Physical Sciences and Mathematics Commons^™

Simple Model For Linear And Nonlinear Mixing At Unstable Fluid Interfaces With Variable Acceleration, John D. Ramshaw

Physics Faculty Publications and Presentations

A simple model is described for predicting the time evolution of the half-width h of a mixing layer between two initially separated immiscible fluids of different density subjected to an arbitrary time-dependent variable acceleration history a(t). The model is based on a heuristic expression for the kinetic energy per unit area of the mixing layer. This expression is based on that for the kinetic energy of a linearly perturbed interface, but with a dynamically renormalized wavelength which becomes proportional to h in the nonlinear regime. An equation of motion for h is then derived from Lagrange's equations. This model reproduces …

Factors Affecting Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan

Physics Faculty Publications and Presentations

Methane emissions from rice fields are affected by a number of environmental and agricultural factors. We have analyzed our 7-year data set on methane emissions from rice fields in Tu Zu, China, to delineate the relationships between emissions and a number of variables that were measured at the same time. Our work was done in fields that were managed under prevailing agricultural practices of the region. Consequently, only the effect of factors that vary from year to year or during the growing season can be calculated. In our study we measured the effects of environmental variables (soil temperature, wind speed, …

Flux Measurements And Sampling Strategies: Applications To Methane Emissions From Rice Fields, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer

Physics Faculty Publications and Presentations

The emissions of methane from rice fields and other sources are often measured by placing chambers on the surface and taking sequential samples. Although static chambers pose several problems that affect the accuracy of the data, there are a few parameters that, if carefully chosen, can improve the reliability of the data and reduce the uncertainties. These parameters are the length of time the chamber is kept on the rice plants, the number of samples that are drawn to estimate the flux, the basal area and height of the chamber, the frequency of measurements during the growing season, and the …

Effects Of Production And Oxidation Processes On Methane Emissions From Rice Fields, M. Khalil, R. A. Rasmussen, Martha J. Shearer

Physics Faculty Publications and Presentations

The emission of methane from rice fields is the difference between the amount produced in the anaerobic zone below the soil and the amount oxidized in the root zone. Plants can also contribute to methane production by exuding organic compounds that may be utilized by methanogenic bacteria. We measured methane emissions from rice fields at Tu Zu in China between 1988 and 1994, which gave average emissions of about 30 mg m⁻² h⁻¹. We estimate that 45-60% of the methane produced was oxidized before reaching the atmosphere; and root exudates may have contributed of the order of 10% of the …

Measurements Of Methane Emissions From Rice Fields In China, M. A. K. Khalil, R. A. Rasmussen, Martha J. Shearer, R. W. Dalluge, Lixin Ren, Chang-Lin Duan

Physics Faculty Publications and Presentations

Rice fields have always been regarded as one of the largest anthropogenic sources of atmospheric methane. Here we report the results of a 7-year study of methane emissions from rice fields in the Sichuan Province of China. In this region, there is one crop of rice per year, the fields are continuously flooded from transplanting to harvest, and there is heavy use of organic fertilizers. Emissions over the entire growing season were measured from each of up to 24 plots. Environmental variables were measured and relevant supporting data on the agricultural practices were recorded. The fields were studied under prevailing …

Complexity Reduction In State-Based Modeling, Martin Zwick

Systems Science Faculty Publications and Presentations

For a system described by a relation among qualitative variables (or quantitative variables "binned" into symbolic states), expressed either set-theoretically or as a multivariate joint probability distribution, complexity reduction (compression of representation) is normally achieved by modeling the system with projections of the overall relation. To illustrate, if ABCD is a four variable relation, then models ABC:BCD or AB:BC:CD:DA, specified by two triadic or four dyadic relations, respectively, represent simplifications of the ABCD relation. Simplifications which are lossless are always preferred over the original full relation, while simplifications which lose constraint are still preferred if the reduction of complexity more …

A Note On The Green Dyadic Calculation Of The Decay Rates For Admolecules At Multiple Planar Interfaces, P.T. Leung, R. L. Hartman, Scott M. Cohen

Physics Faculty Publications and Presentations

The Green dyadic formulation for calculating classical decay rates of admolecules at multiple planar interfaces first published by Chance, Prock and Silbey is reexamined. It is pointed out that, for the case of fluorescing molecules sandwiched between a system of super- and substrate interfaces, the original formalism requires significant modifications in order to lead to results consistent with those obtained from the Sommerfeld radiation theory.

