Understanding numerical errors in long calculations is a very subtle science and is critical to understanding the reliability of the final answer. We will carefully examine the accumulation of numerical errors over time and discuss how these can lead to reliability estimates. The primary focus will be on a newly uncovered understanding of mode resolution which is at the heart of all numerical computations.

Although it may sound like a contradiction in terms, the electron beam ion trap (EBIT) works as an ion trap even when the electron beam is switched off. We present various experiments that exploit the ''magnetic trapping mode'' for investigations of ion confinement, charge exchange processes, atomic lifetime and ion mass measurements.

Dynamic high pressures are applied rapidly to materials to increase density and temperature, to alter. crystal structure and microstructure, and to change physical and chemical properties [1]. These effects are achieved at high pressures and many are retained on release from high pressures. Today it is possible to achieve pressures of order 50 to 500 GPa (5 Mbar), compressions up to fifteen fold greater than initial solid density in the case of hydrogen, and temperatures ranging from 1 K up to several ev (11,600 K) in condensed matter. At these extreme conditions the bonding , structure, physical properties and chemistry of condensed matter are changed substantially from what they are at ambient. This in turn opens up a whole new range of opportunities for novel condensed matter physics, chemistry, and planetary research at extreme conditions. If high pressure phases could be quenched to ambient, then new opportunities would become available in condensed matter and material sciences, as well as for technological applications. This article is concerned with high pressures achieved dynamically by shock compression [2]. In fact, the terms dynamic and shock are used interchangably to describe pressure pulses above 1 GPa (10 kbar) or so. Because dynamic compression is …

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The field of research into the optical properties of silicon nanostructures has seen enormous growth over the last decade. The discovery that silicon nanoparticles exhibit visible photoluminescence (PL) has led to new insights into the mechanisms responsible for such phenomena. The importance of understanding and controlling the PL properties of any silicon based material is of paramount interest to the optoelectronics industry where silicon nanoclusters could be embedded into existing silicon based circuitry. In this talk, we present a combination of quantum Monte Carlo and density functional approaches to the calculation of the electronic, structural, and optical properties of silicon nanostructures.

This paper discusses our efforts to improve the performance of the high-accuracy (HIAC) volume rendering system, based on cell projection, which is used to display unstructured, scientific data sets for analysis. The parallelization of HIAC, using the pthreads and MPI API's, resulted in significant speedup, but interactive frame rates are not yet attainable for very large data sets.

LLNL identification research is focused on the problem of correctly discriminating small-magnitude explosions from a background of earthquakes, mining tremors, and other events. The goal is to reduce the variance within the population of each type of event, while increasing the separation between the explosions and the other event types. We address this problem for both broad categories of seismic waves: body waves and surface waves. First, we map out the effects of propagation and source size in advance so that they can be accounted for and removed from observed events. This can dramatically reduce the population variance. Second, we try to optimize the measurement process to improve the separation between population types. For body waves we focus on the identification power of the short-period regional phases Pn, Pg, Sn and Lg, which can often be detected down to very small magnitudes. Many studies have shown that particular ratios of these phases, such as 6-to 8-Hz Pn/Lg, can effectively discriminate between closely located explosions and earthquakes. To extend this discrimination power over broad areas, we use our revised Magnitude and Distance Amplitude Correction (MDAC2) procedure. This joint source and path model fits the observed spectra and removes magnitude and distance …

The Atmospheric Science Division at Lawrence Livermore National Laboratory uses the Naval Research Laboratory's Couple Ocean-Atmosphere Mesoscale Prediction System (COAMPS) for both operations and research. COAMPS is a non-hydrostatic model, designed as a multi-scale simulation system ranging from synoptic down to meso, storm and local terrain scales. As model resolution increases, the forcing due to small-scale complex terrain features including urban structures and surfaces, intensifies. An urban parameterization has been added to the Naval Research Laboratory's mesoscale model, COAMPS. The parameterization attempts to incorporate the effects of buildings and urban surfaces without explicitly resolving them, and includes modeling the mean flow to turbulence energy exchange, radiative transfer, the surface energy budget, and the addition of anthropogenic heat. The Chemical and Biological National Security Program's (CBNP) URBAN field experiment was designed to collect data to validate numerical models over a range of length and time scales. The experiment was conducted in Salt Lake City in October 2000. The scales ranged from circulation around single buildings to flow in the entire Salt Lake basin. Data from the field experiment includes tracer data as well as observations of mean and turbulence atmospheric parameters. Wind and turbulence predictions from COAMPS are used to drive …

