Water quality assessment of the Borska Reka river using the WPI (Water Pollution Index) method

The Borska Reka river (47 km long, 373 km2 of basin area) is located in eastern Serbia and it is the biggest tributary of the river Veliki Timok. It is also one of the most polluted watercourses in Serbia. Using the data of the Republic Hydrometeorological Service of Serbia, the paper analyzes water pollution using the combined physical-chemical WPI index (water pollution index) over two periods: 1993-1996 and 2006-2009. The analysis of parameters showed significantly increased values of heavy metals (especially iron and manganese) which are indicators of inorganic pollution (primarily because of mining), but also increased values of organic pollution indicators (Biological Oxygen Demand-BOD5, ammonium, coliform germs), as the result of uncontrolled domestic wastewater discharge

Analysis of the change in structural parameters of mechanically alloyed Cu composite materials using different milling methods

In this study, the Cu-Zr-B ternary system was investigated as it has proven to be a promising composite material used in various industries, including aerospace, automotive, electronics, nuclear and tooling, among others. Owing to its versatility and a combination of desirable properties such as high strength and hardness, corrosion and wear resistance, and thermal stability, making it suitable for a wide range of applications. The effects of mechanical alloying (MA) parameters on the Cu-Zr-B properties, including ball-to-powder ratio, rotation speed, milling time, and milling atmosphere, were examined using the X-ray analysis, scanning electron microscopy, stereological analysis, and the Williamson-Hall analysis. Different mills, namely Atritor Mill and Turbula Shaker, were used in order to determine the effect that the type of mill has on the final structural parameters of the Cu-Zr-B. All results are given after 20 hours of mechanical alloying of the composite material. The rotation speed was around 300 rpm for both devices, and the ball-to-powder ratio was 10:1 for all the cases. It was shown that the ball size also plays a significant role in the final microstructural and morphological properties of the MA powders of the Cu-Zr-B. A comprehensive analysis showed that the powders produced in the Atritor mill (Powder 1, with a uniform ball size), as well as the powders produced in the Turbula where there was a range of different ball sizes used (Powder 2), showed lower values of dislocation density and crystalline size values compared to the powders produced in the Turbula with a uniform ball size (Powder 3). It is important to state that, with time, due to the plastic deformation mechanisms present, crystallite size decreases in all cases, with the lowest value again being powder 3.Twenty-First Young Researchers’ Conference - Materials Science and Engineering: Program and the Book of Abstracts; November 29 – December 1, 2023, Belgrade, Serbi

Effect of Convective Drying Method of Chokeberry (Aronia melanocarpa L.) on Drying Kinetics, Bioactive Components and Sensory Characteristics of Bread with Chokeberry Powder

The effects of three dehydration temperatures at 50, 60 and 70 °C of convective drying method on fresh fruits of black chokeberries (Aronia melanocarpa L.) were evaluated. The drying temperatures were found to have significantly different effects on the characteristics of dried fruits and powders, made by the dried fruits. The maximum drying rate at a temperature of 50 °C was 59 g/h, at 60 °C 102 g/h, and at 70 °C 115 g/h, and thus the drying time was 37 hours, 27 hours and 23 hours respectively. The drying temperature at 50 °C caused the least damage to the cell structure of the fresh chokeberries, bioactive components (anthocyanins, flavonoids, phenols) and total antioxidativity. The dehydrated chokeberries at the temperature of 50 °C had the highest ratio of total anthocyanins (376.89 ± 5.73 mg cyn-3-glu / 100 g dm), total flavonoids (1037.19 ± 3.83 mg CE / 100 g dm), phenols (1918.79 ± 3.26 mg GAE / 100 g dm) and antioxidant activity (37.11 ± 0.28 mg TE / 100 g dm). The drying process at a temperature of 50 °C required longer drying period, higher energy need and produced the chokeberry powder, which gave the bread with the best sensory characteristics, compared to a drying process at a temperature of 60 °C and 70 °C

Mechanical alloying as a crucial step in the fabrication process of Cu alloys

Program and book of abstracts / 2nd International Conference on Innovative Materials in Extreme Conditions i. e. (IMEC2024), 20-22 March 2024 Belgrade, Serbia

Tourism and Natural Environment in the NP Taganay (Russia) - Habits And Perceptions of the Visitors

The research analyzes attitudes and habits of the visitors in the National Park (NP) Taganay on South Urals in Russia. The survey method was applied on a sample of 305 respondents in order to investigate visitors’ travel habits, as well as their perceptions regarding different experiences they were exposed to. The results identified a strong positive perception regarding overall experiences from visiting the NP. Specific permanent patterns of behavior were observed and compatibility between visitors’ habits and the environment was determined. The most significant variables affecting perceptions are the frequency of visits and the age. The study has identified certain concerns regarding environmental issues. Respondents were found sensitive to garbage production in public areas and the presence of noise in protected territory. The results of the study provide inputs for solving the long-standing conflict between nature conservation and mass tourism in Russian protected areas

