43,359 research outputs found
Full electrical control of Charge and Spin conductance through Interferometry of Edge States in Topological Insulators
We investigate electron interferometry of edge states in Topological
Insulators. We show that, when inter-boundary coupling is induced at two
quantum point contacts of a four terminal setup, both Fabry-P\'erot-like and
Aharonov-Bohm-like loop processes arise. These underlying interference effects
lead to a full electrically controllable system, where the magnitude of charge
and spin linear conductances can be tuned by gate voltages, without applying
magnetic fields. In particular we find that, under appropriate conditions,
inter-boundary coupling can lead to negative values of the conductance.
Furthermore, the setup also allows to selectively generate pure charge or pure
spin currents, by choosing the voltage bias configuration.Comment: 12 pages, 5 figures (expanded discussion section, corrected typos
Carbon Emission Trading Scheme and the Aviation Sector: An experimental analysis on allocation of allowances
The European Union has proposed a Directive to include aviation activities in the Emission Trading Scheme (ETS) in 2012. The allowance allocation method which will be put in place is relatively easy to implement with low administration cost. However, careful scrutiny suggests that the allocation method does not favor airlines with high energy efficiency. This study proposes an alternative allowance allocation method which is fairer in that it rewards energy efficient airlines. Further, the new method is easy to implement with low administrative cost. The Cournot model serves as the theoretical foundation upon which the experiments are designed to simulate the aviation industry under the ETS. The equilibrium is calculated for each allowance allocation method. Results from experiments suggest consistency with theoretical outcomes.
Characteristics of homogeneous charge compression ignition (HCCI) combustion and emissions of n-heptane
This paper reports the outcome from a systematic investigation carried out on HCCI (Homogeneous Charge Compression Ignition) combustion of a diesel type fuel. The n heptane was chosen in this study to study the premixed diesel HCCI combustion characteristics with port fuel injection. Measurements were carried out in a single-cylinder, 4-stroke and variable compression ratio engine. Premixed n-heptane/air/EGR mixture was introduced into the cylinder by a port fuel injector and an external EGR system. The operating regions with regard to Air/Fuel ratio and EGR rate were established for different compression ratios and intake temperatures. The effects of compression ratios, intake temperatures, Air/Fuel ratios and EGR rates on knock limit, auto-ignition timing, combustion rate, IMEP, and engine-out emissions, such as NOx, CO, and unburned HC, were analysed. The results have shown HCCI combustion of n-heptane could be implemented without intake charge heating with a typical diesel engine compression ratio. The attainable HCCI operating region was mainly limited by the knock limit, misfir, and low IMEP respectively. Higher intake temperature or compression ratio could extend the misfire limit of the HCCI operation at low load but they would reduce the maximum IMEP limit at higher load conditions. Compared with conventional diesel combustion, HCCI combustion lead to extremely low NOx emissions ( less than 5 ppm) and smoke free exhaust. But HCCI diesel combustion was found to produce higher HC and CO emissions. An increase in intake temperature or compression ratio helped to reduce HC and CO emissions.
A discussion of the scaling effect in numerical simulation of the extrusion process
The main objective of the work of this paper is to study the possibility of using a small scale geometrical model in the numerical simulation of aluminium extrusion. The advantages and shortcomings of the application of the
geometrically similar model in FEM simulation are discussed. Thermal – mechanical and metallurgical combined
simulations are performed within two tests using geometrically similar models and assessment is made in terms of mechanical and material properties. It was found that small scale simulation could not reproduce most of the
important forming parameters of the original process, although it could help to bring about significant savings in
computation time
Erratum : Squeezing and entanglement delay using slow light
An inconsistency was found in the equations used to calculate the variance of
the quadrature fluctuations of a field propagating through a medium
demonstrating electromagnetically induced transparency (EIT). The decoherence
term used in our original paper introduces inconsistency under weak probe
approximation. In this erratum we give the Bloch equations with the correct
dephasing terms. The conclusions of the original paper remain the same. Both
entanglement and squeezing can be delayed and preserved using EIT without
adding noise when the decoherence rate is small.Comment: 1 page, no figur
Effects of using different plasmonic metals in metal/dielectric/metal subwavelength waveguides on guided dispersion characteristics
The fundamental guided dispersion characteristics of guided light in a
subwavelength dielectric slit channel embedded by two different plasmonic
metals are investigated when varying the gap width. As a result, an overall and
salient picture of the guided dispersion characteristics is obtained over a
wide spectrum range below and above the plasma frequencies of the two different
plasmonic metals, which is important preliminary information for analyzing this
type of subwavelength waveguide. In particular, the effects of using two
different metals on the guided mode dispersions are emphasized in comparison
with the effects of using the same plasmonic metal cladding.Comment: 13 pages, 3 figures, typos corrected, reference added, text modifie
Three-dimensional single gyroid photonic crystals with a mid-infrared bandgap
A gyroid structure is a distinct morphology that is triply periodic and
consists of minimal isosurfaces containing no straight lines. We have designed
and synthesized amorphous silicon (a-Si) mid-infrared gyroid photonic crystals
that exhibit a complete bandgap in infrared spectroscopy measurements. Photonic
crystals were synthesized by deposition of a-Si/Al2O3 coatings onto a
sacrificial polymer scaffold defined by two-photon lithography. We observed a
100% reflectance at 7.5 \mum for single gyroids with a unit cell size of 4.5
\mum, in agreement with the photonic bandgap position predicted from full-wave
electromagnetic simulations, whereas the observed reflection peak shifted to 8
um for a 5.5 \mum unit cell size. This approach represents a
simulation-fabrication-characterization platform to realize three-dimensional
gyroid photonic crystals with well-defined dimensions in real space and
tailored properties in momentum space
Automated Mixed Traffic Vehicle (AMTV) technology and safety study
Technology and safety related to the implementation of an Automated Mixed Traffic Vehicle (AMTV) system are discussed. System concepts and technology status were reviewed and areas where further development is needed are identified. Failure and hazard modes were also analyzed and methods for prevention were suggested. The results presented are intended as a guide for further efforts in AMTV system design and technology development for both near term and long term applications. The AMTV systems discussed include a low speed system, and a hybrid system consisting of low speed sections and high speed sections operating in a semi-guideway. The safety analysis identified hazards that may arise in a properly functioning AMTV system, as well as hardware failure modes. Safety related failure modes were emphasized. A risk assessment was performed in order to create a priority order and significant hazards and failure modes were summarized. Corrective measures were proposed for each hazard
Programming DNA Tube Circumferences
Synthesizing molecular tubes with monodisperse, programmable circumferences is an important goal shared by nanotechnology, materials science, and supermolecular chemistry. We program molecular tube circumferences by specifying the complementarity relationships between modular domains in a 42-base single-stranded DNA motif. Single-step annealing results in the self-assembly of long tubes displaying monodisperse circumferences of 4, 5, 6, 7, 8, 10, or 20 DNA helices
Hawking Fluxes, Back reaction and Covariant Anomalies
Starting from the chiral covariant effective action approach of Banerjee and
Kulkarni [Phys. Lett. B 659, 827(2008)], we provide a derivation of the Hawking
radiation from a charged black hole in the presence of gravitational back
reaction. The modified expressions for charge and energy flux, due to effect of
one loop back reaction are obtained.Comment: 6 pages, no figures, minor changes and references added, to appear in
Classical and Quantum Gravit
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