Este trabalho trata da análise da propagação de fissuras, independente do tempo, em domínios bidimensionais utilizando uma formulação alternativa do método dos elementos de contorno (MEC). O MEC vem sendo utilizado com sucesso na análise de diversos problemas de engenharia. Considerando problemas de mecânica da fratura, o MEC é especialmente eficiente devido à redução da dimensionalidade de sua malha, o que permite a simulação do crescimento das fissuras sem as dificuldades do processo de remalhamento. Nesta pesquisa, desenvolvem-se formulações não lineares do MEC para a análise da propagação de fissuras em materiais quase frágeis. Nesses materiais, a zona de processo à frente da ponta da fissura introduz efeitos fisicamente não lineares no comportamento estrutural. Assim, para a simulação da presença da zona de processo, modelos não lineares são necessários. Classicamente a formulação dual do MEC é utilizada para modelar propagação de fissuras na quais equações singulares e hipersingulares são escritas para elementos definidos ao longo das faces das fissuras. O presente trabalho propõe uma segunda formulação utilizando um campo de tensões iniciais para a representação da zona coesiva. Nesta formulação, o termo de domínio da equação integral clássica do MEC é degenerado, de forma a atuar somente ao longo do caminho de crescimento das fissuras, sendo que esse procedimento dá origem a uma nova variável denominada dipolo, responsável por garantir o atendimento das condições de contorno. Em conjunto com essa nova formulação, se propõe o uso do operador tangente (OT), que é deduzido no trabalho, a fim de acelerar o processo de convergência da solução. Os resultados obtidos, por meio da formulação alternativa, são comparados tanto com dados experimentais quanto com o MEC dual, ambos disponíveis na literatura. As respostas encontradas foram satisfatórias no sentido de conseguir reproduzir o comportamento real da estrutura explorando as vantagens computacionais proporcionadas pelo OT. / This work presents a time-independent crack propagation analysis, in two-dimensional domains, using an alternative boundary element method (BEM) formulation. BEM has been used successfully to analyze several engineering problems. Considering fracture mechanics problems, BEM is especially efficient due to its mesh reduction aspects, which allows the simulation of crack growth without remeshing difficulties. In this research, nonlinear BEM formulations are develop in order to analyze crack propagation in quasi-brittle materials. Considering these materials, the process zone ahead of the crack tip leads to nonlinear effects related to structural behavior. Thus, nonlinear models are required for simulating the presence of the process zone. Classically, the dual BEM is used for modeling the crack propagation, in which singular and hyper-singular equations are written for elements defined along the crack faces. This work proposes an alternative formulation using the initial stress field to represent the cohesive zone. In this formulation, the classic domain integral term is degenerated in order to be non-null only at the crack growth path. This procedure leads the creation of new variable called dipole, which is responsible for ensuring the compliance of the boundary conditions. In addition to this new formulation, it is proposed the use of the tangent operator (TO), which is derived in this work, in order to accelerate the convergence. The results obtained using the new formulation, are compared with experimental data and dual BEM results available in the literature. The responses were found satisfactory in reproducing the behavior of real structures exploiting the computational advantages provided by the TO.

