To see the other types of publications on this topic, follow the link: Power law distribution.
Dissertations / Theses on the topic 'Power law distribution'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Power law distribution.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Weinstein, Lee. "Scale free networks and their power law distribution." Diss., Connect to the thesis, 2005. http://hdl.handle.net/10066/3880.
Full text
2
Chamberlain, Lauren. "The Power Law Distribution of Agricultural Land Size." DigitalCommons@USU, 2018. https://digitalcommons.usu.edu/etd/7400.
Full textAbstract:
This paper demonstrates that the distribution of county level agricultural land size in the United States is best described by a power-law distribution, a distribution that displays extremely heavy tails. This indicates that the majority of farmland exists in the upper tail. Our analysis indicates that the top 5% of agricultural counties account for about 25% of agricultural land between 1997-2012. The power-law distribution of farm size has important implications for the design of more efficient regional and national agricultural policies as counties close to the mean account for little of the cumulative distribution of total agricultural land. This has consequences for more efficient management and government oversight as a disruption in one of the counties containing a large amount of farmland (due to natural disasters, for instance) could have nationwide consequences for agricultural production and prices. In particular, the policy makers and government agencies can monitor about 25% of total agricultural land by overseeing just 5% of counties.
3
Kim, Jung Eun. "Analysis of Sleep-Wake Transition Dynamics by Stochastic Mean Field Model and Metastable State." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1406206931.
Full text
4
Dashti, Moghaddam Mohammadamin. "Stochastic Phenomena in Finance, Economics, Cognitive Psychology -- Modeling with Generalized Beta Prime." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1571061904950758.
Full text
5
Haro, Berois Martín. "Statistical distribution of common audio features : encounters in a heavy-tailed universe." Doctoral thesis, Universitat Pompeu Fabra, 2013. http://hdl.handle.net/10803/128623.
Full textAbstract:
In the last few years some Music Information Retrieval (MIR) researchers have spotted important drawbacks in applying standard successful-in-monophonic algorithms to polyphonic music classification and similarity assessment. Noticeably, these so called “Bag-of-Frames” (BoF) algorithms share a common set of assumptions. These assumptions are substantiated in the belief that the numerical descriptions extracted from short-time audio excerpts (or frames) are enough to capture relevant information for the task at hand, that these frame-based audio descriptors are time independent, and that descriptor frames are well described by Gaussian statistics. Thus, if we want to improve current BoF algorithms we could: i) improve current audio descriptors, ii) include temporal information within algorithms working with polyphonic music, and iii) study and characterize the real statistical properties of these frame-based audio descriptors. From a literature review, we have detected that many works focus on the first two improvements, but surprisingly, there is a lack of research in the third one. Therefore, in this thesis we analyze and characterize the statistical distribution of common audio descriptors of timbre, tonal and loudness information. Contrary to what is usually assumed, our work shows that the studied descriptors are heavy-tailed distributed and thus, they do not belong to a Gaussian universe. This new knowledge led us to propose new algorithms that show improvements over the BoF approach in current MIR tasks such as genre classification, instrument detection, and automatic tagging of music. Furthermore, we also address new MIR tasks such as measuring the temporal evolution of Western popular music. Finally, we highlight some promising paths for future audio-content MIR research that will inhabit a heavy-tailed universe.En el campo de la extracción de información musical o Music Information Retrieval (MIR), los algoritmos llamados Bag-of-Frames (BoF) han sido aplicados con éxito en la clasificación y evaluación de similitud de señales de audio monofónicas. Por otra parte, investigaciones recientes han señalado problemas importantes a la hora de aplicar dichos algoritmos a señales de música polifónica. Estos algoritmos suponen que las descripciones numéricas extraídas de los fragmentos de audio de corta duración (o frames ) son capaces de capturar la información necesaria para la realización de las tareas planteadas, que el orden temporal de estos fragmentos de audio es irrelevante y que las descripciones extraídas de los segmentos de audio pueden ser correctamente descritas usando estadísticas Gaussianas. Por lo tanto, si se pretende mejorar los algoritmos BoF actuales se podría intentar: i) mejorar los descriptores de audio, ii) incluir información temporal en los algoritmos que trabajan con música polifónica y iii) estudiar y caracterizar las propiedades estadísticas reales de los descriptores de audio. La bibliografía actual sobre el tema refleja la existencia de un número considerable de trabajos centrados en las dos primeras opciones de mejora, pero sorprendentemente, hay una carencia de trabajos de investigación focalizados en la tercera opción. Por lo tanto, esta tesis se centra en el análisis y caracterización de la distribución estadística de descriptores de audio comúnmente utilizados para representar información tímbrica, tonal y de volumen. Al contrario de lo que se asume habitualmente, nuestro trabajo muestra que los descriptores de audio estudiados se distribuyen de acuerdo a una distribución de “cola pesada” y por lo tanto no pertenecen a un universo Gaussiano. Este descubrimiento nos permite proponer nuevos algoritmos que evidencian mejoras importantes sobre los algoritmos BoF actualmente utilizados en diversas tareas de MIR tales como clasificación de género, detección de instrumentos musicales y etiquetado automático de música. También nos permite proponer nuevas tareas tales como la medición de la evolución temporal de la música popular occidental. Finalmente, presentamos algunas prometedoras líneas de investigación para tareas de MIR ubicadas, a partir de ahora, en un universo de “cola pesada”.
En l’àmbit de la extracció de la informació musical o Music Information Retrieval (MIR), els algorismes anomenats Bag-of-Frames (BoF) han estat aplicats amb èxit en la classificació i avaluació de similitud entre senyals monofòniques. D’altra banda, investigacions recents han assenyalat importants inconvenients a l’hora d’aplicar aquests mateixos algorismes en senyals de música polifònica. Aquests algorismes BoF suposen que les descripcions numèriques extretes dels fragments d’àudio de curta durada (frames) son suficients per capturar la informació rellevant per als algorismes, que els descriptors basats en els fragments son independents del temps i que l’estadística Gaussiana descriu correctament aquests descriptors. Per a millorar els algorismes BoF actuals doncs, es poden i) millorar els descriptors, ii) incorporar informació temporal dins els algorismes que treballen amb música polifònica i iii) estudiar i caracteritzar les propietats estadístiques reals d’aquests descriptors basats en fragments d’àudio. Sorprenentment, de la revisió bibliogràfica es desprèn que la majoria d’investigacions s’han centrat en els dos primers punts de millora mentre que hi ha una mancança quant a la recerca en l’àmbit del tercer punt. És per això que en aquesta tesi, s’analitza i caracteritza la distribució estadística dels descriptors més comuns de timbre, to i volum. El nostre treball mostra que contràriament al què s’assumeix, els descriptors no pertanyen a l’univers Gaussià sinó que es distribueixen segons una distribució de “cua pesada”. Aquest descobriment ens permet proposar nous algorismes que evidencien millores importants sobre els algorismes BoF utilitzats actualment en diferents tasques com la classificació del gènere, la detecció d’instruments musicals i l’etiquetatge automàtic de música. Ens permet també proposar noves tasques com la mesura de l’evolució temporal de la música popular occidental. Finalment, presentem algunes prometedores línies d’investigació per a tasques de MIR ubicades a partir d’ara en un univers de “cua pesada”.
6
Blanchet, Thomas. "Essays on the Distribution of Income and Wealth : Methods, Estimates and Theory." Thesis, Paris, EHESS, 2020. http://www.theses.fr/2020EHES0004.
Full textAbstract:
Cette thèse couvre plusieurs sujets sur la répartition des revenus et des richesses. Dans le premier chapitre, nous développons une nouvelle méthode pour exploiter les tabulations de revenu et de richesse, telle que celle publiée par les autorités fiscales. Nous y définissons les courbes de Pareto généralisées comme la courbe des coefficients de Pareto inversés b(p), où b(p) est le rapport entre le revenu moyen ou la richesse au-dessus du rang p et le p-ième quantile Q(p) (c'est-à-dire b(p)=E[X|X>Q(p)]/Q(p)). Nous les utilisons pour caractériser des distributions entières, y compris les endroits comme le sommet où la lois de Pareto est une bonne description, et les endroits plus bas où elles ne le sont pas. Nous développons une méthode pour reconstruire de manière flexible l'ensemble de la distribution sur la base de données tabulées sur le revenu ou le patrimoine, qui produit courbes de Pareto généralisées lisses et réalistes.Dans le deuxième chapitre, nous présentons une nouvelle approche pour combiner les données d'enquête et les tabulations fiscales afin de corriger la sous-représentation des plus riches au sommet. Elle détermine de façon endogène un "point de fusion'' entre les données avant de modifier les poids tout au long de la distribution et de remplacer les nouvelles observations au-delà du support original de l'enquête. Nous fournissons des simulations de la méthode et des applications aux données réelles. Les premières démontrent que notre méthode améliore la précision et la stabilité des estimations de la distribution, par rapport à d'autres méthodes de correction d'enquêtes utilisant des données externes, et même en présence d'hypothèses extrêmes. Les applications empiriques montrent que non seulement les niveaux d'inégalité des revenus peuvent changer, mais aussi les tendances.Dans le troisième chapitre, nous estimons la distribution du revenu national dans 38 pays européens entre 1980 et 2017 en combinant enquêtes, données fiscales et comptes nationaux. Nous développons une méthodologie cohérente combinant des méthodes d'apprentissage statistique, de calage non linéaire des enquêtes et la théorie des valeurs extrêmes afin de produire des estimations de l'inégalité des revenus avant et après impôt, comparables d'un pays à l'autre et conformes aux taux de croissance macroéconomiques. Nous constatons que les inégalités se sont creusées dans une majorité de pays européens, en particulier entre 1980 et 2000. Le 1% les plus riches en Europe a augmenté plus de deux fois plus vite que les 50% les plus pauvres et a capturé 18% de la croissance des revenus régionaux.Dans le quatrième chapitre, je décompose la dynamique de la distribution de la richesse à l'aide d'un modèle stochastique dynamique simple qui sépare les effets de la consommation, du revenu du travail, des taux de rendement, de la croissance, de la démographie et du patrimoine. À partir de deux théorèmes de calcul stochastique, je montre que ce modèle est identifié de manière non paramétrique et qu'il peut être estimé à partir de données en coupes répétées. Je l'estime à l'aide des comptes nationaux distributifs des États-Unis depuis 1962. Je trouve que, de l'augmentation de 15pp. de la part de la richesse détenue par les 1% les plus riches observée depuis 1980, environ 7pp. peut être attribuée à l'inégalité croissante des revenus du travail, 6pp. à la hausse des rendements sur le capital (principalement sous forme de plus-values), et 2pp. à la baisse de la croissance. En suivant les paramètres actuels, la part de la richesse des 1% les plus riches atteindrait sa valeur stationnaire d'environ 45% d'ici les années 2040, un niveau similaire à celui du début du XXe siècle. J'utilise ensuite le modèle pour analyser l'effet d'un impôt progressif sur les patrimoines au sommet de la distributionThis thesis covers several topics on the distribution of income and wealth. In the first chapter, we develop a new methodology to exploit tabulations of income and wealth such as the one published by tax authorities. In it, we define generalized Pareto curves as the curve of inverted Pareto coefficients b(p), where b(p) is the ratio between average income or wealth above rank p and the p-th quantile Q(p) (i.e. b(p)=E[X|X>Q(p)]/Q(p)). We use them to characterize entire distributions, including places like the top where power laws are a good description, and places further down where they are not. We develop a method to flexibly recover the entire distribution based on tabulated income or wealth data which produces smooth and realistic shapes of generalized Pareto curves.In the second chapter, we present a new approach to combine survey data with tax tabulations to correct for the underrepresentation of the rich at the top. It endogenously determines a "merging point'' between the datasets before modifying weights along the entire distribution and replacing new observations beyond the survey's original support. We provide simulations of the method and applications to real data. The former demonstrate that our method improves the accuracy and precision of distributional estimates, even under extreme assumptions, and in comparison to other survey correction methods using external data. The empirical applications show that not only can income inequality levels change, but also trends.In the third chapter, we estimate the distribution of national income in thirty-eight European countries between 1980 and 2017 by combining surveys, tax data and national accounts. We develop a unified methodology combining machine learning, nonlinear survey calibration and extreme value theory in order to produce estimates of pre-tax and post-tax income inequality, comparable across countries and consistent with macroeconomic growth rates. We find that inequality has increased in a majority of European countries, especially between 1980 and 2000. The European top 1% grew more than two times faster than the bottom 50% and captured 18% of regional income growth.In the fourth chapter, I decompose the dynamics of the wealth distribution using a simple dynamic stochastic model that separates the effects of consumption, labor income, rates of return, growth, demographics and inheritance. Based on two results of stochastic calculus, I show that this model is nonparametrically identified and can be estimated using only repeated cross-sections of the data. I estimate it using distributional national accounts for the United States since 1962. I find that, out of the 15pp. increase in the top 1% wealth share observed since 1980, about 7pp. can be attributed to rising labor income inequality, 6pp. to rising returns on wealth (mostly in the form of capital gains), and 2pp. to lower growth. Under current parameters, the top 1% wealth share would reach its steady-state value of roughly 45% by the 2040s, a level similar to that of the beginning of the 20th century. I then use the model to analyze the effect of progressive wealth taxation at the top of the distribution
7
Li, Xiaohu. "Security Analysis on Network Systems Based on Some Stochastic Models." ScholarWorks@UNO, 2014. http://scholarworks.uno.edu/td/1931.
