Search

Subject and Purpose. The paper presents the development and testing of a microwave splitter based on a planar hyperbolic metamaterial with a structural defect. The planar hyperbolic metamaterial is so constructed that a propagating electromagnetic (EM) wave is channeled in a certain direction depending on the metamaterial parameters. The wave splitting is possible where a part of the incident wave is reflected from a defect created inside the metamaterial. As the defect spatial orientation relative to the incident EM wave changes, the propagation direction of the reflected EM wave also changes. By this means the wave propagation control can be implemented in the considered splitter. Methods and Methodology. A defect in a planar hyperbolic metamaterial is created using the circuit theory that relates the material parameters to the equivalent unit-cell capacitances and inductances which, in turn, depend on the parameters of the microstrip line and capacitors. Thus, a change in any parameter of the circuit inside the unit cell changes its material parameters and makes a defect cell. In this work, a defect is created by changing the capacitance of the capacitors in a given set of elementary cells of a planar hyperbolic metamaterial, controlling thereby the size of the defect and its spatial location relative to the propagating wave. The numerical model of EM wave propagation inside a planar hyperbolic metamaterial with a defect is validated by experiment. In it, the field distribution over the metamaterial surface is obtained using the active probe method in the three cases: a defect-free metamaterial and two variants of defect orientation. To insert the electronic control, it is proposed to replace the elementary cell capacitors with varactors. Results. The obtained field distributions show that the defect partially reflects the incident EM wave channelized in the planar hyperbolic metamaterial. As the defect location angle changes, the wave reflection angle also changes. To make a defect unit cell, it will only suffice to change its capacity by 20% from the original, which is quite feasible in modern varactors. Conclusion. The performed studies have shown that the considered planar hyperbolic metamaterial with a structural defect is good for creating tunable electromagnetic wave splitters.

ObjectiveTo evaluate the effects of electromagnetic waves generated by a commercial medical electromagnetic instrument (trade name, TDP, the Chinese phonetic abbreviation of “Te-ding Dian-ci-bo Pu”) as an adjuvant to improve the rate of increase of milk feeds per day by premature infants with necrotizing enterocolitis (NEC).MethodsThis study was a prospective randomized clinical trial. A total of 103 premature infants were diagnosed with NEC II, but there was no need for surgery. The infants were randomly divided into the TDP intervention group and the control group by a randomized method using SPSS 24.0. The patients in the TDP intervention group were treated with TDP irradiation and routine interventions; those in the control group were treated with routine interventions. The rate of increase of milk feeds per day, the time to achieve total gastrointestinal nutrition, the velocity of weight gain, and the complication incidence rate were recorded and compared.ResultsThe rate of increase of milk feeds per day in the TDP intervention group was significantly greater than that in the control group [14.51 (11.58~22.11) ml/kg/d vs. 10.15 (6.15~15.87) ml/kg/d, P = 0.002]. Compared to the control group, the time to achieve total gastrointestinal nutrition (21.45 ± 1.87 d vs. 36.43 ± 2.585 d, P = 0.000) and the velocity of weight gain (19.65 ± 15.27% vs. 13.68 ± 7.15%, P = 0.013) in the TDP intervention group were substantially better than those in the control group. The complication incidence rate was not significantly different between the two groups (P > 0.05).ConclusionTreatment with TDP-generated electromagnetic waves improved the volume of milk consumed per day in premature infants with NEC II and were conducive to improving their clinical outcomes.

The quality criteria for fairing used to protect antenna devices (AD) of radar stations (RS) from environmental influences are the requirements for ensuring and maintaining strength and protective properties with minimal insertion loss of the transmitted electromagnetic wave (EMW). It is important to assess the influence of manufacturing technology on these parameters, identifying narrow critical zones on the product with minimum strength characteristics and maximum EMW insertion loss. Calculation models of the stress state in a three-layer sandwich are presented with the identification of critical places from a given type of loading. A method for flaw detection of fairings is presented, taking into account the influence of the dynamics of changes in the maximum allowable threshold of EMW losses, which is extremely necessary for analyzing the technological process and correcting strength calculations.

This paper deals with the scattering of electromagnetic waves in space, in particular that of radio waves used for broadcasting, TV and telecommunications. The basic features of electromagnetic wave propagation are described without any mathematical development. The principal antenna designs, radiation patterns, the effects of soil electrical conductivity and diffraction caused by obstacles such as buildings and mountains are discussed. To conclude, we address the impact of the antennas on the landscape and the expected trends in antenna technology in the wake of digital modulation. The problem of electromagnetic compatibility is mentioned as it represents a new challenge for many types of equipment powered by electricity.

