Interaction Of Electromagnetic Waves Research Articles

Microwave Frequency Analysis of Dielectric Properties in Biological Tissues: Insights into Dielectric Constant, Conductivity, and Resistivity at 9.4 GHz

This study investigates the dielectric properties of various biological tissues at microwave frequencies, specifically focusing on their dielectric constant, conductivity, resistivity, and loss tangent. Using methods such as Von Hippel’s and Yadav Gandhi’s techniques, the dielectric characteristics of heart, liver, brain, and muscle of chicken tissues were analysed at 9.4 GHz. It is found that tissues with higher water content exhibit greater dielectric constants and conductivities, while those with higher solid content, like liver, display higher resistivity. It has also been observed that tissues with lower dielectric constants and conductivities are those with greater absorption indices, which are typically associated with increased energy dissipation as heat. An increasing amount of energy dissipation may result from tissues with higher absorption rates being less effective at transferring microwave energy, as suggested by this inverse connection, which also emphasizes the complexity of electromagnetic wave interaction within tissues. This work provides critical insights into the interaction of electromagnetic waves with biological tissues, which is essential for applications in medical diagnostics, therapeutic technologies, and electromagnetic exposure safety standards.

New angular momentum conservation laws for electromagnetic waves interacting with dirac fields

Abstract Global conservation laws of angular momentum are well-known in the theory of light-matter interaction. However, local conservation laws, i.e. the conservation law of angular momentum at every point in space, remain unexplored especially in the context of relativistic Dirac-Maxwell fields. Here, we use the QED Lagrangian and Noether's theorem to derive a new local conservation law of angular momentum for Dirac-Maxwell fields in the form of the continuity relation for linear momentum. We separate this local conservation law into four coupled motion equations for spin and orbital angular momentum (OAM) densities. We introduce a helicity current tensor, OAM current tensor, and spin-orbit torque in the motion equations to shed light on the local dynamics of spin-OAM interaction and angular momentum exchange between Maxwell and Dirac fields. We elucidate how our results translate to classical electrodynamics using the example of plane wave interference as well as a dual-mode optical fiber. Our results shine light on angular momentum phenomena related to the relativistic interaction of electromagnetic waves and Dirac fields.

A Two-Layer Graphene Nonwoven Fabric for Effective Electromagnetic Interference Shielding.

Rapid advancements and proliferation of electronic devices in the past decades have significantly intensified electromagnetic interference (EMI) issues, driving the demand for more effective shielding materials. Herein, we introduce a novel two-layer graphene nonwoven fabric (2-gNWF) that shows excellent EMI shielding properties. The 2-gNWF fabric comprises a porous fibrous upper layer and a dense conductive film-like lower layer, specifically designed to enhance EMI shielding through the combined mechanisms of reflection, multiple internal reflections, and absorption of electromagnetic waves. The 2-gNWF exhibits a remarkable EMI shielding effectiveness (SE) of 80 dB while maintaining an impressively low density of 0.039 g/cm3, surpassing the performance of many existing graphene-based materials. The excellent EMI shielding performance of 2-gNWF is attributed to the multiple interactions of incident electromagnetic waves with its highly conductive network and porous structure, leading to efficient energy dissipation. The combination of high EMI SE and low density makes 2-gNWF ideal for applications that require lightweight yet effective shielding properties, demonstrating the significant potential for advanced EMI shielding applications.

Study of the reflection of a plane electromagnetic wave from a layer of chiral metamaterial located on a conducting plane, taking into account the inhomogeneity and dispersion of material parameters

To reduce the radar signature of moving objects, such as cars, boats, manned and unmanned aircraft systems, technologies for creating broadband radio-absorbing materials are being actively developed and improved. Among such materials are composites and chiral metamaterials, which have unique characteristics that make it possible to effectively control the reflection and rotation of the plane of polarization of electromagnetic waves. In addition, devices included in the structure of infocommunication systems are subject to electromagnetic radiation, which can cause undesirable effects and interference. Radio-absorbing coatings based on metamaterials can significantly reduce the reflection of electromagnetic waves and effectively counteract the effects of electromagnetic radiation. The purpose of this study is to solve the scientific and technical problem of determining the reflection coefficients of electromagnetic waves from a radio-absorbing material consisting of a chiral metamaterial located on a conducting surface. The main objective of the work is to study the interaction of a plane electromagnetic wave with the specified layer of metamaterial located on a conducting plane, taking into account the inhomogeneity and dispersion of material parameters.

