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Item Survey on star partial order in indefinite inner product spaces(Matematički institut SANU, 2022) Stanišev, IvanaThis 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.Item Quasihyponormal and Strongly Quasihyponormal Matrices in Inner Product Spaces(International Linear Algebra Society, 2012) Radojević, Ivana; Đorđević, DraganThe notion of quasihyponormal and strongly quasihyponormal matrices is introduced in spaces equipped with possibly degenerate indefinite inner product, based on the works that studied hyponormal and strongly hyponormal matrices in these spaces. Generalizations of some results known for normal and hyponormal matrices are established.Item New results for EP matrices in indefinite inner product spaces(Springer, 2014) Radojević, IvanaIn this paper we study J-EP matrices, as a generalization of EP-matrices in indefinite inner product spaces, with respect to indefinite matrix product. We give some properties concerning EP and J-EP matrices and find connection between them. Also, we present some results for reverse order law for Moore-Penrose inverse in indefinite setting. Finally, we deal with the star partial ordering and improve some results given in the “EP matrices in indefinite inner product spaces” (2012), by relaxing some conditions.Item Moore-Penrose Inverse in Indefinite Inner Product Spaces(University of Niš, Faculty of Sciences and Mathematics, 2017) Radojević, Ivana; Đorđević, DraganWe present the definition and some properties for the Moore-Penrose inverse in possibly degenerate indefinite inner product spaces. The extensions of appropriate results, given for matrices in Euclidean and nondegenerate indefinite inner product spaces are established. All this is done by using the concept of linear relations.Item An ADAM-based approach to unveiling entrepreneurial ecosystems in selected European countries(Emerald, 2025) Popović, Gabrijela; Fedajev, Aleksandra; Mitić, Petar; Meidutė-Kavaliauskienė, IevaPurpose This study aims to integrate the resource-based view (RBV) with other theories that consider external factors necessary to respond successfully to dynamic and uncertain entrepreneurial business conditions. Design/methodology/approach The paper introduces an multi-criteria decision-making (MCDM) approach, utilizing the axial-distance-based aggregated measurement (ADAM) method with weights determined by the preference selection index (PSI) method, to rank eight European countries based on the Global Entrepreneurship Monitor (GEM) data. Additionally, the paper extends the existing entrepreneurial ecosystem taxonomy (EET), offering an additional classification. Findings The performed analysis emphasizes the importance and necessity of involving different dimensions of EE in assessing the countries' entrepreneurship performance, which facilitates creating adequate policy measures. Research limitations/implications The crucial limitations are assessments based only on the GEM data from a particular period, possibly leading to a certain bias. Future research should involve data from various resources to increase the results' reliability. Originality/value The ranking results and country classification obtained using the ADAM-based approach and two distinct taxonomies served as the basis for formulating tailored policy recommendations, aiming to formulate tailored policy implications for increasing the number of new entrepreneurs and improving innovativeness, sustainability and internationalization of existing entrepreneurs for each group of countries.Item Neuro-fuzzy prediction model of occupational injuries in mining(Taylor & Francis, 2024) Ivaz, Jelena; Petrović, Dejan; Stojadinović, Saša; Stojković, Pavle; Petrović, Sanja; Zlatanović, DraganObjectives. This study investigates the possibility of developing a unique model for predicting work-related injuries in Serbian underground coal mines using neural networks and fuzzy logic theory. Accidents are common due to the unique nature of underground mineral extraction involving people, machinery and limited workplaces. Methods. A universal model for predicting occupational accidents takes into account influential factors such as organizational aspects, personal and collective protective equipment, on-the-job training and leadership factors. The selected networks achieved a prediction accuracy of >90%. Results. The study successfully identifies potential risks and critical worker groups leading to injuries. The sensitivity analysis provides insights for targeted safety measures and improved organizational practices. Conclusion. This data-driven approach makes a valuable contribution to safety in the mining industry. Implementation of the predictive model can reduce injuries and machine damage, and improve worker