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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
51

Modelagem matemática de sistemas vibratórios com aplicação de autovalores

Venceslau, Sheyla Maurício Maia 30 May 2015 (has links)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES / The present work aims to contribute to the teaching and learning process of disciplines such as Linear Algebra and Differential Equations, suggesting a study methodology based on mathematical modeling of mechanical systems and application of eigenvalues of problem, as well as encourage high school students to explore mathematics, a revealing and essential science, showing that content such as complex numbers, determinants, trigonometry, etc., some of these mistakenly questioned about its practical utility, can be used for the benefit of people, for example, providing more security and stability to buildings , essential in modern times. Initially, the contents will be displayed formally required for the understanding of vibrating systems with two degrees of freedom to apply them subsequently in the determination of natural frequencies of vibration of a two storey building. Also, a demo will be made of how to calculate the eigenvalues through of computational tools, the softwares MATLAB and R. Using the softwares, the determination of natural frequencies becomes even more practical and thus shows that the application of the problem is quite simple and has obvious practical use. / O presente trabalho visa contribuir para o processo de ensino e aprendizagem de disciplinas como Álgebra Linear e Equações Diferenciais, sugerindo uma metodologia de ensino baseada na modelagem matemática de sistemas mecânicos e na aplicação do problema de autovalores, assim como, estimular alunos do ensino médio a explorar a matemática, uma ciência reveladora e essencial, mostrando que conteúdos como números complexos, determinantes, trigonometria, etc, alguns destes equivocadamente questionados quanto a utilidade prática, podem ser usados em benefício das pessoas, por exemplo, proporcionando mais segurança e estabilidade às edi cações, fundamentais nos tempos atuais. Inicialmente, serão apresentados formalmente os conteúdos necessários ao entendimento de sistemas vibratórios com dois graus de liberdade, para posteriormente aplicá-los na determinação das frequências naturais de vibração de um edi- fício de dois andares. Além disso, será feita uma demonstração de como calcular os autovalores através de ferramentas computacionais, os softwares MATLAB e R. Com o uso do software, a determinação das frequências naturais torna-se ainda mais prática e, portanto, mostrar que a aplicação do referido problema é bastante simples e tem utilidade prática evidente.
52

Estudo do efeito da vibração no tratamento da disfunção temporomandibular através de um protótipo de placa vibratória oclusal / Study of the effectiveness of vibratory plate in the treatment of dysfunction temporomandibular

