Kharchenko Vasul' O.
Principal reasearch assistant;
Senior research assistant
PLACE OF BIRTH: Sumy, Ukraine
DATE OF BIRTH: 25 April 1984
STATUS: Married (to Alina Dvornichenko, son Ivan)
DEGREE: Ph.D. in Theoretical Physics (2009) Institute of Applied Physics NAS of Ukraine
POSITION: Research Fellow (November 2010 – present)
- Russian (native speaker)
- Ukrainian (native speaker)
- English (good)
EDUCATION a) Undergraduate and graduate studies
Institution: Sumy State University, Faculty of Mathematics and Mechanics, (2001–2006)
Degree: Master of Sciences in Mathematics (2006)
Field of Study: Modeling of Complex System
Thesis: “Multifractal representation of generalized statistical systems” (Diploma with Honor)
Thesis advisor: Prof. A.I. Olemskoi
b) Postgraduate study
Institution: Institute of Magnetism of the National Academy of Sciences of Ukraine, Department of Theoretical Physics, (2006–2009)
Degree: Ph.D. in Theoretical Physics (2009)
Field of Research:
- studying conditions of dissipative structures formation;
- transition to a chaotic regime in complex dynamical systems;
- multifractal analysis of complex statistical systems with self-similar phase space;
- non-extensive statistical systems;
- spatially extended stochastic systems;
- spatial organization of point defects;
- nanosize pattern formation;
- first principles (atomistic) calculations of electronic structure for crystals;
- subdiffusion and subdifusive ratchet transport.
- Analytical and numerical investigations.
Thesis: “Features of ordered structures formation in complex dynamic and statistical systems” Supervisor: Prof. E.D. Belokolos
- Additional stipend for excellent students, Sumy State University (2001–2006)
- Diploma with Honor, Sumy State University (2006)
- Postgraduate Studentship, Institute of Magnetism of the National Academy of Sciences of Ukraine (2006–2009)
- Second Prize of Ukrainian competition of young scientists in statistical physics and theory of condensed matter (2009)
- Prize of Verkhovna Rada of Ukraine for talented young scientists in fundamental and applied researches (2009)
2009 to present Research Fellow in the Department of Modeling of Radiation Effects and Microstructures Transformations in Construction Materials in Institute of Applied Physics of the National Academy of Sciences of Ukraine.
PRINCIPAL RESULTS (2006–2010)
- It was found that the main condition for stable periodic irradiation in semi-classical optical systems is an introduction of an additional nonlinear filter.
- It was found a domain of system parameters of a chaotic regime realization. It was proven that chaotic strange attractor is a monofractal with the fractal dimension 2.03 ± 0.02.
- For complex statistical systems relations between thermodynamical and multifractal functions of the corresponding self-similar phase space are found.
- We have shown that the system with non-extensive statistics can be transformed from the regime of anomalous to ordinary diffusion by means of the variation of the multiplicative noise exponent.
- Analysis of spatially extended stochastic systems with a field-dependent kinetic coefficient has shown that an internal noise leads to destabilization of disordered state in the early stages, whereas in stationary case such state is stable. It is found that an increase in the noise intensity leads to second-order phase transitions and uncritical transitions.
- We have found that external athermal flux having both regular and stochastic components influences crucially on pattern selection processes in periodic stochastic systems with the hyperbolic transport. It was shown that regular part of the external flux suppresses such processes, whereas it stochastic constituent promotes the pattern selection.
- Studying the ripple formation processes induced by the ion sputtering under stochastic conditions of illumination under assumption of stochastic nature of the ion beam it was found that as correlation properties of such multiplicative noise as the dispersion in the incidence angles around the average can reduce the domains of the control parameters where the ripples change their orientation at the fixed angle of incidence.
- Studying processes of epitaxial growth of pyramidal patterns in stochastic systems with interacting adsorbates within the framework of phase field approach based on the Burton- Cabrera-Frank model it was shown that the system dynamics depends crucially on the interaction strength of adatoms and the noise intensity of the total flux fluctuations. It was shown that at large interaction strength ε pyramidal patterns are observable, whereas at small ε there are no well pronounced patterns due to large possibility of adatoms to evaporate from the condensate. The noise action results in symmetrical distribution of the height with respect to it average (the height distribution becomes Gaussian).
- Studying overdamped stochastic model describing adsorption/desorption processes with nonequilibrium chemical reactions on the surface we have shown that internal noise satisfying the fluctuation-dissipation relation at small intensities governs transitions between ordered thermodynamical dense and diluted phases. These phase transitions are characterized by an increase of fluctuations of the coverage filed and correlation radius of spatial modulation. At large noise intensity a transition towards disordered phase with chaotic spatial configuration is realized. We have shown that organized stationary patterns are of nano-meter range. We define that both period of stationary structures and corresponding correlation radius depend on the noise intensity.
- Studying spatial organization of point defects in the generalized model of defects formation in elastic medium by taking into account defects production by irradiation influence and stochastic contribution for defects dynamics satisfying the fluctuation dissipation relation, we have found that depending on initial conditions and control parameters reduced to defects generation rate caused by irradiation, temperature and the stochastic source intensity different stationary structures of defects can be organized during the system evolution. Studying phase transitions between phases characterized by low- and high defect densities in stochastic system we have shown that such phenomena are described by mechanisms inherent in entropy-driven phase transitions. Stationary patterns are studied by amplitude analysis of unstable slow modes.
- Studying fluctuating tilt Brownian ratchets based on fractional subdiffusion in sticky viscoelastic media characterized by a power law memory kernel we have found that unlike the normal diffusion case the rectification effect vanishes in the adiabatically slow modulation limit and optimizes in a driving frequency range. It is shown also that anomalous rectification effect is maximal (stochastic resonance effect) at optimal temperature and can exhibit a surprisingly good quality. Moreover, subdiffusive current can flow in the counter-intuitive direction upon a change of temperature or driving frequency. The dependence of anomalous transport on load exhibits a remarkably simple universality. Studying subdiffusive ratchet transport in periodically and randomly flashing potentials we have found that the subdiffusive current is finite at zero temperature for random flashing and it can be finite for periodic flashing for a certain frequency window. Our study generalizes classical Brownian motors towards operating in sticky viscoelastic environments like cytosol of biological cells or dense polymer solutions.
- Studying the structural properties of Zr − xN b alloys at different values of the niobium concentration x with unit cells having BCC and HCP structures by ab-initio calculations we have found, that introduction of Zirconium atoms, as substitutional ones into the BCC crystal of Niobium leads to increase in the lattice constant. Obtained dependence of lattice constant versus Zirconium concentration in the BCC Niobium alloy is in good correspondence with empiric Vegard’s law and is quantitatively consistent with known experimental data. Introduction of substitutional Niobium atoms into HCP Zirconium crystal results to the decrease in the lattice constant and as as result to the increase in the structural relation c/a. The correspondence with the Vegard law, here, is realized only at small Niobium concentration (less then 20%), whereas obtained results are consistent with experimental ones. We have defined that at low (zero) temperature the critical value of the Niobium concentration in alloy Zr − N b, which defines the structural transformation HCP → BCC is (at.%N b)c 20%.
Грант Президента для молодих вчених (2012), Стипендія Президента України (2014), Грант Президента для молодих вчених (2017), Премія Президента України для молодих учених (2017), Ювілейна почесна грамота (2018),