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71.
72.
Solovyov A. V. Markov A. B. Yakovlev E. V. Maksimov O. Y. 《Russian Physics Journal》2020,63(2):270-275
Russian Physics Journal - Results of investigations of acoustic signals induced in a copper plate irradiated with a microsecond lowenergy high-current electron beam (LEHCEB) are presented. The... 相似文献
73.
The Frenkel-Biot theory is used to study the propagation of a longitudinal harmonic wave of the first kind in an isotropic porous matrix with inclusions contrasting in elastic properties and hydrodynamic permeability. The generation of elastic waves of the second kind at the boundaries of inclusions is taken into account. The effective wave number of the longitudinal wave is calculated using the equations of multiple scattering theory. The characteristic size of inhomogeneities is assumed to be much greater than the size of pores. The parameters of the model used for calculations correspond to sandstone with centimeter-scale inhomogeneities. The presence of such inhomogeneities is typical of sedimentary rocks. Calculations show that, in the frequency range of acoustic logging, the effective attenuation factor of the longitudinal wave may noticeably exceed the attenuation factors of longitudinal waves of the first kind in both matrix and inclusions. From the results obtained, it follows that, when studying the propagation of elastic waves in fluid-saturated porous media, it is necessary to take into account the hydrodynamic effects associated with the filtration overflows that arise at the boundaries of inhomogeneities. 相似文献
74.
S. Yu. Mikheev Yu. A. Ryzhov I. I. Shkarban M. M. Gorshkov R. P. Markov 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(3):525-529
Porous aluminum (Al 99.99%) foil membranes prepared by electrochemical anodizing and subsequent removing the continuous barrier
layer by ion-plasma irradiation are described. As a result, Al2O3 membranes about 2–5 μm thick with regular arrangement of channels have been obtained. The possibility has been shown of regulation
of a channel diameter in a range of 20–100 nm by changing the oxidation conditions. The experimental dependences of Al and
Al2O3 sputtering coefficients on the xenon ion energy (100–400 eV) and the angle of incidence have been obtained. 相似文献
75.
V. A. Levin I. S. Manuylovich V. V. Markov 《Computational Mathematics and Mathematical Physics》2016,56(6):1102-1117
Numerical simulation of three-dimensional structures of gas detonation in circular section channels that emerge due to the instability when the one-dimensional flow is initiated by energy supply at the closed end of the channel is performed. It is found that in channels with a large diameter, an irregular three-dimensional cellular detonation structure is formed. Furthermore, it is found that in channels with a small diameter circular section, the initially plane detonation wave is spontaneously transformed into a spinning detonation wave, while passing through four phases. A critical value of the channel diameter that divides the regimes with the three-dimensional cellular detonation and spinning detonation is determined. The stability of the spinning detonation wave under perturbations occurring when the wave passes into a channel with a greater (a smaller) diameter is investigated. It is found that the spin is preserved if the diameter of the next channel (into which the wave passes) is smaller (respectively, greater) than a certain critical value. The computations were performed on the Lomonosov supercomputer using from 0.1 to 10 billions of computational cells. All the computations of the cellular and spinning detonation were performed in the whole long three-dimensional channel (up to 1 m long) rather than only in its part containing the detonation wave; this made it possible to adequately simulate and investigate the features of the transformation of the detonation structure in the process of its propagation. 相似文献
76.
Dmitry A. Gruzdev Galina L. Levit Victor P. Krasnov Evgeny N. Chulakov Liliya Sh. Sadretdinova Aleksandr N. Grishakov Marina A. Ezhikova Mikhail I. Kodess Valery N. Charushin 《Tetrahedron: Asymmetry》2010,21(8):936-942
A comparative study of the kinetic resolution of racemic 2-methyl-1,2,3,4-tetrahydroquinoline and 2,3-dihydro-3-methyl-4H-1,4-benzoxazine using N-phthaloyl-(S)-amino acyl chlorides as chiral acylating agents is described. Temperature and solvent effects on the stereochemical features have been examined. It has been found that N-phthaloyl-(S)-phenylalanyl and N-phthaloyl-(S)-2-phenylglycyl chlorides bearing aromatic substituents close to the stereogenic centre are more stereoselective acylating agents than N-phthaloyl-(S)-alanyl chloride. For the preparative kinetic resolution of racemic amines N-phthaloyl-(S)-phenylalanyl chloride proved to be the most appropriate chiral acylating agent. 相似文献
77.
V. F. Markov L. N. Maskaeva 《Russian Journal of Physical Chemistry A, Focus on Chemistry》2010,84(8):1288-1293
Calculation equations that allow one to determine the boundary conditions of the formation of solid-phase metal sulfides and
selenides with different valences according to the decomposition constants of thio- and selenourea and the kinetic dependence
of the accumulation of chalcogenide ions in the reaction system are proposed. The contribution from the crystallization factor
to the determination of the boundary conditions of the formation of the solid phase is shown with allowance for the nucleation
of metal chalcogenide. The calculation equations determining the boundary conditions of the formation of the main admixture
phases upon the hydrochemical deposition of chalcogenides, metal hydroxide, and cyanamide are derived. 相似文献
78.
Ratnikov MO Lipilin DL Churakov AM Strelenko YA Tartakovsky VA 《Organic letters》2002,4(19):3227-3229
[reaction: see text] The reduction of benzo-1,2,3,4-tetrazine 1,3-dioxides (BTDOs) 1 with Na(2)S(2)O(4) or SnCl(2) is suggested to proceed via intermediate N-nitrosobenzotriazoles 3 to afford benzotriazoles 2. The (15)N-labeling experiments exhibit that the N-3 atom of the tetrazine ring is incorporated into the nitroso group of 3 that is ultimately released into solution. It is possible that the biological activity of BTDOs is due to their ability to release nitrosating species, i.e., N-nitrosotriazol 3 or HNO(2), in the course of reduction. 相似文献
79.
Shestopalov AM Emeliyanova YM Shestopalov AA Rodinovskaya LA Niazimbetova ZI Evans DH 《Organic letters》2002,4(3):423-425
Three-component condensation of 4-piperidinones (7), 5-pyrazolones (8), and malononitrile (4) proceeds chemically and electrochemically and is a convenient one-step means of synthesis of substituted 6-amino-5-cyanospiro-4-(piperidine-4')-2H,4H-dihydropyrazolo[3,4-b]pyrans (12). The electrochemical reactions proceed under milder conditions and with yields 12-15% greater than those of the reactions catalyzed by chemical bases. 相似文献
80.
When the gas particles, which can be considered as a two level quantum system, are affected by frequent collisions with buffer gas particles (thermal reservoir), the spectral densities of the Einstein coefficients for absorption and induced emission are unequal to each other far from the absorption (emission) line. The relationship between the spectral densities at the specified condition reveals new physical phenomena. The mostly convincing example is the fact that population inversion is established in a two level system under nonresonance optical excitation. This effect is experimentally observed as a lasing on sodium resonance transitions. 相似文献