4,681 research outputs found

    Designing and Operating Safe and Secure Transit Systems: Assessing Current Practices in the United States and Abroad, MTI Report 04-05

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    Public transit systems around the world have for decades served as a principal venue for terrorist acts. Today, transit security is widely viewed as an important public policy issue and is a high priority at most large transit systems and at smaller systems operating in large metropolitan areas. Research on transit security in the United States has mushroomed since 9/11; this study is part of that new wave of research. This study contributes to our understanding of transit security by (1) reviewing and synthesizing nearly all previously published research on transit terrorism; (2) conducting detailed case studies of transit systems in London, Madrid, New York, Paris, Tokyo, and Washington, D.C.; (3) interviewing federal officials here in the United States responsible for overseeing transit security and transit industry representatives both here and abroad to learn about efforts to coordinate and finance transit security planning; and (4) surveying 113 of the largest transit operators in the United States. Our major findings include: (1) the threat of transit terrorism is probably not universal—most major attacks in the developed world have been on the largest systems in the largest cities; (2) this asymmetry of risk does not square with fiscal politics that seek to spread security funding among many jurisdictions; (3) transit managers are struggling to balance the costs and (uncertain) benefits of increased security against the costs and (certain) benefits of attracting passengers; (4) coordination and cooperation between security and transit agencies is improving, but far from complete; (5) enlisting passengers in surveillance has benefits, but fearful passengers may stop using public transit; (6) the role of crime prevention through environmental design in security planning is waxing; and (7) given the uncertain effectiveness of antitransit terrorism efforts, the most tangible benefits of increased attention to and spending on transit security may be a reduction in transit-related person and property crimes

    Between the tides: modelling the elevation of Australia’s exposed intertidal zone at continental scale

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    The intertidal zone represents a critical transition between marine and terrestrial ecosystems, supporting a complex mosaic of highly productive and biologically diverse habitats. However, our understanding of these important coastal environments is limited by a lack of spatially consistent topographic data, which can be extremely challenging and costly to obtain at continental-scale. Satellite remote sensing represents an important resource for monitoring extensive coastal zones. Previous approaches to modelling the elevation of the intertidal zone using earth observation (EO) data have been restricted to small study regions or have relied on manual image interpretation, thus limiting their ability to be applied consistently over large geographic extents. In this study, we present an automated open-source approach to generate satellite-derived elevation data for over 15,387 km2 of intertidal terrain across the entire Australian coastline. Our approach combines global tidal modelling with a 30-year time series archive of spatially and spectrally calibrated Landsat satellite data managed within the Digital Earth Australia (DEA) platform. The resulting National Intertidal Digital Elevation Model (NIDEM) dataset provides an unprecedented three-dimensional representation of Australia's vast exposed intertidal zone at 25 m spatial resolution. We validate our model against LiDAR, RTK GPS and multibeam bathymetry datasets, finding that modelled elevations are highly accurate across sandy beach (±0.41 m RMSE) and tidal flat environments (±0.39 m RMSE). Model performance was least accurate (±2.98 m RMSE) within rocky shores and reefs and other complex coastal environments with extreme and variable tidal regimes. We discuss key challenges associated with modelling intertidal elevation including tidal model performance and biased observations from sun-synchronous satellites, and suggest future directions to improve the accuracy and utility of continental-scale intertidal elevation modelling. Our model can be applied to tidally-influenced coastal environments globally, addressing a key gap between the availability of sub-tidal bathymetry and terrestrial elevation data

    The Economics of Fuel Management: Wildfire, Invasive Plants, and the Dynamics of Sagebrush Rangelands in the Western United States

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    In this article we develop a simulation model to evaluate the economic efficiency of fuel treatments and apply it to two sagebrush ecosystems in the Great Basin of the western United States: the Wyoming Sagebrush Steppe and Mountain Big Sagebrush ecosystems. These ecosystems face the two most prominent concerns in sagebrush ecosystems relative to wildfire: annual grass invasion and native conifer expansion. Our model simulates long-run wildfire suppression costs with and without fuel treatments explicitly incorporating ecological dynamics, stochastic wildfire, uncertain fuel treatment success, and ecological thresholds. Our results indicate that, on the basis of wildfire suppression costs savings, fuel treatment is economically efficient only when the two ecosystems are in relatively good ecological health. We also investigate how shorter wildfire-return intervals, improved treatment success rates, and uncertainty about the location of thresholds between ecological states influence the economic efficiency of fuel treatments

