Search results for "LOGISTICS"
showing 10 items of 467 documents
Solutions for districting problems with chance-constrained balancing requirements
2021
Abstract In this paper, a districting problem with stochastic demands is investigated. The goal is to divide a geographic area into p contiguous districts such that, with some given probability, the districts are balanced with respect to some given lower and upper thresholds. The problem is cast as a p -median problem with contiguity constraints that is further enhanced with chance-constrained balancing requirements. The total assignment cost of the territorial units to the representatives of the corresponding districts is used as a surrogate compactness measure to be optimized. Due to the tantalizing purpose of deriving a deterministic equivalent for the problem, a two-phase heuristic is d…
Interactive Nonconvex Pareto Navigator for Multiobjective Optimization
2019
Abstract We introduce a new interactive multiobjective optimization method operating in the objective space called Nonconvex Pareto Navigator . It extends the Pareto Navigator method for nonconvex problems. An approximation of the Pareto optimal front in the objective space is first generated with the PAINT method using a relatively small set of Pareto optimal outcomes that is assumed to be given or computed prior to the interaction with the decision maker. The decision maker can then navigate on the approximation and direct the search for interesting regions in the objective space. In this way, the decision maker can conveniently learn about the interdependencies between the conflicting ob…
Lower and upper bounds for the mixed capacitated arc routing problem
2006
This paper presents a linear formulation, valid inequalities, and a lower bounding procedure for the mixed capacitated arc routing problem (MCARP). Moreover, three constructive heuristics and a memetic algorithm are described. Lower and upper bounds have been compared on two sets of randomly generated instances. Computational results show that the average gaps between lower and upper bounds are 0.51% and 0.33%, respectively.
Using a TSP heuristic for routing order pickers in warehouses
2010
In this paper, we deal with the sequencing and routing problem of order pickers in conventional multi-parallel-aisle warehouse systems. For this NP-hard Steiner travelling salesman problem (TSP), exact algorithms only exist for warehouses with at most three cross aisles, while for other warehouse types literature provides a selection of dedicated construction heuristics. We evaluate to what extent reformulating and solving the problem as a classical TSP leads to performance improvements compared to existing dedicated heuristics. We report average savings in route distance of up to 47% when using the LKH (Lin-Kernighan-Helsgaun) TSP heuristic. Additionally, we examine if combining problem-sp…
Decision making in multiobjective optimization problems under uncertainty: balancing between robustness and quality
2018
As an emerging research field, multiobjective robust optimization employs minmax robustness as the most commonly used concept. Light robustness is a concept in which a parameter, tolerable degradations, can be used to control the loss in the objective function values in the most typical scenario for gaining in robustness. In this paper, we develop a lightly robust interactive multiobjective optimization method, LiRoMo, to support a decision maker to find a most preferred lightly robust efficient solution with a good balance between robustness and the objective function values in the most typical scenario. In LiRoMo, we formulate a lightly robust subproblem utilizing an achievement scalarizi…
Time-Dependent Multiple Depot Vehicle Routing Problem on Megapolis Network under Wardrop's Traffic Flow Assignment
2018
In this work multiple depot vehicle routing problem is considered in case of variable travel times between nodes on a metropolis network. This variant of the classic multiple depot vehicle routing problem is motivated by the fact that in urban contexts variable traffic conditions play an essential role and can not be ignored in order to perform a realistic optimization. Time-travel matrices corresponding to each period of planning horizon were formed by solving the traffic assignment problem in conjunction with shortest path problem. Routing problem instances include from 20 to 100 customers randomly chosen from a road network of Saint-Petersburg. The results demonstrate that taking into ac…
Efficient Port Pricing: A New Methodology Applied to Spanish Commercial Ports
2000
This paper presents a methodology for determining efficient tariffs for the services provided by commercial ports. With this method, efficient unit profits can be obtained for the services offered and their margins of sensitivity can be found. This allows port authorities to determine what actions should be taken with regard to tariffs and/or variable costs in order to optimise their economic results. At the same time, shadow prices of port resources and their limits of sensitivity can be obtained, thus providing port authorities with orientation regarding which resources should be augmented and by how much. In the early 90's, this methodology was applied to all Spanish commercial ports and…
Cycling for Home-to-School Travel in Palermo: A Method for Assessing the Optimal Allocation of New Cycling Infrastructure
2019
In order to reduce the number of cars on the road, one of the most incisive actions is to encourage cycling, e.g. through the introduction of bike-sharing systems. In particular, the activation of special bike-sharing programs for school students could lead students to choose this mode of transport to make their own home-school travel. The success of such initiatives is primarily linked to the presence of a continuous and functional cycle network, which can create safe routes to school. It is, therefore, necessary a cycle network design model that allows determining the optimal allocation of new cycle paths, maximizing the number of users and considering technical and economic constraints. …
A GIS-Based Methodology for Evaluating the Increase in Multimodal Transport between Bicycle and Rail Transport Systems. A Case Study in Palermo
2021
Background: In a world where every municipality is pursuing the goals of more sustainable mobility, bicycles play a fundamental role in getting rid of private cars and travelling by an eco-friendly mode of transport. Additionally, private and shared bikes can be used as a feeder transit system, solving the problem of the first- and last-mile trips. Thanks to GIS (Geographic Information System) software, it is possible to evaluate the effectiveness of such a sustainable means of transport in future users’ modal choice. Methods: Running an accessibility analysis of cycling and rail transport services, the potential mobility demand attracted by these services and the possible multimodality bet…
What?s new in intelligent transportation systems?: An overview of European projects and initiatives
2013
This article is a taxonomy of recent intelligent transportation systems (ITS) initiatives/projects in Europe, and it covers nearly all of the main segments of the transportation sector. The purpose is to appraise the milestones that have been reached so far in the area of ITS. Furthermore, this article will help in identifying directions for future research. By highlighting the potential advantages users get through deployed ITS solutions, this article stimulates the interest of users and relevant stakeholders in the uptake of this technology. Finally, it will also serve as a useful resource for those agents of the scientific community who are interested in taking part in the European Commi…