Fractal Structure of Brain Electrical Activity of Patients With Mental Disorders

This work was aimed at a comparative analysis of the degree of multifractality of electroencephalographic time series obtained from a group of healthy subjects and from patients with mental disorders. We analyzed long-term records of patients with paranoid schizophrenia and patients with depression. To evaluate the properties of multifractal scaling of various electroencephalographic time series, the method of maximum modulus of the wavelet transform and multifractal analysis of fluctuations without a trend were used. The stability of the width and position of the singularity spectrum for each of the test groups was revealed, and a relationship was established between the correlation and anticorrelation dynamics of successive values of the electroencephalographic time series and the type of mental disorders. It was shown that the main differences between the multifractal properties of brain activity in normal and pathological conditions lie in the different width of the multifractality spectrum and its location associated with the correlated or anticorrelated dynamics of the values of successive time series. It was found that the schizophrenia group is characterized by a greater degree of multifractality compared to the depression group. Thus, the degree of multifractality can be included in a set of tests for differential diagnosis and research of mental disorders

Прибор и методики измерения акустической анизотропии и остаточных напряжений металла магистральных газопроводов

One of the main conditions of safe operation of gas pipelines is the use of non-destructive diagnostic methods. Particularly important problem is the earlier operational diagnosis of pipes’ material of main gas pipelines based on the evaluation of the stress-strain state, elastic moduli and properties anisotropy by acoustic methods. The aim of the work is to develop methods for acoustic assessment of the stress-strain state, the elastic moduli and the properties anisotropy of pipeline material and to study these characteristics in different sections of main pipelines using a device based on contactless EMA transducers.Methods are implemented using specialized equipment (the structurescope SEMA) and non-contact electromagnetic acoustic transducers. As an object of research, we used fragments – the cuttings of gas pipelines with circumferential welds both after fabrication and removed from service with stress corrosion cracking, including ones with corrosion damage and without visible damage.The method of determining the plane stress-strain state of pipeline elements is based on the phenomenon of acoustoelasticity – the dependence of the propagation velocity of ultrasonic waves on mechanical stresses. The method for determining the elastic characteristics of materials and the anisotropy of their properties is based on the relationship between the velocities of ultrasonic waves and the elastic properties of the medium. Both techniques are implemented by sounding the sample in one section using a longitudinal wave and two shear waves with mutually perpendicular polarization planes coinciding with the main stresses, and measuring their propagation times.It is shown that the stress state distribution both in the circumferential direction and along the generatrix is uneven which is caused by the peculiarities of samples (presence of a welded joint, stress corrosion cracking, long-term operation). The smallest acoustic anisotropy is observed for the Young's modulus. The anisotropy of the properties of most samples is in the range of 12–14 % for shear modulus, 9–10 % for Young’s modulus, 13–15 % for Poisson’s ratio. For samples with stress corrosion cracking a sharp decrease in the anisotropy coefficient is observed which makes it possible to use the indicated characteristics as informative parameters in detecting stress corrosion cracking.A feature of the proposed methods is high accuracy, due to the absence of necessity to determine the material density and precision measurement of its thickness, the measurement error of which is significant by known methods.Keywords: main gas pipeline, elastic moduli, acoustic anisotropy of properties, the biaxial stress-strain state, longitudinal and transversal waves.Одним из основных условий безопасной эксплуатации магистральных газопроводов является использование неразрушающих методов контроля, что особенно актуально при решении задач ранней оперативной диагностики материала труб. Цель работы – разработка методик акустической оценки напряженно-деформированного состояния, упругих модулей и анизотропии свойств материала трубопровода и исследование этих характеристик в вырезках магистральных трубопроводов с использованием прибора на основе бесконтактных электромагнитно-акустических преобразователей.Методики реализуются с использованием структуроскопа СЭМА и бесконтактных преобразователей. В качестве объекта исследований использованы вырезки магистральных газопроводов с кольцевыми сварными швами, с коррозионным растрескиванием под напряжением и без видимых повреждений. Методика определения плоского напряженно-деформированного состояния элементов трубопровода основана на явлении акустоупругости. Методика определения упругих характеристик материалов и анизотропии их свойств основана на связи скоростей ультразвуковых волн с упругими свойствами среды. Методики реализуются за счет прозвучивания образца с использованием продольной волны и двух сдвиговых волн с взаимно перпендикулярными поляризациями, совпадающими с главными напряжениями.Показано, что распределение напряженного состояния является неравномерным, что обусловлено особенностями образцов. Анизотропия свойств большинства образцов находится в диапазоне 12–14 % по модулю сдвига, 9–10 % по модулю Юнга, 13–15 % по коэффициенту Пуассона. Для образцов с коррозионным растрескиванием под напряжением наблюдается резкое уменьшение коэффициента анизотропии, что позволяет использовать указанные характеристики в качестве информативных параметров при выявлении коррозионного растрескивания под напряжением.Особенностью предложенных методик является высокая точность, обусловленная отсутствием необходимости определения плотности материала и прецизионного измерения его толщины, погрешность измерения которых известными методами значительна

