Electromagnetic Frequency Research Articles

The Behavior of Electromagnetic Wave Propagation in Photonic Crystals with or without a Defect

In this study, the electromagnetic wave propagation behavior of two-dimensional photonic crystal plates with a defect is investigated. For this purpose, the partial differential equation for the electromagnetic wave propagation in various photonic crystal plates containing a defect or not is obtained by using Maxwell’s equations. The defect is also defined in the electromagnetic wave propagation equation appropriately. In order to solve the electromagnetic wave propagation equation, the finite differences method is used. The material property parameters of the photonic crystal plates are determined with respect to the defects. Accordingly, the effects of material property parameters on electromagnetic wave propagation frequencies, phase velocities, and group velocities are examined. The effects of the size and position of the defects on the electromagnetic wave propagation frequencies are also discussed. The highest electromagnetic wave propagation fundamental frequency value obtained from the analyses performed is 1.198 Hz. This fundamental frequency value is obtained for the electromagnetic wave propagation in the t-shaped photonic crystal plate. Electromagnetic field distribution maps for the fundamental frequencies of the photonic crystal plates whose electromagnetic wave propagation behaviors are examined are obtained with the ANSYS package program based on the finite differences time-domain (FDTD) method.

The Influence of Dusty Size Distribution Model on Propagation of Electromagnetic Waves in Inhomogeneous Plasma Sheath

In this paper, a linear distribution model, a double exponential distribution model and a hyperbolic number distribution model are developed, and the effect of dust particle size distribution on its attenuation coefficient is considered. On this basis, the transmission characteristics of electromagnetic waves in dusty plasma under different electron density distribution models are investigated. The attenuation coefficients of electromagnetic waves are derived in detail using analytical methods, and the effects of electromagnetic wave frequency, particle collision frequency and dust particle density on the transmission characteristics of electromagnetic waves are discussed. The results show that the choice of terahertz wave as the carrier wave and the appropriate change of particle collision frequency can improve the attenuation of electromagnetic waves. In summary, the relevant research can provide some theoretical references for propagation science.

Modeling and Harmonic Impact Mitigation of Grid-Connected SCIG Driven by an Electromagnetic Frequency Regulator

The power quality analysis is an essential issue in the integration of distributed energy resources to the grid. Recent standards regulate the harmonics disturbances due to the increasing penetration of intermittent energy sources interconnected with the grid employing power converters. This paper aims to analyze the power quality of an interconnected wind turbine system based on a Squirrel Cage Induction Generator (SCIG) driven by an Electromagnetic Frequency Regulator (EFR). The steady state of the EFR harmonic model is developed in the stationary frame based on the conventional induction generator modeling, which allows the study of the harmonic disturbances in the electrical and mechanical variables due to the PWM inverter of the EFR’s armature voltage. There is no electrical connection between the EFR and SCIG, and the results show that the inherent system inertia contributes to the mitigation of the harmonic content at the grid side generated by the switching. In addition to the steady-state results, the Total Rated Distortion (TRD), which considers the harmonics and interharmonics components, was computed and presented a good performance compared to the IEEE 1547 standard and real data extracted of a single Doubly Fed Induction Generator (DFIG). Finally, the harmonic performance of the proposed system was evaluated considering the impact of the equivalent Thevenin impedance of the grid at the Point of Common Coupling (PCC).

Study on adaptive heat transfer performance of high temperature heat pipe

High temperature heat pipe (HTHP) employs alkali metal or its alloy as working fluid. Due to the large latent heat of its working fluid during phase change heat transfer, HTHP has the advantages of high temperature uniformity, high working temperature and high intensity heat transfer capacity, which has broad application prospects in the field of HTHP cooled nuclear reactors and the thermal protection of hypersonic vehicles. In order to simplify the structure of heat transfer system in nuclear reactors, so that it can safely and reliably realize passive heat transfer without additional pump power under various operating conditions, HTHP must have adaptive heat transfer capacity. In this paper, several HTHPs with excellent heat transfer performance are designed and prepared. The test-bed for frozen startup and heat transfer performance of HTHP is set up, and the electromagnetic induction high frequency heater is used as high temperature heat source. The thermal performance of HTHP with different heating power, heating position and the length of evaporation section (adaptive heat transfer characteristics) is experimentally studied, and the theoretical model is used to validate the experimental result. The experimental and theoretical results show that high vacuum degree is the prerequisite for excellent heat transfer performance of HTHP; high capillary driving force and suction force, reasonable filling ratio of working fluid are the key factors for HTHP to have adaptive heat transfer capacity, and the diameter of HTHP also has important influence on adaptive heat transfer capacity.

