Dissertationen zum Thema „Dynamic rigidity“

The separation of cells by phenotype from heterogeneous mixtures, such as whole blood, is important in a wide range of fields in medicine and biology. Cell separation methods can be classified as either chemical or physical. Chemical separation methods are based on affinity capture and flow cytometry to label and select for specific target cell species. These techniques can be limited by the lack of specific chemistry that uniquely select for the target cell types, including the inability to extract viable cells for propagation in culture. When chemical separation methods cannot be applied, it is sometimes possible to discriminate cells based on their physical properties. As material systems, cells have an enormous range in size and rigidity and these differences can be exploited to achieve separation. Recent advances in microfabrication and microfluidic technologies have presented several innovative methods to approach mechanical cell separation. Our research leverages key characteristics of microfluidic technologies to approach cell separation in a manner similar to liquid chromatography. In chromatography, target species are separated from mixtures by imparting different velocities based on interactions with the column. We apply this process to separate cells based on differences in their size and rigidity using a microfluidic channel with dynamic geometry. This channel is formed between a static surface, containing a series of traps, and a flexible membrane. The device is fabricated using standard microfabrication methods, including photolithography and multi-layer soft lithography. As the cell mixture is flowed through the channel, the height of the channel is varied repeatedly causing periodic entrapment of the larger and more rigid cells, which impart a reduced average velocity to these cells compared to smaller and more deformable cells. Using this technique, we demonstrated chromatographic separation of L5178Y mouse lymphoma cells, representing larger and more rigid species, from human red blood cells, representing smaller and less rigid species. The ratio of the velocities of the target versus background cell types depends upon the duty cycle of the oscillation. We demonstrate the accumulation of mouse lymphoma cells in the microfluidic channel while maintaining cell viability. The system is simple, low-cost and label free.

Eye movements are important to fixate or track an object of interest in the visual field. Eye movements are coordinated by six extraocular muscles (EOM) [1, 2]. These EOMs are responsible for ensuring that the visual axes of both eyes are parallel to each other [1, 2]. The effect of variation in refractive error upon eye movements has not received the same attention in the literature as the sensory aspect. Axial length varies considerably with refractive error [3-8]. Subjects with myopia have been found to have considerably larger eyes, with a longer axial length and lower ocular rigidity [3-5, 7, 8], compared to subjects who are emmetropic or hyperopic [3, 4, 6, 9]. It has also been shown that subjects with hyperopia have significantly smaller eyes with shorter axial lengths [6] and higher ocular rigidity [9]. Despite these marked differences in the physical characteristics of the eye between subjects, little work has been done to examine whether axial length or ocular rigidity influences eye movement response characteristics. The effect of variations in the structural characteristics of the eye upon the eye movement characteristics were explored in this PhD work by measuring eye movements under a number of experimental saccadic, smooth pursuit and vergence paradigms in 93 young visually normal subjects. This thesis showed that the characteristics of saccadic eye movements varied systematically with ocular rigidity. Subjects with lower ocular rigidity (always myopic) produced saccades with significantly slower peak velocity and a longer time to peak velocity. Conversely, subjects with high ocular rigidity (hyperopic) produced saccades with significantly faster peak velocity and a shorter time to peak velocity compared to both emmetropes (medium ocular rigidity) and myopes. Smooth pursuit responses to sinusoidal stimulus movement also varied significantly with ocular rigidity. Subjects with lower ocular rigidity (myopic) showed significantly lower response gain and larger phase lag. Hyperopes showed significantly more accurate responses with higher response gain and lower phase lag compared to emmetropes and myopes. Disparity vergence responses to a sinusoidal moving 3D stimulus varied systematically with ocular rigidity. The high ocular rigidity hyperopic eyes showed significantly higher response gain and lower phase lag than the other two refractive groups. The low ocular rigidity myopic eyes exhibited significantly lower response gain and longer phase lag than the medium ocular rigidity emmetropic eyes. The viewing time has a significant influence upon response quality as both response gain and phase lag deteriorates significantly over a very short period of time. In conclusion, it has been shown in this thesis and for the first time that the dynamic characteristics of saccadic, smooth pursuit and disparity vergence eye movements vary systematically with the structural characteristics of the globe. The results of this work provide substantial evidence of the influence of ocular rigidity upon the characteristics of eye movements.

This diploma thesis deals with the design and optimization of a headstock for machine tool. Thesis was focused to comparison of several types of slide-ways and linear guides of headstock, considering their static and dynamic rigidity. An overview in the field of machine tools, their static and dynamic properties, use materials and design of headstocks, considering types of guideways, types of guideways drives and types of drives of spindle was made. Among the other main goals is included design of several types of guideway of headstock for horizontal machine tool, elaboration of computational models and evaluation of results.

Understanding how different parameters affect the dynamic response of high-speed railway bridges is crucial to selecting an efficient structural form. Despite existing numerous publications within this field, only few address the importance of torsional deformations. The main objective of this thesis is to investigate the influence of the torsional resistance of the deck on the dynamic response of an existing bridge. Ulla River Viaduct is presented as a case study, allowing to analyse some aspects of its design and what their alteration entails. To this end, 6 different 3D FE models are compared, 5 of which show a modification from the original configuration. In addition, several positions of the train are considered to contrast the effects when the torsional modes are excited. The performed dynamic calculations are based on the implicit direct integration procedure. The analysis of the case study demonstrates the benefit of closing the torsional circuit of the deck. The results also evidence the need of including torsional effects in its dynamic assessment when low values of torsional rigidity are considered. All this is not easy when simplified 2D or 3D beam models are used. As a final remark, the original design of the Ulla River Viaduct is found highly efficient from a dynamical point of view.

Une variété riemannienne est dite rigide lorsque la longueur des géodésiques périodiques (cas des variétés fermées) ou des géodésiques diffusées (cas des variétés ouvertes) permet de reconstruire globalement la géométrie de la variété. Cette notion trouve naturellement son origine dans des dispositifs d’imagerie numérique tels que la tomographie par rayons X. Grâce une approche résolument analytique initiée par Guillarmou et fondée sur de l’analyse microlocale (plus particulièrement sur certaines techniques récentes dues à Faure-Sjostrand et Dyatlov-Zworski permettant une étude analytique fine des flots Anosov), nous montrons que le spectre marqué des longueurs, c’est-à-dire la donnée des longueurs des géodésiques périodiques marquées par l’homotopie, d’une variété fermée Anosov ou Anosov à pointes hyperboliques détermine localement la métrique de la variété. Dans le cas d’une variété ouverte avec ensemble capté hyperbolique, nous montrons que la distance marquée au bord, c’est-à-dire la donnée de la longueur des géodésiques diffusées marquées par l’homotopie, détermine localement la métrique. Enfin, dans le cas d’une surface asymptotiquement hyperbolique, nous montrons qu’une notion de distance renormalisée entre paire de points au bord à l’infini permet de reconstruire globalement la géométrie de la surface
A Riemannian manifold is said to be rigid if the length of periodic geodesics (in the case of a closed manifold) or scattered geodesics (in the case of an open manifold) allows to recover the full geometry of the manifold. This notion naturally arises in imaging devices such as X-ray tomography. Thanks to a analytic framework introduced by Guillarmou and based on microlocal analysis (and more precisely on the analytic study of hyperbolic flows of Faure-Sjostrand and Dyatlov-Zworski), we show that the marked length spectrum, that is the lengths of the periodic geodesics marked by homotopy, of a closed Anosov manifold or of an Anosov manifold with hyperbolic cusps locally determines its metric. In the case of an open manifold with hyperbolic trapped set, we show that the length of the scattered geodesics marked by homotopy locally determines the metric. Eventually, in the case of an asymptotically hyperbolic surface, we show that a suitable notion of renormalized distance between pair of points on the boundary at infinity allows to globally reconstruct the geometry of the surface

