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Niemeyer, Liam. "Timestop: A Narrative Podcast Series." Ohio University Honors Tutorial College / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ouhonors1524839167826509.
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Sundström, Emma, and Johanna Kaisäter. "“Having a vagina doesn’t stop me from believing that my balls are bigger than yours” : en kvalitativ studie om kvinnorna i TV-serien Suits." Thesis, Högskolan i Gävle, Avdelningen för humaniora, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:hig:diva-33182.
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Historically, women have been given significantly less space than men on the TV screen andtheir roles have often been secondary to men's. The woman's role has often been a passive supporting role alongside the man's main role that drives the action forward (Greene, 2010, ss.1066–1071). This distribution of gender representation aroused the interest to study a television series from the 2010s with three female lead roles. The choice fell on the American series Suits, which takes place in New York's legal profession, an industry that, according tostatistics, is dominated by the male gender (American Bar Association, 2019). In this essay, a qualitative film analysis is performed, focusing on the three female maincharacters in Suits. The study is based on theories of representation, gender and stereotypes and takes a feminist perspective. The study also delves into Laura Mulvey's psychoanalytic perspective which is used to analyze the female representation. The purpose is to create anawareness of how fiction produces gender and how it affects masculinity and femininity. The study examines how women in a male-dominated profession are portrayed on television and how their roles are consistent with, what according to the study's theories, are considered to be female coded. The material has been analyzed focusing on mise-en-scene, cinematography and editing. The analysis is presented in four different themes based on how the women are portrayed and each theme is exemplified by a number of scenes. The analysis shows that there is an imbalance between the male and female representation. The male characters are dominant and the female usually plays a passive and submissive role.<br>Historiskt sett har kvinnor fått betydligt mindre plats än män i tv-rutan och deras roller har ofta varit sekundära till männens. Kvinnans roll har ofta varit en passiv biroll bredvid mannens huvudroll som driver handlingen framåt (Greene, 2010, ss. 1066–1071). Denna fördelning av könens representation väckte intresset att studera en tv-serie från 2010-talet med tre kvinnliga huvudroller. Valet föll på den amerikanska serien Suits som utspelar sig i New Yorks advokatbransch, en bransch som enligt statistik domineras av det manliga könet (American Bar Association, 2019). I denna uppsats genomförs en kvalitativ filmanalys av Suits med fokus på de tre kvinnliga huvudkaraktärerna. Studien bygger på teorier om representation, genus, stereotyper och intar ett feministiskt perspektiv. Undersökningen fördjupar sig även i Laura Mulveys psykoanalytiska perspektiv som den kvinnliga framställningen analyserats utifrån. Syftet är att skapa en medvetenhet om hur fiktion framställer genus och hur det påverkar vår syn påmanlighet och kvinnlighet. I studien undersöks hur kvinnor i ett mansdominerat yrkeframställs på tv och hur deras roller stämmer överens med vad som enligt studiens teorier anses vara kvinnligt kodat. Materialet har analyserats med fokus på mise-en-scene, cinematografi och redigering. Analysen presenteras i fyra olika teman baserade på hur kvinnorna framställs och varje tema exemplifieras med ett antal scener. Analysen visar att det råder obalans mellan den manliga och kvinnliga representationen. De manliga karaktärerna är dominerande och de kvinnliga intar oftast en passiv och undergiven roll.
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Ledezma, Luis Manuel. "A Study on the Miniaturization of Microstrip Square Open Loop Resonators." Scholar Commons, 2011. http://scholarcommons.usf.edu/etd/3202.
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A miniaturization technique that allows the size of microstrip square open loop resonators to be reduced by more than 80% is presented and studied. The technique is based on the loading of the resonator with a series surface mount capacitor. It is shown that this technique allows the design of microwave bandpass filters with a wider stopband when compared with conventional designs. It is also proved that the insertion loss of the miniaturized filter is not degraded, but in fact can be maintained or even enhanced by the miniaturization process; this is true whenever the quality factor of the lumped capacitor is higher than the quality factor of the microstrip resonator. Finally, the feasibility of using the effect of the capacitor loss in the miniaturized resonator quality factor as a method to measure the effective series resistance of surface mount capacitors is studied, and recommendations towards its implementation are presented.
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Zargarzadeh, MohammadReza. "Filter Design for Interference Cancellation for Wide and Narrow Band RF Systems." Thesis, Virginia Tech, 2016. http://hdl.handle.net/10919/81132.
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In radio frequency (RF), filtering is an essential part of RF transceivers. They are employed for different purposes of band selection, channel selection, interference cancellation, image rejection, etc. These are all translated in selecting the wanted signal while mitigating the rest. This can be performed by either selecting the desired frequency range by a band pass filter or rejecting the unwanted part by a band stop filter.
Although there has been tremendous effort to design RF tunable filters, there is still lack of designs with frequency and bandwidth software-tuning capability at frequencies above 4 GHz. This prevents the implementation of Software Defined Radios (SDR) where software tuning is a critical part in supporting multiple standards and frequency bands. Designing a tunable integrated filter will not only assist in realization of SDR, but it also causes an enormous shrinkage in the size of the circuit by replacing the current bulky off-chip filters. The main purpose of this research is to design integrated band pass and band stop filters aimed to perform interference cancellation.
In order to do so, two systems are proposed for this thesis. The first system is a band pass filter capable of frequency and band with tuning for C band frequency range (4-8 GHz) and is implemented in 0.13 µm BiCMOS technology. Frequency tunability is accomplished by using a variable capacitor (varactor) and bandwidth tuning is carried out by employing a negative transconductance cell to compensate for the loss of the elements. Additional circuitry is added to the band pass filter to enhance the selectivity of the filter. The second system is a band stop filter (notch) with the same capability as the band pass filter in terms of tuning. This system is implemented in C band, similar to its band stop counterpart and is capable of tuning its depth by using a negative transconductance in an LC tank. A negative feedback is added to the circuit to improve the bandwidth. While implemented in the same process as the band pass filter, it only employs CMOS transistors since it is generally more attractive due to its lower cost and scalability. Both of the systems mentioned use a varactor for changing the center frequency which is a nonlinear element. Therefore, the nonlinearity of it is modelled using two different methods of nonlinear feedback and Volterra series in order to gain further understanding of the nonlinear process taking place in the LC tank. After the validation of the models proposed using Cadence Virtuoso simulator, two methods of design and tuning are suggested to improve the linearity of the system.
After post layout-extraction, the band pass filter is capable of Q tuning in the range of 3 to 270 and higher. With the noise figure of 10 to 14 dB and input 1-dB compression point as high as 2 dBm, the system shows a reasonably good performance along its operating frequency of 4 to 8 GHz. The band stop filter which is designed in the same frequency band can achieve better than 55 dB of rejection with the noise figure of 6.7 to 8.8 dB and 1-dB compression point of -4 dBm. With the power consumption of 39 to 70 mW, the band stop filter can be used in a low power receiver to suppress unwanted signals. The technique used in the band stop filter can be applied to higher frequency ranges if the circuit is implemented in a more advanced silicon technology. Implementing the mentioned filters in a receiver along with other elements of low noise amplifiers, mixers, etc. would be a major step toward full implementation of SDR systems. Studying the linearity theory of varactors would help future designers identify the sources of nonlinearity and suggest more efficient tuning techniques to improve the linearity of RF electronic systems.<br>Master of Science
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Bazhar, Sara. "Modélisation, optimisation en vue du dimensionnement d’une nouvelle structure de démarreurs à griffes pour les véhicules « micro-hybrides »." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0131/document.
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Cette thèse propose une nouvelle structure de machine à courant continu pouvant être utilisée dans une application démarreur Stop-Start automobile. Une structure tridimensionnelle à griffes est proposée pour remplacer le stator à plots actuel dans le but de réduire son coût de fabrication. La structure de la machine à griffes est modélisée par un réseau de réluctances permettant la prise en compte de la saturation et de la réaction magnétique d'induit. Grâce à sa rapidité et précision, ce modèle est ensuite intégré dans un processus d’optimisation afin d'obtenir rapidement une machine optimale. Enfin, un prototype de machine à courant continu à griffes est réalisé, montrant ainsi la faisabilité de cette topologie. Par ailleurs, un modèle original combinant réseaux de réluctances et résolution de l'équation de Laplace a été développé pour lever certaines difficultés liées à la modélisation par réseau de réluctances des machines électriques tout en prenant en compte la rotation<br>This thesis deals with a new DC machine structure that can be used in an automotive Stop-Start starter application. A three-dimensional claw pole stator is proposed to replace the current stator in order to reduce its manufacturing cost. The claw pole machine topology is modeled by a reluctance network to take into account the saturation and the magnetic armature reaction. Thanks to its speed and precision, this model is then integrated in an optimization process to obtain an optimal machine. Finally, a prototype of a machine with DC claws is manufactured to show the feasibility of this topology. Moreover, an original model combining reluctance networks and solving the Laplace equation has been developed to overtake some difficulties related to modeling by reluctance network of electrical machines while taking into account the rotation
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Kwon, Joonsuk. "Three Essays on Multi-step forecasting with Partial Least Squares." Thesis, Cergy-Pontoise, 2019. http://www.theses.fr/2019CERG1035.
