Machinery - Repository of the Faculty of Mechanical Engineering, University of Belgrade
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Optimization of Phasor Data Concentrators (PDC) Placement and Communication Infrastructure in Power Systems for Cost-Effective Management
No full textThis paper presents a study on optimizing the placement and required number of Phasor Data Concentrators
(PDCs) to enhance power system management efficiency. With the increasing deployment of Phasor
Measurement Units (PMUs) in power networks for real-time monitoring, efficient data aggregation through
strategically placed PDCs is essential. This research aims to determine the optimal locations for PDCs while
minimizing the overall costs of building the communication infrastructure necessary for data transfer
between PMUs and PDCs. This is very significant nowadays, as the costs of building communication
infrastructure are considerably higher than the prices of PMU devices.
The proposed approach employs advanced optimization techniques, such as genetic algorithms, to analyze
various configurations and assess cost-effectiveness. By incorporating constraints related to the power
network topology, data transmission latency, and reliability, the study identifies cost-optimized locations
that ensure robust system observability and resilience. The methodology also examines the communication
paths to minimize delays and improve data accuracy.
Key findings demonstrate that optimized PDC placement not only reduces infrastructure expenses but also
enhances the speed and reliability of data collection and processing within power systems. The results
provide valuable insights for power system operators in real time and network planners, highlighting the
economic and operational advantages of strategically configured PMU-PDC setups
The Impact of Top and Middle Management Commitment to Occupational Safety and Health on Corporate Social Responsibility in Mining Industry
No full textCorporate social responsibility (CSR) is centered on the idea that organizational leaders have an obligation to make decisions and take actions that are desirable according to the values of society. Nonetheless, a growing corpus of research increasingly focuses on comprehending how individual-level elements, such as managerial engagement and attitudes, influence CSR initiatives within businesses. In that aim, this study examines the impact of managerial commitment to occupational safety and health (OSH) on different dimensions of CSR. Using a quantitative approach, data were collected on the sample sized 33 and analyzed through reliability, factor and regression analysis. The model proved statistically significant relationship between managerial OSH commitment and CSR performance. This paper findings underscore the crucial role that managerial engagement in workplace safety plays important role in CSR plans by showing that higher managerial commitment to OSH improves CSR outcomes. Future research should focus to sample enlargement and structural equations modeling application.contract no. 451-03-65/2024-03/200105 from 05.02.202
COGNITIVE MOBILE ROBOTICS BASED ON INTELLIGENT MECHANISMS OF LEARNING
No full textThe purpose of this contribution is the deployment of digital manufacturing through new cognitive
intelligence mechanisms. With the implementation of Industry 4.0 principles, mobile intelligent robots utilized as transportation vehicles in the manufacturing system need a higher degree of autonomy to fulfill all the requirements of the contemporary market. Although industrial robots are common in manufacturing systems, mobile robotics requires the expertise of specialists in cognitive robotics issues to gain international competitiveness, particularly for small and medium-sized enterprises. The industrial mobile robots’ autonomous subsystems based on deep machine learning provide significantly more flexibility as well as more accurate and robust real-time decisions compared to common deterministic sensor-based algorithms. The main goal of this paper is to create artificial intelligence-based solutions for cognitive mobile robotics within Industry 4.0 using a Machine Learning (ML) based approach, particularly deep learning (convolutional neural networks, recurrent neural networks, etc.). The focus of the paper is the generation of new ML-based cognitive intelligence mechanisms for obstacle avoidance, decision-making, and visual control of intelligent mobile robots, whereas the main goal of the paper is to demonstrate the possibility of integrating intelligent ML-based algorithms into a high-level cognitive architecture by enabling better understanding of the environment in real-time through the processing of higher-quality and more complex sensory data, thereby enhancing the overall flexibility of mobile robotic systems within intelligent manufacturing systems.40th International Conference of Production Engineering (ICPES 2025) - Serbia 2025, Nis, Serbia, 18th - 19th
