Absorption Of Electromagnetic Energy Research Articles

The Development of a Reverberation Chamber for the Assessment of Biological Effects of Electromagnetic Energy Absorption in Mice.

In this paper, we present the design, RF-EMF performance, and a comprehensive uncertainty analysis of the reverberation chamber (RC) exposure systems that have been developed for the use of researchers at the University of Wollongong Bioelectromagnetics Laboratory, Australia, for the purpose of investigating the biological effects of RF-EMF in rodents. Initial studies, at 1950 MHz, have focused on investigating thermophysiological effects of RF exposure, and replication studies related to RF-EMF exposure and progression of Alzheimer's disease (AD) in mice predisposed to AD. The RC exposure system was chosen as it allows relatively unconstrained movement of animals during exposures which can have the beneficial effect of minimizing stress-related, non-RF-induced biological and behavioral changes in the animals. The performance of the RCs was evaluated in terms of the uniformity of the Whole-Body Average-Specific Absorption Rate (WBA-SAR) in mice for a given RF input power level. The expanded uncertainty in WBA-SAR estimates was found to be 3.89 dB. Validation of WBA-SAR estimates based on a selected number of temperature measurements in phantom mice found that the maximum ratio of the temperature-derived WBA-SAR to the computed WBA-SAR was 1.1 dB, suggesting that actual WBA-SAR is likely to be well within the expanded uncertainties.

Atomic-Level Electric Polarization in Entropy-Driven Perovskites for Boosting Dielectric Response.

Dielectric oxides with robust relaxation responsesare fundamental for electronic devices utilized in energy absorption, conversion, and storage. However, the structural origins governing the dielectric response remain elusive due to the involvement of atomically complex compositional and structural environments. Herein, configurational entropy is introduced as a regulatory factor to precisely control the structural heterogeneity in representative perovskite dielectric oxides. Through advanced structural and electric field visualization studies, a novel quantitative relationship is established between atomic-level structural disorder-induced electric field polarization and macroscopic dielectric properties. The results indicate that the degree of atomic delocalization in perovskite oxides exhibits a near-parabolic trend with increasing entropy, reaching a maximum in medium-entropy perovskite. Correspondingly, the atomic electric field vectors display significant asymmetrical distribution, thus greatly enhancing angstrom-scale electric field polarization. Then, it is experimentally proven that entropy-driven electric polarization can improve the dielectric relaxation behavior characterized by broader frequency and stronger intensity of electromagnetic energy absorption, with improvements of approximately 160% and 413% compared to structurally homogeneous control. This study unveils the quantitative correlation between angstrom-scale electric field polarization and dielectric response in perovskite oxides, offering a novel perspective for exploring the structure-propertyrelationship in dielectric materials.

Ground-penetrating radar subsurface attenuation analysis based on a sparsity-promoting time-frequency transform

The attenuation characteristics of a medium involve the absorption of electromagnetic wave energy during its propagation and represent a crucial parameter for describing the properties of subsurface media. Due to the complex nature of signal attenuation, demanding consideration of numerous parameters, quantitative analysis is challenging. Time-frequency (TF) analysis is a promising technique that simultaneously analyzes nonstationary signals in the time and frequency domains. Although the quantitative characterization of attenuation factors using TF tools can be challenging, TF analysis retains substantial potential for qualitatively estimating attenuation from ground-penetrating radar (GPR) data. The sparsity-promoting TF (SPTF) transform method with [Formula: see text] and [Formula: see text] norms joint constraints has a significantly higher TF resolution than the linear TF transform in the time and frequency domains. We develop a method for high-resolution qualitative estimation of GPR attenuation based on the SPTF method. Synthetic experiments indicate that SPTF surpasses other methods regarding TF resolution, noise robustness, and fidelity to dominant frequencies. Subsequent qualitative attenuation results using synthetic and field data agree with synthetic model outcomes and actual leakage ranges. This alignment substantiates the superior resolution and accuracy of our approach compared with alternative methods, affirming its efficacy and superiority in GPR attenuation depiction.

