The ability to adjust structural response to external loading and ensure structural safety and serviceability is a characteristic of Smart Systems. The key to achieving this is through the development and implementation of smart materials. An example of a smart material is a Shape Memory Alloy (SMA). Reinforced concrete structures are designed to sustain severe damage and permanent displacement during strong earthquakes, while maintaining their integrity, and safeguarding against loss of life. The design philosophy of dissipating the energy of major earthquakes leads to significant strains in the steel reinforcement and, consequently, damage in the plastic hinge zones. Most of the steel strain is permanent, thus leading to large residual deformations that can render the structure unserviceable after the earthquake. Alternative reinforcing materials such as superelastic SMAs offer strain recovery upon unloading, which may result in improved post-earthquake recovery. Shape Memory Alloys have the ability to dissipate energy through repeated cycling without significant degradation or permanent deformation. Superelastic SMAs possess stable hysteretic behavior over a certain range of temperature, where its shape is recoverable upon removal of load. Alternatively, Martensite SMAs also possess the ability to recover its shape through heating. Both types of SMA demonstrate promise in civil infrastructure applications, specifically in seismic-resistant design and retrofit of structures. The primary objective of this research is to investigate experimentally the performance of concrete beams and shear walls reinforced with superelastic SMAs in plastic hinge regions. Furthermore, this research program involves complementary numerical studies and the development of a proposed hysteretic constitutive model for superelastic SMAs applicable for nonlinear finite element analysis. The model considers the unique characteristics of the cyclic response of superelastic materials.

L'objectif majeur de la présente thèse de doctorat est la validation structurelle d’une connexion hybride plancher-voile pour la reprise de l'action sismique dans les bâtiments en béton armé à voiles. Le manque de références normatives et scientifiques pour la caractérisation de ce type de système, nous a conduits à concevoir un protocole de caractérisation original basé principalement sur une analyse expérimentale à grande échelle du comportement de la liaison plancher-voile. Tout d'abord, nous présentons quelles ont été les problématiques et les exigences qui ont amené à l'innovation du rupteur de ponts thermiques SLABE, connexion hybride pour la jonction plancher-voile. Nous analysons ensuite les protocoles de caractérisation cyclique pour les systèmes structurels similaires ("coupling beams" ou "shearheads"). Sur base de cette réflexion, nous proposons un programme expérimental composé de trois séries d'essais: deux campagnes à grande échelle visant à restituer au mieux les configurations courantes de chargement dans un bâtiment (sollicitations horizontales et verticales), et une campagne d'essais d'ancrage. Ces essais sont capables de caractériser le comportement de la liaison dans les trois directions de l’espace. Les résultats de chaque campagne d'essais sont présentés dans le détail. Ils montrent notamment que la connexion étudiée, sous chargement cyclique, se comporte de façon quasi-élastique et stable pour les niveaux de charge correspondant aux sollicitations sismiques en France métropolitaine. De plus, ces essais ont souligné la grande réserve de ductilité du système, permettant une redistribution des efforts et contribuant ainsi à une meilleure robustesse du système, indispensable pour une sollicitation sismique présentant, par nature, un fort degré d’incertitude. Enfin, nous évaluons l'impact de la connexion plancher-voile sur le comportement structurel des bâtiments au travers d’une analyse structurelle sur des ouvrages de référence. Nous analysons la réponse modale et la redistribution des efforts entre les voiles de contreventement. Cette évaluation nous permet de définir une démarche de dimensionnement pour les ouvrages béton armé munis de ces éléments et de proposer des outils de calcul adaptés à l’ingénieur. L’exhaustivité de la démarche de validation présentée en fait une référence, déjà reconnue par les instances décernant les agréments techniques français, et qui pourrait être proposée comme protocole standard pour la validation des systèmes de rupteurs de ponts thermiques ou de liaison plancher-voile, au niveau européen. / The main objective of the PhD thesis is the structural evaluation of a hybrid structural connection at the slab-to-wall junction in concrete shear wall buildings under seismic action. The lack of normative and scientific literature for the characterization of this kind of systems leads us to devise an original protocol for the characterization which is mainly built on a large-scale experimental analysis of behaviour of the slab-towall connection. First, we