14,697 research outputs found
A Thermostat-Consistent Fully Coupled Molecular Dynamics-Generalized Fluctuating Hydrodynamics Model
The previously developed multiscale method for concurrently coupling atomistic and continuum hydrodynamic representations of the same chemical substance is extended to consistently incorporate the Langevin‐type thermostat equations in the model. This allows not only to preserve the mass and momentum conservation laws based on the two‐phase flow analogy modeling framework but also to capture the correct local fluctuations and temperature in the pure atomistic region of the hybrid model. Numerical results for the test problem of equilibrium isothermal fluctuations of SPC/E water are presented. Advantages of using local thermostat equations adjusted for the multiresolution model for accurately capturing of the local water density in the atomistic part of the hybrid simulation domain are discussed. Comparisons with the reference pure all‐atom molecular dynamics simulations in GROMACS show that the suggested hybrid models are by a factor of 5–20 faster depending on the simulation domain size
Anomalous microwave response of high-temperature superconducting thin-film microstrip resonator in weak dc magnetic fields
We have studied an anomalous microwave (mw) response of superconducting
YBa_{2}Cu_{3}O_{7-delta} (YBCO) microstrip resonators in the presence of a weak
dc magnetic field, H_{dc}. The surface resistance (R_{s}) and reactance (X_{s})
show a correlated non-monotonic behaviour as a function of H_{dc}. R_{s} and
X_{s} were found to initially decrease with elevated H_{dc} and then increase
after H_{dc} reaches a crossover field, H_{c}, which is independent of the
amplitude and frequency of the input mw signal within the measurements. The
frequency dependence of R_{s} is almost linear at fixed H_{dc} with different
magnitudes (H_{c}). The impedance plane analysis
demonstrates that r_{H}, which is defined as the ratio of the change in
R_{s}(H_{dc}) and that in X_{s}(H_{dc}), is about 0.6 at H_{dc}<H_{c} and 0.1
at H_{dc}>H_{c}. The H_{dc} dependence of the surface impedance is
qualitatively independent of the orientation of H_{dc}.Comment: REVTex 3.1, 5 pages, 6 EPS figures, submitted to Physica
Enhanced Room Temperature Coefficient of Resistance and Magneto-resistance of Ag-added La0.7Ca0.3-xBaxMnO3 Composites
In this paper we report an enhanced temperature coefficient of resistance
(TCR) close to room temperature in La0.7Ca0.3-xBaxMnO3 + Agy (x = 0.10, 0.15
and y = 0.0 to 0.40) (LCBMO+Ag) composite manganites. The observed enhancement
of TCR is attributed to the grain growth and opening of new conducting channels
in the composites. Ag addition has also been found to enhance intra-granular
magneto-resistance. Inter-granular MR, however, is seen to decrease with Ag
addition. The enhanced TCR and MR at / near room temperature open up the
possibility of the use of such materials as infrared bolometric and magnetic
field sensors respectively.Comment: 22 pages of Text +
Figs:comments/suggestions([email protected]
Fast Transition between High-soft and Low-soft States in GRS 1915+105: Evidence for a Critically Viscous Accretion Flow
We present the results of a detailed analysis of RXTE observations of class
which show an unusual state transition between high-soft and low-soft
states in the microquasar GRS 1915+105. Out of about 600 pointed RXTE
observations, the source was found to exhibit such state transition only on 16
occasions. An examination of the RXTE/ASM data in conjunction with the pointed
observations reveals that these events appeared as a series of quasi-regular
dips in two stretches of long duration (about 20 days during each occasions)
when hard X-ray and radio flux were very low. The X-ray light curve and
color-color diagram of the source during these observations are found to be
different from any reported so far. The duration of these dips is found to be
of the order of a few tens of seconds with a repetition time of a few hundred
seconds. The transition between these dips and non-dips which differ in
intensity by a factor of ~ 3.5, is observed to be very fast (~ a few seconds).
It is observed that the low-frequency narrow QPOs are absent in the power
density spectrum (PDS) of the dip and non-dip regions of class and the
PDS is a power law in 0.1 - 10 Hz frequency range. There is a remarkable
similarity in the spectral and timing properties of the source during the dip
and non-dip regions in these set of observations. These properties of the
source are distinctly different from those seen in the observations of other
classes. This indicates that the basic accretion disk structure during both dip
and non-dip regions of class is similar, but differ only in intensity.
To explain these observations, we invoke a model in which the viscosity is very
close to critical viscosity and the shock wave is weak or absent.Comment: Replaced with correct figures, Jour. of Astrophysics and Astronomy
(accepted
Green's function for metamaterial superlens: Evanescent wave in the image
We develop a new method to calculate the evanescent wave, the subdivided
evanescent waves (SEWs), and the radiative wave, which can be obtained by
separating the global field of the image of metamaterial superlens. The method
is based on Green's function, and it can be applied in other linear systems.
This study could help us to investigate the effect of evanescent wave on
metamaterial superlens directly, and give us a new way to design new devices.Comment: 15 pages, 3 figure
Do mutual funds have consistency in their performance?
Using a comprehensive data set of 714 Chinese mutual funds from 2004 to 2015, the study investigates these funds’ performance persistence by using the Capital Asset Pricing model, the Fama-French three-factor model and the Carhart Four-factor model. For persistence analysis, we categorize mutual funds into eight octiles based on their one year lagged performance and then observe their performance for the subsequent
12 months. We also apply Cross-Product Ratio technique to assess the performance
persistence in these Chinese funds. The study finds no significant evidence of persis- tence in the performance of the mutual funds. Winner (loser) funds do not continue to be winner (loser) funds in the subsequent time period. These findings suggest that future performance of funds cannot be predicted based on their past performance.info:eu-repo/semantics/publishedVersio
Solitary Dust--Acoustic Waves in a Plasma with Two-Temperature Ions and Distributed Grain Size
The propagation of weakly nonlinear dust--acoustic waves in a dusty plasma
containing two ion species with different temperatures is explored. The
nonlinear equations describing both the quadratic and cubic plasma
nonlinearities are derived. It is shown that the properties of dust--acoustic
waves depend substantially on the grain size distribution. In particular, for
solitary dust--acoustic waves with a positive potential to exist in a plasma
with distributed grain size, it is necessary that the difference between the
temperatures of two ion species be large that that in the case of unusized
grains.Comment: 16 pages, 6 figure
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