Dissertations / Theses on the topic 'Amplitude variation'

It is known that there is an intraindividual amplitude variation in motor electroneurography when the same person is examined at different times. This variation affects the evaluation the status of the patient. The aim of this study was to investigate if the intraindividual amplitude variation decreased by photographing the electrode position, that later is used in the follow-up study. Twenty test persons were examined by four laboratory scientists. The nerves that were examined were median, ulnar, peroneal and tibial nerve. At the first examination the laboratory scientists used method guidelines and took photographs of the electrode position. The photographs were then used in the follow-up. The results showed that there was an indication of decreased of the intraindividual amplitude variation when photographic documentation was used instead of method guidelines.

L'anémométrie laser à effet Doppler (ALD), dont l'utilisation est très répandue en mécanique des fluides, peut aussi être utilisée pour la mesure de vitesse particulaire acoustique. La nature vectorielle de cette grandeur permet de caractériser les champs à structure complexe ce qui autorise, par exemple, l'étude de phénomènes acoustiques au voisinage de parois vibrantes ou de discontinuités géométriques. L'ALD offre, pour ce type de problème. Le double avantage de présenter une bonne résolution spatiale de la mesure et de ne perttirber que faiblement le champ à explorer. Le Laboratoire d'Acoustique de l'Université du Maine (LAUM) est équipé d'un banc de mesure conçu pour la mesure de vitesse acoustique. Depuis près de huit ans. Les recherches se sont orientées vers la validation expérimentale de cette technique ainsi que vers l'élaboration de méthodes de traitement des signaux propres à extraire la vitesse particulaire dans lin contexte de traitement différé et avec l'hypothèse d'un signal Doppler d'amplittide constante. Cependant, pour que l'ALD soit exploitable efficacement il est indispensable de concevoir un système de mesure. Simple d'utilisation, permettant d'accéder rapidement à la vitesse acoustique et prenant en compte la nature variable de l'amplitude du signal Doppler. L'objectif de cette étude est donc de proposer des méthodes de traitement du signal adaptées à l'estimation de la vitesse particulaire acoustique, dans le cas d'une excitation sinusoi͏̈dale. Et de définir une architecture matérielle et logiciens indispensable à cette mesure. Celle-ci s'opère à partir des composantes en phase et en quadrature du signal Doppler ramené-es en bande de base à l'aide d"un dispositif de démodulation analogique spécialement développé pour cette application. Trois estimateurs sont alors proposés: le premier est basé sur le calcul de la dérivée de la phase du signal Doppler. Sa principale vocation consiste à initialiser une deuxième méthode d'estimation basée sur la recherche du maximum de vraisemblance. Le filtrage de Kalman étendu cmontrent l'influence des paramètres du problème sur la qualité des estimations. Par la suite. Des simulations statistiques de --\,Ionte-Carlo permettent d'évaluer la qualité des trois méthodes. Une estimation sommaire des complexités algorithmiques des estimateurs complète également cette phase dévaluation. Enfin. La validation expérimentale des techniques d'estimation s"articule autour de deux ex- périences Dans un premier temps, la mesure de la vitesse de déplacement sinusoi͏̈dale d'une pointe d'aiguille montée dans un pot vibrant permet de coiifronter les résultats obtenus par ALD à ceux que donne un vibromètre laser. Dans un second temps. La mesure de vitesses particulaires acoustiques rayonnées par un haut-parleur électrodynamique, est proposée. Les valeurs issues de la mesure en champ libre par ALD sont alors coniparées à celles des vitesses de référence obtenues à l'aide de la méthode du doublet microphonique
Laser Doppler Anemometry (LDA), which is widely used in fluid mechanics, can also be used in order to measure acoustic particle velocity. The knowledge of this vector quantity could be especially useful to characterize a complex acoustic field, allowing for example the study of phenomena close to vibrating surfaces or around duct discontinuities. In addition, LDA ensures, for this kind of problem, theoretically non-invasive velocity measurements with an excellent spatial résolution. The Laboratoire d'Acoustique de l'Université du Maine (LAUM) is equipped with a system designed for acoustic velocity measurement. For nearly eight years, research has been directed towards the experimental assessment of this technique and the development of signal processing methods based on post-processing techniques, with the assomption of a constant amplitude Doppler signal. However, in order to design a more integrated set-up, furthermore easy to manipulate, it is essential to design a system providing real-time measurements of acoustic velocity and taking into account the varying amplitude of the Doppler signal. This research work offers signal processing methods adapted to the estimation of acoustic particle velocity, for a sine-wave excitation, and defines hardware and software architectures suited to this measurement. The latter is performed with the help of the in-phase and the quadrature components of the Doppler signal, which is downshifted thanks to an analog quadrature demodulation technique especially designed for this application. Three estimators are then proposed: the first is based on the Doppler phase derivation, and is the starting point of a second method based on maximum likelihood estimation. The extended Kalman filter is the third method explored. Finally, the approximated, though accurate, analytical forms of the Cramer-Rao bounds show the influence of the parameters on the quality of the estimations. Estimator performance is then illustrated by means of statistical Monte-Carlo simulations. An assessment of the complexity of these algorithms also supplements this evaluation. Finally, the assessment of the estimation technique is obtained thanks to two experiments. Firstly, the measurement of the sinusoidal velocity of the displacement of a needle assembled in a vibration exciter allows the comparison of the results obtained by LDA with those obtained with a laser vibrometer. Then, the measurement of the acoustic particle velocity field radiated by a loudspeaker, is proposed. The measurements obtained in free field by LDA are then compared with the reference velocities obtained using a sound intensity probe