Full textAbstract:
Due to great effort from mathematicians, physicists and computer scientists, network science has attained rapid development during the past decades. However, because of the complexity, most researches in this area are conducted only based upon experiments and simulations, it is critical to do research based on theoretical results so as to gain more insight on how the structure of a network affects the security. This dissertation introduces some stochastic and statistical models on certain networks and uses a k-out-of-n tolerant structure to characterize both logically and physically the behavior of nodes. Based upon these models, we draw several illuminating results in the following two aspects, which are consistent with what computer scientists have observed in either practical situations or experimental studies.
Suppose that the node in a P2P network loses the designed function or service when some of its neighbors are disconnected. By studying the isolation probability and the durable time of a single user, we prove that the network with the user's lifetime having more NWUE-ness is more resilient in the sense of having a smaller probability to be isolated by neighbors and longer time to be online without being interrupted. Meanwhile, some preservation properties are also studied for the durable time of a network. Additionally, in order to apply the model in practice, both graphical and nonparametric statistical methods are developed and are employed to a real data set.
On the other hand, a stochastic model is introduced to investigate the security of network systems based on their vulnerability graph abstractions. A node loses its designed function when certain number of its neighbors are compromised in the sense of being taken over by the malicious codes or the hacker. The attack compromises some nodes, and the victimized nodes become accomplices. We derived an equation to solve the probability for a node to be compromised in a network. Since this equation has no explicit solution, we also established new lower and upper bounds for the probability.
The two models proposed herewith generalize existing models in the literature, the corresponding theoretical results effectively improve those known results and hence carry an insight on designing a more secure system and enhancing the security of an existing system.
8
Chow, Jijun. "Power-law distributions in events involving nuclear and radiological materials." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55262.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Nuclear Science and Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 41).
Nuclear and radiological events are large-impact, hard-to-predict rare events, whose associated probability is exceedingly low. They can exert monumental impacts and lead to grave environmental and economic consequences. Identifying common trends of these events can help to assess the threat, and to combat it with better detection capabilities and practices. One way to achieve this is to model the events with established statistical and mathematical distributions. Power-law distribution is a good candidate because it is a probability distribution with asymptotic tails, and thus can be applied to study patterns of rare events of large deviations, such as those involving nuclear and radiological materials. This thesis, based on the hypothesis that nuclear and radiological events follow the power-law growth model, assembles published data of four categories of events - incidents of nuclear and radiological materials, incidents of radioactive attacks, unauthorized activities of illicit trafficking, and incidents of nuclear terrorism, and investigates whether specific distributions such as the power-law can be applied to analyze the data. Data are gathered from a number of sources. Even though data points are collected, the databases are far from complete, mainly due to the limited amount of public information that is available to the outside party, rendering the modeling task difficult and challenging. Furthermore, there may exist many undocumented instances, underscoring the fact that the reporting is an ongoing effort.
(cont.) To compile a comprehensive dataset for analytical purposes, a more efficient method of collecting data should be employed. This requires gathering information through various means, including different departmental or governmental domains that are available to the public as well as professional insight and support. In addition, to facilitate better management of nuclear and radiological events, technological capacities to track them need to be strengthened, and information sharing and coordination need to be enhanced not only on regional but also on national and international levels.
by Jijun Chow.
S.B.
9
Mesgarzadeh, Behzad. "Low-Power Low-Jitter Clock Generation and Distribution." Doctoral thesis, Linköpings universitet, Elektroniska komponenter, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-14896.
Full textAbstract:
Today’s microprocessors with millions of transistors perform high-complexitycomputing at multi-gigahertz clock frequencies. Clock generation and clockdistribution are crucial tasks which determine the overall performance of amicroprocessor. The ever-increasing power density and speed call for newmethodologies in clocking circuitry, as the conventional techniques exhibit manydrawbacks in the advanced VLSI chips. A significant percentage of the total dynamicpower consumption in a microprocessor is dissipated in the clock distributionnetwork. Also since the chip dimensions increase, clock jitter and skew managementbecome very challenging in the framework of conventional methodologies. In such asituation, new alternative techniques to overcome these limitations are demanded. The main focus in this thesis is on new circuit techniques, which treat thedrawbacks of the conventional clocking methodologies. The presented research in thisthesis can be divided into two main parts. In the first part, challenges in design ofclock generators have been investigated. Research on oscillators as central elements inclock generation is the starting point to enter into this part. A thorough analysis andmodeling of the injection-locking phenomenon for on-chip applications show greatpotential of this phenomenon in noise reduction and jitter suppression. In thepresented analysis, phase noise of an injection-locked oscillator has been formulated.The first part also includes a discussion on DLL-based clock generators. DLLs haverecently become popular in design of clock generators due to ensured stability,superior jitter performance, multiphase clock generation capability and simple designprocedure. In the presented discussion, an open-loop DLL structure has beenproposed to overcome the limitations introduced by DLL dithering around the averagelock point. Experimental results reveals that significant jitter reduction can beachieved by eliminating the DLL dithering. Furthermore, the proposed structuredissipates less power compared to the traditional DLL-based clock generators.Measurement results on two different clock generators implemented in 90-nm CMOSshow more than 10% power savings at frequencies up to 2.5 GHz. In the second part of this thesis, resonant clock distribution networks have beendiscussed as low-power alternatives for the conventional clocking schemes. In amicroprocessor, as clock frequency increases, clock power is going to be thedominant contributor to the total power dissipation. Since the power-hungry bufferstages are the main source of the clock power dissipation in the conventional clock distribution networks, it has been shown that the bufferless solution is the mosteffective resonant clocking method. Although resonant clock distribution shows greatpotential in significant clock power savings, several challenging issues have to besolved in order to make such a clocking strategy a sufficiently feasible alternative tothe power-hungry, but well-understood, conventional clocking schemes. In this part,some of these issues such as jitter characteristics and impact of tank quality factor onoverall performance have been discussed. In addition, the effectiveness of theinjection-locking phenomenon in jitter suppression has been utilized to solve the jitterpeaking problem. The presented discussion in this part is supported by experimentalresults on a test chip implemented in 130-nm CMOS at clock frequencies up to 1.8GHz.Mikroprocessorer till dagens datorer innehåller hundratals miljoner transistorersom utför åtskilliga miljarder komplexa databeräkningar per sekund. I stort settalla operationer i dagens mikroprocessorer ordnas genom att synkronisera demmed en eller flera klocksignaler. Dessa signaler behöver ofta distribueras överhela chippet och driva alla synkroniseringskretsar med klockfrekvenser pååtskilliga miljarder svängningar per sekund. Detta utgör en stor utmaning förkretsdesigners på grund av att klocksignalerna behöver ha en extremt högtidsnoggranhet, vilket blir svårare och svårare att uppnå då chippen blir större.Idealt ska samma klocksignal nå alla synkroniseringskretsar exakt samtidigt föratt uppnå optimal prestanda, avvikelser ifrån denna ideala funktionalitet innebärlägre prestanda. Ytterliggare utmaningar inom klockning av digitala chip, är atten betydande andel av processorns totala effekt förbrukas i klockdistributionen.Därför krävs nya innovativa kretslösningar för att lösa problemen med bådeonoggrannheten och den växande effektförbrukningen i klockdistributionen. att lösa de problem som finns i dagens konventionella kretslösningar förklocksignaler på chip. I den första delen av denna avhandling presenterasforskningsresultat på oscillatorer vilka utgör mycket viktiga komponenter igeneringen av klocksignalerna på chippen. Teoretiska studier avfaslåsningsfenomen i integrerade klockoscillatorer har presenterats. Studiernahar visat att det finns stor potential för reducering av tidsonoggrannhet iklocksignalerna med hjälp av faslåsning till en annan signal. I avhandlingensförsta del presenteras även en diskussion om klockgeneratorer baserade påfördröjningslåsta element. Dessa fördröjningslåsta elementen, kända som DLLkretsar, har egenskapen att de kan fördröja en klocksignal med en bestämdfördröjning, vilket möjliggör skapandet av multipla klockfaser. En nykretsteknik har introducerats för klockgenerering av multipla klockfaser vilken reducerar effektförbrukningen och onoggranheten i DLL-baseradeklockgeneratorer. I denna teknik används en övervakningskrets vilken ser till attalla delar i klockgeneratorn utnyttjas effektivt och att oanvända kretsarinaktiveras. Baserat på experimentalla mätresultat från tillverkade testkretsar ikisel har en effektbesparing på mer än 10% uppvisats vid klockfrekvenser påupp till 2.5 GHz tillsammans med en betydande ökning av klocknoggranheten. I avhandlingens andra del diskuteras en klockdistributionsteknik som baseraspå resonans, vilken har visat sig vara ett lovande alternativ till konventionllabufferdrivna klockningstekniker när det gäller minskande effektförbrukning.Principen bakom tekniken är att återanvända den energi som utnyttjas till attladda upp klocklasten. Teoretiska resonemang har visat att storaenergibesparingar är möjliga, och praktiska mätningar på tillverkadeexperimentchip har visat att effektförbrukingen kan mer än halveras. Ettproblem med den föreslagna klockningstekniken är att data som används iberäkningarna kretsen direkt påverkar klocklasten, vilket även påverkarnoggranheten på klocksignalen. För att komma till rätta med detta problemetpresenteras en teknik, baserad på forskning inom ovan nämndafaslåsningsfenomen, som kan minska onoggrannheten på klocksignalen medöver 50%. Både effektbesparingen och förbättringen av tidsnoggranheten harverifierats med hjälp av mätningar på tillverkade chip vid frekvenser upp mot1.8 GHz.
10
Miotto, José Maria. "Modeling and predicting time series of social activities with fat-tailed distributions." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-211323.
Full textAbstract:
Fat-tailed distributions, characterized by the relation P(x) ∝ x^{−α−1}, are an emergent statistical signature of many complex systems, and in particular of social activities. These fat-tailed distributions are the outcome of dynamical processes that, contrary to the shape of the distributions, is in most cases are unknown. Knowledge of these processes’ properties sheds light on how the events in these fat tails, i.e. extreme events, appear and if it is possible to anticipate them. In this Thesis, we study how to model the dynamics that lead to fat-tailed distributions and the possibility of an accurate prediction in this context. To approach these problems, we focus on the study of attention to items (such as videos, forum posts or papers) in the Internet, since human interactions through the online media leave digital traces that can be analysed quantitatively. We collected four sets of time series of online activity that show fat tails and we characterize them.
Of the many features that items in the datasets have, we need to know which ones are the most relevant to describe the dynamics, in order to include them in a model; we select the features that show high predictability, i.e. the capacity of realizing an accurate prediction based on that information. To quantify predictability we propose to measure the quality of the optimal forecasting method for extreme events, and we construct this measure. Applying these methods to data, we find that more extreme events (i.e. higher value of activity) are systematically more predictable, indicating that the possibility of discriminate successful items is enhanced. The simplest model that describes the dynamics of activity is to relate linearly the increment of activity with the last value of activity recorded. This starting point is known as proportional effect, a celebrated and widely used class of growth models in complex systems, which leads to a distribution of activity that is fat-tailed. On the one hand, we show that this process can be described and generalized in the framework of Stochastic Differential Equations (SDE) with Normal noise; moreover, we formalize the methods to estimate the parameters of such SDE. On the other hand, we show that the fluctuations of activity resulting from these models are not compatible with the data. We propose a model with proportional effect and Lévy-distributed noise, that proves to be superior describing the fluctuations around the average of the data and predicting the possibility of an item to become an extreme event.
However, it is possible to model the dynamics using more than just the last value of activity; we generalize the growth models used previously, and perform an analysis that indicates that the most relevant variable for a model is the last increment in activity. We propose a new model using only this variable and the fat-tailed noise, and we find that, in our data, this model is superior to the previous models, including the one we proposed. These results indicate that, even if present, the relevance of proportional effect as a generative mechanism for fat-tailed distributions is greatly reduced, since the dynamical equations of our models contain this feature in the noise. The implications of this new interpretation of growth models to the quantification of predictability are discussed along with applications to other complex systems.
11
Cortobius, Fredriksson Moa. "ProBenefit : Implementing the Convention on Biological Diversity in the Ecuadorian Amazon." Thesis, Södertörn University College, School of Life Sciences, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-2771.
Full textAbstract:
Legislation on benefit sharing dates back to 1992 and the commandment of the UNConvention on Biological Diversity, hence implementation still has few cases to fall back on(CBD, 1992). The case study of the project ProBenefit presented by the thesis highlights howlack of deliberation can undermine a democratic process. The objective of the thesis is thatProBenefit’s attempt to implement the standards of the CBD on access and benefit sharingwill highlight not only problems met by this specific project, but difficulties that generallymeet democratic processes in contexts of high inequality. To define if the project ProBenefitsucceeded in carrying out a deliberative process the project will be analyzed by the criteria:access to information, representation, legitimacy and involvement.The population in the project area of ProBenefit had a long history of social marginalization,which made it hard for foreign projects to gain legitimacy. The lack of independentorganizations and the late establishment of the project, which resulted in time shortage, madeit impossible to prevent the distrust of the local population. The failure of the projectcoordinators to ensure active participation of all stakeholders resulted in a late and lowinvolvement of the local participants. The absence of independent organization also madedemocratic legitimacy of the process questionable. Even if ProBenefit had a vision ofdemocratic deliberation the project was unable to break down the prevailing unequal powerdistribution which resulted in an unsustainable process and failure. The conclusion of thethesis is that the attainment of deliberation foremost depends on how a project deals with theexisting distribution of power and how it succeeds in involving all stakeholders.
