Dissertations / Theses: 'Transition voltage'

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Choi, Jae-Young. "Analysis of Inductor-Coupled Zero-Voltage-Transition Converters." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/28537.

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As is the case for DC-DC converters, multi-phase converters require both high-quality power control and high power-density. Although a higher switching frequency not only improves the quality of the converter output but also decreases the size of the converter, it increases switching losses and electromagnetic interference (EMI) noise. Since the soft-switching topologies reduce the switching losses of the converter main switches, the topologies make converters partially independent from the switching frequency. However, the conventional soft-switching topologies have already proposed most of the possible ways to improve converter performance. In addition, the trends of the newly generated power devices reduce the advantages of soft-switching topologies. This critical situation surrounding soft-switching topologies gives research motivations: What features of soft-switching topologies facilitate their practical applications? Given this motivation, the dissertation discusses two aspects = simplifying auxiliary circuits and accounting for the effects of soft-switching operations on the converter control. Engineers working with medium- and high-power multi-phase converters require simplified soft-switching topologies that have the same level of performance as the conventional soft-switching topologies. This demand is the impetus behind one of the research objectives = simplifying the auxiliary circuits of Zero-Voltage-Transition (ZVT) inverters. Simplifying the auxiliary circuits results in both a smaller number of and lower cost for auxiliary components, without any negative impact on performance. This dissertation proposes two major concepts for the simplification - the Single-Switch Single-Leg (S3L) ZVT cell and the Phase-Lock (PL) concept. Throughout an effort to eliminate circulating currents of inductor-coupled (IC) ZVT converters, the S3L ZVT cell is developed. The proposed cell allows a single auxiliary switch to achieve zero-voltage conditions for both the top and bottom main switches, and it achieves the same level of performance as the conventional ZVT cell, as well. This proposal makes IC ZVT topologies more attractive to multi-phase converter applications. Because all of the top main switches generally have identical sequences for zero-voltage turn-on commutations, one auxiliary switch might handle the commutations of all of the top main switches. This possibility introduces the PL concept, which allows the two auxiliary switches to provide a zero-voltage condition for any main switch commutation. In order to compensate for restrictions of this concept, a modified space-vector modulation (SVM) scheme also is introduced. A soft-switching topology changes the duty ratios of the converter, which affects the controllability of the converter. Therefore, this dissertation selects resolution of this issue as one of the research objectives. This dissertation derives the generalized timing equations of ZVT operations, and the generalized equations formulize the effect of ZVT operation on both duty ratios and DC current. Moreover, the effect of SVM schemes is also investigated. An average model of the ZVT converter is developed using both the timing analysis and the investigation of SVM schemes, and small-signal analysis using the average model predicts the steady-state characteristics of the converter.
Ph. D.

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Ambatipudi, Ravindra. "Modeling and control of zero-voltage transition three-phase PWM boost rectifier." Thesis, This resource online, 1995. http://scholar.lib.vt.edu/theses/available/etd-06162009-063557/.

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Nose, Masafumi. "Studies on Sodium-containing Transition Metal Phosphates for Sodium-ion Batteries." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215565.

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Spitzig, Alyson. "The importance of Joule heating on the voltage-triggered insulator-to-metal transition in VO₂." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/62808.

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The large change in resistivity in the material VO₂ has attracted considerable attention since it was first discovered in 1959. Recently, the ability to trigger the insulator-to-metal transition (IMT) with a strong electric field has been observed, but there has been debate about whether the transition is due to field-effects. We apply a voltage bias across a VO₂ thin film via a conductive atomic force microscope (CAFM) tip and measure the resultant current. We observe the IMT as a jump in the measured current in the IV curves. We fit the IV curves to the Poole-Frenkel (PF) conduction mechanism in the insulating state, immediately preceding the IMT. The PF conduction mechanism describes the thermal excitation of electrons into the conduction band in insulators, facilitated by strong electric fields. The PF mechanism is temperature dependent, and we use the temperature dependence to calculate the local temperature of the film before the transition. We directly compare the local electric field and local temperature of the film immediately preceding the IMT. We determine that the transition is not solely due to the applied electric field, but rather that the tip has locally warmed the film close to its IMT temperature through Joule heating.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

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Cuadros, O. Carlos E. "Modified Space Vector Modulation for a Zero-Voltage Transition Three-Phase to DC Bi-directional Converter." Thesis, Virginia Tech, 1995. http://hdl.handle.net/10919/36712.

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A modified space vector modulation algorithm for a zero-voltage transition three-phase voltage source inverter/boost rectifier is presented. The converter is intended for high performance medium power applications requiring bi-directional power flow. The proposed modified space vector modulation allows the main switches to be operated with constant frequency and soft switching for any phase shift between the three-phase currents and voltages. The modulation algorithm also eliminates any low frequency distortion caused by the zero-voltage transition and can be extended to other soft-switching PWM three-phase converters. Experimental verification of the proposed algorithm is also presented as well as a comparison to the hard switched PWM converter.
Master of Science

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Wu, T. H. "Optimising cell voltage and understanding charge storage mechanism of transition metal oxides and hydroxides for aqueous supercapacitors." Thesis, University of Liverpool, 2016. http://livrepository.liverpool.ac.uk/3002214/.

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This study focuses on aqueous electrochemical capacitors (ECs) for optimising the cell voltage and understanding the charge storage mechanism of transition metal oxides and hydroxides. The first part discusses how to optimise cell voltage of symmetric and asymmetric ECs. In Chapter 4, a commercial activated carbon (ACS–679) was employed as an electroactive material to demonstrate the necessity of charge–balanced condition of aqueous symmetric ECs in order to improve the utilisation of electrochemically stable potential window of electroactive material. Besides, the effect of stable open–circuit potential on electroactive materials is also addressed here. The concept is on the basis of electrochemical charge–balance principle, therefore, it is believed to be applicable to all the symmetric ECs no matter what kind of material is used as electroactive material. The charge–balanced electric double–layer capacitors (EDLCs) was assembled to evaluate the acceptable cell voltage by means of electrochemical analyses, including cyclic voltammogram, constant current charge–discharge, electrochemical impedance spectroscopy and inductance–capacitance–resistance meter measurements. Moreover, charge–unbalanced EDLCs were used to demonstrate the necessity of charge balance in symmetric ECs since those exhibit lower cell voltage and specific energy compared with the charge–balanced case. Similarly, in Chapter 5, asymmetric ECs consisting of reduce graphene oxide and manganese oxide (RGO//MnOx) were employed as an example to establish criteria for determining the highest acceptable cell voltage of asymmetric ECs with excellent reversibility and capacitor−like behaviour. It is very useful to evaluate the practical specific energy of asymmetric ECs by understanding the highest acceptable cell voltage. Besides, RGO//RuO2 was also demonstrated to verify the validity of the proposed criteria. The second part probes the charge storage mechanism of transition metal oxides and hydroxides in aqueous ECs. In Chapter 6, a wide–ranging study on electrochemical activation from Mn3O4 to MnO2 in 0.5 M Na2SO4 medium were presented, which includes in operando monitoring of the structural evolution during the activation process via in situ Raman microscopy. Other advanced material characterisation techniques, such as powder X–ray diffraction, X–ray photoelectron spectroscopy, scanning electron and transmission electron microscopy, were also applied to analyse the as–prepared and activated MnOx. Due to the structural disordering of electrochemically activated birnessite−MnO2 and residual Mn3O4, the charge storage is attributable to the redox reaction between Mn(III) and Mn(IV) at outer surface active sites, rather than cations and/or protons intercalation into layer structures. In Chapter 7, the redox behaviours of γ−NiOOH/α−Ni(OH)2 in various electrolytes (LiOH, NaOH, KOH, CsOH and NH4OH) are discussed. The charge storage mechanism of γ−NiOOH/α−Ni(OH)2 was studied by means of EQCM and in situ Raman microscopy. Moreover, the computational simulation (DFT+U) based on EQCM results gives a better idea on the compositional changes in the first few potential cycles. The insertion/removal of Li+ does not alter the content of water inside the structure, while the insertion of Na+ and K+ leads to a significant removal of water. The removed water molecules cannot be reversibly re−inserted back into the nickel structure, leading to the loss of water molecules in Ni(OH)2 structure during charge–discharge process. The capability to retain water molecules inside the Ni(OH)2 is crucial for the stability of γ−NiOOH/α−Ni(OH)2 redox reaction.

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Powers, Alex D. "A Study of Constant Voltage Anemometry Frequency Response." DigitalCommons@CalPoly, 2016. https://digitalcommons.calpoly.edu/theses/1570.

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The development of the constant voltage anemometer (CVA) for the boundary layer data system (BLDS) has been motivated by a need for the explicit autonomous measurement of velocity fluctuations in the boundary layer. The frequency response of a sensor operated by CVA has been studied analytically and experimentally. The thermal lag of the sensor is quantified by a time constant, MCVA. When the time constant is decreased, the half-amplitude cut-off frequency, fCVA, is increased, thereby decreasing the amount of attenuation during measurements. In this thesis, three main approaches have been outlined in theory and tested experimentally to determine the feasibility and effectiveness of implementing them with CVA to limit attenuation: operation at higher Vw, implementation of software compensation, and utilization of smaller diameter sensors. Operation of CVA at higher voltage results in little improvement in frequency response but is accompanied by increased danger of wire burnout. However, sensors do need to be operated at high wire voltages to be more sensitive to velocity fluctuations and less sensitive to temperature fluctuations, without reaching a temperature high enough for wire burnout. Software compensation of the CVA output has been shown not to be useful for measurements with BLDS. The electrical noise present in the CVA measurement system is amplified by the correction algorithm and creates measurements that are not representative of the fluctuations being measured. Decreasing sensor diameter leads to a significant decrease of MCVA and therefore increase of fCVA. Under similar operating conditions, a 2.5 micron diameter sensor showed less roll off in the frequency spectra (measured higher turbulence intensities) than a 3.8 micron diameter sensor for tests in both a turbulent jet and in a turbulent boundary layer. Smaller sensors are more fragile and have been shown to have a decrease in sensitivity as compared to larger sensors; however, for some applications, the increase in frequency response may be worth the trade-off with fragility and sensitivity.

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Ricoeur, Guillaume. "Caractérisations électriques et analyse de la méthode "Transition Voltage Spectroscopy" sur les jonctions moléculaires à base de molécules alkyles." Thesis, Lille 1, 2012. http://www.theses.fr/2012LIL10091/document.

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Nous avons évalué la méthode de "Transition Voltage Spectroscopy" (TVS) pour déterminer le niveau d'énergie des orbitales moléculaires impliquées dans le transport électronique (ou hauteur de barrière) à travers une jonction moléculaire (électrode-molécule-électrode). Pour cela, nous avons réalisé un grand nombre de jonctions moléculaires, avec des électrodes de différentes formes (goutte, pointe, couche) et de différents métaux (or, aluminium, mercure, gallium-indium). Nous utilisons pour la partie molécule des jonctions moléculaires des monocouches auto-organisées (SAM) réalisées avec différentes molécules alkyles. Nous montrons que la TVS pour les jonctions moléculaires sans oxyde aux interfaces électrode/molécule, donne des tensions de transition qui correspondent à la queue de la densité d’état des orbitales moléculaires, et non au sommet du pic de la densité d'état. Ce résultat a été obtenu en comparant les résultats TVS avec des mesures d'UPS et d'IPES réalisées sur les mêmes SAMs. Pour les jonctions moléculaires avec au moins une interface électrode/molécule oxydée, nous montrons que la tension de transition correspond au niveau d'énergie de l'oxyde à l’interface et non pas aux orbitales moléculaires de la SAM. Nous avons validé cette hypothèse grâce à des mesures de référence sur des jonctions sans SAM. Nous avons également comparé la TVS avec d'autres méthodes comme le modèle de Simmons, et nous avons étudié l'influence sur la TVS de différents paramètres : la force d'appui par C-AFM, l'asymétrie/symétrie de la jonction et la longueur des molécules
We assess the performances of the transition voltage spectroscopy (TVS) method to determine the energies of the molecular orbitals involved in the electronic transport (barrier height) through molecular junctions (electrode-molecule-electrode). For this, we made a large number of molecular junctions with electrodes of various shapes (drop, tip, layer) and various metals (gold, aluminum, mercury, gallium-indium). We use for the molecule part of the molecular jonctions self-assembled monolayers (SAMs) made with various alkyl molecules. We show that the transition voltages obtained by TVS for molecular junctions without oxide at the interfaces electrode / molecule correspond to the tail of the density of states of the molecular orbitals, and not to the top of the density of states. This result was obtained by comparing the TVS results with UPS and IPES measurements performed on the same SAM. In the case of molecular junctions with at least one electrode/molecule interface oxidized, we show that the transition voltage corresponds to the energy level of the oxide at the interface and not to the molecular orbital of the SAM. We validated this hypothesis with reference measurements on junctions without SAM. We also compared the TVS with other methods e.g. the Simmons model, and we studied the influence on TVS of various parameters: loading force by C-AFM, junction asymmetry/symmetry and molecule length

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Weerasinghe, Hasitha C. "Electrical characterization of metal-to-insulator transition in iron silicide thin films on sillicone substrates." [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001677.

