In this essay I defend the notion of deductive explanation mainly against two types of putative counterexamples: those found in genuinely indeterministic systems and those found in complex dynamic systems. Using Railton's notions of explanatory information and ideal explanatory text, deductivism is defended in an indeterministic setting. Furthermore, an argument against non-deductivism that hinges on peculiarities of probabilistic causality is presented. The use of the notion of an ideal explanatory text gives rise to problems in accounting for explanations in complex dynamic systems, regardless of whether they are deterministic or not. These problems are considered in the essay and a solution is suggested. This solution forces the deductivist to abandon the requirement that an explanation consists of a deductive argument, but it is argued that the core of deductivism is saved in so far as we, for full explanations, can still adhere to the fundamental requirement: If A explains B, then A is inconsistent with anything inconsistent with B.

This thesis deals with different computational techniques related to some classes of nonlinear response regimes of engineering interest. The work is mainly divided into two parts. In the first part different numeric-analytic integration techniques for nonlinear oscillators are developed. In the second part, procedures for handling arbitrarily large rotations are addressed and a few novel developments are reported in the process. To begin the first part, we have proposed an explicit numeric-analytic technique, based on the Adomian decomposition method, for integrating strongly nonlinear oscillators. Numerical experiments suggest that this method, like most other numerical techniques, is versatile and can accurately solve strongly nonlinear and chaotic systems with relatively larger step-sizes. It is then demonstrated that the procedure may also be effectively employed for solving two-point boundary value problems with the help of a shooting algorithm. This has been followed up with the derivation and numerical exploration of variants of a recently developed numeric-analytic technique, the multi-step transversal linearization (MTrL), in the context of nonlinear oscillators of relevance in engineering dynamics. A considerable generalization and improvement over the original form of a MTrL strategy is achieved in this study. Finally, we have used the concept of MTrL method on the nonlinear variational (rate) equation corresponding to a nonlinear oscillator and thus derive another family of numeric-analytic techniques, presently referred to as the multi-step tangential linearization (MTnL). A comparison of relative errors through the MTrL and MTnL techniques consistently indicate a superior quality of approximation via the MTrL route. In the second part of the thesis, a scheme for numerical integration of rigid body rotation is proposed using only rudimentary tensor analysis. The equations of motion are rewritten in terms of rotation vectors lying in same tangent spaces, thereby facilitating vector space operations consistent with the underlying geometric structure of rotation. One of the most important findings of this part of the dissertation is that the existing constant-preserving algorithms are not necessarily accurate enough and may not be ideally applicable to cases wherein numerical accuracy is of primary importance. In contrast, the proposed rotation-algorithms, the higher order ones in particular, are significantly more accurate for conservative rotational systems for reasonably long time. Similar accuracy is expected for dissipative rotational systems as well. The operators relating rotation variables corresponding to different tangent spaces are also investigated and this should provide further insight into the understanding of rotation vector parametrization. A rotation update is next proposed in terms of rotation vectors. This update, employed along with interpolation of relative rotations, gives a strain-objective and path independent finite element implementation of a geometrically exact beam. The method has the computational advantage of requiring considerably less nodal variables due to the use of rotation vector parametrization. We have proposed a new isoparametric interpolation of nodal quaternions for computing the rotation field within an element. This should be a computationally efficient alternative to the interpolation of local rotations. It has been proved that the proposed interpolation of rotation leads to the objectivity of strain measures. Several numerical experiments are conducted to demonstrate the frame invariance, path-independence and other superior aspects of the present approach vis-`a-vis the existing methods based on the rotation vector parametrization. It is emphasized that, in order to develop an objective finite element formulation, the use of relative rotation is not mandatory and an interpolation of total rotation variables conforming with the rotation manifold should suffice.

We describe heterogeneous multi-CPU and multi-GPU implementations of Jacobi's iterative method for the 2-D Poisson equation on a structured grid, in both single- and double-precision. Properly tuned, our best implementation achieves 98% of the empirical streaming GPU bandwidth (66% of peak) on a NVIDIA C1060. Motivated to find a still faster implementation, we further consider "wildly asynchronous" implementations that can reduce or even eliminate the synchronization bottleneck between iterations. In these versions, which are based on the principle of a chaotic relaxation (Chazan and Miranker, 1969), we simply remove or delay synchronization between iterations, thereby potentially trading off more flops (via more iterations to converge) for a higher degree of asynchronous parallelism. Our relaxed-synchronization implementations on a GPU can be 1.2-2.5x faster than our best synchronized GPU implementation while achieving the same accuracy. Looking forward, this result suggests research on similarly "fast-and-loose" algorithms in the coming era of increasingly massive concurrency and relatively high synchronization or communication costs.

