Electrospinning is a method of producing nano structured material from a polymer solution or melt using high strength electric fields. It is a process that has yet to find extensive industrial application yet shows promise if obstacles such as low rate of production overcome perhaps by more complete theoretical modelling. This work examines the effects of adding an ionic salt to a solution of poly(vinyl alcohol) in water. The direct effect was an increase the charge density and electric current. It was found that an increase in charge density decreases the mass deposition rate and forms a thinner initial jet. When the sign of the charge on the polymer solution was changed from positive to negative the charge density increased and the initial jet diameter and mass deposition rate also decreased. It was proposed that a smaller radius of curvature is formed by the Taylor cone at higher charge densities resulting in a smaller “virtual orifice”. The extent of the bending instability was explored and it was found that adding ionic salt results in a decrease in the bending instability resulting in thicker fibres. Changing the sign of the charge on the polymer solution from positive to negative resulted in an increase in the bending instability and resulted in thinner fibres. The charge transfer mechanisms used in different electrospinning models are explored and some assumptions not explicitly stated are discussed. From this discussion a generalized equation describing the charge transport mechanisms is proposed.

Thesis (Ph. D.)--University of New South Wales, 2000. / Includes bibliographic references. Also available online.

Thesis (Ph. D.)--University of Akron, Dept. of Chemistry, 2005. / "August, 2005." Title from electronic dissertation title page (viewed 09/24/2005). Advisor, David A. Modarelli; Committee members, Matthew Espe, Michael Taschner, Chrys Wesdemiotis, Stephanie Lopina; Department Chair, David Perry; Dean of the College, Charles B. Monroe; Dean of the Graduate School, George R. Newkome. Includes bibliographical references.

abstract: Implantable medical device technology is commonly used by doctors for disease management, aiding to improve patient quality of life. However, it is possible for these devices to be exposed to ionizing radiation during various medical therapeutic and diagnostic activities while implanted. This commands that these devices remain fully operational during, and long after, radiation exposure. Many implantable medical devices employ standard commercial complementary metal-oxide-semiconductor (CMOS) processes for integrated circuit (IC) development, which have been shown to degrade with radiation exposure. This necessitates that device manufacturers study the effects of ionizing radiation on their products, and work to mitigate those effects to maintain a high standard of reliability. Mitigation can be completed through targeted radiation hardening by design (RHBD) techniques as not to infringe on the device operational specifications. This thesis details a complete radiation analysis methodology that can be implemented to examine the effects of ionizing radiation on an IC as part of RHBD efforts. The methodology is put into practice to determine the failure mechanism in a charge pump circuit, common in many of today's implantable pacemaker designs, as a case study. Charge pump irradiation data shows a reduction of circuit output voltage with applied dose. Through testing of individual test devices, the response is identified as parasitic inter-device leakage caused by trapped oxide charge buildup in the isolation oxides. A library of compact models is generated to represent isolation oxide parasitics based on test structure data along with 2-Dimensional structure simulation results. The original charge pump schematic is then back-annotated with transistors representative of the parasitic. Inclusion of the parasitic devices in schematic allows for simulation of the entire circuit, accounting for possible parasitic devices activated by radiation exposure. By selecting a compact model for the parasitics generated at a specific dose, the compete circuit response is then simulated at the defined dose. The reduction of circuit output voltage with dose is then re-created in a radiation-enabled simulation validating the analysis methodology. / Dissertation/Thesis / M.S. Electrical Engineering 2010

