The thesis entitled “Exploring Intermolecular Space by Charge Density Analysis in Molecular Crystals” consists of five chapters. A short introductory note highlights the importance of intermolecular interactions and presents the current status of charge density analysis to obtain insights into such interactions. Charge density analysis of crystalline materials by using high resolution X-ray diffraction data has become routine and enables derivation of reliable one electron properties associated with the electron density. The results obtained from single crystal X-ray diffraction data at low temperature have been compared with periodic theoretical calculations using B3LYP/6-31G** methods to unequivocally establish the nature of weak interactions. Chapter 1 describes the quantitative analysis of Cl∙∙∙Cl intermolecular interactions in compounds 2-chloro-3-quinolinyl methanol, 2-chloro-3-hydroxypyridine and 2-chloro-3-chloromethyl-8-methylquinoline, which are corresponding to type I (trans and cis) and type II (L) geometries of Cl∙∙∙Cl interactions respectively. The 3D static deformation density plots from charge density analysis unequivocally suggest that both ‘cis’ and ‘trans’ type I geometries show decreased repulsion whereas type II geometry is attractive based on the nature of “polar flattening” of the electron density around the Cl atom. The topological features derived at bond critical point (BCP) of Cl∙∙∙Cl interactions also support the observed results. Chapter 2 discusses hetero-halogen (Cl∙∙∙F) and homo-halogen (F∙∙∙F) intermolecular interactions involving “organic fluorine” in compounds 2-chloro-4-fluorobenzoic acid and 4-flurobenzamide respectively. Charge density distributions show polar flattening effects at both atoms Cl and F, however the extent of polarization is small on F in comparison with that of the Cl atom. 3D static deformation density plots depict δ+ ∙∙∙δ− interactions for Cl∙∙∙F intermolecular interactions while F∙∙∙F interactions show small decreased repulsion features. The topological properties of F∙∙∙F interactions bring out the similarity between F∙∙∙F and Cl∙∙∙Cl interactions. Chapter 3 describes the nature of C−Cl∙∙∙O=C halogen bond in 2, 5-dichloro-1, 4-benzoquinone, a molecule specifically chosen to depict this interaction dominantly. The topological values at bond critical point, three dimensional static deformation density features and electrostatic potential isosurfaces unequivocally establish the attractive nature of C−Cl∙∙∙O=C halogen bond in the crystalline lattice. Chapter 4 discusses the generation of multi-component systems (for example cocrystals and salts) of active pharmaceutical ingredients (API). Two systems associated with nicotinamide, one with salicylic acid and the other with oxalic acid as coformers resulting in 1:1 molecular complexes have been analyzed. The charge density analysis, particularly at the proton transfer region clearly bring out the differences between cocrystal and salt thus providing insights into the continuum in the proton transfer pathways in molecular crystals. Chapter 5 describes a new methodology [supramolecular synthon based fragment approach (SBFA)] concerning transferability of experimental charge density multipole parameters and building a database using well defined supramolecular synthons. The modularity and robustness of supramolecular synthons are used to transfer experimental charge density multipole parameters of synthons derived from a high resolution X-ray diffraction study to target molecules possessing these synthons as fragments in the crystalline lattice. The synthesized charge density and derived topological properties on target molecules using routine single crystal diffraction data are comparable with both experimental and theoretical charge density results. SBFA thus is expected to provide an additional database which can be applied to include intermolecular interactions space in the modeling directly unlike the available ones such as ELMAM, INVARIOM and UBDB. Further, SBFA approach can be extended to the determination and synthesis of charge density properties in macromolecules such as polypeptides, nucleic acids and proteins. APPENDIX contains reprints of the articles published which comprises of the work carried out in addition to the above five chapters.

