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1
PAFUNDI, PIA CLARA. « SPECIFICATION AND ESTIMATION OF COMPLEX STRUCTURAL MODELS WITH COVARIATE EFFECTS ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2014. http://hdl.handle.net/10281/54182.
Texte intégralRésumé :
Molti approcci statistici hanno studiato la specificazione e il fitting di Modelli ad Equazioni Strutturali con covariate esterne. Tali metodi differiscono per modelli di misurazione (modelli formativi o riflessivi, variabili latenti o composite, presenza di variabili osservate esogene e/o endogene con effetti diretti sulle variabili latenti/composite) e strategie di stima (parametriche/algoritmiche).
Il presente lavoro si focalizza in particolare sulla possibilità di inserire covariate esterne che possono influenzare entrambi gli indicatori endogeni direttamente e/o indirettamente, attraverso le composite.
Sono stati introdotti i fondamenti dei Modelli ad Equazioni Strutturali, descrivendo brevemente LISREL, PLS e le metodologie più nuove e innovative, tra cui la Generalized Maximum Entropy (GME), nonché i loro limiti, spiegando se consentono o meno l’inserimento di covariate esterne. È stata quindi discussa l’introduzione di covariate esterne nell’ambito della Component Analysis, attraverso metodi quali la Redundancy Analysis, la Multiblock Redundancy Analysis (MbRA) e la Extended Redundancy Analysis (ERA). Ogni singola metodologia verrà illustrata, esplicitandone vantaggi e svantaggi e miglioramenti giustificanti l’introduzione di una nuova strategia di stima nota come Generalized Redundancy Analysis (GRA), sulla quale è stato condotto uno studio di simulazione completo, con tre diversi scenari, volto a
valutare le performance del GRA nella specificazione di estensioni complesse, covariate e differenti scenari di distribuzione.
2
Abdullah, Aslam. « Quantifying guidelines and criteria for using turbulence models in complex flows ». Thesis, Cranfield University, 2011. http://dspace.lib.cranfield.ac.uk/handle/1826/7454.
Texte intégralRésumé :
A framework for assessing the key statistical parameters of complex flows in
choosing appropriate turbulence prediction methods on a quantitative basis is
developed. These parameters characterise flow/modelling matching
conditions quantified in this work. Matching conditions are important in
classifying complex turbulent flows in order to frame best practice for model
predictions to inform computational aerodynamics design optimisation in the
context of virtual test beds. In the incompressible low Reynolds number shear
flows considered here, the boundaries of the 'conforming domain' within
which turbulence models are valid need to be defined, based on basic
mechanisms of turbulence, and the statistical parameters. This has led to a
new guideline ‘localness map’ for standard model applications. Since the
choice of turbulence model depends on the complexity of the flows
considered, it is useful if systematic sets of the parameters indicate the type of
flow. They are that of residence time, the degree of spatial non-locality, the
straining, and the non-Gaussianity, each of which is appropriately normalised.
It can be demonstrated that the quantified map, in particular that of localness
for the shear flows, provides a firm foundation for evaluating a wider range of
Underlying Flow Regimes, including locating the Underlying Flow Regimes
on the generalised localness modeling map as a framework for best practice
guidelines. This work produces 7 sets of quantitative localness-structural
parameters, which are used as baseline sets for grouping the Underlying Flow
Regimes, and hence it opens the possibility of having complete modelling
maps for Application Challenges to assess the need for zonal modelling.
3
Chauvet, Jocelyn. « Introducing complex dependency structures into supervised components-based models ». Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS008/document.
Texte intégralRésumé :
Une forte redondance des variables explicatives cause de gros problèmes d'identifiabilité et d'instabilité des coefficients dans les modèles de régression. Même lorsque l'estimation est possible, l'interprétation des résultats est donc extrêmement délicate. Il est alors indispensable de combiner à leur vraisemblance un critère supplémentaire qui régularise l'estimateur. Dans le sillage de la régression PLS, la stratégie de régularisation que nous considérons dans cette thèse est fondée sur l'extraction de composantes supervisées. Contraintes à l'orthogonalité entre elles, ces composantes doivent non seulement capturer l'information structurelle des variables explicatives, mais aussi prédire autant que possible les variables réponses, qui peuvent être de types divers (continues ou discrètes, quantitatives, ordinales ou nominales). La régression sur composantes supervisées a été développée pour les GLMs multivariés, mais n'a jusqu'alors concerné que des modèles à observations indépendantes.Or dans de nombreuses situations, les observations sont groupées. Nous proposons une extension de la méthode aux GLMMs multivariés, pour lesquels les corrélations intra-groupes sont modélisées au moyen d'effets aléatoires. À chaque étape de l'algorithme de Schall permettant l'estimation du GLMM, nous procédons à la régularisation du modèle par l'extraction de composantes maximisant un compromis entre qualité d'ajustement et pertinence structurelle. Comparé à la régularisation par pénalisation de type ridge ou LASSO, nous montrons sur données simulées que notre méthode non seulement permet de révéler les dimensions explicatives les plus importantes pour l'ensemble des réponses, mais fournit souvent une meilleure prédiction. La méthode est aussi évaluée sur données réelles.Nous développons enfin des méthodes de régularisation dans le contexte spécifique des données de panel (impliquant des mesures répétées sur différents individus aux mêmes dates). Deux effets aléatoires sont introduits : le premier modélise la dépendance des mesures relatives à un même individu, tandis que le second modélise un effet propre au temps (possédant donc une certaine inertie) partagé par tous les individus. Pour des réponses Gaussiennes, nous proposons d'abord un algorithme EM pour maximiser la vraisemblance du modèle pénalisée par la norme L2 des coefficients de régression. Puis nous proposons une alternative consistant à donner une prime aux directions les plus "fortes" de l'ensemble des prédicteurs. Une extension de ces approches est également proposée pour des données non-Gaussiennes, et des tests comparatifs sont effectués sur données PoissonniennesHigh redundancy of explanatory variables results in identification troubles and a severe lack of stability of regression model estimates. Even when estimation is possible, a consequence is the near-impossibility to interpret the results. It is then necessary to combine its likelihood with an extra-criterion regularising the estimates. In the wake of PLS regression, the regularising strategy considered in this thesis is based on extracting supervised components. Such orthogonal components must not only capture the structural information of the explanatory variables, but also predict as well as possible the response variables, which can be of various types (continuous or discrete, quantitative, ordinal or nominal). Regression on supervised components was developed for multivariate GLMs, but so far concerned models with independent observations.However, in many situations, the observations are grouped. We propose an extension of the method to multivariate GLMMs, in which within-group correlations are modelled with random effects. At each step of Schall's algorithm for GLMM estimation, we regularise the model by extracting components that maximise a trade-off between goodness-of-fit and structural relevance. Compared to penalty-based regularisation methods such as ridge or LASSO, we show on simulated data that our method not only reveals the important explanatory dimensions for all responses, but often gives a better prediction too. The method is also assessed on real data.We finally develop regularisation methods in the specific context of panel data (involving repeated measures on several individuals at the same time-points). Two random effects are introduced: the first one models the dependence of measures related to the same individual, while the second one models a time-specific effect (thus having a certain inertia) shared by all the individuals. For Gaussian responses, we first propose an EM algorithm to maximise the likelihood penalised by the L2-norm of the regression coefficients. Then, we propose an alternative which rather gives a bonus to the "strongest" directions in the explanatory subspace. An extension of these approaches is also proposed for non-Gaussian data, and comparative tests are carried out on Poisson data
4
Hang, Huajiang Engineering & Information Technology Australian Defence Force Academy UNSW. « Prediction of the effects of distributed structural modification on the dynamic response of structures ». Awarded by:University of New South Wales - Australian Defence Force Academy. Engineering & ; Information Technology, 2009. http://handle.unsw.edu.au/1959.4/44275.
Texte intégralRésumé :
The aim of this study is to investigate means of efficiently assessing the effects of distributed structural modification on the dynamic properties of a complex structure. The helicopter structure is normally designed to avoid resonance at the main rotor rotational frequency. However, very often military helicopters have to be modified (such as to carry a different weapon system or an additional fuel tank) to fulfill operational requirements. Any modification to a helicopter structure has the potential of changing its resonance frequencies and mode shapes. The dynamic properties of the modified structure can be determined by experimental testing or numerical simulation, both of which are complex, expensive and time-consuming. Assuming that the original dynamic characteristics are already established and that the modification is a relatively simple attachment such as beam or plate modification, the modified dynamic properties may be determined numerically without solving the equations of motion of the full-modified structure. The frequency response functions (FRFs) of the modified structure can be computed by coupling the original FRFs and a delta dynamic stiffness matrix for the modification introduced. The validity of this approach is investigated by applying it to several cases, 1) 1D structure with structural modification but no change in the number of degree of freedom (DOFs). A simply supported beam with double thickness in the middle section is treated as an example for this case; 2) 1D structure with additional DOFs. A cantilever beam to which a smaller beam is attached is treated as an example for this case, 3) 2D structure with a reduction in DOFs. A four-edge-clamped plate with a cut-out in the centre is treated as an example for this case; and 4) 3D structure with additional DOFs. A box frame with a plate attached to it as structural modification with additional DOFs and combination of different structures. The original FRFs were obtained numerically and experimentally except for the first case. The delta dynamic stiffness matrix was determined numerically by modelling the part of the modified structure including the modifying structure and part of the original structure at the same location. The FRFs of the modified structure were then computed. Good agreement is obtained by comparing the results to the FRFs of the modified structure determined experimentally as well as by numerical modelling of the complete modified structure.
