258 research outputs found
Suppression of DC term in Fresnel digital holography by sequence subtraction of holograms
An experimental method for suppression of DC term in the reconstructed images
from Fresnel digital holograms is presented. In this method, two holograms for
the same object are captured sequentially and subtracted. Since these two
holograms are captured at different moments, they are slightly different from
each other for fluctuations of noises. The DC term is suppressed in the image
reconstructed from the subtraction hologram, while the two virtual and real
images are successfully reconstructed. This method can be potentially used for
the improvement of image quality reconstructed from Fresnel digital holograms
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
Revealing the formation and electrochemical properties of bis(trifluoromethanesulfonyl) imide intercalated graphite with first-principles calculations
Graphite has been reported to have anion as well as cation intercalation
capacities as both cathode and anode host materials for the dual ion battery.
In this work, we study the intercalation of bis(trifluoromethanesulfonyl) imide
(TFSI) anion from ionic liquid electrolyte into graphite with first-principles
calculations. We build models for TFSI-C compounds with systematically
increasing unit cell sizes of graphene sheet and investigate their stabilities
by calculating the formation energy, resulting in the linear decrease and
arriving at the limit of stability. With identified unit cell sizes for stable
compound formation, we reveal that the interlayer distance and relative volume
expansion ratio of TFSI-C increase as increasing the concentration of TFSI
intercalate during the charge process. The electrode voltage is determined to
be ranged from 3.8 V to 3.0 V at the specific capacity ranging from 30 mAh
g to 54 mAh g in agreement with experiment. Moreover, a very low
activation barrier of under 50 meV for TFSI migration and good electronic
conductivity give a proof of using these compounds as a promising cathode.
Through the analysis of charge transfer, we clarify the mechanism of TFSI-C
formation, and reveal new prospects for developing graphite based cathode
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
Exciton-Plasmon Coupling Effects on the Nonlinear Optical Susceptibility of Hybrid Quantum Dot-Metallic Nanoparticle System
We have studied theoretically the exciton-plasmon coupling effects on the
third-order optical nonlinearity of a coherently coupled hybrid system of a
metal nanoparticle and a semiconductor quantum dot in the presence of a strong
control field with a weak probe field
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
Influence of Pulse width and Rabi frequency on the Population dynamics of three-level system in two-photon absorption process
We investigate the population dynamics of the three-level system in the
two-photon absorption (TPA) process, mainly focusing the influence of pulse
width and Rabi frequency on the population dynamics of the system. We observe
the dependency of the population with the Rabi frequency and the pulse width.
We also show that the arbitrary superposition state consisted in two states,
upper state and lower state, is possible by controlling the pulse width and
Rabi frequency. The results obtained can be used to the case of more complex
multilevel system and they can be valuable for coherent quantum control in
quantum information processing.Comment: arXiv admin note: text overlap with arXiv:quant-ph/0402155 by other
authors without attributio
Study on the Vibration Displacement Distribution of a Circular Ultrasonic Motor Stator
In this paper is presented a theoretical consideration on the stator's
displacement distribution, which is one of the most important problems in
defining the structure of the circular ultrasonic motor stator. The results are
compared with results obtained utilizing holographic interferometer, laser
vibrometer and a FEM (finite element method) simulation. They are in a good
agreement with each other
Control of the Optical Response of an Artificial Hybrid Nanosystem Due to the Plasmon-Exciton Plasmon Coupling Effect
The optical response of an artificial hybrid molecule system composed of two
metallic nanoparticles (MNPs) and a semiconductor quantum dot (SQD) is
investigated theoretically due to the plasmon-exciton-plasmon coupling effects
on the absorption properties of the hybrid nanosystem, which depends on the
interaction between the induced dipole moments in the SQD and the MNPs,
respectively. We show that the strong coupling of exciton and localized surface
plasmons in such a hybrid molecules leads to appealing, tunable optical
properties by adjusting the symmetry of the hybrid molecule nanosystem with
controllable interparticle distances. We also address here the influence of the
size of the MNPs and dielectric constant of the background medium on the
optical absorption of the MNPs and SQD, respectively, which results in the
interparticle Foster resonance energy transfer (FRET). Our results will open an
avenue to deal with the surface-enhanced spectroscopies and potential
application of the quantum information
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
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