Optical manipulation in Rubidium-87 atomic medium using Kerr field: Dynamic insights into two-interfering electromagnetic waves

In this manuscript, we investigate the intricate dynamical properties arising from the interaction of two-interfering electromagnetic waves within a Rubidium-87 four-level N-type atomic medium. The study employs a probe field to interact with the atomic medium while incorporating two control fields one of which would be the Kerr field to modulate the system dynamics. The key parameters under scrutiny include the probe field detuning (ΔP/γ), control field parameters such as Rabi frequencies and detunings (Ω1,2/γ, Δ1,2/γ), and the angular orientation (θ) between the two-interfering waves. The research delves into the Energy density W, Momentum density P, Spin Angular momentum density S, Absorption rate Arate, Gradient force Fgrad, and Torque T associated with the two-interfering waves within the atomic medium. Through systematic variations in the aforementioned parameters, significant insights are gained into the nuanced behaviour of the system. The results showcase a rich tapestry of variations in the dynamical properties, shedding light on the underlying physics governing the interaction of electromagnetic waves in this unique atomic medium. This investigation not only contributes to the fundamental understanding of the dynamics within complex atomic systems but also holds potential applications in fields such as quantum information processing and quantum optics. The findings of this manuscript pave the way for further exploration and utilization of these intricate phenomena in the realm of advanced technologies and quantum communication.

Nonlinear helicity anomalies in the cyclotron resonance photoresistance of two-dimensional electron systems

Our studies of the cyclotron resonance (CR) photoresistance in GaAs-based two-dimensional electron systems (2DES) reveal an anomalously low sensitivity to the helicity of the incoming circularly polarized terahertz radiation. We find that this anomaly is strongly intensity dependent, and the ratio of the low-temperature photoresistance signals for the CR-active (CRA) and CR-inactive (CRI) polarities of magnetic field increases with lowering power, but, nevertheless, remains substantially lower than expected from conventional theory assuming interaction of the plane electromagnetic wave with the uniform 2DES. Our analysis shows that all data can be well described by the nonlinear CR-enhanced electron gas heating in both CRA and CRI regimes. This description, however, does not specify the source of anomalous CRI absorption that remains unclear. Published by the American Physical Society 2024

Modelling of electromagnetic wave propagation at free space-human skin interface

The proliferation of the ambient environment with many wireless communication infrastructures has constituted a source of concern, at least from health point of view. Hence, there is a need for the investigation of electromagnetic wave interaction with human tissue. This paper models electromagnetic wave propagation at the free-space-human tissue interface, in an attempt to understand how electromagnetic waves interact with the human skin. Maxwell’s equations were used to derive the governing equations of propagating electromagnetic waves in free space while the solution of the boundary-value problem arising from the incident electromagnetic wave at the free space-human tissue interface was found through the use of appropriate boundary conditions. The solution led to the emergence of four Fresnel equations, a pair each for perpendicular and parallel polarizations of the incident wave, at the boundary. Through the use of the Fresnel equations obtained, components of the incident electromagnetic wave power at the boundary can be quantified. Typical profiles of the normalized reflected and absorbed powers at the free space-human skin interface at 28, 60, and 73 GHz were computed, using measured values of permittivity of human tissue. It is found that the total absorption of the power of the incident wave by the human skin occurs when the angle of incidence is between 690 and 770 for the three frequencies used. This is irrespective of the polarization of the incident wave. Information on such distinct angles of incidence for total absorption of power does not appear to exist in the literature as they represent new, previously unreported facts in the existing body of research. Furthermore, computed profiles of reflected power versus incidence angle displayed here, for perpendicular polarization, demonstrate strong alignments with established literature, thus reinforcing the credibility of the results presented in this paper.