In dieser Arbeit werden die Folgen der Calvo-Annahme in dynamischen makroökonomischen Modellen untersucht. Dafür wird die Calvo-Annahme unter Anwendung des Konzepts der statistischen Hazardfunktion verallgemeinert. Ich untersuche zwei mögliche Anwendungen dieses Ansatzes innerhalb von DSGE-Modellen. Im ersten Artikel zeige ich, dass der Zugewinn an Handhabbarkeit, der aus der Calvo-Annahme für Neu-Keynesianische Modelle folgt, mit unerwünschten Folgen in Bezug auf die Inflationsdynamiken einher geht. Der zweite Artikel schätzt die aggregierte Hazardfunktion unter Verwendung des theoretischen Rahmens des ersten Artikels. Es zeigt sich, dass die Annahme einer konstanten Hazardfunktion, die aus der Calvo-Annahme folgt, von den Daten eindeutig abgelehnt wird. Im dritten Artikel analysiere ich die Implikationen der empirisch geschätzten Hazardfunktion für die Persistenz von Inflation und die Geldpolitik. Die Untersuchungen zeigen, dass mittels der empirisch plausiblen aggregierten Hazardfunktion Zeitreihen simuliert werden können, die mit der Persistenz der inflatorischen Lücke im US Verbraucherpreisindex konsistent sind. Anhand dieser Ergebnisse komme ich zu dem Schluss, dass die Hazardfunktion eine entscheidende Rolle für die dynamischen Eigenschaften von Inflation spielt. Der letzte Artikel wendet den selben Modellierungsansatz auf ein Real-Business-Cycle Model mit rigidem Arbeitsmarkt an. Unter Verwendung eines allgemeineren stochastischen Anpassungsprozess stelle ich fest, dass die Arbeitsmarktdynamiken von einem Parameter beinflusst werden, der das Monotonieverhalten der Hazardfunktion bestimmt. Insbesondere steigt die Volatilität des Beschäftigungsniveaus, wohingegen dessen Persistenz mit zunehmendem Parameterwert abnimmt.
The Calvo assumption (Calvo, 1983) is widely used in the macroeconomic literature to model market frictions that limit the ability of economic agents to re-optimize their control variables. In spite of its virtues, the Calvo assumption also implies singular adjustment behavior at the firm level as well as a restrictive aggregation mechanism for the whole economy. In this study, I examine implications of the Calvo assumption for macroeconomic dynamics. To do so, I extend the Calvo assumption to a more general case based on the concept of the statistical hazard function. Two applications of this approach are studied in the DSGE framework. In the first essay, I apply this approach to a New Keynesian model, and demonstrate that tractability gained from the Calvo pricing assumption is costly in terms of inflation dynamics. The second essay estimates aggregate price reset hazard function using the theoretical framework constructed in the first essay, and shows that the constant hazard function implied by the Calvo assumption is strongly rejected by the aggregate data. In the third essay, I further explore implications of the empirically based hazard function for inflation persistence and monetary policy. I find that the empirically plausible aggregate price reset hazard function can generate simulated data that are consistent with inflation gap persistence found in the US CPI data. Based on these results, I conclude that the price reset hazard function plays a crucial role for generating inflation dynamics. The last essay applies the same modeling approach to a RBC model with employment rigidity. I find that, when introducing a more general stochastic adjustment process, the employment dynamics vary with a parameter, which determines the monotonic property of the hazard function. In particular, the volatility of employment is increasing, but the persistence is decreasing in the value of the parameter.

Motivated by problems in the theory of renormalisation of dynamical systems, we study the properties of Markov families and fractals defined by embedded trees. Our main results concern the classification of Ck+a structures. Two topologically equivalent Markov families are Ck+a conjugate if they converge together rapidly enough. This result implies that the attractors of two systems at the accumulation point of periodic doubling are C2.11 conjugate. We also introduce and study the limit set of an exponential determined Markov family.

In this paper we study local rigidity of actions of simply connected Lie groups. In particular, we apply the Nash-Moser inverse function theorem to give sufficient conditions for the action of a simply connected Lie group to be locally rigid. Let $G$ be a Lie group, $H < G$ a simply connected subgroup and $\Gamma < G$ a cocompact lattice. We apply the result for general actions of simply connected groups to obtain sufficient conditions for the action of $H$ on $\Gamma\backslash G$ by right translations to be locally rigid. We also discuss some possible applications of this sufficient condition
I den här texten så studerar vi lokal rigiditet av gruppverkan av enkelt sammanhängande Liegrupper. Mer specifikt, vi applicerar Nash-Mosers inversa funktionssats för att ge tillräckliga villkor för att en gruppverkan av en enkelt sammanhängande grupp ska vara lokalt rigid. Låt $G$ vara en Lie grupp, $H < G$ en enkelt sammanhängande delgrupp och $\Gamma < G$ ett kokompakt gitter. Vi applicerar resultatet för generella gruppverkan av enkelt sammanhängande grupper för att få tillräckliga villkor för att verkan av $H$ på $\Gamma\backslash G$ med translationer ska vara lokalt rigid. Vi diskuterar också några möjliga tillämpningar av det tillräckliga villkoret.

