2,058 research outputs found
Scattering mechanism in a step-modulated subwavelength metal slit: a multi-mode multi-reflection analysis
In this paper, the scattering/transmission inside a step-modulated
subwavelength metal slit is investigated in detail. We firstly investigate the
scattering in a junction structure by two types of structural changes. The
variation of transmission and reflection coefficients depending on structural
parameters are analyzed. Then a multi-mode multi-reflection model based on ray
theory is proposed to illustrate the transmission in the step-modulated slit
explicitly. The key parts of this model are the multi-mode excitation and the
superposition procedure of the scatterings from all possible modes, which
represent the interference and energy transfer happened at interfaces. The
method we use is an improved modal expansion method (MEM), which is a more
practical and efficient version compared with the previous one [Opt. Express
19, 10073 (2011)]. In addition, some commonly used methods, FDTD, scattering
matrix method, and improved characteristic impedance method, are compared with
MEM to highlight the preciseness of these methods.Comment: 25 pages, 9 figure
Probing the sp^2 dependence of elastic moduli in ultrahard diamond films
The structural and elastic properties of diamond nanocomposites and
ultrananocrystalline diamond films (UNCD) are investigated using both empirical
potentials and tight binding schemes. We find that both materials are extremely
hard, but their superb diamondlike properties are limited by their sp^2
component. In diamond composites, the sp^2 atoms are found in the matrix and
far from the interface with the inclusion, and they are responsible for the
softening of the material. In UNCD, the sp^2 atoms are located in the grain
boundaries. They offer relaxation mechanisms which relieve the strain but, on
the other hand, impose deformations that lead to softening. The higher the sp^2
component the less rigid these materials are.Comment: 10 pages, 3 figures. to appear in Diamond and Relarted Material
Tourism cloud management system: the impact of smart tourism
Abstract
This study investigates the possibility of supporting tourists in a foreign land intelligently by using the Tourism Cloud Management System (TCMS) to enhance and better their tourism experience. Some technologies allow tourists to highlight popular tourist routes and circuits through the visualisation of data and sensor clustering approaches. With this, a tourist can access the shared data on a specific location to know the sites of famous local attractions, how other tourists feel about them, and how to participate in local festivities through a smart tourism model. This study surveyed the potential of smart tourism among tourists and how such technologies have developed over time while proposing a TCMS. Its goals were to make physical/paper tickets redundant via the introduction of a mobile app with eTickets that can be validated using camera and QR code technologies and to enhance the transport network using Bluetooth and GPS for real-time identification of tourists’ presence. The results show that a significant number of participants engage in tourist travels, hence the need for smart tourism and tourist management. It was concluded that smart tourism is very appealing to tourists and can improve the appeal of the destination if smart solutions are implemented. This study gives a first-hand review of the preference of tourists and the potential of smart tourism
Scattering Theory of Dynamic Electrical Transport
We have developed a scattering matrix approach to coherent transport through
an adiabatically driven conductor based on photon-assisted processes. To
describe the energy exchange with the pumping fields we expand the Floquet
scattering matrix up to linear order in driving frequency.Comment: Proceedings QMath9, September 12th-16th, 2004, Giens, Franc
Distribution of spectral weight in a system with disordered stripes
The ``band-structure'' of a disordered stripe array is computed and compared,
at a qualitative level, to angle resolved photoemission experiments on the
cuprate high temperature superconductors. The low-energy states are found to be
strongly localized transverse to the stripe direction, so the electron dynamics
is strictly one-dimensional (along the stripe). Despite this, aspects of the
two dimensional band-structure Fermi surface are still vividly apparent.Comment: 10 pages, 11 figure
Parametric pumping at finite frequency
We report on a first principles theory for analyzing the parametric electron
pump at a finite frequency. The pump is controlled by two pumping parameters
with phase difference . In the zero frequency limit, our theory predicts
the well known result that the pumped current is proportional to .
