Dissertations / Theses: 'Vibrational distribution'

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Roettgen, Andrew M. "Vibrational Energy Distribution, Electron Density and Electron Temperature Behavior in Nanosecond Pulse Discharge Plasmas by Raman and Thomson Scattering." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1428940661.

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Montello, Aaron David. "Studies of Nitrogen Vibrational Distribution Function and Rotational-Translational Temperature in Nonequilibrium Plasmas by Picosecond Coherent Anti-Stokes Raman Scattering Spectroscopy." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1345522814.

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Zschieschang, Torsten. "Schwingungsanalyse an Maschinen mit ungleichförmig übersetzenden Getrieben." Doctoral thesis, Universitätsbibliothek Chemnitz, 2000. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200000876.

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Die Arbeit befaßt sich mit Methoden der Identifikation von Schwingungsursachen anhand gemessener Schwingungssignale an Maschinen mit ungleichförmig übersetzenden Getrieben. Den technischen Hintergrund bilden die Verarbeitungsmaschinen, die als ein Haupteinsatzgebiet der auch als Mechanismen bezeichneten Getriebe gelten. Es werden eine ganze Reihe mechanismentypischer Schwingungsursachen untersucht, die im wesentlichen auf Elastizitäten, veränderliche Parameter, Spiel, Reibung und Unstetigkeiten in den Lagefunktionen zurückzuführen sind. Neben den traditionellen Methoden der Signalanalyse gilt das Hauptaugenmerk den neuen Methoden der Zeit-Frequenz-Analyse, die dem zumeist instationären Charakter der durch die Mechanismen verursachten Schwingungen gerecht werden. Dazu zählen vor allem lineare Transformationen wie die Kurzzeit-Fourier- oder die Wavelet-Transformation, quadratische Verteilungen aus Cohen's Klasse wie die Wigner-Ville und die Choi-Williams Verteilung oder auch höhere Transformationen wie die Adaptive Optimal Kernel oder die Reassignment Methode. Die Untersuchungen münden in einer tabellarischen Zusammenstellung der gefundenen Merkmale. Diese soll der Unterstützung der praktischen Signalanalyse bei Mechanismenschwingungen dienen. Die Anwendung der zur Verfügung stehenden Mittel und Methoden wird an zahlreichen Beispielen aus dem Bereich der Schwingungsdiagnose an Verarbeitungsmaschinen demonstriert
This thesis deals with methods to identify causes of vibrations by investigation of messured signals at machines with mechanisms (with varying velocity ratio). The technical background is the field of manufacturing machines, the main application of such mechanisms. Inspected are the most typical causes of vibrations at mechanisms that comes with elasticity, variable parameters, clearance, friction or nonsmooth transferfunctions. There are used both, traditional methods of signal analysis and time-frequency-analysis methods that are especially advantageous for the often instationary vibrations at this kind of machines. Linear transformations like the Short-Time-Fourier- or the Wavelet-Transformation, quadratic distributions from Cohe's Class like the Wigner-Ville- or the Choi-Williams-Distribution and higher order transformations like the Adaptive Optimal Kernel or the Reassignment Method are used in this Paper. The investigation leads into a tabular form of characteristics wich should be used for identification of vibrational causes during vibrational analysis. The use of available methods is demonstrated by solving various examples on real manufactoring machines

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Zschieschang, Torsten. "Schwingungsanalyse an Maschinen mit ungleichförmig übersetzenden Getrieben." Doctoral thesis, Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200601204.

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Die Arbeit befaßt sich mit Methoden der Identifikation von Schwingungsursachen anhand gemessener Schwingungssignale an Maschinen mit ungleichförmig übersetzenden Getrieben. Den technischen Hintergrund bilden die Verarbeitungsmaschinen, die als ein Haupteinsatzgebiet der auch als Mechanismen bezeichneten Getriebe gelten. Es werden eine ganze Reihe mechanismentypischer Schwingungsursachen untersucht, die im wesentlichen auf Elastizitäten, veränderliche Parameter, Spiel, Reibung und Unstetigkeiten in den Lagefunktionen zurückzuführen sind. Neben den traditionellen Methoden der Signalanalyse gilt das Hauptaugenmerk den neuen Methoden der Zeit-Frequenz-Analyse, die dem zumeist instationären Charakter der durch die Mechanismen verursachten Schwingungen gerecht werden. Dazu zählen vor allem lineare Transformationen wie die Kurzzeit-Fourier- oder die Wavelet-Transformation, quadratische Verteilungen aus Cohen's Klasse wie die Wigner-Ville und die Choi-Williams Verteilung oder auch höhere Transformationen wie die Adaptive Optimal Kernel oder die Reassignment Methode. Die Untersuchungen münden in einer tabellarischen Zusammenstellung der gefundenen Merkmale. Diese soll der Unterstützung der praktischen Signalanalyse bei Mechanismenschwingungen dienen. Die Anwendung der zur Verfügung stehenden Mittel und Methoden wird an zahlreichen Beispielen aus dem Bereich der Schwingungsdiagnose an Verarbeitungsmaschinen demonstriert. - - - Diese Version ersetzt eine ältere Version, Grund: Formatkonvertierung postscript zu pdf. Der Inhalt unterscheidet sich in der Qualität der Abb. 4.23a und 4.23b auf Seite 97 sowie aller Abbildungen auf Seite 111. Der Zugriff auf die Original-Abb. ist über die ältere Version oder die gedruckte Ausgabe möglich. Die gedruckte Ausgabe der Dissertation ist in der Universitätsbibliothek Chemnitz entleihbar
This thesis deals with methods to identify causes of vibrations by investigation of messured signals at machines with mechanisms (with varying velocity ratio). The technical background is the field of manufacturing machines, the main application of such mechanisms. Inspected are the most typical causes of vibrations at mechanisms that comes with elasticity, variable parameters, clearance, friction or nonsmooth transferfunctions. There are used both, traditional methods of signal analysis and time-frequency-analysis methods that are especially advantageous for the often instationary vibrations at this kind of machines. Linear transformations like the Short-Time-Fourier- or the Wavelet-Transformation, quadratic distributions from Cohe's Class like the Wigner-Ville- or the Choi-Williams-Distribution and higher order transformations like the Adaptive Optimal Kernel or the Reassignment Method are used in this Paper. The investigation leads into a tabular form of characteristics wich should be used for identification of vibrational causes during vibrational analysis. The use of available methods is demonstrated by solving various examples on real manufactoring machines. - - - This version replaces an older version, reason is conversion of format from postscript to pdf. Content is different in quality of pictures 4.23a and 4.23b on page 97 and all pictures on page 111. Please see the original pictures in the older version or the printed version. The printed version is borrowable at the Library of Chemnitz University of Technology

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Silva, Junior João Viçozo. "Aplicação do modelo carga-fluxo de dipolo para calcular e interpretar as intensidades no espectro infravermelho dos fluoroclorometanos." [s.n.], 2006. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249358.

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Orientador: Roy Edward Bruns
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-09T10:57:29Z (GMT). No. of bitstreams: 1 SilvaJunior_JoaoVicozo_M.pdf: 455136 bytes, checksum: d8cb42bcd5d75c3d6dd417771ba11425 (MD5) Previous issue date: 2007
Resumo: O momento dipolar molecular, suas derivadas e as intensidades fundamentais no espectro infravermelho dos fluoroclorometanos são determinados a partir de cargas e dipolos atômicos QTAIM, e de seus fluxos no nível MP2/6-311++G(3d,3p). A comparação dos momentos dipolares e das intensidades fundamentais no infravermelho calculados usando parâmetros QTAIM com aqueles obtidos diretamente a partir de cálculos MP2/6-311++G(3d,3p) mostra erros rms (root mean square) de 0,01 D e 5,6 km mol, e erros de 0,04 D e 23,1 km mol quando comparados com valores experimentais. As contribuições de carga, fluxo de carga e fluxo de dipolo são calculadas para todos os modos normais de vibração destas moléculas. Uma correlação negativa significativa (-0,92) é observada entre as contribuições de fluxo de carga e de fluxo de dipolo e indica que a transferência de carga de um lado para outro da molécula durante as vibrações é acompanhada por uma relaxação da densidade eletrônica que se polariza na direção oposta. Os modos normais de estiramento CF, CCl e CH destas moléculas mostram ter conjuntos de valores característicos de contribuições de carga, fluxo de carga e fluxo de dipolo. Embora as deformações FCF e ClCCl também possam ser diferenciadas umas das outras a partir dos tamanhos e sinais destas contribuições, algumas deformações HCH têm contribuições que são parecidas com aquelas das deformações ClCCl
Abstract: The molecular dipole moments, their derivatives and the fundamental infrared intensities of the fluorochloromethanes are determined from QTAIM atomic charges and dipoles and their fluxes at the MP2/6- 311++G(3d,3p) level. Root-mean-square (rms) errors of 0.01 D and 5.6 km mol are found for the dipole moments and fundamental infrared intensities calculated using QTAIM parameters when compared with those obtained directly from the MP2/6-311++(3d,3p) calculations and 0.04 D and 23.1 km mol when compared to the experimental values. Charge, charge flux and dipole flux contributions are calculated for all the normal vibrations of these molecules. A large negative correlation coefficient of -0.92 is calculated between the charge flux and dipole flux contributions and indicates that charge transfer from one side of the molecule to the other during vibrations is accompanied by relaxation with electron density polarization in the opposite direction. The CF, CCl and CH stretching normal modes of these molecules are shown to have characteristic sets of charge, charge flux and dipole flux contributions. Although the FCF and ClCCl deformation normal modes can also be discriminated from one another based on their sizes and signs of these contributions some HCH deformations have contributions that are similar to those for some of the ClCCl deformations
Mestrado
Físico-Química
Mestre em Química

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Burema, Shiri. "Inelastic Electron Tunneling Spectroscopy with the Scanning Tunneling Microscope : a combined theory-experiment approach." Thesis, Lyon, École normale supérieure, 2013. http://www.theses.fr/2013ENSL0821.