Morphogenesis Of Douglas Fir Buds Is Altered At Elevated Temperature But Not At Elevated Co2, Martha E. Apple, Melissa S. Lucash, David M. Olszyk, David T. Tingey

Environmental Science and Management Faculty Publications and Presentations

Global climatic change as expressed by increased CO₂ and temperature has the potential for dramatic effects on trees. To determine what its effects may be on Pacific Northwest forests, Douglas-fir (Pseudotsuga menziesii ) seedlings were grown in sun-lit controlled environment chambers at ambient or elevated (+4°C above ambient) temperature, and at ambient or elevated (+200 ppm above ambient) CO₂. In 1995–1996 and 1996–1997, elevated CO₂ had no effect on vegetative bud morphology, while the following unusual morphological characteristics were found with greater frequency at elevated temperature than at ambient: rosetted buds with reflexed and loosened outer …

Application Of Mathematical Modeling And Computer Simulation For Solving Water Quality Problems, Jacek Makinia, Scott A. Wells, David Crawford, Marian Kulbik

Civil and Environmental Engineering Faculty Publications and Presentations

Deteriorated water resources in Central and Eastern Europe call for actions that should be undertaken to improve current conditions and to protect human and environmental health. Mathematical modeling and computer simulation is often an integral part of the decision-making process. Models and simulations allow rapid and varied evaluation of causes and effects and the principal advantage is that they enable an analysis of even long-term actions with limited investment costs. This paper provides an overview of popular models used for simulation of major elements of a water quality system: surface water quality (QUAL2E), wastewater treatment (Activated Sludge Model No.1), sewer …

A Feedback-Driven Proportion Allocator For Real-Rate Scheduling, David Steere, Ashvin Goel, Joshua Gruenberg, Dylan Mcnamee, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

In this paper we propose changing the decades-old practice of allocating CPU to threads based on priority to a scheme based on proportion and period. Our scheme allocates to each thread a percentage of CPU cycles over a period of time, and uses a feedback-based adaptive scheduler to assign automatically both proportion and period. Applications with known requirements, such as isochronous software devices, can bypass the adaptive scheduler by specifying their desired proportion and/or period. As a result, our scheme provides reservations to applications that need them, and the benefits of proportion and period to those that do not. Adaptive …

Water Balloon Rupture In Low‐G, Mark M. Weislogel, S. Lichter

Mechanical and Materials Engineering Faculty Publications and Presentations

A qualitative study of the bursting of water balloons in a simulated low-gravity environment was conducted aboard NASA Lewis’s DC-9 aircraft.

The tests were performed to develop techniques to rapidly deploy large liquid drops in a microgravity environment.

Synthetic Files: Enabling Low-Latency File I/O For Qos-Adaptive Applications, Dylan Mcnamee, Dan Revel, Calton Pu, David Steere, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Files are a tried and true operating system abstraction. They present a simple byte-stream model of I/O that has proven intuitive for application programmers and efficient for operating system builders. However, current file systems do not provide good support for adaptive continuous media (CM) applications - an increasingly important class of applications that exhibit complex access patterns and are particularly sensitive to variations in I/O performance. To address these problems we propose synthetic files. Synthetic files are specialized views of underlying regular files, and convert complex file access patterns into simple sequential synthetic file access patterns. Synthetic file construction can …

