Publications

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I am pleased to present the CFO's FY06 Financial Report for Sandia National Laboratories (SNL). As a contractor to DOE and other government agencies, the bulk of SNL's revenue is from tax dollars. SNL's FY06 total revenue, total expenditures, and total employment levels were slightly below the FY05 record high levels. Throughout FY06, SNL business staff continued to improve SNL's financial stewardship of entrusted taxpayer funds through implementation of best-in-class practices in financial business operations and internal control policies and procedures to ensure compliance with all accounting standards and provide accountability to our customers. Our FY06 efforts focused on process certification and improvement, implementing OMB Circular A-123, achieving assurance activities, implementation of a Financial Management Competency Program throughout SNL, and continuous assessment of trends and emerging issues.

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The annual program report provides detailed information about all aspects of the Sandia National Laboratories, California (SNL/CA) Environmental Planning and Ecology Program for a given calendar year. It functions as supporting documentation to the SNL/CA Environmental Management System Program Manual. The 2006 program report describes the activities undertaken during the past year, and activities planned in future years to implement the Planning and Ecology Program, one of six programs that supports environmental management at SNL/CA.

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Scanning probe recognition microscopy is a new scanning probe microscopy technique which enables selective scanning along individual nanofibers within a tissue scaffold. Statistically significant data for multiple properties can be collected by repetitively fine-scanning an identical region of interest. The results of a scanning probe recognition microscopy investigation of the surface roughness and elasticity of a series of tissue scaffolds are presented. Deconvolution and statistical methods were developed and used for data accuracy along curved nanofiber surfaces. Furthermore, nanofiber features were also independently analyzed using transmission electron microscopy, with results that supported the scanning probe recognition microscopy-based analysis.

By far the most widely used tool in shock data analysis is the shock response spectrum (SRS). The SRS has gained popularity because of several primary considerations. It has physical significance, it is simple to understand and it is believed to indicate shock severity. Despite its popularity, the SRS has limitations. Foremost among them is the underlying assumption that shock severity is proportional to a time derivative of position, which does not agree with accepted material failure models. Also, the SRS cannot distinguish between naturally occurring, complex shocks and the chirps sometimes used to achieve a desired SRS using electrodynamic shakers with inadequate force capabilities. Thirdly, SODF models used in the computation of the SRS do not accurately predict accelerations in MDOF structures. A relatively new concept has been introduced whereby an analysis is made on the work done on structures by the excitation force. Since work is equal to the change in the energy of a system, this quantity is closely related to failure models based on strain energy such as the Von Mesis criterion. This paper is the first in a series exploring the use of energy-based description of shock motion and structural response. The input energy spectrum has attractive properties which include intuitive physical significance, insensitivity to system parameters such as viscous damping or hysteretic loss, the ability to distinguish between realistic shocks and chirps, and a close relation to accepted material failure models. Input energy spectra can be calculated using SDOF models and, in many cases, accurately predict the energy input to MDOF structures. Finally, this paper gives an introduction to these methods, derives the equations for relevant energy measures and presents relationships to several other shock analysis tools.

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The static and dynamic compaction of ceramic powders was investigated experimentally using a high-pressure friction-compensated press to achieve static stresses of 1.6 GPa and with a novel gas gun setup to stresses of 5.9 GPa for a tungsten carbide powder. Experiments were performed in the partial compaction region to nearly full compaction. The effects of variables including initial density, particle size distribution, particle morphology, and loading path were investigated in the static experiments. Only particle morphology was found to significantly affect the compaction response. Post-test examination of the powder reveals fracture of the grains as well as breaking at particle edges. In dynamic experiments, steady structured compaction waves traveling at very low velocities were observed. The strain rate within the compaction waves was found to scale nearly linearly with the shock stress, in contrast with many fully dense materials where strain rate scales with stress to the fourth power. Similar scaling is found for data from the literature on TiO2 powder. The dynamic response of WC powder is found to be significantly stiffer than the static response, probably because deformation in the dynamic case is confined to the relatively narrow compaction wave front. Comparison of new static powder compaction results with shock data from the literature for SiO2 also reveals a stiffer dynamic response. © 2006 Elsevier Ltd. All rights reserved.

Digital Elevation Models (DEMS) are traditionally acquired from a stereo pair of aerial photographs sequentially captured by an airborne metric camera. Standard DEM extraction techniques can be naturally extended to satellite imagery, but the particular characteristics of satellite imaging can cause difficulties. The spacecraft ephemeris with respect to the ground site during image collects is the most important factor in the elevation extraction process. When the angle of separation between the stereo images is small, the extraction process typically produces measurements with low accuracy, while a large angle of separation can cause an excessive number of erroneous points in the DEM from occlusion of ground areas. The use of three or more images registered to the same ground area can potentially reduce these problems and improve the accuracy of the extracted DEM. The pointing capability of some sensors, such as the Multispectral Thermal Imager (MTI), allows for multiple collects of the same area from different perspectives. This functionality of MTI makes it a good candidate for the implementation of a DEM extraction algorithm using multiple images for improved accuracy. Evaluation of this capability and development of algorithms to geometrically model the MTI sensor and extract DEMs from multi-look MTI imagery are described in this paper. An RMS elevation error of 6.3-meters is achieved using 11 ground test points, while the MTI band has a 5-meter ground sample distance. © 2007 American Society for Photogrammetry and Remote Sensing.

An epoxy-based conformal coating with a very low modulus has been developed for the environmental protection of electronic devices and for stress relief of those devices. The coating was designed to be removable by incorporating thermally-reversible Diels-Alder (D-A) adducts into the epoxy resin utilized in the formulation. The removability of the coating allows us to recover expensive components during development, to rebuild during production, to upgrade the components during their lifetime, to perform surveillance after deployment, and it aids in dismantlement of the components after their lifetime. The removability is the unique feature of this coating and was characterized by modulus versus temperature measurements, dissolution experiments, viscosity quench experiments, and FTIR. Both the viscosity quench experiments and the FTIR measurements allowed us to estimate the equilibrium constant of the D-A adducts in a temperature range from room temperature to 90 °C. © 2007 American Chemical Society.

During the course of processing acceleration data from mechanical systems it is often desirable to integrate the data to obtain velocity or displacement waveforms. However, those who have attempted these operations may be painfully aware that the integrated records often yield unrealistic residual values. This is true whether the data has been obtained experimentally or through numerical simulation such as Runge-Kutta integration or the explicit finite element method. In the case of experimentally obtained data, the integration errors are usually blamed on accelerometer zero shift or amplifier saturation. In the case of simulation data, incorrect integrations are often incorrectly blamed on the integration algorithm itself. This work demonstrates that seemingly small aliased content can cause appreciable errors in the integrated waveforms and explores the unavoidable source of aliasing in both experiment and simulation-the sampling operation. Numerical analysts are often puzzled as to why the integrated acceleration from their simulation does not match the displacement output from the same simulation. This work shows that these strange results can be caused by aliasing induced by interpolation of the model output during sampling regularisation. © 2005 Elsevier Ltd. All rights reserved.

We report on algebraic multilevel preconditioners for the parallel solution of linear systems arising from a Newton procedure applied to the finite-element (FE) discretization of the incompressible Navier-Stokes equations. We focus on the issue of how to coarsen FE operators produced from high aspect ratio elements.

The focus of this paper is a penalty-based strategy for preconditioning elliptic saddle point systems. As the starting point, we consider the regularization approach of Axelsson in which a related linear system, differing only in the (2,2) block of the coefficient matrix, is introduced. By choosing this block to be negative definite, the dual unknowns of the related system can be eliminated resulting in a positive definite primal Schur complement. Rather than solving the Schur complement system exactly, an approximate solution is obtained using a substructuring preconditioner. The approximate primal solution together with the recovered dual solution then define the preconditioned residual for the original system.

A new technique is described for the registration of edge-detected images. While an extensive literature exists on the problem of image registration, few of the current approaches include a well-defined measure of the statistical confidence associated with the solution. Such a measure is essential for many autonomous applications, where registration solutions that are dubious (involving poorly focused images or terrain that is obscured by clouds) must be distinguished from those that are reliable (based on clear images of highly structured scenes). The technique developed herein utilizes straightforward edge pixel matching to determine the "best" among a class of candidate translations. A well-established statistical procedure, the McNemar test, is then applied to identify which other candidate solutions are not significantly worse than the best solution. This allows for the construction of confidence regions in the space of the registration parameters. The approach is validated through a simulation study and examples are provided of its application in numerous challenging scenarios. While the algorithm is limited to solving for two-dimensional translations, its use in validating solutions to higher-order (rigid body, affine) transformation problems is demonstrated. © 2007 IEEE.

