Octavian Baltag

Study of the knitted structures with different designs used for electromagnetic shielding

This paper describes an investigation of the knitted structures with different design used for electromagnetic shielding. The long-term exposure to electromagnetic waves can have harmful effects on human body. It is necessary to find solutions for protection against electromagnetic fields. Different types of knitted structures were practically accomplished on flat manual knitting machine using Bekinox yarns and the results show shielding effectiveness that fulfill this aim.

Investigation of the textile structures with different design used in electromagnetic shielding

This paper describes a study on the development of few textile structures and the possibility to use them in electromagnetic shielding and protection equipment manufacturing. The long-term exposure to electromagnetic waves can seriously damage a persons health. The goal of this research is: to evaluate the implementation possibilities of new materials and composite structure (using amorphous magnetic materials, carbon powders stainless steel yarns and copper yarns), and also to achieve a protective composite textile material with absorbing properties, in order to protect human body and residential areas. Conductive materials have different absorption and reflection behaviors: metals are known for having high reflectivity, whereas carbon fibers and conductive polymers are known for having a high absorption behavior. This general trend was also observed in the results obtained. Conventional textile materials are not suitable for this purpose, but their modification and transformation in composites or other type of structures can be useful.

Bioelectromagnetism laboratory - Case study

The paper presents a case study concerning the emplacement of a laboratory dedicated to bioelectromagnetism researches. It also shows the complex structure of the laboratory and related facilities. Laboratory research is designed in two frequency ranges of magnetic and electromagnetic fields: (0-500) Hz frequency range, explored by biomagnetometry and very low energy electromagnetic radiation corresponding to thermal radiation in the microwave range.The installation components consisting of a nonferromagnetic shielded room, lined inside by microwave absorbent material with pyramidal geometry and a complex triaxial coils system to control the ambient magnetic fields: geomagnetic components and those due natural variations, the fields produced by human activity - the movement of masses of metal, vehicles, magnetic field of 50 Hz etc. The installation permits the detection of magnetic activity of the heart (magnetocardiogram - MCG) and the measurement of the internal temperature of living structures using the microwave radiometry. This is an application for non-invasive early breast cancer detection. Performances of the installation are presented.

The MCG Filtering Based on the Phase Diagram Representation Domain

The magneto-cardiogram (MCG) records the magnetic field generated by the hearts electrical activity. The major advantage of this measurement is its non invasive character as well as the accuracy and resolution compared to the electro-cardiogram (ECG). Still its drawbacks., in terms signal measurement., are its values., which are very small order of pT, which are comparable to noise level. Hereby., the MCG signal has an increased level of noise., making difficult the characterization part. We propose the use of a non-linear filtering method., the phase diagram representation., which has the advantage that it is a data-driven method., therefore., filtering the signal without any assumption about the system.

Magnetic field of parallel and twisted wire pairs

This paper presents a study of the magnetic fields produced by electrical conductors carrying electric current in two situations: two power cables in a parallel configuration and in a twisted configuration. Analytical relationships are shown on the magnetic field of the two configurations relative to the field produced by a single conductor. Analytical results are compared with the results of numerical simulations.

Comparison of signal processing methods applied on a magnetocardiographic signal

This paper describes the process of first recording in Romania of a biomagnetic signal generated by the cardiac activity of an adult heart. Simultaneously, there was recorded the ECG signal for the same subject. In the recorded magnetocardiogram there are found perturbance components, which are due to external stray fields (50 Hz). The processing of the obtained signal was carried out by software and hardware means (primary magnetometer signal processing by a method of electronic subtraction, with reduction of the 50 Hz components). The signal is then processed by several methods and software tools: coherent averaging and Wavelet in LabView, FFT Fourier analysis and filtering components in Matlab, through successive low-pass and stop band filters.

Shielding Efficiency of a Fabric Based on Amorphous Glass-Covered Magnetic Microwires to Radiation Emitted by a Mobile Phone in 2G and 3G Communication Technologies

Abstract A dual band mobile phone model was used to check the shielding properties of an amorphous ferromagnetic textile against the radiation emitted by the handset. Two frequencies belonging to the 2nd and 3rd generation of mobile emission technologies were used, 897 MHz and 1950 MHz. The specific absorption rate (SAR) of energy deposition in a human head phantom was measured in standardized conditions. The textile contained micrometric-diameter wires of a ferromagnetic mixture embedded in a thin glass coat and weaved in a specific way. A set of fabric orientations and configurations (layering) were provided in the experiment in order to achieve a better shielding to the phone’s radiation. Compared with the non-shielded handset, SAR deposited in the head while using the fabric-covered phone could be decreased up to 30 % of its initial value – in case of 2G technology and up to 24 % – in case of 3G technology. This type of material shows one of the highest shielding efficiencies of the electric-field component in near-field exposure conditions reported until now. A cubic curve of SAR decrease in depth of the head was revealed in both uncovered and covered handset, the effect of shielding being larger at the higher frequency.

Aspects regarding the occupational and non-occupational exposure to low frequency and radiofrequency electromagnetic fields

In the context of the implementation of Directive 2013/35/EU, this paper addresses some specific aspects of occupational and non-occupational exposure in distinct situations. There is covered the shipboard personnel exposure to magnetic fields produced by the onboard power plant and ship propulsion system and to radiofrequency fields produced by communications and radar stations. In addition, it is brought into discussion a new chapter in the research of exposure to electromagnetic fields, i.e. the study of the biological effects of electromagnetic fields exposure of fetuses, infants and prematurely born.

Radiation reduction capabilities of some woven fabrics with metallic yarns attached to mobile phones emitting in 2G- and 3G- communication standards

Woven fabrics with metallic yarns were produced and tested for their electromagnetic shielding properties in the ultra high frequency band. After shielding effectiveness was measured in a dual transverse electromagnetic cell, seven types of woven fabrics containing Bekinox, copper and silver yarns were further tested for their capabilities to reduce the mobile phone radiation. Results indicate that shielding effectiveness itself should not be used as a unique indicator of the protective characteristic when it comes to mobile phone radiation. We have proved that the use of such woven fabrics as cover of the handset may result in both reducing and increasing the absorbed energy in the head.

Assessment of the ellipsoidal shell model for ship magnetic signature

There is described and assessed the ellipsoidal shell model for solving the ships magnetic signature. This model relies on the premises of equating the mass of magnetic materials used in the ship hull construction with the mass of material of the ellipsoidal shell. The magnetic field is computed in a horizontal plane situated below the analyzed body, starting from the solution to Laplaces equation formulated in the ellipsoidal coordinate system, and by applying the variable separation method. The field computation is performed in the situations: the external field is parallel to the ellipsoids main axis and perpendicular to it, respectively. The model is analyzed by comparing the computation results to the numerical model constructed in Ansoft Maxwell environment, and, finally, to a set of measurements performed on the actual ship.