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A coordenação entre os segmentos perna e coxa no andar : uma análise a partir da teoria dos sistemas dinâmicosSantos, Luiz Cezar dos January 1995 (has links)
Utilizando-se entre a perna e a coxa os princípios da Teoria dos Sistemas Dinâmicos, foi estudada a coordenação intra-membros durante o andar em 16 sujeitos do sexo feminino. Os movimentos da perna e da coxa e suas relações foram analisados dinamicamente como sistemas acoplados de ciclo limite. Os sujeitos foram filmados lateralmente executando o andar em duas situações experimentais: normal e com uma sandália na perna direita na proporção de 5% do comprimento do segmento inferior. Os dados transformados em variáveis cinemáticas possibilitaram a análise da coordenação em termos de ângulos de fase, ponto de coordenação e fase relativa. Através dos dados angulares, foram testadas as propriedades dos osciladores não-lineares de ciclo limite. Os resultados indicaram que os segmentos apresentam uma órbita atrativa específica para cada um deles, que se mantém invariante ao longo das idades. Esta órbita atrativa representa a organização espaço-temporal do segmento durante o andar, servindo também para a visualização da quantidade de energia dissipada por parte de cada segmento. A análise dos ângulos de fase no momento da reversão, do ponto de coordenação e da fase relativa possibilitaram a identificação do treinamento mútuo e da estabilidade estrutural. / Based on the principles of the Theory of Dynamic Systems, 16 female subjects were studied as to their intra-limb coordination during walk. The movements of lower leg and thigh have been dynamically analised, - as well as their relation, - as limit-cycle coupled systems. Subjects were video-taped laterally, as they performed natural walking movements under two experimental situations: barefoot and with a sandal on the right foot with a thickness of 5% the length of the lower segment. Converted into kinematic variables, the data allowed the analysis of the coordination in terms of phase angle, point of coordination and relative coordination. The angular data made it possible to test the properties of the non-linear limit-cycle oscilator. Results pointed out that each segment involved in walking draws a specific attractive orbit, which is kept invariable throughout the ages. This attractive orbit represents the limb’s spacetemporal organization during walk, being, furthermore, an indication as to how much energy is being dissipated by each segment. The analysis of phase angles at the moment of limb reversion, the point of coordination and the relative phase made it possible to identify mutual training and structural stability.
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Abstractions of Graph ModelsJohnson, Charles Addison 04 June 2020 (has links)
Building models, whether to explain or to predict observed data, is an exercise of describing how the values of observed variables depend on those of others. Black box models only describe relationships between observed variables, and they are evaluated by their ability to accurately describe the values of observed variables in new situations not previously available to the model–such as the output response to a new set of inputs, for example. Black box models describe the observed behavior of the underlying system, but they may not correctly describe the way in which the system computes this behavior. White box models, on the other hand, describe the observed behavior and also incorporate hidden, intermediate variables that are used to describe the specific computation the underlying system uses to generate its observed behavior. In this sense, we say the white box model captures the structure of the system, in addition to its observed behavior. Since a given white box model may be accurately described by an infinite variety of black box models, all computing the same observed behavior but using different structures to do so, we say that any of these black box models is an abstraction of the white box model. This thesis constructs foundational pieces of a unifying theory of linear mathematical abstractions that are central to scientific modeling. It offers a precise description of the spectrums of grey box models linking any white and black box representation. There are various motivations for having this rich variety of representations of a given system. One key motivation is that of consilience, that is, to deepen our understanding of the modeling process by connecting various well developed theories under the umbrella of a broader theory. This work offers a precise relationship between Mason’s signal flow graphs [34] and Willem’s behavioral systems theory [66], in addition to linking the classical transfer function theory used by Nyquist [44], Bode [3], and Weiner [65] to the state space theory preferred by Kalman [27]. Another motivation comes from the application of identification or learning a model of the system from data. Learning problems trade off the number of a priori assumptions that one must make about a system, as well as the richness of available data, with the complexity of a model that one is able to confidently learn from measured observations. This work offers insight into these tradeoffs by characterizing them precisely over entire spectrums of grey box models of increasing complexity. A third motivation comes from the application of vulnerability analysis, which is the study of sensitivities of system behavior to structural perturbations in a grey-box model describing the attack surface, or representation of the system as visible to a potential attacker. The main results of this work, and its specific contributions, are as follows: 1. We define new graph-theoretic constructs and use them to create a unified framework for structural abstractions, 2. We demonstrate that there will always exist a complete, structure preserving, acyclic abstraction for every single-input, fully-connected system, 3. We define structural controllability of an abstraction of a system and argue why our definition is good, and 4. We show how complete abstractions preserve structural controllability. These results were accepted for publication in two papers at the 2020 International Federation of Automatic Control World Congress, each submitted to a different special invited session. These papers comprise Chapters 2 and 3, respectively, of the thesis presented here, and they are expected to appear in print July 2020.
