120 research outputs found
Ionic Diffusion and Electronic Transport in Eldfellite NaFe(SO)
Discovering new electrodes for sodium-ion battery requires clear
understanding of the material process during battery operation. Using
first-principles calculations, we identify mechanisms of ionic diffusion and
electronic transfer in newly developed cathode material, eldfellite
NaFe(SO), reproducing the electrochemical properties in good
agreement with experiment. The inserted sodium atom is suggested to diffuse
along the two-dimensional pathway with preceding movement of the host sodium
atom, and the activation energy is calculated to be reasonable for fast
insertion. We calculate the electronic properties, showing the band insulating
at low composition of inserted sodium, for which the electron polaron formation
and hoping are also suggested. Our results may contribute to opening a new way
of developing innovative cathode materials based on iron and sulfate ion
Intrinsic nonlinear response of surface plasmon polaritons
We offer a model to describe the intrinsic nonlinear response of surface
plasmon polaritons (SPPs). Relation of the complex nonlinear coefficient of
SPPs to the third-order nonlinear susceptibility of the metal is provided. As
reported in a recent study, gold is highly lossy and simultaneously highly
nonlinear due to interband absorption and interband thermo-modulation at a
wavelength shorter than 700 nm. The effect of the high loss of the metal on the
SPP nonlinear propagation is taken into account in our model. With the model we
show difference in sign of real and imaginary parts between the nonlinear
propagation coefficient and the nonlinear susceptibility of component material
for the first time to our knowledge. Our model could have practical importance
in studying plasmonic devices utilizing the nonlinear phase modulation and the
nonlinear absorption of SPPs. For example, it allows one to extract the complex
nonlinear susceptibility of gold through a measurement of SPP nonlinear
propagation at the visible range
New discrete method for investigating the response properties in finite electric field
In this paper we develop a new discrete method for calculating the dielectric
tensor and Born effective charge tensor in finite electric field by using
Berry's phase and the gauge invariance. We present a new method to overcome
non-periodicity of the potential in finite electric field due to the gauge
invariance, and construct the dielectric tensor and Born effective charge
tensor that satisfy translational symmetry in finite electric field. In order
to demonstrate the correctness of this method, we also perform calculations for
the semiconductors AlAs and GaAs under the finite electric field to compare
with the preceding method and the experiment.Comment: arXiv admin note: text overlap with arXiv:cond-mat/0612442 by other
author
Two-dimensional hybrid composites of SnS2 with graphene and graphene oxide for improving sodium storage: A first-principles study
Among the recent achievements of sodium-ion battery (SIB) electrode
materials, hybridization of two-dimentional (2D) materials is one of the most
interesting appointments. In this work, we propose to use the 2D hybrid
composites of SnS2 with graphene or graphene oxide (GO) layers as SIB anode,
based on the first-principles calculations of their atomic structures, sodium
intercalation energetics and electronic properties. The calculations reveal
that graphene or GO film can effectively support not only the stable formation
of hetero-interface with the SnS2 layer but also the easy intercalation of
sodium atom with low migration energy and acceptable low volume change. The
electronic charge density differences and the local density of state indicate
that the electrons are transferred from the graphene or GO layer to the SnS2
layer, facilitating the formation of hetero-interface and improving the
electronic conductance of the semiconducting SnS2 layer. These 2D hybrid
composites of SnS2/G or GO are concluded to be more promising candidates for
SIB anodes compared with the individual monolayers
New Movement and Transformation Principle of Fuzzy Reasoning and Its Application to Fuzzy Neural Network
In this paper, we propose a new fuzzy reasoning principle, so called Movement
and Transformation Principle(MTP). This Principle is to obtain a new fuzzy
reasoning result by Movement and Transformation the consequent fuzzy set in
response to the Movement, Transformation, and Movement-Transformation
operations between the antecedent fuzzy set and fuzzificated observation
information. And then we presented fuzzy modus ponens and fuzzy modus tollens
based on MTP. We compare proposed method with Mamdani fuzzy system, Sugeno
fuzzy system, Wang distance type fuzzy reasoning method and Hellendoorn
functional type method. And then we applied to the learning experiments of the
fuzzy neural network based on MTP and compared it with the Sugeno method.
