Dissertations / Theses on the topic 'Stability'
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Popelář, Vojtěch. "Vliv kompenzace kabelových sítí na stabilitu blízkých zdrojů." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220691.
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This thesis deals with the infulence of compensation cabel network on the stability of nearby power source. This issue is topical with the increase in the ratio of cable networks 110 kV in large cities. The work examines the theoretical concept of stability and factors that affect it. Mainly discusses the stability angle rotor of a synchronous machina. The practical part is performed in MODES software, that performs dynamic simulation of the behavior of the model. In this case, it will be behavior of synchronous machine during short-circuit in network at different values of compensation of this network.
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Špíšková, Marcela. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221541.
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Master`s thesis analyses financial situation of the firm FABORY – CZ and views its financial health. The task of this master`s thesis is to propose solutions leading to the ensuring of financial stability of the company.
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Smejkalová, Helena. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221565.
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The first part of master`s thesis deals with proposal for providing a financial stability of a company. Second part is an application of the analysis to a particular company and designs with result in recovery of problematic spheres and improvement which should improve financial circumstances of the company
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Drzková, Petra. "Měření stability daňových systémů." Master's thesis, Vysoká škola ekonomická v Praze, 2013. http://www.nusl.cz/ntk/nusl-192678.
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The aim of this diploma thesis is to reveal whether the Czech tax system can be considered less stable in comparison with systems of selected five other OECD countries . The examined data cover a period from the year 2000 to 2014. To examine the first hypothesis of this study, stating that the Czech tax system is more unstable than tax systems of Austria, Germany, Ireland, Switzerland and the UK, an "index of changes" has been defined to analyze these changes. Changes are analyzed in relation to personal income tax, corporate income tax and value added tax. The second hypothesis deals with the relationship between the resulting stability of the tax system and statistics of Doing Business evaluating openness of the aforementioned countries towards investments. The result of this study is that the Czech tax system is less stable in comparison with selected countries. It has also not been proven that there is a correlation between stability of the tax system and assessment of the openness to new investments.
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Maatar, Dhouha. "Analyse des signaux stabilométriques et de la stabilité chez l’Homme : application à la biométrie." Thesis, Paris Est, 2013. http://www.theses.fr/2013PEST1161/document.
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La biométrie se réfère à la reconnaissance automatique des individus. Elle est basée sur leurs caractéristiques physiologiques et/ou comportementales. Le contrôle postural, bien que soit une caractéristique comportementale de l'Homme, n'a pas été bien développée dans le domaine de la biométrie. Le travail mené dans cette thèse repose sur l'analyse des signaux stabilométriques et l'application à la biométrie. Dans un premier volet, une étude de l'information posturale, en particulier le signal stabilométrique, est effectuée à travers des méthodes d'analyses classiques à savoir et l'analyse spatio-temporelle, spectrale et stochastique et à travers aussi deux méthodes de décomposition : la décomposition appelée analyse en composantes principales (ACP) et la décomposition en ondelettes. La méthode ACP, basée sur le modèle additif, permet de décomposer le signal en trois composantes: un signal de tendance, un signal d'excursion et un signal de tremblements. La méthode de décomposition en ondelettes permet de décomposer le signal en trois niveaux de signaux de détail et trois niveaux de signaux d'approximation. Suite à l'étude de la stabilité posturale, l'analyse spectrale et l'analyse de la phase des différentes composantes issues de la ACP et de la décomposition en ondelettes, la comparaison de ces deux méthodes conclut que la méthode ACP est plus appropriée que la décomposition en ondelettes pour analyser le stabilogramme. A partir des méthodes de décomposition et des méthodes d'analyses classiques, des paramètres sont extraits afin d'étudier l'effet de différents facteurs sur la stabilité posturale et sur le déplacement du centre de masse. Ces facteurs sont la vision, la direction, la proprioception, l'âge, le genre, la taille et le poids. Un deuxième volet de ce travail est consacré à l'application biométrique, à partir des paramètres extraits et suite à une analyse statistique ANOVA, ceux qui sont les plus discriminatifs sont utilisés pour identifier des sujets et les classer selon leur âge, genre, poids et taille. Cette application biométrique est effectuée par trois méthodes de classification à savoir, K-ppv, ADL et SVM. Les applications biométriques aboutissent à des taux de reconnaissance respectables dépassant 80%. De ce fait, il est à déduire que l'analyse du contrôle postural est prometteuse dans le domaine de la biométrieBiometrics refers to automatic recognition of individuals. It is based on their physiological and / or behavioral. The postural control, despite that is a human behavioral characteristic, has not been well developed in the field of biometrics. The work performed in this thesis is based on the stabilometric signals analysis ant biometric application. Firstly, a study of the postural information especially the stabilometric signal is carried out through traditional analysis namely temporal, frequency and stochastic analysis and two decomposition methods named principle components analysis (ACP) decomposition and wavelet decomposition. The ACP method, based on the additive model, allows decomposing the signal into three components: a trend signal, a rambling signal and a trembling signal. The wavelet decomposition method allows decomposing the signal into three levels of detail signals and three signal levels of approximation. Through the study of postural stability, spectral analysis and phase analysis of the different components from the ACP and the wavelet decomposition, the comparison of these two methods concludes that the ACP method is more appropriate than the wavelet decomposition to analyze the stabilogram. From the decomposition methods and classical methods of analysis, several parameters are extracted to study the effect of different factors on postural stability and the center of mass displacement. These factors are named vision, direction, proprioception, age, gender, height and weight. A second aspect of this work is devoted to the application of biometrics, from the extracted parameters and through ANOVA statistic analysis, those that are most discriminative are used to identify subjects and classify them according to age, gender, weight and size. This biometric application is performed by three classification methods namely, K-NN, LDA and SVM. Biometric applications result in respectable recognition rate exceeding 80%. Therefore, it is inferred that the analysis of postural control is promising in the field of biometrics
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Barros, Ceres. "Etude de la stabilité des écosystèmes à plusieurs échelles spatiales et trophiques." Thesis, Université Grenoble Alpes (ComUE), 2017. http://www.theses.fr/2017GREAV013/document.
