Convex and Abstract Polytopes (Thursday, May 19, 2005 to Sunday, May 22, 2005)

Summary A report on the Convex and Absract Polytopes Workshops held at the Banff International Research Station and The University of Calgary, May 19--22, 2005.     

Exponential fitted Gauss, Radau and Lobatto methods of low order

Several exponential fitting Runge-Kutta methods of collocation type are derived as a generalization of the Gauss, Radau and Lobatto traditional methods of two steps. The new methods are capable of the exact integration (with only round-off errors) of differential equations whose solutions are linear combinations of an exponential and ordinary polynomials. Theorems of the truncation error reveal the good behavior of the new methods for stiff problems. Plots of their absolute stability regions that include the whole of the negative real axis are provided. A different procedure to find the parameter of the method is proposed. The variable step Radau method of two stages is derived. Finally, numerical examples underscore the efficiency of the proposed codes, especially when they are integrating stiff problems.      

Exceptional set of a representation with fractional powers

We prove that for any given c, 1 < c < 17/11, almost all natural numbers are representable in the form [x ^c] + [p ^c], where x is a natural number and p is a prime.     

Design,planning, scheduling,and control problems of flexible manufacturing systems

The design and use of flexible manufacturing systems (FMSs) involve some intricate operations research problems.FMS design problems include, for example, determining the appropriate number of machine tools of each type, the capacity of the material handling system, and the size of buffers.FMS planning problems include the determination of which parts should be simultaneously machined, the optimal partition of machine tools into groups, allocations of pallets and fixtures to part types, and the assignment of operations and associated cutting tools among the limited-capacity tool magazines of the machine tools.FMS scheduling problems include determining the optimal input sequence of parts and an optimal sequence at each machine tool given the current part mix.FMS control problems are those concerned with, for example, monitoring the system to be sure that requirements and due dates are being met and that unreliability problems are taken care of. This paper defines and describes these FMS problems in detail for OR/MS researchers to work on.     

Vertex colorings of graphs without short odd cycles

Motivated by the work of Ne?et?il and Rödl on “Partitions of vertices” we are interested in obtaining some quantitative extensions of their result. In particular, given a natural number r and a graph G of order m with odd girth g, we show the existence of a graph H with odd girth at least g and order that is polynomial in m such that every r‐coloring of the vertices of H yields a monochromatic and induced copy of G. © 2010 Wiley Periodicals, Inc. J Graph Theory 68: 255‐264, 2011     

On graphs with subgraphs having large independence numbers

Let G be a graph on n vertices in which every induced subgraph on vertices has an independent set of size at least . What is the largest so that every such G must contain an independent set of size at least q? This is one of the several related questions raised by Erd?s and Hajnal. We show that , investigate the more general problem obtained by changing the parameters s and t, and discuss the connection to a related Ramsey‐type problem. © 2007 Wiley Periodicals, Inc. J Graph Theory 56: 149–157, 2007     

浅析二阶齐次线性变系数微分方程的一个可积类型

本文讨论了二阶齐次线性变系数微分方程的特殊形式，给出了这种微分方程的一个可积类型．     

Pseudocompact, Locally Compact, First Countable, ccc, 0-dimensional Spaces May Be or May Not Be Lindelof

We construct a pseudocompact, locally compact, first countable, 0-dimensional,eec, non- Lindelof space under the assumption CH or the existence of a Suslin line. Butunder MA+CH, such a space cannot exist.     

Singular discrete (n, p) boundary value problems

This paper discusses a (n, p) singular discrete boundary value problem. Existence of a nonnegative solution is established.     

A sharp interface model for phase transitions in crystals with linear elasticity

A model describing phase transitions coupled with diffusion and linear elasticity in crystals under isothermal conditions is introduced. The elastic deformation as well as the phase parameter are obtained directly by the minimization of the free energy. After stating the model, the existence of strong solutions is proved. Copyright © 2004 John Wiley & Sons, Ltd.     

Periodic Solutions for N-Body-Type Problems

The authors consider non-autonomous N-body-type problems with strong force type potentials at the origin and sub-quadratic growth at infinity. Using Ljusternik Schnirelmann theory, the authors prove the existence of unbounded sequences of critical values for the Lagrangian action corresponding to non-collision periodic solutions.     

Some remarks on solutions to an overdetermined elliptic problem in divergence form in a ball

We prove the existence of a continuum of non-radial pairs (k,u) solutions to the following overposed problem div in B _r , u = 0 and on ∂B _r , where B _r is the Euclidean ball centered at zero of radius r in . Dedicato a Marco e Andrea Provera.     

Spectral sequences in combinatorial geometry: Cheeses, inscribed sets, and Borsuk-Ulam type theorems

Algebraic topological methods are especially well suited for determining the non-existence of continuous mappings satisfying certain properties. In combinatorial problems it is sometimes possible to define a mapping from a space X of configurations to a Euclidean space Rm in which a subspace, a discriminant, often an arrangement of linear subspaces A, expresses a target condition on the configurations. Add symmetries of all these data under a group G for which the mapping is equivariant. If we remove the discriminant from Rm, we can pose the problem of the existence of an equivariant mapping from X to the complement of the discriminant in Rm. Algebraic topology may sometimes be applied to show that no such mapping exists, and hence the image of the original equivariant mapping must meet the discriminant.We introduce a general framework, based on a comparison of Leray-Serre spectral sequences. This comparison can be related to the theory of the Fadell-Husseini index. We apply the framework to:

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solve a mass partition problem (antipodal cheeses) in Rd,

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determine the existence of a class of inscribed 5-element sets on a deformed 2-sphere,

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obtain two different generalizations of the theorem of Dold for the non-existence of equivariant maps which generalizes the Borsuk-Ulam theorem.

     

Poisson方程Cauchy问题对数型稳定性

本文在ｍ＋１维欧几里得空间中讨论Ｐｏｉｓｓｏｎ方程Ｃａｕｃｈｙ问题解的稳定性，利用Ｔｉｋｈｏｎｏｖ，栾文贵，Ｙａｍａｍｏｔｏ的关于不适定问题的解法获得了解的对数型稳定性估计。     

Ekeland type variational principle with applications to quasi-variational inclusion problems

In this paper, we study the Ekeland type variational principle, a Caristi-Kirk type fixed point theorem and a maximal element theorem in the setting of uniform spaces. By using these results, we establish some existence results for solutions of quasi-variational inclusion problems, quasi-optimization problems and equilibrium problems defined on separated and sequentially complete uniformly spaces.