220 Matching Results

Results open in a new window/tab.

An aberration corrected photoemission electron microscope at the advanced light source (open access)

An aberration corrected photoemission electron microscope at the advanced light source

Design of a new aberration corrected Photoemission electron microscope PEEM3 at the Advanced Light Source is outlined. PEEM3 will be installed on an elliptically polarized undulator beamline and will be used for the study of complex materials at high spatial and spectral resolution. The critical components of PEEM3 are the electron mirror aberration corrector and aberration-free magnetic beam separator. The models to calculate the optical properties of the electron mirror are discussed. The goal of the PEEM3 project is to achieve the highest possible transmission of the system at resolutions comparable to our present PEEM2 system (50 nm) and to enable significantly higher resolution, albeit at the sacrifice of intensity. We have left open the possibility to add an energy filter at a later date, if it becomes necessary driven by scientific need to improve the resolution further.
Date: November 1, 2003
Creator: Feng, J.; MacDowell, A. A.; Duarte, R.; Doran, A.; Forest, E.; Kelez, N. et al.
System: The UNT Digital Library
Advanced Interactive Facades - Critical Elements for Future GreenBuildings? (open access)

Advanced Interactive Facades - Critical Elements for Future GreenBuildings?

Building designers and owners have always been fascinated with the extensive use of glass in building envelopes. Today the highly glazed facade has almost become an iconic element for a 'green building' that provides daylighting and a visual connection with the natural environment. Even before the current interest in green buildings there was no shortage of highly glazed building designs. But many of these buildings either rejected sunlight, and some associated daylight and view with highly reflective glazings or used highly transmissive glass and encountered serious internal comfort problems that could only be overcome with large HVAC systems, resulting in significant energy, cost and environmental penalties. From the 1960's to the 1990's innovation in glazing made heat absorbing glass, reflective glass and double glazing commonplace, with an associated set of aesthetic features. In the last decade there has been a subtle shift from trying to optimize an ideal, static design solution using these glazings to making the facade responsive, interactive and even intelligent. More sophisticated design approaches and technologies have emerged using new high-performance glazing, improved shading and solar control systems, greater use of automated controls, and integration with other building systems. One relatively new architectural development is the double …
Date: November 1, 2003
Creator: Selkowitz, Stephen; Aschehoug, Oyvind & Lee, Eleanor S.
System: The UNT Digital Library
Advanced Technology Vehicle Testing (open access)

Advanced Technology Vehicle Testing

The light-duty vehicle transportation sector in the United States depends heavily on imported petroleum as a transportation fuel. The Department of Energy’s Advanced Vehicle Testing Activity (AVTA) is testing advanced technology vehicles to help reduce this dependency, which would contribute to the economic stability and homeland security of the United States. These advanced technology test vehicles include internal combustion engine vehicles operating on 100% hydrogen (H2) and H2CNG (compressed natural gas) blended fuels, hybrid electric vehicles, neighborhood electric vehicles, urban electric vehicles, and electric ground support vehicles. The AVTA tests and evaluates these vehicles with closed track and dynamometer testing methods (baseline performance testing) and accelerated reliability testing methods (accumulating lifecycle vehicle miles and operational knowledge within 1 to 1.5 years), and in normal fleet environments. The Arizona Public Service Alternative Fuel Pilot Plant and H2-fueled vehicles are demonstrating the feasibility of using H2 as a transportation fuel. Hybrid, neighborhood, and urban electric test vehicles are demonstrating successful applications of electric drive vehicles in various fleet missions. The AVTA is also developing electric ground support equipment (GSE) test procedures, and GSE testing will start during the fall of 2003. All of these activities are intended to support U.S. energy independence. …
Date: November 1, 2003
Creator: Francfort, James
System: The UNT Digital Library
Apex Advanced Ferritic Steel, Flibe Self-Cooled First Wall and Blanket Design (open access)

Apex Advanced Ferritic Steel, Flibe Self-Cooled First Wall and Blanket Design

OAK-B135 As an element in the US Advanced Power Extraction (APEX) program, they evaluated the design option of using advanced nanocomposite ferritic steel (AFS) as the structural material and Flibe as the tritium breeder and coolant. They selected the recirculating flow configuration as the reference design. Based on the material properties of AFS, they found that the reference design can handle a maximum surface heat flux of 1 MW/m{sup 2}, and a maximum neutron wall loading of 5.4 MW/m{sup 2}, with a gross thermal efficiency of 47%, while meeting all the tritium breeding and structural design requirements. This paper covers the results of the following areas of evaluation: materials selection, first wall and blanket design configuration, materials compatibility, components fabrication, neutronics analysis, thermal hydraulics analysis including MHD effects, structural analysis, molten salt and helium closed cycle power conversion system, and safety and waste disposal of the recirculating coolant design.
Date: November 1, 2003
Creator: Wong, C. P. C.; Malang, S.; Sawan, M.; Sviatoslavsky, I.; Mogahed, E.; Smolentsev, S. et al.
System: The UNT Digital Library
Baseline Results and Future Plans for the NREL Controls Advanced Research Turbine: Preprint (open access)

