Karyotypes of mygalomorph spiders are not satisfactorily known. This thesis is focused on the basic cytogenetic analysis of selected species of African clades of theraphosid mygalomorphs. It includes four subfamilies: Eumenophorinae, Harpactirinae, Ischnocolinae and Stromatopelminae. Diploid numbers, chromosome morphology, sex chromosome systems and chromosome behaviour in male germline in the selected species of African theraphosid subfamilies were studied. The findings support published results, that refer of high karyotype diversity in Theraphosidae. Diploid chromosome number reduction is probably a basic trend of theraphosid karyotype evolution. The majority of analysed species exhibited one, two or three sex chromosomes. In some species neo-sex chromosome systems were found. In some species one or two sex chromosome pairs (SCP), composed of chromosomes which lack morphological differentiation were detected. Nucleolus organizer regions were detected by fluorescent in situ hybridization in several species. Constitutive heterochromatin detection was performed by C-banding in two species. Keywords: constitutive heterochromatin, diploid number, karyotype, fluorescence in situ hybridization, Mygalomorphae, nucleolus organizer region, SCP, sex chromosome, spider, Theraphosidae

In the global framework of improving vibro-acoustic numerical prediction quality together with the need to decrease the number of prototyping stages, this manuscript focuses on achieving greater accuracy for acoustic numerical simulations by making use of a parametric updating technique, which enables tuning the model parameters inside physically meaningful boundaries. The improved model is used for the next prototyping stages, allowing more accurate results within reduced simulation times. The updating technique is based on recent works dealing with the constitutive relation error method (CRE) applied to acoustics. The updating process focuses on improving the acoustic damping matrix related to the absorbing properties of the materials covering the borders of the acoustic domain. / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

<p align="justify">The conservation of structures of the historical heritage is an increasing concern nowadays for public authorities. The technical design phase of repair operations for these structures is of prime importance. Such operations usually require an estimation of the residual strength and of the potential structural failure modes of structures to optimize the choice of the repairing techniques.</p> <p><p align="justify">Although rules of thumb and codes are widely used, numerical simulations now start to emerge as valuable tools. Such alternative methods may be useful in this respect only if they are able to account realistically for the possibly complex failure modes of masonry in structural applications.</p><p><p align="justify">The mechanical behaviour of masonry is characterized by the properties of its constituents (bricks and mortar joints) and their stacking mode. Structural failure mechanisms are strongly connected to the mesostructure of the material, with strong localization and damage-induced anisotropy.</p><p><p align="justify">The currently available numerical tools for this material are mostly based on approaches incorporating only one scale of representation. Mesoscopic models are used in order to study structural details with an explicit representation of the constituents and of their behaviour. The range of applicability of these descriptions is however restricted by computational costs. At the other end of the spectrum, macroscopic descriptions used in structural computations rely on phenomenological constitutive laws representing the collective behaviour of the constituents. As a result, these macroscopic models are difficult to identify and sometimes lead to wrong failure mode predictions.</p><p><p align="justify">The purpose of this study is to bridge the gap between mesoscopic and macroscopic representations and to propose a computational methodology for the analysis of plane masonry walls. To overcome the drawbacks of existing approaches, a multi-scale framework is used which allows to include mesoscopic behaviour features in macroscopic descriptions, without the need for an a priori postulated macroscopic constitutive law. First, a mesoscopic constitutive description is defined for the quasi-brittle constituents of the masonry material, the failure of which mainly occurs through stiffness degradation. The mesoscopic description is therefore based on a scalar damage model. Plane stress and generalized plane state assumptions are used at the mesoscopic scale, leading to two-dimensional macroscopic continuum descriptions. Based on periodic homogenization techniques and unit cell computations, it is shown that the identified mesoscopic constitutive setting allows to reproduce the characteristic shape of (anisotropic) failure envelopes observed experimentally. The failure modes corresponding to various macroscopic loading directions are also shown to