Through prediction experiments of fuzzy neural network on the precipitation
data and security situation data, learning accuracy and time performance are
clearly improved. Consequently we show that our method based on MTP is
computationally simple and does not involve nonlinear operations, so it is easy
to handle mathematically
Document watermarking based on digital holographic principle
A new method for document watermarking based on the digital Fourier hologram
is proposed. It applies the methods of digital image watermarking based on
holographic principle presented previously in several papers into printed
documents. Experimental results show that the proposed method can not only meet
the demand on invisibility, robustness and non-reproducibility of the document
watermark, and but also has other advantages compared with the conventional
methods for document securities such as embossed hologram, Lippmann photograph
and halftone modulation
Formation and characterization of ceramic coating from alumino silicate mineral powders in the matrix of cement composite on the concrete wall
Enhancement of thermal performance of concrete wall is nowadays of great
importance in reducing the operational energy demand of buildings. We developed
a new kind of inorganic coating material based on \ce{SiO2}-\ce{Al2O3}-rich
minerals and Portland cement (PC) powder. The finely pulverized mineral powder
with the particle size distribution (PSD) of 0.4-40 m was mixed with the
vehicle solvent containing some agents, cement powder with PSD of 2-100 m,
and water in the certain weight ratio, producing the colloid solution. After
application within 2 hours to the plaster layer of concrete wall and sufficient
long hardening period of over three months, the coating layer of 0.6-1.0 mm
thickness was observed to become a densified ceramic. Powder X-ray diffraction
(XRD) experiments were performed to identify the crystalline components of
minerals, cement and ceramic coating powders. Three- and two-dimensional
surface morphologies and chemical compositions of coating material were
obtained with the optical interferometer and scanning electron microscope (SEM)
equipped with an energy dispersive X-ray analyzer (EDX). These XRD and SEM/EDX
analyses demonstrated obviously that the coating layer is mainly composed of
the calcium-silicate-hydrate (C-S-H) and the calcium-aluminate-hydrate (C-A-H)
ceramics with the relatively small number of closed pores (10\% porosity)
compared with the cement mortar and concrete layers. Two-step hydrations of
cement and subsequently \ce{SiO2}-\ce{Al2O3} promoted by the alkali product
\ce{Ca(OH)2} were proposed as the main mechanism of ceramic formation
Apparent Positions of Planets
The apparent positions of planets are determined by means of the fundamental
ephemerides, the precession-nutation models of the Earth, the gravitational
effects and aberrations et al. Around 2000, many astrometrical conceptions,
models and theories had been newly defined and updated:for the fiducial
celestial reference system, the ICRS is introduced, the fundamental ephemerides
- DE405/LE405 et al.,precession-nutation model - IAU 2000A/IAU 2006 model.
Using the traditional algorithm and the updated models, we develop the system
of calculating the apparent positions of planets. The results are compared with
the Astronomical Almanac and proved in their correctness.Comment: 9 pages, 3 figure
Plasmonic Effect on the Population Dynamics and the Optical Response in a Hybrid V-Type Three-Level Quantum Dot-Metallic Nanoparticle Nanosystem
We investigated theoretically the exciton-plasmon coupling effects on the
population dynamics and the absorption properties of a hybrid nanosystem
composed of a metal nanoparticle (MNP) and a V-type three level semiconductor
quantum dot (SQD), which are created by the interaction with the induced dipole
moments in the SQD and the MNP, respectively. Excitons of the SQD and the
plasmons of the MNP in such a hybrid nanosystem could be coupled strongly or
weakly to demonstrate novel properties of the hybrid system. Our results show
that the nonlinear optical response of the hybrid nanosystem can be greatly
enhanced or depressed due to the exciton-plasmon couplings.Comment: 12 pages, 6 figures. arXiv admin note: substantial text overlap with
arXiv:1507.0445
First-principles study of ternary graphite compounds cointercalated with alkali atoms (Li, Na, and K) and alkylamines towards alkali ion battery applications
Using density functional theory calculations, we have investigated the
structural, energetic, and electronic properties of ternary graphite
intercalation compounds (GICs) containing alkali atoms (AM) and normal
alkylamine molecules (nC), denoted as AM-nC-GICs (AM=Li, Na, K, =1, 2,
3, 4). The orthorhombic unit cells have been used to build the models for
crystalline stage-I AM-nC-GICs. By performing the variable cell relaxations
and the analysis of results, we have found that with the increase in the atomic
number of alkali atoms the layer separations decreases in contrast to AM-GICs,
while the bond lengths of alkali atoms with graphene layer and nitrogen atom of
alkylamine decreases. The formation and interlayer binding energies of
AM-nC3-GICs have been calculated, indicating the increase in stability from Li
to K. The calculated energy barriers for migration of alkali atoms suggest that
alkali cation with larger ionic radius diffuses in graphite more smoothly,
being similar to AM-GICs. The analysis of density of states, electronic density
differences, and atomic populations illustrates a mechanism how the insertion
of especially Na among alkali atoms into graphite with first stage can be made
easy by cointercalation with alkylamine, more extent of electronic charge
transfer is occurred from more electropositive alkali atom to carbon ring of
graphene layer, while alkylamine molecules interact strongly with graphene
layer through the hybridization of valence electron orbitals.Comment: 22 pages, 9 figure
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