Acta Medica Okayama 2005 Improvement of zone control induction heating equipment for high-speed processing of semiconductor 1069 1070 EN Daisuke Miyagi Aisya Saitoh Norio Takahashi Naoki Uchida Kazuhiro Ozaki In this paper, the effect of dividing into several small coil groups having different current and frequency on heating characteristics is investigated using FEM (finite element method). The heating characteristics of graphite of each coil is examined, and a useful information for controlling current and frequency, which realize the nearly uniform heating, is obtained. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1999 An open magnetic path type of single sheet tester for measurement of magnetostriction of electrical steel sheet EN Tomoya Nakase Masanori Nakano Koji Fujiwara Norio Takahashi No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 34 4 1998 Measuring system for magnetostriction of silicon steel sheet under AC excitation using optical methods EN Tomoya Nakase Masanori Nakano Koji Fujiwara Norio Takahashi A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined. Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured up to 2.0 T No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 35 5 1999 Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux density 3965 3967 EN Masanori Nakano Hidehiko Nishimoto Koji Fujiwara Norio Takahashi Due to structural limitation, the currently proposed apparatus based on a single sheet tester (SST) cannot measure magnetic properties along arbitrary directions (so-called 2-D magnetic properties) of silicon steel at high flux densities. In this paper, significant improvements are carried out on magnetizing windings and auxiliary yokes of a double excitation type of SST. Furthermore, crosswise overlapped H-coils are introduced so that even an ordinary single-excitation type of SST can be applicable to the measurements of 2-D properties. It is demonstrated that 2-D magnetization property up to 1.9 T can be measured by using the newly developed SST's No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1999 Single sheet tester having open magnetic path for measurement of magnetostriction of electrical steel sheet 3956 3958 EN Tomoya Nakase Masanori Nakano Koji Fujiwara Norio Takahashi A single sheet tester having closed magnetic path (a closed type of SST) has a problem that measurement accuracy of magnetostriction is considerably affected by electromagnetic force between specimen and yoke. Therefore, an open type has been developed. In order to get uniform flux distribution in a sufficiently large region, a compensating magnetizing winding is installed, and a method of waveform control is investigated, in which applied voltages to main and compensating windings are adjusted individually. The effectiveness of the newly developed open type is demonstrated by measuring magnetostrictions of thin amorphous sheet as well as highly grain-oriented silicon steel sheet No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 35 3 1999 Effect of minor loop on magnetic characteristics of permanent magnet type of MRI 1893 1896 EN Norio Takahashi Takeshi Kayano Koji Miyata Ken Ohashi A modeling technique of the minor loop using typical hysteresis loops is shown. The effect of the minor loop and eddy current in the pole piece of a permanent magnet type of MRI on the residual flux density of the probe coil is examined. It is illustrated that the change ΔB of residual flux density occurs due to the minor loop of the pole piece. It is also pointed out that the choice of time interval Δt is important in a nonlinear analysis considering the minor loop No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 39 3 2003 Analysis of the magnetic property of a permanent-magnet-type MRI - Behavior of residual magnetization 1337 1340 EN Norio Takahashi Ryousuke Suenaga Koji Miyata Ken Ohashi The minor loops of B and H of steel due to pulse excitation and eddy currents induced in steel affect the magnetic characteristics of a permanent-magnet-type MRI. In this paper, the magnetic properties of a permanent magnet assembly is examined by using the finite-element method taking into account minor loop. The distribution of residual magnetization in the yoke is illustrated, and the effect of residual magnetization on the behavior of residual flux density is examined. It is shown that the behavior of B and H in minor loops is affected by the eddy currents in the yoke and pole piece. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 31 3 1995 On the continuity of the magnetizing current density in 3-D magnetic field analysis with edge element 1364 1367 EN Koji Fujiwara Takayoshi Nakata Norio Takahashi Hiromitsu Ohashi The effects of the continuity of the magnetizing current density on the convergence of the incomplete Cholesky conjugate gradient method and the accuracy of the calculated flux densities are investigated by imposing different continuity conditions for both nodal and edge elements. It is shown that the continuity condition should be imposed precisely in the case of edge elements No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 2006 Effects of residual magnetism due to minor loop on magnetic property of permanent magnet type of MRI EN Norio Takahashi Ryousuke Suenaga Koji Miyata Ken Ohashi Summary form only given. The flux distribution of a permanent magnet type of MRI shown in Fig.1 is affected by the hysteresis (minor loop) and eddy currents in the pole piece and yoke due to the pulse current (Fig.2) of the gradient coil. In this paper, the effects of the hysteresis and the eddy current in the yoke on the residual flux density of the probe coil are investigated. It can be assumed that the eddy current does not flow in the pole piece because it is divided into pieces. The eddy current flows in the yoke. Fig.3 shows the change of residual flux density /spl Delta/B/sub z/ at the point S(0,0) in Fig.1. /spl Delta/B/sub z/ is given by /spl Delta/B/sub z/=B/sub z1/-B/sub z0/ (1), where B/sub z0/ is the flux density at the instant t=0(I=0A). B/sub z1/ is the flux density at the instant t=i(I=0A). The instant of 1,2,3,... in Fig.2 corresponds to 1,2,3,... in Fig.3. Fig.3 shows that the hysteresis in the pole piece and yoke should be taken into account. The effect of eddy current in the yoke on the residual flux density /spl Delta/B/sub z/ is not negligible. These results suggests that the reduction of the amplitudes of minor loop and eddy current is important in order to improve the operating characteristics of the permanent magnet type of MRI. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 24 1 1988 Improvements of the T-Ω method for 3-D eddy current analysis 94 97 EN Takayoshi Nakata Norio Takahashi K. fujiwara Y. Okada An improved T-Ω method that can analyze magnetic fields produced not only by eddy currents but also by magnetizing currents is proposed. The method is applied to the analysis of 3-D eddy-current models with holes. The usefulness of the method is investigated by comparing calculated results with measured results and with results obtained by the A-Φ method. The T-Ω method has the advantage that the CPU time can be considerably reduced when most of the analyzed region is current-free and the eddy current flows two-dimensionally. The method is especially effective when the shape of the winding is simple and the distribution of magnetizing current is known beforehand. It is not effective when most of the analyzed region is current-carrying No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 36 4 2000 Thin film write head field analysis using a benchmark problem 1784 1787 EN Koji Fujiwara Fumiaki Ikeda Akihisa Kameari Yasushi Kanai Kimio Nakamura Norio Takahashi Koji Tani Takashi Yamada A benchmark problem has been proposed by the Storage Research Consortium (SRC) in Japan, for evaluating the applicability of computer codes to 3-D nonlinear eddy current analysis of thin film magnetic recording write head. Various codes using the finite element method are compared in terms of the write head field and the computational efficiency. The difficulty in 3-D mesh generation of thin film head is also discussed. The write head fields calculated by various codes using different meshes show fairly good agreement. The calculated write head fields are verified by measurement using a stroboscopic electron beam tomography. It is found that the calculation time strongly depends on unknown variables No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1997 Some useful techniques in analysis and design of electric machines EN Norio Takahashi Some new techniques in the analysis and design of electric machines are discussed, namely: the time-periodic analysis of the magnetic field in nonoriented materials, taking into account hysteresis characteristics; 3-D transient analysis of capacitor-discharge impulse magnetizers; and a 3-D optimization method of electric machines considering nonlinearity and eddy currents. The usefulness of these techniques is shown by applying them to actual machines and comparisons with measurement results No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1992 Study on cause of quench at joint between multifilamentary superconducting cable and copper plate using 3-D FEM 294 294 EN Norio Takahashi Takayoshi Nakata Y. Fujii K. Funabiki M. Takeo No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 41 5 2005 Magnetic shield design of perpendicular magnetic recording head by using topology optimization technique 1788 1791 EN Yoshifumi Okamoto Masaya Ohtake Norio Takahashi It is necessary to develop a recording head having large recording field and small stray field to adjacent tracks and adjacent bits in perpendicular magnetic recording system. In this paper, in order to decrease the leakage flux in the adjacent bit, the approach of magnetic shield design of perpendicular magnetic recording head for 200 Gb/in/sup 2/ is performed by using the topology optimization technique. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 32 3 1996 Investigation of simulated annealing method and its application to optimal design of die mold for orientation of magnetic powder 1210 1213 EN Norio Takahashi Kenji Ebihara Koji Yoshida Takayoshi Nakata Ken Ohashi Koji Miyata Factors affecting the convergence characteristics and results obtained by the optimal design method using the finite element method and simulated annealing are investigated systematically, and the optimal parameters for simulated annealing method are obtained. The optimal shape of the die mold for orientation of the magnetic powder (nonlinear magnetostatic problem) is obtained using finite elements and simulated annealing. The experimental verification is also carried out No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 40 2 2004 3-D finite element analysis of current distribution in HTS power cable taking account of E-J power law characteristic 908 911 EN Daisuke Miyagi Tomohiro Wakatsuki Norio Takahashi Shinji Torii Kiyotaka Ueda A method for analyzing the current distribution in high-T/sub c/ superconducting (HTS) power cable is examined by the aid of the novel use of anisotropic conductivity and three-dimensional finite element method in consideration of the E-J power law characteristic. The detailed current distribution in the cable is illustrated and the shielding effect of HTS shield is also examined. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 31 3 1995 Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method 1416 1419 EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Kazuhiro Muramatsu Hiromitsu Ohashi Hui Ling Zhu A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 31 3 1995 Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Kazuhiro Muramatsu Hiromitsu Ohashi Hui Ling Zhu A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 35 3 1999 Magneto-thermal-fluid analysis taking account of natural convection using semi-Lagrange coordinate system 1670 1673 EN Kazuhiro Muramatsu Norio Takahashi Takayuki Mimura A method for magneto-thermal-fluid analysis, taking account of natural convection using a semi-Lagrange coordinate system, is developed. The developed method is applied to a simple induction heating model in which the steel plate is heated due to an eddy current. It is shown that the result, considering the convection in air, is different from the result neglecting it No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 32 4 1996 Numerical and experimental investigations of current distribution at the joint between AC superconducting cable and normal conducting plate 2962 2965 EN Norio Takahashi Kazuhiro Muramatsu Masanori Nakano Y. Sato