On congruences of groupoids closely connected with quasigroups

Conditions when a congruence of a left (right) division groupoid and a left (right) cancellation groupoid is closed (“normal”) are given. Conditions for the simplicity of the above-mentioned groupoids are obtained.     

On the Laplacian spectral ratio of connected graphs

The Laplacian spectrum of a graph is the eigenvalues of the associated Laplacian matrix. The quotient between the largest and second smallest Laplacian eigenvalues of a connected graph, is called the Laplacian spectral ratio. Some bounds on the Laplacian spectral ratio are considered. We improve a relation on the Laplacian spectral ratio of regular graphs. Especially, the first two smallest Laplacian spectral ratios of graphs with given order are determined. And some operations on Laplacian spectral ratio are presented.     

On two functionals connected to the Laplacian in a class of doubly connected domains in space-forms

LetB ₁ be a ball of radiusr ₁ inS ⁿ (ℍⁿ), and letB ₀ be a smaller ball of radiusr ₀ such thatB ₀ ⊂B ₁ . ForS ⁿ we considerr ₁ π. Let u be a solution of the problem- δm = 1 in Ω :=B ₁ /B ₀ vanishing on the boundary. It is shown that the associated functionalJ (Ω) is minimal if and only if the balls are concentric. It is also shown that the first Dirichlet eigenvalue of the Laplacian on Ω is maximal if and only if the balls are concentric.     

On spectral theorems for families of linearly connected self-adjoint operators with given spectra associated with extended Dynkin graphs

We prove spectral theorems for families of linearly connected self-adjoint operators with given special spectra associated with extended Dynkin graphs. We establish that all irreducible families of linearly connected operators with arbitrary spectra associated with extended Dynkin graphs are finite-dimensional. __________ Translated from Ukrains’kyi Matematychnyi Zhurnal, Vol. 58, No. 11, pp. 1556–1570, November, 2006.     

On the design of networks with unicyclic connected components

This is a summary of my PhD thesis supervised by Walid Ben-Ameur and defended on September 29 2009, at Télécom SudParis. The thesis is written in French language and is available from the author upon request at makhlouf.hadji@it-sudparis.eu.     

On some families of cooperative fuzzy games

In a fuzzy cooperative game the players may choose to partially participate in a coalition. A fuzzy coalition consists of a group of participating players along with their participation level. The characteristic function of a fuzzy game specifies the worth of each such coalition. This paper introduces well-known properties of classical cooperative games to the theory of fuzzy games, and studies their interrelations. It deals with convex games, exact games, games with a large core, extendable games and games with a stable core.     

不含P_t的非二部连通图的最小Q-特征值

对于一个连通图而言,它的最小Q-特征值为零当且仅当它是二部图.图的最小Q-特征值常被用来衡量一个图的非二部程度,因而受到研究者的广泛关注.文中研究了图中存在长路的最小Q-特征值条件,分别确定了最小Q-特征值最小的不含路Pt的非二部单圈图和非二部连通图.     

An edge-grafting theorem on Laplacian spectra of graphs and its application

Let 𝒰(n,?d) be the class of unicyclic graphs on n vertices with diameter d. This article presents an edge-grafting theorem on Laplacian spectra of graphs. By applying this theorem, we determine the unique graph with the maximum Laplacian spectral radius in 𝒰(n,?d). This extremal graph is different from that for the corresponding problem on the adjacency spectral radius as done by Liu et al. [Q. Liu, M. Lu, and F. Tian, On the spectral radius of unicyclic graphs with fixed diameter, Linear Algebra Appl. 420 (2007), 449–457].     

On optimal control problems connected with eigenvalue variational inequalities

The eigenvalue optimization problem for a variational inequality over the convex cone is to be dealt with. The control variable appears in the operator of the unilateral problem. The existence theorem for the maximum first eigenvalue optimization problem is stated and verified. The necessary optimality condition is derived. The applications to the optimal design of unilaterally supported beams and plates are presented. The variable thickness of a construction plays the role of a design variable. The convergence of the finite elements approximation is proved. Copyright © 2001 John Wiley & Sons, Ltd.     

The Laplacian spectra of graphs with a tree structure

Trees are very common in the theory and applications of combinatorics. In this article, we consider graphs whose underlying structure is a tree, except that its vertices are graphs in their own right and where adjacent graphs (vertices) are linked by taking their join. We study the spectral properties of the Laplacian matrices of such graphs. It turns out that in order to capture known spectral properties of the Laplacian matrices of trees, it is necessary to consider the Laplacians of vertex-weighted graphs. We focus on the second smallest eigenvalue of such Laplacians and on the properties of their corresponding eigenvector. We characterize the second smallest eigenvalue in terms of the Perron branches of a tree. Finally, we show that our results are applicable to advancing the solution to the problem of whether there exists a graph on n vertices whose Laplacian has the integer eigenvalues 0, 1, …, n ? 1.     

Optimal control of generalized multiobjective games with application to traffic networks modeling

The purpose of this paper is to study some new results on the existence and convergence of the solutions to controlled systems of generalized multiobjective games, controlled systems of traffic networks, and optimal control problems (OCPs). First, we introduce the controlled systems of generalized multiobjective games and establish the existence of the solutions for these systems using Browder-type fixed point theorem in the noncompact case and the $C_i$-quasi-concavity. Results on the convergence of controlled systems of the solutions for such problems using the auxiliary solution sets and the extended $C_i$-convexity of the objective functions are studied. Second, we investigate OCPs governed by generalized multiobjective games. The existence and convergence of the solutions to these problems are also obtained. Finally, as a real-world application, we consider the special case of controlled systems of traffic networks. Many examples are given for the illustration of our results.     

On some optimal control problems connected with the Navier-Stokes system

We consider problems of the form $$\left\{ \begin{gathered} J(y) \to \inf : \hfill \\ L(y) = u, \left\| u \right\| \leqslant M, y(0) = 0, y(T) = v, \hfill \\\end{gathered} \right.$$ whereL is the operator of the Navier-Stokes system. We obtain theorems for existence of a solution and necessary and sufficient conditions for an extremum. We also study the uniqueness of the solution and construct the asymptotics of the solution in terms of the parameter M. Bibliography: 11 titles.     

Generalized implicit function theorem and its application to parametric optimal control problems

Many problems in physics and mathematics may be reduced to solving equations depending on a parameter. The justification of the existence of solutions to the equations and the sensitivity analysis may be conducted based on Implicit Function Theorem (IFT) under certain regularity assumptions. Provided the regularity assumptions do not hold, generalizations of IFT are needed in order to study solutions to the equations. The paper focuses on a particular generalization of IFT which is then applied to a parametric linear time-optimal control problem.     

关于k紧优双环网络的无限族

在李乔等人的L形瓦理论的基础上,使用中国剩余定理等数论理论,证明任给整数k＞2,可以构造k紧优双环网络的无限族,其结点数N(k,e)可以为e的4次多项式,也可以为e的2次多项式且系数含有参数.     

On the use of multiple sinks to extend the lifetime in connected wireless sensor networks

This paper addresses the maximum network lifetime problem in wireless sensor networks. In this problem, the purpose is to schedule a set of wireless sensors, keeping them connected and guaranteeing that all targets are covered, while network lifetime is maximized. Two variants of this problem are considered; in the first case it is assumed that a single sink (base station) is available, the second case considers the presence of several sinks. To solve the problem, a hybrid Column Generation-GRASP heuristic is proposed. The method is shown to be able to find optimal or near optimal solutions efficiently in both cases.