Behaviors of Electromagnetic Wave Propagation in Double-Walled Carbon Nanotubes

In this study, behaviors of electromagnetic wave propagation in a double-walled carbon nanotube (DWCNT) are investigated theoretically. For this purpose, the effects of carbon nanotube’s inner and outer tubes’ material property parameters (μ, ε) on electromagnetic wave propagation are discussed. The effects of interaction between the carbon nanotube’s inner and outer tubes on the electromagnetic wave propagation are defined. Nonlocal effects of the DWCNT on electromagnetic wave propagation are examined. Besides, the electromagnetic wave propagation frequencies are specifically investigated, taking the DWCNT’s nonlocal effects and material property parameters (ε, µ) into account. When the wavenumber, k, is greater than 1.8 × 1010, the frequencies of the fundamental mode and the second mode converge to 3.554 × 108 Hz. Additionally, the electromagnetic wave propagation frequencies decrease with the increase of the DWCNT’s nonlocal parameter (ν) and decrease with material parameter (D).

Research on the method of dual-frequency microwave diagnosis of plasma for solving phase integer ambiguity

In this work, microwaves and terahertz waves have performed a dual-frequency combined diagnosis in high-temperature, large-scale plasma. According to the attenuation and phase shift of electromagnetic waves in the plasma, the electron density and collision frequency of the plasma can be inversely calculated. However, when the plasma size is large and the electron density is high, the phase shift of the electromagnetic wave is large (multiple times 2π period). Due to the limitations of the test equipment, the true phase shift is difficult to test accurately or to recover reality. That is, there is a problem of phase integer ambiguity. In order to obtain a phase shift of less than 180°, a higher electromagnetic wave frequency (terahertz wave with 890 GHz) is used for diagnosis. However, the attenuation of the terahertz wave diagnosis is too small (less than 0.1 dB), only the electron density can be obtained, and the collision frequency cannot be accurately obtained. Therefore, a combined diagnosis was carried out by combining two frequencies (microwave with 36 GHz, terahertz wave with 890 GHz) to obtain electron density and collision frequency. The diagnosis result shows that the electron density is in the range of (0.65–1.5) ×1019 m−3, the collision frequency is in the range of 0.65–2 GHz, and the diagnostic accuracy is about 60%.

