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Detalhes

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Publicações

2019

Maximizing the expected number of transplants in kidney exchange programs with branch-and-price

Autores
Alvelos, F; Klimentova, X; Viana, A;

Publicação
Annals of Operations Research

Abstract
In this paper, we propose a branch-and-price approach for solving the problem of maximizing the expected number of transplants in Kidney Exchange Programs (KEPs). In these programs, the decision on which transplants will be conducted is usually made with the support of optimization models with the assumption that all operations will take place. However, after a plan of transplants is defined, a pair may leave the KEP or a more accurate compatibility evaluation exam may invalidate a transplant. To model these possible events we consider probabilities of failure of vertices and of arcs and the objective of maximizing the expected number of transplants. The proposed approach is based on the so-called cycle formulation, where decision variables are associated with cycles. Built on the concept of type of cycle a branch-and-price algorithm is conceived. One subproblem is defined for each type of cycle. We present computational results of the proposed branch-and-price algorithm and compare them with solving directly the cycle formulation (with a general purpose mixed integer programming solver—CPLEX) showing that the proposed approach is the only one suitable for larger instances. © 2017 Springer Science+Business Media, LLC

2018

Observability of power systems with optimal PMU placement

Autores
Carvalho, M; Klimentova, X; Viana, A;

Publicação
Computers & Operations Research

Abstract

2018

Bi-level and Bi-objective p-Median Type Problems for Integrative Clustering: Application to Analysis of Cancer Gene-Expression and Drug-Response Data

Autores
Ushakov, AV; Klimentova, X; Vasilyev, I;

Publicação
IEEE/ACM Transactions on Computational Biology and Bioinformatics

Abstract

2016

Maximising expectation of the number of transplants in kidney exchange programmes

Autores
Klimentova, X; Pedroso, JP; Viana, A;

Publicação
Computers & OR

Abstract
This paper addresses the problem of maximising the expected number of transplants in kidney exchange programmes. New schemes for matching rearrangement in case of failure are presented, along with a new tree search algorithm used for the computation of optimal expected values. Extensive computational experiments demonstrate the effectiveness of the algorithm and reveal a clear superiority of a newly proposed scheme, subset-recourse, as compared to previously known approaches.

2016

Maximizing expected number of transplants in kidney exchange programs

Autores
Alvelos, F; Klimentova, X; Rais, A; Viana, A;

Publicação
Electronic Notes in Discrete Mathematics

Abstract
In this paper we address the problem of maximizing the expected number of transplants in a kidney exchange program. We propose an integer programming model with an exponential number of decision variables which are associated with cycles. By introducing the concept of type of cycle, we avoid the complete cycle enumeration and develop a branch-and-price approach. © 2016 Elsevier B.V.