Publications

Results 53601–53800 of 99,299

Search results

Jump to search filters

Defect localization, characterization and reliability assessment in emerging photovoltaic devices

Cruz-Campa, Jose L.; Haase, Gaddi S.; Colr, Edward I.; Tangyunyong, Paiboon; Okandan, Murat; Nielson, Gregory N.

Microsystems-enabled photovoltaics (MEPV) can potentially meet increasing demands for light-weight, portable, photovoltaic solutions with high power density and efficiency. The study in this report examines failure analysis techniques to perform defect localization and evaluate MEPV modules. CMOS failure analysis techniques, including electroluminescence, light-induced voltage alteration, thermally-induced voltage alteration, optical beam induced current, and Seabeck effect imaging were successfully adapted to characterize MEPV modules. The relative advantages of each approach are reported. In addition, the effects of exposure to reverse bias and light stress are explored. MEPV was found to have good resistance to both kinds of stressors. The results form a basis for further development of failure analysis techniques for MEPVs of different materials systems or multijunction MEPVs. The incorporation of additional stress factors could be used to develop a reliability model to generate lifetime predictions for MEPVs as well as uncover opportunities for future design improvements.

More Details
TYPE SAND Report YEAR 2014
DOIOSTI

Environmental management system objectives & targets results summary FY 2013

Vetter, Douglas W.

Sandia National Laboratories/New Mexicos (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/NMs operations on the environment. An annual summary of the results achieved towards meeting established Sandia Corporation and SNL/NM Site-specific 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 FY2013.

More Details
TYPE SAND Report YEAR 2014
DOIOSTI

Relationship between Metrics Used to Represent Displacement Damage in Materials

Griffin, Patrick J.

This report provides a set of consistent definitions for metrics relevant to the modeling of displacement damage in materials. The limitations/approximations built into the various metrics are discussed as is the intended application that gave rise to community use of the metric. Recommended sources for numerical tabulations of the neutron displacement kerma and the charged particle non-ionizing energy loss in some important semiconductor materials are also provided.

More Details
TYPE SAND Report YEAR 2014
DOIOSTI

Second harmonic generation from metamaterials strongly coupled to intersubband transitions in quantum wells

Applied Physics Letters

Campione, Salvatore; Benz, Alexander; Sinclair, Michael B.; Brener, Igal

We theoretically analyze the second harmonic generation capacity of two-dimensional periodic metamaterials comprising sub-wavelength resonators strongly coupled to intersubband transitions in quantum wells (QWs) at mid-infrared frequencies. The metamaterial is designed to support a fundamental resonance at ∼30THz and an orthogonally polarized resonance at the second harmonic frequency (∼60THz), while the asymmetric quantum well structure is designed to provide a large second order susceptibility. Upon continuous wave illumination at the fundamental frequency we observe second harmonic signals in both the forward and backward directions, with the forward efficiency being larger. We calculate the overall second harmonic conversion efficiency of the forward wave to be ∼1.3×10-2 W/W2 - a remarkably large value, given the deep sub-wavelength dimensions of the QW structure (about 1/15th of the free space wavelength of 10μm). The results shown in this Letter provide a strategy for designing easily fabricated sources across the entire infrared spectrum through proper choice of QW and resonator designs. © 2014 AIP Publishing LLC.

More Details
TYPE Journal Article YEAR 2014
DOIOSTIScopus

Criegee intermediates in the indoor environment. New insights

Indoor Air

Taatjes, Craig A.

Criegee intermediates are formed in the ozonolysis of alkenes and play an important role in indoor chemistry, notably as a source of OH radicals. Recent studies have shown that these Criegee intermediates react very quickly with NO2, SO2, and carbonyls, and in this study, steady-state calculations are used to inspect the potential impact of these data on indoor chemistry. It is shown that these reactions could accelerate NO3 formation and SO2 removal in the indoor environment significantly. In addition, reaction between Criegee intermediates and halogenated carbonyls could provide a significant loss process indoors, where currently one does not exist.

