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Sawyer, Kimberly C.
Lakkaraju, Kiran
Hart, William E.
Finley, Melissa F.
Lilly, Michael
Rogers, David M.
Buican, Ileana G.
Finley, Patrick D. ; Beyeler, Walter E.
Carney, James
La Bauve, Elisa ; Jones, Howland D.T. ; Sinclair, Michael B. ; Williams, Kelly P. ; Solberg, Owen D. ; Timlin, Jerilyn A. ; Hatch, Anson ; Carson, Bryan
Hermina, Wahid L. ; Kolski, Alyssa J.C. ; Camacho-Lopez, Tara R.
Heinstein, Martin
Daily, Michael R.
Garino, Terry J. ; Brady, Patrick V. ; Mowry, Curtis D.
Mariano, Robert J.
Martinez, Mario J.
Phillips, Julia M.
Liu, Yang
Haase, Gaddi S.
Boyle, Timothy ; Hess, Ryan ; Neville, Michael L. ; Howard, Panit C.
The first step in an attempt to isolate Sc° from a W° crucible was explored by soaking the samples in a series of organic (HOAc) and inorganic (HCl, H2 SO4 , H3 PO4 , HNO3 ) acids. All samples, except the HOAc, yielded a powder. The weight loss suggests that HNO3 is the most efficient solvent; however, the powders were tentatively identified by PXRD and found to contain both W and Sc by-products. The higher weight loss may also indicate dissolution of the Wo crucible, which was further evidenced upon visual inspection of the crucible. The H3 PO4 acid soak yielded the cleanest removal of Sc from the crucible. More work to understand the separation of the Sc° from the W° crucible is necessary but the acid routes appear to hold promise under not as of yet established criteria.
Jakeman, John D. ; Wildey, Timothy
Lakkaraju, Kiran
Miller, Christopher H.
Miller, Christopher H.
Owen, Steven J.
Dai, Steve X.
Hardesty, Jasper
Johnson, Jay ; Flicker, Jack D.
Johnson, Jay ; Flicker, Jack D.
Sun, Amy C.
Blume-Kohout, Robin
Hamlet, Jason ; Brocato, Robert W.
Kelly, Suzanne M. ; Fang, H.E. ; Wagner, Gregory J. ; Templeton, J.A.
Hardin, Ernest
Logistical simulation of spent nuclear fuel (SNF) management in the U.S. combines storage, transportation and disposal elements to evaluate schedule, cost and other resources needed for all major operations leading to final geologic disposal. Geologic repository reference options are associated with limits on waste package thermal power output at emplacement, in order to meet limits on peak temperature for certain key engineered and natural barriers. These package power limits are used in logistical simulation software such as CALVIN, as threshold requirements that must be met by means of decay storage or SNF blending in waste packages, before emplacement in a repository. Geologic repository reference options include enclosed modes developed for crystalline rock, clay or shale, and salt. In addition, a further need has been addressed for open modes in which SNF can be emplaced in a repository, then ventilated for decades or longer to remove heat, prior to permanent repository closure. For each open mode disposal concept there are specified durations for surface decay storage (prior to emplacement), repository ventilation, and repository closure operations. This study simulates those steps for several timing cases, and for SNF with three fuel-burnup characteristics, to develop package power limits at which waste packages can be emplaced without exceeding specified temperature limits many years later after permanent closure. The results are presented in the form of correlations that span a range of package power and peak postclosure temperature, for each open-mode disposal concept, and for each timing case. Given a particular temperature limit value, the corresponding package power limit for each case can be selected for use in CALVIN and similar tools.
Moreland, Kenneth D.
Vaughan, Courtenay T.
Proposed for publication in Nature Geoscience.
Wang, Yifeng
Shoemaker, Paul E.
Robbins, Joshua ; Voth, Thomas E.
Barrett, Richard F.
Mcmahon, Kevin A.
Boruff, Sabine A.
Larson, Kurt
Salloum, Maher ; Templeton, J.A.
Dolan, Daniel H.
Cyr, Eric C. ; Shadid, John N.
Wagnild, Ross M.
Leland, Robert W.
Hoemmen, Mark F.
Brynildson, Mark E.
Brif, Constantin ; Sarovar, Mohan ; Grace, Matthew D.
Carnes, Brian R.
Lin, Paul T. ; Shadid, John N. ; Cyr, Eric C.
Hoemmen, Mark F. ; Heroux, Michael A.
Cortial, Julien ; Boggs, Paul T.
Biedermann, Grant
Stewart, Constantine A.
Finley, Melissa F.
Kotula, Paul G.
Bernstein, Robert ; Von White II, Gregory
Sarovar, Mohan
Lim, Hojun ; Battaile, Corbett C. ; Weinberger, C.R. ; Buchheit, Thomas E.
Nano Letters
Hearne, Sean J. ; Liu, Yang
Benito, Francisco M. ; Stick, Daniel L. ; Maunz, Peter L.W.
Electrophoresis
Sparks, Elizabeth S. ; Moorman, Matthew W. ; Edwards, Thayne L. ; Polsky, Ronen ; Brozik, Susan M.
Samberson, Jonell N. ; White, Michael I. ; Bernstein, Robert ; Hochrein, James M.
Chemical structure and physical properties of materials, such as polymers, can be altered as aging progresses, which may result in a material that is ineffective for its envisioned intent. Butyl rubber formulations, starting material, and additives were aged under thermal-oxidative conditions for up to 413 total days at up to 124 ÀC. Samples included: two formulations developed at Kansas City Plant (KCP) (#6 and #10), one commercially available formulation (#21), Laxness bromobutyl 2030 starting material, and two additives (polyethylene AC-617 and Vanax MBM). The low-molecular weight volatile thermal-oxidative degradation products that collected in the headspace over the samples were preconcentrated, separated, and detected using cryofocusing gas chromatography mass spectrometry (cryo-GC/MS). The majority of identified degradation species were alkanes, alkenes, alcohols, ketones, and aldehydes. Observations for Butyl #10 aged in an oxygen-18 enriched atmosphere (18O2) were used to verify when the source of oxygen in the applicable degradation products was from the gaseous environment rather than the polymeric mixture. For comparison purposes, Butyl #10 was also aged under non-oxidative thermal conditions using an argon atmosphere.
Reno, Matthew J. ; Broderick, Robert J. ; Quiroz, Jimmy E.
Landahl, Andrew J.
Brener, Igal
Carbajal, Armida J. ; Silva, Austin R. ; Nauer, Kevin ; Anderson, Benjamin ; Reed, Theodore ; Forsythe, James C.
Sobolik, Steven
Levy, Scott L.N.
Hale, Lucas M. ; Zimmerman, Jonathan A. ; Weinberger, C.R.
Raynal, Ann M. ; Doerry, Armin W.
