1,720,986 research outputs found
Exploring Similarities in Discrete Facility Location Models with Equality Measures
No full textThere have been a number of discrete facility location models that deal with the use of some equality measures of the distances between the facility and the users. They have been used to guarantee a similar level of equity among the users that may be affected in a positive or in a good way from a facility. These models have been formulated trying to adapt equality measures taken from contexts different from the location one. This way, every measure is very specific to the particular application and it is not highlighted why a measure should be selected and what is the contribution to the equity distribution among the users that can provide. In this article, we propose a facility location problem in which we have to locate a given number of facilities among a set of potential facilities, optimizing an equality measure. We propose a computational study to test the similarities and the differences of a good number of measures with more than a single facility to locate and we point out which measures produce similar results and how they depend on each other
Equality measures properties for location problems
No full textThe objectives underlying location decisions can be various. Among them, equity objectives have received an increasing attention in recent years, especially in the applications related to the public sector, where fair distributions of accessibility to the services should be guaranteed among users. In the literature a huge number of equality measures have been proposed; then, the problem of selecting the most appropriate one to be adopted in the decision-making processes is crucial. For this reason, many authors focused on the analysis of properties that equality measures should satisfy in order to be considered suitable. Most of the proposed properties are too general and related solely to the mathematical formulation of the measure itself (i.e., simpleness, impartiality, invariance). Hence, they do not give any indications about the behaviour of such measures in the optimization contexts. In this work, we propose some new properties to be associated to equality measures in order to describe characteristics which may be useful to drive optimization procedures in the search of optimal (or near-optimal) solutions. To this aim some empirical analyses have been performed in order to understand the typical behavior of remarkable measures in presence of a uniform distribution of demand points in a regular location spaces
Equality measures properties for location problems
Full text linkThe objectives underlying location decisions can be various. Among them, equity objectives have received an increasing attention in recent years, especially in the applications related to the public sector, where fair distributions of accessibility to the services should be guaranteed among users. In the literature a huge number of equality measures have been proposed; then, the problem of selecting the most appropriate one to be adopted in the decision-making processes is crucial. For this reason, many authors focused on the analysis of properties that equality measures should satisfy in order to be considered suitable. Most of the proposed properties are too general and related solely to the mathematical formulation of the measure itself (i.e., simpleness, impartiality, invariance). Hence, they do not give any indications about the behaviour of such measures in the optimization contexts. In this work, we propose some new properties to be associated to equality measures in order to describe characteristics which may be useful to drive optimization procedures in the search of optimal (or near-optimal) solutions. To this aim some empirical analyses have been performed in order to understand the typical behavior of remarkable measures in presence of a uniform distribution of demand points in a regular location spaces
A portfolio approach for the selection and the timing of urban planning projects
No full textThis paper presents a model to support organizations dealing with urban planning decisions. In particular, we deal with the selection and the timing of several projects that can be realised within an urban development project with the aim of optimizing conflicting objectives. The available resources should be allocated in an acceptable way and current and future requirements must be met. In addition, projects can be characterized by qualitative performances and different scenarios can be considered. The model can be handled with different methods. Given its participatory features, it seems that an interactive multiobjective optimization methodology is the most appropriate approach, since the decision maker can express his opinion throughout the resolution process. We present how the model can work through the description of an application based on the execution of the Master Plan of the University of Portsmouth, one of the most fast progressing University in UK. We show the versatility of the model and how it can successfully handle such complex decisions
Balancing the arrival times of users in a two-stage location problem
Full text linkThere has been a number of facility location problems dealing with the introduction of the equity issue in the travel distances distribution. In this paper we analyze a new aspect of equity concerning the distribution of the arrival times of customers. Given a depot and a set of demand points generating flow which also represent potential locations, we consider a discrete two-stage location problem whose aim is to locate a given number of facilities and to allocate the demand points to a facility. We assume as objective the maximization of the minimum difference between two consecutive arrival times of flows to the depot through the patronized facility. This particular equity measure is introduced in order to reduce risks of congestion in the dynamic of flow arrivals at the common destination. The problem is described through two Integer Programming formulations. Computational results for solution methods based on both formulations are then shown and analyzed