More Details
TYPE Journal Article YEAR 2014
OSTIDOI

Circulation within confined droplets in Hele-Shaw channels

Physics of Fluids

Roberts, Christine; Roberts, Scott A.; Nemer, Martin; Rao, Rekha R.

Liquid droplets flowing through a rectangular microfluidic channel develop a vortical flow field due to the presence of shear forces from the surrounding fluid. In this paper, we present an experimental and computational study of droplet velocities and internal flow patterns in a rectangular pressure-driven flow for droplet diameters ranging from 0.1 to 2 times the channel height. Our study shows excellent agreement with asymptotic predictions of droplet and interfacial velocities for infinitesimally small droplets. As the droplet diameter nears the size of the channel height, the droplet velocity slows significantly, and the changing external flow field causes a qualitative change in the location of internal vortices. This behavior is relevant for future studies of mass transfer in microfluidic devices. © 2014 AIP Publishing LLC.

More Details
TYPE Journal Article YEAR 2014
OSTIScopus

Task mapping stencil computations for non-contiguous allocations

Proceedings of the ACM SIGPLAN Symposium on Principles and Practice of Parallel Programming, PPOPP

Leung, Vitus J.; Bunde, David P.; Ebbers, Johnathan; Feer, Stefan P.; Price, Nickolas W.; Rhodes, Zachary D.; Swank, Matthew

We examine task mapping algorithms for systems that allocate jobs non-contiguously. Several studies have shown that task placement affects job running time. We focus on jobs with a stencil communication pattern and use experiments on a Cray XE to evaluate novel task mapping algorithms as well as some adapted to this setting. This is done with the miniGhost miniApp which mimics the behavior of CTH, a shock physics application. Our strategies improve average and single-run times by as much as 28% and 36% over a baseline strategy, respectively.

More Details
TYPE Conference YEAR 2014
ScopusOSTI

Bio-hybrid integrated system for wide-spectrum solar energy harvesting

Proceedings of SPIE - The International Society for Optical Engineering

Swartzentruber, Brian; Martin, Kathleen; Erdman, Matthew; Quintana, Hope; Shelnutt, John; Nogan, John; Martinez, Julio; Lavrova, Olga; Busani, Tito

An integrated hybrid photovoltaic-thermoelectric system has been developed using multiple layers of organic photosensitizers on inorganic semiconductors in order to efficiently convert UV-visible and IR energy into electricity. The hot anode of n-type ZnO nanowires was fabricated using a thermal process on pre-seeded layer and results to be crystalline with a transmittance up to 92 % and a bandgap of 3.32 eV. The visible-UV light-active organic layer was deposited between the anode and cathode at room temperature using a layer-by-layer deposition onto ITO and ZnO and Bi2Te3 nanowires from aqueous solution. The organic layer, a cooperative binary ionic (CBI) solid is composed of oppositely charged porphyrin metal (Zn(II) and Sn(IV)(OH–)2) derivatives that are separately water soluble, but when combined form a virtually insoluble solid. The electron donor/acceptor properties (energy levels, band gaps) of the solid can be controlled by the choice of metals and the nature of the peripheral substituent groups of the porphyrin ring. The highly thermoelectric structure, which acts as a cold cathode, is composed of p-type Bi2Te3 nanowires with a thermoelectric efficiency (ZT) between ~0.7 to 1, values that are twice that expected for bulk Bi2Te3. Lastly, efficiency of the integrated device, was found to be 35 at 0.2 suns illumination and thermoelectric properties are enhanced by the charge transfer between the CBI and the Bi2Te3 is presented in terms of photo- and thermogenerated current and advantages of the low cost fabrication process is discussed.

More Details
TYPE Journal Article YEAR 2014
DOIOSTI

On the damping effect of gas rarefaction on propagation of acoustic waves in a microchannel

Physics of Fluids

Manela, A.; Radtke, G.A.; Pogorelyuk, L.