For the more general situation of a finite frequency, our theory predicts a
non-vanishing pumped current even when the two driving forces are in phase, in
agreement with the recent experimental results. We present the physical
mechanism behind the nonzero pumped current at , which we found to be
due to photon-assisted processes
Conductance fluctuations in a quantum dot under almost periodic ac pumping
It is shown that the variance of the linear dc conductance fluctuations in an
open quantum dot under a high-frequency ac pumping depends significantly on the
spectral content of the ac field. For a sufficiently strong ac field
, where is the dephasing rate induced by
ac noise and is the electron escape rate, the dc conductance
fluctuations are much stronger for the harmonic pumping than in the case of the
noise ac field of the same intensity. The reduction factor in a static
magnetic field takes the universal value of 2 only for the white--noise
pumping. For the strictly harmonic pumping of
sufficiently large intensity the variance is almost insensitive to the static
magnetic field . For the quasi-periodic ac
field of the form with
and we predict the novel
effect of enchancement of conductance fluctuations at commensurate frequencies
.Comment: 4 pages RevTex, 4 eps figures; the final version to appear in
Phys.Rev.
Generation of atom-photon entangled states in atomic Bose-Einstein condensate via electromagnetically induced transparency
In this paper, we present a method to generate continuous-variable-type
entangled states between photons and atoms in atomic Bose-Einstein condensate
(BEC). The proposed method involves an atomic BEC with three internal states, a
weak quantized probe laser and a strong classical coupling laser, which form a
three-level Lambda-shaped BEC system. We consider a situation where the BEC is
in electromagnetically induced transparency (EIT) with the coupling laser being
much stronger than the probe laser. In this case, the upper and intermediate
levels are unpopulated, so that their adiabatic elimination enables an
effective two-mode model involving only the atomic field at the lowest internal
level and the quantized probe laser field. Atom-photon quantum entanglement is
created through laser-atom and inter-atomic interactions, and two-photon
detuning. We show how to generate atom-photon entangled coherent states and
entangled states between photon (atom) coherent states and atom-(photon-)
macroscopic quantum superposition (MQS) states, and between photon-MQS and
atom-MQS states.Comment: 9 pages, 1 figur
Structure, stability and stress properties of amorphous and nanostructured carbon films
Structural and mechanical properties of amorphous and nanocomposite carbon
are investigated using tight-binding molecular dynamics and Monte Carlo
simulations. In the case of amorphous carbon, we show that the variation of
sp^3 fraction as a function of density is linear over the whole range of
possible densities, and that the bulk moduli follow closely the power-law
variation suggested by Thorpe. We also review earlier work pertained to the
intrinsic stress state of tetrahedral amorphous carbon. In the case of
nanocomposites, we show that the diamond inclusions are stable only in dense
amorphous tetrahedral matrices. Their hardness is considerably higher than that
of pure amorphous carbon films. Fully relaxed diamond nanocomposites possess
zero average intrinsic stress.Comment: 10 pages, 6 figure
Uncertainty Principle for Control of Ensembles of Oscillators Driven by Common Noise
We discuss control techniques for noisy self-sustained oscillators with a
focus on reliability, stability of the response to noisy driving, and
oscillation coherence understood in the sense of constancy of oscillation
frequency. For any kind of linear feedback control--single and multiple delay
feedback, linear frequency filter, etc.--the phase diffusion constant,
quantifying coherence, and the Lyapunov exponent, quantifying reliability, can
be efficiently controlled but their ratio remains constant. Thus, an
"uncertainty principle" can be formulated: the loss of reliability occurs when
coherence is enhanced and, vice versa, coherence is weakened when reliability
is enhanced. Treatment of this principle for ensembles of oscillators
synchronized by common noise or global coupling reveals a substantial
difference between the cases of slightly non-identical oscillators and
identical ones with intrinsic noise.Comment: 10 pages, 5 figure
- …