Some unique features of supersonic unsteady gas flow around bodies

We consider unsteady supersonic gas flow about bodies for small Strouhal numbers. The amplitude of the angles of attack is assumed arbitrary under the condition that the bow shock remains attached, and the flow behind the shock is supersonic. A criterion is formulated which permits the comparison of the damping characteristic for small and large amplitudes of the disturbed motion. A comparison is made, using the wedge as an example, of the damping characteristics calculated by various theories, and the hypersonic similarity law is verified. Simple asymptotic equations are presented for the rotary derivatives of the thin wedge in a hypersonic gas stream.     

Electrification of weakly conducting liquids in the neighborhood of a wall

The problem of the generation of an uncompensated electric space charge in weakly conducting viscous fluid channel flows in which the medium interacts electrochemically with an interface is investigated for an arbitrary relation between the mobilities of the charged particles of different kinds. New models of the electrochemical surface processes are considered. The effect of the parameters of these processes on the electrification current and on the time taken by the electric parameters of the medium is studied to reach saturation. The possibility of the generation of strong induced electric fields on the interface is justified theoretically, two basic parameters affecting the strength of these fields are determined, and an explanation of the discharge process observed in the experiments in the form of local fluid glow zones is proposed.     

Features of the scattering of protons and relativistic electrons intersecting a thin planar target at a small angle to its surface

The processes of scattering of protons and relativistic electrons incident on a planar target at a small angle to its surface have been simulated by the Monte Carlo method. The spatial and energy distributions of the beams of particles both passed through the target and reflected from it have been calculated. The dependence of the characteristics of beams on the initial energy and direction of injection of particles, as well as on the material and thickness of the target, has been considered. The transmission, reflection, and absorption coefficients for electrons in the target have been calculated. The initial energy in the calculations is varied in the range of 7–100 MeV and the angle between the trajectory of particles and the surface of the target is in the range of 1°–45°. The thickness of the target varies from 0.2 to 3 mm. Aluminum, iron, and copper targets have been considered. It has been shown that the intersection of targets at small angles not only increases the transverse dimensions of a beam, but also changes the direction of its motion. The results of the reported calculations of the scattering of relativistic electrons intersecting a foil at small angles to its surface are in qualitative agreement with experimental data.     

Qualitative Identification of Milk Fat from Chromatographic Data

The data on the amount of fatty acids in milk, animal, vegetable, and mixed fats were obtained by capillary gas–liquid chromatography. Statistical data on the concentrations of myristic, palmitic, stearic, oleic, linoleic, and linolenic acids in milk fat were considered as criteria of its natural origin. Concepts were formulated for the detection of a multicomponent adulterating additive of variable composition in a product containing variable amounts of the same components. A graphical interpretation of the results of the analysis was proposed based on the identification zone.     

Interaction of a blown gas jet with a supersonic oncoming stream without formation of a three-dimensional region of boundary layer separation

A study is made of the flow resulting from the interaction of a supersonic stream with a transverse sonic or supersonic jet blown at right angles to the direction of the main stream through a nozzle whose exit section is situated on a flat wall.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 3, pp. 137–139, May–June, 1981.     

Theory of cooled electric probes in a dense plasma. Influence of thermal diffusion

The problem of an electric probe in the shape of a sphere in a weakly ionized three-component plasma at rest is studied. It is assumed that the probe diameter is appreciably larger than the mean free path of the charged particles and that the temperature of the probe surface differs from the temperature of the undisturbed plasma. The contribution of thermal-diffusion mass transport is taken into account in the expressions for the densities of the electric currents of the components. A new numerical method is developed to obtain a solution of the problem in a wide range of the determining parameters. The current-voltage characteristics are constructed. The influence of the probe temperature, the transport coefficients, and other parameters on the current-voltage characteristics is analyzed.Translated from Izvestiya Akademii Nauk SSSR, Mekhanika Zhidkosti i Gaza, No. 2, pp. 103–112, March–April, 1979.     

A macrokinetic model of redox sorption on metal–ion exchanger nanocomposites at electrochemical polarization

A conceptual macrokinetic model of redox sorption on metal–ion exchanger nanocomposites upon electrochemical polarization is formulated and a corresponding mathematical model is constructed. The solution to a multi-point boundary value problem for the concentration of a sorbed substance (oxygen) is given. The concentration front of the sorbed substance is characterized by a concentration gradient in the near-surface layer of the solution, by layers of the products of metal oxidation in the composite forming due to both external and internal diffusion transfer, and by chemical and electrochemical reactions at the interphase boundaries. A considerable reduction in the concentration gradient of the sorbate in layers of the products of oxidation of metal and the growth of the diffusion layer of the solution with polarizing currents weaker than the limiting diffusion current are noted.     

Almost cover-free codes and designs

An s-subset of codewords of a binary code X is said to be \((s,\,\ell )\) -bad in X if the code X contains a subset of \(\ell \) other codewords such that the conjunction of the \(\ell \) codewords is covered by the disjunctive sum of the s codewords. Otherwise, the s-subset of codewords of X is called \((s,\,\ell )\) -good in X. A binary code X is said to be a cover-free (CF) \((s,\,\ell )\)-code if the code X does not contain \((s,\,\ell )\)-bad subsets. In this paper, we introduce a natural probabilistic generalization of CF \((s,\,\ell )\)-codes, namely: a binary code X is said to be an almost CF \((s,\,\ell )\)-code if the relative number of its \((s,\,\ell )\)-good s-subsets is close to 1. We develop a random coding method based on the ensemble of binary constant weight codes to obtain lower bounds on the capacity of such codes. Our main result shows that the capacity for almost CF \((s,\,\ell )\)-codes is essentially greater than the rate for ordinary CF \((s,\,\ell )\)-codes.     

Surface topography formation in a region of plate collision: Mathematical modeling

The collision of earth’s crustal plates is modeled mathematically based on a numerical solution of the equations of deformable solid mechanics using a finite element method with the MSC software. The interaction of the plates with each other and with the mantle is described by the solution of the contact problem with an unknown contact boundary between the solids considered. The mantle material is assumed to be ideal elastic-plastic with the Huber-Mises yield surface, and the properties of the plate material are described using an elastic-plastic model with the Drucker-Prager parabolic yield function which takes into account fracture in the tensile stress region. The results of the mathematical modeling show that the surface profiles of the plates in the region of their collision are consistent, both qualitatively and quantitatively, to the surface topography observed in nature under similar conditions.