We consider the response of a gas in a microchannel to instantaneous (smallamplitude) non-periodic motion of its boundaries in the normal direction. The problem is formulated for an ideal monatomic gas using the Bhatnagar, Gross, and Krook (BGK) kinetic model, and solved for the entire range of Knudsen (Kn) numbers. Analysis combines analytical (collisionless and continuum-limit) solutions with numerical (low-variance Monte Carlo and linearized BGK) calculations. Gas flow, driven by motion of the boundaries, consists of a sequence of propagating and reflected pressure waves, decaying in time towards a final equilibrium state. Gas rarefaction is shown to have a "damping effect" on equilibration process, with the time required for equilibrium shortening with increasing Kn. Oscillations in hydrodynamic quantities, characterizing gas response in the continuum limit, vanish in collisionless conditions. The effect of having two moving boundaries, compared to only one considered in previous studies of time-periodic systems, is investigated. Comparison between analytical and numerical solutions indicates that the collisionless description predicts the system behavior exceptionally well for all systems of the size of the mean free path and somewhat larger, in cases where boundary actuation acts along times shorter than the ballistic time scale. The continuum-limit solution, however, should be considered with care at early times near the location of acoustic wavefronts, where relatively sharp flow-field variations result in effective increase in the value of local Knudsen number. © 2014 AIP Publishing LLC.

More Details
TYPE Journal Article YEAR 2014
ScopusOSTI

2-(2-Hydroxy-4-methoxybenzoyl)benzoic acid derivatives of group 4 metal alkoxides

Journal of Coordination Chemistry

Boyle, Timothy; Yonemoto, Daniel T.; Neville, Michael L.

Continued exploration of the coordination behavior of derivatives of 2-benzophenone-based ligands with metal alkoxides ([M(OR)4]) was undertaken from the reaction of 2-(2-hydroxy-4-methoxybenzoyl)benzoic acid (H2-OBzA) with a series of Group 4 precursors. The products of these reactions were identified as: [(OR)2Ti(-(c,c-OBzA))]2 (OR = OCHMe2 (OPri; 1 •2tol); OCMe3 (OBu t; 2 •THF); OCH2CMe3 (ONep; 3)), [[(OPri)3Ti(-OPri)Ti(OPri) 2]2(-(c,-OBzA))2]2 (4), [(ONep)3Zr(-ONep)2Zr(ONep)2] 2(-(c,-OBzA)2) (5 •tol), [(py)(OBut) 3Zr]2(-(c,c-OBzA)) (6), [(OBut) 2Hf(-OBut)]2(-(c,η1-OBzA)) (7) where c = chelating or η2; = bridging or η1, η1(O,O); and c = bridging chelating or η1,η1(O,O); η2: η1. The metal centers for each of these compounds adopt a pseudo-octahedral geometry employing the OBzA ligand in numerous binding modes. The different functional oxygens (carboxylate, hydroxyl, and carbonyl) were employed in a variety of coordination modes for 1-7. The complexity of these OBzA-modified compounds is driven by a combination of the coordination behavior of the OBzA moieties, the size of the metal cation, and the pendant chain of the OR ligand. Solution NMR indicates a complex structure exists in solution that was considered to be consistent with the solid-state structure. © 2014 Taylor & Francis.

More Details
TYPE Journal Article YEAR 2014
OSTIScopus

Protecting against corner impacts: Sensitivities discovered during a rail cask impact limiter design

Packaging, Transport, Storage and Security of Radioactive Material

Harding, David C.; Quevedo, D.G.