Baseline Results and Future Plans for the NREL Controls Advanced Research Turbine: Preprint

During the 2002 - 2003 wind season, several new algorithms were tested on the Controls Advanced Research Turbine (CART) at the National Renewable Energy Laboratory. These include an''Optimally Tracking Rotor'' algorithm proposed before, an adaptive power tracking algorithm and several full-state feedback systems. General results from these algorithms are presented here with detailed results presented elsewhere.
Date: November 1, 2003
Creator: Fingersh, L. J. & Johnson, K. E.
System: The UNT Digital Library
Biodiesel: Today's Agricultural Fuel (open access)

Biodiesel: Today's Agricultural Fuel

Presented at ''Bioenergy: The Future of Rural America'' meeting in Westminster, Colorado on November 6, 2003.
Date: November 1, 2003
Creator: Tyson, K. S.
System: The UNT Digital Library
Cold-Start and Warm-Up Driveability Performance of Hybrid Electric Vehicles Using Oxygenated Fuels (open access)

Cold-Start and Warm-Up Driveability Performance of Hybrid Electric Vehicles Using Oxygenated Fuels

Provides analysis and results of the driveability performance testing from four hybrid electric vehicles--Honda Civic, Toyota Prius, and two Honda Insights--that used oxygenated fuels.
Date: November 1, 2003
Creator: Thornton, M.; Jorgensen, S.; Evans, B. & Wright, K.
System: The UNT Digital Library
Collapsing Radiative Shocks in Argon Gas on the Omega Laser (open access)

Collapsing Radiative Shocks in Argon Gas on the Omega Laser

A number of astrophysical systems involve radiative shocks that collapse spatially in response to energy lost through radiation. Supernova remnants are an example of systems that cool enough to radiatively collapse. This is believed to produce thin, dense shells that are Vishniac unstable. This type of instability may be responsible for the convoluted structure of supernova remnants such as the Cygnus Loop. We are conducting experiments on the Omega laser intended to produce such collapsing shocks and to study their evolution. The experiments use the laser to accelerate a thin slab of driving material (beryllium) through 1.1 ATM of argon gas ({approx}2 mg/cc) at {approx}100 km/sec. The simulations also predict that the dense layer will be pushed ahead of the dense beryllium by the leading edge of the expansion of this material. The experiment is diagnosed in two ways. X-ray radiography has detected the presence of the dense shocked layer. These data indicate that the shock velocity is {approx}100 km/s. A unique, side-on application of the VISAR (Velocity Interferometer System for Any Reflector) technique is used to detect frequency shifts from ionization and any reflections from the edge of the dense shocked layer.
Date: November 1, 2003
Creator: Reighard, A. B.; Drake, R. P.; Dannenberg, K.; Perry, T. S.; Robey, H. A.; Remington, B. A. et al.
System: The UNT Digital Library
Conceptual Design of a Very High Temperature Pebble-Bed Reactor (open access)

Conceptual Design of a Very High Temperature Pebble-Bed Reactor

Efficient electricity and hydrogen production distinguish the Very High Temperature Reactor as the leading Generation IV advanced concept. This graphite-moderated, helium-cooled reactor achieves a requisite high outlet temperature while retaining the passive safety and proliferation resistance required of Generation IV designs. Furthermore, a recirculating pebble-bed VHTR can operate with minimal excess reactivity to yield improved fuel economy and superior resistance to ingress events. Using the PEBBED code developed at the INEEL, conceptual designs of 300 megawatt and 600 megawatt (thermal) Very High Temperature Pebble-Bed Reactors have been developed. The fuel requirements of these compare favorably to the South African PBMR. Passive safety is confirmed with the MELCOR accident analysis code.
Date: November 1, 2003
Creator: Gougar, Hans D.; Ougouag, A. M.; Moore, Richard M. & Terry, W. K.
System: The UNT Digital Library
Consumptive Water Use for U.S. Power Production: Preprint (open access)

