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Kazunori Hasegawa,Hirofumi Akagi 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper focuses on a medium-voltage motor drive requiring no regenerative braking. It is operated not only in a high-speed region but also in a low-speed region with the rated torque, intended for an application to drilling rigs. The power conversion system consists of a front-end diode rectifier, a five-level diode-clamped PWM inverter, and a dc-voltage-balancing circuit including a single coupled inductor. The five-level diode-clamped inverter is characterized by injecting a common ninth-harmonic zerosequence voltage on each of the three-phase reference voltages for mitigating magnetic-flux fluctuation of the coupled inductor of the dc-voltage-balancing circuit. Moreover, the voltage injection can make the power-loss distribution of eight insulated gate bipolar transistors (IGBTs) per leg close to an even profile. Experimental results obtained from a 200-V 5.5-㎾ downscaled model confirm the viability and effectiveness of the power conversion system, indicating that the ninth-harmonic zero-sequence voltage injection mitigates the magnetic-flux fluctuation.
Gravitino problem in minimal supergravity inflation
Hasegawa, Fuminori,Mukaida, Kyohei,Nakayama, Kazunori,Terada, Takahiro,Yamada, Yusuke North-Holland Pub. Co 2017 Physics letters. Section B Vol.767 No.-
<P><B>Abstract</B></P> <P>We study non-thermal gravitino production in the minimal supergravity inflation. In this minimal model utilizing orthogonal nilpotent superfields, the particle spectrum includes only graviton, gravitino, inflaton, and goldstino. We find that a substantial fraction of the cosmic energy density can be transferred to the longitudinal gravitino due to non-trivial change of its sound speed. This implies either a breakdown of the effective theory after inflation or a serious gravitino problem.</P>
Current Status of Ozone Control Measures in the United States and Europe and Implications for Japan
Hideki Hasunuma,Liliana Martinez Rivera,Hirosato Kobayashi,Kenji Aizu,Kazunori Oshima,Jun Shibutani,Yasuyuki Itano,Satoru Chatani,Shuichi Hasegawa,Makiko Yamagami,Junya Hoshi KOSAE·JSAE·CSES-CSAE 2022 Asian Journal of Atmospheric Environment (AJAE) Vol.16 No.3
In Japan, the achievement rate of environmental standards for air pollution has been improving in recent years, but for photochemical oxidants, including ozone, improvement are required. In this study, we investigated trends in ozone countermeasures in the United States and Europe from the State Implementation Plan (SIP) and National Air Pollution Control Program (NAPCP) and examined whether there are any points recommended in Japan. The United States and Europe have different policies on environmental standards for air pollution and ozone control. In the United States, states that do not meet the environmental standards for ozone concentration are required to develop an SIP to attain the standards. There was an urgent need to find a cost-effective approach to addressing the ozone problem, and forest control measures were one of the possibilities. In Europe, the European Union has set “target values” for ozone and NAPCP does not mention forest control measures or ozone sensitivity regimes. The main focus in Europe is on the win-win solution of reducing emissions of air pollutants at the same time as greenhouse gases. Japan should consider a framework including setting feasible step-by-step goals to attain the desired standards. As ozone is greatly affected by advection, wide-regional measures against ozone precursors and prediction of the future precursor reduction and concentration are required. The preparation of an emissions inventory and estimated reduction amount is prerequisites as basic data for simulation. To achieve this, cooperation between national, local and private research institutes is crucial. Since the international community has agreed to prioritize greenhouse gas countermeasures, Japan could consider a win-win solution for both ozone and greenhouse gas reduction.