Polarimetric synthetic aperture radar (SAR) has been used for a variety of dual-use research applications since the 1940's. By measuring the direction of the electric field vector from radar echoes, polarimetry may enhance an analyst's understanding of scattering effects for both earth monitoring and tactical surveillance missions. Polarimetry may provide insight into surface types, materials, or orientations for natural and man-made targets. Polarimetric measurements may also be used to enhance the contrast between scattering surfaces such as man-made objects and their surroundings. This report represents an initial assessment of the utility of, and applications for, polarimetric SAR at Ku-band for airborne or unmanned aerial systems.
Swift, Peter
Najm, Habib N.
Harms, Gary A.
SIAM Journal on Scientific Computing
Kolda, Tamara G. ; Plantenga, Todd ; Comandur, Seshadhri
Amon, Tod T.
Brenkosh, Joseph P.
Reed, Theodore ; Nauer, Kevin ; Silva, Austin R.
Hammer, Ann E. ; Mier, Steven A. ; John, Charles J. ; Mahrous, Karim M.
Rajamanickam, Sivasankaran
Song, Bo ; Lu, Wei-Yang
Paap, Scott M. ; Gupta, Vipin P.
Najm, Habib N.
Hines, Valerie A. ; Ogilvie, Alistair B. ; Bond, Cody R.
Hammond, Simon ; Rajamanickam, Sivasankaran ; Ang, James A. ; Barrett, Richard F. ; Doerfler, Douglas W. ; Heroux, Michael A. ; Laros, James H.
Wang, Yifeng
Reno, Matthew J. ; Stein, Joshua
Lu, Wei-Yang ; Gwinn, Kenneth W. ; Song, Bo
Tucker, Garritt J. ; Foiles, Stephen M.
Bent, Zachary ; Tran-Gyamfi, Mary ; Langevin, Stanley A. ; Brazel, David B. ; Branda, Steven ; Lane, Todd ; Vandernoot, Victoria A.
Rosewater, David ; Ferreira, Summer R.
Maniaci, David C. ; Bossert, David
White, Jonathan R.
Choe, Yung R. ; Wilke, Jeremiah ; Hendry, Gilbert
Burnett, Louann C.
Kirsch, Greg C.
Grainger, Lora A.
Grainger, Lora A.
Safta, Cosmin ; Sargsyan, Khachik ; Debusschere, Bert ; Najm, Habib N.
Grainger, Lora A.
Grainger, Lora A.
Thoreson, Gregory ; Mitchell, Dean J. ; Harding, Lee
The Gamma Detector Response and Analysis Software (GADRAS) software package is capable of simulating the radiation transport physics for one-dimensional models. Spherical shells are naturally one-dimensional, and have been the focus of development and benchmarking. However, some objects are not spherical in shape, such as cylinders and boxes. These are not one-dimensional. Simulating the radiation transport in two or three dimensions is unattractive because of the extra computation time required. To maintain computational efficiency, higher-dimensional geometries require approximations to simulate them in one-dimension. This report summarizes the theory behind these approximations, tests the theory against other simulations, and compares the results to experimental data. Based on the results, it is recommended that GADRAS users always attempt to approximate reality using spherical shells. However, if fissile material is present, it is imperative that the shape of the one-dimensional model matches the fissile material, including the use of slab and cylinder geometry.
Vetter, Douglas W.
Sandia National Laboratories/New Mexico's (SNL/NM) Environmental Management System is the integrated approach for members of the workforce to identify and manage environmental risks. Each Fiscal Year (FY) SNL/NM performs an analysis to identify environmental aspects, and the environmental programs associated with them are charged with the task of routinely monitoring and measuring the objectives and targets that are established to mitigate potential impacts of SNL/NM's operations on the environment. An annual summary of the results achieved towards meeting established objectives and targets provides a connection to, and rational for, annually revised environmental aspects. The purpose of this document is to summarize the results achieved and documented in FY2012.
Munson, Miles A.
A key assumption in supervised machine learning is that future data will be similar to historical data. This assumption is often false in real world applications, and as a result, prediction models often return predictions that are extrapolations. We compare four approaches to estimating extrapolation risk for machine learning predictions. Two builtin methods use information available from the classification model to decide if the model would be extrapolating for an input data point. The other two build auxiliary models to supplement the classification model and explicitly model extrapolation risk. Experiments with synthetic and real data sets show that the auxiliary models are more reliable risk detectors. To best safeguard against extrapolating predictions, however, we recommend combining builtin and auxiliary diagnostics.
Roeder, Peter
IEEE Transactions on Instrumentation and Measurement
Parks, Harold V. ; Novak, James
The ninth North American Josephson voltage standard (JVS) interlaboratory comparison (ILC) at 10 V was completed in 2011. An on-site comparison was conducted between the National Institute of Standards and Technology compact JVS and the pivot laboratory system. A set of four traveling Zener voltage standards was then shipped from the pivot laboratory to the other participants. Here, we give the results from the 2011 ILC and review recent comparisons which have used the same traveling standards and similar procedures.
IEEE Transactions on Visualization and Computer Graphics
Moreland, Kenneth D.
The most common abstraction used by visualization libraries and applications today is what is known as the visualization pipeline. The visualization pipeline provides a mechanism to encapsulate algorithms and then couple them together in a variety of ways. The visualization pipeline has been in existence for over 20 years, and over this time many variations and improvements have been proposed. This paper provides a literature review of the most prevalent features of visualization pipelines and some of the most recent research directions. © 1995-2012 IEEE.
Proceedings of the Combustion Institute
Geier, Manfred ; Shaddix, Christopher R. ; Holzleithner, F.
Reliable prediction of char conversion, heat release, and particle temperature during heterogeneous char oxidation relies upon quantitative calculation of the CO2/CO production ratio. This ratio depends strongly on the surface temperature, but also on the local partial pressure of oxygen and thus becomes more important in simulations of oxy-fuel or pressurized combustion systems. Existing semi-empirical intrinsic kinetic models of char combustion have been calibrated against the temperature-dependence of the CO2/CO production ratio, but have neglected the effect of the local oxygen concentration. In this study we employ steady-state analysis to demonstrate the limitations of the existing 3-step semi-global kinetics models and to show the necessity of using a 5-step model to adequately capture the temperature- and oxygen-dependence of the CO2/CO production ratio. A suitable 5-step heterogeneous reaction mechanism is developed and its rate parameters fit to match CO2/CO production data, global reaction orders, and activation energies reported in the literature. The model predictions are interrogated for a broad range of conditions characteristic of pressurized, oxy-fuel, and conventional high-temperature char combustion, for which essentially no experimental information on the CO2/CO production ratio is available. The results suggest that the CO2/CO production ratio may be considerably lower than that estimated with existing power-law correlations for oxygen partial pressures less than 10 kPa and surface temperatures higher than 1600 K. To assist with implementation of the mechanistic CO2/CO production ratio results, an analytical procedure for calculating the CO2/CO production ratio is presented. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Environmental Science and Technology
Criscenti, Louise ; Cygan, Randall T.
