The isometry classification of hermitian forms over division algebras

The isometry classification problem occupies a central role in the theory of quadratic and hermitian forms. This article is a survey of results on the problem for quadratic and hermitian forms over a field and also for hermitian and skew-hermitian forms over a noncommutative division algebra with involution. Rather than adopting a very abstract approach, the problems are stated in matrix or linear-algebraic terms. The known solutions depend crucially on the particular field considered, although there are some general results which are mentioned. While many of the results date back a long time, some recent results, especially those on skew-hermitian forms over a quaternion algebra over a number field, are included.     

Unifying theory for stability of continuous,discontinuous, and discrete-time dynamical systems

Continuous-time dynamical systems whose motions are continuous with respect to time (called continuous dynamical systems), may be viewed as special cases of continuous-time dynamical systems whose motions are not necessarily continuous with respect to time (called discontinuous dynamical systems, or DDS). We show that the classical Lyapunov stability results for continuous dynamical systems are embedded in the authors’ stability results for DDS (given in [H. Ye, A.N. Michel, L. Hou, Stability theory for hybrid dynamical systems, IEEE Transactions on Automatic Control 43 (4) (1998) 461–474]), in the following sense: if the hypotheses for a given Lyapunov stability result for continuous dynamical systems are satisfied, then the hypotheses of the corresponding stability result for DDS are also satisfied. This shows that the stability results for DDS in [H. Ye, A.N. Michel, L. Hou, Stability theory for hybrid dynamical systems, IEEE Transactions on Automatic Control 43 (4) (1998) 461–474] are much more general than was previously known, and that the quality of the DDS results therein is consistent with that of the classical Lyapunov stability results for continuous dynamical systems.By embedding discrete-time dynamical systems into a class of DDS with equivalent stability properties, we also show that when the hypotheses of the classical Lyapunov stability results for discrete-time dynamical systems are satisfied, then the hypotheses of the corresponding DDS stability results are also satisfied. This shows that the results for DDS in [H. Ye, A.N. Michel, L. Hou Stability theory for hybrid dynamical systems, IEEE Transactions on Automatic Control 43 (4) (1998) 461–474] are much more general than previously known, having connections even with discrete-time dynamical systems!Finally, we demonstrate by the means of a specific example that the stability results for DDS are less conservative than corresponding classical Lyapunov stability results for continuous dynamical systems.     

Effective bandwidths: Call admission,traffic policing and filtering for ATM networks

In this paper we review and extend the effective bandwidth results of Kelly [28], and Kesidis, Walrand and Chang [29, 6]. These results provide a framework for call admission schemes which are sensitive to constraints on the mean delay or the tail distribution of the workload in buffered queues. We present results which are valid for a wide variety of traffic streams and discuss their applicability for traffic management in ATM networks. We discuss the impact of traffic policing schemes, such as thresholding and filtering, on the effective bandwidth of sources. Finally we discuss effective bandwidth results for Brownian traffic models for which explicit results reveal the interaction arising in finite buffers.     

Estimates from Below for Lebesgue Constants

Estimates from below for the norms of linear means of multiple Fourier series are obtained. These means are given by some function λ and generalize the well-known Bochner-Riesz means. Sharpness of these estimates is established. The assumptions on λ are rather weak and of local character. Our results contain as particular cases a number of earlier published results. Proofs are based on the authors' new results on asymptotics of the Fourier transform of piecewise-smooth functions. Some applications of the results obtained are given, namely, orders of growth of the Lebesgue constants for "ovals" and "hyperbolic crosses" are evaluated and sharp conditions on the modulus of smoothness of a function are given, for this function to be approximated by the linear means.     

Solving parabolic Wick-stochastic boundary value problems using a finite element method

A class of linear parabolic stochastic boundary value problems of Wick-type is studied. The equations are understood in a weak sense on a suitable stochastic distribution space, and existence and uniqueness results are provided. The paper continues to discuss a numerical method for this type of problem, based on a Galerkin type of approximation. Estimates showing linear convergence in time and space are derived, and rate of convergence results for the stochastic dimension are reported.     

