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1
Wachelke, Joao. "Structural relations among social representations: cognem association within a representational system." Doctoral thesis, Università degli studi di Padova, 2010. http://hdl.handle.net/11577/3427383.
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Theory and research results about the structure of social representations have been built usually from the study of isolated representations. The studies aiming at identifying structural relations involving two or more representations are more recent. In the literature, different terms have been employed to refer to inter-related social representation sets, managed or not by a superior ideological stance; in those cases, we refer to representation families, systems or networks. In this context, there are coordination relations, in which associations can be identified at the same level of a social thinking architecture. Traditionally, the studies of representations in conjunction – presenting element intersections at the level of their cores or object labels – have been privileged. The present research aims at contributing to the knowledge about disjoint representations. When, at an inter-representation level, there are two or more representation structures linked by relations between cognems or between object-label words, we propose the name of representational system to the macrostructure that is formed, with relations formalized by the basic cognitive schemes model. The main research aim was to identify relations among elements of different social representations, submitting to test the existence of connection points among representations at the same level of the social thinking architecture. It is a model that conceives inter-representation relations at the level of cognems. All the studies concerned the investigation of a representational system including the social representation on aging. Most of the studies were conducted with university undergraduate samples from Padua, Italy – and Studies 1-A and 1-B also had a Brazilian sample of undergraduates and an Italian sample of elderly people. The first studies had the purpose of characterizing the representation system. After a preliminary qualitative study conducted with interviews with people from different age groups, which has allowed to identify the cognems of the social representation on aging, Studies 1-A and 1-B were comparative investigations that characterized the structural status of the elements of that representation and also structural differences linked to age groups and cultural context. Study 2 was a survey marked by paired evaluations of proximity between objects linked to the aging theme which allowed the identification of three social representations highly connected to aging, by means prototypical and similarity analyses: death, health and family. Study 3 had a mixed nature, with characteristics of both a quasi-experiment and a survey. It provided the characterization of the structures of the chosen social representations in the system and also assessed the intensity of relations between social objects in that system. Additionally, participants evaluated pairs of elements of the representation on aging and the other representations and indicated if they perceived a connection or not, enabling the identification of possible connection points. After the identification of those possible relationships, the focus shifted to testing the plausibility of a model for connection points including a bridge relation between those elements. Study 4 consisted of context manipulations of emphasis or relativization of a peripheral element of the social representation on health that was connected to elements from the social representation on aging. It was observed that a context change relative to a peripheral element of a representation interferes on the activation of schemes relative to a second representation, regardless of their structural status; it is a first empirical evidence of the validity of a theoretical conception of coordination relations involving disjoint representations of a same system by means of connection points. Finally, Studies 5-A and 5-B aimed at verifying if denying or confirming the information of cognems from connection points would be associated with activation differences of semantic and evaluative relations (bridge relations) with elements connected to them, from the representation on aging. Differences were identified in the sense that compatibility with the content of the manipulated cognem was associated with higher valences of at least one of the hyperconnectors. As a conclusion, evidence was found of relations among social representations at the level of their elements, and the conception of a theoretical model of inter-representation connection points presented promising results. The model contributes to the understanding of mechanisms of association of social representations in disjunction and also opens possibilities for application especially concerning social representation dynamics, which might also take representation systems into account.Le teorie e i risultati di ricerca sulla struttura delle rappresentazioni sociali sono stati costruiti, in generale, a partire dallo studio di rappresentazioni isolate. Gli studi volti a identificare le relazioni strutturali che coinvolgono due o più rappresentazioni sono più recenti. In letteratura, termini diversi sono stati impiegati per riferirsi a insiemi interconnessi di rappresentazioni sociali, gestiti o non da un’istanza ideologica superiore; in questi casi, ci riferiamo a famiglie, sistemi o reti di rappresentazioni. In questo contesto, vi sono relazioni di coordinamento, in cui le associazioni possono essere identificate allo stesso livello dell’architettura del pensiero sociale. Tradizionalmente, sono stati privilegiati gli studi di rappresentazioni in congiunzione, che presentano intersezioni di elementi al livello dei loro nuclei o etichette di oggetto. La presente ricerca si propone di contribuire alla conoscenza di rappresentazioni disgiunte. Quando, a livello inter-rappresentazione, ci sono due o più strutture legate da relazioni tra cognemi o tra etichette di oggetti, proponiamo il nome di sistema rappresentazionale per la macrostruttura che ne risulta, con relazioni formalizzate dal modello di schemi cognitivi di base. L'obiettivo principale della ricerca è consistito nell’identificazione di relazioni tra elementi di rappresentazioni sociali diverse, sottoponendo a prova l'esistenza di punti di connessione tra rappresentazioni allo stesso livello dell’architettura del pensiero sociale. Si tratta di un modello che concepisce le relazioni interrappresentazione al livello dei cognemi. Tutti i cinque studi condotti hanno coinvolto un sistema di rappresentazioni, tenendo la rappresentazione sociale dell’invecchiamento come punto di riferimento. La maggior parte degli studi è stata svolta con campioni di convenienza di studenti universitari di Padova, Italia. Gli Studi 1-A e 1-B hanno avuto anche un campione brasiliano di studenti e un campione italiano di anziani. I primi studi avevano lo scopo di caratterizzare il sistema rappresentazionale. Dopo un’indagine preliminare qualitativa condotta con interviste a persone di diverse fasce di età, la quale ha permesso di identificare i cognemi della rappresentazione sociale sull’invecchiamento, gli Studi 1-A e 1-B sono stati realizzati tramite ricerche comparative che hanno caratterizzato lo statuto strutturale degli elementi di quella rappresentazione e anche delle differenze strutturali legate a gruppi di età e contesti culturali diversi. Lo Studio 2 è consistito in una ricerca caratterizzata da valutazioni appaiate di prossimità tra oggetti legati al tema dell'invecchiamento, la quale ha permesso l'identificazione di tre rappresentazioni sociali altamente connesse all'invecchiamento attraverso analisi prototipiche e di similitudine: morte, salute e famiglia. Lo Studio 3 ha avuto un carattere misto, con caratteristiche sia di quasi-esperimento sia di survey. Ha fornito la caratterizzazione delle strutture delle rappresentazioni sociali scelte dal sistema ed anche permesso di valutare l'intensità delle relazioni tra oggetti sociali in quel sistema. Inoltre, i partecipanti hanno valutato le coppie di elementi della rappresentazione sull’invecchiamento e sugli altri tre oggetti e hanno indicato se percepivano una relazione o meno tra di loro, permettendo l’individuazione di possibili punti di connessione. Dopo l'individuazione delle relazioni possibili, l'attenzione è stata rivolta a verificare la plausibilità di un modello di punti di connessione tra elementi con una relazione ponte. Lo Studio 4 è consistito nella manipolazione di un elemento periferico della rappresentazione sociale della salute (tramite sua enfasi o relativizzazione), collegata ad elementi della rappresentazione sociale dell’ invecchiamento. E' stato osservato che un cambiamento di contesto rispetto ad un elemento periferico di una rappresentazione interferisce sull’attivazione di schemi relativi ad una seconda rappresentazione del sistema, indipendentemente dal suo statuto strutturale. Si tratta di una prima evidenza empirica della validità di una concezione teorica che sottolinea le relazioni di coordinamento fra rappresentazioni disgiunte in uno stesso sistema per mezzo di punti di connessione. Infine, gli Studi 5-A e 5-B avevano lo scopo di verificare se il negare o confermare le informazioni di cognemi in punti di connessione fosse associato a differenze di attivazione di relazioni semantiche e valutative (relazioni ponte) con elementi ad essi connessi, della rappresentazione dell’invecchiamento. Sono state individuate delle differenze, nel senso che una compatibilità con il contenuto del cognema manipolato è stata associata con valenze più alte di almeno uno degli iperconnettori. In conclusione, si sono trovate evidenze empiriche riguardo relazioni tra rappresentazioni sociali a livello dei loro elementi, e ha trovato sostegno, con risultati promettenti, la concezione di un modello teorico di punti di connessione tra rappresentazioni. Il modello conntribuisce alla comprensione dei meccanismi di associazione di rappresentazioni sociali in disgiunzione e apre anche la possibilità di applicazioni soprattutto per quanto riguarda le dinamiche delle rappresentazioni sociali, attraverso interventi mirati sui sistemi di rappresentazione presi in esame.
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Alexander, Gutkin. "Towards formal structural representation of spoken language : an evolving transformation system (ETS) approach." Thesis, University of Edinburgh, 2006. http://hdl.handle.net/1842/3527.
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Speech recognition has been a very active area of research over the past twenty years. Despite an evident progress, it is generally agreed by the practitioners of the field that performance of the current speech recognition systems is rather suboptimal and new approaches are needed. The motivation behind the undertaken research is an observation that the notion of representation of objects and concepts that once was considered to be central in the early days of pattern recognition, has been largely marginalised by the advent of statistical approaches. As a consequence of a predominantly statistical approach to speech recognition problem, due to the numeric, feature vector-based, nature of representation, the classes inductively discovered from real data using decision-theoretic techniques have little meaning outside the statistical framework. This is because decision surfaces or probability distributions are difficult to analyse linguistically. Because of the later limitation it is doubtful that the gap between speech recognition and linguistic research can be bridged by the numeric representations. This thesis investigates an alternative, structural, approach to spoken language representation and categorisation. The approach pursued in this thesis is based on a consistent program, known as the Evolving Transformation System (ETS), motivated by the development and clarification of the concept of structural representation in pattern recognition and artificial intelligence from both theoretical and applied points of view. This thesis consists of two parts. In the first part of this thesis, a similarity-based approach to structural representation of speech is presented. First, a linguistically well-motivated structural representation of phones based on distinctive phonological features recovered from speech is proposed. The representation consists of string templates representing phones together with a similarity measure. The set of phonological templates together with a similarity measure defines a symbolic metric space. Representation and ETS-inspired categorisation in the symbolic metric spaces corresponding to the phonological structural representation are then investigated by constructing appropriate symbolic space classifiers and evaluating them on a standard corpus of read speech. In addition, similarity-based isometric transition from phonological symbolic metric spaces to the corresponding non-Euclidean vector spaces is investigated. Second part of this thesis deals with the formal approach to structural representation of spoken language. Unlike the approach adopted in the first part of this thesis, the representation developed in the second part is based on the mathematical language of the ETS formalism. This formalism has been specifically developed for structural modelling of dynamic processes. In particular, it allows the representation of both objects and classes in a uniform event-based hierarchical framework. In this thesis, the latter property of the formalism allows the adoption of a more physiologically-concreteapproach to structural representation. The proposed representation is based on gestural structures and encapsulates speech processes at the articulatory level. Algorithms for deriving the articulatory structures from the data are presented and evaluated.
