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51.Introducti0nSince198O)stheoriesandapplicationsofboundaryelementmethods(BEM)orboundaryintegralmethods(BIM)havemadegreatsuccessesfortheparaboliclnit1alboundaryvalueproblems(seeL1-12j),andtheapproachhasbeenappliedtonumericalsolutionsofinitialboundaryva1ueproblemssuccessfully(seeL1-5j'L8j).Thepropertiesofboundaryelementoperatorshavebeenstudiedbyboundaryintegralmethodsbymanyauthors(see.[4j,L6J'[7j'L12J).Theseresultsprovideabasisforconvergencesanderrorestimatesfornumericalapproximationofbou… 相似文献
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三维Helmholtz方程外问题的自然边界元与有限元耦合法 总被引:4,自引:0,他引:4
1.引言 设Γ0是空间闭曲面,Ω是Γ0外部的无界区域,考虑三维Helmholtz 方程外Neumann问题其中 是波数,w是频率,c0为波在均匀介质中的传播速度,v是区域Ω的边界Γ0的外法线方向,即指向由 Γ0包围的内部区域, 为 Γ0上的已知函数.为了保证问题(1.1)和(1.2)的解的存在唯一性,必须附加上无穷远边界条件,即所谓的 Sommerfeld辐射条件其中i是虚数单位, . 许多数学物理问题,例如时间调和声波对不可穿透的障碍物的散射,海洋水下声波的传播,电磁波的绕射与辐… 相似文献
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椭圆外区域上的自然边界元法 总被引:17,自引:5,他引:12
1.引言 二十年来,自然边界元法已在椭圆问题求解方面取得了许多研究成果。它可以直接用来解决圆内(外)区域、扇形区域、球内(外)区域及半平面区域等特殊区域上的椭圆边值问题[1,2,5],也可以结合有限元法求解一般区域上的椭圆边值问题,例如基于自然边界归化的耦合算法及区域分解算法就是处理断裂区域问题及外问题的一种有效手段[2-4,6]。 人们在设计求解外问题的耦合算法或者区域分解算法时,通常选取圆周或球面作人工边界。但对具有长条型内边界的外问题,以圆周或球面作人工边界显然并非最佳选择,它将会导致大量的… 相似文献
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超奇异积分的数值计算是边界元方法中的重要的课题之一,本文得到了牛顿科茨公式计算任意阶超奇异积分误差估计,当误筹函数中的Sκ(p)(Τ)=0时,便得到超收敛现象,并给出了Sκ(p)(Τ)之间的相互关系.相应的数值算例验证了理论分析的正确性. 相似文献
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Zhang B Chen Y Zhang Y Chen X Chi Z Yang J Ou J Zhang MQ Li D Wang D Liu M Zhou J 《Physical chemistry chemical physics : PCCP》2012,14(13):4640-4650
In order to investigate the steric effect of aromatic pendant groups and the electrical bistability in nonconjugated polymers potentially for memory device applications, two π-stacked polymers with different steric structures are synthesized and characterized. They exhibit two conductivity states and can be switched from an initial low-conductivity (OFF) state to a high-conductivity (ON) state. Additionally, they demonstrate nonvolatile write-once-read-many-times (WORM) memory behavior with an ON/OFF current ratio up to 10(4), and flash memory behavior with an ON/OFF current ratio of approximately 10(5). Both steady-state and time-resolved fluorescence spectroscopies are used to examine the conformational change of the polymers responding to an applied external electrical voltage. The results provide useful information on different steric effects of pendant groups in polymer chains, resulting in various electrical behaviors. The possibility in realizing an "erasable" behavior through breaking π-stacked structures of pendant groups by a reversal of the electric field was also discussed on the basis of temperature-dependent fluorescence spectroscopy investigation. These results may thus offer a guideline for the design of practical polymer memory devices via tuning steric structure of π-stacked polymers. 相似文献
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Dongjie Liu Dehao Yu 《计算数学(英文版)》2008,(3):378-389
In this paper, the finite element method and the boundary element method are combined to solve numerically an exterior quasilinear elliptic problem. Based on an appropriate transformation and the Fourier series expansion, the exact quasilinear artificial boundary conditions and a series of the corresponding approximations for the given problem are presented. Then the original problem is reduced into an equivalent problem defined in a bounded computational domain. We provide error estimate for the Galerkin method. Numerical results are presented to illustrate the theoretical results. 相似文献
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In this paper, based on the natural boundary reduction advanced by Feng and Yu, we couple the finite element approach with the natural boundary element method to study the weak solvability and Galerkin approximation of a class of nonlinear exterior boundary value problems. The analysis is mainly based on the variational formulation with constraints. We prove the error estimate of the finite element solution and obtain 相似文献
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在D-N区域分解算法中,松弛因子的选取起着关键作用。应用自然边界归化理论,讨论了无界区域上椭圆型方程边值问题的D-N区域分解算法,给出了其松弛因子的简便的选取方法,保证了算法很好的收敛性。 相似文献
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