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Dans cette thèse, nous comparons les prévisions IMS, DMS et PLS à plusieurs horizons, en nous concentrant sur les propriétés combinatoires des PLS. Nous nous appuyons sur un article intéressant de Franses & Legerstee (2010), qui suggère comment la méthode dite des moindres carrés partiels (PLS) peut être considérée, dans le contexte de la prévision sur plusieurs étapes, comme une technique intermédiaire entre IMS et DMS. En fait, plutôt qu’un «intermédiaire», nous aimons considérer le PLS comme une forme de combinaison de IMS et de DMS.Cette thèse comprend quatre chapitres.Au chapitre 1, nous fournissons une revue de la littérature qui sert de contexte aux chapitres suivants. Ce chapitre sert de motivation pour les analyses ultérieures.Au chapitre 2, nous explorons les fonctionnalités de PLS considérées comme une combinaison d'IMS et de DMS. Nous étudions les propriétés de PLS en utilisant un algorithme suggéré par Garthwaite (1994).Nous étudions la relation entre IMS, DMS et PLS et comparons la précision de leurs prévisions à plusieurs horizons. Nous analysons les propriétés combinatoires de PLS dans la prévision en plusieurs étapes à l'aide d'un modèle simple AR (2). Pour comparer les performances de prévision, nous évaluons leurs propriétés asymptotiques sous des modèles bien spécifiés et mal spécifiés. Nous confirmons notre étude analytique par le biais de simulations approfondies de la précision relative de la prévision des différentes techniques de prévision à plusieurs étapes. A travers ces simulations, nous soutenons l'analyse asymptotique et étudions les conditions qui rendent le PLS meilleur que l'IMS ou le DMS.Au chapitre 3, nous menons une étude empirique de la prévision en plusieurs étapes basée sur des modèles de AR univariés et nous nous concentrons sur les 121 séries chronologiques mensuelles macroéconomiques aux États-Unis.Nous fournissons une analyse empirique visant à déterminer les circonstances qui rendent PLS préférable à IMS ou à DMS. Pour une comparaison plus facile avec la littérature, nous suivons Marcellino et al. (2006) et McCracken & McGillicuddy (2019) à bien des égards. En outre, nous étendons leurs résultats dans certaines directions, telles que l’évaluation de la prévision de trajectoire, les techniques de mesure alternatives et différents sous-échantillons.Nous explorons les avantages en relation avec la persistance de la série mesurée par le degré d'intégration fractionnaire.A travers cette analyse empirique, nous reconfirmons les résultats des études précédentes et découvrons plusieurs faits nouveaux: (i) les avantages relatifs du PLS par rapport au système IMS ont tendance à disparaître à mesure que l'horizon de prévision se développe; (ii) le PLS est généralement meilleur lorsque le modèle utilise des décalages courts; et (iii) les PLS fonctionnent mieux que le système IMS lorsque les données subissent des périodes de forte volatilité.Le dernier chapitre étend le chapitre 3 aux modèles multivariés. Nous comparons une brève étude analytique de la raison d'être du PLS, puis comparons de manière empirique les performances de prévision du SGI, du IMS et du DMS dans le contexte de modèles de prévision à deux variables. Pour chaque modèle de prévision, nous produisons et évaluons des prévisions sur un seul horizon et sur des trajectoires (plages d'horizons). Nos résultats confirment ceux des modèles univariés: la PLS est privilégiée à court terme mais la question cruciale concerne la persistance des données. À cet égard, les données relatives au groupe des prix nominaux, des salaires et de la monnaie font apparaître une forme de persistance qui ne suit pas clairement une tendance I (1) ou I (2) et produit des performances PLS bien supérieures. Globalement, nous trouvons également que le PLS est génériquement préféré au DMS, il devrait donc constituer une alternative pour le praticien chaque fois qu’il peut envisager des techniques de prévision directe<br>In this thesis, we compare IMS, DMS, and PLS forecasts at several horizons, focusing on the combinational properties of PLS.We build upon an interesting article by Franses & Legerstee (2010) who suggest how the method called Partial Least Squares (PLS) can be seen, in the context of multistep forecasting, as an intermediate technique between IMS and DMS.In fact, rather than an ‘intermediate’, we like to see PLS as a form of combination of IMS and DMS.This thesis consists of four chapters.In the first chapter, we provide a review of the literature serves as the context for the following chapters. In particular, we provide definitions for IMS and DMS and discuss the literature which compares them theoretically and empirically. We then move to forecasting combination and also provide a motivation for seeing PLS as a combination between IMS and DMS. This is where we discuss in details some of features of PLS, such as e.g. its origins, competing algorithms and properties. We also provide a comparison with related methods. The chapter serves as a motivation for the subsequent analyses.In Chapter 2, we explore features of PLS seen as a combination of IMS and DMS. We investigate the properties of PLS using an algorithm suggested by Garthwaite (1994).We study the relationship between IMS, DMS, and PLS, and compare their forecast accuracy at several horizons. We analyze the combinational properties of PLS in multistep forecasting using a simple AR(2) model. To compare forecasting performances, we evaluate their asymptotic properties under well- and misspecified models. We confirm our analytical study through an extensive simulations of the relative forecast accuracy of the various multistep forecasting techniques. Through these simulations, we support the asymptotic analysis and study the conditions which render PLS better than IMS or DMS.(These results enable us to revisit the motivating article by Franses & Legerstee (2010).)In Chapter 3, we conduct an extensive empirical study of multistep forecasting based on univariate AR models and focus on the 121 monthly US macroeconomic time series.We provide an empirical analysis which aims to determine the circumstances that make PLS preferable to IMS or DMS. For an easier comparison with the literature, we follow Marcellino et al. (2006) and McCracken & McGillicuddy (2019) in many aspects. In addition, we extend their results in some directions, such as path forecasting evaluation, alternative measurement techniques, and different subsamples.We explore the benefits in relation to the persistence of the series measured by the degree of fractional integration.Through this empirical analysis we reconfirm the results of the previous studies and find several new facts: (i) the relative benefits of PLS over IMS tend to vanish as the forecast horizon grows; (ii) PLS is in general better when the model uses short lags; and (iii) PLS performs better than IMS when the data undergoes periods of high volatility.The last chapter extends Chapter 3 to multivariate models. We compare a short analytical study of the rationale for PLS and then compare empirically the forecasting performances of IMS, DMS, and PLS in the context of bivariate forecasting models. For each forecasting model, we produce and assess single-horizon and path (ranges of horizons) forecasts. Our findings confirm those of the univariate models: PLS is preferred at short horizons but the issue that is crucial concerns the persistence of the data. In this respect, the data that pertains to the group of nominal prices, wages and money exhibit a form of persistence that does not follow clear an I(1) or an I(2) trend and yield much superior PLS performances. Overall, we also find that PLS is generically preferred to DMS so it should constitute an alternative for the practitioner whenever she may consider direct forecasting techniques
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Bazhar, Sara. "Modélisation, optimisation en vue du dimensionnement d’une nouvelle structure de démarreurs à griffes pour les véhicules « micro-hybrides »." Electronic Thesis or Diss., Université de Lorraine, 2017. http://www.theses.fr/2017LORR0131.
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Cette thèse propose une nouvelle structure de machine à courant continu pouvant être utilisée dans une application démarreur Stop-Start automobile. Une structure tridimensionnelle à griffes est proposée pour remplacer le stator à plots actuel dans le but de réduire son coût de fabrication. La structure de la machine à griffes est modélisée par un réseau de réluctances permettant la prise en compte de la saturation et de la réaction magnétique d'induit. Grâce à sa rapidité et précision, ce modèle est ensuite intégré dans un processus d’optimisation afin d'obtenir rapidement une machine optimale. Enfin, un prototype de machine à courant continu à griffes est réalisé, montrant ainsi la faisabilité de cette topologie. Par ailleurs, un modèle original combinant réseaux de réluctances et résolution de l'équation de Laplace a été développé pour lever certaines difficultés liées à la modélisation par réseau de réluctances des machines électriques tout en prenant en compte la rotation<br>This thesis deals with a new DC machine structure that can be used in an automotive Stop-Start starter application. A three-dimensional claw pole stator is proposed to replace the current stator in order to reduce its manufacturing cost. The claw pole machine topology is modeled by a reluctance network to take into account the saturation and the magnetic armature reaction. Thanks to its speed and precision, this model is then integrated in an optimization process to obtain an optimal machine. Finally, a prototype of a machine with DC claws is manufactured to show the feasibility of this topology. Moreover, an original model combining reluctance networks and solving the Laplace equation has been developed to overtake some difficulties related to modeling by reluctance network of electrical machines while taking into account the rotation
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Ben, Taieb Souhaib. "Machine learning strategies for multi-step-ahead time series forecasting." Doctoral thesis, Universite Libre de Bruxelles, 2014. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209234.