12
Jiang, Jian. "Modeling of complex network, application to road and cultural networks." Phd thesis, Université du Maine, 2011. http://tel.archives-ouvertes.fr/tel-00691129.
Full textAbstract:
Many complex systems arising from nature and human society can be described as complex networks. In this dissertation, on the basis of complex network theory, we pay attention to the topological structure of complex network and the dynamics on it. We established models to investigate the influences of the structure on the dynamics of networks and to shed light on some peculiar properties of complex systems. This dissertation includes four parts. In the first part, the empirical properties (degree distribution, clustering coefficient, diameter, and characteristic path length) of urban road network of Le Mans city in France are studied. The degree distribution shows a double power-law which we studied in detail. In the second part, we propose two models to investigate the possible mechanisms leading to the deviation from simple power law. In the first model, probabilistic addition of nodes and links, and rewiring of links are considered; in the second one, only random and preferential link growth is included. The simulation results of the modelling are compared with the real data. In the third part,the probabilistic uncertainty behavior of double power law distribution is investigated. The network optimization and optimal design of scale free network to random failures are discussed from the viewpoint of entropy maximization. We defined equilibrium network ensemble as stationary ensembles of graphs by using some thermodynamics like notions such as "energy", "temperature", "free energy" for network. In the forth part, an union-division model is established to investigate the time evolution of certain networks like cultural or economical networks. In this model, the nodes represent, for example, the cultures. Several quantities such as richness, age, identity, ingredient etc. are used to parameterize the probabilistic evolution of the network. The model offers a long term view on the apparently periodic dynamics of an ensemble of cultural or economic entities in interaction.
13
Cobain, Matthew Robert David. "Fish and their scales : on the power laws of aggregation, size distribution and trophic interaction." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/424756/.
Full textAbstract:
Power law relationships are ubiquitous in ecology, and complex systems in general, and can be used as metrics to describe many aspects of ecosystem structure and function. While ecological interactions and processes predominantly occur at the individual level of biological organisation, currently, most ecological studies aim to estimate “typical” ecosystem behaviour over large spatial and temporal scales. This disconnect results in the under- appreciation of ecosystem dynamics that are potentially important for developing ecological theory and ecosystem modelling. The research presented herein aims to estimate within-ecosystem dynamics, as quantified by power law relationships, to test whether expected ecological dynamics can be captured effectively at smaller scales. I show that Taylor’s power law, a metric of aggregation, varies systematically, both spatially and temporally within the North Sea fish community, with the abiotic environment when populations were considered as cohorts of individual body sizes. By combining estimates of the power law distribution of body size in fish with stable isotopes that can be used to infer trophic interactions, I show that seasonal trends in fish movement patterns and the incorporation of pulsed phytoplankton production can be quantified in a highly dynamic estuarine environment. Estimates of the in situ community predator-prey mass ratio, which describes trophic behaviour, and the apparent trophic transfer efficiency are then derived and shown to exhibit strong seasonal variation, indicative of an estuarine food web that is temporally variable. Finally, I quantify the degree of individual specialisation, a mechanism by which intraspecific competition is modulated, in the diet of a commercially important but over-exploited fish species to inform conservation efforts. This work shows that ecological dynamics can be captured by a range of ecosystem metrics and that, therefore, small scale behaviours can be tested for empirically to direct ecosystem models and theory.
14
Bento, Eli?ngela Paulino. "Fundamenta??o cin?tica da estat?stica n?o gaussiana : efeitos em politr?picas." Universidade Federal do Rio Grande do Norte, 2011. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18595.
Full textAbstract:
Made available in DSpace on 2015-03-03T15:15:26Z (GMT). No. of bitstreams: 1
EliangelaPB_DISSERT.pdf: 614353 bytes, checksum: 050737d0ef158e6082d81254619adac0 (MD5)
Previous issue date: 2011-09-19Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Considering a non-relativistic ideal gas, the standard foundations of kinetic theory are investigated in the context of non-gaussian statistical mechanics introduced by Kaniadakis. The new formalism is based on the generalization of the Boltzmann H-theorem and the deduction of Maxwells statistical distribution. The calculated power law distribution is parameterized through a parameter measuring the degree of non-gaussianity. In the limit = 0, the theory of gaussian Maxwell-Boltzmann distribution is recovered. Two physical applications of the non-gaussian effects have been considered. The first one, the -Doppler broadening of spectral lines from an excited gas is obtained from analytical expressions. The second one, a mathematical relationship between the entropic index and the stellar polytropic index is shown by using the thermodynamic formulation for self-gravitational systems
Considerando um g?s ideal n?o relativ?stico, os fundamentos da teoria cin?tica padr?o s?o investigados no contexto da mec?nica estat?stica n?o-gaussiana introduzida por Kaniadakis. O novo formalismo ? baseado na generaliza??o do teorema-H de Boltzmann e na dedu??o de Maxwell da distribui??o estat?stica. A distribui??o lei de pot?ncia calculada ? parametrizada por um par?metro medindo o grau de n?o-gaussianidade do sistema. No limite = 0, a teoria gaussiana de Maxwell-Boltzmann ? recuperada. Duas aplica??es dos efeitos n?o-gaussiano s?o estudados. Na primeira, o -alargamento Doppler das linhas espectrais de um g?s excitado ? obtido a partir das express?es anal?ticas. Na segunda, uma rela??o matem?tica entre o ?ndice entr?pico e o ?ndice politr?pico estelar ? mostrada usando uma formula??o termodin?mica para sistemas autogravitantes
15
Ahmed, Sara Mohamed. "Modeling of Power Electronics Distribution Systems with Low-frequency, Large-signal (LFLS) Models." Diss., Virginia Tech, 2011. http://hdl.handle.net/10919/27787.
Full textAbstract:
This work presents a modeling methodology that uses new types of models called low-frequency, large-signal models in a circuit simulator (Saber) to model a complex hybrid ac/dc power electronics system. The new achievement in this work is being able to model the different components as circuit-based models and to capture some of the large-signal phenomena, for example, real transient behavior of the system such as startup, inrush current and power flow directionality. In addition, models are capable of predicting most low frequency harmonics only seen in real switching detailed models. Therefore the new models system can be used to predict steady state performance, harmonics, stability and transients. This work discusses the modeling issues faced based on the author recent experiences both on component level and system level. In addition, it recommends proper solutions to these issues verified with simulations.
This work also presents one of the new models in detail, a voltage source inverter (VSI), and explains how the model can be modified to capture low frequency harmonics that are usually phenomena modeled only with switching models. The process of implementing these different phenomena is discussed and the model is then validated by comparing the results of the proposed low frequency large signal (LFLS) model to a complete detailed switching model. In addition, experimental results are also obtained with a 2 kW voltage source inverter prototype to validate the proposed improved average model (LFLS model). In addition, a complete Verification, Validation, and Uncertainty Quantification (VV&UQ) procedures is applied to a two-level boost rectifier. The goal of this validation process is the improvement of the modeling procedure for power electronics systems, and the full assessment of the boost rectifier model predictive capabilities.
Finally, the performance of the new models system is compared with the detailed switching models system. The LFLS models result in huge cut in simulation time (about 10 times difference) and also the ability to use large time step with the LFLS system and still capture all the information needed. Even though this low frequency large signal (LFLS) models system has wider capabilities than ideal average models system, it still can’t predict all switching phenomena. Therefore, another benefit of this modeling approach is the ability to mix different types of models (low frequency large signal (LFLS) and detailed switching) based on the application study they are used for.Ph. D.
16
Barrera, Núñez Víctor Augusto. "Automatic diagnosis of voltage disturbances in power distribution networks." Doctoral thesis, Universitat de Girona, 2012. http://hdl.handle.net/10803/80944.
Full textAbstract:
This thesis proposes a framework for identifying the root-cause of a voltage disturbance, as well as, its source location (upstream/downstream) from the monitoring place. The framework works with three-phase voltage and current waveforms collected in radial distribution networks without distributed generation. Real-world and synthetic waveforms are used to test it. The framework involves features that are conceived based on electrical principles, and assuming some hypothesis on the analyzed phenomena. Features considered are based on waveforms and timestamp information. Multivariate analysis of variance and rule induction algorithms are applied to assess the amount of meaningful information explained by each feature, according to the root-cause of the disturbance and its source location. The obtained classification rates show that the proposed framework could be used for automatic diagnosis of voltage disturbances collected in radial distribution networks. Furthermore, the diagnostic results can be subsequently used for supporting power network operation, maintenance and planning.En esta tesis se propone una metodología para la identificación de la localización relativa (aguas arriba/abajo) y la causa de una perturbación eléctrica. La metodología utiliza las ondas trifásicas de tensión y de corriente registradas en redes de distribución radial sin presencia de generación distribuida. La metodología es validada utilizando perturbaciones eléctricas reales y simuladas. La metodología involucra atributos que han sido concebidos basándose en principios eléctricos e hipótesis de acuerdo a cada uno de los fenómenos eléctricos analizados. Se propusieron atributos tanto basados en la forma de onda como en la fecha de ocurrencia de la perturbación. La cantidad de información contenida y/o explicada por cada atributo es valorada mediante la aplicación del análisis multivariante de la varianza y algoritmos de extracción automática de reglas de decisión. Los resultados de clasificación muestran que la metodología propuesta puede ser utilizada para el diagnóstico automático de perturbaciones eléctricas registradas en redes de distribución radial. Los resultados de diagnóstico pueden ser utilizados para apoyar las tareas de operación, mantenimiento y planeamiento de las redes de distribución.
17
Jooste, Kritzman Phillip. "A load management system for fixed appliances in a safe DC RDP house." Thesis, Cape Peninsula University of Technology, 2017. http://hdl.handle.net/20.500.11838/2634.
Full textAbstract:
Thesis (MTech (Electrical Engineering))--Cape Peninsula University of Technology, 2017.This dissertation represents the design and development of a load management system for fixed appliances in a safe direct current (DC) Reconstruction and Development Programme (RDP) house. A combination of valley filling, load shifting and peak clipping load management techniques were employed to assist in reducing the peaks observed in the RDP house load profile during peak hours. A DC RDP house laboratory model was developed. The study is based on the assumption that the normally 220 V alternative current (AC) grid is replaced by a 350 V DC grid. The assumption is thus that 350 V DC is available at the distribution box in the RDP house laboratory model. All theoretical work was based on a 350 V DC system, but due to the lack of a laboratory 350 V DC supply, all physical tests were conducted by making use of a 300 V DC supply which was available. Consequently all calculations were thus based on 300 V DC as well. The geyser was the main fixed appliance focused on since it contributes to a significant portion of the power used. An AC geyser was successfully modified in order to be used in the DC network. Safety of the system was considered in order to interrupt the power in case of overcurrent or to isolate the power. Electronic switches were also developed and implemented to ensure that the DC power could be safely switched on and off and that the low power DC was isolated from the high power DC. LabVIEW allowed all other appliances in the DC RDP house to be virtually represented so that a holistic view of the power use of the house could be represented. This also allowed the system to be successfully simulated before any physical work was conducted. The load management system was successfully implemented by making use of power line communication. This proved to be a cost effective means to apply the load management algorithm. The algorithm consisted mainly of power on / off instructions that were executed during peak and off-peak times. It follows the normal use of timers used in the AC system to help reduce demand. It was found that the load management system successfully reduced the demand during peak hours without compromising the basic needs of the user. The power line communication modem proved to be very reliable in implementing the load management algorithm.
18
Navarro, Espinosa Alejandro. "Low carbon technologies in low voltage distribution networks : probabilistic assessment of impacts and solutions." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/low-carbon-technologies-in-low-voltage-distribution-networks-probabilistic-assessment-of-impacts-and-solutions(cc5c77df-54fe-4c1c-a599-3bbea8fbd0c1).html.
Full textAbstract:
The main outcome of this research is the development of a Probabilistic Impact Assessment methodology to comprehensively understand the effects of low carbon technologies (LCTs) in low voltage (LV) distribution networks and the potential solutions available to increase their adoption. The adoption of LCTs by domestic customers is an alternative to decreasing carbon emissions. Given that these customers are connected to LV distribution networks, these assets are likely to face the first impacts of LCTs. Thus, to quantify these problems a Monte Carlo-based Probabilistic Impact Assessment methodology is proposed in this Thesis. This methodology embeds the uncertainties related to four LCTs (PV, EHPs, µCHP and EVs). Penetration levels as a percentage of houses with a particular LCT, ranging from 0 to 100% in steps of 10%, are investigated. Five minute time-series profiles and three-phase four-wire LV networks are adopted. Performance metrics related to voltage and congestion are computed for each of the 100 simulations per penetration level. Given the probabilistic nature of the approach, results can be used by decision makers to determine the occurrence of problems according to an acceptable probability of technical issues. To implement the proposed methodology, electrical models of real LV networks and high resolution profiles for loads and LCTs are also developed. Due to the historic passive nature of LV circuits, many Distribution Network Operators (DNOs) have no model for them. In most cases, the information is limited to Geographic Information Systems (GIS) typically produced for asset management purposes and sometimes with connectivity issues. Hence, this Thesis develops a methodology to transform GIS data into suitable computer-based models. In addition, thousands of residential load, PV, µCHP, EHP and EV profiles are created. These daily profiles have a resolution of five minutes. To understand the average behaviour of LCTs and their relationship with load profiles, the average peak demand is calculated for different numbers of loads with and without each LCT.The Probabilistic Impact Assessment methodology is applied over 25 UK LV networks (i.e., 128 feeders) for the four LCTs under analysis. Findings show that about half of the studied feeders are capable of having 100% of the houses with a given LCT. A regression analysis is carried out per LCT, to identify the relationships between the first occurrence of problems and key feeder parameters (length, number of customers, etc.). These results can be translated into lookup tables that can help DNOs produce preliminary and quick estimates of the LCT impacts on a particular feeder without performing detailed studies. To increase the adoption of LCTs in the feeders with problems, four solutions are investigated: feeder reinforcement, three-phase connection of LCTs, loop connection of LV feeders and implementation of OLTCs (on-load tap changers) in LV networks. All these solutions are embedded in the Probabilistic Impact Assessment. The technical and economic benefits of each of the solutions are quantified for the 25 networks implemented.
