检索结果-南通市图书馆

西北地质 1991年第A期12卷 43-46页

作者： popov,vs 陈会鑫

乌拉尔——蒙古活动带Sn—Mo成矿省中的含矿花岗岩

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

吉林地质科技情报 1996年第5期 7-7页

作者： popov,vs

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

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

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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

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

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

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)

Method of reduction of dimensionality in contact and friction mechanics:A linkage between micro and macro scales

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2013年第1期1卷 41-62页

作者： Valentin L.popov Berlin University of Technology Berlin 10623Germany

Computer simulations have been an integral part of the technical development process for a long time *** tribology is one of the last fields in which computer simulations have,until now,played no significant *** is primarily due to the fact that investigating tribological phenomena requires considering all spatial scales from the macroscopic shape of the contact system down to the *** the present paper,we give an overview of the previous work on the so-called method of reduction of dimensionality(MRD),which in our opinion,gives a key for the linking of the micro-and macro-scales in tribological *** in contact mechanics is based on the mapping of some classes of three-dimensional contact problems onto one-dimensional contacts with elastic *** equivalence of three-dimensional systems to those of one-dimension is valid for relations of the indentation depth and the contact force and in some cases for the contact *** arbitrary bodies of revolution,MRD is exact and provides a sort of“pocket edition”of contact mechanics,giving the possibility of deriving any result of classical contact mechanics with or without adhesion in a very simple way.A tangential contact problem with and without creep can also be mapped exactly to a one-dimensional *** can be shown that the reduction method is applicable to contacts of linear visco-elastic bodies as well as to thermal effects in *** method was further validated for randomly rough self-affine surfaces through comparison with direct 3D *** means a huge reduction of computational time for the simulation of contact and friction between rough surfaces accounting for complicated rheology and *** MRD,not only is the dimension of the space reduced from three to one,but the resulting degrees of freedom are independent(like normal modes in the theory of oscillations).Because of this independence,the method is predestinated for parallel calculation on

关键词： contact mechanics rough surfaces static friction sliding friction elastomers adhesion rolling dynamic tangential contacts reduction of dimensionality scale linkage

Active control of friction by transverse oscillations

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Friction 2019年第1期7卷 74-85页

作者： J.BENAD K.NAKANO V.L.popov M.popov Technische Universit?t Berlin Yokohama National University National Research Tomsk Polytechnic University National Research Tomsk State University

The present paper is devoted to a theoretical analysis of sliding friction under the influence of in-plane oscillations perpendicular to the sliding direction. Contrary to previous studies of this mode of active control of friction, we consider the influence of the stiffness of the tribological contact in detail and show that the contact stiffness plays a central role for small oscillation amplitudes. In the present paper we consider the case of a displacement-controlled system, where the contact stiffness is small compared to the stiffness of the measuring system. It is shown that in this case the macroscopic coefficient of friction is a function of two dimensionless parameters— a dimensionless sliding velocity and dimensionless oscillation amplitude. In the limit of very large oscillation amplitudes, known solutions previously reported in the literature are reproduced. The region of small amplitudes is described for the first time in this paper.

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

Degenerations of Jordan Algebras and“Marginal”Algebras

维普期刊数据库

同方期刊数据库评论

在线全文

学校读者我要写书评

暂无评论

Algebra Colloquium 2021年第2期28卷 281-294页

作者： Ilya Gorshkov Ivan Kaygorodov Yury popov Sobolev Institute of Mathematics NovosibirskRussia Universidade Federal do ABC CMCCSanto AndreBrazil Universidade Estadual de Campinas CampinasBrazil

We describe all degenerations of the variety ■3 of Jordan algebras of dimension three over *** particular,we describe all irreducible components in ■*** every n we define an n-dimensional rigid“marginal”Jordan algebra of level ***,we discuss marginal algebras in associative,alternative,left alternative,non-commutative Jordan,Leibniz and anticommutative cases.

关键词： Jordan algebra degeneration rigid algebra irreducible component marginal algebra

Absolute parameters of the three totally-eclipsing W UMa stars NSvs 2443858,NSvs 780649 and V1098 Her

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Research in Astronomy and Astrophysics 2021年第9期21卷 124-134页

作者： Velimir popov Francesco Acerbi Carlo Barani Department of Physics and Astronomy Shumen University115 Universitetska str.9700 ShumenBulgaria Via Zoncada 51 26845 Codogno(LO)Italy Via Molinetto 35 26845 Triulza di Codogno(LO)Italy

We present the first photometric analysis of three totally-eclipsing W UMa binaries,NS vs2443858,NSvs 780649 and V1098 *** absolute astrophysical parameters of the stellar components were determined by means of Gaia distances and light curve *** results show that:(ⅰ)Two of the systems,NSvs 2443858 and V1098 Her,are of A subtype while the obtained temperature of the secondary component of NSvs 780649 indicates that it is a W-subtype system;(ⅱ)The estimated mass ratios approach the lower limit of the mass ratio assumed by researchers in recent years so our targets could be classified as extreme mass ratio binary(EMRB)systems;(ⅲ)All the systems have deep contact configurations,so they also are deep low mass ratio(DLMR)systems;(ⅳ)The components of our systems are stars of F and G spectral type and undergo total eclipses;(ⅴ)The sum 0.871 M⊙of the component masses of NSvs 780649 is below the mass limit of 1.0-1.2 M⊙assumed for the known contact binary stars.

关键词： techinques:photometric binaries:eclipsing stars:fundamental parameters stars:individual