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Jacquet, Quentin. "Li-rich Li3MO4 model compounds for deciphering capacity and voltage aspects in anionic redox materials." Electronic Thesis or Diss., Sorbonne université, 2018. http://www.theses.fr/2018SORUS332.

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Le réchauffement climatique, provoqué par l’augmentation de la concentration de CO2 dans l’atmosphère, est un problème majeur du 21ème siècle. C’est pourquoi, il est d’une importance capitale de valoriser l’utilisation des énergies renouvelables et des technologies de stockage d’énergie telles que les batteries Li-ion. Suivant ce but, les chercheurs ont mis au point un nouveau matériau d’électrode, le Li-rich NMC, dont l’utilisation permet d’augmenter significativement la capacité des batteries Li-ion grâce à la participation des oxygènes de l’oxyde dans la réaction électrochimique. Cependant, ce nouveau phénomène va de pair avec une hystérésis de potentiel qui empêche la commercialisation du Li-rich NMC. Afin de proposer une solution à l’hystérésis de potentiel tout en continuant à augmenter la capacité des électrodes, des études fondamentales sont nécessaires, notamment: la redox anionique a-t-elle une limite de capacité ? et, quelle est l’origine de l’hystérésis ? Pour répondre à la première question, nous avons conçu des matériaux, de composition chimique A3MO4 (A étant du Li ou Na, et M un mix de Ru, Sb, Nb, Ta ou Ir), ayant une redox anionique exacerbée. Après avoir caractérisé la structure de ces nouveaux matériaux, nous avons étudié leur mécanisme électrochimique et montré que la redox anionique est limitée par la décomposition de l’électrode via formation de O2 ou dissolution. Dans un second temps, par l’étude de deux nouveaux matériaux, Li1.3Ni0.27Ta0.43O2 et Li1.3Mn0.4Ta0.3O2 ayant des hystérésis de potentiel très différentes, nous avons montré le lien entre la redox anionique, la taille de la bande interdite, et l’hystérésis de potentiel
Global warming, due to the increasing CO2 concentration in the atmosphere, is a major issue of the 21th century, hence the need to move towards the use of renewable energies and the development of electrical storage devices, such as Li-ion batteries. Along that line, a new electrode material called Li-rich NMCs have been developed, having higher capacity, 290 mAh/g, than commercial materials, like LiCoO2 (150 mAh/g), thanks to participation of oxygen anions into the redox reaction. This process, called anionic redox, unfortunately comes with voltage hysteresis preventing the commercialization of Li-rich NMC. To alleviate this issue while increasing the capacity, fundamental understanding on anionic redox is needed, specifically concerning two points: is anionic redox limited in terms of capacity? And what is the origin of the voltage hysteresis? In a first part, with the aim to assess the limit of anionic redox capacity, we designed new compounds, having enhanced oxygen oxidation behavior, belonging to the A3MO4 family (A being Li or Na and with M a mix of Ru, Ir, Nb, Sb or Ta). We performed their synthesis, deeply characterized their structure, and, by studying their charge compensation mechanism, we showed that anionic redox is always limited by either O2 release or metal dissolution. In a second part, we designed two new materials, Li1.3Ni0.27Ta0.43O2 and Li1.3Mn0.4Ta0.3O2, having different voltage hysteresis, in order to identify the origin of this phenomenon. Coupling spectroscopic techniques with theoretical calculations, we suggest that the electronic structure, namely the size of the charge transfer band gap, plays a decisive role in voltage hysteresis

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Bon, Emeline. "Implication de la sous-unité B4 des canaux sodiques dépendants du voltage dans l'invasivité des cellules cancéreuses mammaires et régulation de son expression par l'acide docosahexaènoïque." Thesis, Tours, 2015. http://www.theses.fr/2015TOUR3310/document.

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La perte de l’expression de la sous-unité β4 des canaux sodiques dépendants du voltage NaV dans les tumeurs mammaires est associée à un grade cancéreux élevé et au développement des métastases. L’extinction de son expression dans les cellules MDA-MB-231 augmente de plus de deux fois leur invasivité. Au cours de cette thèse, nous avons montré que la sous-expression de β4 favorise la transition mésenchymato-amoeboïde et augmente l’invasion cancéreuse indépendante de NaV. Cette transition se caractérise par l’acquisition d’une morphologie plus arrondie, par la présence de blebs à la surface cellulaire et par une augmentation de l’activité RhoA-GTPase. Cette transition est inhibée par la surexpression du domaine intracellulaire C-terminal de la sousunité β4. L’expression de β4 peut être augmentée par un apport en acide docosahexaènoïque (22:6n-3), qui augmente l’activité du promoteur de son gène SCN4B. Le DHA augmente également l’expression de β4 en modulant l’expression des récepteurs nucléaires PPAR, sensibles aux lipides
The loss of voltage gated sodium channel NaVβ4 subunit expression in breast cancer biopsies is associated with high grade tumors and metastatic development. The inhibition of β4 expression in MDA-MB-231 breast cancer cells enhanced their invasiveness by two fold. During this thesis, we have shown that β4 underexpression promotes mesenchymal-amoeboid transition and increases NaV-independent invasion. This transition is characterized by rounded morphology, the presence of blebs at the cell surface and an increased RhoAGTPase activity. This transition is inhibited by β4 C-terminal intracellular domain overexpression. Expression of β4 can be enhanced by a DHA supplementation that increases the encoding SCN4B promoter activity. DHA also increases β4 expression through the modulation of PPARs lipid-sensitive nuclear receptors expression

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Dong, Wei. "Analysis and Evaluation of Soft-switching Inverter Techniques in Electric Vehicle Applications." Diss., Virginia Tech, 2003. http://hdl.handle.net/10919/28859.

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This dissertation presents the systematic analysis and the critical assessment of the AC side soft-switching inverters in electric vehicle (EV) applications. Although numerous soft-switching inverter techniques were claimed to improve the inverter performance, compared with the conventional hard-switching inverter, there is the lack of comprehensive investigations of analyzing and evaluating the performance of soft-switching inverters. Starting with an efficiency comparison of a variety of the soft-switching inverters using analytical calculation, the dissertation first reveals the effects of the auxiliary circuit's operation and control on the loss reduction. Three types of soft-switching inverters realizing the zero-voltage-transition (ZVT) or zero-current-transition (ZCT) operation are identified to achieve high efficiency operation. Then one hard-switching inverter and the chosen soft-switching inverters are designed and implemented with the 55 kW power rating for the small duty EV application. The experimental evaluations on the dynamometer provide the accurate description of the performance of the soft-switching inverters in terms of the loss reductions, the electromagnetic interference (EMI) noise, the total harmonic distortion (THD) and the control complexity. An analysis of the harmonic distortion caused by short pulses is presented and a space vector modulation scheme is proposed to alleviate the effect. To effectively analyze the soft-switching inverters' performance, a simulation based electrical modeling methodology is developed. Not only it extends the EMI noise analysis to the higher frequency region, but also predicts the stress and the switching losses accurately. Three major modeling tasks are accomplished. First, to address the issues of complicated existing scheme, a new parameter extraction scheme is proposed to establish the physics-based IGBT model. Second, the impedance based measurement method is developed to derive the internal parasitic parameters of the half-bridge modules. Third, the finite element analysis software is used to develop the model for the laminated bus bar including the coupling effects of different phases. Experimental results from the single-leg operation and the three-phase inverter operation verify the effectiveness of the presented systematic electrical modeling approach. With the analytical tools verified by the testing results, the performance analysis is further extended to different power ratings and different bus voltage designs.
Ph. D.

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Murphy, Ryan. "Development of an Autonomous Single-Point Calibration for a Constant Voltage Hot-Wire Anemometer." DigitalCommons@CalPoly, 2015. https://digitalcommons.calpoly.edu/theses/1357.

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Traditionally, the measurement of turbulence has been conducted using hot-wire anemometry. This thesis presents the implementation of a constant voltage hot-wire anemometer for use with the Boundary Layer Data System (BLDS). A hot-wire calibration apparatus has been developed that is capable of operation inside a vacuum chamber and flow speeds up to 50 m/s. Hot-wires operated with a constant-voltage anemometer (CVA) were calibrated at absolute static pressures down to 26 kPa. A thermal/electrical model for a hot-wire and the CVA circuit successfully predicted the measured CVA output voltage trend at reduced pressure environments; however, better results were obtained when the Nusselt number was increased. A calibration approach that required only one measured flow speed was developed to allow autonomous calibrations of a CVA hot-wire. The single-point calibration approach was evaluated through comparison with the experimental data from the vacuum chamber over a range of 14-50 m/s and at pressures from 26 to 100 kPa. The thermal-electrical model was used to make predictions of CVA output voltage and the corresponding flow speed for conditions that could not be replicated within a laboratory. The first set of predictions were made for conditions from 7.5 to 100 kPa, at a constant temperature of 25⁰C, within a flight speed range of 40 to 150 m/s. Single-point calibrations were developed from these predictions. Additionally, the thermal-electrical model was used to predict hot-wire response for a change in temperature of 25⁰C at 26 kPa and the single-point calibration developed for the pressure range 7.5 to 100 kPa was tested for its ability to adjust. The temperature variation at a single pressure of 26 kPa proved that the single-point function was capable of adapting to off-standard temperatures with the largest deviations of +/- 7% in the mid-range velocities. With a temperature drop, the deviations were below 5%. The second set of thermal-electrical predictions involved conditions for altitude from 0 to 18 km at flow speeds from 40 to 150 m/s. A single-point calibration was developed for altitude conditions. Furthermore, to test the single-point calibration the thermal-electrical model was used to predict hot-re response for a temperature variation of 25⁰C at 18 km. The single-point calibration developed for altitude proved that it was capable of adjusting to a temperature variation of 25⁰C with maximum deviations of about 5% at mid-range velocities. It is proposed that the single-point calibration approach could be employed for CVA measurements with the Boundary Layer Data System (BLDS) to allow hot-wire data to be acquired autonomously during flight tests.

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Boukadoum, Redouane. "Étude des décharges partielles et de leur transition à l’arc dans la connectique aéronautique du futur." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLC019/document.

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Dans le cadre du projet d’avion plus électrique entamé depuis quelques années, l’objectif visé est le remplacement des énergies hydraulique et pneumatique par l’énergie électrique. Cette transition technologique drastique nécessite une augmentation de puissance électrique à bord des avions, qui se traduit par une élévation des niveaux de tension du réseau embarqué (+/- 270 VDC et 230 VAC). Dans ces conditions, les phénomènes de décharges électriques doivent être considérés, en particulier pour les systèmes présents dans les zones non pressurisées des appareils. Les travaux de thèse ont porté sur l’étude des décharges partielles dans des connecteurs aéronautiques aujourd’hui exploités et susceptibles d’être mis en oeuvre dans les nouvelles conditions de tension. Une modélisation électrostatique du connecteur a été effectuée dans le but de mettre en évidence les zones où règne un fort champ électrique pouvant être à l’origine de l’apparition de décharges partielles. L’influence de paramètres, tels que la géométrie des conducteurs, la pression et la température, a été examinée d’un point de vue théorique par adaptation de la courbe de Paschen. Des mesures expérimentales, effectuées dans différentes conditions d’alimentation électrique, de pression, de température et d’état de vieillissement des connecteurs, ont permis de déterminer les tensions seuil d’apparition des décharges partielles. Ces mesures ont également permis de localiser les décharges au sein du connecteur, et ainsi d’identifier les points faibles de la structure. Des solutions visant à repousser les seuils d’apparition de décharges partielles sont alors proposées
The objective of the more electrical aircraft project is the replacement certain of the hydraulic and pneumatic systems by electrical ones. This drastic technological transition will require the increase of the onboard electrical power, which will result in the increase of voltage levels of the embedded networks. Current systems of 28 VDC and 115 VAC (400 Hz) are to be replaced by +/- 270 VDC and 230 VAC (360 to 1000 Hz). These new conditions of voltage levels will have a significant impact on the appearance of partial discharges that were almost absent up until present. Aeronautical grade electrical connectors being one of the major elements of embedded networks, the aim of this thesis is to study the conditions of occurrence of partial discharges in them. In this work, electrostatic modeling is carried out in order to identify the zones within the connectors where there is a strong electric field facilitating the appearance of partial discharges. Also presented are the results of experiments under both DC and AC voltage in which the ignition voltages of partial discharges and their location within the structure of the connector were studied

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Oliveira, Antônio Wanderley de. "Transporte de portadores minoritários que justificam o regime de ressonância eletrônica em sistemas de carbynes." Universidade Federal do Pará, 2016. http://hdl.handle.net/11612/469.

