Wave-equation migration methods can more accurately account for complex wave phenomena than ray-tracing-based Kirchhoff methods that are based on the high-frequency asymptotic approximation of waves. With steadily increasing speed of massively parallel computers, wave-equation migration methods are becoming more and more feasible and attractive for imaging complex 3D structures. We present an overview of several efficient and accurate wave-equation-based migration methods that we have recently developed. The methods are implemented in the frequency-space and frequency-wavenumber domains and hence they are called dual-domain methods. In the methods, we make use of different approximate solutions of the scalar-wave equation in heterogeneous media to recursively downward continue wavefields. The approximations used within each extrapolation interval include the Born, quasi-Born, and Rytov approximations. In one of our dual-domain methods, we use an optimized expansion of the square-root operator in the one-way wave equation to minimize the phase error for a given model. This leads to a globally optimized Fourier finite-difference method that is a hybrid split-step Fourier and finite-difference scheme. Migration examples demonstrate that our dual-domain migration methods provide more accurate images than those obtained using the split-step Fourier scheme. The Born-based, quasi-Born-based, and Rytov-based methods are suitable for imaging complex structures whose lateral …

The science of toxicology plays an important role in identifying safe conditions of use or exposure for many different kinds of environmental agents. The use of toxicologic information in risk assessment requires careful analysis, evaluation of data, and scientific judgment. These Annapolis Accords are intended to guide appropriate use in risk assessment of the scientific information from toxicology. We believe that application of these principles will improve the scientific credibility of risk assessment and the quality of decisions aimed at reducing and eliminating risks to human health and the environment.

Model independent radiative correction to the recoil proton polarization for the elastic electron-proton scattering is calculated within method of electron structure functions. The explicit expressions for the recoil proton polarization are represented as a contraction of the electron structure and the hard part of the polarization dependent contribution into cross-section. The calculation of the hard part with first order radiative correction is performed. The obtained representation includes the leading radiative corrections in all orders of perturbation theory and the main part of the second order next-to-leading ones. Numerical calculations illustrate our analytical results.

Through three examples the authors illustrate some of the concepts and ingredients required for pattern formation at mesoscopic scales. Two examples built on microscopic models where mesoscopic patterns emerge from homogeneous ground states driven into instability by external forcing. In contrast, the third example builds on a mesoscopic phenomenological Ginzburg-Landan type model of solid-solid structural phase transition. Here, mesoscopic textures emerge as a result of competing length scales arising from the constraints of elastic compatibility.

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The first release of data from the MAXIMA and BOOMERANG experiments has introduced a new era of precision cosmology. The two data sets are essentially independent, consistent and complementary. In a joint effort by the two teams, the two data sets were combined and then used to test cosmological models and determine values of cosmological constants. These results are available because of the success of bolometric detection techniques. The experimental approach is described with references to the MAXIMA-1 experiment. Important new cosmological experiments at far infrared and millimeter wavelengths require major improvements in bolometric techniques. A new technology, the voltage-biased superconducting bolometer, promises to provide the required experimental power.

The radiation pressure coupling with vacuum fluctuations gives rise to energy damping and decoherence of an oscillating particle. Both effects result from the emission of pairs of photons, a quantum effect related to the fluctuations of the Casimir force. We discuss different alternative methods for the computation of the decoherence time scale. We take the example of a spherical perfectly-reflecting particle, and consider the zero and high temperature limits. We also present short general reviews on decoherence and dynamical Casimir effect.

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The introduction of automation systems into many of the facilities dealing with the production, use and disposition of nuclear materials has been an ongoing objective. Many previous attempts have been made, using a variety of monolithic and, in some cases, modular technologies. Many of these attempts were less than successful, owing to the difficulty of the problem, the lack of maturity of the technology, and over optimism about the capabilities of a particular system. Consequently, it is not surprising that suggestions that automation can reduce worker Occupational Radiation Exposure (ORE) levels are often met with skepticism and caution. The development of effective demonstrations of these technologies is of vital importance if automation is to become an acceptable option for nuclear material processing environments. The University of Texas Robotics Research Group (UTRRG) has been pursuing the development of technologies to support modular small automation systems (each of less than 5 degrees-of-freedom) and the design of those systems for more than two decades. Properly designed and implemented, these technologies have a potential to reduce the worker ORE associated with work in nuclear materials processing facilities. Successful development of systems for these applications requires the development of technologies that meet the requirements of …

We report the discovery of two well-defined tidal tails emerging from the sparse remote globular cluster Palomar 5. These tails stretch out symmetrically to both sides of the cluster in the direction of constant Galactic latitude and subtend an angle of 2.6{sup o} on the sky. The tails have been detected in commissioning data of the Sloan Digital Sky Survey (SDSS), providing deep five-color photometry in a 2.5{sup o}-wide band along the equator. The stars in the tails make up a substantial part ({approx} 1/3) of the current total population of cluster stars in the magnitude interval 19.5 {le} i* {le} 22.0. This reveals that the cluster is subject to heavy mass loss. The orientation of the tails provides an important key for the determination of the cluster's Galactic orbit.

