Teses / dissertações: "Zero mode"

1

Kikuchi, Toru. "Relativistic zero-mode dynamics of solitons". 京都大学 (Kyoto University), 2012. http://hdl.handle.net/2433/157758.

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Rowley, Anna Kaspartian. "A new zero-voltage-mode resonant converter". Thesis, Brunel University, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.303182.

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3

Lau, Wai Keung. "Current-mode DC-DC buck converter with dynamic zero compensation /". View abstract or full-text, 2006. http://library.ust.hk/cgi/db/thesis.pl?ECED%202006%20LAU.

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Baghdadi, Jihad Abdul-Hadi III. "Designs for Zero Polarization-Mode Dispersion And Polarization-Maintaining Fibers". Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30522.

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This dissertation addresses several aspects pertaining to polarization in optical fibers and optical waveguide devices. In particular, the analysis and design of fibers that maintain polarization over long lengths, provide zero polarization-mode dispersion, and function as polarizers or mode filters are presented. First, optimum designs for high-birefringence as well as single-polarization single-mode fibers are studied. For high-birefringence fibers, several index profiles were obtained that provided high birefringence while achieving zero or very small dispersion in 1.3 μm and 1.55 μm windows. Also, few index profiles were found that resulted in single-polarization single-mode operation with zero or very small dispersion at about 1.3 μm and 1.55 μm. A wavelength range of 100 nm to 500 nm was achieved for truly single-mode operation. Second, a comprehensive analysis of polarization-mode dispersion in a multiple-clad fiber due to ellipticity of fiber cross-section is carried out. The analysis results are then used to design large effective area single-mode dispersion-shifted fiber that provides zero polarization-mode dispersion at the wavelength 1.55 μm. Effective area on the order of 122 μm² with mode-field diameter of about 10 μm have been attained for this design. Tolerance analysis on the transmission parameters due to ±1% and ±2% variations in the radii of the fiber layers is carried out. Finally, a wedge-shape dielectric waveguides bounded by conducting planes is introduced and analyzed. Conductor and dielectric losses for the fundamental mode in waveguides with wedge angle of π/n; n ≥ 1, and 2π/3 as a special case with noninteger azimuthal number have been evaluated. These waveguides generally support fewer number of modes for smaller wedge angles and the modes cannot be of TM type. They find applications as mode filters and polarizers..
Ph. D.

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5

Van, de Sande Brett. "Renormalization and the zero mode in light-front field theory /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu148785810611862.

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6

Thurn, Emmie, David Gustafsson e Jasenko Arsenovic. "Internationalisering med entry mode i fokus – en fallstudie av Zero Belysningar". Thesis, Linnéuniversitetet, Ekonomihögskolan, ELNU, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-13169.

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Titel: Internationalisering med entry mode i fokus – en fallstudie av Zero Belysningar Kurs: 2FE03E ‐ 15 hp. Kandidatuppsats Författare: David Gustafsson 870926, Emmie Thurn 880909, Jasenko Arsenovic 890119 Bakgrund: Globalisering och inträde på internationella marknader har för SME blivit en trend. Åtskilliga företag väljer att konkurrera på en internationell nivå och internationaliseringen sker snabbare och på flera olika sätt än någonsin tidigare. Att välja rätt entry mode har en stor påverkan på om företaget kommer att nå framgång eller ej på den nya marknaden. Syfte: Syftet med studien är att undersöka olika faktorer som påverkar småföretag val av entry mode vid expansion. För att kunna svara på problemformuleringen har författarna valt att använda ett fallföretag, där deras situation kommer att användas för att undersöka ett svenskt småföretags val av entry mode vid expansion till Norge. Metod: Denna kvalitativa studie har utgått ifrån hermeneutiska antaganden och utförts ut efter en induktiv forskningsansats. En har applicerats där olika intervjuer och granskningar av dokument har agerat datainsamlingsmetoder. Slutsats: Undersökningen visade att ett flertal faktorer påverkar beslutet. Författarna har funnit att faktorerna attraktionskraft, externa påtryckningar och kulturella skillnader, politik och lagar, tidigare erfarenheter, målmarknad och målgrupp, konkurrens och nya aktörer, substitut, kundernas och leverantörernas kraft, företagets storlek och kompetens och resurser har en inverkan på svenska småföretags val av entry mode. Vilket entry mode ett svenskt småföretag bör välja vid expansion beror till stor del på vilka resurser och kompetenser företaget innehar och hur värdlandets struktur ser ut. Författarna finner därför att det inte finns något generellt entry mode för samtliga småföretag. Undersökningen visar på att betydande styrkor för ett småföretag är hög servicekvalitet, differentierade kvalitetsprodukter, unik internkompetens och flexibilitet. Dess betydande svagheter är att de ej utvecklats inom LED‐teknik, skev bild av marknaden, hög prisnivå och långa leveranstider. Eventuella möligheter är delmarknaders tillvätpotential, småkulturella skillnader och lagliga restriktioner och utveckling inom LED‐teknik. Det finns hot i form av nya aktöer, liten aktö, priskäslig marknad och differens i språ och konsumentbeteende. Nyckelord: Entry mode, SME, Porters Five Forces, Resource Based View, SWOT‐analys
Title: Internationalization with entry mode in focus ‐ a case study of Zero Belysningar Course/course code: 2FE03E ‐15 hp. Bachelor thesis Authors: David Gustafsson 870926, Emmie Thurn 880909, Jasenko Arsenovic 890119 Purpose: The purpose with this study is to examine various factors that affect small businesses in the choice of entry mode. In order to answer the problem formulation, the authors have chosen to use an case company, where its situation will be used to investigate a Swedish small firms' choice of entry mode for expansion into Norway. Method: This qualitative study was based upon hermeneutical assumptions and carried out by an inductive research approach. Various interviews and reviews of documents have been used to collect data. Conclusion: The investigation revealed that several factors influence the choice of entry mode. The authors have found that factors of attractiveness, external pressures and cultural differences, politics and laws, past experience, target market and target audience, competition and new entrants, substitutes, customers' and suppliers' power, its size and expertise and resources have an impact on Swedish small firms' choice of entry mode. Which entry mode a Swedish small business should choose depends largely on the resources and competences it holds and how the host‐country’ structure looks like. The authors find that there is no general entry mode for all small businesses. The survey also reveals that significant strengths for a small business is high service quality, differentiated quality products, unique internal competence and flexibility. Its major weakness is that they are not developed in LED technology, distorted picture of the market, high prices and long delivery times. Possible opportunities are submarkets growth potential, small cultural differences and legal restrictions and development in LED technology. There are threats from new entrants, small player, price sensitive market and the difference in language and consumer behavior. Keywords: Entry mode, SME, Porters Five Forces, Resource Based View, SWOT‐analysis.

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Gleeson, Liam M. "Polarisation mode dispersion in non-return-to-zero systems : assessment and impact". Thesis, University of Essex, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343569.

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8

Lee, Anders Wen-Dao. "The design of a high precision, wide common mode range auto-zero comparator". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/100610.

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Thesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2015.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 89-90).
This thesis discusses the design and analysis of a high common-mode input auto-zero comparator for use in a Hot Swap controller. Comparators are essential building blocks within the current limit detection schemes of Hot Swap controllers. However, the current limit detection scheme places a sense resistor in the current path, burning static power. Reducing this power consumption while maintaining the overall accuracy of the detector can be done by decreasing the full scale sense voltage across the sense resistor, decreasing the size of the sense resistor, and increasing the overall accuracy of the comparator. This is realized by using an auto-zero comparator designed in Linear Technology's 0.6 [mu]m BiCMOS process. The overall topology uses the closed loop offset storage with an auxiliary amplifier scheme. The input and auxiliary amplifier are based on the fully differential folded cascode topology with some key changes. The comparator is a typical PMOS comparator with internal hysteresis and additional circuitry added to maintain symmetry for as long as possible. A Widlar bandgap-based circuit provides the necessary internal reference. The comparator was designed and verified using LTspice and Linear Technologys in house models. The resulting design has an absolute accuracy better than +/-200 [mu]V over temperature, increasing the relative accuracy with the sense resistor value halved from previous designs. Additionally, the comparator can handle inputs from zero to sixty volts and settles to a new offset sample in less than 3 [mu]s.
by Anders Wen-Dao Lee.
M. Eng.

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9

Rankin, Paul Edward. "Modeling and Design of a SiC Zero Common-Mode Voltage Three-Level DC/DC Converter". Thesis, Virginia Tech, 2019. http://hdl.handle.net/10919/93176.

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As wide-bandgap devices continue to experience deeper penetration in commercial applications, there are still a number of factors which make the adoption of such technologies difficult. One of the most notable issues with the application of wide-bandgap technologies is meeting existing noise requirements and regulations. Due to the faster dv/dt and di/dt of SiC devices, more noise is generated in comparison to Si IGBTs. Therefore, in order to fully experience the benefits offered by this new technology, the noise must either be filtered or mitigated by other means. A survey of various DC/DC topologies was conducted in order to find a candidate for a battery interface in a UPS system. A three-level NPC topology was explored for its potential benefit in terms of noise, efficiency, and additional features. This converter topology was modeled, simulated, and a hardware prototype constructed for evaluation within a UPS system, although its uses are not limited to such applications. A UPS system is a good example of an application with strict noise requirements which must be fulfilled according to IEC standards. Based on a newly devised mode of operation, this converter was verified to produce no common-mode voltage under ideal conditions, and was able to provide a 6 dB reduction in common-mode voltage emissions in the UPS prototype. This was done while achieving a peak efficiency in excess of 99% with the ability to provide bidirectional power flow between the UPS and battery backup. The converter was verified to operate at the rated UPS conditions of 20 kW while converting between a total DC bus voltage of 800 V and a nominal battery voltage of 540 V.
Master of Science
As material advancements allow for the creation of devices with superior electrical characteristics compared to their predecessors, there are still a number of factors which cause these devices to see limited usage in commercial applications. These devices, typically referred to as wide-bandgap devices, include silicon carbide (SiC) transistors. These SiC devices allow for much faster switching speeds, greater efficiencies, and lower system volume compared to their silicon counterparts. However, due to the faster switching of these devices, there is more electromagnetic noise generated. In many applications, this noise must be filtered or otherwise mitigated in order to meet international standards for commercial use. Consequently, new converter topologies and configurations are necessary to provide the most benefit of the new wide-bandgap devices while still meeting the strict noise requirements. A survey of topologies was conducted and the modeling, design, and testing of one topology was performed for use in an uninterruptible power supply (UPS). This converter was able to provide a noticeable reduction in noise compared to standard topologies while still achieving very high efficiency at rated conditions. This converter was also verified to provide power bidirectionally—both when the UPS is charging the battery backup, and when the battery is supplying power to the load.

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10

Haryani, Nidhi. "Zero Voltage Switching (ZVS) Turn-on Triangular Current Mode (TCM) Control for AC/DC and DC/AC Converters". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/96397.

