Publications

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A self-similar solution is derived for a radially imploding cylindrical plasma with an embedded, azimuthal magnetic field. The plasma stagnates through a strong, outward propagating shock wave of constant velocity. This analysis is an extension of the classic Noh gasdynamics problem to its ideal magnetohydrodynamics (MHD) counterpart. The present exact solution is especially suitable as a test for MHD codes designed to simulate linear Z pinches. To demonstrate the application of the new solution to code verification, simulation results from the cylindrical R - Z version of Mach2 and the 3D Cartesian code Athena are compared against the analytic solution. Alternative routines from the default ones in Athena lead to significant improvement of the results, thereby demonstrating the utility of the self-similar solution for verification. © 2012 American Institute of Physics.

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We present a methodology for optimally locating disinfectant booster stations for response to contamination events in water distribution systems. A stochastic programming problem considering uncertainty in both the location and time of the contamination event is formulated resulting in an extensive form that is equivalent to the weighted maximum coverage problem. Although the original full-space problem is intractably large, we show a series of reductions that reduce the size of the problem by five orders of magnitude and allow solutions of the optimal placement problem for realistically sized water network models. © 2012 Elsevier B.V.

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Many remote sensing systems are undersampled, which traditionally precluded their use with phase diversity algorithms. Phase-diverse phase retrieval (PDPR) algorithms, which assume a point object, have been generalized to deal with the undersampled case by including a number of undersampled, spatially-displaced point source images within the nonlinear optimization. A different approach is presented in which super-resolution is used to generate Nyquist-sampled images prior to phase diversity reconstruction. Experimental results are presented for two PDPR algorithms, but the technique is also extensible to phase diversity imaging. © 2012 OSA.

In ac power systems, including micro-grids, it is important to regulate the amplitude and frequency of the voltages throughout the system. Many of the existing and proposed control strategies for micro-grids are patterned after the classic ac power system. That is, frequency regulation is achieved by designing micro-sources (commonly called Distributed Energy Resources or DERs) to exhibit an output-frequency-versus-power characteristic similar to the speed-versus-power (droop) characteristics of conventional turbo- and hydro-generators. Moreover, voltage regulation strategies are patterned after the output-voltageversus-reactive-power (droop) characteristics of the automatic voltage regulators (AVRs) used in conventional turbo- and hydrogenerators. In this paper, established approaches of frequency and voltage regulation are reviewed. Alternative strategies that utilize modern communication and control technologies are presented and discussed. © 2012 IEEE.

Iwan models have had some exposure recently in modeling the nonlinear response of individual joints. This popularity can be ascribed to their mathematical simplicity, their versatility, and their ability to capture the important responses of mechanical joints under unidirectional loads. There is a lot of history to this category of model. Masing explored kinematic hardening of metals with a model consisting of ten Jenkins elements in series. Soon after, Prandtl explored the behavior of a continuous distribution of such elements. Ishlinskii explored the mathematical structure of such continuous distributions. Much more recently, Iwan demonstrated practical application of such models in capturing various sorts of metal plasticity. Among the features that make such models interesting is a simple relationship between the asymptotic nature of the integral kernel at small values and the power-law relation between force amplitude and dissipation per cycle in harmonic loading. Iwan provided several differential equations for deducing the kernel from force-displacement relations. Segalman and Starr devised methods for deducing kernels from force-displacement curves of arbitrary Masing models. This is illustrated to generate a BPII model equivalent to the Ramberg-Osgood plasticity model. The Segalman-Starr relationship is used to find relationships among several other plasticity models. Copyright © 2012 by ASME.

PyTrilinos is a set of Python interfaces to compiled Trilinos packages. This collection supports serial and parallel dense linear algebra, serial and parallel sparse linear algebra, direct and iterative linear solution techniques, algebraic and multilevel preconditioners, nonlinear solvers and continuation algorithms, eigensolvers and partitioning algorithms. Also included are a variety of related utility functions and classes, including distributed I/O, coloring algorithms and matrix generation. PyTrilinos vector objects are compatible with the popular NumPy Python package. As a Python front end to compiled libraries, PyTrilinos takes advantage of the flexibility and ease of use of Python, and the efficiency of the underlying C++, C and Fortran numerical kernels. This paper covers recent, previously unpublished advances in the PyTrilinos package.

Two acceleration techniques, based on additive corrections are evaluated with a multithreaded 2D Poisson equation solver. The popular multigrid algorithm with 2-level grid is compared with the traditional block-correction strategy. In both, single-processor and distributed architectures, block correction is faster than the multigrid due mainly to the smaller cost that the solution of a 1D linear system has over one 2D linear system. Results in both cluster tested show that block correction can reduce significantly the computing time in the solution of very large linear systems. These calculations confirm that the Red/Black ordering is effective only if data fit entirely in cache memory. © 2012 Published by Elsevier Ltd.

"Sunshine to Petrol" is a grand-challenge research project at Sandia National Laboratories with the objective of creating a technology for producing feedstocks for making liquid fuels by splitting carbon dioxide (and water) using concentrated solar energy [1]. A reactor-level performance model is described for computing the solar-driven thermochemical splitting of carbon dioxide via a two-step metal-oxide cycle. The model simulates the thermochemical performance of the Counter-Rotating-Ring Receiver/Reactor/Recuperator (CR5). The numerical model for computing the reactor thermochemical performance is formulated as a system of coupled first-order ordinary differential equations describing the energy and mass transfer within each reactive ring and radiative energy transfer between adjacent rings. In this formulation, each of the counter-rotating rings is treated in a one-dimensional sense in the circumferential direction; supporting circumferential temperature and species gradients with assumed negligible gradients in both the radial and axial directions. The model includes radiative heat transfer between adjacent counter-rotating rings, variations in the incident solar flux distribution, heat losses to the reactor housing, and energy of reaction associated with the reduction and oxidation reactions. An overview of the physics included in this first-generation numerical model will be presented. Preliminary results include the circumferential distributions of temperature and species within each of the reactive rings. The computed overall chemical conversion efficiency will be presented for a range of design and operating parameters; including ring speed, carrier ring mass, reactive material loading, radiative emissivity, and differing incident flux distributions. Copyright © 2012 by ASME.

This paper will present the design of collective feedback controllers for the integration of renewable energy into networked DC bus microgrids. These feedback controllers are based on a single DC bus microgrid because the networked DC bus microgrids are self-similar. As a result, these feedback controllers are divided into two types. Type 1 is based on a feedback guidance command to determine the boost converter duty cycle. Type 2 is based on Hamiltonian Surface Shaping and Power Flow Control (HSSPFC) [1], [2], [3], [4], [5], [6] to determine the required distributed energy storage systems to ensure stability and performance. Two DC bus microgrids coupled with a transmission line is used as an example. This model architecture can vary from 0% energy storage with transient renewable energy supplies to 100% energy storage with fossil fuel energy supplies which will be useful in the future to demonstrate the benefits and costs of networked microgrids. © 2012 IEEE.

