Effective seismic interrogation of the near subsurface requires that measured parameters, such as compressional and shear velocities and attenuation, be related to important soil properties. Porosity, composition (clay content), fluid content and type are of particular interest. The ultrasonic (100-500 kHz) pulse transmission technique was used to collect data for highly attenuating materials appropriate to the vadose zone. Up to several meters of overburden were simulated by applying low uniaxial stress of 0 to about 0.1 MPa to the sample. The approach was to make baseline measurements for pure quartz sand, because the elastic properties are relatively well known except at the lowest pressures. Clay was added to modify the sample microstructure and ultrasonic measurements were made to characterize the effect of the admixed second phase. Samples were fabricated from Ottawa sand mixed with a swelling clay (Wyoming bentonite). The amount of clay added was 1 to 40% by mass. Compressional (P) velocities are low (228-483 m/s), comparable to the sound velocity in air. Shear (S) velocities are about half of the compressional velocity (120-298 m/s), but show different sensitivity to microstructure. Adding clay increases the shear amplitude dramatically with respect to P, and also changes the sensitivity of the …

The computing power available to scientists and engineers has increased dramatically in the past decade, due in part to progress in making massively parallel computing practical and available. The expectation for these machines has been great. The reality is that progress has been slower than expected. Nevertheless, massively parallel computing is beginning to realize its potential for enabling significant break-throughs in science and engineering. This paper provides a perspective on the state of the field, colored by the authors' experiences using large scale parallel machines at Sandia National Laboratories. We address trends in hardware, system software and algorithms, and we also offer our view of the forces shaping the parallel computing industry.

This volume of the Journal contains the index for the regular session of the Senate of Texas. The index begins on page 5021.

The Journal contains the proceedings of the Senate of Texas including legislation, reports, discussions, votes, and points-of-order. Some volumes also contain supplementary materials.

The Journal contains the proceedings of the Senate of Texas including legislation, reports, discussions, votes, and points-of-order. Some volumes also contain supplementary materials.

Quarterly journal containing articles, field notes, research, reviews, and other analyses of rural health in Texas.

Magazine discussing natural resources, parks, hunting and fishing, and other information related to the outdoors in Texas.

Magazine discussing natural resources, parks, hunting and fishing, and other information related to the outdoors in Texas.

Magazine discussing natural resources, parks, hunting and fishing, and other information related to the outdoors in Texas.

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We present a unique modeling capability to understand the global distribution of trace gases and aerosols throughout both the troposphere and stratosphere. It includes the ability to simulate tropospheric chemistry that occurs both in the gas phase as well as on the surfaces of solid particles. We have used this capability to analyze observations from particular flight campaigns as well as averaged observed data. Results show the model to accurately simulate the complex chemistry occurring near the tropopause and throughout the troposphere and stratosphere.

Annual report compiling information about required groundwater monitoring activities and cases of contamination by state-regulated activities during the 1998 calendar year. Includes tables with the enforcement status of each case of contamination.

We report a novel sol-gel dip-coating process to form dual-layer microporous silica membranes with improved membrane performance and reproducibility. First, we deposit a surfactant-templated silica (STS) intermediate layer on top of a commercial {gamma}-alumina support both to improve its ''surface finish'' and to prevent a subsequently deposited microporous overlayer from penetrating into the support. Second, membranes are processed under clean room conditions to avoid dust contamination and, third, membranes are vacuum-calcined to promote further pore shrinkage and impart surface hydrophobicity. The resulting asymmetric membrane exhibits a gradual change in pore diameter from 50{angstrom} ({gamma}-alumina support layer) to 10-12{angstrom} (STS intermediate layer), and then to 3-4{angstrom} (30nm thick, ultramicroporous silica top-layer). Compared to a single-layer process using only the microporous overlayer, the dual-layer process improves both flux and selectivity. For the industrially important problem of natural gas purification, the combined CO{sub 2} flux [(3{approx} 0.5) x 10{sup {minus}4} cm{sup 3}(STP)/(s{center_dot}cm{sup 2}{center_dot}cm-Hg)] and CO{sub 2}/CH{sub 4} separation factors [200{approx}600] are superior to all previously reported values for separation of a 50/50 (v/v) CO{sub 2}/CH{sub 4} gas mixture. In addition, the membrane selectively separated hydrogen from a simulated reformate from partial oxidation of methanol as evidenced by a high concentration of hydrogen recovery.

A geochemical investigation of well waters from the Cheyenne River Sioux Reservation in South Dakota revealed considerable diversity in the chemistry of the fluids and indicated that waters from the Dakota Formation were the best candidates for direct-use geothermal applications. Geothermometry calculations for all wells suggest that formation temperatures are <90 C. Potential scaling problems from utilization of the waters would most likely be restricted to carbonate scale and could be offset by maintaining CO{sub 2} gas in solution.

A statistical evaluation of sediment data from Technical Area 54, Los Alamos National Laboratory, was used to examine the relation of concentrations of a series of inorganic and radionuclide analytes to general geographic setting and sediment texture. Significant differences exist between results from the north and south sides of Mesita del Buey, with analyte concentrations being generally higher to the north. These differences probably result primarily from variations in background levels in the source materials for the sediments, perhaps reflecting finer particle sizes and/or better developed soils on the north side of the mesa.

The thermally controlled solidification of a binary alloy, nucleated at isolated sites, is described by the evolution of a probability distribution function, whose variables include grain size and distance to nearest neighbor, together with descriptors of shape, orientation, and such material properties as orientation of nonisotropic elastic modulus and coefficient of thermal expansion. The relevant Liouville equation is described and coupled with global equations for energy and solute transport. Applications are discussed for problems concerning nucleation and impingement and the consequences for final size and size distribution. The goal of this analysis is to characterize the grain structure of the solidified casting and to enable the description of its probable response to thermal treatment, machining, and the imposition of mechanical insults.

