Dissertations / Theses on the topic 'Power equations'
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Lagrange, John. "Power Series Solutions to Ordinary Differential Equations." TopSCHOLAR®, 2001. http://digitalcommons.wku.edu/theses/672.
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In this thesis, the reader will be made aware of methods for finding power series solutions to ordinary differential equations. In the case that a solution to a differential equation may not be expressed in terms of elementary functions, it is practical to obtain a solution in the form of an infinite series, since many differential equations which yield such a solution model an actual physical situation. In this thesis, we introduce conditions that guarantee existence and uniqueness of analytic solutions, both in the linear and nonlinear case. Several methods for obtaining analytic solutions are introduced as well. For the sake of pure mathematics, and particularly in the applications involving these differential equations, it is useful to find a radius of convergence for a power series solution. For these reasons, several methods for finding a radius of convergence are given. We will prove all results in this thesis.
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Grey, David John. "Parallel solution of power system linear equations." Thesis, Durham University, 1995. http://etheses.dur.ac.uk/5429/.
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At the heart of many power system computations lies the solution of a large sparse set of linear equations. These equations arise from the modelling of the network and are the cause of a computational bottleneck in power system analysis applications. Efficient sequential techniques have been developed to solve these equations but the solution is still too slow for applications such as real-time dynamic simulation and on-line security analysis. Parallel computing techniques have been explored in the attempt to find faster solutions but the methods developed to date have not efficiently exploited the full power of parallel processing. This thesis considers the solution of the linear network equations encountered in power system computations. Based on the insight provided by the elimination tree, it is proposed that a novel matrix structure is adopted to allow the exploitation of parallelism which exists within the cutset of a typical parallel solution. Using this matrix structure it is possible to reduce the size of the sequential part of the problem and to increase the speed and efficiency of typical LU-based parallel solution. A method for transforming the admittance matrix into the required form is presented along with network partitioning and load balancing techniques. Sequential solution techniques are considered and existing parallel methods are surveyed to determine their strengths and weaknesses. Combining the benefits of existing solutions with the new matrix structure allows an improved LU-based parallel solution to be derived. A simulation of the improved LU solution is used to show the improvements in performance over a standard LU-based solution that result from the adoption of the new techniques. The results of a multiprocessor implementation of the method are presented and the new method is shown to have a better performance than existing methods for distributed memory multiprocessors.
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Ebrahimpour, Mohammad Reza. "An analytical study of the power flow equations with applications to systems with multiple close solutions." Diss., Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/15746.
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García-Blanco, Raquel. "Efficient solvers for power flow equations : parametric solutions with accuracy control assessment." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/458887.
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The Power Flow model is extensively used to predict the behavior of electric grids and results in solving a nonlinear algebraic system of equations. Modeling the grid is essential for design optimization and control. Both applications require a fast response for multiple queries to a parametric family of power flow problems. Different solvers have been introduced especially designed for the algebraic nonlinear power flow equations, providing efficient solutions for single problems, even when the number of degrees of freedom is considerably large. However, there is no existing methodology providing an explicit solution of the Parametric Power Flow problem (viz. a computational vademecum, explicit in terms of the parameters).
This work aims precisely at designing algorithms producing computational vademecums for the Parametric Power Flow problem. Once these solutions are available, solving for different values of the parameters is an extremely fast (real-time) post-process and therefore both the optimal design and the control problem can readily be addressed.
In a first phase, a new family of iteratives solvers for the non-parametric version of the problem is devised. The method is based on a hybrid formulation of the problem combined with an alternated search directions scheme. These methods are designed such that it can be generalized to deal with the parametric version of the problem following a Proper Generalized Decomposition (PGD) strategy.
The solver for the parametric problem is conceived by performing the operations involving the unknowns in a PGD fashion. The algorithm follows the basic steps of the algebraic solver, but some operations are carried out in a PGD framework, that is requiring a nested iterative algorithm. The PGD solver is accompanied with an error assessment technique that allows monitoring the convergence of the iterative procedures and deciding the number of terms required to meet the accuracy prescriptions. Different examples of realistic grids and standard benchmark tests are used to demonstrate the performance of the proposed methodologies.El modelo de flujo de potencias se usa para predecir el comportamiento de redes eléctricas y desemboca en la resolución de un sistema de ecuaciones algebraicas no lineales. Modelar una red es esencial para optimizar su diseño y control. Ambas aplicaciones requieren una respuesta rápida a las múltiples peticiones de una familia paramétrica de problemas de flujo de potencias. Diversos métodos de resolución se diseñaron especialmente para resolver la versión algebraica de las ecuaciones de flujo de potencias. Sin embargo, no existe ninguna metodología que proporcione una solución explícita al problema paramétrico de flujo de potencias (esto quiere decir, un vademecum computacional explícito en términos de los parámetros). Esta tesis tiene como objetivo diseñar algoritmos que produzcan vademecums para el problema paramétrico de flujo de potencias. Una vez que las soluciones están disponibles, resolver problemas para diferentes valores de los parámetros es un posproceso extremadamente rápido (en tiempo real) y por lo tanto los problemas de diseño óptimo y control se pueden resolver inmediatamente. En la primera fase, una nueva familia de métodos de resolución iterativos para la versión algebraica del problema se construye. El método se basa en una formulación híbrida del problema combinado con un esquema de direcciones alternadas. Estos métodos se han diseñado para generalizarlos de forma que puedan resolver la versión paramétrica del problema siguiendo una estrategia llamada Descomposición Propia Generalizada (PGD). El método de resolución para el problema paramétrico calcula las incógnitas paramétricas usando la técnica PGD. El algoritmo sigue los mismo pasos que el algoritmo algebraico, pero algunas operaciones se llevan a cabo en el ambiente PGD, esto requiere algoritmos iterativos anidados. El método de resolución PGD se acompaña con una evaluación del error cometido permitiendo monitorizar la convergencia de los procesos iterativos y decidir el número de términos que requiere la solución para alcanzar la precisión preescrita. Diferentes ejemplos de redes reales y tests estándar se usan para demostrar el funcionamiento de las metodologías propuestas.
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Beardmore, Robert Eric. "A study of bifurcations in singular differential equations motivated by electrical power systems." Thesis, Brunel University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.310143.
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Stein, Martin. "C0-Semigroup Methods for Delay Equations." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2008. http://nbn-resolving.de/urn:nbn:de:bsz:14-ds-1225964082538-00880.
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In der Dissertation werden Werkzeuge zur Analyse von Wohlgestelltheit und Asymptotik von Integro-Differential- und Verzögerungsgleichungen entwickelt. Im ersten Teil der Arbeit (Kapitel 1 und 2) werden Methoden zur Bestimmung der Modulhalbgruppe (kleinste dominierende C0-Halbgruppe) einer C0-Halbgruppe zur Verfügung gestellt, die unter anderem auf Volterra-Halbgruppen (die aus Integro-Differentialgleichungen hervorgehen) und Evolutionshalbgruppen (Rückkopplungsgleichungen mit Zeitverzögerung, Transport in Netzwerken) angewendet werden. Im Mittelpunkt des zweiten Teils (Kapitel 3 und 4) steht ein Integro-Differentialgleichungstyp, der Schwingungsphänomene von Tragswerksflächen im Unterschallbereich beschreibt. Das besondere dieser Gleichung ist das Auftreten der Zeitableitung der gesuchten Funktion im Integralterm. Es werden eine Reihe von Wohlgestelltheitskriterien hergeleitet, welche Wohlgestelltheit der Gleichung liefern, ohne das es möglich ist, durch partielle Integration die Zeitableitung im Integralterm zu beseitigen und dadurch die Gleichung auf einen bekannten Integro-Differentialgleichungstyp zurückzuführen. Die entwickelten Methoden eignen sich auch für die Herleitung neuer Wohlgestelltheitskriterien für andere Verzögerungsgleichungen. Entsprechende Resultate werden in Kapitel 4 hergeleitetIn the dissertation tools for the analysis of well-posedness and asymptotic behaviour of integro-differential equations and delay equations are developed. In the first part (chapter 1 and 2) methods for the determination of the modulus semigroup (smallest dominating C0-semigroup) of a C0-semigroup are provided and applied to various examples such as Volterra semigroups and evolution semigroups and transport evolution equations in networks. The main interest of the second part (chapter 3 and 4) is a type of an integro-differential equation which occurs in the modelling of the flutter of airfoils at subsonic speed. The remarkable property of the equation is the time derivative of the sought function in the integral term. A number of well-posedness criteria are proved for which integration by parts is not possible. The developed methods are also suitable for the derivation of new well-posedness results for other delay semigroups. Corresponding criteria are presented in chapter 4
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Stein, Martin. "C0-Semigroup Methods for Delay Equations." Doctoral thesis, Technische Universität Dresden, 2007. https://tud.qucosa.de/id/qucosa%3A23902.
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In der Dissertation werden Werkzeuge zur Analyse von Wohlgestelltheit und Asymptotik von Integro-Differential- und Verzögerungsgleichungen entwickelt. Im ersten Teil der Arbeit (Kapitel 1 und 2) werden Methoden zur Bestimmung der Modulhalbgruppe (kleinste dominierende C0-Halbgruppe) einer C0-Halbgruppe zur Verfügung gestellt, die unter anderem auf Volterra-Halbgruppen (die aus Integro-Differentialgleichungen hervorgehen) und Evolutionshalbgruppen (Rückkopplungsgleichungen mit Zeitverzögerung, Transport in Netzwerken) angewendet werden. Im Mittelpunkt des zweiten Teils (Kapitel 3 und 4) steht ein Integro-Differentialgleichungstyp, der Schwingungsphänomene von Tragswerksflächen im Unterschallbereich beschreibt. Das besondere dieser Gleichung ist das Auftreten der Zeitableitung der gesuchten Funktion im Integralterm. Es werden eine Reihe von Wohlgestelltheitskriterien hergeleitet, welche Wohlgestelltheit der Gleichung liefern, ohne das es möglich ist, durch partielle Integration die Zeitableitung im Integralterm zu beseitigen und dadurch die Gleichung auf einen bekannten Integro-Differentialgleichungstyp zurückzuführen. Die entwickelten Methoden eignen sich auch für die Herleitung neuer Wohlgestelltheitskriterien für andere Verzögerungsgleichungen. Entsprechende Resultate werden in Kapitel 4 hergeleitet.In the dissertation tools for the analysis of well-posedness and asymptotic behaviour of integro-differential equations and delay equations are developed. In the first part (chapter 1 and 2) methods for the determination of the modulus semigroup (smallest dominating C0-semigroup) of a C0-semigroup are provided and applied to various examples such as Volterra semigroups and evolution semigroups and transport evolution equations in networks. The main interest of the second part (chapter 3 and 4) is a type of an integro-differential equation which occurs in the modelling of the flutter of airfoils at subsonic speed. The remarkable property of the equation is the time derivative of the sought function in the integral term. A number of well-posedness criteria are proved for which integration by parts is not possible. The developed methods are also suitable for the derivation of new well-posedness results for other delay semigroups. Corresponding criteria are presented in chapter 4.