Flame-sampling photoionization mass spectrometry is used for measurements of the absolute molar composition of fuel-rich (φ = 1.8) low-pressure laminar flames of allene and propyne. The experiment combines molecular-beam mass spectrometry with photoionization by tunable vacuum-ultraviolet synchrotron radiation. This approach provides selective detection of individual isomers and unambiguous identifications of other flame species of near-equal mass by near threshold photoionization efficiency measurements. Mole fraction profiles for more than 30 flame species with ion masses ranging from 2 to 78 are presented. The isomeric composition is resolved for most intermediates, for example, mole fraction profiles are presented for both benzene and the fulvene isomer. The results are compared with predictions based on current kinetic models. The mole fractions of the major species are predicted quite accurately, however, some discrepancies are observed for minor species. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The role of ethanol as a fuel additive was investigated in a fuel-rich, non-sooting (C/O = 0.77) flat premixed propene-oxygen-argon flame at 50 mbar (5 kPa). Mole fractions of stable and radical species were derived using two different in situ molecular beam mass spectrometry (MBMS) set-ups, one located in Bielefeld using electron impact ionization (EI), and the other at the Advanced Light Source (ALS) at Berkeley using vacuum UV photoionization (VUV-PI) with synchrotron radiation. A rich propene flame, previously studied in detail experimentally and with flame model calculations, was chosen as the base flame. Addition of ethanol is believed to reduce the concentrations of benzene and small aromatic compounds, while augmenting the formation of other regulated air toxics such as aldehydes. To study the chemical pathways responsible for these effects, quantitative concentrations of about 35 species were determined from both experiments. This is also the first time that a detailed comparison of quantitative species concentrations from these independent MBMS set-ups is available. Effects of ethanol addition on the species pool are discussed with special attention on benzene precursor chemistry and aldehyde formation. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

The effect of exhaust-gas recirculation (EGR) on the equivalence ratio of premixed-burn mixture in diesel combustion was investigated experimentally. The ambient oxygen concentration was systematically decreased from 21% to 10% in a constant-volume combustion vessel to simulate EGR effects in engines. Pressure measurements and time-resolved imaging of high-temperature chemiluminescence were used to characterize the temporal and spatial ignition and premixed burn characteristics of n-heptane diesel jets. With increasing EGR, ignition delay increases and the location of premixed burn occurs further down-stream from the nozzle. Subsequent to first ignition, high temperature reactions stabilize at a quasi-steady lift-off length, showing that lift-off is a bounding parameter for determining premixed-burn region. The equivalence ratio of the fuel-ambient mixture in the premixed-burn region was measured using planar laser Rayleigh scattering. Fuel-oxygen mass distribution functions show that more mass is mixed into the premixed-burn region with increasing EGR, but the equivalence ratio of this mixture is the same. The study shows that an increasing ignition delay with increasing EGR does not necessarily decrease the equivalence ratio as would be desired for reducing soot formation in low-temperature combustion engines. However, measures to improve fuel-ambient mixing, such as shortened injection durations coupled to long ignition delay, could decrease equivalence ratio.

One-dimensional (1-D) line Rayleigh thermometry is used to investigate the effects of spatial resolution and noise on thermal dissipation in turbulent non-premixed CH4/H2/N2 jet flames. The high signal-tonoise ratio and spatial resolution of the measured temperature field enables determination of the cutoff wavenumber in the 1-D temperature dissipation spectrum obtained at each flame location. The local scale inferred from this cutoff is analogous to the Batchelor scale in nonreacting flows. At downstream locations in the flames studied here, it is consistent with estimates of the Batchelor scale based on the scaling laws using local Reynolds numbers. The spectral cutoff information is used to design data analysis schemes for determining mean thermal dissipation. Laminar flame measurements are used to characterize experimental noise and correct for the noise-induced apparent dissipation in the turbulent flame results. These experimentally determined resolution and noise correction techniques are combined to give measurements of the mean thermal dissipation that are essentially fully resolved and noise-free. The prospects of using spectral results from high-resolution 1-D Rayleigh imaging measurements to design filtering schemes for Raman-based measurements of mixture fraction dissipation are also discussed.

The mixture fraction filtered mass density function (FMDF) used in large eddy simulation (LES) of turbulent combustion is studied experimentally using line images obtained in turbulent partially premixed methane flames (Sandia flames D and E). Cross-stream filtering is employed to obtain the FMDF and other filtered variables. The means of the FMDF conditional on the subgrid-scale (SGS) scalar variance at a given location are found to vary from close to Gaussian to bimodal, indicating well-mixed and non-premixed SGS mixing regimes, respectively. The bimodal SGS scalar has a structure (ramp-cliff) similar to the counter-flow model for laminar flamelets. Therefore, while the burden on mixing models to predict the well-mixed SGS scalar is expected to lessen with decreasing filter scale, the burden to predict the bimodal one is not. These SGS scalar structures can result in fluctuations of the SGS flame structure between distributed reaction zones and laminar flamelets, but for reasons different from the scalar dissipation rate fluctuations associated with the turbulence cascade. Furthermore, the bimodal SGS scalar contributes a significant amount of the scalar dissipation in the reaction zones, highlighting its importance and the need for mixing models to predict the bimodal FMDFs. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

Direct numerical simulation of a three-dimensional spatially developing turbulent slot-burner Bunsen flame has been performed with a new reduced methane-air mechanism. The mechanism, derived from sequential application of directed relation graph theory, sensitivity analysis and computational singular perturbation over the GRI-1.2 detailed mechanism is non-stiff and tailored to the lean conditions of the DNS. The simulation is performed for three flow through times, long enough to achieve statistical stationarity. The turbulence parameters have been chosen such that the combustion occurs in the thin reaction zones regime of premixed combustion. The data is analyzed to study possible influences of turbulence on the structure of the preheat and reaction zones. The results show that the mean thickness of the turbulent flame, based on progress variable gradient, is greater than the corresponding laminar flame. The effects of flow straining and flame front curvature on the mean flame thickness are quantified through conditional means of the thickness and by examining the balance equation for the evolution of the flame thickness. Finally, conditional mean reaction rate of key species compared to the laminar reaction rate profiles show that there is no significant perturbation of the heat release layer.

Combinatorial algorithms have long played a crucial, albeit under-recognized role in scientific computing. This impact ranges well beyond the familiar applications of graph algorithms in sparse matrices to include mesh generation, optimization, computational biology and chemistry, data analysis and parallelization. Trends in science and in computing suggest strongly that the importance of discrete algorithms in computational science will continue to grow. This paper reviews some of these many past successes and highlights emerging areas of promise and opportunity. © Springer-Verlag Berlin Heidelberg 2007.

Laboratory experiments on the interaction of a plasma flow, produced by laser ablation of a solid target with the inhomogeneous magnetic field from the Zebra pulsed power generator demonstrated the presence of strong wave activity in the region of the flow deceleration. The deceleration of the plasma flow can be interpreted as the appearance of a gravity-like force. The drift due to this force can lead to the excitation of flute modes. In this paper a linear dispersion equation for the excitation of electromagnetic flute-type modes with plasma and magnetic field parameters, corresponding to the ongoing experiments is examined. Results indicate that the wavelength of the excited flute modes strongly depends on the strength of the external magnetic field. For magnetic field strengths ∼ 0.1 MG the excited wavelengths are larger than the width of the laser ablated plasma plume and cannot be observed during the experiment. But for magnetic field strengths ∼ 1 MG the excited wavelengths are much smaller and can then be detected. © Springer Science+Business Media B.V. 2007.

Atomistic models of the Si(1 0 0)/SiO2 interface were generated using a classical reactive force field, and subsequently optimized using density functional theory. The interfaces consist of amorphous oxide bound to crystalline silicon substrate. Each system has a sub-oxide layer of partially oxidized silicon atoms at the interface, and a distribution of oxygen-deficient centers in the oxide. Both periodic and slab configurations are considered. © 2006.

Oxygen/carbon dioxide recycle coal combustion is actively being investigated because of its potential to facilitate CO2 sequestration and to achieve emission reductions. In the work reported here, the effect of enhanced oxygen levels and CO2 bath gas is independently analyzed for their influence on single-particle pulverized coal ignition of a U.S. eastern bituminous coal. The experiments show that the presence of CO2 and a lower O2 concentration increase the ignition delay time but have no measurable effect on the time required to complete volatile combustion, once initiated. For the ignition process observed in the experiments, the CO 2 results are explained by its higher molar specific heat and the O2 results are explained by the effect of O2 concentration on the local mixture reactivity. Particle ignition and devolatilization properties in a mixture of 30% O2 in CO2 are very similar to those in air.

A 70-MA, 7-MV, ∼100-ns driver for a Z-pinch Inertial Fusion Energy (Z-IFE) power plant has been proposed. In this summary we address the transition region between the 70 Linear Transformer Driver (LTD) modules and the center Recyclable Transmission Line (RTL) load section, which convolves from the coaxial vacuum Magnetically Insulated Transmission Lines (MITL) to a parallel tri-plate and then a bi-plate disk feed. An inductive annular chamber terminates one side of the tri-plate in a manner that preserves vacuum and electrical circuit integrity without significant energy losses. The simplicity is offset by the disadvantage of the chamber size, which is proportional to the driver impedance and decreases with the addition of more parallel modules. Inductive isolation chamber sizes are estimated in this paper, based on an optimized LTD equivalent circuit simulation source driving a matched load using transmission line models. We consider the trade-offs between acceptable energy loss and the size of the inductive isolation chamber; accepting a 6% energy loss would only require a 60-nH chamber.