explain the reasons that led us to design an innovative thermal break system, the SLABE, which is thermally insulated hybrid connection for the slab-to-wall junction. Then we analyse the existing protocols for the cyclic characterization of similar structural systems ("coupling beams" or "shearheads"). Based on the outcome of this investigation, we propose an experimental program composed with three test series: two large-scale campaigns where the actual loading conditions in a building are reproduced (horizontal and vertical shear forces) and an axial test campaign. The test results provided the required information to correctly characterize the behaviour of the hybrid connection in the three directions in space. The results of the experimental campaigns are presented in detail. In particular, they show that the connection, under cyclic loads, exhibits a quasi-elastic and stable behaviour at usual seismic load levels, in France. In addition, these tests highlight the large reserve of ductility of the system that guarantees the robustness of the system. This is essential for seismic actions which have by nature a high degree of uncertainty. The impact of the slab-to-wall connexion on the structural behaviour of buildings is evaluated through a structural analysis on representative structures. We particularly analyse the modal response and the force redistribution between the internal and external shear walls. Based on the outcome of this study, we suggest a seismic design method for reinforced concrete structures equipped with these structural elements. Along with that, we propose a computational tool for engineers. The completeness of the presented validation approach makes it a benchmark, already recognized by the French authorities granting technical approvals. It could be proposed as a standard protocol for the validation of other thermal break systems or hybrid slab-to-wall connections, at European level.

In the light of extreme events of natural disasters (earthquakes or hurricanes) and accidents (fire or explosion), repairing and strengthening of existing concrete structures has become more common during the last decade due to the increasing knowledge and confidence in the use of composite advanced repairing materials. The past experience from real fires shows that it is exceptional for a concrete building to collapse as a result of fire and most fire-damaged concrete structures can be repaired economically rather than completely replacing or demolishing them. In this connection an experimental study was conducted to investigate the effectiveness of fibre reinforced polymer jackets for axial compressive and seismic shear performance of post-heated columns. This study also investigates the effectiveness of ferrocement laminate for the repairing of post-heated reinforced concrete columns.A total of thirty-five reinforced concrete columns were constructed and then tested after categorising them into three main groups: un-heated, post-heated and post-heated repaired. The post-heated columns were initially damaged by heating (to a uniform temperature of 500°C). The concrete cubes were also heated to various temperatures to develop the relation between compressive strength and ultrasonic pulse velocity. The residual compressive strength of the concrete cubes and reinforced concrete columns were determined by ultrasonic testing. The post-heated columns were subsequently repaired with unidirectional glass or carbon fibre reinforced polymer and ferrocement jackets. The experimental programme was divided into two parts. The columns of experimental part-1 were tested under axial compressive loading. The columns of experimental part-2 with a shear span to depth ratio of 2.5 were tested under constant axial and reversed lateral cyclic loading. The results indicated that the trend of reduction in ultrasonic pulse velocity values and in residual compressive strength of concrete was similar with increasing temperature. The reduction in residual stiffness of both post-heated square and circular columns was greater than the reduction in ultimate load. The circular sections benefited more compared to the square cross-sections with fibre reinforced polymers for improving the performance of post-heated columns in terms of compressive strength and ductility tested under axial compression. GFRP and CFRP jackets performed in an excellent way for increasing the shear capacity, lateral strength, ductility, energy dissipation and slowed the rate of strength and stiffness degradation of fire damaged reinforced concrete square and circular columns tested under combined constant axial and reversed lateral cycle loading. However, the effect of a single layer of glass or carbon fibre reinforced polymer on the axial stiffness of post-heated square and circular columns was negligible. The use of a ferrocement jacket for the repairing of post-heated square and circular columns enhanced the axial stiffness and ultimate load carrying capacity of columns significantly.