be correctly captured. The in-plane failure mechanisms are correctly represented by a plane stress description, while the generalized plane state assumption, introducing simplified three-dimensional effects, is shown to be needed to represent out-of-plane failure under biaxial compressive loading. Macroscopic damage-induced anisotropy resulting from the constituents' stacking mode in the material, which is complex to represent properly using macroscopic phenomenological constitutive equations, is here obtained in a natural fashion. The identified mesoscopic description is introduced in a scale transition procedure to infer the macroscopic response of the material. The first-order computational homogenization technique is used for this purpose to extract this response from unit cells. Damage localization eventually appears as a natural outcome of the quasi-brittle nature of the constituents. The onset of macroscopic localization is treated as a material bifurcation phenomenon and is detected from an eigenvalue analysis of the homogenized acoustic tensor obtained from the scale transition procedure together with a limit point criterion. The macroscopic localization orientations obtained with this type of detection are shown to be strongly related to the underlying mesostructural failure modes in the unit cells.</p> <p><p align="justify">A well-posed macroscopic description is preserved by embedding localization bands at the macroscopic localization onset, with a width directly deduced from the initial periodicity of the mesostructure of the material. This allows to take into account the finite size of the fracturing zone in the macroscopic description. As a result of mesoscopic damage localization in narrow zones of the order of a mortar joint, the material response computationally deduced from unit cells may exhibit a snap-back behaviour. This precludes the use of such a response in the standard strain-driven multi-scale scheme.</p> <p><p align="justify">Adaptations of the multi-scale framework required to treat the mesostructural response snap-back are proposed. This multi-scale framework is finally applied for a typical confined shear wall problem, which allows to verify its ability to represent complex structural failure modes.</p><p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

Diese Arbeit basiert auf der Untersuchung von hochfesten und ultrahochfesten Betonen mit und ohne Fasern unter zwei- und dreiaxialer Druckbeanspruchung. Die Auswirkung der unterschiedlichen Betonzusammensetzung ist für verschiedene Beanspruchungen nicht gleich ausgeprägt, dennoch konnten grundlegende Zusammenhänge herausgearbeitet werden. Anhand der Bruchbilder konnten die drei Versagensmechanismen Druck-, Spalt- und Schubbruch identifiziert werden, deren Charakteristik über die Kalibrierung an vier speziellen Versuchswerten direkt in das Bruchkriterium einfließen. Dieses stellt eine Erweiterung der Formulierung von OTTOSEN dar, so dass das spröde und z. T. anisotrope Verhalten von Hochleistungsbeton berücksichtigt wird. Die beobachteten Spannungs-Dehnungs-Verläufe korrelieren mit den Versagensformen. Deshalb wird ein Stoffgesetz getrennt für den Druck- und den Zugmeridian aufgestellt, dessen Parameter sich mit zunehmendem hydrostatischen Druck verändern. In die Anfangswerte fließen die Betonzusammensetzung und herstellungsbedingte Anisotropien ein. Die lastinduzierte Anisotropie infolge einer gerichteten Mikrorissbildung wird in dem vorgestellten Stoffgesetzt über richtungsabhängige Parameter ebenfalls berücksichtigt.

El concepto moderno de la técnica de suelo reforzado data de inicios de la década de los 60. En el tiempo en que esta práctica viene siendo empleada y estudiada, ha gozado de gran popularidad debido a sus relativos bajos costos en comparación con sistemas tradicionales equivalentes, el grado de fiabilidad del sistema, su aspecto y su diversidad arquitectónicos. En el año 2001, la Federal Highway Administration de Estados Unidos desarrolló el manual de diseño y construcción de muros TEM, actualmente FHWA-NHI-10-024 y FHWA-NHI-10-25, los cuales brindan instrucciones y recomendaciones para el diseño y construcción de estas estructuras, basados en las instrucciones de la norma AASHTO LRFD. Estas fuentes incluyen una serie de supuestos, entre los cuales se encuentra el asumir la base del muro como una cimentación equivalente. La norma AASHTO LRFD lo establece de la siguiente manera: “(…) se deberá asumir una cimentación equivalente cuya longitud sea la longitud del muro y cuyo ancho sea la longitud de la cinta de refuerzo al nivel de la fundación. Las presiones a soportar deberán ser modeladas empleando una distribución uniforme de carga en la base, aplicado en un ancho efectivo (B’= L-2e)”. AASHTO LRFD (2010). La presente investigación pretende analizar el modo como se realiza la transferencia de esfuerzos al suelo de fundación de un muro de suelo reforzado con el fin de verificar en que modo dicho supuesto es técnicamente correcto, así como analizar la posibilidad de reducir la extensión