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1.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Мельникова, Светлана Владимировна, Лапташ Н. М.
Заглавие : Влияние атмосферной влажности на симметрию и фазовые переходы слоистых калиевых оксифторидов K2NbOF5·H2O
Место публикации : Физ. тверд. тела. - 2013. - Т. 55, Вып. 6. - С. 1142-1146
Примечания : Работа выполнена при финансовой поддержке гранта Президента РФ (НШ-4828.2012.2)
Аннотация: Выращены кристаллы K2NbOF5·H2O, проведены поляризационно-оптические исследования, измерены двулучепреломление и углы вращения оптической индикатрисы в интервале температур 100-400 K. Установлено, что при комнатной температуре этот слоистый кристалл в зависимости от степени влажности атмосферы может находиться в трех состояниях: A, B и C, различающихся симметрией и свойствами. Кристалл K2NbOF5·H2O в состоянии A, реализующийся при относительной влажности RH=90-100%, испытывает несобственный сегнетоэластический фазовый переход первого рода P 1=ftrightarrow C2/m, сопровождающийся сильными аномалиями оптических характеристик, двойникованием, появлением сдвиговой деформации x6 при температурах T2 downarrow =308 K и T2 uparrow =313 K. Наиболее устойчивое состояние K2NbOF5·H2O --- B (RH =20-90%) --- сохраняет моноклинную симметрию C2/m в области температур 100-370 K. В сухой атмосфере (RH =0-20%) или при T1~370 K кристалл становится безводным (K2NbOF5) с симметрией P4/nmm (состояние C). Различие кристаллов в состояниях A и B объясняется наличием или отсутствием молекул воды в межслоевых пространствах.20-90%) --- сохраняет моноклинную симметрию C2/m в области температур 100-370 K. В сухой атмосфере (RH =0-20%) или при T1~370 K кристалл становится безводным (K2NbOF5) с симметрией P4/nmm (состояние C). Различие кристаллов в состояниях A и B объясняется наличием или отсутствием молекул воды в межслоевых пространствах.
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2.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Mel'nikova S. V., Laptash N. M.
Заглавие : Influence of atmospheric humidity on the symmetry and phase transitions of layered potassium oxyfluorides K2NbOF5 · H2O
Место публикации : Phys. solid state: Springer, 2013. - Vol. 55, Is. 6. - P.1231-1235
Аннотация: Crystals of K2NbOF5 · H2O have been grown, polarization optical investigations have been performed, and the birefringence and rotation angle of the optical indicatrix have been measured in the temperature range 100–400 K. It has been found that, depending on the degree of atmospheric humidity, the layered K2NbOF5 · H2O crystal at room temperature can be in three states, namely, A, B, and C, which differ in symmetry and properties of the crystal. The K2NbOF5 · H2O crystal in the A state exists at a relative humidity RH = 90–100% and undergoes a first-order improper ferroelastic phase transition P 1ˉ ↔ C2/m, which is accompanied by strong anomalies of the optical characteristics, twinning, and shear strain x 6 at temperatures T 2 ↓ = 308 K and T 2 ↑= 313 K. The most stable state of the K2NbOF5 sdH2O crystal is the B state (RH = 20–90%), which retains the monoclinic symmetry C2/m in the temperature range 100–370 K. In a dry atmosphere (RH = 0–20%) or at T 1 ≈ 370 K, the crystal becomes anhydrous (K2NbOF5) with the symmetry P4/nmm (the C state). The difference between the crystals in the states A and B is explained by the presence or absence of water molecules in interlayer spaces.
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3.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Pichugin K. N., Sadreev A. F.
Заглавие : Symmetry breaking for transmission in a photonic waveguide coupled with two off-channel nonlinear defects
Место публикации : Phys. Rev. B: American Physical Society, 2011. - Vol. 83, Is. 4. - Ст.45109. - ISSN 1098-0121, DOI 10.1103/PhysRevB.83.045109
Примечания : Cited References: 50. - This work was partially supported by RFBR Grant No. 09-02-98005-"Siberia" and RFBR Grant No. 11-02-00289.
