Влияние геометрии и граничных условий в области сцепления материалов на рассеяние ультразвуковых волн. Ч. 2. Особенности экспериментального моделирования

Повышение эффективности акустической диагностики объектов со слоистой структурой применительно к выявлению слабо выявляемых дефектов сцепления материалов является важной производственной задачей. Цель работы состояла в экспериментальном моделировании рассеяния ультразвуковых волн на образцах предложенных конструкций имитаторов дефектов с дискретно и плавно изменяющимися граничными условиями, коррелирующими с фазовой характеристикой продольных волн в процессе их взаимодействия с дефектной границей контактирующих материалов.Проведён краткий анализ некоторых методов и средств экспериментального моделирования рассеяния объёмных и поверхностных волн на границах контактирующих материалов применительно к совершенствованию метода обнаружения слабо выявляемых дефектов сцепления (адгезии) материалов. Для этого разработана и изготовлена иммерсионная установка, работающая в теневом режиме и позволяющая моделировать пространственные поля рассеянных продольных волн на неоднородной или дефектной границе сцепления материалов. Как предполагается, взаимодействующие с такой границей волны приобретают дискретный или плавно изменяющийся фазовый сдвиг, существенно сказывающийся на формировании поля рассеяния в его периферийной зоне. Увеличение же этого сдвига позволяет значительно повысить чувствительность обнаружения слабо выявляемых дефектов.Проведено экспериментальное исследование рассеяния продольных волн на разработанной установке и имитаторах дефектов, моделирующих дискретно и плавно изменяющиеся граничные условия, которые согласуются с изменением фазового сдвига рассеиваемых волн. Получены амплитудные зависимости поля рассеяния в зависимости от угла их приема в диапазоне от 20º до + 20º и смещения центра моделируемого дефекта относительно оси зондирующего акустического луча. Как установлено, наблюдается качественное соответствие между расчётными и опытными данными.Настоящие исследования представляют интерес для решения ряда задач по повышению эффективности ультразвукового контроля современных объектов со слоистой структурой и будут способствовать расширению возможностей использования предложенного метода.

Increasing of the Accuracy of Signalsʼ Time Parameters Measuring Using Double Pulse Trains

In modern diagnostics, much attention is paid to measuring of time parameters, as well as their change over time. The purpose of this work is to develop a method for measuring of time intervals which made it possible to increase the measurement accuracy by reducing errors associated with the instability of main parameters of the pulse signal.In the most of approaches used, the error associated with the instability of main parameters of signals under study is not enough taken into account. As an alternative, a spectral method is proposed in which the measurement of time intervals, as well as their changes, is performed based on the analysis of pulse sequences formed on the basis of characteristic points of the measured signal. For this a double pulse sequence was considered, an equation for the amplitudes of its spectral components was obtained, and in accordance with this it was determined that the delay time between double pulses is the most informative parameter.Using the Mathcad software, an analysis of the sensitivity regions was carried out for the change in the main parameters of the pulse sequence, namely the repetition rate, as the main destabilizing factor.As a result of the implementation of the developed technique, a structural diagram of the measuring system is proposed and an analysis of the measurement error associated with the instability of the main parameters of the pulse sequence is carried out. This error is estimated to be less than 0.01 %.The considered method makes it possible to increase the accuracy of measuring time intervals due to the almost complete elimination of the influence of the instability of the reference frequency and the amplitude of the generated pulses which is unattainable with modern hardware, including digital signal processing.

Rationale for the Choice of the Ellipsoidal Reflector Parameters for Biomedical Photometers