L'anémométrie laser à effet Doppler (ALD), dont l'utilisation est très répandue en mécanique des fluides, peut aussi être utilisée pour la mesure de vitesse particulaire acoustique. La nature vectorielle de cette grandeur permet de caractériser les champs à structure complexe ce qui autorise, par exemple, l'étude de phénomènes acoustiques au voisinage de parois vibrantes ou de discontinuités géométriques. L'ALD offre, pour ce type de problème, le double avantage de présenter une bonne résolution spatiale de la mesure et de ne perturber que faiblement le champ à explorer.
Le Laboratoire d'Acoustique de l'Université du Maine est équipé d'un banc de mesure conçu pour la mesure de vitesse acoustique. Depuis près de huit ans, les recherches se sont orientées vers la validation expérimentale de cette technique ainsi que vers l'élaboration de méthodes de traitement des signaux propres à extraire la vitesse particulaire dans un contexte de traitement différé et avec l'hypothèse d'un signal Doppler d'amplitude constante. Cependant, pour que l'ALD soit exploitable efficacement il est indispensable de concevoir un système de mesure, simple d'utilisation, permettant d'accéder rapidement à la vitesse acoustique et prenant en compte la nature variable de l'amplitude du signal Doppler.
L'objectif de cette étude est donc de proposer des méthodes de traitement du signal adaptées à l'estimation de la vitesse particulaire acoustique, dans le cas d'une excitation sinusoïdale, et de définir une architecture matérielle et logicielle indispensable à cette mesure. Celle-ci s'opère à partir des composantes en phase et en quadrature du signal Doppler ramenées en bande de base à l'aide d'un dispositif de démodulation analogique spécialement développé pour cette application. Trois estimateurs sont alors proposés : le premier est basé sur le calcul de la dérivée de la phase du signal Doppler. Sa principale vocation consiste à initialiser une deuxième méthode d'estimation basée sur la recherche du maximum de vraisemblance. Le filtrage de Kalman étendu constitue la troisième méthode explorée. Enfin, les formes analytiques, approchées mais précises, des bornes de Cramer-Rao montrent l'influence des paramètres du problème sur la qualité des estimations. Par la suite, des simulations statistiques de Monte-Carlo permettent d'évaluer la qualité des trois méthodes. Une estimation sommaire des complexités algorithmiques des estimateurs complète également cette phase d'évaluation.
Enfin, la validation expérimentale des techniques d'estimation s'articule autour de deux expériences. Dans un premier temps, la mesure de la vitesse de déplacement sinusoïdale d'une pointe d'aiguille montée dans un pot vibrant permet de confronter les résultats obtenus par ALD à ceux que donne un vibromètre laser. Dans un second temps, la mesure de vitesses particulaires acoustiques rayonnées par un haut-parleur électrodynamique, est proposée. Les valeurs issues de la mesure en champ libre par ALD sont alors comparées à celles des vitesses de référence obtenues à l'aide de la méthode du doublet microphonique.