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Ling, Suiyi. "Perceptual representations of structural and geometric information in images : bio-inspired and machine learning approaches : application to visual quality assessment of immersive media." Thesis, Nantes, 2018. http://www.theses.fr/2018NANT4061/document.
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Ce travail vise à mieux évaluer la qualité perceptuelle des images contenant des distorsions structurelles et géométriques notamment dans le contexte de médias immersifs. Nous proposons et explorons un cadre algorithmique hiérarchique de la perception visuelle. Inspiré par le système visuel humain, nous investiguons plusieurs niveaux de représentations des images : bas niveau (caractéristiques élémentaires comme les segments), niveau intermédiaire (motif complexe, encodage de contours), haut niveau (abstraction et reconnaissance des données visuelles). La première partie du manuscrit traite des représentations bas niveau pour la structure et texture. U n modèle basé filtre bilatéral est d’abord introduit pour qualifier les rôles respectifs de l’information texturale et structurelle dans diverses tâches d’évaluation (utilité, qualité. . . ). Une mesure de qualité d’image/vidéo est proposée pour quantifier les déformations de structure spatiales et temporelles perçues en utilisant une métrique dite élastique. La seconde partie du mémoire explore les représentations de niveaux intermédiaires. Un modèle basé « schetch token » et un autre basé sur codage d’un arbre de contexte sont présentés pour évaluer la qualité perçue. La troisième partie traite des représentations haut niveau. Deux approches d’apprentissage machine sont proposées pour apprendre ces représentations : une basée sur un technique de convolutional sparse coding, l’autre sur des réseaux profonds de type generative adversarial network. Au long du manuscrit, plusieurs expériences sont menées sur différentes bases de données pour plusieurs applications (FTV, visualisation multi-vues, images panoramiques 360. . . ) ainsi que des études utilisateursThis work aims to better evaluate the perceptual quality of image/video that contains structural and geometric related distortions in the context of immersive multimedia. We propose and explore a hierarchical framework of visual perception for image/video. Inspired by representation mechanism of the visual system, low-level (elementary visual features, e.g. edges), mid-level (intermediate visual patterns, e.g. codebook of edges), and higher-level (abstraction of visual input, e.g. category of distorted edges) image/video representations are investigated for quality assessment. The first part of this thesis addresses the low-level structure and texture related representations. A bilateral filter-based model is first introduced to qualify the respective role of structure and texture information in various assessment tasks (utility, quality . . . ). An image quality/video quality measure is proposed to quantify structure deformation spatially and temporally using new elastic metric. The second part explores mid-level structure related representations. A sketch-token based model and a context tree based model are presented in this part for the image and video quality evaluation. The third part explores higher-level structure related representations. Two machine learning approaches are proposed to learn higher-level representation: a convolutional sparse coding based and a generative adversarial network. Along the thesis, experiments an user studies have been conducted on different databases for different applications where special structure related distortions are observed (FTV, multi-view rendering, omni directional imaging . . . )
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Race, David Andrew. "Structural accounts of mathematical representation." Thesis, University of Leeds, 2014. http://etheses.whiterose.ac.uk/7123/.
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Attempts to solve the problems of the applicability of mathematics have gen- erally originated from the acceptance of a particular mathematical ontology. In this thesis I argue that a proper approach to solving these problems comes from an ‘application first’ approach. If one attempts to form the problems and answer them from a position that is agnostic towards mathematical ontology, the difficulties surrounding these problems fall away. I argue that there are nine problems that require answering, and that the problems of representation are the most interesting questions to answer. The applied metaphysical problem can be answered by structural relations, which are adopted as the starting point for accounts of representation. The majority of the thesis concerns arguing in favour of structural accounts of representation, in particular deciding between the Inferential Conception of the Applicability of Mathematics and Pincock’s Mapping Account. Through the case study of the rainbow, I argue that the Inferential Conception is the more viable account. It is capable of answering all of the problems of the applicability of mathematics, while the methodology adopted by Pincock trivialises the answer it can supply to the vital question of how the faithfulness and usefulness of representations are related.
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Tayar, Memduh Ali. "Design approaches to structural optimization." Thesis, Massachusetts Institute of Technology, 1986. http://hdl.handle.net/1721.1/78067.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Architecture, 1986.MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH.
Includes bibliographical references (leaves 84-86).
The objective of this thesis is to develop design approaches to structural optimization. In the example of three-dimensional grid structures, widely known as 'space frames', possible configurations are explored which maximize the load-bearing capacity of the system in relation to its weight. The study has been organized in two chapters: The first chapter starts with a brief review of structural concepts. Along with Gothic as a historical example to optimization, modem analytical methods to optimal structural design are presented which include Maxwell's Lemma, Michell's Fields and Ultimate Strength Analysis. In the second part of the thesis the design solutions are presented. The emphasis lies on a deployable space frame which is based on bar-joist like elements.
by Memduh Ali Tayar.
M.S.
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Herraiz, Cobo Jesús. "Mayotlide: synthetic approaches and structural elucidation." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462881.
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Mayotlide is a marine peptide isolated by PharmaMar S.A. from Spongia sp.. The sequence of the aminoacids were achieved by MS-MS spectrometry, where two of them were tryptophans. The NMR spectroscopy revealed the presence of N1-C3a bond between the tryptophans, which means that one of them was cyclized. On the first structure proposal, the aminoacids were forming two macrocyclic rings: on the ring B, all the aminoacids of molecule were tied by amide bond, remarking the presence of the cyclized tryptophan as a hexahydropyrroloindole unit (HPI). The ring A was established by three aminoacids of the ring B: one tryptophan, one isoleucine and the HPI, which became closed by the N1-C3a bond between the two tryptophans. The aminoacid analysis demonstrated the L configuration of all of them, just remaining the HPI with unknown stereochemistry.
Due to the configuration of the HPI system, there can be four diasteromers. To the best of our knowledge, there were not empirical evidences about which one could be more favorable. Hence, a computational study of the ring A through the MOE program was performed, evidencing that the rings A with the exo HPI adducts (L and D) were more stable than the endo ones. Among the exo ones, another computational study with the whole molecule revealed that the mayotlide with the exo-L adduct of the HPI was more stable.
Once that there was established a starting point with the HPI, it was necessary to find out a synthetic strategy that could fulfill the necessary requirements. A methodology developed by Baran and coworkers for the synthesis of the Trp-HPI fragment on molecules related to mayotlide was adapted to our proposal. On the first step of this strategy, under reaction conditions, the starting tryptophan cyclizes, providing exclusively the HPI with the exo configuration, at the same time that the N1-C3a bond between the HPI and 2-iodoaniline is formed. The 2-iodoaniline, along with a disubstituted alkyne, condense together yielding the upper tryptophan without loss of the former stereochemistry, reaching the Trp-HPI framework in two steps with high yields.
Taking advantage of this methodology and an appropriate use of the protecting groups in order to perform the corresponding cyclizations of the two macrocyclic rings, the mayotlide with the exo-L HPI was accomplished. Nevertheless, nor the NMR neither the MS-MS fragmentation pattern of the final compound coincided with the natural product ones. Thus, the next alternative would consist on repeating the synthesis but with the exo-D adduct of the HPI instead.
During the last synthesis, the bibliography and the analytical data of the natural product were extensively revised. There were no documented precedents of natural peptides with the Trp- HPI motif, and the initial structure did not justify the most important data extracted from the MS-MS spectrometry. the main fragmentation concerned to the isoleucine, and on the first proposal such aminoacid was not forming part of a conflictive scaffold. Likewise, among the eight proposed linear sequences for the ring B, the isoleucine just appear in one as C-terminus of the b-ions, when it is one of the aminoacids that forms part of both macrocycles.
