Scaling of 1/<Emphasis Type="Italic">f</Emphasis> noise in nonequilibrium phase transitions

Investigation of the dynamics of fluctuations of heat and mass transfer reveals that its crisis and transient modes exhibit high-energy pulsations with a power spectrum that is inversely proportional to frequency (flicker or 1/f fluctuations). Such a spectrum suggests energy transfer from high-to low-frequency modes and the possibility of large-scale catastrophic outbursts in the system being considered. The theory shows that such fluctuations arise in the system owing to the simultaneous occurrence of interacting phase transitions in the presence of white noise having a sufficiently high intensity. The distribution of fluctuations for scale transformations of the set of stochastic equations that describe the generation of 1/f noise is investigated. It is shown that, under a scale transformation, the Gaussian distribution of a random process having a 1/f spectrum passes to an exponential distribution, which is characteristic of the statistics of extreme outbursts. The probability of such outbursts must be taken into account in predicting the stability of various heat-transfer modes.     

Consideration of the micromagnetic state of a sample in interpretation of magnetic measurement data

A method is proposed for calculating the magnetization curves taking into account the domain structure of a sample, which, in contrast to the method developed by Néel and other researches, does not use a number of assumptions of the Néel model; i.e., this method is more universal. It allows numerical calculation of the micromagnetic state of a sample within a unified approach and has no limitations on the type of magnet anisotropy.     

Spin-reorientation transitions and domain structure in TbFe<Subscript>11−<Emphasis Type="Italic">x</Emphasis></Subscript> Co<Subscript>x</Subscript>Ti single crystals

The magnetic structure of single-crystal TbFe_11?xCo_xTi compounds has been studied over a broad temperature range and in strong magnetic fields (up to 14 T). Measurements of magnetization and magnetostriction and a study of the domain structure revealed that spin-reorientation transitions (SRTs) in TbFe_11?xCo_xTi single crystals depend substantially on the cobalt concentration. It was established that the SRT temperatures and threshold magnetic fields are governed by the interplay between the magnetic anisotropies of the 3d and terbium sublattices. It is shown that, in these compounds, the low-temperature phase with planar anisotropy is separated in temperature from the high-temperature phase with uniaxial anisotropy by an intermediate metastable phase containing domains of the uniaxial or planar phase.     

Use of a composite fabry-perot interferometer to study transparent inhomogeneities

A multiplex Fabry-Perot system is used with the specimen between one of the pairs of mirrors. The thickness ratio is examined in relation to detection of small phase shifts. Experiment gives the highest sensitivity for equal thicknesses.     

Magnetic anisotropy and magnetostriction in a Lu2Fe17 intermetallic single crystal

The magnetic anisotropy and magnetostriction of a Lu₂Fe₁₇ single crystal are investigated. The temperature dependence of the magnetic anisotropy constant K ₁ is measured in the range 4.2–300 K. The results obtained are compared with the data calculated using the Callen theoretical formula. It is found that the temperature dependence of K ₁ for the Lu₂Fe₁₇ single crystal deviates from the temperature curve predicted by the localized single-ion model. The inference is drawn that a certain contribution to the magnetic anisotropy of the Lu₂Fe₁₇ compound is made by the magnetic anisotropy of band electrons. The longitudinal, transverse, and volume magnetostrictions of the Lu₂Fe₁₇ single crystal are studied, and the magnetostriction constants are calculated. It is demonstrated that the exchange integral of Lu₂Fe₁₇, as for the Y₂Fe₁₇ compound, substantially depends on the atomic volume. This dependence is responsible for the considerable difference between the Curie temperatures of the Lu₂Fe₁₇ and Y₂Fe₁₇ compounds. It is revealed that the magnetostriction of the Lu₂Fe₁₇ single crystal in the temperature range of the magnetic phase transition is determined by the two-ion exchange and single-ion contributions.     

Stochastic resonant response in the transient boiling regime with periodic heat release

Results of experimental investigation into thermal pulsations with a transition from the bubble to the film boiling regime of water in a wire heater with periodic Joule release are presented. The intermittency of the bubble and film regimes was observed with the frequencies of the periodic current component lower than 0.1 Hz. The amplitude of thermal pulsations increased by a factor of approximately 4 in this case. These results are interpreted as the stochastic resonant response of the system when the periodic component of pulsations increases in the presence of noise.     

Specific features of the damage nucleation stage under severe loading of copper

The nucleation and evolution of damage in annealed coarsely crystalline M1-type copper subjected to fast loading to a pressure P ～ 32 GPa, followed by the action of tensile stresses σ _p with an intensity of ≈?2.0 GPa for a time t ≈ 0.3–1.5 μs, have been investigated numerically and experimentally. It has been shown that, at a specific combination of amplitude-time characteristics of the tensile stress pulse, damage localization in some cases at t < 1 μs has been observed in zones (～10–14 mm in size) alternating with “dead” zones (～3–5 mm in size) containing no visible damages. Pores are connected by “yield streamlets.” The existing multistage models of fracture kinetics have neither explained nor predicted the formation of a “band” damage structure or the presence of “yield streamlets” in specimens.