A review on seismic metamaterials: From natural toartificial structures

<p indent="0mm">In the recent three decades, the breath-taking discoveries of phononic crystals in conjunction with research advances in acoustic metamaterials have far-reaching implications in many science and engineering branches. These new discoveries can be traced to the fundamentals of wave manipulation and wave attenuation, etc., within a very wide frequency spectrum from ultrahigh electromagnetic wave frequency to very low seismic frequency ranges. Inspired by electromagnetic and photonic crystals, these newly designed artificial structures are able to control acoustic/elastic waves at relatively low frequency ranges. In periodic systems, Bloch waves are formed by reflection, refraction and scattering of De Broglie, electromagnetic/light and acoustic/elastic waves. These waves contain marvelous band structures which allow transmission or lead to attenuation. Frequency domains for transmission and attenuation correspond to passbands and stopbands, respectively. There exist many studies that materialize the idea of designing metadevices at will by utilizing wave band behaviors. Generally, the mechanism for forming stopbands contains two parts, i.e., Bragg scattering and local resonance, that can also be used to identify phononic crystals and acoustic metamaterials. Especially, a Bragg scattering type metamaterial prohibits waves with a wavelength of the same order as the lattice constant from propagating through the structure. It results in a large-scale structural dimension for a low frequency bandgap. Comparatively, local resonance type metamaterials allow the generation of bandgaps at low frequency ranges with relatively small dimensions as their properties rely primarily on the local resonance. The study of seismic wave propagation in civil engineering has been reinvigorated due to the new, exciting concept of seismic metamaterials. The spectacular designs provide new approaches to control seismic surface (Rayleigh and Love) and bulk (pressure and shear) waves for civil and structural engineers. This review traces the state-of-the-art developments of seismic metamaterials and establishes a link between photonic crystals at nano/micro scale and seismic metamaterials at macro scale. We present a survey of more recent developments in seismic metamaterials in terms of geometry, physics (i.e., the mechanism for forming stopbands) and experimental approaches which range from natural sources to artificial structures. A variety of mathematical and physics tools can be extended from photonic crystals to seismic megastructures, such as effective media theory, Brillouin zone, reciprocal space, rainbow trapping, etc. The development of finite element methods provides the possibility to simulate and analyze these complex artificial designs numerically. A school of forest trees as natural seismic metamaterials is a focal point in this review, which enables attenuation of seismic waves using natural resources and also inspires the discovery of seismic metasurfaces. For artificial structures, designs are generally made based on locations (i.e., metabarriers and metafoundations) or mechanisms (i.e., Bragg scattering and local resonance mechanism). Some metamaterial-like transformed urbanism or cities are also verified to work as seismic shielding or cloaking. Further, similar to experimental methods in other disciplines, scale model experiments and full-scale experiments have been explored to validate the efficiency of seismic metamaterials in wave attenuation. Although research in phononic crystals is moving towards extreme frontiers, metastructures working at low frequencies with stability, high bearing capacity, high ductility, wide bandgap and efficient attenuation zones remain substantial challenges. Besides soil-structure interactions, the combination of various components of seismic waves, ground conditions, soil properties, effects of groundwater table, structural nonlinearity or other ineluctable factors is yet to be fully considered. Ultimately, the emergence of seismic metamaterials broadens the horizons for seismic isolation and seismic vibration control. This review will help future researchers witness the continuous development of seismic metamaterials and comprehend the current challenges in this promising, potential and exciting research.

Investigation of Electromagnetic Wave Propagation Frequencies in Two-Dimensional Photonic Crystals with Finite Differences Method

In this study, frequencies of electromagnetic wave propagation in two-dimensional photonic crystal structures are investigated. For this purpose, the electromagnetic wave propagation equation obtained by using Maxwell equations is solved with the finite differences method. The fundamental frequencies of electromagnetic wave propagation have been obtained with a low error rate of 3.10%.

In-situ metallized carbon nanotubes/poly(styrene-butadiene-styrene) (CNTs/SBS) foam for electromagnetic interference shielding

The porous conductive polymer composites have received great attention owing to their superiority of being utilized in electromagnetic interference (EMI) shielding applications. Herein, lightweight and highly compressible conductive composite foam composed of poly(styrene-block-butadiene-block-styrene) (SBS) polymer matrix, carbon nanotubes (CNTs) and silver nanoparticles (Ag NPs) is fabricated by freeze-drying technology, silver precursor absorption and in-situ reduction process. Three-dimensional CNTs conductive network and partially embedded Ag NPs synergistically endow the foam with excellent mechanical, electrical and EMI shielding performance. The flexible 8Ag/4CNTs/10SBS composite foam with a low density of 0.42 g/cm3 exhibits moderate compressive strength of 169.2 kPa at strain of 50%, remarkable conductivity of 753 S/m, and prominent EMI shielding effectiveness (SE) value of around 91 dB in the electromagnetic wave frequency range of 8.2–12.5 GHz. In addition, the 4Ag/4CNTs/10SBS composite foam exhibits robust mechanical–electrical property upon 1000 compression-release cycles at strain of 50%, and its SE value increased by about 33% compared with the initial state after the cyclic compression test. These results suggest that the Ag/CNTs/SBS foams possess promising potential to be used as lightweight, flexible, and high-performance EMI shielding materials in modern electronic devices.