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Ahmed, Ibrahim. "Comparative evaluation of different power quality issues of variable speed wind turbines." Thesis, Brunel University, 2017. http://bura.brunel.ac.uk/handle/2438/15920.
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The generation of wind energy deliberately becomes a significant part of generated electrical power in developed nations. Factors like fluctuation in natural wind speed and the use of power electronics present issues related power quality in wind turbine application. Following to the fact that there have been remarkable increase of wind energy in the electrical energy production worldwide, the effect on power quality and power system stability caused by wind power is considered significant, and hence the evaluation of this effect is crucial and obligatory. In order to examine and evaluate the characteristics of power quality of grid-integration of wind power in a persistent and authentic manner, several guidelines were introduced and established. One of the widely used guideline to define power quality of wind turbine is IEC standard 61400-21. Moreover, power system operator demands wind turbines to tolerate a certain voltage dip in some countries. The wind turbines concepts such as doubly-fed induction generator wind turbine and the direct driven wind turbine wind turbine with a permanent magnet synchronous generator are considered as the most promising concepts among other wind turbine types since they can operate in wide range of wind speed. The major goal of this PhD work is to examine the power quality character aspects of these wind turbine concepts. The power quality problems were calculated according to that devised by IEC- 61400-21 and then compared afterwards. The research includes the evaluation of the following power quality characteristics: voltage dip response, current harmonics distortion, control of active and reactive power and voltage flicker. Besides the IEC-standard 61400-21, the study also looks into the short-circuit current and fault-ride through with specifications provided by some grid codes, as power system stability is greatly influenced by these aspects. In order to achieve the research's goal, a reliable dynamic model of wind turbine system and control are required. Thus a complete model for both wind turbines systems was developed in PSCAD/EMTDC simulation-program which is the fanatical power system analysis tool, which can achieve a complete simulation of the system dynamic behaviour from the wind turbine. Two controllers are adopted for wind turbine system, converter control and pitch angle control. The converter controlled by a vector control in order to regulate the active and the reactive power whereas the pitch control scheme is put to function to limit the aerodynamic power in high wind speed. The ability of providing adequate state steady and dynamic performances are what wind turbine assures, as examined by simulation results, and via this, problems related to power quality caused by integrating wind turbines to the grid can be studied by wind turbine model.
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Fransson, Jonas. "Lower ramification numbers of wildly ramified power series." Thesis, Linnéuniversitetet, Institutionen för matematik (MA), 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-35313.
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In this thesis we study lower ramification numbers of power series tan- gent to the identity that are defined over fields of positive characteristics. Let f be such a series, then f has a fixed point at the origin and the corresponding lower ramification numbers of f are then, up to a constant, the multiplicity of zero as a fixed point of iterates of f. In this thesis we classify power series having ‘small’ ramification numbers. The results are then used to study ramification numbers of polynomials not tangent to the identity. We also state a few conjectures motivated by computer experiments that we performed.
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Ball, John. "Volterra filtering for applications in nonoverlapping spectral problems." Thesis, Georgia Institute of Technology, 1991. http://hdl.handle.net/1853/15372.
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Ghanavati, Goodarz. "Statistical Analysis of High Sample Rate Time-series Data for Power System Stability Assessment." ScholarWorks @ UVM, 2015. http://scholarworks.uvm.edu/graddis/333.
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The motivation for this research is to leverage the increasing deployment of the phasor measurement unit (PMU) technology by electric utilities in order to improve situational awareness in power systems. PMUs provide unprecedentedly fast and synchronized voltage and current measurements across the system. Analyzing the big data provided by PMUs may prove helpful in reducing the risk of blackouts, such as the Northeast blackout in August 2003, which have resulted in huge costs in past decades.
In order to provide deeper insight into early warning signs (EWS) of catastrophic events in power systems, this dissertation studies changes in statistical properties of high-resolution measurements as a power system approaches a critical transition. The EWS under study are increases in variance and autocorrelation of state variables, which are generic signs of a phenomenon known as critical slowing down (CSD).
Critical slowing down is the result of slower recovery of a dynamical system from perturbations when the system approaches a critical transition. CSD has been observed in many stochastic nonlinear dynamical systems such as ecosystem, human body and power system. Although CSD signs can be useful as indicators of proximity to critical transitions, their characteristics vary for different systems and different variables within a system.
The dissertation provides evidence for the occurrence of CSD in power systems using a comprehensive analytical and numerical study of this phenomenon in several power system test cases. Together, the results show that it is possible extract information regarding not only the proximity of a power system to critical transitions but also the location of the stress in the system from autocorrelation and variance of measurements. Also, a semi-analytical method for fast computation of expected variance and autocorrelation of state variables in large power systems is presented, which allows one to quickly identify locations and variables that are reliable indicators of proximity to instability.
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Caplen, Mark J. S. "The development and testing of a new integration method for the solution of stiff differential equations arising in the digital simulation of fluid power systems." Thesis, University of Bath, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383310.
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Pretorius, Johannes Petrus. "Optimization and control of a large-scale solar chimney power plant." Thesis, Stellenbosch : University of Stellenbosch, 2007. http://hdl.handle.net/10019.1/349.
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Thesis (PhD (Mechanical and Mechatronic Engineering))-- University of Stellenbosch, 2007.ENGLISH ABSTRACT: The dissertation builds on previous research (Pretorius, 2004) and investigates the optimization and control of a large-scale solar chimney power plant. Performance results are based on a reference location near Sishen in South Africa and a so-called reference solar chimney power plant, with a 5000 m collector diameter and a 1000 m high, 210 m diameter chimney. The numerical simulation model is refined and used to perform a sensitivity analysis on the most prominent operating and technical plant specifications. Thermo-economically optimal plant configurations are established from simulation results and calculations according to an approximate plant cost model. The effects of ambient wind, temperature lapse rates and nocturnal temperature inversions on plant performance are examined. Various new technologies are investigated for the purpose of controlling plant output according to specific demand patterns. The incorporation of vegetation under the collector roof of the plant and the influence thereof on plant performance is also explored. Results indicate that, through the modification of the collector roof reflectance, collector roof emissivity, ground surface absorptivity or ground surface emissivity, major improvements on plant performance are possible. Introducing thermal insulation or double glazing of the collector roof also facilitates substantial enhancements on plant yield. Simulations predict a notable sensitivity to the ground surface absorptivity value, while variable atmospheric temperature lapse rates and windy ambient conditions may impair plant performance significantly. Furthermore, sand is found to be unsuitable as plant ground type and thermoeconomically optimal solar chimney plant dimensions are determined to be generally larger than plant dimensions employed in previous studies. Good dynamic control of solar chimney power output is established, suggesting that a solar chimney power plant can be implemented as a base or peak load electricity generating facility. Lastly, results predict that vegetation, when provided with sufficient water, will be able to survive under the collector roof but the inclusion of vegetation will however cause major reductions in plant performance.
AFRIKAANSE OPSOMMING: Die proefskrif bou op vorige navorsing (Pretorius, 2004) en ondersoek die optimering en beheer van 'n grootskaalse sonskoorsteen-kragstasie. Uitsetresultate word baseer op 'n verwysingsligging naby Sishen in Suid-Afrika en 'n sogenaamde verwysingskragstasie, met 'n kollektor deursnee van 5000 m en 'n 1000 m hoë, 210 m deursnee skoorsteen. Die numeriese rekenaarmodel is verbeter en gebruik vir die uitvoering van 'n sensitiwiteits-analise op die belangrikste bedryfs- en tegniese kragstasie spesifikasies. Termo-ekonomiese optimale aanlegkonfigurasies is bepaal volgens die uitsetresultate van die rekenaarmodel en benaderde aanleg-kosteberekeninge volgens 'n eenvoudige kostemodel. Die invloed van wind, atmosferiese temperatuur gradiënte en nagtelike temperatuur inversies op kragstasie uitset word beskou. Verskeie nuwe tegnologië word ondersoek met die doel om aanleg uitset te kan beheer volgens spesifieke elektrisiteit aanvraagspatrone. Die inkorporasie van plantegroei onder die kollektordak, en die invloed daarvan op kragstasie uitset, word ook beskou. Bevindings dui aan dat, deur die wysiging van die kollektordak refleksie, kollektordak emissiwiteit, grondoppervlak absorptiwiteit of grondoppervlak emissiwiteit, groot verbeterings op aanleg uitset moontlik is. Die implementering van termiese isolasie of 'n dubbelglaslaag vir die kollektordak veroorsaak ook 'n beduidende verheffing in kragstasie uitset. Simulasies voorspel 'n merkbare sensitiwiteit teenoor die grondoppervlak absorptiwiteitswaarde, terwyl veranderlike atmosferiese temperatuur daaltempos en winderige omgewingstoestande aanleg uitset beduidend mag belemmer. Verder is bevind dat sand ongeskik is as aanleg grond tipe en dat termo-ekonomiese optimale sonskoorsteen-kragstasie dimensies in die algemeen groter is as die aanvaarde aanlegdimensies van vorige studies. Goeie dinamiese beheer van sonskoorsteen-kragstasie uitset is bevestig, wat suggereer dat die sonskoorsteenkragstasie as 'n basis of pieklas elektrisiteitopwekkings-aanleg ingespan kan word. Ten laaste voorspel resultate dat plantegroei, mits dit voorsien word van genoegsame water, sal kan oorleef onder die kollektordak maar dat die inkorporasie van plantegroei die aanleg uitset beduidend sal benadeel.
Sponsored by the Centre for Renewable and Sustainable Energy Studies
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HIPOLITO, FABIO C. "Avaliação das metodologias de análise de sistemas de tubulações de vapor sujeitas a carregamentos do tipo Steam Hammer." reponame:Repositório Institucional do IPEN, 2016. http://repositorio.ipen.br:8080/xmlui/handle/123456789/26938.
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Submitted by Marco Antonio Oliveira da Silva (maosilva@ipen.br) on 2016-12-21T18:18:35Z
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Carregamentos transientes termo hidráulicos do tipo Steam Hammer são eventos comuns em sistemas de tubulações de vapor com grandes potenciais de catástrofes em plantas de geração de energia. Uma vez iniciado o evento, ondas de pressões são geradas com amplitudes, geralmente, de grande magnitude ocasionando altas pressões no sistema, ruídos, deformações, fadiga, com possibilidade de danos materiais e econômicos e em casos extremos fatalidades. Os procedimentos da indústria para análise deste tipo de sistema consistem realização de análises estáticas equivalentes ou análise de espectro de resposta com carregamentos caracterizados por meio de métodos analíticos baseados em hipóteses simplificadoras do fluido e fluxo. Neste trabalho é proposta a analise de sistema de tubulações por meio do método de integração numérica com superposição modal e carregamento caracterizado por método numérico com base no método das características. Comparações foram efetuadas entre os resultados obtidos pela metodologia proposta e os procedimentos da indústria, demonstrando que, dado ao alto grau de conservadorismo, os procedimentos da indústria acarretam em superdimensionamento de estruturas e tubulações ocasionando custos adicionais de projeto, sendo a otimização do projeto obtida aplicando-se a metodologia proposta no trabalho.
