Faculty of Technical Sciences, Čačak

Permanent URI for this collectionhttps://dspace.unic.kg.ac.rs/handle/123456789/8215

The Faculty is accredited and it offers accredited Undergraduate, Integrated, Master and Doctoral study programmes. The cooperation with leading domestic and International companies such as Oracle, Microsoft, Intergraph, Fujitsu and Schneider-electric enabled our students to gain skills through practice in well-known companies, and prompted our graduates to be distinguished experts in modern technologies.

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Synthesis and characterization of BaTiO3/α-Fe2O3 core/shell structure
(2019) Filipović, Suzana; Pavlović, Vera; Mitric M.; Levic, Steva; Mitrovic, Nebojsa; Maricic, Aleksa; Vlahović B.; Pavlović, Vladimir
Multiferroic materials attracted a lot of attention in recent years because of their significant scientific interest and technological applications. The multiferroic core/shell powders have a better connectivity between the phases, resulting in superior dielectric and magneto electric properties. In this study, the influence of preparation condition on structure and properties of BaTiO3/α-Fe2O3 core/shell composite materials was examined. The five samples were obtained by varying synthesis conditions, such as synthesized method (co-precipitation and sonochemical method) and pH values of solution. XRD and Raman spectroscopy analyses were performed in order to determine phase composition and structural changes within samples. Morphology modifications were examined by SEM and EDS analyses. Finally, effect of structural and microstructural changes on magnetic and electrical properties was detected and explained.
New model for determining criteria weights: Level based weight assessment (lbwa) model
(2019) Žižović, Mališa; Pamucar, Dragan
This paper presents new subjective model for determining weight coefficients in multi-criteria decision-making models. The new Level Based Weight Assessment (LBWA) model enables the involvement of experts from different fields with the purpose of defining the relations between criteria and providing rational decision making. The method can be applied in practical cases in specialized decision-making support systems, as well as in alternative dispute resolutions in virtual environment. The LBWA model has several key advantages over other subjective models based on mutual comparison of criteria, which include the following: (1) the LBWA model allows the calculation of weight coefficients with small number of criteria comparisons, only n-1 comparison; (2) The algorithm of the LBWA model does not become more complex with the increase of the number of criteria, which makes it suitable for use in complex multi-criteria (MCDM) models with a large number of criteria; (3) By applying the LBWA model, optimal values of weight coefficients are obtained with simple mathematical apparatus that eliminates inconsistencies in expert preferences, which are tolerated in certain subjective models (Best Worst Method - BWM and Analytic Hierarchy Process - AHP); (4) The elasticity coefficient of the LBWA model enables, after comparing the criteria, additional corrections of the values of the weight coefficients depending on the preferences of the decision makers. This feature of the LBWA model enables sensitivity analysis of the MCDM model by analyzing the effects of variations in the values of the weights of criteria on final decision.
DECISION MAKING IN INDUSTRIAL ENTERPRISES IN CONDITIONS OF UNCERTAINTY
(2019) Milunović Koprivica, Sandra; Maric A.; Ristic, Olga; Arsovski, Slavko
In this paper analysed the way of the the decision making “produce or purchase” under conditions of uncertainty in the industry enterprises applying the fuzzy sets theory.
COEFFICIENT OF EXPLOSION OF GRAPE OIL REPAS IN RESPECT OF VARIETY, CONTENT OF HUMIDITY AND SURFACE
(2019) Koprivica, Ranko; Veljkovic, Biljana; Turan J.; Đokić, Dragoslav; Radivojevic D.; Ćurčić, Srećko; Mileusnic Z.; Balalić I.
Knowing the coefficient of friction of bio material is important in determining the angle of the grain elevator elevator when designing combines, as well as the angles of gravity tables and pipes in seed finishing. The basic characteristic of biological materials, or seeds of agricultural crops, is that they differ in their physical and morphological characteristics. Therefore, the friction depends on: the types of plants, variety, shape, dimensions and seed content, the humidity of the seed, the intensity of the normal force on the substrate and the roughness of the substrate. The paper presents the results of the study of the influence of individual factors (varieties, water content of the grain and the type of substrate) and their interactions on the grain friction coefficient. The domestic varieties that are grown in Serbia are selected for testing the fruiting grain fruity: Banadanka, Jasna and Slavica. The experimental measurement of the static coefficient of grain slip friction was done using the level of the mechanical device Tribometr. Plastic, plywood, galvanized, steel, aluminum and stainless steel sheet are made for the experiment purposes. Research was carried out with different water content in grains: 6%, 11%, 16% and 24%. The variety Banadanka had a lower friction coefficient compared to Jasna and Slavica varieties on all substrates and with all the water content of the grain. It was found that with the increase of water content in the grain, a significant increase in the friction coefficient of the grains of the tested varieties on all substrates was achieved. The highest friction coefficient for all water content of the grains of the tested varieties was on the base of the plywood board, and the smallest on the base of stainless steel sheet.
