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Marchenko, V S,Panwar, A,Reznik, S N,Ryu, C M IOP 2017 Plasma physics and controlled fusion Vol.59 No.9
<P>In a recent work, we have shown that the plasma flow around the magnetic island can excite the beta-induced Alfvén eigenmode (BAE) (Marchenko <I>et al</I> 2016 <I>Nucl. Fusion</I> <B>56</B> 106021). In the present communication, it is shown that coupling of this primary BAE and magnetic island generates secondary geodesic acoustic mode (GAM), which has the frequency and mode structure identical to those of the primary BAE. The fixed GAM/BAE amplitude ratio, determined by the plasma neutrality, is comparable with the plasma/magnetic pressure ratio. This nonlinear coupling can be responsible for axis-symmetric modes, which accompany island-driven Alfvénic modes observed on HL-2A tokamak (Chen <I>et al</I> 2013 <I>Nucl. Fusion</I> <B>53</B> 113010).</P>
Excitation of the beta-induced Alfvén eigenmode by a plasma flow around the magnetic island
Marchenko, V.S.,Panwar, A.,Reznik, S.N.,Ryu, C.M. IOP 2016 Nuclear fusion Vol.56 No.10
<P>It is well known that the rotation of a magnetic island in the reference frame of plasma guiding centers generates parallel electron current outside the island, which is induced by the geodesic curvature of a magnetic field (Smolyakov <I>et al</I> 2007 <I>Phys. Rev. Lett</I>. <B>99</B> 055002). It is shown in the present work that the surface part of this current located at the island separatrix can drive a pair of counter-propagating, tearing-parity, beta-induced Alfvén eigenmodes, which have the same helicity as that of the magnetic island and form a standing wave in the island frame. These Alfvénic modes can accompany tearing activity in tokamak discharges without energetic particles.</P>
Modeling of the Formation of Long Grooves in the Seabed by Grounded Ice Keels
Marchenko, Aleksey The Society of Naval Architects of Korea 2003 Journal of ship and ocean technology Vol.7 No.4
The motion of passively floating body, whose keel can have a contact with seabed soil, is under the consideration. The body simulates ice ridge floating in shallow water. The force of seabed soil reaction applied to the grounded keel is estimated taking into account soil embankment near the grounded keel. Two-dimensional trajectories of body motion, the shape of the grooves in seabed and the height of soil embankment are calculated when the motion of the body is caused by semidiurnal $M_2$ tide. The influence of wave amplitude and bottom slope on the shapes of body trajectory and the grooves are analyzed.
IT - Education In The Context Of Educational Activities
Marchenko, Olga,Noskova, Margaryta,Fedorenko, Igor,Semenog, Olena,Vovk, Myroslava,Romanyshyn, Ruslana International Journal of Computer ScienceNetwork S 2021 International journal of computer science and netw Vol.21 No.6
The article is based on a model, in the context of which there are two fundamental building blocks of basic library skills and skills in the use of information technology. The former are formed within the framework of educational programs for users of academic libraries, the latter are formed within the framework of initiatives such as the European Computer Driving License. Between the basic and the highest levels of the concept of "information literacy" there are seven heading skills and attributes, the repeated practice of which leads from the position of a competent user to an expert level of reflection and critical awareness of information as an intellectual resource. Freshmen will likely be at the beginning of the arrow, probably practicing only the first four skills, while graduate students and young scientists will be closer to the end and will use seven skills.
Nonlinear Phenomena In Resonant Excitation of Flexural-Gravity Waves
Marchenko, Aleksey The Society of Naval Architects of Korea 2003 Journal of ship and ocean technology Vol.7 No.3
The influence of nonlinear phenomena on the behavior of stationary forced flexural-gravity waves on the surface of deep water is investigated, when the perturbation of external pressure moves with near-resonant velocity. It is shown that there are three branches of bounded stationary solutions turning into asymptotic solutions of the linear problem with zero initial conditions. For the first time ice sheet destruction by turbulent fluctuations of atmosphere pressure in ice adjacent layer in wind conditions is studied.
Excitation of the beta-induced Alfvén eigenmodes by a magnetic island
Marchenko, V.S.,Reznik, S.N. International Atomic Energy Agency 2009 Nuclear fusion Vol.49 No.2
<P>It is shown that a pair of counter-propagating, tearing-parity, beta-induced Alfvén eigenmodes (BAEs) with low mode numbers can be excited in the presence of a magnetic island of the same helicity. The instability mechanism consists of the reversal of ion Landau damping due to island-induced modification of the equilibrium distribution function. This instability seems to be responsible for the BAE excitation in ohmic plasmas with tearing mode activity at the FTU tokamak (Buratti P. <I>et al</I> <A article='0029-5515/45/11/027'>2005 <I>Nucl. Fusion</I> <B>45</B> 1446</A>).</P>
α-particle transport induced by Alfvén eigenmodes in the Helias reactor
International Atomic Energy Agency 2002 Nuclear fusion Vol.42 No.11
<P>It is shown that in the Helias reactor [1], depending on the ratio γ<SUB>L</SUB>/γ<SUB><I>d</I></SUB> with γ<SUB>L(d)</SUB> the linear growth (damping) rate of the Alfvén eigenmode (AE), there are three regimes of the transport of α-particles resonant with AEs. (i) For 1<γ<SUB>L</SUB>/γ<SUB><I>d</I></SUB><<10 the transport is determined solely by the pitch-angle scattering of αs trapped by an AE. In this regime τ<SUB>α</SUB>>>τ<SUB>s</SUB>, with τ<SUB>α(s)</SUB> the α-particle confinement (slowing down) time. (ii) For γ<SUB>L</SUB>/γ<SUB><I>d</I></SUB>∼10 the dominant transport mechanism is the adiabatic convection of the slowing-down αs trapped by an AE, with particle `life time' in resonance with AE limited by pitch-angle scattering. In this regime τ<SUB>α</SUB>∼τ<SUB>s</SUB>. (iii) For γ<SUB>L</SUB>/γ<SUB><I>d</I></SUB>>> 10 the transport become stochastic with τ<SUB>α</SUB><<τ<SUB>s</SUB>.</P>
소재 제거율을 고려한 이송속도 가변형 NURBS 보간기
마르첸코 티혼,고태조,김희술,김정현 한국공작기계학회 2003 한국생산제조학회지 Vol.12 No.2
Conventionally used linear or circular interpolator is undesirable for the precision machining of 3D free-form surface as the following reasons: the transmission errors due to the huge number of data, discontinuity of segmentation, unsmooth motion speed. To this regard, modern CNC machine tools are designed with the function of machining arbitrary parametric curves.. However, these systems don't consider the adaptive federate, which dominates the quality of the machining process. This paper proposes a NURBS interpolator for the constant material removal rate. That is accomplished by the variable feedrate using curvature of curve. The curvature-compensated feederate system has important potential applications in ensuring part accuracy and protecting cutting tool. The simulated results show it can be applicable to the real machining.
마르첸코티혼,백대균,고태조,김희술 한국공작기계학회 2002 한국공작기계학회 춘계학술대회논문집 Vol.2002 No.-
Increasing demands on precision machining of 3D free-form surface have necessitated the tool smoothly varying feedrates. This paper presents one of algorithm for adaptive feedrate on NURBS curve. Since the algorithm for calculating variable feedrate depends on the curvature of curve, it permits to get constant material removal rate. It means that machine tools or cutting tool can be protected in terms of tool chipping, vibration, etc.