Предметные рубрики: CRYSTAL-CIRCUITS
LOCALIZED MODES
BISTABILITY
IMPURITIES
RESONANCE
CAVITIES
STATES
MEDIA
Аннотация: We consider light transmission in a two-dimensional (2D) photonic crystal waveguide coupled with two identical nonlinear defects positioned symmetrically aside the waveguide. With the coupled mode theory, we show three scenarios for the transmission. The first one inherits the linear case and preserves the symmetry. In the second scenario, the symmetry is broken because of different light intensities at the defects. In the third scenario, the intensities at the defects are equal but phases of complex amplitudes are different. That results in a vortical power flow between the defects similar to the dc Josephson effect if the input power over the waveguide is applied and the defects are coupled. All of these phenomena agree well with computations based on an expansion of the electromagnetic field into optimally adapted photonic Wannier functions in a 2D photonic crystal.
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4.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Giant optical vortex in photonic crystal waveguide with nonlinear optical cavity
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 85, Is. 16. - Ст.165305. - ISSN 1098-0121, DOI 10.1103/PhysRevB.85.165305
Примечания : Cited References: 43. - The work is partially supported by RFBR grant 12-02-00483. We thank D. N. Maksimov and K. N. Pichugin for assistance in the manuscript preparation.
Предметные рубрики: SYMMETRY-BREAKING
FIBER
MICROCAVITIES
COUPLER
INSTABILITIES
GRATINGS
MODES
LIGHT
Аннотация: We consider light transmission in a directional photonic crystal waveguide that holds a nonlinear defect with two resonant dipole modes within the light propagation band. For the defect positioned on the center line of the waveguide, there are two ways to break the mirror symmetry with respect to either light intensity or light phase. The latter results in a giant vortex of the Poynting vector of the power current within the defect exceeding the input current by, at least, two orders of magnitude. We also consider the breaking of symmetry relative to the mirror reflection with respect to the cross-sectional axis of the waveguide when light is injected equally into both ends of the waveguide. This leads to different light outputs determined by the vorticity of the optical vortex.
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5.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : All-optical manipulation of light in X- and T-shaped photonic crystal waveguides with a nonlinear dipole defect
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 86, Is. 7. - Ст.75125. - ISSN 1098-0121, DOI 10.1103/PhysRevB.86.075125
Примечания : Cited References: 38. - The work is partially supported by Integration Project of Siberian Branch of RAS (Project No. 29) and RFBR Grant No. 12-02-000094. We thank D. N. Maksimov for critical reading of the manuscript.
Предметные рубрики: SPONTANEOUS SYMMETRY-BREAKING
FIBER
CAVITIES
SYSTEM
FIELDS
Аннотация: We consider light transmission in X- and T-shaped photonic crystal waveguides which hold nonlinear defect with two resonant dipole modes. By use of the coupled-mode theory and by numerical solution of the Maxwell equations for the transverse-magnetic (TM) light mode, we show two stable types of the solutions. The first type has no cross talk, while the second type does owe to nonlinearity of the defect. We show also that direct path transmission processes in the waveguides play an important role for breaking of symmetry.
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6.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F.
Заглавие : Symmetry breaking in photonic crystal waveguide coupled with the dipole modes of a nonlinear optical cavity
Место публикации : J. Opt. Soc. Am. B: Optical Society of America, 2012. - Vol. 29, Is. 10. - P.2924-2928. - ISSN 0740-3224
Примечания : Cited References: 17. - This work is partially supported by the Integration Project of the Siberian Branch of the Russian Academy of Sciences (RAS) (project no. 29) and the Russian Fund of Basic Research (RFBR) grant 12-02-000094. We thank D. N. Maksimov for assistance in the manuscript preparation.
Аннотация: We present stable symmetry breaking solutions in a nonlinear optical cavity with dipole eigenmodes embedded into the propagation band of a directional photonic crystal waveguide for symmetric injecting condition. We demonstrate how this phenomenon can be exploited for all-optical switching of light transmission from the one side of the waveguide to another by application of input pulses. When the light injected to both sides of the waveguide has equal intensities but different phases, we reveal a wealth of new solutions. (c) 2012 Optical Society of America
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7.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Dolgov O. V., Efremov D. V., Korshunov M. M., Charnukha A., Boris A. V., Golubov A. A.
