Film Fabrication Technologies at NREL

The National Renewable Energy Laboratory (NREL) has extensive capabilities for fabricating a variety of high-technology films. Much of the in-house work in NREL's large photovoltaics (PV) program involves the fabrication of multiple thin-film semiconducting layers constituting a thin-film PV device. NREL's smaller program in superconductivity focuses on the fabrication of superconducting films on long, flexible tape substrates. This paper focuses on four of NREL's in-house research groups and their film fabrication techniques, developed for a variety of elements, alloys, and compounds to be deposited on a variety of substrates. As is the case for many national laboratories, NREL's technology transfer efforts are focusing on Cooperative Research and Development Agreements (CRADA's) between NREL researchers and private industry researchers

A novel technique for wide-field polarimetry with a radiotelescope array

We report the use of the Australia Telescope Compact Array (ATCA) to conduct polarimetric observations of the sky at 5 GHz. The ATCA is normally operated as an interferometer array, but these observations were conducted in a split array mode in which the antenna elements were used as single-dishes with their beams staggered to simultaneously cover a wide area of sky with a resolution of 10 arcmin. The linearly polarized sky radiation was fully characterized from measurements, made over a range of parallactic angles, of the cross correlated signals from the orthogonal linear feeds. We describe the technique and present a polarimetric image of the Vela supernova remnant made as a test of the method. The development of the techniques was motivated by the need for wide-field imaging of the foreground contamination of the polarized component of the cosmic microwave background signal.Comment: 13 pages, 2 figures, accepted for publication in A

Relations between extensional tectonics and magmatism within the Southern Oklahoma aulacogen

Variations in the geometry, distribution and thickness of Cambrian igneous and sedimentary units within southwest Oklahoma are related to a late Proterozoic - early Paleozoic rifting event which formed the Southern Oklahoma aulacogen. These rock units are exposed in the Wichita Mountains, southwest Olkahoma, located on the northern margin of a Proterozoic basin, identified in the subsurface by COCORP reflection data. Overprinting of the Cambrian extensional event by Pennyslvanian tectonism obsured the influence of pre-existing basement structures and contrasting basement lithologies upon the initial development of the aulacogen

Fees in an Imperfect World: An Application to Motor Vehicle Emissions

This paper compares an emissions fee on measured vehicle emissions rates to a mandatory regulation that requires all vehicles to maintain emissions below a minimum standard. We model the motorist’s decision under the fee policy and simulate the fee and regulatory policies using data from an emissions inspection program that includes test and repair information for more than 50,000 vehicles. Under ideal conditions with perfect information and no subsidies, the fee on emissions rates performs substantially better than the regulatory policy. When more realistic modeling of available information and market conditions are included, there is little difference in the cost and effectiveness of the fee and regulatory programs. In particular, we find that the ability of the polluter to assess the emissions and cost outcomes of is critical importance for the performance of the fee policy.pollution fees, emissions control, vehicle pollution, inspection and maintenance

Radio sources near the core of globular cluster 47 Tucanae

We present ATCA radio images of the globular cluster 47 Tucanae made at 1.4 and 1.7 GHz and provide an analysis of the radio sources detected within 5 arcmin of the cluster centre. 11 sources are detected, most of which are clustered about the core of 47 Tuc. Both of the pulsars in 47 Tuc whose positions are known can be identified with sources in the 1.4 GHz image. The source distribution has a characteristic radius of ~100 arcsec, larger than the 23 arcsec radius of the cluster core. We compare source positions with the positions of nine X-ray sources and find no correspondence.Comment: 6 pages, 4 postscript figures, LaTeX with MNRAS macro; Accepted by MNRA

Trapped-Ion Quantum Computing: Progress and Challenges

Trapped ions are among the most promising systems for practical quantum computing (QC). The basic requirements for universal QC have all been demonstrated with ions and quantum algorithms using few-ion-qubit systems have been implemented. We review the state of the field, covering the basics of how trapped ions are used for QC and their strengths and limitations as qubits. In addition, we discuss what is being done, and what may be required, to increase the scale of trapped ion quantum computers while mitigating decoherence and control errors. Finally, we explore the outlook for trapped-ion QC. In particular, we discuss near-term applications, considerations impacting the design of future systems of trapped ions, and experiments and demonstrations that may further inform these considerations.Comment: The following article has been submitted to Applied Physics Review

Time-scales of Radio Emission in PSR J0437-4715 at 327 MHz

Time-scales of radio emission are studied in PSR J0437-4715 at 327 MHz using almost half a million periods of high quality data from Ooty Radio Telescope. The radio emission in this milli second pulsar occurs on a short (s) time-scale of approximately 0.026 +- 0.001 periods, and on a (l) time-scale that is much longer than the widths of the components of the integrated profile (approximately 0.05 periods). The width of the s emission increases with its increasing relative contribution to the total radio emission. This may provide constraints for the details of discharge of vacuum gaps above pulsar polar caps. The s emission occasionally takes place in the form of intense spikes, which are confined to the main component of the integrated profile for 90 per cent of the time. The positions of spikes within a component of the integrated profile have no simple relation to the shape of that component. This may have impact on the interpretation of the integrated profile components in terms of independent regions of emission on the polar cap.Comment: Accepted for publication in Vol 543 (1 Nov 2000) of The Astrophysical Journa

Determination of failure limits for sterilizable solid rocket motor

A structural evaluation to establish probable failure limits and a series of environmental tests involving temperature cycling, sustained acceleration, and vibration were conducted on an 18-inch diameter solid rocket motor. Despite the fact that thermal, acceleration and vibration loads representing a severe overtest of conventional environmental requirements were imposed on the sterilizable motor, no structural failure of the grain or flexible support system was detected. The following significant conclusions are considered justified. It is concluded that: (1) the flexible grain retention system, which permitted heat sterilization at 275 F on the test motor, can readily be adopted to meet the environmental requirements of an operational motor design, and (2) if further substantiation of structural integrity is desired, the motor used is considered acceptable for static firing

The Trade-off between Private Lots and Public Open Space in Subdivisions at the Urban-Rural Fringe

In many communities on the urban–rural fringe, subdivisions are subject to “clustering” rules, in which houses must be located on a portion of the total land area and the remainder of the land is left as open space. This open space may be undisturbed forest or pastureland, or it may include recreation facilities and trails. In some communities, the open space may remain in agricultural use as pasture or cropland. Although the open space may provide benefits to subdivision residents, it means that those residents are living in a higher-density setting than people living in conventional subdivisions. It is unclear whether the benefits offset the loss experienced by smaller lots and higher density. This trade-off is the focus of our study. We use data on subdivision house sales occurring between 1981 and 2001 in a county on the fringe of the Washington, DC, metropolitan area to estimate a hedonic price model. We examine how households value being adjacent to open space and having more open space in the subdivision, and how they may be willing to trade off those amenities with their own private lot space. We find that private acreage matters to households—a 10 percent larger lot leads to about a 0.6 percent higher house price, all else being equal. Subdivision open space is also valuable to households, but the marginal effect is much smaller than the marginal effect of private lot space. We also find that subdivision open space does substitute for private land, but the extent of the trade-off is small. We use the results of the estimated hedonic model to simulate the effects on prices of jointly increasing open space and reducing average lot size, holding the size of the subdivision constant. We find that average house prices are lower with clustering, particularly for interior lots that are not adjacent to open space.subdivisions, clustering, hedonic property values, open space