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One of the greatest technological challenges of the world today is reducing the size and weight of the existing products to make them portable. Specifically, in electric vehicles such as electric cars, UAVs and aero planes, the size of battery chargers and inverters needs to be reduced so as to make space for more parts in these vehicles. Electromagnetic Interference (EMI) filters take up a more than 80 % of these power converters, the size of these filters can be reduced by pushing the switching frequency higher. High frequency operation (> 300 kHz) leads to a size in reduction of EMI filters though it also leads to an increase in switching losses thus compromising on efficiency. Thus, soft switching becomes necessary to reduce the losses, adding more electrical components to the converter to achieve soft switching is a common method. However, it increases the physical complexity of the system. Hence, advanced control methods are adopted for today's power converters that enable soft switching for devices specifically ZVS turn-on as the turn-off losses of next generation WBG devices are negligible. Thus, the goal of this research is to discover novel switching algorithms for soft turn-on. The state-of the-art control methods namely CRM and TCM achieve soft turn-on by enabling bi-directional current such that the anti-parallel body diode starts conducting before the device is turned on. CRM and TCM result in variable switching frequency which leads to asynchronous operation in multi-phase and multi-converter systems. Hence, TCM is modified in this dissertation to achieve constant switching frequency, as the goal of this research is to be able to achieve ZVS turn-on for a three-phase converter. Further, Triangular Current Mode (TCM) to achieve soft switching and phase synchronization for three-phase two-level converters is proposed. It is shown how soft switching and sinusoidal currents can be achieved by operating the phases in a combination of discontinuous conduction mode (DCM), TCM and clamped mode. The proposed scheme can achieve soft switching ZVS turn-on for all the three phases. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kW with a density of 110 W/in3. The discussion of TCM in current literature is limited to unity power factor assumption, however this limits the algorithm's adoption in real world applications. It is shown how proposed TCM algorithm can be extended to accommodate phase shift with all the three phases operating in a combination of DCM+TCM+Clamped modes of operation. The algorithm is tested and validated on a GaN converter, 99% efficiency is achieved at 0.7 kVA with a density of 110 W/in3. TCM operation results in 33 % higher rms current which leads to higher conduction losses, as WBG devices have lower on-resistance, these devices are the ideal candidates for TCM operation, hence to accurately obtain the device parameters, a detailed device characterization is performed. Further, proposed TCM+DCM+Clamped control algorithm is extended to three-level topologies, the control is modified to extract the advantage of reduced Common Mode Voltage (CMV) switching states of the three-level topology, the switching frequency can thus be pushed to 3 times higher as compared to state-of-the-art SVPWM control while maintaining close to 99 % efficiency. Two switching schemes are presented and both of them have a very small switching frequency variation (6%) as compared to state-of-the-art methods with >200% switching frequency variation.
Doctor of Philosophy
Power supplies are at the heart of today's advanced technological systems like aero planes, UAVs, electrical cars, uninterruptible power supplies (UPS), smart grids etc. These performance driven systems have high requirements for the power conversion stage in terms of efficiency, density and reliability. With the growing demand of reduction in size for electromechanical and electronic systems, it is highly desirable to reduce the size of the power supplies and power converters while maintaining high efficiency. High density is achieved by pushing the switching frequency higher to reduce the size of the magnetics. High switching frequency leads to higher losses if conventional hard switching methods are used, this drives the need for soft switching methods without adding to the physical complexity of the system. This dissertation proposes novel soft switching techniques to improve the performance and density of AC/DC and DC/AC converters at high switching frequency without increasing the component count. The concept and the features of this new proposed control scheme, along with the comparison of its benefits as compared to conventional control methodologies, have been presented in detail in different chapters of this dissertation.

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Hedir, Melissa. "Design, study, and fabrication of photonic crystal coupled-cavity arrays for investigating non-Hermitian zero-modes". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASP056.

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Les cavités couplées à base de cristal photonique (PhC) représentent des plates-formes intéressantes pour de nombreux protocoles d'information ou de calcul, tant classiques que quantiques. Elles servent également de bancs d'essai très polyvalents pour étudier des phénomènes optiques avancés, tels que les zero-modes photoniques non Hermitiens. Ces zero-modes, des états liés intrigants ayant suscité l'intérêt à travers le cas des zero-modes de Majorana, présentent des valeurs propres d'énergie nulle dans un réseau de cavités ou de guides d'ondes. En tant que modes protégés topologiquement ou symétriquement, on s'attend à ce qu'ils soient robustes face aux désordres de couplage, ouvrant ainsi un large éventail d'applications, de l'ingénierie des modes laser au calcul optique. Ce travail de thèse présentel'observation expérimentale des zer-modes photoniques dans des réseaux unidimensionnels de cavités couplées présentant une distribution de gain/perte, également appelés réseaux non Hermitiens. Notre étude s'est focalisée sur des réseaux composés d'un nombre impair de cavités (trois et cinq). Nous avons notamment constaté que le contrôle du couplage évanescent entre les cavités modifie considérablement le désaccord en fréquence, ce qui entrave la réalisation des zero-modes. Pour contourner ce problème, nous avons développé un nouveau design que nous avons appelée "technique d'ingénierie des barrières images", permettant un contrôle précis de la force de couplage au sein de réseaux unidimensionnels de cavités couplées sans le désaccord en fréquence concomitant causé par les terminaisons dans la chaîne, élargissant ainsiconsidérablement la plage d'observabilité des modes zéro. Cette méthode facilite également la construction de chaînes de cavités avec un couplage non uniforme, ce qui nous permet d'évaluer l'immunité inhérente des zero-modes face aux perturbations de couplage. Remarquablement, la capacité à inverser les signes de couplage permise par notre méthode de contrôle du couplage conduit à une inversion de la symétrie du zero-mode, permettant donc d'élargir le potentiel pour des investigations expérimentales et théoriques de ces modes. Cela offre une possibilité de réaliser une oscillation de zero-mode en phase, une caractéristique intéressante pour exalter le champ lointain des lasers topologiques
Coupled photonic crystal (PhC) cavities are outstanding platforms for many classical and quantum information or computing protocols. They are also highly versatile testbeds for exploring advanced collective optical phenomena, such as the so-called non-Hermitian photonic zero modes. Zero modes are intriguing bound states that have captured attention through the elusive case of Majorana zero modes. In optics, “photonic zero-modes” exhibit zero-energy eigenvalues in a cavity or waveguide array. Being topologically or symmetry-protected modes, they are expected to be robust against coupling disorder, opening up a wide range of applications, from laser mode engineering to optical computing. This thesis work presents the experimental observation of photonic zero modes in small coupled cavity arrays featuring a gain/loss distribution -also called non-Hermitian arrays composed of an odd number of photonic crystal (PhC) cavities, from three to five. Importantly,we have found that controlling the evanescent coupling between the cavities significantly alters the frequency detuning which hampers the realization of zero modes.To address this issue, we developed a new design that we called “image barrier ” engineering technique, which enables precise control of coupling strength within 1D arrays of coupled cavities without the concomitant frequency detuning caused byterminations in the chain, thus, significantly expanding the observability range of zero modes. This method also facilitates the construction of cavity chains with nonuniform coupling, thus allowing us to assess the inherent immunity of zero modesto coupling perturbations. Remarkably, the ability to invert coupling signs enabled by our coupling control method leads to achieving an inversion of the zero mode's symmetry, broadening the potential for experimental and theoretical investigationsof these modes, either symmetry or topologically protected. This gives a handle to realize in-phase zero-mode oscillation, a crucial requirement to improve the far-field of topological lasers

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12

Lee, Moonhyun. "Digital-Based Zero-Current Switching (ZCS) Control Schemes for Three-Level Boost Power-Factor Correction (PFC) Converter". Diss., Virginia Tech, 2020. http://hdl.handle.net/10919/99694.

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With the increasing demands on electronic loads (e.g. desktop, laptop, monitor, LED lighting and server) in modern technology-driven lives, performance of switched-mode power supply (SMPS) for electronics have been growing to prominence. As front-end converters in typical SMPS structure, ac-dc power-factor correction (PFC) circuits play a key role in regulations of input power factor, harmonics and dc output voltage, which has a decisive effect on entire power-supply performances. Universal ac-line and low-power system (90–264 Vrms, up to 300–400 W) is one of the most common power-supply specifications and boost-derived PFC topologies have been widely used for the purpose. In order to concurrently achieve high efficiency and low-cost system in the PFC stage, zero-current switching (ZCS) control schemes are highly employed in control principles. Representative schemes are discontinuous conduction mode (DCM) and critical conduction mode (CRM). Both modes can realize ZCS turn-on without diode reverse recovery so that low switching losses and low-cost diode utilizations are obtainable. Among various boost-family PFC topologies, three-level boost (TLB) converter has generated considerable research interest in high-voltage high-power applications. It is mainly due to the fact that the topology can have halved component voltage stresses, improved waveform qualities and electromagnetic interference (EMI) from phase interleaved continuous conduction mode (CCM) operations, compared to other two-level boost PFC converters. On the other hand, in the field of universal-line low-power applications, TLB PFC has been thoroughly out of focus since doubled component counts and increased control complexity than two-level topologies are practical burden for the low-cost systems. However, recent researches on TLB PFC with ZCS control schemes have found that cost-competitiveness of the topology is actually comparable to two-level boost PFC converters because the halved component voltage stresses enable usage of low voltage-rating components of which unit prices are cheaper than higher-rating ones. Based on the justification, researches on ZCS control schemes for TLB PFC have been conducted to get enhanced waveform qualities and performance factors. Following the research stream, a three-level current modulation scheme that can be adopted in both DCM and CRM is proposed in Chapter 2 of this dissertation. Main concept of the proposed current modulation is additional degree-of-freedom in current-slope shaping by differentiating on-times of two active switches, which cannot be found from any other single-phase boost-derived PFC topologies. Using the multilevel feature, proposed operations in one switching period consist of three steps: common-switch on-time, single-switch on-time and common-switch off-time. The single-switch on-time step is key design factor of the proposed modulation that can be utilized either in fixed or adjustable form depending on control purpose. Based on the basic modulation concept, three-level CRM control scheme, adjustable three-level DCM control scheme, and spread-spectrum frequency modulation (SSFM) with adjustable three-level DCM scheme are proposed in Chapter 3–5, respectively. In each chapter, implemented control scheme aims to improve different performance factors. In Chapter 3, the proposed three-level CRM scheme uses increased single-switch on-time period to reduce peak inductor current and magnitude of variable switching frequency. It is generally accepted fact that CRM operations suffer from high switching losses and poor efficiency at light load due to considerable increment of switching frequency. Thus, efficiency improvement effect by the proposed CRM scheme becomes remarkable as load condition goes lighter. In experimental verifications, maximum improvement is measured by 1.2% at light load (20%) and overall efficiency is increased by at least 0.4% all over the load range. In Chapter 4, three-level DCM control scheme adopts adjustable single-switch on-time period in fixed switching-frequency framework. The purpose of adjustable control scheme is to widen the length of non-zero inductor current period as much as possible so that discontinued current period and high peak current of DCM operations can be minimized. Experiment results show that, compared to conventional two-level DCM control, full-load peak inductor currents are reduced by 20.2% and 17.1% at 110 and 220 Vrms input voltage conditions, respectively. Moreover, due to turn-off switching energy decrements by the turn-off current reductions, efficiency is also improved by at least 0.4% regardless of input voltage and load conditions. In Chapter 5, a downward SSFM technique is developed first for DCM operations of boosting PFC converters including two-level topologies. This chapter aims to achieve significant reduction of high differential-mode (DM) EMI amplitudes from DCM operations, which is major drawback of DCM control. By using the simple linearized frequency modulation, peak DM EMI noise at full load condition is reduced by 12.7 dBμV than conventional fixed-frequency DCM control. On top of the proposed SSFM, the adjustable three-level DCM control scheme in Chapter 4 is adopted to get further reductions of EMI noises. Experimental results prove that the collaborations of SSFM and adjustable DCM scheme reduce the EMI amplitudes further by 2.5 dBμV than the result of SSFM itself. The reduced EMI amplitudes are helpful to design input EMI filter with higher cut-off frequency and smaller size. Different from two-level boosting PFC converters, TLB PFC topology has two output capacitors in series and inherently suffers from voltage unbalancing issue, which can be noted as topological trade-off. In Chapter 6, two simple but effective voltage balancing schemes are introduced. The balancing schemes can be easily built into the proposed ZCS control schemes in Chapter 3–5 and experimental results validate the effectiveness of the proposed balancing principles. For all the proposed control schemes in this dissertation, detailed operation principles, derivation process of key equations, comparative analyses, implementation method with digital controller and experimental verifications with TLB PFC prototype are provided.
Doctor of Philosophy
Electronic-based devices and loads have been essential parts of modern society founded on rapid advancements of information technologies. Along with the progress, power supplying and charging of electronic products become routinized in daily lives, but still remain critical requisites for reliable operations. In many power-electronics-based supplying systems, ac-dc power-factor correction (PFC) circuits are generally located at front-end to feed back-end loads from universal ac-line sources. Since PFC stages have a key role in regulating ac-side current quality and dc-side voltage control, the importance of PFC performances cannot be emphasized enough from entire system point of view. Thus, advanced control schemes for PFC converters have been developed in quantity to achieve efficient operations and competent power qualities such as high power factor, low harmonic distortions and low electromagnetic interferences (EMI) noises. In this dissertation, a sort of PFC topologies named three-level boost (TLB) converter is chosen for target topology. Based on inherent three-level waveform capability of the topology, multiple zero-current switching (ZCS) control schemes are proposed. Compared to many conventional two-level PFC topologies, TLB PFC can provide additional degree-of-freedom to current modulation. The increased control flexibility can realize improvements of various waveform qualities including peak current stress, switching frequency range, harmonics and EMI amplitude. From the experimental results in this dissertation, improvements of waveform qualities in TLB PFC with the proposed schemes are verified with comparison to two-level current control schemes; in terms of efficiency, the results show that TLB PFC with the proposed schemes can have similar converter efficiency with conventional two-level boost converter in spite of increased component counts in the topology. Further, the proposed three-level control schemes can be utilized in adjustable forms to accomplish different control objectives depending on system characteristics and applications. In each chapter of this dissertation, a novel control scheme is proposed and explained with details of operation principle, key equations and digital implementation method. All the effectiveness of proposals and analyses are validated by a proper set of experimental results with a TLB PFC prototype.

