Journal of the Japan Society of Applied Electromagnetics and Mechanics
Online ISSN : 2187-9257
Print ISSN : 0919-4452
ISSN-L : 0919-4452
Volume 27 , Issue 1
Showing 1-30 articles out of 30 articles from the selected issue
Special Issue on the Asia-Pacific Symposium on Applied Electromagnetics and Mechanics (APSAEM2018)
Regular Papers
  • Takeo ISHIKAWA, Kouhei FUKUDA
    2019 Volume 27 Issue 1 Pages 2-7
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     This paper proposes and fabricates a novel hybrid-flux permanent magnet motor with both axial- and radial-flux. The performance of the proposed motor is measured under the vector control, and is compared with that of only radial-flux part. The efficiency of the hybrid-flux motor is about 71.1 % at 100 min-1 and about 80.1 % at 200 min-1 in the region where the output power is large. The efficiency is about 8.2 % higher at 100 min-1 and 3.6 % higher at 200 min-1 than those of only radial-flux part.

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  • Shoichiro Hozumi, Hideo Dohmeki, Kenji Suzuki
    2019 Volume 27 Issue 1 Pages 8-12
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In recent years, the shift from gasoline cars to electric vehicles is accelerating. As a motor mounted in a car, can be interior permanent magnet types synchronous motor (IPMSM) miniaturized and has high output, so it is commonly used. However, there is a weak point that torque ripple is larger than other motors. This will cause deterioration of the comfort of the car. Therefore, I aimed to reduce the torque ripple without lowering the torque by optimizing the rotor shape of the motor using electromagnetic field analysis.

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  • Kenta Takei, Wataru Kitagawa, Takaharu Takeshita, Yoshio Fujimura
    2019 Volume 27 Issue 1 Pages 13-18
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     This paper presents the design and characteristic analysis of small-sized and high thrust electromagnetic actuator in the high temperature field. The proposed actuator is used for application control of hotmelt. Hotmelt is thermoplastic resin and solid at room temperature, and it is used as adhesives. Therefore, the actuator is required small-sized and high thrust in the high temperature field. The actuator is analyzed by 3D-FEM. As a result, the actuator obtains high thrust over required thrust 132 N. In addition, modifying the coil shapes enables to suppress of temperature rise.

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  • Maiko Yoshinari, Masaya Watada
    2019 Volume 27 Issue 1 Pages 19-24
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Endoscopic examination is a method examination of the digestive tract, and a scope endoscope is mainly used. However, since the scope endoscope continuously stimulates the pharynx when inserting camera, it gives pain to the patient. In order to remedy this drawback, a capsule endoscope has been developed. Since the capsule endoscope only corresponds to the small intestine and the large intestine, a scope endoscope is used for the examination of the stomach. Therefore, examination of the stomach gives a pain to the patient. In this study, we design of a self-propelled mechanism to be mounted on a capsule endoscope that made it possible to observe the stomach. In this paper, we propose and design and evaluate the self-propelled mechanism that enables the observation of the stomach. And we also construct a motion analysis system that uses motion simulation.

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  • Gyunam Kim, Katsuhiro Hirata
    2019 Volume 27 Issue 1 Pages 25-30
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     This study presents instantaneous inductance estimation and a sensorless stroke estimation method of a linear resonant actuator (LRA). In LRA, the stroke information is most important since the maximum distance of the mover is not mechanically constrained. In order to estimate the stroke from the voltage equation, motor parameters such as effective resistance, effective inductance and force constant are required. Especially, the inductance of LRA may change due to magnetic saturation. Therefore, it is necessary to estimate the inductance during operation and update its value continuously. This paper proposes a method to estimate the inductance during operation by using the current slope in the pulse width modulation (PWM). Furthermore, a method for estimating the stroke using estimated inductance is proposed. The effectiveness of the proposed method is validated by the results of numerical simulation.

