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Halimi, Meriem. "Observation et détection de modes pour la synchronisation des systèmes chaotiques : une approche unifiée." Phd thesis, Université de Lorraine, 2013. http://tel.archives-ouvertes.fr/tel-00942426.
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Le travail développé dans ce manuscrit porte sur la synchronisation des systèmes chaotiques. Il est articulé autour de deux axes principaux : la synthèse d'observateur et la détection de modes. Dans un premier temps, quelques rappels sur le chaos et les principales architectures de systèmes de chi ffrement chaotiques sont e ffectués. Ensuite, nous montrons comment les systèmes chaotiques à non linéarité polynomiale ou affi nes à commutation peuvent se réécrire sous forme LPV polytopique. Une revue des principaux résultats sur la synthèse d'observateurs LPV polytopiques reposant sur l'utilisation des LMI est faite. Une extension des résultats aux observateurs polytopiques à entrées inconnues, à la fois dans le cas déterministe, bruité ou incertain est proposée. Ces observateurs assurent la synchronisation du chaos et donc le déchiff rement dans les systèmes de chiff rement "modulation paramétrique", "commutation chaotique", "transmission à deux canaux" et "chiff rement par inclusion". Pour les systèmes a ffines à commutation utilisés en tant que générateur du chaos, le cas où l'état discret n'est pas accessible est considéré. Une présentation unifi ée des méthodes fondées sur les espaces de parité, proposées dans la littérature pour les systèmes linéaires et affi nes à commutation à temps discret, est réalisée. Le problème de discernabilité fait l'objet d'une étude approfondie. Une approche pour estimer les retards variables des systèmes a ffines et affi nes à commutation à temps discret, formulée en termes de détection de modes, est proposée en tant que solution à l'estimation de retard pour le chiff rement par injection de retard.
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Papaphilippou, Apostolos D. "Essays on chaotic macroeconomics." Thesis, University of Cambridge, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387675.
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Cai, Qin. "Detecting Chaotic Signals with Nonlinear Models." PDXScholar, 1993. https://pdxscholar.library.pdx.edu/open_access_etds/4564.
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In this thesis we apply chaotic dynamic data analysis to the area of discrete time signal processing. A newly developed Hidden Filter Hidden Markov Model is introduced in detection of chaotic signals. Numerical experiments have verified that this novel nonlinear model outperforms linear AR model in detecting chaotic signals buried by noise having similar power spectra. A simple Histogram Model is proposed which can also be used to do detection on the data sets with chaotic behavior. Receiver Operating Characteristics for a variety of noise levels and model classes are reported.
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Zhao, Yajing. "Chaotic Model Prediction with Machine Learning." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8419.
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Chaos theory is a branch of modern mathematics concerning the non-linear dynamic systems that are highly sensitive to their initial states. It has extensive real-world applications, such as weather forecasting and stock market prediction. The Lorenz system, defined by three ordinary differential equations (ODEs), is one of the simplest and most popular chaotic models. Historically research has focused on understanding the Lorenz system's mathematical characteristics and dynamical evolution including the inherent chaotic features it possesses. In this thesis, we take a data-driven approach and propose the task of predicting future states of the chaotic system from limited observations. We explore two directions, answering two distinct fundamental questions of the system based on how informed we are about the underlying model. When we know the data is generated by the Lorenz System with unknown parameters, our task becomes parameter estimation (a white-box problem), or the ``inverse'' problem. When we know nothing about the underlying model (a black-box problem), our task becomes sequence prediction. We propose two algorithms for the white-box problem: Markov-Chain-Monte-Carlo (MCMC) and a Multi-Layer-Perceptron (MLP). Specially, we propose to use the Metropolis-Hastings (MH) algorithm with an additional random walk to avoid the sampler being trapped into local energy wells. The MH algorithm achieves moderate success in predicting the $\rho$ value from the data, but fails at the other two parameters. Our simple MLP model is able to attain high accuracy in terms of the $l_2$ distance between the prediction and ground truth for $\rho$ as well, but also fails to converge satisfactorily for the remaining parameters. We use a Recurrent Neural Network (RNN) to tackle the black-box problem. We implement and experiment with several RNN architectures including Elman RNN, LSTM, and GRU and demonstrate the relative strengths and weaknesses of each of these methods. Our results demonstrate the promising role of machine learning and modern statistical data science methods in the study of chaotic dynamic systems. The code for all of our experiments can be found on \url{https://github.com/Yajing-Zhao/}
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Tsujimoto, Tsunehiro. "Calibration of the chaotic interest rate model." Thesis, University of St Andrews, 2010. http://hdl.handle.net/10023/2568.
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In this thesis we establish a relationship between the Potential Approach to interest rates and the Market Models. This relationship allows us to derive the dynamics of forward LIBOR rates and forward swap rates by modelling the state price density. It means that we are able to secure the arbitrage-free condition and positive interest rate feature when we model the volatility drifts of those dynamics. On the other hand, we develop the Potential Approach, particularly the Hughston-Rafailidis Chaotic Interest Rate Model. The early argument enables us to infer that the Chaos Models belong to the Stochastic Volatility Market Models. In particular, we propose One-variable Chaos Models with the application of exponential polynomials. This maintains the generality of the Chaos Models and performs well for yield curves comparing with the Nelson-Siegel Form and the Svensson Form. Moreover, we calibrate the One-variable Chaos Model to European Caplets and European Swaptions. We show that the One-variable Chaos Models can reproduce the humped shape of the term structure of caplet volatility and also the volatility smile/skew curve. The calibration errors are small compared with the Lognormal Forward LIBOR Model, the SABR Model, traditional Short Rate Models, and other models under the Potential Approach. After the calibration, we introduce some new interest rate models under the Potential Approach. In particular, we suggest a new framework where the volatility drifts can be indirectly modelled from the short rate via the state price density.
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Yannacopoulos, A. N. "Diffusion models in strongly chaotic Hamiltonian systems." Thesis, University of Warwick, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357654.
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Jamison, Sharon Linda. "Chaotic behaviour in looped car following models." Thesis, University of Ulster, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.442372.
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Selemani, Kamardine. "Analyse et optimisation des chambres réverbérantes à l'aide du concept de cavité chaotique ouverte." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1043/document.
