Electromagnetic Screens Research Articles

The problem of protecting a person from the effects of low-frequency electromagnetic fields in modern society. Possible ways to solve it

The paper considers the problem of the impact of low-frequency electromagnetic fields (EMF) generated by electric vehicles (EV) and household appliances on humans in modern society. The data on the effect of EMF on human health and regulatory documents establishing requirements for electromagnetic safety are presented. The method of electromagnetic shielding and materials for the implementation of this method are considered as a promising method for solving the problem. The levels of electromagnetic radiation from a number of EV and household electrical appliances have been experimentally measured. The efficiency of electromagnetic shielding of materials based on single-layer coatings of Ni80Fe20 alloys, multilayer film structures Ni80Fe20/Cu and amorphous metal alloys AMAG172 has been estimated using a computational method. It is shown that electromagnetic screens based on these materials significantly reduce the levels of exposure to EMF of EV and household electrical appliances on humans, which allows us to approach the hygienic standards recommended by doctors and meet the requirements of regulatory documents on remote control.

Application of Innovative Electromagnetic Screens for Reconstruction and Restoration of Buildings

Protective properties of composite electromagnetic screens on the base of conventional commercial paints were studied. The shielding fillers included metal-containing products from industrial wastewater treatment. Such compositions with a thickness of 100 to 150μm, were found to allow reaching high-frequency electromagnetic radiation shielding coefficients up to 3.0-3.5. Reflection coefficients of electromagnetic waves reach up to 0.3, which meets contemporary technical requirements.

Using Thin Films of Phase-Change Material for Active Tuning of Terahertz Waves Scattering on Dielectric Cylinders.

The scattering of electromagnetic waves by isotropic dielectric cylinders can be dramatically modified by means of vanadium dioxide (VO2) thin-film coatings. Efficient dynamic control of scattering is achieved due to the variations in material parameters realizable by means of external biasing. In this paper, we study the scattering of terahertz waves in a case where the coating shells are made of VO2, a phase-change material, whose thin films may work rather as electromagnetic phase screens in the insulator material phase, but as lossy quasi-metallic components in the metallic material phase. The shells that uniformly cover the dielectric cylinders are investigated. Attention will be paid to the demonstration of the potential of VO2 in the external control of diverse scattering regimes of the dielectric-VO2 core-shell scatterer, while conductivity of VO2 corresponds to rather insignificant variations in temperature. In line with the purposes of this work, it is shown that the different resonant and nonresonant regimes have different sensitivity to the variations in VO2 conductivity. Both the total scattering cross section and field distributions inside and around the core are studied, as well as the angle-dependent scattering cross section.

Obtaining Multicomponent Coatings of a Stable Composition for Electromagnetic Radiation Screens

The formation processes of coatings of Cu–Ni and Ag–Cu systems with a stable elemental composition by the method of electron-beam evaporation are considered. It is shown that in the zone of action of the electron beam on the ingot placed in the crucible at the total vapor pressure of the alloy elements Σp above the pressure under the cap of the installation, the melt boils, and in the outer zone adjacent to the melt zone, the process of sublimation of the hard alloy occurs. The microrelief and elemental composition of the surface layer of the Cu–Ni alloy ingot in the zones of evaporation and sublimation, as well as the elemental composition of the coatings deposited in this case, have been studied. It is shown that the most acceptable way to obtain coatings of the Cu–Ni system with a stable elemental composition is the simultaneous electron-beam evaporation of copper and nickel from two crucibles. The azeotropic composition of the alloy of the Ag–Cu system was calculated and experimentally verified. The research results are used in the manufacture of multilayered screens of electromagnetic radiation.

Principles of designing electromagnetic screens of the resonant type based on liquid protective compositions

