Analysing on the Quality of Head Tomographic Images with Power Intensity Variation

Arthur Barreto de Rangel Moreira Cavalcanti, Rafael Dueire Lins, Antonio Edsom Carvalho Filho

DOI: 10.14209/sbrt.2010.90

Keywords: Tomography Biomedical image processing Image analysis

Abstract

Tomography is a non-invasive exam technique that provides a great amount of visual information of virtually inaccessible areas of the body. This paper analyses the quality of a set of tomographic images taken with different irradiated power, controlled by current value, searching for the smaller current that can provide sufficient quality images.

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Analyzing the Propagation Features of the Texas eZ430-RF2500 Device

Eurico Moura B. Sobral, Rafael Dueire Lins, Zanoni Dueire Lins

DOI: 10.14209/sbrt.2010.91

Keywords: propagation Texas eZ430-RF2500

Abstract

The Texas eZ430-RF2500 is a new device developed for wireless networking applications. This paper analyzes the propagation features of this device for the several operating modes.

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Gunshot detection in noisy environments

Izabela L. Freire, José A. Apolinário Jr.

DOI: 10.14209/sbrt.2010.92

Keywords: gunshot detection gunshot classification impulsive signals Hidden Markov Models Mel-frequency cepstral coefficients stable distributions linear predictive coding

Abstract

Gunshot detection finds application in the fields of law enforcement, forensic science, and defense (military applications). The first task of a sniper detector, aiming to estimate the direction of arrival of a given gunshot, is to detect automatically the presence of this audio event. Since it is a typical on-line application where a fast response is of paramount importance, a non (computationally) expensive procedure is needed. In a recent work, a simple procedure based on the correlation of the audio signal against a template has proved its efficiency as a gunshot detection algorithm. In this paper, we extend its evaluation to a noisy environment and assess its performance, in gunshot recognition and gunshot detection tasks, comparing it to other more complex methods.

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A New Deblurring Algorithm for Textual Document Images

Daniel M. Oliveira, Rafael Lins, Gabriel P. Silva, Jian Fan, Marcelo Thielo

DOI: 10.14209/sbrt.2010.93

Keywords: Deblurring blur camera documents scanner documents

Abstract

Documents digitalized by portable cameras or flatbed scanners may exhibit some blurred areas. Most deblurring algorithms are hard to implement and slow. Often they try to solve the problem for any kind of image. In the case of text document images, the transition between characters and the paper background has a high contrast. With that in mind, a new algorithm is proposed for deblurring of textual documents; there is no need to estimate the PSF and the filter can be directed applied to the image.

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Applying Markov chains to calculate the probability of saturation in digital IIR filters

José Carlos M. Bermudez, Fernando G. Almeida Neto, Vítor H. Nascimento

DOI: 10.14209/sbrt.2010.22

Keywords: Saturation IIR filters Markov chains finite precision arithmetic

Abstract

We propose a new method to model the effect of finite-precision arithmetic in infinite impulse response (IIR) digital filters. As an application, we use the proposed model to compute the probability of saturation or overflow in IIR filters implemented in fixed-point arithmetic. The transition from the current filter output to the next output is modeled as a firstorder Markov chain. The Markov chain transition probability matrix is then used to evaluate the probabilities of saturation or overflow for first and second-order IIR filters.

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An Evaluation of the Effects of Propagation Channels on the Performance of WiMAX (IEEE 802.16-2004)

Carlos Eduardo Rodrigues de Araújo, Antonio Fischer de Toledo

DOI: 10.14209/sbrt.2010.124

Keywords: WiMAX IEEE 802.16-2004 simulation fading performance ITU-R M.1225 mobility

Abstract

The purpose of this paper is to evaluate the performance of fixed-WiMAX (IEEE 802.16-2004) operating in seven propagation channel models, by implementing a WirelessMAN-OFDM physical layer simulator. Through comparative analysis of BER and throughput, the performance of the specified modulation and coding schemes and adaptive control actions were evaluated. Furthermore, the behavior of fixed-WiMAX subjected to a multipath propagation environment and utilization conditions characterized by both stationary and partially mobile applications was also exploited. Thus, this article provides a complementary vision of the standard, which has enabled the determination of customized values for the SNR levels employed for adaptive control, as well as the determination of the capacity obtainable under conditions of partial mobility.

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