To see the other types of publications on this topic, follow the link: Graphs and charts.
Dissertations / Theses on the topic 'Graphs and charts'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Graphs and charts.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Marchant, Edward James. "Graphs with weighted colours and hypergraphs." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609454.
Full text
2
Fausset, Cara Bailey. "On processing line graphs." Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24605.
Full text
3
Haslegrave, John George Ernest. "Extremal results on hypergraphs, trees and regular graphs." Thesis, University of Cambridge, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.609876.
Full text
4
Bodily, Robert Gordon. "Designing, Developing, and Implementing Real-Time Learning Analytics Student Dashboards." BYU ScholarsArchive, 2018. https://scholarsarchive.byu.edu/etd/7258.
Full textAbstract:
This document is a multiple-article format dissertation that discusses the iterative design, development, and evaluation processes necessary to create high quality learning analytics dashboard systems. With the growth of online and blended learning environments, the amount of data that researchers and practitioners collect from learning experiences has also grown. The field of learning analytics is concerned with using this data to improve teaching and learning. Many learning analytics systems focus on instructors or administrators, but these tools fail to involve students in the data-driven decision-making process. Providing feedback to students and involving students in this decision-making process can increase intrinsic motivation and help students succeed in online and blended environments. To support online and blended teaching and learning, the focus of this document is student-facing learning analytics dashboards. The first article in this dissertation is a literature review on student-facing learning analytics reporting systems. This includes any system that tracks learning analytics data and reports it directly to students. The second article in this dissertation is a design and development research article that used a practice-centered approach to iteratively design and develop a real-time student-facing dashboard. The third article in this dissertation is a design-based research article focused on improving student use of learning analytics dashboard tools.
5
El-Zouki, Robert. "Producera mängdgrafer genom BIM : Produce quantity take-off graphs using BIM." Thesis, KTH, Byggnadsteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-209563.
Full textAbstract:
Avvikelser i ett byggprojekt leder till bland annat förseningar. De kan även leda till för tidigt avslutadeaktiviteter. Oavsett blir detta ett problem då kontraktstiden för underentreprenörer är bestämda.Vad detta betyder är att blir en underentreprenör färdig för tidigt kommer det finnas en tidbuffert itidplan mellan färdig- och nästa aktivitet. Detta anses som en kostnad eftersom det inte utförs någotarbete. Blir en underentreprenör sen med färdigställande av en aktivitet blir detta ocksåproblematiskt då detta skjuter fram aktiviteter på den kritiska linjen. Förutsatt att de aktiviteternaligger på den kritiska linjen. Det ska förtydligas att fler former av avvikelser finns. Bland annatfelleverans, försenad transport, oförutsedda hinder under produktion m.m. En metod att åskådliggöra avvikelser tidigt efter initiering är att kontinuerligt under produktion följaupp aktiviteter med hjälp av mängdgrafer. Mängdgrafer är diagram som visar byggd mängd pertidsenhet och kumulativ byggd mängd. De ger en visuell bild över hur produktionen ligger till inuläget och med hjälp av dessa kan beslut fattas om ändringar i produktionen för att projektet skatidsmässigt åter hamna i fas. Mängdgrafer kommer i tre former. Planerade-, aktuella- &prognostiserade mängdgrafer. Syftet med detta examensarbete är att undersöka hur BIM-verktyg under projektering kan stödja ettprojekt under produktion genom att förutse avvikelser. Ifall avvikelser upptäcks tidigt kan resurserjusteras eller arbetstider ändras för att projektet färdigställs enligt tidplan. Studien visar att mängdgraferna kan utvecklas relativt enkelt men det krävs väl genomtänktplanering och struktur på arbetet. Det rekommenderas att samordna en bra arbetsmetod för helaarbetet från början till slut genom att ha en samordnare som styr över modellen men också andratjänstemän som känner till programmet tillräckligt bra för att stötta och avlasta samordnaren vidbehov. Studien visar också att det är viktigt att modellutvecklare levererar modellen med bra ochstrukturerad namnbeteckning för objekten. Detta för att enklare kunna koppla KPI-tal till korrektmängdgraf. CoClass-klassifikationssystem (projektnamn BSAB 2.0) borde ligga till grund förnamngivning av objekt.Deviations in a construction project lead to delays. They can also lead to prematurely completed activities. In any case, this will be a problem since the contract period for subcontractors is determined. What this means is that if a subcontractor completes its task prematurely, there will be a time buffer in the timetable between completed and next activity. This is considered a cost because no work is being done. If a subcontractor completes an activity late, this is also problematic as it displaces activities on the critical line. If the activities are on the critical line. It should be clarified that more types of deviations exist. Including delivery, delayed transport, unforeseen obstructions during production, etc. One method of avoiding deviations is to continuously monitor production activities using quantity take-off graphs. These graphs are charts showing built-up amount per unit of time and cumulative built-up amount. They give a visual picture of the state of production, and from there, decisions can be made about changes in production so that the project will follow the time schedule again. Quantity take-off charts come in three forms. Planned, actual & forecast quantity take-off graphs. The purpose of this degree project is to investigate how BIM tools during design phase can support a project under production phase by predicting deviations. If deviations are early discovered, resources can be adjusted or working hours changed to complete the project according to time schedule. The study shows that the quantity graphs can be developed relatively easily, but well thought out planning and structure are required. It is recommended to coordinate a good working method for the entire work from start to finish by having a coordinator who controls the model but also other officials who know the program well enough to support and relieve the coordinator if necessary. The study also shows that it is important that model developers deliver the model with a good and structured designation of object. This is easier to connect KPI-numbers to the correct quantity takeoff graph. CoClass classification system (project name BSAB 2.0) should be used as the basis for naming of objects.
6
Davison, Benjamin Kenneth. "Universal graph literacy: understanding how blind and low vision students can satisfy the common core standards with accessible auditory graphs." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/47621.
Full textAbstract:
Auditory graphs and active point estimation provide an inexpensive, accessible alternative for low vision and blind K-12 students using number lines and coordinate graphs. In the first phase of this research program, a series of four psychophysics studies demonstrated an interactive auditory number line that enables blind, low vision, and sighted people to find small targets with a laptop, headphones, and a mouse or a keyboard. The Fitts' Law studies showed that, given appropriate auditory feedback, blind people can use a mouse. In addition, auditory feedback can generate target response patterns similar to when people use visual feedback. Phase two introduced SQUARE, a novel method for building accessible alternatives to existing education technologies. The standards-driven and teacher-directed approach generated 17 graphing standards for sixth grade mathematics, all of which emphasized point estimation. It also showed that how only few basic behavioral components are necessary for these graphing problems. The third phase evaluated active point estimation tools in terms of training, classroom situations, and a testing situation. This work shows that students can learn to graph in K-12 environments, regardless of their visual impairment. It also provides several technologies used for graphing, and methods to further develop education accessibility research.
7
Vargas, Gonzalez Andres. "SketChart: A Pen-Based Tool for Chart Generation and Interaction." Master's thesis, University of Central Florida, 2014. http://digital.library.ucf.edu/cdm/ref/collection/ETD/id/6375.
Full textAbstract:
It has been shown that representing data with the right visualization increases the understanding of qualitative and quantitative information encoded in documents. However, current tools for generating such visualizations involve the use of traditional WIMP techniques, which perhaps makes free interaction and direct manipulation of the content harder. In this thesis, we present a pen-based prototype for data visualization using 10 different types of bar based charts. The prototype lets users sketch a chart and interact with the information once the drawing is identified. The prototype's user interface consists of an area to sketch and touch based elements that will be displayed depending on the context and nature of the outline. Brainstorming and live presentations can benefit from the prototype due to the ability to visualize and manipulate data in real time. We also perform a short, informal user study to measure effectiveness of the tool while recognizing sketches and users acceptance while interacting with the system. Results show SketChart strengths and weaknesses and areas for improvement.M.S.
Masters
Electrical Engineering and Computer Science
Engineering and Computer Science
Computer Science
8
Bektasli, Behzat. "The relationships between spatial ability, logical thinking, mathematics performance and kinematics graph interpretation skills of 12th grade physics students." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1149269242.
Full text
9
Simmons, Dayton C. (Dayton Cooper). "Applications of Rapidly Mixing Markov Chains to Problems in Graph Theory." Thesis, University of North Texas, 1993. https://digital.library.unt.edu/ark:/67531/metadc277740/.
Full textAbstract:
In this dissertation the results of Jerrum and Sinclair on the conductance of Markov chains are used to prove that almost all generalized Steinhaus graphs are rapidly mixing and an algorithm for the uniform generation of 2 - (4k + 1,4,1) cyclic Mendelsohn designs is developed.
10
Venkatasubramanian, Ramprasad. "Flowgrapher : generation of conceptual graphs from flowcharts /." Master's thesis, This resource online, 1994. http://scholar.lib.vt.edu/theses/available/etd-10242009-020119/.
Full text
11
Genest, Blaise. "L'odyssée des graphes de diagrammes de séquences ( MSC-Graphes)." Paris 7, 2004. http://www.theses.fr/2004PA077210.
Full text
12
Stoyanov, Tsvetan I. "Isoperimetic and related constants for graphs and markov chains." Diss., Georgia Institute of Technology, 2001. http://hdl.handle.net/1853/29456.
Full text
13
Uyandiran, Ali Sarp. "PHP Library for Graph Generation." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2020. http://www.nusl.cz/ntk/nusl-416674.
Full textAbstract:
The programming languages have always been a useful tool for sustainability and continuity of advancements in multilayered fields as like education and common industries. PHP is a widespread instrument which has an important place in this practices just like many other programming languages. This research is conducted to understand PHP language better and to increase academical familiarity about it. In the end of this practice a basic PHP library for further use has been produced as a representation of the research which has been conducted. This library allows the user to create multivariate basic graphs for visualization of variable different data and it’s hoped that it will be used by further educational and business purposes by various individuals.
14
Lopes, Fabio Marcellus Lima Sá Makiyama. "Limite do fluído para o grafo aleatório de Erdos-Rényi." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/45/45133/tde-05052010-155151/.
