Vol 60, No 7 (2017)

Different sets of constants the fixed values of which may be selected for new definitions of the four units (kilogram, mole, ampere, and kelvin) of the International System of Units are discussed. The concept of the “order of a constant” in a given system of units is proposed. Criteria for arriving at an optimal selection of defining constants as well as a set of constants consisting of Planck’s constant h, Avogadro’s constant N_A, Boltzmann’s constant k, and the magnetic permeability of a vacuum (magnetic constant) μ₀ are considered. The proposed set is an alternative to the base set consisting of h, e, k, and N_A.

Frequencies of acoustic and electromagnetic resonances were measured in a quasispherical acoustic resonator at the temperature of the triple point of water. The resonator was filled with helium ⁴He. Based on the analysis of experimental data, a value for the Boltzmann constant of k_B = 1.380651·10^–23 J·K^–1 with uncertainty of 2.4 ppm was obtained.

A formal procedure by means of which it is possible to select the uniquely definable parameters of objects represented in the form of multi-element, passive, two-terminal networks, where these parameters may assume a finite or infinite number of values, is proposed. The procedure also makes it possible to find conditions under which the largest possible number of parameters of an object become uniquely definable.

Mobile measuring equipment adapted for measurements of low-frequency noise of vacuum tubes with a broad range of impedance characteristics has been developed. Control software making it possible to measure and process the obtained results in automatic mode has been created. The capability of determining the diagnostic parameters of thermionic cathodes of vacuum tubes is shown.

Various approaches to the recovery of geofield surfaces (spline smoothing, controlled filtering) which are limited by linear regularizing and filtering algorithms are analyzed. It is shown that the problem of recovering surfaces (images) is multicriterial. A new method for constructing a set of nondominant solutions is proposed: the Pareto set.

The urgent need for a procedure to use in validation of dynamic force transducers is considered. A model of the dynamic interaction of the elements of a dynamic force transducer in the course of calibration by the test mass method is presented. Mathematical expressions that describe the calibration process are presented. A schematic diagram of a calibration plant that would be most appropriate for dynamic force transducers is proposed.

Special features of the use of the reflectometer method of recording signals of fiber Bragg gratings for monitoring deformations of ferro-concrete test beams were studied. Sensitivity to relative elongation of 2.8 dB/10^–3 and resolution 30·10^–6 in effective range ±2·10^–3 were experimentally demonstrated. It is shown that concrete deformations in a surface layer can substantially differ from deformations of the reinforcement rods located within the concrete, and this is explained by the differences between the strength characteristics of concrete and rebar steel.

The possibility of the effective use of the kinetic indentation method in combination with the acoustic emission method for evaluating the fracture toughness of titanium nitride hardening coatings is shown. It is established that the occurrence of the first jog on the loading line of the kinetic indentation diagram in “load–indentor displacement–time” coordinates is due to the formation of the first crack in the coating and practically coincides in time with the occurrence of the acoustic emission impulse with an increased energy value. This permits a more accurate and substantiated determination of the critical load, indentation depth of the indentor, and hardness at which the first visible ring crack forms around the impression on the coating surface.

A mathematical model of the method for determining the thermophysical properties of heterogeneous materials in a solid phase is given. The design of the measuring device for the realization of the method is considered. We present results of the practical application of the method for studying the changes in the specific heat and thermal conductivity of the solid phase of chemosorbents based on potassium and sodium superoxide in the temperature range 273–383 K during the absorption of carbon dioxide. It is shown that the method and device can be used to monitor the suitability of respiratory protection products based on chemosorbents.

A technique is proposed for estimating the signal-to-noise ratio in fiber-optic transmission systems with spectral multiplexing, multiplexing of orthogonal and non-orthogonal channel subcarriers in the case of cross-channel interference due to four-wave mixing in the fiber. It is shown that it is possible to estimate the signal-to-noise ratio of a system with any number of sub-carriers of channels from the results of measurements of this ratio for a four-channel transmission system.

Blowout resistance is measured using an air stream of fibrous sound-proof materials of three types, with fibers of various diameters. The dependences of the blowout resistance of studied materials on their density are experimentally defined. It is suggested to use dimensionless numbers for analytical approximation of the derived dependences.

The results of a quantitative assessment of the plans for remote irradiation of oropharyngeal cancer patients by means of the “dose–volume histogram” method (tool) are presented. The homogeneity index HI of the dose in the planned target volume PTV, conformity index CI, and other indices are calculated for 37 patients, The results of the calculations for various irradiation method are compared. It is shown that the homogeneity index HI for 80% of the patients and all irradiation technologies is within 0.05–0.12. The conformity index CI for patients does not depend on the irradiation technology.

We have developed a differential, pulsed conductometer for measuring the specific conductivity of biological cells in liquid media as a function of the electric field strength. We present the results of these measurements.