Converter devided into linear converter and switching-mode cinverter. push pull has large hystersis loop,so that it supples large power compared with forward topology.it has another adventage ,is easy to drive than half-bridge or full-bridge .the main purpose of the thesis is to study and design push pull converter . First, it is detail to analysis push pull converter's theorem.afterward the push pull converter is described including the component and circuit design .finally push pull converter is implemented and demonstrated

Duisburg, University, Diss., 2002.

Résumé : Au cours des dernières décennies, la conception de nouveaux polymères «push-pull» a été le sujet d'intenses recherches pour les cellules photovoltaïques. Cette thèse de doctorat comprend deux sujets principaux de recherche, l'une est la synthèse et la caractérisation de polymères organométalliques contenant l’unité trans-bis(éthynyl)bis(tributylphosphine)platine(II) comme l’un de deux blocs de construction et des dérivés quinoniques et anthraquinoniques agissant respectivement comme donneur et accepteur de densité électronique, et ainsi que des composés modèles correspondants pour fins de comparaison. L’autre sujet traite des polymères contenant l’unité zinc(II)porphyrine (donneur) et les mêmes dérivés quinoniques et anthraquinoniques. Habituellement les polymères «push-pull» conjugués sont tout d'abord étudiés car ils peuvent montrer de nouvelles bandes d’absorption dites bandes de transfert de charge vers le rouge du spectre solaire, démontrant ainsi l’existence de communication électronique à travers la chaine du polymère, mais aussi permettant de collecter plus de photons par le matériau. Ce travail est divisé en quatre chapitres. / Abstract : In recent decades, the design of new « push-pull » polymers has been the subject of intense research for photovoltaic cell applications. This thesis deals with two main subjects, one is the synthesis and characterization of organometallic trans-bis(ethynyl)bis(tributylphosphine)platinum(II), ([Pt]) and quinone or anthraquinone derivatives-based polymers. Some model compounds have been produced as well for comparison purposes. Another issue is the synthesis and characterization of polymers built upon zinc(II)porphyrin units and the same quinone and anthraquinone derivatives respectively acting as donor and acceptor of electronic density. Such «push-pull» polymers are used to be investigated because of their so-called charge transfer absorption bands in the red part of the solar spectrum. This phenomenon is due to the electronic communication over the whole chain. This new band allows the material to collect more photons. The whole work is divided into four chapters.

Tese de mestrado integrado. Engenharia Electrotécnica e de Computadores (Major Automação). Faculdade de Engenharia. Universidade do Porto. 2009

Estágio realizado na GE Power Controls Portugal e orientado pelo Eng.º Fernando Braga / Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2010

A series of push-pull systems with different electron donors and electron acceptors were investigated. The carbon-carbon double bond rotational barriers for twelve push-pull ethylene derivatives, NH2CH=CHX, NH2H=CHX and -OCH=CHX (acceptors, X = BH2, CN, NO2, and +CH2) were studied by ab initio calculations. The rotational barrier was chosen as a probe for push-pull effects, as push-pull effects would remove electrons from the central double bond. Complete geometry optimizations and calculations of vibrational frequencies were performed for all minima and transition state structures of the twelve systems. The Synchronous Transit-Guided Quasi-Newton (STQN) method was used to search for the transition state structures. The calculations were carried out at B3LYP/6-31++G(d,p) and MP2/6-311++G(d,p) levels of theory. Electron density maps were used to analyze the electron density distribution. The Merz-Singh-Kollman scheme was chosen to calculate electrostatic potential derived charges on atoms. Calculations at the MP2 level suggest that the strongest push-pull effects result from +CH2 with barriers (to conversion to the transorms) of 10.6, 13.2, and 7.3 kcal/mol for NH2CH=CHCH2+, NH2H=CHCH2+, and -OCH=CHCH2+, respectively. These barriers are about 6, 5, and 9 times smaller than that of ethylene at the same level of theory, respectively. Among the other electron acceptors studied, BH2 was stronger than the cyano and nitro substituents but weaker than CH2+. Solvent effects were examined for the NH2CH=CHX system, X = BH2, CN, NO2, and +CH2 with water and dichloromethane as solvents. Calculations were performed at the B3LYP/6-31++G(d,p) level of theory using three different approaches, the Conductor-like Screening Model (COSMO), the Polarizable Continuum Model (PCM) and the Super-Molecular Approach (SMA). When the solvent is water, SMA calculations retained the barrier-height order of gas phase calculations, while COSMO and PCM reversed the order of BH2 and NO2. Results from this research confirm that both solvents lowered the rotational barriers in all cases. The more polar solvent decreases the rotational barrier more than the less polar solvent due to the existing of a dipolar or charge separated transition states of the push-pull systems.