19
Ford, Elizabeth. "Barabási-Albert random graphs, scale-free distributions and bounds for approximation through Stein's method." Thesis, University of Oxford, 2009. http://ora.ox.ac.uk/objects/uuid:b1091661-33b5-47fe-912c-61286159904a.
Full textAbstract:
Barabási-Albert random graph models are a class of evolving random graphs that are frequently used to model social networks with scale-free degree distributions. It has been shown that Barabási-Albert random graph models have asymptotic scale-free degree distributions as the size of the graph tends to infinity. Real world networks, however, have finite size so it is important to know how close the degree distribution of a Barabási-Albert random graph of a given size is to its asymptotic distribution. Stein’s method is chosen as one main method for obtaining explicit bounds for the distance between distributions. We derive a new version of Stein’s method for a class of scale-free distributions and apply the method to a Barabási-Albert random graph. We compare the evolution of a sequence of Barabási-Albert random graphs with continuous time stochastic processes motivated by Yule’s model for evolution. Through a coupling of the models we bound the total variation distance between their degree distributions. Using these bounds, we extend degree distribution bounds that we find for specific models within the scheme to find bounds for every member of the scheme. We apply the Azuma-Hoeffding inequality and Chernoff bounds to find bounds between the degree sequences of the random graph models and the given scale-free distribution. These bounds prove that the degree sequences converge completely (and therefore also converge almost surely) to our scale-free distribution. We discuss the relationship between the random graph processes and the Chinese restaurant process. Aided by the construction of an inhomogeneous Markov chain, we apply our results for the degree distribution in a Barabási-Albert random graph to a particular statistic of the Chinese restaurant process. Finally, we explore how our methods can be adapted and extended to other evolving random graph processes. We study a Bernoulli evolving random graph process, for which we bound the distance between its degree distribution and a geometric distribution and we bound the distance between the number of triangles in the graph and a normal distribution.
20
Heunis, Schalk W. (Schalk Willem). "The analysis and quantifiaction of uncertainty for least life-cost electrical low voltage distribution design." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51937.
Full textAbstract:
Dissertation (PhD)--University of Stellenbosch, 2000.ENGLISH ABSTRACT: The purpose of this dissertation is to provide methods for designing and managing low voltage residential feeders. These methods can be applied to the problem of planning residential networks under uncertainty while ensuring least life-cycle costs. By analysing collected load data from various communities in South Africa, a new probabilistic model for representing the load uncertainty of residential consumers was derived. This model uses the beta probability distribution to describe individual consumer loads over a period of time. Methods for combining the loads in linear combinations were used to derive a new probabilistic voltage regulation calculation procedure. This new method is different from previously developed voltage calculation methods in that it can be used to estimate the probable voltage performance of a feeder over a period of time. A simplification of the method is proposed which allows it to be implemented in any commercial spreadsheet program. The new probabilistic load model was also applied to the problem of calculating resistive losses in residential low voltage feeders. A new probabilistic method was formulated and this method can be used to estimate the probable range of resistive loss in a feeder for a period of time. This method is simple enough to implement in a commercial spreadsheet program. Probabilistic information about network and load parameter uncertainty is seldom available and these uncertainties are best modelled using fuzzy numbers. The probabilistic calculation methods cannot represent these uncertainties and only after applying a fuzzy-probabilistic approach can both types of uncertainties be used. This is a significant enhancement to the current methods and ensures that the uncertainty about the calculated results is realistically represented. The specification of load parameters for the methods was significantly simplified following a regression analysis of collected load data from South African communities. By specifying the distribution of the consumption of individual consumers in a community, the other load parameters can be estimated using a set of fitted linear regression equations. This greatly reduces the burden of specifying the load parameters and makes it possible for the proposed calculation methods to be applied to the design of new feeders in practice. The distribution of the consumption of individual consumers can be specified using the average and the standard deviation of the consumptions of individual consumers. Accurate estimates of these parameters can be obtained from sales information and can be used to manage existing networks effectively. Using the sales information with the proposed methods enables more cost-effective upgrades of existing feeders low voltage feeders. The identification of potential problems in existing low voltage networks is also possible if the layout of the feeders in a community is known. The use of the proposed methods is illustrated in step-by-step fashion. Typical input parameters are used and all the required calculations with intermediate results are presented.
AFRIKAANSE OPSOMMING: Die doel van hierdie proefskrif is die daarstelling van residensiële laagspanningsnetwerk ontwerp- en bestuursmetodes. Hierdie metodes kan toegepas word vir die beplanning van residensiële laagspanningsnetwerke waar onsekerheid bestaan oor toekomstige kragverbruik en die spesifikasie van die netwerkparameters. Lasdata, wat versamel is in verskeie Suid Afrikaanse gemeenskappe, is geanaliseer en 'n nuwe probabilistiese modellering van die onsekerheid oor die kragverbruik van residensiële verbruikers is ontwikkel. Gebruik is gemaak van die beta waarskynlikheidsdightheidsfunksie om die tydsgebonde kragverbruik van die verbruikers voor te stel. 'n Nuwe probabilistiese spanningsvalberekeningsmetode is ontwikkel en die metode maak gebruik van liniêre kombinasies van die lasstrome van die verbruikers. Die verskil tussen hierdie metode en bestaande metodes is dat dit die tydsgebonde waarskynlikheid van die spanningsregulasie van 'n kabel kan bereken. 'n Vereenvoudiging van die metode is ook verkry en dit kan in enige kommersiële sigblad geïmplementeer word. Die probabilistiese lasstroommodel is ook gebruik om 'n nuwe probabilistiese energieverliesberekeningsmetode te ontwikkel. Hierdie metode kan gebruik word om die tydsgebonde waarskynlikhede van 'n reeks van moontlike energieverlieswaardes te bereken. Die metode is eenvoudig genoeg om in enige kommersiële sigblad te implementeer. Onsekerheid oor die spesifikasie van die parameters van die nuwe metodes asook die netwerkparameters kan nie met probabilistiese metodes voorgestel word nie, aangesien inligting oor die waarskynlikhede van parameters selde beskikbaar is. Hierdie onsekerhede kan beter voorgestel word deur die gebruik van sogenaamde "fuzzy"-metodes. Die voorgestelde probabilistiese metodes is aangepas om hierdie tipe onsekerhede ook in ag te neem. "Fuzzy-probabilistic" metodes is gebruik vir dié aanpassings en word beskou as 'n noemenswaardige verbetering van die metodes. Die verbeterde metodes verkaf meer realistiese voorstellings van die onsekerheid oor berekende resultate. 'n Statisitiese analise van Suid Afrikaanse lasdata het 'n vereenvoudiging van die spesifisering van die parameters van die nuwe metodes tot gevolg gehad. Die waarskynlikheidsverspreiding van die energieverbruik van huishoudelike verbruikers kan gebruik word om akkurate skattings van die ander parameters te verkry. Hierdie vereenvoudiging het tot gevolg dat die nuwe metodes vir praktiese netwerkontwerp gebruik kan word. Die waarskynlikheidsverpreiding van die energieverbruik van verbuikers is beskikbaar in die vorm van energieverkope en kan gebruik word vir die effektiewe bestuur en opgradering van bestaande netwerke. As die uitleg van die bestaande netwerke in 'n gemeenskap beskikbaar is, kan die inligting wat bevat is in die energieverkope gebruik word om probleme in bestaande netwerke te identifiseer. Al die voorgestelde metodes is stap vir stap uiteengesit met voorbeelde van al die berekeninge met tipiese waardes.
21
Vai, Vannak. "Planning of low voltage distribution system with integration of PV sources and storage means : case of power system of Cambodia." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAT044/document.
Full textAbstract:
La consommation d'énergie augmente d'année en année en raison de la croissance de la population et des conditions économiques. Afin de répondre aux besoins de la population et de la société d'utiliser l'électricité, le Gouvernement Cambodgien a mis en place la politique de promotion et d'encouragement du développement de l’électrification ; tous les villages auront de l'électricité d'ici 2020 et au moins 70% des domiciles auront accès à la bonne qualité du réseau électrique d'ici 2030. Pour réussir ces objectifs, l'étude et le développement de la méthodologie du réseau de distribution basse tension (BT) sont étudiés. Cette thèse étudie la planification du réseau de distribution BT avec intégration de Photovoltaïque (PV) et de stockage d’énergie de batterie (BES). La première partie est développée la méthode de planification à long terme pour tacler le défi de l'incertitude sur la charge en zone urbaine ;le nouvel algorithme a été développé pour rechercher l'architecture optimale de minimisation du coût d’investissement (CAPEX) et d’exploitation (OPEX) qui respecte l'ensemble de contraintes topologies et électriques (courant et tension) grâce à la programmation linéaire mixte en nombres entiers à contraintes quadratiques (PLMNECQ), le plus court chemin , first-fit bin-packing, et la méthode de Monte-Carlo. La deuxième partie est traité de l'extension de la zone de couverture de l'électricité avec deux solutions possibles, sont le renforcement du réseau et l'intégration de PV-BES pour le village rural ; l'algorithme génétique (GA) et la technique itérative ont été codés pour rechercher l’emplacement et la capacité. La dernière partie du travail est concentrée sur la planification du réseau de distribution résidentielle BT pour les zones non électrifiées aux rural et urbain grâce à l'architecture optimale et l'intégration de PV-BES sur l'horizon de planificationThe energy consumption is increasing year by year due to the growth of population and the economic conditions. In order to meet the need of population and society to use electricity, the Cambodian government has established the policy to promote and encourage the development of electrification; all the villages will have electricity by the year 2020, and at least 70% of households will have access to grid quality by the year 2030. To achieve these goals, the study and development of methodology on the Low-Voltage (LV) distribution system are investigated. This thesis studies the planning of LV distribution system with integration of Photovoltaic (PV) and Battery Energy Storage (BES). The first part is developed the long-term planning method to tackle the challenge of load demand uncertainty in urban area; the novel algorithm was developed to search for the optimal architecture of minimizing the capital expenditure (CAPEX) and the operation expenditure (OPEX) which respects to the set of topology and electrical (current and voltage) thank to mixed integer quadratically constrained programming (MIQCP), shortest-path, first-fit bin-packing, and Monte-Carlo method. The second part is dealt with the extension of electricity coverage area with two possible solutions which are grid reinforcement and integration of PV-BES for rural village; the Genetic algorithm (GA) and iterative technique were coded to search for location and sizing. The last part is concentrated on the planning of residential low-voltage distribution system in both rural and urban for non-electrified area thanks to the optimal architecture and PV-BES integration over the planning horizon
22
Squaiella, Davi José Ferreira. "Planejamento agregado em redes de distribuição secundária - modelo alternativo para empresas com cadastro de redes reduzido." Universidade de São Paulo, 2004. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-09082005-074944/.
Full textAbstract:
As redes secundárias de distribuição são item de extrema importância no processo de levar a energia produzida de uma fonte até o consumidor final. Dentro de uma Empresa Concessionária de Distribuição de Energia Elétrica o setor de planejamento, juntamente com o grupo técnico, deve realizar o planejamento dos investimentos necessários nos níveis de alta, média e baixa tensão, sendo que para a baixa tensão (redes secundárias de distribuição), normalmente utilizam-se os dados históricos e a média de investimentos dos últimos anos (de três a cinco últimos anos). Em geral não são encontrados nestas Empresas os cadastramentos das redes secundárias de distribuição ou então, quando estes existem, muitas vezes não são confiáveis. Neste ponto, esta dissertação de mestrado apresentará, aplicará e discutirá os resultados de uma metodologia de geração de redes secundárias de distribuição a partir dos dados das redes primárias de distribuição (média tensão) e dos ativos da Empresa, tendo como foco os investimentos necessários para estas dentro do planejamento agregado de investimentos. O trabalho proposto visa criar condições para que as Empresas enquadradas na situação anterior possam realizar o seu planejamento de baixa tensão valendo-se da aplicação de uma metodologia capaz de gerar tais redes. Uma vez criadas, tais redes serão inseridas dentro de um software de planejamento agregado de investimentos que fornecerá o valor total das aplicações necessárias para os próximos dez anos (planejamento decenal longo prazo). Ao final do processo, poderá ser observado que os resultados obtidos são muito próximos dos valores esperados para as redes secundárias reais e, com isto, a dissertação discutirá como a metodologia foi implementada, os detalhes da aplicação e, até mesmo, todo o processo de planejamento para três Empresas Concessionárias de Distribuição de Energia Elétrica. Já de posse dos resultados, poderá afirmar-se que o processo produziu valores de muito boa aderência e, assim, os investimentos obtidos para as redes secundárias poderão ser aceitos pelo grupo de planejamento da Empresa. Como conseqüência dos valores de investimentos obtidos para os dez anos, poderão ser observados ainda, guardadas algumas considerações especiais, os valores dos custos marginais de baixa tensão, item de grande importância no planejamento de redes de distribuição.The low voltage distribution networks are an item of extreme importance in the process of delivering the produced energy from a plant (supply) to the final consumer. In an Electric Power Distribution Company the planning group (sector), together with the technical group, must accomplish the planning of the necessary investments in the high voltage, medium voltage and low voltage levels, and for low voltage distribution networks, usually the historical data and the average of investments of the last years are used (from three to last five years). In general the databases of low voltage networks are not found in these Companies or then, when these exist, a lot of times they are not reliable. For this, this article will show, apply and discuss the results of a methodology for generating low voltage distribution networks starting from the database of the medium voltage distribution networks and of the assets of the Company, having as focus the necessary investments for these networks in planning of investments. The proposed work wishes to create conditions so that the Companies that are in the previous situation can accomplish their planning on low voltage distribution networks using a methodology capable to generate such nets. Once created, such nets will be inserted in a software of planning of investments that will supply the total amount of investments for them for the next ten years (long period planning). In the end of the process, it will be observed that the obtained results are very close to the expected values for the real low voltage distribution networks and, with this, the article will discuss how the methodology was implemented, the details of the application and, even, the whole planning process for three Electric Power Distribution Companies. With the results, it will be affirmed that the process produces values of very good adherence and, for this, the investments obtained for low voltage distribution networks can be accepted by the planning group in the Company. As a consequence of the investments values obtained for the ten years, it will be able to be observed, kept some special considerations, the values of the marginal costs of low voltage, item of great importance in the planning of distribution networks.
