Publications

Glass-to-metal (GTM) seals maintain hermeticity while allowing the passage of electrical signals. Typically, these seals are comprised of one or more metal pins encapsulated in a glass which is contained in a metal shell. In compression seals, the coefficient of thermal expansion of the metal shell is greater than the glass, and the glass is expected to be in compression. Recent development builds of a multi-pin GTM seal revealed severe cracking of the glass, with cracks originating at or near the pin-glass interface, and propagating circumferentially. A series of finite element analyses (FEA) was performed for this seal with the material set: 304 stainless steel (SS304) shell, Schott S-8061 (or equivalent) glass, and Alloy 52 pins. Stress-strain data for both metals was fit by linear-hardening and power-law hardening plasticity models. The glass layer thickness and its location with respect to geometrical features in the shell were varied. Several additional design changes in the shell were explored. Results reveal that: (1) plastic deformation in the small-strain regime in the metals lead to radial tensile stresses in glass, (2) small changes in the mechanical behavior of the metals dramatically change the calculated stresses in the glass, and (3) seemingly minor design changes in the shell geometry influence the stresses in the glass significantly. Based on these results, guidelines for materials selection and design of seals are provided.

We establish that clamping effects, which limit accurate determination of piezoelectric responses in bulk materials and films using piezoelectric force microscopy (PFM), are not present when measuring discrete nanostructures with radii less than five times the tip radius. This conclusion is established by comparing the piezoelectric response in ZnO rods using two electrode configurations: one with the conducting atomic force microscopy tip acting as the top electrode and the other using a uniform metal top electrode. The distributions of piezoelectric coefficients measured with these two types of electrode configurations are the same. Hence, clamping issues do not play a role in the piezoelectric property measurement of nanomaterials using PFM. The role of conduction electrons on the piezoelectric measurement in both cases is also discussed. © 2008 American Institute of Physics.

Thermal gravimetric analysis (TGA) combined with evolved gas analysis by Fourier transform infrared spectroscopy (FTIR) or mass spectrometry (MS) often is used to study thermal decomposition of organic polymers. Frequently, results are used to determine decomposition mechanisms and to develop rate expressions for a variety of applications, which include hazard analyses. Although some current TGA instruments operate with controlled heating rates as high as 500° C/min, most experiments are done at much lower heating rates of about 5° to 50° C/min to minimize temperature gradients in the sample. The intended applications, such as hazard analyses involving fire environments, for rate expressions developed from TGA experiments often involve heating rates much greater than 50° C/min. The heating rate can affect polymer decomposition by altering relative rates at which competing decomposition reactions occur. Analysis of the effect of heating rate on competing first-order decomposition reactions with Arrhenius rate constants indicated that relative to heating rates of 5° to 50° C/min, observable changes in decomposition behavior may occur when heating rates approach 1,000° C/min. Results from experiments with poly(methyl methacrylate) (PMMA) samples that were heated at 5° to 50° C/min during TGA-FTIR experiments and results from experiments with samples heated at rates on the order of 1,000° C/min during pyrolysis-GC-FTIR experiments supported the analyses.

The Wind Energy Technology Department at Sandia National Laboratories (SNL) focuses on producing innovations in wind turbine blade technology to enable the development of longer blades that are lighter, more structurally and aerodynamically efficient, and impart reduced loads to the system. A large part of the effort is to characterize the properties of relevant composite materials built with typical manufacturing processes. This paper provides an overview of recent studies of composite laminates for wind turbine blade construction and summarizes test results for three prototype blades that incorporate a variety of material-related innovations.

The Wind Energy Technology Department at Sandia National Laboratories (SNL) focuses on producing innovations in wind turbine blade technology to enable the development of longer blades that are lighter, more structurally and aerodynamically efficient, and impart reduced loads to the system. A large part of the effort is to characterize the properties of relevant composite materials built with typical manufacturing processes. This paper provides an overview of recent studies of composite laminates for wind turbine blade construction and summarizes test results for three prototype blades that incorporate a variety of material-related innovations.

The two-color resonant four-wave mixing (TC-RFWM) is advertised as a unique spectroscopic device enabling one to directly measure the collisional state-to-state transfer characteristics (rates and correlation times). In contrast to the laser-induced fluorescence, these characteristics are phase-sensitive and open wider opportunities to study the rotational relaxation processes. Further perspectives are offered by the recently recorded collision-induced picosecond TC-RFWM signals of OH. Their quantitative interpretation is now under development. © 2008 American Institute of Physics.

The Multi-Mission Radioisotope Thermoelectric Generator (MMRTG) will use an improved version of the General Purpose Heat Source (GPHS) module as its source of thermal power. This new version, referred to as the Step-2 GPHS Module, has additional and thicker layers of carbon fiber material (Fine Weaved Pierced Fabric) for increased strength over the original GPHS module. The GPHS uses alpha decay of 238Pu in the oxide form as the primary source of heat, and small amounts of other actinides are also present in the oxide fuel. Criticality calculations have been performed by previous researchers on the original version of the GPHS module (Step 0). This paper presents criticality calculations for the present Step-2 version. The Monte Carlo N-Particle extended code (MCNPX) was used for these calculations. Numerous configurations of GPHS module arrays surrounded by wet sand and other materials (to reflect the neutrons back into the stack with minimal absorption) were modeled. For geometries with eight GPHS modules (from a single MMRTG) surrounded by wet sand, the configuration is extremely sub-critical; keff is about 0.3. It requires about 1000 GPHS modules (from 125 MMRTGs) in a close-spaced stack to approach criticality (keff = 1.0) when surrounded by wet sand. The effect of beryllium in the MMRTG was found to be relatively small. © 2008 American Institute of Physics.

Silica based glasses are commonly used as window material in applications which are subject to high velocity impacts. Thorough understanding of the response to shock loading in these materials is crucial to the development of new designs. Despite the lack of long range order in amorphous glasses, the structure can be described statistically by the random network model. Changes to the network structure alter the response to shock loading. Results indicate that in fused silica, substitution of boron as a network former does not have a large effect on the shock loading properties while modifying the network with sodium and calcium changes the dynamic response. These initial results suggest the potential of a predictive capability to determine the effects of other network substitutions.

This paper summarizes the numerical site scale model developed to simulate the transport of radionuclides via ground water in the saturated zone beneath Yucca Mountain.

The practical utility of optimization technologies is often impacted by factors that reflect how these tools are used in practice, including whether various real-world constraints can be adequately modeled, the sophistication of the analysts applying the optimizer, and related environmental factors (e.g. whether a company is willing to trust predictions from computational models). Other features are less appreciated, but of equal importance in terms of dictating the successful use of optimization. These include the scale of problem instances, which in practice drives the development of approximate solution techniques, and constraints imposed by the target computing platforms. End-users often lack state-of-the-art computers, and thus runtime and memory limitations are often a significant, limiting factor in algorithm design. When coupled with large problem scale, the result is a significant technological challenge. We describe our experience developing and deploying both exact and heuristic algorithms for placing sensors in water distribution networks to mitigate against damage due intentional or accidental introduction of contaminants. The target computing platforms for this application have motivated limited-memory techniques that can optimize large-scale sensor placement problems. © 2008 Springer Berlin Heidelberg.

Preparing Computer Aided Design models for successful mesh generation continues to be a crucial part of the design to analysis process. A common problem in CAD models is features that are very small compared to the desired mesh size. Small features exist for a variety of reasons and can require an excessive amount of elements or inhibit mesh generation all together. Many of the tools for removing small features modify only the topology of the model (often in a secondary topological representation of the model) leaving the underlying geometry as is. The availability of tools that actually modify the topology and underlying geometry in the boundary representation (B-rep) model is much more limited regardless of the inherent advantages of this approach. This paper presents a process for removing small featrues from a B-rep model using almost solely functionality provided by the underlying solid modeling kernel. The process cuts out the old topology and reconstructs new topology and geometry to close the volume. The process is quite general and can be applied to complex configurations of unwanted topology.

Systems in flight often encounter environments with combined vibration and constant acceleration. Sandia National Laboratories has developed a new system capable of combining these environments for hardware qualification testing on a centrifuge. To demonstrate that combined vibration plus centrifuge acceleration is equivalent to the vibration and acceleration encountered in a flight environment the equations of motion of a spring mass damper system in each environment were derived and compared. These equations of motion suggest a decrease in natural frequency for spring mass damper systems undergoing constant rotational velocity on a centrifuge. It was shown mathematically and through experimental testing that the natural frequency of a spring-mass system will decrease with increased rotational velocity. An increase of rotational velocity will eventually result in system instability. The development and testing of a mechanical system to demonstrate this characteristic is discussed. Results obtained from frequency domain analysis of time domain data is presented as is the implications these results conclude about centrifuge testing of systems with low natural frequency on small radius centrifuges.

Quantitative studies of material properties and interfaces using the atomic force microscope (AFM) have important applications in engineering, biotechnology and chemistry. Emerging studies require an estimate of the stiffness of the probe so that the forces exerted on a sample can be determined from the measured displacements. Numerous methods for determining the spring constant of AFM cantilevers have been proposed, yet none accounts for the effect of the mass of the probe tip on the calibration procedure. This work demonstrates that the probe tip does have a significant effect on the dynamic response of an AFM cantilever by experimentally measuring the first few modes of a commercial AFM probe and comparing them with those of a theoretical model for a cantilever probe that does not have a tip. The mass and inertia of an AFM probe tip are estimated from scanning electron microscope images and a simple model for the probe is derived and tuned to match the first few modes of the actual probe. Analysis suggests that both the method of Sader and the thermal tune method of Hutter and Bechhoefer give erroneous predictions of the area density or the effective mass of the probe. However, both methods do accurately predict the static stiffness of the AFM probe due to the fact that the mass terms cancel so long as the mode shape of the AFM probe does not deviate from the theoretical model. The calibration errors that would be induced due to differences between mode shapes measured in this study and the theoretical ones are estimated.

