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981.
The conductivity of a macroscopically disordered graphite-paraffin system as a function of the graphite content and temperature
is studied. It is shown that the properties of the heterosystem differ essentially from those of its components. Experimental
data obtained are explained in terms of the percolation theory and concepts of fractal-structure objects. 相似文献
982.
983.
984.
A. V. Shchagin 《JETP Letters》2004,80(7):469-473
The possibility of focusing parametric x rays (PXRs) without x-ray optics has been shown. Parametric x rays are emitted by channeled relativistic charged particles moving along a bent crystal. Parametric x rays emitted from the entire length of the bent crystal are focused at two points on the bending axis of the crystal. The Huygens picture of formation of focused PXRs is given. The width of the spectral peak of this radiation has been estimated. Certain properties of focused PXRs are estimated for typical experimental conditions, and possibilities for the application of focused PXRs are discussed. An experiment for the observation of focused PXRs has been proposed. It has been shown that focused PXRs can be observed for a proton energy of several tens of GeVs or higher. 相似文献
985.
We give a purely algebro-geometric proof of the fact that every nonsingular
projective curve can be defined over a finite extension of its moduli field.
This extends a result byWolfart [7] to curves over fields of arbitrary
characteristic.
Received: 30 November 2001 相似文献
986.
We propose a minimum mean absolute error linear interpolator (MMAELI), based on theL
1 approach. A linear functional of the observed time series due to non-normal innovations is derived. The solution equation
for the coefficients of this linear functional is established in terms of the innovation series. It is found that information
implied in the innovation series is useful for the interpolation of missing values. The MMAELIs of the AR(1) model with innovations
following mixed normal andt distributions are studied in detail. The MMAELI also approximates the minimum mean squared error linear interpolator (MMSELI)
well in mean squared error but outperforms the MMSELI in mean absolute error. An application to a real series is presented.
Extensions to the general ARMA model and other time series models are discussed.
This research was supported by a CityU Research Grant and Natural Science Foundation of China. 相似文献
987.
988.
989.
Y. Gu Igor L. Kuskovsky R.D. Robinson G.F. Neumark S.P. Guo M.C. Tamargo 《Solid State Communications》2005,134(10):677-681
The composition and size of optically active CdxZn1−xSe/ZnSe quantum dots are estimated with a previously developed method. The results are then compared with those obtained for CdxZn1−xSe/Zn0.97Be0.03Se QDs. We show that introducing Be into the barrier material enhances both Cd composition and quantum size effect of optically active quantum dots. 相似文献
990.
A series of 4,6-disubstituted pyrimidines were synthesized via Suzuki and Kumada coupling reaction of 4,6-dichloropyrimidine. 相似文献