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Search Results: 1 - 10 of 462005 matches for " A. Tsvetkov "
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Effect of Electrical Defloration in Liquid and Solid Crystals  [PDF]
Valentin. A. Tsvetkov
Journal of Crystallization Process and Technology (JCPT) , 2013, DOI: 10.4236/jcpt.2013.33016
Abstract: Earlier we observed a movement of the front of ions in the bulk of an ordered LC sample across which the driven voltage was applied [1]. This movement looked as waving zigzag curvatures in the pattern of interference strips. It was shown that behind the movable front of ions, the LC volume was getting charged. The author has found out that, in his pioneer experiments made in 1974, he observed the similar electrooptical phenomena on a single crystal of niobate-strontium-barium (NBS). Just after applying driving voltage (in a crossed electrical field crystal sample geometry) a system of curved interference strips is arising, which is evolving for the time period of about ten minutes at the driven voltage being kept constant. The evolution of the interference stripes pattern near positive, negative electrodes and in middle part of sample occurs in some different ways. At the end of evolution the system of strips disappears and the sample becomes practically homogeneous. The described process can be observed only once at the first applying of the driving voltage. This process is caused by redistribution of charges frozen at the crystallization and which are having an opportunity of the recombination at the first applying of the driving voltage. The obtained results are discussed with the possible applying the given experimental technique for solid and LCs parameters studying.
Transverse optical Josephson plasmons, equations of motion
D. van der Marel,A. A. Tsvetkov
Physics , 2001, DOI: 10.1103/PhysRevB.64.024530
Abstract: A detailed calculation is presented of the dielectric function in superconducttors consisting of two Josephson coupled superconducting layers per unit cell, taking into account the effect of finite compressibility of the electron fluid. From the model it follows, that two longitudinal, and one transverse optical Josephson plasma resonance exist in these materials, for electric field polarization perpendicular to the planes. The latter mode appears as a resonance in the transverse dielectric function, and it couples directly to the electrical field vector of infrared radiation. A shift of all plasma frequencies, and a reduction of the intensity of the transverse optical Josephson plasmon is shown to result from the finite compressibility of the electron fluid.
Application of computer technologies in research of shifting soil mass to different underground mines / Применение компьютерных технологий при исследовании перемещений грунтового массива в окрестности различных подземных выработок
Tsvetkov V. K. / Цветков Владимир Константинович,Skorokhodova A. D. / Скороходова Алевтина Дмитриевна
Internet-Vestnik VolgGASU , 2006,
Abstract: By means of the program for shifting calculation, computing and graphical aids of mathematical package MathCAD the comparative analysis of vertical components of shifting around underground mines of different cross sections was held. Mines of rectangular - parabolic cross section and rectangular cross sections were considered as examples. / С использованием программы для вычисления перемещений, вычислительных и графи-ческих средств математического пакета Mathcad проведен сравнительный анализ вертикальных составляющих перемещений вокруг подземных выработок различных поперечных сечений. В качестве примера рассмотрены выработки прямоугольно-параболического и прямоугольного сечений.
Transverse optical plasmons in layered superconductors
D. van der Marel,A. Tsvetkov
Physics , 1996, DOI: 10.1007/BF02548125
Abstract: We discuss the possible existance of transverse optical plasma modes in superlattices consisting of Josephson coupled superconducting layers. These modes appear as resonances in the current-current correlation function, as opposed to the usual plasmons which are poles in the density-density channel. We consider both bilayer superlattices, and single layer lattices with a spread of interlayer Josephson couplings. We show that our model is in quantitative agreement with the recent experimental observation by a number of groups of a peak at the Josephson plasma frequency in the optical conductivity of La$_{1.85}$Sr$_{0.15}$CuO$_4$
Reflection symmetry instability at high spins in 162,164Yb
R. G. Nazmitdinov,J. Kvasil,A. Tsvetkov
Physics , 2007, DOI: 10.1016/j.physletb.2007.10.004
Abstract: A shape evolution of 162,164Yb in yrast states is traced using the self-consistent Skyrme Hartree-Fock calculations. We found that nonaxial octupole deformations (in particular, Y_{31} term) become favorable at large rotational frequencies (> 0.4 MeV) in 162Yb, while in 164Yb a nonaxial quadrupole shape is dominant at fast rotation. The cranked Nilsson model and random phase approximation are used to understand the dynamics of octupole correlations in both nuclei. We demonstrate that the disappearance of one of the octupole vibrational modes in the rotating frame gives rise to the nonaxial octupole deformations in 162Yb, while the octupole modes are nonzero in 164Yb.
