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Publications

2007

Operation of a single-GEM in noble gases at high pressures

Authors
Amaro, FD; Conceicao, AS; Veloso, JFCA; Coelho, LCC; Fernandes, LMP; Ferreira, LFR; Lopes, JAM; dos Santos, JMF;

Publication
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT

Abstract
We report the performance of a single-Gas Electron Multiplier (GEM) operating in pure Ar, Xe, and in Ar-50lmbar Xe mixtures, in the range of 1-7lbar. The maximum gain and voltage that can be applied to the GEM are investigated as a function of filling pressure and compared to the results obtained with triple-GEM and MHSP (Micro Hole and Strip Plate) multipliers. The maximum gain achieved at llbar Xe is about 103, presenting a fast decrease with pressure to values around 300, 50 and 10 at 2, 3 and 5lbar, respectively. Gains around 100 were achieved in Ar up to 4lbar, decreasing to values of few tens at 6lbar. On the other hand, gains around 500 can be achieved in Ar-50lmbar Xe mixtures up to 5lbar, presenting a fast reduction at higher pressures due to the limitations on the maximum gain imposed by the GEM discharge limit. Nevertheless, gains above 100 can be obtained for pressures between 6 and 7lbar, indicating a good potential for neutron detection.

2007

Voltage and reactive power control in MV networks integrating microgrids

Authors
Madureira, A; Facullty of Engineering of Porto University, Power Systems Unit of INESC Porto, Portugal,; Pecas Lopes, J;

Publication
Renewable Energy and Power Quality Journal

Abstract
The main objective of this paper is to describe a strategy to deal with the voltage/reactive power problem for a MV distribution network integrating microgrids. The global problem, concerning all voltage levels, is detailed here and will imply the optimization of operating conditions by using the control capabilities of power electronic interfaces from DG sources, OLTCs and microgrids, through the application of an EPSO optimization algorithm.

2007

Modal interferometer based on a single non-adiabatic fibre taper - art. no. 66192G

Authors
Frazao, O; Caldas, P; Santos, JL; Araujo, FM; Ferreira, LA;

Publication
Third European Workshop on Optical Fibre Sensors

Abstract
In this work it is presented a novel in-fibre modal interferometer based on a non-adiabatic biconical fused taper that couples light between the cladding and the core, combined with the Fresnel reflection at the fibre end. It is observed that the returned liaht from this fibre structure shows a channelled spectrum similar to that of a two-wave Michelson interferometer. The application of this device as a fibre optic flowmeter sensor is demonstrated.

2007

Strategies for power systems expansion planning in a competitive electrical market

Authors
Andreoni, AM; Garcia Agreda, A; Strada, TJ; Saraiva, JT;

Publication
ELECTRICAL ENGINEERING

Abstract
A new methodology is presented for decision making in long-term expansion planning. Power system expansion planning involves an intrinsic uncertainty on data and parameters, a fact often worsened by the new rules of deregulated electrical markets. The proposed procedure models both the uncertainty in load forecasting and the experience of the planning expert who uses fuzzy sets theory and fuzzy dynamic programming in the model algorithm to find an optimal expansion alternative. This procedure was tested in a realistic model system and the results obtained were arranged in an expansion planning ranking list according to their membership in the decision set.

2007

Head-dependent maximum power generation in short-term hydro scheduling using nonlinear programming

Authors
Mariano, SJPS; Catalao, JPS; Mendes, VMF; Ferreira, LAFM;

Publication
PROCEEDINGS OF THE SEVENTH IASTED INTERNATIONAL CONFERENCE ON POWER AND ENERGY SYSTEMS

Abstract
This. paper is on the problem of short-term hydro scheduling. We propose a method, based on nonlinear programming, which considers hydroelectric power generation as a nonlinear function of water discharge and of the head. The main contribution of this paper is that the maximum power generation is also considered as head-dependent in order to obtain more realistic and feasible results. The proposed method has been applied successfully to solve a case study based on one of the Portuguese cascaded hydro systems, providing a higher profit at an acceptable computation time in comparison with classical optimization methods based on linear programming that ignore head dependence.

2007

A simulation study of an automated system for a shoe factory using arena

Authors
Brito, AC; Marques, PS;

Publication
EUROPEAN SIMULATION AND MODELLING CONFERENCE 2007

Abstract
One of the issues in the shoe industry is that market seeks the fulfilment of product orders for smaller production lots with shorter deadlines. A need therefore arises to respond to these market changes. Such a response includes amongst other things improving the internal organization of the enterprise, by for example rationalizing the production floor layout. A portuguese shoe factory decided to cut costs related to the transportation of all work in progress within the factory plant by implementing a fully automated storage and retrieval system. This Paper presents the development of a Simulation model, using the Arena simulation software tool, to analyse the performance of the automated storage and retrieval system based oil a number of scenarios. The simulation model uses VBA (Visual Basic for Applications) to implement the control logic and graphics to Visualize the sequences of movements and storage / retrieval operations.

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