Toluene fuel-tracer laser-induced fluorescence is employed to quantitatively measure the equivalence ratio distributions in the cylinder of a light-duty diesel engine operating in a low-temperature, high-EGR, and early-injection operating mode. Measurements are made in a non-combusting environment at crank angles capturing the mixture preparation period: from the start-of-injection through the onset of high-temperature heat release. Three horizontal planes are considered: within the clearance volume, the bowl rim region, and the lower bowl. Swirl ratio and injection pressure are varied independently, and the impact of these parameters on the mixture distribution is correlated to the heat release rate and the engine-out emissions. As the swirl ratio or injection pressure is increased, the amount of over-lean mixture in the upper central region of the combustion chamber, in the bowl rim region and above, also increases. Unexpectedly, increased injection pressure results in a greater quantity of over-rich mixture within the squish volume. Copyright © 2012 by ASME.

Coupled thermal-mechanical, three-dimensional, finite-element analyses were used to evaluate generic design concepts for a repository in salt, for spent nuclear fuel and high-level waste. This work used heat generation by spent nuclear fuel (SNF) typical of that presently stored at reactor sites in the U.S. For waste packages containing 4-PWR SNF assemblies, the results show peak temperatures within previously identified ranges acceptable for salt media. Peak temperatures and maximum backfill consolidation occur at the package-salt interface. Significant consolidation of the backfill, and closure of the mined opening, is projected to continue after peak temperatures are realized. For larger 21-PWR SNF packages, the peak temperature could approach 450°C locally or lower, depending on the aging history of the fuel. This ongoing study suggests the feasibility of a SNF management strategy using decay storage and larger (e.g., 21-PWR) waste packages.

We demonstrate the effects of integrating a nanoantenna to a midwave infrared (MWIR) focal plane array (FPA). We model an antenna-coupled photodetector with a nanoantenna fabricated in close proximity to the active material of a photodetector. This proximity allows us to take advantage of the concentrated plasmonic fields of the nanoantenna. The role of the nanoantenna is to convert free-space plane waves into surface plasmons bound to a patterned metal surface. These plasmonic fields are concentrated in a small volume near the metal surface. Field concentration allows for a thinner layer of absorbing material to be used in the photodetector design and promises improvements in cutoff wavelength and dark current (higher operating temperature). While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The geometry of the nanoantenna-coupled detector is optimized to give maximal carrier generation in the active region of the photodiode, and fabrication processes must be altered to accommodate the nanoantenna structure. The intensity profiles and the carrier generation rates in the photodetector active layers are determined by finite element method simulations, and iteration between optical nanoantenna simulation and detector modeling is used to optimize the device structure. © 2012 SPIE.

Pyromark 2500 is a silicone-based high-temperature paint that has been used on central receivers to increase solar absorptance. The cost, application, curing methods, radiative properties, and absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to high-temperature solar selective absorber coatings currently being developed. The directional solar absorptance was calculated from directional spectral absorptance data, and values for pristine samples of Pyromark 2500 were as high as 0.96-0.97 at near normal incidence angles. At higher irradiance angles (>40° - 60°), the solar absorptance decreased. The total hemispherical emittance of Pyromark 2500 was calculated from spectral directional emittance data measured at room temperature and 600°C. The total hemispherical emittance values ranged from ∼0.80-0.89 at surface temperatures ranging from 100°C - 1,000°C. The aging and degradation of Pyromark 2500 with exposure at elevated temperatures were also examined. Previous tests showed that solar receiver panels had to be repainted after three years due to a decrease in solar absorptance to 0.88 at the Solar One central receiver pilot plant. Laboratory studies also showed that exposure of Pyromark 2500 at high temperatures (750°C and higher) resulted in significant decreases in solar absorptance within a few days. However, at 650°C and below, the solar absorptance did not decrease appreciably after several thousand hours of testing. Finally, the absorber efficiency of Pyromark 2500 was determined as a function of temperature and irradiance using the calculated solar absorptance and emittance values presented in this paper. Copyright © 2012 by ASME.

Solar Two was a demonstration of the viability of molten salt power towers. The power tower was designed to produce enough thermal power to run a 10-MWe conventional Rankine cycle turbine. A critical component of this process was the solar tower receiver. The receiver was designed for an applied average heat flux of 430 kW/m2 with an outlet temperature of 565°C (838.15 K). The mass flow rate could be varied in the system to control the outlet temperature of the heat transfer fluid, which was high temperature molten salt. The heat loss in the actual system was calculated by using the power-on method which compares how much power is absorbed by the molten salt when using half of the heliostat field and then the full heliostat field. However, the total heat loss in the system was lumped into a single value comprised of radiation, convection, and conduction heat transfer losses. In this study, ANSYS FLUENT was used to evaluate and characterize the radiative and convective heat losses from this receiver system assuming two boundary conditions: (1) a uniform heat flux on the receiver and (2) a distributed heat flux generated from the code DELSOL. The results show that the distributed-flux models resulted in radiative heat losses that were ∼14% higher than the uniform-flux models, and convective losses that were ∼5-10% higher due to the resulting non-uniform temperature distributions. Comparing the simulations to known convective heat loss correlations demonstrated that surface roughness should be accounted for in the simulations. This study provides a model which can be used for further receiver design and demonstrates whether current convective correlations are appropriate for analytical evaluation of external solar tower receivers. Copyright © 2012 by ASME.

In lithium-ion batteries, the electrochemical reaction between the electrodes and lithium is a critical process that controls the capacity, cyclability and reliability of the battery. Despite intensive study, the atomistic mechanism of the electrochemical reactions occurring in these solid-state electrodes remains unclear. Here, we show that in situ transmission electron microscopy can be used to study the dynamic lithiation process of single-crystal silicon with atomic resolution. We observe a sharp interface (∼1 μnm thick) between the crystalline silicon and an amorphous Li x Si alloy. The lithiation kinetics are controlled by the migration of the interface, which occurs through a ledge mechanism involving the lateral movement of ledges on the close-packed {111} atomic planes. Such ledge flow processes produce the amorphous Li x Si alloy through layer-by-layer peeling of the {111} atomic facets, resulting in the orientation-dependent mobility of the interfaces. © 2012 Macmillan Publishers Limited. All rights reserved.