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Dans un contexte de changement global qui continue de menacer les espèces et l’intégrité des écosystèmes à travers le monde, l’étude de la stabilité des écosystèmes n’a jamais été aussi importante. Jusqu’à aujourd’hui, la plupart des études sur la stabilité des écosystèmes se sont centrées sur des écosystèmes simples et des perturbations individuelles, en focalisant généralement sur le comportement de propriétés écosystémiques particulières, comme les indices de productivité et de diversité. Cependant, les écosystèmes sont soumis simultanément à de multiples perturbations. De plus, à grande échelle spatiale, différents écosystèmes se succèdent, chacun répondant différemment à une perturbation donnée. L’étude de la stabilité des écosystèmes doit donc progresser vers des approches plus intégratives qui seront informatives à des échelles pertinentes pour la gestion des écosystèmes. Cette thèse est un pas en avant dans cette direction. Ici, j’ai utilisé plusieurs approches pour évaluer la façon dont de multiples facteurs de changement global, tels que les changements climatiques graduels et extrêmes et les changements d’usage du sol, affectent la stabilité des écosystèmes à grande échelle spatiale, du point de vue d’un seul niveau trophique à un point de vue multitrophique.Je commence par souligner l’importance de considérer les interactions entre les changements climatiques graduels et extrêmes, en conjonction avec les changements de l’usage du sol, pour la gestion de paysages hétérogènes, comme les Alpes européennes. En utilisant un modèle de végétation dynamique et spatialement explicite, je montre qu’une augmentation de la fréquence et de l’intensité de la sécheresse pourrait drastiquement changer les tendances d’embroussaillement des habitats ouverts alpins et subalpins qui sont généralement prévues par les projections ne prenant pas en compte ces évènements extrêmes dans le futur. J’ai ensuite étudié si la sécheresse et le réchauffement climatique progressif amenaient les communautés végétales à souffrir des transitions différentes, en utilisant une approche innovatrice dans laquelle les états des communautés sont décrits d’une façon multidimensionnelle. Je montre que bien que les effets de la sécheresse sur la structure des forêts et des pâturages ne devraient pas trop affecter les trajectoires à long terme causées seulement par le réchauffement climatique graduel, ils devraient rendre les communautés forestières plus instables que les prairies dans le futur. Cependant, l’analyse des réponses de la végétation reste limitée à un seul niveau trophique. Vu que les réseaux trophiques représentent les flux d’énergie dans un écosystème, l’étude de leur stabilité aux perturbations devrait fournir des informations plus précises sur la stabilité globale de l’écosystème. Donc, j’ai aussi étudié la stabilité des réseaux trophiques dans les aires protégées européennes face à des scénarios futurs d’usage du sol et de climat. Mes résultats montrent que ces réseaux trophiques peuvent être très sensibles aux changements climatiques, même s’ils ne sont soumis à aucun changement d’usage du sol. Notamment, je montre que la prise en compte des phénomènes de dispersion des espèces aura un impact important sur la robustesse des réseaux, et je souligne l’importance de leur prise en compte pour la gestion des écosystèmes.Dans ma thèse, je démontre que les concepts de stabilité de l’écosystème peuvent et doivent être appliqués à des échelles pertinentes pour la gestion des écosystèmes, tout en adoptant la nature multidimensionnelle des écosystèmesAs global change threatens ecosystems worldwide with biodiversity loss, studying ecosystem stability has never been so important. Most ecosystem stability studies have heretofore focused on single ecosystems and disturbances, usually following the behaviour of particular ecosystem properties, such as productivity and diversity indices. However, ecosystems are subjected to multiple disturbances simultaneously and at large spatial scales different ecosystems co-occur, each responding specifically to any given disturbance. Hence, the study of ecosystem stability needs to move towards approaches that can be informative at broad scales that are relevant for ecosystem management. This thesis is a step forward in this direction. Here, I used several approaches to assess how multiple global change drivers, such as climate change, extreme whether events, and land-use changes, affect ecosystem stability at landscape and larger spatial scales, and from single to multi-trophic level perspectives.I begin by highlighting the importance of considering the interactions between gradual and extreme climate changes, in conjunction with land-use changes, for the management of highly diverse landscapes, such as the European Alps. Using a spatially explicit dynamic vegetation model, I show that increasing drought frequency and intensity will likely change the trends of treeline movement expected under future gradual climate warming scenarios. I then investigated whether drought and gradual climate warming caused plant communities to shift in different ways, using n-dimensional hypervolumes to describe community states in multidimensional space. Drought effects on forest and grassland structure did not greatly change the long-term trajectories caused by gradual climate warming alone, but showed that forest communities became more unstable than grasslands in the future. However, focusing on vegetation dynamics remains limited to a single trophic level. Because trophic networks represent energy flows in an ecosystem, studying their stability to disturbances should provide more accurate information on overall ecosystem stability. Hence, I also investigated trophic network stability in European protected areas to future scenarios of land-use and climate changes. My results show that these trophic networks may be highly sensitive to climate changes, even if no land-use changes occur. Importantly, I show that considering different dispersal limitations will greatly impact network robustness, and stress the importance of accounting for these processes in ecosystem management.In my thesis, I demonstrate that ecosystem stability concepts can and should be applied at scales that are relevant for management, while embracing the multidimensional nature of ecosystems
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Das, Nilanjan Ph D. Massachusetts Institute of Technology. "Epistemic stability." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/107096.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Linguistics and Philosophy, 2016."September 2016." Cataloged from PDF version of thesis.
Includes bibliographical references (pages 119-134).
I argue that knowledge and rational belief are subject to stability conditions. A belief that amounts to knowledge couldn't easily have been lost due to the impact of misleading evidence. A belief that is rational couldn't easily have been withdrawn upon reflection on its epistemic credentials. In Chapter 1, I support a picture of epistemic rationality on which a belief, in order to be rational, must be stable under reflection, i.e., it must be capable of surviving reflective scrutiny. To make room for this condition, I defend the possibility of higher-order defeat, where a belief's rationally undermined by misleading higher order evidence, i.e., by evidence about what one's evidence supports. I sketch an account of-higher-order defeat on which higher-order evidence makes an agent's total body of evidence fragmented: even though a piece of evidence is available within the agent's cognitive system, the agent is unable to rationally bring it to bear upon certain questions. In Chapter 2, I explore an analogy between knowledge and moral worth. Just as knowledge requires the agent to non-accidentally believe the truth, so too does morally worthy action require the agent to non-accidentally perform the right action. I argue that the analogy lends support to an explanation-based account of knowledge: a belief amounts to knowledge only if the manner in which the agent forms the belief explains both why the agent holds the belief (rather than losing it) and why she forms a true belief (rather than a false one). I call this view explanationism. In Chapter 3, 1 discuss a consequence of explanationism: a belief that amounts to knowledge couldn't easily be rationally defeated by misleading evidence. This condition-safety from from defeat explains a range of different epistemic phenomena. It accounts for the explanatory role of knowledge in relation to certain kinds of behaviour, like rational perseverance. It obviates certain demanding "internalist" conditions on knowledge. It also illuminates the connection between knowledge and practical interests.
by Nilanjan Das.
Ph. D.
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Wolff, Lars, and Klaus Kroy. "Mechanical stability." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-190323.
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The glassy wormlike chain model is a highly successful phenomenological model recently introduced to describe anomalously slow subdiffusive dynamics in biopolymer networks and living cells. Here we extend this model by proposing a generic scheme how to include nonlinear plastic effects by introducing the possibility of force-dependent opening and closing of internal bonds. Further, we discuss physiological implications of this bond kinetics. Stability arguments lead us to the postulation of a “physiological sheet” in the parameter space. This sheet defines the set of parameters characterizing cells which are flexible enough to perform biological tasks while still being able to bear external perturbations characteristic of their surroundings and their internally generated prestress without damage. At the end of this contribution, we speculate about the connection between prestress and cell stiffness and about the mechanism by which the cell adapts to its mechanical environment.
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Marešová, Eva. "Stabilita a řiditelnost experimentálního letounu VUT 001 Marabu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228431.
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This diploma thesis deals with a stability and manoeuvrability of experimental aircraft VUT 001 MARABU. It contains calculation of aerodynamic stability derivations and other data necessary for evaluation of static and dynamic stability. Assessment of convenient autopilot.
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Matějů, Jiří. "Hodnocení stability a řiditelnosti čtyřmístného, jednomotorového letounu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2013. http://www.nusl.cz/ntk/nusl-231035.
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The diploma thesis deals with evaluation and suggestion of changes for the conceptual design of an airplane TL4000 in terms of stability and controllability. In the first part there are determined stability and controllability derivativations of the aircraft. Thereafter are estimated aircraft weight, moment of inertia and necessary geometric characteristics. In the second part there are calculated stability criteria for a sample case. In the third part, on the basis of this calculation, a program is created. This program combines the advantages of MS Excel, Matlab and Matlab Simulink. By means of this program criteria of stability and controllability were calculated parametrically for different regimes of flight, identified critical cases and compared with the requirements of CS-23rd. Based on this evaluation were recommanded modifications of the conceptual design TL4000.
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Raii, Mohamed. "Formulation, caractérisation et mise en œuvre des barrières perméables réactives à base de phosphate de calcium, utilisation pour la fixation de polluants." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/9123/1/raii.pdf.
