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‣ Análise espectral de sinais atriais e sua correlação topográfica com a inervação parassimpática cardíaca; Spectral analysis of atrial signals and its topographic correlation with cardiac parassimpathetic innervation

Rivarola, Esteban Wisnivesky Rocca
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 22/08/2011 Português
Relevância na Pesquisa
66.80194%
Objetivo. Verificar se as características espectrais dos eletrogramas atriais (EgA) em ritmo sinusal (RS) se correlacionam com a presença de gânglios parassimpáticos cardíacos. Materiais e Resultados. Treze pacientes encaminhados para submeter-se a ablação de fibrilação atrial (FA) foram incluídos de forma prospectiva. Previamente ao início da ablação, realizou-se o registro de EgA em RS em uma série de regiões anatômicas pré-determinadas, seguindo-se uma ordem sequencial. Em seguida, aplicou-se estímulos elétricos de alta frequência (20 Hz de frequência, amplitude de 100 V e duração de pulso de 4 ms), nos mesmos locais. Uma resposta vagal evocada foi definida como um súbito aumento no intervalo RR ou a indução de bloqueio na condução átrio-ventricular imediatamente após a aplicação do estímulo de alta-frequência (EAF). Procedeu-se à análise espectral dos sinais atriais em RS registrados, com amostragem de 1000 Hz, janela Hanning. No total, 1488 EgA oriundos de 186 locais anatômicos foram registrados, sendo 129 de regiões com resposta vagal negativa e 57 correspondentes a regiões de resposta vagal positiva. A duração do eletrograma e o número de deflecções foram similares nos pontos com resposta vagal positiva e negativa. A densidade de potência espectral em locais de resposta vagal positiva...

‣ Spectral analysis of the electromyograph of the erector spinae muscle before and after a dynamic manual load-lifting test

Cardozo, A.C.; Gonçalves, M.; Gauglitz, A.C.F.
Fonte: Associação Brasileira de Divulgação Científica (ABRADIC) Publicador: Associação Brasileira de Divulgação Científica (ABRADIC)
Tipo: Artigo de Revista Científica Formato: 1081-1085
Português
Relevância na Pesquisa
66.64161%
The aim of the present study was to assess the spectral behavior of the erector spinae muscle during isometric contractions performed before and after a dynamic manual load-lifting test carried out by the trunk in order to determine the capacity of muscle to perform this task. Nine healthy female students participated in the experiment. Their average age, height, and body mass (± SD) were 20 ± 1 years, 1.6 ± 0.03 m, and 53 ± 4 kg, respectively. The development of muscle fatigue was assessed by spectral analysis (median frequency) and root mean square with time. The test consisted of repeated bending movements from the trunk, starting from a 45º angle of flexion, with the application of approximately 15, 25 and 50% of maximum individual load, to the stand up position. The protocol used proved to be more reliable with loads exceeding 50% of the maximum for the identification of muscle fatigue by electromyography as a function of time. Most of the volunteers showed an increase in root mean square versus time on both the right (N = 7) and the left (N = 6) side, indicating a tendency to become fatigued. With respect to the changes in median frequency of the electromyographic signal, the loads used in this study had no significant effect on either the right or the left side of the erector spinae muscle at this frequency...

‣ Controle e monitoramento em tempo real do regime de jorro estavel atraves da analise espectral; Control and monitoring on line of the steady regime in the spouted bed process by spectral analysis