    Implications of Climate Change for Agricultural Pest Management

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    Termination ReportThe University Archives has determined that this item is of continuing value to OSU's history.The thermal requirements of crops and insect pests differ significantly; their differential thermal requirements will govern how climate change impacts pest management needs and practices. To investigate the impact of climate change on pest management and the implications for farming communities, we have connected EPIC, a field-scale crop management model, with a temperature-driven model of insect population development (GILSM). EPIC was used to model the corn and soybean rotation common in the Midwest, and GILSM was programmed to model the growth of nine insect pests of corn and/or soybeans. Output from the model system was input to a geographic information system covering the eight-state corn-belt (Indiana, Illinois, Iowa, Kansas, Kentucky, Missouri, Nebraska and Ohio). The models were driven using GFDL-CM2 climate scenario data developed for the period 1901-2100 as part of NOA and IPCC investigations of global climate change. Over the past 100 years, crop productivity has increased several fold as a result of improved cultivation methods, fertilizers and pesticides, and plant breeding. In order to remove the confounding of changes in technology and possible climate change over the past century and unknown changes to come in the next century, a standard crop production protocol was used from 1901-2100. Using the crop production practices used most commonly in 2000 (the midpoint of the period), EPIC/GILSM was run for four 50 year periods (1901-1950, 1951-2000, 2001-2050 and 2051-2100) and the changes in crop yield and insect abundance were examined between periods. Nine insect pests found throughout the region were modeled to examine the range of likely responses of insect pests to climate change and the possible change in crop protection needs over the next 100 years. As expected, the model predicted little or no change between the first and second periods. For most species, change was maximum in the third period and less during the fourth period. In every case the isoclines for pest population density and crop productivity moved northwards, but at different rates, resulting in the isoclines for crop damage increasing as they moved northward. In two cases the pest abundance declined locally even as productivity increased, resulting in a net increase in productivity. No allowance was made for changes in agronomic practices or improvements in breeding pest resistance, both of which have helped to improve productivity over the past century.SEEDS-The OARDC Research Enhancement Competitive Grants Program: Interdisciplinary Team Research Competitio

    The effect of hydrogen peroxide on uranium oxide films on 316L stainless steel

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    For the first time the effect of hydrogen peroxide on the dissolution of electrodeposited uranium oxide films on 316L stainless steel planchets (acting as simulant uranium-contaminated metal surfaces) has been studied. Analysis of the H2O2-mediated film dissolution processes via open circuit potentiometry, alpha counting and SEM/EDX imaging has shown that in near-neutral solutions of pH 6.1 and at [H2O2] 0.1 mol dm(-3) the uranium oxide film, again in analogy to common corrosion processes, behaves as if in a transpassive state and begins to dissolve. This transition from passive to transpassive behaviour in the effect of peroxide concentration on UO2 films has not hitherto been observed or explored, either in terms of corrosion processes or otherwise. Through consideration of thermodynamic solubility product and complex formation constant data, we attribute the transition to the formation of soluble uranyl-peroxide complexes under mildly alkaline, high [H2O2] conditions - a conclusion that has implications for the design of both acid minimal, metal ion oxidant-free decontamination strategies with low secondary waste arisings, and single step processes for spent nuclear fuel dissolution such as the Carbonate-based Oxidative Leaching (COL) process. (C) 2015 Elsevier B.V. All rights reserved

    Adult Education Faculty and Programs in North America: Faculty Background, Work, and Satisfaction

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    Through a textual analysis of websites of Adult Education Graduate Programs and a quantitative survey of North American Adult Education faculty, this study examined: background information about Adult Education faculty and programs; the nature of faculty work interests, motivations and satisfaction; and involvement with the Commission of Professors of Adult Education

    Simulation of Neptunium Extraction in an Advanced PUREX Process — Model Improvement

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    Routing neptunium to a single product in spent nuclear fuel reprocessing is a significant challenge. In this work, we have further improved the simulation of neptunium extraction in an advanced PUREX flowsheet by applying a revised model of the Np(V)-Np(VI) redox reaction kinetics, a new nitric acid radiolysis model and by evaluating various models for the nitrous acid distribution coefficient. The Np disproportionation reaction is shown to have a negligible effect. The models are validated against published ‘cold test’ experimental results; the ‘hot test’ simulation suggests high neptunium radiolysis could help to achieve high recoveries using this flowsheet
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