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This paper analyzes a realistic variant of the Permutation Flow-Shop Problem (PFSP) by considering a non-smooth objective function that takes into account not only the traditional makespan cost but also failure-risk costs due to uninterrupted operation of machines. After completing a literature review on the issue, the paper formulates an original mathematical model to describe this new PFSP variant...
In this paper we analyze several cases related to three different Spanish universities that make use of the World Wide Web to teach simulation courses online. These universities are the Open University of Catalonia, the University of Lleida and the Public University of Navarre. At these three universities different infrastructures, tools and learning models are employed to deliver simulation education...
This paper discusses the convenience of predicting, quantitatively, time-dependent reliability and availability levels associated with most building or civil engineering structures. Then, the paper reviews different approaches to these problems and proposes the use of discrete-event simulation as the most realistic way to deal with them, specially during the design stage. The paper also reviews previous...
Economic models have shown their suitability to allocate resources efficiently, considering an unbalanced supply and demand. As the use of the Grid is extending, a numerous set of distributed resource allocation frameworks have been developed to attain efficient resource management while keeping the scalability of the Grid. However, those frameworks make use of either simple double auction mechanisms...
In this paper we present SR-1, a simulation-based heuristic algorithm for the capacitated vehicle routing oroblem (CVRP). Given a CVRP instance, SR-1 uses an initial ??good solution??, such as the one provided by the classical Clarke and Wright heuristic, in order to obtain observations for the variable ??distance between two consecutive nodes in a route??. These observations are then fitted by a...
During the last decades a lot of work has been devoted to develop algorithms that can provide near-optimal solutions for the capacitated vehicle routing problem (CVRP). Most of these algorithms are designed to minimize an objective function, subject to a set of constraints, which typically represents aprioristic costs. This approach provides adequate theoretical solutions, but they do not always fit...
Collaborative e-learning virtual communities use virtual learning environments provided by the university or tools that are available in Internet. Although this model has proven its feasibility, it has important limitations. A way to deal with them is by defining virtual organizations (VO) that gather the resources and interests of their members in a way that they can lend resources to or borrow them...
The paper presents a bidding specification language and support tools for grid-oriented open resource marketplaces. The structure of bids is based on trees that permit bidders to express their preferences for grid resources by means of logical operators. Additionally, our bidding specification reduces the complexity of existing bidding languages since it permits imprecise description of user's preferences...
In this paper we address the issue of monitoring studentspsila and groupspsila activity in online collaborative learning environments. This issue is especially important in the collaborative e-learning context, since an efficient monitoring process can provide valuable information to online instructors who may guide and support the development of collaborative learning projects. We have developed...
Nowadays, many companies rely on computer systems and networks for functions such as order entry, customer support, supply chain management, and employee administration. Therefore, reliability and availability of such systems and networks are becoming critical factors for the present- day enterprise or institution. Nevertheless, the task of determining reliability/availability levels for time-dependent...
Summary form given only: In this paper we present a case study regarding the modeling and simulation of a real computer system called Castelldefels. This system gives support to the Virtual Campus of the Open University of Catalonia (UOC), an online university that offers e-learning services to thousands of users. After analyzing several alternatives, the OPNET software was selected as the convenient...
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