Advanced search options

Advanced Search Options 🞨

Browse by author name (“Author name starts with…”).

Find ETDs with:

in
/  
in
/  
in
/  
in

Written in Published in Earliest date Latest date

Sorted by

Results per page:

Sorted by: relevance · author · university · dateNew search

You searched for subject:(periodic windows). Showing records 1 – 2 of 2 total matches.

Search Limiters

Last 2 Years | English Only

No search limiters apply to these results.

▼ Search Limiters

1. Baptista, Murilo da Silva. Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos.

Degree: PhD, Física Nuclear, 1996, University of São Paulo

Inicialmente, consideramos o mapa Logístico com os vários fenômenos nele presentes, para depois, ao perturbarmos esse mapa, adicionando periodicamente um termo de amplitude constante, identificarmos os novos fenômenos e as alterações que a introdução da perturbação faz aparecer. Apresentamos o circuito eletrônico de Matsumoto e, em seguida, o consideramos em um regime caótico perturbado por uma tensão elétrica senoidal externa. A introdução desta perturbação faz o circuito permanecer caótico, tornar-se periódico ou quasi-periódico no toro de duas frequências. Aplicamos diversos métodos de controle de caos a três sistemas (mapa Logístico, mapa de Hénon e circuito de Matsumoto). Para a estabilização de uma órbita periódica, consideramos os métodos de Ott-Grebogi-Yorke (OGY), de Romeiras, de Pyragas, de Sinha, de Singer e de H¨ubbler. Para o direcionamento da trajetória para um ponto de equilíbrio, usamos o método de Sinha. Para a transferência da trajetória para um dos atratores coexistentes no sistema de Matsumoto, usamos o método de Jackson-H¨ubbler (OPCL). Usando um conjunto de pertubações constantes em um parâmetro previamente escolhido, mostramos como é possével dirigir rapidamente uma trajetória, de qualquer um dos três sistemas considerados nesta tese, para um determinado alvo. Além disso, é mostrado como esse método pode ser aplicado experimentalmente.

Initially, we consider the Logistic map with its many non-linear phenomena. Then, we use this knowledge to discern new phenomena that shall appear when the map is perturbed, that is the Logistic map perturbed by a periodic and constant term. The Matsumoto\'s circuit is presented and, after we set this circuit to behave chaotically, we perturb it with a sinoidal wave, characterized by its frequency and amplitude. This perturbation is responsible for the appearence of a quasi-periodic and periodic oscillations, or the maintenance of chaos. We presented and applied many methods for controlling chaotic oscillations in three systems (the Logistic and Henon maps, and the Matsumoto\'s circuit), showing many ways for stabilizing a periodic orbit, using the methods of Ott-Grebogi-York (OGY), Romeiras, Singer, Sinhas and Huebbler. For targeting the trajectory to a equilibrium point, the Sinha\'s method was used. To transfer the system trajectory from one to another of the coexisting attractors presented in the Matsumoto\'s circuit, we use the Jackson-Huebbler (OPCL) method. Using a set of constant perturbations, in a previously chosen parameter, we showed how we can rapidly direct a trajectory of any of the considered three systems to a aimed target. Besides, it is shown how this method can be experimentally applied.

Advisors/Committee Members: Caldas, Ibere Luiz.

Subjects/Keywords: 1. Sistemas Dinâmicos 2. Estudo de Comportamento Caótico 3. Controle de Caos 4. Rotas para o Caos; Chaos control; Chua\'s circuit.; homoclinic bifurcation; periodic windows; route to chaos

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Baptista, M. d. S. (1996). Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos. (Doctoral Dissertation). University of São Paulo. Retrieved from http://www.teses.usp.br/teses/disponiveis/43/43131/tde-13122007-093342/ ;

Chicago Manual of Style (16th Edition):

Baptista, Murilo da Silva. “Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos.” 1996. Doctoral Dissertation, University of São Paulo. Accessed July 20, 2019. http://www.teses.usp.br/teses/disponiveis/43/43131/tde-13122007-093342/ ;.

MLA Handbook (7th Edition):

Baptista, Murilo da Silva. “Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos.” 1996. Web. 20 Jul 2019.

Vancouver:

Baptista MdS. Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos. [Internet] [Doctoral dissertation]. University of São Paulo; 1996. [cited 2019 Jul 20]. Available from: http://www.teses.usp.br/teses/disponiveis/43/43131/tde-13122007-093342/ ;.

