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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Managing Dependencies in Knowledge-Based Systems: A Graph-Based Approach

Tapankov, Martin January 2009 (has links)
<p>In knowledge-based engineering, the inference engine plays an important part in the behaviour of the system. A flexible and adaptive execution scheme allows the designer to experiment with different modes of operation and selecting an appropriate one with respect to the initial data set and the execution goal.</p><p>In this project, an extension of an existing research prototype software in the field of knowledge-based engineering will be developed, with the goal of building a reliable and easy to use dependency resolution engine that will replace a less-than-ideal current implementation of the same. A discussion will be included how the knowledge concepts and objects can be represented in an abstract mathematical form, converting at the same time the problem of dependency resolution to a more formally specified one in terms of the data abstraction proposed. Some algorithms and methods that are used to operate on the data set will be discussed from both a theoretical and programming point of view, analysing their complexity, proposing and testing their implementation. Graphical interface controls that can be used to visualize and understand easily the relations in the available knowledge base will be also demonstrated.</p><p>The testing and verification of the resulting software will be presented, comparing its behaviour against reference tools serving similar purposes. Methods for validating the consistency of the knowledge base will also be discussed. Finally, the integration of the newly-developed code within the context of the prototype will be discussed, commenting on the new features and functionality gained.</p>
42

Managing Dependencies in Knowledge-Based Systems: A Graph-Based Approach

Tapankov, Martin January 2009 (has links)
In knowledge-based engineering, the inference engine plays an important part in the behaviour of the system. A flexible and adaptive execution scheme allows the designer to experiment with different modes of operation and selecting an appropriate one with respect to the initial data set and the execution goal. In this project, an extension of an existing research prototype software in the field of knowledge-based engineering will be developed, with the goal of building a reliable and easy to use dependency resolution engine that will replace a less-than-ideal current implementation of the same. A discussion will be included how the knowledge concepts and objects can be represented in an abstract mathematical form, converting at the same time the problem of dependency resolution to a more formally specified one in terms of the data abstraction proposed. Some algorithms and methods that are used to operate on the data set will be discussed from both a theoretical and programming point of view, analysing their complexity, proposing and testing their implementation. Graphical interface controls that can be used to visualize and understand easily the relations in the available knowledge base will be also demonstrated. The testing and verification of the resulting software will be presented, comparing its behaviour against reference tools serving similar purposes. Methods for validating the consistency of the knowledge base will also be discussed. Finally, the integration of the newly-developed code within the context of the prototype will be discussed, commenting on the new features and functionality gained.
43

Large-Sample Logistic Regression with Latent Covariates in a Bayesian Networking Context

Wang, Junhua 01 August 2009 (has links)
We considered the problem of predicting student retention using logistic regression when the most important covariates such as the college variables are latent, but the network structure is known. This network structure specifies the relationship between pre-college to college variables and then from college to student retention variables. Based on this structure, we developed three estimators, examined their large-sample properties, and evaluated their empirical efficiencies using WKU student retention database. Results show that while the hat estimator is expected to be most efficient, the tilde estimator was shown to be more efficient than the check method. This increased efficiency suggests that utilizing the network information can improve our predictions.
44

Essays on the Upper Mississippi River and Illinois Waterway and U.S. grain market

Yu, Tun-Hsiang 29 August 2005 (has links)
This dissertation examines several issues regarding the congestion on the Upper Mississippi River and Illinois Waterway. Chapter II identifies and measures the impact of lock congestion on grain barge rates on these waterways. Results indicate grain barge rates on both rivers are not affected by lagged lock congestion. In present time, however, lock congestion in the lower reaches of the upper Mississippi and Illinois Rivers are found to increase barge rates that link the north central United States to the lower Mississippi Gulf port area. The findings suggest the impact of lock congestion on grain barge rates is moderate. Chapter III explores the interaction between grain prices in export and domestic markets and transportation rates linking these markets over time. Three model frameworks were evaluated and some consistent results are observed. In general, shocks in transportation rates (barge, rail, and ocean) explain a great proportion of the variation in corn and soybean market prices in the long run, suggesting the importance of transportation in grain price determination. The volatile ocean freight rates are the mostimportant transportation rates contributing to the variation in grain prices, while shocks in barge rates on the Upper Mississippi River and Illinois Waterway generally explain less than 15 percent of the variation in grain prices. The dynamic interrelationships among the six evaluated transportation rates are also found. In addition, the north central corn markets likely have the most influence over other markets while soybean export price dominates the soybean market in the long run. Chapter IV estimates the structural demand for grain barge transportation on both the upper Mississippi and Illinois Rivers. Results suggest foreign grain demand is the most influential force affecting grain barge demand on both rivers. Also, results indicate an inelastic demand for grain barge transportation on the Upper Mississippi in the short run; demand is price elastic in the long run. The price elasticity for grain barge demand on the Illinois River is consistently inelastic. Additionally, the winter season and floods affect demand on the Upper Mississippi negatively, while barge demand increases on the Illinois River in winter.
45

