14,088 research outputs found
Review of literature relating to the modeling of soil temperatures based on meteorological factors
Abstracts of 72 papers, journal articles, and other publications are presented. The applicabilities of each is assessed for use in improving winterkill parameters for a winter wheat model
Magnetic activity, differential rotation and dynamo action in the pulsating F9IV star KIC 5955122
We present photometric spot modeling of the nearly four-year long light-curve
of the Kepler target KIC 5955122 in terms of persisting dark circular surface
features. With a Bayesian technique, we produced a plausible surface map that
shows dozens of small spots. After some artifacts are removed, the residuals
are at \,mmag. The shortest rotational period found is days. The equator-to-pole extrapolated differential rotation is rad/d. The spots are roughly half as bright as the unperturbed stellar
photosphere. Spot latitudes are restricted to the zone latitude.
There is no indication for any near-pole spots. In addition, the p-mode
pulsations enabled us to determine the evolutionary status of the star, the
extension of the convective zone, and its radius and mass. We discuss the
possibility that the clear signature of active regions in the light curve of
the F9IV star KIC 5955122 is produced by a flux-transport dynamo action at the
base of the convection zone. In particular, we argue that this star has evolved
from an active to a quiet status during the Q0--Q16 period of observation, and
we predict, according to our dynamo model, that the characteristic activity
cycle is of the order of the solar one.Comment: 9 pages, 12 figures, to be published on A&
Structural gradient based sizing optimization of wind turbine blades with fixed outer geometry
Scattering of first and second sound waves by quantum vorticity in superfluid Helium
We study the scattering of first and second sound waves by quantum vorticity
in superfluid Helium using two-fluid hydrodynamics. The vorticity of the
superfluid component and the sound interact because of the nonlinear character
of these equations. Explicit expressions for the scattered pressure and
temperature are worked out in a first Born approximation, and care is exercised
in delimiting the range of validity of the assumptions needed for this
approximation to hold. An incident second sound wave will partly convert into
first sound, and an incident first sound wave will partly convert into second
sound. General considerations show that most incident first sound converts into
second sound, but not the other way around. These considerations are validated
using a vortex dipole as an explicitely worked out example.Comment: 24 pages, Latex, to appear in Journal of Low Temperature Physic
Effective slip boundary conditions for flows over nanoscale chemical heterogeneities
We study slip boundary conditions for simple fluids at surfaces with
nanoscale chemical heterogeneities. Using a perturbative approach, we examine
the flow of a Newtonian fluid far from a surface described by a heterogeneous
Navier slip boundary condition. In the far-field, we obtain expressions for an
effective slip boundary condition in certain limiting cases. These expressions
are compared to numerical solutions which show they work well when applied in
the appropriate limits. The implications for experimental measurements and for
the design of surfaces that exhibit large slip lengths are discussed.Comment: 14 pages, 3 figure
Optical and near-infrared observations of the GRB 970616 error box
We report on near-infrared and optical observations of the GRB 970616 error
box and of the X-ray sources discovered by ASCA and ROSAT in the region. No
optical transient was found either within the IPN band or in the X-ray error
boxes, similarly to other bursts, and we suggest that either considerable
intrinsic absorption was present (like GRB 970828) or that the optical
transient displayed a very fast decline (like GRB 980326 and GRB 980519).Comment: 2 pages with one encapsulated PostScript figure included. Uses
Astronomy & Astrophysics LaTeX macros. Accepted for publication in Astronomy
& Astrophysics Supplement Serie
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