This paper proposes an analytical volume integration formula which calculates the inhomogeneous term of Poisson equation in its boundary integral equation form. The formula evaluates the integral on the basis of one of the tetrahedral sub-regions of the concerned region, where the inhomogeneous term can be approximated by a polynomial with respect to the coordinates.
It is well known that the Boundary Element Method (B. E. M.) has a great advantage in analyzing engineering problems governed by the homogeneous partial differential equation. Namely, only the surface of the region under consideration needs to be separated into surface elements, where the number of unknowns is reduced, in comparison with that of the domain methods, such as Finite Element Method and Finite Difference Method. The region also has to be subdivided into volume elements, even in B. E. M., when the governing equation has an inhomogeneous term.
It must be stressed that the unknowns don't increase in this situation if the inhomogeneous term can be prescribed. However, the volume integration of the inhomogeneous term has to be carried out with high speed and high accuracy because the computing time of the analysis is almost expended in these integrations and also the weighing function of the integrand can have singularity. The proposed integration formula constitutes the recursive system, where the integral of a higher order term of the polynomial can be evaluated from the result of the lower order one. Moreover, the accuracy and speed of the computation is much higher than that of the ordinary numerical integration, such as the Gauss-Legendre method.

抄録全体を表示

In the analysis of rotationally symmetrical electron optics, it has been a difficult problem to calculate electric potential of the region including a field electron or ion emitter because of an extreme difference in the magnitude of electrode geometry. For such a calculation, the charge simulation method is regarded as more suitable than the finite-difference method or the finiteelement method. However, great skill has been needed in arrangement of charges in order to obtain more accurate solution by using this method. Here, we propose a method named deflation method, which generates reasonable arrangement of charges. By the combination of the deflation method and the assignment method commonly used, an adaptive charge simulation method program is developed. Numerical calculations are carried out for an electrostatic uni-potential lens with various computation errors so that we can determine the appropriate parameters giving the arrangement of charges. Usefulness of this program is shown for a diode structure which involves a field emitter with an apex radius of 0.1μm.

抄録全体を表示

A time dependent expression for an electron plasma wave driven by optical mixing of two electromagenetic waves is derived in a target plasma which has a small amount of high-energy electrons in addition to cold main-body electrons. Numerical analysis indicates that, for counterpropagating electromagnetic waves, the wave amplitude is strongly reduced by the Landau damping of a small amount of high-energy electrons in the target plasma. The resonant excitation of the electron plasma wave is experimentally observed when the difference in frequency between counterpropagating microwaves is equal to the electron plasma frequency. Using a capacitive probe the wave amplitude δn/n0 is found to be proportional to the incident microwave power and is 0.8% at the incident microwave power of 40kW. The experimental results are in reasonable agreement with that expected from the optical mixing theory with damping terms. The dominant damping is ascribed to the Landau damping of high energy electrons co-existing in the background plasma.

抄録全体を表示

Oxygen gas absorbed in polymer has significant influence on treeing phenomena. The AC treeing resistance of low density polyethylene (PE) is drastically improved in oxygen free condition at room temperature or below. XLPE power transmission cable is generally operated at higher temperature. This paper describes the effect of oxygen on AC electrical tree initiation in PE at high temperature (25-100°C).
The degassing treatment of sample carried out at room temperature increases the tree initiation AC voltage Vt at room temperature. However it does not increase the Vt at high temperature. Oxygen molecules strongly attaching to PE matrix, which are not removed by degassing at room temperature, may be gradually released during voltage application at high temperature and cause chain oxidation resulting in tree initiation.
On the other hand, the degassing made at high temperature increases the Vt at high temperature. This result may be well explained by that the high temperature degassing removes better strongly absorbed oxygen molecules than the room temperature degassing does.
The shape of tree changes with temperature. Bush type tree is dominant at room temperature, while branch type tree at high temperature regardless of vacuum-treatment.
The deteriorated region was found around semiconducting electrode tip by the microscopic observation. This region resembles that formed in the sample with steel needle. So, both deteriorated regions may be formed by the same mechanism.

抄録全体を表示

The measurement of somatosensory evoked magnetic fields (SEFs) perpendicular to the scalp over 25 positions was carried out in a nonmagnetically shielded room with a SQUID connected to a second order gradiometer. The tibial nerve of the right ankle was stimulated electrically. SEFs were averaged by 500 measurements at one position with a bandpass filter of 1 to 30Hz. Isofield contour maps for middle and/or long latencies of 75 to 115ms rotated lockwisely on the mesial surface of the scalp representing dipolar and/or dipole-like pattern. To trace the equivalent source localization in the cortex, we calculated, the equivalent current dipole (ECD) in a meaning of the best fit between experimental and theoretical distribution. The calculated ECDs for these latencies were in the range of 19.7mm to 24.1mm as the depth from the scalp. To confirm the validity of the location of ECDs in the cortex, these results were inserted MR head imagings of the subject. As the results, these were concentrated at the postcentral gyrus of the contrary side to timulation site and were in a good agreement with a viewing point of the sensory foot representation area to the functional localization of the brain.

抄録全体を表示

Growth of microscopic cones on PTFE surface by RF sputter etching process are studied. The surface texture changes from initial submicron hillocks to large cones during sputter etching. The hight of these cones is 33-45% of the etching depth calculated from etching rate. Direction of these cones are nearly equal to the ion incident angle. Boundary energy of sputtering and growth of cones are 100eV and 150eV, respectively. It is obtained that the redeposition ratio by back diffusion to sputtered molecule is 11% from the experiment using collector. It is concluded that redeposition and repolymerization process of sputtered material occures in parallel with the ion etching process, and cones futher grow partly during etching.

抄録全体を表示

It is expected that life of oil immersed transformer is about 30 years. In recent years, transformer of 25-30 years lapse is being increased. For that reason, development of life diagnosis technique is carried out actively.
Life of transformer depends on degradation of the insulating paper. Furfural generates by decomposing the insulating paper.
Recently, relationship between amount of furfural and degradation of the insulating paper has investigated by some investigators. We have found that oil immersed insulating paper has property which adsorbs furfural existing in oil. This is important phenomenon for estimation of life because the life is calculated from amount of furfural in oil.
In this study, following basic phenomena investigate for life diagnosis technique.
(1) Influence of degassing on amount of furfural in the insulating oil.
(2) Adsorption phenomena of furfural in the insulating paper.
(3) Relationship between amount of furfural and degree of polymerization of the insulating paper.
(4) Relationship between ratio of furfural and hydroxymethylfurfural and heating temperature.

抄録全体を表示

A tree generated directly from a needle electrode tip is referred to as "initial tree". In polyetylene, the initial tree develops approx. 5 to 10μm in a linear pattern from the needle electrode tip. In order to investigate a cause of the tree development pattern, we have observed detail superstructure near the needle electrode tip using the polarizing microscope. In high density polyethylene (HDPE) and low density polyethylene (LDPE), growths of trans-crystal of approx. 10μm and 5μm respectively have been observed on the electrode surface. In cross-linked polyethylene (XLPE), however, the trans-crystal could not be found. In each polyetylene, AC voltage has been applied to the needle electrode to generate the tree. The tree has developed linearly along the trans-crystal in HDPE and LDPE. However, in XLPE, the tree has been blanched at the needle tip. We have confirmed that the initial tree is influenced by the superstructure in the polyethylene on the electrode surface.

抄録全体を表示