Dissertação (Mestrado em Tecnologia Nuclear)
IPEN/D
Instituto de Pesquisas Energéticas e Nucleares - IPEN-CNEN/SP
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Vaičiulytė, Ingrida. "Vienos išsigimstančios dalinių išvestinių diferencialinių lygčių sistemos sprendinių struktūra." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090827_111608-87412.
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Šiame darbe išnagrinėta išsigimstanti keturių pirmos eilės dalinių išvestinių diferencialinių lygčių sistema. Dalinių išvestinių diferencialinių lygčių sistemai spręsti pritaikytas apibendrintų laipsninių eilučių metodas. Rasti analiziniai šios sistemos sprendiniai ir ištirtos jų savybės išsigimimo daugdaros taškų aplinkoje. Apibendrintų laipsninių eilučių metodas gali būti pritaikytas sprendžiant panašios struktūros dalinių išvestinių diferencialines lygtis, kurių eilė išsigimsta. Darbe gauti rezultatai gali būti pritaikomi modeliuojant ir tiriant realius procesus.In this work the system of four degenerating differential equations with partial derivatives of first order was studied. For the solution of system of differential equations with partial derivatives the method of generalized power series was applied. Analytical solutions of this system were found and properties of solutions on neighbourhood of points of degeneration manifold were investigated. The method of generalized power series can be applied to the solution of systems of differential equations with partial derivatives of similar structure, which order is degenerating. The results, which were obtained in this work, can be applied to modelling and studying the real processes.
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Сиротин, Юрий Александрович. "Компенсация и учет реактивной мощности в электротехнических системах с несимметричными режимами." Thesis, НТУ "ХПИ", 2014. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21116.
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Диссертация на соискание ученой степени доктора технических наук по специальности 05.09.03 - электротехнические комплексы и системы. - Национальный технический университет "Харьковский политехнический институт". - Харьков, 2015.
Диссертационная работа посвящена решению важной научно-технической проблемы создания обобщенной теории мощности (ТМ), единого комплексного подхода к компенсации и учету неактивных составляющих полной мощности (ПМ) для обеспечения оптимального режима потребления электрической энергии (ЭЭ) в точке подключения неидеальной нагрузки к сети с несимметричным напряжением. На основе теоретических исследований, использующих метод ортогонального разложения векторов мгновенных значений 3-фазного тока и напряжения, получена обобщенная векторная математическая модель (ВММ), которая классифицирует электроэнергетические режимы (ЭР) в 3-фазной схеме электроснабжения с помощью векторной мгновенной мощности (ММ). Сформулированы и обоснованы предложения политики повышения качества поставки и потребления электроэнергии в 3-фазной сети, сочетающие установку поставщиком в каждой точке подключения потребителя счетчика, измеряющего каждую ЭКТ, заключение публичного договора, в котором предусмотрена оплата каждой ЭКТ по своему тарифу, установки потребителем КУ, применение компенсации неактивных составляющих ПМ на каждом уровне для уменьшения групповых потерь в сетях поставщика. Предложенная политика позволит учесть разную степень влияния ЭКТ на качество электроэнергии и обеспечит потребителю выбор выгодного для него способа потребления электроэнергии, стимулирует установку КУ, а поставщику обеспечит надежную методологию повышения качества электроэнергии в рамках несимметрии нагрузки и напряжения.Thesis for a Doctor’s degree in Engineering Sciences by specialty 05.09.03 - Electrical Engineering Complexes and Systems. - National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2015. The dissertation is devoted an important scientific and technical issues to improve the power quality of supply and consumption (SC) in three-phase networks through further development of die power theory, development of methods and ways of compensation, proposals for the accounting and payment of the inactive components of the apparent power (AP). A generalized mathematical model (GMM) of electric power processes (EPP) in a 3-phase SC scheme was developed. The model of 3-wire circuit is provided by a special (О-balanced) mode of the model 4-wire circuit The developed GMM classifies the SC modes using the vectorial instantaneous power (IP) and summarizes the class of models used in the theory of IP. For sinusoidal mode with asymmetric voltage the refines vectorial mathematical model (VMV) 3-phasors (complex rms vectors) was created. The analytical expressions for the integral characteristics of the classified modes are founded and their relationship with standard IP and vectorial IP are established. With asymmetrical voltage and asymmetrical loading a sinusoidal mode can be both unbalanced and pulsed. Each mode is represented by its power equation and the equivalent orthogonal decomposition of the 3-phase current Both decompositions are used to create the optimal mode of SC with a constant IP at asymmetrical voltage. The proposed compensator provides the non-puised energy supply with the highest possible power factor and with the same average (active) power as the initial current. Based on the evaluation and calculation of the power equation components of a unbalanced mode was developed a methodology for calculating the loss of the measuring selection. A methodology and technique of analytical calculation of additional losses on the passport data of the connected electrical equipment was proposed. Formulated and proved offers on differential measurement and payment of the energy components of AP will stimulate consumer sets the compensator, and provide a reliable methodology for improving the quality of SC (within unbalance loading and voltage).
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SABUNDJIAN, GAIANE. "Aplicação do método da expansão em funções hierárquicas na solução das equações de Navier-stokes para fluidos incompressíveis." reponame:Repositório Institucional do IPEN, 1999. http://repositorio.ipen.br:8080/xmlui/handle/123456789/11624.
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Tese (Doutoramento)
IPEN/T
Escola Politecnica, Universidade de Sao Paulo - POLI/USP
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González, Zumba Jorge Andrés. "Dynamic Modeling and Stability Analysis of Stochastic Multi-Physical Systems Applied to Electric Power Systems." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/158558.
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[ES] La naturaleza aleatoria que caracteriza algunos fenómenos en sistemas físicos reales (e.g., ingeniería, biología, economía, finanzas, epidemiología y otros) nos ha planteado el desafío de un cambio de paradigma del modelado matemático y el análisis de sistemas dinámicos, y a tratar los fenómenos aleatorios como variables aleatorias o procesos estocásticos. Este enfoque novedoso ha traído como consecuencia nuevas especificidades que la teoría clásica del modelado y análisis de sistemas dinámicos deterministas no ha podido cubrir. Afortunadamente, maravillosas contribuciones, realizadas sobre todo en el último siglo, desde el campo de las matemáticas por científicos como Kolmogorov, Langevin, Lévy, Itô, Stratonovich, sólo por nombrar algunos; han abierto las puertas para un estudio bien fundamentado de la dinámica de sistemas físicos perturbados por ruido.
En la presente tesis se discute el uso de ecuaciones diferenciales algebraicas estocásticas (EDAEs) para el modelado de sistemas multifísicos en red afectados por perturbaciones estocásticas, así como la evaluación de su estabilidad asintótica a través de exponentes de Lyapunov (ELs). El estudio está enfocado en EDAEs d-index-1 y su reformulación como ecuaciones diferenciales estocásticas ordinarias (EDEs). Fundamentados en la teoría ergódica, es factible analizar los ELs a través de sistemas dinámicos aleatorios (SDAs) generados por EDEs subyacentes. Una vez garantizada la existencia de ELs bien definidas, hemos procedido al uso de técnicas de simulación numérica para determinar los ELs numéricamente. Hemos implementado métodos numéricos basados en descomposición QR discreta y continua para el cómputo de la matriz de solución fundamental y su uso en el cálculo de los ELs. Las características numéricas y computacionales más relevantes de ambos métodos se ilustran mediante pruebas numéricas. Toda esta investigación sobre el modelado de sistemas con EDAEs y evaluación de su estabilidad a través de ELs calculados numéricamente, tiene una interesante aplicación en ingeniería. Esta es la evaluación de la estabilidad dinámica de sistemas eléctricos de potencia. En el presente trabajo de investigación, implementamos nuestros métodos numéricos basados en descomposición QR para el test de estabilidad dinámica en dos modelos de sistemas eléctricos de potencia de una-máquina bus-infinito (OMBI) afectados por diferentes perturbaciones ruidosas. El análisis en pequeña-señal evidencia el potencial de las técnicas propuestas en aplicaciones de ingeniería.[CA] La naturalesa aleatòria que caracteritza alguns fenòmens en sistemes físics reals (e.g., enginyeria, biologia, economia, finances, epidemiologia i uns altres) ens ha plantejat el desafiament d'un canvi de paradigma del modelatge matemàtic i l'anàlisi de sistemes dinàmics, i a tractar els fenòmens aleatoris com a variables aleatòries o processos estocàstics. Aquest enfocament nou ha portat com a conseqüència noves especificitats que la teoria clàssica del modelatge i anàlisi de sistemes dinàmics deterministes no ha pogut cobrir. Afortunadament, meravelloses contribucions, realitzades sobretot en l'últim segle, des del camp de les matemàtiques per científics com Kolmogorov, Langevin, Lévy, Itô, Stratonovich, només per nomenar alguns; han obert les portes per a un estudi ben fonamentat de la dinàmica de sistemes físics pertorbats per soroll. En la present tesi es discuteix l'ús d'equacions diferencials algebraiques estocàstiques (EDAEs) per al modelatge de sistemes multifísicos en xarxa afectats per pertorbacions estocàstiques, així com l'avaluació de la seua estabilitat asimptòtica a través d'exponents de Lyapunov (ELs). L'estudi està enfocat en EDAEs d-index-1 i la seua reformulació com a equacions diferencials estocàstiques ordinàries (EDEs). Fonamentats en la teoria ergòdica, és factible analitzar els ELs a través de sistemes dinàmics aleatoris (SDAs) generats per EDEs subjacents. Una vegada garantida l'existència d'ELs ben definides, hem procedit a l'ús de tècniques de simulació numèrica per a determinar els ELs numèricament. Hem implementat mètodes numèrics basats en descomposició QR discreta i contínua per al còmput de la matriu de solució fonamental i el seu ús en el càlcul dels ELs. Les característiques numèriques i computacionals més rellevants de tots dos mètodes s'illustren mitjançant proves numèriques. Tota aquesta investigació sobre el modelatge de sistemes amb EDAEs i avaluació de la seua estabilitat a través d'ELs calculats numèricament, té una interessant aplicació en enginyeria. Aquesta és l'avaluació de l'estabilitat dinàmica de sistemes elèctrics de potència. En el present treball de recerca, implementem els nostres mètodes numèrics basats en descomposició QR per al test d'estabilitat dinàmica en dos models de sistemes elèctrics de potència d'una-màquina bus-infinit (OMBI) afectats per diferents pertorbacions sorolloses. L'anàlisi en xicotet-senyal evidencia el potencial de les tècniques proposades en aplicacions d'enginyeria.
