Efficient GRASP+VND and GRASP+VNS metaheuristics for the traveling repairman problem

The traveling repairman problem is a customer-centric routing problem, in which the total waiting time of the customers is minimized, rather than the total travel time of a vehicle. To date, research on this problem has focused on exact algorithms and approximation methods. This paper presents the first metaheuristic approach for the traveling repairman problem

An Algorithm for the Cycled Shortest Path Problem

For a network with cycle, where at least one cycle exists, the Floyd- Warshall algorithm is probably the most used algorithm to determine he least cost path between every pair of nodes on this network, i.e. the solution for the shortest path problem with cycle. In this paper, a new algorithm for this problem which requires less computational effort than the Floyd-Warshall algorithm has been developed Furthermore, it can be shown that the basis of our algorithm is much easier to be learnt and understood which might be an advantage for educational puposes. A small example validates our algorithm and shows its implementation

Statistical Control of Time and Cost Performance Indices in Construction Projects: A Case Study

The earned value management is a powerful and important technique in analyzing and controlling the project performance. While it allows exact measurement of project progress, it lets corrective actions in a timely manner. In fact, the earned value allows project managers to find out any project time and cost deviations by calculating the performance indices. In this paper, to improve the applicability of the traditional earned value technique, we develop an integrated approach by combining statistical quality control charts with traditional earned value technique, to monitor and control project time and cost performances. The results applied to a real construction project compete favorly against traditional approache

Optimal location of workstations in tandem automated-guided vehicle systems

The way workstations are located in a tandem automated-guided vehicle (AGV) systems affect the total lateness of the system. So far, almost all studies have focused on either minimizing the total flow or minimizing the total AGV transitions in each zone. This study presented a novel approach to locate the workstations in a tandem AGV zones by developing a new mixed-integer programming (MIP) formulation. The objective is to minimize total waiting time of all workstations which is equivalent to minimizing the total lateness of each zone. Lateness is defined as the total idle time of a workstation waiting to be supplied by an AGV. The proposed MIP formulation is very competitive and has the capability to solve instances of up to 25 workstations to optimality in a reasonable amount of time