Comprehensive performance evaluation of HGM hybrid modified resins: Excellent high resistivity terahertz shielding and impact energy absorption properties

AbstractThe development of electronic fuze has placed higher demands on encapsulation resins, which are required to provide not only insulation and protection, but also higher impact resistance and good electromagnetic shielding performance. A new composite material consisting of hollow glass microspheres (HGM) and modified epoxy resin was developed. This material exhibits significant electromagnetic shielding capabilities for terahertz (THz) waves, as well as superior impact energy absorption properties. Bisphenol A‐type epoxy resin (E‐44) was modified using Al(OH)3, red phosphorus, carbon black, and SiO2, and the material properties were optimized by adjusting the HGM content. The electromagnetic shielding effectiveness and impact energy absorption of the composite material in the THz band were comprehensively tested using THz time‐domain spectroscopy and split Hopkinson pressure bar testing systems. Additionally, a comprehensive evaluation of the mechanical and dielectric properties, thermal conductivity, and thermal stability of the material was conducted. The results showed that the electromagnetic shielding effect of 60 vol.% HGM hybrid‐modified resins was the best, reaching 43.78 dB. The 20 vol.% HGM hybrid‐modified resins not only has a specific absorption energy of 18.51 J/cm3, but also has the best overall performance. This work has advanced the design and development of multifunctional and impact‐resistant potting epoxy resins.

MOFs-Derived Strategy and Ternary Alloys Regulation in Flower-Like Magnetic-Carbon Microspheres with Broadband Electromagnetic Wave Absorption

HighlightsMetal–organic frameworks-derived CoNiM@C (M = Cu, Zn, Fe, Mn) microspheres were successfully fabricated with custom-built magnetic alloy-carbon heterogeneous interfaces.Flower-like CoNiMn@C microspheres achieve broadband electromagnetic wave absorption with effective absorption bandwidth of 5.8 GHz at only 2.0 mm thickness.Visual interface charge distribution and hierarchical magnetic coupling were observed to elucidate the electromagnetic energy absorption mechanism.

Improving radio frequency heating uniformity in peanuts: Effects of packaging geometry, electrode gap, particle size and interlayer displacement process

This study aimed to assess the impact of various processing parameters including electrode gap, packaging geometry, and particle size on the heating efficiency of radio frequency (RF) processing for peanut thermal decontamination. In addition, interlayer displacements were presented to evaluate the effect of the mixing on heating uniformity.Experimental studies were carried out using 3D-printed polylactic acid (PLA) containers (square, rectangular, and cylindrical) to place the peanut samples with particle sizes ranging from 0.71 to 2.00 mm at 100–140 mm electrode gaps. Temperature changes within the samples were monitored using fiber optic sensors and surface temperature distributions were determined with an infrared camera. Heating uniformity index (λ) was then calculated to assess the effects of RF processing conditions on RF heating uniformity.Results showed that the cylindrical container exhibited a more consistent and uniform heating profile (λ = 0.12) with 1.58 °C min−1 heating rate compared to other containers, and a single interlayer displacement between top and bottom layers further improved temperature distribution uniformity. Smaller particle sizes also led to faster heating rates from 1.71 to 1.55 °C min−1 with more uniform heating due to the reduced porosity within the particles with increased thermal conduction and electromagnetic energy absorption. This study presented valuable insights for developing an effective RF process as an alternative to conventional thermal treatments for decontamination of low-moisture, high-fat particulate foods. Industrial significanceThis research presented an innovative approach applying RF heating for a possible decontamination process for peanut samples. The research tackled the growing worldwide consumer demand for food products to satisfy food safety regulations while peanuts were selected to demonstrate the process effect due to the recent food safety issues in peanut butter considering that a pre-process for decontamination would lead to a decrease in the resulting safety issues.