[EN] The random nature that characterizes some phenomena in the real-world physical systems (e.g., engineering, biology, economics, finance, epidemiology, and others) has posed the challenge of changing the modeling and analysis paradigm and treat these phenomena as random variables or stochastic processes. Consequently, this novel approach has brought new specificities that the classical theory of modeling and analysis for deterministic dynamical systems cannot cover. Fortunately, stunning contributions made overall in the last century from the mathematics field by scientists such as Kolmogorov, Langevin, Lévy, Itô, Stratonovich, to name a few; have opened avenues for a well-founded study of the dynamics in physical systems perturbed by noise. In the present thesis, we discuss stochastic differential-algebraic equations (SDAEs) for modeling multi-physical network systems under stochastic disturbances, and their asymptotic stability assessment via Lyapunov exponents (LEs). We focus on d-index-1 SDAEs and their reformulation as ordinary stochastic differential equations (SDEs). Supported by the ergodic theory, it is feasible to analyze the LEs via the random dynamical system (RDSs) generated by the underlying SDEs. Once the existence of well-defined LEs is guaranteed, we proceed to the use of numerical simulation techniques to determine the LEs numerically. Discrete and continuous QR decomposition-based numerical methods are implemented to compute the fundamental solution matrix and use it in the computation of the LEs. Important numerical and computational features of both methods are illustrated through numerical tests. All this investigation concerning systems modeling through SDAEs and their stability assessment via computed LEs finds an appealing engineering application in the dynamic stability assessment of power systems. In this research work, we implement our QR-based numerical methods for testing the dynamic stability in two types of single-machine infinite-bus (SMIB) power system models perturbed by different noisy disturbances. The analysis in small-signal evidences the potential of the proposed techniques in engineering applications.
Mi agradecimiento al estado ecuatoriano que, a través del Programa de Becas para el Fortalecimiento y Desarrollo del Talento Humano en Ciencia y Tecnología 2012 de la Secretaría Nacional de Educación Superior, Ciencia y Tecnología (SENESCYT), han financiado mis estudios de doctorado.
González Zumba, JA. (2020). Dynamic Modeling and Stability Analysis of Stochastic Multi-Physical Systems Applied to Electric Power Systems [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/158558
TESIS
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Varga, David. "Bezdrátový přenos výkonu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2011. http://www.nusl.cz/ntk/nusl-218912.
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ork tie together on first project, in which the was designed apparatus for tests wireless transmission energy. Antenna was synthesized and theoretically optimized for experimental operation, in which the will performed series measuring. In first part is practical description of realization proposal. It consists of circuital solution, proposal measuring workplace and mechanical construction with illustration photographs of arrangement. Second part includes results of performed measuring. These measuring will divided by three basic groups: in first group will by testing feature one’s antennae, in second group will series transmission measuring power gain, and in third group will photographed shape of field, and comparison with simple simulation finite difference method. Third part summarises results from measuring, and prepares consecutive balancing visualisation project, which is of thematic bent on chosen aspects theoretical hypothesis and effected experiments.
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Nazareno, Ivo Sechi. "Mecanismo de instabilidade devido a grandes perturbações em sistemas elétricos de potência modelados por equações algébrico-diferenciais." Universidade de São Paulo, 2009. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-16112009-152004/.
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Nesta pesquisa são analisados os mecanismos que levam um sistema elétrico de potência (SEP) à instabilidade proveniente de uma perturbação de grande porte e as formas de se avaliar diretamente a margem de estabilidade desse sistema quando o mesmo é modelado preservando a estrutura da rede de transmissão. O sistema foi matematicamente modelado por um conjunto de equações algébrico-diferenciais (EAD), que permite modelagens mais compreensivas da carga e da rede e possibilita melhor avaliação da estabilidade de um sistema quando comparado com o modelo de equações diferenciais ordinárias (EDO) utilizado tradicionalmente para o estudo de estabilidade transitória. A avaliação direta da margem de estabilidade do sistema de potência modelado por conjuntos de EAD foi realizada usando métodos diretos de análise com base no conceito de ponto de equilíbrio instável de controle (PEIC). Tais métodos permitem a obtenção da margem deforma local e rápida, sem requerer a integração numérica de equações diferenciais do modelo pós-falta. No entanto, existem alguns problemas abertos para se alcançar a completa fundamentação do método PEIC para modelos de EAD. Assim, neste estudo dá-se um passo nesta direção, mostrando que as definições existentes de PEIC e de outros pontos de interesse podem ser falhas, principalmente quando a trajetória de falta do sistema alcança superfícies singulares. Neste sentido, são propostos a correção destas definições e um método direto de detecção do PEIC. O método proposto é adequado para análise direta de estabilidade angular e de tensão de curto-termos devido a grandes perturbações e capaz de fornecer corretos tempos críticos de abertura e a identificação dos mecanismos de instabilização do sistema de EAD, mesmo quando as trajetórias do sistema alcançam superfícies singulares.This thesis addresses to the mechanisms that lead an electric power system to instability due to large disturbances and to the methods to assess directly the stability margin when the system is modeled preserving the network structure. The system is modeled by a set of differential-algebraic equations (DAE) that permits more comprehensive models for the load and network and provides a better stability margin assessment when compared to the model of ordinary differential equations (ODE) traditionally used for transient stability analysis. The direct assessment of the stability margin was realized using direct methods based on the controlling unstable equilibrium point (CUEP) concept and permits to assess the margin in a local and fast manner, without requires the time integration of the post-fault system differential equations. Nevertheless, some open problems remain to be solved in order to provide a complete foundation of the CUEP method for DAE power system models. In this research a further step is given in this direction, showing that the existent definitions for the CUEP and other interest points may fail, mainly when the fault-on trajectory reaches singular surfaces. In this sense, it is proposed the correction of these definitions and a new CUEP method that is adequate to the angular and voltage short-term direct stability assessment due to large disturbances; capable to provide precise critical clearing times and the identification of the instability mechanisms for the DAE modeled power system, even in the presence of singular surfaces.
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Michalkovič, Aleksejus. "Netiesinės algebrinės lygčių sistemos sprendinių skaičiaus analizė." Master's thesis, Lithuanian Academic Libraries Network (LABT), 2010. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20100813_142631-54742.
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Vienas iš svarbiausių šiuolaikinės kriptografijos uždavinių yra saugių vienkrypčių funkcijų paieška. Dabartiniai mokslininkai skiria šiam klausimui ypatingą demėsį. Šiame darbe yra nagrinėjama viena iš naujausių vienkrypčių funkcijų – matricinio laipsnio funkcija. Ši funkcija yra panaudota netiesinės algebrinės lygčių sistemos sudarymui. Pagrindinis demėsys darbe yra skirtas šios lygčių sistemos analizei bei jos praktiniam taikymui. Nustatysime ar matricinio laipsnio funkcija gali būti panaudota kriptografijoje. Taip pat nustatysime lygčių sistemos sprendinių skaičiaus priklausomybę nuo jos parametrų: matricų eilės m bei grupės Z_p parametro p.Since the introduction of Diffie-Hellman key agreement protocol in 1976 computer technology has made a giant step forward. Nowadays there is not much time left before quantum computers will be in every home. However it was theoretically proven that discrete logarithm problem which is the basis for Diffie-Hellman protocol could be solved in polynomial time using such computers. Such possibility would make D-H protocol insecure. Thus cryptologists are searching for different ways to improve the security of the protocol by using hard problems. One of the ways to do so is to introduce secure one-way functions (OWF). In this paper a new kind of OWF called the matrix power function will be analyzed. Professor Eligijus Sakalauskas introduced this function in 2007 and later used this function to construct a Diffie-Hellman type key agreement protocol using square matrices. This protocol is not only based on matrix power function but also on commutative matrices which are defined in finite fields or rings. Thus an algebraic non-linear system of equations is formed. The security of this system will be analyzed. It will be shown that we can use matrix power function in cryptography. We will also be analyzing how does the solution of the system depend on system parameters: the order of matrices and a parameter p which defines a finite group Z_p. We will also briefly discuss the usage of this system in real life and the algebraic properties of the suggested OWF.
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Kong, Yafang, and 孔亚方. "On linear equations in primes and powers of two." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hub.hku.hk/bib/B50533769.
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It is known that the binary Goldbach problem is one of the open problems on linear equations in primes, and it has the Goldbach-Linnik problem, that is, representation of an even integer in the form of two odd primes and powers of two, as its approximate problem. The theme of my research is on linear equations in primes and powers of two. Precisely, there are two cases: one pair of linear equations in primes and powers of two, and one class of pairs of linear equations in primes and powers of two, in this thesis.
In 2002, D.R. Heath-Brown and P.C. Puchta obtained that every sufficiently large even integer is the sum of two odd primes and k powers of two. Here k = 13, or = 7 under the generalized Riemann hypothesis. In 2010, B. Green and T. Tao obtained that every pair of linear equations in four prime variables with coefficients matrix A = (a_ij)s×t with s ≤ t, satisfying nondegenerate condition, that is, A has full rank and the only elements of the row-space of A over Q with two or fewer nonzero entries is the zero vector, is solvable. The restriction on the coefficient matrix means that they excluded the case of the binary Goldbach problem. Motivated by the above results, it is obtained that for every pair of sufficiently large positive even integers B1, B2, the simultaneous equation
{█({B1 = p1 + p2 + 2v1 + 2v2 + · · · + 2vk ,@B2 = p3 + p4 + 2v1 + 2v2 + · · · + 2vk ,)┤ (1)
is solvable, where p1, · · · , p4 are odd primes, each vi is a positive integer, and the positive integer k ≥ 63 or ≥ 31 under the generalized Riemann
hypothesis. Note that, in 1989, M.C. Liu and K.M. Tsang have obtained that subject to some natural conditions on the coefficients, every pair of linear equations in five prime variables is solvable. Therefore one class of pairs of linear equations in four prime variables with special coefficient matrix and powers of two is considered. Indeed, it is deduced that every pair of integers B1 and B2 satisfying B1 ≡ 0 (mod 2), 3BB1 > e^(eB^48 ), B2 ≡ ∑_1^4▒= 1^(a_i ) (mod 2) and |B2| < BB1, where B = max1≤j≤4(2, |aj|), can be represented as
{█(B1 = 〖p1〗_1 + p2 + 2^(v_1 ) + 2^(v_2 )+ · · · + 2^(v_k )@B2 = a1p1 + a2p2 + a3p3 + a4p4 + 2^(v_1 )+ 2^(v_2 )+ · · · + 2^(v_k ) )┤ (2)
with k being a positive integer. Here p1, · · · p4 are odd primes, each 〖v 〗_iis a positive integer and the integral coefficients ai (i = 1, 2, 3, 4) satisfy
{█((〖a 〗_1- 〖a 〗_2, 〖a 〗_3, 〖a 〗_4) = 1,@〖a 〗_1 〖a 〗_2< 0, 〖a 〗_3 〖a 〗_4<0,)┤
Moreover it is calculated that the positive integer k ≥ g(〖a 〗_1- 〖a 〗_2, 〖a 〗_3, 〖a 〗_4) where g(〖a 〗_21- 〖a 〗_22, 〖a 〗_23, 〖a 〗_24) = [(log〖G(〖a 〗_21, …, 〖a 〗_24 〗)-log〖F (〖a 〗_21, …, 〖a 〗_24)〗)/log0.975805-84.0285], (3)
G(〖a 〗_21, 〖a 〗_22, 〖a 〗_23, 〖a 〗_24) = (min(1/(|a_24 |), 1/(|a_23 |)) - (〖|a〗_(21 )- a_22 |)/(|〖a_23 a〗_24 |) 〖(3B)〗^(-1) ×〖(3B)〗^(-1) (1-0.000001)- 〖(3B)〗^(-1-4), with B = max1≤j≤4(2, |a2j|), and
F(a_21, …, a_24) = √(f(a_21)f〖(a〗_22 ))
with
f(a_2i) = {█(4414.15h (a_21-1)+5.088331 if a_21≠1@59.8411 if a_21=1,)┤
for i = 1, 2, and h(n) =∏_(p|n,p>2)▒(p-1)/(p-2). This result, if without the powers of
two, can make up some of the cases excluded in Green and Tao’s paper.published_or_final_version
Mathematics
Doctoral
Doctor of Philosophy
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Peat, Rhona Margaret. "Fractional powers of operators and mellin multipliers." Thesis, University of Strathclyde, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366801.