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Hinojosa-Prieto, Hector R. « Tectonothermal history of the La Noria-Las Calaveras region, Acatlán Complex, southern Mexico implications for Paleozoic tectonic models / ». Ohio : Ohio University, 2006. http://www.ohiolink.edu/etd/view.cgi?ohiou1151434573.
Texte intégral
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Grundmeier, Alexander Peter [Verfasser]. « The water-oxidizing manganese complex of oxygenic photosynthesis : structural models based on X-ray absorption spectroscopy / Alexander Peter Grundmeier ». Berlin : Freie Universität Berlin, 2012. http://d-nb.info/1026883717/34.
Texte intégral
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Ameen, Masood, et Mini Jacob. « Complexity in Projects : A Study of Practitioners’ Understanding of Complexity in Relation to ExistingTheoretical Models ». Thesis, Umeå University, Umeå School of Business, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-18376.
Texte intégralRésumé :
In the last three decades, complexity theory has gained a lot of importance in several scientific disciplines like astronomy, geology, chemistry etc. It has slowly extended its usage in the field of project management. While trying to understand the managerial demands of modern day projects and the different situations faced in projects, the term ‘complexity’ is progressively becoming a benchmark term. In the recent past some of the challenging projects that have been completed are the Heathrow Terminal 5 and the construction of venues for the Beijing Olympics. But can we call these projects complex?It is probably too simplistic to classify projects as complex or non-complex. What is particularly important is to identify the source of the complexity, the level and also the implications of the complexity. Several academicians have studied the different dimensions and established different classifications of complexity. These are put together into models of complexity.But is this classification well-grounded in reality? This is what we aim to explore through this research. The specific questions that we wish to explore by conducting this research are:
- How does the understanding of project complexity in actuality conform to the theoretical complexity models?
In an effort to answer the primary question, our study will also throw some light on factors of complexity across different sectors. We hope that this distinction will pave way for further research within these sectors. This now brings us to our sub-question:- How do the factors that contribute to complexity compare across different sectors?At the outset of this research, the literature on complexity was reviewed. An attempt was made to understand what complexity means with a focus on the field of project management.It was observed that there is a new wave of thinking in this field and a camp which believes that regular project management tools and techniques cannot be used for complex projects.
This has drawn several academicians to generate models of complexity based on various factors. In this research we have focused on some important models like that of Turner and Cochrane, Ralph Stacey, Terry Williams, Kahane and Remington and Pollack. We have tried to see if any of these models fit in with how practitioners understand complexity.To find out how practitioners comprehend complexity, we followed a grounded theory approach and also used quantitative methods to supplement the results in accordance in a mixed methodology. Semi-structured interviews were carried out with nine project managers from different sectors and different geographical locations. The interviews were analyzed and the data was broken down to different categories referred to as open coding where labelling was done. This was followed by Axial coding where we describe the properties and build relations between these categories. The final stage is selective coding where the emerged theory is integrated and refined.Quantitative data was collected through a short questionnaire which listed out some factors which could cause or lead to complexity in projects. A total of 29 responses were obtained for the questionnaires. By analyzing this data we were able to determine the factors that project managers thought caused complexity in projects. A new dimension was also added by analyzing it sector-wise. Since we collected data from two different sources, via interviews and through questionnaires, it gave us the opportunity to triangulate the findings. Wesincerely hope that this piece of work will pave way for future research on similar areas like models of complexity and perception of complexity in project management
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Estienne, Jacques. « Des halogènes dans les édifices moléculaires étioniques : études cristallographiques, corrélations structure-réactivité, structure-conductivité, modèles structuraux ». Aix-Marseille 1, 1986. http://www.theses.fr/1986AIX11001.
Texte intégralRésumé :
Etude structurale de substances pouvant intervenir en tant que catalyseurs ou conducteurs electriques dans le monde industriel, dans le cadre de trois modeles : modele de l'atome cl mu -ponsteur co::(3) cl(c::(2)f::(3)o::(2))::(3)(so::(4))(c::(4)h::(10)o::(2))::(3) et mn::(4)cl::(4)(c::(2)f::(3)o::(2))::(4)(c::(4)h::(10)o)::(6), modele de l'ion tribromure dans des composes organiques et modele de l'iodure simple (iodures organiques comportant des dications diazoniatricycliques c::(14)h::(28)n::(2)**(2+). 2i**(-) et c::(15)h::(30)n::(2)**(2+). 2i**(-) et de l'ion iodoargentate (ag::(4) i::(8)**(4-). 2c::(15)h::(30)n::(2)**(2+))
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Sun, Daning. « Structured policies for complex production and inventory models ». Thesis, University of British Columbia, 1990. http://hdl.handle.net/2429/31002.
Texte intégralRésumé :
For inventory models minimizing the long-run average cost over an infinite horizon, the existence of optimal policies was an open question for a long time. Consider a deterministic, continuous time inventory system satisfies the following conditions: the production network is acyclic, the joint setup cost function is monotone, the holding cost and the backlogging cost rates are nonnegative, the demand rates are constant over time, the production rates are infinite or finite non-increasing, and backlogging may be allowed or not. For this very general extension of the Wilson-Harris EOQ model, we prove the existence of optimal policies. Very few properties of optimal policies have been discovered since the 1950's. Restricting the above inventory model to infinite production rates, we present some new properties of optimal policies, such as the Latest Ordering Property, and explicit expressions for echelon inventories and order quantities in terms of ordering instants.
An assembly production system with n facilities has a constant external demand occurring at the end facility. Production rates at each facility are finite and non-increasing along any path in the assembly network. Associated with each facility are a set-up cost and positive echelon holding cost rate. The formulation of the lot-sizing problem is developed in terms of integer-ratio lot size policies. This formulation provides a unification of the integer-split policies formulation of Schwarz and Schrage [34] (1975) and the integer-multiple policies formulation of Moily [20] (1986), allowing either assumption to be operative at any point in the system. A relaxed solution to this unified formulation provides a lower bound to the cost of any feasible policy. The derivation of this Lower Bound Theorem is novel and relies on the notion of path holding costs, a generalization of echelon holding costs. An optimal power-of-two lot size policy is found by an 0(n³ log n) algorithm and its cost is within 2% of the optimum in the worst case.
Mitchell [18] (1987) extended Roundy's 98%-effectiveness results for one-warehouse multi-retailer inventory systems with backlogging. We extend this 98%-effectiveness result
for series inventory systems with backlogging. The nearly-integer-ratio policies still work. The continuous relaxation provides a lower bound on the long-run average cost of any feasible policy. The backlogging model is also reduced in 0{n) time to an equivalent model without backlogging. Roundy's results [27] (1983) are then applied for finding a 98%-effective backlogging policy in O(nlogn) time.
In an EOQ model with n products, joint setup costs provide incentives for joint replenishment. These joint setup costs may be modelled as a positive, nondecreasing, submodular set function. A grouping heuristic partitions the n products into groups, and all products in the same group are always jointly replenished. Each group is then considered as a single "aggregate product" being replenished independently of the other groups, and therefore according to the EOQ formula. As a result, possible savings when several groups are simultaneously replenished are simply ignored. Our main result is that the cost of the best such grouping solution cannot be worse than 44.8% above the optimum cost. Known examples show that it can be as bad as 22.4% above the optimum cost. These results contrast with earlier results for power-of-two policies, the best of which never being worse than about 2% above the optimum cost.Business, Sauder School of
Graduate
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Sele, Céleste. « Caractérisation structurale des interactions moléculaires au sein du complexe de réplication du virus de la vaccine ». Thesis, Grenoble, 2011. http://www.theses.fr/2011GRENV085.