The wavefronts of high frequency (HF) radio waves received after reflection from the ionosphere exhibit both spatial non-linearities and temporal variations which limit the performance of large aperture receiving arrays. The objective of this investigation was to measure the phase and amplitude of ionospherically propagated signals in order to relate these parameters to the reflection process. This thesis describes the design and construction of a large aperture multi-element array and its implementation for wavefrot investigations. The hardware and software developed to control the equipment and to record the measurements are described. The procedures required to verify the performance of the experimental system are discussed and results are presented which demonstrate the accuracy of the measurements. The array was utilised for studies of signals received from several transmitters situated throughout Western Europe. The results obtained demonstrate the widely different behaviour of signals received over the various propagation paths and these have been related to the modal content of the received signals. Limited periods existed during which a single ionospheric mode was received and data corresponding to this condition have been compared with those which would be expected if the signal consisted of both a specular component and a cone of diffracted rays. This model is unable to explain the experimental results. Numerical models of the received signal were therefore developed. Results of these and comparisons with experimental results suggest that the measured parameters can be explained by the existence of a specular component with a varying direction of arrival (DOA), plus some contribution from random components. The experimental results indicate that the random or diffracted components normally contribute less than 10% of the received power in a single moded signal.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1986.
Microfiche copy available in Archives and Science
Bibliography: leaves 198-208.
by Kiyoshi Yomogida.
Ph.D.

The limiter is a commonly used device in communication receiving systems to remove the amplitude variations of the received signal, but it is usually observed that limiter degrades the envelope detection performance of a single tone. In this thesis, it is demonstrated that the limiter-generated third harmonic can be used to improve the envelope detection performance of a single tone over that of the linearly processed fundamental. Differences in the probability distributions of the limiter-generated harmonics cause differences in their detection probabilities, which lead to differences in the performance of subsequent envelope detection. Comparison of the envelope detection performance of the limiter-generated third harmonic and the input to the limiter shows a maximum detection probability gain of 1.12 and also error probability gain of 2.4 in linear scale, whereas the fundamental harmonic does not show any practically significant gain. The envelope detection performance of the vector sum of the limiter-generated fundamental and third harmonics is also evaluated. This combination provides better performance than do the individual harmonics, especially for a large clipping parameter of the limiter. The combined harmonics shows a maximum detetction probability gain of 1.15 and error probability gain of 14, over that of the envelope detection performance of a tone without limiter. It is also observed that the envelope detection performance of a tone with limiter-generated higher harmonics shows non-monotonic behaviour as functions of either noise or the limiter-clipping parameter, which is a signature of stochastic resonance. The theoretical results from earlier research on the envelope detection of a single tone embedded in additive white Gaussian noise, both with and without a limiter, are presented and shown to match our simulation results. In previous work when a limiter was used in the envelope detection of a single tone, only the envelope of the fundamental harmonic was considered under very specific conditions. By contrast we also take notice of the limiter-generated higher harmonics and obtain improved envelope detection performance in the detection of a single tone.

Les ondes de surface de période 10-100 secondes sont sensibles à la rigidité de la lithosphère échantillonnée. Dans ce travail de thèse, nous nous sommes intéressés à l'étude des variations latérales de la lithosphère par l'analyse des ondes de surface. La longueur d'onde des variations latérales étudiées est de l'ordre de grandeur décakilométrique. Les méthodes habituellement utilisées avec des stations sismologiques espacées de plusieurs centaines de kilomètres ne sont donc plus satisfaisantes. C'est pourquoi nous avons développé des analyses dites de réseaux denses ou régionaux. Ainsi nous pouvons déterminer les variations latérales de la structure lithosphérique et étudier la propagation des ondes de surface à l'échelle régionale. Nous avons appliqué ces analyses de réseau pour trois études régionales différentes. Tout d'abord nous avons montré les variations brutales de la structure crustale de part et d'autre de la suture du Tsangpo au sud du plateau tibétain. Pour cela, nous avons analysé la vitesse de phase locale ainsi que les variations d'amplitude au travers de la suture. Au nord de la suture du Tsangpo nous avons déterminé une zone à moindre vitesse dans la croûte inférieure alors que nous ne l'observons pas au sud de la suture. Nous avons aussi étudié la lithosphère dans les Alpes françaises et nous avons montré qu'elle s'épaississait d'ouest en est, de 85 à plus de 200 km d'épaisseur sous l'axe de la chaîne alpine. Par ailleurs, nous nous sommes intéressés aux anomalies de la propagation des ondes de surface dans cette région en dissociant les effets dus aux échelles globale et locale. Finalement, nous avons aussi travaillé sur la zone de Sorgenfrei-Tornquist qui sépare l'Europe phanérozoïque à l'ouest de l'Europe paléozoïque à l'est. Nous montrons qu'au sud-ouest de cette zone la lithosphère est peu épaisse, autour de 50-100 km, et qu'au nord-est elle atteint une épaisseur supérieure à 200 km sous le bouclier baltique. Au niveau de la transition, la lithosphère est épaisse de 120 km .

