1,482 research outputs found
A Theory of the Role of Magnetic Activity During Star Formation
Under the assumption that magnetic activity is due to the action
of a magnetic field in a rotating star with a convective zone, it is
possible to draw the following picture of a sequence of events in the
Hertzsprung-Russell diagram.
The H-R diagram is divided into two regions by an almost vertical
line. Stars of later type have a hydrogen convective zone of great
extension (region C); stars of earlier type have no hydrogen convective
zone or a convective zone of small extension (region D).
Stars in region C show stellar activity of electrodynamic origin
like solar activity; stars in region D show little or no stellar activity.
When matter is ejected by a star, the magnetic field compels the
matter to rotate with the star even at very large distances where it
carries away large angular momentum per unit mass. Stars which reach the
main sequence in region C may lose a large amount of angular momentum,
while stars reaching the main sequence in region D lose only a little
Penalty approximation for non smooth constraints in vibroimpact
We examine the penalty approximation of the free motion of a material point
in an angular domain; we choose an over-damped penalty, and we prove that if
the first impact point is not at the vertex, then, the limit of the
approximation exists and is described by Moreau's rule for anelastic impacts.
The proofs rely on validated asymptotics and use some classical tools in the
theory of dynamical systems.Comment: two figures, 32 pages, LaTeX2
Acoustic Testing of the Bell 699 Rotor on the Tiltrotor Test Rig (TTR) in the National Full-Scale Aerodynamics Complex 40- by 80- Foot Wind Tunnel in Conversion and Airplane Configuration
The Tiltrotor Test Rig (TTR) provides new proprotor testing capabilities to the National Aeronautics and Space Administration (NASA) and the Department of Defense (DoD). A checkout test for the TTR with the 699 proprotor was performed in the National Full-Scale Aerodynamics Complex (NFAC) 40- by 80 Foot Wind Tunnel from 2017 to 2018. Four microphones were placed around the rotor to capture acoustic data. Revolution based acoustic data processing techniques are evaluated for appropriateness in both helicopter and airplane configurations. This paper presents the acoustic data acquired for the rotor in conversion and airplane configuration
An inviscid model for the vortex-street wake
An inviscid model for the Karman vortex street, containing vortices of uniform vorticity surrounded by irrotational fluid, is related to the wake behind a bluff body by a global analysis requiring the conservation of momentum, energy and vorticity. Some comparison is made with experimental results reported in the literature. A qualitative procedure is proposed whereby the slow evolution of the wake through viscous effects is approximated. Some comments are made regarding the relevance of the stability properties of the inviscid street. Some calculations are made for the ‘secondary vortex street’ that is observed after breakdown and rearrangement, and comparison is made with experiment
Stability of a vortex street of finite vortices
The stability of the finite-area Kármán ‘vortex street’ to two-dimensional disturbances is determined. It is shown that for vortices of finite size there exists a finite range of spacing ratio κ for which the array is stable to infinitesimal disturbances. As the vortex size approaches zero, the range narrows to zero width about the classical von Kármán value of 0·281
A survey of medical doctors considerations when prescribing birth control and contraceptive devices : an honors thesis ([HONRS] 499)
The purpose of this study was to determine some of the considerations doctors utilize when giving information about or prescribing birth control or contraceptive methods.Honors CollegeThesis (B.?.
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