Calculation of the acid-base equilibrium constants at the alumina/electrolyte interface from the ph dependence of the adsorption of singly charged ions (Na<Superscript>+</Superscript>, Cl<Superscript>−</Superscript>)

A procedure was proposed for the calculation of the acid-base equilibrium constants at an alumina/electrolyte interface from experimental data on the adsorption of singly charged ions (Na⁺, Cl⁻) at various pH values. The calculated constants (pK ₁⁰= 4.1, pK ₂⁰= 11.9, pK ₃⁰= 8.3, and pK ₄⁰= 7.7) are shown to agree with the values obtained from an experimental pH dependence of the electrokinetic potential and the results of potentiometric titration of Al₂O₃ suspensions.     

A Generalized Function in Heat Conductivity Problems for Multilayer Structures with Heat Sources

An accurate analytical solution of the stationary problem of heat conductivity for a multilayer structure with heat sources under asymmetric boundary conditions of the third kind is obtained based on the use of the theory of generalized functions. Using the asymmetric unit function (Heaviside function), the problem for a multilayer structure is reduced to a single-layer with discontinuous (piecewise-continuous) medium properties. By introducing a new independent variable, the nonlinear differential equation (nonlinearity of the second kind—the thermal-physical properties depend on the spatial variable) is reduced to a linear one, direct integration of which allows obtaining an accurate analytical solution of the problem considered. Examples of investigations of the temperature fields for some certain multilayer structures are given.     

The Schwarzschild Singularity: A Semiclassical Bounce?

We discuss the opportunity that the singularity inside a Schwarzschild black hole could be replaced by a regular bounce, described as a regular minimum of the spherical radius (instead of zero) and a regular maximum of the longitudinal scale (instead of infinity) in the corresponding Kantowski-Sachs metric. Such a metric in a vicinity of the bounce is shown to be a solution to the Einstein equations with the stress-energy tensor representing vacuum polarization of quantum matter fields, described by a combination of curvature-quadratic terms in the effective action. The indefinite parameters of the model can be chosen in such a way that it remains a few orders of magnitude apart from the Planck scale (say, on the GUT scale), that is, in a semiclassical regime.     

Control of the structure of titanium alloys by the method of thermohydrogen treatment

We show the possibility of controlling the structure of titanium alloys of different classes by means of their thermohydrogen treatment and consider the process of structure formation in shaped castings of VT20L alloy under additional alloying with hydrogen. Depending on the hydrogen content in the course of thermohydrogen treatment, the transformation of a course-lamellar structure into a fine-lamellar one with α-particle sizes from several micrometers to nanometers is possible. We describe the mechanism of phase and structural transformations in titanium alloys with a heightened content of β-eutectoid stabilizers (Ti-12Cr) or aluminum (VT6, VT23) under the action of hydrogen. We also show the possibility of producing a composite structure of the β-phase and TiCr₂ intermetallic compound or noncoherent particles of the α₂-and α-phases, depleted with aluminum. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 3, pp. 28–34, May–June, 2008.     

Increasing the Stability of Mechanical Properties of Semifinished Products from Ti–6Al–4V Alloys by Correcting the Alloying Range and Annealing Modes

Metallurgist - Statistical studies on the stability of the mechanical properties of various semifinished products made from Ti–6Al–4V alloys depending on the content of alloying...     

Earthquake resistance of a gravity dam with consideration of the linear character of concrete deformation

Use of nonlinear dynamic analysis with application of concrete-strain diagrams has permitted more adequate evaluation of the stress-strain state of a structure subject to seismic effects. __________ Translated from Gidrotekhnicheskoe Stroitel’stvo, No. 1, January, 2007, pp. 4–10.     

Analysis of the technical condition of the dam at the Sayano-Shushenskaya HPP based on measurements of radial displacements and angles of incline of horizontal segments

Radial displacements and angles of rotation of horizontal segments of the dam at the Sayano-Shushenskaya HPP are analyzed. The primary purpose of the analysis was to evaluate the technical condition of the dam based on measurements of diagnostic indicators by geodetic methods, and to establish the existence of residual (irreversible) displacements of the dam prior to and after the failure. Data derived from field measurements during the period after the completion of repair work (May 2004 – May 2010) served as initial data. Field measurements from an earlier period were not utilized, since the structure of the dam prior to its repair differed from the structure that existed after the repair (from 1996 through 2003, large-scale overhaul operations were conducted in the concrete located at the thrust face of the dam, and in the near-contact zone of its bed).