Numerous molecular dynamics simulation studies of radiation cascades in Si have elucidated many of the general features of the initial defect production. However, the resulting defect structures have been analyzed with techniques that are not sensitive to changes in the local bonding topology. Here the results of analyzing the ring content in Si cascades, in addition to more traditional defect characterization such as Wigner-Seitz cell analysis, will be presented for recoil energies ranging from 25 eV up to 25 keV. The ring content of local amorphous regions in the cascades will be compared to the ring content in simulations of bulk amorphous Si. The number of atoms in the amorphous regions and the number of point defects as a function of recoil energy are determined. © 2006 Elsevier B.V. All rights reserved.

This paper focuses on the application of the large eddy simulation (LES) technique to a swirling particle-laden flow in a model combustion chamber. A series of calculations have been performed and compared directly with detailed experimental measurements. The computational domain identically matches the laboratory configuration, which effectively isolates effects related to dilute particle dispersion and momentum coupling. Results highlight the predictive capabilities of LES when implemented with the appropriate numerics, grid resolution (as dictated by the class of models employed) and well-defined boundary conditions. The case study provides a clearer understanding of the effectiveness and feasibility of current state-of-the-art models and a quantitative understanding of relevant modeling issues by analyzing the characteristic parameters and scales of importance. The novel feature of the results presented is that they establish a baseline level of confidence in our ability to simulate complex flows at conditions representative of those typically observed in gas-turbine (and similar) combustors. © 2006 The Combustion Institute. Published by Elsevier Inc. All rights reserved.

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In this paper, the term tensor refers simply to a multidimensional or N-way array, and we consider how specially structured tensors allow for efficient storage and computation. First, we study sparse tensors, which have the property that the vast majority of the elements are zero. We propose storing sparse tensors using coordinate format and describe the computational efficiency of this scheme for various mathematical operations, including those typical to tensor decomposition algorithms. Second, we study factored tensors, which have the property that they can be assembled from more basic components. We consider two specific types: A Tucker tensor can be expressed as the product of a core tensor (which itself may be dense, sparse, or factored) and a matrix along each mode, and a Kruskal tensor can be expressed as the sum of rank-1 tensors. We are interested in the case where the storage of the components is less than the storage of the full tensor, and we demonstrate that many elementary operations can be computed using only the components. All of the efficiencies described in this paper are implemented in the Tensor Toolbox for MATLAB. © 2007 Society for Industrial and Applied Mathematics.

MFI zeolite membranes have been synthesized on tubular α-alumina substrates to investigate the separation of p-xylene (PX) from m-xylene (MX) and o-xylene (OX) in multicomponent mixtures and ranges of feed pressure and operating temperature. 1,3,5-triisopropylbenzene was added to the feed stream for online membrane modification. Separation of PX from MX and OX through the MFI membranes relies primarily on shape-selectivity when the xylene sorption level in the zeolite is sufficiently low. For an eight-component mixture containing hydrogen, hydrocarbons, PX, MX, and OX, PX/(MX+OX) selectivity of 7.71 with PX flux of 6.8×10-6mol/m2.s was obtained at 250°C and atmospheric feed pressure. © 2007 Elsevier B.V. All rights reserved.

Evaluating the performance of finite-difference algorithms typically uses a technique known as von Neumann analysis. For a given algorithm, application of the technique yields both a dispersion relation valid for the discrete time-space grid and a mathematical condition for stability. In practice, a major shortcoming of conventional von Neumann analysis is that it can be applied only to an idealized numerical model - that of an infinite, homogeneous whole space. Experience has shown that numerical instabilities often arise in finite-difference simulations of wave propagation at interfaces with strong material contrasts. These interface instabilities occur even though the conventional von Neumann stability criterion may be satisfied at each point of the numerical model. To address this issue, I generalize von Neumann analysis for a model of two half-spaces. I perform the analysis for the case of acoustic wave propagation using a standard staggered-grid finite-difference numerical scheme. By deriving expressions for the discrete reflection and transmission coefficients, I study under what conditions the discrete reflection and transmission coefficients become unbounded. I find that instabilities encountered in numerical modeling near interfaces with strong material contrasts are linked to these cases and develop a modified stability criterion that takes into account the resulting instabilities. I test and verify the stability criterion by executing a finite-difference algorithm under conditions predicted to be stable and unstable. © 2007 Society of Exploration Geophysicists.

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We report what is believed to be the first application of coherent anti-Stokes Raman scattering (CARS) to full-scale fire testing. A CARS instrument has been constructed at the newly commissioned FLAME (Fire Laboratory for Accreditation of Models and Experiments) facility at Sandia, where the CARS system has been used for thermometry in 2-m-diameter, turbulent methanol pool fires. Fielding of CARS in such a large-scale facility presents several challenges, including long-distance propagation of laser beams, shielding of optics from intense heat, the impact of beam steering and fiber-optic coupling of the CARS signal to remotely located detection equipment. The details of a CARS instrument that meets these challenges are presented, along with the construction of the unique new FLAME facility itself, which has been designed to accommodate optical and laser-based diagnostics to full-scale fire experimentation. The performance of the CARS instrument is investigated in a premixed methane-air flat flame to estimate the precision in single-shot CARS temperatures. Single-shot CARS spectra and best-fit temperatures from a methanol pool fire are presented, and an estimate of the pdf of the temperature fluctuations from the pool-fire environment is obtained.

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This paper examined the high frequency time harmonic localization of modal fields in two dimensional cavities along unstable periodic orbits. The elliptic formalism, combined with the random phase approach, allowed the treatment of both convex and concave boundary geometries.

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It is shown that for any material or structural model expressible as a Masing model, there exists a unique parallel-series (displacement-based) Iwan system that characterizes that model as a function of displacement history. This poses advantages both in terms of more convenient force evaluation in arbitrary deformation histories as well as in terms of model inversion. Characterization as an Iwan system is demonstrated through the inversion of the Ramberg-Osgood model, a force(stress)-based material model that is not explicitly invertible. An implication of the inversion process is that direct, rigorous comparisons of different Masing models, regardless of the ability to invert their constitutive relationship, can be achieved through the comparison of their associated Iwan distribution densities.

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Motivation: Methods available for the inference of genetic regulatory networks strive to produce a single network, usually by optimizing some quantity to fit the experimental observations. In this article we investigate the possibility that multiple networks can be inferred, all resulting in similar dynamics. This idea is motivated by theoretical work which suggests that biological networks are robust and adaptable to change, and that the overall behavior of a genetic regulatory network might be captured in terms of dynamical basins of attraction. Results: We have developed and implemented a method for inferring genetic regulatory networks for time series microarray data. Our method first clusters and discretizes the gene expression data using k-means and support vector regression. We then enumerate Boolean activation-inhibition networks to match the discretized data. Finally, the dynamics of the Boolean networks are examined. We have tested our method on two immunology microarray datasets: an IL-2-stimulated T cell response dataset and a LPS-stimulated macrophage response dataset. In both cases, we discovered that many networks matched the data, and that most of these networks had similar dynamics. © The Author 2007. Published by Oxford University Press. All rights reserved.

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Network simulation models for water distribution systems typically assume the mixing at pipe intersections is complete and instantaneous. Recent data show that mixing may be incomplete at pipe junctions (pipe crosses and tees) under most conditions. In general, computational fluid dynamic (CFD) simulations agree with the experimental data, establishing confidence in the CFD approach for application to other situations. However, in the case of unequal inlet flow rates and equal outlet flow rates in a cross, the simulation results and experimental data show significantly different results. The reasons for this discrepancy are investigated, and a revised model is developed that is consistent with the experimental data. © 2007 ASCE.

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Spectrofluorometric imaging microscopy is demonstrated in a confocal microscope using a supercontinuum laser as an excitation source and a custom-built prism spectrometer for detection. This microscope system provides confocal imaging with spectrally resolved fluorescence excitation and detection from 450 to 700 nm. The supercontinuum laser provides a broad spectrum light source and is coupled with an acousto-optic tunable filter to provide continuously tunable fluorescence excitation with a 1-nm bandwidth. Eight different excitation wavelengths can be simultaneously selected. The prism spectrometer provides spectrally resolved detection with sensitivity comparable to a standard confocal system. This new microscope system enables optimal access to a multitude of fluorophores and provides fluorescence excitation and emission spectra for each location in a 3D confocal image. The speed of the spectral scans is suitable for spectrofluorometric imaging of live cells. Effects of chromatic aberration are modest and do not significantly limit the spatial resolution of the confocal measurements.