Orientador: Amir Ordacgi Caldeira / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin / Made available in DSpace on 2018-08-18T12:04:56Z (GMT). No. of bitstreams: 1 GarciaRodriguez_AlexisOmar_D.pdf: 2441638 bytes, checksum: 00dfa78fb7b0c9f69778a51704c587b7 (MD5) Previous issue date: 2011 / Resumo: Este trabalho foi motivado por várias dificuldades encontradas no estudo do artigo de M. Ueda, Transmission Spectrum of a Tunneling Particle Interacting with Dynamical Fields: Real- Time Functional Integral Approach, Phys. Rev. B 54, 8676 (1996). Nesse artigo, num formalismo de tempo real, é descrito o tunelamento de uma partícula através de uma barreira utilizando tempos não reais de travessia através dessa barreira. No presente trabalho é proposto um formalismo mais amplo de tempo real para uma introdução mais natural de valores complexos do tempo na descrição do tunelamento de uma partícula cm interação com o ambiente. Esta proposta está baseada no chamado método do tempo complexo utilizado no caso do tunelamento de uma partícula sem interação com o ambiente estudado nos trabalhos de D. W. McLaughlin, J. Math. Phys. 13, 1099 (1972) c B. R. Holstein c A. R. Swift, Am. J. Phys. 50, 833 (1982). Seguindo o trabalho citado de Ueda, o ambiente da partícula é representado através de um conjunto, ou banho térmico, de osciladores harmônicos caracterizados por uma função de densidade espectral J(w). Utilizando o método de Feynman de integrais de trajetória, integramos sobre as coordenadas dos osciladores do banho c obtemos uma expressão exata para o espectro de transmissão da partícula para uma temperatura do banho T > O. Limitando-nos então ao caso mais simples T = O, estudamos o tunelamento dissipativo da partícula através da barreira. Considerando h um parâmetro pequeno (limite semiclássico), aproximamos o espectro de transmissão da partícula através da contribuição das trajetórias clássicas c suas trajetórias vizinhas. Nesta aproximação consideramos a variação da ação efetiva da partícula para tempos dados de duração das trajetórias c deste modo substituímos o procedimento variacional seguido no trabalho indicado de Ueda onde não é considerada a variação nos tempos de travessia da partícula através da barreira. Num segundo problema variacional nos tempos de duração das trajetórias clássicas de acordo com o método do tempo complexo e considerando também a variação nas posições iniciais c finais dessas trajetórias, obtemos as equações de movimento das chamadas trajetórias clássicas especiais. Este tratamento das coordenadas iniciais c finais das trajetórias clássicas substitui o procedimento seguido no trabalho de Ueda onde é considerc1da uma aceleração nula durante todo o trajeto de movimento incluindo o trajeto na região da barreira. Diferentemente do artigo citado de Ueda, no presente trabalho utilizamos pacotes de ondas relativamente bem localizados para descrever os estados inicial e final da partícula. Em consequência, aproximamos o espectro de transmissão da partícula através de trajetórias clássicas especiais com coordenadas iniciais c finais iguais ao valor médio da coordenada para esses pacotes de ondas. O procedimento seguido neste trabalho, baseado no método do tempo complexo, permite obter o fator ele acoplamento apropriado entre as duas trajetórias que descrevem a ação efetiva ela partícula substituindo assim o procedimento de tipo ad hoc seguido com este fim no trabalho indicado de Ueda. O método do tempo complexo permite obter também o termo ela diferença entre a ação efetiva da partícula c o expoente ele tunelamento, sendo que estas grandezas são tratadas como iguais no trabalho citado de Ueda. Considerando termos até primeira ordem num campo elétrico externo c na interação da partícula com o banho de osciladores, obtemos expressões gerais para o expoente de tunelamento, o espectro de transmissão, a taxa total de tunelamento c o tempo de travessia da partícula através da barreira, válidas para um banho de osciladores com uma função de densidade espectral arbitrária. Assim temos que a interação da partícula com um banho de osciladores com uma função de densidade espectral arbitrária diminui a taxa total de tunelamento. Adicionalmente, obtemos que a interação da partícula com os osciladores do banho com frequências ?a = ?C ~ 1.9 T , onde T0 é o tempo característico de travessia através da barreira no caso cm que não há interação