A Methodology Proposal for Selecting the Optimal Location for Small Hydropower Plants

The hydropower potential in the Republic of Serbia, as the most important renewable energy source, has been estimated at around 17000 GW·h per year, where approximately 2000 GW·h could be obtained from small hydropower plants (SHP). Small hydropower plants in Serbia currently produce 150 GW·h. Accordingly, the share of the electricity production from small hydropower plants in the total electricity production in Serbia is too small. The paper presents a model for the selection of optimal locations for small hydropower plants, which includes an ecological criterion, along with technical and economic criteria. The ecological criterion is eliminatory, i.e. those parts of the watercourse that border on or pass through protected natural assets are not taken into account when considering potential optimal locations for SHPs. All technical and economic criteria are included in the calculation of the weighted arithmetic mean with the aim of determining the optimal position for the construction of small hydropower plants. The model is implemented in the SHPOP software and its application is demonstrated on five watercourses in Southeastern Serbia

Risk education in Serbia

Natural disaster risk reduction can be achieved through vulnerability reduction, as well as through strengthening the resilience of the population. One of the segments leading to these aims is a proper risk education. It is the public (compulsory) education system that reaches the greatest number of participants and represents a good platform for the natural disaster knowledge transfer. Geography, as a complex subject that includes both natural and social components, is the most appropriate to transfer the knowledge necessary to improve the resilience. Research done in Serbia (detailed analyses of curricula, textbooks, teachers' role and pupils' knowledge) shows that children do learn about natural disasters but not in a way which provides usable knowledge

A Stochastic Model for Achieving Required Level of Availability Based on the Repair Rate Analysis

The aim of this paper is to set framework for the repair rate in order to achieve required availability of a repairable system with alternating renewal process where the failure rate is Weibull distributed. In order to accomplish this goal, this paper proposes a novel model for a complete stochastic analysis of the repair rate. The resulting equation for probability density function of the repair rate enables precise modelling of the repair rate process for related values of availability and failure rate. The obtained results can be used for dynamic forecasting of system’s characteristics, planning of maintenance activities, inventory and servicing capacities

Synthesis and characterization of BiFeO3 fine powders

Bismuth ferrite (BiFeO3) is one of the most studied multiferroic system with a large number of published articles. This is mainly because BiFeO3 material possesses both ferromagnetic and ferroelectric properties observed at room temperature, which opens great possibility for industrial and technological applications. Well-crystallized single-crystal BiFeO3 nanopowder has been successfully synthesized with the hydrothermal method. Structural analysis showed that non-annealed powder can be perfectly fitted to rhombohedral space group R3c and contains a very small amount of secondary phase, whereas the final product (annealed at 800 °C) represents single-phase perovskite powder with high crystallinity. HRTEM analysis confirmed existence of twin stacking faults, which are responsible for enhanced magnetic properties. EPR measurements suggested existence of electrons trapped by vacancies or defects. It has been proposed that existence of Fe3+ −OV defect complex could be generated at elevated temperatures followed by formation of trivalent Fe ions, which intensely provide local 3d moments.V Serbian Ceramic Society Conference : program and the book of abstracts; June 11-13, 2019; Belgrad

BiFeO3 fine powder controlled hydrothermal process synthesis and characterization

From the technological point of view, the mutual control of electric and magnetic properties is an attractive possibility, but the number of candidate multiferroic materials is limited. One of the most studied of them, BiFeO3 , has critical conditions for synthesizing single phase since the phase temperature stability range is very narrow. Bismuth ferrite (BFO) particles were synthesized by controlled hydrothermal process, where the particles of small sizes and high purity were obtained. A fitting refinement procedure using the Rietveld method was performed. Bismuth ferrite crystallizes in the perovskite type structure (α-BiFeO3 ) with rhombohedral space group R3c. The effects of thermal treatment through applied hydrothermal method on the obtained BFO grains morphology were evaluated by SEM and TEM analyses.SEM analysis showed that grains are very well crystallized, with non- fragmented crystal flats. Individual particles HRTEM analysis confirmed the evidence of ultra-fine single crystal particles, with characteristic (012) crystal planes. Furthermore, HRTEM confirmed the existence of twin stacking faults responsible for synthesized fine particles enhanced magnetic properties. The EPR results suggested the existence and participation of electrons trapped by vacancies or defects. It has been proposed that the existence of Fe 3+−OV defect complex could be generated at elevated temperatures followed by formation of Fe 3+ ions, which intensely provide the local 3d moments.IX Serbian Ceramic Society Conference - Advanced Ceramics and Application : new frontiers in multifunctional material science and processing : program and the book of abstracts; September 20-21, 2021; Belgrad