Les rigidités du marché du travail ont souvent fait l’objet de spéculations dans la littérature en réponse à la volatilité excessive du chômage. Les questions d’économie positive mais aussi les questions normatives liées au fonctionnement des institutions du marché du travail ont animé un important débat. Cependant, les deux aspects du débat n’ont été que très peu orientés sur les interactions entre ces rigidités et la configuration optimale des institutions. L’objectif de cette thèse est de mettre en lumière le rôle de ces rigidités sur la dynamique du chômage et de l’inflation. On s’intéresse aux sources de fluctuations du marché du travail ainsi qu’aux questions liées au financement de l’assurance chômage en privilégiant les systèmes d’experience rating. Les résultats principaux sont les suivants. Premièrement, la prise en compte de frictions d’appariement et de rigidités de salaires est cruciale pour expliquer la dynamique du marché du travail mais leur estimation révèle que les chocs spécifiques au marché du travail comptabilisent une partie importante des fluctuations du chômage et des emplois vacants, impliquant une certaine déconnection avec les autres marchés. Deuxièmement, les systèmes d’assurance chômage basés sur l’experience rating stabilisent fortement les fluctuations du marché du travail en réduisant de façon considérable la volatilité du chômage et des séparations d’emplois mais également le coût en bien être associé aux imperfections du marché du travail. La prise en compte des non linéarités de ces systèmes permet de rendre compte des distorsions dans le comportement d’embauche et de licenciement des entrepreneurs
The excessive volatility of unemployment has raised an intense debate on the positive and the normative aspects of labor market rigidities and labor market institutions. However, on both sides of the debate there is little discussion on how rigidities interact with each other nor on the optimal design of institutions. The purpose of this thesis is to highlight the role of labor market rigidities for unemployment and inflation dynamics. We are interested in the sources of labor market fluctuations as well as the unemployment insurance financing mode. We focus on experience rating systems. The main results are the followings. First, matching frictions and wage rigidities are crucial to explain the labor market dynamics but estimations of structural models show that the bulk of variation in labor market variables is solely explained by disturbances pertaining to the labor market. Second, unemployment insurance experience rating systems reduce considerably the volatility of labor market outcomes and the welfare cost coming from labor market imperfections. The tax schedule of experience rating is highly non linear, which induce sizeable distortions in the firms' hiring and firing behavior

Esta investigación aborda la real influencia que tiene el agrietamiento de los elementos estructurales en la reducción de rigidez cuando se produce un evento sísmico. Para ello, en primer lugar, describió la realidad problemática, los antecedentes y generalidades previos acerca del tema para determinar qué tipo de edificación utilizar. En segundo lugar, el marco teórico expuso un conjunto de conceptos fundamentales necesarios para entender el agrietamiento del concreto, la obtención de la inercia efectiva, la irregularidad de edificaciones y se dio un repaso sobre las consideraciones de normas extranjeras. En tercer lugar, se determinó trabajar con 6 planos de viviendas multifamiliares, de los cuales 3 fueron estructuras regulares y 3 fueron irregulares. Asimismo, se subdividió las estructuras en alturas de 5, 10 y 15 pisos, ya que son el tipo de edificación que más se construyen en Lima. Después se halló los parámetros geográficos, de uso y geométricos a partir de la Norma E-030, para luego realizar el análisis sísmico lineal (estático y dinámico). Luego, se realizó los diagramas de momento – curvatura (vigas, columnas y placas), para que, a partir de ellos, obtener un factor de reducción de la inercia bruta y realizar un nuevo análisis sísmico considerando este valor como efecto del agrietamiento. Finalmente, se realizó un análisis comparativo entre los resultados obtenidos de acuerdo a la altura en edificaciones regulares e irregulares.
This research addresses the real influence of the cracking of structural elements in the reduction of rigidity when a seismic event occurs. To do this, first, he described the problematic reality, the background and previous generalities about the topic to determine what type of building to use. Secondly, the theoretical framework exposed a set of fundamental concepts necessary to understand the cracking of concrete, the obtaining of effective inertia, the irregularity of buildings and a review of the considerations of foreign standards. In the third place, it was determined to work with 6 multifamily housing plans, of which 3 were regular structures and 3 were irregular. Likewise, the structures were subdivided into heights of 5, 10 and 15 floors, since they are the type of building that is most constructed in Lima. Afterwards, the geographic, use and geometrical parameters were found from the E-030 standard, to then perform the linear seismic analysis (static and dynamic). Then, the moment diagrams - curvature (beams, columns and plates) were made, so that from them, obtain a reduction factor of the gross inertia and perform a new seismic analysis considering this value as an effect of cracking. Finally, a comparative analysis was made between the results obtained according to the height in regular and irregular buildings.
Tesis

O trabalho desenvolvido tem como objetivo avaliar a influência da rigidez estrutural no comportamento dinâmico do veículo baseando-se em manobra de raio constante em condição quase estática e análise de sensibilidade através de simulação numérica computacional. São apresentados dois modelos para avaliar a transferência de carga lateral do veículo quando sujeito à aceleração lateral (manobra de raio constante), um modelo completo de veículo elaborado em ambiente multicorpos tendo a carroceria e o sub-chassi modelados como corpos flexíveis, e outro modelo analítico com a consideração da rigidez torcional (obtida de modelo de elementos finitos) da estrutura. Com o modelo analítico atendendo o nível de correlação necessário para o propósito deste trabalho, discute-se neste ponto as variações na transferência de carga devido à rigidez torcional da estrutura. Em seguida, com o intuito de abranger, além do parâmetro de transferência de carga lateral, quais comportamentos do veículo são afetados pela sua rigidez estrutural, é proposta a utilização do método de engenharia robusta para a identificação das condições externas que geram diferentes resultados de comportamento dinâmico do veículo com a variação da rigidez estrutural. Este estudo permite identificar manobras ou situações nas quais as considerações de flexibilidade estrutural num modelo multicorpos, ou mesmo numa condição física real, são relevantes e podem afetar a segurança, dirigibilidade e o conforto do veículo.
The work aims to evaluate the influence of structural stiffness on the dynamic behavior of the vehicle based on a constant radius maneuver in a quasi-static condition and a sensitivity analysis through computer numerical simulation. Two models were developed to evaluate the lateral load transfer of the vehicle when subjected to lateral acceleration (constant radius maneuver), a complete vehicle built in multibody environment with the body and the sub-chassis modeled as flexible bodies, and an analytical model with consideration of structure torsional stiffness (obtained from finite element model). With the analytical model presenting the required correlation for the purpose of this paper, we discuss, at this point, the lateral load transfer variations due to torcional structural stiffness. Then, in order to cover, in addition to lateral load transfer, how the vehicle behavior is affected by its structural stiffness, the robust engineering method is considered for identifying the external conditions that generate different dynamic behavior results for the variation of structural stiffness. This study allows us to identify maneuvers or situations in which considerations of structural flexibility in multibody model, or even in a real physical condition, are relevant and can affect the safety, ride and handling of the vehicle.