da partícula com o banho de osciladores nem campo elétrico, não afeta o tempo característico de travessia através da barreira. Por outro lado, a interação da partícula com os osciladores do banho que têm frequências ?a < ?C (?a > ?C) diminui (aumenta) o tempo característico de travessia através da barreira. No caso de um banho de osciladores com uma única frequência w c uma constante de acoplamento com a partícula dada por Ca = Ca (wT)a , são identificados cinco comportamentos diferentes em função de w para o expoente característico de tunelamento e o tempo característico de travessia através da barreira. Estes comportamentos correspondem aos valores de s < 1, s = 1, 1 < s < 2, s = 2 e s > 2. No trabalho de M. Ueda, Phys. Rev. B 54, 8676 (1996), foi considerado somente o expoente característico de tunelamento no caso s = 1. No caso de um banho ôhmico de osciladores a temperatura zero, assim corno no caso de um banho de osciladores com uma única frequência, obtemos que o espectro de transmissão da partícula é zero para urna energia final característica da partícula maior que a energia inicial característica. Este resultado corrige o resultado correspondente no trabalho citado de Ueda, o qual não é consistente do ponto de vista físico, permitindo também obter de um modo mais coerente a corrente de tunelamento entre dois metais separados por um material isolante a temperatura zero. Obtém-se também que a interação da partícula com um banho ôhmico de osciladora não afeta o tempo característico de travessia através da barreira até primeira ordem nessa interação / Abstract: This work was motivated by several difficulties found when studying the article by M . Ueda, Transmission Spectrum of a Tunneling Particle Interacting with Dynamical Fields: Real-Time Functional-Integral Approach, Phys. Rev. B 54, 8676 (1996). In that paper, using a real-time formalism, a tunneling particle is described by complex traversal times of tunneling. In the present work we propose a broader real-time formalism that allows for a more natural introduction of complex values of time in the description of a tunneling particle interacting with the environment. This proposal is based on the well-known complex time method used in the case of a tunneling particle with no interaction with the environment studied in the works of D. W. McLaughlin, J. Math. Phys. 13, 1099 (1972) and B. R. Holstein and A. R. Swift, Am. J. Phys. 50, 833 (1982). Following the cited work of Ueda, the environment of the particle is represented by a set, or heat bath, of harmonic oscillators which is characterized by a spectral density function J(w). Using the Feynman path integrals method, we integrate out the coordinates of the bath oscillators and obtain an exact expression for the transmission spectrum of the particle for a bath temperature T > O. Limiting ourselves to the simpler case T = O, we study the case of a dissipative tunneling of the particle. Considering h a small parameter (semiclassical limit) we approximate the transmission spectrum of the particle by the contribution of the classical trajectories and its neighboring paths. In this approach we consider the variation of the effective action of the particle for given duration times of the paths and replace the variation procedure followed in the cited work of Ueda where the variation in the traversal times of tunneling is not considered. In a second variation problem for the duration times of the classical paths, according to the complex time method and considering also the variation in the initial and final positions of these paths, we obtain the equations of motion for the so-called special classical paths. This treatment of the initial and final coordinates of the classical paths replaces the procedure followed in the cited work of Ueda where an acceleration equal to zero is considered during the entire path of motion including the region under the barrier. Unlike the cited article of Ueda, we use in the present work wave packets relatively well localized to describe the init.ial and final statics of the particle. Conscqncnt.ly, we approximate the transmission spectrum of the particle through special classical paths with initial and final coordinates equal to the average value of the coordinate for those wave packets. The procedure followed in this work, based on the complex time method, gives the appropriate coupling factor between