The work explores the possibilities of creating resonance-type electromagnetic shields to protect workers and the population from man-made electromagnetic fields. It is shown that traditional resonant screens are not technological enough to cover large surfaces and are tuned to monochrome or narrow-band electromagnetic fields. Based on the analysis of the experience of using liquid shielding mixtures, the possibility of creating a multilayer structure without fixed layer thicknesses, which will allow protection against the influence of the frequency band, has been proven. At the same time, the wave resistance of the outer layer allows you to minimize the reflection coefficients of electromagnetic waves, which makes the material practically absorbent. A calculator for the preliminary calculation of the electrophysical properties of each layer is presented, which allows rationalizing the required coefficients. For calculations, the formulas of Odelevsky and Debye for the dielectric constant of mixtures are adapted. Experimentally obtained empirical coefficients are presented, which are a component of the ratio for obtaining acceptable screen parameters. To determine the exact concentration of the shielding filler in the matrix, a correction factor is provided. This is associated with errors when determining the volume content of the filler of low dispersion and differences in the morphology of the filler particles, which does not allow for an accurate calculation of the depolarization coefficient of the filler particles. Given the lack of reference data on the electrophysical parameters of the compositions due to their diversity, it is advisable to conduct thorough laboratory studies with different compositions of the compositions. This will make it possible to form a reference database that will speed up the execution of electromagnetic safety work and reduce their cost.

Analysis of technology methods and study of properties of high-temperature superconducting ceramics based on YTTIRIUM

Based on the analysis of the studied properties, the paper presents the developed technology for the manufacture of high-temperature superconducting (HTSC) ceramics based on ultrafine powders; in this case, the method of dry pressing under the influence of an ultrasonic signal is considered. Based on the analysis, the optimal technology variants for synthesizing HTSC ceramics were selected. Data are presented on the performance properties of HTSC ceramics, samples of electromagnetic field screens, volumetric microwave resonators, and ceramic squids. Also, a method of positron annihilation is described, measuring the lifetime of positrons and measuring the curves of the angular distribution of annihilation photons (ADRP), which makes it possible to identify defects of the vacancy type (vacancies, clusters of vacancies, loops, dislocations).

EMI Shielding Using Flexible Optically Transparent Screens for Smart Electromagnetic Environments

Past generations of wireless systems focused largely toward power and bandwidth to support higher data rates, coverage, and quality of service. Smart electromagnetic environments, on the other hand, are aimed at meeting these expectations through modifications in the electromagnetic properties of the geometry, which were once considered an uncontrollable part of a wireless system. This is done through careful placement of smart electromagnetic structures that can constructively manipulate the propagation of electromagnetic waves. In this work, we present optically transparent electromagnetic screens for shielding applications that require visual observation. New aluminum-doped zinc oxide (AZO) thin films, that are low-loss, and optically transparent, are deposited on plastic for use as absorbing-type shields. We also present a simple and reliable technique to fabricate all-metallic single-layer reflecting-type shields. All these shields have a unique combination of shielding effectiveness (SE) and optical transparency that advance the state of the art. They can be used as curtains or walls in indoor environments, windows for autonomous vehicles and as covers to shield smart IoT devices.

Spin Supercurrent as a ¡°Strange¡± Radiation in Low-Energy Nuclear Reactions

The numerous experiments in which the features of Low-Energy Nuclear Reactions (LENR) were researched show that the emergence of new chemical elements in the reactions are accompanied by a radiation that has been detected on nuclear photographic plates located outside of the work chamber. Besides interactions between the radiation with various materials and absence of shielding by electromagnetic and molecular screens, it is characterized by other properties as well: nonmagnetic and nonelectric nature, the accompaniment by electromagnetic radiation, magnetization of nonmagnetic materials, etc. However, the nature of the radiation is left unknown, therefore this radiation is referred to as i°strangei± radiation. With the aim of determining the physical nature of i°strangei± radiation the properties of such process as spin supercurrent are analyzed in this work. The spin supercurrent emerges between objects having precessing spin and tends to equalize the respective characteristics of the spins (angles of precession and angles of nutation); that is, it transforms the angular momentum associated with spins. The investigations of spin supercurrent were conducted from 1976; in 2008 Yu. Bunkov, V. Dmitriev and I. Fomin, were awarded the Fritz London Memorial Prize for the studies of spin supercurrents in superfluid 3§¯§O-B. The comparison of the properties of spin supercurrent with properties of i°strangei± radiation allows us to conclude the following: the spin supercurrent may be the physical process which accompanies Low-Energy Nuclear Reactions and called as i°strangei± radiation. From conducted investigations it follows that spin supercurrent does not only accompany Low-Energy Nuclear Reactions but it may stimulate the accomplishment of these reactions as well.

