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T. Matsui,E. Taketani,H. Tanaka,K. Morii,N. Fujimura,T. Ito 한국물리학회 2003 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.42 No.IV
We have succeeded in preparing single crystalline lms of BaFeO3, which may contain unusual Fe4+ ions, on (100) SrTiO3 substrates by pulsed laser beam deposition. The RHEED patterns for the lms on the (100) substrates apparently show a C4 symmetry, suggesting that the sample had a pseudo-cubic perovskite structure rather than hexagonal unit cell. The (100) epitaxially grown lms were found to be highly insulating, up to the leakage current density lower than 1 A/cm2 at the bias voltage of ..1:5 V. In addition, the lms showed a high value of dielectric constant of " = 59, and relatively small dissipation factor of about 0.07 at 100 kHz. The samples were also revealed to have a remanent magnetization at 300 K.
Experimental Studies on Drive Performances of Less Rare-Earth PM Hybrid Excitation Motor
T. Kosaka,T. Hirose,N. Matsui 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper presents feasibility studies on hybrid excitation motor (HEM) as a candidate of less rare-earth permanent magnet and high power density machine for hybrid electric vehicle drives. The construction, the basic working principle focusing on variable field control capability and the design concept of HEM are overviewed. After making the design restrictions and specifications clear, the drive performances of HEM designed are evaluated based on 3D-FEA. As a result, the proposed motor makes possible to reduce the volume of rare permanent magnet by approximately half of that used in existing interior permanent magnet synchronous motor for LEXUS RX400h while keeping the power density intact. With comparisons between the measured and the computed drive performances of the trial manufacturing of the downsized motor, it is verified that HEM becomes an attractive candidate as a less-rare-earth permanent magnet and high power density motor for HEV drives.
M. Sridharbabu,T. Kosaka,N. Matsui 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
This paper presents design analysis and improvement of the proposed high speed hybrid excitation motor (HEM) for main spindle drive in machine tools based on experimental results obtained using prototype motor. The proposed HEM is intentionally designed using 3D-FEA for target application taking into account of practical design constraints. The basic working principle and the unique field weakening control method of the proposed HEM are studied from the prototype machine. The influence of manufacturing constraints in the design parameters of the motor are studied carefully and an improved design of the proposed HEM is analyzed. In particular, the induced voltage distortion, magnetic flux saturation in the stator pole shoe have been a major factor which has impact in the performance of the test machine, are considered in the improvement of machine design.
( Akihiro Koga ),( Toshiyuki Matsui ),( Noritaka Takatsu ),( Yasumichi Takada ),( Masahiro Kishi ),( Yutaka Yano ),( Takahiro Beppu ),( Yoichiro Ono ),( Kazeo Ninomiya ),( Fumihito Hirai ),( Takashi N 대한장연구학회 2018 Intestinal Research Vol.16 No.2
Background/Aims: Decreased trough levels of infliximab (TLI) and antibodies to infliximab (ATI) are associated with loss of response (LOR) in Crohn’s disease. Two prospective studies were conducted to determine whether TLI or ATI better correlates with LOR (Study 1), and whether TLI could become a predictor of mucosal healing (MH) (Study 2). Methods: Study 1 was conducted in 108 patients, including those with LOR and remission to compare ATI and TLI in discriminating the 2 conditions based on receiver operating characteristic (ROC) curve analyses. Study 2 involved 35 patients who were evaluated endoscopically. Results: In Study 1, there were no differences between the 2 assays in ROC curve analyses; the TLI cutoff value for LOR was 2.6 μg/mL (sensitivity, 70.9%; specificity, 79.2%), and the ATI cutoff value was 4.9 μg/mL (sensitivity, 65.5%; specificity, 67.9%). The AUROC (area under the ROC curve) of TLI was greater than that of ATI. AUROC was useful for discriminating between the 2 conditions. In Study 2, the TLI was significantly higher in the colonic MH group than in the non-MH group (2.7 μg/mL vs. 0.5 μg/mL, P=0.032). Conclusions: TLI is better than ATI for clinically diagnosing LOR, and a correlation was observed between TLI and colonic MH. (Intest Res 2018;16:223-232)