Proposed carbon dioxide sequestration scenarios in sedimentary reservoirs require investigation into the interactions between supercritical carbon dioxide, brines, and the mineral phases found in the basin and overlying caprock. Molecular simulations can help to understand the partitioning of metal cations between aqueous solutions and supercritical carbon dioxide where limited experimental data exist. In this effort, we used classical molecular dynamics simulations to compare the solvation of alkali and alkaline-earth metal cations in water and liquid CO2 at 300 K by combining a flexible simple point charge model for water and an accurate flexible force field for CO2. Solvation energies for these cations are larger in water than in carbon dioxide, suggesting that they will partition preferentially into water. In both aqueous and CO2 solutions, the solvation energies decrease with cation size and increase with cation charge. However, changes in solvation energy with ionic radii are smaller in CO2 than in water suggesting that the partitioning of cations into CO2 will increase with ion size. Simulations of the interface between aqueous solution and supercritical CO2 support this suggestion in that some large cations (e.g., Cs + and K+) partition into the CO2 phase, often with a partial solvation sphere of water molecules. © 2012 American Chemical Society.
Applied Energy
Klebanoff, Leonard E. ; Munoz-Ramos, Karina ; Akhil, Abbas A. ; Curgus, Dita B. ; Schenkman, Benjamin L.
Deployed on a commercial airplane, proton exchange membrane (PEM) fuel cells may offer emissions reductions, thermal efficiency gains, and enable locating the power near the point of use. This work seeks to understand whether on-board fuel cell systems are technically feasible, and, if so, if they could offer a performance advantage for the airplane when using today's off-the-shelf technology. We also examine the effects of the fuel cell system on airplane performance with (1) different electrical loads, (2) different locations on the airplane, and (3) expected advances in fuel cell and hydrogen storage technologies.Through hardware analysis and thermodynamic simulation, we found that an additional fuel cell system on a commercial airplane is technically feasible using current technology. Although applied to a Boeing 787-type airplane, the method presented is applicable to other airframes as well. Recovery and on-board use of the heat and water that is generated by the fuel cell is an important method to increase the benefit of such a system. The best performance is achieved when the fuel cell is coupled to a load that utilizes the full output of the fuel cell for the entire flight. The effects of location are small and location may be better determined by other considerations such as safety and modularity.Although the PEM fuel cell generates power more efficiently than the gas turbine generators currently used, when considering the effect of the fuel cell system on the airplane's overall performance we found that an overall performance penalty (i.e., the airplane will burn more jet fuel) would result if using current technology for the fuel cell and hydrogen storage. However, we found that with expected developments in PEM fuel cell and hydrogen storage technology, PEM fuel cell systems can provide an overall benefit to airplane performance. © 2012 Elsevier Ltd.
Conference Proceedings of the Society for Experimental Mechanics Series
Reu, P.L.
Understanding the final uncertainty in position, displacement and strain for digital image correlation (DIC) is a difficult or impossible enterprise when done analytically. In contrast, this paper will present a new approach using a pseudo-experimental method for estimating the 2D matching uncertainty, a Monte Carlo approach for understanding the calibration uncertainty, and the propagation of these error contributions to calculate a final 3D uncertainty. The methodology of calculating the errors will be presented using a sample measurement case. Additionally, the sensitivity of the position and motion errors to the various DIC parameters will be discussed. © The Society for Experimental Mechanics, Inc. 2013.
Surface and Interface Analysis
Ohlhausen, J.A. ; Coker, Eric N. ; Ambrosini, Andrea A. ; Miller, James E.
A procedure for quantitative time-of-flight secondary ion mass spectrometry (ToF-SIMS) analysis of the re-oxidation thermally-reduced of iron oxide particles in a ceramic matrix is discussed. Iron oxide is reacted with yttria stabilized zirconia (YSZ) to create a composite that facilitates the high-temperature reduction of CO2 and H2O to produce CO and H2 (syngas). The reactivity of this two-step solar-thermochemical process is being investigated by varying the concentration of iron in YSZ up to and past its solid solubility point, thus affecting the size of iron oxide particles in the matrix, and hence their rate and extent of re-oxidation. YSZ samples containing natural abundance iron oxide were mixed with an organic binder, isostatically pressed into a disc and calcined in air at 1450 °C. The discs (∼ 10 mm diameter, 2 mm thickness) were thermally reduced in inert gas at 1400 °C and then re-oxidized at 1100 °C in the presence of C18O2. The ratio of 18O to 16O shows the extent of oxygen exchange for each iron oxide particle. ToF-SIMS data are acquired in a fashion that maximizes the ability to correct for detector saturation, thus providing quantitative oxygen isotopic results with little error. The data analysis method uses a combination of multivariate analysis for particle identification and conventional analysis for quantitative isotopic ratioing. The results indicate that large iron oxide particles are only poorly utilized, likely due to slow transport, as 18O penetration into the particles is limited. Published 2012. This article is a U.S. Government work and is in the public domain in the USA. © Published 2012. This article is a U.S. Government work and is in the public domain in the USA.
Proceedings of the Combustion Institute
Skeen, Scott A. ; Yang, B.; Michelsen, Hope A. ; Miller, J.A.; Violi, A.; Hansen, Nils
We have designed an opposed-flow flame system to investigate the chemical composition of non-premixed flames using in situ flame-sampling molecular-beam mass spectrometry with synchrotron-generated tunable vacuum-ultraviolet light as an ionization source. This paper provides details of the experimental apparatus, sampling method, and data-reduction procedures. To test the system, we have investigated the chemical composition of three low-pressure (30-50 Torr), non-premixed, opposed-flow acetylene( Ar)/O2(Ar) flames. We measured quantitative mole-fraction profiles as a function of the distance from the fuel outlet for the major species and several intermediates, including the methyl and propargyl radicals. We determined the temperature profiles of these flames by normalizing a sampling-instrument function to thermocouple measurements near the fuel outlet. A comparison of the experimental temperature and major species profiles with modeling results indicates that flame perturbations caused by the sampling probe are minimal. The observed agreement between experimental and modeled results, apparent for most combustion species, is similar to corresponding studies of premixed flames. © 2012 The Combustion Institute.
Journal of Computational Physics
Scovazzi, Guglielmo S. ; Collis, Samuel S. ; Gerstenberger, Axel G.
We present a new approach to the simulation of gravity-driven viscous fingering instabilities in porous media flow. These instabilities play a very important role during carbon sequestration processes in brine aquifers. Our approach is based on a nonlinear implementation of the discontinuous Galerkin method, and possesses a number of key features. First, the method developed is inherently high order, and is therefore well suited to study unstable flow mechanisms. Secondly, it maintains high-order accuracy on completely unstructured meshes. The combination of these two features makes it a very appealing strategy in simulating the challenging flow patterns and very complex geometries of actual reservoirs and aquifers. This article includes an extensive set of verification studies on the stability and accuracy of the method, and also features a number of computations with unstructured grids and non-standard geometries.