Integration of geophysical methods for groundwater exploration: A case study of El Sheikh Marzouq area, Farafra Oasis, Egypt

Newly, the Egyptian government initiated huge national projects for the reclamation and sustainable development of 1.5 million acres. Farafra Oasis is recognized as the focus of the first phase of this project where groundwater is the wellspring of the water for irrigation and drinking. Hence, exploration and assessment of groundwater aquifers are very essential in such area. A reconnaissance geophysical survey was conducted in the centre of Farafra oasis using Vertical Electric Sounding (VES), Transient electromagnetic (TEM), Audio-Magnetotelluric (AMT), Control-source Magnetotelluric (CSAMT), and Very Low Frequency (VLF) techniques for the investigation of shallow and deep groundwater reservoirs. In addition, geologic and stratigraphic information from the nearest well was utilized to confirm the geophysical outcomes. Integrated geophysical measurements succeeded to delineate the three zones A, B and C of the Nubian aquifer system in the investigated area. Also, several fault elements were delineated which control the influx and aggregating of the groundwater in both units; shallow and deeper one. Deeper aquifer (zone C) shows generally higher resistivity values, which consider the major aquifer of Nubian sandstone in the Western Desert of Egypt. Geochemical examinations of the groundwater sample show that the water is remarkable for all agriculture purposes (TDS = 95).

Thermal Effects of 5G Frequency EM Waves on Ocular Tissue

This research article aims to investigate the thermal effects on human eye due to exposure of EM (electromagnetic) field at 5G frequencies. A secondary purpose of the article is to show that SPICE, one of the most commonly used tools in circuit analysis, can be used to solve complex EM and bioheat transfer problems. Both electric field and temperature distributions in human eye are simulated with transmission line modelling (TLM) method. Also, finite element method (FEM) calculations are carried out for comparison. Temperature distributions are calculated for 30 minutes of EM radiation exposure. As a subject of the simulation, a human is chosen that the power density of incoming field at the human eye is assumed as the maximum of the ICNIRP general public exposure limits. A good consistency between TLM and FEM based simulations is found. A new transmission line model based on Debye parametric model is generated for simulation of EM field distribution in the tissues. With this generated transmission line, the results for the frequencies of interest can be obtained via single simulation. Also, a new transmission line model is developed for the temperature distribution simulation in which the effects of noncompressible fluid flow such as non-unidirectional blood flow in tissues and flow in aqueous humor are taken into consideration.

The influence of the extraneous field on the conductivity tensor in cylindrical quantum wire with electron-optical phonon scattering

This work calculates conductivity tensors in cylindrical quantum wires with parabolic potential, with the presence of an electromagnetic wave field, a laser field, and is only considered for the case of electron-optical phonon scattering. By using the quantum kinetic equation for the electron in the quantum wire with the parabolic potential, combined with the presence of two external fields, the expression of conductivity tensor is computed for the case of optical electron-phonon scattering. This conductivity tensor expression depends on the electromagnetic wave frequency, the laser field frequency, the laser field amplitude, and the quantities that characterize the cylindrical quantum wire with parabolic potential. The figure of the dependence of the conductivity tensor to the external field will be plotted, examined, and analyzed for the quantum wire GaAs / GaAsAl.

Massive MIMO for Underwater Industrial Internet of Things Networks

Massive multiple-input–multiple-output (MIMO) systems which include a large number of service antennas have received a great deal of attention as a means to improve both spectral efficiency (SE) and energy efficiency (EE) of wireless communication systems. In this article, we study the feasibility of using Massive MIMO to support a vast amount of underwater Industrial Internet of Things (IIoT) devices. By using a large number of antennas as compensation entities for the low bandwidth in the underwater channel, we show that underwater Massive MIMO can simultaneously support a massive amount of underwater IIoT devices. Electromagnetic radio frequency (RF) and acoustic waves are used to present the performance with respect to SE, throughput (TP) per user equipment (UE), and coverage. Additionally, we show that both Massive MIMO with RF and acoustic waves have the same closed-form upper bounds which can be used as an important design tool of underwater IIoT networks. Numerical results verify the theoretical analysis.

