Los transformadores, junto con los generadores, son los equipos más importantes de las redes eléctricas. Sería inimaginable transmitir energía eléctrica a grandes distancias sin estos equipos, ya que con ellos podremos transformar un nivel de tensión a otro superior para así disminuir las corrientes, y por consiguiente atenuar las pérdidas en la transmisión de dicha energía. Bastaría instalar otro transformador cerca de los consumidores, para poder así trabajar con tensiones más bajas que nos permitan tener equipos con menos aislamientos (por lo tanto, más económicos), y trabajar con más seguridad. Si una red no está adecuadamente planificada, una falla en un transformador puede dejar desabastecida de energía eléctrica a una zona o toda una ciudad, dependiendo de la capacidad e importancia de esta. Por ello se justifica la necesidad de estudiar las contingencias que pudieran ocurrir en la puesta en servicio y operación de los transformadores de potencia. Estas contingencias obligan que el transformador sea diseñado con características dieléctricas, térmicas y electrodinámicas superiores a las que se tienen en condiciones normales de operación (tensiones y corrientes nominales).

No description available.

A lo largo de su historia, Zig Zag ha sido uno de los puntales en el desarrollo de la vida cultural, de entretención y educación en Chile, y por otro lado sentó las bases de diversas áreas del diseño gráfico, como el cómic o el diseño editorial. Como Zig Zag actualmente está enfocada hacia el sector educacional, dentro de sus labores ha dejado de lado todo lo que significó la publicación de revistas, hoy en día parte de la identidad chilena, por lo que el problema que se presenta es la poca valorización de este gran legado y más aún en el año de su centenario. El campo del diseño tiene un gran potencial y una gran importancia para desarrollar soluciones al respecto, ya que cuenta con las herramientas necesarias, siendo las mismas que le dieron su jerarquía, para valorizar su legado, pudiendo canalizar la información visual y escrita sobre un soporte gráfico que las de a conocer en forma meritoria y atractiva

Les nanotubes de carbone (NTC) n'ont eu de cesse, depuis leur (re)-découverte par Sumio Iijima en 1991, de passionner la communauté scientifique. Leurs propriétés électroniques, optiques et mécaniques exceptionnelles en font l'un des matériaux les plus prometteurs dans le domaine des nanotechnologies. Néanmoins, l'utilisation des NTC en microélectronique se heurte à de nombreux problèmes. En particulier, les propriétés électroniques de ces nanotubes sont dépendantes de plusieurs paramètres : leur diamètre, leur organisation et le nombre de feuillets qui le composent. Ainsi, l’obtention de nanotubes exclusivement semiconducteurs (recherchées pour réaliser un dispositif microélectronique tel qu’un transistor) ne peut être garantie par les techniques de synthèse actuelles. Ces techniques (CVD, ablation laser, etc…) ne conduisent en général qu’à un mélange de nanotubes semiconducteurs et métalliques, difficiles à trier.Dans le cas spécifique des nanotubes de carbone « zig-zag », leur comportement électronique n’est défini que par le diamètre. Une synthèse de nanotubes exclusivement « zig-zag » et de diamètres contrôlés apporterait donc une solution définitive à ce problème.La chimie des calixarènes peut apporter des réponses à cette problématique. On utiliserait alors la chimie moléculaire pour former le NTC de façon séquentielle. L’objectif du travail réalisé est d'obtenir une structure de type « zig-zag » avec un diamètre strictement contrôlé par la taille du calixarène de départ.Nous avons abordé plusieurs méthodes de synthèse en fonction du motif de répétition envisagé pour la croissance séquentielle du nanotube de carbone. Dans un premier temps, une stratégie basée sur le motif cyclacène a été utilisée. Les résultats de ces travaux seront présentés dans le chapitre II. Au cours de ce chapitre nous présenterons la synthèse et la fonctionnalisation des calixarènes de départ, en vue de leur utilisation pour des réactions de types Wittig Horner ou Oléfination de Julia.Enfin, au cours du chapitre III, nous présenterons les résultats obtenus par utilisation d’une autre stratégie, basée sur la répétition d’un motif métacyclopolyphénylène. Cette stratégie est basée sur une succession de réactions de couplage de Suzuki, catalysés par des complexes de palladium. / Since their re-discovery in 1991 by Sumio Ijima, carbon nanotubes (CNT’s) have not stopped fascinating the scientific community. Their electronic, optical, and mechanical properties render them one of the most promising materials in the field of nanotechnology. Nevertheless, the use of CNT’s is has been hampered by a number of problems due to the fact that the electronic properties of CNT’s are dependent on several parameters such as diameter, organization and number of sheets that make them up. Because of these factors, obtaining nanotubes that function exclusively as semiconductors (such as those used for fabricating microelectronic devices such as transistors) cannot be guaranteed with the synthetic methods used today. These techniques (CVD, laser ablation, etc) are only capable of yielding a mixture of semiconducting and metallic nanotubes difficult to separate.In the particular case of « zig-zag » nanotubes, their electronic behavior is defined by their diameter. Thus, a synthetic method capable of rendering exclusively « zig-zag » nanotubes with discrete diameters would yield a solution to the problem.Calixarene chemistry can give answers to this problem. Using molecular chemistry in order to form CNT’s in a sequential fashion, the objective of this work will be to obtain exclusively « zig-zag » nanotubes with discrete diameters that are imposed by the size of the calixarene used as a starting block. We have tried several methods for the synthesis of CNT’s depending on the repetition motif used for the sequential growth of the desired carbon nanotube. Firstly, a strategy based on the acene functionality was used. The results of this work are presented in chapter II, where we will describe the synthesis and functionalization of the starting calixarenes used in reaction types such as Wittig Horner and Julia Olefination.Chapter III shows the results obtained using a different strategy based on the repetition of the metacyclopolyphenylene unit. This strategy is based on the reiteration of successive Suzuki coupling reactions catalyzed by palladium complexes.