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  • Masayuki KATO, Yoshinori KONO, Masataka YASUKAWA, Katsuhiro HIRATA, No ...
    2019 Volume 27 Issue 1 Pages 31-36
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Mobile haptic devices that employ vibration have been studied extensively because they have great potential for use as information transfer devices. Some studies have reported a method for haptic feedback using asymmetric oscillation made by slider-crank mechanism. Authors have proposed a small two-degree-of-freedom (2-DOF) oscillatory actuator for a mobile haptic device. However, the continuous operating time was estimated to be only few hours because its power consumption is large. To solve this problem, this paper proposes a power-saving method of the 2-DOF oscillatory actuator using mechanical resonance. As a result, the proposed method improved by more than 99% in the power consumption.

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  • Kazuaki TAKAHARA, Katsuhiro HIRATA, Noboru NIGUCHI
    2019 Volume 27 Issue 1 Pages 37-42
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Multi-Degree-of-Freedom (Multi-DOF) actuating systems are composed of several single-DOF motors, which results in large, heavy and complicated structures. In order to solve these problems, various multi-DOF spherical actuators have been actively studied. Among them, a spherical actuator can generate torques in arbitrary positions and directions. However due to this, it is difficult to evaluate the torque characteristics at any position all over the movable range. In order to evaluate the spherical actuators, we proposed a torque evaluation method under copper loss limiting. However, in the proposed method, only copper losses can be considered. In this paper, we propose a new torque evaluation method considering a maximum current limiting. Finally, the torque characteristics of our multi-DOF actuators are evaluated using the proposed method and the effectiveness of the proposed method is verified.

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  • Yoshinori Ando, Koji Chigira, Ryohei Takei, Takahito Kurahashi, Iwanor ...
    2019 Volume 27 Issue 1 Pages 43-48
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     The magnetic harmonic gear has been studied because of its high magnet use efficiency. However the magnetic harmonic gear are difficult to assemble. So, a new type of the magnetic harmonic gear was proposed. This magnetic gear has the stackable structure and is assembled easily. It was confirmed by simulation that the radial magnetic flux was strengthened by alternately arranging the axially magnets with the same poles and the maximum transfer torque and the magnet utilization efficiency improved. Therefore, we make a prototype of the stackable harmonic type magnetic gear using Halbach array and measure and examine torque characteristics.

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  • Ryohei SUWAHARA, Ryota KATO, Koki MURATA, Tomoki WATANABE, Yuichi SHIM ...
    2019 Volume 27 Issue 1 Pages 49-54
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     A Coil for wireless power transmission was manufactured by using of sewing techniques. The sewing methods and electric characteristics were described. The coils were sewn with a cross stitch. The inductance and loss resistance of the sewn coils was measured. It is assumed that the power receiving side coil is attached to biomedical implantable devices. The coupling coefficient between the power receiving side coil and the sewn coil was measured. The maximum coupling coefficient was 0.75. The maximum efficiency of 75.0% was obtained when the coupling coefficient was maximum. Inverter and rectifier were attached the circuit and the load voltage was measured. The maximum load voltage was 4.77 V.

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  • Masahiro OSA, Toru MASUZAWA, Ryoga ORIHARA, Eisuke TATSUMI
    2019 Volume 27 Issue 1 Pages 55-60
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Compact mechanical circulatory support (MCS) devices, such as continuous flow rotary blood pumps, have been clinically demanded for pediatric heart treatment. In this research, a miniaturized 5-degrees of freedom (DOF) con-trolled double stator maglev motor is undergoing development for use in pediatric MCS devices which have high du-rability and better blood compatibility. This paper reported improvement of the 5-DOF controlled maglev motor by modifying the magnetic circuit to enhance magnetic suspension performance and energy efficiency. The static sus-pension characteristics and energy efficiency of the developed motor with modified magnetic circuit were then inves-tigated. The axial suspension force and the inclination torque were increased by more than 45%. The input power was reduced by 1-5 W, and the motor efficiency increased by 5-8%. The significantly improved suspension force and energy efficiency due to design refinement indicated feasibility of high performance next generation pediatric MCS device.