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L'objectif principal de cette thèse est la formulation des mélanges stables contenant l'hydroxyapatite gel synthétisée (Ca-HAGel). Le comportement rhéologique des mélanges Eau/(sulfate de calcium) et hydroxyapatite/(sulfate de calcium) a été étudié. Les résultats ont montré que tout les mélanges sont caractérisés par un comportement rhéologique rhefluidifiant et thixotrope. Le potentiel zeta a été utilisé dans cette étude pour mieux appréhender les interactions entre les particules et leur effet sur le comportement des mélanges. La fixation de sulfate sur la surface de Ca- HA favorise la stabilité de la structure du Ca-HAGel. Les analyses de caractérisation effectuées sur les formulations ont montré la formation de nouveaux composés tels que le sulfate-phosphate de calcium hydrate et l'Ardealite. Les tests de lixiviation et de percolation ont révélé que le taux de relargage de soufre et strontium à partir des sous-produits de gypse était négligeable pour les mélanges contenant Ca-HAGel. Ca- HAGel stabilise les métaux lourds relargués à partir du gypse et plâtre. Les particules du gypse améliorent les performances hydrauliques de Ca-HAGel et le plâtre hydraté stabilise la structure de Ca-HAGel par la formation des particules agglomérées. Le test colonne effectué sur la formulation AWPG2 a montré une grande performance à retenir le plomb et le cadmium avec des capacités de rétention de plus de 99% et 88% respectivement. Le traitement des métaux lourds était lié aux particules de Ca-HA et aux phosphate et calcium libres. La formulation AWPG2 peut être utilisée dans les barrières perméables réactives pour traiter les eaux souterraines contaminées.
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Fernier, Alexandre. "Couplage multi-échelle pour l'intéraction fluide structure en dynamique rapide." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLY001/document.
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Dans l’industrie nucléaire, la simulation de transitoires accidentels à l’échelle d’un réacteur devient une composante d’importance croissante de la démonstration de sûreté à destination des agences de surveillance nationales. Elle permet ainsi de limiter le recours à des expériences complexes et coûteuses tout en facilitant l’évaluation des stratégies de mitigation. Cependant, les modèles mis en jeu sont inévitablement volumineux et construits avec une finesse de modélisation rendant difficile la prise en compte de détails géométriques locaux pourtant susceptibles d’influencer significativement la solution globale. Dans ce travail de thèse, on propose ainsi des approches multi-modèles pour l’intégration de tels détails dans un modèle global sans modification du maillage initial (on parle aussi de zoom numérique). Des techniques sont proposées aussi bien pour les structures que pour les fluides, avec un souci de démontrer la précision et la stabilité de la solution multi-modèles couplée comparée à une solution de référence à une seule échelle. Ce travail intègre deux spécificités propres, à savoir son adéquation avec les contraintes de la dynamique rapide avec intégration temporelle explicite et l’objectif de traiter simultanément la superposition de modèles et l’interaction fluide-structureIn nuclear industry, simulating accidental transient sequences at full reactor scale is becoming an increasingly important feature of the safety demonstration towards national agencies. It thus allows limiting the number of complex and costly experiments, while simplifying and accelerating the evaluation of mitigation strategies. However, the implemented numerical models are inevitably heavy to build and maintain, with a global modelling scale making it difficult to account for local geometric details yet able to significantly influence the physical solution. To provide an answer to these problems, this PhD work is dedicated to multi-model approaches designed to integrate such details into bigger models with no modification at the global level (techniques often designated as numerical zoom techniques). Some methods are proposed for both structures and fluids, with special care given to the accuracy and stability of the coupled multi-scale solution compared to a single-scale reference solution. This work handles two very specific topics, namely its compatibility with numerical features imposed by fast transient dynamics with explicit time integration, and the general objective of simultaneously dealing with superimposed models and fluid-structure interaction
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Liu, Xiyuan. "Stability test and stability conditions for retarded delay differential systems /." [S.l.] : [s.n.], 1985. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=7778.
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Sandby-Thomas, Peter. "The legitimating logic of stability : analysing the CCP's stability discourse." Thesis, University of Nottingham, 2008. http://eprints.nottingham.ac.uk/13552/.
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This thesis addresses the question of why the Chinese Communist Party (CCP) has remained in power since the Tiananmen Incident in 1989 by deploying the concept of political legitimacy. In this, the focus is not on whether the CCP is legitimate per se but rather on how the Party has legitimated its authority in this period. To that end, the Weberian conceptualisation of legitimation is situated within the Strategic-Relational Approach and, in so doing, allows, through the concept of "discursive selectivity", for legitimation to be reconceptualised as a dialectical relationship consisting of both material and ideational factors. The effect of this move is to provide a suitable framework in which to consider additional legitimating strategies that are employed by the CCP. Consequently, this paper moves beyond the conventional explanation of "economic performance + nationalism" to argue that the CCP's use of the stability discourse in the post-Tiananmen period has contributed to the regime's legitimation. In order to understand how this discourse has been used, a critical discourse analysis is performed on selected articles from the People's Daily published during the Beijing Spring, the "anti-Falun Gong" campaign and the "anti-Japan" demonstrations on the basis that these exceptional instances inform its usage in conventionalised slogans. This analysis found that the term "stability" took the form of an "empty signifier", making most use of positive argument schemes to project a negative Chinese future without CCP authority. Finally, this thesis concludes that, in terms of legitimation, the events in 1989 constituted a strategic moment in the formation of the stability discourse, in that the Party's hegemonic interpretation of these events allowed for this discourse to "resonate" with people in the period that has followed.
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Pfeifer, Lukáš. "Interakce a kompatibilita měnové a makroobezřetnostní politiky v České republice." Doctoral thesis, Vysoká škola ekonomická v Praze, 2015. http://www.nusl.cz/ntk/nusl-199393.
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The thesis deals with the interaction of monetary and macroprudential policy, or with the compatibility of the objectives of these policies in the Czech Republic. The main attention is given to the use of interest rate instruments for the purpose of achieving financial stability during the accumulation phase of cyclical dimension of systemic risk. For this purpose the crucial item is the relationship of financial and price stability in the economy. On the Czech economy data is therefore tested the relationship between credit activity and asset prices, to be subsequently quantified the relationship between the prices of selected assets and consumer prices. The model results open the door to greater use of industrial producer price index for the coordination of monetary and macroprudential policy. The thesis for the same reason also recommends continuing research into the development of the general price level during the financial cycle.
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Malinka, František. "Strojové učení v úloze predikce vlivu aminokyselinových mutací na stabilitu proteinu." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2014. http://www.nusl.cz/ntk/nusl-236035.
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This thesis describes a new approach to the detection of protein stability change upon amino acid mutations. The main goal is to create a new meta-tool, which combines the outputs of eight well-established prediction tools and due to suitable method of consensus making, it is able to improve the overall prediction accuracy. The optimal strategy of combination of outputs of these tools is found by using a various number of machine learning methods. From all tested machine learning methods, KStar showed the highest prediction accuracy on the training dataset compiled from experimentally validated mutations originating from ProTherm database. Due to this reason, it is chosen as an optimal prediction technique. The general prediction abilities is validated on the testing dataset composed of multi-point amino acid mutations extracted also from ProTherm database. Since the multi-point mutations were not used for training any of integrated tools, we suppose that such comparison is objective. As a result, the developed meta-tool based on KStar technique improves the correlation coefficient about 0.130 on the training dataset and 0.239 on the testing dataset, respectively (the comparison is being made against the most succesful integrated tool). Based on the obtained results, it is possible to claim that machine learning methods are suitable technique for the problems from area of protein predictions.
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Kaván, Ondřej. "Statistické zpracování naměřených dat skeletu typu PROXIMA." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2009. http://www.nusl.cz/ntk/nusl-228357.
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This diploma thesis deals with the description of selected statistical process control tools, applied to Proxima frame cab tractor made by Zetor company. There is also a statistical evaluation of measured data and determination of significant correlations.
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Kohlíčková, Jana. "Stabilita bank za krize." Master's thesis, Vysoká škola ekonomická v Praze, 2013. http://www.nusl.cz/ntk/nusl-197667.