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13

Auger, Thomas. "Translocation de biopolymères à travers des pores naturels ou artificiels". Thesis, Sorbonne Paris Cité, 2016. http://www.theses.fr/2016USPCC128/document.

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La translocation de biopolymères à travers un nanopore intervient dans de nombreux processus biologiques et technologiques, comme le transport nucléocytoplasmique dans le pore nucléaire des cellules eucaryotes, la sécrétion de protéines, le séquençage rapide de l’ADN ou l’électrophorèse capillaire.Nous proposons une technique optique en molécule unique originale pour l’étude de la translocation de biopolymères à travers un nanopore basée sur l’effet Zero-Mode Waveguide. Nous nous sommes intéressés au passage d’ADN double-brin de plusieurs tailles, d’ADN simple-brin et d’ARN, entraînés par un flux à travers une membrane nanoporeuse track-etched. Nous montrons qu’il existe un flux critique régissant le passage des biopolymères indépendant du rayon des pores ainsi que de la taille des biopolymères et de leur nature, conformément aux prédictions théoriques de Brochard et de Gennes.Le pore nucléaire est un nanopore biologique responsable du transport sélectif entre le noyau et lecytoplasme des cellules. Nous avons étudié l’influence de la concentration en importinBeta1 – une protéine nécessaire au transport nucléocytoplasmique – sur l’organisation du canal central du pore nucléaire deXenopus laevis en mesurant la diffusion de molécules de Dextran fluorescentes à travers celui-ci. Nous observons une ouverture du canal central à basse concentration suivi d’un rétrécissement de celui-ci à plus forte concentration. Cette évolution du rayon du canal central avec la concentration en importin Beta1est conforme aux modèles en champ moyen de Opferman et coll. et de Ando et coll. et aux observations expérimentales sur des systèmes reconstitués in vitro de Lim et coll. et Zahn et coll
The translocation of biopolymers through a nanopore is a feature common to many biological andtechnological processes such as the nucleocytoplasmic transport through the nuclear pore complex(NPC), protein secretion, fast DNA sequencing or capillary electrophoresis.We have developed an original single molecule optical detection technique for the study of biopolymerstranslocation through a nanopore based on the Zero-Mode Waveguide effect. We studied thepassage of double stranded DNA of different sizes, of single stranded DNA and of double-stranded RNAdriven by a flux through track-etched nanoporous membranes. We demonstrate that translocation isgoverned by a critical flux independent of both biopolymer size and nature and of the pore radius inagreement with the theoretical predictions of Brochard and de Gennes.The NPC is a biological nanopore responsible for the selective transport between cytoplasm andnucleus in cells. We studied the influence of importinBeta1 concentration – a protein involved in the nucleocytoplasmictransport – on the structure of the central channel of the NPC of Xenopus laevis byassessing the diffusion of fluorescently labeled Dextran molecules through the NPC. We observe anopening of the central channel at low concentration followed by a shrinking at higher concentrationin importinBeta1 in agreement with mean-field models from Opferman et al. and Ando et al. and withexperiments on biomimetic in vitro systems from Lim et al. and Zahn et al

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14

Al, Shammeri Bashar Mohammed Flayyih. "A novel induction heating system using multilevel neutral point clamped inverter". Thesis, University of Plymouth, 2017. http://hdl.handle.net/10026.1/8305.

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This thesis investigates a novel DC/AC resonant inverter of Induction Heating (IH) system presenting a Multilevel Neutral Point Clamped (MNPCI) topology, as a new part of power supply design. The main function of the prototype is to provide a maximum and steady state power transfer from converter to the resonant load tank, by achieving zero current switching (ZCS) with selecting the best design of load tank topology, and utilizing the advantage aspects of both the Voltage Fed Inverter (VFI) and Current Fed Inverter (CFI) kinds, therefore it can considered as a hybrid-inverter (HVCFI) category . The new design benefits from series resonant inverter design through using two bulk voltage source capacitors to feed a constant voltage delivery to the MNPCI inverter with half the DC rail voltage to decrease the switching losses and mitigate the over voltage surge occurred in inverter switches during operation which may cause damage when dealing with high power systems. Besides, the design profits from the resonant load topology of parallel resonant inverter, through using the LLC resonant load tank. The design gives the advantage of having an output current gain value of about Quality Factor (Q) times the inverter current and absorbs the parasitic components. On the contrary, decreasing inverter current means decreasing the switching frequency and thus, decreasing the switching losses of the system. This aspect increases the output power, which increases the heating efficiency. In order for the proposed system to be more reliable and matches the characteristics of IH process , the prototype is modelled with a variable LLC topology instead of fixed load parameters with achieving soft switching mode of ZCS and zero voltage switching (ZVS) at all load conditions and a tiny phase shift angle between output current and voltage, which might be neglected. To achieve the goal of reducing harmonic distortion, a new harmonic control modulation is introduced, by controlling the ON switching time to obtain minimum Total Harmonic Distortion (THD) content accompanied with optimum power for heating energy.

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15

Huang, Weixing. "Design of a Radial Mode Piezoelectric Transformer for a Charge Pump Electronic Ballast with High Power Factor and Zero Voltage Switching". Thesis, Virginia Tech, 2003. http://hdl.handle.net/10919/31818.

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In a conventional electronic ballast for a fluorescent lamp, inductor-capacitor-transformer tank circuit is used. A Piezoelectric Transformer (PT) can potentially be used to replace such a tank circuit to save space and cost. In the past, ballast design using a PT requires selecting a PT from available samples which are normally not matched to specific application and therefore resulting in poor performance. In this thesis, a design procedure was proposed for designing a PT tailored for a 120-V 32-W electronic ballast with high power factor, high efficiency and Zero-Voltage-Switching (ZVS) of the inverter transistors that drive the lamp. This involves selection of PT materials, determination of geometries and the number of physical layers of the PT. A radial mode piezoelectric transformer prototype based on this design process was fabricated by Face Electronics Inc. and was tested experimentally, the results showed that the ballast using this custom-made PT achieved high power factor, Zero-Voltage-Switching and a 83% overall efficiency.
Master of Science

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16

Yeh, Chih-Shen. "Synchronous-Conduction-Mode Tapped-Inductor Buck Converter for Low-Power, High-Density Application". Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/81722.

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General-purpose step-down converter is essential in electronic system for processing energy from high-voltage rail to low-voltage circuits. The applications can be found at the auxiliary supplies in automobile, industrial and communication systems. Buck converter is a common circuit topology to fulfill step-down conversion, especially in low-power application since it is well-studied and straightforward. However, it suffers from low duty cycle under high step-down condition, and typically operates in continuous conduction mode (CCM) that generates large switching loss. On the other hand, as an extension of the buck converter, tapped-inductor (TI) buck converter has larger duty cycle while maintaining the structural simplicity. Therefore, the main objective of this thesis is to explore the potential of TI buck converter as a wide conversion range, high power density and high efficiency topology for low power application. To achieve high efficiency at switching frequency of MHz-level, synchronous conduction mode (SCM) is applied for turn-on losses elimination. The operation principle and power stage design of SCM TI buck is first introduced. The design of high switching frequency coupled inductor is emphasized since its size plays a critical role in power density. Loss breakdown is also provided to perform a comprehensive topological study. Secondly, detailed zero-voltage-switching (ZVS) condition of SCM TI buck is derived so that the converter does not experience redundant circulating energy. The experimental results of 15-W SCM TI buck converter prototypes are provided with 90.7% of peak power stage efficiency. The size of coupled inductor is down to 116 mm3. To enhance light-load efficiency, a variable frequency control scheme based on derived ZVS conditions is implemented with the switching frequency ranging from 2 MHz to 2.9 MHz.
Master of Science
General-purpose step-down converter is essential in electronic system for processing energy from high-voltage rail to low-voltage circuits. The applications can be found at the auxiliary supplies in automobile, industrial and communication systems. Typically, the ultimate goals of general-purpose step-down converter are versatility, high efficiency and compact size. Recently, tapped-inductor (TI) buck converter is studied since it could overcome the drawback of commonly used buck converter under high step-down conversion. Therefore, the potential of TI buck converter as a general-purpose step-down converter candidate is explored in this thesis, including control method, hardware design, etc. The thesis verifies that TI buck converter could have compact size while remaining efficient and adaptable.

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17

Heucke, Stephan F. Verfasser], e Hermann E. [Akademischer Betreuer] [Gaub. "Advancing nanophotonic devices for biomolecular analysis : force spectroscopy and nanopositioning of single molecules in zero-mode waveguides / Stephan F. Heucke. Betreuer: Hermann Gaub". München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1046785311/34.

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18

Komulainen, P. (Petri). "Coordinated multi-antenna techniques for cellular networks:Pilot signaling and decentralized optimization in TDD mode". Doctoral thesis, Oulun yliopisto, 2013. http://urn.fi/urn:isbn:9789526202815.

