Kubík Ľ., Zeman S., 2013. Determination of oxygen permeability of polyethylene and polypropylene nonwoven fabric foils. Res. Agr. Eng., 59: 105-113.The paper deals with determination of oxygen permeability of the polyethylene and polypropylene foils applied in mulching and food packaging. The construction of the equipment of measurement of gas permeability through the foils is discussed. The design and construction of the equipment was realized with applying of the Standard STN EN 77 0333. The measurement of permeability of oxygen through the polyethylene Bralen 2-63 with 9% colored concentrate Maxithen HP 533041 -violet foil, Polyten®MLB black&white foil and black polypropylene nonwoven fabric foil were realized by means of the modified method.
Energy balance of the photovoltaic system is influenced by many factors. In this article the effect of tilt and azimuth angle changes of the photovoltaic system energy production is analyzed. These parameters have significant impact on the amount of solar radiation which hits on the photovoltaic panel surface and therefore also on the energy absorbed by the module surface. The main aim of research was identification of the optimal position of photovoltaic system installation in the southern Slovakia regions. The experimental apparatus had two setups consisting of polycrystalline photovoltaic modules. The first setup was used for identification of the tilt angle changes in the range (0–90°). The second one was focused on the detection of the azimuth angle effect to the energy production. The measurement results were statistically processed and mathematically analyzed. Obtained dependencies are presented as two-dimensional and three-dimensional graphical relations. Regression equations characterize time relations between the tilt or azimuth angle and the energy produced by the photovoltaic system in Southern Slovakia. Obtained simplified mathematical model was verified by analytical model. Presented models can be used for the dimensioning and optimization of the photovoltaic system energy production.
A b s t r a c t . Sawdust from six wood species typical of Eastern Europe: beech (Fagus L.), birch (Betula L.), oak (Quercus L.), pine (Pinus sylvestris L.), poplar (Populus L.) and willow (Salix L.) with a moisture content of 8% were compacted at a compressive pressure of 120 MPa in a laboratory mould with a diameter of 10 mm. Diametral compression tests were performed to determine the mechanical strength of the pellets. Discrete element method simulations were performed to reproduce the compaction process and the mechanical reaction of the pellets to diametral compression. It was found that the difference between the bulk density of the compacted and the relaxed pellets decreased with increases in the breakage strength of a pellet. The DEM simulations reproduced well the experimental data of the diametral compression test.K e y w o r d s: sawdust pellets, diametral compression, tensile strength, DEM
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