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Sandia National Laboratories California Pollution Prevention Program Annual Report February 2008

Farren, Laurie J.

The annual program report provides detailed information about all aspects of the SNL/CA Pollution Prevention Program for a given calendar year. It functions as supporting documentation to the SNL/CA Environmental Management System Program Manual. The program report describes the activities undertaken during the past year, and activities planned in future years to implement the Pollution Prevention Program, one of six programs that supports environmental management at SNL/CA.

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TYPE SAND Report YEAR 2008
DOIDOIOSTIOSTI

Yucca Mountain licensing support network archive assistant

Dunlavy, Daniel D.; Basilico, Justin D.; Verzi, Stephen J.; Bauer, Travis L.

This report describes the Licensing Support Network (LSN) Assistant--a set of tools for categorizing e-mail messages and documents, and investigating and correcting existing archives of categorized e-mail messages and documents. The two main tools in the LSN Assistant are the LSN Archive Assistant (LSNAA) tool for recategorizing manually labeled e-mail messages and documents and the LSN Realtime Assistant (LSNRA) tool for categorizing new e-mail messages and documents. This report focuses on the LSNAA tool. There are two main components of the LSNAA tool. The first is the Sandia Categorization Framework, which is responsible for providing categorizations for documents in an archive and storing them in an appropriate Categorization Database. The second is the actual user interface, which primarily interacts with the Categorization Database, providing a way for finding and correcting categorizations errors in the database. A procedure for applying the LSNAA tool and an example use case of the LSNAA tool applied to a set of e-mail messages are provided. Performance results of the categorization model designed for this example use case are presented.

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TYPE SAND Report YEAR 2008
DOIOSTI

The application of taylor weighting, digital phase shifters, and digital attenuators to phased-array antennas

Brock, Billy C.

Application of Taylor weighting (taper) to an antenna aperture can achieve low peak sidelobes, but combining the Taylor weighting with quantized attenuators and phase shifters at each radiating element will impact the performance of a phased-array antenna. An examination of array performance is undertaken from the simple point of view of the characteristics of the array factor. Design rules and guidelines for determining the Taylor-weighting parameters, the number of bits required for the digital phase shifter, and the dynamic range and number of bits required for the digital attenuator are developed. For a radar application, when each element is fed directly from a transmit/receive module, the total power radiated by the array will be reduced as a result of the taper. Consequently, the issue of whether to apply the taper on both transmit and receive configurations, or only on the receive configuration is examined with respect to two-way sidelobe performance.

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TYPE SAND Report YEAR 2008
DOIOSTI

Sustaining knowledge in the neutron generator community and benchmarking study

Huff, Tameka B.; Turgeon, Jennifer T.; Baldonado, Esther B.; Stubblefield, W.A.; Kennedy, Bryan C.; Saba, Antony S.

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

Material morphology and electrical resistivity differences in EPDM rubbers

Proposed for publication in the Journal of Applied Polymer Science.

Domeier, Linda A.; Yang, Nancy Y.

Electrical resistance anomalies noted in EPDM gaskets have been attributed to zinc-enriched surface sublayers, about 10-{micro}m thick, in the sulfur cured rubber material. Gasket over-compression provided the necessary connector pin contact and was also found to cause surprising morphological changes on the gasket surfaces. These included distributions of zinc oxide whiskers in high pressure gasket areas and cone-shaped features rich in zinc, oxygen, and sulfur primarily in low pressure protruding gasket areas. Such whiskers and cones were only found on the pin side of the gaskets in contact with a molded plastic surface and not on the back side in contact with an aluminum surface. The mechanisms by which such features are formed have not yet been defined.

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TYPE Journal Article YEAR 2008
OSTI

Kinetic investigation of electron-electron scattering in nanometer-scale metal- oxide-semiconductor field-effect transistors

Semiconductor Science and Technology

Fixel, D.A.; Hitchon, W.N.G.

The effects of electron-electron scattering on the electron energy distribution, as well as substrate and gate currents in short channel MOSFETs (metal-oxide-semiconductor field-effect transistors) are explored using the convective scheme, or CS, a method of characteristics. Effects of electron-electron scattering are explored for a MOSFET with uniform doping in the channel as well as for an asymmetric device structure, a focused-ion-beam (FIBMOS) transistor, for both 70 nm and 250 nm channel length devices. Effects of electron-electron scattering on a standard 35 nm channel length MOSFET are also included. The high substrate doping that is required for such short channel length devices leads to large electric fields. The purpose of the FIB implant is to improve hot-carrier reliability by reducing the electric field in the channel. Electron-electron scattering increases the amount of electrons in the tail, despite the fact that the applied potential is significantly below the threshold for injection of electrons into the gate oxide. The ratio of gate-to-substrate current, Ig/Isub, is investigated as an indicator of the level of degradation. At such short channel lengths, there are degrading and non-degrading components of gate and substrate current. The non-degrading components of gate and substrate current correlate strongly, so that the ratio of Ig/Isub is an efficient indicator of device degradation. The energy thresholds for impact ionization and for emission of electrons into the gate oxide are crucial in determining the ratio of these currents. The substrate and gate currents obtained indicate that hot-carrier effects continue to be an issue for device performance, even for nanometer-scale devices. The density of electrons is higher at very short channel lengths due to the need to have shallow junctions and leads to a greater amount of Coulomb collisions. Increased Coulomb collisions may lead to strongly reduced lifetimes in nanometer-scale devices. © 2008 IOP Publishing Ltd.

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TYPE Journal Article YEAR 2008
ScopusOSTIDOI
Results 76801–77000 of 96,771
Results 76801–77000 of 96,771