The catalytic effect of iridium on the oxidation of water-soluble porphyrin — 5,10,15,20-tetrakis (4-sulfonatophenyl) porphin (TSPP) with sodium periodate is studied for the first time. A method for determination of the iridium micro-content by the catalytic effect of iridium on the oxidation of water-soluble porphyrin 5,10,15,20-tetrakis (4-sulfonatophenyl) porphin with sodium periodate in a flow-injection system is developed. The lower limit of the determined iridium concentrations is 0.2 × 10^–5 μg/ml (P = 0.95), which is lower than that for the methods described in the literature. Optimal conditions for determination have been specified: pH 3; concentration of the reagents in the flows of a given hydraulic mixing scheme 0.5 × 10^–5 M TSPP and 0.15 M NaIO₄; room temperature for the indicator reaction. A linear calibration characteristic was obtained under chosen optimal conditions in the range of iridium concentrations (0.2 – 2.0) × 10 – 5 μg/ml. The effect of the elements accompanying iridium in industrial and natural materials was studied. Molar excesses of platinum and non-ferrous metals do not interfere with iridium determination: 20-fold Rh (III); 15-fold Pt (IV) and Fe (II); and 20-fold molar excess of Ni (II). Correctness of the results is confirmed by spike recovery tests on model iridium-containing solutions. S_r of the results of iridium determination under selected conditions at n = 3, P = 0.95 on model solutions is no more than 0.04. A comparison of the obtained results with literature data showed that the main advantages of the proposed method for iridium determination are room temperature of the reaction, more simple hardware design and lower limit of the iridium determination.

The possibility of using cerium (IV) sulfate as an oxidizing reagent in analysis of various organic compounds is considered and exemplified specifically in determination of phenolic hydroxyl group. Cerium sulfate quantitatively reacts with a phenolic hydroxyl group to form quinoid compounds. Techniques for determination of phenols of different structures (including perchlorinated and perfluorinated phenols) using potentiometric titration with a solution of cerium sulfate in a sulfuric acid medium with a redoxometric indicator electrode are proposed. The presence of the substituents with reducing properties in the aromatic ring interferes with the determination. Cerimetric potentiometric titration was also used to study the structure of polymers based on methylol derivatives of phenolphthalein which are crosslinking agents and serve to obtain thermostatic structural materials with high strength properties. It is shown that the methylol hydroxyl group, which is also quantitatively oxidized by cerium sulfate, can be determined simultaneously with a phenolic hydroxyl group. The results obtained by the proposed method of cerimetric titration and well-known method of acetylation appeared identical. The determined number of hydroxyl groups in the analyzed samples is indicative of the polymer structure. Proceeding from the technique of cerimetric titration we propose a method for determination of free xylenols in fire-resistant turbine oil. The developed technique is more rapid and less labor-consuming compared to generally accepted technique TU 3470.11335–07 based on the bromination of xylenols with a bromide-bromate mixture.

Calibration by the concentration ratio provides better metrological characteristics compared to other calibration modes when using the inductively coupled plasma atomic emission spectrometry (ICP-AES) for analysis of geological samples and technical materials on their base. The main reasons for the observed improvement are: i) elimination of the calibration error of measuring vessels and the error of weighing samples of the analyzed materials from the total error of the analysis; ii) high intensity of the lines of base element; and iii) higher accuracy of measuring the ratio of intensities compared to that of measuring the absolute intensities. Calcium oxide is better suited as a base when using calibration by the concentration ratio in analysis of carbonate rocks, technical materials, slags containing less than 20% SiO₂ and more than 20% CaO. An equation is derived to calculate the content of components determined in carbonate materials when using calibration by the concentration ratio. A method of ICP-AES with calibration by the concentration ratio is developed for determination of CaO (in the range of contents 20 – 100%), SiO₂ (2.0 – 35%), Al₂O₃ (0.1 – 30%), MgO (0.1 – 20%), Fe₂O₃ (0.5 – 40%), Na₂O (0.1 – 15%), K₂O (0.1 – 5%), P₂O₅ (0.001 – 2%), MnO (0.01 – 2%), TiO₂ (0.01 – 2.0%) in various carbonate materials. Acid decomposition of the samples in closed vessels heated in a HotBlock 200 system is proposed. Correctness of the procedure is confirmed in analysis of standard samples of rocks. The developed procedure was used during the interlaboratory analysis of the standard sample of slag SH17 produced by ZAO ISO (Yekaterinburg, Russia).