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Movement Kinematics and Fractal Properties in Fitts’ Law TaskJanuary 2019 (has links)
abstract: Fractal analyses examine variability in a time series to look for temporal structure
or pattern that reveals the underlying processes of a complex system. Although fractal
property has been found in many signals in biological systems, how it relates to
behavioral performance and what it implies about the complex system under scrutiny are
still open questions. In this series of experiments, fractal property, movement kinematics,
and behavioral performance were measured on participants performing a reciprocal
tapping task. In Experiment 1, the results indicated that the alpha value from detrended
fluctuation analysis (DFA) reflected deteriorating performance when visual feedback
delay was introduced into the reciprocal tapping task. This finding suggests that this
fractal index is sensitive to performance level in a movement task. In Experiment 2, the
sensitivity of DFA alpha to the coupling strength between sub-processes within a system
was examined by manipulation of task space visibility. The results showed that DFA
alpha was not influenced by disruption of subsystems coupling strength. In Experiment 3,
the sensitivity of DFA alpha to the level of adaptivity in a system under constraints was
examined. Manipulation of the level of adaptivity was not successful, leading to
inconclusive results to this question. / Dissertation/Thesis / Masters Thesis Psychology 2019
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Stochastic Block Model DynamicsNithish Kumar Kumar (10725294) 29 April 2021 (has links)
<div>The past few years have seen an increasing focus on fairness and the long-term impact of algorithmic decision making in the context of Machine learning, Artificial Intelligence and other disciplines. In this thesis, we model hiring processes in enterprises and organizations using dynamic mechanism design. Using a stochastic block model to simulate the workings of a hiring process, we study fairness and long-term evolution in the system. </div><div> </div><div> We first present multiple results on a deterministic variant of our model including convergence and an accurate approximate solution describing the state of the deterministic variant after any time period has elapsed. Using the differential equation method, it can be shown that this deterministic variant is in turn an accurate approximation of the evolution of our stochastic block model with high probability.</div><div> </div><div> Finally, we derive upper and lower bounds on the expected state at each time step, and further show that in the limiting case of the long-term, these upper and lower bounds themselves converge to the state evolution of the deterministic system. These results offer conclusions on the long-term behavior of our model, thereby allowing reasoning on how fairness in organizations could be achieved. We conclude that without sufficient, systematic incentives, under-represented groups will wane out from organizations over time.</div>
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Exploring Feedback Modalities Using Wearable Device for Complex Systems Training ProgramsAkilan, Layla January 2018 (has links)
No description available.
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AN APPLICATION OF SINGULAR PERTURBATION THEORY TO THESTUDY OF THE LONGITUDINAL MOTION OF A DISCRETIZEDVISCOELASTIC RODKane, Joshua Paul 09 July 2020 (has links)
No description available.
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Impact of Attention on Perception in Cognitive Dynamic SystemsAmiri, Ashkan 30 September 2014 (has links)
The proposed aim of this thesis, inspired by the human brain, is to improve on the performance of a perceptual processing algorithm, referred to as a “perceptor”. This is done by trying to bridge the gap between neuroscience and engineering. To this end, we build on localized perception-action cycle in cognitive neuroscience by categorizing it under the umbrella of perceptual attention, which lends itself to increase gradually the contrast between relevant information and irrelevant information. Stated in another way, irrelevant information is filtered away while relevant information about the environment is enhanced from one cycle to the next. Accordingly, we propose to improve on the performance of a perceptor by modifying it to operate under the influence of perceptual attention. For this purpose, we first start with a single-layered perceptor and investigate the impact of perceptual attention on its performance through two computer experiments: The first experiment uses simulated (real-valued) data that are generated to purposely make the problem challenging. The second experiment uses real-life radar data that are complex-valued, hence the proposal to introduce Wirtinger calculus into derivation of our proposed method. We then take one step further and extend our proposed method to the case where a perceptor is hierarchical. In this context, every constitutive component of a hierarchical perceptor is modified to operate under the influence of perceptual attention. Then, another experiment is carried out to demonstrate the positive impact of perceptual attention on the performance of that hierarchical perceptor, just
described. / Dissertation / Doctor of Philosophy (PhD)
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Ett dynamiskt perspektiv på individuella skillnader av heuristisk kompetens, intelligens, mentala modeller, mål och konfidens i kontroll av mikrovärlden MoroElg, Fredrik January 2002 (has links)
Theories predicting performance of human control of complex dynamic systems must assess how decision makers capture and utilise knowledge for achieving and maintaining control. Traditional problem solving theories and corresponding measures such as Ravens matrices have been applied to predict performance in complex dynamic systems. While they assume stable properties of decision makers to predict control performance in decision-making tasks these tests have shown to provide only a limited degree of prediction in human control of complex dynamic systems. This paper reviews theoretical developments from recent empirical studies and tests the theoretical predictions of a model of dynamic decision-making using a complex dynamic microworld – Moro. The requirements for control of the microworld is analysed in study one. Theoretical predictions from the reviewed theory and results from study one are tested in study two. In study three additional hypotheses are derived by including meta cognitive dynamics to explain anomalies found in study two. A total of 21 Hypotheses are tested. Results indicate that for predicting human control of complex dynamic opaque systems a number of meta cognitive processes play an important role in determining outcome. Specifically, results show that we cannot expect a lower risk of failure in complex dynamic opaque systems from people with high problem solving capabilities when these also express higher goals. Further research should seek to explore the relative contribution of task characteristics to determine conditions under which these meta cognitive processes of decision makers take a dominant role over problem-solving capabilities – enabling improved decision-maker selection and support. / <p>Rapportkod: LiU-Tek-Lic-2002:4. I den tryckta versionen är bilagorna bifogade som CD-skiva. Den elektroniska versionen innehåller den kompletta avhandlingen.</p>
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Analyzing Robustness of an Agent Based Model on Action Potentials in Cardiac TissueLara, Marion Jon Zollinger 01 June 2023 (has links) (PDF)
An agent based model (ABM) is a computational model with ``agents'' that interact with each other in an ``environment.'' This paper analyzes a particular ABM simulating individual ions in cardiac tissue, with the goal of modelling the strength and consistency of the electrical signals needed for a healthy heartbeat. We build several frameworks based on work by M. A. Yereniuk and S. D. Olson to demonstrate robustness of the original model. We conclude a moderate level of robustness using those frameworks, through a combination of proofs and empirical evidence.
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Dynamics of Affordance ActualizationNordbeck, Patric C. January 2017 (has links)
No description available.
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