Type B packages for the transportation of radioactive materials must remain 'essentially leak tight' under severe regulatory accident conditions, defined in the US Nuclear Regulatory Commission's 10 CFR 71·73 and the International Atomic Energy Agency's TS-R-1. The 9-m free drop test requirement onto an unyielding surface is performed in an orientation 'for which maximum damage is expected'. Analytical techniques are used to evaluate various possible impact orientations before testing, and historically these maximal damage orientations have been side, slap-down, end, and centre-ofgravity over corner. Other orientations are rarely considered. Sandia National Laboratories (SNL) was asked by Equipos NuclearesSA (ENSA) todesign, analyse, and test animpact limiter system for a newly designed rail cask. During the conceptual design process, SNL performed due diligence and evaluated a wide spectrum of possible impact orientations, in order to assure that peak cask body acceleration design goals were not exceeded. However, design of the impact limiter, including not only crush strength of constituent materials (which can be orientation and temperature dependent), but also the shape of the impact limiter, greatly affects peak acceleration response during 9-m drops in various orientations. Although many impact limiter design shapes resemble truncated right circular cylinders attached to each end of the cask, some tend to round the outer corners or truncate those corners with conical sections. SNL's original conceptual design followed a similar theme, intending to use polyurethane foam or aluminium honeycomb within a bevelled corner shaped cylindrical shell. Detailed finite element analyses indicated excellent impact resistance at regulatory cold temperatures in the stereotypically tested side, slap-down, end, and CGOC impact orientations. Shortly before proceeding to engineering design, a rarely-considered impact orientation of 45° from horizontal indicated that cask body acceleration levels jumped unexpectedly, exceeding the design goal due to insufficient crushable material protecting the sharp corner of the cask. A complete re-design of the impact limiter was necessary, and the lessons learned from this experience could have implications for future impact limiter designs, and possibly existing designs that may not have considered this atypical impact orientation during the design process.

More Details
TYPE Conference YEAR 2014
ScopusOSTIDOI

Signatures of hot electrons and fluorescence in Mo Kα emission on Z

Physics of Plasmas

Hansen, Stephanie B.; Ampleford, David J.; Cuneo, Michael E.; Ouart, N.; Jones, Brent M.; Jennings, C.A.; Dasgupta, A.; Coverdale, Christine A.; Rochau, G.A.; Dunham, G.S.; Giuliani, J.L.; Apruzese, J.P.

Recent experiments on the Z accelerator have produced high-energy (17 keV) inner-shell K-alpha emission from molybdenum wire array z-pinches. Extensive absolute power and spectroscopic diagnostics along with collisional-radiative modeling enable detailed investigation into the roles of thermal, hot electron, and fluorescence processes in the production of high-energy x-rays. We show that changing the dimensions of the arrays can impact the proportion of thermal and non-thermal K-shell x-rays. © 2014 AIP Publishing LLC.

More Details
TYPE Conference YEAR 2014
ScopusOSTI

Ductile tearing predictions with Wellman's failure model

International Journal of Fracture

Neilsen, Michael K.; Dion, Kristin; Fang, H.E.; Kaczmarowski, Amy K.

Predictions for the Sandia National Laboratories fracture challenge (Boyce et al. in Int J Fract 2013) were generated using a transient dynamic finite element code with a multi-linear elastic plastic failure model developed by Wellman (Simple approach to modeling ductile failure. Sandia National Laboratories, Albuquerque 2012). This model is a conventional, rate independent, von Mises plasticity model for metals with user-prescribed hardening as a function of equivalent plastic strain. In addition to conventional plasticity, this model has empirical criteria for crack initiation and growth. Ductile tearing predictions generated with this model were found to be in good agreement with experimental measurements and observations. © 2013 Springer Science+Business Media Dordrecht (outside the USA).