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Abstract This thesis concentrates on the design and evaluation of spatial user multiplexing methods via linear transmit-receive processing for wireless cellular multi-user multiple-input multiple-output (MIMO) communication systems operating in the time-division duplexing (TDD) mode. The main focus is on the acquisition of effective channel state information (CSI) that facilitates decentralized processing so that the network nodes – base stations (BS) and user terminals (UT), each employing an arbitrary number of antenna elements – are able to locally participate in the network adaptation. The proposed methods rely on the uplink-downlink channel reciprocity and spatially precoded over-the-air pilot signaling. Considering (single-cell) multi-user MIMO systems, coordinated zero-forcing transmit-receive processing schemes for the uplink (UL) are proposed. The BS computes the transmission parameters in a centralized manner and employs downlink (DL) pilot signals to convey the information of the beamformers to be used by the UTs. When coexisting with the DL zero-forcing, the precoded DL demodulation pilots can be reused for UL beam allocation, and the precoded UL demodulation pilots are reused in turn for partial channel sounding (CS). As a result, only the precoded pilot symbols are needed in both UL and DL. Moreover, a concept for reducing the number of the required orthogonal UL CS pilot resources is presented. Based on their DL channel knowledge, the multi-antenna UTs form fewer pilot beams by spatial precoding than conventionally needed when transmitting antenna-specific pilots. In the context of DL zero-forcing, when taking into account the CSI estimation error at the BS, the overhead reduction turns out to improve robustness and increase the average system capacity. Considering multi-cell multi-user MIMO systems, decentralized coordinated DL beamforming strategies based on weighted sum rate (WSR) maximization are proposed. An optimization framework where the WSR maximization is carried out via weighted sum mean-squared-error minimization is utilized, and the approach is generalized by employing antenna-specific transmit power constraints. The iterative processing consists of optimization steps that are run locally by the BSs. In one novel strategy, the coordinating cells update their transmit precoders and receivers one cell at a time, which guarantees monotonic convergence of the network-wide problem. The strategy employs separate uplink CS and busy burst pilot signaling to reveal the effective channels of the UTs to the neighboring BSs. In another novel strategy, the monotonic convergence is sacrificed to devise a faster scheme where the BSs are allowed to optimize their variables in parallel based on just the CS responses and additional low-rate backhaul information exchange. The numerical results demonstrate that WSR maximization has the desirable property that spatial user scheduling is carried out implicitly. Finally, methods for UL CS overhead reduction are presented, and the effect of CSI uncertainty is addressed
Tiivistelmä Tämä väitöskirja keskittyy lineaarisella lähetys- ja vastaanottoprosessoinnilla toteutettavien tilajakomonikäyttömenetelmien suunnitteluun ja arviointiin langattomissa moniantennisissa solukkoverkoissa, jotka hyödyntävät aikajakodupleksointia (TDD). Erityisesti tarkastellaan efektiivisen kanavatiedon hankintaa, joka mahdollistaa hajautetun prosessoinnin siten että verkkoelementit – tukiasemat ja terminaalit, jotka kukin hyödyntävät useaa antennielementtiä – voivat osallistua paikallisesti verkon adaptaatioon. Esitetyt menetelmät perustuvat ylä- ja alalinkin kanavien resiprookkisuuteen ja tilatasossa esikoodattuun opetus- eli pilottisignalointiin ilmarajapinnan yli. Yksisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään ylälinkin koordinoituja nollaanpakottavia lähetys- ja vastaanottomenetelmiä. Tukiasema laskee lähetysparametrit keskitetysti ja käyttää pilottisignaaleja kertomaan millaista lähetyskeilanmuodostusta terminaalien tulee käyttää. Alalinkin nollaanpakotuksen yhteydessä esikoodattuja demodulaatiopilotteja voidaan uudelleenkäyttää ylälinkin lähetyskeilojen allokointiin, ja esikoodattuja ylälinkin demodulaatiopilotteja uudelleenkäytetään puolestaan osittaiseen kanavan luotaukseen (sounding). Näin ollen molempiin suuntiin tarvitaan vain esikoodatut pilotit. Lisäksi työssä esitetään menetelmä ylälinkin luotauspilottiresurssitarpeen vähentämiseksi. Kanavatietoon perustuen moniantenniset terminaalit muodostavat tilatasossa esikoodattuja pilottilähetyskeiloja, joita tarvitaan vähemmän kuin perinteisiä antennikohtaisia pilotteja. Kun otetaan huomioon kanavanestimointivirhe tukiasemassa, resurssiensäästömenetelmä parantaa häiriösietoisuutta ja nostaa järjestelmän keskimääräistä kapasiteettia alalinkin nollaanpakotuksen yhteydessä. Monisoluisille monikäyttäjä- ja moniantennijärjestelmille esitetään hajautettuja koordinoituja alalinkin keilanmuodostusstrategioita, jotka perustuvat painotetun summadatanopeuden (WSR) maksimointiin. Valitussa optimointikehyksessä WSR:n maksimointi toteutetaan painotetun summaneliövirheen minimoinnin kautta, ja työssä menettelytapa yleistetään antennikohtaisten lähetystehorajoitusten tapaukseen. Iteratiivinen prosessointi koostuu optimointiaskelista, jotka tukiasemat paikallisesti suorittavat. Yhdessä esitetyssä strategiassa yhteistoiminnalliset solut päivittävät lähettimensä ja vastaanottimensa yksi solu kerrallaan, mikä takaa verkonlaajuisen ongelmanratkaisun monotonisen konvergenssin. Tämä strategia käyttää erillisiä ylälinkin luotaussignaaleja sekä varattu-signaaleja ilmaistakseen terminaalien efektiiviset kanavat naapuritukiasemille. Toisessa strategiassa monotoninen konvergenssi uhrataan ja kehitetään nopeammin adaptoituva menetelmä, jossa tukiasemat saavat optimoida muuttujansa rinnakkain, perustuen vain luotaussignaaleihin ja tukiasemien väliseen informaationvaihtoon. Numeeriset tulokset osoittavat, että WSR:n maksimointi toteuttaa aktiivisten käyttäjien valinnan tilatasossa implisiittisesti. Lopuksi esitetään menetelmiä luotauspilottiresurssitarpeen vähentämiseksi ja käsitellään kanavatiedon epävarmuuden vaikutusta

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19

Bobinski, Tomasz. "Métamatériaux pour les ondes à la surface de l'eau". Thesis, Paris 6, 2016. http://www.theses.fr/2016PA066125/document.

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Cette thèse porte sur l’étude numérique et expérimentale de l’utilisation de métamatériaux pour le contrôle des ondes à la surface de l’eau. Dans la première partie, nous avons montré comment focaliser les ondes à la surface de l’eau en utilisant une analogie existant avec des métamatériaux électromagnétiques de permittivité diélectrique quasi nulle qualifiés de ”epsilon-near-zero”. Cela a permis d’adapter le motif de phase à l’interface circulaire entre deux domaines présentant un contraste élevé de profondeur d’eau. L’analogie a donné lieu a un comportement fortement non linéaire des ondes, qui se manifeste par la génération d’une cascade de points focaux associés à des sous-multiples de longueurs d’onde par rapport à l’onde incidente. La deuxième application envisagée des métamatériaux pour les ondes à la surface est de rendre invisible les défauts géométriques d’un guide pour un observateur situé en champ lointain. Dans le premier projet lié au cloaking, des guides d’onde possédant différentes sections transverses ont été analysés. L’efficacité de la bathymétrie, donnée par la cartographie conformationnelle, a été evaluée numériquement en termes de propriétés de diffusion. Dans le second projet, nous avons montré numériquement comment rendre invisible un cylindre qui est décalé de l’axe d’un guide d’onde. Utiliser une bathymétrie de cloaking lisse autour du cylindre permet de reduire de manière significative la dispersion dans une large gamme de frequences. Des experiences réalisées avec des bathymétries conformes aux simulations ont confirmé une augmentation de la transmission par rapport à un scenario de référence avec fond plat
This thesis presents numerical and experimental results concerning usage of metamaterials for water waves control. Two applications were considered. Firstly, we showed how to focus water waves using analogy to a group of metamaterials called epsilon-near-zero. This allowed to tailor phase pattern at the circular interface between two domains with high contrast in water depth. The analogy resulted in highly nonlinear behaviour of waves, manifested by sub-wavelength cascade of focal spots with respect to the incident wave. The second considered application of metamaterials for water waves was hiding (cloaking) defects in a waveguide from the far-field observer. In the first project, related to cloaking, waveguide with varying cross-sections was analyzed. The efficiency of bathymetry, rendered by conformal mapping, was evaluated in terms of scattering properties. The influence of water waves dispersivity on the cancellation of scattering was also determined. Cloaking properties of the obtained bathymetry were experimentally confirmed using a wave packet characterized by broadband spectrum. In the second project, we showed how to cloak a cylinder that is shifted from the centreline of a waveguide. Smooth cloaking bathymetry surrounding a cylinder was able to significantly reduce the scattering in broad range of frequencies. The experimental counterparts confirmed increase in transmission with respect to a reference case with flat bathymetry. The remainder of the thesis presents novel method for the analysis of fringe profilometry images. Performance of the new method was compared to the Fourier Transform Profilometry. We obtained significant enhancement in spectral capabilities

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20

Fuentes, Andrés. "Abolishing Stockholm’s Public Transport Fares". Thesis, Uppsala universitet, Institutionen för geovetenskaper, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-332459.

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The decrease of car emission levels has stagnated in the latter years in Stockholm, Sweden. Since the city’s publictransit system is highly developed via its large access to areas located in the city’s outskirts, it could serve as a tool topartially replace the city's car traffic and reduce emissions. This study therefore aims to examine expected travelbehavior changes from a fare-free public transport system and investigate potential limitations when increasing thepublic transport travel degree in Stockholm. The theoretical background consists of the mode choice theory thatdissects the reasons behind travel habits, and the zero-price effect which explains the effects from abolishing priceswhen purchasing a service product. The methodological approach was conducted through a random probabilitysurvey conducted in a face-to-face mix mode survey interviews in outdoor environments and via computer-assistedtelephone interviewing. The data was then analyzed through MS Excel and SPSS to extract patterns and correlations.The results thereafter implicated preferences from the survey participants implying their desire to primarily reduce orabolish the public transport fares, which would lead to significant travel habits changes among the majority ofrespondents. This would result in a high number of both frequent car drivers and frequent public transit commutersthat would commute more by public transit and drive less.

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21

Hartono, Aryudha. "Microgrid Safety and Protection Strategies". Thesis, KTH, Elektroteknisk teori och konstruktion, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-226593.

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One of the challenging issues with the Microgrid is that the bidirectional power flow providedby the distributed generator (DG) which modify the fault current level. Furthermore, theinverter based-renewable energy source (IB-RES) limits the total fault current contributionto the grid due to its thermal capability. Since Microgrid should be able to operate in gridconnectedand islanded mode, protection strategies are needed to solve this challenging issue.By only having IB-RES and battery storage system, the fault condition and normaloperation cannot be distinguished. Apart from fault clearing issue, there is a consideration tostudy the fault isolation in the Microgrid under the limited fault current provided by IB-RES.To have fault isolation capability, the intelligent electrical device (IED) is needed. The firststep is to find a method that can detect a fault under the fault level modification constraint.This thesis presents a zero and negative sequence current protection to detect a fault.However, to make it selective, this protection will be applied directionally. It is common thatthe distribution grid has unbalanced load operation, thus providing zero and negativesequence component in the grid. To apply the directional zero and negative sequence currentprotection, the unbalanced load flow is simulated to distinguish the fault and normaloperation under unbalanced load condition.Safety and regulation are discussed briefly in this thesis. It is important that each of theIB-RES has fault ride-through (FRT) capability that follows a regulation. However, thisregulation is expected to have a coordination with the proposed protection in the Microgridso the reliability, selectivity, and sensitivity can be achieved in grid-connected and islandedmode. This thesis shows the coordination between fuses, IED, and inverter FRT capability.After providing a protection strategy, the adaptability of the proposed protection isassessed regarding of Microgrid expansion. The result shows that by applying the schemeand following the grading margin requirement that is presented in this thesis, the Microgridexpansion will not disrupt the proposed protection coordination. Since it is known that thedistribution grid is expanding its load capacity and microgeneration in continuous basis, it isconvenient that the proposed protection in the IED is expected to be adaptable, means that ithas a fixed IED setting when the grid is expanded. The analysis is performed by electrical transient analysis program (ETAP) and MatlabSimulink. The short circuit analysis, sequence-of-operation, and unbalanced load flow aresimulated by ETAP, while the protection stability is simulated by Matlab Simulink.
Ett problem som finns med microgrid är att de distribuerade produktionsgeneratorerna harett dubbelriktat effektflöde som modifierar felströmmen. Dessutom, inverterbaseradeförnyelsebara energikällor (IB-RES) begränsar det totala felströmsbidraget på grund av desstermiska kapacitet. Eftersom microgrids ska vara operativ vid både anslutning till externt nätsamt önätsdrift behövs skyddsstrategier för att kunna hantera fel, speciellt vid önätsdrift.Om endast IB-RES och batterilager används kan feldrift och normal drift inte särskiljas.Bortsätt från felhantering är det viktigt att studera felbortkoppling för microgrid underbegränsad felström som fås av IB-RES. För att kunna åstadkomma felbortkoppling behöveren IED (från engelskans Intelligent Electronic Device). Det första steget är att finna en metodför att kunna detektera fel under fel nivå modifiering. Denna avhandling tittar på att användanoll- och minusföljds ström sekvensskydd för att detektera fel. För att göra skyddet selektivtkommer det att titta på riktningen av effektflödet. I distributionsnät är det vanligt att haobalanserade laster vilket medför noll- och negativa sekvenskomponenter i nätet. För atttillämpa riktningsskydd för noll och negativ sekvens ström simuleras ett obalanserateffektflöde för att särskilja på feldrift och normal drift vid obalanserad last.Säkerhet och förordningar diskuteras kortfattat i denna avhandling. Det är viktigt att varjeIB-RES har en feltålighet som följer vissa förordningar. Denna förordning förväntassamordna det föreslagna skyddet i micronåt så att pålitlighet, selektivitet och känslighet kanåstadkommas vid nätanslutning och önätsdrift. Denna avhandling visar samordningen mellansäkringar, IED och feltåligheten för växelomriktare.Anpassningsförmågan för det föreslagna skyddet bedöms med avseende på expansion avmicrogrid. Resultatet visar att en expansion av ett microgrid inte kommer att störa denföreslagna samordningen om skyddsmetoden och tidsfördröjningskravet som presenteras idenna avhandling följs. Eftersom det är känt att distributionsnätet kommer att fortsätta ökasin lastkapacitet och mikrogenerering, är det lämpligt att skyddet förväntas varaanpassningsbart vilket innebär att det har en fast IED inställning när nätet expanderas.Analysen genomförs med mjukvarorna electrical transient analysis program (ETAP) ochMatlab Simulink. Kortslutningsanalysen, arbetssekvensen och obalanserad lastflödesimuleras av ETAP, medan skyddsstabiliteten simuleras av Matlab Simulink.