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The Xyce{trademark} Parallel Electronic Simulator has been written to support the simulation needs of the Sandia National Laboratories electrical designers. As such, the development has focused on providing the capability to solve extremely large circuit problems by supporting large-scale parallel computing platforms (up to thousands of processors). In addition, they are providing improved performance for numerical kernels using state-of-the-art algorithms, support for modeling circuit phenomena at a variety of abstraction levels and using object-oriented and modern coding-practices that ensure the code will be maintainable and extensible far into the future. The code is a parallel code in the most general sense of the phrase--a message passing parallel implementation--which allows it to run efficiently on the widest possible number of computing platforms. These include serial, shared-memory and distributed-memory parallel as well as heterogeneous platforms. Furthermore, careful attention has been paid to the specific nature of circuit-simulation problems to ensure that optimal parallel efficiency is achieved even as the number of processors grows.

Sub-wavelength periodic texturing (gratings) of crystalline-silicon (c-Si) surfaces for solar cell applications can be designed for maximizing optical absorption in thin c-Si films. We have investigated c-Si grating structures using rigorous modeling, hemispherical reflectance, and internal quantum efficiency measurements. Model calculations predict almost {approximately}100% energy coupling into obliquely propagating diffraction orders. By fabrication and optical characterization of a wide range of 1D & 2D c-Si grating structures, we have achieved broad-band, low ({approximately} 5%) reflectance without an anti-reflection film. By integrating grating structures into conventional solar cell designs, we have demonstrated short-circuit current density enhancements of 3.4 and 4.1 mA/cm{sup 2} for rectangular and triangular 1D grating structures compared to planar controls. The effective path length enhancements due to these gratings were 2.2 and 1.7, respectively. Optimized 2D gratings are expected to have even better performance.

Ultra-high strength metallic multilayers are ideal for investigating the effects of length scales in plastic deformation of metallic materials. Experiments on model systems show that the strengths of these materials increase with decreasing bilayer period following the Hall-Petch model. However, as the layer thickness is reduced to the nm-scale, the number of dislocations in the pile-up approaches one and the pile-up based Hall-Petch model ceases to apply. For nm-scale semi-coherent multilayers, we hypothesize that plastic flow occurs by the motion of single dislocation loops, initially in the softer layer, that deposit misfit type dislocation arrays at the interface and transfer load to the harder phase. The stress concentration eventually leads to slip in the harder phase, overcoming the resistance from the misfit arrays at the interface. A model is developed within the framework of classical dislocation theory to estimate the strengthening from this mechanism. The model predictions are compared with experimentally measured strengths.

The radiation transport and linearized thermal energy equations have been analyzed to find the temporal dependence of the component modes in a radiation/thermal front. The fully resolved spectral variation of the opacity as a function of energy, as well as the exact time and angular dependence, is treated in this work. As we are able to study arbitrarily complicated opacity spectra, we stress the importance of the new results as a check on the effect of using opacity averages.

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Published breakthrough time, adsorption rate, and capacity data for components of organic vapor mixtures adsorbed from flows through fixed activated carbon beds have been analyzed. Capacities (as stoichiometric centers of constant pattern breakthrough curves) yielded stoichiometric times {tau}, which are useful for determining elution orders of mixture components. We also calculated adsorption rate coefficients k{sub v} of the Wheeler (or, more general Reaction Kinetic) breakthrough curve equation, when not reported, from breakthrough times and {tau}. Ninety-five k{sub v} (in mixture)/ k{sub v} (single vapor) ratios at similar vapor concentrations were calculated and averaged for elution order categories. For 43 first-eluting vapors the average ratio (1.07) was statistically no different (0.21 standard deviation) than unity, so that we recommend using the single-vapor k{sub v} for such. Forty-seven second-eluting vapor ratios averaged 0.85 (0.24 standard deviation), also not significantly different from unity; however, other evidence and considerations lead us recommend using k{sub v} (in mixture) = 0.85 k{sub v} (single vapor). Five third- and fourth-eluting vapors gave an average of 0.56 (0.16 standard deviation) for a recommended k{sub v} (in mixture) = 0.56 k{sub v} (single vapor) for such.