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How much electricity is going to be consumed for the next 24 hours? What will be the temperature for the next three days? What will be the number of sales of a certain product for the next few months? Answering these questions often requires forecasting several future observations from a given sequence of historical observations, called a time series. <p><p>Historically, time series forecasting has been mainly studied in econometrics and statistics. In the last two decades, machine learning, a field that is concerned with the development of algorithms that can automatically learn from data, has become one of the most active areas of predictive modeling research. This success is largely due to the superior performance of machine learning prediction algorithms in many different applications as diverse as natural language processing, speech recognition and spam detection. However, there has been very little research at the intersection of time series forecasting and machine learning.<p><p>The goal of this dissertation is to narrow this gap by addressing the problem of multi-step-ahead time series forecasting from the perspective of machine learning. To that end, we propose a series of forecasting strategies based on machine learning algorithms.<p><p>Multi-step-ahead forecasts can be produced recursively by iterating a one-step-ahead model, or directly using a specific model for each horizon. As a first contribution, we conduct an in-depth study to compare recursive and direct forecasts generated with different learning algorithms for different data generating processes. More precisely, we decompose the multi-step mean squared forecast errors into the bias and variance components, and analyze their behavior over the forecast horizon for different time series lengths. The results and observations made in this study then guide us for the development of new forecasting strategies.<p><p>In particular, we find that choosing between recursive and direct forecasts is not an easy task since it involves a trade-off between bias and estimation variance that depends on many interacting factors, including the learning model, the underlying data generating process, the time series length and the forecast horizon. As a second contribution, we develop multi-stage forecasting strategies that do not treat the recursive and direct strategies as competitors, but seek to combine their best properties. More precisely, the multi-stage strategies generate recursive linear forecasts, and then adjust these forecasts by modeling the multi-step forecast residuals with direct nonlinear models at each horizon, called rectification models. We propose a first multi-stage strategy, that we called the rectify strategy, which estimates the rectification models using the nearest neighbors model. However, because recursive linear forecasts often need small adjustments with real-world time series, we also consider a second multi-stage strategy, called the boost strategy, that estimates the rectification models using gradient boosting algorithms that use so-called weak learners.<p><p>Generating multi-step forecasts using a different model at each horizon provides a large modeling flexibility. However, selecting these models independently can lead to irregularities in the forecasts that can contribute to increase the forecast variance. The problem is exacerbated with nonlinear machine learning models estimated from short time series. To address this issue, and as a third contribution, we introduce and analyze multi-horizon forecasting strategies that exploit the information contained in other horizons when learning the model for each horizon. In particular, to select the lag order and the hyperparameters of each model, multi-horizon strategies minimize forecast errors over multiple horizons rather than just the horizon of interest.<p><p>We compare all the proposed strategies with both the recursive and direct strategies. We first apply a bias and variance study, then we evaluate the different strategies using real-world time series from two past forecasting competitions. For the rectify strategy, in addition to avoiding the choice between recursive and direct forecasts, the results demonstrate that it has better, or at least has close performance to, the best of the recursive and direct forecasts in different settings. For the multi-horizon strategies, the results emphasize the decrease in variance compared to single-horizon strategies, especially with linear or weakly nonlinear data generating processes. Overall, we found that the accuracy of multi-step-ahead forecasts based on machine learning algorithms can be significantly improved if an appropriate forecasting strategy is used to select the model parameters and to generate the forecasts.<p><p>Lastly, as a fourth contribution, we have participated in the Load Forecasting track of the Global Energy Forecasting Competition 2012. The competition involved a hierarchical load forecasting problem where we were required to backcast and forecast hourly loads for a US utility with twenty geographical zones. Our team, TinTin, ranked fifth out of 105 participating teams, and we have been awarded an IEEE Power & Energy Society award.<p><br>Doctorat en sciences, Spécialisation Informatique<br>info:eu-repo/semantics/nonPublished
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IbaÌñez, Juan-Carlos. "New tools for multi-step forecasting of nonlinear time series." Thesis, Lancaster University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.435881.
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Edlund, Per-Olov. "Preliminary estimation of transfer function weights : a two-step regression approach." Doctoral thesis, Stockholm : Economic Research Institute, Stockholm School of Economics [Ekonomiska forskningsinstitutet vid Handelshögsk.] (EFI), 1989. http://www.hhs.se/efi/summary/291.htm.
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Manero, Font Jaume. "Deep learning architectures applied to wind time series multi-step forecasting." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/669283.
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Forecasting is a critical task for the integration of wind-generated energy into electricity grids. Numerical weather models applied to wind prediction, work with grid sizes too large to reproduce all the local features that influence wind, thus making the use of time series with past observations a necessary tool for wind forecasting. This research work is about the application of deep neural networks to multi-step forecasting using multivariate time series as an input, to forecast wind speed at 12 hours ahead.
Wind time series are sequences of meteorological observations like wind speed, temperature, pressure, humidity, and direction. Wind series have two statistically relevant properties; non-linearity and non-stationarity, which makes the modelling
with traditional statistical tools very inaccurate.
In this thesis we design, test and validate novel deep learning models for the wind energy prediction task, applying new deep architectures to the largest open wind data repository available from the National Renewable Laboratory of the US (NREL) with 126,692 wind sites evenly distributed on the US geography. The heterogeneity of the series, obtained from several data origins, allows us to obtain conclusions about the level of fitness of each model to time series that range from highly stationary locations to variable sites from complex areas.
We propose Multi-Layer, Convolutional and recurrent Networks as basic building blocks, and then combined into heterogeneous architectures with different variants, trained with optimisation strategies like drop and skip connections, early
stopping, adaptive learning rates, filters and kernels of different sizes, between others. The architectures are optimised by the use of structured hyper-parameter setting strategies to obtain the best performing model across the whole dataset.
The learning capabilities of the architectures applied to the various sites find relationships between the site characteristics (terrain complexity, wind variability, geographical location) and the model accuracy, establishing novel measures of site predictability relating the fit of the models with indexes from time series spectral or stationary analysis. The designed methods offer new, and superior, alternatives to traditional methods.<br>La predicció de vent és clau per a la integració de l'energia eòlica en els sistemes elèctrics. Els models meteorològics es fan servir per predicció, però tenen unes graelles geogràfiques massa grans per a reproduir totes les característiques locals que influencien la formació de vent, fent necessària la predicció d'acord amb les sèries temporals de mesures passades d'una localització concreta. L'objectiu d'aquest treball d'investigació és l'aplicació de xarxes neuronals profundes a la predicció \textit{multi-step} utilitzant com a entrada series temporals de múltiples variables meteorològiques, per a fer prediccions de vent d'ací a 12 hores. Les sèries temporals de vent són seqüències d'observacions meteorològiques tals com, velocitat del vent, temperatura, humitat, pressió baromètrica o direcció. Les sèries temporals de vent tenen dues propietats estadístiques rellevants, que són la no linearitat i la no estacionalitat, que fan que la modelització amb eines estadístiques sigui poc precisa. En aquesta tesi es validen i proven models de deep learning per la predicció de vent, aquests models d'arquitectures d'autoaprenentatge s'apliquen al conjunt de dades de vent més gran del món, que ha produït el National Renewable Laboratory dels Estats Units (NREL) i que té 126,692 ubicacions físiques de vent distribuïdes per total la geografia de nord Amèrica. L'heterogeneïtat d'aquestes sèries de dades permet establir conclusions fermes en la precisió de cada mètode aplicat a sèries temporals generades en llocs geogràficament molt diversos. Proposem xarxes neuronals profundes de tipus multi-capa, convolucionals i recurrents com a blocs bàsics sobre els quals es fan combinacions en arquitectures heterogènies amb variants, que s'entrenen amb estratègies d'optimització com drops, connexions skip, estratègies de parada, filtres i kernels de diferents mides entre altres. Les arquitectures s'optimitzen amb algorismes de selecció de paràmetres que permeten obtenir el model amb el millor rendiment, en totes les dades. Les capacitats d'aprenentatge de les arquitectures aplicades a ubicacions heterogènies permet establir relacions entre les característiques d'un lloc (complexitat del terreny, variabilitat del vent, ubicació geogràfica) i la precisió dels models, establint mesures de predictibilitat que relacionen la capacitat dels models amb les mesures definides a partir d'anàlisi espectral o d'estacionalitat de les sèries temporals. Els mètodes desenvolupats ofereixen noves i superiors alternatives als algorismes estadístics i mètodes tradicionals.<br>Arquitecturas de aprendizaje profundo aplicadas a la predición en múltiple escalón de series temporales de viento.
La predicción de viento es clave para la integración de esta energía eólica en los sistemas eléctricos. Los modelos meteorológicos tienen una resolución geográfica demasiado amplia que no reproduce todas las características locales que influencian en la formación del viento, haciendo necesaria la predicción en base a series temporales de cada ubicación concreta.
El objetivo de este trabajo de investigación es la aplicación de redes neuronales profundas a la predicción multi-step usando como entrada series temporales de múltiples variables meteorológicas, para realizar predicciones de viento a 12 horas.
Las series temporales de viento son secuencias de observaciones meteorológicas tales como, velocidad de viento, temperatura, humedad, presión barométrica o dirección. Las series temporales de viento tienen dos propiedades estadísticas relevantes, que son la no linealidad y la no estacionalidad, lo que implica que su modelización con herramientas estadísticas sea poco precisa.
En esta tesis se validan y verifican modelos de aprendizaje profundo para la predicción de viento, estos modelos de arquitecturas de aprendizaje automático se aplican al conjunto de datos de viento más grande del mundo, que ha sido generado por el National Renewable Laboratory de los Estados Unidos (NREL) y que tiene 126,682 ubicaciones físicas de viento distribuidas por toda la geografía de Estados Unidos. La heterogeneidad de estas series de datos permite establecer conclusiones válidas sobre la validez de cada método al ser aplicado en series temporales generadas en ubicaciones físicas muy diversas.
Proponemos redes neuronales profundas de tipo multi capa, convolucionales y recurrentes como tipos básicos, sobre los que se han construido combinaciones en arquitecturas heterogéneas con variantes de entrenamiento como drops, conexiones skip, estrategias de parada, filtros y kernels de distintas medidas, entre otros. Las arquitecturas se optimizan con algoritmos de selección de parámetros que permiten obtener el mejor modelo buscando el mejor rendimiento, incluyendo todos los datos.
Las capacidades de aprendizaje de las arquitecturas aplicadas a localizaciones físicas muy variadas permiten establecer relaciones entre las características de una ubicación (complejidad del terreno, variabilidad de viento, ubicación geográfica) y la precisión de los modelos, estableciendo medidas de predictibilidad que relacionan la capacidad de los algoritmos con índices que se definen a partir del análisis espectral o de estacionalidad de las series temporales. Los métodos desarrollados ofrecen nuevas alternativas a los algoritmos estadísticos tradicionales.
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Jansson, Lina. "Vinstlott, reklamavbrott och en stor jäkla jackpott." Thesis, Konstfack, Grafisk design & illustration, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:konstfack:diva-7871.
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Whitby, Andrew. "Asymptotic analysis of the 1-step recursive Chow test (and variants) in time series model." Thesis, University of Oxford, 2013. http://ora.ox.ac.uk/objects/uuid:0bb70f36-580d-44f0-bb13-98429f75e31f.