Full textAbstract:
Neste trabalho, aplicamos o algoritmo Breadth-First Search para encontrar o tamanho de uma componente conectada no grafo aleatório de Erdos-Rényi. Uma cadeia de Markov é obtida deste procedimento. Apresentamos alguns resultados bem conhecidos sobre o comportamento dessa cadeia de Markov. Combinamos alguns destes resultados para obter uma proposição sobre a probabilidade da componente atingir um determinado tamanho e um resultado de convergência do estado da cadeia neste instante. Posteriormente, aplicamos o teorema de convergência de Darling (2002) a sequência de cadeias de Markov reescaladas e indexadas por N, o número de vértices do grafo, para mostrar que as trajetórias dessas cadeias convergem uniformemente em probabilidade para a solução de uma equação diferencial ordinária. Deste resultado segue a bem conhecida lei fraca dos grandes números para a componente gigante do grafo aleatório de Erdos-Rényi, no caso supercrítico. Além disso, obtemos o limite do fluído para um modelo epidêmico que é uma extensão daquele proposto em Kurtz et al. (2008).In this work, we apply the Breadth-First Search algorithm to find the size of a connected component of the Erdos-Rényi random graph. A Markov chain is obtained of this procedure. We present some well-known results about the behavior of this Markov chain, and combine some of these results to obtain a proposition about the probability that the component reaches a certain size and a convergence result about the state of the chain at that time. Next, we apply the convergence theorem of Darling (2002) to the sequence of rescaled Markov chains indexed by N, the number of vertices of the graph, to show that the trajectories of these chains converge uniformly in probability to the solution of an ordinary dierential equation. From the latter result follows the well-known weak law of large numbers of the giant component of the Erdos-Renyi random graph, in the supercritical case. Moreover, we obtain the uid limit for an epidemic model which is an extension of that proposed in Kurtz et al. (2008).
15
Streib, Noah Sametz. "Planar and hamiltonian cover graphs." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43744.
Full textAbstract:
This dissertation has two principal components: the dimension of posets with planar cover graphs, and the cartesian product of posets whose cover graphs have hamiltonian cycles that parse into symmetric chains. Posets of height two can have arbitrarily large dimension. In 1981, Kelly provided an infinite sequence of planar posets that shows that the dimension of planar posets can also be arbitrarily large. However, the height of the posets in this sequence increases with the dimension. In 2009, Felsner, Li, and Trotter conjectured that for each integer h at least 2, there exists a least positive integer c(h) so that if P is a poset with a planar cover graph (the class of posets with planar cover graphs includes the class of planar posets) and the height of P is h, then the dimension of P is at most c(h). In the first principal component of this dissertation we prove this conjecture. We also give the best known lower bound for c(h), noting that this lower bound is far from the upper bound. In the second principal component, we consider posets with the Hamiltonian Cycle--Symmetric Chain Partition (HC-SCP) property. A poset of width w has this property if its cover graph has a hamiltonian cycle which parses into w symmetric chains. This definition is motivated by a proof of Sperner's theorem that uses symmetric chains, and was intended as a possible method of attack on the Middle Two Levels Conjecture. We show that the subset lattices have the HC-SCP property by showing that the class of posets with the strong HC-SCP property, a slight strengthening of the HC-SCP property, is closed under cartesian product with a two-element chain. Furthermore, we show that the cartesian product of any two posets from this strong class has the (weak) HC-SCP property.
16
Varloot, Rémi. "Dynamic network formation." Thesis, Paris Sciences et Lettres (ComUE), 2018. http://www.theses.fr/2018PSLEE048/document.
Full textAbstract:
Cette thèse porte sur la rapidité du temps de mélange de chaînes de Markov sur des graphes. La contribution principale concerne les graphes avec des dynamiques locales sur les arêtes, la topologie du graphe évoluant au fur et à mesure que les arêtes glissent les unes le long des autres. Nous proposons une classification des différents modèles existants de graphes dynamiques, tout en illustrant l’importance des transitions le long d’une structure mouvante pour améliorer la vitesse de convergence. Cette étude est complétée par la preuve, pour l’une de ces dynamiques, d’un temps de mélange rapide. Nous définissons notamment l’expansion partielle d’un graphe. Celle-ci permet de suivre l’avancement de la dynamique, partant d’un état de faible expansion, jusqu’à obtention d’une bonne expansion à l’équilibre. La fin de cette thèse porte sur une amélioration de l’algorithme de simulation parfaite de Propp et Wilson. Nous introduisant un oracle pour les transitions, inspiré de l’échantillonnage préférentiel, qui permet de réduire la complexité de l’algorithme. Nous fournissons une preuve de correction, ainsi qu’une étude de l’impact de cette méthode sur la vitesse d’échantillonnage d’ensembles indépendants pour certains graphesThis thesis focuses on the rapid mixing of graph-related Markov chains. The main contribution concerns graphs with local edge dynamics, in which the topology of a graph evolves as edges slide along one another. We propose a classification of existing models of dynamic graphs, and illustrate how evolving along a changing structure improves the convergence rate. This is complemented by a proof of the rapid mixing time for one such dynamic. As part of this proof, we introduce the partial expansion of a graph. This notion allows us to track the progression of the dynamic, from a state with poor expansion to good expansion at equilibrium. The end of the thesis proposes an improvement of the Propp and Wilson perfect sampling technique. We introduce oracle sampling, a method inspired by importance sampling that reduces the overall complexity of the Propp and Wilson algorithm. We provide a proof of correctness, and study the performance of this method when sampling independent sets from certain graphs
17
Dayson, Gaynor. "Children’s concepts about the slope of a line graph." Thesis, University of British Columbia, 1985. http://hdl.handle.net/2429/25377.
Full textAbstract:
This study is concerned with how children interpret the slope of a line graph. Today with the vast accumulations of data which are available from computers, people are being faced with an ever increasing amount of pictorial representation of this data. Therefore it is of the utmost importance that children understand pictorial representation. Yet in spite of the popularity of graphs as tools of communication, studies show that many adults experience difficulty in reading information presented in a graphical form.
The slope of the graph was chosen for this investigation because it is in this aspect of graphing (as shown by the results of the 1981 B.C. Assessment) that children in British Columbia seem to have the greatest difficulty when they reach Grade 8. The study dealt with positive, negative, zero and infinite slopes, combinations of these slopes, curvilinear graphs and qualitative graphs, that is, graphs that have no numerical data shown on the axes.
The researcher chose to use a structured individual interview as a means of collecting data about how the students interpreted the slope of a line graph. Graphs used in the interviews dealt with temperature, height, weight and distance. Twenty-two students were chosen for this study.
The students were found to have problems mainly with graphs dealing with distance related to time. This problem may be due to the fact that many students read only one axis and when interpreting distance seem to include direction as an added dimension of the graph. Infinite slope graphs were misinterpreted by every student, which may be due to the fact that they ignore the time axis. In general students used two methods of interpreting graphs. In some cases they observed the direction of the graph from left to right, that is, whether the slope went up or down from left to right. In other cases they examined the end points on the graph and drew their conclusions from them. The choice of method varied with the contextual material shown on the graph, which may be due to the children's concept of the parameter in the physical world and whether they see the parameter as being able to increase and decrease over time.
From the study the investigator feels that more discussion of graphing by teachers and students is needed if the misconceptions are to be cleared up. Discussion of the parameters of both axes by teachers might help clear up the misconceptions students have about distance travelled over a period of time when this is expressed as a graph. There would be less chance of a graph being read as a map if the relationships between the two axes were demonstrated to students. Teachers also need to be aware of both methods used by students in interpreting graphs.Education, Faculty of
Graduate
18
Johnson, Amanda Rachel. "Off the Charts: how to make a scene." Thesis, University of Iowa, 2015. https://ir.uiowa.edu/etd/1649.
Full textAbstract:
This body of work explores multiple technical and aesthetic methods of representing complex statistical information in an approachable visual language, bridging the boundaries between data science, graphic design and fine arts. Ordinary data charts are combined together with other charts and diagrams and transformed in unexpected ways in order to form the basic structure of mythical landscape scenes. Line plots over time become the rising and falling curves of hills and mountains, bar charts are morphed into industrial factories on the horizon, and bubble charts become billowing smoke, a forest of trees, or a school of fish. The hope is that the work will act as an engaging alternative to traditional data representation and will encourage curiosity and a fresh perspective.
19
Pati, Amrita. "Graph-based genomic signatures." Diss., Virginia Tech, 2008. http://hdl.handle.net/10919/27423.
Full textAbstract:
Genomes have both deterministic and random aspects, with the underlying DNA sequences exhibiting features at numerous scales, from codons to regions of conserved or divergent gene order. Genomic signatures work by capturing one or more such features e±ciently into a compact mathematical structure. This work examines the unique manner in which oligonucleotides fit together to comprise a genome, within a graph-theoretic setting. A de Bruijn chain (DBC) is a marriage of a de Bruijn graph and a finite Markov chain. By representing a DNA sequence as a walk over a DBC and retaining specific information at nodes and edges, we are able to obtain the de Bruijn chain genomic signature (DBCGS), based on both graph structure and the stationary distribution of the DBC. We demonstrate that DBCGS is information-rich, efficient, sufficiently representative of the sequence from which it is derived, and superior to existing genomic signatures such as the dinucleotides odds ratio and word frequency based signatures. We develop a mathematical framework to elucidate the power of the DBCGS signature to distinguish between sequences hypothesized to be generated by DBCs of distinct parameters. We study the effect of order of the DBCGS signature on accuracy while presenting relationships with genome size and genome variety. We illustrate its practical value in distinguishing genomic sequences and predicting the origin of short DNA sequences of unknown origin, while highlighting its superior performance compared to existing genomic signatures including the dinucleotides odds ratio.
Additionally, we describe details of the CMGS database, a centralized repository for raw and value-added data particular to C. elegans.Ph. D.
