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Kindermann, Lars. "Neuronale Netze zur Berechnung Iterativer Wurzeln und Fraktionaler Iterationen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2002. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-200201544.
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Diese Arbeit entwickelt eine Methode, Funktionalgleichungen der Art g(g(x))=f(x) bzw. g^n(x)=f(x) mit Hilfe neuronaler Netze zu lösen. Gesucht ist eine Funktion g(x), die mehrfach hintereinandergeschaltet genau einer gegebenen Funktion f(x) entspricht. Man nennt g=f^1/n eine iterative Wurzel oder fraktionale Iteration von f. Lösungen für g zu finden, stellt das inverse Problem der Iteration dar oder die Erweiterung der Wurzel- bzw. Potenzoperation auf die Funktionsalgebra. Geschlossene Ausdrücke für Funktionswurzeln einer gegebenen Funktion zu finden, ist in der Regel nicht möglich oder sehr schwer. Numerische Verfahren sind nicht in allgemeiner Form beschrieben oder als Software vorhanden. Ausgehend von der Fähigkeit eines neuronalen Netzes, speziell des mehrschichtigen Perzeptrons, durch Training eine gegebene Funktion f(x) zu approximieren, erlaubt eine spezielle Topologie des Netzes auch die Berechnung von fraktionalen Iterationen von f. Ein solches Netz besteht aus n identischen, hintereinandergeschalteten Teilnetzen, die, wenn das Gesamtnetz f approximiert, jedes für sich g = f^1/n annähern. Es ist lediglich beim Training des Netzes darauf zu achten, dass die korrespondierenden Gewichte aller Teilnetze den gleichen Wert annehmen. Dazu werden mehrere Verfahren entwickelt: Lernen nur im letzten Teilnetz und Kopieren der Gewichte auf die anderen Teile, Angleichen der Teilnetze durch Kopplungsfaktoren oder Einführung eines Fehlerterms, der Unterschiede in den Teilnetzen bestraft. Als weitere Näherungslösung wird ein iteriertes lineares Modell entwickelt, das durch ein herkömmliches neuronales Netz mit hoher Approximationsgüte für nichtlineare Zusammenhänge korrigiert wird.
Als Anwendung ist konkret die Modellierung der Bandprofilentwicklung beim Warmwalzen von Stahlblech gegeben. Einige Zentimeter dicke Stahlblöcke werden in einer Walzstraße von mehreren gleichartigen, hintereinanderliegenden Walzgerüsten zu Blechen von wenigen Millimetern Dicke gewalzt. Neben der Dicke ist das Profil - der Dickenunterschied zwischen Bandmitte und Rand - eine wichtige Qualitätsgröße. Sie kann vor und hinter der Fertigstraße gemessen werden, aus technischen Gründen aber nicht zwischen den Walzgerüsten. Eine genaue Kenntnis ist jedoch aus produktionstechnischen Gründen wichtig. Der Stand der Technik ist die Berechnung dieser Zwischenprofile durch das wiederholte Durchrechnen eines mathematischen Modells des Walzvorganges für jedes Gerüst und eine ständige Anpassung von adaptiven Termen dieses Modells an die Messdaten. Es wurde gezeigt, dass mit einem adaptiven neuronalen Netz, das mit Eingangs- und Ausgangsprofil sowie allen vorhandenen Kenn- und Stellgrößen trainiert wird, die Vorausberechnung des Endprofils mit deutlich höherer Genauigkeit vorgenommen werden kann. Das Problem ist, dass dieses Netz die Übertragungsfunktion der gesamten Straße repräsentiert, Zwischenprofile können nicht ausgegeben werden. Daher wird der Versuch gemacht, beide Eigenschaften zu verbinden: Die genaue Endprofilmodellierung eines neuronalen Netzes wird kombiniert mit der Fähigkeit des iterierten Modells, Zwischenprofile zu berechnen. Dabei wird der in Form von Messdaten bekannte gesamte Prozess als iterierte Verknüpfung von technisch identischen Teilprozessen angesehen. Die Gewinnung eines Modells des Einzelprozesses entspricht damit der Berechnung der iterativen Wurzel des Gesamtprozesses.
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Winqvist, David. "Augmenting communication channels toward the evolution of autonomous construction sites." Thesis, Blekinge Tekniska Högskola, Institutionen för maskinteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-12752.
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Context In the last centuries, we have been generating and building infrastructure at a faster pace than ever before. Simultaneously the costs for labor and construction sectors as road and house building is increasing. This provides room for autonomous machines. The development of infrastructure is accomplished through highly efficient and productive construction machinery that progressively modernizes to form the society. In order to increase the pace of development, both cars and industry are getting more and more automated. Volvo Construction Equipment is exploring the autonomous vehicle space. The new machines complement and perfect the human work with efficiency, reliability, and durability. There is however, a question of trust between the human workers and the autonomous machines, I will in this thesis investigate methods on how to develop trust through communication systems with autonomous machines. Objectives To create recommendations and solutions for products that build trust between human and automated machines on a construction site. Method Outcome is reached through a case study exploration with validated learning, meaning that it will incorporate learnings through prototype iterations. Results The result evaluates how trust could be developed between humans and autonomous machinery at a construction site and how communication methods between these parties could be implemented while maintaining high levels of efficiency and safety. Conclusion Findings in this thesis indicates that trust is developed over time with reliable systems that provide colleagues with updated information available at any time. The results can be introduced in both today’s and tomorrow’s construction sites at various levels of advanced technology.Sammanhang De senaste hundra åren har vi gett upphov till att bygga infrastruktur i en snabbare takt än någonsin tidigare. Samtidigt ökar kostnaderna för både arbetskraft och byggsektorer som väg- och bostadsbyggnader. Denna situation ger utrymme för autonoma maskiner. Utvecklingen av infrastruktur sker genom effektiva och produktiva konstruktionsmaskiner som successivt moderniseras för att forma samhället. För att öka utvecklingstakten moderniseras både bilar och industri för att möta en mer automatiserad vardag. Volvo Construction Equipment undersöker det autonoma fordonsutrymmet för nästa generations maskiner. Automationen kompletterar de nya maskinerna och fulländar det mänskliga arbetet med effektivitet, tillförlitlighet och hållbarhet. Det finns dock en fråga om relationen mellan mänskliga arbetare och autonoma maskiner, jag kommer i denna avhandling undersöka metoder för hur man kan utveckla tillit genom kommunikationssystem mellan arbetare och autonoma maskiner. Mål Att skapa rekommendationer och lösningar för produkter som bygger tillit mellan mänskliga och automatiserade maskiner på en byggarbetsplats. Metod Resultatet uppnås genom användandet av fallstudie forskning kombinerat med validerande lärande. Detta innebär lärdomar med hjälp av en iterativ process utav prototyper som testas och valideras. Resultat Resultatet utvärderar hur förtroende kan utvecklas mellan människor och autonoma maskiner på en byggarbetsplats. Hur kommunikationsmetoder mellan dessa parter skulle kunna genomföras samtidigt som hög effektivitet och säkerhet upprätthålls . Slutsats Lärandet i denna avhandling tyder på att förtroendet utvecklas över tid med tillförlitliga system som ger medarbetare uppdaterad nödvändig information tillgänglig när som helst. Resultaten kan införas i både dagens och framtidens anläggningsplatser på olika nivåer av avancerad teknik.
Vissa delar är borttagan på grund av konfidentialitet.
ME310 Design Innovation at Stanford University
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Laaksonen, Tobias. "Värdet av iterativa designprocesser i teknikundervisning i grundskolan." Thesis, Uppsala universitet, Institutionen för teknikvetenskaper, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-266973.
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This thesis aims to test whether students learn more technology, and become more interested in technology, by designing in iterative processes versus linear ones. The thesis has been conducted as a five-week field study, in which technology teachers have been provided with a teacher’s manual, lesson plans and teaching material especially adapted to a school project with iterative design as working method. Students and teachers have evaluated the project afterwards through an online survey. In total, seven teachers and approximately 300 students have participated in the field study. The thesis’ results can be summarized in the following conclusions; Students learn more, and become more interested in technology, if the education is conducted as team assignments in which the students use iterative design There is a difference between how much boys and girls perceive having learned from the iterative way of designing. Boys, to a higher degree than girls, think that they learn more from iterative design than from linear. There are also interesting results worth discussing further; The study suggests that it is important for students’ learning that the teacher is having fun teaching. There are no differences between boys and girls or different ages regarding how much fun the students had designing iteratively.
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Hanus, Pawel Grzegorz. "Examples and Applications of Infinite Iterated Function Systems." Thesis, University of North Texas, 2000. https://digital.library.unt.edu/ark:/67531/metadc2642/.