We obtained single-mode lasing in GaN nanowires by using a limited number of cavity modes and a narrow gain spectra. The fabrication was achieved by a top-down technique in high quality GaN films. © OSA 2012.

Hydrocarbon polymers, foams and nanocomposites are increasingly being subjected to extreme environments. Molecular scale modeling of these materials offers insight into failure mechanisms and complex response. Classical molecular dynamics (MD) simulations of the principal shock Hugoniot were conducted for two hydrocarbon polymers, polyethylene (PE) and poly(4-methyl-1-pentene) (PMP). We compare these results with recent density functional theory (DFT) calculations and experiments conducted at Sandia National Laboratories. Here, we extend these results to include low-density polymer foams using nonequilibrium MD techniques. We find good quantitative agreement with experiment. Further, we have measured local temperatures to investigate the formation of hot spots and polymer dissociation near foam voids.

We explore the spectral and angular selectivity of near surface normal transmission of grating modified metallic surfaces and their ultimate potential for application as narrow-band spectro-polarimetric planar filter components in the development of advanced infrared focal plane arrays. The developed photonic microstructures exhibit tailored spectral transmission characteristics in the long wavelength infrared, and can be fabricated to preferentially transmit a given linear polarization within the design band. Modification of the material and structural properties of the diffractive optical element enables sub-pixel tuning of the spectro-polarimetric response of the device allowing for intelligent engineering of planar filter components for development of advanced focal plane arrays in the long wavelength infrared. The planar nature of the developed components leaves them immune to fabrication issues that typically plague thin film interference filters used for similar applications in the infrared, namely, deposition of multiple low-stress quarter-wavelength films and modification of the film thicknesses for each pixel. The solution developed here presents the opportunity for subpixel modification of the spectral response leading to an efficient, versatile filter component suitable for direct integration with commercially available focal plane array technologies via standard fabrication techniques. We will discuss the theoretical development and analysis of the described components and compare the results to the current state-of-the-art. © 2012 SPIE.

A near infrared (NIR) and long-wavelength infrared (LWIR) dual-band infrared photodetector, which can switch detection bands with light bias, is demonstrated at 77 K. The demonstrated scheme consists of series connected photodetectors for different bands. The basic operating principle of the scheme is that without light bias, shorter wavelength detector limits the total current and thus the device operates in NIR mode. With light bias on the NIR detector, the LWIR detector becomes the current limiting device and the device then operates in LWIR mode. Proposed design allows single indium-bump per pixel focal plane arrays, and in principle allows covering all tactical bands such as UV, visible, NIR, SWIR, MWIR and LWIR bands with a single pixel. © 2012 SPIE.

An approach for incorporating embedded simulation and analysis capabilities in complex simulation codes through template-based generic programming is presented. This approach relies on templating and operator overloading within the C++ language to transform a given calculation into one that can compute a variety of additional quantities that are necessary for many state-of-the-art simulation and analysis algorithms. An approach for incorporating these ideas into complex simulation codes through general graph-based assembly is also presented. These ideas have been implemented within a set of packages in the Trilinos framework and are demonstrated on a simple problem from chemical engineering. © 2012 - IOS Press and the authors. All rights reserved.

Modal-based methods for structural health monitoring require the identification of characteristic frequencies associated with a structure's primary modes of failure. A major difficulty is the extraction of damage-related frequency shifts from the large set of often benign frequency shifts observed experimentally. In this study, we apply peridynamics in combination with modal analysis for the prediction of characteristic frequency shifts throughout the damage evolution process. Peridynamics, a nonlocal extension of continuum mechanics, is unique in its ability to capture progressive material damage. The application of modal analysis to peridynamic models enables the tracking of structural modes and characteristic frequencies over the course of a simulation. Shifts in characteristic frequencies resulting from evolving structural damage can then be isolated and utilized in the analysis of frequency responses observed experimentally. We present a methodology for quasi-static peridynamic analyses, including the solution of the eigenvalue problem for identification of structural modes. Repeated solution of the eigenvalue problem over the course of a transient simulation yields a data set from which critical shifts in modal frequencies can be isolated. The application of peridynamics to modal analysis is demonstrated on the benchmark problem of a simply-supported beam. The computed natural frequencies of an undamaged beam are found to agree well with the classical local solution. Analyses in the presence of cracks of various lengths are shown to reveal frequency shifts associated with structural damage. Copyright © 2012 by ASME.

Unidirectional carbon fiber reinforced epoxy composite samples were tested to determine the response to one dimensional shock loading. The material tested had high fiber content (68% by volume) and low porosity. Wave speeds for shocks traveling along the carbon fibers are significantly higher than for those traveling transverse to the fibers or through the bulk epoxy. As a result, the dynamic material response is dependent on the relative shock - fiber orientation. Shocks traveling along the fiber direction in uniaxial samples travel faster and exhibit both elastic and plastic characteristics over the stress range tested; up to 15 GPa. Results detail the anisotropic material response which is governed by different mechanisms along each of the two principle directions in the composite.

The longitudinal merging of wave packets and turbulent spots in a hypersonic boundary layer was studied on the nozzle wall of the Boeing/AFOSR Mach-6 Quiet Tunnel. Two pulsed glow perturbations were created in rapid succession to generate two closely spaced disturbances. The time between the perturbations was varied from run to run to simulate longitudinal merging. Preliminary results suggest that the growth of the trailing distur- bance seems to be suppressed by the presence of the leading disturbance. Conversely, the core of the leading disturbance appears unaffected by the presence of the trailing distur- bance and behaves as if isolated. This result is consistent with low-speed studies as well as DNS computations of longitudinal merging. However, the present results may be influ- enced by the perturber performance and therefore further studies of longitudinal merging are necessary to confirm the effect on the internal pressure structure of the interacting disturbances.

Steel pressure vessels are commonly used for the transport of pressurized gases, including gaseous hydrogen. In the majority of cases, these transport cylinders experience relatively few pressure cycles over their lifetime, perhaps as many as 25 per year, and generally significantly less. For fueling applications, as in fuel tanks on hydrogen-powered industrial trucks, the hydrogen fuel systems may experience thousands of cycles over their lifetime. Similarly, it can be anticipated that the use of tube trailers for large-scale distribution of gaseous hydrogen will require lifetimes of thousands of pressure cycles. This study investigates the fatigue life of steel pressure vessels that are similar to transport cylinders by subjecting full-scale vessels to pressure cycles with gaseous hydrogen between nominal pressure of 3 and 44 MPa. In addition to pressure cycling of vessels that are similar to those in service, engineered defects were machined on the inside of several pressure vessels to simulate manufacturing defects and to initiate failure after relatively low number of cycles. Failure was not observed in as-manufactured vessels with more than 55,000 pressure cycles, nor in vessels with relatively small, engineered defects subjected to more than 40,000 cycles. Large engineered defects (with depth greater than 5% of the wall thickness) resulted in failure after 8,000 to 15,000 pressure cycles. Defects machined to depths less than 5% wall thickness did not induce failures. Four pressure vessel failures were observed during the course of this project and, in all cases, failure occurred by leak before burst. The performance of the tested vessels is compared to two design approaches: fracture mechanics design approach and traditional fatigue analysis design approach. The results from this work have been used as the basis for the design rules for Type 1 fuel tanks in the standard entitled "Compressed Hydrogen-Powered Industrial Truck, On-board Fuel Storage and Handling Components (HPIT1)" from CSA America. Copyright © 2012 by ASME.

