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Dye aggregates formed in Langmuir-Blodgett films of amphiphilic merocyanine dyes
Keiichi Ikegami 한국물리학회 2006 Current Applied Physics Vol.6 No.4
The electronic absorption spectra of pure Langmuir (L) lms of 6MeDS prepared upon MgCl2, CaCl2, CdCl2, and CuCl2 aque-ous solutions have shown that the Mg2+,Ca2+, and Cd2+ cations promote the J-aggregation of the dye, but the Cu2+ cation inhibitsit. Instead, the Cu2+ cation promotes the formation of another type of dye aggregate (D-aggregate), which exhibits a split electronicabsorption band. These L lms have been transferred onto solid substrates by the LangmuirBlodgett (LB) technique. The vibronicabsorption spectra observed for the obtained LB lms have shown the similarity between the metalcation-containing J-aggregateand the metal-free J-aggregate of the dye, the latter of which was characterized in the previous study [K. Ikegami, J. Chem. Phys. 121(2004) 2337]. These spectra have also indicated that the bimolecular metal chelation plays an important role in the J-aggregation,like the intermolecular hydrogen bonding in the metal-free case.
Ikegami, Kozo,Shirasawa, Yo,Yokotsuka, Tomohito,Niitsu Yasushi 대한금속재료학회(대한금속학회) 1998 METALS AND MATERIALS International Vol.4 No.4
Cyclic plastic deformation of stainless steel SUS 304 is experimentally investigated at low temperature of liquid nitrogen (77 K) under various cyclic loading conditions. Thin walled tubular specimens are subjected to cyclic loading under constant strain ranges. At low temperature, the material shows remarkable hardening by cyclic loading comparing with cyclic loading at room temperature. The hysteresis curves of stress-strain relations by cyclic loading are saturated by increasing the cycle numbers. The saturation tendency depends on loading direction. The saturated stress values are related with cumulative plastic strain of cyclic loading. The prestraining is given at 77 K by axial and torsional loadings, and subsequent cyclic loading under constant strain range is conducted at 77 K. The cyclic stress-strain curves are saturated by increasing cyclic numbers. At small cyclic numbers, cyclic plastic deformation depends on the prestrain direction. The directional effect of pre-strain on cyclic loading becomes small with increasing number of cycles.
Status and Prospects of OTEC Integrated with Seawater Desalination in Japan
Yasuyuki Ikegami,Sami Mutair,Takafumi Morisaki 한국해양환경·에너지학회 2012 한국해양환경공학회 학술대회논문집 Vol.2012 No.11
Oceans cover approximately 71% of the total surface area of earth; hence oceans are considered the biggest solar collectors on earth. Most of the heat energy transferred by sunlight is absorbed by the thin layer of the ocean’s water near the surface. Below this layer, however, the temperature declines gradually with depth. Ocean Thermal Energy Conversion (OTEC) is a system that converts the temperature difference between the surface and the deep waters of the ocean into electricity. In addition, OTEC provides a clean source of fresh water by further utilization of the remaining temperature difference between the seawaters discharging from the power generation plant in driving the desalination process. This paper describes the evolution of OTEC and desalination research in Japan.
A Basic Study on Chip Size Determination of MOSFETs to Minimize Total Power Loss
Y. Ikegami,H. Obara,Y. Sato 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6
Chip area of power semiconductor devices is one of the key parameters to realize highly-efficient converters. In the case of MOSFETs, a larger chip area results in lower on-state resistance. However, switching loss and gate drive loss may become dominant due to increase in parasitic capacitances when the chip area is too large. Thus, the chip area must be determined adequately considering given operating conditions and characteristics of the devices. In this paper, relationship between the chip area and loss reduction effect in three different types of MOSFETs, that is, silicon MOSFETs, silicon-carbide MOSFETs, and super-junction MOSFETs, is investigated experimentally. From the results, it is clarified that each MOSFET has the optimum points of the chip area for the loss reduction depending on the switching frequency and current. A determination criterion of the optimum chip area is discussed on the basis of the theoretical calculation of the losses.