THE IMPACT OF INTELLIGENT SYSTEMS FOR DECISION SUPPORT APPLICATION ON IMPROVEMENT OF THE BUSINESS DECISIONS QUALITY
(2019) Nesic, Zoran; Šalić R.; Radojicic M.; Miletović N.
This paper presents some considerations about the impact of intelligent decision support systems as modern tools that enable not only increasing the efficiency of decision-making process but also the quality of business decisions that are being made. Considerations relate to the wider field of information technology application in terms of supporting complex business problems solving with the ultimate purpose of achieving the desired state of the system. The paper presents some of the characteristics and possibilities of such information technology support in the function of improving the quality of managerial decision-making.
SURFACE BASE EFFECTS ON ZINC COATING CHARACTERISTICS
(2019) Jovanovic D.; Nedic, Bogdan; Baralić, Jelena
Galvanic zinc coating applied in addition to perform appropriate performances of the base material surface such as corrosion resistance, chemical stability, required aesthetic impression etc. Galvanic zinc coating examinations are focused mostly on Zn connection with the base material, while we have poor data about the influence of the surface on the characteristics of the coating. Previous final processing has a large impact on the physical and mechanical properties and coating structure. This paper presents the results of research on the properties of zinc coatings deposition on the surface obtained by various final processing with different hardness and topography.
PYROTECHNIC SAFETY IN THE PROCESS OF DEMILITARIZATION OF EXPLOSIVE ORDNANCE FROM THE ASPECT OF APPLICATION OF NEW TECHNOLOGIES
(2019) Đurić, Milena; Nedic, Bogdan; Baralić, Jelena; Miljkovic A.
The application of new technologies in result of improving the pyrotechnic safety system, represents one of the priorities in the field of demilitarization of the EO. The conventional demilitarization procedures are partially or does not meet the prescribed standards at all in the field of pyrotechnic safety systems. The use of water-based techniques for the purpose of projectile delaboration directly influences the improvement of the pyrotechnic safety system, as well as the reduction of emissions of harmful and toxic chemical compounds into the working environment. The paper analyzes and research the possibility of improving the pyrotechnic safety system using abrasive waterjet and washout waterjet technology. Current research and conducted experiments show a wide area for the implementation of technology for the needs of projectile delaboration.
ANALYSIS OF THE SERBIA’S INNOVATION PROFILE
(2019) Puzović, Sanja; Vesić Vasović, Jasmina; Paunovic, Vladan; Nesic, Zoran; Karapavlović, Nemanja
The paper highlights the importance of strengthening the country's innovative potential due to it’s economic prosperity. Also the paper points out to the importance of application an appropriate metrics for assessing the effectiveness of the national innovation systems and innovation policies. In addition, the Serbia`s innovation profile was presented, through the analysis of innovation potential indicators as the factors that affect how new products, services and processes are generated, developed and implemented. Based on this analysis, proposals have been put forward for strengthening the innovation potential of Serbia and creating conditions in which organizations across the country can successfully innovate.
SOME INFLUENTIAL ASPECTS ON THE QUALITY OF RAILWAY BUSINESS OPERATIONS
(2019) Antić Z.; Nesic, Zoran; Miletović N.; Mihailović Đ.
The railway system is a very complex system of operations influenced by many factors. In this paper are given some considerations on the influence factors on improvement of the quality of the railway system operation. Considerations relate to several aspects in order to improve the quality of rail operations. The analysis is concerned with the results of the research on the proposal of measures for improvement of the quality of rail operations.