T. Kondo The effect of the configuration of the joint between an ac superconducting cable and a normal conducting plate on the current distribution and the joule loss is investigated by using the 3-D finite element method. It is shown that the concentration of current can be reduced by changing the configuration of joint. The effectiveness of the analysis is verified by measuring the current distribution on the surface of a copper plate and the quenching current No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 28 2 1992 Investigation of effectiveness of edge elements 1619 1622 EN Norio Takahashi Takayoshi Nakata K. Fujiwara T. Imai The effectiveness of the edge element is investigated by comparing systematically the number of unknown variables with that of the nodal element. It is shown that the edge element is superior to the nodal element from the standpoints of computer storage and CPU time. The 3-D periodic boundary condition for the edge element is also derived in order to reduce the computer storage and the CPU time No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1989 3-D non-linear eddy current analysis using the time-periodic finite element method EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Akira Ahagon A three-dimensional finite element method using the A-φ formulation for analyzing time-periodic nonlinear magnetic fields with eddy currents has been developed. The CPU time of this method can be reduced to below that of the conventional step-by-step method, because the new method calculates the time-periodic phenomena directly, not through the transient phenomena. The finite element discretization of the method is described in detail. As an example of application, a loaded transformer is analyzed No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 27 5 1991 3-D finite element analysis of coupling current in multifilamentary AC superconducting cable 4061 4064 EN Norio Takahashi Takayoshi Nakata Y. Fujii Kazuhiro Muramatsu M. Kitagawa Jun Takehara A method for analyzing the 3-D coupling current which is induced by an AC magnetic field in a multifilamentary superconducting cable is developed. In this method, such a superconducting cable, in which many twisted filaments are embedded in a matrix, is treated as macroscopic, having anisotropic conductivity. The method for treating the anisotropy of conductivity and the 3-D finite-element formulation are presented. The effectiveness of the technique is illustrated by the analysis of the 3-D coupling currents of superconducting cables. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 36 4 2006 Investigation of evolution strategy and optimization of induction heating model 1085 1088 EN Makoto Horii Norio Takahashi Takashi Narita An optimal design method using the finite element method and the evolution strategy (ES) is investigated. The evolution strategy is applied to the optimization of induction heating model. The position of auxiliary coil, frequency and ampere-turns are optimized so that the distribution of eddy current density on the surface of steel becomes uniform. It is shown that the selection of the appropriate parameter is important in the practical application of ES No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1989 Optimal design method of 3-D nonlinear magnetic circuit by using magnetization integral equation method EN Norio Takahashi Takayoshi Nakata N. Uchiyama A novel method for determining the sizes of iron parts in a magnetic circuit, which preserves the requirement of prescribed flux densities, has been developed. In order to take into account the nonlinear characteristics of iron, the magnetization integral equation method is used in the analysis. The effectiveness of the method is examined by applying it to the pole shape of an electromagnet. The developed software was verified by comparing calculated results with measured ones No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1997 3-D eddy current analysis in moving conductors of permanent magnet type retarders using moving coordinate system EN Kazuhiro Muramatsu Norio Takahashi Tomohiro Hashino Chuji Yamada Susumu Kobayashi Tohru Kuwahara A 3-D DC steady state eddy current analysis of a permanent magnet type retarder which rotates at high speed is carried out using a moving coordinate system. The method of DC steady state analysis using a moving coordinate system is described. The calculated results, braking torque etc., are compared with measured ones No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 25 5 1989 3-D non-linear eddy current analysis using the time-periodic finite element method 4150 4152 EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Akira Ahagon A three-dimensional finite element method using the A-φ formulation for analyzing time-periodic nonlinear magnetic fields with eddy currents has been developed. The CPU time of this method can be reduced to below that of the conventional step-by-step method, because the new method calculates the time-periodic phenomena directly, not through the transient phenomena. The finite element discretization of the method is described in detail. As an example of application, a loaded transformer is analyzed No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 27 6 1991 Factors affecting errors due to 2-D approximate analysis of 3-D magnetic fields with eddy currents [rotating machines] 5223 5225 EN Norio Takahashi Takayoshi Nakata K. Fujiwara T. Nishimura The effects of the leakage flux, eddy current path, and end coil of electric machines on the flux and eddy current density analyzed by the 2-D approximation are investigated systematically by making a comparison with 3-D analysis. It is shown that, when the gap length is relatively large, the difference between the fluxes calculated by 2-D and 3-D analyses is pronounced due to the leakage flux. The flux in the pole obtained by 3-D analysis is larger than that obtained by 2-D analysis under constant current excitation, and the flux obtained by 3-D analysis is less than that obtained by 2-D analysis under constant voltage excitation. When the eddy current flows in the thin core, a larger error occurs in the 2-D analysis, because there is a great difference in eddy current paths between 2-D and 3-D models No potential conflict of interest relevant to this article was reported.