What constitutes a validated model? What are the criteria that allow one to defensibly make the claim that they are using a validated model in an analysis? These questions get to the heart of what model validation really implies (conceptually, operationally, interpretationally, etc.), and these details are currently the subject of substantial debate in the V&V community. This is perhaps because many contemporary paradigms of model validation have a limited modeling scope in mind, so the validation paradigms do not span different modeling regimes and purposes that are important in engineering. This paper discusses the different modeling regimes and purposes that it is important for a validation theory to span, and then proposes a validation paradigm that appears to span them. The author's criterion for validated models proceeds from a desire to meet an end objective of "best estimate plus uncertainty" (BEPU) in model predictions. Starting from this end, the author works back to the implications on the model validation process (conceptually, operationally, interpretationally, etc.). Ultimately a shift is required in the conceptualization and articulation of model validation, away from contemporary paradigms. Thus, this paper points out weaknesses in contemporary model validation perspectives and proposes a conception of model validation and validated models that seems to reconcile many of the issues. Copyright © 2007 SAE International.

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New low-temperature combustion (LTC) strategies can reduce both NOx and soot emissions from compression-ignition engines, but unburned hydrocarbon (UHC) emissions typically increase. Incylinder UHC evolution can be marked by formaldehyde, an intermediate species in the combustion process. Formaldehyde is formed during the first stage of ignition of diesel-like fuels, and it persists along with UHC in regions that do not achieve complete combustion. During the second stage of ignition, fuel and formaldehyde are largely consumed as OH radicals become prominent. The appearance of OH therefore indicates second-stage ignition and relatively complete combustion of fuel. Simultaneous planar laser-induced fluorescence (PLIF) images of formaldehyde and OH are acquired for two LTC conditions with different ignition delays, using neat n-heptane fuel. For both cases, formaldehyde PLIF is initially observed throughout the jet. Later, OH PLIF first appears downstream in the jet, where formaldehyde and UHC are locally consumed. For the shorter ignition-delay condition, OH PLIF quickly appears upstream locally where formaldehyde PLIF decreases, marking second-stage ignition and consumption of formaldehyde and UHC. For the longer ignition-delay condition, however, OH PLIF does not appear upstream, even late in combustion. Rather, formaldehyde PLIF, and therefore UHCs, persist near the injector late in combustion, indicating that regions near the injector do not achieve complete combustion, and may contribute to UHC emissions for the longer ignition delay condition.

Specially designed Pnp heterojunction bipolar transistors (HBT's) in the AlGaAs/GaAs material system can offer improved radiation response over commercially-available silicon bipolar junction transistors (BJT's). To be a viable alternative to the silicon Pnp BJT, improvements to the manufacturability of the HBT were required. Utilization of a Pd/Ge/Au non-spiking ohmic contact to the base and implementation of a PECVD silicon nitride hard mask for wet etch control were the primary developments that led to a more reliable fabrication process. The implementation of the silicon nitride hard mask and the subsequent process improvements increased the average electrical yield from 43% to 90%. © The Electrochemical Society.

As the amount of real time data collected during drilling continues to rise, sophisticated methods for analyzing and displaying data are needed to make sense out of large volumes of data. This paper describes a novel use of the concepts of computational geometry to analyze and display data from a downhole drilling data tool. The use of a mathematical transformation called a convex hull allows one to create a boundary around a set (cloud) of data points. This is most easily visualized in two dimensions as putting a rubber band around the set of points. Imagine that the rubber band is such that it will be tightly stretched when it is around all the points, so that certain points in the data cloud dictate the resulting outline. A convex hull software routine, the best known of which is the"qhull" program from the University of Minnesota, fits line segments around a cloud of points in up to nine dimensions. Utilizing the convex hull output one can calculate the volume in 3-D or area in 2-D described by data clouds. The result is used as an indicator of bit and drill string behavior. Copyright 2007, Society of Petroleum Engineers.

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Over the years, researchers have been investigating large-scale pool fores, both experimentally and numerically, because of the risk they pose during transport accidents. In the course of developing and validating computational models, researchers have come to realize that knowledge of the soot concentration, temperature and optical properties within fires is required to quantify the amount of heat transferred. In turn, such knowledge may help in understanding the dynamics of fires, particularly large accidental ones.

A shear test was used to investigate the effect of shielding gas (Argon, Nitrogen and air) on the mechanical properties of laser spot welds in Fe-28Ni-17Co alloy (Kovar). The load vs. displacement curves obtained, while superficially resembling those of a standard tensile test, were quite non-reproducible, and obscured the differences due to process conditions. Fractographic examination of the samples and analysis of the testing conditions led to significant conclusions about how to correctly interpret the shear test results, which in turn enabled a determination of the real effects of the change in shielding gas. Several different types of fracture morphology were noted, depending upon how the fracture surface developed relative to the original weld. This resulted in the disparate nature of the load-displacement curves. The results of the shear testing, fractography and metallography will be used to support interpretation of the differences found with respect to porosity formation, strength and work hardening behavior.

A top level overview of the effect cables have on the dynamic response of precision structures is presented. The focus of this paper is on precision, low-damping, low-first modal frequency space structures where cables are not implicitly designed to be in the load path. The paper presents the top-level, Phase I results which include pathfinder tests, an industry/government/academia survey, modeling and testing of individual cable bundles, and modeling and testing of cables on a simple structure. The end goal is to discover a set of practical approaches for updating well defined dynamical models of cableless structures. Knowledge of the cable type, position and tie-down method is assumed to be known. Simulation sensitivity analysis of the effect cables have on a precision structure has also been completed. Each section of the paper will focus on the details of each area.

This paper presents experimental results and modeling aspects for electrical power and signal cable harnesses used for space applications. Dynamics of large precision structures can be significantly influenced by subsystems such as electrical cables and harnesses as the structural mass of those structures tends to become smaller, and the quantity of attached cables continues to increase largely due to the ever increasing complexity of such structures. Contributions of cables to structural dynamic responses were observed but never studied, except for a low scale research effort conducted at the Air Force Research Laboratory, Space Vehicles Directorate (AFRL/VSSV). General observations were that at low frequencies cables have a mass loading effect while at higher frequencies they have a dissipative effect. The cables studied here adhere to space industry practices, identified through an extensive industry survey. Experimental procedures for extracting structural properties of the cables were developed. The structural properties of the cables extracted from the extensive experimental database that is being created can be used for numerical modeling of cabled structures. Explicit methods for analytical modeling of electrical cables attached to a structure in general are yet to be developed and the goal of this effort is to advance the state of the art in modeling cable harnesses mounted on lightweight spacecraft structures.

Signal and power harnesses on spacecraft buses and payloads can alter structural dynamics, as has been noted in previous flight programs. The community, however, has never undertaken a thorough study to understand the impact of harness dynamics on spacecraft structures. The Air Force Research Laboratory is leading a test and analysis program to develop fundamental knowledge of how spacecraft harnesses impact dynamics and develop tools that structural designers could use to achieve accurate predictions of cable-dressed structures. The work described in this paper involved a beam under simulated free boundary conditions that served as a validation test bed for model development.

Verification and validation of software in the field of scientific computing is increasingly being recognized as a critical part of the software, algorithm, and model development cycle. Multi-mechanics coupling represents an important and challenging role in providing confidence in the integrated multi-mechanics codes. This paper presents an overview of the math models implemented within the Sandia National Laboratories Advanced Simulation and Computing SIERRA Mechanics code project that supports the engulfed object-in-a-fire scenario. This scenario is characterized by coupling turbulent fluid mechanics, combustion, soot generation and transport, participating media radiation (PMR), thermal conduction and in the case of propellant fires, reacting Lagrangian particles. Attaining an adequate state of code verification for such a complex engineering mechanics scenario represents a daunting challenge. A systematic approach is therefore required. Examples of single and multiple mechanics verification methodologies will be presented.

In this paper, we evaluate a commercially available high density plasma chemical vapor deposition (HDP-CVD) process to grow low temperature (i.e., Tin-situ & Tepitaxy < ∼460°C) germanium epitaxy for a p+-Ge/p-Si/n+-Si NIR separate absorption and multiplication avalanche photodetectors (SAM-APD). A primary concern for SAM-APDs in this material system is that high fields will not be sustainable across a highly defective Ge/Si interface. We show Ge-Si SAM-APDs that show avalanche multiplication and avalanche breakdown. A dark current of ∼0.1 mA/cm2 and a 3.2×10-4 A/W responsivity at 1310 nm were measured at punch-through. An over 400x photocurrent multiplication was demonstrated at room temperature. These results indicate that high avalanche multiplication gain is achievable in these Ge/Si heterostructures despite the highly defective interface and therefore trap assisted tunneling through the defective Ge/Si interface is not dominant at high fields. © 2007 Materials Research Society.