ENSURING QUALITY FOR ENROLLMENT, RENEWAL OF REGISTRATION AND CHANGES IN AGRICULTURAL FARM USING INFORMATION TECHNOLOGIES
(2019) Ćurčić, Srećko; Blagojević, Marija; Ristic, Olga
The request for registration, renewal of registration and notification of the change of the data of the family agricultural holding to farmers is submitted in paper form. Agricultural producers have the opportunity to make mistakes in filling, neglecting certain fields, not submitting the request in time, etc. Some of these deficiencies can be solved by creating an electronic form for filling out, with additional explanations for the user and quicker submission of forms. By completing the form of the home and the necessary guidelines for filling up, the created electronic form would have many advantages. In this paper, the methodology for formulating the formulation, as well as the modeling of the same, was proposed, in order to ensure quality in the process of registration, renewal and registration of changes in the agricultural holding.
Objective methods for determining criteria weight coefficients:a modificationof the critic method
(2020) Žižović, Mališa; Miljković B.; Marinkovic, Dragan
Determining criteria weight coefficients is a crucial step in multi-criteria decision making models. Therefore, this problem is given great attention in literature. This paper presents a new approach in modifying the CRiteria Importance Through Intercreteria Correlation (CRITIC) method, which falls under objective methods for determining criteria weight coefficients. Modifying the CRITIC method (CRITIC-M) entails changing the element normalization process of the initial decision matrix and changing data aggregation from the normalized decision matrix. By introducing a new normalization process, we achieve smaller deviations between normalized elements, which in turn causes lower values of standard deviation. Thus, the relationships between data in the initial decision matrix are presented in a more objective way. By introducing a new process of aggregation of weight coefficient values in the CRITIC-M method, a more comprehensive understanding of data in the initial decision matrix is made possible, leading to more objective values of weight coefficients. The presented CRITIC-M method has been tested in two examples, followed by a discussion of results via comparison to the classic CRITIC method.
Influence of different hard-facing procedures on quality of surfaces of regenerated gears
(2021) Nikolic, Ruzica; Marković, Svetislav; Arsić, Dušan; Lazic, Vukic; Hadzima, Branislav; Ulewicz, Robert
During the process of regeneration of machine parts, certain phenomena occur that have a significant impact on the loss of their working ability. Hereditary properties are expressed by the interdependence of geometric and physical-mechanical-metallurgical parameters of gear teeth created during the technological operations of regeneration of worn teeth by hard-facing. The influence of the type of additional material (electrodes and their combinations) on the tribological characteristics of welded gear teeth was considered, whereby the so-called hard additional materials were applied. Those are the additional materials that give the required surface hardness of the teeth without subsequent thermal or thermochemical treatment. This research did not involve the regeneration of specific worn gears removed from machine systems, but the new gears were made, which were then damaged and then regenerated by hard-facing using the shielded metal arc welding (SMAW) procedure. Thus, all the tested gears were made of the same material, belonged to one batch and were machined on the same machines with the same machining regimes. The tests were performed on samples made of 20MnCr5 steel for cementation, on a tribometer by the block on discmethod, which was designed to simulate the operating conditions of coupled teeth of concrete gears in the exploitation conditions. Based on the conducted tribological tests, the average coefficients of friction and topography of the surfaces were determined by measuring the wear trace and it was defined which additional materials give the best tribological characteristics of the surfaces of gears regenerated by hard-facing.
Using Branch Current Measurements for Parameter Identification in Extended Kalman Filter based Distribution System State Estimation
(2021) Ćetenović, Dragan; Ranković, Aleksandar; Zhao J.; Terzija V.; Can H.
Driven by increased penetration from distributed generation, distribution networks require improved operational state awareness tools in the presence of low measurement redundancy. This can be achieved by utilizing Kalman filter based state estimation in case process noise covariance matrix is optimally assessed. This paper aims to investigate the possibility of using readily available conventional branch current flow measurements to assess process noise covariance matrix in extended Kalman filter (EKF) based state estimation for distribution networks. The process noise covariance matrix has a significant impact on EKF's performance. Recently, a method for optimizing the process noise covariance matrix is proposed leveraging the correlation between the estimation error and the cost function via the innovations of branch power flow measurements. This paper extends that to include the innovations of branch current flow measurements in the cost function. Performances of the proposed approach are evaluated on the modified IEEE 13- and IEEE 37-bus distribution test systems. It is demonstrated that the proposed method is robust to different loading conditions and different measurement configurations. Comparison results with the weighted least square estimator show that our method achieves significantly improved estimation accuracy.