Consumptive Water Use for U.S. Power Production: Preprint

Evaporative cooling systems have been criticized for their water use and acclaimed for their low energy consumption, especially when compared to typical cooling systems. In order to determine the overall effectiveness of cooling systems, both water and energy need to be considered; however, there must be a metric to compare the amount of energy used at the site to the amount of water used at the power plant. A study of power plants and their respective water consumption was completed to effectively analyze evaporative cooling systems.
Date: November 1, 2003
Creator: Torcellini, P.; Long, N. & Judkoff, R.
System: The UNT Digital Library
The dependence of natural graphite anode performance on electrode density (open access)

The dependence of natural graphite anode performance on electrode density

The effect of electrode density for lithium intercalation and irreversible capacity loss on the natural graphite anode in lithium ion batteries was studied by electrochemical methods. Both the first-cycle reversible and irreversible capacities of the natural graphite anode decreased with an increase in the anode density though compression. The reduction in reversible capacity was attributed to a reduction in the chemical diffusion coefficient for lithium though partially agglomerated particles with a larger stress. For the natural graphite in this study the potentials for Li (de)insertion shifted between the first and second formation cycles and the extent of this shift was dependent on electrode density. The relation between this peak shift and the irreversible capacity loss are probably both due to the decrease in graphite surface area with compression.
Date: November 1, 2003
Creator: Shim, Joongpyo & Striebel, Kathryn A.
System: The UNT Digital Library
Design of a Production Process to Enhance Optical Performance of 3(omega) Optics (open access)

Design of a Production Process to Enhance Optical Performance of 3(omega) Optics

Using the Phoenix pre-production conditioning facility we have shown that raster scanning of 3{omega} optics using a XeF excimer laser and mitigation of the resultant damage sites with a CO{sub 2} laser can enhance their optical damage resistance. Several large-scale (43 cm x 43 cm) optics have been processed in this facility. A production facility capable of processing several large optics a week has been designed based on our experience in the pre-production facility. The facility will be equipped with UV conditioning lasers--351-nm XeF excimer lasers operating at 100 Hz and 23 ns. The facility will also include a CO{sub 2} laser for damage mitigation, an optics stage for raster scanning large-scale optics, a damage mapping system (DMS) that images large-scale optics and can detect damage sites or precursors as small as {approx} 15 {micro}m, and two microscopes to image damage sites with {approx} 5 {micro}m resolution. The optics will be handled in a class 100 clean room, within the facility that will be maintained at class 1000.
Date: November 1, 2003
Creator: Prasad, R R; Bruere, J R; Halpin, J; Lucero, P; Mills, S; Bernacil, M et al.
System: The UNT Digital Library
Design of Controls to Attenuate Loads in the Controls Advanced Research Turbine: Preprint (open access)

Design of Controls to Attenuate Loads in the Controls Advanced Research Turbine: Preprint

Designing wind turbines to maximize energy production and increase fatigue life is a major goal of the wind industry. To achieve this goal, we must design wind turbines to extract maximum energy and reduce component and system loads. This paper applies modern state-space control design methods to a two-bladed teetering-hub upwind machine located at the National Wind Technology Center*. The design objective is to regulate turbine speed in region 3 (above rated wind speed) and enhance damping in several low-damped flexible modes of the turbine. The controls approach is based on the Disturbance Accommodating Control (DAC) method and provides accountability for wind-speed disturbances. First, controls are designed using the single control input rotor collective pitch to stabilize the first drive-train torsion as well as the tower first fore-aft bending modes. Generator torque is then incorporated as an additional control input. This reduces some of the demand placed on the rotor collective pitch control system and enhances first drive train torsion mode damping. Individual blade pitch control is then used to attenuate wind disturbances having spatial variation over the rotor and effectively reduces blade flap deflections caused by wind shear.
Date: November 1, 2003
Creator: Wright, A. D. & Balas, M. J.
System: The UNT Digital Library
Detection and Location of Damage on Pipelines (open access)

Detection and Location of Damage on Pipelines

The INEEL has developed and successfully tested a real-time pipeline damage detection and location system. This system uses porous metal resistive traces applied to the pipe to detect and locate damage. The porous metal resistive traces are sprayed along the length of a pipeline. The unique nature and arrangement of the traces allows locating the damage in real time along miles of pipe. This system allows pipeline operators to detect damage when and where it is occurring, and the decision to shut down a transmission pipeline can be made with actual real-time data, instead of conservative estimates from visual inspection above the area.
Date: November 1, 2003
Creator: Moore, Karen A.; Carrington, Robert & Richardson, John
System: The UNT Digital Library
Development of a Process Model for CO(2) Laser Mitigation of Damage Growth in Fused Silica (open access)

