Maria Eugénia Captivo - Academia.edu (original) (raw)

Papers by Maria Eugénia Captivo

European Journal of Operational Research, 2019

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

This work addresses a real world problem proposed to us by a Portuguese automotive company. Every... more This work addresses a real world problem proposed to us by a Portuguese automotive company. Every day this company needs to establish a plan to pack a set of boxes onto a truck. Since the transport is made directly from the suppliers to the factory, we don't need to consider the problem of establishing a route or to worry with multi-drop situations. So, we will only address the operations for packing the boxes. The cargo consists of rectangular boxes with different sizes and weight, and the vehicle is a single truck. There are different types of boxes that are divided into two major groups: group A consists of small boxes with no lid that, before being placed inside the truck, need to be combined onto a pallet; group B consists of bigger, completely formed, boxes that are packed individually in the truck. We can divide our problem into two successive phases: the construction of pallets (a manufacturer's pallet loading problem) and the loading of the cargo into the truck (a single container loading problem). These two phases should not be solved independently, since the final dimensions of the pallets will have an impact on the final packing plan of the whole cargo. According to Wäscher et. al. (2007) typology, this problem can be classified as a Three-Dimensional Rectangular Single Large Object Placement Problem. Since this is a real application, some practical constraints cannot be overlooked, like load stability and box orientation constraints, weight limit of the truck and uniform distribution of weight inside the truck. To solve this problem, we propose a constructive heuristic based on a layer arrangement approach, with a star strategy and with a weighted average measure for the boxes. For each layer, the main idea is to spread the heaviest boxes along the container in a star form, from the sides to the centre of the container. This heuristic is based on a corner selection that, instead of finding the appropriate corner for the current selected box, finds the appropriate box for the current corner. When we are left with a small number of boxes that weren't placed in the current layer, or when there isn't a sufficient number of boxes of the same height to build a complete layer, we will have to do some local changes in order to try to obtain a feasible solution. The application of this constructive heuristic to the company's data and the corresponding results will be presented and discussed.

Proceedings of 18th Annual International Conference of the IEEE Engineering in Medicine and Biology Society, 1997

A prototype of a Decision Support System (DSS) to the location of hospital facilities, which uses... more A prototype of a Decision Support System (DSS) to the location of hospital facilities, which uses a bicriteria model is presented. This DSS is being developed for a Windows platform using Visual Basic and having an open architecture

International Transactions in Operational Research, 2014

ABSTRACT This work addresses a real-world problem proposed by a Portuguese company. Every day thi... more ABSTRACT This work addresses a real-world problem proposed by a Portuguese company. Every day this company needs to define a plan to pack a set of boxes onto a single truck. The truck will have to make as many trips as necessary to deliver the entire set of boxes. In the literature, this is known as the bin-packing problem. As this is a real-world application, practical constraints, such as load stability and box orientation constraints, weight limit of the truck, and uniform distribution of weight inside the truck, should be ensured. To solve this problem, we propose a constructive heuristic based on a layer arrangement approach that comprises a corner selection strategy for placing the boxes. Some experiments are conducted with the company's data, and the quality of the solutions is evaluated regarding the occupancy rates and distribution of the cargo weight inside the truck.

Metaheuristics: Computer Decision-Making, 2004

... Sridharan (1993) describes a Lagrangean heuristic for the problem that im-proves and extends ... more ... Sridharan (1993) describes a Lagrangean heuristic for the problem that im-proves and extends the one presented by Nauss (1978) for the Capacitated Plant Location Problem where customer assignment constraints are dualized. ...

Frontiers in Artificial Intelligence and Applications, 2010

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Encyclopedia of Decision Making and Decision Support Technologies, 2008

2010 International WaterSide Security Conference, 2010

SAFE-PORT is a recently started project addressing the complex issue of determining the best conf... more SAFE-PORT is a recently started project addressing the complex issue of determining the best configurations of resources for harbour and port surveillance and protection. More specifically, the main goal is to find, for any given scenario, an adequate set of configuration solutions-i.e., number and type of sensors and equipments, their locations and operating modes, the corresponding personnel and other support resources-that maximize protection over a specific area. The project includes research and development of sensors models, novel algorithms for optimization and decision support, and a computer-based decision support system (DSS) to assist decision makers in that task. It includes also the development of a simulation environment for modelling relevant aspects of the scenario (including sensors used for surveillance, platforms, threats and the environment), capable to incorporate data from field-trials, used to test and validate solutions proposed by the DSS. Test cases will consider the use of intelligent agents to model the behaviour of threats and of NATO forces in a realistic way, following experts' definitions and parameters.

