1,398 research outputs found
On the well-posedness for the Ideal MHD equations in the Triebel-Lizorkin spaces
In this paper, we prove the local well-posedness for the Ideal MHD equations
in the Triebel-Lizorkin spaces and obtain blow-up criterion of smooth
solutions. Specially, we fill a gap in a step of the proof of the local
well-posedness part for the incompressible Euler equation in \cite{Chae1}.Comment: 16page
Electrostatic modification of infrared response in gated structures based on VO2
We investigate the changes in the infrared response due to charge carriers
introduced by electrostatic doping of the correlated insulator vanadium dioxide
(VO2) integrated in the architecture of the field effect transistor.
Accumulation of holes at the VO2 interface with the gate dielectric leads to an
increase in infrared absorption. This phenomenon is observed only in the
insulator-to-metal transition regime of VO2 with coexisting metallic and
insulating regions. We postulate that doped holes lead to the growth of the
metallic islands thereby promoting percolation, an effect that persists upon
removal of the applied gate voltage.Comment: 14 pages, including 4 figure
Global classical solutions for partially dissipative hyperbolic system of balance laws
This work is concerned with (-component) hyperbolic system of balance laws
in arbitrary space dimensions. Under entropy dissipative assumption and the
Shizuta-Kawashima algebraic condition, a general theory on the well-posedness
of classical solutions in the framework of Chemin-Lerner's spaces with critical
regularity is established. To do this, we first explore the functional space
theory and develop an elementary fact that indicates the relation between
homogeneous and inhomogeneous Chemin-Lerner's spaces. Then this fact allows to
prove the local well-posedness for general data and global well-posedness for
small data by using the Fourier frequency-localization argument. Finally, we
apply the new existence theory to a specific fluid model-the compressible Euler
equations with damping, and obtain the corresponding results in critical
spaces.Comment: 39 page
On the global well-posedness of a class of Boussinesq- Navier-Stokes systems
In this paper we consider the following 2D Boussinesq-Navier-Stokes systems
\partial_{t}u+u\cdot\nabla u+\nabla p+ |D|^{\alpha}u &= \theta e_{2}
\partial_{t}\theta+u\cdot\nabla \theta+ |D|^{\beta}\theta &=0 \quad with
and . When , , where is an explicit function
as a technical bound, we prove global well-posedness results for rough initial
data.Comment: 23page
Chromospheric Magnetic Reconnection caused by Photospheric Flux Emergence: Implications for Jet-like Events Formation
Magnetic reconnection in the low atmosphere, e.g. chromosphere, is
investigated in various physical environments. Its implications for the
origination of explosive events (small--scale jets) are discussed. A
2.5-dimensional resistive magnetohydrodynamic (MHD) model in Cartesian
coordinates is used. It is found that the temperature and velocity of the
outflow jets as a result of magnetic reconnection are strongly dependent on the
physical environments, e.g. the magnitude of the magnetic field strength and
the plasma density. If the magnetic field strength is weak and the density is
high, the temperature of the jets is very low (~10,000 K) as well as its
velocity (~40 km/s). However, if environments with stronger magnetic field
strength (20 G) and smaller density (electron density Ne=2x10^{10} cm^{-3}) are
considered, the outflow jets reach higher temperatures of up to 600,000 K and a
line-of-sight velocity of up to 130 km/s which is comparable with the
observational values of jet-like events.Comment: 9 pages, 8 figures, 1 table, submitted to A&
Collective magnetism at multiferroic vortex domain walls
Topological defects have been playgrounds for many emergent phenomena in
complex matter such as superfluids, liquid crystals, and early universe.