Development of a Process Model for CO(2) Laser Mitigation of Damage Growth in Fused Silica

A numerical model of CO{sub 2} laser mitigation of damage growth in fused silica has been constructed that accounts for laser energy absorption, heat conduction, radiation transport, evaporation of fused silica and thermally induced stresses. This model will be used to understand scaling issues and effects of pulse and beam shapes on material removal, temperatures reached and stresses generated. Initial calculations show good agreement of simulated and measured material removal. The model has also been applied to LG-770 glass as a prototype red blocker material.
Date: November 1, 2003
Creator: Feit, M D; Rubenchik, A M; Boley, C & Rotter, M D
System: The UNT Digital Library
DOE's Public Database for Green Building Case Studies: Preprint (open access)

DOE's Public Database for Green Building Case Studies: Preprint

To help capture valuable information on''green building'' case studies, the U.S. Department of Energy has created an online database for collecting, standardizing, and disseminating information about high-performance, green projects. Type of information collected includes green features, design processes, energy performance, and comparison to other high-performance, green buildings.
Date: November 1, 2003
Creator: Torcellini, P. A. & Crawley, D. B.
System: The UNT Digital Library
Effect of Load Phase Angle on Wind Turbine Blade Fatigue Damage: Preprint (open access)

Effect of Load Phase Angle on Wind Turbine Blade Fatigue Damage: Preprint

This paper examines the importance of phase angle variations with respect to fatigue damage. The operating loads on a generic conventional three-bladed upwind 1.5-MW wind turbine blade were analyzed over a range of operating conditions, and an aggregate probability distribution for the actual phase angles between the in-plane (lead-lag) and out-of-plane (flap) loads was determined. Using a finite element model of a generic blade and Miner's Rule, the accumulated theoretical damage (based on axial strains) resulting from a fatigue test with variable phase angles was compared to the damage resulting from a fatigue test with a constant phase angle. The nodal damage distribution at specific blade cross-sections are compared for the constant and variable phase angle cases. The sequence effects of various phase angle progressions were also considered. For this analysis, the finite element results were processed using the nonlinear Marco-Starkey damage accumulation model. Each phase angle sequence was constrained to have the same overall phase angle distribution and the same total number of cycles but the order in which the phase angles were applied was varied.
Date: November 1, 2003
Creator: White, D. L. & Musial, W. D.
System: The UNT Digital Library
Enhanced Performance of Large 3(omega) Optics Using UV and IR Lasers (open access)

Enhanced Performance of Large 3(omega) Optics Using UV and IR Lasers

We have developed techniques using small-beam raster scanning to laser-condition fused silica optics to increase their damage threshold. Further, we showed that CO{sub 2} lasers could be used to mitigate and stabilize damage sites while still on the order of a few tens of microns in size, thereby greatly increasing the lifetime of an optic. We recently activated the Phoenix pre-production facility to condition and mitigate optics as large as 43 cm x 43 cm. Several full-scale optics have been processed in Phoenix. The optics were first photographed using a damage mapping system to identify scratches, digs, or other potential sites for initiation of laser damage. We then condition the optic, raster scanning with the excimer laser. The first scan is performed at a low fluence. A damage map is then acquired and any new damage sites or any sites that have grown in size are mitigated using the CO{sub 2} laser. The process is repeated at successively higher fluences until a factor of 1.7 above the nominal operating fluence is reached. After conditioning, optics were tested in a large beam 3{omega} laser and showed no damage at fluences of 8 J/cm{sup 2} average.
Date: November 1, 2003
Creator: Prasad, R. R.; Bruere, J. R.; Peterson, J. E.; Halpin, J. M.; Borden, M. R. & Hackel, R. P.
System: The UNT Digital Library
Feasibility of Floating Platform Systems for Wind Turbines: Preprint (open access)

