Physical Sciences and Mathematics Commons^™

Observations Of Cross Channel Structure Of Flow In An Energetic Tidal Channel, Mario Caceres, Arnoldo Valle-Levinson, Larry P. Atkinson

CCPO Publications

[1] Measurements of velocity and density profiles were made to describe the transverse structure of flow in Chacao Channel, Southern Chile (41.75 degreesS), where typical tidal velocities are similar to4 m/s. Current profiles were obtained with a 307.2 kHz Acoustic Doppler Current Profiler (ADCP) over 25 repetitions of a cross-channel transect during one semidiurnal tidal cycle. The 2.2 km long transect ran northeast/southwest across the channel. A northern channel (120 m deep) and a southern channel (85 m deep) were separated by Remolinos Rock, a pinnacle that rises to 20 m depth at similar to0.7 km from the southern side. …

River Meandering Dynamics, Boyd F. Edwards, D. H. Smith

All Physics Faculty Publications

The Ikeda, Parker, and Sawai river meandering model is reexamined using a physical approach employing an explicit equation of motion. For periodic river shapes as seen from above, a cross-stream surface elevation gradient creates a velocity shear that is responsible for the decay of small-wavelength meander bends, whereas secondary currents in the plane perpendicular to the downstream direction are responsible for the growth of large-wavelength bends. A decay length D=H/2C_f involving the river depth H and the friction coefficient C_f sets the scale for meandering, giving the downstream distance required for the fluid velocity profile to recover from …

Impact Of Sea Grass Density On Carbonate Dissolution In Bahamian Sediments, David J. Burdige, Richard C. Zimmerman

OES Faculty Publications

Carbonate dissolution has been widely observed in shallow water tropical sediments. However, sediment budgets C have generally not been closed with respect to the amount of acid required to produce the observed carbonate dissolution. Recently it has been suggested that enhanced oxygen transport into sediments through the roots and rhizomes of sea grasses might play a role in resolving this mass balance problem. We conducted studies of sea grass-carbonate sediment interactions around Lee Stocking Island, Exuma Islands, Bahamas to further examine this problem. Our studies showed that alkalinity, total dissolved inorganic carbon (ΣCO₂) and Ca²⁺ increased with …

Single-Particle Model For A Granular Ratchet, Albert J. Bae, Welles Antonio Martinez Morgado, J. J. P. Veerman, Giovani L. Vasconcelos

Mathematics and Statistics Faculty Publications and Presentations

A simple model for a granular ratchet corresponding to a single grain bouncing off a vertically vibrating sawtooth-shaped base is studied. Depending on the model parameters, horizontal transport is observed in both the preferred and unfavoured directions. A phase diagram is presented indicating the regions in parameter space where the different regimes (no current, normal current, and current reversal) occur.

Open Strings, 2d Gravity, And Ads/Cft Correspondence, Mariano Cadoni, Marco Cavaglia

Physics Faculty Research & Creative Works

We present a detailed discussion of the duality between dilaton gravity on AdS₂ and open strings. The correspondence between the two theories is established using their symmetries and field theoretical, thermodynamic, and statistical arguments. We use the dual conformai field theory to describe two-dimensional black holes. In particular, all the semiclassical features of the black holes, including the entropy, have a natural interpretation in terms of the dual microscopic conformai dynamics. The previous results are discussed in the general framework of the anti-de Sitter/conformal field theory dualities.

Molecular Dynamics Simulation Of Biomolecular Systems, Wilfred Van Gunsteren, Dirk Bakowies, Roland Buergi, Indira Chandrasekhar, Markus Christen, Xavier Daura, Peter Gee, Alice Glaettli, Tomas Hansson, Chris Oostenbrink, Christine Peter, Jed Pitera, Lukas Schuler, Thereza Soares, Haibo Yu

Faculty of Science - Papers (Archive)

The group for computer-aided chemistry at the ETH Zurich focuses its research on the development of methodology to simulate the behavior of biomolecular systems and the use of simulation techniques to analyze and understand biomolecular processes at the atomic level. Here, the current research directions are briefly reviewed and illustrated with a few examples.

Geometrical Models For Grain Dynamics, Giovani L. Vasconcelos, J. J. P. Veerman

Mathematics and Statistics Faculty Publications and Presentations

We study models for the gravity-driven, dissipative motion of a single grain on an inclined rough surface. Imposing some conditions on the momentum loss due to the collisions between the particle and the surface, we arrive at a class of models in which the grain dynamics is described by one-dimensional maps. The dynamics of these maps is studied in detail. We prove the existence of various dynamical phases and show that the presence of these phases is independent of the restitution law (within the class considered).

