المؤلفون: V. V. Zakharenko, O. O. Kostenko, O. O. Konovalenko, D. M. Vavriv, S. L. Prosvirnin, Y. M. Yampolski

المصدر: Radio Physics and Radio Astronomy, Vol 29, Iss 2, Pp 137-169 (2024)

مصطلحات موضوعية: leonid m. lytvynenko (a.k.a. leonid n. litvinenko), national academy of sciences of ukraine, radio physics, radio astronomy, astrophysics, electromagnetic waves, difraction and wave propagation theory, "successive reonements" technique, Astronomy, QB1-991

الوصف: This paper is an attempt of paying tribute to the memory of Leonid Mykolayovych Lytvynenko (LML), an outstanding Ukrainian scientist, Full Member of the National Academy of Sciences who worked most fruitfully in the fields of radio science and radio astronomy. Starting of 1985, Dr. Lytvynenko was, over a 30-plus years period, at the head of the Institute of Radio Astronomy, Acad. Sci. of the Ukrainian SSR (currently the National Academy of Sciences of Ukraine) that had been established owing to his vigorous and direct participation in the process. In 1996 LML promoted foundation of a new scientific journal, namely the "Radio Physics and Radio Astronomy", which he devotedly served for, in the Editor-in-Chief capacity, during the 25 years that followed. Dr. L. Lytvynenko was one of the brightest representatives of the school of theoretical radio physics that had developed within the O. Usikov Institute for Radio Physics and Electronics in Kharkiv and further flourished within the Institute of Radio Astronomy. He is known as the founder of a new branch of radio science, specifically theory of electromagnetic wave diffraction and propagation through composite and multilayered periodic structures.

وصف الملف: electronic resource

العلاقة: http://rpra-journal.org.ua/index.php/ra/article/view/1443/pdfTest; https://doaj.org/toc/1027-9636Test; https://doaj.org/toc/2415-7007Test

الوصول الحر: https://doaj.org/article/b8793cf8fac24e179c75f0a58405a629Test

المؤلفون: A. V. Bukin, V. G. Gutnik, Yu. F. Lohvinov, N. G. Reznichenko

المصدر: Radio Physics and Radio Astronomy, Vol 28, Iss 3, Pp 224-233 (2023)

مصطلحات موضوعية: radio wave propagation, backscattering, specific effective scattering surface, Astronomy, QB1-991

الوصف: Subject and Purpose. The article is devoted to the analysis of theoretically and experimentally obtained values of the specific effective sea-scattering surface in the region of super-high-frequencies (SHF). The study is reasoned by the need to know characteristics of the electromagnetic wave scattering from various objects at the modeling stage. The focus is on the choice of backscattering model with a methodology of specific effective scattering surface estimation that takes into account the shadowing effect of the sea surface under given conditions. Methods and Methodology. The study is based on mathematical modeling techniques and is accompanied by the comparison of the modeling results with experiment. Results. Proceeding from the simulation results with the effect of sea-surface shadowing taken into account and relying on the check of consistency with the measured data, a comparison analysis has been performed among theoretical models of specific effective sea-scattering surface calculation at low grazing angles. Conclusion. Analysis has been given to the specific effective sea-scattering surface obtained by the facet and two-scale models and to the values measured by experiment. Quantitative estimates of the specific effective scattering surface have been obtained with the shadowing effect of the sea surface taken into account. Analysis of the quantitative estimates has been carried out.

وصف الملف: electronic resource

العلاقة: http://rpra-journal.org.ua/index.php/ra/article/view/1420/pdfTest; https://doaj.org/toc/1027-9636Test; https://doaj.org/toc/2415-7007Test

الوصول الحر: https://doaj.org/article/8e670241b72e46919c69c693b28ef7fdTest

المؤلفون: Рябінін, Святослав Олександрович, Захаров, Артем Вячеславович, Майзеліс, Антоніна Олександрівна, Притиченко, Ганна Вікторівна