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The aim of this work is the study of infinite conformal iterated function systems. More specifically, we investigate some properties of a limit set J associated to such system, its Hausdorff and packing measure and Hausdorff dimension. We provide necessary and sufficient conditions for such systems to be bi-Lipschitz equivalent. We use the concept of scaling functions to obtain some result about 1-dimensional systems. We discuss particular examples of infinite iterated function systems derived from complex continued fraction expansions with restricted entries. Each system is obtained from an infinite number of contractions. We show that under certain conditions the limit sets of such systems possess zero Hausdorff measure and positive finite packing measure. We include an algorithm for an approximation of the Hausdorff dimension of limit sets. One numerical result is presented. In this thesis we also explore the concept of positively recurrent function. We use iterated function systems to construct a natural, wide class of such functions that have strong ergodic properties.
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Kindermann, Lars. "Neuronale Netze zur Berechnung Iterativer Wurzeln und Fraktionaler Iterationen." [S.l. : s.n.], 2001. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10424174.
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Al-Qaysi, Ibrahim, and Yonas Ghidei. "Tre-stegsmetod för att kvantifiera komplexitet för IT-förslag." Thesis, KTH, Skolan för informations- och kommunikationsteknik (ICT), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-188920.
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Moderna företag är under ständig förändring. Företagen behöver således förändra, bygga ut och modifiera de applikationer som stödjer verksamheten. Att göra ändringar i arkitekturer på stora IT-system är inte heltbekymmerfritt. Det är ofta väldigt dyrt och tidskrävande. Problemet är att det inte finns några enkla metoder för att kvantifiera komplexitet på IT-förslag i tidigt skede av en implementation. Många verksamheter har således behov avatt kvantifiera komplexiteten på IT-förslag i deras beslutsprocess för att avgöra vilka system som är dyra och tidskrävande att implementera. Ett av dem är Sveriges militära försvarsorganisation, Försvarsmakten. Syftet förstudien blir sålunda att presentera en metod för att kvantifiera komplexitet och optimera implementation för IT-förslag. Målet för studien är därmed att presentera en modell som gör det möjligt för verksamheter att identifiera komplexa förslag som kan medföra onödiga projektrisker. Denna studie använder sig utav en kombination av kvalitativ och kvantitativ forskningsmetod med en induktiv forskningsansats. Studien evaluerar vilka olika sätt Försvarsmaktens mobilapplikation, FMTK kan implementeras på och vilken av implementationerna som är mest optimal beträffande komplexitet. Därefter presenteras resultatet för studien, Tre-stegsmetoden som inkorporerar den bästa implementationen. Slutligen drar studien slutsatsen, med hjälp av analyser och utvärderingar, att Tre-stegsmetoden är överlägsen andra metoder.Modern enterprises are under constant change. Therefore, enterprises need to change, extend and modify the applications that support their businesses. Making changes in the architectures of large IT-systems however, are not straightforward. It is often very costly and time consuming. The problem is that there are no easy methods to quantify complexity and optimize an implementation in early phases of an application construction. Thus, many companies are in need of a method to quanitfy complexity of their IT-businessproposals in order to facilitate their decision-making process. One of them is the Swedish Armed Forces (sv. Försvarsmakten). The purpose of this study is therefore to present a simple method to quantify complexity and optimize implementation for IT-proposals. The purpose aligns with the goal, which is to present a model, which forms the basis for IT-proposals, for companies to consider in their process. This study uses a combination of a qualitative and quantitative research with an inductive research approach. Furthermore, this study evaluates in which ways Swedish Armed Forces application FMTK can be implemented and which implementations that are most optimal in terms of complexity. A method which incorporates the implementation is thereafter presented as a result of the study. Conclusively, the study shows with the help of analyses and evaluations that the presented method, namely the Three-stepmethod is superior to other methods.
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Ayob, Kibret. "Varumärkesstrategi på webben : Tillämpning av användarcentrerad design för positionering på webben." Thesis, Linnéuniversitetet, Institutionen för informatik (IK), 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-48519.
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Syfte: Företag har svårt att positionera sig på webben då de misslyckas att utveckla sina webbsidor för att stödja dess varumärkesstrategi. Syftet med denna studie är att undersöka hur ett företag kan tillämpa designstrategi ur ett användarcentrerat designperspektiv för att stödja företagets övergripande varumärkesstrategi på webben. Kunskapslucka: Denna studie har identifierat en kunskapslucka vad gäller hur företag fastställer och verkställer designstrategi för att stödja övergripande varumärkesstrategi på webben. Metod: Studien avser att undersöka tillämpning av designstrategi genom att ta fram ett designförslag som baserats på en användarcentrerad designprocess. För att göra detta har intervjuer med experter samt expertutvärdering av webbsidor utförts för att kartlägga en billeverantörs återförsäljares domän, baserat på motsvarande strategi för köpresa som är avsedd för att leda besökaren till billeverantörens produkt- och tjänsteutbud som representeras av återförsäljare och dess webbsidor. Denna datainsamling ligger till grund för persona och kontextscenarion som översätts till identifierade krav som motsvarar produktens designstrategi. Designstrategin ligger sedan till grund för det skapande momentet i den användarcentrerade designprocessen, där iterativ design leder till förädlande av framtagna ramverksskisser till interaktiv prototyp. Resultat och slutsats: Resultatet av studien som var en framtagen interaktiv prototyp visar att användarcentrerad design som tillämpar designstrategi, genom att fastställa företagets och användarens mål och behov samt innehålls- och funktionalitetskrav, är ett alternativ som tillåter strukturerad förädling av en webbsida till den punkt att webbsidan uppfyller sin designstrategi. Resultatet visar också att beroende på hur grundlig en kartläggning är och hur välformulerad designstrategin är påverkar hur väl framtagen webbsida, vare sig det är en prototyp eller slutprodukt, uppfyller sitt syfte.Purpose: Corporations experience difficulties positioning themselves on the web as a result of not developing their websites in a way that is inline with their overall business strategy. The purpose of this study is to explore how corporations should apply design strategy, based on a user-centered design perspective, to support their overall business strategy on the web. Originality/value: This study has identified a knowledge gap in terms of how corporations define and apply design strategy in order to support their overall business strategy on the web. Methodology: This study aims to research the application of design strategy by creating a prototype through the use of a user-centered design process. This was done by interviewing experts as well as evaluating websites, in order to explore the domain of a car manufacturers retailers, which was based on the corresponding strategy of leading the visitor to the car manufacturers offerings that are represented by the retailers and their websites. This data collection was the foundation in the creation of a persona and context scenarios that was translated into identified needs that represented the products design strategy. The design strategy in turn was the foundation for the creating phase of the user-centered design process, where iterative design lead to refining framework sketches and an interactive prototype. Findings and conclusion: The study which resulted in an interactive prototype shows that user-centered design, which applies design strategy by defining the corporations and the users goals and needs, is an alternative that allows for structured refinement to the point that the website fulfills its design strategy. The results also show that depending on how well the domain exploration is executed as well as how well the design strategy is defined will affect the resulting website and to what extent it fulfills its purpose, whether it’s is still a prototype or if it’s the end result.
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Snyder, Jason Edward. "The Global Structure of Iterated Function Systems." Thesis, University of North Texas, 2009. https://digital.library.unt.edu/ark:/67531/metadc9917/.
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I study sets of attractors and non-attractors of finite iterated function systems. I provide examples of compact sets which are attractors of iterated function systems as well as compact sets which are not attractors of any iterated function system. I show that the set of all attractors is a dense Fs set and the space of all non-attractors is a dense Gd set it the space of all non-empty compact subsets of a space X. I also investigate the small trans-finite inductive dimension of the space of all attractors of iterated function systems generated by similarity maps on [0,1].
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Reid, James Edward. "Numerical Values of the Hausdorff and Packing Measures for Limit Sets of Iterated Function Systems." Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011825/.
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In the context of fractal geometry, the natural extension of volume in Euclidean space is given by Hausdorff and packing measures. These measures arise naturally in the context of iterated function systems (IFS). For example, if the IFS is finite and conformal, then the Hausdorff and packing dimensions of the limit sets agree and the corresponding Hausdorff and packing measures are positive and finite. Moreover, the map which takes the IFS to its dimension is continuous. Developing on previous work, we show that the map which takes a finite conformal IFS to the numerical value of its packing measure is continuous. In the context of self-similar sets, we introduce the super separation condition. We then combine this condition with known density theorems to get a better handle on finding balls of maximum density. This allows us to extend the work of others and give exact formulas for the numerical value of packing measure for classes of Cantor sets, Sierpinski N-gons, and Sierpinski simplexes.