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La Spectroscopie par Effet Tunnel Inélastique (IETS) avec un Microscope à Effet Tunnel (STM) est une nouvelle technique de spectroscopie vibrationnelle, qui permet de caractériser des propriétés très fines de molécules adsorbées sur des surfaces métalliques. Des règles de selection d’excitation vibrationnelle basées sur la symétrie ont été proposées, cependant, elles ne semblent pas exhaustives pour expliquer la totalité du mécanisme et des facteurs en jeu; elles ne sont pas directement transposables pour les propriétés d'un adsorbat et sont lourdes d'utilisation. Le but de cette thèse est donc d'améliorer ces règles de selection par une étude théorique. Un protocole de simulation de l'IETS a été développé, paramétré, et évalué, puis appliqué pour calculer des spectres IETS pour différentes petites molécules, qui sont systématiquement liées, sur une surface de cuivre. Des principes additifs de l'IETS ont été developpés, notamment concernant l’extension dans le vide de l’état de tunnel, l'activation/ quench sélectif de certains modes du aux propriétés électroniques de certains fragments moléculaires, et l'application de certaines règles d'addition de signaux IETS. De plus, des empreintes vibrationnelles par des signaux IETS ont été determinées pour permettre de différentier entre les orientations des adsorbats, la nature chimique des atomes et les isomères de structures. Une stratégie simple utilisant les propriétés de distribution de la densité électronique de la molécule isolée pour prédire les activités IETS sans des couts importants de calculs a aussi été développée. Cette expertise a été utilisée pour rationaliser et interpréter les mesures expérimentales des spectres IETS pour des métalloporphyrines et métallophtalocyanines adsorbées. Ces études sont les premières études IETS pour des molécules aussi larges et complexes. L'approche expérimentale a permis de déterminer les limitations actuelles des simulations IETS. Les défauts associés à l'identification ont été résolus en faisant des simulations d'images STM complémentaires
Inelastic Electron Tunneling Spectroscopy (IETS) with the Scanning Tunneling Microscope (STM) is a novel vibrational spectroscopy technique that permits to characterize very subtle properties of molecules adsorbed on metallic surfaces. Its proposed symmetry-based propensity selection rules, however, fail to fully capture its exact mechanism and influencing factors; are not directly retraceable to an adsorbate property and are cumbersome. In this thesis, a theoretical approach was taken to improve them. An IETS simulation protocol has been developed, parameterized and benchmarked, and consequently used to calculate IETS spectra for a set of systematically related small molecules on copper surfaces. Extending IETS principles were deduced that refer to the tunneling state’s vacuum extension, the selective activating/quenching of certain types of modes due to the moieties’ electronic properties, and the applicability of a sum rule of IETS signals. Also, fingerprinting IETS-signals that enable discrimination between adsorbate orientations, the chemical nature of atoms and structural isomers were determined and a strategy using straightforward electronic density distribution properties of the isolated molecule to predict IETS activity without (large) computational cost was developed. This expertise was used to rationalize and interpret experimentally measured IETS spectra for adsorbed metalloporphyrins and metallophthalocyanines, being the first IETS studies of this large size. This experimental approach permitted to determine the current limitations of IETS-simulations. The associated identification shortcomings were resolved by conducting complementary STM-image simulations

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Mazánková, Věra. "Spektroskopické studium dohasínajících výbojů v dusíku a jeho směsích." Doctoral thesis, Vysoké učení technické v Brně. Fakulta chemická, 2009. http://www.nusl.cz/ntk/nusl-233291.

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Presented thesis gives results obtained during the spectroscopic observations of post –discharges of the pure nitrogen plasma with small oxygen admixture and in the nitrogen – argon mixture and the effect of the pink afterglow in it. The DC discharge in the flowing regime has been used for the plasma generation. The decaying plasma was study by optical emission spectroscopy, mainly in the range of 300–800 nm. The first positive, second positive, first negative nitrogen spectral system and NO spectral systems were observed in measured spectra. The band head intensities of these bands have been studied in the dependencies on experimental conditions. Simultaneously, the relative vibrational populations on the given nitrogen states have been calculated. Two discharge tubes made from different materials (PYREX glass and QUARTZ glass) were used in the case of nitrogen plasma containing low oxygen traces (up to 0.2 %). These experiments have been carried out at two wall temperatures for the determination of the temperature effect on the post-discharge. The discharge tube around the observation point was kept at the ambient temperature (300 K) or it was cooled down to 77 K by liquid nitrogen vapor. The total gas pressure of 1 000 Pa and the discharge current of 200 mA were conserved for all these experiments. The relative populations of electronic states were calculated in the dependence on the post-discharge time. The dependencies on oxygen concentration were given, too. The results showed no simple dependence of vibrational populations on oxygen concentration. Generally, slight increase of neutral nitrogen states populations was observed with the increase of oxygen concentration. These observations were well visible due to the intensity of nitrogen pink afterglow effect that was well visible at all oxygen concentrations. The pink afterglow maximal intensity was reached at about 5–10 ms at the wall temperature of 300 K in the PYREX tube. The molecular ion emission was strongly quenched by the oxygen and as this was dominant process for the pink afterglow emission the pink afterglow effect disappears at oxygen concentration of about 2000 ppm. The temperature and wall material influences were observed, too. The post-discharge in nitrogen argon mixtures was studied only in the PYREX tube at the ambient wall temperature of 300 K. The power dissipated in an active discharge was constant of 290 kW. The experimental studies had two new parameters – total gas pressure (500 Pa – 5 000 Pa) and the argon concentrations that were varied in the range of 0–83 %. Also in this case the dependencies of relative intensities of the bands given above were obtained and further the relative populations of electronic states as a function of decay time, total gas pressure and on argon concentration were obtained. The pink afterglow effect was observed at all applied discharge powers and total gas pressures. At the highest argon concentrations, especially at lower pressure, the pink afterglow effect disappeared. The presented experimental work is one of the hugest sets of experiments in the nitrogen with oxygen traces and in nitrogen-argon mixtures. These data can be used as a very good fundament for the further studies using wide numeric modeling of the post-discharge kinetic processes.

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Midgley, Jonathan Peter. "Intramolecular dynamics in small aromatic molecules : vibrational redistribution and the application of photoelectron angular distributions." Thesis, University of Nottingham, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.713703.

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Photochemistry and photophysics are prominent and important phenomena, being involved in such diverse processes as photosynthesis, vision and solar energy capture. An understand› ing of the mechanisms of energy flow after photoexcitation is integral to the reproduction or control of these processes. Such dynamical considerations are intimately related to spec› troscopy - the study of the interaction of light with matter - and by their nature must be treated using quantum mechanical methods. This work aims to build on the current understanding of, and the methods of monitor› ing , photo-initiated dynamics within individual gas-phase aromatic molecules. Multiphoton ionisation and valence photoelectron spectroscopy are used to excite and probe gas phase molecules that have been cooled by means of a supersonic expansion. A time-resolved ap› proach is employed in order to study the process of vibrational redistribution in electronically excited states; dynamics are initiated by a laser pulse of picosecond duration, and a second ionisation pulse, arriving a variable time delay later, is used to probe the changing state of the molecule. The vibrational state of the molecule is indicated by the energy distribution of the photoelectrons, which is measured using the velocity map imaging (VMI) technique. There is the possibility of resolving peaks corresponding to individual ionic vibrational states due to the relatively narrow bandwidth of the laser pulses. Observations are made of os› cillatory dynamics at a number of different energies in the first electronically excited state of para-difluorobenzene. Analysis reveals previously unobserved vibrational structure and sheds further light on the mechanisms of vibrational redistribution . These observations are compared and contrasted with those from fluorobenzene, toluene and para-fluorotoluene in order to investigate the effect of reducing symmetry and the presence of different functional groups on the observed dynamics. The angular distribution of the photoelectrons is also recorded as part of a VMI measurement. These distributions are determined by interference the between the partial waves that describe the wavefunctions of the outgoing electrons, and can be sensitive to the quantum states and alignment of molecules. The potential for using measurements of photoelectron angular distributions (PADs) to monitor intramolecular dynamics is evaluated.

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Chen, Yan Pei. "De la dissymétrie des distributions locales des vitesses dans un gaz granulaires stationnaires excités par vibration, et de l'impossibilité de sa description à l'aide de l'hydrodynamique classique." Thesis, Châtenay-Malabry, Ecole centrale de Paris, 2014. http://www.theses.fr/2014ECAP0016/document.

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La présente thèse est consacrée à l'étude expérimentale et la simulation de la dynamique des gaz granulaires vibro-fluidisés. Les gaz granulaires sont caractérisés par une dissipation due aux collisions inélastiques. Pour maintenir cet état à l'équilibre mécanique (stationnarité), l'énergie est injectée en continu depuis les bords vibrant pour équilibrer la dissipation des vibrations. Ce système fournit une base d'étude de la physique des systèmes non-linéaires, hors équilibre thermodynamique et dissipatifs. Cette thèse insiste sur la nécessité d'intégrer, de comprendre et de rendre compte de la situation inhomogène de la distribution locale dans les gaz granulaires et permet la construction d'un nouveau modèle de gaz granulaires fluidisés par des vibrations. Cette approche inclut (i) des résultats expérimentaux 2d en micro-gravité dans l'Airbus A300 0-g de Novespace, des expériences 2d avec des cellules (et des vibrations) horizontales, des expériences 2d sur plan incliné (avec vibrations et cellules inclinées et avec une gravité effective variable), ainsi que des simulations de dynamique moléculaire par la méthode " event-driven" appliquée à chaque choc. Ces résultats confortent les simulations 3D de Liu et al. Les expériences en micro-gravité dans Airbus A380 (vol parabolique) permettent d'éviter les frottements avec les parois planes et éliminent l'effet de gravité. Les distributions locales de la vitesse dans la direction de vibrations sont asymétriques partout (à l'exception de la zone centrale de la cellule par raison de symétrie). L' équipartition de l'énergie n'est pas vérifiée dans la cellule, l'énergie est distribuée de manière inhomogène, anisotrope et directionnelle. La " température granulaire " n'est plus une mesure efficace pour décrire un tel système. On rend compte de ces résultats à l'aide d'une superposition de deux modèle gaussien pour décrire les profils locaux de vitesse asymétriques le long de la direction de vibration. Les résultats des simulations de dynamique moléculaire 2d en gravité nulle montrent les mêmes tendances et confortent les résultats l'expérimentaux (dissymétrie des distributions de vitesse locales). Cette dissymétrie est un effet à longue portée et est liée à la dissipation du système: Elle augmente si le coefficient de restitution billes-billes diminue ou lorsque le nombre de particules augmente. La dissymétrie disparaît lorsque les chocs billes-billes sont élastiques. Cet effet ne peut être ignoré et doit être traité comme la frontière d'une "nouvelle hydrodynamique". Dans les expériences de vibrations sur cellule 2D et plan inclinés parallèles aux vibrations, l'angle d'inclinaison a été modifié de façon systématique de l'horizontale à la verticale, pour simuler différentes gravités effectives. Les résultats confirment une dissymétrie locale des distributions de vitesse locales, à laquelle se rajoute une dissymétrie supplémentaire liée à la gravité, provoquant une densité différente en haut et en bas de la cellule. Ces études sont les prémices, nous le pensons, d’une nouvelle vision de la mécanique des gaz granulaires réels dissipatifs
The present thesis is dedicated to the experimental and simulation study of vibro-fluidized granular gases dynamics. Granular gases are characterized by dissipation due to inelastic collisions. To keep a steady state, continuous energy is injected to balance dissipation by vibration. This system provides a platform to study the physics of non-linear, non-equilibrium and dissipative systems. This dissertation insisted on the necessity of understanding the local state in the granular gases and building a new model for vibration-fluidized granular gases. Research approach included experiments in micro-gravity, event-driven molecular dynamic simulation and experiments in tilted plane with various gravity. Micro-gravity experiments were performed on Airbus A380 (Parabolic flight) to avoid friction with the bottom and gravity field. A long range boundary effect is found to exist in 2D vibration granular gases. Local distributions of the velocity component in the vibration direction are asymmetric in the whole cell except for the center bin. In the system, energy equi-partition breaks down. ``Granular temperature" is not efficient to describe such a system. We proposed a superposition of two Gaussian model to describe the local asymmetric velocity profiles along the vibration direction. We demonstrated the performance of this model by the Airbus experimental data and others’ simulation works. Event-driven molecular dynamics simulation was utilized. Results showed support for experiment results. Furthermore, we found this long range boundary effect is related to the system dissipation. This effect becomes pronounced if the coefficient of restitution (e<1) decreased or the number of particles increased. For the elastic situation, there is no such effect. This effect cannot be ignored and treated only as a local boundary effect as in hydrodynamics. We studied a 2D vibration fluidized granular system in a tilted plane systematically. The inclined angle is changed from horizontal to vertical, changing the "effective gravity". These results also showed asymmetric local velocity distributions. Other than the number density profiles deviate from an exponential form, the spatial profiles of the number density of particles moving up and down are not equal, and non symetric from cell center

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Asnaashari, Erfan. "Vibration-based damage detection in structures." Thesis, University of Manchester, 2014. https://www.research.manchester.ac.uk/portal/en/theses/vibrationbased-damage-detection-in-structures(09061582-55fb-4fba-846e-2156dd4ef172).html.