Carlos Eduardo Pitta de Luca 13 December 2010 (has links)
Este estudo teve como objetivo estudar uma placa oclusalcom estimulação vibratória (POV) de base, para o tratamento da dor crônica miofascial. Foram selecionados 18 pacientes com mialgia crônica facial, de acordo com os Critérios para Diagnóstico em Pesquisa RDC . Os pacientes tinham entre 18 e 65 anos de idade, pertenciam ao sexo feminino e haviam usado placa estebilizadora acrílica por mais de 6 meses, e permaneciam com dor muscular. Foram excluídos pacientes com Disfunção Temporomandibular, que haviam feito uso de analgésicos ou de moduladores de sono, e pacientes desdentados parciais ou totais. A variável analisada foi a dor reportada pelos pacientes, usando a Escala Visual Analógica (EVA) de 100mm, medindo-se antes da instalação da POV, e um mes após o seu uso. Das 18 POV instaladas, 10 apresentaram falhas no mecanismo vibratório. As médias da EVA para os 8 pacientes que utilizaram a POV durante 1 mês foram de 56,62±22.82mm na aferição inicial e média de EVA final de 24,75±20,52mm, com p=0,011. Dos 8 pacientes apenas 4 concordaram com o uso da placa oclusal inativa (POI) por 30 dias, separadas por um período de wash-out de pelo menos 8 meses. Os níveis de dor da escala VAS foram a única variável analisada, e foram registrados antes e após o uso das placas. Foram utilizadas os testes t-teste pareado e ANOVA para medidas repetidas, para se obter os resultados estatísticos. No início do estudo, os níveis médios da VAS de dor antes de se utilizar a placa vibratória de maneira ativa e inativa foram 54,5±19,8 milímetros, e 44,0±13,6 milímetros, respectivamente. A comparação entre esses valores de referência não apresentaram diferença estatística (p> 0,05, teste t pareado). A variação média nos níveis de dor (VAS póspré) ao usar o mesmo tipo de placa, de maneira ativa e inativa foi de -42,0±-30,3 milímetros e 29,5±21,5 milímetros, e o t-teste revelou uma diferença significativa entre os dois grupos (p = 0,07). Foi feitauma nova análise, utilizando-se as mesmas medidas, através da Análise de Variância ANOVA, onde encontrou-se diferença estatisticamente significante (f(3,9)=7.543, p=0.008) antes do uso das placas ativas e das inativas. Entretanto, após o uso da correção com o teste de Bonferroni, foram encontrados resultados condizentes com aqueles obtidos na análise feita pelo programa do teste t. (p>0.05). Pode-se concluir que do uso da vibração como mecanismo de controle da DTM foi eficaz, mas a POV falhou na maioria dos casos devido a problemas mecânicos. / This study aimed to study an occlusal splint with vibratory stimulation (VibsS) as standard, for the treatment of chronic myofascial pain. Were selected 18 patients with chronic facial myalgia, according to the Research Diagnostic Criteria for Temporomandibular Disorders, RDC-TMD.The patients were between 18 and 65years old, female, using stabilization splints for more than six months, and that remained with muscle pain. Were excluded patients with Temporomandibular Disorders, which had made use of analgesics or sleeps modulators and those who were partially or totally edentulous. The analyzed variable was pain reported by patients using visual analog scale (VAS) of 100mm, measuring before the installation of VibsS, and one month after its use. Were installed 18 VibsS; 10 failures in the vibrating mechanism.The mean VAS for the 8 patients who used the VibsS for 1 month were 56.62 ± 22.82mm to measure initial and final mean VAS of 24.75 ± 20.52 mm, p = 0.011. From these 8 patients, only four agreed to the use of an occlusal splints inactive for 30 days, separated by a wash-out period of at least 8 months. The levels of pain-VAS score was the only variable analyzed, and were recorded before and after use of the splints. Were used paired t-tests and ANOVA for repeated measures to obtain the statistics. At baseline, mean levels of VAS pain before using the vibrating splint active and inactive were 54.5±19.8 mm, and 44.0±13.6 mm, respectively. The comparison of these reference values showed no statistical difference (p> 0.05, paired t-test). The average change in pain levels (VAS post-pre) when using the same type of analysis, with active and inactive splints was -42.0±- 30.3 and 29.5 mm±21.5 mm, and the t-test showed a significant difference between the two groups (p = 0.07). After that, was made, a new analysis, using the same measures through the analysis of variance ANOVA, where were found a statistically significant difference (f (3,9) = 7543, p = 0.008) before the use of active boards and inactive. However, after using the correction with the Bonferroni test, we found results consistent with those obtained in the analysis performed by the test program t. (p>0.05). Conclusion: This study showed that is an effective use of vibration as a control mechanism of TMD, but this VibsS failed in most cases due to mechanical problems.
53

Comportement statique et dynamique d'une suspension de haut-parleur à joint de ferrofluide / Static and dynamic behavior of a loudspeaker suspension by ferrofluid seals

