Results of 3-D of discharge channel displacement simulation, acquired by means of the Fluent program during one current half-period of AC arc, indicate that the obtained images of the phenomenon are qualitatively similar to those, recorded with a high-speed digital camera, while the computer simulation enables much a more comprehensive analysis of the acquired data. In addition to selected arc simulation frames and corresponding distributions of mass velocity vectors and current density vectors on a plane, the distributions of temperature, current density and mass velocity values are presented on the axis of the electrode arrangement model. The composite motion (continuous and jumping) of discharge channels was analyzed, taking into account mass displacement and matter state changes.
Sensing technology has been developed for detection of gases in some environmental, industrial, medical, and scientific applications. The main tasks of these works is to enhance performance of gas sensors taking into account their different applicability and scenarios of operation. This paper presents the descriptions, comparison and recent progress in some existing gas sensing technologies. Detailed introduction to optical sensing methods is presented. In a general way, other kinds of various sensors, such as catalytic, thermal conductivity, electrochemical, semiconductor and surface acoustic wave ones, are also presented. Furthermore, this paper focuses on performance of the optical method in detecting biomarkers in the exhaled air. There are discussed some examination results of the constructed devices. The devices operated on the basis of enhanced cavity and wavelength modulation spectroscopies. The experimental data used for analyzing applicability of these different sensing technologies in medical screening. Several suggestions related to future development are also discussed.
Filtering nonwovens produced with melt-blown technology are one of the most basic materials used in the construction of respiratory protective equipment (RPE) against harmful aerosols, including bio- and nanoaerosols. The improvement of their filtering properties can be achieved by the development of quasi-permanent electric charge on the fibres. Usually corona discharge method is utilized for this purpose. In the presented study, it was assumed that the low-temperature plasma treatment could be applied as an alternative method for the manufacturing of conventional electret nonwovens for the RPE construction. Low temperature plasma treatment of polypropylene nonwovens was carried out with various process gases (argon, nitrogen, oxygen or air) in a wide range of process parameters (gas flow velocity, time of treatment and power supplied to the reactor electrodes). After the modification, nonwovens were evaluated in terms of filtration efficiency of paraffin oil mist. The stability of the modification results was tested after 12 months of storage and after conditioning at elevated temperature and relative humidity conditions. Moreover, scanning electron microscopy and ATR-IR spectroscopy were used to assess changes in surface topography and chemical composition of the fibres. The modification of melt-blown nonwovens with nitrogen, oxygen and air plasma did not result in a satisfactory improvement of the filtration efficiency. In case of argon plasma treatment, up to 82% increase of filtration efficiency of paraffin oil mist was observed in relation to untreated samples. This effect was stable after 12 months of storage in normal conditions and after thermal conditioning in (70 ± 3)°C for 24 h. The use of low-temperature plasma treatment was proven to be a promising improvement direction of filtering properties of nonwovens used for the protection of respiratory tract against harmful aerosols.