Le présent travail de thèse traite de la modélisation vibratoire et de la caractérisation dynamique de matériaux multicouches anisotropes. Dans le premier chapitre, une classification de quelques modèles analytiques de multicouche et techniques de caractérisation expérimentales de structures planes est établie sous la forme d'une synthèse bibliographique. Elle regroupe les récents résultats publiés autour du sujet. Le second chapitre propose une extension d'un modèle équivalent de multicouche au cas des structures anisotropes. Ce modèle décrit les premières courbes de dispersion de la structure et tient compte des phénomènes de cisaillement pouvant agir sur le mode de flexion en hautes fréquences. Le principal avantage du modèle réside dans sa simplicité et sa rapidité grâce à son nombre de variables cinématiques indépendant du nombre de couches. Les caractéristiques du multicouche sont définies par les 5 rigidités de flexion d'une plaque équivalente mince qui est comparée à ce dernier. L'extension de modèle est validée à l'aide d'une étude expérimentale réalisée sur des plaques composites en fibres de carbone. Un intérêt tout particulier est porté sur la modélisation de l'amortissement structurel. Une définition énergétique du facteur de perte, décrite par une formulation spatiale et temporelle de l'atténuation, est comparée à une définition équivalente. Une nouvelle définition de la formulation spatiale est proposée dans le cas de structures très amorties et est comparée aux résultats de la littérature. Dans le troisième chapitre, la technique de caractérisation RIC est étendue au cas des structures anisotropes. Cette méthode inverse s'appuie sur l'analyse du champ de déplacement de la structure et possède, grâce à son aspect local, des atouts non négligeables pour des applications industrielles. La méthodologie est tout d'abord présentée pour l'identification de sources (objectif initial de la méthode) et est ensuite adaptée à la caractérisation. Plusieurs applications numériques et expérimentales sont présentées afin de valider cette extension. Enfin, le quatrième chapitre porte sur la caractérisation expérimentale d'un sandwich en nids d'abeille sur une large bande fréquentielle (1 à 300 kHz). Le comportement dynamique complexe de cette structure épaisse est décrit au travers des résultats prometteurs fournis par les simulations de notre modèle et les estimations de RIC. Ces résultats sont également comparés à ceux d'un modèle de référence et d'autres méthodes de caractérisation
This PhD thesis concerns the modelling and the dynamic characterisation of anisotropic multilayered structures. In the first chapter, a classification of some analytical models and experimental methods of characterisation is presented in the form of a bibliographical synthesis where the main published results are gathered. The second chapter introduces an extension of an equivalent model of multilayered structures to the case of anisotropic materials. This model describes the first dispersion curves of the structure and considers the shear phenomena that can affect the bending mode in high frequencies. The main advantage of the model lies in its simplicity and rapidity thanks to a number of kinematic variables independent of the number of layers. The characteristics of the multilayer are defined by the 5 flexural rigidities of a thin equivalent plate which is compared to the multilayer. The results of the model are validated by means of an experimental study on carbon fiber composite plates. A particular interest is dedicated to the modelling of structural damping. An energetic loss factor, based on a temporal and spatial definition of the attenuation, is compared to an equivalent one. A new definition of the spatial attenuation is suggested for high damped structures and is compared to literature. In the third chapter, the methodology of the characterisation technique CFAT is adapted for anisotropic plates. This inverse method is based on the displacement field analysis of the structure and has, by means of its local aspect, relevant advantages for industrial applications. This adaptation is, as a first step, introduced for the identification of sources (initial objective of the method) and applied, in a second step, for the characterisation. Several numerical and experimental applications are presented to validate the results of the method. Finally, the fourth chapter deals with the experimental characterisation of a honey comb sandwich on a high frequency range (1 to 300 kHz). The complex dynamic behaviour of this thick structure is described through the promissing results given by the simulations of our model and the estimations of RIC. These results are also compared to the ones of a reference model and other characterisation methods

La cellule eukaryote est organisée en plusieurs compartiments, appelés organelles, délimités par des membranes. La fission des membranes est nécessaire pour le transport intracellulaire entre organelles. L'endocytose est un mécanisme de transport depuis la membrane plasmique vers les autres organelles. La Dynamine est une guanosine triphosphatase (GTPase) impliquée dans la fission des vésicules pendant l'endocytose médiée par la Clathrine. Elle polymérise en hélice au coup des bourgeons endocytiques. Après hydrolyse du GTP, la structure de l'hélice est modifiée : le rayon interne diminue de 10 à 5 nm et le pas hélical de 13 à 9 nm. Ces modifications indiquent un mécanisme de constriction. La dynamique de constriction est étudiée en suivant la rotation de microbilles attachées à des tubes lipidiques recouverts de Dynamine. La déformation des hélices de Dynamine est concertée et amortie par la friction entre membrane et Dynamine. Cependant la constriction ne suffit pas pour la fission. Pour comprendre davantage son mécanisme, la fission par la Dynamine est étudiée à l'aide de tubes lipidiques extraits de vésicules unilamellaires géantes. La fission se produit au bord de l'hélice, où la membrane est fortement courbée. D'après l'analyse statistique des temps de fission, la réaction de fission peut être modélisée par une unique barrière énergétique. La dépendance du temps de fission en rigidité de membrane, en tension de membrane et en couple est établie théoriquement et validée expérimentalement. Ce travail établit le profil énergétique de la réaction de fission membranaire et évalue à 70 kT la barrière énergétique.

Les verres de chalcogénure sont ont une grande importance dans des applications optoélectroniques, mais aussi pour leur réseau covalent qui leur procure une "variabilité structurale" accrue. Ce projet étudie des alliages Ge-Se et utilise l'association d'analyses dynamique moléculaire (AIMD), de simulations et de diffusion des rayons X afin de déterminer la structure et la dynamique des phases liquide et vitreuse sous pression. Les alliages de Ge-Se permettent la "formation de verre" sur une large gamme de conditions, ce qui permet de contrôler la rigidité du réseau en augmentant le nombre moyen de coordination en fonction de la teneur en Ge ce qui affectera les propriétés macroscopiques du matériau, comme la résistance au vieillissement, la dureté, la conductivité et la fragilité. Dans cette optique, nous étudions 10 compositions générées/calculées par AIMD, et 5 autres compositions déterminées expérimentalement (i.e par trempe ) couvrant les domaines transitions élastiques souple-rigide suivant les critères de stabilité isostatique de Maxwell. Dans le cas de l'état liquide, la comparaison au préalable des données de la expérimentale permet de valider les modèles structuraux, pour ensuite examiner la dynamique des liquides de Ge-Se à pression ambiante. En partant du postulat que la mobilité atomique du système décroit en devenant plus rigide, l'étude des coefficients de diffusion et de la viscosité à 1050 K a montré des anomalies flagrantes
Among network forming glasses, chalcogenide glasses are of great importance not only for their optoelectronic applications, but also for the network structure that displays enhanced structural variability due to the covalent bonding network. In this project, we study the Ge-Se binary alloy as the target system in order to investigate the structure and dynamics of the liquid and glassy phases under pressure by using a combination of ab initio molecular dynamics (AIMD) simulations and X-ray scattering experiments