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Thesis: "The stability of banks in the crisis" presents an analysis of the impact of the financial crisis on the banking sector and individual banks and a demonstration of the behavior of banks in crisis situation. The thesis is divided into four chapters. The first chapter deals with the definition of instability and explain the functioning of the financial crisis. The second chapter discusses the issue of deposit insurance and the possibility of compensation payments during the bank's collapse. The third chapter shows the influence and role of central banks as the creator of the banking environment and as the main supervisory authority. The fourth chapter focuses on the stability of banks from different perspectives, that the bank's activity was not significantly affected during and after the financial crisis.
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Reeves, Bryan Anthony. "Slope stability radar /." [St. Lucia, Qld.], 2003. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe17049.pdf.
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Dhingra, Manuj. "Compressor stability management." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-01102006-174943/.
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Thesis (Ph. D.)--Aerospace Engineering, Georgia Institute of Technology, 2006.Prasad, J.V.R., Committee Chair ; Neumeier, Yedidia, Committee Member ; Seitzman, Jerry, Committee Member ; Sankar, Lakshmi, Committee Member ; Wadia, Aspi, Committee Member.
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Ko, Tung Yeung. "Stability of networks /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?PHYS%202007%20KO.
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McColl, Samuel Thomas. "Paraglacial Rockslope Stability." Thesis, University of Canterbury. Department of Geological Sciences, 2012. http://hdl.handle.net/10092/7331.
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The aim of this research was to study the relationship between rock slope stability and glacial processes. An in-depth analysis of our current understanding of how glaciated rock slopes develop instability and movement during deglaciation is presented; this shows that understanding is incomplete without an appreciation of the variable mechanical behaviour of glacier ice. In this thesis, I argue that:
(1) The ductile behaviour of ice at low strain rates allows movement of rock slopes buttressed by ice. Field evidence and simple force models are used to explore rate of movement of ice-contact slopes and the conditions under which they evolve. The results indicate that large rockslides can move and deform glacial ice at rates of 10-2 to 102 m-yr. This implies that ice-contact slope movement may be important for slope evolution and the erosion and entrainment processes of glaciers; and
(2) the elastic strength of glacier ice at the high strain rates associated with seismic shaking enables ice to modify the response of the surrounding rock to seismic shaking. To explore this, numerical analyses of the interaction between glacial erosion, glacier mass, topography, and earthquake shaking intensity are undertaken. Shaking of mountains of variable shape and with different levels of ice inundation is simulated using FLAC 6.0. The results suggest that complete inundation by ice can significantly reduce shaking intensity. This, in combination with glacial steepening of slopes, may make recently deglaciated slopes more prone to coseismic failure.
In the final chapter of the thesis, I present a conceptual model of the evolution of slope stability during stages of glaciation and deglaciation. The model incorporates the ideas presented in the thesis. I then offer recommendations for how our understanding of these processes can be further advanced.
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Hammond, Max Leonard. "Imine catalyst stability." Thesis, University of Warwick, 2006. http://wrap.warwick.ac.uk/1172/.
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Chapter 1 presents a review of the background and current research regarding Schiff-base olefin polymerization catalysts, with special reference to the salicylaldimine species. An attempt is made to review trends within the current literature. Chapter 2 describes the synthesis and polymerization properties of tetradentate ligands with a bibenzyl backbone at titanium and zirconium centres, prepared with the intent of sterically hindering a 1,2-Migratory Insertion into the ligand imine functionality. A custom-built polymerization reactor was used to determine the stability of the catalytic systems. Steric protection is moderately successful in enhancing the stability of these systems. Chapter 3 reports the synthesis and detailed polymerization behaviour of a series of group 4 catalysts based on salicyloxazoline ligands, which should be resistant to 1,2-Migratory Insertion. Comparisons are made between polymerization under different conditions, including using High-Throughput methodology to screen catalysts under a range of differing conditions rapidly. Such systems are extremely active for polymerization of ethene, but demonstrate limited stability at elevated temperature. Chapter 4 presents our investigations into the polymerization behaviour of salicyloxazoline catalysts containing a para-methoxy substituent on the phenoxy donor unit. This substituent significantly enhances the stability of the catalysts at elevated temperature. Chapter 5 explores the nature of the active species in polymerizations with group 4 salicyloxazoline species. Alkyl cations of such species are generated from metal alkyl species with borate activators, and also from metal chloride species with MAO. We conclude that the primary deactivation mechanism is loss of ligand to aluminium co-catalyst, and that the methoxy substituent prevents this. A computational approach (DFT) is also applied, to examine the catalytic pathways which may be available to various stereoisomers of the catalyst. Chapter 6 details the experimental procedures used during this work.
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Farrell, Natalie Jane Charlotte. "Quantifying fault stability." Thesis, University of Aberdeen, 2016. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=229386.
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Nejedlý, Jakub. "Řízení stability kvadrokoptéry." Master's thesis, Vysoké učení technické v Brně. Fakulta informačních technologií, 2015. http://www.nusl.cz/ntk/nusl-234916.
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This work deals with physical laws affecting behavior of a quadcopter as a mobile robot. It describes methods of controlling movements and stability. The result of the theoretical analysis is creation of simulation model. Moreover it depicts practical software developement of a real machine controller unit with its own conclusion, comparison between simulation and practical experiments and the workflow of the physical system construction.
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Ikeda, Hiroshi. "Stability of endomorphisms /." Electronic version of summary, 1995. http://www.wul.waseda.ac.jp/gakui/gaiyo/2106.pdf.
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Singh, Gurinder Pal. "Power system stability." Thesis, Singh, Gurinder Pal (2018) Power system stability. Honours thesis, Murdoch University, 2018. https://researchrepository.murdoch.edu.au/id/eprint/44793/.
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In order to understand the stability it is essential to become familiar with the basic operations of a power system. There are three main components of a power system i.e. generation, transmission and distribution. Electrical power is generated mostly from synchronous machines. The primary sources of energy (fossil, hydraulic) are converted into mechanical energy through prime movers. Mechanical energy is used by synchronous generators to produce electrical power and most of the electric power systems are three phase AC systems operating at constant voltage. Three phase equipment is also used by generation and transmission facilities along with industrial residential and commercial loads that are equally distributed among all the phases to form a three‐phase balanced system [1]. A power system entirely relies upon its voltage, frequency and rotor angle stability. The main causes behind the instabilities, analysis techniques and methods used to improve the overall system stability will be discussed in this report.
This report will explore the main aspects of power system instabilities by reviewing existing literature, analysing through simulation and finally correcting the grid instability with regard to voltage, frequency, and rotor angle. A small nine bus transmission network using Power Factory to analyse and match the theoretical factors that determine the reliability and operation as mentioned in current literature. The Power Factory provides numerous inbuilt global models of Automatic voltage regulator (Avr), Governor and Turbine (Gov), and power system stabilizer (PSS) etc. to reduce the complexity and avoid building the differential functions from scratch. The system will be analysed under four random avr and gov models by introducing a three‐phase fault at one of the transmission lines. The response of one of the generator will be examined on the basis of its variables like rotor angle, speed, output powers, terminal and excitation voltages. The ideal combination of avr and gov will be used to carry out PV and QV curve analysis to find the weakest bus in the system. Lastly, the performance of that bus will be analysed by varying the load and reactive power compensation. Stability of the system will be enhanced by using various Avr, Gov models through testing pre‐existing parameters.
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Kostečka, Petr. "Posouzení stability procesu." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2012. http://www.nusl.cz/ntk/nusl-230076.
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This master`s thesis is focused on the application of statistic process control in engineering production and it is focused on comparison with method Beta correction. The aim of the diploma thesis is to find suitable regulation of the producing process with respect to provision of sufficiently high level of quality of products at the process of achievement of adequate costs conneced with process monitoring. The basic principles of both methods are solved in the theoretical part of this diploma thesis. Both methods are compared in particular producing process in the practical part of the thesis. Conclusions and suggestions are done on the base of gained data.
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Wang, Mengjie. "Stability analysis of three-dimensional boundary layers with parabolized stability equations /." The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487858106119026.
