69,953 research outputs found
Bidding Strategy with Forecast Technology Based on Support Vector Machine in Electrcity Market
The participants of the electricity market concern very much the market price
evolution. Various technologies have been developed for price forecast. SVM
(Support Vector Machine) has shown its good performance in market price
forecast. Two approaches for forming the market bidding strategies based on SVM
are proposed. One is based on the price forecast accuracy, with which the being
rejected risk is defined. The other takes into account the impact of the
producer's own bid. The risks associated with the bidding are controlled by the
parameters setting. The proposed approaches have been tested on a numerical
example.Comment: 8pages, 13figures, paper for the conference "Applications of Physics
in Financial Analysis 6th International Conference
Aggregate Hazes in Exoplanet Atmospheres
Photochemical hazes have been frequently used to interpret exoplanet
transmission spectra that show an upward slope towards shorter wavelengths and
weak molecular features. While previous studies have only considered spherical
haze particles, photochemical hazes composed of hydrocarbon aggregate particles
are common throughout the solar system. We use an aerosol microphysics model to
investigate the effect of aggregate photochemical haze particles on
transmission spectra of warm exoplanets. We find that the wavelength dependence
of the optical depth of aggregate particle hazes is flatter than for spheres
since aggregates grow to larger radii. As a result, while spherical haze
opacity displays a scattering slope towards shorter wavelengths, aggregate haze
opacity can be gray in the optical and NIR, similar to those assumed for
condensate cloud decks. We further find that haze opacity increases with
increasing production rate, decreasing eddy diffusivity, and increasing monomer
size, though the magnitude of the latter effect is dependent on production rate
and the atmospheric pressure levels probed. We generate synthetic exoplanet
transmission spectra to investigate the effect of these hazes on spectral
features. For high haze opacity cases, aggregate hazes lead to flat, nearly
featureless spectra, while spherical hazes produce sloped spectra with clear
spectral features at long wavelengths. Finally, we generate synthetic
transmission spectra of GJ 1214b for aggregate and spherical hazes and compare
them to space-based observations. We find that aggregate hazes can reproduce
the data significantly better than spherical hazes, assuming a production rate
limited by delivery of methane to the upper atmosphere.Comment: 17 figures, accepted to Ap
Further Results on Active Magnetic Bearing Control with Input Saturation
We study the low-bias stabilization of active magnetic bearings (AMBs)
subject to voltage saturation based on a recently proposed model for the AMB
switching mode of operation. Using a forwarding-like approach, we construct a
stabilizing controller of arbitrarily small amplitude and a control-Lyapunov
function for the AMB dynamics. We illustrate our construction using a numerical
example.Comment: 9 pages, 2 figures. IEEE Transactions on Control Systems Technology,
accepted for publication in January 200
Statistics of Substructures in Dark Matter Haloes
We study the amount and distribution of dark matter substructures within dark
matter haloes, using a large set of high-resolution simulations ranging from
group size to cluster size haloes, and carried our within a cosmological model
consistent with WMAP 7-year data. In particular, we study how the measured
properties of subhaloes vary as a function of the parent halo mass, the
physical properties of the parent halo, and redshift. The fraction of halo mass
in substructures increases with increasing mass. There is, however, a very
large halo-to-halo scatter that can be explained only in part by a range of
halo physical properties, e.g. concentration. At given halo mass, less
concentrated haloes contain significantly larger fractions of mass in
substructures because of the reduced strength of tidal disruption. Most of the
substructure mass is located at the outskirts of the parent haloes, in
relatively few massive subhaloes. This mass segregation appears to become
stronger at increasing redshift, and should reflect into a more significant
mass segregation of the galaxy population at different cosmic epochs. When
haloes are accreted onto larger structures, their mass is significantly reduced
by tidal stripping. Haloes that are more massive at the time of accretion
(these should host more luminous galaxies) are brought closer to the centre on
shorter time-scales by dynamical friction, and therefore suffer of a more
significant stripping. The halo merger rate depends strongly on the environment
with substructure in more massive haloes suffering more important mergers than
their counterparts residing in less massive systems. This should translate into
a different morphological mix for haloes of different mass.Comment: 13 pages, 11 figures and 1 table. MNRAS 2011 in pres
Mechanism of microstructural modification of the interfacial transition zone by using blended materials
Applying blended materials with finer particle size or high reactivity could be an effective and economic way for improving the microsturcture of interfacial transition zone (ITZ). In this study, the porosity characteristics of ITZ in concrete made with OPC and blended binders were determined quantitatively by using backscattered electron microscopy (BSE) image analysis and mercury intrusion porosimetry (MIP) measurements. This paper especially focused on the effects of slag and limestone filler on the thickness and pore structure of the ITZ. Results indicated that the porosity at each distance reduces with increasing limestone filler from 0 to 5%, and a significant increase is observed in the sample with 10% of limestone filler. The addition of 5% of limestone filler is able to densify the pore structure of both ITZ and bulk matrix. The reduction in pore volume in the range coarser than 100 nm contributed to the largest decrease in the total pores. Increasing the incorporation level of limestone filler to 10% resulted in an increase in the total porosity. The influences of slag on the porosity characteristics were highly dependent on the replacement level and the determined pore size regions. The addition of 35% of slag reduces the porosity at all distances and produces a denser microstructure both in the ITZ and bulk cement matrix. However, this improvement disappears when the substitution amount reaches to 70%. The incorporation of slag as a partial substitute for Portland cement tends to refine the pore structure
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