Steel pressure vessels are commonly used for the transport of pressurized gases, including gaseous hydrogen. In the majority of cases, these transport cylinders experience relatively few pressure cycles over their lifetime, perhaps as many as 25 per year, and generally significantly less. For fueling applications, as in fuel tanks on hydrogen-powered industrial trucks, the hydrogen fuel systems may experience thousands of cycles over their lifetime. Similarly, it can be anticipated that the use of tube trailers for large-scale distribution of gaseous hydrogen will require lifetimes of thousands of pressure cycles. This study investigates the fatigue life of steel pressure vessels that are similar to transport cylinders by subjecting full-scale vessels to pressure cycles with gaseous hydrogen between nominal pressure of 3 and 44 MPa. In addition to pressure cycling of vessels that are similar to those in service, engineered defects were machined on the inside of several pressure vessels to simulate manufacturing defects and to initiate failure after relatively low number of cycles. Failure was not observed in as-manufactured vessels with more than 55,000 pressure cycles, nor in vessels with relatively small, engineered defects subjected to more than 40,000 cycles. Large engineered defects (with depth greater than 5% of the wall thickness) resulted in failure after 8,000 to 15,000 pressure cycles. Defects machined to depths less than 5% wall thickness did not induce failures. Four pressure vessel failures were observed during the course of this project and, in all cases, failure occurred by leak before burst. The performance of the tested vessels is compared to two design approaches: fracture mechanics design approach and traditional fatigue analysis design approach. The results from this work have been used as the basis for the design rules for Type 1 fuel tanks in the standard entitled "Compressed Hydrogen-Powered Industrial Truck, On-board Fuel Storage and Handling Components (HPIT1)" from CSA America. Copyright © 2012 by ASME.

Impact is a phenomenon that is ubiquitous in mechanical design; however, the modeling of impacts in complex systems is often a simplified, imprecise process. In high fidelity finite element simulations, the number of elements required to accurately model the constitutive properties of an impact event is impractical. Consequently, rigid body dynamics with approximate representations of the impact dynamics are commonly used. These approximations can include a constant coefficient of restitution, penalty stiffness, or single degree of freedom constitutive model for the impact dynamics that is specific to the type of materials involved (elastic-plastic, viscoelastic, etc.). In order to understand the effect of the impact model on the system's dynamics, simulations investigate single degree of freedom and two degrees of freedom systems with rigid stops limiting the amplitude of vibration. Five contact models are considered: a coefficient of restitution, penalty stiffness, two similar elastic-plastic constitutive models, and a dissimilar elastic-plastic constitutive model. Frequency sweeps show that simplified contact models can lead to incorrect assessments of the system's dynamics and stability, which can significantly affect the prediction of wear and damage in the system.

Christopher J. Orendorff shares his views on the role of separators in lithium-ion cell safety. One of the most critically important cell components to ensure cell safety is the separator, which is a thin porous membrane that physically separates the anode and cathode. The main function of the separator is to prevent physical contact between the anode and cathode, while facilitating ion transport in the cell. The challenge with designing safe battery separators is the trade-off between mechanical robustness and porosity/transport properties. Most commercially available nonaqueous lithium-ion separators designed for small batteries are single layer made of polyoleins. Many of the multilayer separators are designed with a shutdown feature where two of the layers have different phase transition temperatures. The lower melting component melts and fills the pores of the other solid layer and stops ion transport and current low in the cell, as the temperature of a cell increases.

This paper provides an analysis of high-pressure phenomena and its potential effects on the fundamental physics of fuel injection in Diesel engines. We focus on conditions when cylinder pressures exceed the thermodynamic critical pressure of the injected fuel and describe the major differences that occur in the jet dynamics compared to that described by classical spray theory. To facilitate the analysis, we present a detailed model framework based on the Large Eddy Simulation (LES) technique that is designed to account for key high-pressure phenomena. Using this framework, we perform a detailed analysis using the experimental data posted as part of the Engine Combustion Network (see www.sandia.gov/ECN): namely the "Baseline n-heptane" and "Spray-A (n-dodecane)" cases, which are designed to emulate conditions typically observed in Diesel engines. Calculations are performed by rigorously treating the experimental geometry, operating conditions and relevant thermo-physical gas-liquid mixture properties. Results are further processed using linear gradient theory, which facilitates calculations of detailed vapor-liquid interfacial structures, and compared with the high-speed imaging data. Analysis of the data reveals that fuel enters the chamber as a compressed liquid and is heated at supercritical pressure. Further analysis suggests that, at certain conditions studied here, the classical view of spray atomization as an appropriate model is questionable. Instead, nonideal real-fluid behavior must be taken into account using a multicomponent formulation that applies to arbitrary hydrocarbon mixtures at high-pressure supercritical conditions.

While DNA sequencing technology is advancing at an unprecedented rate, sample preparation technology still relies primarily on manual bench-top processes, which often can be slow, labor-intensive, inefficient, or inconsistent. To address these disadvantages, we developed an integrated microfluidic platform for automated preparation of DNA libraries for next generation sequencing. This sample-to-answer system has great potential for rapid characterization of novel and emerging pathogens from clinical samples.

Human reliability analysis (HRA) is used in the context of probabilistic risk assessment (PRA) to provide risk information regarding human performance to support risk-informed decision-making with respect to high-reliability industries. In the current state of the art of HRA, variability in HRA results is still a significant issue, which in turn contributes to uncertainty in PRA results. The existence and use of different HRA methods that rely on different assumptions, human performance frameworks, quantification algorithms, and data, as well as inconsistent implementation from analysts, appear to be the most common sources for the issue, and such issue has raised concerns over the robustness of HRA methods. In two large scale empirical studies (Bye et al., 2012; Forester et al., 2012), the Accident Sequence Evaluation Program (ASEP) HRA Procedure, along with other HRA methods, was used to obtain HRA predictions for the human failure events (HFEs) in accident scenarios. The predictions were then compared with empirical crew performance data from nuclear power plant (NPP) simulators by independent assessors to examine the reasonableness of the predictions. This paper first provides a brief overview of the study methodology and results, and then discusses the study findings with respect to ASEP and their implications in the context of challenges to HRA in general.

