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Publications

Publications by LIAAD

2005

Filtered and recovering beam search algorithms for the early/tardy scheduling problem with no idle time

Authors
Valente, JMS; Alves, RAFS;

Publication
COMPUTERS & INDUSTRIAL ENGINEERING

Abstract
In this paper, we present filtered and recovering beam search algorithms for the single machine earliness/tardiness scheduling problem with no idle time, and compare them with existing neighbourhood search and dispatch rule heuristics. Filtering procedures using both priority evaluation functions and problem-specific properties have been considered. The computational results show that the recovering beam search algorithms outperform their filtered counterparts, while the priority-based filtering procedure proves superior to the rules-based alternative. The best solutions are given by the neighbourhood search algorithm, but this procedure is computationally intensive and can only be applied to small or medium size instances. The recovering beam search heuristic provides results that are close in solution quality and is significantly faster, so it can be used to solve even large problems.

2005

Protein sequence classification through relevant sequence mining and Bayes Classifiers

Authors
Ferreira, PG; Azevedo, PJ;

Publication
PROGRESS IN ARTIFICIAL INTELLIGENCE, PROCEEDINGS

Abstract
We tackle the problem of sequence classification using relevant subsequences found in a dataset of protein labelled sequences. A subsequence is relevant if it is frequent and has a minimal length. For each query sequence a vector of features is obtained. The features consist in the number and average length of the relevant subsequences shared with each of the protein families. Classification is performed by combining these features in a Bayes Classifier. The combination of these characteristics results in a multi-class and multi-domain method that is exempt of data transformation and background knowledge. We illustrate the performance of our method using three collections of protein datasets. The performed tests showed that the method has an equivalent performance to state of the art methods in protein classification.

2005

Protein sequence pattern mining with constraints

Authors
Ferreira, PG; Azevedo, PJ;

Publication
KNOWLEDGE DISCOVERY IN DATABASES: PKDD 2005

Abstract
Considering the characteristics of biological sequence databases, which typically have a small alphabet, a very long length and a relative small size (several hundreds of sequences), we propose a new sequence mining algorithm (gIL). gIL was developed for linear sequence pattern mining and results from the combination of some of the most efficient techniques used in sequence and itemset mining. The algorithm exhibits a high adaptability, yielding a smooth and direct introduction of various types of features into the mining process, namely the extraction of rigid and arbitrary gap patterns. Both breadth or a depth first traversal are possible. The experimental evaluation, in synthetic and real life protein databases, has shown that our algorithm has superior performance to state-of-the art algorithms. The use of constraints has also proved to be a very useful tool to specify user interesting patterns.

2005

A Hybrid Method for Discovering Distance-Enhanced Inter-Transactional Rules

Authors
Ferreira, PG; Alves, R; Azevedo, PJ; Belo, O;

Publication
Actas de las X Jornadas de Ingeniería del Software y Bases de Datos (JISBD 2005), September 14-16, 2005, Granada, Spain

Abstract

2005

Difference equations for the higher order moments and cumulants of the INAR(p) model

Authors
Silva, ME; Oliveira, VL;

Publication
JOURNAL OF TIME SERIES ANALYSIS

Abstract
Here we obtain difference equations for the higher order moments and cumulants of a time series {X-t} satisfying an INAR(p) model. These equations are similar to the difference equations for the higher order moments and cumulants of the bilinear time series model. We obtain the spectral and bispectral density functions for the INAR(p) process in state-space form, thus characterizing it in the frequency domain. We consider a frequency domain method - the Whittle criterion - to estimate the parameters of the INAR(p) model and illustrate it with the series of the number of epilepsy seizures of a patient.

2005

Statistical analysis of neuromuscular blockade response: contributions to an automatic controller calibration

Authors
Silva, ME; Mendonca, T; Silva, I; Magalhaes, H;

Publication
COMPUTATIONAL STATISTICS & DATA ANALYSIS

Abstract
Muscle relaxant drugs are currently given during surgical operations. The design of controllers for the automatic control of neuromuscular blockade benefits from an individual tuning of the controller to the characteristics of the patient. A novel approach to the characterization of the neuromuscular blockade response induced by an initial bolus at the beginning of anaesthesia is proposed. This approach is based on the statistical analysis of the data using principal components and Walsh-Fourier spectral analysis. These methods provide information about the patients dynamics, allowing the on-line autocalibration of the controller, using multiple linear regression techniques. Observed and simulated data are used to compare different approaches to the characterization of the bolus response.

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