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91.
The problem of sound propagation in a spatially inhomogeneous underwater sound channel is considered. The effect of ray escape, i.e., the ray incidence on the absorbing bottom due to the chaotic swing of rays, is studied. With the use of the Poincaré map and maps of escape, the relation of ray escape to the properties of the phase space of the set of ray equations is demonstrated. It is found that the maximum escape occurs under the vertical resonance conditions, i.e., at the resonance of the ray oscillations in the waveguide with the vertical oscillations of the sound velocity perturbation. A qualitative theory of the vertical resonance is developed. It is shown that the ray escape considerably shortens the time spreading of the signal. 相似文献
92.
The morphology and structure of Pt deposited on a WSe2(0 0 0 1) van der Waals surface have been investigated by reflection high energy electron diffraction and scanning tunneling microscopy. At room temperature, the initial growth is characterized by the formation of three-dimensional fcc Pt islands with (1 1 1) orientation. In contrast, at higher temperatures of about 450 °C the formation of a novel chemically ordered Pt-Se alloy is observed. Based on the diffraction patterns, a tetragonal DO22-type structure of a Pt3Se compound is suggested. With increasing Pt thickness, this chemically ordered alloy disappears and an additional superstructure occurs, which is accompanied by the coalescence of the islands. The observed superstructure is attributed to a strong Se diffusion towards the growth surface, forming most likely a PtSe2 alloy with the CdI2-type layered structure on the top surface. Due to the lateral lattice mismatch between the Pt(1 1 1) layers and the PtSe2(1 1 1) top layer, a Moiré pattern with a period of 1.1 nm is created, which might be used as a long-range atomic pattern for further nanostructure growth. 相似文献
93.
Nina P. Gritsan Alexander Yu. Makarov Andrey V. Zibarev 《Applied magnetic resonance》2011,41(2-4):449-466
This paper gives a brief overview of a new approach to chalcogen–nitrogen heterocyclic π-radicals, particularly 1,2,3- and 1,3,2-benzodithiazolyls, based on thermolysis or photolysis of closed-shell precursors (such as 1,3,2,4-benzodithiadiazines and their 1-Se congeners, 1,2,4,3,5- and 1,3,5,2,4-benzotrithiadiazepines, and some other sulfur–nitrogen rings and cages). The approach allows obtaining radicals hardly accessible or inaccessible in other ways, especially, fluorinated radicals. The identity of radicals prepared is confirmed by electron paramagnetic resonance spectroscopy in combination with density functional theory calculations. 相似文献
94.
95.
Makarov V. N. Mazukhina S. I. Vasil'eva T. N. Kremenetskaya I. P. Korytnaya O. P. 《Russian Journal of Applied Chemistry》2001,74(12):2045-2050
The reaction of nickel(II) and copper(II) sulfate solutions with carbonate flour prepared from carbonatite was simulated thermodynamically and studied experimentally. The conditions under which open systems and those isolated from the atmosphere attain stationary state (carbonatite consumption and grain size, pH of the medium) were determined. The ionic and mineral composition of new formations and the theoretically possible degree of purification were found. 相似文献
96.
97.
R. Wordel M. Baier G. Schneider F. E. Wagner V. E. Antonov E. G. Ponyatovsky Yu. Kopilovskii E. F. Makarov 《Hyperfine Interactions》1990,54(1-4):891-894
Hydrides of iron and cobalt prepared at pressures between 4.0 and 9.5 GPa were studied by57Fe Mössbauer spectroscopy at 4.2 K. Iron hydride was found to be nearly stoichiometric FeH. The two iron sites in its dhep lattice have hyperfine fields of 33.8 and 28.8 T. Practically the same results were found for the deuteride. In hep ε-CoHx, the hyperfine fields decrease with hydrogen content by about 6% betweenx=0 andx=0.5. In all studied hydrides the electron densities at the57Fe nuclei are smaller than in the pure metals. 相似文献
98.
Simulation of elastic–plastic deformation and fracture of materials at micro-, meso- and macrolevels
P. V. Makarov S. Schmauder O. I. Cherepanov I. Yu. Smolin V. A. Romanova R. R. Balokhonov D. Yu. Saraev E. Soppa P. Kizler G. Fischer S. Hu M. Ludwig 《Theoretical and Applied Fracture Mechanics》2001,37(1-3)
Physical Mesomechanics of materials is a new branch of mechanics that focuses attention on a mesovolume of loaded material. It is a macro particle in classical continuum mechanics and its behavior under load is equivalent to the bulk. The structural elements for a particular application requires specific models while the computational techniques have to be developed.These research groups have been studying heterogeneous materials behavior at the mesolevel under different types of loading. Hierarchical models are developed to study deformation and fracture of solids at the micro- meso- and macrolevels. Taken into account are the influence of micro- and mesostructure of loaded material in relation to its macro behavior.This work focuses on unifying the method of approach to be supported by tests and calculations. In particular, deformation and fracture mechanisms at the micro-, meso- and macrolevels are examined for metals and composites. 相似文献
99.
We prove that on the Sobolev spaces HN0 H^N_0 (N S 0) of 1-periodic functions in HNloc (\Bbb R) H^N_{loc} ({\Bbb R}) with average 0, the Korteweg-deVries equation (KdV) admits global Birkhoff coordinates. 相似文献
100.