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Your search keyword '"Stirling, James R."' showing total 11 results
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11 results on '"Stirling, James R."'

1. Dynamical system models of patchiness in estuaries

Author

Stirling, James R.

Subjects
628.168, Water pollution & oil pollution
Abstract

We develop three models for the flow in an estuary. The first being a 2 1-dimensional time-periodic model of a flow in the vertical cross section. The second model adds a third un-coupled velocity field U, in the along-estuary direction. The final model is a 3 + 1-dimensional, fully-coupled, time-periodic flow. We study the transport of material in each model using what are called lobe diagrams. Such diagrams allow us to separate the flow into different regions and then calculate the transport of material between adjacent regions. We also study the presence and bifurcations of curves which form partial barriers (ie. cantori and barriers formed from segments of unstable and stable manifolds of hyperbolic periodic points) or complete barriers (ie. KAM curves and other invariant circles) to transport. We use these models to develop an understanding of both the mixing within the flow and the formation and leakage of patches of higher concentration within a cloud of pollution released into the estuary. We also study the time taken for particles to exit the bounds of the estuary. As a result we get an understanding of which regions of the flow flush pollution out of the estuary in the least time and out of which end of the estuary they flush the pollution. We apply this understanding, and that gained from studying the mixing and formation of patches, to the problem of the optimal discharge of effluent into an estuary.

Published
1998

2. Mathematical tools for identifying the fetal response to physical exercise during pregnancy

Author

Zakynthinaki, Maria S., Barakat Carballo, Rubén O., and Stirling, James R.

Abstract

As physical exercise has become part of everyday life, it is natural that most of the women that become pregnant wish to continue their exercise routine. It is, however, very important to obtain information regarding the effects of exercise during pregnancy regarding both fetal and maternal anatomy and physiology in order to avoid any possible negative effects on the fetus.

Published
2021

4. Obtaining the basic response pattern of physiological time series data : a comparison of methods

Author

Zakynthinaki, Maria S., Stirling, James R., Sillero, M., Sampedro, J., and Refoyo, I.

Abstract

An understanding of the kinetics of physiological variables such as the heart rate or the rate of change of volume of oxygen uptake is fundamental not only to training methodology and competitive success in sport and exercise, but also to our knowledge of cardiovascular health. A correct and efficient means of interpreting and analyzing the data obtained is of vast importance, as exercise testing is routinely used in both of these areas.

Published
2007

5. Geometry and transport in a model of two coupled quadratic nonlinear waveguides

Author

Stirling, James R., Bang, Ole, Christiansen, Peter Leth, Zakynthianaki, Maria S., Johansen, Steffen Kjær, Stirling, James R., Bang, Ole, Christiansen, Peter Leth, Zakynthianaki, Maria S., and Johansen, Steffen Kjær

Abstract

This paper applies geometric methods developed to understand chaos and transport in Hamiltonian systems to the study of power distribution in nonlinear waveguide arrays. The specific case of two linearly coupled X(2) waveguides is modeled and analyzed in terms of transport and geometry in the phase space. This gives us a transport problem in the phase space resulting from the coupling of the two Hamiltonian systems for each waveguide. In particular, the effect of the presence of partial and complete barriers in the phase space on the transfer of intensity between the waveguides is studied, given a specific input and range of material properties. We show how these barriers break down as the coupling between the waveguides is increased and what the role of resonances in the phase space has in this. We also show how an increase in the coupling can lead to chaos and global transport and what effect this has on the intensity. ©2008 American Institute of Physics

Published
2008

10. Modeling the basin of attraction as a two-dimensional manifold from experimental data: applications to balance in humans.

Author

Zakynthinaki MS, Stirling JR, Martínez CA, de Durana AL, Quintana MS, Romo GR, and Molinuevo JS

Subjects
Adult, Algorithms, Biophysics methods, Humans, Male, Models, Statistical, Models, Theoretical, Movement, Nonlinear Dynamics, Normal Distribution, Oscillometry methods, Stochastic Processes, Postural Balance
Abstract

We present a method of modeling the basin of attraction as a three-dimensional function describing a two-dimensional manifold on which the dynamics of the system evolves from experimental time series data. Our method is based on the density of the data set and uses numerical optimization and data modeling tools. We also show how to obtain analytic curves that describe both the contours and the boundary of the basin. Our method is applied to the problem of regaining balance after perturbation from quiet vertical stance using data of an elite athlete. Our method goes beyond the statistical description of the experimental data, providing a function that describes the shape of the basin of attraction. To test its robustness, our method has also been applied to two different data sets of a second subject and no significant differences were found between the contours of the calculated basin of attraction for the different data sets. The proposed method has many uses in a wide variety of areas, not just human balance for which there are many applications in medicine, rehabilitation, and sport.

Published
2010
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11. Geometry and transport in a model of two coupled quadratic nonlinear waveguides.

Author

Stirling JR, Bang O, Christiansen PL, Zakynthinaki MS, and Johansen SK

Abstract

This paper applies geometric methods developed to understand chaos and transport in Hamiltonian systems to the study of power distribution in nonlinear waveguide arrays. The specific case of two linearly coupled chi((2)) waveguides is modeled and analyzed in terms of transport and geometry in the phase space. This gives us a transport problem in the phase space resulting from the coupling of the two Hamiltonian systems for each waveguide. In particular, the effect of the presence of partial and complete barriers in the phase space on the transfer of intensity between the waveguides is studied, given a specific input and range of material properties. We show how these barriers break down as the coupling between the waveguides is increased and what the role of resonances in the phase space has in this. We also show how an increase in the coupling can lead to chaos and global transport and what effect this has on the intensity.

Published
2008
Full Text
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