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Song, Xuefeng. "Dynamic modeling issues for power system applications." Texas A&M University, 2003. http://hdl.handle.net/1969.1/1591.
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Power system dynamics are commonly modeled by parameter dependent nonlinear differential-algebraic equations (DAE) x p y x f ) and 0 = p y x g ) . Due to
(,, (,, the algebraic constraints, we cannot directly perform integration based on the DAE. Traditionally, we use implicit function theorem to solve for fast variables y to get a reduced model in terms of slow dynamics locally around x or we compute y numerically at each x . However, it is well known that solving nonlinear algebraic equations analytically is quite difficult and numerical solution methods also face many uncertainties since nonlinear algebraic equations may have many solutions, especially around bifurcation points. In this thesis, we apply the singular perturbation method to model power system dynamics in a singularly perturbed ODE (ordinary-differential equation) form, which makes it easier to observe time responses and trace bifurcations without reduction process. The requirements of introducing the fast dynamics are investigated and the complexities in the procedures are explored. Finally, we propose PTE (Perturb and Taylors expansion) technique to carry out our goal to convert a DAE to an explicit state space form of ODE. A simplified unreduced Jacobian matrix is also introduced. A dynamic voltage stability case shows that the proposed method works well without complicating the applications.
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Masaki, Satoshi. "Asymptotic expansion of solutions to the nonlinear Schrödinger equation with power nonlinearity." 京都大学 (Kyoto University), 2009. http://hdl.handle.net/2433/124383.
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Teixeira, Denis Leocádio. "Determinação do gradiente de pressão estática do ar para sistemas de compostagem por aeração forçada." Universidade Federal de Viçosa, 2014. http://locus.ufv.br/handle/123456789/3672.
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Although there equations and graphics in scientific literature to estimate the static pressure gradient of airflow through layers of grains and seeds, studies using organic waste submitted to composting treatment are scarce. The objective of this study was to adjust equations to estimate the static pressure gradient of airflow through layers of different organic residues. The waste used were chicken litter and as bulking agents and carbon source: sugarcane bagasse, sawdust and coffee husk which were mixed in the ratio of 0; 10; 20; 30 e 40% (volumetric basis), of chicken litter in relation to bulking agents, as well as mixture with C/N ratio of 25/1, which were submitted to composting process. Measurements of static pressure drop in layers of organic waste before and after the composting process, and in layers of material from the different proportions of chicken litter added to bulking agents, were performed using a prototype with specific airflow rates ranging from 0.02 to 0.13 m 3 s -1 m -2. The static pressure drop of airflow increased as a power of the material layer thickness. Static pressure gradient in layers of organic waste decrease with the composting process. Shedd, Hukill & Ives and Hunter models may be used to predict the static pressure gradient of air to be blown through the organic residues layers, however, the Shedd model was that which best represented the phenomenon studied. Lower values of static pressure gradient were obtained in layers without chicken litter and the higher values obtained in layers composed of mixture of chicken litter in proportion of 40%. Equations to estimate the static pressure gradient for different proportions of chicken litter may be clustered, yielding models that can explain the variation of pressure gradient for each bulking agent and carbon source.
Embora existam, na literatura científica, equações e gráficos para estimativa do gradiente de pressão estática do ar, quando forçado em camadas de grãos e sementes, são poucos os trabalhos realizados utilizando-se resíduos orgânicos submetidos ao tratamento por compostagem. Neste trabalho, teve-se por objetivo o ajuste de equações que possibilitassem a estimativa do gradiente de pressão estática do ar, quando insuflado em camadas de diferentes materiais orgânicos. Os resíduos utilizados foram a cama de frango e, como agentes estruturantes e fonte de carbono, o bagaço de cana-de-açúcar, a serragem de madeira e a palha de café, os quais foram misturados nas proporções de 0; 10; 20; 30 e 40% (base volumétrica) de cama de frango em relação aos agentes estruturantes, além de misturas com relação C/N de 25/1, as quais foram submetidas ao tratamento por compostagem. As medições da queda de pressão estática do ar, ao atravessar camadas de material orgânico, antes e depois de ter sido submetido ao tratamento por compostagem, e nas camadas de materiais provenientes das diferentes proporções de cama de frango adicionada aos agentes estruturantes, foram realizadas utilizando-se um protótipo, no qual o material foi submetido a vazões específicas de ar que variaram de 0,02 a 0,13 m 3 s -1 m -2 . A queda na pressão estática do ar aumentou de forma potencial com a espessura da camada de material. No que se refere ao decurso do processo de compostagem, este contribuiu para redução do gradiente de pressão estática do ar ao atravessar as camadas de material orgânico. Os modelos matemáticos de Shedd, Hukill & Ives e Hunter podem ser utilizados para predizer o gradiente de pressão estática do ar, ao ser insuflado em camadas de resíduos orgânicos, no entanto, o modelo de Shedd pode ser considerado, em termos estatísticos, o que melhor representou o fenômeno em estudo. Menores valores de gradientes de pressão estática do ar foram obtidos em camadas sem adição de cama de frango e os maiores obtidos nas camadas constituídas pela mistura com cama de frango na proporção de 40%. As equações obtidas para estimativa do gradiente de pressão estática do ar, para as diferentes proporções de cama de frango, podem ser agrupadas, originando modelos capazes de explicar a variação do gradiente de pressão para cada agente estruturante e fonte de carbono.
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CRUZ, Thamires Santos. "Uma teoria de regularidade para equações de volterra fracionárias com dados iniciais locais e não locais." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18454.
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CNPQ
Este trabalho trata da teoria de existência, unicidade, regularidade, continuação e alternativa de Blow-up de solução brandas para Equação de Volterra Fracionarias com condições iniciais locais cujo termo não linear satisfaz certas propriedades localmente Lipschitz. Analisamos também o caso de condições iniciais não locais e não linearidades verificando condições do tipo Caratheodory. Neste caso estudamos as propriedades topológicas do conjunto soluções de tais equações.
his work deals with existence, uniqueness, regularity, continuation and Blow up Alternative of mild solutions for Fractional Volterra Equations with local initial conditions, whose nonlinear terms satisfy some locally Lipschitz properties. Moreover we analyse thecase of nonlocal initial conditions and nonlinearities of Caratheodory type. In this case, we study topological properties of the solution set of such equations.
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Gu, Chunguang 1970. "Constitutive equations for granular materials : application to dry sand and powder metal." Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/9263.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2000.Includes bibliographical references (leaves 138-139).
Strain localization into shear bands is commonly observed in natural soil masses, as well as in human-built embankments, footings, retaining walls and other geotechnical structures. Although the onset of strain localization can be derived from standard bifurcation analyses, few numerical simulations of the complete process of strain localization in granular materials have been previously reported. Predictions for the onset and process of shear band formation are critically dependent upon the constitutive equations employed. In this thesis, a new physically based constitutive model is formulated for describing the plastic flow of cohesionless granular materials. This constitutive model has been implemented in the finite element package ABAQUS/explicit(1999) and is used to predict the strain localization in geomaterials. The numerical calculations are shown to be in good quantitative agreement with the recent corresponding experiments of Han and Drescher(1993) and Alsiny et al. (1992) on the localization in dry Ottawa sand under low pressure conditions. The physical description for the plastic flow enables the model to reproduce the macroscopic stress strain response and the complete strain localization process. The complex evolution of the strain localization from "Riedel shear" to "boundary shear" in the shearing experiment of a simulated gouge layer (Marone et al., 1990,1999) has been captured in our simulations. This physically based constitutive model is also able to predict the startling "stress dip" in a static sandpile - the vertical stress is not maximum under the apex of the pile, but shows a local dip there. Next, we shall focus on metal powders, which are commonly used in powder metallurgy industry to form net- or near-net-shaped components with high relative density by cold compaction. A new constitutive model for cold compaction of metal powders has been developed. The plastic flow of metal powders at the macroscopic level is assumed to be representable as a combination of a distortion mechanism, and a consolidation mechanism. For the distortion mechanism the model employs a pressure-sensitive, Mohr-Coulomb type yield condition, and a new physically based non-associated flow rule. For the consolidation mechanism the model employs a smooth yield function which has a quarter-elliptical shape in the mean-normal pressure and the equivalent shear stress plane, together with an associated flow rule. The constitutive model has been implemented in a finite element program. The material parameters in the constitutive model have been calibrated for MH-100 iron powder by fitting the model to reproduce data from true triaxial compression experiments, torsion ring-shear experiments, and simple compression experiments. The predictive capability of the constitutive model and computational procedure is checked by simulating two simple powder forming processes: (i) a uniaxial strain compression of a cylindrical sample, and (ii) forming of a conical shaped-charge liner. In both cases the predicted load-displacement curves and density variations in the compacted specimens are shown to compare well with corresponding experimental measurements.
by Chunguang Gu.
Ph.D.
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Martin, Andrew John. "A High Performance Parallel Sparse Linear Equation Solver Using CUDA." Kent State University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=kent1310603635.
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Brown, Robert Winston, and rwb@rmit edu au. "Electrical and Thermal Modelling of Low Power Metallised Polypropylene Capacitors." RMIT University. Electrical and Computer Engineering, 2007. http://adt.lib.rmit.edu.au/adt/public/adt-VIT20080130.155318.
