2008
Autores
Frazao, O; Egypto, D; Aragao Bittencourt, L; Giraldi, MTMR; Marques, MB;
Publicação
IEEE PHOTONICS TECHNOLOGY LETTERS
Abstract
This work presents a method to tune the sensitivity of the sensor in a highly birefringent erbium-doped fiber loop mirror (FLM) when it is pumped. This concept was used for simultaneous measurement of strain and temperature. The FLM is sequentially pumped and unpumped by a high pump laser at 980 nm to change the erbium-doped fiber properties. The sensing head changes its sensitivity when subjected to strain and/or temperature variations due to thermal effects originated by the pump laser.
2008
Autores
Magalhaes, F; Carvalho, JP; Ferreira, LA; Araujo, FM; Santos, JL;
Publicação
Proceedings of IEEE Sensors
Abstract
An optoelectronic system for detection and monitoring of methane has been developed and implemented. The signal processing technique used in the proposed system is based on Wavelength Modulation Spectroscopy (WMS). When associated with the revolutionary microstructured fibres, this scheme revealed an effective way to measure gas concentration. Aiming the optimization of the sensing head design, the methane diffusion time inside a hollow-core fibre was evaluated. An error of 2.8% between experimental and theoretical values was obtained, thus validating the adopted model. These results were very encouraging towards the implementation of a practical unit for remote gas monitoring applications. © 2008 IEEE.
2008
Autores
Wu, AY; Gonzalez Aguilar, G; Vilarinho, PM; Salvado, IMM; Costa, MEV;
Publicação
JOURNAL OF ELECTROCERAMICS
Abstract
The comparison of macroscopic and microscopic properties of ferroelectric thin films in the systems of lead zirconate titanate (PZT) and strontium bismuth tantalate (SBT) with and without seeds is carried out. Microscopic properties were studied by piezo-response force microscopy (PFM). The local piezoelectric properties with and without seeds are compared with their macroscopic electric properties measured by conventional techniques. Previous microstructure analysis of PZT thin films showed that an intermetallic Pt(x)Pb layer between PZT and Pt, formed during the annealing process, was reduced and even eliminated in seeded PZT films. In SBT films, the addition of SBT seeds suppressed the interdiffusion of Pt and film components. Hence, the interfaces of PZT/substrate and SBT/substrate are modified by the presence of seeds, and their electrical properties are improved. In both PZT and SBT films, the remanent polarization values are higher in seeded films than in unseeded ones. Similarly, local piezo-response signal of single grain showed higher longitudinal piezoelectric coefficient d(33) in seeded films than in unseeded ones. The critical voltage in which the ferroelectric domain starts to switch is lower in seeded films than in unseeded ones. The analysis of nanoscale switching in PZT and SBT films by PFM is presented and related to the corresponding macroscopic electric properties.
2008
Autores
Silva, ML; Ferreira, JC;
Publicação
2008 INTERNATIONAL CONFERENCE ON FIELD PROGRAMMABLE AND LOGIC APPLICATIONS, VOLS 1 AND 2
Abstract
The paper presents a method for generating partial bitstreams on-line for use in systems with run-time reconfigurable FPGAs. Bitstream creation is performed at run-time by merging partial bitstreams from individual component modules. The process includes the capability to create connections between the modules by selection from a set of routes found during an off-line pre-processing step. Placement and interconnection of modules must follow a precise set of rules. While restricting the number of possible module arrangements, this approach allows bitstream, creation to be performed with relatively few computational resources. Using a demonstration system with a Virtex-II Pro FPGA with a PowerPC 405 CPU, the process of creating at run-time a partial bitstream for 22% of the device area takes 24 ms.
2008
Autores
Massink, M; Latella, D; Ter Beek, MH; Harrison, MD; Loreti, M;
Publicação
Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)
Abstract
The analysis of usability aspects of multi-user systems, such as co-operative work systems and pervasive systems, pose particular problems because group behavior of their users may have considerable impact on usability. Model-based analysis of such features leads to state-space explosion because of the sheer number of entities to be modeled when automatic techniques such as model checking are used. In this paper we explore the use of a recently proposed scalable model-based technique based on solving sets of Ordinary Differential Equations (ODEs). Starting from a formal model specified using the Performance Evaluation Process Algebra (PEPA), we show how different groupware usage patterns may be modeled and analyzed using this approach. We illustrate how the approach can explore different design options and their impact on group behavior by comparing file access policies in the context of a groupware application. © 2008 Springer Berlin Heidelberg.
2008
Autores
Sousa, AV; Mendonca, AM; Campilho, A;
Publicação
IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING
Abstract
In this paper, we propose and evaluate methodologies for the classification of images from thin-layer chromatography. Each individual sample is characterized by an intensity profile that is further represented into a feature space. The first steps of this process aim at obtaining a robust estimate of the intensity profile by filtering noise, reducing the influence of background changes, and by fitting a mixture of Gaussians. The resulting profiles are represented by a set of appropriate features trying to characterize the state of nature, here spread out over four classes, one for normal subjects and the other three corresponding to lysosomal diseases, which are disorders responsible for severe nerve degeneration. For classification purposes, a novel solution based on a hierarchical structure is proposed. The main conclusion of this paper is that an automatically generated decision tree presents better results than more conventional solutions, being able to deal with the natural imbalance of the data that, as consequence of the rarity of lysosomal disorders, has very few representative cases in the disease classes when compared with the normal population.
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