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Uma das metas para a expansão do conhecimento em eletrônica molecular pode ser encontrada no projeto relacionado com a criação de circuitos em nanoescala com base em características de corrente-tensão não lineares, composto por moléculas ligadas a eletrodos metálicos sob a ação de um campo elétrico externo. O desenvolvimento de dispositivos eletrônicos moleculares que utilizam sistemas exibindo recursos semelhantes como materiais semicondutores intrínsecos é uma das metas a serem atingidas por uma extensa pesquisa em nanotecnologia. Assim, este trabalho tem como objetivo a expansão do conhecimento não só do transporte eletrônico, mas também as características físicas que justificam o regime de ressonância para o transporte eletrônico, como a condutância e Espectroscopia de Voltagem de Transição. Foi investigado teoricamente o transporte de carga eletrônica em um sistema molecular composto por estruturas de carbyne levando em conta as variações nos tipos de ligações −≡− (ligações simples e triplas para cada carbono). Os cálculos e aproximações ab initio são realizados para investigar a distribuição de estados de elétrons através da molécula na presença de um campo elétrico externo. Este novo dispositivo nanoeletrônico suscitará vantagem para o projeto de grandes circuitos orgânicos/metálicos híbridos 1D com um aumento do fluxo eletrônico que é importante para as necessidades da nanotecnologia.
One of the goals for the expansion of knowledge in molecular electronics may be found in the Project related to the creation of nanoscale circuits based on nonlinear current–voltage characteristics composed by molecules connected to metallic electrodes under the action of an external electric field. The development of molecular electronic devices using systems exhibiting similar feature as intrinsic semiconductor materials is one of the goals to be achieved by an extensive research in nanotechnology. Thus, this work aims at expanding of knowledge not only of the electronic transport, but also the physical features that justify the resonant regime for electronic transport, such as conductance and Transition Voltage Spectroscopy. We theoretically investigate the electronic charge transport in a molecular system composed by carbyne structures taking into account the variations in the bonds −≡− type (simple and triple bonds for each carbon). Ab initio calculations approximations are performed to investigate the distribution of electron states over the molecule in the presence of an external electric field. This new nanoelectronic device raise up advantage for the design of large 1D hybrid organic/metallic circuits with an increased electronic flow that is importante for the needs of nanotechnology.

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Kinn, M. C. "An analysis of the sociotechnical transition process from the existing centralised alternating current voltage electrical system in the UK to one where distributed direct current voltage is used to meet the energy needs of the built environment." Thesis, University of Salford, 2016. http://usir.salford.ac.uk/40962/.

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This study concerns the potential sociotechnical transition of the current UK centralised alternating current (AC) electricity system to one where distributed direct current (DC) systems may proliferate. The development of the new distributed DC system has the potential to address a number of global challenges including the UN’s 17 Sustainability Challenges, particularly in terms of city and disaster resilience, energy security and energy independence. With the development of renewables and small-scale storage, among other technologies, this transition becomes a technical possibility. As transitions theory identifies energy systems as sociotechnical, transitions are a complex and people-centred process, an issue that has been identified that creates barriers to technical transitions. The multi-level perspective (MLP) is used as the theoretical framework and its applicability for future transitions is considered. The research proposes a “bottom-up” approach, focused on the demand side within the built environment, to avoid the transition developing into a wicked problem. Using a mixture of primary interview data, analysed using thematic analysis, supported by data, from published academic and industry/governmental literature, a multi-method case study approach is used to develop a transitions model between the “as is” state and the potential future state with DC systems. Also identified were the institutions within the social and technical networks of the electricity regime, barriers and enablers to the transition, boundary points between the networks and the structurations of institutions within these networks. Key findings are a lack of interdisciplinary thinking among different academic disciplines, a lack of DC standards and home appliances, and that DC is in focus for the office rather than the home. Knowledge dissemination especially via education, government procurement and energy policy, and the importance of independence from the market are key components for a successful proliferation. A conundrum connecting renewable generation, the carbon debate and energy policy, is identified. With a deeper understanding of the regime, landscape and with a multi-systems approach, a tentative solution is provided. Contributions to knowledge are: the transitions model; the sociotechnical characterisation of the electricity system; a better understanding of how liability, living standards, disaster risk reduction and city resilience can be impacted by failure chains associated with power cuts; and a deeper understanding of the MLP model.

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Jarecki, Brian W. "GATING OF THE SENSORY NEURONAL VOLTAGE-GATED SODIUM CHANNEL NAv1.7: ANALYSIS OF THE ROLE OF D3 AND D4 / S4-S5 LINKERS IN TRANSITION TO AN INACTIVATED STATE." Thesis, Connect to resource online, 2010. http://hdl.handle.net/1805/2119.

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Thesis (Ph.D.)--Indiana University, 2010.
Title from screen (viewed on April 1, 2010). Department of Pharmacology and Toxicology, Indiana University-Purdue University Indianapolis (IUPUI). Advisor(s): Theodore R. Cummins, Grant D. Nicol, Gerry S. Oxford, Andy Hudmon, John H. Schild. Includes vitae. Includes bibliographical references (leaves 232-266).

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Yu, Huijie. "Driver Based Soft Switch for Pulse-Width-Modulated Power Converters." Diss., Virginia Tech, 2005. http://hdl.handle.net/10919/26399.

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The work in this dissertation presents the first attempt in the literature to propose the concept of â soft switchâ . The goal of â soft switchâ is to develop a standard PWM switch cell with built-in adaptive soft switching capabilities. Just like a regular switch, only one PWM signal is needed to drive the soft switch under soft switching condition. The core technique in soft switch development is a built-in adaptive soft switching circuit with minimized circulation energy. The necessity of minimizing circulation energy is first analyzed. The design and implementation of a universal controller for implementation of variable timing control to minimize circulation energy is presented. The controller has been tested successfully with three different soft switching inverters for electric vehicles application in the Partnership for a New Generation Vehicles (PNGV) project. To simplify the control, several methods to achieve soft switching with fixed timing control are proposed by analyzing a family of zero-voltage switching converters. The driver based soft switch concept was originated from development of a base driver circuit for current driven bipolar junction transistor (BJT). A new insulated-gate-bipolar-transistor (IGBT) and power metal-oxide-semiconductor field-effect-transistor (MOSFET) gated transistor (IMGT) base drive structure was initially proposed for a high power SiC BJT. The proposed base drive method drives SiC BJTs in a way similar to a Darlington transistor. With some modification, a new base driver structure can adaptively achieve zero voltage turn-on for BJT at all load current range with one single gate. The proposed gate driver based soft switching method is verified by experimental test with both Si and SiC BJT. The idea is then broadened for â soft switchâ implementation. The whole soft switched BJT (SSBJT) structure behaves like a voltage-driven soft switch. The new structure has potentially inherent soft transition property with reduced stress and switching loss. The basic concept of the current driven soft switch is then extended to a voltage-driven device such as IGBT and MOSFET. The key feature and requirement of the soft switch is outlined. A new coupled inductor based soft switching cell is proposed. The proposed zero-voltage-transition (ZVT) cell serves as a good candidate for the development of soft switch. The â Equivalent Inductorâ and state plane based analysis method are used to simply the analysis of coupled inductor based zero-voltage switching scheme. With the proposed analysis method, the operational property of the ZVT cell can be identified without solving complicated differential equations. Detailed analysis and design is proposed for a 3kW boost converter example. With the proposed soft switch design, the boost converter can achieve up to 98.9% efficiency over a wide operation range with a single gate drive. A high power inverter with coupled inductor scheme is also designed with simple control compared to the earlier implementation. A family of soft-switching converters using the proposed â soft switchâ cell can be developed by replacing the conventional PWM switch with the proposed soft switch.
Ph. D.

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19

Albrecht, Martin. "Enabling socio-technical transitions – electric vehicles and high voltage electricity grids as focal points of low emission futures." Licentiate thesis, KTH, Miljöstrategisk analys (fms), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-206973.

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Today humankind is facing numerous sustainability challenges that require us to question CO2 intensive practices like those present in the transport and energy sector. To meet those challenges, many countries have adopted ambitious climate targets. Achieving such targets requires an understanding of the wider socio-technical context of transitions. The aim of this licentiate thesis is therefore to analyse such socio-technical transitions towards low-emission futures enabled by the electrification of passenger cars and high voltage grid development. A combination of different transitions theories (for ex. Multi-level perspective and Technological innovation systems) and institutional theory has been used. To reach the aim paper I analyses the climate impacts of electric vehicles (EVs) and policy measures to achieve a breakthrough scenario for EVs. The results show that a mixture of short and long term policies are needed that take into account the technology development stage and behavioural aspects of EV adopters. Paper II addresses the need to include the high voltage transmission grid and its planning procedures as a central part of debates on transitions. Therefore the opportunities, challenges and reasons for conflict in the established regime are studied. The results show that in order to achieve a sustainable grid development regime, it is necessary to spend time on achieving legitimacy and social sustainability. The third paper uses semi-structured expert interviews and focuses on innovation dynamics for EV adoption. By focusing on dynamics instead of single policy measures, it is possible to grasp interactions within a niche, but also in between a niche, regime and landscape. The results show that strong initial technology legitimacy was needed to start substantial innovation dynamics. This could be further strengthened with a strong and broad coalition of actors. Both those factors led, if present, to an improved variety and match of policy instruments. As such this thesis has shown that transitions are not just about technology or policy instruments as such but about the dynamics and processes needed to enable them. This can be relevant in other transitions that otherwise may underestimate the importance of these components.

QC 20170512

Norstrat

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Clements, Joseph Shelby II. "Synthesis of Insecticidal Mono- and Diacylhydrazines for Disruption of K+ Voltage-Gated Channels, and Elucidation of Regiochemistry and Conformational Isomerism by NMR Spectroscopy and Computation." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77918.

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Based on the success of diacyl-tert-butylhydrazines RH-5849 and RH-1266 in controlling agricultural crop pests, we endeavored to synthesize our own diacylbenzyl- and arylhydrazine derivatives for use against the malaria vector Anopheles gambiae. In the process of producing a library of compounds for assay against An. gambiae, it became clear that employing regioselective acylation techniques (in molecules that feature two nucleophilic, acyclic nitrogen atoms α to one another) would be imperative. Synthesis of the library derivatives proceeded rapidly and after topical assay, we found three compounds that were more toxic than the RH-series leads. One of the three displayed an LD50 value of half that of RH-1266, though patch clamp assay concluded that toxicity was not necessarily linked to inhibition of mosquito K+ channel Kv2.1. The acylation of monoarylhydrazines appears simple, but its regioselectivity is poorly understood when assumed as a function of basicity correlating to nucleophilic strength. We determined the ratio of the rate constants for distal to proximal N-acylation using 19F NMR spectroscopic analysis of reactions of 4-fluorophenylhydrazine with limiting (0.2 equiv) acylating agent in the presence of various bases. Acid anhydrides gave consistent preference for distal acylation. The selectivity of acylation by acyl chlorides when using pyridine gives strong distal preference, whereas use of triethylamine or aqueous base in conjunction with aroyl chlorides showed a moderate preference for proximal acylation. This observation yielded a convenient one-step method to synthesize proximal aroylarylhydrazines in yields comparable or superior to that provided by the standard three-step literature approach. Combined with NMR evidence of the distal nitrogen as the unambigiously stronger base of the two nitrogens, we propose a single electron transfer mechanism that predicts the regiochemistry of arylhydrazines toward acylating agents better than the nucleophilicity model based on pKa values. While synthesizing the acylhydrazine library for assay against An. gambiae, NMR spectroscopy revealed rotational isomerisms of two types: chiral helicity (M)/(P) and acyl (E)/(Z)-isomerism due to hindered rotation. Variable temperature NMR allowed the measurement of N-N bond rotational barriers, as well as estimate the barrier of (E)/(Z) interconversion. We obtained the X-ray crystal structures of four diacylhydrazines to test this hypothesis and revealed both the twist conformation around the N-N bond axis and (E)/(Z)-isomerism around the proximal acyl group. Computation (which agreed with the crystal structures) allowed us to estimate which (E)/(Z)-isomers were most likely being observed in solution at room temperature by NMR spectroscopy. In addition, we were able to calculate transition structures corresponding to N-N bond rotational barriers of (E,Z)- and (Z,Z)-isomers of model molecules and rationalize the difference in coalescence temperatures between (E,Z)- and (Z,Z)-isomers.
Ph. D.