Current published models for predicting squeeze film damping (SFD), which are based on different assumptions, give widely different results in the free-molecule regime. The work presented here provides experimental data for validating SFD models in that regime. The test device was an almost rectangular micro plate supported by beam springs. The structure was base-excited. The rigid plate oscillated vertically while staying parallel to the substrate. The velocities of the plate and of the substrate were measured with a laser Doppler vibrometer and a microscope. The damping ratio was calculated by performing modal analysis of the frequency response functions. The test structures were contained in a vacuum chamber with air pressures controlled to provide a five-order-of-magnitude range of Knudsen numbers. The damping coefficients from the measurements were compared with predictions from various published models. The results show that the continuum-base Reynolds equation predicts squeeze-film damping accurately if used with correct boundary conditions. The accuracy of molecular-based models depends heavily on the assumptions used in developing the models.

Full-waveform seismic reflection responses of an isolated porous sandstone layer are simulated with three-dimensional (3D) isotropic poroelastic and isotropic elastic finite-difference (FD) numerical algorithms. When the pore-filling fluid is brine water with realistic viscosity, there is about a ∼10% difference in synthetic seismograms observed in an AVO recording geometry. These preliminary results suggest that equivalent elastic medium modeling is adequate for general interpretive purposes, but more refined investigations (such as AVO waveform analysis) should account for poroelastic wave propagation effects.

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Open MPI was initially designed to support a wide variety of high-performance networks and network programming interfaces. Recently, Open MPI was enhanced to support networks that have full support for MPI matching semantics. Previous Open MPI efforts focused on networks that require the MPI library to manage message matching, which is sub-optimal for some networks that inherently support matching. We describes a new matching transport layer in Open MPI, present results of micro-benchmarks and several applications on the Cray XT platform, and compare performance of the new and the existing transport layers, as well as the vendor-supplied implementation of MPI. © Springer-Verlag Berlin Heidelberg 2007.

The default messaging model for the OpenFabrics "Verbs" API is to consume receive buffers in order - regardless of the actual incoming message size - leading to inefficient registered memory usage. For example, many small messages can consume large amounts of registered memory. This paper introduces a new transport protocol in Open MPI implemented using the existing OpenFabrics Verbs API that exhibits efficient registered memory utilization. Several real-world applications were run at scale with the new protocol; results show that global network resource utilization efficiency increases, allowing increased scalability - and larger problem sizes - on clusters which can increase application performance in some cases. © Springer-Verlag Berlin Heidelberg 2007.

Fuel stratification has been investigated as a means of improving the low-load combustion efficiency in an HCCI engine. Several stratification techniques were examined: different GDI injectors, increased swirl, and changes in injection pressure, to determine which parameters are effective for improving the combustion efficiency while maintaining NOx emissions below U.S. 2010 limits. Performance and emission measurements were obtained in an all-metal engine. Corresponding fuel distribution measurements were made with fuel PLIF imaging in a matching optically accessible engine. The fuel used was iso-octane, which is a good surrogate for gasoline. For an idle fueling rate (φ = 0.12), combustion efficiency was improved substantially, from 64% to 89% at the NOx limit, using delayed fuel injection with a hollow-cone injector at an injection pressure of 120 bar. Relative to this base case, changing to an 8-hole injector provided the single largest improvement, increasing combustion efficiency to 92%. The effects of swirl varied with injector type, but increased injection pressure was beneficial for both injectors. The highest combustion efficiency of 92.5% at the NOx limit was achieved with the 8-hole injector and an injection pressure of 170 bar, with low swirl. Quantitative fuel-distribution maps derived from the PLIF images showed good agreement with the combustion-efficiency and NO x-emission measurements in the metal engine. The images showed that at the NOx limit, fuel distributions and maximum equivalence ratios (φ) are similar for the two injectors, with delayed injection producing a single large fuel pocket. Fuel-mass histograms suggest that the 8-hole injector improved the combustion-efficiency at the NOx limit by reducing the fraction of low-φ regions, but a wider field of view is required to fully confirm this. The images also show that increased swirl inhibited the mixing of fuel into the center of the combustion chamber, explaining the slower mixing rates observed in the metal engine. A general finding is that the combustion-efficiency/NOx tradeoff improves when fuel can be injected as late as possible with acceptable levels of NOx. Therefore, techniques that provide even faster mixing have the potential for further improvements.

Pre-oxidized and glass-to-metal (GtM) sealed austenitic stainless steels were found to display a ferritic layer near the metal/oxide interface, as determined by electron backscatter diffraction (EBSD). Electron probe microanalysis (EPMA) showed that this layer was depleted in alloying elements due to the oxidation and sealing process. Characterization of the morphology suggested that it formed through the martensite transformation mechanism. Moreover, this observed layer was correlated to the composition gradient through published empirical relationships for martensite-start (Ms) temperatures. Due to Cr, Mn, and Si depletion during pre-oxidation and glass sealing, Ms temperatures near room temperature are possible in this surface region. Further support for a martensitic transformation was provided by thermochemical modeling. Possible detrimental ramifications of bulk composition, surface depletion, and phase transformations on GtM sealing are discussed. Copyright © 2007 MS&T'07®.

The impact of localized polarization of aluminum in aqueous chloride is studied using in situ atomic force microscopy (AFM). The primary goal of this study is to determine whether nanostructural degradation in the form of passivity loss and pit initiation can be induced by applying potential pulses between a conductive AFM probe tip and an aluminum surface. Nanoscopic imaging of the mechanically compliant hydrous oxide on an Al(111) textured film with 0.5 wt.% Cu is demonstrated. A correlation is made between characteristic nanostructural changes observed for localized and macroscopic area polarization. Pit initiation proximity to the AFM tip is also demonstrated arguing for millisecond time periods as being sufficient to drive pit initiation within a targeted area. A significant degree of spatial variance in proximity is observed, which suggests a larger length scale, intrinsic susceptibility to pit initiation not dictated by known structural heterogeneity like grain boundary structure. © The Electrochemical Society.

Volumetric and gravimetric energy density are the primary performance metrics for the evaluation of automotive hydrogen storage systems. The purpose of this study was to determine the effects of material properties such as thermal conductivity, and thermodynamic properties such as enthalpy of formation on these energy densities. This was accomplished by first defining volumetric and gravimetric energy density in terms of global system parameters, followed by defining relationships between these upper level parameters and the more tangible hydride properties. These relationships were built using a generalized hydrogen storage system design and included structural and heat transfer calculations. The end result was a complex set of equations relating hydrogen storage system energy densities to the properties of the hydride contained in the system. These equations were solved for a range of metal hydride properties including effective capacity (amount of hydrogen per unit weight the metal hydride can absorb in a defined time period), material density, hydriding pressure, operating temperature, enthalpy of formation, thermal conductivity, and specific heat. The results show the relationship of these parameters to hydrogen storage system energy density. The combined effects of all variables in this multidimensional parameter space are presented as well as the isolated effect of each property on system volumetric and gravimetric energy density. The results indicate that while effective hydrogen capacity is the most influential metal hydride property, several other properties are nearly as important. Specifically, metal hydride enthalpy and density are revealed as key contributors to a viable hydrogen storage system. Also, the combination of specific heat and operating temperature is shown to be important when desorption heating is considered as a parasitic loss. Other metal hydride properties such as thermal conductivity and operating pressure are shown to be less significant. Copyright © 2007 MS&T'07®.

The ability to study material response during isentropic compression has been a grand challenge of the scientific community for several decades. However, development of precision techniques for producing isentropic compression at high pressures has been limited. The revolutionary advance for using planar magnetic loading on the Z accelerator accelerated this goal by enabling quasi-isentropic studies on macroscopically sized materials to over 5 Mbar. In addition, the accelerator is easily configured to launch flyer plates to velocities more than four times higher than possible with conventional launchers, thus allowing shock compression studies in the laboratory to pressures exceeding 20 Mbar.

Advantages and limitations of fiber-based laser systems for trace-gas detection will be reviewed. I will present example applications and instruments for in situ and remote detection at wavelengths from the mid-IR through the deep-UV. © 2007 Optical Society of America.

An experimental apparatus is described that measures gas-surface thermal accommodation coefficients from the pressure dependence of the conductive heat flux between parallel plates separated by a gas-filled gap. Heat flux between the plates is inferred from measurements of temperature drop between the plate surface and an adjacent temperature-controlled water bath. Thermal accommodation coefficients are determined from the pressure dependence of the heat flux at a fixed plate separation. The apparatus is designed to conduct tests with a variety of gases in contact with interchangeable, well-characterized surfaces of various materials (e.g., metals, ceramics, semiconductors) with various surface finishes (e.g., smooth, rough). Experiments are reported for three gases (argon, nitrogen, and helium) in contact with pairs of 304 stainless steel plates prepared with one of two finishes: lathe-machined or mirror-polished. For argon and nitrogen, the measured accommodation coefficients for machined and polished plates are near unity and independent of finish to within experimental uncertainty. For helium, the accommodation coefficients are much lower and show a slight variation with surface roughness. Two different methods are used to determine the accommodation coefficient from experimental data: the Sherman-Lees formula and the GTR formula. These approaches yield values of 0.87 and 0.94 for argon, 0.80 and 0.86 for nitrogen, 0.36 and 0.38 for helium with the machined finish, and 0.40 and 0.42 for helium with the polished finish, respectively, with an uncertainty of ±0.02. The GTR values for argon and nitrogen are generally in better agreement with the results of other investigators than the Sherman-Lees values are, and both helium results are in reasonable agreement with values in the literature.

