871 research outputs found
The obnoxious facilities planar p-median problem
In this paper we propose the planar obnoxious p-median problem. In the
p-median problem the objective is to find p locations for facilities that
minimize the weighted sum of distances between demand points and their closest
facility. In the obnoxious version we add constraints that each facility must
be located at least a certain distance from a partial set of demand points
because they generate nuisance affecting these demand points. The resulting
problem is extremely non-convex and traditional non-linear solvers such as
SNOPT are not efficient. An efficient solution method based on Voronoi diagrams
is proposed and tested. We also constructed the efficient frontiers of the test
problems to assist the planers in making location decisions
The planar multiple obnoxious facilities location problem: A Voronoi based heuristic
Consider the situation where a given number of facilities are to be located in a convex polygon with the objective of maximizing the minimum distance between facilities and a given set of communities with the important additional condition that the facilities have to be farther than a certain distance from one another. This continuous multiple obnoxious facility location problem, which has two variants, is very complex to solve using commercial nonlinear optimizers. We propose a mathematical formulation and a heuristic approach based on Voronoi diagrams and an optimally solved binary linear program. As there are no nonlinear optimization solvers that guarantee optimality, we compare our results with a popular multi-start approach using interior point, genetic algorithm (GA), and sparse non-linear optimizer (SNOPT) solvers in Matlab. These are state of the art solvers for dealing with constrained non linear problems. Each instance is solved using 100 randomly generated starting solutions and the overall best is then selected. It was found that the proposed heuristic results are much better and were obtained in a fraction of the computer time required by the other methods.The multiple obnoxious location problem is a perfect example where all-purpose non-linear non-convex solvers perform poorly and hence the best way forward is to design and analyze heuristics that have the power and the exibility to deal with such a high level of complexity
Sensor Deployment for Network-like Environments
This paper considers the problem of optimally deploying omnidirectional
sensors, with potentially limited sensing radius, in a network-like
environment. This model provides a compact and effective description of complex
environments as well as a proper representation of road or river networks. We
present a two-step procedure based on a discrete-time gradient ascent algorithm
to find a local optimum for this problem. The first step performs a coarse
optimization where sensors are allowed to move in the plane, to vary their
sensing radius and to make use of a reduced model of the environment called
collapsed network. It is made up of a finite discrete set of points,
barycenters, produced by collapsing network edges. Sensors can be also
clustered to reduce the complexity of this phase. The sensors' positions found
in the first step are then projected on the network and used in the second
finer optimization, where sensors are constrained to move only on the network.
The second step can be performed on-line, in a distributed fashion, by sensors
moving in the real environment, and can make use of the full network as well as
of the collapsed one. The adoption of a less constrained initial optimization
has the merit of reducing the negative impact of the presence of a large number
of local optima. The effectiveness of the presented procedure is illustrated by
a simulated deployment problem in an airport environment
A new model for the hazardous waste location-routing problem
Cataloged from PDF version of article.Hazardous waste management involves the collection, transportation, treatment and disposal of hazardous wastes. In this paper a new multiobjective location-routing model is proposed. Our model also includes some constraints, which were observed in the literature but were not incorporated into previous models. The aim of the proposed model is to answer the following questions: where to open treatment centers and with which technologies, where to open disposal centers, how to route different types of hazardous waste to which of the compatible treatment technologies, and how to route waste residues to disposal centers. The model has the objective of minimizing the total cost and the transportation risk. A large-scale implementation of the model in the Central Anatolian region of Turkey is presented. © 2005
The hazardous waste location-routing problem
Cataloged from PDF version of article.As a result of high industrialization and technology hazardous waste
management problem has now become an unavoidable problem of the world.
Hazardous waste management involves collection, transportation, treatment
and disposal of hazardous wastes. In this thesis, the existing models in the
literature are analyzed in terms of applicability. A new multiobjective
location-routing model is proposed by combining the applicable aspects from
different models. Our model also includes the constraints that reflect certain
requirements that have been observed in the literature but could not been
incorporated into the models correctly together with the additional constraints
that we propose. The aim of the model is to decide on the following
questions: where to open treatment centers with which technologies, where to
open disposal centers, how to route different types of hazardous wastes to
which of the compatible treatment technologies, and how to route waste
residues to disposal centers. The model has two objectives of minimizing total
cost and minimizing transportation risk. A large scale implementation of the
model in the Central Anatolian Region of Turkey is presented.Alumur, SibelM.S
Problemas de localização-distribuição de serviços semiobnóxios: aproximações e apoio à decisão
Doutoramento em Gestão IndustrialA presente tese resulta de um trabalho de investigação cujo objectivo se
centrou no problema de localização-distribuição (PLD) que pretende abordar,
de forma integrada, duas actividades logísticas intimamente relacionadas: a
localização de equipamentos e a distribuição de produtos.