Dans le but de clarifier les aspects dynamiques des modèles galactiques triaxiaux, le potentiel logarithmique est étudié a travers la méthode d'analyse en fréquence. Les caractéristiques dynamiques principales du système sont présentées en utilisant le formalisme hamiltonien approprié. Afin de comparer cette nouvelle approche avec des études précédentes, la méthode est appliquée a la version axisymétrique du potentiel. La précision de la méthode est démontrée a travers des techniques de perturbation et des transformations numériques en variables action-angle. En outre, la construction des applications fréquence pour plusieurs valeurs du paramètre de perturbation permet de fournir une vision globale de la dynamique du potentiel plan. Les zones chaotiques, les résonances importantes ainsi que les orbites périodiques sont détectées. La méthode est appliquée ensuite a la version tridimensionnelle du potentiel logarithmique. Les approximations quasi-périodiques fournies par la méthode permettent de clarifier la dynamique des types d'orbites principales et leur connexion avec des perturbations du hamiltonien général. Tous les détails fins de la dynamique, qui sont associés a l'addition du troisième degré de liberté, sont représentés dans les applications fréquence complètes, des images instantanées du réseau d'Arnold (''Arnol'd web'') du système. Ainsi, nous pouvons visualiser l'étendu des zones chaotiques et l'influence des lignes résonantes dans l'espace physique du système. Cette approche révèle plusieurs caractéristiques dynamiques inconnues des potentiels galactiques triaxiaux et indique que le chaos doit être une caractéristique importante des configurations triaxiales. Nous discutons finalement l'influence de ces résultats sur la construction des modèles galactiques auto-consistants.

Thesis (MA)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: The advent of the computer age has seen many fundamental changes in the economics. The ease with which organisations can store and transmit information in unprecedented quantities and speeds has changed the face of the economy as well as the way in which organisations conduct their day to day operations. Information has become the primary resource for organisational competitiveness and this has seen an increasing drive for efficient information generation and management in an economy that is interconnected on a global scale. The demand for better information management practices is driven by the realisation that the global economy is susceptible to sudden and unpredictable changes that can potentially have global consequences. The more information organisations have at their disposal, the better their chances are of remaining competitive and relevant in the global economy. The informational economy confronts organisations with two very significant problems, the first is information overload due to the sheer volume of information that is available to them. The second problem is that despite the volume of available information organisations still are not privy to all the information that is required to lessen the impact of uncertainty that is so characteristic of the global economy. Organisations therefore always run the' risk of becoming irrelevant if they do not change constantly. This drive for continuous change and the dependence on information has led some organisational theorists and economists to compare the global economy and organisations to nonlinear systems found in nature. Examples of nonlinear systems are living organisms, ecologies and solar systems. All of these systems are characterised by high levels of interconnectedness and interdependence among individual units within a shared environment, which they co-create. Nonlinear systems are of particular interest to organisational theorists because these systems process information about the environment to adapt in an unpredictable way to unpredictable changes. Such systems are incredibly resilient because they are able to learn and adapt to different conditions. Another notable aspect of nonlinear systems is the clear structured and complex organisation that they exhibit in the absence of centralised control mechanisms. Every unit has the liberty to experiment with new designs and from the success of individual units an organised and stable system emerges with a strong link between the success of individuals and the whole system. The order that exists within nonlinear systems is known as self-organisation because it is not