Paula Edilene Pavanelli
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 15/09/2006 Português
Relevância na Pesquisa
66.681216%
Este trabalho apresenta o controle e monitoramento em tempo real do regime de jorro estável através do método de identificação dos regimes de contato gás-sólido por medidas de pressão no leito de jorro. O trabalho foi realizado em duas etapas: 1) identificação em tempo real dos regimes fluidodinâmicos no processo em leito de jorro baseada na análise espectral das flutuações de queda de pressão do leito e 2) controle do processo em regime estável por malha PI. O sistema constitui-se de um leito construído em acrílico com dimensões de 0,70m de altura de coluna e 0,143m de diâmetro interno, operando com três diferentes partículas, esferas de vidro (dp = 2,59mm e Pp = 2,487 g/cm3), poliestireno (dp = 2,19mm e Pp = 1,196 g/cm3) e ABS (dp = 3,08mm e Pp = 1,029 g/cm3). Determinou-se a faixa da freqüência dominante 7,2-7,9 Hz, característico do regime de jorro estável, através do algoritmo da Transformada Rápida de Fourier (FFT) para cada partícula. Todas as medidas de pressão do leito durante o processo foram coletadas pelo sistema de aquisição através da placa PCI 6024E (National Instruments) utilizando o software LabView 7.1TM. Com o intuito de controlar o regime de jorro estável no processo em leito de jorro foram definidas como variáveis controlada e manipulada a freqüência dominante do espectro de potência (Hz) e o sinal de comando para o inversor de freqüência (V)...

‣ Controle do regime fluidodinâmico estável durante o processo de umedecimento de inertes em leito de jorro utilizando análise espectral; Control of fluid dynamics regime in spouted bed wetting process using spectral analysis

José Júnior Butzge
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 30/08/2012 Português
Relevância na Pesquisa
66.77511%
A técnica do leito de jorro têm sido utilizada em diversos processos industriais e com maior ênfase nos setores químico, alimentício e farmacêutico, visto que apresenta como principais vantagens excelentes taxas de transferência de calor e massa. Contudo, tais características estão diretamente condicionadas à manutenção do regime de jorro estável, sendo, portanto, um ponto crítico de controle e objetivo operacional que deve ser satisfeito. Em geral, as condições operacionais executadas durante a secagem de pastas em leito de jorro produzem uma atmosfera interna com elevado conteúdo de umidade devido à aspersão de líquidos, promovendo notória dificuldade de operação e manutenção do regime fluidodinâmico desejado neste tipo de processo. Uma forma de superar os problemas efetivos associados à dificuldade de manutenção do regime de jorro estável é através da engenharia de controle e automação de processos. Dentro deste contexto e objetivando a manutenção do regime dinâmico estável durante o processo de umedecimento de inertes em leito de jorro, utilizou-se a metodologia de análise espectral dos sinais de flutuação de queda de pressão no leito para estudar o comportamento dos regimes fluidodinâmicos e implementar uma estratégia de monitoramento e controle do processo. Como partículas inertes foram utilizadas microesferas de vidro...

‣ Determination of background concentrations for air quality models using spectral analysis and filtering of monitoring data

Tchepel, O.; Costa, A. M.; Martins, H.; Ferreira, J.; Monteiro, A.; Miranda, A. I.; Borrego, C.
Fonte: Elsevier Publicador: Elsevier
Tipo: Artigo de Revista Científica
Português
Relevância na Pesquisa
66.681216%
The use of background concentrations in air pollution modelling is usually a critical issue and a source of errors. The current work proposes an approach for the estimation of background concentrations using air quality measured data decomposed on baseline and short-term components. For this purpose, the spectral density was obtained for air quality monitoring data based on the Fourier series analysis. After, short-term fluctuations associated with the influence of local emissions and dispersion conditions were extracted from the original measurements using an iterative moving-average filter and taking into account the contribution of higher frequencies determined from the spectral analysis. The deterministic component obtained by the filtering is characterised by wider spatial and temporal representativeness than original monitoring data and is assumed to be appropriate for establishing the background values. This methodology was applied to define background concentrations of particulate matter (PM10) used as input data for a local scale CFD model, and compared with an alternative approach using background concentrations provided by a mesoscale air quality modelling system. The study is focused on a selected domain within the Lisbon urban area (Portugal). The results present a better performance for the microscale model when initialised by decomposed time series and demonstrate the importance of the proposed methodology in reducing the uncertainty of the model predictions. The decomposition of air quality measurements and the removal of short-term fluctuations discussed in the work is a valuable technique to determine representative background concentrations.

