5,463 research outputs found
The Trade-off Between Static and Dynamic Efficiency in Electricity Markets - A Cross Country Study
This paper is the first to explicitly test for the presence of a trade-off between static and dynamic
efficiency in a regulated industry, the electricity industry. We show for 16 European countries over the
period 1998-2007 that higher electricity end-user prices in a country subsequently lead to higher
investments in the capital stock, i.e. in generation, distribution and transmission assets. Moreover,
there is a trade-off between vertical economies and competition. Ownership unbundling and forced
access to the incumbent transmission grid increase competition but come at the cost of lost vertical
economies. Generally, we find that regulation that affect only the market like the establishment of a
wholesale market or free choice of suppliers increase investment activity via spurring competition.
Regulation, however, that adversely affects the incumbent directly, like ownership unbundling,
decreases aggregate investment spending. (author's abstract)Series: Working Papers / Research Institute for Regulatory Economic
Kinetic Energy Transport in Rayleigh--B\'enard Convection
The kinetic energy balance in Rayleigh--B\'{e}nard convection is investigated
for the Prandtl number range and for fixed Rayleigh number
. The kinetic energy balance is divided into a dissipation, a
production and a flux term. We discuss profiles of all terms and find that the
different contributions to the energy balance can be spatially separated into
regions where kinetic energy is produced and where kinetic energy is
dissipated. Analysing the Prandtl number dependence of the kinetic energy
balance, we show that the height-dependence of the mean viscous dissipation is
closely related to the flux of kinetic energy. We show that the flux of kinetic
energy can be divided into four additive contributions, each representing a
different elementary physical process (advection, buoyancy, normal viscous
stresses and viscous shear stresses). The behaviour of these individual flux
contributions is found to be surprisingly rich and exhibits a pronounced
Prandtl number dependence. Different flux contributions dominate the kinetic
energy transport at different depth, such that a comprehensive discussion
requires a decomposition of the domain into a considerable number of
sub-layers. On a less detailed level, our results reveal that advective kinetic
energy fluxes play a key role in balancing the near-wall dissipation at low
Prandtl number, whereas normal viscous stresses are particularly important at
high Prandtl number. Finally, our work reveals that classical velocity boundary
layers are deeply connected to the kinetic energy transport, but fail to
correctly represent regions of enhanced viscous dissipation
Many Masses on One Stroke: Economic Computation of Quark Propagators
The computational effort in the calculation of Wilson fermion quark
propagators in Lattice Quantum Chromodynamics can be considerably reduced by
exploiting the Wilson fermion matrix structure in inversion algorithms based on
the non-symmetric Lanczos process. We consider two such methods: QMR (quasi
minimal residual) and BCG (biconjugate gradients). Based on the decomposition
of the Wilson mass matrix, using QMR, one can carry
out inversions on a {\em whole} trajectory of masses simultaneously, merely at
the computational expense of a single propagator computation. In other words,
one has to compute the propagator corresponding to the lightest mass only,
while all the heavier masses are given for free, at the price of extra storage.
Moreover, the symmetry can be used to cut
the computational effort in QMR and BCG by a factor of two. We show that both
methods then become---in the critical regime of small quark
masses---competitive to BiCGStab and significantly better than the standard MR
method, with optimal relaxation factor, and CG as applied to the normal
equations.Comment: 17 pages, uuencoded compressed postscrip
Cooling and aggregation in wet granulates
Wet granular materials are characterized by a defined bond energy in their
particle interaction such that breaking a bond implies an irreversible loss of
a fixed amount of energy. Associated with the bond energy is a nonequilibrium
transition, setting in as the granular temperature falls below the bond energy.
The subsequent aggregation of particles into clusters is shown to be a
self-similar growth process with a cluster size distribution that obeys
scaling. In the early phase of aggregation the clusters are fractals with
D_f=2, for later times we observe gelation. We use simple scaling arguments to
derive the temperature decay in the early and late stages of cooling and verify
our results with event-driven simulations.Comment: 4 pages, 6 figures, suggestions of the referees implemented, EPAPS
supplementary material added:
http://netserver.aip.org/cgi-bin/epaps?ID=E-PRLTAO-102-00391
Modeling working memory: a computational implementation of the Time-Based Resource-Sharing theory
Working memory is a core concept in cognition, predicting about 50% of the variance in IQ and reasoning tasks. A popular test of working memory is the complex span task, in which encoding of memoranda alternates with processing of distractors. A recent model of complex span performance, the Time-Based-Resource-Sharing (TBRS) model of Barrouillet and colleagues, has seemingly accounted for several crucial findings, in particular the intricate trade-off between deterioration and restoration of memory in the complex span task. According to the TBRS, memory traces decay during processing of the distractors, and they are restored by attentional refreshing during brief pauses in between processing steps. However, to date, the theory has been formulated only at a verbal level, which renders it difficult to test and to be certain of its intuited predictions. We present a computational instantiation of the TBRS and show that it can handle most of the findings on which the verbal model was based. We also show that there are potential challenges to the model that await future resolution. This instantiated model, TBRS*, is the first comprehensive computational model of performance in the complex span paradigm. The Matlab model code is available as a supplementary material of this articl
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