well-being.Item Western Balkan countries’ innovation as determinant of their future growth and development(Taylor & Francis, 2024) Fedajev, Aleksandra; Panić, Marija; Živković, ŽivanThe Western Balkan (WB) countries (Albania, Bosnia & Herzegovina, Kosovo, Montenegro, North Macedonia, and Serbia) have been trying to become members of the EU for a long time, but they are increasingly moving away from the EU average in terms of development level. The question is whether these countries will be able to catch up with the EU countries in the near future and how they will do it. The reason for such results should be searched into insufficient innovation in these countries. This research aims to perform a comparative analysis of the capabilities and efficiency of the National Innovation System (NIS) in WB and CEE countries using the entropy-based PROMETHEE method for ranking. The rankings are performed using the two most reputable 2022 reports in this area: Global Innovation Index (GII) and European Innovation Scoreboard (EIS). For summarizing the results, the Borda rule is applied. The ranking results for both NIS capabilities and NIS efficiency indicate that WB countries are at the bottom of the rankings, having considerable disadvantages compared to CEE countries. Certain recommendations and guidelines for policymakers in these countries for improving innovation in the future have been defined according to practices from identified benchmarking countries.Item Exploring the Nexus of Distance Learning Satisfaction: Perspectives from Accounting Students in Serbian Public Universities During the Pandemic(Springer Nature, 2025) Fedajev, Aleksandra; Jovanović, Dejan; Janković-Perić, Marina; Radulescu, MagdalenaAmid the COVID-19 pandemic, teachers globally transitioned to distance learning, presenting significant challenges, particularly in developing countries. In that sense, the study investigates the usefulness and satisfaction (US) of distance learning (DL) among accounting students in Serbian public universities during the COVID-19 pandemic. The research focuses on three key factors affecting perceived US derived from existing literature, including teaching process quality (TPQ), technical qualities of distance learning platforms (TQ), and compatibility with social and pandemic conditions (CSPC). The developed theoretical model is predominantly based on the user satisfaction model. Data from 373 surveyed students, gathered through a validated questionnaire, underwent analysis using the partial least squares structural equation model (PLS-SEM). Results reveal that CSPC and TPQ significantly impact the US, whereas TQ has a minor and statistically insignificant effect. The R2 value indicates these three constructs explain a significant portion of the variance for the US, with moderate effects of CSPC and TPQ and a small effect of TQ, indicated by f2 values. Moreover, the model is found to be significantly predictive, according to the Q2 value. Besides theoretical implications, the study suggests important practical implications for university management, emphasizing regular student surveys, continuous improvement of DL systems, and effective and continuous teacher training as the vital measures for enhancing teaching quality. Improving TPQ and TQ also impacts the Serbian economy by fostering workforce development, enhancing digital transformation, stimulating telecommunication industry growth, driving digital information sector development, attracting investment and innovation, boosting global competitiveness, and promoting lifelong learning.Item Star partial order in indefinite inner product spaces(Taylor & Francis, 2022) Stanišev, IvanaWe define the star partial order for matrices in spaces with an indefinite inner product. We also give a characterization of that order in terms of matrices and their Moore-Penrose inverses. Finally, some interesting properties are shown.Item Characterization of the Cu-Ge-In: microstructural, mechanical, electrical properties, scheil and laver simulation(Polish Academy of Sciences, 2025) Đorđević, Aleksandar; Zečević, MIlena; Minić, Duško; Kolarević, Milan; Balanović, Ljubiša; Manasijević, Dragan; Petrović, MilenkoBased on application of Cu-based alloys and special application of Ge-based alloys it is from huge interest to study properties of the Cu-Ge-X alloys. In this paper selected system is Cu-Ge-In. This system was previously studied by our group. In this paper results are focused on electrical and mechanical properties. Experimental tests were performed on 12 ternary alloys. Six different experimental techniques were used to test the ternary alloys. The microstructure was tested using light optical microscopy (LOM) and scanning electron microscopy (SEM). The composition of the phases and the composition of the alloys