‣ Onset of Nucleate Boiling and Onset of Fully Developed Subcooled Boiling Using Pressure Transducers Signals Spectral Analysis

Castro,Alfredo José Alvim de; Maprelian,Eduardo; Ting,Daniel Kao Sun
Fonte: The Brazilian Society of Mechanical Sciences Publicador: The Brazilian Society of Mechanical Sciences
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/01/2001 Português
Relevância na Pesquisa
66.62756%
The experimental technique used for detection of subcooled boiling through analysis of the fluctuation contained in pressure transducer signals is presented. This work was partly conducted at the Institut für Kerntechnik und zertörungsfreie Prüfverfahren von Hannover (IKPH, Germany) in a thermal-hydraulic circuit with one electrically heated rod with annular geometry test section. Piezoresistive pressure sensors are used for onset of nucleate boiling (ONB) and onset of fully developed boiling (OFDB) detection using spectral analysis/ signal correlation techniques. Experimental results are interpreted by phenomenological analysis of these two points and compared with existing correlation. The results allow us to conclude that this technique is adequate for the detection and monitoring of the ONB and OFDB.

‣ Spectral analysis of the electromyograph of the erector spinae muscle before and after a dynamic manual load-lifting test

Cardozo,A.C.; Gonçalves,M.; Gauglitz,A.C.F.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/07/2004 Português
Relevância na Pesquisa
66.64161%
The aim of the present study was to assess the spectral behavior of the erector spinae muscle during isometric contractions performed before and after a dynamic manual load-lifting test carried out by the trunk in order to determine the capacity of muscle to perform this task. Nine healthy female students participated in the experiment. Their average age, height, and body mass (± SD) were 20 ± 1 years, 1.6 ± 0.03 m, and 53 ± 4 kg, respectively. The development of muscle fatigue was assessed by spectral analysis (median frequency) and root mean square with time. The test consisted of repeated bending movements from the trunk, starting from a 45º angle of flexion, with the application of approximately 15, 25 and 50% of maximum individual load, to the stand up position. The protocol used proved to be more reliable with loads exceeding 50% of the maximum for the identification of muscle fatigue by electromyography as a function of time. Most of the volunteers showed an increase in root mean square versus time on both the right (N = 7) and the left (N = 6) side, indicating a tendency to become fatigued. With respect to the changes in median frequency of the electromyographic signal, the loads used in this study had no significant effect on either the right or the left side of the erector spinae muscle at this frequency...

‣ A spectral analysis of the myoelectric activity of the left colon in patients with schistosomiasis mansoni

Ferraz,A.A.B.
Fonte: Associação Brasileira de Divulgação Científica Publicador: Associação Brasileira de Divulgação Científica
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/05/2005 Português
Relevância na Pesquisa
66.60073%
The objective of the present study was to perform a spectral analysis of the electrical activity of the left colon of patients with hepatosplenic schistosomiasis. Thirty patients were studied, divided into 2 groups: group A was composed of 14 patients (9 males and 5 females) with hepatosplenic schistosomiasis and group B was composed of 16 female patients without schistosomiasis mansoni. Three pairs of electrodes were implanted in the left colon at the moment of the surgical treatment. The signals of the electric activity of the colon were captured after postoperative recovery from the ileus and fed into a computer by means of a DATAQ data collection system which identified and captured frequencies between 0.02 and 10 Hz. Data were recorded, stored and analyzed using the WINDAQ 200 software. For electrical analysis, the average voltage of the electrical wave in the three electrodes of all patients, expressed as millivolts (mV), was considered, together with the maximum and minimum values, the root mean square (RMS), the skewness, and the results of the fast Fourier transforms. The average RMS of the schistosomiasis mansoni patients was 284.007 mV. During a long period of contraction, the RMS increased in a statistically significant manner from 127.455 mV during a resting period to 748.959 mV in patients with schistosomiasis mansoni. We conclude that there were no statistically significant differences in RMS values between patients with schistosomiasis mansoni and patients without the disease during the rest period or during a long period of contraction.

