Methods used for preparation of the samples of different metal-containing secondary raw materials (catalysts, electronic scrap, sludge, etc.) for subsequent analysis in the form of solutions are reviewed: dissolution in a mixture of mineral acids, alloying with various fluxes, leaching et al. Different impacts used to promote sample preparation - elevated temperature and pressure, ultrasound and microwave radiation - are discussed. Methods of sample preparation using sorption concentration for subsequent determination not only noble, but also non-ferrous and rare metals and toxic elements are considered. The stage of sample preparation is shown to be extremely important to diclose the potentiality of the applied analytical methods most completely.

X-ray fluorescence analysis (XRF) is used to study chemical composition of the samples of technogenic raw materials - fired slag and batch of vanadium production. The feasibility of x-ray photoelectron spectroscopy (XPS) in determination of the oxidation numbers of the elements in technogenic raw materials is studied. We determined that about 30% of vanadium is present in the slag as V (III), whereas the content of V (V) and V (IV) in the batch samples is about 80 and 20%, respectively. No compounds of vanadium in lower oxidation states were detected. Iron in the slag and batch samples is present in the form of Fe₃O₄, manganese, apparently, is present mainly in the form of Mn (III). Analysis of the possibility of determining the oxidation state of vanadium in the slag and batch from the ratio of the line intensities of K- and L-series in XRF spectra revealed, however, inexpediency of using the procedure because of a low accuracy of the results.

A rapid procedure of copper and zirconium determination in their binary alloys Cu_100xZr_x in the range of the mass content corresponding to area of the bulk amorphization (x = 30 - 70) is developed using inductively coupled plasma-atomic emission spectroscopy (ICP-AES). Optimization of operation conditions of the spectrometer; selection of the analytical spectral lines (Cu II 224.700 nm and Zr II 354.262 nm), methods of calibration and sample preparation (dissolution in the mixture of HNO₃ and HF added with HCl) provided the lowest standard deviation of the analytical signal. A procedure of oxygen determination in the studied alloys using inert gas fusion method and a procedure providing spectrophotometric determination of copper and gravimetric determination of zirconium from the same sample weigh along with ICP-AES quality control are developed. The results of analysis of Cu_100xZr_x alloys obtained according to all developed techniques satisfactory match each other and, taking into account the correction for the oxygen content, coincide (to the error about 0.5 wt.%) with content of copper and zirconium introduced upon the synthesis.

Method of stripping voltammetry with mercury film and modified glassy carbon electrodes is used for determination of lactic acid. We specified conditions of voltammetric determination of lactic acid at 0.1 M KCl as background solution and studied the impact of concomitant hydroxy carboxylic acids on the analytical signal of lactic acid. An algorithm of lactic acid determination in veterinary preparations on a mercury film electrode is developed. The accuracy of the procedure is confirmed in spiking tests. The determinable concentrations range from 2 to 100 g/dm³.

We obtain the basic equations of the method of fundamental parameters for X-ray analysis of thin coatings with allowance for direct excitation and secondary fluorescence. Introduction of the secondary fluorescence becomes especially important when radiation of the atoms of coating (or substrate) can excite the atoms of the substrate (or coating). We have shown the necessity of taking into account the thickness of substrate films containing heavy elements and incorrectness of using full analytical expression of the integrals for secondary fluorescence instead of numerical calculations by the angle. Sources of the reference data for mass absorption coefficients and photoabsorption, probability of electron transitions and fluorescence used in formulas are indicated. An algorithm for determination of the composition of such coatings on x-ray fluorescence spectrometers configured for analysis of bulk (uncoated) samples, and methods of improving the accuracy of the calculation are proposed.

Quantitative x-ray texture analysis (QXTA) based on the measurements of direct pole figures and electron backscattered diffraction (EBSD) are used to study features of texture and structure formation of MA2-1pch magnesium alloy subjected to equal channel angular pressing (ECAP) and subsequent annealing. Shear bands (60 μm) oriented at an angle of 45 - 50° to pressing direction are observed. An inclined dissipated basal texture present in the shear bands changes to a prismatic texture outside them. This results in activation of the basal slip in the shear bands which is confirmed by Schmid factor distributions. The effect of texture and orientation of the shear bands on the anisotropy of the strength mechanical properties of the alloy is discussed.

