33,874 research outputs found

    Comparison of vortex lattice predicted forces with wind tunnel experiments for the F-4E(CCV) airplane with a closely coupled canard

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    The F-4E (CCV) wind tunnel model with closely coupled canard control surfaces was analyzed by means of a version of a vortex lattice program that included the effects of nonlinear leading edge or side edge vortex lift on as many as four individual planforms. The results were compared with experimental data from wind tunnel tests of a 5% scale model tested at a Mach number M = 0.6. They indicated that a nonlinear vortex lift developed on the side edges due to tip vortices, but did not appear to develop on the leading edges within the range of angles of attack that were studied. Instead, substantial leading edge thrust was developed on the lifting surfaces. A configuration buildup illustrated the mutual interference between the wing and control surfaces. On the configuration studied, addition of the wing increased the loading on the canard, but the additional load on the canard due to adding the stabilator was small

    The moduli space of (111)-polarized abelian surfaces is unirational

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    We prove that the moduli space A\cal A11lev of (1,11)-polarized Abelian surfaces with level structure of canonical type is birational to Klein's cubic hypersurface in P4. Therefore, A\cal A11lev is unirational but not rational, and there are no Γ11-cusp forms of weight 3. The same methods also provide an easy proof of the rationality of A\cal A9lev

    Normalization of the covariant three-body bound state vertex function

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    The normalization condition for the relativistic three nucleon Bethe-Salpeter and Gross bound state vertex functions is derived, for the first time, directly from the three body wave equations. It is also shown that the relativistic normalization condition for the two body Gross bound state vertex function is identical to the requirement that the bound state charge be conserved, proving that charge is automatically conserved by this equation.Comment: 24 pages, 9 figures, published version, minor typos correcte

    A description of the NSSL cases used for a simulated VAS retrieval study

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    A documentation of eight National Severe Storm Laboratory severe storm cases, which serve as a basis for a simulated VISSR Atmospheric Sounder retrieval study, is presented in this paper. Six of the selected cases provide a control data set to complete the statistical information needed for retrieval techniques based upon the use of regression matrices. The other two cases are to be used in the actual retrieval experiments. The selection was based upon the presence of moisture gradients in the analysis region, the availability of satellite images at the selected time periods, and the extent of cloud cover within the observing network

    Addressing Geriatric Falls in the Outpatient Setting: A Prevention Initiative

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    With approximately 25% of older aged 65 or greater falling each year, and 20% of these incidents resulting in serious injury, falls are of significant concern for both the geriatric community and the healthcare system at large. In 2017, Vermont ranked 41st in the nation with respect to the percent of older adults with self-reported falls in the past 12 months, according to the United Health Foundation’s “America’s Health Rankings report. Many patients at risk for falling remain uneducated regarding environmental, pharmacological, and/or behavioral risk factors that may be contributing to their fall risk. In addition, providers often have limited time during office visits to counsel patients regarding strategies to combat these risk factors. The purpose of this work was to develop discharge instruction strategies for geriatric patients at Hinesburg Family Medicine to combat environmental (home hazards), behavioral, and pharmacological factors that may be increasing their risk for falls.https://scholarworks.uvm.edu/fmclerk/1545/thumbnail.jp

    Three component laser Doppler measurements in an axisymmetric jet

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    A three-component laser Doppler anemometer (LDA) was used to acquire a detailed set of three-dimensional mean and fluctuating velocity measurements in a low-speed air jet entering a stagnant ambient, over the first 20 jet exit diameters along the jet trajectory. These data are physically consistent with previous measurements in axisymmetric jets. The relative difficulty of obtaining three-dimensional and two-dimensional LDA data is briefly discussed

    Lagrangian with off-shell vertices and field redefinitions

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    Meson exchange diagrams following from a lagrangian with off-shell meson-nucleon couplings are compared with those generated from conventional dynamics. The off-shell interactions can be transformed away with the help of a nucleon field redefinition. Contributions to to the NNNN- and 3N3N-potentials and nonminimal contact e.m. meson-exchange currents are discussed, mostly for an important case of scalar meson exchange. (pacs 11.10.Lm, 13.75.Cs, 21.30.-x, 24.10.Jv)Comment: 18 pages (Revtex), 4 eps figure

    Calabi–Yau threefolds and moduli of abelian surfaces I

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    We describe birational models and decide the rationality/unirationality of moduli spaces A\cal Ad (and A\cal Alevd) of (1, d)-polarized Abelian surfaces (with canonical level structure, respectively) for small values of d. The projective lines identified in the rational/unirational moduli spaces correspond to pencils of Abelian surfaces traced on nodal threefolds living naturally in the corresponding ambient projective spaces, and whose small resolutions are new Calabi–Yau threefolds with Euler characteristic zero

    Two-pion exchange potential and the πN\pi N amplitude

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    We discuss the two-pion exchange potential which emerges from a box diagram with one nucleon (the spectator) restricted to its mass shell, and the other nucleon line replaced by a subtracted, covariant πN\pi N scattering amplitude which includes Δ\Delta, Roper, and D13D_{13} isobars, as well as contact terms and off-shell (non-pole) dressed nucleon terms. The πN\pi N amplitude satisfies chiral symmetry constraints and fits πN\pi N data below \sim 700 MeV pion energy. We find that this TPE potential can be well approximated by the exchange of an effective sigma and delta meson, with parameters close to the ones used in one-boson-exchange models that fit NNNN data below the pion production threshold.Comment: 9 pages (RevTex) and 7 postscript figures, in one uuencoded gzipped tar fil

    Quasi-periodic spatiotemporal models of brain activation in single-trial MEG experiments

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    Magneto-encephalography (MEG) is an imaging technique which measures neuronal activity in the brain. Even when a subject is in a resting state, MEG data show characteristic spatial and temporal patterns, resulting from electrical current at specific locations in the brain. The key pattern of interest is a ‘dipole’, consisting of two adjacent regions of high and low activation which oscillate over time in an out-of-phase manner. Standard approaches are based on averages over large numbers of trials in order to reduce noise. In contrast, this article addresses the issue of dipole modelling for single trial data, as this is of interest in application areas. There is also clear evidence that the frequency of this oscillation in single trials generally changes over time and so exhibits quasi-periodic rather than periodic behaviour. A framework for the modelling of dipoles is proposed through estimation of a spatiotemporal smooth function constructed as a parametric function of space and a smooth function of time. Quasi-periodic behaviour is expressed in phase functions which are allowed to evolve smoothly over time. The model is fitted in two stages. First, the spatial location of the dipole is identified and the smooth signals characterizing the amplitude functions for each separate pole are estimated. Second, the phase and frequency of the amplitude signals are estimated as smooth functions. The model is applied to data from a real MEG experiment focusing on motor and visual brain processes. In contrast to existing standard approaches, the model allows the variability across trials and subjects to be identified. The nature of this variability is informative about the resting state of the brain
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