5,709 research outputs found
Probability distribution of residence times of grains in models of ricepiles
We study the probability distribution of residence time of a grain at a site,
and its total residence time inside a pile, in different ricepile models. The
tails of these distributions are dominated by the grains that get deeply buried
in the pile. We show that, for a pile of size , the probabilities that the
residence time at a site or the total residence time is greater than , both
decay as for where
is an exponent , and values of and in the two
cases are different. In the Oslo ricepile model we find that the probability
that the residence time at a site being greater than or equal to ,
is a non-monotonic function of for a fixed and does not obey simple
scaling. For model in dimensions, we show that the probability of minimum
slope configuration in the steady state, for large , varies as where is a constant, and hence .Comment: 13 pages, 23 figures, Submitted to Phys. Rev.
Fast trimers in one-dimensional extended Fermi-Hubbard model
We consider a one-dimensional two component extended Fermi-Hubbard model with
nearest neighbor interactions and mass imbalance between the two species. We
study the stability of trimers, various observables for detecting them, and
expansion dynamics. We generalize the definition of the trimer gap to include
the formation of different types of clusters originating from nearest neighbor
interactions. Expansion dynamics reveal rapidly propagating trimers, with
speeds exceeding doublon propagation in strongly interacting regime. We present
a simple model for understanding this unique feature of the movement of the
trimers, and we discuss the potential for experimental realization.Comment: 10 pages, 10 figure
Do rules control power? GATT articles and arrangements in the Uruguay Round
Many complain and offer evidence that in recent years the GATT system has become more power-oriented, less stable, and less equitable. A concern to reverse this drift was one of the motives that brought the international community to agree to undertake the Uruguay Round. Rules control power, assumed the signers of the Punte del Este declaration, therefore elaborating and extending GATT rules would move the international community toward a fairer, more stable international trading system. Finger and Dhar contend that the opposite is true. Particularly in the 1980s, the elaboration and application of GATT rules has been an exercise in the application of economic and political power, not in its control. GATT rules, in theory, are there to limit national trade restrictions. Finger and Dhar contend that in fact things work the other way around: national practice comes first, and determines what the GATT rules mean. GATT's rules do not put limits on national practices, but provide international santion for these practices. Such rules are not part of the thereforelution but are part of the problem. Theirs is a situation-specific argument, say Finger and Dhar, not a generic one. Their target is not"rules", nor is it"GATT". Rather, it is the GATT rules.Rules of Origin,TF054105-DONOR FUNDED OPERATION ADMINISTRATION FEE INCOME AND EXPENSE ACCOUNT,Common Carriers Industry,Transport and Trade Logistics,Trade Policy
Effect of phonon-phonon interactions on localization
We study the heat current J in a classical one-dimensional disordered chain
with on-site pinning and with ends connected to stochastic thermal reservoirs
at different temperatures. In the absence of anharmonicity all modes are
localized and there is a gap in the spectrum. Consequently J decays
exponentially with system size N. Using simulations we find that even a small
amount of anharmonicity leads to a J~1/N dependence, implying diffusive
transport of energy.Comment: 4 pages, 2 figures, Published versio
Heat conduction in disordered harmonic lattices with energy conserving noise
We study heat conduction in a harmonic crystal whose bulk dynamics is
supplemented by random reversals (flips) of the velocity of each particle at a
rate . The system is maintained in a nonequilibrium stationary
state(NESS) by contacts with Langevin reservoirs at different temperatures. We
show that the one-body and pair correlations in this system are the same (after
an appropriate mapping of parameters) as those obtained for a model with
self-consistent reservoirs. This is true both for the case of equal and
random(quenched) masses. While the heat conductivity in the NESS of the ordered
system is known explicitly, much less is known about the random mass case. Here
we investigate the random system, with velocity flips. We improve the bounds on
the Green-Kubo conductivity obtained by C.Bernardin. The conductivity of the 1D
system is then studied both numerically and analytically. This sheds some light
on the effect of noise on the transport properties of systems with localized
states caused by quenched disorder.Comment: 19 pages, 8 figure
Sampling rare fluctuations of height in the Oslo ricepile model
We have studied large deviations of the height of the pile from its mean
value in the Oslo ricepile model. We sampled these very rare events with
probabilities of order by Monte Carlo simulations using importance
sampling. These simulations check our qualitative arguement [Phys. Rev. E, {\bf
73}, 021303, 2006] that in steady state of the Oslo ricepile model, the
probability of large negative height fluctuations about
the mean varies as as with
held fixed, and .Comment: 7 pages, 8 figure
Simultaneous Ejection of Six Electrons at a Constant Potential by Hexakis(4-ferrocenylphenyl)benzene
A simple synthesis of a dendritic hexaferrocenyl electron donor (5) is described in which six ferrocene moieties are connected at the vertices of the propeller of the hexaphenylbenzene core. The molecular structure of 5 is confirmed by X-ray crystallography. An electrochemical analysis along with redox titrations (which are tantamount to coulometry) confirmed that it ejects six electrons at a single potential
A new concept for high-cycle-life LEO: Rechargeable MnO2-hydrogen
The nickel-hydrogen secondary battery system, developed in the early 1970s, has become the system of choice for geostationary earth orbit (GEO) applications. However, for low earth orbit (LEO) satellites with long expected lifetimes the nickel positive limits performance. This requires derating of the cell to achieve very long cycle life. A new system, rechargeable MnO2-Hydrogen, which does not require derating, is described here. For LEO applications, it promises to have longer cycle life, high rate capability, a higher effective energy density, and much lower self-discharge behavior than those of the nickel-hydrogen system
- …