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Lindström, Edvard, and Andréas Isaksson. "Hör-Ser-Gör : En utforskning inom ljudbaserade rörelsespel." Thesis, Blekinge Tekniska Högskola, Institutionen för teknik och estetik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-18284.
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Detta kandidatarbete handlar om utforskningen inom alternativa ljudspelsformer. Vi ville utforska vilken ny kunskap som kan hämtas från spelljudsteori när den applicerades i ett ljudbaserat rörelsespel. Vi försöker uppnå detta genom en iterativ och experimentell designprocess. Vi skapade två olika ljudbaserade spelprototyper där vi applicerade olika spelljudsteorier. Genom att designa prototyper och analysera dem, genom induktivt resonemang och deltagande observation, kunde vi observera att spelaren kunde använda icke-visuella gränssnitt i ett ljudbaserat rörelsespel. Som resultat presenterar vi processens mest avgörande designproblem. Utmaningen med att utveckla icke-visuella gränssnitten var att instruera spelaren i att använda dem genom icke-vokala ljud. Vi presenterar även ett nytt sätt att förstå akusmatiska ljud i icke-visuella ljudbaserade spel. Som avslutande del så diskuteras undersökningens relevans och framtida undersökningsområden föreslås.This bachelor thesis is about exploration within alternative forms of audio game. We wanted to explore what new knowledge could be extracted from game audio theory when it is applied to a movement based audio game. We aim to do this through an iterative and experimental design process. We created two different audio game prototypes where different game audio theories were applied. By designing prototypes and analyzing them, through inductive reasoning and participant observation, we could observe that players were able to use non-visual interfaces in an non-visual audio game. As our results we present the process’s most critical design problems. The challenge in creating these non-visual interfaces was instructing the player on how to use them through non-vocal audio. We also present a new way of understanding acousmatic sound in non-visual audio games. Lastly the study’s relevance is discussed and future research areas are suggested.
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Åström, Freddie, Michael Felsberg, George Baravdish, and Claes Lundström. "Targeted Iterative Filtering." Linköpings universitet, Centrum för medicinsk bildvetenskap och visualisering, CMIV, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-89674.
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The assessment of image denoising results depends on the respective application area, i.e. image compression, still-image acquisition, and medical images require entirely different behavior of the applied denoising method. In this paper we propose a novel, nonlinear diffusion scheme that is derived from a linear diffusion process in a value space determined by the application. We show that application-driven linear diffusion in the transformed space compares favorably with existing nonlinear diffusion techniques.VIDI
GARNICS
SM10-002
BILDLAB
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Majors, Michael David. "Iterative robot control." Thesis, University of Cambridge, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.625008.
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Marczewska, Kaja. "The iterative turn." Thesis, Durham University, 2015. http://etheses.dur.ac.uk/11034/.
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This thesis investigates the implications of the increasingly prominent propensity to copy as a creative practice in contemporary culture. While debates about plagiarism, copyright infringement, and the state of copyright inform this project, the focus here is on broader issues. The argument is formulated as an attempt at defining a cultural condition that triggers novel attitudes to creativity in order to explore the possibilities of a reconceptualisation of copying as a creative category. The aesthetic tendencies identified in this project are presented as heavily influenced by the emergence of new technologies. But the thesis is not an analysis of the twenty-first century new media culture. Instead, the contemporary technological moment is discussed as a condition of postproduction, in an attempt to devise a historical and critical framework that goes beyond questions of the intersection of creativity and technology. By doing so, this project strives to interrogate the restrictions and inadequacies of the dominant categories of originality, creativity, and authorship, in legal and creative terms, to propose the notion of iteration as a possible alternative. Practices of copying are represented as a necessary condition of contemporary culture and a manifestation of a shift in aesthetics, here defined as the Iterative turn. Chapter 1 formulates a critical framework for discussing iteration and positions the contemporary Iterative turn in relation to developments in the visual arts, literature, publishing, and law. Chapters 2, 3, and 4 offer a discussion of representative approaches to contemporary iterative writing and possible ways of conceptualising the means by which they engage with notions of originality, creativity, and authorship. While the focus here is first and foremost on literary texts, extensive references are made to the arts broadly conceived: the media and media theory, philosophy, literary and art theory, as well as case law and critical legal studies, to arrive at a more comprehensive formulation of the aesthetics of iteration for the emergent cultural condition. In its attempt to think about the contemporary, the thesis posits a framework for looking beyond the established paradigms of writing.
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Nikazad, Touraj. "Algebraic Reconstruction Methods." Doctoral thesis, Linköping : Linköpings universitet, Department of Mathematics Scientific Computing, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-11670.
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Scheben, Fynn. "Iterative methods for criticality computations in neutron transport theory." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.545319.
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This thesis studies the so-called “criticality problem”, an important generalised eigenvalue problem arising in neutron transport theory. The smallest positive real eigenvalue of the problem contains valuable information about the status of the fission chain reaction in the nuclear reactor (i.e. the criticality of the reactor), and thus plays an important role in the design and safety of nuclear power stations. Because of the practical importance, efficient numerical methods to solve the criticality problem are needed, and these are the focus of this thesis. In the theory we consider the time-independent neutron transport equation in the monoenergetic homogeneous case with isotropic scattering and vacuum boundary conditions. This is an unsymmetric integro-differential equation in 5 independent variables, modelling transport, scattering, and fission, where the dependent variable is the neutron angular flux. We show that, before discretisation, the nonsymmetric eigenproblem for the angular flux is equivalent to a related eigenproblem for the scalar flux, involving a symmetric positive definite weakly singular integral operator(in space only). Furthermore, we prove the existence of a simple smallest positive real eigenvalue with a corresponding eigenfunction that is strictly positive in the interior of the reactor. We discuss approaches to discretise the problem and present discretisations that preserve the underlying symmetry in the finite dimensional form. The thesis then describes methods for computing the criticality in nuclear reactors, i.e. the smallest positive real eigenvalue, which are applicable for quite general geometries and physics. In engineering practice the criticality problem is often solved iteratively, using some variant of the inverse power method. Because of the high dimension, matrix representations for the operators are often not available and the inner solves needed for the eigenvalue iteration are implemented by matrix-free inneriterations. This leads to inexact iterative methods for criticality computations, for which there appears to be no rigorous convergence theory. The fact that, under appropriate assumptions, the integro-differential eigenvalue problem possesses an underlying symmetry (in a space of reduced dimension) allows us to perform a systematic convergence analysis for inexact inverse iteration and related methods. In particular, this theory provides rather precise criteria on how accurate the inner solves need to be in order for the whole iterative method to converge. The theory is illustrated with numerical examples on several test problems of physical relevance, using GMRES as the inner solver. We also illustrate the use of Monte Carlo methods for the solution of neutron transport source problems as well as for the criticality problem. Links between the steps in the Monte Carlo process and the underlying mathematics are emphasised and numerical examples are given. Finally, we introduce an iterative scheme (the so-called “method of perturbation”) that is based on computing the difference between the solution of the problem of interest and the known solution of a base problem. This situation is very common in the design stages for nuclear reactors when different materials are tested, or the material properties change due to the burn-up of fissile material. We explore the relation ofthe method of perturbation to some variants of inverse iteration, which allows us to give convergence results for the method of perturbation. The theory shows that the method is guaranteed to converge if the perturbations are not too large and the inner problems are solved with sufficiently small tolerances. This helps to explain the divergence of the method of perturbation in some situations which we give numerical examples of. We also identify situations, and present examples, in which the method of perturbation achieves the same convergence rate as standard shifted inverse iteration. Throughout the thesis further numerical results are provided to support the theory.
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Hassine, Khaled. "Contribution à l'élaboration d'une approche de décomposition des traitements itératifs sur des architectures MIMD : application aux traitements de séquences d'images sur réseau de transputers." Valenciennes, 1994. https://ged.uphf.fr/nuxeo/site/esupversions/6059845e-087a-474f-94a6-09cb96fbf246.
