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K. Muraoka 한국조명·전기설비학회 1999 한국조명·전기설비학회 학술대회논문집 Vol.1999 No.-
Laser diagnostics have been extensively used to understand plasma behaiviour under different discharge conditions. Measurements were performance for (ⅰ) electric field, (ⅱ) electron temperature and density, and (ⅲ) reaction products due to chemical reactions by electron impacts. The knowledge thus gained has been extensively used to realize novel plasma performances, such as epitaxial thin film depositions using plasma sputtering, performance improvements of discharge-pumped excimer lasers, and developments of environmental equipment. Abstract
1600V, 300A STATIC INDUCTION (SI) THYRISTOR
J.Nishizawa,K.Muraoka,Y.Ohtsubo,K.Yoshioka 전력전자학회 1989 ICPE(ISPE)논문집 Vol.- No.-
Static Induction (SI) thyristors were invented by NISHIZAWA in 1973 (I). Since then, intensive researches have been made to put them into practice in various fields as large power devices (2) {3). Among them, 1200V, 300A SI thyristor has been developed to be applied to a high frequency application equipment (4). This device has bee applied to develop a high frequency inverter (6), active filter {7), current source high frequency inverter (8), etc. These applications proved that the items of device tosses considerably varied depending on the circuit design and operation mode of the voltage source inverter, current source inverter and an e-quipment using a resonance circuit. It is expected, therefore, that a device be designed to meet a particular circuit and operation mode to improve the equipment conversion efficiency. We have recently developed two types of 1600V, 300A class SI thyris-tors whose peak turn-off current is 800A so as to apply them to the voltage source and current source inverters for PWM circuit and for resonance circuit respectively. Their device characteristics will be outlined as follows .
Development of Computer Simulation Code of Excimer Lasers and Experimental Confirmation
M.Maeda,T.Okada,K.Muraoka,K.Uchino 한국조명·전기설비학회 1999 한국조명·전기설비학회 학술대회논문집 Vol.1999 No.-
In order to analyze the discharge-pumped KrF excimer laser, computer simulation code is developed. On the other hand, the electron velocity distribution in a discharge plasma, measured by the Thomson scattering method, showed the Maxwellian, while the code predicted non-Maxwellian. This disagreement was solved by introducing the electron-electron collision into the simulation code. We also developed a simulation code on the CO₂ laser-heated plasma in high-pressure Ar gas, ana estimated the formation process of Ar₂ excimer. The code predicted the possibility of the Ar₂ laser action at 126 nm.
Piezoelectric Properties of Potassium Niobate Single Crystals by Domain Engineering
S. Wada,H. Kumagai,H. Kakemoto,K. Muraoka,T. Tsurumi 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
Potassium niobate (KNbO3) single crystals were grown by a TSSG method. At rst, the electric eld was applied along the [001]c (cubic notation system) direction of KNbO3 crystals to induce the engineered domain congurations into KNbO3 crystals. Prior to domain engineering, the piezoelectric properties of [001]c-oriented KNbO3 single-domain crystals were measured. These measurement values were completely consistent with the calculated apparent d31 and d32. Finally, the engineered domain congurations were induced into KNbO3 crystals. As a result, piezoelectric properties increased with decreasing domain sizes of the engineered domain conguration. However, the symmetry of the KNbO3 crystals was mm2, and there were four kinds of domain structures such as 90,180, 60 and 120 domains. Thus, the engineered domain structure induced in this study was very complicated, and the piezoelectric properties were also ependent on domain pattern and kinds of domain walls.
Behavior of Rotating Stall Cell in a High Specific-Speed Diagonal Flow Fan
Shiomi, Norimasa,Cai, W.X.,Muraoka, A.,Kaneko, K.,Setoguchi, T. The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.12
An experimental investigation was carried out to clarify unsteady flow fields with rotating stall cell, especially behavior of stall cell, in a high specific-speed diagonal flow fan. As its specific-speed is vary high for a diagonal flow fan, its pressure-flow rate curve tends to indicate unstable characteristics caused by rotating stall similar to axial flow fan. Although for an axial flow fan many researchers have investigated such the flow field, for a diagonal flow fan tittle study has been done. In this study, velocity fields at rotor Inlet in a high specific-speed diagonal flow fan were measured by use of a single slant hot-wire probe. These data were processed by using the "Double Phase-Locked Averaging"(DPLA) technique, i. e. phases of both the rotor blade and the stall cell were taken into account. The behaviors of stall cell at rotor inlet were visualized for the meridional, tangential and radial velocity.
Noh, N. J.,Lee, S. J.,Jo, W.,Han, S.,Yoon, T. K.,Chung, H.,Muraoka, H.,Son, Y. ELSEVIER 2016 ANNALS OF FOREST SCIENCE Vol.73 No.2
<P>In the open-field warming experiment using infrared heaters, 3 A degrees C warming affected soil respiration more in the deciduous Quercus variabilis Blume plot than in the evergreen Pinus densiflora Sieb. et Zucc. plot, but did not affect the plant biomass in either species. Understanding the species-specific responses of belowground carbon processes to warming is essential for the accurate prediction of forest carbon cycles in ecosystems affected by future climate change. This study aimed to investigate the effect of experimental warming on soil CO2 efflux, soil-air CO2 concentration, and plant biomass for two taxonomically different temperate tree species. Experimental warming was conducted in an open-field planted with Q. variabilis and P. densiflora seedlings. Infrared heaters increased the air temperature by 3 A degrees C in the warmed plots compared with the air temperature in the control plots over a 2-year period. The increase in air and soil temperature stimulated soil CO2 efflux by 29 and 22 % for the Q. variabilis and P. densiflora plots, respectively. Seasonal variation in the warming effect on soil CO2 efflux was species-specific. Soil CO2 efflux was also positively related to both soil temperature and soil water content. The soil moisture deficit decreased the difference in soil CO2 efflux between the control and warmed plots. Warming did not affect soil CO2 concentration and plant biomass in either species; however, the mean soil CO2 concentration was positively correlated with root and total biomass. Warming increased soil CO2 efflux in both Q. variabilis and P. densiflora plots, while the increase showed remarkable seasonal variations and different magnitudes for the two species.</P>