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Ce travail porte sur l'optimisation de la géométrie de chambre réverbérante en s'inspirant du concept de cavité chaotique. Les chambres réverbérantes (RC) sont de plus en plus utilisées comme moyen de test de compatibilité électromagnétique. Elles sont utilisées au-delà d'une fréquence minimale à parti de laquelle les champs sont, dans le volume central de la cavité, statistiquement homogènes et isotropes ; l'obtention de ces propriétés statistiques nécessite l'utilisation d'un mécanisme de brassage, pouvant être mécanique ou électronique. Or, dans les cavités chaotiques, la plupart des modes sont associés à des champs statistiquement homogènes et isotropes, et ceci sans avoir recours à aucun brassage. C'est pourquoi un rapprochement entre chambres réverbérantes et cavités chaotiques a été fait dans ce travail.En premier lieu, nous nous intéressons à des cavités chaotiques 2D obtenues par des modifications successives d'une cavité rectangulaire. Les mesures effectuées dans ces cavités à l'aide d'une théorie perturbative, validées par des résultats de simulation, montrent qu'un champ électrique homogène est obtenu. Les principes retenus pour modifier la géométrie de la cavité rectangulaire seront repris dans les cavités 3D.Les propriétés de trois cavités 3D obtenues en modifiant une cavité parallélépipédique sont étudiées et comparées à celles d'une chambre réverbérante classique munie d'un brasseur de modes. Les modes propres et fréquences de résonance sont déterminés pour ces quatre cavités à l'aide du logiciel HFSS d'Ansoft, tout d'abord en considérant des cavités de géométrie figée, puis en y incluant un brassage mécanique.L'étude de l'homogénéité et de l'isotropie des modes propres montre clairement que les meilleures performances sont obtenues pour une des cavités chaotiques proposées, et ceci quels que soient les critères utilisés.Par ailleurs, il est montré que, dans la chambre réverbérante classique, un grand nombre de modes présente une forte localisation spatiale de l'énergie électrique, alors que ce phénomène ne se produit pas dans la cavité chaotique retenue. Ce phénomène, non détectable par les mesures classiquement effectuées en chambre réverbérante, est dommageable à l'obtention des propriétés d'homogénéité et d'isotropie requises dans le volume de travail.Enfin, l'étude de la distribution des écarts entre fréquences de résonance montre, comme prédit par la Théorie des Matrices Aléatoire, une concordance entre le suivi de la loi asymptotique prévue dans une cavité chaotique et les propriétés d'homogénéité et d'isotropie des champs. Ceci ouvre la voie vers l'utilisation de critères de caractérisation basés sur les fréquences de résonance et non plus uniquement sur les distributions des champsThis work deals with the optimization of the geometry of a reverberation chamber, drawing inspiration from the concept of chaotic cavity. Reverberation chambers, widely used for electromagnetic compatibility tests, are used above a minimal frequency from which the fields are statistically isotropic and uniform; however to respect these properties, a mode stirring process is necessary, that can be mechanical or electronic. As, in chaotic cavities, most modes are isotropic and uniform without the help of any stirring process, we take advantage of the knowledge gained from the studies of chaotic cavities to optimize reverberation chamber behavior.We firstly consider 2D chaotic cavities obtained by modifying a rectangular cavity. Measurements besed on a perturbative approch, and validated by simulations, show uniformly distributed electric fields. Similar geometrical modifications are then proposed in 3D.Three 3D different geometries of cavities obtained from a 3D rectangular cavity are then studied, and their properties are compared with those of a classical reverberation chamber equipped witdh a mode stirrer. Eigenmodes and resonant frequencies are determined numerically using Ansoft HFSS software, first by considering fixed cavity geometries, then by moving the stirrer.Electric field uniformity and isotropy are studied using several criteria; all of them clearly show that the best performances are attained within one of the proposed chaotic cavities.Moreover, a strong energy localization effect appears for numerous modes in the classical reverberation chamber, whereas it is not observed in the proposed 3D chaotic cavity. This effect, never reported in reverberation chamber studies, affects the field uniformity and isotropy within the working volume.The cavities properties are also compared width respect to their eigenfrequency spacing distributions. As predicted by the Random matrix Theory, the best agrement width the asymptotic law associated to chaotic cavities corresponds to the best field properties in terms of uniformity and isotropy. It leads to the proposal of reverberation chamber characterization criteria based on resonant frequencies instead of field distributions
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Alhawarat, Mohammad Omar Ibrahim. "Learning and memory in chaotic spiking neural models." Thesis, Oxford Brookes University, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.444297.
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Mizuno, Yoshinori. "Chaotic mixing in a model of static mixer." 京都大学 (Kyoto University), 2005. http://hdl.handle.net/2433/145321.
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Schwiete, Georg. "Supermatrix models for disordered, chaotic and interacting electron systems." [S.l.] : [s.n.], 2004. http://deposit.ddb.de/cgi-bin/dokserv?idn=973471522.
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Trunins, Jevgenijs. "Experimental and mathematical investigation of the chaotic dripping mode." Thesis, Kingston University, 2018. http://eprints.kingston.ac.uk/41115/.
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The dynamics of fluid flow unveils complicated dynamical behaviour. Systems such as a dripping tap are no exception. Flow through a nozzle produces three different modes: periodic dripping, chaotic dripping and jetting streams. This research concentrates on a study of the chaotic behaviour of a dripping tap. This involves both mathematical model studies and experimental studies. In addition, the work involves the development of an experimental facility to allow future study of the system in microgravity conditions. The facility to achieve microgravity conditions is a Drop Tower type, which uses a novel approach to achieve these conditions. The novelty is in the use of linear electromagnetic motors. The facility was built and is in the final stage of the commissioning process, and when it is ready it will allow up to 2.12 s of test time. The mathematical model uses an existing Mass-Spring-Damper model, with Reynolds numbers between 4 to 175, and a step size of 0.4. The results showed multiple bifurcation regions appearing before chaotic regions. Similarly, experimental results showed that some instabilities exist in this region. The model also explained and showed multiple bifurcations and an increase in dripping time due to instabilities, and has identified that those processes are due either to perturbations of the system or due to initial instabilities of the system. These results were confirmed by experiment. To achieve the required experimental goals a test module was developed whose requirements were set to fulfil the microgravity experiment conditions, in case future research is required. The experimental results showed some similarities with the mathematical model. At the same time, there was found to be quite a lot of disagreement. Results identified two different limit cycle attractors in periodic dripping mode: strong single-point attractors and regional attractors. Also, limit cycle attractors and strange attractors in chaotic mode were identified. More importantly, it has been identified that the chaotic region consists of areas where the system is stable (and produces a single region attractor), and others where the system is not (and this produces strange attractors), and there are points where, depending on the disturbances to the system, both types can be observed. The work done has led to several discoveries and achievements. Although the Drop Tower project could not be completed it may nonetheless be considered as a success. The facility has been fully assembled and calibrated to meet the set of design requirements, and to some extent was commissioned allowing future progress to discover modification requirements. The study of the Mass-Spring-Damper model led to the conclusion that the model is oversimplified and in its current state should be used only for descriptive purposes, when illustrating chaotic behaviour. Additionally, it was found that the model predicts bifurcations outside the experimentally determined chaotic region. Nevertheless, the work identified some possible improvements to the model. Experimentally it was found that the region of chaotic behaviour is located around a Reynolds number of 43 in contrast to what was previously reported. The study of the periodic dripping region showed that the system, if disturbed, can develop history dependent phenomena (where the subsequent drop periods follow a well identified sequence). Satellite drops were discovered to exist beyond the previously predicted value of flow rate. It was discovered that the fluid supply system can have a major effect on the drop dynamics (different types of post-detachment developments were found - termed here regular residual mass and wetted mass - along with the discovery of different types of drop detachment (regular mass, mid-size drops and jets) coexisting within the chaotic region. The drop horizontal disturbance study led to the unconfirmed discovery of two modes of vibrations, where the system response follows a standard damped response and an amplitude modulated damped response.
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Pilolli, Massimo <1966>. "A dynamical system approach to data assimilation in chaotic models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2008. http://amsdottorato.unibo.it/984/.
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The Assimilation in the Unstable Subspace (AUS) was introduced by Trevisan and Uboldi
in 2004, and developed by Trevisan, Uboldi and Carrassi, to minimize the analysis and forecast
errors by exploiting the flow-dependent instabilities of the forecast-analysis cycle system, which
may be thought of as a system forced by observations. In the AUS scheme the assimilation is
obtained by confining the analysis increment in the unstable subspace of the forecast-analysis
cycle system so that it will have the same structure of the dominant instabilities of the system.
The unstable subspace is estimated by Breeding on the Data Assimilation System (BDAS). AUS-
BDAS has already been tested in realistic models and observational configurations, including a
Quasi-Geostrophicmodel and a high dimensional, primitive equation ocean model; the experiments
include both fixed and“adaptive”observations. In these contexts, the AUS-BDAS approach greatly
reduces the analysis error, with reasonable computational costs for data assimilation with respect,
for example, to a prohibitive full Extended Kalman Filter.
This is a follow-up study in which we revisit the AUS-BDAS approach in the more basic, highly
nonlinear Lorenz 1963 convective model. We run observation system simulation experiments in a
perfect model setting, and with two types of model error as well: random and systematic. In the
different configurations examined, and in a perfect model setting, AUS once again shows better
efficiency than other advanced data assimilation schemes. In the present study, we develop an
iterative scheme that leads to a significant improvement of the overall assimilation performance
with respect also to standard AUS. In particular, it boosts the efficiency of regime’s changes
tracking, with a low computational cost.
Other data assimilation schemes need estimates of ad hoc parameters, which have to be tuned
for the specific model at hand. In Numerical Weather Prediction models, tuning of parameters —
and in particular an estimate of the model error covariance matrix — may turn out to be quite
difficult. Our proposed approach, instead, may be easier to implement in operational models.
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Lyubchyk, Leonid, and Galina Grinberg. "Inverse Dynamic Models in Chaotic Systems Identification and Control Problems." Thesis, Ternopil National Economic University, 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/36824.
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Inverse dynamic models approach for chaotic system synchronization in the presence of uncertain parameters is considered. The problem is identifying and compensating unknown state-dependent parametric disturbance describing an unmodelled dynamics that generates chaotic motion. Based on the method of inverse model control, disturbance observers and compensators are synthesized. A control law is proposed that ensures the stabilization of chaotic system movement along master reference trajectory. The results of computational simulation of controlled Rösller attractor synchronization are also presented.