Bi-functional dynamic tunable absorber and highly robust polarisation converter for graphene-based metasurface

In this study, a graphene-based metasurface structure with bi-functional dynamically tunable absorber and highly robust polarisation converter is proposed. The device primarily consists of two functional tiers. The top tier of cyclically patterned graphene and the back of a fully reflective gold mirror, which are separated by an intermediate tier of SiO2 dielectric to form a typical sandwich structure. The proposed device is numerically calculated by finite element method (FEM), and the equivalent R-L-C circuit model is built to validate the calculated results. The proposed reflective-type circularly to circularly polarisation converter (RCCPC) has a wide operating band of 0.8 THz (2.12 THz to 2.92 THz) and can obtain near unity polarisation conversion rate (χPCR). It is worth noting that the device is also immune to structural parameter deviations. In addition, due to the excited charge of monolayer graphene has the cyclotron property in a static magnetic field, the cross-polarised component of the polarisation converter can be increased by applying a vertical magnetic field, which provides a feasible method to improve the energy conversion rate of the device. At the same time, the device can also serve as a narrowband dual channel absorber, with 95 % absorption effect. In addition, the tunability of graphene is based on the correlation between conductivity and Fermi energy. As the Fermi energy changes, the working frequency of the device is shifted, realizing the dynamic tunable absorber and polarisation converter. It is believed that these findings provide a way to implement a variety of novel multifunctional photonic device, including polarisation imaging, electromagnetic energy absorption, and integrated photonic devices.

Dynamics in a light-sensitive neuron with two capacitive variables

Involvement of two capacitive variables into neuron models provides better description of the cell membrane property and then the diversity effect of electromagnetic field inner and outer of the cell membrane can be estimated in clear way. Specific electric components can be combined to build equivalent neural circuits for reproducing similar neural activities under some self-adaptive control schemes. A phototube converts external light into electric stimuli and the injected energy is encoded to excite the cell membranes for presenting suitable firing patterns. Two capacitors are connected via a linear resistor for mimicking the energy exchange and changes of membrane potentials. Combination of memristor into an additive branch circuit of the neural circuit can estimate the effect of electromagnetic induction and energy absorption. The energy function H for this light-sensitive and memristive neuron is calculated in theoretical way, and the average energy function 〈H〉 can predict the occurrence of stochastic resonance, which can be confirmed by estimating the distribution of signal to noise ratios. The firing mode is relative to the energy value of the neuron, and a control law is suggested to control the mode transition in neural activities in an adaptive way.

Active low frequency band expansion mechanism of electromagnetic wave absorber composite structure

Bandwidth expansion of modern antennas and communication systems raises growing demand for electromagnetic wave absorber in compatibility equipment. Single absorption mechanism is hard to reach well-balanced characteristics including wide bandwidth, low frequency absorption and small thickness. Based on the composite structure concept, composite structure for electromagnetic wave absorber’s active low frequency band expansion is proposed, by combining circuit-analog absorber and active absorber to form a superimposed structure. The characteristic of composite structure is better than the single absorber structure, which improves enhancement mechanism brought by the composite structure. Sample fabrication and experiments indicate reflectivity curve envelope reaches −10 dB in 2.15–18 GHz frequency range (relative bandwidth 157.3%), and the tunable absorption frequency range in low-frequency domain is greater than 1.3 GHz. The structure has good adaptation on TE and TM polarizations, as well as good angle insensitivity. This composite structure has application potential in intelligent response system related with electromagnetic compatibility, energy absorption and object security management.

A compact circuit-based metasurface for enhancing magnetic resonance imaging

Herein, we propose a compact 0.36 T MRI-enhancing circuit-based metasurface working at its third order mode. Different from most MRI-enhancing metasurface designs which exploit the fundamental mode with the highest enhancement, our choice is a trade-off between the enhancement and homogeneity. The metasurface is organized with capacitively-loaded metal wires where the capacitors decrease the electric length of the wires thus enabling a deep subwavelength scale. The working frequency of metasurface is tuned to the Larmor frequency, contributing to the redistribution of transmitted field. Full-wave simulations based on CST Microwave Studio compare the magnetic field in a mimicked MRI environment with and without the metasurface. The utilization of metasurface leads to a field enhancement ratio of 9.36-fold over a 28 × 28 cm2 area at 2 cm height while exceeding unity till almost 12 cm. Meanwhile, the variation of the quasi-homogenous magnetic field is less than 1/3 over a relatively large area. The impact of metasurface is further demonstrated by simulations with a head bio-model to evaluate the transmitted field strength and electromagnetic energy absorption. A preliminary measuring experiment is also conducted to validate the special mode pattern. The proposed metasurface effectively enhances the transmitted efficiency thus can be employed in clinical MRI to enhance imaging quality or reduce the input power. Moreover, this design paradigm is compatible with other enhancing approaches due to the nonmagnetic inclusions and frequency-dependent response and can be adapted for higher-field MRI systems by adjusting the length of metal wires and the value of loaded capacitors.

