V. N. Skokov

Self-organization of a critical state and 1/fα-fluctuations at film boiling

Abstract 1/ f and 1/ f 2 -fluctuations have been first revealed by experiment at film boiling on a vertically oriented platinum heater. Fluctuations of 1/ f α -spectrum have been observed over both a wide range of governing parameters and a band of five decimal orders. The experimental results testify to a possible self-organized critical behaviors of a dynamical system at nonequilibrium phase transitions.

Noise-induced transition and \(\frac{1}{f}\) fluctuations while intersecting nonequilibrium phase transitions

non in nature [1]. It is observed in radio engineering devices, in solid-state physics, in fracture mechanics, in chemical reactions, etc. An intrinsic feature of systems with noise lies in the fact that the power spectrum in this case is inversely proportional to the frequency f. Such a dependence suggests that a considerable part of the fluctuation energy is associated with slow processes and, moreover, implies a possibility of huge catastrophic surges in the system.

1/f noise in oscillatory modes of combustion

Fluctuation processes whose power spectrum varies inversely proportional to the frequency (flicker noise, or 1/f noise) are a subject of thorough investigations for many years. First discovered in electric circuits, 1/f noise is observed in systems of various nature (geophysical, astrophysical, biological, ecological, etc.). Presently, extensive data concerning the properties of the flicker noise in particular systems (see, e.g., reviews [1, 2]) are accumulating. For example, one of the most known studies involves a model according to which the 1/f noise is the consequence of the superposition of independent Lorentz sources having the relaxation-time distribution function g(τ) ~ τ–1 [1, 2]. Thermal models are also widely discussed in which the thermal conduction mechanisms [3] are considered to be responsible for the 1/f noise in solids. Explaining experimental manifestations of 1/f noise in particular physical systems can be problematic when using the current models; we run into problems in attempting to explain the origin of the 1/f noise in systems of different natures. In spite of long-standing efforts, no commonly accepted picture of this phenomenon has been available until now and the mechanisms leading to fluctuations obeying the 1/f spectrum are often unclear. Therefore, the problem of searching for new systems with flicker noise and of constructing new models for this phenomenon remains urgent.

Self-organization of critical fluctuations and 1/f spectra under conditions of critical boiling

The results are given of an experimental investigation of the dynamics of vaporization under conditions of changing modes of water boiling on a platinum wire heater and with local Joule heating of aqueous electrolytic solutions. It is found that thermal fluctuations with spectral characteristics inversely proportional to frequency (flicker or 1/f noise) are generated under conditions of film boiling on a vertically oriented heater in a wide range of loads. In the region of loss of stability of film boiling, frequency spectra vary in inverse proportion to the square of the frequency. In experiments in Joule heating of aqueous electrolytes, the flicker noise is observed in the region of changing modes of vapor generation. The experimental results are indicative of the self-organization of the critical behavior of the system in the case of nonequilibrium phase transitions.

1/fNoise under Conditions of Interaction between Phase Transitions

Vibrational modes of combustion under conditions of combustible liquid boiling before the reaction front are investigated experimentally. Fluctuations are observed with the spectral density inversely proportional to frequency (1/fnoise). This phenomenon is associated with the intersection and interaction of nonequilibrium phase transitions. A mathematical model is suggested of the emergence of fluctuations with a 1/fspectrum under conditions of interaction between subcritical and supercritical phase transitions in a distributed system.

Regular and chaotic thermal oscillations in current-carrying thin HTSC films

We present the results of an experimental study of the dynamics of thermal self-oscillations of a normal zone in thin films of high-temperature superconductors (HTSC) connected to an external circuit with an inductance and cooled by boiling nitrogen. The response of the system to a harmonic driving force has been studied. Spectral and dynamical characteristics of various oscillative regimes have been determined. It is shown there arises a state of a deterministic chaos in some range of driving frequencies and amplitudes. An effective of synchronization of periodic self-oscillations of a normal zone and thermo-hydrodynamical oscillations caused by the boiling of liquid nitrogen near a film surface has been recognized.

Self-sustained oscillations and chaotic transitions in current-carrying thin HTSC-films cooled by boiling nitrogen

Abstract An increase of the relaxation oscillations in the nonlinear system of a thin film of a high-temperature superconductor (HTSC) connected to an external electric circuit with an inductance, boiling nitrogen, has been shown experimentally. With increasing dc bias voltage one could observe an upset of the periodic oscillations and a transition to chaotic ones. Also, relaxation oscillations and chaos transitions have been studied experimentally in the case when a dc bias voltage was added to a harmonic component.