Damage in a material includes localized softening or cracks in a structural component due to high operational loads, or the presence of flaws in a structure due to various manufacturing processes. Methods that identify the presence, the location and the severity of damage in the structure are useful for non-destructive evaluation procedures that are typically employed in agile manufacturing and rapid prototyping systems. The current state-of-the art techniques for these inverse problems are computationally intensive or ill conditioned when insufficient data exists. Early work by a number of researchers has shown that data mining techniques can provide a potential solution to this problem. In this paper, they investigate the use of data mining techniques for predicting failure in a variety of 2D and 3D structures using artificial neural networks (ANNs) and decision trees. This work shows that if the correct features are chosen to build the model, and the model is trained on an adequate amount of data, the model can then correctly classify the failure event as well as predict location and severity of the damage in these structures.

X-ray photoemission and x-ray photoabsorption were used to study the composition and the electronic structure of ytterbium doped strontium fluoroapatite (Yb:S-FAP). High resolution photoemission measurements on the valence band electronic structure was used to evaluate the density of occupied states of this fluoroapatite. Element specific density of unoccupied electronic states in Yb:S-FAP were probed by x-ray absorption spectroscopy (XAS) at the Yb 4d (N{sub 4,5}-edge), Sr 3d (M{sub 4,5}-edge), P 2p (L{sub 2,3}-edge), F 1s and O 1s (K-edges) absorption edges. These results provide the first measurements of the electronic structure and surface chemistry of this material.

In conclusion, we have observed the production of 2.45 MeV deuterium fusion neutrons when a gas of deuterium clusters is irradiated with a 120 mJ, 35 fs laser pulse. When the focal position is optimized, we have observed as many as 10{sup 4} neutrons per laser shot. This yield is consistent with some simple estimates for the fusion yield. We also find that the fusion yield is a sensitive function of the deuterium cluster size in the target jet, a consequence of the Coulomb explosion origin of the fast deuterons. We also find that the neutron pulse duration is fast, with a characteristic burn time of well under 1 ns. This experiment may represent a means for producing a compact, table-top source of short pulse fusion neutrons for applications. Furthermore, we have measured hard x-ray yield from femtosecond laser interactions with both solid and micron scale droplet targets. Strong hard x-ray production is observed from both targets. However, the inferred electron temperature is somewhat higher in the case of irradiation of the droplets. These data are consistent with PIC simulations. This finding indicates that quite unique hot electron dynamics occur during the irradiation of wavelength scale particles by an intense …

Over the last decade an unfolding cognitive-psychology research program on how learners use examples to develop effective problem solving expertise has yielded well-established empirical findings. Chi et al., Renkl, Reimann, and Neubert (in various papers) have confirmed statistically significant differences in how good and poor learners inferentially elaborate (self explain) example steps as they study. Such example elaboration is highly relevant to software documentation and training, yet largely neglected in the current literature. This paper summarizes the neglected research on example use and puts its neglect in a disciplinary perspective. The author then shows that differences in support for example elaboration in commercial software documentation reveal previously over looked usability issues. These issues involve example summaries, using goals and goal structures to reinforce example elaborations, and prompting readers to recognize the role of example parts. Secondly, I show how these same example elaboration techniques can build cognitive maturity among underperforming high school students who study technical writing. Principle based elaborations, condition elaborations, and role recognition of example steps all have their place in innovative, high school level, technical writing exercises, and all promote far transfer problem solving. Finally, I use these studies to clarify the constructivist debate over what writers …

Wind is the fastest growing source for electricity in the United States. During 2001, U.S. wind power plant installations are expected to increase by 1,850 megawatts (MW), resulting in a total installed capacity of about 4,400 MW. The market expansion is supported by a variety of Federal and state incentives in the form of production tax credits, renewable energy production incentives, renewable energy portfolio standards, and others. New mechanisms include green power offerings, green tags, and government power purchases. Deregulation of the electric power industry is continuing. In some cases this is allowing higher electricity rates that may increase the rate of wind plant development. Power shortages, natural gas price increases, and enforcement of clean air laws are increasingly important wind market drivers in some regions. Continuing research and technology development has reduced wind energy costs dramatically to less than $0.04/kWh for large projects at sites with ave rage wind speeds higher than 7.0 m/s, making wind the least-cost option in some power markets. The recently published National Energy Policy contains recommendations to increase wind energy development and improve the power transmission system.