Texte intégralRésumé :
Le virus de la vaccine (VACV) est un grand virus à ADN, modèle du genre orthopoxvirus, et partage plus de 97% d'identité de séquence avec le virus de la variole (VARV), un pathogène humain majeur éradiqué en 1977 grâce au programme de vaccination mondial avec le VACV. Celle-ci ayant été stoppée dans les années 80, un pourcentage significatif de la population mondiale est aujourd'hui considérée comme immunologiquement naïf vis à vis du virus de la variole, ce qui fait de lui un agent bioterroriste potentiel. De plus, la vaccination implique un grand nombre de complications, particulièrement graves chez les personnes immunodéprimées ; et les antiviraux disponibles sont peu développés, ce qui souligne le besoin de nouvelles molécules. Le complexe de réplication apparait comme étant une cible privilégiée, de par son importance dans le cycle viral mais aussi par sa localisation cytoplasmique qui le rend plus accessible aux molécules antivirales. Nous nous sommes intéressés à 4 protéines essentielles de ce complexe : l'ADN polymérase E9, le facteur de processivité composé de la protéine A20 et de l'uracile ADN glycosylase D4 et l'hélicase-primase D5. Nous avons pu exprimer ces protéines de manière recombinante, seules ou en complexe ainsi que les caractériser biochimiquement et biophysiquement. Nous avons finalement abouti à une reconstruction strcuturale du complexe A20D4E9 à basse résolution grâce à la technique de SAXS, ce qui nous a permis de proposer le premier modèle structural de la fourche de réplication du virus de la vaccineVaccinia virus (VACV) is a large DNA virus, prototypic virus of the orthopoxvirus genus, and shows over 97% amino acid sequence identity with the variola virus (VARV), a major human pathogene eradicated in 1977 thanks to the universal vaccination program with VACV. As this vaccination was halted in the 1980s, a significant percentage of the world population is now immunologically naïve, which makes the VARV a potent bioterrorist agent. Vaccination against smallpox may result in a variety of complications, particularly in immunologically depressed patients, and the available antiviral therapeutics are rare, which enhance the need of new molecules. The replication complex appears as an ideal target because of its importance in the viral cycle and its cytoplasmic localization, more accessible for the molecules. We have focused our study on 4 essential proteins of this complex: the DNA polymerase E9, the processivity factor composed by the A20 protein and the uracil DNA glycosylase D4 and the helicase-primase D5. We could express these recombinant proteins, alone and in complex, and characterize them biochemically and biophysically. Using the SAXS technic, we finally reached a low resolution model of the A20D4E9 complex which allow us to propose the first structural model of the vaccinia virus replication fork
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Forsman, Åsa. « Identification of simple structures in complex substance transport models / ». Linköping : Faculty of Arts and Sciences, Univ, 2002. http://www.bibl.liu.se/liupubl/disp/disp2002/stat1s.pdf.
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Choe, Sehyo Charley. « Models of complex adaptive systems with underlying network structure ». Thesis, University of Oxford, 2007. https://ora.ox.ac.uk/objects/uuid:1cb8cb96-d27f-4543-9065-0e38a4297435.
Texte intégralRésumé :
This thesis explores the effect of different types of underlying network structure on the dynamical behaviour of a competitive population - a situation encountered in many real-world complex systems. In the first part of the thesis, I focus on generic, but abstract, multi-agent systems. I start by presenting analytic and numerical results for a population of heterogeneous, decision-making agents competing for some limited global resource, in which connections arise unintentionally between agents as a by-product of their strategy choices. I show that accounting for the resulting groups of strongly-correlated agents - in particular, the crowds and so-called 'anticrowds' - yields an accurate analytic description of the systems dynamics. I then introduce a local communication network between the agents, enabling them to intentionally share information among themselves. Such an interaction network leads to highly non-trivial dynamics, forcing a trade-off between individual and global success. Introducing corruption into the information being exchanged between agents, gives rise to a novel phase transition. I then provide a quantitative analytic theory of these various numerical results by generalizing the Crowd-Anticrowd formalism to include such local interactions. In the second part of the thesis, I consider a real-world system which also features competitive populations and networks - a cancer tumour, which contains cancerous cells competing for space and nutrients in the presence of an underlying vasculature structure. To simplify the analysis and comparison to real clinical data, the model chosen is far simpler than that discussed in the first part of the thesis - however despite its simplicity, the model is shown to yield remarkably good agreement with empirical findings. In addition, the model shows how different treatment methods can lead to a wide variety of unexpected re-growth behaviours of the tumour.
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Rodriguez, Jesus. « Modeling of complex systems using nonlinear, flexible multibody dynamics ». Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/12344.
Texte intégral
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Levy, Marc. « Shareholders' control in complex corporate structures ». Doctoral thesis, Universite Libre de Bruxelles, 2012. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/209768.
Texte intégralRésumé :
In this global world, many firms present a complex shareholding structure withindirect participation, such that it may become difficult to assess a firm’s controllers.
Furthermore, if there are numerous dominant shareholders, the control can be shared between
them. Determining who has the most influence is often a difficult task. To measure this
influence, game theory allows the modeling of voting games and the computing of the
Banzhaf index. This thesis develops models to measure the Banzhaf indices in any ownership structure (pyramidal ownership structures and cross-ownership structures). The models are then applied to real cases studies such Colruyt, Elia, Lafarge and Allianz.
Doctorat en Sciences économiques et de gestion
info:eu-repo/semantics/nonPublished
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Guo, Xu. « Checking the adequacy of regression models with complex data structure ». HKBU Institutional Repository, 2014. https://repository.hkbu.edu.hk/etd_oa/90.
Texte intégralRésumé :
In this thesis, we investigate the model checking problem for parametric regression model with missing response at random and nonignorable missing response. Besides, we also propose a hypothesis-adaptive procedure which is based on the dimension reduction theory. Finally, to extend our methods to missing response situation, we consider the dimension reduction problem with missing response at random. The .rst part of the thesis introduces the model checking for parametric models with response missing at random which is a more general missing mechanism than missing completely at random. Di.erent from existing approaches, two tests have normal distributions as the limiting null distributions no matter whether the inverse probability weight is estimated parametrically or nonparametrically. Thus, p-values can be easily determined. This observation shows that slow convergence rate of nonparametric estimation does not have signi.cant e.ect on the asymptotic behaviours of the tests although it may have impact in .nite sample scenarios. The tests can detect the alternatives distinct from the null hypothesis at a nonparametric rate which is an optimal rate for locally smoothing-based methods in this area. Simulation study is carried out to examine the performance of the tests. The tests are also applied to analyze a data set on monozygotic twins for illustration. In the second part of the thesis, we consider model checking for general linear regression model with non-ignorable missing response. Based on an exponential tilting model, we .rst propose three estimators for the unknown parameter in the general linear regression model. Three empirical process-based tests are constructed. We discuss the asymptotic properties of the proposed tests under null and local alternative hypothesis with di.erent scenarios. We .nd that these three tests perform the same in the asymptotic sense. Simulation studies are also carried out to assess the performance of our proposed test procedures. In the third part, we revisit traditional local smoothing model checking procedures. Noticing that the general nonparametric regression model can be considered as a special multi-index model, we propose an adaptive testing procedure based on the dimension reduction theory. To our surprise, our method can detect local alternative at faster rate than the traditional optimal rate. The theory indicates that in model checking problem, dimensionality may not have strong impact. Simulations are carried out to examine the performance of our methodology. A real data analysis is conducted for illustration. In the last part, we study the dimension reduction problem with missing response at random. Based on the work in this part, we can extend the adaptive testing procedure introduced in the third part to the missing response situation. When there are many predictors, how to e.ciently impute responses missing at random is an important problem to deal with for regression analysis because this missing mechanism, unlike missing completely at random, is highly related to high-dimensional predictor vector. In su.cient dimension reduction framework, the fusion-re.nement (FR) method in the literature is a promising approach. To make estimation more accurate and e.cient, two methods are suggested in this paper. Among them, one method uses the observed data to help on missing data generation, and the other one is an ad hoc approach that mainly reduces the dimension in the nonparametric smoothing in data generation. A data-adaptive synthesization of these two methods is also developed. Simulations are conducted to examine their performance and a HIV clinical trial dataset is analysed for illustration. Keywords: Model checking; Inverse probability weight; Non-ignorable missing response; Adaptive; Central subspace; Dimension reduction; Data-adaptive Synthesization; Missing recovery; Missing response at random; Multiple imputation.
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Li, Miaoqi. « Statistical models and algorithms for large data with complex dependence structures ». University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1584015958922068.
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Nascimento, Fábio Fialho do 1983. « Análise estocástica linear de estruturas complexas usando meta-modelo modal ». [s.n.], 2015. http://repositorio.unicamp.br/jspui/handle/REPOSIP/265736.