Application of multigraph sampling method in network traffic design of simulation model of integrated telecommunication and computer network
(2021) Miletic, Natasa; Mladenovic, Vladimir; Pokrajac I.
Designing an integrated telecommunications and computer network using a simulation model requires defining all the network and communication elements that make up the network and network communication. The accuracy, quality, and usability of the simulation results depend on the accuracy and the way of defining the network traffic as a timed event between the source and the destination in the network. In this paper, the method for a more accurate definition of network traffic required for the development of a simulation model using the software tool OPNET is proposed. Network traffic can be represented using a multigraph associated with an appropriate matrix of network traffic over time. Time definition of network traffic is enabled by applying the method of sampling multigraphs with the mathematical derivation of the corresponding statistical distribution function. Predicted or existing communication in the network describes using the derived function of network traffic distribution and precisely defines the OPNET simulation model.
An Ontology-Driven Learning Assessment Using the Script Concordance Test
(2022) Radović, Maja; Petrovic, Nenad; Tosic, Milorad
Assessing the level of domain-specific reasoning acquired by students is one of the major challenges in education particularly in medical education. Considering the importance of clinical reasoning in preclinical and clinical practice, it is necessary to evaluate students’ learning achievements accordingly. The traditional way of assessing clinical reasoning includes long-case exams, oral exams, and objective structured clinical examinations. However, the traditional assessment techniques are not enough to answer emerging requirements in the new reality due to limited scalability and difficulty for adoption in online education. In recent decades, the script concordance test (SCT) has emerged as a promising tool for assessment, particularly in medical education. The question is whether the usability of SCT could be raised to a level high enough to match the current education requirements by exploiting opportunities that new technologies provide, particularly semantic knowledge graphs (SCGs) and ontologies. In this paper, an ontology-driven learning assessment is proposed using a novel automated SCT generation platform. SCTonto ontology is adopted for knowledge representation in SCT question generation with the focus on using electronic health records data for medical education. Direct and indirect strategies for generating Likert-type scores of SCT are described in detail as well. The proposed automatic question generation was evaluated against the traditional manually created SCT, and the results showed that the time required for tests creation significantly reduced, which confirms significant scalability improvements with respect to traditional approaches.
Development of a Modular Didactic Laboratory Set for the Experimental Study of Friction
(2022) Miljojkovic, Jasmina; Kočović, Vladimir; Lukovic, Milentije; Zivkovic A.; Šimunovic̈ K.
The paper presents the results related to the development of a modular didactic laboratory set for the experimental study of friction and its implementation in engineering education. Successfully implemented in laboratory exercises and research, the modular set has been upgraded over time. A newly developed module is presented for investigating the kinetic coefficient of friction based on the differential equation of motion on an inclined plane. The authors deal with the most critical case-a free fall of a shell-shaped pin down the cylindrical guide when, theoretically, the friction force is equal to zero, while the air resistance force has a maximum value. Based on the time data recorded by inductive sensors, measurements were performed to determine the discrepancy between the theoretical and experimental acceleration values. After introducing the calculation model, the authors quantify very small energy losses and analyse the relationship between the unknown resistance force, caused primarily by the imperfections of the experiment, and the air resistance force.
Mask Estimation Using Phase Information and Inter-channel Correlation for Speech Enhancement
(2022) Sowjanya D.; S, Shoba; Kar, Asutosh; Mladenovic, Vladimir
The most commonly used training target is masking-based approach which maps noisy speech to the time–frequency (T–F) unit and has a remarkable impact on the performance in the supervised learning algorithms. Traditional T–F masks like ideal ratio mask (IRM) demonstrate a strong performance but are limited to only the magnitude domain in enhancement. Though bounded IRM with phase constraint (BIRMP) includes phase difference but doesn’t exploit channel correlation, the proposed ratio mask (pRM) considers channel correlation but is computed only in the magnitude domain. This work proposes a new mask, i.e., phase correlation ideal ratio mask (PCIRM), which includes both inter-channel correlation and phase difference between the noisy speech (NS), noise (N) and clean speech (CS). Considering these factors increases the percentage of CS and readily decreases the percentage of unwanted noise in the speech components and conversely for the noise components making the mask more precise. The experimental results are conducted under different SNR levels using TIMIT dataset and NOISEX-92 dataset and also compared with the existing state-of-the-art approaches. The results prove that the proposed mask has higher performance than BIRMP and pRM in terms of speech quality and intelligibility.