A large range of applications have been identified based upon the communication of underground sensors deeply buried in the soil. The classical electromagnetic wave (EM) approach, which works well for terrestrial communication in air medium, when applied for this underground communication, suffers from significant challenges attributing to signal absorption by rocks, soil, or water contents, highly varying channel condition caused by soil characteristics, and requirement of big antennas. As a strong alternative of EM, various magnetic induction (MI) techniques have been introduced. These techniques basically depend upon the magnetic induction between two coupled coils associated with transceiver sensor nodes. This paper elaborates on three basic MI communication mechanisms i.e. direct MI transmission, MI waveguide transmission, and 3D coil MI communication with detailed discussion of their working mechanism, advantages and limitations. The comparative analysis of these MI techniques with each other as well as with EM wave method will facilitate the users in choosing the best method to offer enhanced transmission range (upto 250 m), reduced path loss (

Using WKB method the peculiarities of the temporal spectrum of an ordinary and extraordinary electromagnetic wave scattered in a weakly randomly inhomogeneous three-dimensional nonstationary and conductive magnetized plasma are investigated. On the basis of the stochastic differential transport equation for the frequency fluctuation the broadening and the displacement of the temporal spectrum for both waves are obtained for the polar terrestrial ionosphere. These statistical characteristics contains anisotropic parameters: velocity of a plasma stream, conductivities of the ionosphere, elongated electron density irregularities are characterized by the anisotropy factor and inclination angle with respect to the geomagnetic lines of forces. The analysis of the power spectrum of the waves as a function of the propagation distance and the nondimensional frequency parameter containing the carrier frequency and characteristic temporal scale of electron density fluctuations are carried out. Analytical and numerical calculations have shown that the terrestrial conductivity and anisotropy factors exert a substantial influence on evaluation of the temporal spectrum than the inclination angle. It was found that the wave spectrum increases initially as the square root of the propagation distance, but at large distances it approaches a limiting value. Statistical moments of a scattered ordinary and extraordinary waves do not depend on an absorption sign and valid for both absorptive and active media.

This article proposes a new refined definition of light, which makes it possible to harmonize the wave and corpuscular concepts of this object of matter and quantitative relations that describe the wave-corpuscular nature of the phenomena of interference, diffraction, dispersion, polarization, external and internal photoeffects as phenomena as well as such electroluminescence and photoluminescence associated with light. [ABSTRACT FROM AUTHOR]

Copyright of Railway Signalling & Communication Engineering is the property of Railway Signalling & Communication Engineering 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.)

The two equations E = h x f and E=(h x c)/λ for the quantum of energy of electromagnetic radiation provide the same result but describe electromagnetic radiation very differently. E = (h x c)/λ describes the quantum of energy of electromagnetic radiation to be located already in one wavelength and therefore like a particle. E = h x f describes the quantum of energy distributed over 299 792 458 m and therefore like a wave. To obtain h x f for the quantum of energy, we have to refer the quantum of energy to 299 792 458 m. Only then we obtain from E = (h x c)/(299 792 458 m), as the distance of 299 792 458 m of the velocity c is cancelling out now, E = h x 1/s = h x Hz, which is the precondition to obtain the correct value for the quantum of energy by multiplying Planck's constant h by the frequency f. This already indicates the necessity of today's physics to have to speak of a particle-wave duality. It turns out that electromagnetic radiation consists of the first wavelength that carries the quantum of energy and behaves like a particle, which today is called "photon," and a few following wavelengths that do not carry a further quantum of energy and behave like a wave, which today is called "electromagnetic wave." By this knowledge, the particle-wave duality vanishes, and we obtain one single physical phenomenon, which I call "photon-wave." The strange behavior of quantum objects at a single slit, at double-slits, and at beam splitters can now be understood in a causal way. "God does not play dice!" Einstein was right. [ABSTRACT FROM AUTHOR]

In this paper, we present a structural topology optimization code for two-dimensional electromagnetic wave problems in the context of polarized electric field driven by the wave equation in the frequency domain for microwave range. The optimization process follows a phase field design approach, which is based on the reaction–diffusion equation combined with the double well potentials. In addition, a modified adaptive gradient algorithm is introduced for better performance and faster convergence rate. The salient features of the code are elaborated for the educational purpose; especially focused on the derivation of weak form in the finite element analysis for physical behavior simulation and the update of design variables. The corresponding code is written in the open-source software FreeFEM++, and it can be downloaded from the website http://ssd.yonsei.ac.kr. [ABSTRACT FROM AUTHOR]

The method used to factorize the longitudinal wave equation has been known for many decades. Using this knowledge, the classical 2nd-order partial differential Equation (PDE) established by Cauchy has been split into two 1st-order PDEs, in alignment with D'Alemberts's theory, to create forward- and backward-traveling wave results. Therefore, the Cauchy equation has to be regarded as a two-way wave equation, whose inherent directional ambiguity leads to irregular phantom effects in the numerical finite element (FE) and finite difference (FD) calculations. For seismic applications, a huge number of methods have been developed to reduce these disturbances, but none of these attempts have prevailed to date. However, a priori factorization of the longitudinal wave equation for inhomogeneous media eliminates the above-mentioned ambiguity, and the resulting one-way equations provide the definition of the wave propagation direction by the geometric position of the transmitter and receiver. [ABSTRACT FROM AUTHOR]