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L’objectif de cette thèse consiste à étudier les modèles de parallélisation pour répondre aux besoins en puissance de calcul de deux outils de mesure de la direction du regard et d'analyse gestuelle. Le support, étant des séquences d'images, a introduit des contraintes temporelles sévères. Une étude algorithmique des traitements de séquences d'images et de nos applications a permis de dégager leur adaptation au parallélisme. La conception parallèle est par la suite abordée. Différentes techniques de parallélisation sont décrites. Le modèle Spmd (same program multiple data), le plus adapté à nos traitements, est détaillé. Ce modèle ne tient pas compte explicitement des surcharges inhérentes au parallélisme. Pour remédier à ces insuffisances, une approche de décomposition basée sur le modèle Spmd est proposée. L’approche présente une restructuration du parallélisme inhérent à une application en optimisant les différentes surcharges dues au parallélisme. Une transparence vis-à-vis de la machine cible est assurée. Les éventuelles contraintes temporelles liées aux applications sont prises en considération. L’approche est appliquée pour les traitements envisagés par les deux applications sur un réseau de transputers. Les résultats expérimentaux sont analysés en fonction des contraintes temporelles imposées. Des idées d'extensions sont proposées concernant le développement des applications et l'approche de parallélisation.
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Townley, Tracy Yvette. "Predictive iterative learning control." Thesis, University of Exeter, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246383.
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Munde, Gurubachan. "Adaptive iterative learning control." Thesis, University of Exeter, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.390139.
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TEIXEIRA, Jonathan da Cunha. "Simulação por Linhas de Fluxo com Acoplamento Geomecânico." Universidade Federal de Pernambuco, 2015. https://repositorio.ufpe.br/handle/123456789/19872.
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Aimportânciadageomecânicaedoestudodeesquemasdeacoplamentoentreageomecânica e fluxo multifásico têm sido cada vez mais importantes e utilizados pela indústria a medida que formações cada vez mais profundas vêem sendo descobertas e exploradas. O entendimento do comportamento do estado de tensão em um reservatório permite produzir um melhor entendimento das implicações geomecânicas que ocorrem durante a fase de explotação, isso porque durante esta fase, as alterações na poro-pressão conduzem perturbações no equilíbrio mecânico afetando o estado de tensão de formações profundas, de maneira a alterar as propriedades da rocha tais como permeabilidade e porosidade. No entanto, a simulação acoplada (hidromecânica) em um grande campo heterogêneo implica na solução de equações de fluxo e mecânica, associadas a um grande número de graus de liberdade que torna esse tipo de abordagem inviável e computacionalmente cara. Neste contexto, um simulador geomecânico-linhas de fluxoé apresentado dentro de um algoritmo sequencial iterativo. Neste trabalho, aplica-se o método de elementos finitos com volume de controle para o subproblema poro-mecânico que fornece um campo de velocidade de Darcy pós-processado e a porosidade como entradas para o subproblema de transporte. Este subproblema é resolvido através do método de decomposição de operador, no qual basea-se em um esquema preditor-corretor com os passos preditor e corretor discretizados pelos esquemas baseados em tempo de vôo e volumes finitos, respectivamente. Simulações numéricas de injeção de água foram comparadas com soluções encontradas na literatura, mostrando bons resultados. Em problemas dominados pela advecção, envolvendo um reservatório naturalmente fraturado, a abordagem implementada foi capaz de predizer a distribuição do campo de saturação ao longo de toda simulação. Além disso, para avaliar a resposta geomecânica, simulações numéricas foram realizadas em um grande sistema de reservatório-rocha capeadora em uma fase de recuperação primária de hidrocarboneto, mostrou que a formulação apresentada provou ser: uma alternativa promissora para simulação hidro-geomecânica tradicional; úteis para o modelo de fluxo de redução de ordem nos casos em que o comportamento geomecânico são mais importantes do que o comportamento de fluxo e de uma ferramenta complementar para simulação geomecânica convencional.
The importance of geomechanics and the study of coupling between geomechanics and multiphase flow have been increasingly recognized and used by the industry as deeper formations are discovered and exploited. The knowledge of the state of stress in a reservoir yields a better understanding of the geomechanical implications during exploitation stage, because during the primary recovery stage, changes in pore pressure leads to perturbations inthemechanicalequilibrium,affectingthestressstateintheformationsinawaythatalters the rock properties such as permeability and porosity. However, the coupled simulation (hydromechanical) in large field heterogeneous models involves stress and flow equations solving, associated with a large number of degrees-of-freedom which becomes infeasible and computationally costly. In this context, a geomechanical-streamline simulator is presented within a iteratively coupled framework algorithm. In the present work, we applied control volume finite element method for the poromechanics subproblem which provides a Darcy velocityfieldthroughapost-processingvelocityprocedureandporosityasinputfieldstothe transportsubproblem.Suchsubproblemissolvedbymeansofanoperatorsplittingmethod, which is based on a predictor-corrector scheme with the predictor and corrector steps discretized by a time-of-flight and a finite volume based schemes, respectively. Numerical simulations of water-flooding are compared to the numerical results available in literature, showing good results. In convection-dominated problems, involving a naturally fractured reservoir, the approach was able to predict the saturation distributions for the whole simulation correctly. Furthermore, to appraisal the geomechanical response, numerical simulation was performed in a large reservoir-caprock system in a primary hydrocarbon recovery stage, showing that the formulation presented proved be: an promising alternative to traditional hydro-geomechanical simulation; useful for flow model order reduction in cases where the geomechanical behavior are more important than the flow behavior and a complementary tool for conventional geomechanical simulations.
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Wallén, Johanna. "Estimation-based iterative learning control." Doctoral thesis, Linköpings universitet, Reglerteknik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-64017.
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In many applications industrial robots perform the same motion repeatedly. One way of compensating the repetitive part of the error is by using iterative learning control (ILC). The ILC algorithm makes use of the measured errors and iteratively calculates a correction signal that is applied to the system. The main topic of the thesis is to apply an ILC algorithm to a dynamic system where the controlled variable is not measured. A remedy for handling this difficulty is to use additional sensors in combination with signal processing algorithms to obtain estimates of the controlled variable. A framework for analysis of ILC algorithms is proposed for the situation when an ILC algorithm uses an estimate of the controlled variable. This is a relevant research problem in for example industrial robot applications, where normally only the motor angular positions are measured while the control objective is to follow a desired tool path. Additionally, the dynamic model of the flexible robot structure suffers from uncertainties. The behaviour when a system having these difficulties is controlled by an ILC algorithm using measured variables directly is illustrated experimentally, on both a serial and a parallel robot, and in simulations of a flexible two-mass model. It is shown that the correction of the tool-position error is limited by the accuracy of the robot model. The benefits of estimation-based ILC is illustrated for cases when fusing measurements of the robot motor angular positions with measurements from an additional accelerometer mounted on the robot tool to form a tool-position estimate. Estimation-based ILC is studied in simulations on a flexible two-mass model and on a flexible nonlinear two-link robot model, as well as in experiments on a parallel robot. The results show that it is possible to improve the tool performance when a tool-position estimate is used in the ILC algorithm, compared to when the original measurements available are used directly in the algorithm. Furthermore, the resulting performance relies on the quality of the estimate, as expected. In the last part of the thesis, some implementation aspects of ILC are discussed. Since the ILC algorithm involves filtering of signals over finite-time intervals, often using non-causal filters, it is important that the boundary effects of the filtering operations are appropriately handled when implementing the algorithm. It is illustrated by theoretical analysis and in simulations that the method of implementation can have large influence over stability and convergence properties of the algorithm.Denna avhandling behandlar reglering genom iterativ inlärning, ILC (från engelskans iterative learning control). Metoden har sitt ursprung i industrirobottillämpningar där en robot utför samma rörelse om och om igen. Ett sätt att kompensera för felen är genom en ILC-algoritm som beräknar en korrektionssignal, som läggs på systemet i nästa iteration. ILC-algoritmen kan ses som ett komplement till det befintliga styrsystemet för att förbättra prestanda. Det problem som särskilt studeras är då en ILC-algoritm appliceras på ett dynamiskt system där reglerstorheten inte mäts. Ett sätt att hantera dessa svårigheter är att använda ytterligare sensorer i kombination med signalbehandlingsalgoritmer för att beräkna en skattning av reglerstorheten som kan användas i ILC-algoritmen. Ett ramverk för analys av skattningsbaserad ILC föreslås i avhandlingen. Problemet är relevant och motiveras utifrån experiment på både en seriell och en parallel robot. I konventionella robotstyrsystem mäts endast de enskilda motorpositionerna, medan verktygspositionen ska följa en önskad bana. Experimentresultat visar att en ILC-algoritm baserad på motorpositionsfelen kan reducera dessa fel effektivt. Dock behöver detta inte betyda en förbättrad verktygsposition, eftersom robotmotorerna styrs mot felaktiga värden på grund av att modellerna som används för att beräkna dessa referensbanor inte beskriver den verkliga robotdynamiken helt. Skattningsbaserad ILC studeras både i simulering av en flexibel tvåmassemodell och en olinjär robotmodell med flexibla leder, och i experiment på en parallell robot. I studierna sammanvägs motorpositionsmätningar med mätningar från en accelerometer på robotverktyget till en skattning av verktygspositionen som används i ILC-algoritmen. Resultaten visar att det är möjligt att förbättra verktygspositionen med skattningsbaserad ILC, jämfört med när motorpositionsmätningarna används direkt i ILC-algoritmen. Resultatet beror också på skattningskvaliteten, som förväntat. Slutligen diskuteras några implementeringsaspekter. Alla värden i uppdateringssignalen läggs på systemet samtidigt, vilket gör det möjligt att använda icke-kausal filtering där man utnyttjar framtida signalvärden i filteringen. Detta gör att det är viktigt hur randeffekterna (början och slutet av signalen) hanteras när man implementerar ILC-algoritmen. Genom teoretisk analys och simuleringsexempel illustreras att implementeringsmetoden kan ha stor betydelse för egenskaperna hos ILC-algoritmen.
