Analysis of the regimes of controlling transient processes in pipelines

This paper considers the problem of optimal control of the process of going from one stable regime to another in piping the hydrocarbon raw material. We have investigated the influence of the transient period on the dissipation factor of the system, the length of the part of the pipeline, and the difference between the parameters of the initial and final stable regimes with account for the technological limitations set on the control actions and phase variables. The dependence of the optimal transient period on the class and range of permissible control functions, the process parameter, and its initial and final regimes has been analyzed.     

Thermal instability and transient processes in gas-cooled current leads

The conditions under which burnup of gas-cooled galvanic current lead occurs are investigated theoretically and experimentally.Translated from Inzhenero-Fizicheskii Zhurnal, Vol. 46, No. 6, pp. 943–949, June, 1984.     

Analysis of parameters of electric and magnetic phenomena accompanying explosion and shock processes

Parameters of electric and magnetic fields generated by an explosion of chemical explosives and impact of metallic bodies are determined. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 70, No. 3, pp. 442–449, May–June, 1997.     

Principles of identification of the physical processes caused by variation of thermodynamic parameters in solids

A method is proposed which permits identification of the reversible and irreversible thermodynamic processes occurring in solids as thermodynamic conditions vary, and definition of the contribution of each process to the whole. Theoretical values have been obtained of the ratio of the rates of change of enthalpy and volume as well as the ratio of the total heat and volume effects for a series of processes in solids. The method is applied to some actual special cases.     

A thermodynamic description of the melting process in nanometer-sized particles

The melting behavior of nanometer-sized Sn particles with radius in the range between 5 and 50 nm is analyzed within the conceptual framework of classical thermodynamics. Experimentally observed size-dependent melting points and latent heats of fusion are exploited to point out the occurrence of pre-melting phenomena at the particle surface. The size-dependent values of the thermodynamic state functions associated with the solid–liquid interface are estimated together with the thickness of the interface layer.     

The nature of amorphization in crystalline systems

The conditions of the transition from the crystalline to amorphous state and the process of amorphization of crystalline systems under cold plastic deformation have been studied. Two concepts of crystalline system amorphization are considered. Fusion and amorphization in the solid state are analysed, particularly in terms of the thermodynamics of reversible processes of the transition from the crystalline to the amorphous state. The mechanism of amorphization of a crystalline alloy is considered when it undergoes deformation or low-temperature annealing. The emphasis is on the system of Fe-B alloys.     

Non-Linearity of a thermodynamic instability in high-Tc superconductors

Submitting high-T _c superconductors to the effect of a large temperature gradient and a thermal pulse, damped oscillation of d.c. and a.c. voltages is detected on the samples. It represents the appearance of a novel type of thermodynamic instability, which manifests itself in temporal fluctuation of normal-superconducting and superconducting-normal transitions of coherent domains, depending on the local structural properties of the material at a given temperature and magnetic field. The strong non-linearity of this phenomenon is attributed mainly to thermodynamic cross-effects, taking into account the dissipation of the vortex motion, too. General motion equations of irreversible thermodynamics characterize correctly the decaying behaviour of the disturbed state.     

Cumulative instability of the surface of condensed substances

It is shown that the development of instability on the curved surface of a condensed material under impact loading conditions can follow a pattern that is different from the classical Richtmyer-Meshkov scenario and resembles the process of cumulative jet formation. Using analytical estimates and the results of numerical calculations, a region of the existence of the jetlike instability is determined and the main relations describing this process are obtained.     

