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Jin-Luen Lee Rainer Bleck Alexander E. MacDonald 《Journal of computational physics》2010,229(24):9284-9298
A multistep flux-corrected transport (MFCT) scheme is developed to achieve conservative and monotonic tracer transports for multistep dynamical cores. MFCT extends Zalesak two-time level scheme to any multistep time-differencing schemes by including multiple high-order fluxes in the antidiffusive flux, while computing the two-time level low-order monotone solution. The multistep time-differencing scheme used in this study is the third-order Adams–Bashforth (AB3) scheme implemented in a finite-volume icosahedral shallow-water model. The accuracy of AB3 MFCT is quantified by the shape-preserving advection experiments in non-divergent flow, as well as a cosine bell whose shape changes during advection in shear flow. AB3 MFCT has been shown to be insensitive to time step size. This make AB3 MFCT an attractive transport scheme for explicit high resolution model applications with small time step. MFCT is tested in shallow-water model simulations to demonstrate that the use of MFCT maintains positive-definite tracer transport, while at the same time conserving both fluid mass and tracer mass within round-off errors in the AB3 dynamic core. 相似文献
75.
Quantum Hall ferromagnetism in graphene 总被引:4,自引:0,他引:4
Graphene is a two-dimensional carbon material with a honeycomb lattice and Dirac-like low-energy excitations. When Zeeman and spin-orbit interactions are neglected, its Landau levels are fourfold degenerate, explaining the 4e2/h separation between quantized Hall conductivity values seen in recent experiments. In this Letter we derive a criterion for the occurrence of interaction-driven quantum Hall effects near intermediate integer values of e2/h due to charge gaps in broken symmetry states. 相似文献
76.
We report on a theoretical study of spin-polarized quantum transport through a Ni-bezenedithiol(BDT)-Ni molecular magnetic tunnel junction (MTJ). Our study is based on carrying out density functional theory within the Keldysh nonequilibrium Green's function formalism, so that microscopic details of the molecular MTJ are taken into account from first principles. A magnetoresistance ratio of approximately 27% is found for the Ni-BDT-Ni MTJ which declines toward zero as bias voltage is increased. The spin currents are nonlinear functions of bias voltage, even changing sign at certain voltages due to specific features of the coupling between molecular states and magnetic leads. 相似文献
77.
R.J. MacDonald 《物理学进展》2013,62(80):457-524
Considerable interest has developed in the last decade in the study of atomic collisions in solids, particularly single crystal solids. This has been heightened by the observation of channelling and the interest in industrial aspects of ion implantation. In the following article, we present an up-to-date account of the work being done on the particles ejected from a single crystal, following ion bombardment. These particles include sputtered atoms and ions, scattered atoms and ions and secondary electrons. An attempt has been made to indicate the similarities and differences, particularly between the energy and angular distributions of these ejected particles. The major link involving the dependence of these distributions of all particles on crystallography is stressed. 相似文献
78.
We analyze the influence of current-induced torques on the magnetization configuration of a ferromagnet in a circuit containing a compensated antiferromagnet. We argue that these torques are generically nonzero and determine their form by considering spin-dependent scattering at a compensated antiferromagnetic interface. Because of symmetry dictated differences in the form of the current-induced torque, the phase diagram which expresses the dependence of the ferromagnetic configuration on the current and external magnetic field differs qualitatively from its ferromagnet-only counterpart. 相似文献
79.
80.
Sancheeta Kolay Kallol K. Ghosh Amy MacDonald Jonathan Moulins Rama M. Palepu 《Journal of solution chemistry》2008,37(1):59-72
The thermodynamics of micellization and other micellar properties of alkyl- (C10-, C12-, C14- and C16-) triphenylphosphonium bromides in water + ethylene glycol (EG) (0 to 30% v/v) mixtures over a temperature range of 298 to
318 K and cetyltriphenylphosphonium bromide in water + diethylene glycol (DEG) mixtures (0 to 30% v/v) at 298 K have been
studied conductometrically. In all cases, an increase in the percentage of co-solvent results in an increase in the cmc values.
On the basis of these results, the thermodynamic parameters, the Gibbs energy (ΔG
mo), enthalpy (ΔH
mo) and entropy (ΔS
mo) of micellization have been evaluated. In addition to the conductivity measurements, kinetic experiments have also been done
to determine the dependence of observed rate constant for the nucleophilic substitution reaction of p-nitrophenyl acetate and benzohydroxamate ions in the presence of the surfactant cetyltriphenylphosphonium bromide with a
varying concentration of EG and DEG ranging from 0 to 50% v/v at pH=7.9 and 300 K. All of the reactions followed pseudo-first-order
kinetics. An increase in the surfactant concentration results in an increase in the reaction rate and for a given surfactant
concentration, the rate constant decreases as the concentration of co-solvent in the mixture increases. The kinetic micellar
effects have been explained by using the pseudophase model. The thermodynamic and structural changes originating from the
presence of solvents control the micellar kinetic effects. 相似文献