Pinho, Marcos 25 January 2011 (has links)
Cette thèse a pour objectif l’étude du comportement vibratoire des suspensions à joint de ferrofluide utilisées dans un nouveau type de haut-parleur. Le moteur de ce haut-parleur, conçu pour réduire les non-linéarités d’origine magnétique, permet l’utilisation de joints de ferrofluide comme alternative aux suspensions viscoélastiques traditionnelles : sous la forme de deux joints annulaires, ils réalisent la liaison entre la partie fixe et la partie mobile du système. L’originalité du travail présenté a trait aux forts niveaux du champ magnétique présent dans le haut-parleur et à la caractérisation en dynamique des joints en terme de masse, raideur et amortissement. La première partie est une analyse expérimentale de la raideur radiale statique d’un joint au sein d’un moteur magnétique. La connaissance de cette raideur est nécessaire pour dimensionner le guidage de l’équipage mobile. Elle est étudiée en fonction du volume et de la saturation magnétique du ferrofluide. Les résultats sont en bon accord avec les simulations. Dans une deuxième partie, nous présentons une étude expérimentale sur le comportement visqueux des ferrofluides en condition de cisaillement oscillatoire et sous champ magnétique homogène et stationnaire. Cette étude s’élargie dans la suite aux conditions magnétiques du moteur, où le champ n’est plus homogène. Les propriétés sont étudiées en fonction du volume, de la viscosité et de la saturation magnétique. Un modèle pour les pertes du haut-parleur est proposé en fonction des propriétés magnétovisqueuses du ferrofluide. / The aim of this thesis is the study of the vibratory behavior of ferrofluid seals suspensions used in a new type of loudspeaker. The motor of this loudspeaker has been designed to reduce magnetic nonlinearities and allows ferrofluid seals, as two annular seals, to be used as an alternative to classical viscoelastic suspensions. Seals serve as a link between mobile to fixed part of the system. The originality of this configuration is the presence of high level magnetic field in the loudspeaker, which require a dynamic characterization of seals in term of mass, stiffness and damping. First part of this thesis is an experimental analysis of static radial stiffness of one seal inside a magnetic engine. This parameter is necessary for centering the moving part. The influence of the volume and saturation magnetization of the ferrofluid are analyzed. There is a good agreement between experimental results and simulations. In the second part, an experimental study of the viscous ferrofluid behavior under an oscillatory shear excitation and homogeneous and stationary magnetic field is presented. It is then broaden to real non homogeneous loudspeaker motor conditions. The influence of ferrofluid seals volume, viscosity and saturation magnetization are analyzed. A model which depends on the magnetoviscous properties of the ferrofluid is suggested for the loudspeaker internal losses.
54

Étude comportementale des interactions entre une mère lycose errante, Pardosa saltans (Araneae), et son cocon / Behavioural study of interactions between wandering wolf spider female, Pardosa saltans (Araneae), and her egg-sac.

Ruhland, Fanny 09 November 2016 (has links)
Les soins parentaux sont observés dans de nombreux taxons et sont exprimés de façon plus ou moins complexe. L’étude de ces comportements chez les arthropodes, en particulier chez les araignées, nous permet de mieux comprendre comment les soins à la progéniture se sont mis en place au cours de l’évolution. Au cours de cette thèse nous avons étudié le comportement d’une espèce errante Pardosa saltans (Lycosidae) vis-à-vis de son cocon, puis de ses jeunes. Nous avons décrit les comportements manifestés par la mère pendant toute la période de soin au cocon (période de développement embryonnaire et postembryonnaire des jeunes). Notre étude a permis de mettre en évidence qu’il existe une ontogenèse comportementale dans le cadre des soins parentaux chez cette espèce. Elle a permis également d’évaluer les dépenses énergétiques subies par la mère pendant cette période. Et enfin nous avons identifié, pour la première fois, les composés chimiques présents à la surface du cocon. Nos expériences montrent que ces composés chimiques associés aux vibrations émises par les juvéniles à l’intérieur du cocon sont utilisés par la mère détecter l’état de développement de sa progéniture. / Parental care is widespread among animal kingdom and is more or less expressed. Thus, the study of these behaviours among primitive species, can let us understand how parental behaviours were implemented during evolution. In this thesis we studied maternal behaviour in a wandering spider Pardosa saltans (Lycosidae) with her egg-sac and her young which she actively transports. We have described maternal behaviour towards the egg-sac and highlighted the presence of ontogeny of maternal behavior in this species. Furthermore, we were able to evaluate some of the physiological and ecological investment associated with maternal care of the egg-sac and young. Finally, we have, for the first time, identify chemical compounds on the surface of the silk egg-sac, and placed in evidence the presence of a chemical and vibrational communication between the mother and her cocoon.
55