Les secousses sismiques sont des catastrophes naturelles, affectant la croûte terrestre, qui peuvent avoir des effets destructeurs majeurs dans les zones urbanisées. Même si des méthodes précises de calcul d'ouvrages en situation sismique existent, il est nécessaire de disposer de méthodes adaptées aux ingénieries mises en oeuvre. L'évolution de la réglementation parasismique (Eurocode 8 et annexes nationales) et du zonage sismique en France fait évoluer de manière significative la nécessité de prise en compte de l'action sismique dans la conception des bâtiments. Dans un calcul sismique, il est indispensable de prendre en compte des effets de la torsion qui peuvent conduire à des conséquences graves, en termes de dommages affectant les ouvrages de génie civil. Le présent travail expose une démarche incluant différents niveaux d'approches pour prendre en compte ce phénomène. Les structures particulièrement visées par ce travail sont les ossatures dites souples et plus spécifiquement les constructions en bois. Une étude paramétrique est menée avec une méthode de combinaison multidimensionnelle pour analyser l'influence de différentes configurations de contreventement sur la sensibilité de l'ouvrage aux phénomènes de torsion. Cette étape est basée sur l'adaptation pour des structures en bois, dans le contexte des Eurocodes (torsion structurale et torsion accidentelle), d'une méthode néozélandaise développée par Priestley et Paulay initialement proposée pour des bâtiments en béton armé. L'étude du comportement des bâtiments en bois en situation sismique s'inscrit dans une approche utilisant la méthode de linéarisation équivalente par coefficient de comportement. L'action sismique peut ainsi être modélisée par des forces statiques équivalentes qui sont ensuite transmises aux éléments structuraux verticaux par des diaphragmes horizontaux. Ce travail permet de définir des distributions d'efforts sismiques sur chaque contreventement avec la prise en compte de la torsion à partir d'une cartographie d'implantation des contreventements et des masses. Cette méthode originale de prise en compte de la torsion est mise en application et l'ensemble des résultats obtenus conduit à la réalisation d'une base de données conséquente sur les effets de la torsion, pour une situation sismique, dans le cas d'un dimensionnement en capacité, avec contreventements ductiles à comportement linéarisé par coefficient de comportement et diaphragmes horizontaux rigides. Après mise en application de cette méthode, une approche numérique du comportement de structures génériques est conduite afin d'illustrer les effets de différents niveaux de simplification inhérents à la méthode originale mise en place. Dans cette étape, les calculs utilisent la méthode des éléments finis en s'appuyant sur le logiciel Cast3m. Les calculs dynamiques sont réalisés sur la base de comportements linéaires ou linéarisés afin d'analyser les effets de différentes méthodes de calcul proposées par l'Eurocode 8, partie 1. Les calculs menés dans cette phase permettent notamment de valider des conditions d'application de méthodes simplifiées pour des structures en bois, et d'approcher les effets de la torsion sur ces structures avec différents degrés de précision.

No presente trabalho consideramos homeomorfismos do círculo sem pontos periódicos e com o mesmo número finito de pontos críticos todos de tipo non-flat. Provamos que se existe uma conjugação topológica entre dois destes mapas que leva ponto crítico em ponto crítico, sem necessidade de preservar criticalidades, então dita conjugação é uma transformação quase-simétrica com distorção quase-simétrica local uniformemente limitada. Estes resultados são válidos para qualquer número de rotação irracional e são independentes da natureza das criticalidades dos pontos críticos, de modo que nossos resultados são válidos para toda criticalidade real.
In this work we consider circle homeomorphisms without periodic points and with finite number of critical points all of them being non-flat. We prove that if there exists a topological conjugacy between two of those maps which sends critical point into critical point, which not necessarily preserve criticalities, then this conjugacy is a quasi-symmetric map with quasi-symmetric distortion universally bounded. All these results are valid for any irrational rotation number and are independent of the nature of the criticalities, therefore our results are valid for all real criticalities.

In the present work reduced order models (ROM) that are independent from the full order finite element models (FOM) considering geometrical non linearities are developed and applied to the dynamic study of rotating structures. The structure is considered to present nonlinear vibrations around the pre-stressed equilibrium induced by rotation enhancing the classical linearised approach. The reduced nonlinear forces are represented by a polynomial expansion obtained by the Stiffness. Evaluation Procedure (STEP) and then corrected by means of an original procedure by means of a Proper Orthogonal Decomposition (POD) that filters the full order nonlinear forces before projection. The latter model is named STEP with Correction (StepC). Different types of reduced basis are presented and tested. Some of these bases are parametrised with respect to the rotating velocity reducing considerably the construction of the ROM. The results obtained with the StepC ROM are in good agreement with the solutions of the FOM and are capable of reproducing the coupled motion of the structure. Furthermore they are more accurate than the classsical Linearised ROM solutions and than the STEP ROM without correction. The proposed StepC ROM provides the best compromise between accuracy and time consumption of the ROM
Dans le présent travail, des modèles d’ordre réduits (ROM) indépendant des modèles ́eléments finis d’haute fidélité (FOM) ont ́eté d ́eveloppés pour l’etude de la dynamique non linéaire des structures en rotation. Les vibrations de la structure autour de l’équilibre précontraint induit par la rotation sont considérées comme non linéaires, améliorant l’approche linéarisée classique. Les forces généralisées non linéaires sont approximées par un polynôme d’ordre trois obtenu avec la procédure Stiffness Evaluation Procedure (STEP). Ici, une approche originale est proposée pour corriger les forces non linéaires à l’aide d’une base de forces non linéaires obtenue avec une décomposition orthogonale aux valeurs propres (POD). Ce modèle est nommé STEP avec Correction (StepC). Différents types de base réduite sont présentés et testés. Certaines de ces bases sont paramétrées en fonction de la vitesse de rotation, ce qui réduit considérablement le temps de construction du modèle réduit. Les résultats obtenus avec le modèle StepC ROM sont en bon accord avec le FOM et sont capables de reproduire le couplage en déplacement entre les dégrés de liberté de la structure. De plus, elles sont plus précises que les solutions ROM linéarisées classiques et que le modèle STEP ROM sans correction. Le modèle StepC ROM proposé offre le meilleur compromis entre précision et temps de construction du ROM

En realistisk simulation kräver att alla simulerade objekten ska interaktivt och dynamiskt animeras. Delar av objektens kropp ska deformeras och andra delar ska sönderfalla vid en krock med ett annat objekt. De flesta 3d applikationer har som gemensamt vissa tekniker som används vid dynamiska simulationer. Tyvärr så finns det inte en smidig och snabb teknik för att deformera solida objekt vid kollisioner, detta gäller även Maya som jag använde i detta arbete. Detta arbete ska visa en smidig teknik att deformera vissa delar av en komplicerad modell och få andra delar att splittras och spridas i en dynamisk simulation som är både fysiskt rätt och ser visuellt bra ut. Resultatet är en kort animationsfilm som visar teknikerna i praktiken. Enskilda användare av 3Dapplikationer exempelvis studenter kommer ha nytta av arbetets olika delmoment och kan hänvisa till informationen.