Proceedings of the Combustion Institute
Zador, Judit ; Miller, James A.
Unimolecular pressure- and temperature-dependent decomposition rate coefficients of radicals derived from n- and i-propanol by H-atom abstraction are calculated using a time-dependent master equation in the 300-2000 K temperature range. The calculations are based on a C3H7O potential energy surface, which was previously tested successfully for the propene + OH reaction. All rate coefficients are obtained with internal consistency with particular attention paid to shallow wells. After minor adjustments very good agreement with the few available experimental results is obtained. Several interesting pathways are uncovered, such as the catalytic dehydration, well-skipping reactions and reactions forming enols. The results of the calculations can be readily used in CHEMKIN simulations or to assess important channels for higher alcohols. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Metallurgical and Materials Transactions A: Physical Metallurgy and Materials Science
Nibur, Kevin A.; Somerday, Brian P. ; San Marchi, Chris ; Foulk, James W. ; Dadfarnia, Mohsen; Sofronis, Petros
Threshold stress intensity factors were measured in high-pressure hydrogen gas for a variety of low alloy ferritic steels using both constant crack opening displacement and rising crack opening displacement procedures. Thresholds for crack extension under rising displacement, K THi, for crack extension under constant displacement, KTHi*, and for crack arrest under constant displacement K THa, were identified. These values were not found to be equivalent, i.e. K THi < K THa < K THi*. The hydrogen assisted fracture mechanism was determined to be strain controlled for all of the alloys in this study, and the micromechanics of strain controlled fracture are used to explain the observed disparities between the different threshold measurements. K THa and K THi differ because the strain singularity of a stationary crack is stronger than that of a propagating crack; K THa must be larger than K THi to achieve equivalent crack tip strain at the same distance from the crack tip. Hydrogen interacts with deformation mechanisms, enhancing strain localization and consequently altering both the nucleation and growth stages of strain controlled fracture mechanisms. The timing of load application and hydrogen exposure, i.e., sequential for constant displacement tests and concurrent for rising displacement tests, leads to differences in the strain history relative to the environmental exposure history and promotes the disparity between K THi* and K THi. K THi is the only conservative measurement of fracture threshold among the methods presented here. © 2012 The Minerals, Metals & Materials Society and ASM International.
51st AIAA Aerospace Sciences Meeting including the New Horizons Forum and Aerospace Exposition 2013
Casper, Katya M. ; Beresh, Steven J. ; Henfling, John F. ; Spillers, Russell ; Pruett, Brian
A high-speed schlieren system was developed for the Sandia Hypersonic Wind Tunnel. Schlieren images were captured at 290 kHz and used to study the growth and breakdown of second-mode instabilities into turbulent spots on a 7° cone. At Mach 5, wave packets would intermittently occur and break down into isolated turbulent spots surrounded by an otherwise smooth, laminar boundary layer. At Mach 8, the boundary layer was dominated by second-mode instabilities which would break down into larger regions of turbulence. Second-mode waves surrounded these turbulent patches as opposed to the smooth laminar flow seen at Mach 5. Detailed pressure and thermocouple measurements were also made along the cone at Mach 5, 8 and 14, in a separate tunnel entry. These measurements give an average picture of the transition behavior that complements the intermittent behavior captured by the schlieren system. At Mach 14, the boundary-layer remained laminar so the transition process could not be studied. However, the first measurements of second-mode waves were made in HWT-14.
Conference Proceedings of the Society for Experimental Mechanics Series
Song, Bo ; Lu, Wei-Yang
A current Kolsky tension bar has been implemented with pre-tension-load capability to investigate the effect of preload on the high-rate response in tension of materials and structures. In this study, fully threaded brass studs have been experimentally investigated in terms of pre-tension-load effect on the tensile stress-strain response at the same high strain rate. The preload is not observed to significantly influence the plastic flow stress. The failure responses are quite different, however, when different pre-tension loads are applied. © The Society for Experimental Mechanics, Inc. 2013.
Conference Proceedings of the Society for Experimental Mechanics Series
Lu, Wei-Yang ; Song, Bo ; Gwinn, Kenneth W.
Various loading and measuring configurations have been developed in Hopkinson bar fracture toughness experimental techniques. It is well known that several fundamental issues, such as force equilibrium, pulse shaping, stress-wave propagation, etc., must be evaluated in order to obtain a reliable measurement. In our previous work of characterizing Mode II dynamic fracture toughness of a woven composite, highly sensitive polyvinylidene fluoride (PVDF) force transducers were employed to check the forces on the front wedge and back spans in a SHPB ENF experiment. The results show that proper pulse shaping is necessary so the specimen can achieve stress equilibrium before the crack starts to propagate. This study addresses the issue that stress wave propagates through the non-uniform section, which is between the incident and transmission bars including the specimen, loading wedge, and supporting fixture. The transmitted signals are compared with PVDF measurements, and also with numerical simulations of stress waves propagate through supporting fixture and down to the transmission bar. © The Society for Experimental Mechanics, Inc. 2013.
Conference Proceedings of the Society for Experimental Mechanics Series
Antoun, Bonnie R. ; Song, Bo
This paper describes the development of infra-red imaging methods to visualize and monitor damage evolution in metallic alloys. Imaging is performed in-situ during tensile and notched tensile experiments at the microstructural grain level. Specimen preparation and imaging techniques are described. The results are anticipated to guide and improve alloy-specific damage evolution constitutive models to enable improved deformation and failure predictions. © The Society for Experimental Mechanics, Inc. 2013.
Conference Proceedings of the Society for Experimental Mechanics Series
Song, Bo ; Lu, Wei-Yang
A current Kolsky tension bar has been implemented with pre-tension-load capability to investigate the effect of preload on the high-rate response in tension of materials and structures. In this study, fully threaded brass studs have been experimentally investigated in terms of pre-tension-load effect on the tensile stress-strain response at the same high strain rate. The preload is not observed to significantly influence the plastic flow stress. The failure responses are quite different, however, when different pre-tension loads are applied. © The Society for Experimental Mechanics, Inc. 2013.
Journal of Nuclear Materials
Donovan, David C. ; Buchenauer, D.A. ; Watkins, J.; Leonard, A.; Wong, C.; Schaffer, M.; Rudakov, D.; Lasnier, C.; Stangeby, P.