20
Miranda, Maria do Carmo da Silva Rodrigues. "Uma trajetória hipotética de aprendizagem: leitura e interpretação de gráficos e tabelas e medidas de tendência central em uma perspectiva construtivista." Pontifícia Universidade Católica de São Paulo, 2011. https://tede2.pucsp.br/handle/handle/10859.
Full textAbstract:
Made available in DSpace on 2016-04-27T16:57:05Z (GMT). No. of bitstreams: 1
Maria do Carmo da Silva Rodrigues Miranda.pdf: 4466440 bytes, checksum: 78da9e3297c73fa1710f24e092943e46 (MD5)
Previous issue date: 2011-05-13Secretaria da Educação do Estado de São Paulo
This study aimed to determine how to develop a Hypothetical Learning Trajectory (HLT), according to constructivist perspectives, considering the reading and interpreting of figures, charts and measures of mean, median and mode. Thus, It was analyzed the performance of the mathematics teachers in relation to the planning and development of a hypothetical learning trajectory, consistent with the constructivist perspective of learning. For the theoretical background, it was used the theory of Simon (1995), because it defends the formulation of models of teaching based on a constructivist perspective. The study is part of a research project entitled "Construction of Hypothetical Learning Trajectories and Implementation of Curriculum Innovation in Mathematics Teaching in High School." In order to answer the research questions, It was carried out a qualitative study, with the participation of three teachers under cooperation of the State of São Paulo and 90 students of the 3rd Grade of high school. The (HLT) was established by the researcher based on the results of researches conducted about reading and interpreting graphs and statistical charts, measures of mean, median and mode which includes tasks, containing charts of gross data, problem-situations, graphics representations and tasks involved in exploratory data analysis. Supported by the results found, we inferred that the use of research results contributes to the planning of teaching and learning situations, however, it is necessary to review how they could reach the teachers. It is considered that, despite the use of (HLT) be relevant and truly important as a reference point for planning teaching activities; its development is a difficult task within the framework of a learning process, according to the assumptions of a constructivist perspective. In addition to, it was noticed that only the (HLT) is not enough to happen a meaningful learning
Este estudo teve como objetivo verificar como desenvolver uma trajetória hipotética de aprendizagem (THA), de acordo com as perspectivas construtivistas, contemplando a leitura e a interpretação de gráficos, tabelas e medidas de média, moda e mediana. Assim, analisou-se a atuação do professor de Matemática, no que se refere ao planejamento e desenvolvimento de uma trajetória hipotética de aprendizagem, de forma compatível com a perspectiva construtivista de aprendizagem. Para a fundamentação teórica, a teoria de Simon (1995) foi usada, pois defende a formulação de modelos de ensino, baseados em uma perspectiva construtivista. O estudo faz parte de um projeto de pesquisa denominado Construção de Trajetórias Hipotéticas de Aprendizagem e Implementação de Inovações Curriculares em Matemática no Ensino Médio . Com a finalidade de responder às questões de pesquisa, realizou-se um estudo de natureza qualitativa, contando com a participação de três professores em regime de colaboração da rede pública do Estado de São Paulo e 90 alunos da 3.ª série do Ensino Médio. A THA foi elaborada pela pesquisadora com base nos resultados de pesquisas já realizadas sobre leitura e interpretação de gráficos e tabelas estatísticas, medidas de média, moda e mediana que contemplam tarefas, contendo tabelas de dados brutos, situações-problema, representações gráficas e tarefas que envolveram a análise exploratória dos dados. Apoiada nos resultados obtidos, inferiu-se, que o uso dos resultados de pesquisa contribui de forma relevante para o planejamento de situações de ensino e aprendizagem, porém, é necessário rever como estas poderão chegar aos professores. Considera-se que, apesar do uso das THAs ser relevantes e servir realmente de ponto de referência para o planejamento das atividades de ensino, sua elaboração é uma tarefa difícil dentro do âmbito de uma aprendizagem, segundo os pressupostos de uma perspectiva construtivista. Ressalta-se ainda que apenas a THA não é suficiente, para que ocorra uma aprendizagem significativa
21
Ayala-Hoffmann, Jose. "Global behavior of graph dynamics with applications to Markov chains." [Ames, Iowa : Iowa State University], 2008.
Find full text
22
Tupin, Florence. "Champs de Markov sur graphes pour le traitement des images radar /." Paris : École nationale supérieure des télécommunications, 2007. http://catalogue.bnf.fr/ark:/12148/cb41098170v.
Full textAbstract:
Habilitation à diriger des recherches--Traitement du signal et des images--Paris--ENST, 2007.La p. de titre et la couv. portent en plus : "Département Traitement du signal et des images. Groupe Traitement et interprétation des images" Bibliogr. p. 103-117.
23
Espinasse, Thibault. "Champs et processus gaussiens indexés par des graphes, estimation et prédiction." Toulouse 3, 2011. http://thesesups.ups-tlse.fr/1578/.
Full textAbstract:
L'objet de cette thèse est l'étude de processus gaussiens indexés par des graphes. Le but est de fournir des outils pour la modélisation, l'estimation, et la prédiction de tels champs ou processus, utilisant fortement la structure du graphe. Dans un premier travail, nous nous intéressons au problème de prédiction aveugle de séries chronologiques et montrons que le biais de l'erreur de prédiction décroît à une vitesse qui dépend de la régularité de la densité spectrale, sous une hypothèse de courte mémoire. Nous utilisons ensuite la structure spectrale du graphe pour proposer des modèles de covariance pour des champs gaussiens indexés par ce graphe. Cela fournit immédiatement une représentation spectrale, qui permet d'étendre l'approximation de Whittle et l'estimation par quasi-maximum de vraissemblance à ce cadre. Enfin, cette constructionet le lemmede Szegöpeuventêtre étendus au cas spatiotemporel. Cela permet de mettre en pratique la théorie sur des données réellesIn this work, westudy Gaussian processes indexed by graphs. Weaim at providing tools for modelisation, estimation, and prediction, that uses the structure of the underlying graphs. In the first Chapter,we deal with the blind prediction problem, and compute, in the case of short range dependancy, the rate of convergence of the bias in the prediction error. This rate depends on the regularity of the spectral density of the process. Then, we use the eigenstructure of the adjacency operatorofa graphto propose some models for covariance operators of Gaussian fields indexedby this graph. It leads to aspectral representation for this operator, that can be used to extend Whittle approximation, and quasi-maximum likelihoo destimation. Finally, this construction may be extended to the spatio-temporal case, where the Szegö lemma still holds
24
Benaddi, Tarik. "Sparse graph-based coding schemes for continuous phase modulations." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/16037/1/Benaddi_Tarik.pdf.
Full textAbstract:
The use of the continuous phase modulation (CPM) is interesting when the channel represents a strong non-linearity and in the case of limited spectral support; particularly for the uplink, where the satellite holds an amplifier per carrier, and for downlinks where the terminal equipment works very close to the saturation region. Numerous studies have been conducted on this issue but the proposed solutions use iterative CPM demodulation/decoding concatenated with convolutional or block error correcting codes. The use of LDPC codes has not yet been introduced. Particularly, no works, to our knowledge, have been done on the optimization of sparse graph-based codes adapted for the context described here. In this study, we propose to perform the asymptotic analysis and the design of turbo-CPM systems based on the optimization of sparse graph-based codes. Moreover, an analysis on the corresponding receiver will be done.
25
Levitz, Michael. "Separation, completeness, and Markov properties for AMP chain graph models /." Thesis, Connect to this title online; UW restricted, 2000. http://hdl.handle.net/1773/9564.
Full text
26
Valenzuela, Pacheco Patricio E. "Optimal input design for nonlinear dynamical systems : a graph-theory approach." Licentiate thesis, KTH, Reglerteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-155136.
Full textAbstract:
Optimal input design concerns the design of an input sequence to maximize the information retrieved from an experiment. The design of the input sequence is performed by optimizing a cost function related to the intended model application. Several approaches to input design have been proposed, with results mainly on linear models. Under the linear assumption of the model structure, the input design problem can be solved in the frequency domain, where the corresponding spectrum is optimized subject to power constraints. However, the optimization of the input spectrum using frequency domain techniques cannot include time-domain amplitude constraints, which could arise due to practical or safety reasons. In this thesis, a new input design method for nonlinear models is introduced. The method considers the optimization of an input sequence as a realization of the stationary Markov process with finite memory. Assuming a finite set of possible values for the input, the feasible set of stationary processes can be described using graph theory, where de Bruijn graphs can be employed to describe the process. By using de Bruijn graphs, we can express any element in the set of stationary processes as a convex combination of the measures associated with the extreme points of the set. Therefore, by a suitable choice of the cost function, the resulting optimization problem is convex even for nonlinear models. In addition, since the input is restricted to a finite set of values, the proposed input design method can naturally handle amplitude constraints. The thesis considers a theoretical discussion of the proposed input design method for identification of nonlinear output error and nonlinear state space models. In addition, this thesis includes practical applications of the method to solve problems arising in wireless communications, where an estimate of the communication channel with quantized data is required, and application oriented closed-loop experiment design, where quality constraints on the identified parameters must be satisfied when performing the identification step.QC 20141110
27
Di, Natale Anna. "Stochastic models and graph theory for Zipf's law." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/17065/.
Full textAbstract:
In questo elaborato ci siamo occupati della legge di Zipf sia da un punto di vista applicativo che teorico. Tale legge empirica afferma che il rango in frequenza (RF) delle parole di un testo seguono una legge a potenza con esponente -1.
Per quanto riguarda l'approccio teorico abbiamo trattato due classi di modelli in grado di ricreare leggi a potenza nella loro distribuzione di probabilità. In particolare, abbiamo considerato delle generalizzazioni delle urne di Polya e i processi SSR (Sample Space Reducing). Di questi ultimi abbiamo dato una formalizzazione in termini di catene di Markov. Infine abbiamo proposto un modello di dinamica delle popolazioni capace di unificare e riprodurre i risultati dei tre SSR presenti in letteratura.