23
Gutierrez, Lagos Luis Daniel. "Advanced voltage control for energy conservation in distribution networks." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/advanced-voltage-control-for-energy-conservation-in-distribution-networks(2718dcf1-f5db-45df-84e2-4890956ba8b1).html.
Full textAbstract:
The increasing awareness on the effect of carbon emissions in our planet has led to several countries to adopt targets for their reduction. One way of contributing to this aim is to use and distribute electricity more efficiently. In this context, Conservation Voltage Reduction (CVR), a well-known technique that takes advantage of the positive correlation between voltage and demand to reduce energy consumption, is gaining renewed interest. This technique saves energy by only reducing customer voltages, without relying on customer actions and, therefore, can be controlled by the Distribution Network Operator (DNO). CVR not only brings benefits to the electricity system by reducing generation requirements (fewer fossil fuel burning and carbon emissions), but also to customers, as energy bill reductions. The extent to which CVR can bring benefits mainly depends on the customers load composition and their voltages. While the former dictates the voltage-demand correlation, the latter constraints the voltage reduction that can be applied without violating statutory limits. Although CVR has been studied for many years, most of the studies neglect the time-varying voltage-demand characteristic of loads and/or do not assess end customer voltages. While these simplifications could be used to estimate CVR benefits for fixed and limited voltage reductions, realistic load and network models are needed to assess the performance of active CVR schemes, where voltages are actively managed to be close to the minimum limit. Moreover, distribution networks have been traditionally designed with limited monitoring and controllability. Therefore, CVR has been typically implemented by adopting conservative voltage reductions from primary substations, for both American and European-style networks. However, as new infrastructure is deployed in European-style LV networks (focus of this work), such as monitoring and on-load tap changers (OLTCs), the opportunity arises to actively manage voltages closer to end customer (unlocking further energy savings). Although these technologies have shown to effectively control voltages in LV networks, their potential for CVR has not been assessed before. Additionally, most CVR studies were performed in a context where distributed generation (DG) was not common. However, this has changed in many countries, with residential photovoltaic (PV) systems becoming popular. As this is likely to continue, the interactions of residential PV and CVR need to be studied. This thesis contributes to address the aforementioned literature gaps by: (i) proposing a simulation framework to characterise the time-varying voltage-demand correlation of individual end customers; (ii) developing a process to model real distribution networks (MV and LV) from DNO data; (iii) adopting a Monte Carlo-based quantification process to cater for the uncertainties related to individual customer demand; (iv) assessing the CVR benefits that can be unlocked with new LV infrastructure and different PV conditions. To accomplish (iv), first, a simple yet effective rule-based scheme is proposed to actively control voltages in OLTC-enabled LV networks without PV and using limited monitoring. It is demonstrated that by controlling voltages closer to customers, annual energy savings can increase significantly, compared to primary substation voltage reductions. Also, to understand the effect of PV on CVR, a centralized, three-phase AC OPF-based CVR scheme is proposed. This control, using monitoring, OLTCs and capacitors across MV and LV networks, actively manages voltages to minimize energy consumption in high PV penetration scenarios whilst considering MV-LV constraints. Results demonstrate that without CVR, PV systems lead to higher energy imports for customers without PV, due to higher voltages. Conversely, the OPF-based CVR scheme can effectively manage voltages throughout the day, minimising energy imports for all customers. Moreover, if OLTCs at secondary substations are available (and managed in coordination with the primary substation OLTC), these tend to regulate customer voltages close to the minimum statutory limit (lower tap positions), while the primary OLTC delivers higher voltages to the MV network to also reduce MV energy losses.
24
Bellisardi, Federico. "Study of gaseous structures in axisymmetric rotation in presence of a black hole." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18422/.
Full textAbstract:
L’oggetto di tale tesi é lo studio di sistemi gassosi in rotazione assisimmetrica con distribuzioni barocline.
Nella prima parte dell’elaborato, vengono discussi i concetti fondamentali della dinamica dei fluidi; le equazioni del moto di fluidi in rotazione soggetti ad un potenziale gravitazionale vengono derivate e studiate.
Successivamente viene introdotta l’analisi sulla stabilità lineare e vengono derivati i criteri di Schwarzschild e di Rayleigh. Tali criteri vengono poi generalizzati introducendo il criterio di Solberg-Hoiland.
Soluzioni stazionarie per fluidi in rotazione assisimmetrica vengono introdotte e vengono discusse le differenze nei casi barotropico e baroclino.
Viene poi presentata una famiglia di sistemi baroclini in equilibrio in un potenziale gravitazionale assisimmetrico.
Successivamente ho considerato una famiglia di tori gassosi con una distribuzione di densità a legge di potenza. Sono stati studiati due casi: tori auto-gravitanti e tori in equilibrio in presenza della loro auto-gravità e di un buco nero centrale.
Infine, il criterio di Solberg-Hoiland é stato utilizzato per determinare in quali condizioni i sistemi toroidali auto-gravitanti sono linearmente stabili e per ottenere una formulazione analitica della condizione di stabilità per tori in equilibrio in presenza della loro auto-gravità e di un buco nero centrale.
25
Turetsky, Abraham I. "Making Heads and Tails of Distributional Patterns: A Value-Creation-Type and Sector-Based Analysis Among Private-Equity-Owned Companies." Case Western Reserve University School of Graduate Studies / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=case1522719854667863.
Full text
26
Bassi, Welson. "Estudo de surtos em redes secundárias de distribuição devido a descargas atmosféricas diretas na rede primária." Universidade de São Paulo, 1999. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-10102017-100131/.
Full textAbstract:
Este trabalho apresenta uma análise dos surtos em redes aéreas secundárias de distribuição causados por descargas atmosféricas diretas no circuito primário. Alguns trabalhos publicados sobre o fenômeno são comentados, sendo também analisados vários outros estudos relativos à modelagem de componentes. No trabalho, os principais componentes da rede foram modelados e incluídos na representação de uma topologia típica (com as linhas primária e secundária). Assim, foram considerados: transformador de distribuição, isoladores, pára-raios, cargas (consumidores) e resistências de aterramento. Os modelos foram validados, quando possível, através de ensaios em laboratório. Algumas alternativas de proteção da rede secundária foram consideradas. Foi verificada a influência de alguns parâmetros relevantes tais como amplitude e tempo de frente da corrente da descarga, resistências de aterramento, modelos de cargas e posição da descarga. Os resultados foram obtidos por simulações computacionais realizadas através do programa ATP (Alternative Transients Program). São apresentadas formas de onda de sobretensões nos consumidores. Também são apresentados e discutidos valores de corrente e energia nos dispositivos de proteção, fornecendo informações sobre as alternativas de proteção.This work presents an evaluation of surges in low-voltage overhead distribution lines caused by direct lightning strikes in medium voltage lines. Some publications concerning the phenomenon are commented and several other studies used during the process of modeling of the components are also analysed. The main components of the distribution system were modeled and included. So, a typical distribution network topology (with the primary and secondary lines) was represented including its components: distribution transformer, insulators, surge arresters, loads and ground resistances. The performance of the developed models, whenever possible, was verified by laboratory tests. Some possibilities of the secondary protection were included. Parameters having major effect on the results, such as the lightning current amplitude and front time, the values of grounding resistances, the models of the loads and the lightning strike position were taken into consideration in the study. The results were obtained by simulations performed using the ATP (Alternative Transients Program). Waveforms are presented in order to provide information on the characteristics of the overvoltages in the consumers along the line. Currents, as well as energy absorbed by the low-voltage surge arresters are aldo presented and discussed, providing useful information about the performance of some protection alternatives.
27
Häggblom, Johan, and Jonathan Jerner. "Photovoltaic Power Production and Energy Storage Systems in Low-Voltage Power Grids." Thesis, Linköpings universitet, Fordonssystem, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-156875.
Full textAbstract:
In recent years, photovoltaic (PV) power production have seen an increase and the PV power systems are often located in the distribution grids close to the consumers. Since the distributions grids rarely are designed for power production, investigation of its effects is needed. It is seen in this thesis that PV power production will cause voltages to rise, potentially to levels exceeding the limits that grid owners have to abide by. A model of a distribution grid is developed in MathWorks MATLAB. The model contains a transformer, cables, households, energy storage systems (ESS:s) and photovoltaic power systems. The system is simulated by implementing a numerical Forward Backward Sweep Method, solving for powers, currents and voltages in the grid. PV power systems are added in different configurations along with different configurations of ESS:s. The results are analysed, primarily concerning voltages and voltage limits. It is concluded that addition of PV power production in the distribution grid affects voltages, more or less depending on where in the grid the systems are placed and what peak power they have. It is also concluded that having energy storage systems in the grid, changing the power factor of the inverter for the PV systems or lowering the transformer secondary-side voltage can bring the voltages down.På senare tid har det skett en ökning i antalet solcellsanläggningar som installeras i elnätet och dessa är ofta placerade i distributionsnäten nära hushållen. Eftersom distributionsnäten sällan är dimensionerade för produktion så behöver man utreda effekten av det. I det här arbetet visas det att solcellsproduktion kommer att öka spänningen i elnätet, potentiellt så mycket att de gränser elnätsägarna måste hålla nätet inom överstigs. En modell över lågspänningsnätet skapas i MathWorks MATLAB. Modellen innehåller transformator, kablar, hushåll, energilager och solcellsanläggningar. Systemet simuleras med hjälp av en numerisk Forward Backward Sweep-lösare som beräknar effekter, strömmar och spänningar i elnätet. Solcellanläggningarna placeras ut i elnätet i olika konfigurationer tillsammans med olika konfigurationer av energilager. Resultaten från simuleringarna analyseras främst med avseende på spänningen i elnätet utifrån dess gränser. De slutsatser som dras i arbetet är att solcellsproduktion kommer att påverka spänningen, mycket beroende på var i elnätet anläggningarna placeras och storleken hos dem. Det visas också att energilager, justering av effektfaktor hos solcellsanläggningarna eller en spänningssänkning på transformatorns lågspänningssida kan få ner spänningen i elnätet.
LiTH-ISY-EX--19/5194--SE
28
Guiot, François-Vivien. "La distinction du fait et du droit par la Cour de justice de l'Union européenne : recherche sur le pouvoir juridictionnel." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0396.
Full textAbstract:
La distinction du fait et du droit est une problématique centrale dansl’organisation des voies de droit. Elle exerce en effet, au-delà d’une variété de formes et designifications, une influence décisive sur l’office du juge ainsi que sur la fonction desautorités soumises à son contrôle. Pour appréhender pleinement la portée qu’elle revêt dansl’équilibre des pouvoirs établi par la Cour de justice de l’Union européenne, il est nécessairede se défaire de toute préconception de la distinction du fait et du droit (notamment auregard des pratiques observées en droit interne), afin de comprendre comment le juge del’Union européenne exerce un pouvoir de détermination à son égard, que ce soit dans lecontrôle de validité des actes juridiques ou dans les voies de recours dirigées contre desactes juridictionnels. Dans cette opération, elle reste toutefois soucieuse d’assurerl’acceptabilité de ses décisions, et prend donc en considération certaines contraintesjuridiques qui se présentent à elle dans son office. Autorité normatrice et ordonnatrice, laCour de justice en tant qu’interprète authentique utilise en réalité la distinction du fait et dudroit comme un instrument de répartition des compétences entre les différents acteursconcernés par la réalisation du droit de l’Union européenne. Elle définit ainsi, à travers ladétermination de la distinction du fait et du droit dans chacune de ses manifestations,l’habilitation que leur confère le système juridique. En ce sens, elle apparaît comme lajuridiction suprême de cet espace normatifThe distinction between fact and law is central to the organization of remedies.It exerts, through its variety of forms and meanings, a decisive influence on the Court and onthe function of the authorities that the former reviews. In order to fully grasp its significance inthe balance of power that the European Court of Justice has established, one has to discardany preconception related to the distinction between fact and law (especially those present inmunicipal law). This in turn leads to the understanding of the manner in which the EuropeanCourt specifies the distinction, should it concern the review against legal acts or the ways ofchallenging case law. Whilst doing this, the European Court remains wary of the acceptabilityof its decisions, thus taking into account several legal constraints. As a normative authorityand as the authentic interpreter, the European Court of Justice uses the distinction betweenfact and law as a way to divide the competences of the actors concerned with theimplementation of EU law. By performing this specification, it defines the way the legalsystem entitles these actors. In this way, the European Court of Justice emerges as theSupreme Court of this normative space
29
Bassi, Welson. "Caracterização de equipamentos e instalações residenciais de baixa tensão aplicada ao estudo de transitórios de origem atmosférica." Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/3/3143/tde-10102017-111817/.