Reciprocal action of natural bianisotropy and artificial chirality on electromagnetic propagation in medium

Background. The present article investigates the reciprocal action of specific medium effects on electromagnetic waves propagation. The object of study is a moving dielectric, which at rest already demonstrate bianisotropic properties, i. e., it is a synthetic material, e. g., chiral media with Ω-particles. Bianisotropic material equations are the most general for describing the effects of electromagnetic waves interaction with complex medium. Studying and analyzing them is proving to be a notable scientific problem. Natural bianisotropy is a property of simple media under special conditions (state of motion, internal currents and diffusion processes), whereas artificial bianisotropy is an inherent property of the synthetic material itself (composite material, material with different metaparticles).
 Aim. The main goal of the work is to generalize the already available data. On it basis, then, obtain analytical expressions, which can be effectively used for the experiments designing, creating new computational techniques for solving direct and inverse electromagnetic diffraction problems.
 Methods. In this paper, analytical methods are applied to obtain the resulting close-form expressions.
 Results. Three classes of effects have been identified that have a significant reciprocal effect on each other: gyrotropy, spatial dispersion, and temporal dispersion. In this article it was shown that the gyrotropy of the medium has not only a simple additive effect, but under some, specific conditions, can be related to the system emergence.
 Conclusion. The reciprocal action of the spatial dispersion of the moving chiral medium, generally has different scales in range. Temporal dispersion was investigated, which does not have a simple additive property, because even an isotropic medium acquires fundamentally new material properties of bianisotropy when it moves.

Elucidating the coherent and incoherent reflection of plane-waves in finite thickness media: a practical pedagogical application

The propagation of light through a thin film interfaced between two semi-infinite media serves as a compelling illustration for elucidating electromagnetic wave interactions with matter at the undergraduate level. Despite its pedagogical significance and diverse technological applications, this model often receives inadequate attention in foundational electromagnetism literature, limiting early student exposure to this emblematic concept. In this pedagogical initiative, we present a comprehensive analysis of electromagnetic wave propagation through a dielectric medium positioned between semi-infinite media. We examine interference phenomena arising from back-and-forth reflected waves within the dielectric, focusing on the coherent and incoherent reflection regimes as limiting cases. Employing rigorous analytical treatment, we delineate transmittance and reflectance profiles, offering students a lucid understanding of how the refractive index’s real and imaginary components compete and manifest under specific conditions. This analytical approach enhances students’ comprehension of electromagnetic wave behavior within diverse mediums. Furthermore, we extend this theoretical foundation to practical applications, emphasizing renewable energy contexts. By calculating absorptance, we estimate the maximum photo-generated current and power conversion efficiency of a prototype solar cell, establishing a tangible link between theoretical knowledge and real-world solar energy utilization.

Efficient monostatic anisotropic point scatterer model for high performance computing

ABSTRACT High performance computing (HPC) electromagnetic (EM) emulators are used to simulate real-time EM wave interactions between numerous radar targets. Radar Cross Section (RCS) data stores reflection profiles of radar targets as a table; however, the needed storage size increases with frequency sampling density, aspect angle sampling density, and number of target types. The large quantity of data often exceeds storage capability and limits manipulation and representation feasibility. The spherical harmonic based monostatic anisotropic point scatterer model is proposed for HPC EM simulations where scattering responses can be computed with finite impulse response (FIR) filters. An efficient algorithm constructing this model with large scale RCS data is discussed. The scatterer position and the reflection profile of each scatterer are solved using least squares methods and particle swarm optimization (PSO). In addition, the function evaluations in PSO are accelerated by taking advantage of the matrix structure, making the algorithm 22 times faster

A tunable flat terahertz lens using Dirac semimetals: a simulation study

We propose and design a flat and tunable terahertz lens achieved through a two-dimensional photonic crystal composed of an array of rods made of a Dirac semimetal placed in air as the background medium. The structure of interest is a graded index photonic crystal, made possible by the slight variations in the rods’ radii in a direction perpendicular to the direction of the light propagation. Dirac semimetals' ability to respond to variations in their Fermi energy level manifested as a change in the refractive index provides the tunability of our proposed lens. The interaction of electromagnetic waves with the designed structure is investigated for both transverse magnetic and transverse electric polarizations using two-dimensional finite-difference time-domain method.