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La démarche expérimentale menée dans cette thèse a eu comme objectif l'étude des facteurs qui influent l'efficacité de collecte des médias non-tissés chargés par décharge couronne, utilisés pour la filtration de l'air. Les recherches se sont focalisées sur les techniques faisant appel à la décharge couronne en configuration fil-plan et en configuration triode (électrode duale + grille + plan de masse). L'étude s'est déroulée en trois phases : (1) mise au point de dispositifs expérimentaux pour générer la décharge couronne et mesurer le potentiel électrique à la surface des échantillons chargés ; (2) caractérisation de l'état de charge des médias ; (3) évaluation de l'efficacité de collecte, en corrélation avec les résultats des mesures de charge. La distribution de charges a été plus homogène en configuration triode et le niveau de charge a été meilleur en polarité positive. Le déplacement de l'échantillon dans la zone de décharge électrique permet de mieux uniformiser la distribution de la charge. L'augmentation du courant de décharge et du potentiel de grille permet d'amplifier le niveau de charge des médias, suite à l'intensification du champ électrique moyen entre l'électrode active et le plan de masse (en configuration fil – plan), ou entre la grille et le plan de masse (en configuration triode). L'efficacité de la collecte est meilleure si la charge est uniformément déposée, sous l'action d'un champ électrique plus intense. Elle est plus élevée pour les configurations dites « multicouches » où la captation des particules est améliorée par l'association de plusieurs mécanismes physiques, mettant en jeux des forces électriques et mécaniques. / The experimental approach undertaken in this thesis was aimed at the study of the factors affecting the collection efficiency of nonwoven media charged by corona discharge, used for air filtration. Research was focused on techniques using the corona discharge generated by wire-plane and triode configurations (dual electrode + grid + ground plane). The study was conducted in three phases: (1) development of experimental devices to generate corona discharge and measure the electrical potential on the surface of charged samples; (2) characterization of the electrostatic charge state of the media; (3) evaluation of the collection efficiency, correlated with the results of charge measurements. The charge distribution was more homogeneous in triode configuration and the charge level was higher in positive polarity. The sample movement in the electric discharge zone allowed for more uniform distribution of the charge. The increase of the discharge current and gate voltage amplifies the charge level of the media, due to the intensification of the average electric field between the active electrode and the ground plane (configuration wire - plane) or between the gate and the ground plane (in triode configuration). The collection efficiency is better when the charge is uniformly deposited, under the action of a strong electric field. It is higher for the so-called "multi-layer" configurations where the capture of the particles is improved by the combination of several physical mechanisms, involving electrical and mechanical forces.

La démarche expérimentale menée dans cette thèse a eu comme objectif l'étude de la faisabilité de la séparation électrostatique d'une large gamme de mélanges de matériaux pulvérulents provenant du recyclage des déchets (Al, Cu, ABS, polycarbonate, polystyrène) ou de l'industrie agro-alimentaire (paille, copeaux de bois, semoule). Les recherches se sont focalisées sur des techniques faisant appel à trois mécanismes physiques différents pour la charge des matériaux : la décharge couronne, l'induction électrostatique et l'effet tribo-électrique. Deux nouvelles installations ont été conçues et réalisées, permettent de faciliter la compréhension des phénomènes physiques rencontrés lors de la séparation des particules sous-millimétriques, dont les trajectoires sont difficile à contrôler, en raison des importantes forces aérodynamiques en jeu. La première installation, le séparateur électrostatique multifonctions à électrode-convoyeur, donne la possibilité d'étudier un ou plusieurs des trois mécanismes de charge, en rapport avec les propriétés électriques des matériaux à traiter. La deuxième installation, le séparateur tribo-aéro-électrostatique à électrodes-disques-tournantes, utilise seulement l'effet tribo-électrique pour la charge des matériaux isolants dans un lit fluidisé. Le système de mesures simultanées et continues de la masse et de la charge électrique des produits collectés a facilité l'analyse des phénomènes. Les recherches ont permis de confirmer la séparabilité électrostatique des mélanges de matériaux pulvérulents, en faisant appel à la méthodologie des plans d'expériences pour identifier les facteurs influents et trouver le point de fonctionnement optimal. / The experimental approach undertaken in this thesis was aimed at the study of the feasibility of the electrostatic separation of a wide range mixtures of powdery materials originating from the recycling of waste electric and electronic equipment (Al, Cu, ABS, polycarbonate, polystyrene), or processed in the food industry (straw, wood chips, meal). Researches were focused on techniques using three different physical mechanisms for electrical charging of the materials: corona discharge, electrostatic induction and triboelectric effect. Two new installations have been designed end engineered to facilitate the understanding of the physical phenomena involved in the separation of powdery particles, the trajectories of which are difficult to control, as strongly affected by the aerodynamic forces. The first installation, the belt-type multifunction electrostatic separator, offers the possibility to study one or several of the three charging mechanisms, in relation with the electrical properties of the materials to be processed. The second installation, two-rotating-disks-type tribo-aero-electrostatic separator uses only the triboelectric effect for charging mixtures of insulating materials in a fluidized bed. A system of simultaneous and continuous measurement of mass and electric charge of collected products facilitated the investigation of the physical phenomena. These researches confirm the feasibility of the electrostatic separation of powdery materials, by taking advantage of the design of experiments methodology to identify the influential factors and find the optimum operation conditions.