A large volume-headspace apparatus that permits the heating of pottery fragments for direct analysis by gas chromatography/mass spectrometry (GC/MS) is described here. A series of fermented-corn beverages were produced in modern clay pots and the pots were analyzed to develop organic-species profiles for comparison with fragments of ancient pottery. Brewing pots from the Tarahumara of northern Mexico, a tribe that produces a corn-based fermented beverage, were also examined for volatile residues and the organic-species profiles were generated. Finally, organic species were generated from ancient potsherds from an archeological site and compared with the modern spectra. The datasets yielded similar organic species, many of which were identified by computer matching of the resulting mass spectra with the NIST mass spectral library. Additional analyses are now underway to highlight patterns of organic species common to all the spectra. This presentation demonstrates the utility of thermal desorption coupled with GC/MS for detecting fermentation residues in the fabric of unglazed archaeological ceramics after centuries of burial. © 2008 Materials Research Society.

Abstract not provided.

Advancements in our capabilities to accurately model physical systems using high resolution finite element models have led to increasing use of models for prediction of physical system responses. Yet models are typically not used without first demonstrating their accuracy or, at least, adequacy. In high consequence applications where model predictions are used to make decisions or control operations involving human life or critical systems, a movement toward accreditation of mathematical model predictions via validation is taking hold. Model validation is the activity wherein the predictions of mathematical models are demonstrated to be accurate or adequate for use within a particular regime. Though many types of predictions can be made with mathematical models, not all predictions have the same impact on the usefulness of a model. For example, predictions where the response of a system is greatest may be most critical to the adequacy of a model. Therefore, a model that makes accurate predictions in some environments and poor predictions in other environments may be perfectly adequate for certain uses. The current investigation develops a general technique for validating mathematical models where the measures of response are weighted in some logical manner. A combined experimental and numerical example that demonstrates the validation of a system using both weighted and non-weighted response measures is presented.

We investigated the synthesis of bismuth oxy-iodide and iodate compounds, in an effort to develop materials for iodine recovery from caustic waste streams and/or final waste disposal if repository conditions included ambient conditions similar to those under which the iodine was initially captured. The results presented involve the in-situ crystallization of layered bismuth oxide compounds with aqueous dissolved iodine (which resides as both iodide and iodate in solution). Although single-phase bismuth oxy-iodide materials have already been described in the context of capturing radioiodine, our unique contribution is the discovery that there is a mixture of Bi-O-I compositions, not described in the prior work, which optimize both the uptake and the degree of insolubility (and leachability) of iodine. The optimized combination produces a durable material that is suitable as a waste form for repository conditions such as are predicted at the Yucca Mountain repository (YMP) or in a similar type of repository that could be developed in coordination with iodine production via Global Nuclear Energy Program (GNEP) production cycles. © 2008 Materials Research Society.

Peridynamics (PD) is a continuum theory that employs a nonlocal model to describe material properties. In this context, nonlocal means that continuum points separated by a finite distance may exert force upon each other. A meshless method results when PD is discretized with material behavior approximated as a collection of interacting particles. This paper describes how PD can be implemented within a molecular dynamics (MD) framework, and provides details of an efficient implementation. This adds a computational mechanics capability to an MD code, enabling simulations at mesoscopic or even macroscopic length and time scales. © 2008 Elsevier B.V.

Cellular autofluorescence, though ubiquitous when imaging cells and tissues, is often assumed to be small in comparison to the signal of interest. Uniform estimates of autofluorescence intensity obtained from separate control specimens are commonly employed to correct for autofluorescence. While these may be sufficient for high signal-to-background applications, improvements in detector and probe technologies and introduction of spectral imaging microscopes have increased the sensitivity of fluorescence imaging methods, exposing the possibility of effectively probing the low signal-to-background regime. With spectral imaging, reliable monitoring of signals near or even below the noise levels of the microscope is possible if autofluorescence and background signals can be accurately compensated for. We demonstrate the importance of accurate autofluorescence determination and utility of spectral imaging and multivariate analysis methods using a case study focusing on fluorescence confocal spectral imaging of host-pathogen interactions. In this application fluorescent proteins are produced when bacteria invade host cells. Unfortunately the analyte signal is spectrally overlapped and typically weaker than the cellular autofluorescence. In addition to discussing the advantages of spectral imaging for following pathogen invasion, we present the spectral properties of mouse macrophage autofluorescence. The imaging and analysis methods developed are widely applicable to cell and tissue imaging. © 2008 Copyright SPIE - The International Society for Optical Engineering.

Force and moment measurements have been made on an instrumented subscale fin model at transonic speeds in Sandia's Trisonic Wind Tunnel to ascertain the effects of Mach number and angle of attack on the interaction of a trailing vortex with a downstream control surface. Components of normal force, bending moment, and hinge moment were measured on an instrumented fin downstream of an identical fin at Mach numbers between 0.85 and 1.24, and combinations of angles of attack between -5° and 10° for both fins. The primary influence of upstream fin deflection is to shift the downstream fin's forces in a direction consistent with the vortex-induced angle of attack on the downstream fin. Secondary non-linear effects of vortex lift were found to increase the slopes of normal force and bending moment coefficients when plotted versus fin deflection angle. This phenomenon was dependent upon Mach number and the angles of attack of both fins. The hinge moment coefficient was also influenced by the vortex lift as the center of pressure was pushed aft with increased Mach number and total angle of attack.

In 2002, Sandia National Laboratories (SNL) initiated a research program to demonstrate the use of carbon fiber in wind turbine blades and to investigate advanced structural concepts through the Blade Systems Design Study, known as the BSDS. One of the blade designs resulting from this program, commonly referred to as the BSDS blade, resulted from a systems approach in which manufacturing, structural and aerodynamic performance considerations were all simultaneously included in the design optimization. The BSDS blade design utilizes "flatback" airfoils for the inboard section of the blade to achieve a lighter, stronger blade. Flatback airfoils are generated by opening up the trailing edge of an airfoil uniformly along the camber line, thus preserving the camber of the original airfoil. This process is in distinct contrast to the generation of truncated airfoils, where the trailing edge the airfoil is simply cut off, changing the camber and subsequently degrading the aerodynamic performance. Compared to a thick conventional, sharp trailing-edge airfoil, a flatback airfoil with the same thickness exhibits increased lift and reduced sensitivity to soiling. Although several commercial turbine manufacturers have expressed interest in utilizing flatback airfoils for their wind turbine blades, they are concerned with the potential extra noise that such a blade will generate from the blunt trailing edge of the flatback section. In order to quantify the noise generation characteristics of flatback airfoils, Sandia National Laboratories has conducted a wind tunnel test to measure the noise generation and aerodynamic performance characteristics of a regular DU97-300-W airfoil, a 10% trailing edge thickness flatback version of that airfoil, and the flatback fitted with a trailing edge treatment. The paper describes the test facility, the models, and the test methodology, and provides some preliminary results from the test.

This report focuses on our recent advances in the fabrication and processing of barium strontium titanate (BST) thin films by chemical solution depositiion for next generation fuctional integrated capacitors. Projected trends for capacitors include increasing capacitance density, decreasing operating voltages, decreasing dielectric thickness and decreased process cost. Key to all these trends is the strong correlation of film phase evolution and resulting microstructure, it becomes possible to tailor the microstructure for specific applications. This interplay will be discussed in relation to the resulting temperature dependent dielectric response of the BST films.

To protect drinking water systems, a contamination warning system can use in-line sensors to detect accidental and deliberate contamination. Currently, detection of an incident occurs when data from a single station detects an anomaly. This paper considers the possibility of combining data from multiple locations to reduce false alarms and help determine the contaminant's injection source and time. If we consider the location and time of individual detections as points resulting from a random space-time point process, we can use Kulldorff's scan test to find statistically significant clusters of detections. Using EPANET, we simulate a contaminant moving through a water network and detect significant clusters of events. We show these significant clusters can distinguish true events from random false alarms and the clusters help identify the time and source of the contaminant. Fusion results show reduced errors with only 25% more sensors needed over a nonfusion approach. © 2008 ASCE.

We propose scalable models and centralized heuristics for the concurrent and coordinated movement of multiple sinks in a wireless sensor network (WSN). The proposed centralized heuristic runs in polynomial time given the solution to the linear program and achieves results that are within 2% of the LP-relaxation-based upper bound. It provides a useful benchmark for evaluating centralized and distributed schemes for controlled sink mobility. © 2008 IEEE.

