arXiv subjects

I. A. Shuda

Publications and source records attributed to I. A. Shuda.

8 recordsLinked to original sources

arXiv2020

Dislocation loops growth and radiation growth in neutron irradiated Zr-Nb alloys: rate theory modelling

A generalized model to study dislocation loops growth in irradiated binary Zr-based alloys is presented. It takes into account temperature effects, efficiencies of loops to absorb point defects dependent on the loop size, an influence of locality of grain boundary sink strength, and concentration of the alloying element. This model is used to describe the dynamics of loop radii growth in zirconium-niobium alloys under neutron irradiation at reactor conditions. A growth of both loop radii and strains is studied at different grain sizes, location from grain boundaries, and concentration of niobium. It is shown that locality of grain boundary sinks results in a non-uniform deformation of the crystal inside the grains. Additionally, an introduction of niobium as an alloying element decreases the loop radii but promotes the growth of local strains inside the grains.

cond-mat.mtrl-sci↗

arXiv2018

Phase field modelling voids nucleation and growth in binary systems

We present a comprehensive study of voids formation, nucleation and growth in a prototype model of binary alloys subjected to irradiation by using a combined approach based on phase field and rate theories. It is shown that voids formation is caused by interaction of irradiation-produced vacancies through elastic deformation of a lattice and vacancy coupling with composition field of the alloy. Phase diagrams illustrating the formation of states related to solid solution, phase decomposition, and patterning are obtained. Formation of voids from supersaturated ensemble of vacancies is accompanied by composition rearrangement of alloy components. It was found that elastic inhomogeneity leading to the formation of anisotropic precipitates in an initially prepared binary alloy results in the formation of a void super-lattice under irradiation. It was shown that voids nucleate and grow with dose according to diffusion controlled precipitation processes, where universal dynamics of voids growth is revealed. Estimations of main quantitative and statistical characteristics of voids by using material parameters relevant to most of alloys and steels give good agreement with experimental observations.

cond-mat.stat-mech↗

arXiv2011

Analytical and numerical studies of creation probabilities of hierarchical trees

We consider the creation conditions of diverse hierarchical trees both analytically and numerically. A connection between the probabilities to create hierarchical levels and the probability to associate these levels into a united structure is studied. We argue that a consistent probabilistic picture requires the use of deformed algebra. Our consideration is based on the study of the main types of hierarchical trees, among which both regular and degenerate ones are studied analytically, while the creation probabilities of Fibonacci, scale-free and arbitrary trees are determined numerically.

cond-mat.stat-mech↗

arXiv2010

Statistical field theories deformed within different calculi

Within framework of basic-deformed and finite-difference calculi, as well as deformation procedures proposed by Tsallis, Abe, and Kaniadakis to be generalized by Naudts, we develop field-theoretical schemes of statistically distributed fields. We construct a set of generating functionals and find their connection with corresponding correlators for basic-deformed, finite-difference, and Kaniadakis calculi. Moreover, we introduce pair of additive functionals, whose expansions into deformed series yield both Green functions and their irreducible proper vertices. We find as well formal equations, governing by the generating functionals of systems which possess a symmetry with respect to a field variation and are subjected to an arbitrary constrain. Finally, we generalize field-theoretical schemes inherent in concrete calculi in the Naudts spirit.

cond-mat.stat-mech↗

arXiv2010

Suppression of oscillations by Levy noise

We find analytical solution of pair of stochastic equations with arbitrary forces and multiplicative Lévy noises in a steady-state nonequilibrium case. This solution shows that Lévy flights suppress always a quasi-periodical motion related to the limit cycle. We prove that difference between stochastic systems driven by Lévy and Gaussian noises is that the Lévy variation $ΔL\sim(Δt)^{1/α}$ with the exponent $α<2$ is much less than the Gaussian one $ΔW\sim(Δt)^{1/2}$ in the $Δt\to 0$ limit. Moreover, this difference is shown to remove the problem of the calculus choice because related addition to the physical force is of order $(Δt)^{2/α}\llΔt$.

cond-mat.stat-mech↗

arXiv2009

Noise induced oscillations in non-equilibrium steady state systems

We consider effect of stochastic sources upon self-organization process being initiated with creation of the limit cycle. General expressions obtained are applied to the stochastic Lorenz system to show that departure from equilibrium steady state can destroy the limit cycle at certain relation between characteristic scales of temporal variation of principle variables. Noise induced resonance related to the limit cycle is found to appear if the fastest variations displays a principle variable, which is coupled with two different degrees of freedom or more.

cond-mat.stat-mech↗

arXiv2009

Self-similarity degree of deformed statistical ensembles

We consider self-similar statistical ensembles with the phase space whose volume is invariant under the deformation that squeezes (expands) the coordinate and expands (squeezes) the momentum. Related probability distribution function is shown to possess a discrete symmetry with respect to manifold action of the Jackson derivative to be a homogeneous function with a self-similarity degree $q$ fixed by the condition of invariance under $(n+1)$-fold action of the dilatation operator related. In slightly deformed phase space, we find the homogeneous function is defined with the linear dependence at $n=0$, whereas the self-similarity degree equals the gold mean at $n=1$, and $q\to n$ in the limit $n\to\infty$. Dilatation of the homogeneous function is shown to decrease the self-similarity degree $q$ at $n>0$.

cond-mat.stat-mech↗

arXiv2006

Hopf Bifurcation within Thermodynamic Representation

On base of Hamiltonian formalism, we show that Hopf bifurcation arrives, in the course of the system evolution, at creation of revolving region of the phase plane being bounded by limit cycle. A revolving phase plane with a set of limit cycles is presented in analogy with revolving vessel containing superfluid He$^4$. Within such a representation, fast varying angle is shown to be reduced to phase of complex order parameter whose module squared plays a role of action. Respectively, vector potential of conjugate field is reduced to relative velocity of movement of the limit cycle interior with respect to its exterior.

cond-mat.stat-mech↗