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New observations and transit solutions of the inflated exoplanets HAT-P-40b and HAT-P-51b

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Research in Astronomy and Astrophysics 2021年第2期21卷 157-160页

作者： Diana P.Kjurkchieva Nikola I.Petrov Velimir a.popov Department of Physics and Astronomy Shumen University115 Universitetska str.9700 ShumenBulgaria Institute of Astronomy and NAO Bulgarian Academy of SciencesTsarigradsko shossee 721784 SofiaBulgaria

We present high-precision photometric observations of the transiting exoplanets HAT-P-40 b and HAT-P-51 b by the Rozhen 2-m *** newly-observed transit of HAT-P-40 b is the first one with a complete *** orbital periods of the two targets were *** modeled the observed transits and found bigger stellar radii than those derived from the stellar *** planet radii of HATP-40 b and HAT-P-51 b obtained from our transit solutions are bigger than the values calculated by the empirical relations for Jupiter-mass and Saturn-mass planets *** values reveal the highlyinflated nature of the two targets,especially that of HAT-P-51 *** established that the best transit solutions correspond to a quadratic limb-darkening *** fitted limb-darkening coefficients of HAT-P-40 are close to the theoretical ones while those of HAT-P-51 are a little *** precise astrometric Gaia distances of the two targets are smaller by 6%–7%than the calculated values from the stellar *** propose the Gaia distances to be used for improvement of the stellar models as well as for more reliable calculation of the parameters of the known exoplanets.

关键词： (Stars )planetary systems-techniques photometric-Stars individual(HAT-P-40 and HAT-P-51)

The W UMa binaries USNO-A2.0 1350-17365531,V471 Cas,V479 Lac and V560 Lac:light curve solutions and global parameters based on Gaia distances

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Research in Astronomy and Astrophysics 2019年第1期19卷 141-148页

作者： Diana P.Kjurkchieva Velimir a.popov Yordanka Eneva Nikola I.Petrov Department of Physics and Astronomy Shumen University Medical University Institute of Astronomy and NAO Bulgarian Academy of Sciences

We present photometric observations in Sloan filters g′, i′of the eclipsing W UMa stars USNOA2.0 1350-17365531, V471 Cas, V479 Lac and V560 Lac. The sinusoidal-like O-C diagram of V471 Cas indicates the presence of a third body with mass 0.12 M_⊙(a red dwarf) at distance 897 R_⊙. The O-C diagram of V479 Lac reveals a period decrease of d P/dt =-1.69 × 10-6d yr-1. The results of the light curve solutions are:(i) the targets are overcontact binaries with small fill-out factors;(ii) their components are F–K stars, comparable in size, whose temperature differences are below 80 K;(iii) all targets undergo partial eclipses and to limit the possible mass ratios we carried out two-step q-search analysis. The target global parameters(luminosities, radii, masses) were obtained on the basis of their Gaia distances and the results of our light curve solutions. The obtained total mass of V560 Lac turns out to be smaller than the lower mass limit for presently known W UMa binaries of 1.0-1.2 M_⊙, i.e. this target is a peculiar overcontact system.

关键词： binaries:close binaries:eclipsing methods:data analysis stars:fundamental parameters stars:individual(USNO-A2.0 1350-17365531,V471 Cas,V479 Lac,V560 Lac)

V2551 Cyg:a pulsating star with enigmatic peculiarities

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Research in Astronomy and Astrophysics 2017年第7期17卷 57-66页

作者： Diana P.Kjurkchieva Velimir a.popov Dragomir V.Marchev Kenneth T.Menzies Nikola I.Petrov Department of Physics Shumen University IRIDA Observatory Rozhen NAO Tigh Speuran Observatory Institute of Astronomy and NAO Bulgarian Academy of Sciences

Intensive photometric and spectral observations of the variable star V2551 Cyg are *** light curve shape reveals that the target is a pulsating star, contrary to its previous classification as an eclipsing binary. The period and amplitude of the light curve, the amplitudes of color changes and the radial velocity curve of V2551 Cyg are similar to those of a high-amplitude δ Scuti variable. The target seems to pulsate with the fundamental mode. However, V2551 Cyg exhibits several important peculiarities：（i） the decreasing branch of its light curve is steeper than the increasing one;（ii） the radial velocity curve has a flat section in the phase range 0.7-1.2 and short increase of the negative radial velocity at phase 0.7;（iii） the rotational velocity is quite big for a HADS star;（iv） the Fourier coefficients of V2551 Cyg are quite different from those of HADS stars. The target classification is difficult due to these peculiarities.