Pyromark 2500 is a silicone-based high-temperature paint that has been used on central receivers to increase solar absorptance. The cost, application, curing methods, radiative properties, and absorber efficiency of Pyromark 2500 are presented in this paper for use as a baseline for comparison to high-temperature solar selective absorber coatings currently being developed. The directional solar absorptance was calculated from directional spectral absorptance data, and values for pristine samples of Pyromark 2500 were as high as 0.96-0.97 at near normal incidence angles. At higher irradiance angles (>40° - 60°), the solar absorptance decreased. The total hemispherical emittance of Pyromark 2500 was calculated from spectral directional emittance data measured at room temperature and 600°C. The total hemispherical emittance values ranged from ∼0.80-0.89 at surface temperatures ranging from 100°C - 1,000°C. The aging and degradation of Pyromark 2500 with exposure at elevated temperatures were also examined. Previous tests showed that solar receiver panels had to be repainted after three years due to a decrease in solar absorptance to 0.88 at the Solar One central receiver pilot plant. Laboratory studies also showed that exposure of Pyromark 2500 at high temperatures (750°C and higher) resulted in significant decreases in solar absorptance within a few days. However, at 650°C and below, the solar absorptance did not decrease appreciably after several thousand hours of testing. Finally, the absorber efficiency of Pyromark 2500 was determined as a function of temperature and irradiance using the calculated solar absorptance and emittance values presented in this paper. Copyright © 2012 by ASME.

Central receiver power towers are regarded as a proven concentrating solar power (CSP) technology for generating utility-scale electricity. In central receiver systems, improper alignment (canting and focusing) of heliostat facets results in beam spillage at the receiver and leads to significant degradation in performance. As a result, proper alignment of heliostats is critical for increasing plant efficiency. Past tools used for analyzing and correcting heliostat alignment at the National Solar Thermal Test Facility (NSTTF) have proven to be laborious and inaccurate, sometimes taking up to six hours per heliostat. In light of these drawbacks, Sandia National Labs (SNL) and New Mexico Tech (NMT) have created the Heliostat Focusing and Canting Enhancement Technique (H-FACET). H-FACET uses a high-resolution digital camera to observe the image of a stationary target reflected by a heliostat facet. By comparing this image to a theoretical image generated via a custom software package, technicians can efficiently identify and correct undesirable deviations in facet orientation and shape. Previous tests have only proven the viability of H-FACET for canting heliostats. As a result, SNL and NMT have expanded H-FACET's capabilities and analyzed the system's ability to simultaneously cant and focus heliostats. Initial H-FACET focusing test results have shown improved beam sizes and shapes for single facets. Furthermore, simulations of these tests revealed an approximated system accuracy of better than 1.80 milliradians. This accuracy accounted for technician, position, and additional error sources, suggesting that H-FACET was capable of focusing facets to an even greater accuracy than those seen in the initial tests. When implemented for simultaneous canting and focusing of heliostats, H-FACET has demonstrated its capability to increase peak flux and decrease beam size. These full alignment test results demonstrated an average total system accuracy of 1.17 milliradians on five heliostats. As before, this accuracy included multiple error sources which cannot be corrected by H-FACET. Additionally, these tests revealed that H-FACET can align heliostats in about 1 hour and 30 minutes. Finally, two heliostats aligned with H-FACET maintained average accuracies 1.46 and 1.24 milliradians over a four hour window centered about solar noon. This implies that H-FACET is capable of aligning heliostats to a true off-axis alignment over NSTTF's operating window. In light of these results, SNL has implemented both the focusing and canting portions of H-FACET at the NSTTF. Copyright © 2012 by ASME.

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Serious games present a relatively new approach to training and education for Defense and Homeland Security. Although serious games are often deployed as stand-alone solutions, they can also serve as entry points into training content that is delivered via different media. The present paper explores the application of transmedia storytelling used by entertainment, advertising, and the commercial game industries to sustain audience engagement with memorable experiences. Transmedia storytelling is the art and science of designing a consistent message that is delivered and reinforced across multiple media utilizing diverse entry points into a narrative to generate audience involvement with content. This approach is consistent with the goals of the Army Learning Model 2015 to deliver training and education to Soldiers across multiple media. Transmedia storytelling also provides a practical framework for developing media-rich training. In the present paper, we introduce the notion of transmedia storytelling, also known as transmedia or cross-media, as related to the use of serious games for training and education. We discuss why the human brain is wired for transmedia storytelling and demonstrate how the Simulation Experience Design Method can be used to create transmedia story worlds and serious games. Examples of how the U.S. Army has utilized transmedia for strategic communication and game-based training are provided. Finally, we conclude with strategies the reader can use today to incorporate transmedia storytelling elements such as Internet, TV, radio, print, social media, graphic novels, machinima, blogs, and alternate reality gaming into defense and homeland security serious game training. Copyright© (2012) by CAL-TEK S.r.l.

We studied theoretically the laser-plasma interaction, and performed experiments to investigate the mechanisms giving rise to optical damage in Borosilicate glass using nanosecond laser pulses at wavelength 1064 nm. Our experimental result shows that the optical damage process generated by nanosecond laser pulses is the result of an optically induced plasma. The plasma is initiated when the laser irradiance frees electrons from the glass. Although it may be debated, the electrons are likely freed by multi-photon absorption and the number density grows via impact ionization. Later when the electron gas density reaches the critical density, the electron gas resonantly absorbs the laser beam through collective excitation since the laser frequency is equal to the plasma frequency. The laser energy absorbed through the collective excitation is much larger than the energy absorbed by multi-photon ionization and impact ionization. Our experimental result also shows the plasma survives until the end of the laser pulse and the optical damage occurs after the laser pulse ceases. The plasma decay releases heat to the lattice. This heat causes the glass to be molten and soft. It is only as the glass cools and solidifies that stresses induced by this process cause the glass to fracture and damage. We also show the experimental evidence of the change of the refractive index of the focusing region as the density of the electron gas changes from sub-critical to overcritical, and the reflection of the over-critical plasma. This reflection limits the electron gas density to be not much larger than the critical density. © 2012 SPIE.

We report on unique heterogeneous multijunction solar cell structures being created with advanced micro-and nano-system technologies with the potential for enhanced efficiency by removing or reducing losses present in traditional monolithic multijunction solar cells. © 2012 OSA.