Energy demand and GDP per capita are strongly correlated, while public concern over the role of energy in climate change is growing. Nuclear power plants produce 16% of world electricity demands without greenhouse gases. Generation-IV advanced nuclear energy systems are being designed to be safe and economical. Minimizing the handling and storage of nuclear waste is important. NIF and ITER are bringing sustainable fusion energy closer, but a significant gap in fusion technology development remains. Fusion-fission hybrids could be a synergistic step to a pure fusion economy and act as a technology bridge. We discuss how a pulsed power-driven Z-pinch hybrid system producing only 20 MW of fusion yield can drive a sub-critical transuranic blanket that transmutes 1280 kg of actinide wastes per year and produces 3000 MW. These results are applicable to other inertial and magnetic fusion energy systems. A hybrid system could be introduced somewhat sooner because of the modest fusion yield requirements and can provide both a safe alternative to fast reactors for nuclear waste transmutation and a maturation path for fusion technology. The development and demonstration of advanced materials that withstand high-temperature, high-irradiation environments is a fundamental technology issue that is common to both fusion-fission hybrids and Generation-IV reactors. © 2008 Elsevier B.V. All rights reserved.

Geometric features with characteristic lengths on the order of the size of the contact patch interface may be at least partly responsible for the variability observed in experimental measurements of structural stiffness and energy dissipation per cycle in a bolted joint. Experiments on combinations of two different types of joints (statically determinate single-joint and statically indeterminate three-joint structures) of nominally identical hardware show that the structural stiffness of the tested specimens varies by up to 25% and the energy dissipation varies by up to nearly 300%. A pressure-sensitive film was assembled into the interfaces of jointed structures to gain a qualitative understanding of the distribution of interfacial pressures of nominally conformal surfaces. The resultant pressure distributions suggest that there are misfit mechanisms that may influence contact patch geometry and also structural response of the interface. These mechanisms include local plateaus and machining induced waviness. The mechanisms are not consistent across nominally machined hardware interfaces. The proposed misfit mechanisms may be partly responsible for the variability in energy dissipation per cycle of joint experiments.

Damping in a micro-cantilever beam was measured for a very broad range of air pressures from atmosphere (10 5 Pa) down to 0.2 Pa. The beam was in open space free from squeeze films. The damping ratio, due mainly to air drag, varied by a factor of 10 4 within this pressure range. The damping due to air drag was separated from other sources of energy dissipation so that air damping could be measured at 10 -6 of critical damping factor. The linearity of the damping was confirmed over a wide range of beam vibration levels. Lastly, the measured damping was compared with several existing theories for air-drag damping for both rarified and viscous flow gas theories. The measured data indicate that, in the rarefied regime the air damping is proportional to pressure, independent of viscosity, and in the viscous regime the damping is determined by viscosity.

The development of transmitter and receiver Multichip Module subassemblies implemented in LTCC for an S-band radar application followed an approach that reduces the number of discrete devices and increases reliability. The LTCC MCM incorporates custom GaAs RF integrated circuits in faraday cavities, novel methods of reducing line resistance and enhancing lumped element Q, and a thick film back plane which attaches to a heat sink. The incorporation of PIN diodes on the receiver and a 50W power amplifier on the transmitter required methods for removing heat beyond what thermal vias can accomplish. The die is a high voltage pHEMT GaAs power amplifier RFIC chip that measures 6.5 mm × 8 mm. Although thermal vias are adequate in certain cases, the thermal solution includes heat spreaders and thermally conductive backplates. Processing hierarchy, including gold-tin die attach and various use of polymeric attachment, must allow rework on these prototypical devices. LTCC cavity covers employ metallic coatings on their exterior surfaces. The processing of the LTCC and its effect on the function of the transmitter and receiver circuits is discussed in the poster session.

Placing sensors in municipal water networks to protect against a set of contamination events is a classic p-median problem for most objectives when we assume that sensors are perfect. Many researchers have proposed exact and approximate solution methods for this p-median formulation. For full-scale networks with large contamination event suites, one must generally rely on heuristic methods to generate solutions. These heuristics provide feasible solutions, but give no quality guarantee relative to the optimal placement. In this paper we apply a Lagrangian relaxation method in order to compute lower bounds on the expected impact of suites of contamination events. In all of our experiments with single objectives, these lower bounds establish that the GRASP local search method generates solutions that are provably optimal to to within a fraction of a percentage point. Our Lagrangian heuristic also provides good solutions itself and requires only a fraction of the memory of GRASP. We conclude by describing two variations of the Lagrangian heuristic: an aggregated version that trades off solution quality for further memory savings, and a multi-objective version which balances objectives with additional goals. © 2008 ASCE.

We study proton and heavy ion irradiation effects on Phase Change Memories (PCM) with MOSFET and BJT selectors and the effect of the irradiation on the retention characteristics of these devices. Proton irradiation produces noticeable variations in the cell distributions in PCM with MOSFET selectors mostly due to leakage currents affecting the transistors. PCM with BJT selectors show only small variations after proton irradiation. PCM cells do not appear to be impacted by heavy-ion irradiation. Using high temperature accelerated retention tests, we demonstrate that the retention capability of these memories is not compromised by the irradiation. © 2006 IEEE.

Abstract not provided.

This paper summarizes operational histories of three Russian-designed photovoltaic (PV) lighthouses in Norway and Russia. All lighthouses were monitored to evaluate overall system and Nickel Cadmium (NiCad) battery bank performance to determine battery capacity, charging trends, temperature, and reliability. The practical use of PV in this unusual mode, months of battery charging followed by months of battery discharging, is documented and assessed. This paper presents operational data obtained from 2004 through 2007.

In order for the IAEA to draw valid safeguards conclusions, they must be assured that the data used to draw those conclusions are authentic. In order to provide that assurance, authentication measures are applied to the safeguards equipment and the data from the equipment. These authentication measures require that IAEA personnel have direct electronic and physical access to the equipment and severely limit access to the equipment by the operator. Providing the necessary access for the IAEA personnel can be intrusive and potentially disruptive to plant operations. If the equipment is to be used jointly by the operator and the IAEA, the authentication measures can cause difficulties for the operator by limiting his ability to repair and maintain the hardware. In many cases, tamper indicating conduit and enclosures are also required. The installation, sealing, and inspection of this tamper indicating hardware also add to the intrusiveness of the safeguards activities and increase the cost of safeguards. This paper discusses these impacts and proposes methods for mitigating them.

The Cognitive Foundry is a unified collection of tools for Cognitive Science and Technology applications, supporting the development of intelligent agent models. The Foundry has two primary components designed to facilitate agent construction: the Cognitive Framework and Machine Learning packages. The Cognitive Framework provides design patterns and default implementations of an architecture for evaluating theories of cognition, as well as a suite of tools to assist in the building and analysis of theories of cognition. The Machine Learning package provides tools for populating components of the Cognitive Framework from domain-relevant data using automated knowledge-capture techniques. This paper describes the Cognitive Foundry with a focus on its application within the context of agent behavior modeling.

A non-selective electrode array is presented for the quantification of fructose, galactose, and glucose in mixed solutions. A unique feature of this electrode array relative to other published work is the wide diversity of electrode materials incorporated within the array, being constructed of 41 different metals and metal alloys. Cyclic voltammograms were acquired for solutions containing a single sugar at varying concentrations, and the correlation between current and sugar concentration was calculated as a function of potential and electrode array element. The correlation plots identified potential regions and electrodes that scaled most linearly with sugar concentration, and the number of electrodes used in building predictive models was reduced to 15. Partial least squares regression models relating electrochemical response to sugar concentration were constructed using data from single electrodes and multiple electrodes within the array, and the predictive abilities of these models were rigorously compared using a non-parametric Wilcoxon test. Models using single electrodes (Pt:Rh (90:10) for fructose, Au:Ni (82:18) for galactose, and Au for glucose) were judged to be statistically superior or indistinguishable from those built with multiple electrodes. Additionally, for each sugar, interval partial least squares regression successfully identified a subset of potentials within a given electrode that generated a model of statistically equivalent predictive ability relative to the full potential model. While including data from multiple electrodes offered no benefit in predicting sugar concentration, use of the array afforded the versatility and flexibility of selecting the best single electrode for each sugar. © 2008 Elsevier B.V. All rights reserved.

Determination of fracture toughness for metals under quasi-static loading conditions can follow well-established procedures and ASTM standards. The use of metallic materials in impact-related applications requires the determination of dynamic fracture toughness for these materials. There are two main challenges in experiment design that must be overcome before valid dynamic data can be obtained. Dynamic equilibrium over the entire specimen needs to be approximately achieved to relate the crack tip loading state to the far-field loading conditions. The loading rate at the crack tip should be maintained nearly constant during an experiment to delineate rate effects on the values of dynamic fracture toughness. A recently developed experimental technique for determining dynamic fracture toughness of brittle materials has been adapted to measure the dynamic initiation fracture toughness of high strength steel alloys. A split-Hopkinson pressure bar is used to apply the dynamic loading. A pulse shaper is used to achieve constant loading rate at the crack tip and dynamic equilibrium across the specimen. A four-point bending configuration is used at the impact section of the setup. ©2008 Society for Experimental Mechanics Inc.

Simulation of potential radionuclide transport in the saturated zone from beneath the proposed repository at Yucca Mountain to the accessible environment is an important aspect of the total system performance assessment (TSPA) for disposal of high-level radioactive waste at the site. Analyses of uncertainty and sensitivity are integral components of the TSPA and have been conducted at both the sub-system and system levels to identify parameters and processes that contribute to the overall uncertainty in predictions of repository performance. Results of the sensitivity analyses indicate that uncertainty in groundwater specific discharge along the flow path in the saturated zone from beneath the repository is an important contributor to uncertainty in TSPA results and is the dominant source of uncertainty in transport times in the saturated zone for most radionuclides. Uncertainties in parameters related to matrix diffusion in the volcanic units, colloid-facilitated transport, and sorption are also important contributors to uncertainty in transport times to differing degrees for various radionuclides.

