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Transfer function model-assisted probability of detection for lap joint multi site damage detection

AIP Conference Proceedings

Newcomer, Justin T.; Fitchett, Stephanie

The use of the Transfer Function approach to Model-Assisted Probability of Detection (MAPOD) is explored by inspecting airplane lap joint specimen sets with multiple site fatigue damage. Four specimen sets representing a matrix with structure type and defect types as the two axes were inspected using ultrasonic linear array. Probability of Detection (POD) curves were generated in each quadrant for 4 inspectors. POD curves in the fourth quadrant, which represents actual in-service crack detection in real airplane structures were predicted from other quadrant curves. Predicted POD curves were compared to observed curves. © 2012 American Institute of Physics.

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TYPE Conference YEAR 2012
OSTIScopus

New mechanistic insights to the O(3P) + propene reaction from multiplexed photoionization mass spectrometry

Physical Chemistry Chemical Physics

Savee, John D.; Welz, Oliver W.; Taatjes, Craig A.; Osborn, David L.

The reaction of O(3P) with propene (C3H6) has been examined using tunable vacuum ultraviolet radiation and time-resolved multiplexed photoionization mass spectrometry at 4 Torr and 298 K. The temporal and isomeric resolution of these experiments allow the separation of primary from secondary reaction products and determination of branching ratios of 1.00, 0.91 ± 0.30, and 0.05 ± 0.04 for the primary product channels CH3 + CH2CHO, C2H5 + HCO, and H2 + CH3CHCO, respectively. The H + CH3CHCHO product channel was not observable for technical reasons in these experiments, so literature values for the branching fraction of this channel were used to convert the measured product branching ratios to branching fractions. The results of the present study, in combination with past experimental and theoretical studies of O(3P) + C3H6, identify important pathways leading to products on the C3H6O potential energy surface (PES). The present results suggest that up to 40% of the total product yield may require intersystem crossing from the initial triplet C3H6O PES to the lower-lying singlet PES. © the Owner Societies.

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TYPE Conference YEAR 2012
OSTIScopus

Separability of tight and roaming pathways to molecular decomposition

Journal of Physical Chemistry A

Harding, Lawrence B.; Klippenstein, Stephen J.; Jasper, Ahren W.

Recent studies have questioned the separability of the tight and roaming mechanisms to molecular decomposition. We explore this issue for a variety of reactions including MgH2 → Mg + H2, NCN → CNN, H2CO → H2 + CO, CH3CHO → CH 4 + CO, and HNNOH → N2 + H2O. Our analysis focuses on the role of second-order saddle points in defining global dividing surfaces that encompass both tight and roaming first-order saddle points. The second-order saddle points define an energetic criterion for separability of the two mechanisms. Furthermore, plots of the differential contribution to the reactive flux along paths connecting the first- and second-order saddle points provide a dynamic criterion for separability. The minimum in the differential reactive flux in the neighborhood of the second-order saddle point plays the role of a mechanism divider, with the presence of a strong minimum indicating that the roaming and tight mechanisms are dynamically distinct. We show that the mechanism divider is often, but not always, associated with a second-order saddle point. For the formaldehyde and acetaldehyde reactions, we find that the minimum energy geometry on a conical intersection is associated with the mechanism divider for the tight and roaming processes. For HNNOH, we again find that the roaming and tight processes are dynamically separable but we find no intrinsic feature of the potential energy surface associated with the mechanism divider. Overall, our calculations suggest that roaming and tight mechanisms are generally separable over broad ranges of energy covering most kinetically relevant regimes. © 2012 American Chemical Society.

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TYPE Journal Article YEAR 2012
ScopusOSTI

AndroidLeaks: Automatically detecting potential privacy leaks in Android applications on a large scale

Lecture Notes in Computer Science (including subseries Lecture Notes in Artificial Intelligence and Lecture Notes in Bioinformatics)

Gibler, Clint; Crussell, Jonathan; Erickson, Jeremy L.; Chen, Hao

As mobile devices become more widespread and powerful, they store more sensitive data, which includes not only users' personal information but also the data collected via sensors throughout the day. When mobile applications have access to this growing amount of sensitive information, they may leak it carelessly or maliciously. Google's Android operating system provides a permissions-based security model that restricts an application's access to the user's private data. Each application statically declares the sensitive data and functionality that it requires in a manifest, which is presented to the user upon installation. However, it is not clear to the user how sensitive data is used once the application is installed. To combat this problem, we present AndroidLeaks, a static analysis framework for automatically finding potential leaks of sensitive information in Android applications on a massive scale. AndroidLeaks drastically reduces the number of applications and the number of traces that a security auditor has to verify manually. We evaluate the efficacy of AndroidLeaks on 24,350 Android applications from several Android markets. AndroidLeaks found 57,299 potential privacy leaks in 7,414 Android applications, out of which we have manually verified that 2,342 applications leak private data including phone information, GPS location, WiFi data, and audio recorded with the microphone. AndroidLeaks examined these applications in 30 hours, which indicates that it is capable of scaling to the increasingly large set of available applications. © 2012 Springer-Verlag.