Au cours de ce travail, la génération de second harmonique optique des molécules biologiques a été étudiée. Cette technique optique non linéaire possède un caractère cohérent qui permet d’accéder aux propriétés de symétrie des molécules dont la taille est très inférieure aux longueurs d’onde optiques visibles utilisées et l’hyperpolarisabilité quadratique des acides aminés aromatiques a été mesurée en solution par diffusion non linéaire. L’hyperpolarisabilité des acides aminés non aromatiques a été obtenue de manière indirecte grâce à des mesures effectuées sur le collagène, une protéine ne contenant pas d’acide aminé aromatique. Le collagène possède en fait une très forte réponse non linéaire et fait l’objet d’études intenses en microscopie optique non linéaire. Par un modèle de sommation cohérente des champs harmoniques réémis, l’origine de la très forte efficacité non linéaire de cette protéine, liée à sa grande rigidité et à son organisation spatiale en triple hélice, a pu être obtenue. En parallèle, l’étude de plusieurs petits peptides synthétiques possédant de un à quatre tryptophanes a permis de comprendre la construction de la réponse optique non linéaire de ces objets à partir de motifs répétés. Par ailleurs, pour apporter des informations supplémentaires sur les nano systèmes, un nouveau montage expérimental a été développé. La grande sensibilité du montage a permis notamment d’atteindre la sensibilité d’une seule particule dans le volume sondé et de mettre en place un système de cartographie en trois dimensions par diffusion Hyper Rayleigh. La démonstration a été réalisée pour des nanoparticules métalliques uniques d’argent piégées dans une matrice de gélatine / This thesis presents an experimental study of second-harmonic generation of biological molecules. The coherent nature of this process allows obtaining the symmetries of molecules whose size is less than the wavelengths used. The hyperpolarizabilities of aromatic amino acids were measured in solution and the hyperpolarizability of non-aromatic amino acids was measured indirectly through measurements on the collagen molecule. Thus, all the building blocks of proteins are characterized. Among the biological molecules, collagen has a very strong non-linear response despite the absence of harmonophore. A model of coherent summation of the fields reissued to understand the origin of the very high non-linear efficiency from the rigidity and the spatial arrangement of amino acids in triple helix. In the same way, the study of several peptides with one to four tryptophans has enabled us to quantify the importance of conformation and the ionic environment of proteins in the nonlinear response. To provide additional information on nano systems, a new setup has been developed, combining two beams of excitation. Thus, the dipole and quadrupole radiation are differentiated to obtain the symmetry of molecular arrangements. Finally, the great sensitivity of the setup allows mapping in three dimensions, with the Hyper Rayleigh scattering, singles metal nanoparticles catch in a gelatin matrix.

Une étude théorique ab initio des structures électroniques des molécules Diatomiques polaires BN, SiN et LaH dans la représentation 2s+1Λ(+/-)Ont été effectués par la méthode du champ auto-cohérent de l'espace Actif complet (CASSCF), suivie par l'interaction de la configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. L'ensemble de l'espace de configuration de CASSCF a été utilisé comme référence dans le calcul MRCI, qui a été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l'interface graphique Gabedit. Quarante-deux de plus bas états électroniques dans la représentation 2s+1Λ(+/-)au-dessous de 95000 cm-1 ont été étudiés de la molécule BN. Alors que vingt-huit états électroniques dans les représentations 2s+1Λ(+/-) jusqu'à 70000 cm-1 de la molécule de SiN ont été étudiés. D'autre part, les vingt-quatre bas états électroniques de LaH dans les représentations 2s+1Λ(+/-) au-dessous de 70000 cm-1 ont été étudiées par deux méthodes différentes et en prenant en considération l'effet des spin-orbite de la molécule LaH et nous avons observé la division énergétique des huit états électroniques. Les courbes d'énergie potentielle ont été construites avec la fréquence co-harmonique ωe, la distance internucléaire de l'équilibre re, les constantes de rotation Be. L'énergie électronique par rapport à l'état fondamentale Te a été calculé pour les états électroniques considérés comme des BN, SiN et la molécule LaH respectivement. En utilisant l'approche des