Computation of electromagnetic fields

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Computation of transient electromagnetic fields due to switching in high voltage substations

Computation of transient electromagnetic fields due to switching in high voltage substations

Abstract—Switching operations of circuit breakers and discon- nect switches radiate transient electromagnetic fields within high- voltage substations. The generated fields may interfere and dis- rupt normal operations of electronic equipment. Hence, the elec- tromagnetic compatibility (EMC) of this electronic equipment has to be considered as early as the design stage of substation planning and operation. Also, microelectronics are being introduced into the substation environment and are located close to the switching de- vices in the switchyards more than ever before, often referred to as distributed electronics. Hence, there is the need to re-evaluate the substation environment for EMC assessment, accounting for these issues. This paper deals with the computation of transient elec- tromagnetic fields due to switching within a typical high-voltage air-insulated substation (AIS) using the finite-difference time-do- main (FDTD) method.
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A new submodelling technique for multi-scale finite element computation of electromagnetic fields: application in bioelectromagnetism

A new submodelling technique for multi-scale finite element computation of electromagnetic fields: application in bioelectromagnetism

Submodelling is the common approach which is successfully used in computational mechanics [6] in order to reduce the time of computation with almost no loss of accuracy of the solution. Currently existing technique involves the improvement of the solution, for example stress concentration values at the points of interest and works only in one direction, from the large scale (coarse model) to the lowest scale (stress concentrator). Our new approach is designed in order to be implemented in electromagnetic problems where the solution must be improved not only at the points of interest but also in full computational domain.
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Network models of three dimensional electromagnetic fields

Network models of three dimensional electromagnetic fields

One of the oldest techniques for electromagnetic field analysis and computation relies on magnetic and/or electric field equivalent circuits. Historically such circuits tended to be simple with few degrees of freedom due to limitations to available computing power and memory; notwithstanding, these methods are still helpful in providing efficient estimates of global parameters and are used for teaching purposes as they are well based physically and avoid complicated mathematical descriptions. They are also used in real time simulations and for analysis of complex structures. Dramatic increases in computer speed and available memory have removed many restrictions and progressively more accurate models are being used based mainly on the finite element (FE) formulations.
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An Electroscalar Energy of the Sun: Observation and Research

An Electroscalar Energy of the Sun: Observation and Research

The longitudinality of the wave imposes certain requirements on the action of the field, particularly, on such a property of the field as the superposition principle. The equations for the electromagnetic field (Maxwell equations) contain only the equations for the full charge conservation (equations of continuity) but not the equations of motion for the field producing charges. In the case of the electromagnetic field, the distribution and motion of charges can be specified arbitrarily provided that the full charge is conserved. The character of the charges' distribution is determined then by solving the Maxwell equations using the field produced by the charges. As experience shows, the electromagnetic field obeys this principle which implies that if a charge produces a field, and another charge produces another field, then the total field is a result of superposition of these fields. Such a superposition principle will be referred to as the method of transverse summation of fields. The equations of motion of the electroscalar field contain not only the equations of continuity and full charge conservation, which cannot be determined arbitrarily. But the field itself and the charges' motion must be determined concurrently with the field of the produced charges’ field. The principle of superposition of the electroscalar field is longitudinal as summation of the fields’ charges occurs only for those located along the line between the charges. This means that the strengths of the resultant electroscalar fields at each point are equal to a sum of the strengths of all the longitudinal fields at this point. Any solution of equations for these fields is a field that can be realized in nature and, consequently, must obey the electroscalar field equations. In the electroscalar field the distribution of charges and their motion must be defined by solving field equations with given initial conditions for the longitudinal superposition of charges. Thus, while
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A Review of Electromagnetic Activity in Cellular Mechanics

A Review of Electromagnetic Activity in Cellular Mechanics

The implication of the title is that electromagnetic effects are not only important but also essential in cellular mechanics. Unfortunately, however, the electromagnetic effects are often omitted, or not discussed in depth, in biology papers and books. But upon a close examination of intracellular mechanics, and in particular with the centrioles, the presence of electromagnetic forces is evident. Perhaps the most persuasive evidence is the observed forces exerted at a distance during centriole pair separation and during mitosis via the kinetochores [3]-[6].