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Structural health monitoring systems have a great potential for cost saving and safety improvement in different types of structures. One of the most important tasks of these systems is to identify damage at an early stage of its development. A variety of methods may be used to identify, locate, or quantify the extent of damage or fault in a structural or mechanical component. However, the preferable method is the one which maximises the probability of detecting the flaw, while also considering feasibility of in-situ testing, ease of use and economic factors. Cracks are one of the common defects in structural components that may ultimately lead to failure of structures if not detected. The presence of cracks in a structure brings about local variations in the stiffness of the structure. These variations cause the dynamic behaviour of the cracked structure to be different from that of a healthy one. Vibration-based damage detection methods have attracted considerable attention over the past few decades. These methods generally use changes to the physical properties of structures for the purpose of crack detection. In this thesis, two new vibration-based methods have been developed for damage detection in beam-like and rotor-type structures. The first method performs the entire signal processing required for crack detection in time domain. It is based on assessing the normality of vibration responses using the normal probability plot (NPP). The amount of deviation between the actual and normal distribution of measured vibration responses was calculated along the length of the structure to localise the crack. The second proposed method converts the vibration responses into frequency domain for further processing. Excitation of the cracked structure at a given frequency always generates higher harmonic components of the exciting frequency due to the breathing of the crack. This method uses the operational deflection shape of the structure at the exciting frequency and its higher harmonics to identify the crack location. Avoiding complicated signal processing in frequency domain is the main advantage of the first method. However, more precise identification of crack locations can be obtained through the second method. Generally, both methods have the advantage of being easy, reference-free and applicable to in-situ testing for any structure. The concept and computational approach of both methods along with their validations through numerical and experimental examples have been presented. Moreover, different input excitations have been used to evaluate the capability of the developed methods in detecting the crack location(s).

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Flandrin, Patrick. "Représentations temps-fréquence des signaux non-stationnaires." Grenoble INPG, 1987. http://www.theses.fr/1987INPG0048.

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Analyse spectrale non paramétrique des signaux non stationnaires. Description d'une représentation temps-frequence modélisée par des contraintes pour définir une classe générale d'estimateurs afin d'évaluer les performances

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Anis, Fatima. "Role of nuclear rotation in H[subscript]2[superscript]+ dissociation by ultra short laser pulses." Diss., Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/2181.

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Mohd, Yusoff Sabariah. "Clustering classification and human perception of automative steering wheel transient vibrations." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15849.

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In the 21st century, the proliferation of steer-by-wire systems has become a central issue in the automobile industry. With such systems there is often an objective to minimise vibrations on the steering wheel to increase driver comfort. Nevertheless, steering wheel vibration is also recognised as an important medium that assists drivers in judging the vehicle's subsystems dynamics as well as to indicate important information such as the presence of danger. This has led to studies of the possible role of vibrational stimuli towards informing drivers of environment conditions such as road surface types. Numerous prior studies were done to identify how characteristics of steering wheel vibrational stimuli might influence driver road surface detection which suggested that there is no single, optimal, acceleration gain that could improve the detection of all road surface types. There is currently a lack of studies on the characteristics of transient vibrations of steering wheel as appear to be an important source of information to the driver road surface detection. Therefore, this study is design to identify the similarity characteristics of transient vibrations for answering the main research question: "What are the time-domain features of transient vibrations that can optimise driver road surface detection?" This study starts by critically reviewing the existing principles of transient vibrations detection to ensure that the identified transient vibrations from original steering wheel vibrations satisfy with the definition of transient vibrations. The study continues by performing the experimental activities to identify the optimal measurement signal for both identification process of transient vibrations and driver road surface detection without taking for granted the basic measurement of signal processing. The studies then identify the similarity of transient vibrations according to their time-domain features. The studies done by performing the high-dimensional reduction techniques associated with clustering methods. Result suggests that the time-domain features of transient vibrations that can optimise driver road surface detection were found to consist of duration (Δt), amplitude (m/s2), energy (r.m.s) and Kurtosis.

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Pesaresi, Emanuele. "Leptokurtic signals in random control vibration testing." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017.

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In several industrial sectors, some components are subjected to mechanical vibrations which may lead to a premature failure. To ensure that they operate properly during their service life, the utilization of qualification tests has been consolidated over the years. It is often required to carry out accelerated tests for obvious reasons as feasibility and cost: the aim is to limit the duration of tests. The Test Tailoring procedure requires an appropriate definition for vibratory test profiles to be utilized as an excitation in terms of motion generated by vibrating tables or shakers. The synthesis of such profiles requires that signals be measured in real environments and then that their most important characteristics be reproduced in a laboratory, in particular their spectral content and damage potential.The conventional procedures permit the synthesis of an accelerated test profile in terms of a Power Spectral Density, which is characterized by a Gaussian distribution of the corresponding timeseries values. Such a kind of synthesis might be unfit to represent the real environment signal taken as a reference, owing to the latter’s usual non-Gaussianity. As a consequence, reliability could be compromised since the “nature” of the real signal is not preserved. Typical examples of non-Gaussian signals coming forth in real applications are the so-called Leptokurtic signals, whose high amplitude peaks originate a strongly non Gaussian probability distribution. A parameter called kurtosis is often employed to represent the number and severity of the peaks of the signal. A common reference is made to “kurtosis control” whenever it is required that the synthesized and the measured signal have not only the same spectral content but the same kurtosis value as well. In this work some novel Mission Synthesis algorithms are proposed, which generate test profiles by controlling precisely the kurtosis value and complying with the spectral content of the reference signal.

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15

Johnson, Alan M. "Relaxation of Vibrationally Excited Trifluorobenzene and Tetrafluorobenzene by Collisions with Carbon Dioxide." BYU ScholarsArchive, 2009. https://scholarsarchive.byu.edu/etd/2177.

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An investigation into the relaxation of highly vibrationally excited trifluorobenzene and tetrafluorobenzene following collisions with carbon dioxide was performed using diode laser transient absorption spectroscopy. A 248 nm excimer laser prepared the vibrationally hot (E'~41,000 cm-1) fluorobenzene molecules. Large amounts of translational and rotational energy are transferred through collisions between the hot donor molecule and CO2. Rate constants and collisional probabilities were calculated by probing the high J states (J=58~80) of CO2 in the vibrational ground state, 0000, with measurements taken 1 µsec, ¼ the mean gas collision time, following each excimer laser pulse. The energy transfer probability distribution function, P(E,E'), was calculated for each molecule using the state-resolved probabilities and the energy gain of the bath. The study found a relationship between the fraction of strong collisions and the donor's dipole moment. Additionally, these findings support an application of Fermi's Golden rule to collisional energy transfer by linking the shape of P(E,E') to the shape of the donor's density of states as a function of ΔE.

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16

Benhalima, Reda Bachir. "Contribution à l'étude de la couche limite laminaire tridimensionnelle autour d'un corps de révolution en vibrations harmoniques." Valenciennes, 1996. https://ged.uphf.fr/nuxeo/site/esupversions/fca1e588-6ef6-4e1b-86e6-3c672e09ad49.

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Notre étude s'inscrit dans un cadre purement fondamental et complémentaire à tous les travaux effectués dans le domaine des écoulements instationnaires, allant de l'obtention de solutions exactes de quelques cas très simples à des solutions asymptotiques au voisinage de basses ou hautes fréquences (ou amplitudes) de vibration. On s'est intéressé plus particulièrement à la structure de la couche limite (détermination des composantes de vitesse ainsi que les coefficients de frottement) autour d'un ellipsoïde de révolution placé sous incidence et mis en vibrations harmoniques dans un écoulement laminaire d'un fluide visqueux newtonien incompressible. L’approche a été purement théorique et reposant nécessairement sur deux procédés de résolution des équations de la couche limite. La méthode des approximations successives qui consiste sous certaines conditions physiques à construire la solution de proche en proche sous la forme d'une série, la convergence de cette série dépend de ces conditions physiques. La méthode de lin qui s'applique bien dans le cas où l'écoulement extérieur est perturbé par des hautes fréquences. On note aussi l'introduction de quelques paramètres de contrôle de la couche limite tel que le paramètre magnétique et le facteur de glissement à la paroi de l'obstacle considéré.

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17

Shepard, William Steve Jr. "The impact of attached feature scales and spatial distributions on the response of structural-acoustic systems." Diss., Georgia Institute of Technology, 1996. http://hdl.handle.net/1853/18911.

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18

Hua, Wei. "Interfacial Water Organization and Ion Distributions Investigated with Vibrational Sum Frequency Spectroscopy: Answering Fundamental Questions for Environmental Chemistry." The Ohio State University, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=osu1385593745.

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19

Guadagnini, David. "Measurement and Analysis of the Physical and Climatic Distribution Environment for Air Package Shipment." DigitalCommons@CalPoly, 2017. https://digitalcommons.calpoly.edu/theses/1752.

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The modern air parcel distribution industry has significantly grown to become one of the most commonly employed methods to quickly transport goods throughout the world. Although it comes with many benefits, including higher speed, greater reliability, and tighter security, the multimodal transport system within it can expose packages to a wide variety of climatic and physical distribution hazards. In a single route of transportation, packages could be included in different types of small delivery vans, large commercial semi trucks, cargo dollies, feeder aircraft, and high altitude commercial jetliners. The varying hazard level presented during distribution could directly weaken the packaging components and/or cause product damage. For this reason, it is of utmost importance to properly account for them during package design. Although there have been many past studies to quantify the hazards experienced in specific modes of transport, an over-arching profile of entire distribution route has not yet been developed. Furthermore, after a review of the current testing standards presented in the Code of Federal Regulations as outlined in 49 CFR Part 178, Subpart M, it can be found that many of these currently used testing profiles are not truly representative of the conditions experienced in actual distribution. This study quantifies each hazard element experienced within the modern air parcel distribution environment and develops single testing profiles to accurately represent them. In order to develop single testing profiles for each hazard element, instrumented test packages were sent to multiple domestic and international destinations. Throughout each of these distribution routes, data was collected on the hazard levels experienced. Afterwards, by identifying the amount of time a package spends within each mode of transport, correctly weighted testing profiles were developed. These newly developed profiles represent the minimum hazard level to be included in package performance testing that represents the normal conditions of the air transport environment. Although these composite testing profiles are developed, it is the responsibility of testing laboratories to integrate these updated profiles into their practice.

