An approach to sorptive separation of Se (IV) from solutions on a novel S,N-containing sorbent with subsequent determination of the analyte in the sorbent phase by micro-x-ray fluorescence method is presented. The sorbent copolymethylenesulfide-N-alkyl-methylenamine (CMA) was synthesized using «snake in the cage» procedure and proven to be stable in acid solutions. Conditions for quantitative extraction of Se (IV) were determined: sorption in 5 M HCl or 0.05 M HNO₃ solutions when heated to 60°C, phase contact time being 1 h. The residual selenium content in the solution was determined by inductively coupled plasma mass spectrometry (ICP-MS) using ⁸²Se isotope. The absence of selenium losses is proved and the mechanism of sorption interaction under specified conditions is proposed. The method of micro-x-ray fluorescence analysis (micro-RFA) with mapping revealed a uniform distribution of selenium on the sorbent surface. The possibility of determining selenium in the sorbent phase by micro-RFA is shown. When comparing the obtained results with the results of calculations by the method of fundamental parameters, it is shown the necessity of using standard samples of sorbates to obtain correct results of RFA determination of selenium in the sorbent phase.

A technique of the microwave digestion of mafic and ultramafic rocks is developed for ICP-MS determination of the rare earth elements. A series of experiments was carried out to optimize the digestion parameters (temperature, acid ratio, sample mass) in a microwave system MARS-5. A mixture of acids HF and HNO₃ in a volume ratio of 4:1 was used at the first stage (60 min, 190°C, maximum pressure 20 atm), and after distilling off the excess fluorides in the form of SiF₄ the dry residue was treated with aqua regia (60 min, 190°C, maximum pressure 20 atm). Measurements were carried out using a double-focusing ICP mass spectrometer ELEMENT Finnigan Mat. Multielement standard solution with an acidic composition similar to the analyzed solutions was used for external calibration and indium was used as an internal standard. The detection limits were 0.0002 – 0.008 μg/g. The digestion technique was validated by analysis of the geological reference materials BHVO-2 and BCR-2 (basalts), UB-N (serpentinite), JP-1 (peridotite). The relative standard deviations for the determined elements were below 8% for reference materials BHVO-2, BCR-2, and UB-N, and ranged within 10 – 35% for JP-1 sample. The developed technique was used for determination of the rare earth elements in Kola Peninsula rocks. The correctness of the results was confirmed by comparison with the results of ICP-MS analysis after fusion with lithium metaborate. The rapidity compared to acid decomposition without using a microwave system and low detection limits compared to fusion are the apparent advantages of the developed technique.

Zinc sulfate is the main component in the composition of the acidic zinc plating electrolyte. Deviation in the electrolyte composition from the optimum content leads to destabilization of the electrolysis process and deteriorate the quality of the resulting zinc coating. The proper quality of a zinc coating obtained by galvanic deposition can be ensured only with timely monitoring and adjustment of the electrolyte composition. A technique of X-ray fluorescence determination of zinc (in terms of zinc sulfate) in an acidic zinc plating electrolyte is proposed. The study was carried out using an ARL Quant’X energy dispersive spectrometer (Thermo Fisher Scientific, USA) with a semiconductor silicon-lithium detector. The features of the spectrometer design are presented. The optimal parameters of excitation and detection of zinc radiation were specified when the electrolyte sample was diluted 1:1000. The ZnKα₁ line was used as an analytical line. The plotted calibration graph is linear, the correlation coefficient being 0.999234. The results of zinc determination according to the developed method were compared with the data of the reference method of complexometric titration to prove the reliability of the procedure. The results are characterized by good convergence and accuracy. The proposed method of X-ray fluorescence zinc determination in a zinc plating electrolyte equals complexometric titration in the limiting capabilities and even exceeds the latter in terms of the simplicity of sample preparation and rapidity. The developed method of X-ray fluorescence determination of zinc is implemented in analysis of the electrolyte used in the continuous galvanizing unit at «METSERVIS LLC».

Promising domestic gas and gas condensate fields are characterized by the presence of CO₂ in the composition of the extracted raw materials which (in combination with moisture condensation and a number of other factors) stimulates the intensive development of local corrosion processes). The paper presents the results of studying corrosion of gas production objects using methods of analytical control (gas chromatography with mass spectrometry, X-ray fluorescence spectrometry, X-ray diffraction). It is shown that key parameters (CO₂ partial pressure, mineralization, pH factor, total pressure, etc.) should be considered with allowance for their expected changes during the life cycle of the field and production facilities. To determine the ultimate local corrosion rates, corrosion tests were carried out under conditions of moisture condensation. The corrosion development under CO₂ conditions is shown to depend on the amount of moisture formed during condensation on metal surfaces, composition and content of the condensate in the vapor phase. Monoethylene (MEG) glycol which is used in gas production as a hydrate formation inhibitor can be also present in the condensed medium. MEG concentration also significantly contributes to the rate of corrosion processes Local carbon dioxide corrosion rate can attain several millimeters per year. Analytical methods can be successfully used in combination with other control methods to predict and monitor a corrosion situation (content of a corrosion inhibitor, presence of the corrosion products or deposits, etc.) at gas production facilities.