fonctions canoniques, les valeurs propres Ev, les constantes rotationnelles Bv, la constante de distorsion centrifuge Dv et les abscisses des points de retournement Rmin and Rmax ont été calculés pour les états électroniques au niveau de vibration v=51 pour LaH molécule. Dix-huit et neuf états électroniques ont été étudiées pour la molécule BN et SiN respectivement. Pour LaH, vingt-trois états électroniques de la molécule LaH et l'effet de spin-orbite de molécule LaH sont donnés ici pour la première fois. La comparaison avec les données expérimentales et théoriques pour la plupart des constantes calculées démontre une très bonne précision. Enfin, ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules. Nos résultats ont été publiés dans le Canadian Journal of Chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer, nous avons deux autres articles en préparation à soumettre. / In the present work a theoretical investigation of the lowest molecular states of BN, SiN and LaH molecule, in the representation 2s+1Λ(+/-), has been performed via complete active space self-consistent field method (CASSCF) followed by multireference single and double configuration interaction method (MRSDCI). The Davidson correction noted as (MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. The entire CASSCF configuration space was used as a reference in the MRCI calculation which has been performed via the computational chemistry program MOLPRO and by taking advantage of the graphical user interface Gabedit. Forty-two singlet, triplet, and quintet lowest electronic states in the 2s+1Λ(+/-) representation below 95000 cm-1 have been investigated of the molecule BN. While twenty-eight electronic states in the representation2s+1Λ(+/-)up to 70000 cm-1 of the SiN molecule have been investigated.On the other hand the Twenty four low-lying electronic states of LaH in the representation 2s+1Λ(+/-) below 35000 cm-1 have been studied by two different methods and by taking into consideration the spin orbit effect of the molecule LaH we give in the energy splitting of the eight electronic states. The potential energy curves (PECs) together with the harmonic frequency ωe, the equilibrium internuclear distance re, the rotational constants Be and the electronic energy with respect to the ground state Te have been calculated for the considered electronic states of BN, SiN and LaH molecule respectively. Using the canonical functions approach, the eigenvalues Ev, the rotational constants Bv ,the centrifugal distortion constants Dv and the abscissas of the turning points Rmin and Rmax have been calculated for electronic states up to the vibrational level v =51 for LaH molecule.Eighteen and Nine electronic states have been investigated here for the first time for the molecules of BN and SiN respectively, while for LaH, news results are performed for twenty three electronic states of LaH molecule and the spin-orbit effect of LaH molecule is given here for the first time. A comparison with experimental and theoretical data for most of the calculated constants demonstrated a very good accuracy. Finally, we expect that the results of our work should invoke further experimental investigations for these molecules. Our results have been published in Canadian journal of chemistry, Journal of Quantitative Spectroscopy and Radiative Transfer and we have two other papers in preparation to submit.

L’optimisation de cellules solaires organiques repose sur l’amélioration de différents paramètres électroniques et structuraux. En particulier, les processus de séparation et de transport de charge doivent être optimisés pour obtenir des rendements élevés. Les processus de séparation de charge dans ces dispositifs s’effectuent aux interfaces donneur/accepteur suite à un décalage entre les niveaux électroniques de ces deux matériaux. Suivant leur nature, des interactions aux interfaces peuvent conduire à l’apparition d’un dipôle pouvant favoriser ou défavoriser la génération de charges libres ; toutefois, l’origine de ce dipôle d’interface est très mal connue. Ainsi, la première partie de cette thèse s’est attaché à une meilleure compréhension de l’origine de ce dipôle en appliquant une approche théorique multi-échelle sur un système D/A typique : l’interface pentacène/C60. L’amélioration des cellules solaires organiques repose également sur l’augmentation des longueurs de diffusion d’exciton et de la mobilité des porteurs de charge dans les couches actives. Ainsi, l’extension de l’ordre structural au sein d’une hétérojonction constituée de deux