E. Sulaiman,T. Kosaka,N. Matsui 전력전자학회 2011 ICPE(ISPE)논문집 Vol.2011 No.5
Hybrid excitation flux switching synchronous machine (HEFSSM) has several attractive features compared to interior permanent magnet synchronous machines (IPMSM) conventionally employed in hybrid electric vehicles (HEV). Among various types of HEFSSM, the machine with both permanent magnet (PM) and field excitation coil (FEC) on the stator has the advantages of robust rotor structure together with variable flux control capabilities that make this machine becoming more attractive to apply for high-speed motor drive systems. This paper presents an investigation into the design possibility and parameter optimization study of 12Slot-10Pole HEFSSM for traction drives in HEV. The research target is to design a machine with reduced amount of rare-earth magnet, a maximum torque of 210Nm, a maximum power of more than 123㎾, and a maximum power density of more than 3.5㎾/㎏. Extensions in speed and torque ranges are chosen for optimization aims. The deterministic design approach is used to treat ten design parameters in an effort to achieve the target performances. As a result, the designed HEFSSM with 0.4㎏ PM is able to get much higher power density compared to existing IPMSM installed on a commercial SUV-HEV.
Real-space observation of a two-dimensional skyrmion crystal
Yu, X. Z.,Onose, Y.,Kanazawa, N.,Park, J. H.,Han, J. H.,Matsui, Y.,Nagaosa, N.,Tokura, Y. Macmillan Publishers Limited. All rights reserved 2010 Nature Vol.465 No.7300
Crystal order is not restricted to the periodic atomic array, but can also be found in electronic systems such as the Wigner crystal or in the form of orbital order, stripe order and magnetic order. In the case of magnetic order, spins align parallel to each other in ferromagnets and antiparallel in antiferromagnets. In other, less conventional, cases, spins can sometimes form highly nontrivial structures called spin textures. Among them is the unusual, topologically stable skyrmion spin texture, in which the spins point in all the directions wrapping a sphere. The skyrmion configuration in a magnetic solid is anticipated to produce unconventional spin??electronic phenomena such as the topological Hall effect. The crystallization of skyrmions as driven by thermal fluctuations has recently been confirmed in a narrow region of the temperature/magnetic field (T??B) phase diagram in neutron scattering studies of the three-dimensional helical magnets MnSi (ref. 17) and Fe<SUB>1−x</SUB>Co<SUB>x</SUB>Si (ref. 22). Here we report real-space imaging of a two-dimensional skyrmion lattice in a thin film of Fe<SUB>0.5</SUB>Co<SUB>0.5</SUB>Si using Lorentz transmission electron microscopy. With a magnetic field of 50??70 mT applied normal to the film, we observe skyrmions in the form of a hexagonal arrangement of swirling spin textures, with a lattice spacing of 90 nm. The related T??B phase diagram is found to be in good agreement with Monte Carlo simulations. In this two-dimensional case, the skyrmion crystal seems very stable and appears over a wide range of the phase diagram, including near zero temperature. Such a controlled nanometre-scale spin topology in a thin film may be useful in observing unconventional magneto-transport effects.
A NEW ANALYTICAL MODEL AND SENSORLESS APPROACH FOR SWITCHED RELUCTANCE MOTORS
S.Saha,T.Kosa.ka,N.Matsui,Y.Takeda 전력전자학회 1998 ICPE(ISPE)논문집 Vol.- No.-
In this paper a new analytical model for the non-linear flux-linkage/ current characteristics of the switched reluctance motors at different rotor positions is proposed. The model has been successfully verified by the simulation and the experimental results of the instantaneous current waveforms and the average torque values in both single pulse and multiple pulse operation of the motor The uniqueness of the model lies in its defining a simple algorithm for determining the rotor position ($). Hence, sen-sorless operation of the motor can be easily implemented with the aid of this model.<br/>