Measurement System for Characterization of Ferromagnetic Cores Under Controlled Magnetic Field Waveform
(2022) Koprivica, Branko; plazinic, milan
The aim of this letter is to present a prototyping measurement system for the characterization of ferromagnetic cores under a controlled magnetic field. The main part of the system is a short-circuited magnetizing coil that forms a relatively large square loop. The loop stands fixed in the vertical plane, and it is equipped on one side of the square with a connector for opening and closing of the loop. Thus, a ring-shaped core made of grain-oriented electrical steel can be placed around the loop and become magnetized. A number of measurements have been performed using the system to validate its applicability. Experiments were performed for the sinusoidal and triangular waveforms of the magnetic field, under quasistatic and dynamic conditions. In addition to the presentation of the measurement system, this letter also presents measured hysteresis loops and corresponding energy loss. Part of the results obtained with the presented method are compared with the results obtained using the standardized method. The main features of the measurement system are discussed.
Effects of Poly(diallyldimethylammonium chloride) addition on the curing kinetics of urea-formaldehyde adhesives for particleboards
(2022) Popovic, Milica; Vukić, Nevena; Điporovíc-Momčilovíč, Milanka; Budinski-Simendic, Jaroslava; Gavrilovic-Grmusa, Ivana; Popovic, Jasmina; Ristić, Ivan
Addition of poly(diallyldimethylammonium chloride) (PDDA) on the performances of urea-formaldehyde (UF) adhesives was evaluated in this work. Three types of UF adhesives were prepared, one without PDDA addition, and two types with PDDA addition of 1 and 3 wt.% per dry UF adhesive mass. These UF adhesive systems were used for producing experimental particleboard panels. The addition of PDDA decreased the thickness swelling of the panel samples, while the internal bond of the particleboards increased significantly only at the highest PDDA content (3 wt.%). Differential scanning calorimetry (DSC) was applied to address the influence of PDDA on UF adhesive curing kinetics. DSC scans were performed in non-isothermal regimes using different heating rates (5, 10, and 20 °C∙min−1). The activation energy (Ea) of the curing reaction showed slightly lower values for the UF adhesive systems containing PDDA. However, the peak temperatures and enthalpy of reaction did not change significantly. The Kissinger-Akahira-Sunose and Friedman iso-conversional methods were applied to investigate the effects of PDDA addition on the UF adhesive curing process.
Comparison of Hydroxyapatite/Poly(lactide-co-glycolide) and Hydroxyapatite/Polyethyleneimine Composite Scaffolds in Bone Regeneration of Swine Mandibular Critical Size Defects: In Vivo Study
(2022) Stevanovic, Mirjana; Selakovic, Dragica; Vasovic, Miroslav; Ljujic, Biljana; Zivanovic, Suzana; Papić, Miloš; Živanović, Marko; Milivojević, Nevena; Mijovic M.; Tabaković S.; Jokanovic, Vukoman; Arnaut, Aleksandra; Milanović P.; Jovicic, Nemanja; Rosic, Gvozden
Reconstruction of jaw bone defects present a significant problem because of specific aesthetic and functional requirements. Although widely used, the transplantation of standard autograft and allograft materials is still associated with significant constraints. Composite scaffolds, combining advantages of biodegradable polymers with bioceramics, have potential to overcome limitations of standard grafts. Polyethyleneimine could be an interesting novel biocompatible polymer for scaffold construction due to its biocompatibility and chemical structure. To date, there have been no in vivo studies assessing biological properties of hydroxyapatite bioceramics scaffold modified with polyethyleneimine. The aim of this study was to evaluate in vivo effects of composite scaffolds of hydroxyapatite ceramics and poly(lactide-co-glycolide) and novel polyethyleneimine on bone repair in swine’s mandibular defects, and to compare them to conventional bone allograft (BioOss). Scaffolds were prepared using the method of polymer foam template in three steps. Pigs, 3 months old, were used and defects were made in the canine, premolar, and molar area of their mandibles. Four months following the surgical procedure, the bone was analyzed using radiological, histological, and gene expression techniques. Hydroxyapatite ceramics/polyethyleneimine composite scaffold demonstrated improved biological behavior compared to conventional allograft in treatment of swine’s mandibular defects, in terms of bone density and bone tissue histological characteristics.

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