49 research outputs found
Numerically simulated 3D-structures of the fluctuating fields
Numerical simulation of a structure of the fluctuating field appearing at a kinetic
stage of the phase transition is performed for the systems with scalar
and two-component (complex) order parameters. It is found that the ordering
process is accompanied by a large-scale filamentary structure of
the fluctuating field. The dense local groups and chains of the nuclei are
created in the system. A complicated topology of the ordering is found in
the system with complex order parameter. This system creates specific
“toroidal” vortices. Kinetic scenarios in 3D-space are compared with the
2D- and 1D projections of the analogous structures previously found.Чисельне моделювання структури флуктуюючого поля виникаючого на рівні кінетичного опису фазового переходу здійснено для систем з скалярним і дво-компонентним параметрами порядку. Виявлено, що процес впорядкування супроводжується велико-масштабною
волокнистою структурою флуктуюючого поля. В системі утворюються густі локальні групи і ланцюжки ядер. Виявлено складну топологію впорядкування в системі з двокомпонентним параметром порядку. Така система утворює складні тороїдальні завихрення. Кінетичний
сценарій в 3-вимірному просторі порівнюється з попередньо одержаними дво- і одновимірними проекціями аналогічних структур
Stationary vs. singular points in an accelerating FRW cosmology derived from six-dimensional Einstein-Gauss-Bonnet gravity
Six-dimensional Einstein-Gauss-Bonnet gravity (with a linear Gauss-Bonnet
term) is investigated. This theory is inspired by basic features of results
coming from string and M-theory. Dynamical compactification is carried out and
it is seen that a four-dimensional accelerating FRW universe is recovered, when
the two-dimensional internal space radius shrinks. A non-perturbative structure
of the corresponding theory is identified which has either three or one stable
fixed points, depending on the Gauss-Bonnet coupling being positive or
negative. A much richer structure than in the case of the perturbative regime
of the dynamical compactification recently studied by Andrew, Bolen, and
Middleton is exhibited.Comment: 9 pages, 20 figures, accepted in PL
Один из способов управления технологическим процессом дуговой сталеплавильной печи
В статье приводится описание комплексной математической модели, используемой для рационального управления работой дуговых электросталеплавильных печей.In article the description of the complex mathematical model used for rational management by work of arc electrosteel-smelting furnaces is resulted
Study of KS KL Coupled Decays and KL -Be Interactions with the CMD-2 Detector at VEPP-2M Collider
The integrated luminosity about 4000 inverse nanobarn of around phi meson
mass ( 5 millions of phi mesons) has been collected with the CMD-2 detector at
the VEPP-2M collider. A latest analysis of the KS KL coupled decays based on 30
% of available data is presented in this paper.
The KS KL pairs from phi meson decays were reconstructed in the drift chamber
when both kaons decayed into two charged particles. From a sample of 1423
coupled decays a selection of candidates to the CP violating KL into pi+ pi-
decay was performed. CP violating decays were not identified because of the
domination of events with a KL regenerating at the Be beam pipe into KS and a
background from KL semileptonic decays.
The regeneration cross section of 110 MeV/c KL mesons was found to be 53 +-
17 mb in agreement with theoretical expectations. The angular distribution of
KS mesons after regeneration and the total cross section of KL for Be have been
measured.Comment: 14 pages, 8 figure
Branch-and-lift algorithm for deterministic global optimization in nonlinear optimal control
This paper presents a branch-and-lift algorithm for solving optimal control problems with smooth nonlinear dynamics and potentially nonconvex objective and constraint functionals to guaranteed global optimality. This algorithm features a direct sequential method and builds upon a generic, spatial branch-and-bound algorithm. A new operation, called lifting, is introduced, which refines the control parameterization via a Gram-Schmidt orthogonalization process, while simultaneously eliminating control subregions that are either infeasible or that provably cannot contain any global optima. Conditions are given under which the image of the control parameterization error in the state space contracts exponentially as the parameterization order is increased, thereby making the lifting operation efficient. A computational technique based on ellipsoidal calculus is also developed that satisfies these conditions. The practical applicability of branch-and-lift is illustrated in a numerical example. © 2013 Springer Science+Business Media New York
1D model of precursors to frictional stick-slip motion allowing for robust comparison with experiments
We study the dynamic behaviour of 1D spring-block models of friction when the
external loading is applied from a side, and not on all blocks like in the
classical Burridge-Knopoff-like models. Such a change in the loading yields
specific difficulties, both from numerical and physical viewpoints. To address
some of these difficulties and clarify the precise role of a series of model
parameters, we start with the minimalistic model by Maegawa et al. (Tribol.
Lett. 38, 313, 2010) which was proposed to reproduce their experiments about
precursors to frictional sliding in the stick-slip regime. By successively
adding (i) an internal viscosity, (ii) an interfacial stiffness and (iii) an
initial tangential force distribution at the interface, we manage to (i) avoid
the model's unphysical stress fluctuations, (ii) avoid its unphysical
dependence on the spatial resolution and (iii) improve its agreement with the
experimental results, respectively. Based on the behaviour of this improved 1D
model, we develop an analytical prediction for the length of precursors as a
function of the applied tangential load. We also discuss the relationship
between the microscopic and macroscopic friction coefficients in the model.Comment: 13 pages, 14 figures, accepted in Tribology Letter
Conformational dynamics and internal friction in homopolymer globules: equilibrium vs. non-equilibrium simulations
We study the conformational dynamics within homopolymer globules by solvent-implicit Brownian dynamics simulations. A strong dependence of the internal chain dynamics on the Lennard-Jones cohesion strength ε and the globule size N [subscript G] is observed. We find two distinct dynamical regimes: a liquid-like regime (for ε ε[subscript s] with slow internal dynamics. The cohesion strength ε[subscript s] of this freezing transition depends on N G . Equilibrium simulations, where we investigate the diffusional chain dynamics within the globule, are compared with non-equilibrium simulations, where we unfold the globule by pulling the chain ends with prescribed velocity (encompassing low enough velocities so that the linear-response, viscous regime is reached). From both simulation protocols we derive the internal viscosity within the globule. In the liquid-like regime the internal friction increases continuously with ε and scales extensive in N [subscript G] . This suggests an internal friction scenario where the entire chain (or an extensive fraction thereof) takes part in conformational reorganization of the globular structure.American Society for Engineering Education. National Defense Science and Engineering Graduate Fellowshi