Nutritional attributes of wheat bread fortified with convectively dried chokeberry powder

Chokeberry (Aronia melanocarpa L.) has a positive effect on human health, and therefore it can be used as a beneficial component for food (e.g. wheat bread) fortification. Dried chokeberry powder (CP), obtained by convective drying at 50, 60, and 70°C, fortified bread samples by replacing wheat flour at levels of 1, 2.5, 5 and 10%. Bread samples fortified with chokeberry were characterized by a decrease in total starch and protein contents and an increase in total sugar, mineral (Mg, Ca, Cu), and fat components; unsaturated oleic acid was reduced, unlike unsaturated linoleic and linolenic acids. All developed mathematical models for starch, protein, fat, and minerals in bread supplemented with CP were characterized by statistically insignificant residual variances and high values of R2. Z-score analysis showed the optimal segment and total scores of bread fortified with CP. Chokeberries dried at a temperature of 60°C showed the best nutritional attributes. Wheat bread enriched with CP in the amount of 10% had the highest level of fortification.Publishe

A method of determining parameters of Bofang model on the example of "Bileca" reservoir

In this research paper, measurement data of air and water temperatures and water levels for "Bileca" reservoir for a period between 1967. and 2017. are presented. Based on the averaged measurement data values, an analytical expressions for amplitude of periodic temperature variation of "Bileca" reservoir are derived and an average annual temperature, as a function of the observed depth, is obtained, based on Bofang model. The obtained results allow thermal stress analysis, which represents an important factor for stability and safety monitoring of dams

Uticaj sadržaja vlage na koeficijent toplotne provodnosti betona

In this paper, physical processes of adsorption and transport of humidity, which has dominant influence on the physical and thermal characteristics of concrete, has been described. The impact of structure of concrete especially pores dimensions and distribution has been explained. The drastic increase in the coefficient of thermal conductivity λ of concrete at increasing relative humidity has been analyzed. An analytic formula for λ, as a function of the concrete density and moisture content in exploitation conditions, starting from light autoclaved aerated to heavy concrete, has been given. The formula is based on experimental values for λ available in the literature. It has been confirmed that the thermal conductivity of all concretes are directly related to density and inversely to porosity and pores diameters.Zbornik radova Građevinskog fakultet

Позитрон - 31

Нови број нашег часописа отварамо кратким водичем за бруцоше кроз који представљамо катедре, службе, центре на Хемијском факултету, као и друге институције које се налазе у згради, а ту су и мапе за оријентацију на факултету. Кроз интервју са предметним професорима Опште хемије приказујемо на шта све треба обратити пажњу зарад ефикасног почетка изучавања хемије. Упознајемо вас са студентским организацијама на Хемијском факултету – са Студентским парламентом и његовим центрима, као и са Савезом студената Хемијског факултета. Разговарали смо и са нашом алумнисткињом која је са нама поделила своја искуства из периода студирања, као и са посла којим се данас бави. У овом броју имамо част да објавимо превод једног сјајног текста објављеног у часопису Nature, а чији је један од аутора академик и професор Хемијског факултета. Нова Управа Хемијског факултета се представила кроз кратке интервјуе. Испратили смо Десети скуп Међународне асоцијације физико-хемичара о чему можете прочитати наш извештај. Подсећамо се и сјајне изложбе „Кабинет Симе Лозанића“ организоване у част овог изузетног научника. Имаћете прилику да у овом броју пронађете и најзанимљивије фотографије са Позитроновог фото-конкурса које илуструју студентски живот на Хемијском факултету

Actual contamination of the Danube and Sava Rivers at Belgrade (2013)

This study was focussed on a comprehensive investigation on the state of pollution of the Danube and Sava Rivers in the region of Belgrade. Different complementary analytical approaches were employed covering both i) organic contaminants in the river water by target analyses of hormones and neonicotinoids as well as non-target screening analyses and ii) heavy metals in the sediments. Finally, some common water quality parameters were analysed. The overall state of pollution is on a moderate level. Bulk parameters did not reveal any unusual observations. Moreover, quantification of preselected organic contaminants did not indicate to elevated pollution. More significant contaminations were registered for chromium, nickel, zinc and partially copper in sediments with values above the target values according to Serbian regulations. Lastly, non-target screening analysis revealed a wider spectrum of organic contaminants comprising pharmaceuticals, technical additives, personal care products and pesticides. The study presented a comprehensive view on the state of pollution of the Sava and Danube Rivers and is the base for setting up further monitoring programs. As a superior outcome, it was illustrated how different chemical analyses can result in different assessments of the river quality. A comparison of target and non-target analyses pointed to potential misinterpretation of the real state of pollution