Дисертації з теми "Transformers efficients"
Щоб переглянути інші типи публікацій з цієї теми, перейдіть за посиланням: Transformers efficients.
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Transformers efficients".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
1
Condevaux, Charles. "Méthodes d'apprentissage automatique pour l'analyse de corpus jurisprudentiels." Thesis, Nîmes, 2021. http://www.theses.fr/2021NIME0008.
Анотація:
Les décisions de justice contiennent des informations déterministes (dont le contenu est récurrent d'une décision à une autre) et des informations aléatoires (à caractère probabiliste). Ces deux types d'information rentrent en ligne de compte dans la prise de décision d’un juge. Les premières peuvent la conforter dans la mesure où l’information déterministe est un élément récurrent et bien connu de la jurisprudence (i.e. des résultats d’affaires passées). Les secondes, apparentées à des caractères rares ou exceptionnels, peuvent rendre la prise de décision difficile et peuvent elles-mêmes modifier la jurisprudence. L’objet de cette thèse est de proposer un modèle d’apprentissage profond mettant en évidence ces deux types d’information afin d’en étudier leur impact (contribution) dans la prise de décision d’un juge. L'objectif est d’analyser des décisions similaires, de mettre en évidence les informations aléatoires et déterministes dans un corpus de décisions et de quantifier leur importance dans le processus de jugementJudicial decisions contain deterministic information (whose content is recurrent from one decision to another) and random information (probabilistic). Both types of information come into play in a judge's decision-making process. The former can reinforce the decision insofar as deterministic information is a recurring and well-known element of case law (ie past business results). The latter, which are related to rare or exceptional characters, can make decision-making difficult, since they can modify the case law. The purpose of this thesis is to propose a deep learning model that would highlight these two types of information and study their impact (contribution) in the judge’s decision-making process. The objective is to analyze similar decisions in order to highlight random and deterministic information in a body of decisions and quantify their importance in the judgment process
2
TANTEH, DERICK NJOMBOG, SHAFIQ YOUSEF AL-LIDDAWI, and DANIEL SSEKASIKO. "PROPERTIES OF TRANSFORMER OIL THAT AFFECT EFFICIENCY." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2664.
Анотація:
Abstract. Transformer explosions caused by dielectric failure account for over 50% of the disasters. The aim of this thesis is to examine, compare and outline the differences, in function, as dielectric insulators, vegetables oil has, with respect to the mineral oil used in high-power transformers. We will first consider the vegetable oil which has less dielectric capabilities than the mineral oil used in power transformers. Later in the experiments, we will focus mainly to examine the breakdown voltage property, as we try to alter some properties of the respective oils used. Considering the fact that vegetable oil has low viscosity, with its chemical compounds constituting less molecular masses compared to mineral oil, we endorse, from our experimental findings, that mineral oil is indeed worthy and reasonable to be used as a dielectric in high power transformers. In this write-up, we have considered eleven transformer oil properties. In the experiment proper, we considered only the acidity, whose concentration in the transformer oil increases with aging if the transformer, moisture, and a ‘suitable’ impurity like NaOH(aq). At first glance, one would be tempted to think, as we were, that since the increase in acid content of the oil deteriorates its dielectric performance, an increase in alkaline content of the transformer oil, would increase its dielectric ability; reversing the acid effect. But as we see in the results from our experiments, this is false. We think that the visible degradation of the insulating property of the oil, with the introduction of NaOH(aq), is because it acts as an impurity to suitable dielectric function. From the experiments, the heating procedures resulted in the production of toxic gases. This indicated the actual loss of chemical structure and significant breakage of chemical bonds. The resulting chemical composition of the oil does not produce the same dielectric properties as the initial oil sample. Also, here has been considerable inconsistency in the addition of NaOH(aq) or HCl(aq) to both oils. We only added HCl(aq), before every measurement, in two of the experiments. The other experiments were either with moisture, or a single addition of 2cm3 of either HCl(aq) or NaOH(aq) before heating; after which several measurements were taken, at specific intervals, as the mixture cools. We did so, in the latter, in which we had only one addition of a 2cm3 chemical, because in real life, given the short time frame of the experiment, the total amount of acid in the oil has a negligible change. So, in a functioning heated transformer, within a short time frame, there is actually deterioration in oil insulation properties
3
Liu, Du. "Efficient Video Coding with Motion-Compensated Orthogonal Transforms." Thesis, KTH, Ljud- och bildbehandling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91858.
Анотація:
Well-known standard hybrid coding techniques utilize the concept of motioncompensated predictive coding in a closed-loop. The resulting coding dependencies are a major challenge for packet-based networks like the Internet. On the other hand, subband coding techniques avoid the dependencies of predictive coding and are able to generate video streams that better match packet-based networks. An interesting class for subband coding is the socalled motion-compensated orthogonal transform. It generates orthogonal subband coefficients for arbitrary underlying motion fields. In this project, a theoretical lossless signal model based on Gaussian distribution is proposed. It is possible to obtain the optimal rate allocation from this model. Additionally, a rate-distortion efficient video coding scheme is developed that takes advantage of motion-compensated orthogonal transforms. The scheme combines multiple types of motion-compensated orthogonal transforms, variable block size, and half-pel accurate motion compensation. The experimental results show that this scheme outperforms individual motion-compensated orthogonal transforms.
4
Pasini, Damiano. "A new theory for modelling the mass efficiency of material, shape and form." Thesis, University of Bristol, 2002. http://hdl.handle.net/1983/a88a3e49-72b2-4605-974b-1cc589649c82.
5
Hamood, Monir Taha. "Development of efficient algorithms for fast computation of discrete transforms." Thesis, University of Newcastle Upon Tyne, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576637.
Анотація:
Transforms are widely used in diverse applications of science, engineering and technology. In particular, the field of digital signal processing has grown rapidly and achieved their performance through the development of fast algorithms for computing discrete transforms. This thesis focuses on the computation, generalisation and applications of four commonly used transforms, namely the new Mersenne number transform (NMNT), the discrete Fourier transform (DFT), the discreet Hartley transform (DHT), and the Walsh-Hadamard transform (WHT). As a result, several new algorithms are developed and two number theoretic transforms (NTTs) are introduced. The NMNT has been proved to be an important transform as it is utilised for error- free calculation of convolution and correlation with long transform lengths. In this thesis, new algorithms for the fast calculation of the NMNT based on the Rader- Brenner approach are developed, where the transform's structure is enhanced and the lowest multiplicative complexity among all existing NMNT algorithms is achieved. Two new NTTs defined modulo the Mersenne primes, named odd NMNT (ONMNT) and odd-squared NMNT (02NMNT), are introduced for incorporation into generalised NMNT (GNMNT) transforms which are categorised by type, with detailed instructions regarding their derivations. Development of their radix-2 and split radix algorithms, along with an example of the calculation of different types of convolutions, shows that these new transforms are suitable for wide range of applications. In order to take advantage of the simplest structural complexity provided by the radix-2 algorithm and the reduced computational complexity offered by a higher radix algorithm, a technique suitable for combining these two algorithms has been proposed, producing new fast Fourier transform (FFT) algorithms known as radix-Z' FFTs. In this thesis, a general decomposition method for developing these algorithms is introduced based on the decimation in time approach, applicable to one and multidimensional FFTs. The DHT has been proposed as an efficient alternative to the DFT for real data applications, because it is a real-to-real transform and possesses similar properties as the DFT. Based on the relationship between the DHT and complex-valued OFT, a unified 'FFT to FHT transition approach' is presented, providing a translation of FFT algorithms into their fast Hartley transform (FHT) counterparts. Using this approach, many new FHT algorithms in one and multidimensional cases are obtained. Finally, the combination of the WHT with the DFT has been proved to be a good candidate for improving the performances of orthogonal frequency division multiplexing (OFDM) systems. Therefore, part of this thesis deals with the Walsh- Hadamard-Fourier transform (WFT) that combines these transforms into a single orthogonal transform. Development of fast WFT (FWFT) algorithms has shown a significant reduction in the number of arithmetic operations and computer run times.
6
Pang, Erwin. "Parameter estimation and efficient implementation of affine transforms for digital images." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp01/MQ28850.pdf.
7
Al-Azawi, Saad Mohammed Saleh. "Efficient architectures for multidimensional discrete transforms in image and video processing applications." Thesis, University of Newcastle upon Tyne, 2013. http://hdl.handle.net/10443/2131.
Анотація:
This thesis introduces new image compression algorithms, their related architectures and data transforms architectures. The proposed architectures consider the current hardware architectures concerns, such as power consumption, hardware usage, memory requirement, computation time and output accuracy. These concerns and problems are crucial in multidimensional image and video processing applications. This research is divided into three image and video processing related topics: low complexity non-transform-based image compression algorithms and their architectures, architectures for multidimensional Discrete Cosine Transform (DCT); and architectures for multidimensional Discrete Wavelet Transform (DWT). The proposed architectures are parameterised in terms of wordlength, pipelining and input data size. Taking such parameterisation into account, efficient non-transform based and low complexity image compression algorithms for better rate distortion performance are proposed. The proposed algorithms are based on the Adaptive Quantisation Coding (AQC) algorithm, and they achieve a controllable output bit rate and accuracy by considering the intensity variation of each image block. Their high speed, low hardware usage and low power consumption architectures are also introduced and implemented on Xilinx devices. Furthermore, efficient hardware architectures for multidimensional DCT based on the 1-D DCT Radix-2 and 3-D DCT Vector Radix (3-D DCT VR) fast algorithms have been proposed. These architectures attain fast and accurate 3-D DCT computation and provide high processing speed and power consumption reduction. In addition, this research also introduces two low hardware usage 3-D DCT VR architectures. Such architectures perform the computation of butterfly and post addition stages without using block memory for data transposition, which in turn reduces the hardware usage and improves the performance of the proposed architectures. Moreover, parallel and multiplierless lifting-based architectures for the 1-D, 2-D and 3-D Cohen-Daubechies-Feauveau 9/7 (CDF 9/7) DWT computation are also introduced. The presented architectures represent an efficient multiplierless and low memory requirement CDF 9/7 DWT computation scheme using the separable approach. Furthermore, the proposed architectures have been implemented and tested using Xilinx FPGA devices. The evaluation results have revealed that a speed of up to 315 MHz can be achieved in the proposed AQC-based architectures. Further, a speed of up to 330 MHz and low utilisation rate of 722 to 1235 can be achieved in the proposed 3-D DCT VR architectures. In addition, in the proposed 3-D DWT architecture, the computation time of 3-D DWT for data size of 144×176×8-pixel is less than 0.33 ms. Also, a power consumption of 102 mW at 50 MHz clock frequency using 256×256-pixel frame size is achieved. The accuracy tests for all architectures have revealed that a PSNR of infinite can be attained.