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Appel, Daniel. "Optimalizácia návrhu spínaného regulovateľného DC-DC konvertora." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242181.

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The main goal of this project was an optimization of DC-DC converter design from company Meatest with regards to its efficiency, minimalizing power loses and radiated electromagnetic inference, while maintaining its price on reasonable level. The first part of this paper is introduction to the most common converter topologies. In the second part, design and optimization of converter are discussed. The third part is about measurement automatization in Simple. Measurements of converter prototype can be found in fourth part.

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Hering, Maria. "Überschlagsverhalten von Gas-Feststoff-Isoliersystemen unter Gleichspannungsbelastung." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-200879.

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Gasisolierte Systeme im Gleichspannungsbetrieb vereinen für Anwendungen moderner Energieübertragung die Forderungen nach kleinräumigen Anlagen und verlustarmem Energietransport über große Entfernungen. Für einen zuverlässigen und sicheren Betrieb muss das Verhalten der eingesetzten Gas-Feststoff-Isolierung im technologischen System bis an die Grenzen des Isolationsvermögens bekannt sein. Gegenstand der vorliegenden Arbeit ist deshalb das Überschlagsverhalten von Gas-Feststoff-Isoliersystemen unter Gleichspannungsbelastung. Dabei stehen zwei wesentliche Einflussfaktoren im Vordergrund: die Temperatur, motiviert durch reale Stromwärmeverluste, und eine feste Störstelle auf der Gas-Feststoff-Grenzfläche, motiviert durch in der Praxis nicht völlig auszuschließende, metallische Partikel. Die Effekte dieser beiden Parameter auf die Feldverteilung, die Oberflächen- und Raumladungsbildung sowie das Isolationsvermögen bei Gleichspannung werden zunächst in zwei Versuchsanordnungen separat experimentell untersucht. Anschließend wird deren Zusammenwirken und gegenseitige Beeinflussung im Gesamtsystem analysiert. Die betriebsbedingte Erwärmung der Leiter gasisolierter Systeme führt zu einer inhomogenen Temperaturverteilung, die sich auf die Eigenschaften der Isolierstoffe Gas und Epoxidharz auswirkt. Die von der Temperatur abhängige Leitfähigkeit der Feststoffisolatoren führt zu einer temperaturabhängigen Feldverteilung, bei der sich der Ort der Höchstfeldstärke verschiebt. Dabei kann sich der Absolutwert der Höchstfeldstärke erhöhen und somit das Isolationsvermögen verringern. Gleichzeitig weist das Isoliergas nahe des erwärmten Leiters lokal eine geringere Dichte und damit eine geringere dielektrische Festigkeit auf. Die thermisch bedingte Minderung des Isolationsvermögens bei Gleichspannung beträgt in der untersuchten Anordnung (25 ... 35) %. In den schwach inhomogenen Feldern gasisolierter Anlagen erweisen sich metallische Partikel auf Isolatoren ab drei Millimetern Länge als besonders kritisch. Bei einem Gasdruck unterhalb von 0,3 MPa setzen an den Partikelspitzen zum Teil bereits ab 50 % der Durchschlagsspannung ohne Partikel Teilentladungen ein, sodass die Koronastabilisierung zu einer vergleichsweise hohen Überschlagsspannung führt. Durch diese stabilen Glimmentladungen kann die Störstelle bei Gleichspannung durch die üblichen Detektionsverfahren jedoch nicht zweifelsfrei nachgewiesen werden. Oberhalb von 0,3 MPa treten vor dem Überschlag keine Teilentladungen auf. Aufgrund der fehlenden Koronastabilisierung kann die Isolationsfestigkeit durch einen erhöhten Gasdruck nicht oder nur stark unterproportional gesteigert werden. Die mit der Modellanordnung gewonnenen Erkenntnisse sind nachweislich auf Isolatoren kommerzieller Anlagen übertragbar. Das in der vorliegenden Arbeit untersuchte Überschlagsverhalten von Gas-Feststoff-Isoliersystemen unter Gleichspannungsbelastung wird maßgeblich durch die Temperaturverteilung und durch feste Störstellen auf der Grenzfläche beeinflusst. Oberflächen- und Raumladungen verändern das üblicherweise ohmsch-kapazitiv beschriebene Verhalten des Isolierstoffsystems bei Gleich- und Mischspannungsbelastung. Der Einfluss zusätzlicher Ladungsträger auf die stark temperaturabhängige Feldumbildung demonstriert, dass das Isoliergas in diesem Fall mit teilchendichte- und feldstärkeabhängigen Drift- und Diffusionsprozessen zur Modellierung des transienten Verhaltens von Gleichspannungssystemen berücksichtigt werden muss. Die Untersuchung des Systemverhaltens an den Grenzen des Isolationsvermögens ist wichtiger Bestandteil bei der Entwicklung innovativer Technologien der modernen Energieübertragung bei steigender Übertragungsleistung
DC operated gas-insulated systems combine the demand for space saving installations and lowloss energy transport over long distances for applications of recent energy transmission. In order to ensure a reliable and safe operation, the behaviour of the gas-solid insulation, which is used in the technological system, has to be known up to the limits of the insulation properties. Hence, this thesis deals with the flashover behaviour of gas-solid insulation systems under DC voltage stress. Thereby, it focuses on two main influence factors: the temperature, due to real current heat losses, and an adhesive defect on the gas-solid interface, due to metallic particles that cannot be fully excluded in practice. Firstly, it is investigated experimentally in two test arrangements, how each parameter separately affects the electrical field distribution, the surface and volume charge accumulation and the insulation performance under DC voltage stress. Following that, their interaction and mutual influence is analysed in the whole system. Due to operating currents, the heating of the conductors in gas-insulated systems causes an inhomogeneous temperature distribution, that affects the properties of the insulating materials gas and epoxy resin. The temperature-dependent conductivity of the solid insulators leads to a temperature-dependent field distribution. Thereby, the location of the highest field strength is shifted. Since the absolute value of the highest field strength can increase, the insulation performance can decrease. Simultaneously, the insulating gas close to the heated conductor locally has a lower gas density and therefore a lower dielectric strength. The thermal related reduction of the insulation performance under DC voltage stress amounts to (25 ... 35) % in the investigated arrangement. Metallic particles, with a length of more than three millimetres and adhering on spacers, turn out to be particularly critical in the weakly inhomogeneous field of gas-insulated systems. At pressures below 0,3 MPa, partial discharges at the particle tips partly ignite already at 50 %of the breakdown voltage without a particle. The corona stabilisation leads to a relatively high flashover voltage. However, due to these stable glow discharges under DC voltage stress, the defect can not be unequivocally proven by usual detection methods. Above 0,3 MPa, no partial discharges occur before the flashover. Due to the missing corona stabilisation, with a higher gas pressure, the insulation strength is not or only disproportionately low increasing. The findings gained with the model arrangement are evidently applicable to spacers of commercial installations. The flashover behaviour of gas-solid insulation systems under DC voltage stress, examined in this thesis, is influenced significantly by the temperature distribution and adhesive particles on the interface. Surface and volume charges change the generally resistive-capacitive described behaviour of the insulation system under DC and superimposed voltage stress. The influence of additional charge carriers on the strongly temperature-dependent field transition demonstrates, that in this case, the insulating gas with its drift and diffusion processes, depending on the particle density and the field strength, has to be considered, when modelling the transient behaviour of DC operated systems. Investigating the system behaviour to the limits of the insulation properties is a crucial element of developing innovative technologies of the modern energy transmission at increasing transmissions powers

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Girbino, Michael James. "Detecting Distribution-Level Voltage Anomalies by Monitoring State Transitions in Voltage Regulation Control Systems." Case Western Reserve University School of Graduate Studies / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=case1550483383962611.

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24

Rivera-Hernandez, Margarita. "Scanning tunnelling microscopy studies of liquid crystals." Thesis, University of Bristol, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389236.

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Ndoye, Mamadou Mustapha. "Contribution à l'étude du transistor bipolaire hyperfréquence sur puce de silicium." Bordeaux 1, 1997. http://www.theses.fr/1997BOR10682.

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Ce travail est une contribution à l'étude du transistor bipolaire hyperfréquence sur puce de silicium. Il présente tout d’abord deux méthodes originales permettant de réduire la Capacité extrinsèque Base-Collecteur, d'augmenter la tension de claquage Base-Collecteur, d'augmenter la tension Early VA, d'augmenter le gain en puissance maximal Gpmax et d'augmenter la fréquence de transition FT. Il présente ensuite un nouveau transistor, de structure hybride entre le NPN vertical et le NPN latéral, baptisé bipolaire-CLEV (à Collecteur Latéral-Emetteur Vertical). Ce travail est généralisable à d'autres technologies de transistors hyperfréquences telles que les transistors à substrats III-V ou les transistors à hétérojonctions
This work is a contribution to the study of the high-speed bipolar transistor on silicon chip. First, it presents two original methods allowing to reduce the Base-Collector extrinsic Capacitance, to increase the Base-Collector breakdown voltage, to increase the Voltage Early VA, to increase the maximum power gain Gpmax and to increase the transition frequency FT. Then, it presents a new transistor, hybrid structure between the vertical NPN and the lateral NPN, named bipolar-CLEV (lateral collector-vertical emitter). This study can be generalized to other high speed transistor technologies such as III-V substrate transistors or heterojunction transistors

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Festin, Örjan. "On the Zero and Low Field Vortex Dynamics : An Experimental Study of Type-II Superconductors." Doctoral thesis, Uppsala University, Department of Engineering Sciences, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3907.

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Dynamic properties of type-II superconductors have been experimentally studied in zero and low magnetic fields using SQUID magnetometry and I–V measurements.

In zero magnetic field close to the critical temperature, the physical properties of type-II superconductors are dominated by spontaneously created vortices. In three dimensions (3D) such vortices take the form of vortex loops and in two dimensions (2D) as vortex-antivortex pairs.

The 2D vortex dynamics has been probed using mutual inductance and flux noise measurements on YBa₂Cu₃O₇ (YBCO) and MgB₂ thin films in zero and low magnetic fields. In such measurements, information about vortex correlations is obtained through a temperature dependent characteristic frequency, below (above) which the vortex movements are uncorrelated (correlated). The results obtained in zero magnetic field indicate that sample heterogeneities influence the vortex physics and hinder the divergence of the vortex-antivortex correlation length.

In low magnetic fields the vortex dynamics is strongly dependent on the applied magnetic field and a power law dependence of the characteristic frequency with respect to the magnetic field is observed. The results indicate that there is a co-existence of thermally and field generated vortices.

The I–V characteristics of untwinned YBCO single crystals show that only a small broadening of the transition region influences the length scale over which the vortex movements are correlated. The dynamic and static critical exponents therefore exhibit values being larger in magnitude as compared to values predicted by relevant theoretical models. The results also suggest that the copper oxide planes in YBCO decouple slightly below the mean field critical temperature and hence, the system has a crossover from 3D to 2D behaviour as the temperature is increased.

From temperature dependent DC-magnetisation measurements performed on untwinned YBCO single crystals in weak applied fields, detailed information about the critical current density and the irreversibility line is obtained.

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Carbonell, Cortés Carla. "Customizing a low temperature system for microwave transmission measurements. Quantum transport in thin TiN films and nanostructures." Doctoral thesis, Universitat de Barcelona, 2012. http://hdl.handle.net/10803/83635.

