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Sustaining knowledge in the neutron generator community and benchmarking study

Huff, Tameka B.; Turgeon, Jennifer; Baldonado, Esther; Stubblefield, William A.; Kennedy, Bryan C.; Saba, Anthony W.

In 2004, the Responsive Neutron Generator Product Deployment department embarked upon a partnership with the Systems Engineering and Analysis knowledge management (KM) team to develop knowledge management systems for the neutron generator (NG) community. This partnership continues today. The most recent challenge was to improve the current KM system (KMS) development approach by identifying a process that will allow staff members to capture knowledge as they learn it. This 'as-you-go' approach will lead to a sustainable KM process for the NG community. This paper presents a historical overview of NG KMSs, as well as research conducted to move toward sustainable KM.

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TYPE SAND Report YEAR 2008
DOIOSTI

Trailing edge modifications for flatback airfoils

Kahn, Daniel L.; Van Dam, C.P.; Berg, Dale E.

The adoption of blunt trailing edge airfoils (also called flatback airfoils) for the inboard region of large wind turbine blades has been proposed. Blunt trailing edge airfoils would not only provide a number of structural benefits, such as increased structural volume and ease of fabrication and handling, but they have also been found to improve the lift characteristics of thick airfoils. Therefore, the incorporation of blunt trailing edge airfoils would allow blade designers to more freely address the structural demands without having to sacrifice aerodynamic performance. These airfoils do have the disadvantage of generating high levels of drag as a result of the low-pressure steady or periodic flow in the near-wake of the blunt trailing edge. Although for rotors, the drag penalty appears secondary to the lift enhancement produced by the blunt trailing edge, high drag levels are of concern in terms of the negative effect on the torque and power generated by the rotor. Hence, devices are sought that mitigate the drag of these airfoils. This report summarizes the literature on bluff body vortex shedding and bluff body drag reduction devices and proposes four devices for further study in the wind tunnel.

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TYPE SAND Report YEAR 2008
DOIOSTI

Computational design and analysis of flatback airfoil wind tunnel experiment

Mayda, Edward A.; Van Dam, C.P.; Chao, David D.; Berg, Dale E.

A computational fluid dynamics study of thick wind turbine section shapes in the test section of the UC Davis wind tunnel at a chord Reynolds number of one million is presented. The goals of this study are to validate standard wind tunnel wall corrections for high solid blockage conditions and to reaffirm the favorable effect of a blunt trailing edge or flatback on the performance characteristics of a representative thick airfoil shape prior to building the wind tunnel models and conducting the experiment. The numerical simulations prove the standard wind tunnel corrections to be largely valid for the proposed test of 40% maximum thickness to chord ratio airfoils at a solid blockage ratio of 10%. Comparison of the computed lift characteristics of a sharp trailing edge baseline airfoil and derived flatback airfoils reaffirms the earlier observed trend of reduced sensitivity to surface contamination with increasing trailing edge thickness.

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TYPE SAND Report YEAR 2008
DOIOSTI

Screening analysis of solar thermochemical hydrogen concepts

Kolb, Gregory J.; Diver, Richard B.

A screening analysis was performed to identify concentrating solar power (CSP) concepts that produce hydrogen with the highest efficiency. Several CSP concepts were identified that have the potential to be much more efficient than today's low-temperature electrolysis technology. They combine a central receiver or dish with either a thermochemical cycle or high-temperature electrolyzer that operate at temperatures >600 C. The solar-to-hydrogen efficiencies of the best central receiver concepts exceed 20%, significantly better than the 14% value predicted for low-temperature electrolysis.

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TYPE SAND Report YEAR 2008
DOIOSTI

Summary report on transportation of nuclear fuel materials in Japan : transportation infrastructure, threats identified in open literature, and physical protection regulations

Cochran, John R.

This report summarizes the results of three detailed studies of the physical protection systems for the protection of nuclear materials transport in Japan, with an emphasis on the transportation of mixed oxide fuel materials1. The Japanese infrastructure for transporting nuclear fuel materials is addressed in the first section. The second section of this report presents a summary of baseline data from the open literature on the threats of sabotage and theft during the transport of nuclear fuel materials in Japan. The third section summarizes a review of current International Atomic Energy Agency, Japanese and United States guidelines and regulations concerning the physical protection for the transportation of nuclear fuel materials.