АНАЛІЗ ЕФЕКТИВНОСТІ ПЕРЕДАЧІ ЕЛЕКТРИЧНОЇ ЕНЕРГІЇ В СИСТЕМІ БЕЗДРОТОВОЇ ЗАРЯДКИ АКУМУЛЯТОРНОЇ БАТАРЕЇ ЕЛЕКТРОМОБІЛЯ

Theoretical researches of efficiency of electric energy transfer in the wireless charger of inductive type with serial resonance in circles of transmitting and receiving coils are carried out. It is shown that this efficiency depends on the parameter (the product of the magnetic coupling coefficient and the Q- factor of the coils) and the ratio of the active resistances of the battery and the coil. It is shown that there is an optimal value of this ratio, at which the efficiency of the device is maximum (when ) and its value increases monotonically with increasing parameter . Moreover, to achieve an efficiency greater than 0.8, it is necessary to have a system of coils with a value of 10. The graphical dependences that determine the value of this efficiency as a function of these two parameters and set the allowable interval for changing the resistance ratio in terms of high energy efficiency. Numerical calculation of the high-frequency magnetic field (with an operating frequency of 100 kHz) generated by the coils was performed, in two cases - in the absence of shielding and in the presence of aluminum electromagnetic screens and showed high efficiency of such screens. The peculiarity of the calculation is that to determine the values of complex currents in both coils, which depend on the mode of operation of the whole device, use their preliminary calculation based on the created Simulink-model of the device. References 14, figures 5, table 2.

Computer materials science of electrical construction composite materials with specified properties

This article is devoted to computer materials science of electrical construction composite materials for obtaining materials with specified properties. The idea, principles and distinctive features of computer materials science are given. An approach to solving a number of problems is described, which makes it possible to fully take into account the presence of random elements that are present in the process of forming composite materials. Implementation of algorithms is implemented, in which results obtained in previous stages affect progress of algorithms execution in subsequent stages. The radar absorbing material is considered in detail using the example of radar absorbing concrete. It has been proved that with multi-factor dependence, it is possible to optimize the composition only using an automated computer system that calculates the composition of the concrete mixture. One possible computer material science problem has shown that in order to increase absorption efficiency, it is necessary to substantially increase the effective absorption volume, which can be achieved by increasing the non-conductive layers in order to reduce the through conductivity of the radar absorbent concrete, i.e., as if to break the material into a large number of small electromagnetic screens. In this case, the volume of interaction of the material with the electromagnetic field extends deep into the material and is made commensurate with the size of the sample. In conclusion, a possible list of tasks and directions for the development of computer materials science is presented.

Ways to reduce the influence of high frequency currents on the human body under induction surfacing

Devices with thermal and electromagnetic shields for induction heating and surfacing of machine parts using a ferrite magnetic circuit with a single-turn inductor, devices with double-turn and three-turn inductors, in which the surfacing zone is completely closed from the influence on workers are designed. This allows to improve the working conditions, as well as to develop new technological processes using high frequency currents. It is shown that the use of thermal and electromagnetic screens can reduce the surfacing time by 10–20 s and decrease the energy consumption by 15–20%, depending on the powdered hard alloy, taking into account health and safety issues.

Experimental researches of the characteristics of antennas in the presence of electromagnetic screens

When placing various antenna systems in a confined space, one has to deal with a complex electromagnetic environment and insufficient isolation between the antennas. And, although the methods of ensuring electromagnetic compatibility of such groups of radio electronic means are well known, taking into account the peculiarities of the objects under consideration, they have very limited application. The use of innovative technologies developing in recent years, including the use of screens made of metamaterials, makes it possible to significantly expand the "limits of applicability" of these methods. As the studies have shown, the screen made of metamaterial has special characteristics in comparison with traditional screens, namely: at the operating frequency of the antenna, the screen is practically permeable to electromagnetic radiation, and at the interference frequency it becomes low-transparent and works as a reflector. The results can be used to improve isolation between closely spaced antennas, such as at the tops of towers or masts.