The drift-shadow effect describes capillary diversion of water flow around a drift or cavity in porous or fractured rock, resulting in lower water flux directly beneath the cavity. This paper presents computational simulations of drift-shadow experiments using dual-permeability models, similar to the models used for performance assessment analyses of flow and seepage in unsaturated fractured tuff at Yucca Mountain. Results show that the dual-penneability models capture the salient trends and behavior observed in the experiments, but constitutive relations (e.g., fracture capillary-pressure curves) can significantly affect the simulated results. An evaluation of different meshes showed that at the grid refinement used, a comparison between orthogonal and unstructured meshes did not result in large differences.

Uncertainty and sensitivity analyses of the expected dose to the reasonably maximally exposed individual in the Yucca Mountain 2008 total system performance assessment (TSPA) are presented. Uncertainty results are obtained with Latin hypercube sampling of epistemic uncertain inputs, and partial rank correlation coefficients are used to illustrate sensitivity analysis results.

The Total System Performance Assessment (TSPA) for the proposed high level radioactive waste repository at Yucca Mountain, Nevada, uses a sampling-based approach to uncertainty and sensitivity analysis. Specifically, Latin hypercube sampling is used to generate a mapping between epistemically uncertain analysis inputs and analysis outcomes of interest. This results in distributions that characterize the uncertainty in analysis outcomes. Further, the resultant mapping can be explored with sensitivity analysis procedures based on (i) examination of scatterplots, (ii) partial rank correlation coefficients, (iii) R2 values and standardized rank regression coefficients obtained in stepwise rank regression analyses, and (iv) other analysis techniques. The TSPA considers over 300 epistemically uncertain inputs (e.g., corrosion properties, solubilities, retardations, defining parameters for Poisson processes, ⋯) and over 70 time-dependent analysis outcomes (e.g., physical properties in waste packages and the engineered barrier system, releases from the engineered barrier system, the unsaturated zone and the saturated zone for individual radionuclides, and annual dose to the reasonably maximally exposed individual (RMEI) from both individual radionuclides and all radionuclides. The obtained uncertainty and sensitivity analysis results play an important role in facilitating understanding of analysis results, supporting analysis verification, establishing risk importance, and enhancing overall analysis credibility. The uncertainty and sensitivity analysis procedures are illustrated and explained with selected results for releases from the engineered barrier system, the unsaturated zone and the saturated zone and also for annual dose to the RMEI.

Placing sensors in municipal water networks to protect against a set of contamination events is a classic p-median problem for most objectives when we assume that sensors are perfect. Many researchers have proposed exact and approximate solution methods for this p-median formulation. For full-scale networks with large contamination event suites, one must generally rely on heuristic methods to generate solutions. These heuristics provide feasible solutions, but give no quality guarantee relative to the optimal placement. In this paper we apply a Lagrangian relaxation method in order to compute lower bounds on the expected impact of suites of contamination events. In all of our experiments with single objectives, these lower bounds establish that the GRASP local search method generates solutions that are provably optimal to to within a fraction of a percentage point. Our Lagrangian heuristic also provides good solutions itself and requires only a fraction of the memory of GRASP. We conclude by describing two variations of the Lagrangian heuristic: an aggregated version that trades off solution quality for further memory savings, and a multi-objective version which balances objectives with additional goals. © 2008 ASCE.

It is generally acknowledged that once a highly conductive channel is established between two charged and conducting materials, electrical breakdown is well established and difficult to interrupt. An understanding of the initiation mechanism for electrical breakdown is crucial for devising mitigating methods to avoid catastrophic failures. Both volumetric and surface discharges are of interest. An effort is underway where experiments and theory are being simultaneously developed. The experiment consists of an impedance matched discharge chamber capable of investigating various gases and pressures to ten atmospheres. In addition to current and voltage measurements, a high dynamic range streak camera records streamer velocities. The streamer velocities are particularly valuable for comparison with theory. A streamer model is being developed which includes photo-ionization and particle interactions with an insulating surface. The combined theoretical and experimental effort is aimed at detailed comparisons of streamer development as well as a quantitative understanding of how streamers interact with dielectric surfaces and the resulting effects on breakdown voltage. © 2008 IEEE.

For the Yucca Mountain Project nuclear waste repository design, the emplaced waste packages are covered by a self-supported inverted U-shaped drip shield fabricated from Ti Grade 7 with Ti Grade 29 structural support members. This paper reports experimental results obtained to characterize the corrosion behavior of several titanium alloys. General corrosion rates were obtained using weight loss and electrochemical techniques such as cyclic potentiodynamic polarization and electrochemical impedance spectroscopy. Localized corrosion resistance was assessed from the results of cyclic potentiodynamic polarization and long-term corrosion potential measurements. The results indicate the drip shield titanium alloys are highly resistant to general and localized corrosion under repository-relevant conditions. © 2009 by NACE International.

Historically, (PCM/FM) receivers have used simple detection schemes yielding low performance. Using multi-symbol detection methods, PCM/FM can be received with better error performance than either SOQPSK or multi-h CPM. We present an approximation by which PCM/FM can be reinterpreted as a phase modulation scheme, allowing the use of coherent detection techniques. This is backward compatible with existing receivers. We also present an extension by which the error performance of the approximated PCM/FM can be improved even further with no change to the spectral properties. This improved waveform can be used in systems where compatibility with existing frequency allocation schemes is required. © International Foundation for Telemetering, 2008.

Dual-modular-redundancy (DMR) architectures use duplication and self-voting asynchronous circuits to mitigate single event transients (SETs). The area and performance of DMR circuitry is evaluated against conventional triple-modular-redundancy (TMR) logic. Benchmark ASIC circuits designed with DMR logic show a 1024% area improvement for flip-flop designs, and a 33% improvement for latch designs. © 2006 IEEE.

A seven cavity LTD system has been assembled and tested in a voltage adder configuration capable of producing approximately 1-MV into a 7-Ω, critically damped load. Individual cavities have been tested with a resistive load. The seven cavity adder has been tested with a large area electron beam diode. The output pulse when tested into a resistive load is that of an RLC circuit. When tested with a dynamic load impedance, the output voltages of the cavities have an added oscillation. The oscillation affects the output pulse shape but is not harmful to the cavity components. © 2008 IEEE.

Functional modeling and SysML/UML are defined communication languages that engineers and related disciplines use to communicate the nature of engineering products. We often see functional modeling and SysML/UML used to describe large, physical entities, such as airplanes or space craft. Systems engineers use functional modeling to decompose these large systems into subsystems. Each subsystem has defined requirements, defined roles and responsibilities (functions), and definable interfaces. Each subsystem consists of electrical hardware, mechanical hardware, and computer software. Functional modeling and SysML/UML can also be used for modeling program/project management processes, systems engineering processes, and manufacturing processes. Many organizations use an array of flow charts, organization charts, network diagrams, and spreadsheets to define engineering processes. This paper presents how Sandia National Laboratories (SNL) used functional modeling and SysML/UML to define the design and development processes and procedures for a product realization process (PRP) called the Integrated Phase Gate (IPG) Process. The use of functional modeling helped the organization more readily accept the use of systematic modeling for developing PRP. Additionally, this paper will explore the value of using SysML/UML over functional modeling in order to completely specify process and process artifacts. © 2008 by Georgia Artery, Mark De Spain and Regina Griego.

We present a rapid method for the identification of viruses using microfluidic chip gel electrophoresis (CGE) of high-copy number proteins to generate unique protein profiles. Viral proteins are solubilized by heating at 95°C in borate buffer containing detergent (5 min), then labeled with fluorescamine dye (10 s), and analyzed using the μChemLab CGE system (5 min). Analyses of closely related T2 and T4 bacteriophage demonstrate sufficient assay sensitivity and peak resolution to distinguish the two phage. CGE analyses of four additional viruses - MS2 bacteriophage, Epstein - Barr, respiratory syncytial, and vaccinia viruses - demonstrate reproducible and visually distinct protein profiles. To evaluate the suitability of the method for unique identification of viruses, we employed a Bayesian classification approach. Using a subset of 126 replicate electropherograms of the six viruses and phage for training purposes, successful classification with non-training data was 66/69 or 95% with no false positives. The classification method is based on a single attribute (elution time), although other attributes such as peak width, peak amplitude, or peak shape could be incorporated and may improve performance further. The encouraging results suggest a rapid and simple way to identify viruses without requiring specialty reagents such as PCR probes and antibodies. © 2008 American Chemical Society.

This report evaluates transportation risk for nuclear material in the proposed Global Nuclear Energy Partnership (GNEP) fuel cycle. Since many details of the GNEP program are yet to be determined, this document is intended only to identify general issues. The existing regulatory environment is determined to be largely prepared to incorporate the changes that the GNEP program will introduce. Nuclear material vulnerability and attractiveness are considered with respect to the various transport stages within the GNEP fuel cycle. It is determined that increased transportation security will be required for the GNEP fuel cycle, particularly for international transport. Finally, transportation considerations for several fuel cycle scenarios are discussed. These scenarios compare the current "once-through" fuel cycle with various aspects of the proposed GNEP fuel cycle.

Refractive elements are commonly used on Cassegrain-form telescopes to correct off-axis aberrations and both widen and flatten the field. Early correctors used two lenses with spherical surfaces, but their performance was somewhat limited. More recent correctors have three or four lenses with some including at least one aspheric surface. These systems produce high resolution images over relatively wide fields but often require the corrector and mirrors to be optimized together. Here we present a new corrector design using five spherical lenses. This approach produces high image quality with low distortion over wide fields and has sufficient degrees of freedom to allow corrector to be optimized independent of the mirrors if necessary. © 2008 Copyright SPIE - The International Society for Optical Engineering.