Biomedical photometersʼ information-measuring systems with ellipsoidal reflectors have acceptable results in determining of biological tissues optical properties in the visible and near-infrared spectral range. These photometers make it possible to study the optical radiation propagation in turbid media for direct and inverse problems of light-scattering optics. The purpose of this work is to study the influence of the ellipsoidal reflectors design parameters on the results of biomedical photometry when simulating the optical radiation propagation in a system of biological tissue and reflectors in transmitted and reflected light.The paper substantiates the choice of the ellipsoidal reflectors’ focal parameter for efficient registration of forward and backscattered light. The methodology of the process is illustrated by the results of a model experiment using the Monte Carlo simulation for samples of human brain white and gray matter at the visible range of 405 nm, 532 nm, and 650 nm. The total transmittance, diffuse reflectance, and absorption graphs depending on the sample thickness were obtained. Based on the introduced concepts of the ellipsoidal reflector efficiency index and its efficiency factor, the expediency of choosing the ellipsoidal reflectors focal parameter is analyzed to ensure the registration of the maximum amount of scattered light. The graphs of efficiency index in reflected and transmitted light for different thickness samples of white and gray matter and efficiency factors depending on the sample thickness were obtained.The influence of the reflectors ellipticity on the illuminance of various zones of photometric images using the example of an absorbing biological medium – pig liver tissue – at wavelength of 405 nm with a Monte Carlo simulation was analyzed.The optical properties of biological media (scattering and absorption coefficients, scattering anisotropy factor, refractive index) and the samples’ geometric dimensions, particularly the thickness, are predetermined when choosing the ellipsoidal reflectors parameters for registration of the scattered light. Coordinates of the output of photons and their statistical weight obtained in the Monte Carlo simulation of light propagation in biological tissue have a physical effect on a characteristic scattering spot formation in the receiving plane of a biomedical photometer with ellipsoidal reflectors.

Autonomous Streaming Space Objects Detection Based on a Remote Optical System

Traditional image processing techniques provide sustainable efficiency in the astrometry of deep space objects and in applied problems of determining the parameters of artificial satellite orbits. But the speed of the computing architecture and the functions of small optical systems are rapidly developing thus contribute to the use of a dynamic video stream for detecting and initializing space objects. The purpose of this paper is to automate the processing of optical measurement data during detecting space objects and numerical methods for the initial orbit determination.This article provided the implementation of a low-cost autonomous optical system for detecting of space objects with remote control elements. The basic algorithm model had developed and tested within the framework of remote control of a simplified optical system based on a Raspberry Pi 4 single-board computer with a modular camera. Under laboratory conditions, the satellite trajectory had simulated for an initial assessment of the compiled algorithmic modules of the computer vision library OpenCV.Based on the simulation results, dynamic detection of the International Space Station in real-time from the observation site with coordinates longitude 25o41′49″ East, latitude 53o52′36″ North in the interval 00:54:00–00:54:30 17.07.2021 (UTC + 03:00) had performed. The video processing result of the pass had demonstrated in the form of centroid coordinates of the International Space Station in the image plane with a timestamps interval of which is 0.2 s.This approach provides an autonomous raw data extraction of a space object for numerical methods for the initial determination of its orbit.

Compositionally Disordered Doped with Cerium Crystalline Garnet Type Materials for Brighter and Faster Scintillations

Ce-doped tetracationic garnets (Gd, M)3Al2Ga3O12(M = Y, Lu) form a family of new multipurpose promising scintillation materials. The aim of this work was to evaluate the scintillation yield in the materials of quaternary garnets activated by cerium ions with partial isovalent substitution of the matrix-forming gadolinium ions by yttrium or lutetium ions.Materials were obtained in the form of polycrystalline ceramic samples, and the best results were shown by samples obtained from the raw materials produced by the coprecipitation method. It was found that ceramics obtained from coprecipitated raw materials ensure a uniform distribution of activator ions in the multi-cationic matrices, which enables the high light yield and fast scintillation kinetics of the scintillation. It was demonstrated that the superstoichiometric content of lutetium/gadolinium in the material is an effective method to suppress phosphorescence accompanied scintillation. For ceramics with the composition (Gd, Lu)3Al2Ga3O12 , a scintillation yield of more than 50.000 ph/MeV was achieved. The scintillation kinetics was measured to be close to the kinetics with a decay constant of 50 ns.In terms of the set of the parameters, the developed scintillation materials are close to the recently developed alkali halide materials LaBr3:Ce, GdBr3:Ce. Moreover, they have high mechanical hardness, are characterized by the absence of hygroscopicity, and are better adapted to the manufacture of pixel detectors used in modern devices for medical diagnostics.

