AEEE. 2008, vol. 7

Permanent URI for this collectionhttp://hdl.handle.net/10084/83536

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Now showing 1 - 20 out of 106 results

High-frequency EMI noise suppression by polymer-based composite magnetic materials
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Dosoudil, R.; Franek, J.; Ušáková, M.; Olah, V.; Sláma, J.
The complex permeability and EM-wave absorption properties of hybrid polymer-based composite magnetic materials (with MnZn and LiZn ferrite fillers and PVC matrix) prepared with constant total filler content (65 vol%) and particle size (0-250 mm) have been investigated in the 1-1000 MHz frequency range. Within this filler concentration the permeability of composites changed continuously with the change of ferrite filler content ratio between two types of ferrite fillers. The observed relaxation type of permeability dispersion was due to the domain wall and natural ferromagnetic resonance phenomena and was also attributed to the high damping of spin motion. Measured values of permeability were used to determine the EM-wave absorption properties (return loss RL, matching frequency fm, matching thickness dm and bandwidth Df for RL £ -20 dB). The calculation of these properties was based on a model of single-layered absorber backed by a perfect conductor using transmission-line and EM-field theory. The composite with the volume fraction ratio of hybrid MnZn:LiZn ferrite filler set to 0.5:0.5 has shown a return loss of -57 dB (> 99 % power absorption) at fm = 714 MHz with the -20 dB bandwidth of Df = 232 MHz for an absorber thickness of 7.79 mm. The prepared composites can fruitfully be utilized for suppression of conducted and/or radiated EMI noise especially in wireless and portable electronic equipments.
Electromagnetic properties of selected hexaferrites
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Grusková, A.; Sláma, J.; González, A.; Ďurman, V.; Ušáková, M.; Jančárik, V.; Šoka, M.
New nanocrystalline materials for power electronics applications
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Ušák, E.; Švec, P.; Kuchta, J.; Bydžovský, J.
New nanocrystalline materials for the applications in the power electronics systems are developed and tested. These materials are intended to be used in the magnetic circuits of switching-mode power supplies (SMPS). The aim was to achieve extremely low hysteresis and non-linearity in operating region resulting in increased efficiency and decreased weight and size whilst keeping low price of the high-power frequency converters for SMPS.
Magnetic spectra analysis of dielectrics
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Sláma, J.; Olah, V.; Grusková, A.; Jančárik, V.; Hudec, I.; Dosoudil, R.; Široký, P.; Šoka, M.
Method of magnetic spectroscopy is used to analyze and to interpret the experimental data obtained by magnetic measurement of the complex permeability spectra of Mg ferrite and NiZn ferritepolymers. Ferritepolymers were prepared from various concentration of NiZn ferrite particles as a soft magnetic fillers dispersed in PVC polymer matrix. Effect of the filler content on the permeability spectra of NiZn ferritepolymers was examined and compared with presented sintered ferrite samples. The variations of permeability and relaxation frequency due to ferrite filler concentration in composite are presented and discussed from point of view the magnetization processes in samples.
The resistance of breakdown in transformer oil
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Kúdelčík, Jozef
The conditions under which breakdown of composite liquid - solid insulation can be occurred, e.g., in transformer, play an important role in designing of such insulation. The initial state of breakdown development is explained on the basis of bubble theory and formation of a plasma channel between the electrodes. The electrical resistance of plasma channel is calculated using several theories and its changes from a few ohms to a few hundred milliohms due to Joule heating caused by high arc current which flows through the plasma. The dynamics of the arc current depends on the parameters of outer circuit and is represented by RLC circuit.
Simulation of electrical parameters for Ru/Ta2O5/SiO2/Si(p) high-k MOS structure
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Racko, J.; Harmatha, L.; Breza, J.; Benko, P.; Donoval, D.
The contribution presents the results of simulation of direct tunnelling of free charge carriers through a thin gate insulator in MOS structures consisting of a Ta2O5/SiO2 bilayer taking into account also indirect tunnelling of free charge carriers through the SiO2/Si interface traps. The calculated I–V and C–V curves reveal the processes of electron and hole tunnelling through the insulator-to-semiconductor potential barrier that can be divided into four classes.