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Lukášová, Klára. "Návrh na zajištění finanční stability podniku." Master's thesis, Vysoké učení technické v Brně. Fakulta podnikatelská, 2007. http://www.nusl.cz/ntk/nusl-221404.
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This thesis asses the financial health of the company in the years 2002 – 2005 at the basis of sesected methods of the financial analysis. It comprieses proposals of possible solutions of identified problems which should result in the improvement of financial situation and ensurance of financial stability of the firm in future years.
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Jugier, Rémi. "Stabilité bidimensionnelle de modèles de sillage d’aéronefs." Thesis, Toulouse, ISAE, 2016. http://www.theses.fr/2016ESAE0021/document.
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Le contrôle des tourbillons de sillages d'aéronefs permet de réduire leur dangerosité et d'augmenter par conséquent le débit de décollages et d'atterrissages dans les aéroports. Ce contrôle permettrait également d'agir sur la formation des rainées de condensation et des cirrus artificiels en haute atmosphère dans le but de réduire le forçage radiatif terrestre causé par l'aviation. Brion (2014) ont montré par analyse de stabilité modale que le dipôle de Lamb-Chaplygin, souvent utilisé comme un modèle représentatif des tourbillons de sillage en champ lointain, est bidimensionnellement instable à des nombres de Reynolds faibles. Nous étendons premièrement cette analyse de stabilité modale bidimensionnelle à des modèles de dipôles plus réalistes, pour une large gamme de rapport d'aspect, et obtenons, à faibles nombre de Reynolds, des instabilités de même nature (modes de déplacement) que pour le dipôle de Lamb-Chaplygin. Nous montrons cependant que la croissance des instabilités observées dépend fortement du rapport d'aspect du dipôle, et que cette croissance est fortement diminuée lorsque la diffusion du dipôle est prise en compte. Nous étudions ensuite la stabilité bidimensionnelle transitoire en champ lointain (dipôles) et en champ proche (nappes de vorticité), en atmosphères homogène et stratifiée. Dans tous les cas, les perturbations optimales sont des spirales de vorticité orientées à contre-cisaillement et situées en périphérie des tourbillons, qui conduisent in fine aux instabilités écrites par l'analyse modale grâce à un mécanisme de contamination du cœur des tourbillons, initialement identifié par Antkowiak & Brancher 2004 sur un tourbillon isoléAircraft wake vortex control allows for reducing of their dangerousness and consequently improve airport take-off / landing requencies. Contrails and artificial cirrus clouds formation could also be influenced through this control of wake vortices and allow for reducing of terrestrial radiative forcing generated by aviation. Brion (2014) have shown by a modal stability analysis that the Lamb-Chaplygin dipole, often used as a far-field model for aircraft wake vortices, is unstable to two-dimensional perturbations at Iow Reynolds numbers. We first extend this twodimensional modal stability analysis to more realistic dipole models, for a Wide range of aspect ratios, and obtain, for Iow Reynolds numbers, instabilities of the same nature (displacement modes) as for the Lamb-Chaplygin dipole. However, we show that the growth of those modes depends greatly on the dipole aspect ratio, and that this growth is greatly diminished hen the dipole diffusion is taken into account. We then study two-dimensional transient growth for far-field models (dipoles) and near-field models (vorticity sheets), in homogeneous and stratified atmospheres. ln all cases, optimal perturbations are vorticity spirals oriented against shear and located at the periphery of the vortices, which eventually lead to development of the instabilities described in the modal analysis through a contamination mechanism of the vortex cores, initially identified by Antkowiak & Brancher (2004) for an isolated vortex
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Mitra, Chiranjit. "Stability of dynamical processes on complex networks." Doctoral thesis, Humboldt-Universität zu Berlin, 2018. http://dx.doi.org/10.18452/19117.
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Die vorliegende Arbeit umfasst die Entwicklung eines Rahmens zur Bewertung der Stabilität von (multistabilen) komplexen (vernetzten) dynamischen Systemen. Als ersten Beitrag schlagen wir die multiple-node basin stability (MNBS) vor, um die Stabilität vernetzter dynamischer Systeme als Reaktion auf nicht-infinitesimale Störungen zu messen, die gleichzeitig mehrere Knoten des Systems beeinflussen. Weiterhin beziehen wir uns auf das Konzept der Resilienz zur Charakterisierung von Multistabilität. Inspiriert vom Konzept der ökologischen Resilienz schlussfolgern wir, dass die Stabilität der verschiedenen Attraktoren eines multistabilen Systems von der Gesamtstruktur ihrer jeweiligen Einzugsgebiet bestimmt wird. Insbesondere identifizieren wir sowohl die lokale Dynamik des Systems im Zustandsraum als auch die relative Position des Attraktors im Einzugsgebiet zusätzlich zum dessen Volumen als entscheidende Aspekte, welche die Gesamtstabilität eines Attraktors charakterisieren. Die genannten Aspekte werden im Maß der integral stability (IS) für die ganzheitliche Quantifizierung von Multistabilität zusammengeführt. Komplementär lässt sich auch das Konzept der technischen Resilienz betrachten, welches sich auf die Rückkehrgeschwindigkeit eines Systems zu seinem Gleichgewicht, in Folge einer Störung, bezieht. Im spezifischen Kontext von vernetzten dynamischen Systemen definieren wir die single-node recovery time (SNRT). Diese stellt ein neues Maß zur Schätzung der relativen Zeitskalen dar, die der transienten Knotendynamik eines Netzwerks zugrunde liegen, welches nach einer nicht-infinitesimalen Störung an einem Knoten in seinen gewünschten Betriebszustand zurückkehrt. Schliesslich befassen wir uns mit der Untersuchung der Synchronisationsstabilität in speziellen komplexen Netzwerken, welche entweder die Kleine-Welt-Eigenschaft aufweisen oder eine Kombination aus skalenfreier Knotengradverteilung und hierarchischer Organisation zeigen.The present endeavour comprises the development of a framework for the assessment of the stability of (multistable) complex (networked) dynamical systems. As a first contribution, we propose the framework of multiple-node basin stability (MNBS) for gauging the stability of networked dynamical systems in response to non-infinitesimal perturbations simultaneously affecting multiple nodes of the system. We then turn to the theoretical framework of resilience in identifying the different aspects characterizing multistability. Inspired by the concept of ecological resilience, we assert that the stability of the different attractors of a multistable system is determined by the overall structure of their respective basins of attraction. In particular, we identify the local dynamics of the system in the state space and the relative position of the attractor within the basin, in addition to the volume of the basin of attraction as crucial aspects determining overall stability of an attractor. We combine the aforementioned aspects in proposing the measure of integral stability (IS) for holistically quantifying multistability. We also draw inspiration from the concept of engineering resilience, which relates to the speed of return of the system to its equilibrium, following a perturbation. In the specific context of networked dynamical systems, we propose the framework of single-node recovery time (SNRT) for obtaining an estimate of the relative time scales underlying the transient dynamics of the nodes of a network returning to its desired operational state, following a non-infinitesimal perturbation to any specific node. Finally, we delve into the explicit investigation of the stability of synchronization on complex dynamical networks exhibiting small-world properties and of those, simultaneously displaying scale-free behaviour and hierarchical organization.
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Nováková, Tereza. "Chemická a termická stabilita huminových komplexů." Master's thesis, Vysoké učení technické v Brně. Fakulta chemická, 2014. http://www.nusl.cz/ntk/nusl-217078.
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The aim of this diploma thesis was the study of relation between chemical and thermal stability of complexes of humic acids with heavy metals, namely nickel, cobalt and copper. Complexes were prepared with metal solutions of three different initial concentrations. Through UV-VIS spectrophotometry were determined adsorbed amounts of incorporated metal ions in the structure of humic acid; it was affirmed that amount of bounded metal ions increases with increasing initial concentration. Chemical stability was determined as an amount of released metal ions, two of extraction agents were used (solution of MgCl2 and HCl), total bounded amount was distribute into three different fractions; residual fraction, strongly bound fraction and mobile and ion-exchangeable fraction. Changes that occured in the structure of humic acids after complexation and extraction were investigated by FT-IR spectrometry. Thermo-oxidative stability was tested through thermogravimetric analysis (TGA) and differential scanning calorimetry. The results of this diploma thesis has showed comparision of complexes of two different humic acids. They have confirmed an impact of each metal ion on thermo-oxidative stability of humic acids. The relation between chemical and thermal stability was compared through correlation of data obtained by these methods.
