Analysis and design of constant-frequency peak-current-controlled high-power-factor boost rectifier with slope compensation

This paper presents the analysis and the design of a peak-current-controlled high-power-factor boost rectifier, with slope compensation, operating at constant frequency. The input current shaping is achieved, with continuous inductor current mode, with no multiplier to generate a current reference. The resulting overall circuitry is very simple, in comparison with the average-current-controlled boost rectifier. Experimental results are presented, taken from a laboratory prototype rated at 370 W and operating at 67 kHz. The measured power factor was 0.99, with a input current THD equal to 5.6%, for an input voltage THD equal to 2.26%.

Common architecture for discrete wavelet transform analysis and synthesis with sequential and constant processing elements

This paper adresses the problem on processing biological data such as cardiac beats, audio and ultrasonic range, calculating wavelet coefficients in real time, with processor clock running at frequency of present ASIC's and FPGA. The Paralell Filter Architecture for DWT has been improved, calculating wavelet coefficients in real time with hardware reduced to 60%. The new architecture, which also processes IDWT, is implemented with the Radix-2 or the Booth-Wallace Constant multipliers. Including series memory register banks, one integrated circuit Signal Analyzer, ultrasonic range, is presented.

Dynamic analysis of a new piezoelectric flextensional actuator using the J1-J4 optical interferometric method

Piezoelectric actuators are widely used in positioning systems which demand high resolution such as scanning microscopy, fast mirror scanners, vibration cancellation, cell manipulation, etc. In this work a piezoelectric flextensional actuator (PFA), designed with the topology optimization method, is experimentally characterized by the measurement of its nanometric displacements using a Michelson interferometer. Because this detection process is non-linear, adequate techniques must be applied to obtain a linear relationship between an output electrical signal and the induced optical phase shift. Ideally, the bias phase shift in the interferometer should remain constant, but in practice it suffers from fading. The J1-J4 spectral analysis method provides a linear and direct measurement of dynamic phase shift in a no-feedback and no-phase bias optical homodyne interferometer. PFA application such as micromanipulation in biotechnology demands fast and precise movements. So, in order to operate with arbitrary control signals the PFA must have frequency bandwidth of several kHz. However as the natural frequencies of the PFA are low, unwanted dynamics of the structure are often a problem, especially for scanning motion, but also if trajectories have to be followed with high velocities, because of the tracking error phenomenon. So the PFA must be designed in such a manner that the first mechanical resonance occurs far beyond this band. Thus it is important to know all the PFA resonance frequencies. In this work the linearity and frequency response of the PFA are evaluated up to 50 kHz using optical interferometry and the J1-J4 method.

Spectral analysis and low-frequency multipath mitigation for kinematic applications

Low-frequency multipath is still one of the major challenges for high precision GPS relative positioning. In kinematic applications, mainly, due to geometry changes, the low-frequency multipath is difficult to be removed or modeled. Spectral analysis has a powerful technique to analyze this kind of non-stationary signals: the wavelet transform. However, some processes and specific ways of processing are necessary to work together in order to detect and efficiently mitigate low-frequency multipath. In this paper, these processes are discussed. Some experiments were carried out in a kinematic mode with a controlled and known vehicle movement. The data were collected in the presence of a reflector surface placed close to the vehicle to cause, mainly, low-frequency multipath. From theanalyses realized, the results in terms of double difference residuals and statistical tests showed that the proposed methodology is very efficient to detect and mitigate low-frequency multipath effects. © 2008 IEEE.

On the analytical solution for the slewing flexible beam-like system: analysis of the linear part of the perturbed problem

The dynamical system investigated in this work is a nonlinear flexible beam-like structure in slewing motion. Non-dimensional and perturbed governing equations of motion are presented. The analytical solution for the linear part of these perturbed equations for ideal and for non-ideal cases are obtained. This solution is necessary for the investigation of the complete weak nonlinear problem where all nonlinearities are small perturbations around a linear known solution. This investigation shall help the analyst in the modelling of dynamical systems with structure- actuator interactions.