The convergence behavior of the Direct Simulation Monte Carlo (DSMC) method is investigated for transient flows. Two types of flows are considered: a Couette-like flow, in which an initial velocity profile decays in time, and a Fourier-like flow, in which an initial temperature profile decays in time. DSMC results are presented for hard-sphere argon with Knudsen numbers in the range 0.01-0.4. Low-Knudsen-number DSMC results are compared with Navier-Stokes results. The DSMC discretization errors from finite time step and finite cell size (in the limit of infinite number of computational molecules per cell) are compared with the predictions of Green-Kubo theory for conditions in this regime.

By using a radio frequency (RF) audio distortion measurement test setup, communication devices can be evaluated for degradation caused by electromagnetic interference (EMI) from active vehicle components. This measurement technique can be used to determine the performance of a radio receiver under a variety of conditions. The test setup consists of making measurements on a baseband audio signal that is sent to the device under test (receiver) via over-the-air RF transmissions. Once a baseline is established, active components on the vehicle can be powered on to determine their contribution to the receiver's degradation. The degradation measured is a result of distortion caused by conducted, radiated, and/or coupled EMI from active components into the receiver's passband.

Many unstructured mesh finite volume discretization schemes are based upon structured mesh schemes. Structured mesh higher-order schemes rely on non-local data support to reconstruct interface values and fluxes. Since this data support is difficult to obtain or may not exist in the context of unstructured mesh codes, due to limited mesh connectivity or element topology, several approaches have been developed to overcome this problem. Three techniques that have been employed in vertex centered schemes are: gradient extrapolation, most collinear edge, and virtual edge extension/element interpolation. The current paper describes these three techniques in detail and compares numerical solutions to the inviscid and viscous flow equations, using these techniques, with an emphasis on grids containing high aspect ratio and high curvature cells.

The electrical, thermal, and mechanical responses of surface micromachined (SMM) 2-beam actuators have been simulated using the Calagio code, a coupled physics analysis tool. The present analysis, unlike previous analyses, includes the surrounding air in the computational domain so that heat losses from the beams onto the silicon substrate will be accurately modeled. This setup is essential because the existing 'shape factor' correlations have difficulty capturing the threedimensional geometric effect of the heat loss in the shuttle at the center that connects the bent beams. In addition, results from the present analysis reveal that because the local heat flux can be extremely high, a significant temperature jump can occur across the air-structure interfaces.

Boundary layer transition continues to be a critical factor in hypersonic fight vehicle design. Measurements of transition during hypersonic flight testing provide valuable data for the development and verification of transition prediction techniques. A summary of transition measurement techniques used on vehicles flown by Sandia National Laboratories is presented, including sample flight data to illustrate the type of transition indication obtained from each measurement technique. SHARP-B2, a ballistic vehicle flown by Sandia for NASA, is used as a case study to illustrate how transition is determined for a flight vehicle and to illustrate some of the difficulties associated with these types of measurements.

This paper presents heterodyne mixer measurements at 2.9 THz using quantum cascade lasers (QCLs) as sources. The linewidth of the laser was explored by biasing it to run in dual mode operation and observing the linewidth of the beat note. In addition the frequency of the QCL is determined by beating it against a deuterated methanol line from a molecular gas laser.

Prior HCCI optical engine experiments utilizing laser-induced fluorescence (LIF) measurements of stratified fuel-air mixtures have demonstrated the utility of probability density function (PDF) statistics for correlating mixture preparation with combustion. However, PDF statistics neglect all spatial details of in-cylinder fuel distribution. The current computational paper examines the effects of spatial fuel distribution on combustion using a novel combination of a 3-D CFD model with a 1-D linear-eddy model of turbulent mixing. In the simulations, the spatial coarseness of initial fuel distribution prior to the start of heat release is varied while keeping PDF statistics constant. Several cases are run, and as the initial mixture is made coarser, combustion phasing monotonically advances due to high local equivalence ratios that persist longer. The effect of turbulent mixing is more complex. For the case where the length scale of the initial distribution matches the integral length scale of turbulence, turbulent mixing leads to moderation of peak heat-release rate. The randomness of turbulence is captured in the simulation, and for the above case, cycle-to-cycle variation of the combustion is evident. In contrast, when the initial fuel distribution is significantly finer or coarser than the turbulence length scale, turbulent mixing does not affect combustion for two different reasons. For fine distributions, molecular diffusion alone homogenizes the fuel-air mixture prior to ignition, so turbulence adds nothing. For initial distributions that are coarse compared to the turbulence length scale, diffusion and turbulence are both ineffective at mixing, so again turbulence has a minimal effect on combustion.

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Cracking was observed in the side walls of gold (Au) filled vias in low-temperature, co-fired ceramic (LTCC) substrates. Further analysis indicated the likely source as the constituents of the glassy phase component of the gold-platinum-palladium (Au-Pt-Pd) thick film used for the conductor traces and pads. The successful approach toward mitigating the cracking phenomenon was to place a Au thick film layer between the Au-Pt-Pd layer and the LTCC substrate, which significantly curtailed the diffusion of glassy phase components into the latter. However, it was necessary to determine the effects of the additional thick film layer on the microstructure and overall mechanical strength of tin-lead (Sn-Pb) solder joints made to device pads. Acceptable pull strengths were measured in the range of 3.5 - 4.0 lbs. The solder joint pull strength was sensitive to the number of firing steps as defined by the thick film layer construction. Both the solder/thick film and thick film/LTCC interface strengths had roles in this trend, thereby affirming the synergism between material, interfaces, and the firing processes The pull strength was optimized when the pad length ratio, 4596:5742, was 1.0:0.5, which was characterized by a reduced occurrence of the thick film/LTCC failure mode. © 2007 IEEE.

Sandia National Laboratories has world-class facilities for building and testing lithium and lithium-ion batteries. In this article we describe the in-house facilities for fabricating electrodes and cells in detail. Our in-house facility includes equipment for: 1) electrode coating, 2) electrode slitting, 3) electrode winding, 4) cell grooving, 5) electrolyte filling, 6) cell crimping and more. We also have a 48-channel Maccor tester and several impedance units for electrochemical characterization. These facilities provide flexibility for cell fabrication techniques which in turn allows us to continually improve cell performance. Under an internally funded program we are developing in-house capability to fabricate and evaluate 18650 Li/(CFx)n cells using "Li-ion" electrode fabrication methodologies to prepare the thin film (CFx)n electrodes. At a C/400 discharge rate cell delivered ~3.6 Ahrs capacity. We also evaluated cathodes of two different lengths for uniformity of loading. The loading along the electrode length was found to be extremely uniform, as the delivered capacity was proportional to cathode length. For example, a 0.91 meters long x 4.2 mil thick electrode gave 3.6 Ahrs capacity while a 0.72 meters long × 4.2 mil thick electrode (19.4% less length) gave 2.9 Ahr of capacity (19.4% less capacity). We also discharged the cells with 0.71 meters long electrodes at different temperatures. The cells delivered practically the same capacity over temperatures from 25 to 72°C. At -20°C the cells delivered 81% of the room temperature capacity at a C/200 rate; however, at -40°C the cells delivered close to 47% of the room temperature capacity under similar test conditions. The performance behavior of 18650 cells will be discussed in more detail in the paper. © 2007 by ESG.

The influence of the constant C3, which multiplies the mean flow divergence term in the model equation for the turbulent kinetic energy dissipation, is examined in a motored diesel engine for three different swirl ratios and three different spatial locations. Predicted temporal histories of turbulence energy and its dissipation are compared with experimentally-derived estimates. A "best-fit" value of C3 = 1.75, with an approximate uncertainty of ±0.3 is found to minimize the error between the model predictions and the experiments. Using this best-fit value, model length scale behavior corresponds well with that of measured velocity-correlation integral scales during compression. During expansion, the model scale grows too rapidly. Restriction of the model assessment to the expansion stroke suggests that C3 = 0.9 is more appropriate during this period. Copyright © 2007 SAE International.

Cyclic ethers, like tetrahydrofuran (THF), are formed during the autoignition of alkanes and subsequently influence their combustion chemistry. To learn more about the oxidation chemistry of these ether intermediates, a fuel-rich THF flame (π = 1.75) has been studied using the versatile technique of flame-sampling Molecular Beam Mass Spectrometry (MBMS) in combination with single-photon ionization. Several cyclic intermediates which are potentially formed by dehydrogenation of the fuel are identified by their ionization energies. Ethylene, propene, ketene and formaldehyde are major stable decomposition products of THF and their mole fraction profiles are presented. Detected oxygenated species include ethenol, acetaldehyde and propanal. Despite the fuel-rich conditions, the concentrations of benzene and other aromatic hydrocarbons are near the detection limit.

