Measurement of complex reflection coefficients and complex transmission coefficients of radio engineering devices in waveguide paths is widely used in radar and radio navigation in the development, production, testing and operation of microwave devices and components. These parameters characterize the quality of matching of transmit-receive paths at ultra-high frequencies. Before the introduction of the State primary standard of units of complex reflection coefficient and complex transmission coefficient in waveguide paths in the frequency range from 2.14 to 178.4 GHz GET 219-2024, metrological traceability of units of complex reflection coefficient and complex transmission coefficient in waveguide paths was ensured to the working standards developed in the 1980s. The operating frequency ranges and automation level of outdated standards did not meet modern requirements and did not fully provide a solution to modern measuring tasks. In order to ensure the uniformity of measurements of complex reflection coefficients and complex transmission coefficients, the State primary standard of units of complex reflection coefficient and complex transmission coefficient in waveguide paths in the frequency range from 2.14 to 178.4 GHz has been developed and approved. The standard provides reproduction, storage and transmission of units of complex reflection coefficient and complex transmission coefficient in 16 domestic and 22 foreign waveguide paths. The block diagram, technical and metrological characteristics of the standard are given. The research results confirmed that standard has comparable metrological characteristics with the standards of national metrological institutes of other countries.

The problem of the format (the form of representation by difference, scattering parameter, distribution) of the characteristics of the accuracy of the results in solving measurement problems in terms of the theory of errors and the concept of uncertainty is considered. It is shown that for the error as a difference, the key question is the uncertainty of the so-called true value. For measurement uncertainty, when switching to estimating the scattering parameter based on a set of repeated measurements and getting rid of the adjective true, a number of key issues of a different plan arise – the lack of logic of statistical inference, the inconsistency of the term “confidence level” with the term “confidence probability” in state verification schemes and the practical uselessness of measurement uncertainty characteristics in risk analysis tasks. However, the endless improvement of measurement methods and tools in the theory of errors and an unlimited amount of information for a complete description of the measured value in the concept of uncertainty is a common defect of both approaches, only in other words. Conceptually, the transition from error to uncertainty is an intermediate stage to the representation of accuracy characteristics by probability distributions. A brief overview of the transformation of the point of view of international metrology on this issue is given. The evaluation of the accuracy of the results is presented as a structural-parametric identification of the drift of metrological characteristics of measuring instruments and standards, as well as metrological certification of methods for solving measurement problems in the cross-observation scheme in terms of probability distributions. This allows you to get rid of the problems of incompleteness of other formats for representing accuracy characteristics. The most complete characterization of accuracy for the theory of errors and the concept of uncertainty is the format of the probability distribution. However, the endless improvement of measurement methods and tools in the theory of errors and an unlimited amount of information for a complete description of the measured value in the concept of uncertainty is a common defect of both approaches, only in other words. Conceptually, the transition from error to uncertainty is an intermediate stage to the representation of accuracy characteristics by probability distributions. A brief overview of the transformation of the point of view of international metrology on this issue is given. The evaluation of the accuracy of the results is presented as a structural-parametric identification of the drift of metrological characteristics of measuring instruments and standards, as well as metrological certification of methods for solving measurement problems in the cross-observation scheme in terms of probability distributions. This allows you to get rid of the problems of incompleteness of other formats for representing accuracy characteristics. The most complete characteristic of accuracy for the theory of errors and the concept of uncertainty is the format of the probability distribution.