Development and Application of Thin Wide-Band Screening Composite Materials

The paper is dedicated to the development of effective composite coatings with the use of carbon fillers of different morphology, their research, and application in the broadband frequency range. Electromagnetic loss studies were performed according to international standards ASTM D4935, IEEE-STD-299, and the US Department of Defence standard MIL-STD 461F. The impact of hybrid carbon nanomaterial "graphene/nanotubes" on the electrophysical properties of the composite material has been analyzed. As a result, the research laboratory technologies of production of composite coating on water and non-water (alcohol) basis are developed based on the carbon fillers of various morphology and also magnetite. The shielding properties of most of the created composites are estimated in the frequency range from 50 MHz to 30 GHz. The state enterprise “All-Ukrainian center for standardization, metrology, certification, and consumers’ rights protection” (here and after “Ukrmetrteststandart”) conducted comparative tests of the developed coating (in the form of paint) with a protective coating # 842 MG Chemicals (Burlington, Ontario, Canada) based on silver microparticles. Developed water-based composites can be used for interior decoration, in the formation of electromagnetic screens, thin gradient coatings to protect people from electromagnetic radiation in the microwave range.

Control of Shielding Effectiveness of Optically Transparent Films by Modification of the Edge Termination Geometry

This article deals with the design, fabrication, and characterization of optically transparent electromagnetic screens to protect optical sensors against high-intensity radiated fields. To ensure the best tradeoff between high optical transparency over the entire visible light spectrum and high shielding effectiveness at microwaves, micrometric mesh metal films printed on glass substrates were selected. Changing the micrometric mesh pattern allows reaching various shielding effectiveness values required for different applications, but implies important adjustments of the design and fabrication processes. The variation of the number of contact ribbons between the mesh screen and its direct peripheral area consists of an alternative solution to modify the screen shielding effectiveness, while keeping the meshed part of the screen identical. An analytical model, which predicts the shielding effectiveness variation measured under statistically uniform illumination in a reverberation chamber as a function of the number of metal ribbons and the aperture sizes between them was specifically developed. Experimental results follow the trend predicted by the analytical model. As a result, adjusting the number of peripheral contact ribbons enables the shielding effectiveness to be fitted to specified requirements at constant optical transparency.

Estimation of the electromagnetic screens efficiency for the compensation of slot leakage fluxes in the pulsed electromechanical generator

Purpose. There are considered in the paper the four possible configurations of electromagnetic screens for compensation of the flux leakage of slots in the electromechanical pulse generator with a compression of magnetic flux. It is underlined the expediency of slot leakage inductance reduction as the method for increasing of coefficient of magnetic energy amplification in the process of flux compression. Methodology. Efficiency of each configuration of screens has been evaluated on the reduction of slot leakage inductance magnitude. To realize it the problem of pulsed field distribution in the teeth zone of generator has been solved by the finite elements method with application of professional version of software program QuickField v.6.1. Originality. There was manufactured the physical model of teeth zone in which the active conductor of slots was divided on 9 parallel sections along the height of slot. Results. With current supply from the source of alternating current at frequency 400 Hz that was measured a current distribution between the sections of active conductor both at the absence of electromagnetic screens and at their presence. Practical value. It is shown, that screening of slot leakage flux provides the more uniform distribution of current along the sections of active conductor with a corresponding reduction of slot leakage inductance..

ЗАГАЛЬНІ ЗАСАДИ ПРОЕКТУВАННЯ ЕЛЕКТРОМАГНІТНИХ ЕКРАНІВ ТА ЕКРАНУЮЧИХ КОНСТРУКЦІЙ

В умовах складної електромагнітної обстановки, що формується за рахунок впливу зовнішніх та внутрішніх джерел, а також внаслідок широкого застосування бездротових систем передачі інформації, завдання, пов’язані із застосуванням екрануючих конструкцій значно ускладнюються. Зокрема, необхідність забезпечення стабільної роботи мобільного зв’язку накладає певні обмеження на коефіцієнти екранування захисних матеріалів. Це потребує визначення загальних підходів до запровадження екранування на принципах розумної достатності, враховуючи як захист людей від електромагнітних впливів, так і виробничі потреби. Встановлено, що необхідним є розроблення схеми проектування електромагнітних екранів з урахуванням складності електромагнітної обстановки. Мета роботи – розроблення загальних засад проектування екрануючих матеріалів та конструкцій з урахуванням гранично допустимих рівнів магнітних та електромагнітних полів різного походження. Обґрунтовано, що для проектування магнітних та електромагнітних екранів доцільно використати експериментальні дані щодо залежності коефіцієнтів екранування від товщини захисного матеріалу, вмісту екрануючої металевої та металовмісної субстанції у полімерній матриці тощо. Визначено коефіцієнти екранування магнітного поля промислової частоти, електромагнітного поля частотою 1,8 ГГц та геомагнітного поля композиційними металополімерними матеріалами різної товщини та характеристик. Встановлено, що оптимізація параметрів матеріалів щодо впливів полів цих трьох походжень неможлива. Наведено схему, яка може бути використана за наявності електромагнітних полів різного походження та широкого частотного спектра. Але передумовою таких робіт є проведення моніторингу електромагнітної обстановки у виробничих приміщеннях з визначенням амплітудно-частотних характеристик електромагнітних полів різного походження. Здійснення проектних та впроваджувальних робіт за розробленою схемою є найбільш доцільним підходом щодо проектування захисних матеріалів та екрануючих конструкцій. Такий підхід мінімізує витрати часу та коштів на роботи з електромагнітної безпеки

