We investigate a variant of the Fixed Charge Shortest Paths problem which enumerates the sequence of optimal solutions that arise as the focus shifts from the fixed cost parameters, (generating a Minimum Spanning Tree problem instance), to the variable costs, (generating a Shortest Paths problem instance). Thus we provide insight into the behavior of the problem, which is NP-hard and requires s...

In a previous paper we formulated the fixed-charge multiple knapsack problem (FCMKP), and developed an exact algorithm to solve this problem to optimality by combining pegging test and branch-and-bound technique. Although the developed algorithm was quite successful for instances with small number of knapsacks (m), for larger m the problem was hard to solve by this method. Here we present some ...

Transportation is one of the important infrastructures constituting the base and requisite for different levels of people’s access and movement to various locations. Transportation systems are one of the indices of the development of a region. Optimizing these systems contributes to improving performance and reducing costs of offering services to users. Hence, methods should be adopted with whi...

This article deals with the intermodal transportation problem for the commodities delivery between different locations. The time – dependent shortest path planning, in which the travel time along each arc is a known function of the departure time along the arc, is a very important problem and arises in many practical application such as a routing system of a container used in the time – depende...

A number of factors influence the efficiency, productivity, and welfare of transportation networks. Travel demand, user costs, and facility supply costs equili-brate on various time scales under a set of pricing (taxes and tolls), investment and ownership policies. Two types of equilibria exist in a transportation network, short-run traffic equilibrium and long-run supply-demand equilibrium. Th...

scheduling is an important subject of production and operations management area. in flow-shop scheduling, the objective is to obtain a sequence of jobs which when processed in a fixed order of machines, will optimize some well defined criteria. the concept of transportation time is very important in scheduling. transportation can be done by robots. in situations that robots are used to transpor...

We present a continuous, bilinear formulation for the fixed charge network flow problem. This formulation is used to derive an exact algorithm for the fixed charge network flow problem converging in a finite number of steps. Some preliminary computational experiments are reported to show the performance of the algorithm.

The production-transportation problem (PTP) is a generalization of the transportation problem. In PTP, we decide not only the level of shipment from each source to each sink but also the level of supply at each source. A concave production cost function is associated with the assignment of supplies to sources. Thus the objective function of PTP is the sum of the linear transportation costs and ...

We discuss a moving boundary problem arising from a model of gas ionization in the case of negligible electron diffusion and suitable initial data. It describes the time evolution of an ionization front. Mathematically, it can be considered as a system of transport equations with different characteristics for positive and negative charge densities. We show that only advancing fronts are possibl...