Texte intégralRésumé :
Orientador: José Maria Campos dos SantosDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecânica
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Resumo: Este trabalho tem como objetivo geral investigar abordagens para a análise de incerteza em problemas de dinâmica estrutural, de forma computacionalmente eficiente, no contexto industrial. Neste sentido, utilizou-se um metamodelo, baseado no método da superfície de resposta, para simplificar a etapa do cálculo dos modos e das frequências naturais na análise de resposta em frequência da estrutura. Para viabilizar a análise de grandes modelos, a solução de elementos finitos foi realizada pelo Nastran®. O MatLab® foi utilizado para manipular os autovalores e autovetores, e calcular as FRFs. Já o processo de amostragem das variáveis, a preparação da superfície de resposta e a integração com os demais aplicativos, foram realizados por meio do Isight®. Inicialmente, a abordagem foi avaliada em um modelo simples de um para-brisa veicular, com espessura, modo de elasticidade e densidade como parâmetros incertos. Posteriormente, o método foi aplicado para um modelo de uma estrutura veicular com milhares graus de liberdade. Neste caso, as variáveis aleatórias consideradas foram espessuras de vinte peças estampadas. Todas as variáveis foram consideradas com distribuição normal. Para quantificar a incerteza na resposta dinâmica, a simulação por Monte Carlo foi conduzida em conjunto com o metamodelo. A variabilidade das frequências naturais e da FRF é comparada com o resultado do Monte Carlo direto
Abstract: This work has as general objective to investigate approaches for uncertainty analysis in structural dynamics problems in a computational efficient manner in an industrial context. In this sense, we used a metamodel based on the response surface method to simplify the process of modes and natural frequencies calculation for frequency response analysis of a structure. In order to make the process feasible for large models, the finite element solution was performed using Nastran®. MatLab® was used to manipulate the eigenvalues and eigenvectors and calculate the FRFs. Isight® was responsible for the variable sampling process, response surface preparation and integrating other applications as well. Initially, the approach was assessed in a simple model of a car windshield with its thickness, Young¿s modulus and material density as uncertain parameters. Later the method was applied to a vehicle structure model with thousands degrees of freedom. In this case, the random variables considered were thicknesses of twenty stamped parts. Gaussian distribution was considered for all variables. For the purpose of uncertainty quantification in the dynamic response, Monte Carlo simulation was performed over the metamodel. The variability of the natural frequencies and FRF is compared against to direct Monte Carlo results
Mestrado
Mecanica dos Sólidos e Projeto Mecanico
Mestre em Engenharia Mecânica
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Abade, André da Silva. « Uma abordagem de teste estrutural de uma transformações M2T baseada em hipergrafos ». Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/8721.
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Context: MDD (Model-Driven Development) is a software development paradigm in which the main artefacts are models, from which source code or other artefacts are generated. Even though MDD allows different views of how to decompose a problem and how to design a software to solve it, this paradigm introduces new challenges related to the input models, transformations and output artefacts. Problem Statement: Thus, software testing is a fundamental activity to reveal defects and improve confidence in the software products developed in this context. Several techniques and testing criteria have been proposed and investigated. Among them, functional testing has been extensively explored primarily in the M2M (Model-to-Model) transformations, while structural testing for M2T (Model-to-Text) transformations still poses challenges and lacks appropriate approaches. Objective: This work aims to to present a proposal for the structural testing of M2T transformations through the characterisation of input models as complex data, templates and output artefacts involved in this process. Method: The proposed approach was organised in five phases. Its strategy proposes that the complex data (grammars and metamodels) are represented by directed hypergraphs, allowing that a combinatorial-based traversal algorithm creates subsets of the input models that will be used as test cases for the M2T transformations. In this perspective, we carried out two exploratory studies with the specific purpose of feasibility analysis of the proposed approach. Results and Conclusion: The evaluation of results from the exploratory studies, through the analysis of some testing coverage criteria, demonstrated the relevance and feasibility of the approach for characterizing complex data for M2T transformations testing. Moreover, structuring the testing strategy in phases enables the revision and adjustment of activities, in addition to assisting the replication of the approach within different applications that make use of the MDD paradigm.
Contexto: O MDD (Model-Driven Development ou Desenvolvimento Dirigido por Modelos) e um paradigma de desenvolvimento de software em que os principais artefatos são os modelos, a partir dos quais o código ou outros artefatos são gerados. Esse paradigma, embora possibilite diferentes visões de como decompor um problema e projetar um software para soluciona-lo, introduz novos desafios, qualificados pela complexidade dos modelos de entrada, as transformações e os artefatos de saída. Definição do Problema: Dessa forma, o teste de software e uma atividade fundamental para revelar defeitos e aumentar a confiança nos produtos de software desenvolvidos nesse contexto. Diversas técnicas e critérios de teste vem sendo propostos e investigados. Entre eles, o teste funcional tem sido bastante explorado primordialmente nas transformações M2M (Model-to-Model ou Modelo para Modelo), enquanto que o teste estrutural em transformações M2T (Model-to-Text ou Modelo para Texto) ainda possui alguns desafios e carência de novas abordagens. Objetivos: O objetivo deste trabalho e apresentar uma proposta para o teste estrutural de transformações M2T, por meio da caracterização dos dados complexos dos modelos de entrada, templates e artefatos de saída envolvidos neste processo. Metodologia: A abordagem proposta foi organizada em cinco fases e sua estratégia propõe que os dados complexos (gramáticas e metamodelos) sejam representados por meio de hipergrafos direcionados, permitindo que um algoritmo de percurso em hipergrafos, usando combinatória, crie subconjuntos dos modelos de entrada que serão utilizados como casos de teste para as transformações M2T. Nesta perspectiva, realizou-se dois estudos exploratórios com propósito específico da analise de viabilidade quanto a abordagem proposta. Resultados: A avaliação dos estudos exploratórios proporcionou, por meio da analise dos critérios de cobertura aplicados, um conjunto de dados que demonstram a relevância e viabilidade da abordagem quanto a caracterização de dados complexos para os testes em transformações M2T. A segmentação das estratégias em fases possibilita a revisão e adequação das atividades do processo, além de auxiliar na replicabilidade da abordagem em diferentes aplicações que fazem uso do paradigma MDD.
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Nasri, Habib. « Synthese et caracterisation de porphyrines de fe(ii) et fe(iii) : modelisation du site actif du centre p460 present dans l'hydroxylamine oxydoreductase de la bacterie nitrosomonas europaea ». Université Louis Pasteur (Strasbourg) (1971-2008), 1987. http://www.theses.fr/1987STR13149.
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Synthese de modeles du site actif du cytochrome p460 a l'etat reduit. Donc synthese et caracterisation d'une serie de complexes (fe(ii) (or)t piv pp)**(-) ou or=ome, oph, ophf::(4), oac; et des complexes fe(iii)cltpivpp, fe(iii)(oac)tpivpp, fe(iii)(so::(3)cf::(3))(h::(2)o)tpivpp
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Posenato, Daniele. « Model-free data interpretation for continuous monitoring of complex structures / ». [S.l.] : [s.n.], 2009. http://library.epfl.ch/theses/?nr=4481.
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Strojny, Brandan Thomas. « EXCITATION AND ANALYSIS OF CHARACTERISTIC MODES ON COMPLEX ANTENNA STRUCTURES ». The Ohio State University, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=osu1301006813.
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Oodally, Ajmal. « Estimation in frailty models with complex correlation structures through stochastic approximation algorithms ». Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASM003.
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Cette thèse porte sur l’estimation dans les modèles de fragilité en analyse de survie. Notre première contribution concerne une nouvelle méthode d’estimation basée sur la vraisemblance partielle intégrée dans le modèle de fragilité. Cette méthode ne réalise aucune approximation de la vraisemblance partielle intégrée contrairement aux autres méthodes proposées dans la littérature. Nous mettons en œuvre une approximation stochastique de l’algorithme Expectation Maximization (EM) pour calculer les estimateurs du maximum de vraisemblance partielle des paramètres du modèle. De plus, nous établissons les propriétés théoriques de convergence de l’algorithme. Notre méthode permet de considérer des modèles de fragilité avec différentes structures de corrélations et une large gamme de lois de fragilité. Notre deuxième contribution porte sur l'étude des vitesses de convergence des estimateurs du maximum de vraisemblance dans les modèles à fragilités partagées paramétriques. En particulier, les vitesses diffèrent selon la factorisation de la vraisemblance conditionnelle. Nous étudions ce phénomène au travers d’une étude de simulation. Nous mettons aussi en évidence l’influence du niveau des covariables sur les vitesses de convergence à travers une étude de simulation intensive dans les modèles de fragilité et de façon analytique dans un modèle linéaire à effets mixtes. Notre troisième contribution présente un nouveau modèle de fragilité qui permet de prendre en compte les corrélations spatiales présentes dans les données. Cette nouvelle modélisation spatiale a été motivée par des données d’infection de malaria en Éthiopie. Les distances entre les individus jouant un rôle important dans la transmission de la maladie, il s’avère judicieux de les prendre en compte dans le modèle. Une version stochastique de l’algorithme EM adaptée à ce contexte est mise en œuvre et étudiée. La méthode d’estimation est validée sur des données simulées puis mise en œuvre pour analyser les données de malariaThis thesis deals with estimation in frailty models in survival analysis. Our first contribution concerns a new estimation method based on integrated partial likelihood in the frailty model. No approximation of the integrated partial likelihood is made as compared to other methods proposed in the literature. We implement a stochastic approximation of the Expectation Maximization (EM) algorithm to calculate the maximum of partial likelihood estimators of the model parameters. We also establish the theoretical convergence properties of the algorithm. Our method allows for different correlation structures and for a wide range of frailty distributions. Our second contribution concerns the study of the convergence rates of maximum likelihood estimators in parametric shared frailty models. The convergence rates of are notably different following the factorization of the conditional likelihood. We study this phenomenon via a simulation study. We also highlight the influence of the level of covariates on convergence rates analytically in a linear mixed effects model. We illustrate these differences via an intensive simulation study on a parametric frailty model. Our third contribution presents a new frailty model which takes into account spatial correlations which may be present in data. This new spatial modeling is motivated by malaria infection data collected in Ethiopia. Since the distances between individuals play an important role in the transmission of the disease, it may be relevant to take them into account in the model. A stochastic version of the EM algorithm adapted to this context is implemented and studied. The estimation method is validated on simulated data and then implemented to analyze the malaria data
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Elwany, Alaa H. « Sensor-based prognostics and structured maintenance policies for components with complex degradation ». Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/37198.