МЕТОДИКА И УСТРОЙСТВО ДЛЯ ЭКСПЕРИМЕНТАЛЬНОЙ ОЦЕНКИ АКУСТИЧЕСКОГО ИМПЕДАНСА ВЯЗКОУПРУГИХ СРЕД

Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. One of the complex acoustic parameters is the impedance, which allows one to fully evaluate the characteristics of viscoelastic media. Most of impedance methods of measurements require using two or more reference media and the availability of calibrated acoustic transducers. The aim of this work ware introduced a methods and construction for the experimental evaluation of the longitudinal and shear impedance of viscoelastic media based on measuring the parameters of the amplitude-frequency characteristics and calculating the elements of the electric circuit for replacing the piezoelectric element which vibrating in the test medium.The paper introduces a methods and construction of the experimental evaluation of the impedances of viscoelastic media. The suggested methods is allowed measuring longitudinal and shear impedances and determining velocities of longitudinal and transverse ultrasonic waves and the values of the elastic moduli of viscoelastic media, including in various aggregate states. The technique is fairly simple to implement and can be reproduced using simple laboratory equipment.The obtained values of the acoustic impedances of the investigated media are in satisfactory agreement with their reference data. In contrast to the known methods for determining the acoustic impedance, the developed technique allows us to estimate with sufficient accuracy the parameter of the shear impedance of viscoelastic media that is difficult to measure at the frequencies of the megahertz range, which determines the shear modulus of the material and characterizes its resistance to shear deformations. The results of the implementation of the developed technique for the estimation of acoustic parameters for a number of media with zero shear elasticity (alcohol, acetone) and viscoelastic media (glycerin, architectural clay, silicone sealant and glue МР-55 before and after polymerization) are presented.Измерение характеристик технологических жидкостей позволяет оценить их качество, биологических тканей – дифференцировать здоровые ткани и ткани с патологиями. Одним из комплексных акустических параметров является импеданс, позволяющий наиболее полно оценивать характеристики вязкоупругих сред. Большинство методов измерения импеданса требуют использования двух и более эталонных сред и наличия калиброванных акустических преобразователей. Целью данной работы являлась разработка новой методики и установки для экспериментальной оценки продольного и сдвигового импедансов вязкоупругой среды, основанных на измерении параметров амплитудно-частотных характеристик и расчете элементов электрической схемы замещения пьезопластины, колеблющейся в исследуемой среде.В работе описываются методика и устройство для экспериментальной оценки импедансов вязкоупругих сред. Предложенная методика позволяет измерить продольный и сдвиговый импедансы и определить скорости продольных и поперечных ультразвуковых волн и значений упругих модулей вязкоупругих сред, в том числе в различных агрегатных состояниях. Методика достаточно проста в реализации и может быть воспроизведена с помощью несложного лабораторного оборудования.Полученные значения акустических импедансов исследованных сред удовлетворительно согласуются с их справочными данными. В отличие от известных методов определения акустического импеданса, разработанная методика позволяет с достаточной точностью оценивать трудно поддающееся измерению на частотах мегагерцового диапазона значение сдвигового импеданса вязкоупругих сред, определяющее модуль сдвига материала и характеризующее его сопротивление сдвиговым деформациям. Приведены результаты реализации разработанной методики для оценки акустических параметров на примере ряда сред с нулевой сдвиговой упругостью (спирт, ацетон) и вязкоупругих сред (глицерин, архитектурный пластилин, силиконовый герметик, клей MP-55 до и после полимеризации)