September 2025,
Editors:
Prof. dr Miodrag T. Manić, University of Niš, Faculty of Mechanical Engineering,
Prof. dr Saša S. Ranđelović, University of Niš, Faculty of Mechanical Engineering
Time Minimization During Simultaneous Longitudinal and Rotational Motion of a Chaplygin Sleigh
No full textThe problem of minization of the time of motion of a Chaplygin sleigh in the horizontal
plane is analyzed. The force directed along the linear velocity vector and the torque are considered as
control inputs. The use of the Pontryagin maximum principle allows for establishing that three types
of control are possible: regular control, taking the boundary values (bang-bang) for the force and the
torque, first-order singular control for the force, and second-order singular control for the torque. If
the control is singular for the force on the entire interval, the solution of the optimization problem is
not unique. The second-order control segment can be connected with nonsingular control only by
means of the “chattering” regime. A simpler suboptimal control is proposed that contains a finite
number of switchings. Examples are considered for the specified end states and partially specified end
states. Analysis of possible combinations of singular and regular arcs of the trajectory is performed.Ruska verzija rada:
А. Обрадовичa, Ю. Д. Селюцкий , О. Ю. Черкасов,МИНИМИЗАЦИЯ ВРЕМЕНИ ПРИ ОДНОВРЕМЕННОМ
ПРОДОЛЬНОМ И ВРАЩАТЕЛЬНОМ ДВИЖЕНИИ КОНЬКА ЧАПЛЫГИНА,ИЗВЕСТИЯ РАН. ТЕОРИЯ И СИСТЕМЫ УПРАВЛЕНИЯ, 2025, № 5, с. 47–6
Dimensional accuracy assessment of 3D-printed CT specimens produced by selective laser sintering
No full textAdditive manufacturing is increasingly used for producing standardized fracture-mechanics specimens, allowing the fabrication of Compact Tension (CT) samples with complex geometries that would be difficult to machine conventionally. However, the dimensional accuracy of selective laser sintering remains a crucial factor for ensuring reliable mechanical and fracture-toughness measurements. In this study, the geometric accuracy of 3D-printed cobalt–chromium CT specimens was evaluated by comparing three design variants to their corresponding CAD reference models. Optical scanning and qualitative surface-deviation mapping revealed that differences in accuracy were strongly influenced by specimen geometry, particularly in regions involving sharp transitions and stress-concentrating features. While some designs showed noticeable deviations attributable to manufacturing complexity, others remained within acceptable tolerance limits for fracture testing, requiring minimal post-processing. These findings underscore the importance of carefully optimizing build orientation, scanning strategies, and post-processing protocols when using additive manufacturing to produce CT specimens intended for high-precision mechanical characterization
Evaluation of the compressive properties of different 3D-printed Ti6Al4V lattice structures
No full textCurrent Developments in the Field of Sound Monitoring in the Beehives
No full textIn the past ten years, beekeepers and academics have become increasingly concerned about honeybee mortality due to their critical role in pollination. As a result, reliable and accurate monitoring of beehives has become an effective method for tracking honeybee health. The bees use sounds and vibrations to interact within the hive, and with the help of microphones and a recording system, their analysis can provide important information about the colony’s health and help identify any sudden abnormalities. Even though plenty of these signals have been recognized and examined, research on using vibration and acoustics to monitor population health and behavior continuously is still in its early stages. Literature shows most bee sounds are emitted at frequencies lower than 1000 Hz. One potential method for identifying changes in beehive noises is to apply acoustic categorization to recordings of those sounds. The presence of a queen and the readiness for swarming are two signs that beekeepers should consider when evaluating the health of their colonies. These factors can cause colony collapse or diminished honey yield. The research presented here attempts to review the fascinating approaches that have been put together over time for analysis of the sound made by honeybees and the information that may be gathered from their recordings
APPLICATION OF SEM ANALYSIS IN THE EVALUATION OF SURFACE CHARACTERISTICS OF CONTEMPORARY PROSTHETIC MATERIALS AFTER PROFESSIONAL HYGIENE PROCEDURES
