25,065 research outputs found

    Commercial air transport hazard warning and avoidance system. Volume 1 - Summary Final report

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    Operational requirements for commercial air transport hazard warning and avoidance syste

    Propagation of the 2012 March Coronal Mass Ejections from the Sun to Heliopause

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    In 2012 March the Sun exhibited extraordinary activities. In particular, the active region NOAA AR 11429 emitted a series of large coronal mass ejections (CMEs) which were imaged by STEREO as it rotated with the Sun from the east to west. These sustained eruptions are expected to generate a global shell of disturbed material sweeping through the heliosphere. A cluster of shocks and interplanetary CMEs (ICMEs) were observed near the Earth, and are propagated outward from 1 AU using an MHD model. The transient streams interact with each other, which erases memory of the source and results in a large merged interaction region (MIR) with a preceding shock. The MHD model predicts that the shock and MIR would reach 120 AU around 2013 April 22, which agrees well with the period of radio emissions and the time of a transient disturbance in galactic cosmic rays detected by Voyager 1. These results are important for understanding the "fate" of CMEs in the outer heliosphere and provide confidence that the heliopause is located around 120 AU from the Sun.Comment: 13 pages, 5 figures, accepted for publication in ApJ Letter

    Parameter estimates for fractional autoregressive spatial processes

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    A binomial-type operator on a stationary Gaussian process is introduced in order to model long memory in the spatial context. Consistent estimators of model parameters are demonstrated. In particular, it is shown that d^Nd=OP((LogN)3N)\hat{d}_N-d=O_P(\frac{(\operatorname {Log}N)^3}{N}), where d=(d1,d2)d=(d_1,d_2) denotes the long memory parameter.Comment: Published at http://dx.doi.org/10.1214/009053605000000589 in the Annals of Statistics (http://www.imstat.org/aos/) by the Institute of Mathematical Statistics (http://www.imstat.org

    An Analysis of Whole Farm Revenue Safety Net Options in Agriculture

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    Despite many years of experience, the federal government continues to seek a farm program that holds the potential for providing a politically acceptable safety net for farmers. This study demonstrates that, with the 2002 Farm Bill, AMTA, and marketing loan provisions continuing, a whole farm revenue safety net has the potential for simplifying existing farm programs, while enhancing the financial position of US farmers. There remains the need for further analysis of the impacts of the options analyzed on supply response by farmers.Agricultural and Food Policy,

    IMPACT OF ALTERNATIVE FARM PROGRAMS ON DIFFERENT SIZE COTTON FARMS IN THE TEXAS SOUTHERN HIGH PLAINS: A SIMULATION APPROACH

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    Eight Texas High Plains cotton farms, ranging in size from 189 acres to 5,570 acres, were simulated under six alternative farm program provisions to determine the likely structural impacts of these programs. The results indicate mid-size farms benefit more from farm programs than either small or large farms since the programs allow them to remain in business. Denying mid-size commercial farms access to the farm program would likely accelerate the trend towards a bimodal distribution of farm sizes on the High Plains.Agribusiness, Crop Production/Industries,
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