4,083 research outputs found
Disaggregated Bundle Methods for Distributed Market Clearing in Power Networks
A fast distributed approach is developed for the market clearing with
large-scale demand response in electric power networks. In addition to
conventional supply bids, demand offers from aggregators serving large numbers
of residential smart appliances with different energy constraints are
incorporated. Leveraging the Lagrangian relaxation based dual decomposition,
the resulting optimization problem is decomposed into separate subproblems, and
then solved in a distributed fashion by the market operator and each aggregator
aided by the end-user smart meters. A disaggregated bundle method is adapted
for solving the dual problem with a separable structure. Compared with the
conventional dual update algorithms, the proposed approach exhibits faster
convergence speed, which results in reduced communication overhead. Numerical
results corroborate the effectiveness of the novel approach.Comment: To appear in GlobalSIP 201
Risk-Aware Management of Distributed Energy Resources
High wind energy penetration critically challenges the economic dispatch of
current and future power systems. Supply and demand must be balanced at every
bus of the grid, while respecting transmission line ratings and accounting for
the stochastic nature of renewable energy sources. Aligned to that goal, a
network-constrained economic dispatch is developed in this paper. To account
for the uncertainty of renewable energy forecasts, wind farm schedules are
determined so that they can be delivered over the transmission network with a
prescribed probability. Given that the distribution of wind power forecasts is
rarely known, and/or uncertainties may yield non-convex feasible sets for the
power schedules, a scenario approximation technique using Monte Carlo sampling
is pursued. Upon utilizing the structure of the DC optimal power flow (OPF), a
distribution-free convex problem formulation is derived whose complexity scales
well with the wind forecast sample size. The efficacy of this novel approach is
evaluated over the IEEE 30-bus power grid benchmark after including real
operation data from seven wind farms.Comment: To appear in Proc. of 18th Intl. Conf. on DSP, Santorini Island,
Greece, July 1-3, 201
Propagation of gaseous detonation waves in a spatially inhomogeneous reactive medium
Detonation propagation in a compressible medium wherein the energy release
has been made spatially inhomogeneous is examined via numerical simulation. The
inhomogeneity is introduced via step functions in the reaction progress
variable, with the local value of energy release correspondingly increased so
as to maintain the same average energy density in the medium, and thus a
constant Chapman Jouguet (CJ) detonation velocity. A one-step Arrhenius rate
governs the rate of energy release in the reactive zones. The resulting
dynamics of a detonation propagating in such systems with one-dimensional
layers and two-dimensional squares are simulated using a Godunov-type
finite-volume scheme. The resulting wave dynamics are analyzed by computing the
average wave velocity and one-dimensional averaged wave structure. In the case
of sufficiently inhomogeneous media wherein the spacing between reactive zones
is greater than the inherent reaction zone length, average wave speeds
significantly greater than the corresponding CJ speed of the homogenized medium
are obtained. If the shock transit time between reactive zones is less than the
reaction time scale, then the classical CJ detonation velocity is recovered.
The spatio-temporal averaged structure of the waves in these systems is
analyzed via a Favre averaging technique, with terms associated with the
thermal and mechanical fluctuations being explicitly computed. The analysis of
the averaged wave structure identifies the super-CJ detonations as weak
detonations owing to the existence of mechanical non-equilibrium at the
effective sonic point embedded within the wave structure. The correspondence of
the super-CJ behavior identified in this study with real detonation phenomena
that may be observed in experiments is discussed
Black holes and Higgs stability
We study the effect of primordial black holes on the classical rate of
nucleation of AdS regions within the standard electroweak vacuum. We find that
the energy barrier for transitions to the new vacuum, which characterizes the
exponential suppression of the nucleation rate, can be reduced significantly in
the black-hole background. A precise analysis is required in order to determine
whether the the existence of primordial black holes is compatible with the form
of the Higgs potential at high temperature or density in the Standard Model or
its extensions.Comment: 27 pages, 10 figures, conclusions expanded, to appear in JCA
A spectrally-accurate FVTD technique for complicated amplification and reconfigurable filtering EMC devices
The consistent and computationally economical analysis of demanding amplification and filtering structures is introduced in this paper via a new spectrally-precise finite-volume time-domain algorithm. Combining a family of spatial derivative approximators with controllable accuracy in general curvilinear coordinates, the proposed method employs a fully conservative field flux formulation to derive electromagnetic quantities in areas with fine structural details. Moreover, the resulting 3-D operators assign the appropriate weight to each spatial stencil at arbitrary media interfaces, while for periodic components the domain is systematically divided to a number of nonoverlapping subdomains. Numerical results from various real-world configurations verify our technique and reveal its universality
W production at large transverse momentum at the Large Hadron Collider
We study the production of W bosons at large transverse momentum in pp
collisions at the Large Hadron Collider (LHC). We calculate the complete
next-to-leading order (NLO) corrections to the differential cross section. We
find that the NLO corrections provide a large increase to the cross section
but, surprisingly, do not reduce the scale dependence relative to leading order
(LO). We also calculate next-to-next-to-leading-order (NNLO) soft-gluon
corrections and find that, although they are small, they significantly reduce
the scale dependence thus providing a more stable theoretical prediction.Comment: 12 pages, 7 figure
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