330,150 research outputs found
To improve model soil moisture estimation in arid/semi-arid region using in situ and remote sensing information
Soil moisture plays a key role in water and energy exchange in the land hydrologic process. Effective soil moisture information can be used for many applications in weather and hydrological forecasting, water resources, and irrigation system management and planning. However, to accurate modeling of soil moisture variation in the soil layer is still very challenging. In this study, in situ and remote sensing information of near-surface soil moisture is assimilated into the Noah land surface model (LSM) to estimate deep-layer soil moisture variation. The sequential Monte Carlo-Particle Filter technique, being well known for capability of modeling high nonlinear and non-Gaussian processes, is applied to assimilate surface soil moisture measurement to the deep layers. The experiments were carried out over several locations over the semi-arid region of the US. Comparing with in situ observations, the assimilation runs show much improved from the control (non-assimilation) runs for estimating both soil moisture and temperature at 5-, 20-, and 50-cm soil depths in the Noah LSM. © 2012 Springer-Verlag
On quantum vertex algebras and their modules
We give a survey on the developments in a certain theory of quantum vertex
algebras, including a conceptual construction of quantum vertex algebras and
their modules and a connection of double Yangians and Zamolodchikov-Faddeev
algebras with quantum vertex algebras.Comment: 18 pages; contribution to the proceedings of the conference in honor
of Professor Geoffrey Maso
Gravitational effects of condensate dark matter on compact stellar objects
We study the gravitational effect of non-self-annihilating dark matter on
compact stellar objects. The self-interaction of condensate dark matter can
give high accretion rate of dark matter onto stars. Phase transition to
condensation state takes place when the dark matter density exceeds the
critical value. A compact degenerate dark matter core is developed and alter
the structure and stability of the stellar objects. Condensate dark matter
admixed neutron stars is studied through the two-fuid TOV equation. The
existence of condensate dark matter deforms the mass-radius relation of neutron
stars and lower their maximum baryonic masses and radii. The possible effects
on the Gamma-ray Burst rate in high redshift are discussed
Charge pumping in monolayer graphene driven by a series of time-periodic potentials
We applied the Floquet scattering-matrix formalism to studying the electronic
transport properties in a mesoscopic Dirac system. Using the method, we
investigate theoretically quantum pumping driven by a series of time-periodic
potentials in graphene monolayer both in the adiabatic and non-adiabatic
regimes. Our numerical results demonstrate that adding harmonic modulated
potentials can break the time reversal symmetry when no voltage bias is applied
to the graphene monolayer. Thus, when the system is pumped with proper dynamic
parameters, these scatterers can produce a nonzero dc pumped current. We also
find that the transmission is anisotropic as the incident angle is changed.Comment: 8 pages, 6 figure
Swift Observations of X-ray supernovae
We present a result of X-ray supernovae (SNe) survey using the Swift
satellite public archive. An automatic searching program was designed to search
X-ray SNe among all of the Swift archival observations between November 2004
and February 2011. Using the C++ program, 24 X-ray detectable supernovae have
been found in the archive and 3 of them were newly-discovered in X-rays which
are SN 1986L, SN 2003lx, and SN 2007od. In addition, SN 2003lx is a Type Ia
supernova which may be the second X-ray detectable Type Ia after SN 2005ke
(Immler et al. 2006). Calibrated data of luminous type Ib/c supernovae was
consistent to the X-ray emission model done by Chevalier & Fransson (1994).
Statistics about the luminosities and hardness ratio have been done to purpose
of getting the X-ray emission features of the X-ray supernovae. The results
from this work help investigating the X-ray evolution of SNe and developing
similar X-ray SNe surveys in various X-rays missions
Classification of Multipartite Entanglement via Negativity Fonts
Partial transposition of state operator is a well known tool to detect
quantum correlations between two parts of a composite system. In this letter,
the global partial transpose (GPT) is linked to conceptually multipartite
underlying structures in a state - the negativity fonts. If K-way negativity
fonts with non zero determinants exist, then selective partial transposition of
a pure state, involving K of the N qubits (K leq N) yields an operator with
negative eigevalues, identifying K-body correlations in the state. Expansion of
GPT interms of K-way partially transposed (KPT) operators reveals the nature of
intricate intrinsic correlations in the state. Classification criteria for
multipartite entangled states, based on underlying structure of global partial
transpose of canonical state, are proposed. Number of N-partite entanglement
types for an N qubit system is found to be 2^{N-1}-N+2, while the number of
major entanglement classes is 2^{N-1}-1. Major classes for three and four qubit
states are listed. Subclasses are determined by the number and type of
negativity fonts in canonical state.Comment: 5 pages, No figures, Corrected typo
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