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WANG, XIN. "A DIGITAL ENCRYPTION AND RECOVERY MODEL USING SELF-SYNCHRONIZING CHAOTIC DYNAMICS." University of Cincinnati / OhioLINK, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1069440508.
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Danforth, Christopher M. "Making forecasts for chaotic processes in the presence of model error." College Park, Md. : University of Maryland, 2006. http://hdl.handle.net/1903/3370.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2006.Thesis research directed by: Applied Mathematics and Scientific Computation Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Hillebrand, Malcolm. "Chaotic Dynamics of Polyatomic Systems with an Emphasis on DNA Models." Doctoral thesis, Faculty of Science, 2021. http://hdl.handle.net/11427/33834.
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In this work we investigate the chaotic behaviour of multiparticle systems, and in particular DNA and graphene models, by applying various numerical methods of nonlinear dynamics. Through the use of symplectic integration techniques—efficient routines for the numerical integration of Hamiltonian systems—we present an extensive analysis of the chaotic behaviour of the Peyrard-Bishop-Dauxois (PBD) model of DNA. The chaoticity of the system is quantified by computing the maximum Lyapunov exponent (mLE) across a spectrum of temperatures, and the effect of base pair disorder on the dynamics is investigated. In addition to the inherent heterogeneity due to the proportion of adenine-thymine (AT) and guanine-cytosine (GC) base pairs, the distribution of these base pairs in the sequence is analysed through the introduction of the alternation index. An exact probability distribution for arrangements of base pairs and their alternation index is derived through the use of Pólya counting theory. We find that the value of the mLE depends on both the base pair composition of the DNA strand and the arrangement of base pairs, with a changing behaviour depending on the temperature. Regions of strong chaoticity are probed using the deviation vector distribution, and links between strongly nonlinear behaviour and the formation of bubbles (thermally induced openings) in the DNA strand are studied. Investigations are performed for a wide variety of randomly generated sequences as well as biological promoters. Furthermore, the properties of these thermally induced bubbles are studied through large-scale molecular dynamics simulations. The distributions of bubble lifetimes and lengths in DNA are obtained and discussed in detail, fitted with simple analytical expressions, and a physically justified threshold distance for considering a base pair to be open is proposed and successfully implemented. In addition to DNA, we present an analysis of the dynamical stability of a planar model of graphene, studying the behaviour of the mLE in bulk graphene sheets as well as in finite width graphene nanoribbons (GNRs). The wellattested stability of the material manifests in a very small mLE, with chaos being a slow process in graphene. For both possible kinds of GNR, armchair and zigzag edges, the mLE decreases with increasing width, asymptotically reaching the bulk behaviour. This dependence of the mLE on both energy density and ribbon width is fitted accurately with empirical expressions.
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Dimassi, Habib. "Synchronisation des systèmes chaotiques par observateurs et applications à la transmission d'informations." Phd thesis, Université Paris Sud - Paris XI, 2012. http://tel.archives-ouvertes.fr/tel-00856590.
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Dans ce travail de thèse, nous développons des méthodes de synchronisation des systèmes chaotiques pour les applications de transmission d'informations. La première méthode de synchronisation que nous proposons est basée sur les observateurs adaptatifs à entrées inconnues pour une classe des systèmes chaotiques présentant des incertitudes paramétriques et des perturbations dans leurs dynamiques et du bruit dans les signaux de sortie (bruit dans le canal de communication). La méthode développée repose sur les techniques adaptatives pour la compensation des non-linéarités et des incertitudes paramétriques et pour la restauration des messages transmis. Elle se base également sur les méthodes de synthèse d'observateurs à entrées inconnues pour supprimer l'influence des perturbations et du bruit. Ensuite, nous développons une deuxième méthode de synchronisation utilisant un observateur adaptatif à ''modes glissants" pour une classe des systèmes chaotiques présentant des entrées inconnues et dont les signaux de sortie sont bruités. La synthèse de l'observateur s'appuie sur la théorie des modes glissants, les techniques de synthèse d'observateurs singuliers et les techniques adaptatives dans le but d'estimer conjointement l'état et les entrées inconnues malgré la présence du bruit dans les équations de sortie. Cette approche de synchronisation est ensuite employée dans un nouveau schéma de communication chaotique sécurisée dont l'objectif est d'augmenter le nombre et l'amplitude des messages transmis, améliorer le niveau de sécurité ainsi que la robustesse aux bruits présents dans le canal de communication. En outre, le scénario de présence des retards de transmission est étudié en élaborant une troisième approche de synchronisation à base d'observateurs adaptatifs pour une classe des systèmes chaotiques de Lur'e avec des non-linéarités à pente restreinte et des signaux de sortie retardés. En se basant sur la théorie de Lyapunov-Krasovskii et en utilisant une hypothèse d'excitation persistante, l'observateur adaptatif proposé garantit la synchronisation maitre-esclave et la restauration des informations transmises malgré l'existence des retards de transmission. Les résultats théoriques obtenus dans ce travail de thèse sont vérifiés à travers des applications de transmission d'informations utilisant différents modèles des systèmes chaotiques tout en étudiant les différents scénarios et cas de figure pouvant se présenter en pratique et en analysant les aspects de sécurité de ces systèmes.
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Hsu, Tseng-Hsing. "Control of a Chaotic Double Pendulum Model for a Ship Mounted Crane." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/26305.
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An extension of the original Ott-Grebogy-Yorke control scheme is used on a simple double pendulum. The base point of the double pendulum moves in both horizontal and vertical directions which leads to rather complicated behavior.A delay coordinate is used to reconstruct the attractor. The required dimension is determined by the False Nearest Neighbor analysis. A newly developed Fixed Point Transformation method is used to identify the unstable periodic orbit (UPO). Two different system parameters are used to control the motion. Minimum parameter constraints are studied. The use of discrete values for parameter changes is also investigated. Based on these investigations, a new on-off control scheme is proposed to simplify the implementation of the controller and minimize the delay in applying the control.Ph. D.
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Conradie, Willem Stefaan. "Conceptualising and quantifying the nonlinear, chaotic climate: implications for climate model experimental design." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/16527.
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Includes bibliographical referencesUncertainty in climate system initial conditions (ICs) is known to limit the predictability of future atmospheric states. On weather time scales (i.e. hours to days), the separation between two atmospheric model trajectories, initially "indistinguishable" (compared to unavoidable uncertainties) from one another, diverges exponentially-on-average over time, so that the "memory" of model ICs is eventually lost. In other words, there is a theoretical limit in the lead time for skilful weather forecasts. However, the influence of perturbations to climate system model ICs - particularly in more slowly evolving climate system components (e.g., the oceans and ice sheets) - on the evolution of model "climates" on longer time scales is less well understood. Hence, in order to better understand the role of IC uncertainty in climate predictability, particularly in the context of climate change, it is necessary to develop approaches for investigating and quantifying - at various spatial and temporal scales - the nature of the influence of ICs on the evolution of climate system trajectories. To this end, this study explores different conceptualisations and competing definitions of climate and the climate system, focussing on the role of ICs. The influence of ICs on climate quantifications, using probability distributions, is subsequently investigated in a climate model experiments using a low-resolution version of the Community Climate System Model version 4 (CCSM4). The model experiment consists of 11 different 50-member ensemble simulations with constant forcing, and three 50-member ensemble simulations under a climate change scenario with transient forcing. By analysing the output at global and regional scales, at least three distinct levels of IC influence are detected: (a) microscopic influence; (b) interannual-scale influence; and (c) intercentennial-scale influence. Distinct patterns of interannual-scale IC influence appear to be attributable to aperiodic and quasi-periodic variability in the model. It is found that, over some spatial domains, significant (p < 0.01) differences in atmospheric variable "climatologies", taken from 60-year distributions of model trajectories, occur due to IC differences of a similar order to round-off error. In addition, climate distributions constructed using different approaches are found to differ significantly. There is some evidence that ensemble distributions of multidecadal temperature response to transient forcing conditions can be influenced by ICs. The implications for quantifying and conceptualising climate are considered in the context of the experimental results. It is concluded that IC ensemble experiments can play a valuable role in better understanding climate variability and change, as well as allowing for superior quantification of model climates.