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Synek, Josef. "Systém pro měření aerobní stability fermentovaných krmiv." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2012. http://www.nusl.cz/ntk/nusl-219741.
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Aerobic stability is a term which nutritionists use to define the length of time that forage remains stabil and don‘t degrade. Once fermentation is completed and the forage is exposed to air during feeding or during storage (leaky silos, poor packaging) increases the temperature of the forage initiated by yeasts or lesser extent by the action of some bacterias. This temperature is measured using temperature sensors and it is compared with the ambient temperature of the surroundings. Aerobic stability is given as the time, for which the forage temperature rises by 3°C above ambient temperature.
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Storvann, Vegar. "Maintaining Voltage Stability : An Analysis of Voltage Stability Indicators and Mitigating Actions." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-19039.
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The society's dependency of a reliable power supply is increasing, and properly identifying the distance to the stability limits of the power system and avoiding large disturbances is thus becoming increasingly important. In this thesis, a system integrity protection scheme (SIPS) for voltage instability is proposed. First, six voltage stability indicators are studied and compared, and their performance is tested in several power system models. They are first tested in a two-bus system where the load impedance is gradually increased until the load-side voltage reaches zero. The performance of the indicators is then tested under circuit contingencies in models of the IEEE Reliability Test System and of the Norwegian power system. From the results, the most reliable indicators seem to be the ones that are based on local measurements (SDI, ISI and VSIscc).Several actions to mitigate voltage instability are described and tested in the power system models, including load shedding, switching of reactive compensation equipment, increasing AVR set points and increasing the active power generation. Of the unconventional actions, increasing AVR set points appears to be the most effective mitigation action.A SIPS is proposed based on the above mitigation actions, voltage stability indicators and signals from activation of OELs. The principle behind the scheme is to avoid load shedding as far as possible by using indicator values and OEL activation signals to initiate preventive mitigation actions to relieve the situation when the system is approaching instability. This also reduces the necessary amount of load to shed to stabilise the system.Simulations show that the proposed SIPS works as long as it has an adequate amount of mitigation actions available. In the simulations in the model of the Hammerfest/Skaidi region in Northern Norway, there was a general lack of possible mitigation actions, providing no alternative other than shedding large amounts of load to prevent voltage collapse after critical contingencies.
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Nakashima, Akira, Jingtai Li, and Yoshikazu Hayakawa. "Stability Analysis of Grasped Object by Soft-Fingers based on Moment Stability." IEEE, 2008. http://hdl.handle.net/2237/12099.
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Palmer, Thomas Gerard. "EFFECTS OF PROXIMAL STABILITY TRAINING ON SPORT PERFORMANCE AND PROXIMAL STABILITY MEASURES." UKnowledge, 2012. http://uknowledge.uky.edu/rehabsci_etds/9.
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Proximal stability, or the ability to stabilize and actively control the spine, pelvis and trunk, has been reported to influence sport performance. Traditional training practices for the proximal segments have had little success improving sport performance. The purpose of this dissertation was to investigate the effects a sport specific proximal stability training program can have on throwing velocity and measures of muscular endurance and power which target the proximal segments of the pelvis, spine and trunk.
A stratified randomized clinical trial was implemented with a pre- to post-intervention design. Forty-six healthy, Division III collegiate female softball (n=17) and male baseball (n=29) players were randomly assigned to one of two training groups for 7 weeks; a traditional endurance training group (ET) (n=21) or a power stability training group (PS) (n=25). The primary outcome measures were the change in peak throwing velocity/Kg of body weight in mph. Mean throwing velocity, power outputs from a one-repetition maximum chop test and lift test (watts/Kg body weight), and muscular endurance plank tests. Student’s independent t-tests were used to compare differences between change scores of all dependent variables. Peak throwing velocity change scores were significantly faster (ET= .21 ±.55 mph, PS= 3.4 ±1.1 mph, p< .001) in the PS at post-intervention when compared to the ET group. Change scores were significantly greater in the PS group for mean throwing velocity, (ET= 1.1 ±1.6 mph vs. PS= 3.7 ±1.8 mph, p< .001), chop (watts), (ET= 20 ±78 watts vs. PS= 105 ±68 watts, p< .001), and lift, (ET= 49 ±62 watts vs. PS= 114 ±73 watts, p= .003). There were no change score differences for the side and prone plank endurance measures in seconds (p≥ .60). The PS group increased primary outcome measures over the ET program, indicating a more sport specific training regimen targeting the proximal segments is beneficial to both the power measures and throwing performance.
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Bylund, Mats. "Stability in Hamiltonian Systems : KAM stability versus instability around an invariant torus." Thesis, KTH, Matematik (Avd.), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-201616.
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In his ICM-54 lecture, Kolmogorov introduced a now fundamental result regarding the persistence of a large (in the measure theoretic sense) set of invariant tori, in a certain category of almost-integrable Hamiltonian systems. 44 years later, in his ICM-98 talk, Herman conjectured that given any analytic Hamiltonian system with an invariant diophantine torus, this torus will always be accumulated by a positive measure set of invariant KAM tori, i.e. it will be KAM stable. In this thesis, we build upon recent results and provide a counterexample in three degrees of freedom to KAM stability around an invariant torus, in the category of smooth Hamiltonian systems. The thesis is self-contained in the sense that it also includes a brief introduction to Hamiltonian systems, as well as an exposition of Kolmogorov's classic result.Under sin ICM-54 föreläsning introducerade Kolmogorov ett numera fundamentalt resultat angående bevarandet av en måtteoretiskt stor mängd invarianta torusar, inom en viss kategori av nästan intagrabla Hamiltonska system. 44 år senare, under sitt ICM-98 tal, formulerade Herman en förmodan om att en invariant diofantisk torus tillhörande en analytisk Hamiltonian alltid omges av en mängd invarianta KAM torusar av positivt mått. Detta examensarbete bygger vidare på befintliga resultat och ger i fallet tre frihetsgrader ett motexempel till KAM stabilitet kring en invariant torus, i kategorin glatta Hamiltonska system. Arbetet är självtillräckligt i den mening att det även ges en kort introduktion till Hamiltonska system, samt en exposition av Kolmogorovs klassiska resultat.
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Guillemin, François. "Bank Disclosure and Financial Stability." Thesis, Besançon, 2016. http://www.theses.fr/2016BESA0004/document.
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Cette thèse examine l'impact de la transparence informationnelle des banques sur la stabilité financière pendant la période 1990-2013. Elle est composée de deux essais empiriques, un essai théorique, ainsi que d'une revue de la littérature. Le premier chapitre met en lumière la littérature existante, théorique et empirique, qui servira comme tremplin pour le reste de la dissertation, Le chapitre 2 teste les effets de la transparence informationnelle des banques sur les prix des swaps de crédit pendant la crise de la dette souveraine européenne, sut- la période 2010-2013. Les banques les plus transparentes sont les banques qui souffrent le moins de la volatilité des prix des swaps de crédit au moment des annonces de dégradation des notes des états. La transparence, via la gouvernance des marchés financiers participent à améliorer la stabilité financière. Le chapitre 3 teste, théoriquement, les incitations à retirer des déposants en présence d'ambiguïté et dans le cas où l'information est imparfaite. Les résultats montrent que plus leur degré de pessimisme génère une incitation supérieure à retirer leurs dépôts de l'institution dans laquelle ils ont déposés. La combinaison de l'ambiguïté et de l'asymétrie d'information ouvre la porte à de nouvelles perspectives en termes de transparence informationnelle de la part des banques en direction des déposants et participant ainsi à l'amélioration de la stabilité financière en évitant les paniques bancaires. Le chapitre 4 teste empiriquement les résultats obtenus dans le chapitre précédent. Nous testons l'attractivité, pour les déposants, des banques les plus transparentes sur la période 1990-2013 tout en prenant en considération l'ambiguïté. Les résultats confirment que l' ambiguïté a un effet négatif sur le montant des dépôts totaux des banques et que la transparence informationnelle peut activer des incitations au retrait chez les déposantsThis thesis tries to understand the relationship between banking disclosure and financial stability for several actors of bank's governance. Disclosure has a positive impact on financial market participant made possible by a reduction of the information premium. Regarding depositors, we decided to partially reject the hypothesis of perfect rationality by introducing the ambiguity notion. We were able to show that a negative relationship exists between ambiguity and deposit levels bath theoretically and empirically. Disclosure policies have therefore a negative impact on European total deposit empirically
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Houghton, Timothy Oliver. "Axial compressor stability enhancement." Thesis, University of Cambridge, 2010. https://www.repository.cam.ac.uk/handle/1810/252194.