Water Flow Through Temperate Glaciers, Andrew G. Fountain, Joseph S. Walder

Geography Faculty Publications and Presentations

Understanding water movement through a glacier is fundamental to several critical issues in glaciology, including glacier dynamics, glacier-induced floods, and the prediction of runoff from glacierized drainage basins. To this end we have synthesized a conceptual model of water movement through a temperate glacier from the surface to the outlet stream. Processes that regulate the rate and distribution of water input at the glacier surface and that regulate water movement from the surface to the bed play important but commonly neglected roles in glacier hydrology. Where a glacier is covered by a layer of porous, permeable firn (the accumulation zone), …

The Role Of Soil Test Information In Reducing Groundwater Pollution, Ronald A. Fleming, Richard M. Adams, David E. Ervin

Economics Faculty Publications and Presentations

Testing soils for nutrients is expected to improve groundwater quality. However, it is unknown whether soil testing will improve groundwater quality sufficiently to decrease the demand for direct regulation of agricultural practices. Focusing on an irrigated agricultural region in eastern Oregon, the economic and environmental aspects of soil testing are assessed using a spatially distributed, dynamic simulation model which links economic behavior with the physical processes that determine groundwater quality. Results indicate that soil testing of all fields increases farm profits and reduces groundwater nitrate concentration. However, the benefits are small in terms of potential improvements in groundwater quality.

Quality Of Service Semantics For Multimedia Database Systems, Jonathan Walpole, Charles Krasic, Ling Liu, David Maier, Calton Pu, Dylan Mcnamee, David Steere

Computer Science Faculty Publications and Presentations

Quality of service (QoS) support has been a hot research topic in multimedia databases, and multimedia systems in general, for the past several years. However, there remains little consensus on how QoS support should be provided. At the resource-management level, systems designers are still debating the suitability of reservation- based versus adaptive QoS management. The design of higher system layers is less clearly understood, and the specification of QoS requirements in domain-specific terms is still an open research topic. To address these issues, we propose a QoS model for multimedia databases. The model covers the specification of user-level QoS preferences …

Path Integral For The Quantum Harmonic Oscillator Using Elementary Methods, Scott M. Cohen

Physics Faculty Publications and Presentations

We present a purely analytical method to calculate the propagator for the quantum harmonic oscillator using Feynman’s path integral. Though the details of the calculation are involved, the general approach uses only matrix diagonalization and well-known integrals, techniques which an advanced undergraduate should understand. The full propagator, including both the prefactor and the classical action, is obtained from a single calculation which involves the exact diagonalization of the discretized action for the system.

General Formulation Of The Semirelativistic Approach To Atomic Sum Rules, P.T. Leung, Scott M. Cohen

Physics Faculty Publications and Presentations

A general scheme is presented for obtaining systematic relativistic corrections to quantum-mechanical sum rules for various calculations in atomic physics. The single-particle picture and the Foldy-Wouthuysen transformation [Phys. Rev. 78, 29 (1950)] are adopted to derive such corrections. Results are obtained for the ldquogeneralized Bethe sums,rdquo which include all higher moments of the energy transfer, and explicit results are given to the lowest order of relativistic corrections.

Location Independent Names For Nomadic Computers, David Steere, Mark Morrissey, Peter Geib, Calton Pu, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Recent advances in the Domain Name System (DNS) and the Dynamic Host Configuration Protocol (DHCP) have enabled a new approach to supporting mobile users: location independent naming. In this approach, machines use the same hostname from any internet location, but use an IP address that corresponds to their current location. We describe a protocol that implements location independent naming for nomadic computers, i.e., machines that do not need transparent mobility. Our protocol allows hosts to move across security domains, uses existing protocols, and preserves existing trust relationships. Therefore, it preserves the performance and security of normal IP for nomadic computers …

Adaptation Space: Surviving Non-Maskable Failures, Crispin Cowan, Lois Delcambre, Anne-Francoise Le Meur, Ling Liu, David Maier, Dylan Mcnamee, Michael Miller, Calton Pu, Perry Wagle, Jonathan Walpole