The most related family of peptides to mayotlide are the kapakahines. Kapakahines, instead of having a Trp-HPI moiety as the central part of the molecule, exhibit a Trp-α carboline, with an
aminoacid establishing the bridge for a very tensioned tetracyclic system. Such structure may justify the isoleucine fragmentation pattern, but on the other hand the sequence of the aminoacids did not fix. It was necessary to invert the central sequence of the aminoacids to reach out a final structure proposal which justifies all the requirements, relabeled as “kapakahine H”.La mayotlida es un producto natural de origen marino aislado por PharmaMar. SA.. En la primera propuesta que se hizo, se elucidó como un péptido con dos anillos macrocíclicos: en el anillo B estaban contenidos todos los aminoácidos de la molécula, destacando la presencia de una unidad de HPI, que procede de la ciclación intramolecular del extremo amino de un triptófano con el C2 del anillo de indol. El anillo A está formado por tres aminoácidos del anillo B: un triptófano, una isoleucina y el HPI, quedando cerrado por la formación de un enlace entre el N1 del triptófano y el C3a del HPI. El análisis de aminoácidos demostró la configuración L de todos ellos, quedando desconocida la estereoquímica del HPI. El HPI posee tres estereocentros: los C3a y C8a, que siempre están en cis por la propia configuración del anillo y se pueden considerar como un conjunto, y el estereocentro del Cα. Por tanto, son cuatro el número total de diasterómeros posibles. El anillo A con las cuatro posibilidades de HPI fue estudiado energéticamente con el programa MOE, llegando a la conclusión que los aductos exo son más estables que los endo, y que el aducto exo-L es más estable que el exo-D. Para abordar la síntesis de la mayotlida exo-L se adaptó una metodología desarrollada por Phil Baran y colaboradores para moléculas con una estructura relacionada a la mayotlida. Tras conseguir la síntesis de la mayotlida con el aducto exo-L del HPI, se comprueba que los espectros de RMN y de MS-MS presentan grandes divergencias. Ante la incapacidad de interpretar las diferencias existentes entre el producto natural y la mayotlida exo-L, se tomó la decisión de abordar la síntesis de la mayotlida con el aducto exo-D del HPI. En el transcurso de la síntesis exo-D se revisó extensivamente la bibliografía y los datos analíticos relacionados con la mayotlida: no existían antecedentes de productos naturales peptídicos con estructura Trp-HPI, y la estructura no encajaba con los datos más transcendentales del MS-MS. La estructura fue revisada, llegando a la conclusión de que podía pertenecer a la familia de las kapakahines, con una estructura central Trp-α carbolina y con la secuencia central de los aminoácidos invertida, rebautizada como kapakahina H.
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Yu, Xun. "3D Face Recognition Based on Structural Representation." Thesis, Griffith University, 2017. http://hdl.handle.net/10072/365949.
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3D face recognition has gained favour in the scientific community and industry due to the rapid development and decreasing cost of 3D sensors, with various novel techniques for face recognition presented in recent years. In comparison to 2D face images, 3D face images contain more explicit information, which is very useful to manage pose and illumination problems. However, the field of 3D face recognition is yet to fully mature and become widely used in industrial or commercial communities, mainly because of high error in non-cooperative and uncontrolled scenarios—particularly in challenging conditions of occlusions and partial data. Further, many existing 3D face recognition techniques require a training stage in their approach, which can suffer dramatic performance drop or even fail to work if only one training sample per person is available to the system. Thus, the one training sample issue is an important factor hindering the performance of 3D face recognition systems. In this thesis, we propose several 3D face recognition approaches to address the above issues. In the first half of this thesis, we propose two low-level structural representations 3D polygonal line chains (3DPLC) and 3D directional vertices (3D2V) to encode and match 3D faces.Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Engineering
Science, Environment, Engineering and Technology
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Delli, Ponti Riccardo 1987. "Approaches to characterize structural properties of RNA." Doctoral thesis, Universitat Pompeu Fabra, 2019. http://hdl.handle.net/10803/665962.
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The secondary structure of an RNA molecule is fundamental for its function. However, structural conservation and the structure of RNA in vivo are still poorly understood. Data from recent high-throughput experiments can provide new insights, but they have not yet been systematically exploited. The aim of my doctoral studies was to exploit these experimental data to develop computational approaches for discovering and analyzing structural properties of RNA. I developed two algorithms: CROSS predicts the secondary structure propensity profile of an RNA, and CROSSalign discovers structural similarities among different RNAs. In addition, I studied the effect of the presence of protein binding motifs on the prediction of the RNA structure, in vivo and investigated how the propensity of RNAs to bind to proteins could be exploited to create a predictive tool. The suite of tools that I developed opens new possibilities for studying the structural properties of long RNA molecules and for investigating structural conservation in large-scale analyses.La estructura secundaria del ARN es fundamental para su función. Sin embargo, la conservación estructural y la estructura del ARN in vivo son poco conocidas. Los datos provenientes de experimentos de alto rendimiento pueden proporcionar nuevos conocimientos, pero aun no han sido usados sistemáticamente. El objetivo de mis estudios de doctorado fue emplear estos datos experimentales con el fin de desarrollar metodos computacionales para el descubrimiento y el analisis de las propiedades estructurales del ARN. Como resultado de mi tesis desarrollé dos algoritmos: CROSS, que predice el perfil de propensión de estructura secundaria de un ARN; y CROSSalign, que busca similitudes estructurales entre diferentes ARNs. Además, estudié el efecto de la presencia de dominios de unión protéinica en la predicción de la estructura del ARN in vivo; e investigué como la propensión de los ARNs a unirse a las proteínas podría usarse para crear un modelo predictivo. El conjunto de herramientas que desarrollé abre nuevas posibilidades para estudiar las propiedades estructurales de moléculas de ARN largas y para investigar la conservación estructural en análisis a gran escala.
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Giger, Mathias. "Representation concepts in evolutionary algorithm-based structural optimization /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=17017.
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De, Boyrie Maria Eugenia. "Out-of-sample exchange rate forecasting structural and non-structural nonlinear approaches." FIU Digital Commons, 1994. http://digitalcommons.fiu.edu/etd/2727.
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Forecasting foreign exchange rates is a perennial dilemma for exporters, importers, foreign exchange rate traders, and the business community as a whole. Foreign exchange rate models using popular linear and non-linear specifications do not produce particularly accurate forecasts. In point of fact, these models have not improved much upon the random walk model, especially in out-of-sample forecasting. Given these results, this dissertation constructs and evaluates new forecasting models to generate as accurate as possible out-of-sample forecasts of foreign exchange rates.
The information content of futures contracts on foreign exchange rates is investigated and used to forecast future exchange rates using alternative techniques, both structural (econometric) and non-structural (fuzzy) models. The results of two specifications of a structural model are compared against the well-known random walk model. The first specification assumes future exchange rates are determined by futures prices and a lagged structure of spot rates. The second specification assumes that future spot rates are a function of only a lagged structure of the futures prices.
The forecasting accuracy of the models is tested for both in-sample and out-of-sample periods; out-of-sample tests range from the short term to the long term (30- to 180-day forecasts). The results indicate that the random walk model remains a competitive alternative. In out-of-sample predictions, however, we can improve upon it in certain cases. The results also show that the predictive accuracy of the models is better in the short term (30 to 60 days) than in the longer term (180 days).
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Smith, Barbara S. "Uncertainty reasoning and representation: a comparison of several alternative approaches /." Online version of thesis, 1990. http://hdl.handle.net/1850/10580.
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Krolla, Bernd [Verfasser]. "Heterogeneous Reconstruction Approaches for Object and Scene Representation / Bernd Krolla." München : Verlag Dr. Hut, 2016. http://d-nb.info/1100967923/34.
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Giorgis, Stavros. "Evaluation of Approaches for Representation and Sentiment of Customer Reviews." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-291214.
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Classification of sentiment on customer reviews is a real-world application for many companies that offer text analytics and opinion extraction on customer reviews on different domains such as consumer electronics, hotels, restaurants, and car rental agencies. Natural Language Processing’s latest progress has seen the development of many new state-of-the-art approaches for representing the meaning of sentences, phrases, and words in the text using vector space models, so-called embeddings. In this thesis, we evaluated the most current and most popular text representation techniques against traditional methods as a baseline. The evaluation dataset consists of customer reviews from different domains with different lengths used by a text analysis company. Through a train dataset exploration, we evaluated which datasets were the most suitable for this specific task. Furthermore, we explored different techniques that could be used to alter a language model’s decisions without retraining it. Finally, all the methods were evaluated against their time performance and the resource requirements to present an overall experimental assessment that could potentially help the company decide which is the most appropriate technique to replace its system in a production environment.Klassificeringen av attityd och känsloläge i kundrecensioner är en tillämpning med praktiskt värde för flera företag i marknadsanalysbranschen. Aktuell forskning i språkteknologi har etablerat vektorrum som standardrepresentation för ord, fraser och yttranden, så kallade embeddings. Denna uppsats utvärderar den senaste tidens mest framgångsrika textrepresentationsmodeller jämfört med mer traditionella vektorrum. Utvärdering görs genom att jämföra automatiska analyser med mänskliga bedömningar för kundrecensioner av varierande längd från olika domäner tillhandahållna av ett textanalysföretag. Inom ramen för studien har olika testmängder jämförts och olika sätt att modifera en språkmodells klassficering utan om träning. Alla modeller har också jämförts med avseende på resurs- och tidsåtgång för träning för att hjälpa uppdragsgivaren fatta beslut om vilken teknik som utgör den mest ändamålsenliga utvecklingsvägen för dess driftsatta system.
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Miller, Shannon J. "Two Approaches to Clifford's Theorem." Youngstown State University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1619792031825711.
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BADAOUI, RAOUL. "APPROACHES FOR PARASITIC-INCLUSIVE SYMBOLIC CIRCUIT REPRESENTATION AND EXTRACTION FOR SYNTHESIS." University of Cincinnati / OhioLINK, 2005. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1132193275.
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Caravà, Marta <1989>. "The Problem of Representation between Extended and Enactive Approaches to Cognition." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amsdottorato.unibo.it/8545/1/carava%27_marta_tesi.pdf.
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Recent works in philosophy of mind and the cognitive sciences draw an “unconventional” picture of cognitive processes and of the mind. Instead of conceiving of cognition as a process that takes place within the boundaries of the skull and the skin, some contemporary theories claim that cognition is a situated process that encompasses the human agent’s boundaries. In particular, the Extended Mind Hypothesis (EMH) and the Enactive approach to cognition claim that embodied action is constitutive of cognitive processes, and thus of the mind.