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Implementation of Acoustic Analogies in OpenFOAM for Computation of Sound Fields

Implementation of Acoustic Analogies in OpenFOAM for Computation of Sound Fields

∂ (2.22) and its principle behavior is similar to boundary conditions for compressible fluid flow, which is often used for transonic or supersonic simulations. The advective or waveTransmissive boundary condition are applicable on patches defined as outlet only. For a lot of cases these might be insufficient. To overcome this limitation the in this work the computation domain boundary patches are set up as stated in [17]. According to their and Goldsteins [18] proposal the boundary value method is used for several simulation cases. Therefore in inviscid flows the RHS of Equation (2.7) might be set to zero on patches, if the flow velocity on that patches might be neglected.
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Computation of electric fields in and around high voltage insulators.

Computation of electric fields in and around high voltage insulators.

coincided with the conductor surface. Using the process of successive images, Sarma and Janischewskyj calculated the electric field around the bundle conductors. The ground effect was taken into account by placing images of line charges below the ground plane. Although the values of electric field obtained by this method were accurate for higher ratios of r/2s (r = radius of cylinder, 2s = distance between line charge and the centre of the cylinder), the number of line charges required to simulate the parallel conductor system became very large for the electric field computation for bundle conductor transmission lines.
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Impact of electromagnetic fields on morphogenesis and physiological indices of tomato

Impact of electromagnetic fields on morphogenesis and physiological indices of tomato

In the first stage of research, tomato apical meristem zones were affected by electromagnetic fields during the whole vegetation period. The investigated electromagnetic fields stimulated the development of plants, but their impact depended on the organogenesis stages. Seedlings developed rapidly and grew up the highest when they were affected by the electromagnetic field of the power of 1500 Am -1 (~H) (Table 1). Such plants, also, formed the biggest leaf area (Stašelis et al., 2000a). According to other data, such electromagnetic fields did not have any impact on the 1,0
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Aspects of electromagnetic radiation reaction in strong fields

Aspects of electromagnetic radiation reaction in strong fields

In parallel with the motivation provided by the advent of ELI and other planned large-scale facilities, it is worth noting that radiation reaction in strong fields has also received much attention from the gravitational physics community during recent years [5]. Understanding the behaviour of inspiralling black hole binary systems requires efficient and accurate numerical methods for modelling strong-field gravitational radiation reaction, and such work is vital for the development of matched filters (templates) used to extract information from a binary system’s gravitational wave emission. Some of the recent progress in electromagnetic radiation reaction [6] has been made as a consequence of modern interest in the gravitational radiation reaction of extreme-mass-ratio binary systems.
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Electromagnetic Fields of Lightning Return Strokes- Revisited

Electromagnetic Fields of Lightning Return Strokes- Revisited

Now, we are in a position to write down the expressions for the electromagnetic fields. The electromagnetic fields generated by the channel element can be divided into different components as follows. (a) The electric and magnetic radiation fields generated at the initiation and termination of the current at the end points of the channel element due to charge acceleration and deceleration, respectively. (b) The electric and magnetic velocity fields generated by the movement of charges along the channel element. (c) The static field generated by the accumulation of charges at the two ends of the channel element. Let us consider these different field components separately. In writing down these field components, we will depend heavily on the results published previously by Cooray and Cooray [10, 11]. The field expressions identified by Equations 12 to 23 can be constructed easily from the results presented in [10].
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Unified Theory of Force Fields (Electromagnetic and Gravitational)

Unified Theory of Force Fields (Electromagnetic and Gravitational)

In this paper, the superfluid substance is described by the same equations of the electromagnetic field and the gravitational field. The gravitational mass is sufficiently considered as the gravitational charge, having the same dimen- sions as electric charge.

