A discussion of the prospects for creating a multi-element atomic absorption (AA) spectrometer leads to the conclusion regarding the expediency of using spectral devices of relatively low resolution. Previous studies showed that the spectrometer with instrumental bandwidth 0.12 nm equipped with a CCD detector could provide the absorption measurements within a wavelength range of 200 – 400 nm using low-noise radiation sources, e.g., deuterium or low current xenon lamps. The rate of data acquisition was sufficient for vapour spectra monitoring during the pulse atomisation in graphite furnace atomizer. The loss in sensitivity due to low resolution is compensated by the possibility of direct determination of several elements in a single liquid or powder sample. Feasibility of multi-element simultaneous AA spectrometry depends on the efficiency of atomization technique and technology of data processing. The concurrent problems are discussed by the example of new calculation algorithm and its application to the analysis of multi-element nitrate and halogen containing reference materials. It is shown that linearization of the calibration curves for about 10 – 15 elements, which are not subject to chemical impacts, can be carried out automatically in a concentration range up to 4 – 5 orders of magnitude with 5 – 10 % deviation from the linearity at the ends of the interval. For the elements forming stable molecular compounds further improvement of the atomization technique is required.

An approach to detection of triterpene glycosides in ginseng extracts is developed using high performance liquid chromatography/mass spectrometry (HPLC-MS). Enhanced selectivity compared to commonly used HPLC-UV techniques provides simultaneous registration of chromatographic peaks and determination of 23 major and minor ginsenosides. For this purpose, in addition to the use of highly selective MS detection of adduct ions of sodium ginsenoside molecules and fragmentary sapogenin ions, special conditions of chromatographic separation on a sorbent modified with pentafluorophenyl (PFP) groups were specified. The effect of column temperature and mobile phase composition on the separation selectivity of glycosides was also studied. Though we failed to achieve complete chromatographic separation of the peaks for several compounds (F4 and Rg6, Rk3 and Rh4), their determination appeared possible in case of their joint attendance due to registration of the signals that differ in the value of m/z ratio. For all studied compounds, the linearity ranges and calibration equations along with the metrological characteristics such as the detection limit and reproducibility were determined. The developed approach was tested in standardization of the reference extracts of Asian (P. ginseng) and American (P. quinquefolius) ginseng roots. For some ginsenosides, the content declared by the manufacture did not match the actual content, but for others the concentrations were close to the declared values. Moreover, we managed to expand the range of ginsenosides under control which is rather important for their use in medicine.

Glutathione (GSH) is one of the most important thiol-containing antioxidants involved into various biochemical processes in the human body. Glutathione determination in biological fluids (saliva, urine, serum) and pharmaceutical preparations is rather important for clinical practice. Various analytical methods — spectrophotometry, fluorimetry, high-performance liquid chromatography, NMR spectroscopy, capillary electrophoresis and electrochemical methods — are widely used for this purpose. Electrochemical methods are characterized by easy implementation, low cost and possibility of miniaturization. The electrochemical behavior of reduced (GSH) and oxidized (GSSG) glutathione on a gold-carbon-containing electrode (AuCE) was studied using cathodic voltammetry with different methods of removing oxygen from an electrochemical cell: nitrogen sparging and addition of sodium sulfite (4 mol/dm3). It has been shown that traces of H2O2 that remain in the near-electrode layer on the AuCE even after oxygen removal influence the electrochemical properties of GSH at a cathode sweep of the potential from 0 to –1.8 V: GSH is oxidized by H2O2 to GSSG, the most important product of this reaction is O2. An indirect determination of GSH by the current of oxygen reduction in the Na2SO3 medium in the concentration range from 0.5 × 10–8 to 4.2 × 10–8 mol/dm3 with a detection limit of 2.5 × 10–9 mol/dm3 is proposed. The developed voltammetric method is approved for the determination of GSH in certain pharmaceutical preparations.