Shape and Measurement Monitoring of Inrush Current Characteristics of a Battery-Capacitive Energy Storage Device with Two-Channel Digital Oscilloscope

The main reason of voltage instability in stand-alone power supply systems is the electric drive motors inrush current, which are usually higher than their nominal value. The most reasonable way to solve this problem is using capacitive energy storage. The purpose of research is shape and measurement monitoring of battery-capacitive energy storage device inrush current characteristics. Parameters comparative analysis for lithium-ion battery (LIB) part and capacitive part of the energy storage device was holding with the twochannel digital oscilloscope.Measuring testing bench included parallel connected LIB part and capacitive part of the storage device and connected to the power source. The LIB part of the storage device is made on the basis of the ATOM 10 multifunctional motor drive device of the new generation, which contains 15 V lithium-ion battery and 9.4 A·h capacity. The capacitive part of the storage device is the INSPECTOR Booster supercapacitor with an 80 F electrostatic capacitance and 15.5 V voltage. A 12 V AC/DC step-down converter was used as a power source. An electric air automobile compressor M-14001 was used as a current drain. The testing bench measuring part consisted of a two-channel digital oscilloscope and two standard measuring shunts with 15000 μOm resistance serial attached to LIB part and capacitive part of the storage device. Shape and measurement monitoring of inrush current characteristics of LIB part and capacitive part of the energy storage device was held synchronously using a two-channel digital oscilloscope with recording data to FAT32 file system USB flash drive. Obtained data was transferred to a personal computer and analyzed.The measurement results showed that 82.3 % of the energy losses compensation of the motor start is taken over by the capacitive part of the energy storage device, what makes longer LIB’s life. By adjusting the oscilloscope sweep trace index you can analyze more detailed time response shape and its duration. The values of the inrush current amplitudes were calculated in proportion to the voltage drop on the shunts and their resistances.The developed method for monitoring shape and measurement inrush current characteristics can be used in various technical applications: smart stand-alone photovoltaic system, uninterruptible power supply devices, electric drive control systems, etc.

Application of the Correlation Measurement Method for Reconstructing of the Velocity Profile with Spatial and Temporal Discretization in Studies of the Hydrodynamics of Turbulent Flows Based on the Matrix Conductometry Method

The correlation method for measuring of the coolant fl rate is used in the operation of nuclear power plants and is widespread in research practice including study of turbulent fl hydrodynamics. However the question of its applicability and possibilities in studies using the matrix conductometry method remains open. Earlier the algorithm for determining of the correlation fl rate using a conductometric measuring system was highlighted and the error of the results obtained was estimated and the dependence of the influence of noise and the time of data collection on the reliability of results was investigated. These works were carried out using two independent mesh sensors and the issue of the resolution of local velocity components was not covered. The purpose of this work was to test the correlation method for measuring velocity with temporal and spatial sampling using two-layer mesh conductometric sensors.As the result velocity cartograms were obtained over the cross-section of the experimental model with quasi-stationary mixing and the value of the average flow rate is in good agreement with the values obtained from the standard flow meters of the stand. Also measurements were carried out at a non-stationary setting of the experiment and realizations of the flow rate and velocity components of the flow at the measuring points were obtained.Analysis of the obtained values allows to conclude about the optimal data collection time for correlation measurements, as well as the reliability of results.

Application of Solutions of Uncorrected Tasksʼ Theory for Managing of Production Processesʼ Robustness