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Wenzel, Wolfgang. "Mean-field theories of the Hubbard model and periodic orbits in chaotic maps /." The Ohio State University, 1990. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487683756125101.
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Beyan, Timur. "A New Fuzzy-chaotic Modelling Proposal For Medical Diagnostic Processes." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12605924/index.pdf.
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Main reason of this study is to set forth the internal paradox of the basic approach of the artificial intelligence in the medical field to by discussing on the theoretical and application levels and to suggest solutions in theory and practice against that. In order to rule out the internal paradox in the medical decision support systematic, a new medical model is suggested and based on this, concepts such as disease, health, etiology, diagnosis and treatment are questioned. Meanwhile, with the current scientific data, a simple application sample based on how a decision making system which was set up by fuzzy logic and which is based on the perception of human as a complex adaptive system has been explained. Finally, results of the research about accuracy and validity of this application, current improvements based on the current model and the location on the artificial intelligence theory is discussed.
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Zheng, Xing. "Statistics of impedance and scattering matrices in microwave chaotic cavities the random coupling model /." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2920.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Hughes, Ryan Patrick. "Nonsmooth Bifurcations and the Role of Density Dependence in a Chaotic Infectious Disease Model." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/96567.
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Discrete dynamical systems can exhibit rich and interesting dynamics at lower dimensions (and co-dimensions) than that of ODE models. Classically, the minimal dimension to observe chaotic behavior in an ODE model is three; whereas it can be achieved in a one-dimensional discrete map. It is often the choice of mathematical biologists to use discrete systems as it fills many roles such as sparse data, incorporation of life cycle stages and noisy measurements. This work is analyzes a discrete time model of an infected salmon population. It provides an in-depth analysis of non-smooth bifurcations for alternate functional forms for density dependence in the growth function of a given model. These demonstrate interesting structures and chaotic behaviors with biologically feasible interpretations such as intrinsic growth rate and probability of death. The choice of density dependence function, as well as parameterization, leads to whether chaos occurs or not.Master of Science
Often times biological processes do not happen in a continuous streamlined chain of events. We observe discrete life stages, ages, and morphological differences. Similarly, data is generally collected in discrete (and often fixed) time intervals. This work focuses on the role that population density has on the behavior of these systems. We dive into a case study for a viral infection in a salmon population. We show chaotic behavior can be observed as low as a single dimension model and discuss the biological implications. Additionally, we show that the choice of density dependence in a given infectious disease model directly impacts disease dynamics and can allow or prohibit chaotic behavior.
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Filippi, Tomáš. "Model pro sledování hodnoty služeb podnikové informatiky: systémový/deterministicky chaotický model." Master's thesis, Vysoká škola ekonomická v Praze, 2009. http://www.nusl.cz/ntk/nusl-15456.
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This study deals with the value of ICT services. Enterprise Informatics is a widespread line of business and it is part of every company. There are not only software and hardware resources in enterprise informatics, but also people belong into and work with informatics every day. Currently, there are new trends how to manage enterprise informatics. Based on the same principles as for the business. A prerequisite for effective management is accurate overview of the costs and benefits. For this purpose there is a group of metrics which ensure measuring the amount of inputs, outputs and quality of services. The value of ICT services should be positive. Benefits should be greater than costs. The aim of this work is to create a model for monitoring the value of enterprise Informatics. Model simulate the dynamics of enterprise informatics and describe all important parameters in terms of value. Model should also find out if there are some external or internal factors, which could bring on some random element complicating the process of effective management.
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Hart, James Aamodt. "Scattering from chaotic cavities exploring the random coupling model in the time and frequency domains /." College Park, Md.: University of Maryland, 2009. http://hdl.handle.net/1903/9549.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2009.Thesis research directed by: Dept. of Physics. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Skufca, Joseph D. "Understanding a chaotic saddle with focus on a 9-variable model of Planar Couette flow." College Park, Md. : University of Maryland, 2005. http://hdl.handle.net/1903/2897.
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Thesis (Ph. D.) -- University of Maryland, College Park, 2005.Thesis research directed by: Applied Mathematics Program. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
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Du, S., Wyk BJ Van, G. Qi, and C. Tu. "Chaotic system synchronization with an unknown master model using a hybrid HOD active control approach." Elsevier, 2009. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001363.
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a b s t r a c t
In this paper, a hybrid method using active control and a High Order Differentiator (HOD)
methodology is proposed to synchronize chaotic systems. Compared to some traditional
active control methods, this new method can synchronize chaotic systems where only output
states of the master system are available, i.e. the system is considered a black box. The
HOD is used to estimate the derivative information of the master system followed by an
active control methodology relying on HOD information. The Qi hyperchaotic system is
used to verify the performance of this hybrid method. The proposed method is also compared
to some traditional methods. Experimental results show that the proposed method
has high synchronization precision and speed and is robust against uncertainties in the
master system. The circus implements of the proposed synchronizing scheme are included
in this paper. The simulation results show the feasibility of the proposed scheme.
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Niu, Junying [Verfasser]. "Suppressing Electromagnetic Interference in Switching-Mode Power Supplies by Chaotic Carrier Frequency Modulation / Junying Niu." Hagen : Fernuniversität Hagen, 2016. http://d-nb.info/1119250633/34.
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Jalali, Mohammad Mahdi. "Curvilinear shallow flow and particle tracking model for a groyned river bend." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/23467.
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Hydraulic structures such as dykes and groynes are commonly used to help control river flows and reduce flood risk. The present research aims to develop an idealized model of the hydrodynamics in the vicinity of a large river bend, and the advection and mixing processes where groynes are located. In this study a curvilinear model of shallow water equations is applied to investigate chaotic advection of particles in a river bend similar in dimensions to a typical bend in the River Danube, Hungary. First, a curvilinear grid generator is developed based on Poisson-type elliptic partial differential equations. The grid generator is verified for benchmark tests concerning a circular domain and for distorted grids in a rectangular domain. It is found that multi-grid (MG) and conjugate gradient (CG) methods performed better computationally than successive over-relaxation (SOR) in generating the curvilinear grids. The open channel hydrodynamics are modelled using the shallow water equations (SWEs) derived by depth-averaging the continuity and Navier-Stokes momentum equations. Both Cartesian and curvilinear forms of the shallow water equations are presented. Both sets of equations are discretized spatially using finite differences and the solution marched forward in time using fourth-order Runge-Kutta scheme. The shallow water solvers are verified and validated for uniform flow in the rectangular channel, wind-induced set up in rectangular and circular basins, flow past a sidewall expansion, and Shallow flow in a rectangular channel with single groyne. A Lagrangian particle tracking model is used to predict the trajectories of tracer particles, and bilinear interpolation is used to provide a representation of the continuous flow field from discrete results. The particle tracking model is verified for trajectories in the flow field of a single free vortex and in the alternating flow field of a pair of blinking vortices. Excellent agreement is obtained with analytical solutions, previously published results in the literature. The combined shallow flow and Lagrangian particle tracking model is then used to simulate particle advection in the flow past a side-wall cavity containing a groyne and reasonable agreement is obtained with published experimental and alternative numerical data. Finally, the combined model is applied to simulate the shallow flow hydrodynamics, advection and mixing processes in the vicinity of groynes in river bend, the dimensions representative of a typical bend in the Danube River, Hungary.
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Hahlin, Axel. "Coupled waves as a model to describe chaotic turbulence pumped by radio waves in the ionosphere." Thesis, Uppsala universitet, Institutet för rymdfysik, Uppsalaavdelningen, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-356265.
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Experimental results concerning plasma turbulence pumped in theionosphere by powerful radio waves suggest that the turbulence is due todeterministic chaos. To investigate the possibility of deterministic chaosin the ionosphere coupled wave systems have been studied to see chaoticdynamics. If coupled waves can exhibit chaos it is a possible way tomodel ionospheric chaos. The result showed that chaos was present inboth wave systems studied which means that they could possibly explainthe chaos, to verify this more studies needs to be done on theparameters relevant to the coupled wave systems in the ionosphere andfind if they are in a regime where chaos developsStudier av plasmaturbulens i jonosfären som pumpas av kraftfulla radiovågor antyder att turbulensen är kopplat till deterministiskt kaos. För att undersöka möjligheten för deterministiskt kaos i jonosfären studeras kopplade vågsystem om de kan innehålla kaotiska regimer. Om dessa system visar kaotiskt beteende skulle de kunna användas för att beskriva kaos i jonosfären. Resultatet visade att kaos var närvarande i de kopplade vågsystem som studerats, för att verifiera om de kan användas för att beskriva kaos i jonosfären måste närmare studier av de parametrar som modellen använder sig av göras för att se om de faller inom ett intervall där kaos uppstår.
