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L. A. Prokudina 《Journal of Experimental and Theoretical Physics》2014,118(3):480-488
A mathematical model is presented for the state of a free surface of a thin fluid layer (a fluid film) in heat-mass-exchange processes of condensation and evaporation. The wave motion of a fluid film is studied under inhomogeneous surface tension. Nonlinear development of perturbations belonging to a continuous band of wave numbers on the surface of a thin fluid layer is investigated within the framework of a non-linear parabolic equation. It is shown that wave packets with carrier wave lying near the harmonic of maximum increment become self-ordered; as a result, a monochromatic wave is generated on the surface of the fluid film. When a wave packet is generated in the neighborhood of the neutral stability curve, one can observe a phenomenon of directed energy transfer to the waves in the neighborhood of the harmonic of maximum increment. 相似文献
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采用分子动力学方法,研究了模型二元有序合金体系的平衡界面结构和界面处原子的扩散行为.计算结果表明,该二元有序合金的固液界面属于光滑界面.由于固体中同时存在结构和化学有序,从而导致界面处的原子结构与单质以及异质固液界面的结构明显不同.在界面法向方向上,粒子数密度呈复杂的波动行为,并延伸到液体中约30 (A).对界面层的二维结构分析表明,固液转变层部分原子形成了二维固体团簇.从固体到液体,扩散系数从零逐渐增加到一个饱和值.在界面处附近,平行于界面方向的扩散系数明显比垂直于界面方向的大. 相似文献
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It is shown how that the combination of atomic deposition and nonlinear diffusion may lead, below a critical temperature, to the growth of nonuniform layers on a substrate. The dynamics of such a system is of the Cahn–Hilliard type, supplemented by reaction terms representing adsorption–desorption processes. The instability of growing uniform layers leads to the formation of nanostructures which correspond to regular spatial variations of substrate coverage. Patterns wavelengths and symmetries are selected by the dynamics and not by variational arguments. For temperatures below critical, one should observe hexagonal arrays of high coverage dots on the surface of otherwise uniform growing layers. On decreasing further the temperature, these structures should transform into hexagonal arrays of low coverage domains, within the growing layer. 相似文献
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We propose a physical model which explains the existence of finite thickness wetting layers in epitaxially strained films. The finite wetting layer is shown to be stable due to the variation of the nonlinear elastic free energy with film thickness. We show that anisotropic surface tension gives rise to a metastable enlarged wetting layer. The perturbation amplitude needed to destabilize this wetting layer decreases with increasing lattice mismatch. We observe the development of faceted islands in unstable films. 相似文献
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《Physics letters. A》1986,114(3):148-152
The space-time evolution of the process of ultrarelativistic electron (positron) radiation in a thin layer of substance has been considered. It is shown that a series of effects occuring in the radiation of fast particles in thin amorphous and crystal plates are closely associated with the phenomenon of a prolonged existence of the particle in a half-bare state, i.e., when the particle stays to a large extent without its normal Coulomb field. 相似文献
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E. S. Minina A. B. Muratova J. J. Cerdá S. S. Kantorovich 《Journal of Experimental and Theoretical Physics》2013,116(3):424-441
In this work we present a characterization of the bidisperse ferrofluid microstructures that appear in thin layers of ferrofluid. These layers have been studied by a combination of Langevin dynamics simulations and density functional theory. Our results allow us to compare the microstructures that exist in quasi-two-dimensional ferrofluid nanolayers with the microstructures found in three-dimensional bidisperse ferrofluids. Furthermore, our results allow us to explain the influence of the geometry of the sample on the topology and size-distribution of the observed aggregates of magnetic nanoparticles. 相似文献
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T. A. Prokopieva V. A. Danilov S. S. Kantorovich 《Journal of Experimental and Theoretical Physics》2011,113(3):435-449
Using a fine weave of theoretical analysis and computer simulations, we found various aggregates of magnetic single-domain nanoparticles, which can form in a quasi-two-dimensional (q2D) ferrofluid layer at low temperatures. Our theoretical investigation allowed us to obtain exact expressions and their asymptotes for the energies of each configuration. Thus, for ferrofluid q2D layers it proved possible to identify the ground states as a function of the particle number, size, and other system parameters. Our suggested approach can be used for the investigation of ground state structures in systems with more complex interparticle interactions. 相似文献