Wideband metasurface-loaded rectenna for azimuth-insensitive electromagnetic energy absorption using characteristic mode analysis

In this paper, a wideband metasurface-loaded (MTS-L) rectenna system is proposed to capture electromagnetic (EM) energy at arbitrary azimuth angles. The radiation patterns of different modes in the original MTS configuration are analyzed using the characteristic mode theory, and potential modes with omnidirectional radiation are screened out. By the arrangement of patches, the roundness performance of the radiation pattern can be ameliorated, and the omnidirectional characteristic is obtained over a wide frequency band. Subsequently, the surface current density of the selected mode is carefully and artificially designed to facilitate probe excitation as well as refrain from introducing complex power-combining networks. A wideband rectifier circuit is designed as the load of the proposed antenna. Eventually, measured results show that it operates from 4.6 to 9.6 GHz with a fractional bandwidth of 70.4%, and the peak system efficiency is 52.2%. The proposed system demonstrates excellent potential for wireless power transmission and EM energy harvesting in indoor environments.

Multilayer Bolometric Structures for Efficient Wideband Communication Signal Reception.

It is known that the dielectric layer (resonator) located behind the conducting plate of the bolometer system can significantly increase its sensitivity near the resonance frequencies. In this paper, the possibility of receiving broadband electromagnetic signals in a multilayer bolometric meta-material made of alternating conducting (e.g., silicon semiconductor) and dielectric layers is demonstrated both experimentally and numerically. It is shown that such a multilayer structure acts as a lattice of resonators and can significantly increase the width of the frequency band of efficient electromagnetic energy absorption. The parameters of the dielectric and semiconductor layers determine the frequency bands. Numerical modeling of the effect has been carried out under the conditions of our experiment. The numerical results show acceptable qualitative agreement with the experimental data. This study develops the previously proposed technique of resonant absorption of electromagnetic signals in bolometric structures.

Molecular Absorption Scanning and Assay of Serotonin Reception Inhibitor Antidepressant Drugs

Background:: Spectrophotometric techniques are based on the absorption of electromagnetic energy by the molecules of the substance analyzed and can be applied to drug analysis. Objective:: This study has been proposed to carry out molecular absorption scanning and assay in the ultraviolet region of generic antidepressant drugs of the serotonin reuptake inhibitor class produced by three Brazilian laboratories, addressing the importance of good manufacturing practices, drug quality control, and the use of qualitative and quantitative analytical techniques. Methods:: The physicochemical analyses were performed in a Marte Científica (580 UVP) UV-Vis spectrophotometer, and the result was evaluated according to the acceptance interval described in the Brazilian Pharmacopoeia. Results:: When calculating the dosage of the fluoxetine hydrochloride sample, the value of 90.95% was obtained and, therefore, the drug was approved for the dosage test. The dosage test for the drugs, citalopram hydrobromide and sertraline hydrochloride, was also approved, obtaining values of 102.4% and 98.2%, respectively. Conclusion:: The results presented provide future perspectives regarding the rigor of the need for good drug handling practices, maintenance and qualification of quality control laboratory equipment, and the guarantee of validation of analytical methodologies used in the pharmaceutical industries, contributing to the improvement of the quality of production and pharmaceutical products analysis.