Self-consistent interaction of linear gravitational and electromagnetic waves in non-magnetized plasma

This paper explores the hybridization of linear metric perturbations with linear electromagnetic (EM) perturbations in non-magnetized plasma for a general background metric. The local wave properties are derived from first principles for inhomogeneous plasma, without assuming any symmetries of the background metric. First, we derive the effective (“oscillation-center”) Hamiltonian that governs the average dynamics of plasma particles in a prescribed quasimonochromatic wave that involves metric perturbations and EM fields simultaneously. Then, using this Hamiltonian, we derive the backreaction of plasma particles on the wave itself and obtain gauge-invariant equations that describe the resulting self-consistent gravito-electromagnetic (GEM) waves in a plasma. The transverse tensor modes of gravitational waves are found to have no interaction with the plasma and the EM modes in the geometrical-optics limit. However, for longitudinal GEM modes with large values of the refraction index, the interplay between gravitational and EM interactions in plasma can have a strong effect. In particular, the dispersion relation of the Jeans mode is significantly affected by electrostatic interactions. As a spin-off, our calculation also provides an alternative resolution of the so-called Jeans swindle.

Reconstructing Long-Term Synthetic Aperture Radar Backscatter in Urban Domains Using Landsat Time Series Data: A Case Study of Jing–Jin–Ji Region

Synthetic aperture radar (SAR) records important information about the interaction of electromagnetic waves with the Earth’s surface. However, long-term and high-resolution backscatter coefficient data are still lacking in many urban studies (e.g., building height estimation). Here, we proposed a framework to reconstruct the 1-km backscatter coefficient in 1990–2022 utilizing the Sentinel-1 Ground Range Detected data and Landsat time series data in the Jing–Jin–Ji (JJJ) region. First, we developed a regression model to convert the optical signals from Landsat into backscatter coefficients as the Sentinel-1 data, using observations from 2015 to 2022. Then, we reconstructed backscatter coefficients from 1990 to 2022 using the long-term Landsat data. Using the reconstructed backscatter coefficients, we analyzed the dynamic patterns of building height over the past decades. The proposed approach performs well on estimating the backscatter coefficient and its spatial pattern, with the annual mean absolute error, root mean square error, and R 2 of 1.10 dB, 1.50 dB, and 0.64, respectively. The temporal trends revealed from the reconstructed backscatter data are reliable compared with satellite observations at a relatively coarse resolution, with Pearson’s coefficients above 0.92 in 6 sample cities. The derived building height from the reconstructed SAR data indicates that the JJJ region experienced a noticeable upward expansion in 1990–2022, e.g., Beijing has the fastest growth rate of 0.420 km 3 /decade regarding the total building volumes. The proposed framework of reconstructing SAR data from optical satellite images provides a new insight to complement the long-term and high-resolution backscatter from local to global scales.

Nutritional value and quality aspects of wheat produced and consumed in Albania

Wheat and its flour-processed foods constitute the staple food of the Albanians. Nutritional importance relates to its role as an essential source of microelements and its flexibility to be processed in a wide range (e.g., bread, pasta, pastry, baked products). Global wheat markets have become increasingly demanding concerning wheat quality indicators. The country has a tradition of wheat cultivation connected with politics in the past decades. The study has analyzed the wheat quality according to physicochemical indicators: protein, gluten, starch, moisture, and sedimentation index, by Near-infrared spectroscopy (NIRS). A non-destructive technique based on electromagnetic wave interactions of molecules in the analyzed matrix. Seventy-five wheat samples were collected from agricultural regions during the harvesting season 2022. Protein content varied in the interval 9.6-15.0 %, with an average of 12.7 %. The gluten content analyzed was 19.4-37.5%, with an average of 27.5%. Starch content varied in the interval 66.3 -71.5 %, with an average of 68.9%. The sedimentation index was measured in the interval 21.1-57.8 with an average value of 37.6. Finally, the moisture level varied at 9.8-12.5%, indicating no wheat sample exceeded the threshold max level of 14.5%, in accordance with national and EU food legislation.

