Pojednostavljena elektromagnetsko-toplinska analiza izloženosti ljudi zračenju antena baznih stanica

Electromagnetic-thermal analysis of the human body exposed to base station antennas radiation is presented in this paper. The formulation of the problem is based on a simplified cylindrical representation of the human body. Electromagnetic part of the analysis involves incident and internal field dosimetry, while the thermal model deals with the bio-heat transfer processes in the body. The electric field induced in the body is determined through the corresponding axial current induced in the body. This current distribution along the body is obtained by solving the Pocklington integral equation for a thick cylinder. The Pocklington integral equation is solved numerically via the Galerkin-Bubnov Boundary Element Method (GB-BEM). Once the internal electric field and related total absorbed power in the human body is obtained, it is possible to calculate a corresponding temperature rise in the body due to the GSM exposure. This temperature rise is determined by solving the bio-heat transfer equation via the conventional finite element method (FEM).U ovom radu izložena je elektromagnetsko-toplinska analiza ljudskog tijela izloženog zračenju antena baznih stanica. Formulacija problema zasniva se na cilindričnom modelu ljudskog tijela. Elektromagnetski dio analize uključuje dozimetriju upadnog i unutarnjeg polja, dok se toplinskim modelom opisuje prijenos topline u tijelu. Električno polje inducirano u tijelu određuje se preko struje inducirane u tijelu. Raspodjela struje uzduž tijela dobivena je rješavanjem Pocklingtonove integralne jednadžbe za »debeli« cilindar. Pocklingtonova integralna jednadžba numerički je riješena primjenom Galerkin-Bubnove metode rubnih elemenata. Jednom kada je dobiveno unutarnje električno polje i ukupna snaga apsorbirana u tijelu, moguće je izračunati odgovarajući porast temperature u tijelu zbog izloženosti GSM zračenju. Ovaj porast temperature određuje se rješavanjem bio-toplinske jednadžbe primjenom metode konačnih elemenata

An Improved Algorithm for Indirect Time domain Analysis of Thin Wire Structures

The algorithm for an indirect time domain (TD) analysis using arbitrary frequency domain method is presented. In previous work, an optimized version of the indirect timedomain method based on adaptive sampling iterative algorithm used in combination with inverse Fast Fourier Transform (FFT) was presented. In this paper, the algorithm is further improved by circumventing the use of inverse FFT altogether, and using the simple formula based on the analytical inverse Fourier transform. The proposed approach is simpler and more convenient for use with the underlying iterative optimization method, as only a part of the frequency domain (FD) signal has to be transformed to the time domain during each iteration procedure, the frequency domain discretisation does not have to be uniform, and the time domain discretisation does not have to be performed. These advantages can also lead to the reduced computational time cost of the frequency to time domain transformation when compared with the standard inverse FFT

Assessment of Transmitted Power Density in the Planar Multilayer Tissue Model due to Radiation from Dipole Antenna

Recent relevant safety guidelines IEEE-Std C95.1- 2019 and ICNIRP-RF Guidelines 2020 have converged towards 6 GHz as a transition frequency from specific absorption rate (SAR), as basic restriction quantity, to absorbed power density (APD). Namely, the penetration of electromagnetic waves into the human tissue rapidly decreases as frequency increases, therefore, tissue heating can be considered as superficial above 6 GHz. However, besides the APD, an alternative internal dosimetric quantity transmitted power density or TPD is sometimes computed since its relation to SAR is more obvious and is easier to obtain. This paper deals with an analytical/numerical approach to determine TPD in planar multi-layered model of the human tissue exposed to the dipole antenna radiation. Analytical approach deals with assumed sinusoidal current distribution, while numerical approach pertains to the determination of current by solving the corresponding Pocklington integro-differential equation via Galerkin-Bubnov Indirect Boundary Element Method. The novelty presented in this paper with respect to previous work is a multilayer geometry whose effects are considered via the corresponding Fresnel plane wave reflection/transmission approximation. Some illustrative results for current distribution, transmitted field, volume power density (VPD) and TPD at various frequencies and distances of the antenna from the interface are given

Simple analytical models for the calculation of the electric field radiated by the base station antenna

This paper outlines four different models for the assessment of the electric field radiated by the base station antenna system, thus featuring the Free Space Model (FS), Perfect Ground Model (PG), Fresnel Reflection Coefficient Model (RC) and Modified Image Theory Model (MIT). The results obtained with these approaches are compared to the results computed via Numerical Electromagnetics Code (NEC). Several variables have been varied to examine the accuracy of each calculation model. The calculations have been undertaken for the far field only. As many European countries perform the field assessment using the FS model, the final goal of this work is to come up with the most convenient model for the field calculation

Exposure to Non-Ionising Electromagnetic Fields from Extremely Low to Microwave Frequencies