The advent of the nuclear renaissance gives rise to a concern for the effective design of nuclear fuel cycle systems that are safe, secure, nonproliferating and cost-effective. We propose to integrate the monitoring of the four major factors of nuclear facilities by focusing on the interactions between Safeguards, Operations, Security, and Safety (SOSS). We proposed to develop a framework that monitors process information continuously and can demonstrate the ability to enhance safety, operations, security, and safeguards by measuring and reducing relevant SOSS risks, thus ensuring the safe and legitimate use of the nuclear fuel cycle facility. A real-time comparison between expected and observed operations provides the foundation for the calculation of SOSS risk. The automation of new nuclear facilities requiring minimal manual operation provides an opportunity to utilize the abundance of process information for monitoring SOSS risk. A framework that monitors process information continuously can lead to greater transparency of nuclear fuel cycle activities and can demonstrate the ability to enhance the safety, operations, security and safeguards associated with the functioning of the nuclear fuel cycle facility. Sandia National Laboratories (SNL) has developed a risk algorithm for safeguards and is in the process of demonstrating the ability to monitor operational signals in real-time though a cooperative research project with the Japan Atomic Energy Agency (JAEA). The risk algorithms for safety, operations and security are under development. The next stage of this work will be to integrate the four algorithms into a single framework.

This paper summarizes the results of a Phenomena Identification and Ranking Table (PIRT) exercise performed for nuclear power plant (NPP) fire modeling applications conducted on behalf of the U.S. Nuclear Regulatory Commission (NRC) Office of Nuclear Regulatory Research (RES). A PIRT exercise is a formalized, facilitated expert elicitation process. In this case, the expert panel was comprised of seven international fire science experts and was facilitated by Sandia National Laboratories (SNL). The objective of a PIRT exercise is to identify key phenomena associated with the intended application and to then rank the importance and current state of knowledge of each identified phenomenon. One intent of this process is to provide input into the process of identifying and prioritizing future research efforts. In practice, the panel considered a series of specific fire scenarios based on scenarios typically considered in NPP applications. Each scenario includes a defined figure of merit; that is, a specific goal to be achieved in analyzing the scenario through the application of fire modeling tools. The panel identifies any and all phenomena relevant to a fire modeling-based analysis for the figure of merit. Each phenomenon is ranked relative to its importance to the fire model outcome and then further ranked against the existing state of knowledge and adequacy of existing modeling tools to predict that phenomenon. The PIRT panel covered several fire scenarios and identified a number of areas potentially in need of further fire modeling improvements. The paper summarizes the results of the ranking exercise.

One source of concern in the nuclear power community is associated with performing PRAs on the passive systems used in Advanced Light Water Reactors. Passive systems rely on physical phenomena in order to perform safety actions. This leads to questions about how one should model the reliability of the system, such as how one should model the uncertainty in physical parameters that define the operational characteristics of the passive system and how to determine the degradation and failure characteristics of a system. Hierarchical Bayesian techniques provide a means for assessing the types of problems presented by passive systems. They allow the analyst to collect multiple types of data, including expert judgment and historical data from different sources and then combine them in one analysis. The importance of this feature is that it allows an analyst to perform a mathematically consistent PRA without large amounts of data for the specific system under scrutiny. As data become available, they are incorporated into the analysis using Bayes' rule. As the dataset becomes large, the data dominate the analysis. A study is performed whereby data are collected from a set of resistors in a corrosive environment. A model is created that related the environmental conditions of the sensors being used to the performance of the sensors. Prior distributions are then proposed for the uncertain parameters. Both longitudinal and failure data are recorded for the sensors. These data are then used to update the model and obtain the posterior distributions related to the uncertain parameters.

Dual-modular-redundancy (DMR) architectures use duplication and self-voting asynchronous circuits to mitigate single event transients (SETs). The area and performance of DMR circuitry is evaluated against conventional triple-modular-redundancy (TMR) logic. Benchmark ASIC circuits designed with DMR logic show a 1024% area improvement for flip-flop designs, and a 33% improvement for latch designs. © 2006 IEEE.

A series of thin electrodeposited Cu foils and Cu foil/Kapton flex circuits were tested in bending fatigue according to ASTM E796 and IPC-TM-650. The fatigue behavior was analyzed in terms of strain vs. number of cycles to failure, using a Coffin-Manson approach. The effects of Cu foil thickness and Cu trace width are discussed. The Cu foils performed as expected and the Cu foil/Kapton® (E.I. du Pont de Nemours and Company, Wilmington, DE) composites showed significant improvement in fatigue lifetime due to the composite strengthening effect of the Kapton layers. However, the flex circuits showed more scatter in fatigue life based on electrical continuity. The effect of the Kapton layers manifests itself by significantly more widespread microcracking in the Cu traces and the extent of microcracking depended on the strain level. *Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the United States Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000. © 2008 MS&T'08 ®.

Artifacts in the field evaporation behavior of small precipitates have limited the accuracy of atom probe tomography analysis of clusters and precipitates smaller than 2 nm. Here, we report on specific observations of reconstruction artifacts that were obtained in case of precipitates with radii less than 10 nm in Al alloys, focusing particularly on a shift that appears in the relative positioning of matrix and precipitate atoms. We show that this chemically dependent behavior, referred to as "chromatic aberration," is due to the electrostatic field above the emitter and the variations in field evaporation of the elements constituting the precipitates. © Microscopy Society of America 2008.

The Explosive Destruction System (EDS) was developed by Sandia National Laboratories for the US Army Product Manager for Non-Stockpile Chemical Materiel (PMNSCM) to destroy recovered, explosively configured,chemical munitions. PMNSCM currently has five EDS units that have processed over 850 items. The system uses linear and conical shaped charges to open munitions and attack the burster followed by chemical treatment of the agent. The main component of the EDS is a stainless steel, cylindrical vessel, which contais the explosion and the subsequent chemical treatment. Extensive modeling and testing have been, and continue to be used, to design and qualify the vessel for different applications and conditions. This has included explosive overtests using small, geometrically scaled vessels to study overloads, plastic deformation, and failure limits. Recently the ASME Task Group on Impulsively Loaded Vessels has developed a Code Case under Section VIII Division 3 of the ASME Boiler and Pressure Vessel Code for the design of vessel like the EDS. In this article, a representative EDS subscale vessel is investigated against the ASME Design Codes for vessels subjected to impulsive loads. Topics include strain-based plastic collapse, fatigue and fracture analysis, and leak-before-burst. Vessel design validation is based on model results, where the high explosive (HE) pressure histories and subsequent vessel response (strain histories) are modeled using the analysis codes CTH and LSDYNA, respectively. Copyright © 2008 by ASME.

The drift-shadow effect describes capillary diversion of water flow around a drift or cavity in porous or fractured rock, resulting in lower water flux directly beneath the cavity. This paper presents computational simulations of drift-shadow experiments using dual-permeability models, similar to the models used for performance assessment analyses of flow and seepage in unsaturated fractured tuff at Yucca Mountain. Results show that the dual-penneability models capture the salient trends and behavior observed in the experiments, but constitutive relations (e.g., fracture capillary-pressure curves) can significantly affect the simulated results. An evaluation of different meshes showed that at the grid refinement used, a comparison between orthogonal and unstructured meshes did not result in large differences.

Ground Truth, a training game developed by Sandia National Laboratories in partnership with the University of Southern California GamePipe Lab, puts a player in the role of an Incident Commander working with teammate agents to respond to urban threats. These agents simulate certain emotions that a responder may feel during this high-stress situation. We construct psychology-plausible models compliant with the Sandia Human Embodiment and Representation Cognitive Architecture (SHERCA) that are run on the Sandia Cognitive Runtime Engine with Active Memory (SCREAM) software. SCREAM's computational representations for modeling human decision-making combine aspects of ANNs and fuzzy logic networks. This paper gives an overview of Ground Truth and discusses the adaptation of the SHERCA and SCREAM into the game. We include a semiformal descriptionof SCREAM. ©2008 IEEE.

We present the TEVA-SPOT Toolkit, a sensor placement optimization tool developed within the USEPA TEVA program. The TEVA-SPOT Toolkit provides a sensor placement framework that facilitates research in sensor placement optimization and enables the practical application of sensor placement solvers to real-world CWS design applications. This paper provides an overview of its key features, and then illustrates how this tool can be flexibly applied to solve a variety of different types of sensor placement problems. © 2008 ASCE.

We describe an entirely statistics-based, unsupervised, and language-independent approach to multilingual information retrieval, which we call Latent Morpho-Semantic Analysis (LMSA). LMSA overcomes some of the shortcomings of related previous approaches such as Latent Semantic Analysis (LSA). LMSA has an important theoretical advantage over LSA: it combines well-known techniques in a novel way to break the terms of LSA down into units which correspond more closely to morphemes. Thus, it has a particular appeal for use with morphologically complex languages such as Arabic. We show through empirical results that the theoretical advantages of LMSA can translate into significant gains in precision in multilingual information retrieval tests. These gains are not matched either when a standard stemmer is used with LSA, or when terms are indiscriminately broken down into n-grams. © 2008 Licensed under the Creative Commons.