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Lopes, Renato da Rocha. "Iterative estimation, equalization and decoding." Diss., Georgia Institute of Technology, 2003. http://hdl.handle.net/1853/15026.
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Katsaggelos, Aggelos Konstantinos. "Constrained iterative image restoration algorithms." Diss., Georgia Institute of Technology, 1985. http://hdl.handle.net/1853/15830.
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Al-Askary, Omar. "Iterative decoding of product codes." Licentiate thesis, KTH, Signals, Sensors and Systems, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1615.
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Iterative decoding of block codes is a rather old subjectthat regained much interest recently. The main idea behinditerative decoding is to break up the decoding problem into asequence of stages, iterations, such that each stage utilizesthe output from the previous stages to formulate its ownresult. In order for the iterative decoding algorithms to bepractically feasible, the complexity in each stage, in terms ofnumber of operations and hardware complexity, should be muchless than that for the original non-iterative decoding problem.At the same time, the performance should approach the optimum,maximum likelihood decoding performance in terms of bit errorrate.
In this thesis, we study the problem of iterative decodingof product codes. We propose an iterative decoding algorithmthat best suits product codes but can be applied to other blockcodes of similar construction. The algorithm approaches maximumlikelihood performance. We also present another algorithm whichis suboptimal and can be viewed as a practical implementationof the rst algorithm on product codes. The performance of thesuboptimal algorithm is investigated both analytically and bycomputer simulations. The complexity is also investigated andcompared to the complexity of GMD and Viterbi decoding ofproduct codes.
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Shaheem, Asri. "Iterative detection for wireless communications." University of Western Australia. School of Electrical, Electronic and Computer Engineering, 2008. http://theses.library.uwa.edu.au/adt-WU2008.0223.
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[Truncated abstract] The transmission of digital information over a wireless communication channel gives rise to a number of issues which can detract from the system performance. Propagation effects such as multipath fading and intersymbol interference (ISI) can result in significant performance degradation. Recent developments in the field of iterative detection have led to a number of powerful strategies that can be effective in mitigating the detrimental effects of wireless channels. In this thesis, iterative detection is considered for use in two distinct areas of wireless communications. The first considers the iterative decoding of concatenated block codes over slow flat fading wireless channels, while the second considers the problem of detection for a coded communications system transmitting over highly-dispersive frequency-selective wireless channels. The iterative decoding of concatenated codes over slow flat fading channels with coherent signalling requires knowledge of the fading amplitudes, known as the channel state information (CSI). The CSI is combined with statistical knowledge of the channel to form channel reliability metrics for use in the iterative decoding algorithm. When the CSI is unknown to the receiver, the existing literature suggests the use of simple approximations to the channel reliability metric. However, these works generally consider low rate concatenated codes with strong error correcting capabilities. In some situations, the error correcting capability of the channel code must be traded for other requirements, such as higher spectral efficiency, lower end-to-end latency and lower hardware cost. ... In particular, when the error correcting capabilities of the concatenated code is weak, the conventional metrics are observed to fail, whereas the proposed metrics are shown to perform well regardless of the error correcting capabilities of the code. The effects of ISI caused by a frequency-selective wireless channel environment can also be mitigated using iterative detection. When the channel can be viewed as a finite impulse response (FIR) filter, the state-of-the-art iterative receiver is the maximum a posteriori probability (MAP) based turbo equaliser. However, the complexity of this receiver's MAP equaliser increases exponentially with the length of the FIR channel. Consequently, this scheme is restricted for use in systems where the channel length is relatively short. In this thesis, the use of a channel shortening prefilter in conjunction with the MAP-based turbo equaliser is considered in order to allow its use with arbitrarily long channels. The prefilter shortens the effective channel, thereby reducing the number of equaliser states. A consequence of channel shortening is that residual ISI appears at the input to the turbo equaliser and the noise becomes coloured. In order to account for the ensuing performance loss, two simple enhancements to the scheme are proposed. The first is a feedback path which is used to cancel residual ISI, based on decisions from past iterations. The second is the use of a carefully selected value for the variance of the noise assumed by the MAP-based turbo equaliser. Simulations are performed over a number of highly dispersive channels and it is shown that the proposed enhancements result in considerable performance improvements. Moreover, these performance benefits are achieved with very little additional complexity with respect to the unmodified channel shortened turbo equaliser.
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Moher, Michael L. "Cross-entropy and iterative detection." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq22171.pdf.
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Berkmann, Jens. "Iterative decoding of nonbinary codes /." Düsseldorf : VDI-Verl, 2001. http://www.gbv.de/dms/bs/toc/329228277.pdf.
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Zhu, Qiwei. "High performance stationary iterative methods." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498981.
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Iterative methods are well-established in the context of scientific computing. They solve a problem by finding successive approximations to the true solution starting from an initial guess. Iterative methods are preferred when dealing with large size problems, as direct methods would be prohibitively expensive. They are commonly used for solving polynomial systems, systems of linear equations, and partial differential equations. Iterative methods normally make heavy demands on computational resources, both in terms of computing power and data storage requirements, and are thus required to be partitioned and executed in parallel. However, their standard sequential order offers little opportunity for parallelism. Hence, it is necessary to re-order their execution in order to exploit the parallel computing power of the underlying computational resources.
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Papagiannis, Evangelos. "Convergence improvement of iterative decoders." Thesis, University of Plymouth, 2006. http://hdl.handle.net/10026.1/1636.
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Iterative decoding techniques shaked the waters of the error correction and communications field in general. Their amazing compromise between complexity and performance offered much more freedom in code design and made highly complex codes, that were being considered undecodable until recently, part of almost any communication system. Nevertheless, iterative decoding is a sub-optimum decoding method and as such, it has attracted huge research interest. But the iterative decoder still hides many of its secrets, as it has not been possible yet to fully describe its behaviour and its cost function. This work presents the convergence problem of iterative decoding from various angles and explores methods for reducing any sub-optimalities on its operation. The decoding algorithms for both LDPC and turbo codes were investigated and aspects that contribute to convergence problems were identified. A new algorithm was proposed, capable of providing considerable coding gain in any iterative scheme. Moreover, it was shown that for some codes the proposed algorithm is sufficient to eliminate any sub-optimality and perform maximum likelihood decoding. Its performance and efficiency was compared to that of other convergence improvement schemes. Various conditions that can be considered critical to the outcome of the iterative decoder were also investigated and the decoding algorithm of LDPC codes was followed analytically to verify the experimental results.
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Fagervik, Kjetil. "Iterative decoding of concatenated codes." Thesis, University of Surrey, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268307.
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MacHardy, William R. "Iterative methods for parameter estimation." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA246174.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Tummala, Murali. Second Reader: Therrien, Charles W. "December 1990." Description based on title screen as viewed on April 1, 2010. DTIC Identifier(s): Iterations, Parametric Analysis, Algorithms, Estimates, Theses, Computerized Simulation, Convergence. Author(s) subject terms: Finite Impulse Response, Infinite Impulse Response, Matrix Splitting, Matrix Portioning, Toeplitz, Symmetric, Condition Number. Includes bibliographical references (p. 90). Also available in print.
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Moher, Michael L. Carleton University Dissertation Engineering Systems and Computer. "Cross-entropy and iterative detection." Ottawa, 1997.
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Röscheisen, Andreas. "Iterative connections and Abhyankar's conjecture." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:16-opus-71796.
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Horn, Gavin B. McEliece Robert J. "Iterative decoding and pseudo-codewords /." Diss., Pasadena, Calif. : California Institute of Technology, 1999. http://resolver.caltech.edu/CaltechETD:etd-02062008-130016.
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Aji, Srinivas M. McEliece Robert J. "Graphical models and iterative decoding /." Diss., Pasadena, Calif. : California Institute of Technology, 2000. http://resolver.caltech.edu/CaltechETD:etd-04112003-162805.
