Abstract

Abstract
A virtual enterprise (VE) is a temporary organisation that pools the core competencies of its member enterprises in order to exploit fast-changing market opportunities. Making successful collaborative partnerships is, in this context, a major challenge in today's competitive business environments. The success of such a 'virtual' organisation is strongly dependent on its composition, and the selection of partners becomes therefore a crucial issue. This problem is particularly difficult because of the uncertainties related to information, market dynamics, customer expectations and technology speed-up, with a strongly stochastic decision-making context. In this paper, a chance-constrained approach to rank alternative VE configurations in business environments with uncertainty, and vague and random information, is proposed. This approach is based on a two-stage model: a chance-constraint multi-objective directional Tabu Search metaheuristic, complemented by a 2-tuple fuzzy linguistic representation model. Preliminary computational results clearly demonstrate the potential of the approach for practical application.

Abstract
A virtual enterprise management platform is proposed with the objective to simplify the formation, management, adaptation and monitoring of the dynamic manufacturing process in VE. Within this platform an integration black box is highlighted to monitor the process data. This black box is used as a smart object to collect updated data or information from the business process or equipment within the VE. The raw data for predictive maintenance is collected by the black box from programmable logic controllers via gateway interface. A dashboard user interface is also designed and developed within the scope of this research that acts as a visualization tool to display the process monitored data. The theme of this research is designed and developed within the scope of the European Commission NMP priority of the Seventh RTD Framework Programme for the ADVENTURE (ADaptive Virtual ENterprise ManufacTURing Environment) project. © Springer International Publishing Switzerland 2015.

Abstract
This study reviews performance criteria adequate to validate simulation models through the comparison of two quantitative data sets, concerning historical and simulated data. The criteria reviewed were organized according to its characteristics into the groups: error-based measures, information theory measures, information criteria, parametric tests, non-parametric tests, distance-based measures and combined measures. Each criterion is reviewed through its mathematic definition, its applications in literature and the identification of its advantages and drawbacks. The features assessed by each criterion are identified and discussed. This study provides a concise outline over the criteria reviewed, which can be used as a guide to help developers of simulation models into the decision on the most appropriate criteria to validate their models.

Abstract
This paper presents a management model developed to promote the sustainability of artisanal fisheries, considering socioeconomic and environmental dimensions. The management of artisanal fisheries faces many challenges, including the lack of appropriate tools to support policy makers and stakeholders in the decision-making process. The model presented in this study is based on system dynamics and allows the simulation of the behavior of the artisanal dredge fishery on the south coast of Portugal, including four main species and two fleets. Two scenarios were simulated to assess the impact of regulatory measures on the system sustainability: scenario 1 simulated a permanent reduction of fishing effort, returning an improvement of biologic and economic sustainability; scenario 2 simulated the closure of one species for a period of one year to allow its recovery. It was found that although the revenue of fisheries decreases in that year, the system is able to return to the average levels of revenue three years after the closure. The study aimed to guide decision makers in the selection of the most appropriate measures toward the preservation of marine ecosystems and socioeconomic stability of fishing communities. The developed system dynamics model, combining available data with knowledge of fisheries experts, proved to be a useful scientific tool to identify management policies and organizational structures leading to greater success. This technique can be applied to the study of other fishery systems worldwide.

Abstract
This study pursues the operational improvement of urban transportation services. Non-foreseen events lead to the occurrence of delays, which are further propagated during the daily operations of bus services. This paper applies an optimization model to obtain robust schedules of bus lines. The model builds a new schedule which minimizes delays and anticipations from a set of observations. The decision variables are the slack time to be allocated at each segment of two subsequent stops. The solutions obtained are assessed with two robustness measures: price of robustness (i.e. the deviations from schedule) and the percentage of absorbed delays. The results obtained in a real-world case study (a bus line operating in Porto) are promising. © 2015, Springer International Publishing Switzerland.