‣ Leak detection in pipelines through spectral analysis of pressure signals

Souza,A.L.; Cruz,S.L.; Pereira,J.F.R.
Fonte: Brazilian Society of Chemical Engineering Publicador: Brazilian Society of Chemical Engineering
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2000 Português
Relevância na Pesquisa
66.681216%
The development and test of a technique for leak detection in pipelines is presented. The technique is based on the spectral analysis of pressure signals measured in pipeline sections where the formation of stationary waves is favoured, allowing leakage detection during the start/stop of pumps. Experimental tests were performed in a 1250 m long pipeline for various operational conditions of the pipeline (liquid flow rate and leakage configuration). Pressure transients were obtained by four transducers connected to a PC computer. The obtained results show that the spectral analysis of pressure transients, together with the knowledge of reflection points provide a simple and efficient way of identifying leaks during the start/stop of pumps in pipelines.

‣ EMG spectral analysis of incremental exercise in cyclists and non-cyclists using Fourier and Wavelet transforms

Vitor-Costa,Marcelo; Bortolotti,Henrique; Camata,Thiago Viana; Cardoso,Jefferson Rosa; Silva,Rubens Alexandre da; Abrão,Taufik; Moraes,Antonio Carlos de; Altimari,Leandro Ricardo
Fonte: Universidade Federal de Santa Catarina Publicador: Universidade Federal de Santa Catarina
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2012 Português
Relevância na Pesquisa
66.64161%
The aim of this study was to compare the electromyographic indices of fatigue (slope of median frequency) calculated with the fast Fourier transform (FFT) and wavelet transform (WT) in trained and untrained individuals during cycle exercise. A second objective was to compare the variance of the spectral parameters (median frequency - MF) obtained by the FFT and WT during exercise. Twelve cyclists and non-cyclists performed a maximal incremental test to determine the peak power (Wp) and electromyographic activity of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), semitendinous (ST) and tibialis anterior (TA). Mean values of median frequency, determined by the FFT and WT, were used for the spectral analysis of the electromyographic signals of the studied muscles. The analyzed parameters were obtained for each time period corresponding to 0, 25, 50, 75, and 100% of total duration of the maximal incremental test. No statistically significant differences were found in the values of MF and electromyographic indices of fatigue between the two techniques (FT and WT) both in the cyclists and non-cyclists group (P>0.05). Regarding the MF variance, statistically significant differences were found in all analyzed muscles...

‣ Spatio-spectral analysis on the unit sphere

Khalid, Zubair
Fonte: Universidade Nacional da Austrália Publicador: Universidade Nacional da Austrália
Tipo: Thesis (PhD); Doctor of Philosophy (PhD)
Português
Relevância na Pesquisa
66.99985%
This thesis is focussed on the development of new signal processing techniques to analyse signals defined on the sphere. Analysis and processing of signals defined on the sphere find applications in various fields of science and engineering, such as cosmology, geophysics and medical imaging. The objective to develop new signal processing methods is served by formulating, extending and tailoring existing Euclidean domain signal processing theories in ways that they become suitable for analysis of signals defined on the sphere. The first part of this thesis develops a new type of convolution between two signals on the sphere. This is the first type of convolution on the sphere which is commutative. Two other advantages, in comparison with existing definitions in the literature, are that the new convolution admits anisotropic filters and signals and the domain of the output remains on the sphere. The spectral analysis of the convolution is provided and a fast algorithm for efficient computation of convolution output is developed. The second part of the thesis is focused on the development of signal processing techniques to analyse signals on the sphere in joint spatio-spectral~(spatial-spectral) domain. A transform analogous to short-time Fourier transform(STFT) in time-frequency analysis is formulated for signals defined on the sphere...

‣ Spektralanalyse im Virtuellen Observatorium; Spectral Analysis in the Virtual Observatory

