Abstract
Data in this article results from a study of simulation about the procurement of addictives for lubricants in the Oil Refinery of Porto (Portugal). Here we describe the real case under study as well as the method we have chosen to board it by means of simulation, which finally leaded us to some interesting results regarding the choices on purchasing the addictives from the suppliers. Costs including transportation, holding and stockouts have been considered during the simulation as well as in the final conclusions, which let us recommend a more frequent reordering of materials at the lubricants plant. This we expect to result in the saving of around 0.3MEURO/year in global costs.

Abstract
In this paper is presented firstly the traffic and emission characterization of Via de Cintura Interna (VCI), an urban highway at Oporto city, Portugal, with more than 4 000 vehicles/hour during rush hours. Emission estimates were carried through on the basis of emission factors to road transport published in the Atmospheric Emission Inventory Guidebook. A weighed emission factor has beer, calculated for nitrogen oxides (NOx) and vehicle class, according to the Portuguese fleet composition (vehicles age, type of engine and average speed). Furthermore, during a three-week period, an outdoor nitrogen dioxide (NO2) monitoring campaign was carried out in a domain around the VCl (100 m for each side), in particular near residential buildings. The results demonstrate that higher NO2 concentrations are seen in the sub-domain with higher circulation of heavy-duty vehicles and where buildings are adjacent to VCI hindering pollutant dispersion. Meteorological conditions, such as wind intensity and direction, temperature and solar radiation were monitorized too. The NO2 concentrations obtained by the monitoring campaign have been used to create scenarios of population exposure to NO2, having taken into account the time-activity patterns of residents. It was verified that higher exposures occur when the population lives in Boavista, in contrast with the favourable scenario that corresponds to life in Prelada and those working in Espinho city. The work and results presented in this paper are a part of the methodology used in the scope of the ImpactAir Project. This project, started in 2003 in Oporto city, has the main objective of evaluating the impact of urban highway (VCI) traffic emissions on air quality and the health of the local population.

Abstract
Make-to-order companies, such as job shops, have been extensively studied. Some of those studies emphasise the importance of the workload control in order to improve manufacturing operations. In this paper a multiple decision-making scheme, with the purpose of planning and controlling operations and getting better delivery and workload related performance measures, as well as one order release decision rule are proposed. The decision-making scheme includes four main decisions: (i) accept or reject an in-coming order; (ii) define the order's due date; (iii) release the accepted jobs; and (iv) dispatch the jobs at the station level. Extensive simulation experiments were performed to compare the proposed rule with the benchmark mechanisms, as well as with rules presented in previous studies. They led to the conclusion that considering the four decisions simultaneously can improve the job shop measures of performance, and that the proposed release rule is the best in almost all instances.

Abstract
BM_virtual enterprise (BM_VE) is a virtual enterprise (VE) in a total or partial conformance with the BM_virtual enterprise architecture reference model (BM_VEARM). BM_VE is a kind of VE characterized as a dynamically reconfigurable network integrated over the global domain, satisfying the requirements for integrability, distributivity, agility, and virtuality as competitiveness factors. BM_VE uses three main mechanisms, or tools: market of resources, broker, and virtuality. This chapter presents the three fundamental mechanisms for the VE reconfiguration dynamics and virtuality; introduces the basic concept of the BM_VEARM, which serves as the conceptual and formal base for building BM_VE instances; shows the formal specification and theory of the structural aspects of the BM_VE as well as some aspects of the BM_VE reconfiguration dynamics; presents the BM_VE as an agile/virtual enterprise (A/VE); and finally, describes some important consequences of virtuality in BM_VE, i.e., that the BM_VE structure is hierarchical, a new definition of the VE (in which the network as the VE characteristic is irrelevant from the operational unit's point of view), and the process of a "traditional" enterprise virtualization. © 2005, Idea Group Inc.

Abstract
The implementation of the virtual enterprise (VE) model requires an agent, called a broker, who undertakes several functions and whose increased performance contributes to the searched agility of this organisational model. From the set of functions that the broker can provide to the VE, there are some that may explicitly contribute to the process of VE integration. One of the processes that contributes to VE integration, either in the project phase, during the resources system configuration, or in the operation phase, when the system reconfiguration is required, is the resources system selection process. We will approach, in this work, the importance of the broker in the resources system selection through the comparison of his performance in that process to the performance expected of the VE itself, if the person for whom it is responsible (or principal) performs the same process. This comparison is made based on the simulation results obtained from a numeric demonstrator specifically constructed to quantify the time and cost of the selection process for both the selectors (the broker and the principal). We demonstrate that the domain of advantage for the broker, i.e., where the broker's performance exceeds the principal's, grows with the dimension of the tasks plan and with the number of preselected resources, and also with the complexity of the selection method. © 2005, Idea Group Inc.

Abstract
The search for increased competitiveness and efficiency during the last decade resulted in several organizational approaches that presented flexibility as a main characteristic. Some of these approaches rely on dynamically reconfigurable partnerships in permanent alignment with the market and strongly supported by information and communication technology, with the agile/virtual enterprise (A/VE) organizational model as a leading example. Several technologies and valuable applications have been developed to support some of these emerging models, however, the full potential of the A/VE model requires an environment coping with its requirements, and the Market of Resources concept is defended as a solution for virtual enterprise (VE) integration. The chapter discusses the requirements for the A/VE model and introduces the global structure and functionalities of the Market of Resources. © 2005, Idea Group Inc.