Carbon microcoils (CMCs) were formed on stainless steel substrates using C2H2 + SF6 gas flows in a thermal chemical vapor deposition (CVD) system. The manipulation of the SF6 gas flow rate and the SF6 gas flow injection time was carried out to obtain controllable CMC geometries. The change in CMC geometry, especially CMC diameter as a function of SF6 gas flow injection time, was remarkable. In addition, the incorporation of H2 gas into the C2H2 + SF6 gas flow system with cyclic SF6 gas flow caused the formation of the hybrid of carbon nanofibers–carbon microcoils (CNFs–CMCs). The hybrid of CNFs–CMCs was composed of numerous small-sized CNFs, which formed on the CMCs surfaces. The electromagnetic wave shielding effectiveness (SE) of the heating film, made by the hybrids of CNFs–CMCs incorporated carbon paste film, was investigated across operating frequencies in the 1.5–40 GHz range. It was compared to heating films made from commercial carbon paste or the controllable CMCs incorporated carbon paste. Although the electrical conductivity of the native commercial carbon paste was lowered by both the incorporation of the CMCs and the hybrids of CNFs–CMCs, the total SE values of the manufactured heating film increased following the incorporation of these materials. Considering the thickness of the heating film, the presently measured values rank highly among the previously reported total SE values. This dramatic improvement in the total SE values was mainly ascribed to the intrinsic characteristics of CMC and/or the hybrid of CNFs–CMCs contributing to the absorption shielding route of electromagnetic waves.

We investigate the axial vector spin–torsion coupling effects in the framework of the Poincaré gauge theory of gravity with the general Yang–Mills type Lagrangian. The dynamical equations for the “electric” and “magnetic” components of the torsion field variable are obtained in the general form and it is shown that the helicity density and the spin density of the electromagnetic field appear as the physical sources. The modified Maxwell’s equations for the electromagnetic field are derived, and the electromagnetic wave propagation under the action of the uniform homogeneous torsion field is considered. We demonstrate the Faraday effect of rotation of the polarization for such a wave and establish the strong bound on the possible cosmic axial torsion field from the astrophysical data.

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department 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.)

Copyright of Journal of Beijing University of Technology is the property of Journal of Beijing University of Technology, Editorial Department 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.)

The ability to detect abnormalities in infrastructure automatically and remotely with a small number of sensors would greatly contribute to efficient and timely infrastructure inspection. Here, we propose a passive sensor that can be installed by painting. The painted waveguide-based sensor detects abnormalities in infrastructure from abnormality-induced changes in the resonance frequency of electromagnetic waves resonating inside the sensor. In this paper, the principle of detecting loose bolts with the painted waveguide-based sensor is demonstrated by simulation and experiment. The sensor is designed and fabricated as a resonator with resonance frequencies from 100 kHz to 2.5 GHz, which includes the UHF radio-frequency identification band, and the measurement frequency was set within this range. The fabricated sensor is capable of detecting not only a single loose bolt but also two or more loose bolts on the waveguide of the sensor to monitor. [ABSTRACT FROM AUTHOR]

Photoelectron ejection is important in technological applications. Recently, the photoelectric effect was explained based on the electromagnetic (EM) wave concept. According to the EM wave concept, an electron within the conduction band of a photocell moves circularly. In this paper, we explain few facts regarding the photoelectric emission process, such as the radius of circular motion, maximum ejection angle, and depth of the photoelectron, based on the EM wave concept. Further, the effects of the intensity and frequency on these parameters are discussed. The ejection angle depends on the frequency and intensity of the light and the depth of the photoelectrons. The explanations herein may increase the applications of light energy. [ABSTRACT FROM AUTHOR]

Wireless underground sensor network (WUSN) is widely used in agriculture, frontier defense, and other fields with great research value. This paper takes the propagation characteristics of the electromagnetic waves that propagate in WUSN as research target, and systematically tests the effect of influence factors on the communication quality of electromagnetic waves. The influence factors are chosen on the basis of the propagation theory of electromagnetic waves. Specifically, the influence factors include the burial depth of sensor sub-node, the horizontal distance between nodes, the communication frequency, and the thickness of snow. Moreover, the experiments are carried out in normal and snow-covered soil. The propagation characteristic of electromagnetic waves is measured by received signal strength (RSS) and symbol error rate (SER). Finally, the selection of communication frequency in different application scenarios is concluded. The conclusions have a great significance for guiding the arrangement of WUSN nodes in different scenarios. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology 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.)

China accounts for more than 22% of the total energy consumption worldwide. Building energy consumption, among which consumption in public buildings was about 40% took the second place. With the problems of high energy waste, error rate and complexity of the control systems available, an indoor intelligent lighting system based on occupants' location is proposed in this paper to improve the energy efficiency of the current lighting systems indoors. The transmission model of electromagnetic wave in free space is optimized in both aspects of reference signal strength and attenuation coefficient radiation in complex environment dynamically based on which occupants' positions are obtained. The smart lighting system will turn on or off corresponding lights adaptively to provide a more energy efficient platform. Experimental results show that the proposed system is able to improve the energy efficiency of indoor lighting by at least 15%, with a lower error rate below 2% compared with the existing lighting systems based on voice control. [ABSTRACT FROM AUTHOR]