A process temperature is studied during microarc thermo-chemical treatment of steel product immersed in a container with powdered coal and heated by electric current. Feature of the process consists in formation of microarc discharges concentrated around the product. Theoretical temperature of coal combustion is calculated. Platinum-platinum-rhodium thermocouple is used for measurements. Thermocouple contacts are connected to a digital multimeter and then gained information is transmitted to a personal computer. Experimental time dependence of the sample surface temperature exhibits 4 sections corresponding to different kinetics of sample heating. A decrease in the sample heating rate within a temperature range of 200 - 270 °C is attributed to endothermic reactions in the coal whereas stabilization of the sample temperature at a level of 1250 °C is associated with the special features of heat release during combustion of coal in the working cell.

Determination of the glass transition temperature of wet samples is complicated by moisture desorption during measurements which leads to overestimated results especially at low heating rates. Study of the possibility of eliminating this problem using extrapolation techniques described in ISO 6721-11 showed the limited applicability of the method since the linear dependence of the glass transition temperature on the heating rate is broken under certain degree of moisture saturation. It is shown that the maximum value of the mechanical loss modulus can be used as a characteristic temperature of glass transition instead of the inflection point on the storage modulus curve thus providing a linear dependence of the extrapolated temperature of glass transition on the time of sample boiling.

Data of studying characteristics of linear and nonlinear fracture mechanics using numerical methods of calculation are presented. The results provide for casting of the surface crack developing up to the exit to the surface of the part. Furthermore, they provide an opportunity to specify the estimation of the survivability and durability of the elements of responsible equipment with allowance for kinetics of local processes of fracture along a contour of surface inclined semi-elliptical cracks considering local 3D character of the stress state and their relative depth.

Samples of working steam turbine blades - native and coated with a protective layer are studied. Cylindrical samples with one-side notch of varying depth are used to evaluate the effect of the depth of erosion damage to the blades on the durability of the material and to test them for cyclic crack resistance. Both optical microscope measurements and crack opening displacement (COD) method are used to monitor and study the crack depth and crack length during tests. The effect of protective coatings on the static load strength, fatigue life, durability and cyclic crack resistance of the blade material is estimated.

An example of using acoustic emission (AE) in determination of the critical points in tribological tests on a standard friction machine is presented. A distinctive feature of the proposed approach is a method of measuring and setting fracture loading, as well as simulation of the dominant wear processes in a tribological device. The approach can be used as a method of identification of AE sources which are registered upon friction and wear of different friction units. It is shown that confocal laser scanning microscopy is self-consistent and effective procedure for tribological tests and, thus, can replace most of the methods that are commonly used in assessing wear.

A problem of constructing a stable forecasting model using feature selection methods is considered. We propose to use a multicollinearity detection criterion which is necessary in the case of excessive number of features. Model is considered stable if small changes of the feature vector entail small changes of the target output vector. Mathematical definition of the model stability is also presented. Multicollinearity problem comes from correlation between features and causes loss of stability of the model. To study the properties of the detection criterion an additional research was undertaken which led to development of Belsley method. To prove the correctness and applicability of the approach to the problem of multicollinearity both theoretical reasoning and extra experiment are provided. The proposed criterion runs an algorithm to exclude correlated features, reduce dimensionality of the feature space and obtain robust estimations of the model parameters. The algorithm is based on step-regression method. The main idea is to add and remove the features consequently according to this criterion. The Lasso and LARS algorithms were chosen as the basic ones to compare with. The computational experiment is used to study an hourly-price forecasting curve problem with the proposed and the basic (reference) algorithms. The experiment is carried out using real time series of the German electricity tariffs.

The main problem of the theory of estimation is to find optimal estimates for the unknown parameters. There are two approaches to solving those problems: an approach based on a sample of the finite size and the asymptotic approach, based on a sample of the growing size. The asymptotic approaches can exhibit the properties of optimality as n → ∞. One of them is the approach of asymptotic minimax estimates. This property is called the local asymptotic minimax estimates and is based on the asymptotic behavior of the sequence of statistical experiments at approaching sequences of alternative hypotheses. In this paper we consider the asymptotic normality of the estimates of Bayesian type and asymptotical minimax efficiency of maximum likelihood estimates using the property of the local asymptotic normality of the likelihood ratio statistics in a model ofrandom censoring from both sides.