| Project/Area Number |
06650073
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Engineering fundamentals
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| Research Institution | The University of Tokyo |
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Principal Investigator |
HAYAMI Ken University of Tokyo, School of Engineering, Associate Professor, 大学院・工学系研究科, 助教授 (20251358)
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| Co-Investigator(Kenkyū-buntansha) |
IMAI Toshiyuki University of Tokyo, School of Engineering, Assistant, 大学院・工学系研究科, 助手 (90213214)
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| Project Period (FY) |
1994 – 1996
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| Project Status |
Completed (Fiscal Year 1996)
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| Budget Amount *help |
¥1,900,000 (Direct Cost: ¥1,900,000)
Fiscal Year 1996: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 1995: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1994: ¥600,000 (Direct Cost: ¥600,000)
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| Keywords | Numerical Analysis / Boundary Element Method / Numerical Integration / Fast Multipole Method / Panel Clustering Method / Simulation of the Electron-Gun / Elastostatics / Inverse Problem / 偏微分方程式 / 脳内電流双極子推定 / 数値積分法 / 多粒子系 / 連立一次方程式 / 反復解法 / 多重極展開法 / 連立一時方程式 |
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| Research Abstract |
The Boundary element Method (BEM) is a powerful method for solving partial differential equations. This research project is concerned with making the method more accurate and efficient, and on its application to inverse problems.
1. Making the solution more efficient
In BEM,each element is related to all the other elements, so that the amount of computation (O (n^3)) and required memory (O (n^2)) for generating and solving the dense system of linear equations becomes prohibitive as the number elements (n) becomes large.
In order to overcome this problem, we have applied the Fast Multipole Method (FMM) and the Panel Clustering Method to the 2-D potential problem, 3-D Poisson problem and 2-D and 3-D elastostatics. The methods use multipole expansions or Taylor expansions in order to approximate and cluster effects between elements far apart within the required accuracy, so that the computation and memory is reduced to nearly O (n).
We have also applied the FMM to the three-dimensional boundary element simulation of the electron gun, taking the space charge effect of charged particles into account. Further, we developed a method for treating the periodic boundary condition when calculating the forces acting between vortices in 2-D using the FMM.
2. Accurate computation of integrals
We have developed an automatic numerical integration method using variable transformations for the calculation of nearly singular integrals which appear in the boundary element method when treating thin structures and gaps or when calculating the field very near the boundary.
3. Application to inverse problems
We applied 3-D BEM and nonlinear optimization to the problem of identifying a current dipole in the brain, where the head is modelled by three regions with different conductivity. This was made possible by introducing a new object function based on the virtual potantial due to the dipole placed in the infinite homogeneous region.
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