Vol 62, No 9 (2019)

The dependence between the sampling interval of the domain of values of a one-dimensional random variable and the blur coefficient of the kernel probability density estimate is determined. The studies used the results of an analysis of the asymptotic properties of a nonparametric estimate of the probability density of the Rosenblatt–Parzen type and its modification. It is shown that the modification of the kernel probability density estimate is a smoothed histogram. The optimal expressions for the kernel function blur coefficient and the length of the sampling interval of the domain of values of a one-dimensional random variable are considered. These parameters are obtained from the condition of minimum mean square deviations of the considered probability density estimates. On this basis, a relationship was established between the studied parameters, which is determined by a constant and depends on the applied kernel function and the volume of the initial statistical data. The values of the detected constant are characterized by the form of the reconstructed probability density and are independent of its parameters. According to the data of computational experiments, formulas are proposed for estimating the analyzed constant by the value of the antikurtosis coefficient for symmetric and asymmetric distribution laws. To estimate the antikurtosis coefficient, we used the initial statistical data in the problem of reconstructing the probability density. The results obtained make it possible to quickly determine the length of the sampling interval from the value of the kernel function blur coefficient, which is relevant when testing hypotheses about the distributions of random variables. The presented conclusions are confirmed by the results of computational experiments.

Using the example of a three-channel system for measuring the level of filling of tanks of launch vehicles, we perform a comparative assessment of the accuracy and robustness of various algorithms for processing measurement information received from three measuring channels of the same type. We consider various processing algorithms of three equal-precision measurements: finding the arithmetic mean of three equal-precision measurements and a majority choice of three equal-precision measurements. For these algorithms, the probability density function of the measurement errors and confidence limits of the measurement error are found using the assumption of uniform or normal laws of the error distribution of three equally accurate measurements. A generalized algorithm for processing redundant information is proposed. The essence of the generalized algorithm is the addition of three equally accurate measurements taking into account individual weighting factors. Weight coefficients are selected based on the values of three equally accurate measurements: the minimum and maximum values are assigned the same weighting coefficient, and the median is assigned a coefficient which normalizes the sum of the three weighting factors to one. For a generalized algorithm by means of simulation modeling, the confidence limits of the measurement error are determined depending on the selected weighting factors. The robustness of the considered processing algorithms is evaluated for three equally accurate measurements performed on three measuring channels identical in design, with a random perturbation applied to one of the channels. Recommendations on the selection of weights for three equal measurements are given. For the fuel level measurement system under consideration, it is justified to use an algorithm for processing measurement information based on a majority choice of three equally accurate measurements.

A nonparametric method for estimating the mean square functional of a multimodal probability density of a one-dimensional random variable is examined. The proposed method is based on using the Sturgis and Heinhold–Gaede formulas and an optimum sampling procedure for sampling a range of values of random quantities. This method is compared with the traditional approach based on choosing a spread coefficient using the condition for the maximum of the likelihood function. The conditions for competence of this method are determined.

Procedural, technical and operational difficulties that arise with the use of flowmeters, both ultrasonic flowmeters and flowmeters constructed with the use of constriction devices (orifice-based flowmeters), for measuring feedwater flow rates at nuclear power plant reactors are considered. Results of measurements of these flowmeters are used to calculate the thermal power of the reactor plant and are important for controlling the nuclear reactor. It is shown that periodic inspection of welded-in orifice devices used at nuclear power plants of Russian design is not possible. Practical aspects of tests of ultrasonic flowmeters under normal conditions with assigned high precision for operation under the conditions of a power-generating unit are considered. New approaches to evaluation (inspection) of the state of constriction devices used in cooling agent flowmeters that are not accessible to examination throughout the entire operating period at nuclear power plants are proposed. It is shown that a method of direct comparison of the results of simultaneous measurements with a more precise mobile ultrasonic flowmeter may be used to estimate the error of flowmeters constructed with the use of constriction devices. A unified method is suggested for evaluating the state of constriction devices without dismantling the devices from the pipeline based on information on the total error of the flowmeters along with a complex of measures for the development of technical, procedural, and managerial means of controlling the reliability of flowmeter measurements with the use of constriction devices and ultrasonic and flowmeters.

We consider the problem of determination of the intelligibility of speech of a speaker according to a finite fragment of the speech signal. It is shown that the main difficulties in the solution of this problem are connected with the necessity of analysis of small samples. To overcome the problem of small samples, we proposed a new high-speed method for measuring the intelligibility of speech signals on the sonic level of its perception. The proposed method is based on the information indicator of speech intelligibility in the Kullback-Leibler metric. We consider an example of practical realization of the new method with the use of a self-regression model of minimum sound units from the speech flow of a speaker. The characteristics of efficiency of the new method are analyzed. It is shown that, under certain conditions, the application of the information indicator enables us to realize the general systems principle of guaranteed result. On the basis of the software developed by the authors, we designed and performed full-scale experiments and established quantitative estimates for the speed of this method. It is shown that, with the help of this method, quite accurate and reliable estimates of the information indicator are obtained for short (2–3 min) segments of speech signals. The accumulated results and the conclusions made on their basis are intended for applications in the development of new systems and improvement of the existing systems of automatic speech processing and recognition intended for the operation in the real-time mode.

