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Frequency Regulation for Parallel-Connected UPS system under Independent Control
Atsuo Kawamura,Ryota Oikawa,Yasunari Yoshioka,Yasushi Matsumoto 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
This paper proposes a frequency regulation technique for the stable operation of parallel connected UPS system under the independent control proposed by authors group. The features of independent control of parallel UPS are (1) stable operation is guaranteed by sensing the output current of each UPS, and no communication is required between the UPS’s, (2) The phase and amplitude of each UPS voltage are generated by a simple PI controller, (3) The lateral current between the UPS’s are compensated by the lateral current compensator, (4) the load sharing is autonomously achieved, (5) the system frequency changes depending on the control gains and load. The last disadvantage is now solved by adding a simple control loop in the independent control. The paper presents the theory, simulation and experiments.
Morphological control of nanoparticles by femtosecond laser irradiation
Atsuo Nakao,Masayuki Nishi,Kiyotaka Miura,Kazuyuki Hirao,Yasuhiko Shimotsuma 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.4
We report on the fabrication and evolution of metal nanowires with a length of 5 μm and a diameter of 100 nm which were successfully photo-converted from scale-like copper micro-flakes, dispersed in an alcohol solution, under ultrashort pulse laser radiation and a subsequent aging treatment. The dependence of the observed copper nanowires on the conditions of the laser irradiation and aging treatment, and the influence of the surrounding solvent were also investigated. The photoinduced morphology changes are unusual and their optical properties are striking. These previously unknown metal nanowires have a very high aspect ratio, and are created by nuclear growth mechanisms. We report on the fabrication and evolution of metal nanowires with a length of 5 μm and a diameter of 100 nm which were successfully photo-converted from scale-like copper micro-flakes, dispersed in an alcohol solution, under ultrashort pulse laser radiation and a subsequent aging treatment. The dependence of the observed copper nanowires on the conditions of the laser irradiation and aging treatment, and the influence of the surrounding solvent were also investigated. The photoinduced morphology changes are unusual and their optical properties are striking. These previously unknown metal nanowires have a very high aspect ratio, and are created by nuclear growth mechanisms.
SURVEY OF REAL TIME DIGITAL FEEDBACK CONTROL OF PWM INVERTER FOR SINUSOIDAL WAVEFORM SYNTHESIS
Atsuo KAWAMURA 전력전자학회 1989 ICPE(ISPE)논문집 Vol.- No.-
In 1985, the first paper on the deadbcat control of a single phase PWM inverter aimed for UPS (Uninterruptible Power Supply) appeared. Since then, various papers have been published on the real time digital feedback control of single phase and three phase PWM inverters for sinusoidal output waveform synthesis, which are surveyed and summarized in this paper.<br/>
Zinc-containing tricalcium phosphate and related materialsfor promoting bone formation
Atsuo Ito,Makoto Otsuka,Haruo Kawamura,Masako Ikeuchi,Hajime Ohgushi,Yu Sogo,Noboru Ichinose 한국물리학회 2005 Current Applied Physics Vol.5 No.5
Calcium phosphate is a suitable carrier of zinc, an essential element that has stimulatory effects on bone formation in vitro and in vivo as well as an inhibitory effect on osteoclastic bone resorption in vitro. The highest zinc content is attained in b-tricalcium phosphate, where the zinc content reaches 6 wt%. Both rat and human bone marrow cells (BMCs) cultured on zinc-containing b-tricalcium phosphate and hydroxyapatite composite ceramics differentiated more than BMCs cultured on zinc-free composite ceramics in the presence of b-glycerophosphate and dexamethasone. The acceptable dose of zinc was higher for human BMCs than for rat BMCs. The solubility of ZnTCP, which contains a nontoxic level of zinc, decreased to 52–92% that of pure TCP in the pH range of 5.0–7.4. However, the resorbed volume of ZnTCP was much lower than that expected from the in vitro solubility of ZnTCP, becoming as low as 26–20% that of TCP, which indicates that the reduction in the resorbability of ZnTCP would be attributable principally to its lowered cellular activation property relative to that associated with pure TCP. Probably due to the lowered cellular activation property associated with ZnTCP, bone loss at the bone-implant interface was significantly arrested in the longterm implantation of ZnTCP/HAP. The intramuscular injection of ZnTCP powder is effective in increasing bone mineral density in the vicinity of the injected site in osteopenic animals. All these findings suggest that zinc-containing calcium phosphate is a biomaterial that promotes bone formation.