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20

Wilson, Ann Cindy. "Expected Vibration Performance of Wood Floors As Affected by MSR vs. VSR Lumber E-Distribution." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/36705.

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A simulation study was done to investigate the effect of the coefficient of variation of the modulus of elasticity ((E) on the vibrational performance of joist floor systems. Eight floor cases were studied and two types of lumber were considered: MSR and VSR lumber where (E is 0.11 and 0.25, respectively. The expected floor vibrational performance of MSR versus VSR lumber floors was evaluated by: 1) the probability that the fundamental frequency is less than 10 Hz and 2) the ratio of the first percentile of predicted fundamental frequency of MSR to VSR lumber.
Master of Engineering

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21

Griffiths, Katharine Rhiannon. "An improved method for simulation of vehicle vibration using a journey database and wavelet analysis for the pre-distribution testing of packaging." Thesis, University of Bath, 2013. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.589639.

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Vehicle vibration is inherently random and non-stationary with a non-Gaussian distribution. In addition, variations in vehicle parameters, product payloads and distribution journeys mean that the characteristics of vibration are not identical for all distribution journeys. Because vehicle vibration and shock are key causes of damage during distribution, their simulation in pre-distribution testing is vital in order to ensure that adequate protection is provided for transported products. The established method set out in the current testing standards utilises a global set of averaged accelerated power spectral density spectra to construct random vibration signals. These signals are stationary with Gaussian distributions and, therefore, do not fully represent actual vehicle vibration, only an average. The aim of the investigation, reported on in this Thesis, was to create an improved test regime for simulating vehicle vibration for pre-distribution testing of packaging. This aim has been achieved through the construction of representative tests and the creation of realistic simulations with statistical significance. A journey database has been created, in which historic road profile data along with a quarter vehicle model have been used to approximate a known vehicle’s vibration on a specific distribution journey. Additionally, a wavelet decomposition method, in which wavelet analysis is used to decompose the approximate vehicle vibration in to a series of Gaussian approximations of varying amplitude and spectral content, has been developed. Along with theoretical work, case studies have been undertaken in order to validate the test regime.

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22

Polowin, Joel Evan Carleton University Dissertation Chemistry. "The effects of potential energy surface features on product vibrational distributions for the reaction F + H [subscript] 2 -] HF + H." Ottawa, 1988.

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23

Bayissa, Wirtu Lemessa. "Damage identification and condition assessment of civil engineering structures through response measurement /." Connect to thesis, 2007. http://eprints.unimelb.edu.au/archive/00003631.

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24

Hamel, Myriam. "Influence de la variation de la température ambiante sur les vibrations induites par effet de couronne /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1991. http://theses.uqac.ca.

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Oehlmann, Harald. "Analyse temps-fréquence de signaux vibratoires de boites de vitesses." Nancy 1, 1996. http://docnum.univ-lorraine.fr/public/SCD_T_1996_0216_OEHLMANN.pdf.

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Ce mémoire est relatif à l'analyse TF de signaux vibratoires de boites de vitesses. Le premier chapitre concerne l'acquisition et la modélisation du signal vibratoire dans le cas d'une boite saine ainsi qu'avec des défauts d'engrenages et de roulements. Le deuxième chapitre présente les idées principales de l'analyse temps-fréquence (TF). Sur la base du modèle précédent, on justifie l'intérêt d'une telle approche. Dans le cadre de la classe de Cohen, le problème de la réduction des interférences (crucial pour une bonne interpretabilite) revient a définir un noyau global. La méthode du noyau optimal permet le calcul d'un noyau adapté au signal. Une nouvelle distribution tf à interférences réduites est proposée au chapitre trois. Appelée distribution de Wigner-ville locale, elle consiste à effectuer un lissage local (c'est à dire dépendant du point TF considéré) de la distribution de wigner-ville. Les dimensions de la fenêtre de lissage, optimales au sens de la réduction des interférences, sont obtenues à partir d'une procédure d'estimation. On montre que cette distribution est membre d'une classe étendue caractérisée par un noyau dépendant du point TF considéré. Certaines propriétés de cette classe sont étudiées. Le quatrième chapitre présente la discrétisation de la méthode nécessaire à son implantation. Une évaluation de ses performances sur des signaux synthétiques montre son efficacité pour la réduction des interférences. Enfin, le cinquième chapitre concerne l'analyse tf des signaux vibratoires. Une méthodologie d'analyse est notamment proposée puis appliquée aux signaux obtenus sur boite saine, avec défauts d'engrenage puis de roulement. Pour chaque cas, on met en évidence les composantes caractéristiques et on fournit une interprétation physique. L'ensemble des résultats permet de proposer un modèle vibratoire de la boite de vitesses.

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Derakhshanian, Mahin. "Simulations numériques des vibrations induites par effet de couronne sur un court conducteur soumis à une pluie artificielle /." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2001. http://theses.uqac.ca.

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Astfalck, Allen Electrical Engineering Australian Defence Force Academy UNSW. "Analysis of electromagnetic force and noise in inverter driven induction motors." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Electrical Engineering, 2002. http://handle.unsw.edu.au/1959.4/38671.

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This thesis is part of a major research project to analyse vibro-acoustic characteristics from variable speed inverter driven induction motors (VSIDIM). The overall projects??? aimed at providing a better understanding of the mechanisms of sound generation from electromagnetic origins and developing a numerical model to predict the sound power emitted from a VSIDIM. The scope of this thesis is to assess experimentally the effect of various controller strategies on the radiated sound power and to develop a finite element method for calculating the electromagnetic force distribution over the stator. Various sources of noise in induction motors and their behaviour with speed and load have been reviewed. Models of the electromagnetic field and vibro-acoustic character have been discussed. An outline of various techniques of reducing noise in induction motors through design of inverters and modifications to the motor structure has been given. Experiments were conducted to assess the effect of controller strategies on the radiated sound power. Three different supplies were tested: a dynamotor which produces an almost sinusoidal supply with very low harmonic content, an inverter with a low switching frequency (less than 1kHz) and an inverter with a high switching frequency (8kHz) and various levels of random modulation. Results indicate that the sound power level of the MSC drive is a lot higher than that of the VSC 2000 drive and the dynamotor drive. The sound power level of the VSC 2000 drive and the dynamotor drive increases almost linearly with motor speed, that for the MSC drive is almost independent of speed. The sound power level of the MSC drive is almost 28dB higher than that of the dynamotor drive at 450rpm and the difference is reduced to 14dB at 1500rpm where the aerodynamic noise becomes more dominant. It has been found that at the rated speed (1500rpm), the sound power level varies by less than 3dB from no load to full load for all three sources. Although increasing the switching frequency increases the cost of the inverters and switching losses, results from the MSC and VSC 2000 drives clearly show that it reduces the radiated sound power by shifting the harmonics into higher and inaudible frequency range. The tonal nature around the switching frequency has been reduced by increasing the levels of random modulation to spread the energy over a wider range of frequencies, although the sound power level has not varied by more than 0.2dB. A finite element model has been developed to calculate the electromagnetic force distribution. The quasi-static solution method has been implemented by stepping the rotor through the time domain using a fine regular mesh in the air gap. The stator currents were experimentally obtained while the rotor currents were obtained using a 4 parameter state space model of the motor. Results of the simulation indicate the influence of stator and rotor slots, saturation and time harmonics in the current. The calculated electromagnetic force distribution has been used in a FEM/BEM acoustic model and SEA acoustic model to predict the radiated sound power which agrees reasonably well with the measured sound, thus validating indirectly the electromagnetic force simulations.

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Decker, Aubrey Jeanette. "Test Method for Predicting Failure Modes in Protective Films." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7429.

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In the business of packaging engineering, a large consumption of time is placed on evaluating new materials to provide cost savings to a company. This evaluation is made by using test methods such as those found in ASTM D4169-16, which helps to simulate shipping and distribution conditions. A key problem is that this test method can take up to multiple months, and sometimes years to complete. The apparatus created in this study allows for a comparison to be made between currently used films and prospective films in approximately ten hours. This allows for a prescreening of new films to be done before completing full ASTM shipment and distribution testing.This study focuses on coextruded multilayer polymer films and the damage brought upon them in forms of puncture and abrasion through shipment and distribution.

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29

Yuan, Han. "Static and dynamic stiffness analysis of cable-driven parallel robots." Thesis, Rennes, INSA, 2015. http://www.theses.fr/2015ISAR0003/document.

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Cette thèse contribue à l'analyse des raideurs statique et dynamique des robots parallèles à câbles dans un objectif d'amélioration de la précision de positionnement statique et de la précision de suivi de trajectoire. Les modélisations statique et dynamique proposées des câbles considèrent l'effet du poids du câble sur son profil et l'effet de masse du câble sur la dynamique de ce dernier. Sur la base du modèle statique de câble proposé, l'erreur de pose statique au niveau de l'organe terminal du robot est définie et sa variation en fonction de la charge externe appliquée est utilisée pour évaluer la raideur statique globale de la structure. Un nouveau modèle dynamique vibratoire de robots à câbles est proposé en considérant le couplage de la dynamique des câbles avec les vibrations de l'organe terminal. Des validations expérimentales sont réalisées sur des prototypes de robots à câbles. Une série d'expériences de statique, d'analyses modales, d'analyses en régime libre et de suivi de trajectoire sont réalisées. Les modèles statiques et dynamiques proposés sont confirmés. Les dynamiques des câbles et du robot ainsi que leur couplage sont discutées montrant la pertinence des modèles développés pour l’amélioration des performances des robots à câbles en termes de design et le contrôle. Outre l'analyse des raideurs statique et dynamique, les modèles proposés sont appliqués dans l'amélioration du calcul de la distribution des efforts dans les câbles des robots redondants. Une nouvelle méthode de calcul de la distribution des efforts dans les câbles basée sur la détermination de la limite inférieure des forces dans les câbles est présentée. La prise en compte de la dépendance à la position dans l'espace de travail permet de limiter les efforts dans les câbles et ainsi d'améliorer l'efficience des robots d'un point de vue énergétique
This thesis contributes to the analysis of the static and dynamic stiffness of cable-driven parallel robots (CDPRs) aiming to improve the static positioning accuracy and the trajectory tracking accuracy. The proposed static and dynamic cable modeling considers the effect of cable weight on the cable profile and the effect of cable mass on the cable dynamics. Based on the static cable model, the static pose error of the end-effector is defined and the variation of the end-effector pose error with the external load is used to evaluate the static stiffness of CDPRs. A new dynamic model of CDPRs is proposed with considering the coupling of the cable dynamics and the end-effector vibrations. Experimental validations are carried out on CDPR prototypes. Static experiments, modal experiments, free vibration experiments and trajectory experiments are performed. The proposed static and dynamic models are verified. Cable dynamics, robot dynamics and their coupling are discussed. Results show the relevance of the proposed models on improving the performances of CDPRs in terms of design and control. Besides stiffness analysis, the proposed models are applied on the force distribution of redundant actuated CDPRs. A new method on the calculation of the cable forces is proposed, where the determination of the lower-boundary of the cable forces is presented. The consideration of the pose-dependence of the lower force boundary can minimize the cable forces and improve the energy efficiency of CDPRs

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Maxit, Laurent. "Extension et reformulation du modèle SEA par la prise en compte de la répartition des énergies modales." Phd thesis, INSA de Lyon, 2000. http://tel.archives-ouvertes.fr/tel-00777764.