In 1999, we presented our plan to upgrade the adaptive optics (AO) system on the Lick Observatory Shane telescope (3m) from a prototype instrument pressed into field service to a facility instrument. This paper updates the progress of that plan and details several important improvements in the alignment and calibration of the AO bench. The paper also includes a discussion of the problems seen in the original design of the tip/tilt (t/t) sensor used in laser guide star mode, and how these problems were corrected with excellent results.

By accurately profiling the users via their unique attributes, it is possible to view the intrusion detection problem as a classification of authorized users and intruders. This paper demonstrates that artificial neural network (ANN) techniques can be used to solve this classification problem. Furthermore, the paper compares the performance of three neural networks methods in classifying authorized users and intruders using synthetically generated data. The three methods are the gradient descent back propagation (BP) with momentum, the conjugate gradient BP, and the quasi-Newton BP.

The technique of using a nsec pulse to preform and ionize the plasma followed by a psec pulse to heat the plasma has enabled low-Z nickel-like ions to achieve saturated output when driven by small lasers with less than ten joules of energy. We model experiments done using the COMET laser at LLNL and the P 102 laser at Limeil to produce Ni-like Pd and Ag lasers. The COMET experiments use a 2 J, 600 ps prepulse followed 700 psec later by a 6 J, 6 psec drive pulse in a 1.6 cm long line focus. The P102 experiments used a somewhat larger energy and were able to use different combinations of frequency doubled light for both the prepulse and short pulse drive. The LASNEX code is used to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the CRETIN code, which then does the kinetics calculations to determine the gain. The temporal and spatial evolution of the plasmas are studied both with and without radiation transport included to understand the role of the self photopumping process on the gain of the Ni-like 4f {yields} 4d laser lines as well as the gain of the …

Emerging CMOS and MEMS technologies enable the implementation of a large number of wireless distributed microsensors that can be easily and rapidly deployed to form highly redundant, self-configuring, and ad hoc sensor networks. To facilitate ease of deployment, these sensors should operate on battery for extended periods of time. A particular challenge in maintaining extended battery lifetime lies in achieving communications with low power. This paper presents a direct-sequence spread-spectrum modem architecture that provides robust communications for wireless sensor networks while dissipating very low power. The modem architecture has been verified in an FPGA implementation that dissipates only 33 mW for both transmission and reception. The implementation can be easily mapped to an ASIC technology, with an estimated power performance of less than 1 mW.

As the U.S. and the Russian Federation get closer to deploying systems for monitoring nuclear material within arms control and nonproliferation transparency regimes, the level of inspectability of the system hardware and software must increase beyond the systems demonstrated to date. These systems include the Trilateral Initiative prototype, the Fissile Material Transparency Technology Demonstration (FMTTD) system, and the Trusted Radiation Attribute Demonstration System (TRADS). Toward this goal, several alternative technologies will be discussed along with ways in which they would increase inspectability. Some examples of such technologies include the use of microcontrollers instead of fully capable computers, open source operating systems, rantime environments, and compilers.

The Muon (g-2) Experiment (E821) at Brookhaven National Laboratory (BNL) started data taking in 1997. The latest result a{sub {mu}{sup +}} = 11659202(14)(6) x 10{sup -10}, based on statistics of about 1 billion decays collected in 1999, is in good agreement with the previous measurement. With the precision of 1.3 ppm, the result, compared with the Standard Model evaluation a{sub {mu}}(SM) = 11659159.6(6.7) x 10{sup -10}, shows a difference of a{sub {mu}}(exp)-a{sub {mu}}(SM) = 43(16) x 10{sup -10}.

