Rangel Arthur

Reliability and validity of digital assessment of perifoveal capillary network measurement using high-resolution imaging

Background Assessment of the perifoveal capillary network (PCN) might indicate macular function and could reflect the systemic microcirculation. The quantification and reliability of this measurement is currently unknown. The aim of this study was to validate quantification of the PCN by a non-invasive technique from high-resolution retinal images. Methods Ten healthy volunteers were included in this validation study. At least 320 high-resolution retinal images were used for assessment of inter- and intra-observer reliability. Non-invasive capillary perfusion mapping was performed using a retinal function imager. After the images were enhanced and segmented, the reproducibility was verified by comparing the values of two independent examiners and of a single examiner at two different time points. Results The inter-observer concordance coefficients were highly significant for PCN (intraclass correlation coefficient (ICC)=0.901, 95% CI 0.655 to 0.975, p<0.001) and normalised PCN (ICC=0.727, 95% CI 0.262 to 0.923, p=0.004). The intra-observer measurements at two different time points were also highly concordant for PCN (ICC=0.879, 95% CI 0.598 to 0.968, p<0.001) and for normalised PCN (ICC=0.960, 95% CI 0.851 to 0.990, p<0.001). Conclusions The reliability of PCN measurement is reproducible and could be used as a new tool to quantify the capillary perfusion network of the macular area.

Analysis of electronic buffers in optical packet/burst switched mesh networks

We present in this paper the study of electronic buffering in an innovative architecture for optical packet/burst switched network (OPSN). This architecture comprises optical bufferless nodes with electronic packet queuing out of the optical layer, deflection routing to perform contention resolution and fully connected mesh topologies under uniform traffic distribution. We demonstrate, by means of simulation, that the studied architecture has a great improvement in performance when we introduce such electronic buffers, which are more efficient when used with the optimized mesh topologies.

Implementation of a fixed-point 2D Gaussian Filter for Image Processing based on FPGA

One of the very useful techniques in Image Processing is the 2D Gaussian Filter, especially when smoothing images. However, the implementation of a 2D Gaussian Filter requires heavy computational resources, and when it comes down to real-time applications, efficiency in the implementation is vital. Floating-point math represents an obstacle for this, as its implementation requires a large amount of computational power in order to achieve real-time image processing. On the other hand, a fixed-point approach is much more suitable; implementation of a 2D Gaussian Filter in FPGA using fixed-point arithmetic provides efficiency in the processing and reduction in computational costs. The purpose of this study is to present the FPGA resource usage for different sizes of Gaussian Kernel; to provide a comparison between fixed-point and floating point implementations; and to define the amount of bits are necessary to use in order to have a Root Mean Square Error (RMSE) below 5%.

Estudo do amortecimento do pêndulo simples: uma proposta para aplicação em laboratório de ensino

The pendula are largely used in teaching activities of physical introductory courses. Often, in these activities an ideal model is used to study the behavior of the pendulum. In this work a model that takes into account the oscillation damping is suggested. An experimental methodology is purposed aiming to detect the falling down of oscillation amplitude and to fit these data to a mathematical model. The results show that the simple pendulum, set up by a small volume sphere and oscillating on low speed, can be studied with simplified models. The methodology and the mathematical model are appropriated for the knowledge level of the students from physic introductory courses and offer a more realistic insight about the pendulum behavior.

Remote instrumentation control and monitoring based on LabVIEW and SMS

Remote applications are becoming widely used in various fields such as industry, education, and security. This paper presents a low cost system to monitor and control laboratory instruments remotely by Short Message Service (SMS). The system has been designed using the National Instruments Laboratory Virtual Instrument Engineering Workbench (LabVIEW) development system. The user sends commands using a mobile phone remotely connected to a modem. The software recognizes the received code and transmits the command to the instrument. The system was successfully tested locally and remotely in a signal measurement procedure.

ISDB-Tb field trials and coverage measurements with gap-filler in suburban environments

The expansion of digital television in South America and Africa demand new cheaper solutions for the coverage problem. The use of gap-fillers and SFN are very important instruments to design broadcasting television. Many countries start trials and tests according their particularities. The solutions found are been related in papers and make a valuable acknowledge for future projects related. Comparison between field application and coverage prediction software optimize the results of broadcasting network. This paper presents the results of a field measurement with Gap-Filler in suburban environment. This paper presents the results of a field measurement and a description of implantation of a Gap-Filler in suburban environment‥

Expansion Planning of the Digital TV Broadcasting Service in Brazil using SFN

This work aims to discuss briefly the relevant technical aspects for introduction and expansion of Digital TV retransmission services based on OFDM Multiplexing. The initial channel allocation, proposed for introduction of Digital TV in Brazil, will carry the spectral overload problems of the current analogical systems.The use of single frequency networks (SFN) appears as an efficient solution for channel allocation.

Maps of distances for evaluating the tracking and measurement of electrical arcs by 3D-snake

This paper presents a 3D reconstruction (by 3D-snake) of the longitudinal axis of an electrical arc (discharge) in evolution based on stereo pairs of images. The accuracy of such tracking depends strongly on the halting of the iterative relaxation process that adjusts the 3D-snake. The key aspect to make such decision is detecting when each projection of the 3D-snake matches special features in the pair of images. For this sake, this paper proposes a simple and effective strategy based on the projection matrices of the cameras and tables named Maps of Distances (MDs) which are obtained by image processing.

Performance comparison of convolutional and turbo convolutional codes for ISDB-T in AWGN and Brazilian channels

This work intends to demonstrate the improvements applied in the integrated system digital broadcasting-terrestrial (ISDB-T). The turbo processing has been considered one of the most promising techniques for the improvement of performance in communication systems. The use of turbo convolutional codes (TCCs) combined with soft decision demapping is proposed for reduction of signal to noise rate (SNR) threshold at reception. Some simulations are done using AWGN and typical multipath Brazilian channels. Therefore, it is concluded that the proposed Turbo ISDB-T performance is better than the conventional ISDB-T in those cases.

Improving DVB-T for Brazilian environments

In this paper the improvement in the performance obtained by a Time Interleaving applied to DVB-T scheme are analyzed in impulsive noise environments. The performance is evaluated in terms of bit error rate probability for Oms, 100 ms and 200 ms of time interleaving length. The results are compared with the standard DVB-T (digital video broadcasting - terrestrial) evaluated on Impulsive Noise channel and Multipath combined with impulsive noise channel. Simulation results shows that employing Time Interleaving only with 100 ms the overall system performance can improve significantly. These results are obtained applying an appropriate interleaving after the Mapper of DVB-T system.