Nenad Cvetković

Electric field distribution and SAR in human head from mobile phones

This paper presents the distribution of electric field inside a human head as well as around the electromagnetic field source, i.e. the mobile phone. Specific Absorption Rate (SAR), which is obtained inside a human head and the thermal effect due to exposure to electric field from mobile phone was presented. For this research two different models of human head have been used. In the first case electromagnetic parameters of biological tissues of human head were modeled with a volumetric interpolation function that estimates the characteristics of a given tissue inside the human head while in the second case model with layers was used. The layers represent human head parts (skin, fat tissue, muscles, the skull, and the brain). The parts of the human head are based on their electromagnetic properties (conductivity, electric permittivity, and magnetic permeability). In order to obtain the electric field distribution for different cross-sections, the numerical calculation based on the Finite Integration Technique (FIT) and Finite Element Method (FEM) was performed.

Model for Analyzing a Pillar Grounding System with Cylindrically-Shaped Concrete Foundation

Abstract Unknown currents along the pillar grounding systems wire conductors are determined in this article. The system consists of a vertical wire electrode inside the cylindrical concrete foundation and a ring electrode fed by two earthing conductors. The article includes one simple procedure for modeling the influence of a concrete cylinder surrounding a vertical ground electrode on a grounding system, which reduces this problem to analysis of an equivalent single wire in the homogeneous ground. Unknown currents of polynomial form are determined, solving the integral equation system using the Method of Moments. Afterward, self-, mutual, and total impedances of the system are determined.

Predicting the Biological Effects of Mobile Phone Radiation Absorbed Energy Linked to the MRI-obtained Structure

The nature of an electromagnetic field is not the same outside and inside a biological subject. Numerical bioelectromagnetic simulation methods for penetrating electromagnetic fields facilitate the calculation of field components in biological entities. Calculating energy absorbed from known sources, such as mobile phones when placed near the head, is a prerequisite for studying the biological influence of an electromagnetic field. Such research requires approximate anatomical models which are used to calculate the field components and absorbed energy. In order to explore the biological effects in organs and tissues, it is necessary to establish a relationship between an analogous anatomical model and the real structure. We propose a new approach in exploring biological effects through combining two different techniques: 1) numerical electromagnetic simulation, which is used to calculate the field components in a similar anatomical model and 2) Magnetic Resonance Imaging (MRI), which is used to accurately locate sites with increased absorption. By overlapping images obtained by both methods, we can precisely locate the spots with maximum absorption effects. This way, we can detect the site where the most pronounced biological effects are to be expected. This novel approach successfully overcomes the standard limitations of working with analogous anatomical models.

Influence of foundation on pillar grounding system's characteristics

Purpose – The purpose of this paper is to estimate influence of the pillar concrete foundation approximated by a semiconducting semi‐sphere on the pillar grounding system.Design/methodology/approach – Unknown current distributions and impedance of pillar grounding system, which consists of a ferro armature modelled as a single electrode inside concrete foundation, ring electrode and two earthing conductors, are determined in this paper. Concrete foundation is approximated by a semi‐spherical semiconducting inhomogeneity. The expressions for electric scalar potential are formed using the quasi‐stationary image theory, including a recently proposed Greens function for the point source in the presence of a semiconducting sphere. Based on the quasi‐stationary antenna model, unknown currents are determined solving the system of integral equations using the moment method and polynomial approximation for current distributions.Findings – The influence of inhomogeneity is not negligible for real values of specifi...

Assessment of emissions from electrical equipment regarding human exposure — Approaches for application of the generic standard IEC 62311

In a lot of countries and regions there are requirements regarding electromagnetic emissions from electrical equipment. Such emissions can be looked at under two aspects: the emissions might interfere with other equipment in the vicinity causing potential malfunction (EMC aspect), or might be considered with regard to human exposure (EMF aspect). Limitation of such emissions related to the EMC aspect is part of EMC activities and is mostly due to the need to protect radio services from being interfered. Applicable limits depend on the type of equipment under concern and of the locations where equipment is intended to be operated. However, more and more such emissions are looked at also under a human exposure point of view within the frame of EMF regulations. As both aspects deal with entirely different objective targets consequently different limits, different measurement procedures and different assessment methods are to be applied. This could mean in practice that basically two kinds of measurements have to be carried out. This paper introduces an approach how to use results obtained by means of EMC measurements for the purpose of EMF assessments. As an example for an assessment the EMC data in the frequency range between 30 MHz and 230 MHz are used as part of an EMF assessment.

Square-shaped electrode as pillar grounding system

The pillar grounding system formed of a basic horizontal linear ground square-shaped electrode and an iron armature connected to the main grounding connector is analyzed in the paper. During analysis, a recently proposed procedure for modelling the influence of a concrete cylinder on a grounding system is used. Afterwards, the system of integral equations having leakage currents¿ distributions as unknowns is solved.

Current Distribution and Impedance of Ring Electrode Pillar Grounding System: Quasistationary Antenna Model

Unknown current distributions (UCDs) and grounding impedance of horizontal linear ground ring electrode fed by two earthing conductors are determined in this paper. The position and shape of earthing conductors corresponds to practical realization of such system. In order to solve this problem, quasistationary antenna model of linear grounding system (LGS) is formed. Based on this model UCDs are determined by numerical solving of the system of integral equations using method of moments (MoM) and entire domain polynomial approximation for UCDs. Afterwards, the LGS impedance and electric scalar-potential (ESP) distribution at the ground surface in the pillar surrounding are determined.

FEM analysis of single-phase electromechanical meter at non-sinusoidal power supply

In this paper, the transient magnetic model of single-phase electromechanical meter using FEM is designed. Different power supply regimes of non-sinusoidal voltage and current waveforms were analysed with the considered impact of higher harmonics. Single-phase electromechanical electricity meters based on the principle of Ferraris energy meter for FEM application and as a source of measured data that can then be validate and compared with the simulation results are used in educational purpose.

Thermal effects on human head from mobile phones

The subject of this paper is monitoring of thermal effects on human head from mobile phones. In this paper temperature distribution and SAR at surface of human head close to source of electromagnetic radiation are shown. Results of simulation were compared with experimental results obtained with thermal imaging camera.

Modelling of hemispherical ground inhomogeneities

The influence of a semi-conducting hemispherical inhomogeneity on ground electrode placed inside of it, is analyzed. The applied procedure is based on a recently proposed approximate Greens function for the point source inside a semiconducting hemisphere. The results are compared with those obtained by other two different models based on application of the boundary elements method, i.e. the Greens function for the point source inside a double-layered hemispherical inhomogeneity.