Jasna Tolmac, Slavica Prvulovic, Marija Nedic and Dragisa Tolmac
The paper analyzes the development opportunities of solar systems in the Republic of Serbia. Renewable energy sources and their energy potential, such as solar energy, should be considered in order to meet the needs of consumers. Solar energy can be considered the most modern renewable energy whose utility is still developing, and it is not represented as the utilization of hydro energy sources. Researches show that Serbia is a country with a high RES potential and that it has favorable conditions for production of electrical and heat energy from renewable sources. The aim of this paper is to present the possibilities of using solar energy in Serbia. Energy supply from renewable energy sources is a key factor for each country's strategy, because it directly contributes to reducing the negative effect on the environment.
A photocode in Polish is a common name for a two-dimensional code, which is characterized by higher information capacity than a traditional barcode. The paper analyses the use of the two-dimensional coding system - DataMatrix to identify and classify the material stream in the production process. The analysis showed the effectiveness of the implementation of the coding system in the context of increased availability, machine use and increased product quality. The improvement in the production process is confirmed by an increase in the OEE index. As part of further improvement measures, the coding system should be implemented throughout the enterprise, its compatibility with existing systems should be ensured and applied to all products.
In the most service life models of reinforced concrete structures the initiation phase is the most crucial, because according to models, service life of the structure will end underestimation on conservative side when carbonation achieves the reinforcement for the first time. The square root model is widely used in predicting carbonation depth of reinforced concrete. The model is based on diffusion laws and thereby arguable for inhomogeneous concrete. The model was evaluated by field measurements from one existing concrete building by conducting condition investigation twice at a time interval of 20 years. Samples were taken from exposed aggregate concrete sandwich panels and balcony side panels. Compared to the data collected from large number of buildings, the measured carbonation rates were very common for Finnish concrete buildings made during the 1960s and 1970s. According to this study, in solid concrete the progress of carbonation of concrete can be predicted reliably with Fick’s second law. This model, however, gives too pessimistic predictions for concrete suffering from freeze-thaw damage. Therefore, a new model has been presented for damaged concrete.
Dinara Sobola, Pavel Kaspar, Alois Nebojsa, Dušan Hemzal, Lubomír Grmela and Steve Smith
This study focuses on the description of oxidation of CdTe monocrystal surfaces after selective chemical etching. Measurements of surface morphology of the oxides occurring in short time are valuable for deeper understanding of the material degradation and fabrication of reliable devices with enhanced performance. The samples with (1 1 1) orientation were selectively etched and cleaned of oxide. Exposure of the oxide-free surfaces of CdTe to air at normal atmospheric conditions over 24 hours leads to an appearance of characteristic surface features. The oxidized surfaces were investigated by scanning electron microscopy, scanning probe microscopy, Raman spectroscopy and ellipsometry. The results indicate clear differences in the oxidation of Cd-terminated and Te-terminated surfaces.
The impact of substitution of cement paste with uncalcined clay (bentonite and kaolinite) in the range of 5% by volume of paste on the development of hydration and properties of mortar was investigated. Two issues were addressed, the expected filler effect of the dispersed sub-micron clay particles, and the possible chemical reactivity of the clay.
The study indicated that Portland cement paste may be modified by addition of well dispersed clay and that the impact includes accelerated cement hydration as well as altered distribution of products. Compressive strength development was accelerated, but later age strength was reduced, especially for the bentonite mixes. In contrast, microscopic porosity measurements indicated no detrimental impact on the coarse capillary porosity.
The investigation indicates that for durability related engineering properties, the application of uncalcined clay might be a potential means for reduction of the clinker factor in concrete in support of sustainability.
Stanisław Parafiniuk, Alaa Kamel Subr, Marek Milanowski and Anna Krawczuk
Three different types of nozzles (different wear rate) were used in this study. They are classified depending on the severity of their wear to three groups: new, worn and damaged nozzles. Those nozzles were spraying with the same application rate (303 l/ha) on two-year field trials; this was achieved by changing the spraying pressure for each group of nozzles in order to get the same application rate. This practice is usually done by operators of sprayers, who calibrate the sprayers on the same application rate every year without changing the nozzles, so they tend to reduce the spraying pressure in order to compensate the flow rate increase due to the nozzles yearly wear. Two types of plant growth regulators (PGR) agents were used in this study, namely: Moddus and Kelpak, they were applied to wheat plants field to reduce lodging. The results showed that applying PGR in the year 2015 produced an increase in the wheat yield and reduction in the plant height regardless the nozzle type, although there was not any occurrence of wheat lodging. In the year 2016, the new nozzles produced higher values of wheat yield than other two types of nozzles.
Tuomas Lehtonen, Matias Hirvikoski and Julius Rajamäki
In the beginning of 2017 the design method for punching shear in Finland was changed. The method presented in Eurocode 2 was adopted with some nationally determined parameters and rules. During 2016 and 2017 computational analyses were conducted to compare the previous national design method and the new one. Comparison setups were created in which different parameters were varied. The results were presented the predicted punching resistances differ differences are significant and can be almost 60% in some cases.
M. Kucinska, M.Z. Szymanski, I. Frac, F. Chandezon and J. Ulanski
Charge-carrier transport in the channel of bottom gate, top contact organic field effect transistors with anisotropic layers of 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-Pentacene) obtained by zone casting was investigated using scanning Kelvin probe microscopy combined with atomic force microscopy. The TIPS-Pentacene continuous layers consisted of thin crystals unidirectionally oriented in the channel. Devices with perpendicular and parallel charge flow in the transistor channel were prepared. It was found that irregularities in the surface morphology at the semiconductor layer in the transistor channel are correlated with the local potential profile, and that the channel resistance strongly depends on the orientation of the TIPS-Pentacene crystals.
J. Fojt, V. Hybasek, P. Jarolimova, E. Pruchova, L. Joska and J. Malek
The titanium bioactivity could be increased by surface nanostructuring. Titanium alloys are using for dental implants manufacturing. It represents a specific problem because of using of the dental treatments with high concentration of fluoride ions and with acidic pH. The corrosion resistance of nanostructured surface of titanium beta alloy in environments with fluoride ions was examined by common electrochemical technique. The electrochemical impedance measurement showed high corrosion resistance in physiological solution. The fluoride ions have expected negative influence on corrosion behaviour of the layer. The nanotube bottom was preferentially attacked which resulted in layer undercoroding and its detachment.
D. Kajánek, B. Hadzima, J. Tkacz, J. Pastorková, M. Jacková and J. Wasserbauer
The coating prepared by plasma electrolytic oxidation (PEO) was created on AZ31 magnesium alloy surface with the aim to evaluate its effect on corrosion resistance. The DC current was applied on the sample in solution consisted of 10 g/l Na3PO4·12H2O and 1 g/l KOH. Additional samples were prepared with 2 and 4 minutes of preparation to observe evolution of the PEO coating. Morphology of the coatings was evaluated by scanning electron microscopy and chemical composition was examined by EDX analysis. Electrochemical characteristic were measured by potentiodynamic polarization tests and electrochemical impedance spectroscopy in 0.1 M NaCl at the laboratory temperature. Obtained data were presented in form of potentiodynamic curves and Nyquist diagrams. Results of analysis showed that plasma electrolytic oxidation coating positively influence corrosion resistance of AZ31 magnesium alloy in chosen corrosive environment.