Miloslav Steinbauer

Numerical Method of Simulation of Material Influences in Mr Tomography

Abstract—Generally all Magnetic Resonance Imaging (MRI) techniques are affected by magnetic and electric properties of measured materials, resulting in errors in MR image. Using numerical simulation we can solve the effect of changes in homogeneity of static and RF magnetic fields caused by specimen made from conductive and/or magnetic material in MR tomograph. This paper deals with numerical simulation of material susceptibility influence to magnetic field.

Inversion Reconstruction of Signals Measured by the NMR Techniques

The paper describes the magnetic resonance imaging method applicable mainly in MRI and MRS in vivo studies. There is discussed and solved the efiect of changes of magnetic flelds in MR tomography. This article deals with the reverse reconstruction results obtained from the numerical simulation of MR signals by various techniques, which will be usable for the experimental results veriflcation. Nuclear Magnet Resonance (NMR) is well known diagnostic non-destructive and non-invasive method (2{6). It is used to investigation of the materials properties. One of the often use of NMR is medical application (8,11). The magnetic resonance imaging (MRI) is used to the propel a ferromagnetic core. The concept was studied for future development of microdevices designed to perform minimally invasive interventions in remote sites accessible through the human cardiovascu- lar system. A mathematical model is described (3) taking into account various parameters such as the size of blood vessels, the velocities and viscous properties of blood, the magnetic properties of the materials, the characteristics of MRI gradient coils, as well as the ratio between the diameter of a spherical core and the diameter of the blood vessels. Other paper (4) present a MRI-compatible micromanipulator, which can be employed to provide medical and biological scientists with the ability to concurrently manipulate and observe micron-scale objects inside an MRI gantry. The micromanipulator formed a two-flnger micro hand, and it could handle a micron-scale object using a chopstick motion. The material engineering use the NMR too. For example NMR logging is an advanced method in formation evaluation and oil fleld production. It can provide the porosity, permeability, bound water volume, free ∞uid volume and oil viscosity. NMR logging is playing more and more important roles in oil and gas exploitation.

Measurement of weakly magnetic material using new MR technique

Materials with different magnetic susceptibility can cause deformation of magnetic field in MR tomograph, resulting in errors in obtained image. Using simulation and experimental verification we can solve the effect of changes in homogeneity of static magnetic fields caused by specimen made from magnetic material in MR tomograph. This paper describes theoretical base and experimental measurement of new magnetic resonance imaging method for susceptibility measurement. This technique is suitable for substances with no signal in MR tomography. The method uses deformation of magnetic induction field in specimen vicinity. For MR purposes it is necessary to immerse specimen into reference medium with measurable MR signal (water is suitable).

Numerical model a graphene component for the sensing of weak electromagnetic signals

The paper discusses a numerical model and provides an analysis of a graphene coaxial line suitable for sub-micron sensors of magnetic fields. In relation to the presented concept, the target areas and disciplines include biology, medicine, prosthetics, and microscopic solutions for modern actuators or SMART elements. The proposed numerical model is based on an analysis of a periodic structure with high repeatability, and it exploits a graphene polymer having a basic dimension in nanometers. The model simulates the actual random motion in the structure as the source of spurious signals and considers the pulse propagation along the structure; furthermore, the model also examines whether and how the pulse will be distorted at the beginning of the line, given the various ending versions. The results of the analysis are necessary for further use of the designed sensing devices based on graphene structures.

Magnetic Field Approximation in MR Tomography

This paper describes a method, which can be used for creating map of magnetic fleld. Method has a great usage in magnetic resonance tomography, when we need to get in- formation about homogeneity and characteristics of magnetic fleld inside the working space of the MR tomograph. The main purpose of this article is to describe basic principles of magnetic resonance phenomenon and mathematical method of Legendre polynoms which can be used for signal processing of FID (Free Induction Decay) signal obtained from tomograph detection coils. In the end of my article is experimental solution of magnetic fleld and models of magnetic fleld created by Matlab.