L’objet de ce travail de thèse est l’étude du polyéthylène réticulé chimiquement (PRC) utilisé pour les câbles haute tension à courant continu (HTCC). Les propriétés électriques du PRC ont été largement étudiées en alternatif mais sont moins bien connues dans le cadre d’une contrainte continue. Une meilleure compréhension des propriétés diélectriques et de la durée de vie pourraient permettre aux fabricants et utilisateurs de proposer des tests de qualification et s’assurer du bon fonctionnement des systèmes de câble durant leur exploitation.Ces travaux présentent les câbles utilisés pour le transport HTCC ainsi que les contraintes physiques et chimiques endurées par le PRC en service. Le PRC est issu de la réaction de réticulation du polyéthylène basse densité (LDPE) amorcée par le peroxyde dicumylique. Il en résulte la présence de sous-produits, dont la majorité est évacuée par un traitement de dégazage du câble. Un additif antioxydant est par ailleurs ajouté à l’isolant du câble pour protéger le PRC durant la production puis l’exploitation du câble. Les contraintes appliquées au câble peuvent influencer les propriétés diélectriques. Notamment, la présence de charges électriques piégées (ou charges d’espace) peuvent influencer la durée de vie de l’isolant.Les propriétés d’injection/conduction, les mécanismes de pertes, la rigidité électrique, la charge d’espace et des propriétés chimiques de plaques circulaires de XLPE munies d’électrodes semiconductrices ont été étudiées. Sous l’effet des contraintes thermoélectriques, des charges électriques peuvent acquérir assez d’énergie pour être injectées dans l’isolant, selon différents mécanismes possibles, puis traverser l’isolant jusqu’à atteindre l’électrode opposée selon, là aussi, différents mécanismes. Selon le champ électrique appliqué, le mécanisme d’injection dominant est l’effet Schottky et le mécanisme de transport est le courant limité par charge d’espace (usuellement appelé SCLC). En ce qui concerne les mécanismes de pertes, à faible fréquence, le mécanisme de conduction quasi DC a été identifié à température ambiante tandis qu’à 70, 80 et 90°C, la conduction DC a été mise en évidence. De plus, les pertes augmentent lorsque la température d’étude augmente. La rigidité diélectrique a été déterminée à l’aide d’un panel d’échantillons. Sa valeur, déterminée par la loi de Weibull est de 375 kV/mm à température ambiante. La charge d’espace a été étudiée en utilisant la méthode de l’onde thermique (MOT). Ces analyses ont montré deux types de charges dominantes dans le matériau : homocharge et hétérocharge. La prédominance d’un type de charge par rapport à un autre est influencée par le champ électrique et la température. Le champ électrique total (addition du champ électrique dû à la charge d’espace et avec le champ électrique appliqué) atteint jusqu’à 100 kV/mm en appliquant 60 kV.mm. Les caractérisations chimiques ont montré une température de fusion de 103°C et une cristallinité de 39 %. Avant l’application de contraintes, l’index carbonyle, indiquant la présence de liaisons carbonyles est de 0,5.L’impact de contraintes thermoélectriques sur les propriétés diélectriques du PRC a été étudié à 70, 80 et 90°C sous 30 et 60 kV/mm. Des augmentations de la capacité et du facteur de pertes ont été observées et pourraient être assignées à la consommation presque totale de l’antioxydant à 90°C quelle que soit la contrainte électrique. La charge d’espace a elle aussi montré des évolutions significatives. Des différences ont été observées en fonction de la température, du champ électrique et du temps de vieillissement. Ces résultats ont été utilisés pour proposer une cinématique de vieillissement prenant en compte la charge d’espace et basé sur la consommation d’antioxydant menant à la croissance d’une couche de PRC oxydé contenant de nouvelles liaisons carbonyles comme le montre l’évolution de l’index de carbonyles. / The present work concerns the study of the cross-linked polyethylene (XLPE) used for high voltage direct current (HVDC) cable insulation. The electrical properties of XLPE have been widely studied under AC stress, however the behaviour of these materials under high DC stress is less known and needs thorough investigation. The insulation should be better understood in terms of dielectric behaviour and lifetime. A better knowledge of HVDC insulation could allow manufacturers, utilities and TSO’s to propose a relevant qualification processes and to ensure that cable systems will remain safe and operational during their entire lifetime.This work introduces HVDC cables and especially the physical and chemical stresses assumed by the cross linked polyethylene (XLPE) insulation due to operational conditions. XLPE insulation is the result of the reticulation of low density polyethylene (LDPE), obtained with the decomposition of the cumyl peroxide. It causes the presence of byproducts in the insulation. The cables, degassed in order to extract these byproducts contains antioxidant agents, protecting the insulation during the production of HVDC cables and during the exploitation. The stresses can influence the insulation dielectric properties. As example, the presence of electric charges could influence the lifetime of the insulation.The injection/conduction, loss mechanisms, dielectric rigidity, space charge and chemical properties have been investigated at initial state. Under thermal and electric stresses, charges can reach the injection energy according with different mechanisms. Then, charges can be carrier to the opposite electrode with different mechanisms. Dominant mechanisms have been identified: Schottky injection and Space Charge Limited