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Real-time Analysis of the Spinmotive Force due to Domain Wall Motion
Jun’ichi Ieda,Sadamichi Maekawa,Yuta Yamane 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12
Using numerical simulations, we study the spinmotive force induced by domain wall motion in ahigh magnetic field region far above the Walker breakdown field. We find that the DC componentof the spinmotive force scales with the applied magnetic field even in a field range where the wallmotion is no longer associated with periodic angular rotation of the wall magnetization. As the fieldis increased, spikes in the voltage signals start to appear, which are mainly attributed to vortex corecollisions, nucleation, and annihilation, and this tendency is enhanced with further increases in thefield. At high fields, the slope of the generated DC voltage vs. applied field curve is expected todepend only on the spin polarization of conduction electrons and, thus, can be used to accuratelydetermine the degree of spin polarization in various materials.
A note on almost contact Riemannian 3-manifolds II
Jun-ichi Inoguchi 대한수학회 2017 대한수학회보 Vol.54 No.1
We classify Kenmotsu 3-manifolds and cosymplectic $3$-mani\-folds with $\eta$-parallel Ricci operator.
Voltage Control Method in Non-linear Dead-time Effect Region for Dual Active Bridge DC-DC Converter
Jun-ichi Itoh,Kengo Kawauchi,Hayato Higa,Hiroki Watanabe,Keisuke Kusaka 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a voltage control method for a Dual Active Bridge (DAB) converter with three-level operation in the dead-time effect region. The non-linear transmission power error is reduced by controlling the zero current phase to the dead-time or more because the nonlinear error of the transmission power occurs when the inductor current reaches zero during the dead-time. In addition, the voltage control is operated under the linear region which is decided from the output current and the zerovoltage period. The validation of the proposed method is confirmed by a 2.3-kW prototype. In the experiments, the non-linear error in the transmission power is reduced by 76.3%. The linearity between a control variable and an output current is confirmed. In addition, a load step between two modes of three-level operation is achieved without the dc offset in the inductor current. Moreover, the RMS value of the inductor current is reduced by 50.2% compared with the conventional triangular modulation.
Jun-ichi Suto,Misaki Kojima 아세아·태평양축산학회 2019 Animal Bioscience Vol.32 No.12
Objective: Testicular growth and development are strongly influenced by androgen. Although both testis weight and plasma testosterone level are inherited traits, the interrelationship between them is not fully established. Males of DDD/Sgn (DDD) mice are known to have extremely heavy testes and very high plasma testosterone level among inbred mouse strains. We dissected the genetic basis of testis weight and analyzed the potential influence of plasma testosterone level in DDD mice. Methods: Quantitative trait loci (QTL) mapping of testis weight was performed with or without considering the influence of plasma testosterone level in reciprocal F2 intercross populations between DDD and C57BL/6J (B6) mice, thereby assessing the influence of testosterone on the effect of testis weight QTL. Candidate genes for testis weight QTL were investigated by next-generation sequencing analysis. Results: Four significant QTL were identified on chromosomes 1, 8, 14, and 17. The DDD-derived allele was associated with increased testis weight. The F2 mice were then divided into two groups according to the plasma testosterone level (F2 mice with relatively “low” and “high” testosterone levels), and QTL scans were again performed. Although QTL on chromosome 1 was shared in both F2 mice, QTL on chromosomes 8 and 17 were identified specifically in F2 mice with relatively high testosterone levels. By whole-exome sequencing analysis, we identified one DDD-specific missense mutation Pro29Ser in alpha tubulin acetyltransferase 1 (Atat1). Conclusion: Most of the testis weight QTL expressed stronger phenotypic effect when they were placed on circumstance with high testosterone level. High testosterone influenced the QTL by enhancing the effect of DDD-derived allele and diminishing the effects of B6-derived allele. Since Pro29Ser was not identified in other inbred mouse strains, and since Pro29 in Atat1 has been strongly conserved among mammalian species, Atat1 is a plausible candidate for testis weight QTL on chromosome 17.
Jun-ichi Itoh,Ryosuke Iso,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a voltage unbalance compensation method of series-connected switching devices for high voltage application such as DC distribution systems. In the series connection, a turn-off voltage unbalance occurs in switching devices due to a parasitic parameter mismatch and a switching timing mismatch among switching devices. In this paper, a capacitor snubber and Zero Voltage Switching (ZVS) operation are utilized to reduce voltage unbalance. In particular, the proposed method reduces the parasitic capacitor (collector-emitter capacitance) mismatch among series-connected devices by a capacitor snubber circuit, whereas the switching losses are effectively reduced by ZVS. As the simulation results, it is confirmed that the collector-emitter voltage unbalance is reduced by 88% by the proposed method in comparison with a snubber-less configuration. Finally, in order to confirm the effectiveness of the proposed method, experiments with a test circuit applied with the proposed method are conducted. According to the experimental results, the voltage unbalance is reduced by 86.0% due to the application of the proposed method.
Reduction of a Boost Inductance using a Switched Capacitor DC-DC Converter
Jun-ichi Itoh,Koichi Matsuura,Koji Orikawa 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
The loss analysis of a switched capacitor converter (SCC) with a boost reactor is discussed in this paper. The proposed SCC can deliver an output voltage independent from the circuit structure comparing to other voltage control methods. The main feature of this circuit is that most of the energy for the boost up function is transferred from a flying capacitor which results the inductance of the input reactor can be reduced. The reactor size of the proposed SCC is smaller than that of the conventional boost converters. A 1000 W 3-level SCC prototype has been built and tested. The efficiency of 97.8% is achieved at 1000 W when the boost up ratio is three times. Moreover, the loss analysis shows the main loss of the proposed SCC is the diode conduction loss.
Jun-ichi Itoh,Kazuya Kawai,Koroku Nishizawa,Hiroki Watanabe 전력전자학회 2019 ICPE(ISPE)논문집 Vol.2019 No.5
This paper proposes a design method of the flux-axis angular speed estimation using induced voltage in a speed sensor-less field oriented control for induction motor (IM) drive systems. In this method, the d-axis induced voltage is regulated to zero by a feedback control to estimate the fluxaxis angular speed. A low pass filter (LPF) is necessary in this estimation to avoid the recursive calculation. In this paper, the design method of compensation gain kpem and the cut-off angular frequency of LPF ωlpf are considered. As a result, the relation between kpem, ωlpf, convergence time of the d-axis induced voltage have a match to the equation and designed model in this paper. Furthermore, the maximum error between the simulation and estimated results of the time constant of the flux-axis angular speed introduced due to LPF is 3.7% when ωlpf is 200 rad/s. As the experimental results, when a torque step of 100% is applied to the induction motor, the convergence time of the motor speed is 1.6 s as the worst case with kpem set as 2.0 p.u. and the cut-off angular frequency set as 1000 rad/s. However, if kpem is set as 2.0 p.u. and ωlpf is set as 400 rad/s, the convergence time of the motor speed is 0.43 s as the best case, which is reduced by 73.1% compared to the worst case. As the result, kpem should decide by the target steady-state error, lpf should bigger than the cut-off angular frequency of the PI controller ωASR. Where, if the ωlpf is high, the convergence time of the motor speed is high.