Although both theories give an “extended” or “extensive” picture of cognition and of the mind, they disagree on the epistemic value of internal representations. The EMH claims that we need to posit internal action-oriented representations (AORs). AORs would account for action-selection, action-control, and for the prediction of incoming perceptual information.
The enactive approach to cognition argues against AORs. The concept of AOR does not fulfill the representational conditions necessary to talk about representations properly. Furthermore, AORs are expressive of an internalistic prejudice, which makes the EMH weak.
Moreover, a semiotic analysis of AORs shows that these epistemic posits are not active at all. Therefore, AORs play no interesting job in the project of “mind-extension” through action.
Therefore I claim that AORs have to be rejected. Action-control, action-selection, and the anticipation of aspects of action-perception loops can be explained in a more enactive way. Embodied action in a field of affordances explains how agents respond selectively to environmental features and how action-perception loops are anticipated by the “affective agent”.
Furthermore, the enactive approach to cognition - especially if coupled with a semiotic description of cognitive niches and with some insights from the affective sciences (e.g. appraisal of core relational themes) - gives an explanation of action that is actually able to “extend the mind”.
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Piermattéo, Anthony. "Représentations sociales, émotions et rapports intergroupes : l'approche structurale comme facteur d'enrichissements mutuels." Thesis, Aix-Marseille, 2013. http://www.theses.fr/2013AIXM3028.
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Dans le cadre de ce travail de thèse nous nous attachons à articuler l'approche structurale des représentations sociales avec les champs des émotions et des rapports intergroupes. Ce travail se compose ainsi de deux axes de recherche. Le premier axe (n = 340) s'intéresse à l'impact de l'infirmation ou de la confirmation de cognitions centrales ou périphériques sur les émotions dans l'optique d'éclairer le rôle que pourraient jouer ces dernières dans le cadre de la dynamique représentationnelle. Les deux recherches réalisées à cette occasion nous amènent à considérer que le système périphérique serait générateur d'émotions et que celles-ci se situeraient alors au cœur du processus conduisant les individus à réagir à une modification de leur environnement immédiat. Le second axe (n = 920) se focalise sur les liens entre l'approche structurale et les rapports intergroupes. Il témoigne de l'importance de la fonction identitaire des représentation sociales en indiquant que le fait de partager ou non un élément central d'une représentation sociale agirait sur la manière dont les individus s'auto-catégorisent et catégorisent autrui comme membre du groupe. Finalement, au travers de la prise en compte de l'approche structurale, ce travail souligne l'intérêt d'une articulation entre la théorie des représentations sociales et des champs d'étude généralement appréhendés indépendamment de cette dernièreWithin the framework of this PhD thesis we attempt to articulate the structural approach of social representations with the fields of emotions and intergroup relations. Thus, this work gets organized around two main lines of research. The first part (n = 340) focuses on the impact of the invalidation or the confirmation of central or peripheral cognitions on emotions with the goal of enlightening the role that the latter might play within the representational dynamic. Both research conducted in this occasion bring us to consider that the peripheral system would generates emotions that would lie at the heart of the process leading people to react to changes in their immediate environment. The second part (n = 920) focuses on the links between the structural approach and intergroup relations. It highlights the importance of the social identity function of social representations by indicating that fact of sharing (or not) a central element of a social representation would influence the way people self-categorize and categorize others as members of the group. Finally, through the consideration of the structural approach, this work emphasizes the interest of establishing connections between the social representation theory and other fields of study that are generally considered as independant
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Jackson, Stuart Andrew. "Representation grounding : investigating a connectionist procedural semantics for structural analogues." Thesis, University of Exeter, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332929.
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Davies, Z. "Application of representation theory to magnetic and structural phase transitions." Thesis, University College London (University of London), 2009. http://discovery.ucl.ac.uk/18908/.
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The tools of representation theory offer us a powerful insight in those terms in a system’s Hamiltonian which cause it to become ordered. Such is its power that, in many fields, the vocabulary of representations has become conventional; crystallography remains a notable exception. This thesis develops the existing methods for applying representation theory to symmetry lowering phase transitions in crystalline systems, and presents examples of its use. The opening section reviews the foundations and previous applications of representation theory to magnetic and structural phase transitions. Complimentary to the mathematical framework is a discussion of the physical interpretation of irreducible representations and basis vectors, the building blocks of any system model constructed in this way. Symmetry arguments are used to qualitatively discuss the symmetry breaking in ferroelectric materials and the role of phase factors in the loss of centro-symmetry. The body of this work is concerned with developing fast, reliable and repeatable methods for applying representation theory to displacive transitions. Calculation of a system’s basis vectors requires both a reliable method, and suitable starting resources. In this section, the first verifiable validation of the tables of Kovalev is presented, along with a strategy for determining the appropriate set of trial functions for use with the method of projection operators. Further, a new module in SARAh-Refine has been written which performs basis vector refinement of powder diffraction data to facilitate quantitative analysis using these techniques. Finally, the techniques of representation theory are applied to two experimental investigations: iron oxyborate and potassium selenate. The use of a single symmetry framework to discuss the structural, magnetic and charge-ordering transitions in these systems demonstrate the power of this technique. Representation theory provides a bridge between structure and properties; this work aims to strengthen the foundations of that bridge.
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Jubran, Rachel, Hannah White, Alyson Chroust, Alison Heck, and Ramesh S. Bhatt. "Experimental Evidence of Structural Representation of Hands in Early Infancy." Digital Commons @ East Tennessee State University, 2018. https://dc.etsu.edu/etsu-works/2731.
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Hands convey important social information, such as an individual’s emotions, goals, and desires, are used to direct attention through pointing, and are a major organ for haptic perception. However, very little is known about infants’ representation of human hands. In Experiment 1, infants tested in a familiarization/novelty preference task discriminated between images of intact hands and images that contained first-order structure distortions (i.e., with locations of fingers altered to result in an unnatural configuration). In Experiment 2, infants tested in a spontaneous preference task exhibited a preference for scrambled hand images over intact images, indicating that 3.5-month-olds have gained sufficient sensitivity to the configural properties of hands to discriminate between intact versus scrambled images without any training in the laboratory. In both procedures, infants’ performance was disrupted by the inversion of images, suggesting that infants’ performance in upright conditions was not based on low-level features. These results indicate that sensitivity to the structure of hands develops early in life. This may lay the foundation for the development of the functional use of hand information for social communication.
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NICOLINO, ENRICA. "Bayesian Analysis of AR Copula Models with Tree Structural Representation." Doctoral thesis, Università degli studi di Pavia, 2017. http://hdl.handle.net/11571/1203371.
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Källblad, Per. "G-protein-coupled receptors : statistical modelling and structural approaches." Thesis, University of Cambridge, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621096.
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Ma, Yanhang. "Structural study of nano-structured materials: electron crystallography approaches." Doctoral thesis, Stockholms universitet, Institutionen för material- och miljökemi (MMK), 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-129233.
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The structural analysis serves as a bridge to link the structure of materials to their properties. Revealing the structure details allows a better understanding on the growth mechanisms and properties of materials, and a further designed synthesis of functional materials. The widely used methods based on X-ray diffraction have certain limitations for the structural analysis when crystals are small, poorly crystallized or contain many defects. As electrons interact strongly with matter and can be focused by electromagnetic lenses to form an image, electron crystallography (EC) approaches become prime candidates for the structural analysis of a wide range of materials that cannot be done using X-rays, particularly nanomaterials with poor crystallinity. Three-dimensional electron diffraction tomography (3D EDT) is a recently developed method to automatically collect 3D electron diffraction data. By combining mechanical specimen tilt and electronic e-beam tilt, a large volume of reciprocal space can be swept at a fine step size to ensure the completeness and accuracy of the diffraction data with respect to both position and intensity. Effects of the dynamical scattering are enormously reduced as most of the patterns are collected at conditions off the zone axes. In this thesis, 3D EDT has been used for unit cell determination (COF-505), phase identifications and structure solutions (ZnO, Ba-Ta3N5, Zn-Sc, and V4O9), and the study of layer stacking faults (ETS-10 and SAPO-34 nanosheets). High-resolution transmission electron microscope (HRTEM) imaging shows its particular advantages over diffraction by allowing observations of crystal structure projections and the 3D potential map reconstruction. HRTEM imaging has been used to visualize fine structures of different materials (hierarchical zeolites, ETS-10, and SAPO-34). Reconstructed 3D potential maps have been used to locate the positions of metal ions in a woven framework (COF-505) and elucidate the pore shape and connectivity in a silica mesoporous crystal. The last part of this thesis explores the combination with X-ray crystallography to obtain more structure details.
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Kanagawa, Katie M. "Girl avengers : revising feminist approaches to sexuality, violence and power in representation /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2009. http://uclibs.org/PID/11984.
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Pan, Xiang. "Approaches for edge detection, pose determination and object representation in computer vision." Thesis, Heriot-Watt University, 1994. http://hdl.handle.net/10399/1378.
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PACCINI, MARTINA. "Novel Approaches to the Representation and Analysis of 3D Segmented Anatomical Districts." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1038601.
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Nowadays, image processing and 3D shape analysis are an integral part of clinical
practice and have the potentiality to support clinicians with advanced analysis
and visualization techniques. Both approaches provide visual and quantitative information
to medical practitioners, even if from different points of view. Indeed,
shape analysis is aimed at studying the morphology of anatomical structures, while
image processing is focused more on the tissue or functional information provided
by the pixels/voxels intensities levels. Despite the progress obtained by research in
both fields, a junction between these two complementary worlds is missing. When
working with 3D models analyzing shape features, the information of the volume
surrounding the structure is lost, since a segmentation process is needed to obtain
the 3D shape model; however, the 3D nature of the anatomical structure is represented
explicitly. With volume images, instead, the tissue information related to the
imaged volume is the core of the analysis, while the shape and morphology of the
structure are just implicitly represented, thus not clear enough.
