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Publicações

Publicações por CEGI

2021

Modelling and optimisation in European Kidney Exchange Programmes

Autores
Biro, P; van de Klundert, J; Manlove, D; Pettersson, W; Andersson, T; Burnapp, L; Chromy, P; Delgado, P; Dworczak, P; Haase, B; Hemke, A; Johnson, R; Klimentova, X; Kuypers, D; Costa, AN; Smeulders, B; Spieksma, F; Valentin, MO; Viana, A;

Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
The complex multi-criteria optimisation problems arising in Kidney Exchange Programmes have received considerable attention both in practice and in the scientific literature. Whereas theoretical advancements are well reviewed and synthesised, this is not the case for practice. We present a synthesis of models and methods applied in present European Kidney Exchange Programmes, which is based on detailed descriptions we created for this purpose. Most descriptions address national programmes, yet we also present findings on emerging cross-national programmes. The synthesis provides a systematic and detailed description of the models and methods the programmes use, revealing important commonalities as well as considerable variation among them. Rather than distilling a single best practice from these results, we find that the variation in models and methods arises because of variation in country characteristics, policies, and ethics. The synthesised state of the art may benefit future national and cross-national initiatives and direct future theoretical contributions within and across the boundaries of the Operations Research discipline. (c) 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/)

2021

Data and optimisation requirements for Kidney Exchange Programs

Autores
Smeulders, B; Pettersson, W; Viana, A; Andersson, T; Bolotinha, C; Chromy, P; Gentile, M; Hadaya, K; Hemke, A; Klimentova, X; Kuypers, D; Manlove, D; Robb, M; Slavcev, A; Tubertini, P; Valentin, MO; van de Klundert, J; Ferrari, P;

Publicação
HEALTH INFORMATICS JOURNAL

Abstract
Kidney Exchange Programs (KEP) are valuable tools to increase the options of living donor kidney transplantation for patients with end-stage kidney disease with an immunologically incompatible live donor. Maximising the benefits of a KEP requires an information system to manage data and to optimise transplants. The data input specifications of the systems that relate to key information on blood group and Human Leukocyte Antigen (HLA) types and HLA antibodies are crucial in order to maximise the number of identified matched pairs while minimising the risk of match failures due to unanticipated positive crossmatches. Based on a survey of eight national and one transnational kidney exchange program, we discuss data requirements for running a KEP. We note large variations in the data recorded by different KEPs, reflecting varying medical practices. Furthermore, we describe how the information system supports decision making throughout these kidney exchange programs.

2021

Positive and Negative Social-Cultural, Economic and Environmental Impacts of Tourism on Residents

Autores
Ferreira, FA; Castro, C; Gomes, AS;

Publicação
ADVANCES IN TOURISM, TECHNOLOGY AND SYSTEMS, VOL 1

Abstract
Tourism is a socio-cultural phenomenon that has intensified with technological development and with the advancement of communication and transport systems. However, the increase in the number of people moving around the world does not necessarily represent success or tourist access, but it can mostly serve more immediate marketing interests. Since tourism is considered a phenomenon, the sociological interest to study it arises. Tourist practice is an educational process, a learning process, which is established through the relationship between visitors and residents and their cultural backgrounds. Several authors dedicate their studies to this field, and several are also those who try to understand the relations between tourists and the residents in the host region. The purpose of this work is to review the scientific literature that is focused on the sociology of tourism as a subject to study the economic, social, and environmental impacts of tourism on societies and residents and how residents perceived the benefits and costs of tourism developments in the local community. Review of literature suggests that interactions between visitors and the host community can lead to short and long term positive and negative social-cultural, economic and environmental impacts on destinations.

2021

A comparison of matching algorithms for kidney exchange programs addressing waiting time

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

Publicação
CENTRAL EUROPEAN JOURNAL OF OPERATIONS RESEARCH

Abstract
Kidney exchange programs (KEP) allow an incompatible patient-donor pair, whose donor cannot provide a kidney to the respective patient, to have a transplant exchange with another in a similar situation if there is compatibility. Exchanges can be performed via cycles or chains initiated by non-directed donors (NDD), i.e., donors that do not have an associated patient. The objective for optimization in KEP is generally to maximize the number of possible transplants. Following the course of recent approaches that consider a dynamic matching (exchanges are decided every time a pair or a NDD joins the pool), in this paper we explore two matching policies to find feasible exchanges: periodic, where the algorithm runs within some period (e.g each 3 month); and greedy, in which a matching run is done as soon as the pool is updated with a new pair or NDD. For each policy, we propose a matching algorithm that addresses the waiting times of pairs in a pool. We conduct computational experiments with the proposed algorithms and compare the results with those obtained when periodic and greedy matching aim at maximizing the number of transplants.

2021

A Branch-Price-And-Cut Algorithm for Stochastic Crowd Shipping Last-Mile Delivery with Correlated Marginals

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

Publicação
21st Symposium on Algorithmic Approaches for Transportation Modelling, Optimization, and Systems, ATMOS 2021, September 9-10, 2021, Lisbon, Portugal (Virtual Conference).

Abstract
We study last-mile delivery with the option of crowd shipping, where a company makes use of occasional drivers to complement its vehicle's fleet in the activity of delivering products to its customers. We model it as a data-driven distributionally robust optimization approach to the capacitated vehicle routing problem. We assume the marginals of the defined uncertainty vector are known, but the joint distribution is difficult to estimate. The presence of customers and available occasional drivers can be random. We adopt a strategic planning perspective, where an optimal a priori solution is calculated before the uncertainty is revealed. Therefore, without the need for online resolution performance, we can experiment with exact solutions. Solving the problem defined above is challenging: not only the first-stage problem is already NP-Hard, but also the uncertainty and potentially the second-stage decisions are binary of high dimension, leading to non-convex optimization formulations that are complex to solve. We propose a branch-price-and-cut algorithm taking into consideration measures that exploit the intrinsic characteristics of our problem and reduce the complexity to solve it.

2021

Designing sustainable services with the ECO-Service design method: Bridging user experience with environmental performance

Autores
Sierra Perez, J; Teixeira, JG; Romero Piqueras, C; Patricio, L;

Publicação
JOURNAL OF CLEANER PRODUCTION

Abstract
Eco-design is focused on incorporating environmental criteria early in the design process to reduce the environmental impacts of new products. However, while services now represent the largest share of the world & rsquo;s economy, the incorporation of environmental sustainability in the design of new services is very limited. This research proposes the ECO-Service Design (ECO-SD) method that integrates eco-design and service design to conceptualize new environmentally sustainable services. The ECO-SD method bridges environmental criteria from eco-design with the human-centred approach of service design, to foster the environmental sustainability of new services, while offering a desirable user experience. To this end, this method encompasses four stages: service exploration, to understand the service context and how users interact with it; service visualization, to visually identify the barriers to environmental performance and user experience during service provision; service ideation, to conceptualize a new service that overcomes the identified barriers; and service assessment, to understand the changes in environmental sustainability and user experience of the newly designed service. The application of the ECO-SD method to two in-dividual shared transport services shows how it enables integrated identification of opportunities to overcome environmental and user experience barriers in the existing services.

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