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Publicações

2007

Radon variability at the Elat granite, Israel: Heteroscedasticity and nonlinearity

Autores
Barbosa, SM; Steinitz, G; Piatibratova, O; Silva, ME; Lago, P;

Publicação
GEOPHYSICAL RESEARCH LETTERS

Abstract
The basic statistical features of radon time series from continuous radon monitoring at the Elat granite, Israel are analysed. A similar analysis is carried out for ancillary and possibly related geophysical parameters for the Elat area. The results show that air temperature, precipitable water and longwave radiation time series exhibit constant variance over the analyzed period, while radon time series, atmospheric pressure, short-wave radiation and total electron content exhibit heteroscedasticity. Furthermore, for radon and shortwave radiation the variability is associated with the overall mean level, while for atmospheric pressure such an association is not present. The analyzed radon time series not only are non-stationary but also nonlinear, reflecting the complex dynamics of radon emanation and transport in natural subsurface systems.

2007

Intelligent farmer agent for multi-agent ecological simulations optimization

Autores
Cruz, F; Pereira, A; Valente, P; Duarte, P; Reis, LP;

Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE, PROCEEDINGS

Abstract
This paper presents the development of a bivalve farmer agent interacting with a realistic ecological simulation system. The purpose of the farmer agent is to determine the best combinations of bivalve seeding areas in a large region, maximizing the production without exceeding the total allowed seeding area. A system based on simulated annealing, tabu search, genetic algorithms and reinforcement learning, was developed to minimize the number of iterations required to unravel a semi-optimum solution by using customizable tactics. The farmer agent is part of a multi-agent system where several agents, representing human interaction with the coastal ecosystems, communicate with a realistic simulator developed especially for aquatic ecological simulations. The experiments performed revealed promising results in the field of optimization techniques and multi-agent systems applied to ecological simulations. The results obtained open many other possible uses of the simulation architecture with applications in industrial and ecological management problems, towards sustainable development.

2007

Establishing a musical channel of communication between dancers and musicians in computer-mediated collaborations in dance performance

Autores
Guedes, C;

Publicação
Proceedings of the 7th International Conference on New Interfaces for Musical Expression, NIME '07

Abstract
In this demonstration, I exemplify how a musical channel of communication can be established in computer-mediated interaction between musicians and dancers in real time. This channel of communication uses a software library implemented as a library of external objects for Max/MSP[1], that processes data from an object or library that performs frame-differencing analysis of a video stream in real time in this programming environment.

2007

Is face-view only enough for the aesthetic evaluation of breast cancer conservative treatment (BCCT)?

Autores
Cardoso, MJ; Cardoso, JS; Vrieling, C; Christie, D; Joahensen, J; Costa, S; Almeida, T;

Publicação
EJC SUPPLEMENTS

Abstract

2007

GRAND: toward scalability in a grid environment

Autores
Vargas, PK; Dutra, IC; do Nascimento, VD; Santos, LAS; da Silva, LC; Geyer, CFR; Schulze, B;

Publicação
CONCURRENCY AND COMPUTATION-PRACTICE & EXPERIENCE

Abstract
One of the challenges in Grid computing research is to provide a means to automatically submit, manage, and monitor applications whose main characteristic is to be composed of a large number of tasks. The large number of explicit tasks, generally placed on a centralized job queue, can cause several problems: (1) they can quickly exhaust the memory of the submission machine; (2) they can deteriorate the response time of the submission machine due to these demanding too many open ports to manage remote execution of each of the tasks; (3) they may cause network traffic congestion if all tasks try to transfer input and/or output files across the network at the same time; (4) they make it impossible for the user to follow execution progress without an automatic tool or interface; (5) they may depend on fault-tolerance mechanisms implemented at application level to ensure that all tasks terminate successfully. In this work we present and validate a novel architectural model, GRAND (Grid Robust ApplicatioN Deployment), whose main objective is to deal with the submission of a large numbers of tasks. Copyright (c) 2006 John Wiley & Sons, Ltd.

2007

Connecting the intraday energy and reserve markets by an optimal redispatch

Autores
Garcia Gonzalez, J; Roque, AMS; Campos, FA; Villar, J;

Publicação
IEEE TRANSACTIONS ON POWER SYSTEMS

Abstract
Electricity markets based on simple bids provide a very high degree of transparency and simplicity. However, simple bids fail to capture many well-known characteristics of generating units and, therefore, the responsibility for obtaining feasible schedules is transferred to market participants. The purpose of this paper is to help the generating utility to automatically analyze the last energy program cleared in the market and, in case this program is technically unfeasible, to provide an alternative schedule by redispatching the generating units. This is achieved by formulating an optimization problem where the objective is to find the cheapest and feasible instantaneous power trajectory of each generator, trying to minimize the differences between its hourly average values and the last energy program. As the objectives of the utility can vary during the day, three different models are presented. Two of them are formulated as a joint energy and reserve dispatch in order to take into account possible commitments acquired in the ancillary services market of AGC regulation. In this sense, a novel approach for considering discontinuous ancillary regulation curves is proposed. Some numerical examples are included to illustrate the essential features of the models.

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