 W. Optical emission spectroscopic study for SiO2 deposition in the gas phase showed that emission intensities of both atomic oxygen and atomic hydrogen depended strongly on RF power. Further mass spectrometric study in N2O plasma indicated that atomic oxygen increased with RF power due to decomposition of N2O to N2 and O. In addition, we tried to prepare SiO2 films using TEOS and He in order to study the role of oxidants. It was found that low-impurity SiO2 films can be obtained at temperatures lower than 200 °C with higher RF power through the effects of oxidation by atomic oxygen and electron impact decomposition. © 1998 Scripta Technica. Electr Eng Jpn, 121(4): 11–17, 1997 相似文献
999.
100 μm porous p(styrene-co-divinylbenzene) (PS-DVB) microspheres were synthesized by employing a particular membrane emulsification technique, and subsequent swelling of the seed droplets. DVB dissolving a water-insoluble substance, hexadecane (HD), and an initiator was permeated through a SPG (Shirasu porous glass) membrane, and the uniform (seed) droplets were released to a stabilizer solution acting as the continuous phase. The average droplet size was around 30 μm, and this emulsion was mixed with a secondary emulsion of much smaller size consisting of more hydrophilic components, a mixture of styrene, middle chain alcohol (C6 to C8), dichlorobenzene, and isoamyl acetate, which promotes the degradative diffusion process of the components. After all the droplets in the secondary emulsion virtually disappeared, the seed droplets were swollen to a maximum 110 μm. Polymerization was carried out at 348 K under a nitrogen atmosphere. Uniform porous spheres of 100 μm with the coefficient of variation less than 10% were obtained. Specific surface area was 350 m2/g. Careful controlling of the specific gravity of swollen droplets and the choice of solvents balancing between the good solvency for the polymer and polarity (solubility in water) proved vital in order that the polymerization may proceed without an extensive phase separation in the early stage, which eventually induces breakup of the droplets. The three component system, isoamyl acetate-hexanol-o-dichlorobenzene, provided an adequate cosolvent for these purposes. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 63: 931–942, 1997 相似文献
1000.
Akira Mochizuki Yukio Seita T. Nak Azaki T. Fukuoka K. Matsushima Shuzo Yamashita 《应用聚合物科学杂志》1997,65(9):1723-1729
In order to apply a blood-compatible polymer to hemodialysis membrane, a new polyether-segmented nylon which dissolved in common organic solvents was designed. The basic polyether-segmented nylon was synthesized by melt polycondensation from sebacic acid, m-xylenediamine, and α,ω-bisaminopropyl-poly(ethylene oxide). To improve the solubility, azelaic acid and hexamethylenediamine were copolycondensed with the basic copolymer. The solubility was correlated with the heat of fusion (ΔHm) of the copolymer. When ΔHm is < 30 mJ/mg, the polymer is soluble in dimethylsulfoxide and makes a stable solution. The nonthrombogenicity was investigated in the viewpoint of adhesion of platelet onto the copolymer surface. It is made clear that the surface of the block copolymer, having > 10 wt % of poly(ethylene oxide), suppresses the adhesion of platelet, and the composition of the nylon block has no effect on the adhesion of platelet. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 65:1723–1729, 1997 相似文献