Müller-Ringat, Ellen
Fonte: Universidade de Tubinga Publicador: Universidade de Tubinga
Tipo: Dissertação
Português
Relevância na Pesquisa
66.90777%
Anfang des Jahrtausends wurde das Virtuelle Observatorium (VO) gegründet, dessen Ziel es ist astronomische Daten über das Internet zugänglich zu machen, Standards für eine einheitliche Verarbeitung zu definieren und intuitiv zu bedienende Analysewerkzeuge zu entwickeln. Im Rahmen eines German Astrophysical Virtual Observatory (GAVO) Projekts wurden vom Institut für Astronomie und Astrophysik Tübingen (IAAT) VO-Dienste entwickelt, über die theoretische Sternspektren über das Internet zur Verfügung gestellt werden und Spektralanalyse jedem ermöglicht wird. Der Nutzer kann bereits berechnete synthetische Spektren über den TheoSSA-Dienst herunterladen. Für genauere Analysen können über den TMAW-Dienst individuelle Spektren erzeugt werden. Erfahrene Nutzer können die zugrunde liegenden Atomdaten aus der TMAD-Datenbank herunterladen. Die vorliegende Arbeit beschäftigt sich mit der Weiterentwicklung dieser Dienste. Dafür wurden sowohl die bestehenden Dienste erweitert als auch neue Dienste erzeugt und diese in Spektralanalysen angewandt. TIRO: Mit diesem neu entwickelten Dienst kann der VO-Nutzer individuelle Querschnitte und Modellatome für Eisengruppenelemente berechnen lassen. Die Berücksichtigung der Eisengruppenelemente in der Spektralanalyse erfolgt aufgrund ihrer Vielzahl an Energieniveaus und zugehörigen Linienübergängen nicht analog zu anderen Elementen. Ein statistisches Verfahren ist nötig...

‣ Terms of trade cycles in extreme land abundant countries, 1870-2009. Spectral analysis

Arrufat, José Luis; Martín Díaz Cafferata, Alberto; Viceconte, José Antonio
Fonte: Universidad de Alcalá. Instituto Universitario de Análisis Económico y Social Publicador: Universidad de Alcalá. Instituto Universitario de Análisis Económico y Social
Tipo: Trabalho em Andamento Formato: application/pdf
Português
Relevância na Pesquisa
66.696133%
Spectral analysis is applied to the empirical identification of terms of trade cycles, in the secular evolution, 1870-2009, of a group of extreme-land-abundant countries: Argentina, Australia, Canada, New Zealand, and Uruguay. Estimates of the power density spectrum functions produce statistically significant spectral peaks associated with long-run cycle periods between 24 and 56 years, with a mode of about 28 years for all five countries, and the variance decomposition shows that these long-run cycles account for a very substantial fraction, between 68% and 83%, of the TOT total variance. These results are very robust to changes in the choice of truncation lag, as well as to the type of spectral window (Parzen and Bartlett) used in the estimations.; Mediante aplicación del análisis espectral se descompone el ciclo empírico de los términos de intercambio en ciclos teóricos periódicos, para un grupo de países que denominamos “de extrema abundancia de tierra”. Para Argentina, Australia, Nueva Zelanda y Uruguay en el período 1870-2009 las funciones de densidad espectral identifican picos correspondientes a ciclos de largo plazo de sus términos de intercambio de entre 24 y 56 años, con una media de 28 años. La descomposición de la varianza indica que tales movimientos cíclicos de largo plazo explican una fracción sustancial de entre el 68% y el 83% de la varianza total. Los resultados estadísticos son robustos a la elección de los parámetros y del tipo de ventana espectral...

‣ A robust support vector algorithm for nonparametric spectral analysis

Rojo-Álvarez, José Luis; Martínez-Ramón, Manel; Figueiras-Vidal, Aníbal R.; García-Armada, Ana; Artés-Rodríguez, Antonio
Fonte: IEEE Publicador: IEEE
Tipo: info:eu-repo/semantics/acceptedVersion; info:eu-repo/semantics/article Formato: application/pdf; text/plain
Publicado em /11/2003 Português
Relevância na Pesquisa
66.64161%
A new approach to the nonparametric spectral estimation on the basis of the support vector method (SVM) framework is presented. A reweighted least squared error formulation avoids the computational limitations of quadratic programming. The application to a synthetic example and to a digital communication problem shows the robustness of the SVM spectral analysis algorithm.