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Metallised polypropylene (MPP) capacitors, the dominant capacitor type used in a wide range of power and electronic circuit applications, offer high volumetric capacitor density, low cost, excellent frequency characteristics and a unique ability to recover from point failures in the dielectric film. However MPP capacitors have a generic weakness that is not well understood, failure of the self-healing process leading to ongoing catastrophic failure. The work described in this thesis includes the derivation of an improved electrical model of a capacitor and the uncovering of a mechanism for the catastrophic failure mode. Corrosion of the thin metallic field is firmly linked to drastic increases in metal film current densities and generation of hot spots in capacitors. In the work, novel formulae were derived relating capacitor parameters such as equivalent series resistance and equivalent series capacitance to frequency and physical characteristics such as metal film resistivity and physical dimensions of multiple layer capacitors. Modelling using numerical methods and diffusion equation showed that capacitors with double-end connection topology have more uniform voltage and power distribution than single-end connected capacitors. External characteristics of both connection topologies were shown to be virtually identical up to frequencies well above typical self-resonance. The aggregate spatial distribution of power from both layers and the voltage across the dielectric were found to be fundamentally different in the two circuit connection topologies. In this work it was shown that above singularity frequencies defined by distributed capacitance and metal film spreading resistance, equivalent series resistance and capacitance both fall with the square root of frequency Analysis of the inductance of typical MPP capacitors for single-end and double-end connected topologies and for circumferentially connected capacitor metallization showed that the magnitude and effect of distributed inductance in typical MPP power capacitors was insignificant compared to packaging inductance. Thermal and electrical modelling and experimental measurements showed that corrosion effects could readily account for the generic catastrophic failure mode of metallised polypropylene capacitors. Modelling showed that remnant vestiges of metal bridging corrosion gaps between the schooping and the metallic film could also pose serious thermal danger to the affected capacitor. Fusing current modelling and experimental measurement showed that fusing in metallic films typically occurred for current densities of several hundred thousand amperes per square centimetre. The partial disconnection of the metallic layers from the schooping edge by corrosion for example, was shown to result in large increases in dissipation factor and power loss in a capacitor readily explaining how capacitors
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Guarguaglini, Marco. "Laser-driven shock compression of liquid mixtures and silica up to extreme thermodynamic conditions of interest for planetary interior models." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLX075/document.
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L’étude du comportement des composantes des intérieurs planétaires dans des conditions extrêmes de pression (megabar) et température (milliers de Kelvin) est essentielle afin de construire des modèles fiables décrivant l’évolution et la structure des planètes. Dans ce travail, nous avons étudié plusieurs composantes par compression par choc laser sur les installations LULI2000 (France) et GEKKO XII (Japon).Nous avons employé des chocs décroissants pour étudier des conditions de haute-pression / haute-température. Afin d’accéder à des conditions de température modérée, nous avons utilisé des techniques de pre-compression statique (couplage compression par choc — cellules à enclumes de diamant) et dynamique (génération de doubles chocs).Nous avons étudié l’équation d’état des mélanges eau-ethanol-ammoniac et de l’eau et ammoniac purs, d’intérêt pour la description des intérieurs des planètes géantes de glace. L’étude de l’ammoniac a été particulièrement délicate en raison de sa forte réactivité et donc de la complexité du design des cibles ; nous présentons les premières données obtenues par choc laser, dans un domaine de pression jamais exploré. Les données des mélanges confirment des calculs ab initio récents basés sur une approximation de mélange linéaire.Nous avons également mesuré la réflectivité des mélanges liquides et de la silice, une composante-clé des intérieurs des planètes terrestres. Nous avons ensuite estimé la conductivité électrique — un paramètre crucial pour modéliser la génération des champs magnétiques planétaires dans les intérieurs via un mécanisme dynamo — de ces composantes.Eau, ammoniac et mélanges eau-ethanol-ammoniac affichent des réflectivités différentes, ce qui suggère que l’eau pure ne peut pas être considérée comme représentative des mélanges planétaires dans les modèles dynamo.Par ailleurs, nous avons apporté une confirmation expérimentale de calculs ab initio récents selon lesquels la conductivité de la silice n’est pas monotone le long d’une ligne isotherme pour des températures modérées.Nos données supportent des calculs qui prédisent qu’une dynamo peut avoir lieu dans les océans de magma dans des super-Terres ainsi que dans la jeune TerreCharacterising the behaviour of planetary interiors’ components at extreme conditions (megabar pressures, temperatures of a few thousand Kelvin) is essential to build reliable models describing the evolution and structure of planets. In this thesis, we investigated various components on a wide set of conditions using laser-driven shock compression techniques at the LULI2000 (France) and GEKKO XII (Japan) facilities.Single decaying shocks were employed to study high-pressure / high-temperature states. To reach moderate-temperature conditions, closer to planetary interior profiles, we employed static and dynamic pre-compression techniques coupling Diamond Anvil Cells to shock compression and generating double shocks, respectively.We studied the equation of state of water-ethanol-ammonia mixtures and of pure liquid water and ammonia, of interest for icy giant structure models. Pure ammonia measurements have been particularly challenging due to cell design complexity in reason of its reactivity; we provide the first data obtained with laser shocks, in a pressure domain up to now unexplored. Mixtures data are in agreement with recent ab initio calculations based on the linear mixing approximation.We measured the optical reflectivity of liquid mixtures and silica, a key component of rocky planets’ interiors. From reflectivity data we estimated the electrical conductivity of such components — a crucial parameter for modelling the generation of planetary magnetic fields in the interiors via a dynamo mechanism.Water, ammonia, and water-ethanol-ammonia mixtures exhibit different reflectivity (hence conductivity) behaviours as a function of pressure and temperature. This suggests that pure water should not be used in dynamo models as representative of the icy mixtures.Moreover, we provide the first experimental confirmation of recent ab initio studies showing that the conductivity of silica along isothermal lines is not monotonic at moderate temperatures. Our data provide experimental support for the calculations predicting a dynamo action to occur in super-Earths’ and early Earth’s magma oceans
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Dowling, Alexander W. "An Equation-based Framework for Large-Scale Flowsheet Optimization and Applications for Oxycombustion Power System Design." Research Showcase @ CMU, 2015. http://repository.cmu.edu/dissertations/568.
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Over the past thirty years, flowsheet optimization methods have evolved from “black box” approaches to sophisticated equation-oriented methods for simultaneous flowsheet convergence and optimization. This thesis explores the next generation of flowsheet optimization tools that leverage completely open models (with exact first and second derivatives) and utilizes start-of-theart nonlinear programming (optimization) solvers. A five part framework is proposed in this thesis: 1. Embedded cubic equation of state thermodynamic models with complementarity constraints to accommodate vanishing and reappearing phases 2. Simultaneous heat integration and process optimization using the pinch location method 3. Aggregate short-cut and rigorous tray-by-tray distillation models 4. Steam cycle equipment (e.g., turbine) and boiler models 5. Trust region optimization algorithm to incorporate models with expensive derivatives into the equations-based framework A systematic initialization routine based on model refinement and multistart procedure are also presented as practical alternatives to global optimization. Complementarity constraints are used throughout the framework to model switches, such as vanishing phases. Degeneracy Hunter, an algorithm that identifies irreducible sets of degenerate constraints (i.e., constraints with a rank deficient Jacobian) is proposed and used to refine the models. The framework is demonstrated in a series of case studies related to the design of oxycombustion power systems with CO2 capture. Two case studies focus on the simultaneous optimization of gases separation systems and their accompanying multistream heat exchangers. In one of these case studies, the optimization procedure identifies common air separation unit configurations with comparable specific energy requirements to industrial designs. The framework is also used to optimize regenerate Rankine cycles, where steam flowrates from nine extraction points for boiler feedwater heating are considered as optimization variables. This allows for waste heat from compression to the completely integrated into the steam cycle. Steam table lookups (without derivatives) are incorporated using reduced models and a trust region optimization algorithm.
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WENG, CHIYUAN. "Transient Stability Analysis of Power Systems with Energy Storage." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1348453228.
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Лютий, Тарас Володимирович, Тарас Владимирович Лютый, Taras Volodymyrovych Liutyi, Станіслав Іванович Денисов, Станислав Иванович Денисов, Stanislav Ivanovych Denysov, Олександр Юрійович Поляков, Александр Юрьевич Поляков, Oleksandr Yuriiovych Poliakov, and C. Binns. "Power Loss of the Nanoparticle Magnetic Moment in Alternating Fields." Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/35370.
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Using the Landau-Lifshitz equation, the dependencies of the power loss of the nanoparticle magnetic
moment on the amplitude and frequency of alternating magnetic fields are calculated numerically. A special
attention is paid to the different precessional modes of the magnetic moment and their influence on
power loss value. The results for the circularly and linearly polarized fields are compared in order to choose
the optimal one with respect to the power loss.
When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/35370
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Tekaya, Wajdi. "Risk neutral and risk averse approaches to multistage stochastic programming with applications to hydrothermal operation planning problems." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47582.
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The main objective of this thesis is to investigate risk neutral and risk averse approaches to multistage stochastic programming with applications to hydrothermal operation planning problems. The purpose of hydrothermal system operation planning is to define an operation strategy which, for each stage of the planning period, given the system state at the beginning of the stage, produces generation targets for each plant. This problem can be formulated as a large scale multistage stochastic linear programming problem. The energy rationing that took place in Brazil in the period 2001/2002 raised the question of whether a policy that is based on a criterion of minimizing the expected cost (i.e. risk neutral approach) is a valid one when it comes to meet the day-to-day supply requirements and taking into account severe weather conditions that may occur. The risk averse methodology provides a suitable framework to remedy these deficiencies. This thesis attempts to provide a better understanding of the risk averse methodology from the practice perspective and suggests further possible alternatives using robust optimization techniques. The questions investigated and the contributions of this thesis are as follows.
First, we suggest a multiplicative autoregressive time series model for the energy inflows that can be embedded into the optimization problem that we investigate. Then, computational aspects related to the stochastic dual dynamic programming (SDDP) algorithm are discussed. We investigate the stopping criteria of the algorithm and provide a framework for assessing the quality of the policy. The SDDP method works reasonably well when the number of state variables is relatively small while the number of stages can be large. However, as the number of state variables increases the convergence of the SDDP algorithm can become very slow. Afterwards, performance improvement techniques of the algorithm are discussed. We suggest a subroutine to eliminate the redundant cutting planes in the future cost functions description which allows a considerable speed up factor. Also, a design using high performance computing techniques is discussed. Moreover, an analysis of the obtained policy is outlined with focus on specific aspects of the long term operation planning problem. In the risk neutral framework, extreme events can occur and might cause considerable social costs. These costs can translate into blackouts or forced rationing similarly to what happened in 2001/2002 crisis. Finally, issues related to variability of the SAA problems and sensitivity to initial conditions are studied. No significant variability of the SAA problems is observed.