The industrial revolution of “Industry 4.0” is currently underway at an active pace. Individualization of provided products and services, transition to single production, the issues of acceptability of production processes at the stage of development and design have became urgent. The aim of this work was to develop a strategy for a fundamental solution to the task of guaranteed acceptability of production processes as an integral quality characteristic.We have proposed a systematic approach to strategy development. The basis of the approach was the theory of incorrect tasks solving. We adapted signs of correctness of mathematical tasks by J. Adamar to the tasks of ensuring acceptability of production processes (technological and measurement). They were used in the part of identification of properties of display of incorrectness and ways of incorrectnessʼ management.We have proposed to consider the property of robustness as a generalized index of acceptability for production processes (technological and measurement). We substantiate the equivalence of the concepts of incorrectness of tasks according to J. Adamar and losses of robustness of production processes. We conclude that the developed approaches and techniques of the theory of incorrect tasks can be put in a basis of the system approach to an estimation and management of losses of robustness of production processes. We have proposed a classification of situations of robustness losses in production processes in accordance with the classification of the signs of incorrect tasks by J. Adamar.We have developed a two-step algorithm for ensuring the robustness of production processes at the stage of their development. It included identification of the sources of robustness losses and management of input factors that cause significant variation in process output. This has given a practical implementation of a strategy to guarantee the acceptability of production processes. We have systematized the sources of potential losses in the robustness of production processes and proposed a two-stage mechanism for managing them. We have justified rational methods of ensuring the robustness of production processes for each stage based on, the practice of uncorrected tasks solving. We have proposed a method for ensuring high efficiency of robustness loss management in certain situations. The principles of G. Taguchiʼs robust redesigning of production processes formed the basis of our method.

Determination of the Error in Transferring of Length Unit’s Size when Measuring the Nanoparticles’ Diameter Using an Analyzer of Particles’ Differential Electrical Mobility

The quality of nanomaterials and nanotechnologies is largely determined by the stability of the applied technologies, which, to a large extent, depend on the constancy of particle sizes. In this regard, metrological problems arise that are associated both with measuring the dimensions of the microstructure of aerosols, suspensions and powders, and with ensuring the uniformity of measurements when transferring a unit of a physical quantity from a standard to working measuring instruments. The purpose of this work was to determine and calculate the error in transferring the size of a unit of length when measuring the diameter of nanoparticles.An analyzer of differential electric mobility of particles was determined as a reference measuring instrument for which the calculation was made. It allows the separation of aerosol particles based on the dependence of their electrical mobility on the particle size. In combination with a condensation particle counter, it allows you to scan an aerosol and build a particle size distribution function. This measurement method is the most accurate in the field of measuring the diameters of particles in aerosols, therefore, the error in the transmission of particle size must be set as for a standard.The paper describes the physical principles of measurement by this method and presents an equation for determining the diameter of nanoparticles. Based on this equation, the sources of non-excluded systematic error were identified. Also, an experimental method was used to determine the random component of the measurement error of nanoparticles and to calculate the error in transferring the size of a unit of length when measuring the diameter of nanoparticles.The obtained results will be used for metrological support of standard samples of particle size, ensuring traceability of measurements of aerosol particle counters and for aerosol research.

Impulsively-Laser Excitation and Propagation of Ultrasonic Waves through Nanomagnetic Fluid

Magnetic fluids belong to the class of nanomaterials with a high gain of light absorption, aggregative and sedimentation stability as well as controllability by external fields, which is of interest to use in the field of optoacoustics. The purpose of the work was to experimentally study the effect of the optoacoustic transformation in a magnetic fluid, depending on the concentration of magnetic colloidal particles, boundary conditions, intensity of the laser as well as to identify the possibilities of using the magnetic fluid as an element of the optoacoustic transformation in a number of applications.A brief analysis of the optoacoustic transformation mechanism in a magnetic fluid was carried out and a technique and an installation that implements the shadow measurement variant developed. A Lotis type laser was used as a source of ultrasonic pulse-laser excitation in magnetic fluids. A quartz and air were used as a material transmitting the energy of laser radiation in a magnetic fluid. Receiving of ultrasound signals was made by a piezoelectric probe at a working frequency of 5 MHz. In the measurement process, the concentration of the dispersed phase in tmagnetic fluid was varied from zero to 8 % and the energy in the impulse – from zero to 10 mJ.For the first time, it was established that: a) an amplitude of the function of the optoacoustic transformation in a magnetic fluid, depending on the concentration of the dispersed phase, has a maximum determined by the fluid physical properties and boundary conditions; b) for all samples within the measurement error, a quasilinear dependence of the specified amplitude of energy in the laser pulse in the range of 0–8 MJ has been established.A number ways of the optoacoustic effects in magnetic fluids to use in ultrasonic testing, measuring the intensity of the laser radiation had been suggested.