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The work presented in this thesis consists of two distinct parts. The first years of my work focused on the development and improvement of a new equipment built to study magnetic and electrical properties, particularly applying microwaves in reflection and transmission conditions. The sample space in conventional cryostats with superconducting magnets is usually smaller than 10-mm-diameter. Our equipment consists of a hollow cylindrical cryostat having a 33-mm-diameter hole all along its vertical axis. These characteristics enable the measurement of large samples and the use of big resonant cavities to get to a wider microwave (MW) range, particularly in transmission measurements. The cryostat has a superconducting magnet made of a solenoid that applies a magnetic field from -5 T to 5 T, and a temperature controller that works in the range 1.8 - 300 K. The system is cooled down with nitrogen and helium and the temperature can be controlled with the precision required by each experiment using a heater and a needle valve. Different probes for a wide range of experiments in our cryostat have been developed in order to be as versatile as possible. Following this idea each one has been divided in two halves that can be combined as it is preferred in each experiment. Each probe is made of a 8-to-10-mm-diameter stainless steel tube that is used to protect and give some stiffness to the measuring device. A coaxial cable and different waveguides are added to these stainless steel jackets, so we end up having nine halves, four upper parts that can be combined with five lower parts. There are three waveguides working in the frequency ranges 33-50 GHz (WR22), 50-75 GHz (WR15) and 75-110 GHz (WR10), and a coaxial cable that maintains the fundamental mode at a frequency of 60 GHz. In the extra lower part a 16-pin Fischer connector is added at the bottom in order to be able to perform more resistance experiments. Once the probes have been built, they have been tested to make sure the system is able to reach high vacuum and to be cooled down. Problems found along the way have been solved and at the end all the probes work properly. Different sample holders have been designed and built according to the needs in each experiment. The system has been tested by reproducing experimental results with Mn12-acetate, as quantum tunneling and magnetic avalanches, and by obtaining new results on microwave transmission in thin TiN films. The second part of the thesis focuses on the measurements of thin TiN films in a dilution refrigerator working with a mixture of 3He and 4He that enables experiments at a few tens of millikelvins. The cryostat also contains a superconductor magnet which can apply a magnetic field up to 5 T. Low-temperature transport properties of nanoperforated superconducting TiN films have been experimentally studied. Resistance measurements have been performed in the critical region of the superconductor-insulator transition (SIT), applying the magnetic field perpendicular to the plane of the structure or the dc current through the sample. SIT is a transition from a superconductor to an insulator state by localizing the Cooper pairs. The evolution of the SIT with temperature, magnetic field and dc current has been investigated in detail. Characteristic parameters have been determined for as-cast thin films using the theory of quantum corrections to conductivity. Disorder-driven and field-induced SITs have been measured. Commensurability effects have been observed down to the lowest experimental temperature, and are emphasized in the more disordered samples. The SIT has been observed for a dc current applied across the sample as changes in the curvature at zero bias current. Experiments prove that electronic transport in the nanoperforated samples is mediated by Andreev conversion. Finally, the existence of the superinsulator state has been experimentally proved.
El treball que es presenta en aquesta tesi consta de dues parts ben diferenciades. La primera pretén el desenvolupament d’un equip experimental concebut per a l’estudi de propietats magnètiques i elèctriques en materials diversos i, en especial, el treball amb radiació de microones en condicions de reflexió i transmissió. La segona s’ha centrat en les mesures de transport d’una capa fina superconductora de nitrur de titani (TiN) de 5 nm de gruix en un criòstat de dilució.

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Masoud, Khalid Hasan. "Circuits and controls for grid-connected inverters." Thesis, Queensland University of Technology, 2002.

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Gürlek, Akif. "Zum Entladungsprozess der Spitze-Spitze-Elektrodenanordnung bei standardisierter und oszillierender Blitzspannung." Universitätsverlag Chemnitz, 2020. https://monarch.qucosa.de/id/qucosa%3A73246.

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Diese Dissertation widmet sich der Erfassung, Identifikation und Beschreibung von Entladungsprozessen, die an Überschlägen bei Blitzspannung auftreten. Es wird ein Messsystem entwickelt, welches die elektrischen und optischen Parameter der Entladungsprozesse an der Spitze-Spitze-Elektrodenanordnung bei standardisierter und oszillierender Blitzspannung mit hoher Empfindlichkeit und Synchronisationsgenauigkeit aufzeichnet. Mithilfe der Strommessungen und der fotografischen Aufzeichnungen von Entladungen können drei Phasen des Durchschlagprozesses identifiziert werden: In der Reihenfolge ihres Auftretens handelt es sich um die Streamerphase, die Kanalübergangsphase und die Kanalbildungsphase. Diese Phasen werden für die standardisierte und oszillierende Blitzspannung aufgezeigt, wobei Gemeinsamkeiten und Unterschiede herausgestellt werden. Anhand von statistischen Beschreibungen des Durchschlagverhaltens und des Entladungsverhaltens werden daraufhin Abhängigkeiten in den Entladungsprozessen abgeleitet.
This thesis is dedicated to the acquisition, identification and description of discharge processes, which occur under lightning impulse voltage. A measuring system has been developed that records the electrical and optical parameters of the discharge processes with a high sensitivity and synchronization accuracy on a rod-rod electrode arrangement under standardised and oscillated lightning impulse voltage. With the current measurements and the photographic records of discharges, three phases of the breakdown process can be identified. In order of their occurrence these are the streamer phase, the channel transition phase and the channel formation phase. These phases are shown for the standardised and oscillated lightning impulse voltage, whereby similarities and differences are presented in detail. Using statistical descriptions of the breakdown and the discharge behaviour, dependencies in the discharge process will be derived.

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Magnan, Romain. "Oxyde transparent conducteur de ZnO : V à partir d'une cible de nanoparticules : de l’ablation par laser pulsé à un procédé de décharge à barrière diélectrique double fréquence à pression atmosphérique Transparent and conductive vanadium doped zinc oxide thin films by pulsed laser deposition from different targets Atmospheric pressure dual RF-LF frequency discharge: Influence of LF voltage amplitude on the RF discharge behavior Atmospheric pressure dual RF-LF frequency discharge: transition from α to α-γ-mode." Thesis, Perpignan, 2020. http://www.theses.fr/2020PERP0008.

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Cette thèse en cotutelle entre la France et le Canada a pour objectif de développer une méthode innovante d’élaboration de couches minces nano-composites de ZnO:V, basée sur la mise en vol et le dépôt de nanoparticules (NPs) de ZnO :V par des Décharges à Barrière Diélectrique (DBDs) double fréquence. Cette méthode de dépôt vise à réduire le coût de production par l’utilisation de nanoparticules synthétisées par méthode sol-gel et de DBDs dans une configuration permettant le dépôt de couches minces en continu à pression atmosphérique. Les travaux se sont déroulés en trois phases :- L’étude des OTC obtenus par ablation laser à partir d’une cible de NPs de ZnO:V(1 %at.) et de cibles métalliques de ZnV. La résistivité la plus faible (4 x 10 4 Ω.cm) est observée pour les dépôt faits à 250 °C à partir d’une cible de Zn :V(3 %at.) alors que les meilleures propriétés optiques sont celles d’une couche mince quasi-amorphe obtenue à 20 °C à partir de la cible de NPs de ZnO:V. Ces couches minces présentent une transmission de 40% dans l’UV à 250 nm, 90% dans le visible et 80% dans le PIR à 2500 nm) avec une résistivité de 6 x 10-2 Ω.cm. - La recherche et l’optimisation d’une source plasma DBD pour mettre en vol des NPs de ZnO:V dans une configuration compatible avec le dépôt de couches minces contrôlées. La démarche a consisté à chercher à accroître le flux et l’énergie des ions à la cathode en appliquant, sur une des électrodes, une tension radiofréquence (5 MHz) qui génère une forte densité d’ions (~2 x 1011/cm3) et sur l’autre électrode une tension basse fréquence (50 kHz) afin de transporter les ions vers la cathode. La première étape a été de bien comprendre la physique de la DBD RF-BF en couplant la caractérisation optique de la décharge et la modélisation fluide 1D. Lorsque la tension BF augmente, la décharge initialement RF en régime α bascule en régime α-γ durant 1/5 du cycle BF. Les résultats montrent qu’en régime γ la décharge est auto-entretenue dans la gaine et le flux d’ions à la cathode est multiplié par un facteur 7 alors que leur énergie s’accroit d’un facteur 4. L’étude expérimentale montre que lorsqu’une cible de NPs interagit avec une DBD RF-BF, des NPs sont mises en vol.- La conception et le test d’une configuration de réacteur DBD comprenant 2 zones plasmas successives : la première pour mettre en vol les NPs d’une cible, la deuxième pour déposer les NPs sur un substrat. Cette dernière est basée sur une DBD double fréquence BF-BF obtenue par application d’une tension 50 kHz qui génère des électrons pour charger les NPs et une tension 1 kHz dont on sait qu’elle peut assurer le transport des NPs chargées du volume vers les surfaces. La faisabilité a été montrée par l’observation de NPs sur le substrat
This thesis jointly supervised by France and Canada aims to develop an innovative method for the development of thin nanocomposite layers of ZnO: V, based on the sputtering and deposition of ZnO: V nanoparticles (NPs) using Double Frequency Dielectric Barrier Discharges (DBDs). This deposition method aims to reduce the cost of production by using nanoparticles synthesized by the sol-gel method and DBD in a configuration allowing the deposition of thin films continuously at atmospheric pressure. The work took place in three phases:- The study of TCO obtained by pulsed laser deposition from a target of NPs of ZnO: V (1% at.) and metal targets of ZnV. The lowest resistivity (4 x 10-4 Ω.cm) is observed for the deposits made at 250 ° C from a Zn: V target (3% at.) While the best optical properties are those of a quasi-amorphous thin layer obtained at 20 ° C from the NPs target of ZnO: V. These thin films have a transmission of 40% in UV at 250 nm, 90% in the visible and 80% in the PIR at 2500 nm) with a resistivity of 6 x 10-2 Ω.cm.- Research and optimization of a DBD plasma source to sputter ZnO: V NPs in a configuration compatible with the deposition of controlled thin films. The approach consisted in increase the flow and energy of the ions at the cathode by applying, on one of the electrodes, a radiofrequency voltage (5 MHz) which generates a high density of ions (~ 2 x 1011 / cm3) and on the other electrode a low frequency voltage (50 kHz) in order to transport the ions to the cathode. The first step was to understand the physics of the DBD RF-BF by coupling the optical characterization of the discharge and the 1D fluid modeling. When the LF voltage increases, the initially RF discharge in the α regime switches to the α-γ regime for 1/5 of the LF cycle. The results show that in γ regime the discharge is self-sustaining in the sheath and the flow of ions at the cathode is multiplied by a factor of 7 while their energy increases by a factor of 4. The experimental study shows that when an NPs target interacts with an RF-BF DBD, NPs are brought into flight.- The design and testing of a DBD reactor configuration comprising 2 successive plasma zones: the first to launch the NPs of a target, the second to deposit the NPs on a substrate. The latter is based on a double frequency BF-LF DBD obtained by applying a 50 kHz voltage which generates electrons to charge the NPs and a 1 kHz voltage which we know can ensure the transport of charged NPs from the volume to surfaces. The feasibility was shown by the observation of NPs on the substrate

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Duffiet, Marie. "Compréhension des mécanismes structuraux limitant les performances de LiCoO2 à haut potentiel dans des batteries Li-ion et optimisations des matériaux par dopage Al." Thesis, Bordeaux, 2019. http://www.theses.fr/2019BORD0083.