Successivamente siamo passati all'analisi quantitativa dell'andamento del RF sulle parole di un corpus di testi. Infatti in questo caso si osserva che la RF non segue una pura legge a potenza ma ha un duplice andamento che può essere rappresentato da una legge a potenza che cambia esponente. Abbiamo cercato di capire se fosse possibile legare l'analisi dell'andamento del RF con le proprietà topologiche di un grafo. In particolare, a partire da un corpus di testi abbiamo costruito una rete di adiacenza dove ogni parola era collegata tramite un link alla parola successiva. Svolgendo un'analisi topologica della struttura del grafo abbiamo trovato alcuni risultati che sembrano confermare l'ipotesi che la sua struttura sia legata al cambiamento di pendenza della RF. Questo risultato può portare ad alcuni sviluppi nell'ambito dello studio del linguaggio e della mente umana. Inoltre, siccome la struttura del grafo presenterebbe alcune componenti che raggruppano parole in base al loro significato, un approfondimento di questo studio potrebbe condurre ad alcuni sviluppi nell'ambito della comprensione automatica del testo (text mining).
28
Montégut, Fabien. "Limites d'échelle de marches aléatoires contraintes." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30163.
Full textAbstract:
Cette thèse s'inscrit dans le domaine des théorèmes limites pour les chaînes de Markov. Nous considérons des suites de chaînes de Markov et cherchons à montrer des doubles asymptotiques pour des processus lorsque le temps et l'indice de la suite tendent vers l'infini. Dans une première phase, nous nous concentrerons sur le modèle des prisonniers dans lequel un nombre fini de marcheurs aléatoires sont contraints de rester proches les uns des autres. Notre objectif est de déterminer le comportement limite lorsque le temps et le nombre de prisonniers augmentent, en utilisant la décomposition de Hodge d'une fonctionnelle additive d'une marche aléatoire sur un graphe fini, dans la lignée de travaux antérieurs de Boissard, Cohen, Espinasse et Norris. Ensuite, nous tenterons de développer une généralisation de ce modèle dans lequel la décomposition de Hodge peut être utilisée pour prouver des théorèmes limites en double asymptotique. Enfin, nous considérerons deux autres modèles - les marches aléatoires dans le graphite et les hypercubes de dimension dollar K dollar - dans lesquels les techniques précédentes nous permettent de prouver des limites d'échelle dans ces deux contextesThis thesis falls within the field of limit theorems for Markov chains. We consider sequences of Markov chains, and focus on proving double asymptotics for such processes as both the time and the index in the sequence tend to infinity. In a first phase we will focus on the prisonners model in which a finite number of random walkers are constrained to stay close to each other. Our goal is to determine the limit behavior as the time and the number of prisonners is increasing, using the Hodge decomposition of an additive functionnal of a random walk on a finite graph, in line with previous work of Boissard, Cohen, Espinasse and Norris. Then we develop a generalisation of this model in which the Hodge decomposition can be used to prove limit theorem in double asymptotics. Finally we will consider two other models - the random walks in graphite and the dollar K dollar-dimensional hypercubes - in which the previous techniques allow us to prove scaling limits in both contexts
29
Abbey, Karen Diane. "Students' Understanding of Deriving Properties of a Function's Graph from the Sign Chart of the First Derivative." Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/AbbeyKD2008.pdf.
Full text
30
Isasi, Esteban. "Méthode de scission modulaire et symétries quantiques des graphes non-simplement lacés en théorie de champs comforme." Phd thesis, Université de la Méditerranée - Aix-Marseille II, 2006. http://tel.archives-ouvertes.fr/tel-00393835.
Full textAbstract:
Le premier objet de cette thése est de présenter une méthode de résolution pour l'équation de scission modulaire, équation qui permet de déterminer les symétries quantiques d'une théorie de champs conforme. On peut l'utiliser dans le cadre des théories associées aux graphes simplement lacés (les ADE de la famille SU2, ou leurs généralisations) et retrouver ainsi des résultats connus, en particulier la structure des groupoides quantiques associés.Le second objet de cette thése est d'appliquer cette technique dans le cadre plus général des graphes non simplement lacés afin de déterminer les algébres de symétries quantiques correspondantes, et d'explorer leurs propriétés. Plusieurs exemples de ce type sont analysés.
31
Isasi, Catalá Esteban. "Méthode de scission modulaire et symétries quantiques des graphes non-simplement lacés en théorie de champs conforme." Aix-Marseille 2, 2006. http://theses.univ-amu.fr.lama.univ-amu.fr/2006AIX22033.pdf.
Full textAbstract:
Le premier objet de cette thèse est de présenter une méthode de résolution pour l'équation de scission modulaire, équation qui permet de déterminer les symétries quantiques d'une théorie de champs conforme. On peut l'utiliser dans le cadre des théories associées aux graphes simplement lacés (les ADE de la famille SU2, ou leurs généralisations) et retrouver ainsi des résultats connus, en particulier la structure des groupoides quantiques associés. Le second objet de cette thèse est d'appliquer cette technique dans le cadre plus général des graphes non simplement lacés afin de déterminer les algèbres de symétries quantiques correspondantes, et d'explorer leurs propriétés. Plusieurs exemples de ce type sont analysésThe first purpose of this thesis is to present a method of resolution for the modular splitting equation, this method allows to to determine the quantum symmetries of a conformal field theory. The formalism can be applied to solve the quantum symmetries problem associated to simply laced graphs (ADE of the SU2 family, or their generalization) which leads to some known results, in particular, the structure of the associated quantum groupoid. The second purpose of this thesis is to apply this technique to the more general framework of the non simply laced graphs in order to determine the algebras of the corresponding quantum symmetries, and to explore their properties. Several examples of this type are analyzed
32
Linzner, Dominik [Verfasser], Heinz [Akademischer Betreuer] Köppl, and Manfred [Akademischer Betreuer] Opper. "Scalable Inference in Graph-coupled Continuous-time Markov Chains / Dominik Linzner ; Heinz Köppl, Manfred Opper." Darmstadt : Universitäts- und Landesbibliothek, 2021. http://d-nb.info/1225040817/34.
Full text
33
Fécamp, Vivien. "Recalage/Fusion d'images multimodales à l'aide de graphes d'ordres supérieurs." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC005/document.
Full textAbstract:
L’objectif principal de cette thèse est l’exploration du recalage d’images à l’aide de champs aléatoires de Markov d’ordres supérieurs, et plus spécifiquement d’intégrer la connaissance de transformations globales comme une transformation rigide, dans la structure du graphe. Notre cadre principal s’applique au recalage 2D-2D ou 3D-3D et utilise une approche hiérarchique d’un modèle de champ de Markov dont le graphe est une grille régulière. Les variables cachées sont les vecteurs de déplacements des points de contrôle de la grille.Tout d’abord nous expliciterons la construction du graphe qui permet de recaler des images en cherchant entre elles une transformation affine, rigide, ou une similarité, tout en ne changeant qu’un potentiel sur l’ensemble du graphe, ce qui assure une flexibilité lors du recalage. Le choix de la métrique est également laissée à l’utilisateur et ne modifie pas le fonctionnement de notre algorithme. Nous utilisons l’algorithme d’optimisation de décomposition duale qui permet de gérer les hyper-arêtes du graphe et qui garantit l’obtention du minimum exact de la fonction pourvu que l’on ait un accord entre les esclaves. Un graphe similaire est utilisé pour réaliser du recalage 2D-3D.Ensuite, nous fusionnons le graphe précédent avec un autre graphe construit pour réaliser le recalage déformable. Le graphe résultant de cette fusion est plus complexe et, afin d’obtenir un résultat en un temps raisonnable, nous utilisons une méthode d’optimisation appelée ADMM (Alternating Direction Method of Multipliers) qui a pour but d’accélérer la convergence de la décomposition duale. Nous pouvons alors résoudre simultanément recalage affine et déformable, ce qui nous débarrasse du biais potentiel issu de l’approche classique qui consiste à recaler affinement puis de manière déformableThe main objective of this thesis is the exploration of higher order Markov Random Fields for image registration, specifically to encode the knowledge of global transformations, like rigid transformations, into the graph structure. Our main framework applies to 2D-2D or 3D-3D registration and use a hierarchical grid-based Markov Random Field model where the hidden variables are the displacements vectors of the control points of the grid.We first present the construction of a graph that allows to perform linear registration, which means here that we can perform affine registration, rigid registration, or similarity registration with the same graph while changing only one potential. Our framework is thus modular regarding the sought transformation and the metric used. Inference is performed with Dual Decomposition, which allows to handle the higher order hyperedges and which ensures the global optimum of the function is reached if we have an agreement among the slaves. A similar structure is also used to perform 2D-3D registration.Second, we fuse our former graph with another structure able to perform deformable registration. The resulting graph is more complex and another optimisation algorithm, called Alternating Direction Method of Multipliers is needed to obtain a better solution within reasonable time. It is an improvement of Dual Decomposition which speeds up the convergence. This framework is able to solve simultaneously both linear and deformable registration which allows to remove a potential bias created by the standard approach of consecutive registrations
34
Faronius, Hofmann Therese, and Linda Håkansson. "Visualization Design Effects on Credibility and Data Perception, and the Importance of Digital Interaction." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-453694.