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Chen, Cong. "High-Dimensional Generative Models for 3D Perception." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103948.
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Modern robotics and automation systems require high-level reasoning capability in representing, identifying, and interpreting the three-dimensional data of the real world. Understanding the world's geometric structure by visual data is known as 3D perception. The necessity of analyzing irregular and complex 3D data has led to the development of high-dimensional frameworks for data learning. Here, we design several sparse learning-based approaches for high-dimensional data that effectively tackle multiple perception problems, including data filtering, data recovery, and data retrieval. The frameworks offer generative solutions for analyzing complex and irregular data structures without prior knowledge of data.
The first part of the dissertation proposes a novel method that simultaneously filters point cloud noise and outliers as well as completing missing data by utilizing a unified framework consisting of a novel tensor data representation, an adaptive feature encoder, and a generative Bayesian network. In the next section, a novel multi-level generative chaotic Recurrent Neural Network (RNN) has been proposed using a sparse tensor structure for image restoration. In the last part of the dissertation, we discuss the detection followed by localization, where we discuss extracting features from sparse tensors for data retrieval.Doctor of Philosophy
The development of automation systems and robotics brought the modern world unrivaled affluence and convenience. However, the current automated tasks are mainly simple repetitive motions. Tasks that require more artificial capability with advanced visual cognition are still an unsolved problem for automation. Many of the high-level cognition-based tasks require the accurate visual perception of the environment and dynamic objects from the data received from the optical sensor. The capability to represent, identify and interpret complex visual data for understanding the geometric structure of the world is 3D perception. To better tackle the existing 3D perception challenges, this dissertation proposed a set of generative learning-based frameworks on sparse tensor data for various high-dimensional robotics perception applications: underwater point cloud filtering, image restoration, deformation detection, and localization. Underwater point cloud data is relevant for many applications such as environmental monitoring or geological exploration. The data collected with sonar sensors are however subjected to different types of noise, including holes, noise measurements, and outliers. In the first chapter, we propose a generative model for point cloud data recovery using Variational Bayesian (VB) based sparse tensor factorization methods to tackle these three defects simultaneously. In the second part of the dissertation, we propose an image restoration technique to tackle missing data, which is essential for many perception applications. An efficient generative chaotic RNN framework has been introduced for recovering the sparse tensor from a single corrupted image for various types of missing data. In the last chapter, a multi-level CNN for high-dimension tensor feature extraction for underwater vehicle localization has been proposed.
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Khamallag, Masoud M. "Towards an Improved Framework of E-Government Implementation in Chaotic Environment; Proposed Social Collaboration Model: Case study of Libya." Thesis, University of Bradford, 2018. http://hdl.handle.net/10454/17449.
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E-government is basically described as using all available electronic media to provide an online public services companies, agencies, citizens or persons in certain country or region. This provision can be provided by the government institutions, agencies, or organisation, in addition to public and private sectors subject to government policies and legislation. Political instability, armed conflict, corruption and chaotic situations are considered to be an obstacle confronting public services delivery and governance in some developing countries around the world. Therefore, Libya is selected a case study of this research.
Post the 2011 ousting of the Gadhafi regime in Libya, the country has been experiencing a severe and deep-rooted environment of conflict and chaos, which has destabilised and in some cases dismantled government institutions throughout the country. Within this environment, the original aim of this study was to explore the possibility of implementing e-government services that can provide public services to citizens and, if so, how and what services could be utilised.
An exploratory qualitative pilot study was conducted to investigate the feasibility of e-government implementation in Libya utilising the knowledge of government officials. The study found that, the Libyan government had recently and successfully implemented an online e-passport service. An extensive literature review carried out in relation to e-government implementation to help understanding lesions learned and factors behind such success then to utilise the knowledge for further services implementations. Critical success factors of e-government implementation were addressed but available ones are related to stable countries under normal situations. This research is aiming to investigate its implementation in chaotic environment where not much of research is available. During the chaotic environment and instability, different factors may emerge to drive the implementation and the usage of e-services such environment. From government perspectives, it is noticed that cases of corruption, lack of citizens’ safety and poor infrastructure were found to be drivers behind the success of existing government institutions and departments of implement e-passport system. Social collaboration and trust in government institutions’ commitment were emerged from the citizens’ perspectives as factors encouraged the citizens to use the e-passport system. Quantitative data analysed using structural equation modelling techniques using SmartPLS (3.2.7) together with the SPSS 23 were used to analyse the collected data. The outcome were used to propose a framework that can improve the implementation of public e-services while the country at unrest. Another contribution of this studies is the proposal of social collaboration model towards better e-services in such environment.
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Gąska, Damian. "Model research of load-carrying crane structures and hoist load dynamics in the context of regular and chaotic vibrations." Praca habilitacyjna, Wydawnictwo Politechniki Śląskiej, 2019. https://delibra.bg.polsl.pl/dlibra/docmetadata?showContent=true&id=73325.
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Espinoza-Camino, P., I. Macassi-Jaurequi, C. Raymundo-Ibañez, and F. Dominguez. "Warehouse management model using FEFO, 5s, and chaotic storage to improve product loading times in small- and medium-sized non-metallic mining companies." Institute of Physics Publishing, 2020. http://hdl.handle.net/10757/656393.
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This article addresses one of the main problems faced by small- and medium-sized business in the non-metallic mining sector in Peru. These companies own warehouses and face the major problem of failing to deliver orders correctly and in a timely manner. This problem usually occurs when the business grows from a small- to medium-sized company in a short span of time; this situation leads to new processes within warehouses that are mostly not standardized. Besides, facilities are no longer optimal in space and the workers are not properly trained. The case study shows that the orders were not delivered on time due to factors such as lack of product identification, although the products have an expiration date and a warehouse without signaling and surrounded by traffic. To tackle this situation, a labeling process has been designed for the products, an adequate distribution technique is used in the warehouse through a newly designed warehouse layout, and a First Expired, First Out system has been implemented. Similarly, the design is accompanied by the 5s tool to provide a basis for order and continuous improvement. The results show that deliveries with delays were reduced from 38% to 10%. These results show that companies can grow rapidly and maintain quality of service through orderly management.
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Chen, Leiming. "Tilt phase transitions in disordered systems /." view abstract or download file of text, 2006. http://proquest.umi.com/pqdweb?did=1251884301&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.
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Thesis (Ph. D.)--University of Oregon, 2006.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 126-128). Also available for download via the World Wide Web; free to University of Oregon users.
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Wilson, Mark M. J. "Supply chains behaving badly : a dynamic model of inter-organisational supply chain exchange behaviour under rational, relational and chaotic paradigms." Phd thesis, Lincoln University. Commerce Division, 2006. http://theses.lincoln.ac.nz/public/adt-NZLIU20080229.095848/.
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Supply chain exchange relationships are complex and sometimes chaotic sociological and organisational phenomena. This complexity is compounded by the boundary spanning necessity of forming supply chain partnerships that are further exacerbated by goal divergence and asymmetric information. One of the main questions for consideration is how these dyadic exchange relationships are maintained and develop over time in response to the various channel behaviours of the actors (the buyer and seller)? In particular, exchange relationships are theorised to be sensitive in some degree to attempts at economic appropriation, and conversely coordinative efforts. Such efforts manifest themselves into the mutually opposing forces broadly labelled as opportunistic and collaborative behavioural paradigms. Drawing from the concepts of Systems and Chaos/Complexity theories, it is theorised that the movement from one form of relational arrangement to another is enacted in a non-linear and dynamic manner with periods of relational equilibrium disrupted by bifurcations resulting in the emergence of new levels of relationship. However, not all exchange relationships are susceptible to constant change, rather, there should be some threshold barrier or relationship inertia that must be overcome before a bifurcation occurs. Yet what is not known is how strong these bonds are to the enactment of opportunistic and collaborative partner behaviours. Hence, 189 manufacturing supply chain relationships were survey-interviewed in order to determine the impact that collaborative and opportunistic behaviours have on supply chain relational movement. The results show that generally exchange relationships do in fact change in response to these enacted behaviours, and that actual levels of supply chain behaviour over a range of 12 variables could be measured. Indeed, the level of opportunistic behaviour experienced by the sample was disturbing. In addition, the level of tolerance (zone of tolerance) for specific behaviours was measured for the first time in the field. Overall, it was found that supply chain exchange relationships do indeed evolve in a non-linear dynamic manner in response to opportunistic and collaborative manoeuvres by the dyadic actors. Finally, these ideas were summarised in the Dynamic Relational Development (DRD) concept that explains how supply chain relationships dynamically change. In addition, the dualistic nature of the collaborative versus opportunistic behaviour choice for exchange actors is tentatively reconciled by the deontological approach of the Supply Chain Citizen theory offered in this research.
