46,650 research outputs found

    Shallow Surveying in Hazardous Waters

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    Of order one importance to any study of nearshore processes is knowledge of the bathymetry in shallow water. This is true for studies on open coast sandy beaches where surf zone dynamics drive the system, inlet environments where bathymetric evolution can rapidly change navigation channels, and in more benign, lower-energy coastal environments that evolve slowly over 10’s to 100’s of years. Difficulties in obtaining shallow bathymetry where depth-limited wave breaking occurs, submerged hazards are present, or other harsh environments has led to the development of survey systems on highly maneuverable personal watercraft (Beach, et al., 1994; Cote, 1999; Dugan, et al., 1999; MacMahan, 2001). In this work we discuss shallow water surveying from the Coastal Bathymetry Survey System (CBASS), a Yamaha Waverunner equipped with differential GPS, single-beam 192 KHz acoustic echo-sounder, and onboard navigation system. Data obtained with the CBASS in three regions will be discussed, including an energetic surf zone located in southern California during the 2003 Nearshore Canyon Experiment (NCEX), on Lake Erie in 2002 (and compared with historical surveys dating back 150 years), and around Piscataqua River Inlet, NH, in 2007. Estimated accuracy (for sandy bottoms) in water depths ranging 1–10 m are 0.07-0.10 m in the vertical, and on the order of 0.1-1 m horizontally depending on water depth and bottom slope. The high maneuverability of the personal watercraft makes very shallow water bathymetric surveys possible with acoustic altimeters, particularly in regions where airborne remote sensing systems fail (owing to water clarity issues) or where repeated high resolution surveys are required (e.g., where an erodible bottom is rapidly evolving)

    Permutation Inference for Canonical Correlation Analysis

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    Canonical correlation analysis (CCA) has become a key tool for population neuroimaging, allowing investigation of associations between many imaging and non-imaging measurements. As other variables are often a source of variability not of direct interest, previous work has used CCA on residuals from a model that removes these effects, then proceeded directly to permutation inference. We show that such a simple permutation test leads to inflated error rates. The reason is that residualisation introduces dependencies among the observations that violate the exchangeability assumption. Even in the absence of nuisance variables, however, a simple permutation test for CCA also leads to excess error rates for all canonical correlations other than the first. The reason is that a simple permutation scheme does not ignore the variability already explained by previous canonical variables. Here we propose solutions for both problems: in the case of nuisance variables, we show that transforming the residuals to a lower dimensional basis where exchangeability holds results in a valid permutation test; for more general cases, with or without nuisance variables, we propose estimating the canonical correlations in a stepwise manner, removing at each iteration the variance already explained, while dealing with different number of variables in both sides. We also discuss how to address the multiplicity of tests, proposing an admissible test that is not conservative, and provide a complete algorithm for permutation inference for CCA.Comment: 49 pages, 2 figures, 10 tables, 3 algorithms, 119 reference

    Developing modern multifunctional agroforestry systems for sustainable intensification

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    Agroforestry is a land-use system that integrates trees and shrubs with crops and/or livestock production. It has been identified by the International Assessment of Agricultural Knowledge, Science and Technology for Development (IAASTD, 2008) as a ‘win-win’ approach that balances the production of commodities (food, feed, fuel, fibre, etc.) with non-commodity outputs such as environmental protection and cultural and landscape amenities. This paper will review the potential of agroforestry as part of a multifunctional working landscape in temperate regions, and will consider management and policy implications of widespread adoption of this form of land-use

    London May Term

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    Meaningful international programs and experiences don\u27t happen by accident. Much attention and intentionality are required to keep these programs from simply becoming educational tourism. This project will highlight the multiple ways in which the London May term program has been designed and executed in order to ensure a meaningful and significant educational and life experience

    U.S. commercial electricity consumption

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    Commercial electricity usage exceeds that of industrial usage and is almost as large as residential electricity consumption in the United States. In this study, regional economic, demographic, and climatic data are used to analyze commercial electricity demand in the United States. Results indicate that total commercial demand for electricity is negatively related to price. In addition, the number of businesses and service income positively affect electricity demand for commercial use. The results are similar for equations estimated for kilowatt-hours demanded per business. The regional dummy variables exhibit different signs, which may occur due to climate factors because warm weather regions experience greater volumes of cooling degree-days, while cool weather regions observe larger amounts of heating degree-days. Although coefficients for the price of natural gas are positive, they do not satisfy the 5-percent significance criterion. The latter suggests that natural gas may not be a substitute good for electricity within the commercial sector of the U.S. economy.Commercial Electricity Consumption; Regional Economics

    Ultimate Acceptability, Cultural Bias, and an American Indian World : reflections on Nelson Goodman

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    Nelson Goodman maintains that there is a plurality of internally consistent, equally privileged, well-made actual worlds constructed through the use of very special symbol systems-right or ultimately acceptable world versions. Using evidence from American Indian traditions, I will argue that Goodman's criteria for ultimately acceptability are culturally biased against any non-Western world version-especially a Native version. I will then offer a culturally sensitive interpretation of Goodman's criteria for ultimate acceptability that an American Indian world version satisfies, and so is numbered among the internally consistent, equally privileged, well-made actual worlds.Nelson Goodman sostiene que hay una pluralidad de mundos internamente consistentes, igualmente privilegiados, bien construidos y reales que se erigen mediante el uso de sistemas simbólicos muy especiales, a saber, versiones de mundo correctas o en última instancia aceptables. Utilizando como evidencia algunas tradiciones de los indios americanos, argumentaré que los criterios de Goodman para la aceptabilidad última están culturalmente sesgados en detrimento de cualquier versión del mundo no occidental, en particular, una versión nativa. Ofreceré entonces una interpretación culturalmente sensible de los criterios de Goodman para la aceptabilidad última satisfechos por una versión del mundo de los indios americanos, de modo que se cuente entre los mundos internamente consistentes, igualmente privilegiados, bien construidos y reales
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