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Workshop on Incomplete Network Data Held at Sandia National Labs – Livermore

Soundarajan, Sucheta; Wendt, Jeremy

While network analysis is applied in a broad variety of scientific fields (including physics, computer science, biology, and the social sciences), how networks are constructed and the resulting bias and incompleteness have drawn more limited attention. For example, in biology, gene networks are typically developed via experiment -- many actual interactions are likely yet to be discovered. In addition to this incompleteness, the data-collection processes can introduce significant bias into the observed network datasets. For instance, if you observe part of the World Wide Web network through a classic random walk, then high degree nodes are more likely to be found than if you had selected nodes at random. Unfortunately, such incomplete and biasing data collection methods must be often used.

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TYPE Other Report YEAR 2016
DOIOSTI

DARMA 0.3.0-alpha Specification

Wilke, Jeremiah; Hollman, David S.; Slattengren, Nicole L.; Lifflander, Jonathan; Kolla, Hemanth; Rizzi, Francesco; Teranishi, Keita; Bennett, Janine C.

In this document, we provide the specifications for DARMA (Distributed Asynchronous Resilient Models and Applications), a co-design research vehicle for asynchronous many-task (AMT) programming models that serves to: 1) insulate applications from runtime system and hardware idiosyncrasies, 2) improve AMT runtime programmability by co-designing an application programmer interface (API) directly with application developers, 3) synthesize application co-design activities into meaningful requirements for runtime systems, and 4) facilitate AMT design space characterization and definition, accelerating the development of AMT best practices.

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TYPE SAND Report YEAR 2016
DOIOSTI

Evidence of a Shockley-Read-Hall Defect State Independent of Band-Edge Energy in InAs/In(As,Sb) Type-II Superlattices

Physical Review Applied

Aytac, Y.; Olson, B.V.; Kim, Jin K.; Shaner, Eric A.; Hawkins, Samuel D.; Klem, John F.; Flatte, M.E.; Boggess, T.F.

A set of seven InAs/InAsSb type-II superlattices (T2SLs) were designed to have speci c bandgap energies between 290 meV (4.3 m) and 135 meV (9.2 m) in order to study the e ects of the T2SL bandgap energy on the minority carrier lifetime. A temperature dependent optical pump-probe technique is used to measure the carrier lifetimes, and the e ect of a mid-gap defect level on the carrier recombination dynamics is reported. The Shockley-Read-Hall (SRH) defect state is found to be at energy of approximately -250 12 meV relative to the valence band edge of bulk GaSb for the entire set of T2SL structures, even though the T2SL valence band edge shifts by 155 meV on the same scale. These results indicate that the SRH defect state in InAs/InAsSb T2SLs is singular and is nearly independent of the exact position of the T2SL bandgap or band edge energies. They also suggest the possibility of engineering the T2SL structure such that the SRH state is removed completely from the bandgap, a result that should signi cantly increase the minority carrier lifetime.

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TYPE Journal Article YEAR 2016
DOIOSTI

Graphene–Metamaterial Photodetectors for Integrated Infrared Sensing

ACS Photonics

Luxmoore, Isaac J.; Liu, Qiang; Li, Penglei; Faist, Jerome; Nash, Geoffrey R.

We study metamaterial-enhanced graphene photodetectors operating in the mid-IR to THz. The detector element consists of a graphene ribbon embedded within a dual-metal split ring resonator, which acts like a cavity to enhance the absorption of electromagnetic radiation by the graphene ribbon, while the asymmetric metal contacts enable photothermoelectric detection. The detectors we designed for the mid-IR demonstrate peak responsivity (referenced to total power) of ~120 mV/W at 1500 cm-1 and are employed in the spectroscopic evaluation of vibrational resonances, thus demonstrating a key step toward a platform for integrated surface-enhanced sensing.

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TYPE Journal Article YEAR 2016
DOIOSTI

Silicon Damage Response Function Derivation and Verification: Assessment of Impact on ASTM Standard E722

Depriest, Kendall R.

Unsuccessful attempts by members of the radiation effects community to independently derive the Norgett-Robinson-Torrens (NRT) damage energy factors for silicon in ASTM standard E722-14 led to an investigation of the software coding and data that produced those damage energy factors. The ad hoc collaboration to discover the reason for lack of agreement revealed a coding error and resulted in a report documenting the methodology to produce the response function for the standard. The recommended changes in the NRT damage energy factors for silicon are shown to have significant impact for a narrow energy region of the 1-MeV(Si) equivalent fluence response function. However, when evaluating integral metrics over all neutrons energies in various spectra important to the SNL electronics testing community, the change in the response results in a small decrease in the total 1- MeV(Si) equivalent fluence of ~0.6% compared to the E722-14 response. Response functions based on the newly recommended NRT damage energy factors have been produced and are available for users of both the NuGET and MCNP codes.

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TYPE SAND Report YEAR 2016
DOIOSTI

IDC Re-Engineering Phase 2 Iteration E2 Use Case Realizations

Harris, James M.; Burns, John F.; Hamlet, Benjamin R.; Lober, Randall R.; Vickers, James W.