Sputtered of ZnO:Al thin films for application in photovoltaic solar cells
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Flickyngerová, S.; Řeháková, A.; Tvarožek, V.; Novotný, I.
High transparent and conductive, aluminium - doped zinc oxide thin films (ZnO:Al), were prepared by radio – frequency (RF) diode sputtering from ZnO+2 wt. % Al2O3 target on Eutal glass substrates. Surfaces of the samples were treated by various technological steps during preparation. The ion bombardment and the substrate temperature modified their structure, surface morphology, electrical and optical parameters. In this work we present changes between samples prepared at room temperature (RT) and at 200°C, between samples on ion etched substrate and non-modified substrate, and effect of ion etching of the sample surface. We measured transmittance, resistivity and microroughness by AFM on all samples.
Ofstatistical and fractal properties of semiconductor surface roughness
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Jurečka, Stanislav; Jurečková, Mária; Kobayashi, Hikaru; Takahashi, Masao; Madani, Mohammad; Pinčík, Emil
Surface morphology evolution is of primary significance for the thin-film growth and modification of surface and interface states. Surface and interface states substantially influence the electrical and optical properties of the semiconductor structure. Statistical and fractal properties of semiconductor rough surfaces were determined by analysis of the AFM images. In this paper statistical characteristics of the AFM height function distribution, fractal dimension, lacunarity and granulometric density values are used for the surface morphology of the SiC samples description. The results can be used for solution of the microstructural and optical properties of given semiconductor structure.
Modeling of A-DLTS spectra of MOS structures
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Hockicko, Peter; Sidor, Peter; Bury, Peter; Kúdelčík, Jozef; Jamnický, I.
Acquisition of basic characteristic of defects has become possible through a wide class of measurement techniques which probe the interface, the near interface, as well as the bulk of semiconductor. Results presented here are based essentially on the acoustic version of Deep Level Transient Spectroscopy (A-DLTS) measurements. This method is based on the acoustoelectric response effect observed at the interface. The A-DLTS uses the acoustoelectric response signal (ARS) produced by MOS structure interface when a longitudal acoustic wave propagates through a structure. The ARS is extremely sensitive to external conditions of the structure and reflects any changes in the charge distribution connected with charged traps. The temperature dependence of ARS after bias voltage step application is investigated and the activation energies and some other parameters of traps at the insulator – semiconductor interface are determined. The results obtained form Arrhenius plots of A-DLTS spectra of selected MOS structures are compared with results obtained from modeling of ADLTS spectra using theoretical model.
On nanometer ordering in thin amorphous hydrogenated silicon
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Müllerová, Jarmila; Vavruňková, Veronika; Šutta, P.
We investigated thin films of amorphous hydrogenated silicon (a-Si:H) deposited by PECVD under increasing dilutions of silane plasma by hydrogen. We found out that under increasing additional hydrogen at the depositions, thin films obtain less hydrogen bonded to silicon. The optical band gap energies determined from UV Vis transmittance and reflectance spectra were found to be increasing function of the dilution. We deduce that optical band gaps expanse due to the decreasing dimensions of silicon nanocrystals. They were calculated to be of 2 – 4 nm which proves the medium-range order in a-Si:H.
Optimalization method of EMI power filters and its measurement
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Sedláček, J.; Szabó, Z.
One of the most important problems solved nowadays is the improvement of the electronic systems immunity. This paper deals with the modelling and synthesis of EMC power filters. This is very important in the field of the electromagnetic compatibility and EMC filter design and optimisation. Various types of EMC filters are discussed. Idea of the synthesis and optimisation of EMC filters is illustrated on example. Results of our synthesis of EMC filter are shown at the conclusion.
A new identification method of both magnetization characteristic and parameters of an unloaded transformer
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Orság, Petr; Kijonka, Jaromír
In this paper a new method of identification of both the magnetization characteristic and the instantaneous parameters G(t) and K(t) of a single-phase transformer under a sinusoidal supply voltage is proposed. The instantaneous conductance G(t) and inverse inductance K(t) of the transformer cross section are determined by the scalar product of time functions. The magnetization characteristic is derived by means of the inverse inductance K(t). The method is practically applied to an isolating transformer.