Full textAbstract:
An effective visualization can often give an insight into data that would otherwise be difficult to analyze. The company Assedon aims to make data understandable to their clients by using data visualization in an interactive user interface. The goal of this study was to create an interactive visual representation of data from the Swedish Public Employment Service with the use of dynamically created digital graphs that are considered credible and beneficial for data perception. Moreover, the goal was to study data perception of the digitally displayed and interactive graphs. The study was conducted by interviewing 19 people with different backgrounds, using a combination of a qualitative and a quantitative interview technique. The interviewees were shown three different designs of a graph type, and rated the graph as well as commented on the graph. The results of this study indicated that a graph is more likely to be perceived as credible if it looks modern and professional. This also means that the design of the graphs needs more attention than people might normally appreciate. The perception of data presented in digitally displayed graphs will be affected by several factors, but most prominently the choice of color can either enhance the perception or confuse. Lastly, interaction with the data will benefit the perception and create another dimension of the data, but only to a certain extent. If the graph is too difficult to evaluate, the purpose of the graph is lost and the interaction becomes a necessity instead of an asset.En graf kan ge insikt i data som annars är svår att analysera. It-företaget Assedons mål är att konvertera data till digitala interaktiva lösningar som gör data förståelig för deras klienter. Målet med denna studie var att skapa en interaktiv visuell representation av Arbetsförmedlingens data i ett användarvänligt gränssnitt. Detta gjordes genom att skapa digitala grafer som anses trovärdiga och fördelaktiga för datauppfattningen. Målet var även att undersöka hur datauppfattningen av digitala grafer påverkades av interaktion med dessa grafer. Studien utfördes genom att intervjua 19 personer från olika bakgrunder med användning av kvalitativa och kvantitativa intervjutekniker. Deltagarna i studien visades tre olika interaktiva designer av en graf typ och betygsatte dessa samt kommenterade. Resultaten visade att en digital graf är mer sannolik att uppfattas som trovärdig om den ser modern och professionell ut. Datauppfattningen påverkades av flera faktorer, främst färgvalen som kan förtydliga data, men även förvirra läsaren. Avslutningsvis, så kan interaktion erbjuda en ytterligare dimension till grafer och därmed förbättra förståelsen av data. Dock till en viss gräns, är grafen för svår att evaluera utan tillgång till interaktionen så förloras syftet med grafen och interaktionen blir en nödvändighet istället för en tillgång.
35
Lê-Huu, Dien Khuê. "Nonconvex Alternating Direction Optimization for Graphs : Inference and Learning." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLC005/document.
Full textAbstract:
Cette thèse présente nos contributions àl’inférence et l’apprentissage des modèles graphiquesen vision artificielle. Tout d’abord, nous proposons unenouvelle classe d’algorithmes de décomposition pour résoudrele problème d’appariement de graphes et d’hypergraphes,s’appuyant sur l’algorithme des directionsalternées (ADMM) non convexe. Ces algorithmes sontefficaces en terme de calcul et sont hautement parallélisables.En outre, ils sont également très générauxet peuvent être appliqués à des fonctionnelles d’énergiearbitraires ainsi qu’à des contraintes de correspondancearbitraires. Les expériences montrent qu’ils surpassentles méthodes de pointe existantes sur des benchmarkspopulaires. Ensuite, nous proposons une relaxationcontinue non convexe pour le problème d’estimationdu maximum a posteriori (MAP) dans les champsaléatoires de Markov (MRFs). Nous démontrons quecette relaxation est serrée, c’est-à-dire qu’elle est équivalenteau problème original. Cela nous permet d’appliquerdes méthodes d’optimisation continue pour résoudrele problème initial discret sans perte de précisionaprès arrondissement. Nous étudions deux méthodes degradient populaires, et proposons en outre une solutionplus efficace utilisant l’ADMM non convexe. Les expériencessur plusieurs problèmes réels démontrent quenotre algorithme prend l’avantage sur ceux de pointe,dans différentes configurations. Finalement, nous proposonsune méthode d’apprentissage des paramètres deces modèles graphiques avec des données d’entraînement,basée sur l’ADMM non convexe. Cette méthodeconsiste à visualiser les itérations de l’ADMM commeune séquence d’opérations différenciables, ce qui permetde calculer efficacement le gradient de la perted’apprentissage par rapport aux paramètres du modèle.L’apprentissage peut alors utiliser une descente de gradientstochastique. Nous obtenons donc un frameworkunifié pour l’inférence et l’apprentissage avec l’ADMMnon-convexe. Grâce à sa flexibilité, ce framework permetégalement d’entraîner conjointement de-bout-en-boutun modèle graphique avec un autre modèle, telqu’un réseau de neurones, combinant ainsi les avantagesdes deux. Nous présentons des expériences sur un jeude données de segmentation sémantique populaire, démontrantl’efficacité de notre méthodeThis thesis presents our contributions toinference and learning of graph-based models in computervision. First, we propose a novel class of decompositionalgorithms for solving graph and hypergraphmatching based on the nonconvex alternating directionmethod of multipliers (ADMM). These algorithms arecomputationally efficient and highly parallelizable. Furthermore,they are also very general and can be appliedto arbitrary energy functions as well as arbitraryassignment constraints. Experiments show that theyoutperform existing state-of-the-art methods on popularbenchmarks. Second, we propose a nonconvex continuousrelaxation of maximum a posteriori (MAP) inferencein discrete Markov random fields (MRFs). Weshow that this relaxation is tight for arbitrary MRFs.This allows us to apply continuous optimization techniquesto solve the original discrete problem withoutloss in accuracy after rounding. We study two populargradient-based methods, and further propose a more effectivesolution using nonconvex ADMM. Experimentson different real-world problems demonstrate that theproposed ADMM compares favorably with state-of-theartalgorithms in different settings. Finally, we proposea method for learning the parameters of these graphbasedmodels from training data, based on nonconvexADMM. This method consists of viewing ADMM iterationsas a sequence of differentiable operations, whichallows efficient computation of the gradient of the trainingloss with respect to the model parameters, enablingefficient training using stochastic gradient descent. Atthe end we obtain a unified framework for inference andlearning with nonconvex ADMM. Thanks to its flexibility,this framework also allows training jointly endto-end a graph-based model with another model suchas a neural network, thus combining the strengths ofboth. We present experiments on a popular semanticsegmentation dataset, demonstrating the effectivenessof our method
36
Pereira, Mike. "Champs aléatoires généralisés définis sur des variétés riemanniennes : théorie et pratique." Thesis, Paris Sciences et Lettres (ComUE), 2019. http://www.theses.fr/2019PSLEM055.
Full textAbstract:
La géostatistique est la branche des statistiques s’intéressant à la modélisation des phénomènes ancrés dans l’espace au travers de modèles probabilistes. En particulier, le phénomène en question est décrit par un champ aléatoire (généralement gaussien) et les données observées sont considérées comme résultant d’une réalisation particulière de ce champ aléatoire. Afin de faciliter la modélisation et les traitements géostatistiques qui en découlent, il est d’usage de supposer ce champ comme stationnaire et donc de supposer que la structuration spatiale des données se répète dans le domaine d’étude.Cependant, lorsqu’on travaille avec des jeux de données spatialisées complexes, cette hypothèse devient inadaptée. En effet, comment définir cette notion de stationnarité lorsque les données sont indexées sur des domaines non euclidiens(comme des sphères ou autres surfaces lisses)? Quid également du cas où les données présentent structuration spatiale qui change manifestement d’un endroit à l’autre du domaine d’étude? En outre, opter pour des modèles plus complexes,lorsque cela est possible, s’accompagne en général d’une augmentation drastique des coûts opérationnels (calcul et mémoire), fermant alors la porte à leur application à de grands jeux de données. Dans ce travail, nous proposons une solution à ces problèmes s’appuyant sur la définition de champs aléatoires généralisés sur des variétés riemanniennes. D’une part, travailler avec des champs aléatoires généralisés permet d’étendre naturellement des travaux récents s’attachant à tirer parti d’une caractérisation des champs aléatoires utilisés en géostatistique comme des solutions d’équations aux dérivées partielles stochastiques. D’autre part, travailler sur des variétés riemanniennes permet à la fois de définir des champs sur des domaines qui ne sont que localement euclidiens, et sur des domaines vus comme déformés localement (ouvrant donc la porte à la prise en compte du cas non stationnaire). Ces champs généralisés sont ensuite discrétisés en utilisant une approche par éléments finis, et nous en donnons une formule analytique pour une large classe de champs généralisés englobant les champs généralement utilisés dans les applications. Enfin, afin de résoudre le problème du passage à l’échelle pour les grands jeux de données, nous proposons des algorithmes inspirés du traitement du signal sur graphe permettant la simulation, la prédiction et l’inférence de ces champs par des approches "matrix-free"Geostatistics is the branch of statistics attached to model spatial phenomena through probabilistic models. In particular, the spatial phenomenon is described by a (generally Gaussian) random field, and the observed data are considered as resulting from a particular realization of this random field. To facilitate the modeling and the subsequent geostatistical operations applied to the data, the random field is usually assumed to be stationary, thus meaning that the spatial structure of the data replicates across the domain of study. However, when dealing with complex spatial datasets, this assumption becomes ill-adapted. Indeed, how can the notion of stationarity be defined (and applied) when the data lie on non-Euclidean domains (such as spheres or other smooth surfaces)? Also, what about the case where the data clearly display a spatial structure that varies across the domain? Besides, using more complex models (when it is possible) generally comes at the price of a drastic increase in operational costs (computational and storage-wise), rendering them impossible to apply to large datasets. In this work, we propose a solution to both problems, which relies on the definition of generalized random fields on Riemannian manifolds. On one hand, working with generalized random fields allows to naturally extend ongoing work that is done to leverage a characterization of random fields used in Geostatistics as solutions of stochastic partial differential equations. On the other hand, working on Riemannian manifolds allows to define such fields on both (only) locally Euclidean domains and on locally deformed spaces (thus yielding a framework to account for non-stationary cases). The discretization of these generalized random fields is undertaken using a finite element approach, and we provide an explicit formula for a large class of fields comprising those generally used in applications. Finally, to solve the scalability problem,we propose algorithms inspired from graph signal processing to tackle the simulation, the estimation and the inference of these fields using matrix-free approaches
37
Dridi, Sara. "Recent advances in regional controllability of cellular automata." Thesis, Perpignan, 2019. http://www.theses.fr/2019PERP0021/document.