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  • Yuma TAKEI, Masaya WATADA
    2019 Volume 27 Issue 1 Pages 61-66
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Lately, minimally invasive surgeries have been gaining popularity. Laparoscopic surgery is a type of minimally invasive surgeries and is known to minimize scars and reduce the damage of patients, which allows a quick recovery. However, since the surgeon performs surgery in the limited area in the abdominal cavity, the surgeon’s advanced techniques are required for operating forceps. As a countermeasure, we are developing an operation support system. The operation support system assists the surgeon to manipulate the forceps in the limited area. This system includes a support equipment and a master-slave combined robotic forceps. In this research, we will develop a control system for the support equipment. The paper will particularly outline overview and development of the operation support system for medical operations using a forceps and evaluate results of three control systems. As a result of the evaluation, it was confirmed that the developed system satisfies three functions.

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  • Tadashi YAMAGUCHI, Yoshihiro KAWASE, Shota ISHIMURA
    2019 Volume 27 Issue 1 Pages 67-72
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     We analyzed a three-phase transformer made of laminated non-oriented electrical steel sheets using the 3-D parallel finite element method in order to numerically investigate the influence of the magnetic properties of the electrical steel sheets on the eddy current loss. The difference of the distribution of the magnetic flux and the eddy current between non-oriented and grain-oriented electrical steel sheets are numerically investigated. Moreover, the influence of the magnetic properties of the electrical steel sheets on the eddy current loss around the lap joint parts is clarified.

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  • Misato NIREI, Masaya WATADA, Mutsuo YAMADA
    2019 Volume 27 Issue 1 Pages 73-78
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In recent years, the population of disabled people has been increasing tendency in Japan. Among them, physical disability due to hemiplegia is the most common. For hemiplegic patients to live independent living, grasp and pinch motions are necessary. To realize this movement, it is necessary to move the first finger and the fifth finger separately. The purpose of my research was to development of hand rehabilitation equipment which for enables hemiplegic patients independent movements of first finger and fifth finger at the home. In this paper, first we propose rehabilitation equipment. Then, we investigate whether we can use the feature values of sEMG obtained from the forearm as a control signal for the proposed rehabilitation equipment. As a result, we considered that the discrimination result of each motion were insufficient in the evaluation using the threshold. Furthermore, the discrimination rate of flexion motion and extension motion by SVM was 64%. In the future, we will make measurements at several places for improve accuracy. Based on it, we consider effective electrodes position.

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  • Mohachiro OKA, Masato ENOKIZONO
    2019 Volume 27 Issue 1 Pages 79-84
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Development of a small, high-speed and high-power motor is necessary to improve the performance of machines such as robots, and drones. The motor is excited by a high frequency voltage when the motor rotates high-speed. Moreover, the motor is driven by the pulse width modulation (PWM) inverter because efficiency and controllability is good. The driving voltage of the PWM inverter contains many higher harmonics waves. In such a motor, generation of heat due to the loss is a major problem. The loss of the motor includes an iron loss, a copper loss, and a machine loss; here we focus on the iron loss. Eddy-current loss increases especially under a condition of high frequency excitation. To suppress the eddy-current loss, we produced the stator core for a small, high-speed and high-power motor using a 0.08-mm-thick ultrathin electrical steel sheet. Additionally, to evaluate the magnetic properties of this new stator core with complex shape, we also developed a stator winding excitation method using a dummy rotor made of the 0.08-mm-thick ultrathin electrical steel sheet. In this paper, the effectiveness of a small, high-speed, and high-power motor stator core made of the 0.08mm-thick ultrathin electrical steel sheet is shown using the stator winding excitation method when it is excited by the PWM wave.