Full textAbstract:
Este trabalho apresenta um estudo de caracterização das impedâncias de entrada, em função da frequência, de instalações residenciais de baixa tensão e diversos equipamentos eletro-eletrônicos comumente encontrados. As respostas em frequência medidas são ajustadas e modeladas por redes RLC simples, mas efetivas, que podem ser utilizadas em qualquer programa computacional para simulações de transitórios. A faixa de frequências, até 5 MHz, permite o uso desses modelos em estudos associados a transitórios atmosféricos ou causados por chaveamentos. É importante ressaltar a existência de muito poucos trabalhos nesse assunto, pois, usualmente, as instalações de baixa tensão, ou os equipamentos conectados, são representadas por simples elementos concentrados, resistores, indutores ou capacitores. Por outro lado, sabe-se que os níveis de sobretensões em um sistema, ou instalação, são fortemente dependentes das cargas conectadas e, quanto mais precisos os modelos, melhores e mais confiáveis simulações são obtidas. Este trabalho inclui simulações com o programa computacional ATP utilizando os modelos desenvolvidos para avaliação de surtos em uma rede de distribuição típica submetida a descargas atmosféricas diretas no circuito primário. Além disso, utilizando o programa Pspice, são realizadas simulações da resposta interna de uma instalação residencial, com diversos equipamentos conectados, e submetida a surtos atmosféricos em sua entrada. O trabalho concentra informações práticas e úteis sobre estudos de surtos em sistemas e instalações de baixa tensãoThis work presents a study of impedance characteristics, over a wide range of frequencies, of residential low-voltage installations and electric-electronic appliances, commonly found in residential installations. The measured frequency responses are fitted and modeled by simple, but effective, RLC networks, that can be used in any software for transient simulations. The range of frequencies, up to 5 MHz, allows the use of these models considering lightning or switching studies. It is of importance to point the lack of publications focusing this topic, because usually the low-voltage installations, or connected equipment, are represented by simple lumped components inductances, resistances or capacitances. Otherwise, it is well known that the overvoltage level of a system, or installation, is strongly dependent on the connected loads and for more precise models, better and more reliable simulation results are obtained. This work includes ATP software simulations using the developed models for evaluation of surges in a typical distribution network subjected to direct lightning strikes at the primary circuit. Furthermore, simulations of internal response of a low-voltage installation with connected equipment and subjected to lightning surges in its entrance is performed using the Pspice software. The work summarizes practical and useful information about the low-voltage surge studies on low-voltage systems.
30
Danisman, Batuhan. "Analysis Of Conventional Low Voltage Power Line Communication Methods For Automatic Meter Reading And The Classification And Experimental Verification Of Noise Types For Low Voltage Power Line Communication Network." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/12610469/index.pdf.
Full textAbstract:
In this thesis, the conventional low voltage power line communication methods is
investigated in the axis of automated meter reading applications and the classification
and experimental verification of common noise types for low voltage power line
communication network. The investigated system provides the real time transmission
of electricity consumption data recorded by electricity meters, initially to a local
computer via a low voltage line through a low speed PLC (Power Line Carrier)
environment and subsequently to a corporate network through a high speed data
transmission medium. The automated meter system provides a more effective
tracking and data acquisition, a more detailed and vigorous knowledge about
consumer behavior for subscriber assessment in electricity distribution in association
with a brand new management and system supervision concept in electricity
distribution control and management technology. The theoretical studies are
experimentally verified for the Turkish low voltage power infrastructure through
laboratory experiments performed in METU Electrical and Electronics Engineering
Department, Electrical Machines and Drives Laboratory and R&D Laboratories of MAKEL facilities in Hadimkö
y. The single phase voltage of the mains line between the phase and neutral is monitored to exhibit the disturbing effects of various noise sources. The resulting voltage spectrum is logged by using digital data acquisition devices in time and frequency domain. The waveforms are converted to frequency domain using the Fast Fourier Transform (FFT) functions of the MATLAB. The experimental results are compared to the theoretical findings obtained through literature survey.
31
López, Claudio David. "Shortening time-series power flow simulations for cost-benefit analysis of LV network operation with PV feed-in." Thesis, Uppsala universitet, Elektricitetslära, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-242099.
Full textAbstract:
Time-series power flow simulations are consecutive power flow calculations on each time step of a set of load and generation profiles that represent the time horizon under which a network needs to be analyzed. These simulations are one of the fundamental tools to carry out cost-benefit analyses of grid planing and operation strategies in the presence of distributed energy resources, unfortunately, their execution time is quite substantial. In the specific case of cost-benefit analyses the execution time of time-series power flow simulations can easily become excessive, as typical time horizons are in the order of a year and different scenarios need to be compared, which results in time-series simulations that require a rather large number of individual power flow calculations. It is often the case that only a set of aggregated simulation outputs is required for assessing grid operation costs, examples of which are total network losses, power exchange through MV/LV substation transformers, and total power provision from PV generators. Exploring alternatives to running time-series power flow simulations with complete input data that can produce approximations of the required results with a level of accuracy that is suitable for cost-benefit analyses but that require less time to compute can thus be beneficial. This thesis explores and compares different methods for shortening time-series power flow simulations based on reducing the amount of input data and thus the required number of individual power flow calculations, and focuses its attention on two of them: one consists in reducing the time resolution of the input profiles through downsampling while the other consists in finding similar time steps in the input profiles through vector quantization and simulating them only once. The results show that considerable execution time reductions and sufficiently accurate results can be obtained with both methods, but vector quantization requires much less data to produce the same level of accuracy as downsampling. Vector quantization delivers a far superior trade-off between data reduction, time savings, and accuracy when the simulations consider voltage control or when more than one simulation with the same input data is required, as in such cases the data reduction process can be carried out only once. One disadvantage of this method is that it does not reproduce peak values in the result profiles with accuracy, which is due to the way downsampling disregards certain time steps in the input profiles and to the averaging effect vector quantization has on the them. This disadvantage makes the simulations shortened through these methods less precise, for example, for detecting voltage violations.
32
Li, Yun. "Voltage balancing on three-phase low voltage feeder." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/voltage-balancing-on-threephase-low-voltage-feeder(4320ec9a-f287-4e83-86fd-c8e29e8d49f4).html.
Full textAbstract:
Voltage imbalance in low voltage (LV) networks is expected to deteriorate as low carbon technologies, e.g. electric vehicles (EVs) and heat pumps (HPs) are increasingly deployed. The new electrical demand attributable to EVs and HPs would increase the voltage magnitude variation, increasing the possibility of voltages moving outside the statutory LV magnitude limits. Moreover, the single-phase nature of EVs and HPs, which will be connected via a single-phase 'line & neutral' cable to a 3-phase four-wire LV mains cable buried beneath the street, further entangles this voltage management problem; the non-balanced voltage variations in the three phases boost the levels of voltage imbalance. Excessive voltage imbalance and magnitude variation need to be mitigated to limit their adverse effects on the electric network and connected plant. The voltage imbalance in LV networks is conventionally reduced by reinforcing the network, generally at a high cost. Some modern methods for voltage imbalance mitigation have been introduced in recent years. The power electronic converter based methods are inadequate due to the generation of harmonics, significant power losses and short lifetime. Besides, automatic supply phase selection and smart EV charging rely on an advanced smart communication system, which currently is not available. This project aims to develop alternative solutions that mitigate the voltage imbalance seen in LV networks. A voltage balancing method based on Scott transformer (ST) is proposed. This method does not generate harmonics and is independent of the smart communication system. Computer simulations demonstrated the proposed method is able to convert a non-balanced 3-phase voltage into a balanced 3-phase voltage at either a point on the LV feeder or a 3-phase load supply point with the predefined voltage magnitude. Besides, a physical voltage balancing system was created based on the proposed method and it was tested in an LV network in the laboratory. The test results show the balancing system is capable of maintaining a low level of voltage imbalance on the LV feeder by rapidly compensating for the voltage rises and sags caused by single-phase load variations. This voltage balancing method is a potential solution for the network utilities to accommodate the significant penetration of low carbon technologies without breaching the network voltage limits. The impact of EVs and HPs on the LV network voltages is investigated based on a Monte Carlo (MC) simulation platform, which comprises a statistical model of EV charging demand, profiles generators of residential and HP electrical demand, and a distribution network model. The MC simulation indicates the impact of EVs and HPs is related to their distribution; when more than 21EVs and 13HPs are non-evenly distributed on a 96-customer LV feeder, the voltage limits are likely to be violated. Moreover, the effectiveness of the ST based voltage balancing method and the demand response based TOU tariff, implemented either alone or together, in mitigating the impact of EVs and HPs is investigated based on the established MC simulation platform. The results indicate the ST based balancing method alone is able to completely mitigate the voltage limit violations regardless of the penetration levels of EVs and HPs. Moreover, using both of the two investigated methods further enhances the balancing effectiveness of the ST based voltage balancing method.
33
Lee, Judy S. "Advances in simulation: validity and efficiency." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/53457.
Full textAbstract:
In this thesis, we present and analyze three algorithms that are designed to make computer simulation more efficient, valid, and/or applicable.
The first algorithm uses simulation cloning to enhance efficiency in transient simulation. Traditional simulation cloning is a technique that shares some parts of the simulation results when simulating different scenarios. We apply this idea to transient simulation, where multiple replications are required to achieve statistical validity. Computational savings are achieved by sharing some parts of the simulation results among several replications. We improve the algorithm by inducing negative correlation to compensate for the (undesirable) positive correlation introduced by sharing some parts of the simulation. Then we identify how many replications should share the same data, and provide numerical results to analyze the performance of our approach.
The second algorithm chooses a set of best systems when there are multiple candidate systems and multiple objectives. We
provide three different formulations of correct selection of the Pareto optimal set, where a system is Pareto optimal if it is not inferior in all objectives compared to other competing systems. Then we present our Pareto selection algorithm and prove its validity for all three formulations. Finally, we provide numerical results aimed at understanding how well our algorithm performs in various settings.
Finally, we discuss the estimation of input distributions when theoretical distributions do not provide a good fit to existing data. Our approach is to use a quasi-empirical distribution, which is a mixture of an empirical distribution and a distribution for the right tail. We describe an existing approach that involves an exponential tail distribution, and adapt the approach to incorporate a Pareto tail distribution and to use a different cutoff point between the empirical and tail distributions. Then, to measure the impact, we simulate a stable M/G/1 queue with a known inter-arrival and unknown service time distributions, and estimate the mean and tail probabilities of the waiting time in queue using the different approaches. The results suggest that if we know that the system is stable, and suspect that the tail of the service time distribution is not exponential, then a quasi-empirical distribution with a Pareto tail works well, but with a lower bound imposed on the tail index.
34
Papp, Aminnejad Benjamin, and Daniel Wieweg. "Magnetfält i elkraftanläggningar : Ett projekteringsverktyg i Excel för bedömning av magnetfält från elkraftsutrustning på lågspänningssidan." Thesis, KTH, Data- och elektroteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-179827.
Full textAbstract:
Exponering av det lågfrekventa ELF (Extremely low frequency) magnetfältet som genereras vid dagens elnät är något som är relativt nytt för människokroppen och den ökar ständigt i och med den tekniska utvecklingen. Eftersom det inte finns ett klart svar på hur fältet påverkar kroppen så tillämpas försiktighet för att hålla exponeringsnivåerna nere och försäkra sig om att ingen skada sker. Med hjälp av tidigare forskning inom området och uppmätta värden från olika anläggningar samt överslagsberäkningar har ett verktyg i Excel tagits fram för att kunna uppskatta magnituden av magnetfältet. Verktyget innehåller information om styrkan på magnetfältet från transformatorer, ställverk, elcentraler, kraftledningar och kanalskenor. Användaren skriver in ett antal parametrar för att få utdata om hur starkt magnetfältet är på olika avstånd ifrån källan. Detta presenteras i form av en tabell och en graf för respektive utrustning. Eftersom magnetfält alstras beroende på strömmens riktning, påverkar själva geometrin i olika elanläggningar magnetfältets styrka. För att beräkna exakta värden krävs då avancerade simuleringsprogram. Med detta verktyg kan projektörer redan vid ett tidigt skede uppskatta magnetfältet.The exposure of ELF (Extremely low frequency) magnetic field generated by today’s electrical power system, is something that is relatively new to the human body and it is constantly increasing as more technology is developed. As there is no clear answer on how the field actually affects the body, a measure of caution is applied to ensure that the exposure levels are kept down to make sure no harm is done. With the help of previous research in the field, measured values from different locations and approximate calculations, a tool was developed in Excel to estimate the magnitude of the magnetic fields. The tool provides information about the magnitude of magnetic fields from transformers, switchgears, switchboards, powerlines and busbars. The user enters a number of parameters and the tool provides output data with the magnitude of the magnetic field at different distances from the source. This is presented in the form of a table and a graph for each equipment. Since the magnetic field is generated depending on the currents direction, the actual geometry of the electrical system needs to be taken in consideration when calculating the exact magnetic field. This requires an advanced simulation software to be accurate. With this tool, designers have the opportunity to estimate the magnetic fields at an early stage of development.