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22

Ghorbani, Ghomeshi Ramin. "Pair Production and the Light-Front Vacuum". Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-83444.

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Dominated by Heisenberg's uncertainty principle, vacuum is not quantum mechanically an empty void, i.e. virtual pairs of particles appear and disappear persistently. This nonlinearity subsequently provokes a number of phenomena which can only be practically observed by going to a high-intensity regime. Pair production beyond the so-called Sauter-Schwinger limit, which is roughly the field intensity threshold for pairs to show up copiously, is such a nonlinear vacuum phenomenon. From the viewpoint of Dirac's front form of Hamiltonian dynamics, however, vacuum turns out to be trivial. This triviality would suggest that Schwinger pair production is not possible. Of course, this is only up to zero modes. While the instant form of relativistic dynamics has already been at least theoretically well-played out, the way is still open for investigating the front form. The aim of this thesis is to explore the properties of such a contradictory aspect of quantum vacuum in two different forms of relativistic dynamics and hence to investigate the possibility of finding a way to resolve this ambiguity. This exercise is largely based on the application of field quantization to light-front dynamics. In this regard, some concepts within strong field theory and light-front quantization which are fundamental to our survey have been introduced, the order of magnitude of a few important quantum electrodynamical quantities have been fixed and the basic information on a small number of nonlinear vacuum phenomena has been identified. Light-front quantization of simple bosonic and fermionic systems, in particular, the light-front quantization of a fermion in a background electromagnetic field in (1+1) dimensions is given. The light-front vacuum appears to be trivial also in this particular case. Amongst all suggested methods to resolve the aforementioned ambiguity, the discrete light-cone quantization (DLCQ) method is applied to the Dirac equation in (1+1) dimensions. Furthermore, the Tomaras-Tsamis-Woodard (TTW) solution, which expresses a method to resolve the zero-mode issue, is also revisited. Finally, the path integral formulation of quantum mechanics is discussed and, as an alternative to TTW solution, it is proposed that the worldline approach in the light-front framework may shed light on different aspects of the TTW solution and give a clearer picture of the light-front vacuum and the pair production phenomenon on the light-front.

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23

Ye, Zhihong. "Modeling and Control of Parallel Three-Phase PWM Converters". Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/29476.

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This dissertation studies modeling and control issues of parallel three-phase pulse-width modulated (PWM) converters. The converters include three-phase boost rectifiers, voltage source inverters, buck rectifiers and current source inverters. The averaging of the parallel converters is performed based on a generic functional switching unit, which is called a phase leg in boost rectifiers and voltage source inverters, and a rail arm in buck rectifiers and current source inverters. Based on phase-leg and rail-arm averaging, the developed models are not only equivalent to the conventional three-phase converter models that are based on phase-to-phase averaging, but they also preserve common-mode information, which is critical in the analysis of the parallel converters. The models reveal such parallel dynamics as reactive power circulation and small-signal interaction. A unique feature of the parallel three-phase converters is a zero-sequence circulating current. This work proposes a novel zero-sequence control concept that uses variable zero-vectors in the space-vector modulation (SVM) of the converters. The control can be implemented within an individual converter and is independent from the other control loops for the converter. Therefore, it greatly facilitates the design and expansion of a parallel system. Proper operation of the parallel converters requires an explicit load-sharing mechanism. In order to have a modular design, a droop method is recommended. Traditionally, however, a droop method has to compromise between voltage regulation and load sharing. After parametric analysis, a novel droop method using a gain-scheduling technique is proposed. The numeric analysis shows that the proposed droop method can achieve both good voltage regulation and good load sharing. An interleaving technique is often used in parallel converter systems in order to reduce current ripples. Because of its symmetrical circuit structure, the parallel three-phase converter system can reduce both differential-mode and common-mode noise with a center-aligned symmetrical SVM. Based on the concept that a symmetrical circuit can reduce common-mode dv/dt noise, a conventional three-phase, four-leg inverter is modified so that its fourth leg is symmetrical to the other three legs. The common-mode dv/dt noise can be practically eliminated with a new modulation strategy. Meanwhile, with a modified control design, the new four-leg inverter still can handle low-frequency common-mode components that occur due to unbalanced and nonlinear load.
Ph. D.

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24

Lovgren, Nicholas Keith. "Energy Harvesting From Exercise Machines: Forward Converters with a Central Inverter". DigitalCommons@CalPoly, 2011. https://digitalcommons.calpoly.edu/theses/520.

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This thesis presents an active clamp forward converter for use in the Energy Harvesting From Exercise Machines project. Ideally, this converter will find use as the centerpiece in a process that links elliptical trainers to the California grid. This active clamp forward converter boasts a 14V-60V input voltage range and 150W power rating, which closely match the output voltage and power levels from the elliptical trainer. The isolated topology outputs 51V, higher than previous, non-isolated attempts, which allows the elliptical trainers to interact with a central grid-tied inverter instead of many small ones. The final converter operated at greater than 86% efficiency over most of the elliptical trainer’s input range, and produced very little noise, making it a solid choice for this implementation.

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Kaya, Mehmet Can. "Design, Implementation, And Control Of A Two&amp". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610106/index.pdf.

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In this thesis a two-stage AC/DC/DC power converter is designed and implemented. The AC/DC input stage of the converter consists of the two&
#8211
phase interleaved boost topology employing the average current mode control principle. The output stage consists of a zero voltage switching phase shifted full bridge (ZVS&
#8211
PS&
#8211
FB) DC/DC converter. For the input stage, main design goals are obtaining high input power factor, low input current distortion, and well regulated output dc voltage, and obtaining these attributes in a power converter with high power density. For the input stage, the interleaved structure has been chosen in order to obtain reduced line current ripple and EMI, reduced power component stresses, and improved power density. The control of the pre&
#8211
regulator is provided by utilizing a new commercial monolithic integrated circuit, which provides interleaved continuous conduction mode power factor correction (PFC). The output stage is formed by utilizing the available prototype hardware of a ZVS&
#8211
PS&
#8211
FB DC/DC converter and mainly the system integration and controller design and implementation studies have been conducted. The converter small signal model is derived and utilizing its transfer function and employing voltage loop control, the output voltage regulator has been designed. The output voltage controller is implemented utilizing a digital signal processor (DSP). Integrating the AC/DC preregulator and DC/DC converter, a laboratory AC/DC/DC converter system with high overall performance has been obtained. The overall system performance has been verified via computer simulations and experimental results obtained from laboratory prototype.

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26

Liu, Hai. "Semiparametric regression analysis of zero-inflated data". Diss., University of Iowa, 2009. https://ir.uiowa.edu/etd/308.

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Zero-inflated data abound in ecological studies as well as in other scientific and quantitative fields. Nonparametric regression with zero-inflated response may be studied via the zero-inflated generalized additive model (ZIGAM). ZIGAM assumes that the conditional distribution of the response variable belongs to the zero-inflated 1-parameter exponential family which is a probabilistic mixture of the zero atom and the 1-parameter exponential family, where the zero atom accounts for an excess of zeroes in the data. We propose the constrained zero-inflated generalized additive model (COZIGAM) for analyzing zero-inflated data, with the further assumption that the probability of non-zero-inflation is some monotone function of the (non-zero-inflated) exponential family distribution mean. When the latter assumption obtains, the new approach provides a unified framework for modeling zero-inflated data, which is more parsimonious and efficient than the unconstrained ZIGAM. We develop an iterative algorithm for model estimation based on the penalized likelihood approach, and derive formulas for constructing confidence intervals of the maximum penalized likelihood estimator. Some asymptotic properties including the consistency of the regression function estimator and the limiting distribution of the parametric estimator are derived. We also propose a Bayesian model selection criterion for choosing between the unconstrained and the constrained ZIGAMs. We consider several useful extensions of the COZIGAM, including imposing additive-component-specific proportional and partial constraints, and incorporating threshold effects to account for regime shift phenomena. The new methods are illustrated with both simulated data and real applications. An R package COZIGAM has been developed for model fitting and model selection with zero-inflated data.

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27

Roemmele, Eric S. "A Flexible Zero-Inflated Poisson Regression Model". UKnowledge, 2019. https://uknowledge.uky.edu/statistics_etds/38.

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A practical problem often encountered with observed count data is the presence of excess zeros. Zero-inflation in count data can easily be handled by zero-inflated models, which is a two-component mixture of a point mass at zero and a discrete distribution for the count data. In the presence of predictors, zero-inflated Poisson (ZIP) regression models are, perhaps, the most commonly used. However, the fully parametric ZIP regression model could sometimes be restrictive, especially with respect to the mixing proportions. Taking inspiration from some of the recent literature on semiparametric mixtures of regressions models for flexible mixture modeling, we propose a semiparametric ZIP regression model. We present an "EM-like" algorithm for estimation and a summary of asymptotic properties of the estimators. The proposed semiparametric models are then applied to a data set involving clandestine methamphetamine laboratories and Alzheimer's disease.

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28

Sattar, T. P. "Self-tuning control with pole-zero placement". Thesis, London South Bank University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379446.

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29

Roxlo, Thomas (Thomas Q. ). "Zero sound modes in the AdS/CFT correspondence". Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/78493.

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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Physics, 2012.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 41-42).
We examine the effects of zero sound wave excitations of charged fermion species living around the charged black hole of an AdS/CFT spacetime. In particular, we show that these bulk modes cause corresponding singularities in the correlation functions of boundary gauge fields. Possible implications for the study of non-Fermi liquids are discussed.
by Thomas Roxlo.
S.B.

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30

Breve, Danilo Gondim. "Zero waste: design sustentável aplicado ao ensino de moda". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/100/100133/tde-20122018-001634/.

