Georgiana Rosu

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.

Environmental magnetic field assessment. A case study

This paper describes the magnetic field measurements performed in a public access area - a market place, situated in the close vicinity of a transformer substation part of the Romanian national power grid. The measurement results were compared to the limits, regarding the human exposure to electromagnetic fields, imposed by normative documents. An analytical simplified estimation was performed too. It was found that in some areas of the market place the magnetic field exceeds the levels imposed by current limiting exposure normative and guidelines. In the same areas, persons working in the market place reported frequent electrostatic discharges.

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.

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.

Contributions for reducing the magnetic field created by an equipment component of a ship

The paper presents the study of the magnetic signature for a component equipment of the engine sincron generator located on board a ship built from non-magnetic materials. The equipment is analysed in terms of physical and geometrical similarity criteria. The algorithm for computing the electrical circuits from the global compensation windings was correlated with the ships geometrical shape. In was taken into consideration the fact that the winding arrangement is symmetrical to the ship diametrical plan, as well as the ship magnetic field. The paper purpose is to realise the equipment permanent and inductive magnetization compensation.

The effect of a magnetic treatment on ship magnetic signature

The ship magnetic signature represents the ship magnetic field distribution, having as main source the magnetization of the ship ferromagnetic hull in the Earths magnetic field. The danger represented by underwater weapons, such as magnetic mines, determine the necessity of reducing the ship magnetic signature. This reduction is achieved in specialized ranges, with considerable amounts of human, financial and time resources. For the purpose of analyzing the impact of a magnetic treatment on the signature shape and magnitude, there was constructed a ship physical model at scale 1 : 100. Within the research, there was determined the degree of geometric and physical similarity between ship and model, and the model magnetic signature components were measured at the reference depth. Then the ship model was subjected to a complex magnetic treatment, after which there was analyzed the process impact and efficiency.

Evaluation of a numerical model for ship magnetic signature induced by an external field

In order to assess the ship magnetism induced by the Earths magnetic field, a virtual ship was built, which was further analyzed in the Ansoft Maxwell environment. The virtual ship models main dimensions and material characteristics were similar to the ones of the actual ship. The ship model was considered a metallic shell of 12 mm width. The analysis studied the impact on ship magnetization of an external magnetic field oriented vertically and afterwards horizontally. Finally, there was determined the magnetization induced by the geomagnetic field, consisting of the previously considered components. The external magnetic field values were chosen from the main geomagnetic field reference model (IGRF) for the area near the Romanian coast of the Black Sea. Simulation results were compared to a set of measurements performed on the ship itself, and differences between simulated and measured values were discussed.