关键词： stars variables delta Scuti - stars variables RR Lyrae - stars individual (V2551 Cyg)

Symmetry Reduction upon Size Mismatch:The Non-lcosahedral Intermetalloid Cluster [Co@Ge12]^3-

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Chinese Journal of Chemistry 2018年第12期36卷 1165-1168页

作者： Chao Liu Lei-Jiao Li Ivan a.popov Robert J.Wilson Cong-qiao Xu Jun Li Alexander I.Boldyrev Zhong-Ming Sun State Key Laboratory of Rare Earth Resource Utilization Changchun Institute of Applied ChemistryChinese Academy of Sciences5625 Renmin StreetChangchunJilin 130022China University of Chinese Academy of Sciences Beijing 100049China School of Materials Science and Engineering Research Center of Rare Earth and Inorganic Functional MaterialsNankai UniversityTianjin 300350China School of Chemistry & Environmental Engineering Chang chun University of Science & TechnologyChangchunJilin 130022China Department of Chemistry and Biochemistry Utah State University0300 Old Main HillLosanUtah84322-0300USA Fachbereich Chemie und Wissenschaftliches Zentrum fur Materialwissenschaften (WZMW) Philipps-Universtat MarburgHans-Meerwein-Straβe35043 MarburgGermany Department of Chemistry and Key Laboratory of Organic Optoelectronics & Molecular Engineering of Ministry of Education Tsinghua UniversityBeijing 200084China

A new complex comprising [Co@Ge12]3- cluster core was synthesized through the reaction of CoMe(PMe3)4 and K4Ge9 in ethylenediamine solution. The pseudo‐D5d geometry of this cluster can be viewed as structurally derived from an icosahedral cage via Jahn‐Teller effect, leading to notable bonding differences from Ih‐[M@E12]q− clusters (E = Sn, Pb with q = 2, 3). The [Co@Ge12]3- cluster represents a structural conundrum. On the basis of the geometric considerations it could be viewed as a sandwich complex. However, chemical bonding analysis revealed that there is a direct covalent multicenter bonding between the two pentagons, thus indicating that the structure should be viewed as an elongated icosahedron. Further theoretical calculations on [M@Ge12]3− (M = Rh, Ir, Mt) indicate that similar compounds of larger‐size metal atoms can drive the complete transformation of [M@Ge12]3− clusters from icosahedron structure to a sandwich one.

关键词： Zintl ions intermetalloid cluster icosahedron Sandwich complex

Web service for biodiversity estimation using remote sensing data

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International Journal of Digital Earth 2008年第4期1卷 367-376页

作者： Mikhail a.popov Nataliia N.Kussul Sergey A.Stankevich Anna A.Kozlova Andrii Yu.Shelestov Oleksii M.Kravchenko Mykhailo B.Korbakov Serhiy V.Skakun Scientific Centre for Aerospace Research of the Earth KievUkraine Department of Space Information Technologies and Systems Space Research Institute NASU-NSAUKievUkraine

This paper presents a technique for the assessment and mapping of land biodiversity by using remote sensing *** proposed approach uses a fuzzy model that encapsulates different ecological factors influencing *** imple... 详细信息

关键词： potential biodiversity index remote sensing data product pre-Black Sea region of the Ukraine web service

Gazeau–Klauder coherent states examined from the viewpoint of diagonal ordering operation technique

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Chinese Physics B 2016年第7期25卷 114-123页

作者： Dusan popov Romeo Negrea Miodrag popov Politehnica University Timisoara Department of Physical Foundations of Engineering 300223 Timisoara Romania Politehnica University of Timisoara Department of Mathematics 300006 Timisoara Romania politehnica University Timisoara Department of Architecture and Urban Planning 300223 Timisoara Romania

In this paper we investigate the Gazeau–Klauder coherent states using a newly introduced diagonal ordering operation technique, in order to examine some of the properties of these coherent states. The results coincide with those obtained from other purely algebraic methods, but the calculations are greatly simplified. We apply the general theory to two cases of Gazeau–Klauder coherent states： pseudoharmonic as well as the Morse oscillators.