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  • Tadashi YAMAGUCHI, Yoshihiro KAWASE, Atsuyoshi NAGASE, Shota ISHIMURA
    2019 Volume 27 Issue 1 Pages 85-90
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     We developed a 3-D hybrid parallel finite element method with the process-parallelization by MPI and the thread-parallelization by OpenMP. In this method, the domain decomposition method is used in the process-parallelization and the multicolor ordering is used in the thread-parallelization. In this paper, we analyze the performance of the hybrid-parallelization through the cogging torque analysis of an IPM motor. As a result, it is possible to calculate the magnetic field faster using MPI and OpenMP at the same time. Hybrid parallelized computation at 8 nodes × 4 threads is 8.7 time faster than non-parallelized computation. Parallelization with OpenMP using the multicolor ordering was able to efficiently parallelize the forward-backward substitutions of ICCG. However, number of ICCG iterations increases due to the multicolor ordering in the hybrid parallelization.

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  • Dang Trang NGUYEN, Kaname IWAI, Toshihiro OZAWA, Kozo TAGUCHI
    2019 Volume 27 Issue 1 Pages 91-96
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In this research, we fabricated a low-cost, disposable, paper-based bio fuel cell that used an activated carbon-based anode with the pre-inoculated biofilm of Bacillus Subtilis bacteria. The biofilm anode was dried for long-term storage and the bio fuel cell could generate electricity on-demand within some minutes after adding a drop of tap water to the dry biofilm anode. The anodic activated carbon substrate was treated by a plasma cleaner to increase hydrophilization before inoculating bacterial biofilm. The fuel cell case was made of a normal paper filter. We integrated directly the air-cathode and proton exchange membrane on the fuel cell case. The paper-based bio fuel cell can be potentially used for micropower biosensor applications.

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  • Dang Trang NGUYEN, Yoshiki KUROKAWA, Ryota FUJIMOTO, Kozo TAGUCHI
    2019 Volume 27 Issue 1 Pages 97-101
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     A quasi-solid electrolyte dye-sensitized solar cell (QSDSSC) was fabricated, which used an environment-friendly organic MK2 dye. The quasi-solid electrolyte was fabricated based on I-/I3- redox couple and polymethylmethacrylate (PMMA) polymer. Ozone treatment technique has been utilized to clean and improve the hydrophilicity of TiO2 thin films, as a result, its dye-adsorption capacity was enhanced. Experimental results with a solar simulator showed that 40 % improvement of the conversion efficiency was obtained with the QSDSSCs fabricated with the photoanodes undergone the ozone treatment compared with the QSDSSCs fabricated with the photoanodes without the ozone treatment. Furthermore, we also conducted a stability test on the QSDSSCs fabricated with the ozone-treated photoanodes to study the stability of the organic MK2 dye and the PMMA-based gel electrolyte.

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  • Kaname IWAI, Dang Trang NGUYEN, Kozo TAGUCHI
    2019 Volume 27 Issue 1 Pages 102-107
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     We fabricated a microbial fuel cell (MFC) which was composed of three parts: a piece of towel paper for membrane, an anode electrode with photosynthetic bacteria biofilm and a cathode electrode coated potassium ferricyanide. The MFC could generate electricity with 20 μl water adding to the dry biofilm anode for activation. We measured repeatedly electricity generation every week using the MFC. This paper studies three points: (1) the dry-surface biofilms of Purple photosynthetic bacteria can generate electricity when activated by water; (2) the bacteria can survive in the condition of dry-surface biofilms for several weeks; (3) carbon nanotube (CNT) improves the performance of the electrodes. As a result, the MFC generated the maximum power density and current density of 2.90 µW/cm2 and 24.1 µA/cm2, respectively.

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  • Tatsuya OKOBIRA, Dang Trang NGUYEN, Kozo TAGUCHI
    2019 Volume 27 Issue 1 Pages 108-114
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     This study devoted to developing water-activated aluminum air batteries, which could repeatedly generate electricity by adding water to the electrolyte. Two aluminum air batteries, using polymer gelation electrolyte and paper-absorbent electrolyte, have been investigated. In addition, we also considered two materials for the cathode electrode, which were carbon sheet and carbon nanotube-loaded carbon sheet. The aluminum air batteries used environmentally-friendly sodium chloride (NaCl) for the electrolyte. The developed batteries are portable and flexible, which can be used for low-power and on-demand electricity generation activated by water.

