6,243 research outputs found
Quantized superfluid vortex dynamics on cylindrical surfaces and planar annuli
Superfluid vortex dynamics on an infinite cylinder differs significantly from
that on a plane. The requirement that a condensate wave function be single
valued upon once encircling the cylinder means that such a single vortex cannot
remain stationary. Instead, it acquires one of a series of quantized
translational velocities around the circumference, the simplest being , with the mass of the superfluid particles and the radius
of the cylinder. A generalization to a finite cylinder automatically includes
these quantum-mechanical effects through the pairing of the single vortex and
its image in either the top or bottom end of the surface. The dynamics of a
single vortex on this surface provides a hydrodynamic analog of Laughlin
pumping. The interaction energy for two vortices on an infinite cylinder is
proportional to the classical stream function , and it
crosses over from logarithmic to linear when the intervortex separation becomes larger than the cylinder radius. An Appendix summarizes the
connection to an earlier study of Ho and Huang for one or more vortices on an
infinite cylinder. A second Appendix reviews the topologically equivalent
planar annulus, where such quantized vortex motion has no offset, but Laughlin
pumping may be more accessible to experimental observation.Comment: 16 pages, 7 figures; published version, with thoroughly revised
Appendice
The nature of p-modes and granulation in HD 49933 observed by CoRoT
Context: Recent observations of HD49933 by the space-photometric mission
CoRoT provide photometric evidence of solar type oscillations in a star other
than our Sun. The first published reduction, analysis, and interpretation of
the CoRoT data yielded a spectrum of p-modes with l = 0, 1, and 2. Aims: We
present our own analysis of the CoRoT data in an attempt to compare the
detected pulsation modes with eigenfrequencies of models that are consistent
with the observed luminosity and surface temperature. Methods: We used the
Gruberbauer et al. frequency set derived based on a more conservative Bayesian
analysis with ignorance priors and fit models from a dense grid of model
spectra. We also introduce a Bayesian approach to searching and quantifying the
best model fits to the observed oscillation spectra. Results: We identify 26
frequencies as radial and dipolar modes. Our best fitting model has solar
composition and coincides within the error box with the spectroscopically
determined position of HD49933 in the H-R diagram. We also show that
lower-than-solar Z models have a lower probability of matching the observations
than the solar metallicity models. To quantify the effect of the deficiencies
in modeling the stellar surface layers in our analysis, we compare adiabatic
and nonadiabatic model fits and find that the latter reproduces the observed
frequencies better.Comment: accepted to be published in A&A, 9 pages, 5 figure
Gust penetration loads and elastic vehicle response for Saturn 5 launch vehicles
Analysis of gust penetration loads and associated elastic vehicle response of Saturn 5 launch vehicles AS-505 through AS-508 penetrating sinusoidal gust
An evaluation of aft-end ignition for solid propellant rocket motors
Performance evaluation of solid propellant rocket motor ignition to determine igniter design and parameters to avoid overpressurizatio
Engaging the articulators enhances perception of concordant visible speech movements
PURPOSE
This study aimed to test whether (and how) somatosensory feedback signals from the vocal tract affect concurrent unimodal visual speech perception.
METHOD
Participants discriminated pairs of silent visual utterances of vowels under 3 experimental conditions: (a) normal (baseline) and while holding either (b) a bite block or (c) a lip tube in their mouths. To test the specificity of somatosensory-visual interactions during perception, we assessed discrimination of vowel contrasts optically distinguished based on their mandibular (English /ɛ/-/æ/) or labial (English /u/-French /u/) postures. In addition, we assessed perception of each contrast using dynamically articulating videos and static (single-frame) images of each gesture (at vowel midpoint).
RESULTS
Engaging the jaw selectively facilitated perception of the dynamic gestures optically distinct in terms of jaw height, whereas engaging the lips selectively facilitated perception of the dynamic gestures optically distinct in terms of their degree of lip compression and protrusion. Thus, participants perceived visible speech movements in relation to the configuration and shape of their own vocal tract (and possibly their ability to produce covert vowel production-like movements). In contrast, engaging the articulators had no effect when the speaking faces did not move, suggesting that the somatosensory inputs affected perception of time-varying kinematic information rather than changes in target (movement end point) mouth shapes.
CONCLUSIONS
These findings suggest that orofacial somatosensory inputs associated with speech production prime premotor and somatosensory brain regions involved in the sensorimotor control of speech, thereby facilitating perception of concordant visible speech movements.
SUPPLEMENTAL MATERIAL
https://doi.org/10.23641/asha.9911846R01 DC002852 - NIDCD NIH HHSAccepted manuscrip
Experience with fluorine and its safe use as a propellant
The industrial and the propulsion experience with fluorine and its derivatives is surveyed. The hazardous qualities of fluorine and safe handling procedures for the substance are emphasized. Procedures which fulfill the safety requirements during ground operations for handling fluorinated propulsion systems are discussed. Procedures to be implemented for use onboard the Space Transportation System are included
- …