35
Manzano-Guerrero, Orlando. "El desafio independentista de las élites nacionalistas catalanas : Analisis de un proceso inconcluso (2012-2017)." Thesis, Montpellier 3, 2019. http://www.theses.fr/2019MON30015.
Full textAbstract:
Après avoir dominé presque sans interruption le paysage politique catalan et avoir contribué à la stabilité et à la gouvernance politiques du pays, les élites nationalistes conservatrices affiliées à la fédération Convergència i Unió opérèrent un changement de cap radical dans leur agenda politique, en promouvant depuis les institutions autonomes sous leur contrôle ce que l’on a appelé le processus souverainiste catalan. Pour le lancement de ce vaste mouvement de contestation politique et sociale, initié à la fin de l’année 2012, ses promoteurs firent valoir la nécessité de permettre aux Catalans de décider de leur avenir politique collectif dans le cadre d’une consultation populaire. Parallèlement, diverses mesures furent prises afin de préparer le terrain en vue de l’éventuelle création d’un État catalan souverain. Bien que le défi lancé par les élites nationalistes fût effectivement freiné par les autorités centrales de l’État à la fin de l’année 2017, aucune solution ne fut apportée aux graves problèmes à l’origine de la crise déclenchée dans la région. Leur projet bénéficie encore d’un large soutien au sein de la classe politique et l’opinion publique de la Communauté Autonome. Enfin, il est impossible d’affirmer que d’autres tentatives de rupture similaires ne se reproduiront pas dans un avenir proche. C’est pourquoi, le défi de l’Independence de la Catalogne est abordé ici comme un processus inachevé. Ce travail de recherche est essentiellement axé sur l’analyse des évènements qui eurent lieu pendant la période 2012-2017 et a pour but de contribuer à éclairer plusieurs points importants auxquels les études existantes sur la question n’apportent pas encore des réponses suffisamment satisfaisantesAfter dominating the region’s political landscape almost without interruption since the establishment of democracy in Spain and having played an important role in the political stability and governability of the country ever since, the Catalan nationalist elites affiliated with Convergència i Unió, a coalition of conservative parties, opted for a fundamental change of course in their political agenda, by promoting and undertaking – while still in power at regional level – what is commonly referred to as the Catalan independence process. It was a broad-based political and social protest movement aimed at allowing the Catalans to decide their collective future in a referendum. In parallel, various other measures were taken to pave the way for the potential creation of an independent Catalan state. Although the challenge laid down by the Catalan nationalist elites was effectively stopped towards the end of the year 2017, the significant problems that led to the current crisis have not been resolved. The independence project has still widespread political and public support in Catalonia. Finally, it is impossible to affirm that similar attempts to break away from Spain will not follow in the near future. That is why the independence challenge needs to be addressed – from our point of view – as an unfinished process. This research study focuses essentially in the analysis of the events that took place during the period between 2012 and 2017 and its main purpose is to highlight some important points to which the few existing studies on the subject do not provide yet complete responses
36
Pedral, Jacques, and Josef Abriren. "Analys av lågspänningsfördelning till signalanläggningar." Thesis, KTH, Data- och elektroteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-192837.
Full textAbstract:
I denna rapport utreds hur systemdesignen av lågspänningsfördelningen för järnvägen kan kostnadseffektiviseras. I dagsläget har det utarbetats en norm kring systemdesignen som tenderar att efterbildas från år till år vilket har medfört brist på innovation inom området. Syftet med arbetet var att designa två typstationer med signalställverken M11 respektive M95, där placering samt nominell storlek av UPS:er skulle fastställas för att tillhandahålla en kostnadseffektiv lösning. Dessutom skulle kablage dimensioneras för typstationerna samt se över möjligheten att ersätta UPS:er med likriktarsystem. Stationerna baserades på två redan existerande driftplatser, Fagersta C (M11) och Skänninge (M95). Slutligen skulle olika energilagringsalternativ för UPS-system jämföras för att tillhandahålla det lämpligaste alternativet. Genom simuleringar och beräkningar i bland annat datorprogrammet El-Vis har lågspänningsfördelningen dimensionerats för typstationerna. Arbetet visar på att ett distribuerat UPS-system är att föredra ur ett ekonomiskt perspektiv gentemot ett centraliserat UPS-system. Vidare har det konstaterats att likriktarsystemet Rectiverter kan ersätta UPS:er samt att ackumulatorer är det mest passande energilagringsalternativet.This report identifies how the system design of low voltage power distribution of the railway can be more cost effective. In the current situation there is a norm on the system design that tends to be replicated each year. This has brought a lack of innovation in the field. The purpose of the thesis was to come up with two model stations with the interlocking system M11 respectively M95, where the positioning and nominal size of the UPS:s would be determined to provide a cost effective solution. Furthermore, the cable dimensioning of the model stations was computed as well as the possibility of replacing UPS-systems with rectifier-systems. The model stations were based on two already existing operating sites, Fagersta C (M11) and Skänninge (M95). Lastly, different energy storage alternatives for UPS-systems were compared to acquire the most appropriate choice. Through simulations and calculations in, inter alia, the computer program El-Vis, the low voltage power distribution was dimensioned for the model stations. The thesis shows that a distributed UPS-system is preferred in an economical point of view compared to a centralized UPS-system. Furthermore, the thesis establishes that the rectifier system Rectiverter can replace UPS:s. It also states that accumulators are the most suitable alternative for energy storage.
37
Guazzelli, Amanda Salis. "A busca da justiça distributiva no judiciário por meio das relações contratuais: uma análise a partir dos planos de saúde." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/2/2133/tde-28112013-142249/.
Full textAbstract:
A partir da Constituição Federal de 1988, são introduzidos novos contornos ao ordenamento jurídico brasileiro. O texto constitucional incorpora diversos direitos sociais e dá caráter normativo a princípios de justiça social. No direito privado, verifica-se, também, a introdução de um conteúdo social por meio da inserção de cláusulas gerais na legislação infraconstitucional, especialmente no que diz respeito aos contratos. Nesse novo quadro institucional, o Poder Judiciário passa a ocupar lugar de destaque, pois há um deslocamento de decisões políticas e sociais dos Poderes Legislativo e Executivo para o Judiciário. Observa-se um crescimento exponencial da judicialização de casos envolvendo os direitos sociais, principalmente no que tange a questões relacionadas à saúde. A judicialização tem atingido também as relações contratuais entre particulares. Todavia, nessa atuação do Judiciário podem ser identificados problemas, como a falta de preocupação com os impactos produzidos pelas decisões na sociedade. Dentro desse contexto, o objetivo do presente trabalho é analisar empiricamente a forma como os ministros do Superior Tribunal de Justiça decidem conflitos contratuais no campo da saúde suplementar. Para tanto, a primeira parte do trabalho é dedicada à caracterização e contextualização do setor da saúde suplementar brasileiro. Após, relato de forma breve o histórico de sua regulamentação. A segunda parte do trabalho aborda os principais aspectos jurídicos e econômicos que envolvem os contratos de plano de saúde. Na terceira parte, são apresentados os resultados quantitativos obtidos a partir de coleta e sistematização de dados das decisões judiciais analisadas. Por fim, na quarta e última parte do trabalho, é feito um esforço de reflexão crítica acerca dos argumentos trazidos pelos ministros do STJ, a luz, principalmente, da literatura de análise econômica do direito, sendo verificado se há alguma relação, ainda que hipotética, entre a forma de decidir dos juízes e possíveis efeitos socioeconômicos apontados pela doutrina.From the 1988 Brazilian Constitution, are introduced alterations in the Brazilian legal system. The Constitution incorporates many social rights and gives normative character to principles of social justice. In private law, there is also the introduction of a social content through insertion of general terms in the infra-constitutional legislation, especially as regards contracts. In this new institutional framework, the Judiciary holds a prominent place, because there is a shift of political and social decisions of the Legislative and Executive to the Judiciary. There is an exponential growth of judicialization of cases involving social rights, especially in regard to health issues. The judicialization has also reached the contractual relations among individuals. However, problems can be identified in this proceeding of the Judiciary, such as lack of concern about the impacts of the decisions in society. In this context, the aim of this study is to analyze empirically how the justices of the Superior Court of Justice decide contract disputes in the private healthcare sector. In order to do such, the first part of the work is dedicated to the characterization and contextualization of Brazilian private healthcare sector. After, it is briefly presented the history of its regulation. The second part addresses the main legal and economic aspects involving health insurance contracts. In the third part, I present the quantitative results obtained from data collection and systematization of judicial decisions analyzed. Finally, in the fourth and final part of the work, a critic effort is made to analyze the arguments brought by justices of the Superior Court of Justice, in the light of the economic analysis of law, and also examined whether there is any relationship, even though hypothetical, between how the judges decide possible socioeconomic effects pointed by doctrine.
38
Saint-Laurent, Martin. "Modeling and Analysis of High-Frequency Microprocessor Clocking Networks." Diss., Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7271.
Full textAbstract:
Integrated systems with billions of transistors on a single chip are a now reality. These systems include multi-core microprocessors and are built today using deca-nanometer devices organized into synchronous digital circuits. The movement of data within such systems is regulated by a set of predictable timing signals, called clocks, which must be distributed to a large number of sequential elements. Collectively, these clocks have a significant impact on the frequency of operation and, consequently, on the performance of the systems. The clocks are also responsible for a large fraction of the power consumed by these systems.
The objective of this dissertation is to better understand clock distribution in order to identify opportunities and strategies for improvement by analyzing the conditions under which the optimal tradeoff between power and performance can be achieved, by modeling the constraints associated with local and global clocking, by evaluating the impact of noise, and by investigating promising new design strategies for future integrated systems.
39
Foltýn, Petr. "Řešení elektrizace nové lokality elektrickou energií." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-219030.
Full textAbstract:
This master’s thesis is concerned with the proposal of new locality electrification. There are 59 detached houses. The thesis is divided into theoretical part and computational part. In the theoretical part, there are all documents necessary for the successful proposal of the electrification. In the computational part is drafted distribution substation, high voltage power cable, proposal of low voltage power cables and protection. Each part is made for two versions (for the degree of electrification A and for the degree of electrification C) and recorded in cadastral maps. The proposal of distribution substation and high voltage power cable is made by traditional method - all calculations are processed by the designer. Low-voltage power cables and protection are implemented in a computer program Sichr (version 11.01) OEZ company.
40
Jestřáb, Tomáš. "Vliv akumulace na provoz distribuční sítě." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-317079.
Full textAbstract:
This diploma thesis introduces the reader to the possible types of electric energy storage technologies, their comparisons and utilization. After its introduction, it follows the description of individual technologies and principles that are currently meaningful and useful in practice. The thesis continues with the part characterizing the ways of using the accumulation in the grid. However, the main points of this thesis include the analysis of the influence of the photovoltaic installation on the specified distribution grid operation at the low voltage level and the analysis of the influence on the grid with connected accumulation. Another important objective was the model for the calculation of steady-state, which was programmed on the basis of the theory supported by the principles of production from intermittent sources and the principle of accumulation function. The outputs of the model in the form of the calculated voltage ratios at the individual supply points and current flows at the distribution transformer point were used to evaluate the analyzes mentioned above. The courses of the calculated parameters are broken down by different scenarios (according to the period, the degree of integration of production and the accumulation or the power output of the production), graphically processed and compared from the point of view of voltage fluctuations and changes in the power (or current) balance of the supply transformer.
41
Oprea, Elena-Alina. "Droit de l'Union européenne et lois de police." Thesis, Paris 2, 2011. http://www.theses.fr/2011PA020028.