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We propose a mathematical framework that integrates low-level sensory signals from monitoring engineering systems and their components with high-level decision models for maintenance optimization. Our objective is to derive optimal adaptive maintenance strategies that capitalize on condition monitoring information to update maintenance actions based upon the current state of health of the system. We refer to this sensor-based decision methodology as "sense-and-respond logistics".
As a first step, we develop and extend degradation models to compute and periodically update the remaining life distribution of fielded components using in situ degradation signals. Next, we integrate these sensory updated remaining life distributions with maintenance decision models to; (1) determine, in real-time, the optimal time to replace a component such that the lost opportunity costs due to early replacements are minimized and system utilization is increased, and (2) sequentially determine the optimal time to order a spare part such that inventory holding costs are minimized while preventing stock outs.
Lastly, we integrate the proposed degradation model with Markov process models to derive structured replacement and spare parts ordering policies. In particular, we show that the optimal maintenance policy for our problem setting is a monotonically non-decreasing control limit type policy. We validate our methodology using real-world data from monitoring a piece of rotating machinery using vibration accelerometers. We also demonstrate that the proposed sense-and-respond decision methodology results in better decisions and reduced costs compared to other traditional approaches.
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Bradshaw, Darren. « Towards structural analogues of metallobiosites : synthesis and characterisation of dinuclear zinc complexes ». Thesis, University of Sheffield, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.369959.
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Kovur, Srinivasulu Raju. « Synthesis and Enzymatic Oxidation of Model Lignin Carbohydrate Complexes ». Fogler Library, University of Maine, 2008. http://www.library.umaine.edu/theses/pdf/KovurSR2008.pdf.
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林德華 et Tak-wah Lam. « Topological data structure and algorithms for cell-complex based non-manifold form feature modeling ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1994. http://hub.hku.hk/bib/B3121244X.
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Lam, Tak-wah. « Topological data structure and algorithms for cell-complex based non-manifold form feature modeling / ». Hong Kong : University of Hong Kong, 1994. http://sunzi.lib.hku.hk/hkuto/record.jsp?B19672214.
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Murray, Kevin Paul. « The design of antenna systems on complex structures using characteristic modes ». Thesis, University of Liverpool, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385200.
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Mirschel, Sebastian [Verfasser]. « Interactive Visualization of Complex Structures in Modular Models for Systems Biology / Sebastian Mirschel ». Aachen : Shaker, 2012. http://d-nb.info/1067735712/34.
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Nhleko, Olivia Lebogang. « Implications of the geological structure of the Qoqodala Dolerite ring complex for groundwater dynamics. / ». Thesis, Online access, 2008. http://etd.uwc.ac.za/usrfiles/modules/etd/docs/etd_gen8Srv25Nme4_8728_1263434292.pdf.
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Devkota, Batsal. « Structural studies of ribonucleoprotein complexes using molecular modeling ». Diss., Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/22713.
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Thesis (Ph. D.)--Biology, Georgia Institute of Technology, 2008.Committee Chair: Harvey, Stephen C; Committee Member: Hud, Nicholas V; Committee Member: McCarty, Nael A; Committee Member: Wartell, Roger M.
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Bernard-Lambert, Elisabeth. « Complexes binucléaires du fer : modèles chimiques du site actif des phosphatases acides pourpres ». Université Joseph Fourier (Grenoble), 1995. http://www.theses.fr/1995GRE10086.
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Les phosphatases acides pourpres appartiennent a la classe des enzymes a fer non heminique a site actif binucleaire. Ces proteines ont ete etudiees par diverses techniques spectroscopiques, mais leur structure cristallographique n'a pas encore ete resolue. Dans le but de mieux connaitre les proprietes structurales des phosphatases acides pourpres, nous avons synthetise des complexes modeles de leur site actif a partir de nouveaux ligands phenoliques binucleants dissymetriques. Ces analogues synthetiques sont les premiers a reproduire plusieurs aspects essentiels des sites naturels, notamment leur dissymetrie, la coordination d'un seul groupement phenolate terminal et leurs proprietes electrochimiques. La dissymetrie des complexes a permis d'observer des caracteristiques propres aux enzymes, telles que la localisation des valences en solution et la stabilisation des formes a valence mixte. L'etude electrochimique a montre que la presence d'un seul groupement phenolate terminal etait essentielle pour modeliser les proprietes redox particulieres des phosphatases acides pourpres
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Rahman, Brian M. « Sensor Placement for Diagnosis of Large-Scale, Complex Systems : Advancement of Structural Methods ». The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1562859497638274.
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Nichols, Jonathan Tyler. « Application of Load Updating to a Complex Three Dimensional Frame Structure ». Thesis, Virginia Tech, 2017. http://hdl.handle.net/10919/78274.
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This thesis presents a novel method for the correlation of FEM results to experimental test results known as the "Load updating method." Specifically, the load updating method uses the math model from the FEM and the strains measured from experimental or flight test data as inputs and then predicts the loads in the FEM which would result in strains that would correlate best to the measured strains in the least squared sense. In this research, the load updating method is applied to the analysis of a complex frame structure whose validation is challenging due to the complex nature of its structural behavior, load distributions, and error derived from residual strains. A FEM created for this structure is used to generate strain data for thirty-two different load cases. These same thirty-two load cases are replicated in an experimental setup consisting of the frame, supporting structure, and thirty actuators which are used to load the frame according to the specifications for each of the thirty-two load conditions. A force-strain matrix is created from the math model in NASTRAN using unit loads which are separately applied to each load point in order to extract strain results for each of the locations of the seventy-four strain gages. The strain data from the structural test and the force-strain matrix is then input into a Matlab code which is created to perform the load updating method. This algorithm delivers a set of coefficients which in turn gives the updated loads. These loads are applied to the FEM and the strain values extracted for correlation to the strains from test data. It is found that the load updating method applied to this structure produces strains which correlate well to the experimental strain data. Although the loads found using the load updating method do not perfectly match those which are applied during the test, this error is primarily attributed to residual strains within the structure. In summary, the load updating method provides a way to predict loads which, when applied to the FEM, would result in strains that correlate best to the experimental strains. Ultimately, this method could prove especially useful for predicting loads in experimental and flight test structures and could aid greatly in the Federal Aviation Administration (FAA) certification process.Master of Science
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Perez-Navarro, Montserrat [Verfasser]. « The Structure and Function of the Water-Oxidizing Complex of Photosystem II and Related Model Complexes Investigated by Pulse EPR Spectroscopy / Montserrat Perez-Navarro ». Düsseldorf : Universitäts- und Landesbibliothek der Heinrich-Heine-Universität Düsseldorf, 2019. http://d-nb.info/1176189093/34.
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Goodsell, L. S. « High resolution structural models of ribosome nascent chain complexes restrained by experimental NMR data ». Thesis, University College London (University of London), 2015. http://discovery.ucl.ac.uk/1470654/.