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L’oxyde lamellaire LiCoO2 (LCO) est un des matériaux d’électrode positive les plus communément utilisés dans les batteries Li-ion commerciales. Les efforts fournis pour contrôler la morphologie des particules de LCO ont grandement contribué à améliorer la compacité des électrodes, augmentant de fait la densité d’énergie des batteries. Celle-ci pourrait être encore améliorée grâce à l’augmentation du potentiel limite haut atteint lors de la charge de la batterie.Dans une première partie de ce manuscrit, plusieurs séries de poudres de LCO ont été synthétisées en effectuant un contrôle poussé de la taille des particules et de la stoechiométrie en Li (1.00 ≤ Li/Co ≤ 1.04) dans l’optique de caractériser leurs propriétés électrochimiques. Une étude par diffraction des rayons X (DRX) in situ a permis de suivre les changements structuraux observés lors de la désintercalation des ions Li dans deux matériaux LCO chargés à 5.2 V: les transitions de phase observées dans le cas de LCO dit « stoechiométrique » (Li/Co = 1.00) s’avèrent être plus nombreuses que précédemment reporté dans la littérature scientifique. La formation des phases H1 3 et O1 est confirmée, avec l’apparition supplémentaire d’une structure hybride entre ces deux phases. L’existence de défauts dans le matériau surlithié n’empêche pas la formation des phases H1 3 et O1, mais retarde leur apparition et modifie leurs paramètres structuraux.Dans une deuxième partie, le dopage aluminium à 4%at de ces poudres est envisagé. Plusieurs matériaux LiCo0.96Al0.04O2 (LCA) à stoechiométrie Li/(Co+Al) variable ont été synthétisés par voie solide afin d’obtenir un dopage le plus homogène possible. La caractérisation fine de ces matériaux par DRX et spectroscopie RMN du solide des noyaux 7Li, 27Al, 59Co permettent de démontrer qu’une répartition d’aluminium homogène est possible au sein de LiCo0.96Al0.04O2 grâce à une préparation en deux étapes : formation d’un LCA surlithié (Li/(Co+Al) > 1.00) suivi d’un réajustement de la stoichiométrie en Li (Li/(Co+Al) = 1.00)
Lithium cobalt oxide (LCO) is widely used as positive electrode material for Li-ion batteries. In order to achieve higher energy density, significant improvement of LCO’s packing density has been recently done by controlling the particles morphology and electrode processing. However, the upper charge cutoff voltage of LCO has barely changed, and would be a way to further enhance the energy density.In this PhD, we focus first in a careful preparation of different LCO samples with an accurate control of the Li stoichiometry (1.00 ≤ Li/Co ≤ 1.04) and particles size to characterize their electrochemical properties. For some selected samples, we study the phase transition mechanisms involved at high voltage during Li de intercalation using in situ synchrotron X-ray diffraction (SXRD): more phase transitions than previously reported have been evidenced for the stoichiometric LCO (Li/Co = 1.00) charged up to 5.2 V. In particular, while the formation of the H1 3 and O1 phases is confirmed, intermediate intergrowth structures are also stabilized. The existence of defects in overlithiated LCO (Li/Co > 1.00) does not hinder, but delay the formation of the high voltage of H1 3 and O1 phases, although structurally modified.In a second part, we focus on the material optimization though 4% Al-doping using a solid state route. Several compounds were prepared using various Li/(Al+Co) stoichiometries, with different particles sizes. Our efforts were dedicated to accurately characterize the Al doping homogeneity in the samples that affects the electrochemical properties. Using SXRD and 7Li, 27Al and 59Co MAS NMR as complementary tools, we show that homogeneous Al-doping in stoichiometric LCO can be achieved using Li-excess in a first step of the synthesis followed by a stoichiometry readjustment to Li/(Co+Al) = 1.00

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Fortes, Carmen Beatriz Borges. "Caracterização e propriedades das resinas acrílicas de uso odontológico : um enfoque voltado para a biossegurança." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2007. http://hdl.handle.net/10183/11014.

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O Brasil, à semelhança de outros países, está envelhecendo rapidamente. Os indivíduos com mais de 60 anos compõem hoje o segmento que mais cresce em termos proporcionais, mostrando um incremento da ordem de 500%, em 40 anos. A estimativa para o ano de 2020 é de que o Brasil tenha em torno de 32 milhões de indivíduos idosos, e desta população, uma parcela significativa será parcial ou totalmente desdentada, necessitando de aparelhos protéticos. Apesar da Odontologia apresentar avanços científicos notáveis na reabilitação da saúde bucal, muitos ainda usarão estes aparelhos. Sabe-se que o uso contínuo de próteses pode propiciar o desenvolvimento da estomatite protética, cuja etiologia é multifatorial, destacando-se principalmente a má higiene bucal e da prótese, e geralmente associada à presença de Candida albicans. Desta forma, há necessidade de se propor um método de desinfecção, que se mostre eficaz, que seja seguro quanto à toxicidade, que represente baixo risco ocupacional, que seja de fácil manuseio e que não interfira nas propriedades dos materiais utilizados na confecção destes aparelhos. Portanto, a proposição deste trabalho foi avaliar a influência de dois métodos de desinfecção, nas propriedades das resinas acrílicas empregadas na confecção das próteses.As propriedades avaliadas foram: resistência e módulo de flexão, resistência ao impacto Izod, microdureza Knoop, rugosidade, massa específica e grau de inchamento, grau de conversão do monômero, temperatura de transição vítrea, sorção e solubilidade. Os corpos de prova foram confeccionados de acordo com os requisitos de cada ensaio, tanto para os grupos controle (sem tratamento), quanto para os tratados (submetidos a um dos processos de desinfecção). Os tratamentos de desinfecção consistiram de: a) irradiação com energia de microondas na potência de 840 W, durante 1 minuto; b) imersão em ácido peracético durante 5 minutos. A eficácia da desinfecção foi avaliada através de ensaios microbiológicos que consistiram em verificar o crescimento no meio de cultura e na superfície do corpo de prova de Candida albicans, após a desinfecção dos corpos de prova, previamente contaminados com uma cepa conhecida do fungo (ATCC 10231). Como as resinas acrílicas são materiais muito utilizados em todas as áreas de atuação da Odontologia, o conhecimento das suas propriedades é de interesse do cirurgião-dentista. As resinas acrílicas tipo 1 (de termopolimerização), tipo 2 (quimicamente ativada) e tipo 5 (ativada por microondas) foram avaliadas neste trabalho. Os resultados mostraram que as resinas acrílicas tipo 1 e tipo 5 apresentam valores semelhantes em todas as propriedades analisadas. A resina acrílica tipo 2 apresentou valores inferiores àqueles encontrados nas tipo 1 e 5. O ciclo de polimerização com melhores resultados foi aquele proposto pelo respectivo fabricante daresina acrílica. A presença de fibras de nylon e de corante não influenciou as propriedades da resina acrílica tipo 5. Das técnicas de desinfecção, a imersão em ácido peracético apresentou os melhores resultados para todas as propriedades avaliadas ao longo do tempo de 20 meses. Por outro lado a irradiação de microondas, a longo prazo, apresentou os piores resultados para todas as propriedades avaliadas. Ambas as técnicas de desinfecção foram eficazes do ponto de vista microbiológico. Mas, para o uso prolongado, a técnica de desinfecção com ácido peracético pode ser recomendada com toda a segurança, no que diz respeito às propriedades avaliadas neste trabalho.
Brazil, similar to other countries, is aging quickly. The individuals with more than 60 years old compose today the segment that more grows in proportional terms, showing an increment of about 500% in 40 years. The estimate for 2020 is that Brazil has around 32 million elderly and a significant parcel of them will be partial or totally toothless, needing prosthetic equipments. In spite of notable scientific advance in the rehabilitation of the oral health, many people still will use these equipments. The continuous use of the prosthesis can propitiate the development of denture stomatitis, whose etiology is multifactorial, being generally, associated to the presence of fungus Candida albicans. Bad oral hygiene and prosthesis is still distinguished as factor of risk. Therefore, it very necessary for the elderly a efficient, safe and easy handling method of disinfection with low occupational risk and that doesn’t intervene with the properties of the materials used in the confection of these prosthetic equipments. The aim of this work is to evaluate the influence of two disinfection methods on the properties of acrylic resin used in the confection of dental prosthesis. Samples had been confectioned in accordance with the requirements of each test for the control groups (without treatment), as for the treated (submitted to one of the disinfection process). The evaluated properties had been resistance and module of flexure, Izod impact, Knoop microhardness, rugosity, specific mass and degree of swelling, degree of conversion of monomer, glass transition temperature, sorption and solubility. The treatments of disinfection had consisted of: a) irradiation with energy of microwaves, in the power of 840 W, during 1 min, or b) immersion in peracetic acid during 5 min. The effectiveness of the disinfection was evaluated by means of microbiological tests, in which was verified the occurrence of growth of Candida albicans through of culture and sample surface. For that, the samples were previously contaminated with one type of fungus (known as ATCC 10231) and, after, submitted to one of the two considered processes of disinfection. The work was studied the behavior of three commercial acrylic resins of dental use: acrylic resins of thermal polymerization, self-polymerization and polymerization for energy of microwaves (type 1, 2 and 5 respectively) from two different suppliers The results had shown that the acrylic resins of type 1 and type 5 presented similar values in all the analyzed properties. The acrylic resins of type 2 had also similar values in all the properties, but statistically lower than ones of type 1 and 5. The best polymerization cycle, which did not modify the resin properties, was that one considered by the respective manufacturer of the acrylic resin. The nylon fiber presence and colouring did not influence the properties of the acrylic resin of type 5. The first irradiation with microwaves significantlyincreased the evaluated properties and the first immersion in peracetic acid did not modify these properties, in comparison to the control groups. After 20 months, the immersion in peracetic acid did not modify the properties of the material, while the microwave irradiation showed alterations in some properties. Both disinfection techniques had been efficient of the microbiological point of view. On the basis of these results, can be concluded that the microwave irradiation after the polymerization of the material (first cycle), can be recommended, since it increased all the values of the evaluated properties, specially to the conversion degree monomer/polymer. Nevertheless, for prolonged use, the disinfection by means of the immersion in peracetic acid must be recommended, it is efficient for elimination of fungal microorganism and security, characterized for the maintenance of the properties of the acrylic resin evaluated in this work.

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Rocha, Pedro Paulo Forain. "Modelo de dimensionamento de frota de helicópteros para um sistema de distribuição física de pessoas voltado às atividades offshore de exploração de produção de uma bacia petrolífera." Florianópolis, SC, 2001. http://repositorio.ufsc.br/xmlui/handle/123456789/81545.

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Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico. Programa de Pós-Graduação em Engenharia de Produção.
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O presente trabalho consiste no desenvolvimento de um modelo matemático de dimensionamento de frota de helicópteros, compatível com um sistema de distribuição física de pessoas e adequado à utilização no planejamento de frota voltada ao atendimento às atividades offshore de exploração e produção de uma bacia petrolífera.

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Even, Raymond. "Les premiers semiconducteurs moleculaires : les derives radicalaires des phtalocyanines." Paris 6, 1987. http://www.theses.fr/1987PA066161.

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Synthese de composes pc::(2)lu, pc::(2)ln(ln = yb,tm,dy,nd) a l'etat de grande purete et etude de leurs proprietes electriques intrinseques, ainsi que de celles de pcli, sur monocristaux et sur couches minces; mise en evidence de la possibilite de dopage de pc::(2)lu avec des composes organiques donneurs et accepteurs et avec pcli. Etude de l'absorption optique et observation de bandes de transfert de charge intramoleculaire, confirmee par ailleurs par rpe. Possibilite d'application de couches minces de pclu a la detection de gaz

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Lefebvre, Solène. "Applications de la fluorescence pour la caractérisation structurale et dynamique d'intermédiaires conformationnels des récepteurs-canaux pentamériques." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS207.