La mise en place de l'Euro en 1999 a constitué un événement économique majeur pour les Etats européens. La crise financière de 2007, puis la crise de la dette souveraine en 2010, ont amené à remettre en question la pérennité de la zone Euro, et la capacité de certains de ses membres à respecter leurs engagements vis-à-vis de la monnaie unique. Les mesures d'austérité mises en oeuvre au sein de l'Union Economique et Monétaire dans le contexte actuel de crise peuvent constituer pour certains Etats une tentation supplémentaire pour quitter la monnaie unique et recouvrer leur indépendance monétaire et fiscale. Une sortie de la zone Euro de la Grèce, voire d'autres Etats membres en difficulté (Portugal, Irlande, Italie, et Espagne) n'est aujourd'hui plus un scénario à exclure. Cette thèse se propose de considérer la question du régime monétaire optimal, régime de change flexible ou union monétaire, pour les 17 pays de la zone Euro, dans le cadre des crises financières et de dettes souveraines qui les affectent actuellement. Le premier chapitre est général et vise à démontrer formellement la survenue d'une rupture structurelle due au passage à la monnaie unique en 1999. Il montre qu'une telle rupture s'est bien produite pour les pays de la zone Euro autour de l'année 1992, qui a marqué l'adoption du traité de Maastricht et la mise en place des critères de convergence pour l'adoption de l'Euro. Cette rupture n'est pas partagée par les trois pays européens qui ont préservé leur monnaie (Royaume-Uni, Suède, et Danemark). Le second chapitre constitue le coeur de ce travail. Il présente le modèle de référence utilisé pour mener la comparaison entre les deux régimes monétaires considérés pour la zone Euro. Il s'agit d'un modèle à deux pays intégrant des rigidités financières dans le cadre des transactions interbancaires conclues entre les Etats membres. Le modèle, une fois étalonné pour la zone Euro, suggère que les rigidités financières peuvent jouer un rôle considérable dans la dynamique de ces Etats, les chocs affectant les économies partenaires pouvant contribuer de manière significative à la dynamique nationale. Les simulations numériques préliminaires de crise financières menées sur le modèle ne permettent pas d'apporter de réponse concluante quant aux performances des deux régimes monétaires envisagés, le régime de change flexible semblant amener une stabilité accrue, là où une union monétaire permet une récupération plus rapide suite à la crise initiale. Le dernier chapitre remplit un double objectif. Il propose d'abord un critère de bien-être formel pour l'évaluation des performances respectives des deux régimes considérés. Il développe également un certain nombre d'extensions au modèle de référence, afin d'intégrer la dette souveraine, et les politiques de crédit (Covered Bonds Purchase Programme et Securities Markets Programme) mises en place par la BCE depuis le début de la crise. Les résultats montrent qu'en l'absence de politiques interventionnistes de la part de la Banque Centrale Européenne, une grande majorité des Etats de la zone Euro (15 sur 17) bénéficieraient d'un plus haut niveau de bien-être dans un régime de change flexible. Toutefois, les conclusions s'inversent dans le cadre du Securities Markets Programme, où les Etats membres deviennent alors majoritairement favorables au régime d'union monétaire. Celà suggère que la BCE a un rôle à jouer au sein de l'espace monétaire Européen qui va au-delà de sa fonction première d'instigatrice de la politique monétaire
The introduction of the Euro currency in 1999 represented a major event for the European economies. The 2007 financial crisis and the subsequent 2010 sovereign debt crisis have led to question the sustainability of the Euro area and the capacity of certain member states to fulfil their commitments with respect to the single currency. The numerous austerity plans implemented within the Economic and Monetary Union in the current context of crisis constitute additional arguments for certain states to leave the single currency and retrieve their fiscal and monetary independences. It is not unconceivable anymore for countries such as Greece, Portugal, Ireland, Italy and Spain (the PIIGS) to envisage exiting the Euro area. This thesis considers the issue of determining the optimal monetary regime  flexible exchange rates or monetary union  for the 17 Eurozone countries, accounting for the current financial and sovereign debt crises. Chapter 1 is general and aims at formally establishing the occurrence of a structural break attributable to the 1999 passage to the single currency. It shows that such a break did take place for Euro area countries around 1992, the year which marked the adoption of the Maastricht Treaty and the settlement of the convergence criteria for the Euro. This break is not shared by the three European States which chose to preserve their own currencies (the United Kingdom, Sweden and Denmark). Chapter 2 constitutes the core of this work. It introduces the benchmark model used to perform the comparison between the two monetary regimes considered for the Euro area. It features a two-country open-economy model integrating financial frictions through cross-border interbank markets. Once calibrated for the Euro area, the model suggests that financial rigidities may play a substantial role in the dynamics of Eurozone economies, with a potentially significant impact of shocks affecting the partner economies over national developments. Preliminary financial crisis simulations run on the model prove inconclusive to assess the performances of the two monetary regimes contemplated. On the one hand, the flexible exchange rate regime results in improved stability, but on the other hand the monetary union typically allows for faster recovery following the initial crisis trigger. The third and final chapter meets a double purpose. It first proposes a formal welfare criteria to assess the respective performances of the two monetary regimes under consideration for the Euro area. It then augments the benchmark model with a number of extensions, so as to integrate sovereign debt and the diverse credit policies (Covered Bonds Purchase Programme and Securities Markets Programme) implemented by the ECB since the beginning of the crisis to the basic framework. The results show that absent credit policies, a vast majority of Euro area members (15 out of 17) would enjoy higher welfare levels under a flexible exchange rate regime. These conclusions nevertheless reverse under the Securities Markets Programme, where a majority of member states then favour the monetary union. This suggests that the ECB has a role to play for the Euro area which goes beyond its primary function of monetary policy maker