Tree Dielectric Response as an Earthquake Forecasting

Seismic precursor identification is vital in the Himalayan range and near active fault lines to offer early earthquake warnings, as India and nearby areas face a high risk of seismic activity. This laboratory-based research conducted simulations aimed at replicating electromagnetic signals generated by artificial seismic events spanning frequencies from 1 Hz to 59 Hz. High-frequency seismic signal attenuation upon interaction with the Earth's surface was observed, focusing on emulating electromagnetic waves within the ultra-low frequency (ULF) to very high frequency (VHF) range and investigating energy transfer dynamics within conductive materials. Findings included a reduction in green stem ring diameter, an inversely correlated penetration depth with frequency, and fluctuations in the dielectric constant of tree tissues, linked to water molecule polarization with frequency changes. By applying an electric field, lower dielectric constants were observed at lower frequencies, stabilizing at around 40 eV as frequency increased from 1 Hz to 59 Hz. As frequency levels escalated, especially transitioning into the radio or microwave spectrum, alterations in the dielectric constant of tree tissues were noted, often marked by an increase in dielectric loss, signifying heightened absorption of electromagnetic energy and its conversion into heat. Banyan tree roots exhibited responses well in advance of any discernible alterations in the subsurface environment, offering valuable early indicators of impending seismic activity. This discovery encourages further exploration and holds the potential to advance earthquake prediction using deep-rooted trees as biosensors, ultimately contributing significantly to the preservation of human lives and overall safety.

Non-resonant absorption of the X-band electromagnetic wave power in a narrow-gap PbS semiconductor at temperatures of 2.6–8 K in the range of magnetic fields 0–100 mT

Studies of magnetically dependent effects of nonresonant absorption of electromagnetic wave energy in the resonator of the X-band EPR spectrometer related to the superconductivity of metallic lead inclusions and microscopic structural defects in crystals of narrow-band semiconductors PbS1 – x and PbS1 – x:Mn have been performed. It is shown that nanoscale lead particles present in polycrystalline material PbS0.96 with a high content of sulfur vacancies at temperatures of 2.6–8 K manifest themselves as superconductors of the 2nd kind and demonstrate high thermomagnetic stability. It was found that in a single-crystal sample PbS0.996 with a significantly lower concentration of sulfur vacancies under the influence of the electric component of the microwave field in the resonator of the ESR spectrometer, non-periodic bursts of microwave power absorption associated with avalanches of Abrikosov vortices and demonstrating the absence of thermomagnetic stability of superconducting regions associated with defects in the crystal structure of the sample PbS0.996 are observed.

An FCC-FDTD Method on Nonuniform Grids With Guaranteed Stability for Electromagnetic Analysis

The finite-difference time-domain (FDTD) method based on nonuniform face-centered cubic (FCC) grids, termed as NU-FCC-FDTD method, is proposed in this article. The FCC-FDTD method with uniform grids has a smaller numerical dispersion error than the traditional FDTD methods. To further enhance its efficiency and scalability, the NU-FCC-FDTD method is proposed to solve complex electromagnetic problems. Unlike the traditional FDTD methods based on Yee’s grids, for which the nonuniform grid technique is relatively straightforward, instability may occur when trying to apply nonuniform grids into the FCC-FDTD method. To ensure stability, cell-size-based correction factors are carefully defined in the time-marching formulations after taking cell sizes into consideration. Through comprehensive numerical dispersion analysis, the NU-FCC-FDTD method shows numerical dispersion advantage over the FDTD methods and the FCC-FDTD method with uniform grids. Furthermore, the stability condition is also given by using the parameter scanning method and verified in numerical examples. Four examples, including electromagnetic wave propagation, a dielectric rod (DR) resonator, a composite metallic-dielectric radome and the electromagnetic energy absorption of human head, are carried out to demonstrate its performance. Results show that the proposed NU-FCC-FDTD method can significantly improve efficiency compared with that of the FCC-FDTD method without compromising accuracy.

Study on the shielding effect of low resistance body when using transient electromagnetic to detect urban underground space.

Transient electromagnetic Method (TEM) is an efficient geophysical detection technology suitable for detection of urban near-surface space. However, its detection results are well affected by the low resistance anomaly, which interferes with the interpretation of the inversion results. This article used finite element method to simulate the entire process of urban underground pipeline under TEM detection. The causes of interference and the degree of interference under different working conditions were analyzed. The results demonstrate that low resistance anomaly in magnetic field will caused electromagnetic energy absorption and resulting eddy current losses, which lead to a distortion of the primary magnetic field in the vicinity of the pipeline, and formation of a weak field zone beneath the pipeline. The size and shape of the shielding zone are affected by burial depth, transmitter coil diameter, and anomaly size. When the burial depth exceeds 10 times the diameter of the coil or pipeline, the shielding range stabilizes at 1.5-2 times the pipeline's transverse diameter. Moreover, when the pipeline's transverse diameter exceeds twice the transmitter coil diameter, the weak field zone beneath the pipeline will transform into a strong field zone, this is due to the refractive and reflective effects of the electromagnetic field. Finally, experiments were conducted and the inverted results was found to be larger than the actual pipeline diameter, with an error margin similar to that explained by the simulation. These results have implications for high accuracy detecting underground pipelines in urban areas.