were examined by energy dispersive spectroscopy (EDS). X-ray diffractometric analysis (XRD) was used to determine the phases. Properties such as hardness and electrical conductivity tests were performed. Those properties were used for calculation and modeling those properties along all composition ranges. Isothermal section at 25°C were predicted. Calculated isothermal section and were compared with results of the EDS and XRD test. Good agreement of calculated and experimental result has been reached. Best results of electrical conductivity and hardness give alloys with composition Cu80.93Ge9.86In9.21.Item Investigation of the thermal properties of X155CrVMo12-1 steel after quenching and tempering(Scientific-Technical Union of Mechanical Engineering “Industry-4.0”, Bulgaria, 2025) Stamenković, Uroš; Marković, Ivana; Mladenović, Srba; Manasijević, Dragan; Nedeljković, Milan; Milanović, PetarThis paper investigates the effects of oil quenching and tempering at various temperatures on the mechanical and thermal properties of X155CrVMo12-1 tool steel. The steel specimens were austenitized at 1030 °C for half an hour, followed by quenching in oil and tempering at temperatures ranging from 50 °C to 700 °C. Mechanical properties were assessed by measuring the microhardness of the samples after each heat treatment. Thermal properties were investigated using the Xenon flash method (DXF analysis) to measure thermal diffusivity, thermal conductivity, and specific heat. The results show that the highest microhardness values were achieved after quenching, while the lowest values were observed for thermal diffusivity and thermal conductivity. Following quenching, the microhardness values gradually decreased with an increase in tempering temperature, whereas the values of thermal diffusivity and thermal conductivity increased. Even after tempering at 500 °C, the microhardness values remained quite high, with only a 23.41% decrease from the quenched state. Furthermore, there was a significant improvement in thermal properties, with thermal diffusivity increasing by 38.34% and thermal conductivity improving by 23.99%.Item Permanentno termovizijsko praćenje skladišta uglja i drugih zapaljivih materijala u cilju prevencije samozapaljenja(Univerzitet u Beogradu, Tehnički fakultet u Boru, 2024) Stević, Zoran; Dimitrijević, Stevan; Dimitrijević, Silvana; Petrović, Sanja J.; Stolić, PredragSamozapaljenje uglja na otvorenim skladištima česta je pojava. Pored nastale štete zbog gubitka korisne materije, odnosno toplotne moći, postoje i troškovi gašenja u slučaju da dođe do intenzivnog sagorevanja. U takvoj situaciji nanosi se ogromna šteta okolini emisijom štetnih gasova i čestica. Klasične metode suzbijanja samozapaljenja uglja pokazale su se nedovoljno efikasnim ili skupim i komplikovanim, tako da je neophodno uvesti nove tehnologije i u ovu oblast. Termovizija se pokazala kao veoma efikasna tehnika za rešavanje problema ranog otkrivanja samozagrevanja naslaga uglja. U kombinaciji sa elementima kontinualnog nadzora i sistema ranog obaveštavanja omogućava stvaranje jednog održivog rešenja za sprečavanje pojava incidentnih situacija, odnosno preventivno delovanje na onim lokacijama koje ispoljavaju tendenciju samozapaljenja na osnovu analiziranih termovizijskih parametara.Item Application of mullein leaf for biosorption of Zn(II) and Ni(II) ions from synthetic solutions(University of Banja Luka, Faculty of Technology, 2025) Nujkić, Maja; Tasić, Žaklina; Medić, Dragana; Milić, Snežana; Stanković, Sonja; Pešić, MarinaIn this study, the potential of mullein leaves (Verbascum thapsus) for the biosorption of Zn(II) and Ni(II) ions from synthetic solutions was investigated. Several factors affecting the biosorption efficiency of mullein leaf powder were investigated, including initial Zn(II) and Ni(II) concentration (25–400 mg L−1), solution pH (3–7), contact time (10–120 min), and biosorbent dosage (2–20 g L−1). The concentration of Zn(II) and Ni(II) before and after biosorption was determined using an optical emission spectrometer with inductively coupled plasma. The maximum biosorption efficiency of 86.46% was observed at a biosorbent dosage of 20 g L−1, pH = 4, contact time 90 min and an initial Zn(II) oncentration of 100 mg L−1. Also, the good biosorption efficiency of 76.51% for Ni(II) ions was achieved at a contact time of 90 minutes. Therefore, mullein was most effective in removing Zn(II) ions from synthetic solutions. Thus, mullein has the potential to be a cost-effective biosorbent for wastewater treatment, but further studies on modified mullein should be conducted.Item Investigation of thermal properties of Al–Cu eutectic alloy for phase change energy storage applications(Springer, 2025) Manasijević, Dragan; Balanović, Ljubiša; Cimpoesu, Nicanor; Markovic, Ivana; Gorgievski, Milan; Stamenković, Uroš; Stepanović, AleksandraThe