The propagation of electromagnetic waves in an ideal regular waveguide with the magnetodielectric filling periodically modulated in space and time is studied. It is assumed that the modulation depths are small, so the modulation of waveguide filling does not lead to the interaction between different waveguide modes. Wave equations are obtained for transverse electric (TE) and transverse magnetic (TM) fields in the waveguide with respect to the longitudinal components of the magnetic and electric vectors, respectively. They are second order partial differential equations with periodic coefficients. By changing the variables, these equations are reduced to ordinary differential equations of the Mathieu–Hill type with periodic coefficients. Solutions to these equations for small modulation depths in the region of weak interaction between the signal and modulation waves (the Wolfe–Bragg condition is not satisfied) are found in the first approximation. The results obtained in the above approximation show that the TE and TM fields in the waveguide can be expressed as the sum of three space–time harmonics (the zero harmonics and the first harmonics with the plus and minus signs) with complex amplitudes and frequencies. [ABSTRACT FROM AUTHOR]

Ferrites are an important group of magnetic materials which are used as absorbers. The incorporation of ferrite and conducting polymer achieves great enhancement in microwave absorption properties. The nanocomposites of hexagonal ferrites embedded by conducting polymers such as polypyrrole, polyaniline and polythiophene (PTH) have been paid much attention. In the present study, strontium hexagonal ferrite doped by Zr and Zn with the final formula of SrFe 12-x (ZrZn) 0.5x O19 considering x = 0.9 and embedded by PTH was produced to achieve a nanocomposite with the highest microwave absorbing ability. In this study, after synthesis of SrFe 12 O 19 (ZrZn) 0.5x O19 and PTH, the nanocomposite was prepared by in situ polymerization. Wrapping the ferrite particles and PTH chains could form nanocomposite properly, and therefore acceptable interactions were observable between SrFe 12-x (ZrZn) 0.5x O19ferrite particles and PTH polymer chains in the composites. Assessing the X-ray diffraction (XRD) patterns of SrFe 12-x (ZrZn) 0.5x O19, PTH, and PTH/SrFe 12-x (ZrZn) 0.5x O19 nanocomposite indicated that the PTH characteristic peak shifts slightly and its peak intensity reduces, which may be attribute to the coating of PTH polymer chains onto SrFe 12-x (ZrZn) 0.5x O19 particles. We revealed also lower magnetic properties in the obtained nanocomposite. The morphological assessment also suggested that PTH could effectively coat the SrFe 12-x (ZrZn) 0.5x O19 particles. The synergistic effect of SrFe 12-x (ZrZn) 0.5x O19 particle plus PTH leads to microwave absorption percentage higher than 95% by PTH/SrFe 12-x (ZrZn) 0.5x O19 nanocomposite. Overall, nanocomposite creating by coupling interaction between SrFe 12-x (ZrZn) 0.5x O19 particles (x = 0.9) and PTH can effectively lead to achieve the highest rate of absorption of electromagnetic waves. [ABSTRACT FROM AUTHOR]

Calcium cobaltate thin films were prepared by coating and sintering on alumina ceramic substrate with calcium cobaltate powder prepared by sol-gel method. The phase structure, temperature resistance characteristics and wave-absorbing properties of the thin films were studied. It is found that the calcium cobaltate powders prepared by sol-gel method are composed of Ca9Co12O28 phase, and the powder particles are uniform, with a certain orientation growth and obvious lamellar structure. The sintered calcium cobaltate film is composed of fine Ca3 Co4 O9 phase, which is closely bound to the alumina substrate. The thickness is about 20 µm. The square resistance of the films decreases rapidly with the increase of temperature, and keep around 20 Ω/□ at 300 °C to 800 °C. At 800 °C, the resistance-film type metamaterial absorber exhibits double absorption peaks at 8 GHz to 18 GHz. [ABSTRACT FROM AUTHOR]

The requirement in resolving electromagnetic (EM) problems in stealth warhead technologies are excellent absorption ability, lightweight, and thin dimensions. In this direction, this study provides a straightforward hydrothermal one-pot method to synthesize superparamagnetic Mn-based ferrite co-doped with Co and Cu (MCCF), and the article presents its microwave absorption properties. Using cutting-edge techniques, the MCCF nanocomposite phase structure, morphological, superparamagnetic, and microwave absorption properties were measured and analyzed. MCCF-822 ferrite shows superparamagnetic properties simultaneously with a high M s value 71.4 emu/g. Vector network analysis of MCCF-822 with 70 wt% loading demonstrates an effective absorption bandwidth (EAB) of 5.2 GHz with a maximum reflection loss (RL max) of −19.2 dB at 2 mm thickness, and it spans almost 92.77 % frequency region (3.3–18 GHz range with RL < −10 dB) by varying thickness 1.7 mm–6 mm. At 60 wt% loading, it covers the whole X & K u band with a thickness range from 2 to 9 mm with a good EAB of 4.3 GHz at 2.5 mm thickness with RL max of −16 dB. The dual absorption bands are also present in MCCF-613, which increases the EAB with RL max −52.99 dB at 9 mm, fulfilling the superparamagnetic properties. Thus, MCCF-822 is proposed as a cost-effective superior ferrite nanocomposite for microwave absorption applications. [Display omitted] • The superparamagnetic nanocubes within 3–27 nm range of dimensions are synthesized hydrothermally. • The Ms value 71.4 emu/g was obtained for MCCF ferrite. • The maximum RL of −19.2 dB at 2 mm thickness with EAB 5.2 GHz was attained, covering 20 % of X band and 68 % of K u band. • Superparamagnetic nanocubes can be used as an efficient microwave-absorbing material. [ABSTRACT FROM AUTHOR]