8
Ngounda, Edgard. "Efficient numerical methods based on integral transforms to solve option pricing problems." Thesis, University of the Western Cape, 2012. http://hdl.handle.net/11394/4223.
Анотація:
Philosophiae Doctor - PhDIn this thesis, we design and implement a class of numerical methods (based on integral transforms) to solve PDEs for pricing a variety of financial derivatives. Our approach is based on spectral discretization of the spatial (asset) derivatives and the use of inverse Laplace transforms to solve the resulting problem in time. The conventional spectral methods are further modified by using piecewise high order rational interpolants on the Chebyshev mesh within each sub-domain with the boundary domain placed at the strike price where the discontinuity is located. The resulting system is then solved by applying Laplace transform method through deformation of a contour integral. Firstly, we use this approach to price plain vanilla options and then extend it to price options described by a jump-diffusion model, barrier options and the Heston’s volatility model. To approximate the integral part in the jump-diffusion model, we use the Gauss-Legendre quadrature method. Finally, we carry out extensive numerical simulations to value these options and associated Greeks (the measures of sensitivity). The results presented in this thesis demonstrate the spectral accuracy and efficiency of our approach, which can therefore be considered as an alternative approach to price these class of options.
9
Islas, Michael. "EFFICIENCY IMPROVEMENT TECHNIQUES FOR HIGH VOLTAGE CAPACITOR CHARGING METHODS." Master's thesis, University of Central Florida, 2009. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/2969.
Анотація:
The goal of this thesis is to design and fabricate a DC-to-DC converter for use in high-voltage capacitor charging applications. The primary objectives include increasing the efficiency and reducing the cost of traditional methods used for this application. Traditional methods were not designed specifically for high-voltage capacitor charging and were thus very primitive and exhibited lower efficiency. Prior methods made use of a high voltage power supply and a current limiting resistor or control scheme. The power supply would often only operate efficiently at a single voltage value and would thus function poorly over a range used in charging a capacitor. The resistor would also dissipate a fair amount of power, also limiting efficiency. This design makes use of a traditional flyback topology utilizing a controller developed specifically for this application, centering the design approach on the LT3750. Hence, taking full advantage of the efficiency improving control scheme it provides. Additionally, through the use of advanced techniques to eliminate noise and power losses, the efficiency may be significantly improved. A detailed theoretical analysis of the charger is also presented. The analysis will then be applied to optimization techniques to select ideal component values to meet specific design specifications. In this research, a specifically designed and developed prototype will be used to experimentally verify the theoretical work and optimization techniques.M.S.E.E.
School of Electrical Engineering and Computer Science
Engineering and Computer Science
Electrical Engineering MSEE
10
Toivonen, T. (Tuukka). "Efficient methods for video coding and processing." Doctoral thesis, University of Oulu, 2008. http://urn.fi/urn:isbn:9789514286957.
Анотація:
Abstract
This thesis presents several novel improvements to video coding algorithms, including block-based motion estimation, quantization selection, and video filtering. Most of the presented improvements are fully compatible with the standards in general use, including MPEG-1, MPEG-2, MPEG-4, H.261, H.263, and H.264.
For quantization selection, new methods are developed based on the rate-distortion theory. The first method obtains locally optimal frame-level quantization parameter considering frame-wise dependencies. The method is applicable to generic optimization problems, including also motion estimation. The second method, aimed at real-time performance, heuristically modulates the quantization parameter in sequential frames improving significantly the rate-distortion performance. It also utilizes multiple reference frames when available, as in H.264. Finally, coding efficiency is improved by introducing a new matching criterion for motion estimation which can estimate the bit rate after transform coding more accurately, leading to better motion vectors.
For fast motion estimation, several improvements on prior methods are proposed. First, fast matching, based on filtering and subsampling, is combined with a state-of-the-art search strategy to create a very quick and high-quality motion estimation method. The successive elimination algorithm (SEA) is also applied to the method and its performance is improved by deriving a new tighter lower bound and increasing it with a small constant, which eliminates a larger part of the candidate motion vectors, degrading quality only insignificantly. As an alternative, the multilevel SEA (MSEA) is applied to the H.264-compatible motion estimation utilizing efficiently the various available block sizes in the standard.
Then, a new method is developed for refining the motion vector obtained from any fast and suboptimal motion estimation method. The resulting algorithm can be easily adjusted to have the desired tradeoff between computational complexity and rate-distortion performance. For refining integer motion vectors into half-pixel resolution, a new very quick but accurate method is developed based on the mathematical properties of bilinear interpolation.
Finally, novel number theoretic transforms are developed which are best suited for two-dimensional image filtering, including image restoration and enhancement, but methods are developed with a view to the use of the transforms also for very reliable motion estimation.
11
Zheng, Cong. "Loosely Coupled Transformer and Tuning Network Design for High-Efficiency Inductive Power Transfer Systems." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/52893.
Анотація:
Transfer signal without wire has been widely accepted after the introduction of cellular technology and WiFi technology, hence the power cable is the last wire that has yet to be eliminated. Inductive power transfer (IPT) has drawn substantial interest in both academia and industry due to its advantages including convenience, nonexistence of cable and connector, no electric shock issue, ability to work under some extreme environment, and so on. After performing thorough literature review of IPT systems, two major drawbacks including low power efficiency and coil displacement sensitivity are identified as the main obstacles that have to be solved in order for these systems to reach full functionality and compete with existing wired solutions.
To address the limitations and design challenges in the IPT systems, a detailed electric circuit modeling of individual part of the IPT DC-DC stage is performed. Several resonant DC-AC inverters and output AC-DC rectifiers are compared based on their performance and feasibility in inductive charging applications. Different equivalent circuit models for the loosely coupled
transformer (LCT) are derived which allows for better understanding on how power is distributed among the circuit components. Five compensation networks to improve the power transfer efficiency are evaluated and their suitable application occasions are identified.
With comprehensive circuit model analysis, the influence of the resonant compensation tank parameters has been investigated carefully for efficient power transfer. A novel tuning network parameters design methodology is proposed based on multiple given requirement such as battery charging profile, geometry constraints and operating frequency range, with the aim of avoiding bifurcation phenomenon during the whole charging process and achieving decent efficiency. A 4-kW hardware prototype based on the proposed design approach is built and tested under different gap and load conditions. Peak IPT system DC-DC efficiencies of 98% and 96.6% are achieved with 4-cm and 8-cm air gap conditions, which is comparable to the conventional plug-in type or wired charging systems for EVs. A long-hour test with real EV batteries is conducted to verify the wireless signal transmission and CC/CV mode seamless transition during the whole charging profile without bifurcation.
To reduce the IPT system sensitivity to the gap variation or misalignment, a novel LCT design approach without additional complexity for the system is proposed. With the aid of FEA simulation software, the influence of coil relative position and geometry parameters on the flux distribution and coupling coefficient of the transmitter and receiver is studied from an electromagnetic perspective. An asymmetrical LCT based on the proposed design method is built to compare with a traditional symmetrical LCT. With fixed 10-mm gap and 0 to 40-mm misalignment variation, the coupling coefficient for the symmetrical LCT drops from 0.354 to 0.107, and the corresponding efficiency decrease is 16.6%. The operating frequency variation is nearly 100 kHz to maintain same input/output condition. When employing the proposed asymmetrical LCT, the coupling coefficient changes between 0.312 and 0.273, and the maximum efficiency deviation is kept within 0.67% over the entire 40-mm misalignment range. Moreover, the required frequency range to achieve same operation condition is less than 10 kHz.
Lastly, some design considerations to further improve the IPT system efficiency are proposed on the basis of the designed asymmetrical LCT geometry. For given circuit specifications and LCT coupling conditions, determination of the optimal primary winding turns number could help achieve minimal winding loss and core loss. For lower output power, the optimal primary winding turns number tends to be larger compared to that for higher output power IPT system. Two asymmetrical LCT with similar dimension but different number of turns are built and tested with a 100-W hardware prototype for laptop inductive charging. The proposed efficiency improvement methodology is validated by the winding loss and core loss from experimental results.Ph. D.
12
Nestler, Franziska. "Efficient Computation of Electrostatic Interactions in Particle Systems Based on Nonequispaced Fast Fourier Transforms." Universitätsverlag der Technischen Universität Chemnitz, 2017. https://monarch.qucosa.de/id/qucosa%3A23376.
Анотація:
The present thesis is dedicated to the efficient computation of electrostatic interactions in particle systems, which is of great importance in the field of molecular dynamics simulations. In order to compute the therefor required physical quantities with only O(N log N) arithmetic operations, so called particle-mesh methods make use of the well-known Ewald summation approach and the fast Fourier transform (FFT). Typically, such methods are able to handle systems of point charges subject to periodic boundary conditions in all spatial directions. However, periodicity is not always desired in all three dimensions and, moreover, also interactions to dipoles play an important role in many applications.
Within the scope of the present work, we consider the particle-particle NFFT method (P²NFFT), a particle-mesh approach based on the fast Fourier transform for nonequispaced data (NFFT). An extension of this method for mixed periodic as well as open boundary conditions is presented. Furthermore, the method is appropriately modified in order to treat particle systems containing both charges and dipoles. Consequently, an efficient algorithm for mixed charge-dipole systems, that additionally allows a unified handling of various types of periodic boundary conditions, is presented for the first time. Appropriate error estimates as well as parameter tuning strategies are developed and verified by numerical examples.Die vorliegende Arbeit widmet sich der Berechnung elektrostatischer Wechselwirkungen in Partikelsystemen, was beispielsweise im Bereich der molekulardynamischen Simulationen eine zentrale Rolle spielt. Um die dafür benötigten physikalischen Größen mit lediglich O(N log N) arithmetischen Operationen zu berechnen, nutzen sogenannte Teilchen-Gitter-Methoden die Ewald-Summation sowie die schnelle Fourier-Transformation (FFT). Typischerweise können derartige Verfahren Systeme von Punktladungen unter periodischen Randbedingungen in allen Raumrichtungen handhaben. Periodizität ist jedoch nicht immer bezüglich aller drei Dimensionen erwünscht. Des Weiteren spielen auch Wechselwirkungen zu Dipolen in vielen Anwendungen eine wichtige Rolle. Zentraler Gegenstand dieser Arbeit ist die Partikel-Partikel-NFFT Methode (P²NFFT), ein Teilchen-Gitter-Verfahren, welches auf der schnellen Fouriertransformation für nichtäquidistante Daten (NFFT) basiert. Eine Erweiterung dieses Verfahrens auf gemischt periodische sowie offene Randbedingungen wird vorgestellt. Außerdem wird die Methode für die Behandlung von Partikelsystemen, in denen sowohl Ladungen als auch Dipole vorliegen, angepasst. Somit wird erstmalig ein effizienter Algorithmus für gemischte Ladungs-Dipol-Systeme präsentiert, der zusätzlich die Behandlung sämtlicher Arten von Randbedingungen mit einem einheitlichen Zugang erlaubt. Entsprechende Fehlerabschätzungen sowie Strategien für die Parameterwahl werden entwickelt und anhand numerischer Beispiele verifiziert.