Comparisons have been made between heat flux measurements from Langmuir probes and embedded thermocouples in the divertor of DIII-D. Good agreement has been found near the outer strike point (OSP) during L-mode operation with Neutral Beam Injection (NBI) using a sheath power transmission factor (SPTF) of 7, predicted by collisionless 1-D sheath theory. Previous SPTF measurements taken from Langmuir probes and IR imagery on DIII-D demonstrated values below the theoretical limit. The Langmuir probe array has since been upgraded and an embedded thermocouple array has been utilized to measure heat flux. The SPTF has also been measured during a NBI heated H-mode shot. This shot demonstrated a SPTF greater than 7 neat the OSP, which is due to a larger scrape-off layer (SOL) current density during H-mode operation. These studies represent a significant advancement towards finding agreement between theoretical predictions of the SPTF at the divertor and experimental measurements from the divertor diagnostics. © 2013 Published by Elsevier B.V.
Procedia Engineering
Haill, Thomas A. ; Mattsson, Thomas ; Root, Seth ; Magyar, Rudolph J.
Hydrocarbon polymers and foams are utilized in high energy-density physics (HEDP) and inertial confinement fusion (ICF) experiments as tampers, energy conversion and radiation pulse shaping layers in dynamic hohlraum Z-pinches, and ablators in ICF capsule implosions. Shocked foams frequently are found to be mixed with other materials either by intentional doping with high-Z elements or by instabilities and turbulent mixing with surrounding materials. In this paper we present one-dimensional and three-dimensional mesoscale hydrodynamic simulations of high-Z doped poly-(4-methyl-1-pentene) (PMP or TPX) foams in order to examine the validity of various equation of state (EOS) mixing rules available in two state-of-the-art simulation codes. Platinum-doped PMP foam experiments conducted at Sandia's Z facility provide data that can be used to test EOS mixing rules. We apply Sandia's ALEGRA-MHD code and the joint LLNL/SNL KULL HEDP code to model these doped foam experiments and exercise the available EOS mixing methods. One-dimensional simulations homogenize the foam with platinum dopant and show which EOS mixing methods produce results that are consistent with measured Hugoniot states. These simulations produce sharp shock fronts that are well described by traditional Hugoniot relations. Three-dimensional mesoscale simulations explicitly model the foam structure embedded with discrete platinum particles. The heterogeneous structure of the foam results in diffuse shock fronts and an unsteady post-shock state with large fluctuations about an average state. We compare shock propagation through pure foam and Pt-doped foams (50-50 mixture by weight) at equal average initial density, and examine how well the results compare to the experimentally measured Hugoniot states. © 2013 The Authors.
Journal of Nuclear Materials
Wampler, W.R.; Stangeby, P.C.; Watkins, J.G.; Buchenauer, D.A. ; Rudakov, D.L.; Wong, C.P.C.
The net erosion of molybdenum by the divertor plasma in the DIII-D tokamak was determined from the reduction in thickness of a thin film test sample after a short exposure to well controlled plasma conditions. The spatial distribution of Mo deposited on adjacent carbon surfaces was also measured. Integration of the total quantity of Mo deposited within 2 cm of the source, gave only 19% of the amount lost from the film indicating that most of the Mo is transported to greater distances, in spite of the short pathlength for ionization of Mo in the divertor plasma. These measurements provide benchmark data for comparisons between gross and net erosion and between measurements and simulations of erosion and deposition, which are discussed in companion papers at this conference. Erosion and deposition of carbon, and deuterium retention were also examined. © 2013 Published by Elsevier B.V.
Health Physics
Potter, Charles G.A.
An important paper by Skrable et al. included a retention function for compartment contents during a continuous intake, including the same time variable in both the numerator and denominator of the replacement function. In fact, the time in the denominator should have been represented as a constant describing the ultimate period length for the continuous intake, whether greater than, less than, or equal to the time variable for the associated measurement. Copyright © 2012 Health Physics Society.
Procedia Engineering
Brundage, Aaron
The Tillotson equation of state (EOS), which was originally developed for the hypervelocity impact of metals, was augmented with an additional region in expansion to provide full coverage of the density-energy space and a new cavitation model for liquids. This EOS was implemented into CTH, Sandia National Laboratories Eulerian, finite-volume, shock physics code, for the general purpose of simulating hypervelocity impacts of metals, geologic materials, and liquids; however, the salient features of this EOS in both compression and expansion are evaluated for water given the ubiquity of available data. Addition of a cavitation model allows for treatment of liquid spall when the local pressure drops below the vapor pressure in events such as underwater blasts and high speed projectiles or fragments in liquids. The EOS is evaluated by comparing the response to previously published dynamic compression experiments. Additionally, the model results are compared against the Mie-Gruneisen and SESAME equations of state already in the CTH database. © 2013 The Authors.
ECS Transactions
Atcitty, Stanley ; Kaplar, Robert ; Dasgupta, Sandeepan ; Marinella, Matthew ; Armstrong, Andrew A. ; Biedermann, Laura B. ; Smith, Mark A.
Emerging semiconductor switches based on the wide-bandgap semiconductor GaN have the potential to significantly improve the efficiency of portable power applications such as transportable energy storage. Such applications are likely to become more widespread as renewables such as wind and solar continue to come on-line. However, the long-term reliability of GaN-based power devices is relatively unexplored. In this paper, we describe joint work between Sandia National Laboratories and MIT on highvoltage AlGaN/GaN high electron mobility transistors. It is observed that the nature of current collapse is a strong function of bias conditions as well as device design, where factors such as Al composition in the barrier layer and surface passivation play a large role. Thermal and optical recovery experiments are performed to ascertain the nature of charge trapping in the device. Additionally, Kelvin-force microscopy measurements are used to evaluate the surface potential within the device. © The Electrochemical Society.
ECS Transactions
Nielson, Gregory N. ; Okandan, Murat ; Cruz-Campa, Jose L. ; Gupta, Vipin P. ; Resnick, Paul ; Sanchez, Carlos A. ; Paap, Scott M. ; Kim, B.; Sweatt, W.C. ; Lentine, Anthony L. ; Cederberg, Jeffrey G. ; Tauke-Pedretti, Anna ; Jared, B.H.; Anderson, Benjamin J. ; Biefeld, Robert M. ; Nelson, J.S.
Microsystem technologies have the potential to significantly improve the performance, reduce the cost, and extend the capabilities of solar power systems. These benefits are possible due to a number of significant beneficial scaling effects within solar cells, modules, and systems that are manifested as the size of solar cells decrease to the sub-millimeter range. To exploit these benefits, we are using advanced fabrication techniques to create solar cells from a variety of compound semiconductors and silicon that have lateral dimensions of 250 - 1000 μm and are 1 - 20 μm thick. These fabrication techniques come out of relatively mature microsystem technologies such as integrated circuits (IC) and microelectromechanical systems (MEMS) which provide added supply chain and scale-up benefits compared to even incumbent PV technologies. © The Electrochemical Society.
Proceedings of SPIE - The International Society for Optical Engineering
Peters, David ; Boye, Robert ; Kemme, Shanalyn A.