The utilization of three-dimensional hierarchical porous foam structures has proven to be a successful approach in creating lightweight and wide bandwidth microwave absorbers with superior performance. In this study, a honeycomb-shaped polyurethane (PU) foam was utilized as the substrate for an absorber. It was combined with a new nanocomposite consisting of GO-rGO as the dielectric parts and SmCo 5 as the magnetic component. The concept of utilizing a GO-rGO nanocomposite with varying bandgap within the synthesized composite foam led to the creation of multiple heterogeneous interfaces, enhancing interfacial polarization and ultimately achieving optimal impedance matching. Furthermore, the incorporation of GO-rGO nanocomposites in the synthesis of SmCo 5 aimed to facilitate the thorough amalgamation of the components, mitigate the self-agglomeration of the magnetic particles, and establish a two-dimensional matrix of aligned magnetic particles, resulting in an improvement in magnetic loss phenomena. Additionally, the 3D hierarchical structure of the porous foam serves to create an intricate network, thereby enhancing the transmission pathways and enabling the activation of a greater number of attenuation phenomena. The findings suggest that the compound presents remarkable abilities in absorbing microwaves, boasting a reflection loss of −32.5 dB at 10.6 GHz and an effective absorption bandwidth of 4 GHz at a 1.4 mm thickness. The outstanding microwave absorption properties can be credited to the activation of a variety of attenuation mechanisms, including interfacial polarization, multiple reflections and scattering of waves, enhanced impedance matching, and resilient magneto dielectric losses. • Lightweight and wideband width multicomponent porous absorber is prepared. • GO-rGO/SmCo 5 nanocomposite embedded in PU foam for preparing thin thickness absorber. • 3D porous hierarchical structure improved Z in /Z 0 factor and loss mechanism of the components. • The sample achieved RL of −32.5 dB with 1.4 mm thickness and 4 GHz EAB. [ABSTRACT FROM AUTHOR]

The scientific community has shown great interest in high-performance multifunctional nanomembranes due to their increasing demand. Nevertheless, the development of multifunctional composite nanofibrous membranes faces a limitation in achieving consistent and optimal performance with balancing conflicting requirements across multiple functionalities. However, addressing this challenge, a single composite nanofibers membrane has been successfully fabricated, demonstrating effective antibacterial activity, waterproofing properties, and excellent electromagnetic (EM) wave absorption. The multifunction composite nanofibers (CNFs0.6-Co@Fe3) exhibited remarkable microwave absorption performance, with a reflection loss (RL) of 29.10 dB at 15–20 GHz and a thickness of 1.5 mm. Additionally, the nanocomposite displayed flexibility, hydrophobicity with a water contact angle larger than 95° and low surface energy, and significant antibacterial properties against Escherichia coli (E. coli). These multifunctional nanocomposites offer a unique combination of outstanding EM wave absorption, cost-effective fabrication, environmental friendliness, and lightweight characteristics, holding great promise for future applications in nanocomposite products. [Display omitted] ● The study investigates the fabrication of multifunctional composite nanofibrous membranes by incorporating magnetic nanoparticles into PAN/PVA composite. ● The incorporation of magnetic nanoparticles into the composite enhances the waterproof properties with excellent antibacterial activity. ● The composite demonstrates broad-range EM absorption properties, attributing to the unique EM properties of the magnetic nanoparticles. ● The resulting multifunctional composite can be used in a range of applications, including biomedical devices, outdoor environments, and EM shielding. [ABSTRACT FROM AUTHOR]

• The absorption performances of rare earth-based absorbents are summarized. • Strategies for enhancing microwave absorption performances in rare-earth transition metal alloys and compounds, including the intrinsic and the extrinsic modifications are discussed. • This review aims to guide future development of rare earth-based magnetic microwave absorbers. Because of the unique electronic structures of rare earth elements, the rare earth-transition metal alloys could exhibit impressive hard and soft magnetic properties. Especially, in the high-frequency applications, the rare earth-transition metal alloys possess higher magnetic loss and tunable magnetic anisotropies when comparing to the traditional metallic soft magnets. As a result, there has been an increasing interest recently in the research of rare earth-transition metal alloys for electromagnetic wave absorption. In this paper, we will provide a comprehensive overview on the energy converting mechanisms as well as a systematical summary of the recent achievements of rare earth-transition metal alloys and their compounds as microwave absorbers. Typically, the progress and prospective aspects of the rare earth based magnetic absorbers will also be emphasized. Consequently, it is hoped that this review could give a meaningful insight for the development of novel and efficient rare earth based magnetic microwave absorbents in the future. [ABSTRACT FROM AUTHOR]

Electromagnetic wave is a viable means of introducing energy into reservoirs for the recovery of residual oil. However, previous studies have not considered the precise frequency of the electromagnetic (EM) wave. These studies focused on EM heating, not considering the efficiency dependence of EM transmitter and EM propagation on the EM properties of the medium. Thus, sandstone effective permittivity was experimentally measured, and electrical conductivity calculated for different saturation stages encountered in the nanofluid enhanced oil recovery process. The effective permittivity at the resonant frequency of the sandstone increased from 10.94 to 19.1 with a simultaneous frequency shift from 1.2 to 0.6 GHz due to the inclusion of magnetite nanofluid. This implies that the maximum transfer of EM energy for stimulation and activation of injected nanofluid can be achieved by irradiating the EM wave of this frequency within the reservoir for mobilization of the residual oil.