Any material can be considered a composite consisting of grains of different orientations which possess different properties depending on the history of their reorientation upon thermomechanical processing. A well-known selective character of X-ray methods is attributed to the fact that only grains of certain orientations participate in the formation of reflected radiation. A comprehensive description of the material including information about the substructure of grains of all orientations necessitates developing of the method providing description of the substructural state of grains located in the volume under study by analyzing the profile of x-ray lines. The proposed x-ray diffractometric method of Generalized Direct Pole Figures (GPF) which suggests combination of texture imaging and recording the profile of x-ray lines appeared to be rather efficient in a systematic x-ray study of the substructural heterogeneity of textured metallic materials. The measured parameters of the X-ray line profile — the true angular half-width β and angular peak position 2θ — are determined by the distortion (fragmentation) of the reflecting grains and interplanar spacings in their crystal lattice, respectively. The method provides a possibility to compare the substructure features of grains with different crystallographic orientations. An algorithm for calculation of the true physical half-width of the x-ray line using the necessary computer programs is presented. GPF β and GPF 2θ are presented for metal materials with hcp, fcc, and bcc crystalline lattices, as well as characteristic diagrams of their mutual correlation with texture PF. The use of the developed GPF method makes it possible to identify patterns of the formation of substructural heterogeneity during plastic deformation of metals.

An innovative method of measuring and control of the steel corrosion rate by changing magnetic characteristics is developed. The impact of heat treatment on the corrosion rate of the samples of high-carbon steels (maximum corrosion loss is observed at a tempering temperature of 400°C) is attributed to the appearance of micro-galvanic pairs (MGP) between the phase components of the material. MGP undergo redistribution under heat treatment thus changing conditions of the galvanic current flow. The structural phase composition, in turn, determines the magnetic properties of steel and correlation between the magnetic properties and corrosiveness. The goal of the study is demonstration of the possibility and expediency of using the magnetic parameters of steel for determination of the steel corrosion rate. A close correlation dependence is observed between the coercive force and the electrochemical potential (relative to the silver chloride electrode) which are direct indicators of the corrosiveness. Case study of a pipeline made of 09G2S steel along which change in the coercive force attained 25% revealed rather high risk of developing micro-galvanic pairs. A rapid method of scanning magnetic parameters is proposed to detect potentially corrosive zones. A multi-parameter approach can be used to solve the problem of the ambiguity of the relationship between the corrosiveness and magnetic parameters. Harmonic decomposition of magnetic hysteresis loops of 45Kh steel samples is used to obtain a number of odd harmonics. Some of them weakly correlate with the corrosion loss, whereas complexes of several harmonics correlate to a greater extent. The results can be used in technical diagnostics and prediction of the corrosion activity of steel structures before their operation. The results can be used in technical diagnostics and forecasting of the corrosiveness of steel structures prior to their operation.

Variable electrodynamic parameters of composite materials are determined using the methods providing simultaneous measuring of the free- space permittivity and magnetic permeability within a broad band. Thus, the problems regarding reflection of an electromagnetic wave from the boundary of a dielectric layer and modeling of the phase shift of the wave reflected from a dielectric plate become rather relevant. We report the results of studying the effect of the electrodynamic parameters of composite materials on the characteristics of the wave reflected from a dielectric plate. Analytical expressions are derived for the phase of the reflected wave when an incident plane wave is oriented at an angle to the composite plate with variable electrodynamic parameters. The matrix method is used to obtain the equations for calculating the phase shift of the reflected wave. It is shown that for incident waves with a vector of electric field lying in the plane of incidence (TM waves) and normal to it (TE waves), a jump in the phase shift by π is observed for the electric thickness of the plate multiple of the half-wavelength. A similar phase jump is observed in the case of an incident TM wave near the Brewster angle. An analysis of the frequency dependences of the phase shift, including the phase shift and amplitude drop at a corresponding frequency, as well as data on the effect of losses in the plate material on the phase shift of the reflected wave are presented. The results of studying the angular dependence of the phase shift of the reflected wave in the region of the Brewster angle can be used in solving applied problems of electrodynamics (e.g., when developing a broadband broad-band direction finding device).

The history of appearance and the current state of instrumented indentation are briefly described. It is noted that the materials instrumented indentation methods using a pyramid and ball indenters are actively developing and are currently regulated by several Russian and international standards. These standards provide formulas for calculating the Young’s modulus and hardness at maximum indentation load. Instrumented indentation diagrams «load F – displacement α» of a ball indenter for metallic materials were investigated. The special points on the instrumented indentation diagrams «F – α» loading curves in the area of elastic into elastoplastic deformation transition, and in the area of stable elastoplastic deformation are revealed. A loading curve area with the load above which the dF/dα begins to decrease is analyzed. A technique is proposed for converting «F – α» diagrams to «unrestored Brinell hardness HB_t – relative unrestored indent depth t/R» diagrams. The elastic and elastoplastic areas of «HB_t – t/R» diagrams are described by equations obtained analytically and experimentally. The materials strain hardening parameters during ball indentation in the area of elastoplastic and plastic deformation are proposed. The similarity of «HB_t – t/R» indentation diagram with the «stress σ – strain δ» tensile diagrams containing common zones and points is shown. Methods have been developed for determining hardness at the elastic limit, hardness at the yield strength, and hardness at the ultimate strength by instrumented indentation with the equations for their calculation. Experiments on structural materials with different mechanical properties were carried out by instrumented indentation. The values of hardness at the elastic limit, hardness at the yield strength and hardness at the ultimate strength are determined. It is concluded that the correlations between the elastic limit and hardness at the elastic limit, yield strength and hardness at the yield strength, ultimate tensile strength and hardness at the ultimate strength is more justified, since the listed mechanical characteristics are determined by the common special points of indentation diagrams and tensile tests diagrams.