No full textScanning electron microscopy (SEM) offers a high-resolution method for detecting microstructural surface changes in dental materials caused by routine professional hygiene procedures. This in vitro study utilized SEM to investigate the effects of ultrasonic scaling and professional brushing on the surface microtopography of zirconia restorations, fabricated by CAD/CAM milling or veneered with ceramic. Specimens (n = 36; 4 × 4 × 2 mm) were obtained from 3Y-TZP-LA zirconia blocks and divided into four groups based on surface finish (polished or glazed) and fabrication method. Each subgroup was subjected to either ultrasonic scaling or brushing with an abrasive polishing paste for 1 minute, repeated in 10 cycles to simulate the effects of five years of clinical maintenance SEM imaging at 150×magnification (Model JSM-6390, JEOL, Japan) was performed before and after treatment to evaluate micromorphological changes. SEM allowed precise identification of surface defects, including microcracks, abrasive wear and glaze degradation. The most significant changes were observed in glazed samples exposed to ultrasonic scaling, with surface alterations measured at 88.31 μm for veneered zirconia and 45.38 μm for CAD/CAM-milled zirconia.The results demonstrate that standard professional hygiene procedures can significantly affect the surface integrity of glazed zirconia restorations. SEM analysis proved to be an essential diagnostic tool for early detection of clinically relevant surface damage, offering insights into material behavior and supporting the development of tailored maintenance protocols
Carnot battery with steam accumulator and pebble bed thermal energy storage
No full textCarnot batteries can store excess electricity from intermittent renewable solar or wind sources and generate power in periods of peak consumption. A novel design of the Carnot battery is proposed based on thermal energy storage by the combination of a steam accumulator and a pebble bed in a series configuration. During the Carnot battery charging, steam is generated by high temperature heat pumps with CO2 compression cycles, pressurized and superheated by electrically driven steam compressors. The obtained superheated steam flows through the pebble bed porous structure and transfers heat to alumina balls in direct contact. Steam from the pebble bed inflows the steam accumulator. During the Carnot battery discharging phase, the steam outflows the steam accumulator, superheats in the pebble bed and expands through the steam turbine, which is connected to the electric generator for power production. The advantages of the studied Carnot battery are a simple design and operation of the steam accumulator as the thermal energy storage unit, the accumulated steam directly serves as working fluid in the steam turbine and the coupling of the pebble bed with the steam accumulator enables steam superheating that is required for an increased steam turbine efficiency in power generation. Water is low-cost
and more convenient in respect to safety, plant engineering and operational aspects in comparison with other working fluids. In addition, there is no need for additional heat exchangers for the heat transfer between the working fluid and the storage medium. Maximum temperature and pressure of the thermal storage medium are 303 ◦C and 0.7 MPa, respectively. The temperature and low-pressure values enable application of mature technology and lower investment costs, where the capacity specific cost of 471 €/kWhe is reached. The presented
Carnot battery design is supported with numerical simulations of thermal energy charging and discharging transients in the pebble bed and the steam accumulator with own original and validated modelling approaches.
The obtained Carnot battery charging electric power is 9.5 MWe for 6.9 h, while discharging power is 2.3 MWe for 9.4 h, which is suitable for the electric grid power control on a daily period
CAVITATION EROSION PARAMETERS OF LASER SINTERED MS1 STEEL TESTED ACCORDING TO ASTM G32 STANDARD
No full textThe paper analyses data obtained from cavitation erosion testing of MS1 tool steel. The testing samples, cylindrical in shape with a height of 5 mm and a diameter of 10 mm, were fabricated using Direct Metal Laser Sintering (DMLS), a 3D printing technique. The samples were subjected to cavitation erosion testing in accordance with the ASTM G32 standard for a total duration of 4 hours. Mass loss measurements were recorded every 30 minutes. Based on the collected data, key parameters such as Cumulative Mass Loss, Cumulative Volume Loss, Mean Depth of Cavitation Erosion (MDE), and Mean Depth Erosion Rate (MDER) were determined and analyzed. Understanding material behaviour under cavitation conditions is crucial for its potential application in manufacturing mechanical components, particularly gears, bearings, and valves, where cavitation-induced damage is a common issue in operational environments. Given that the specimens were produced by metal powder-based 3D printing, it is especially relevant to assess the performance of such material under these conditions. This insight is particularly valuable for the geometric optimization of components to minimize erosion, where additive manufacturing offers significant advantages over conventional production technologies.Contracts: 451-03-137/2025-03/ 200105 and 451-03-136/2025-03/20013