13
Lee, Ockgoo. "High efficiency switching CMOS power amplifiers for wireless communications." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37145.
Анотація:
High-efficiency performance is one of the most important requirements of power
amplifiers (PAs) for wireless applications. However, the design of highly efficient CMOS
PAs for watt-level applications is a challenging task. This dissertation focuses on the
development of the design method for highly efficient CMOS PAs to overcome the
fundamental difficulties presented by CMOS technology.
In this dissertation, the design method and analysis for a high-power and highefficiency
class-E CMOS PA with a fully integrated transformer have been presented.
This work is the first effort to set up a comprehensive design methodology for a fully
integrated class-E CMOS PA including effects of an integrated transformer, which is
very crucial for watt-level power applications. In addition, to improve efficiency of
cascode class-E CMOS PAs, a charging acceleration technique is developed. The method
accelerates a charging speed to turn off the common-gate device in the off-state, thus
reducing the power loss. To demonstrate the proposed cascode class-E PA, a prototype
CMOS PA was implemented in a 0.18-μm CMOS process. Measurements show an
improvement of approximately 6% in the power added efficiency. The proposed cascode
class-E PA structure is suitable for the design of high-efficiency class-E PAs while it
reduces the voltage stress across the device.
14
Habibi, Saeid. "Wireless charging of electric vehicles based on resonant inductive power transformers." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
Анотація:
Abstract
Electric vehicles and their charging stations are among important applications in today's world. The E-mobility industry is changing day-to-day with new ways to reduce charging time of electric vehicles, ease of use in charging process, increasing the efficiency and sometimes remote control access of the charging system.
To accomplish this, resonant inductive power transfers is one of the method that can be hired to transfer power to electric vehicles (EVs) over an air-gap and can remarkably improve the range, safety and convenience of the EV battery charging. However, implementation of a large scale wireless charging infrastructure of electric vehicles (e.g. for taxi fleet in a city) is still one of the major difficulties of such technology. Issues related to determining the physical sizes of the coil pads, standardization, technical interoperability, safety and designing the appropriate wireless charging system to be used for different EVs are among those difficulties.
The important target of doing this study is to understand the feasibility of installation of wireless charging stations for electric vehicle in terms of technical and financial issues, and understanding that which size of chargers are needed to install for electric vehicles. Electrical synchronization and interoperability of primary and secondary coils are other issues investigated. In the following chapters, financial and economic analysis of implementation of the wireless charging infrastructure for the taxi and van fleet in an urban area are discussed.
It can be concluded that implementation of wireless charging infrastructure for electric vehicles in urban areas for taxi fleet and delivery van drivers could bring many advantages because of specific working routine and stop time that they have during each working day. Increment of anxiety range, and reduction of charging time, convenience, being needless of tedious conventional charging cables, saving money are major advantages.
15
Helmrich, Christian [Verfasser], and Bernd [Gutachter] Edler. "Efficient Perceptual Audio Coding Using Cosine and Sine Modulated Lapped Transforms / Christian Helmrich ; Gutachter: Bernd Edler." Erlangen : Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), 2017. http://d-nb.info/1137055502/34.
16
MARON, CARLOS ANDRES AGUILAR. "EFFICIENCY ASSESSMENT OF ADVANCED MODAL ANALYSIS AS COMPARED TO TECHNIQUES BASED ON NUMERICAL INVERSE TRANSFORMS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2008. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=13046@1.
Анотація:
COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIORCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Uma técnica bem conhecida para resolver problemas dependentes do tempo é a formulação, desses problemas, no domínio da frequência por meio da transformada de Laplace ou Fourier, com as consequêntes expressões apropriadas desses resultados utilizando inversões numéricas. Embora de fácil implementação, tais inversões numéricas, são computacionalmente dispendiosas quando resultados mais exatos são desejados e suscetíveis a instabilidades num´ericas. Para problemas de tipo difusão, o algoritmo de Gaver-Stehfest parece ser satisfatório. Problemas gerais de dinâmica demandam algoritmos mais robustos, usualmente baseados em expansões em séries de Fourier tal como foi proposto inicialmente por Dubner e Abate. Algoritmos de outros tipos já são implementados em softwares matemáticos tais como Matlab e Mathematica. A livraria de Fortran possui um algoritmo proposto por Crump e aperfei¸coado por de Hoog e colegas. Mais recentemente, foi proposto resolver problemas transientes de potencial e elasticidade pelo uso de uma técnica avançada de superposição modal que é aplicado a modelos de elementos finitos e elementos de contorno baseados em equilíbrio. O método começa com a formulação no domínio da frequência a qual leva a uma matriz de rigidez efetiva, simétrica-complexa (quando amortecimento viscoso é considerado), expressa como uma série de potências de frequência com matrizes generalizadas de rigidez, amortecimento e massa. Após a solução do problema de autovalor não linear associado, obtém-se uma solução modal avançada do problema, a qual permite uma rápida solução no domínio do tempo obtendo as expressões imediatamente de qualquer resultado de interesse. O objetivo deste trabalho é comparar o desempenho computacional da técnica de superposição modal avançada com as técnicas baseadas em transformadas inversas numéricas de Laplace como aplicações a problemas generais de grande porte. A bibliografia relevante é revista e as principais diferenças conceituais desses métodos são brevemente tratados. Todos os algoritmos são implementados em Fortran com o intuito de garantir uma base comum de comparação. Alguns resultados iniciais são mostrados, conclusões mais definitivas so poderão ser obtidas após uma grande série de simulações numéricas.
An established technique to solve time-dependent problems is the formulation of a complete frequency-domain analysis via Laplace or Fourier transforms, with subsequent ad hoc expression of results by numerical inversion. Although usually easy to implement, such a transform inversion is computationally intensive, if accurate results are desired, and liable to numerical instabilities. For diffusion-type problems, the Gaver-Stehfest algorithm seems well suited. General dynamics problems demand more robust algorithms usually based on Fourier series expansions, as firstly proposed by Dubner and Abate. Algorithms of either kind are already implemented in mathematical languages such as Matlab and Mathematica. The Fortran library has a Fourier-series algorithm proposed by Crump and improved by de Hoog et al. More recently, it has been proposed to solve transient problems of potential and elasticity by using an advanced mode superposition technique that applies to equilibrium-based finite element and boundary element models. One starts with a frequency-domain formulation that leads to a complex-symmetric (if viscous damping is included), effective stiffness matrix expressed as a frequency power series with generalized stiffness, dumping and mass matrices. After solution of the associated complex-symmetric, non-linear eigenvalue problem, one arrives at an advanced modal solution of the problem, which leads to the straightforward solution in the time domain and the immediate expression of any results of interest. Aim of the present research work is to compare the computational efficiency of the proposed advanced modal analysis with the techniques based on numerical inverse transforms, as applied to general, large scale problems. The relevant literature is reviewed and the main conceptual differences of the investigated methods are briefly outlined. All algorithms are implemented in Fortran so as to assure a common basis of comparison. Some initial results are displayed, as more definitive conclusions can only be expected after a large series of numerical simulations.
17
Gu, Bin. "Power Converter and Control Design for High-Efficiency Electrolyte-Free Microinverters." Diss., Virginia Tech, 2014. http://hdl.handle.net/10919/25236.
Анотація:
Microinverter has become a new trend for photovoltaic (PV) grid-tie systems due to its advantages which include greater energy harvest, simplified system installation, enhanced safety, and flexible expansion. Since an individual microinverter system is typically attached to the back of a PV module, it is desirable that it has a long lifespan that can match PV modules, which routinely warrant 25 years of operation. In order to increase the life expectancy and improve the long-term reliability, electrolytic capacitors must be avoided in microinverters because they have been identified as an unreliable component. One solution to avoid electrolytic capacitors in microinverters is using a two-stage architecture, where the high voltage direct current (DC) bus can work as a double line ripple buffer.
For two-stage electrolyte-free microinverters, a high boost ratio dc-dc converter is required to increase the low PV module voltage to a high DC bus voltage required to run the inverter at the second stage. New high boost ratio dc-dc converter topologies using the hybrid transformer concept are presented in this dissertation. The proposed converters have improved magnetic and device utilization. Combine these features with the converter's reduced switching losses which results in a low cost, simple structure system with high efficiency. Using the California Energy Commission (CEC) efficiency standards a 250 W prototype was tested achieving an overall system efficiency of 97.3%.
The power inversion stage of electrolyte-free microinverters requires a high efficiency grid-tie inverter. A transformerless inverter topology with low electro-magnetic interference (EMI) and leakage current is presented. It has the ability to use modern superjunction MOSFETs in conjunction with zero-reverse-recovery silicon carbide (SiC) diodes to achieve ultrahigh efficiency. The performance of the topology was experimentally verified with a tested CEC efficiency of 98.6%.
Due to the relatively low energy density of film capacitors compared to electrolytic counterparts, less capacitance is used on the DC bus in order to lower the cost and reduce the volume of electrolyte-free microinverters. The reduced capacitance leads to high double line ripple voltage oscillation on DC bus. If the double line oscillation propagates back into the PV module, the maximum power point tracking (MPPT) performance would be compromised. A control method which prevents the double line oscillation from going to the PV modules, thus improving the MPPT performance was proposed.
Finally, a control technique using a single microcontroller with low sampling frequency was presented to effectively eliminate electrolyte capacitors in two-stage microinverters without any added penalties. The effectiveness of this control technique was validated both by simulation and experimental results.Ph. D.
