24,477 research outputs found

    On satellite meteorology studies Final report

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    Satellite meteorology research on polar energy budget, atmospherics detection, and Mars atmospheric circulatio

    Development of a magneforming process for the fabrication of thin-wall tungsten cylinders final report

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    Magneforming process - high energy rate metal forming technique for fabrication of thin wall tungsten cylinder

    X-ray and infrared studies of several ruthenium-sulfur dioxide complexes

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    X-ray and infrared data on crystal and molecular structure of ruthenium-sulfur dioxide complexe

    Comparing Simulations and Observations of the Lyman-Alpha Forest I. Methodology

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    We describe techniques for comparing spectra extracted from cosmological simulations and observational data, using the same methodology to link Lyman-alpha properties derived from the simulations with properties derived from observational data. The eventual goal is to measure the coherence or clustering properties of Lyman-alpha absorbers using observations of quasar pairs and groups. We quantify the systematic underestimate in opacity that is inherent in the continuum fitting process of observed spectra over a range of resolution and signal-to-noise ratio. We present an automated process for detecting and selecting absorption features over the range of resolution and signal-to-noise of typical observational data on the Lyman-alpha "forest". Using these techniques, we detect coherence over transverse scales out to 500 h^{-1}_{50} kpc in spectra extracted from a cosmological simulation at z = 2.Comment: 52 pages, includes 14 figures, to appear in ApJ v566 Feb 200

    Robo-line storage: Low latency, high capacity storage systems over geographically distributed networks

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    Rapid advances in high performance computing are making possible more complete and accurate computer-based modeling of complex physical phenomena, such as weather front interactions, dynamics of chemical reactions, numerical aerodynamic analysis of airframes, and ocean-land-atmosphere interactions. Many of these 'grand challenge' applications are as demanding of the underlying storage system, in terms of their capacity and bandwidth requirements, as they are on the computational power of the processor. A global view of the Earth's ocean chlorophyll and land vegetation requires over 2 terabytes of raw satellite image data. In this paper, we describe our planned research program in high capacity, high bandwidth storage systems. The project has four overall goals. First, we will examine new methods for high capacity storage systems, made possible by low cost, small form factor magnetic and optical tape systems. Second, access to the storage system will be low latency and high bandwidth. To achieve this, we must interleave data transfer at all levels of the storage system, including devices, controllers, servers, and communications links. Latency will be reduced by extensive caching throughout the storage hierarchy. Third, we will provide effective management of a storage hierarchy, extending the techniques already developed for the Log Structured File System. Finally, we will construct a protototype high capacity file server, suitable for use on the National Research and Education Network (NREN). Such research must be a Cornerstone of any coherent program in high performance computing and communications

    Reionization history constraints from neural network based predictions of high-redshift quasar continua

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    Observations of the early Universe suggest that reionization was complete by z∌6z\sim6, however, the exact history of this process is still unknown. One method for measuring the evolution of the neutral fraction throughout this epoch is via observing the Lyα\alpha damping wings of high-redshift quasars. In order to constrain the neutral fraction from quasar observations, one needs an accurate model of the quasar spectrum around Lyα\alpha, after the spectrum has been processed by its host galaxy but before it is altered by absorption and damping in the intervening IGM. In this paper, we present a novel machine learning approach, using artificial neural networks, to reconstruct quasar continua around Lyα\alpha. Our QSANNdRA algorithm improves the error in this reconstruction compared to the state-of-the-art PCA-based model in the literature by 14.2% on average, and provides an improvement of 6.1% on average when compared to an extension thereof. In comparison with the extended PCA model, QSANNdRA further achieves an improvement of 22.1% and 16.8% when evaluated on low-redshift quasars most similar to the two high-redshift quasars under consideration, ULAS J1120+0641 at z=7.0851z=7.0851 and ULAS J1342+0928 at z=7.5413z=7.5413, respectively. Using our more accurate reconstructions of these two z>7z>7 quasars, we estimate the neutral fraction of the IGM using a homogeneous reionization model and find xˉHI=0.25−0.05+0.05\bar{x}_\mathrm{HI} = 0.25^{+0.05}_{-0.05} at z=7.0851z=7.0851 and xˉHI=0.60−0.11+0.11\bar{x}_\mathrm{HI} = 0.60^{+0.11}_{-0.11} at z=7.5413z=7.5413. Our results are consistent with the literature and favour a rapid end to reionization

    Plasmarings as dual black rings

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    We construct solutions to the relativistic Navier-Stokes equations that describe the long wavelength collective dynamics of the deconfined plasma phase of N=4 Yang Mills theory compactified down to d=3 on a Scherk-Schwarz circle and higher dimensional generalisations. Our solutions are stationary, axially symmetric spinning balls and rings of plasma. These solutions, which are dual to (yet to be constructed) rotating black holes and black rings in Scherk-Schwarz compactified AdS(5) and AdS(6), and have properties that are qualitatively similar to those of black holes and black rings in flat five dimensional supergravity.Comment: 40 pages, 40 figures. (v2) Correction to black brane equation of state, additional reference

    Do Homebuyers Care about the 'Quality' of Natural Habitats?

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    We study if homebuyers in Tucson, Arizona care about the condition of natural habitats and if they have preferences between natural and manmade habitats. Using field work data we examine whether homebuyers willingness to pay is influenced by the biological condition of the neighboring riparian habitat and how homebuyers value alternative manmade green areas, specifically golf courses. We also explore the relationship between the field data and remote sensing vegetation indices. The results of a hedonic analysis of houses that sold within 0.2 miles of 51 stratified-random selected riparian survey sites in Tucson, Arizona reveals that homebuyers significantly value habitat quality and negatively value manmade park-like features. Homebuyers are willing to pay twenty percent more to live near a riparian corridor that is densely vegetated and contains more shrub and tree species, particularly species that are dependent on perennial water flow. These environmental premiums are significant, outweighing structural factors such as an additional garage or swimming pool. Likewise, proximity to a riparian habitat with low biological quality or to a golf course lowers property values.Land Economics/Use,
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