Minisum and minimax transfer point location problem with random demands points

This paper is concerned with analyzing some models of the weighted transfer point location problem under the minisum and minimax criterions when demand points are randomly distributed over regions of the plane and the location of the service facility is known. In case of minisum objective with rectilinear distance, an iterative procedure was constructed for estimating the optimal transfer point location using the hyperbolic application procedure. Exact analytic solution was obtained when the random demand points follow uniform distributions. A unified analytic optimal solution was provided for all types of probability distributions of the random demand points when the distance is the squared Euclidean distance. For minimax objective with squared Euclidean distance, an iterative procedure based on Karush-Kuhn-Tucker conditions was developed to produce an approximate solution to the optimal solution. Illustrative numerical examples were provided

Mathematical Programming Model for the Two-Level Facility Location Problem: The Case of Tanzanian Emergence Maize Distribution Network for 2004–2010 Maize Data

A two-level facility location problem (FLP) has been studied in the transportation network of emergence maize crop in Tanzania. The facility location problem is defined as the optimal location of facilities or resources so as to minimize costs in terms of money, time, distance and risks with the relation to supply and demand points. Distribution network design problems consist of determining the best way to transfer goods from the supply to the demand points by choosing the structure of the network such that the overall cost is minimized. The three layers, namely production centres (PCs), distribution centres (DCs) and customer points (CPs) are considered in the two-level FLP. The flow of maize from PCs to CPs through DCs is designed at a minimum cost under deterministic mathematical programming model. The four decisions to be made simultaneously are: to determine the locations of DCs (including number of DCs), allocation of CPs to the selected DCs, allocation of selected DCs to PCs, and to determine the amount of maize crop transported from PCs to DCs and then from DCs to CPs. The modelled problem generated results through optimization with respect to optimal location-allocation strategies. The results of the optimized network shows the improvement in costs saving compared to the manually operated existing network. The results show the costs saving of up to 18% which is equivalent to $2,910 thousand (TZS 2.9 billion). Keywords:    Optimization; Maize crop; Transportation network; Deterministic model; Facility locatio

Penerapan Konsep Vehicle Routing Problem Dalam Kasus Pengangkutan Sampah Di Perkotaan

. Cities in developing countries still operate a traditional waste transport and handling where rubbish were collected at regular intervals by specialized trucks from curb-side collection or transfer point prior to transport them to a final dump site. The problem are worsening as some cities experience exhausted waste collection services because the system is inadequately managed, fiscal capacity to invest in adequate vehicle fleets is lacking and also due to uncontrolled dumpsites location. In this paper problem of waste collection and handling is formulated based on Capacitated Vehicle Routing Problem Time Window Multiple Depo Intermediete Facility (CVRPTWMDIF). Each vehicle was assigned to visit several intermediate transfer points, until the truck loading or volume capacity reached then waste are transported to final landfill or dump site. Finally all trucks will return to a depot at the end of daily operation. Initially the solution of CVRPTWMDIF problem was tested on a simple hypothetical waste handling before being implemented into a real case problem. Solutions found using CVRPTWMDIF compared with the practice of waste transport and handling in the city of Bandung. Based on a common hours of operation and the same number of transport fleets, it was found that CVRPTWMDIF can reduce the volume of waste that is not transported by almost half by the end of the daily operations

Locating a bioenergy facility using a hybrid optimization method

In this paper, the optimum location of a bioenergy generation facility for district energy applications is sought. A bioenergy facility usually belongs to a wider system, therefore a holistic approach is adopted to define the location that optimizes the system-wide operational and investment costs. A hybrid optimization method is employed to overcome the limitations posed by the complexity of the optimization problem. The efficiency of the hybrid method is compared to a stochastic (genetic algorithms) and an exact optimization method (Sequential Quadratic Programming). The results confirm that the hybrid optimization method proposed is the most efficient for the specific problem. (C) 2009 Elsevier B.V. All rights reserved

Coordination of Mobile Mules via Facility Location Strategies

In this paper, we study the problem of wireless sensor network (WSN) maintenance using mobile entities called mules. The mules are deployed in the area of the WSN in such a way that would minimize the time it takes them to reach a failed sensor and fix it. The mules must constantly optimize their collective deployment to account for occupied mules. The objective is to define the optimal deployment and task allocation strategy for the mules, so that the sensors' downtime and the mules' traveling distance are minimized. Our solutions are inspired by research in the field of computational geometry and the design of our algorithms is based on state of the art approximation algorithms for the classical problem of facility location. Our empirical results demonstrate how cooperation enhances the team's performance, and indicate that a combination of k-Median based deployment with closest-available task allocation provides the best results in terms of minimizing the sensors' downtime but is inefficient in terms of the mules' travel distance. A k-Centroid based deployment produces good results in both criteria.Comment: 12 pages, 6 figures, conferenc

Locating Two Transfer Points on a Network with a Trip Covering Criterion and Mixed Distances

In this paper we consider a set of origin-destination pairs in a mixed model in which a network embedded in the plane represents an alternative high-speed transportation system, and study a trip covering problem which consists on locating two points in the network which maximize the number of covered pairs, that is, the number of pairs which use the network by acceding and exiting through such points. To deal with the absence of convexity of this mixed distance function we propose a decomposition method based on formulating a collection of subproblems and solving each of them via discretization of the solution set.Ministerio de Educación, Ciencia e Innovación MTM2009-14243Ministerio de Economía y Competitividad MTM2012-37048Junta de Andalucía P09-TEP-5022Junta de Andalucía P10-FQM-584

Unequal Exposure to Ecological Hazards 2005: Environmental Injustices in the Commonwealth of Massachusetts

Unequal Exposure to Ecological Hazards 2005 documents Massachusetts residents' unequal exposure to environmental hazards. More specifically, the report analyzes both income basedand racially-based disparities in the geographic distribution of some 17 different types ofenvironmentally hazardous sites and industrial facilities in the Commonwealth of Massachusetts. This report provides evidence that working class communities and communities of color are disproportionately impacted by toxic waste disposal, incinerators, landfills, trash transfer stations, power plants, and polluting industrial facilities. In some cases, not only are new toxic facilities and dump sites located in poorer neighborhoods and communities of color, but as in the case of the public housing development and playgrounds near the Alewife station in Cambridge, housing for people of color and low income populations is sometimes located on top of preexisting hazardous waste sites and/or nearby polluting facilities. We conclude that striking inequities in the distribution of these environmentally hazardous sites and facilities are placing working class families and people of color at substantially greater risk of exposure to human health risks. We advocate the adoption of a number of measures, including a comprehensive environmental justice act, to reduce pollution and address unequal exposure to ecological threats