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A Gate Drive Circuit of Power MOSFETs and IGBTs for Low Switching Losses
Toshihisa Shimizu,Keiji Wada 전력전자학회 2007 ICPE(ISPE)논문집 Vol.- No.-
In order to increase the power density of power converters, reduction of the switching losses at a high-frequency switching condition is one of the most important issues. This paper presents a new gate drive circuit that enables to reduce the switching loss on both the Power MOSFET and the IGBT. A distinctive feature of this method is that both the turn on loss and the turn off loss can be decreased simultaneously without using the conventional ZVS circuit, such as quasi-resonant adjunctive circuit. Some experimental results of the switching loss of Power MOSFET and IGBT used on the buck-chopper circuit is shown and confirmed the effectiveness of the proposed circuit.
A Novel Flyback-type Utility Interactive Inverter for AC Module Systems
Toshihisa Shimizu,Naoki Nakamura,Keiji Wada 전력전자학회 2001 ICPE(ISPE)논문집 Vol.2001 No.10
In recent years, natural energy has attracted growing interest because of environmental concerns Many studies have been focused on photovoltaic power generation systems because of the ease of use in urban areas On the conventional system, many photovoltaic modules (PV modules) are connected in series in order to obtain the sufficient DC-bus voltage for generating AC output voltage at the inverter circuit. However, the total generation power on the PV modules sometimes decreases remarkably because of the shadows that partially cover the PV modules In order to overcome this drawback, an AC module strategy is proposed On this system, a small power DC-AC utility interactive inverter is mounted on each PV module individually and the inverter operates so as to generate the maximum power from the corresponding PV module This paper presents a novel flyback-type utility interactive inverter circuit suitable for AC module systems. The feature of the proposed system are, (1) small in volume and light in weight, (2) stable AC current injection, (3) enabling a small DC capacitor. The effectiveness of the proposed system is clarified through the simulation and the experiments.<br/>
Toshihisa Sato,Motoyuki Akamatsu,Nobuhiro Imacho,Takashi Sato,Yuji Munehiro,Yoshiyuki Yoneyama,Yoshiyuki Tashiro 한국자동차공학회 2008 한국자동차공학회 Symposium Vol.2008 No.9
This paper describes an investigation of driver’s behavior assessment while driving on downgrades with different gradients and effect of road safety countermeasures using a coloured pavement or a light-emitting delineator. The driving simulator used in the experiments consists of 300-degree fields of view screen, a hexapod motion platform, a sound system with spatial placed eight speakers, and so on. The target was two kinds of downgrades after curved and more gradual downgrade section: one is the existent downgrade with 8% gradient and with one traffic lane in each direction, and another has 7% gradient with two lanes that will be constructed for improvement of the existing downgrade. The existent downgrade has a temporary road structure and we investigated the effective countermeasures of the coloured pavement or a light-emitting delineator to reduce driving speed on the temporary downgrade. The simulator precisely represented these road structures using CAD data of the real and planned roads. Two downgrade sections were connected each other in one experimental route in order to compare the driving between on different downgrades and the driving with and without the countermeasures. The results of participated 31 drivers suggest that there are almost no differences in road safety between the existent and improved downgrades in terms of objective and subjective assessments. The evaluation results of the effect of the countermeasures imply the necessity of the interface design that affords drivers easy recognition of onset location of the steep downgrade.
Thermal Expansions of Ferroelectric Rb2CdI4
Toshihisa Yamaguchi,Fuminao Shimizu,Masaaki Takashige,Tadashi Kurihama 한국물리학회 2005 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.46 No.1
The ferroelectric Rb2CdI4 shows the largest peak of the dielectric constant at the Curie point (Tc = 211 K) among the Tl2ZnI4 group ferroelectrics of Sr2GeS4-type crystal structure (monoclinic system). Furthermore, the shoulder-like anomaly in the dielectric constant of Rb2CdI4, as for most ferroelectrics of this group, appears at the temperature (Ts = 150 K), which is lower by 50 degrees than Tc. In this research, thermal expansions of the crystal grown by the Bridgman method were measured in the temperature range from 4 K to 500 K by using a clip-type strain-gauge dilatometer. The feature of a second-order transition had appeared clearly at Tc = 211 K in thermal expansions xi (i = a, b, and c; a is perpendicular to the a-plane); however, anomalies were not seen clearly around the Ts.