Multiphysics simulation of phase field interface development and geomechanical deformation in radio frequency heating of oil shale

A novel multiphysics finite element framework, developed to numerically model in-situ pyrolysis of oil shale by radio frequency heating in a two-dimensional (2D) domain, is extended to include deformation analysis of the target formation and adjacent regions as a result of dielectric heating. This framework is constructed by explicitly coupling equations describing thermal, phase field front tracking, mechanical deformation and electromagnetics (TPME) to track the conversion of high yield oil shale to liquid oil. The finite element method is used to model heat generation by the conversion of electromagnetic energy in the formation then the solid-liquid conversion interface is tracked by the Allen-Cahn phase field method. The objective of this work is to analyze the evolution of the conversion interface and the subsequent mechanical deformation of the target formation by evaluating disparate geologic model descriptions to capture the anticipated subsurface behavior. These geologic models possess variations in complexity so that the appropriate level of detail in the geological model description can be assessed for further TPME simulation studies of radio frequency heating. The evaluated geologic models include those which are comprised of: heterogeneous or homogeneous high yield kerogen-rich properties in addition to the inclusion or omission of under- and overburden surrounding the target formation at varying electrode separation distances and applied electromagnetic frequencies. Parameterization of the numerical model was performed following characteristics of the Green River oil shale. Results show the variation in conversion interface of solid kerogen to liquid oil by way of interface arrival times at domain boundaries as well as the extent of formation deformation under the disparate geological model descriptions. Based on these results oil shale conversion timelines are compared and highlight the need to include mechanical deformation analysis of the target formation, including a kerogen-poor under- and overburden, in the numerical modeling of radio frequency heating as a process of oil shale in-situ pyrolysis.

Conductivity tensor in semiconductor with the presence of a laser field and an electromagnetic wave field for the case of scattering on ionized impurities

There are a lot of studies on semiconductors and in semiconductors also appear many dynamic effects, from the research results that have many applications in science and technology. Conductivity tensor is a familiar concept in physics in general and semiconductors in particular, but research on scattering on ionized impurities is still limited. This paper presents the influence of laser field and electromagnetic waves on conductivity tensor for the case of scattering on ionized impurities in semiconductor. The particle system is placed in an electromagnetic wave field and a laser field. Using quantum kinetic equations for electrons in semiconductor under the action of an electromagnetic wave field, a laser field, the conductivity tensor is calculated with case of scattering on ionized impurities. Conductivity tensor depends on the frequency of the laser field, the laser field amplitude, the electromagnetic wave frequency and typical parameters for semiconductor system. With different frequency bands, the dependence of tensor conductivity on the frequency is different, and the special conductivity tensor is strongly dependent on the amplitude of the laser field but depends very little on its frequency. The results will be plotted and discussed with GaAs semiconductor case and compared with studies for different scattering cases.

Novel 4‐bit second‐order multifunction frequency selective surface

An innovative four-bit second order multifunction active frequency selective structure controlled via four PIN diodes with nine different combinations is introduced . The proposed design is equipped with electromagnetic switching, frequency switching and polarization selection at two passbands. The coding states 0000 and 1111 offer transmission to the passbands centred at 1.96 and 4.98 GHz frequencies and shield to the bands centred at 4.98 and 1.96 GHz for transverse electric (TE)/transverse magnetic (TM) waves, respectively. The coding state 1010 offers transmission to the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively and shields the TM and TE waves at 1.96 GHz and 4.98 GHz, respectively. Contrarily, the coding state 0101 offers transmission to the TE and TM waves at 4.98 GHz and 1.96 GHz, respectively and shields the TE and TM waves at 1.96 GHz and 4.98 GHz, respectively. The coding states 1000/0100 and 1101/1110 allow transmission to the TE wave at 1.96 and 4.98 GHz frequencies, respectively and shield to both the passbands at TM wave. Conversely, the coding states 0001/0100 and 1011/0111 allow transmission to the TM wave at 1.96 and 4.98 GHz frequencies, respectively and shields to both the passbands at TE wave. The coding state 1100/0011 provides shield to all the frequencies below 7.7 GHz. The designed structure is validated through the measured response of the fabricated prototype.