The aim of this Thesis work is the integration of these two approaches in order to increase
the amount of information available for physicians, allowing a more accurate
analysis of each patient. An augmented visualization tool able to provide information
on both the anatomical structure shape and the surrounding volume through a
hybrid representation, could reduce the gap between the two approaches and provide
a more complete anatomical rendering of the subject.
To this end, given a segmented anatomical district, we propose a novel mapping of
volumetric data onto the segmented surface. The grey-levels of the image voxels are
mapped through a volume-surface correspondence map, which defines a grey-level
texture on the segmented surface. The resulting texture mapping is coherent to the
local morphology of the segmented anatomical structure and provides an enhanced
visual representation of the anatomical district. The integration of volume-based and
surface-based information in a unique 3D representation also supports the identification
and characterization of morphological landmarks and pathology evaluations.
The main research contributions of the Ph.D. activities and Thesis are:
• the development of a novel integration algorithm that combines surface-based
(segmented 3D anatomical structure meshes) and volume-based (MRI volumes)
information. The integration supports different criteria for the grey-levels mapping
onto the segmented surface;
• the development of methodological approaches for using the grey-levels mapping
together with morphological analysis. The final goal is to solve problems
in real clinical tasks, such as the identification of (patient-specific) ligament
insertion sites on bones from segmented MR images, the characterization of
the local morphology of bones/tissues, the early diagnosis, classification, and
monitoring of muscle-skeletal pathologies;
• the analysis of segmentation procedures, with a focus on the tissue classification
process, in order to reduce operator dependency and to overcome the
absence of a real gold standard for the evaluation of automatic segmentations;
• the evaluation and comparison of (unsupervised) segmentation methods, finalized
to define a novel segmentation method for low-field MR images, and for
the local correction/improvement of a given segmentation.
The proposed method is simple but effectively integrates information derived from
medical image analysis and 3D shape analysis. Moreover, the algorithm is general
enough to be applied to different anatomical districts independently of the segmentation
method, imaging techniques (such as CT), or image resolution. The volume
information can be integrated easily in different shape analysis applications, taking
into consideration not only the morphology of the input shape but also the real
context in which it is inserted, to solve clinical tasks. The results obtained by this
combined analysis have been evaluated through statistical analysis.
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Gay, Joanna. "Structural representation models for multi-modal image registration in biomedical applications." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-410820.
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In clinical applications it is often beneficial to use multiple imaging technologies to obtain information about different biomedical aspects of the subject under investigation, and to make best use of such sets of images they need to first be registered or aligned. Registration of multi-modal images is a challenging task and is currently the topic of much research, with new methods being published frequently. Structural representation models extract underlying features such as edges from images, distilling them into a common format that can be easily compared across different image modalities. This study compares the performance of two recent structural representation models on the task of aligning multi-modal biomedical images, specifically Second Harmonic Generation and Two Photon Excitation Fluorescence Microscopy images collected from skin samples. Performance is also evaluated on Brightfield Microscopy images. The two models evaluated here are PCANet-based Structural Representations (PSR, Zhu et al. (2018)) and Discriminative Local Derivative Patterns (dLDP, Jiang et al. (2017)). Mutual Information is used to provide a baseline for comparison. Although dLDP in particular gave promising results, worthy of further investigation, neither method outperformed the classic Mutual Information approach, as demonstrated in a series of experiments to register these particularly diverse modalities.
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Perelli, Alessandro <1985>. "Sparse Signal Representation of Ultrasonic Signals for Structural Health Monitoring Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6321/1/Perelli_Alessandro_tesi.pdf.
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Assessment of the integrity of structural components is of great importance for aerospace systems, land and marine transportation, civil infrastructures and other biological and mechanical applications. Guided waves (GWs) based inspections are an attractive mean for structural health monitoring. In this thesis, the study and development of techniques for GW ultrasound signal analysis and compression in the context of non-destructive testing of structures will be presented. In guided wave inspections, it is necessary to address the problem of the dispersion compensation. A signal processing approach based on frequency warping was adopted. Such operator maps the frequencies axis through a function derived by the group velocity of the test material and it is used to remove the dependence on the travelled distance from the acquired signals. Such processing strategy was fruitfully applied for impact location and damage localization tasks in composite and aluminum panels. It has been shown that, basing on this processing tool, low power embedded system for GW structural monitoring can be implemented. Finally, a new procedure based on Compressive Sensing has been developed and applied for data reduction. Such procedure has also a beneficial effect in enhancing the accuracy of structural defects localization. This algorithm uses the convolutive model of the propagation of ultrasonic guided waves which takes advantage of a sparse signal representation in the warped frequency domain. The recovery from the compressed samples is based on an alternating minimization procedure which achieves both an accurate reconstruction of the ultrasonic signal and a precise estimation of waves time of flight. Such information is used to feed hyperbolic or elliptic localization procedures, for accurate impact or damage localization.
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Perelli, Alessandro <1985>. "Sparse Signal Representation of Ultrasonic Signals for Structural Health Monitoring Applications." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2014. http://amsdottorato.unibo.it/6321/.
Full textAbstract:
Assessment of the integrity of structural components is of great importance for aerospace systems, land and marine transportation, civil infrastructures and other biological and mechanical applications. Guided waves (GWs) based inspections are an attractive mean for structural health monitoring. In this thesis, the study and development of techniques for GW ultrasound signal analysis and compression in the context of non-destructive testing of structures will be presented. In guided wave inspections, it is necessary to address the problem of the dispersion compensation. A signal processing approach based on frequency warping was adopted. Such operator maps the frequencies axis through a function derived by the group velocity of the test material and it is used to remove the dependence on the travelled distance from the acquired signals. Such processing strategy was fruitfully applied for impact location and damage localization tasks in composite and aluminum panels. It has been shown that, basing on this processing tool, low power embedded system for GW structural monitoring can be implemented. Finally, a new procedure based on Compressive Sensing has been developed and applied for data reduction. Such procedure has also a beneficial effect in enhancing the accuracy of structural defects localization. This algorithm uses the convolutive model of the propagation of ultrasonic guided waves which takes advantage of a sparse signal representation in the warped frequency domain. The recovery from the compressed samples is based on an alternating minimization procedure which achieves both an accurate reconstruction of the ultrasonic signal and a precise estimation of waves time of flight. Such information is used to feed hyperbolic or elliptic localization procedures, for accurate impact or damage localization.
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Chaulk, Steven George. "New chemical approaches for the investigation of RNA structural dynamics." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp05/NQ63597.pdf.
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Stamatelou, Ismini Christina. "Clustering approaches for extracting structural determinants of enzyme active sites." Thesis, Uppsala universitet, Institutionen för biologisk grundutbildning, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-426221.
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The study of enzyme binding sites is an essential but rather demanding process of increased complexity since the amino acids lining these areas are not rigid. At the same time, the minimization of side effects and the specificity of new ligands is a great challenge in the structure-based drug design approach. Using glycogen phosphorylase - a validated target for the development of new antidiabetic agents - as a case study, this project focuses on the examination of side-chain conformations of amino acids that play a key role in the catalytic site of the enzyme. Specifically, different rotamers of each amino acid were collected to build a dataset of different conformations of the catalytic site. The rotamers were filtered by their probability of occurrence and subsequently, all rotamers that create steric clashes were rejected. Then, these conformations were clustered based on their similarity. Three different clustering algorithms and multiple numbers of clusters were tested using the silhouette scores evaluation for the clustering process. In order to measure the similarity, the Euclidean metric was used which due to the correspondence of the coordinates between the conformations was very similar to the cRMSD metric. Two-level clustering was applied to the dataset for more in-depth observations. According to the clustering results, specific aminoacids with major geometrical variations in their rotamers play the most important role in the separation of the clusters. Additionally, all rotamers of an amino acid can be grouped based on their structure, something that was confirmed using “Chimera” software as a visualization tool. To this end, the ultimate aim of this study is to examine whether the clustering of conformations produces clusters with points geometrically similar to each other, in order to identify near neighbors, i.e. conformations that are quite similar in structure but do not play a determinant role in the function and those that are quite diverse and could be further exploited.
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Barthorpe, Robert James. "On model- and data-based approaches to structural health monitoring." Thesis, University of Sheffield, 2010. http://etheses.whiterose.ac.uk/1175/.
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Structural Heath Monitoring (SHM) is the term applied to the process of periodically monitoring the state of a structural system with the aim of diagnosing damage in the structure. Over the course of the past several decades there has been ongoing interest in approaches to the problem of SHM. This attention has been sustained by the belief that SHM will allow substantial economic and life-safety benefits to be realised across a wide range of applications. Several numerical and laboratory implementations have been successfully demonstrated. However, despite this research effort, real-world applications of SHM as originally envisaged are somewhat rare. Numerous technical barriers to the broader application of SHM methods have been identified, namely: severe restrictions on the availability of damaged-state data in real-world scenarios; difficulties associated with the numerical modelling of physical systems; and limited understanding of the physical effect of system inputs (including environmental and operational loads). This thesis focuses on the roles of law-based and data-based modelling in current applications of. First, established approaches to model-based SHM are introduced, with the aid of an exemplar ‘wingbox' structure. The study highlights the degree of difficulty associated with applying model-updating-based methods and with producing numerical models capable of accurately predicting changes in structural response due to damage. These difficulties motivate the investigation of non-deterministic, predictive modelling of structural responses taking into account both experimental and modelling uncertainties. Secondly, a data-based approach to multiple-site damage location is introduced, which may allow the quantity of experimental data required for classifier training to be drastically reduced. A conclusion of the above research is the identification of hybrid approaches, in which a forward-mode law-based model informs a data-based damage identification scheme, as an area for future work
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Zanardo, Gabriele. "Structural Modification Approaches to Modal Design Optimisation of Vibrating Systems." Doctoral thesis, Università degli studi di Padova, 2011. http://hdl.handle.net/11577/3427526.
