798 research outputs found
Spin-spin interaction in the bulk of topological insulators
We apply mean-field theory and Hirsch-Fye quantum Monte Carlo method to study
the spin-spin interaction in the bulk of three-dimensional topological
insulators. We find that the spin-spin interaction has three different
components: the longitudinal, the transverse and the transverse
Dzyaloshinskii-Moriya-like terms. When the Fermi energy is located in the bulk
gap of topological insulators, the spin-spin interaction decays exponentially
due to Bloembergen-Rowland interaction. The longitudinal correlation is
antiferromagnetic and the transverse correlations are ferromagnetic. When the
chemical potential is in the conduction or valence band, the spin-spin
interaction follows power law decay, and isotropic ferromagnetic interaction
dominates in short separation limit.Comment: 9 pages, 10 figure
Measuring the phonon-assisted spectral function by using a non-quilibrium three-terminal single-molecular device
The electron transport through a three-terminal single-molecular transistor
(SMT) is theoretically studied. We find that the differential conductance of
the third and weakly coupled terminal versus its voltage matches well with the
spectral function versus the energy when certain conditions are met.
Particularly, this excellent matching is maintained even for complicated
structure of the phonon-assisted side peaks. Thus, this device offers an
experimental approach to explore the shape of the phonon-assisted spectral
function in detail. In addition we discuss the conditions of a perfect
matching. The results show that at low temperatures the matching survives
regardless of the bias and the energy levels of the SMT. However, at high
temperatures, the matching is destroyed.Comment: 9 pages, 5 figure
The Pairing of Spin-orbit Coupled Fermi Gas in Optical Lattice
We investigate Rashba spin-orbit coupled Fermi gases in square optical
lattice by using the determinant quantum Monte Carlo (DQMC) simulations which
is free of the sign-problem. We show that the Berezinskii-Kosterlitz-Thoules
phase transition temperature is firstly enhanced and then suppressed by
spin-orbit coupling in the strong attraction region. In the intermediate
attraction region, spin-orbit coupling always suppresses the transition
temperature. We also show that the spin susceptibility becomes anisotropic and
retains finite values at zero temperature.Comment: 10 pages, 9 figure
A Natural Hand Gesture System for People with Brachial Plexus Injuries
This paper focuses on a design case study of a natural hand gesture system for users with intact motion control of the metacarpophalangeal joint and thumb basal joint of the hand after brachial plexus injuries. The lexicon of hand gestures had eight entries and was demonstrated to be natural and ergonomic with the limited hand motions. A cooperative multi-cue system was proposed for the key hand posture recognition of the proposed hand gestures. We utilized the designed system into a remote smart car control and electric wheelchair control. Experimental a results demonstrated the robustness and potential feasibility of the system in human-computer interaction for the proposed users
A Dual-Fluorescent Composite of Graphene Oxide and Poly(3-Hexylthiophene) Enables the Ratiometric Detection of Amines
A composite prepared by grafting a conjugated polymer, poly(3-hexylthiophene) (P3HT), to the surface of graphene oxide was shown to result in a dual-fluorescent material with tunable photoluminescent properties. Capitalizing on these unique features, a new class of graphene-based sensors that enables the ratiometric fluorescence detection of amine-based pollutants was developed. Moreover, through a detailed spectroscopic study, the origin of the optical properties of the aforementioned composite was studied and was found to be due to electronic decoupling of the conjugated polymer from the GO. The methodology described herein effectively overcomes a long-standing challenge that has prevented graphene based composites from finding utility in sensing and related applications.Meng, Dongli, Shaojun Yang, Dianming Sun, Yi Zeng, Jinhua Sun, Yi Li, Shouke Yan, Yong Huang, Christopher W. Bielawski, and Jianxin Geng. "A dual-fluorescent composite of graphene oxide and poly (3-hexylthiophene) enables the ratiometric detection of amines." Chemical Science 5, no. 8 (Apr., 2014): 3130-3134.Chemistr
The Influences of Key Factors on the Consequences Following the Natural Gas Leakage from Pipeline
AbstractThe effects of the environmental dispersion (i.e. atmospheric stability, wind speed, temperature, humidity and ground roughness) and source release factors (i.e. pipeline diameter, length, pressure and release opening area) on the suffocation distance, flammable vapor cloud distance, overpressure distance and thermal radiation distance after the natural gas released from pipeline were evaluated and analyzed. The results show that all the environmental dispersion factors except humidity have an effect on the flammable vapor cloud distance. The more stable atmospheric condition, lower wind speed and smaller ground roughness lead to the longer flammable vapor cloud distance. The atmosphere temperature has a very limited influence on the flammable vapor cloud distance. The higher ambient temperature and larger humidity result in the longer downwind thermal radiation distance, while the atmospheric stability, wind speed and ground roughness nearly does not. All the four source release factors significantly influence the flammable vapor cloud distance and thermal radiation distance, which is due to the different release amount, release rate and initial momentum
Combustion Behaviour of Fe2O3-coated Zirconium Particles in Air
AbstractZirconium metal powder is widely used in aerospace and military as a metal fuel because of its high combustion rate and heat. This powder is used to produce flash powder, fireworks, artillery shells, timing bomb fuses and solid propellant rocket fuel. To comply with the special requirements for aerospace and military applications, zirconium particles are coated with Fe2O3 ferrite magnetite nanoparticles to form a core-shell structure. This process alters the combustion performance of the coated zirconium dust. In this study, the combustion behaviour of Fe2O3-coated zirconium particles in the air is explored. Scanning electron microscopy, X-ray diffraction, thermogravimetry and differential scanning calorimetry are used to examine the micromorphology, phase composition, crystal structure, thermal stability and reactivity of Fe2O3-coated zirconium particles. The combustion behaviour is presented, with the coating layer of Fe2O3-coated zirconium particles generating a replacement reaction with the inner core zirconium. The inner zirconium induced an oxidation-reduction reaction with oxygen and pure Fe was oxidised at high temperatures. The decomposition reaction was due to the residue of Fe2O3 that did not react with zirconium
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