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This thesis concerns the asymptotic behaviour of the sequence of 1-step recursive Chow statistics and various tests derived therefrom. The 1-step statistics are produced as diagnostic output in standard econometrics software, and are expected to reflect model misspecification. Such misspecification testing is important in validating the assumptions of a model and so ensuring that subsequent inference is correct. Original contributions to the theory of misspecification testing include (i) a result on the pointwise convergence of the 1-step statistics; (ii) a result on the extreme-value convergence of the maximum of the statistics; and (iii) a result on the weak convergence of an empirical process formed by the statistics. In Chapter 2, we describe the almost sure pointwise convergence of the 1-step statistic for a broad class of time series models and processes, including unit root and explosive processes. We develop an asymptotic equivalence result, and use this to establish the asymptotic distribution of the maximum of a sequence of 1-step statistics with normal errors. This allows joint consideration of the sequence of 1-step tests via its maximum: the sup-Chow test. In Chapter 3, we use simulation to investigate the power properties of this test and compare it with benchmark tests of structural stability. We find that the sup-Chow test may have advantages when the nature of instability is unknown. In Chapter 4, we consider how the test may be adapted to situations in which the errors cannot be assumed normal. We evaluate several promising approaches, but also note a trade-off between robustness and power. In Chapter 5 we analyse an empirical process formed from the 1-step statistics, and prove a weak convergence result. Under the assumption of normal errors, the limiting distribution reduces to that of a Brownian bridge. The asymptotic approximation appears to works well even in small samples.
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Francisco, sousa alves Luciano. "Series-connected SiC-MOSFETs : A Novel Multi-Step Packaging Concept and New Gate Drive Power Supply Configurations." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALT050.
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Ce travail de thèse étudie de nouvelles configurations d'alimentation de commande rapprochée et un nouveau concept de packaging afin d'améliorer les performances des MOSFETs SiC connectés en série. Les nouvelles configurations de commande rapprochée sont proposées afin de réduire les courants de bruit qui circulent dans la partie commande du système électrique. De plus, une nouvelle alimentation de commande de grille est proposée pour augmenter le dv / dt de la cellule de commutation. Ces améliorations, c'est-à-dire la réduction du courant de bruit et l'amplification du dv/dt, sont obtenues en modifiant l'impédance des circuits de commande de grille. Le nouveau concept de packaging est proposé afin d'améliorer les performances d’équilibrage de tension. Les nouvelles configurations de commande rapprochée et les concepts de packaging sont introduits et analysés grâce à des modèles analytique et des simulations. Ensuite, des essayes expérimentales sont effectuées pour confirmer que les concepts proposés sont meilleurs que les concepts traditionnels en termes d'équilibrage de tension, de vitesse de commutation et de réduction EMI conduite<br>This work investigates new gate drive power supply configurations and a novel multi-steppackaging concept in order to improve the performance of series-connected SiC-MOSFETs. The new gate drive configurations are proposed in order to reduce noise currents that circulate in the control part of the electrical system. Furthermore, a new gate drive power supply is proposed to increase the dv/dt of the switching cell. These improvements, i.e., noise current reduction and dv/dt boosting, are achieved by modifying the impedance of the gate drive circuitry. The novel multi-step packaging concept is proposed in order to improve the voltage sharing performance. The proposed package geometry considers optimal dielectric isolation for each device leading to a multi-step geometry. It has a significant impact on the parasitic capacitances introduced by the packaging structure that are responsible for voltageunbalances. The new gate driver configurations and the proposed multi-step packaging concepts are introduced and analysed thanks to equivalent models and time domain simulations. Then, experimental set-ups are performed to confirm that the proposed concepts are better than traditional ones in terms of voltage balancing, switching speed and conducted EMI reduction
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Dadi, Kamalaker Reddy. "Circadian Rhythms in the Brain - A first step." Thesis, Linköpings universitet, Institutionen för medicinsk teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-89698.
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Circadian Rhythms (CR) are driven by a biological clock called as suprachiasmaticnucleus (SCN), located in a brain region called the hypothalamus. These rhythms are very much necessary in maintaining the sleep and wake cycle at appropriate times in a day. As a starting step towards non-invasive investigation of CR, aim is to study changes in the physiological processes of two Regions of Interest (ROI), the hypothalamus and the visual cortex. This was studied using a functional Magnetic Resonance Imaging (fMRI) technique to investigate for any changes or differences in the Blood Oxygen Level Dependent (BOLD)signals extracted from the ROI during a visual stimulation. We acquired and processed fMRI data to extract BOLD signals from ROI and the extracted signals are again further used to study the correlation with the experimental ON-OFF design paradigm. The extracted BOLD signals varied a lot between the two specified brain regions within the same subject and between three types of fMRI data. These variations were found in terms of number of activated voxels and also Signal to Noise ratio(SNR) level present in the signals. The number of activated voxels and SNR werehigh in visual cortex whereas low number of activated voxels and low SNR were found in hypothalamus. The correlation between BOLD responses from primaryvisual cortex were shown as positive with the experimental stimulation whereas BOLD responses extracted from hypothalamus have shown a negative correlation in time with the experimental stimulation. As a start up of the project, these BOLD responses can provide references for a future use in research studies, especially to further study about change in phase of the BOLD signal extracted exactly from the SCN. These phase responses can then be used to study physiological processing in subjects affected by sleep disorders.
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Ostos, Giraldo Juan Carlos. "Analysis of a new family of DC-DC converters with input-parallel output-series structure." Thesis, The University of Sydney, 2014. http://hdl.handle.net/2123/12881.
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There is an increasing trend of development and installation of switching power supplies due to their highly efficient power conversion, fast power control and high quality power conditioning for applications such as renewable energy integration and energy storage management systems. In most of these applications, high voltage conversion ratio is required. However, basic switching converters have limited voltage conversion ratio. There has been much research into development of high gain power converters. While most of the reported topologies focus on high gain and high efficiency, in this thesis, the input and output ripple currents and reliability are also considered to derive a new converter structure suitable for high step-up voltage conversion applications. High ripple currents and voltages at the input and output of dc-dc converters are not desirable because they may affect the operation of the dc source or the load. A number of converters operating in an interleaved manner can reduce these ripples. This thesis proposes a dc/dc switching converter structure which is capable of reducing the ripple problem through interleaved action, in addition to high gain and high efficiency voltage conversion. The thesis analyses the proposed converter structure through a dual buck-boost converter topology. The structure allows different converter topologies and combinations of them for different applications to be configured. The study begins with a motivation and a literature review of dc/dc converters. The new family of high step-up converters is introduced with an interleaved buck-boost as an example, followed by small-signal analysis. Experimental verifications, conclusions and future work are discussed.
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Li, Yang. "The time-series approaches in forecasting one-step-ahead cash-flow data of mining companies listed on the Johannesburg Stock Exchange." Thesis, University of the Western Cape, 2007. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_1552_1254470577.
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<p>Previous research pertaining to the financial aspect of the mining industry has focused predominantly on mining products' values and the companies' sensitivity to exchange rates. There has been very little empirical research carries out in the field of the statistical behaviour of mning companies' cash flow data. This paper aimed to study the time-series behaviour of the cash flow data series of JSE listed mining companies.</p>
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Ladoucette, Laura <1993>. "Il riordino delle serie Cinema del Fondo Storico dell'Archivio Storico delle Arti Contemporanee (Biennale di Venezia)." Master's Degree Thesis, Università Ca' Foscari Venezia, 2019. http://hdl.handle.net/10579/14141.
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Il cuore di questo elaborato risiede nel riordino della serie Cinema del Fondo Storico dell'Archivio Storico delle Arti Contemporanee, ovvero l'archivio della Biennale di Venezia. Ripercorrendo la storia della Biennale e dell'archivio, siamo giunti a un ulteriore tappa della storia dell'istituto: il riordino completo del Fondo Storico, di cui fa parte la serie di nostro interesse. Il lavoro descrive le modalità dell'inventariazione e critica, nel positivo e nel negativo, le scelte eseguite, le difficoltà incontrate e le loro soluzioni.
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Ainscough, Thomas Stephen. "Addition of contingency management to stop smoking services in opiate users : a pilot and feasibility study." Thesis, King's College London (University of London), 2018. https://kclpure.kcl.ac.uk/portal/en/theses/addition-of-contingency-management-to-stop-smoking-services-in-opiate-users(2f0fe1cd-d886-4316-900b-a84ba82d69d1).html.
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Prevalence of tobacco smoking amongst those in treatment for opiate dependence is almost five times greater than that of the general population. Despite this, very few of those undergoing treatment for opiate addiction receive help to stop smoking. Contingency management (CM) is a behavioural intervention, based on the principles of operant conditioning, where desired behaviours are positively reinforced with some form of reward. CM may represent a potentially useful addition to standard stop smoking treatments for those in opiate addiction treatment, but has never been tested in this context in the UK. This thesis describes the development and piloting of an intervention, investigating the addition of a contingency management intervention for tobacco smoking, to standard stop smoking services treatment, in individuals undergoing treatment for opiate addiction. A meta-analysis was first conducted, investigating the use of CM as an intervention for the use of non-prescribed drug use during opiate addiction treatment. CM was found to be to be more effective than control in engendering abstinence from a wide range of drugs. Moderator analysis showed CM to be more effective than control in preventing use of cocaine, cocaine and opiates, tobacco, and poly-substance use, but not of opiates. Whilst carrying out the meta-analysis, it was discovered that no tool currently existed for assessing the quality of CM studies. This was addressed by the design and testing of a new tool, the CMQAT (Contingency Management Quality Assessment Tool). The tool underwent three stages of reliability and validity testing. Inter-rater reliability increased from slight at stage one, to fair at stage two, and was better than that of an established quality assessment tool (EPHPP) that achieved only slight agreement. Predictive validity could not be established at any stage. The results of the meta-analysis and CMQAT development were used to design a feasibility and pilot study, testing the addition of a CM intervention, to standard stop smoking services treatment. Forty opiate addiction patients were recruited into the study, and 37 were randomised to either an experimental (CM for smoking abstinence) or control (CM for attendance at the clinic) condition. The rate of recruitment was greater than that of other similar studies, yet only ten participants completed the intervention, two from the experimental condition and eight from the control, with none of the participants attending follow-up. The most widely reported reason for dropping out of the study was that the smoking clinic was not run at convenient times. Overall, I believe this thesis constitutes a significant contribution to the CM literature. The findings of the meta-analysis offer further support for the efficacy of CM as an intervention for non-prescribed drug use during opiate addiction treatment. The CMQAT forms the foundation for future work to improve both the accuracy of quality assessments of CM trials, and the reporting of methods and data in published reports of CM trials. The feasibility/pilot study represented the first time in the UK that CM had been used as an intervention for tobacco smoking during opiate addiction treatment. The primary observation from this study was that with the CM protocol used, retention in treatment was poor, with only 25% of participants completing the five-week intervention. Taken together, the findings have a number of implications for research, practice and policy. Perhaps the most important of these though, is that implementing CM in a clinical setting alongside standard stop smoking services treatment, introduces a number of new challenges not encountered in a laboratory setting. Further feasibility and pilot work is required before a full scale randomised controlled trial can be carried out.