This architecturally significant use case describes how the System acquires meteorological data to build atmospheric models used in automatic and interactive processing of infrasound data. The System requests the latest available high-resolution global meteorological data from external data centers and puts it into the correct formats for generation of infrasound propagation models. The system moves the meteorological data from Data Acquisition Partition to the Data Processing Partition and stores the meteorological data. The System builds a new atmospheric model based on the meteorological data. This use case is architecturally significant because it describes acquiring meteorological data from various sources and creating dynamic atmospheric transmission model to support the prediction of infrasonic signal detection

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TYPE Other Report YEAR 2016
DOIOSTI

Residual Stress Developed During the Cure of Thermosetting Polymers: Optimizing Cure Schedule to Minimize Stress

Kropka, Jamie M.; Stavig, Mark E.; Jaramillo, Rex K.

When thermosetting polymers are used to bond or encapsulate electrical, mechanical or optical assemblies, residual stress, which often affects the performance and/or reliability of these devices, develops within the structure. The Thin-Disk-on-Cylinder structural response test is demonstrated as a powerful tool to design epoxy encapsulant cure schedules to reduce residual stress, even when all the details of the material evolution during cure are not explicitly known. The test's ability to (1) distinguish between cohesive and adhesive failure modes and (2) demonstrate methodologies to eliminate failure and reduce residual stress, make choices of cure schedules that optimize stress in the encapsulant unambiguous. For the 828/DEA/GMB material in the Thin-Disk-on-Cylinder geometry, the stress associated with cure is significant and outweighs that associated with cool down from the final cure temperature to room temperature (for measured lid strain, IεcureI > IεthermalI). The difference between the final cure temperature and the temperature at which the material gels, Tf-Tgel, was demonstrated to be a primary factor in determining the residual stress associated with cure. Increasing Tf-Tgel leads to a reduction in cure stress that is described as being associated with balancing some of the 828/DEA/GMB cure shrinkage with thermal expansion. The ability to tune residual stress associated with cure by controlling Tf-Tgel would be anticipated to translate to other thermosetting encapsulation materials, but the times and temperatures appropriate for a given material may vary widely.

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TYPE SAND Report YEAR 2016
DOIOSTI

How reduced vacuum pumping capability in a coating chamber affects the laser damage resistance of HfO2/SiO2 antireflection and high reflection coatings

Proceedings of SPIE - The International Society for Optical Engineering

Field, Ella; Bellum, John C.; Kletecka, Damon

Optical coatings with the highest laser damage thresholds rely on clean conditions in the vacuum chamber during the coating deposition process. A low base pressure in the coating chamber, as well as the ability of the vacuum system to maintain the required pressure during deposition, are important aspects of limiting the amount of defects in an optical coating that could induce laser damage. Our large optics coating chamber at Sandia National Laboratories normally relies on three cryo pumps to maintain low pressures for e-beam coating processes. However, on occasion, one or more of the cryo pumps have been out of commission. In light of this circumstance, we explored how deposition under compromised vacuum conditions resulting from the use of only one or two cryo pumps affects the laser-induced damage thresholds of optical coatings. Finally, the coatings of this study consist of HfO2 and SiO2 layer materials and include antireflection coatings for 527 nm at normal incidence, and high reflection coatings for 527 nm, 45⁰ angle of incidence (AOI), in P-polarization (P-pol).

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TYPE Journal Article YEAR 2016
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A Photovoltaic System Payback Calculator

Riley, Daniel; Fleming, Jeffrey; Gallegos, Gerald R.

The Roof Asset Management Program (RAMP) is a DOE NNSA initiative to manage roof repairs and replacement at NNSA facilities. In some cases, installation of a photovoltaic system on new roofs may be possible and desired for financial reasons and to meet federal renewable energy goals. One method to quantify the financial benefits of PV systems is the payback period, or the length of time required for a PV system to generate energy value equivalent to the system's cost. Sandia Laboratories created a simple spreadsheet-based solar energy valuation tool for use by RAMP personnel to quickly evaluate the estimated payback period of prospective or installed photovoltaic systems.

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TYPE SAND Report YEAR 2016
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Simulation of Photovoltaic Power Output for Solar Integration Studies in the Southeast US

Hansen, Clifford; Martin, Curtis

We describe the method used to simulate one year of AC power at one-minute intervals for a large collection of hypothetical utility-scale photovoltaic plants of varying size, employing either fixed-tilt PV modules or single-axis tracking, and for distribution-connected photovoltaic (DPV) power systems assumed for a number of metropolitan areas. We also describe the simulation of an accompanying day-ahead forecast of hourly AC power for utility-scale plants and DPV systems such that forecast errors are consistent with errors reported for current forecasting methods. The results of these simulations are intended for use in a study that examines the possible effects of increased levels of photovoltaic (PV) generation bulk on power variability within the Tennessee Valley Authority (TVA) and Southern Company service territories.

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TYPE SAND Report YEAR 2016
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Results 41601–41800 of 99,299
Results 41601–41800 of 99,299