‣ Identification of random loads impinging on the RAH-66 Comanche Helicopter empennage using spectral analysis

Mason, Patrick H.
Fonte: Monterey, California. Naval Postgraduate School Publicador: Monterey, California. Naval Postgraduate School
Tipo: Tese de Doutorado Formato: viii, 146 p.;28 cm.
Português
Relevância na Pesquisa
66.70804%
Approved for public release; distribution is unlimited; The Army RAH-66 ComancheHelicopter is currently undergoing developmental flight testing. Theempennage of the aircraft isexperiencing buffeting where the horizontal and vertical tail vibrate at resonant frequencies. These high buffet loads are manifested in higher than anticipated fitting loads, particularly on the tail, and vibrations in the crew stations and at the nose cone where the targeting sensors are located. Significant effort has been devoted to identifying the sources of excitation and the nature of the structural response. This thesis determines the location andmagnitude of empennage vibratory airloads. Because the nature of the excitation is a random function, spectral analysis is used. To obtain the loads, a three step process was utilized. First, from aircraft differential pressure transducers and accelerometers, the spectral content of theresponse and excitation was determined. Then, using aNASTRAN model modified to replicate the flight test aircraft, frequency response functions were determined between selected points on the aircraft's tail and the accelerometers. Finally, using this information, a solution was obtained for the vibratory airloads. Having provided information on the nature of the driving forces...

‣ Applications of Multitaper Spectral Analysis to Nonstationary Data

Rahim, KARIM
Fonte: Quens University Publicador: Quens University
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
66.932285%
This thesis is concerned with changes in the spectrum over time observed in Holocene climate data as recorded in the Burgundy grape harvest date series. These changes represent nonstationarities, and while spectral estimation techniques are relatively robust in the presence of nonstationarity--that is, they are able to detect significant contributions to power at a given frequency in cases where the contribution to power at that given frequency is not constant over time--estimation and prediction can be improved by considering nonstationarity. We propose improving spectral estimation by considering such changes. Specifically, we propose estimating the level of change in frequency over time, detecting change-point(s) and sectioning the time series into stationary segments. We focus on locating a change in frequency domain in time, and propose a graphical technique to detect spectral changes over time. We test the estimation technique in simulation, and then apply it to the Burgundy grape harvest date series. The Burgundy grape harvest date series was selected to demonstrate the introduced estimator and methodology because the time series is equally spaced, has few missing values, and a multitaper spectral analysis, which the methodology proposed in this thesis is based on...

‣ Alzheimer's disease qEEG: spectral analysis versus coherence. which is the best measurement?

Anghinah,Renato; Kanda,Paulo Afonso Medeiros; Lopes,Helder Frederico; Basile,Luis Fernando Hindi; Machado,Sérgio; Ribeiro,Pedro; Velasques,Bruna; Sameshima,Koichi; Takahashi,Daniel Yasumasa; Pinto,Lécio Figueira; Caramelli,Paulo; Nitrini,Ricardo
Fonte: Academia Brasileira de Neurologia - ABNEURO Publicador: Academia Brasileira de Neurologia - ABNEURO
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/12/2011 Português
Relevância na Pesquisa
66.60073%
There is evidence in electroencephalography that alpha, theta and delta band oscillations reflect cognitive and memory performances and that quantitative techniques can improve the electroencephalogram (EEG) sensitivity. This paper presents the results of comparative analysis of qEEG variables as reliable markers for Alzheimer's disease (AD). We compared the sensitivity and specificity between spectral analysis (spectA) and coherence (Coh) within the same group of AD patients. SpectA and Coh were calculated from EEGs of 40 patients with mild to moderate AD and 40 healthy elderly controls. The peak of spectA was smaller in the AD group than in controls. AD group showed predominance of slow spectA in theta and delta bands and a significant reduction of inter-hemispheric Coh for occipital alpha 2 and beta 1 and for frontal delta sub-band. ROC curve supported that alpha band spectA was more sensitive than coherence to differentiate controls from AD.

