P. Marcon

Magnetic susceptibility measurement using 2D magnetic resonance imaging

The authors describe a nuclear magnetic resonance (NMR) method for measuring the magnetic susceptibility of bar-shaped samples that have an arbitrary cross-section and do not produce an MR signal. The method is based on the measurement of the 2D map of the reaction field in the vicinity of a non-ferromagnetic sample and on the calculation of magnetic susceptibility from a known reaction field. The verification of the technique was realized via modelling the measured configuration in the ANSYS program by means of the finite element method and through an experimental measurement of MR-compatible and MR-incompatible materials carried out on a tomograph. A great advantage of the proposed susceptibility evaluation method consists in the use of only standard commercially used devices without the need of any special sequences. The method is suitable for bar-shaped samples having an arbitrary cross-section; moreover, conditions are given for the selection of the cross-section/length ratio of a sample to be measured.

Diffusion MRI: mitigation of magnetic field inhomogeneities

Abstract The article reports on certain artifacts that emerge during the in vitro diffusion-weighted imaging of physical samples. In this context, the authors analyze the influence of magnetic field inhomogeneity, temperature, or eddy currents and consider artifact mitigation procedures. A technique reducing the examined spurious effects was designed, experimentally verified, and denominated as the three measurement method. The technique proved to be useful mainly for the evaluation of a DWI image measured with a diffusion gradient in the z axis, where the relative measurement error decreased to 3.38 % (during measurement using two images, the relative error was greater than 19 %). For small errors within the measurement of diffusion constants of a deionized water sample (< 5 %) it was necessary to select a b-factor value larger than 200·106 s.m-2. Temperature stabilization with accuracy better than 0.1 °C during the entire measuring process is a necessary prerequisite for the measurement of biological or material samples with relative accuracy lower than 1 %.

Correction of artifacts in diffusion-weighted MR images

The authors describe the techniques for measuring diffusion coefficients and creating DWI and DTI images. In order to increase the accuracy of diffusion coefficient measurement, it is necessary to eliminate the influence of artifacts such as the influence of magnetic field inhomogeneity, eddy currents, or temperature. For these artifact sources, the article presents experimental detection of the magnitude of errors, which is realized using the three measurements method, and proposes correction possibilities. The results are compared with diffusion measurements at different sizes of 6-factors.

Energy Sources for an Experimental Electrical Network: PV Panel and Micro-Hydroelectric Power Plants

Abstract The authors present energy sources for an Experimental Electrical Network (E.E.N). The main sources applied are photovoltaic and hydroelectric power plants. For the purposes of modelling the experimental network, the authors describe the measured values of the output power provided by the plants. The performance of the photovoltaic station was measured for the period of three weeks; as expected, the resulting value is strongly dependent on the weather. In the small hydroelectric station, we monitored the relation between the turbine output power and the water level in the weir. Moreover, we also produced a six-hour record of the performance of the station. Based on this characteristic, the relation between the water level and the output power was determined using approximation of the exponential function. The paper also describes the perspectives of remote sensing of the data acquired from a power plant and analyzes the possibilities of storing the data to an SQL server.

Stabilisation of low voltage distribution networks with renewable energy sources

Abstract Recent development in the area of renewable energy sources (RES) shows, that situation in countries supporting a great growth of RES, particularly photovoltaic, leads to big problems. Modelling studies show that in a very near future there will be a big surplus of electrical energy production in networks of NN (low voltage networks). It would evoke necessity to transfer energy into higher voltage networks. However it will not be possible while protection systems of high voltage networks are developed for the opposite flow of energy. Contribution deals with possible solution of stability of NN distribution networks by means of smart metering – smart grid system. Proposal of electronic instrumentation of measurement and control is presented in the contribution.

MRI-Based Visualization of the Relaxation Times of Early Somatic Embryos

Abstract The large set of scientific activities supported by MRI includes, among others, the research of water and mineral compounds transported within a plant, the investigation of cellular processes, and the examination of the growth and development of plants. MRI is a method of major importance for the measurement of early somatic embryos (ESE) during cultivation, and in this respect it offers several significant benefits discussed within this paper. We present the following procedures: non-destructive measurement of the volume and content of water during cultivation; exact three-dimensional differentiation between the ESEs and the medium; investigation of the influence of ions and the change of relaxation times during cultivation; and multiparametric segmentation of MR images to differentiate between embryogenic and non-embryogenic cells. An interesting technique consists in two-parameter imaging of the relaxation times of the callus; this method is characterized by tissue changes during cultivation at a microscopic level, which can be monitored non-destructively.

Multiparametric data collection of animal tissues in magnetic resonance imaging

In this article a magnetic resonance multiparametric data collection is described. The spin echo and the gradient echo sequences for magnetic resonance measurement were used. Images obtained by a nuclear magnetic resonance tomographare proton density, longitudinal relaxation time T1, transversal relaxation time T2 and magnetic susceptibility weighted. As a measured sample chicken wing was used. Several parameters as a maximal value, minimal value, mean value and standard deviation were evaluated in skin, fat, muscle, bone and bone marrow tissues. Obtained data could be used for multi-parametric analysis and for image segmentation.

Analysis of magnetic properties measurement in closed samples

This paper contains an analysis of magnetic properties of a coil core material. Methods of demagnetizing the sample before measurement are discussed. Static and dynamic hysteresis loops, initial magnetization curve, and normal magnetization curve are measured. The authors show the corrections of systematic errors for all measurements and indicate the specific conditions under which the measurement of the characteristics is realized.

Mini- and microgenerators applicable in the MEMS technology

The article presents certain general conclusions obtained from an investigation of a vibration-powered milli- or microgenerator functioning as a harvester. In this context, the authors summarize the parameters that are critical in designing optimal generators to retrieve the residual energy contained in an electromechanical system and transferred through the vibrations of an independent structure. The discussion exploits our previous results, which theoretically define the properties characterizing the models of individual basic configurations of a generator based on Faraday’s law of induction.

Diagnosing brain tumors with MRI

The present paper discusses the improvement of accuracy in overall diagnostics related to brain tumors. The proposed measures include, for example, maximizing the use of image modifications and decreasing the radiation doses received by a patients body. The wider project is centered on the diagnostics of pathological tissues in the brain; it describes and compares the classification and identification of particular brain tumors.