95,328 research outputs found
Power load forecasting
For the electric power factory, the power load forecasting problem, including load forecasting and consumption predicting, is crucial to work planning. According to the predicting time, it can be divided into long-term forecasting, mid-term forecasting, short-term forecasting and ultra-short-term forecasting. The long-term and mid-term forecasting are mainly used for macro control, and their forecasting time arrange are from one year to ten years and from one month to twelve months respectively. The short-term forecasting which prediction time is from one day to seven days is used in generators macroeconomic control, power exchange plan and some other areas. Predicting the situation in next 24 hours is named as the ultra-short-term forecasting which is used for failure prediction, emergency treatment and frequency control. In general, the forecast accuracy is different for different prediction time. The longer is the time, the lower accurate is the prediction.
As the unique power supplier in Huizhou (China), Huizhou Electric Power wants to know the solution to the problems: 1. Prediction of the total electrical consumption and the peak load of the city in 2006 based on the economy development and the feature of the city. 2. Monthly prediction of the consumption and peak load in 2006. 3. Daily prediction of the consumption and peak load from July 10th to 16th in 2006. 4. Prediction of the load every 15 minutes of July 10th. 5. Real-time forecasting which means to amend the existing load prediction for next 15 minute
Applications of inverse simulation to a nonlinear model of an underwater vehicle
Inverse simulation provides an important alternative
to conventional simulation and to more formal
mathematical techniques of model inversion. The
application of inverse simulation methods to a nonlinear
dynamic model of an unmanned underwater vehicle with
actuator limits is found to give rise to a number of
challenging problems. It is shown that this particular
problem requires, in common with other applications that
include hard nonlinearities in the model or discontinuities
in the required trajectory, can best be approached using a
search-based optimization algorithm for inverse
simulation in place of the more conventional Newton-
Raphson approach. Results show that meaningful inverse
simulation results can be obtained but that multi-solution
responses exist. Although the inverse solutions are not
unique they are shown to generate the required
trajectories when tested using conventional forward
simulation methods
Can the jet steepen the light curves of GRB afterglow?
Beaming of relativistic ejecta in GRBs has been postulated by many authors in
order to reduce the total GRB energy, thus it is very important to look for the
observational evidence of beaming. Rhoads (1999) has pointed out that the
dynamics of the blast wave, which is formed when the beamed ejecta sweeping the
external medium, will be significantly modified by the sideways expansion due
to the increased swept up matter. He claimed that shortly after the bulk
Lorentz factor () of the blast wave drops below the inverse of the
initial opening angle () of the beamed ejecta, there will be a
sharp break in the afterglow light curves. However, some other authors have
performed numerical calculations and shown that the break of the light curve is
weaker and much smoother than the one analytically predicted. In this paper we
reanalyse the dynamical evolution of the jet blast wave, calculate the jet
emission analytically, we find that the sharp break predicted by Rhoads will
actually not exist, and for most cases the afterglow light curve will almost
not be affected by sideways expansion unless the beaming angle is extremely
small. We demonstrate that only when , the afterglow light
curves may be steepened by sideways expansion, and in fact there cannot be two
breaks as claimed before. We have also constructed a simple numerical code to
verify our conclusion.Comment: 12 pages, 2 figures, accepted by ApJ, added numerical calculation
Symmetry protected fractional Chern insulators and fractional topological insulators
In this paper we construct fully symmetric wavefunctions for the
spin-polarized fractional Chern insulators (FCI) and time-reversal-invariant
fractional topological insulators (FTI) in two dimensions using the parton
approach. We show that the lattice symmetry gives rise to many different FCI
and FTI phases even with the same filling fraction (and the same
quantized Hall conductance in FCI case). They have different
symmetry-protected topological orders, which are characterized by different
projective symmetry groups. We mainly focus on FCI phases which are realized in
a partially filled band with Chern number one. The low-energy gauge groups of a
generic FCI wavefunctions can be either or
the discrete group , and in the latter case the associated low-energy
physics are described by Chern-Simons-Higgs theories. We use our construction
to compute the ground state degeneracy. Examples of FCI/FTI wavefunctions on
honeycomb lattice and checkerboard lattice are explicitly given. Possible
non-Abelian FCI phases which may be realized in a partially filled band with
Chern number two are discussed. Generic FTI wavefunctions in the absence of
spin conservation are also presented whose low-energy gauge groups can be
either or . The constructed wavefunctions
also set up the framework for future variational Monte Carlo simulations.Comment: 24 pages, 13 figures, published versio
Strangeness production in heavy ion collisions at SPS and RHIC within two-source statistical model
The experimental data on hadron yields and ratios in central Pb+Pb and Au+Au
collisions at SPS and RHIC energies, respectively, are analysed within a
two-source statistical model of an ideal hadron gas. These two sources
represent the expanding system of colliding heavy ions, where the hot central
fireball is embedded in a larger but cooler fireball. The volume of the central
source increases with rising bombarding energy. Results of the two-source model
fit to RHIC experimental data at midrapidity coincide with the results of the
one-source thermal model fit, indicating the formation of an extended fireball,
which is three times larger than the corresponding core at SPS.Comment: Talk at "Strange Quarks in Matter" Conference (Strangeness'2001),
September 2001, Frankfurt a.M., German
Scalable Text and Link Analysis with Mixed-Topic Link Models
Many data sets contain rich information about objects, as well as pairwise
relations between them. For instance, in networks of websites, scientific
papers, and other documents, each node has content consisting of a collection
of words, as well as hyperlinks or citations to other nodes. In order to
perform inference on such data sets, and make predictions and recommendations,
it is useful to have models that are able to capture the processes which
generate the text at each node and the links between them. In this paper, we
combine classic ideas in topic modeling with a variant of the mixed-membership
block model recently developed in the statistical physics community. The
resulting model has the advantage that its parameters, including the mixture of
topics of each document and the resulting overlapping communities, can be
inferred with a simple and scalable expectation-maximization algorithm. We test
our model on three data sets, performing unsupervised topic classification and
link prediction. For both tasks, our model outperforms several existing
state-of-the-art methods, achieving higher accuracy with significantly less
computation, analyzing a data set with 1.3 million words and 44 thousand links
in a few minutes.Comment: 11 pages, 4 figure
Phase structures of strong coupling lattice QCD with overlap fermions at finite temperature and chemical potential
We perform the first study of lattice QCD with overlap fermions at finite
temperature and chemical potential . We start from the Taylor expanded
overlap fermion action, and derive in the strong coupling limit the effective
free energy by mean field approximation. On the () plane and in the
chiral limit, there is a tricritical point, separating the second order chiral
phase transition line at small and large , and first order chiral
phase transition line at large and small
Determination of activation volumes of reversal in perpendicular media
We discuss a method for the determination of activation volumes of reversal in perpendicular media. This method does not require correction for the self-demagnetizing field normally associated with these media. This is achieved by performing time dependence measurements at a constant level of magnetization. From the difference in time taken for the magnetization to decay to a fixed value at two fields-separated by a small increment DeltaH, the activation volume can be determined. We report data for both CoCrPt alloy films and a multilayer film, typical of those materials under consideration for use as perpendicular media. We find activation volumes that are consistent with the hysteresis curves of the materials. The activation volume scales qualitatively with the exchange coupling. The alloy films have significantly lower activation volumes, implying that they would be capable of supporting a higher data density
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