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As understanding of the ways in which the complex cellular environment affects the in vivo folding of proteins improves, improved methods for their study are required. It is possible to produce limited quantities of ribosome-nascent chain complexes (RNCs) and techniques for gathering data about them are improving, but no single technique provides all the information required to understand folding of nascent proteins on the ribosome and there are still significant data that cannot be obtained experimentally. In particular, while NMR chemical shift and residual dipolar couplings may be recorded, the samples are of too low concentration and stability to conduct the most informative NOESY experiments that are traditionally used for revealing atomic-resolution structure. Recently, the ability to use chemical shifts to reveal structural details and dynamic properties of small proteins has been developed. By simulating multiple molecules and predicting the average chemical shift of the ensemble, the simulation may be restrained to conform to the experimentally measured data, making testable predictions about the atomic-resolution dynamic properties of the molecule. By adapting these methods to the macromolecular RNC structures it is theorized that the limited chemical shift data available may be used to provide structural details of the protein as it emerges from a ribosome. This, however, is faced by many challenges, including the ability to simulate such large number of atoms in a suitable timescale and applying the restraints to the nascent chain alone. The thesis presented describes the development of computational techniques to characterize RNCs, including the concepts and challenges faced, the chemical-shift restrained simulation of nascent chains alone, the development of techniques to perform chemical-shift restrained molecular dynamics simulations of the RNCs and the application of these techniques to a model system.
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Simacek, Jiri. « Vérification de programmes avec structures de données complexes ». Phd thesis, Université de Grenoble, 2012. http://tel.archives-ouvertes.fr/tel-00805794.
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Les travaux décrits dans cette thèse portent sur le problème de vérification des systèmes avec espaces d'états infinis, et, en particulier, avec des structures de données chaînées. Plusieurs approches ont émergé, sans donner des solutions convenables et robustes, qui pourrait faire face aux situations rencontrées dans la pratique. Nos travaux proposent une approche nouvelle, qui combine les avantages de deux approches très prometteuses: la représentation symbolique a base d'automates d'arbre, et la logique de séparation. On présente également plusieurs améliorations concernant l'implementation de différentes opérations sur les automates d'arbre, requises pour le succès pratique de notre méthode. En particulier, on propose un algorithme optimise pour le calcul des simulations sur les systèmes de transitions étiquettes, qui se traduit dans un algorithme efficace pour le calcul des simulations sur les automates d'arbre. En outre, on présente un nouvel algorithme pour le problème d'inclusion sur les automates d'arbre. Un nombre important d'expérimentes montre que cet algorithme est plus efficace que certaines des méthodes existantes.
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Hui, Zi. « Spatial structure of complex network and diffusion dynamics ». Thesis, Le Mans, 2013. http://www.theses.fr/2013LEMA1005/document.
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Dans le développement récent des sciences de réseau, réseaux contraints spatiales sont devenues un objet d'une enquête approfondie. Spatiales des réseaux de contraintes sont intégrées dans l'espace de configuration. Leurs structures et les dynamiques sont influencées par la distance spatiale. Ceci est prouvé par les données empiriques de plus en plus sur des systèmes réels montrant des lois exponentielles ou de distribution d'énergie distance spatiale de liens. Dans cette thèse, nous nous concentrons sur la structure de réseau spatial avec une distribution en loi de puissance spatiale. Plusieurs mécanismes de formation de la structure et de la dynamique de diffusion sur ces réseaux sont pris en considération. D'abord, nous proposons un réseau évolutif construit en l'espace de configuration d'un mécanisme de concurrence entre le degré et les préférences de distance spatiale. Ce mécanisme est décrit par un a^'fc- + (1 — a)^'lL_,1, où ki est le degré du noeud i et rni est la distance spatiale entre les noeuds n et i. En réglant le paramètre a, le réseau peut être fait pour changer en continu à partir du réseau spatiale entraînée (a = 0) pour le réseau sans échelle (a = 1). La structure topologique de notre modèle est comparé aux données empiriques de réseau de courrier électronique avec un bon accord. Sur cette base, nous nous concentrons sur la dynamique de diffusion sur le réseau axé sur spatiale (a — 0). Le premier modèle, nous avons utilisé est fréquemment employée dans l'étude de la propagation de l'épidémie: ['spatiale susceptible-infecté-susceptible (SIS) modèle. Ici, le taux de propagation entre deux noeuds connectés est inversement proportionnelle à leur distance spatiale. Le résultat montre que la diffusion efficace de temps augmente avec l'augmentation de a. L'existence d'seuil épidémique générique est observée, dont la valeur dépend du paramètre a Le seuil épidémique maximum et le ratio minimum fixe de noeuds infectés localiser simultanément dans le intervalle 1.5 < a < 2.Puisque le réseau spatiale axée a bien défini la distance spatiale, ce modèle offre une occasion d'étudier la dynamique de diffusion en utilisant les techniques habituelles de la mécanique statistique. Tout d'abord, compte tenu du fait que la diffusion est anormale en général en raison de l'importante long plage de propagation, nous introduisons un coefficient de diffusion composite qui est la somme de la diffusion d'habitude constante D des lois de la Fick appliqué sur différentes distances de transfert possibles sur le réseau. Comme prévu, ce coefficient composite diminue avec l'augmentation de a. et est une bonne mesure de l'efficacité de la diffusion. Notre seconde approche pour cette diffusion anormale est de calculer le déplacement quadratique moyen (l²) à identifier une constante de diffusion D' et le degré de la anomalousness y avec l'aide de la loi de puissance (l²) = 4D'ty. D' comportements de la même manière que D, i.e.. elle diminue avec l'augmentation de a. y est inférieur à l'unité (subdiffusion) et tend à un (diffusion normale) que a augmenteIn the recent development of network sciences, spatial constrained networks have become an object of extensive investigation. Spatial constrained networks are embedded in configuration space. Their structures and dynamics are influenced by spatial distance. This is proved by more and more empirical data on real Systems showing exponential or power laws spatial distance distribution of links. In this dissertation, we focus on the structure of spatial network with power law spatial distribution. Several mechanisms of structure formation and diffusion dynamics on these networks are considered. First we propose an evolutionary network constructed in the configuration space with a competing mechanism between the degree and the spatial distance preferences. This mechanism is described by a ki + (1 — a), where ki is the degree of node i and rni is the spatial distance between nodes n and i. By adjusting parameter a, the network can be made to change continuously from the spatial driven network (a = 0) to the scale-free network (a = 1). The topological structure of our model is compared to the empirical data from email network with good agreement. On this basis, we focus on the diffusion dynamics on spatial driven network (a = 0). The first model we used is frequently employed in the study of epidemie spreading : the spatial susceptible-infected-susceptible (SIS) model. Here the spreading rate between two connected nodes is inversely proportional to their spatial distance. The result shows that the effective spreading time increases with increasing a. The existence of generic epidemic threshold is observed, whose value dépends on parameter a. The maximum épidemic threshold and the minimum stationary ratio of infected nodes simultaneously locate in the interval 1.5 < a < 2. Since the spatial driven network has well defined spatial distance, this model offers an occasion to study the diffusion dynamics by using the usual techniques of statistical mechanics. First, considering the fact that the diffusion is anomalous in general due to the important long-range spreading, we introduce a composite diffusion coefficient which is the sum of the usual diffusion constant D of the Fick's laws applied over different possible transfer distances on the network. As expected, this composite coefficient decreases with increasing a and is a good measure of the efficiency of the diffusion. Our second approach to this anomalous diffusion is to calculate the mean square displacement (l²) to identify a diffusion constant D' and the degree of thé anomalousness y with the help of the power law {l²} = 4D'ty. D' behaviors in the same way as D, i.e., it decreases with increasing a. y is smaller than unity (subdiffusion) and tends to one (normal diffusion) as a increases
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Roth, Alexander. « Nano-mechanics of biomimetic models of the actin based cytoskeleton from single molecules to complex composite structures / ». [S.l. : s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=972309322.
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Cederbaum, Jona [Verfasser], et Sonja [Akademischer Betreuer] Greven. « Functional linear mixed models for complex correlation structures and general sampling grids / Jona Cederbaum ; Betreuer : Sonja Greven ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2017. http://d-nb.info/1156851998/34.
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Chen, Yang. « A universal species ion implantation model for implants into topographically complex structures with multiple materials ». Access restricted to users with UT Austin EID Full text (PDF) from UMI/Dissertation Abstracts International, 2001. http://wwwlib.umi.com/cr/utexas/fullcit?p3025007.
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Abou, Jaoude Dany. « Computationally Driven Algorithms for Distributed Control of Complex Systems ». Diss., Virginia Tech, 2018. http://hdl.handle.net/10919/85965.
Texte intégralRésumé :
This dissertation studies the model reduction and distributed control problems for interconnected systems, i.e., systems that consist of multiple interacting agents/subsystems. The study of the analysis and synthesis problems for interconnected systems is motivated by the multiple applications that can benefit from the design and implementation of distributed controllers. These applications include automated highway systems and formation flight of unmanned aircraft systems.
The systems of interest are modeled using arbitrary directed graphs, where the subsystems correspond to the nodes, and the interconnections between the subsystems are described using the directed edges. In addition to the states of the subsystems, the adopted frameworks also model the interconnections between the subsystems as spatial states. Each agent/subsystem is assumed to have its own actuating and sensing capabilities. These capabilities are leveraged in order to design a controller subsystem for each plant subsystem. In the distributed control paradigm, the controller subsystems interact over the same interconnection structure as the plant subsystems.