18
Salvatori, Stefano. "Text-to-Image Information Retrieval Basato sul Transformer Lineare Performer: Sviluppo e Applicazioni per l'Industria della Moda." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Анотація:
Il lavoro svolto si inserisce nell’ambito dei Neural Ranking Models, modelli che stanno gradualmente superando lo stato dell’arte raggiunto dai classici sistemi di Information Retrieval sfruttando i più recenti sviluppi ottenuti sulle reti neurali profonde. Una delle architetture più utilizzate in questo contesto è quella del Transformer, che si è dimostrata essere estremamente versatile ed efficace in svariati domini applicativi. Uno dei problemi che caratterizzano però questo modello è la complessità spaziale e
temporale quadratica rispetto alla dimensione dell’input che non permette di sfruttare una dimensione del batch size ottimale e una lunghezza delle sequenze in input sufficientemente grande. Lo scopo di questo lavoro è studiare i miglioramenti ottenibili in un sistema di Information Retrieval basato su Neural Ranking Models applicando il transformer efficiente Performer. È stato scelto come caso di studio il dominio della moda, per il quale sono state proposte in letteratura diverse soluzioni nell’ambito dell’intelligenza artificiale per task di retrieval e non. Gao, Dehong, et al. in particolare, hanno ottenuto risultati
allo stato dell’arte sviluppando FashionBERT, un neural ranking model basato BERT applicato a problemi di Text-Image Matching (dire se una descrizione ed un’immagine sono o meno legate allo stesso prodotto) e Retrieval (data una query testuale, ritrovare l’immagine dell’indumento che descrive).
In questo lavoro si vuole mostrate innanzitutto come sia possibile migliorare i risultati di FashionBERT sia in termini di efficacia che efficienza sostituendo il layer di attention quadratica con la rispettiva versione lineare proposta in Performer. Vengono infine condotti ulteriori esperimenti applicando il modello sviluppato
ad un task di Metric Learning dimostrando che è possibile in questo modo superare lo stato dell'arte ottenuto nel paper originale di FashionBERT.
19
Souza, Kleymilson do Nascimento. "Optimization in calculation of active part three phase distribution transformer with use genetic algorithms aiming better efficiency and less cost." Universidade Federal do CearÃ, 2012. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=8364.
Анотація:
CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel SuperiorThe present work is a study of a methodology that seeks to be more economical and efficient compared to traditional methods, the design of three phase distribution transformers. To this end, we use a tool of Computational Intelligence, based on previous calculations made in the traditional way by manufacturing industries and books that address this matter. It is evident here, another way to design the active part of the transformer, the dimension of the core and coil, for this, used Genetic Algorithms (GA) which will assist in the calculation and selection of parameters, providing the best choice of design of the transformer, minimizing, on average, 5% in the cost and losses in 2.5% as input parameters the following standard. With changes in the fitness function of GA, one can simply adapt to new requirements and standards. As a result of using the genetic algorithm can find a design solution that is more efficient than that used by the manufacturers. The losses calculated values meet established by NBR-5440.
O presente trabalho faz um estudo de uma metodologia que busca ser mais econÃmica e eficiente, em comparaÃÃo com mÃtodos tradicionais, no projeto de transformadores de distribuiÃÃo trifÃsico. Para tal, utiliza-se uma ferramenta de InteligÃncia Computacional, tendo como base cÃlculos anteriores feitos de forma tradicional por indÃstrias fabricantes e livros que tratam desse assunto. Evidencia-se, aqui, mais uma maneira de projetar a parte ativa do transformador, ou seja, o dimensionamento do nÃcleo e bobinas; para isso, utiliza-se Algoritmos GenÃticos (GA), que irÃo auxiliar no cÃlculo e escolha dos parÃmetros, proporcionando a melhor escolha do projeto do transformador, minimizando, em mÃdia, o custo em 5 % e as perdas em 2,5 %, conforme parÃmetros de entrada seguindo a norma. Com modificaÃÃes na funÃÃo de fitness do GA, pode-se adequar de maneira simples a novas exigÃncias e normas. Como consequÃncia da utilizaÃÃo do Algoritmo GenÃtico pode-se encontrar uma soluÃÃo de projeto que à mais eficiente do que a utilizada pelos fabricantes. As perdas calculadas atendem valores estabelecidos pela norma NBR-5440.
20
Nestler, Franziska [Verfasser], Daniel [Akademischer Betreuer] Potts, Daniel [Gutachter] Potts, Gabriele [Gutachter] Steidl, and Christian [Gutachter] Holm. "Efficient Computation of Electrostatic Interactions in Particle Systems Based on Nonequispaced Fast Fourier Transforms / Franziska Nestler ; Gutachter: Daniel Potts, Gabriele Steidl, Christian Holm ; Betreuer: Daniel Potts." Chemnitz : Universitätsverlag der Technischen Universität Chemnitz, 2018. http://d-nb.info/1214820778/34.
21
Vimond, Myriam. "Inférence statistique par des transformées de Fourier pour des modèles de régression semi-paramétriques." Phd thesis, Université Paul Sabatier - Toulouse III, 2007. http://tel.archives-ouvertes.fr/tel-00185102.
Анотація:
Dans cette thèse, nous étudions des modèles semi-paramétriques dits de forme invariante. Ces modèles consistent en l'observation d'un nombre fixés de fonctions de régression identiques à un opérateur de déformation paramétriques près. Ce type de modèles trouve des applications dans les problèmes d'alignement de signaux continus (images 2D, rythmes biologiques, ...) ou discrets (electroencéphalogramme, ...). Pour différents groupes de déformations, nous proposons des M-estimateurs pour les paramètres caractérisant les opérateurs associés aux fonctions de régression. Ces estimateurs minimisent ou maximisent des fonctions de contraste, construites à partir de la moyenne synchronisée des transformées de Fourier des données. De plus, pour l'un des modèles étudiés, nous prouvons l'efficacité semi-paramétrique de cet estimateur ainsi défini, et nous proposons un test d'adéquation du modèle de forme invariante construit à partir d'une des fonctions de contraste.
22
Sagen, Markus. "Large-Context Question Answering with Cross-Lingual Transfer." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-440704.
Анотація:
Models based around the transformer architecture have become one of the most prominent for solving a multitude of natural language processing (NLP)tasks since its introduction in 2017. However, much research related to the transformer model has focused primarily on achieving high performance and many problems remain unsolved. Two of the most prominent currently are the lack of high performing non-English pre-trained models, and the limited number of words most trained models can incorporate for their context. Solving these problems would make NLP models more suitable for real-world applications, improving information retrieval, reading comprehension, and more. All previous research has focused on incorporating long-context for English language models. This thesis investigates the cross-lingual transferability between languages when only training for long-context in English. Training long-context models in English only could make long-context in low-resource languages, such as Swedish, more accessible since it is hard to find such data in most languages and costly to train for each language. This could become an efficient method for creating long-context models in other languages without the need for such data in all languages or pre-training from scratch. We extend the models’ context using the training scheme of the Longformer architecture and fine-tune on a question-answering task in several languages. Our evaluation could not satisfactorily confirm nor deny if transferring long-term context is possible for low-resource languages. We believe that using datasets that require long-context reasoning, such as a multilingual TriviaQAdataset, could demonstrate our hypothesis’s validity.
23
Colucci, Lucas. "O impacto na ponderação do peso da Prova Brasil e do indicador de rendimento no perfil das escolas municipais do ensino fundamental consideradas eficientes pela técnica DEA em transformar investimento financeiro em desempenho no IDEB em 2011." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/96/96132/tde-18072014-145200/.
Анотація:
Este estudo tem como objetivo apresentar as alterações que ocorrem nos perfis das escolas públicas municipais do ensino fundamental classificadas como eficientes por meio da aplicação da técnica de Análise Envoltória de Dados (DEA), conforme se modificam as proporções dos valores percentuais da nota média na Prova Brasil e do indicador de rendimento no cálculo do Índice de Desenvolvimento da Educação Básica (IDEB). Para isso, foram coletados dados sobre as notas na Prova Brasil e sobre os indicadores de rendimento de 2011 a partir da base de dados do Instituto Nacional de Estudos e Pesquisas Educacionais (INEP), o número de alunos por escola pública municipal por meio da base de dados do Censo Escolar de 2011, que também é disponibilizado pelo INEP e finalmente, os dados sobre os recursos públicos destinados para a educação nos municípios em 2011 obtidos no Finanças do Brasil (FINBRA). Desta maneira, identificou-se as escolas mais eficientes por meio da técnica DEA que tem a finalidade de mensurar a eficiência relativa de unidades consideradas homogêneas e comparáveis, em um universo de pesquisa composto por 17.124 escolas públicas municipais do ensino fundamental. Em seguida, foram estabelecidos cinco padrões de ponderação em relação à nota média da Prova Brasil e à média do indicador de rendimento, por meio dos quais evidenciou-se que as escolas públicas municipais classificadas como eficientes se localizam principalmente em municípios pequenos e que conforme se aumenta o valor percentual da nota média da Prova Brasil ocorre uma mudança de eixo de eficiência saindo da região nordeste em direção as regiões sudeste e sul. Portanto, o presente estudo fornece subsídios e suporte para a discussão, alteração, criação e desenvolvimento de sistemas avaliativos padronizados que melhor transpareçam a realidade educacional brasileira, de tal modo, que os seus resultados possibilitem a proposição de soluções mais efetivas para combater os baixos indicadores educacionais do país.This study aims to present the changes that occur in the profiles of local public elementary schools classified as efficient by applying the technique of Data Envelopment Analysis (DEA), as modify the proportions of the percentages of the average grade in the Prova Brasil and the performance indicator in calculating the Índice de Desenvolvimento da Educação Básica (IDEB). For this, data on the grades in Prova Brasil on performance indicators from 2011 from the database of the Instituto Nacional de Estudos e Pesquisas Educacionais (INEP) were collected, the number of students per public school through the base data from the Censo Escolar 2011, which is also available by INEP and finally, data on public resources for education in the municipalities in 2011 obtained the Finanças do Brasil (FINBRA). Thus, we identified the most effective schools through the DEA technique that aims to measure the relative efficiency of units considered homogeneous and comparable, in a research universe consists of 17.124 municipal public elementary schools. Then, five patterns were established weighting relative to the average grade of Prova Brasil and the average performance indicator, by means of which became evident that public schools classified as efficient lie mostly in small towns and as if increases the percentage of the average grade of Prova Brasil a change of axis of efficiency out of the northeast toward the southeast and south occurs. Therefore, the present study provides grants and support for discussion, modification, creation and development of standardized assessment systems that better showing through and the Brazilian, so educational reality, their results allow to propose more effective solutions to combat the low indicators education in the country.
24
He, Chao. "Advanced wavelet application for video compression and video object tracking." Connect to resource, 2005. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1125659908.
