96,266 research outputs found
Exploring computer-generated line graphs through virtual touch
This paper describes the development and evaluation of a haptic interface designed to provide access to line graphs for blind or visually impaired people. Computer-generated line graphs can be felt by users through the sense of touch produced by a PHANToM force feedback device. Experiments have been conducted to test the effectiveness of this interface with both sighted and blind people. The results show that sighted and blind people have achieved about 89.95% and 86.83% correct answers respectively in the experiment
Do High Frequency QPOs Depend on Phase of Low Frequency QPOs in XTE J1550-564 ?
We have studied the dependence of the high frequency Quasi-periodic
Oscillation (QPO) (~284 Hz) on the phase of the low frequency QPO (~6 Hz) in
the black hole X-ray binary XTE J1550-564 in the observations of the Rossi
X-ray Timing Explorer (RXTE) performed on MJD 51241. By selecting the local
maxima and the local minima in the light curve on the 6 Hz QPO time scale, we
have found the corresponding high frequency QPO frequencies are consistent
within 1.5 sigma. However, the average central QPO frequency of the maxima and
the minima is about 2.0 sigma lower than the average high frequency QPO
frequency obtained in the entire observation. This marginally suggests that the
high frequency QPOs probably varies in frequency on short time scales. We
briefly discuss these results and their consequences.Comment: 3 pages, 1 figure, to appear in the Proceedings of the 4th
Microquasar Workshop, eds. Ph Durouchoux, Y. Fuchs and J. Rodriguez,
published by the Center for Space Physics: Kolkat
Correlation femtoscopy of small systems
The basic principles of the correlation femtoscopy, including its
correspondence to the Hanbury Brown and Twiss intensity interferometry, are
re-examined. The main subject of the paper is an analysis of the correlation
femtoscopy when the source size is as small as the order of the uncertainty
limit. It is about 1 fm for the current high energy experiments. Then the
standard femtoscopy model of random sources is inapplicable. The uncertainty
principle leads to the partial indistinguishability and coherence of closely
located emitters that affect the observed femtoscopy scales. In thermal systems
the role of corresponding coherent length is taken by the thermal de Broglie
wavelength that also defines the size of a single emitter. The formalism of
partially coherent phases in the amplitudes of closely located individual
emitters is used for the quantitative analysis. The general approach is
illustrated analytically for the case of the Gaussian approximation for
emitting sources. A reduction of the interferometry radii and a suppression of
the Bose-Einstein correlation functions for small sources due to the
uncertainty principle are found. There is a positive correlation between the
source size and the intercept of the correlation function. The peculiarities of
the non-femtoscopic correlations caused by minijets and fluctuations of the
initial states of the systems formed in and collisions are also
analyzed. The factorization property for the contributions of femtoscopic and
non-femtoscopic correlations into complete correlation function is observed in
numerical calculations in a wide range of the model parameters.Comment: 34 pages, 5 figures. In the version 4 some stylistic improvements
were made, some misprints were corrected. The results and conclusions are not
change
Vibration Powered Radiation of Quaking Magnetar
In juxtaposition with the standard model of rotation powered pulsar, the
model of vibration powered magnetar undergoing quake-induced torsional Alfven
vibrations in its own ultra strong magnetic field experiencing decay is
considered. The presented line of argument suggests that gradual decrease of
frequencies (lengthening of periods) of long-periodic pulsed radiation detected
from a set of X-ray sources can be attributed to magnetic-field-decay induced
energy conversion from seismic vibrations to magneto-dipole radiation of
quaking magnetar.Comment: Text of talk presented at "Mini-Workshop on Pulsars", Nov. 12th,
2010; KIAA-PKU, Beijin
Relative importance of crystal field versus bandwidth to the high pressure spin transition in transition metal monoxides
The crystal field splitting and d bandwidth of the 3d transition metal
monoxides MnO, FeO, CoO and NiO are analyzed as a function of pressure within
density functional theory. In all four cases the 3d bandwidth is significantly
larger than the crystal field splitting over a wide range of compressions. The
bandwidth actually increases more as pressure is increased than the crystal
field splitting. Therefore the role of increasing bandwidth must be considered
in any explanation of a possible spin collapse that these materials may exhibit
under pressure.Comment: 7 pages, 4 figure
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