the two paths describing the effective action of the particle and thus replaces the ad hoc procedure followed for this purpose in the cited work of Ueda. The complex time method also allows us to obtain the difference term between the effective action of the particle and the tunneling exponent. These quantities are treated as equal in Ueda\'s work. Considering terms up to first order in an external electric field and the interaction of the particle with the bath of oscillators, we obtain general expressions for the tunneling exponent, transmission spectrum, total tunneling rate and traversal time of tunneling, which are valid for a bath of oscillators with an arbitrary spectral lenity function. We find that the interaction of the particle with a bath of oscillators with an arbitrary spectral density function decreases the total tunneling rate. Also, we find that the interaction of the particle with the bath oscillators with frequencies ?a = ?C ~ 1.9 T , where To is the characteristic traversal time of tunneling when there is no interaction of the particle with the bath of oscillators nor electric field. , does not affect the characteristic traversal time of tunneling. On the other hand, the interaction of the particle with the bath oscillators having frequencies ?a< ?c (?a: > ?c decreases (increases) the characteristic traversal time of tunneling. In the case of a bath of oscillators with a single frequency w and a coupling constant with the particle given by Ca = Ca (wT)a we identify five different behaviors deepening on w for the characteristic tunneling exponent and the characteristic traversal time of tunneling. These behaviors correspond to the values of s < 1, s = 1, 1 < s < 2, s = 2 and s > 2. In the work of M. Ueda, Phys. Rev. B 54, 8676 (1996), it was only considered the characteristic tunneling exponent in the case s = 1. In the case of an ohmic bath of oscillators at zero temperature, as well as in the case of a bath of oscillators with a single frequency, we obtain that the transmission spectrum of the particle is ;1,cro for a final characteristic energy of the particle greater than the initial characteristic energy. This result corrects the corresponding result in Ueda work, which is not consistent from a physical point of view, allowing also for a more coherent derivation of the tunneling current between two metals separated by an insulating material at zero temperature. It is also obtained that the interaction of the particle with an ohmic bath of oscillators does not affect the characteristic traversal time of tunneling up to first order in that interaction / Doutorado / Física / Doutor em Ciências

The diploma thesis is focused on the evaluation of the suppression of supercritical current energy in the area of the river bed extension. The hydraulic model was used to simulate current conditions for different variants of river bed arrangement. Individual variants were then evaluated according to the relevant criteria and compared with each other. Results can be applied in hydrotechnical practice based on model similarity.

Dans l’optique de la conception et du développement d’un siège aéronautique et afin derespecter la règlementation sécuritaire en vigueur, la structure du siège développé doitpermettre une dissipation rapide de l’énergie perçue en cas de crash aérien (Fig. 1), ceci dansle but de protéger les passagers. La majorité des systèmes intégrés à la structure des sièges etpermettant cette absorption d’énergie (Fig. 2) est constituée de composants métalliques qui sedéforment plastiquement pour dissiper l’énergie due au crash. Actuellement, l’industrie et larecherche se tournent vers les matériaux composites pour substituer de tels systèmes.Cependant le comportement de ces matériaux lors de sollicitations mécaniques sévères estfortement différent des matériaux métalliques, notamment dû au fait que les mécanismesd’endommagement sont très distincts.Le but de cette étude portant sur des structures tubulaires composites est d’évaluer leurcapacité à dissiper l’énergie. A cette fin, différentes stratifications ont été testées encompression (Fig. 3 et 4) dans le but de déterminer leur comportement, comparer leurspropriétés et calculer leurs valeurs de SEA (absorption d'énergie spécifique, en kJ.kg-1)servant à évaluer leur aptitude à dissiper l’énergie engendrée en cas de crash. Ces dernièressont issues des courbes