المصدر: Bulletin of the National Technical University "KhPI". Series: Chemistry, Chemical Technology and Ecology; No. 2(10) (2023): Bulletin of the National Technical University «KhPI». Series: Chemistry, Chemical Technology and Ecology; 53-60 ; Вестник НТУ"ХПИ" серия "Химия, химическая технология и экология"; № 2(10) (2023): Вісник Національного технічного університету «ХПІ». Серія: Хімія, хімічна технологія та екологія; 53-60 ; Вісник Національного технічного університету «ХПІ». Серія: Хiмiя, хiмiчнi технологiї та екологiя; № 2(10) (2023): Вісник Національного технічного університету «ХПІ». Серія: Хімія, хімічна технологія та екологія; 53-60 ; 2708-5252 ; 2079-0821

مصطلحات موضوعية: алюмосилікатні склокристалічні матеріали, бронеелемент, ударостійкість, швидкість розповсюдження хвиль, фізико-хімічні властивості, aluminosilicate glass-crystalline materials, armor element, impact resistance, speed of wave propagation, physical and chemical properties

الوصف: An analysis of world experience in the direction of modern developments of high-strength aluminosilicate glass-crystalline materials, in particular, in the creation of lightweight armor, was carried out. The trends and current state of the glass-ceramics market from 2019 to 2023 have been determined, and an increase in demand for glass-crystalline materials for technical purposes has been established. It was determined that the orientation of the global glass-ceramic market towards fragmentation will allow domestic manufacturers to reduce import dependence and increase the competitiveness of domestic glass-ceramic materials on the world market. The prospect of using high-strength aluminosilicate glass-crystalline materials as a basis for the production of armor protection elements has been established. The criteria for the synthesis of high-strength armored steels have been selected. The choice of oxide systems for the production of protective glass-crystalline materials is substantiated, model glasses are synthesized and the technological parameters of production of impact-resistant sitals, which include cooking, forming, annealing and heat treatment, are determined. Model glasses were synthesized and their structure under thermal treatment conditions was investigated in relation to the physical and chemical properties of the materials based on them. It was established that the developed glass-crystalline materials based on lithium disilicate are characterized by high operational properties and can be used in the creation of modern armor. It was established that the developed high-strength spodumene glass-crystalline materials under the conditions of low-temperature two-stage heat treatment are characterized by high operational properties and can be used as a basis for the development of a composite element of individual armor protection. A comparative assessment of the operational properties and technical and economic indicators of known ceramic and glass-ceramic materials for armor protection made it possible ...

وصف الملف: application/pdf

العلاقة: http://ccte.khpi.edu.ua/article/view/296732/289729Test; http://ccte.khpi.edu.ua/article/view/296732Test

الإتاحة: http://ccte.khpi.edu.ua/article/view/296732Test

المؤلفون: V. G. Sinitsin, Yu. M. Yampolski

المصدر: Radio Physics and Radio Astronomy, Vol 27, Iss 3, Pp 240-245 (2022)

مصطلحات موضوعية: p.v.bliokh, national academy of sciences, radio wave propagation, space radio physics, schumann resonances, gravitational lenses, dusty plasma, Astronomy, QB1-991

الوصف: The paper is dedicated to the memory of Pavel V. Bliokh, an outstanding Ukrainian scientist in the fields of theoretical and radio physics, on the occasion of his 100th anniversary. P.V.Bliokh (PhD, D.Sc, Professor, Honored Scientist of Ukraine) was one of the founders of the ‘space radiophysics’ branch of research. While working in that direction, he created a well-known scientific school at the O.Ya. Usikov Institute of Radiophysics and Electronics and the Institute of Radio Astronomy, National Academy of Sciences of Ukraine.

وصف الملف: electronic resource

العلاقة: http://rpra-journal.org.ua/index.php/ra/article/view/1398/pdfTest; https://doaj.org/toc/1027-9636Test; https://doaj.org/toc/2415-7007Test

الوصول الحر: https://doaj.org/article/8b70c74d13814ef6b299e3d139deea0eTest

المؤلفون: Z.E. Eremenko, V.A. Pashynska, K.S. Kuznetsova, O.I. Shubnyi, N.I. Sklyar, A.V. Martynov

المصدر: Радиофизика и электроника, Vol 26, Iss 3, Pp 30-37 (2021)

مصطلحات موضوعية: complex permittivity, complex wave propagation coefficient, dielectrometry method, high-loss liquids, waveguide-differential dielectrometer, Electronics, TK7800-8360