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  • Masaaki MOTOZAWA, Naoto NAKAYAMA, Mitsuhiro FUKUTA
    2019 Volume 27 Issue 1 Pages 115-121
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Streamwise variation of flow field and heat transfer characteristics of turbulent magnetic fluid flow in magnetic field area was investigated experimentally. Ultrasonic velocity profiling (UVP) method was used to measure the velocity field and analyze the turbulent statistics. The test section is a rectangular duct, which has 18 mm × 18 mm of the cross section and 950 mm of the length. Magnetic field is applied to magnetic fluid flow in the perpendicular direction to the direction of heat flux. Streamwise length of the magnetic field area is 600 mm and magnetic field intensities are 50 mT and 130 mT. Reynolds number based on the hydraulic diameter is varied from 6500 to 9500. As a result of this study, the heat transfer is gradually suppressed from the entrance of the magnetic field area toward the downstream, and the suppression of heat transfer is saturated. Similar to the suppression of heat transfer, the Reynolds shear stress is also gradually suppressed toward the downstream of magnetic field area.

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  • Taichiro SUMI, Norihiro SATO, Makoto SONEHARA, Toshiro SATO, Hiroyuki ...
    2019 Volume 27 Issue 1 Pages 122-127
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Non-contact type brake is excellent in maintainability so it is optimum as an axle brake for aircraft. In this paper, basic experiments were carried out using magnetrheological fluid brake experimental equipment to study non-contact type brakes, the axle size of regional jets was investigated. The maximum brake torque of a regional jet's axle size based on the experimental equipment was 2,421 Nm. This can satisfy only about 27 % of the necessary torque. In order to increase brake torque, increase the number of discs and decrease the gap h.

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  • Yuhiro IWAMOTO, Atsushi YOSHIOKA, Yasushi IDO, Jhon CUYA, Balachandran ...
    2019 Volume 27 Issue 1 Pages 128-133
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Nanofluids have attracted much attention in the field of heat transfer because of their exceptional heat transfer ability. The authors have proposed a silver nanowire-dispersed magnetic nanofluid. Interestingly, its thermal conductivity is tunable by the direction of the applied magnetic field, because the dispersed Ag nanowires orient to the field direction. But the dynamic behavior of Ag nanowires is not well understood. In the present study, the translation process of the neighboring two Ag nanowires was theoretically analyzed. When the Ag nanowires are dispersed in the magnetic fluid and exposed to the magnetic field, the Ag nanowires apparently behave as a diamagnetic material because the surface of the Ag nanowires is magnetically charged. With assuming that single magnetic moment places at the center of Ag nanowires, the magnetic dipole interaction force, which is the attraction force, acts on the Ag nanowires, and the wires contact each other with taking a long time.

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  • Shunsuke NOGUCHI, Hideo DOHMEKI
    2019 Volume 27 Issue 1 Pages 134-139
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     Ballscrew drive system has non-linear friction elements, so it makes ballscrew control accuracy worse. It is also required to construct a mechanism with robustness against any disturbance including nonlinear friction. And the system integrating PMSM with ballscrew leads toughness more increasing, so it is able to make higher output. But the motor becomes affected more directly by disturbance, it is more increased requirements of high precision driving.
     In this paper, we target that realizing high precision positioning servo system without affected disturbance, we experimentally considered improving control response from a view of motor control by applying variable gain controller and feed forward control.

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  • Noboru NIGUCHI, Katsuhiro HIRATA, Akira KOHARA, Kazuaki TAKAHARA
    2019 Volume 27 Issue 1 Pages 140-145
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     We propose a current superimposition variable flux reluctance motor for a traction motor of hybrid electric vehicles. This motor has 2 sets of 3-phase coils, and 2 current control methods (single and twin vector controls) can be applied. However, any effective control methods have not seen. This paper discusses the current control method of the current superimposition variable flux reluctance motor. Single and twin vector controls are compared. The single vector control is effective for the current superimposition variable flux reluctance motor because even orders of the currents are removed by composing 2 phase currents. In addition, harmonic components of the phase current under single vector control contribute to increase a torque.

