2,505 research outputs found

    A dual telescope for spectroheliography in the extreme ultra-violet

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    Dual reflecting telescope design for ultraviolet spectroheliograph

    Techniques for improving reliability of computers

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    Modular design techniques improve methods of error detection, diagnosis, and recovery. Theoretical computer (MARCS (Modular Architecture for Reliable Computer Systems)) study deals with postulated and modeled technology indigenous to 1975-1980. Study developments are discussed

    Town of Colonial Beach Survey of Central and Castlewood Beaches

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    The Town of Colonial Beach occupies a peninsula between the Potomac River and Monroe Bay. Approximately 2.5 miles of the shoreline is publicly-owned. Two areas on the Potomac River have been enhanced as recreational beaches for swimming and sunbathing. Central Beach is located just south of the Town Pier and is the main recreational beach. Castlewood Beach is south of Central Beach near the entrance to Monroe Bay

    Parrotts Creek Dredge Channel Data Report

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    Parrotts Creek is located along the Rappahannock River in Middlesex County, VA. The mouth of the creek is about 850 ft wide, but just inside the mouth of the creek, a spit extends from the upland narrowing the creek to about 300 ft before it widens again. Overall, this is a relatively short, undeveloped creek. Most of the development (wharfs, ramps, piers) occur near the mouth. Most of the more inland areas of the creek are surrounded by woodland. The federally-authorized channel was established in 1955 due to the presence of a public ramp and landing area, as well as oyster and seafood packing houses located on the creek. It is a 4,800 ft long, 60 ft wide channel with a 120 ft by 120 ft turning basin, and a controlling depth of -6 ft MLLW. (...

    Metal-insulator transition in a doped semiconductor

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    Millikelvin measurements of the conductivity as a function of donor density and uniaxial stress in bulk samples of phosphorus-doped silicon establish that the transition from metal to insulator is continuous, but sharper than predicted by scaling theories of localization. The divergence of the dielectric susceptibility as the transition is approached from below also points out problems in current scaling theories. The temperature dependence of the conductivity and the magnetoresistance in the metal indicate the importance of Coulomb interactions in describing the behavior of disordered systems

    Performance of Sills: St. Mary’s City, St. Mary’s River, Maryland

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    Living shorelines represent a shoreline management option that combines various erosion control methodologies and/or structures while at the same time restoring or preserving natural shoreline vegetation communities. A common living shoreline design in Chesapeake Bay includes a low offshore rock sill to absorb wave energy with an emergent wetland landward of the sill to enhance erosion control, provide critical habitat, and improve water quality condition. This study is part of a larger, ongoing project to (1) evaluate erosion control effectiveness and the sustainability of offshore sill and fringing marsh design and structure, (2) evaluate ecological services (e.g., habitat value, water quality remediation) provided by the various components of the living shoreline design, and (3) develop design criteria that may enhance services provided by living shoreline designs in low and moderate energy environments. This project measures the performance of sills in Chesapeake Bay in support of developing design guidance. In particular, it assesses how the windows (or gaps/vents) in some sills affect their value for shore protection and water quality. The approach utilizes both field data collection (e.g., site assessment and survey, water quality data collection) and hydrodynamic modeling methodology. Two sites, varying in construction design and age, were assessed at St. Mary’s City, Maryland on the St. Mary’s River (Figure 1-1). Site 1 is part of a larger project and has about 1,000 feet of shoreline with a gapped sill that was built in 2002 (Figure 1-2). Site 2, a 1,000 feet non-gapped sill, was built in 1998 and is adjacent to Site 1 (Figure 1-2). Previous data exists for Site 1, which includes the implemented construction plan and the as-built survey. Both sites were surveyed to provide the present dimensions of the sill systems. Modeling methodology was used to assess residence time and age of water that flushes through sill structures and associated fringing wetland along part of Site 1. Also analyzed was the impact of several different window configurations and dimensions on beach shape and shore protection as well as the site substrate and vegetation characteristics, surface water and groundwater quality, and nekton

    Multi-label classification using ensembles of pruned sets

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    This paper presents a Pruned Sets method (PS) for multi-label classification. It is centred on the concept of treating sets of labels as single labels. This allows the classification process to inherently take into account correlations between labels. By pruning these sets, PS focuses only on the most important correlations, which reduces complexity and improves accuracy. By combining pruned sets in an ensemble scheme (EPS), new label sets can be formed to adapt to irregular or complex data. The results from experimental evaluation on a variety of multi-label datasets show that [E]PS can achieve better performance and train much faster than other multi-label methods

    Extreme Ultra-Violet Spectroscopy of the Lower Solar Atmosphere During Solar Flares

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    The extreme ultraviolet portion of the solar spectrum contains a wealth of diagnostic tools for probing the lower solar atmosphere in response to an injection of energy, particularly during the impulsive phase of solar flares. These include temperature and density sensitive line ratios, Doppler shifted emission lines and nonthermal broadening, abundance measurements, differential emission measure profiles, and continuum temperatures and energetics, among others. In this paper I shall review some of the advances made in recent years using these techniques, focusing primarily on studies that have utilized data from Hinode/EIS and SDO/EVE, while also providing some historical background and a summary of future spectroscopic instrumentation.Comment: 34 pages, 8 figures. Submitted to Solar Physics as part of the Topical Issue on Solar and Stellar Flare