Ceramic samples of Pb0.99La0.01 (Zr 0.91Ti0.09)O3 were studied by dielectric and time-of-flight neutron diffraction measurements at 300 and 250 K versus pressure. Isothermal dielectric data (300/250 K) suggest structural transitions with onsets near 0.35/0.37 GPa, respectively, for increasing pressure. On pressure release, only the 300K transition occurs (0.10 GPa; none indicated at 250 K). Diffraction data at 300 K show the sample has the R3c structure, remaining in that phase cooling to 250 K. Pressure increase (either 300 or 250 K) above 0.3 GPa yields a Pnma-like (AO) phase (two other prominent peaks in the spectra suggest a possible incommensurate cell). Temperature/pressure excursions show considerable phase hysteresis.

The representation of disruptive events (seismic and igneous events) and early failures of waste packages and drip shields in the 2008 total system performance assessment (TSPA) for the proposed high-level radioactive waste repository at Yucca Mountain, Nevada is described, in the context of the 2008 TSPA, disruptive events and early failures are treated as phenomena that occur randomly (e.g., the time of a seismic event) and also have properties that are random (e.g., the peak ground velocity associated with a seismic event). Specifically the following potential disruptions are considered: (i) early failure of individual drip shields, (ii) early failure of individual waste packages, (iii) igneous intrusion events that result in the filling of the waste disposal drifts with magma, (iv) volcanic eruption events that result in the dispersal of waste into the atmosphere, (v) seismic events that damage waste packages and drip shields as a result of strong vibratory ground motion, and (vi) seismic events that damage waste packages and drip shields as a result of shear displacement along a fault. Example annual dose results are shown for the two most risk-significant events: strong seismic ground motion and igneous intrusion.

The development of separation distances for hydrogen facilities can be determined in several ways. A conservative approach is to use the worst possible accidents in terms of consequences. Such accidents may be of very low frequency and would likely never occur. Although this approach bounds separation distances, the resulting distances are generally prohibitive. The current separation distances in hydrogen codes and standards do not reflect this approach. An alternative deterministic approach that is often utilized by standards development organizations and allowed under some regulations is to select accident scenarios that are more probable but do not provide bounding consequences. In this approach, expert opinion is generally used to select the accidents used as the basis for the prescribed separation distances.

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Full tape thickness features (FTTF) using conductors, high K and low K dielectrics, sacrificial volume materials, and magnetic materials are useful as both technically and cost-effective approaches to multiple needs in laminate microelectronic and microsystem structures. Lowering resistance in conductor traces of all kinds, raising Q-factors in coils, and enhancing EMI shielding in RF desingns are a few of the modern needs. By filling with suitable dielectric compositions one can deliver embedded capacitors with an appropriate balance between mechanical compatibility and safety factor for fabrication. Similar techniques could be applied to magnetic materials without wasteful manufacturing processes when the magnetic material is a small fraction of the overall circuit area. Finally, to open the technology of unfilled volumes for radio frequency performance as well as microfluidics and mixed cofired material applications, the full tape thickness implementation of sacrificial volume materials is also considered. We discuss implementations of FTTF structures and discuss technical problems and the promise such structures hold for the future.

Radiation sensing applications for SNM detection, identification, and characterization all face the same fundamental problem: each to varying degrees must infer the presence, identity, and configuration of a radiation source given a set of radiation signatures. This is a problem of inverse radiation transport: given the outcome of a measurement, what was thesource and transport medium that caused that observation? This paper presents a framework for solving inverse radiation transport problems, describes its essential components, and illustrates its features and performance. © 2008 IEEE.

A series of modal tests were performed in order to validate a finite element model of a complex aerospace structure. Data was measured using various excitation methods in order to extract clean modes and damping values for a lightly damped system. Model validation was performed for one subassembly as well as for the full assembly in order to pinpoint the areas of the model that required updating and to better ascertain the quality of the joint models connecting the various components and subassemblies. After model updates were completed, using the measured modal data, the model was validated using frequency response functions (FRFs) as the independent validation metric. Test and model FRFs were compared to determine the validity of the finite element model.

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Optical tweezers has become a powerful and common tool for sensitive determination of electrostatic interactions between colloidal particles. Two optical trapping based techniques, blinking tweezers and direct force measurements, have become increasingly prevalent in investigations of interparticle potentials. The blinking laser tweezers method repeatedly catches and releases a pair of particles to gather physical statistics of particle trajectories. Statistical analysis is used to determine drift velocities, diffusion coefficients, and ultimately colloidal forces as a function of the center-center separation of the particles. Direct force measurements monitor the position of a particle relative to the center of an optical trap as the separation distance between two continuously trapped particles is gradually decreased. As the particles near each other, the displacement from the trap center for each particle increases proportional to the inter-particle force. Although commonly employed in the investigation of interactions of colloidal particles, there exists no direct comparison of these experimental methods in the literature. In this study, an experimental apparatus was developed capable of performing both methods and is used to quantify electrostatic potentials between two sizes of polystyrene particles in an AOT hexadecane solution. Comparisons are drawn between the experiments conducted using the two measurement techniques, theory, and existing literature. Forces are quantified on the femto-Newton scale and results agree well with literature values.

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Communities of vertices within a giant network such as the World-Wide-Web are likely to be vastly smaller than the network itself. However, Fortunato and Barthelemy have proved that modularity maximization algorithms for community detection may fail to resolve communities with fewer than {radical} L/2 edges, where L is the number of edges in the entire network. This resolution limit leads modularity maximization algorithms to have notoriously poor accuracy on many real networks. Fortunato and Barthelemy's argument can be extended to networks with weighted edges as well, and we derive this corollary argument. We conclude that weighted modularity algorithms may fail to resolve communities with fewer than {radical} W{epsilon}/2 total edge weight, where W is the total edge weight in the network and {epsilon} is the maximum weight of an inter-community edge. If {epsilon} is small, then small communities can be resolved. Given a weighted or unweighted network, we describe how to derive new edge weights in order to achieve a low {epsilon}, we modify the 'CNM' community detection algorithm to maximize weighted modularity, and show that the resulting algorithm has greatly improved accuracy. In experiments with an emerging community standard benchmark, we find that our simple CNM variant is competitive with the most accurate community detection methods yet proposed.

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We have conducted a molecular dynamics (MD) simulation study of water confined between methyl-terminated and carboxyl-terminated alkylsilane self-assembled monolayers (SAMs) on amorphous silica substrates. In doing so, we have investigated the dynamic and structural behavior of the water molecules when compressed to loads ranging from 20 to 950 MPa for two different amounts of water (27 and 58 water molecules/nm{sup 2}). Within the studied range of loads, we observe that no water molecules penetrate the hydrophobic region of the carboxyl-terminated SAMs. However, we observe that at loads larger than 150 MPa water molecules penetrate the methyl-terminated SAMs and form hydrogen-bonded chains that connect to the bulk water. The diffusion coefficient of the water molecules decreases as the water film becomes thinner and pressure increases. When compared to bulk diffusion coefficients of water molecules at the various loads, we found that the diffusion coefficients for the systems with 27 water molecules/nm{sup 2} are reduced by a factor of 20 at low loads and by a factor of 40 at high loads, while the diffusion coefficients for the systems with 58 water molecules/nm{sup 2} are reduced by a factor of 25 at all loads.

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The computational work in many information retrieval and analysis algorithms is based on sparse linear algebra. Sparse matrix-vector multiplication is a common kernel in many of these computations. Thus, an important related combinatorial problem in parallel computing is how to distribute the matrix and the vectors among processors so as to minimize the communication cost. We focus on minimizing the total communication volume while keeping the computation balanced across processes. In [1], the first two authors presented a new 2D partitioning method, the nested dissection partitioning algorithm. In this paper, we improve on that algorithm and show that it is a good option for data partitioning in information retrieval. We also show partitioning time can be substantially reduced by using the SCOTCH software, and quality improves in some cases, too.

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The Heavy Ion Fusion Science Virtual National Laboratory has achieved 60-fold longitudinal pulse compression of ion beams on the Neutralized Drift Compression Experiment (NDCX) [P. K. Roy et al., Phys. Rev. Lett. 95, 234801 (2005)]. To focus a space-charge-dominated charge bunch to sufficiently high intensities for ion-beam-heated warm dense matter and inertial fusion energy studies, simultaneous transverse and longitudinal compression to a coincident focal plane is required. Optimizing the compression under the appropriate constraints can deliver higher intensity per unit length of accelerator to the target, thereby facilitating the creation of more compact and cost-effective ion beam drivers. The experiments utilized a drift region filled with high-density plasma in order to neutralize the space charge and current of an {approx}300 keV K{sup +} beam and have separately achieved transverse and longitudinal focusing to a radius <2 mm and pulse duration <5 ns, respectively. Simulation predictions and recent experiments demonstrate that a strong solenoid (B{sub Z} < 100 kG) placed near the end of the drift region can transversely focus the beam to the longitudinal focal plane. This paper reports on simulation predictions and experimental progress toward realizing simultaneous transverse and longitudinal charge bunch focusing. The proposed NDCX-II facility would capitalize on the insights gained from NDCX simulations and measurements in order to provide a higher-energy (>2 MeV) ion beam user-facility for warm dense matter and inertial fusion energy-relevant target physics experiments.

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An important step towards realizing the advantages of quantum dots in electro-optic applications is to understand the excitation dependences of optical properties. This paper discusses results obtained using a microscopic theory. The calculations uncovered complicated carrier density and electronic structure influences on absorption, gain and refractive index that can be attributed to a delicate balancing of electronic-structure and many-body effects in a coupled quantum-dot-quantum-well system.