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This dissertation addresses the problem of assigning the desired dynamic behaviour to vibrating systems, with particular attention on the generality of the approaches proposed. The main focus of this work is in developing structural modification approaches ensuring the feasibility and the optimality of the computed solution. The proposed approaches are suitable for both the design of new mechanical systems, and the performance optimisation of existing ones. Three formulations are proposed: in the first, the original system is modelled by means of mass and stiffness matrices, while in the second the Frequency Response Functions of the original system are employed. The final formulation allows for discrete structural modification, by casting the structural modification problem as a mixed-integer non-linear optimisation problem.
Compared with most of the approaches appearing in literature, one of the strengths of the approaches proposed is the capability to handle different design tasks. Also, the proposed approaches allow the modification of an arbitrary number of parameters (even in the presence of linear interrelated modifications) and of assigned vibration modes (regardless of their magnitude), as well as the possibility of dealing with mass and stiffness matrices with an arbitrary topology. To this purpose, the structural modification problem is formulated as a constrained inverse eigenvalue problem. The problem is constrained in the sense that a wide family of parameter constraints can be included in the formulations adopted in order to incorporate the physical constraints to the system modifications. Moreover, a regularization term biases the solution towards preferable modifications and assures good numerical conditioning. The problem is then solved within the frame of constrained convex optimisation, which ensures that a unique, and hence global, optimal and feasible solution exists and that it can be efficiently computed by means of reliable numerical algorithms.
The effectiveness and the capabilities of the proposed approaches are demonstrated by firstly applying it to theoretical test cases and secondly through experiments on industrial and laboratory test cases. Such test cases involve lumped and distributed parameter modifications, as well as multimode and single mode assignments.In questa Tesi si affronta il problema di assegnare il comportamento dinamico desiderato a sistemi vibranti, e si dedica particolare attenzione alla generalità degli approcci proposti. Questo lavoro si concentra sullo sviluppo di approcci per il calcolo di modifiche strutturali che siano in grado di assicurare la realizzabilità fisica e l’ottimalità della soluzione calcolata. Gli approcci proposti sono adatti sia al progetto di nuovi sistemi meccanici, sia all’ottimizzazione delle performance di quelli esistenti. Vengono proposte tre formulazioni: nella prima il sistema originale é modellato per mezzo di matrici di massa e rigidezza, mentre nella seconda vengono impiegate le funzioni di risposta in frequenza (Frequency Response Functions). La terza formulazione prende in considerazione modifiche strutturali discrete, in quanto il problema delle modifiche strutturali viene formulato come un problema di ottimizzazione non-lineare mista-intera. In confronto agli approcci presenti in letteratura, uno dei punti di forza degli approcci proposti risiede nella capacità di poter affrontare obiettivi di progetto diversificati tra loro. Degna di nota é la modifica di un numero arbitrario di parametri (anche in presenza di modifiche tra loro linearmente correlate) e di modi di vibrare (a prescindere dalla loro normalizzazione), cosi pure la possibilità di trattare matrici di massa e rigidezza con topologia arbitraria. A tale fine, il problema di modifica strutturale viene formulato come un problema agli autovalori inverso vincolato. Il problema é vincolato nel senso che una ampia famiglia di vincoli sui parametri può essere introdotta nelle formulazioni adottate, per includere nel problema i vincoli fisici sulle modifiche del sistema. Inoltre, un termine di regolarizzazione permette di dirigere la soluzione verso modifiche preferenziali, ed assicura un buon condizionamento numerico. Il problema è risolto all’interno del contesto matematico dell’ottimizzazione convessa vincolata, che assicura l’esistenza di un’unica, e quindi globale, soluzione ottima realizzabile, e che tale soluzione sia calcolabile efficacemente per mezzo di algoritmi numerici consolidati ed affidabili. L’efficacia degli approcci proposti, e la loro capacità di fornire soluzioni realizzabili è stata dapprima dimostrata applicandoli dapprima su esempi teorici, e successivamente su test case industriali e da laboratorio. Tali test case includono sia modifiche di parametri concentrati che parametri distribuiti, così come l’assegnazione di uno o più modi di vibrare.
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Eidheim, Ole Christian. "New Approaches for Representation and Segmentation of Organs in CT and MR Scans." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for datateknikk og informasjonsvitenskap, 2009. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11209.
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Analysis of medical images is resource demanding and time-consuming, and automatic procedures are needed to reduce the workload of medical staff in a pre-operative planning phase. In this thesis, the main focus has been on methods that automatically segment CT and MR volume data, in particular new approaches for representation and segmentation of the liver, hepatic vessels and the kidney. The two main contributions in this thesis are a new 3D skeleton procedure and a texture-based segmentation method. The skeleton procedure is iterative, without user-defined parameters, and produces a minimalistic representation of binary objects without known artifacts. Compared to previous work, this skeleton method produces more reliable results and does not need tuning for each individual representation task. The new texture-based segmentation algorithm is used to segment the selected organs, where only a few parameters influence the end result. Moreover, the parameters of this method are relatively easy to set, and a wide parameter range yields acceptable results. This method is more robust than popular previously published procedures that are typically based on edge information. Additionally, there are two minor contributions in this thesis. A new general representation of binary objects with an interior is presented. This representation is used to automatically derive the parameters of the texturebased segmentation method based on a statistical template. Furthermore, parallel processing on modern graphics cards and multiple CPU processors have been studied and compared to serial algorithms. A significant decrease in runtime was shown on many common image processing techniques in addition to the proposed texture-based segmentation algorithm. Even though the results are promising, more research is needed before reliable analysis of medical volume data can be performed. In particular, a combination of the proposed techniques incorporated with shape-based and statistical models is suggested for future research. The contributions in this thesis, however, are noticeable and represent a step forward in deriving complete automatic procedures for segmentation of medical volume data.
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Wong, Yuet-wai, and 王悦惠. "Questioning identities: structuralist and deconstruction approaches to the representation of race in threenovels." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1999. http://hub.hku.hk/bib/B31952483.
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Larsen, Jeffrey James. "Continuum structural representation of flexure and tension stiffened one-dimensional spacecraft architectures." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/larsen/LarsenJ0509.pdf.
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Spacecraft designs are a result of system properties and design variables that ensure the spacecraft will operate to mission objectives. The focus of this effort is a set of global system variables for frequency, length, total mass and the ratio between the payload mass and the support structure mass. These properties will be explored to observe the behavior of the system and develop relationships that govern the trade-offs between the variables and assist mission planners in future spacecraft design. These variables will be observed in one-dimensional structures where the dominating dimension is many times larger than the other two dimensions and the system is comprised of a support and a payload member. To observe the interaction between the payload and the support, the system was varied for different system variables and observed through ABAQUS finite element software. Attempts were made to predict the system frequency through mathematical approaches. The finite element work was able to generate several approximate relationships between the system variables and the fundamental natural frequency of the system. From these relationships an approximate equation was developed for the frequency for a fixed mass ratio and load ratio as a function of the length, bending stiffness, and total mass of the system. Additional work into the changes to the system as the number of connect points is increased shows the system converging towards a frequency solution which results in a minimized dependence on the connection points. These results were then compared to those of several derived analytical models to determine if a closed-form solution could be used to predict system behavior over the same range of structural characteristics. This closed form solution proved to correlate well to analytical predictions only for the case where the support structure dominates the total system mass, and thus the structural system performs like a beam under compression. Further work is necessary to accurately predict the system frequency through an analytical approach. These insights promise to aid mission designers in objectively evaluating new structural architectures based on structural performance rather than on an unbalanced adherence to heritage or in some cases personal preference.
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Cervera, Eva. "Evolutionary structural optimisation based on boundary element representation of B-spline geometry." Thesis, Durham University, 2003. http://etheses.dur.ac.uk/2004/.
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Evolutionary Structural Optimisation (ESO) has become a well-established technique for determining the optimum shape and topology of a structure given a set of loads and constraints. The basic ESO concept that the optimum topology design evolves by slow removal and addition of material has matured over the last ten years. Nevertheless, the development of the method has almost exclusively considered finite elements (FE) as the approach for providing stress solutions. This thesis presents an ESO approach based on the boundary element method. Non-uniform rational B-splines (NURBS) are used to define the geometry of the component and, since the shape of these splines is governed by a set of control points, use can be made of the locations of these control points as design variables. The developed algorithm creates internal cavities to accomplish topology changes. Cavities are also described by NURBS and so they have similar behaviour to the outside boundary. Therefore, both outside and inside are optimised at the same time. The optimum topologies evolve allowing cavities to merge between each other and to their closest outer boundary. Two-dimensional structural optimisation is investigated in detail exploring multi-load case and multi-criteria optimisation. The algorithm is also extended to three-dimensional optimisation, in which promising preliminary results are obtained. It is shown that this approach overcomes some of the drawbacks inherent in traditional FE-based approaches, and naturally provides accurate stress solutions on smooth boundary representations at each iteration.
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Mcculloch, Jenna Elaine. "Women's Political Representation in Europe: An Analysis of Structural and Attitudinal Factors." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4153.