del refuerzo empleado por medio de una optimización del cálculo a través de un modelo más cercano a la realidad. Para ello, se pretende realizar un Análisis por Elementos Finitos empleando un Modelo Constitutivo que incorpore al modelo el comportamiento no-lineal del suelo, tanto para el material de relleno como para el suelo de fundación. / The modern concept of the reinforced earth technique dates to the early 1960s. In the time this practice has been used and studied, it has enjoyed great popularity due to its relatively low costs compared to equivalent traditional systems, the degree of reliability of the system, its architectural appearance and diversity. In 2001, the United States Federal Highway Administration developed the MSE wall design and construction manual, currently FHWA-NHI-10-024 and FHWA-NHI-10-25, which provide instructions and recommendations for the design and construction of these structures, based on the instructions of the AASHTO LRFD standard. These sources include a series of assumptions, among which is the assumption of the base of the wall as an equivalent foundation. The AASHTO LRFD standard states it as follows: “(…) An equivalent footing shall be assumed whose length is the length of the wall, and whose width is the length of the reinforcement strip at the foundation level. Bearing pressures shall be computed using a uniform base pressure distribution over an effective width (B ’= L-2e)”. AASHTO LRFD (2010). The present research aims to analyze the way in which stresses are transferred to the foundation soil of a reinforced soil wall to verify in which way that assumption is technically correct. As well as to analyze the possibility of reducing the extension of the reinforcement used, by means of an optimization of the calculation through a model closer to reality. To do this, it is intended to carry out a Finite Element Analysis using a Constitutive Model that incorporates the non-linear behavior of the soil into the model, both for the filling material and for the foundation soil. / Tesis

<p><b>Part I: Micromechanics of dense suspensions</b></p><p>Particulate suspensions are ubiquitous in the industry & nature. Fresh concrete, uncured solid rocket fuel, & biomass slurries are typical industrial applications, while milk & blood are examples of naturally occurring suspensions. These suspensions exhibit many non-Newtonian properties like rate-dependent rheology & normal stresses. Other than volume fraction, particle material, inter-particle interactions determine the rheological behavior of suspension. The average inter-particle gaps between the neighboring particles decrease significantly as the suspension volume fraction approaches the maximum packing fraction in dense suspensions. So, in this regime, the short-ranged non-contact interactions are important. In addition, the particles come into contact due to asperities on their surfaces. The surface asperities are present even in the case of so-called smooth particles, as particles in real suspensions are not perfectly smooth. Hence, contact forces become one of the essential factors to determine the rheology of suspensions.</p><p> </p><p>Part I of this thesis investigates the effects of microscopic inter-particle interactions on the rheological properties of dense suspensions of non-Brownian particles by employing discrete particle simulations. We show that increasing the roughness size results in a rise in the viscosity & normal stress difference in the suspensions. Furthermore, we observe that the jamming volume fraction decreases with the particle roughness. Consequently, for suspensions close to jamming, increasing the asperity size reduces the critical shear rate for shear thickening (ST) transition, resulting in an early onset of discontinuous ST (DST, a sudden jump in the suspension viscosity) in terms of volume fraction, & enhances the strength of the ST effect. These findings are in excellent agreement with the recent experimental measurements & provide a deeper understanding of the experimental findings. Finally, we propose a constitutive model to quantify the effect of the roughness size on the rheology of dense ST suspensions to span the entire phase-plane. Thus, the constitutive model and the experimentally validated numerical framework proposed can guide experiments, where the particle surface roughness is tuned for manipulating the dense suspension rheology according to different applications. </p><p> </p><p>A typical dense non-Brownian particulate suspension exhibits shear thinning (decreasing viscosity) at a low shear rate followed by a Newtonian plateau (constant viscosity) at an intermediate shear rate values which transition to ST (increasing viscosity) beyond a critical shear rate value and finally, undergoes a second shear-thinning transition at an extremely high shear rate values. This part unifies & quantitatively reproduces all the disparate rate-dependent regimes & the corresponding transitions for a dense non-Brownian suspension with increasing shear rate. The inclusion