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Perez, Andrade Isaac. "Timing-error-tolerant iterative decoders." Thesis, University of Southampton, 2016. https://eprints.soton.ac.uk/400254/.
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Iterative decoders such as Low-Density Parity-Check (LDPC) and turbo decoders have an inherent capability to correct the transmission errors that originate during communication over a hostile wireless channel. This capability has engendered the widespread use of LDPC and turbo decoders in current communications standards. As a result, signficant research efforts have been made in order to conceive efficient Very-Large-Scale Integration (VLSI) implementations of both LDPC and turbo decoders. Typically, these efforts have focused on optimizing only one of the various trade-offs associated with the hardware implementation of iterative decoders, such as the chip area, latency, throughput, energy efficiency or Bit Error Ratio (BER) performance. However, tolerance to timing errors that occur during the iterative decoding processing are typically not considered in these implementations. Owing to this, the BER performance and hardware efficiency of the proposed designs may be severely degraded, if timing errors occur during the iterative decoding process. Against this background, this thesis demonstrates that iterative decoders are capable of exploiting their inherent error correction capability to correct not only transmission errors, but also timing errors caused by overclocking and power supply variations. Moreover,we propose modifications to the iterative decoders designs, which further enhance their inherent tolerance to timing errors. We achieve this by considering the close relationship between the different trade-offs associated with the hardware implementation of iterative decoders, with the aim of achieving Pareto optimality, where none of these trade-offs can be further improved without degrading at least one of the others. Owing to this, our proposed timing-error-tolerant design methodology simultaneously considers the design constraints and parameters that affect not only the BER performance, but also the hardware efficiency of each implementation. We first investigate the benefits of stochastic computing in iterative decoders, by characterizing the inherent timing-error tolerance of Stochastic LDPC Decoders (SLDPCDs) and Stochastic Turbo Decoders (STDs). Moreover, we propose modifications to the SLDPCD and STD in order to further improve their inherent tolerance to timing errors. This is achieved by performing extensive transistor-level and post-layout simulations, in order to develop different timing analyses for determining the causes and effects of timing errors in these stochastic decoders. Following this, we propose a novel Reduced-Latency STD (RLSTD), which improves the latency of the state-of-the-art STD by an order of magnitude, without increasing its chip area or energy consumption. Our experimental results demonstrate that our proposed RLSTD achieves ultra-low-latencies required by next-generation Mission-Critical Machine-Type Communication (MCMTC). We also investigate the inherent tolerance to timing errors of a recently-proposed Fully-Parallel Turbo Decoder (FPTD). Furthermore, we propose a novel Reduced-Critical-Path Fully-Parallel Turbo Decoder (RCP-FPTD) algorithm and the employment of Better-Than-Worst-Case (BTWC) design techniques in FPTD and RCP-FPTD implementations, for the sake of improving their throughput and their tolerance to timing errors caused by overclocking. We demonstrate that the FPTD and RCP-FPTD implementations improve the throughput of the state-of-the-art turbo decoder by an order of magnitude. Finally, despite operating in the presence of timing errors, our proposed Better-Than-Worst-Case Reduced-Critical-Path Fully-Parallel Turbo Decoder (BTWC-RCP-FPTD) achieves throughputs on the order of tens of Gbps, which may be expected to be a requirement in next-generation wireless communication standards.
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Lechner, Patrick O. "Iterative methods for heterogeneous media." Thesis, University of Bath, 2006. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432374.
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Csató, Lehel. "Gaussian processes : iterative sparse approximations." Thesis, Aston University, 2002. http://publications.aston.ac.uk/1327/.
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In recent years there has been an increased interest in applying non-parametric methods to real-world problems. Significant research has been devoted to Gaussian processes (GPs) due to their increased flexibility when compared with parametric models. These methods use Bayesian learning, which generally leads to analytically intractable posteriors. This thesis proposes a two-step solution to construct a probabilistic approximation to the posterior. In the first step we adapt the Bayesian online learning to GPs: the final approximation to the posterior is the result of propagating the first and second moments of intermediate posteriors obtained by combining a new example with the previous approximation. The propagation of em functional forms is solved by showing the existence of a parametrisation to posterior moments that uses combinations of the kernel function at the training points, transforming the Bayesian online learning of functions into a parametric formulation. The drawback is the prohibitive quadratic scaling of the number of parameters with the size of the data, making the method inapplicable to large datasets. The second step solves the problem of the exploding parameter size and makes GPs applicable to arbitrarily large datasets. The approximation is based on a measure of distance between two GPs, the KL-divergence between GPs. This second approximation is with a constrained GP in which only a small subset of the whole training dataset is used to represent the GP. This subset is called the em Basis Vector, or BV set and the resulting GP is a sparse approximation to the true posterior. As this sparsity is based on the KL-minimisation, it is probabilistic and independent of the way the posterior approximation from the first step is obtained. We combine the sparse approximation with an extension to the Bayesian online algorithm that allows multiple iterations for each input and thus approximating a batch solution. The resulting sparse learning algorithm is a generic one: for different problems we only change the likelihood. The algorithm is applied to a variety of problems and we examine its performance both on more classical regression and classification tasks and to the data-assimilation and a simple density estimation problems.
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McKay, Melanie. "Iterative methods for incompressible flow." Thesis, University of Ottawa (Canada), 2009. http://hdl.handle.net/10393/28063.
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The goal of this thesis is to illustrate the effectiveness of iterative methods on the discretized Navier Stokes equations. The standard lid-driven cavity in both 2-D and 3-D test cases are examined and compared with published results of the same type. The numerical results are obtained by reducing the partial differential equations (PDEs) to a system of algebraic equations with a stabilized P1-P1 Finite Element Method (FEM) in space. Gear's Backward Difference Formula (BDF2) and an adaptive time stepping scheme utilizing a first order Backward Euler (BE) startup and BDF2 are then utilized to discretizc the time derivative of the Javier-Stokes equations. The iterative method used is the Generalized Minimal Residual (GMRES) along with the selected preconditioners Incomplete LU Factorization (ILU), Jacobi preconditioner and the Block Jacobi preconditioner.
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Deane, Jonathan H. B. "Iterative electronic circuits and chaos." Thesis, University of Surrey, 1990. http://epubs.surrey.ac.uk/842739/.
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Iterative electronic circuits - that is, circuits whose behaviour can be described by a mapping in which time is not explicitly present - are investigated, and particular attention is paid to those circuits which can be shown to display chaotic behaviour. Examples emanating mainly from the fields of power electronics and digital electronics are discussed. The emphasis is on the derivation of analytical results wherever this is possible, although numerical calculations have also been much relied upon. Some of these results are supported by experimental investigations. Many of the results are presented in the form of diagrams. The implications of chaotic behaviour for electronic engineers have been indicated. A brief discussion of the relation between iterative circuits and circuits that are described by non-linear differential equations is included.
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Masters, David M. "Verifying Value Iteration and Policy Iteration in Coq." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1618999718015199.
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Hamitou, Okba. "Efficient preconditioning method for the CARP-CG iterative solver for the solution of the frequency-domain visco-elastic wave equation." Thesis, Université Grenoble Alpes (ComUE), 2016. http://www.theses.fr/2016GREAM087/document.