Заглавие : Multiband description of optical conductivity in ferropnictide superconductors
Место публикации : J. Supercond. Nov. Magn. - 2013. - Vol. 26, Is. 8. - P.2637-2640. - ISSN 1557-1939, DOI 10.1007/s10948-013-2150-3
Ключевые слова (''Своб.индексиров.''): effects of disorder--multiband superconductivity--optical conductivity--effects of disorder--experimental datum--multi-band superconductors--multiband superconductivity--novel superconductor--order parameter symmetry--paramagnetic impurity--single-band superconductors--optical conductivity--paramagnetism--superconductivity--superconducting materials
Аннотация: We study optical properties of the multiband superconductors with an s В± order parameter symmetry. By comparing results of our theory with experimental data on optical conductivity for Ba0.68K 0.32Fe2As2 single crystals, we show that satisfactory description of the novel superconductors can be obtained only considering a strong electron-boson coupling. We reexamine the effect of disorder and demonstrate that multiband superconductors are more robust with respect to it than naively expected by simple analogy with paramagnetic impurities in single-band superconductors. Moreover, disorder may give rise to new effects, in particular to a phase transition s В±s ++. We discuss how the systematic study of disorder impact on the density of states and the optical conductivity may provide information on the underlying order parameter structure. В© 2013 Springer Science+Business Media New York.
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8.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Maksimov D. N., Sadreev A. F.
Заглавие : Symmetry breaking in binary chains with nonlinear sites
Место публикации : Phys. Rev. E. - 2013. - Vol. 88, Is. 3. - Ст.032901. - P. - ISSN 1539-3755, DOI 10.1103/PhysRevE.88.032901
Аннотация: We consider a system of two or four nonlinear sites coupled with binary chain waveguides. When a monochromatic wave is injected into the first (symmetric) propagation channel, the presence of cubic nonlinearity can lead to symmetry breaking, giving rise to emission of antisymmetric wave into the second (antisymmetric) propagation channel of the waveguides. We found that in the case of nonlinear plaquette, there is a domain in the parameter space where neither symmetry-preserving nor symmetry-breaking stable stationary solutions exit. As a result, injection of a monochromatic symmetric wave gives rise to emission of nonsymmetric satellite waves with energies differing from the energy of the incident wave. Thus, the response exhibits nonmonochromatic behavior. В© 2013 American Physical Society.
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9.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Fialko O., Delattre M.C., Brand J., Kolovsky A. R.
Заглавие : Nucleation in finite topological systems during continuous metastable quantum phase transitions
Место публикации : Phys. Rev. Lett.: American Physical Society, 2012. - Vol. 108, Is. 25. - Ст.250402. - ISSN 0031-9007, DOI 10.1103/PhysRevLett.108.250402
Примечания : Cited References: 31. - We acknowledge stimulating discussions with Jean-Sebastien Caux and Lincoln Carr. A. K. thanks Massey University for hospitality. O. F., M. C. D., and J. B. were supported by the Marsden Fund (Contract No. MAU0910) administrated by the Royal Society of New Zealand.
Предметные рубрики: SYMMETRY-BREAKING
VORTEX NUCLEATION
BROKEN SYMMETRY
THERMALIZATION
SUPERFLUID
DYNAMICS
STATE
Аннотация: Finite topological quantum systems can undergo continuous metastable quantum phase transitions to change their topological nature. Here we show how to nucleate the transition between ring currents and dark soliton states in a toroidally trapped Bose-Einstein condensate. An adiabatic passage to wind and unwind its phase is achieved by explicit global breaking of the rotational symmetry. This could be realized with current experimental technology.
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10.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Bulgakov E. N., Sadreev A. F., Pichugin K. N.
Заглавие : Ligth-induced breaking of symmetry in photonic crystal waveguides with nonlinear defects as a key for all-optical switching circuits
Место публикации : Spontaneous symmetry breaking, self-trapping, and Josephson oscillations/ ed. B. A. Malomed: Springer, 2013. - P.89-124. - (Progress in optical science and photonics; Vol. 1). - ISSN 978-3-642-21206-2, DOI 10.1007/10091_2011_1
Аннотация: We consider light transmission in 2D photonic crystal waveguide coupled with two identical nonlinear defects positioned symmetrically aside the waveguide. We show that with growth of injected light power there is a breaking of symmetry by two ways. In the first way the symmetry is broken because of different light intensities at the defects. In the second way the intensities at the defects are equaled but phases of complex amplitudes are different. That results in a vortical power flow between the defects similar to the DC Josephson effect if the input power over the waveguide is applied and the defects are coupled. As application of these phenomena we consider the symmetry breaking for the light transmission in a T-shaped photonic waveguide with two nonlinear defects. We demonstrate as this phenomenon can be explored for all-optical switching of light transmission from the left output waveguide to the right one by application of input pulses. Finally we consider the symmetry breaking in the waveguide coupled with single defect presented however by two dipole modes.