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  • Tadashi YAMAGUCHI, Yoshihiro KAWASE, Masahide SHIBATA, Tomoyasu FURUKA ...
    2019 Volume 27 Issue 1 Pages 146-151
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In this paper, we analyzed the interbar current taking into account of the contact resistance between the secondary conductor and the steel sheets of two V-skewed squirrel-cage induction motors using the 3-D parallel finite element method. We clarified the influence of the contact resistance on the interbar current in the V-skewed IM.

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  • Tadashi YAMAGUCHI, Yoshihiro KAWASE, Koshiro MATSUDA, Keiichi MORINAGA
    2019 Volume 27 Issue 1 Pages 152-157
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In this paper, we analyzed the magnetic field of an outer-rotor IPM motor using the three-dimensional parallel finite element method in order to investigate the influence of the shape and the arrangement of the permanent magnets. We clarified that providing a flux barrier between the divided magnets is able to reduce the leakage magnetic flux between the divided magnets and to prevent the torque from decreasing. Furthermore, it was clarified that the torque ripple can be reduced while maintaining the average torque by changing the arrangement of the magnets.

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  • Sayaka MATSUDA, Akira MORI, Masaya WATADA, Takamichi HIRATA, Chihiro K ...
    2019 Volume 27 Issue 1 Pages 158-164
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In recent years, atmospheric-pressure plasmas are applied in the medical applications. Although the mechanism of action remains unclear, new biomedical applications of plasma have been found. Experiments using atmospheric pressure plasmas confirmed several effects such as burn healing with angiogenesis. In addition, umbilical cord blood is expected to be applied to the field of regenerative medicine due to the presence of mesenchymal stem cells. We have been focusing treatment of Hypoxic Ischemic Encephalopathy (HIE). HIE caused by the discontinuation of blood supplied means that a part of the brain is necrotized, and a brain function is impaired. There is no fundamental therapy for HIE except for symptomatic therapy as of now. Because of preservation and recovery of brain functions can be expected, as a study on HIE treatment, we consider and report on a method of administrating atmospheric-pressure plasma and umbilical cord blood to HIE model rat.

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  • Kunihisa TASHIRO, Hiroyuki WAKIWAKA, Kaiko MINAKATA, Toichiro KIMURA, ...
    2019 Volume 27 Issue 1 Pages 165-168
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     novel eddy current method for magnetic plate identification is presented. This method uses the magnetic property in low frequency and conductive property in high frequency of the magnetic plates. The frequency profiles are measured with a conventional impedance analyzer, as a function of lift-off, which represents the distance between the coil and magnetic plate. If a coil is placed to a magnetic plate, there is a cross frequency at which the measured value is as same as inductance of coil only. The measured value of cross frequency depends on the coil diameter, placed magnetic plate, not strongly depends on the liftoff. In this paper, identification of iron and nickel plates are successfully demonstrated. A discussion with an iron plate with nickel plating of 40 μm is also mentioned.

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  • D.S. PAMUJI, M.A. BRAMANTYA
    2019 Volume 27 Issue 1 Pages 169-174
    Published: 2019
    Released: July 17, 2019
    JOURNALS FREE ACCESS

     In this research, the effect of number of blades (2 and 3) of counter rotating wind turbine (CRWT) were simulated in transient condition to be further analyzed the performance and the fluid flow characteristic formed. The simulations used finite volume method approach with additional turbulance model SST k-omega under transient condition to be analyzed the development of the fluid flow started from idling rotors until rotated on their own steady angular velocities. Results of this research show that 2-bladed CRWT had higher steady angular velocity characteristic than 3-bladed CRWT, both of the front and rear rotors, but 3-bladed CRWT had faster performance in term of time to achieve their steady angular velocities than 2-bladed CRWT during the transient process. In term of mechanical power produced, the 3-bladed CRWT performed better than 2-bladed CRWT, around 10.5% in their own steady angular velocities. This results were supported by velocity deficit flow visualizations and velocity profile in selected regions.

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