A fluorescent nanosensor based on colloidal quantum dots CdSe/ZnS modified with mercaptoacetic acid to determine reduced glutathione, a non-protein compound that plays an important role in protection against oxidative stress, is developed. Sample preparation protocols that allow determination of reduced glutathione in a wide range of concentrations are presented. Dependence of the fluorescence intensity of the system on the incubation time for a number of concentrations of reduced glutathione was measured. The possibility of using the proposed nanosensor for reliable and sensitive determination of reduced glutathione in the concentration range from 10 to 1000 μM is confirmed. The results can be used for quantitative determination of reduced glutathione in physiological media, which is of considerable interest for medical diagnostics.

A source of correlated photon pairs based on spontaneous parametric scattering is developed and created. The source may be used both as a probabilistic source of single-photon radiation with low value of the parameter g⁽²⁾(0) and as a bi-photon source for the quantum distribution of keys based on the Einstein–Podolskiy–Rosen paradox as well as for the Klyushko–Penin reference method of determining the quantum efficiency of detectors of low-photon radiation. Experimental results of the generation of bi-photons for pairs of wavelengths of 651 nm (signal wave) and 1100 nm (idler wave) are presented. The quantum efficiency of a low-photon 651-nm wavelength detector is measured by means of this source using the Klyushko–Penin reference method. The new source may be tuned comparatively easily over a broad range of wavelengths from 558 to 1550 nm.

A calibration device intended for metrological assurance of instruments used to measure deformations and displacements by methods of electronic speckle interferometry and shearography is developed. The optical methods presented here may be applied to different types of materials possessing rough surfaces. The proposed device reproduces stress-strain states by means of elastic deformation of the surface of a membrane through the use of a rod and leverage. Calibration of the device is performed, its transfer characteristics are investigated, and the nonlinearity of the displacement of the surface of the membrane is estimated. Results of experiments designed to measure the stress-strain state with the use of the noncontact method of shearography are presented. The phase image produced by deformation of the membrane is described and the metrological characteristics of the calibrated device are estimated. It is shown that through the use of the present calibration device it is possible to use optical methods not only for qualitative assessment of the deformation of objects of complex shape, but also for quantitative estimation of the geometric characteristics of these objects.

A new radio-wave method of reconstruction of the relative permittivities and thicknesses of multilayer materials and coatings is proposed. The method is based on the solution of inverse problems in the reconstructionof the structure of the electrophysical parameters of special multilayer materials and coatings from the frequency dependence of the attenuation coefficient of the field of a slow surface electromagnetic wave. The principal differences of the new method from well-known radio wave methods of determining the electrophysical parameters of multilayer materials are demonstrated. In contrast to methods that involve an informative parameter – the complex reflection coefficient – the proposed method yields an increase in the precision and reliability of the reconstruction of the structure of the relative permittivitties and thicknesses. Improved precision and reliability is achieved by taking into account the linear dependence of the attenuation coefficient on frequency as well as reducing the number of fixed measurement frequencies. The results of experimental studies that confirm the linear dependence of the attenuation coefficient of the field of a surface electromagnetic wave on frequency as well as a decrease in the number of fixed measurement frequencies are presented. The method implements a simple measurement procedure, since only the values of the field strength of the surface electromagnetic wave are measured and there is no need for phase measurements in the method. Reconstruction of the permittivity of a three-layer coating consisting of polymethyl methacrylate, F-4D PTFE, and semi-hard rubber with precision acceptable for practical applications is realized with the use of experimental results of measurements in a multifrequency measurement complex in the range 9–10 GHz by means of the new method. Experimental investigations of a multilayer dielectric coating demonstrated the theoretical capabilities gained with measurement of the relative permittivity and thickness of the individual layers with relative error not greater than 8 and 6%, respectively.

We study the causes complicating the application of the tone-burst method for the calibration of underwater vector sound receivers. We describe an experiment performed to confirm the correctness of the procedure of calibration of a vector receiver by the method of moving complex weighted averaging when the sensitivity measured in the reverberating sound field cannot be compared with the results of other independent methods. As a criterion, we use the correctness of measurements of the parameters of distortions introduced by the sound waves reflected from the water–air interface in the direct wave of the emitter. The proposed technique makes it possible to experimentally establish the possibility of selection of the vector quantity of the direct wave from the emitter in the reverberating sound field formed in the water tank within the frequency range overlapping the range of the tone-burst method and extended to the frequencies of the chamber of standing sound waves.

Hydrogen is a key parameter that determines the safe operation of defense and civilian facilities. The maximum allowable level of hydrogen concentration in high-strength steels and aluminum alloys for aviation is 0.05–0.5 ppm. For technological control of the quality of materials and ensuring the principle of unity of measurement tools, state standard samples (SSS) are required, in which the certified values of the hydrogen content are in this range. The article presents data on the development and study of the stability of the certified value of the new generation of SSS. The production of these samples, together with the AV-1 precision mass spectrometric analyzer of hydrogen, completes the work of the team of authors to create a metrological quality control system for modern materials for the aerospace industry.