IEEE Acta Medica Okayama 1051-8223 14 2 2004 The shielding effect of HTS power cable based on E-J power law 654 657 EN Daisuke Miyagi Satoru Iwata Tomohiro Wakatsuki Norio Takahashi Shinji Torii Kiyotaka Ueda Kenji Yasuda A method for analysing the current distribution in high-T/sub c/ superconducting (HTS) power cable is examined by the aid of the novel use of anisotropic conductivity and 3-D finite element method considering E-J power law characteristic. The detailed current distribution in the cable is illustrated and the shielding effect of HTS shield layer with intervals is also examined. It is shown that AC losses in shield layer with intervals are increased when the interval between wires becomes large. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1992 Accuracy of Advanced Energy Method for Calculating Electromagnetic Force EN Norio Takahashi Takayoshi Nakata K. Fujiwara T. Moriwake No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 36 4 2000 Optimal design of tank shield model of transformer 1089 1093 EN Norio Takahashi Tetsuro Kitamura Makoto Horii Jun Takehara A tank shield model of a transformer which is proposed by the Investigation Committee of IEE of Japan is analyzed. This is a model having the constraint that the maximum eddy current density should be less than a specified value. The automatic 3D mesh generation technique for hexahedral element is investigated for the optimal design of such a model. It is shown that reasonable results that satisfy the specified constraints can be obtained using Rosenbrock's method within the acceptable CPU time. The experimental verification is also carried out No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 30 6 1994 Magnetostriction measurements with a laser Doppler velocimeter 4563 4565 EN Takayoshi Nakata Norio Takahashi Masanori Nakano Kazuhiro Muramatsu Masahide Miyake A new method for measuring the magnetostriction of silicon steel sheet using a laser Doppler velocimeter has been developed. This method has the following advantages: (a) non-contact measurement, (b) better resolution (less than 4×10-8 m under the condition that the error is within 1%) than conventional methods, (c) measurement of magnetostriction in any direction of anisotropic material and (d) little operator skill required No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 40 4 2004 Analysis of writing characteristics of CF-SPT head using 3-D read/write simulation system 2613 2615 EN Masaya Ohtake Norio Takahashi Kiminari Shinagawa Recently, the increase of areal recording density is remarkable. In order to develop a high density recording device, a read/write (R/W) simulation using three dimensional (3-D) magnetic field analysis is indispensable. In this paper, the magnetic field in a cusp-field single-pole-type (CF-SPT) head with discrete track media is analyzed using a 3-D R/W simulation system, in which edge-based finite element method and 3-D medium hysteresis model based on the ensemble of the Stoner-Wohlfarth (SW) particles are combined. The effects of ampereturns and the discrete track media on the distribution of recorded magnetization are investigated. The detailed behavior of flux around the discrete track media and continuous media is illustrated. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 34 5 1997 Optimization of permanent magnet type of retarder using 3-D finite element method and direct search method 441 416 EN Norio Takahashi Mitsutoshi Natsumeda Kazuhiro Muramatsu Chuji Yamada Makoto Ogawa Shin Kobayashi Tohru Kuwahara 3-D optimization method using the combined experimental design method and direct search method is developed to apply to the optimal design of a permanent magnet type of retarder. It is shown that the braking torque is increased by using the optimization method. The CPU time can be considerably reduced by utilizing the initial values obtained by the experimental design method No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 25 5 1989 Optimal design method of 3-D nonlinear magnetic circuit by using magnetization integral equation method 4144 4146 EN Norio Takahashi Takayoshi Nakata N. Uchiyama A novel method for determining the sizes of iron parts in a magnetic circuit, which preserves the requirement of prescribed flux densities, has been developed. In order to take into account the nonlinear characteristics of iron, the magnetization integral equation method is used in the analysis. The effectiveness of the method is examined by applying it to the pole shape of an electromagnet. The developed software was verified by comparing calculated results with measured ones No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 39 3 2003 Study on problems in detecting plural cracks by alternating flux leakage testing using 3D nonlinear eddy current analysis 1527 1530 EN Yuji Gotoh Norio Takahashi The alternating magnetic flux leakage testing is used for the detection of cracks in a steel plate. A new technique of how to detect plural cracks, which are located at a very short distance from each other, using the parallel (x-) component of the leakage flux density is proposed. The behavior of leakage flux is examined using a three-dimensional edge-based hexahedral finite-element method. The effects of dimensions of search coils and cracks on the detection accuracy are illustrated. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 36 4 2000 Effect of continuity of potential on accuracy in magnetic field analysis using nonconforming mesh 1578 1582 EN Kazuhiro Muramatsu Yasuhiro Yokoyama Norio Takahashi Andrew Nafalski Ozdemir Gol Methods of analyzing magnetic fields in rotating machines using nonconforming meshes, in which only an interpolation technique is applied, are investigated. The effect of the continuity of potentials at nonconforming surfaces on accuracy is examined, it is shown that although the flux distribution is not affected by the discontinuity of the potential, the force and torque are fairly affected by the discontinuity. Therefore, it is shown that a continuous method, or a discontinuous method using a fine mesh should be used especially in force and torque calculation. An analysis of an induction motor is also carried out using a nonconforming mesh No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 37 5 2000 3-D optimization of design variables in x-, y- and z-directions of transformer tank shield model 3631 3634 EN Makoto Horii Norio Takahashi Jun Takehara By using the automatic 3-D mesh generation technique using hexahedral elements, which is applicable when design variables are changed in x-, y- and z-directions, a transformer tank shield model is optimized. The volume of tank shield can be considerably reduced by using the Rosenbrock's method (RBM) compared with the previous result having design variables in one direction. It is shown that the determination of initial values for RBM using the experimental design method (EDM) is indispensable for the practical application of the optimization method to obtain a desired result within an acceptable CPU time No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 2002 Effect of eddy current in shielding plate and electron gun on flux distribution in CRT EN Norio Takahashi Koji Shimada H. Wakasono Summary form only given. An inner magnetic shield (IMS) is set inside a cathode ray tube (CRT) to reduce the disturbance from outside of the CRT, such as geomagnetism. The eddy current induced in the IMS due to the changing current in the deflection coil may affect the flux distribution in the CRT. The eddy current is also induced in the electron gun when coils for velocity modulation (VM) are set near the gun. Although the effect of the eddy current is important, reports about the analysis of this phenomenon are few. In this paper, the effect of the eddy current in the IMS and electron gun on flux distribution in the CRT is analyzed by using the 3-D finite element method. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 29 2 1992 A simple algorithm for adaptive refinement of tetrahedral meshes combined with edge elements 1898 1901 EN Piotr Olszewski Takayoshi Nakata Norio Takahashi Koji Fujiwara A simple algorithm yielding unique face subdivision patterns of locally refined tetrahedral elements by the Delaunay tessellation process is presented. Due to the numerous advantages of edge elements, the algorithm is combined with the magnetostatic edge element computer code. A comparative analysis of four different error estimates used to locate elements for refinement, including a new one suitable for edge elements, is described. The performance of the proposed algorithm and the effectiveness of the error estimates are demonstrated by means of three-dimensional test problems No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 34 4 1998 Measuring system for magnetostriction of silicon steel sheet under AC excitation using optical methods 2072 2074 EN Tomoya Nakase Masanori Nakano Koji Fujiwara Norio Takahashi A measuring system for magnetostriction of silicon steel sheet using optical methods and a single sheet tester has been developed to establish a standard test method for IEC and JIS. Various factors affecting measurement accuracy and reproducibility of the developed system are examined. Two optical instruments, such as a laser Doppler vibrometer and a heterodyne displacement meter, are compared. 3-D characteristics of magnetostriction under ac excitation in the rolling direction are measured up to 2.0 T No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 28 5 1992 Study on cause of quenching at the joint between multifilamentary superconducting cable and normal conducting cable using 3D FEM 2826 2828 EN Norio Takahashi Takayoshi Nakata Y. Fujii K. Funaki M. Takeo Investigates the cause of quenching at the joint between a multifilamentary superconducting cable and a normal conducting cable. The 3D current distribution is analyzed. It is found that the cause of quenching is the extreme concentration of current in the joint due to the pronounced skin effect at liquid helium temperature. The mechanism of the concentration of current which is affected by the twist pitch and skin depth is also clarified quantitatively by numerical analysis No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1993 Measurement of Magnetic characteristics in arbitrary directions of grain-oriented silicon steel EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Masanori Nakano No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 38 2 2002 A proposal of finite-element analysis considering two-dimensional magnetic properties 889 892 EN Koji Fujiwara Takayuki Adachi Norio Takahashi A technique for analyzing the magnetic field in anisotropic material using the effective anisotropic reluctivity proposed by Enokizono is examined. It is shown that the Enokizono model can be transformed into another model having a conventional form. By expanding the examination of such a conventional form, a new finite element formulation for taking account of the two-dimensional (2-D) magnetic property is