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Aircraft jet engines must operate in a stable manner at all times. One source of instability is compressor stall. Stall problems can be reduced by machining cavities into the compressor casing adjacent to the rotor blades. This ?casing treatment? is the focus of the present work. Two treatment configurations are tested: circumferential grooves cut into the casing above the rotor blades, and axial slots cut into the casing adjacent to the rotor blade leading edges. The performance of a single casing groove is measured at different axial locations over the blade tips. For the first time, it is shown that there are two locations where compressor stability is maximised; near the leading edge and near mid-chord. The interaction between the groove and the compressor flow field is then studied. It is found that when located near the leading edge, the groove has a strong interaction with the near-casing flow and tip leakage vortex, but when located near mid-chord, the interaction is more subtle and less damaging to efficiency. Since the groove works well in both locations, it is concluded that manipulating the tip leakage vortex is not critical for improving compressor stability. Different groove numbers and cross-sections are then tested. For multiple grooves, the effi- ciency reduction is the sum of the constituent grooves, while the stall margin improvement is less than this sum. A simple square-section groove is found difficult to improve on, although in certain circumstances, a new ?intermittent groove? geometry is beneficial. The performance of axial slots is then investigated. Different slot shapes are tested and the results added to previous work to suggest an optimum slot geometry. A computational flow study shows that large variations in blade loading occur as the blades pass the slots, which could cause noise and vibration. It is found that while the flow inside the slot is principally a quasi-steady recirculation, the interaction between the slots and blades is highly unsteady, and this unsteadiness should not be neglected in design. In general, it is found that casing treatments that generate large stability improvements cause large efficiency losses. It is shown for the first time that the performance of casing grooves can be seriously reduced by changes in the stall inception mechanism. Maximum performance is achieved when the treated compressor stalls with a spike inception. Models from the literature are tested, but do not predict the stall inception mechanism well, which makes predicting the performance of casing grooves in a given compressor hard. Finally, it is shown that designing the blades and casing treatment as a unit may improve compressor performance.
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McLean, M. R. "Analysis of wellbore stability." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/7178.
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Finbow, Wendy. "On stability of polytopes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk2/tape15/PQDD_0025/MQ36437.pdf.
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Ernst, P. "Stability of Pit Growth." Thesis, University of Manchester, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520793.
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Kröncke, Klaus. "Stability of Einstein Manifolds." Phd thesis, Universität Potsdam, 2013. http://opus.kobv.de/ubp/volltexte/2014/6963/.
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This thesis deals with Einstein metrics and the Ricci flow on compact mani-
folds. We study the second variation of the Einstein-Hilbert functional on Ein-
stein metrics. In the first part of the work, we find curvature conditions which
ensure the stability of Einstein manifolds with respect to the Einstein-Hilbert
functional, i.e. that the second variation of the Einstein-Hilbert functional at
the metric is nonpositive in the direction of transverse-traceless tensors.
The second part of the work is devoted to the study of the Ricci flow and
how its behaviour close to Einstein metrics is influenced by the variational be-
haviour of the Einstein-Hilbert functional. We find conditions which imply that
Einstein metrics are dynamically stable or unstable with respect to the Ricci
flow and we express these conditions in terms of stability properties of the metric with respect to the Einstein-Hilbert functional and properties of the Laplacian spectrum.Die vorliegende Arbeit beschäftigt sich mit Einsteinmetriken und Ricci-Fluss auf kompakten Mannigfaltigkeiten. Wir studieren die zweite Variation des Einstein- Hilbert Funktionals auf Einsteinmetriken. Im ersten Teil der Arbeit finden wir Krümmungsbedingungen, die die Stabilität von Einsteinmannigfaltigkeiten bezüglich des Einstein-Hilbert Funktionals sicherstellen, d.h. die zweite Varia- tion des Einstein-Hilbert Funktionals ist nichtpositiv in Richtung transversaler spurfreier Tensoren. Der zweite Teil der Arbeit widmet sich dem Studium des Ricci-Flusses und wie dessen Verhalten in der Nähe von Einsteinmetriken durch das Variationsver- halten des Einstein-Hilbert Funktionals beeinflusst wird. Wir finden Bedinun- gen, die dynamische Stabilität oder Instabilität von Einsteinmetriken bezüglich des Ricci-Flusses implizieren und wir drücken diese Bedingungen in Termen der Stabilität der Metrik bezüglich des Einstein-Hilbert Funktionals und Eigen- schaften des Spektrums des Laplaceoperators aus.
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Andersson, Christian. "Rigid Pipelay Curve Stability." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for marin teknikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-25882.
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Pipeline installation would generally involve curved sections in the horizontal plane, due to existing subsea infrastructure or natural seabed characteristics. At a small curve radius, the lateral seabed friction could be insufficient providing on-bottom stability of the pipeline. Hence, additional measures like lateral supports, so called turnpoints, may be required. The effect of installing such turnpoints have been studied in this thesis, using a computer software called SIMLA. Both static and dynamic analyses have been performed in order to preserve the curve stability and control the load effect on the pipeline and the turnpoints. In the static analyses, the pipe is being fed out from the Seven Navica lay vessel. In this way, history effects get introduced as the pipe elements experience the operation from being fed out until it rests on the seabed. The dynamic analyses is carried out at the stage in the laying process that results in the highest dynamic response.The pipeline investigated is a 10" ID production pipeline laid between two templates. The route is assumed to have a constant water depth, and consists of two straight distances having a curved section with a curve radius of 400 [m] in between. In the route, originally 10 turnpoints have been installed. In order to investigate whether this is a over-conservative number, the analyses performed in this thesis have been conducted for 3-10 turnpoints along the route.In the static feeding analysis, the axial friction is turned off during laying. This is done since the results obtained with axial friction activated gave less credible results, as the simulations indicated that the static axial force distribution was changed with increased number of turnpoints. Given that the pipe is assumed laid at a constant water depth, deactivating the axial friction can be justified. The reason is that the constant water depth gives rise to a stable departure angle, and thus an approximately constant tension in the pipe during laying.From the static results, it is found that introducing more turnpoints along the route resulted in a flattening of the equivalent moment-curve. This makes sense, since the distance between the turnpoints is reduced. In the same manner, the contact force between the turnpoints and the pipeline gets reduced, as the force is more distributed and shared between additional supports. It is further noted that both the contact force and the moment is symmetrically distributed over the pipeline curvature. Based on this, symmetry of the problem could probably be exploited, reducing the size of the model.Several parameter studies have been carried out in order to obtain the overall worst case results. Based on the parameter study, the dynamic analysis was set up. The following parameters have been applied in the dynamic analyses:- A current direction of 90° pushing the pipe towards the turnpoint- A touchdown position right behind the last turnpoint.\\- A wave heading of 45°from behind on the vessel, introducing both roll and pitch motion. With a significant wave height of HS = 2.5 [m] and a wave period of TP = 7 [s].The dynamic analysis has been carried out during a 3-hour sea state, prescribed by the Jonswap-spectrum. In order to reduce the computational time running the analyses, the worst response during the sea state was found, and then all the analyses was carried out in a short time interval, based on the most critical time.The dynamic tension in the pipeline increases as more turnpoints are installed, i.e. the system gets stiffer. As the system gets stiffer with more turnpoins installed, the contact force between the turnpoints and the pipeline is actually at its lowest when only 3 turnpoints are installed. This can be explained by the increase of tension in the pipeline. A stiffer system gives higher dynamic response. As far as the moment distribution is concerned, the same applies as for the static analyses, i.e. the moment gets reduced when the number of turnpoints is increased.A local buckling check has been performed in order to control the results against DNV's standard for local buckling. It is found that neither 3 nor 4 turnpoints along the route is sufficient to satisfy the local buckling criteria. Hence, 5 or more turnpoints must be installed. In addition to this criteria, the turnpoints used in the case investigated have a geotechnical capacity of 80 [kN]. The contact force between the turnpoint and pipe must therefore be kept below this capacity.As the turnpoints are installed with a certain turnpoint tolerance, an analysis investigating the effect of such tolerance has been performed. As the tolerance was set to 0.5 [m] in the lateral direction, there was an increase in the contact forces, the moment and the tension in the pipeline. The contact force remained within the geotechnical limitations of the turnpoints utilized. However, the results showed that 5 turnpoints along the curvature is not sufficient to fulfil the local buckling criteria. Hence, installation of 6 turnpoints is proposed. This is lower than the originally 10 turnpoints that have been installed for the case investigated. Hence, the method utilized by Subsea 7 is found to be over-conservative.In order to create a picture of how the turnpoint tolerance affects the results, an analysis has been carried out for 1 [m] lateral tolerance as well. This resulted in a significant increase of moments and contact force between the pipe and the turnpoints. Furthermore, the local buckling utilization is considerably increased when the tolerance is as high as 1 [m] in the lateral direction. It is evident that the turnpoint tolerance is of high importance. Keeping the tolerance as low as possible is essential in order to install as few turnpoints as possible.