superimposed but emerges instead in a spontaneous manner. Nonlinear systems are therefore more than just the sum of their parts. The notion of nonlinear systems and self-organisation has seen authors such as Stacey, Wheatley and Senge develop new ideas about organisational development, leadership and organisational strategic thinking. Their ideas are based on what is popularly known as 'The New Science'. These ideas attempt to encourage organisations realise that the global economy functions as a nonlinear system and that organisations stand a better chance of success if they learn to understand the principles of nonlinear systems and to utilise the inherent creative and organising characteristics of such systems. / AFRIKAANSE OPSOMMING: Die aanvang van die rekenaar era het verskeie fundamentele veranderinge in ekonomie mee gebring. Die gemak en snelheid waarmee organisasies informasie kan stoor en versprei is ongekend en het terselfde tyd die voorkoms van die ekonomie verander asook die wyse waarop organisasies op 'n daaglikse basis funksioneer. Informasie het die belangrikste hulpbron geword vir organisasies in terme van kompetering en dit het 'n groter dryfkrag vir doeltreffende informasie ontginning en bestuur mee gebring in 'n ekonomie wat op 'n wereldwye skaal in mekaar gevleg is. Die aanvraag vir beter informasie bestuur praktyke word gedryf deur die wete dat die wereld ekonomie vatbaar is vir skielike en onvoorspelbare veranderinge wat potensieel 'n wereldwye impak kan he. Hoe meer informasie organisasies tot hul beskikking het hoe beter is hul kans om relevant en kompeterend te bly in die wereld ekonomie. Die informasie ekonomie konfronteer organisasies met twee fundamentele probleme. Die eerste gevaar is dat organisasies oorlaai kan word met informasie as gevolg van die absolute volume van beskikbare informasie. Die tweede probleem spruit voort uit die feit dat ten spyte van die beskikbare informasie, lei organisasies steeds aan 'n gebrek aan algehele informasie, organisasies kan dus nooit toegang he tot al die informasie wat benodig word om die impak te verminder van die onsekerheid wat so kenmerkend is van die wereld ekonomie. Organisasies loop dus altyd die gevaar om irrelevant te raak as hulle nie konstant aanpas by nuwe omstandighede nie. Hierdie soeke na konstante verandering en die afhanklikheid op informasie het verskeie organisasie teoretici en ekonome daartoe gelei om 'n vergelyking te tref tussen die wereld ekonomie en organisasies aan die een kant en nie-Iiniere sisteme wat in die natuur voorkom. Voorbeelde van sulke sisteme sluit lewende organismes, ekostelsels en sterre stelsels in. Die komponente van al hierdie sisteme is op 'n komplekse wyse inmekaar geweef en interafhanklik op mekaar binne die raamwerk van gemeenskaplike omgewing waarvoor hierdie komponente mede verantwoordelik is. Nie-liniere sisteme is van besondere belang vir organisasie teoretici omdat die betrokke sisteme informasie verwerk aangaande hul omgewing om op 'n onvoorspelbare wyse aan te pas by onvoorspelbare veranderinge in die omgewing. Sulke sisteme is uitsonderlik standvastig deurdat hulle kan leer en aanpas by verskillende omstandighede. Nog 'n merkbare aspek van sulke sisteme is die duidelik gestruktureerde en komplekse organisasie wat bestaan ten spyte van 'n algehele gebrek aan gesentraliseerde beheer meganismes. Elke komponent is vry om met 'n nuwe ontwerp te eksperimenteer en vanuit die sukses van die komponente spruit die sukses van die sisteem. Die organisasie wat sigbaar is in nie-liniere sisteme staan bekend as self-organisasie omdat dit nie voortspruit uit 'n sentrale beheer meganisme nie maar instede spontaan onstaan as 'n gevolg van die aksies van komponente. Nie-Iiniere sisteme het die potensiaal om meer te kan wees as die somtotaal van hul komponente. Die beginsel van nie-liniere sisteme en selforganisasie het skrywers soos Stacey, Wheatley en Senge daartoe gelei om nuwe idees te ontwikkel rakende organisasie ontwikkeling, leierskap en strategiese beplanning in organisasies. Hierdie idees is gegrond in wat algemeen bekend staan as 'The New Science'. Die idees van hierdie skrywers is gemik daarop om organisasies aan te moedig om raak te sien dat die wereld ekonomie soos 'n nie-liniere sisteem funksioneer en dat organisasies as sulks 'n beter kans staan om sukses te behaal as hulle sou leer om die beginsels van nie-liniere sisteme te begryp en die inherente kreatiewe en organiserings eienskappe van sulke sisteme uit te buit.

