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Computational Fluid Dynamics Study of Biomass Moisture Content Impact on Particle Matter Emissions
No full textWood combustion is a significant energy source, but it also contributes to air pollution due to the emission of gaseous and particle matter. Understanding the formation and behaviour of gaseous and particle emissions is crucial for environmental and health concerns. To simulate and analyse beech wood combustion, a mathematical model for computational fluid dynamics (CFD) simulation was developed. This model considered various parameters such as fuel properties, combustion kinetics, and fluid dynamics. The model enables the prediction of temperature profiles, species concentrations, and soot particle emissions. To validate the accuracy of the CFD model, experimental measurements were conducted on an actual beech wood combustion setup. The experimental data, including flue gas temperature, CO2 and CO concentrations, and soot particle measurements, were compared with the simulation results. The validation process was aimed to ensure the reliability and fidelity of the CFD model for predicting beech wood combustion behaviour. Furthermore, a parametric analysis was performed using the validated model to investigate the influence of different moisture content levels in the fuel on the combustion process and emission characteristics. The moisture content varied from 10 to 40%, representing a range of realistic conditions. The results of the parametric analysis provided insights into the relationship between moisture content and combustion performance. The findings contributed to optimizing beech wood combustion processes, improving energy efficiency, and reducing emissions. The study emphasized the importance of considering moisture content as a critical parameter in designing and operating wood combustion systems to achieve sustainable and environmentally friendly practices. © The Author(s), under exclusive licence to Springer Nature Switzerland AG 2024.Contract no.451-03-47/2023-01/20010
Mechanical Properties of Repaired Welded Pipe Joints Made of Heat-Resistant Steel P92
No full textThis research provides a detailed investigation into the mechanical properties and microstructural evolution of heat-resistant steel P92 subjected to both initial (i) welding procedures and simulated (ii) repair welding. The study addresses the influence of critical welding parameters, including preheating temperature, heat input, and post-weld heat treatment (PWHT), with a particular emphasis on the metallurgical consequences arising from the application of repair welding thermal cycles. Through the analysis of three welding probes—initially welded pipes using the PF (vertical upwards) and PC (horizontal–vertical) welding positions, and a PF-welded pipe undergoing a simulated repair welding (also in the PF position)—the research compares microstructure in the parent material (PM), weld metal (WM), and heat-affected zone (HAZ). Recognizing the practical limitations and challenges associated with achieving complete removal of the original WM under the limited (in-field) repair welding, this study provides a comprehensive comparative analysis of uniaxial tensile properties, impact toughness evaluated via Charpy V-notch testing, and microhardness measurements conducted at room temperature. Furthermore, the research critically analyzes the influence of the complex thermal cycles experienced during both the initial welding and repair welding procedures to elucidate the practical application limits of this high-alloyed, heat-resistant P92 steel in demanding service conditions
THE ROLE AND SIGNIFICANCE OF PRIMARY WASTE SEPARATION IN SUSTAINABLEWASTE MANAGEMENT
No full textPrimary waste separation plays a crucial role in both environmental protection and public safety. In Serbia, over 90% of
waste ends up in landfills, with minimal recycling—opposite to EU standards. Such practices reduce landfill lifespan and waste
resource potential. Introducing source-level separation supports circular economy principles and aligns with the waste hierarchy,
where disposal is a last resort. Key steps include prevention, reuse, recycling, and energy recovery. Waste management begins at the
point of generation, making citizen education essential. This paper examines the importance of primary separation and the impact of
public awareness on municipal waste reduction
Drying Kinetics and Stability of Fatty Acids in Grape Pomace Seeds Under Mild Thermal Conditions
No full textGrape pomace, a significant by-product of the wine industry, is rich in
health-promoting compounds, including polyunsaturated fatty acids,
dietary fiber, and polyphenols, and holds strong potential for use in
functional foods and nutraceuticals. This study investigates the effects of
low-temperature convective drying at 40°C on the drying behavior and
fatty acid composition of grape seeds from ten Vitis vinifera L. cultivars.
To model the drying process, six thin-layer drying models were applied.
