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851.
B. D. Kabulov K. A. Akhundzhanov F. U. Yunusov O. A. Shpigun S. S. Negmatov 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2007,81(3):354-356
The hydrolytic polycondensation of tetraethoxysilane in the presence of various polymers (polyacrylonitrile, polycaproamide, and chitosan) as templates was performed with the use of the sol-gel technology to obtain nanohybrid composite polymer-silica sorbents-nanofractals. 相似文献
852.
E. Baggio Saitovitch F. J. Litterst I. Souza Azevedo R. B. Scorzelli 《Hyperfine Interactions》1989,50(1-4):529-535
The Mössbauer spectra of YBa2(Cu1?x Fe x )3O7 at room temperature show several doublets attributed to Fe in Cu(1) sites with different oxygen configurations. Here we present a systematic study performed at 4.2 K forx=0.005, 0.01, 0.03, 0.05, 0.10, 0.15. To obtain information about the magnetic ordered state two samples, withx=0.005 andx=0.15, have been studied at 4.2 K underB ext=5 T. The Mössbauer spectra indicate that the iron moments are polarized forx=0.005, while in the ordered state (x=0.15) they have an antiferromagnetic or spin-glass-like arrangement with high anisotropy. 相似文献
853.
The hyperfine fields for the systems140CeLa and140CeLu have been determined by time differential perturbed angular correlations (TDPAC) in the temperature range 4.2 K≤T≤330 K. Magnitude and temperature dependence of the paramagnetic enhancement factor β indicate that cerium in either system
is of intermediate valence. This behaviour is discussed in terms of a theory proposed by Ramakrishnan et al. [1–3]. 相似文献
854.
This paper is devoted to the proof of almost global existence results for Klein‐Gordon equations on Zoll manifolds (e.g., spheres of arbitrary dimension) with Hamiltonian nonlinearities, when the Cauchy data are smooth and small. The proof relies on Birkhoff normal form methods and on the specific distribution of eigenvalues of the Laplacian perturbed by a potential on Zoll manifolds. © 2007 Wiley Periodicals, Inc. 相似文献
855.
The three dimensional problem of steady fluid deposition on an inclined rotating disk is solved by similarity transform. For a given spraying rate there may be one, two or no steady state solution. The inclination causes a downward draining flow and a lateral flow. Perturbation solutions compare well with exact similarity solutions when the fluid film is thin. 相似文献
856.
J.T. Elizalde Galindo A.H. Adair C.E. Botez V. Corral Flores D. Bueno Baques L. Fuentes Cobas J.A. Matutes-Aquino 《Applied Physics A: Materials Science & Processing》2007,87(4):743-747
Measurements of ac-susceptibility and dc-magnetization were carried out on samples of Ni1-xZnxFe2O4 nanoparticles (x=0, 0.25, 0.5, 0.75) with average diameters 〈D〉≈7 nm. Values of the superparamagnetic blocking temperature
T̄B were obtained from the characteristic temperature behavior of the imaginary susceptibility χimag. An Arrhenius-type law, which accurately describes the relationship between the observation time τobs and the blocking temperature, was used to determine the effective energy barrier to magnetization reversal Ueff. A Zn-content dependence of the energy barrier is observed, where Ueff changes little for 0≤x≤0.25, it peaks at x=0.5, and decreases back upon further Zn-doping. The large increase of Ueff at x=0.5 is attributed to an enhanced magnetic anisotropy induced by the crossover between two spatial arrangements of spins
in the A and B sub-lattices of the ferrimagnetic inverse spinel.
PACS 75.50.Bb; 75.50.Gg; 75.30.Et 相似文献
857.
In this paper, we study the consistency of a variant of fractionalstep Runge–Kutta methods. These methods are designed tointegrate efficiently semi-linear multidimensional parabolicproblems by means of linearly implicit time integration processes.Such time discretization procedures are also related to a splittingof the space differential operator (or the spatial discretizationof it) as a sum of simpler linear differentialoperators and a nonlinear term. 相似文献
858.
J Whittaker C Whitehead M Somers 《The Journal of the Operational Research Society》2007,58(7):911-921
A principled technique for monitoring the performance of a consumer credit scorecard through time is derived from Kalman filtering. Standard approaches sporadically compare certain characteristics of the new applicants with those predicted from the scorecard. The new approach systematically updates the scorecard combining new applicant information with the previous best estimate. The dynamically updated scorecard is tracked through time and compared to limits calculated by sequential simulation from the baseline scorecard. The observation equation of the Kalman filter is tailored to take the results of fitting local scorecards by logistic regression to batches of new clients that arrive in the current time interval. The states in the Kalman filter represent the true or underlying score for each attribute in the card: the parameters of the logistic regression. Their progress in time is modelled by a random walk and the filter provides the best estimate of the scores using past and present information. We illustrate the technique using a commercial mortgage portfolio and the results indicate significant emerging deficiencies in the baseline scorecard. 相似文献
859.
Y.-Q. Peng J.-H. Yang F.-P. Lu Q.-S. Yang H.-W. Xing X.-S. Li C.-A. Song 《Applied Physics A: Materials Science & Processing》2007,86(2):225-229
Based on the assumption of Gaussian energy distributions of the lowest unoccupied molecular orbital (LUMO) and the highest occupied molecular orbital (HOMO), analytical expressions of generalized Einstein relation in chemically doped organic semiconductor are developed, by approximation of Coulomb traps with a rectangle potential well. Numerical calculations show that traditional Einstein relations do not hold for chemically doped organic semiconductors. Similar to physical doping, the dependence of diffusion coefficient to mobility D/μ ratio on the carrier concentration has a maximum. An essential difference between chemical doping and physical doping is that, the D/μ ratio in chemically doped organic semiconductors depends not only on carrier concentration and doping concentration, but also on the applied electric field. PACS 71.20.Rv; 72.90.+y; 73.50.-h 相似文献
860.