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81.
82.
This paper presents theoretical investigation of the propagation of surface acoustic waves (SAWs) across the boundary between metallized (electrically shorted) and unmetallized (electrically open) regions on the surface of potassium niobate crystals. Potassium niobate is a very strong piezoelectric material and has the interesting property that only one type of SAW, namely a Rayleigh wave, can exist on unmetallized surface, where as two types of SAWs, namely Rayleigh and Bleustein-Gulyaev (BG), can exist on a metallized surface. Analysis shows that the Rayleigh wave propagates through the interface with very little change in amplitude or polarization. On the other hand, almost total reflection of the BG wave is expected. Details of the theoretical analysis and calculated results will be presented. 相似文献
83.
84.
Yu.?V.?PetukhovEmail author E.?L.?Borodina V.?G.?Burdukovskaya 《Acoustical Physics》2018,64(4):479-491
The paper considers the regular patterns that can be manifested in the behavior of the invariant of the spatial–frequency interference structure of an acoustic field in oceanic waveguides that are homogeneous and inhomogeneous along a track. Using the WKB and adiabatic approximations, an analytic expression is obtained for the invariant that, when certain conditions are fulfilled, reduces to the well-known classical expression independent of the mode numbers, their parity, or the emission frequency. It has been established that the approximate classical expression for the invariant correctly describes the slope of interference lines only in ranges of variation in the grazing angles of modes where the dependence of the cycle length of their corresponding Brillouin waves on the ray parameter is quite smooth and monotonic. The paper studies the formation of the spatial–frequency interference structure of an acoustic field propagating from a shallowwater isovelocity waveguide to a relatively deep-water waveguide with a near-surface sound channel. 相似文献
85.
Ulyana Borodina Anna Likhacheva Alexander Golovin Sergei Goryainov Sergey Rashchenko Andrey Korsakov 《高压研究》2018,38(3):293-302
A rare mineral shortite, Na2Ca2(CO3)3, occurs among groundmass minerals in unaltered kimberlites, which suggests its participation in the evolution of kimberlite system. This work presents a high pressure Raman spectroscopic study of natural shortite (Udachnaya east kimberlites) compressed in KBr up to 8?GPa in a diamond anvil cell. At ambient pressure the spectrum contains two strong bands related to symmetric C-O stretching vibrations, four in-plane bending modes, and several low-frequency modes of lattice vibrations. Upon the pressure increase up to 8?GPa, almost all the bands exhibit positive shift with the rate of 1–4?cm?1/GPa for the lattice modes and 3.6 and 3.9?cm?1/GPa for the C-O stretching modes. The shifts of Raman modes are rather regular, which implies the absence of reconstructive phase transitions within the studied pressure range, similarly to the behavior of nyerereite, a related carbonate mineral. However, minor anomalies in the ν/P and FWHM/P dependences, observed at about 2?GPa, suggest some rearrangement and disordering of carbonate groups. The obtained data can be used for the estimation of residual pressure in shortite-bearing inclusions in deep-seated minerals. 相似文献
86.
Vladimir A. Potapov Roman S. Ishigeev Svetlana V. Amosova Tatyana N. Borodina 《Tetrahedron letters》2019,60(6):475-479
Regioselective synthesis of a novel family of water-soluble 2H,3H-[1,3]chalcogenazolo[3,2-a]pyridin-4-ium derivatives was developed based on 2-pyridinesulfenyl and -selenenyl halides and unsaturated compounds. The annulation reactions with divinyl sulfide, selenide and N-vinylpyrrolidin-2-one led to addition of the chalcogen atom to the terminal carbon of the double bond whereas the reaction with tetravinylsilane proceeded with opposite regiochemistry. Tricyclic condensed heterocycles were obtained from 2,3-dihydrofuran and cycloalkenes. The products represent novel promising scaffolds for organic synthesis and possible drug discovery. 相似文献
87.
Kushchenko O. M. Rudyi S. S. Borodina L. N. Cherevkov S. A. Rozhdestvensky Yu. V. 《Optics and Spectroscopy》2020,128(8):1221-1225
Optics and Spectroscopy - Here we present the analyses of fractal properties of CdTe dendrites. The spectral characteristics of dendrites obtained at different acids of the initial solution were... 相似文献
88.
Acoustical Physics - Using approximate analytical calculations based on the WKB and adiabatic approximations for the mode representation of the field, as well as numerical simulation based on the... 相似文献
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90.
E. S. Buyanova S. A. Petrova Yu. V. Emel’yanova N. A. Borodina R. G. Zakharov V. M. Zhukovskii 《Russian Journal of Inorganic Chemistry》2009,54(6):864-872
Existence boundaries, structure, and transport parameters were studied for Bi4V2 ? x Cu x/2Ti x/2O11 ? x solid solutions. Doping levels within x = 0.025–0.15 distort the C2/m crystal lattice (this lattice is characteristic of individual the Bi4V2O11 phase) and lowers its symmetry to triclinic. The solid solutions with 0.25 ≤ x ≤ 0.30 crystallize in tetragonal space group I4/mmm. High-temperature X-ray diffraction and dilatometry measurements for Bi4V2 ? x Cu x/2Ti x/2O11 ? x (x ≤ 0.35) solid solutions verified the existence of three structural varieties within 298–1023 K. Electrical conductivity of BICUTIVOX was studied by impedance spectroscopy as a function of temperature, composition, and oxygen partial pressure. Equivalent circuits of cells were analyzed. Features of electrical conductivity versus temperature for the structural varieties are noted. Above 873 K, the solid solutions samples with x = 0.05 have the highest conductivity. At lower temperatures, higher conductivities are in the solid solutions that retain the γ phase in the low-temperature region. The dominant oxygen-ion conduction mechanism was discovered in the solid solutions. 相似文献