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La résolution de l'équation des ondes acoustiques et élastiques en 3D dans le domaine fréquentiel représente un enjeu majeur dans le cadre de l'inversion des formes d'ondes pour l'imagerie haute résolution de cibles crustales (Virieux, 2009). Après discrétisation, ce problème revient à résoudre un système linéaire à valeurs complexes, creux, de grande taille non défini et mal conditionné. Les méthodes d'inversion sismique requièrent la solution de ce problème pour l'évaluation du problème direct pour un grand nombre de sources (plusieurs milliers voir dizaines de milliers). Dans l'approximation acoustique, les méthodes directes sont privilégiées. Cependant, le coût mémoire de ces méthodes les rendent aujourd'hui inutilisables pour résoudre les problèmes élastiques 3D. En raison de leur plus faible coût mémoire, les méthodes itératives pour les équations en fréquence peuvent être considérées pour l'élastodynamique. Cependant, une convergence rapide passe par des préconditionneurs adaptés pour les solveurs itératifs. Par ailleurs, les stratégies pour résoudre des systèmes linéaires avec des seconds membres multiples ne sont pas aussi efficaces que pour les méthodes directes. La modélisation dans le domaine temporelle quant à elle présente une importante complexité en coût de calcul et cette complexité croît linéairement avec le nombre de sources.Dans cette thèse, l'approche utilisant un solveur itératif est considérée. Le solveur itératif CARP-CG introduit par Gordon (2010) est considéré. Cette méthode est basée sur la méthode de Kaczmarz qui transforme un système linéaire mal conditionné en un système hermitien, positif et qui peut être résolu en utilisant les méthodes du type gradient conjugué (CG). Dans des configurations de forts contrastes et hétérogénéités, ce solveur s'est révélé être extrêmement robuste alors que les méthodes itératives standards basées sur les sous-espaces de Krylov telles que GMRES et BiCGSTAB nécessitent l'utilisation d'un préconditionneur pour converger (Li, 2015). Malgré les bonnes propriétés de la méthode CARP-CG, le nombre d'itérations nécessaires pour atteindre une précision suffisante reste néanmoins élevé. Je présente alors une stratégie de préconditionnement adaptée au problème de propagation des ondes et à la méthode CARP-CG. Ce préconditionneur est un inverse creux et approché d'un opérateur de propagation des ondes fortement amorti. Le calcul du préconditionneur est réalisé grâce un algorithme massivement parallèle pour les architectures à mémoire distribuée.La méthode développée est appliquée à des cas d'étude réalistes. Les applications sont faites sur des modèles synthétiques 2D dans l'approximation visco-acoustique pour des fréquences allant jusqu'à 40 Hz puis dans l'approximation élastique pour des fréquences allant jusqu'à 20 Hz. Ces études montrent l'efficacité de la méthode CARP-CG munie de la stratégie de préconditionnement. Le nombre d'itérations est fortement réduit (jusqu'à un facteur 9) permettant d'améliorer considérablement la complexité de la méthode CARP-CG. Des gains en temps de calcul allant jusqu'à un facteur 3.5 sont ainsi obtenus. La méthode est ensuite appliquée à un cas 3D synthétique et réaliste dans l'approximation visco-élastique pour des fréquences allant de 1.25 Hz à 7.5 Hz. Des résultats encourageants sont obtenus. Munie du préconditioneur, la méthode CARP-CG permet de résoudre ces systèmes linéaires deux fois plus rapidement.La stratégie de préconditionnement implique la nécessité de plus grandes ressources en mémoire pour le solveur itératif; cependant, elles ne constituent pas une limitation pour la méthode et restent très négligeables devant celles requises par les solveurs directs. La principale limitation réside dans le temps de calcul qui demeure assez significatif. Cependant, cette méthode constitue un solveur compétitif comparé aux autres solveurs en temps et direct utilisés aujourd'hui dans le cadre de l'inversion des formes d'ondesA robust and efficient wave modeling method is the cornerstone of high resolution seismic inversion methods such as the frequency-domain Full Waveform Inversion (Virieux, 2009). After discretization, frequency-domain wave modeling amounts to the solution of large (up to several billion of unknowns for realistic case studies), sparse, indefinite and ill-conditioned linear systems. Furthermore, seismic inversion methods require the solution of this problem for numerous sources (from several thousands up to tens of thousands). In the acoustic approximation, 3D real case studies can be handled efficiently using direct solvers. However because of their tremendous intrinsic memory requirements, they are not yet adapted to the solution of the 3D elastodynamics equations. Iterative solvers provide an alternative to direct solvers. However, they require a preconditioning strategy to ensure convergence for the frequency-domain wave equation. Besides, multiple right-hand sides linear systems are not treated as efficiently as direct solvers do.In this thesis, we are interested in the use of a robust iterative solver adapted to the solution of these systems called CARP-CG (Gordon, 2010). The CARP-CG method has shown robust convergence properties for 2D and 3D elastic problems in highly heterogeneous media compared to standard Krylov methods such as GMRES or Bi-CGSTAB which require the use of a preconditioner to ensure convergence (Li, 2015). Despite the good convergence properties of CARP-CG, the latter still requires a large number of iterations to reach sufficient accuracy. I introduce an efficient preconditioning strategy adapted to the CARP-CG method and the frequency-domain wave problem. This preconditioner is computed as a sparse approximate inverse of a strongly damped wave propagation operator. The computation of the preconditioner is performed in a massively parallel algorithm for distributed memory architectures.The efficiency of the preconditioner is evaluated on several case studies. First, applications are performed on realistic synthetic models in the 2D visco-acoustic approximation (up to $40$ Hz) and the 2D visco-elastic approximation (up to $20$ Hz). These studies show that the CARP-CG method together with the preconditioning strategy is robust and efficient. The number of iterations is significantly reduced (up to a factor $9$) enabling a speedup in the computation time by a factor up to $3.5$. Second, this method is investigated in the 3D elastic approximation on a realistic synthetic case study on the range of frequencies 1.25 to 7.5 Hz. Very encouraging results are obtained with a significant reduction in the number of iterations. A slow increase of the number of iterations with respect to the frequency is noted.This preconditioning strategy adapted to the CARP-CG method implies larger memory requirements. However, this extra memory cost remains one order lower compared to direct solver memory requirement, and should be affordable on standard HPC facilities. The main bottleneck preventing from the possible use of this iterative solver for 3D elastic FWI remains the computation time for the wave equation solves
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Freitag, Melina. "Inner-outer iterative methods for eigenvalue problems : convergence and preconditioning." Thesis, University of Bath, 2007. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.512248.
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Many methods for computing eigenvalues of a large sparse matrix involve shift-invert transformations which require the solution of a shifted linear system at each step. This thesis deals with shift-invert iterative techniques for solving eigenvalue problems where the arising linear systems are solved inexactly using a second iterative technique. This approach leads to an inner-outer type algorithm. We provide convergence results for the outer iterative eigenvalue computation as well as techniques for efficient inner solves. In particular eigenvalue computations using inexact inverse iteration, the Jacobi-Davidson method without subspace expansion and the shift-invert Arnoldi method as a subspace method are investigated in detail. A general convergence result for inexact inverse iteration for the non-Hermitian generalised eigenvalue problem is given, using only minimal assumptions. This convergence result is obtained in two different ways; on the one hand, we use an equivalence result between inexact inverse iteration applied to the generalised eigenproblem and modified Newton's method; on the other hand, a splitting method is used which generalises the idea of orthogonal decomposition. Both approaches also include an analysis for the convergence theory of a version of inexact Jacobi-Davidson method, where equivalences between Newton's method, inverse iteration and the Jacobi-Davidson method are exploited. To improve the efficiency of the inner iterative solves we introduce a new tuning strategy which can be applied to any standard preconditioner. We give a detailed analysis on this new preconditioning idea and show how the number of iterations for the inner iterative method and hence the total number of iterations can be reduced significantly by the application of this tuning strategy. The analysis of the tuned preconditioner is carried out for both Hermitian and non-Hermitian eigenproblems. We show how the preconditioner can be implemented efficiently and illustrate its performance using various numerical examples. An equivalence result between the preconditioned simplified Jacobi-Davidson method and inexact inverse iteration with the tuned preconditioner is given. Finally, we discuss the shift-invert Arnoldi method both in the standard and restarted fashion. First, existing relaxation strategies for the outer iterative solves are extended to implicitly restarted Arnoldi's method. Second, we apply the idea of tuning the preconditioner to the inner iterative solve. As for inexact inverse iteration the tuned preconditioner for inexact Arnoldi's method is shown to provide significant savings in the number of inner solves. The theory in this thesis is supported by many numerical examples.
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Franciscani, Juliana de Fátima [UNESP]. "Consenso Iterativo: geração de implicantes primos para minimização de funções booleanas com múltiplas saídas." Universidade Estadual Paulista (UNESP), 2016. http://hdl.handle.net/11449/144517.
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Com a evolução e difusão do desenvolvimento de equipamentos utilizando microtecnologia e nanotecnologia, circuitos cada vez menores, mais eficientes e que consomem menos energia, são necessários. Os métodos de minimização de funções booleanas tornam-se relevantes por possibilitarem a otimização de circuitos lógicos, através da geração de circuitos que possuam a mesma funcionalidade, porém, minimizados. Estudos na área de minimização de funções booleanas são realizados há muito tempo, e estão sendo adaptados às novas tecnologias. A geração de implicantes primos de uma função booleana é um dos passos para a cobertura dos mintermos da função e, consequentemente, para a obtenção da função de custo mínimo. Neste trabalho, a Primeira Fase do Método de Quine-McCluskey para Funções Booleanas com Múltiplas Saídas (QMM) foi implementada para posterior comparação com os Métodos Propostos GPMultiplo e MultiGeraPlex (baseados na filosofia do algoritmo GeraPlex). Os métodos propostos geram os implicantes primos de uma função booleana com múltiplas saídas e utilizam a operação de consenso iterativo para comparar dois termos. Os resultados obtidos, através da comparação do GPMultiplo, MultiGeraPlex e da Primeira Fase do Método de QMM, puderam comprovar que a aplicação dos métodos propostos torna-se mais viável e vantajosa por permitir menor tempo de execução e uso de memória, menor quantidade de implicantes gerados e de comparações entre os termos.