The results of unique experimental studies of the strength and service life of a metal-composite high-pressure tank are presented. The goal of the study is to analyze the fracture mechanisms and evaluate the strength characteristics of the structure. The methodology included tests of full-scale samples of the tank for durability under short-term static, long-term static and cyclic loading with internal pneumatic pressure. Generalized test results and data of visual measurements, instrumental and acoustic-emission control of deformation processes, accumulation of damages and destruction of full-scale tank samples are presented. Analysis of the strength and stiffness of the structure exposed to internal pneumatic pressure is presented. The types of limiting states of the tanks have been established experimentally. Change in the stress-strain state of the tank under cyclic and prolonged static loading is considered. Specific features of the mechanisms of destruction of a metal-composite tank are determined taking into account the role of strain of the metal liner. The calculated and experimental estimates of the energy potential of destruction and the size of the area affected upon destruction of the tank are presented. Analysis of test results showed that the tank has high strength and resource characteristics that meet the requirements of the design documentation. The results of the experiments are in good agreement with the results of numerical calculations and analysis of the stress-strain state and mechanisms of destruction of the metal-composite tank.

Analysis of the kinetics of the stress-strain state was carried out using data of tensometry as one of the methods for monitoring the integrity of the aircraft structure and a promising approach to ensure safety of aviation equipment during long-term operation. The advantages of condition monitoring using on-board systems prior to routine procedures aimed at maintaining the airworthiness (which consist mainly in periodic inspections) are presented. The results of using monitoring when studying the fatigue characteristics of the aircraft structure elements at the Central Aerohydrodynamic Institute (Russia) are shown. The study was carried out on samples of longitudinal fuselage joints. Several types of fatigue damages typical for operation of longitudinal joints are considered. The possibility of detecting defects by monitoring of the local stress-strain state with the help of strain gauges under various modes of destruction is assessed. Data on the of fracture surfaces of the damaged elements, fronts and crack propagation rates corresponding to different number of applied cycles were used. The assessment of the controllability of several typical structural and technological variants of longitudinal joints is presented. The results of determining zones of changes in stress-strain state in a bearing sheet with a single main crack are presented, which is the most typical fatigue damage to the longitudinal fuselage joints. The optimal location of the sensors for monitoring the integrity of the joint is proposed. Studies proved that the method of structural health monitoring using tensometry data can be successfully applied to tests for durability and has a prospect of being used in maintaining the integrity of joints and other places of limited access by instrumental non-destructive test methods.

The cycle configuration at two-frequency loading regimes depends on the number of parameters including the absolute values of the frequencies and amplitudes of the low-frequency and high-frequency loads added during this mode, the ratio of their frequencies and amplitudes, as well as the phase shift between these harmonic components, the latter having a significant effect only with a small ratio of frequencies. Presence of such two-frequency regimes or service loading conditions for parts of machines and structures schematized by them can significantly reduce their endurance. Using the results of experimental studies of changes in the endurance of a two-frequency loading of specimens of cyclically stable, cyclically softened and cyclically hardened steels under rigid conditions we have shown that decrease in the endurance under the aforementioned conditions depends on the ratio of frequencies and amplitudes of operation low-frequency low-cycle and high-frequency vibration stresses, and, moreover, the higher the level of the ratios of amplitudes and frequencies of those stacked harmonic processes of loading the greater the effect. It is shown that estimation of such a decrease in the endurance compared to a single frequency loading equal in the total stress (strains) amplitudes can be carried out using an exponential expression coupling those endurances through a parameter (reduction factor) containing the ratio of frequencies and amplitudes of operation cyclic loads and characteristic of the material. The reduction is illustrated by a set of calculation-experimental curves on the corresponding diagrams for each of the considered types of materials and compared with the experimental data.

A new known modification for simulation of annealing to search the global extremum of the functions of many variables uses the fact that the function when n → ¥ converges to the δ-function concentrated at the point of global maximum of f(x). The case when the function has many equal extrema is discussed in detail. Problems of this type are often present, particularly in the design of regression experiments. Here we introduce the reader to an extremum search method that is effective in solving a wide range of applied problems, and also illustrate the use of the method in some of the simplest problems of designing the regression experiments. The proposed modification of simulated annealing uses quasi-random search at the intermediate stages. This is not the most rapid, but very reliable method which provide a complete exploring of the function domain. When solving numerical examples, the so-called exact D-optimal designs are constructed, which are very difficult to be obtained by other methods. Although with the increase in the number of variables, the complexity of the method (as well as the complexity of other well-known methods) increases dramatically due to an increase in the order of the determinant, the proposed algorithm is simple, reliable, and easily parallelized. It is known that the gain from using optimal designs in some cases can justify any computational costs of developing those designs. Using the described technique, the reader will be able to construct (even using the laptop capacity) the optimal designs in different areas at moderate values of the parameters (for example, for quadratic regression for s variables in variables for s ≤ 10).