Contribution des catalyseurs contenant un carbène N-hétérocyclique pour la chimie des nucléosides / Contribution of N-heterocyclic carbene-containing catalysts in the nucleoside chemistry

Broggi, Julie 16 February 2009 (has links)
Ces dernières années, les analogues nucléosidiques ont eu un rôle majeur dans le traitement de maladies virales infectieuses tels le SIDA, les hépatites, l’herpès, la variole ou la grippe. Cependant, l’apparition de nouveaux virus ou de mutations virales ont renforcé la nécessité de développer des antiviraux plus efficaces et plus résistants. L’intensive recherche de dérivés nucléosidiques cliniquement actifs a permis l’émergence d’une multitude de nouvelles approches pour leurs synthèses. Parmi ce panel, les réactions catalysées par des métaux de transition tardifs font certainement partie des méthodes les plus importantes pour accéder à une large gamme de pharmacomodulations. Lors de ce projet de recherche, nous nous sommes intéressés à la conception, la synthèse et la découverte de nouveaux dérivés nucléosidiques en tant qu’antiviraux contre le virus de la variole. Pour ce faire, nous avons ciblé des 1,2,3-triazolo-carbanucléosides en série racémique ou énantiosélective ainsi que des nucléosides phosphonates acycliques. Dans un effort de développement et/ou d’amélioration de leurs méthodes de synthèse, nous avons également étudié la contribution de complexes au ruthénium et au cuivre contenant un carbène Nhétérocyclique (CNH) dans des réactions de métathèse croisée et de cycloaddition 1,3-dipolaire de Huisgen. Enfin, en vue d’obtenir des outils efficaces utilisables en synthèse nucléosidique, nous avons développés des nouveaux complexes au palladium portant un ligand CNH et testé leurs réactivités dans des réactions de Narylation de Buchwald-Hartwig et d’hydrogénation d’oléfines. / In the last decades, nucleoside analogues have played a major role in the treatment of viral infectious diseases, such as AIDS, hepatitis, herpes, smallpox or influenza. Nevertheless, the apparition of new or mutated viruses highlights the need of more potent and resistant antiviral therapeutics. The intense search for clinically useful nucleoside derivatives has resulted in a wealth of new approaches for their synthesis. Among them, latetransition metal-catalyzed reactions are certainly the most important methods to access variety of appealing pharmacomodulations. In this research project, we were interested in the conception, the synthesis and the discovery of new nucleoside derivatives as antiviral agents against smallpox viruses. Hence, we have targeted racemic or enantiomerically pure 1,2,3-triazolo-carbanucleosides as well as acyclic nucleoside phosphonates. In our effort into the development or/and the improvement of their synthetic methodologies, we have also studied the contribution of ruthenium and copper complexes bearing N-heterocyclic carbene (NHC) ligands in cross-metathesis and Huisgen 1,3-dipolar cycloaddition reactions. Finally, in order to obtain efficient tools useful in nucleoside synthesis, we have developed new NHC-containing palladium complexes and examined their reactivity in Buchwald-Hartwig N-arylation and olefins hydrogenation reactions.
46

Scheduling of parallel real-time DAG tasks on multiprocessor systems / Ordonnancement temps réels des tâches parallèles sur des systèmes multiprocesseurs.

