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Publications

2008

Limits on spin-dependent WIMP-nucleon cross sections from the XENON10 experiment

Authors
Angle, J; Aprile, E; Arneodo, F; Baudis, L; Bernstein, A; Bolozdynya, A; Coelho, LCC; Dahl, CE; DeViveiros, L; Ferella, AD; Fernandes, LMP; Fiorucci, S; Gaitskell, RJ; Giboni, KL; Gomez, R; Hasty, R; Kastens, L; Kwong, J; Lopes, JAM; Madden, N; Manalaysay, A; Manzur, A; McKinsey, DN; Monzani, ME; Ni, K; Oberlack, U; Orboeck, J; Plante, G; Santorelli, R; dos Santos, JMF; Shagin, P; Shutt, T; Sorensen, P; Schulte, S; Winant, C; Yamashita, M;

Publication
PHYSICAL REVIEW LETTERS

Abstract
XENON10 is an experiment to directly detect weakly interacting massive particles (WIMPs), which may comprise the bulk of the nonbaryonic dark matter in our Universe. We report new results for spin-dependent WIMP-nucleon interactions with (129)Xe and (131)Xe from 58.6 live days of operation at the Laboratori Nazionali del Gran Sasso. Based on the nonobservation of a WIMP signal in 5.4 kg of fiducial liquid xenon mass, we exclude previously unexplored regions in the theoretically allowed parameter space for neutralinos. We also exclude a heavy Majorana neutrino with a mass in the range of similar to 10 GeV/c(2) -2 TeV/c(2) as a dark matter candidate under standard assumptions for its density and distribution in the galactic halo.

2008

A web application for mathematics education

Authors
Tomas, AP; Leal, JP; Domingues, MA;

Publication
ADVANCES IN WEB BASED LEARNING - ICWL 2007

Abstract
AGILMAT is a web application designed to help students learn Mathematics, with focus on high-school algebra and calculus drills. A modular and extensible architecture and a wizard-based configuration interface decoupled from the system core are major design features of AGILMAT. The drill expressions are specified by grammars and constraints imposed by default profiles and user options, so that AGILMAT may support distinct learning levels and stages. The core system uses symbolic manipulation and automated reasoning to provide correct answers for the drills. The paper shows how AGILMAT may be used to create and customize drills automatically.

2008

Fibre refractometer based on a Fabry-Perot interferometer

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

Publication
19TH INTERNATIONAL CONFERENCE ON OPTICAL FIBRE SENSORS, PTS 1 AND 2

Abstract
It is described a fibre optic sensor for liquid refractive index measurement based on the visibility variations of a Fabry-Perot interferometer with interfering waves generated in a short Bragg grating and in the fibre tip (Fresnel reflection) in contact with the liquid. The sensor was characterized emerging the fibre tip in distilled water with different concentrations of ethylene glycol. A linear relation was obtained, with a readout resolution of similar to 10(-3). It was also observed that the temperature direct cross sensitivity is residual.

2008

Fuzzy present worth analysis with correlated and uncorrelated cash flows

Authors
Dimitrovski, A; Matos, M;

Publication
Studies in Fuzziness and Soft Computing

Abstract
This chapter first presents arithmetic operations over independent fuzzy numbers and economic concepts review. Then, it gives the techniques for comparing and ordering fuzzy numbers of independent numbers and dependent numbers. It examines fuzzy case with partial correlation. The chapter also includes many numerical applications. © 2008 Springer-Verlag Berlin Heidelberg.

2008

Optimising power generation efficiency for head-sensitive cascaded reservoirs in a competitive electricity market

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

Publication
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS

Abstract
This paper is on the problem of short-term hydro scheduling (STHS), particularly concerning head-sensitive reservoirs under competitive environment. We propose a novel method, based on nonlinear programming (NLP), for optimising power generation efficiency. This method 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 water discharge, thus giving 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 optimisation methods based on linear programming (LP) that ignore head dependence.

2008

Coupling optimization to the algorithm for a mixer-settler system

Authors
Gomes, EF; Pinto, GA; Guimaraes, MML; Ribeiro, LM;

Publication
Proceedings of the 6th International Conference on Engineering Computational Technology

Abstract
We have been working on a model for the shallow-layer settler, in a mixer-settler system, which is able to describe the hydrodynamic phenomena of the transient state of a liquid-liquid system. The mathematical model used includes parameters of the drop transport process as well as of the drop-drop and drop-interface coalescence with the active interface. The most adequate values of these parameters are unknown. In order to tune the model parameters we have linked the mixer-settler simulation algorithm to an optimization procedure. Due to its simplicity and robustness we've used the Hooke-Jeeves optimization algorithm to fit these parameters to given experimental results. © 2008 Civil-Comp Press.

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