High Frequency Electromagnetic Field Research Articles

Remarks on High-Frequency Electromagnetic Field Analysis of Magnetic Components for Power Electronics

Remarks on High-Frequency Electromagnetic Field Analysis of Magnetic Components for Power Electronics

High Frequency Electromagnetic Field Exposure in Paediatric and Female Patients with Implanted Cardiac Pacemaker

High Frequency Electromagnetic Field Exposure in Paediatric and Female Patients with Implanted Cardiac Pacemaker

Microwave device for heat treatment of meat by-products and waste

BACKGROUND: In the conditions of farms, there is a problem of neutralizing unpleasant odors during heat treatment of secondary meat raw materials to preserve the consumer properties of protein feed at low operating costs. AIM: Development of the device for heat treatment with disinfection and neutralization of the unpleasant odor of crushed secondary meat raw materials with the integral effect of an ultra−high frequency electromagnetic field, a bactericidal flow of UV rays and ozone in a continuous mode with electromagnetic safety ensured. METHODS: The raw materials are the stomach chambers of ruminants. The basic idea, principle of operation and design of the device are based on the propagation of microwave oscillations in a resonator with a spiral decelerating system. The microwave device contains a non-ferromagnetic cylinder with a perforated lower base, a coaxially arranged non-ferromagnetic spiral cylinder and an electrically driven fluoroplastic auger with a solid screw surface. The average perimeter of the annular volume, between the cylinder and the spiral cylinder forming the coaxial resonator, and its height are multiples of half-wavelength. Corona brushes are mounted to the annular base of the cylinder, under which electric gas discharge lamps powered by 1 kHz frequency generators are radially located, and a ceramic annular spherical surface is located under the lamps. Magnetrons are mounted along the perimeter of the outer cylinder with a shift of 120 degrees. The crackling is removed using a pneumatic conveyor. RESULTS: The feature of the coaxial resonator is that the inner core is formed as a spiral decelerating system. Therefore, the intrinsic Q-factor of the resonator is high, about 115000, therefore, the expected thermal efficiency is 0.7–0.75. The factor of dielectric losses of raw materials with a decrease in humidity from 76% to 30% is reduced by five times. Thus, while keeping the electric stress at the level of 1.2–2 kV/cm, the electromagnetic field power dissipated in a unit of the volume of the crackling decreases by five times, from 34 500 to 6800 W/cm3. CONCLUSIONS: A new design solution with a spiral coaxial resonator, the use of a ceramic reflector, and a number of physical factors made it possible to develop the design of the operation chamber for the heat treatment of ruminant slaughter waste with the neutralization of unpleasant odors with a capacity of 30–35 kg/h and specific energy costs of 0.16–0.19 kWh/kg.

Mobile phone specific radiation disturbs cytokinesis and causes cell death but not acute chromosomal damage in buccal cells: Results of a controlled human intervention study

Several human studies indicate that mobile phone specific electromagnetic fields may cause cancer in humans but the underlying molecular mechanisms are currently not known. Studies concerning chromosomal damage (which is causally related to cancer induction) are controversial and those addressing this issue in mobile phone users are based on the use of questionnaires to assess the exposure. We realized the first human intervention trial in which chromosomal damage and acute toxic effects were studied under controlled conditions. The participants were exposed via headsets at one randomly assigned side of the head to low and high doses of a UMTS signal (n = 20, to 0.1 W/kg and n = 21 to 1.6 W/kg Specific Absorption Rate) for 2 h on 5 consecutive days. Before and three weeks after the exposure, buccal cells were collected from both cheeks and micronuclei (MN, which are formed as a consequence of structural and numerical chromosomal aberrations) and other nuclear anomalies reflecting mitotic disturbance and acute cytotoxic effects were scored. We found no evidence for induction of MN and of nuclear buds which are caused by gene amplifications, but a significant increase of binucleated cells which are formed as a consequence of disturbed cell divisions, and of karyolitic cells, which are indicative for cell death. No such effects were seen in cells from the less exposed side. Our findings indicate that mobile phone specific high frequency electromagnetic fields do not cause acute chromosomal damage in oral mucosa cells under the present experimental conditions. However, we found clear evidence for disturbance of the cell cycle and cytotoxicity. These effects may play a causal role in the induction of adverse long term health effects in humans.

Process Parameters of High Frequency Welding.

