De Carvalho R.L.,Federal University of Tocantins |
Rosa P.F.F.,Brazilian Military Institute of Engineering
IEEE International Symposium on Industrial Electronics | Year: 2010
This work proposes an identification system for smart buildings using footstep information. Basically, the system has three modules: pre-processing, feature extraction and selection, and classification of the information. Gait frequency, spectral envelope, cepstral and mel-cepstral analysis and loudness compose the set of parameters used to identify subjects in the smart building. In order to select features, the Fisher's criterion was used. For the classification task, K-Means and K-NN algorithms were performed along with different methodologies for test and validation. Moreover, the best sets were gathered, increasing the accuracy of classification. Several experiments were performed with 15 subjects wearing 6 different footwear. The classification rates were in the range from 33.5% to 97.5%. © 2010 IEEE.
Nicolalde Rodriguez D.P.,Brazilian Military Institute of Engineering |
Apolinario Jr. J.A.,Brazilian Military Institute of Engineering |
Biscainho L.W.P.,Federal University of Rio de Janeiro
IEEE Transactions on Information Forensics and Security | Year: 2010
This paper addresses a forensic tool used to assess audio authenticity. The proposed method is based on detecting phase discontinuity of the power grid signal; this signal, referred to as electric network frequency (ENF), is sometimes embedded in audio signals when the recording is carried out with the equipment connected to an electrical outlet or when certain microphones are in an ENF magnetic field. After down-sampling and band-filtering the audio around the nominal value of the ENF, the result can be considered a single tone such that a high-precision Fourier analysis can be used to estimate its phase. The estimated phase provides a visual aid to locating editing points (signalled by abrupt phase changes) and inferring the type of audio editing (insertion or removal of audio segments). From the estimated values, a feature is used to quantify the discontinuity of the ENF phase, allowing an automatic decision concerning the authenticity of the audio evidence. The theoretical background is presented along with practical implementation issues related to the proposed technique, whose performance is evaluated on digitally edited audio signals. © 2010 IEEE.
de Oliveira L.F.,Federal University of Rio de Janeiro |
Luporini Menegaldo L.,Brazilian Military Institute of Engineering
Journal of Biomechanics | Year: 2010
EMG-driven models can be used to estimate muscle force in biomechanical systems. Collected and processed EMG readings are used as the input of a dynamic system, which is integrated numerically. This approach requires the definition of a reasonably large set of parameters. Some of these vary widely among subjects, and slight inaccuracies in such parameters can lead to large model output errors. One of these parameters is the maximum voluntary contraction force (Fom). This paper proposes an approach to find Fom by estimating muscle physiological cross-sectional area (PCSA) using ultrasound (US), which is multiplied by a realistic value of maximum muscle specific tension. Ultrasound is used to measure muscle thickness, which allows for the determination of muscle volume through regression equations. Soleus, gastrocnemius medialis and gastrocnemius lateralis PCSAs are estimated using published volume proportions among leg muscles, which also requires measurements of muscle fiber length and pennation angle by US. Fom obtained by this approach and from data widely cited in the literature was used to comparatively test a Hill-type EMG-driven model of the ankle joint. The model uses 3 EMGs (Soleus, gastrocnemius medialis and gastrocnemius lateralis) as inputs with joint torque as the output. The EMG signals were obtained in a series of experiments carried out with 8 adult male subjects, who performed an isometric contraction protocol consisting of 10s step contractions at 20% and 60% of the maximum voluntary contraction level. Isometric torque was simultaneously collected using a dynamometer. A statistically significant reduction in the root mean square error was observed when US-obtained Fom was used, as compared to Fom from the literature. © 2010 Elsevier Ltd.
Zao L.,Brazilian Military Institute of Engineering |
Coelho R.,Brazilian Military Institute of Engineering
IEEE Signal Processing Letters | Year: 2011
This letter proposes a colored noise based multicondition training technique for robust speaker identification in unknown noisy environments. The colored noise samples generation is based on filtering a white Gaussian sequence that leads to a power spectral density (PSD) proportional to 1/f β, where β ε [0, 2]. Gaussian mixture models (GMM) are applied to obtain the speaker models using the noisy speech signals with a single signal-to-noise ratio (SNR). The colored noise based multicondition training is evaluated for the speaker identification task considering the test utterances corrupted with real acoustic noises and different values of SNR. The results show that the proposed technique outperforms the white noise based multicondition and the clean-speech training approaches. © 2011 IEEE.
Franca T.C.C.,Brazilian Military Institute of Engineering
Journal of Biomolecular Structure and Dynamics | Year: 2015
In the last decades, homology modeling has become a popular tool to access theoretical three-dimensional (3D) structures of molecular targets. So far several 3D models of proteins have been built by this technique and used in a great diversity of structural biology studies. But are those models consistent enough with experimental structures to make this technique an effective and reliable tool for drug discovery? Here we present, briefly, the fundamentals and current state-of-the-art of the homology modeling techniques used to build 3D structures of molecular targets, which experimental structures are not available in databases, and list some of the more important works, using this technique, available in literature today. In many cases those studies have afforded successful models for the drug design of more selective agonists/antagonists to the molecular targets in focus and guided promising experimental works, proving that, when the appropriate templates are available, useful models can be built using some of the several software available today for this purpose. Limitations of the experimental techniques used to solve 3D structures allied to constant improvements in the homology modeling software will maintain the need for theoretical models, establishing the homology modeling as a fundamental tool for the drug discovery. © 2014 Taylor & Francis.