knowledge of thermal properties such as thermal conductivity, specific heat, and latent heat of melting is essential for the development of phase change materials (PCMs) for latent heat energy storage applications. Due to their good properties, aluminum-based eutectic alloys have become the most widely studied metal-based PCMs. In the present study, microstructure, thermal diffusivity, thermal conductivity, specific heat capacity, and latent heat of melting of the Al-33.6 mass% Cu eutectic alloy were examined using scanning electron microscopy, energy dispersion spectroscopy, differential scanning calorimetry, and light flash method. The results show that the microstructure of the investigated alloy consists of fine and coarse (Al) + Al2Cu eutectic regions. Specific heat, thermal diffusivity, and thermal conductivity increase with increasing temperature in the temperature range 25–400 °C. The thermal conductivity of the studied alloy at room temperature is 134.3 Wm−1 K−1. The measured latent heat is 319.5 Jg−1. The obtained results indicate that the Al–Cu eutectic alloy has considerable potential for application in the field of phase change energy storage materials.Item Tekstilna industrija(Savez inženjera i tehničara tekstilaca Srbije, 2024) Urošević, Snežana; Urošević, SnežanaItem Effect of Chemical Composition on the Corrosion Resistance, Microstructure, Hardness and Electrical Conductivity of the Ge–In–Sn Alloys(Springer, 2023) Zečević, Milena; Tosković, Nemanja; Đorđević, Aleksandar; Minić, Duško; Tošković, Dragan; Kolarević, Milan; Ristić, Vladica; Tasić, ŽaklinaThis paper presents the results of experimental and analytical testing of the ternary Ge–In–Sn system. Experimental part includes results of the corrosion resistance, microstructure, hardness and electrical properties of the selected ternary Ge–In–Sn alloys. The prepared alloys were tested using X-ray powder diffraction (XRD) method, scanning electron microscopy with energy dispersive spectrometry (SEMEDS), hardness and electrical conductivity tests. For the obtained values of hardness and electrical conductivity, a mathematical model was used in order to determine the properties of the alloy in the entire range of the composition. The results of the Brinell hardness test show that the Ge80In10Sn10 ternary alloy has the highest hardness of all tested ternary alloys, 254.2 MN/m2 . While, results of the electrical conductivity test show that the Ge10In10Sn80 ternary alloy has the highest conductivity of all tested ternary alloys and the highest corrosion resistance. Calculated isothermal section at 25 C, were confirmed with XRD and EDS results.Item The Granger causality of digital connectivity and trade globalization in the health crisis(University of Belgrade, Technical Faculty in Bor, 2024) Petkovski, Ivana; Fedajev, Aleksandra; Milošević, IsidoraThe widespread adoption of digital technology in the last decade has caused global changes, leading to the belief that technology is altering the global connectivity of economies. This is especially emphasized in light of the global health crisis in 2020. To efficiently monitor this process, it is vital to assess the anticipatory potential of this type of digital connectivity and the growth of globalization in trade. An effective analysis of this issue necessitates looking into the causative relationship between digital technology connections and trade globalization. This is performed by applying the statistical approach of Granger causality to a data set consisting of 35 European countries from 2010 to 2022. A Granger causality study was performed using the lag value estimated based on the Akaike information criterion, which equals 2. The findings suggested that there is a unidirectional causal relationship between active mobile-broadband subscriptions and imports, with the former influencing the latter. However, this causal relationship fails to be valid in the opposite direction. The examination revealed a reciprocal relationship between fixed-telephone subscriptions and exports, as well as a reciprocal relationship between fixed-telephone subscriptions and imports. The results reveal the bidirectional value of the number of fixed telephone subscriptions as a measure of digital connectivity.Item Fostering Green Transition in Central and Eastern Europe: Carbon Dioxide Emissions, Industrialization, Financial Development, and Electricity Nexus(Vilnius Gediminas Technical University, Lithuania, 2024) Mitić, Petar; Fedajev, Aleksandra; Radulescu, Magdalena; Hudea, Oana Simona; Streimikiene, DaliaClimate change presents a substantial impediment for the global community and prompts policymakers worldwide to prioritize environmental goals when defining national development