19,465 research outputs found

    User benefits and funding strategies

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    The justification, economic and technological benefits of NASA Space Programs (aside from pure scientific objectives), in improving the quality of life in the United States is discussed and outlined. Specifically, a three-step, systematic method is described for selecting relevant and highly beneficial payloads and instruments for the Interim Upper Stage (IUS) that will be used with the space shuttle until the space tug becomes available. Viable Government and private industry cost-sharing strategies which would maximize the number of IUS payloads, and the benefits obtainable under a limited NASA budget were also determined. Charts are shown which list the payload instruments, and their relevance in contributing to such areas as earth resources management, agriculture, weather forecasting, and many others

    Asymptotic Exit Location Distributions in the Stochastic Exit Problem

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    Consider a two-dimensional continuous-time dynamical system, with an attracting fixed point SS. If the deterministic dynamics are perturbed by white noise (random perturbations) of strength Ļµ\epsilon, the system state will eventually leave the domain of attraction Ī©\Omega of SS. We analyse the case when, as Ļµā†’0\epsilon\to0, the exit location on the boundary āˆ‚Ī©\partial\Omega is increasingly concentrated near a saddle point HH of the deterministic dynamics. We show that the asymptotic form of the exit location distribution on āˆ‚Ī©\partial\Omega is generically non-Gaussian and asymmetric, and classify the possible limiting distributions. A key role is played by a parameter Ī¼\mu, equal to the ratio āˆ£Ī»s(H)āˆ£/Ī»u(H)|\lambda_s(H)|/\lambda_u(H) of the stable and unstable eigenvalues of the linearized deterministic flow at HH. If Ī¼<1\mu<1 then the exit location distribution is generically asymptotic as Ļµā†’0\epsilon\to0 to a Weibull distribution with shape parameter 2/Ī¼2/\mu, on the O(ĻµĪ¼/2)O(\epsilon^{\mu/2}) length scale near HH. If Ī¼>1\mu>1 it is generically asymptotic to a distribution on the O(Ļµ1/2)O(\epsilon^{1/2}) length scale, whose moments we compute. The asymmetry of the asymptotic exit location distribution is attributable to the generic presence of a `classically forbidden' region: a wedge-shaped subset of Ī©\Omega with HH as vertex, which is reached from SS, in the Ļµā†’0\epsilon\to0 limit, only via `bent' (non-smooth) fluctuational paths that first pass through the vicinity of HH. We deduce from the presence of this forbidden region that the classical Eyring formula for the small-Ļµ\epsilon exponential asymptotics of the mean first exit time is generically inapplicable.Comment: This is a 72-page Postscript file, about 600K in length. Hardcopy requests to [email protected] or [email protected]

    Hay and ensilage harvesting costs

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    Cover title

    Resistance of hay to air flow

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    Digitized 2007 AES.Includes bibliographical references (pages 22-23)

    Phase diagram of the antiferromagnetic XY model in two dimensions in a magnetic field

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    The phase diagram of the quasi-two-dimensional easy-plane antiferromagnetic model, with a magnetic field applied in the easy plane, is studied using the self-consistent harmonic approximation. We found a linear dependence of the transition temperature as a function of the field for large values of the field. Our results are in agreement with experimental data for the spin-1 honeycomb compound BaNi_2V_2O_3Comment: 3 page

    Theories of developmental dyslexia: Insights from a multiple case study of dyslexic adults

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    A multiple case study was conducted in order to assess three leading theories of developmental dyslexia: the phonological, the magnocellular (auditory and visual) and the cerebellar theories. Sixteen dyslexic and 16 control university students were administered a full battery of psychometric, phonological, auditory, visual and cerebellar tests. Individual data reveal that all 16 dyslexics suffer from a phonological deficit, 10 from an auditory deficit, 4 from a motor deficit, and 2 from a visual magnocellular deficit. Results suggest that a phonological deficit can appear in the absence of any other sensory or motor disorder, and is sufficient to cause a literacy impairment, as demonstrated by 5 of the dyslexics. Auditory disorders, when present, aggravate the phonological deficit, hence the literacy impairment. However, auditory deficits cannot be characterised simply as rapid auditory processing problems, as would be predicted by the magnocellular theory. Nor are they restricted to speech. Contrary to the cerebellar theory, we find little support for the notion that motor impairments, when found, have a cerebellar origin, or reflect an automaticity deficit. Overall, the present data support the phonological theory of dyslexia, while acknowledging the presence of additional sensory and motor disorders in certain individuals

    A framework for understanding the factors influencing pair programming success

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    Pair programming is one of the more controversial aspects of several Agile system development methods, in particular eXtreme Programming (XP). Various studies have assessed factors that either drive the success or suggest advantages (and disadvantages) of pair programming. In this exploratory study the literature on pair programming is examined and factors distilled. These factors are then compared and contrasted with those discovered in our recent Delphi study of pair programming. Gallis et al. (2003) have proposed an initial framework aimed at providing a comprehensive identification of the major factors impacting team programming situations including pair programming. However, this study demonstrates that the framework should be extended to include an additional category of factors that relate to organizational matters. These factors will be further refined, and used to develop and empirically evaluate a conceptual model of pair programming (success)

    Water livestock the automatic way

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    Cover title."The bulletin reports on Department of Agricultural Engineering research project 282-1, Farm Electricity"--P. [2]

    Tuning magnetic frustration on the diamond lattice of the A-site magnetic spinels CoAl2āˆ’x_{2-x}Gax_xO4_4: Lattice expansion and site disorder

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    The spinels CoB2_2O4_4 with magnetic Co2+^{2+} ions on the diamond lattice A site can be frustrated because of competing near-neighbor (J1J_1) and next-near neighbor (J2J_2) interactions. Here we describe attempts to tune the relative strengths of these interactions by substitution on the non-magnetic B-site. The system we employ is CoAl2āˆ’x_{2-x}Gax_xO4_4, where Al is systematically replaced by the larger Ga, ostensibly on the B site. As expected, Ga substitution expands the lattice, resulting in Co atoms on the A-site being pushed further from one other and thereby weakening magnetic interactions. In addition, Ga distributes between the B and the A site in a concentration dependent manner displacing an increasing amount of Co from the A site with increasing xx. This increased inversion, which is confirmed by neutron diffraction studies carried out at room temperature, affects magnetic ordering very significantly, and changes the nature of the ground state. Modeling of the magnetic coupling illustrates the complexity that arises from the cation site disorder.Comment: 9 pages, 10 figure
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