The pressure between two parallel planar surfaces at equal electric potentials is derived using the modified Poisson-Boltzmann (MPB) equation to account for finite ion size. The effects of finite ion size are presented for a z:z symmetric electrolyte and compared with the pressure derived by the classical Poisson-Boltzmann (PB) equation. The pressures predicted by the two models differ more as the bulk ion concentration, surface potential, and ion size increase. The ratio of the pressures predicted by the two models is presented by varying the ion concentration, surface potential, ion size and distance of separation. The ratio of pressures is relatively independent of the distance of separation between the two surfaces. An elastic beam suspended horizontally over a substrate in liquid electrolyte is subjected to electric, osmotic, and van der Waals forces. The continuous beam structure, not a discrete spring, which is governed by four nondimensional parameters, is solved using the finite element method. The effects of ion concentration and electric potentials to the pull-in instability are especially focused by parametric studies with a carbon nanotube cantilever beam. The pull-in voltage of a double-wall carbon nanotube suspended over a graphite substrate in liquid can be less than or greater than the pull-in voltage in air, depending on the bulk ion concentration. The critical separation between the double-walled carbon nanotube (DWCNT) and the substrate increases with the bulk ion concentration. However, for a given bulk ion concentration, the critical separation is independent of the electric potentials. Furthermore, the critical separation is approximately equal in liquid and air. Stiction, the most common failure mode of the cantilever-based devices, is studied in a liquid environment, including elastic energy, electrochemical work done, van der Waals work done and surface adhesion energy. We extend the classical energy method of the beam peeling for micro-electro-mechanical systems (MEMS) in the air to an energy method for nano-electro-mechanical systems (NEMS) in liquid electrolyte. We demonstrate a useful numerical processing method to find the parameters to free the stiction of the beams and to obtain the detachment length of the beams.

The topic of thesis is motivation of experienced employees toward to starting own business. The purpose is to identify the attitudes of respondents to leave their job and decide to start own business within push-pull theory. Research is carried out on the basis of questionnaire which is divided into three parts. Results of thesis will be suggestions for companies to reduce workers leaving the job depending on push factors.

Titel: Konsumenternas attityd till reklam på Snapchat Nivå: Kandidatuppsats inom företagsekonomi med inriktning på internationell marknadsföring (15 HP), VT-2016. Författare: Emelie Tillack & Jonathan Ekhamn Handledare: Navid Ghannad Examinator: Hélène Laurell Syfte: Syftet med den här studien är att skapa en ökad kunskap ochförståelse kring konsumenternas attityd till reklam på Snapchat. Metod: Denna uppsats utgår från ett deduktivt förfaringssätt. Detta kombinerat med både en kvantitativ och en kvalitativ ansats harutmynnat i en enkätundersökning samt åtta djupintervjuer med respondenter som är aktiva på Snapchat. Teoretiskt Ramverk: Detta kapitel behandlar teorier om vad en attityd är, en attitydmodell, attityder på sociala medier, integritet samt push och pullmarknadsföring. Empiri: Kapitlet redogör för den empiri som samlats in genom vår enkätundersökning och de åtta djupintervjuerna. Slutsats: Undersökningen visar att konsumenternas attityd till reklam på Snapchat är positiv. Anledningen till detta är att reklamen på Snapchat är frivillig. Genom underhållande och trovärdig reklam ökar konsumenternas positiva attityd. Nyckelord: Snapchat, Attityd, Push & Pull, Integritet, Sociala medier, Reklam

Tese de mestrado integrado. Engenharia Mecânica. Faculdade de Engenharia. Universidade do Porto. 2010