Technical Faculty in Bor
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Recent Submissions
Analysis and statistical modeling of copper ions biosorption onto calcined chicken eggshell
(Serbian Chemical Society, 2025) Miljan Marković; Milan Gorgievski; Nada Štrbac; Vesna Grekulović; Milica Zdravković; Marina Marković; Dalibor Stanković
The study on the possible use of calcined chicken eggshells as a biosorbent for copper ions removal from aqueous solutions, as well as some comparisons between raw and calcined eggshells, are presented in this paper. SEM-EDS and FTIR analysis of the calcined chicken eggshell samples were performed. In addition, the DTA-TGA analysis on raw chicken eggshells was performed. The influence of various process parameters, such as solution pH, stirring rate, biosorbent mass and Cu2+ concentration, was investigated. The kinetic analysis using four different empirical kinetic models was performed. The equilibrium analysis was done using the Langmuir, Freundlich and Temkin isotherm models. The process was optimized using the response surface methodology based on the Box–Behnken design (RSM-BBD). The obtained results are compared to our previous study on raw eggshells as a biosorbent for Cu2+ removal, in order to determine the justification for biosorbent modification (i.e., the calcination of raw eggshells).
Effect of heat treatment on the mechanical and structural properties of X155CrVMo12-1 steel
(Univerzitet u Zenici, Fakultet inženjerstva i prirodnih nauka, 2025) Stamenković, Uroš; Marković, Ivana; Mladenović, Srba; Manasijević, Dragan; Milanović, Petar; Nedeljković, Milan
This paper investigates the effects of oil quenching and tempering at various temperatures on the mechanical and structural properties of X155CrVMo12-1 tool steel. The steel specimens were austenitized at 1030 °C for half an hour, followed by quenching and tempering at different temperatures. Mechanical properties were assessed by measuring the hardness of the samples after each heat treatment. Using the conversion formula, the tensile strength values were calculated based on the measured hardness. Structural changes were analyzed using optical microscopy. The results indicate that the highest hardness values were achieved after the quenching process. However, an increase in tempering temperature led to a decrease in hardness. Optical microscopy revealed that quenching caused the appearance of martensite in the microstructure, while tempering at various temperatures caused alterations in the martensite structure.
Shifting from Physical to Virtual Classroom in Accounting Education: A Study of Students’ Experiences During the COVID-19 Pandemic in Serbia
(Springer Nature, 2024) Fedajev, Aleksandra; Jovanović, Dejan; Veličković, Milica
The COVID-19 pandemic onset has caused significant changes in all areas of human activities, with changes in education being among the most evident. The change in educational systems was particularly challenging for developing countries like Serbia, where most higher education institutions were still in the early stages of implementing information and communication technology (ICT) in education. The pandemic forced higher education institutions in Serbia to shift from traditional to distance learning to enable continuous teaching while implementing pandemic prevention measures. The purpose of this study was to explain how two variables—technological environment and educational environment during online courses—influence students’ perceived satisfaction with online courses and their ability to acquire additional professional skills. The statistical analysis in the study is based on surveying 180 bachelor students attending accounting education in distance learning mode. Study findings are used to define some recommendations for accounting educators in Serbia for updating future learning practices based on lessons learned during the pandemic. The derived recommendations may be useful for similar disciplines and other developing countries.
Journal of Mining and Metallurgy, 60 A (1) (2024)
(Univeristy of Belgrade, Technical Faculty in Bor, 2024) Bogdanović, Grozdanka; Sokolović, Jovica; Cocić, Mira; Stojković, Pavle; Balanović, Katarina
Survey on star partial order in indefinite inner product spaces
(Matematički institut SANU, 2022) Stanišev, Ivana
This is a short survey on the star partial order for matrices which is considered in the spaces with indefinite metric. The specific geometry of these spaces effects even on the definition of a star partial order, demanding the existence of the Moore--Penrose inverse of a certain matrix. A characterization of this partial order is also given. Some of the interesting properties are generalized and illustrated by the appropriate examples.