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TYPE SAND Report YEAR 2008
DOIOSTI

Experiments for Calibration and Validation of Plasticity and Failure Material Modeling: 6061-T651 Aluminum

Lee, Kenneth L.; Korellis, John S.; Rogillio, Brendan R.

Experimental data for material plasticity and failure model calibration and validation were obtained from 6061-T651 aluminum, in the form of a 4-in. diameter extruded rod. Model calibration data were taken from smooth tension, notched tension, and shear tests. Model validation data were provided from experiments using thin-walled tube specimens subjected to path-dependent combinations of internal pressure, extension, and torsion.

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TYPE SAND Report YEAR 2008
DOIOSTI

Simulations of nanotribology with realistic probe tip models

Langmuir

Chandross, Michael; Lorenz, Christian D.; Stevens, Mark J.; Grest, Gary S.

We present the results of massively parallel molecular dynamics simulations aimed at understanding the nanotribological properties of alkylsilane self-assembled monolayers (SAMs) on amorphous silica. In contrast to studies with opposing flat plates, as found in the bulk of the simulation literature, we use a model system with a realistic AFM tip (radius of curvature ranging from 3 to 30 nm) in contact with a SAM-coated silica substrate. We compare the differences in response between systems in which chains are fully physisorbed, fully chemisorbed, and systems with a mixture of the two. Our results demonstrate that the ubiquitous JKR and DMT models do not accurately describe the contact mechanics of these systems. In shear simulations, we find that the chain length has minimal effects on both the friction force and coefficient. The tip radius affects the friction force only (i.e., the coefficient is unchanged) by a constant shift in magnitude due to the increase in pull-off force with increasing radius. We also find that at extremely low loads, on the order of 10 nN, shearing from the tip causes damage to the physisorbed monolayers by removal of molecules. © 2008 American Chemical Society.

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TYPE Journal Article YEAR 2008
ScopusOSTI

High resolution electrochemical STM: New structural results for underpotentially deposited Cu on Au(1 1 1) in acid sulfate solution

Journal of Electroanalytical Chemistry

Vasiljevic, Natasa V.; Viyannalage, Lasantha T.; Dimitrov, Nikolay; Sieradzki, Karl

Adsorption of sulfate assists Cu monolayer underpotential deposition (upd) on Au(1 1 1) in a unique way, rendering two distinct structural stages: (i) formation of a low-density Cu phase at coverage of 2/3 ML known as the fenced(sqrt(3) × sqrt(3)) R 30 ° or honeycomb phase; (ii) formation of a complete monolayer, i.e., Cu-(1 × 1) phase pseudomorphic with respect to underlying Au(1 1 1) substrate. In this paper we present new structural in situ scanning tunneling microscopy (STM) results for this system. We show and discuss the STM imaging of the copper honeycomb superstructure probed underneath the co-adsorbed fenced(sqrt(3) × sqrt(3)) R 30 ° sulfate adlayer in the low-density phase. High resolution imaging during the phase transition from the low to high density copper phase unambiguously shows the existence of an ordered sulfate structure p(2 × 2) on the pseudomorphic Cu-(1 × 1) layer. The new structure is seen during the co-existence of two copper phases as well as upon completion of the Cu-(1 × 1) monolayer. While supported by earlier chronocoulometric measurements in the same system, the new structural results raise questions that need to be addressed in a future work. © 2007 Elsevier B.V. All rights reserved.

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TYPE Journal Article YEAR 2008
ScopusOSTI

The application of high-speed digital image correlation

Proposed for publication in Journal of Strain Analysis.

Digital image correlation (DIC) is a method of using digital images to calculate two-dimensional displacement and deformation or for stereo systems three-dimensional shape, displacement, and deformation. While almost any imaging system can be used with DIC, there are some important challenges when working with the technique in high- and ultra-high-speed applications. This article discusses three of these challenges: camera sensor technology, camera frame rate, and camera motion mitigation. Potential solutions are treated via three demonstration experiments showing the successful application of high-speed DIC for dynamic events. The application and practice of DIC at high speeds, rather than the experimental results themselves, provide the main thrust of the discussion.

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TYPE Journal Article YEAR 2008
OSTIDOI
Results 78701–78800 of 99,299
Results 78701–78800 of 99,299