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991.
992.
The effect of the nonparallelism of the boundary layer flow over a flat plate on its stability characteristics has been investigated
by several authors, and it was claimed that the results of the theoretical calculations are already in good agreement with
the experimental observations. However, this is not true. In this paper, this problem is reinvestigated, using two different
methods. It is found that within the framework of linear theory, the theoretical results are in fact not in good agreement
with the experimental observations. To settle this problem, nonlinear effect must be taken into consideration.
Projects Supported by the Science Fund of the Chinese Academy of Sciences 相似文献
993.
D. A. Carlson 《Journal of Optimization Theory and Applications》1986,49(2):207-225
In this paper, we are concerned with the question of the existence of optimal solutions for infinite-horizon optimal control problems of Lagrange type. In such problems, the objective or cost functional is described by an improper integral. As dictated by applications arising in mathematical economics, we do nota priori assume that this improper integral converges. This leads us to consider a weaker type of optimality, known as catching-up optimality. The results presented here utilize the classical convexity and seminormality conditions typically imposed in the existence theory for the case of finite intervals. These conditions are significantly weaker than those imposed by other authors; as a consequence, their existence results are contained as special cases of the results presented here. The method of proof utilizes the Carathéodory-Hamilton-Jacobi theory previously developed by the author for infinite-horizon optimal control problems.This research forms part of the author's doctoral dissertation written at the University of Delaware, Newark, Delaware under the supervision of Professor T. S. Angell. 相似文献
994.
For Principal Component Analysis in Reproducing Kernel Hilbert Spaces (KPCA), optimization over sets containing only linear
combinations of all n-tuples of kernel functions is investigated, where n is a positive integer smaller than the number of data. Upper bounds on the accuracy in approximating the optimal solution,
achievable without restrictions on the number of kernel functions, are derived. The rates of decrease of the upper bounds
for increasing number n of kernel functions are given by the summation of two terms, one proportional to n
−1/2 and the other to n
−1, and depend on the maximum eigenvalue of the Gram matrix of the kernel with respect to the data. Primal and dual formulations
of KPCA are considered. The estimates provide insights into the effectiveness of sparse KPCA techniques, aimed at reducing
the computational costs of expansions in terms of kernel units. 相似文献
995.
G. Dattoli B. Germano M.R. Martinelli P.E. Ricci 《Mathematical and Computer Modelling》2009,50(9-10):1332-1337
We show that the combination of the formalism underlying the principle of monomiality and of methods of an algebraic nature allows the solution of different families of partial differential equations. Here we use different realizations of the Heisenberg–Weyl algebra and show that a Sheffer type realization leads to the extension of the method to finite difference and integro-differential equations. 相似文献
996.
Positive solutions of Neumann problems with singularities 总被引:1,自引:0,他引:1
In this paper, we study the existence of positive solutions to second order singular equations with Neumann boundary conditions. The proof of the main result relies on a nonlinear alternative principle of Leray-Schauder, together with a truncation technique. 相似文献
997.
998.
本文讨论了与腔体组装方法、温度梯度和边界条件等有关的温度控制问题及其对金刚石生长的影响。 相似文献
999.
The numerical solution of the time‐dependent Navier–Stokes equations in terms of the vorticity and a stream function is a well tested process to describe two‐dimensional incompressible flows, both for fluid mixing applications and for studies in theoretical fluid mechanics. In this paper, we consider the interaction between the unsteady advection–diffusion equation for the vorticity, the Poisson equation linking vorticity and stream function and the approximation of the boundary vorticity, examining from a practical viewpoint, global iteration stability and error. Our results show that most schemes have very similar global stability constraints although there may be small stability gains from the choice of method to determine boundary vorticity. Concerning accuracy, for one model problem we observe that there were cases where the boundary vorticity discretization did not propagate to the interior, but for the usual cavity flow all the schemes tested had error close to second order. Copyright © 2005 John Wiley & Sons, Ltd. 相似文献
1000.
N. U. Ahmed 《Journal of Optimization Theory and Applications》1986,50(2):213-237
Using Cesari's approach, we prove the existence of optimal controls for a class of systems governed by differential inclusions on a Banach space having the Radon-Nikodym property. Theorem 3.1 gives the existence result for optimal relaxed controls under fairly general assumptions on the system and the admissible controls. This result depends on a fundamental result (Theorem 2.1) that proves the existence of mild solutions of differential inclusions on a Banach space, which has also independent interest. Further, the preparatory results, such as Lemma 3.1 and Lemma 3.2, are also useful in the study of time-optimal and terminal control problems.For illustration of the results, we present two examples, one on distributed controls for a class of systems governed by nonlinear parabolic equations and the other on boundary controls with discontinuous boundary operator.This work is supported in part by the National Science and Engineering Council of Canada under Grant No. 7109. 相似文献