Pile – Soil Interaction during Vibratory Sheet Pile Driving : a Full Scale Field Study

Guillement, Claire January 2013 (has links)
Urban construction sites require strict control of their environmental impact, which, for vibratory sheet pile driving, can include damage to nearby structures due to ground vibrations. However, the lack of knowledge concerning the generation of soil vibrations makes the prediction of ground vibration levels difficult. This MSc. thesis in particular, focuses on a crucial link in the vibration transfer chain: the sheet pile – soil interface, which is also one of the least documented. The aim of this thesis is first, to carry out a full-scale field test consisting in the monitoring of sheet pile and ground vibrations during sheet pile vibratory driving. And second, to analyze a selected portion of the collected data with focus on the sheet pile – soil vibration transfer. Both aspects of the thesis work aim, more generally, to contribute to the understanding of ground vibration generation under vibratory sheet pile driving. The full-scale field study was performed in Solna in May 2013. It consisted in the vibratory driving of seven sheet piles, out of which three were fitted with accelerometers. During the driving, ground vibrations were measured by accelerometers, the closest ones placed only 0.5 m from the sheet pile line. The design and installation of the soil instrumentation was innovative in as much as accelerometers were not only set on the ground surface but also at three different depths (~ 3 m, 5 m and 6 m). The analysis presented in this thesis is primarily a comparison between sheet pile vibrations and ground vibrations measured 0.5 m from the sheet pile line. The principal aspects considered in the comparison are: the influence of penetration through different soil layers, the sheet pile – soil vibration transfer efficiency, the frequency content of sheet pile and soil vibrations, and differences between toe- and shaft-generated vibrations. The main conclusions from this study are:  Most of the vibration loss occurs in the near field: 90-99% of the sheet pile vibration magnitude was dispersed within 0.5 m from the driven sheet pile. Moreover, the sheet pile – soil vibration transfer efficiency was reduced for higher sheet pile acceleration levels and higher frequencies.  The soil characteristics strongly influence the sheet pile vibration levels. A clear distinction could be made between "smooth" and "hard" driving, the latter being associated with an impact situation at the sheet pile toe.  The focus of ground vibration studies should not only be the vertical vibrations. Indeed, the ground vibrations’ horizontal component was found to be of the same or even higher magnitude than the vertical component.
56

