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Publicações

2006

Diffusion processes in seeded and unseeded SBT thin films with varied stoichiometry

Autores
Aguilar, GG; Wu, A; Reis, MA; Ramos, AR; Salvado, IMM; Alves, E; Costa, MEV;

Publicação
SURFACE SCIENCE

Abstract
SrBi2Ta2O9 (SBT) is a bismuth layered perovskite (BLP) with interesting ferroelectric properties for memories applications. The previous study on the synthesis of seeded and unseeded SBT thin films by the authors G. Gonzalez Aguilar, M.E.V. Costa, I.M. Miranda Salvado, J. Eur. Ceram. Soc. 25 (2005) 2331] has shown an increase of the crystallinity of the films and an improvement of the thin film ferroelectric properties when using SBT seeds. However, the detailed role of the seeds as an improver of the thin film properties has not been investigated so far. In the present work we study the role of the seeds, particularly with respect to the reactions between film and (bottom) underlying platinum electrode. The comparison of the results obtained by characterizing the seeded and unseeded thin films via Rutherford backscattering (RBS) and particle induced X-ray emission (PIXE) techniques reveals an effective modification of the substrate-thin film interface by the presence of the seeds. Moreover, the evaluation of the thin film ferroelectric properties by atomic force microscopy (AFM) shows an improvement of the local piezoelectric hysteresis loops by the seeds. These seeding effects as well as those observed in non-stoichiometric SBT thin films with different bismuth contents are used to discuss the barrier-like role of the SBT seeds against reactions between film and the platinum electrode and its contribution to the improvement of the thin film properties.

2006

The class imbalance problem in TLC image classification

Autores
Sousa, AV; Mendonca, AM; Campilho, A;

Publicação
IMAGE ANALYSIS AND RECOGNITION, PT 2

Abstract
The paper presents the methodology developed to solve the class imbalanced problem that occurs in the classification of Thin-Layer Chromatography (TLC) images. The proposed methodology is based on resampling, and consists in the undersampling of the majority class (normal class), while the minority classes, which contain Lysosomal Storage Disorders (LSD) samples, are oversampled with the generation of synthetic samples. For image classification two approaches are presented, one based on a hierarchical classifier and another uses a multiclassifier system, where both classifiers are trained and tested using balanced data sets. The results demonstrate a better performance of the multiclassifier system using the balanced sets.

2006

Structural proof theory as rewriting

Autores
Santo, JE; Frade, MJ; Pinto, L;

Publicação
TERM REWRITING AND APPLICATIONS, PROCEEDINGS

Abstract
The multiary version of the lambda-calculus with generalized applications integrates smoothly both a fragment of sequent calculus and the system of natural deduction of von Plato. It is equipped with reduction rules (corresponding to cut-elimination/normalisation rules) and permutation rules, typical of sequent calculus and of natural deduction with generalised elimination rules. We argue that this system is a suitable tool for doing structural proof theory as rewriting. As an illustration, we investigate combinations of reduction and permutation rules and whether these combinations induce rewriting systems which are confluent and terminating. In some cases, the combination allows the simulation of non-terminating reduction sequences known from explicit substitution calculi. In other cases, we succeed in capturing interesting classes of derivations as the normal forms w.r.t. well-behaved combinations of rules. We identify six of these "combined" normal forms, among which are two classes, due to Herbelin and Mints, in bijection with normal, ordinary natural deductions. A computational explanation for the variety of "combined" normal forms is the existence of three ways of expressing multiple application in the calculus.

2006

Exploiting dynamic reconfiguration of platform FPGAs: implementation issues

Autores
Silva, ML; Ferreira, JC;

Publicação
20th International Parallel and Distributed Processing Symposium (IPDPS 2006), Proceedings, 25-29 April 2006, Rhodes Island, Greece

Abstract
The effective use of dynamic reconfiguration requires the designer to address many implementation issues. The market introduction of feature-full platform FPGAs equipped with embedded CPU blocks expands the number of situations where dynamic reconfiguration may be applied to improve overall performance and logic utilization. The paper compares the design of two similar systems supporting dynamic reconfiguration and the issues that were addressed in their implementation. The first system supports 32-bit data transfers between CPU and the dynamically reconfigurable circuits. The other implementation supports 64-bit transfers, but its effective use is more complicated and several restrictions must be taken into account. The work includes a performance comparison of the two designs on several simple tasks, including pattern matching, image processing and hashing. © 2006 IEEE.

2006

Performance evaluation of image segmentation

Autores
Monteiro, FC; Campilho, AC;

Publicação
IMAGE ANALYSIS AND RECOGNITION, PT 1

Abstract
In spite of significant advances in image segmentation techniques, evaluation of these methods thus far has been largely subjective. Typically, the effectiveness of a new algorithm is demonstrated only by the presentation of a few segmented images that axe evaluated by some method, or it is otherwise left to subjective evaluation by the reader. We propose a new approach for evaluation of segmentation that takes into account not only the accuracy of the boundary localization of the created segments but also the under-segmentation and over-segmentation effects, regardless to the number of regions in each partition. In addition, it takes into account the way humans perceive visual information. This new metric can be applied both to automatically provide a ranking among different segmentation algorithms and to find an optimal set of input parameters of a given algorithm.

2006

Lecture Note in Computer Science (including subseries Lecture Note in Artificial Intelligence and Lecture Note in Bioinformatics): Preface

Autores
Lammel, R; Saraiva, J; Visser, J;

Publicação
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Abstract

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