Papers

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2020-07-11
10:41
Chalcopyrite Solar Cells
Škvarenina, Ľubomír
Thin-film chalcopyrite based Cu(In;Ga)Se2 solar cells with a metal wrap through interconnection were investigated by non-destructive methods in our research. The primary focus of this investigation was a detection and a localization of microstructural defects in this type of Cu(In;Ga)Se2 solar cells. A combination of a visible and near infrared electroluminescence with a lock-in thermography was used for these purposes. Mainly the electroluminescence was a very sensitive tool for an indication of pre-breakdown sites influenced by a trap-assisted tunneling or stress-induced leakage currents. A strong correlation between electroluminescence maps and lock-in thermograms was obtained after a local breakdown accompanied by a creation of permanent defect.

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2020-07-11
10:41
Lead-Acid Battery Evaluation Based On Opencircuit Voltage Fluctuation Measurement
Kuparowitz, Tomáš ; Kuparowitz, Martin
The state of charge and the state of health are two crucial parameters of batteries. Current state of the art methods of their estimation include some as simple as measuring open circuit voltage, all the way to fuzzy logic estimation and constant online battery overview. Some main problems of such methods are either the length of single parameter evaluation cycle, or their inherent inaccuracy due to limitations in battery manufacture precision. This article proposes novel method of the lead-acid battery state of the health estimation, based on open circuit noise measurement. It reports the nature of changes in low frequency noise spectral density, that occur after catastrophic self-discharge failure or avalanche voltage drop in lead-acid batteries.

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2020-07-11
10:41
Characteristics Of Gallium Arsenide Solar Cellsat High Temperature
Papež, Nikola
This article reviews a work on processing of gallium arsenide (GaAs) solar cells. The performance of the cells before and after 300 _x000E_C thermal processing was correlated with topography identified by optical camera, atomic force microscope (AFM) and scanning electron microscope (SEM). Experiment indicates insignificant changes in topography of GaAs solar cells, but electrical characteristics show an excellent resistance of the samples to processing temperature.

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2020-07-11
10:41
Neural Network For Testing
Smetana, Bedřich
This article describes basics of neural networks, specifically aimed at usage of freeware to test freeware for creation simple neural network. Discussion focuses on the use of generally available programs and problems with use of freeware applications. Attention is devoted to a comparison of real and theoretical conditions connected with practical computer support.

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2020-07-11
10:41
Automated Detection Of Retinal Venous Pulsations From Video Sequences
Hracho, Michal
The aim of this paper is to propose a method of automated detection and parametrization of spontaneous venous pulsations, that can occur in patients with various degrees of glaucoma. The method uses uncompressed video sequences acquired from fundus video-ophthalmoscope. A parameter of pulsation is then acquired and tested for correlation with occurrence of spontaneous venous pulsations.

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2020-07-11
10:41
Silicon Solar Cell Parameters Change After Focused Ion Beam Milling
Gajdos, Adam
Silicon is still one of the most used materials for fabrication of solar cells. Some imperfections and defects may appear during production process. These local imperfections could be eliminated by focused ion beam (FIB). Nevertheless, FIB milling process modifies the crystal structure of the material by ions implantation. Samples under investigation are monocrystalline silicon solar cells. The impact of FIB milling is shown and discussed through current-voltage measurement before and after milling process.

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2020-07-11
10:41
Powers Of Certain Automaton And Createdapproximation Space
Staněk, David
This paper focuses on the n-th power of a special case of an automaton A formed by homogeneous product of mentioned automaton A. Moreover, the number of isomorphic embeddings of A into An based on the number of components of An is discussed

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2020-07-11
10:41
Detection Of P Wave During Second-Degree Atrioventricular Block In Ecg Signals
Maršánová, Lucie ; Němcová, Andrea ; Smíšek, Radovan
Automatic detection of P wave during the second-degree AV block is the main condition for automatic detection of this pathology. This work deals with developing of the algorithm for P wave detection. The algorithm is appropriate for ECG signals with AV block as well as signals with other rhythm types (it does not produce false positive P wave detections). For P wave detection, the phasor transform is applied and several innovative rules are created. These rules are based on knowledge of heart manifestation during both physiological and pathological heart function. The proposed algorithm consists of four parts – filtration, QRS complex detection, application of rules, and P wave detection. The accuracy of the P wave detection algorithm is 99.74 % for signals with AV block, and 99.82 % for signals without any pathologies.

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2020-07-11
10:41
Preparation Of Cold Field Emission Cathodes Withultra Sharp Tips
Jurčík, Michal
This article deals with preparation of very sharp cold field emission cathodes made from polycrystalline tungsten wire which is widely used by other researchers and manufacturers. Common manufacturing process of electrochemical etching in NaOH solution is improved by separation of electrolyte surfaces between anode and cathode. This method prevents hydrogen bubbles, formed on cathode, to fine down the electrolyte surface near anode that cause shockwaves which affect the progress of etching. Separation of surfaces leads to sharper tips of the final cathode which is the main goal of my research.

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2020-07-11
10:41
Tantalum Capacitor As A Mis Structure: Transport Characteristics Temperature Dependencies
Kuparowitz, Martin ; Kuparowitz, Tomáš
Temperature dependencies of a leakage current in normal mode are explained on the basis of a model, in which the solid state tantalum capacitor is considered as a metal-insulatorsemiconductor (MIS) heterostructure. The measurement was performed in temperature range from 105 to 155°C. Ohmic conductivity increases exponentially with increasing temperature with activation energy 0.94 eV. Tunneling voltage parameter and tunneling energy barrier decreases with increasing temperature, reaching values 0.45 to 0.26 eV.

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