The purpose of the work, the results of which are presented within the framework of the article, was to analyze the operation of the radar goniometer system under the conditions of a signal generated by coherent radiation sources from two points in space (cross-eye interference). To achieve the goal in the present work, a study was made of the dependence of the settings of the goniometric system on the ratio of the parameters of the cross-eye jammer and the angular coordinate meter itself. As a goniometric system, an angular coordinate meter was used, operating by the method of amplitude instantaneous signal comparison. The studies were carried out by the method of theoretical analysis of the influence of the radiation pattern parameters of the antenna system of the meter on the result of measuring the angular position of a virtual radiation source. As a result, an equation is obtained that relates the angular position of the virtual radiation source with the radiation pattern parameters of the antenna system of the meter, the shape of which was approximated by a gaussian curve. To illustrate the functioning of the goniometric system at specific values of the parameters supplied to its input signals, the method of mathematical modeling was used. Modeling was performed for the given parameters, which determine both the position of the radiation sources in space and the algorithm of operation of the angular coordinate meter. Based on the results obtained, it is shown that the angular coordinate meter has three stationary states corresponding to the position of the virtual radiation source in space. It is shown that only two of these states are stable. The latter means that, depending on the initial conditions, the angular coordinate meter can fix one of the two possible positions of the virtual radiation source in space. The scientific novelty of this work is to establish a relationship between the position of the virtual radiation source in space and the parameters of the angular coordinate meter.

In recent years, there has been a rapid increase in the number of electromagnetic radiation sources such as mobile phones and base stations of mobile telephony. This radiation has been classified by the International Agency for Research on Cancer as a possible human carcinogen (group 2B). For this reason, many studies have been carried out on the impact of mobile telephony on human health. The largest of the experiments were carried out on animals. Due to the divergent results of many studies, there was no clear answer on the possible carcinogenic effects of this type of radiation on health. Detection of cancer shortly after an exposure is the most difficult task in analyzing the results. Some of the studies require repetition and verification of the results. In the case of negative effects of electromagnetic fields on brain activity, sleep, heart rate, cognitive function and blood pressure, no consistent evidence has been obtained either. In view of the increasing popularity of mobile phones, their location at short distances from the body (mainly the head) and the development of mobile phone technologies (which entails an increase in the number of base stations), further research, especially among young people, is needed. The duration of human exposure to electromagnetic radiation is subject to an increase and only further research can provide an answer on the possible negative effects of mobile phones and base stations.

We discuss and compare the results obtained from experimental measurements of a two-layer, Ni and TiO2 nanometric structure deposited on siliceous glass. Utilizing previous theoretical models of multilayers or periodic systems and their verifications, the paper focuses on measurement in the NIR, visible, UV, X-ray, and gamma bands of the electromagnetic spectrum; the wavelength of the incident electromagnetic wave is respected. The proposed evaluation comprises a brief description of a Snell’s law-based semi-analytic model of electromagnetic wave propagation through a layered material. We also demonstrate the expected anti-reflective and shielding effects in the X-ray and gamma-ray bands, respectively.

Сonsistent physics and mathematics model of electromagnetic waves propagation in heterogeneous medium using the generalized wave equation and the Dirichlet theorem is built. The data of numerical simulation of the electromagnetic interference interaction with a fibrous material having a double porosity. The results of numerical simulation show that the presence of micro- and macropores (medium with double porosity) of the fabric ensures maximum masking effect.

The front of electromagnetic wave generated by coherent sources of radiation from two points of space is analyzed in the article. General expressions are obtained that allow to estimate the directions of the arrival of the wave at a point in the space where the observer is situated (the angle-system), depending on the parameters of the radiators system. It is shown that the obtained relations for some particular cases coincide with the expressions presented in known publications on the subject under consideration.

This study aims to investigate the toxicity of the plant to heavy elements (HMs). For this purpose, the estimated daily intake (EDI) parameters of potentially toxic elements (PTE) per kilogram of body weight, target hazard quotient (THQ) for non-carcinogenic disorders, total hazard index (HI), and bioconcentration factor (BCF) are determined in the plant at different stages of growth. In this study, the reaction of the plant to different electromagnetic waves at different stages of growth (DSG) is also investigated, and the relationship between the THQ values and electromagnetic waves is prepared. The results show that Pb has the highest EDI value (5.97), Pb (74.67) and Cd (9.75) have the highest THQ values, and Cd has the highest BCF value (30.44). Also, the results show that HI values are higher than the threshold in the growth (69.98), flowering (71.38), and fruiting (68.06) stages. Results of BCF indicate Pb, and Cd has absorption rate in Capsicum towards. Contaminated Capsicum plants submitted to electromagnetic waves showed a significant relationship between Pb and the b490, and b560 spectra, Cd and Ni the b450 spectrum, and Zn the b460 spectrum. This finding highlights the salience of employing electromagnetic waves in assessing contamination in plants. Put differently, THQ can be estimated using electromagnetic waves without any need for laboratory studies. [ABSTRACT FROM AUTHOR]

