1. Control model for ground crew scheduling problem at small airports : case of SerbiaLena Đorđević Milutinović, Dragana Makajić-Nikolić, Slobodan Antić, Marija Živić, Andrej Lisec, 2021, original scientific article Abstract: Present-day airline industry is quite a competitive field and crew scheduling represents one of the crucial problems due to significant impact on the airline's cost. The crew scheduling problem is based on the assignment of crew members to operate different tasks of route. The main goal of this paper is to provide an analysis and a solution to one of the biggest problems detected on a small airport in the Serbia - the problem of ground crew scheduling. The paper presents the main characteristics, goals and limitations of a real-life problem identified at this small airport. In order to solve the problem, we developed a dynamic discrete simulation model. The model is developed in a spreadsheet environment of Microsoft Excel. Some of the main limitations found in the development of the model are strong constraints and multiple goals. The model presented in the paper is designed as a useful management tool for smaller airports and is aimed at the improvement of operative processes. Keywords: crew scheduling problem, modelling, air transport, small airport, management, spreadsheets Published in DKUM: 01.10.2024; Views: 0; Downloads: 1
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2. Application of gas condensing boilers in domestic heatingMarija Živić, Antun Galović, Jurij Avsec, Antun Barac, 2019, original scientific article Abstract: A growing number of households have had condensing boilers built in to be used for the heating of spaces and for the hot water supply. The use of condensing boilers is justified from the point of view of energy because they achieve higher thermal efficiency than traditional boilers. Condensation of water vapour occurs in the flue gases, whereby the heat released by condensation is used to heat the water in the boiler. How much water vapour will condense depends on the temperature to which the flue gases are cooled. In this paper, a thermodynamic analysis of thirteen built-in gas condensing boilers was performed; data on the flue gas composition and temperature, as well as on the excess air required for combustion were obtained for that purpose. The calculation results consisting of the amount of condensed water, the thermal efficiency of the boiler, and the volume flow rates of the air and fuel are presented in tables. The analysis identified the cases in which the water vapour condensation occurred and determined the amount of the condensed water. The cases without water vapour condensation were also identified. Keywords: gas condensing boilers, thermodynamic analysis, thermal efficiency of the boiler Published in DKUM: 22.02.2024; Views: 281; Downloads: 20
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3. Exergy analysis of a Brayton cycle with variable physical properties and variable composition of working substanceMarija Živić, Antun Galović, Jurij Avsec, Mario Holik, 2016, original scientific article Abstract: The exergy analysis of a Brayton cycle is performed in the paper. The four input variables: the ratio of the compressor exit and inlet pressures, the ratio of inlet temperature of gases in turbine and inlet temperature of air in compressor and the isentropic efficiencies of the compressor and turbine are analysed. The temperature ratio is varied in a way that the compressor inlet temperature of air is maintained constant, while the turbine inlet temperature of flue gases is varied from 900 to 1200°C. In the combustion chamber methane is completely combusted with excess air ratio which is determined by the temperature of flue gases at the turbine inlet. The analysis further includes variability of the molar heat capacities of air and flue gases with temperature and variability of their heat capacity ratios. The exergy destruction in turbine, compressor and combustion chamber and also total exergy efficiency of the cycle are considered in the analysis. Keywords: Brayton cycle, variable physical properties, variable composition of working substance, maximum work output, maximum thermal efficiency Published in DKUM: 12.07.2017; Views: 2263; Downloads: 356
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