Submitted by Marco Antonio de Freitas Contessoto (marco_contessoto@hotmail.com) on 2018-06-19T06:27:03Z No. of bitstreams: 1 Marcoeditado.pdf: 1251669 bytes, checksum: 5fe5c25a4002aeefa7831bd4137fb1f8 (MD5) / Approved for entry into archive by Elza Mitiko Sato null (elzasato@ibilce.unesp.br) on 2018-06-19T14:26:54Z (GMT) No. of bitstreams: 1 contessoto_maf_me_sjrp.pdf: 1242012 bytes, checksum: e5b5acc9695b0f3103a68a1f1f32edac (MD5) / Made available in DSpace on 2018-06-19T14:26:54Z (GMT). No. of bitstreams: 1 contessoto_maf_me_sjrp.pdf: 1242012 bytes, checksum: e5b5acc9695b0f3103a68a1f1f32edac (MD5) Previous issue date: 2018-03-09 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O objetivo dessa dissertação é apresentar parte do artigo [2] de Gunnar Carlsson, onde se discute a adaptação de métodos da teoria usual de homologia para problemas de reconhecimento topológico de padrões em conjuntos de dados. Esta adaptação conduz aos conceitos de homologia de persistência e de barcodes. Atualmente, várias aplicações são obtidas com o uso deste método. Apresentaremos alguns casos onde a homologia de persistência é usada, ilustrando diferentes modos em que podem ser aplicados. Descreveremos, também baseado no artigo de Carlsson, um novo método para estudar a persistência de características topológicas através de uma família de conjuntos de dados, chamado persistência zig-zag . Este método generaliza a teoria de homologia de persistência e chama atenção de situações que não são cobertas pela outra teoria. Além disso, são apresentadas algumas aplicações dessa ferramenta para a obtenção de informações de alguns conjuntos de dados / The main goal of this work is to present a part of the Gunnar Carlsson paper [2], where the adaptation of the theory of usual homology to topological pattern recognition problems in point cloud data sets is discussed. This adaptation leads to the concepts of persistence homology and barcodes. Several applications have been obtained using this method. We will present some cases where persistence homology is used, illustrating different ways in which the method can be applied. We will describe,alsobasedintheCarlsson’spaper,anewmethodtostudythepersistence oftopologicalfeaturesthroughpointclouddatasets,calledzig-zagpersistence. This method generalizes the homology persistent theory and we will pay attention to situations that are not covered by the other theory. In addition, some applications of this tool are presented to obtain information from some data sets. / 2016/25659-3