Dans cette thèse ont été développés de nouveaux outils de calcul théorique de spectres moléculaires rovibrationnels qui permettent de mieux traiter les états vibrationnels très excités ainsi que les mouvements de grandes amplitudes avec la méthode d’interactions de configurations en champ moyen. Dans un premier temps, nous avons discuté la question du choix des bases modales et les différents compromis à trouver afin de pallier aux défauts possibles des surfaces d'énergie potentielle. Dans ce cadre nous avons également développé un critère de sélection visant à améliorer la qualité des fonctions d'ondes rovibrationnelles de base. Ces approches ont été appliquées avec succès à la molécule de méthane CH4.Dans un second temps, nous avons implémenté un algorithme de calcul formel des opérateurs d'énergie cinétique en coordonnées quelconques qui permet d'avoir des expressions exactes ainsi que leurs développements en série de Taylor ou Fourier, qui exploite au mieux les potentialités du logiciel MATHEMATICA et a permis d'obtenir des hamiltoniens rovibrationnels en coordonnées de valence de façon particulièrement efficace. Enfin, nous avons généralisé la méthode d’interactions de configurations en champ moyen en ajoutant de façon perturbative un champ effectif d'ordre deux. Nous avons appliqué cette généralisation à la molécule de péroxyde d'hydrogène HOOH, ce qui a permis de montrer son intérêt tant pour l'amélioration des niveaux d'énergie que des fonctions d'onde associées, lorsqu'on a affaire à des groupes de degrés de liberté bien séparés énergétiquement
In this thesis we developed new theoretical tools for molecular rovibrational spectra for a better description of the excited vibrational states and movements with large amplitudes using mean field configuration interaction method. First, we discussed the choice of modal basis and different trade-off to overcome the possible shortcomings of potential energy surfaces. In this context we have also developed selection criteria to improve the quality of rovibrational wave functions. These approaches have been successfully applied to the methane molecule (CH4). Secondly, we have implemented a formal algorithm for calculating the kinetic energy operators in arbitrary coordinates that allows the derivation of exact expressions and their Taylor and Fourier series, using, in a very efficient way, the capabilities of the software MATHEMATICA which yield to the derivation of rovibrational Hamiltonians in valence coordinated. Finally, we have generalized the mean-field configuration interaction method by adding perturbatively a second order effective field. We applied this generalization to the hydrogen peroxide molecule (HOOH), which has shown an improvement for both energy levels and the associated wave functions, when dealing with groups of degrees of freedom that are energetically well separated

Current trends in industry are leaning towards specialized production systems and sedentary computer work tasks that are associated with low and less varying mechanical exposures. It has been suggested that physical variation is an effective intervention to reduce local fatigue and potentially musculoskeletal disorders. However, little is known in how the differences between physical variation patterns affect physiological and psychophysical responses. The general purpose of this thesis was to explore the biophysical effects of varying force amplitudes using forces, cycle times, and duty cycles that are relevant to occupation and longer-term health outcomes. Fifteen healthy males performed an elbow extensor sustained isometric exertion at 15% Maximum Voluntary Force (MVF), an intermittent contraction between 0% MVF and 30% MVF (On/Off), an intermittent contraction between 7.5% MVF and 22.5% MVF (MinMax), an intermittent contraction between 1% MVF and 29% MVF (1 Percent), and a sinusoidal contraction between 0% and 30% MVF (Sinusoidal). Eight commonly used measurement tools recorded biophysical responses as participants performed each condition for up to 60 minutes or until exhaustion, during 60 minutes recovery, and at 24 hours post-exercise. Measures included electromyography of the triceps muscles, mechanomyography, blood flow, heart rate, stimulated tetani and twitch responses, maximum exertions, and perceived exertion. The rate of response during exercise and comparisons between baseline, cessation, and recovery values were used to assess fatigue responses. This research shows that implementing physical variation, at the same mean amplitude, may provide reduced fatigue rate and that the magnitude and shape of the intermittent force variations affect exercise and recovery measures. Time varying forces may therefore provide the necessary mechanism to encourage beneficial physiological responses that would improve long-term health and well being of workers at low-load jobs.

碩士
元智大學
光電工程學系
104
In this paper, the amplitude variation and frequency of regular pulse from semiconductor lasers subject to both optoelectronic feedback and optical feedback are discussed by numerical simulation. We controlled the optical feedback strength, delay time of optical, optoelectronic feedback strength and delay time of optoelectronic, in order to inspect the regular pulse state accurately. When the optical feedback system applied to optoelectronic feedback system, the amplitude variation of regular pulse state are reduced from the analysis of the electrical power spectra, time series and phase portraits. We also investigated the amplitude variation of regular pulse with different operational parameters by numerically calculated mapping. Under proper operational conditions, the stability region of regular pulse state is increased in dual feedback systems. Compared to the optoelectronic feedback system, the amplitude variation of regular pulse state generated by dual feedback systems is reduced, and the improved percentage can be enhanced to 100%. Furthermore, we also study frequency of regular pulse by numerically calculated mapping. When the optoelectronic feedback is high, modulation range of frequency is increased.