L'objectif de cette thèse a été d'explorer la possibilité d'utiliser la charge électrostatique pour améliorer les conditions de contact glissant sec ou lubrifié (deux huiles avec viscosités différentes et de l’eau distillée) entre matériaux polymériques (PP, PE, PS, ABS et deux types de PVC). Trois nouvelles installations expérimentales ont été conçues et réalisées. La première installation est un tribomètre linéaire qui permet le réglage de quatre variables de contrôle du processus de charge (la force normale, la vitesse, la durée et l’amplitude du mouvement de glissement) et la mesure de trois caractéristiques du régime de frottement (la force tangentielle, la variation de la force normale et le déplacement relatif entre les éprouvettes). La deuxième installation est un dispositif pour mesurer la distribution de la charge électrique de surface et la corréler avec des cartographies de température. Une troisième installation est destinée à l'étude de l’influence de la charge électrique sur l’angle de contact de gouttelettes déposées en surface. Les expériences réalisées ont montré que le niveau de la charge généré par frottement sec dépend du temps de frottement, de l’usure, de la pression de contact et de la rugosité des surfaces. Une charge générée par effet triboélectrique ou par décharge couronne peut augmenter le frottement à sec. En revanche, la présence d’une charge électrique à la surface du polymère améliore le frottement lubrifié. Les mesures d’angles de contact ont mis en évidence que celui-ci dépend de la nature du liquide et du polymère étudiés, ainsi que de l’état de charge électrique des échantillons. / The approach undertaken in this thesis is to explore the possibility of using the electrostatic charge to improve the dry or lubricated (two oils with different viscosity and distilled water) sliding contacts between polymeric materials (PP, PE, PS, and ABS, two types of PVC). Three experimental benches were designed and built. The first installation is a linear tribometer designed to study the sliding contacts between solids with dry or lubricated friction. It allows the adjustment to four control variables of the tribocharging process: normal force, sliding speed, time and stroke, and the measurement of three characteristics of the friction regime: the tangential force, the variation of the normal force and the relative displacement between the specimens. The second installation is a device for measuring the distribution of the surface electrical charge, and for correlating it with the temperature mappings. A third installation is designed to study the influence of the electric charge on the contact angle of droplets deposited on the surface. The experiments showed that the level of the charge generated by dry friction depends on the friction time, the wear, the contact pressure and the roughness. A charge generated by friction or by corona discharge can increase dry friction. On the other hand, the presence of electric charge on the surface of polymers can improve a lubricated contact. The contact angle measurements pointed out the influence of the nature of both solid and liquid materials involved in the contact, as well as of the electric charge of the samples.