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Interaction of Medical Implants with the MRI Electromagnetic Fields

Interaction of Medical Implants with the MRI Electromagnetic Fields

the MR electromagnetic fields is important. Two of the MR fields, the static magnetic field and the pulsed gradient fields do not show any appreciable interaction with an implant that does not contain any magnetic materials [1]. The main interaction is with the third field, the MR radiofrequency (RF) field. The scattered RF field that is produced causes heating of the tissue surrounding the implant. The tissue around the ends of implanted leads is especially prone to this RF — induced heating. This is due to the waveguiding effect that occurs in the insulation surrounding any long metal wire in a lead implant. Electromagnetic wave energy propagates in the insulation and is conveyed to the ends of the lead where it dissipated as heat in tissue. The temperature rises that result can be found by in-vitro measurements made in phantoms. Alternatively, electromagnetic fields can be computed using a numerical method such as the method of moments (MoM) [1, 2], or the finite difference time domain (FDTD) method [3, 4], or the finite element method (FEM) [5, 6]. Leads are often implanted below the skin and the implantation depth can vary. The present paper investigates the interaction of the MRI RF field with leads at various implantation depths, an aspect that has not been examined thoroughly before.
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ENERGY MOMENTUM TENSOR OF DYONS

ENERGY MOMENTUM TENSOR OF DYONS

Where E and H are the electric and magnetic fields, respectively. The energy momentum tensor is the conserved Noethern current associated with space-time translations. When gravity is negligible and using a Cartesian coordinate system for space-time, the divergence of the non-gravitational energy momentum will be zero. In other words, non-gravitational energy and momentum are conserved

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Nondrug Antimicrobial Techniques: Electromagnetic Fields and Photodynamic Therapy

Nondrug Antimicrobial Techniques: Electromagnetic Fields and Photodynamic Therapy

Developing nondrug antimicrobial and antibacterial treatment techniques are necessary because of the emergence of antibiotic resistance worldwide. Photodynamic therapy (PDT) and electromagnetic therapy (EMFT) are two examples of these approaches. Antimicrobial photodynamic therapy is a novel and promising technique that involves the simultaneous presence of visible light, oxygen and a photosensitizer (PS). It can be applied for eradicating pathogenic microorganisms such as Gram-positive and Gram-negative bacteria, yeasts and fungi. Moreover, electric fields, magnetic fields and pulsed EMFs (PEMFs) are common approaches showing promising antimicrobial effects. These treatments can be used as alternative or adjunctive treatment for some infections. This paper reviews the recent developments and basic principles of nondrug antimicrobial techniques focusing on EMFs and PDT techniques. The future perspectives of these techniques as well as clinical considerations are discussed.
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Evaluation of the Exposure to Electromagnetic Fields in Computer Labs of Schools

Evaluation of the Exposure to Electromagnetic Fields in Computer Labs of Schools

Computers, like most of electrical appliances, emit both ionizing and non ionizing radiation [8]. Most critical device in respect of electromagnetic radiation is com- puter video display unit (VDU); most of them in our country still are of cathode ray tube (CRT) type. A VDU emits in almost the entire electromagnetic spectrum [9]. The optical radiation emitted includes visible light (VIS) which forms the image that the VDU is intended to pro- duce; very small amounts of ultraviolet (UV) are emitted from the tube; infrared (IR) appears as heat dissipated by

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A Second Order Eigen Theory for Static Electromagnetic Fields

A Second Order Eigen Theory for Static Electromagnetic Fields

In this paper, we construct the standard spaces under the physical presentation by solving the eigen-value problem of the matrixes of dielectric permittivity and magnetic permeability, in which we get the eigen dielectric per- mittivity and eigen magnetic permeability, and the cor- responding eigen vectors. The former are coordinate- independent and the latter are coordinate-dependent. Be- cause the eigen vectors show the principal directions of electromagnetic media, they can be used as standard spaces. Based on the spaces, we get the modal equations of static electromagnetic fields by converting the classi- cal Maxwell’s vector equation to the eigen Maxwell’s scalar equation, each of which shows the existence of an static electromagnetic field. For example, there is only one kind of static electromagnetic field in isotropic crys- tal, which is identical with the classical result; there are two kinds of static electromagnetic fields in uniaxial crystal; three kinds of static electromagnetic fields in biaxial crystal and three kinds of distorted static electro-
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Dimensionality of random light fields