U radu se razmatra izloženost čovjeka elektromagnetskim poljima od ekstremno niskih do mikrovalnih frekvencija. Ljudsko tijelo predstavljeno je realističnim računalnim modelima u smislu geometrije i električnih svojstava organa. Modeli na niskim frekvencijama temelje se na kvazistatičkim aproksimacijama, Laplaceovoj jednadžbi i numeričkome modeliranju primjenom metode rubnih elemenata. Modeli na visokim frekvencijama zasnovani su na cjelovitom elektromagnetskome modelu i odgovarajućoj Helmholtzovoj jednadžbi. U radu se razmatraju primjeri vezani za izloženost glave čovjeka elektrostatskom polju monitora, izloženost trudnice i fetusa poljima niskih frekvencija te izloženost oka mikrovalnim frekvencijama. Dobiveni rezultati upućuju na činjenicu da su pod nekim ekstremnim okolnostima mogući scenariji u okviru kojih karakteristični parametri polja prelaze granične vrijednosti propisane domaćom i međunarodnom legislativom. Primjerice, prilikom izloženosti trudne žene električnom polju dalekovoda, u fetusu se inducira višestruko veća gustoća struje od vrijednosti koja se inducira u mozgu trudnice. U radu su nadalje opisani mehanizmi interakcije elektromagnetskih polja s ljudskim tijelom. Nakon toga iznesene su dosadašnje spoznaje vezane za biološke učinke polja ekstremno niskih frekvencija i radio-frekvencija. Također su raspravljene zaštitne mjere vezane za međunarodne i domaće sigurnosne smjernice i granice izloženosti.This article describes a simulation method to assess human exposure to electromagnetic fields (EMF) from extremely low to microwave frequencies. Human body is represented by realistic computational models taking into account the geometry and electrical properties of organs. Low frequency models are based on quasistatic approximations, Laplace equation, and related numerical modelling via the boundary element method. High frequency models are based on the full wave model and the corresponding Helmholtz equation. The articles gives examples of computational models for the human head exposed to a video display unit, for a pregnant woman and foetus exposed to low frequency fields, and for the human eye exposed to microwave frequencies. In extreme scenarios, external and internal field levels exceed national and international tresholds. For example, pregnant woman exposure to power line electric fi eld causes several times higher values of current density in the foetus than the internal current density in the female brain. The article also discusses the interaction between EMF and human body and presents new fi ndings on biological effects of extremely low and high frequency EMF. It concludes with a discussion about protection measures required by international and national safety guidelines and exposure limits

Current Density Induced in the Human Body due to Power Distributions Lines using the Boundary Element Method

The paper presents the human exposure assessment to Extremely Low Frequency fields (ELF) by means of the three dimensional Boundary Element Method (BEM). The formulation is based on a rather realistic representation of the human body. The paper analizes the response of the density current due to variations on the detail of the conceptual model considered. Variations on the geometry model and the inclusion of organs have been considered. The results obtained with and without considering the rough representations of the internal organs were compared. This comparison allows to estimate their relevance in numerical modellings at ELF

Numerical comparison of compound and extracted eye models for high frequency dosimetry

This paper compares the numerical results for the induced electric field, the specific absorption rate (SAR), and the corresponding temperature increase in two detailed models of the human eye. The first model features the human eye placed in the free space, while the second one incorporates the eye model in the realistic head model obtained from the magnetic resonance imaging (MRI) scans. The electromagnetic model is based on the hybrid FEM/BEM formulation for the biological tissue, whereas the thermal dosimetry model is based on the bioheat equation solved by using the finite element method. The preliminary analysis showed a similar distribution of the induced electric field along the pupillary axis obtained in both models, however, the numerical results for the SAR and related temperature increase showed discrepancy between the two models, which can be attributed to the high values of induced field in the corneal and scleral regions obtained in the compound eye model

A note on the use of analytical and domain discretisation methods for the analysis of some phenomena in engineering physics

The paper reviews some applications of the well-established analytical and domain discretisation methods (finite difference method-FDM, finite element method-FEM) in the modelling of the magnetohydrodynamics (MHD) phenomena for the fusion-related research and quantum structures for use in nanodevices. Hence, Grad-Shafranov Equation (GSE) for the plasma equilibrium has been implemented for certain simple excitation forms, and the results obtained for the rectangular plasma have been presented. Furthermore, the stationary Schrödinger equation is solved analytically and numerically via FDM and FEM, respectively

Frequency and Time Domain Analysis of Influence of the Grounding Electrode Conductivity on Induced Current Distribution

The paper deals with an assessment of the influence of finite conductivity to the current induced along the horizontal grounding electrode. Analysis is performed in frequency and time domain, respectively. Current distribution along the grounding electrode buried in a lossy half-space is determined via analytical solution of the corresponding Pocklington equation in the frequency domain. The corresponding time domain response is obtained by means of Inverse Fast Fourier Transform (IFFT). The electrode is excited via an equivalent current source. Presence of the earth-air interface is taken into account via the simplified reflection coefficient arising from the Modified Image Theory (MIT). The electrode current is calculated for the case of perfectly conducting (PEC) electrode and for the electrodes made of copper and aluminum. Comparison of results shows no significant discrepancy between these electrodes, justifying the use of a PEC electrode approximation

Ostvarivanje zakonske politike kažnjavanja u praksi Županijskog suda u Osijeku kao drugostupanjskog suda u razdobljima 1993.-1997. i 1998.-2002.

Autori u radu iznose rezultate istraživanja odnosa zakonske politike kažnjavanja i politike kažnjavanja Županijskog suda u Osijeku kao drugostupanjskog suda za odabrana kaznena djela u dva petogodišnja razdoblja: od 1993. do 1997. i od 1998. do 2002. Rezultati pokazuju da između promatranih razdoblja nema bitnih razlika sa stajališta intenziteta primjena kaznenopravne prisile, iako je Kazneni zakon iz 1997. upravo kod analiziranih djela značajno ublažio kaznene okvire. Takva promjena ipak je pridonijela većoj iskorištenosti kaznenih okvira, a time i utjecala na postupno približavanje zakonske i sudske politike kažnjavanja