Direct Electromagnetic Wave Scattering Calculation Using Methods of Moments through Layered Rough Surface

This thesis focuses on the direct calculation of electromagnetic wave scattering through layered rough surfaces using the Method of Moments. The study aims to contribute to existing knowledge by addressing the problems associated with accurately predicting scattered electromagnetic fields from rough surfaces with layered structures. By using the Method of Moments, this research seeks to provide insights into the behavior of electromagnetic waves when interacting with multi-layered rough surfaces, offering valuable implications for practical engineering applications and the development of advanced computational tools for electromagnetic wave analysis. In practical terms, the surface is typically divided into small patches, and the electromagnetic field at each patch is determined using MoM. This involves solving integral equations describing the interaction between the induced currents on the surface and the incident field. The layered structure may require additional equations to model the reflection of waves and the transmission at the boundaries between the layers. The direct problem is also examined in a two-dimensional picture, where the rough surface profile and the medium are known parameters, and the electromagnetic waves scattered from the surface to the entire space are the unknowns. The rough surface is considered to have a finite length and can be deterministic or arise from a stationary stochastic random process, with a focus on Gaussian-type rough surfaces. The roughness is considered as two basic types: as a perfect electric conductor (PEC) in free space and as a boundary between two dielectric media. The equations of integration obtained are based on the scalar solution of Green's theory, Helmholtz equations, and using Hankel type green functions as kernels due to the one-dimensional nature. The MoM is extensively used to solve these integral equations and is compared to asymptotic approaches and analytical. Various simulations are conducted to test the feasibility of the algorithms, and the results are thoroughly discussed. The study of electromagnetic wave scattering in one-dimensional rough surfaces involves the direct problem, where the field distribution in the whole space is determined using the equation of integration. These equations take into account the surface roughness and medium parameters they are solved using the Method of Moments (MoM) by expressing the field distribution on the surface using basis functions. The direct calculation of electromagnetic wave scattering through a layered rough surface using the Method of Moments (MoM) is a computationally intensive process and complex and. It contains simulating the interaction of EM waves with a complex surface, which presents challenges due to the multiple layers with different properties, and a roughly surface causing and diffraction of incident waves and scattering. When working with a layered rough surface increases the electromagnetic wave interaction complexity. Additional multiple layers introduce considerations, such as layer interfaces and accounting for different material abilities. This requires careful modeling and analysis to exactly capture the behavior of electromagnetic waves as they traverse through and interact with layers. MoM, a commonly used numerical method for solving electromagnetic scattering problems, discreteness the surface into small segments and solves integral equations to determine the fields that is scattered. This approach allows for a maximum analysis of electromagnetic interactions at a grained level.

Persistent Pitch Angle Anisotropies of Relativistic Electrons in the Outer Radiation Belts

AbstractPitch angle distributions (PADs) in the radiation belts are well characterized with sinn(α). By tracking the exponent “n,” termed pitch angle index, we are able to observe persistent and cross‐energy changes in PADs of Van Allen radiation belt electrons using Van Allen Probes particle observations. The PAD measurements are well fit down to a single satellite spin, and therefore can track spatially and temporally confined changes to determine the connection between particles and waves. With this method, we study long‐lasting and high‐energy anisotropic electron PADs during a quiet period over 2 days, 26 and 27 June 2013. One potential driver for these changes is electromagnetic ion cyclotron wave interaction with the particles. We use several ground magnetometer stations from Canadian Array for Realtime Investigations of Magnetic Activity and Finnish pulsation magnetometer network of Sodankylä Geophysical Observatory to observe waves during the 2 days of interest. The connection between the waves and particles is inconclusive, although there is some temporal overlap of the phenomenon.

Implementation of the Hybrid ADI-FDTD Scheme to Maxwell Equation for Mathematical Modeling of Breast Tumor

Breast cancer is the most common cancer in women, and non-destructive detection of the tumor is vital. The interaction of electromagnetic waves with breast tissue and the behavior of waves after interaction are used to model tumor detection mathematically. The behavior of electromagnetic waves in a medium is described using Maxwell's equations. Electromagnetic waves propagate according to the electrical properties of a medium. Since the electrical properties of tumor tissue are different from those of normal breast tissue, it is assumed that the tumor is a lossy dielectric sphere, and the breast is a lossy dielectric medium. Under this assumption, Maxwell's equations are used to calculate the scattered field from the tumor. The field scattered by the tumor is different from other tissues because their dielectric properties are different. The location and size of the tumor can be determined by utilizing the difference in scattering from the tissues. While the scattering field from the tumor in spherical geometric form is analytically calculated, it is not analytically possible to calculate the scattering field from the tumor in different geometric shapes. In addition to non-destructive detection of the tumor, an efficient numerical method, the finite difference time domain method (FDTD), is used to simulate the field distribution. After the location of the tumor is determined, the Alternating Direction Implicit (ADI) FDTD method, which gives simulation results by dividing the computation domain into smaller sub-intervals, can be used. Scattered fields are calculated analytically in the geometry where the tumor is in the form of a smooth sphere, and in more complex geometry, the field distributions are successfully obtained with the help of MATLAB using FDTD and ADI-FDTD algorithms.