cristaux liquides colonnaires électroniquement complémentaires pourrait aider à améliorer ces paramètres. En deuxième partie, nous avons donc analysé l’impact du désordre structural présent au sein d’un auto-assemblage monodimensionnel de perylène diimide sur les paramètres électroniques gouvernant le transport de charge en couplant des calculs de dynamique moléculaire à des calculs de chimie quantique. Les mobilités des porteurs de charge ont été estimées en simulant des mesures de mobilité en temps de vol calculées dans le cadre du formalisme de Marcus puis comparées à l’expérience. Des résultats préliminaires issus de simulations de dynamique moléculaire sur une hétérojonction entre deux cristaux liquides électroniquement complémentaire récemment synthétisés ont été reportés en dernière partie. / The development of efficient organic solar cells relies on the optimization of different correlated electronic and structural parameters. In particular, efficient charge separation and charge transport processes are essential to get high conversion yields. The charge separation processes in these devices occur at the donor/acceptor interfaces due to the energetic mismatch between the electronic structures of the two materials. Depending on the nature of these materials, interfacial interactions may lead to the appearance of a significant dipole that can help or disadvantage the generation of free charges. However, the origin of this interface dipole is still unclear. Thus, the first part of this thesis presents a multiscale theoretical approach to address the origin of the interface dipole at a prototypical D/A interface: the pentacene/C60 interface. Improving of the conversion efficiency of organic solar cells also relies on the increase of both the exciton diffusion length and of the charge carrier mobilities. For this purpose, a possible route is to expand the structural order inside the heterojunction via the self-organization of two electronically complementary columnar liquid crystals. This point is investigated in the second part of this thesis. First, we address the impact of the structural disorder on the electronic parameters mediating the charge transport properties in a one-dimensional self-assembly of perylene diimides by coupling molecular dynamics simulations to quantum-chemical calculations. The charge carrier mobilities are evaluated by means of time-of-flight numerical simulations in the framework of the Marcus formalism and compared to the experience. Then, we present preliminary results issued from atomistic molecular dynamics simulations on the heterojunction between two recently synthesized electronically complementary discotic liquid crystals.

Orientadores: Michel Zamboni Rached, Guillermo Gerardo Cabrera Oyarzún / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin / Made available in DSpace on 2018-09-01T02:33:12Z (GMT). No. of bitstreams: 1 Pachon_EdwinGermanPinilla_D.pdf: 4993091 bytes, checksum: 788c9fb47dfe7b9fea6cc0935ad94d54 (MD5) Previous issue date: 2016 / Resumo: Nesta tese, propõe-se um novo método para realizar guiamento de átomos neutros resfriados. Este método envolve o uso da pressão de radiação por ressonância para efetuar o guiamento dos átomos através de um campo óptico (feixe) oco. Particularmente, usa-se a força de dipolo óptico e um tipo específico de campo óptico não difrativo, chamado de "Frozen Wave" (FW), na versão tradicional e estendida, para estudar o guiamento atômico. Os campos ópticos FW¿s, que são uma solução exata da equação de onda, surgem como uma resposta aos problemas relacionados com a difração e com a impossibilidade de fazer qualquer tipo de modelamento (ou localização) longitudinal e transversal de intensidade, dos campos ópticos tradicionais usados no guiamento de átomos, como por exemplo, nos campos Laguerre-Gauss e Bessel. Assim, planejam-se algumas soluções mediante os métodos tradicional e estendido que permitem criar estruturas de luz (localizadas) resistentes à difração e nas quais o padrão de intensidade longitudinal e transversal (restringido) pode ser modelado a priori. De acordo com isso, o estudo teórico do método tradicional e da generalização das FW¿s foi realizado junto com sua comprovação experimental e foram calculados os respectivos potenciais de dipolo óptico junto com a profundidade de penetração dos átomos na barreira de potencial para cada campo óptico. Nos resultados conseguiu-se modelar algumas estruturas de luz (tanto no método tradicional como no estendido) tais como um cilindro, três cilindros concatenados, um