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Publicações

Publicações por SEM

2013

New business models elements oriented to product-service machinery industry

Autores
Azevedo A.; Ribeiro H.;

Publicação
Lecture Notes in Mechanical Engineering

Abstract
Nowadays, business models play a key role in competitiveness. Each industry has specific needs regarding the customization of their business models. Through a personalized business model, organizations can enjoy a customized mapping of all the business activities. In the machinery industry domain and specifically producers of integrated Products and Services, the need for a customized business model has been growing due to the specifications of the industry. The existing business models do not satisfy the capital goods companies’ needs, therefore a study was conducted to analyze and understand companies’ specifications, the existing supporting business frameworks to further proceed with the creation of a new methodology and framework that supports the businesses of this specific industry.

2013

Pricing, relaxing and fixing under lot sizing and scheduling

Autores
Guimaraes, L; Klabjan, D; Almada Lobo, B;

Publicação
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH

Abstract
We present a novel mathematical model and a mathematical programming based approach to deliver superior quality solutions for the single machine capacitated lot sizing and scheduling problem with sequence-dependent setup times and costs. The formulation explores the idea of scheduling products based on the selection of known production sequences. The model is the basis of a matheuristic, which embeds pricing principles within construction and improvement MIP-based heuristics. A partial exploration of distinct neighborhood structures avoids local entrapment and is conducted on a rule-based neighbor selection principle. We compare the performance of this approach to other heuristics proposed in the literature. The computational study carried out on different sets of benchmark instances shows the ability of the matheuristic to cope with several model extensions while maintaining a very effective search. Although the techniques described were developed in the context of the problem studied, the method is applicable to other lot sizing problems or even to problems outside this domain.

2013

The influence of catch quotas on the productivity of the Portuguese bivalve dredge fleet

Autores
Oliveira, MM; Camanho, AS; Gaspar, MB;

Publicação
ICES JOURNAL OF MARINE SCIENCE

Abstract
Among the Portuguese artisanal fishing fleets, the bivalve dredge fleet is one of the most profitable. In the last decade, after the implementation of a quotas system, the management of this fishery has been largely focused on adjusting catch to the conservation status of the resources exploited. The present work aims to understand how changes in the amount of quota attributed to each vessel each year and shifts in the quota regime affected vessel productivity. Boostrapped Malmquist indices, complemented with an efficiency assessment using a directional distance function, were used to quantify productivity changes between 1999 and 2011 for the fleets operating in two areas along the Portuguese coast (northwest and southwest). The results showed that the implementation of a weekly quota, as opposed to a daily quota, led to a significant improvement in productivity. This was mainly due to the decrease in fishing days and fuel consumption. It is predicted that the implementation of weekly quotas in the south area would lead to an overall reduction of about 12% in fishing days and fuel consumption, even though the variation in fuel consumption may be affected by the status of the resources. The results achieved provide important insights for future management actions and showed the potential advantages of applying this type of management to other fisheries worldwide, mainly those using active gear.

2013

Operations research in agriculture: Better decisions for a scarce and uncertain world

Autores
Carravilla, MA; Oliveira, JF;

Publicação
Agris On-line Papers in Economics and Informatics

Abstract
Operations Research/Management Science (OR/MS) can be described as the discipline of applying advanced analytical methods to help making better decisions and has been around in the agricultural and forestry management sectors since the fifties, approaching decision problems that range from more strategic sectorlevel planning to farm operation issues and integrated supply chain management. In this paper insights are given on the use of OR/MS in agriculture, illustrating them with cases drawn from the literature on this topic while keeping the descriptions accessible to uninitiated readers. The presence of OR/MS in Agriculture and Forest Management applications is already extensive but the potential for development is huge in times where resources are becoming increasingly scarce and more has to be done with less, in a sustainable way.

2013

Mono-stage formulations for the soft drink production process with two synchronized stages [Formulações monoestágio para o problema de programação da produção de bebidas dois estágios com sincronia]

Autores
Ferreira, D; Almada Lobo, B; Morabito, R;

Publicação
Producao

Abstract
In this work we present single-stage formulations for the integrated soft drink lot-sizing and scheduling problem with two-stage synchronization. It is a multi-product, multi-machine problem, with sequence-dependent setup times and costs. Without loss of generality, these single-stage reformulations address the problem correctly and, in general, reduce the size of the synchronized two-stage model of Ferreira, Morabito e Rangel (2009), regarding the number of variables and constraints. The preliminary computational experiments on real-world instances from a soft-drink company show the competitiveness of the single-stage models against other formulations and solution approaches reported in the literature.

2013

Benchmarking countries' environmental performance

Autores
Zanella, A; Camanho, AS; Dias, TG;

Publicação
JOURNAL OF THE OPERATIONAL RESEARCH SOCIETY

Abstract
Environmental performance assessments are often conducted using environmental indicators. Although these indicators provide a starting point for performance assessments, they do not provide guidelines that countries should follow to improve performance. This paper develops an enhanced Data Envelopment Analysis (DEA) model that provides a single summary measure of countries' environmental performance, based on the aggregation of the indicators that underlie the estimation of the Environmental Performance Index (EPI). The DEA model used is based on a novel specification of weight restrictions. The main contribution of the methodology used in this paper is to enable benchmarking in such a way that it becomes possible to identify the strengths and weaknesses of each country, as well as the peers with similar features to the country under assessment. These peers provide examples of good environmental practices that countries with worse performance should follow to improve performance. Journal of the Operational Research Society (2013) 64, 426-438. doi:10.1057/jors.2012.62 Published online 16 May 2012

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