16,705 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 ϵ\epsilon, the system state will eventually leave the domain of attraction Ω\Omega of SS. We analyse the case when, as ϵ0\epsilon\to0, the exit location on the boundary Ω\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 Ω\partial\Omega is generically non-Gaussian and asymmetric, and classify the possible limiting distributions. A key role is played by a parameter μ\mu, equal to the ratio λs(H)/λu(H)|\lambda_s(H)|/\lambda_u(H) of the stable and unstable eigenvalues of the linearized deterministic flow at HH. If μ<1\mu<1 then the exit location distribution is generically asymptotic as ϵ0\epsilon\to0 to a Weibull distribution with shape parameter 2/μ2/\mu, on the O(ϵμ/2)O(\epsilon^{\mu/2}) length scale near HH. If μ>1\mu>1 it is generically asymptotic to a distribution on the O(ϵ1/2)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 Ω\Omega with HH as vertex, which is reached from SS, in the ϵ0\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-ϵ\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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    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

    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 CoAl2x_{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 CoAl2x_{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

    Salmonella prosthetic joint septic arthritis

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    Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72297/1/j.1469-0691.2002.00466.x.pd
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