The angular sensitivity of guided mode resonant filters (GMRF) is well known. While at times useful for angle tuning of the response, this sensitivity can also be a major detriment as angular changes of tenths of a degree can shift the wavelength response in a narrow bandwidth device by an amount greater than the width of the resonance peak. We identify geometries where the resonance is more angularly stable, demonstrating high reflectivity at the design wavelength for several degrees in both azimuth and inclination angular directions with virtually no change in lineshape of the response. The investigation of GMRFs in both classical and conical mounts through simulation using rigorous coupled wave analysis reveals that there are preferred mounts for greater angular tolerance. We simulate a grating at telecom wavelengths using a design that we have previously fabricated. The identical grating placed in different mounts can exhibit angular tolerances that differ by well over an order of magnitude (60x). The most commonly used classical mount has a much more sensitive angular tolerance than does the conical mount. The lineshape of the resonant response shows only negligible changes across the angular band. The angular band for the sample grating is simulated to be several degrees in the conical mount as opposed to a tenth of a degree in the classical mount. We could thus expand the application space for narrow-band GMRFs into areas where angular tolerance cannot be controlled to the degree that we have believed required in the past. © 2013 SPIE.
Proceedings of the Combustion Institute
Savee, John D. ; Eskola, Arkke J. ; Sheps, Leonid ; Osborn, David L. ; Taatjes, Craig A.
Butanol isomers are promising next-generation biofuels. Their use in internal combustion applications, especially those relying on low-temperature autoignition, requires an understanding of their low-temperature combustion chemistry. Whereas the high-temperature oxidation chemistry of all four butanol isomers has been the subject of substantial experimental and theoretical efforts, their low-temperature oxidation chemistry remains underexplored. In this work we report an experimental study on the fundamental low-temperature oxidation chemistry of two butanol isomers, tert-butanol and isobutanol, in low-pressure (4-5.1 Torr) experiments at 550 and 700 K. We use pulsed-photolytic chlorine atom initiation to generate hydroxyalkyl radicals derived from tert-butanol and isobutanol, and probe the chemistry of these radicals in the presence of an excess of O2 by multiplexed time-resolved tunable synchrotron photoionization mass spectrometry. Isomer-resolved yields of stable products are determined, providing insight into the chemistry of the different hydroxyalkyl radicals. In isobutanol oxidation, we find that the reaction of the a-hydroxyalkyl radical with O2 is predominantly linked to chain-terminating formation of HO2. The Waddington mechanism, associated with chain-propagating formation of OH, is the main product channel in the reactions of O2 with b-hydroxyalkyl radicals derived from both tert-butanol and isobutanol. In the tert-butanol case, direct HO2 elimination is not possible in the b-hydroxyalkyl + O2 reaction because of the absence of a beta C-H bond; this channel is available in the b-hydroxyalkyl + O2 reaction for isobutanol, but we find that it is strongly suppressed. Observed evolution of the main products from 550 to 700 K can be qualitatively explained by an increasing role of hydroxyalkyl radical decomposition at 700 K. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Proceedings of the Combustion Institute
Eskola, Arkke J. ; Welz, Oliver W. ; Savee, John D. ; Osborn, David L. ; Taatjes, Craig A.
Product formation in laser-photolytic Cl-initiated low-temperature (550-700 K) oxidation of isobutane in a slow-flow reactor was investigated by tunable synchrotron photoionization mass spectrometry. These experiments probed the time-resolved formation of products following photolytic initiation of the oxidation, and identify isomeric species by their photoionization spectra. The relative yields of oxygenated product isomers (2,2-dimethyloxirane, methylpropanal, and 3-methyloxetane) are in reasonable concord with measurements from Walker and co-workers (J. Chem. Soc. Faraday Trans. 74 (1) (1978) 2229-2251) at higher temperature. Oxidation of isotopically labeled isobutane, (CH3)3CD, suggests that methylpropanal formation can proceed from both (CH3)2CCH2OOH and CH 3CH(CH2)CH2OOH isomers. Bimodal time behavior is observed for product formation; the initial prompt formation reflects "formally direct" channels, principally chemical activation, and the longer-timescale "delayed" component arises from dissociation of thermalized ROO and QOOH radicals. The proportion of prompt to delayed signal is smaller for the oxygenated products than for the isobutene product. This channel-specific behavior can be qualitatively understood by considering the different energetic distributions of ROO and QOOH in formally direct vs. thermal channels and the fact that the transition states involved in the formation of oxygenated products are "tighter" than that for isobutene formation. © 2012 Published by Elsevier Inc. on behalf of The Combustion Institute.
Proceedings of the Combustion Institute
Prager, Jens ; Najm, Habib N. ; Zador, Judit
Theoretical methods to obtain rate coefficients are essential to fundamental combustion chemistry research, yet the associated uncertainties are largely unexplored in a systematic manner. In this paper we focus on the study of parametric uncertainties for a hydrogen-atom-abstraction reaction, CH 3CH(OH)CH3 + OH → CH3C (OH)CH3 + H2O, which bears significant importance in low-temperature alcohol combustion and especially in autoignition models. After identifying the parameters causing significant uncertainty in the rate-coefficient calculations, Bayesian inference is employed to determine the joint probability density function (PDF) thereof using the experimental data of Dunlop and Tully (1993) [6] on isopropanol + OH. The inferred PDFs are compared to the various parameter values obtained from high-level electronic-structure calculations in order to assess the limitations of current methodologies. To gain insight on modeling the kinetic isotope effect (KIE), the reaction of the hydroxyl radical with deuterated isopropanol is also investigated. © 2012 The Combustion Institute. Published by Elsevier Inc. All rights reserved.
Shock and Vibration
Guthrie, Michael
A limit state function is developed for the estimation of structural reliability in shock environments. This limit state function uses peak modal strain energies to characterize environmental severity and modal strain energies at failure to characterize the structural capacity. The Hasofer-Lind reliability index is briefly reviewed and its computation for the energy-based limit state function is discussed. Applications to two degree of freedom mass-spring systems and to a simple finite element model are considered. For these examples, computation of the reliability index requires little effort beyond a modal analysis, but still accounts for relevant uncertainties in both the structure and environment. For both examples, the reliability index is observed to agree well with the results of Monte Carlo analysis. In situations where fast, qualitative comparison of several candidate designs is required, the reliability index based on the proposed limit state function provides an attractive metric which can be used to compare and control reliability. © 2013 - IOS Press and the authors. All rights reserved.
Speciation Studies in Soil, Sediment and Environmental Samples
Xiong, Yongliang
Thallium has numerous applications in industry. It is also of great environmental concern because of its high toxicity. Therefore, stabilities of its aqueous and solid species under low temperature environments are fundamentally important to its impact on environments. In previous publications (Xiong 2007, 2009), a number of aqueous and solid thallium species and their stabilities were addressed. However, several thallium species that are potentially important to soil environments, especially saline soil environments, have not been covered.