The purpose of the research presented here is two fold. We present preliminary results for the assessment of flux surface quality for a candidate configuration for the National Compact Stellarator Experiment (NCSX) experiment. We also present preliminary results of the assessment of our 3-D MHD tools, PIES[1] and VMEC[2]. We first illustrate the flux surface quality in C82 by showing PIES results for several snapshots in the evolution of the plasma from 0% beta to 3.5% beta. C82 is a quasi-axisymmetric candidate configuration for the NCSX experiment. Next, as part of our effort to qualify the PIES code for current carrying stellarators, we present results for a W7-AS experimental shot. Lastly, we show evidence from the PIES code that the equilibrium produced by VMEC violate the Hamada condition.

The major goal of this work is to provide a means to characterize the final structure of a metal that has solidified from a melt. The thermally controlled solidification of a binary alloy, nucleated at isolated sites, is described by the evolution of a probability distribution function (PDF). The relevant equation required for propagating the PDF is developed with variables for grain size and distance to nearest neighbor. The phenomena of nucleation, growth, and impingement of the grains are discussed, and used as the basis for developing rate equations that evolve the PDF. The complementary equations describing global heat and solute transfer are discussed, and coupled with the microstructure evolution equations for grain growth and PDF evolution. The full set of equations is solved numerically and results are compared with experimental data for the plutonium 1 weight percent gallium system. The three principal results of this work are: (1) The formulation of transient evolution equations for the PDF description of nucleation, growth, and impingement of a distribution of grain sizes and locations; (2) Solution of the equations to give a correlation for final average grain size as a function of material parameters, nucleation site density, and cooling rate; and (3) …

The notion of perspective, when supported in an object-based knowledge representation, can facilitate better abstractions of reality for modeling and simulation. The object modeling of complex physical and chemical processes is made more difficult in part due to the poor abstractions of state and phase changes available in these models. The notion of perspective can be used to create different views to represent the different states of matter in a process. These techniques can lead to a more understandable model. Additionally, the ability to record the progress of a process from start to finish is problematic. It is desirable to have a historic record of the entire process, not just the end result of the process. A historic record should facilitate backtracking and re-start of a process at different points in time. The same representation structures and techniques can be used to create a sequence of process markers to represent a historic record. By using perspective, the sequence of markers can have multiple and varying views tailored for a particular user's context of interest.

Research in fabrication for inertial confinement fusion (ICF) comprises at least three broad categories: targets for high energy density physics on existing drivers, ignition capsule fabrication, and cryogenic fuel layer formation. The latter two are being pursued primarily for the National Ignition Facility (NIF). Scientists from over 14 laboratories, universities, and businesses contributed over 100 papers on all aspects of ICF target fabrication. The NIF is well along in construction and photos of poured concrete and exposed steel added to the technical excitement. It was clear from the meeting that there has been significant progress toward the fabrication of an ignition target for NIF and that new techniques are resulting in higher quality targets for high energy density research.

Results of microbalance, pressure-volume-temperature, and mass spectrometric measurements show that a higher oxide of plutonium, PuO{sub 2+x}, and hydrogen are formed by reaction of plutonium dioxide with water at 25 C to 350 C. PuO{sub 2+x} has an intense green color consistent with the presence of Pu(VI). An oxide composition in excess of PuO{sub 2.25} is identified, but the maximum value of x is undefined. Reaction rates derived from linear mass-time and pressure-time data are described by an Arrhenius relationship that yields an activation energy of 9.4 {+-} 0.6 kcal/mol for the PuO{sub 2} + H{sub 2}O reaction. X-ray diffraction data for PuO{sub 2+x} shows that the oxide has a fluorite-related structure consistent with substitution of Pu(VI) on cationic lattice sites and accommodation of additional oxygen on interstitial sites. The cubic lattice parameter has a low, but well-defined, linear dependence on the O:Pu ratio, suggesting that PuO{sub 2+x} forms as a continuous solid solution. The failure of earlier attempts to prepare higher oxides of plutonium is attributed to slow oxidation kinetics and insensitivity of diagnostic techniques. Similarities of the PuO{sub 2+x} and UO{sub 2+x} phase are examined and relevance of the results to plutonium technology and environmental issues is discussed.

This paper describes the microseismic mapping of repeated injections of drill cuttings into two separate formations at a test site near Mounds, OK. Injections were performed in sandstone and shale formations at depths of 830 and 595 m, respectively. Typical injection disposal was simulated using multiple small-volume injections over a three-day period, with long shut-in periods interspersed between the injections. Microseismic monitoring was achieved using a 5-level array of wireline-run, triaxial- accelerometer receivers in a monitor well 76 m from the disposed well. Results of the mapped microseismic locations showed that the disposal domti W= generally aligns with the major horizontal stress with some variations in azimuth and that wide variations in height and length growth occurred with continued injections. These experiments show that the cuttings injection process cm be adequately monitored from a downhole, wireline-run receiver array, thus providing process control and environmental assurance.

This research addresses the application of a large eddy simulation (LES) to Arbitrary Lagrangian Eulerian (ALE) simulations of Rayleigh-Taylor instability. First, ALE simulations of simplified Rayleigh-Taylor instability are studied. The advantages of ALE over Eulerian simulations are shown. Next, the behavior of the LES is examined in a more complicated ALE simulation of Rayleigh-Taylor instability. The effects of eddy viscosity and stochastic backscatter are examined. The LES is also coupled with ALE to increase grid resolution in areas where it is needed. Finally, the methods studied above are applied to two sets of experimental simulations. In these simulations, ALE allows the mesh to follow expanding experimental targets, while LES can be used to mimic the effect of unresolved instability modes.