This thesis is concerned with experimental investigations of properties of the top quark and processes involving this particle. In the first part of the thesis, the first determination of the electric charge of the top quark is presented. The measurement was made using top quark pair events produced in proton-antiproton collisions recorded by the D0 detector at the Fermilab Tevatron. It is based on the reconstruction of the charge of the top quarks decay products from the dominant decay to a W boson and a b-quark. The method uses a jet charge algorithm, calibrated with data, to discriminate between b- and antib-quark jets. A constrained kinematic fit is also performed to resolve the ambiguities of the pairing of the top quark decay products and to extract the top quark electric charge. The result is in good agreement with the Standard Model top quark electric charge of 2e/3 and an upper limit of 0.8 at 90\% confidence level on the fraction of exotic quarks with charge 4e/3 in the data sample is obtained. The second part of the thesis concerns the estimation of the top quark pair background to searches for new physics, such as supersymmetry, with the ATLAS  experiment at the CERN Large Hadron Collider. These searches will require a robust estimation of standard model backgrounds in order to make any claims of discovery or to exclude models of new physics. For searches with a final state signature characterized by two isolated charged leptons, multiple jets and large missing transverse energy the largest source of background is expected to be top quark pairs with leptonic decay of the two W bosons from the top quarks in the event. A data-driven method to estimate this contribution based on full kinematic reconstruction of the top quark pair events is studied using simulated proton-proton collisions. It is shown that the method is capable of estimating the top quark pair background to within 12% using data corresponding to approximately 1fb-1. The systematic uncertainty is of the order of 20% and, depending on the model, the contamination of signal events can potentially be large. / QC 20100730

In this work we present a theoretical and computational study of the mechanism of ferroelectricity in multiferroic hexagonal manganite LuMnO3. Some structural and electronic properties are described in both paraelectric (PE) and ferroelectric (FE) phases. As theoretical and computation tool was employed the Full Potential Linear Augmented Plane Wave method, based on Density Functional Theory and embodied in WIEN2k computer code. The crystal structure of both PE and FE phases was optimized using two different types of exchange and correlation potentials. The local density approximation (LDA) and generalized gradient approximation (GGA). The lattice parameters from GGA calculation were obtained in better agreement with experimental than LDA result. Also, were analyzed two different GGA parameterizations: the so-called Perdew - Burke - Ernzerhof (PBE) and Wu - Cohen (WC). Comparing them, the result from GGA-PBE calculation is in better agreement with the experimental. After the structural optimization, the atomic positions were fully relaxed. In this step, was utilized the GGA with the PBE parameterization. The electronic properties were calculated from these optimized and relaxed structures and using the Tran and Blaha modified Becke-Johson potential. From these calculations were obtained an indirect band gap of 0,3 eV and a direct band gap of 1,6 eV in the PE and FE phases, respectively. The valence electronic density maps were obtained along the c axis of the phases PE and FE. It was observed when leave of the PE to the FE phase, the ionic character of Lu-O bonds was changed. By careful analysis of the calculated partial density of states, we showed that the loss of ionicity of the chemical bond is associated with the rehybridization of the 5dz2 - Lu with 2pz - O orbitals. This description corroborates with the model in which the mechanism of ferroelectricity of the hexagonal manganites is related with the rehybridization of the dz2 - Y or - Lu orbitals with 2pz - O s orbitals that are along the crystalline c axis. / No presente trabalho foi realizado um estudo teórico e computacional sobre o mecanismo da ferroeletricidade na manganita hexagonal multiferróica LuMnO3. Foram obtidas algumas das propriedades estruturais e eletrônicas desse composto nas fases paraelétrica (PE) e ferroelétrica (FE). Como ferramenta teórica e computacional foi utilizado o método de cálculo de estrutura eletrônica denominado de Full Potential Linearized Augmented Plane Wave que é baseado na Teoria do Funcional da Densidade e implementado no código computacional WIEN2k. Foi realizada a otimização dos parâmetros de rede usando duas diferentes aproximações para o potencial de troca e correlação. A aproximação da densidade local (LDA) e a do gradiente generalizado (GGA). Os parâmetros de rede obtidos com o cálculo GGA foram mais próximos do experimental do que aqueles obtidos usando a aproximação LDA. Para o cálculo usando a aproximação GGA foram testadas duas formas de parametrização: Perdew - Burke - Ernzerhof (PBE) e Wu - Cohen (WC). Nesse caso, o resultado obtido com a parametrização PBE é a que melhor se compara com o resultado experimental. Após a otimização dos parâmetros de rede, foram relaxadas as posições atômicas. Nessa etapa do cálculo, foi utilizada a aproximação GGA-PBE. Para o cálculo da estrutura eletrônica, foi usado o potencial modificado de troca de Becke-Johnson (mBJ). Com ele foi possível obter um band gap indireto de 0,3 eV na fase PE e um band gap direto de 1,6 eV na fase FE. Foram obtidos mapas de densidade eletrônica valência ao longo do eixo c cristalino das fases PE e FE. Observou-se, saindo da fase PE para a FE, que o caráter iônico da ligação Lu - O foi alterado. A análise da densidade de estados parciais mostrou que a perda da ionicidade da ligação química está associada à rehibridização dos orbitais 5dz2 do Lu com os orbitais 2pz do O. Esta descrição corrobora com o modelo em que o mecanismo da ferroeletricidade das manganitas hexagonais está associado à rehibridização dos orbitais dz2 do átomo R (Lu ou Y) com os orbitais 2pz dos átomos de oxigênio que estão ao longo do eixo cristalino c.