Lyon Freire I.,Brazilian Military Institute of Engineering
Journal of the Acoustical Society of America | Year: 2014
This work investigates the direction-of-arrival problem. A time-delay-estimate (TDE) obtained from a peak of a correlation function is subject to two types of error: type I, approximation errors, and type II, errors due to spurious signals. The iterative least-squares algorithm tentatively selects spatially coherent subsets of TDEs containing no type II errors and minor contributions of type I errors ("matched-lags"). Simulations use a seven-microphone array and a gunshot signal. The evaluation methodology is rigorous, comparing empirical distribution functions of estimation error of algorithms through two-sample, one-sided Kolmogorov-Smirnov tests, and quantifying differences with Cohen's D. The direction-of-arrival estimate is improved, specifically at low signal-to-noise ratios. © 2014 Acoustical Society of America.
Silva S.S.C.,Brazilian Military Institute of Engineering |
Silva R.M.P.,Brazilian Military Institute of Engineering |
Pinto R.C.G.,Brazilian Military Institute of Engineering |
Salles R.M.,Brazilian Military Institute of Engineering
Computer Networks | Year: 2013
Botnets, which are networks formed by malware-compromised machines, have become a serious threat to the Internet. Such networks have been created to conduct large-scale illegal activities, even jeopardizing the operation of private and public services in several countries around the world. Although research on the topic of botnets is relatively new, it has been the subject of increasing interest in recent years and has spawned a growing number of publications. However, existing studies remain somewhat limited in scope and do not generally include recent research and developments. This paper presents a comprehensive review that broadly discusses the botnet problem, briefly summarizes the previously published studies and supplements these with a wide ranging discussion of recent works and solution proposals spanning the entire botnet research field. This paper also presents and discusses a list of the prominent and persistent research problems that remain open. © 2012 Elsevier B.V. All rights reserved.
ZaO L.,Brazilian Military Institute of Engineering |
Coelho R.,Brazilian Military Institute of Engineering
IET Signal Processing | Year: 2012
This study proposes a method for generating acoustic noise sequences with different distributions coloured spectra. The noise samples are obtained by passing a non-Gaussian white noise through a finite impulse response filter. The resulting power spectral density is proportional to 1/fβ, where β is a positive power-law exponent. The noise samples pattern is determined by the Kurtosis ratio. The proposed generator is evaluated by comparing real artificial acoustic noises statistics in the time frequency domains. The results show that the generated coloured sequences achieved the PSD decaying rate also the non-Gaussian pattern of the real environmental acoustic noises. © 2012 The Institution of Engineering Technology.
Monteiro S.N.,Brazilian Military Institute of Engineering |
Vieira C.M.F.,State University of the North Fluminense Darcy Ribeiro
Construction and Building Materials | Year: 2014
Recently, the production of bricks from waste materials was reviewed by Zhang in Construction and Building Materials. The main focus was a division into three producing methods: firing, cementing and geopolymerization. Both firing and cementing methods were indicated to consume significant amount of energy and release large quantities of greenhouse gases. Based on these drawbacks and taking into account the need to protect clay resources, it was concluded that geopolymerization seems to be the trend to follow. Most of the reviewed works on the firing method, published since 1987, were related to wastes incorporated into clay ceramics. In the present work, starting from previous review articles, additional information was added to extend the knowledge, not covered by Zhang, on the incorporation of wastes into clay ceramics. The particular case of Brazil, in which large and easy to mine clay deposits support an extensive network of ceramic industries, is surveyed. Fuel containing wastes contribute to save in firing energy, while fluxing wastes improve the ceramic properties. At least for the next decades, clay ceramic incorporation seems to be the most realistic solution for recycling industrial wastes in countries, such as Brazil, with vast clay resources. © 2014 Elsevier Ltd. All rights reserved.
De Abreu C.S.,Brazilian Military Institute of Engineering |
Salles R.M.,Brazilian Military Institute of Engineering
Ad Hoc Networks | Year: 2014
A Delay and Disruption-Tolerant Network (DTN) is a fault-tolerant network where end-to-end connections are not required for message transmissions between nodes. Usually, a DTN is implemented as a wireless mobile ad hoc network that can be applied, for instance, to rapidly build a basic telecommunication infrastructure in case of catastrophes and disasters, or to support communication in a disruptive military environment. It is important to model DTN behavior to better understand system dynamics and related physical laws, which may impact network performance. An accurate model will be useful to support the design of the network in such challenging scenarios and may allow to test design ideas before actually building the real system. This work proposes a mathematical model for message diffusion in epidemical DTN. Our approach is based on previous models for the spread of human epidemical diseases, namely SIR. Simulation results on message diffusion times in an epidemical DTN show that the model is accurate regarding expected values, however large deviations above and below average are also observed on diffusion times. We further study such deviations and provide insights on how to reduce and deal with them, making the model useful for DTN applications. © 2014 Elsevier B.V. All rights reserved.