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Résumé Dans cette thèse, on propose une approche permettant d'étendre le domaine de validité de la méthode SEA (Statistical Energy Analysis). Elle repose sur une double formulation modale et une reformulation du modèle SEA en ne posant pas l'hypothèse d'équirépartition des énergies modales. La double formulation modale qui est décrite dans le cas général du couplage de systèmes continus tridimensionnels, consiste en une décomposition modale non standard faisant intervenir une double formulation contrainte-déplacement. Les équations modales obtenues sont alors en cohérence avec le modèle supposé de la SEA et se caractérisent à partir des modes des sous-systèmes découplés. Le modèle SmEdA qui découle de la reformulation de la SEA permet d'améliorer la qualité de la prédiction, notamment quand le recouvrement modal est faible ou quand les sous-systèmes sont excités localement. Un des points forts de l'approche proposée est qu'elle peut être facilement associée à une démarche SEA. Il est possible d'appliquer le modèle SmEdA uniquement pour les couplages des sous-systèmes où une amélioration de la prédiction peut être présumée obtenue, et utiliser le modèle SEA pour les autres couplages. L'application du modèle SmEdA à des structures industrielles est possible grâce à l'utilisation de modèles Eléments Finis des sous-systèmes. En supposant l'hypothèse d'équirépartition respectée, il découle de cette approche une nouvelle technique de calcul des facteurs de perte par couplage SEA. Celle-ci ne requière que le calcul des modes des sous-systèmes découplés par Éléments Finis. Les facteurs SEA sont alors obtenus par identification des coefficients des équations modales, sans les résoudre.

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Demers, Pierre. "Simulation numerique des vibrations induites par effet de couronne sur les conducteurs a haute tension." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 1994. http://theses.uqac.ca.

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32

Maynadier, Jérôme. "Approches statistiques et fiabilités en dynamique des structures." Toulouse, INSA, 2003. http://www.theses.fr/2003ISAT0017.

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L'amélioration de la fiabilité des structures à symétrie cyclique des turbomachines nécessite une estimation précise des vibrations extrêmes qu'atteignent ces composants. Les amplitudes de réponse des structures à symétrie cyclique varient significativement en fonction de petites perturbations structurales nommées désaccords. En général, les désaccords sont des paramètres aléatoires. Leur effet sur les amplitudes de vibrations est encore estimé à partir de l'expérience de chaque motoriste. Pour faire face aux évolutions technologiques les approches numériques sont cependant nécessaires. En dynamique des structures, la méthode classique pour estimer la probabilité d'atteindre une amplitude vibratoire est la méthode de Monte-Carlo, efficace pour les probabilités les plus grandes, mais extrêmement coûteuse en temps de calcul pour les probabilités faibles. Les amplitudes de vibrations critiques correspondant précisément aux petites probabilités, les approches probabilistes FORM et SORM sont d'abord envisagées. Nous développons ensuite une méthode originale dite " méthode à variables séparées ". Enfin, une approche statistique fondée sur les modèles de valeurs extrêmes, pour estimer la distribution des amplitudes les plus grandes à partir d'un nombre restreint de simulations est retenue : la distribution généralisée de Pareto,modélisant la probabilité de dépassement d'un seuil. Après avoir validé ces différentes approches sur des exemples académiques, les plus performantes sont appliquées à une structure à symétrie cyclique modélisée par un système réduit. Ce type de modélisation simplifiée permet de représenter la plupart des configurations rencontrées en fonctionnement
The improvement of the cyclic symmetry structures in turboshaft engines requires an accurate valuation of extreme vibrations which are reaching by these components. The amplitudes of the response of cyclic symmetry structures vary significantly in function of small perturbations named "mistuning". In general, mistunings are random parameters. Usually their effects on the vibration amplitudes are estimated from the experience of each motorist. Hence, at the present time, they are verified with the help of experiences by installation of strain gauges on pieces. To anticipate the evolutions of technologies the numerical approaches are necessary. In structure dynamics, the classical approach used to estimate the probability to reach a vibratory amplitude is the Monte Carlo method, efficient to the biggest probabilities, but extremely expensive when probabilities decrease. The most critical vibration amplitudes corresponding to the lowest probabilities, the probabilistic methods FORM and SORM are first considered. We develop then an original method named "separated variables method". Finally, a statistical approach by extreme values distribution on threshold overstepping with a Pareto law is kept to predict the queue of the distribution of the maximal amplitude of the forced responses. This law bases on a minimum quantities of simulations. After the validation of these different approaches on academic examples, the most efficient one are applied on industrial cases. We consider a cyclic symmetric structure modelled by a reduced model. This type of simplified modelization is able to represent the greatest part of configurations met when running

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33

Stevenson, Nathan. "Vibration Signal Features for the Quantification of Prosthetic Loosening in Total Hip Arthroplasties." Queensland University of Technology, 2003. http://eprints.qut.edu.au/15808/.

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This project attempts to quantify the integrity of the fixation of total hip arthro- T plasties (THAs) by observing vibration signal features. The aim of this thesis is, therefore, to find the signal differences between firm and loose prosthesis. These difference will be expressed in different transformed domains with the expectation that a certain domain will provide superior results. Once the signal differences have been determined they will be examined for their ability to quantify the looseness. Initially, a new definition of progressive, femoral component loosening was created, based on the application of mechanical fit, involving four general conditions. In order of increasing looseness the conditions (with their equivalent engineering associations) are listed as, firm (adherence), firm (interference), micro-loose (transition) and macro-loose (clearance). These conditions were then used to aid in the development and evaluation of a simple mathematical model based on an ordinary differential equation. Several possible parameters well suited to quantification such as gap displacement, cement/interface stiffness and apparent mass were the identified from the model. In addition, the development of this model provided a solution to the problem of unifying early and late loosening mentioned in the literature by Li et al. in 1995 and 1996. This unification permitted early (micro loose) and late (macro loose) loosening to be quantified, if necessary, with the same parameter. The quantification problem was posed as a detection problem by utilising a varying amplitude input. A set of detection techniques were developed to detect the quantity of a critical value, in this case a force. The detection techniques include deviation measures of the instantaneous frequency of the impulse response of the system (accuracy of 100%), linearity of the systems response to Gaussian input (total accuracy of 97.9% over all realisations) and observed resonant frequency linearity with respect to displacement magnitude (accuracy of 100%). Note, that as these techniques were developed with the model in mind their simulated performance was, therefore, considerably high. This critical value found by the detector was then fed into the model and a quantified output was calculated. The quantification techniques using the critical value approach include, ramped amplitude input resonant analysis (experimental accuracy of 94%) and ramped amplitude input stochastic analysis (experimental accuracy of 90%). These techniques were based on analysing the response of the system in the time-frequency domain and with respect to its short-time statistical moments to a ramping amplitude input force, respectively. In addition, other mechanically sound forms of analysis, were then applied to the output of the nonlinear model with the aim of quantifying the looseness or the integrity of fixation of the THA. The cement/interface stiffness and apparent mass techniques, inspired by the work of Chung et.al. in 1979, attempt to assess the integrity of fixation of the THA by tracking the mechanical behaviour of the components of the THA, using the frequency and magnitude of the raw transducer data. This technique has been developed fron the theory of Chung etal but with a differing perspective and provides accuracies of 82% in experimentation and 71% in simulation for the apparent mass and interface stiffness techniques, respectively. Theses techniques do not quantify all forms of clinical loosening, as clinical loosening can exist in many different forms, but they do quantify mechanical loosening or the mechanical functionality of the femoral component through related parameters that observe reduction in mechanical mass, stiffness and the amount of rattle generated by a select ghap betweent he bone/cement or prosthesis/cement interface. This form of mechanical loosening in currently extremely difficult to detect using radiographs. It is envisaged that a vibration test be used in conjunction with radiographs to provide a more complete picture of the integrity of fixation of the THA.

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Bolmsvik, Åsa. "Structural-acoustic vibrations in wooden assemblies: : Experimental modal analysis and finite element modelling." Doctoral thesis, Linnéuniversitetet, Institutionen för bygg- och energiteknik (BE), 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-24562.

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This doctoral thesis concerns flanking transmission in light weight, wooden multi-storey buildings within the low frequency, primarily 20-120 Hz. The overall aim is to investigate how the finite element method can contribute in the design phase to evaluate different junctions regarding flanking transmission. Two field measurements of accelerations in light weight wooden buildings have been evaluated. In these, two sources; a stepping machine, and an electrodynamic shaker, were used. The shaker was shown to give more detailed information. However, since a light weight structure in field exhibit energy losses to surrounding building parts, reliable damping estimates were difficult to obtain. In addition, two laboratory measurements were made. These were evaluated using experimental modal analysis, giving the eigenmodes and the damping of the structures. The damping for these particular structures varies significantly with frequency, especially when an elastomer is used in the floor-wall junction. The overall damping is also higher when elastomers are used in the floor-wall junction in comparison to a screwed junction. By analysing the eigenmodes, using the modal assurance criterion, of the same structure with two types of junctions it was concluded that the modes become significantly different. Thereby the overall behavior differs. Several finite element models representing both the field and laboratory test setups have been made. The junctions between the building blocks in the models have been modeled using tie or springs and dashpots. Visual observation and the modal assurance criterion show that there is more rotational stiffness in the test structures than in the models. The findings in this doctoral thesis add understanding to how modern joints in wooden constructions can be represented by FE modelling. They will contribute in developing FE models that can be used to see the acoustic effects prior to building an entire house. However, further research is still needed.
Denna doktorsavhandling behandlar flanktransmission i flervåningshus med trästomme, inom det lågfrekventa området, främst 20-120 Hz. Det övergripande målet är att undersöka hur finita elementmetoden kan bidra i konstruktionsfasen för att utvärdera olika knutpunkters inverkan på flanktransmissionen. Två fältmätningar av accelerationer i trähus har utvärderats. I dessa har två olika lastkällor använts, i den första en stegljudsapparat och i den andra en elektrodynamisk vibrator (shaker). Det visades att shakern kan ge mer detaljerad information, men eftersom vibrationerna även sprider sig till omgivande byggnadsdelar vid fältmätningarna var det svårt att estimera tillförlitliga dämpningsdata även då shaker användes. Fältmätningarna följdes av två mätningar i laborationsmiljö. Dessa två experiment utvärderades med experimentell modalanalys, vilket ger egenmoder och dämpning hos strukturerna. Dämpningen för dessa trähuskonstruktioner varierar kraftigt med frekvens. Extra stora variationer registreras då en elastomer användes i knutpunkten mellan golv och vägg. Den totala dämpningen är generellt högre när elastomerer används i knutpunkten mellan golv och vägg i jämförelse med då knutpunkten är skruvad. Genom att analysera egenmoder och deras korrelationer (MAC), för samma trästruktur men med olika typer av knutpunkter, drogs slutsatsen att knutpunkten drastiskt förändrar strukturens dynamiska beteende. Flera finita elementmodeller av både fält- och laboratorieuppställningar har gjorts. I dessa har knutpunkterna mellan byggnadsdelar modellerats helt styvt eller med hjälp av fjädrar och dämpare. Visuella observationer av egenmoder och korrelationen dem emellan visar att det finns mer rotationsstyvhet i försöken än i finita elementmodellerna. Resultaten i denna doktorsavhandling har gett förståelse för hur knutpunkter i träkonstruktioner beter sig och kan simuleras med finit elementmodellering. Vidare kan resultaten bidra till utvecklingen av FE-modeller som kan användas för att kunna se de akustiska effekterna redan under konstruktionsstadiet. Dock behövs ytterligare forskning inom området.

