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11.
Haibo Peng Boyu Wu Qiong Song Fei Lu Shuyun Luo 《International Journal of Infrared and Millimeter Waves》2003,24(9):1587-1596
Hybrid electrode combined coplanar waveguide (CPW) and microstrip lines in ultra-broadband electro-optic modulators. The characteristics of the modulators with hybrid electrode is like that of the modulator with the microstrip lines, in which the microstrip electrode is loaded above only one arm of Mach-Zehnder (M-Z) optical waveguide, besides the problem of microstrip line to coaxial transition and corona polarization in polymer modulators have been best solved at the same time. By using finite element method (FEM), the characteristic parameters such as half-wave voltage, modulation bandwidth characteristic impedance, effective microwave refractive index of polymer modulators with microstrip line and hybrid electrode are analysed and compared in this paper. The results present that velocity match, impendence match and lower microwave propagating loss is easily realized in modulators with hybrid electrode. 相似文献
12.
L. C. Lew Yan Voon C. Galeriu M. Willatzen 《Physica E: Low-dimensional Systems and Nanostructures》2003,18(4):547-549
We argue that the two-dimensional elliptic quantum dot problem with finite barrier cannot be exactly solved, contrary to a recent assertion (van den Broek and Peeters, Physica E 11 (2001) 345. We also prove it explicitly by numerically calculating the correct energy spectrum. 相似文献
13.
We present a practical polynomial-time algorithm for computing the
zeta function of a Kummer curve over a finite field of small
characteristic. Such algorithms have recently been obtained using a
method of Kedlaya based upon Monsky–Washnitzer cohomology, and are of
interest in cryptography. We take a different approach.
The problem is reduced to that of computing the L-function
of a multiplicative character sum. This latter task is achieved via a
cohomological formula based upon the work of Dwork and Reich. We show,
however, that our method and that of Kedlaya are very closely related.Dedicated to the memory of Gian-Carlo Rota 相似文献
14.
LiuYuqi LiZhigang YahYakun 《Acta Mechanica Solida Sinica》2004,17(1):58-64
By using the Finite Element Inverse Approach based on the Hill quadratic anisotrop-ically yield criterion and the quadrilateral element, a fast analyzing software-FASTAMP for the sheet metal forming is developed. The blank shapes of three typical stampings are simulated and compared with numerical results given by the AUTOFORM software and experimental results, respectively. The comparison shows that the FASTAMP can predict blank shape and strain distribution of the stamping more precisely and quickly than those given by the traditional methods and the AUTOFORM. 相似文献
15.
16.
In this work, the effect of flexibility on the trajectory of a planar two-link manipulator is studied using integrated computer-aided design/analysis (CAD/CAE) procedures. The solid models and finite element models of the parts of the manipulator are created by using the CAD/CAE software I-DEAS. The assembly is defined, and knowing the payload and the end point trajectory, the velocities and accelerations of the parts, joint forces and driving torques are calculated using the rigid body dynamics. All the time dependent nodal forces acting on the parts including distributed gravity and inertia forces are created in files with the I-DEAS program file format. The finite element vibration analysis of the parts is performed by I-DEAS. The end point vibrations and the deviations from the rigid-body trajectory are analyzed for different types of end point acceleration curves. A circular trajectory is considered as an example. It is observed that the precision of the manipulator can be increased by testing different end point acceleration curves without changing the trajectory and the duration of the end point work. The procedure explained in this work can be used for this purpose successfully. 相似文献
17.
关于具有给定Sylow子群正规化子的有限群Ⅱ 总被引:1,自引:0,他引:1
本文在有限可解群中解决了:任意m-秩≤2的子群闭的局部群系具有性质:“如果群G的非单位Sylow子群的正规化子属于,则群G也属于的一个充分必要条件. 相似文献
18.
L. Bergamaschi G. Gambolati G. Pini 《Journal of Computational and Applied Mathematics》2007,210(1-2):64-70
Integration of the subsurface flow equation by finite elements (FE) in space and finite differences (FD) in time requires the repeated solution to sparse symmetric positive definite systems of linear equations. Iterative techniques based on preconditioned conjugate gradients (PCG) are one of the most attractive tool to solve the problem on sequential computers. A present challenge is to make PCG attractive in a parallel computing environment as well. To this aim a key factor is the development of an efficient parallel preconditioner. FSAI (factorized sparse approximate inverse) and enlarged FSAI relying on the approximate inverse of the coefficient matrix appears to be a most promising parallel preconditioner. In the present paper PCG using FSAI, diagonal and pARMS (parallel algebraic recursive multilevel solvers) preconditioners is implemented on the IBM SP4/512 and CLX/768 supercomputers with up to 32 processors to solve underground flow problems of a large size. The results show that FSAI may allow for a parallel relative efficiency larger than 50% on the largest problems with p=32 processors. Moreover, FSAI turns out to be significantly less expensive and more robust than pARMS. Finally, it is shown that for p in the upper range may be much improved if PCG–FSAI is implemented on CLX. 相似文献
19.
Man Young Kim Seung Wook Baek 《Journal of Quantitative Spectroscopy & Radiative Transfer》2005,90(3-4):377-388
Radiative heat transfer in an axisymmetric enclosure with absorbing, emitting, and scattering medium is studied here by using the different methods such as MDOM, FVM, and MFVM with emphasis on the treatment of angular derivative term, which appears in curvilinear coordinates due to angular redistribution. After final discretization equation for MFVM is introduced by using the step scheme and directional weights, the present approach is validated by applying it to three different benchmarking problems with absorbing, emitting, and scattering medium. All of the results presented here support its accuracy as well as moderate efficiency. Finally, the present approaches are applied to a truncated cone-shaped enclosure as a body-fitted geometry case. 相似文献
20.
S. Neukirch G.H.M. van der HeijdenJ.M.T. Thompson 《Journal of the mechanics and physics of solids》2002,50(6):1175-1191
We use three different approaches to describe the static spatial configurations of a twisted rod as well as its stability during rigid loading experiments. The first approach considers the rod as infinite in length and predicts an instability causing a jump to self-contact at a certain point of the experiment. Semi-finite corrections, taken into account as a second approach, reveal some possible experiments in which the configuration of a very long rod will be stable through out. Finally, in a third approach, we consider a rod of real finite length and we show that another type of instability may occur, leading to possible hysteresis behavior. As we go from infinite to finite length, we compare the different information given by the three approaches on the possible equilibrium configurations of the rod and their stability. These finite size effects studied here in a 1D elasticity problem could help us guess what are the stability features of other more complicated (2D elastic shells for example) problems for which only the infinite length approach is understood. 相似文献