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991.
In this paper we introduce the concept of solving strategy for a linear semi-infinite programming problem, whose index set is arbitrary and whose coefficient functions have no special property at all. In particular, we consider two strategies which either approximately solve or exactly solve the approximating problems, respectively. Our principal aim is to establish a global framework to cope with different concepts of well-posedness spread out in the literature. Any concept of well-posedness should entail different properties of these strategies, even in the case that we are not assuming the boundedness of the optimal set. In the paper we consider three desirable properties, leading to an exhaustive study of them in relation to both strategies. The more significant results are summarized in a table, which allows us to show the double goal of the paper. On the one hand, we characterize the main features of each strategy, in terms of certain stability properties (lower and upper semicontinuity) of the feasible set mapping, optimal value function and optimal set mapping. On the other hand, and associated with some cells of the table, we recognize different notions of Hadamard well-posedness. We also provide an application to the analysis of the Hadamard well-posedness for a linear semi-infinite formulation of the Lagrangian dual of a nonlinear programming problem. 相似文献
992.
A class of vector-parallel schemes for solution of steady compressible or incompressible viscous flow is developed and performance studies carried out. The algorithms employ an artificial transient treatment that permits rapid integration to a steady state. In the present work a four-stage explicit Runge-Kutta scheme employing variable local step size is utilized for the ODE system integration. The RK-4 scheme is restructured to allow vectorization and enhance concurrency in the calculation for a streamfunction-vorticity formulation of the flow problem. The parameters of the resulting RK scheme can be selected to accelerate convergence of the RK recursion. Four main procedures are considered which permit vector-parallel solution: a Jacobi update, a hybrid of the Jacobi and Gauss-Seidel method, red-black ordering and domain decomposition. Numerical performance studies are conducted with a representative viscous incompressible flow calculation. Results indicate that a scheme involving domain decomposition with a Gauss-Seidel type of update for the RK four-stage scheme is most effective and provides performance in excess of 8 Gflops on the Cray C-90. 相似文献
993.
A novel domain element shape parameterization method is presented for computational fluid dynamics‐based shape optimization. The method is to achieve two aims: (1) provide a generic ‘wrap‐around’ optimization tool that is independent of both flow solver and grid generation package and (2) provide a method that allows high‐fidelity aerodynamic optimization of two‐ and three‐dimensional bodies with a low number of design variables. The parameterization technique uses radial basis functions to transfer domain element movements into deformations of the design surface and corresponding aerodynamic mesh, thus allowing total independence from the grid generation package (structured or unstructured). Independence from the flow solver (either inviscid, viscous, aeroelastic) is achieved by obtaining sensitivity information for an advanced gradient‐based optimizer (feasible sequential quadratic programming) by finite‐differences. Results are presented for two‐dimensional aerofoil inverse design and drag optimization problems. Inverse design results demonstrate that a large proportion of the design space is feasible with a relatively low number of design variables using the domain element parameterization. Heavily constrained (in lift, volume, and moment) two‐dimensional aerofoil drag optimization has shown that significant improvements over existing designs can be achieved using this method, through the use of various objective functions. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
994.
Ranjan Das Balu Venkataraman Vinod R Bhagat Ajit S Ghangrekar Thomas Kuruvilla B K Chaturvedi G S Isola B M Marwaha P G Nair R S Parolia B K Sarkar 《Pramana》1986,27(5):661-677
A computer-controlled X-band time domain electron paramagnetic resonance (EPR) spectrometer, with a time resolution of the
order of 0.5μsec, has been constructed with many of the crucial microwave components designed and fabricated by the Microwave Engineering
Group of TIFR. The spectrometer operates either in a microwave power pulsed mode for determination of spin-lattice relaxation
times by the saturation recovery technique or in the kinetic mode for determination of the time dependence of EPR signal after
laser excitation. It has an automatic frequency control, an automatic phase control and, most importantly, a field-frequency
lock which ensures good stability of the EPR line positions enabling signal averaging for extended periods. The constructional
details of the spectrometer and its performance in both the modes are described here by reporting results on certain typical
systems. 相似文献
995.
利用标量区衍射理论分析了正交二元矩形软X射线衍射光栅的光学特性,给出了理论设计的初步结果。 相似文献
996.
Chongwei Zheng 《Optik》2005,116(12):563-567
Based on a tensor method, the propagation formulae of elliptical flat-topped beam through aligned and misaligned optical systems in spatial-frequency domain are derived analytically. The derived formulae provide a powerful tool for treating the propagation and transformation of elliptical flat-topped beam through complex optical systems in spatial-frequency domain. As a numerical example, the propagation properties of elliptical flat-topped Gaussian beam in free space are studied in spatial-frequency domain. 相似文献
997.
The parameters calculation for the modified Debye model in the electromagnetic finite difference time domain (FDTD) method is discussed. Validation for the selected parameters is done comparing the FDTD results with the Mie analytical solutions of a gold nanometer sphere under an optical plane wave incidence. Good agreement with an average relative error 6.7% has been demonstrated as to total electrical field amplitudes on the surface of the gold sphere. It indicates FDTD could be adopted in the optical region for a material even with a negative real relative permittivity particularly as metals. 相似文献
998.
This paper studies noncompact feasible sets of a semi-infinite optimization problem which are defined by finitely many equality constraints and infinitely many inequality constraints. The main result is the equivalence of the overall validity of the Extended Mangasarian Fromovitz Constraint Qualification with certain (topological) stability conditions. Furthermore, two perturbation theorems being of independent interest are presented.This work was supported by the Deutsche Forschungsgemeinschaft under grant Gu 304/1-2. 相似文献
999.
畴壁钉扎模型的矫顽力可以表示为Hc=αpink2K1/μ0Ms-NeffMs,计算了微结构参数αpink随面缺陷内磁性参数A′和K′1的变化情况.结果表明,αpink可以在很宽的范围里取值.结合纳米单相Nd2Fe14B磁体,研究了晶粒边界的磁性参数和晶界厚度对αpink的影响,当A′/A=05,K′1/K1=01,以及晶界厚度r0=332nm时,αpink最大.同时研究了纳米复相Nd2Fe14B/α-Fe磁体的αpink随α-Fe晶粒尺寸r0的变化情况,当r0=7nm时,αpink最大.
关键词:
面缺陷
矫顽力
钉扎机理
纳米晶 相似文献
1000.
Jana Björn Nageswari Shanmugalingam 《Journal of Mathematical Analysis and Applications》2007,332(1):190-208
In the setting of metric measure spaces equipped with a doubling measure supporting a weak p-Poincaré inequality with 1?p<∞, we show that any uniform domain Ω is an extension domain for the Newtonian space N1,p(Ω) and that Ω, together with the metric and the measure inherited from X, supports a weak p-Poincaré inequality. For p>1, we obtain a near characterization of N1,p-extension domains with local estimates for the extension operator. 相似文献