Vibration caused by sheet pile driving- effect of driving equipment

Tsegay, Haftom Tesfay January 2018 (has links)
In many construction works in urban areas vibratory driving is the most widely used technique toinstall sheet piles. But due to vibration-sensitive equipment and structures the amount of inducedground vibration need to be minimized. Hence, it is important to select appropriate vibratorparameters that will minimize the level of induced ground vibration.The main objective of this thesis is to study the effect of the vibratory parameter eccentricmoment (vibrator displacement amplitude) on the induced ground vibration during sheet piledriving. To achieve the objective, a literature review and a full-scale field test has beenconducted. The literature review was conducted to provide guidance for the evaluation of thefield test results.The field study was performed in Uppsala in June 2018, where a series of six sheet pile drivingtests were conducted, the first three sheet piles were driven with lower vibrator displacementamplitude and the next three with higher vibrator displacement amplitude, but the same drivingfrequency was used for all six sheet piles. Five tri-axial accelerometers were used to measure thevibration amplitude on vibrator, sheet pile and ground.Important findings of the field study confirmed that, driving sheet piles with higher eccentricmoment will induce lower ground vibration and higher sheet pile penetration speed incomparison to driving with lower eccentric moment. Limitations and possible future researchworks are pointed out. / I många byggnadsarbeten i tätorter är vibrerade drivning den mest använda tekniken för attinstallera sponter. Men på grund av vibrationskänslig utrustning och konstruktioner måstemängden inducerad markvibration minimeras. Därför är det viktigt att välja lämpligavibratorparametrar som minimerar graden av inducerad markvibration.Huvudsyftet med detta examensarbete är att studera effekten av vibrationsparameternsexcentriskamoment (vibratorförskjutningsamplituden) på den inducerade markvibrationen underspontdrivning. För att uppnå målet har en litteraturöversikt och en fullskalig fältundersökning utförts. Litteraturstudien genomfördes för att ge underlag för utvärderingen av fältundersökningenresultanten.Fältstudien utfördes i Uppsala i juni 2018, där en serie av sex spontdrivnings test utfördes, deförsta tre sponten kördes med lägre vibrator-förskjutningsamplitud och de närmaste tre medhögre vibrator-förskjutningsamplitud, men samma körfrekvens användes för alla sex sponter.Fem treaxiala accelerometrar användes för att mäta vibrationsamplituden på vibratorn, spontenoch jorden.Slutsatserna från fältstudien bekräftade att körsponter med högre excentriskt moment kommer attinducera lägre vibrationer och högre penetrationshastighet för sponten i jämförelse med körningmed lägre excentriskt moment. Begränsningar och möjliga framtida forskningsarbeten påpekas.
57

Jämförelse av mattor för vibrationsmatare med hjälp av försöksplanering / Comparison of carpets for vibratory feeders, using design of experiments

Johannesson, Simon, Mohammad Ishaq, Shukrullah January 2023 (has links)
Detab is a company in Jönköping that develops systems for feeding parts for robots and packaging processes. To control the flow of parts on their vibratory feeders, Detab uses different carpets with angled straws. The two mainly used carpets have been discontinued and must now be replaced. A newly emerged option is a contender in replacing one of the carpets. The new white carpet is completely additively manufactured. To compare the old carpet and the new carpet, data is needed to show how different settings affect the flow of the parts. Through design of experiments and response surface methods, tests can be performed in a systematic and mathematical way compare the performance of different settings. Some basic parameters were defined to begin the investigation of which design of experiments method would be used to best compare the carpets. The parameters defined where the parts that would be used in the tests, the factors that were to be adjusted during the tests, the maximum and minimum values of the selected factors and how the results would be measured. Different methods were tested, and finally optimal design was chosen and executed using the program Design-Expert. The completed tests resulted in response surfaces that were constructed using Design-Expert. These response surfaces were analyzed and several similarities and differences between the different carpets were observed. Primarily, it was found that the green carpet had more settings that resulted in a flow above 0 parts/minute. Using Design-Expert, the response surfaces could be analyzed to find the optimal settings and their expected response. These points and more were then compared with tests performed afterwards to see if the expected values matched reality. It turned out that there were some uncertainties in how well the surfaces could predict the response in comparison with reality. Based on the experiments carried out, recommendations were made on how the company should proceed to be able to assess whether the new carpet is worth using in future construction of their machines.
58

Seismic Communication in a Wolf Spider

Gibson, Jeremy S. 17 July 2006 (has links)
No description available.
59

Interface circuits for readout and control of a micro-hemispherical resonating gyroscope