Full textAbstract:
Le sujet abordé dans cette thèse concerne la contrôlabilité d’une classe de systèmes spatio-temporels, entièrement discrets de type automates cellulaires (AC). Le but de cette étude est de mettre en lumière de nouvelles pistes pour prouver la contrôlabilité des systèmes complexes. Plus spécifiquement, cette thèse se focalise sur la contrôlabilité régionale qui consiste à se restreindre à une région du domaine où le système devra atteindre un objectif donné à travers des actions ciblées. Le cas d’AC Booléens a été particulièrement examiné tout au long de cette thèse. La première partie est consacrée à l’étude du problème de la contrôlabilité régionale des AC déterministes lorsque les actions sont exercées sur la frontière de la régioncontrôlée. Une première démarche que nous avons utilisée s’appuie sur les chaines de Markov et la contrôlabilité est caractérisée en établissant une matrice similaire à leur matrice de transition en utilisant les définitions d’une chaîne ergodique et régulière. Cette étude a été étendue au cas des AC probabilistes qui sont largement utilisés pour modéliser de nombreux phénomènes réels. Le même problème a été appréhendé en utilisant des outils de la théorie des graphes. Nous proposons des conditions nécessaires et suffisantes pour la contrôlabilité régionale des AC déterministes en utilisant les notions de circuit hamiltonien et de composante fortement connexe. Le contrôle qui assure la contrôlabilité régionale est défini à travers un algorithme préimages. La deuxième partie est dédiée au problème de la contrôlabilité régionale frontière des AC Booléens qui consiste à agir sur la frontière du domaine pour atteindre un objectif sur une région cible. Nous considérons d’abord des AC linéaires pour lesquels nousdonnons un résultat de caractérisation grâce à la condition de Kalman. Nous proposons un algorithme pour déterminer le contrôle qui permet de forcer l’apparition d’une configuration désirée dans la région d’étude. Le cas des AC non linéaires a été également considéré en utilisant un algorithme de recherche des préimagesThe issue addressed in this thesis concerns the controllability of a class of discrete spatio-temporal systems named cellular automata (CA). The purpose of this study is to highlight new ways to prove the controllability of complex systems. Morespecifically, this thesis focuses on regional controllability which consists in restricting the study to a subregion of the domain where the system will have to achieve a given objective through targeted actions. The case of Boolean CA have been particularly examined throughout this thesis. The first part is devoted to the study of the problem of the regional controllability of deterministic CAs when the actions are exerted on the boundaries of the controlled region. A first approach that we used relies on Markov chains and controllability is characterized by establishing a matrix similar to their transition matrix using the definitions of a regular and ergodic chain. This study has been extended to the case of probabilistic CAs that are widely used tomodel many real phenomena. The same problem has been apprehended using tools of graph theory. We proposenecessary and sufficient conditions for the regional controllability of deterministic CAs using the notions of Hamiltonian circuit and strongly connected component. The control that ensures regional controllability is defined through a preimage algorithm.The second part is devoted to the problem of the boundary regional controllability of Boolean CAs, which consists of acting on the boundary of the domain in order to reach a desired goal in a target region. We first consider linear CAs for which we givea characterization result using the Kalman condition. We propose an algorithm to determine the control that allows to force the appearance of a desired configuration in the study area. The case of nonlinear CAs was also considered using a preimagesearch algorithm
38
Borovac, Stefan. "A graph based approach to the convergence of some iterative methods for singular M-matrices and Markov chains." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980599490.
Full text
39
Pace, Bruno. "O modelo de Axelrod com tensão superficial." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26042012-123155/.
Full textAbstract:
Nesta dissertação foram estudados alguns modelos vetoriais que pretendem modelar e descrever alguns aspectos de sistemas sociais e de sua organização cultural. Partimos do modelo de Axelrod, um processo estocástico definido em uma rede, e introduzimos uma pequena alteração no modelo que desencadeou mudanças qualitativas interessantes, especialmente o surgimento de uma tensão superficial, que leva ao aparecimento de estados metaestáveis e de regiões culturais mais fixamente localizadas no espaço. Através da ótica da mecânica estatística e de extensas simulações computacionais, exploramos alguns dos aspectos que julgamos mais importantes na caracterização desse rico modelo.Axelrod\'s model for cultural dissemination is a discrete vector representation for modeling social and cultural systems. In this work we have studied it and other related models, and a subtle change in the model\'s rule was proposed. Our slight alterations to the model yielded significant qualitative changes, specifically the emergence of surface tension, driving the system to metastable states. Using concepts from statistical mechanics and extensive numerical simulations, we explored some of the aspects that better describe the rich model devised, such as its transient and stationary behaviour.
40
Le, bars Batiste. "Event detection and structure inference for graph vectors." Thesis, université Paris-Saclay, 2021. http://www.theses.fr/2021UPASM003.
Full textAbstract:
Cette thèse aborde différents problèmes autour de l'analyse et la modélisation de signaux sur graphes, autrement dit des données vectorielles observées sur des graphes. Nous nous intéressons en particulier à deux tâches spécifique. La première est le problème de détection d'événements, c'est-à-dire la détection d'anomalies ou de ruptures, dans un ensemble de vecteurs sur graphes. La seconde tâche consiste en l'inférence de la structure de graphe sous-jacente aux vecteurs contenus dans un ensemble de données. Dans un premier temps notre travail est orienté vers l'application. Nous proposons une méthode pour détecter des pannes ou des défaillances d'antenne dans un réseau de télécommunication.La méthodologie proposée est conçue pour être efficace pour des réseaux de communication au sens large et tient implicitement compte de la structure sous-jacente des données. Dans un deuxième temps, une nouvelle méthode d'inférence de graphes dans le cadre du Graph Signal Processing est étudiée. Dans ce problème, des notions de régularité local et global, par rapport au graphe sous-jacent, sont imposées aux vecteurs. Enfin, nous proposons de combiner la tâche d'apprentissage des graphes avec le problème de détection de ruptures. Cette fois, un cadre probabiliste est considéré pour modéliser les vecteurs, supposés ainsi être distribués selon un certain champ aléatoire de Markov. Dans notre modélisation, le graphe sous-jacent aux données peut changer dans le temps et un point de rupture est détecté chaque fois qu'il change de manière significativeThis thesis addresses different problems around the analysis and the modeling of graph signals i.e. vector data that are observed over graphs. In particular, we are interested in two tasks. The rst one is the problem of event detection, i.e. anomaly or changepoint detection, in a set of graph vectors. The second task concerns the inference of the graph structure underlying the observed graph vectors contained in a data set. At first, our work takes an application oriented aspect in which we propose a method for detecting antenna failures or breakdowns in a telecommunication network. The proposed approach is designed to be eective for communication networks in a broad sense and it implicitly takes into account the underlying graph structure of the data. In a second time, a new method for graph structure inference within the framework of Graph Signal Processing is investigated. In this problem, notions of both local and globalsmoothness, with respect to the underlying graph, are imposed to the vectors.Finally, we propose to combine the graph learning task with the change-point detection problem. This time, a probabilistic framework is considered to model the vectors, assumed to be distributed from a specifc Markov Random Field. In the considered modeling, the graph underlying the data is allowed to evolve in time and a change-point is actually detected whenever this graph changes significantly
41
Alverson, Charlotte Y. "Exploring differences in teachers', administrators', and parents' preferences for data display and whether type of graphic display influences accuracy when extracting information /." Connect to title online (ProQuest), 2008. http://proquest.umi.com/pqdweb?did=1617305601&sid=4&Fmt=2&clientId=11238&RQT=309&VName=PQD.
Full textAbstract:
Thesis (Ph. D.)--University of Oregon, 2008.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 147-151). Also available online in ProQuest, free to University of Oregon users.
42
Ferrante, Enzo. "Recalage déformable à base de graphes : mise en correspondance coupe-vers-volume et méthodes contextuelles." Thesis, Université Paris-Saclay (ComUE), 2016. http://www.theses.fr/2016SACLC039/document.