The models assumed for the subsystems are linear time-varying or linear parameter-varying. Linear time-varying models are useful for describing nonlinear equations that are linearized about prespecified trajectories, and linear parameter-varying models allow for capturing the nonlinearities of the agents, while still being amenable to control using linear techniques. It is clear from the above description that the size of the model for an interconnected system increases with the number of subsystems and the complexity of the interconnection structure. This motivates the development of model reduction techniques to rigorously reduce the size of the given model. In particular, this dissertation presents structure-preserving techniques for model reduction, i.e., techniques that guarantee that the interpretation of each state is retained in the reduced order system. Namely, the sought reduced order system is an interconnected system formed by reduced order subsystems that are interconnected over the same interconnection structure as that of the full order system. Model reduction is important for reducing the computational complexity of the system analysis and control synthesis problems.
In this dissertation, interior point methods are extensively used for solving the semidefinite programming problems that arise in analysis and synthesis.Ph. D.
The work in this dissertation is motivated by the numerous applications in which multiple agents interact and cooperate to perform a coordinated task. Examples of such applications include automated highway systems and formation flight of unmanned aircraft systems. For instance, one can think of the hazardous conditions created by a fire in a building and the benefits of using multiple interacting multirotors to deal with this emergency situation and reduce the risks on humans. This dissertation develops mathematical tools for studying and dealing with these complex systems. Namely, it is shown how controllers can be designed to ensure that such systems perform in the desired way, and how the models that describe the systems of interest can be systematically simplified to facilitate performing the tasks of mathematical analysis and control design.
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Agip, Ahmed-Noor. « Developing mouse complex I as a model system : structure, function and implications in mitochondrial diseases ». Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/283201.
Texte intégralRésumé :
Complex I (NADH:ubiquinone oxidoreductase), located in the mitochondrial inner membrane, is a major electron entry point to the respiratory chain. It couples the energy released from electron transfer (from NADH to ubiquinone) to the concomitant pumping of protons across the membrane, to generate an electrochemical proton motive force. Mammalian complex I is composed of 45 subunits, 14 of which comprise its simpler bacterial homologues. It is encoded by both the mitochondrial and nuclear genomes, and pathological mutations in both sets of subunits result in severe neuromuscular disorders such as Leigh syndrome. Several structures of mammalian complex I from various organisms have been determined, but the limited resolutions of the structures, which typically refer to poorly characterised enzyme states, has hampered detailed analyses of mechanistic features. The first part of this thesis describes development of a method for purifying complex I from the genetically amenable and medically relevant model organism Mus musculus (mouse), in a pure, stable and active state. The enzyme from mouse heart mitochondria was then comprehensively characterised, to ensure the presence of all the expected subunits and co-factors, and to define its kinetic properties. The second part of this thesis describes structural studies by single particle electron cryomicroscopy (cryo-EM) on the purified mouse enzyme in two distinct states, the 'active' and 'de-active' states. The active state was determined to 3.3 Å resolution, the highest resolution structure of a eukaryotic complex I so far. Subsequently, comparison of the two mouse structures, together with previously determined mammalian and bacterial structures, revealed variations in key structural elements in the membrane domain, which may be crucial for the catalytic mechanism. Moreover, in the high-resolution active mouse complex I structure a nucleotide co-factor was observed bound to the nucleoside kinase subunit NDUFA10. Finally, complex I from the Ndufs4 knockout mouse model, which recapitulates the effects of a human mutation that causes Leigh syndrome, was purified and subjected to kinetic and proteomic analyses. Following cross-linking and preliminary structural studies, it was concluded that the detrimental effects of deleting NDUFS4 are due to lack of stability of the mature complex.
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Zemanová, Lucia. « Structure-function relationship in hierarchical model of brain networks ». Phd thesis, Universität Potsdam, 2007. http://opus.kobv.de/ubp/volltexte/2008/1840/.
Texte intégralRésumé :
The mammalian brain is, with its numerous neural elements and structured complex connectivity, one of the most complex systems in nature. Recently, large-scale corticocortical connectivities, both structural and functional, have received a great deal of research attention, especially using the approach of complex networks. Here, we try to shed some light on the relationship between structural and functional connectivities by studying synchronization dynamics in a realistic anatomical network of cat cortical connectivity. We model the cortical areas by a subnetwork of interacting excitable neurons (multilevel model) and by a neural mass model (population model). With weak couplings, the multilevel model displays biologically plausible dynamics and the synchronization patterns reveal a hierarchical cluster organization in the network structure. We can identify a group of brain areas involved in multifunctional tasks by comparing the dynamical clusters to the topological communities of the network. With strong couplings of multilevel model and by using neural mass model, the dynamics are characterized by well-defined oscillations. The synchronization patterns are mainly determined by the node intensity (total input strengths of a node); the detailed network topology is of secondary importance. The biologically improved multilevel model exhibits similar dynamical patterns in the two regimes. Thus, the study of synchronization in a multilevel complex network model of cortex can provide insights into the relationship between network topology and functional organization of complex brain networks.Das Gehirn von Säugetieren stellt mit seinen zahlreichen, hochgradig vernetzten Neuronen ein natürliches Netzwerk von immenser Komplexität dar. In der jüngsten Vergangenheit sind die großflächige kortikale Konnektivitäten, sowohl unter strukturellen wie auch funktionalen Gesichtspunkten, in den Fokus der Forschung getreten. Die Verwendung von komplexe Netzwerke spielt hierbei eine entscheidende Rolle. In der vorliegenden Dissertation versuchen wir, das Verhältnis von struktureller und funktionaler Konnektivität durch Untersuchung der Synchronisationsdynamik anhand eines realistischen Modells der Konnektivität im Kortex einer Katze näher zu beleuchten. Wir modellieren die Kortexareale durch ein Subnetzwerk interagierender, erregbarer Neuronen (multilevel model) und durch ein Modell von Neuronenensembles (population model). Bei schwacher Kopplung zeigt das multilevel model eine biologisch plausible Dynamik und die Synchronisationsmuster lassen eine hierarchische Organisation der Netzwerkstruktur erkennen. Indem wir die dynamischen Cluster mit den topologischen Einheiten des Netzwerks vergleichen, sind wir in der Lage die Hirnareale, die an der Bewältigung komplexer Aufgaben beteiligt sind, zu identifizieren. Bei starker Kopplung im multilevel model und unter Verwendung des Ensemblemodells weist die Dynamik klare Oszillationen auf. Die Synchronisationsmuster werden hauptsächlich durch die Eingangsstärke an den einzelnen Knoten bestimmt, während die genaue Netzwerktopologie zweitrangig ist. Eine Erweiterung des Modells auf andere biologisch relevante Faktoren bestätigt die vorherigen Ergebnisse. Die Untersuchung der Synchronisation in einem multilevel model des Kortex ermöglicht daher tiefere Einblicke in die Zusammenhänge zwischen Netzwerktopologie und funktionaler Organisation in komplexen Hirn-Netzwerken.
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Rossi, Véronique. « Structure et fonction d'une protéase modulaire : étude de la région catalytique de la sous-unité C1s du complexe C1 du complément humain ». Université Joseph Fourier (Grenoble ; 1971-2015), 1997. http://www.theses.fr/1997GRE10033.
Texte intégralRésumé :
La sous-unite catalytique du complexe c1 du systeme complementaire humain est un tetramere ca#2#+-dependant (c1s-c1r-c1r-c1s) constitue de deux proteases a serine modulaires homologues, c1s et c1r. La protease c1s (673 acides amines, pm 79800), activee par c1r a la suite de la fixation de c1q a un activateur, declenche la voie classique du complement, par proteolyse de ses substrats c4 et c2. La proteolyse limitee de c1s par la plasmine produit le fragment catalytique gammab (270-673) constitue de deux modules ccp (complement control protein repeat) contigus, 4 et 5 (environ 60 residus chacun), d'un segment intermediaire (15 residus) et d'un domaine protease a serine (251 residus). Le travail presente dans cette these se situe dans le cadre de l'etude des relations structure-fonction de la protease c1s et a pour objectifs principaux: (i) l'etude de l'assemblage de la region catalytique de c1s, (ii) l'etude de l'implication des modules ccp 4 et 5 non proteasiques dans la proteolyse de ses substrats naturels, c4 et c2. Dans un premier temps, nous avons elabore un modele tridimensionnel de l'agencement des modules ccp 4, 5, du segment intermediaire et du domaine protease a serine. Une deuxieme partie du travail a consiste a verifier les hypotheses emises a l'aide du modele 3d, selon lesquelles les deux modules ccp 4 et 5, non proteasiques, confereraient a la protease c1s, sa haute specificite vis-a-vis du substrat c4. Cette partie du travail a egalement ete focalisee sur l'etude des regions de c1s impliquees dans la reconnaissance du deuxieme substrats de c1s, c2, pour lequel nous n'avons aucune indication. Deux fragments tronques de la region catalytique gammab de c1s, correspondant a une deletion du module ccp 4 seul, ou des deux modules ccp 4 et 5, ont ete produits sous forme proenzyme, dans un systeme eucaryote, cellules d'insecte sf21/baculovirus, en utilisant le systeme bac-to-bac#t#m. Nous avons montre que le fragment 5-b est activable par c1r de la meme maniere que c1s intact. Nous avons egalement montre que les informations necessaires pour la proteolyse de c2 sont toutes contenues dans le fragment 5-b tandis que certains elements de reconnaissance de c4 sont contenus dans le module ccp 4
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Kassem, Morad. « Champs de densité d'énergie pour la vibroacoustique basse et moyenne fréquence des structures complexes utilisant un modèle numérique stochastique : application à la partition structurale des automobiles ». Phd thesis, Université Paris-Est, 2009. http://tel.archives-ouvertes.fr/tel-00539048.
