Relative potentials of concentrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications

The purpose of this study is to assess the relative economic potentials of concenrating and two-axis tracking flat-plate photovoltaic arrays for central-station applications in the mid-1990's. Specific objectives of this study are to provide information on concentrator photovoltaic collector probabilistic price and efficiency levels to illustrate critical areas of R&D for concentrator cells and collectors, and to compare concentrator and flat-plate PV price and efficiency alternatives for several locations, based on their implied costs of energy. To deal with the uncertainties surrounding research and development activities in general, a probabilistic assessment of commercially achievable concentrator photovoltaic collector efficiencies and prices (at the factory loading dock) is performed. The results of this projection of concentrator photovoltaic technology are then compared with a previous flat-plate module price analysis (performed early in 1983). To focus this analysis on specific collector alternatives and their implied energy costs for different locations, similar two-axis tracking designs are assumed for both concentrator and flat-plate options

1-loop matching and NNLL resummation for all partonic 2 to 2 processes in QCD

The Wilson Coefficients for all 4-parton operators which arise in matching QCD to Soft-Collinear Effective Theory (SCET) are computed at 1-loop. Any dijet observable calculated in SCET beyond leading order will require these results. The Wilson coefficients are separated by spin and color, although most applications will involve only the spin-averaged hard functions. The anomalous dimensions for the Wilson coefficients are given to 2-loop order, and the renormalization group equations are solved explicitly. This will allow for analytical resummation of dijet observables to next-to-next-to-leading logarithmic accuracy. For each channel, there is a natural basis in which the evolution is diagonal in color space. The same basis also diagonalizes the color evolution for the soft function. Even though soft functions required for SCET calculations are observable dependent, it is shown that their renormalization group evolution is almost completely determined by a universal structure. With these results, it will be possible to calculate hadronic event shapes or other dijet observables to next-to-leading order with next-to-next-to-leading log resummation.Comment: 28 pages, 5 tables; v2: typo corrected in Eq. (56

Vertical Equity in the Taxation of Single Family Homes

Vertical equity in ad valorem real property taxation is the concept that all properties within a taxing jurisdiction are assessed in equal proportion to their fair market value. This study examines the assessment of single family homes in Bellingham, Washington, utilizing a database of 1,118 home sales in the southern half of Bellingham that sold during the time period of January, 1990 through June, 1994. The results of several empirical tests suggest the presence of regressive vertical inequity. It appears that higher market value homes are assessed at a lower proportion of their value (sales price) than less expensive homes. These results suggest that property taxation at the local level magnifies the regessivity of Washington State's already highly regressive state tax system. Why does this apparent regressive vertical inequity exist? The authors offer several possibilities including the propensity of wealthy homeowners to challenge property tax assessments, the difficulty of valuing the amenities inside an upper-end home, the heterogeneity of the upper-end home market coupled with a small number of transactions, and the lack of ample staff and other resources at the County Assessor's office.

An Examination of Vertical Equity Over Two Reassessment Cycles

This article examines vertical equity in the assessment of single-family homes over two assessment cycles in Bellingham, Washington. The two assessment periods, which are four years apart, followed two differing property appreciation periods. The 1992 reassessment followed an explosion in home values, while the 1996 reassessment came after more moderate price appreciation. The assessed value/ market value ratio is the basic tool of this study with actual sales prices assumed to be market value. Utilizing a database of 721 home sales from January, 1990 to December, 1992, this study’s empirical analysis suggests regressive vertical inequity in 1992. This situation appears to have changed in 1996. Results from a second database consisting of 835 home sales from January, 1994 through December, 1996, suggest a substantial reduction in vertical inequity. Overall, it appears that the County Assessor’s office addressed the previous problem with positive results for the average property taxpayer of Whatcom County.

The Upper Limit Solar Gamma-ray Spectrum to 10 Mev

Balloon flight data on upper limit solar gamma ray spectrum from quiet su

Preliminary results of the University of California X-ray experiment on the OSO-3

Cosmic and solar X ray data obtained by Orbiting Solar Observatory /OSO-3

All-Optical Depletion of Dark Excitons from a Semiconductor Quantum Dot

Semiconductor quantum dots are considered to be the leading venue for fabricating on-demand sources of single photons. However, the generation of long-lived dark excitons imposes significant limits on the efficiency of these sources. We demonstrate a technique that optically pumps the dark exciton population and converts it to a bright exciton population, using intermediate excited biexciton states. We show experimentally that our method considerably reduces the DE population while doubling the triggered bright exciton emission, approaching thereby near-unit fidelity of quantum dot depletion.Comment: 5 pages, 3 figure

The Influence of Canadian Investment on U.S. Residential Property Values

This study is an examination of the impact of foreign investors on an American residential real estate market. Point Roberts, Washington, a real estate market that is dominated by Canadians, is the focus of the analysis. Utilizing a ten-year database of home sales, the empirical analysis suggests that the Canadian/U.S. dollar exchange rate and market conditions in nearby Vancouver, British Columbia, strongly influence Point Roberts residential property price levels. A rising Canadian dollar seems to motivate increased demand for Point Roberts property by Canadian investors, for example. The sensitivity of real estate prices to exchange-rate changes appears to be a three-to-six-month lagged function. In general, it appears that a higher Canadian dollar will increase the Canadian demand for Point Roberts real estate which, in turn, leads to higher transaction prices. In addition, transaction prices in Point Roberts are slightly more volatile than are prices in the Vancouver market.

Determinisitic Writing and Control of the Dark Exciton Spin using Short Single Optical Pulses

We demonstrate that the quantum dot-confined dark exciton forms a long-lived integer spin solid state qubit which can be deterministically on-demand initiated in a pure state by one optical pulse. Moreover, we show that this qubit can be fully controlled using short optical pulses, which are several orders of magnitude shorter than the life and coherence times of the qubit. Our demonstrations do not require an externally applied magnetic field and they establish that the quantum dot-confined dark exciton forms an excellent solid state matter qubit with some advantages over the half-integer spin qubits such as the confined electron and hole, separately. Since quantum dots are semiconductor nanostructures that allow integration of electronic and photonic components, the dark exciton may have important implications on implementations of quantum technologies consisting of semiconductor qubits.Comment: Added two authors, minor edits to figure captions, expanded discussion of dark exciton eigenstate