Les dernières décennies ont été marquées par un intérêt accru pour les non-linéarités dues aux défauts localisés dans les solides (les fissures fermées par exemple) et aux interfaces de contact en général. En conséquence, un certain nombre de méthodes non-linéaires ont été développés pour la détection de ces défauts et caractérisation des interfaces de contact. Cependant, la compréhension des mécanismes physiques liés aux non-linéarités due contact reste limitée. Dans ce cadre, ce travail de thèse vise à étudier l'interaction non-linéaire entre une onde et une interface tout en intégrant plusieurs mécanismes liés au contact, afin de proposer, à terme, une méthode CND efficace pour la caractérisation des interfaces. L'étude de l'évolution du second harmonique pour caractériser ce type de défauts localisés et plus généralement les interfaces de contact sera au coeur de ce travail.L'interaction non-linéaire entre une onde longitudinale et une interface de contact est modélisée en combinant deux approches. L'une est basée sur des méthodes acoustiques et utilisée en traction, tandis que l'autre est basée sur l’analyse vibratoire structurelle et utilisée en compression. La première consiste à modéliser le contact avec une loi RCCM. L'étude propose une analyse détaillée du comportement de l'interface en traction tout en intégrant l'adhérence. Elle permet d'identifier les paramètres clés qui régissent la signature non-linéaire de la loi RCCM et ainsi permet de mieux comprendre la physique derrière cette interaction non-linéaire. La deuxième méthode, utilisée en compression, est basée sur un modèle de rigidité d'interface non-linéaire où la rigidité d'interface est décrite en fonction de la pression de contact nominale. L'étude consiste en une analyse numérique et expérimentale complémentaires de la composante non-linéaire de la réponse dynamique du système due à la présence d'interface de contact. Elle montre que la tendance de la rigidité à faibles pressions a un effet majeur sur la réponse non-linéaire des systèmes avec des interfaces de contact. Enfin, les lois de contact proposées en compression et traction sont combinées en une seule loi pour permettre une meilleure corrélation entre les différents mécanismes de contact en compression et en traction et donc une meilleure caractérisation de la réponse non-linéaire du système. Les résultats numériques sont prometteurs en vue de la caractérisation d'interfaces de contact à partir de la réponse non-linéaire du système excité par une source extérieure et applicables à la détection non-destructive de l’endommagement
The past decades have been marked by a significant increase in research interest in nonlinearities in cracked solids. As a result a number of different nonlinear methods have been developed for damage detection. However, there still limited understanding of physical mechanisms related to the various nonlinearities due to contacts. This thesis is addressed to study the nonlinear interaction between a wave and an interface while taking into account adhesion, in order to, eventually, propose an efficient NDT method for characterization of contact interfaces. The study of the second-harmonic evolution to characterize the damage will be the focus of this work. The nonlinear interaction between a longitudinal wave and a contact interface is considered in one-dimensional medium by using the Finite Elements method.Numerically, the contact interface is modelled by combining two approaches. One is based on acoustic methods and used in traction, while the other one is based on vibration methods and used in compression. The first one, consists in modelling the contact with an RCCM law. The study propose a detailed analysis on the interface behaviour in traction while taking into account the adhesion. It allows identifying the key parameters that govern the nonlinear signature of the RCCM contact law and so better understanding the interaction between a compression wave and a contact interface that exhibits adhesion in traction. The second one, used in compression, is based on a nonlinear interface stiffness model where the stiffness property of the contact interface is described as a function of the nominal contact pressure. The study consists in a complementary numerical and experimental analysis of nonlinear vibrational response due to the contact interface. It shows that the stiffness-pressure trend at lower pressures has a major effect on the nonlinear response of systems with contact interfaces.Finally, in order to exploit the proposed contact law defined in compression and traction, a strategy to identify the interface parameters during the interaction between a wave and an interface is proposed. The numerical results are promising in view of the characterization of contact interfaces

L'étude s'inscrit dans le cadre de la prévision des niveaux vibratoires induits par les chocs pyrotechniques lors de la phase de séparation des étages du lanceur Ariane 5, et plus particulièrement de la prévision des niveaux vibratoires dans la case a équipements. On développe une approche simplifiée permettant de déterminer la réponse dynamique de la structure à partir du calcul de matrices de rigidité dynamique exactes. Cette approche est réservée a des structures de type guides d'ondes dans lesquelles la direction de propagation des ondes est connue. On s'intéresse également a la prise en compte de liaisons entre structures ; on montre qu'il est possible de déterminer la matrice de rigidité dynamique des liaisons a partir de la connaissance des coefficients de réflexion et de transmission des ondes et des relations force-déplacement dans les éléments relies a la liaison.

碩士
國立中山大學
海洋環境及工程學系研究所
93
In this paper，the cable structures considering sag effect and flexural rigidity are used to the series of dynamic analysis.It dedatees on vibration of the cables by the harmonic force and win－rain induced vibration. Using the finite element method to analyze the effect of the sge and the effect of the sag and the flexural rigidity，including frequencies of the cable and displacement of every nodes at arbitrarily time.

碩士
國立彰化師範大學
機電工程學系
106
Modal analysis is one of the powerful tools to not only assist the development of precision platforms in industry, but also find the designing mistakes. The rigidities of mechanical systems are employed to judge the mechanical performance of those systems. The main subject of this study is to determine the influence produced by the variation of the rigidity of structural joint surface to the performance of a mechanical system. In this study, it was found that the location of the interface of the 3D printer was found to be a long column on both sides of the machine and a fixed whole machine, as well as the use of different frequencies to find a suitable environment for measuring the natural frequency of the machine. The result can provide useful designing parameters for future design.

This thesis describes a study of the effect of environmental cues including physical attribute of the cellular environment on cellular force and force transduction. Different mechanical parameters such as geometry and rigidity of the substrate are controlled independently and forces exerted by cells were measured. The experimental system for this study is based on fabrication of micron and submicron pillar substrates and their surface functionalization and finally measurement of forces that cells exert to these substrates. In chapter 2, the interplay between the rigidity of the substrate and the cell's force response was studied. Arrays of flexible PDMS pillars used to measure the pattern of traction force generation on matrices. Using three different pillar diameters (2, 1 and 0.5 micrometers), and three different pillar stiffnesses for each diameter, we showed that cells treat larger, fibronectin-coated pillars fundamentally differently than sub-micron pillars during initial contact formation. In the case of larger pillars, mouse embryo fibroblasts generated a constant force per unit area of about 1 nN/m2 on pillars of different stiffness by causing different displacements; whereas, the sub-micrometer pillars were displaced by about 60 nm irrespective of stiffness. In addition, micron-scale pillars are all pulled toward the center of the cell, whereas sub-micron pillars were also pulled toward each other locally. Further, the focal adhesion protein, paxillin, was concentrated at the edges of large pillars but it was focused on the tops of small pillars in a pattern analogous to the pattern on continuous substrates. Thus, we suggested that initial rigidity sensing involves measuring the force needed to produce displacements of about 60 nm in local regions (1m) of the substrate. In addition, these results suggested that, to examine the effects of substrate rigidity on cellular behavior, sub-micron pillars more closely approximate continuous substrates than do micron-scale pillars. In chapter 3, a technique was described for fabricating substrates whose rigidity can be controlled locally without altering the contact area for cell spreading. The substrates consist of elastomeric pillar arrays in which the top surface is uniform but the pillar height is changed across a sharp step. Results demonstrated the effects on cell migration and morphology at the step boundary. In chapter 4, a technique was described for the fabrication of arrays of elastomeric pillars whose top surfaces are treated with selective chemical functionalization to promote cellular adhesion in cellular force transduction experiments. The technique involves the creation of a rigid mold consisting of arrays of circular holes into which a thin layer of Au is deposited, while the top surface of the mold and the sidewalls of the holes are protected by a sacrificial layer of Cr. When an elastomer is formed in the mold, Au adheres to the tops of the molded pillars. This can then be selectively functionalized with a protein that induces cell adhesion, while the rest of the surface is treated with a repellent substance. An additional benefit is that the tops of the pillars can be fluorescently labeled for improved accuracy in force transduction measurements. The same fabrication process was used for fabrication of magnetically actuated pillars in order to be able to exert external force to cells and study the eect of localized mechanostimulation.

