The supply chain optimization of continuous process networks is essential for most chemical companies. The dynamic nature of this problem leads to systems that involve types of chemicals as well as multiple time periods, and ultimately many complex and large combinatorial optimization models. These models become very difficult to solve, and sometimes not even solvable. Hence, such models requir...

The set k-covering problem is a variant of the classical set covering problem, in which each object is required to be covered at least k times. We describe a hybrid Lagrangean heuristic, named LAGRASP, which combines subgradient optimization and GRASP with path-relinking to solve the set kcovering problem. Computational experiments carried out on 135 test instances show experimentally that by p...

We consider the solution of nite element discretized optimum sheet problems by an iterative algorithm. The problem is that of maximizing the stiiness of a sheet subject to constraints on the admissible designs and unilateral contact conditions on the displacements. The model allows for zero design volumes, and thus constitutes a true topology optimization problem. We propose and evaluate a subg...

For a class of nonconvex nonsmooth functions, we consider the problem of computing an approximate critical point, in the case of inexact oracles. The latter means that only an inexact function value and an inexact subgradient are available, at any given point. We assume that the errors in function and subgradient evaluations are merely bounded, and in principle need not vanish in the limit. We ...

We present the numerical behavior of a projection method for convex minimization problems which was studied by Cegielski [1]. The method is a modification of the Polyak subgradient projection method [6] and of variable target value subgradient method of Kim, Ahn and Cho [2]. In each iteration of the method an obtuse cone is constructed. The obtuse cone is generated by a linearly independent sys...