Plusieurs types de dispositifs mécaniques (à vibration, à cylindre tournant, à lit fluidisé) mettant en jeu l'effet triboélectrique sont actuellement utilisés pour charger électriquement les constituants des mélanges de matériaux isolants granulaires, en vue de leur séparation dans un champ électrique intense. La non-uniformité de la charge des granules à la sortie de ces dispositifs affecte l'efficacité de la séparation, d'où l'intérêt des recherches visant la mise au point de procédés électrostatiques nouveaux, notamment pour des applications dans le domaine du recyclage des déchets. L'utilisation simultanée de l'effet triboélectrique, de la force de Coulomb et de la force d'image électrique est la solution innovante selon laquelle ont été conçus les quatre dispositifs à lit fluidisés réalisés ou améliorés dans le cadre de cette thèse. L'évaluation des performances de ces dispositifs a été rendue possible par la mise en oeuvre de systèmes de mesure complexes, permettant l'enregistrement continu et simultané des charges et des masses des produits de la séparation. Ainsi, la méthode des plans d'expériences pour surfaces de réponse a pu être utilisée pour modéliser le processus de séparation et déterminer les valeurs optimales des variables de contrôle de chacun des dispositifs, tels que le niveau de la haute tension d'alimentation ou la vitesse de l'air de fluidisation. Les résultats obtenus sur les installations de laboratoire et sur un prototype préindustriel recommandent cette classe de procédés tribo-aéro-électrostatiques comme la solution de choix pour le recyclage des déchets granulaires d'équipements électriques et électroniques. / Several types of mechanical devices (vibratory trays, rotating drums, fluidized beds) make use of the triboelectric effect for electrically charge the constituents of insulating materials granular mixtures, in view of their separation in a high-intensity electric field. The non-uniformity of granule charge at the exit of these devices adversely affects the separation efficiency, justifying the researches aimed at the development of novel electrostatic processes, mainly for applications in the field of waste recycling. Simultaneous usage of the triboelectric effect, the Coulomb force and the electric image force is an innovative technical solution according to which four fluidized bed devices were built or improved within the framework of this thesis. The performances of these devices could be evaluated by setting up complex measurement systems that enable the continuous and simultaneous recording of the charges and masses of the separated products. Thus, the experimental design methodology could be used for modeling the separation process and identify the optimum values of the control variables of each device, such as the high voltage level of the speed of the fluidization air. The results obtained on laboratory devices as well on an semi-industrial pilot installation recommend this class of tribo-aero-electrostatic separation processes as the solution of choice for the selective sorting of plastics from waste electric and electronic equipment.