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Carbonelli, Alexandre. "Caractérisation vibro-acoustique d'une cascade de distribution poids lourd." Phd thesis, Ecole Centrale de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00779231.

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L'objectif de ce travail est la compréhension et la modélisation des phénomènes physiques qui gouvernent la réponse vibro-acoustique d'une cascade de distribution de poids lourd. On s'intéresse en particulier au bruit de sirènement d'une cascade de six engrenages, qui correspond à la réponse aux excitations internes générées par le processus d'engrènement et au bruit de claquement, qui correspond à la réponse aux vibro-impacts entre dentures sous charge induits par les fluctuations des efforts extérieurs couplées aux excitations internes. Dans un premier temps, les corrections de denture sont optimisées par une méthode méta-heuristique (essaims particulaires), afin de minimiser les fluctuations des erreurs statiques de transmission en prenant en compte la large plage de couples de fonctionnement et les dispersions géométriques induites par les tolérances de fabrication des engrenages. Le bruit de sirènement est alors modélisé à partir d'une méthode spectrale qui prend en compte le couplage entre les différentes excitations internes de la cascade de dentures. Le gain apporté par l'optimisation des corrections sur le bruit de sirènement de la cascade de dentures a pu être estimé. Dans un second temps, le bruit de claquement est analysé à partir de modèles non linéaires prenant en compte les jeux entre dentures. Une méthode de continuation couplée à une discrétisation par la méthode des différences centrées et une méthode d'intégration temporelle directe sont mises en oeuvre. Le comportement dynamique de la cascade induit par la fluctuation des efforts extérieurs couplée aux excitations internes est complexe : les réponses des différents pignons peuvent être périodiques, pseudo-périodiques ou chaotiques avec possibilité d'observer des pertes de contact multiples, et notamment des chocs entre les flancs rétros des dentures si l'acyclisme moteur est élevé. Les régimes de type vibro-impacts peuvent être établis sur une large plage de vitesses de fonctionnement.

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Daoud, Atef. "Etude expérimentale de la liaison entre l'acier et le béton autoplaçant : contribution à la modélisation numérique de l'interface." Toulouse, INSA, 2003. http://www.theses.fr/2003ISAT0011.

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Le travail décrit dans le présent mémoire est une contribution à l'étude de la liaison entre l'acier et le béton autoplaçant (BAP). Le changement de composition et surtout de mise en œuvre de ce type de béton sont des raisons suffisantes pour s'interroger sur la qualité de l'interface armature/béton. En effet, l'absence de vibration, l'utilisation de nombreux adjuvants et l'incorporation d'additions minérales ont une influence non négligeable sur la liaison acier-béton. C'est ce qu'a révélé l'étude bibliographique relative au béton autoplaçant. L'étude de la liaison acier-béton autoplaçant a été menée à partir d'essais d'arrachement (RILEM) et d'essais tirants avec pour objectif de quantifier l'influence des paramètres constitutifs de la liaison sur l'adhérence et la fissuration des bétons autoplaçants et détecter éventuellement les différences de comportement avec le béton vibré. Il a été établi que l'adhérence et la fissuration des bétons autoplaçants et des bétons vibrés sont régis par les mêmes phénomènes physiques. Cependant, il convient de noter la sensibilité du BAP à l'absence de rugosité. Une étude de l'arrangement géométrique des grains autour de la barre, conduite par analyse d'image et analyse linéaire, semble établir une corrélation satisfaisante entre la résistance à l'arrachement et la qualité (isotropie) de l'arrangement. Cette étude a permis, également, de montrer l'existence d'une couche fine de béton pauvre en gros granulats autour de la barre, dans le cas du béton autoplaçant. Cette couche est pratiquement inexistante dans le cas du béton vibré; ceci peut être à l'origine de la sensibilité du BAP à l'absence de rugosité. Une contribution à la modélisation numérique de l'interface acier-béton a été développée. Le modèle proposé consiste en une loi d'interface couplée avec un modèle d'endommagement du béton. Il a été montré que ce modèle permet de décrire correctement le transfert de contrainte entre l'acier et le béton et d'observer le développement de la fissuration d'une membrure tendue. C'est ce qu'attestent les résultats de la simulation de deux cas de base, essai d'arrachement et essai tirant, pour les armatures lisses et à haute adhérence
This research work is a contribution to the study of the connection between steel and self-compacting concrete (SCC). The change of proportioning and the casting of the concrete without vibration are two sufficient reasons to wonder about the quality of the connection steel-SCC. Indeed, the bibliographical study has shown that the absence of vibration, the use of admixtures, the incorporation of mineral additions have an incidence on the steel-concrete interface. The experimental study has been carried out by means of pull-out and reinforced concrete ties tests. The objectives were to quantify the influence of the intrinsic parameters of the connection on the anchorage and the cracking behaviour of self-compacting concrete, allowing a comparison with the known performances of the vibrated concrete. It has been shown that self-compacting concrete and vibrated concrete present identical performances in terms of bond strength and cracking behaviour. However, SCC seems to be more sensitive to bar roughness than vibrated concrete. A study of the aggregate distribution around the bar, given by image analysis, provides a satisfactory relationship between bond strength and the distribution isotropy. This study has shown that, in the case of SCC, the concrete layer located around the bar has a weak aggregate proportion. This layer is not observed in the case of vibrated concrete, which can explain the sensitivity of SCC to bar roughness. A numerical contribution to the interface modelling has been proposed. The present model consists on a bond-slip law associated with a concrete damage model. It has been shown that the model describes accurately the stress transfer between steel and concrete and allows to observe the cracking growth

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Rahmoune, Miloud. "Contribution à l'étude d'un système d'ondes mécaniques généré par des matériaux piézoélectriques. Application au processus antifouling de l'instrumentation océanographique." Montpellier 2, 1994. http://www.theses.fr/1994MON20111.

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L'effet des ondes mecaniques contre le fouling a ete largement confirme ces dernieres annees. L'optimisation de ce phenomenes requiert une modelisation de la propagation des ondes mecaniques dans une structure immergee dans un fluide et une analyse experimentale en fonction des differents parametres gouvernant l'amplitude modale. C'est l'objectif du travail presente. Une definition, par spectroscopie optique des conditions optimales d'applications des ondes mecaniques a la prevention du fouling a ete etablie

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Roth, Claudio Weissheimer. "TRANSMISSIBILIDADE DA VIBRAÇÃO E DISTRIBUIÇÃO DA PRESSÃO NA INTERFACE ASSENTO-OPERADOR DE TRATORES AGRÍCOLAS EM CONDIÇÕES DINÂMICAS." Universidade Federal de Santa Maria, 2010. http://repositorio.ufsm.br/handle/1/3587.

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Substantive changes introduced in the agricultural work, driven by further increases in productivity in the agricultural machinery are the basis of this study. The tractor is a machine used in most activities of tillage, by concentrating most of the physical and mechanical actions to perform these activities. The tractor seat is one of the most important factors to be considered in the design of the workplace, it is the area where the operator remains for hours. The aim of this study was to analyze the transmissibility of vibration and pressure distribution in the seat-operator interface in two types of seats in agricultural tractors, in two settings for suspension in three forward speeds and three different types of micro-reliefs. Were performed simultaneous field experiments with measurements of amplitude of vibrations and pressure distribution on a path of 40 meters in three distinct areas, consolidated, ploughed and asphalt, in three average speeds, 4.66, 5.57 and 6.58 km/h. The data of operator exposure to whole body vibration were obtained through the RT Pro Photon 6.30 system, which performs simultaneous readings in the triaxial axes x, y and z and to measure the pressure distribution was used a blanket sensorized interface module of the X-sensor system. Later, the parameters which allowed the evaluation of the transmissibility of vibration were calculated, as well as the distribution of pressures on the trunk of the operator in the seat. Was performed an Analysis of Variance (ANOVA) and Duncan Test. The level of significance was the 95% reliability. It was concluded that in consolidated and ploughed areas the effective accelerations exceeded the upper limit of the little discomfort zone of standard 2631-1:1997 and that the actual magnitude of the transmissibility of vibration increased on frequencies of 2.5 and 12.5 Hz. The maximum limit of comfort and daily work of eight hours have been overcome by the magnitude of the effective accelerations in all the tests and by the accelerations in more than one direction, in the frequency ranges of 2.5 and 5 Hz on consolidated and mined areas. The values of the average pressures of seat B1 were around 25% lower than the seat B2 medium pressure on consolidated and ploughed areas and their distribution was similar between the two benches, regardless of the setting of the suspension regulation. The dynamic capability to mitigate sudden changes of pressure of seat B1 was higher in regulation R1 and on seat B2, in the regulation R2, considering that on the wrought soil regulation R2 of seat B2 showed an ability to reduce the sudden pressure 50% lower than the regulation R1. Areas of effective contact in the seat-operator interface were 20% higher on the seat B1 than seat B2.
As alterações substanciais introduzidas no trabalho agrícola, impulsionadas por aumentos adicionais de produtividade nas máquinas agrícolas são a base deste estudo. O trator é a máquina mais usada nas atividades agrícolas, por concentrar a maioria das ações físicas e mecânicas para executar essas atividades. O assento do trator é um dos mais importantes fatores a ser considerado no projeto do posto de trabalho, pois é o local onde o operador permanece por mais horas. O objetivo deste estudo foi analisar a transmissibilidade das vibrações e a distribuição da pressão na interface assento-operador em dois tipos de bancos de tratores agrícolas, em duas regulagens de suspensão, em três velocidades de deslocamento e três diferentes tipos de micro-relevos. Foram realizados experimentos simultâneos a campo com medição da amplitude das vibrações e da distribuição da pressão na superfície de contato entre o homem e o banco em trajetos de 40 metros em três distintas áreas, consolidada, lavrada e asfáltica, em três velocidades médias, 4,66, 5,57 e 6,58 km/h. Os dados da exposição do operador à vibração de corpo inteiro foram obtidos através do sistema RT Pro Photon 6,30, que executa simultaneamente leituras nos eixos triaxiais x, y e z e para medir a distribuição da pressão foi utilizada uma manta sensorizada do sistema X-sensor. Posteriormente, foram calculados os parâmetros que permitiram a avaliação da transmissibilidade das vibrações, assim como da distribuição das pressões do tronco dos operadores no assento do banco. Foi realizada a Análise de Variância (ANOVA) e Teste de Duncan. O nível de significância aceito foi de 95% de confiabilidade. Concluiu-se que nas áreas consolidada e lavrada as acelerações eficazes ultrapassaram o limite superior da zona de pouco desconforto da norma 2631-1:1997 e que a amplitude efetiva da transmissibilidade das vibrações aumentou nas frequências de 2,5 e 12,5 Hz. Os limites máximos conforto e de trabalho diário de 8 horas foram ultrapassados pelas magnitudes das acelerações eficazes na totalidade dos ensaios e pelas acelerações em mais de uma direção, nas faixas de frequência de 2,5 e 5 Hz nas áreas consolidada e lavrada. Os valores das pressões médias do banco B1 foram em torno de 25% menores que as pressões médias do banco B2 nas áreas consolidada e lavrada e sua distribuição ocorreu de maneira semelhante entre os dois bancos, independente do tipo de regulagem da suspensão. A capacidade dinâmica de atenuar as mudanças repentinas de pressão do banco B1 foi superior na regulagem R1 e no banco B2, na regulagem R2, sendo que no solo lavrado a regulagem R2 do banco B2 apresentou uma capacidade 50% menor do que a regulagem R1. As áreas de efetivo contato na interface banco-operador foram 20% maiores no banco B1 que no banco B2.