Dimensionality of random light fields

Since D ( r, ω) is generally not an integer, it should not be identified as such with the actual physical dimensionality of the light [specified by Eqs. (4)–(6)], but as an effec- tive dimension characterizing the intensity-distribution spread. Figure 1 provides an interpretative illustration for the polarimetric dimension, in which principal-intensity distributions for three different 3D light fields have been depicted. In the left panel a 1 is significantly larger than

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Evaluation of the diffusion equation for modeling reverberant electromagnetic fields

Evaluation of the diffusion equation for modeling reverberant electromagnetic fields

Abstract —Determination of the distribution of electromagnetic energy inside electrically large enclosed spaces is important in many electromagnetic compatibility applications, such as certification of aircraft and equipment shielding enclosures. The field inside such enclosed environments contains a dominant diffuse component due to multiple randomizing reflections from the enclosing surfaces. The power balance technique has been widely applied to the analysis of such problems; however, it is unable to account for the inhomogeneities in the field that arise when the absorption in the walls and contents of the enclosure is significant. In this paper we show how a diffusion equation approach can be applied to modeling diffuse electromagnetic fields and evaluate its potential for use in electromagnetic compatibility applications. Two canonical examples were investigated: A loaded cavity and two cavities coupled by a large aperture. The predictions of the diffusion model were compared to measurement data and found to be in good agreement. The diffusion model has a very low computational cost compared to other applicable techniques, such as full-wave simulation and ray-tracing, offering the potential for a radical increase in the efficiency of the solution high frequency electromagnetic shielding problems with complex topologies.
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Radiofrequency	Electromagnetic	Fields: Carcinogenic and Other Biological Effects

Radiofrequency Electromagnetic Fields: Carcinogenic and Other Biological Effects

In the electromagnetic spectrum, structural damage to living tissues per unit of absorbed energy tends to increase with the decrease of a wavelength which is evident not only for ultraviolet and ionizing radiation but also for the infrared and visible light. By causing thermal damage after absorbing energies that would be harmless for radiofrequency electromagnetic fields (EMF), tissues are evenly heated. There are no prima facie reasons to expect more damage from EMF than from infrared radiation which is believed to be harmless in terms of thermal damage. Several studies reported possible associations between EMF, glioma and other tumors. Other research did not confirm such associations or even identified a reduced risk of brain tumors among mobile phone (MP) users. An elevation in the application of MP has been observed in some countries and age groups which is out of proportion. Improving imaging technology and access to health care units have contributed to an increased incidence rate. Bias is known to occur in epidemiologic research. At the beginning of the MP era, the use of MP was associated with a high income which, in turn, must be associated with better diagnostics results. Admittedly, nowadays MPs are affordable for the majority of people and it is unclear whether the socioeconomic bias still plays a significant role. In conclusion, there is neither compelling evidence nor theoretic plausibility for the concept that EMF is more harmful than infrared radiation per unit of absorbed energy.
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Health hazards from mobile phone transmission towers

Health hazards from mobile phone transmission towers

This relation represents the rate at which the electromagnetic energy is converted into heat through well-established interaction mechanisms. It provides a valid quantitative measure of all interaction mechanisms that are dependent on the intensity of the internal electric field (Kumar et al., 2010). The amount of heating produced in a living organism depends primarily on the intensity of the radiation once it has penetrated inside the body. Specific absorption rate (SAR) is the most appropriate metric for determining such exposure near the fields of such radiation sources. This SAR also varies with the dimension of tissues (Abdal et al., 2006, Sirav, 2009). The absorbed microwave energy produces molecular vibration and converts the energy into heat. If the organism cannot dissipate this heat is produced, the internal temperature of the body will rise. This heat may damage these biological tissues permanently. Microwave frequency for which the wavelength are of the same magnitude as the dimensions of the human body produce close coupling between the body and microwave field. A large number of heats can be generated to cause severe damage in the body. Such effect of microwave is termed as ‘thermal effect’.
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