effort-déplacement obtenues lors des essais d’écrasement (Fig. 5). Lesdifférents essais de compression ont été instrumentés et suivis au moyen de caméras rapides etdes images post-essais ont été réalisées par tomographie pour comprendre les mécanismesd’endommagement mis en jeu (Fig. 4 et 6). Ces essais ont été réalisés à vitesse de chargementquasi-statique puis dynamique et selon diverses conditions limites. Les différents résultats decomportement en compression sont également utilisés dans le but de construire et enrichir unmodèle de calcul par éléments finis (Fig. 7 et 8) permettant de simuler la réponse de structurescomposites de différentes natures soumises au crash en intégrant la géométrie et lacomposition de la structure (Fig. 8).L’objectif de ce travail de recherche est ainsi d’évaluer l’énergie pouvant être dissipée par desstructures tubulaires composites, de comparer les absorptions induites par des structurescomposites de compositions différentes, et/ou bi-matériaux, et enfin de fournir un modèleéléments finis représentant le comportement de structures composites en compression jusqu’àl’endommagement et la ruine de la structure.Il a ainsi été établi qu’en chargement statique, un stratifié unidirectionnel orienté à 0° etstabilisé par des plis de tissus répond fortement aux attentes en terme de dissipation d’énergie,mais pas en sollicitation dynamique. Dans ce cas, une stratification à 90° semble plusadéquate. D’autre part, un confinement forcé vers l’intérieur est avantageux dans la plupartdes cas, réduisant le pic d’effort initial sans diminuer drastiquement la valeur de SEA. / With the perspective of the design and development of an aircraft seat and in order to respectthe safety regulations in effect, the structure of the developed seat must allow for a swiftdissipation of the energy received in the event of an aircraft crash (Fig. 1) so as to protect thepassengers. The majority of systems integrated into the seats structure and allowing energydissipation (Fig. 2) consists of metal components that sustain plastic deformation to dissipatethe energy induced by the crash. Currently, industry and research sectors are turning theirfocus towards composite materials to substitute such systems. However, the behavior of thesematerials during severe mechanical stress is strongly different from metallic materials, inparticular due to the fact that damage mechanisms are very distinct.The purpose of this study on composite tubular structures is to evaluate their ability todissipate the energy. To this end, different laminate structures were tested in compression(Fig. 3 and 4) in order to identify their behavior, compare their properties and calculate theirSEA value (Specific Energy Absorption, in kJ.kg-1) used to evaluate their capacity to dissipatethe energy generated during a crash. Those are resulting from the load-displacement curvesobtained during the crushing tests (Fig. 5). The various compression tests were instrumentedand monitored by means of rapid imaging cameras and post-crushing tomographic imaginghas been realized in order to understand the damage mechanisms involved (Fig. 4 and 6).Testing has been carried out under quasi-static and dynamic loading and using severalboundary conditions. The different results of compression and crushing behavior are also usedin order to build and improve a finite element calculation model (Fig. 7 and 8) allowing tosimulate the response of composite structures of different natures subjected to crash byintegrating the geometry and the composition of the structure (Fig. 8).The objective of this research work is thus to evaluate the energy that can be dissipated bycomposite tubular structures, to compare the absorption values induced by compositestructures of different compositions, and/or bi-materials, and, finally, to provide a finiteelement model representing the behavior of composite structure submitted to compressionuntil damage and fracture of the structure.It has consequently been established that in static loading, a unidirectional laminate orientedat 0° and stabilized by woven plies strongly meets the expectations in terms of energydissipation, but that is not the case in dynamic loading. In this case, a 90° stratification seemsmore adequate. Incidentally, an inner constrained containment is more effective in most cases,reducing the initial peak load without drastically reducing the SEA value.