الوصف: Subject and Purpose. This study focuses on the original waveguide-differential dielectrometer designed for complex permittivity measurements of high-loss liquids in the microwave range towards the determination of pharmaceutical ingredient concentrations in water solutions at room temperature. The suitability of the device and effectiveness of the dielectrometry method are tested on such pharmaceutical ingredients as lincomycin and levofloxacin over a wide range of concentrations. Methods and Methodology. The main idea of the method consists in that the complex propagation coefficients of the HE11 wave are obtained from the amplitude and phase shift differences acquired by the wave after it has passed through the two measuring cells of the waveguide-differential dielectrometer. Results. We have shown that the proposed dielectometry method allows a real-time determination of pharmaceutical ingredient concentrations in water solution by measuring the wave attenuation and phase shift differences. We have found that unless concentrations of pharmaceutical ingredients are low, few free water molecules in water solution are bound to the pharmaceutical ingredients. The number of free water molecules in solution decreases as the concentration of pharmaceutical ingredients rises. Conclusion. The current study confirms that the dielectometry method and the device developed provide effective determination of pharmaceutical ingredient concentrations in water solutions.

وصف الملف: electronic resource

العلاقة: http://re-journal.org.ua/sites/default/files/file_attach/2021-3/7.pdfTest; https://doaj.org/toc/1028-821XTest; https://doaj.org/toc/2415-3400Test

الوصول الحر: https://doaj.org/article/e03fd558aeaa4ec1b7e7cac8dcbaa1c0Test

المؤلفون: A.V. Bukin, V.G. Gutnik, Yu.F. Lohvinov, N.G. Reznichenko

المصدر: Радиофизика и электроника, Vol 25, Iss 3, Pp 34-41 (2020)

مصطلحات موضوعية: backscattering, radio wave propagation, surface discretization, Electronics, TK7800-8360

الوصف: Subject and Purpose. The article is devoted to the modeling of electromagnetic field backscattering in the millimeter and centimeter wave regions. The relevance of such studies proceeds from the need to have wave scattering characteristics of various objects at the modeling stage. The aim of the work is to determine an acceptable step size of the surface discretization, no matter whether a well-known or perspective method of the scattered field calculation is used. Methods and Methodology. To achieve the goal as defined, mathematical and statistical modeling methods are used. The modeling and theoretical results are compared. Results. Numerical simulations of the electromagnetic field scattering have been performed using the Fresnel-Kirchhoff diffraction formula and the method of surface representation by a set of elementary flat faces. For such simplest objects as a ball and a plane, a comparison of the theoretical and modelling results on effective scattering surface has been performed and made it possible to determine an acceptable step size of the surface discretization in the electromagnetic field backscattering. It has been shown that once the surface discretization has been chosen properly, the determination of the field strength by the Fresnel-Kirchhoff method provides an effective scattering surface value that coincides with the theoretical results most accurately. Conclusion. It has been shown that the Fresnel-Kirchhoff method describes basic properties of the scattered field most well. The employment of the modeling method of surface representation by a set of flat faces with relevant scattering patterns requires a normalization of the results with the relevant theoretical and experimental data taken into account.

وصف الملف: electronic resource

العلاقة: http://re-journal.org.ua/sites/default/files/file_attach/2020-3/6.pdfTest; https://doaj.org/toc/1028-821XTest; https://doaj.org/toc/2415-3400Test

الوصول الحر: https://doaj.org/article/2ecb03ad042149489cd164b0d6fa4114Test

المؤلفون: Alexey Savostin, Amandyk Tuleshov, Kayrat Koshekov, Galina Savostina, Alexandr Largin

المصدر: Eastern-European Journal of Enterprise Technologies, Vol 5, Iss 2(119), Pp 62-74 (2022)

مصطلحات موضوعية: blood pressure, machine learning, photoplethysmogram, bioelectric signals, pulse wave propagation time, Technology (General), T1-995, Industry, HD2321-4730.9

