Jan Mikeš

Effect of TiO2 on Various Regions of Active Electrode on Surface Dielectric Barrier Discharge in Air

For surface dielectric barrier discharge in air, we examined the effect of titanium dioxide on various regions of the active electrode on the electrical parameters of discharge, on its emission spectra, and for demonstration of the obtained results also on the concentration of ozone produced by the discharge. We used the active electrode in the form of nine interconnected parallel strips and a square counter electrode. The TiO2 layer covered either only the strips, the region between the strips, or all active electrode. As reference discharge we used the discharge without any layer of TiO2. We found that direct application potential has a version when the strips of the active electrode are covered with a layer of TiO2, because the concentration of ozone produced by the discharge is the highest in all investigated cases. This finding could therefore be used for construction of more efficient ozone generators.

Experimental and modelling study of the effect of airflow orientation with respect to strip electrode on ozone production of surface dielectric barrier discharge

This study examines the effect of airflow orientation with respect to the strip active electrode on concentration of ozone and nitrogen dioxide produced in a planar generator based on the surface dielectric barrier discharge. The orientation of the airflow was tested in parallel and perpendicular with respect to the strips. It was found that in the investigated range of average discharge power, the ozone concentration increases approximately by 25% when airflow was oriented in parallel with respect to the strips in comparison with perpendicular orientation of the airflow. Similarly the increase of nitrogen dioxide concentration was observed for parallel orientation of the airflow with respect to the strips in comparison with the perpendicular orientation of the airflow. Within the range of wavelengths from 250 to 1100 nm, the changes of intensities of spectral lines associated with airflow orientation have been observed. A 3D numerical model describing ion trajectories and airflow patterns have also been ...

The Impact of Active Conductors on Czech and Hungarian Lightning Protection Legislation

This paper summarizes the developmental conditions for the emergence of protection against lightning. It reviews the legislation especially in the Czech Republic over the last 15 years, and its application for active lightning conductors. The paper presents examples of the damage caused bylightning strikes on buildings protected by ESE lightning rods constructed using the French nationalstandard NFC 17-102 [1] and STN 34 1391 [2]. Installation of lightning conductors based on thesestandards is not, however, in accordance with the valid legislation in the Czech Republic and Hungary.In response to a growing number of ESE installations in the Czech Republic, it is vital to inform boththe broader professional publc and the lay public of cases involving failures of this type of lightningconductor.

Telemetry system for research stratospheric balloon

The paper presents telemetry system for stratospheric balloon mission based on the UHF transceivers designed for Internet of Things. The system operates in 869.5 MHz frequency band. The system uses very short packet without channel coding that can be successfully received and decoded under low signal to noise ratio. The modem sensitivity −124 dBm and the transmission power 25 dBm can ensure reliable communication for distances longer than 100 km with omnidirectional antennas and 200 km with 10 dBi ground station directional antenna. The telemetry system uses GFSK modulation of bit rate 1200 Bd and is designed for a transmission of the balloon position and status.

Influence of the wall material of the lightning protected object size induced surges

The authors verify the separation distance coefficient /s/ setting of the distance according to the International standards IEC 62305, ed. 2, based on mathematical modeling. The coefficient of the separation distance is established in standards according to the empirical relationships. The authors wants to point out the possibility of more precise verification provided by real model experiments on building materials that are commonly used worldwide. For this purpose, mathematical models were carried out in collaboration with the Czech Technical University in Prague and the company DEHN + SÖHNE and compiled several artificial wall materials (air, concrete, PE and PVC). Behind them, object wiring (installation loop) was adjusted. In front of the wall, down-conductor was established. The assembly was tested by current impulse of 10/350 μs; 0.25/100 μs; 1/200 μs. The result is a set of adjustments that could be accepted by the international standardization committees for the revision of the standards IEC 62305 and the national standards STN 34 1398 and NF C 17-102.

A LIGHTNING CONDUCTOR MONITORING SYSTEM BASED ON A WIRELESS SENSOR NETWORK

Automated heating, lighting and irrigation systems are nowadays standard features of industrial and commercial buildings, and are also increasingly found in ordinary housing. In addition to the benefits of user comfort, automated technology for buildings saves energy and, above all, it provides enhanced protection against leakage of water and hazardous gases, and against fire hazards. Lightning strikes are a natural phenomenon that poses a significant threat to the safety of buildings. The statistics of the Fire and Rescue Service of the Czech Republic show that buildings are in many cases inadequately protected against lightning strikes, or that systems have been damaged by previous strikes. A subsequent strike can occur within the period between regular inspections, which are normally made at intervals of 2–4 years. Over the whole of Europe, thousands of buildings are subjected to the effects of direct lightning strikes each year. This paper presents ways to carry out wireless monitoring of lightning strikes on buildings and to deal with their impact on lightning conductors. By intervening promptly (disconnecting the power supply, disconnecting the gas supply, sending an engineer to inspect the structure, submitting a report to ARC, etc.) we can prevent many downstream effects of direct lightning strikes on buildings (fires, electric shocks, etc.) This paper introduces a way to enhance contemporary home automation systems for monitoring lightning strikes based on wireless sensor networks technology.

Nuclear Energy in Czechoslovakia. An Outline and Description of Its Development Trends

La nuclearisation de la Tchecoslovaquie s’est operee apres la Seconde Guerre mondiale au carrefour des donnes naturelle (importantes ressources en uranium), technique (differentes filieres en competition) et, evidemment, politique (contrainte sovietique). L’article retrace ces dynamiques et les suit jusqu’au temps present, en abordant notamment la question de la gestion des dechets et du demantelement de certaines installations dans le nouveau contexte de l’entree dans l’Europe communautaire et des normes environnementales renforcees.