This thesis describes a comprehensive study of understanding the mechanism of rigidity sensing by quantitative analysis using submicron pillar array substrates. From mechanobiology perspective, we explore and study molecular pathways involved in rigidity and force sensing at cell-matrix adhesions with regard to cancer, regeneration, and development by quantification methods. In Chapter 2 and 3, we developed fabrication and imaging techniques to enhance the performance of a submicron pillar device in terms of spatial and temporal measurement ability, and we discovered a correlation of rigidity sensing forces and corresponding proteins involved in the early rigidity sensing events. In Chapter 2, we introduced optical effect arising from submicron structure imaging, and we described a technique to identify the correct focal plane of pillar tip by fabricating a substrate with designed-offset pillars. From calibration result, we identified the correct focal plane that was previously overlooked, and verified our findings by other imaging techniques. In Chapter 3, we described several techniques to selectively functionalize elastomeric pillars top and compared these techniques in terms of purposes and fabrication complexity. Techniques introduced in this chapter included direct labeling, such as stamping of fluorescent substances (organic dye, nano-diamond, q-dot) to pillars top, as well as indirect labeling that selectively modify the surface of molds with either metal or fluorescent substances. In Chapter 4, we examined the characteristics of local contractility forces and identified the components formed a sarcomere like contractile unit (CU) that cells use to sense rigidity. CUs were found to be assembled at cell edge, contain myosin II, α-actinin, tropomodulin and tropomyosin (Tm), and resemble sarcomeres in size (~2 μm) and function. Then we performed quantitative analysis of CUs to evaluate rigidity sensing activity over ~8 hours time course and found that density of CUs decrease with time after spreading on stiff substrate. However addition of EGF dramatically increased local contraction activity such that about 30% of the total contractility was in the contraction units. This stimulatory effect was only observed on stiff substrate not on soft. Moreover, we find that in the early interactions of cells with rigid substrates that EGFR activity is needed for normal spreading and the assembly of local contraction units in media lacking serum and any soluble EGF. In Chapter 5, we performed high temporal- and spatial-resolution tracking of contractile forces exerted by cells on sub-micron elastomeric pillars. We found that actomyosin-based sarcomere-like CUs simultaneously moved opposing pillars in net steps of ~2.5 nm, independent of rigidity. What correlated with rigidity was the number of steps taken to reach a force level that activated recruitment of α-actinin to the CUs. When we removed actomyosin restriction by depleting tropomyosin 2.1, we observed larger steps and higher forces that resulted in aberrant rigidity sensing and growth of non-transformed cells on soft matrices. Thus, we conclude that tropomyosin 2.1 acts as a suppressor of growth on soft matrices by supporting proper rigidity sensing.

A comprehensive study is made of an approximate model for the computation of the dynamic pressures and associated forces induced by ground shaking on rigid embedded vaults (2, 10). For rigidly supported vaults, it is shown that, due to the lack of shearing resistance of the medium surrounding the vault, the model is unable to predict the forces induced under static conditions of loading, and that it generally leads to much higher results than those obtained by available exact solutions (20). The soil surrounding the vault is hence modelled by a new set of impedances (20). It is shown then that the effect of base flexibility is to reduce the forces induced on massless vaults. Evaluation is also made of the effect of the vault mass. It is finally shown that the difference in the responses computed by the original and modified models decreases in importance with increasing flexibility.

碩士
中原大學
機械工程研究所
82
In this thesis, we study the motion of a fixed-free Euler-Be- rnoulli beam. The beam is clamped at one end at the top of the rigid circular foundation, and the other end is free. The physi- cal property is specified for the fixed end, however, when the system deforms, a moving boundary point is obtained geometric constraint of the circular foundation. Under downward vibration configuration of this system, we find it has an undetermined and moving boundary, which is importance to our research. For solving the motion of the beam, we utilizes Galerkin app- roximations reduce the partial differential equations to a set of non-linear ordinary differential equations. The transient am- plitude and the position of moving boundary are simulated by Ru- nge-Kutta algorithm. Besides, this thesis also derives the equilibrium configurat- ion of the fixed-free Euler-Bernoulli beam when it carrys a uni- form load under circular foundation. When applying with the uni- form load only and without the motion of the beam, it becomes static equilibrium rigid circular foundation. The increasing of the load intensity will increase the length that lies on the fo- undation. In the past, the static equilibrium discusses in plain references just considered that the beam could only contacts li- ttle with the circular foundation, it is incorrect and can not satisfy the physical condition when the uniform load increases. A cantilever beam is used to investigate its exact solution with some load intensity and its results are documented in the appen- dix C. After this research, some of the view point about the co- ntact point on the circular foundation is improved.

Conformational selection is the idea that proteins traverse positions on the conformational space represented by their potential energy landscape, and in particular positions considered as local energy minima. Conformational selection a useful concept in ligand binding studies and in exploring the behavior of protein structures within that energy landscape. Often, research that explores protein function requires the generation of conformational ensembles, or collections of protein conformations from a single structure. We describe a method of conformational ensemble generation that uses joint-constrained rigid-body dynamics (an approach that allows for explicit consideration of rigidity) and the elastic network model (providing structurally derived directional guides for the rigid-body model). We test our model on a selection of unbound proteins and examine the structural validity of the resulting ensembles, as well as the ability of such an approach to generate conformations with structural overlaps close to the ligand-bound versions of the proteins.

The thesis tries to explain different nature of the dynamics during the upward and downward part of the last house price cycle in Spain, characterized by important rigidities. Covered bonds are introduced as an instrument which may accelerate a house price boom, while it may also serve as a source of correction to overvalued house prices in downturn. In a serious economic stress, lack of investment opportunities motivates investors to buy the covered bonds due to the strong guarantees provided, which may in turn help to revitalize the credit and housing markets. To address such regime shift, house price dynamics is modelled within a framework of mutually related house price, credit and business cycles using smooth transition vector autoregressive model. Linear behaviour of such system is rejected, indicating the need to model house prices in a nonlinear framework. Also, importance of modelling house prices in the context of credit and business cycles is confirmed. Possible causality from issuance of covered bonds to house price dynamics was identified in this nonlinear structure. Finally, threat to financial stability resulting from rising asset encumbrance both in the upward and downward part of the house price cycle was identified, stressing the need to model impact of the covered bonds on house prices in...