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<p><strong>Aim</strong> <br />Plastic clips are a diamagnetic material and produce fewer artefacts in the MR field than titanium clips, which are standard<br />in neurosurgery. However, alongside their physical properties, the shape of the clips, and their very geometry subtlety affects their behaviour in the magnetic field. Therefore, we performed a simulation in order to establish which clips cause less disturbance in the magnetic field from the point of view of the geometry of the body.<br /><strong>Methods</strong> <br />The simulation tool used for the research was the software package COMSOL Mph version 4.3. Since it was a question of<br />magnetics, the models were prepared in the AC/DC module within the option Magnetic Fields, No Currents (mfnc). Within this module we were able to analyse electro-magnetic fields for a specific geometrical structure, using the Finite Element Method in order to resolve the two-dimensional electromagnetic problems.<br /><strong>Results</strong> <br />The value of the magnetic field with titanium clips with their specific geometric reference lines reached the value of c.<br />(A/m). The simpler geometry of the plastic clips resulted in a less intensive magnetic field, amounting to c. (A/m), which is an entire order of magnitude less than the field with the titanium clips.<br /><strong>Conclusion</strong> <br />The simpler geometry of the plastic clips and the type of material from which they are made causes less disturbance to<br />the magnetic field, which was precisely confirmed with the simulation model. The use of plastic clips in neurosurgery and neuroradiology will facilitate the interpretation of MR images.</p>

Line surge arresters are mainly used for transmission line lightning performance improvement. Calculation of energy stresses of lines surge arrester is of extreme importance for the selection of the arrester class. Energy stresses of transmission line surge arresters due to multicomponent lightning flashes are analysed in this paper. To obtain lightning data two approaches were used: direct measurements using instrumented towers and lightning location systems. Both lightning monitoring systems are described. Data obtained from lightning monitoring systems are compared and used in simulations. Detailed modelling procedure for a transient analysis of the transmission lines is also described. Multicomponent lightning flash and 110 kV transmission line were modelled using Electromagnetic Transient Program -Restructured Version (EMTP – RV). The arrester current shapes and arrester energy duties are presented in order to clearly show influence of lightning current parameters to arrester energy duty.

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