Current (SCLC) conduction, according with applied electric field. Concerning loss mechanisms, the low frequency mechanisms are nearly DC conduction at room temperature and DC conduction for higher temperatures. Moreover, the dielectric loss factor increases when temperature increases. The dielectric rigidity has been measured with Weibull’s law on a panel of 12 samples. The value of this property is 375 kV/mm, at room temperature. The space charges have been measured using the Thermal Step Method (TSM). These analyses show that two types of charge are present in the material (homocharge and heterocharge). This effect is influenced by temperature and electric field. The total electric field (addition of the applied electric field and electric field due to space charge) reaches until 100 kV/mm whereas 60 kV/mm is applied. Concerning the chemical properties of XLPE samples, the melting point has been measured at 103°C and the crystallinity is about 39 %. Before ageing stresses, the carbonyl index is worth 0.5 due to the slight presence of carbonyl bonds.The impact of a combined electric and thermal stress on dielectric properties is studied at 70, 80 and 90°C under 30 and 60 kV/mm. Increases of capacitance and loss factor possibly linked to the nearly total consumption of the antioxidant have been observed at 90°C for each electrical stress. Space charge analysis has shown significant variations. Differences have been observed as a function of ageing test temperature, applied electric field stress and ageing time. These results have been used to propose an ageing mechanism taking into account the development of space charges and based on the consumption of the antioxidant leading to the grow of an XLPE oxidised coat containing new carbonyl bonds as indicated by the carbonyl index after 857 days under stresses.

Actuellement, les principaux thèmes pour le secteur de transport sont le réchauffement global et la crise énergétique, ce qui encourage les chercheurs à développer des technologies alternatives et efficaces. Le concept ‘HCCI’ (combustion d’une charge homogène, allumée par compression) est l’une des solutions pour le moteur de véhicules. Ce mode de combustion, indépendant d’une notion de propagation de flamme, permet de réduire fortement les émissions critiques de NOX et de suies dans les gaz d'échappement. Cette combustion de type HCCI du carburant diesel se caractérise par une combustion à deux étapes. Parallèlement, l’apparition de nouveaux carburants, comme le bio-alcool, est une autre voie de recherche. Les bio-alcools ont un nombre d’indice d'octane élevé qui peut se mélanger avec du carburant diesel pour optimiser la combustion de HCCI des carburants diesel. L’objectif de cette thèse est donc de caractériser les deux étapes de la combustion HCCI en étudiant l’influence de l’impact de l’ajout d’une fraction d’alcools dans diesel. La comparaison avec un mélange d’iso-octane, hydrocarbure à indice d'octane élevé de paraffine et des mélanges dilués via les gaz d’échappement est aussi analysée en tant que verrous potentiels pour améliorer la combustion de type HCCI. Dans cette thèse, le n-heptane est choisi comme composé principal représentatif du diesel, l'éthanol et 1-butanol sont choisis comme bio-alcools. L’analyse présentée ici se repose sur trois approches différentes : l’analyse expérimentale de la pression cylindre, l'analyse d'images de chimiluminescence spontanée de certaines espèces et les résultats issus de la modélisation cinétique de la combustion. / Currently, the major issues for the transportation sector are the global warming and energy crisis which encourage researchers to develop an alternative green efficient technology. The homogeneous charge compression ignition (HCCI) can be one of solutions for the automotive engine. This combustion concept is independent on the high temperature flame propagation which releases lowest critical emissions (NOX and PM) in the exhaust gas. HCCI combustion of diesel fuel presents specific characteristic of two-stage ignition that over-advances the main heat release. As the importance of bio-alcohol fuels increases, it is interesting to evaluate the potential of the fuels, to optimize the HCCI combustion of diesel fuels. This is the objective of this phD thesis. The two-stage ignition characteristic of the diesel hydrocarbon is described and the influence of alcohol fuel fraction in diesel blends is investigated in comparison with high octane paraffin hydrocarbon diesel blends and EGR addition. All potentials are concluded to the potential for HCCI combustion improvement. In this thesis, n-heptane was selected as the major diesel representative component and ethanol and 1-butanol as the considered alcohol fuels. Three approaches were used based on experimental cylinder pressure analysis, the chemiluminescence emissions image analysis and the chemical kinetic analysis results from the engine modeling. A detailed chemical kinetic scheme was specifically developed from sub-scheme of all considered fuel.