Runtime Analysis of Ant Colony Optimization with Best-So-Far Reinforcement

The paper provides some theoretical results on the analysis of the expected time needed by a class of Ant Colony Optimization algorithms to solve combinatorial optimization problems. A part of the study refers to some general results on the expected runtime of the considered class of algorithms. These results are then specialized to the case of pseudo-Boolean functions. In particular, three well known functions and a combination of two of them are considered: the OneMax, the Needle-in-a-Haystack, the LeadingOnes, and the OneMax-Needle-in-a-Haystack. The results obtained for these functions are also compared to those from the well-investigated (1+1)-Evolutionary Algorithm. The results shed light on a suitable parameter choice for the considered class of algorithms. Furthermore, it turns out that for two of the four studied problems, the expected runtime for the considered class, expressed in terms of the problem size, is of the same order as that for (1+1)-Evolutionary Algorithm. For the other two problems, the results are significantly in favour of the considered class of Ant Colony Optimization algorithms.      

Numerical evaluation of analytic functions by Cauchy's theorem

The use of the Cauchy theorem (instead of the Cauchy formula) in complex analysis together with numerical integration rules is proposed for the computation of analytic functions and their derivatives inside a closed contour from boundary data for the analytic function only. This approach permits a dramatical increase of the accuracy of the numerical results for points near the contour. Several theoretical results about this method are proved. Related numerical results are also displayed. The present method together with the trapezoidal quadrature rule on a circular contour is investigated from a theoretical point of view (including error bounds and corresponding asymptotic estimates), compared with the numerically competitive Lyness-Delves method and rederived by using the Theotokoglou results on the error term. Generalizations for the present method are suggested in brief.     

Refinements on Gap Functions and Optimality Conditions for Vector Quasi-Equilibrium Problems via Image Space Analysis

By means of some new results on generalized systems, vector quasi-equilibrium problems with a variable ordering relation are investigated from the image perspective. Lagrangian-type optimality conditions and gap functions are obtained under mild generalized convexity assumptions on the given problem. Applications to the analysis of error bounds for the solution set of a vector quasi-equilibrium problem are also provided. These results are refinements of several authors’ works in recent years and also extend some corresponding results in the literature.     

Stability and error estimation for component adaptive grid methods

Component adaptive grid (CAG) methods for solving hyperbolic partial differential equations (PDEs) are discussed in this paper. Applying recent stability results for a class of numerical methods on uniform grids, the convergence of these methods for linear problems on component adaptive grids is established here. Furthermore, the computational error can be estimated on CAGs using these stability results. Using these estimates, the error can be controlled on CAGs. Thus, the solution can be computed efficiently on CAGs within a given error tolerance. Computational results for time dependent linear problems in one and two space dimensions are presented.     

图的因子和因子分解的若干进展

本文综述了图的的因子和因子分解近年来的一些新结果。主要有图的因子与各种参数之间的关系,图有某种因子的一些充分必要条件,特别是图有ｋ－因子的一些充分条件以及关于图的因子分解和正交因子分解的一些新结果。文中提出了一些新的问题和猜想。     

Effect of the rotation on a non-homogeneous infinite cylinder of orthotropic material

The present investigation is concerned with a study effect of non-homogeneous on the elastic stresses in rotating orthotropic infinite circular cylinder subjected to certain boundary conditions. Closed form stress solutions are obtained for rotating orthotropic cylinder with constant thickness for three cases: (1) a solid cylinder; (2) cylinder mounted on a circular rigid shaft; and (3) cylinder with a circular hole at the center. Analytical expressions for the components of the displacement and the stress in different cases are obtained. The effect of the rotation and non-homogeneity on the displacement and stress are studied. Numerical results are given and illustrated graphically for each case is considered. The effects rotating and non-homogeneity are discussed. Comparisons are made with the results predicted in the presence and absence of rotation.     

Mappings Which Have a Parametric Representation in Several Complex Variables

In this paper, the sharp distortion theorems of the Fr\''echet-derivative type for a subclass of biholomorphic mappings which have a parametric representation on the unit ball of complex Banach spaces are established, and the corresponding results of the above generalized mappings on the unit polydisk in $\mathbb{C}^n$ are also given. Meanwhile, the sharp distortion theorems of the Jacobi determinant type for a subclass of biholomorphic mappings which have a parametric representation on the unit ball with an arbitrary norm in $\mathbb{C}^n$ are obtained, and the corresponding results of the above generalized mappings on the unit polydisk in $\mathbb{C}^n$ are got as well. Thus, some known results in prior literatures are generalized.     