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Della, Bianca Matilde <1995>. "La serie "Sentenze e conciliazioni dei Giudici di Pace di Aviano e Maniago" (1807-1813) del fondo "Pretura di Maniago" (1807-1948). Inventario archivistico analitico." Master's Degree Thesis, Università Ca' Foscari Venezia, 2021. http://hdl.handle.net/10579/19639.
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Il presente lavoro nasce da una preliminare ricognizione del fondo della Pretura di Maniago conservato nell’Archivio di Stato di Pordenone e prende in esame in sub-fondo composto da sedici volumi di sentenze dei giudici di pace di Aviano e Maniago emesse durante il periodo napoleonico (1807-1813). Lo studio vuole indagare la peculiare e poco studiata figura del giudice di pace all’interno del territorio friulano, e non solo, in un contesto di grandi cambiamenti istituzionali caratterizzati dalla necessità di razionalizzazione dell’organizzazione amministrativa e giudiziaria ed analizzando l’impatto di questa condizione a livello archivistico. Si è investigato sui motivi della presenza di carte della giudicatura di pace di Aviano unite a quelle della giudicatura di pace di Maniago, sulla soppressione dell’istituzione e sugli elementi di dissomiglianza e continuità con le successive.
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Pathirana, Vindya Kumari. "Nearest Neighbor Foreign Exchange Rate Forecasting with Mahalanobis Distance." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5757.
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Foreign exchange (FX) rate forecasting has been a challenging area of study in the past. Various linear and nonlinear methods have been used to forecast FX rates. As the currency data are nonlinear and highly correlated, forecasting through nonlinear dynamical systems is becoming more relevant. The nearest neighbor (NN) algorithm is one of the most commonly used nonlinear pattern recognition and forecasting methods that outperforms the available linear forecasting methods for the high frequency foreign exchange data. The basic idea behind the NN is to capture the local behavior of the data by selecting the instances having similar dynamic behavior. The most relevant k number of histories to the present dynamical structure are the only past values used to predict the future. Due to this reason, NN algorithm is also known as the k-nearest neighbor algorithm (k-NN). Here k represents the number of chosen neighbors.
In the k-nearest neighbor forecasting procedure, similar instances are captured through a distance function. Since the forecasts completely depend on the chosen nearest neighbors, the distance plays a key role in the k-NN algorithm. By choosing an appropriate distance, we can improve the performance of the algorithm significantly. The most commonly used distance for k-NN forecasting in the past was the Euclidean distance. Due to possible correlation among vectors at different time frames, distances based on deterministic vectors, such as Euclidean, are not very appropriate when applying for foreign exchange data. Since Mahalanobis distance captures the correlations, we suggest using this distance in the selection of neighbors.
In the present study, we used five different foreign currencies, which are among the most traded currencies, to compare the performances of the k-NN algorithm with traditional Euclidean and Absolute distances to performances with the proposed Mahalanobis distance. The performances were compared in two ways: (i) forecast accuracy and (ii) transforming their forecasts in to a more effective technical trading rule. The results were obtained with real FX trading data, and the results showed that the method introduced in this work outperforms the other popular methods.
Furthermore, we conducted a thorough investigation of optimal parameter choice with different distance measures. We adopted the concept of distance based weighting to the NN and compared the performances with traditional unweighted NN algorithm based forecasting.
Time series forecasting methods, such as Auto regressive integrated moving average process (ARIMA), are widely used in many ares of time series as a forecasting technique. We compared the performances of proposed Mahalanobis distance based k-NN forecasting procedure with the traditional general ARIM- based forecasting algorithm. In this case the forecasts were also transformed into a technical trading strategy to create buy and sell signals. The two methods were evaluated for their forecasting accuracy and trading performances.
Multi-step ahead forecasting is an important aspect of time series forecasting. Even though many researchers claim that the k-Nearest Neighbor forecasting procedure outperforms the linear forecasting methods for financial time series data, and the available work in the literature supports this claim with one step ahead forecasting. One of our goals in this work was to improve FX trading with multi-step ahead forecasting. A popular multi-step ahead forecasting strategy was adopted in our work to obtain more than one day ahead forecasts. We performed a comparative study on the performance of single step ahead trading strategy and multi-step ahead trading strategy by using five foreign currency data with Mahalanobis distance based k-nearest neighbor algorithm.
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Halimani, Mahantappa [Verfasser], and Jens [Akademischer Betreuer] Rettig. "Syntaxin11 serves as a t-SNARE for the final fusion step of lytic granules in human cytotoxic t lymphocytes / Mahantappa Halimani. Betreuer: Jens Rettig." Saarbrücken : Saarländische Universitäts- und Landesbibliothek, 2014. http://d-nb.info/105372523X/34.
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Pospíšil, Josef. "Vývoj a ověření DC/DC měniče pro budoucí automobilové osvětlovací systémy s palubním napětím 48V." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-377150.
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The aim of this master thesis is to describe the requirements put on electronics and headlights within car industry, above all on the newly emerging 48V power network. In the thesis the principles of chosen DC/DC buck converter topologies are briefly described. In the next part of this thesis the converters are designed and manufactured. Further, the EMC chamber measurement of these converters and their subsequent evaluation is performed. In the last part the proposed converters are compared and evaluated.
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ALIEV, KHURSHID. "Internet of Things Applications and Artificial Neural Networks in Smart Agriculture." Doctoral thesis, Politecnico di Torino, 2018. http://hdl.handle.net/11583/2697287.
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Internet of Things (IoT) is receiving a great attention due to its potential strength and ability to be integrated into any complex systems and it is becoming a great tool to acquire data from particular environment to the cloud. Data that are acquired from Wireless Sensor Nodes(WSN) could be predicted using Artificial Neural Network(ANN) models. One of the use case fields of IoT is smart agriculture and there are still issues on developing low cost and power efficient WSN using advanced radio technologies for short and long-range applications and implementation of prediction tools. This is the reason why the target of this thesis is to develop a low cost and power efficient WSN and IoT based control system and analyze the best predictive model for such systems. With this purpose, we developed BLESensor node for short-range IoT applications and Internet of Plant(IoP) for long distance smart agriculture applications. A non-linear prediction model is developed in order to forecast acquired data from sensor nodes. BLESensor node Experimental test results reveal that newly developed BLESensor node has a good impact on the improved lifetime and applications could possibly make this emerging technological area more useful. The Android software has been tested on Samsung Galaxy SM-T311, running Android 4.4.2 and it works without any issues and it is supposed to work on all other Android devices equipped with BLE. The working temperature range of the BLESensor node is supposed to work goes from -20 °C to 70 °C due to battery temperature limits. The system has been tested in the climatic chamber (Challenge 250 from Angelantoni) present at the Neuronica Lab, which allowed the sensor to be software calibrated. Several measurements have been proven that each node offers an uncertainty of 1.2 °C for temperature. These values are acceptable for the type of application for which they are intended. The power consumption has been measured directly from scope analysis and simulating the code step by step and calculations resulted that the lifetime of the node lasts for a month. Considering a normal use of these sensors with a reasonable sampling time the lifetime could be increased. IoP node IoP node is a prototype device that works with WiFi protocol and collects temperature, humidity and soil moisture data of plants to the cloud. For IoP node, we have implemented a firmware, tested a prototype device and designed the PCB in OrCAD software and generated a Gerber file and developed an android application. Prediction model Comparisonofthreenon-linearmodelswithOakdatasetresultedinbetterperformance of NNARX model and we used NNARX model to predict 10 days step ahead maximum and minimum temperature and described the results of performances. The performance given by trained models in terms of Mean Square Error (MSE) for maximum temperature prediction provided an error of 0.8826 on unseen data for the month of September. Similarly, the performance of model predicting minimum temperature was tested and it resulted in an error value of 0.944. In conclusion, this work must be intended only as a proof-of-concept, although, the developed BLESensor system, IoP prototype device and predictive models showed expected optimum results, both in terms of functionalities and usability.
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Rincon, Guillermo. "Kinetics of the electrocoagulation of oil and grease." ScholarWorks@UNO, 2011. http://scholarworks.uno.edu/td/131.
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Research on the electrocoagulation (EC) of hexane extractable materials (HEM) has been conducted at the University of New Orleans using a proprietary bench-scale EC reactor. The original reactor configuration forced the fluid to follow a vertical upward-downward path. An alternate electrode arrangement was introduced so that the path of flow became horizontal. Both configurations were evaluated by comparing the residence time distribution (RTD) data generated in each case. These data produced indication of internal recirculation and stagnant water when the fluid followed a vertical path. These anomalies were attenuated when the fluid flowed horizontally and at a velocity higher than 0.032 m s-1 . A series of EC experiments were performed using a synthetic emulsion with a HEM concentration of approximately 700 mg l-1. It was confirmed that EC of HEM follows first-order kinetics, and kinetic constants of 0.0441 s-1 and 0.0443 s-1 were obtained from applying both the dispersion and tanks-in-series (TIS) models, respectively. In both cases R2 was 0.97. Also, the TIS model indicated that each cell of the EC behaves as an independent continuous-stirred-tank reactor.