strategies. Prioritizing these goals is particularly challenging for governments of developing economies still relying on fossil fuels, foreign capital, and industry contribution to GDP. This study examines the relationships between carbon dioxide emissions, industry value added, financial development, and electricity generation in 15 Central and Eastern European countries from 1995 to 2021. To achieve this objective, we examined stationarity and cointegration and employed a vector error correction model to investigate causalities between the variables, along with a variance decomposition analysis. Our findings suggest that the short-run unidirectional causalities exist from industry value-added to carbon dioxide emissions and from carbon dioxide emissions to financial development and electricity generation. Long-term causality exists between carbon dioxide emissions and industry value added. The findings shed light on the challenges and opportunities these countries face in transitioning to climate neutrality and meeting the decarbonization targets. Within this context, the findings underscore the significance of crafting customized strategies for these economies to navigate the complex landscape of climate change while promoting sustainable industrial, electricity and financial sector development.Item Technology-based factors of globalization in market and transition economies. Is there a difference?(Vilnius Gediminas Technical University, Lithuania, 2024) Petkovski, Ivana; Fedajev, Aleksandra; Mihajlovic, IvanPurpose – The global crises that emerged during the last two decades proved that economies that focus their development on demand are the most vulnerable during crises. However, development strategies depend on specific internal and external circumstances impacting development of particular country. In that sense, this research aims to identify how digitalization, science and technology, and ICT trade impact globalization in market and transition economies. Research methodology – Authors employed the PLS-SEM methodology on available dataset for 32 European economies. Findings – According to the findings, digitalization is the factor that has the highest positive impact on globalization in market economies, while ICT trade has the greatest positive impact on globalization in transition economies. Science and technological advancements have a diverse impact. The MGA results stressed out the difference between these groups even more clear. Research limitations – The presented model does not consider country-level analysis of globalization. Practical implications – The study is providing theoretical and empirical base for strategy and policy development in the globalization domain in line with economy character. Originality – The value of the research is found in contributing to the globalization topic in market, and particularly in transition economie that lack empirical research in this field.Item The MCDM-based Assessment of Solutions for Transition to Sustainable Industry 4.0: The Case of Serbia(Institut ekonomskih nauka, Beograd, 2024) Popović, Gabrijela; Fedajev, Aleksandra; Stanujkić, DragišaIndustry 4.0 implies the transformation of organizations into digital entities. It represents a new level of industrial development that has changed demands, competition, industry structure, and sustainability awareness. The primary objective of this paper is to use Multiple-Criteria Decision Making (MCDM) to identify the principal obstacles and solutions for successfully adopting the technologies that will facilitate a transition of the Serbian industry to sustainable Industry 4.0. The barriers' significance was defined using the Preference Selection Index – PSI. The assessment of the solutions was performed by three decision-makers using the following MCDM methods: PSI, Compromise Ranking of Alternatives from Distance to Ideal Solution – CRADIS, and Integrated Simple Weighted Sum-Product Method—WISP. The results revealed that logistics, reverse logistics management, and technology integration are the most significant barriers. The significance of logistics and warehousing management lies in their role as crucial facilitators for the sustainable development of industries, ensuring efficient and responsible movement, storage, and distribution of goods. Also, the application and development of new technologies can improve efficiency and reduce the environmental impact of the Serbian industry. Based on the MCDM methods, the framework enabled the assessment of the barriers and solutions for technology adoption in light of the current business conditions in the Republic of Serbia. Managers and policymakers can easily perceive the main obstacles and optimal actions needed to fulfill the requirements of Industry 4.0 and promote sustainable operations.