Among them, the Logarithmic model provided the best fit for most
cultivars, showing excellent agreement between predicted and
experimental drying curves. Effective moisture diffusivity values varied
considerably among cultivars, reflecting differences in pomace structure
and seed composition. Fatty acid analysis via gas chromatography
revealed that polyunsaturated fatty acids—particularly linoleic acid—were
the predominant lipid class in fresh grape seeds. After drying, a moderate
reduction in polyunsaturated fatty acids was observed, accompanied by a
corresponding increase in saturated fatty acids. Despite these changes,
certain cultivars, such as Prokupac and Merlot, retained favorable
nutritional profiles. The results support the application of mild drying
protocols to preserve the functional quality of grape seeds while improving
energy efficiency. This research contributes to the sustainable valorization
of grape pomace and highlights its potential applications, such as
functional oil ingredients, antioxidants in skincare, and encapsulated
nutraceutical formulations.Contract No. 451-03-137/2025- 03/200116 and Contract No. 451-03-137/2025-03/ 20010
DEVICE FOR TESTING BOND STRENGTH BETWEEN ARTIFICIAL TOOTH AND DENTURE BASE UNDER VARIABLE LOADING ANGLES
No full textThe presented device is a technically innovative solution designed to test the bond strength between various biomaterials, with specific application in dentistry—especially in analyzing the adhesion between artificial teeth and denture base materials. Conventional bond strength testing methods typically involve uniaxial loading, which does not reflect the complex multidirectional forces acting within the oral cavity during mastication and functional jaw movements. These forces include both vertical (compressive) and horizontal (shear) components, influenced by anterior tooth relationships and incisal guidance angles—factors often neglected in standard tests. This tool is compatible with universal testing machines and allows force application at precise, adjustable angles, there by more accurately simulating physiological conditions. Its adjustable holder geometry and gripping system ensure secure positioning of samples without introducing artifacts or pre-test damage. The device enables systematic analysis of how different loading angles affect bond strength, which is crucial for evaluating adhesive systems, surface treatments, and new materials. By incorporating this device into experimental protocols, researchers can achieve more accurate, repeatable, and clinically relevant results. Its application may significantly improve the understanding and optimization of prosthetic materials, leading to increased longevity and functional reliability of dental restorations, particularly within the scope of digital and CAD/CAM prosthodontic workflows
CYCLE ANALYSIS OF A SINGLE-STAGE TRANSCRITICAL R744 SYSTEM IN SUPERMARKETS: THE IMPACT OF ISENTROPIC EFFICIENCY AND OIL
No full textCarbon dioxide is increasingly present in modern refrigeration systems,
finding significant application in commercial cooling, especially in
supermarkets. However, its application encounters many challenges due to its
unfavorable thermodynamic properties. This serves as a starting point for
numerous engineering solutions, as well as for many theoretical and
experimental analyses of various systems utilizing R744. Some analyses often
overlook the fact that, in addition to the refrigerant, oil also passes through
all the system components in a certain quantity, which subsequently impacts
heat transfer as well as the cycle itself. This paper presents a cycle analysis
of a typical single-stage transcritical CO2 system used for medium-
temperature (MT) cooling applications in a supermarket. The analysis
included the impact of oil, considering several realistic steady-state scenarios
with predicted OCR (Oil Circulation Ratio) values. In addition to the effect of
oil, the study was expanded by examining available equations for the
isentropic efficiency of the compressor. The results showed that considering a
realistic compression process leads to an efficiency reduction of 15.4% to
39.9%, while the presence of oil decreases it by 5.7% to 27.8% under varying
conditions.Ugovor br. 451-03-137/2025-03/20010
Analysis of the effect of piezoelectric sensor ageing on indicated parameters
No full textThe research examines the ageing behavior of piezoelectric pressure sensors for internal combustion engine studies while concentrating on their declining sensitivity as time progresses. Reliable measurement of in-cylinder pressure demands precise monitoring of sensor performance to support both thermodynamic analysis and evaluation of engine performance. Research experiments performed with a single-cylinder research engine (SCRE) determine how the working cycle operational parameters relate to sensor properties, especially the indicated mean effective pressure (IMEP) and polytropic coefficients of the compression/expansion phase of the engine working process. The study demonstrates that monitoring polytropic coefficients provides an efficient technique for detecting sensitivity degradation without needing continuous pressure sensor recalibration, improving both accuracy and efficiency during prolonged engine testing. The approach allows researchers to detect sensor degradation on time, which helps maintain data integrity throughout lengthy research campaigns
Quadratures with quasi-degree of exactness
No full textMonic orthogonal polynomials satisfy a three-term recurrence relation whose coefficients determine a symmetric tridiagonal Jacobi matrix. To efficiently compute the nodes and weights of Gauss quadrature, the Golub-Welsch algorithm, based on the observations that the nodes are the eigenvalues of the Jacobi matrix and that the weights are proportional to the square of the first components of corresponding normalized eigenvectors, can be applied. The Gauss quadrature with nodes is exact for all polynomials of degree and represents a unique optimal interpolatory quadrature rule. After choosing arbitrary points (at which the integrand is defined), we transform the given integral into a sum of an integral that does not cause a quadrature error and an integral with a property that the points are the zeros of its modified integrand. Then, we approximate the integral of the modified integrand by an -point quadrature whose nodes and weights are simply expressed in terms of the nodes and weights of associated -point Gauss quadrature. Formula is exact for all polynomials of degree with fixed zeros , but those fixed zeros should not be a disadvantage, since the modified integrand has the same zeros
Neural Network-Based Visual Servoing of Wheeled Mobile Robot with Fish-Eye Camera
No full textIn the era of rapid technological invitation, artificial intelligence techniques have become a driving force in the evolution of various fields, and the
robotics domain is no exception. One of the areas where AI has proven to be
especially influential is in robotics vision, where machine learning algorithms,
particularly artificial neural networks, are revolutionizing how robots perceive
and interact with their environment. Therefore, in this paper, we examine the use
of artificial neural networks in the context of mobile robot visual servoing. Differential drive mobile robot RAICO equipped with a fish-eye lens camera is utilized.
The fish-eye lenses have a significant advantage regarding their wide-angle field
of view; however, they also introduce significant optical distortions that can affect
the accuracy of the robot’s perception and, therefore, 3D pose estimation, which is
paramount for visual servoing. Position-based visual servoing based on the ArUco
marker is employed within the 3-step switching mobile robot controller. Given the
pose estimation errors inherited by distortions in the fish-eye lens, the accuracy of
pose estimation is enhanced by utilizing neural networks. The experimental results
show a high level of final pose accuracy achieved by RAICO with the proposed
control algorithm