Ce manuscrit présente une mesure de la section efficace de production des bosons W et de l'asymétrie de charge dans les collisions proton-proton avec l'expérience ATLAS à une énergie dans le centre de masse de 7 TeV. Ces mesures posent des contraintes sur la fraction d'impulsion des protons portée par les partons qui contribuent à la production des bosons W et donc elles permettent d'ameliorer notre compréhension des fonctions de distribution de partons. Dans l'analyse, les événements de signal sont sélectionnés dans le canal électronique W −→eν . Le calorimètre électromagnétique à Argon Liquide joue un rôle important pour la détection des électrons. L'auteur de cette thèse a travaillé sur la reconstruction en ligne de l'énergie dans les détecteurs à LAr. Un aspect important pour les mesures liées à la charge électrique, comme l'asymétrie de charge du boson W, est l'évaluation du taux de misidentification de la charge pour des électrons et des positons. Dans ce manuscrit, la section efficace de production de bosons W multipliée par le rapport de branchement est présentée de façon inclusive, en fonction de la pseudorapidité du lepton, et comme mesure différentielle en deux dimensions (c'est à dire en fonction de la pseudorapidité et de l'énergie transverse du lepton). La mesure de l'asymétrie de charge est aussi présentée en fonction de la pseudorapidité du lepton uniquement et en fonction de la pseudorapidité et de l'énergie transverse du lepton. Les données ont été enregistrées par l'expérience ATLAS en 2011 et correspondent à 4.7 fb−1 . / This document presents a measurement of the production cross section of W bosons and of its charge asymmetry in proton-proton collisions at a centre of mass energy of 7 TeV with the ATLAS detector. These measurements provide information on the momentum fraction of the protons carried by the partons contributing to the W production and therefore allow to better understand the parton distribution functions of the proton. The W candidate events are selected in the W −→ eν decay mode. The LAr electromagnetic calorimeter plays an important role in the detection of electrons and the author has worked on the on-line energy reconstruction in the LAr detectors. A subject which is treated in some detail is the evaluation of the charge misidentification rates for electrons and positrons. This is a key ingredient for charge related measurements such as the W charge asymmetry. In this document, the W production cross section times the branching ratio is studied inclusively, as a function of the lepton pseudorapidity and as a double differential measurement as a function of the lepton pseudorapidity and transverse energy. The charge asymmetry measurement is presented as a function of the lepton pseudorapidity and as a double differential measurement as well. The data were recorded by the ATLAS detector in 2011 and correspond to 4.7 fb−1 .

Made available in DSpace on 2015-05-07T15:09:10Z (GMT). No. of bitstreams: 1 arquivototal.pdf: 2441751 bytes, checksum: 84e04bccf99a5e4fa151e0793c515fc3 (MD5) Previous issue date: 2014-05-13 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Le présent travail recherche le discours sur l usage pédagogique de la charge dans l Éducation de Jeunes et Adultes (EJA). La littérature consultée sur la question remarque que la charge peut être comprise comme une représentation graphique du caractère critique et harmonieux de certains faits sociaux actuel. La charge a été identifié comme un événement discursif, situé dans le scénario de la culture visuelle, objective sur divers places sociales d apprentissage et artefacts culturels, par exemple de l école et des matériels didactiques pédagogiques qu'elle utilise. La recherche analyse et décrit les singularités des discours pédagogiques qui énoncent et cherchent la charge comme une stratégie par rapport à la formation des sujets de l EJA. Cet établissement met en évidence l existence d un ensemble de savoirs sur le sujet qui sont matérialisés dans les livres et les productions académiques. En ayant en vue la spécification de cet ensemble, a été employée la théorie méthodologique de l analyse archéologie du discours proposé par Michel Foucault (2012). De cette façon, a été identifié les séries énonciatives qui montrent les particularités des artefacts visuels en plus, de la charge. Et plus spécifiquement, les séries qui montrent l'usage de la charge dans l'éducation, et d'une manière particulière dans l`EJA. Pendant l'analyse, la recherche caractérise et décrit cet ordre discursif, selon les objectifs de la