Computer Science Faculty Publications and Presentations

Some failures cannot be masked by redundancies, because an unanticipated situation occurred, because fault-tolerance measures were not adequate, or because there was a security breach (which is not amenable to replication). Applications that wish to continue to offer some service despite nonmaskable failure must adapt to the loss of resources. When numerous combinations of non-maskable failure modes are considered, the set of possible adaptations becomes complex. This paper presents adaptation spaces, a formalism for navigating among combinations of adaptations. An adaptation space describes a collection of possible adaptations of a software component or system, and provides a uniform way of …

The Selfish Book. Review Of: The Origins Of Virtue: Human Instincts And The Evolution Of Cooperation By Matt Ridley, Robert Costanza

Institute for Sustainable Solutions Publications and Presentations

Book Review of The Selfish Book. Review of: The Origins of Virtue: Human Instincts and the Evolution of Cooperation by Matt Ridley

Comparison Of Ice-Shelf Creep Flow Simulations With Ice-Front Motion Of Filchner-Ronne Ice Shelf, Antarctica, Detected By Sar Interferometry, Christina L. Hulbe, Eric Rignot, D. R. Macayeal

Geology Faculty Publications and Presentations

Comparison between numerical model ice-shelf flow simulations and synthetic aperture radar (SAR) interferograms is used to study ice-flow dynamics at the Hemmen Ice Rise (HIR) and Lassiter Coast (LC) corners of the iceberg-calving front of the Filchner-Ronne Ice Shelf, Antarctica. The interferograms are constructed from SAR images provided by the European Space Agency's remote-sensing satellites (ERS-lj2). Narrow bands of large shear strain rate are observed along the boundaries between fastflowing ice-shelf ice and no-flow boundaries. Large rifts, opened where the ice shelf separates from the coast, appear to be filled with a melange of sea ice, ice-shelf fragments, and snow. …

Ecological Tax Reform, Robert Costanza, Steve Bernow, Herman E. Daly, Robert Degennaro, Paul Hawken

Institute for Sustainable Solutions Publications and Presentations

Provides an overview detailing the benefits of ecological tax reform. What ecological tax reform would include; Origin of ecological taxes; Implementation in the United States and Europe; Specifics on an ecological tax reform proposal; The need to phase in tax reforms gradually.

The Surface Plasmon Enhancement Effect On Adsorbed Molecules At Elevated Temperatures, P.T. Leung, Hai-Pang Chiang, W. S. Tse

Physics Faculty Publications and Presentations

The surface plasmon enhancement effect on adsorbed molecules at elevated substrate temperatures is studied theoretically using surface enhanced Raman scattering (SERS) as an example. The surface structure is idealized to be a monodisperse spherical particle with its nonlocal dielectric response accounted for. The temperature effects are modeled using a temperature-dependent collision frequency in the Drude model. Numerical results show that only a small decrease in the SERS enhancement ratio occurs for temperatures up to the melting point of the substrate, even for scattering close to the surface plasmon resonance frequency of the metal. More definitive results are subjected to more …

Specific Heat And Critical Fields Of The Organic Superconductor Β″–(Bedt-Ttf)2sf5ch2cf2so3, S. Wanka, J. Hagel, D. Beckmanm, J. Wosnitza, J. A. Schlueter, Jack M. Williams, P. G. Nixon, Rolf Walter Winter, Gary L. Gard

Chemistry Faculty Publications and Presentations

We report on specific-heat, magnetization, and ac-susceptibility measurements of β″–(BEDT-TTF)₂SF₅CH₂CF₂SO₃, an organic superconductor with Tc=4.5 K, where BEDT-TTF stands for bis(ethylenedithio)-tetrathiafulvalene. The jump of the specific heat C at Tc and the exact form of the specific heat difference between C in the superconducting (B=0 T) and in the normal (B=3.5 T) state can be well described by BCS theory with strong coupling. We estimate an electron-phonon coupling parameter λ≈1.1. From measurements of C in magnetic fields we extract the upper critical field Bc₂(T). Low-field dc-magnetization measurements were used to determine the temperature dependence of the lower critical field Bc₁. …

Morphology, Eruption Rates, And Rheology Of Lava Domes: Insights From Laboratory Models, Jonathan H. Fink, Ross W. Griffiths