Evaluation of the Effectiveness of Radio-Absorbing Coatings for Information Security Problems

The paper investigates the weakening effects of screens of various kinds on the electromagnetic waves passing through them. With such solutions, it is possible to make estimates for the weakening effect of electromagnetic screens of arbitrary shape and for radiation with arbitrarily given characteristics.

Засади автоматизованого проектування електромагнітних екранів з урахуванням просторових факторів

The purpose of the work is to develop the principles of designing electromagnetic screens taking into account diffraction phenomena and methodological approaches to the automation of design work. Results. The principal approaches to the design of materials and structures for shielding electromagnetic radiation are considered. It is shown that for shielding radiation with frequencies up to 1 GHz, it is necessary to take into account the diffraction phenomena at the edges of flat structures, which cause the presence of “penumbra”. A convenient mathematical apparatus for determining the size of the penumbra depending on the wavelength of incident electromagnetic radiation is provided. The need to account the reflection of electromagnetic waves from building structures, flat surfaces of technological equipment, and other objects in the design of electromagnetic screens is substantiated. The corresponding computation procedure is offered. Practical significance. The obtained functions allow modelling the propagation of radiation in the protected area and selecting the necessary parameters of the composite shielding material in the automated mode. The main parameters are the content and dispersion of the metal substance and the thickness of the material. They determine the contribution of the reflection and absorption coefficients of electromagnetic waves to the overall shielding coefficient. This makes it possible to optimize the parameters of the shielding design on the principles of reasonable sufficiency.

Development of Absorbing Coatings for Protection Against Electromagnetic Pollution of the Environment

Radioabsorbing materials are materials whose composition and structure provides effective absorption (with little reflection) of electromagnetic energy in a certain range of radio wavelengths.The paper investigates the weakening effects of screens of various kinds on the electromagnetic waves passing through them. With such solutions, it is possible to make estimates for the weakening effect of electromagnetic screens of arbitrary shape and for radiation with arbitrarily given characteristics.

Development and investigation of protective properties of the electromagnetic and soundproofing screen

We have developed a technology for manufacturing an universal electromagnetic and soundproofing screen based on foam-latex and foam-polystyrene. The dispersity and physical characteristics of components in a material for shielding electromagnetic field and noise have been investigated. The designed material consists of latex and iron ore dust with dominating dispersion of 12 µm. In order to improve the soundproofing properties, latex was supplemented during fabrication with a foam-forming agent − synthetic oleic acid. To reduce the weight, we added granulated foam-polystyrene with the size of granules 1−3 mm to the material. We examined screens with a thickness of 5 mm and 10 mm with a different content of the metallic substance. It was determined that the shielding coefficients of the material 5 mm think containing 5‒20 % of iron ore content are as follows: for electromagnetic field of frequency 2.4‒2.6 GHz ‒ 1.8−44; for the magnetic field of industrial frequency ‒ 1.2−15.0. For the material with a thickness of 10 mm they are 2.9−52.0 and 2.3‒38.4, respectively. The noise reduction index of 41−44 dB is achieved at noise frequencies of 6−8 kHz, which is the most critical for humans. The structural study of the materials' surface was performed. It has been established that at the content of the metallic substance above 15 %, its distribution in the bulk of the material becomes non-homogenous. In order to improve the efficiency of electromagnetic protection, it is expedient to produce a magnetic or rheological fluid from iron dust in advance, to apply it in the technological process for foam-latex fabrication. It has been proven that the combined electromagnetic and soundproofing (acoustic) screens, that are small in thickness and low in weight, could provide reduction of the levels of electromagnetic fields and noise to match the norms, which is especially important when they are applied in the transportat industry