2003
Autores
Soares, C;
Publicação
PROGRESS IN ARTIFICIAL INTELLIGENCE
Abstract
We propose a methodology to investigate the relevance for the real world of repositories of benchmark problems like the one commonly known as the UCI repository. It compares the distribution of relative performance of algorithms in data sets from a given repository and from the "real world". If the distributions are different, the knowledge about the relative performance of algorithms obtained from the repository in question is mostly useless. In the case of the UCI repository, this would mean that a significant proportion of published results would be of little practical use. However, this is not what our results indicate. We also propose an adaptation of this method to test whether tool developers are "overfitting" repositories, which also yields negative results in the UCI repository.
2003
Autores
Pinho, LM; Vasques, F;
Publicação
IEEE TRANSACTIONS ON COMPUTERS
Abstract
Controller Area Network (CAN) is a fieldbus network suitable for small-scale Distributed Computer Controlled Systems (DCCS), being appropriate for sending and receiving short real-time messages at speeds up to 1 Mbit/sec. Several studies are available on how to guarantee the real-time requirements of CAN messages, providing preruntime schedulability conditions to guarantee the real-time communication requirements of DCCS traffic. Usually, it is considered that CAN guarantees atomic multicast properties by means of its extensive error detection/signaling mechanisms. However, there are some error situations where messages can be delivered in duplicate or delivered only by a subset of the receivers, leading to inconsistencies in the supported applications. In order to prevent such inconsistencies, a middleware for reliable communication in CAN is proposed, taking advantage of CAN synchronous properties to minimize the runtime overhead. Such middleware comprises a set of atomic multicast and consolidation protocols, upon which the reliable Communication properties are guaranteed. The related timing analysis demonstrates that, in spite of the extra stack of protocols, the real-time properties of CAN are preserved since the predictability of message transfer is guaranteed.
2003
Autores
Azevedo, F; Vale, ZA; Do Vale, AA;
Publicação
2003 IEEE Bologna PowerTech - Conference Proceedings
Abstract
The Pool, in many countries, was adopted for the participants of the electricity market to trade the electrical energy in a basis of each half-hour or one hour of the next day. However, like the traditional markets, the agents of electrical market are now exposed to the volatility of market price. In some countries, to face that problem and to turn the market more liquid, the derivatives markets - futures and options - were introduced to negotiate products with electrical energy as underlying active. In this context, there is a need of decision-support tools to assist those agents for the use of derivatives markets with the objective of practicing the hedge. In this paper, we present a decision model that supports producers to establish contracts with the objective to maximize the profit expected utility. © 2003 IEEE.
2003
Autores
Santos, VCF; Sousa, MFM; Ferreira, AJS;
Publicação
PATTERN RECOGNITION AND IMAGE ANALYSIS, PROCEEDINGS
Abstract
This paper describes a method for automatically assessing the quality of manufactured roof-tiles using digital audio signal processing and pattern recognition techniques. A prototype system has been developed that is based on a mixed PC/DSP platform, where the real-time constraint is one of the main key issues. The suitability of the classification process for implementation in an industrial environment is also addressed.
2003
Autores
Soares, MG; Malheiro, B; Restivo, FJ;
Publicação
ETFA 2003: IEEE CONFERENCE ON EMERGING TECHNOLOGIES AND FACTORY AUTOMATION, VOL 1, PROCEEDINGS
Abstract
The goal of the work presented in this paper is to provide mobile platforms within our campus with a GPS based data service capable of supporting precise outdoor navigation. This can be achieved by providing campus-wide access to real time Differential GPS (DGPS) data. As a result, we designed and implemented a three-tier distributed system that provides Internet data links between remote DGPS sources and the campus and a campus-wide DGPS data dissemination service. The Internet data link service is a two-tier client/server where the server-side is connected to the DGPS station and the client-side is located at the campus. The campus-wide DGPS data provider disseminates the DGPS data received at the campus via the campus Intranet and via a wireless data link. The wireless broadcast is intended for portable receivers equipped with a DGPS wireless interface and the Intranet link is provided for receivers with a DGPS serial interface. The application is expected to provide adequate support for accurate outdoor campus navigation tasks.
2003
Autores
Pires, EJS; Machado, JAT; Oliviera, PBD;
Publicação
SIGNAL PROCESSING
Abstract
This work addresses the signal propagation and the fractional-order dynamics during, the evolution of a genetic algorithm (GA), for generating a robot manipulator trajectory. The GA objective is to minimize the trajectory space/time ripple without exceeding the torque requirements. In order to investigate the phenomena involved in the GA population evolution, the mutation is exposed to excitation perturbations and the corresponding fitness variations are evaluated. The chaos-like noise and the input/output signals are studied revealing a fractional-order dynamics, characteristic of a long-term system memory.
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