High frequency (HF) welding of polymer materials is increasingly used in modern manufacturing processes. The literature on HF welding process parameters was reviewed and it was found that 3-5 basic welding parameters were considered, which is insufficient for the scientific study of HF welding of polymeric materials. This article presents the mathematical expressions for the evaluation combining 17 influential parameters. For the first time, the specific and latent heat of the welded polymer material were used. The breaking forces of welds made by RF welding are investigated by varying the anode current, the coupling capacitor, and the exposure time of the HF electromagnetic fields. It was found that the amount of HF energy supplied depends on the breaking forces of the weld. A characteristic inflection point was also observed in the graph of the dependence of the breaking forces on the percentage of the coupling capacitor and the anode current. During elongation, it was observed that the weld is separated by peeling before the inflection point and breaks after the inflection point by tearing at the extruded edges of the weld. If the HF energy is applied to the weld for too long, there will be excessive melting of the material in the weld, thinning of the weld, unfavourable appearance of the extruded edges and electrical breakdown, and a drastic drop in the breaking force.

High-Frequency Electromagnetic Field Coupling to Transmission Line With Discontinuity Above a Lossy Ground

High-Frequency Electromagnetic Field Coupling to Transmission Line With Discontinuity Above a Lossy Ground

Laboratory Studies on the Separation of Various Oil–Water Emulsions in a High-Frequency Electromagnetic Field

Laboratory Studies on the Separation of Various Oil–Water Emulsions in a High-Frequency Electromagnetic Field

Modeling Electrodynamic Interactions in Brownian Dynamics Simulations

There is a great deal of interest in interactions between biomolecules and high frequency electromagnetic (EM) fields. To investigate these interactions, a variety of simulation methods are available. For small length and time scales (approximately <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&lt; $</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1 \,\mathrm{\mu }\mathrm{s}$</tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$100 \,\mathrm{n}\mathrm{m}$</tex-math></inline-formula> ), All-Atom Molecular Dynamics simulates every atom in the system. This captures the relevant physics to a high degree of accuracy. Phenomena such as electric field screening by counter-ions are emergent properties from the collective interactions of these atoms. For larger systems on longer time scales, however, this method is too computationally expensive. To reduce complexity, other simulation techniques such as Brownian Dynamics treat the solvent as a continuum, instead of explicitly. One typical assumption is that electric field interactions are electrostatic and subjected to Debye screening. Once charges start moving at high frequencies and velocities, however, charges are able to outrun the counter-ion cloud and this assumption breaks down. We propose a method of removing the electrostatic assumption without explicitly modeling the solvent or imposing a grid on the simulation. We demonstrate the charged wake can be modeled using a finite trail of charges. Interactions can be computed using electrostatic expressions only, but still capture electrodynamics.

High-Density Ice Ih Obtained by Crystallization of Water in a High-Frequency Electromagnetic Field

The processes of crystallization and melting, and the structure of ice formed under freezing in an alternating electromagnetic field with a frequency of 2.45 GHz have been studied using thermometry, differential scanning calorimetry, and X-ray diffraction. Using X-ray powder diffraction at 85 K, it was determined that the obtained samples consisted of several phases of hexagonal ice Ih, with a density 0.43 ÷ 2.58% higher than that of ordinary ice. The time necessary for this ice to crystallize was approximately 2.2 times shorter than that of ordinary ice not exposed to an alternating electromagnetic field. According to the data of differential scanning calorimetry, the melting of this ice was accompanied by an endothermic heat effect 9% greater than that of ordinary ice, and a melting point that was 1 °C lower. A similar effect is typical of the melting of metastable phases. We assume that the formation of ice Ih with increased density results from the action of an alternating electromagnetic field on the network of hydrogen bonds of liquid water which is a precursor for ice formation.

Alterations in membrane stability after in vitro exposure of human erythrocytes to 2.41 GHz electromagnetic field