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Esta pesquisa apresenta um estudo sobre a aplicação da estratégia de design zero waste como instrumento de ensino, objetivando desenvolver noções de design sustentável em estudantes de curso técnico de moda. O zero waste (zero resíduos) possui um método de criação cujo principal objetivo é não gerar resíduos sólidos têxteis durante o processo de confecção da roupa, que possam impactar o meio ambiente. É uma técnica ainda pouco conhecida no Brasil e pouco utilizada, tanto no ensino técnico de moda quanto nas empresas. Este estudo apresenta uma pesquisa bibliográfica e pesquisa-ação sobre a técnica de design zero waste, com a finalidade de evoluir com as experiências e pesquisas já realizadas sobre o assunto e identificar referências que possam incrementar atividades aplicáveis ao ensino técnico de moda. Diante disso, propõe-se um conjunto de exercícios de design sustentável utilizando a técnica zero waste. Os exercícios são aplicados em forma de workshop para gerar informações que possam contribuir com a discussão de resultados sobre a sua aplicabilidade e aceitação
This research presents a study on the application of the zero waste design technique as a teaching tool, aiming to develop notions of sustainable design in fashion technical course students. Zero waste has a method of creation whose main objective is not to generate solid textile waste during the garment making process, which can impact the environment. It is a technique still little known in Brazil and little used, both in fashion teaching and in companies. This study presents a bibliographical research and action research on the technique of zero waste design, in order to learn from the experiences and research already done on the subject and to identify references that may increase activities applicable to fashion technical teaching. Therefore, a set of exercises of sustainable design using the zero waste technique is proposed. The exercises are applied in the form of a workshop to generate information that can contribute to the discussion of results on its applicability and acceptance

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31

Zavaleta, Katherine Elizabeth Coaguila. "Modelo destrutivo com variável terminal em experimentos quimiopreventivos de tumores em animais". Universidade Federal de São Carlos, 2012. https://repositorio.ufscar.br/handle/ufscar/4561.

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Made available in DSpace on 2016-06-02T20:06:07Z (GMT). No. of bitstreams: 1 4375.pdf: 903031 bytes, checksum: 03118f406867a5d7be3cbc63571d4a2b (MD5) Previous issue date: 2012-04-12
Financiadora de Estudos e Projetos
The chemical induction of carcinogens in chemopreventive animal experiments is becoming increasingly frequent in biological research. The purpose of these biological experiments is to evaluate the effect of a particular treatment on the rate of tumors incidence in animals. In this work, the number of promoted tumors per animal will be parametrically modeled following the suggestions given by Kokoska (1987) and Freedman et al. (1993). The study of these chemopreventive experiments will be presented in the context of the destructive model proposed by Rodrigues et al. (2010) with terminal variable that allows or censures the experiment at time of the animal death. Since the data analyzed in this field are subject to excess of zeros (Freedman et al. (1993)), we propose for the number of promoted tumors a negative binomial distribution (NB), a zero-inflated Poisson distribution (ZIP), and a zero-inflated Negative Binomial distribution (ZINB). The selection of these models will be made through the likelihood ratio test and the AIC, BIC criteria. The estimation of its parameters will be obtained by using the method of maximum likelihood, and further simulation studies will also be realized. As a future proposition to finalize this project, it is suggested the Bayesian methodology as an alternative to the method of maximum likelihood via the EM algorithm.
A indução química de substâncias cancerígenas em experimentos quimiopreventivos em animais é cada vez mais frequente em pesquisas biológicas. O objetivo destes experimentos biológicos é avaliar o efeito de um determinado tratamento na taxa de incidência de tumores em animais. Neste trabalho o número de tumores promovidos por animal será modelado parametricamente seguindo as sugestões dadas por Kokoska (1987) e por Freedman et al. (1993). O estudo desses experimentos quimiopreventivos será apresentado no contexto do modelo destrutivo proposto por Rodrigues et al. (2010) com variável terminal que condiciona ou censura o experimento no instante de morte do animal. Os dados analisados possuem uma grande quantidade de zeros, portanto será proposto para o número de tumores promovidos as seguintes distribuições: binomial negativa, a distribuição de Poisson com zeros inflacionados e a distribuição binomial negativa com zeros inflacionados. A seleção destes modelos será feita através do teste da razão de verossimilhança e os critérios AIC, BIC. As estimativas dos respectivos parâmetros serão obtidas utilizando o método de máxima verossimilhança e serão feitos estudos de simulação. Para continuar este projeto, a proposta futura é utilizar a metodologia Bayesiana como alternativa ao método de máxima verossimilhança via algoritmo EM.

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32

BARBAGLIA, ANDREA. "ELECTRO-TUNABLE OPTICAL DEVICES FOR MOLECULAR AND CELLULAR STUDIES". Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1001750.

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In the present scenario of information technology, researchers are looking for new systems able to deal more efficiently with the increasing amount of information produced by modern society. Nowadays, these tasks are accomplished by CMOS transistors and FLASH memories. Despite their wide implementation, these devices are facing serious issues along their road of development, mainly related to stable operation and power dissipation managing. Advancements in this field could boost the application of artificial intelligence and Big Data analysis, as well as enable new data communication protocols. By taking inspiration from the brain, a very powerful system characterized by low power consumption and high interconnectivity, new proposed devices, such as RRAM memories, aim at overcoming these issues. Properly engineered systems of this typology could act moreover as platforms for more precise and comprehensive biomedical studies. In this thesis, a new class of electro-tunable optical devices is presented in the framework of next-generation memory systems. The model device possesses very favorable characteristics, such as high density and interconnectivity. Moreover, the optical readout, performed by a camera, enables parallel operation. Two realizations of this device concept were studied. The first one is a new configuration for Zero-Mode Waveguides (ZMWs), a well-known nanophotonic system used to perform studies on fluorophore dispersion at the single molecule level. In the proposed device, the interplay of an electric voltage allows to control fluorophore concentration and residence time inside the ZMWs. The light intensity coming from the ZMWs gives information about these two parameters. In the second realization, the developed ZMWs platform is used to perform an optical detection of cardiomyocytes action potentials (APs). The cells are cultured on a thin substrate placed above the fluorophore dispersion. The substrate features an array of pass-through electrodes, which allow the electric APs to be transferred from the cells to the fluorophore dispersion. APs were successfully measured with high SNR. Moreover, the device proved able to detect the effects of a drug administered to the cell culture. This device could find application as a new system for in-vitro electrophysiology, including drugs cardiotoxicity studies. Due to the optical readout scheme, it promises to offer very high spatial resolution, orders of magnitude higher than conventional multi-electrode arrays systems.

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33

Sedlák, Jiří. "Zero Waste - "Valuation and business planning" pro potenciálního investora". Master's thesis, Vysoká škola ekonomická v Praze, 2015. http://www.nusl.cz/ntk/nusl-206492.

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The target of Zero Waste "Valuation and business planning" for a potential investor is to explore and evaluate the identified market opportunity. Business plan concerns the foundation of food and consumer goods retail business which is aimed towards reducing consumers negative impact on the environment, supporting local jobs and sustainable farming. The thesis is based on theoretical knowledge from the publications listed in the resources which were confronted with the reality in interviews with the owners of comparable businesses. Resulting from the business planning a calculation of present value of the proposed model enterprise has been made. Value calculated using discounted cash flows had shown that cannot be unequivocally recommended to establish the company. Pessimistic scenario shows a negative net present value and realistic option shows a positive net present value. However it is necessary to understand the thesis as a model business plan for valuation of such businesses. As for example with a different form of funding or reduction of initial investment, the company may change to a version that would be recommendable to implement.

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34

Grammenidis, Ackis, e Anna Fattor. "Zero impact or zero reliability? : An empirical test of Capital Asset Pricing Model during periods ofzero risk-free rate". Thesis, Umeå University, Umeå School of Business, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-25631.

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1.3. Research Questions.

With this in mind, the research questions of this work are:

1. Is the Capital Asset Pricing Model still applicable despite the heavy impact of the financial crisis on the financial systems?

2. What happens to this model when the risk free rate approaches zero?

3. Is there a relationship between the riskiness of an asset and the risk-free interestrate when the latter is approaching the zero level?

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35

Wang, Shin Cheng. "Analysis of Zero-Heavy Data Using a Mixture Model Approach". Diss., Virginia Tech, 1998. http://hdl.handle.net/10919/30357.

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The problem of high proportion of zeroes has long been an interest in data analysis and modeling, however, there are no unique solutions to this problem. The solution to the individual problem really depends on its particular situation and the design of the experiment. For example, different biological, chemical, or physical processes may follow different distributions and behave differently. Different mechanisms may generate the zeroes and require different modeling approaches. So it would be quite impossible and inflexible to come up with a unique or a general solution. In this dissertation, I focus on cases where zeroes are produced by mechanisms that create distinct sub-populations of zeroes. The dissertation is motivated from problems of chronic toxicity testing which has a data set that contains a high proportion of zeroes. The analysis of chronic test data is complicated because there are two different sources of zeroes: mortality and non-reproduction in the data. So researchers have to separate zeroes from mortality and fecundity. The use of mixture model approach which combines the two mechanisms to model the data here is appropriate because it can incorporate the mortality kind of extra zeroes. A zero inflated Poisson (ZIP) model is used for modeling the fecundity in Ceriodaphnia dubia toxicity test. A generalized estimating equation (GEE) based ZIP model is developed to handle longitudinal data with zeroes due to mortality. A joint estimate of inhibition concentration (ICx) is also developed as potency estimation based on the mixture model approach. It is found that the ZIP model would perform better than the regular Poisson model if the mortality is high. This kind of toxicity testing also involves longitudinal data where the same subject is measured for a period of seven days. The GEE model allows the flexibility to incorporate the extra zeroes and a correlation structure among the repeated measures. The problem of zero-heavy data also exists in environmental studies in which the growth or reproduction rates of multi-species are measured. This gives rise to multivariate data. Since the inter-relationships between different species are imbedded in the correlation structure, the study of the information in the correlation of the variables, which is often accessed through principal component analysis, is one of the major interests in multi-variate data. In the case where mortality influences the variables of interests, but mortality is not the subject of interests, the use of the mixture approach can be applied to recover the information of the correlation structure. In order to investigate the effect of zeroes on multi-variate data, simulation studies on principal component analysis are performed. A method that recovers the information of the correlation structure is also presented.
Ph. D.

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36

Guo, Yixuan. "Bayesian Model Selection for Poisson and Related Models". University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439310177.

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Abbas, Ghulam. "Analysis, modelling, design and implementation of fast-response digital controllers for high-frequency low-power switching converters". Thesis, Lyon, INSA, 2012. http://www.theses.fr/2012ISAL0055.

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L'objectif de la thèse est de concevoir des compensateurs discrets qui permettent de compenser les non-linéarités introduites par les différents éléments dans la boucle de commande numérique, tout en maintenant des performances dynamiques élevées, des temps de développement rapide, et une structure reconfigurable. Ces compensateurs discrets doivent également avoir des temps de réponse rapide, avoir une déviation de la tension minimale et avoir, pour un étage de puissance donné, un temps de récupération rapide de la tension. Ces performances peuvent être atteintes par des compensateurs discrets conçus sur la base de techniques de contrôle linéaires et non linéaires. Pour obtenir une réponse rapide et stable, la thèse propose deux solutions : La première consiste à utiliser des techniques de contrôle linéaires et de concevoir le compensateur discret tout en gardant la bande passante la plus élevée possible. Il est communément admis que plus la bande passante est élevée, plus la réponse transitoire est rapide. L‘obtention d’une bande passante élevée, en utilisant des techniques de contrôle linéaires, est parfois difficile. Toutes ces situations sont mises en évidence dans la thèse. La seconde consiste à combiner les techniques de contrôle linéaires avec les techniques de contrôles non linéaires tels que la logique floue ou les réseaux de neurones. Les résultats de simulations ont permis de vérifier que la combinaison des contrôleurs non-linéaires avec les linéaires ont un meilleur rendement dynamique que les contrôleurs linéaires lorsque le point de fonctionnement varie. Avec l'aide des deux méthodes décrites ci-dessus, la thèse étudie également la technique de l’annulation des pôles-zéros (PZC) qui annule la fonction de transfert du convertisseur. Quelques modifications des techniques classiques de contrôle sont également proposées à partir de contrôleurs numériques afin d’améliorer les performances dynamiques. La thèse met également en évidence les non-linéarités qui dégradent les performances, propose les solutions permettant d'obtenir les meilleures performances, et lève les mystères du contrôle numérique. Une interface graphique est également introduite et illustrée dans le cas de la conception d'un convertisseur abaisseur de tension synchrone. En résumé, cette thèse décrit principalement l'analyse, la conception, la simulation, l’optimisation la mise en œuvre et la rentabilité des contrôleurs numériques. Une attention particulière est portée à l'analyse et l'optimisation des performances dynamique à haute fréquence et pour de faibles puissances des convertisseurs DC-DC abaisseur de tension. Ces convertisseurs fonctionnent en mode de conduction continue (CCM) à une fréquence de commutation de 1 MHz et s’appuie sur des techniques de contrôle linéaires et non linéaires de façon séquentielle
The objective of the thesis is to design the discrete compensators which counteract the nonlinearities introduced by various elements in the digital control loop while delivering high dynamic performance, fast time-to-market and scalability. Excellent line and fast load transient response, which is a measure of the system response speed, with minimal achievable voltage deviation and a fast voltage recovery time for a given power stage can be achieved through the discrete compensators designed on the basis of linear and nonlinear control techniques. To achieve a stable and fast response, the thesis proposes two ways. One way is to use linear control techniques to design the discrete compensator while keeping the bandwidth higher. It is well-known fact that the higher the bandwidth, the faster is the transient response. Achieving higher bandwidth through linear control techniques sometimes becomes tricky. All those situations are highlighted in the thesis. The other way is to hybridize the linear control techniques with the nonlinear control techniques such as fuzzy logic or neural network based control techniques. Simulation results verify that hybridization of nonlinear controllers with the linear ones have better dynamic performance over linear controllers under the change of operating points. Along with using the two methodologies described above, the thesis also investigates the pole-zero cancellation (PZC) technique in which the poles and zeros of the compensator are placed in such a way that they cancel the effect of the poles or zeros of the buck converter to boost the phase margin at the required bandwidth. Some modifications are also suggested to the classical control techniques based digital controllers to improve the dynamic performance. The thesis highlights the nonlinearities which degrade the performance, a cost-effective solution that achieves good performance and the mysteries of digital control system. A graphical user interface is introduced and demonstrated for use with the design of a synchronous-buck converter. In summary, this thesis mainly describes the analysis, design, simulation, optimization, implementation and cost effectiveness of digital controllers with particular focus on the analysis and the optimization of the dynamic performance for high-frequency low-power DC-DC buck converter working in continuous conduction mode (CCM) operating at a switching frequency of 1 MHz using linear and nonlinear control techniques in a very sequential and comprehensive way