Fatigue cracks in the piston heads of the connecting rods of opposed compressors can occasionally develop in service. A study of the loading of the connecting rods of the compressors operating in chemical production was carried out to assess the probability of their failure-free operation. Since the experimental study of stresses acting in large structural elements is rather difficult, the study of the stress state was carried out using computational methods with subsequent comparison of the results with the experimental data. When loading the connecting rod, there is an area affected by the distributed load and another area with a gap between the cylindrical surfaces where the contact pressure is absent. The forces acting on the boundary of the contact areas and the gap of the finger with the connecting rod bore are determined: the radial force N, tangential force Q and bending moment M. N and Q are considered functions of the contact angle α. Using numerical experiments, we determined the stresses in the zone from the angle α corresponding to the end of the contact zone to the angle of transition of the head in the shank of connecting rod in conditions of varied operational loads and gaps in the connecting rod — finger coupling. The values and character of changes in the loads affecting the crank mechanism of the compressor during operation are determined experimentally. The distribution of stresses in the sections of the connecting rod and the most loaded cross-sections are specified. the results of the numerical experiment are compared with the experimental data. Comparison of the results of numerical and field experiments has shown that the numerical experiment provides the similar assessment of the stress distribution, moreover, the numerical experiment allows us to estimate the simultaneous effect of both loads and gaps on the stress growth which is almost impossible to be determined by experimental studies.

A method of the hysteresis loop relates to the direct methods for determination of the energy dissipation and studying the inelasticity in the material. The method is based on the direct formation of the mechanical hysteresis loop by static loading and unloading of the sample and measuring of the corresponding deformations. The relative energy dissipation is defined as the ratio of the hysteresis loop area to the elastic energy corresponding to the maximum amplitude of strain. Construction of the hysteresis loop is performed on the installation «torsional pendulum for determination of the mechanical properties of materials» which can work as a device for measuring internal energy dissipation by damped oscillations, and as a precision torsion test machine using a deforming device. The aim of this work is to determine the area of the static hysteresis loop through the choice of the mathematical models of loading and unloading curves with subsequent numerical integration using the ordinate values at equidistant points. The analysis of using polynomials of the second or third degree was carried out according to the criterion of the smallest sum of squared deviations between the empirical and calculated values of the function. The experimentally obtained coordinates of the points of the deformation diagram of the sample during loading and unloading were used as initial data for estimation of regression coefficients in polynomial equations. A distinctive feature of the proposed method is that analytical dependences between stresses and strains obtained by N. N. Davidenkov and containing hard-to-determine geometric parameters of the loop, which must be pre-set from the known values of the logarithmic decrement of oscillations obtained from the experiment are not used in the developed method to calculate the area of the static hysteresis loop. It is shown that a comparative assessment of the relative energy scattering in the ferrite gray iron performed by the direct method of determining the area of the mechanical hysteresis loop at different amplitudes of shear deformation, is in good agreement with the data obtained by the indirect method of damped oscillations on an installation of the similar class.

The problem of constructing Q-optimal experimental designs for polynomial regression on the interval [–1, 1] is considered. It is shown that well-known Malyutov – Fedorov designs using D-optimal designs (so-called Legendre spectrum) are other than Q-optimal designs. This statement is a direct consequence of Shabados remark which disproved the Erdős hypothesis that the spectrum (support points) of saturated D-optimal designs for polynomial regression on a segment appeared to be support points of saturated Q-optimal designs. We present a saturated exact Q-optimal design for polynomial regression with s = 3 which proves the Shabados notion and then extend this statement to approximate designs. It is shown that when s = 3, 4 the Malyutov – Fedorov theorem on approximate Q-optimal design is also incorrect, though it still stands for s = 1, 2. The Malyutov – Fedorov designs with Legendre spectrum are considered from the standpoint of their proximity to Q-optimal designs. Case studies revealed that they are close enough for small degrees s of polynomial regression. A universal expression for Q-optimal distribution of the weights p_i for support points x_i for an arbitrary spectrum is derived. The expression is used to tabulate the distribution of weights for Malyutov – Fedorov designs at s = 3, ..., 6. The general character of the obtained expression is noted for Q-optimal weights with A-optimal weight distribution (Pukelsheim distribution) for the same problem statement. In conclusion a brief recommendation on the numerical construction of Q-optimal designs is given. It is noted that in this case in addition to conventional numerical methods some software systems of symbolic computations using methods of resultants and elimination theory can be successfully applied. The examples of Q-optimal designs considered in the paper are constructed using precisely these methods.