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Adolfsson, Tobias, and Axel Dellenby. "Pre-study of optical LED units for shunting signals." Thesis, KTH, Hälsoinformatik och logistik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296561.
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Alstom wanted to investigate the possibility of adapting its light emitting diode (LED) technology for shunting signals in train traffic. The LED technology uses 50V, but Alstom wants to adapt it for 12V. The LED technology is energy efficient but needs to be adapted for existing signal interlocking by drawing a higher current. This meant that the possibility of reactive power compensation was investigated to obtain lower thermal dissipation in dwarf signal. The essay presents a couple of possible solutions. One of the solutions is to raise the voltage by using a booster converter to use the existing 50V LED unit. Capacitors were reviewed to be used in reactive power compensation to increase current supply. One of the solutions then became a capacitor bank. Simulations indicated that a booster converter and a capacitor bank can be used to adapt the circuit. However, some modifications must be made.<br>Alstom ville undersöka möjligheten att anpassa sin lysdiodsteknik för dvärgsignaler i tågtrafiken. Lysdiodstekniken använder 50V men Alstom vill anpassa den för 12V. Lysdiodtekniken är strömsnål och behöver anpassas för befintliga signalställverk genom att dra en högre ström. Detta innebar att möjligheten för reaktiv kompensering undersöktes för att få en låg värmeutvecklingen i dvärgsignalen. I uppsatsen presenteras ett par möjliga lösningar. En av lösningarna för spänningen är en step-up omvandlare för att nyttja 50Vs enheten. Det gjordes också en genomgång av kondensatorer för att nyttjas i reaktivkompensering för att öka strömförbrukningen. En av lösningarna blev då ett kondensatorbatteri. Det kunde konstateras med matematisk simulering att step-up omvandlare och ett kondensatorbatteri kan användas för att anpassa kretsen dock måste vissa modifieringar utföras.
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Vala, Jiří. "Regulační soustavy." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2007. http://www.nusl.cz/ntk/nusl-412766.
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The MSc Thesis deals with real-time modelling, especially with the control circuits, where we focus on the regulation circuit with auxiliary model of the regulated system. The introduction contains the Theory of Controls and regulation. The work is divided into two basic parts. The first part deals with the problems from the theoretical point of view. The theoretical part is concerned with the general systems. Various definitions of systems, their partition and mathematical methods for their description are mentioned after introducing. A description the regulation circuits, their partition, structures and types follows. There are shown the particular regulators and different types of regulated systems in details. Mathematical methods applied to solve the differential equations that describe the models of the systems are summarized in the second part of the work. The end of this chapter is concerned with the TKSL system. In the practical part I have produced Microsoft Power Point program which summarizes the results of experiments, made in the TKSL and TKSL/C system. The output of simulation was transformed into the graphs in the format of Microsoft Excel. The last part deals with suggestion and implementation simulators of control circuits.
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Hanák, Kamil. "Pracoviště pro dynamické testování solárních článků." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217871.
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This work deals with method for characterization of photovoltaic solar cells based on evaluation of solar cell response to fast transients. The voltage of the cell in both forward and reverse polarisation was controlled by current pulse exciting. Real reverse breakdown voltage and exact value of serial resistance of the cell can be obtained easily by evaluation of the transient curves recorded by digital osciloscope. By negotiation of the time constants of the cell response to excitation in forward polarisation the lifetime of minority carriers in semiconductor bulk can be estimated.
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Adamík, Pavel. "Řízení dynamických systémů v reálném čase." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2009. http://www.nusl.cz/ntk/nusl-236759.
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This thesis focuses on the methodology of controlling dynamic systems in real time. It contents a review of the control theory basis and the elementary base of regulators construction. Then the list of matemathic formulaes follows as well as the math basis for the system simulations using a difeerential count and the problem of difeerential equations solving. Furthermore, there is a systematic approach to the design of general regulator enclosed, using modern simulation techniques. After the results confirmation in the Matlab system, the problematics of transport delay & quantization modelling follow.
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Sehnalová, Pavla. "Stabilita a konvergence numerických výpočtů." Doctoral thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2011. http://www.nusl.cz/ntk/nusl-261248.
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Tato disertační práce se zabývá analýzou stability a konvergence klasických numerických metod pro řešení obyčejných diferenciálních rovnic. Jsou představeny klasické jednokrokové metody, jako je Eulerova metoda, Runge-Kuttovy metody a nepříliš známá, ale rychlá a přesná metoda Taylorovy řady. V práci uvažujeme zobecnění jednokrokových metod do vícekrokových metod, jako jsou Adamsovy metody, a jejich implementaci ve dvojicích prediktor-korektor. Dále uvádíme generalizaci do vícekrokových metod vyšších derivací, jako jsou např. Obreshkovovy metody. Dvojice prediktor-korektor jsou často implementovány v kombinacích modů, v práci uvažujeme tzv. módy PEC a PECE. Hlavním cílem a přínosem této práce je nová metoda čtvrtého řádu, která se skládá z dvoukrokového prediktoru a jednokrokového korektoru, jejichž formule využívají druhých derivací. V práci je diskutována Nordsieckova reprezentace, algoritmus pro výběr proměnlivého integračního kroku nebo odhad lokálních a globálních chyb. Navržený přístup je vhodně upraven pro použití proměnlivého integračního kroku s přístupe vyšších derivací. Uvádíme srovnání s klasickými metodami a provedené experimenty pro lineární a nelineární problémy.
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Robles, Martínez Ángel. "Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater." Doctoral thesis, Editorial Universitat Politècnica de València, 2013. http://hdl.handle.net/10251/34102.
Full textAbstract:
El reactor anaerobio de membranas sumergidas (SAnMBR) está considerado como tecnología
candidata para mejorar la sostenibilidad en el sector de la depuración de aguas residuales,
ampliando la aplicabilidad de la biotecnología anaerobia al tratamiento de aguas residuales de
baja carga (v.g. agua residual urbana) o a condiciones medioambientales extremas (v.g. bajas
temperaturas de operación). Esta tecnología alternativa de tratamiento de aguas residuales es
más sostenible que las tecnologías aerobias actuales ya que el agua residual se transforma en
una fuente renovable de energía y nutrientes, proporcionando además un recurso de agua
reutilizable. SAnMBR no sólo presenta las principales ventajas de los reactores de membranas
(i.e. efluente de alta calidad, y pocas necesidades de espacio), sino que también presenta las
principales ventajas de los procesos anaerobios. En este sentido, la tecnología SAnMBR
presenta una baja producción de fangos debido a la baja tasa de crecimiento de los
microorganismos implicados en la degradación de la materia orgánica, presenta una baja
demanda energética debido a la ausencia de aireación, y permite la generación de metano, el
cual representa una fuente de energía renovable que mejora el balance energético neto del
sistema. Cabe destacar el potencial de recuperación de nutrientes del agua residual bien cuando
el efluente es destinado a irrigación directamente, o bien cuando debe ser tratado previamente
mediante tecnologías de recuperación de nutrientes.
El objetivo principal de esta tesis doctoral es evaluar la viabilidad de la tecnología SAnMBR
como núcleo en el tratamiento de aguas residuales urbanas a temperatura ambiente. Por lo tanto,
esta tesis se centra en las siguientes tareas: (1) implementación, calibración y puesta en marcha
del sistema de instrumentación, control y automatización requerido; (2) identificación de los
parámetros de operación clave que afectan al proceso de filtración; (3) modelación y simulación
del proceso de filtración; y (4) desarrollo de estrategias de control para la optimización del
proceso de filtración minimizando los costes de operación.
En este trabajo de investigación se propone un sistema de instrumentación, control y
automatización para SAnMBR, el cual fue esencial para alcanzar un comportamiento adecuado
y estable del sistema frente a posibles perturbaciones. El comportamiento de las membranas fue
comparable a sistemas MBR aerobios a escala industrial. Tras más de dos años de operación
ininterrumpida, no se detectaron problemas significativos asociados al ensuciamiento
irreversible de las membranas, incluso operando a elevadas concentraciones de sólidos en el
licor mezcla (valores de hasta 25 g·L-1
). En este trabajo se presenta un modelo de filtración
(basado en el modelo de resistencias en serie) que permitió simular de forma adecuada el proceso de filtración. Por otra parte, se propone un control supervisor basado en un sistema
experto que consiguió reducir el consumo energético asociado a la limpieza física de las
membranas, un bajo porcentaje de tiempo destinado a la limpieza física respecto al total de
operación, y, en general, un menor coste operacional del proceso de filtración.
Esta tesis doctoral está integrada en un proyecto nacional de investigación, subvencionado por
el Ministerio de Ciencia e Innovación (MICINN), con título ¿Modelación de la aplicación de la
tecnología de membranas para la valorización energética de la materia orgánica del agua
residual y la minimización de los fangos producidos¿ (MICINN, proyecto CTM2008-06809-
C02-01/02). Para obtener resultados representativos que puedan ser extrapolados a plantas
reales, esta tesis doctoral se ha llevado a cabo utilizando un sistema SAnMBR que incorpora
módulos comerciales de membrana de fibra hueca. Además, esta planta es alimentada con el
efluente del pre-tratamiento de la EDAR del Barranco del Carraixet (Valencia, España).<br>Robles Martínez, Á. (2013). Modelling, simulation and control of the filtration process in a submerged anaerobic membrane bioreactor treating urban wastewater [Tesis doctoral]. Editorial Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/34102<br>Alfresco<br>Premiado
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Cheng, Claire Hui fang, and 鄭惠方. "Movie Purchasing decision-A case study of Step Up Series." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/xzzus7.