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Thomas, Olivier. "Dynamique linéaire et non linéaire de structures élastiques et piézoélectriques. Instruments de musique, micro/nano systèmes électromécaniques, contrôle de vibration." Habilitation à diriger des recherches, École normale supérieure de Cachan - ENS Cachan, 2011. http://tel.archives-ouvertes.fr/tel-00718727.
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Le présent manuscrit propose une synthèse des travaux de recherche de l'auteur de ces dix dernières années. Il est divisé en deux grandes parties. La première partie regroupe les modèles et techniques de résolution développés par l'auteur pour résoudre des problèmes de dynamique non linéaire des structures élastiques et piézoélectriques. Le fil conducteur de cette partie est celui de la résolution d'un problème de mécanique. La première étape est le choix d'un modèle adapté. Ainsi, on propose une synthèse des modèles non linéaires géométriques de milieux minces, classés et comparés à la fois en terme de formulation et d'hypothèses. Des modèles analytiques et numériques sont mis en regard, depuis leur fondement dans la mécanique des milieux continus non linéaire, jusqu'à leur écriture opérationnelle. Ensuite, des méthodes de résolution adaptées sont décrites : discrétisation des modèles analytiques par projection modale, réduction de modèles éléments finis par la même technique, modes non linéaires, méthodes numériques de continuation. Des techniques expérimentales spécifiques aux vibrations non linéaires sont aussi décrites. La seconde partie donne une vue d'ensemble des principaux résultats associés aux trois thèmes d'application des recherches de l'auteur : la dynamique non linéaire des plaques et des coques, avec des applications aux instruments de musique à percussion, la réduction de vibration de structures par shunts piézoélectriques et enfin les vibrations non linéaires de micro/nano systèmes électromécaniques. Cette seconde partie fait largement référence aux résultats généraux de la première et en donne ainsi des illustrations et des applications.
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Schumann, Michael. "Nonlinear dynamics in oscillating waterfalls." PDXScholar, 1992. https://pdxscholar.library.pdx.edu/open_access_etds/4421.
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De, Beer A. J. "The development of a generic model for strategic planning for small and medium manufacturing enterprises in a turbulent environment." Thesis, Stellenbosch : Stellenbosch University, 2000. http://hdl.handle.net/10019.1/51957.
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Thesis (MBA)--Stellenbosch University, 2000.ENGLISH ABSTRACT: Continuous change has become one of the major characteristics of the South African manufacturing environment. Such an unstable dynamic environment, where continuous change is a normal occurrence, necessitates an appropriate response in order to regain or sustain competitive advantage. The environment is changing so fast that most small and medium manufacturing enterprises barely have the ability to survive the day-to-day challenges, without even seeing or thinking about the real challenges of surviving in the future, and more importantly, not only surviving, but actually prospering through these new challenges. The conventional approaches of strategic management do not satisfy the fast decision making requirements of today's organisations. The development of the different schools of strategic planning clearly shows how the strategic management process has developed with the changing times. One of the enduring problems facing the field of strategic management is the lack of theoretical tools available to describe and predict the behaviour of firms and industries. The fundamental problem is that industries evolve in a dynamic way over time as a result of complex interactions among firms, government, labour, financial institutions and other elements of the environment. These interactions are strategic in the sense that decisions by one party take into account anticipated reactions by others, and thus reflect recognition of interdependence. Existing models tend to assume relatively simple linear relationships without feedback. Chaos theory, which is the study of non-linear dynamic systems, promises to be a useful conceptual framework that reconciles the essential unpredictability of industries with the emergence of distinctive patterns. To understand the relevance of chaos theory to strategy, industries need to be conceptualised as complex, dynamic, non-linear systems. A basic strategic planning model was developed, incorporating some aspects of chaos theory, containing the following basic elements: vision, environmental scanning, strategic objectives, measurements, strategies and performance evaluation. The final aspects covered are some aspects of strategy implementation, concluding with some final notes confirming that one of the main reasons for strategic assessment of the organisation's situation is to exploit possible advantages from external, discontinuous changes and so gain first mover advantages by surprising the 'enemy'. To cope with chaos, a quickly responsive, organic corporation needs to be crafted.
AFRIKAANSE OPSOMMING: Een van die hoofkenmerke van die huidige Suid-Afrikaanse vervaardigingsomgewing is voortdurende verandering. Ten einde 'n mededingende voordeel in hierdie veranderende, dinamiese milieu te verkry en te behou, verg besondere vaardighede en innoverende tegnieke. Die meeste klein- en mediumgroot-ondernemings bevind hulself midde-in hierdie vinnig veranderende omgewing, waar hulle nie net daagliks moet oorleef nie, maar ook die uitdaging van langtermyn oorlewing die hoof moet bied. Ongelukkig vorm langtermynoorlewing en groei dikwels nie deel van meeste ondernemings se beplanning nie. Konvensionele benaderings tot strategiese beplanning kan nie meer die moderne onderneming se behoefte aan vinnige besluitneming bevredig nie. Die ontwikkeling van die verskillende denkskole oor strategiese beplanning toon ook 'n duidelike beweging in die rigting van sneller verandering in strategiese bestuur. Een van die probleme ten opsigte van strategiese bestuur, is die gebrek aan teoretiese modelle om die gedrag van ondernemings te beskryf en te voorspel. Die onderliggende probleem is egter dat ondernemings oor 'n lang tydperk groei en ontwikkel as deel van 'n komplekse interaksie met ander ondernemings, asook met die regering, arbeid, kapitaal en ander elemente binne die bedryf. Sodanige interaksie is van strategiese belang, aangesien 'n spesifieke rolspeler telkens antisipeer watter impak elke besluit wat geneem word, op die res van die omgewing gaan hê. Bestaande teoretiese modelle impliseer relatief eenvoudige, lineêre verwantskappe wat geen terugvoer bied nie. Daarteenoor skep die sogenaamde chaosteorie, dit wil sê die studie van dinamiese, nie-lineêre stelsels, 'n konseptuele raamwerk met bepaalde patrone waarmee die onvoorspelbaarheid van ondernemings verklaar en beskryf kan word. Die relevansie van die chaosteorie vir strategiese beplanning en bestuur kan egter slegs begryp word indien ondernemings as komplekse, dinamiese, nie-lineêre stelsels beskou word. In hierdie studie is 'n basiese strategiese beplanningsmodel ontwikkel. Belangrike aspekte wat gedek is, is einddoel, omgewingstudie, strategiese doelwitte, meting, strategieë en prestasie-evaluering. Daar word ook kortliks gekyk na moontlike probleme om dié model te implementeer, met verwysings na die impak van chaosteorie op die tradisionele beplannings- en implementerings-modelle. Ter afsluiting word daar klem gelê op die geleenthede wat deur die snelveranderende omgewing geskep word, en die noodsaaklikheid daarvan dat 'n onderneming gereed moet wees om binne hierdie omgewing vinnig en effektief op te tree. Die kern van enige onderneming se sukses lê in sy vermoë om verandering raak te sien, geleenthede te identifiseer en onmiddellik daarop te reageer.
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Beig, Mirza Tanweer Ahmad. "Fractional Calculus and Dynamic Approach to Complexity." Thesis, University of North Texas, 2015. https://digital.library.unt.edu/ark:/67531/metadc822832/.
