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31.
32.
Rumyantcev R. V. Zolotareva N. V. Novikova O. V. Petrov B. I. Lazarev N. M. Semenov V. V. 《Crystallography Reports》2021,66(3):441-447
Crystallography Reports - Reactions of nitrilotriacetic acid with 2-aminoethanol, 2-amino-2-(hydroxymethyl)propane-1,3-diol, and 2,2'-(ethylenedioxy)bis(ethylamine) afford the following salts... 相似文献
33.
Nonlinear Dynamics - In this paper, we generalize the Preisach model to the case when parameters of elementary relays are random variables. We show that an output state of the stochastic Preisach... 相似文献
34.
Shcherbakov S. V. Nalogin A. G. Kostishin V. G. Semenov A. S. Adiatulina N. E. Alekseev A. A. Belokon’ E. A. Timofeev A. V. Chitanov D. N. 《Technical Physics》2020,65(5):749-753
Technical Physics - Temperature dependences of the effective magnetic anisotropy field and ferromagnetic resonance linewidth in samples of isotropic and anisotropic hexaferrite... 相似文献
35.
Living polymers are formed by reversible association of primary units (unimers). Generally the chain statistical weight involves
a factor σ < 1 suppressing short chains in comparison with free unimers. Living polymerization is a sharp thermodynamic transition
for σ ≪ 1 which is typically the case. We show that this sharpness has an important effect on the kinetics of living polymerization
(one-dimensional association). The kinetic model involves i) the unimer activation step (a transition to an assembly-competent
state); ii) the scission/recombination processes providing growth of polymer chains and relaxation of their length distribution.
Analyzing the polymerization with no chains but unimers at t = 0 , with initial concentration of unimers M ≳ M
* (M* is the critical polymerization concentration), we determine the time evolution of the chain length distribution and find
that: 1) for M
* ≪ M ≪ M
*/σ the kinetics is characterized by 5 distinct time stages demarcated by 4 characteristic times t1, t2, t3 and t*; 2) there are transient regimes (t
1 ≲ t ≲ t
3) when the molecular-weight distribution is strongly non-exponential; 3) the chain scissions are negligible at times shorter
than t2. The chain growth is auto-accelerated for t
1 ≲ t ≲ t
2 : the cut-off chain length (= polymerization degree 〈n〉w
N
1 ∝ t
2 in this regime. 4) For t
2 < t < t
3 the length distribution is characterized by essentially 2 non-linear modes; the shorter cut-off length N1 is decreasing with time in this regime, while the length scale N2 of the second mode is increasing. (5) The terminal relaxation time of the polymer length distribution, t*, shows a sharp maximum in the vicinity of M*; the effective exponent
is as high as ∼ σ-1/3 just above M*. 相似文献
36.
V. V. Afrosimov R. N. Il’in V. I. Sakharov I. T. Serenkov D. V. Yanovskii S. F. Karmanenko A. A. Semenov 《Physics of the Solid State》1999,41(4):527-533
The initial stages in the formation and growth of yttrium-barium cuprate films have been studied in the course of magnetron
sputtering of a ceramic target by combining medium-energy-ion scattering (MEIS) and scanning-electron microscopy. The growth
mechanisms of YBa2Cu3O7−x
films on MgO and substrates having the perovskite structure, SrTiO3 and LaAlO3, at deposition temperatures of 700–780 °C and (Ar+O2) pressure of ∼70 Pa were found to be essentially different. Simulation of MEIS spectra (H+ or He+ ions with initial energies of 150–250 keV) and comparison of these results with experimental data revealed that in the first
case a film forms from pyramid-shaped islands and, in the second, it grows by a two-dimensional layer-by-layer process starting
practically with the first monolayer. For the island mechanism, MEIS permitted determination of the substrate surface coverage
and showed the growth of the YBa2Cu3O7−x
phase to be paralleled by formation of epitaxial nuclei of a Cu2O phase. After the first, initial stage in the film formation, the second stage, regular growth within reduced thicknesses
of 7–15 nm, sets in. This stage is characterized by a practically complete coverage of the substrate and a stable composition.
The third stage, regular growth, of an apparently helical nature, was observed to set in at thicknesses above 100 nm. In this
stage, the quality of film structure in the bulk and on the surface was found to be somewhat inferior to that of YBa2Cu3O7−x
single crystals and did not depend on substrate type.
Fiz. Tverd. Tela (St. Petersburg) 41, 588–595 (April 1999) 相似文献
37.
An approach to the simulation of low frequency vector wave fields in stratified media (mainly in the ocean) is considered. The approach is characterized by an improved stability with respect to dividing the medium into many layers of arbitrary thickness. The model for the sound field of a point source is based on an integral representation of two-dimensional, cylindrically symmetric vector wave fields in inhomogeneous media, so that the contributions of all types of waves are included automatically. The model medium is subdivided into N horizontally homogeneous layers for which 4(N?1) equations are formulated to satisfy the boundary conditions between adjacent layers. The method of the generalized Schmidt matrix is used to obtain the coefficients of the equations; these coefficients are substituted into the expressions (of the Fourier-Bessel integral type) for the local parameters of the field. The latter are calculated according to the numerical procedure, and the results are used to model the distributions of the acoustic pressure and the horizontal and vertical components of the particle velocity in liquid and elastic media. The instability of the calculation procedure may result in a disagreement between the model and the exact solution. However, the disagreement is shown to occur mainly in models containing excessively thick layers. A way for improving the stability of the numerical model is suggested. The simulation results are compared with the exact analytical solution for the simplest example and with the results obtained according to the commonly used generalized matrix procedure (the benchmark problem). The examples of the practical application of the model for investigating more complex seismoacoustic wave fields in the ocean are presented. 相似文献
38.
V. E. Semenov 《Journal of Experimental and Theoretical Physics》2006,102(1):34-39
Propagation through a Kerr medium of short pulses depending only on the longitudinal coordinate is investigated. High values of the peak intensity are considered for which the nonlinear part of the relative permittivity is on the order of unity. When a short pulse propagates through such a medium, the leading edge of the pulse is extended, while the trailing edge runs into the slowly propagating central part of the pulse; shock waves are generated at the trailing edge, giving rise to high spatial frequencies and backward reflected radiation. The duration of the pulse increases due to the high-frequency jet that forms at the trailing edge, and the peak intensity decreases. The spectrum of the backward reflected radiation is investigated as a function of the peak intensity of the pulse and the characteristics of the time dispersion of the medium. 相似文献
39.
The propagation and absorption of high-frequency sound in the isotropic phase of cholesteryl miristate is studied in a wide frequency range using the data of both Brillouin spectroscopy and acoustooptic measurements. The parameters of the relaxation process associated with the volume viscosity relaxation are calculated using the experimental data on the velocity and absorption of sound. 相似文献
40.
N. V. Vysotina A. S. Naumov N. N. Rozanov R. L. Sabirov V. E. Semenov V. A. Smirnov T. V. Starchikova S. V. Fedorov S. A. Chizhov V. E. Yashin 《Optics and Spectroscopy》2004,97(3):411-415
The final stage of self-focusing of 500-ps pulses of a neodymium laser in silicate and phosphate glasses and in the nonlinear liquids perfluorooctane, benzene, and toluene is studied theoretically and experimentally. The formation of spatial solitons, which are stable due to the nonlinearity saturation, is demonstrated. It is found that the intensity of the nonlinearity saturation is close to that of the threshold breakdown for glasses and the role of stimulated Raman scattering is significant for liquids. 相似文献