Location Science, 1998

ABSTRACT

TOP, 2007

The quickest path problem is related to the classical shortest path problem, but its objective fu... more The quickest path problem is related to the classical shortest path problem, but its objective function concerns the transmission time of a given amount of data throughout a path, which involves both cost and capacity. The K-quickest simple paths problem generalises the latter, by looking for a given number K of simple paths in non-decreasing order of transmission time. Two categories of algorithms are known for ranking simple paths according to the transmission time. One is the adaptation of deviation algorithms for ranking shortest simple paths (

OR Spectrum, 2012

The scope of this work covers a real case of elective surgery planning in a Lisbon hospital. The ... more The scope of this work covers a real case of elective surgery planning in a Lisbon hospital. The aim is to employ more efficiently the resources installed in the surgical suite of the hospital in question besides improving the functioning of its surgical service. Such a planning sets out to schedule elective surgeries from the waiting list on a weekly time horizon with the objective of maximizing the use of the surgical suite. For this purpose, the authors develop an integer linear programming model. The model is tested using real data obtained from the hospital's record. The non-optimal solutions are further improved by developing a custom-made, simple and efficient improvement heuristic. Application of this heuristic effectively improves almost all non-optimal solutions. The results are analyzed and compared with the actual performance of the surgical suite. This analysis reveals that the solutions obtained using this approach comply with the conditions imposed by the hospital and improve the use

Operational Research, 2007

In this paper several dynamic multi-level location problems are formulated as mixed-integer linea... more In this paper several dynamic multi-level location problems are formulated as mixed-integer linear programs. Both uncapacitated and capacitated versions of the problem are studied. The models presented are more complete than the ones known from the literature: they are dynamic and consider the possibility of a facility being open, closed and reopen more than once during the planning horizon. They may include both upper and lower limits on the used capacity of each facility and may also consider the situation where there is no flow conservation in the intermediate facilities. Primal-dual heuristics were developed to solve efficiently the proposed models. Computational results are presented and discussed.

Journal of Decision Systems, 2008

This paper reports on a real-world application addressing the coordination between cross function... more This paper reports on a real-world application addressing the coordination between cross functionality of marketing and production. We focus on the critical issues of this interface, namely: capacity planning and long-range to medium range sales forecasting, production short-term scheduling and short-range sales forecasting. We present a case study concerning the development of a decision support system for the paper industry. It assists both marketing and production decision makers, leading to a reduction of conflicts. The decision-making process is generalized into a framework that allows the sharing of the same decision models but with different perspectives. This framework may be adapted to other industries.

European Journal of Operational Research, 2003

The single source capacitated location problem is considered. Given a set of potential locations ... more The single source capacitated location problem is considered. Given a set of potential locations and the plant capacities, it must be decided where and how many plants must be open and which clients must be assigned to each open plant. A Lagrangean relaxation is ...

Computación y Sistemas, 2009

Location problems are, in general, multidimensional in nature, particularly if sustainable develo... more Location problems are, in general, multidimensional in nature, particularly if sustainable development planning is required. So, multicriteria approaches seem adequate in many situations. Nevertheless, only a very small percentage of the publications in this area concern multicriteria models or tools. Generally, the different criteria are formulated as constraints imposing some minimum or maximum value, or are addressed by a surrogate criterion (like distance) on a single objective structure. In this paper we outline the more relevant multicriteria mixed-integer location models and approaches taking into account several issues. The adequacy of the available models to reality is discussed. We also put in evidence the importance of interactive approaches, namely, discussing a decision support tool in which we are co-authors.

Computación y sistemas, 2008

... 2, 2008, pp 216-231 ISSN 1405-5546 Page 13. 228 Maria Eugénia Captivo and João Namorado Clíma... more ... 2, 2008, pp 216-231 ISSN 1405-5546 Page 13. 228 Maria Eugénia Captivo and João Namorado Clímaco ... Some attempts to design interactive procedures for the same type of problems, but considering more than two criteria, are presented in Coutinho-Rodrigues et al. (1997). ...

Computers & Operations Research, 2008

A different approach to the capacitated single allocation hub location problem is presented. Inst... more A different approach to the capacitated single allocation hub location problem is presented. Instead of using capacity constraints to limit the amount of flow that can be received by the hubs, we introduce a second objective function to the model (besides the traditional cost minimizing function), that tries to minimize the time to process the flow entering the hubs. Two bi-criteria single allocation hub location problems are presented: in a first model, total time is considered as the second criteria and, in a second model, the maximum service time for the hubs is minimized. To generate non-dominated solutions an interactive decision-aid approach developed for bi-criteria integer linear programming problems is used. Both bi-criteria models are tested on a set of instances, analyzing the corresponding non-dominated solutions set and studying the reasonableness of the hubs flow charge for these nondominated solutions. The increased information provided by the non-dominated solutions of the bi-criteria model when compared to the unique solution given by the capacitated hub location model is highlighted.

Computers & Operations Research, 2006

In this paper, we propose a discrete location problem, which we call the Single Source Modular Ca... more In this paper, we propose a discrete location problem, which we call the Single Source Modular Capacitated Location Problem (SS-MCLP). The problem consists of finding the location and capacity of the facilities, to serve a set of customers at a minimum total cost. The demand of each customer must be satisfied by one facility only and the capacities of the open facilities must be chosen from a finite and discrete set of allowable capacities. Because the SS-MCLP is a difficult problem, a lagrangean heuristic, enhanced by tabu search or local search was developed in order to obtain good feasible solutions. When needed, the lower bounds are used in order to evaluate the quality of the feasible solutions. Our method was tested computationally on randomly generated test problems some of which are with large dimensions considering the literature related to this type of problem. The computational results obtained were compared with those provided by the commercial software Cplex.

Pesquisa Operacional, 2007