S. Selim Seker

GSM Base Station Electromagnetic Radiation and Oxidative Stress in Rats

The ever increasing use of cellular phones and the increasing number of associated base stations are becoming a widespread source of nonionizing electromagnetic radiation. Some biological effects are likely to occur even at low-level EM fields. In this study, a gigahertz transverse electromagnetic (GTEM) cell was used as an exposure environment for plane wave conditions of far-field free space EM field propagation at the GSM base transceiver station (BTS) frequency of 945 MHz, and effects on oxidative stress in rats were investigated. When EM fields at a power density of 3.67 W/m2 (specific absorption rate = 11.3 mW/kg), which is well below current exposure limits, were applied, MDA (malondialdehyde) level was found to increase and GSH (reduced glutathione) concentration was found to decrease significantly (p < 0.0001). Additionally, there was a less significant (p = 0.0190) increase in SOD (superoxide dismutase) activity under EM exposure.

Electromagnetic scattering from a dielectric cylinder of finite length

The dyadic scattering amplitude is determined for a planar electromagnetic wave incident on a dielectric cylinder of finite length and circular cross section under the assumption that the internal fields induced within the finite-length cylinder can be approximated by those within an infinite-length cylinder. These internal fields are then used to calculate the dyadic scattering amplitude in terms of the cylinders physical dimensions, orientation, and dielectric properties. The theoretical development is complemented by numerical calculations, and its validity assessed by comparison with experiment. >

Weighted extended b-splines for one-dimensional electromagnetic problems

This paper considers the weighted extended b-splines as basis function for finite element method in electromagnetics and compares with the standard finite element method applied to the two-point boundary value problems with different boundary conditions. This new approach, which provides more accurate results than standard finite element method, is presented to compare other numerical techniques and applied to one-dimensional electromagnetic problems. Computed results are compared with other numerical results in literature.

FEM modeling of SAR distribution and temperature increase in human brain from RF exposure

The assessment of radiofrequency exposure level and the exposure setup are critical, because if the exposure levels (related to frequency, power, position, and other variables) are not known, the biological results are not meaningful. In this regard, this study aims to design, implement, and analyze numerical setups for the simulations of radiofrequency exposure related specific absorption rate and temperature increase in the human brain and head. For this purpose, specific models for human head and telephone antenna are chosen, and the FEM is selected for solving PDEs related to electromagnetic wave equations and bioheat equation. After the verification of the methodology chosen by achieving comparable results with the literature, the scope of the study is then turned to the effects of different parameters on the exposure levels. In the end, comprehensive information can be obtained from the simulation results so that risk management policies for electromagnetic radiation can be reevaluated to minimize the possible health hazards. Copyright

Radially symmetric weighted extended b-spline model

In this paper, the weighted extended basis splines approach in the finite element method is applied to the electrostatic, electromagnetic wave and bioheat problems for inhomogeneous boundary conditions and radially symmetric structures. This new method, which does not need mesh generation, overcomes some of the drawbacks of using meshes and piecewise-uniform or linear trial functions. Two-dimensional radially symmetric electrostatic and electromagnetic wave equations are evaluated. We also attempt to propose a three-dimensional radially symmetric unexposed human eye model for simulating changes in corneal temperature using these new finite elements in conjunction with linear, quadratic and cubic b-splines. Our findings indicate that weighted extended basis spline solutions improve the standard finite element method. The simulation results which are verified using the values reported in the literature, point out to better efficiency in terms of the accuracy level.

Theoretical and experimental study of EM fields and shielding effectiveness due to high voltage transmission lines

In this study, the EM fields produced by high power 3-phase transmission lines are investigated. The dependence of the magnetic field with respect to vertical and horizontal distances from the transmission lines are illustrated and the minimum distance from the lines for human safety is specified according to ICNIRP standards. In addition, a quasi-static examination to the magnetic shielding of several enclosures are performed. In the analysis, the integral form of Maxwells equations with boundary conditions are used to derive the shielding effectiveness (SE) equations. An experiment is carried out to verify the validity of the theory developed for magnetic fields of transmission lines and the SE provided by the building. An excellent agreement is obtained for experimental and theoretical results.

Radio propagation path loss prediction of UMTS for an urban area

In this paper, three path loss models were used to predict path loss for the UMTS, in Istanbul, Turkey. Used models are Advanced Okumura-Hata model and Algorithm 9999 from the empirical path loss model class and Advanced Walfisch-Ikegami model from the deterministic path loss model class. The study concentrates on comparative parametric analysis for propagation path loss in macro cell region using different models and contains comparative study with real measurements obtained from a WCDMA based wireless network. This study concluded that among three models, the Advanced Walfisch-Ikegami model gives the best result in the urban environment for Istanbul.

Use of web-splines for waveguide of arbitrary domain

This paper illustrates web-splines and their implementations for electromagnetic problems such as waveguide of arbitrary domain. The cutoff wave numbers of modes for the coaxial waveguides are studied for illustrating the two dimensional concept. The numerical results have been compared with the analytical results. The significance of web-splines is that the number of nodes and computing time is reduced and instability problem is solved by using web-splines. The analyses presented in this study show the suitability of proposed method to complex electromagnetic problems. The finite element method which uses web-splines is applied to coaxial waveguides. With different ratio of radius of coaxial waveguides, accurate results are obtained by using web-splines. Web-splines and extended b-splines are used to find the wave number of TM and TE mode respectively.

UHF ray tracing propagation model for corridors

Wave propagation for rectangular corridors is studied. Ray theory and uniform theory of diffraction (UTD) were combined to predict wave strength. The model was checked doing measurements at 1 GHz. The results show good agreement between theory and measurements for different locations. Since some parts of corridors have different properties (e.g. constructed by glass, wood and/or cement, etc.). We prepared a useful database considering all possible effects at any point of reflection

Modeling of snow attenuation at mobile frequencies

Snow attenuation depends on many factors which are hard to observe and identify or classify. Modeling of snow attenuation is relatively complex. There are two main classes of methods used in snow attenuation prediction: the empirical method and the physical method. Physical method which we used in this work focuses on reproducing the physical behavior of factors involved in the process. The attenuation in the frequencies of mobile communication due to snow is simulated using Discrete Propagation Model. For this modeling, certain ice-crystal categories are chosen to be investigated. Needles, plates and branches are the main 3 groups which are focused, and 13 different models of snow particles in total are chosen to represent snow. The element in each group is chosen according to similar physical characteristics of ice crystal. It was found that attenuation due to snow is higher than rain attenuation specifically due to differences in particle size. In our simulations, frequencies of GSM communication, 900MHz, 1800MHz and 2270MHz, are used for calculation of attenuation.