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Xinwen Huang 《Applied Surface Science》2009,255(7):4274-4278
The effect of the amorphous thin layer on the surface growth of amorphous/crystalline binary multilayer films has been studied by using a continuum model. It is shown that both the surface roughness and the growth exponent of amorphous/crystalline binary multilayer films decrease with increasing thickness ratio between amorphous and crystalline layers. Our simulations have also revealed, in contrast to the monotonous rise in surface roughness observed in single-layer films grown on flat substrates, the surface growth of a multilayer film consists of two processes: interface smoothing and roughening, namely the film roughness decreases during the growth of amorphous thin layers but increases monotonously during the growth of crystalline thin layers. The observed interface smoothing and roughening can be obviously influenced by the change in the thickness ratio between amorphous and crystalline layers. The rise in thickness ratio between amorphous and crystalline layers enhances the interface smoothing effect but lowers the interface roughening effect and consequently shows a marked smoothing effect on the surface roughness. 相似文献
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I. V. Kuznetsova Yu. P. Morozova O. K. Bazyl' B. V. Korolev 《Russian Physics Journal》2000,43(7):608-613
The composition of the solvation sheath of a p-nitroaniline molecule in the ground state in mixed solvents (hexane+tetrachloromethane
and hexane+isopropyl alcohol) is determined based on the dependence of the ππ*-absorption band shift on the composition of
the binary solvent. The interaction of the nitro-group with isopropyl alcohol and water is considered based on results of
calculations by the method of intermediate neglect of differential overlap (INDO) and experimental data. It is shown that
when the hydrogen bond is formed, the lower singlet level corresponds to the ππ* state. Because of the high rate constant
of intercombination conversion, only phosphorescence is characteristic of p-nitroaniline.
Tomsk State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 86–91, July, 2000. 相似文献
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Lionel Agostini Michael Leschziner Jonathan Poggie Nicholas J. Bisek Datta Gaitonde 《Journal of Turbulence》2017,18(8):760-780
The properties of spectral subranges of scales in a boundary layer at Mach=2.3 and friction Reynolds number Reτ = 570 are investigated by analysing DNS data. One major aim is to examine whether footprinting and modulation of small-scale near-wall motions by outer large structures, observed at high Reynolds numbers, also pertain to this low-Reynolds-number case, or whether the logarithmic layer simply contains a continuous hierarchy of motions without specific outer scales playing a distinctive role. To this end, the spectrum of scales is decomposed into modes by application of the “Empirical Mode Decomposition”. The properties of different scales are then investigated by means of spectra, maps of isotropy/anisotropy parameters, the premultiplied derivative of the second-order structure function, correlation coefficients and joint probability density function (PDF), the last constructed from conditionally sampled data for the small-scale motions within the large-scale footprints. A clear commonality is identified between interactions in high-Reynolds-number channel flow and the present low-Reynolds-number boundary layer. 相似文献
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A long-wave model for thin layers consisting of two miscible fluids is presented. The model is a development of a simplified
2D model variant which considers the temperature and the concentration fields as linear functions on the vertical coordinate
and neglect the convective terms from the corresponding equations. Now, the 2D thin film equation is coupled to complete 3D
energy and mass conservations equation. We discuss the extended system in the linear approximation and in the initial nonlinear
stage. 相似文献
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V. M. Korovin 《Technical Physics》2013,58(12):1721-1729