Full textAbstract:
Les méthodes de recalage d’images, qui ont pour but l’alignement de deux ou plusieurs images dans un même système de coordonnées, sont parmi les algorithmes les plus anciens et les plus utilisés en vision par ordinateur. Les méthodes de recalage servent à établir des correspondances entre des images (prises à des moments différents, par différents senseurs ou avec différentes perspectives), lesquelles ne sont pas évidentes pour l’œil humain. Un type particulier d’algorithme de recalage, connu comme « les méthodes de recalage déformables à l’aide de modèles graphiques » est devenu de plus en plus populaire ces dernières années, grâce à sa robustesse, sa scalabilité, son efficacité et sa simplicité théorique. La gamme des problèmes auxquels ce type d’algorithme peut être adapté est particulièrement vaste. Dans ce travail de thèse, nous proposons plusieurs extensions à la théorie de recalage déformable à l’aide de modèles graphiques, en explorant de nouvelles applications et en développant des contributions méthodologiques originales.Notre première contribution est une extension du cadre du recalage à l’aide de graphes, en abordant le problème très complexe du recalage d’une tranche avec un volume. Le recalage d’une tranche avec un volume est le recalage 2D dans un volume 3D, comme par exemple le mapping d’une tranche tomographique dans un système de coordonnées 3D d’un volume en particulier. Nos avons proposé une formulation scalable, modulaire et flexible pour accommoder des termes d'ordre élevé et de rang bas, qui peut sélectionner le plan et estimer la déformation dans le plan de manière simultanée par une seule approche d'optimisation. Le cadre proposé est instancié en différentes variantes, basés sur différentes topologies du graph, définitions de l'espace des étiquettes et constructions de l'énergie. Le potentiel de notre méthode a été démontré sur des données réelles ainsi que des données simulées dans le cadre d’une résonance magnétique d’ultrason (où le cadre d’installation et les stratégies d’optimisation ont été considérés).Les deux autres contributions inclues dans ce travail de thèse, sont liées au problème de l’intégration de l’information sémantique dans la procédure de recalage (indépendamment de la dimensionnalité des images). Actuellement, la plupart des méthodes comprennent une seule fonction métrique pour expliquer la similarité entre l’image source et l’image cible. Nous soutenons que l'intégration des informations sémantiques pour guider la procédure de recalage pourra encore améliorer la précision des résultats, en particulier en présence d'étiquettes sémantiques faisant du recalage un problème spécifique adapté à chaque domaine.Nous considérons un premier scénario en proposant un classificateur pour inférer des cartes de probabilité pour les différentes structures anatomiques dans les images d'entrée. Notre méthode vise à recaler et segmenter un ensemble d'images d'entrée simultanément, en intégrant cette information dans la formulation de l'énergie. L'idée principale est d'utiliser ces cartes estimées des étiquettes sémantiques (fournie par un classificateur arbitraire) comme un substitut pour les données non-étiquettées, et les combiner avec le recalage déformable pour améliorer l'alignement ainsi que la segmentation.Notre dernière contribution vise également à intégrer l'information sémantique pour la procédure de recalage, mais dans un scénario différent. Dans ce cas, au lieu de supposer que nous avons des classificateurs arbitraires pré-entraînés à notre disposition, nous considérons un ensemble d’annotations précis (vérité terrain) pour une variété de structures anatomiques. Nous présentons une contribution méthodologique qui vise à l'apprentissage des critères correspondants au contexte spécifique comme une agrégation des mesures de similarité standard à partir des données annotées, en utilisant une adaptation de l’algorithme « Latent Structured Support Vector Machine »Image registration methods, which aim at aligning two or more images into one coordinate system, are among the oldest and most widely used algorithms in computer vision. Registration methods serve to establish correspondence relationships among images (captured at different times, from different sensors or from different viewpoints) which are not obvious for the human eye. A particular type of registration algorithm, known as graph-based deformable registration methods, has become popular during the last decade given its robustness, scalability, efficiency and theoretical simplicity. The range of problems to which it can be adapted is particularly broad. In this thesis, we propose several extensions to the graph-based deformable registration theory, by exploring new application scenarios and developing novel methodological contributions.Our first contribution is an extension of the graph-based deformable registration framework, dealing with the challenging slice-to-volume registration problem. Slice-to-volume registration aims at registering a 2D image within a 3D volume, i.e. we seek a mapping function which optimally maps a tomographic slice to the 3D coordinate space of a given volume. We introduce a scalable, modular and flexible formulation accommodating low-rank and high order terms, which simultaneously selects the plane and estimates the in-plane deformation through a single shot optimization approach. The proposed framework is instantiated into different variants based on different graph topology, label space definition and energy construction. Simulated and real-data in the context of ultrasound and magnetic resonance registration (where both framework instantiations as well as different optimization strategies are considered) demonstrate the potentials of our method.The other two contributions included in this thesis are related to how semantic information can be encompassed within the registration process (independently of the dimensionality of the images). Currently, most of the methods rely on a single metric function explaining the similarity between the source and target images. We argue that incorporating semantic information to guide the registration process will further improve the accuracy of the results, particularly in the presence of semantic labels making the registration a domain specific problem.We consider a first scenario where we are given a classifier inferring probability maps for different anatomical structures in the input images. Our method seeks to simultaneously register and segment a set of input images, incorporating this information within the energy formulation. The main idea is to use these estimated maps of semantic labels (provided by an arbitrary classifier) as a surrogate for unlabeled data, and combine them with population deformable registration to improve both alignment and segmentation.Our last contribution also aims at incorporating semantic information to the registration process, but in a different scenario. In this case, instead of supposing that we have pre-trained arbitrary classifiers at our disposal, we are given a set of accurate ground truth annotations for a variety of anatomical structures. We present a methodological contribution that aims at learning context specific matching criteria as an aggregation of standard similarity measures from the aforementioned annotated data, using an adapted version of the latent structured support vector machine (LSSVM) framework
43
Junior, José de Ribamar Braga Pinheiro. "Xenia: um sistema de segurança para grades computacionais baseado em cadeias de confiança." Universidade de São Paulo, 2008. http://www.teses.usp.br/teses/disponiveis/45/45134/tde-05082008-152432/.
Full textAbstract:
Os Sistemas de Grades Computacionais são intrinsecamente mais vulneráveis às ameaças de segurança que os Sistemas tradicionais, uma vez que abrangem um grande número de usuários e os recursos e as aplicações são geridas por diferentes domínios administrativos. A autenticação e a autorização são fatores imperativos para os Sistemas de Grade Computacional. Da mesma forma, a escalabilidade e a distribuição de dados vêm também sendo objeto de estudo de vários pesquisadores da área. Os serviços providos pelas Grades Computacionais devem evitar implementações centralizadas pela dificuldade do gerenciamento global. Outro importante requisito das Grades Computacionais é prover mecanismos para a delegação de direitos de acesso aos recursos. O proprietário do recurso deve ser capaz de delegar permissões para outro usuário, talvez por um tempo limitado, com base na confiança que possui neste. No entanto, a delegação deve ser usada com cuidado, pois uma longa cadeia de delegações poderia conduzir a uma utilização abusiva dos recursos pelos usuários maliciosos. Para tratar os principais requisitos de segurança das Grades Computacionais, desenvolvemos uma Arquitetura de Segurança denominada Xenia. Esta arquitetura é baseada em SPKI/SDSI, um modelo de segurança flexível, extensível e descentralizado que fornece autenticação, confidencialidade e controle de acesso. Propusemos uma extensão ao modelo SPKI/SDSI baseada em lógica subjetiva para representar relações de confiança entre indivíduos.Grid Computing Systems are inherently more vulnerable to security threats than traditional systems, since they potentially encompass a large number of users, resources, and applications managed by different administrative domains. Authentication and authorization are imperative for grid systems. Since scalability and distribution are major concerns on grid environments, those services implementations should avoid centralized solutions. Another relevant requirement to consider is the provision of mechanisms for delegating access rights, since they minimize the overhead of grid administrators on providing access rights to grid resources. The owner of an access right should be able to delegate permissions to another user, maybe for a limited time, based on his trust on that user. However, delegation must be used with care. A long chain of delegations could lead to improper use of resources by malicious users. Confidentiality and integrity are also important security requirements for many grid applications. To address these problems, we designed a Security Architecture for Grid Systems named Xenia. This architecture is based on SPKI/SDSI, a flexible and extensible decentralized security model that provides authentication, confidentiality, and access control. We proposed an extension to the SPKI/SDSI model to represent trust relations between subjects based on subjective logic.
44
Chen, Rui. "Dynamic optimal control for distress large financial networks and Mean field systems with jumps Optimal connectivity for a large financial network Mean Field BSDEs and Global Dynamic Risk Measures." Thesis, Paris Sciences et Lettres (ComUE), 2019. https://portail.bu.dauphine.fr/fileviewer/index.php?doc=2019PSLED042.
Full textAbstract:
Cette thèse propose des modèles et des méthodes pour étudier le contrôle du risque dans de larges systèmes financiers. Nous proposons dans une première partie une approche structurelle : nous considérons un système financier représenté comme un réseau d’institutions connectées entre elles par des interactions stratégiques sources de financement mais également par des interactions qui les exposent à un risque de contagion de défaut. La nouveauté de notre approche réside dans le fait que ces deux types d’interaction interfèrent. Nous proposons des nouvelles notions d’équilibre pour ces systèmes et étudions la connectivité optimale du réseau et le risque systémique associé. Dans une deuxième partie, nous introduisons des mesures de risque systémique définies par des équations différentielles stochastiques rétrogrades dirigées par des opérateurs à champ moyen et étudions des problèmes d’arrêt optimal associés. La dernière partie aborde des questions de liquidation optimale de portefeuillesThis thesis presents models and methodologies to understand the control of systemic risk in large systems. We propose two approaches. The first one is structural : a financial system is represented as a network of institutions. They have strategic interactions as well as direct interactions through linkages in a contagion process. The novelty of our approach is that these two types of interactions are intertwined themselves and we propose new notions of equilibria for such games and analyze the systemic risk emerging in equilibrium. The second approach is a reduced form.We model the dynamics of regulatory capital using a mean field operator : required capital depends on the standalone risk but also on the evolution of the capital of all other banks in the system. In this model, required capital is a dynamic risk measure and is represented as a the solution of a mean-field BDSE with jumps. We show a novel dual representation theorem. In the context of meanfield BSDEs the representation gives yield to a stochastic discount factor and a worst-case probability measure that encompasses the overall interactions in the system. We also solve the optimal stopping problem of dynamic risk measure by connecting it to the solution of reflected meanfield BSDE with jumps. Finally, We provide a comprehensive model for the order book dynamics and optimal Market making strategy appeared in liquidity risk problems
45
Klímová, Nela. "Zpráva o Ateliéru grafického designu 1." Master's thesis, Vysoké učení technické v Brně. Fakulta výtvarných umění, 2018. http://www.nusl.cz/ntk/nusl-377178.
Full text
46
El, sabbagh Alexandre. "Caractérisation du mécanisme de glissement aux joints de grains dans l’aluminium à haute température par mesures de champs in situ MEB." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLX098/document.