Modelling soot formation in turbulent nonpremixed combustion is a difficult problem. Unlike most gaseous combustion species, soot lacks a strong state relationship with the mixture fraction due to unsteady formation rates which overlap transport timescales, and strong differential diffusion between gaseous species and soot. The conditional moment closure model (CMC) has recently been applied to the problem of turbulent soot formation. A challenge in CMC modelling is the treatment of differential diffusion. Three-dimensional direct numerical simulation (DNS) of a nonpremixed ethylene jet flame with soot formation has been performed for the first time, using a nineteen species reduced ethylene mechanism and a four-step, three-moment, semi-empirical soot model. The DNS provides full resolution of the turbulent flow field and is used to perform a-priori analysis of a new CMC model derived from the joint scalar PDF transport equation. Unlike other approaches, this CMC model does not require additional transport equations to treat differentially diffusing species. A budget of the terms of the CMC equation for both gaseous species and soot is presented. In particular, exact expressions for unclosed terms are compared to typical closure models for scalar dissipation, cross dissipation, differential diffusion, and reactive source terms.

Direct numerical simulation of a nonpremixed, turbulent, ethylene jet flame is performed to investigate fundamental mechanisms of extinction and reignition processes. A reduced ethylene mechanism consisting of nineteen transported and ten quasi-steady state species, with 167 reactions was used, along with mixture averaged transport properties. The flow configuration is a temporally-evolving slot jet at a Reynolds number of 5,120. Extreme extinction of the nonpremixed flame occurs, followed by a period of intense turbulent scalar mixing between reactants and quenched products in which less than 2stratified mixture with nonhomogeneous composition and temperature. Various modes of reignition are analyzed-autoignition, edge flame propagation, and premixed flame propagation-by monitoring Takeno's flame index [H. Yamashitia, M. Shimada, and T. Takeno, Proc. Combust. Inst., 26 (1996) 27-34], homogeneous ignition delay times by sampling the mixture prior to reignition, and the turbulent displacement speed of the reaction front. The dominant reignition mechanism is found to be premixed flame propagation commencing from a few high temperature flame kernels which survive near global extinction.

Recent advances in electrode fabrication and tailoring electrolyte properties for numerous applications have generated wide-spread interest in (CFx)x chemistry since it has the highest theoretical capacity and hence longer life of the four well known Li-primary chemistries. We are applying "Li-ion technology" electrode fabrication methodologies and preparing thin film (CFx)n electrodes in-house for evaluation. In this program we have evaluated 4 different (CFx) n materials for performance in coin cells in the temperature regime -55 to 72°C. We continue to evaluate the top performer in 18650 cell configuration and obtained ∼3.6 Ahrs capacity at a C/400 rate. We also evaluated cathodes of different lengths for uniformity of loading. For example, a 36'' long × 4.2 mil thick electrode gave 3.6 Ahrs while a 29'' long × 4.2 mil thick electrode gave 2.9 Ahrs of capacity. We also measured impedance at different voltages and thermal abuse response of the 18650 cells. © The Electrochemical Society.

Accurate simulation of biological networks is difficult not only due to the computational cost associated with large-scale systems simulation, but also due to the inherent limitations of mathematical models. We address two components to improve biological circuit simulation accuracy: 1) feasible initial conditions, and 2) identification of critical yet unknown model parameters. For those parameters that may not be available from experimental data, we incorporate reachability analysis to enhance our optimization/simulation framework and estimate those parameters that are capable of creating behaviors consistent with known experimental data. We apply these techniques to a biological circuit model of tryptophan biosynthesis in E. coli, and quantify the improvement in simulation accuracy when reachability analysis is used. © 2008 IEEE.

With the lowering of the EPA maximum contaminant level of arsenic from 50 parts per billion (ppb) to 10 ppb, many public water systems in the country and in New Mexico in particular, are faced with making decisions about how to bring their system into compliance. This document provides detail on the options available to the water systems and the steps they need to take to achieve compliance with this regulation. Additionally, this document provides extensive resources and reference information for additional outreach support, financing options, vendors for treatment systems, and media pilot project results.

This document is a review of five documents on information assurance from the Department of Defense (DoD), namely 5200.40, 8510.1-M, 8500.1, 8500.2, and an ''interim'' document on DIACAP [9]. The five documents divide into three sets: (1) 5200.40 & 8510.1-M, (2) 8500.1 & 8500.2, and (3) the interim DIACAP document. The first two sets describe the certification and accreditation process known as ''DITSCAP''; the last two sets describe the certification and accreditation process known as ''DIACAP'' (the second set applies to both processes). Each set of documents describes (1) a process, (2) a systems classification, and (3) a measurement standard. Appendices in this report (a) list the Phases, Activities, and Tasks of DITSCAP, (b) note the discrepancies between 5200.40 and 8510.1-M concerning DITSCAP Tasks and the System Security Authorization Agreement (SSAA), (c) analyze the DIACAP constraints on role fusion and on reporting, (d) map terms shared across the documents, and (e) review three additional documents on information assurance, namely DCID 6/3, NIST 800-37, and COBIT{reg_sign}.

The purpose of this four-week late start LDRD was to assess the current status of science and technology with regard to the production of biofuels. The main focus was on production of biodiesel from nonpetroleum sources, mainly vegetable oils and algae, and production of bioethanol from lignocellulosic biomass. One goal was to assess the major technological hurdles for economic production of biofuels for these two approaches. Another goal was to compare the challenges and potential benefits of the two approaches. A third goal was to determine areas of research where Sandia's unique technical capabilities can have a particularly strong impact in these technologies.

This report documents activities performed in FY2006 under the ''Gas-Powder Two-Phase Flow Modeling Project'', ASC project AD2006-09. Sandia has a need to understand phenomena related to the transport of powders in systems. This report documents a modeling strategy inspired by powder transport experiments conducted at Sandia in 2002. A baseline gas-powder two-phase flow model, developed under a companion PEM project and implemented into the Sierra code FUEGO, is presented and discussed here. This report also documents a number of computational tests that were conducted to evaluate the accuracy and robustness of the new model. Although considerable progress was made in implementing the complex two-phase flow model, this project has identified two important areas that need further attention. These include the need to compute robust compressible flow solutions for Mach numbers exceeding 0.35 and the need to improve conservation of mass for the powder phase. Recommendations for future work in the area of gas-powder two-phase flow are provided.

The present work demonstrates the use of light to move liquids on a photoresponsive monolayer, providing a new method for delivering analyses in lab-on-chip environments for microfluidic systems. The light-driven motion of liquids was achieved on photoresponsive azobenzene modified surfaces. The surface energy components of azobenzene modified surfaces were calculated by Van Oss theory. The motion of the liquid was achieved by generation of a surface tension gradient by isomerization of azobenzene monolayers using UV and Visible light, thereby establishing a surface energy heterogeneity on the edge of the droplet. Contact angle measurements of various solvents were used to demonstrate the requirement for fluid motion.

This 3-year research and development effort focused on what we believe is a significant technical gap in existing modeling and simulation capabilities: the representation of plausible human cognition and behaviors within a dynamic, simulated environment. Specifically, the intent of the ''Simulating Human Behavior for National Security Human Interactions'' project was to demonstrate initial simulated human modeling capability that realistically represents intra- and inter-group interaction behaviors between simulated humans and human-controlled avatars as they respond to their environment. Significant process was made towards simulating human behaviors through the development of a framework that produces realistic characteristics and movement. The simulated humans were created from models designed to be psychologically plausible by being based on robust psychological research and theory. Progress was also made towards enhancing Sandia National Laboratories existing cognitive models to support culturally plausible behaviors that are important in representing group interactions. These models were implemented in the modular, interoperable, and commercially supported Umbra{reg_sign} simulation framework.

Microtubules and motor proteins are protein-based biological agents that work cooperatively to facilitate the organization and transport of nanomaterials within living organisms. This report describes the application of these biological agents as tools in a novel, interdisciplinary scheme for assembling integrated nanostructures. Specifically, selective chemistries were used to direct the favorable adsorption of active motor proteins onto lithographically-defined gold electrodes. Taking advantage of the specific affinity these motor proteins have for microtubules, the motor proteins were used to capture polymerized microtubules out of suspension to form dense patterns of microtubules and microtubule bridges between gold electrodes. These microtubules were then used as biofunctionalized templates to direct the organization of functionalized nanocargo including single-walled carbon nanotubes and gold nanoparticles. This biologically-mediated scheme for nanomaterials assembly has shown excellent promise as a foundation for developing new biohybrid approaches to nanoscale manufacturing.

