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Smallness in Size Makes High Power CO2 Lasers Attroctive
Junichi Nishimae, Kenji Yoskizawa
1992 Volume 112 Issue 1 Pages
1-8
Published: January 20, 1992
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Kaneyuki Ohta, Koichiro Sawa
1992 Volume 112 Issue 1 Pages
9-15
Published: January 20, 1992
Released on J-STAGE: July 15, 2008
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In the case of applying BEM to the 3-D magnetostatic field calculation, the two scalar potentials method introduced by J. Simkin and C. W. Trowbridge, is effective, because it needs fewer unknowns than the vector potential method and brings less calculation error than one potential method. But in the two scalar potentials method we must calculate line integrals on the boundary for making interface conditions between the inhomogeneous regions. In order to improve this disadvantage, we propose a new technique in which the interface conditions can be obtained without this line integrals and consequently we could shorten the calculation time.
In BEM, it is the most significant problem that the nearly singularity of surface integrals appears in calculating the coefficient matrices and potentials at internal points. Especially when the internal point becomes closer to the boundary, the nearly singularity of the integrands becomes severer and numerical calculation of this integrals becomes more difficult. Therefore, we apply Takeda's analytical integral formula to the two scalar potentials method, and have confirmed its validity in accuracy and calculation time.
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Keiichi Mori, Nariaki Yanagisawa, Toshiharu Kimura, Machiko Totoki
1992 Volume 112 Issue 1 Pages
16-20
Published: January 20, 1992
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To estimate the magnetic field outside a ferromagnetic hollow object such as ship or wheeled vehicle from the inside field measurements, we have developed a method to represent the object by the distribution of virtual magnetic charges on two sheets of confocal spheroidal surfaces. In the method, the magnetic field both inside and outside the object is expanded in prolate spheroidal harmonic functions of the lowest degree, and the surfaces are determined such that the charges when distributed axially and radially on them produce the same amount of the corresponding harmonic both inside and outside the object as the actual one respectively. In an example of an oblong steel box of the length L magnetized by the earth's field, the estimated field on a line extending parallel to the major axis with a distance 0.25L and a coverage ±0.7L was equal to the measured one with a standard error amounting to 9% of the peak field.
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Motoo Tanaka, Hajime Tsuboi, Takayoshi Misaki
1992 Volume 112 Issue 1 Pages
21-26
Published: January 20, 1992
Released on J-STAGE: July 15, 2008
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Boundary element method is suitable for the three-dimensional analysis of magnetostatic field in the homogenous material without magnetic saturation. However, the requirement of the computer resources for the three-dimensional boundary element analysis becomes large because the cofficient matrix of the final simultaneous equations is dense. In this paper, the authors try to reduce the number of unknowns by the use of accurate and stable approximation of unknown vector variables for efficient computation. An edge element on which magnetic flux density is defined as a vector variable and its divergence is equal to zero is proposed. In this case, we can expect that the computational accuracy is improved by introducing the zero-divergence constraint of the tangential components of the magnetic flux density. On the element, the discretized values of the tangential components and normal component are defined at the middle points of the edges and the center of gravity, respectively. The applicability of the proposed method is investigated by the computation results of the magnetic sphere model and the benchmark model of the IEE of Japan for the three-dimensional magnetostatic problems.
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Motoo Tanaka, Hajime Tsuboi, Takayoshi Misaki
1992 Volume 112 Issue 1 Pages
27-34
Published: January 20, 1992
Released on J-STAGE: July 15, 2008
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Boundary element method is the one of the practical methods for three-dimensional eddy current analysis. The boundary element method using electric field and magnetic flux density as unknown variables was developed and its effectiveness has been shown. However, the large requirement of computer resources is a severe problem for the three-dimensional analysis. In this paper, a boundary element method using edge elements are proposed. The tangential components of unknown vector variable on the edge element are approximated by the linear vector function with respect to the area coordinates. On the edge element, the divergence of the linear vector function becomes zero and the rotation of the vector function becomes constant vector whose value is defined by the geometry of the edge element and the discretized values of the unknown vector variable. Using the vector function and the Maxwell's equations, the normal component of the electric field can be related to the tangential components of the magnetic flux density, and the normal component of the magnetic flux density can be related to the tangential components of the electric field. As a result of the relations, we can choose only the tangential components of the electric field and magnetic flux density as unknowns. Therefore, the number of unknowns is reduced remarkably, so that the computer resources for three-dimensional eddy current analysis may be reduced. In this paper, the formulation of the boundary element method using the edge elements is described and the applicability of the boundary element method is verified by numerical examples.
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Tatsuya Ito, Saburo Takano, Juichi Irisawa
1992 Volume 112 Issue 1 Pages
35-40
Published: January 20, 1992
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In this paper, a vacuum gap triggerd by exploding a wire set near the main electrodes is proposed. The process of an exploding wire was simulated by the Runge-Kutta method applied to a model circuit incorporating the temperature-dependent, nonlinear resistance of the wire. The time needed for the complete melting of the wire gave a good estimate of the delay time of the gap. The delay time was independent of the width of the gap, the applied voltage with fixed width, and the position of the wire. A delay time of less than 10 microseconds and a jitter of less than 1 microsecond were obtained. The triggering mechanism has not yet been confirmed, but it is clear that the diffusion of metal vapor can not explain the triggering characteristics of the gap.