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Fractional calculus enables the possibility of using real number powers or complex number powers of the differentiation operator. The fundamental connection between fractional calculus and subordination processes is explored and affords a physical interpretation for a fractional trajectory, that being an average over an ensemble of stochastic trajectories. With an ensemble average perspective, the explanation of the behavior of fractional chaotic systems changes dramatically. Before now what has been interpreted as intrinsic friction is actually a form of non-Markovian dissipation that automatically arises from adopting the fractional calculus, is shown to be a manifestation of decorrelations between trajectories. Nonlinear Langevin equation describes the mean field of a finite size complex network at criticality. Critical phenomena and temporal complexity are two very important issues of modern nonlinear dynamics and the link between them found by the author can significantly improve the understanding behavior of dynamical systems at criticality. The subject of temporal complexity addresses the challenging and especially helpful in addressing fundamental physical science issues beyond the limits of reductionism.
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Slezák, Josef. "Evoluční syntéza analogových elektronických obvodů s využitím algoritmů EDA." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-233666.
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Disertační práce je zaměřena na návrh analogových elektronických obvodů pomocí algoritmů s pravěpodobnostními modely (algoritmy EDA). Prezentované metody jsou na základě požadovaných charakteristik cílových obvodů schopny navrhnout jak parametry použitých komponent tak také jejich topologii zapojení. Tři různé metody využití EDA algoritmů jsou navrženy a otestovány na příkladech skutečných problémů z oblasti analogových elektronických obvodů. První metoda je určena pro návrh pasivních analogových obvodů a využívá algoritmus UMDA pro návrh jak topologie zapojení tak také hodnot parametrů použitých komponent. Metoda je použita pro návrh admitanční sítě s požadovanou vstupní impedancí pro účely chaotického oscilátoru. Druhá metoda je také určena pro návrh pasivních analogových obvodů a využívá hybridní přístup - UMDA pro návrh topologie a metodu lokální optimalizace pro návrh parametrů komponent. Třetí metoda umožňuje návrh analogových obvodů obsahujících také tranzistory. Metoda využívá hybridní přístup - EDA algoritmus pro syntézu topologie a metoda lokální optimalizace pro určení parametrů použitých komponent. Informace o topologii je v jednotlivých jedincích populace vyjádřena pomocí grafů a hypergrafů.
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Erasmus, Gert Botha. "Stochastic models of steady state and dynamic operation of systems of congestion." Thesis, Pretoria : [s.n.], 2006. http://hdl.handle.net/2263/28814.
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(i) The thesis sets out to address the problematic phenomenon of Systems of Congestion via Basic Queueing Theory. The theory, and its application in practice, appears to be a field of study which is the common domain of “theorists” and “practitioners”. (ii) This professional dichotomy has come about due to diverging interests in that one group is mainly interested in the purity of mathematical modelling, and the other group is motivated to use modelling, which conveniently employs applications oriented solutions. (iii) The schism between the groups has been accentuated by the “practitioners” who in addition to having an interest in steady state system behaviour make use of methods of modelling of the transient operation of complex Systems of Congestion. (iv) At the outset the thesis demonstrates how closed form solutions are obtained for steady state and transient state operation of a selection of Systems of Congestion. The attendant mathematical derivations are elegant and intricate. (v) Having revealed the limited utility of closed-form solutions the thesis proceeds to investigate the feasibility of using dynamical systems theory to study the transient behaviour of complex Systems of Congestion. (vi) The creation of Chaos Theory in recent decades suggests that it may be employed as a useful tool in analysing Systems of Congestion. Iterative Chaos Theory methods of orbit generation for complete Systems of Congestion are therefore examined. The use of such orbit generation methods is found to be satisfactory for simple Systems of Congestion. More than a perfunctory knowledge of chaos mapping is however required. The simplicity of modelling is emphasized. (vii) Based on the results of benchmarking the creation of dynamic system orbits against an existing simulation method, the research advances to modelling of the transient operation of complex systems. Once again the iterative method of orbit generation displays the ease of modelling while simultaneously unfolding system dynamics graphically. (viii) One may hopefully contend that a tool of eminent utility has been developed to aid practitioners in studying and optimizing Systems of Congestion.Thesis (PhD (Industrial Engineering))--University of Pretoria, 2006.
Industrial and Systems Engineering
Unrestricted
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Perkins, Adam Christopher. "Mechanisms of instability in Rayleigh-Bénard convection." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/42768.
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In many systems, instabilities can lead to time-dependent behavior, and instabilities can act as mechanisms for sustained chaos; an understanding of the dynamical modes governing instability is thus essential for prediction and/or control in such systems. In this thesis work, we have developed an approach toward characterizing instabilities quantitatively, from experiments on the prototypical Rayleigh-Bénard convection system. We developed an experimental technique for preparing a given convection pattern using rapid optical actuation of pressurized SF6, a greenhouse gas. Real-time analysis of convection patterns was developed as part of the implementation of closed-loop control of straight roll patterns. Feedback control of the patterns via actuation was used to guide patterns to various system instabilities. Controlled, spatially localized perturbations were applied to the prepared states, which were observed to excite the dominant system modes. We extracted the spatial structure and growth rates of these modes from analysis of the pattern evolutions. The lifetimes of excitations were also measured, near a particular instability; a critical wavenumber was found from the observed dynamical slowing near the bifurcation. We will also describe preliminary results of using a state estimation algorithm (LETKF) on experimentally prepared non-periodic patterns in a cylindrical convection cell.
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Marques, João Francisco Magro. "Dynamics of financial markets : study of an agent-based model." Master's thesis, Instituto Superior de Economia e Gestão, 2015. http://hdl.handle.net/10400.5/9328.
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Mestrado em Matemática FinanceiraNas últimas décadas, o mercado financeiro mundial tem enfrentado vários problemas e colapsos que motivaram anos conturbados para a economia real e para as famílias. Os sistemas dinâmicos apareceram na literatura de matemática financeira para ajudar a compreender melhor as características únicas destes mercados financeiros e a dinâmica do preço ao longo do tempo. Este trabalho consiste principalmente numa aproximação estatística ao sistema dinâmico de modelo de mercado com um ponto de descontinuidade introduzido por Tramontana, Westerhoff e Gardini (2010). Usando uma versão do modelo que produz órbitas caóticas, podemos observar, para parâmetros específicos, distribuições estacionárias. Por outras palavras, o sistema dinâmico pode ser caótico do ponto de vista do estudo das órbitas, porém, em termos estatísticos, é assintoticamente previsível, isto é, a maioria das trajetórias converge para um atractor que nós conseguimos descrevê-lo estatisticamente. Ainda, para os parâmetros apropriados, o modelo pode projetar um comportamento absolutamente errático, mesmo numa aproximação estatística. Para este último, nós concluímos que a previsão do preço é impossível uma vez que só conseguimos restringir os nossos prognósticos a um intervalo invariante suficientemente grande que contém toda a dinâmica do preço.
Over the past few decades, the global financial market has been facing multiple distresses and crashes which led to troubled years for the real economy and families. Dynamical systems emerged in the mathematical finance literature to help comprehending better the unique characteristics of these financial markets and the price dynamics over the time. This work consists mainly of a statistical approach of the one discontinuity point dynamical system market model introduced by Tramontana, Westerhoff and Gardini (2010). Using a model's version that produces chaotic orbits, we can observe stationary distributions under specific parameters. In other words, the dynamical system can be chaotic in a point-wise perspective, however, from a statistical approach, it can be asymptotically predictable, that is, most trajectories converge to an attractor which we can describe statistically. Still, under the proper parameters, the model may project an absolute erratic behavior, even in the statistical approach sense. For the latter, we conclude the price forecast is impossible because we can only restrict our prognoses to an invariant set sufficient large whose contain the whole price dynamic.
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Fedorková, Lucie. "Metody stabilizace nestabilních řešení diskrétní logistické rovnice." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-400443.
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Diplomová práce pojednává o stabilizaci diskrétního logistického modelu pomocí několika řídících metod. Je zde provedena především stabilizace rovnováh, 2-periodických cyklů a 3-periodických cyklů. Ke stabilizaci systému je využito proporčního zpětně-vazebního řízení, zpětně-vazebního řízení s časovým zpožděním a řízení založeného na predikci. U každé metody je diskutovaná stabilizační množina pro řídící zesilovač spolu s oblastmi stability pro odpovídající kontrolovaná řešení. Všechny teoretické výsledky jsou ilustrovány grafickými interpretacemi v softwaru MATLAB. Podpůrné výpočty jsou provedeny pomocí softwaru Maple.