The key point of 3D printing by selective laser sintering is the necessity of complete filling of the working chamber of the printer with a powder material. Since the powder is not completely consumed during the printing process, 25 – 30 wt.% of secondary (unused in the previous cycle) power is added to the primary material in each cycle. Repeated recirculation leads to degradation of the properties of the working powder mixture and increases the probability of rejects. We present the results of a colorimetric study of aging of polyamide-12 powder used in 3D printing by the method of selective laser sintering. Scanning and computer processing of digital images of primary and secondary polyamide powders obtained by colorimetry were performed using MathLab program package. Colorimetric analysis included the expression of the sample color using the parameters of color models applied in digital technologies for synthesizing colored images. The number of cycles before the onset of intensive destruction is no more than three, which is consistent with the practical experience in printing by selective laser sintering. The results characterizing change in the color of the secondary powder depending on the duration of thermal exposure and the gas medium are presented. It is shown that long-term storage of the powder for subsequent use is not advisable, since the initiators of destruction are already present in the material. Thermal oxidative destruction is shown to be a critical factor limiting the use of secondary powder along with changes in the crystallinity and fractional composition of particles. Computer processing of images of polymer powder obtained by the colorimetric method can be used to control the aging process of consumables and to predict the probability of rejections in 3D printing.

The manufacturing process of ferrite production consists in a chain of structural and phase transformations resulted in formation of ferrite ceramics from disperse systems (their solid phase is represented by metal oxides). The forces of surface tension play a crucial role at all stages of the technological process. A decrease in surface tension forces during grinding due to the use of surfactants (surface active substances) leads to better disaggregation of the components (both original and ferritized). The use of surfactants reduces interparticle friction and provides manufacturing of more dense workpieces at the stage of pressing. Microadditives promote faster formation of contact isthmuses. The goal of the study is to develop a method for determining the surface tension coefficient of 600NN ferrite material during sintering. The proposed approach is based on measurements of the shrinkage of various fragments of a vertically sintered ferrite rod, which are used to determine the values of the coefficient. It is shown that the surface tension coefficient of the studied ferrite material during sintering was σ = 65.2 ± 13.0 N/m with a confidence probability of 95%. The results obtained can be used to study the effect of the sintering temperature, the size of sintered particles, the amount and quality of alloying additives on the forces of surface tension. Moreover, the data can be used in the study of the relationship between the value of the surface tension coefficient and the parameters of the microstructure.

Duplex stainless steels (DSSs) possess a typical biphasic microstructure consisting of equal amount of ferrite and austenite, which provides better combination of the mechanical and corrosion properties compared to the austenitic grade. Despite their good processability, they suffer from embrittlement of secondary phases in a very specific temperature range 450 – 1000°C depending on the composition. Solubilizing treatment after processing is required to obtain a perfect balance between austenite and ferrite and moreover, to dissolve any secondary phases that could have been formed during processing. This implies very high energy consumption of forming processes due to a high temperature (above 1000°C) or high power needed for the forming machines. The electroplastic effect could be used to reduce the force needed to form the material and extend the forming limits. The effect consists in direct interaction between the electrons of the electrical current and the ions of the material. The current mode (e.g., continuous current, pulsed current, pulse duration and duty cycle) plays an important role in the occurrence and the extent of the electroplastic effect. The electroplastic effect is investigated under tension in two-phase duplex stainless steel UNS S32205. Tensile tests under different current conditions (current density and frequency) are compared to room temperature tests. The best effect in terms of reduction of the ultimate tensile strength and increase in the fracture strain is achieved by introducing a multi-pulse current with the maximum density and pulse duration.