A technique has been developed for constructing a phase equilibrium line in the range from the triple to the critical point for a technically important substance, perfluorooctane (C₈F₁₈), which is currently used in various fields of industry and medicine. The proposed phase equilibrium line model includes the following equations: vapour pressure; saturated liquid density; saturated vapour density; “apparent” heat of vaporization. In this case, the vapour pressure equation satisfies the requirements of the scale theory of critical phenomena near the critical point, and the Wegner model in the vicinity of the triple point. The coexistence curve model in the vicinity of the critical point satisfies the Yang-Yang model and renormalization group theory for asymmetric systems, and in the region of rarefied gas it satisfies the linear model of average diameter. In the temperature range 246.15–496.99 K, table for perfluorooctane have been developed, including pressure and density of saturated vapor, density of saturated liquid, heat of vaporization, first and second derivatives of saturated vapor pressure. Using latest experimental data, as well as experimental data on the critical pressures of perfluoroalkanes as a function of their molecular weight, the following values of critical parameters were selected: critical pressure – 1.548 MPa, critical density – 596.4 kg/m³, critical temperature – 496.99 K. A number of statistical characteristics were calculated, including absolute mean deviation and standard deviation, characterizing the accuracy of the proposed phase equilibrium line model when describing experimental data obtained in generally recognized international thermophysical laboratories. The results obtained are useful for high-tech companies engaged in the development of innovative technologies: in the field of radio-electronic and electrical industries, in which perfluorooctane is used as a liquid dielectric and coolant; in medicine, where perfluorooctane is used as a gas transport liquid and is used for ophthalmic purposes; magnetic fluid sealers for the purpose of isolating hazardous substances from the environment and seals for devices operated in vacuum conditions or in contact with aggressive substances; magnetic fluid separators for separating non-ferrous metals by density, etc. The results of this study can also be used in developing the fundamental equation of state for perfluorooctane. The results obtained are useful for high-tech companies engaged in the development of innovative technologies: in the field of radio-electronic and electrical industries, in which perfluorooctane is used as a liquid dielectric and coolant; in medicine, where perfluorooctane is used as a gas transport liquid and is used for ophthalmic purposes; magnetic fluid sealers for the purpose of isolating hazardous substances from the environment and seals for devices operated in vacuum conditions or in contact with aggressive substances; magnetic fluid separators for separating non-ferrous metals by density, etc. The results of this study may also be useful in developing the fundamental equation of state for perfluorooctane.

The paper considers the improvement of the quality of products of machined production in connection with the quality of machining of various products and, accordingly, with the accuracy of the equipment used. It is noted that geometrical errors, which account for up to 40 % of the total error of a multi-axis, especially three-axis, metal-cutting machine tool, have the greatest influence on the accuracy of product machining. In order to improve the quality of product machining, it is necessary to correct its parameters according to the measurement information received during machine tool operation, for which the methods of mathematical modelling are used. Models of the volumetric error of a three-coordinate metal-cutting machine tool are developed, taking into account the summands of the first (linear) and second (quadratic) order of smallness. A comparative analysis of the developed models is carried out. The results of experiments on measurement of volumetric errors of the STAN S500 complex and their correction on the basis of the nonlinear theoretical model are given. It is found that in the range of angular errors 0–2.5′ the consideration of quadratic terms of the model in addition to linear ones does not lead to a significant reduction of the volumetric error. It is shown that when processing measurement information of multi-axis metal-cutting machines it is sufficient to limit the consideration of components of the volumetric error not higher than the first order of smallness. The research results are useful for the acceptance and periodic control of the volumetric error of metal-cutting machines, as well as for the programme reduction of the volumetric error.

The cells of fixed freezing points of metals are an important component of the working standards of temperature of the 0th category. These standards are intended to reproduce the unit of temperature kelvin in accordance with ITS-90, which is currently the main method in the temperature range from –189 to 1084 °C. The transfer of the temperature unit is carried out by comparing the cells of the working standards of temperature with the cells of the state secondary standard of temperature. In order to develop recommendations for increasing the interval between comparisons and changing the requirements of the State Verification Scheme, one of the most important characteristics of the cells of the working standards of temperature was studied – the instability of the cell temperature in the interval between comparisons. The paper summarizes the results of the study of 26 cells of fixed points of tin, zinc and aluminum, the service life of which was from 2 to 10 years, and the interval between comparisons was from 2 to 5 years. Possible causes of instability of the reproducible temperature are described and the uncertainty of comparisons of working standard cells with secondary standard cells is calculated. The analysis of the results showed that the instability values over a long period of time do not exceed 1.02 mK for tin cells, 1.75 mK for zinc cells and 6.47 mK for aluminum cells. The most probable cause of deviation of the temperature of working standard cells from secondary standard cells is the different purity of the metals used. It is noted that the destruction of the quartz shell of the cell without mechanical action is unlikely, and the effect of pressure on the temperature of the reference point is absent. Based on the results of the comparative analysis, it was concluded that it is possible to increase the interval between comparisons for ampoules of tin and zinc to five years. Such an increase in the interval has a positive economic effect by reducing the cost of operating the state secondary temperature standard and transporting ampoules to the comparison site. For aluminum cells, an individual approach to setting the interval between comparisons is recommended based on the analysis of the results of previous comparisons. The materials published in this paper may be useful to specialists of metrological centers working with working temperature standards, as well as to all scientists studying the processes occurring in cells for measuring the solidification temperature of metals.