Mayberry, Curtis Lee 12 January 2015 (has links)
Gyroscopes are inertial sensors that measure the rate or angle of rotation. One of the most promising technologies for reaching a high-performance MEMS gyroscope has been development of the micro-hemispherical shell resonator. (μHSR) This thesis presents the electronic control and read-out interface that has been developed to turn the μHSR into a fully functional micro-hemispherical resonating gyroscope (μHRG) capable of measuring the rate of rotation. First, the μHSR was characterized, which both enabled the design of the interface and led to new insights into the linearity and feed-through characteristics of the μHSR. Then a detailed analysis of the rate mode interface including calculations and simulations was performed. This interface was then implemented on custom printed circuit boards for both the analog front-end and analog back-end, along with a custom on-board vacuum chamber and chassis to house the μHSR and interface electronics. Finally the performance of the rate mode gyroscope interface was characterized, showing a linear scale factor of 8.57 mv/deg/s, an angle random walk (ARW) of 34 deg/sqrt(hr) and a bias instability of 330 deg/hr.
60

Réduction des modèles numériques en dynamique linéaire basse fréquence des automobiles / Reduction of numerical models in the low-frequency range in linear dynamic for the automotive vehicles

Arnoux, Adrien 03 October 2012 (has links)
L'objectif de cette recherche est de construire un modèle réduit de petite dimension pour prévoir les réponses dynamiques dans une bande BF sur les parties rigides d'un véhicule automobile complet. Un tel modèle réduit "léger" est une aide à la phase de conception en "Avant Projet" de ces véhicules qui ont la particularité de présenter de nombreux modes élastiques locaux en BF dues à la présence de nombreuses parties flexibles et d'équipements. Pour la construction du modèle réduit, nous avons introduit une base non usuelle de l'espace admissible des déplacements globaux. La construction de cette base requiert la décomposition en sous-domaines du domaine de la structure qui peut présenter une très grande complexité géométrique et dont les modèles EF font intervenir de très nombreux types d'éléments finis. Cette décomposition en sous-domaines a été réalisée par la Fast Marching Method que nous avons due étendre pour pouvoir traiter la complexité des modèles EF des véhicules automobiles. Puis les équations matricielles du modèle EF sont projetées sur cette base. Afin de prendre en compte les incertitudes sur les paramètres du modèle, les incertitudes de modèle induites par les erreurs de modélisation et enfin les incertitudes liées à la non prise en compte des contributions locales dans le modèle réduit des déplacements globaux, un unique modèle probabiliste non paramétrique de ces trois sources d'incertitude a été implémenté sur le modèle réduit construit avec les vecteurs propres globaux. Les paramètres de dispersion de ce modèle probabiliste ont été identifiés en utilisant le principe du maximum de vraisemblance et des réponses obtenues à l'aide d'un modèle stochastique de référence qui inclut des informations expérimentales résultant de travaux précédents. Le modèle réduit stochastique, pour la prévision des déplacements globaux sur les parties rigides dans la bande BF qui a été développé, a été validé sur un modèle de structure automobile "nue" puis a été appliqué avec succès sur un modèle complet de véhicule automobile / The objective of this research is to construct a reduced-order model to predict the dynamical response, in the LF band, of the stiff parts of a complete automotive vehicle in order to facilitate the draft design. The vehicles under consideration have many elastic modes in LF due to the presence of many flexible parts and equipments. To build such a model, we introduced a non-usual basis of the admissible space of global displacements. The construction of this basis requires the decomposition of the domain of the structure. This subdomain decomposition is performed by using the Fast Marching Method that we have extended to take into account the high complexity of the mesh of an automotive vehicle. Then the matrix equations of the FE model are projected on this basis. To take into account the system parameters uncertainties, the model uncertainties induced by the modeling errors and finally, the uncertainties related to the neglecting of local contributions in the reduced-order model, a nonparametric probabilistic model of the three sources of uncertainties has been implemented on the reduced-order model constructed with the global displacements eigenvectors. The dispersion parameters of the probabilistic model are identified using the maximum likelihood method and the responses obtained from a stochastic reference model which includes experimental data resulting from previous works. This stochastic model which has been designed for the prediction of the global displacements of the rigid parts in the LF band is validated on a simple structure of an automotive model and has been successfully applied on a complete model of automotive vehicle

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