Dissertação de mestrado em Optometria Avançada
crescente uso de dispositivos eletrónicos de variados tamanhos em ambientes não ergonómicos e a exigência quer no estudo quer na atividade profissional, obriga à eficácia, rapidez e precisão no sistema visual. O estilo e a qualidade de vida influenciam o comportamento humano em que a visão é afetada provocando anomalias na visão binocular, alterações no erro refrativo e sintomatologia associada. Existem estudos longitudinais sobre estas variações. O objetivo deste trabalho foi verificar se existe alguma variação nos parâmetros acomodativos ao longo do dia perante atividades normais do dia-a-dia de cada pessoa. Pretendeu-se ainda verificar, no caso de existirem alterações, quais os fatores que poderiam influenciar essas alterações. Neste estudo, participaram 30 estudantes com a idade entre os 19 anos e os 27 anos a quem se realizaram exames de acuidade visual, amplitude de acomodação, atraso acomodativo e flexibilidade acomodativa em três horários diferentes durante o mesmo dia. Os resultados deste trabalho mostraram haver uma diminuição estatisticamente significativa na amplitude de acomodação entre o final da manhã e o final da tarde (0,43D) com maior diferença nos miopes. Na flexibilidade acomodativa verificou-se um aumento estatisticamente significativo entre o início da manhã e o final da tarde (1,3cpm).
The increasing use of electronic devices of varying sizes and non-ergonomic environment either in study or in professional activity requires the efficiency, speed and accuracy of the visual system. The style and quality of life influences human behavior in which vision is affected causing abnormalities in binocular vision, changes in refractive error and associated symptomatology. There are longitudinal studies about these variations. The aim of this study was to ascertain whether there is any variation in accommodative parameters through a normal day of each person and the most reported symptoms. We also aim to evaluate what factors could influence those changes. In this study, 30 students participated with age between 19 years and 27 years old to whom visual acuity tests, the amplitude of accommodation, accommodative lag and accommodative flexibility were carried out in three different times during the same day. The results of this study showed a statistically significant decrease in the amplitude of accommodation between the end of the morning and the afternoon (0.43D) with greater difference in miopes. Accommodative flexibility showed a statistically significant increase from the early morning and the late afternoon (1, 3cpm).

Thesis (M. Sc.)--University of Alberta, 2010.
Title from pdf file main screen (viewed on Mar. 18, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Master of Science in Geophysics, Department of Physics, University of Alberta. Includes bibliographical references.

碩士
國立交通大學
控制工程系
82
In this thesis, we study the tracking problem for stable minimum phase system with control input amplitude constraints, external bounded disturbances and parameter variations. We present a projection algorithm with a dead-zone and analyze various properties of the algorithm. Meanwhile, we prove that the closed-loop system is BIBO stable for stable minimum phase systems. Furthermore, we explore how the disturbances, parameter variations and constraints on the control input signal influence the ideal system signals. Meantime, prediction error, asymptotic input matching and tracking error cannot approach zero when disturbances and parameter variations exist in the working environment, but we can determine upper bounds on prediction error, asymptotic input matching and tracking error respectively. And we find a condition to ensure the upper bound of tracking error when the unconstrained control input signal approach the constrained control input signal as time tends to infinity. Finally, some simulation results are given to demonstrate the validity of the theoretical results.

碩士
崑山科技大學
機械工程研究所
94
Variations of the tribo-electrification voltage had been successfully applied to monitor the tribological properties between the metal films and for appraising the solid-film lubrication of the metal films. Moreover, the novel method of using continuous tribo-electrification variations for monitoring the tribological properties between the soft metal films is more “sensitive” and “discriminative” than that by the continuous friction coefficient variations as usual. Therefore, this paper uses the self-developed reciprocating friction tester with the measurement system to investigate the tribo-spreading function between the metal films by measuring the variations of the tribo-electrification, the friction coefficient and the vertical displacement during the dynamic frictional process. Moreover, after the friction test; SEM is used to observe and to analyze the nano-wear structure and the composition. According to the experimental results, the noble method of using tribo-electrification variations for monitoring the tribo-spreading function between the metal films can be proposed. Since the above experimental procedures had been preliminary tested, this project can be investigated easily in the future. The results of this investigate have not only an original opinion, but it is also very helpful in the quality of machined products and in the manufacturing process of the film coating process.