Qamhieh, Manar 26 January 2015 (has links)
Les applications temps réel durs sont celles qui doivent exécuter en respectant des contraintes temporelles. L'ordonnancement temps réel a bien été étudié sur mono-processeurs depuis plusieurs années. Récemment, l'utilisation d'architectures multiprocesseurs a augmenté dans les applications industrielles et des architectures parallèles sont proposées pour que le logiciel devienne compatible avec ces plateformes. L'ordonnancement multiprocesseurs de tâches parallèles dépendantes n'est pas une simple généralisation du cas mono-processeur et la problématique d'ordonnancement devient plus complexe et difficile.
Dans cette thèse, nous étudions le problème d'ordonnancement temps réel de graphes de tâches parallèles acycliques sur des plateformes multiprocesseurs. Dans ce modèle, un graphe est composé d'un ensemble de sous-tâches dépendantes sous contraintes de précédence qui expriment les relations de précédences entre les sous-tâches. L'ordre d'exécution des sous-tâches est dynamique, c'est-à-dire que les sous-tâches peuvent s'exécuter en parallèle ou séquentiellement par rapport aux décisions de l'ordonnanceur temps réel. Pour traiter les contraintes de précédence, nous proposons deux méthodes pour l'ordonnancement des graphes : par transformation du modèle de graphe de sous tâches parallèles en un modèle de tâches séquentielles indépendantes, plus simple à ordonnancer et par ordonnancement direct des graphes en prenant en compte les relations de dépendance entre les sous-tâches. Nous proposons un ordonnancement des graphes en prenant directement en compte les paramètres temporels des graphes et un ordonnancement au niveau des sous-tâches, par rapport à des paramètres temporels attribués aux sous-tâches par un algorithme spécifique.
Enfin, nous prouvons que les deux méthodes d'ordonnancement de graphes ne sont pas comparables. Nous fournissons alors des résultats de simulation pour comparer ces méthodes en utilisant les algorithmes d'ordonnancement globaux EDF et DM. Nous avons développé un logiciel nommé YARTISS pour générer des graphes aléatoires et réaliser les simulations / The interest for multiprocessor systems has recently been increased in industrial applications, and parallel programming API's have been introduced to benefit from new processing capabilities. The use of multiprocessors for real-time systems, whose execution is performed based on certain temporal constraints is now investigated by the industry. Real-time scheduling problem becomes more complex and challenging in that context. In multiprocessor systems, a hard real-time scheduler is responsible for allocating ready jobs to available processors of the systems while respecting their timing parameters.
In this thesis, we study the problem of real-time scheduling of parallel Directed Acyclic Graph (DAG) tasks on homogeneous multiprocessor systems. In this model, a DAG task consists of a set of subtasks that execute under precedence constraints. At all times, the real-time scheduler is responsible for determining how subtasks execute, either sequentially or in parallel, based on the available processors of the system. We propose two DAG scheduling approaches to determine the execution form of DAG tasks. The first approach is the DAG Stretching algorithm, from the Model Transformation approach, which forces DAG tasks to execute as sequentially as possible. The second approach is the Direct Scheduling, which aims at scheduling DAG tasks while respecting their internal dependencies. We provide real-time schedulability analyses for Direct Scheduling at DAG-Level and at Subtask-Level.
Due to the incomparability of DAG scheduling approaches, we use extensive simulations to compare performance of global EDF with global DM scheduling using our simulation tool YARTISS
47

Circular coloring and acyclic choosability of graphs / Coloration circulaire et coloration acyclique par listes de graphes

Roussel, Nicolas 14 December 2009 (has links)
Dans cette thèse, nous nous intéressons à la coloration circulaire des graphes planaires. Des bornes supérieures ont été données pour des graphes avec degré maximum borné, avec girth, la longueur de son plus petit cycle, bornée, avec des cycles manquants, etc. Ici nous donnerons de nouvelles bornes pour les graphes avec degré moyen maximum borné. Nous étudions également la coloration totale et la coloration (d,1)-totale de plusieurs familles infinies de graphes. Nous décrivons le nouveau concept de coloration (d,1)-totale circulaire. Enfin, nous discutons les conditions nécessaires pour qu'un graphe planaire admette une coloration acyclique par listes de taille 4. / In this thesis, we study the circular coloring of planar graphs. Upper bounds have been given for graphs with bounded maximum degree, with bounded girth, that is the length of its smallest cycle, with missing cycles, and so on. It has also been studied for graphs with bounded maximum average degree. Here we give new upper bounds for that latter case. We also study the total coloring and ($d,1$)-total labeling of a few infinite families of graphs and describe the new concept of circular ($d,1$)-total labeling of graphs. In the last part, we will discuss conditions for a planar graph to be acyclically $4$-choosable.
48

Automates codéterministes et automates acycliques : analyse d'algorithmes et génération aléatoire / codeterministic automata and acyclic automata : analysis of algorithmes and random generation