Cette thèse considère quatre systèmes physiques complexes pour lesquels il est exceptionnellement possible d’identifier des variables lentes qui contrôlent l'évolution à temps long du système complet. La séparation d'échelle de temps entre ces variables lentes et les autres variables permet d'utiliser la technique de moyennisation stochastique pour obtenir une dynamique effective pour les variables lentes. Cette thèse considère la possibilité de prédire les événements rares dans le système solaire. Nous avons étudié deux types d’événements rares. Le premier est un renversement possible de l'axe de rotation de la Terre en l'absence des effets de marée de la Lune. Le second est la désintégration de l'ensemble du système solaire interne suite à une instabilité dans l'orbite de Mercure. Pour chacun des deux problèmes, il existe des variables lentes non triviales, qui ne sont pas données par des variables physiques naturelles. La moyennisation stochastique a permis de découvrir le mécanisme physique qui conduit à ces événements rares et de donner, par une approche purement théorique, l'ordre de grandeur de la probabilité de ces phénomènes. Nous avons également montré que la déstabilisation de Mercure sur un temps inférieur à l'âge du système solaire obéit à un mécanisme d'instanton bien décrit par la théorie des grandes déviations. Le travail effectué dans cette thèse ouvre donc un nouveau champ d'action pour l'utilisation d'algorithmes de calcul d'événements rares. Nous avons utilisé pour la première fois les théorèmes de moyennisation stochastique dans le cadre de la mécanique céleste pour quantifier l'effet stochastique des astéroïdes sur la trajectoire des planètes. Enfin, une partie du travail porte sur un problème de turbulence géophysique: dans l'atmosphère de Jupiter, on peut observer des structures zonales (jets) à grande échelles évoluant beaucoup plus lentement que les tourbillons environnants. Nous montrons qu'il est pour la première fois possible d'obtenir explicitement le profil de ces jets par moyennisation des degrés de liberté turbulents rapides. / The present thesis describes four complex dynamical systems. In each system, the long-term behavior is controlled by a few number of slow variables that can be clearly identified. We show that in the limit of a large timescale separation between the slow variables and the other variables, stochastic averaging can be performed and leads to an effective dynamics for the set of slow variables. This thesis also deals with rare events predictions in the solar system. We consider two possible rare events. The first one is a very large variation of the spin axis orientation of a Moonless Earth. The second one is the disintegration of the inner solar system because of an instability in Mercury’s orbit. Both systems are controlled by non-trivial slow variables that are not given by simple physical quantities. Stochastic averaging has led to the discovery of the mechanism leading to those rare events and gives theoretical bases to compute the rare events probabilities. We also show that Mercury’s short-term destabilizations (compared to the age of the solar system) follow an instanton mechanism, and can be predicted using large deviation theory. The special algorithms devoted to the computation of rare event probabilities can thus find surprising applications in the field of celestial mechanics. We have used for the first time stochastic averaging in the field of celestial mechanics to give a relevant orders of magnitude for the long-term perturbation of planetary orbits by asteroids. A part of the work is about geophysical fluid mechanics. In Jupiter atmosphere, large scale structures (jets) can be observed, the typical time of evolution of which is much larger than that of the surrounding turbulence. We show for the first time that the mean wind velocity can be obtained explicitly by averaging the fast turbulent degrees of freedom.

