Energy dispersive x-ray (EDX) spectrum imaging has been performed in a scanning electron microscope (SEM) on a metal/ceramic braze to characterize the elemental distribution near the interface. Statistical methods were utilized to extract the relevant information (i.e., chemical phases and their distributions) from the spectrum image data set in a robust and unbiased way. The raw spectrum image was over 15 Mbytes (7500 spectra) while the statistical analysis resulted in five spectra and five images which describe the phases resolved above the noise level and their distribution in the microstructure.

The issue of fission source convergence in Monte Carlo eigenvalue calculations is of interest because of the potential consequences of erroneous criticality safety calculations. In this work, the authors compare two different techniques to improve the source convergence behavior of standard Monte Carlo calculations applied to challenging source convergence problems. The first method, super-history powering, attempts to avoid discarding important fission sites between generations by delaying stochastic sampling of the fission site bank until after several generations of multiplication. The second method, stratified sampling of the fission site bank, explicitly keeps the important sites even if conventional sampling would have eliminated them. The test problems are variants of Whitesides' Criticality of the World problem in which the fission site phase space was intentionally undersampled in order to induce marginally intolerable variability in local fission site populations. Three variants of the problem were studied, each with a different degree of coupling between fissionable pieces. Both the superhistory powering method and the stratified sampling method were shown to improve convergence behavior, although stratified sampling is more robust for the extreme case of no coupling. Neither algorithm completely eliminates the loss of the most important fissionable piece, and if coupling is absent, the …

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This case study presents initial results from research targeted at the development of cost-effective scalable visualization and rendering technologies. The implementations of two 3D graphics libraries based on the popular sort-last and sort-middle parallel rendering techniques are discussed. An important goal of these implementations is to provide scalable rendering capability for extremely large datasets (>> 5 million polygons). Applications can use these libraries for either run-time visualization, by linking to an existing parallel simulation, or for traditional post-processing by linking to an interactive display program. The use of parallel, hardware-accelerated rendering on commodity hardware is leveraged to achieve high performance. Current performance results show that, using current hardware (a small 16-node cluster), they can utilize up to 85% of the aggregate graphics performance and achieve rendering rates in excess of 20 million polygons/second using OpenGL{reg_sign} with lighting, Gouraud shading, and individually specified triangles (not t-stripped).

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The authors present a more detailed account of the study (hep-ph/9903238) for the supersymmetry reach of the Tevatron in channels with isolated leptons and identified tau jets. They review the theoretical motivations for expecting such signatures, and describe the relevant parameter space in the minimal supergravity and the minimal gauge-mediated models. With explicit Monte Carlo simulations they then show that for certain parameter ranges, channels with two leptons and one tau jet offer a better reach in Run 2 than the clean trilepton signal. They emphasize that improving on tau ID is an important prerequisite for successful searches in multiple tau jet channels. Finally, they discuss some triggering issues.

Despite extensive safety analysis and application of safety measures, there is a frequent lament, ``Why do we continue to have accidents?'' Two breakdowns are prevalent in risk management and prevention. First, accidents result from human actions that engineers, analysts and management never envisioned and second, controls, intended to preclude/mitigate accident sequences, prove inadequate. This paper addresses the first breakdown, the inability to anticipate scenarios involving human action/inaction. The failure of controls has been addressed in a previous publication (Forsythe and Grose, 1998). Specifically, this paper presents an approach referred to as surety. The objective of this approach is to provide high levels of assurance in situations where potential system failure paths cannot be fully characterized. With regard to human elements of complex systems, traditional approaches to human reliability are not sufficient to attain surety. Consequently, an Organic Model has been developed to account for the organic properties exhibited by engineered systems that result from human involvement in those systems.

Pressure studies have provided new insights into the physics of compositionally-disordered ABO{sub 3} oxide relaxors. Specifically, results will be presented and discussed on a pressure-induced ferroelectric-to-relaxer crossover phenomenon, the continuous evolution of the energetic and dynamics of the relaxation process, and the interplay between pressure and electric field in determining the dielectric response.

A pressure-induced crossover from normal Ferroelectric-to-Relaxer behavior has been observed in single crystal [Pb(Zn{sub 1/3}Nb{sub 2/3})O{sub 3}]{sub 0.905}(PbTiO{sub 3}){sub 0.0095}, or PZN - 9.5% PT. Analogy with similar observations for other perovskites indicates that this crossover is a general feature of compositionally-disordered soft mode ferroelectrics. The Pressure-Temperature phase diagram has been also determined.

In May of 1989, a six month-long small magnitude earthquake swarm began beneath the Pleistocene-aged dacitic cumulovolcano Mammoth Mountain. The following year, increased mortality of trees in the Horseshoe Lake region was observed. Their deaths were initially attributed to the Sierran drought of the 1980's. In 1994 however, soil gas measurements made by the USGS confirmed that the kills were due to asphyxiation of the vegetation via the presence of 30-96 % CO{sub 2} in ground around the volcano[1]. Physiological changes in vegetation due to negative inputs into the ecological system such as anomalously high levels of magmatic CO{sub 2}, can be seen spectrally. With this phenomena in mind, as well as many other unanswered geological and geobotanical questions, seven lines of hyperspectral 5-meter HyMap data were flown over Long Valley Caldera located in eastern California on September 7, 1999. HyMap imagery provides the impetus to address geobotanical questions such as where the treekills are currently located at Mammoth and other locales around the caldera as well as whether incipient kills can be identified. The study site of the Horseshoe Lake treekills serves as a focus to the initial analyses of this extensive HyMap dataset due to both the treekill's …

One of the key elements of the Stochastic Finite Element Method, namely the polynomial chaos expansion, has been utilized in a nonlinear shock and vibration application. As a result, the computed response was expressed as a random process, which is an approximation to the true solution process, and can be thought of as a generalization to solutions given as statistics only. This approximation to the response process was then used to derive an analytically-based design specification for component shock response that guarantees a balanced level of marginal reliability. Hence, this analytically-based reference SRS might lead to an improvement over the somewhat ad hoc test-based reference in the sense that it will not exhibit regions of conservativeness. nor lead to overtesting of the design.

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