Full textAbstract:
碩士<br>國立政治大學<br>國際經營管理英語碩士學位學程(IMBA)<br>104<br>Each year, only around 10% of the produced films will go to theatrical release, and 90% of the produced films might be the missing jewels lost in time. In Taiwan, movie distributors will act as this filter role to find out those 10% films. In this case, we will introduce the basic knowledge of the industry and discuss the evaluation process of the distributors and at the end reaching our conclusions and suggestions.
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Infante, Enrico. "Two-Step Reconciliation of Time Series New Formulation and Validation." Tesi di dottorato, 2017. http://www.fedoa.unina.it/11731/1/Infante_Enrico_28.pdf.
Full textAbstract:
Two-step reconciliation methods solve the temporal constraint in the first step, while in the second step the contemporaneous constraint is satisfied without altering the temporal constraint. Both in Quenneville and Rancourt and in Di Fonzo and Marini methods, the methodology used applies the Denton benchmarking technique in the first step.
The work done in this study is based on an alternative two-step procedure for the reconciliation of systems of time series, proposing an algorithm which allows to choose one of the two different solutions for the second step, and introduces the possibility of using well-known established techniques in the first step, such a Chow and Lin, Fernandez and Litterman. Furthermore, a way of dealing with the reconciliation of hierarchical systems of time series is presented. An innovative test for detecting common seasonal patterns in time series is also presented. Such test could be used for deciding at which level to seasonally adjust an aggregated time series before applying reconciliation.
Moreover, together with a simulation study, several aspects of the validation of a reconciliation technique are shown, including a new methodology for detecting whether the outliers at the end of series are consistent. Two real examples using the European industrial production index and the euro area quarterly sector accounts data will also be presented.
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Li, Chun Hsien, and 李俊賢. "Improved Multi-step Forecasts in Time Series by Composite Least Square Methods." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/63081236171617229056.
Full textAbstract:
碩士<br>國立清華大學<br>統計學研究所<br>104<br>Multi-step forecast is an important issue in time series analysis. Among linear forecasts, the direct and recursive methods are both popular in use. The former
is solved by minimizing the h-step-ahead prediction mean squared error directly. The latter, also called plug-in or iterated method, is recursively computing the
multi-step-ahead prediction by repeatedly plug in the one-step-ahead best linear predictors to unobserved lag variables. Both methods are theoretically justified,
while their empirical performance relative to the other is depending on the tradeoff between the bias and estimation variance which is typically sensitive to the working model, the forecast horizon, and the underlying data scenario. This thesis proposes a composite inference for parameter estimation as well as for the multi-step
forecasting by combining the estimating functions from both direct and recursive methods. This new composite method is easy to compute and is expected to remain the advantages from both sides. In particular, the new method can automatically adjust the optimal weights between both predictors via a cross validation approach. Simulation studies show that the proposed composite forecast performs effectively and adaptive towards the better one among the traditional direct and recursive forecasts under a variety of linear and nonlinear data generating scenarios. Some practical recommendations and computational issues are also addressed.
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Hoevenaars, Eric. "Temporal resolution in time series and probabilistic models of renewable power systems." Thesis, 2012. http://hdl.handle.net/1828/3927.
Full textAbstract:
There are two main types of logistical models used for long-term performance prediction of autonomous power systems: time series and probabilistic. Time series models are more common and are more accurate for sizing storage systems because they are able to track the state of charge. However, the computational time is usually greater than for probabilistic models. It is common for time series models to perform 1-year simulations with a 1-hour time step. This is likely because of the limited availability of high resolution data and the increase in computation time with a shorter time step. Computation time is particularly important because these types of models are often used for component size optimization which requires many model runs.
This thesis includes a sensitivity analysis examining the effect of the time step on these simulations. The results show that it can be significant, though it depends on the system configuration and site characteristics. Two probabilistic models are developed to estimate the temporal resolution error of a 1-hour simulation: a time series/probabilistic model and a fully probabilistic model. To demonstrate the application of and evaluate the performance of these models, two case studies are analyzed. One is for a typical residential system and one is for a system designed to provide on-site power at an aquaculture site. The results show that the time series/probabilistic model would be a useful tool if accurate distributions of the sub-hour data can be determined. Additionally, the method of cumulant arithmetic is demonstrated to be a useful technique for incorporating multiple non-Gaussian random variables into a probabilistic model, a feature other models such as Hybrid2 currently do not have. The results from the fully probabilistic model showed that some form of autocorrelation is required to account for seasonal and diurnal trends.<br>Graduate
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CHEN, CHIH-EN, and 陳志恩. "Novel Series Input Parallel Output Soft-Switching High Step-Down Forward Converter : Analysis and Implementation." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/27649180371780072782.
Full text
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Chan, Hsiang-Hao, and 詹翔豪. "Step-Stress Accelerated Life Tests of Series Systems with Interval Data Under Exponential Lifetime Distributions." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/78997803927014708140.
Full textAbstract:
碩士<br>國立中央大學<br>統計研究所<br>102<br>High reliability products have longer lifetime under normal environment. Accelerated life tests are
usually used to reduce the experiment time. In a series system, the system fails when any of the
components fails, while the cause of system failure may not be observed which is known as masked
data. In this thesis, we consider the step-stress accelerated life tests for series systems with Type-I
censoring, in which the lifetimes of components are exponentially distributed. We not only consider
those distributions are independent, but also consider the Marshall-Olkin bivariate distribution for
two-components series systems. Assume that there exists log-linear relationship between the mean
lifetime of components and the levels of the environmental stress variables under the cumulative exposure model, and the data analyzed are interval data in the sense only the numbers of failures are observed at the times of changing stress levels. Maximum likelihood inference is developed
incorporated with the EM algorithm as well as the missing information principle to achieving the Fisher information. Simulation study is carried out in the reliability analysis. It shows that the proposed method is more accurate and efficient than the bootstrap method.
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Zheng, Yu-Jun, and 鄭宇君. "An AC/AC Buck Inverter with Three-Step Current Commutation for Series Dynamic Voltage Regulator." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/96b5d8.
Full textAbstract:
碩士<br>國立中山大學<br>電機工程學系碩士班<br>107<br>This thesis derives the relationship between input and output of the AC/AC step-down inverter from the traditional Buck converter as the prototype. To suppress the surge voltage on inductor and IGBTs during the commutation of inductor current, this thesis analyzes the current loop of inductor and uses the three-step current commutation. While voltage fluctuation of system is happened, the controller compensates voltage by ac/ac inverter as the dynamic voltage regulator.
Experiment tests are carried out by the laboratory prototype with ac/ac inverter. Using the programmable ac source to simulate voltage sag of system. Experimental results show that the dynamic voltage regulator can compensate load voltage and fix it to the nominal voltage in different load characteristics and power factors. Besides, it can suppress the surge voltage on inductor and IGBTs effectively.
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Peng, Kuan-Jung, and 彭冠榕. "Reliability Analysis of a Series System on Weibull Step-stress Accelerated Life Tests with Masked Data." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/25914046086483791727.
Full textAbstract:
碩士<br>國立中央大學<br>統計研究所<br>98<br>In this thesis, reliability analysis of a series system consisting of J independent Weibull lifetime components is the main purpose. Due to high reliability product, we can not collect enough data under normal environment. A step-stress accelerated life test is employed for K-stage and M-stress variables under Type-I censoring scheme. In reality, not only the system lifetimes but also the sets containing the possible causes of failure are observed since the failure cause of the system may be lost. Such data are called masked. In general, the symmetry assumption for masking probabilities is assumed. We will consider the scale parameters of the Weibull lifetime distributions of the components is of a log-linear relationship with the stress variables. Bayesian approach via the Markov chain Monte Carlo procedure and the maximum likelihood approach with EM-algorithm and parametric bootstrap method are both developed for reliability analyses of the components as well as the system. Simulation studies and illustrative examples are presented.
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Chiu, Bo-Lung, and 邱柏龍. "Comparison of Constant-Stress and Step-Stress Accelerated Life Tests for Series Systems under Exponentila Life Distribution." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/46498819835365642065.
Full textAbstract:
碩士<br>國立中央大學<br>統計研究所<br>101<br>Accelerated life testing (ALT) is a process of testing products by subjecting it to strict
conditions, in order to observe more failure data in a short time period. In this thesis,
we consider the ALT of series system, each consists of two components whose life time
distributions follow independent exponential distributions. Optimal designs on the sample
allocation for the two-level constant-stress ALT(CSALT) and on the time for changing stress
levels for the two-level step-stress ALT(SSALT) are considered based on V-optimality, D-
optimality and A-optimality, respectively. Under Type-I censoring, it shows, by numerical
results, that the optimal SSALT is better than the optimal CSALT in terms of the resulting
objective functions. We also prove that the two optimal ALTs are indeed equivalent without
censoring. In addition, we use the optimal CSALT as the baseline ALT to obtain an equivalent
SSALT plan. A real data is analyzed to demonstrate the performance of both ALT plans
under the three optimality criteria as well as the equivalent test plans.
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LIN, CHUAN-KAI, and 林川凱. "Implementation of An Interleaved Input-Parallel Output-Series High Step-Up DC-DC Converter with Voltage Multiplier Module." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/q67hg3.
Full textAbstract:
碩士<br>崑山科技大學<br>電機工程研究所<br>104<br>An interleaved input-parallel output-series high step-up DC-DC converter with voltage multiplier module is proposed in the thesis. The circuit configuration is based on two boost converter with input-parallel output-series connection and a voltage multiplier module with two coupled-inductors is stacked on the output side. The switches are driven by the interleaved PWM operation with half switching period phase shift to form a interleaved high step-up DC-DC converter.