The review of publications devoted to the study and features of the registration of electromagnetic emission observed during the loading of samples of rocks, metals, composite materials in laboratory conditions, as well as in areas of disintegration of rock massifs at mining sites is given. Electromagnetic emission observed during the destruction of rock samples in laboratory experiments and field conditions can appear itself not only in the high and low frequency ranges (1000–3·10⁶ Hz and 500–1000 Hz, respectively), but also in the very low and ultra-low frequency (200–500 Hz and 0.01–200.00 Hz, respectively) ranges. However, the overwhelming majority of experimental studies of rock samples under the influence of a destructive load in laboratory conditions are aimed at measuring electromagnetic emission of the high frequency range. An instrumentation and measurement complex is described that allows recording electromagnetic emission in the ultra-low frequency range. The composition of the instrumentation and measurement complex includes magnetic modulation transducers of magnetic induction as magnetic field sensors. The methodology of laboratory experiments on recording electromagnetic signals arising from the influence of an external load on rock samples using an instrumentation and measuring complex is presented. An example of uniaxial loading of a basalt sample is given. When loading the sample under consideration, the amplitude of the electromagnetic emission pulses exceeds the background values of technogenic magnetic noise by two orders of magnitude. The high sensitivity of the magnetic modulation transducer of magnetic induction allows it to be used to register the components of magnetic induction in the process of destruction of rock samples in conditions of interference from technogenic magnetic noise. The results obtained are important for monitoring and forecasting the process of cracking before mining impacts, as well as for studying the geological environment and processes that generate low-frequency electromagnetic emission in the mining areas.

Within the framework of a dynamically developing direction of research in the field of acoustic measurements, the task of spectral analysis of speech signals in automatic speech recognition systems is considered. The low efficiency of the systems in unfavorable speech production conditions (noise, insufficient intelligibility of speech sounds) compared to human perception of oral speech is noted. To improve the efficiency of automatic speech recognition systems, a two-stage algorithm for spectral analysis of speech signals is proposed. The first stage of speech signal processing consists of its parametric spectral analysis using an autoregressive model of the vocal tract of a conditional speaker. The second stage of processing is the transformation (modification) of the obtained spectral estimate according to the principle of frequency-selective amplification of the amplitude of the main formants of the intra-periodic power spectrum. The software implementation of the proposed algorithm based on the high-speed computational procedure of the fast Fourier transform is described. Using the author’s software, a full-scale experiment was carried out: an additive mixture of vowel sounds of the control speaker’s speech with white Gaussian noise was studied. Based on the results of the experiment, it was concluded that the amplitude of the main speech signal formants were amplified by 10–20 dB and, accordingly, a significant improvement in the speech sounds intelligibility. The scope of possible application of the developed algorithm covers automatic speech recognition systems based on speech signal processing in the frequency domain, including the use of artificial neural networks.

Monitoring of operational parameters of X-ray diagnostic equipment, including computer tomographs, is mandatory during acceptance and periodic tests in medical organizations. The importance of control of anode voltage of X-ray radiator is described (as one of the main technical parameters in diagnostic tests of patients, which can influence the quality of visualization and safe operation of the equipment). Anode voltage is evaluated by non-invasive methods using universal dosimeters in the user mode of equipment operation. The influence of profiled filters of Somatom Definition AS, SOMATOM go.All (Siemens, Germany) scanners on the accuracy of anode voltage measurement was investigated. The tests were conducted in clinic conditions without partial removal of the gantry (a structural element of the tomograph, inside which the system “X-ray emitter – detector” is located) and connection to the high-voltage circuit of the device. The distance between the sensitive elements of the measuring device and the displacement of the center of the sensing area relative to the position of the central axis of the X-ray beam of computed tomography scanner were taken into account. Normalized curves of kerma values, anode voltage values and their approximating analytical functions were obtained using a Piranha R&F/M 657 universal dosimeter (RTI Electronics AB, Sweden) at its displacement relative to the laser centralizer of computed tomography scanner. Based on the scheme for noninvasive estimation of anode voltage value, a formula of the relative deviation of the measured value of the anode voltage associated with the presence of a profiled filter at the output of the X-ray emitter of the tomograph and the displacement of the center point of the sensitive area of the measuring device relative to the central axis of the X-ray beam of the tomograph is obtained. The validity of the data based on the formula is confirmed experimentally. The results of the study will be helpful to technical specialists who maintain or control the X-ray computed tomography operating parameters.