Criteria for the occurrence of fission-fragment tracks in crystalline substances

The tracks left in minerals by fission fragments arising from the spontaneous decay of uranium impurities serve as an important method for geological dating. If it is assumed that fission tracks in crystalline substances have a structure similar to that of an amorphous phase, then four criteria concerning whether such substances will be useful for dating can be made. These are the existence of amorphization following heavy-ion impact, the identification of an etchant, a high enough crystallization temperature, and the position of the substance on a scale of amorphizability. The criteria are illustrated by applying them to apatite, cobalt titanate, and columbite. Amorphization occurred with all three following bombardment with 10 to 35 keV Kr⁺ ions. Amorphous apatite was more successfully etched with aqueous KOH than with the commonly used HNO₃, while amorphous columbite could be etched with an HF-HNO₃ mixture. The crystallization temperatures, which lay in the interval 810 to 905 K for experiments of short duration, were judged to be sufficiently high to insure track retention at the temperature of the surface of the earth over a geological time scale. The positions on a scale of amorphizability were established by noting the bombardment doses at which there was sufficient amorphization to cause the loss of one-half of an inert-gas marker when specimens were heated or etched. Considering all four criteria, it is concluded that apatite and columbite but not cobalt titanate should be useful for dating, with a similar conclusion holding for other substances which are structurally or chemically similar.This paper is dedicated to Professor C.A. Winkler of McGill University on the occasion of his sixty-fifth birthday by one of his former students (R.K.).     

Generalized integral variational principles of phenomenological thermodynamics of irreversible processes,and the nature of variation of thermodynamic action

Generalized integral variational principles of phenomenological thermodynamics of irreversible processes (PTIP), as formulated by the present author, are stated.     

On the temperature of melting of nanoparticles and nanocrystalline substances

A new expression for the temperature of melting of a nanoparticle, which agrees with the well-known result of the Debye model, has been obtained within the framework of a rather strict thermodynamic approach. It is shown that the characteristic Debye temperature and the melting temperature can depend in a critical manner on the fractal structure of the nanocrystalline solid.     

Universal equation of transient plane jet in concurrent stream

An equation is derived and subsequently integrated which is universal not only with respect to velocity of the concurrent stream and initial conditions of jet discharge but also with respect to choice of characteristic scale for the transverse coordinate.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 43, No. 5, pp. 753–759, November, 1982.     

Variation in thermal conductivity of organic substances in melting phase changes

The thermal conductivity of 15 organic compounds near the melting phase change temperature is studied experimentally. An evaluation of the variation in thermal conductivity accompanying these phase changes is conducted.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 4, pp. 702–706, October, 1971.     

The variation of the parameters of front processes of thermal decomposition of condensed systems in the vicinity of the limit of thermodynamic stability

Analysis is made of the variation of the basic parameters of front processes of thermal decomposition of condensed systems, namely, the velocity of front motion, the surface temperature, and the thickness of zones of chemical reactions and heating, as the intensity of thermal impact increases and the temperatures in the front approach the limit of thermodynamic stability.     

Triple-points of low melting substances and their use in cryogenic work

Some practical uses of the constancy of the triple-point temperature (T_t) of a pure substance in cryogenic work are described. Simple techniques for attaining constant and known temperatures are discussed, as is the degree of impurity which can be tolerated while meeting desired limits of uncertainty of, and variation in, temperature. A comprehensive survey of low-melting elements and compounds has been carried out, covering 190 substances from neon to carbon tetrachloride, which span T_t values from 24.5 to 250.5 K. These substances have been divided into three groups according to their availability, the state of purity in which they can be purchased or alternatively the ease with which they can be purified, and the reliability with which T_t is known in the IPTS-68. Group 1 includes substances of particular importance for which T_t is accurately known and which are readily available in a high state of purity. Group 2 lists substances which are fairly readily available and for which at least one reasonably reliable measurement of T_t has been made, while Group 3 comprises all the remaining substances, for which at least one apparently careful determination of T_t has been published.     

Motion and thermodynamic instability of a liquid in a variable capillary

The flow of a liquid in a capillary of variable cross section formed by moving surfaces is analyzed. It is shown that a liquid flow with definite parameters (viscosity, surface tension, etc.) is characterized by a definite negative (relative to atmospheric) pressure, which is responsible for thermodynamic instability of the liquid layer and the formation of discontinuities in it. The theoretical results are consistent with the experimental.