Methods of air ion concentration measurement

There are positively and negatively charged ions with different mobility and size in air. Previous research have demonstrated the positive influence of light negative ions and air cleanness on human health. Therapeutic effect is used in some speleotherapeutics caves. This article shows the possibility of the air ion field measurement and the most used measurement methods.

Gerdien condenser measuring and numerical modeling of air ion fields

An electric state analysis of air shows the presence of various ion sorts. The therapeutic effect of negative high-mobility ions of proper concentration is known. This positive effect was observed in caves that are used for speleotherapy. This article presents capability of measurement methods of ion concentration and ion spectral analysis.

Design, Numerical Analysis and Test of HF Absorber

The paper presents numerical analysis of the microwave absorber design. It is possible to use modifled concept of the absorber. There were used novel numerical methods (flnite element method (FEM)) for thin layers modelling with sandwich non-isotropic electromagnetic materials. Modifled absorber has appropriate properties and it is possible to use it in non- re∞ecting chamber construction. The non-re∞ecting chamber will be used for open space testing of relativistic microwave pulse generator; Pmax = 500MW, tp = 10i100ns. An experimental testing of the proposed pyramidal absorbers was done in the laboratories at University of Defence Brno, Czech Republic. DOI: 10.2529/PIERS060901094301 Figure 2: The shielded laboratory. The calorimetric sensor has disc design. The carbon with changed crystal lattice is used as one of the thin layers. Combined calorimetric sensors was designed for microwave vircator with output power Pmax = 500MW, length of pulse tp 2 ns. Usually, two types of the absorber materials (non-re∞ecting) are used. The polyurethane foam impregnated by graphite is used in high frequency range (more than 1GHz) | the foam employs heat losses in material. The ferrite absorber is used in low frequency range | the ferrite absorber employs magnetic losses. The mentioned materials are used to prevent re∞ection of the electromag- netic waves inside the laboratory. The idea is to rebuild the laboratory in Fig. 2 to the shielded non-re∞ecting chamber for measurements and experiments with power microwave pulse generators iPmax = 500MW, length of pulse tp 2 ns. 2. SHIELDING OF THE WALLS It is possible to deflne an electromagnetic shielding by help of shielding coe-cient ?. It represents the ratio of the electrical fleld Et (magnetic fleld Ht) in the given place of the chamber to the electrical fleld Ei (magnetic fleld Hi) incoming at the absorber. ? = Et

Testing an Impedance Non-destructive Method to Evaluate Steel-Fiber Concrete Samples

Abstract Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to the development of cracks. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite have been distributed evenly. The current methods to evaluate the distribution and concentration of a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses tests related to the evaluation of the density and orientation of fibers in a composite material. Compared to the approaches used to date, the proposed technique is based on the evaluation of the electrical impedance Z in the band close to the resonance of the sensor–sample configuration. Using analytically expressed equations, we can evaluate the monitored part of the composite and its density at various depths of the tested sample. The method employs test blocks of composites, utilizing the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of between f=3 kHz and 400 kHz.

A Non-Destructive Impedance Method Using Resonance to Evaluate the Concentration of Steel Fibers in Concrete

Abstract Steel-fiber reinforced concrete is a composite material characterized by outstanding tensile properties and resistance to cracking. The concrete, however, exhibits such characteristics only on the condition that the steel fibers in the final, hardened composite are distributed evenly. Current methods to evaluate the distribution and concentration in a fiber composite are either destructive or exhibit a limited capability of evaluating the concentration and orientation of the fibers. In this context, the paper discusses auxiliary techniques and laboratory tests that evaluate the density and orientation of the fibers in a composite material, presenting an innovative approach to impedance-based non-destructive testing. The actual methodology utilizes the resonance of the measuring device and the measured sample set; the desired state occurs within the interval of f = 10 kHz and 2 GHz.