具有阻尼项的二阶非线性微分方程的区间振动准则

本文研究一类具有阻尼项的二阶非线性微分方程,利用平均函数和一个广义Riccati变换,得到了该方程的新的区间振动准则,这些准则不同于已知的依赖于整个区间[t0,∞)的性质的结果,而是仅依赖于区间[t0,∞)的子区间列的性质．所得结果推广和改进了Kong的振动准则．特别,还给出了几个例子以说明本文所得结果的优越性．     

On a Fermat principle in general relativity. A Ljusternik-Schnirelmann theory for light rays

Summary In this paper existence and multiplicity results for lightlike geodesics joining a point with a timelike curve on a class of Lorentzian manifolds are proved under intrinsic assumptions. Such results are obtained using an extension to Lorentzian Geometry of the classical Fermat principle in optics. The results are proved using critical point theory on infinite dimensional manifolds. An application to the gravitational lens effect is presented.     

Composite Laguerre-Legendre spectral method for exterior problems

In this paper, we propose a composite Laguerre-Legendre spectral method for two-dimensional exterior problems. Results on the composite Laguerre-Legendre approximation, which is a set of piecewise mixed approximations coupled with domain decomposition, are established. These results play important roles in the related spectral methods for exterior problems. As examples of applications, the composite spectral schemes are provided for two model problems, with the convergence analysis. An efficient implementation is described. Numerical results demonstrate the spectral accuracy in space of this new approach, and confirm the analysis. The approximation results and techniques developed in this paper are also applicable to other problems defined on unbounded domains.     

随机游动的阶梯高度和最大值及其在风险理论中的应用

该文研究了均值为负的实值随机游动的阶梯高度及最大值, 在指数估计的条件不满足的情况下,得到了它们分布的局部渐近估计和尾渐近估计, 并将这些结果应用到风险理论中的Sparre Andersen 风险模型上, 得到了一些关于破产概率的新结果.     

Second-order properly elliptic boundary value problems on irregular plane domains

Conditions are presented under which properly elliptic second-order boundary value problems are well posed on irregular plane domains. The coefficients can be discontinuous. The results include known results for coercive forms, and also reduce to known results on proper ellipticity when the coefficients and domain are smooth. The main tool is an “inverse five-lemma” which relates the Neumann problem on a plane domain to a related modified Dirichlet problem. This inverse five-lemma can be used in a variety of settings. We show how it can be used to translate results of Grisvard on the index of Dirichlet operators in Sobolev spaces $\text{H}{}^{\mathrm{s}}\text{(Ω)}$ to results on Neumann operators, and examine the implications for regularity.     

A class of nondifferentiable continuous programming problems

Optimality conditions, duality and converse duality results are obtained for a class of continuous programming problems with a nondifferentiable term in the integrand of the objective function. The proofs are based on a Fritz John theorem for constrained optimization in abstract spaces. The results generalize various well-known results in variational problems with differentiable functions, and also give a dynamic analogue of certain nondifferentiable programming problems.     

Jostling for position: local improvement for irregular cutting patterns

This paper introduces a new improvement heuristic for irregular cutting and packing problems. The method is based on a small number of repetitions of any leftmost placement policy and is particularly effective in situations where computation time is strictly limited but exceeds that required for a single pass approach. Both the algorithm and the geometry required for implementation are described in full and the results of computational experiments on a variety of data are presented. These results show that the algorithm is an effective technique for producing good packings.     

Burnett models of the structure of a strong shock wave in a binary mixture of monatomic gases

The applicability of the complete and modified systems of Burnett's equations for problems on the structure of a strong shock wave in a binary mixture of monatomic gases are investigated. The results of calculations using the establishment method are compared with the results of calculations based on the Navier-Stokes equations and results obtained by direct statistical modelling. The limiting laws of intermolecular interaction (Maxwellian molecules and molecules treated as elastic spheres) are used.