Анотація:
Thesis (Ph. D.)--Ohio State University, 2005.Title from first page of PDF file. Document formatted into pages; contains xvii, 158 p.; also includes graphics (some col.). Includes bibliographical references (p. 150-158). Available online via OhioLINK's ETD Center
25
Silva, Paulo Roberto da. "OTIMIZAÇÃO DO PROJETO DE TRANSFORMADORES DE DISTRIBUIÇÃO QUE EMPREGAM NÚCLEO AMORFO E ÓLEO VEGETAL ISOLANTE." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/8570.
Анотація:
This paper presents a methodology for optimizing the distribution transformers project, considering the capitalized cost, employing concurrently in your project amorphous core and insulating vegetable oil. The use of amorphous core technology provides a significant reduction of the load losses as the use of the insulating vegetable oil which is a non-toxic fluid and rapidly biodegradable when in contact with the environment, it allows increasing the machine's operating temperature . The use of these two materials have provided considerable percentage improvements in efficiency and cost / power compared to conventional distribution transformers manufactured. The methodology is aimed to create and select designs that have a lower total cost, namely the sum of the transformer manufacturing cost capitalized cost of losses during the useful life envisaged for the equipment. In addition, it presents the case study of a 75 kVA designed distribution transformer and manufactured with amorphous core and insulating vegetable oil, routine employed optimization (developed in VBA Excel), the theoretical results obtained from the optimized design and the experimental results.Este trabalho apresenta uma metodologia de otimização do projeto de transformadores de distribuição, considerando o custo capitalizado, que empregam concomitantemente em seu projeto núcleo amorfos e óleo vegetal isolante. O emprego da tecnologia de núcleo amorfo proporciona significativa redução das perdas em vazio, enquanto a utilização do óleo vegetal isolante, que é um fluído não tóxico e de rápida biodegradação quando em contato com o meio ambiente, possibilita o aumento da temperatura de operação do equipamento. A utilização desses dois materiais propiciaram melhoras percentuais consideráveis na eficiência e na relação custo/potência em comparação aos transformadores de distribuição convencionalmente fabricados. A metodologia visa criar e selecionar projetos que tenham um menor custo total, ou seja, a soma do custo de fabricação do transformador com o custo capitalizado das perdas durante a vida útil considerada para o equipamento.Além disso, é apresentado o estudo de caso de um transformador de distribuição de 75 kVA projetado e fabricado com o núcleo amorfo e óleo vegetal isolante, a rotina de otimização empregada (desenvolvida em VBA Excel), os resultados teóricos obtidos a partir do projeto otimizado e os resultados experimentais.
26
Scanlon, Shagufta Anjum. "A comparative study of data transformations for efficient XML and JSON data compression : an in-depth analysis of data transformation techniques, including tag and capital conversions, character and word N-gram transformations, and domain-specific data transforms using SMILES data as a case study." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14180.
Анотація:
XML is a widely used data exchange format. The verbose nature of XML leads to the requirement to efficiently store and process this type of data using compression. Various general-purpose transforms and compression techniques exist that can be used to transform and compress XML data. More compact alternatives to XML data have been developed, namely JSON due to the verbosity of XML data. Similarly, there is a requirement to efficiently store and process SMILES data used in Chemoinformatics. General-purpose transforms and compressors can be used to compress this type of data to a certain extent, however, these techniques are not specific to SMILES data. The primary contribution of this research is to provide developers that use XML, JSON or SMILES data, with key knowledge of the best transformation techniques to use with certain types of data, and which compression techniques would provide the best compressed output size and processing times, depending on their requirements. The main study in this thesis, investigates the extent of which using data transforms prior to data compression can further improve the compression of XML and JSON data. It provides a comparative analysis of applying a variety of data transform and data transform variations, to a number of different types of XML and JSON equivalent datasets of various sizes, and applying different general-purpose compression techniques over the transformed data. A case study is also conducted, to investigate data transforms prior to compression to improve the compression of data within a data-specific domain.
27
Scanlon, Shagufta A. "A Comparative Study of Data Transformations for Efficient XML and JSON Data Compression. An In-Depth Analysis of Data Transformation Techniques, including Tag and Capital Conversions, Character and Word N-Gram Transformations, and Domain-Specific Data Transforms using SMILES Data as a Case Study." Thesis, University of Bradford, 2015. http://hdl.handle.net/10454/14180.
Анотація:
XML is a widely used data exchange format. The verbose nature of XML leads to the requirement to efficiently store and process this type of data using compression. Various general-purpose transforms and compression techniques exist that can be used to transform and compress XML data. More compact alternatives to XML data have been developed, namely JSON due to the verbosity of XML data.
Similarly, there is a requirement to efficiently store and process SMILES data used in Chemoinformatics. General-purpose transforms and compressors can be used to compress this type of data to a certain extent, however, these techniques are not specific to SMILES data.
The primary contribution of this research is to provide developers that use XML, JSON or SMILES data, with key knowledge of the best transformation techniques to use with certain types of data, and which compression techniques would provide the best compressed output size and processing times, depending on their requirements.
The main study in this thesis, investigates the extent of which using data transforms prior to data compression can further improve the compression of XML and JSON data. It provides a comparative analysis of applying a variety of data transform and data transform variations, to a number of different types of XML and JSON equivalent datasets of various sizes, and applying different general-purpose compression techniques over the transformed data.
A case study is also conducted, to investigate data transforms prior to compression to improve the compression of data within a data-specific domain.The files of software accompanying this thesis are unable to be presented online with the thesis.
28
Heller, Jacques. "Modélisation et caractérisation de transducteurs ultrasonores capacitifs micro-usinés appliqués à la réalisation de transformateurs pour l'isolation galvanique." Thesis, Tours, 2018. http://www.theses.fr/2018TOUR4009/document.
Анотація:
Ces travaux présentent l'étude de transformateurs par voie acoustique, basés sur la technologie CMUT (Capacitive Micromachined Ultrasonic Transducer ), visant à développer des composants monolithiques assurant l'isolation électrique au sein de la commande des interrupteurs à semi-conducteurs. S'agissant de microsystèmes électromécaniques, les CMUTs offrent des perspectives intéressantes en terme d'intégrabilité monolithique avec les interrupteurs à semi-conducteurs. L'architecture proposée est constituée de deux transducteurs CMUTs de part et d'autre d'un substrat en silicium. Un outil de modélisation a été développé dans le but de prédire le comportement du transformateur. Des protocoles de mesure du rendement des dispositifs fabriqués ont été mis en place permettant une évaluation quantitative des performances des prototypes (un rendement de 32 % est atteint avec une marge de progression à 60 %). L'exploitation du modèle développé, et validé par les résultats de caractérisation, a permis de mettre en évidence les limites et perspectives d'amélioration de ces dispositifsThis work is a study of CMUT (Capacitive Micromachined Ultrasonic Transduer)based acoustical transformers as a step in the development of insulating components in semiconductor switches control chain. CMUT transducers being electromechanical systems (MEMS), their monolithic integration with semiconductor switches is full of interesting perspectives . The proposed architecture consists of two CMUTs layered on each side of a silicon substrate. A computational tool was designed to predict the behaviour of the transformer. Measurement protocols of the power efficiency of the constructed transformers were set up and allowed to quantify the prototypes' performances (A 32 % efficiency is currently reached, with improvements attainable up to 60 %). Exploring the results of the developed model, validated by bench measurements, allowed to determine the current limits of the transformers as well as perspectives of improvement
29
Fiala, Zbyněk. "Budiče spínacích výkonových tranzistorů GaN MOSFET." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-242073.
Анотація:
The thesis describes the procedure during the proposal of the driver circuits for the GaN MOSFET transistors, which are known for their fast switching especially. In the first instance of this thesis the issue of GaN MOSFET transistors is described and also the thesis describes the different types of MOSFET transistors in the way of their electrical and mechanical attributes. The specific type driver circuit is stated in the thesis, which was selected in the semestral thesis. For this circuit the boost converter with an output power 600W and high switching frequency 800kHz was proposed as an attempt measurement circuit. This boost converter was measured after its construction was done. The waveforms captured by the oscilloscope are commented also. In the conclusion the assessment is done about this new technology of power switching transistors.
30
Besri, Abdelhadi. "Modélisation analytique et outils pour l'optimisation des transformateurs de puissance haute fréquence planars." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00612344.
Анотація:
Avec un encombrement minimal et rendement de 99% les transformateurs planars haute fréquence sont des solutions technologiques importantes pour les systèmes de conversion et de conditionnement de l'énergie électrique en électronique de puissance. L'objectif de l'étude consiste à rechercher un modèle du composant permettant à la fois de simuler son comportement dans un circuit d'électronique de puissance et d'optimiser ses performances lors de sa conception. Les modèles proposés prennent en compte les propriétés physiques et géométriques du composant. Les validations sont basées sur des confrontations avec les mesures. Une autre motivation forte de ce travail est que les modélisations numériques doivent prendre en compte simultanément les effets des courants induits et les capacités parasites, ce qui conduit, en haute fréquence, à des besoins prohibitifs en termes de capacité mémoire ou de temps de calcul. En se limitant aux transformateurs planar. La modélisation (dite LEEC) présentée ici s'appuie sur une discrétisation à échelle intermédiaire : spire par spire, c'est-à-dire couche par couche. Elle assemble deux approches analytiques déjà introduites par l'équipe : la première traite les aspects électrocinétiques (incluant les courants induits) et magnétiques et l'autre les aspects électrostatiques. Les circuits à constantes localisées basés sur la méthode LEEC montrent un très bon accord avec toutes les mesures jusqu'à 40 MHz. Des outils numériques sont aussi développés pour faciliter l'obtention de ces différents circuits en partant : soit de la description du composant, soit de mesures d'impédances. Pour compléter, la représentation des capacités d'un transformateur quelconque, développée en plusieurs étapes par l'équipe, est résumée et des précautions expérimentales originales appliquées à l'impédancemétrie sont exposées dans le détail. D'autres travaux visant à élargir le champ d'application de la méthode LEEC sont également présentés.
31
Al-Zubaidi, R.-Smith Nawfal. "Metody numerické inverzní Laplaceovy transformace pro elektrotechniku a jejich použití." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-390290.