Research on electromagnetic energy absorption and conversion device with four-ring multi-resistance structure

A device for electromagnetic energy absorption and conversion was investigated as an electromagnetic energy harvester, which is based on a four-ring multi-resistance unit. The device can convert microwave energy to thermal energy and then to electrical energy through the Bi2Te3 thermoelectric material adhered to the load resistance. The energy harvesting efficiency, power loss distribution, and current density distribution of the harvester were analyzed. In addition, the energy harvesting efficiency of the unit under different incident angles and polarization angles was studied, and the effect of incident power on the temperature and energy conversion efficiency of the unit was analyzed. The simulation results showed that the energy harvesting efficiency of the harvester reaches 99.5% at 5.8 GHz. Each unit in the harvester can generate an output voltage of 171.8 mV under 7 W incident wave power, and the maximum output power is 9.71 mW. To verify the effectiveness of this method, a 5 × 5 unit array model was fabricated and measured, and the measurement results were consistent with the simulation results.

Dynamic tunable narrow-band perfect absorber for fiber -optic communication band based on liquid crystal

At present, most of the reported metasurface structure absorbers show that its working band cannot be regulated actively. In this study, a dynamic tunable narrow-band perfect absorption structure for fiber-optic communication band based on liquid crystal (LC) is proposed and studied. The structure is mainly composed of two effective tiers. The top tier gold array and the bottom tier reflective gold film, which are separated by a SiO2-LC dielectric medium interlayer to form a metal–dielectric–metal structure. Due to the unique optical properties of LCs, its index of refraction can be changed by adjusting the bias voltage and temperature, so as to adjust the resonance wavelength actively. The designed structure is analyzed by finite element method and the coupled mode theory is used to verify the analysis results. The designed structure has a 99.92% absorption effect in the most commonly used band of fiber-optic communication. Due to the symmetry of the absorber structure, the device is not sensitive to the polarization state of the excitation source. Moreover, the absorber exhibits an unusual dependence on the incident angle, which can be attributed to the anisotropy of the LC. Based on the dependence of incident angle, a plasma optical switch with large ON/OFF ratio (η) of 27.395 dB and nearly flawless modulation depth of 99.818% can be realized. It is believed that this structure can provide a method for the dynamic control of near infrared electromagnetic waves, and to be applied in electromagnetic energy absorption, filtering and plasma optical switch system.

Characterization of dielectric properties of residual ashes obtained from rice husk and annoni grass

This paper presents a study about the characterization of dielectric properties (dielectric constant {varepsilon }_{r} and dielectric-loss constant mathrm{tan}delta) of samples derived from two different biomass types: rice husk ash (RHA) and annoni grass ash (AGA).The procedure is carried out using the resonant cavity method along with a vector network analyzer. For this purpose, four different ashes were produced, by burning rice husk and annoni grass at two different temperatures and burning times: 400 °C/30 min (RHA40030 and AGA40030) and 800 °C/5 h (RHA8005h and AGA8005h). These ashes were combined with Bakelite to produce cylindrical samples with diameter of 30 mm and thickness of 4.5 mm, which were characterized considering the frequency in the test band for 5G technologies ({f}_{o}=3.5 GHz). Experimental results showed that the samples burnt at high temperature showed very high mathrm{tan delta } when compared to the samples burnt at low temperature, mainly for AGA8005h. These values are mathrm{tan delta }= 0.1690 and 1.4900 for RHA8005h and AGA8005h, respectively. The resulting dielectric constants are {varepsilon }_{r} = 3.87 for RHA8005h and {varepsilon }_{r} = 15.14 for AGA8005h). These very high dielectric loss tangent, indicate that these materials exhibit formidable properties for electromagnetic energy absorption, hence allowing the application as radiation-absorbent material (RAM).