Cette thèse s'intéresse au transformateur de puissance qui constitue l'élément central de toute alimentation à découpage. La recherche s'articule selon deux axes: l'analyse des champs et le calcul des pertes cuivre d'une part, et la modélisation par schéma équivalent (en vue de réaliser des simulations électriques du convertisseur) d'autre part.<p><p>Selon le premier axe de recherche, l'idée est d'utiliser un logiciel de simulation de champs électromagnétiques par éléments finis pour analyser les champs en deux et en trois dimensions dans le transformateur. Outre une compréhension globale de la répartition des champs, on cherche à analyser finement les pertes cuivre générées dans les enroulements.<p><p>Aux fréquences utilisées dans les alimentations actuelles (typiquement quelques centaines de kilohertz), la densité de courant se répartit en effet de manière non uniforme dans les conducteurs suite aux effets quasi statiques (effet pelliculaire et effet de proximité). Les pertes cuivre doivent donc être calculées avec des outils spécifiques qui en tiennent compte. Or les modèles analytiques classiquement utilisés dans ce but (formules de Dowell et apparentées) reposent sur une analyse unidimensionnelle du transformateur, suivant une hypothèse dont la portée est mal connue et mise en cause par plusieurs auteurs.<p><p>Grâce aux simulations par éléments finis, la thèse dresse un inventaire inédit des effets quasi¬statiques 2D et 3D dans les enroulements. Les différents effets sont expliqués physiquement. La fiabilité des méthodes 1D est analysée et l'erreur commise par celles ci est quantifiée suivant le type d'enroulement et la fréquence. Trois méthodes alternatives de calcul des pertes en deux dimensions sont également analysées et critiquées.<p><p>Pour un type précis d'enroulement (une couche de ruban entre une valeur nulle et une valeur maximale de la force magnétomotrice), une "formule semi empirique" est encore développée. Celle-¬ci rassemble en une seule expression un grand nombre de simulations couvrant toutes les situations géométriques envisageables pour le type d'enroulement considéré. On crée ainsi un outil sans équivalent actuellement, qui allie la rapidité des méthodes 1D à la précision des simulations 2D. La formule semi empirique offre de nombreux avantages pour les concepteurs, dont une forme analytique particulière et la possibilité de réaliser des études paramétriques.<p><p>D'autre part, la thèse montre également que le "facteur de remplissage", notion présente dans la plupart des formules unidimensionnelles de calcul des pertes cuivre, résulte d'une erreur dans l'article de base de Dowell et se révèle donc sans fondement théorique. Ce facteur garde néanmoins une utilité pratique par le fait qu'il reproduit fortuitement certains effets 2D.<p><p>Selon le second axe de recherche, la modélisation, divers schémas équivalents sont analysés. Compte tenu du fait que les transformateurs utilisés dans les alimentations à découpage comprennent généralement plusieurs sorties et voient des formes d'onde fortement chargées en harmoniques, deux types de schémas particuliers sont retenus: le schéma "Coupled Choke Secondaries" (schéma CCS) et les schémas du Laboratoire d'Electrotechnique de Grenoble (schémas LEG). Le schéma CCS est validé sur un transformateur réel et implémenté dans une application conviviale.<p> / Doctorat en sciences appliquées / info:eu-repo/semantics/nonPublished

The subject of this dissertation is a theoretical and experimental study of electromagnetic and acoustic emission generated in the course of crack formation in solid dielectric materials. Theoretical part of this work is focused on the electromagnetic emission method, because it is related to a number of unsolved problems in the field of generated emission signals measurement, as well as in the field of the correct interpretation of obtained experimental data. Consequently, issues of emission signals detection by capacitance sensors and the transformation of crack primary parameters on the measured variables within the proposed transfer system have been dealt with. The results in this area were an extension of application range of the electromagnetic emission method on composite materials (especially on fiber reinforced polymer composites), identification and evaluation of the most significant emission sources in investigated composites and developing a methodology for evaluating of the crack primary parameters based on the measured emission signals waveforms in time and frequency domain. The experimental part of this dissertation was focused on a complex methodology for emission signals (including data from additional sensors) continual recording, processing and evaluation and for monitoring the response of stressed material to an applied mechanical load in real-time. Partial results from different research areas were also implemented into this methodology. This included the detection of emission signals, design and implementation of the appropriate measuring apparatus, analysis of measured signals in the time and frequency domain and advanced methods for processing and evaluation of measured data.