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Stelzer, Rainer. "Une méthode énergétique pour les systèmes vibro-acoustiques couplés." Phd thesis, INSA de Lyon, 2012. http://tel.archives-ouvertes.fr/tel-00780602.

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Ce mémoire de thèse présente le développement de la méthode "statistical modal energy distribution analysis (SmEdA)" pour des systèmes vibro-acoustiques couplés. Cette méthode de calcul est basée sur le bilan énergétique dans des sous-systèmes fermés couplés, comme une structure ou une cavité. L'interaction entre de tels systèmes est décrite par des couplages entre les modes. La version initiale de SmEdA prend en compte seulement les modes qui ont une fréquence propre dans le bande d'excitation. Le travail présenté ici étudie l'effet des modes non résonants sur la réponse et identifie les cas dans lesquels un tel effet devient important. L'introduction des modes non résonants permet d'utiliser la méthode SmEdA dans des cas d'applications plus larges. En outre, une nouvelle méthode de post-traitement a été développée pour calculer des distributions d'énergie dans les sous-systèmes. Finalement, une nouvelle méthode d'approximation pour la prise en compte des modes de systèmes de grandes dimensions ou mal définis a été formulée. Toutes ces méthodes ont été comparées avec d'autres méthodes de calcul via des exemples académiques et industriels. Ainsi, la nouvelle version de SmEdA incluant le post-traitement pour obtenir des distributions d'énergie a été validé et les avantages et possibilités d'applications sont montrés.

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Biben, Christophe. "Contribution à l'étude d'un dispositif de détection de chocs sur conduites de gaz enterrées." Toulouse, ENSAE, 1996. http://www.theses.fr/1996ESAE0011.

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Suite à des chocs de nature mécanique, des réseaux de canalisations sont souvent endommagés. Ces incidents qui nécessitent une intervention plus ou moins rapide, doivent être connus de l'exploitant. La détection de ces chocs impose la connaissance des mécanismes de propagation des ondes de structure dans les conduites cylindriques. Une étude théorique est alors menée pour décrire les vibrations libres d'une coque mince cylindrique. Elle est basée sur les équations de Donnell, complétées par la formulation de Flügge. Le système matriciel ainsi obtenu conduit à l'équation de dispersion. Celle-ci permet d'une part de calculer les fréquences des modes propres transverses vibratoires, et, d'autre part, d'identifier les types d'ondes se propageant dans la structure (longitudinale, cisaillement, flexion). La notion de perte en amplitude du signal vibratoire le long de l'axe du cylindre est alors prise en compte dans cette étude théorique en considérant le cas de conduite de longueur infinie. Les lois mathématiques traduisant cette décroissance sont recherchées à l'aide d'expérimentations. L'étude expérimentale menée permet de quantifier l'atténuation en amplitude d'un mode transverse se propageant le long de conduites droites ou d'un réseau complexe comprenant diverses singularités. Ainsi, deux séries d'essais sont réalisées, la première sur un réseau en site laboratoire (conduite placé en milieu aérien), la seconde sur un réseau en site industriel (conduite enterrée), prenant en considération la charge du sol. Les lois de décroissance associées aux facteurs d'atténuation des différentes singularités constituent les éléments d'un modèle permettant de simuler la propagation d'onde de structure le long d'un réseau de canalisations. Une application au dimensionnement de la position des systèmes de détection en fonction de l'agencement du réseau est alors proposé. La validation du modèle appliqué à une conduite industrielle reste néanmoins à effectuer.

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Souhassou, Mohamed. "Densité d'électrons dans les composés peptidiques par méthode X-X et calcul théorique : LA (N) acétyl-L-tryptophane-méthylamide et la (N)-acétyl-alpha-béta -dehydrophenylalanine-methylamide, influence de La alpha -beta -déhydrogénation et étude critique des modèles multipolaires." Nancy 1, 1988. http://www.theses.fr/1988NAN10418.

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Détermination de la densité de déformation dans ces deux composés par diffraction de rayons X (méthode X-X) et calculs ab initio SCF, après avoir calculé et comparé les phases des facteurs de structure à partir de deux modèles multipolaires (hansen-coppens et hirshfeld)

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Bartošek, Nikola. "Analýza potíží výměníku tepla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-232124.

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The master thesis is focused on analysis of specific cross-flow in-line tube bundle heat exchanger which deals with significant operational problems. Thermal, hydraulic and vibration calculation analysis of selected parts of the heat exchanger is performed based on CFD flow distribution results. Calculation is performed by using Maple software. Thermal and hydraulic calculations are compared with results obtained by commercial software HTRI.

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Passos, Sébastien. "Dynamique des systèmes d'entraînement par courroie synchrone intégrant des poulies à profils innovants." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI049.

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Dans le domaine automobile, l’utilisation de poulies ayant un profil primitif non circulaire (NC) est devenue chose courante pour la conception des façades de distribution par courroie synchrone des moteurs à combustion interne. Pour des paramètres de conception bien choisis (forme, calage angulaire), ces poulies innovantes permettent à priori de réduire l’impact vibratoire des sources d’excitation angulaire affectant la façade. La phénoménologie associée aux poulies NC s’avère toutefois complexe et difficile à prédire par le calcul. Le dimensionnement des façades équipées de ces dispositifs s’avère délicat mais primordial. Dans ce contexte, un modèle numérique adapté à la simulation de la dynamique angulaire des façades de distribution intégrant des poulies NC a été proposé. Ce modèle est fondé sur une approche discrète (0D/1D) inspirée de modèles classiquement utilisés pour l’étude des transmissions intégrant uniquement des poulies circulaires. La courroie est associée à un solide élastique 1D uniforme en prise sur l’enveloppe de solides 2D indéformables représentant les poulies. L’interaction poulie-courroie est concentrée aux points de tangence localisés aux frontières des brins de courroies. En ces points, s'exercent les efforts de tension résultant de l’élongation des brins. Le mouvement des points tangence, engendré par les poulies NC, est pris en compte par l’emploi d’une formulation originale pour le calcul de l'élongation des brins. Cette formulation est obtenue par l’application d’un bilan de matière opéré sur la courroie via une méthode Lagrangienne-Eulérienne. En parallèle de la Modélisation, des travaux expérimentaux ont permis d’analyser l’impact d’une poulie bilobée sur la dynamique angulaire d’une façade de distribution (moteur à 4 cylindres). Le dispositif expérimental utilisé a été spécialement développé dans le cadre de cette thèse. Son instrumentation permet une analyse complète du comportement en dynamique angulaire de la façade. Des comparaisons calculs/essais ont finalement permis de valider le modèle numérique proposé
In response to ever-stricter requirements for internal combustion engine efficiency, noise and reliability, car manufacturers now commonly design Timing belt drives comprising innovative pulleys with non-circular (NC) profiles. For well-chosen design parameters (profile shape, angular phasing), the use of a NC pulley can considerably improve the vibratory performances of a timing belt transmission. Nevertheless, designing efficiently a belt transmission including NC pulleys remains hard to accomplish. To achieve this, it is important to clearly understand and identify the impact of such pulleys on the dynamic behaviour of Timing belt drives. In this context, a numerical model able to simulate the angular dynamics of Timing belt drives comprising NC pulleys has been developed. The model is based on a discrete approach (0D/1D), similar to the models of transmissions with circular pulleys only. The belt is modelled as a 1D linear elastic material (wire) and the pulley are considered as rigid bodies represented by rotary inertias. Rotations of the driven pulleys are the degrees of freedom of the discrete system. The pulley rotation is actuated by the effect of the belt span tensions applied at the belt/pulley seating/unseating points. In the case of a NC pulley, these points are mobile and their motion has to be tracked rigorously. To achieve this, a novel formulation has been written by establishing a feed-in/out balance on the belt spans using a Lagrangian-Eulerian method. In parallel to the numerical developments, experimentations have been performed for analysing the impact of an oval pulley on Timing belt drive angular dynamics (4 cylinder engine). The experimental test rig has been fully developed during this thesis. It is equipped with numerous sensors that enable a complete analysis of belt transmission angular dynamics. Finally, comparative analyses have shown a quite good agreement between experiments and simulations

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Huang, Fei. "Contributions à l'élaboration des modèles à partir de données pour l'estimation de la durée de vie résiduelle des roulements." Electronic Thesis or Diss., Université de Lorraine, 2020. http://www.theses.fr/2020LORR0019.

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Cette thèse de doctorat porte sur l’estimation de la durée de vie résiduelle d’un roulement sur la base des signatures obtenues à partir des signaux de vibration collectés pour un nombre restreint de roulements identiques durant un cycle complet de fonctionnement. Nous avons élaboré de nouvelles signatures qui ont une évolution monotone croissante avec l’état de dégradation des roulements et nous avons proposé un modèle d’estimation de la durée de vie résiduelle des roulements, basé sur un système d’inférence floue. Les paramètres du modèle sont identifiés par apprentissage à partir d’une petite quantité de données, en utilisant la méthode d’analyse du maximum de vraisemblance d’un mélange de distributions. Un ensemble de données d’apprentissage de petite taille ne permettant pas d’estimer les paramètres du modèle avec une grande précision. Nous avons donc élaboré une méthode de mise à jour des paramètres du modèle par un processus adaptatif de capitalisation de connaissances
Remaining useful life (RUL) estimation for bearings degradation monitoring is an important metric for decision making in condition based maintenance of rotating mechanics. RUL estimation involves generally two steps: degradation indicator extraction and model identification. Common vibration signal based features for bearings degradation monitoring are sensible on the last stage of the degradation process. In this thesis, we propose new bearing degradation monitoring indicators that are monotonic and incorporate historical degradation information. To overcome the drawback of a small size training datasets for model identification, we elaborated a mixture distribution analysis based fuzzy model identification method for RUL estimation. Furthermore, we proposed a method to tune the parameters of the fuzzy models for bearings RUL estimation when new knowledge becomes available. The aim is to improve the accuracy of the RUL estimation through a knowledge accumulation process