Council of Science Editors:

Baptista MdS. Perturbando Sistemas Não-Lineares, uma Abordagem do Controle de Caos. [Doctoral Dissertation]. University of São Paulo; 1996. Available from: http://www.teses.usp.br/teses/disponiveis/43/43131/tde-13122007-093342/ ;

2. Thompson, Garth John. Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns.

Degree: PhD, Biomedical Engineering (Joint GT/Emory Department), 2013, Georgia Tech

While task-based functional magnetic resonance imaging (fMRI) has helped us understand the functional role of many regions in the human brain, many diseases and complex behaviors defy explanation. Alternatively, if no task is performed, the fMRI signal between distant, anatomically connected, brain regions is similar over time. These correlations in “resting state” fMRI have been strongly linked to behavior and disease. Previous work primarily calculated correlation in entire fMRI runs of six minutes or more, making understanding the neural underpinnings of these fluctuations difficult. Recently, coordinated dynamic activity on shorter time scales has been observed in resting state fMRI: correlation calculated in comparatively short sliding windows and quasi-periodic (periodic but not constantly active) spatiotemporal patterns. However, little relevance to behavior or underlying neural activity has been demonstrated. This dissertation addresses this problem, first by using 12.3 second windows to demonstrate a behavior-fMRI relationship previously only observed in entire fMRI runs. Second, simultaneous recording of fMRI and electrical signals from the brains of anesthetized rats is used to demonstrate that both types of dynamic activity have strong correlates in electrophysiology. Very slow neural signals correspond to the quasi-periodic patterns, supporting the idea that low-frequency activity organizes large scale information transfer in the brain. This work both validates the use of dynamic analysis of resting state fMRI, and provides a starting point for the investigation of the systemic basis of many neuropsychiatric diseases. Advisors/Committee Members: Keilholz, Shella D. (advisor), Hu, Xiaoping (committee member), Jaeger, Dieter (committee member), Stanley, Garrett B. (committee member), Epstein, Charles M. (committee member).

Subjects/Keywords: fMRI; Dynamic analysis; Sliding window; Sliding windows; Resting state; Default mode; Functional connectivity; Functional network; Correlation; Coherence; Functional magnetic resonance imaging; Local field potentials; LFP; Band-limited power; BLP; Inter-individual; Intra-individual; Spontaneous activity; Brain; Primary somatosensory cortex; Rodent; Rat; Human; Simultaneous experiments; Neural basis; Glial basis; Neurons; Astrocytes; Vasomotion; Hemodynamic response; Dynamic; Spatiotemporal dynamics; Quasi-periodic patterns; Brain networks; Resting state networks; Anesthesia; Dexmedetomidine; Isoflurane; Awake; Global signal; Magnetic resonance imaging; Brain Pathophysiology; Brain mapping

…sliding windows and quasi-periodic (periodic but not constantly active) spatiotemporal… …2.3.7 Generation of Masks in 12.3s Windows (Figure 2.10)… …63 2.4 Movies of networks generated within 12.3s windows… …70 2.5.3 Correlation within entire functional imaging runs vs. 12.3 second windows… …123 NEURAL BASIS OF DYNAMIC RESTING STATE FMRI DEFINED BY QUASI-PERIODIC PATTERNS… 

Record DetailsSimilar RecordsGoogle PlusoneFacebookTwitterCiteULikeMendeleyreddit

APA · Chicago · MLA · Vancouver · CSE | Export to Zotero / EndNote / Reference Manager

APA (6th Edition):

Thompson, G. J. (2013). Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns. (Doctoral Dissertation). Georgia Tech. Retrieved from http://hdl.handle.net/1853/49083

Chicago Manual of Style (16th Edition):

Thompson, Garth John. “Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns.” 2013. Doctoral Dissertation, Georgia Tech. Accessed July 20, 2019. http://hdl.handle.net/1853/49083.

MLA Handbook (7th Edition):

Thompson, Garth John. “Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns.” 2013. Web. 20 Jul 2019.

Vancouver:

Thompson GJ. Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns. [Internet] [Doctoral dissertation]. Georgia Tech; 2013. [cited 2019 Jul 20]. Available from: http://hdl.handle.net/1853/49083.

Council of Science Editors:

Thompson GJ. Neural basis and behavioral effects of dynamic resting state functional magnetic resonance imaging as defined by sliding window correlation and quasi-periodic patterns. [Doctoral Dissertation]. Georgia Tech; 2013. Available from: http://hdl.handle.net/1853/49083

.