37,365 research outputs found
Enhanced thermoelectric figure of merit in vertical graphene junctions
In this work, we investigate thermoelectric properties of junctions
consisting of two partially overlapped graphene sheets coupled to each other in
the cross-plane direction. It is shown that because of the weak van-der Waals
interactions between graphene layers, the phonon conductance in these junctions
is strongly reduced, compared to that of single graphene layer structures,
while their electrical performance is weakly affected. By exploiting this
effect, we demonstrate that the thermoelectric figure of merit can reach values
higher than 1 at room temperature in junctions made of gapped graphene
materials, for instance, graphene nanoribbons and graphene nanomeshes. The
dependence of thermoelectric properties on the junction length is also
discussed. This theoretical study hence suggests an efficient way to enhance
thermoelectric efficiency of graphene devices.Comment: 6 pages, 4 figures, submitte
Strong disorder renormalization group on fractal lattices: Heisenberg models and magnetoresistive effects in tight binding models
We use a numerical implementation of the strong disorder renormalization
group (RG) method to study the low-energy fixed points of random Heisenberg and
tight-binding models on different types of fractal lattices. For the Heisenberg
model new types of infinite disorder and strong disorder fixed points are
found. For the tight-binding model we add an orbital magnetic field and use
both diagonal and off-diagonal disorder. For this model besides the gap spectra
we study also the fraction of frozen sites, the correlation function, the
persistent current and the two-terminal current. The lattices with an even
number of sites around each elementary plaquette show a dominant
periodicity. The lattices with an odd number of sites around each elementary
plaquette show a dominant periodicity at vanishing diagonal
disorder, with a positive weak localization-like magnetoconductance at infinite
disorder fixed points. The magnetoconductance with both diagonal and
off-diagonal disorder depends on the symmetry of the distribution of on-site
energies.Comment: 19 pages, 20 figure
Seafood Import Demand in the Caribbean Region
Cointegration analysis and an Error Correction Model are used to estimate aggregate seafood import demand functions for selected Caribbean countries. The results show that seafood import demand is price elastic. Exchange rate has a negative effect on seafood import quantity. Income and tourist arrivals have positive impacts on seafood imports. Seafood import negatively affects domestic fishery production. Tariff and production support policies reduce seafood imports, and enhance domestic production. Both policies increase producer surplus, but a tariff reduces consumer surplus, and a production expansion policy increases consumer surplus. A production expansion subsidy is a more appropriate policy instrument than a tariff for small open economies, like the Caribbean States, to increase domestic production and generate net economic surplus.Seafood, import demand, cointegration, economic surplus, Agricultural and Food Policy, International Relations/Trade, Q17, Q22, C32,
Dissipation in a superconducting artificial atom due to a single non-equilibrium quasiparticle
We study a superconducting artificial atom which is represented by a single
Josephson junction or a Josephson junction chain, capacitively coupled to a
coherently driven transmission line, and which contains exactly one residual
quasiparticle (or up to one quasiparticle per island in a chain). We study the
dissipation in the atom induced by the quasiparticle tunneling, taking into
account the quasiparticle heating by the drive. We calculate the transmission
coefficient in the transmission line for drive frequencies near resonance and
show that, when the artificial atom spectrum is nearly harmonic, the intrinsic
quality factor of the resonance increases with the drive power. This
counterintuitive behavior is due to the energy dependence of the quasiparticle
density of states
Geometrically nonlinear isogeometric analysis of laminated composite plates based on higher-order shear deformation theory
In this paper, we present an effectively numerical approach based on
isogeometric analysis (IGA) and higher-order shear deformation theory (HSDT)
for geometrically nonlinear analysis of laminated composite plates. The HSDT
allows us to approximate displacement field that ensures by itself the
realistic shear strain energy part without shear correction factors. IGA
utilizing basis functions namely B-splines or non-uniform rational B-splines
(NURBS) enables to satisfy easily the stringent continuity requirement of the
HSDT model without any additional variables. The nonlinearity of the plates is
formed in the total Lagrange approach based on the von-Karman strain
assumptions. Numerous numerical validations for the isotropic, orthotropic,
cross-ply and angle-ply laminated plates are provided to demonstrate the
effectiveness of the proposed method
Model for Anisotropic Directed Percolation
We propose a simulation model to study the properties of directed percolation
in two-dimensional (2D) anisotropic random media. The degree of anisotropy in
the model is given by the ratio between the axes of a semi-ellipse
enclosing the bonds that promote percolation in one direction. At percolation,
this simple model shows that the average number of bonds per site in 2D is an
invariant equal to 2.8 independently of . This result suggests that
Sinai's theorem proposed originally for isotropic percolation is also valid for
anisotropic directed percolation problems. The new invariant also yields a
constant fractal dimension for all , which is the same
value found in isotropic directed percolation (i.e., ).Comment: RevTeX, 9 pages, 3 figures. To appear in Phys.Rev.
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