ECS Transactions
Douglas, E.A.; Gila, B.P.; Abernathy, C.R.; Ren, F.; Pearton, S.J.
Sub-micron AlGaN/GaN high electron mobility transistors were RF stressed at various drain bias conditions at 10 GHz under 3 dB and 3.7 dB compression. Rapid degradation was observed above a drain bias of 20 V, with significant degradation of the Schottky contact. Additionally, electroluminescence and cathodoluminescence was performed on stressed devices. Localization of 2.2 eV defect emission was observed on a device suffering from infant mortality. © The Electrochemical Society.
Journal of Nuclear Materials
Stangeby, P.C.; Rudakov, D.L.; Wampler, W.R.; Brooks, J.N.; Brooks, N.H.; Buchenauer, D.A. ; Elder, J.D.; Hassanein, A.; Leonard, A.W.; McLean, A.G.; Okamoto, A.; Sizyuk, T.; Watkins, J.G.; Wong, C.P.C.
Experimental observation of net erosion of molybdenum being significantly reduced compared to gross erosion in the divertor of DIII-D is reported for well-controlled plasma conditions. For the first time, gross erosion rates were measured by both spectroscopic and non-spectroscopic methods. In one experiment a net erosion rate of 0.73 ± 0.03 nm/s was measured using ion beam analysis (IBA) of a 1 cm diameter Mo-coated sample. For a 1 mm diameter Mo sample exposed at the same time the net erosion rate was higher at 1.31 nm/s. For the small sample redeposition is expected to be negligible in comparison with the larger sample yielding a net to gross erosion estimate of 0.56 ± 12%. The gross rate was also measured spectroscopically (386 nm MoI line) giving 2.45 nm/s ± factor 2. The experiment was modeled with the REDEP/WBC erosion/redeposition code package coupled to the ITMC-DYN mixed-material code, with plasma conditions supplied by the OEDGE code using Langmuir probe data input. The code-calculated net/gross ratio is =0.46, in good agreement with experiment. © 2013 Published by Elsevier B.V.
ECS Transactions
Mayberry, C.; Nguyen, D.D.; Kouhestani, C.; Kambour, K.E.; Hjalmarson, Harold P. ; Devine, R.A.B.
The increase in the magnitude of the threshold voltage of a positive-channel metal oxide semiconductor (PMOS) under negative gate biasing (negative bias temperature instability) is attributed to the build-up of charge in the gate insulator. We have studied the charging and discharging of nitrided SiO2 gate insulator field effect transistors and through the use of pseudo-DC and pulsed stressing methods, have extracted, at least, three charging components. These components are (a) the charging of interface states at the semiconductor/insulator boundary, (b) dynamically recoverable positive charging in the bulk' of the insulator, and (c) positive charging in the insulator, which can be eliminated' only by application of a positive electric field across the insulator. It is proposed that the charge elimination' in (c) arises via a charge neutralization process involving electron capture at switching traps, as opposed to de-trapping, and that this can be reversed by the application of a small negative field. © The Electrochemical Society.
Green
Cordaro, Joseph G.
Molten salts have been widely considered as the leading candidate heat transfer fluids (HTF) used in high temperature, concentrated solar power plants. Specifically, nitrate and nitrite based salts have been investigated as a HTF and even deployed in pilot plants generating up to 19.9 MW of electricity at operating temperatures above 500 °C. New plant designs requiring higher operating temperatures for better efficiencies are pushing the stability limit of HTF. This paper presents an overview of the thermophysical properties of nitrate and nitrite salts and discusses thermodynamic and kinetic stability limitations as they relate to concentrated solar power generation.
ECS Transactions
Yates, B.R.; Darby, B.L.; Petersen, D.H.; Hansen, O.; Lin, R.; Nielsen, P.F.; Doyle, B.L. ; Kontos, A.; Jones, K.S.
The residual implanted dose of ultra-shallow B+ implants in Ge was characterized using elastic recoil detection and was determined to correlate well with simulations with a dose loss of 23% due to ion backscattering for 2 keV implants in Ge. The electrical characterization of ultra-shallow B+ implants at 2 keV to a dose of 5.0×1014 cm-2 at beam currents ranging from 0.4 to 6.4 mA has been studied using micro Hall effect measurements after annealing at 400°C for 60 s. It has been shown that the sheet number increases with beam current across the investigated range with electrical activation being 76% higher at 6.4 mA as compared to 0.4mA. However, at 6.4 mA, the electrically active fraction remained low at 11.4%. Structural characterization revealed that the implanted region remained crystalline and amorphization is not able to explain the increased activation. The results suggest the presence of a stable B:Ge cluster whose formation is altered by point defect recombination during high flux implantation which results in increased B activation. © The Electrochemical Society.
12th International Conference on Autonomous Agents and Multiagent Systems 2013, AAMAS 2013
Letchford, Joshua; Vorobeychik, Yevgeniy
We present a Stackelberg game model of security in which the defender chooses a mitigation strategy that interdicts potential attack actions, and the attacker responds by computing an optimal attack plan that circumvents the deployed mitigations. First, we offer a general formulation for deterministic plan interdiction as a mixed-integer program, and use constraint generation to compute optimal solutions, leveraging state-of-the-art partial satisfaction planning techniques. We also present a greedy heuristic for this problem, and compare its performance with the optimal MILP-based approach. We then extend our framework to incorporate uncertainty about attacker's capabilities, costs, goals, and action execution uncertainty, and show that these extensions retain the basic structure of the deterministic plan interdiction problem. Introduction of more general models of planning uncertainty require us to model the attacker's problem as a general MDP, and demonstrate that the MDP interdiction problem can still be solved using the basic constraint generation framework. Copyright © 2013, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
SAE Technical Papers
Mueller, Charles J.
This study summarizes the peer-reviewed literature regarding the use of raw pyrolysis liquids (PLs) created from woody biomass as fuels for compression-ignition (CI) engines. First, a brief overview is presented of fast pyrolysis and the potential advantages of PLs as fuels for CI engines. Second, a discussion of the general composition and properties of PLs relative to conventional, petroleum-derived diesel fuels is provided, with emphasis on the differences that are most likely to affect PL performance in CI-engine applications. Next, a synopsis is given of the peer-reviewed literature describing experimental studies of CI engines operated using neat PLs and PLs combined in various ways with other fuels. This literature conclusively indicates that raw PLs and PL blends cannot be used as drop-in replacements for diesel fuel in CI engines, which is reflected in part by none of the cited studies reporting successful operation on PL fuels for more than twelve consecutive hours. Based on the reported failure modes, some recommendations are offered for improving performance, reliability, and safety when fueling CI engines with PLs. It appears that PL-derived fuels are most likely to find sustainable CI-engine applications only after a cost-effective pre-use processing strategy is identified to address significant issues regarding fuel instability, materials incompatibilities (e.g., corrosivity), poor ignition quality, high viscosity, and undesirable water/solids/energy contents. Copyright © 2013 SAE International.