Geometrical Model For A Particle On A Rough Inclined Surface, Giovani L. Vasconcelos, J. J. P. Veerman

Mathematics and Statistics Faculty Publications and Presentations

A simple geometrical model is presented for the gravity-driven motion of a single particle on a rough inclined surface. Adopting a simple restitution law for the collisions between the particle and the surface, we arrive at a model in which the dynamics is described by a one-dimensional map. This map is studied in detail and it is shown to exhibit several dynamical regimes (steady state, chaotic behavior, and accelerated motion) as the model parameters vary. A phase diagram showing the corresponding domain of existence for these regimes is presented. The model is also found to be in good qualitative agreement …

Crossing Of Disclinations In Nematic Slabs, T. Ishikawa, Oleg Lavrentovich

Oleg Lavrentovich

It is shown experimentally that crossing and intercommutation of disclinations in a bounded nematic cell depend on surface orientation of the director and the relative strength of disclinations. Lines of opposite strength switch the pinned ends between the bounding plates and vanish independently of each other if the surface orientation is tangential. In contrast, tilted surface orientation preserves the stability of lines.

Integrable Unsteady Motion With An Application To Ocean Eddies, A. D. Kirwan Jr., Bruce L. Lipphardt

CCPO Publications

Application of the Brown-Samelson theorem, which shows that particle motion is integrable in a class of vorticity-conserving, two-dimensional incompressible hows, is extended here to a class of explicit time dependent dynamically balanced flows in multilayered systems. Particle motion for nonsteady two-dimensional flows with discontinuities in the vorticity or potential vorticity fields (modon solutions) is shown to be integrable. An example of a two-layer modon solution constrained by observations of a Gulf Stream ring system is discussed.

Modeling The Uptake And Transpiration Of Tce Using Phreatophytic Trees, Douglas P. Wise

Theses and Dissertations

Phytoremediation is a recent addition to the numerous methods used today to remediate ground water contaminants. It is proving more effective and efficient compared to existing remediation techniques. The use of phreatophytes, or water seeking trees, has great potential for phytoremediation. These trees are fast growing, long lived, grow their roots down to the ground water table, transpire large amounts of water, and are proven to actively remove contaminants from the soil horizon. The purpose of this research is to develop quantitative concepts for understanding the dynamics of TCE uptake and transpiration by phreatophytic trees over a short rotation woody …

Fourth Siam Conference On Applications Of Dynamical Systems, Siam Activity Group On Dynamical Systems

All U.S. Government Documents (Utah Regional Depository)

No abstract provided.

Inclusive Electron Scattering From Nuclei At X≃1, J. Arrington, P. Anthony, R. G. Arnold, E. J. Beise, J. E. Belz, P. E. Bosted, H.- J. Bulten, M. S. Chapman, K. P. Coulter, F. Dietrich, R. Ent, M. Epstein, B. W. Filippone, H. Gao, R. A. Gearhart, D. F. Geesaman, J.- O. Hansen, R. J. Holt, H. E. Jackson, C. E. Jones, C. E. Keppel, E. R. Kinney, S. Kuhn, K. Lee, W. Lorenzon, A. Lung, N.C.R. Malkins, D. J. Margaziotis, R. D. Mckeown, R. G. Milner, B. Mueller, J. Napolitano, J. Nelson, T.G. O'Neill, V. Papavassiliou, G. G. Petratos, D. H. Potterveld, S. E. Rock, M. Spengos, Z. M. Szalata, L. H. Tao, K. Van Bibber, J.F.J. Van Den Brand, J. L. White, D. Winter, B. Zeidman

Physics Faculty Publications

The inclusive A(e,e') cross section for x≃1 was measured on ²H, C, Fe, and Au for momentum transfers Q² from 1 to 6.8 (GeV/c)². The scaling behavior of the data was examined in the region of transition from y scaling to x scaling. Throughout this transitional region, the data exhibit ξ scaling, reminiscent of the Bloom-Gilman duality seen in free nucleon scattering.

Complex Dynamics And Multistability In A Damped Harmonic Oscillator With Delayed Negative Feedback, Sue Ann Campbell, Jacques Bélair, Toru Ohira, John Milton

WM Keck Science Faculty Papers

A center manifold reduction and numerical calculations are used to demonstrate the presence of limit cycles, two-tori, and multistability in the damped harmonic oscillator with delayed negative feedback. This model is the prototype of a mechanical system operating with delayed feedback. Complex dynamics are thus seen to arise in very plausible and commonly occurring mechanical and neuromechanical feedback systems.

