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Publications

Publications by BIO

2007

Mathematical modeling, system identification, and controller design of a two tank system

Authors
Ramos, JA; dos Santos, PL;

Publication
PROCEEDINGS OF THE 46TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14

Abstract
In this paper we present a case study involving mathematical modeling, system identification, and controller design of a two tank fluid level system. The case study is motivated by a realistic application of a two tank problem. We address some fundamental control oriented issues such as physical plant design and identification, transformation from discrete-time to continuous-time, and finally the controller design. We also introduce a novel physical system identification algorithm consisting of subspace identification, followed by a similarity transformation computation to extract the physical parameters of the system. The controller design is done by Pole Placement.

2007

CAALYX: a new generation of location-based services in healthcare

Authors
Boulos, MNK; Rocha, A; Martins, A; Vicente, ME; Bolz, A; Feld, R; Tchoudovski, I; Braecklein, M; Nelson, J; Laighin, GO; Sdogati, C; Cesaroni, F; Antomarini, M; Jobes, A; Kinirons, M;

Publication
INTERNATIONAL JOURNAL OF HEALTH GEOGRAPHICS

Abstract
Recent advances in mobile positioning systems and telecommunications are providing the technology needed for the development of location-aware tele-care applications. This paper introduces CAALYX - Complete Ambient Assisted Living Experiment, an EU-funded project that aims at increasing older people's autonomy and self-confidence by developing a wearable light device capable of measuring specific vital signs of the elderly, detecting falls and location, and communicating automatically in real-time with his/her care provider in case of an emergency, wherever the older person happens to be, at home or outside.

2007

Coccoid form of Helicobacter pylori as a morphological manifestation of cell adaptation to the environment

Authors
Azevedo, NF; Almeida, C; Cerqueira, L; Dias, S; Keevil, CW; Vieira, MJ;

Publication
APPLIED AND ENVIRONMENTAL MICROBIOLOGY

Abstract
After characterization of preferred conditions for Helicobacter pylori survival in the sessile state, it was observed that the bacterium transforms from spiral to coccoid under mild circumstances, whereas under extreme ones it is unable to undergo shape modification. This strongly supports the view that transformation into the coccoid form is an active, biologically led process, switched on by the bacterium as a protection mechanism.

2006

Mining approximate motifs in time series

Authors
Ferreira, PG; Azevedo, PJ; Silva, CG; Brito, RMM;

Publication
DISCOVERY SCIENCE, PROCEEDINGS

Abstract
The problem of discovering previously unknown frequent patterns in time series, also called motifs, has been recently introduced. A motif is a subseries pattern that appears a significant number of times. Results demonstrate that motifs may provide valuable insights about the data and have a wide range of applications in data mining tasks. The main motivation for this study was the need to mine time series data from protein folding/unfolding simulations. We propose an algorithm that extracts approximate motifs, i.e. motifs that capture portions of time series with a similar and eventually symmetric behavior. Preliminary results on the analysis of protein unfolding data support this proposal as a valuable tool. A.dditional experiments demonstrate that the application of utility of our algorithm is not limited to this particular problem. Rather it can be an interesting tool to be applied in many real world problems.

2006

Query Driven Sequence Pattern Mining

Authors
Ferreira, PG; Azevedo, PJ;

Publication
XXI Simpósio Brasileiro de Banco de Dados, 16-20 de Outubro, Florianópolis, Santa Catarina, Brasil, Anais/Proceedings

Abstract

2006

A vectorized principal component approach for solving the data registration problem

Authors
Ramos, JA; dos Santos, PL; Verrie, EI;

Publication
PROCEEDINGS OF THE 45TH IEEE CONFERENCE ON DECISION AND CONTROL, VOLS 1-14

Abstract
The problem of estimating the motion and orientation parameters of a rigid object from two m - D point set patterns is of significant importance in medical imaging, electrocardiogram (ECG) alignment, and fingerprint matching. The rigid parameters can be defined by an m x m rotation matrix, a diagonal m x m scale matrix, and an m x 1 translation vector. All together, the total number of parameters to be found is m(m + 2). Several least squares based algorithms have recently appeared in the literature. These algorithms are all based on a singular value decomposition (SVD) of the m x m cross-covariance matrix between the two data sets. However, there are cases where the SVD based algorithms return a reflection matrix rather than a rotation matrix. Some authors have introduced a simple correction for guarding against such cases. Other types of algorithm are based on unit quaternions which guarantee obtaining a true rotation matrix. In this paper we introduce a principal component based registration algorithm which is solved in closed-form. By using matrix vectorization properties the problem can be cast as one of finding a rank-1 symmetric projection matrix. This is equivalent to solving a Sylvester equation with equality constraints. Once the solution is obtained, we apply the inverse vectorization operation to estimate the rotation and scale matrices, along with the translation vector. We apply the proposed algorithm to the alignment of ECG signals and compare the results to those obtained by the SVD and quaternion based algorithms.

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