Texte intégralRésumé :
Ce travail de recherche s'inscrit dans le cadre de l'analyse vibroacoustique des structures complexes. Il propose une nouvelle approche énergétique utilisant le champ de densité d'énergie afin de simplifier une telle analyse. Cette approche est basée sur un modèle numérique stochastique construit à l'aide de l'approche probabiliste non paramétrique des incertitudes de modélisation et de paramètres. L'approche énergétique stochastique développée correspond à une nouvelle représentation du système vibroacoustique en terme des grandeurs énergétiques aléatoires. Un modèle vibroacoustique énergétique moyen est alors construit en prenant la moyenne statistique des grandeurs énergétiques. On dispose alors d'un modèle énergétique moyen pour analyser la vibroacoustique des systèmes complexes dans la bande des basses et des moyennes fréquences alors que la méthode SEA ne permet pas d'analyser cette bande de fréquence. L'analyse des propriétés des grandeurs énergétiques moyennes utilisées pour la construction du modèle vibroacoustique énergétique permet de construire une version simplifiée conduisant à un modèle énergétique simplifié pour lequel une méthodologie de partition structurale par zone est établie. Une application de cette approche énergétique et de la méthodologie de partition structurale par zone est présentée pour une voiture constituée d'une structure automobile couplée avec sa cavité acoustique interne
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Shao, L. (Lan). « An extended model of decision field theory integrated with AHP structure for complex decision making problems ». Master's thesis, University of Oulu, 2015. http://urn.fi/URN:NBN:fi:oulu-201505261672.
Texte intégralRésumé :
Decision Field Theory (DFT) provides an approach to explain the deliberation process of decision making under dynamic environment. However, the performance of original DFT theory is imperfect when the dynamic environment is getting complex. This research is aimed to build an extended model of DFT with good explanation and prediction abilities under complex dynamic environment. The dynamic structure of Analytic Hierarchy Process (AHP) was used in order to improve the flexibility and adaptability of extended model.
In this study, the systematic literature review (SLR) was conducted to explore the previous research in dynamic decision making field. The review protocol, regarding to review questions, review purpose and review method was developed during planning phase. After performing several steps of selection, 62 primary studies were selected. According to the results of analysis, limited number of primary studies are related to the practical application of DFT in specific context. Therefore, it is necessary to extend the DFT model.
In practice, class attending behavior of students was selected, as one example of complex dynamic making problems, to evaluate the extended model. In order to collect relevant data of decision making, three rounds of web survey were conducted. The students from University of Oulu are the respondents of the web survey.
In conclusion, the analysis results of data proved that proposed model is able to explain and predict the dynamic behavior of decision making well. This research opens space for future research about model studying and building.
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RAVAZZANO, LINDA. « STRUCTURE, DYNAMICS AND PHASE TRANSITIONS OF BIOLOGICAL MATTER ». Doctoral thesis, Università degli Studi di Milano, 2022. http://hdl.handle.net/2434/926571.
Texte intégralRésumé :
The work presented in this PhD Thesis aims to investigate, with the methods of
soft matter physics, systems of biological interest. Inspired by the observation
of algae, migrating cells and and protein complexes inside the single cell,
simple mathematical models have been implemented to obtain computer
simulations of complex systems of biological interest and to deepen our
understanding on their physical properties. The first part of the work deals with active matter systems, in which each
particle is able to self-propel. Active self-rotations are rarely studied in this
context, although present in biological systems such as Chlamydomonas
reinhardtii algae. We built a simple model for active particles in 2D based on
ABPs (Active Brownian Particles) model, accounting for inter-particle
interactions and adding an active torque to each particle to simulate the
ability of self-rotating. Employing MD simulations, we studied this model system
of active rotators in different conditions, to shed light on the role of self-
rotation in active matter systems at the jammed-unjammed transition. We
then applied our model based on ABPs to the study of interacting active
matter invading narrow channels, to investigate the role of single particles
properties in determining invasion behavior. The second part of the work deals with nuclear pores, protein complexes
inserted in the nuclear envelope of eukaryotic cells, acting as
communication gates between nucleus and cytoplasm. Nuclear pores
spatial organization and geometric arrangement on the nuclear surface are
still poorly understood. Hence we propose the use of tools commonly
employed to study the atomic structural and topological features of soft
matter, to study nuclear pores spatial organization. Furthermore, to interpret
the experimental results, we hypothesize an effective interaction among
nuclear pores and implemented it in extensive numerical simulations of
octagonal clusters, mimicking typical pore shapes.
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Silvestre, Daniel Gomes Marques. « Cooperação e Conflito em Modelos de Vesículas Pré-Bióticas ». Universidade de São Paulo, 2006. http://www.teses.usp.br/teses/disponiveis/76/76132/tde-05122006-154100/.
Texte intégralRésumé :
A crise primordial da informação genética tal como delineada pelo modelo de quasi-espécies tem permanecido há mais de três décadas como um desafio as teorias de origem da vida e evolução pré-biótica. A despeito das diversas soluções propostas ao longo desse período, não há ainda uma que seja plenamente aceita pela comunidade científica. Dentro dessa gama de soluções, os modelos que usam uma abordagem de seleção em múltiplos níveis destacam-se como uma alternativa ao paradigma da área, o celebrado modelo de hiperciclos. Denominados modelos de vesículas pré-bióticas, entre os quais destaca-se o corretor estocástico, estes assumem a cooperação, de forma mais ou menos explícita, como ingrediente essencial para vencer a crise da informação genética. A cooperação tem sido vista como capaz de proporcionar um modo de contornar a crise sucitada por Eigen ao permitir a divisão da informação essencial em diversas partes, todas abaixo do limiar da catastrofe de erro. Entretanto, até muito recentemente, havia pouca literatura especializada explorando esta classe de modelos, especialmente no que tange à questões de coexistência. O objetivo desta dissertação é estudar mais profundamente alguns modelos deste tipo dando ênfase a este tipo de problema. Inicialmente, vamos explorar um modelo determinístico de seleção de grupo similar ao corretor estocástico, baseado no famoso Wrights Island Model com algumas modificações. Em especial, relaxamos a necessidade de tempos de geração iguais nos dois níveis da dinãmica. Além deste, também vamos estudar uma versão menos restritiva do modelo de compartimentos original. Nos dois casos, a idéia geral é buscar as condições que garantam a coexistência dos diversos tipos de genes envolvidos.The primordial genetic information crisis as defined by the Eigens quasispecies model, which can be used as a paradigm here, has been a challenge to any theory about the origin of life and prebiotic evolution for more than three decades. Despite several tentative solutions proposed along this period, theres no consensual solution to the scientific community. Among that diversity of solutions, models that use a multilevel selection approach have been seen as an viable alternative to areas paradigm, the hypercycles model. Those called prebiotic vesicle models, whose principal example is the stochastic corrector model, assume cooperation, in a more or less explicit fashion, as an essencial ingredient to solve the genetic crisis. Cooperation has been seen as capable of providing means to bypass the genetic crisis by dividing the essential information into several pieces, each one bellow the error threshold. Until recently, no complete treatment for such a model could be found in the specialized literature, specially in relation to replicators coexistence questions. So, the main purpose of this dissertation is the throughly exploration of some of those models with emphasis in coexistence aspects. Initially, we will explore a deterministic group selection model based in the celebrated Wrights Island Model with some modifications. We relax some of the assumptions os the model to accommodate distinct time scales between the different levels of the model. Besides this model, we will study a less restrictive version of a compartment model. In both cases, we give special emphasis in the search of coexistence conditions that guarantee the survival of the different templates.
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Zissimos, Andreas M. « Structural studies of model compounds of salicylaldoxime metal extractants and their complexes, and of related metal complexes of dioxime systems ». Thesis, London Metropolitan University, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323383.
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