Current Meter Observations In The Old Bahama Channel, L. P. Atkinson, T. Berger, P. Hamilton, E. Waddell, K. Leaman, T. N. Lee

CCPO Publications

Current meter observations were made at 50, 250, and 435 m in 495 m of water at the center of the Old Bahama Channel between November 1990 and November 1991. The mean speed at those depths was 2.6, 50, and 26 cm s^-1 toward the Straits of Florida. A maximum speed of 193 cm s^-1 was found at the 250-m level. There was evidence of a speed maximum between 50 and 250 m. Large internal diurnal tidal currents were observed that produced high shears in the water column under some conditions. Transport calculated from the single mooring using …

Geometrical Phases And Symmetries In Dissipative Systems, Adam S. Landsberg

WM Keck Science Faculty Papers

A geometrical phase is constructed for dissipative dynamical systems possessing continuous symmetries. It emerges as the natural analog of the holonomy associated with the adiabatic variation of parameters in quantum-mechanical and classical Hamiltonian systems. In continuous media, the physical manifestation of this phase is a spatial shift of a wave pattern, typically a translation or rotation. An illustration associated with pattern formation in fluids is provided.

Effects Of Wind, Density, And Bathymetry On A One-Layer Southern Ocean Model, John M. Klinck

CCPO Publications

Steady solutions from a one-layer, wind-driven, primitive equation model are analyzed to determine the importance of wind forcing, pressure gradient force due to the climatological density distribution and bottom form drag on circulation in the Southern Ocean. Five simulations are discussed: three wind-forced simulations, with differing bathymetry (flat bottom, 15% bathymetry, and full bathymetry), one case with full bathymetry forced with the density-induced pressure force, and one case with full bathymetry forced by both wind and density-induced pressure gradients. The simulations presented here confirm the previous speculation (Munk and Palmen, 1951) that form drag is effective in balancing the driving …

Bounds On Constraint Weight Parameters Of Hopfield Networks For Stability Of Optimization Problem Solutions, Gursel Serpen

Electrical & Computer Engineering Theses & Dissertations

The purpose of the presented research is to study the convergence characteristics of Hopfield network dynamics. The relation between constraint weight parameter values and the stability of solutions of constraint satisfaction and optimization problems mapped to Hopfield networks is investigated. A theoretical development relating constraint weight parameter values to solution stability is presented. The dependency of solution stability on constraint weight parameter values is shown employing an abstract optimization problem. A theorem defining bounds on the constraint weight parameter magnitudes for solution stability of constraint satisfaction and optimization problems is proved. Simulation analysis on a set of optimization and constraint …

A Mathematical Model Of The Dynamics Of An Optically Pumped Four-Level Solid State Laser System, Lila Freeman Roberts

Mathematics & Statistics Theses & Dissertations

This is a study of a mathematical model of the dynamics of an optically pumped four-level solid state laser system. A general mathematical model that describes the spatial and temporal evolution of the electron populations in the laser rod as well as the development of the left and right traveling photon fluxes in the cavity is developed. The model consists of a coupled set of first order semilinear partial differential equations. While the model was developed for Titanium-doped sapphire lasers, it is applicable to three and four level lasers in general.

The analysis of the model is conducted in two …

The Role Of Diffusion In The Binding Of Carbon Monoxide To Protoheme In High-Viscosity Solvents, David Peak

All Physics Faculty Publications

Studies of the flash photolysis of heme‐bearing proteins have often assessed the role of ligand diffusion in very approximate ways and a disagreement about the importance of ligand diffusion exists in the literature as a result. This paper provides a somewhat more sytematic analysis of diffusional effects than has been given previously for the simple case of ligand–protoheme binding. The model developed here is fit to the available data for the ligand CO in glycerol–water solvents. The fit suggests that diffusional motions become important for the kinetics of this system for temperatures below 270 K and that these motions are …

The Phosphorus Dynamics Of A Eutrophic Prairie Reservoir, John F. Bender

School of Natural Resources: Dissertations, Theses, and Student Research

No abstract provided.

Population Dynamics And Harvest Of Canada Geese In Utah, John Tautin

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A twenty-one year (1952-72) accumulation of banding data for Canada geese in Utah was studied to determine the distribution and chronology of the harvest of the geese and the effects that hunting regulations have had upon harvests and population parameters. The banding data were also used in an attempt to develop a population model capable of predicting population trends and desirable survival rates.

Within Utah, the bulk of the annual harvest (78 percent) takes place in the northern portion of the State in the vicinity of the Great Salt Lake marshes. In Northern Utah the harvest peaks on the opening …