This thesis constitutes a narrative that explores an alternative meaning construction for the experience of loss. During the telling of this story, I consider the appropriateness of adopting the 'new paradigm' approach for this particular thesis, and the constructivist and social constructionist epistemological assumptions underlying such an approach. I delve into the use of 'self as researcher under this epistemological umbrella. This is followed by an exploration of 'chaos theory' and its application to social systems. And finally, I consider the usefulness of this theory in constructing meanings for loss experiences on various systemic levels within my own family system. / Psychology / M.A.(Clinical Psychology)

The concept of strategy has advanced significantly from when the emphasis fell on comprehensive, systematic and rational planning. However, many of the assumptions that were embedded in traditional strategy models were deemed to be inadequate and outdated as we approached a new competitive milieu (Maritz, 2010). Strategic Management is still a comparatively young field and the existing toolbox of concepts and techniques remains woefully inadequate (Grant, 2010). This reality should force a re-examination of the traditional strategy paradigms (Maritz, 2010). The literature review has confirmed the observations by Maritz (2010) and Grant (2010) that indeed current strategic management paradigms or approaches were inadequate for unique business environments obtaining in a developing country in Africa, such as Zimbabwe. The motivation for this research, therefore, was to identify and recommend strategic management approaches or paradigms applicable to banks operating in a turbulent and chaotic environment. Based on an extensive literature review, in-depth interviews were conducted with six commercial banks (three that survived the turbulence and three that failed) during the period under review. The study established that the banks that survived the turbulence had a different strategic management approach from the traditional designed ones. It was also noted in this study that in turbulent environments, strategy-making is birthed through an emergent process. When events are moving at an unprecedented speed, as was happening in Zimbabwe, the time intervals between obtaining information, analysing information, taking decisions and implementing those decisions need to be tightly compressed. The researcher coined this process Strategic Intensity (SI). On the other hand, diversification as a strategy was found to be very risky for businesses that did not have a strong foundation and that were lacking in the appreciation of the risk complexion of the businesses into which they were diversifying. This research makes a significant contribution by identifying and recommending Strategic Management approaches applicable to businesses operating in a turbulent and chaotic environment in developing markets such as Zimbabwe. Furthermore, this research also contributes towards the current debate in academic literature amongst practitioners of strategy, about how strategy is really made in organisations (Maritz, 2010). The debate centres around two opposing views: one associated with strategy-making as a formal, deliberate plan, and the other associated with strategies as evolving, ever-changing sets of outcomes that are eventually realised. Finally, the researcher proposes that further studies be conducted at the end of this study. / Business Management / DBL

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Submitted by Bruna Rodrigues (bruna92rodrigues@yahoo.com.br) on 2016-10-04T14:03:27Z No. of bitstreams: 1 DissDPL.pdf: 3012901 bytes, checksum: 29c2df84e5e59e8e598fae154f0983d2 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-14T14:18:34Z (GMT) No. of bitstreams: 1 DissDPL.pdf: 3012901 bytes, checksum: 29c2df84e5e59e8e598fae154f0983d2 (MD5) / Approved for entry into archive by Marina Freitas (marinapf@ufscar.br) on 2016-10-14T14:18:43Z (GMT) No. of bitstreams: 1 DissDPL.pdf: 3012901 bytes, checksum: 29c2df84e5e59e8e598fae154f0983d2 (MD5) / Made available in DSpace on 2016-10-14T14:18:52Z (GMT). No. of bitstreams: 1 DissDPL.pdf: 3012901 bytes, checksum: 29c2df84e5e59e8e598fae154f0983d2 (MD5) Previous issue date: 2016-03-04 / Não recebi financiamento / Kalman filters are rooted in the technical literature, as a way of predicting new states in nonlinear systems providing a recursive solution to the problem of linear optimal filtering. Therefore, 56 years after its discovery, many modifications have been proposed in order to obtain better accuracy and speed. Some of these changes are used in this work; these being the Extended Kalman Filter (EKF), Unscented Kalman Filter (UKF) and Kalman Filter Cubature (CKF). This work , divided into three distinct parts: Implementation / Comparative analysis of prediction of Kalman filters in complex systems (Series), qualitative analysis of the possible uses of the Kalman filter variants for neural network training and position and velocity determination a displaced object on a simulated plane with some trajectories Having these analyzes key role in fostering the studies cited in the scientific literature , proving the possibility of such algorithms and methods are used for positioning in unstructured environments / Filtros de Kalman estão consagrados na literatura técnica, como uma das formas de prever novos estados em sistemas não-lineares, fornecendo uma solução recursiva para o problema da filtragem ideal linear. Após 56 anos de sua descoberta, muitas modificações e melhorias foram propostas, procurando obter uma maior precisão e velocidade na predição de novos estados. Algumas dessas mudanças são utilizadas neste trabalho; sendo elas o Filtro de Kalman Estendido (EKF), Unscented Kalman Filter (UKF) e Filtro de Kalman de Cubagem Esférica Radial (CKF).O objetivo deste trabalho, divido em três partes distintas, porém complementares: Implementação/Análise comparativa da predição dos Filtros de Kalman em sistemas complexos (Series), Análise qualitativa das possíveis utilizações das variantes do Filtro de Kalman para treinamento de Redes Neurais e Determinação de posição e velocidade de um objeto deslocado sobre um plano simulado. Possuindo essas análises papel fundamental na fomentação dos estudos citados na literatura científica durante o trabalho, e comprovando a possibilidade desses algoritmos/ métodos serem utilizados em tarefas de posicionamento em ambientes não estruturados.