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Hossan, Md Shakawat. "Prediction Model to Estimate the Zero Crossing Point for Faulted Waveforms". UKnowledge, 2014. http://uknowledge.uky.edu/ece_etds/53.

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In any power system, fault means abnormal flow of current. Insulation breakdown is the cause of fault generation. Different factors can cause the breakdown: Wires drifting together in the wind, Lightning ionizing air, wires with contacts of animals and plants, Salt spray or pollution on insulators. The common type of faults on a three phase system are single line-to-ground (SLG), Line-to-line faults (LL), double line-to-ground (DLG) faults, and balanced three phase faults. And these faults can be symmetrical (balanced) or Unsymmetrical (imbalanced).In this Study, a technique to predict the zero crossing point has been discussed and simulated. Zero crossing point prediction for reliable transmission and distribution plays a significant role. Electrical power control switching works in zero crossing point when a fault occurs. The precision of measuring zero crossing point for syncing power system control and instrumentation requires a thoughtful approach to minimize noise and external signals from the corrupted waveforms A faulted current waveform with estimated faulted phase/s, the technique is capable of identifying the time of zero crossing point. Proper Simulation has been organized on MATLAB R2012a.

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Pedersen, Kristen E. "Sample Size Determination in Auditing Accounts Receivable Using a Zero-Inflated Poisson Model". Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-theses/421.

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In the practice of auditing, a sample of accounts is chosen to verify if the accounts are materially misstated, as opposed to auditing all accounts; it would be too expensive to audit all acounts. This paper seeks to find a method for choosing a sample size of accounts that will give a more accurate estimate than the current methods for sample size determination that are currently being used. A review of methods to determine sample size will be investigated under both the frequentist and Bayesian settings, and then our method using the Zero-Inflated Poisson (ZIP) model will be introduced which explicitly considers zero versus non-zero errors. This model is favorable due to the excess zeros that are present in auditing data which the standard Poisson model does not account for, and this could easily be extended to data similar to accounting populations.

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40

Zeileis, Achim, Christian Kleiber e Simon Jackman. "Regression Models for Count Data in R". Foundation for Open Access Statistics, 2008. http://epub.wu.ac.at/4986/1/Zeileis_etal_2008_JSS_Regression%2DModels%2Dfor%2DCount%2DData%2Din%2DR.pdf.

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The classical Poisson, geometric and negative binomial regression models for count data belong to the family of generalized linear models and are available at the core of the statistics toolbox in the R system for statistical computing. After reviewing the conceptual and computational features of these methods, a new implementation of hurdle and zero-inflated regression models in the functions hurdle() and zeroinfl() from the package pscl is introduced. It re-uses design and functionality of the basic R functions just as the underlying conceptual tools extend the classical models. Both hurdle and zero-inflated model, are able to incorporate over-dispersion and excess zeros-two problems that typically occur in count data sets in economics and the social sciences-better than their classical counterparts. Using cross-section data on the demand for medical care, it is illustrated how the classical as well as the zero-augmented models can be fitted, inspected and tested in practice. (authors' abstract)

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41

Senturk, Huseyin. "An Empirical Comparison Of Interest Rate Models For Pricing Zero Coupon Bond Options". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609786/index.pdf.

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The aim of this study is to compare the performance of the four interest rate models (Vasicek Model, Cox Ingersoll Ross Model, Ho Lee Model and Black Der- man Toy Model) that are commonly used in pricing zero coupon bond options. In this study, 1{5 years US Treasury Bond daily data between the dates June 1, 1976 and December 31, 2007 are used. By using the four interest rate models, estimated option prices are compared with the real observed prices for the begin- ing work days of each months of the years 2004 and 2005. The models are then evaluated according to the sum of squared errors. Option prices are found by constructing interest rate trees for the binomial models based on Ho Lee Model and Black Derman Toy Model and by estimating the parameters for the Vasicek and the Cox Ingersoll Ross Models.

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42

SILENZI, FEDERICO. "DYNAMIC THERMAL ANALYSIS OF NEARLY ZERO EMISSION BUILDINGS WITH GEOTHERMAL AND SOLAR PLANTS". Doctoral thesis, Università degli studi di Genova, 2020. http://hdl.handle.net/11567/1002027.

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At the present day, the need for the reduction of energy consumption is one of the main issues, from the technical, economic and environmental point of view. Buildings are responsible for more than 40% of energy utilization in European countries in 2017 [1]. Thus, actions that increase building energy efficiency are mandatory. Some interventions on the envelope and the internal operating conditions are addressed to the reduction of the heating and cooling loads of the building (i.e. the energy needs). Others pertain directly to the plants that must be properly selected and sized considering, if possible, also the use of renewable energies. In this framework, the present study is devoted to the analysis of energy-efficient buildings, with features aimed to reduce the loads and equipped with efficient plant solutions including innovative ground coupled water-to-water heat pumps and high efficiency air to air heat pump with energy recovery. The first part of the study is devoted to the ground heat exchangers and in particular to the modeling of energy geopiles in which the geothermal heat exchangers are integrated into the foundations of the building. To correctly size a ground heat exchanger (HE) field, in terms of total length, the number of HE and spacing, the ground response is needed and is provided in terms of g–function. A new semi-analytical method is proposed, based on the spatial superposition of a basic analytical solution, namely the single point source solution. This method allows generating ground response function (g-functions) for shapes of the heat exchanger different from classical linear one, as for the case of helix. The method has been validated by comparison with literature analytical solutions and with FEM simulations with Comsol Multiphysics. The second part of the research is devoted to developing a comprehensive model for dynamical energy simulations of a Nearly-Zero-Emission-Building. The model, developed with three different software (Sketch-Up, Openstudio and Energy Plus), represents the Smart Energy Building (SEB) located in the Savona Campus of the University of Genoa. The SEB is a very innovative building for both the envelope (ventilated facades) and the energy systems (i.e. geothermal heat pump and high efficiency air-to-air heat pump with energy recovery). Moreover, it has a complete monitoring system with numerous sensors that provide in real-time numerous thermal and electrical data (temperature, mass flow rates, electrical power, current, etc). All the detailed features of the building have been analyzed: the geometry, the materials, and the internal operating conditions. The climatic conditions of the site where the building is located are considered through a proper weather file. That information allows evaluating, firstly, the heating and cooling loads, which means the energy needs of the building during winter and summer. Then, the thermal plants have been introduced into the model, namely the ground coupled water-to-water heat pump and the air handler associated to a high efficiency air-to-air heat pump with energy recovery. For both the heat pumps, the performance (COP and EER) depends on the load and source-side fluid temperatures. This feature has been carefully implemented in the Energyplus model. The main results from the simulations are zone temperatures and primary energy consumption from the heating and cooling plants. Finally, the PV modules located on the roof of the SEB have been included in the model. The PV field has been analyzed considering electrical power production, cell temperature and solar irradiance received. The SEB is included in the complex and complete monitoring system of the Smart Polygeneration Microgrid of the Savona Campus The validation process of the model with real measurements from the SEB monitoring system would represent an important and original contribution of this study. Unfortunately, a complete analysis is not possible at the moment due to the unavailability of data series about the ventilation system. However, a preliminary comparison between model and measured data has been realized for the electrical production from the PV modules of the roof of the building. In particular, the EnergyPlus model has been updated by inserting a properly modified weather file with the measured values of outdoor air temperature and solar irradiance (global horizontal value). The calculation is done for two sample months (i.e. January and June 2018). The comparison shows a quite good agreement between simulated data trends and measured values, with a discrepancy at peak values. It is not clear if this disagreement is imputable to poor simulation parameter choice or errors in measures acquisition. Future work will be aimed towards completing the validation of the model using the huge amount of data from the monitoring system. Moreover, the model will be used to study the SEB thermal flexibility to different control strategies.

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Dufner, Michael, Daniel Leising e Jochen E. Gebauer. "Which Basic Rules Underlie Social Judgments?: Agency Follows a Zero-Sum Principle and Communion Follows a Non-Zero-Sum Principle". Sage, 2016. https://tud.qucosa.de/id/qucosa%3A35366.

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How are people who generally see others positively evaluated themselves? We propose that the answer to this question crucially hinges on the content domain: We hypothesize that Agency follows a “zero-sum principle” and therefore people who see others as high in Agency are perceived as low in Agency themselves. In contrast, we hypothesize that Communion follows a “non-zero-sum principle” and therefore people who see others as high in Communion are perceived as high in Communion themselves. We tested these hypotheses in a round-robin and a half-block study. Perceiving others as agentic was indeed linked to being perceived as low in Agency. To the contrary, perceiving others as communal was linked to being perceived as high in Communion, but only when people directly interacted with each other. These results help to clarify the nature of Agency and Communion and offer explanations for divergent findings in the literature.

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44

Ånestad, Astrid. "Net electricity load profiles of Zero Emission buildings : A Cost Optimization Investment Model for Investigating Zero Balances, Operational Strategies and Grid Restrictions". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-27253.

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On the way to meet the internationally sanctioned climate targets, zero emission buildings / zero energy buildings (ZEB) will be an important step. Research is ongoing on what a reasonable definition of ZEB will contain. In Norway, it is decided that the building code should be nearly zero energy buildings from the year 2020. In this master’s thesis, an optimization model for finding cost-optimal investment and operational strategies for ZEB is developed. The building modelled, is a passive school with a hydronic heat distribution system. Possible investments include photovoltaic solar cells (PV), solar collectors, heat pumps, biomass boilers, electric boiler, heat storage and connection to the district heating grid. The model is designed as a dynamic mixed integer programming model, and implemented in Mosel Xpress. The model minimizes the total discounted costs of operations and investments over the lifetime of the building. Different restrictions of zero CO2 emissions, zero primary energy consumption and level of grid burden can be applied. The analysis shows that if a zero CO2 restriction with Norwegian CO2 factors are applied, the least expensive way to reach ZEB is by investing in PV in combination with pellet biomass boiler as base load and district heating to cover peak demand. To reach the zero balance for the school with Norwegian CO2 factors, the highest hourly value for export of electricity per hour exceeds the maximum hourly value of imports by about 120%. If European factors for CO2 is applied, it will be more reasonable to reach ZEB than with Norwegian factors. If asymmetric primary energy factors are used instead of symmetric factors, investment in PV becomes higher, and the peak export values increases. The model is developed as a deterministic model, and does not take into account uncertainties in input data. To compensate for this, various sensitivity analyses are conducted. Future work includes testing the model with load profiles for other types of buildings.