Comparison of Car Following Behavior between UK and Japan
Toshihisa Sato,Motoyuki Akamatsu,Pengjun Zheng,Mike McDonald 제어로봇시스템학회 2009 제어로봇시스템학회 국제학술대회 논문집 Vol.2009 No.8
This paper describes a comparison study of driver’s car following behavior between Southampton (UK) and Tsukuba (Japan). AIST and TRG have developed instrumented vehicles, and filed experiments for behavioral datacollection were conducted in each country. The research focused on the static (distribution of inter-vehicle distances and desired headway distance) and the dynamic aspects (acceleration rate according to relative speeds and distancedivergence) of the car following behavior. The dynamic aspect was evaluated using fuzzy logic car following model developed at TRG. The results suggest that Southampton drivers tend to take shorter distance headway and acceleratemore strongly when the velocity of the leading vehicle is faster. The distance headway of Tsukuba drivers was found tobe longer and the deceleration was stronger while approaching a leading vehicle. The implications and future directionof car-following behavior comparison study are discussed.
Mouse Models for the Evaluation of Osteocyte Functions
Toshihisa Komori 대한골대사학회 2014 대한골대사학회지 Vol.21 No.1
Osteocytes establish an extensive intracellular and extracellular communication systemvia gap junction-coupled cell processes and canaliculi, through which cell processes passthroughout bone, and the communication system is extended to osteoblasts on thebone surface. To examine the osteocyte function, several mouse models were estab-lished. To ablate osteocytes, osteocytes death was induced by diphtheria toxin. However,any types of osteocyte death result in necrosis, because dying osteocytes are not phago-cytosed by scavengers. After the rupture of cytoplasmic membrane, immunostimulatorymolecules are released from lacunae to bone surface through canaliculi, and stimulatemacrophages. The stimulated macrophages produce interleukin (IL)-1, IL-6, and tumornecrosis factor-alpha (TNF- α), which are the most important proinflammatory cytokinestriggering inflammatory bone loss. Therefore, the osteocyte ablation results in necrosis-induced severe osteoporosis. In conditional knockout mice of gap junction protein al-pha-1 (GJA1), which encodes connexin 43 in Gap junction, using dentin matrix protein 1(DMP1) Cre transgenic mice, osteocyte apoptosis and enhanced bone resorption occur,because extracellular communication is intact. Overexpression of Bcl-2 in osteoblasts us-ing 2.3 kb collagen type I alpha1 (COL1A1) promoter causes osteocyte apoptosis due tothe severe reduction in the number of osteocyte processes, resulting in the disruption ofboth intracellular and extracellular communication systems. This mouse model unrav-eled osteocyte functions. Osteocytes negatively regulate bone mass by stimulating os-teoclastogenesis and inhibiting osteoblast function in physiological condition. Osteo-cytes are responsible for bone loss in unloaded condition, and osteocytes augment theirfunctions by further stimulating osteoclastogenesis and further inhibiting osteoblastfunction, at least partly, through the upregulation of receptor activator of nuclear factor-kappa B ligand (RANKL) in osteoblasts and Sost in osteocytes in unloaded condition.
A Gate Drive Circuit for Low Switching Losses and Snubber Energy Recovery
Toshihisa Shimizu,Keiji Wada 전력전자학회 2009 JOURNAL OF POWER ELECTRONICS Vol.9 No.2
In order to increase the power density of power converters, reduction of the switching losses at high-frequency switching conditions is one of the most important issues. This paper presents a new gate drive circuit that enables the reduction of switching losses in both the Power MOSFET and the IGBT. A distinctive feature of this method is that both the turn-on loss and the turn-off loss are decreased simultaneously without using a conventional ZVS circuit, such as the quasi-resonant adjunctive circuit. Experimental results of the switching loss of both the Power MOSFET and the IGBT are shown. In addition, an energy recovery circuit suitable for use in IGBTs that can be realized by modifying the proposed gate drive circuit is also proposed. The effectiveness of both the proposed circuits was confirmed experimentally by the buck-chopper circuit.