More Details
TYPE Journal Article YEAR 2014
OSTIScopus

Biomolecular motors in nanoscale materials, devices, and systems

Wiley Interdisciplinary Reviews: Nanomedicine and Nanobiotechnology

Bachand, George D.; Bouxsein, Nathan F.; Vandelinder, Virginia; Bachand, Marlene

Biomolecular motors are a unique class of intracellular proteins that are fundamental to a considerable number of physiological functions such as DNA replication, organelle trafficking, and cell division. The efficient transformation of chemical energy into useful work by these proteins provides strong motivation for their utilization as nanoscale actuators in ex vivo, meso- and macro-scale hybrid systems. Biomolecular motors involved in cytoskeletal transport are quite attractive models within this context due to their ability to direct the transport of nano-/micro-scale objects at rates significantly greater than diffusion, and in the absence of bulk fluid flow. As in living organisms, biomolecular motors involved in cytoskeletal transport (i.e., kinesin, dynein, and myosin) function outside of their native environment to dissipatively self-assemble biological, biomimetic, and hybrid nanostructures that exhibit nonequilibrium behaviors such as self-healing. These systems also provide nanofluidic transport function in hybrid nanodevices where target analytes are actively captured, sorted, and transported for autonomous sensing and analytical applications. Moving forward, the implementation of biomolecular motors will continue to enable a wide range of unique functionalities that are presently limited to living systems, and support the development of nanoscale systems for addressing critical engineering challenges. © 2013 Wiley Periodicals, Inc.

More Details
TYPE Journal Article YEAR 2014
DOIOSTIScopus

Reactive sputtering of substoichiometric Ta2Ox for resistive memory applications

Journal of Vacuum Science and Technology A: Vacuum, Surfaces and Films

Lohn, Andrew J.; Decker, Seth; Doyle, B.L.; Mickel, Patrick R.; Marinella, Matthew

A major class of resistive memory devices is based on transition metal oxides, where mobile oxygen vacancies allow these devices to exhibit multiple resistance states. Ta2O5 based devices in particular have recently demonstrated impressive endurance and forming-free results. Deposition of substoichiometric Ta2Ox (x < 5) films is a critical process in order to produce the required oxygen vacancies in these devices. This paper describes a physical vapor deposition (PVD) reactive sputtering process to deposit substoichiometric Ta2Ox films. The desired film stoichiometry is achieved by feedback control of the oxygen partial pressure in the PVD chamber. A calibration procedure based on Rutherford backscattering spectroscopy is described for locating the optimum oxygen partial pressure.

More Details
TYPE Journal Article YEAR 2014
OSTIScopus

A toolkit for integrated deterministic and probabilistic assessment for hydrogen infrastructure

Groth, Katrina M.

There has been increasing interest in using Quantitative Risk Assessment [QRA] to help improve the safety of hydrogen infrastructure and applications. Hydrogen infrastructure for transportation (e.g. fueling fuel cell vehicles) or stationary (e.g. back-up power) applications is a relatively new area for application of QRA vs. traditional industrial production and use, and as a result there are few tools designed to enable QRA for this emerging sector. There are few existing QRA tools containing models that have been developed and validated for use in small-scale hydrogen applications. However, in the past several years, there has been significant progress in developing and validating deterministic physical and engineering models for hydrogen dispersion, ignition, and flame behavior. In parallel, there has been progress in developing defensible probabilistic models for the occurrence of events such as hydrogen release and ignition. While models and data are available, using this information is difficult due to a lack of readily available tools for integrating deterministic and probabilistic components into a single analysis framework. This paper discusses the first steps in building an integrated toolkit for performing QRA on hydrogen transportation technologies and suggests directions for extending the toolkit.

More Details
TYPE Conference YEAR 2014
OSTI

Commuter Assistance Program Administrative Operating Procedure

Catechis, Christopher S.

Sandia National Laboratories/New Mexico’s (SNL/NM) Commuter Assistance Program (CAP) offers commuting alternatives to driving a single-occupant vehicle (SOV) to members of the workforce (MOW). The goal of this program is to reduce SOV use for commuting to and from SNL/NM, provide MOW opportunities to reduce their transportation costs, reduce greenhouse gas emissions, and reduce parking congestion at SNL/NM. The CAP advocates alternative transportation strategies such as carpooling, vanpooling, bicycling, and using public transportation. The Commuter Assistance Program website is the portal for MOW to access information about the different commuting alternatives available. Additionally, the website provides information on the City of Albuquerque’s Park and Ride program, traffic conditions, and the City of Albuquerque’s Guaranteed Ride Home.

More Details
TYPE Other Report YEAR 2014
DOIOSTI
Results 53601–53800 of 99,299
Results 53601–53800 of 99,299