Geology Faculty Publications and Presentations

The growth of lava domes can be either quiescent or violent, with transitions between styles of behavior commonly occurring with little warning. Here we propose that the behavior depends on the eruption rate, the magma rheology, and the thickness ofthe cooling surface. We present a model, based on laboratory simulations, field measurements, and photographic analysis, that relates the morphology and texture of a dome to the thickness of its cooled carapace, and thence to eruption conditions. A sequence of four main types of dome (spiny, lobate, platy, and axisymmetric) is identified in laboratory analog experiments with a Bingham plastic. These …

Photoadaptation Rate Of Synechococcus Wh7803 Cultures At Two Iron Concentrations, Jon Daniel Moulton

Dissertations and Theses

The marine cyanobacterium Synechococcus WH7803 adapts to changes in light intensity by changing its photosynthetic physiology. This work is a study o f the rate o f photoadaptation of Synechococcus WH7803 in laboratory cultures. Cultures were shifted from constant 8 µEm^-2s^-1 light to constant 80 µEm^-2s^-1 light, from constant 80 µEm^-2s^-1 light to 8 µEm^-2s^-1 light and from different light regimes to a single fluctuating light regime. The response of high iron cultures grown in modified aquil culture medium at 5*10^-6M Fe was compared with the …

Self-Consistent Effective Binary Interaction Approximation For Strongly Coupled Multifluid Dynamics, John D. Ramshaw

Physics Faculty Publications and Presentations

An improved self-consistent effective binary diffusion approximation for multicomponent diffusion was recently described [1]. Here we develop an analogous self-consistent effective binary interaction (SCEBI) approximation for simplifying multifluid dynamical descriptions in which each fluid is strongly coupled to the other fluids by pairwise frictional forces. The net drag force on each fluid is the summation of the drag forces due to each of the other fluids. This summation is approximated by a single term proportional to the velocity of the fluid in question relative to an appropriately weighted average velocity. This approximation permits an explicit numerical solution for the fluid …

Soil Moisture Gradients And Controls On A Southern Appalachian Hillslope From Drought Through Recharge, J. Alan Yeakley, W. T. Swank, L. W. Swift, G. M. Hornberger, H. H. Shugart

Environmental Science and Management Faculty Publications and Presentations

Soil moisture gradients along hillslopes in humid watersheds, although indicated by vegetation gradients and by studies using models, have been difficult to confirm empirically. While soil properties and topographic features are the two general physio-graphic factors controlling soil moisture on hillslopes, studies have shown conflicting results regarding which factor is more important. The relative importance of topographic and soil property controls was examined in an upland forested watershed at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains. Soil moisture was measured along a hillslope transect with a mesic-to-xeric forest vegetation gradient over a period spanning precipitation extremes. The hillslope …

Will Business-Led Environmental Initiatives Grow In Agriculture?, Sandra S. Batie, David E. Ervin

Economics Faculty Publications and Presentations

This article was stimulated by a 1997 American Agricultural Economics Association annual meeting preconference designed by Batie and Ervin. The authors felt that there was considerable interest and activity in business-led environmental management (also caLLed corporate environmental management)-but most of the interest was found outside of the agricultural sector and the profession. The conference was a means to investigate the extent, motivation, and consequences of business-led poLLution prevention activities. The DuPont and the StahLbush Island Farms examples used in this article were drawn from discussions that took place at the conference and which were published in the proceedings. In the …

Filtration Modeling Of A Plate-And-Frame Press, Scott A. Wells

Civil and Environmental Engineering Faculty Publications and Presentations

The porosity distribution and filtrate production during cake filtration in a plate-and-frame filter press were simulated mathematically. The model considered filtration that occurs after the filling process, not filtration that occurs as the suspension fills the cell. Governing equations for the temporal porosity distribution were developed for a plateand- frame press. The governing equations were solved numerically using an alternating-direction-implicit scheme. Appropriate initial and boundary conditions were determined based on characteristics of the plate-and-frame press and of the suspension properties. Predicted porosity and velocity distributions were calculated for assumed constitutive parameters.