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JÃnior, Josà Maria Pires de Menezes. "Redes neurais dinÃmicas para prediÃÃo e modelagem nÃo-linear de sÃries temporais." Universidade Federal do CearÃ, 2006. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=2090.
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Neste trabalho, redes neurais dinÃmicas sÃo avaliadas como modelos nÃo-lineares eficientes para prediÃÃo de sÃries temporais complexas. Entre as arquiteturas avaliadas estÃo as redes FTDNN, Elman e NARX. A capacidade preditiva destas redes sÃo testadas em tarefas de prediÃÃo de um-passo-adiante e mÃltiplos-passos-adiante. Para este fim, sÃo usadas as seguintes sÃries temporais: sÃrie laser caÃtico, sÃrie caÃtica Mackey-Glass, alÃm de sÃries de trÃfego de rede de computadores com caracterÃsticas auto-similares. O uso da rede NARX em prediÃÃo de sÃries temporais à uma contribuiÃÃo desta dissertaÃÃo. Esta rede possui uma arquitetura neural recorrente usada originalmente para identificaÃÃo entrada-saÃda de sistemas nÃo-lineares. A entrada da rede NARX à formada por duas janelas deslizantes (sliding time window), uma que desliza sobre o sinal de entrada e outra que desliza sobre sinal de saÃda. Quando aplicada para prediÃÃo caÃtica de sÃries temporais, a rede NARX à projetada geralmente como um modelo autoregressivo nÃolinear (NAR), eliminando a janela de atraso da saÃda. Neste trabalho, à proposta uma estratÃgia simples, porÃm eficiente, para permitir que a rede NARX explore inteiramente as janelas de tempo da entrada e da saÃda, a fim de melhorar sua capacidade preditiva. Os resultados obtidos mostram que a abordagem proposta tem desempenho superior ao desempenho apresentado por preditores baseados nas redes FTDNN e Elman.
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Sousa, Fabiano Berardo de. "Análise de modelo de Hopfield com topologia de rede complexa." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-30012014-111520/.
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Redes neurais biológicas contêm bilhões de células (neurônios) agrupadas em regiões espacial e funcionalmente distintas. Elas também apresentam comportamentos complexos, tais como dinâmicas periódicas e caóticas. Na área da Inteligência Artificial, pesquisas mostram que Redes Neurais Caóticas, isto é, modelos de Redes Neurais Artificiais que operam com dinâmicas complexas, são mais eficientes do que modelos tradicionais no que diz respeito a evitar memórias espúrias. Inspirado pelo fato de que o córtex cerebral contém agrupamentos de células e motivado pela eficiência no uso de dinâmicas complexas, este projeto de pesquisa investiga o comportamento dinâmico de um modelo de Rede Neural Artificial Recorrente, como o de Hopfield, porém com a topologia sináptica reorganizada a ponto de originar agrupamentos de neurônios, tal como acontece em uma Rede Complexa quando esta apresenta uma estrutura de comunidades. O modelo de treinamento tradicional de Hopfield também é alterado para uma regra de aprendizado que posta os padrões em ciclos, gerando uma matriz de pesos assimétrica. Resultados indicam que o modelo proposto oscila entre comportamentos periódicos e caóticos, dependendo do grau de fragmentação das sinapses. Com baixo grau de fragmentação, a rede opera com dinâmica periódica, como consequência da regra de treinamento utilizada. Dinâmicas caóticas parecem surgir quando existe um alto grau de fragmentação. Mostra-se, também, que é possível obter caoticidade em uma topologia adequadamente modular, ou seja, como uma estrutura de comunidades válida. Desta forma, este projeto de pesquisa provê uma metodologia alternativa para se construir um modelo de Rede Neural Artificial que realiza tarefas de reconhecimento de padrões, explorando dinâmicas complexas por meio de uma estrutura de conexões que se mostra mais similar à topologia existente no cérebroBiological neural networks contain billions of neurons divided in spatial and functional clusters to perform dierent tasks. It also operates with complex dynamics such as periodic and chaotic ones. It has been shown that Chaotic Neural Networks are more efficient than conventional recurrent neural networks in avoiding spurious memory. Inspired by the fact that the cerebral cortex has speficic groups of cells and motivated by the efficiency of complex behaviors, in this document we investigate the dynamics of a recurrent neural network, as the Hopfield one, but with neurons coupled in such a way to form a complex network community structure. Also, we generate an asymmetric weight matrix placing pattern cycles during learning. Our study shows that the network can operate with periodic and chaotic dynamics, depending on the degree of the connection\'s fragmentation. For low fragmentation degree, the network operates with periodic dynamic duo to the employed learning rule. Chaotic behavior seems to rise for a high fragmentation degree. We also show that the neural network can hold both chaotic dynamic and a high value of modularity measure at the same time, indicating an acceptable community structure. These findings provide an alternative way to design dynamical neural networks to perform pattern recognition tasks exploiting periodic and chaotic dynamics by using a more similar topology to the topology of the brain
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BANDEIRA, Heliovânio Torres. "Modelo caótico e a memória da cinética dos canais iônicos." Universidade Federal Rural de Pernambuco, 2006. http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/4997.
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Ionic channels are formed by one or few protein molecules found in biological membranes and constitute one of the possible ways for the transport of ions through these membranes. These proteins can assume different conformational open and closed states, phenomenon named ion channel kinetics. The transitions from one state to another are dependent on the potential energy barrier that separates them and can be controlled by electric field, ions, chemical substances and other physical agents. The dwell times in which the proteinchannel stays in one these conformational states have been modeled assuming that the process is Markovian. A chaotic model also was proposed for modeling the ion channel kinetics (LIEBOVITCH e TÓTH., 1991).In this work we use the R/S Hurst analysis to test the long-range correlation found in calcium-activated potassium channel kinetics in Leydig cells. The Hurst coefficient H, a parameter that show the memory existent in a kinetic process (NOGUEIRA et al., 1995), was calculated to a calcium-activated potassium channel in Leydig cells recording and it was equal to H = 0,66±0,044 (n=4), disclosing that the system presents a persistent memory. The R/S analysis when applied to the opening and closing dwell time series obtained from ion channel simulated data using a chaotic model was inadequate to describe the long-term correlation previously found in the experimental data. As conclusion, this work shows that: (i) really, opening and closing dwell times for the single calciumactivated potassium channel of Leydig cells present long-term correlation and (ii) the chaotic model, proposed by Liebovitch and Thót (1991), is not adequate to describe the memory found in the kinetic of this channel.
Canais iônicos são compostos de uma ou poucas moléculas de proteínas que se encontram nas membranas biológicas e constituem uma das vias possíveis para o transporte de íons através dessas membranas. Essas proteínas podem assumir diferentes estados conformacionais, abertos e fechados, fenômeno denominado de cinética de canais iônicos. As transições entre os estados cinéticos dos canais dependem das barreiras de energias potenciais que separam esses estados e, que podem ser controladas por campo elétrico, íons, substâncias químicas e outros agentes. Os tempos de permanências dos canais em cada um dos estados conformacionais têm sido modelados assumindo-se que este processo é markoviano. Um modelo caótico também foi proposto para modelar a cinética de canal iônico (LIEBOVITCH e TÓTH, 1991). Neste trabalho utilizamos a análise R/S de Hurst para testar a correlação de longo alcance (memória) na cinética de um canal para potássio ativado por cálcio em células de Leydig. O coeficiente de Hurst H, um parâmetro que mostra a memória existente em um processo cinético (NOGUEIRA et al., 1995), foi calculado para um registro de um canal para potássio ativado por cálcio e foi encontrado um valor de H = 0,66 ± 0,044 (n=4), evidenciando que o sistema apresenta uma memória persistente. A análise R/S aplicada à seqüência temporal de aberturas e fechamentos obtida para um canal iônico simulado por um modelo caótico mostrou que esse modelo é inadequado para descrever a correlação de longo alcance encontrada nos dados experimentais. Como conclusão, este trabalho mostra que: (i) tempos de permanência para aberturas e fechamentos do canal para potássio ativado por cálcio em células de Leydig apresentam correlação de longo alcance (memória);(ii) o modelo caótico, proposto por Liebovitch e Tóth (1991), é inadequado para descrever a memória encontrada na cinética do canal.
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Ghosh, Dastidar Samanwoy. "Models of EEG data mining and classification in temporal lobe epilepsy: wavelet-chaos-neural network methodology and spiking neural networks." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1180459585.
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