220 research outputs found
The initial investigation of the design and energy sharing algorithm using two-ways communication mechanism for Swarm Robotic System
Swarm Robotics (SR) is a new field of study that is mainly concerned with con-trolling and coordinating a multiple small robots. SR has several key characteristics that make it a preferable choice for a variety of tasks. The characteristics include lower cost, easiness to program, scalability of tasks and fault tolerance. The robustness from fault tolerance in SR comes from having a group of small robots working on the same task and thus enabling them to tolerate the loss of a few members of the swarm as the other members can still continue with the mission. However it has shown that continuous failure of members of a swarm such as those due to low energy have a significant impact on the overall performance of the swarm. In addition, the possibility of completion of the task is also dependent on the percentage of the swarm falling out of the group due insufficient energy. Some of the work that has been proposed by the researchers is by adding a charging station or a removable charger. However, these techniques have their own limitations. Therefore a work on having the robot(s) to charger themselves without the help of the charging station or a removable charger is proposed. But the work is only proven successful in simulation without a proper design and testing in a real robots scenario. This paper is therefore will describe our initial investigation on the design and the implementation of energy sharing algorithm using two-ways robotic swarm communication mechanism with NRF2401
Time-resolved broadband analysis of slow-light propagation and superluminal transmission of electromagnetic waves in three-dimensional photonic crystals
A time-resolved analysis of the amplitude and phase of THz pulses propagating
through three-dimensional photonic crystals is presented. Single-cycle pulses
of THz radiation allow measurements over a wide frequency range, spanning more
than an octave below, at and above the bandgap of strongly dispersive photonic
crystals. Transmission data provide evidence for slow group velocities at the
photonic band edges and for superluminal transmission at frequencies in the
gap. Our experimental results are in good agreement with
finite-difference-time-domain simulations.Comment: 7 pages, 11 figure
Plasmonically enhanced hot electron based photovoltaic device
Cataloged from PDF version of article.Hot electron photovoltaics is emerging as a candidate for low cost and ultra thin solar cells. Plasmonic means can be utilized to significantly boost device efficiency. We separately form the tunneling metal-insulator-metal (MIM) junction for electron collection and the plasmon exciting MIM structure on top of each other, which provides high flexibility in plasmonic design and tunneling MIM design separately. We demonstrate close to one order of magnitude enhancement in the short circuit current at the resonance wavelengths. (C) 2013 Optical Society of Americ
Perfect antireflection via negative refraction
We suggest a geometrical framework to discuss the action of slabs of
negatively refracting materials. We show that these slabs generate the same
orbits as normal materials, but traced out in opposite directions. This
property allows us to confirm that the action of any lossless multilayer can be
optically cancelled by putting it together with the multilayer constructed as
the inverted mirror image, with and reversed in sign.Comment: Some typos corrected. New references addes. Accepted for publication
in Physics Letters
Anisotropy and oblique total transmission at a planar negative-index interface
We show that a class of negative index (n) materials has interesting
anisotropic optical properties, manifest in the effective refraction index that
can be positive, negative, or purely imaginary under different incidence
conditions. With dispersion taken into account, reflection at a planar
negative-index interface exhibits frequency selective total oblique
transmission that is distinct from the Brewster effect.
Finite-difference-time-domain simulation of realistic negative-n structures
confirms the analytic results based on effective indices.Comment: to appear in Phys. Rev.
The concentration parameter thermal microstresses as the thermophysical characteristics of two-phase materials
The increase in the emission of greenhouse gases (GHG) is one of the most important problems in the world. Decreasing GHG emissions will be a big challenge in the future. The transportation sector uses a significant part of petroleum production in the world, and this leads to an increase in the emission of GHG. The result of this issue is that the population of the world befouls the environment by the transportation system automatically. Electric Vehicles (EV) have the potential to solve a big part of GHG emission and energy efficiency issues such as the stability and reliability of energy. Therefore, the EV and grid relation is limited to the Vehicle-to-Grid (V2G) or Grid-to-Vehicle (G2V) function. Consequently, the grid has temporary energy storage in EVs’ batteries and electricity in exchange for fossil energy in vehicles. The energy actors and their research teams have determined some targets for 2050; hence, they hope to decrease the world temperature by 6 °C, or at least by 2 °C in the normal condition. Fulfilment of these scenarios requires suitable grid infrastructure, but in most countries, the grid does not have a suitable background to apply in those scenarios. In this paper, some problems regarding energy scenarios, energy storage systems, grid infrastructure and communication systems in the supply and demand side of the grid are reviewed
Bose-Einstein condensation in a two-dimensional, trapped,interacting gas
We study Bose-Einstein condensation phenomenon in a two-dimensional (2D)
system of bosons subjected to an harmonic oscillator type confining potential.
The interaction among the 2D bosons is described by a delta-function in
configuration space. Solving the Gross-Pitaevskii equation within the two-fluid
model we calculate the condensate fraction, ground state energy, and specific
heat of the system. Our results indicate that interacting bosons have similar
behavior to those of an ideal system for weak interactions.Comment: LaTeX, 4 pages, 4 figures, uses grafik.sty (included), to be
published in Phys. Rev. A, tentatively scheduled for 1 October 1998 (Volume
58, Number 4
Toroidal optical dipole traps for atomic Bose-Einstein condensates using Laguerre-Gaussian beams
We theoretically investigate the use of red-detuned Laguerre-Gaussian (LG)
laser beams of varying azimuthal mode index for producing toroidal optical
dipole traps in two-dimensional atomic Bose-Einstein condensates. Higher-order
LG beams provide deeper potential wells and tighter confinement for a fixed
toroid radius and laser power. Numerical simulations of the loading of the
toroidal trap from a variety of initial conditions is also given.Comment: 12 pages, 5 figures, submitted to Phys. Rev.
Collective excitations of a two-dimensional interacting Bose gas in anti-trap and linear external potentials
We present a method of finding approximate analytical solutions for the
spectra and eigenvectors of collective modes in a two-dimensional system of
interacting bosons subjected to a linear external potential or the potential of
a special form , where is the chemical
potential. The eigenvalue problem is solved analytically for an artificial
model allowing the unbounded density of the particles. The spectra of
collective modes are calculated numerically for the stripe, the rare density
valley and the edge geometry and compared with the analytical results. It is
shown that the energies of the modes localized at the rare density region and
at the edge are well approximated by the analytical expressions. We discuss
Bose-Einstein condensation (BEC) in the systems under investigations at and find that in case of a finite number of the particles the regime of BEC
can be realized, whereas the condensate disappears in the thermodynamic limit.Comment: 10 pages, 2 figures include
Bose-Einstein condensation in a one-dimensional interacting system due to power-law trapping potentials
We examine the possibility of Bose-Einstein condensation in one-dimensional
interacting Bose gas subjected to confining potentials of the form , in which , by solving the
Gross-Pitaevskii equation within the semi-classical two-fluid model. The
condensate fraction, chemical potential, ground state energy, and specific heat
of the system are calculated for various values of interaction strengths. Our
results show that a significant fraction of the particles is in the lowest
energy state for finite number of particles at low temperature indicating a
phase transition for weakly interacting systems.Comment: LaTeX, 6 pages, 8 figures, uses grafik.sty (included), to be
published in Phys. Rev.
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