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The MIGHTY NORTH event was a precision high explosive test performed in jointed Salem limestone for a modeling verification and validation program sponsored by DTRA. The test bed was subjected to a cylindrical shock front, making the response applicable for comparison to 2-D plane strain computations. While other investigators modeled the rock response with various elastic-plastic failure criteria, we demonstrate that simple elastic-perfectly brittle response with a tensile failure criterion replicates the experiment quite well. This paper provides comparisons between results of numerical simulations of the test event and the published test bed response.

Fission product cross sections of (p,f)-reaction in thin samples of {sup 208}Pb, {sup nat}HgO, {sup nat}W irradiated with high-energy protons are measured. The irradiations were made using proton beams extracted from the ITEP synchrotron. The nuclide yields were {gamma}-spectrometered directly using a high-resolution Ge-detector. The GENIE2000 code was used to process the measured {gamma}-spectra and the ITEP-developed SIGMA code was used together with the PCNUDAT nuclear decay database to identify the {gamma}-lines and to determine the cross-sections. The {sup 27}Al(p,x){sup 22}Na reaction was used to monitor the proton flux. The LAHET, CEM2k, CEM95, CASCADE/INPE, CASCADE, INUCL, and YIELDX codes were used for computer simulation of the products measured. Comparison of simulated and experimental values shows insufficient predictive power of the existing fission models. The results obtained are of importance in studying the parameters of the Pb, Hg and W target modules of the hybrid Accelerator-Driven System (ADS) facilities.

Micro-robots will soon be available for deployment by the thousands. Consequently, controlling and coordinating a force this large to accomplish a prescribed task is of great interest. This paper describes a flexible architecture for modeling thousands of autonomous agents simultaneously. The agents’ behavior is based on a subsumption architecture in which individual behaviors are prioritized with respect to all others. The primary behavior explored in this work is a group formation behavior based on social potential fields (Reif and Wang 1999). This paper extends the social potential field model by introducing a neutral zone within which other behaviors may exhibit themselves. Previous work with social potential fields has been restricted to models of “perfect” autonomous agents. The paper evaluates the effect of social potential fields in the presence of agent death (failure) and imperfect sensory input.

The fracture strength of silicon carbide (SiC) plate deposits produced by Chemical Vapor Deposition (CVD) was determined from room-temperature to 1500 C using a standard 4-point flexural test method (ASTM Cl 161). CVD SiC materials produced by two different manufacturers are shown to have only slightly different flexural strength values, which appear to result from differences in microstructure. Although CVD deposition of SiC results in a textured grain structure, the flexural strength was shown to be independent of the CVD growth direction. The orientation of machining marks was shown to have the most significant influence on flexural strength, as expected. The fracture strength of tubular forms of SiC produced by CVD deposition directly onto a mandrel was comparable to flexural bars machined from a plate deposit. The tubular (o-ring) specimens were much smaller in volume than the flexural bars, and higher strength values are predicted based on Weibull statistical theory for the o-ring specimens. Differences in microstructure between the plate deposits and deposits made on a mandrel result in different flaw distributions and comparable strength values for the flexural bar and o-ring specimens. These results indicate that compression testing of o-rings provides a more accurate strength measurement for tubular product …

Various: (1)TriState 2000 Genetics in the Courts (2) Growing impact of the new genetics on the courts (3)Human testing (4) Legal analysis - in re G.C. (5) Legal analysis - GM ''peanots'', and (6) Legal analysis for State vs Miller

We consider the problem of pixel-by-pixel classification of a multi-spectral image using supervised learning. Conventional supervised classification techniques such as maximum likelihood classification and less conventional ones such as neural networks, typically base such classifications solely on the spectral components of each pixel. It is easy to see why the color of a pixel provides a nice, bounded, fixed dimensional space in which these classifiers work well. It is often the case however, that spectral information alone is not sufficient to correctly classify a pixel. Maybe spatial neighborhood information is required as well. Or may be the raw spectral components do not themselves make for easy classification, but some arithmetic combination of them would. In either of these cases we have the problem of selecting suitable spatial, spectral or spatio-spectral features that allow the classifier to do its job well. The number of all possible such features is extremely large. How can we select a suitable subset? We have developed GENIE, a hybrid learning system that combines a genetic algorithm that searches a space of image processing operations for a set that can produce suitable feature planes, and a more conventional classifier which uses those feature planes to output a …