recherche. On comprend que la charge est utilisée pédagogiquement comme modalité de lecture relative à la réflexion, la compréhension, l'interprétation, la créativité et le dialogue. On décrit que leur usage pédagogique promet un rapport triade, dans le quel existe le sujet, le texte et la réalité qui constituent un processus qui pose le problème et la compréhension critique. Dans ce scénario, le professeur apparaît dans une position de sujet médiateur et l'élève de l´EJA comme un sujet constructeur et souverain dans le travail pédagogique. / A presente pesquisa investiga o discurso sobre o uso pedagógico da charge na Educação de Jovens e Adultos (EJA). A literatura consultada sobre a questão assinala que a charge pode ser entendida como uma representação gráfica de caráter crítico e humorístico que aborda determinados fatos sociais atuais. Ao identificar a charge como um acontecimento discursivo, situado no cenário da cultura visual, objetivados em diversos lugares sociais de aprendizagem e artefatos culturais, a exemplo da escola e dos materiais didático-pedagógicos que ela utiliza, a pesquisa analisa e descreve as singularidades dos discursos pedagógicos que anunciam e recorrem à charge como uma estratégia relacionada à formação dos sujeitos da EJA. Esta constatação evidencia a existência de um acúmulo de saberes sobre o assunto, que são materializados em livros e produções acadêmicas. Tendo em vista a especificidade desta pesquisa, utiliza-se como ferramenta a Análise Arqueológica do Discurso de Michel Foucault (2012). Assim sendo, são identificadas séries de enunciados que apontam as particularidades dos artefatos visuais e mais precisamente, da charge. Ademais, identificam-se as séries enunciativas que apontam o uso da charge na educação e, em particular, na modalidade EJA. No curso da análise, a investigação caracteriza e descreve essa ordem discursiva, conforme os objetivos da pesquisa. Dessa forma, compreende-se que a charge é utilizada pedagogicamente como modalidade de leitura no que tange a reflexão, a compreensão, a interpretação, a criticidade e o diálogo. Descreve-se que seu uso pedagógico promove uma relação triádica, na qual se inserem o sujeito, o texto e a realidade, constituindo um processo de problematização e compreensão crítica. Nesse cenário, o professor aparece em uma posição de sujeito de mediador e o aluno da EJA como um sujeito construtor e autônomo no trabalho pedagógico.

São apresentadas as soluções aproximadas de alguns problemas de transporte de carga em dielétricos, inexpugnáveis ainda a um tratamento rigoroso, usando-se o Método de Galerkin. Com ele reduz-se o sistema de equações a derivadas parciais, que descrevem o transporte na presença de armadilhas, em um sistema de equações diferenciais ordinárias que são, então, integradas numericamente. Sempre que possível, a solução aproximada é comparada com alguma exata ou quase-exata, como a que se obtém da integração numérica direta do sistema de equações a derivadas parciais com o Método das Diferenças Finitas. Três diferentes condições de contorno são empregadas aqui: circuito aberto, curto circuito e circuito fechado com uma voltagem aplicada entre os eletrodos; em alguns casos considera-se temperatura variável. Este método requer que seja escollhida a priori, a forma da distribuição de carga livre; verifica-se que a corrente é mais sensível a esta distribuição do que o potencial de superfície, que sempre resulta muito próximo do exato, mesmo quando a aproximação parece grosseira. / Approximate solutions for some problems of charge transport in dielectrics, unsolved yet by exact methods, are presented using Galerkin\'s Method. This allows to transforming the system of partial differential equations, describing transport with trapping, into a system of ordinary differential equations which are, then, integrated numerically. Whenever possible, a comparison is made between this approximate solution with some exact or quasi-exact solution as, for example, that obtained from the direct numerical integrated of the system of partial differential equations using the Finite Difference Method. Three different boundary conditions are considered here: open circuit, short circuit and closed circuit with a voltage applied between the electrodes; in some cases the temperature was allowed to vary. Use of Galerkin\'s Method requires a priori choice of the free charge distribution; there results that the current is more sensitive to this distribution than the surface potential which leads to good results even when the approximation seems crude.