Octupole deformations in actinides at high spins within the cranking Skyrme-Hartree-Fock approach
A. Tsvetkov,J. Kvasil,R. G. Nazmitdinov
Physics , 2000, DOI: 10.1088/0954-3899/28/8/305
Abstract: The cranked Skyrme III effective Hamiltonian is applied for the analysis of the rotational dependence of the quadrupole and octupole moments in Ra, Th, and U isotopes. A comparison of the intrinsic electric dipole moments calculated in the model with available experimental and theoretical values is presented. It is found that the non-axial octupole deformation $Y_{32}$ becomes favorable at high spins for the actinide nuclei.
Matrices Associated with Moving Least-Squares Approximation and Corresponding Inequalities  [PDF]
Svetoslav Nenov, Tsvetelin Tsvetkov
Advances in Pure Mathematics (APM) , 2015, DOI: 10.4236/apm.2015.514080
Abstract: In this article, some properties of matrices of moving least-squares approximation have been proven. The used technique is based on known inequalities for singular-values of matrices. Some inequalities for the norm of coefficients-vector of the linear approximation have been proven.
Photometric Evolution of SNe Ib/c 2004ao, 2004gk and 2006gi
A. Elmhamdi,D. Tsvetkov,I. J. Danziger,A. Kordi
Physics , 2010, DOI: 10.1088/0004-637X/731/2/129
Abstract: Photometric observations of three core collapse supernovae (SNe 2004ao, 2004gk and 2006gi), covering about 200 days of evolution are presented and analyzed. The photometric behaviour of the three objects is consistent with their membership of the envelope-stripped type Ib/c class. Pseudo-bolometric light curves are constructed. The corresponding measured $e$-folding times are found to be faster compared to the $^{56}$Co decay (i.e. 111.3 d), suggesting that a proportion of $\gamma$-rays increasing with time have escaped without thermalization, owing to the low mass nature of the ejecta. SN 2006gi has almost identical post maximum decline phase luminosities as SN 1999ex, and found to be similar to both SNe 1999dn and 1999ex in terms of the quasi-bolometric shape, placing it among the fast decliner Ib objects. SN 2004ao appears to fit within the slow decliner Ib SNe. SNe 2004ao and 2004gk display almost identical luminosities in the [50-100] days time interval, similar to SN 1993J. A preliminary simplified $\gamma -$ray deposition model is described and applied to the computed pseudo-bolometric light curves, allowing one to find a range in the ejecta and $^{56}$Ni masses. The optical and quasi-bolometric light curves, and the $B-V$ colour evolution of SN 2004gk are found to show a sudden drop after day 150. Correlating this fact to dust formation is premature and requires further observational evidence.
In-plane optical response of Bi2Sr2CuO6
A. A. Tsvetkov,J. Schuetzmann,D. van der Marel
Physics , 1997, DOI: 10.1103/PhysRevB.55.14152
Abstract: We report on infrared reflectivity measurements of the $ab$-plane response of superconducting Bi$_2$Sr$_2$CuO$_6$ single crystals. The frequency dependent conductivity has a maximum near 700 cm$^{-1}$ at room temperature, which shifts to lower frequency and merges with a Drude-peak below 100 K. We attribute the unusual behaviour of the mid-infrared conductivity to low frequency transitions between electronic bands of mainly BiO character near the $\overline{M}$ point. The linear temperature dependence of the low-frequency resistivity can be followed down to approximately 40 K where it saturates.
Wine Metabolite Profiling: Possible Application in Winemaking and Grapevine Breading in Bulgaria
I. Atanassov , Tz. Hvarleva , K. Rusanov , I. Tsvetkov , A. Atanassov
Biotechnology & Biotechnological Equipment , 2009, DOI: 10.2478/V10133-009-0011-9
Abstract: Metabolite profiling of wine provides important information for characterization of grape and wine typicity and quality. A brief overview on wine metabolite profiling using mass spectrometry technology is presented. Possibilities for application of metabolite profiling for winemaking and grapevine breeding in Bulgaria are pointed out.
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