proposed. As the modeling of the 2-D magnetic property at the high flux density region is important in the practical analysis of the magnetic device, the extrapolation method of the magnetic property is examined. It is shown that the Bezier interpolation is fairly effective to stabilize the convergence characteristic of the Newton-Raphson (N-R) iteration in the nonlinear magnetic field analysis, taking account of the 2-D magnetic property No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 38 2 2002 Effective optimal design of 3-D magnetic device having complicated coil using edge element and Biot-Savart method 1021 1024 EN Takuma Ohnishi Norio Takahashi It is troublesome and time consuming to treat a coil of complicated shape with optimization methods using edge elements, because the current vector potential in the coil of changed shape (changed mesh) should be calculated at each iteration of the optimization. In this paper, an effective optimal design method using the Biot-Savart method (As method) and the evolution strategy is investigated. As it is not necessary to generate a mesh for the coil by using the As method, the mesh becomes simple and, moreover, it is not necessary to calculate the current vector potential in the changed coil at each iteration in order to give the current vector potential in the coil. The usefulness of the proposed method is illustrated by applying it to the optimal design of a deflection coil for a cathode-ray tube No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 31 3 1995 Practical analysis of 3-D dynamic nonlinear magnetic field using time-periodic finite element method 1416 1419 EN Norio Takahashi Koji Fujiwara Takayoshi Nakata Yoichi Ogura A practical 3-D finite element method using edge elements for analyzing stationary nonlinear magnetic fields with eddy currents in electric apparatus, in which the flux interlinking the voltage winding is given, has been proposed. The method is applied to the analysis of magnetic fields in the Epstein frame No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 35 3 1999 Problems in practical finite element analysis using Preisach hysteresis model 1243 1246 EN Norio Takahashi Shun-ichi Miyabara Koji Fujiwara An efficient method, which is called the “inverse distribution function method”, for calculating the magnetic field strength H from the flux density B through the Preisach model is developed. By using the method, H can be directly obtained without iteration from B which is calculated by the usual FEM, with the magnetic vector potential as an unknown variable. The effects of the dimension n of the inverse distribution function on the CPU time and the memory requirements are investigated through a numerical example by increasing the dimension n of the inverse distribution function. It is shown that the additional CPU time for taking account of hysteresis is negligible when n is less than about 200 No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 30 5 1994 Investigation of a model to verify software for 3-D static force calculation 3483 3486 EN Norio Takahashi Takayoshi Nakata H. Morishige Requirements for a model to verify software for 3-D static force calculation are examined, and a 3-D model for static force calculation is proposed. Some factors affecting the analysis and experiments are investigated in order to obtain accurate and reproducible results No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 41 5 2005 Investigation of AC loss of permanent magnet of SPM motor considering hysteresis and eddy-current losses 1964 1967 EN A. Fukuma Susumu Kanazawa Daisuke Miyagi Norio Takahashi NdFeB sintered magnets are widely used in rotating electrical machines. In order to develop an efficient rotating machine, it is important to estimate ac loss of the permanent magnet of rotor precisely. In this paper, the ac losses of the permanent magnet of IEEJ model (surface permanent-magnet motor model) are examined by using the three-dimensional finite-element method taking into account the newly measured hysteresis losses of permanent magnet. The result shows that we should consider not only the eddy-current loss but also the hysteresis loss, when the frequency of ac field due to a slot ripple is of the order of several hundred hertz. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1992 Low loss transformer using rotating magnetic field 28 28 EN Takayoshi Nakata Norio Takahashi Koji Fujiwara Masanori Nakano M. Nagao No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 42 4 2006 3-D topology optimization of single-pole-type head by using design sensitivity analysis 1087 1090 EN Yoshifumi Okamoto Koji Akiyama Norio Takahashi It is necessary to develop a write head having a large recording field and small stray field in adjacent tracks and adjacent bits in perpendicular magnetic recording systems. In this paper, a practical three-dimensional topology optimization technique combined with the edge-based finite-element method is proposed. A technique for obtaining a smooth topology is also shown. The optimization of single-pole-type head having a magnetic shield is performed by using the topology optimization technique so that the leakage flux in the adjacent bit can be reduced. A useful shape of the magnetic shield obtained by the proposed technique is illustrated. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 38 2 2002 3-D nonlinear eddy-current analysis of alternating magnetic flux leakage testing - analysis of one crack and two cracks 1209 1212 EN Yuji Gotoh Norio Takahashi The alternating magnetic flux leakage testing has been applied in the nondestructive inspection process for detecting cracks on the surface of steel. This paper describes numerical analysis using three-dimensional (3-D) edge-based hexahedral finite element method for this testing. The necessity of nonlinear analysis is clarified in comparison with the linear analysis (jω method). The characteristic of leakage flux is confirmed by verification experiment. The possibility of distinguishing two cracks is examined by calculating the detailed distribution of leakage flux around cracks No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 37 5 2000 Nonlinear analysis of eddy current and hysteresis losses of 3-D stray field loss model (Problem 21) 3672 3675 EN Norio Takahashi Toshiomi Sakura Zhiguang Cheng The evaluation method of stray field loss of engineering oriented loss model (TEAM Workshop Problem 21) is investigated. It is shown that the nonlinear eddy current analysis is obligatory in order to investigate the eddy current loss in the steel plate, because the flux and eddy current in steel are affected by the permeability of the plate. The hysteresis loss in such a steel plate having a substantial skin effect is not negligible, even if the flux density in air is small No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 33 2 1997 3-D time-periodic finite element analysis of magnetic field in non-oriented materials taking into account hysteresis characteristics 1584 1587 EN Kazuhiro Muramatsu Norio Takahashi Takayoshi Nakata Masanori Nakano Yasuo Ejiri Problems in analyzing 3-D stationary nonlinear magnetic field in non-oriented material taking into account hysteresis characteristics and eddy current, such as finite element formulation and convergence of nonlinear iteration, are discussed No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 32 3 1996 Linear AC steady-state eddy current analysis of high speed conductor using moving coordinate system 749 752 EN Kazuhiro Muramatsu Takayoshi Nakata Norio Takahashi Koji Fujiwara A method for linear analysis of AC steady state eddy currents in a moving conductor using a moving coordinate system is investigated. It is shown that the moving coordinate system is superior to a fixed coordinate system for the analysis of a high speed conductors from the standpoint of stability of the solution. The applicable extent of the moving coordinate system is also discussed for the modelling of electric machine characteristics No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 24 1 1988 Physical meaning of gradФ in eddy current analysisusing magnetic vector potential 178 181 EN N. Nakata Norio Takahashi K. Fujiwara The physical meaning of the gradφ in the A-φ method is investigated in order to determine when it can be safely neglected in order to reduce computation time. The relationship between eddy current distribution and gradφ and the effects of boundary conditions on gradφ are examined for several 2-D examples. It is shown that gradφ in 2-D analysis is a constant that modifies the interlinkage flux of the conductor, which is denoted by the magnetic vector potential A No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 36 4 2000 Analysis of magnetic characteristics of three-phase reactor made of grain-oriented silicon steel 1894 1897 EN Takashi Kohsaka Norio Takahashi Shuichi Nogawa Minoru Kuwata Flux and iron loss distributions of three-phase reactor are analyzed using the finite element method considering 2-D B-H curves and iron losses in arbitrary directions which are measured up to high flux density. It is shown that the total iron loss of reactor yoke does not change so much by the yoke dimension, although the local iron loss is increased when the width of yoke is decreased. The experimental verification of flux and iron loss distributions are also carried out No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 1999 Improvements of single sheet testers for measurement of 2-D magnetic properties up to high flux density EN Masanori Nakano Hidehiko Nishimoto Koji Fujiwara Norio Takahashi Due to structural limitation, the currently proposed apparatus based on a single sheet tester (SST) cannot measure magnetic properties along arbitrary directions (so-called 2-D magnetic properties) of silicon steel at high flux densities. In this paper, significant improvements are carried out on magnetizing windings and auxiliary yokes of a double excitation type of SST. Furthermore, crosswise overlapped H-coils are introduced so that even an ordinary single-excitation type of SST can be applicable to the measurements of 2-D properties. It is demonstrated that 2-D magnetization property up to 1.9 T can be measured by using the newly developed SST's No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 38 5 2002 Effect of eddy current in shielding plate and electron gun on flux distribution in CRT 2352 2354 EN Norio Takahashi Yoshiyuki Ochi Katsumi Nakano Koji Shimada Hiromi Wakasono The eddy current induced in an inner magnetic shield (IMS) and an electron gun affect the flux distribution of a cathode ray tube, causing a possible degrade of picture quality. In this paper, the effect of the distance between an IMS and a deflection coil on the eddy-current distribution is examined. The eddy current induced in the electron gun, when the coils for velocity modulation (VM) are set near the electron gun, is also analyzed. It is found that the variation of flux distribution is mainly affected by the shape of VM coil. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 39 3 2003 Study on problems in detecting plural cracks by alternating flux leakage testing using 3D nonlinear eddy current analysis 1527 1530 EN Yuji Gotoh Norio Takahashi The alternating magnetic flux leakage testing is used for the detection of cracks in a steel plate. A new technique of how to detect plural cracks, which are located at a very short distance from each other, using the parallel (x-) component of the leakage flux density is proposed. The behavior of leakage flux is examined using a three-dimensional edge-based hexahedral finite-element method. The effects of dimensions of search coils and cracks on the detection accuracy are illustrated. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 35 5 1999 Single sheet tester having open magnetic path for measurement of magnetostriction of electrical steel sheet 3956 3958 EN Tomoya Nakase Masanori Nakano Koji Fujiwara Norio Takahashi A single sheet tester having closed magnetic path (a closed type of SST) has a problem that measurement accuracy of magnetostriction is considerably affected by electromagnetic force between specimen and yoke. Therefore, an open type has been developed. In order to get uniform flux distribution in a sufficiently large region, a compensating magnetizing winding is installed, and a method of waveform control is investigated, in which applied voltages to main and compensating windings are adjusted individually. The effectiveness of the newly developed open type is demonstrated by measuring magnetostrictions of thin amorphous sheet as well as highly grain-oriented silicon steel sheet No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 42 2 2006 Improvement of zone control induction heating equipment for high-speed processing of semiconductor devices 292 294 EN Daisuke Miyagi Aisya Saitou Norio Takahashi Naoki Uchida Kazuhiro Ozaki In order to process a semiconductor device of high quality, uniform heating is necessary, but it is not easy to heat uniformly with conventional induction heating equipment. To solve this problem, zone control induction heating equipment has been jointly developed. In this paper, we examine the effect of dividing an induction heater into several small coil groups having different current and frequency, using the finite-element method. We describe the heating characteristics of the zone control coil groups and show that nearly uniform heating is possible by controlling both current and frequency. No potential conflict of interest relevant to this article was reported.

Acta Medica Okayama 42 4 2006 3-D topology optimization of single-pole-type head by using design sensitivity analysis 1087 1090 EN Yoshifumi Okamoto Koji Akiyama Norio Takahashi It is necessary to develop a write head having a large recording field and small stray field in adjacent tracks and adjacent bits in perpendicular magnetic recording systems. In this paper, a practical three-dimensional topology optimization technique combined with the edge-based finite-element method is proposed. A technique for obtaining a smooth topology is also shown. The optimization of single-pole-type head having a magnetic shield is performed by using the topology optimization technique so that the leakage flux in the adjacent bit can be reduced. A useful shape of the magnetic shield obtained by the proposed technique is illustrated. No potential conflict of interest relevant to this article was reported.

岡山大学工学部 Acta Medica Okayama 0475-0071 18 1 1984 Finite Element Analysis of Transformer Cores 1 31 EN 10.18926/15762 The quantitative analysis of localized flux distributions in transformer cores has become easy through the progress of numerical field calculations. In this paper, the effects of core constructions, joint configurations, magnetizing characteristics of materials on the flux distributions are examined using newly developed techniques such as a gap element, an approximate method for solving three-dimensional magnetic fields, the time periodicity finite element method, an efficient technique for treating hysteresis characteristics and so on. A method for the optimum design of transformer cores is also discussed. Main results obtained can be summarized as follows: (a) The building factor of the core made of higely-oriented silicon steel is larger than that of the conventional core. (b) The iron losses at joints are much affected by overlap lengths, number of laminations per stagger layer and a small irregularity of the arrangement of sheets. (c) It is clarified that examinations of the optimum construction of core and the most desirable magnetic characteristics of core material are possible using the finite element method. No potential conflict of interest relevant to this article was reported.

岡山大学工学部 Acta Medica Okayama 0475-0071 14 1 1979 Iron Losses of Silicon Steel due to Rotating Fluxes (Inclined Rotating Flux and Distorted One) 15 28 EN 10.18926/15736 Characteristics of iron losses in silicon steel due to inclined rotating fluxes and distorted ones are described. Iron losses due to rotating fluxes have been measured at various conditions for grain-oriented and non-oriented silicon steels by using an improved thermistor-bridge method. Loss measurements indicate that the iron loss due to the inclined rotating flux is greater than that due to the non-inclined one. However, the iron loss due to the distorted rotating flux is not always greater than that due to the non-distorted one. No potential conflict of interest relevant to this article was reported.