1,583 research outputs found
What Workers Say: Employee Voice in the Anglo-American Workplace
[Excerpt] This book is about employee voice in the workplaces of the highly developed Anglo-American economies: the United States, Canada, the United Kingdom, Ireland, Australia, and New Zealand. These are among the most economically successful countries in the world. Despite being located in three different geographic areas, the Anglo-American countries have a common language and legal tradition, have close economic and political ties, and are linked by flows of people, goods, and capital. Many of the same firms operate in each country. The unions in each pay more attention to their counterparts within the group than to unions in other countries. The Anglo-American brand of capitalism – market oriented and open to competition, with modest welfare sates and income transfer systems – differentiates the countries from countries in the “social dialogue” model of the European Union (although the United Kingdom and Ireland are part of the Union) and from the highly unionized labor system in Scandinavia
The effect of forcing on the spatial structure and spectra of chaotically advected passive scalars
The stationary distribution of passive tracers chaotically advected by a
two-dimensional large-scale flow is investigated. The tracer field is force by
resetting the value of the tracer in certain localised regions. This problem is
mathematically equivalent to advection in open flows and results in a fractal
tracer structure. The spectral exponent of the tracer field is different from
that for a passive tracer with the usual additive forcing (the so called
Batchelor spectrum) and is related to the fractal dimension of the set of
points that have never visited the forcing regions. We illustrate this
behaviour by considering a time-periodic flow whose effect is equivalent to a
simple two-dimensional area-preserving map. We also show that similar structure
in the tracer field is found when the flow is aperiodic in time.Comment: 7 pages, 9 figure
Factors influencing the distribution of charge in polar nanocrystals
We perform first-principles calculations of wurtzite GaAs nanorods to explore
the factors determining charge distributions in polar nanostructures. We show
that both the direction and magnitude of the dipole moment of a
nanorod, and its electic field, depend sensitively on how its surfaces are
terminated and do not depend strongly on the spontaneous polarization of the
underlying lattice. We identify two physical mechanisms by which
is controlled by the surface termination, and we show that the excess charge on
the nanorod ends is not strongly localized. We discuss the implications of
these results for tuning nanocrystal properties, and for their growth and
assembly.Comment: Accepted for publication in Phys. Rev. B Rapid Communication
Accurate ionic forces and geometry optimization in linear-scaling density-functional theory with local orbitals
Linear scaling methods for density-functional theory (DFT) simulations are formulated in terms of localized orbitals in real space, rather than the delocalized eigenstates of conventional approaches. In local-orbital methods, relative to conventional DFT, desirable properties can be lost to some extent, such as the translational invariance of the total energy of a system with respect to small displacements and the smoothness of the potential-energy surface. This has repercussions for calculating accurate ionic forces and geometries. In this work we present results from onetep, our linear scaling method based on localized orbitals in real space. The use of psinc functions for the underlying basis set and on-the-fly optimization of the localized orbitals results in smooth potential-energy surfaces that are consistent with ionic forces calculated using the Hellmann-Feynman theorem. This enables accurate geometry optimization to be performed. Results for surface reconstructions in silicon are presented, along with three example systems demonstrating the performance of a quasi-Newton geometry optimization algorithm: an organic zwitterion, a point defect in an ionic crystal, and a semiconductor nanostructure.<br/
Diffusion of passive scalar in a finite-scale random flow
We consider a solvable model of the decay of scalar variance in a
single-scale random velocity field. We show that if there is a separation
between the flow scale k_flow^{-1} and the box size k_box^{-1}, the decay rate
lambda ~ (k_box/k_flow)^2 is determined by the turbulent diffusion of the
box-scale mode. Exponential decay at the rate lambda is preceded by a transient
powerlike decay (the total scalar variance ~ t^{-5/2} if the Corrsin invariant
is zero, t^{-3/2} otherwise) that lasts a time t~1/\lambda. Spectra are sharply
peaked at k=k_box. The box-scale peak acts as a slowly decaying source to a
secondary peak at the flow scale. The variance spectrum at scales intermediate
between the two peaks (k_box0). The mixing
of the flow-scale modes by the random flow produces, for the case of large
Peclet number, a k^{-1+delta} spectrum at k>>k_flow, where delta ~ lambda is a
small correction. Our solution thus elucidates the spectral make up of the
``strange mode,'' combining small-scale structure and a decay law set by the
largest scales.Comment: revtex4, 8 pages, 4 figures; final published versio
Density-functional investigation of the rhombohedral to simple cubic phase transition of arsenic
We report on our investigation of the crystal structure of arsenic under
compression, focusing primarily on the pressure-induced A7 to simple cubic (sc)
phase transition. The two-atom rhombohedral unit cell is subjected to pressures
ranging from 0 GPa to 200 GPa; for each given pressure, cell lengths and
angles, as well as atomic positions, are allowed to vary until the fully
relaxed structure is obtained. We find that the nearest and next-nearest
neighbor distances give the clearest indication of the occurrence of a
structural phase transition. Calculations are performed using the local density
approximation (LDA) and the PBE and PW91 generalized gradient approximations
(GGA-PBE and GGA-PW91) for the exchange-correlation functional. The A7 to sc
transition is found to occur at 21+/-1 GPa in the LDA, at 28+/-1 GPa in the
GGA-PBE and at 29+/-1 GPa in the GGA-PW91; no volume discontinuity is observed
across the transition in any of the three cases. We use k-point grids as dense
as 66X66X66 to enable us to present reliably converged results for the A7 to sc
transition of arsenic.Comment: To be published in Physical Review B; material supplementary to this
article is available at arXiv:0810.169
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