Time filter

Source Type

Mavrotas G.,National Technical University of Athens | Figueira J.R.,Higher Institute of Management | Antoniadis A.,National Technical University of Athens
Journal of Global Optimization

We propose a methodology for obtaining the exact Pareto set of Bi-Objective Multi-Dimensional Knapsack Problems, exploiting the concept of core expansion. The core concept is effectively used in single objective multi-dimensional knapsack problems and it is based on the "divide and conquer" principle. Namely, instead of solving one problem with n variables we solve several sub-problems with a fraction of n variables (core variables). In the multi-objective case, the general idea is that we start from an approximation of the Pareto set (produced with theMulti-Criteria Branch and Bound algorithm, using also the core concept) and we enrich this approximation iteratively. Every time an approximation is generated, we solve a series of appropriate single objective Integer Programming (IP) problems exploring the criterion space for possibly undiscovered, new Pareto Optimal Solutions (POS). If one or more new POS are found, we appropriately expand the already found cores and solve the new core problems. This process is repeated until no new POS are found from the IP problems. The paper includes an educational example and some experiments. © Springer Science+Business Media, LLC. 2010. Source

Saadaoui F.,Higher Institute of Management
Computational Statistics and Data Analysis

EM-type algorithms are popular tools for modal estimation and the most widely used parameter estimation procedures in statistical modeling. However, they are often criticized for their slow convergence. Despite the appearance of numerous acceleration techniques along the last decades, their use has been limited because they are either difficult to implement or not general. In the present paper, a new generation of fast, general and simple maximum likelihood estimation (MLE) algorithms is presented. In these cyclic iterative algorithms, extrapolation techniques are integrated with the iterations in gradient-based MLE algorithms, with the objective of accelerating the convergence of the base iterations. Some new complementary strategies like cycling, squaring and alternating are added to that processes. The presented schemes generally exhibit either fast-linear or superlinear convergence. Numerical illustrations allow us to compare a selection of its variants and generally confirm that this category is extremely simple as well as fast. © 2008 Elsevier B.V. All rights reserved. Source

Mota R.P.,University of Lisbon | Domingos T.,University of Lisbon | Martins V.,Higher Institute of Management
Ecological Economics

The context of this paper is the measurement of welfare and weak sustainability (defined as non-declining utility) in dynamic economies, i.e., comprehensive or green accounting. We estimate green net national income (GNNI) and genuine saving (GS) for Portugal, for the years 1990 to 2005, accounting for the disamenity of air pollution emissions, the depreciation of commercial forests and the value of time, discussing the implications of the assumptions underlying the inclusion of these terms in the green accounting model. The influence of short-run cycles is analyzed by estimating GNNI excluding business cycles. Our results suggest that business cycles affect the sustainability message of GNNI. We find that potential GNNI is growing and GS is positive in the analyzed period, thereby not indicating a weak sustainability problem in Portugal, although both depict a trend towards unsustainability. Excluding technological progress there is a contradiction in the sustainability message of GNNI and GS. © 2010 Elsevier B.V. Source

Hachicha W.,University of Sfax | Elmsalmi M.,Higher Institute of Management
Journal of Risk Research

Supply networks are complex and suffer always from various risks. An effective supply chain management requires suitable strategies to mitigate them. In previous literature, there has been a range of research into risk in firms but little in supply networks. This can be explained due to the huge number of risk variables and their direct and indirect interrelations that may suffer all supply chain partners (firms). Therefore, for better risk mitigation, a risk prioritization step is vital. To this end, the purpose of this paper is to propose a new integrated approach based on two structural modeling tools. Firstly, interpretive structural modeling has been used to present a hierarchical model showing the interrelationships between the risk sources. Secondly, MICMAC analysis has been used to quantify and classify the risk variables based on their mutual influence and dependence. The objective is to ascertain the key risk variables and theirs relationships. These prioritized risk variables provide a useful tool to supply network managers to focus on those key variables that are most essential for effective risk management strategies. A real case study in food industry is provided in order to illustrate the application of the proposed approach. The findings may be useful to the practitioners in risk management and may also interest academicians, since the method used here can be applied in other areas of industrial management as well. © 2013 © 2013 Taylor & Francis. Source

Agency: Cordis | Branch: H2020 | Program: RIA | Phase: DRS-07-2014 | Award Amount: 3.85M | Year: 2015

Increasing Europes resilience to crises and disasters is a topic of highest political concern in the EU and its Member States and Associated Countries. Regarding the specific case of transport systems, it can be said that those have developed a prominent safety and business critical nature, in view of which current management practices have shown evidence of important limitations in terms of resilience management. Furthermore, enhancing resilience in transport systems is considered imperative for two main reasons: such systems provide critical support to every socio-economic activity and are currently themselves one of the most important economic sectors and secondly, the paths that convey people, goods and information, are the same through which risks are propagated. RESOLUTE is answering those needs, by proposing to conduct a systematic review and assessment of the state of the art of the resilience assessment and management concepts, as a basis for the deployment of an European Resilience Management Guide (ERMG), taking into account that resilience is not about the performance of individual system elements but rather the emerging behaviour associated to intra and inter system interactions. The final goal of RESOLUTE is to adapt and adopt the identified concepts and methods from the defined guidelines for their operationalization and evaluation when addressing Critical Infrastructure (CI) of the Urban Transport System (UTS), through the implementation of the RESOLUTE Collaborative Resilience Assessment and Management Support System (CRAMSS), that adopts a highly synergic approach towards the definition of a resilience model for the next-generation of collaborative emergency services and decision making process.

Discover hidden collaborations