Second, we analyze the risk averse approach and its application to the hydrothermal operation planning problem. A review of the methodology is suggested and a generic description of the SDDP method for coherent risk measures is presented. A detailed study of the risk averse policy is outlined for the hydrothermal operation planning problem using different risk measures. The adaptive risk averse approach is discussed under two different perspectives: one through the mean-$avr$ and the other through the mean-upper-semideviation risk measures. Computational aspects for the hydrothermal system operation planning problem of the Brazilian interconnected power system are discussed and the contributions of the risk averse methodology when compared to the risk neutral approach are presented. We have seen that the risk averse approach ensures a reduction in the high quantile values of the individual stage costs. This protection comes with an increase of the average policy value - the price of risk aversion. Furthermore, both of the risk averse approaches come with practically no extra computational effort and, similarly to the risk neutral method, there was no significant variability of the SAA problems.
Finally, a methodology that combines robust and stochastic programming approaches is investigated. In many situations, such as the operation planning problem, the involved uncertain parameters can be naturally divided into two groups, for one group the robust approach makes sense while for the other the stochastic programming approach is more appropriate. The basic ideas are discussed in the multistage setting and a formulation with the corresponding dynamic programming equations is presented. A variant of the SDDP algorithm for solving this class of problems is suggested. The contributions of this methodology are illustrated with computational experiments of the hydrothermal operation planning problem and a comparison with the risk neutral and risk averse approaches is presented. The worst-case-expectation approach constructs a policy that is less sensitive to unexpected demand increase with a reasonable loss on average when compared to the risk neutral method. Also, we comp are the suggested method with a risk averse approach based on coherent risk measures. On the one hand, the idea behind the risk averse method is to allow a trade off between loss on average and immunity against unexpected extreme scenarios. On the other hand, the worst-case-expectation approach consists in a trade off between a loss on average and immunity against unanticipated demand increase. In some sense, there is a certain equivalence between the policies constructed using each of these methods.
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Lindsay, Tara Reeves. "Applying Adaptive Prognostics to Rolling Element Bearings." Thesis, Georgia Institute of Technology, 2005. http://hdl.handle.net/1853/7568.
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Rolling element bearing failure can cause problems for industries ranging from mild inconveniences such as simple replacement to catastrophic damage such as large production-line equipment failure. Rolling element bearing failure has plagued industries for many years. Bearings are currently monitored to determine whether or not there is a defect in the bearing, but the remaining lifetime of the bearing remains unknown. This research estimates the bearings remaining lifetime through digital signal processing in conjunction with a modified version of Pariss equationa fatigue-failure equation well known in rotating machinery prognostics.
An energy quantity, coined the Power Spectrum Value (PSV), is the maximum amplitude of the frequencies within a relatively small band around the resonant frequency of the system. The current PSV is estimated and updated using a chronologically weighted least squares algorithm. It is this PSV which is implemented in the modified Paris equation to determine the remaining lifetime of the bearing. This research presents a non-intrusive method of determining the lifetime of the bearing so that the bearings utility is maximized and reactive maintenance procedures are minimized.
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MARTINS, FERNANDO R. "Medidas de parametros nucleares de um reator de potencia zero aplicando a tecnica de analise de ruidos." reponame:Repositório Institucional do IPEN, 1992. http://repositorio.ipen.br:8080/xmlui/handle/123456789/10294.
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Dissertacao (Mestrado)
IPEN/D
Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP
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Whitman, Daniel Joseph. "Electromagnetic Fields, Power Losses, and Resistance of High-Frequency Magnetic Devices." Wright State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=wright1268951694.
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Kuntz, Sarah Louise. "Feasibility of Attaining Fully Equiaxed Microstructure through Process Variable Control for Additive Manufacturing of Ti-6Al-4V." Wright State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=wright1464557846.
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Wang, Rui. "Distributed Cooperative Communications and Wireless Power Transfer." Digital WPI, 2018. https://digitalcommons.wpi.edu/etd-dissertations/62.
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In telecommunications, distributed cooperative communications refer to techniques which allow different users in a wireless network to share or combine their information in order to increase diversity gain or power gain. Unlike conventional point-to-point communications maximizing the performance of the individual link, distributed cooperative communications enable multiple users to collaborate with each other to achieve an overall improvement in performance, e.g., improved range and data rates.
The first part of this dissertation focuses the problem of jointly decoding binary messages from a single distant transmitter to a cooperative receive cluster. The outage probability of distributed reception with binary hard decision exchanges is compared with the outage probability of ideal receive beamforming with unquantized observation exchanges. Low- dimensional analysis and numerical results show, via two simple but surprisingly good approximations, that the outage probability performance of distributed reception with hard decision exchanges is well-predicted by the SNR of ideal receive beamforming after subtracting a hard decision penalty of slightly less than 2 dB. These results, developed in non-asymptotic regimes, are consistent with prior asymptotic results (for a large number of nodes and low per-node SNR) on hard decisions in binary communication systems.
We next consider the problem of estimating and tracking channels in a distributed transmission system with multiple transmitters and multiple receivers. In order to track and predict the effective channel between each transmit node and each receive node to facilitate coherent transmission, a linear time-invariant state- space model is developed and is shown to be observable but nonstabilizable. To quantify the steady-state performance of a Kalman filter channel tracker, two methods are developed to efficiently compute the steady-state prediction covariance. An asymptotic analysis is also presented for the homogenous oscillator case for systems with a large number of transmit and receive nodes with closed-form results for all of the elements in the asymptotic prediction covariance as a function of the carrier frequency, oscillator parameters, and channel measurement period. Numeric results confirm the analysis and demonstrate the effect of the oscillator parameters on the ability of the distributed transmission system to achieve coherent transmission.
In recent years, the development of efficient radio frequency (RF) radiation wireless power transfer (WPT) systems has become an active research area, motivated by the widespread use of low-power devices that can be charged wirelessly. In this dissertation, we next consider a time division multiple access scenario where a wireless access point transmits to a group of users which harvest the energy and then use this energy to transmit back to the access point. Past approaches have found the optimal time allocation to maximize sum throughput under the assumption that the users must use all of their harvested power in each block of the "harvest-then-transmit" protocol. This dissertation considers optimal time and energy allocation to maximize the sum throughput for the case when the nodes can save energy for later blocks. To maximize the sum throughput over a finite horizon, the initial optimization problem is separated into two sub-problems and finally can be formulated into a standard box- constrained optimization problem, which can be solved efficiently. A tight upper bound is derived by relaxing the energy harvesting causality.
A disadvantage of RF-radiation based WPT is that path loss effects can significantly reduce the amount of power received by energy harvesting devices. To overcome this problem, recent investigations have considered the use of distributed transmit beamforming (DTB) in wireless communication systems where two or more individual transmit nodes pool their antenna resources to emulate a virtual antenna array. In order to take the advantages of the DTB in the WPT, in this dissertation, we study the optimization of the feedback rate to maximize the energy efficiency in the WPT system. Since periodic feedback improves the beamforming gain but requires the receivers to expend energy, there is a fundamental tradeoff between the feedback period and the efficiency of the WPT system. We develop a new model to combine WPT and DTB and explicitly account for independent oscillator dynamics and the cost of feedback energy from the receive nodes. We then formulate a "Normalized Weighted Mean Energy Harvesting Rate" (NWMEHR) maximization problem to select the feedback period to maximize the weighted averaged amount of net energy harvested by the receive nodes per unit of time as a function of the oscillator parameters. We develop an explicit method to numerically calculate the globally optimal feedback period.
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Mukherjee, Swagato. "Parabolic Wave Equation based Model for Propagation through Complex and Random Environments." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595529187539516.
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Abraham, Etimbuk. "Adaptive supervisory control scheme for voltage controlled demand response in power systems." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/adaptive-supervisory-control-scheme-for-voltage-controlled-demand-response-in-power-systems(3e64537d-52c7-4eb5-87f2-b73fe920b9cb).html.
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Radical changes to present day power systems will lead to power systems with a significant penetration of renewable energy sources and smartness, expressed in an extensive utilization of novel sensors and cyber secure Information and Communication Technology. Although these renewable energy sources prove to contribute to the reduction of CO2 emissions into the environment, its high penetration affects power system dynamic performance as a result of reduced power system inertia as well as less flexibility with regards to dispatching generation to balance future demand. These pose a threat both to the security and stability of future power systems. It is therefore very important to develop new methods through which power system security and stability can be maintained. This research investigated the development of methods through which the contributions of on-load tap changing transformers/transformer clusters could be assessed with the intent of developing real time adaptive voltage controlled demand response schemes for power systems. The development of such a scheme enables more active system components to be involved in the provision of frequency control as an ancillary service and deploys a new frequency control service with low infrastructural investment, bearing in mind that OLTC transformers are already very prevalent in power systems. In this thesis, a novel online adaptive supervisory controller for ensuring optimal dispatch of voltage-controlled demand response resources is developed. This novel controller is designed using the assessment results of OLTC transformer impacts on steady-state frequency and was tested for a variety of scenarios. To achieve the effective performance of the adaptive supervisory controller, the extensive use of statistical techniques for assessing OLTC transformer contributions to voltage controlled demand response is presented. This thesis also includes the use of unsupervised machine learning techniques for power system partitioning and the further use of statistical methods for assessing the contributions of OLTC transformer aggregates.
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Su, Heyin. "Modeling of Proposed Changes to SIUC Central Heating, Air-Conditioning, and Power Plant Incorporating Variable Frequency Drive (VFD) and High Efficiency Turbine." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/708.
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Currently, the Southern Illinois University Carbondale (SIUC) power plant produces steam at high pressure to drive a high pressure (HP) turbine to make a portion of the electrical power needed by campus, then using 969 kPa (125 psig) steam to provide hot water all year, heat buildings, and to operate a low pressure (LP) turbine that powers the compressor of the central air conditioning (A/C) system. In the proposed system, the HP turbine is replaced by a much higher efficiency, multi-level turbine, the LP turbine is replaced with a motor and Variable Frequency Drive (VFD), and a cooling tower is added to condense more possible steam. This thesis has provided computer models to evaluate the economical feasibility of the proposed system, which are written by using Engineering Equation Solver (EES) software. The results of the study are presented in two cases. Case 1 examines the same amount of coal use between current and proposed systems, while Case 2 exames operating the high pressure boiler at the maximum rate. The results are a cost savings of $1,921,000 and $3,604,000 with payback periods of 4 and 2.2 years for Case 1 and Case 2, respectively. The annual primary energy saved and CO2 reduction from this modification was 200,000 GJ and 564,814 moles, respectively.
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Dolan, Amanda Avery. "Synthesizing Undergraduate College Student Persistence: A Meta-analytic Structural Equation Model." Kent State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=kent1554756614807579.