A simple mathematical model of the initial stage of nonlinear evolution of the Rosenzweig instability in a thin layer of a nonlinearly magnetized viscous ferrofluid coating a horizontal nonmagnetizable plate is constructed on the basis of the system of equations and boundary conditions of ferrofluid dynamics. A dispersion relation is derived and analyzed using the linearized equations of this model. The critical magnetization of the initial layer with a flat free surface, the threshold wavenumber, and the characteristic time of evolution of the most rapidly growing mode are determined. The equation for the neutral stability curve, which is applicable for any physically admissible law of magnetization of a ferrofluid, is derived analytically. 相似文献
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I. I. Argatov 《Doklady Physics》2005,50(10):524-528
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S. V. Danilov V. A. Dovzhenko F. V. Dolzhanskii V. G. Kochina 《Journal of Experimental and Theoretical Physics》2002,95(1):48-56
The results of laboratory measurements of decaying quasi-two-dimensional turbulence in a thin liquid layer are considered. It is shown that the enstrophy-to-energy ratio decreases according to a power law on a certain decay interval. The exponent in the power law is a function of the Reynolds number. The enstrophy decay is found to be anomalously slow as predicted in a number of numerical studies. It is shown that the anomalous decay in the quasi-two-dimensional flow under investigation is not due to intense vortex formation as in the numerical decaying turbulence, but due to the limited range of scales on which a flow can be regarded as two-dimensional. 相似文献
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We used scanning tunneling microscopy (STM) to characterize PdO(101) thin films grown on Pd(111), and the structural changes that occur during isothermal decomposition. We find that the PdO(101) thin films have high-quality surface structures that are characterized by large, crystalline terraces with low concentrations of point defects. Small domains of single-layer oxide are also present on the top layer of relatively thick PdO(101) films grown at 500 K. The thinner PdO(101) films exhibit negligible quantities of such domains, apparently because new domains agglomerate rapidly as the film thickness decreases. We find that the isothermal decomposition rate of a PdO(101) film at 720 K exhibits an autocatalytic regime in which the rate of oxygen desorption increases as the oxide decomposes. Our STM results demonstrate that reduced sites created during oxide decomposition catalyze further PdO decomposition, and reveal strong kinetic anisotropies in the decomposition. The kinetic anisotropies produce one-dimensional reaction fronts that propagate preferentially along the atomic rows of the PdO(101) surface, resulting in the formation of long chains of reduced sites. We also find that reduced sites promote oxygen recombination in neighboring rows of the Pd(101) structure, causing loops and larger aggregates of reduced sites to form. The promotion of decomposition across the atomic rows can qualitatively explain the autocatalytic desorption kinetics. Finally, the STM images provide evidence that underlying PdO(101) layers transfer oxygen to reduced surface domains, thus producing large domains of PdO(101) islands that coexist with reduced domains as well as the larger PdO(101) terraces of the initial surface. Re-oxidation of the surface acts to sustain the autocatalytic decomposition kinetics, and provides a mechanism for oxygen atoms to ultimately evolve from the subsurface of the PdO(101) film. 相似文献
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《Physica D: Nonlinear Phenomena》1999,125(1-2):85-104
We consider an artificial reaction system whose components are binary strings. Upon encounter, two binary strings produce a third string which competes for storage space with the originators. String types or species can only survive when produced in sufficient numbers. Spatial interactions through introduction of a topology and rules for distance-dependent reactions are discussed. We observe various kinds of survival strategies of binary strings. 相似文献
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N. I. Stas’kov A. B. Sotsky L. I. Sotskaya A. N. Petlitskii 《Optics and Spectroscopy》2012,112(6):881-883
The solution of the inverse problem of spectral ellipsometry is obtained for titanium with a surface layer of titanium oxide that was formed as a result of thermal (450°C) oxidation of the metal substrate. Using the Drude-Zener and Cauchy dispersion models, it is shown that a rather thick (46 nm) inhomogeneous binary surface layer including about 23% of titanium and 77% of titanium oxide is present on the studied samples of pure polycrystalline titanium. A natural weakly absorbing surface layer with a thickness of 13 nm is on this layer. 相似文献