Utilizing Electromagnetic Radiation in Remote Sensing for Vegetation Health Analysis Using NDVI Approach with Sentinel-2 Imagery

The process of utilizing electromagnetic radiation from the radiometric values (Near-Infrared/NIR) and RED in the Normalized Difference Vegetation Index (NDVI) on Sentinel-2 imagery involves measuring light reflection at specific wavelengths reflected by vegetation. NDVI is computed by taking the difference between NIR and RED reflectance, then dividing it by their sum. In-depth analysis of electromagnetic wave interaction and plant spectral characteristics, such as NIR light reflection in healthy leaves, enables mapping vegetation health levels. The research aims to process image data and create a model visualizing vegetation health in the Sentinel-2 research area. Across the total area of 601,971,281.26 m2, 30.37% is healthy vegetation, 12.52% is moderate, and 53.33% is low or unhealthy. The least healthy area has an NDVI of -0.2006, while the healthiest area has a value of 0.6043.

Simulation and Modelling of Tree Roots using GPR and Numerical Analysis

Traditional methods to check tree roots are complicated due to their destructive nature and limited quantitative assessments in long-term research. Therefore, this study aims to understand the synergistic use of the Ground Penetrating Radar (GPR) to obtain accurate information on tree root health. For this purpose, geophysical and surveying techniques are used. In the study, image data of tree roots were obtained using IDS Duo GPR under normal conditions. To obtain the most accurate results in GPRMax, the simulation used the greatest contrast dielectric value of soil and roots. Then, an analysis is conducted to compare synthetic and real data. Modelling is crucial to understand electromagnetic wave propagation and interaction with tree roots. First, the synthetic hyperbola’s shape is compared with the real root’s hyperbola. Second, roots with increasing diameters were simulated and the time interval associated with each diameter was determined to produce a regression line model. Finally, depending on the real-time interval and the collected data, the regression model is utilised to estimate the true diameter. The study found the following: (1) the results show that the high dielectric value of the detected roots, real and synthetic hyperbola, have similar amplitude and tail; (2) the findings demonstrate that the estimation model is good with an average error of ±8 mm under ideal conditions and ±20 mm under normal conditions. The estimation variation is strongly influenced by soil moisture. The GPR resolution and signal deteriorate when the high soil moisture content is high. As a result, this study could provide vital insight for more effective assessment of tree roots and serve as an important reference for researchers seeking to expand on present findings.

Design and Fabrication of a Novel Corona-Shaped Metamaterial Biosensor for Cancer Cell Detection.

The early detection and diagnosis of cancer presents significant challenges in today's healthcare. So, this research, suggests an original experimental biosensor for cell cancer detection using a corona-shaped metamaterial resonator. This resonator is designed to detect cancer markers with high sensitivity, selectivity, and linearity properties. By exploiting the unique properties of the corona metamaterial structure in the GHz regime, the resonator provides enhanced interaction of electromagnetic waves and improved detection skills. Through careful experimental, simulation, and optimization studies, we accurately demonstrate the resonator's ability to detect cancer. The proposed detection system is capable of real-time non-invasive cancer detection, allowing for rapid intervention and better patient outcomes. The sensitivity value was confirmed through simulation, estimated at 0.1825 GHz/RIU. The results of two different simulation methods are used: the simulation software CST Studio Suite (version 2017) based on the finite element method (FEM), and the simulation software ADS (version 2019) based on the equivalent circuit method, thereby increasing confidence in the convergence of simulation and measurement results. This work opens new avenues for developing advanced detection technologies in the field of oncology, and paves the way for more effective cancer diagnosis. The experimental study verified that this realized sensor has very small frequency shifts, significantly small electrical dimension and miniaturization, high sensitivity, and good linearity. The suggested configurations showed a capacity for sensing cancer cells in the GHz regime.