Thermal rectification occurs when a device permits heat to flow preferentially in one direction direction while restricting it in the opposite direction. Thermal rectification can occur whenever an asymmetry is present in a device, and has been demonstrated to arise in bulk materials that have asymmetric geometry, in the contact of two materials with different thermal properties and in nanomaterials. Herein, a thermal diode that utilizes thermal expansion to directionally control interfacial conductance between two contacting surfaces is presented. Essentially, the device consists of two thermal reservoirs contacting a beam with one rough and one smooth end. When the temperature of reservoir in contact with the smooth surface is raised, a similar temperature rise will occur in the beam, causing it to expand, thus increasing the contact pressure at the rough interface and reducing the interfacial contact resistance. However, if the temperature of the reservoir in contact with the rough interface is raised, the large contact resistance will prevent a similar temperature rise in the beam. As a result, the contact pressure will be marginally affected and the contact resistance will not change appreciably. Owing to the decreased contact resistance of the first scenario compared to the second, thermal rectification occurs. A parametric analysis is used to determine optimal device parameters including surface roughness, contact pressure and device length. Modeling predicts rectification factors greater than 2 are possible at thermal biases as small as 3 K. Copyright © 2012 by ASME.

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The Advanced Concepts Group at Sandia National Laboratory and the Consortium for Science, Policy and Outcomes at Arizona State University convened a workshop in May 2006 to explore the potential policy implications of technologies that might enhance human cognitive abilities. The group's deliberations sought to identify core values and concerns raised by the prospect of cognitive enhancement. The workshop focused on the policy implications of various prospective cognitive enhancements and on the technologies/nanotechnology, biotechnology, information technology, and cognitive science--that enable them. The prospect of rapidly emerging technological capabilities to enhance human cognition makes urgent a daunting array of questions, tensions, ambitions, and concerns. The workshop elicited dilemmas and concerns in ten overlapping areas: science and democracy; equity and justice; freedom and control; intergenerational issues; ethics and competition; individual and community rights; speed and deliberations; ethical uncertainty; humanness; and sociocultural risk. We identified four different perspectives to encompass the diverse issues related to emergence of cognitive enhancement technologies: (1) Laissez-faire--emphasizes freedom of individuals to seek and employ enhancement technologies based on their own judgment; (2) Managed technological optimism--believes that while these technologies promise great benefits, such benefits cannot emerge without an active government role; (3) Managed technological skepticism--views that the quality of life arises more out of society's institutions than its technologies; and (4) Human Essentialism--starts with the notion of a human essence (whether God-given or evolutionary in origin) that should not be modified. While the perspectives differ significantly about both human nature and the role of government, each encompasses a belief in the value of transparency and reliable information that can allow public discussion and decisions about cognitive enhancement. The practical question is how to foster productive discussions in a society whose attention is notably fragmented and priorities notably diverse. The question of what to talk about remains central, as each of the four perspectives is concerned about different things. Perhaps the key issue for initial clarification as a condition for productive democratic discussion has to do with the intended goals of cognitive enhancement, and the mechanisms for allowing productive deliberation about these goals.

We present a maximum-entropy theory of mesoscopic kinetics. The theory gives fully nonlinear nonequilibrium thermodynamic relationships and has no explicit requirement for either microscopic bath variables, an equilibrium energy, or an equilibrium partition function. The entropy maximization process is instead carried out over transition probability distributions with constraints on particle position and velocity updates. The Lagrange multipliers for these constraints express the instantaneous temperature and pressure of external (or microscopic) thermostatic driving systems, with which the distinguished system may or may not eventually reach equilibrium. We show that the analogues of the Gibbs-Maxwell relations and free energy perturbation techniques carry over to fluctuation-dissipation theorems and nonequilibrium ensemble reweighting techniques as should be expected. The result is a fully time-dependent, non-local description of a nonequilibrium ensemble coupled to reservoirs at possibly time-varying thermostatic or mechanical states. We also show that the thermodynamic entropy production extends the generalized fluctuation theorem through the addition of an instantaneous information entropy term for the end-points, leading to a concise statement of the second law of thermodynamics. © Published under licence by IOP Publishing Ltd.

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Over the last several years, there has been considerable growth in camera based observation systems for a variety of safety, scientific, and recreational applications. In order to improve the effectiveness of these systems, we frequently desire the ability to increase the number of observed objects, but solving this problem is not as simple as adding more cameras. Quite often, there are economic or physical restrictions that prevent us from adding additional cameras to the system. As a result, we require methods that coordinate the tracking of objects between multiple cameras in an optimal way. In order to accomplish this goal, we present a new cooperative control algorithm for a camera based observational system. Specifically, we present a receding horizon control where we model the underlying optimal control problem as a mixed integer linear program. The benefit of this design is that we can coordinate the actions between each camera while simultaneously respecting its kinematics. In addition, we further improve the quality of our solution by coupling our algorithm with a Kalman filter. Through this integration, we not only add a predictive component to our control, but we use the uncertainty estimates provided by the filter to encourage the system to periodically observe any outliers in the observed area. This combined approach allows us to intelligently observe the entire region of interest in an effective and thorough manner.

Density Functional Theory (DFT) based Equation of State (EOS) construction is a prominent part of Sandia's capabilities to support engineering sciences. This capability is based on amending experimental data with information gained from computational investigations, in parts of the phase space where experimental data is hard, dangerous, or expensive to obtain. A prominent materials area where such computational investigations are hard to perform today because of limited accuracy is actinide and lanthanide materials. The Science of Extreme Environment Lab Directed Research and Development project described in this Report has had the aim to cure this accuracy problem. We have focused on the two major factors which would allow for accurate computational investigations of actinide and lanthanide materials: (1) The fully relativistic treatment needed for materials containing heavy atoms, and (2) the needed improved performance of DFT exchange-correlation functionals. We have implemented a fully relativistic treatment based on the Dirac Equation into the LANL code RSPt and we have shown that such a treatment is imperative when calculating properties of materials containing actinides and/or lanthanides. The present standard treatment that only includes some of the relativistic terms is not accurate enough and can even give misleading results. Compared to calculations previously considered state of the art, the Dirac treatment gives a substantial change in equilibrium volume predictions for materials with large spin-orbit coupling. For actinide and lanthanide materials, a Dirac treatment is thus a fundamental requirement in any computational investigation, including those for DFT-based EOS construction. For a full capability, a DFT functional capable of describing strongly correlated systems such as actinide materials need to be developed. Using the previously successful subsystem functional scheme developed by Mattsson et.al., we have created such a functional. In this functional the Harmonic Oscillator Gas is providing the necessary reference system for the strong correlation and localization occurring in actinides. Preliminary testing shows that the new Hao-Armiento-Mattsson (HAM) functional gives a trend towards improved results for the crystalline copper oxide test system we have chosen. This test system exhibits the same exchange-correlation physics as the actinide systems do, but without the relativistic effects, giving access to a pure testing ground for functionals. During the work important insights have been gained. An example is that currently available functionals, contrary to common belief, make large errors in so called hybridization regions where electrons from different ions interact and form new states. Together with the new understanding of functional issues, the Dirac implementation into the RSPt code will permit us to gain more fundamental understanding, both quantitatively and qualitatively, of materials of importance for Sandia and the rest of the Nuclear Weapons complex.