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Hitoshi Hattori, Tairo Ito, Yoshiyasu Ehara, Yoshio Miyata
1992 Volume 112 Issue 1 Pages
41-46
Published: January 20, 1992
Released on J-STAGE: July 15, 2008
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At present, the silent discharge is mainly used for ozone synthesis with ozonizers. And it is known that the surface discharge is also an effective means for ozone synthesis. Then we made a ozonizer in which the silent discharge and the surface discharge can be superposed, and studied the characteristics of ozone synthesis when different discharges were superposed. The discharge tube which was used in this study was consisted of an inner and an outer coaxial pyrex tube. The outer tube was rolled in aluminum foil which used as a HV electrode for the silent discharge. Besides a 20% salt solution was enclosed in the inner tube and Nickel rod was put at the center of the tube and used as a HV electrode for the surface discharge. The inner tube was rolled in spiral Nickel wire which used as a ground electrode for both discharges. Oxygen was flowed between the inner and the outer tube. The experiment was done at the following conditions. We changed the phase difference of both discharge voltages on condition (3).
(1) The case only the silent discharge was generated
(2) The case only the surface discharge was generated
(3) The case simultaneous discharge of both discharges were generated. The result was that the yield efficiency of ozone by simultaneous discharge increased from the phase difference of 0° to 90° and from 180° to 270°, on the other hand decreased from 90° to 180° and from 270° to 360° as the phase difference increased. In other words, at the phase difference of 90° and 270°, the yield efficiency of ozone by simultaneous discharge was the largest value and more than the sum of yield efficiency of ozone by several discharges by about 20%. We could confirm by this result and the confirmation experiment that the yield efficiency of ozone increased as the stoppage time of discharge got shorter.
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Hirofumi Takikawa, Tateki Sakakibara, Mafumi Miyashita, Tadahiro Sakut ...
1992 Volume 112 Issue 1 Pages
47-52
Published: January 20, 1992
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The radial temperature distributions at the central part of arcs burning through polyethylene (PE) tubes are estimated by measuring the half-width of Hα line spectrum and using the electron density versus Stark half-width and the electron density versus temperature characteristics. Estimation is carried out for various tube inner diameters (2 and 4mm) and DC arc currents (5, 10 and 15A). The result shows that the temperature at the arc center is around 10, 000K, and it tends to increase as the tube inner diameter becomes narrow and/or the arc current increases.
The overall temperature distributions from the arc axis to the tube wall are obtained by combining these inner temperature distributions with outer temperature distributions which have been derived from C
2 spectra. They are found to take a form of typical two-temperature distributions of ablation stabilized arcs.
The electric field strengths of PE arcs are evaluated from the temperature distributions and the electrical conductivity versus temperature characteristics of thermally decomposed polyethylene vapor gas. The results agree well with experimental values.
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Akira Yamori, Suguru Furukawa, Masahisa Yanagisawa, Nobuki Kawasima
1992 Volume 112 Issue 1 Pages
54-60
Published: January 20, 1992
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This paper describes the current status of the development of electromagnetic launchers such as the railgun at ISAS. The railgun is the most improved accelerator of Electromagnetic Launchers (EML). EML offers a potential of accelerating projectile to much greater velocities than those may be achived with conventional powder guns or light gas guns. But there has been little progress in increasing the velocity of EMLs since the experiment by Rashleigh and Marshall. A few experiments have reported achieving velocities more than 6km/s.
We have achieved the velocities more than 6km/s by reducing plasma leakage which is one of factors limiting velocity. In this paper a 6km/s launch is reported, comparing with the results of two other shots considering from a point of view of plasma leakage, and the effect of entrainment of eroded material into the armature by rail ablation were discussed on the basis of simulated numerical calculations.
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Noboru Yoshimura, Masashi Itoi, Shigeki Sato, Haruo Taguchi, Atushi It ...
1992 Volume 112 Issue 1 Pages
61-67
Published: January 20, 1992
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The ZrO
2 thin films were prepared by sol-gel method using metal alkoxide [Zr(O-n-Bu)
4]. These films were monoclinic crystalline phase ZrO
2 which can't be prepared by general method. The electrical properties of ZrO
2 thin film show good electrical insulation ones. It seems that the ZrO
2 film's breakdown occurs by the electron avalanche from the following results: ∂EB/∂T_??_0 and ∂E
B/∂d<0. The ZrO
2 thin film is expected as the capacitor and coating for insulating film.
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Koichi Tsuruta, Katsunori Suzuki, Koji Kunitsu
1992 Volume 112 Issue 1 Pages
68-69
Published: January 20, 1992
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Masayoshi Nagata, Junji Kawamura, Naoyuki Shimomura
1992 Volume 112 Issue 1 Pages
70-71
Published: January 20, 1992
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Masateru Yanagiwara, Noboru Yoshimura
1992 Volume 112 Issue 1 Pages
72-73
Published: January 20, 1992
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Hisayasu Mitsui, Makoto Takata
1992 Volume 112 Issue 1 Pages
74-75
Published: January 20, 1992
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Kazuhiko Arai, Munemitu Hamada, Noboru Yoshimura
1992 Volume 112 Issue 1 Pages
76-77
Published: January 20, 1992
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Masayoshi Masui
1992 Volume 112 Issue 1 Pages
78-79
Published: January 20, 1992
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