of traditional hydrodynamic interactions, attractive/repulsive DLVO (Derjaguin and Landau, Verwey and Overbeek), contact interactions, & constant friction reproduce the initial thinning as well as the ST transition. However, to quantitatively capture the intermediate Newtonian plateau and the second thinning, an additional interaction of non-DLVO origin & a decreasing coefficient of friction, respectively, are essential; thus, providing the first explanation for the presence these regimes. Expressions utilized for various interactions and friction are determined from experimental measurements, resulting in an excellent quantitative agreement with previous experiments. </p><p><br></p><p><b>Part II: Motion in a stratified fluid</b></p><p>Density variations due to temperature or salinity greatly influence the dynamics of objects like particles, drops, and microorganisms in oceans. Density stratification hampers the vertical flow & substantially affects the sedimentation of an isolated object, the hydrodynamic interactions between a pair, and the collective behavior of suspensions in various ways depending on the relative magnitude of stratification inertia (advection), and viscous (diffusion) effects. This part investigates these effects and elicits the hydrodynamic mechanisms behind some commonly observed fluid-particle transport phenomena in oceans, like aggregation in horizontal layers. The physical understanding can help us better model these phenomena and, hence, predict their geophysical, engineering, ecological, and environmental implications. </p><p><br></p><p>We investigate the self-propulsion of an inertial swimmer in a linear density stratified fluid using the archetypal squirmer model, which self-propels by generating tangential surface waves. We quantify swimming speeds for pushers (propelled from the rear) and pullers (propelled from the front) by direct numerical solution. We find that increasing stratification reduces the swimming speeds of swimmers relative to their speeds in a homogeneous fluid while reducing their swimming efficiency. The increase in the buoyancy force experienced by these squirmers due to the trapping of lighter fluid in their respective recirculatory regions as they move in the heavier fluid is one of the reasons for this reduction. Stratification also stabilizes the flow around a puller, keeping it axisymmetric even at high inertia, thus leading to otherwise absent stability in a homogeneous fluid. On the contrary, a strong stratification leads to instability in the motion of pushers by making the flow around them unsteady 3D, which is otherwise steady axisymmetric in a homogeneous fluid. Data for the mixing efficiency generated by individual squirmers explain the trends observed in the mixing produced by a swarm of squirmers. </p><p><br></p><p>In addition, the ubiquitous vertical density stratification in aquatic environments significantly alters the swimmer interactions affecting their collective motion &consequently ecological and environmental impact. To this end, we numerically investigate the interactions between a pair of model swimming organisms with finite inertia in a linear density stratified fluid. Depending on the squirmer inertia and stratification, we observe that the squirmer interactions can be categorized as i) pullers getting trapped in circular loops, ii) pullers escaping each other with separating angle decreasing with increasing stratification, iii) pushers sticking to each other after the collision and deflecting away from the collision plane, iv) pushers escaping with an angle of separation increasing with stratification. Stratification also increases the contact time for squirmer pairs. The results presented can help understand the mechanisms behind the accumulation of planktonic organisms in horizontal layers in a stratified environment like oceans and lakes. </p><p><br></p><p>Much work has been done to understand the settling dynamics of spherical particles in a homogeneous and stratified fluid. However, the effects of shape anisotropy on the settling dynamics in a stratified fluid are not entirely understood. To this end, we perform numerical simulations for settling oblate and prolate spheroids in a stratified fluid. We find that both the oblate and prolate spheroids reorient to the edge-wise and partially edge-wise orientations, respectively, as they settle in a stratified fluid completely different from the steady-state broad-side on orientation observed in a homogeneous fluid. We observe that reorientation instabilities emerge when the velocity magnitude of the spheroids falls below a particular threshold. We also report the enhancement of the drag on the particle from stratification. The torque due to buoyancy effects tries to orient the spheroid in an edge-wise orientation, while the hydrodynamic torque tries to orient it to a broad-side orientation. The buoyancy torque dominates below the velocity threshold, resulting in reorientation instability.<br></p>