الوصف: Determining the level of blood pressure (BP) in a non-invasive way and without a sphygmomanometer cuff is of great relevance when conducting continuous monitoring or screening studies. In this regard, a method for predicting BP parameters based on the signals of the photoplethysmogram (PPG) and electrocardiogram (ECG) signals has been developed. It is proposed to use, as informative features, the time of pulse wave propagation (PTT) and a set of calculated pulse parameters of PPG. PTT is defined as the time intervals between the R-wave of the ECG and the corresponding characteristic points on the PPG acquired optically from the finger. As parameters of the PPG pulse, the known characteristics of this signal described in the literature are used, as well as additional informative features selected during the study. In accordance with the above, the tools of machine learning theory were used to construct a classifier model and regression models. The approach described in this paper to determine BP makes it possible to use 10-second ECG signals in any of the 12 common leads and PPG signals from any optical type of sensor. The built model of the classifier detects three levels of BP: low, normal, and high, at the accuracy metric=0.8494. The regression models predict systolic, diastolic, and mean BP parameters in accordance with the requirements of the British Hypertension Society (BHS) standard by the magnitude of the absolute error. The proposed method for assessing the level of BP involves real-time measurements and can be used in the design of measuring equipment for screening studies, as well as in continuous monitoring tasks within the framework of BHS requirements.

العلاقة: http://journals.uran.ua/eejet/article/view/265066Test; https://doaj.org/toc/1729-3774Test; https://doaj.org/toc/1729-4061Test; https://doaj.org/article/1f651c41b2d943258a66d7c8129efd92Test

الإتاحة: https://doi.org/10.15587/1729-4061.2022.265066Test
https://doaj.org/article/1f651c41b2d943258a66d7c8129efd92Test

العنوان البديل: DETERMINATION OF ALL PIEZOELECTRIC COEFFICIENTS AND ELASTIC STIFFNESS CONSTANTS IN LiTaO3 CRYSTALS BASED ON MEASUREMENTS OF ACOUSTIC WAVE VELOCITIES. (English)

المؤلفون: Мартинюк-Лотоць&, I., Їдак, І., Корнєєв, О., Ратич, А., Андрущак, А.

المصدر: Journal of Physical Studies; 2021, Vol. 25 Issue 4, p4602-1-4602-5, 5p

مصطلحات موضوعية: SPEED of sound, ELASTIC constants, ULTRASONIC measurement, SOUND waves, ELASTICITY, ACOUSTIC wave propagation

مستخلص: This paper presents the results of ultrasonic measurements in trigonal LiTaO3 crystals. The samples of direct section with faces perpendicular to the main crystallographic axes and X/45 sections of LiTaO3 crystals were manufactured for experimental studies. The velocities of longitudinal and transverse acoustic waves along the three principal crystallographic axes and two additional axes in theYZ plane in trigonal crystals of point group 3m LiTaO3 crystals were measured using the pulse-echo overlap method. In the piezoelectric crystals, elastic and electrical properties are related and the propagation of an acoustic wave is accompanied by the appearance of electric fields, which must be taken into account in the calculations. The relations for the complete determination of all components of the matrices of elastic stiffness and piezoelectric coefficients based on all necessary acoustic wave velocities measured were derived from the Christoffel equation for the piezoelectric crystals. Using the obtained ratios, all components of the tensors of piezoelectric coefficients, elastic stiffness constants, as well as all elastic compliances of LiTaO3 crystals are calculated. The obtained results are consistent with the literature data and will be used in further measurements and calculation of the spatial anisotropy of induced (electro-, piezo- and acousto-optical) effects on the same crystal samples in order to select the most effective geometry of their possible practical use. [ABSTRACT FROM AUTHOR]

: Copyright of Journal of Physical Studies is the property of Journal of Physical Studies and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

المؤلفون: Березкін, А.Л.