In analysis of variance models the hypotheses about factor significance form comparisons of the levels of the same factor. If there are no reasons according to the criterion for testing such hypotheses to reject the hypothesis about the equality of some levels of factors, then these levels are considered significantly different. The goal of the article is to find out whether the levels of factors have a significant effect on the response variable. Linear models of analysis of variance (AV) under conditions of complete and incomplete factor design are considered. As a computational scheme for processing the AV models the procedure for transforming incomplete rank models into a full rank models and representing the space of linear estimated forms as a direct sum of orthogonal subspaces corresponding to each of the qualitative facts of the model has been developed. Choosing different groups of linearly independent columns in the initial observation matrix and orthogonalizing this system of vectors (as columns of the matrix) we can obtain various orthogonal bases for the space of linear forms under estimation. Projections of the response vector to the vectors of orthogonal basis corresponding to the same basis determine the contribution of this factor to the total sum of squares obtained as a result of the response projection to the entire space of linear forms being estimated. With different orthogonal bases of the space of linear estimated forms, these contributions of factors change. Under conditions of incomplete factor design, one can distinguish an orthogonal basis of the space of linear estimated forms which provides the greatest significance of any comparison of one of the factors, and, consequently, of the factor itself. This allows determination of the best (in a certain sense) experimental design which ensures the greatest significance of the factors selected. To prove the results obtained the method of ranking factors LASSO was used.

The main magnetic parameters sensitive to the structure of steels are the parameters of their saturation loop of magnetic hysteresis: the coercive force Hcs and remanent magnetization Mrs. The saturation magnetization or saturation intensity Mr is most sensitive to the phase composition of steels. The variety of steel grades and modes of technological treatment (e.g., heat treatment, mechanical load) determined the use of magnetic structurescopy and magnetic characteristics — the coercive force Hc, remanent magnetization Mr , and specific hysteresis losses Wh on the subloops of the magnetic hysteresis of steels — as control parameters in diagnostics of the stressed and structural states of steel structures and pipelines. It has been shown that changes in Hc, Mr , and Wh are more sensitive to structural stresses and structures of steels than the parameters of the saturation hysteresis loop of magnetic hysteresis (Hcs, Mrs, and Mrs). The formulas for calculating Hc, Mr and Wh are presented to be used for estimation of changes in the parameters upon heat treatment of steels. Features of the structural sensitivity of the subloop characteristics and expediency of their use for magnetic structural and phase analyzes are determined. Thus, the range of changes in Ìr attributed to the structural changes in steels upon gradual Hm decrease is many times wider compared to the range of possible changes in Mrs under the same conditions. Conditions (relations between the magnetic parameters) and recommendations regarding the choice of the field strength Hm are given which provide the justified use of Hc, Mr and Wh parameters in magnetic structurescopy

The influence of the structure and properties of 30KhGSA steel on the shaping of round-shaped blanks using the method of plastic bending is studied. Bending of the initial steel rod sample results in the sample fracture. Methods of mechanical tests and metallographic analysis used in the study showed that the steel sample in the initial satate has a structure of lamellar perlite. A comparative evaluation of the structure and properties of the steel samples prior to and after additional heat treatment (spheroidizing annealing) revealed that annealing enhanced the plastic properties of the sample and changed the sample structure from lamellar to globular perlite. Formation of the granular perlite structure indicates to the devision of the plates into smaller particles and their further spheroidization due to transferring carbon through the surrounding solid solution. Thus, additional cyclic heat treatment of steel in the state of delivery, allowed us to solve the problem of the rod fracture upon subsequent plastic bending. As a result of the research, the values of the mechanical properties of steel were obtained experimentally, which ensure the process of bending the rod into a round shaped blank without destroying it. The proposed mode of cyclic heat treatment (spheroidizing annealing) can be used to improve the plasticity characteristics of the metal upon shaping by the method of plastic bending.