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11.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Chubukov A. V., Maiti S., Korshunov M. A., Maier T., Hirschfeld P.J.
Заглавие : Evolution of symmetry and structure of the gap in Fe-based superconductors with doping and interactions
Коллективы : APS March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA), American Physical Society March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA)
Место публикации : Bull. Amer. Phys. Soc. - 2012. - Vol. 57, № 1. - P.316
Аннотация: We present a detailed study of the symmetry and structure of the pairing gap in Fe-based superconductors. We treat them as quasi-2D systems, decompose the pairing interaction into s− wave and d− wave channels and into contributions from scattering between different Fermi surfaces and analyze how each scattering evolves with doping and input parameters. We verify that each interaction is well approximated by the lowest angular harmonics and use this simplification to analyze the interplay between the interaction with and without spin-fluctuation components, the origin of the attraction in the s± and d x 2 −y 2 channels, the competition between them, the nature of angular dependence of the s± gaps along the electron Fermi surface, the conditions under which s± gap develops nodes, and the origin of superconductivity in heavily electron- or hole-doped systems, when only Fermi surfaces of one type are present. In particular, we find that with increased electron and hole doping, the competition from d− wave grows. In the case of strong hole doping, there is some ambiguity over the leading solution, but in the case of strong electron doping, d− wave emerges as clear winner.
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12.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Maiti, Saurabh, Korshunov M. M., Chubukov A.
Заглавие : Gap Symmetry in KFe2As2
Коллективы : APS March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA), American Physical Society March Meeting (2012 ; 27 Feb.-2 March; Boston, Massachusetts, USA)
Место публикации : Bulletin of the American Physical Society. - 2012. - Vol. 57, № 1. - P.316
Аннотация: We revisit the issue of the gap symmetry in KFe 2 As 2 , which is an Fe-pnictide superconductor with only hole pockets. Previous theoretical studies mostly argued for a d− wave gap in KFe 2 As 2 since transport and thermodynamic measurements point to the presence of the gap nodes. However, a d− wave gap is inconsistent with recent laser-based angle-resolved photoemission measurements. We propose the scenario for a nodal s− wave superconductivity induced by a non-magnetic intra-band and inter-band interactions between fermions near the two hole pockets at Γ point. The superconducting gap that we find changes sign between the two hole pockets at Γ point and has cos4θ angular dependence and can have accidental nodes on one or several hole pockets. We argue that strong angle dependence is the consequence of near-degeneracy between inter-pocket and intra-pocket interaction on the hole pockets. We also provide a connection between the the relative phase of 4θ oscillations and the shapes of the Fermi surface and discuss the implications in the light of photoemission and tunneling experiments.
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13.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Krylov A. S., Krylova S. N., Laptash N. M., Vtyurin A. N.
Заглавие : Raman scattering study of temperature induced phase transitions in crystalline ammonium heptafluorozirconate, (NH4)3ZrF7
Место публикации : Vib. Spectrosc.: Elsevier Science BV, 2012. - Vol. 62. - P.258-263. - ISSN 0924-2031, DOI 10.1016/j.vibspec.2012.07.003
Примечания : Cited References: 31. - This work was partly supported by integration project SB RAS No 28, Russian Foundation for Basic Research project No 11-02-98002-r_siberia, No 12-02-00056, SS-4828.2012.2. The authors are grateful to Dr. I.N. Flerov for helpful discussions. The assistance of Dr. S. Skokov is sincerely appreciated.
Предметные рубрики: VIBRATIONAL-SPECTRA
X-RAY
DISORDER
DIFFRACTION
ELPASOLITE
SYMMETRY
RB2KSCF6
IF7
Ключевые слова (''Своб.индексиров.''): raman spectroscopy--phase transition--ammonium heptafluorozirconate--low temperature
Аннотация: This paper reports on a Raman spectroscopy investigation of phase transitions in (NH4)3ZrF7 crystal. Raman spectra were obtained and analyzed in a wavenumber range from 3800 to 15 cm−1 and in the temperature range from 7 to 360 K. The anomalies caused by a series of subsequent structural phase transitions have been analyzed. A soft phonon mode restoring in the distorted phase was found. The spectral changes observed in the current study are similar to those typically found in phase transitions near a tricritical point. The spectral changes in the middle wavenumber range, 700–150 cm−1, indicate that the phase transitions are due to structural ordering of pentagonal ZrF73− bipyramids. Spectral data also show that a phase transition near 225 K is accompanied by an increase of the unit cell volume. In addition, spectral changes in the range of internal vibrations of ammonium ions indicate that the ion's motion slows down with decrease of temperature.
