2006
Authors
Fontes, DBMM; Hadjiconstantinou, E; Christofides, N;
Publication
EUROPEAN JOURNAL OF OPERATIONAL RESEARCH
Abstract
In this paper, we describe a dynamic programming approach to solve optimally the single-source uncapacitated minimum cost network flow problem with general concave costs. This class of problems is known to be NP-Hard and there is a scarcity of methods to solve them in their full generality. The algorithms previously developed critically depend on the type of cost functions considered and on the number of nonlinear arc costs. Here, a new dynamic programming approach that does not depend on any of these factors is proposed. Computational experiments were performed using randomly generated problems. The computational results reported for small and medium size problems indicate the effectiveness of the proposed approach.
2006
Authors
Coelho, LCC; Veloso, JFCA; Covita, DS; Requicha Ferreira, LF; dos Santos, JMF;
Publication
NUCLEAR INSTRUMENTS & METHODS IN PHYSICS RESEARCH SECTION A-ACCELERATORS SPECTROMETERS DETECTORS AND ASSOCIATED EQUIPMENT
Abstract
The performance of a high-pressure xenon gas proportional scintillation counter/microstrip gas chamber (GPSC/MSGC) hybrid detector has been investigated for filling pressures from 1 up to 10 bar, for 22-, 30- and 60-keV photons. GPSC/MSGC hybrid detectors are based on a xenon-GPSC instrumented with a CsI-coated microstrip plate photosensor placed directly within the xenon envelope, as a substitute for the photomultiplier tube. This design avoids the constraints due to the use of a quartz scintillation window for GPSC-photosensor coupling, which absorbs a significant amount of scintillation and is a drawback for applications where large detection areas and high filling pressures are needed. The lowest energy resolutions are achieved for 2 bar (5.5% and 3.4%, FWHM, for 22- and 60-keV photons, respectively). Increasing the pressure to the 5-6 bar range, competitive energy resolutions of 7 % and 4.5 % are still achieved for 22- and 60-keV photons, respectively. This detector could be a compelling alternative in applications where compactness, large detection area, insensitivity to strong magnetic fields, room temperature operation, large signal-to-noise ratio and good energy resolution are important requirements.
2006
Authors
Rego, G; Ivanov, OV; Marques, PVS; Santos, JL;
Publication
Optics InfoBase Conference Papers
Abstract
By measuring intensity distributions of cladding modes and using an optimization technique we show that the perturbation which forms arc-induced gratings in standard fibers is antisymmetric, while the perturbation in boron-germanium codoped fibers is symmetric. © 2006 Optical Society of America.
2006
Authors
Leitao, P; Barbosa, J;
Publication
DIS 2006: IEEE Workshop on Distributed Intelligent Systems: Collective Intelligence and Its Applications, Proceedings
Abstract
Disturbance handling is a crucial issue in the development of intelligent and reconfigurable manufacturing control systems, supporting the fast and promptly response to the occurrence of unexpected disturbances. In holonic manufacturing control systems, the disturbance handling functions are distributed by the several autonomous control units. In this paper, a predictive disturbance handling approach is presented, transforming the traditional "fail and recover" practices into "predict and prevent" practices, allowing improving the control system performance.
2006
Authors
Ferreira, F; Ferreira, F; Pinto, A;
Publication
PROCEEDINGS OF THE 25TH IASTED INTERNATIONAL CONFERENCE ON MODELLING, IDENTIFICATION, AND CONTROL
Abstract
On a symmetric differentiated Stackelberg duopoly model in which there is asymmetric demand information owned by leading and follower firms, we show that the leading firm does not necessarily have advantage over the following one. The reason for this is that the second mover can adjust its output level after observing the realized demand, while the first mover chooses its output level only with the knowledge of demand distribution.
2006
Authors
Meng, S; Barbosa, LS;
Publication
THEORETICAL COMPUTER SCIENCE
Abstract
This paper characterises refinement of state-based software components modelled as pointed coalgebras for some Set endofunctors. The proposed characterisation is parametric on a specification of the underlying behaviour model introduced as a strong monad. This provides a basis to reason about (and transform) state-based software designs. In particular, it is shown how refinement can be applied to the development of the inequational subset of a calculus of generic software components.
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