Device and Methods for Measuring of Acoustic Anisotropy and the Residual Stress in the Main Gas Pipelines’ Metal

One of the main conditions of safe operation of gas pipelines is the use of non-destructive diagnostic methods. Particularly important problem is the earlier operational diagnosis of pipes’ material of main gas pipelines based on the evaluation of the stress-strain state, elastic moduli and properties anisotropy by acoustic methods. The aim of the work is to develop methods for acoustic assessment of the stress-strain state, the elastic moduli and the properties anisotropy of pipeline material and to study these characteristics in different sections of main pipelines using a device based on contactless EMA transducers.Methods are implemented using specialized equipment (the structurescope SEMA) and non-contact electromagnetic acoustic transducers. As an object of research, we used fragments – the cuttings of gas pipelines with circumferential welds both after fabrication and removed from service with stress corrosion cracking, including ones with corrosion damage and without visible damage.The method of determining the plane stress-strain state of pipeline elements is based on the phenomenon of acoustoelasticity – the dependence of the propagation velocity of ultrasonic waves on mechanical stresses. The method for determining the elastic characteristics of materials and the anisotropy of their properties is based on the relationship between the velocities of ultrasonic waves and the elastic properties of the medium. Both techniques are implemented by sounding the sample in one section using a longitudinal wave and two shear waves with mutually perpendicular polarization planes coinciding with the main stresses, and measuring their propagation times.It is shown that the stress state distribution both in the circumferential direction and along the generatrix is uneven which is caused by the peculiarities of samples (presence of a welded joint, stress corrosion cracking, long-term operation). The smallest acoustic anisotropy is observed for the Young's modulus. The anisotropy of the properties of most samples is in the range of 12–14 % for shear modulus, 9–10 % for Young’s modulus, 13–15 % for Poisson’s ratio. For samples with stress corrosion cracking a sharp decrease in the anisotropy coefficient is observed which makes it possible to use the indicated characteristics as informative parameters in detecting stress corrosion cracking.A feature of the proposed methods is high accuracy, due to the absence of necessity to determine the material density and precision measurement of its thickness, the measurement error of which is significant by known methods.Keywords: main gas pipeline, elastic moduli, acoustic anisotropy of properties, the biaxial stress-strain state, longitudinal and transversal waves

TECHNIQUE AND DEVICE FOR THE EXPERIMENTAL ESTIMATION OF THE ACOUSTIC IMPEDANCE OF VISCOELASTIC MEDIUM

Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. Measuring the characteristics of process fluids allows us to evaluate their quality, biological tissues – to differentiate healthy tissues and tissues with pathologies. One of the complex acoustic parameters is the impedance, which allows one to fully evaluate the characteristics of viscoelastic media. Most of impedance methods of measurements require using two or more reference media and the availability of calibrated acoustic transducers. The aim of this work ware introduced a methods and construction for the experimental evaluation of the longitudinal and shear impedance of viscoelastic media based on measuring the parameters of the amplitude-frequency characteristics and calculating the elements of the electric circuit for replacing the piezoelectric element which vibrating in the test medium.The paper introduces a methods and construction of the experimental evaluation of the impedances of viscoelastic media. The suggested methods is allowed measuring longitudinal and shear impedances and determining velocities of longitudinal and transverse ultrasonic waves and the values of the elastic moduli of viscoelastic media, including in various aggregate states. The technique is fairly simple to implement and can be reproduced using simple laboratory equipment.The obtained values of the acoustic impedances of the investigated media are in satisfactory agreement with their reference data. In contrast to the known methods for determining the acoustic impedance, the developed technique allows us to estimate with sufficient accuracy the parameter of the shear impedance of viscoelastic media that is difficult to measure at the frequencies of the megahertz range, which determines the shear modulus of the material and characterizes its resistance to shear deformations. The results of the implementation of the developed technique for the estimation of acoustic parameters for a number of media with zero shear elasticity (alcohol, acetone) and viscoelastic media (glycerin, architectural clay, silicone sealant and glue МР-55 before and after polymerization) are presented