关键词： coherent states operator technique density operator

Reduction of friction by normal *** of contact stiffness

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Friction 2017年第1期5卷 45-55页

作者： M.popov V.L.popov N.V.popov Berlin University of Technology Berlin 10623 GermanyTomsk Polytechnic University Tomsk 634050 RussiaTomsk State University Tomsk 634050 Russia Berlin University of Technology Berlin 10623 Germany

The present paper is devoted to a theoretical analysis of sliding friction under the influence of oscillations perpendicular to the sliding *** contrast to previous works we analyze the influence of the stiffness of the tribological contact in detail and also consider the case of large oscillation amplitudes at which the contact is lost during a part of the oscillation period,so that the sample starts to 'jump'.It is shown that the macroscopic coefficient of friction is a function of only two dimensionless parameters-a dimensionless sliding velocity and dimensionless oscillation *** function in turn depends on the shape of the contacting *** the present paper,analysis is carried out for two shapes:a flat cylindrical punch and a parabolic *** we consider 'stiff systems',where the contact stiffness is small compared with the stiffness of the *** role of the system stiffness will be studied in more detail in a separate paper.

关键词： sliding friction out-of-plane oscillation contact stiffness coefficient of friction active control of friction

Non-adhesive and adhesive contacts of an elastic quarter-or eighth-space with freely sliding sides

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Friction 2024年第9期12卷 2052-2063页

作者： Qiang LI Valentin L.popov Technische Universität Berlin Berlin 10623Germany

The contact of an elastic quarter-or eighth-space is studied under the condition that the movement of the side surface of the quarter-space is constrained:It can slide freely along the plane of the side surface but its normal movement is blocked(for example,by a rigid wall).The solution of this contact problem can be easily achieved by additionally applying a mirrored load to an elastic ***-adhesive contact and the Johnson–Kendall–Roberts(JKR)-type adhesive contact between a rigid sphere and an elastic quarter-space under such a boundary condition is numerically simulated using the fast Fourier transform(FFT)-assisted boundary element method(BEM).Contacts of an elastic eighth-space are investigated using the same *** on the position of the sphere relative to the side edge,different contact behavior is *** the case of adhesive contact,the force of adhesion first increases with increasing the distance from the edge of the quarter-space,achieves a maximum,and decreases further to the JKR-value in large distance from the *** enhancement of the force of adhesion compared to the half-space-contact is associated with the pinning of the contact area at the *** provide the maps of the force of adhesion and their analytical approximations,as well as pressure distributions in the contact plane and inside the quarter-/eighth-space.

关键词： quarter-space eighth-space adhesion edge effect boundary element method(BEM)

Reduction of friction by normal oscillations.Ⅱ.In-plane system dynamics

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Friction 2017年第2期5卷 534-535,536页

作者： Xinyu MAO Valentin L.popov Jasminka STARCEVIC Mikhail popov Technische Universit(a)t Berlin Berlin 10623 GermanyTsinghua University Beijing 100084 China Technische Universit(a)t Berlin Berlin 10623 GermanyTomsk Polytechnic University Tomsk 634050 RussiaTomsk State University Tomsk 634050 Russia Technische Universit(a)t Berlin Berlin 10623 GermanyTomsk State University Tomsk 634050 Russia

The influence of out-of-plane oscillations on friction is a well-known phenomenon that has been studied extensively with various experimental methods,e.g.,pin-on-disk ***,existing theoretical models have yet achieved only qualitative correspondence with *** we argue that this may be due to the system dynamics (mass and tangential stiffness) of the pin or other system components being *** paper builds on the results of a previous study [19] by taking the stiffness and resulting dynamics of the system into *** main governing parameters determining macroscopic friction,including a dimensionless oscillation amplitude,a dimensionless sliding velocity and the relation between three characteristic frequencies (that of externally excited oscillation and two natural oscillation frequencies associated with the contact stiffness and the system stiffness) are *** the limiting cases of a very soft system and a very stiff system,our results reproduce the results of previous *** between these two limiting cases there is also a resonant case,which is studied here for the first *** resonant case is notable in that it lacks a critical sliding velocity,above which oscillations no longer reduce *** obtained for the resonant case are qualitatively supported by experiments.

关键词： sliding friction out-of-plane oscillation stiffness system dynamics macroscopic friction coefficient