Time series of high resolution CFHT spectra of four δ Scuti stars are examined for consistency with the presence of nonradial pulsations (nrp). Each series exhibits a progression of subfeatures moving from blue to red through the absorption lines. We have reproduced the profile variations using a geometrical model which imposes sectorial modes on the surface of the star. Modeling of the low-degree modes is guided by radial-velocity variations and the known photometric variations. Synthetic spectra generated with the appropriate Teff and log g for each star are used as input for the model. In this way, the entire wavelength region covered by the observations can be reproduced and the effects of blending on the nrp profiles are included explicitly. The extension from a single-line model to one generated over a wide spectral region provides a much more sensitive comparison with the observations. In general, we find that the data can be reproduced by the combination of a high-degree mode (ℓ > 8) and a low-degree mode [ℓ < 2). The intrinsic line widths and υ sinί together set a limit on the resolution of the stellar surface and by including this resolution in our treatment we can estimate the velocity amplitude of the oscillations (~ 5 km/s). We find that low values of k (≤ 0.1) expected for p-mode oscillations are consistent with the observations. A possible relationship between the periods of the high- and low-degree modes is noted, the question of uniqueness is addressed and comparisons are made with models invoking starspots. For at least one of the stars (қ² Boo), it is impossible to fit the observations by a starspot model without assuming unrealistic values of radius or equatorial velocity. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Energy dissipation due to sloshing liquid in torus shaped nutation dampers is studied using the potential flow model with nonlinear free surface conditions in conjunction with the boundary layer correction. Special consideration is given to the case of resonant interactions which were found to yield interesting damping characteristics. An extensive test program with the dampers undergoing steady-state oscillatory translation is then undertaken to establish the optimal damper parameters. Low liquid heights and large diameter ratios with the system operating at the liquid sloshing resonance are shown to result in increased damping, while low Reynolds numbers and presence of baffles tend to reduce the peak efficiency by restricting the action of the free surface. Tests with two-dimensional as well as three-dimensional models in laminar flow and boundary layer wind tunnels suggest that the dampers can successfully control both the vortex resonance and galloping types of instabilities. Applicability of the concept to vertically oscillating structures such as transmission lines is also demonstrated with dampers undergoing a rotational motion about their horizontal axis. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Mémoire (M.Sc.A.)-- Université du Québec à Chicoutimi, 1988. / Document électronique également accessible en format PDF. CaQCU

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This thesis describes the 1983 solar shape investigation performed at the Santa Catalina Laboratory for Experimental Relativity by Astrometry (SCLERA). Solar diameter measurements, with the North Solar Pole defined as θ = 0° polar angle, have been made between the following polar coordinates: from θ = 0° to θ = 180° (the polar diameter), from θ = 90° to θ = -90° (the equatorial diameter), from θ = -45° to θ = 135° and from θ = 45° to θ = -135°. Expressing the Sun's apparent shape in terms of a Legendre series, these diameters have enabled the calculation of the P₂ (quadrupole) and P₄ (hexadecapole) shape coefficients. The theoretical framework used to provide a relationship between the observed shape of the Sun and the multipole moments of the solar gravitational potential field has been improved to include, in general, the effect of differential rotation in both latitude and radius. Using the shape coefficients and the theoretical framework, the gravitational potential multipole moments, expressed as the P₂ and P₄ coefficients of a Legendre series, have been found to be J₂ = (3.4 ± 1.3)E-6 and J₄ = (1.7 ± 1.1)E-6, respectively. It has been found that the contribution to the perihelion precession of Mercury's orbit, caused by the combined effects from the gravitational quadrupole term and general relativity, was approximately 1σ different from the observed amount after all other known Newtonian contributions had been removed from the observed precession. The total apparent oblateness ΔR (equator-polar radii) found from SCLERA observations is ΔR = 13.8 ± 1.3 milliarcseconds. The surface rotation contribution ΔR' to the apparent solar shape is ΔR' = 7.9 milliarcseconds. The quoted uncertainties represent formal statistical 1σ errors only. Also, it has been shown that large changes in the apparent limb darkening functions were occurring near the equatorial regions of the Sun during the time of the observations. Evidence for periodic shape distortions near the equator have also been found.