The effect of sample microstructure on water dynamic wetting behavior was examined for superhydrophobic ZnO films. Surface morphology ranging from needle arrays to overlapping platelets was controlled through judicious choice of hydrothermal reaction conditions. Structure modification with alkyl and perfluoroalkyl chains yielded films characterized by advancing contact angles that ranged from 159° to 171°. Contact angle hysteresis was less than 2° with needles (tip diameter <30 nm) and less than 11° for rods (diameter <250 nm). Relatively thick (diameter ∼600 nm) structures were still characterized by advancing contact angles exceeding 165° and hysteresis <30°. Formation of nanometer-scale roughness on top of the microstructure via silica deposition significantly enhanced the surface superhydrophobicity. Similarly, following perfluoro-alkane treatment, all examined microstructures exhibited advancing contact angles > 169° and hysteresis < 7°. © 2008 American Chemical Society.

During the 1990's the Electric Power Research Institute (EPRI) developed methods for fire risk analysis to support its utility members in the preparation of responses to Generic Letter 88-20, Supplement 4, "Individual Plant Examination - External Events" (IPEEE). This effort produced a Fire Risk Assessment methodology for at-power that was used by the majority of US Nuclear Power Plants (NPPs) in support of the IPEEE program and several NPPs oversees. Although these methods were acceptable for accomplishing the objectives of the IPEEE, EPRI and the U.S. Nuclear Regulatory Commission (NRC) recognized that these methods require upgrades to support current requirements for Risk-Informed/Performance-Based (RI/PB) applications. In 2001 EPRI and the NRC Office of Nuclear Regulatory Research (RES) embarked on a cooperative project to improve the state-of-the-art in fire risk assessment to support this new risk-informed environment in fire protection. This project produced a consensus document, NUREG/CR-6850 (EPRI 1011989), entitled "Fire PRA Methodology for Nuclear Power Facilities" which addresses fire risk for at-power operations. This report developed: 1) the process for identification and inclusion of the post-fire Human Failure Events (HFEs), 2) the methodology for assigning quantitative screening values to these HFEs, and 3) the initial considerations of performance shaping factors (PSFs) and related fire effects that may need to be addressed in developing best-estimate Human Error Probabilities (HEPs). However, this document does not describe a methodology to develop these best-estimate HEPs given the PSFs and the fire-related effects. In 2007 EPRI and NRC's RES embarked on another cooperative project to develop explicit guidance for estimating HEPs for human error events under fire generated conditions, building upon existing human reliability analysis (HRA) methods. This paper will describe the progress to date on the development and testing of the fire HRA methodology, which includes addressing the range of fire procedures used in existing plants, the range of strategies for main control room abandonment, and the potential impact of fire-induced spurious electrical effects on crew performance. In addition to developing a detailed HRA approach, one goal of the project is to develop a fire HRA scoping quantification approach that allows derivation of more realistic HEPs than those in the screening approach from NUREG/CR-6850 (EPRI 1011989), while requiring less analytic resources than a detailed HRA. In this approach, detailed HRA will be used only for the more complex actions that cannot meet the criteria for the scoping approach.

This paper discusses the interplay between networks and control systems. As we gain more understanding about the structure and dynamics of physical networks, their effects on the performance of closed-loop control systems, as well as the ability to control such networks, provide fertile areas of research. The paper reviews such research with special emphasis on the connectivity and delays in the information transfer across networks. © 2008 Elsevier Ltd. All rights reserved.

A simple and effective approach is presented to construct coarse spaces for overlapping Schwarz preconditioners. The approach is based on energy minimizing extensions of coarse trace spaces, and can be viewed as a generalization of earlier work by Dryja, Smith, and Widlund. The use of these coarse spaces in overlapping Schwarz preconditioners leads to condition numbers bounded by C(1 + H/δ)(1 + log(H/h)) for certain problems when coefficient jumps are aligned with subdomain boundaries. For problems without coefficient jumps, it is possible to remove the log(H/h) factor in this bound by a suitable enrichment of the coarse space. Comparisons are made with the coarse spaces of two other substructuring preconditioners. Numerical examples are also presented for a variety of problems.

This paper investigates the use of strip transect sampling to estimate object abundance when the underlying spatial distribution is assumed to be Poisson. A design-rather than model-based approach to estimation is investigated through computer simulation, with both homogeneous and non-homogeneous fields representing individual realizations of spatial point processes being considered. Of particular interest are the effects of changing the number of transects and transect width (or alternatively, coverage percent or fraction) on the quality of the estimate. A specific application to the characterization of unexploded ordnance (UXO) in the subsurface at former military firing ranges is discussed. The results may be extended to the investigation of outcrop characteristics as well as subsurface geological features. © 2008 Springer-Verlag Berlin Heidelberg.

Several antennas with integrated high-impedance surfaces are presented. The high-impedance surface is implemented as a composite right/left-handed (CRLH) metamaterial fabricated from a periodic structure characterized by a substrate, filled with an array of vertical vias and capped by capacitive patches. Omnidirectional antennas placed in close proximity to the high-impedance surface radiate hemispherically with an increase in boresight far-field pattern gain of up to 10 dB and a front-to-back ratio as high as 13 dB at 2.45 GHz. Several TEM rectangular horn antennas are realized by replacing conductor walls with high-impedance surfaces. The TEM horn antennas are capable of operating below the TE{sub 1,0} cutoff frequency of a standard all-metal horn antenna, enabling a reduction in antenna volume. Above the cutoff frequency the TEM horn antennas function similarly to standard rectangular horn antennas.

This paper outlines a comparison between two cognitive modeling frameworks: Atomic Components of Thought - Rational (ACT-R; Anderson & Lebiere, 1998) and a framework under development at Sandia National Laboratories. Both frameworks are based on the cognitive psychological literature, although they represent different theoretical perspectives on cognition, with ACT-R being a production-rule-based system and the Sandia framework being a dynamical-systems or connectionist-type approach. This comparison involved a complex driving domain in which both the car being driven and the driver were equipped with sensors that provided information to each framework. The output of each framework was a classification of the real-world situation that the driver was in, e.g., being overtaken on the autobahn. Comparisons between the two frameworks included validation against human ratings of the driving situations via videotapes of driving sessions, along with twelve creation and performance metrics regarding the method and ease of framework population, processor requirements, and maximum real-time data sampling rate.

In this chapter, we apply a nonnegative tensor factorization algorithm to extract and detect meaningful discussions from electronic mail messages for a period of one year. For the publicly released Enron electronic mail collection, we encode a sparse term-author-month array for subsequent three-way factorization using the PARAllel FACtors (or PARAFAC) three-way decomposition first proposed by Harshman. Using nonnegative tensors, we preserve natural data nonnegativity and avoid subtractive basis vector and encoding interactions present in techniques such as principal component analysis. Results in thread detection and interpretation are discussed in the context of published Enron business practices and activities, and benchmarks addressing the computational complexity of our approach are provided. The resulting tensor factorizations can be used to produce Gantt-like charts that can be used to assess the duration, order, and dependencies of focused discussions against the progression of time. © 2008 Springer-Verlag London.

Optimal design, parameter estimation, and inverse problems arising in the modeling of semiconductor devices lead to optimization problems constrained by systems of PDEs. We study the impact of different state equation discretizations on optimization problems whose objective functionals involve flux terms. Galerkin methods, in which the flux is a derived quantity, are compared with mixed Galerkin discretizations where the flux is approximated directly. Our results show that the latter approach leads to more robust and accurate solutions of the optimization problem, especially for highly heterogeneous materials with large jumps in material properties. © 2008 Springer.

Verdict is a collection of subroutines for evaluating the geometric qualities of triangles, quadrilaterals, tetrahedra, and hexahedra using a variety of functions. A quality is a real number assigned to one of these shapes depending on its particular vertex coordinates. These functions are used to evaluate the input to finite element, finite volume, boundary element, and other types of solvers that approximate the solution to partial differential equations defined over regions of space. This article describes the most recent version of Verdict and provides a summary of the main properties of the quality functions offered by the library. It finally demonstrates the versatility and applicability of Verdict by illustrating its use in several scientific applications that pertain to pre, post, and end-to-end processing.

Hexahedral refinement increases the density of an all-hexahedral mesh in a specified region, improving numerical accuracy. Previous research using solely sheet refinement theory made the implementation computationally expensive and unable to effectively handle concave refinement regions and self-intersecting hex sheets. The Selective Approach method is a new procedure that combines two diverse methodologies to create an efficient and robust algorithm able to handle the above stated problems. These two refinement methods are: 1) element by element refinement and 2) directional refinement. In element by element refinement, the three inherent directions of a Hex are refined in one step using one of seven templates. Because of its computational superiority over directional refinement, but its inability to handle concavities, element by element refinement is used in all areas of the specified region except regions local to concavities. The directional refinement scheme refines the three inherent directions of a hexahedron separately on a hex by hex basis. This differs from sheet refinement which refines hexahedra using hex sheets. Directional refinement is able to correctly handle concave refinement regions. A ranking system and propagation scheme allow directional refinement to work within the confines of the Selective Approach Algorithm.

This paper presents methods and applications of sheet insertion in a hexahedral mesh. A hexahedral sheet is dual to a layer of hexahedra in a hexahedral mesh. Because of symmetries within a hexahedral element, every hexahedral mesh can be viewed as a collection of these sheets. It is possible to insert new sheets into an existing mesh, and these new sheets can be used to define new mesh boundaries, refine the mesh, or in some cases can be used to improve quality in an existing mesh. Sheet insertion has a broad range of possible applications including mesh generation, boundary refinement, R-adaptivity and joining existing meshes. Examples of each of these applications are demonstrated.