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14.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Maiti S., Korshunov M. M., Chubukov A.V.
Заглавие : Gap symmetry in KFe2As2 and the cos 4θ gap component in LiFeAs
Место публикации : Phys. Rev. B: American Physical Society, 2012. - Vol. 85, Is. 1. - Ст.14511. - ISSN 1098-0121, DOI 10.1103/PhysRevB.85.014511
Примечания : Cited References: 49. - We are thankful to S. Borisenko, S. Davis, R. Fernandes, P. Hirschfeld, I. Eremin, D. Evtushinsky, A. Kordyuk, K. Kuroki, Y. Matsuda, A. Rost, M. Vavilov, and V. Zabolotnyy for useful discussions. This work was supported by NSF-DMR-0906953 (SM and AVC) and by the Humboldt Foundation (AVC). MMK is grateful for support from RFBR (Grant No. 09-02-00127), the Presidium of RAS program N5.7, the FCP Scientific and Research and Educational Personnel of Innovative Russia for 2009-2013 (GK P891 and GK16.740.12.0731), and the President of Russia (Grant No. MK-1683.2010.2).
Предметные рубрики: SUPERCONDUCTING GAPS
IRON
Аннотация: We revisit the issue of the gap symmetry in KFe2As2, which is an Fe pnictide superconductor with only hole pockets. Previous theoretical studies mostly argued for a d−wave gap in KFe2As2 since transport and thermodynamic measurements point to the presence of the gap nodes. However, a d-wave gap is inconsistent with recent laser-based angle-resolved photoemission measurements. We propose a scenario for a nodal s−wave superconductivity induced by a nonmagnetic intraband and interband interactions between fermions near hole pockets. The superconducting gap changes sign between the hole pockets and has cos4θ angular dependence and accidental nodes on one or several hole pockets. We argue that strong angle dependence is the consequence of near-degeneracy between interpocket and intrapocket interaction on the hole pockets. We also analyze the cos4θ angular dependence of the gap in other Fe pnictides and compare theoretical results with the photoemission experiments of LiFeAs.
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15.

Вид документа : Статья из сборника (однотомник)
Шифр издания :
Автор(ы) : Sadreev A. F., Bulgakov E. N., Maksimov D. N., Pichugin K. N.
Заглавие : Symmetry breaking in open quantum nonlinear systems
Место публикации : Nonlinear phenomena in complex systems: from nano to macro scale: Springer, 2015. - P.235-252. - (NATO science for peace and security series C: Environmental security). - DOI 10.1007/978-94-017-8704-8_17. - ISBN 978-94-017-8704-8. - ISBN 978-94-017-8703-1
Аннотация: We consider symmetry breaking in the simplest open quantum nonlinear systems such as dimer and plaquette of four nonlinear sites coupled with linear tight-binding wires. If the solution is stationary, the total Hilbert space can be projected into the inner states of the dimer or plaquette by the Feshbach procedure. That derives a nonlinear analogue of the Lippmann-Schwinger equation with injected wave as a source. By neglecting radiation shifts the Lippmann-Scwinger equation limits to the coupled mode theory equations widely used in optics. We show three scenarios for the transmission through the nonlinear quantum systems. The first one inherits the linear case and preserves the symmetry. In the second scenario the symmetry is broken because of different intensities at the dimer sites. In the third scenario the intensities at the sites are equaled but phases of complex wave function are different. That results in a vortical power flow between the nonlinear sites similar to the DC Josephson current. We show how the phenomenon of symmetry breaking can used for switching of outputs symmetrically coupled to the quantum dimer . Also we reveal a domain in the parameter space where none of stationary solutions exist. As a result injection of a monochromatic symmetric wave gives rise to emission of nonsymmetric satellite waves with energies different from the energy of the incident wave. Thus, the response exhibits non monochromatic behavior.
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16.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Prodaivoda G. T., Aleksandrov K. S., Vyzhva S. A., Nazarenko L. V.
