Navegando por CNPq "CNPQ::ENGENHARIAS::ENGENHARIA BIOMEDICA"

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Acesso aberto (Open Access)
Desenvolvimento de métodos de processamento e inteligência computacional no ECG ambulatorial
(Universidade Federal do Pará, 2012-04-26) EVANGELISTA NETO, João; VÁZQUEZ SEISDEDOS, Carlos Román; http://lattes.cnpq.br/5337885650253619; OLIVEIRA, Roberto Célio Limão de; http://lattes.cnpq.br/4497607460894318
Ambulatory monitoring of the electrocardiogram (ECG) allows to follow the patient's daily activities during periods of 24 hours (or more) making possible the study of cases with potentially fatal arrhythmic episodes. However, the major technological challenge that this type of monitoring faces is the loss of information due to the presence movement-related noise and artefacts. The analysis of the QT interval of the surface electrocardiogram or ventricular depolarization and repolarization interval is a non-invasive technique with a high value for the diagnosis and prognostics of cardiopathies and neuropathies, as well as for the prediction of sudden cardiac death. The analysis of the QT-interval standard deviation provides information about the dispersion (time or spatial) of ventricular repolarization. Hovever the presence of noise leads to errors in the detection of the T-wave end, which are non negligible due to small values of QT standard deviation in both pathological and healthy subjects. The main aim of this PhD thesis is to improve ambulatory ECG processing methods using computational intelligence, and specifically those involved in the detection of the T wave end and morphologic recognition of heartbeats, which could invalidate the QT interval variability analysis. A new approach and algorithm was proposed to identify the T-wave end, based on the computation of Trapezium’s areas. The method was validated (in terms of accuracy and repeatability), using signals from the Physionet QT Database. The performance of the proposed method in noisy conditions has been tested and compared with one of the most used approaches for estimating the T-wave end point, based on the threshold on the first derivative. The suggested computational intelligence method combines the features extraction using non-linear principal components analysis method and the multilayer perceptron neural network. The trapezium-based approach showed a good performance in noisy conditions and does not rely on any empirical threshold. It is adequate for use in scenarios where the levels of broadband noise are significant. The beats morphologic recognition methods were evaluated using ambulatory signals with and without artefacts from international prestigious databases, showing a good performance.
Acesso aberto (Open Access)
Estudo e desenvolvimento de um protótipo para redução da interferência de modo comum usando balanceamento dinâmico de impedância aplicado em biosensores e sensores eletroresistivos
(Universidade Federal do Pará, 2013-10-25) NEGRÃO, João Francisco Ribeiro; ARAÚJO, Guilherme Augusto Limeira; http://lattes.cnpq.br/8261564685433904; COSTA JÚNIOR, Carlos Tavares da; http://lattes.cnpq.br/6328549183075122
Electromagnetic interference caused by the electric power line adversely affects the signals of electronic instruments, especially those with low amplitude levels. This type of interference is known as common-mode interference. There are many methods and architectures used to minimize the influence of this kind of interference on electronic instruments, the most common of which is the use of band-reject filters. This paper presents the analysis, development, prototype and test of a new reconfigurable filter architecture for biomedical instruments and measuring data of high complexity fluid flow, such as two phase flows, interference in the measurement circuit may affect the measured data, aiming to reduce the common-mode interference and preserve the useful signal components in the same frequency range as that of the noise, using the technique of dynamic impedance balancing. . Also, any measurement system also suffers interference in the power line frequency (50/60 Hz in Brazil and France, 60Hz in United States of America). The circuit blocks were mathematically modeled and the overall closed-loop transfer function was derived. Then the project was described and simulated in the VHDL_AMS language and also in an electronics simulation software, using discrete component blocks, with and without feedback. After theoretical analysis and simulation results, a prototype circuit was built and tested using as input a signal obtained from ECG electrodes and Resistivity Needle Probes. The results from the experimental circuit matched those from simulation: a 97.6% noise reduction was obtained in simulations using a sinusoidal signal, and an 86.66% reduction was achieved using ECG electrodes in experimental tests. In both cases, the useful signal was preserved. The method and its architecture can be applied to attenuate interferences, which occur in the same frequency band as that of the useful signal components, while preserving these signals.
Acesso aberto (Open Access)
Modelamento matemático de interfaces neurológicas
(Universidade Federal do Pará, 2009) GOMES, Fernando Antonio Pinheiro; DMITRIEV, Victor Alexandrovich; http://lattes.cnpq.br/0684541646225359
The study of de dynamic behavior of the neuron transistor junction has been the aim of several great research centers lately. These studies basically give rise to two mathematical models that describes the neuron transistor junctions: the point contact model and the area contact model. Through the area contact model, this work shows how to obtain solutions of the differential equation that describe the dynamic behavior of the neuron transistor junction using two different analytical methods. In the first method chosen the solution of the differential equation give rise from summation between the solutions of the homogeneous equation and the particular equation. The second choice uses de Green´s functions to obtain the solution of the equation. At last, is proved that the two methods are fully equivalent between each other.
Acesso aberto (Open Access)
Sistema robotizado para reabilitação de acometidos pelo acidente vascular encefálico - AVE
(Universidade Federal do Pará, 2017-08-03) ZAHLAN, Amir Samer; SILVA FILHO, Manoel da; http://lattes.cnpq.br/2032152778116209
Stroke is in the fifth place among the diseases that kill the most in the United States andis also one of the most leading causes of neurological disability in the world. Recently, robotic therapy has been more often used in the rehabilitation of individuals affected by stroke. In some cases, it proves more efficient than conventional therapy. There are few studies about the rehabilitation of the trunk and the equilibrium reactions with seated patient in individuals affected by stroke despite many daily activities are performed in this position. Robotic systems are used on stroke rehabilitation due it is possible to provide a high dosage and intensity of repetitive training aimed at specific activities. We propose a new platform to evaluate the reactions of individuals affected by stroke using robotic technologies. A model was constructed to simulate the movements of the system using pieces machined in plastic. A graphic control interface was developed to generate movement protocols where the physiotherapist can insert the parameters of these movements as commands, such as: angulation, speed and axis of the movement. It was possible to show that the platform moves accordingly to the programmed from repetitive tests of accelerometers data using moving average filter, expecting a precision of up to 1°. It is expected that this device may serve a large number of patients as an alternative in the rehabilitation of the stroke providing a safe and conducive environment for the rehabilitation.