Les nanotubes de carbone (NTC) n'ont eu de cesse, depuis leur (re)-découverte par Sumio Iijima en 1991, de passionner la communauté scientifique. Leurs propriétés électroniques, optiques et mécaniques exceptionnelles en font l'un des matériaux les plus prometteurs des nanotechnologies. Néanmoins, l'utilisation des NTC en microélectronique se heurte à de nombreux problèmes. En particulier, les propriétés électroniques de ces nanotubes sont dépendantes de plusieurs paramètres : le diamètre du NTC, son organisation et le nombre de feuillets qui le composent. Ainsi, l’obtention de nanotubes exclusivement semiconducteurs (recherchées pour réaliser un dispositif microélectronique tel qu’un transistor) ne peut être garantie par les techniques de synthèse actuelles. Ces techniques (CVD, ablation laser, etc…) ne conduisent en général qu’à un mélange de nanotubes semiconducteurs et métalliques, difficiles à trier. Dans le cas spécifique des nanotubes de carbone « Zig-Zag », leur comportement électronique n’est défini que par le diamètre. Une synthèse de nanotubes exclusivement « Zig-Zag » et de diamètres contrôlés apporterait donc une solution définitive à ce problème. La chimie des calixarènes peut apporter des solutions pour résoudre cette problématique. On utiliserait alors la chimie covalente pour former le NTC de façon séquentielle. Le but de mon travail est d'obtenir une structure de type « zig-zag » avec un diamètre strictement contrôlé par la taille du calixarène de départ. Nous avons envisagé plusieurs méthodes de synthèses en fonction du motif de répétition que nous souhaitions introduire pour la croissance séquentielle du nanotube de carbone. Dans un premier temps, une stratégie basée sur le motif cyclacène a été utilisée. Les résultats de ces travaux seront présentés dans le chapitre 2. Nous présenterons la synthèse et la fonctionnalisation des calixarènes de départ ainsi que du synthon que nous avons choisi pour effectuer la croissance séquentielle. Le couplage entre ces deux composés sera effectué via une réaction de type Wittig Horner. Ce motif de répétition sera également utilisé lors du chapitre 3 pour présenter une nouvelle stratégie de croissance basée sur l’utilisation de la réaction de Heck afin d’effectuer la croissance séquentielle. Enfin, dans une dernière partie, nous présenterons les résultats obtenus par utilisation d’une autre stratégie, basée sur la répétition d’un motif métacyclopolyphénylène. Cette stratégie est basée sur une succession de réactions de couplage de Suzuki, catalysés par des complexes de palladium. / Since their rediscovery by Iijima in 1991, carbon nanotubes (CNT) has been a main subject of interest. Their extraordinary properties may open large fields of applications in different domains such as electronics, medicine, or optics. But their use in microelectronics is limited by the lack of control of the electronics properties of each carbon nanotubes. These properties are depending on different parameters such as diameter, chirality, or the number of layers of graphène. Obtaining exclusively semi conducting CNT using current synthetic methods of synthesis is not guaranteed. These technics (CVD, Laser ablation…) leads, in general, to a very complex mixture of semi conducting and metallic CNT, quite difficult to sort out. In the specific case of “zig-zag” CNT, their electronic properties only depend of the diameter of the tube. An exclusive synthesis of a “zig-zag”, diameter controlled CNT should thus solve this problem. We propose here the use of organic, molecular chemistry, and more specifically, calixarene chemistry to achieve this goal. Two different synthetic strategies were explored, as a function of the repeating unit considered for the growth of “zig-zag” carbon nanotubes. During the first part of this work, we have used a strategy based on a cyclacene-type pattern as a repeating unit. These results will be presented in the second chapter. We will describe the results dealing with calixarene functionalization and the synthesis of a new bifunctionnal molecule to be used as a building block for the sequential growth. The coupling between these two species is performed by a Wittig reaction or a Wittig/Horner reaction. The same cyclacene-type repeating unit is also envisioned during the first part of the third chapter for a second strategy for zig-zag SWCNTs synthesis, based on Heck coupling reactions. Finally, during the last part of the third chapter, we will present the results obtained by the use of a new repetition pattern , the metacyclophenylene unit. This strategy relies on the use of successive Suzuki couplings.