Binary manipulation techniques are increasing in popularity. They support program transformations tailored toward certain program inputs, and these transformations have been shown to yield performance gains beyond the scope of static code optimizations without profile-directed feedback. They even deliver moderate gains in the presence of profile-guided optimizations. In addition, transformations can be performed on the entire executable, including library routines. This work focuses on program instrumentation, yet another application of binary manipulation. This paper reports preliminary results on generating partial data traces through dynamic binary rewriting. The contributions are threefold. First, a portable method for extracting precise data traces for partial executions of arbitrary applications is developed. Second, a set of hierarchical structures for compactly representing these accesses is developed. Third, an efficient online algorithm to detect regular accesses is introduced. These efforts are part of a larger project to counter the increasing gap between processor and main memory speeds by means of software optimization and hardware enhancements.

Numerical analysis software packages which employ a coarse first mesh or an inadequate initial mesh need to undergo a cumbersome and time consuming mesh refinement studies to obtain solutions with acceptable accuracy. Hence, it is critical for numerical methods such as finite element analysis to be able to determine a good initial mesh density for the subsequent finite element computations or as an input to a subsequent adaptive mesh generator. This paper explores the use of data mining techniques for obtaining an initial approximate finite element density that avoids significant trial and error to start finite element computations. As an illustration of proof of concept, a square plate which is simply supported at its edges and is subjected to a concentrated load is employed for the test case. Although simplistic, the present study provides insight into addressing the above considerations.

The Lawrence Livermore National Laboratory (LLNL) Ground-Based Nuclear Event Monitoring (GNEM) program has made significant progress populating a comprehensive Seismic Research Knowledge Base (SRKB) and deriving calibration parameters for the Middle East, North Africa and Western Eurasia (ME/NA/WE) regions. The LLNL SRKB provides not only a coherent framework in which to store and organize very large volumes of collected seismic waveforms, associated event parameter information, and spatial contextual data, but also provides an efficient data processing/research environment for deriving location and discrimination correction surfaces. The SRKB is a flexible and extensible framework consisting of a relational database (RDB), Geographical Information System (GIS), and associated product/data visualization and data management tools. This SRKB framework is designed to accommodate large volumes of data (almost 3 million waveforms from 57,000 events) in diverse formats from many sources (both LLNL derived research and integrated contractor products), in addition to maintaining detailed quality control and metadata. We have developed expanded look-up tables for critical station parameter information (including location and response) and an integrated and reconciled event catalog data set (including specification of preferred origin solutions and associated phase arrivals) for the PDE, CMT, ISC, REB and selected regional catalogs. Using the SRKB framework, we …

We present a new wavelet compression and multiresolution modeling approach for sets of contours (level sets). In contrast to previous wavelet schemes, our algorithm creates a parametrization of a scalar field induced by its contoum and compactly stores this parametrization rather than function values sampled on a regular grid. Our representation is based on hierarchical polygon meshes with subdivision connectivity whose vertices are transformed into wavelet coefficients. From this sparse set of coefficients, every set of contours can be efficiently reconstructed at multiple levels of resolution. When applying lossy compression, introducing high quantization errors, our method preserves contour topology, in contrast to compression methods applied to the corresponding field function. We provide numerical results for scalar fields defined on planar domains. Our approach generalizes to volumetric domains, time-varying contours, and level sets of vector fields.

In the past year a spare NASA/GSFC Astro-E microcalorimeter has been installed, tested, and run successfully on the electron beam ions traps EBIT-I and EBIT-II at the Lawrence Livermore National Laboratory. The microcalorimeter complements crystal and grating spectrometers already part of the LLNL ebit program making it possible to measure a broad bandwidth ({approx}0.3-10 keV) with moderate resolution while simultaneously measuring a narrow bandwidth ({approx}0.7-1.3 keV) with high resolution. An overview of recent work, including measurements by the microcalorimeter of absolute excitation cross is presented. These results continue our effort to provide atomic data of high quality to be used as benchmarks of theoretical calculations and to be included in atomic data bases employed by spectral fitting packages used to interpret spectra obtained by XMM-Newton and the Chandra X-Ray Observatory.