Microscopic and Macroscopic Stress with Gravitational and Rotational Forces

Many recent papers have questioned Irving and Kirkwood's atomistic expression for stress. In Irving and Kirkwood's approach both interatomic forces and atomic velocities contribute to stress. It is the velocity-dependent part that has been disputed. To help clarify this situation we investigate [1] a fluid in a gravitational field and [2] a steadily rotating solid. For both problems we choose conditions where the two stress contributions, potential and kinetic, are significant. The analytic force-balance solutions of both these problems agree very well with a smooth-particle interpretation of the atomistic Irving-Kirkwood stress tensor.Comment: Fifteen pages with seven figures, revised according to referees' suggestions at Physical Review E. See also Liu and Qiu's arXiv contribution 0810.080

Phase-change materials handbook

Handbook describes relationship between phase-change materials and more conventional thermal control techniques and discusses materials' space and terrestrial applications. Material properties of most promising phase-change materials and purposes and uses of metallic filler materials in phase-change material composites are provided

THE ESTIMATION OF COTTON COSTS IN THE SOUTHEAST

Crop Production/Industries,

History of nutrient inputs to the northeastern United States, 1930–2000

Humans have dramatically altered nutrient cycles at local to global scales. We examined changes in anthropogenic nutrient inputs to the northeastern United States (NE) from 1930 to 2000. We created a comprehensive time series of anthropogenic N and P inputs to 437 counties in the NE at 5 year intervals. Inputs included atmospheric N deposition, biological N2 fixation, fertilizer, detergent P, livestock feed, and human food. Exports included exports of feed and food and volatilization of ammonia. N inputs to the NE increased throughout the study period, primarily due to increases in atmospheric deposition and fertilizer. P inputs increased until 1970 and then declined due to decreased fertilizer and detergent inputs. Livestock consistently consumed the majority of nutrient inputs over time and space. The area of crop agriculture declined during the study period but consumed more nutrients as fertilizer. We found that stoichiometry (N:P) of inputs and absolute amounts of N matched nutritional needs (livestock, humans, crops) when atmospheric components (N deposition, N2 fixation) were not included. Differences between N and P led to major changes in N:P stoichiometry over time, consistent with global trends. N:P decreased from 1930 to 1970 due to increased inputs of P, and increased from 1970 to 2000 due to increased N deposition and fertilizer and decreases in P fertilizer and detergent use. We found that nutrient use is a dynamic product of social, economic, political, and environmental interactions. Therefore, future nutrient management must take into account these factors to design successful and effective nutrient reduction measures

Remarks on NonHamiltonian Statistical Mechanics: Lyapunov Exponents and Phase-Space Dimensionality Loss

The dissipation associated with nonequilibrium flow processes is reflected by the formation of strange attractor distributions in phase space. The information dimension of these attractors is less than that of the equilibrium phase space, corresponding to the extreme rarity of nonequilibrium states. Here we take advantage of a simple model for heat conduction to demonstrate that the nonequilibrium dimensionality loss can definitely exceed the number of phase-space dimensions required to thermostat an otherwise Hamiltonian system.Comment: 5 pages, 2 figures, minor typos correcte

Parametric Relationships of Conventional Versus Repetitive Loading Triaxial Tests

This investigation was developed to examine response of a field-mixed asphalt-treated granular base material to 100,000 repetitions of a load whose magnitude was determined by a failure criterion proposed by Hoover (1970), and Fish and Hoover (1969). Axial strain and load at the point of maximum volume of a specimen during a conventional triaxial test appear to produce a proportional limit, indicating that failure may have started. Axial stress at this point was applied in the repetitive loading triaxial test at the same confining pressure, during which axial strain and pore pressure continuously increased and specimen volume decreased in each of three series of tests. Post repetitive specimen condition, determined by retesting in the conventional manner indicated that none of the specimens had failed during repetitive loading. Results of this series of tests indicate a further potential feasibility of the use of minimum volume failure criteria for thickness design of a granular base material

Deformation Moduli of Asphalt Cement-Treated Granular Materials

Triaxial compression studies of asphalt cement-treated granular materials indicate that each material exhibited a volume decrease during initial phases of stress-strain. The stress-strain curve was nearly linear until the material reached minimum volume, after which curvature increased rapidly. The analysis presented is based on the assumption that the point of minimum volume represents a yield point similar to proportional limit. Deformation moduli, M, were evaluated by applying linear regression analyses to that portion of the effective stress ratio versus strain curves occurring prior to minimum volume, instead of using a tangent or secant modulus. Plots of M versus σ3 were analyzed to determine the relationship between M and the confining pressure, σ3 Poisson\u27s ratio, μ, was evaluated by assuming that volume change is a function of either octahedral or deviator stresses. Results of linear regression analyes showed that deformation moduli will generally tend to increase with increasing lateral constraint. However, statistical analyses of M versus σ3 plots indicated that this relationship is not well defined and in many cases M is essentially constant for the range of lateral pressures studied. By using average values of M, it was found that limestone and dolomitic aggregates treated with asphalt cement have moduli generally greater than gravel. Both method of evaluation of μ gave values generally in the range of 0.36 - 0.44, indicating that volume change was primarily a function of deviator stress

Stacking-fault energies for Ag, Cu, and Ni from empirical tight-binding potentials

The intrinsic stacking-fault energies and free energies for Ag, Cu, and Ni are derived from molecular-dynamics simulations using the empirical tight-binding potentials of Cleri and Rosato [Phys. Rev. B 48, 22 (1993)]. While the results show significant deviations from experimental data, the general trend between the elements remains correct. This allows to use the potentials for qualitative comparisons between metals with high and low stacking-fault energies. Moreover, the effect of stacking faults on the local vibrational properties near the fault is examined. It turns out that the stacking fault has the strongest effect on modes in the center of the transverse peak and its effect is localized in a region of approximately eight monolayers around the defect.Comment: 5 pages, 2 figures, accepted for publication in Phys. Rev.

Miniature Triaxial Shear Testing of a Quaternary Ammonium Chloride Stabilized Loess

Compressive bearing characteristics of a stabilized soil may be determined by several methods, in each of which the soil specimens are loaded to failure. The resistance to failure of the stabilized soil depends on the maximum cohesion and internal friction between the soil particles after compaction. The Triaxial Shear Test is employed to provide a measure of these two soil properties. In most highway base and sub-base design problems, or in any similar soil foundation study, the capacity of the underlying soil to withstand and support vertical and/or lateral forces is directly related to the cohesive and frictional forces present in the soil mass. The purpose of the investigation was to determine the effect of a quaternary ammonium chloride soil stabilizing agent on the cohesive and frictional properties of a sample of western Iowa loess. A miniature triaxial shear testing apparatus, developed by the Iowa Engineering Experiment Station Soil Research Laboratory, was used for the investigation