O PLD, nomeadamente a sua modelação matemática, tem sido estudado na
literatura, dando origem a diversas aproximações que resultam de diferentes
cenários reais. Importa portanto agrupar as diferentes variantes por forma a
facilitar e potenciar a sua investigação. Após fazer uma revisão e propor uma
taxonomia dos modelos de localização-distribuição, este trabalho foca-se na
resolução de alguns modelos considerados como mais representativos. É feita
assim a análise de dois dos PLDs mais básicos (os problema capacitados com
procura nos nós e nos arcos), sendo apresentadas, para ambos, propostas de
resolução. Posteriormente, é abordada a localização-distribuição de serviços
semiobnóxios. Este tipo de serviços, ainda que seja necessário e
indispensável para o público em geral, dada a sua natureza, exerce um efeito
desagradável sobre as comunidades contíguas. Assim, aos critérios
tipicamente utilizados na tomada de decisão sobre a localização destes
serviços (habitualmente a minimização de custo) é necessário adicionar
preocupações que reflectem a manutenção da qualidade de vida das regiões
que sofrem o impacto do resultado da referida decisão.
A abordagem da localização-distribuição de serviços semiobnóxios requer
portanto uma análise multi-objectivo. Esta análise pode ser feita com recurso a
dois métodos distintos: não interactivos e interactivos. Ambos são abordados
nesta tese, com novas propostas, sendo o método interactivo proposto
aplicável a outros problemas de programação inteira mista multi-objectivo.
Por último, é desenvolvida uma ferramenta de apoio à decisão para os
problemas abordados nesta tese, sendo apresentada a metodologia adoptada
e as suas principais funcionalidades. A ferramenta desenvolvida tem grandes
preocupações com a interface de utilizador, visto ser direccionada para
decisores que tipicamente não têm conhecimentos sobre os modelos
matemáticos subjacentes a este tipo de problemas.This thesis main objective is to address the location-routing problem (LRP)
which intends to tackle, using an integrated approach, two highly related
logistics activities: the location of facilities and the distribution of materials.
The LRP, namely its mathematical formulation, has been studied in the
literature, and several approaches have emerged, corresponding to different
real-world scenarios. Therefore, it is important to identify and group the
different LRP variants, in order to segment current research and foster future
studies. After presenting a review and a taxonomy of location-routing models,
the following research focuses on solving some of its variants. Thus, a study of
two of the most basic LRPs (capacitated problems with demand either on the
nodes or on the arcs) is performed, and new approaches are presented.
Afterwards, the location-routing of semi-obnoxious facilities is addressed.
These are facilities that, although providing useful and indispensible services,
given their nature, bring about an undesirable effect to adjacent communities.
Consequently, to the usual objectives when considering their location (cost
minimization), new ones must be added that are able to reflect concerns
regarding the quality of life of the communities impacted by the outcome of
these decisions.
The location-routing of semi-obnoxious facilities therefore requires to be
analysed using multi-objective approaches, which can be of two types: noninteractive
or interactive. Both are discussed and new methods proposed in this
thesis; the proposed interactive method is suitable to other multi-objective
mixed integer programming problems.
Finally, a newly developed decision-support tool to address the LRP is
presented (being the adopted methodology discussed, and its main
functionalities shown). This tool has great concerns regarding the user
interface, as it is directed at decision makers who typically don’t have specific
knowledge of the underlying models of this type of problems
Hazardous waste management problem: The case for incineration
We define the hazardous waste management problem as the combined decisions of selecting the disposal method, siting the disposal plants and deciding on the waste flow structure. The hazardous waste management problem has additional requirements depending on the selected disposal method. In this paper we focus on incineration, for which the main additional requirement is to satisfy the air pollution standards imposed by the governmental restrictions. We propose a cost-based mathematical model in which the satisfaction of air pollution standards is also incorporated. We used the Gaussian Plume equation in measuring the air pollution concentrations at population centers. A large-scale implementation of the proposed model within Turkey is provided. © 2005 Elsevier Ltd. All rights reserved
Sustainable Lighting Layout in Urban Areas: Maximizing Implicit Coverage and Minimizing Installation Cost
A key decision in the design of urban lighting is the location of the luminaries that are used to illuminate the specified region. The decision needs to account for coverage requirements identified in certain areas, based on safety considerations and nature of work activity, along with ensuring the cost effectiveness of the installation pattern adopted. In this work, a novel approach is presented via a multi-objective mathematical optimization model that results in a sustainable layout of light poles in urban region. A maximal coverage objective, with implicit demand cover, is formulated as a measure of the social requirement in urban lighting, which models security and safety associated with night-time lighting of the urban region. At the same time, the economical aspect of the layout is considered via minimizing the installation cost of the lighting layout. A realistic case example is then solved using the ϵ-constraint method. A Pareto optimal front for the case considered is constructed and analyzed
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