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Xu, Guangquan. "Wellbore stability in geomechanics." Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/11475/.
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Borehole instabilities can be encountered at any stage in the life of a well and they are the main cause of drilling difficulties, resulting in substantial expenditures, expensive loss of time, sometimes even in the loss of part of or even whole boreholes. The main aim of this research is to use new method and theory in geomechanics to conduct the stability analysis of wellbore. The cavity contraction theory is used to get the new elastic-perfectly plastic solutions for vertical borehole with anisotropic stress field. The solutions for Mohr-Coulomb and Hoek-Brown criteria are derived in this paper. A new alternative criterion, which is to limit the radius of plastic zone around borehole, to predict the wellbore instability was also recommended. The finite element code ABAQUS is applied to analyse the mechanical behaviour of wells with different inclinations and different azimuths. A Generalized Plane Strain Model is used in the calculation. The failure wellbore pressure, borehole closure, plastic zone distribution of different direction wells are given in this paper. In order to accurately predict the wellbore behaviour in soft and porous rocks, a suitable and advanced constitutive model of rocks is the key issue of the borehole instability research. A new model, called CASM (Clay And Sand Model) which is based on critical state theory and formulated in terms of the state parameter concept is applied in this research. The non-coaxiality theory is incorporated into CASM to analyse the wellbore stability. Compared with coaxial model, non-coaxial model gives more pessimistic results. However, it was found that the influence of non-coaxiality on wellbore stability depended on initial conditions of wellbore.
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Lewington, J. "Plasmid stability in pseudomonads." Thesis, Cardiff University, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373879.
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Malik, Satish Vasudeo. "Stability of interfacial flows." Thesis, University of the West of England, Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431161.
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MORALES, DANIA GONZALEZ. "STABILITY OF MINIMAL SURFACES." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2014. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=24800@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIROCONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO
Este trabalho tem como propósito o estudo da estabilidade de hipersuperfícies mínimas imersas em R n mais 1. Apresentamos algumas caracterizações de hipersuperfícies mínimas deduzindo as fórmulas da primeira e segunda variação do funcional da área. Em seguida, a partir do cálculo de variações, estabelecemos a relação entre a teoria espectral e a estabilidade. Em particular, estudamos a caraterização variacional do primeiro autovalor do operador de estabilidade. Com base nesta relação mostramos alguns critérios de estabilidade para hipersuperfícies mínimas imersas em R n mais 1. Em especial, exibimos em detalhes o critério de estabilidade de Barbosa-Do Carmo para a estabilidade de superfícies mínimas em R3. Assim como o critério de Fischer-Colbrie-Shoen para superfícies mínimas completas, não compactas, usando a teoria elíptica. Concluímos com a análise da estabilidade do catenoide em R3 e em R n mais 1. Obtemos os domínios de estabilidade do catenoide em R3 a partir da teoria de Sturm Liouville. Exibimos o teorema de estabilidade de Lindelof em R3 e em R n mais 1 e a propriedade do catenoide ter índice 1.
This work aims to study the stability of minimally immersed hypersurfaces in R n more 1. We present some characterizations of minimal hypersurfaces deducting the formulas of the first and second variation of area. Afterwards, from the variational calculus, we establish the relationship between spectral theory and stability. Particulary, we study a variational characterization of the first eigenvalue associated to the stability operator. Based in this relationship we show some stability criteria for minimally immersed hypersurfaces in R n more 1. In particular, we exhibit in details the Barbosa-Do Carmo criterion for the stability of minimal surfaces in R3. We also establish the Fischer- Colbrie-Shoen criterion for complete, non compact, minimal surfaces using the elliptic theory. We conclude with the analysis of the stability of the catenoid in R3 and in Rn more 1. This is done by studying the stability domains of the catenoid in R3 using the Sturm-Liouville theory. We explain the Lindelof stability theorem in R3 and in R n more 1 and the property of the catenoids have index 1.
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Bakoush, Mohamed. "Essays on financial stability." Thesis, University of Southampton, 2019. https://eprints.soton.ac.uk/428060/.
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The thesis analyses dynamics of systemic risk and contagion in securitization, interbank and derivatives markets, and the subsequent implications for financial stability and macroprudential policy. In doing so, three distinctive lines of research are pursued. First, we examine the impact of securitization on bank stability and systemic risk. Following this, we analyse distress spillover from the OTC derivatives market into the interbank market, due to the interaction between margin procyclicality in OTC derivatives markets, and funding liquidity risk in the interbank market. Finally, we develop a macroprudential stress test, that explicitly links liquidity risk and solvency risk of banks, as well as account for interconnectedness among them. We provide evidence that securitization activities are destabilizing at both the individual bank level and the banking system level, and tend to increase commonality of asset returns among banks leading to increased interconnectedness and systemic risk. Moreover, we show that distress due to margin procyclicality in the OTC derivatives market can spillover to the interbank market leading to episodes of systemic liquidity risk. We also show that central clearing might increase the possibility of systemic liquidity risk due to tight margin requirements and the timing of cash flows required from banks. Further, using the proposed stress test, we effectively identify the systemic vulnerability of individual banks and the resilience of the banking system as a whole to economic shocks. The results of this thesis have far-reaching policy implications. First, given the current increasing pace in monetary policy tightening, our findings on the destabilizing effect of securitization activities are of great interest to policy makers in their attempts to revive securitization markets, as they provide a framework for regulators to think about the effects of securitization at both the bank level and the banking system level. Moreover, our findings on the negative consequences of margin requirements should inform regulators about the importance of striking the balance between limiting counterparty credit risk through tight margin requirements, and the side effect of increasing the possibility and magnitude of systemic liquidity crises. Finally, the proposed stress test provides an effective tool for the banking system supervisors to analyse the current state of the system stability and to monitor the evolution of contagion and systemic risk within the system.