For operation of an ion source in an intense ion beam diode, it is desirable to form a localized and robust source of high purity. A cryogenically operated ion source has great promise, since the ions are formed from a condensed high-purity gas, which has been confined to a relatively thin ice layer on the anode surface. Previous experiments have established the principles of operation of such an ion source, but have been limited in repetitive duration due to the use of short-lived liquid He cooling of the anode surface. We detail here the successful development of a Cryo-Diode in which the cooling was achieved with a closed-cycle cryo-pump. This results in an ion source design that can potentially be operated for an indefinite duration. Time-of-flight measurements with Faraday cups indicate that the resultant ion beam is of high-purity, and composed of singly charged ions formed out of the gas frozen out on the anode surface. © 2008 Copyright Cambridge University Press 2008.

Using a slab of Massillon Sandstone, laboratory-scale solute tracer experiments were carried out to test numerical simulations using the Advection-Dispersion Equation (ADE). While studies of a similar nature exist, our work differs in that we combine: (1) experimentation in naturally complex geologic media, (2) X-ray absorption imaging to visualize and quantify two-dimensional solute transport, (3) high resolution transport property characterization, with (4) numerical simulation. The simulations use permeability, porosity, and solute concentration measured to sub-centimeter resolution. While bulk breakthrough curve characteristics were adequately matched, large discrepancies exist between the experimental and simulated solute concentration fields. Investigation of potential experimental errors suggests that the failure to fit solute concentration fields may lie in loss of intricate connectivity within the cross-bedded sandstone occurring at scales finer than our property characterization measurements (i.e., sub-centimeter). © 2008 Elsevier Ltd. All rights reserved.

With the continuing development of more capable data gathering sensors, comes an increased demand on the bandwidth for transmitting larger quantities of data. To help counteract that trend, a study was undertaken to determine appropriate lossy data compression strategies for minimizing their impact on target detection and characterization. The survey of current compression techniques led us to the conclusion that wavelet compression was well suited for this purpose. Wavelet analysis essentially applies a low-pass and high-pass filter to the data, converting the data into the related coefficients that maintain spatial information as well as frequency information. Wavelet compression is achieved by zeroing the coefficients that pertain to the noise in the signal, i.e. the high frequency, low amplitude portion. This approach is well suited for our goal because it reduces the noise in the signal with only minimal impact on the larger, lower frequency target signatures. The resulting coefficients can then be encoded using lossless techniques with higher compression levels because of the lower entropy and significant number of zeros. No significant signal degradation or difficulties in target characterization or detection were observed or measured when wavelet compression was applied to simulated and real data, even when over 80% of the coefficients were zeroed. While the exact level of compression will be data set dependent, for the data sets we studied, compression factors over 10 were found to be satisfactory where conventional lossless techniques achieved levels of less than 3.

This report describes progress in designing a neutral atom trap capable of trapping sub millikelvin atom in a magnetic trap and shuttling the atoms across the atom chip from a collection area to an optical cavity. The numerical simulation and atom chip design are discussed. Also, discussed are preliminary calculations of quantum noise sources in Kerr nonlinear optics measurements based on electromagnetically induced transparency. These types of measurements may be important for quantum nondemolition measurements at the few photon limit.

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The Department of Energy (DOE) National Laboratories support the Department of Homeland Security (DHS) in the development and execution of a research and development (R&D) strategy to improve the nation's preparedness against terrorist threats. Current approaches to planning and prioritization of DHS research decisions are informed by risk assessment tools and processes intended to allocate resources to programs that are likely to have the highest payoff. Early applications of such processes have faced challenges in several areas, including characterization of the intelligent adversary and linkage to strategic risk management decisions. The risk-based analysis initiatives at Sandia Laboratories could augment the methodologies currently being applied by the DHS and could support more credible R&D roadmapping for national homeland security programs. Implementation and execution issues facing homeland security R&D initiatives within the national laboratories emerged as a particular concern in this research.

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This report provides an assessment of well construction technology for EGS with two primary objectives: 1. Determining the ability of existing technologies to develop EGS wells. 2. Identifying critical well construction research lines and development technologies that are likely to enhance prospects for EGS viability and improve overall economics.

In this report, we present the novel functionality of parallel tetrahedral mesh refinement which we have implemented in MOAB. This report details work done to implement parallel, edge-based, tetrahedral refinement into MOAB. The theoretical basis for this work is contained in [PT04, PT05, TP06] while information on design, performance, and operation specific to MOAB are contained herein. As MOAB is intended mainly for use in pre-processing and simulation (as opposed to the post-processing bent of previous papers), the primary use case is different: rather than refining elements with non-linear basis functions, the goal is to increase the number of degrees of freedom in some region in order to more accurately represent the solution to some system of equations that cannot be solved analytically. Also, MOAB has a unique mesh representation which impacts the algorithm. This introduction contains a brief review of streaming edge-based tetrahedral refinement. The remainder of the report is broken into three sections: design and implementation, performance, and conclusions. Appendix A contains instructions for end users (simulation authors) on how to employ the refiner.

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The Advanced Engineering Environment (AEE) is a model for an engineering design and communications system that will enhance project collaboration throughout the nuclear weapons complex (NWC). Sandia National Laboratories and Parametric Technology Corporation (PTC) worked together on a prototype project to evaluate the suitability of a portion of PTC's Windchill 9.0 suite of data management, design and collaboration tools as the basis for an AEE. The AEE project team implemented Windchill 9.0 development servers in both classified and unclassified domains and used them to test and evaluate the Windchill tool suite relative to the needs of the NWC using weapons project use cases. A primary deliverable was the development of a new real time collaborative desktop design and engineering process using PDMLink (data management tool), Pro/Engineer (mechanical computer aided design tool) and ProductView Lite (visualization tool). Additional project activities included evaluations of PTC's electrical computer aided design, visualization, and engineering calculations applications. This report documents the AEE project work to share information and lessons learned with other NWC sites. It also provides PTC with recommendations for improving their products for NWC applications.

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Scoping studies have demonstrated that ceragenins, when linked to water-treatment membranes have the potential to create biofouling resistant water-treatment membranes. Ceragenins are synthetically produced molecules that mimic antimicrobial peptides. Evidence includes measurements of CSA-13 prohibiting the growth of and killing planktonic Pseudomonas fluorescens. In addition, imaging of biofilms that were in contact of a ceragenin showed more dead cells relative to live cells than in a biofilm that had not been treated with a ceragenin. This work has demonstrated that ceragenins can be attached to polyamide reverse osmosis (RO) membranes, though work needs to improve the uniformity of the attachment. Finally, methods have been developed to use hyperspectral imaging with multivariate curve resolution to view ceragenins attached to the RO membrane. Future work will be conducted to better attach the ceragenin to the RO membranes and more completely test the biocidal effectiveness of the ceragenins on the membranes.

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Shielded special nuclear material (SNM) is very difficult to detect and new technologies are needed to clear alarms and verify the presence of SNM. High-energy photons and neutrons can be used to actively interrogate for heavily shielded SNM, such as highly enriched uranium (HEU), since neutrons can penetrate gamma-ray shielding and gamma-rays can penetrate neutron shielding. Both source particles then induce unique detectable signals from fission. In this LDRD, we explored a new type of interrogation source that uses low-energy proton- or deuteron-induced nuclear reactions to generate high fluxes of mono-energetic gammas or neutrons. Accelerator-based experiments, computational studies, and prototype source tests were performed to obtain a better understanding of (1) the flux requirements, (2) fission-induced signals, background, and interferences, and (3) operational performance of the source. The results of this research led to the development and testing of an axial-type gamma tube source and the design/construction of a high power coaxial-type gamma generator based on the {sup 11}B(p,{gamma}){sup 12}C nuclear reaction.

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Cognitive science research investigates the advancement of human cognition and neuroscience capabilities. Addressing risks associated with these advancements can counter potential program failures, legal and ethical issues, constraints to scientific research, and product vulnerabilities. Survey results, focus group discussions, cognitive science experts, and surety researchers concur technical risks exist that could impact cognitive science research in areas such as medicine, privacy, human enhancement, law and policy, military applications, and national security (SAND2006-6895). This SAND report documents a surety engineering framework and a process for identifying cognitive system technical, ethical, legal and societal risks and applying appropriate surety methods to reduce such risks. The framework consists of several models: Specification, Design, Evaluation, Risk, and Maturity. Two detailed case studies are included to illustrate the use of the process and framework. Several Appendices provide detailed information on existing cognitive system architectures; ethical, legal, and societal risk research; surety methods and technologies; and educing information research with a case study vignette. The process and framework provide a model for how cognitive systems research and full-scale product development can apply surety engineering to reduce perceived and actual risks.

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A system dynamics model was developed in response to the apparent decline in STEM candidates in the United States and a pending shortage. The model explores the attractiveness of STEM and STEM careers focusing on employers and the workforce. Policies such as boosting STEM literacy, lifting the H-1B visa cap, limiting the offshoring of jobs, and maintaining training are explored as possible solutions. The system is complex, with many feedbacks and long time delays, so solutions that focus on a single point of the system are not effective and cannot solve the problem. A deeper understanding of parts of the system that have not been explored to date is necessary to find a workable solution.

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