Spectral reflectance indices as a phenotyping tool for assessing morpho-physiological traits of winter wheat (Triticum aestivum L.)

Morpho-physiological traits of wheat such as a grain weight per plant, total leaf chlorophyll content, carotenoids, relative dry matter and nitrogen content are important traits for the growth of winter wheat genotypes. However, methods to estimate these traits are laborious and destructive. Spectral reflectance indices based on combination of visible and near-infrared wavelengths such as NDVI (Normalized Difference Vegetation Index), represent one of the most promising tools for application in field phenotyping with potential to provide complex information on different morpho-physiological traits of wheat. The aim of this study was to assess the utility of NDVI measurements of wheat canopy in identification of a specific growth stage in which remotely sensed data show the largest correlation with final grain yield, grain weight per plant, total leaf chlorophyll and carotenoid content, relative dry matter and nitrogen content in 29 winter wheat (Triticum aestivum L.) genotypes. The NDVI was measured using an active hand-held sensor GreenSeeker (NTech Industries Inc., Ukiah, California, USA) and hyperspectral camera (Ximea Corp., Lakewood, CO USA) at four growth stages of wheat: full flowering (BBCH 65), medium milk (BBCH 75), early dough (BBCH 83) and fully ripe stage (BBCH 89). Overall 66 different hyperspectral NDVIs were calculated from two-band combinations between red (600-700 nm) or far red (700-740 nm) and near-infrared (756-946 nm) regions. Pearson’s correlation coefficient was used to explore the relationship among examined traits and NDVI measured at different growth stages of wheat. Obtained results indicate that most of observed NDVI indices showed negative correlation with the relative dry matter content at all observed growth stages. Significant positive correlations (higher than 0.6 and significant at P < 0.05) were found between the specific hyperspectral NDVIs measured at medium milk stage and grain weight per plant, total leaf chlorophyll, carotenoid and nitrogen content, as well as with final grain yield of wheat. The strong positive relationship between NDVI and examined traits found at medium milk stage suggests that this stage is the most appropriate for estimation of these traits of winter wheat in semiarid or similar wheat growing conditions. The overall results indicate that spectral reflectance tools based on combined visible and near-infrared wavelengths, such as NDVI, could be successfully applied to assess morpho-physiological traits of a large number of winter wheat genotypes in a rapid and non-destructive manner. Furthermore, although neither device appeared to have a sizeable advantage over the other, NDVI acquired by hyperspectral camera does appear to be more indicative than NDVI acquired by GreenSeeker sensor, suggesting that alternative spectral combinations can be used in assessing targeted traits of winter wheat genotypes. Abstract boo

Vulnerability to natural disasters in Serbia: spatial and temporal comparison

The frequency of natural disasters and the extent of their consequences at a global level are constantly increasing. This trend is partially caused by increased population vulnerability, which implies the degree of population vulnerability due to high magnitude natural processes. This paper presents an analysis of vulnerability to natural disaster in Serbia in the second half of the twentieth and the early twenty-first century. Vulnerability changes were traced on the basis of demographic–economic indicators derived from statistical data for local government units (municipalities) provided by the Statistical Office of the Republic of Serbia. Calculations were performed in the geographical information system environment. The results of the study show that spatial and temporal vulnerability variations are causally correlated with changes in the selected components. Significant rise of vulnerability is related to urban areas, while lower values are characteristic for other areas of Serbia; this is primarily a consequence of different population density