This report details the current progress in the design, implementation, and validation of the signal conditioning circuitry used in a measurement instrumentation system. The purpose of this text is to document the current progress of a particular design in signal conditioning circuitry in an instrumentation system. The input of the signal conditioning circuitry comes from a piezoresistive transducer and the output will be fed to a 250 ksps, 12-bit analog-to-digital converter (ADC) with an input range of 0-5 V. It is assumed that the maximum differential voltage amplitude input from the sensor is 20 mV with an unknown, but presumably high, sensor bandwidth. This text focuses on a specific design; however, the theory is presented in such a way that this text can be used as a basis for future designs.

This Lab-Directed Research and Development (LDRD) sought to develop technology that enhances scenario construction speed, entity behavior robustness, and scalability in Live-Virtual-Constructive (LVC) simulation. We investigated issues in both simulation architecture and behavior modeling. We developed path-planning technology that improves the ability to express intent in the planning task while still permitting an efficient search algorithm. An LVC simulation demonstrated how this enables 'one-click' layout of squad tactical paths, as well as dynamic re-planning for simulated squads and for real and simulated mobile robots. We identified human response latencies that can be exploited in parallel/distributed architectures. We did an experimental study to determine where parallelization would be productive in Umbra-based force-on-force (FOF) simulations. We developed and implemented a data-driven simulation composition approach that solves entity class hierarchy issues and supports assurance of simulation fairness. Finally, we proposed a flexible framework to enable integration of multiple behavior modeling components that model working memory phenomena with different degrees of sophistication.

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This document reports on the research of Kenneth Letendre, the recipient of a Sandia Graduate Research Fellowship at the University of New Mexico. Warfare is an extreme form of intergroup competition in which individuals make extreme sacrifices for the benefit of their nation or other group to which they belong. Among animals, limited, non-lethal competition is the norm. It is not fully understood what factors lead to warfare. We studied the global variation in the frequency of civil conflict among countries of the world, and its positive association with variation in the intensity of infectious disease. We demonstrated that the burden of human infectious disease importantly predicts the frequency of civil conflict and tested a causal model for this association based on the parasite-stress theory of sociality. We also investigated the organization of social foraging by colonies of harvester ants in the genus Pogonomyrmex, using both field studies and computer models.

A lightning flash consists of multiple, high-amplitude but short duration return strokes. Between the return strokes is a lower amplitude, continuing current which flows for longer duration. If the walls of a Faraday cage are made of thin enough metal, the continuing current can melt a hole through the metal in a process called burnthrough. A subsequent return stroke can couple energy through this newly-formed hole. This LDRD is a study of the protection provided by a Faraday cage when it has been compromised by burnthrough. We initially repeated some previous experiments and expanded on them in terms of scope and diagnostics to form a knowledge baseline of the coupling phenomena. We then used a combination of experiment, analysis and numerical modeling to study four coupling mechanisms: indirect electric field coupling, indirect magnetic field coupling, conduction through plasma and breakdown through the hole. We discovered voltages higher than those encountered in the previous set of experiments (on the order of several hundreds of volts).

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Since May 2010, we have been recording continuous seismic data at Sandia's FACT site. The collected signals provide us with a realistic archive for testing algorithms under development for local monitoring of explosive testing. Numerous small explosive tests are routinely conducted around Kirtland AFB by different organizations. Our goal is to identify effective methods for distinguishing these events from normal daily activity on and near the base, such as vehicles, aircraft, and storms. In this report, we describe the recording system, and present some observations of the varying ambient noise conditions at FACT. We present examples of various common, non-explosive, sources. Next we show signals from several small explosions, and discuss their characteristic features.

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A fully coupled electrochemical and thermal model for lithium-ion batteries is developed to investigate the impact of different thermal management strategies on battery performance. In contrast to previous modeling efforts focused either exclusively on particle electrochemistry on the one hand or overall vehicle simulations on the other, the present work predicts local electrochemical reaction rates using temperature-dependent data on commercially available batteries designed for high rates (C/LiFePO₄) in a computationally efficient manner. Simulation results show that conventional external cooling systems for these batteries, which have a low composite thermal conductivity (~1 W/m-K), cause either large temperature rises or internal temperature gradients. Thus, a novel, passive internal cooling system that uses heat removal through liquid-vapor phase change is developed. Although there have been prior investigations of phase change at the microscales, fluid flow at the conditions expected here is not well understood. A first-principles based cooling system performance model is developed and validated experimentally, and is integrated into the coupled electrochemical-thermal model for assessment of performance improvement relative to conventional thermal management strategies. The proposed cooling system passively removes heat almost isothermally with negligible thermal resistances between the heat source and cooling fluid. Thus, the minimization of peak temperatures and gradients within batteries allow increased power and energy densities unencumbered by thermal limitations.

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We report the development of new experimental capabilities and ab initio modeling for real-time studies of Li-ion battery electrochemical reactions. We developed three capabilities for in-situ transmission electron microscopy (TEM) studies: a capability that uses a nanomanipulator inside the TEM to assemble electrochemical cells with ionic liquid or solid state electrolytes, a capability that uses on-chip assembly of battery components on to TEM-compatible multi-electrode arrays, and a capability that uses a TEM-compatible sealed electrochemical cell that we developed for performing in-situ TEM using volatile battery electrolytes. These capabilities were used to understand lithiation mechanisms in nanoscale battery materials, including SnO₂, Si, Ge, Al, ZnO, and MnO₂. The modeling approaches used ab initio molecular dynamics to understand early stages of ethylene carbonate reduction on lithiated-graphite and lithium surfaces and constrained density functional theory to understand ethylene carbonate reduction on passivated electrode surfaces.