This efforts objective was to identify and hybridize a suite of technologies enabling the development of predictive decision aids for use principally in combat environments but also in any complex information terrain. The technologies required included formal concept analysis for knowledge representation and information operations, Peircean reasoning to support hypothesis generation, Mill's's canons to begin defining information operators that support the first two technologies and co-evolutionary game theory to provide the environment/domain to assess predictions from the reasoning engines. The intended application domain is the IED problem because of its inherent evolutionary nature. While a fully functioning integrated algorithm was not achieved the hybridization and demonstration of the technologies was accomplished and demonstration of utility provided for a number of ancillary queries.

Understanding internal dissipation in resonant mechanical systems at the micro- and nanoscale is of great technological and fundamental interest. Resonant mechanical systems are central to many sensor technologies, and microscale resonators form the basis of a variety of scanning probe microscopies. Furthermore, coupled resonant mechanical systems are of great utility for the study of complex dynamics in systems ranging from biology to electronics to photonics. In this work, we report the detailed experimental study of internal dissipation in micro- and nanomechanical oscillators fabricated from amorphous and crystalline diamond materials, atomistic modeling of dissipation in amorphous, defect-free, and defect-containing crystalline silicon, and experimental work on the properties of one-dimensional and two-dimensional coupled mechanical oscillator arrays. We have identified that internal dissipation in most micro- and nanoscale oscillators is limited by defect relaxation processes, with large differences in the nature of the defects as the local order of the material ranges from amorphous to crystalline. Atomistic simulations also showed a dominant role of defect relaxation processes in controlling internal dissipation. Our studies of one-dimensional and two-dimensional coupled oscillator arrays revealed that it is possible to create mechanical systems that should be ideal for the study of non-linear dynamics and localization.

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This study examines the effects of the degradation experienced in the steel drywell containment at the Oyster Creek Nuclear Generating Station. Specifically, the structural integrity of the containment shell is examined in terms of the stress limits using the ASME Boiler and Pressure Vessel (B&PV) Code, Section III, Division I, Subsection NE, and examined in terms of buckling (stability) using the ASME B&PV Code Case N-284. Degradation of the steel containment shell (drywell) at Oyster Creek was first observed during an outage in the mid-1980s. Subsequent inspections discovered reductions in the shell thickness due to corrosion throughout the containment. Specifically, significant corrosion occurred in the sandbed region of the lower sphere. Since the presence of the wet sand provided an environment which supported corrosion, a series of analyses were conducted by GE Nuclear Energy in the early 1990s. These analyses examined the effects of the degradation on the structural integrity. The current study adopts many of the same assumptions and data used in the previous GE study. However, the additional computational recourses available today enable the construction of a larger and more sophisticated structural model.

Z-Pinch Inertial Fusion Energy (Z-IFE) complements and extends the single-shot z-pinch fusion program on Z to a repetitive, high-yield, power plant scenario that can be used for the production of electricity, transmutation of nuclear waste, and hydrogen production, all with no CO{sub 2} production and no long-lived radioactive nuclear waste. The Z-IFE concept uses a Linear Transformer Driver (LTD) accelerator, and a Recyclable Transmission Line (RTL) to connect the LTD driver to a high-yield fusion target inside a thick-liquid-wall power plant chamber. Results of RTL and LTD research are reported here, that include: (1) The key physics issues for RTLs involve the power flow at the high linear current densities that occur near the target (up to 5 MA/cm). These issues include surface heating, melting, ablation, plasma formation, electron flow, magnetic insulation, conductivity changes, magnetic field diffusion changes, possible ion flow, and RTL mass motion. These issues are studied theoretically, computationally (with the ALEGRA and LSP codes), and will work at 5 MA/cm or higher, with anode-cathode gaps as small as 2 mm. (2) An RTL misalignment sensitivity study has been performed using a 3D circuit model. Results show very small load current variations for significant RTL misalignments. (3) The key structural issues for RTLs involve optimizing the RTL strength (varying shape, ribs, etc.) while minimizing the RTL mass. Optimization studies show RTL mass reductions by factors of three or more. (4) Fabrication and pressure testing of Z-PoP (Proof-of-Principle) size RTLs are successfully reported here. (5) Modeling of the effect of initial RTL imperfections on the buckling pressure has been performed. Results show that the curved RTL offers a much greater buckling pressure as well as less sensitivity to imperfections than three other RTL designs. (6) Repetitive operation of a 0.5 MA, 100 kV, 100 ns, LTD cavity with gas purging between shots and automated operation is demonstrated at the SNL Z-IFE LTD laboratory with rep-rates up to 10.3 seconds between shots (this is essentially at the goal of 10 seconds for Z-IFE). (7) A single LTD switch at Tomsk was fired repetitively every 12 seconds for 36,000 shots with no failures. (8) Five 1.0 MA, 100 kV, 100 ns, LTD cavities have been combined into a voltage adder configuration with a test load to successfully study the system operation. (9) The combination of multiple LTD coaxial lines into a tri-plate transmission line is examined. The 3D Quicksilver code is used to study the electron flow losses produced near the magnetic nulls that occur where coax LTD lines are added together. (10) Circuit model codes are used to model the complete power flow circuit with an inductive isolator cavity. (11) LTD architectures are presented for drivers for Z-IFE and high yield. A 60 MA LTD driver and a 90 MA LTD driver are proposed. Present results from all of these power flow studies validate the whole LTD/RTL concept for single-shot ICF high yield, and for repetitive-shot IFE.

Sandia National Laboratories and Mytek, LLC have collaborated to develop a monolithically-integrated vertical-cavity surface-emitting laser (VCSEL) assembly with controllable polarization states suitable for use in chip-scale atomic clocks. During the course of this work, a robust technique to provide polarization control was modeled and demonstrated. The technique uses deeply-etched surface gratings oriented at several different rotational angles to provide VCSEL polarization stability. A rigorous coupled-wave analysis (RCWA) model was used to optimize the design for high polarization selectivity and fabrication tolerance. The new approach to VCSEL polarization control may be useful in a number of defense and commercial applications, including chip-scale atomic clocks and other low-power atomic sensors.

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In the summer of 2006, the Environmental Programs and Assurance Department of Sandia National Laboratories in Albuquerque, New Mexico (SNL/NM), collected surface soil samples at 37 locations within one mile of the vicinity of the newly constructed Thermal Test Complex (TTC) for the purpose of determining baseline conditions against which potential future impacts to the environs from operations at the facility could be assessed. These samples were submitted to an offsite analytical laboratory for metal-in-soil analyses. This work provided the SNL Environmental Programs and Assurance Department with a sound baseline data reference set against which to assess potential future operational impacts at the TTC. In addition, it demonstrates the commitment that the Laboratories have to go beyond mere compliance to achieve excellence in its operations. This data are presented in graphical format with narrative commentaries on particular items of interest.

Sandia National Laboratories and the Institute of Nuclear Energy Research, Taiwan have collaborated in a technology transfer program related to low-level radioactive waste (LLW) disposal in Taiwan. Phase I of this program included regulatory analysis of LLW final disposal, development of LLW disposal performance assessment capabilities, and preliminary performance assessments of two potential disposal sites. Performance objectives were based on regulations in Taiwan and comparisons to those in the United States. Probabilistic performance assessment models were constructed based on limited site data using software including GoldSim, BLT-MS, FEHM, and HELP. These software codes provided the probabilistic framework, container degradation, waste-form leaching, groundwater flow, radionuclide transport, and cover infiltration simulation capabilities in the performance assessment. Preliminary performance assessment analyses were conducted for a near-surface disposal system and a mined cavern disposal system at two representative sites in Taiwan. Results of example calculations indicate peak simulated concentrations to a receptor within a few hundred years of LLW disposal, primarily from highly soluble, non-sorbing radionuclides.

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The purpose of this LDRD was to demonstrate a compact, multi-spectral, refractive imaging systems using active optical compensation. Compared to a comparable, conventional lens system, our system has an increased operational bandwidth, provides for spectral selectivity and, non-mechanically corrects aberrations induced by the wavelength dependent properties of a passive refractive optical element (i.e. lens). The compact nature and low power requirements of the system lends itself to small platforms such as autonomous vehicles. In addition, the broad spectral bandwidth of our system would allow optimized performance for both day/night use, and the multi-spectral capability allows for spectral discrimination and signature identification.

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A probabilistic performance assessment has been conducted to evaluate the fate and transport of radionuclides (americium-241, cesium-137, cobalt-60, plutonium-238, plutonium-239, radium-226, radon-222, strontium-90, thorium-232, tritium, uranium-238), heavy metals (lead and cadmium), and volatile organic compounds (VOCs) at the Mixed Waste Landfill (MWL). Probabilistic analyses were performed to quantify uncertainties inherent in the system and models for a 1,000-year period, and sensitivity analyses were performed to identify parameters and processes that were most important to the simulated performance metrics. Comparisons between simulated results and measured values at the MWL were made to gain confidence in the models and perform calibrations when data were available. In addition, long-term monitoring requirements and triggers were recommended based on the results of the quantified uncertainty and sensitivity analyses.

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