‣ Spectral analysis of multi-spindle machining heads

Wells, Allan R.
Fonte: Rochester Instituto de Tecnologia Publicador: Rochester Instituto de Tecnologia
Tipo: Tese de Doutorado
Português
Relevância na Pesquisa
66.70804%
Vibration analysis can be extremely useful in predictive/ preventative maintenance. In this investigation, multi-spindle machining heads were analyzed using equipment from Technology for Energy Corporation. A spectral analysis program was also written in order to better understand black box results provided by commercial software. Three case studies indicate that gear mesh frequencies, bearing noise, and the natural frequencies of spindles and shafts represent the majority of the peaks found in the frequency spectrum for multi-spindle heads. These frequencies were calculated analytically and then identified in each frequency spectrum. The results show that in many cases the gear mesh frequencies are too close to the natural frequencies of the spindles and shafts. This causes the spindles to be excited at their natural frequency and can lead to premature failure of the spindle bearings.

‣ EMG spectral analysis of incremental exercise in cyclists and non-cyclists using Fourier and Wavelet transforms; Análise espectral do sinal EMG de exercício incremental em ciclistas e não ciclistas usando as transformadas de Fourier e Wavelet

Costa, Marcelo Vitor da; Universidade Estadual de Londrina. Group of Study and Research in Neuromuscular System and Exercise. Londrina, PR. Brazil.; Bortolotti, Henrique; Universidade Estadual de Londrina. Group of Study and Research in Neuromuscular Syst
Fonte: Universidade Federal de Santa Catarina. Florianópolis, SC. Brasil Publicador: Universidade Federal de Santa Catarina. Florianópolis, SC. Brasil
Tipo: info:eu-repo/semantics/article; info:eu-repo/semantics/publishedVersion; "Avaliado por Pares",; Descriptive; Avaliado por Pares; Descritivo trasnversal Formato: application/pdf
Publicado em 18/10/2012 Português
Relevância na Pesquisa
66.64161%
http://dx.doi.org/10.5007/1980-0037.2012v14n6p660The aim of this study was to compare the electromyographic indices of fatigue (slope of median frequency) calculated with the fast Fourier transform (FFT) and wavelet transform (WT) in trained and untrained individuals during cycle exercise. A second objective was to compare the variance of the spectral parameters (median frequency - MF) obtained by the FFT and WT during exercise. Twelve cyclists and non-cyclists performed a maximal incremental test to determine the peak power (Wp) and electromyographic activity of the vastus lateralis (VL), rectus femoris (RF), biceps femoris (BF), semitendinous (ST) and tibialis anterior (TA). Mean values of median frequency, determined by the FFT and WT, were used for the spectral analysis of the electromyographic signals of the studied muscles. The analyzed parameters were obtained for each time period corresponding to 0, 25, 50, 75, and 100% of total duration of the maximal incremental test. No statistically significant differences were found in the values of MF and electromyographic indices of fatigue between the two techniques (FT and WT) both in the cyclists and non-cyclists group (P>0.05). Regarding the MF variance, statistically significant differences were found in all analyzed muscles...

‣ Spectral analysis and gravity modelling in the Yagoua, Cameroon, sedimentary basin

Njandjock Nouck,Philippe; Manguelle-Dicoum,Eliezer; Ndougsa-Mbarga,Théophile; Charles Tabod,Tabod
Fonte: Instituto de Geofísica, UNAM Publicador: Instituto de Geofísica, UNAM
Tipo: Artigo de Revista Científica Formato: text/html
Publicado em 01/09/2006 Português
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A gravity survey is carried out in the far north of Cameroon, covering an area of about 15 000 km² in the Yagoua sedimentary basin, located between longitudes 14°20' to 15°50'E, and latitudes 9°45' to 11°N. Using a density of 2.7 g/cm³ for the crust and removing a second-degree trend surface for modelling, we determined the residual anomalies. Further investigations provide depth of gravity sources, basement structural trend, nature of intrusive bodies and thickness of sediments in the basin. A negative anomaly of about -18 mGal near Moulvouday suggests a thickness of sediments of 3.1 km extending north east. A 2.5D modelling has been carried out along two profiles P1 and P2. The depths estimated from spectral analysis and 2.5D modelling are coherent. The combination of the spectral analysis and 2.5 D modelling has led to the demarcation of the Yagoua basin.