Анотація:
Numerické metody inverzní Laplaceovy transformace (NILT) se staly důležitou částí numerické sady nástrojů praktikujících a výzkumných pracovníků v mnoha vědeckých a inženýrských oborech, zejména v aplikované elektrotechnice. Techniky NILT zejména pomáhají při získávání výsledků simulací v časové oblasti v různých aplikacích. Příkladem jsou řešení obyčejných diferenciálních rovnic, které se objevují např. při analýze obvodů se soustředěnými parametry, nebo řešení parciálních diferenciálních rovnic objevujících se v systémech s rozprostřenými parametry, např. při zkoumání problematiky integrity signálů. Obecně platí, že většina dostupných 1D NILT metod je velmi specifická, tj. funguje dobře na několika typech funkcí a tudíž na omezeném počtu aplikací; Cílem této práce je podrobně se věnovat těmto numerickým metodám, vývoji univerzálních metod NILT a jejich rozšíření na multidimenzionální NILT, které mohou pokrývat širokou oblast aplikací a mohly by poskytnout praktický mechanism pro efektivnější způsob analýzy a simulace v časové oblasti. Myšlenky výzkumu jsou prezentovány v rámci diskusí nad širokou škálou případových studií a aplikací; Například metody NILT se používají při řešení přenosových vedení, včetně vícevodičových, a dokonce i při řešení slabě nelinárních obvodů při použití NILT více proměnných. Pomocí metody NILT mohou být s výhodou uvažovány parametry prvků závislé na kmitočtu a prvky necelistvých řádů v jejich příslušných modelech mohou být zahrnuty velmi přesným a jednoduchým způsobem.
32
Lopes, Israel Filipe. "Projeto e compensação de parâmetros de transformador de núcleo separado destinado ao carregamento de baterias de veículos subaquáticos autônomos." Universidade Federal de Juiz de Fora, 2013. https://repositorio.ufjf.br/jspui/handle/ufjf/1201.
Анотація:
Submitted by Renata Lopes (renatasil82@gmail.com) on 2016-04-06T14:20:59Z
No. of bitstreams: 1
israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5)Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2016-04-24T03:51:36Z (GMT) No. of bitstreams: 1 israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5)
Made available in DSpace on 2016-04-24T03:51:36Z (GMT). No. of bitstreams: 1 israelfilipelopes.pdf: 3821077 bytes, checksum: 03973b1d4356ce4b46316762af40ac71 (MD5) Previous issue date: 2013-02-26
Este trabalho apresenta um estudo sobre transferência de energia elétrica sem contato para carregamento de baterias de veículos autônomos subaquáticos (AUV - Autonomous Underwater Vehicles) utilizando transformadores de núcleo separado (TNS). Inicialmente, é feito um projeto para construção de um transformador de núcleo separado. Posteriormente, são desenvolvidas as equações que modelam o funcionamento do transformador, com base em seu circuito elétrico equivalente. Em seguida, o trabalho propõe uma alternativa para estimar os parâmetros do circuito equivalente do transformador operando com valores de entreferro diferentes, validando seu modelo matemático aproximado com simulações realizadas no software PSIM, versão 9.0. Com o modelo matemático do TNS, é feita uma avaliação da sua capacidade de transferência de energia, mostrando que, em virtude do entreferro, o transformador apresenta baixa eficiência e baixos valores de tensão de saída. Nesse sentido, metodologias para compensar os efeitos de queda de tensão na impedância de dispersão, bem como aumentar a eficiência do transformador, são investigadas introduzindo-se capacitâncias no circuito elétrico equivalente e variando-se a frequência de operação. Aplicando os resultados dessa metodologia de otimização, é mostrado, por meio de experimentos em laboratório, que o TNS é capaz de transmitir energia através de um entreferro de 10 mm, atendendo às condições de tensão e potência da carga, com eficiência relativamente elevada. Em seguida, é feito um experimento com água do mar a fim de verificar a aplicabilidade do TNS em veículos subaquáticos. Por fim, é apresentada uma simulação digital realizada no software PSIM, versão 9.0, com um conversor c.c./c.c. controlador de carga para o sistema de carregamento de bateria. Os resultados obtidos demonstram o funcionamento do sistema, verificando a metodologia para estimativa do modelo e a metodologia de otimização do TNS.
This work presents a study on contactless electrical energy power transfer for charging batteries of autonomous underwater vehicles (AUV - Autonomous Underwater Vehicles) using transformers with separated core (TNS). Initially, a project is made for building a transformer with separated core. After, the equations that model the operation of the transformer, based on its electrical equivalent circuit, are developed. Then, the work proposes an alternative to estimate the parameters of the equivalent circuit of the transformer operating with different gap values, validating its mathematical model with simulations in PSIM software, version 9.0. With the mathematical model of TNS, an evaluation of its ability to transfer power is made, showing that, because of the air gap, the transformer has a low efficiency and low output voltage. Therefore, methodologies to compensate for the effects of voltage drop in the leakage impedance and increase the efficiency of the transformer are investigated by introducing capacitances in the equivalent circuit and varying the of operating frequency. Applying the results of optimization methodology is shown, through laboratory experiments, that the TNS is capable of transmitting power through an air gap of 10 mm, given the voltage and load power conditions, with relatively high efficiency. Then, an experiment is done with seawater in order to verify the applicability of TNS for underwater vehicles. Finally, the work presents a simulation in PSIM with a d.c./d.c. charge controller for battery. The results demonstrate the operation of the system, verifying the methodology for estimation of the model and optimization methodology of TNS.
33
Michl, Pavel. "Začleňování fotovoltaických elektráren do elektrizační soustavy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218537.
Анотація:
The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.
34
Ragavan, K. "An Efficient Solution To Generalized Model Of A Transformer Winding And Localization Of Discrete Changes Based On Measurements." Thesis, 2006. http://hdl.handle.net/2005/354.
Анотація:
High voltage power transformers are designed to withstand a variety of overvoltages and short circuit forces. Occurrence of these events in a power system is natural, inevitable, and one of the main causes of transformer failure. Therefore, an early and reliable detection of an incipient fault is paramount. To this end, diagnostic testing and condition monitoring, not only enables power utilities in early detection of incipient fault-like conditions, but also is a practical way of optimizing existing assets, lowering operating costs, scheduling maintenance, preventing unplanned outages, etc. and consequently improve efficiency.
Over the years, many monitoring and diagnostic methods have evolved. In par-
ticular, low voltage impulse and frequency response analysis or transfer function
approaches have emerged as useful tools in detecting winding deformations. Literature study reveals that although much has been acclaimed about these methods, advancement in interpretation of acquired data must be rigorously pursued, to facilitate a more meaningful assessment. As a matter of fact, diagnosis (which means interpretation of monitored data) has at-the-most been confined to a mere comparison of two subsequently acquired data sets. This philosophy certainly needs to be improved, to realize the true potential of monitoring/diagnostic tools. Achieving this goal calls for newer impetus. It is natural that there will arise many problems while achieving this goal and they will have to be resolved. Keeping these aspects in mind, the objective of this thesis was aimed at developing Solutions to two specific topics that are closely related to and concern the
transformer winding, namely,
* An efficient solution to the generalized model of a transformer winding, with no particular limitation on the size of network and number of windings, no restriction on circuit topology and terminal condition, etc.
* Propose a method to locate the position, quantum and type of change (i.e. deformation) a model winding undergoes, based on terminal measurements.
Details of these approaches are presented in this thesis, which is divided into two parts.
1. A comprehensive analysis of the behaviour of a transformer winding under impulse excitation and its interaction with adjacent windings was until now severely limited, due to the simplifying assumptions imposed (by the existing approaches), like neglecting interaction with neighbouring windings, Ignoring loss, considering only a few sections, etc. thereby rendering the computed results less accurate. A solution considering all these aspects often times results in a very large-sized circuit that needs to be solved. Although circuit simulation software afford iterative solutions, a direct estimation of poles and zeros of any desired network function is not possible.
In the first part of the thesis, a novel and closed-form (i.e. analytical) solution based on state space analysis is proposed. It is shown, how the renders the entire computation to be purely numeric. Thus, time-consuming symbolic manipulations are avoided. With this feature, there is practically no limit on the size of network and no restriction on circuit topologies that can be considered. So, virtually any number of windings of a transformer can be considered, permitting a comprehensive analysis of winding behaviour and its interactions. Further, the formulation also permits computation of poles and zeros of any desired network function (e.g. transfer admittance), response to any excitation (e.g. neutral current, transferred surge), estimation of voltage distribution, etc. with
little extra effort. Hence, it would be apppropriate to term the proposed method as a \Generalized" solution. For the sole purpose of demonstration, a large-sized network (representing a two-winding transformer with 250 sections/winding) was solved and required only 700 seconds. This shows the time-efficiency achieved, and also that it is free from issues like numerical
instability, convergence problems, etc. encountered in some of the existing methods.
2. Detection of mechanical deformation in transformer windings can be achieved with a fair degree of sensitivity using frequency response methods. However, a major challenge that has remained elusive is ascertaining the \extent of damage" and likewise \its location along the winding". It is needless to say that finding these answers is crucial. Ideally, a diagnosis tool is expected to be endowed with powers to answer these questions. Therefore, it is desirable
to explore alternative ways of harnessing these embedded features, if any. This was the next motivation. Obviously, a direct solution to this problem on an actual transformer winding is far too complex. Hence, in this preliminary effort a solution was attempted considering a model winding.
However, care was taken to incorporate other winding-related nuances as far as practicable. The method was formulated based on quantities measured at the terminals.
In the second part of the thesis, a novel algorithm is proposed for determining the location, extent and type of changes intrroduced in a model winding, based on terminal measurements. It employs the well-known properties of driving-point functions and adopts an iterative circuit synthesis approach. From knowledge of the measured short-circuit and open-circuit natural frequencies, and some relevant winding design data, an equivalent circuit was synthesized (called reference circuit). Next, changes were introduced at different locations in the model winding and natural frequencies measured again. Corresponding to every new set of measured natural frequencies, a fresh circuit was synthesized (with topology remaining unchanged). A comparison of these circuits with the reference circuit revealed that a mapping could be established between changes introduced in the model winding and those predicted by the synthesized circuits. Initially, the underlying principle is discussed, and thereafter, the experimental results are presented for both continuous-disc and interleaved winding representations. The case studies involved examples wherein changes in the model winding were made to elements connected to a single tap, two physically different tap positions, multiple changes to different elements, and so on. In all cases, the positions of all the `changes' were reasonably well locatable, and so was the `type of change'. The results were very encouraging. In summary, localization of changes based on terminal measurements, is shown to be a possibility. Lastly, it is conjectured that these findings could be of some assistance in addressing the ultimate task of locating mechanical deformations in actual transformer windings.
35
Lutchman, Poonam. "Evaluation of an efficient transformer core design." Thesis, 2013. http://hdl.handle.net/10539/12390.
