119 research outputs found
A model solution of the generalized Langevin equation: Emergence and Breaking of Time-Scale Invariance in Single-Particle Dynamics of Liquids
It is shown that the solution of generalized Langevin equation can be
obtained on the basis of simple comparison of the time scale for the velocity
autocorrelation function of a particle (atom, molecule) and of the time scale
for the corresponding memory function. The result expression for the velocity
autocorrelation function contains dependence on the non-Markovity parameter,
which allows one to take into account memory effects of the investigated
phenomena. It is demonstrated for the cases of liquid tin and liquid lithium
that the obtained expression for the velocity autocorrelation function is in a
good agreement with the molecular dynamics simulation results.Comment: Dedicated to the memory of Prof. Renat M. Yulmetye
Use of liquid grystals for metal machining
The paper presents results of measurements of surface roughness of holes reamed in steel and cast iron workpieces, when mineral industrial oil with and without liquid crystals additives was used as coolant for reaming. Four types of twisted nematic liquid crystals (cholesterol esters) were tested: cholesterol valerate, cholesterol caproate, cholesterol stearate and cholesterol oleate. The concentration of the liquid crystals in oil was 0.5% by oil volume. The dependence of average roughness Ra of the reamed surface on coolant composition was establishe
Universal Approach to Overcoming Nonstationarity, Unsteadiness and Non-Markovity of Stochastic Processes in Complex Systems
In present paper we suggest a new universal approach to study complex systems
by microscopic, mesoscopic and macroscopic methods. We discuss new
possibilities of extracting information on nonstationarity, unsteadiness and
non-Markovity of discrete stochastic processes in complex systems. We consider
statistical properties of the fast, intermediate and slow components of the
investigated processes in complex systems within the framework of microscopic,
mesoscopic and macroscopic approaches separately. Among them theoretical
analysis is carried out by means of local noisy time-dependent parameters and
the conception of a quasi-Brownian particle (QBP) (mesoscopic approach) as well
as the use of wavelet transformation of the initial row time series. As a
concrete example we examine the seismic time series data for strong and weak
earthquakes in Turkey () in detail, as well as technogenic
explosions. We propose a new way of possible solution to the problem of
forecasting strong earthquakes forecasting. Besides we have found out that an
unexpected restoration of the first two local noisy parameters in weak
earthquakes and technogenic explosions is determined by exponential law. In
this paper we have also carried out the comparison and have discussed the
received time dependence of the local parameters for various seismic phenomena
Relaxation time scales in collective dynamics of liquid alkali metals
In this paper the investigation of the dynamical processes of liquid alkali
metals is executed by analyzing the time scales of relaxation processes in
liquids. The obtained theoretical dynamic structure factor for
the case of liquid lithium is found to be in excellent agreement with the
recently received inelastic X-ray scattering data. The comparison and
interrelation with other theories are given here. Finally, an important part of
this paper is the confirmation of the scale uniformity of the dynamic processes
in liquid alkali metals predicted by some previous molecular dynamic simulation
studies
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