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951.
为改造正线性算子以提高其逼近阶,本文利用有限振荡核方法,从常见的Fejer算子出发,构造出一种莼性多项式算子Ln^(m)(f;x),称F-B算子,它的表达式具有良好的递推性能;通过对其收敛性和饱和性的讨论,证得F-B算子对充分光滑函数的逼近阶可达O(1/n^2m+1),优于Butzer与Stark的结果(O(1/n^4)),并包含Baskakov的结果(O(1/n^3)与O(1/n^5))为其特例 相似文献
952.
Given a sequence of i.i.d. random variables, new proofs are given for limit theorems for the number of observations near the maximum up to time n, as n → ∞. The proofs rely on a Poisson approximation to conditioned binomial laws, and they reveal the origin in the limit laws of mixing with respect to extreme value laws. For the case of attraction to the Fréchet law, the effects of relaxing a technical condition are examined. The results are set in the broader context of counting observations near upper order statistics. This involves little extra effort. 相似文献
953.
Some possible modifications of the governing equations of the linear theory of elasticity are considered. The stress–strain relation is specified by an integral equality instead of the local Hooke’s law. The modified integrodifferential boundary value problem is reduced to the minimization of a nonnegative functional under differential constraints. A numerical algorithm based on polynomial approximations of unknown functions (stresses and displacements) is developed and applied to linear elasticity problems. The bilateral estimation criteria of solution errors are proposed in order to analyze the algorithm convergence rate. The numerical results obtained by applying the integrodifferential relation method and the conventional variational method are compared and discussed. 相似文献
954.
The time-dependent Navier–Stokes equations and the energy balance equation for an incompressible, constant property fluid in the Boussinesq approximation are solved by a least-squares finite element method based on a velocity–pressure–vorticity–temperature–heat-flux ( u –P–ω–T– q ) formulation discretized by backward finite differencing in time. The discretization scheme leads to the minimization of the residual in the l2-norm for each time step. Isoparametric bilinear quadrilateral elements and reduced integration are employed. Three examples, thermally driven cavity flow at Rayleigh numbers up to 106, lid-driven cavity flow at Reynolds numbers up to 104 and flow over a square obstacle at Reynolds number 200, are presented to validate the method. 相似文献
955.
Nonlinearity effects in multidimensional scaling 总被引:1,自引:0,他引:1
When multidimensional scaling of n cases is derived from dissimilarities that are functions of p basic continuous variables, the question arises of how to relate the values of the variables to the configuration of n points. We provide a methodology based on nonlinear biplots that expresses nonlinearity in two ways: (i) each variable is represented by a nonlinear trajectory and (ii) each trajectory is calibrated by an irregular scale. Methods for computing, calibrating and interpreting these trajectories are given and exemplified. Not only are the tools of immediate practical utility but the methodology established assists in a critical appraisal of the consequences of using nonlinear measures in a variety of multidimensional scaling methods. 相似文献
956.
A. Belafhal M. IbnchaikhK. Nassim 《Journal of Quantitative Spectroscopy & Radiative Transfer》2002,72(4):385-402
This work is devoted to a theoretical study of scattering of light by absorbing and nonabsorbing oriented spheroidal particles in the Wentzel-Kramers-Brillouin (WKB) approximation. Within the framework of the scattering theory, we investigate the form factor and the scattering amplitude for this approximation. The Rayleigh-Gans-Debye theory (RGD), the diffraction approximation (DA), and the anomalous diffraction (AD) are treated as particular cases for nonabsorbing spheroids. To illustrate our formalism, we analyze some numerical examples. 相似文献
957.
Telhat Ozdogan 《理论物理通讯》2002,38(10)
Higher electric multipole moments for the ground-state electronic configuration of some polyatomicmolecules, i.e. CH4, NH3, H2O, were calculated from SCF-HFR wavefunctions using Slater-type orbital basis sets.The calculated results for electric multipole moments of these molecules are in good agreement with the theoretical andexperimental ones. 相似文献
958.
Dr. G. S. Georgiev 《Colloid and polymer science》1996,274(1):49-58
A new model of mixed surfactant systems have been developed in the work presented. It includes two parameters only connected directly with the Gibbs free energy of the surfactant aggregation. They can be determined using both the aggregation equilibrium constant values or the phase composition data. It has been shown also the relation between these new parameters and the same of the regular solution approximation and the alternative models. The possibility to describe the available experimental information about the micelle composition as a function of the singly dispersed surfactant mixture composition better than by the other models has been shown also. 相似文献
959.
本文改进了复域中用Hermite-Fejer插值一致逼近与平均逼近[1]的边界条件且简化了证明过程 相似文献
960.
Introducing the notion of the formal continued fractions solutions of the generalized second order Riccati equations, one
can compute either a rational approximation of the solution or a rational solution and perform a location of the singularities
in the complex plane.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献