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Les récepteurs canaux pentamériques (RCPs) sont des protéines membranaires présentes à la fois chez les eucaryotes comme les récepteurs à la glycine GlyR, et à la sérotonine 5-HT3R et chez certains procaryotes comme GLIC. Chez l’Homme, ces récepteurs sont impliqués dans la transmission synaptique rapide, ils sont une cible thérapeutique importante par exemple pour les anesthésiques généraux ou les anxiolytiques, et leur mutation entraine des pathologies sévères telles que des myasthénies, des épilepsies ou des maladies neurologiques rares comme l’hyperekplexie. La liaison de l’agoniste sur ces récepteurs favorise des réorganisations structurales qui amènent à un état actif pour lequel le canal est ouvert et permet le passage d’ions. Les propriétés structurales et fonctionnelles de ces récepteurs ont été étudiées et combinées dans ce travail pour explorer la dynamique conformationnelle des RCPs. Plusieurs approches par fluorescence ont été utilisées pour : 1) déterminer la cinétique de pré-activation de GLIC qui se passe à l’échelle de la centaine de microsecondes, 2) mesurer l’effet de mutations sur GLIC qui impactent profondément les réorganisations globales ce qui démontre l’importance du couplage allostérique des différentes régions de la protéine pour permettre son activation, 3) caractériser des états intermédiaires des RCPs eucaryotes qui se trouvent en amont de l’activation. Combiné à l’analyse structurale, les données de fluorescence obtenues permettent de détailler des intermédiaires conformationnels de l’activation des RCPs et d’approfondir les connaissances sur les mécanismes moléculaires qui régissent le fonctionnement normal et pathologique de ces récepteurs
Pentameric ligand-gated ion channels (pLGICs) are membrane proteins found in both eukaryotes such as the glycine and serotonin receptors and in some prokaryotes like GLIC. In Humans, these receptors are involved in fast synaptic transmission and are a major therapeutic target for general anesthetics or anxiolytics and their mutation lead to severe diseases such as myasthenia, epilepsies or rare neurological diseases like hyperekplexia. Agonist binding on these receptors promote structural reorganizations leading to the active state with an open pore allowing ion flux. Structural and functional properties of these receptors have been studied and combined in this work to explore conformational dynamics of pLGICs. Several approaches have been used to: 1) determine pre-activation kinetics of GLIC at the hundreds of milliseconds timescale, 2) measure the effect of mutations deeply impacting global reorganizations highlighting the major role of allosteric coupling of different protein domains to permit its activation, 3) characterize intermediate states of eukaryotic pLGICs upstream activation. Combined to structural analysis, fluorescence data obtained provide detailed description of conformational intermediates of pLGICs activation and deepen the knowledge of molecular mechanisms determining normal and pathological functioning of these receptors

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Mallangi, Siva Sai Reddy. "Low-Power Policies Based on DVFS for the MUSEIC v2 System-on-Chip." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-229443.

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Multi functional health monitoring wearable devices are quite prominent these days. Usually these devices are battery-operated and consequently are limited by their battery life (from few hours to a few weeks depending on the application). Of late, it was realized that these devices, which are currently being operated at fixed voltage and frequency, are capable of operating at multiple voltages and frequencies. By switching these voltages and frequencies to lower values based upon power requirements, these devices can achieve tremendous benefits in the form of energy savings. Dynamic Voltage and Frequency Scaling (DVFS) techniques have proven to be handy in this situation for an efficient trade-off between energy and timely behavior. Within imec, wearable devices make use of the indigenously developed MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). This system is optimized for efficient and accurate collection, processing, and transfer of data from multiple (health) sensors. MUSEIC v2 has limited means in controlling the voltage and frequency dynamically. In this thesis we explore how traditional DVFS techniques can be applied to the MUSEIC v2. Experiments were conducted to find out the optimum power modes to efficiently operate and also to scale up-down the supply voltage and frequency. Considering the overhead caused when switching voltage and frequency, transition analysis was also done. Real-time and non real-time benchmarks were implemented based on these techniques and their performance results were obtained and analyzed. In this process, several state of the art scheduling algorithms and scaling techniques were reviewed in identifying a suitable technique. Using our proposed scaling technique implementation, we have achieved 86.95% power reduction in average, in contrast to the conventional way of the MUSEIC v2 chip’s processor operating at a fixed voltage and frequency. Techniques that include light sleep and deep sleep mode were also studied and implemented, which tested the system’s capability in accommodating Dynamic Power Management (DPM) techniques that can achieve greater benefits. A novel approach for implementing the deep sleep mechanism was also proposed and found that it can obtain up to 71.54% power savings, when compared to a traditional way of executing deep sleep mode.
Nuförtiden så har multifunktionella bärbara hälsoenheter fått en betydande roll. Dessa enheter drivs vanligtvis av batterier och är därför begränsade av batteritiden (från ett par timmar till ett par veckor beroende på tillämpningen). På senaste tiden har det framkommit att dessa enheter som används vid en fast spänning och frekvens kan användas vid flera spänningar och frekvenser. Genom att byta till lägre spänning och frekvens på grund av effektbehov så kan enheterna få enorma fördelar när det kommer till energibesparing. Dynamisk skalning av spänning och frekvens-tekniker (såkallad Dynamic Voltage and Frequency Scaling, DVFS) har visat sig vara användbara i detta sammanhang för en effektiv avvägning mellan energi och beteende. Hos Imec så använder sig bärbara enheter av den internt utvecklade MUSEIC v2 (Multi Sensor Integrated circuit version 2.0). Systemet är optimerat för effektiv och korrekt insamling, bearbetning och överföring av data från flera (hälso) sensorer. MUSEIC v2 har begränsad möjlighet att styra spänningen och frekvensen dynamiskt. I detta examensarbete undersöker vi hur traditionella DVFS-tekniker kan appliceras på MUSEIC v2. Experiment utfördes för att ta reda på de optimala effektlägena och för att effektivt kunna styra och även skala upp matningsspänningen och frekvensen. Eftersom att ”overhead” skapades vid växling av spänning och frekvens gjordes också en övergångsanalys. Realtidsoch icke-realtidskalkyler genomfördes baserat på dessa tekniker och resultaten sammanställdes och analyserades. I denna process granskades flera toppmoderna schemaläggningsalgoritmer och skalningstekniker för att hitta en lämplig teknik. Genom att använda vår föreslagna skalningsteknikimplementering har vi uppnått 86,95% effektreduktion i jämförelse med det konventionella sättet att MUSEIC v2-chipets processor arbetar med en fast spänning och frekvens. Tekniker som inkluderar lätt sömn och djupt sömnläge studerades och implementerades, vilket testade systemets förmåga att tillgodose DPM-tekniker (Dynamic Power Management) som kan uppnå ännu större fördelar. En ny metod för att genomföra den djupa sömnmekanismen föreslogs också och enligt erhållna resultat så kan den ge upp till 71,54% lägre energiförbrukning jämfört med det traditionella sättet att implementera djupt sömnläge.

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Calamba, Katherine. "Phase stability and defect structures in (Ti1-x,Alx)Ny hard coatings." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0322.

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Cette étude met en évidence le rôle des lacunes d’azote et des défauts structuraux dans l’ingénierie de revêtements durs à stabilité de phase améliorée et dont les propriétés mécaniques sont compatibles avec des applications à haute température. Le nitrure de titane et d’aluminium (Ti,Al)N sous forme de revêtements est un matériau de choix pour la protection des outils de coupe pour métaux en raison de sa résistance supérieure à l’oxydation et à l’usure à haute température. La décomposition spinodale à haute température de la phase métastable cubique (Ti,Al)N en domaines cohérents de taille nanométrique de c-TiN et de c-AlN donne une dureté importante aux températures élevées. Un apport thermique encore plus élevé conduit à la transformation de c-AlN en w-AlN, ce qui nuit aux propriétés mécaniques du revêtement. Un moyen de retarder cette transformation est d'introduire des lacunes d'azote. Dans cette thèse, je montre que la combinaison d’une réduction de la teneur globale en azote du revêtement c-(Ti,Al)Ny(y <1) avec une faible tension de polarisation du substrat lors du dépôt par arc cathodique induit un retard encore plus prononcé de la transformation de la phase c-AlN en w-AlN. Dans de telles conditions, le durcissement par vieillissement est conservé jusqu'à 1100 ° C, ce qui correspond à la température la plus élevée signalée pour les films de (Ti,Al)N. Au cours des opérations de coupe, le mécanisme d'usure des films c-(Ti0.52Al0.48)Ny déposés par arc cathodique avec des teneurs en N de y = 0.92, 0.87 et 0.75 est influencé par l'interaction des lacunes d'azote, de la microstructure et des réactions chimiques avec le matériau de la pièce. Le revêtement y = 0.75 contient le plus grand nombre de macroparticules et présente, après usinage, une microstructure non homogène qui en abaisse la résistance à l'usure sur les flancs et les cratères. Le durcissement par vieillissement de l'échantillon y = 0.92 entraîne une résistance supérieure à l'usure sur le flanc, tandis que la structure dense de l'échantillon y = 0.87 empêche l'usure chimique qui se traduit par une excellente résistance à l'usure sur les cratères. Des films hétéroépitaxiés c-(Ti1-x, Alx)Ny (y = 0.92, 0.79 et 0.67) ont été déposés sur des substrats de MgO(001) et (111) en utilisant une technique de pulvérisation magnétron pour examiner en détail les défauts structuraux pendant la décomposition spinodale. À 900 °C, les films se décomposent pour former des domaines cohérents riches en c-AlN et c-TiN de forme allongée le long de la direction <001>. Les cartographies de déformation montrent que la plupart des contraintes se trouvent près de l'interface des domaines ségrégés et à l'intérieur des domaines c-TiN. Les dislocations s'agrègent favorablement dans c-TiN plutôt que dans c-AlN car ce dernier a une directionnalité plus forte des liaisons chimiques covalentes. À température élevée, la taille de domaine des films de c- (Ti, Al)Ny orientés (001) et (111) augmente avec la teneur en azote. Cela indique qu'il y a un retard dans le grossissement dû à la présence de plus de lacunes d’azote dans le film. [...]
This study highlights the role of nitrogen vacancies and defect structures in engineering hard coatings with enhanced phase stability and mechanical properties for high temperature applications. Titanium aluminum nitride (Ti,Al)N based materials in the form of thin coatings has remained as an outstanding choice for protection of metal cutting tools due to its superior oxidation resistance and high-temperature wear resistance. High-temperature spinodal decomposition of metastable (Ti,Al)N into coherent c-TiN and c-AlN nm-sized domains results in high hardness at elevated temperatures. Even higher thermal input leads to transformation of c-AlN to w-AlN, which is detrimental to the mechanical properties of the coating. One mean to delay this transformation is to introduce nitrogen vacancies. In this thesis, I show that by combining a reduction of the overall N-content of the c-(Ti,Al)Ny (y < 1) coating with a low substrate bias voltage during cathodic arc deposition an even more pronounced delay of the c-AlN to w-AlN phase transformation is achieved. Under such condition, age hardening is retained until 1100 °C, which is the highest temperature reported for (Ti,Al)N films. During cutting operations, the wear mechanism of the cathodic-arc-deposited c-(Ti0.52Al0.48)Ny with N-contents of y = 0.92, 0.87, and 0.75 films are influenced by the interplay of nitrogen vacancies, microstructure, and chemical reactions with the workpiece material. The y = 0.75 coating contains the highest number of macroparticles and has an inhomogeneous microstructure after machining, which lower its flank and crater wear resistance. Age hardening of the y = 0.92 sample causes its superior flank wear resistance while the dense structure of the y = 0.87 sample prevents chemical wear that results in excellent crater wear resistance. Heteroepitaxial c-(Ti1-x,Alx)Ny (y = 0.92, 0.79, and0.67) films were grown on MgO(001) and (111) substrates using magnetron putter deposition to examine the details of their defect structures during spinodal decomposition. At 900 °C, the films decompose to form coherent c-AlN- and c-TiN- rich domains with elongated shape along the elastically soft <001> direction. Deformation maps show that most strains occur near the interface of the segregated domains and inside the c-TiN domains. Dislocations favorably aggregate in c-TiN rather than c-AlN because the later has stronger directionality of covalent chemical bonds. At elevated temperature, the domain size of (001) and (111)- oriented c-(Ti,Al)Ny films increases with the nitrogen content. This indicates that there is a delay in coarsening due to the presence of more N vacancies in the film. The structural and functional properties (Ti1-x,Alx)Ny are also influenced by its Al content (x). TiN and (Ti1-x,Alx)Ny (y = 1, x = 0.63 and x = 0.77) thin films were grown on MgO(111) substrates using magnetron sputtering technique. Both TiN and Ti0.27Al0.63N films are single crystals with cubic structure. (Ti0.23,Al0.77)N film has epitaxial cubic structure only in the first few atomic layers then it transitions to an epitaxial wurtzite layer, with an orientation relationship of c-(Ti0.23,Al0.77)N(111)[1-10]ǀǀw-(Ti0.23,Al0.77)N(0001)[11-20]. The w-(Ti0.23,Al0.77)N shows phase separation of coherent nm-sized domains with varying chemical composition during growth. After annealing at high temperature, the domains in w-(Ti0.23,Al0.77)N have coarsened. The domains in w-(Ti0.23,Al0.77)N are smaller compared to the domains in c-(Ti0.27,Al0.63)N film that has undergone spinodal decomposition. The results that emerged from this thesis are of great importance in the cutting tool industry and also in the microelectronics industry, because the layers examined have properties that are well suited for diffusion barriers

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38

Chen, Ming-Ren, and 陳明仁. "Interleaved Flyback Converter with Zero-Voltage-Transition." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/62814697601088122192.