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TYPE Conference YEAR 2012
ScopusOSTI

Accelerated Cartesian expansions for the rapid solution of periodic multiscale problems

IEEE Transactions on Antennas and Propagation

Baczewski, Andrew D.; Dault, Daniel L.; Shanker, Balasubramaniam

We present an algorithm for the fast and efficient solution of integral equations that arise in the analysis of scattering from periodic arrays of PEC objects, such as multiband frequency selective surfaces (FSS) or metamaterial structures. Our approach relies upon the method of Accelerated Cartesian Expansions (ACE) to rapidly evaluate the requisite potential integrals. ACE is analogous to FMM in that it can be used to accelerate the matrix vector product used in the solution of systems discretized using MoM. Here, ACE provides linear scaling in both CPU time and memory. Details regarding the implementation of this method within the context of periodic systems are provided, as well as results that establish error convergence and scalability. In addition, we also demonstrate the applicability of this algorithm by studying several exemplary electrically dense systems.

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TYPE Journal Article YEAR 2012
DOIOSTI

Rapid thermal pyrolysis of interferometrically patterned resist

Carbon

Spoerke, Eric; Polsky, Ronen; Burckel, David B.; Bunker, B.C.

In recent years pyrolysis of interferometrically-patterned photoresists has produced three-dimensionally nanopatterned, electrically conductive carbon films with applications from energy storage to biological sensing. We investigate here conditions for rapid thermal pyrolysis that drastically reduce film processing time (from hours to minutes) while preserving the films' unique nanoscale morphology, film adhesion, and electrochemical properties. We specifically show that heating rate dramatically affects nanoscale morphology, while reducing atmosphere composition, dwell time, and dwell temperature impact the electrochemical performance of these rapidly pyrolyzed nanostructures. Accelerated processing with rapid thermal pyrolysis may facilitate the expanded applicability and rapid fabrication of these promising nanostructured materials. © 2012 Elsevier Ltd. All rights reserved.

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TYPE Journal Article YEAR 2012
OSTIScopus

Parametric analysis of technology and policy tradeoffs for conventional and electric light-duty vehicles

Energy Policy

Barter, Garrett E.; Reichmuth, David; Westbrook, Jessica; Malczynski, Leonard A.; West, Todd H.; Manley, Dawn K.; Guzman, Katherine D.; Edwards, Donna M.

A parametric analysis is used to examine the supply demand interactions between the US light-duty vehicle (LDV) fleet, its fuels, and the corresponding primary energy sources through 2050. The analysis emphasizes competition between conventional internal combustion engine (ICE) vehicles, including hybrids, and electric vehicles (EVs), represented by both plug-in hybrid and battery electric vehicles. We find that EV market penetration could double relative to our baseline case with policies to extend consumers' effective payback period to 7 years. EVs can also reduce per vehicle petroleum consumption by up to 5% with opportunities to increase that fraction at higher adoption rates. However, EVs have limited ability to reduce LDV greenhouse gas (GHG) emissions with the current energy source mix. Alone, EVs cannot drive compliance with the most aggressive GHG emission reduction targets, even if the electricity grid shifts towards natural gas powered sources. Since ICEs will dominate the LDV fleet for up to 40 years, conventional vehicle efficiency improvements have the greatest potential for reductions in LDV GHG emissions and petroleum consumption over this time. Specifically, achieving fleet average efficiencies of 72. mpg or greater can reduce average GHG emissions by 70% and average petroleum consumption by 81%. © 2012 Elsevier Ltd.

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TYPE Journal Article YEAR 2012
OSTIScopus

Phase diversity with undersampled systems via superresolution preprocessing

Optics Letters

Shields, Eric A.

Phase diversity algorithms allow a wavefront to be reconstructed from through-focus measurements of a point source or extended scene. These algorithms have traditionally been limited to systems that are Nyquist sampled. Many optical systems for remote sensing applications are designed to be undersampled, however. One approach to phase diversity with undersampled systems is to employ superresolution techniques to first create properly sampled scenes. This is demonstrated experimentally for a point object, but is applicable to extended scenes as well. © 2012 Optical Society of America.

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TYPE Journal Article YEAR 2012
DOIOSTIScopus

Goal-oriented adaptivity and multilevel preconditioning for the poisson-boltzmann equation

Journal of Scientific Computing

Aksoylu, Burak; Bond, Stephen D.; Cyr, Eric C.; Holst, Michael

In this article, we develop goal-oriented error indicators to drive adaptive refinement algorithms for the Poisson-Boltzmann equation. Empirical results for the solvation free energy linear functional demonstrate that goal-oriented indicators are not sufficient on their own to lead to a superior refinement algorithm. To remedy this, we propose a problem-specific marking strategy using the solvation free energy computed from the solution of the linear regularized Poisson-Boltzmann equation. The convergence of the solvation free energy using this marking strategy, combined with goal-oriented refinement, compares favorably to adaptive methods using an energy-based error indicator. Due to the use of adaptive mesh refinement, it is critical to use multilevel preconditioning in order to maintain optimal computational complexity. We use variants of the classical multigrid method, which can be viewed as generalizations of the hierarchical basis multigrid and Bramble-Pasciak-Xu (BPX) preconditioners. © 2011 Springer Science+Business Media (outside the USA).

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TYPE Conference YEAR 2012
ScopusOSTI

Using embedded fibers to measure the detonation velocity of sensitized nitromethane

Podsednik, Jason W.; Navarro, Rudolfo J.; Parks, Shawn M.

Single-mode fibers were cleverly embedded into fixtures holding nitromethane, and used in conjunction with a photonic Doppler velocimeter (PDV) to measure the associated detonation velocity. These measurements have aided us in our understanding of energetic materials and enhanced our diagnostic capabilities.

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TYPE SAND Report YEAR 2012
DOIOSTI
Results 64401–64600 of 101,000
Results 64401–64600 of 101,000
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