12,520 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
The Detection of a 3.5-h Period in the Classical Nova Velorum 1999 (V382 Vel) and the Long Term Behavior of the Nova Light Curve
We present CCD photometry, light curve and time series analysis of the
classical nova V382 Vel (N Vel 1999). The source was observed for 2 nights in
2000, 21 nights in 2001 and 7 nights in 2002 using clear filters. We report the
detection of a distinct period in the light curve of the nova P=0.146126(18) d
(3.5 h). The period is evident in all data sets, and we interpret it as the
binary period of the system. We also measured an increase in the amplitude
modulation of the optical light (in magnitude) by more than 55% from 2000 to
2001 and about 64% from 2001 to 2002. The pulse profiles in 2001 show
deviations from a pure sinusoidal shape which progressively become more
sinusoidal by 2002. The main cause of the variations in 2001 and 2002 can be
explained with the occultation of the accretion disk by the secondary star. We
interpret the observed deviations from a pure sinusoidal shape as additional
flux resulting from the aspect variations of the irradiated face of the
secondary star.Comment: 16 pages and 4 figures, accepted as it stands to be published in the
Astronomical Journal (AJ
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
Wess-Zumino-Witten model off criticality
We study the renormalization group flow properties of the Wess-Zumino-Witten
model in the region of couplings between and , by
evaluating the two-loop Zamolodchikov's -function. We also discuss the
region of negative couplings.Comment: 8 page
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
User Experience Evaluation in BCI: Filling the Gap
Brain-computer interface (BCI) systems can improve the user experience (UX) when used in entertainment technologies. Improved UX can enhance user acceptance, improve quality of life and also increase the system performance of a BCI system. Therefore, the evaluation of UX is essential in BCI research. However, BCI systems are generally evaluated according to the system aspect only so there is no methodology to evaluate UX in BCI systems. This paper gives an overview of such methods from the human-computer interaction field and discusses their possible uses in BCI research
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