Full textAbstract:
L’interaction du droit de l’Union européenne avec le droit international privé se manifeste avec une acuité particulière en matière de lois de police, continuant et renouvelant les discussions suscitées par celles-ci. La promotion des intérêts de l’Union européenne par ce mécanisme de DIP peut être facilement observée. Il reste que des questions peuvent surgir quant à l’aménagement, dans les systèmes juridiques nationaux, de l’articulation des lois de police de source nationale et européenne. Le transfert de certaines compétences des Etats membres vers l’Union, le rapprochement des législations des Etats membres ou le poids plus important accordé aux raisonnements et aux intérêts européens au moment de la qualification mettent en lumière une catégorie « lois de police » avec des contours nouveaux. La mise en oeuvre des lois de police porte, elle aussi, l’empreinte de l’influence du droit de l’Union européenne. L’intégration des données liées à la réalisation du marché intérieur entraîne une perturbation significative du mécanisme traditionnel des lois de police, accompagnée d’une diminution de l’efficacité de ces normes dans les relations entre les Etats membres. L’objectif de création, au sein de l’Union, d’un espace de liberté, de sécurité et de justice s’est matérialisé par la mise en place de corps de règles européennes de DIP dans diverses matières. La méthode des lois de police en ressort transformée, suite tant à la prise de position directe du législateur européen sur les conditions de son intervention, qu’en raison des évolutions enregistrées par d’autres méthodes concurrentes de droit international privéThe interaction between the European Union law and the private international law is particularly acute in the field of internationally mandatory rules, maintaining and renewing the debate which always accompanied this kind of norms. If the internationally mandatory rules occupy a special place in the European legislation, being an extremely effective tool of European policy, some difficulties arise as to the articulation, in the Member States’ legal systems, of the both national and European different sources of lois de police. The transfer of powers from Member States to the European Union, the harmonization of national legislations and the greater weight given to European reasoning and interests at the time of qualification highlight a new dimension of the internationally mandatory rules concept. Also the implementation of internationally mandatory rules is highly influenced by the European Union Law. The Member States’ obligations concerning the completing of the internal market and the removal of restrictions to changes involve a significant disturbance to this traditional PIL mechanism; a decrease in the effectiveness of internationally mandatory rules in relations between Member States may be observed. The purpose of establishing an area of freedom, security and justice within the European Union was materialized in the establishment of European private international law rules in various fields; the internationally mandatory rules method is transformed as a result of the European legislator direct intervention on his definition and regime, but also as a result of the evolution that affects other concurring private international law methods
42
Račuch, Marek. "Analýza a návrh náhrady konkrétního venkovního vedení distribuční sítě." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2017. http://www.nusl.cz/ntk/nusl-319302.
Full textAbstract:
The diploma thesis deals with the issue of the reconstruction of outdoor cables of low voltage distribution network in exchange for the cable line. It analyzes the important factors which are necessary for the preparation of the project documentation for the issue of the territorial consent. The thesis is divided into 4 main chapters. After the first chapter there is introduced chapter 2, which shows the differences between cable and outdoor cables with their advantages and disadvantages. Chapter 3 deals with the guiding principles for low-voltage cable design and the types of equipment needed for the proper operation of a particular distribution network while respecting the requirements of valid PNEs and ČSNs. Chapter 4 explains the chronology of the process leading to the formulation of a basic technical proposal, which is further addressed in Chapter 5, which deals with the complete formulation of the project documentation for the issue of territorial consent.
43
Michl, Pavel. "Začleňování fotovoltaických elektráren do elektrizační soustavy." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2010. http://www.nusl.cz/ntk/nusl-218537.
Full textAbstract:
The thesis discuses an integration of photovoltaic power stations to electric network. The first part describes connecting conditions of small sources to distribution system, including administrative requirements, feasibility study, and requirements to the energy meters, measuring, control devices, switching devices and protection. The second part is aimed to describe problems of the photovoltaic system. Solar radiation generating and reducing of its intensity incident upon the earth surface are described in this part. The quantum of produced electric power depends on climatic conditions in the fixed area, seasons, etc. This work also discusses the types of photovoltaic cells and their actual efficiency. Inverters are further important components of the photovoltaic system. The parameters of the inverters have a great influence on the total actual efficiency of the photovoltaic system. Different methods of the photovoltaic panels’ connection with the inverters and their advantages and disadvantages are also mentioned. The supporting structure of the photovoltaic panels and eventually transformer are further important components of photovoltaic system. The work also analyze the methods of connection of the photovoltaic power station to distributive low voltage and medium voltage network, electric energy accumulation and possibilities of the sale of produced electric energy. The large number of the connected photovoltaic power stations has negative influences to electric network. The third part contains the design of a photovoltaic power plant with a capacity of 516,24 kWp on the scoped area in southern Bohemia. The project documentation for the location where the power plant is designed is also made. It contains the design of photovoltaic panels, the design of the inverters to get an optimal power load. This part also contains a calculation of the photovoltaic system losses and the design of transformer and the cable junction calculation of the distributive system. The feasibility study of the power plant connected to distributive system is also conducted. Its delivery rate will be connected to the distribution point Řípov (110/22 kV). The calculation results show us that this photovoltaic power plant can be linked to the distribution system. The final part of this paper contains an economic estimate of the photovoltaic power plant operating and the calculation of the return. An Economic return is influenced by the wide range of values that affect the total return rate. The calculation of an operating economy is made for several variants. The return rate in refer to contemporary redemption price for 2010 with no consideration for a bank loan is 7 years. If we consider the bank loan it would be 12 years. The penetrative reduction of the redemption price is expected for 2011. Calculation works with the decline of 30 %. It would extend the rate of return to 11 years without a bank loan or to 22 years with the bank loan. The bank loan is considered to cover 80 % of the investment.
44
Kouznetsov, Serguei. "La mise en œuvre de la Convention européenne des droits de l’homme dans le nouveau contexte fédéral russe : (1993-2012)." Thesis, Bordeaux 4, 2012. http://www.theses.fr/2012BOR40062.
Full textAbstract:
Après la chute de l’Union des Républiques Socialistes Soviétiques en décembre 1991, la Fédération de Russie affirme à maintes reprises son engagement à suivre un développement démocratique et à faire partie de « l’Europe sans frontières ». Pour atteindre cet objectif, elle adhère à toute une série de traités européens, entre autres, à la Convention européenne de sauvegarde des droits de l’homme et des libertés fondamentales. Toutefois, malgré la volonté affichée par la Russie de faire partie du système européen de protection des droits fondamentaux, les problèmes de transition politique, institutionnelle et économique rendent cette tâche très difficile. Entre autres le fédéralisme, qu’on peut qualifier de « complexe », crée un système juridique très singulier dont certains éléments ne sont pas toujours compatibles avec les instruments internationaux en matière des droits de l’homme ratifiés par la Russie. L’objectif de ce travail est d’étudier les problèmes de la mise en œuvre de la Convention européenne de sauvegarde des droits de l’homme et des libertés fondamentales et des décisions de la Cour européenne des droits de l’homme en Fédération de Russie et leur possible influence sur le développement des instruments de protection des droits fondamentaux dans les conditions du système fédéral existant en RussieAfter the fall of the Union of Soviet Socialist Republics in December 1991, the Russian Federation stated repeatedly its commitment to democratic development and to be part of "Europe without borders". To achieve this goal it joins a number of European treaties, among others, the European Convention for the Protection of Human Rights and Fundamental Freedoms. However, despite the willingness of Russia to be part of the European system of protection of fundamental rights, the problems of political transition, economic and institutional development make this task very difficult. Among other the federalism, which could be qualified as "complex", creates a very singular legal system. Some of its elements are not always compatible with international instruments on human rights protection ratified by Russia. The objective of this work is to study the problems of implementation of the European Convention for the Protection of Human Rights and Fundamental Freedoms and the decisions of the European Court of Human Rights in the Russian Federation and their possible influence on the development of national instruments for the protection of fundamental rights under the Russian federal system
45
Broussard, Ryan Sawyer. "Analytical and Numerical Solutions for the Case of a Horizontal Well with a Radial Power-Law Permeability Distribution--Comparison to the Multi-Fracture Horizontal Case." Thesis, 2013. http://hdl.handle.net/1969.1/149312.
Full textAbstract:
In this work, I present the development of analytical solutions in the Laplace domain for a fully-penetrating, horizontal well producing at a constant flow rate or constant wellbore pressure in the center of a composite, cylindrical reservoir system with an impermeable outer boundary. The composite reservoir consists of two regions. The cylindrical region closest to the wellbore is stimulated, and the permeability within this region follows a power-law function of the radial distance from the wellbore. The unstimulated outer region has homogeneous reservoir properties.
The current norm for successful stimulation of low permeability reservoir rocks is multi-stage hydraulic fracturing. The process of hydraulic fracturing creates thin, high permeability fractures that propagate deep into the reservoir, increasing the area of the rock matrix that is exposed to this low-resistance flow pathway. The large surface area of the high conductivity fracture is what makes hydraulic fracturing so successful. Unfortunately, hydraulic fracturing is often encumbered by problems such as high capital costs and a need for large volumes of water. Therefore, I investigate a new stimulation concept based upon the alteration of the permeability of a large volume around the producing well assembly from its original regime to that following a power-law function. I evaluate the effectiveness of the new concept by comparing it to conventional multi-stage hydraulic fracturing.
The results of this investigation show that the power-law permeability reservoir (PPR) has a performance advantage over the multi-fractured horizontal treatment (MFH) only when the fracture conductivity and fracture half-length are small. Most importantly, the results demonstrate that the PPR can provide respectable flow rates and recovery factors, thus making it a viable stimulation concept for ultra-low permeability reservoirs, especially under conditions that may not be conducive to a conventional MHF treatment.
46
Sridharan, Ajay Promodh. "Topological features of online social networks." Thesis, 2011. http://hdl.handle.net/1828/3396.
Full textAbstract:
The first-order properties like degree distribution of nodes and the clustering co-efficient have been the prime focus of research in the study of structural properties of networks. The presence of a power law in the degree distribution of nodes has been considered as an important structural characteristic of social and information networks. Higher-order structural properties such as edge embeddedness may also play a more important role in many on-line social networks but have not been studied before. In this research, we study the distribution of higher-order structural properties of a network, such as edge embeddedness, in complex network models and on-line social networks. We empirically study the embeddedness distribution of a variety of network models and theoretically prove that a recently-proposed network model, the random $k$-tree, has a power-law embedded distribution. We conduct extensive experiments on the embeddedness distribution in real-world networks and provide evidence on the correlation between embeddedeness and communication patterns among the members in an on-line social network.Graduate
47
Hsueh, Min-shen, and 薛明生. "Invariability and universality of the power law of population distribution in time and space: a case study of the Taiwan Island." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/35932031736572181900.
Full textAbstract:
碩士國立臺北大學
公共行政暨政策學系
90
The objective of the thesis is to explore the self-organization characteristics of population distribution in time and space. The research design is grounded on two-way ANOVA analyses of the regional population distribution data on the Taiwan island using time and space as the two factors, in order to examine whether the discovered power laws are affected by these factors. Firstly, the thesis investigates the significance of the power law in the regional context. It then introduces the policy variable of the construction of the first high way in the design to investigate the variable’s effect on the power law. Finally, the thesis explores into the question of whether the invariability and universality of the power law would be affected by time and space. Since the power law represents the relation between urban hierarchy and population distribution, the thesis applies the City Rank-size Rule or Zipf’s Law tothe understanding of how the variability of population aggregation and the significance of power law characteristics change across time and space using the real population. In order to understand the explanatory relation between the regression coefficient of population differences and the significance of power law, the research conducts further regression analyses. The results show that the power law characteristics are significant not only in individual regional contexts, but also across different scales of time and space based on comprehensive examinations, confirming the hypothesis that the power law is invariable in time and universal in space. The highway construction policy indeed affects the power law characteristics.
48
Kück, Fabian. "Convergence Rates in Dynamic Network Models." Doctoral thesis, 2017. http://hdl.handle.net/11858/00-1735-0000-002E-E362-F.
Full text
49
Betken, Carina. "Limit theorems in preferential attachment random graphs." Doctoral thesis, 2019. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-201905171547.
Full textAbstract:
We consider a general preferential attachment model, where the probability that a newly arriving vertex connects to an older vertex is proportional to a (sub-)linear function of the indegree of the older vertex at that time. We provide a limit theorem with rates of convergence for the distribution of a vertex, chosen uniformly at random, as the number of vertices tends to infinity. To do so, we develop Stein's method for a new class of limting distributions including power-laws. Similar, but slightly weaker results are shown to be deducible using coupling techniques. Concentrating on a specific preferential attachment model we also show that the outdegree distribution asymptotically follows a Poisson law. In addition, we deduce a central limit theorem for the number of isolated vertices. We thereto construct a size-bias coupling which in combination with Stein’s method also yields bounds on the distributional distance.
50
Taubert, Franziska. "Modelling and Analysing the Structure and Dynamics of Species-rich Grasslands and Forests." Doctoral thesis, 2014. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2014041412381.
Full textAbstract:
Ecosystems provide important functioning and services, like biomass for bioenergy
production or storage of atmospheric carbon. Two examples of such ecosystems are temperate
grasslands and tropical forests. Both vegetation are rich of various species, whereby each of the respective ecosystem benefits from its species-richness concerning their functioning, i.e.
productivity. In this thesis both vegetation are in the focus of the investigations. In the first chapter, a review of existing grassland and vegetation models provides an overview of important aspects, which have to be considered for modelling temperate grasslands in the context of biomass production. Based on the review, new conceptual modelling approaches for temperate grasslands are proposed. In the third chapter, derived from the suggested
concept, the process-oriented and individual-based grassland model Grassmind is presented. In the fourth chapter, the model Grassmind is used in order to parameterize and simulate the annual dynamics of a typical Central European grass species. Grassmind is able to reproduce
the structure and dynamics of a temperate grass species. With reference to the parameterized grass species, a simulation study using defined species groups is performed in order to investigate on the effect of the richness of species groups on aboveground productivity. We do not observe a significant positive effect of species group richness on productivity, which is
explained by limitations of using the parameterized grass species as a reference. In the fifth chapter, comprehensive investigations are carried out on the example of stem size distributions in forests concerning their statistical analyses, i.e. by using maximum likelihood
estimation. The effects of uncertainties, i.e. binning of measured stem sizes or random
measurement errors, are examined in detail. Uncertainties bias the analyses of maximum
likelihood estimations. It is shown, that the use of modified likelihood functions, which include either binning or measurement errors, reduce these biases to a large extent. For both studies, i.e. modelling of temperate grasslands and analysing stem size distributions of forests, the presented investigations are discussed and possible examinations are suggested for future
research in the last chapter.