Abstract
This paper describes a communication model to integrate repositories of programming problems with other e-Learning software components. The motivation for this work comes from the EduJudge project that aims to connect an existing repository of programming problems to learning management systems. When trying to use the existing repositories of learning objects we realized that they are mainly specialized search engines and lack features for integration with other e-Learning systems. With this model we intend to clarify the main features of a programming problem repository, in order to enable the design and development of software components that use it. The two main points of this model are the definition of programming problems as learning objects and the definition of the core functions exposed by the repository. In both cases, this model follows the existing specifications of the IMS standard and proposes extensions to deal with the special requirements of automatic evaluation and grading of programming exercises. In the definition of programming problems as learning objects we introduced a new schema for meta-data. This schema is used to represent meta-data related to automatic evaluation that cannot be conveniently represented using the standard: the type of automatic evaluation; the requirements of the evaluation engine; or the roles of different assets - tests cases, program solutions, etc. In the definition of the core functions we used two different web services flavours - SOAP and REST - and described each function as an operation for each type of interface. We describe also the data types of the arguments of each operation. These data types consist mainly on learning objects and their identifications, but include also usage reports and queries using XQuery.

Abstract
Most of the Power Quality surveys in industrialized countries are performed according to the parameters defined in the EN50160 standard, which sets one-week measurement periods with ten-minute sampling time for most power quality disturbances such as flicker and harmonics. Both the sampling periods and the measurement period have a great influence on the significance of the values obtained as well as on the conclusions taken. In this paper, an attempt is made to compare the values obtained with different sample frequencies and time windows, working on instantaneous flicker (Ifl) values for a wind turbine over three weeks.

Abstract
In this paper, we consider a Stackelberg duopoly competition with differentiated goods and with unknown costs. The firms' aim is to choose the output levels of their products according to the well-known concept of perfect Bayesian equilibrium. There is a firm (F(1)) that chooses first the quantity q(1) of its good; the other firm (F(2)) observes q(1) and then chooses the quantity g(2) of its good. We suppose that each firm has two different technologies, and uses one of them following a probability distribution. The use of either one or the other technology affects the unitary production cost. We show that there is exactly one perfect Bayesian equilibrium for this game. We analyse the advantages, for firms and for consumers, of using the technology with the highest production cost versus the one with the cheapest cost.

Abstract
The restructuring of power systems has often originated the organization of power system operation planning in a set of chronological sequence of activities that are reasonably decoupled. This means that the Market Operator purely economic schedule together with bilateral contracts is conveyed to the System Operator to be validated from a technical point of view. The System Operator also has to schedule reactive power but some of its reactive power requirements may be unfeasible given the previous active power schedules and the alternator capability diagram. Apart from this aspect, active and reactive powers are coupled in determining the eventual violation of branch thermal limits and reactive power has a well-known local nature. While recognizing the Coupling between active and reactive powers, the models presented in this paper admit that the Market Operator schedule may have to be altered either because there are branch limit or nodal voltage violations or because the System Operator requires a reactive output that can not be provided Clue to the previous active schedule. The changes on the initial schedule are determined by solving an optimization problem that uses adjustment generator or demand bids. Apart from that, we adopted a symmetric fuzzy programming approach recognizing that some constraints have a soft nature, namely the ones related with voltage and branch flow limits. To solve the resulting non-linear problem we used Sequential Linear Programming, SLP. At its final iteration this problem also Outputs active and reactive nodal marginal prices useful to build more effective tariff systems. The paper includes a case study based on the IEEE 24 bus test system.

Abstract
This paper addresses the generation expansion-planning problem describing a model that generation companies can use to get insight to this problem and to more completely study and characterize different investment decisions. In the last 20 years, the generation activity evolved from a situation in which it was part of vertical companies to unbundled market agents that face a much more risky and uncertain environment. This explains the need to develop this kind of simulation tools to help them building their investment plans as well as analyzing the impact of possible decisions of other players. The simulation model considers a number of possible generation technologies and aims at characterizing the corresponding investment plans from an economic point of view having in mind that market prices, the demand growth, investment and operation costs, as well as other factors, are affected by uncertainties. These uncertainties are modeled by pdf functions and the solution approach uses a Monte Carlo Simulation to sample particular values used to analyse the different investment alternatives from an economic point of view. Finally, the paper presents results from a Case Study illustrating the use of this approach.

Abstract
Labelled transition systems admit different but equivalent characterizations either as relational structures or coalgebras for the powerset functor, each of them with their own merits. Notions of simulation and bisimulation, for example, are expressed in the pointfree relational calculus in a very concise and precise way. On the other hand, the coalgebraic perspective regards processes as inhabitants of a final universe and allows for an intuitive definition of the semantics of process' combinators. This paper is an exercise on such a dual characterisation. In particular, it discusses how a notion of weak bisimilarity can be lifted from the relational to the coalgebraic level, to become an effective reasoning tool on coinductively defined process algebras.