Patellofemoral pain syndrome: Electromyography in a frequency domain analysis

The Patellofemoral Pain Syndrome (PFPS), has a multifactorial etiology and affects approximately 7 to 15% of the population, mostly women, youth, adults and active persons. PFPS causes anterior or retropatelar pain that is exacerbated during functional motor gestures, such as up and down stairs or spending long periods of time sitting, squatting or kneeling. As the diagnostic evaluation of this syndrome is still indirect, different mechanisms and methodologies try to make a classification that distinguishes patients with PFPS in relation to asymptomatic. Thereby, the purpose of this investigation was to determine the characteristics of the electromyographic (EMG) signal in the frequency domain of the vastus medialis oblique (VMO) and vastus lateralis (VL) in patients with PFPS, during the ascent of stairs. 33 young women (22 control group and 11 PFPS group), were evaluated by EMG during ascent of stairs. The VMO mean power frequency (MPF) and the VL frequency 95% (F95) were lower in symptomatic individuals. This may be related to the difference in muscle recruitment strategy exerted by each muscle in the PFPS group compared to the control group.

Allele frequency of hereditary equine regional dermal asthenia in American Quarter horses in Brazil determined by quantitative real-time PCR with high resolution melting analysis

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Analysis of localized muscle fatigue in elderly women with and without a history of falls using electromyographic signal frequency parameters

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Cogeneration design problem Computational complexity analysis and solution through an expert system

Purpose - The purpose of this paper is twofold: to analyze the computational complexity of the cogeneration design problem; to present an expert system to solve the proposed problem, comparing such an approach with the traditional searching methods available.Design/methodology/approach - The complexity of the cogeneration problem is analyzed through the transformation of the well-known knapsack problem. Both problems are formulated as decision problems and it is proven that the cogeneration problem is np-complete. Thus, several searching approaches, such as population heuristics and dynamic programming, could be used to solve the problem. Alternatively, a knowledge-based approach is proposed by presenting an expert system and its knowledge representation scheme.Findings - The expert system is executed considering two case-studies. First, a cogeneration plant should meet power, steam, chilled water and hot water demands. The expert system presented two different solutions based on high complexity thermodynamic cycles. In the second case-study the plant should meet just power and steam demands. The system presents three different solutions, and one of them was never considered before by our consultant expert.Originality/value - The expert system approach is not a "blind" method, i.e. it generates solutions based on actual engineering knowledge instead of the searching strategies from traditional methods. It means that the system is able to explain its choices, making available the design rationale for each solution. This is the main advantage of the expert system approach over the traditional search methods. On the other hand, the expert system quite likely does not provide an actual optimal solution. All it can provide is one or more acceptable solutions.

Analysis of acoustic frequency and wave amplitude generated by the Oscillatory Thoracic Thixotropic Device (Diottix(r)) in human chest

Diottix(r) was calibrated at 25 Hz to achieve the frequency indicated in literature as being effective to mobilize the airways secretions. However, the amplitude and frequency of the waves generated by the equipment in different regions of the chest still need to be investigated. The objective of this study was to analyze the frequency and amplitude of waves generated by Diottix(r) in chests of healthy subjects. Diottix(r) was used in the anterior and posterior regions of the chest. The mechanical waves were captured using stethoscopes connected to electret microphones, which were connected to a digital oscilloscope. Frequency and amplitude data were recorded by the stethoscope, positioned in six points in the anterior region and six in the posterior region of the chest, following the positions commonly used in pulmonary auscultation. Signals were recorded and transferred to a computer with software for their analysis. The frequency of waves did not present a significant change (from 24.9 to 26.4 Hz). The wave amplitude in the anterior versus the posterior region in each area of the lung, the upper, middle and lower, had differences. Diottix(r) produces frequencies in the chest according to the calibrated; thus, it can be a complementary resource to bronchial hygiene maneuvers. The amplitudes of waves seem to be affected by other structures like bone parts and heart.

Analysis of linearity and frequency response of a novel piezoelectric flextensional actuator using a homodyne interferometer and the J(1)-J(4) method

Piezoelectric transducers are widely used in high-resolution positioning systems. This paper reports the experimental analysis of a novel piezoelectric flextensional actuator (PFA), which is designed by using the topology-optimization method through a low-cost homodyne Michelson interferometer. By applying the J(1) - J(4) method for signal demodulation, which provides a linear and direct measurement of dynamic optical phase shift independent of fading, the nanometric displacements of the PFA were determined. Linearity and frequency response of the PFA were evaluated up to 50 kHz. PFA calibration factor and amplification rate were determined for the PFA operating in the quasi-static regime. To confirm the observed frequencies of resonance, an impedance analyzer is also utilized to measure the magnitude and phase of the PFA admittance.

Television violence and young adults in Brazil: a content analysis of the popular telenovella, Malhação = Violência na televisão brasileira e jovens : uma análise de conteúdo da telenovela popular, Malahção

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)