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Sfredo, Marilia Assunta. "Estudo da dispersão na secagem de frutos de café em secador de bandejas vibradas." Universidade Federal de Uberlândia, 2006. https://repositorio.ufu.br/handle/123456789/15067.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
To study the dispersion of the coffee fruits during the drying, a vibrated tray drier with recycle was used. The dryer consists basically of four sections: drying vertical tunnel, vibration system, system of warm air supply to the drying tunnel and recycle system of coffee fruits. The drying tunnel contains four perforated trays through which the coffee fruits and air flow out, in cross flow. The coffee fruits drying was carried out using two experimental design, where the studied variables were, for the first design: coffee fruits temperature (40; 45 and 50ºC); mass of coffee fruits (11.5; 12.5 and 13.5 kg) and air mass rate (7; 8 and 9 kg air/min); the varieties of coffee fruits were: Acaiá, Catuaí and Mundo Novo; and for the second design: mass of coffee fruits (10; 12 and 14 kg) and air mass rate (7; 8 and 9 kg air/min), with coffee fruits temperature around 45ºC and the coffee variety Mundo Novo. For the first experimental design, the coffee fruits temperature only influenced significantly the drying time, where the largest temperature level reduces in 26.77 h the drying time. For the second experimental design, the studied variables were not significant on drying time. Coffee fruit sphericity, density, sticky decreased with the decrease of the moisture content. With reference to the quality of coffee grain, the best operational conditions were obtained with greater coffee fruits mass and air mass rate. The coffee fruits flow in the drying tunnel is promoted by vibration of the trays coupled to electromagnetic vibrators. The vibration amplitude was determined by an accelerometer connected to a signal conditioner and an analogical oscilloscope. The vibration amplitude decreased with the reduction of the coffee fruits moisture content due to the shrinkage and decrease of the mass, sticky, density and particle size coffee fruits. The coffee fruits mass rate and the residence time distribution were determined (RTD), during the drying. At the end of the drying, the flow occurs with easiness due to: absence of sticky of the coffee fruits; decrease of the particle mass and particle vibration damping decrease, due to particle rigidity acquired in the drying. The dispersion coefficient (Ez) was determined by Taylor Dispersion Model, Free Dispersion Model and Modified Free Dispersion Model. For the great majority of the experiments, the model that better fitted the experimental data (greater coefficient of correlation) was the model of the Modified Free Dispersion. The dispersion coefficient (Modified Free Dispersion) ranged from 1.31×10-4 to 68.67×10-4 m2/s. The Péclet number ranged from 1.15 to 31.00.
Para estudar a dispersão dos frutos de café durante a secagem, utilizou-se um secador de bandejas vibradas com reciclo. O secador consiste basicamente de quatro seções: túnel vertical de secagem, sistema de vibração, sistema de injeção de ar aquecido no túnel de secagem e sistema de reciclo dos frutos de café. O túnel de secagem contém quatro bandejas perfuradas por onde escoam os frutos de café e o ar, em fluxo cruzado. A secagem dos frutos de café foi realizada utilizando-se dois planejamentos experimentais, onde as variáveis estudadas foram, para o primeiro planejamento de secagem: temperatura dos frutos de café (40; 45 e 50ºC); massa de frutos de café alimentada (11,5; 12,5 e 13,5 kg) e vazão de ar de secagem (7; 8 e 9 kg ar/min), a variedade dos frutos de café foram: Acaiá, Catuaí e Mundo Novo; e para o segundo planejamento de secagem: massa de frutos de café (10; 12 e 14 kg) e vazão de ar (7; 8 e 9 kg ar/min), mantendo-se a temperatura dos frutos em 45ºC e a variedade Mundo Novo. Para o primeiro planejamento somente a temperatura dos frutos influenciou significativamente o tempo de secagem, onde o maior nível de temperatura reduz em 26,77 h o tempo de secagem. Para o segundo planejamento as variáveis estudadas não foram significativas para o tempo total de secagem dos frutos de café. Durante a secagem ocorre encolhimento dos frutos de café, diminuição da esfericidade, da pegajosidade, da densidade aparente e aumento da área superficial específica com a diminuição do conteúdo de umidade dos frutos de café. Em relação à qualidade do grão de café, as melhores condições operacionais foram obtidas com maior massa e maior vazão de ar de secagem. O escoamento do café no túnel de secagem é promovido pela vibração das bandejas acopladas a vibradores eletromagnéticos. A amplitude de vibração foi determinada por um acelerômetro acoplado a um condicionador de sinal e a um osciloscópio analógico. A amplitude vibracional diminuiu com a diminuição da umidade dos frutos de café devido ao encolhimento e à diminuição da massa, da pegajosidade, da densidade e do diâmetro dos frutos de café. Durante a secagem foram determinadas a vazão mássica dos frutos de café e a distribuição do tempo de residência (DTR). Ao final da secagem, o escoamento dos frutos de café ocorre com maior facilidade devido a: ausência de pegajosidade dos frutos de café; diminuição da massa das partículas e redução do amortecimento da vibração dos frutos de café devido à rigidez adquirida na secagem. O coeficiente de dispersão (Ez) foi determinado pelos modelos da Dispersão de Taylor, da Dispersão Livre e da Dispersão Livre Modificado. Para a grande maioria dos experimentos, o modelo que melhor se ajustou aos dados experimentais (maior coeficiente de correlação) foi o Modelo da Dispersão Livre Modificado. O coeficiente de dispersão dos frutos de café variou de 1,31×10-4 a 68,67×10-4 m2/s. O número de Péclet variou de 1,15 a 31,00.
Doutor em Engenharia Química

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46

Akbari, Amin. "The Quantification of Force Distribution of a Vibrational Device for Accelerating Tooth Movement." Thesis, 2019. http://hdl.handle.net/1805/20086.

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Indiana University-Purdue University Indianapolis (IUPUI)
One of the most common concern among patients who need orthodontic treatment is treatment duration. The ability to accelerate orthodontic tooth movements would be bene cial to reduce the undesired side-effects of prolonged treatment. Methods have been used in conjugate with common orthodontic appliances to shorten the treatment. One of them is to use vibrational force (VF), which is non-invasive. The VF stimulates bone modeling and remodeling, which is essential to tooth movement. However, commercial devices used in the clinic failed to deliver consistent outcomes. The effects of the VF highly depend on its intensity the tooth receives. There must be a range of stimulation that optimizes the ffeects. The stimulation outside the range either have no effects or creates damages, which adversely affects the orthodontic treatment. Since these devices have generic mouthpiece and teeth are in di erent heights, hence some teeth cannot get force stimulation and others may be overloaded. The current designs also do not have ability to adjust the level of VF intensity that individual tooth needs, as in some cases orthodontists are required to move a tooth faster than others or even slower, which needs the device to be personalized. There- fore, the primary cause of inconsistent clinical outcomes is the inadequate design of the mouthpiece of the current device. The goal of this study is to design a better vibratory device that not only guarantees VF delivery but also enables orthodontists to control the level of VF on the individual tooth, which meets the patient's treat- ment needs. This is a preliminary study to understand the effects of different design parameters affecting the VF distribution on teeth. A nite element model, which consists of human upper and lower jaws in their occlusal positions and a mouthpiece, was created. The VF was from a vibratory source with a peak load of 0.3N and speci ed frequencies (30 and 120 Hz). The element size was determined through a convergence test and the model was validated experimentally. Results showed that the VF distribution among the teeth relies on the material property of the mouthpiece. The distribution is uneven, meaning some teeth bearing much more load than others. This means, with the current device design, teeth would be a ected with di erent level of force stimulation, which results in di erent clinical outcomes consequently. Dynamic load (VF) changes the force distribution on the teeth comparing to the dis- tribution from a static load. Frequency does not affect the peak load. Finally, the study demonstrated that the level of VF stimulation can be adjusted by introducing clearance or interference between the teeth and mouthpiece. It is feasible to control the level of the VF intensity for individual tooth based on treatment requirement.

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47

(7047659), amin akbari. "THE QUANTIFICATION OF FORCE DISTRIBUTION OF A VIBRATIONAL DEVICE FOR ACCELERATING TOOTH MOVEMENT." Thesis, 2020.

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Abstract:

One of the most common concern among patients who need orthodontic treatment is treatment duration. The ability to accelerate orthodontic tooth movements would be beneficial to reduce the undesired side-effects of prolonged treatment. Methods have been used in conjugate with common orthodontic appliances to shorten the treatment. One of them is to use vibrational force (VF), which is non-invasive. The VF stimulates bone modeling and remodeling, which is essential to tooth movement. However, commercial devices used in the clinic failed to deliver consistent outcomes. The effects of the VF highly depend on its intensity the tooth receives. There must be a range of stimulation that optimizes the effects. The stimulation outside the range either have no effects or creates damages, which adversely affects the orthodontic treatment. Since these devices have generic mouthpiece and teeth are in different heights, hence some teeth cannot get force stimulation and others may be overloaded. The current designs also do not have ability to adjust the level of VF intensity that individual tooth needs, as in some cases orthodontists are required to move a tooth faster than others or even slower, which needs the device to be personalized. Therefore, the primary cause of inconsistent clinical outcomes is the inadequate design of the mouthpiece of the current device. The goal of this study is to design a better vibratory device that not only guarantees VF delivery but also enables orthodontists to control the level of VF on the individual tooth, which meets the patient’s treatment needs. This is a preliminary study to understand the effects of different design parameters affecting the VF distribution on teeth. A finite element model, which consists of human upper and lower jaws in their occlusal positions and a mouthpiece, xii was created. The VF was from a vibratory source with a peak load of 0.3N and specified frequencies (30 and 120 Hz). The element size was determined through a convergence test and the model was validated experimentally. Results showed that the VF distribution among the teeth relies on the material property of the mouthpiece. The distribution is uneven, meaning some teeth bearing much more load than others. This means, with the current device design, teeth

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48

Ching-Yi, Hsu. "Vibrational distribution of Br2 molecule following photodissociation of CF2Br2 by using cavity ring down absorption spectroscopy." 2005. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-2806200517430200.

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Hsu, Ching-Yi, and 許靜怡. "Vibrational distribution of Br2 molecule following photodissociation of CF2Br2 by using cavity ring down absorption spectroscopy." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/58807109571972625439.

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碩士
國立臺灣大學
化學研究所
93
Cavity ring-down Spectroscopy (CRDS) is a relatively new direct absorption technique and its applications are developed very quickly in recently years. The method is based on measurement of the decay rate of a pulse light trapped in an optical cavity which is formed by a pair of highly reflective(R>99.9%) mirrors. A plot of decay rate as a function of laser frequency gives the absorption spectrum. As for photodissociation studies of CF2Br2, the major dissociation channels are found to be CF2Br2 → CF2Br + Br ΔH=274 kJ/mol CF2Br2 → CF2 + Br2 ΔH=231 kJ/mol We used a cavity ring-down spectroscopy (CRDS) to study of nascent Br2 following photodissociation of CF2Br2. The quantum yield of Br2 is found to be 0.038±0.009 following photodissociation of CF2Br2 at 248nm. According to the absorption spectrum, the nascent vibrational distribution was obtained. A comparison with the CHBr3 case reveals that nascent vibrational distribution leads to vibrationally cool. The excited parent molecules (CF2Br2) may transfer into highly vibrational levels of their electronic ground state via internal conversion. The results agree with a given theoretical calculation.

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Huang, Hong-Yi. "Topic I:Rotational and vibrational energy transfer effect of CH B2Sigma-(v'=1) Topic II:Vibrational distribution of Br2 molecule following photo-dissociation of bromine containing molecules by using cavity ring down absorption spectroscopy." 2004. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0001-1307200420511500.

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