The demand for electromagnetic interference (EMI) shielding has increased strongly in the last few years, owing to the fast technological developments in the electronics industry. In order to meet these markedly increased demands, many new layer-structured materials (as well as other structures with various morphologies) are being investigated to replace conventionally used metal sheets for the purpose of EMI shielding. Carbon-based nanostructures and their composites are used for EMI protection due to their low weight, cost-effectiveness, and good thermal/electrical properties. Polymers are also low density materials, with the added benefits of low cost and easy processing. Composites combining various polymers with different types of conducting carbon fillers have been proposed as EM wave absorbers. MXene-based 2D layered materials have also received tremendous attention for application in EMI shielding. In this review article, we have systematically summarized the recent research on materials designed for microwave/radio wave absorption and EMI shielding. The text covers carbon-based nanostructured materials, various kinds of polymers, layered inorganic materials and their composite hybrids. The review is concluded with a brief discussion of the perspectives and outstanding challenges for future EMI shielding applications of carbon, polymers and MXene-based materials. The main classes of materials used for EMI shielding and possible attenuation mechanisms for EM waves incident on a slab of EMI shielding material. [Display omitted] [ABSTRACT FROM AUTHOR]

Wideband operation ability becomes an obstacle for many metamaterial applications since they are generally based on effective material (medium) hypothesis, which is intrinsically functional on single frequency or narrowband. Effective biological camouflage strategies involve concealment under sunlight with multiple frequency (color) components, for example, a shark could fuse itself into sea water environment for better invisibility and hunting effectiveness. A wideband 3-D metasurface ground cloak in gigahertz frequency order is proposed and realized in the experiment with a hemispherical profile. A complex unit structure to broaden the operational frequency range for a phase-preserved electromagnetic metasurface based on the difference of elevation is also proposed. Comparison between the wideband and its contrast narrowband metasurface clearly indicates the scattering improvement effect that demonstrates the proposed metasurface’s significance. Both instantaneous electric field scanning and reflection cross section shrinking quantitatively give strong evidence of the wideband operational functions. Comparison between simulation and experiment validated each other. These results indicate that the proposed metasurface conceals itself into a background inside a wide frequency spectrum of 7.0–9.5 GHz. This structure has a great application value for object security under wave package illumination and in landscape fusion. This mechanism also demonstrates the possibility to change other effective material properties in a wide frequency band. [ABSTRACT FROM AUTHOR]

In this article we construct a special class of the generalized functions for the rigorous justification of joining method of solving some diffraction problems of electromagnetic waves by thin conducting screens. Linear functionals on a set of linear combinations of Hermit functions are considered as the generalized functions. The traces of the solutions of Helmholtz equation on the plane are interpreted in the generalized sense. The infinite sets of linear algebraic equations are derived directly from the generalized boundary conditions. The results of the computing experiment are presented. [ABSTRACT FROM AUTHOR]

Different variants of the problem of diffraction of spherical electromagnetic wave by axial-symmetric bodies are researched in the work. These problems are reduced to infinite sets of linear algebraic equations. The joining method is used. The conductive bodies, dielectric bodies and spherical conductive screens on the coordinate and non-coordinate boundaries are considered. The results of the computational experiment are presented. [ABSTRACT FROM AUTHOR]

The electromagnetic wave absorption performances and the dielectric properties of multi-walled carbon nanotube (MWCNT) functionalization with carboxyl (-COOH) group/cement composites with different shapes; chiral, zigzag and armchair were investigated. In this study, the influence of the sample thickness and the MWCNT shape on the electromagnetic wave reflection loss, insertion loss and absorption were studied in the frequency range of 8–12 GHz. The addition of 0.1 wt% MWCNT dramatically increases the absorption properties of the cement mortar in the frequency range of 8–10 GHz. With the increase of thickness from 3 mm to 6 mm, the frequency bandwidths of the reflection loss for MWCNT/cement composites increases but the number of peaks decreases. Moreover, the reflection loss peak has increased dramatically with increasing thickness. In composite specimens prepared with a thickness of 3 mm, the chiral sample has higher absorption than the zigzag and armchair samples. The absorption behavior of composites with thickness of 6 mm at 10 GHz to 11.5 GHz is different to each other. The chiral sample shows higher absorption before 9 GHz and after 11 GHz. Experimental results show that the composite specimens at both thicknesses of 3 mm and 6 mm at frequencies below 10–10.5 GHz have higher absorption properties than the control sample. The peaks created on the relative permittivity curves also showed the nonlinear dielectric resonant behavior. Furthermore, the structural analysis and surface morphology of MWCNT/cement composites with different shapes have been explored using SEM technique. [ABSTRACT FROM AUTHOR]

The paper presents the results of constructing the physical and mathematical model of high-frequency electromagnetic waves propagation in slowly moving media of finite dimensions, which takes into account the phenomena of specular reflection of these waves. The constructed model is based on formulas designed to determine the speed of electromagnetic waves propagation in slowly moving media of finite dimensions, as well as on equations designed to describe these waves. The advantageous feature of these equations is that they take into account the Fresnel drag coefficient for electromagnetic waves propagation speed. The approach to solving of these equations, as well as the approach to modeling of the process of electromagnetic waves propagation in slowly moving media of finite dimensions, based on the use of a difference scheme, in which the motion of these media is taken into account, is proposed. It has been determined that the proposed model and approaches can be used in solving problems related to the construction of receiving-transmitting paths, as well as in solving problems of aeroacoustics.