Заглавие : Computation of effective elastic constants in anisotropic microseamy rocks
Место публикации : Geol. Geofiz. - 2000. - Vol. 41, Is. 3. - P.436-449. - ISSN 0016-7886
Примечания : Cited References: 25
Предметные рубрики: WAVE-PROPAGATION
SYMMETRY
Ключевые слова (''Своб.индексиров.''): anisotropy--modeling--orientation of microcracks--elastic waves
Аннотация: A generalized method of conditional moments for computation of effective elastic constants of anisotropic rocks with spatially oriented microcracks is considered. The method involves an additional operation of averaging of known solution data for a modeled rock of orthorhombic structure with ellipsoidal microcracks whose semiaxes are oriented along the coordinate axes. The averaging is performed using the distribution function of rock microcrack orientations, which is expanded into a series in terms of generalized spherical functions. The expansion coefficients are determined by an experiment. In calculating the effective elastic constants of anisotropic rocks, there are no constraints on the concentration of microcracks. We have studied the parameters of azimuthal anisotropy of elastic-wave velocities in modeled amphibolites with ellipsoidal hornblende grains oriented along the coordinate axes and with three-planar and spatially oriented systems of microcracks. The obtained results agree with experimental data of ultrasonic determinations of elastic constants for amphibolite samples.
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17.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Prodaivoda G. T., Aleksandrov K. S.
Заглавие : Elastic symmetry and anisotropic parameters of specimens of Archean gneisses and Kola superdeep-borehole amphibolites
Место публикации : Geol. Geofiz. - 1998. - Vol. 39, Is. 3. - P.375-385. - ISSN 0016-7886
Примечания : Cited References: 22
Предметные рубрики: ROCKS
Ключевые слова (''Своб.индексиров.''): kola superdeep borehole--gneisses--amphibolites--elastic symmetry--anisotropy--bulk elastic waves--microfracture orientation
Аннотация: Using an invariant-polarization ultrasound method, we have studied the velocities of elastic waves in the gneisses and amphibolites of the second rock mass of the Archean complex of the Kola superdeep borehole (7622-9456 m) and calculated the determinate components of acoustic tensor and elastic-constant tensor and their symmetry. The symmetry of the studied structures is shown to be rhombic and triclinic. The stereoprojections of mineral's crystallographic orientation and normals to microfractures are built by the data on the inversion of the azimuthal dependence of elastic constants.
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18.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volcov V. A., Kovalev Y. G., Fokina N. P., Ovchinnikov S. G., Chernov V. K., Vasiliev A. D., Aleksandrov K. S.
Заглавие : Tl-based high-T(C) superconductor with cubic symmetry
Коллективы : International conference on the physics of transition metals
Место публикации : Int. J. Mod. Phys. B. - 1993. - Vol. 7, Is. 1-3. - P.162-165. - ISSN 0217-9792, DOI 10.1142/S0217979293000366
Примечания : Cited References: 3
Аннотация: Ceramic samples of the system Tl-Pb-Sr-Ca-Ba-Cu-O-F have been prepared by modification of standard Tl-based ceramics by BaF2. A cubic structure with parameter a = 6.04 A is found by powder X-ray analysis. Both electric and magnetic data reveal superconductivity with T(ci) = 117 K. Electron conductivity is found at T = 300 K.
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19.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Aleksandrov K. S.
Заглавие : Phase-transitions and distortions of the structure in the family of crystals related to alpha-k2so
Место публикации : Kristallografiya. - 1993. - Vol. 38, Is. 1. - P.128-139. - ISSN 0023-4761; Crystallogr. Rep.
Примечания : Cited References: 38
Предметные рубрики: X-RAY
EXPECTED STRUCTURES
A2BX4 COMPOUNDS
TEMPERATURE
(NH4)2BEF4
CHEMISTRY
DISORDER
SYMMETRY
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20.

Вид документа : Статья из журнала
Шифр издания :
Автор(ы) : Volkov V. E., Vasiliev A. D., Kovalev Y. G., Ovchinnikov S. G., Fokina N. P., Chernov V. K., Aleksandrov K. S.
Заглавие : Electron-conductivity high-Tc superconductor with cubic symmetry
Место публикации : JETP Letters. - 1992. - Vol. 55, Is. 10. - P.616-620. - ISSN 0021-3640
Примечания : Cited References: 4
Аннотация: Ceramic samples which exhibit a superconductivity with T(c) = 117 K have been synthesized in the Tl-Pb-Sr-Ca-Ba-Cu-O-F system. According to x-ray diffraction, the symmetry of the samples is cubic, with a lattice constant a = 6.04 angstrom. At room temperature the conductivity is of the n type.
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