Fuzzy linear programming problems as bi-criteria optimization problems

In this paper, we consider fuzzy linear programming (FLP) problems which involve fuzzy numbers only in coefficients of objective function. First, we shall give concepts of optimal solutions to (FLP) problems and investigate their properties. Next, in order to find all optimal solutions, we define three types of bi-criteria optimization problems.     

A note on quasi-equilibrium problems

The purpose of this paper is to prove the existence of solutions of quasi-equilibrium problems without any generalized monotonicity assumption. Additionally, we give some applications.     

Using tropical optimization techniques in bi-criteria decision problems

Computational Management Science - We consider decision problems of rating alternatives based on their pairwise comparisons according to two criteria. Given pairwise comparison matrices for each...     

运输问题表上作业法的一点注记

表上作业法是运输问题的经典算法,然而按照表上作业法闭回路构建方法有时竟然不能成功,为此本文重新设计了新的闭回路构建方法,改进了表上作业法.     

A note on noncommutative moment problems

Noncommutative moment problems for C*-algebras are studied. We generalize a result of Hadwin on tracial states to nontracial case. Our results are applied to obtain simple solutions to moment problems on the square and the circle as well as extend the positive unital functionals from a (discrete) complex group algebra to states on the group C*-algebra.     

A note on two fixed point problems

We extend the applicability of the Exterior Ellipsoid Algorithm for approximating n-dimensional fixed points of directionally nonexpanding functions. Such functions model many practical problems that cannot be formulated in the smaller class of globally nonexpanding functions. The upper bound 2n²ln(2/) on the number of function evaluations for finding -residual approximations to the fixed points remains the same for the larger class. We also present a modified version of a hybrid bisection-secant method for efficient approximation of univariate fixed point problems in combustion chemistry.     

A note on multi-point boundary value problems

Multi-point boundary value problems for a second-order ordinary differential equation are considered in this note. An existence result is obtained with the help of coincidence degree theory.     

A note on two source location problems

We consider Source Location ($\mathsf{SL}$) problems: given a capacitated network $G=(V,E)$, cost $c(v)$ and a demand $d(v)$ for every $v\in V$, choose a min-cost $S\subseteq V$ so that $\lambda (v,S)⩾d(v)$ holds for every $v\in V$, where $\lambda (v,S)$ is the maximum flow value from v to S. In the directed variant, we have demands $d^{\mathit{in}}(v)$ and $d^{\mathit{out}}(v)$ and we require $\lambda (S,v)⩾d^{\mathit{in}}(v)$ and $\lambda (v,S)⩾d^{\mathit{out}}(v)$. Undirected $\mathsf{SL}$ is (weakly) NP-hard on stars with $r(v)=0$ for all v except the center. But, it is known to be polynomially solvable for uniform costs and uniform demands. For general instances, both directed an undirected $\mathsf{SL}$ admit a $(\ln D+1)$-approximation algorithms, where D is the sum of the demands; up to constant this is tight, unless P = NP. We give a pseudopolynomial algorithm for undirected $\mathsf{SL}$ on trees with running time $O(|V|{\Delta }^3)$, where $\Delta ={\max }_{v\in V}d(v)$. This algorithm is used to derive a linear time algorithm for undirected $\mathsf{SL}$ with $\Delta ⩽3$. We also consider the Single Assignment Source Location ($\mathsf{SASL}$) where every $v\in V$ should be assigned to a single node $s(v)\in S$. While the undirected $\mathsf{SASL}$ is in P, we give a $(\ln |V|+1)$-approximation algorithm for the directed case, and show that this is tight, unless P = NP.     

A note on solving large p-median problems

In a previous paper we presented a tree search algorithm for the p-median problem, the problem of locating p facilities (medians) on a network, which was based upon La grangean relaxation and subgradient optimisation. That algorithm solved (optimally) problems with an arbitrary number of medians and having up to 200 vertices.In this note we show that it is possible to enhance that algorithm to solve (optimally) problems having up to 900 vertices using the Cray-1S computer.     

A note on termination in optimal control problems

Attention is called to the possibility of optimal trajectories terminating at a time that is larger than the first time of reaching the target set. An example is given.This research was supported by the Office of Naval Research, Grant No. N00014-69-1012.     

A note on skewcirculant preconditioners for elliptic problems

In a recent paper Chan and Chan study the use of circulant preconditioners for the solution of elliptic problems. They prove that circulant preconditioners can be chosen so that the condition number of the preconditioned system can be reduced fromO(n ² ) toO(n). In addition, using the Fast Fourier Transform, the computation of the preconditioner is highly parallelizable. To obtain their result, Chan and Chan introduce a shift /p/n ² for some >0. The aim of this paper is to consider skewcirculant preconditioners, and to show that in this case the condition number ofO(n) can easily be shown without using the somewhat unsatisfactory shift /p/n ². Furthermore, our estimates are more precise.     

A note on singular nonlinear boundary value problems

In this paper we study the existence and multiplicity of solutions of the following operator equation in Banach space E:

u=λAu,0<λ<+∞,u∈P?{θ},     

A note on invex problems with nonnegative variable

We provide sufficient optimality conditions involving invexity for mathematical programming problems with nonnegative variable. We also show that upon certain assumptions on the scaling function η, these problems are convex transformable. Hence certain associated convex problems should be solved. Some applications are shown.     

A note on minimization problems and multistep methods

Summary. We use the qualitative properties of the solution flow of the gradient equation to compute a local minimum of a real-valued function . Under the regularity assumption of all equilibria we show a convergence result for bounded trajectories of a consistent, strictly stable linear multistep method applied to the gradient equation. Moreover, we compare the asymptotic features of the numerical and the exact solutions as done by Humphries, Stuart (1994) and Schropp (1995) for one-step methods. In the case of -stable formulae this leads to an efficient solver for stiff minimization problems. Received July 10, 1995 / Revised version received June 27, 1996     

A note on concentrations for integral two-scale problems

This work is devoted to the characterization of the asymptotic behavior, as \({\{\varepsilon_n\}}\) goes to zero, of a family of integral functionals of the form \({\int_{\Omega}f(x,\langle x/\varepsilon_n \rangle, \nabla u_{n}(x))\, dx}\) in terms of measures of oscillation and concentration associated to the sequence \({\{(\langle x/\varepsilon_n\rangle, \nabla u_{n}(x))\}}\).     

A note on equi-integrability in dimension reduction problems

In the framework of the asymptotic analysis of thin structures, we prove that, up to an extraction, it is possible to decompose a sequence of ‘scaled gradients’ (where is the gradient in the k-dimensional ‘thin variable’ x _β) bounded in (1 < p < + ∞) as a sum of a sequence whose p-th power is equi-integrable on Ω and a ‘rest’ that converges to zero in measure. In particular, for k = 1 we recover a well-known result for thin films by Bocea and Fonseca (ESAIM: COCV 7:443–470; 2002).      

A note on semigroup arguments in nonstandard problems

In this note we investigate a nonstandard problem determined by a system of differential equations and initial conditions. We use the techniques of the mild solutions to obtain continuous dependence estimates, uniqueness and existence of solutions. We also make some comments on nonexistence and nonuniqueness of solutions.     

A note on stability for parametric equilibrium problems

In this paper we consider equilibrium problems in vector metric spaces where the function f and the set K are perturbed by the parameters ε,η. We study the stability of the solutions, providing some results in the peculiar framework of generalized monotone functions, first in the particular case where K is fixed, then under both data perturbation.