Stability of a random process with a 1/f spectrum under deterministic action

The stability of the resultant process, which appears upon the interaction of a random process having a 1/f spectrum with a deterministic action, is analyzed using the entropy maximum principle. Under the action of a harmonic force, stable resultant processes are divided into two branches depending on the amplitude of the harmonic force. Due to an exponential relaxation upon an increase in the damping coefficient, the resultant process acquires the Lorentz spectrum without high-energy low-frequency spikes.     

Comparison of Lithium Divertor Options for the DEMO-FNS Tokamak

Technical Physics - The choice of an idea for a divertor with evaporating liquid lithium that meets the requirements for removing the thermal load from the edge plasma and provides an acceptable...     

Effect of hydrogenation on spin-reorientation phase transitions and magnetic anisotropy constants of RFe11Ti single crystals (R=Lu, Ho, and Er)

The magnetic anisotropy and spin-reorientation phase transitions in single crystals of the RFe₁₁Ti (R=Lu, Ho, and Er) compounds and their hydrides are investigated. Measurements are carried out on capacitance and torque magnetometers. The magnetic anisotropy constants K ₁ and K ₂ are determined by the mathematical processing of experimental magnetization curves in terms of the phenomenological theory of the anisotropic ferromagnet magnetization. It is demonstrated that the hydrogenation strongly affects the magnitude and the sign of magnetic anisotropy constants, as well as the spin-reorientation phase transitions. The hydrogenation of the HoFe₁₁Ti compound leads to the change in sign of the magnetic anisotropy constant K ₁. The inference is made that a change in the atomic volume and the axial ratio c/a cannot result in the observed effects. A change in the magnetic anisotropy constants upon hydrogenation is primarily due to the change in the interaction of the quadrupole moment of a 4f electron subshell of rare-earth ions with surrounding ions of the crystal lattice and also with valence and conduction electrons.     

1/f Noise in a nonequilibrium phase transition: Experiment and mathematical model

The results of an experimental investigation of a high-power source of broad-band 1/f noise, which can be generated in a system of two interacting nonequilibrium phase transitions, are presented. This process takes place when a normal conductor-superconductor phase transition is superposed on the critical liquid-vapor transition in a boiling coolant. A mathematical model describing a nonequilibrium phase transition in a complicated nonlinear system with two interacting order parameters, which involves the conversion of white noise into stochastic fluctuations of the order parameters with 1/f and 1/f ² spectra, is proposed. The properties of the model fluctuations with a 1/f spectrum agree qualitatively with the experimentally observed properties. A characteristic difference between the model fluctuations with a 1/f ² spectrum and random walks is also noted. Zh. éksp. Teor. Fiz. 113, 1748–1757 (May 1998)     

Arc current fluctuation power spectra in the system of a solid metal electrode and carbonate melt

Arc current fluctuations between a solid metal electrode and a liquid melt of alkaline carbonates at atmospheric pressure are measured. Arc current fluctuation power spectra are determined from the measurement data. It is shown that the fluctuation power is inversely proportional to the frequency (1/f-fluctuations). The fluctuations have a normal Gaussian distribution. The observed 1/f fluctuations exhibit scale invariance. __________ Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 1, pp. 11–15, January–February, 2007.     

An entropy-based stability analysis of extreme fluctuations in a system featuring a 1/<Emphasis Type="Italic">f</Emphasis> spectrum

Extreme fluctuations are modeled by a point system of stochastic equations, in which power spectra inversely proportional to the frequency are produced under the effect of white noise. The distribution of extreme fluctuations corresponds to the maximum of statistical entropy, which points to their stability in nature. By calculating the spectral entropy of random processes, it becomes possible to investigate their stability directly from power spectra without the need to calculate the amplitude distribution functions. The spectral entropy as a function of white noise amplitude has a minimum. The position of the spectral entropy minimum corresponds to the critical state of the system in which the spectra of fluctuating quantities are inversely proportional to the frequency.     

Relaxation and power spectra of low-frequency fluctuations in foams

The dynamics of foam formation in a water-glycerin solution was studied to establish the relationship between the relaxation characteristics and the fluctuation power spectrum for a stochastic process. Foaming occurred during the dissociation of the gas-saturated solution and during bubbling of the solution through a porous filter. Two types of relaxation of the foam—exponential and power-law—were revealed. The power-law type of relaxation was observed upon exposure to ultrasound. Relationships between the type of relaxation and the distribution of lowfrequency fluctuations and power spectra was established.