The growing use of wireless communication devices has been significantly increasing the level of high frequency electromagnetic fields (EMFs) in the environment, which raises a concern for possible deleterious effects on living organisms. Long lasting exposure to low-intensity EMFs can cause effects on the molecular and cellular level, and a number of morphological and physiological changes. The aim of this work was to investigate the effects of 2.41 GHz EMF emitted by wireless communication systems on human erythrocytes after in vitro irradiation. The amount of the hemoglobin released from the cells was measured as an indicator for membrane destabilization. Effects of different exposure times (20 min or 4 h) and time elapsed after exposure to 2.41 GHz pulsed or continuous EMFs with different intensities, emitted from a textile (0.213–0.238 V/m) or a dipole (5, 20, 40 and 180 V/m) antenna, were investigated. The obtained results showed that the low intensity EMF had no significant effect on the hemoglobin release from irradiated cells; even a slight tendency for membrane stabilization was noticed 3–4 hours after the end of 20-min exposure to 0.213–0.238 V/m, 2.41 GHz EMF. There was no difference in the effects of continuous and pulsed EMFs. Increased hemoglobin release was observed only during the 4-hour exposure to 180 V/m, 2.41 GHz continuous EMF. Under these conditions, the temperature of the cell suspension had been rising, so we compared the results obtained under EMF with the effects of conventional heating. Moreover, after 1-hour exposure to 180 V/m the released hemoglobin level was a bit higher than the control one but the difference disappears within an hour after terminating the irradiation. In conclusion, the in vitro exposure to 2.41 GHz EMF emitted by wireless communication devices with power density below the reference level for population exposure does not change the stability of the cell membrane of human erythrocytes.

Non thermal 2.45 GHz electromagnetic exposure causes rapid changes in Arabidopsis thaliana metabolism

Numerous studies report different types of responses following exposure of plants to high frequency electromagnetic fields (HF-EMF). While this phenomenon is related to tissue heating in animals, the situation is much less straightforward in plants where metabolic changes seem to occur without tissue temperature increase. We have set up an exposure system allowing reliable measurements of tissue heating (using a reflectometric probe and thermal imaging) after a long exposure (30 min) to an electromagnetic field of 2.45 GHz transmitted through a horn antenna (about 100 V m−1 at the plant level). We did not observe any heating of the tissues, but we detected rapid increases (60 min) in the accumulation of transcripts of stress-related genes (TCH1 and ZAT12 transcription factor) or involved in ROS metabolism (RBOHF and APX1). At the same time, the amounts of hydrogen peroxide and dehydroascorbic acid increased while glutathione (reduced and oxidized forms), ascorbic acid, and lipid peroxidation remained stable. Therefore, our results unambiguously show that molecular and biochemical responses occur rapidly (within 60min) in plants after exposure to an electromagnetic field, in absence of tissue heating.

Electromagnetic Fields - Do They Pose a Cardiovascular Risk?

Mobile wireless communication technologies have now become an everyday part of our lives, 24 hours a day, 7 days a week. Monitoring the autonomous system under exposition to electromagnetic fields may play an important role in broading of our still limited knowledge on their effect on human body. Thus, we studied the interaction of the high frequency electromagnetic field (HF EMF) with living body and its effect on the autonomic control of heart rate using Heart Rate Variability (HRV) linear and nonlinear analyses in healthy volunteers. A group of young healthy probands (n=30, age mean: 24.2 ± 3.5 years) without any symptoms of disease was exposed to EMF with f=2400 MHz (Wi Fi), and f=2600 MHz (4G) for 5 minutes applied on the chest area. The short-term heart rate variability (HRV) metrics were used as an indicator of complex cardiac autonomic control. The evaluated HRV parameters: RR interval (ms), high frequency spectral power (HF-HRV in [ln(ms2)]) as an index of cardiovagal control, and a symbolic dynamic index of 0V %, indicating cardiac sympathetic activity. The cardiac-linked parasympathetic index HF-HRV was significantly reduced (p =0.036) and sympathetically mediated HRV index 0V % was significantly higher (p=0.002) during EMF exposure at 2400 MHz (Wi-Fi), compared to simulated 4G frequency 2600 MHz. No significant differences were found in the RR intervals. Our results revealed a shift in cardiac autonomic regulation towards sympathetic overactivity and parasympathetic underactivity indexed by HRV parameters during EMF exposure in young healthy persons. It seems that HF EMF exposure results in abnormal complex cardiac autonomic regulatory integrity which may be associated with higher risk of later cardiovascular complications already in healthy probands.