In this study, the degree of corrosion of steel reinforcement is compared to the reflected voltage of electromagnetic waves and the ASTM C876 specification. This study conducted some tests on steel bars with different degrees of corrosion by transmitting electromagnetic waves in the reinforced concrete. In the test, a corrosion potentiometer was used to analyze and compare the experimental results. The electromagnetic wave reflection signals from the image generated by the ground penetrating radar were used to capture the different media in the concrete components. The reflection coefficient method was used to analyze the calculated relative dielectric constant of the media and to obtain the reflection energy and phase changes on the medium interface. We compared and discussed the corrosion potential and the reflected voltage from the corroded steel bars in the reinforced concrete. The reflected voltage analysis of the ground penetrating radar showed that the average corrosion potential on the corroded plate on the 3rd floor was −280 m V (Area C). According to ASTM C876, the steel bars in the concrete were moderately corroded. The reflected voltage analysis of the electromagnetic waves concluded that areas A and B were moderately corroded, which is consistent with the conclusion from ASTM C876. Using the innovative method, this study has established a reference standard for the degree of corrosion of steel bars based on ASTM C876 and has calculated the quantitative state of corroded steel bars. The variations of the electromagnetic wave reflected voltage of the ground penetrating radar can mark the changes in the corrosion interface of concrete and steel reinforcement with different degrees of corrosion and different thicknesses of the protective layer.

The spin Hall effect of electromagnetic wave has important application prospects in the fields of Optical-electromechanical conversion, condensed matter and high energy physics. Based on the Euler–Lagrange equations of electromagnetic field by four-dimensional covariation, a deflection model of electromagnetic wave reflecting and refracting on interface of media is established in this paper. By using Lie group analysis method, the allowable infinitesimal symmetries, conserved quantities of partial differential equations and motion equation of energy center are derived. More importantly, their detailed analytical expressions and properties are given. The content of this paper can reveal the mechanism and influencing factors for transverse shift of the electromagnetic wave energy center, and provide a powerful theoretical basis for the numerical simulation of nonlinear photoelectric wave equation and spin regulation. [ABSTRACT FROM AUTHOR]

There is a very strong link between the behavior of ground penetrating radar (GPR) wave propagation in zinc-contaminated soil and the dielectric properties of soil. This relationship can be of significant use in the practices of quick detecting the degree of pollution in zinc-contaminated soil. In this research, measurements were conducted on the zinc-contaminated soil samples with different soil index properties (i.e., zinc ion concentration, wet density and moisture content). The radar reflection wave data of the common midpoint and common-offset sounding mode were obtained by using the 600 MHz antenna, and the relative permittivity was measured using the vector network analyzer. The attribute analysis of radar reflection wave shows that the wave velocity is affected by wet density and moisture content, but independent of zinc ion concentration. Both the amplitude and the peak frequency decrease with the increase in zinc ion concentration, wet density and moisture content. For the soil dielectric properties, the metal ions can change the conductivity of solution in soil, affecting the imaginary part of relative permittivity, but with little effect on the real part. The positive correlations between the relative permittivity with density and moisture content are caused by the variation of three-phase composition of soil. Besides, the measured soil dielectric properties and the radar reflected wave attributes confirm each other, which can well explain the change rules of electromagnetic wave velocity, amplitude and central frequency. The presented results can increase understanding and confidence on GPR for quantitative monitoring and detecting of zinc-contaminated soil. [ABSTRACT FROM AUTHOR]

A closed time-reversal (TR) cavity has been considered a purely theoretical concept whose experimental realization was assumed to be impossible. In this article, we demonstrate that it is, in fact, possible to realize a closed TR cavity using a network of transmission lines. The network is excited by either lumped voltage or current sources at arbitrary locations, and it is terminated on matched impedances. This system is an exact closed TR cavity in the sense that, in the backward-propagation stage, by back-injecting time-reversed measured responses (voltage or current) generated by a source at each line terminal, a time-reversed copy of the current and voltage distribution in the forward-propagation stage is obtained. We report for the first time an experimental realization of a TR cavity formed by a network of inhomogeneous transmission lines, in which the spatial and temporal signal distribution along the network is reproduced as in a sequence of the system state (i.e., voltages and or current along the lines) being played in reverse. We also discuss the interfering effect of the so-called diverging wave for observation points in the vicinity of the source. An active realization of a TR sink is proposed to effectively overcome the interfering effect caused by the diverging waves. [ABSTRACT FROM AUTHOR]