tipo de cilindro com tampa e um funil óptico, entre outras; e mostrou-se as vantagens do uso deste tipo de estruturas de luz quando comparadas com os campos ópticos tradicionais para o guiamento atômico. Finalmente, concluiu-se que usar este tipo de campos não difrativos elimina as restrições dos campos tradicionais e é possível fazer o guiamento de átomos neutros resfriados com estes tipos de estruturas de luz. O método estendido dá uma generalização que permite pensar estes tipos de estruturas de luz para aplicações mais globais nas diferentes áreas da óptica e fotônica / Abstract: This thesis proposes a new method to perform cold neutral atom guiding. This method involves the use of resonance radiation pressure to make the atom guiding along a hollow (beam) optical field. Particularly, it uses the optical dipole force and a specific type of non-diffracting optical field, called "Frozen Wave" (FW), in these traditional and extended versions, to study the atom guiding. The FW¿s optical fields, which are an exact solution of the wave equation, appear as an answer to the problems related to the high diffraction and impossibility of any type of longitudinal and transverse intensity modeling (or location) of traditional optical fields used in atom guiding, for example the Laguerre-Gaussian and Bessel optical fields. Thus, some solutions were planned by the traditional and extended methods, which allow to create localized light structures resistant to diffraction and model a priori longitudinal and transverse (restricted) intensity pattern. Accordingly, the theoretical study of the traditional method and his generalization were carried out with their experimental evidence. Also, his respective optical dipole potential was calculated with the atom penetration depth in the potential barrier for each optical field. In the results was possible to model some light structures (both in the traditional and extended method) such as a cylinder, three concatenated cylinders, one cylinder with a lid and an optical funnel, among others; and it is showed the advantages of using this type of light structures when it is compared with the conventional optical fields for the atom guiding. Finally, it is concluded that use this type of non-diffracting fields eliminates the restrictions of the traditional fields and it is possible the cold neutral atoms guiding with this type of light structures. The FW¿s extended method gives a generalization and it permits to suggest this type of light structures for more complete applications in different areas of optics and photonics / Doutorado / Física / Doutor em Ciências / 141977/2013-2 / CNPQ

The main idea of this thesis is measurements of dielectric materials by using a device Tettex. The thesis is about basic physic properties of dielectric materials. The determination of a dielectric material is considered. The behavior of these materials in electrical fields and reasons, those can have an influence on it, are considered as well. In the text are described measuring methods of chosen parameters of dielectric materials by device Tettex and its functional principles. There are an evaluation of measurements, which were done, and a discussion about achieved results.

The thesis is focused on the design of a measuring antenna for 1 – 6 GHz band. It deals with the types of log periodic antennas with the the detailed elaboration of log periodic dipole antennas (LPDA). One can find the description of their functions, maximum features and the possibilities to use the asymmetrical feeder. Also there is the procedure of LPDA design and the realization of the design itself including simulation in 4NEC2 programme. In the next part there is a planar LPDA realization with the microstrip-to-balanced stripline balun symmetrization. This design was simulated and tested within the frames of Zeland IE3D programme. The last part contains the measuring results of S parametres as well as beam characteristics of the planar version of LPDA.

This thesis describes design and experimental verification of three types of the wideband antenna Bow-tie antenna, Vivaldi antenna and Spiral antenna. The tracked parameters are bandwidth, input impedance, gain and directivity patterns. Next step is design of millimeter-wave horn antennas. Attention is turned to the proper construction of a wideband feeder of the horn. For the final antenna structure, a bow-tie dipole and a Vivaldi antenna were chosen. The antenna construction is aimed to provide a wide bandwidth on one hand and a high gain on the other hand.