This document is a final report for the polyvinyl toluene (PVT) neutron-gamma (PVT-NG) project, which was sponsored by the Domestic Nuclear Detection Office (DNDO). The PVT-NG sensor uses PVT detectors for both gamma and neutron detection. The sensor exhibits excellent spectral resolution and gain stabilization, which are features that are beneficial for detection of both gamma-ray and neutron sources. In fact, the ability to perform isotope identification based on spectra that were measured by the PVT-NG sensor was demonstrated. As described in a previous report, the neutron sensitivity of the first version of the prototype was about 25% less than the DNDO requirement of 2.5 cps/ng for bare ²⁵²Cf. This document describes design modifications that were expected to improve the neutron sensitivity by about 50% relative to the PVT-NG prototype. However, the project was terminated before execution of the design modifications after portal vendors demonstrated other technologies that enable neutron detection without the use of ³He. Nevertheless, the PVT-NG sensor development demonstrated several performance goals that may be useful in future portal designs.

Uncertainty quantification (UQ) methods bring rigorous statistical connections to the analysis of computational and experiment data, and provide a basis for probabilistically assessing margins associated with safety and reliability. The DAKOTA toolkit developed at Sandia National Laboratories implements a number of UQ methods, which are being increasingly adopted by modeling and simulation teams to facilitate these analyses. This report disseminates results as to the performance of DAKOTA's stochastic expansion methods for UQ on a representative application. Our results provide a number of insights that may be of interest to future users of these methods, including the behavior of the methods in estimating responses at varying probability levels, and the expansion levels for the methodologies that may be needed to achieve convergence.

The Department of Defense (DoD) provides its standard for information assurance in its Instruction 8500.2, dated February 6, 2003. This Instruction lists 157 'IA Controls' for nine 'baseline IA levels.' Aside from distinguishing IA Controls that call for elevated levels of 'robustness' and grouping the IA Controls into eight 'subject areas' 8500.2 does not examine the nature of this set of controls, determining, for example, which controls do not vary in robustness, how this set of controls compares with other such sets, or even which controls are required for all nine baseline IA levels. This report analyzes (1) the IA Controls, (2) the subject areas, and (3) the Baseline IA levels. For example, this report notes that there are only 109 core IA Controls (which this report refers to as 'ICGs'), that 43 of these core IA Controls apply without variation to all nine baseline IA levels and that an additional 31 apply with variations. This report maps the IA Controls of 8500.2 to the controls in NIST 800-53 and ITGI's CoBIT. The result of this analysis and mapping, as shown in this report, serves as a companion to 8500.2. (An electronic spreadsheet accompanies this report.)

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Micro-Gas-Analyzers have many applications in detecting chemical compounds present in the air. MEMS valves are used to perform sampling of gasses, as they enable control of fluid flow at the micro level. Current generation electrostatically actuated MEMS valves were tested to determine their ability to hold off a given gauge pressure with an applied voltage. Current valve designs were able to hold off 98 psi with only 82 V applied to the valves. The valves were determined to be 1.83 times more efficient than older valve designs, due to increasing the electrostatic area of the valve and trapping oxide between polysilicon layers. Newer valve designs were also proposed and modeled using ANSYS multiphysics, which should be able to hold off 100 psi with only 29 V needed. This performance would be 2.82 times more efficient than current designs, or 5.17 times more efficient than older valve designs. This will be accomplished by further increasing the valve radius and decreasing the gap between the valve boss and electrode.

In this work, we demonstrated engineered modification of propagation of thermal phonons, i.e. at THz frequencies, using phononic crystals. This work combined theoretical work at Sandia National Laboratories, the University of New Mexico, the University of Colorado Boulder, and Carnegie Mellon University; the MESA fabrication facilities at Sandia; and the microfabrication facilities at UNM to produce world-leading control of phonon propagation in silicon at frequencies up to 3 THz. These efforts culminated in a dramatic reduction in the thermal conductivity of silicon using phononic crystals by a factor of almost 30 as compared with the bulk value, and about 6 as compared with an unpatterned slab of the same thickness.

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The Ground-Based Monitoring R and E Component Evaluation project performs testing on the hardware components that make up Seismic and Infrasound monitoring systems. The majority of the testing is focused on the Digital Waveform Recorder (DWR), Seismic Sensor, and Infrasound Sensor. The software tool used to capture and analyze the data collected from testing is called TALENT: Test and Analysis Evaluation Tool. This document is the manual for using TALENT. Other reports document the testing procedures that are in place (Kromer, 2007) and the algorithms employed in the test analysis (Merchant, 2011).

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Ceragenins were used to create biofouling resistant water-treatment membranes. Ceragenins are synthetically produced antimicrobial peptide mimics that display broad-spectrum bactericidal activity. While ceragenins have been used on bio-medical devices, use of ceragenins on water-treatment membranes is novel. Biofouling impacts membrane separation processes for many industrial applications such as desalination, waste-water treatment, oil and gas extraction, and power generation. Biofouling results in a loss of permeate flux and increase in energy use. Creation of biofouling resistant membranes will assist in creation of clean water with lower energy usage and energy with lower water usage. Five methods of attaching three different ceragenin molecules were conducted and tested. Biofouling reduction was observed in the majority of the tests, indicating the ceragenins are a viable solution to biofouling on water treatment membranes. Silane direct attachment appears to be the most promising attachment method if a high concentration of CSA-121a is used. Additional refinement of the attachment methods are needed in order to achieve our goal of several log-reduction in biofilm cell density without impacting the membrane flux. Concurrently, biofilm forming bacteria were isolated from source waters relevant for water treatment: wastewater, agricultural drainage, river water, seawater, and brackish groundwater. These isolates can be used for future testing of methods to control biofouling. Once isolated, the ability of the isolates to grow biofilms was tested with high-throughput multiwell methods. Based on these tests, the following species were selected for further testing in tube reactors and CDC reactors: Pseudomonas ssp. (wastewater, agricultural drainage, and Colorado River water), Nocardia coeliaca or Rhodococcus spp. (wastewater), Pseudomonas fluorescens and Hydrogenophaga palleronii (agricultural drainage), Sulfitobacter donghicola, Rhodococcus fascians, Rhodobacter katedanii, and Paracoccus marcusii (seawater), and Sphingopyxis spp. (groundwater). The testing demonstrated the ability of these isolates to be used for biofouling control testing under laboratory conditions. Biofilm forming bacteria were obtained from all the source water samples.

Significant deformation of thin films occurs when measuring thickness by mechanical means. This source of measurement error can lead to underestimating film thickness if proper corrections are not made. Analytical solutions exist for Hertzian contact deformation, but these solutions assume relatively large geometries. If the film being measured is thin, the analytical Hertzian assumptions are not appropriate. ANSYS is used to model the contact deformation of a 48 gauge Mylar film under bearing load, supported by a stiffer material. Simulation results are presented and compared to other correction estimates. Ideal, semi-infinite, and constrained properties of the film and the measurement tools are considered.

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