Tri-level optimization problems are optimization problems with three nested hierarchical structures, where in most cases conflicting objectives are set at each level of hierarchy. Such problems are common in management, engineering designs and in decision making situations in general, and are known to be strongly NP-hard. Existing solution methods lack universality in solving these types of pro...

In this paper, we propose a hierarchical optimization technique of the PCB assembly line including multi-head non-identical surface mounting machines. The optimization problem related to the PCB assembly line is generally divided into three sub-problems: a line balancing problem, a reel assignment problem and a pick-and-place sequencing problem. Since each problem is known to be combinatorial a...

Vehicle Routing Problem is a well-known problem in logistics and transportation, and the variety of such problems is explained by the fact that it occurs in many real-life situations. It is an NP-hard combinatorial optimization problem and finding an exact optimal solution is practically impossible. In this work, SiteDependent Truck and Trailer Routing Problem with hard and soft Time Windows an...

Abstract. We consider a conic-quadratic (and in particular a quadratically constrained) optimization problem with uncertain data, known only to reside in some uncertainty set U . The robust counterpart of such a problem leads usually to an NP-hard semidefinite problem; this is the case, for example, when U is given as the intersection of ellipsoids or as an n-dimensional box. For these cases we...

1 Overview Among hard combinatorial optimization problems there is an increasing body of special cases known in which optimal solutions can be obtained eeciently. These special cases may be expressed as constraints on graph structure, such as chordal or interval graphs 4, 6] which allow linear-time solution of problems like vertex coloring, or Monge matrix edge weights which allow eecient solut...

Ant colony optimization (ACO) performs very well on many hard optimization problems, even though no good worst-case guarantee can be given. Understanding the effects of different ACO parameters and the structural features of the considered problem on algorithm performance has become an interesting problem. In this paper, we study structural features of easy and hard instances of the traveling s...

Scheduling of large number of jobs/tasks is a tedious and time taking work. With the increase is demand of products, the manufacturing industries have been facing a lot of trouble in fulfilling those demands while optimizing the production. Job shop scheduling problem (JSSP) is a well known combinatorial optimization problem with NP hard difficulty. Job shop scheduling (JSS) is the efficient al...

in a logistic system, decisions on location of depot, vehicle routing and assignment of routes to vehicles should be considered simultaneously. the location-routing problems are defined to find the optimal number and locations of depots, and at the same time with the distribution routes for the vehicles. because of the complexity and the time consuming computation, this problem belongs to a cla...

this paper considers identical parallel machines scheduling problem with past-sequence-dependent setup times, deteriorating jobs and learning effects, in which the actual processing time of a job on each machine is given as a function of the processing times of the jobs already processed and its scheduled position on the corresponding machine. in addition, the setup time of a job on each machin...

Floating operation is very critical in power management in hard disk drive (HDD), during which no control command is applied to the read/write head but a fixed current to counteract actuator flex bias. External disturbance induced drift of head may result in interference of head and bump on the disk during drifting, leading to consequent scratches and head degradation, which is a severe reliabi...