L'objectif de cette thèse est l'étude des échanges et de la dissipation d'énergie aux échelles mésoscopiques, à travers l'étude de nanotubes, de nanofils ou de pointes taillées par exemple. Notre intérêt pour la dissipation d'énergie nous portera vers les NEMS (Nano Electro Mechanical Systems) et leur facteur de qualité. Pour étudier les échanges d'énergie nous nous intéresserons à la thermodynamique aux petites échelles et notamment aux machines thermiques qui exploitent ces échanges d'énergie pour extraire un travail utile (mécanique, électrique...). Ce travail se concentre dans un premier temps sur la dissipation d'énergie et plus particulièrement sur le facteur de qualité de nanotubes de carbone mono-paroi à température ambiante et sur la façon de l'augmenter par application d'une tension électrique. Cette tension électrique induit un fort tirage sur le nanotube et la modification concomitante de la forme du mode résonant modifie la dissipation d’énergie. Ce phénomène, couplé à une modification des propriétés de l’ancrage (effet d’ancrage mou ajustable en tension) résultant également de la tension, diminue drastiquement la dissipation d’énergie et on atteint alors des facteurs de qualité record. Dans un second temps, nous nous intéressons aux machines thermiques : une machine stochastique cyclique et une machine électrique continue. La machine thermique stochastique est réalisée avec un nanofil vibrant sous ultra haut vide. La thermodynamique stochastique permet de redéfinir le travail et la chaleur pour un objet qui stocke des quantités d’énergies similaires aux fluctuations du bain thermique avec lequel il est en contact. Le premier objectif est de réaliser un cycle de Carnot permettant d'atteindre le rendement du même nom, inaccessible pour les machines macroscopiques. Pour la machine thermique continue nous étudions numériquement un prototype de machine thermique électrique basé sur des effets de résonance d'effet tunnel qui pourrait être une amélioration du principe des machines thermoïoniques. L’utilisation de l’effet tunnel permet à priori de réduire la température de la source chaude de la machine puisque l’on a plus besoin de vaincre le travail de sortie des deux électrodes. Les résonances dans l’effet tunnel, obtenues par confinement dans une dimension, permettent un filtrage en énergie des électrons passant d’un réservoir thermique à l’autre, ce qui a pour effet d’améliorer le rendement de la machine / The purpose of this work is the study of energy transfer and dissipation at the mesoscopic scale, through the study of nanotubes, nanowires, or sharp tips for example. Our interest for energy dissipation will lead us to dive into Nano Electro Mechanical Systems (NEMS) and their quality factor. Energy transfers will be studied with small scale thermodynamics and stochastic heat engines which use those energy transfers to produce useful work (mechanical, electrical…). This work is focused in a first time on the energy dissipation and particularly on the quality factor of single wall carbon nanotubes at room temperature and the ways to improve it by applying an electrical voltage. This voltage induces a strong pulling on the nanotube and the resulting vibrating shape modification changes the dissipation. This phenomenon, coupled with a clamping modification (tunable soft clamping) also stemming from the voltage, drastically reduces the dissipation. We can then achieve record high quality factors. In a second time we take interest in heat engines: a stochastic cyclic heat engine and a continuous electrical heat engine. The stochastic heat engine is realized with a vibrating nanowire under high vacuum. The stochastic thermodynamics allow us to redefine work and heat for an object that stores energies of the order of magnitude of thermal fluctuations in the thermal bath it interacts with. The aim is to build a Carnot cycle and achieve the corresponding yield, out of reach for macroscopic engines. Concerning the continuous heat engine we study numerically a prototype for an electrical heat engine based on resonant tunneling which could be an improvement of the thermionic heat engines. Allowing the thermal reservoirs to exchange electrons through tunneling allows in principle to reduce the temperature of the hot source because overcoming the work function of both electrodes is not necessary anymore. The resonances in the tunnel effect, obtained through confinement of one dimension, is useful for filtering the energy of the electrons tunneling from one reservoir to another, thus increasing the yield of the heat engine

This work, conceived as a second step in the development of high-performance damping materials suitable for seismic application, describes the preparation and characterization of complex natural rubber-based composites containing hybrid nano- and conventional fillers. The cluster–cluster aggregation model was used to assess the apparent filler networking energy. The values obtained suggested that the presence of the hybrid nanofiller strengthens the filler networking. The same model was used to understand the mechanisms of energy dissipation. The damping coefficient was found to be in the sought range between 10% and 20% (at 0.5 Hz and high shear strain).

No description available.

No description available.