De Félice, Sven 01 July 2014 (has links)
Le cadre générale de cette thèse est l'analyse quantitative des objets issus de la théorie des langages rationnels. On adapte des techniques d'analyse d'algorithmes (complexité en moyenne, complexité générique, génération aléatoire, ...) à des objets et à des algorithmes qui font intervenir des classes particulières d'automates. Dans une première partie nous étudions la complexité de l'algorithme de minimisation de Brzozowski. Bien qu'ayant une mauvaise complexité dans le pire des cas, cet algorithme a la réputation d'être efficace en pratique. En utilisant les propriétés typiques des applications et des permutations aléatoires, nous montrons que la complexité générique de l'algorithme de Brzozowski appliqué à un automate déterministe croît plus vite que tout polynôme en n, où n est le nombre d'états de l'automate. Dans une seconde partie nous nous intéressons à la génération aléatoire d'automates acycliques. Ces automates sont ceux qui reconnaissent les ensembles finis de mots et sont de ce fait utilisés dans de nombreuses applications, notamment en traitement automatique des langues. Nous proposons deux générateurs aléatoires. Le premier utilise le modèle des chaînes de Markov, et le second utilise la "méthode récursive", qui tire partie des décompositions combinatoires des objets pour faire de la génération. La première méthode est souple mais difficile à calibrer, la seconde s'avère plutôt efficace. Une fois implantée, cette dernière nous a notamment permis d'observer les propriétés typiques des grands automates acycliques aléatoires / The general context of this thesis is the quantitative analysis of objects coming from rational language theory. We adapt techniques from the field of analysis of algorithms (average-case complexity, generic complexity, random generation...) to objects and algorithms that involve particular classes of automata. In a first part we study the complexity of Brzozowski's minimisation algorithm. Although the worst-case complexity of this algorithm is bad, it is known to be efficient in practice. Using typical properties of random mappings and random permutations, we show that the generic complexityof Brzozowski's algorithm grows faster than any polynomial in n, where n is the number of states of the automaton. In a second part, we study the random generation of acyclic automata. These automata recognize the finite sets of words, and for this reason they are widely use in applications, especially in natural language processing. We present two random generators, one using a model of Markov chain, the other a ``recursive method", based on a cominatorics decomposition of structures. The first method can be applied in many situations cases but is very difficult to calibrate, the second method is more efficient. Once implemented, this second method allows to observe typical properties of acyclic automata of large size
49

Syntéza nového typu acyklických nukleosid fosfonátů a příprava proléčiv a systémů doručení léčiva / Synthesis of novel types of acyclic nucleoside phosphonates and preparation of prodrugs and drug delivery systems

Kalčic, Filip January 2021 (has links)
First part of this thesis was focused on the previously overlooked field of C1'-branched acyclic nucleoside phosphonates (ANPs). Five diverse synthetic approaches were developed/optimized affording key 6-chloropurine intermediates bearing N9 -phosphonomethoxyethyl (PME) branched at C1' position in 2-4 steps. It was demonstrated that these intermediates can be further vastly diversified into ANPs bearing both natural and unnatural nucleobases. Single enantiomers as well as racemates of final C1'-branched ANPs (overall 48 final compounds) were prepared and selected compounds were evaluated with respect to their biological properties. The aforementioned ANPs showed no antiviral potency against studied viruses and only weak to moderate cytostatic activity. Adenine C1'-branched ANPs proved to be the most potent currently known inhibitors of Trypanosoma brucei adenine phosphoribosyl transferase (TbrAPRT), an enzyme involved in purine salvage pathway (PSP) of T. brucei. Further biological evaluation of prepared compounds is in progress. Second part of this thesis was focused on development of novel prodrug moieties with higher selectivity index (i.e. toxicity/potency ratio - SI) based on so-called ProTide prodrugs where phenol (present in ProTides) was replaced by tyrosine derivatives. Tenofovir was...
50

Vliv acyklických nukleosidfosfonátů PMEG a PMEDAP na p38 kinasovou signalizaci v lidských leukemických buňkách / The influence of acyclic nucleotide phosphonates PMEG and PMEDAP on p38 kinase signaling in human leukemic cells

Nejedlá, Michaela January 2010 (has links)
PMEG [9-(2-phosphonomethoxyethyl)guanine] and PMEDAP [9-phosphonomethoxy- ethyl)-2,6-diaminopurine] are acyclic nucleoside phosphonates possessing cytotoxic properties. Antiproliferative effect of PMEG was demonstrated in various tumor cell lines in vitro. PMEG also represents an active component of some experimental prodrugs with enhanced selectivity and efficacy (such as GS-9219). PMEDAP seems to have weaker effect in vitro compared to PMEG, however it exhibited pronounced antitumor effect in SD-rats with spontaneous lymphoma. Therefore it was included in the present study as well. The aim of this study was to describe the interactions of PMEG and PMEDAP with p38 MAP kinase signaling and its relationship to the apoptosis. We investigated the influence of these compounds on the expression of four genes encoding p38 MAPK isoforms and whether this change is translated into the protein. It was found that PMEG up-regulates p38β and γ mRNA in CCRF-CEM cells and p38 β and δ in HL-60 cells. The effect of PMEDAP was less pronounced than that of PMEG. However, total p38 protein level remained unaffected by PMEG and PMEDAP. Activation of p38 MAPK cascade was also measured in the cells exposed to these agents using phospho-specific antibodies. We found that neither PMEG nor PMEDAP activated p38 kinase...

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