The advantages of the proposed converter are as follows. The converter achieves high voltage gain without operating at extreme duty ratio. The voltage stresses on the power switches are greatly lower than the output voltage such that the low-voltage-rated MOSFETs with low conducting resistors can be used to reduce the conduction losses. The parallel input connection can share the input current, reduce the conduction losses and handle large input current applications. The input current ripple is decreased by the interleaved operation. The output-diodes reverse-recovery problem can be alleviated by the leakage inductances of the coupled inductors. The leakage energy of the coupled inductors is recycled such that the voltage spikes on the switches are avoided and the efficiency is improved.
The converter operation analysis, design considerations, and driving circuit design are presented in this thesis. Finally, a 1000 W prototype converter with 40 V input and 400 V output operating at a switching frequency 40 kHz is built in the laboratory. In addition, a feedback controller is designed to diminish the effect of the variations of input voltage and load on the output voltage. The experimental results are presented to verify the theoretical analysis and the measured maximal efficiency is 97.44%.
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Elliott, David B., Richard J. Foster, David J. Whitaker, Andy J. Scally, and John G. Buckley. "Analysis of lower limb movement to determine the effect of manipulating the appearance of stairs to improve safety: a linked series of laboratory-based, repeated measures studies." 2015. http://hdl.handle.net/10454/8225.
Full textAbstract:
yes<br>Background: Falls on stairs are a common and dangerous problem for older people. This series of studies
evaluated whether or not selected changes to the appearance of stairs could make them safer for older
people to negotiate.
Objectives: To determine the effect of (1) a step edge highlighter and its position and (2) an optimised
horizontal–vertical (H–V) visual illusion placed on a step riser on gait safety during stair descent and ascent.
Design: A series of studies using a repeated measures, laboratory-based design, investigating gait control
and safety in independently mobile older people.
Setting: The University of Bradford Vision and Mobility Laboratory.
Participants: Fit and healthy older people aged 60 years of age or more, independently mobile,
reasonably active and with normal healthy eyes and corrected vision.
Interventions: A step edge highlighter in a variety of offsets from the stair edge and an optimised H–V visual
illusion placed on the stair riser. The H–V illusion was provided on a staircase by horizontal step edge
highlighters on the tread edges and vertical stripes on the step risers.
Main outcome measures: Gait parameters that are important for safe stepping in ascent and descent,
particularly toe clearance during stair ascent and heel clearance during stair descent.
Results: The step edge highlighter increased the precision of heel clearance during stepping and its
positioning relative to the tread edge determined the extent of heel clearance over the tread edge.
Positioning the highlighter away from the tread edge, as is not uncommonly provided by friction strips,
decreased heel clearance significantly and led to greater heel scuffs. Although psychophysics experiments
suggested that higher spatial frequencies of the H–V illusion might provide greater toe clearance on stair
ascent, gait trials showed similar increased toe clearances for all spatial frequencies. When a 12 cycle per
step spatial frequency H–V illusion was used, toe clearance increases of approximately 1 cm (17.5%)
occurred without any accompanying changes in other important gait parameters or stability measures.
Conclusions: High-contrast tread edge highlighters present on steps and stairs and positioned flush with
the edge of the tread or as near to this as possible should improve stair descent safety in older people. A
H–V illusion positioned on the riser of a raised surface/walkway (e.g. kerbs) and/or the top and/or bottom
of a stairway is likely to increase foot clearance over the associated step/stair edge, and appears not to
lead to any decrement in postural stability. Thus, their use is likely to reduce trip risk and hence improve
stair ascent safety. The effect of the step and stair modifications should be assessed in older people with
visual impairment. The only other remaining assessment that could be made would be to assess fall
prevalence on steps and stairs, perhaps in public buildings, with and without these modifications.<br>National Institute for Health Research, Public Health Research programme. PHR programme as project number 10/3009/06
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Joshi, T. G. Subhash. "Power Electronic Technologies for Medium and High Power High Voltage Power Supplies." Thesis, 2017. http://etd.iisc.ac.in/handle/2005/4322.
Full textAbstract:
The performance of systems used in various high voltage applications depend majorly on the output voltage ripple of High Voltage Power Supplies (HVPS). One of the failure mode of microwave tube (MWT) commonly used in these applications is due to the energy accumulation above the specified limit during fault events due to higher stored energy in HVPS. This demands either a protection for MWT or reduced ripple voltage without increasing the stored energy.
This thesis investigates a protection device for MWT that operate with MW power level HVPS, and design method to reduce the output voltage ripple for medium power HVPS.
A crowbar is an energy diverting device connected in parallel with the MWT. It protects the tube during fault by providing an alternative path for the ow of energy. Conventional crowbars are built using either mercury or nitrogen gas-based switches. Due to the environmental concern and higher operational cost, the state-of-the-art is to replace these devices with semiconductor devices, referred to as solid state crowbar (SSC). This research, models and designs the subcomponents of an SSC, including: (i) Modelling of fault current, and a fuse wire that is used to emulate a MWT during internal arc (ii) Design of di=dt limiting inductor (iii) Design of static and dynamic voltage balancing network for the thyristor (iv) Mechanical assembly design that ensures meeting the required crowbar electrical characteristics (v) Selection of cost-effective semiconductor device for crowbar application (vi) Thermal modelling of crowbar for pulse power applications (vii) Selection of cable for the pulse power application.
In a switched converter topology, the causes of output voltage ripple are: the switch action, input dc ripple, and variations in the load. In this thesis the influence of input voltage ripple on the output dc voltage, called Audio Susceptibility (AS), is discussed. AS of load resonant converters has not been widely studied in literature. This research uses exact discretization method to obtain: (i) The analytical large signal and cyclic steady state model of the Series Resonant Converter (SRC) considering the resonant tank and output filter states (ii) The analytical small signal AS model of the SRC, and resonant gain condition for input ripple (iii) The design of an SRC for superior AS performance (iv) A comparison of SRC design for (a) superior AS performance and (b) maximum power transfer capability (v) A selection of SRC components including the high voltage high frequency magnetics and selection of the MosFET.
All the modelling and design method considered in this work has been verified by experimental studies on two 10MW, 10kV peak power SSC and a 10kW, 10kV SRC that has been fabricated as a part of the research.
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Denys, Mateusz. "Analysis of interevent times by methods of statistical physics." Doctoral thesis, 2017. https://depotuw.ceon.pl/handle/item/2469.
Full textAbstract:
The problem of excessive losses is significant in economic theory and investment practice, as well as for random processes analysis. One of the recently discovered characteristics of losses and profits on financial markets, which was discovered by Bogachev, Bunde, Ludescher, and Tsallis and is not entirely explained yet, is the universality of the distribution of times between losses (or profits) exceeding a given threshold value. In other words, this distribution does not depend on the underlying asset type or the time resolution of data, but rather only depends on the particular threshold height. Interestingly, similar results were obtained, e.g., in geophysical time series (describing the earthquakes exceeding a particular magnitude). In this thesis I present a thorough description of this universality, employing two complementary approaches: (i) an analytical approach, based on the extreme value theory (EVT) and the continuous-time random walk (CTRW) model, and (ii) a numerical approach, based on the Potts model from statistical mechanics. The thesis makes original contributions to the field of knowledge with the following: (i) an analytical model of the aforementioned universality, with a thorough empirical verification for losses and some proposed applications to value-at-risk simulation, profits description, and geophysical data description, and (ii) an agent-based spin model of financial markets with the novel interpretation of the spin variable (as regards financial-market models), reproducing the main empirical stylized facts, such as the shape of a usual and an absolute-value autocorrelation function of the returns as well as the distribution of times between superthreshold losses. These results extend the knowledge and understanding of stochastic processes, agent-based modeling, financial markets and geophysical systems.<br>Zagadnienie dużych strat jest kluczowe zarówno z teoretycznego punktu widzenia (w tym w analizie stochastycznej), jak i z punktu widzenia inwestorów giełdowych. Jedną z ostatnio odkrytych (przez Bogacheva, Bundego, Ludeschera i Tsallisa) i dotąd w pełni niewyjaśnionych własności strat i zysków w finansowych szeregach czasowych jest uniwersalność rozkładu czasów pomiędzy kolejnymi stratami (lub zyskami) przekraczającymi zadaną wysokość progową. Innymi słowy, rozkład ten nie zależy od rodzaju rozpatrywanego instrumentu finansowego czy skali czasowej danych, które bierzemy pod uwagę, a jedynie od zadanej wysokości progu. Podobne wyniki uzyskano także np. dla geofizycznych szeregów czasowych (dla trzęsień ziemi przekraczających zadaną magnitudę). W niniejszej rozprawie przedstawiam gruntowny opis tej uniwersalności, wykorzystujący dwa komplementarne podejścia: (i) podejście analityczne, oparte na teorii wartości ekstremalnych (extreme value theory, EVT) i na modelu błądzenia losowego w czasie ciągłym (continuous-time random walk, CTRW) oraz (ii) podejście numeryczne, oparte na modelu Pottsa z mechaniki statystycznej. Oryginalny wkład w rozwój wiedzy z dziedziny, której praca jest poświęcona, stanowią: (i) analityczny model wyżej wymienionej uniwersalności wraz z dokładnym sprawdzeniem jego poprawności za pomocą różnorodnych danych empirycznych dla strat i propozycjami zastosowań do symulacji zmian wielkości value at risk (VaR), do opisu zysków i do opisu danych geofizycznych oraz (ii) agentowy spinowy model rynków finansowych z nowatorską (jeśli chodzi o modele rynków finansowych) interpretacją zmiennej spinowej, odtwarzający szereg empirycznych faktów stylizowanych, takich jak kształt funkcji autokorelacji zwykłych i absolutnych stóp zwrotu oraz wspomniany rozkład czasów pomiędzy ponadprogowymi stratami. Wyniki przedstawione w pracy poszerzają wiedzę na temat procesów stochastycznych, modelowania agentowego, rynków finansowych oraz zjawisk geofizycznych.