Multiobjective Combinatorial Optimization with Interactive Evolutionary Algorithms: the case of facility location problems
Full text linkWe consider multiobjective combinatorial optimization problems handled by preference-driven efficient heuristics. They look for the most preferred part of the Pareto front based on some preferences expressed by the user during the process. In general, the Pareto set of efficient solutions is searched for in this case. However, obtaining the Pareto set does not solve the decision problem since one or more solutions, being the most preferred for the user, have to be selected. Therefore, it is necessary to elicit their preferences. What we are proposing can be seen as one of the first structured methodologies in facility location problems to search for optimal solutions taking into account the preferences of the user. To this aim, we use an interactive evolutionary multiobjective optimization procedure called NEMO-II-Ch. It is applied to a real-world multiobjective location problem with many users and many facilities to be located. Several simulations have been performed. The results obtained by NEMO-II-Ch are compared with those obtained by three algorithms knowing the user’s “true” value function that is, instead, unknown to NEMO-II-Ch. They show that in many cases, NEMO-II-Ch finds the best subset of locations more quickly than the methods knowing the whole user’s true preferences
Applications of agent-based models for optimization problems: A literature review
No full textAgent based models (ABM) have been recently applied to solve optimization problems whose domains present several inter-related components in a distributed and heterogeneous environment. In this work we illustrate the state of the art related to the use and to the application of ABM as optimization technique, given their peculiarity in dealing with the representation and the simulation of complex systems. After a description of the approach and a comparison with classical heuristics, an extensive review aimed at evaluating the impact of these methodologies in the Operational Research/Management Science literature is provided. © 2011 Elsevier Ltd. All rights reserved
The Deck-of-cards-based Ordinal Regression method and its application for the development of an ecovillage
Full text linkThis paper presents the deck-of-cards-based Ordinal Regression (DOR), a new multicriteria decision-aiding procedure that conjugates the deck-of-cards method with an ordinal regression approach to define a multicriteria value function representing the preferences of the decision maker (DM). The deck-of-cards method allows the DM to express the ranking order of a set of reference alternatives along with the intensity of preferences between reference alternatives. An ordinal regression procedure is then used to define a multicriteria value function that represents the ranking of the reference alternatives as well as the preference intensity.
This approach can be applied to define value functions with different formulations, such as weighted sum,
additive value, or Choquet integral. The value function thus obtained can be used to comprehensively
evaluate alternatives of a multi-criteria decision problem. The value function provided by DOR can also
be applied to a multi-objective optimisation problem. In this study, we applied DOR to handle urban and
regional planning decisions in which facilities are required to be selected, located, and planned. In particular, we consider the interactions between criteria and synergies between facilities in an enriched version of the so-called space-time model. We applied this methodology to a real-world problem to plan the development of a sustainable ecovillage in the province of Turin (Italy), thus supporting the president of the cooperative owning the ecovillage in his decisions regarding which structures to select, where to locate them, and when to plan their realisation
An AHP parsimonious based approach to handle manufacturing errors in production processes
No full textThis paper introduces a new hybrid tool to classify manufacturing errors in production processes. Our tool is a hybrid procedure based on the combination of the parsimonious AHP method with a clustering method. Parsimonious AHP permits to use a much smaller number of pairwise comparisons with respect to classical-AHP. At the same time, the use of a clustering method, allows for the assignment of the alternatives on the basis of their closeness to each other and not on the basis of some reference profiles as happens in several other methods. Furthermore, some veto systems help the decision maker to better define how the errors belong to different classes in a participative way. The approach has been tested in a largest automotive plants in Italy. This approach has provided the company with a participative and robust theoretically funded tool that supports the understanding of the seriousness of the manufacturing errors. From a methodological point of view, the hybrid tools, for the first time, combine the newly developed parsimonious AHP with a clustering method. From a practical point of view, this paper has introduced a new tool to classify and improve the production quality of the processes to an extremely competitive sector
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