Made available in DSpace on 2015-09-25T12:20:34Z (GMT). No. of bitstreams: 1 PDF - Marcelo Rodrigo da Silva.pdf: 7342832 bytes, checksum: 1d8582994e59bfeaa4b0dab570adab1c (MD5) Previous issue date: 2010-06-18 / The virtuality and cyberspace have brought remarkable changes to communication and are still spaces in potential discovery and experimentation in contemporary regarded as Post-modern. The Virtual Charges are examples of this ongoing process and present as fruitful field for study of interculturality, from the analysis of the articulation of its structure signic in the translation process of cultural signs. Thus, the keynote of this research is to observe the Virtual Charge as the environment of the interculturality, through cultural signs designed and coded in translator's action of cartoonist.To do so, at first, will be investigated the potential of virtual support and the definitions of Virtual Charges, identifying the changes that have marked their language due to the change in support. At this point will be taken conceptualizations about cyberspace and the virtual environment and studied the settings on the Virtual Charges as part of opinionated journalism and literary genre; will also be identified the changes caused by the change to the virtual support, observing features characteristic of his language, like humor, parody and irony, coupled with the concept of dialogism. In the second chapter will be thorough the studies about the concept of mediasphere, and audiovisual language; will also be studied the links between semic hues that result in the articulation of language with cultural signs in the narrative. The third chapter will be done an application of the studies about semiosphere, as well as the concept of Translation Intersemiotic (IT) as moored Julio Plaza; will also be studied the speech of the charges using the concepts of mimesis and semiosis. In the fourth and final chapter will be done an explanation about the influence of the Territoriality on the approach of te charges and Will be further detailed the studies of the Interculturalism. In compliance with the elements and concepts studied, was observed that the translator action of the Virtual Charge provides the Interculturalism, in that the characters are imbued with cultural signs and carry meanings related to crops where they came from, whether these cultural signs revealed under hues semics sound, visual or verbal. / A virtualidade e o ciberespaço trouxeram transformações marcantes à comunicação e ainda são espaços em potencial descoberta e experimentação na contemporaneidade tida como Pós-moderna. As Charges Virtuais são exemplos desse processo em curso e apresentam-se como campo frutífero para o estudo sobre a interculturalidade, a partir da análise da articulação de sua estrutura sígnica no processo de tradução dos signos culturais. Sendo assim, a tônica da presente pesquisa é observar a Charge Virtual como ambiente da interculturalidade, através dos signos culturais elaborados e codificados na ação tradutora do chargista. Para tanto, em um primeiro momento, serão estudadas as potencialidades do suporte virtual e as definições de Charge Virtual, identificando as mudanças que marcaram sua linguagem em decorrência da mudança de suporte. Neste ponto são adotadas conceituações sobre o ciberespaço e o ambiente virtual e estudadas as definições sobre as Charges Virtuais enquanto elemento do jornalismo opinativo e gênero literário; também são identificadas as transformações causadas pela mudança para o suporte virtual, observando-se recursos característicos de sua linguagem, como o humor, a paródia e a ironia, atrelados ao conceito de dialogismo. No segundo capítulo serão aprofundados os estudos sobre o conceito de Midiasfera, e a linguagem audiovisual; também serão estudadas as articulações entre as matizes sêmicas que resultam na articulação da linguagem com os signos culturais na narrativa. No terceiro capítulo será feita uma aplicação dos estudos sobre Semiosfera, assim como do conceito de Tradução Intersemiótica (TI), ancorado em Júlio Plaza; também será estudado o discurso chárgico à luz dos conceitos de mimeses e semioses. No quarto e último capítulo será feita uma explanação sobre a influência da Territorialidade na abordagem chárgica e serão aprofundados os estudos sobre a Interculturalidade. Com a observância dos elementos e conceitos estudados, foi possível verificar que a ação tradutora da Charge Virtual propicia a Interculturalidade, na medida em que as personagens são imbuídas de signos culturais e carregam consigo significados relacionados às culturas de onde são provenientes, sejam esses signos culturais revelados sob matizes sêmicas sonoras, visuais ou verbais.