Full textAbstract:
Dans de nombreuses applications industrielles les matériaux polycristallins sont soumis à de hautes températures, auxquelles le mécanisme de glissement aux joints de grains (GBS pour grain boundary sliding) tient un rôle essentiel. Il est fortement couplé à la plasticité intra cristalline, cependant peu de modèles tiennent compte de ce couplage. Le GBS est encore un mécanisme mal compris pour lequel nous manquons de quantifications expérimentales. Nous avons développé à cette fin un dispositif pour réaliser des expériences de compression in-situ dans un microscope électronique à balayage, équipé d’une mesure de température sans contact. Les essais ont été menés sur un aluminium à gros grains contenant 0.1% de manganèse entre 25°C et 400°C, à faible vitesse de déformation. Les champs cinématiques mesurés par corrélation d’images numérique ont permis d’analyser la mise en place des mécanismes de plasticité durant la déformation et leur évolution en fonction de la température. Nous avons mis en évidence un fort couplage entre les mécanismes plastiques intragranulaires et le GBS. A mesure que la température augmente nous avons constaté une forte évolution de la plasticité. La déformation se localise de plus en plus aux joints de grains, tandis que la plasticité dans les grains se complexifie impliquant de plus en plus de systèmes de glissement. Une méthode de corrélation d’images a été utilisée pour mesurer les discontinuités du champ cinématique aux joints de grains et quantifier la contribution du GBS à la déformation globale à 200°C. Celui-ci s’active dès le début et tout au long de la déformation. Nous avons constaté que malgré une taille de grains importante la contribution du GBS n’est pas négligeable, elle est plus importante en début de déformation puis semble atteindre un palier. Une approche locale a été développée pour quantifier l’amplitude locale du GBS. Cela a permis d’étudier et de discuter l’influence sur celui-ci de paramètres comme l’angle de désoriention du joint, un coefficient caractérisant le transfert du glissement intragranulaire à travers le joint, et l’orientation du joint par rapport à la direction de chargement. Ce dernier paramètre semble le plus influent, mais il ne suffit pas pour caractériser l’amplitude du glissement. Il apparaît que les propriétés locales de la microstructure influencent fortement celui-ci et ne peuvent être négligésIn many industrial applications, polycrystalline materials are subjected to high temperatures at which grain boundary sliding (GBS) plays an essential part. It is however strongly coupled with intracrystalline plasticity, but very few models account for this coupling. GBS is not well understood and poorly quantified experimentally. To do so we have developed a set-up to perform in-situ compression experiments inside a scanning electron microscope, with a contactless temperature measurement. The tests have been done with large grained aluminium samples (0.1 % wt Mn) at several temperatures between 25°C and 400°C and a low strain rate. The kinematic fields measured by digital image correlation (DIC) have allowed the analysis of the start and development of plasticity mechanisms during deformation and their evolution with temperature. We have shown a strong coupling between intragranular plasticity and GBS. At higher temperature, the deformation is more concentrated at the grain boundaries while intragranular slip gets more complex, involving more glide systems. A DIC method has been used to measure the discontinuities at the grain boundaries and thus quantify the part of GBS with respect to the total plastic deformation at 200°C. Despite a large grain size, GBS contributes significantly to the deformation. GBS appears from the start of the deformation process, then reaches a limit. A local approach has been developed to quantify the local amplitude of GBS. This has allowed to weigh the influence of some geometrical parameters, such as grain misorientation, a coefficient which measures the transfer of intragranular sliding across the grain boundary and the orientation of the grain boundary with respect to the direction of solicitation. This last parameter seems to be the most relevant, but does not suffice to characterize the amplitude of the slip. The local properties of the microstructure cannot be neglected
47
Korček, František. "Návrh projektu zavedení elektronického obchodu s využitím metodiky projektového managementu." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2014. http://www.nusl.cz/ntk/nusl-224453.
Full textAbstract:
Master´s thesis focuses on the utilisation of project management methodology within the design of a project in a selected company. It specifies theoretical sources which are the key for the project plan proposal. It applies the theory to the project of introducing electronic commerce in the field of building material sale. The thesis containts the plan proposal and optimisation of the project in terms of time, costs and use of available resources, together with the analysis of a company environment.
48
Beyer, Doreen, Shiyong Wang, Carlo A. Pignedoli, Jason Melidonie, Bingkai Yuan, Can Li, Jan Wilhelm, et al. "Graphene Nanoribbons Derived from Zigzag Edge-Encased Poly(para-2,9-dibenzo[bc,kl]coronenylene) Polymer Chains." ACS Publications, 2019. https://tud.qucosa.de/id/qucosa%3A37010.
Full textAbstract:
In this work, we demonstrate the bottom-up on-surface synthesis of poly(para-dibenzo[bc,kl]-coronenylene) (PPDBC), a zigzag edge-encased analog of poly(para-phenylene) (PPP), and its lateral fusion into zigzag edge-extended graphene nanoribbons (zeeGNRs). Toward this end, we designed a dihalogenated di(meta-xylyl)anthracene monomer displaying strategic methyl groups at the substituted phenyl ring and investigated its applicability as precursor in the thermally induced surface-assisted polymerization and cyclodehydrogenation. The structure of the resulting zigzag edge-rich (70%) polymer PPDBC was unambiguously confirmed by scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM). Remarkably, by further thermal treatment at 450 °C two and three aligned PPDBC chains can be laterally fused into expanded zeeGNRs, with a ribbon width of nine (N = 9) up to 17 (N = 17) carbon atoms. Moreover, the resulting zeeGNRs exhibit a high ratio of zigzag (67%) vs armchair (25%) edge segments and feature electronic band gaps as low as 0.9 eV according to gaps quasiparticle calculations.
49
Vieira, Susana Rita Coelho. "The 2000 and 2014 suppliers and users networks : a network analysis of trade in value added." Master's thesis, Instituto Superior de Economia e Gestão, 2018. http://hdl.handle.net/10400.5/16502.
Full textAbstract:
Mestrado em Economia Internacional e Estudos EuropeusAs Cadeias Globais de Valor (CVG) representam a fragmentação da produção em várias fases, cada uma localizada num país diferente. Neste contexto, as estatísticas tradicionais de comércio não refletem a fragmentaão da produção internacional, sendo responsáveis pela dupla-contagem nos dados de importações e exportações. Para preencher esta lacuna, surgiram bases de dados Input-Output com links internacionais. Vários economistas internacionais e econofísicos defendem o potencial da análise de redes para a análise e visualização de redes de comércio, contudo, a utilização de estatísticas tradicionais de comércio compromete os resultados. Mais recentemente, um número significante de trabalhos tem utilizado o método da análise de redes no estudo das CGV. O presente trabalho utiliza o método de análise de redes para caracterizar a evolução do comércio de valor acrescentado mundial entre 2000 e 2014. Os dados, da base de dados WIOD (2016), primeiramente utilizados para a criação de indicadores de comércio de valor acrescentado que serão posteriormente utilizados para a visualização dos grafos e para o cálculo e análise de três medidas de análise de redes. Em contraste com estudos anteriores, este trabalho inclui momentos temporais mais recentes, permitindo a consolidação de resultados anteriores. Em consonância com estudos anteriores, conclui-se que somente um pequeno número de países ocupa posições centrais nas redes de produção mundiais. Esta condição verifica-se quer no número de parceiros, valor das relações bilaterais e na conexação com outros parceiros mais centrais.
Global Value Chains represent the fragmentation of production in several stages, each taking place in a different country. In this context, traditional statistics do not fully capture the fragmentation of international production, being responsible for double counting in import and export data. To fill this gap, a handful of internationally linked IO datasets have emerged. Several international economists and econophysicists have advocated the potential of the network analysis method to the analysis and visualisation of the trade networks, however, the use of trade statistics leads to incomplete conclusions. Therefore, a relatively recent body of literature has applied network analysis in the study of GVCs. This work makes use of the network analysis method to characterize the evolution of the world’s trade in value added between 2000 and 2014. It uses data from the latest release of the WIOD database to build trade in value added indicators that will be later used for graph visualization and for computation and analysis of three network based-measures. In contrast with previous studies, it includes more recent time moments, consolidating of some of the previous conclusions. In line with previous studies, we conclude that only a small number of occupy central positions in the production networks. This condition is verifiable either in the number of partners, in the value of bilateral supply and/or use relationships and in the connections with other central partners.
info:eu-repo/semantics/publishedVersion
50
Silva, Maria Teresa Morais de Paiva Martins e. "Equilíbrio e taxas de convergência em sistemas dinâmicos discretos não autónomos." Doctoral thesis, Universidade de Évora, 2015. http://hdl.handle.net/10174/18209.
Full textAbstract:
Na primeira parte deste trabalho estudamos a convergência para a distribuição de equilíbrio em grafos não autónomos periódicos. Introduzimos a noção de equilíbrio em grafos não autónomos e apresentamos uma estimativa superior para a distância ao equilíbrio, `a custa do segundo valor próprio em módulo das matrizes produto, supondo todas as matrizes erg´odicas e pelo menos uma delas reversível. A estimativa obtida depende explicitamente da dimensão das matrizes consideradas. Estabelecemos a relação entre grafos autónomos e cadeias de Markov não homogéneas. Ilustramos, com um exemplo, a aplicação a sistemas dinâmicos não autónomos. Estendemos o estudo a matrizes n˜ao reversíveis demonstrando um resultado análogo ao caso reversível, no contexto autónomo e não autónomo, que utiliza a factorização da matriz através da forma normal de Jordan. Finalmente discutimos a pertinência dos resultados originais obtidos comparando-os com resultados conhecidos. Esta parte corresponde aos capítulos 2 e 3. A segunda parte, capítulo 4, ´e dedicada ao estudo detalhado de uma família de sistemas não autónomos de período 2, gerados pela iteração sequencial de duas funções do tipo tenda cortada. Apresentamos os conceitos de dinâmica simbólica, renormalização e produto estrela no contexto não autónomo, com o objectivo de calcular a taxa de convergência de sucessões de pontos no espaço de parâmetros, construidas através de produtos estrela/renormalizaçõesconsecutivas, generalizando assim as sequências de Feigenbaum. Concluímos que as taxas de convergência são independentes do ponto inicial, mostrando assim que o contexto não autónomo exibe propriedades universais do tipo encontrado por Feigenbaum em famílias de sistemas autónomos; Abstract: In the first part of this thesis we study the convergence for the equilibrium distribution in periodic non autonomous graphs. We introduce the notion of equilibrium in non autonomous graphs and give an upper bound for the distance to the equilibrium, using the second largest eigenvalue in modulus of the product matrices, assuming all of them ergodic and, at least, one reversible. The estimate obtained depends explicitly on the dimension of the considered matrices. We set the relation between non autonomous graphs and non homogeneous Markov chains. We illustrate the applications to the non autonomous dynamical systems with an example. We extend the study to non reversible matrices proving an analogous result, in both autonomous and non autonomous settings, using the matrix factorization with the Jordan normal form. Finally we discuss the relevance of the results obtained comparing them with the previously known results. This is the subject of chapters 2 and 3. The second part, chapter 4, is dedicated to studying a family of non autonomous systems with period 2, generated by the sequential iteration of two stunted sawtooth maps. We present the concepts of symbolic dynamics, renormalization and star product in the non autonomous setting, in order to compute the convergence rates of sequences of points in the parameter space. These sequences are obtained through consecutive star products/renormalizations, generalizing in this way the Feigenbaum sequences. We show that the convergence rates are independent of the initial point, thus, concluding that the non autonomous setting has universal properties of the type founded by Feigenbaum in families of autonomous systems.