[pt] Um estudo experimental em modelos reduzidos do duto PE-3, construído na Baía de Guanabara em 2003, é descrito neste trabalho. O duto PE-3 tem diâmetro externo de 457,2 mm e a sua principal característica é a sua geometria em ziguezague. Este duto transporta óleo combustível à temperatura de 80ºC da Refinaria de Duque de Caxias aos terminais de navios na Ilha D´Água. O presente estudo foi realizado em modelos reduzidos com semelhança física, e teve como objetivo avaliar experimentalmente o comportamento do modelo variando-se o ângulo de ziguezague e o comprimento do duto. Os modelos foram submetidos à variação de temperatura, pressão interna e condições de apoio lateral e longitudinal, simulando as condições reais de trabalho do protótipo. Para cada comprimento (12, 16 e 18 metros) e ângulo de ziguezague (5º, 10º e 15º) foram realizados ensaios com o modelo sem reação lateral do solo, com reação lateral simulando 1 metro de enterramento no protótipo, com reação lateral simulando 1 metro de enterramento e vão central livre, e com imperfeição horizontal. Foram realizados ainda 2 ensaios com um duto reto para efeito de comparação com o modelo zig-zag. Os resultados mostraram que a geometria em ziguezague minimiza os esforços gerados pela expansão térmica do duto. / [en] An experimental study on reduced scale models of the PE-3 pipeline, built in Guanabara Bay in 2003, is described in this work. The main characteristic of the PE-3 pipeline is the zig-zag geometry. This pipeline has an external diameter of 18 and is used to transport heavy heated oil from the Duque de Caxias refinary to a shipping terminal. The present study was carried out in reduced models with physic similitude, and the objective is to evaluate experimentally the behavior of the model, varying the zig-zag angle and the length of the pipeline. The models were submitted to temperature variation, internal pressure and different conditions of lateral and longitudinal support, simulating the real working conditions of the prototype. For each length (12m, 16m and 18m) and zig-zag angle (5°, 10° and 15°) tests were carried out with the model without lateral reaction of the soil, with lateral reaction simulating 1 meter of buried prototype, with lateral reaction simulating 1 meter of buried prototype and central free span, and with horizontal imperfection. Two straight pipeline tests were carried out in order to compare with the zig-zag model. The results showed that the zig-zag geometry minimizes the effects caused by the thermal expansion of the pipeline.

No description available.