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Dehghanikiadehi, Abbas. "Commande vectorielle innovante pour véhicules électriques ou hybrides". Thesis, Université Clermont Auvergne‎ (2017-2020), 2017. http://www.theses.fr/2017CLFAC012/document.

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Durant ces dernières années, l'intérêt pour les technologies des véhicules à faibles émissions de carbone a fait un bond important à travers l'Union européenne (UE) et au-delà, encouragé en cela par les gouvernements et les constructeurs automobiles. De grands espoirs ont été mis plus récemment dans les véhicules électriques (VE) et les véhicules électriques hybrides (VEH) en tant que technologies clés pour atténuer le changement climatique, améliorer la sécurité énergétique et favoriser une nouvelle branche de l'industrie dans le secteur automobile. Ainsi, l'électrification des transports a été considérée comme une stratégie clé pour réduire les émissions de CO2 dans le secteur des transports. Le principal défi est d’augmenter l’autonomie des véhicules (ce qui a toujours été au coeur de la concurrence des industries du transport), ainsi que la durée de vie des volumineuses et coûteuses batteries. Par conséquent, ceci indique que le rendement du convertisseur de puissance est un des points clés à développer pour les générations des véhicules électriques à venir. L’autre paramètre influant est la qualité de la tension et du courant (en particulier la suppression des harmoniques basses fréquences) qui permet de réduire la taille des filtres d'entrée et de sortie de ces convertisseurs. L'objectif de cette thèse est de parvenir à un meilleur rendement en proposant de nouvelles structures de convertisseur de puissance et des commandes vectorielles modifiées ; le choix de deux onduleurs alimentant un moteur ouvert aux deux extrémités. Après l'analyse étape par étape, modèle théorique, simulation et enfin une mise en oeuvre expérimentale, il a été constaté que les nouvelles méthodes proposées sont compétitives et peuvent s’appliquer aux cas des VEH et des VE afin d’apporter des caractéristiques supérieures en termes d’efficacité et de qualité de tension et de courant
Over the last decade, the interest for low-carbon vehicle technologies has surged among both governments and automotive manufacturers across and beyond the European Union (EU). Great hopes have been put, first, on biofuel vehicles and more recently on electric vehicles (EVs) and hybrid electric vehicles (HEVs) as key technologies to mitigate climate change, enhance energy security and nurture new industry branches within the automotive sector. So electrification of vehicles has been seen as a key strategy to reduce CO2 emissions from the transport sector. The main challenge toward EVs and HEVs is to keep driving for longer distance (which has been always fields for competition among traction industries) as well as lifetime battery cells as storage system. As a result, these indicate importance of power converter efficiency as a key gate for next generations of these up-coming vehicles. The next parameter is the quality of output voltage/current (especially by suppressing low-order harmonics) to reduce the size of filtering. The aim of this thesis is to achieve better efficiency and output voltage/current Total Harmonic Distortion (THD) by proposing novel power converter and associated Pulse Width Modulation (PWM) methods while imposing modification on power converter topology. As a result, dual-inverter is proposed to supply open-end motor from both sides. To this aim, three PWM methods are suggested as: The first one, Modified Space Vector Modulation (MSVM) for dual-inverter supplied by single dc source, improves efficiency by 4-5% (while having lower switching losses), and reduces Common Mode Voltage (CMV) levels by 66%, as well. The voltage/current harmonics are analytically analyzed which shows mainly better performance. Effective switching frequency is also reduced by 66% due to the reduction of number of commutations. In the second one, Near State PWM (NSPWM) is adapted for dual-inverter supplied by single dc source in order to eliminate triplen harmonics (therefore Zero Sequence Voltage, ZSV) and improve efficiency (by 3-4%) compared to Space Vector Modulation (SVM). Additionally due to avoiding use of zero vectors, CMV is improved by 66%. While having 8 commutations instead of 12 in SVM, effective switching frequency is improved by 33%. And finally, the third proposed method deals with NSPWM for dual-inverter supplied by two isolated dc sources wherein efficiency and CMV levels show the same performance as previous one. However, in this method, voltage THD is highly reduced compared to SVM. Triplen harmonics of the output voltage are inherently suppressed by the structure. These 3 proposed methods are analytically studied and their performances are step by step simulated in Matlab/Simulink environment. Then the methods are implemented in dualinverter fed open-end motor in laboratory setup; and the results are compared with these of SVM. Finally, it is found that novel proposed methods are so competitive solutions to be applied in HEVs and EVs and bring superior efficiency and voltage/current harmonic features

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Tạ, Ngọc Trí. "Results on the number of zero modes of the Weyl-Dirac operator". Thesis, Lancaster University, 2009. http://eprints.lancs.ac.uk/30804/.

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For a given magnetic potential A one can define the Weyl-Dirac operator σ·(-i∇-A) on R³. An L² eigenfunction of σ·(-i∇-A) corresponding to 0 is called a zero mode. In this thesis we will be concerned with the zero mode problem for the Weyl-Dirac operator and some related problems. The main results are: (i) upper bounds for the number of zero modes of the Weyl-Dirac operator in three dimensions when scaling a given magnetic field. A similar version for the Dirac operator in two dimensions is also obtained. There are also related results to estimate the number of zero modes of the massless Dirac operator, and the dimension of the eigenspaces at threshold energies for the Dirac operator with positive mass. (ii) construction of Dirac operators on the unit ball S² of R³ as well as the determination of their spectrum in case of "constant" magnetic fields. We also show another proof for the Aharonov-Casher theorem for S² based on results about spectral properties of Dirac operators that we have obtained. (iii) a formula giving the number of zero modes of the Weyl-Dirac operator for a special magnetic field, which is the result of pullbacks from the "constant" volume form of S². We also obtain a lower bound for the number of zero modes for the Weyl-Dirac operator corresponding to certain scaled magnetic fields; the magnetic fields are parallel to fibres of the Hopf fibration (pulled-back to R³ using inverse stereographic projection).

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47

Walters, David Nathan. "The 3+1 dimensional lattice NJL model at non-zero baryon density". Thesis, Swansea University, 2003. https://cronfa.swan.ac.uk/Record/cronfa42346.

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Lattice simulations of the 3+1 dimensional Nambu-Jona-Lasinio model are undertaken that provide non-perturbative evidence for the existence of a BCS superfluid phase in the low temperature, high density regime. Standard analytic methods are used to fit the model's free parameters to low energy vacuum phenomenology. The model is simulated numerically for a range of baryon chemical potential mu, with the introduction of a diquark source j to allow for the observation of spontaneous U(1) global symmetry breaking in a finite volume system. For mu ≥ 0.6 inverse lattice spacings and in the limit that j → 0, a non-zero diquark condensate, a vanishing diquark susceptibility ratio and an energy gap Delta ≠ 0 about the Fermi surface in the fermion dispersion relation are all consistent with the ground-state being that of a U(l)-broken BCS superfluid. The ratio between the gap at mu = 0.8 and the vacuum fermion mass is found to be 0.15(2). This is interpreted as tentative non-perturbative evidence for the existence of a colour superconducting phase in cold, dense QCD. The effects of simulating on a finite volume, and any conditions this places on the above conclusions, are investigated. Finally, the results of some initial studies at non-zero isospin chemical potential and the prospect of simulations at non-zero temperature are discussed.

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48

Adams, Rory Montague. "Zero modes and degrees of freedom of topological solitons on the plane". Master's thesis, University of Cape Town, 2003. http://hdl.handle.net/11427/13891.

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Includes bibliographical references.
In this thesis we analyse the coaxial multivortices of the Ginzburg-Landau, the Euclidean complex sine-Gordon-1 and -2 theories on the plane. More specifically, we determine the number of continuous free parameters describing the largest family of solutions, with these vortices as members. This is accomplished by obtaining the zero modes of the vortices. For the Ginzburg-Landau model we show that the multivortices do not belong to a larger family of solutions and only depend on parameters describing their global U(1) symmetry and translations in the plane. Thus it is not possible to continuously deform these coaxial multivortices into a system of multiple, separated vortices. In contrast, the multivortices of complex sine-Gordon-1 model are shown to have an infinite number of zero modes and can be continuously deformed into a configuration of multiple, separated vortices. We also show that the largest family of solutions, with these coaxial multivortices as members, is a recently discovered family describing non-coaxial multivortices. For the complex sine-Gordon-2, we show the coaxial multivortices belong to a larger family of solutions which depend on a finite number of continuous free parameters. We also speculate as to the form of solutions that this larger family can describe.

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Fan, Taian. "Zero-Group-Velocity Propagation Of Electromagnetic Wave Through Nanomaterial". ScholarWorks @ UVM, 2016. https://scholarworks.uvm.edu/graddis/549.

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This research will investigate the problem on the propagation of electromagnetic wave through a specific nanomaterial. The nanomaterial analyzed is a material consisting of a field of Pt nanorods. This field of Pt nanorods are deposited on a substrate which consists of a RuO2 nano structure. When the nanorod is exposed to an electron beam emitted by a TEM (Transmission electron microscopy). A wave disturbance has been observed. A video taken within the chamber shows a wave with a speed in the scale of um/s (Á?10Á?^(-6) m/s), which is 14 orders of magnitude lower than speed of light in free space (approximate 3ÁÁ?10Á?^8 m/s ). A physical and mathematical model is developed to explain this phenomenon. Due to the process of fabrication, the geometry of the decorated Pt nanorod field is assumed to be approximately periodic. The nanomaterials possess properties similar to a photonic crystal. Pt, as a noble metal, shows dispersive behaviours that is different from those ones of a perfect or good conductors. A FDTD algorithm is implemented to calculate the band diagram of the nanomaterials. To explore the dispersive properties of the Pt nanorod field, the FDTD algorithm is corrected with a Drude Model. The analysis of the corrected band diagram illustrates that the group velocity of the wave packet propagating through the nanomaterial can be positive, negative or zero. The possible zero-group velocity is therefore used to explain the extremely low velocity of wave (wave envelope) detected in the TEM.

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Olinde, Lindsay. "Sediment Oxygen Demand Kinetics". Thesis, Virginia Tech, 2007. http://hdl.handle.net/10919/42437.

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Hypolimnetic oxygen diffusers increase sediment oxygen demand (SOD) and, if not accounted for in design, can further exacerbate anoxic conditions. A study using extracted sediment cores, that included both field and laboratory experiments, was performed to investigate SOD kinetics in Carvinâ s Cove Reservoir, a eutrophic water supply reservoir for Roanoke, Virginia. A bubble-plume diffuser is used in Carvinâ s Cove to replenish oxygen consumed while the reservoir is thermally stratified. The applicability of zero-order, first-order, and Monod kinetics to describe transient and steady state SOD was modeled using analytical and numerical techniques. Field and laboratory experiments suggested that first-order kinetics characterize Carvinâ s Cove SOD. SOD calculated from field experiments reflected diffuser flow changes. Laboratory experiments using mini-diffusers to vary dissolved oxygen concentration and turbulence were conducted at 4Â°C and 20Â°C. Similar to field observations, the laboratory results followed changes in mini-diffuser flow. Kinetic-temperature relationships were also observed in the laboratory experiments. A definitive conclusion could not be made on the broad applicability of first-order kinetics to Carvinâ s Cove SOD due to variability within field experiments. However, in situ experiments are underway that should assist in the overall understanding of the reservoirâ s SOD kinetics.
Master of Science

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