Abstract
This paper presents some lines of thinking related with the establishment of a concrete mathematical basis to measure the ability of enterprises in a supply chain to maintain equilibrium under unexpected variations. It will be argued that flexibility will be the most appropriate term to classify the concept behind such idea and that agility can be understood as a special case of flexibility. Then, a simple theory of flexibility directed to demand variations in the supply chain is deduced and commented, as well as some results achieved by dynamic supply chain simulation presented and discussed.

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This paper presents the implementation of fractional-order algorithms both for hybrid and cascade position/force control of robotic manipulators. The system performance and robustness is analyzed in the time and frequency domains. The effects joint backlash and flexibility are also investigated.

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Here we present a computer application planned to be used as an interactive tool for Supply Chain Management Training. Implemented with Visual C++, this application embeds the "Cranfield Blocks Game" (Richard Saw, 2002) network structure, and uses precisely the same demand patterns as the manual version of the game. Anyhow, instead of reducing the play to 12 reorder cycles, as the manual version does, this application extends those patterns throughout the time till any number of reorder cycles, what let the results become more useful and interesting even for didactic purposes. At the same time, the present application substitutes the classroom table by the computer screen, and can be made to run in AUTOPLAY mode, meaning the game can also be played with only one player or even automatically, with no players at all. In a certain way, this comes closer to some kind of Distributed Supply Chain Simulation, apart from the fact each lead time is fixed, as the "Cranfield Blocks Game" states, and the AUTOPLAY stock policy is empirical. As each application communicates with the SERVER using the TCP/IP protocol, the players can be spread by different computers and even placed at different geographic locations if connected to the INTERNET. In the end of this paper, results achieved with an automatic running session and with the involvement of a group of students from the Escola de Gestao do Porto (EGP) will be presented and compared.

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This paper addresses the short-term allocation of active/reactive power supplies in transmission systems in a market environment. In many papers market mechanisms to allocate active power within a pool or by bilateral contracts are described. in several Countries Volt/Var control also started to be considered, at least partially, as a marketable service and so new methodologies are required to support this process. This paper presents an integrated multi-objective formulation for the active/reactive power dispatch based on bids from market agents. The local nature of Volt/Var control is provided by the AC power flow equations. The formulation also considers two more objective functions related to system operational efficiency and security. The operation of discrete components as transformer taps and capacitor sections is accurately considered using Simulated Annealing. The proposed methodology is applied on the 30-bus IEEE test system highlighting its advantages and demonstrating the feasibility of its use in real systems.

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