Energetics and kinetics of Li intercalation in irradiated graphene scaffolds

In the present study we investigate the irradiation-defects hybridized graphene scaffold as one potential building material for the anode of Li-ion batteries. Designating the Wigner V22 defect as a representative, we illustrate the interplay of Li atoms with the irradiation-defects in graphene scaffolds. We examine the adsorption energetics and diffusion kinetics of Li in the vicinity of a Wigner V22 defect using density functional theory calculations. The equilibrium Li adsorption sites at the defect are identified and shown to be energetically preferable to the adsorption sites on pristine (bilayer) graphene. Meanwhile the minimum energy paths and corresponding energy barriers for Li migration at the defect are determined and computed. We find that while the defect is shown to exhibit certain trapping effects on Li motions on the graphene surface, it appears to facilitate the interlayer Li diffusion and enhance the charge capacity within its vicinity because of the reduced interlayer spacing and characteristic symmetry associated with the defect. Our results provide critical assessment for the application of irradiated graphene scaffolds in Li-ion batteries.Comment: 23 pages, 5 figure

Nonlinear robust controller design for multi-robot systems with unknown payloads

This work is concerned with the control problem of a multi-robot system handling a payload with unknown mass properties. Force constraints at the grasp points are considered. Robust control schemes are proposed that cope with the model uncertainty and achieve asymptotic path tracking. To deal with the force constraints, a strategy for optimally sharing the task is suggested. This strategy basically consists of two steps. The first detects the robots that need help and the second arranges that help. It is shown that the overall system is not only robust to uncertain payload parameters, but also satisfies the force constraints

Gravitational Effects on the Neutrino Oscillation

The propagation of neutrinos in a gravitational field is studied. A method of calculating a covariant quantum-mechanical phase in a curved space-time is presented. The result is used to calculate gravitational effects on the neutrino oscillation in the presence of a gravitational field. We restrict our discussion to the case of the Schwartzschild metric. Specifically, the cases of the radial propagation and the non-radial propagation are considered. A possible application to gravitational lensing of neutrinos is also suggested.Comment: 15 pages, RevTex, No figures. Minor modifications and some typos correcte

Effect of excited states and applied magnetic fields on the measured hole mobility in an organic semiconductor

Copyright 2010 by the American Physical Society. Article is available at

Charmonium mass splittings at the physical point

We present results from an ongoing study of mass splittings of the lowest lying states in the charmonium system. We use clover valence charm quarks in the Fermilab interpretation, an improved staggered (asqtad) action for sea quarks, and the one-loop, tadpole-improved gauge action for gluons. This study includes five lattice spacings, 0.15, 0.12, 0.09, 0.06, and 0.045 fm, with two sets of degenerate up- and down-quark masses for most spacings. We use an enlarged set of interpolation operators and a variational analysis that permits study of various low-lying excited states. The masses of the sea quarks and charm valence quark are adjusted to their physical values. This large set of gauge configurations allows us to extrapolate results to the continuum physical point and test the methodology.Comment: 7 pp, 6 figs, Lattice 201

Low lying charmonium states at the physical point

We present results for the mass splittings of low-lying charmonium states from a calculation with Wilson clover valence quarks with the Fermilab interpretation on an asqtad sea. We use five lattice spacings and two values of the light sea quark mass to extrapolate our results to the physical point. Sources of systematic uncertainty in our calculation are discussed and we compare our results for the 1S hyperfine splitting, the 1P-1S splitting and the P-wave spin orbit and tensor splittings to experiment.Comment: For the Fermilab Lattice and MILC Collaborations; 7 pages, 6 figures; Contribution to the 32nd International Symposium on Lattice Field Theory, 23-28 June, 2014, Columbia University New York, N