12th International Conference on Autonomous Agents and Multiagent Systems 2013, AAMAS 2013
An, Bo; Brown, Matthew; Vorobeychik, Yevgeniy ; Tambe, Milind
Stackelberg games have been used in several deployed applications to allocate limited resources for critical infrastructure protection. These resource allocation strategies are randomized to prevent a strategic attacker from using surveillance to learn and exploit patterns in the allocation. Past work has typically assumed that the attacker has perfect knowledge of the defender's randomized strategy or can learn the defender's strategy after conducting a fixed period of surveillance. In consideration of surveillance cost, these assumptions are clearly simplistic since attackers may act with partial knowledge of the defender's strategies and may dynamically decide whether to attack or conduct more surveillance. In this paper, we propose a natural model of limited surveillance in which the attacker dynamically determine a place to stop surveillance in consideration of his updated belief based on observed actions and surveillance cost. We show an upper bound on the maximum number of observations the attacker can make and show that the attacker's optimal stopping problem can be formulated as a finite state space MDP. We give mathematical programs to compute optimal attacker and defender strategies. We compare our approaches with the best known previous solutions and experimental results show that the defender can achieve significant improvement in expected utility by taking the attacker's optimal stopping decision into account, validating the motivation of our work. Copyright © 2013, International Foundation for Autonomous Agents and Multiagent Systems (www.ifaamas.org). All rights reserved.
Journal of the Electrochemical Society
Deng, Jie ; Muller, Richard P.
Journal of Vacuum Science and Technology B:Nanotechnology and Microelectronics
Klem, John F. ; Hawkins, Samuel D. ; Kim, Jin K. ; Leonhardt, Darin ; Shaner, Eric A. ; Fortune, Torben ; Keeler, Gordon A.
InPSb and InAsPSb have been investigated for use as absorber materials in GaSb-based n-type/barrier/n-type (nBn) detectors with cutoff wavelengths shorter than 4.2 μm. The growth temperature window for high-quality InPSb lattice-matched to GaSb by molecular beam epitaxy is approximately 440-460 °C. InPSb films with thicknesses greater than approximately 1 μm or films grown outside this temperature window have high densities of large defects, with films grown at lower temperatures exhibiting evidence of significant phase separation. In contrast, InAsPSb films can be grown with excellent surface morphologies and no apparent phase separation over a wide temperature range. InAsPSb samples with low-temperature photoluminescence between 3.0 and 3.4 μm and lattice mismatch of less than 1 × 10-3 have been grown, although both photoluminescence and x-ray diffraction data exhibit peak splitting indicative of compositional nonuniformity. AlAsSb-barrier nBn detectors with InPSb and InAsPSb absorbers have been fabricated. At 160 K, InPSb-absorber devices have a photocurrent responsivity edge at approximately 2.8 μm and a dark current of approximately 1.4 × 10-7 A/cm2, and InAsPSb devices with responsivity edges of 3.1-3.2 μm have a dark current of 2.3 × 10-8 A/cm2. Both InPSb and InAsPSb devices require significant reverse bias for full photocurrent collection at low temperature, suggesting the existence of an undesirable valence band energy discontinuity. The temperature dependence of dark current indicates that it is dominated by a mechanism other than generation in the undepleted absorber region. © 2013 American Vacuum Society.
Science
Taatjes, Craig A. ; Welz, Oliver W. ; Eskola, Arkke J. ; Savee, John D. ; Scheer, Adam M. ; Rotavera, Brandon ; Osborn, David L.
Proposed for publication in Reliability Engineering and System Safety.
Hansen, Clifford ; Mattie, Patrick ; Sallaberry, Cedric J. ; Sevougian, Stephen D.
Finley, Melissa F.
Proposed for publication in Reliability Engineering and System Safety.
Sallaberry, Cedric J. ; Hansen, Clifford
Rechard, Robert P.
Proposed for publication in Reliability Engineering and System Safety.
Hansen, Clifford ; Mattie, Patrick ; Sallaberry, Cedric J. ; Sevougian, Stephen D.
Vugrin, Eric
Denman, Matthew R. ; Lachance, Jeffrey L.
Rechard, Robert P. ; Bonano, Evaristo J.
Proposed for publication in Academic Peace Orchestra Middle East Policy Briefs.
Bonin, Benjamin J.
Finley, Melissa F. ; Van Brass, Hildren
Finley, Melissa F.
Ferreira, Kurt ; Thompson, A.P. ; Trott, Christian R.
Carnes, Brian R.
Timlin, Jerilyn A. ; Collins, Aaron M. ; Jones, Howland D.T. ; Beechem, Thomas E. ; Davis, Ryan W.
Proposed for publication in Journal of Computational Physics.
Guba, Oksana ; Taylor, Mark A.
Barrett, Richard F. ; Vaughan, Courtenay T. ; Hammond, Simon
Vorobeychik, Yevgeniy
Comandur, Seshadhri ; Kolda, Tamara G.
Phillips, Cynthia A.
Lenberg, Laura L.
Proposed for publication in Channels .
Moczydlowski, Edward M.
Leblanc, Bruce P.
Colbaugh, Richard ; Johnson, Curtis M.
Finley, Melissa F.
Bacon, Larry D. ; Williams, Jeffery T. ; Turner, C.D. ; Walker, Michael J. ; Zeek, Erik C.
Starr, Michael ; Guthrie, Michael
Proposed for publication in Reliability Engineering and System Safety.
Sallaberry, Cedric J.
Hughart, David R. ; Marinella, Matthew ; Mickel, Patrick R. ; Dodd, Paul E. ; Shaneyfelt, Marty R. ; Bielejec, Edward S. ; Vizkelethy, Gyorgy
Barone, Matthew F.
Shulenburger, Luke N.
Gearhart, Jared L. ; Brown, Nathanael J.K. ; Jones, Dean A.
Hart, William E.
Finley, Melissa F.
Wang, George T.
Jones, Kyle R.
Jones, Kyle R.
Carr, Robert D.
Barrett, Richard F. ; Laros, James H. ; Hammond, Simon
Olsson, Roy H. ; Pluym, Tammy
Hardin, Ernest ; Clayton, Daniel J.
Arnold, Bill W. ; Brady, Patrick V.
Pawlowski, Roger
Proposed for publication in Reliability Engineering and System Safety.
Hansen, Clifford ; Naugle, Asmeret B. ; Mattie, Patrick ; Sallaberry, Cedric J. ; Sevougian, Stephen D.
Finley, Melissa F.
Guildenbecher, Daniel ; Reu, P.L.
Moreland, Kenneth D.
Heck, Stephen L. ; Young, Christopher J.
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