A new instrument has been developed for making unimaged whole-disk observations of low-degree solar normal-mode oscillations. The apparatus, referred to as the sky monitor, does not track the solar disk, but instead measures the radiant flux scattered by the Earth's atmosphere at 1.6 and 0.5 μ. The expected diurnal flux variation was obtained from a detailed radiative transfer calculation. Data were acquired for 15.5 months during 1991-92. Seventy-two days of data were analyzed for evidence of solar p modes in the frequency range 1800-4776 μHz. Noise generated by the Earth's atmosphere was reduced by scaling the Fourier amplitude computed from the infrared signal and subtracting it from the Fourier amplitude computed from the visible signal. A superimposed frequency analysis was then performed which revealed ∼ 2 σ peaks within 0.3 μHz of symmetry-allowed locations, while no excess power was detected at the symmetry-forbidden frequencies. The probability of obtaining by chance the observed excess power density at symmetry-allowed frequencies and deficit of power density at symmetry-forbidden frequencies was computed to be 6.9 x 10⁻³. Correcting the frequencies for solar-cycle variations, the probability was reduced to 2.9 x 10⁻⁴. These results indicate that it is quite unlikely that the observed symmetry properties have occurred by chance, and support the hypothesis that solar normal-mode signals are manifested in the data. The amplitudes I'/Iₒ averaged over radial order n of the ℓ = 0 and ℓ = 2, m = 0 modes were found to be (7.54 ± 0.54) x 10⁻⁷ and (7.68 ± 0.56) x 10⁻⁷, respectively. These results are about a factor of two smaller than the amplitude of total irradiance oscillations measured from space. While the rotational splitting of the ℓ = 2 multiplet appears to be consistent with that reported by Hill (1985a), results for ℓ = 1 and ℓ = 3 are inconclusive.

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No description available.

evel relative vorticity, a decrease in westerly vertical wind shear, and increased convection in the West African monsoon (WAM). The second and third modes of an empirical orthogonal function (EOF) analysis of the 700-hPa height anomalies identify a distinct Rossby-wave pattern. Significant variability in the Southern Hemisphere mid-latitude circulations is related to the two EOF modes and to equatorward Rossby-wave dispersion. Formation of a large cyclonic anomaly over the southeast Pacific, west of Chile, is related to equatorward propagation of a Rossby-like wave across South America, toward the equatorial Atlantic. The cyclonic anomaly precedes an increase in WAM convection by an average of two days, which then precedes westerly wind anomalies over the equatorial North Atlantic by several days. Tropical cyclone formation is found to be enhanced when the increased equatorial westerly anomalies coincide with reduced vertical wind shear, which is related to Northern Hemisphere midlatitude circulations / US Air Force (USAF) author.

This thesis aims at the neutrino oscillations phenomena and the role of longbaseline neutrino oscillation experiments and NOνA in particular in oscillation parameters search. The standard formalism of 3 neutrinos model is described, NOνA experiment and its main features and physics goals (mixing angles θ13 and θ23, CP violation, the value of the CP phase δ and mass hierarchy determination) are introduced. The effects of media to neutrino propagation are explained and effective matter oscillation parameters are derived. The way to resolve the mass hierarchy exploiting matter effects in long-baseline neutrino oscillation experiments is depicted and consequent problems regarding the recent knowledge of oscillation parameters, i.e. δ-, θ13- and θ23-degeneracies, are discussed. In the last part GLoBES software is used to simulate NOνA results and to compute the estimated sensitivities to the mass hierarchy in case of 3 years ν run and 1.5ν+1.5ν years run in order to show the advantage of an earlier switch to antineutrino mode in mass hierarchy determination.