Анотація:
Distribution transformers have inherently high efficiencies of up to 99%, however they are in
continuous operation and have a long lifespan, hence their power loss cost is still significant.
A small efficiency improvement can lead to a considerable amount of energy savings over
the lifetime of the transformer.
Symmetric core design has the potential to improve transformer efficiency. The aim of this
dissertation is to evaluate a relatively new symmetrical triangular core transformer for use in
the Eskom Distribution network in South Africa. The transformer is called the hexatransformer.
A three phase 100 kVA hexa-transformer unit has been purchased from Hexaformer AB in
Sweden. The unit has been routinely tested. A 50% no-load loss reduction has been
achieved. The transformer was also opened and examined. The results indicated sound
manufacturing quality. The economic analysis indicated a life cycle saving of R 2 727.41 per
a transformer over a 25 year period when compared to a conventional E-core transformer of
the same rating. It is recommended that Eskom consider these units for future
implementation in their Distribution network.
36
Huang, I.-Ting, and 黃譯霆. "Characteristic Analyses of Commercial Single-phase High-efficiency Transformers." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/96220242944835226603.
Анотація:
碩士國立成功大學
電機工程學系碩博士班
92
The aim of this thesis is to analyze the influence of different lamination shape and its improvement on magnetic field distribution inside the iron core of single-phase transformers. Traditionally, the laminated core is generally adopted and the laminated iron sheets are cut in E-shape and I-shape sheets to reduce core loss in the studied transformer. The reluctance of the magnetic flux path inside the iron core of the studied transformer is affected by the condition of press, shape of laminated core property, effective length and area of flux path. To reduce the reluctance between connection points, the E-shape and I-shape laminated sheets are interchanged to avoid obvious connection line between laminated sheets. This thesis is to simulate magnetic filed distribution of single-phase transformers using electromagnetic field software. The effectiveness of the improved E- and I-shape laminated core will be evaluated in depth for future design of single-phase low-voltage distribution transformers with high-quality, high efficiency, and low core loss. For simulate the inrush current, another model of single-phase transformer written by FORTRAN is compared with experience in this thesis.
37
Wang, Jiun-Lung, and 王俊隴. "EFFICIENT RECURSIVE STRUCTURES FOR DISCRETE COSINES TRANSFORMS." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/10490926827771364154.
Анотація:
碩士國立成功大學
電機工程學系
87
Discrete cosine transform (DCT) is widely used in video and image compression. In this thesis, we proposed two new recursive structures for computing DCT. This recursive structure is based on finite impulse response filter (IIR). One kind of them is the IIR form with fixed and selected filter coefficient. The advantage is that it only needs one filter module for computing all DCT components. The other kind is using several IIR structures for concurrent computing DCT components. The advantages are efficiency and high throughput rate. They are also suitable for VLSI implementation because of their regularity and modularity. In thesis, we contribute a VLSI realization with efficient recursion DCT algorithm. We use COMPASS 0.6μm high performance cell library for TSMC SPTM 0.6μm process technology. It integrates about 36k gates in a 4mm 4mm silicon area. The measurement result shows that this chip can operate at 29MHz clock rate.
38
Sripathi, Deepika Foo Simon Y. "Efficient implementations of discrete wavelet transforms using FPGAs." Diss., 2003. http://etd.lib.fsu.edu/theses//available/etd-11242003-185039.
Анотація:
Thesis (M.S.)--Florida State University, 2003.Advisor: Dr. Simon Y. Foo, Florida State University, College of Engineering, Dept. of Electrical and Computer Engineering. Title and description from dissertation home page (viewed Mar. 3, 2004). Includes bibliographical references.
39
Huntley, Shannon Kelly. "Improved pulping efficiency in C4H-F5H transformed poplar." Thesis, 2003. http://hdl.handle.net/2429/14351.
Анотація:
Changes in wood chemistry could have significant impact on both environmental and economic
aspects of the pulp and paper industry. Consequently, a considerable amount of effort has been
devoted to altering lignin content and/or modifing lignin monomer composition, a cell wall
component whose removal is a major part of the chemical pulping process. Analysis of poplar
transformed with a cinnamate 4-hydroxylase (C4H):ferulate5-hydroxylase (F5H) construct
confirmed significant increases in the mole percent syringyl lignin in transgenic lines. Further,
this study demonstrated significant increases in pulping efficiency from greenhouse grown
transgenic trees. Compared to wild-type pulp, decreases of 23 kappa units (residual lignin) and
increases of >20 ISO brightness units were observed in tree lines exhibiting high syringyl
monomer concentrations (93.5% mol S). These changes were associated with no significant
change in total lignin content or observed phenotypic differences in the trees. Additionally,
pulp yields were not affected by the enhanced removal of lignin.. Furthermore, transgenic lines
exhibit reduced fibre coarseness and increased cellulose viscosity. These results suggest that
C4H-F5H transformed trees could be used to produce pulp for paper with substantially less
severe delignification conditions (lower chemical loading or less energy), and that the pulp
produced is of comparable quality to that of the wild-type poplar. Consequently, the ecological
footprint left on the environment, measured by the amount of deleterious pulping by-products
released into the environment may be significantly reduced.
40
Yu, Chu, and 游竹. "Design of Efficient VLSI Architectures for Discrete Wavelet Transforms." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/83122262389772640876.
Анотація:
博士國立臺灣大學
電機工程學研究所
87
The wavelet transform, similar to the Short-Time Fourier Transform, provides an alternative approach to signal processing, especially suitable for the analysis of spatial and spectral locality where signal contains discontinuities and sharp spikes. In this Dissertation, we describe the algorithms, VLSI architectures, and single-chip implementations for the 1-D and 2-D discrete wavelet transforms. In the 1-D case, we improve the performance of an existing 1-D DWT VLSI architecture, and then present two other VLSI architectures to further reduce the hardware cost. In the 2-D case, we propose a separable implementation of DWT VLSI architecture based on the Modified Recursive Pyramid Algorithm (MRPA) algorithm. We also devise a non-separable implementation of DWT VLSI architecture based on our proposed 2-D semi-pyramid algorithm, and then map this architecture into a VLSI single chip to verify its function. Moreover, to reconstruct a decomposed image into the original one, a 2-D inverse DWT VLSI architecture using our proposed Recursive Quarter-Tree Pyramid Algorithm (RQTPA) is devised. Since the proposed 1-D and 2-D DWT/IDWT architectures have fast computation time, spend lower hardware cost, and own a regular hardware structure, they are suited for not only VLSI single-chip implementation, but also applications in digital signal processing, such as codec-based MPEG-4 and JPEG 2000.
41
Cheng, Zhan-Yuan, and 程占遠. "Efficient Discrete Cosine Transforms for Advanced Video Coding Systems." Thesis, 2004. http://ndltd.ncl.edu.tw/handle/44057078250906825565.
Анотація:
碩士國立成功大學
電機工程學系碩博士班
92
This thesis focuses on the efficient implementation of the transform coding in video coding systems. It consists of two parts. In the first part, we propose a unified fixed-coefficient recursive structure for computing the general length discrete transforms. After regular preprocessing, the general discrete transforms are realized in a second-order infinite-impulse response (IIR) filter. The proposed recursive structure only requires half the recursive cycles and achieves more accurate results than the existing ones. The proposed algorithm can be applied to many popular transforms, such as subband synthesis filtering, inverse modified discrete cosine transform (IMDCT) and all discrete cosine transform (DCT) types. In the second part, high throughput hardware architectures for fast computation of the 4×4 transforms suggested in H.264 advanced video coders (AVC) are proposed. The proposed architectures could provide higher throughput rate and realize in a smaller chip area than the conventional row-column approaches. The proposed architectures are synthesized with TSMC 0.35 �慆 technology. The synthesized multiple transform architecture could process 800 M samples/sec at 100 MHz for all three transforms.
42
Dionísio, João Pedro Gonçalves. "A Mixed-Integer Optimization Model for Efficient Power Transformer Maintenance and Operation." Master's thesis, 2021. https://hdl.handle.net/10216/138587.
43
Crafford, Crafford Hendrik Lambert Helberg Hendrik Lambert Helberg. "Design and development of a high efficiency modulated Class E amplifier." Thesis, 2006. http://hdl.handle.net/10352/270.
Анотація:
M. Tech. (Chemical Engineering, Faculty of Engineering and Technology), Vaal University of TechnologyAmplitude modulation is not commonly associated with effective amplifying. This work focuses on implementing amplitude modulation into a high efficiency Class E amplifier. Different types of amplifiers are compared with each other, to show the advantages of using a Class E amplifier. The theory of the Class E amplifier is dealt with in detail. A harmonic filter is designed for the amplifier to make it radio spectrum friendly. The modulation process is implemented with the aid of a transformer into the Class E amplifier. The advantage of this is that the transformer serves both as a radio frequency choke for the Class E circuit as well as a modulator. The implementation of the amplitude modulation into the high efficient Class E circuit was successful. The final Class E circuit had superb efficiency, the harmonic filter showed good harmonic attenuation and the modulation process had low distortion. All this resulted in a fine low power AM transmitter.
44
"High Power Density, High Efficiency Single Phase Transformer-less Photovoltaic String Inverters." Doctoral diss., 2017. http://hdl.handle.net/2286/R.I.45041.
Анотація:
abstract: Two major challenges in the transformer-less, single-phase PV string inverters are common mode leakage currents and double-line-frequency power decoupling. In the proposed doubly-grounded inverter topology with innovative active-power-decoupling approach, both of these issues are simultaneously addressed. The topology allows the PV negative terminal to be directly connected to the neutral, thereby eliminating the common-mode ground-currents. The decoupling capacitance requirement is minimized by a dynamically-variable dc-link with large voltage swing, allowing an all-film-capacitor implementation. Furthermore, the use of wide-bandgap devices enables the converter operation at higher switching frequency, resulting in smaller magnetic components. The operating principles, design and optimization, and control methods are explained in detail, and compared with other transformer-less, active-decoupling topologies. A 3 kVA, 100 kHz single-phase hardware prototype at 400 V dc nominal input and 240 V ac output has been developed using SiC MOSFETs with only 45 μF/1100 V dc-link capacitance. The proposed doubly-grounded topology is then extended for split-phase PV inverter application which results in significant reduction in both the peak and RMS values of the boost stage inductor current and allows for easy design of zero voltage transition. A topological enhancement involving T-type dc-ac stage is also developed which takes advantage of the three-level switching states with reduced voltage stress on the main switches, lower switching loss and almost halved inductor current ripple.
