1,906 research outputs found
The azimuthal asymmetry in single longitudinally polarized Drell-Yan process
We study the azimuthal asymmetry in the Drell-Yan
process, when the nucleon is longitudinally polarized. The asymmetry is
contributed by the combination of the Boer-Mulders function and the
longitudinal transversity distribution function. We consider the Drell-Yan
processes by beams colliding on the proton and deuteron targets,
respectively. We calculate the azimuthal asymmetries in these
processes using the Boer-Mulders function and the longitudinal transversity
from spectator models. We show that the study on single polarized
Drell-Yan processes can not only give the information on the new 3-dimensional
parton distribution functions in momentum space, but also shed light on the
chiral-odd structure of the longitudinally polarized nucleon.Comment: 7 pages, 3 figures. Final version for publication in PR
Nanoscale capacitance: a classical charge-dipole approximation
Modeling nanoscale capacitance presents particular challenge because of
dynamic contribution from electrodes, which can usually be neglected in
modeling macroscopic capacitance and nanoscale conductance. We present a model
to calculate capacitances of nano-gap configurations and define effective
capacitances of nanoscale structures. The model is implemented by using a
classical atomic charge-dipole approximation and applied to calculate
capacitance of a carbon nanotube nano-gap and effective capacitance of a
buckyball inside the nano-gap. Our results show that capacitance of the carbon
nanotube nano-gap increases with length of electrodes which demonstrates the
important roles played by the electrodes in dynamic properties of nanoscale
circuits.Comment: 11 pages, 6 figure
Effects of Finite Deformed Length in Carbon Nanotubes
The effect of finite deformed length is demonstrated by squashing an armchair
(10,10) single-walled carbon nanotube with two finite tips. Only when the
deformed length is long enough, an effectual metal-semiconductor-metal
heterojunction can be formed in the metallic tube. The effect of finite
deformed length is explained by the quantum tunnelling effect. Furthermore,
some conceptual designs of nanoscale devices are proposed from the
metal-semiconductor-metal heterojunction.Comment: 4 pages, 4 figure
Metal-to-semiconductor transition in squashed armchair carbon nanotubes
Journal ArticleWe investigate electronic transport properties of the squashed armchair carbon nanotubes, using tight-binding molecular dynamics and the Green's function method. We demonstrate a metal-to-semiconductor transition while squashing the nanotubes and a general mechanism for such a transition. It is the distinction of the two sublattices in the nanotube that opens an energy gap near the Fermi energy. We show that the transition has to be achieved by a combined effect of breaking of mirror symmetry and bond formation between the flattened faces in the squashed nanotubes
Structural Trends Interpretation of the Metal-to-Semiconductor Transition in Deformed Carbon Nanotubes
Two mechanisms that drive metal-to-semiconductor transitions in single-walled
carbon nanotubes are theoretically analyzed through a simple tight-binding
model. By considering simple structural trends, the results demonstrate that
metal-to-semiconductor transitions can be induced more readily in metallic
zigzag nanotubes than in armchair nanotubes. Furthermore, it is shown that both
mechanisms have the effect of making the two originally equivalent sublattices
physically distinguishable.Comment: 4 pages, 4 figure
The Effects of the Tractor and Semitrailer Routing Problem on Mitigation of Carbon Dioxide Emissions
The incorporation of CO2 emissions minimization in the vehicle routing problem (VRP) is of critical importance to enterprise practice. Focusing on the tractor and semitrailer routing problem with full truckloads between any two terminals of the network, this paper proposes a mathematical programming model with the objective of minimizing CO2 emissions per ton-kilometer. A simulated annealing (SA) algorithm is given to solve practical-scale problems. To evaluate the performance of the proposed algorithm, a lower bound is developed. Computational experiments on various problems generated randomly and a realistic instance are conducted. The results show that the proposed methods are effective and the algorithm can provide reasonable solutions within an acceptable computational time
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