Factors affecting the temperature variation rate of bamboo during high-frequency heating

High-frequency electromagnetic fields refer to electromagnetic waves with frequencies ranging from 100 kHz to 300 MHz. High-frequency medium heating has the advantages of uniform heating, rapid energy consumption, and environmental protection. While it has a wide range of applications, the use of high-frequency dielectric heating in the bamboo industry is rare. Understanding the influence of bamboo temperature rise rate in high-frequency heating could promote bamboo industry development. In this work, curved bamboo was tested with high-temperature energy for continuous heating. The influence of moisture content of bamboo, sample thickness, and high-frequency processing power on temperature rise rate were studied. The results showed that the water content of bamboo affected the temperature rise rate. The effect of high-frequency heating was highest when the moisture content of bamboo was close to 11%. The thickness of sample had little effect on the temperature rise rate, but the high-frequency power had a significant effect on the temperature rise rate. The temperature rise rate of the lower and higher frequency power levels increased slowly and was close to constant. The heating power was 11 kW, and the temperature rise rate was the highest.

Studies of Dielectric Characteristics of Polymer Films in a High-Frequency Electromagnetic Field

Establishing the relationship between the structure of solids, on the one hand, and macroscopic physical properties, on the other, makes it possible to obtain detailed information about the structure and nature of interactions in the system involved. The solution to this problem makes it possible to formulate recommendations for the creation of materials with specified properties. In this work, much attention is paid to polymer films of syndiotactic 1,2-polybutadiene (1,2-SPB). The properties of polymer films differ from the properties of bulk materials of the same chemical composition as films. The polymer (1,2-SPB) has an amorphous, irregular structure and, due to its significant irregular structure and makeup, has important electrical, physical and chemical properties. Its physical properties make this polymer promising for use in various fields of mechanical engineering, agriculture, construction, and healthcare. The paper reports the results of a study of relaxation processes by the method of thermoactivation spectroscopy of a relatively new polymer - syndiotactic 1,2-polybutadiene. The mechanisms of deformation and relaxation polarization are described and studied in detail. A technique for preparing samples and processing the experimental results of the dielectric characteristics of polymer films are described. Dielectric measurements were performed using a standard R-571 bridge. Experimental temperature dependences of dielectric constant, dielectric loss factor and loss tangent before and after exposure to a high-frequency electromagnetic field are shown. An atomic force microscopy (AFM) survey of a 1,2-SPB polymer film is presented. Particle analysis by AFM provides a unique opportunity to determine the size and shape of particles.

Quantum Floquet spectra of surface and bulk state of topological insulator

Topological insulator is a new class of material, which consists of insulating bulk and conducting surface state. In this study, we investigated the behaviour of bulk and surface state of topological insulator under a high frequency electromagnetic field, produce a kind of oscillation called as Floquet oscillation. We successfully identified the classical and quantum behavior of Floquet oscillation in the prospective of collapse revival spectra. This work shows the bulk and surface states behaviour of a topological insulator with the help of Floquet and Rabi frequency and describes the dominancy of Floquet oscillation in the low energy physics. Numerical simulation has been applied for verifying the Floquet approximation.

Effective removal of antibiotic resistance genes by high-frequency electromagnetic field combined with chlorine disinfection

The presence of antibiotic resistance genes (ARGs) and antibiotic-resistant bacteria (ARB) in the environment is of great concern to human health. This study developed a new combination of high-frequency electromagnetic field (HEMF) and low-dosage chlorine disinfection to reduce the abundance of extracellular ARG (eARG) sul2 and intracellular ARG (iARG) adeF. The removal efficiencies of sul2 and adeF from sulfamethoxazole- and multidrug-resistant Acinetobacter junii were measured by quantitative PCR (qPCR). Compared to chlorine disinfection alone, the combination of HEMF treatment exhibited significantly improved ARG removal efficiency. The highest removal efficiencies of sul2 and adeF under the combination were 75.7% and 91.4%, respectively. Treatment time and the dosage of chlorine played pivotal roles in the removal efficiency of ARGs via HEMF treatment and chlorine disinfection, respectively. Importantly, a combination of low-dose chlorine with HEMF treatment could serve as a viable alternative to high-dose chlorine disinfection. This work offers essential process parameters for optimizing the elimination of iARGs and eARGs and presents a viable solution for addressing the issue of ARG contamination.