In addition, this thesis also proposed two new schemes to improve the efficiency of conventional H-bridge inverter topology. The first scheme is to add an auxiliary zero-voltage-transition (ZVT) circuit to realize zero-voltage-switching (ZVS) for all the main switches and inherent zero-current-switching (ZCS) for the auxiliary switches. The advantages include the provision to implement zero state modulation schemes to decrease the inductor current THD, naturally adaptive auxiliary inductor current and elimination of need for large balancing capacitors. The second proposed scheme improves the system efficiency while still meeting a given THD requirement by implementing variable instantaneous switching frequency within a line frequency cycle. This scheme aims at minimizing the combined switching loss and inductor core loss by including different characteristics of the losses relative to the instantaneous switching frequency in the optimization process.Dissertation/Thesis
Doctoral Dissertation Electrical Engineering 2017
45
Shu, Ying-Jie, and 舒穎婕. "Explore the Efficiency of the Rotor Concentrator Thermal Oxidizer in Transformer Industry." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/3q5scv.
Анотація:
碩士國立中央大學
環境工程研究所在職專班
106
Both internal and foreign literatures indicate that volatile organic compounds (VOCs) would affect human body and the environment. However, many of our internal industries produce VOCs during their productions. Especially in the process of painting transformer of electrical equipment manufacturing. Respond to the growth in energy demand all over the world, the VOCs may be increased when promoting the market upgrowth. Through the field research and the air pollution test reports in the past, we acknowledged the emissions status and material composition of the air pollution in the process of painting transformer of electrical equipment manufacturing. So that we can estimate the efficiency of processing VOCs by air pollution control devices - rotor concentrator thermal oxidizer system. The factory in this thesis has the exhaust gas with high air volume and low concentration. And the highest content of hazardous ingredients in the exhaust gas is Xylene. So we use the rotor concentrator to transform the exhaust gas to low air volume and high concentration. The emissions of Xylene after processing was estimated to be lower than the standard 0.033 g/s. The recycle rate of thermal oxidizer can reach 94% and reduce the usage of the liquefied petroleum gas. The total reducing rate of rotor concentrator is over 90% and for thermal oxidizer is 94%. But due to the reason that the hazard components and characteristics of the industry are different, the best operating parameters are different. When choosing the prevention equipment, we need to consider the production and the coating properties. So that the prevention can work with efficiency and becoming the reference in the future of purchasing the prevention equipment in the factory.
46
Chen, Che-Hong, and 陳奇宏. "Efficient Recursive Structures for Forward and Inverse Modified Discrete Cosine Transforms." Thesis, 2000. http://ndltd.ncl.edu.tw/handle/70164365153808374242.
Анотація:
碩士國立成功大學
電機工程學系
88
The MP3 audio format uses the MPEG-1 audio Layer 3, which is one of the most advanced MPEG (Moving Picture Experts Group) standards for digital audio compression. The MPEG-1 audio Layer 3 has been widely used in internet and wireless communication and storage applications. The modified discrete cosine transform (MDCT) and its inverse transform (IMDCT) are the most complex operations in the MPEG-1 Layer 3 audio coding standard. In this thesis, we propose the new recursive structures for computing MDCT and IMDCT. This recursive structure is based on finite impulse response filters (IIR). We can use several IIR structures for concurrent computing MDCT and IMDCT components. The advantages of the proposed recursive IIR structure are rapid computational efficiency and high throughput rate. With regularity and modularity, the proposed recursive MDCT and IMDCT figured is suitable for VLSI implementation. In this thesis, we also realize a VLSI chip, which can perform both of the efficient recursion algorithms by using COMPASS 0.35µm high performance cell library with TSMC SPQM 0.35µm process technology. The realized VLSI takes about 7.5k gates in 2mm 2mm silicon area. The measurement result shows that the chip can work at about 50MHz clock rate.
47
Hsu, Fang-Chii, and 許芳綺. "Efficient Memory Arrangement Methods and VLSI Implementations for Discrete Fourier and Cosine Transforms." Thesis, 2001. http://ndltd.ncl.edu.tw/handle/61599713560978766382.
Анотація:
碩士國立中山大學
資訊工程學系研究所
89
The thesis proposes using the efficient memory arrangement methods for the implementation of radix-r multi-dimensional Discrete Fourier Transform (DFT) and Discrete Cosine Transform (DCT). By using the memory instead of the registers to buffer and reorder data, hardware complexity is significantly reduced. We use the recursive architecture that requires only one arithmetic-processing element to compute the entire DFT/DCT operation. The algorithm is based on efficient coefficient matrix factorization and data allocation. By exploiting the features of Kronecker product representation in the fast algorithm, the multi-dimensional DFT/DCT operation is converted into its corresponding 1-D problem and the intermediate data is stored in several memory units. In addition to the smaller area, we also propose a method to reduce the power consumption of the DFT/DCT processors.
48
Wang, Wen-Hsin, and 王雯欣. "A Study of Light-Load Efficiency Improvement on Series-Resonant Converter by Applying Integrated Transformer." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/z34mnr.
Анотація:
碩士國立臺灣科技大學
電子工程系
106
The purpose of this thesis is to develop the research and implementation on the light-load efficiency improvement of series-resonant converters using integrated transformers. For a series-resonant converter, zero-voltage-switching on power switching devices is a common technique; besides, the power devices are increasingly improved on their operation losses. Therefore, further loss reduction on series-resonant converters has reached a bottleneck. In addition to the device losses, the major loss is resulted from the magnetic components. As a result, in order to pursue high efficiency and high power density on this kind of converters, it is an important issue to improve the magnetic components. The integrated transformer integrates multiple magnetic cores to form a single one. By using an integrated core structure, the input voltage can be shared by the multiple cores to reduce the magnetic flux density on the individual cores, thereby reducing core loss. Furthermore, by elegantly arranging the core placement, the flux cancellation is achieved to reduce the effective magnetic circuit length of the integrated transformer and also the magnetic reluctance. Not only the core loss is further reduced, the integrated transformer can possess a lower magnetizing inductance without increasing the cross-sectional area of the transformer and turns number. This feature increases the magnetizing current, making it easier for the circuit to achieve zero-voltage switching under light-load conditions. Another advantageous feature to mention is that the distributively placed windings gain more space to dissipate the generated heat and lower the transformer temperature. A series-resonant converter with a switching frequency of 325 kHz, 800 V on both input and output, and maximum load of 7.2 kW is implemented.
49
Hsiao, Yu-Feng, and 蕭淯方. "Research of K-band CMOS Transformer Combined Power Amplifier With 3-D Architecture and Efficiency Enhancement Technique." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/15253413046392828272.
Анотація:
碩士國立臺灣大學
電信工程學研究所
101
With the development of wireless communication, the radial frequency integrated circuit with CMOS technology is valued gradually in the industry. Among the transceiver, power amplifier is the most critical component. As the reasons, the design and analysis of CMOS power amplifier is focused in this thesis. In chapter 2, an ultra-compact 24-GHz power amplifier implemented in 180-nm CMOS process. For compact chip size design, transformers are adopted to accomplish the functions of power combining, impedance matching and single-to-differential ended simultaneously. A virtual ground is generated at the symmetry of circuit by push-pull topology. DC bias can be fed directly without large value bypass capacitors, and the chip size is further reduced. The power amplifier achieves the smallest chip size 0.26 mm2 and the highest area efficiency around 24-GHz. In chapter 3, a K-band high output power transformer combined power amplifier with 3-D architecture implemented in 65-nm CMOS process. In order to achieve high output power, 8-ways power combining is realized by the radial splitter and radial combiner. The radial networks with the function of impedance transformation to alleviate the loss of input and output matching networks caused by large impedance transformation ratio. Thanks to the radial structure, the power splitter and power combiner can share the center area of the circuit by a 3-D architecture, therefore the area occupied by power splitter and power combiner can be reduced significantly. The power amplifier achieves the highest saturated output power 26.1 dBm with excellent area efficiency at K-band. In chapter 4, a 2-GHz Doherty power amplifier implemented in 180-nm CMOS process. All passive elements with λ/4 topology are fabricated off-chip on FR-4 board to diminish the chip size and mitigate the loss caused by elements to improve efficiency. The power amplifier performs 20% PAE and maintains 19% PAE at 6 dB power back-off.
50
Li, Cheng-Tai, and 李承泰. "Cost-Efficiency Analysis on Full-Scale Outdoor Oil-filled Substation Replacement for Pad-mounted Transformer – taking the Hsinchu Air Force Base as example." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/d64f8z.
Анотація:
碩士中華大學
營建管理學系碩士在職專班
104
The Hsinchu Air Force Base is located at the coastal area, which may result in the serious aging of the HV power supply system-related equipment due to the salt corrosion effect and occasional tripping that would occur without warning. To facilitate the movement of fighter jets, the height restrictions are imposed on the surrounding buildings so that the airfield will not constantly face very strong wind gusts. During the typhoon season, there’s even the case where the top plate of the armored HV box was lifted off by the wind and it may hurt the persons working on the field or the fighter jet when taking off or landing. In view of this, it would be required to improve the high-voltage power supply system. As the national defense budget is originated from the taxes paid by the people, it is required that a cost-efficient solution must be developed to solve the current situation. To improve the electrical efficiency to the Hsinchu Air Force Base thus enhancing the stability of the power supply system and to prevent the equipment and armored box in the field from being blown off by strong winds, this research suggests that the transformer should be entirely changed to the pad-mounted transformer to reduce the unexpected power interruption event by updating the equipment. In the meantime, the cost-efficiency of changing to the pad-mounted transformer is analyzed through the Net Present Value, Internal Rate of Return, and Transformer Operating Cost Analysis. After being calculated, the results indicated that it would be less cost-efficient when changing to the pad-mounted transformer; therefore, the more high efficiency transformer is used as an alternative in certain areas. Under the condition of meeting the cost-efficiency and the requirements of the Hsinchu Air Force Base, the Net Present Value and Internal Rate of Return were selected again to Transformer Operating Cost Analysis. After evaluating the cost-efficiency with the aforesaid two methods, it was found that the cost-efficiency of the high efficiency transformer was higher than the pad-mounted transformer. To prevent the strong winds on the field and achieve more effective cost-efficiency, it is suggested that the pad-mounted transformer be selected for the field area and the high efficiency transformer be used in other administrative areas. After being calculated, such kind of combination will be the optimum solution and it will be proposed for the Hsinchu Air Force Base for use as the reference of the subsequent HV power supply system improvement plan.