Thesis (MScEng)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: This thesis is about the design, simulation and measuring of ultra wide band antennas for use in the Square Kilometre Array (SKA). The SKA is a radio astronomy project with one of the aims of detecting hydrogen particles in deep space. Several thousand antennas over a wide band of frequencies are needed to receive the radiation from these particles. This motivates the need for a low-cost ultra wide band antenna with the focus on the low frequency part of the SKA. In this thesis we present two design strategies: The first design strategy is for a printed LPDA on a substrate and design curves are generated. A scale model was built and measurements did not correlate with simulation results. This is due to manufacturing tolerances and assembly of the pyramidal structure. The second design strategy is for a full scale zig-zag antenna and design curves were also generated. The aim here is to produce a low-cost prototype by using brazing rods for the wire structure and mount it on a wooden frame. A full scale model was built and measurements on the roof produced much interference for the radiation pattern, but the reflection coefficient was good. We suggest doing measurements in an interference free environment in order to achieve the needed results. To conclude we suggest using the zig-zag antenna for the SKA. Some issues do however need more attention as the transformer has some losses, the cross polarisation is probably not good enough and the beamwidth does not reach the specification. We demonstrated a low cost prototype and there is the possibility of low-cost large scale manufacturing but this needs to be addressed. This has however not been analysed as many factors for large scale manufacturing are very difficult to predict beforehand and lies outside the scope of this thesis. / AFRIKAANSE OPSOMMING: Hierdie tesis gaan oor die ontwerp, simulasie en opmeting van ultrawyebandantennas vir gebruik in die SKA ("Square Kilometre Array"). Die SKA is ’n radioastronomie projek met die doel om waterstof partikels op te spoor in die ruimte. Duisende antennas wat oor ’n wye band van frekwensies strek is nodig om die energie van die partikels op te vang. Hieruit is daar ’n aanvraag vir lae-koste ultrawyebandantennas met die fokus op die lae frekwensie deel van die SKA. In hierdie tesis word twee ontwerpstrategieë voorgestel: Die eerste ontwerpstrategie is vir ’n gedrukte logaritmies periodiese dipool reeks (LPDR) op ’n substraat tesame met ontwerpskurwes wat gegenereer word. ’n Skaal model is gebou en die gemete resultate stem nie ooreen met die simulasie nie. Dit kan toegeskryf word aan vervaardigingstoleransies en die aanmekaar sit van die piramide struktuur. Die tweede ontwerpstrategie is vir ’n vol skaal sigsag ("zig-zag") antenna met ontwerpskurwes wat ook gegenereer word. Die doel is om ’n lae-koste prototipe te bou deur sweissoldeerdraad te gebruik vir die draadstruktuur en dan op ’n hout raam te plaas. ’n Vol skaal model is gebou en metings op die dak het baie interferensie veroorsaak vir die stralingsveld, maar tog was die weerkaatskoëffisient goed. Ons stel voor om die metings te herhaal in ’n steuringvrye omgewing om sodoende die korrekte resultate te verkry. Om af te sluit stel ons voor om die sigsag antenna vir die SKA te gebruik. Sekere kwessies soos die transformator wat verlieserig is, die kruispolarisasie wat moontlik nie goed genoeg is nie en die bundelwydte wat nie die spesifikasie haal nie moet nog aandag geniet. Ons het ’n lae-koste prototipe gedemonstreer en daar is die moontlikheid om dit op grootskaalse vervaardiging ook goedkoop te doen, maar dit moet nog uigesorteer word. Dit was wel nie geanaliseer nie, siende dat vele faktore ’n rol speel by grootskaalse vervaardiging wat uiters moeilik is om voor die tyd te voorspel en buite die omvang van die tesis lê.

>Magister Scientiae - MSc / A novel monomer (Phenazine-2,3-diimino(pyrrole-2-yl)–PDP) derived from the condensation reaction between 2,3-diaminophenazine and a pyrrole derivative has been synthesized as a hinge molecule in the design of a zig-zag polymer with actuation possibility. The monomer was polymerized chemically and electrochemically to produce the new polymer material – polymerized Phenazine-2,3-diimino(pyrrole-2-yl) PPDP. Two very crucial properties of a good actuator material, relate specifically to its solubility testing and electrical conductivity. The hinged polymer material was studied intensively in terms of its spectroscopy; Fourier Transform Infrared - FTIR, 1H’NMR, thermal properties (Differential Scanning Calorimetry-DSC and Thermogravimetric Analysis-TGA) as well as voltammetry and conductivity. Conductivity was evaluated using three different approaches including; 4 probe measurements, plotting of I/V curves based on potentiostatic measurements and an electrochemical impedance experiment using a dielectric Solartron interface. Electrochemical kinetics of the polymer prepared as a thin film at glassy carbon electrode (GCE) was also done and it was clear that the thin film conductivity was vastly different from the compressed pellet conductivity (thick film). The zig-zag polymer was then further modified by homogeneous inclusion of gold nanoparticles to improve conductivity and solubility, in the thick film arrangement. Conductivity of the thin film was studied by electrochemical impedance spectroscopy with the relative charge transfer values being determined for unmodified and modified polymer systems. The solubility testing of the material plays an important role as it is required for a wide range of experimental applications. The zig-zag polymer showed great promise for applications; in dye sensitized solar cells and free standing interpenetrating polymer network (IPN), solubility testing and electrical conductivity would need to be improved in order to be used in these applications.