A new destructive method for quantitative determination of the damage accumulation in the vicinity of a stress concentrator has been proposed and verified. Increase of damage degree in local area with a high level of the strain gradient was achieved through preliminary low-cycle pull-push loading of plane specimens with central open holes. The above procedure is performed for three programs at the same stress range (333.3 MPa) and different stress ratio values 0.33, – 0.66 and – 1.0, and vice versa for two programs at the same stress ratio – 0.33 and different stress range 333.3 and 233.3 MPa. This process offers a set of the objects to be considered with different degree of accumulated fatigue damages. The key point of the developed approach consists in the fact that plane specimens with open holes are tested under real operation conditions without a preliminary notching of the specimen initiating the fatigue crack growth. The measured parameters necessary for a quantitative description of the damage accumulation process were obtained by removing the local volume of the material in the form of a sequence of narrow notches at a constant level of external tensile stress. External load can be considered an amplifier enhancing a useful signal responsible for revealing the material damage. The notch is intended for assessing the level of fatigue damage, just as probe holes are used to release residual stress energy in the hole drilling method. Measurements of the deformation response caused by local removing of the material are carried out by electronic speckle-pattern interferometry at different stages of low-cycle fatigue. The transition from measured in-plane displacements to the values of the stress intensity factor (SIF) and the T-stress was carried out on the basis of the relations of linear fracture mechanics. It was shown that the normalized dependences of the stress intensity factor on the durability percentage for the first notch (constructed for four programs of cyclic loading with different parameters), reflect the effect of the stress ratio and stress range of the loading cycle on the rate of damage accumulation. The data were used to obtain the explicit form of the damage accumulation function that quantitatively describes damage accumulation process. The functions were constructed for different stress ratios and stress ranges.

We present methodological developments and approach to the formation of the database proceeding from the results of mechanical tests of the samples obtained by Fused Deposition Method (FDM) on a Fortus 380 mc 3D-printer using ABS-plastic. The material of 3D-printed structures reveals a natural anisotropy of the mechanical characteristics which are to be studied prior to developing of the mathematical models. Such studies are always limited by the goals and capabilities of researchers, on the one hand, but, on the other hand, they are aimed at sharing and integrating of the results obtained by various research groups. The accumulated data provide the opportunities for in-depth study and understanding of the general patterns and features of deformation of the materials obtained by additive technologies. Therefore, the data on their mechanical testing and processing should be available in the open (or limited) access. Data of standard tests for three-point bending of the samples that differ in the orientation of deposited layers considered together with the initial data and documents, the developed test program and data the final report were used to form a desired database. Formation of this database is an example that demonstrates an approach to arranging the scientific data which implements the key principles of data availability. The developed approach provides the possibility of structuring complex data sets keeping an independent access to each of the objects. The generated database is available at https://od.ict.sc/DuPXcR.

Increased attention to the development of modern approaches to probabilistic evaluation of research results in the field of forensic science is attributed to the trends of critical analysis of the current state of forensic science and requirements for clear characteristics of limitations of research results, including indicators of uncertainty of the data obtained and associated estimated probabilities. One of the fundamental provisions of the modern theory of evaluating judicial evidence, along with the admissibility and desirability of using probabilities, is the principle of comparing these probabilities in the light of their conditionality by competing versions arising from the adversarial nature of justice. In this regard, the purpose of this article is to develop methodological approaches to the use of the likelihood ratio as the most appropriate form of determining the significance of conclusions sent by an expert to the court for the formation of evidence. The empirical basis of the article is based on a brief review of publications from 2000 to 2018, devoted to the application of the concept of the likelihood ratio in forensic activities. According to many scientists, the use of this concept can provide a real assessment of the reliability of the evidence. In legal proceedings, evidence is generally understood as information about facts obtained in accordance with the procedure provided for by law, on the basis of which the presence or absence of circumstances that are important for the proper consideration and resolution of the case is established. In this publication, the term «evidence» is considered through an expert-technological prism and is presented as various quantitative continuous measurements (properties and characteristics of objects of forensic expertise), which are used when comparing a known and questioned sample to solve the question of their origin from one or from different sources. The article discusses the most common normal distribution of continuous data and a general approach to calculating the likelihood ratio (LR) using probability density functions (pdf). It is shown that in order to account for the variability of compared samples, three databases are required for calculating LR: a potential database, a control database of a known sample, and a comparative database of a questioned sample. Examples of calculating the LR and strength of evidence performed for various types of examinations are given. The procedures for calculating LR are generally the same, but the authors suggest different techniques to calculate and graphically represent the strength of the proof. In more detail, the publications present the so-called value of the cost or penalty for an incorrect forecast (C_lLR), introduced the terms of trueness and reproducibility, as well as the confidence interval of this value. The article highlights a number of features of calculating LR for multidimensional continuous data. Of great interest is the use of the speaker model in sound recording expertise in the form of a weighted sum of Gaussian densities M components (Gaussian mixture models — GMM). Each density component in this sum is a D-dimensional Gaussian pdf with an average vector value and a covariance matrix. It can be assumed that the use of GMM-pdf in LR calculations is effective not only for forensic examination of speaker recognition, but also for other types of examinations. The universality of assessing the similarity/difference of objects of forensic research using the likelihood ratio indicates the prospects for applying the concept.