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Publicações

2009

Bioimplantable impedance and temperature monitor low power micro-system suitable for estrus detection

Autores
Miranda, N; Morais, R; Dias, M; Viegas, C; Silva, F; Serodio, C; Almeida, J; Azevedo, J; Reis, MC;

Publicação
PROCEEDINGS OF THE EUROSENSORS XXIII CONFERENCE

Abstract
Based on cyclic physiologic animal bioimpedance and body temperature a new method is being evaluated to predict estrus in dairy cattle with the aim of improving artificial insemination efficiency. Preceding in-vivo tests are being performed with a dedicated system based on the impedance converter AD5933, and a two-electrode configuration bioimplantable capsule. Acquired results will allow the optimal design of an implantable and autonomous low-power system. The implantable microsystem is being designed and simulated employing low-power techniques in a 0.35 mu m CMOS standard process.

2009

Precision and Recall for Regression

Autores
Torgo, L; Ribeiro, R;

Publicação
DISCOVERY SCIENCE, PROCEEDINGS

Abstract
Cost sensitive prediction is a key task in many real world applications. Most existing research in this area deals with classification problems. This paper addresses a related regression problem: the prediction of rare extreme values of a continuous variable. These values are often regarded as outliers and removed from posterior analysis. However, for many applications (e.g. in finance, meteorology, biology, etc.) these are the key values that we want to accurately predict. Any learning method obtains models by optimizing some preference criteria. In this paper we propose new evaluation criteria that are more adequate for these applications. We describe a generalization for regression of the concepts of precision and recall often used in classification. Using these new evaluation metrics we are able to focus the evaluation of predictive models on the cases that really matter for these applications. Our experiments indicate the advantages of the use of these new measures when comparing predictive models in the context of our target applications.

2009

Cancer cell detection and invasion depth estimation in brightfield images

Autores
Quelhas, P; Marcuzzo, M; Mendonca, AM; Oliveira, MJ; Campilho, A;

Publicação
British Machine Vision Conference, BMVC 2009 - Proceedings

Abstract
The study of cancer cell invasion under the effect of different conditions is fundamental for the understanding of the invasion mechanism and to test possible therapies for its regulation. In this study, to simulate cancer cell invasion across tissue basement membrane, biologists established in vitro invasion assays with cancer cells invading extracellular matrix components. However, analysis of the assay is manual, being time-consuming and error-prone, which motivates an objective and automated analysis tool. With the objective of automating the analysis of cell invasion assays we present a new methodology to detect cells in 3D matrix cell assays and correctly estimate their invasion, measured by the depth of the penetration in the gel. Detection is based on the sliding band filter, by evaluating the gradient convergence and not intensity. As such it can detect low contrast cells which otherwise would be lost. For cell depth estimation we present a new tool based on the analysis of cell detections from multiple brightfield images taken at different depths of focus, using a new focus estimation approach based on the convergence gradient's magnitude. The final cell detection's precision and recall are of 0.896 and 0.910 respectively, and the average error in the cell's position estimate is of 0.41µm, 0.37µm and 3.7µm in the x, y and z directions, respectively. © 2009. The copyright of this document resides with its authors.

2009

Inscription of Fiber Bragg Grating Arrays in Pure Silica Suspended Core Fibers

Autores
Becker, M; Fernandes, L; Rothhardt, M; Brueckner, S; Schuster, K; Kobelke, J; Frazao, O; Bartelt, H; Marques, PVS;

Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS

Abstract
Fiber Bragg grating (FBG) arrays in pure silica four-leaf-clover-shaped suspended core fibers were inscribed with two-beam interference and a deep UV femtosecond laser source. The target fibers are pure silica and do not contain any dopants, nor were they treated with hydrogen before grating inscription. The inscription method is appropriate to measure the effective mode field index of the fiber and allows confinement factors of the guided modes to be derived. Applications of such FBGs can be expected especially for fiber sensing.

2009

An activation circuit for battery-powered biomedical implantable systems

Autores
Morais, R; Frias, CM; Silva, NM; Azevedo, JLF; Serodio, CA; Silva, PM; Ferreira, JAF; Simoes, JAO; Reis, MC;

Publicação
SENSORS AND ACTUATORS A-PHYSICAL

Abstract
Biomedical implantable devices in real-time telemetry applications offer many advantages to study and monitor physiologic parameters in human and animal bodies. As in power-constrained implantable devices, batteries and wires are two key issues that usually compromise their application. Inductive coupling is a well-established technology because it replaces simultaneously the wired connection and avoids the use of batteries. In stand-alone applications that requires total freedom of movements, this technology may present some constrains. On the other hand,very-low power electronics, advanced energy harvesting techniques and smaller implantable rechargeable batteries makes now possible the conception of fully autonomous implantable devices. This paper describes an activation circuit used to completely turn-off battery-powered implantable devices. In addition, it allows the reception of embedded commands, suitable for calibration and sensor selection purposes. Results from an experimental device to be used in a smart hip prosthesis telemetry system for loosening detection shows the usefulness of the proposed activation concept.

2009

A Windows-Based Software Package to Evaluate Residual Stresses by the Incremental Hole-Drilling Technique

Autores
Nobre, JP; Dias, AM; Domingos, AJ; Morais, R; Reis, MJCS;

Publicação
COMPUTER APPLICATIONS IN ENGINEERING EDUCATION

Abstract
A new software package for the incremental hole-drilling technique (IHD) is presented in connection with undergraduate mechanical engineering education. The main available technical residual stresses evaluation procedures for applying MID in isotropic materials are reviewed and have been included in the package, it has an easy-to-use, friendly interface, and can be used as a tool to teach the IHD technique or as a laboratory to study its applicability to real world problems. A set of exercises have been prepared, which are freely distributed to our students, in order to show the full potential of the package, but the students can also do simulations and experiments with their own data. (C) 2009 Wiley Periodicals, Inc. Comput Appl Eng Educ 17: 351-362, 2009; Published online in Wiley InterScience (www.interscience.wiley.com); DOI 10.1002/cae.20225

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