Recently, vortex-like topological defects with six interlocked structural
antiphase and ferroelectric domains merging into a vortex core were revealed in
multiferroic hexagonal manganites. Numerous vortices are found to form an
intriguing self-organized network. Thus, it is imperative to find out the
magnetic nature of these vortices. Using cryogenic magnetic force microscopy,
we discovered unprecedented alternating net moments at domain walls around
vortices that can correlate over the entire vortex network in hexagonal ErMnO3
The collective nature of domain wall magnetism originates from the
uncompensated Er3+ moments and the correlated organization of the vortex
network. Furthermore, our proposed model indicates a fascinating phenomenon of
field-controllable spin chirality. Our results demonstrate a new route to
achieving magnetoelectric coupling at domain walls in single-phase
multiferroics, which may be harnessed for nanoscale multifunctional devices.Comment: 18 pages, 10 figure
Relationship between eruptions of active-region filaments and associated flares and CMEs
To better understand the dynamical process of active-region filament
eruptions and associated flares and CMEs, we carried out a statistical study of
120 events observed by BBSO, TRACE, and t(SOHO/EIT) from 1998 to 2007 and
combined filament observations with the NOAA's flare reports, MDI magnetograms,
and LASCO data, to investigate the relationship between active-region filament
eruptions and other solar activities. We found that 115 out of 120 filament
eruptions are associated with flares. 56 out of 105 filament eruptions are
found to be associated with CMEs except for 15 events without corresponding
LASCO data. We note the limitation of coronagraphs duo to geometry or
sensitivity, leading to many smaller CMEs that are Earth-directed or well out
of the plane of sky not being detected by near-Earth spacecraft. Excluding
those without corresponding LASCO data, the CME association rate of
active-region filament eruptions clearly increases with X-ray flare class from
about 32% for C-class flares to 100% for X-class flares. The eruptions of
active-region filaments associated with Halo CMEs are often accompanied by
large flares. About 92% events associated with X-class flare are associated
with Halo CMEs. Such a result is due to that the Earth-directed CMEs detected
as Halo CMEs are often the larger CMEs and many of the smaller ones are not
detected because of the geometry and low intensity. The average speed of the
associated CMEs of filament eruptions increases with X-ray flare size from
563.7 km/s for C-class flares to 1506.6 km/s for X-class flares. Moreover, the
magnetic emergence and cancellation play an important role in triggering
filament eruptions. These findings may be instructive to not only in respect to
the modeling of active-region filament eruptions but also in predicting flares
and CMEs.Comment: 19 Pages, 7 figures, Accepted for publication in MNRA
Time-Varying Dark Energy Constraints From the Latest SN Ia, BAO and SGL
Based on the latest SNe Ia data provided by Hicken et al. (2009) with using
MLCS17 light curve fitter, together with the Baryon Acoustic Oscillation(BAO)
and strong gravitational lenses(SGL), we investigate the constraints on the
dark energy equation-of-state parameter in the flat universe, especially
for the time-varying case . The constraints from SNe data
alone are found to be: (a) as the best-fit
results; (b) for
the two parameters in the time-varying case after marginalizing the parameter
; (c) the likelihood of parameter has a high non-Gaussian
distribution; (d) an extra restriction on is necessary to improve
the constraint of the SNe Ia data on the parameters (, ). A joint
analysis of SNe Ia data and BAO is made to break the degeneracy between and
, and leads to the interesting maximum likelihoods and
. When marginalizing the parameter , the fitting results are
found to be . After
adding the splitting angle statistic of SGL data, a consistent constraint is
obtained and the constraints on time-varying
dark energy are further improved to be , which indicates that the phantom type models are
disfavored.Comment: 24 pages, 9 figures, to be published in JCA
CH3NH3PbI3 perovskites: Ferroelasticity revealed
Ferroelectricity has been proposed as a plausible mechanism to explain the high photovoltaic conversion efficiency in organic-inorganic perovskites; however, convincing experimental evidence in support of this hypothesis is still missing. Identifying and distinguishing ferroelectricity from other properties, such as piezoelectricity, ferroelasticity, etc., is typically nontrivial because these phenomena can coexist in many materials. In this work, a combination of microscopic and nanoscale techniques provides solid evidence for the existence of ferroelastic domains in both CH3NH3PbI3 polycrystalline films and single crystals in the pristine state and under applied stress. Experiments show that the configuration of CH3NH3PbI3 ferroelastic domains in single crystals and polycrystalline films can be controlled with applied stress, suggesting that strain engineering may be used to tune the properties of this material. No evidence of concomitant ferroelectricity was observed. Because grain boundaries have an impact on the long-term stability of organic-inorganic perovskite devices, and because the ferroelastic domain boundaries may differ from regular grain boundaries, the discovery of ferroelasticity provides a new variable to consider in the quest for improving their stability and enabling their widespread adoptio
Controlled Synthesis of Monolayer Graphene Toward Transparent Flexible Conductive Film Application
We demonstrate the synthesis of monolayer graphene using thermal chemical vapor deposition and successive transfer onto arbitrary substrates toward transparent flexible conductive film application. We used electron-beam-deposited Ni thin film as a synthetic catalyst and introduced a gas mixture consisting of methane and hydrogen. To optimize the synthesis condition, we investigated the effects of synthetic temperature and cooling rate in the ranges of 850–1,000°C and 2–8°C/min, respectively. It was found that a cooling rate of 4°C/min after 1,000°C synthesis is the most effective condition for monolayer graphene production. We also successfully transferred as-synthesized graphene films to arbitrary substrates such as silicon-dioxide-coated wafers, glass, and polyethylene terephthalate sheets to develop transparent, flexible, and conductive film application
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