Iterrative correction of measurement with averaging of dithered samples
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Kamenský, M.; Kováč, K.
Self-calibration techniques could eliminate measurement errors caused by time changes and component aging. For ADC performance enhancement also averaging is necessary. In the paper the iterative measurement error correction method is presented in combination with averaging. Dither theory for Gaussian noise has been used for exhibition of averaging abilities in ADC characteristic improvement. Experimental ENOB value improvement is more than 1.5 bit.
Temperature dependence of biological tissues complex permitivity at microwave frequencies
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Faktorová, Dagmar
In the paper an universal overview of polarizing mechanisms with an emphasis on dipolar materials as the investigated tissues are regarded. Experimental apparatus is presented with giving its specificity as well as the method used at calculation of complex permittivity. The experimental part is aimed at temperature dependence of complex permittivity measurement of pig biological tissues with different properties. Experimental results are presented graphically with the commentary for courses of particular tissues.
Measurement evaluation of EMF effect by mobile phone on human head phantom
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Pšenáková, Z.; Bečová, M.
Interaction of electromagnetic field (EMF) with environment and with tissue of human beings is still under discussion and many research teams are investigating it. One of electromagnetic devices is mobile phone. There are many simulations and measurements on models or phantoms of human body to biological effect of EMF acquirement. This paper deals with laboratory measurement evaluation of EMF effect by mobile phone on human head phantom.
Application of neutral network by EEG signal classification
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Gála, Michal; Mohylová, Jitka; Krajča, Vladimír
Analysis of long-term EEG requires that it is segmented into piece-wise stationary sections and classified. Neural network architecture is introduced for the problem of classification of EEG signals. This paper deals with basic signal classification into two classes. This work is a ground towards creating an algorithm to sleep status analysis. Signal is first worked by signal segmentation and then is used a neural network to classification into two class.
The EEG signal prediction bz using neural network
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Babušiak, Branko; Mohylová, Jitka
The neural network is computational model based on the features abstraction of biological neural systems. The neural networks have many ways of usage in technical field. They have been applied successfully to speech recognition, image analysis and adaptive control, in order to construct software agents or autonomous robots. In this paper is described usage of neural networks for ECG signal prediction. The ECG signal prediction can be used for automated detection of irregular heartbeat – extrasystole. The automated detection system of unexpected abnormalities is also described in this paper.
Electromechanical model of blood flow in vessels
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Čáp, Ivo; Czippelová, B.
The present paper deals with some theoretical derivations connected with very efficient method of solution of hydrodynamic problems of blood flow in human cardiovascular system. The electromechanical analogy of liquid flow in a tube and electromagnetic wave propagating along an electric transmission line is discussed. We have derived a detailed circuit-like model of an elementary section of the elastic tube with viscose Newtonian liquid. The analogy harmonic current electrical circuit has been designed.
Some thoughts on electrical interventions for the control of tremor in parkinson's disease
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Hearn, A. N.; Lowery, M. M.; De Paor, Annraoi
Ideas from control theory – state variable feedback, dither injection, the equivalent nonlinearity and the describing function-are applied to models developed to help understand the mechanisms of electrical interventions such as deep brain stimulation (DBS) for the alleviation of Parkinsonian tremor.
Inspection of conductive prosthetic replacements using electromagnetic methods of non-destructive testing
(Žilinská univerzita v Žiline. Elektrotechnická fakulta, 2008) Strapáčová, T.; Smetana, M.; Čápová, Klára
This paper describes the use of electromagnetic methods of non-destructive testing for detecting of inhomogeneities presence in a prosthetic replacement with focus on strut fractures in prosthetic heart valves. In the first part of this paper there are described a basic principle of eddy current testing, heart valve replacement and materials which are usually used for it. The experimental part contains description of simulated problem, obtained simulation results and their interpretation for use in medicine.

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