المصدر: Problems of Informatization and Management; Vol. 2 No. 66 (2021); 11-16 ; Проблемы информатизации и управления; Том 2 № 66 (2021); 11-16 ; Проблеми iнформатизацiї та управлiння; Том 2 № 66 (2021); 11-16 ; 2073-4751

مصطلحات موضوعية: распространение радиоволн, многолучевое распространение, математическая модель, дифракция, интерференция, радиопланирование, розповсюдження радіохвиль, багатопроменеве розповсюдження, математична модель, дифракція, інтерференція, радіопланування, radio wave propagation, multipath propagation, mathematical model, diffraction, interference, radio planning

الوصف: The factors and conditions affecting the model of the distribution of the energy of the electromagnetic field during the propagation of electromagnetic waves in mining are considered. The analysis of well-known publications is carried out and the principles of assessing the influence of existing factors in mine workings from the point of view of classical models of the propagation of electromagnetic waves on the formation of a model of the distribution of the energy of the electromagnetic field at a given point of development are proposed. A mathematical model of the energy of the electromagnetic field at a given point is proposed. The type of the model of the distribution of the energy of the electromagnetic field in the mine workings as zonal-Fresnel was determined. Methods are proposed that simplify the construction of a mathematical model of the distribution of the energy of the electromagnetic field, allows to reduce the number of analyzed factors, but does not affect the overall quality of the model. The significance of the developed model from the point of view of radio planning in mine workings, the introduction of new radio communication systems in mines and other similar objects has been proved. ; Рассмотрены факторы и условия, влияющие на модель распределение энергии электромагнитного поля при распространении электромагнитных волн в горных выработках. Проведен анализ известных публикаций и предложены принципы оценки влияния существующих факторов в горных выработках с точки зрения классических моделей распространения электромагнитных волн на формирование модели распределения энергии электромагнитного поля в заданной точке выработки. Предложена математическую модель энергии электромагнитного поля в заданной точке. Определен тип модели распределения энергии электромагнитного поля в горных выработках как зонально – френелевскую. Предложены методики, которая упрощает построения математической модели распределения энергии электромагнитного поля, позволяет уменьшить количество анализируемых факторов, но не ...

وصف الملف: application/pdf

العلاقة: http://jrnl.nau.edu.ua/index.php/PIU/article/view/15711/22908Test; http://jrnl.nau.edu.ua/index.php/PIU/article/view/15711Test

الإتاحة: https://doi.org/10.18372/2073-4751.66.15711Test
http://jrnl.nau.edu.ua/index.php/PIU/article/view/15711Test

المؤلفون: Vitalii Kovalchuk, Ivan Kravets, Olga Nabochenko, Arthur Onyshchenko, Olexander Fedorenko, Andriy Pentsak, Oleksiy Petrenko, Nataliya Hembara

المصدر: Eastern-European Journal of Enterprise Technologies, Vol 1, Iss 5 (109), Pp 6-15 (2021)

مصطلحات موضوعية: subgrade, impact's elastic wave, inertial study, wave propagation rate, density, Technology (General), T1-995, Industry, HD2321-4730.9

الوصف: This paper reports the analysis of the methods for estimating the technical condition of the subgrade underneath a constructed railroad track or road during its operation. The study results have proven that the issue related to monitoring and controlling high-quality compaction of a heterogeneous subgrade remains relevant and requires the construction of reliable experimental methods for assessing the subgrade degree of compaction. A procedure for determining the compaction of subgrade in the laboratory has been devised, based on inertial microcomputer technologies, which makes it possible to assess the degree of compaction of subgrade soils depending on the propagation rate of an impact's elastic waves. An experimental study has been performed into the propagation rate of elastic waves across a homogeneous subgrade made of coarse-grained sand and a heterogeneous subgrade made of coarse sand with a layer of clay in the middle of the prism. The study results established that the propagation rate of an elastic wave in a heterogeneous subgrade accepts a lower value than the rate of wave propagation in a homogeneous subgrade. Through the dynamic interpretation, by using a discriminant statistical analysis, the characteristic features have been defined in the distribution of accelerations in the body of the homogeneous and heterogeneous subgrade, depending on the degree of compaction, which would make it possible to monitor the state of the subgrade during operation. As the degree of the subgrade soil compaction affects the technical condition of roads

العلاقة: http://journals.uran.ua/eejet/article/view/225520Test; https://doaj.org/toc/1729-3774Test; https://doaj.org/toc/1729-4061Test; https://doaj.org/article/018da2e5f3a54153b2adac65afd290e1Test

الإتاحة: https://doi.org/10.15587/1729-4061.2021.225520Test
https://doaj.org/article/018da2e5f3a54153b2adac65afd290e1Test