Les travaux de thèse portent sur l'identification paramétrique en dynamique transitoire à partir des mesures fortement bruitées, l'un des objectifs à long terme étant de proposer une méthode d’identification peu intrusive afin de pouvoir être implémentée dans des codes de calcul éléments finis commerciaux. Dans ce travail, le concept de l'erreur en relation de comportement modifiée a été retenu pour traiter le problème d’identification des paramètres matériau. La minimisation de la fonctionnelle coût sous contraintes débouche, dans le cas de la dynamique transitoire, sur un problème dit « aux deux bouts » dans lequel il s’agit de résoudre un problème différentiel spatio-temporel avec des conditions à la fois initiales et finales en temps. Il en résulte un problème couplé entre les champs direct et adjoint dont le traitement est délicat. Dans un premier temps, des méthodes précédemment développées telles que la « méthode de Riccati » et la « méthode de tirs » ont été étudiées. Il est montré que l’identification par ces méthodes est robuste même pour des mesures fortement corrompues, mais qu’elles sont limitées par la complexité d’implémentation dans un code industriel, des problèmes de conditionnement ou de coût de calcul. Dans un second temps, une approche itérative basée sur une méthode de sur-relaxation a été développée et comparée à celles précédemment mentionnées sur des exemples académiques, validant l’intérêt de cette nouvelle approche. Enfin, des comparaisons ont été menées entre cette technique et une variante « discrétisée » de la formulation introduite par Bonnet et Aquino [Inverse Problems, vol. 31, 2015]. / This thesis deals with parameters identification in transient dynamic in case of highly noisy experimental data. One long-term goal is the derivation of a non-intrusive method dedicated to the implementation in a commercial finite element code.In this work, the modified error in the constitutive relation framework is used to treat the identification of material parameters. The minimization of the cost function under constraints leads, in the case of transient dynamics, to a « two points boundary value problem » in which the differential space-time problem involves both initial and final time conditions. This results in a problem coupling the direct and adjoint fields, whose treatment is difficult.In the first part, methods such as those based on the « Riccati equations » and the « shooting methods » have been studied. It is shown that the identification is robust even in the case of highly corrupted measures, but these methods are limited either by the implementation intrusiveness, conditioning problems or the numerical cost.In the second part, an iterative over-relaxation approach is developed and compared to the aforementioned approaches on academic problems in order to validate the interest of the method. Finally, comparisons are carried out between this approach and a « discretized » variation of the formulation introduced by Bonnet and Aquino [Inverse Problems, vol. 31, 2015].

Dizertační práce se zabývá věrohodností mechanického testování měkkých biologických tkání a predikčními schopnostmi různých modelů materiálů. Obě oblasti byly zkoumány užitím metody konečných prvků. První část práce je věnována úvodu do problému a popisu měkkých biologických tkání, které s problémem souvisí, a rešerši nynějšího způsobu jejich mechanického testování. Druhá část práce se zabývá hledáním optimálního nastavení experimentálního zařízení za použití počítačového modelování pomocí virtuální simulace mechanických testů. Výsledky analýzy potvrdily, že dvě úzké svorky po délce hrany, stejně jako běžně používané háčky, jsou použitelné pro dvouosé tahové zkoušky různých měkkých tkání za použití čtvercového vzorku. Použití svorek je proto časově úsporná, jednoduchá a spolehlivá alternativa, která není podřadná použití háčků. V práci byla rovněž provedena analýza, jejímž výsledkem jsou doporučení ohledně typu, počtu a velikosti uchycení pro různě velké vzorky. Třetí část práce zkoumá predikční schopnosti modelů materiálů měkkých tkání a závislosti těchto schopností. Lze shrnout, že výsledné mechanické chování proloženého modelu materiálu závisí na počátečních parametrech a že neexistují „ideální“ počáteční parametry při prokládání experimentálních dat. Navzdory absenci „ideálních“ počátečních parametrů je navržen v rámci možností nejefektivnější způsob aproximace experimentálních dat z mnoha jejich souborů. Dále je možné shrnout, že omezení hodnot parametrů modelu při prokládání experimentálních dat ústí v nepředvídatelný vliv na kvalitu aproximace. V závěrečné části práce byl analyzován předpoklad afinní a neafinní deformace modelů materiálů za účelem vysvětlení velkých rozporů mezi výsledky strukturně založených modelů a výsledky dvouosých testů při různých testovacích protokolech. Ačkoli byly zjištěny určité rozdíly mezi výsledky analyzovaných modelů, přece nebyly dostatečně významné, aby vysvětlily výše uvedené velké rozpory. V poslední části práce jsou zmíněny další možné oblasti výzkumu.

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