Thermogravimetry of bentonite "navbahor" in nanocatalytic extraction technology and investigation of the convective ehfef drying process

This study presents the results of a study of the process of thermography and convective drying of the retention substance bentonite used in the production of nanocatalysts based on Zol-gel technology. The study of the drying process using the energy of the convex-EHFEF EMF (extremely high-frequency electromagnetic field) in the preparation of a nanocatalystsfrom the retaining substance of bentonite is illuminated by the derivatogram of bentonite from the Navbahor deposit determined by the thermographic method. The determination of the porous structure and the comparable surface surface of the catalysts was carried out in an automatic gas adsorption analyzer using the Brunauer, Emmet, and Wyres (bet) method.The size and pore size of the catalysts were determined from data on desorption and adsorption isotherms, respectively, at a relative pressure R/R0=0.99 in accordance with the BJH (Barette-Joyner-Halend) model. Based on the purpose of the work, the study of the drying process in the technology of obtaining a nan catalyst and the acceleration of its process and technology with its introduction into EHFEF (extremely high frequency electromagnetic field) EMC, was achieved to improve the quality of the porosity of catalysts. In particular, the analysis of the results obtained on the experimental scheme of the grooved-convex drying device, textural descriptions of bentonite of the Navbahor deposit, determined on the basis of standard techniques, porosity of the sample by the method of temperature nitrogen adsorption is presented.

DEVELOPMENT OF THE PROCESS OF STAMPING BY ROLLING OF TUBULAR PREPARATIONS USING INDUCTION HEATING

Methods of pressure treatment of metals based on the action of technological load in the conditions of a localized plastic cell. The main purpose of such methods is that the change in shape at any time is performed only on a fraction of the volume of the workpiece and when moving the deformation center covers the entire volume. These are well-studied and widely used in the production of free forging, rotary forging, rolling, etc. A relatively new method of MP - stamping by rolling, is characterized by a number of positive effects: - reduction of deformation force in comparison with traditional methods in 5-30 times; - the possibility of processing metal in the cold state with the same technological effort as in hot processing; - the equipment corresponds to a high level of labor safety; - reducing the size, weight and cost of equipment; - the possibility of implementing various technological operations. Modern mechanical engineering, instrument making and other metalworking industries widely use and manufacture parts with a large ratio of cross-sectional dimensions, the production of which by existing methods of metal forming is either inefficient or impossible. The most technological are the processes of SHO, in which the workpiece has a tubular or annular shape. Such blanks are well amenable to induction heating, which while providing a high frequency electromagnetic field allows them to be heated quickly and efficiently. This can heat a limited amount of workpiece material. Thus, the use of induction heating in the processes of SHO significantly expands their technological capabilities, which determines the relevance of the chosen topic. The main advantages of induction heating include: transmission of electrical energy does not require contact devices, is carried out directly into the workpiece, which increases the heating rate; due to the possibility of controlling the frequency of the current, the maximum power is released in the limited thickness of the surface layer of the product, which is especially effective when heating the pipe blanks; induction heating can increase productivity and improve working conditions.

Investigation of the influence of microwave energy on the kinetics of the release of juice from apples

This article presents the results of experimental research on the effect of high-frequency electromagnetic field treatment on fruit juice. The interaction of high-frequency electromagnetic field energy with food was studied on the example of apples. Based on the dependence of the kinetics of juice release from fruits on the duration of exposure to an extremely high frequency electromagnetic field. Comparative analysis of apple juice obtained by treatment with ultra-high frequency electromagnetic field energy and by traditional methods. Treatment of fruits with 2400 MHz ultra-high frequency electromagnetic field energy was found to increase excess air pressure in pores, capillaries, and cells due to juice release and core-to-surface temperature. As a result of the occurrence of microbursts in the cells, 70-75% juice was released after pressing of apples due to coagulation of proteins and cell permeability.

An Efficient Model of High-Frequency Electromagnetic Field Coupling to Multiconductor Transmission Lines With the Presence of the Lossy Ground

The modeling of the high-frequency electromagnetic field coupling to multiconductor transmission lines (MTLs) is the essential subject for the protection of power lines. When the wavelength of the electromagnetic wave is smaller than the cross sections between MTLs, the response of MTLs cannot be evaluated by the classical transmission line approximation. Even though the full-wave method can deal with this problem, it is time consuming to evaluate the response of long MTLs. This article presents a theory and an efficient method to solve the problem of the high-frequency electromagnetic field coupling to MTLs with the presence of the lossy ground. The asymptotic method, adopted for its high computational efficiency, is extended to obtain the solutions of MTLs above the lossy ground. The problem is solved semianalytically using the proposed method, which is much more computationally efficient in dealing with long MTLs. Several numerical examples are presented to validate the accuracy and efficiency of the proposed method.