With the evolution and spread of the development of equipment using microtechnology and nanotechnology, circuits in need are smaller, more efficient and consume less power. Methods of Minimizing Boolean Functions become important as they allow optimization of logic circuits by generating circuits having the same functionality, but minimized. Studies in Minimizing Boolean Functions area are carried out long ago, and are being adapted to new technologies. The generation of prime implicants of a Boolean function is one of the steps for covering the function of the minterms, and consequently to obtain the minimum cost function. In this work, the first phase of the Quine-McCluskey Method for Booleans Functions with Multiple Output (QMM) was implemented for comparison with Proposed Methods GPMultiplo and MultiGeraPlex (based on the philosophy of GeraPlex algorithm). The proposed methods generates the prime implicants of a Boolean Function with Multiple Output and using the iterative consensus operation to compare two terms. The results obtained by comparing the GPMultiplo, MultiGeraPlex and the first phase of the QMM Method, were able to prove that the application of the proposed methods becomes more feasible and advantageous, by allowing smaller execution time, number of implicants and number of comparisons.
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Franciscani, Juliana de Fátima. "Consenso Iterativo : geração de implicantes primos para minimização de funções booleanas com múltiplas saídas /." Ilha Solteira, 2016. http://hdl.handle.net/11449/144517.
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Orientador: Alexandre Cesar Rodrigues SilvaResumo: Com a evolução e difusão do desenvolvimento de equipamentos utilizando microtecnologia e nanotecnologia, circuitos cada vez menores, mais eficientes e que consomem menos energia, são necessários. Os métodos de minimização de funções booleanas tornam-se relevantes por possibilitarem a otimização de circuitos lógicos, através da geração de circuitos que possuam a mesma funcionalidade, porém, minimizados. Estudos na área de minimização de funções booleanas são realizados há muito tempo, e estão sendo adaptados às novas tecnologias. A geração de implicantes primos de uma função booleana é um dos passos para a cobertura dos mintermos da função e, consequentemente, para a obtenção da função de custo mínimo. Neste trabalho, a Primeira Fase do Método de Quine-McCluskey para Funções Booleanas com Múltiplas Saídas (QMM) foi implementada para posterior comparação com os Métodos Propostos GPMultiplo e MultiGeraPlex (baseados na filosofia do algoritmo GeraPlex). Os métodos propostos geram os implicantes primos de uma função booleana com múltiplas saídas e utilizam a operação de consenso iterativo para comparar dois termos. Os resultados obtidos, através da comparação do GPMultiplo, MultiGeraPlex e da Primeira Fase do Método de QMM, puderam comprovar que a aplicação dos métodos propostos torna-se mais viável e vantajosa por permitir menor tempo de execução e uso de memória, menor quantidade de implicantes gerados e de comparações entre os termos.
Mestre
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Reichler, Joakim. "Utvecklingsprocessen av ett företags produktionssystem : En kvalitativ intervjustudie om hur ett medelstort företag beaktar användarcentrerad systemdesign i utvecklingsprocessen av ett nytt produktionssystem." Thesis, Södertörns högskola, Institutionen för naturvetenskap, miljö och teknik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-19530.
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I denna studie har författaren undersökt hur ett medelstort företag gick tillväga vid framtagan-det av ett produktionssystem och jämfört processen med de teorier och riktlinjer som finns för användarcentrerad systemdesign. Studien har genomförts baserat på litteraturstudier och semistrukturerade intervjuer. Intervjuobjekten har utsetts tillsammans med handledaren, tillika linjechef för utvecklings-gruppen, på företaget för att redovisa olika perspektiv på utvecklingsarbetet. I resultatavsnittet presenteras utvecklingsprocessen med en modell av flödet tillsammans med en beskrivande text. Genom interna instruktioner för utveckling av datoriserade system anslu-ter företaget bl.a. till olika teorier inom användarcentrerad systemdesign. I det studerade ut-vecklingsprojektet var olika användare inledningsvis med informellt och allteftersom systemet växte så fick de vara med och göra acceptanstester och utvärderingar innan nya uppdateringar skulle släppas. Slutsatsen av studien är att flera inslag av användarcentrerad systemdesign applicerats i ut-vecklingsarbetet i företaget vilket sammantaget gör att användarnas synpunkter tagits tillvara. Dock följer företaget inte någon speciell metod inom området vilket sannolikt skulle förbättra utvecklingsprocessen i framtida projekt.
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Kim, JoonBeom. "Iterative Channel Estimation for Wireless Communications." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/14064.
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The main objective of this dissertation is to present the structural design, performance evaluation, and complexity reduction of iterative joint channel estimation and data detection receivers. One of the main technical challenges in advanced wireless communications stems from the characteristics of a wireless channel, e.g., time selectivity of a channel, mobility of users, and multipath propagation. Channel estimation is essential for achieving reliable information transmission for practical wireless communication applications. Numerous channel estimation structures have been developed for different underlying channels using pilot-symbol assisted modulation (PSAM) approaches. However, since pilot symbols carry no data information, the time and the power spent on pilot symbols degrades the efficiency and the throughput of the system. Therefore, it is necessary to minimize the pilot insertion ratio without degrading the error performance. This motivates our research on iterative joint channel estimation and data detection receivers with full- and reduced- or low-complexity.
In this thesis, we first propose an iterative channel estimator (ICE), based on a maximum a posteriori (MAP) algorithm, for single-carrier systems with PSAM structures. In contrast to existing MAP channel estimators, the proposed channel estimator has a lower computational complexity, which increases linearly with the modulation alphabet size. The computational complexity is reduced by exploiting a survivor in an efficient manner, while achieving comparable error performance to a full complexity receiver. For orthogonal frequency division multiplexing (OFDM) systems, we also propose novel signal constellations to facilitate channel estimation without pilot symbol transmission, and analyze the bit error rate for the proposed constellations. We also develop a suitable joint channel estimation and data detector with full- and low-complexity for the proposed constellations. This low-complexity ICE achieves an error performance comparable to the ICE with full-complexity. Finally, for vertical Bell Laboratories layered space-time OFDM systems, we propose an ICE based on a PSAM structure for time-varying multipath fading channels. By exploiting the statistical properties of a wireless channel, we also develop a method to suppress intercarrier interference due to the channel time selectivity, and propose a low-complexity ICE that exploits a priori information in an efficient manner.
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Ito, Masayuki, 直史 高木, Naofumi Takagi, and Shuzo Yajima. "Square rooting by iterative multiply-additions." Elsevier, 1996. http://hdl.handle.net/2237/2752.
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Schulze, Bert-Wolfgang. "The iterative structure of corner operators." Universität Potsdam, 2008. http://opus.kobv.de/ubp/volltexte/2009/3035/.
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We give a brief survey on some new developments on elliptic operators on manifolds with polyhedral singularities. The material essentially corresponds to a talk given by the author during the Conference “Elliptic and Hyperbolic Equations on Singular Spaces”, October 27 - 31, 2008, at the MSRI, University of Berkeley.
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Patrick, Brian Glen. "An analysis of iterative-deepening-A* /." Thesis, McGill University, 1991. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=70298.
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Iterative-deepening-A* (IDA*) is an admissible heuristic search algorithm which is optimal with respect to space complexity and the cost of solution found over the class of admissible best-first tree search algorithms. However, the optimality of IDA* with respect to time complexity is subject to a number of conditions. It is the focus of this dissertation to identify the conditions that give rise to the worst case performance of IDA* and to delineate a time complexity spectrum between its optimal and worst case performance. In addition, the expected case performance of IDA* is derived with respect to a probabilistic model of computation that assumes the differential edge costs are independently and identically distributed as random non-negative integers. Under this assumption, IDA* exhibits asymptotic optimal performance for any integer probability distribution that satisfies a couple of weak conditions. Finally, to redress the worst case phenomenon of expanding only a few additional nodes over several iterations, a new admissible search algorithm, called Binary IDA* (BIDA*), is presented and compared against the performance of IDA* on the Euclidean traveling salesperson problem. It is shown in a small empirical study that BIDA* is a significant improvement over IDA* as both the tour size and the precision of the edge costs increase.
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Röllin, Stefan Karl. "Parallel iterative solvers in computational electronics /." Zürich, 2005. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=15859.
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