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Publicações

Publicações por CTM

2008

Analyzing TDMA With Slot Skipping

Autores
Andersson, B; Pereira, N; Tovar, E;

Publicação
IEEE TRANSACTIONS ON INDUSTRIAL INFORMATICS

Abstract
Distributed real-time system, such as factory automation systems, require that computer nodes communicate with a known and low hound on the communication delay. This can be achieved with traditional time division multiple access (TDMA). But improved flexibility and simpler upgrades are possible through the use of TDMA with slot-skipping (TDMA/SS), meaning that a slot is skipped whenever it is not used and consequently the slot after the skipped slot starts earlier. We propose a schedulahility analysis for TDMA/SS. We assume knowledge of all message streams in the system, and that each node schedules messages in its output queue according to deadline monotonic. Firstly, we present a non-exact (but fast) analysis and then, at the cost of computation time, we also present an algorithm that computes exact queuing times.

2008

How a cyber-physical system can efficiently obtain a snapshot of physical information even in the presence of sensor faults

Autores
Andersson, B; Pereira, N; Tovar, E;

Publicação
PROCEEDINGS OF THE SIXTH INTERNATIONAL WORKSHOP ON INTELLIGENT SOLUTIONS IN EMBEDDED SYSTEMS

Abstract
We present a distributed algorithm for cyber-physical systems to obtain a snapshot of sensor data. The snapshot is an approximate representation of sensor data; it is an interpolation as a function of space coordinates. The new algorithm exploits a prioritized Medium Access Controll (MAC) protocol to efficiently transmit information of the sensor data. It scales to a very large number of sensors and it is able to operate in the presence of sensor faults.

2008

A simple mixture to enhance muscle transmittance

Autores
Oliveira, L; Lage, A; Clemente, MP; Tuchin, VV;

Publicação
OPTICAL TECHNOLOGIES IN BIOPHYSICS AND MEDICINE IX

Abstract
Skeletal muscle is a fibrous tissue composed by muscle fibers and interstitial fluid. Due to this constitution, the muscle presents a non uniform refractive index profile that origins strong light scattering. One way to improve tissue transmittance is to reduce this refractive index mismatch by immersing the muscle in an optical clearing agent. As a consequence of such immersion tissue also suffers dehydration. The study of the optical clearing effect created by a simple mixture composed by ethanol, glycerol and distilled water has proven its effectiveness according to the variations observed in the parameters under study. The effect was characterized in terms of its magnitude, time duration and histological variations. The applied treatment has created a small reduction of the global sample refractive index that is justified by the long time rehydration caused by water in the immersing solution. From the reduction in sample pH we could also identify the dehydration process created in the sample. The immersion treatment has originated fiber bundle contraction and a spread distribution of the muscle fiber bundles inside. New studies with the mixture used, or with other combinations of its constituents might be interesting to perform with the objective to develop new clinical procedures.

2007

Design of circuits and integrated systems

Autores
Teixeira, JP; Matos, JS; Tomas, J; Teixeira, IC;

Publicação
IET COMPUTERS AND DIGITAL TECHNIQUES

Abstract

2007

Optimum receivers for non-linear distortion compensation of OFDM signals in fiber supported wireless applications

Autores
Oliveira, JMB; Rodrigues, MRD; Salgado, HM;

Publicação
2007 INTERNATIONAL TOPICAL MEETING ON MICROWAVE PHOTONICS

Abstract
In this paper, we study the performance of the optimum receiver for nonlinear distorted OFDM signals in RoF applications, which is composed by a demodulator followed by an ML detector. The demodulator observes the various intermodulation products to compute a set of sufficient statistics, while the detector observes the sufficient statistics to compute an estimate of the original data. Particularly, we concentrate on the uplink of intensity modulation/direct detection RoF system where the OFDM signal suffers from linear distortion (fading), nonlinear distortion and noise. We demonstrate that the optimum receiver outperforms the conventional OFDM receiver by several orders of magnitude.

2007

Low-pass filter design using two overlapped periodic EBG structures with low spurious responses

Autores
Lima, NB; Miranda, HC; Pereira, JR; Salgado, HM;

Publicação
2007 International Conference on Electromagnetics in Advanced Applications, ICEAA'07

Abstract
This paper presents the design of a low-pass microwave filter based on the EBG (Electromagnetic Bandgap) concept. The structure is composed of a microstrip line in one of the layers and two different periodic superimposed EBG structures in the ground plane. The first structure defines the characteristics of the filter in the pass-band whereas the second periodic structure is used to reduce the second harmonic spurious response. The filter exhibits a flat pass-band response and a cut-off rate better than 380 dB/octave. © 2007 IEEE.

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