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Kim, H. Y.,Takizawa, S.,Oh, K. The Royal Society of Chemistry 2016 Organic & biomolecular chemistry Vol.14 No.30
<P>Catalyst-dependent divergent pathways of 2-naphthol derivatives have been investigated. A readily available CuCl2-DMAP catalyst system promotes the aerobic oxidation of 2-naphthol derivatives to ortho-naphthoquinones whereas switching the catalyst system to Cu(OAc)(2)-DBN under an argon atmosphere allows the oxidative coupling of 2-naphthols to 1,1'-bi-2-naphthols (BINOLs) in good to excellent yields.</P>
Origin of Ultrahigh Dielectric Constants for Barium Titanate Nanoparticles
Satoshi Wada,C Moriyoshi,H. Yasuno,K Kakemoto,K Takizawa,M Ohishi,T Hoshina,T Tsurumi,Y Kuroiwa 한국물리학회 2007 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.51 No.2I
Barium titanate (BaTiO3) nanoparticles with various particle sizes from 17 to 1,000 nm were prepared by using the 2-step thermal decomposition method of barium titanyl oxalate under various degree of vacuum. Various characterizations revealed that these particles were impurity-free, defectfree, dense BaTiO3 nanoparticles. When the degree of vacuum was high (pressure of 150 Pa at 650 C), the dielectric constant of BaTiO3 particles with a size of around 60 nm exhibited a maximum of around 15,000. On the other hand, when the degree of vacuum was low (pressure of 400 Pa at 650 C), no dielectric maximum was observed. To explain this size dependence, we precisely investigated a particle structure by using synchrotron radiation. As a result, the particles were always composed of two layers, i.e., a surface cubic layer and a bulk tetragonal layer, and the thickness of the surface cubic layer decreased with increasing degree of vacuum during the preparation of BaTiO3 nanoparticles. Thus, we confirmed that the surface structure was an important factor in determining the dielectric properties of BaTiO3 nanoparticles.
Analysis on Surge Voltage in Inverter-fed Motor Using Frequency Response Analysis
M. Fujieda,Y. Takahashi,N. Kimura,T. Wakimoto,S. Nagai,N. Koshino,K. Takizawa 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
In this paper, distribution of voltages between coils in inverter-fed motor and its mechanism are discussed. Insulation reliability of inverter-fed motor is one of major problems in HEV application. To ensure the reliability of insulation, enough thickness of insulation layer of coil-wire is desired to avoid partial discharge in air gap between coilwires, though the voltages between coils changes complexly due to its high frequency response. To analyze distribution of the voltages between coils, the simultaneous measurements of the voltages in various points in motor were performed. In addition, frequency response analyses of the voltages between coils were performed to understand its high frequency response. From these measurements and analysis , the fact that the LC-resonance between coil inductance and its stray capacitance causes surge voltage in motor is revealed.