Feasibility of Floating Platform Systems for Wind Turbines: Preprint

This paper provides a general technical description of several types of floating platforms for wind turbines. Platform topologies are classified into multiple- or single-turbine floaters and by mooring method. Platforms using catenary mooring systems are contrasted to vertical mooring systems and the advantages and disadvantages are discussed. Specific anchor types are described in detail. A rough cost comparison is performed for two different platform architectures using a generic 5-MW wind turbine. One platform is a Dutch study of a tri-floater platform using a catenary mooring system, and the other is a mono-column tension-leg platform developed at the National Renewable Energy Laboratory. Cost estimates showed that single unit production cost is $7.1 M for the Dutch tri-floater, and $6.5 M for the NREL TLP concept. However, value engineering, multiple unit series production, and platform/turbine system optimization can lower the unit platform costs to $4.26 M and $2.88 M, respectively, with significant potential to reduce cost further with system optimization. These foundation costs are within the range necessary to bring the cost of energy down to the DOE target range of $0.05/kWh for large-scale deployment of offshore floating wind turbines.
Date: November 1, 2003
Creator: Musial, W.; Butterfield, S. & Boone, A.
System: The UNT Digital Library
First Measurement of Pressure Gradient-Driven Currents in Tokamak Edge Plasmas (open access)

First Measurement of Pressure Gradient-Driven Currents in Tokamak Edge Plasmas

Localized currents driven by pressure gradients play a pivotal role in the magnetohydrodynamic stability of toroidal plasma confinement devices. We have measured the currents generated in the edge of L- (low) and H- (high confinement) mode discharges on the DIII-D tokamak, utilizing the Zeeman effect in an injected lithium beam to obtain high resolution profiles of the poloidal magnetic field. We find current densities in excess of 1 MA/m{sup 2} in a 1 to 2 cm region near the peak of the edge pressure gradient. These values are sufficient to challenge edge stability theories based on specific current formation models.
Date: November 1, 2003
Creator: Thomas, D. M.; Leonard, A. W.; Lao, L. L.; Osborne, T. H.; Mueller, H. W. & Finkenthal, D. K.
System: The UNT Digital Library
Functional and Phylogenetic Analyses of a Conserved Regulatory Program in the Phloem of Minor Veins (open access)

Functional and Phylogenetic Analyses of a Conserved Regulatory Program in the Phloem of Minor Veins

This article discusses functional and phylogenetic analyses of a conserved regulatory program in the phloem of minor veins, which are developmentally and physiologically distinct from the phloem in the rest of the vascular system.
Date: November 2003
Creator: Ayre, Brian G.; Blair, Jaime E. & Turgeon, Robert
System: The UNT Digital Library
Growth of Laser Initiated Damage in Fused Silica at 527 nm (open access)

Growth of Laser Initiated Damage in Fused Silica at 527 nm

The effective lifetime of optics is limited by both laser-induced damage and the subsequent growth of laser initiated damage sites. We have measured the growth rate of laser-induced damage in fused silica in both air and vacuum at 527 nm. For damage on the exit surface, the data shows exponential growth in the lateral size of the damage site with shot number. The exponential growth coefficient depends linearly on the laser fluence. The behavior at the fluence threshold for growth is contrasted to that observed at 351 nm. The growth rate was not significantly affected by either the wavelength of the initiating fluence or the presence of 10 torr of air as compared to vacuum. When the damage is located on the input surface, it has both a higher threshold for growth and does not grow exponentially.
Date: November 1, 2003
Creator: Norton, M A; Donohue, E E; Hollingsworth, W G; McElroy, J N & Hackel, R P
System: The UNT Digital Library
Hybrid Power System with a Controlled Energy Storage: Preprint (open access)

Hybrid Power System with a Controlled Energy Storage: Preprint

We investigated a small isolated hybrid power system that used two types of power generation; wind turbine and diesel generation. The interaction of diesel generation, the wind turbine, and the local load is complicated because both the load and the wind turbine fluctuate during the day. These fluctuations create imbalances in power distribution (energy sources are not equal to energy sinks) that can affect the frequency and the voltage in the power system. The addition of energy storage will help balance the distribution of power in the power network. For this paper, we studied the interaction among hybrid power system components and the relative size of the components. We also show how the contribution of wind energy affects the entire power system and distribution and the role of energy storage under the transient conditions caused by load changes and wind turbine start ups.
Date: November 1, 2003
Creator: Muljadi, E. & Bialasiewicz, J. T.
System: The UNT Digital Library
IEEE 1547 National Standard for Interconnecting Distributed Generation: How Could It Help My Facility? Preprint (open access)

IEEE 1547 National Standard for Interconnecting Distributed Generation: How Could It Help My Facility? Preprint

This article summarizes the purpose, development, and impact of the Institute of Electrical and Electronics Engineers 1547 Standard for Interconnecting Distributed Resources With Electric Power Systems. Also included is a short explanation of supporting standards IEEE P1547.1, P1547.2, and P1547.3.
Date: November 1, 2003
Creator: Basso, T. & Friedman, N. R.
System: The UNT Digital Library