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In this mixed methods study, I explore the reasons for the low level of women in elected office in Europe. I analyze the impact of three structural factors (number of years since women's suffrage was enacted, type of electoral system, and presence of legal gender quotas) and three attitudinal factors (level of gender equality, percentage of female professionals, and level of religiosity) on the percentage of women in national legislatures in each of the European countries. Specifically, I pose the following research question: Which structural and/or attitudinal factors are more influential for women's political representation in European countries?
In order to answer this question, I begin by performing ordinary least squares (OLS) regression analyses of the variables. My Europe-wide and Western Europe regression results indicate that there is a statistically significant positive relationship between the favorability of a country's electoral system to the election of women and the level of women's political representation in that country. Proportional representation electoral systems are particularly beneficial to female candidates. In addition, unlike previous scholars who focus on the dominant religion, I apply the concept of religiosity (the importance of religion to a country's citizens) to women's political representation. I find a statistically significant negative relationship between the level of religiosity in a country and the level of women's political representation in that country. Countries in which citizens are particularly religious tend to be conservative and less likely to encourage the election of women. However, none of the variables are statistically significant in the regression analysis of Eastern Europe, which indicates the need to take regional factors into consideration.
In the second part of the study, I examine four case studies (Sweden, Ireland, Hungary, and Macedonia). The case studies permit in-depth analyses of the individual countries, and show the manner in which structural and attitudinal factors interact in a particular country context. In the case of Macedonia, structural factors have mitigated the effects of negative attitudinal factors. In most of the case studies, however, a combination of structural (electoral system and gender quotas) and attitudinal factors (gender equality and religiosity) affect the level of women's political representation in the country. Ultimately, the case studies demonstrate how the country-specific context impacts the election of women to parliament.
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Illingworth, C. J. R. "Structural and electrostatic flexibility in proteins:-computational approaches to ligand binding." Thesis, University of Essex, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486625.
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A significant proportion of our understanding of protein-ligand interactions comes about through static pictures, generated through X-ray crystallography. However, in vivo, such interactions occur in a dynamic environment, characterised by flexibility in both the physical , structure, and the electrostatic properties of the molecules involved. Here we assess the importance of such flexibility in the process ofligand binding. Firstly, examining flexibility in ligand confonnation, we apply an algorithmic approach to a representative sample of proteases, and demonstrate that proteases selectively bind ligands in an extended confonnation. Secondly, through the development of a measure ofthe spatial flexibility of residues in a protein structure, we produce a means of predicting the location of ligand binding sites, and, appiying this to the structure of rhodopsin, generate a result that is consistent with recent experimental work on the binding of chlorine to a novel binding site. Finally, we t~rn to a substantial investigation ofthe importance of flexibility in the electronic distribution of a molecule, examining this through a method of modelling molecular mechanics polarisation through atom-centred point charges.
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Baghalian, Amin. "Detecting Structural Defects Using Novel Smart Sensory and Sensor-less Approaches." FIU Digital Commons, 2017. https://digitalcommons.fiu.edu/etd/3560.
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Monitoring the mechanical integrity of critical structures is extremely important, as mechanical defects can potentially have adverse impacts on their safe operability throughout their service life. Structural defects can be detected by using active structural health monitoring (SHM) approaches, in which a given structure is excited with harmonic mechanical waves generated by actuators. The response of the structure is then collected using sensor(s) and is analyzed for possible defects, with various active SHM approaches available for analyzing the response of a structure to single- or multi-frequency harmonic excitations. In order to identify the appropriate excitation frequency, however, the majority of such methods require a priori knowledge of the characteristics of the defects under consideration. This makes the whole enterprise of detecting structural defects logically circular, as there is usually limited a priori information about the characteristics and the locations of defects that are yet to be detected. Furthermore, the majority of SHM techniques rely on sensors for response collection, with the very same sensors also prone to structural damage. The Surface Response to Excitation (SuRE) method is a broadband frequency method that has high sensitivity to different types of defects, but it requires a baseline. In this study, initially, theoretical justification was provided for the validity of the SuRE method and it was implemented for detection of internal and external defects in pipes. Then, the Comprehensive Heterodyne Effect Based Inspection (CHEBI) method was developed based on the SuRE method to eliminate the need for any baseline. Unlike traditional approaches, the CHEBI method requires no a priori knowledge of defect characteristics for the selection of the excitation frequency. In addition, the proposed heterodyne effect-based approach constitutes the very first sensor-less smart monitoring technique, in which the emergence of mechanical defect(s) triggers an audible alarm in the structure with the defect. Finally, a novel compact phased array (CPA) method was developed for locating defects using only three transducers. The CPA approach provides an image of most probable defected areas in the structure in three steps. The techniques developed in this study were used to detect and/or locate different types of mechanical damages in structures with various geometries.
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Wong, Yuet-wai. "Questioning identities : structuralist and deconstruction approaches to the representation of race in three novels /." Hong Kong : University of Hong Kong, 1999. http://sunzi.lib.hku.hk/hkuto/record.jsp?B21161677.
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Mostefaï-Ithier, Amel. "Contribution à l'étude de l'art rupestre tassilien : à la recherche d'un sens à Ozan Ehéré (Tasîli-n-Ajjer, sahara central, Algérie)." Thesis, Toulouse 2, 2014. http://www.theses.fr/2014TOU20035/document.
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En se basant sur le profil des figurations humaines et sur quelques présupposés particulièrement tenaces sur un monde des masques et un animisme considérés comme proprement noir-africains, nombre des auteurs ayant traité des images rupestres du Sahara central ont confondu «culture» et «identité raciale», canons artistiques et types anthropologiques, s'appliquant à écrire une Histoire culturelle hachée que rien ne justifie a priori. Ainsi, à Ozan Ehéré, de remarquables cas de rapports explicites illustrés par des scènes montrant un anthropomorphe touchant un zoomorphe invitent à suggérer un parallèle entre des figurations en style des Têtes Rondes et des images bovidiennes (styles de Séfar - Ozan Ehéré, d’Abañher, d’Iheren), alors que ces groupes sont généralement tenus pour indépendants l’un de l’autre et cloisonnés par souci typologique. Une première approche structurale de l’art rupestre de la zone permet aussi d’ouvrir quelques pistes stimulantes quant à la nature des êtres représentés sur les parois (qui ne sont peut-être pas des humains et des animaux ordinaires vaquant à quelque occupation banale), et conduit à s’interroger sur la fonction de ces images. À la lumière de leur possible dimension féminine, quelques peintures en style des Têtes Rondes pourraient sortir du dossier des représentations énigmatiques et l’on pourrait également — sans recours à des lectures littérales — faire quelque peu quitter aux images bovidiennes le monde de la peinture décorative et celui de la chronique historiéeConsidering the face of human representations and evoking particularly firm presuppositions on a world of masks and animism considered as strictly black - African, number of the authors who studied the rupestral images of central Sahara mixed up "culture" and " racial identity ", artistic canons and anthropological kind, establishing a chopped cultural History, which is not argued. In Ozan Ehéré, remarkable cases of relationships illustrated by scenes showing an anthropomorphic touching a zoomorphic invite to suggest a parallel between representations in style of the Round Heads and the bovidians images (styles of Séfar - Ozan Ehéré, of Abañher, Iheren), while these groups are considered generally independent one of the other one and divided up by typological concern. A first structural approach of the rock art of the zone finally allows us to open stimulating ways, for example about the nature of beings represented on walls (who may not be human beings and ordinary animals attending to some commonplace occupation), and drives us to wonder about the function of these images. According to their possible feminine dimension, some Round Heads paintings could be taken out from the file of enigmatic representations. We could also get bovidians images out from the world of ornamental paintings, or of the chronicle - without appeal to literal readings
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Peri, C. "INVESTIGATING AND PREDICTING THE DETERMINANTS OF PROTEIN-PROTEIN INTERACTIONS THROUGH COMPUTATIONAL-STRUCTURAL BIOLOGY APPROACHES: IMPLICATIONS FOR STRUCTURAL VACCINOLOGY." Doctoral thesis, Università degli Studi di Milano, 2014. http://hdl.handle.net/2434/243392.
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Clarifying the physico-chemical principles of protein-protein interactions is critically important to understand the relationships between biological structures and functions in all biochemical mechanisms. In this project we aim to develop, validate and apply new computational-theoretical methods to study and predict the binding regions of proteins starting from 3D structural information and from the analysis of the conformational and physico-chemical properties of the constituting amino acids. In particular, this project entails the integrated analysis of the energetic properties of different datasets of proteins solved at high resolution. In this context, we have focused on four main subjects with different, yet highly intertwined, objectives. The first subject will address the application of an energy-based computational predictor for the identification of possible antibody-binding surfaces (epitopes) of protein antigens from the pathogen Burkholderia pseudomallei, responsible for human melioidosis. The second will focus on the expansion of the same rationale, adapting the method towards different applications, and including as a novel functionality the prediction of MHC-II coupled epitopes to elicit the intervention of T helper cells. The third objective concerns the design and characterization of peptides and peptidomimetics to optimize the properties of the identified epitopes as better vaccine candidates. The fourth one will pursue the investigation of the energetic determinants of interacting proteins in a more general context (not limited to immunogenic epitopes), aiming at the identification of an energy-based property describing the interaction event at the atomistic level of resolution. This part of the project is aimed at the development of a computational tool based on such property to help improve the understanding of the determinants of protein interactions and help predict their binding interfaces and orientation. All four subjects have been investigated in the broad spectrum of activities of an academic consortium, devoted to the identification of antigens from B. pseudomallei showing sufficient immunogenic potential to be considered as components for a vaccine against the pathogen. The computational methods developed and tested within this framework have theoretical as well as practical implications, from the physico-chemical study and characterization of protein-protein interactions, to the design of biologically active molecules.
