12,402 research outputs found
On the unsteady behavior of turbulence models
Periodically forced turbulence is used as a test case to evaluate the
predictions of two-equation and multiple-scale turbulence models in unsteady
flows. The limitations of the two-equation model are shown to originate in the
basic assumption of spectral equilibrium. A multiple-scale model based on a
picture of stepwise energy cascade overcomes some of these limitations, but the
absence of nonlocal interactions proves to lead to poor predictions of the time
variation of the dissipation rate. A new multiple-scale model that includes
nonlocal interactions is proposed and shown to reproduce the main features of
the frequency response correctly
Off-Shell Electromagnetic Form Fators of the Nucleon in Chiral Perturbation Theory
We study the electromagnetic form factors of a nucleon in next-to-leading
order chiral perturbation theory (CPT) in the case where one of the nucleons is
off its mass shell. We calculate the leading nonanalytic contributions to
relevant measures for the off-shell dependence in the limited kinematical range
allowed.Comment: 3 pages LaTeX with worldsci.sty (available by mailing
[email protected] and typing "get worldsci.sty" in the subject line),
invited talk given at the International Symposium on Medium Energy Physics,
Beijing, August 199
Extreme Lagrangian acceleration in confined turbulent flow
A Lagrangian study of two-dimensional turbulence for two different
geometries, a periodic and a confined circular geometry, is presented to
investigate the influence of solid boundaries on the Lagrangian dynamics. It is
found that the Lagrangian acceleration is even more intermittent in the
confined domain than in the periodic domain. The flatness of the Lagrangian
acceleration as a function of the radius shows that the influence of the wall
on the Lagrangian dynamics becomes negligible in the center of the domain and
it also reveals that the wall is responsible for the increased intermittency.
The transition in the Lagrangian statistics between this region, not directly
influenced by the walls, and a critical radius which defines a Lagrangian
boundary layer, is shown to be very sharp with a sudden increase of the
acceleration flatness from about 5 to about 20
Gender nonconformity, sexual orientation, and Dutch adolescents' relationship with peers
Same-sex attraction and gender nonconformity have both been shown to negatively affect the relationships of adolescents with their peers. It is not clear, though, whether same-sex attracted adolescents are more likely to have negative peer relationships because they are same-sex attracted or because they are more likely to be gender nonconforming. It is also possible that both stressors affect peer relationships independently or amplify each other in their impact. We explored these questions in a sample of 486 Dutch adolescents (M age = 14.02 years). We found that same-sex attraction and gender nonconformity both had an independent effect and that gender nonconformity moderated, but not mediated, the associations between same-sex attraction and peer relationships at school. Same-sex attraction was more strongly associated with poorer relationships with peers in adolescents who were more gender nonconforming. These findings indicate the importance of including gender nonconformity in the understanding of same-sex attracted adolescents’ relationships and suggest that in order to improve same-sex attracted adolescents’ social position at school, acceptance of gender diversity should be promoted as well
Sclera solar diameter observations
Focus is given to possible variations in solar luminosity and accurate methods of monitoring it. Aside from direct bolometry, one methodology for this type of research makes use of measurements of the solar diameter and limb darkening function as indirect indicators of the solar luminosity. This approach was reviewed
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