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Mahmoodi, Foad. "Compression Mechanics of Powders and Granular Materials Probed by Force Distributions and a Micromechanically Based Compaction Equation." Doctoral thesis, Uppsala universitet, Institutionen för farmaci, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-171874.
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The internal dynamics of powder systems under compression are as of yet not fully understood, and thus there is a necessity for approaches that can help in further clarifying and enhancing the level of understanding on this subject. To this end, the internal dynamics of powder systems under compression were probed by means of force distributions and a novel compaction equation. The determination of force distributions hinged on the use of carbon paper as a force sensor, where the imprints transferred from it onto white paper where converted through calibration into forces. Through analysis of these imprints, it was found that the absence of friction and bonding capacity between the particles composing the powder bed had no effect on how the applied load was transferred through the system. Additionally, it was found that pellet strength had a role to play in the homogeneity of force distributions, where, upon the occurrence of fracture, force distributions became less homogenous. A novel compaction equation was derived and tested on a series of systems composed of pellets with differing mechanical properties. The main value of the equation lay in its ability to predict compression behavior from single particle properties, and the agreement was especially good when a compact of zero porosity was formed. The utility of the equation was tested in two further studies, using a series of pharmaceutically relevant powder materials. It was established that the A parameter of the equation was a measure of the deformability of the powder material, much like the Heckel 1/K parameter, and can be used as a means to rank powders according to deformability, i.e. to establish plasticity scale. The equation also provided insights into the dominating compression mechanisms through an invariance that could be exploited to determine the point, at which the powder system became constrained, i.e. the end of rearrangement. Additionally, the robustness of the equation was demonstrated through fruitful analysis of a set of diverse materials. In summary, this thesis has provided insights and tools that can be translated into more efficient development and manufacturing of medicines in the form of tablets.
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Kipps, Mark Rew. "A modular approach to modeling an isolated power system on a finite voltage bus using a differential algebraic equation solving routine." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1994. http://handle.dtic.mil/100.2/ADA281036.
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Štumpf, Martin. "Implementation and Test of a 2D-integral-equation MoM-algorithm for the Analysis of Power-Bus Structures on Printed Circuit Boards." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217683.
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Tato práce se zabývá analýzou power-bus struktur využitím metody založené na formulaci problému 2D hraniční integrální rovnicí ve frekvenční oblasti. Uvedená metoda byla implementována v Matlabu. Program umožňuje analyzovat obecné polygonální power-bus struktury s možností nastavení parametrů substrátu a libovolného počtu a umístění budících portů. Výstupem programu je frekvenční závislost rozložení elektrického pole mezi deskami struktury, vztahy mezi porty struktury vyjádřené např. impedanční maticí a vyzařovací diagram. Dále byla implementována možnost převodu výsledné impedanční matice do tzv. Touchstone formátu, pomocí něhož je možné modelovat analyzované struktury jako obecné N-porty (např. v ANSOFT Designeru), což umožňuje analýzu power-bus struktur s dalšími obvodovými prvky. Výsledky byly ověřeny pomocí existujících analytických vztahů pro jednoduché obdélníkové struktury, využitím komerčního simulačního programu a praktickým experimentem.
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Macêdo, Renata Araripe de. "Algoritmo baseado na equação diferencial para proteção rápida de linhas de transmissão." Universidade de São Paulo, 2000. http://www.teses.usp.br/teses/disponiveis/18/18133/tde-16042018-145737/.
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Este trabalho apresenta o desenvolvimento de um algoritmo baseado na modelagem do sistema de transmissão por meio de equações diferenciais, formuladas através dos parâmetros resistência e indutância da linha de transmissão a ser protegida. Nesta abordagem não é necessário que a entrada do algoritmo seja puramente senoidal, admitindo-se a presença de harmônicos e componentes CC presentes na falta como parte da solução do problema. Utilizou-se o software ATP para a modelagem do sistema elétrico estudado e a obtenção do conjunto de dados para análise e testes, permitindo-se a representação detalhada da linha de transmissão por meio das características dos condutores e suas respectivas disposições geométricas nas torres de transmissão, além da modelagem das diversas manobras e defeitos que os afetam, buscando-se uma aproximação com uma situação real. Com relação ao uso direto das equações diferenciais para a tarefa de proteção das linhas, constatou-se que sua aplicação não produz uma estimativa aceitável para ser usada em relés digitais por possuírem convergência em tempos normalmente superiores a dois ciclos. Assim, foi feita uma filtragem das respostas do algoritmo, proporcionando-se um diagnóstico mais rápido das estimativas. Para isso foi usado um filtro de mediana de 5ª ordem para o cálculo da localização da falta. Para todos os tipos de falta testados, a estimativa da localização da falta com o uso do referido filtro mostrou-se altamente satisfatória para a finalidade de proteção, convergindo em menos de um ciclo e meio de pós-falta, após a filtragem das estimativas, imprimindo maior velocidade de resposta para os relés digitais.The present work shows the development of an algorithm based on the modeling of the transmission system utilizing differential equations. The differential equation for the line is solved having its resistance and inductance as parameters. In this approach there is no need for the algorithm inputs to be pure sinusoidal, allowing the presence of harmonic and DC components in the line as a part of the solution to the problem. The software ATP was utilized for the modeling of the electric system under study as well as data collection for analysis and tests. This representation allowed a detailed representation of the transmission line through the characteristics of the conductors and its geometrical disposition in the transmission towers, as well as the simulation of faults that usually affect the electric system, reproducing a realistic situation. The direct use of differential equations do not give an acceptable estimation as far as digital relays are concerned because they have convergence times over two cycles. In this sense, a 5th order median filter was utilized, providing faster diagnosis for the fault location estimation. The estimation of the fault location has proved to be a coherent criteria for the algorithm. For the fault types tested, the estimation for the fault location utilizing line parameters has shown itself highly satisfactory for protection purposes. This work has shown that the algorithm oulputs converge in less than 1 and a half cycles afler the fault occurrence, presenting a much faster response for digital relays.
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Vellmer, Sebastian. "Applications of the Fokker-Planck Equation in Computational and Cognitive Neuroscience." Doctoral thesis, Humboldt-Universität zu Berlin, 2020. http://dx.doi.org/10.18452/21597.
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In dieser Arbeit werden mithilfe der Fokker-Planck-Gleichung die Statistiken, vor allem die Leistungsspektren, von Punktprozessen berechnet, die von mehrdimensionalen Integratorneuronen [Engl. integrate-and-fire (IF) neuron],
Netzwerken von IF Neuronen und Entscheidungsfindungsmodellen erzeugt werden.
Im Gehirn werden Informationen durch Pulszüge von Aktionspotentialen kodiert.
IF Neurone mit radikal vereinfachter Erzeugung von Aktionspotentialen haben sich in Studien die auf Pulszeiten fokussiert sind als Standardmodelle etabliert. Eindimensionale IF Modelle können jedoch beobachtetes Pulsverhalten oft nicht beschreiben und müssen dazu erweitert werden. Im erste Teil dieser Arbeit wird eine Theorie zur Berechnung der Pulszugleistungsspektren von stochastischen, multidimensionalen IF Neuronen entwickelt. Ausgehend von der zugehörigen Fokker-Planck-Gleichung werden partiellen Differentialgleichung abgeleitet, deren Lösung sowohl die stationäre Wahrscheinlichkeitsverteilung und Feuerrate, als auch das Pulszugleistungsspektrum beschreibt.
Im zweiten Teil wird eine Theorie für große, spärlich verbundene und homogene Netzwerke aus IF Neuronen entwickelt, in der berücksichtigt wird, dass die zeitlichen Korrelationen von Pulszügen selbstkonsistent sind. Neuronale Eingangströme werden durch farbiges Gaußsches Rauschen modelliert, das von einem mehrdimensionalen Ornstein-Uhlenbeck Prozess (OUP) erzeugt wird. Die Koeffizienten des OUP sind vorerst unbekannt und sind als Lösung der Theorie definiert. Um heterogene Netzwerke zu untersuchen, wird eine iterative Methode erweitert.
Im dritten Teil wird die Fokker-Planck-Gleichung auf Binärentscheidungen von Diffusionsentscheidungsmodellen [Engl. diffusion-decision models (DDM)] angewendet. Explizite Gleichungen für die Entscheidungszugstatistiken werden für den einfachsten und analytisch lösbaren Fall von der Fokker-Planck-Gleichung hergeleitet. Für nichtliniear Modelle wird die Schwellwertintegrationsmethode erweitert.This thesis is concerned with the calculation of statistics, in particular the power spectra, of point processes generated by stochastic multidimensional integrate-and-fire (IF) neurons, networks of IF neurons and decision-making models from the corresponding Fokker-Planck equations. In the brain, information is encoded by sequences of action potentials. In studies that focus on spike timing, IF neurons that drastically simplify the spike generation have become the standard model. One-dimensional IF neurons do not suffice to accurately model neural dynamics, however, the extension towards multiple dimensions yields realistic behavior at the price of growing complexity. The first part of this work develops a theory of spike-train power spectra for stochastic, multidimensional IF neurons. From the Fokker-Planck equation, a set of partial differential equations is derived that describes the stationary probability density, the firing rate and the spike-train power spectrum. In the second part of this work, a mean-field theory of large and sparsely connected homogeneous networks of spiking neurons is developed that takes into account the self-consistent temporal correlations of spike trains. Neural input is approximated by colored Gaussian noise generated by a multidimensional Ornstein-Uhlenbeck process of which the coefficients are initially unknown but determined by the self-consistency condition and define the solution of the theory. To explore heterogeneous networks, an iterative scheme is extended to determine the distribution of spectra. In the third part, the Fokker-Planck equation is applied to calculate the statistics of sequences of binary decisions from diffusion-decision models (DDM). For the analytically tractable DDM, the statistics are calculated from the corresponding Fokker-Planck equation. To determine the statistics for nonlinear models, the threshold-integration method is generalized.
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Weitzel, William R. "EVALUATION OF OVERPRESSURE WAVE TRANSITION BY AIRBLAST OVERPRESSURE AND SHOCK WAVE ATTENUATION ANALYSIS USING A SMALL BLACK POWDER CHARGE." UKnowledge, 2014. http://uknowledge.uky.edu/mng_etds/17.
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Eight flush mount pressure sensors were used in a series of 3 test sequences to measure air overpressure produced by a firecracker. Overpressure was recorded at a range of 1 inch to 21 inches away from detonation, and charge weight was determined to be 0.1mg of black powder. Air overpressure prediction equations were developed from test series then compared to collected data for subsequent tests. Overpressure wave velocity was measured using wave arrival time and distance between sensors. This wave velocity was compared to calculated wave velocity using overpressure and ideal gas law. Overpressure and wave velocity are directly related to each other in shock wave behavior. The goal of these tests was to identify at what point the in elastic-plastic region the overpressure wave no longer closely resembled a shock wave, but an elastic wave instead.