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161.
162.
V. P. Uryadov G. G. Vertogradov V. G. Vertogradov S. V. Kubatko A. A. Ponyatov Yu. N. Cherkashin I. V. Krasheninnikov V. A. Valov G. P. Komrakov A. V. Makarov D. V. Bredikhin 《Radiophysics and Quantum Electronics》2009,52(4):241-251
We describe the operation of an ionosonde/position finder with chirp modulation of the signal. The first results of measuring
the characteristics of short-wave radio signals scattered by artificial small-scale inhomogeneities, which were obtained by
means of an ionosonde/position finder on the IZMIRAN—“SURA”—Rostov-on-Don path are presented. It was found that under certain
ionospheric conditions, the angular and frequency selection of the scattered signals take place, in which case the signals
are observed simultaneously in several frequency intervals (mainly, in three, namely, 6–9.5 MHz, 10–12 MHz, and 15–18 MHz)
with different angles of incidence of radio waves in the vertical plane. In this case, the incidence angles were 20◦–35◦,
18◦–32◦, and 10◦–20◦ from the horizon for the first, second, and third frequency interval, respectively. Ionograms of oblique
sounding were modeled allowing for the scattering of radio waves by artificial small-scale inhomogeneities. It is shown that
at frequencies from 10 to 12 MHz, aspect conditions are fulfilled for the signals ducting along the high-angle beam (Pedersen
mode). At frequencies 15–18 MHz (higher than the maximum observable frequency of the forward signal on the path IZMIRAN—Rostov-on-Don),
aspect scattering conditions are fulfilled for the signals incident on a scattering area in the ascending part of the trajectory.
At low frequencies 6–9.5 MHz (below the maximum observed frequency of the forward signal on the IZMIRAN—Rostov-on-Don path),
the observable additional signals are caused by the scattering of radio waves by artificial inhomogeneities with subsequent
relfection of the scattered signal from the Earth on the “SURA”—Rostov-on-Don path.
Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 52, No. 4, pp. 267–278, April 2009. 相似文献
163.
R. A. Dilanyan S. S. Khasanov S. I. Bredikhin A. F. Gurov V. V. Kveder Yu. A. Osip’yan A. I. Shalynin 《Journal of Experimental and Theoretical Physics》2001,93(6):1239-1244
The structure and phase transitions of C60 crystals doped with lithium by injecting metal ions from the superionic crystal-C60 single crystal heterojunction under electrodiffusion conditions are reported. The sample experienced irreversible transitions resulting in the virtually complete disappearance of EPR signals and MW conduction in the temperature range 320–370 K. In this temperature interval, a new C60 phase was formed; the phase contained polymeric chains of C60 molecules along the crystallographic c axis and lithium clusters. The structure of this phase was determined. Annealing at 620 K restored the EPR signal and, according to the X-ray data, the initial cubic structure of pure C60. The X-ray pattern, however, contained additional diffraction peaks, which was evidence of the presence of one more phase with a structure yet unknown. 相似文献
164.
The paper presents the results of experimental research into the nonlinear acoustic properties of carbonate rocks depending on saturation. The linear acoustic properties of the same sample depending on saturation were presented earlier in Physical Acoustics. The previously obtained data point to the isotropy of the material, which makes it possible to restrict analysis to only two vibration modes. Responses for finite deformations were measured for the longitudinal and shear modes of an isotropic sample, which made it possible to analyze the nonlinear properties of macroscopic deformations with a change in volume and pure displacement. A heretofore unknown feature of the response was revealed for finite deformation values; it is related to the occurrence of a jumplike transition from classical nonlinearity to a hysteresis type of nonlinearity. As well, the deformation amplitude corresponding to the transition depends on fluid saturation. We studied the slow relaxation that occurs after long-term excitation of a sample with a deformation amplitude on the order of 10?6. Data are presented on relaxation for deformation from pure displacement and deformation with a change in volume, which made it possible to isolate features related to the type of deformation and to compare the obtained data with the earlier published theoretical model. These data are compared with the results of other research groups. 相似文献
165.
We characterize fields which are maximal with respect to the property of having two different linear orderings. The Galois group of the algebraic closure of a maximal field is described. An example of non-uniqueness of the maximal extension is mentioned.Translated from Matematicheskie Zametki, Vol. 7, No. 5, pp. 525–536, May, 1970. 相似文献
166.
167.
Congruently grown LiNbO3 single crystals show both high oxygen and lithium ion conductivity at temperatures above 500 °C. The high oxygen ion conductivity
can be understood in terms of a certain amount of oxygen vacancies already present in congruently grown LiNbO3 single crystals. Thermal treatment of LiNbO3 produces additional oxygen vacancies. The absorption bands introduced by this procedure are investigated. It is found that
the electrons which are generated during the reduction process are homogeneously distributed among all oxygen vacancies in
the LiNbO3 single crystals. The electrocoloration phenomenon in LiNbO3 single crystals is due to the process of injection of lithium ions and electrons into LiNbO3 by a double charge mechanism. Investigations of the optical and electrical properties of electrocolored LiNbO3 crystals are reported. It is shown that the absorption spectra of thermally and electrochemically reduced samples are identical
and that the origin of the absorption processes has to be therefore the same in both cases. That means, additional electrons
produced by the double charge injection of lithium ions and electrons are also homogeneously distributed among the oxygen
vacancies. This supports our hypothesis that a certain amount of oxygen vacancies has to be present already in as-grown LiNbO3 single crystals. 相似文献
168.
169.
170.