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碩士
國立東華大學
電機工程學系
97
This paper proposes a novel interleaved flyback converter which is composed of two parallel-operated basic flyback converters in addition to an auxiliary inductor and two snubber circuits. This circuit is able to transfer higher power at a much higher efficiency than conventional flyback converters. There are two efficiency boosting features in this proposed circuit. First, both the active power switches are zero- voltage-switched and therefore the switching losses are reduced. Second, the reverse recovery losss on the rectifying diodes are reduced. This is because of the auxiliary inductor which makes the diode currents smoothly ramp down to zero instead of abruptly turn off. The two basic flyback converters are identical, which makes operation analysis and circuit design simpler. A test circuit is built and the experimental result shows satisfactory agreement to the theoretical analysis. The experimental results show that this proposed converter promotes its conversion efficiency up to 91%.

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39

Hsieh, Bing-Hao, and 謝秉浩. "Battery Charger with Zero-Voltage-Transition Boost Converter." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/tzy778.

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碩士
崑山科技大學
電機工程研究所
97
Since traditional hard-switching power switch components have non-ideal characteristics, a voltage surge or current surge generated under conduction and cutoff, the power switch components reduces the efficiency, increases the component stress and facilitates breakage. This work employs soft-switching technology to realize a novel battery charger with a zero-voltage-transition (ZVT) boost converter which increases the charging efficiency above, reduces the switching losses below, and reduces the electromagnetic interference (EMI) below, those of battery chargers with conventional boost converters. The optimal circuit parameters are set based on circuit analyses under the conduction and cut-off conditions of two active switches using equivalent circuits and the circuit operation equations. Experimental results demonstrate the theoretical effectiveness of the proposed battery charger. The practical mean charging efficiency of the developed battery charger is as high as 88.2%.

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40

Hsueh, Te-Chin, and 薛德欽. "High-Efficiency Interleaved Boost Converter with Zero-Voltage Transition." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/77u9y3.

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碩士
國立東華大學
電機工程學系
96
This thesis proposes a high-efficiency interleaved boost converter with zero-voltage transition, which is composed of two shunted elementary boost converters and an auxiliary inductor. This converter is able to turn on both the active power switches at zero voltages to reduce their switching losses and evidently raise the conversion efficiency. Since the two parallel-operated elementary boost converters are identical, operation analysis and design for the converter module becomes quite simple. A laboratorial test circuit is built and the circuit operation shows satisfactory agreement to the theoretical analysis. The experimental results show that this converter module performs very well with the output efficiency as high as 95%.

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41

Lin, Syuan-Li, and 林軒立. "Analysis of the Zero-Voltage Transition PWM Boost Converter." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/y6gnjj.

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碩士
國立臺灣海洋大學
電機工程學系
102
The purpose of this thesis is to analyze a new Zero-Voltage Transition PWM Boost Converter. The converter operates with an active snubber cell, which provides main switch to turn ON with zero-voltage transition (ZVT) and to turn OFF with zero-current transition (ZCT). Furthermore, all semiconductor devices of this converter operate with soft switching at high frequency. The structure of this converter is simple and easy to control. The operation principle and steady-state analysis of the novel boost converter are presented. Finally, the converter feature is proved by simulation.

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42

Chen, Yu-Jen, and 陳妤甄. "An Interleaved Twin-Buck Converter with Zero-Voltage-Transition." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/r465zf.

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碩士
國立中山大學
電機工程學系研究所
97
A twin-buck converter with zero-voltage-transition (ZVT) is proposed in this thesis. The converter comprises two identical buck conversion units connected in parallel by an interleaved inductor. The ZVT is accomplished by the resonating the currents between the interleaved inductor and the parasitic capacitances of the power MOSFETs. The circuit efficiency can be further improved by introducing synchronous rectification to reduce the condition loss on the diodes. The detailed circuit analysis and operation characteristics are provided. A laboratory circuit rated at 300 W is designed and tested. Experimental results show that the switching losses can be effectively reduced by smoothly transiting the currents of the active power switches.

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43

ChenMu-Shi and 陳木禧. "Zero Voltage Transition Pulse-Widith-Modulated Boost Converter for Chargers." Thesis, 2007. http://ndltd.ncl.edu.tw/handle/89458817054810528918.

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碩士
崑山科技大學
電機工程研究所
95
This thesis realizes a zero-voltage-transition pulse-width-modulated boost battery charger for reducing switching losses caused by the switch to enhance the charging efficiency of battery charger. The main switch in the presented battery charger is conducted under zero-voltage condition and the boost diode is cut off under zero-current condition. The switching operation of the switch is completed under the occurrence of resonance condition. The developed battery charger with soft-switching technology has higher efficiency, lower stress on the switch and lower electro-magnetic interference (EMI) over the battery charger with traditional boost converter. This thesis employs the pulse-width-modulated control mode for the switching of two active switches. The operation modes of the circuit and the equivalent circuits are constructed by analyzing the operating principles of the circuit, based on the turn-on conditions of the active switches. The equations used to determine the circuit parameters are derived from the equivalent circuits. Experimental results have demonstrated the theoretical effectiveness of the developed battery charger circuit. The practical mean charging efficiency of the developed battery charger is 91.25%.

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44

Jyh-Herng, Chou, and 周志恆. "Zero Voltage Transition Technology Applied To AC/DC Motor Drives." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/50698877426770441160.

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碩士
國立雲林科技大學
電機工程技術研究所
86
Zero-Voltage-Transition techniques which combine PWM with the soft-switching characteristics make all semiconductor devices be operated at constant frequency. ZVT structure also has very low voltage and current stress and the soft-switching characteristic of the rectifier diode. Therefore, ZVT converters have the minimum conduction loss. This thesis will analyze and discuss the characteristics of the ZVT-PWM technique applied to the dc and ac motor drives. First, the effects of switching frequency and duty cycle on efficiency,speed characteristics and ripple current of the various dc motor are investig ated. Comparison of ZVT-PWM converter-fed dc motor with the traditional hard-switching PWM topology shows the ZVT-PWM converter-fed dc motor can reduce switching loss, ripple current and improve the efficiency even the load variation is very large. In tradition, the hard-switching inverter applied to the three phase induction motor is subject to high switching loss and consequently reduces the performance and efficiency of the inverter system. Therefore, This thesis applied a new type of Parallel Resonant DC Link ﹙PRDCL﹚topology which can provide the zero voltage switching of switches of the inverter and minimize the peak voltage stress of the switches. In addition, The Space Voltage Vector Pulse-Width-Modulation }SVPWM﹚strategy is applied to the inverter. It can reduce the voltage and current harmonics in the inverter output and consequently provide the operation of induction motor smoothly. Digital Signal Processor TM S320C14﹙T.I.﹚is used to implement the SVPWM strategy. Experimental results show that the new PRDCL combines with SVPWM can reduce the switching loss and the current harmonic. The structure can also minimize the voltage stresses and improve the efficiency while it is applied to induction motor drives system.

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45

Su, Ding-Tsair, and 蘇丁財. "Design and Implementation of Zero-Voltage-Transition Boost Power Factor Corrector." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/52781086863305326926.

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碩士
國立雲林科技大學
電機工程系碩士班
91
The purpose of this thesis is to design and implement a high performance single- phase power factor corrector. A zero-voltage-transition (ZVT) boost power factor correction converter features high power factor, high efficiency, and low harmonics line current. The trend in switching power converter is towards increasingly higher power densities. This thesis proposes a ZVT power factor corrector operating at 100kHz and using an average current mode control. The main power stage components experience no more voltage or current stress than normal, the switch and diode both experience soft switching transitions. The results suggest that the soft switching transitions not only reduce the switching losses significantly, but also reduce electromagnetic interference. The operation principle was described in detail for different operating modes and their respective equivalent circuit and design method were also discussed. A ZVT boost power factor correction circuit capable for an output power 750W was designed and verified by PSpice simulation. The feasibility of the proposed control is confirmed through experimental results.

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46

Hsieh, Ying-Tsai, and 謝英材. "A Study of Optimizing the manufacturing Process for Transition Voltage Regulator." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/57106895598142059505.

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碩士
臺北城市科技大學
嵌入式系統產業研發碩士專班
100
Embedded systems, electronic components can basically be divided into passive components and active components. Resistor belongs to the passive components which you can use its resistance value to adjust the size of the circuit elements. The regulator in the manufacturing process will be generated the failure of the automatically sporadic selected electrical resistance. This results in poor transition voltage or defective goods. We must spend hours to maintenance. After several times to find the real reason is still unable to prevent the transition voltage or defective goods. In order to further investigate the configuration of the components used by the basic line and seek a stable voltage variation, we use the extension method to find the best solution. I hope to take advantage of the matter element extension to establish the correlation function. The synchronous rectification technology can effectively reduce the conduction losses caused by the rectifier diodes. We use the embedded microprocessor to adjust the output of the function, design a high efficiency, low electromagnetic interference, and the output of the quasi-harmonic flyback converter, and enhance the efficiency of immense benefit. This method can select the optimal process to improve efficiency and product yield rate, and thus increase productivity and reduce production cost.

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47

Leu, Yau-Jiun, and 呂堯君. "Implementation and Design of Buck Zero-Voltage-Transition Pulse- Width-Modulated Converter." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/82257249551270227796.

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碩士
大同工學院
電機工程研究所
81
In this thesis , a comprehensive analysis of the buck zero- voltage-transition (ZVT) pulse-width-modulated (PWM) coverter is presented . Both active and passive switches achieve zero- voltage switching without significantly increasing their voltage and current stresses . Due operation under the constant frequency , the optimization of the circuit is easily attainable . A novel control approach is introduced . The approach is simple and provides switches with switching. Using results of the dc analysis and dc conversion ratios, a design procedure with the switching property is proposed , and is used to build prototype circuit operating at the switching frequency 296KHz . It has been proven useful for design and when the ZVT PWM converter is implemented at higher frequencies.

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48

Chen, Chuen-Shiu, and 陳春旭. "The design of zero-voltage-transition(ZVT) power factor correction(PFC) circuit." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/16706264659421257343.

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49

Chou, Po-Han, and 周柏翰. "Sliding-Mode Control on an Interleaved Boost Converter with Zero-Voltage Transition." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/83388771928931374001.

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碩士
國立東華大學
電機工程學系
99
The objective of this thesis is to develop and implement a control algorithm applying frequency-modulation based sliding mode control (SMC) for a novel interleaved boost converter with zero-voltage transition. It is well known that the major advantage of SMC is its insensitivity upon parameter variations and/or external disturbances. Once the system state reaches and keeps on the sliding surface, neither parameter variation nor disturbance will sway the system out of the stable state. In this thesis, output voltage error is embraced into the sliding function, and then equivalent control force is derived, such that the system state trajectory is forced toward the sliding surface and converges to a stable operation point. Moreover, the approaching condition is proven that the system will reach sliding surface within a limited time period. SMC algorithm here guarantees the stability of the output voltage of the interleaved boost converter even if load variation and external load disturbance exist. The proposed sliding mode control is implemented in a 32-bit fixed-point DSP controller. Finally, experimental results are illustrated to show the validity of the proposed sliding mode control algorithm.

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50

Liu, Yung-Hiang, and 劉永祥. "Design and Implementation of a Zero-Voltage-Transition Boost Power Factor Correction Circuit." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/44608802976964266381.

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碩士
國立交通大學
電機與控制工程系
87
This thesis presents the design and implementation of a zero-voltage-transition power factor correction (PFC) converter having high power factor, low harmonic line current, high efficiency, and high switching frequency. Conventional boost zero-voltage-transition with auxiliary switches can reduce switching loss, however, the hard switching of the auxiliary switches can significantly increase additional switching losses. Soft switching techniques can be applied to these auxiliary switches to reduce the switching losses. By using zero-voltage-transition techniques, a lossless snubber circuit has been developed to reduce the switching losses of the auxiliary switch. The operational principle and equivalent circuits of the proposed zero-voltage-transition converter are analyzed in detail. In addition, a systematic design procedure has been given to design the converter. Computer simulation using Ispice has been carried out in analyzing the proposed zero-voltage-transition soft-switching PFC scheme. A 3kW, 200kHz prototype of the boost zero-voltage-transition PFC converter has been constructed. Experimental results can verify the efficiency improvement and EMI reduction by the proposed soft-switching PFC scheme.

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