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Hodigere, Renuka. "¿Structural analysis of the under-representation of women on boards of public corporations." Case Western Reserve University School of Graduate Studies / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=case1388408832.
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Herranz-Trillo, Fatima. "Disentangling structural complexity in proteins by decomposing SAXS data with chemometric approaches." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT044/document.
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De nombreux systèmes biologiques sont intrinsèquement polydispersés, présentant de multiples espèces coexistantes, de taille, de forme ou de conformation différentes (c'est-à-dire, mélanges oligomèriques, des complexes faiblement liés se dissociant en composantes individuelles ou des espèces apparaissant lors de processus amyloïdogéniques). L'étude de tels systèmes complexes est une tâche difficile en raison de l'instabilité des espèces concernées, de leurs concentrations relatives faibles et interdépendantes et des difficultés rencontrées pour l'isolation des composantes pures. Dans cette thèse, j'ai développé des approches méthodologiques pour appliquer la diffusion des rayons X aux petits angles (SAXS), une technique de biologie structurale, à l'étude de systèmes polydispersés. SAXS est une technique additive et par conséquent, le diagramme de diffusion mesuré pour un échantillon polydispersé correspond à la somme pondérée en concentration des contributions de chacune des composantes individuelles du mélange. Cependant, la décomposition des données de SAXS en des spectres spécifiques des espèces et de leurs concentrations relatives est extrêmement laborieuse et ambigue. Dans cette thèse, je présente d'abord une approche objective pour solidement décomposer les jeux de données de SAXS en composantes individuelles. Cette approche adapte la méthode chimiométrique « Multivariable Curve Resolution Alternate Least Squares » (MCR-ALS) aux spécificités des données de SAXS. Notre méthode permet une décomposition rigoureuse et robuste des données de SAXS en introduisant simultanément différentes représentations de ces données et par conséquent, en mettant l'accent sur des changements moléculaires à différentes plages de temps et de résolution structurale. Nous avons appliqué cette approche, que nous appelons COSMiCS (Analyse structurelle objective complexe des systèmes multi-composants) pour étudier deux systèmes polydispersés: la fibrillation des protéines, et les fluctuations conformationnelles de protéines grâce à l'analyse de données obtenues à l'aide d’une technique de couplage de chromatographie d'exclusion de taille (SEC) avec le ligne de SAXS (SEC-SAXS). L'importance d'étudier les processus de fibrillation réside dans leur implication dans des pathologies amyloïdogéniques telles que les maladies de Parkinson ou d'Alzheimer. Il existe de fortes indications que les espèces oligomériques solubles, et non les fibrilles matures, sont la cause principale de la cytotoxicité et des dommages neuronaux. Cette observation souligne l'importance de caractériser les premiers stades des processus de fibrillation. Notre approche COSMiCS a permis d'étudier les processus amyloïdogéniques de l'insuline et du mutant familial E46K de l'α-synucléine, une protéine associée à la maladie de Parkinson. Cette analyse permet la caractérisation structurale des espèces présentes (y compris les espèces oligomériques) et la caractérisation cinétique de leurs transformations.La deuxième partie de la thèse est consacrée à l'utilisation de COSMiCS pour analyser des données de SEC-SAXS. Le SEC-SAXS est extrêmement populaire et a été implémenté sur plusieurs lignes de SAXS à travers le monde. En utilisant des données synthétiques, je démontre la capacité des approches chimiométriques à décomposer des profils chromatographiques complexes. À l'aide de cette approche, j'ai décomposé l’ensemble des données SEC-SAXS mesurés pour la Prolyl OligoPeptidase (POP).En résumé, cette thèse présente une nouvelle approche chimiométrique qui peut être généralement appliquée à tout mélange macromoléculaire pouvant subir une modifacation de son équilibre et pouvant être abordé par SAXS. Les complexes biomoleculaires transitoires, les processus de repliement, les réarrangements structuraux dépendants d’un ligand ou la formation de grands ensembles supramoleculaires peuvent être sondés de façon structurale en utilisant l'approche COSMiCSMany biological systems are inherently polydisperse, presenting multiple coexisting species differing in size, shape or conformation (i.e. oligomeric mixtures, weakly bound complexes, and species appearing along amyloidogenic processes). The study of such complex systems is challenging due to the instability of the species involved, their low and interdependent relative concentrations, and the difficulties to isolate the pure components. In this thesis, I have developed methodological approaches to apply Small-Angle X-ray Scattering (SAXS), a low-resolution structural biology technique, to the study of polydisperse systems. As an additive technique, the SAXS pattern measured for a polydisperse sample corresponds to the concentration-weighted sum of the contributions from each of the individual components. However, decomposition of SAXS data into species-specific spectra and relative concentrations is laborious and burdened by ambiguity. In this thesis, I present an approach to decompose SAXS datasets into the individual components. This approach adapts the chemometrics Multivariate Curve Resolution Alternating Least Squares (MCR-ALS) method to the specificities of SAXS data. Our method enables the rigorous and robust decomposition of SAXS data by simultaneously introducing different representations of these data and, consequently, emphasizing molecular changes at different time and structural resolution ranges. We have applied this approach, which we name COSMiCS (Complex Objective Structural analysis of Multi-Component Systems), to study two polydisperse systems: amyloid fibrillation by analysing time-dependent SAXSdata, and conformational fluctuations through the analysis of data obtained using on-line size-exclusion chromatography coupled to SAXS (SEC-SAXS). The importance of studying fibrillation processes lies in their implication in amyloidogenic pathologies such as Parkinson’s or Alzheimer’s diseases. There exist strong indications that soluble oligomeric species, and not mature fibrils, are the main cause of cytotoxicity and neuronal damage emphasizing the importance of characterizing early stages of fibrillation. The first application of our COSMiCS approach has allowed the study of the amyloidogenic mechanisms of insulin and the familial mutant E46K of ↵-synuclein, a Parkinson’s disease related protein. The analysis enables the structural characterization of all the species present as well as their kinetic transformations. The second part of the thesis is dedicated to the use of COSMiCS to analyze on-line SEC-SAXS experiments. Using synthetic data, I demonstrate the capacity of chemometric approaches to decompose complex chromatographic profiles. Using this approach, I have studied the conformational fluctuations in prolyl oligopeptidase (POP), a protein related to synaptic functions and neuronal development. In summary, this thesis presents a novel chemometrics approach that can be generally applied to any macromolecular mixture with a tuneable equilibrium that is amenableto SAXS. Transient biomolecular complexes, folding processes, or ligand-dependent structural rearrangements can be probed structurally using COSMiCS
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Dhani, Sonja Urmilla. "Experimental approaches for the structural characterization of membrane-spanning segments in proteins." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape2/PQDD_0020/MQ53330.pdf.
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Guerry, Paul. "New solid-state NMR approaches to the structural characterisation of phosphate glasses." Thesis, University of Warwick, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.495018.
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New techniques for quantifying distributions of J couplings and phosphate chains lengths have been developed using a combination of theoretical calculations, numerical simulations and NMR experiments on a cadmium phosphate glass x(CdO)-(1-x)(P205) (x=57.5 mol%). In addition, the effect of ageing and a novel sol-gel preparation route have been investigated in sodium borophosphate glasses.
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Janes, Daniel Peter. "Structural and functional approaches to myosin linked regulation using expressed protein fragments." Thesis, Royal Veterinary College (University of London), 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.249481.
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Menke, Matthew Ewald 1978. "Computational approaches to modeling the conserved structural core among distantly homologous proteins." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/55118.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 95-103).
Modem techniques in biology have produced sequence data for huge quantities of proteins, and 3-D structural information for a much smaller number of proteins. We introduce several algorithms that make use of the limited available structural information to classify and annotate proteins with structures that are unknown, but similar to solved structures. The first algorithm is actually a tool for better understanding solved structures themselves. Namely, we introduce the multiple alignment algorithm Matt (Multiple Alignment with Translations and Twists), an aligned fragment pair chaining algorithm that, in intermediate steps, allows local flexibility between fragments. Matt temporarily allows small translations and rotations to bring sets of fragments into closer alignment than physically possible under rigid body transformation. The second algorithm, BetaWrapPro, is designed to recognize sequences of unknown structure that belong to specific all-beta fold classes. BetaWrapPro employs a "wrapping" algorithm that uses long-distance pairwise residue preferences to recognize sequences belonging to the beta-helix and the beta-trefoil classes. It uses hand-curated beta-strand templates based on solved structures. Finally, SMURF (Structural Motifs Using Random Fields) combines ideas from both these algorithms into a general method to recognize beta-structural motifs using both sequence information and long-distance pairwise correlations involved in beta-sheet formation. For any beta-structural fold, SMURF uses Matt to automatically construct a template from an alignment of solved 3-D structures.
(cont.) From this template, SMURF constructs a Markov random field that combines a profile hidden Markov model together with pairwise residue preferences of the type introduced by BetaWrapPro. The efficacy of SMURF is demonstrated on three beta-propeller fold classes.
by Matthew Ewald Menke.
Ph.D.
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Walkingshaw, Andrew D. "Aspects of structural and electronic disorder in network materials : approaches to simulation." Thesis, University of Cambridge, 2007. https://www.repository.cam.ac.uk/handle/1810/218854.
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Disorder in solids is one of the critical problems facing exponents of simulation-based studies in the mineral sciences. This thesis presents some novel techniques which can be used to probe the structure and dynamics of such systems under simulation. Two techniques are focussed upon. Firstly, the use of simulated charge as a probe to investigate the bonding and electrochromic properties of materials (particularly tungsten trioxide); secondly, derivation of a novel algorithm (Constrained Linear Maximization) for prediction of transition states by simulation, and its application to diffusion simulations in both crystalline network silicates and silica glass.