Das Top-Quark ist das schwerste bekannte Elementarteilchen. Im Standardmodell (SM) der Elementarteilchenphysik ist die Erzeugung in Paaren durch die starke Wechselwirkung der dominante Beitrag zu seiner Produktion. Top-Quarks können durch die schwache Wechselwirkung ebenfalls einzeln produziert werden. Die Einzelproduktion ist trotz ihres schwierigen experimentellen Nachweises wegen ihrer Komplementarität zur Paarproduktion interessant. So sind einzeln produzierte Top-Quarks stark polarisiert. Diese Polarisation führt wegen des Zerfalls von Top-Quarks vor ihrer Hadronisierung zu experimentell zugänglichen Auswirkungen auf die Zerfallsprodukte. Weiterhin erlaubt die Beteiligung von Bottom-Quarks im Anfangszustand die Untersuchung der zugehörigen Partonverteilungsfunktion. In dieser Arbeit werden für phänomenologische Vorhersagen Wirkungsquerschnitte für die Produktion einzelner Top-Quarks oder Top-Antiquarks in Assoziation mit zwei Jets im SM berechnet. Dabei werden die Korrekturen in der nächstführenden Ordnung der Quantenchromodynamik (QCD) berücksichtigt. Diese Korrekturen bilden den wichtigsten Beitrag jenseits der führenden Ordnung zur Verbesserung der theoretischen Vorhersage. Präzise theoretische Vorhersagen für Wirkungsquerschnitte sind für die Suche nach Physik jenseits des SM mit dem Large Hadron Collider am CERN unerlässlich. Im Unterschied zu den im Jahr 2002 veröffentlichten Korrekturen in der QCD zur Produktion einzelner Top-Quarks wurde ein zusätzliches Teilchen im Endzustand berücksichtigt. Als Folge treten neue partonische Anfangszustände und Beiträge mit Farbaustausch zwischen den Quark-Linien auf. Da Top-Quarks nach kurzer Zeit in ein W-Boson und ein Bottom-Quark zerfallen, muss zugleich eine konsistente Abgrenzung von der Produktion einzelner Top-Quarks in Assoziation mit einem W-Boson und von der Paarproduktion vorgenommen werden. / The top quark is the heaviest known elementary particle. In the standard model (SM) of elementary particle physics it is produced predominantly in pairs by the strong interaction. The weak interaction enables the production of single top-quarks as well. Despite its difficult experimental signature, the production of single top-quarks is interesting as it is complementary to the production of pairs. For instance single top-quarks are highly polarized. As top quarks decay before they hadronize, the polarization affects the decay products of the top quark in an experimentally accessible way. Furthermore, the participation of bottom-quarks in the initial state allows a study of the corresponding parton distribution functions. This thesis makes phenomenological predictions for the SM by calculating cross sections for the production of single top-quarks in association with two jets. Next-to-leading order corrections in quantum chromodynamics (QCD) are taken into account. These corrections are the most important contribution for precise predictions beyond the leading order calculation. Precise theoretical predictions for cross sections are mandatory for the search for new physics at the Large Hadron Collider at CERN. In contrast to the QCD corrections for the production of single top-quarks published in 2002 an additional particle in the final state was taken into account. As a consequence, new partonic initial states and contributions with exchange of color charge between the quark lines occur. As top quarks decay rapidly into a W boson and a bottom quark, a consistent separation from the production of top quark pairs and from the production of single top-quarks in association with a W boson must be ensured.

Vessels constructed in electrically conductive materials give rise to frequency-dependent, induced magnetic fields when waves of water cause them to roll in the Earth's magnetic field. These fields, typically referred to as roll-induced magnetic vortex fields, are a component of the ship's overall signature, where signature refers to measurable quantities which can reveal or identify objects. It is crucial for military platforms to keep the signature low and thereby increase the possibilities of operation. For magnetic signatures, this is done through strategic design and construction of the platform or by using magnetic silencing systems. The signature is then decreased to minimize the risk of detection from naval mines and marine detection systems.  This report covers the initial research on the subject of an inverse source model for roll induced magnetic fields. By limiting the analysis to two basic objects and applying a time variant magnetic field to them, we induce a magnetic field which we then model. The inverse modeling is done using magnetic dipoles as sources which are placed around the area of the object. The parameters of the model are then found by applying a least squares algorithm coupled with Tikhonov regularization. The focus of this report is the configuration of this setup in terms of measurements and sources, as well as finding a proper regularization parameter. Since the applied magnetic field is dependent on the roll frequency, also the inverse model depends on a frequency parameter in addition to the geometry and material of the object. The objects here studied are of two simple geometries, a rectangular block and a hollow cylinder. Both objects are constructed in an aluminum alloy with well known material parameters. Measurement data is gathered using a numerical solver utilizing the finite element method for solving the partial differential equations. The numerical measurement data is compared to physical measurements as well. The physical measurement data is gathered by placing the objects in a Helmholtz-cage which is used to apply a homogeneous time variant magnetic field upon them. The project was carried out at the Swedish Defence Research Agency (FOI) at the department of underwater research.