Measuring fundamental jet properties with multiwavelength fast timing of the black hole X-ray binary MAXI J1820+070

ABSTRACT We present multiwavelength fast timing observations of the black hole X-ray binary MAXI J1820+070 (ASASSN-18ey), taken with the Karl G. Jansky Very Large Array (VLA), Atacama Large Millimeter/Sub-Millimeter Array (ALMA), Very Large Telescope (VLT), New Technology Telescope (NTT), Neutron Star Interior Composition Explorer (NICER), and XMM–Newton. Our data set simultaneously samples 10 different electromagnetic bands (radio – X-ray) over a 7-h period during the hard state of the 2018–2019 outburst. The emission we observe is highly variable, displaying multiple rapid flaring episodes. To characterize the variability properties in our data, we implemented a combination of cross-correlation and Fourier analyses. We find that the emission is highly correlated between different bands, measuring time-lags ranging from hundreds of milliseconds between the X-ray/optical bands to minutes between the radio/sub-mm bands. Our Fourier analysis also revealed, for the first time in a black hole X-ray binary, an evolving power spectral shape with electromagnetic frequency. Through modelling these variability properties, we find that MAXI J1820+070 launches a highly relativistic ($\Gamma =6.81^{+1.06}_{-1.15}$) and confined ($\phi =0.45^{+0.13}_{-0.11}$ deg) jet, which is carrying a significant amount of power away from the system (equivalent to $\sim 0.6 \, L_{1-100{\rm keV}}$). We additionally place constraints on the jet composition and magnetic field strength in the innermost jet base region. Overall, this work demonstrates that time-domain analysis is a powerful diagnostic tool for probing jet physics, where we can accurately measure jet properties with time-domain measurements alone.

Alternative method for the determination of the ideal electromagnetic reverberant frequency with frequency stirring technique

Alternative method for the determination of the ideal electromagnetic reverberant frequency with frequency stirring technique

Plasma characteristics and broadband electromagnetic wave absorption in argon and helium capacitively coupled plasma* *Project supported by the Key Research and Development Plan of Anhui Province, China (Grant No. 201904a07020013).

A one-dimensional self-consistent calculation model of capacitively coupled plasma (CCP) discharge and electromagnetic wave propagation is developed to solve the plasma characteristics and electromagnetic wave transmission attenuation. Numerical simulation results show that the peak electron number density of argon is about 12 times higher than that of helium, and that the electron number density increases with the augment of pressure, radio frequency (RF) power, and RF frequency. However, the electron number density first increases and then decreases as the discharge gap increases. The transmission attenuation of electromagnetic wave in argon discharge plasma is 8.5-dB higher than that of helium. At the same time, the transmission attenuation increases with the augment of the RF power and RF frequency, but it does not increase or decrease monotonically with the increase of gas pressure and discharge gap. The electromagnetic wave absorption frequency band of the argon discharge plasma under the optimal parameters in this paper can reach the Ku band. It is concluded that the argon CCP discharge under the optimal discharge parameters has great potential applications in plasma stealth.

The influence of electromagnetic waves and laser fields on conductivity tensor for the case of electron - optical phonon scattering in quantum wells with a parabolic potential

This paper studies the influence of electromagnetic waves and laser fields on conductivity tensor with the case of electron - optical phonon scattering in quantum wells. Because electrons are confined in the quantum well in one direction, the conductivity tensor in the quantum well is different from the conductivity tensor in the bulk semiconductor. The carrier system in a quantum well is located in an electromagnetic wave field and a laser field. Using quantum kinetic equation for electrons in quantum wells in the presence of an electromagnetic wave and a laser field, from the quantum kinetic equation it is possible to calculate the conductivity tensor. The conductivity tensor expression is a function of the electromagnetic wave frequency, laser field frequency and quantum well characteristic parameters. Survey and plot the dependence of conductivity tensor on electromagnetic wave frequency, laser field frequency, laser field amplitude with GaAs / GaAsAl quantum well case.