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Radau- and Lobatto-type averaged Gauss rules
No full textWe describe numerical methods for the construction of interpolatory quadrature rules of Radau and Lobatto types. In particular, we are interested in deriving efficient algorithms for computing optimal averaged Gauss–Radau and Gauss–Lobatto type javascript:undefined;quadrature rules. These averaged rules allow us to estimate the quadrature error in Gauss–Radau and Gauss–Lobatto quadrature rules. This is important since the latter rules have higher algebraic degree of exactness than the corresponding Gauss rules, and this makes it possible to construct averaged quadrature rules of higher algebraic degree of exactness than the corresponding “standard” averaged Gauss rules available in the literature
Structural integrity analysis of the pre-stressed concrete dome of the Belgrade fair hall 1
Get PDFBelgrade fair hall 1 is well known for its dome, which is still the world largest self-supported construction made of pre-stressed concrete, with its diameter of 106 m. In this paper the Finite Element Method (FEM) was performed to analyze different loading and supporting conditions. At the same time, crack growth in a support column was simulated by the extended FEM (XFEM). Results of numerical calculations indicate ingenious design of such a complex structure which was based on “hand” calculation decades ago, without computers. In addition to classical engineering and more advanced numerical calculations, risk based analysis was performed taking into account artificially introduced crack and Failure Analysis Diagram, obtained using stress intensity factor and net stress, as well as fracture toughness and critical stress. This analysis, made for the first time for Belgrade fair hall 1, proved that its structural integrity is jeopardized only when a crack reaches half the thickness of a steel bar
Influence of Aging on the Flexural Strength of PLA and PLA-X 3D-Printed Materials
Get PDFThe three-point bending test is a valuable method for evaluating the mechanical properties of 3D-printed biomaterials, which can be used in various applications. The use of 3D printing in specimen preparation enables precise control over material composition and microstructure, facilitating the investigation of different printing parameters and advanced materials. The traditional approach to analyzing the mechanical properties of a material using a three-point bending test has the disadvantage that it provides only global information about the material’s behavior. This means that it does not provide detailed insight into the local strain distribution within the material. However, the 2D Digital Image Correlation (DIC) method offers additional insight, especially in terms of strain localization. DIC is an optical technique that measures full-field displacements and strains on the surface of a sample. PLA and enhanced PLA-X material were utilized to create three-point bending samples. The aim of this paper was to analyze and compare the influence of aging on the mechanical properties of PLA and enhanced PLA-X materials using three-point bending coupled with the DIC method. The results showed statistically significant differences between the PLA and PLA-X, for both the new and aged materials. The aged PLA samples had the highest average value of maximal force around 68 N, which was an increase of 8.8% compared to the new PLA samples. On the other hand, the aged PLA-X material had an increase of 7.7% in the average maximal force compared to the new PLA-X samples. When comparing the two materials, the PLA samples had higher maximal force values, 6.2% for the new samples, and 7.3% for the aged samples. The DIC results showed that both the new PLA and PLA-X samples endured higher strain values at Points 1 and 2 than the aged ones, except for the aged PLA-X sample at Point 2, where the new sample had higher strain values. However, for the first 5 min of the experiment, both materials exhibited identical behavior, after which point significant differences started to occur for both materials, as well as at Points 1 and 2. A more profound comprehension of the biomechanical characteristics of both PLA and PLA-X material is essential to enhance the knowledge for potential biomedical applications. The DIC method was found to be a powerful tool for analyzing the deformation and failure behavior of samples and for complementing the traditional approach to material testing
An overview of XR technologies usage for industrial robot programming
Get PDFIndustrial robot programming can be a challenging
task, especially in today's age, where robots are more widespread
outside the large manufacturing companies, but rather in small
and medium enterprises where users are not necessarily fully
qualified individuals. The Extended Reality technologies may be
the ongoing answer to improved robot programming experience.
Current solutions for robot programming using Extended Reality
technologies are explored in this overview. In this paper, a
summarized description of certain solutions is given, focusing on
how are the XR technologies utilized in developing the robot
programming systems. Categorization by devices and motion
planners used is also given
Analysis of remaining life assessment of three-phase gravity separator for oil rectification with the simultaneous usean RBI matrix
No full textThe paper presents a detailed description of the oil rectification process used in upstream oil and gas plants, including the significant equipment involved. One such equipment highlighted in the study is a pressure vessel utilized as a separator to separate the liquid and gas phases. This pressure vessel has been in operation for over two decades. A thorough examination of the mentioned pressure equipment was conducted during the process evaluation. It was discovered that the internal side of the vessel, particularly its back elliptical head, had suffered extensive damage due to erosion and corrosion, emerging as the most significant cause of the deterioration. The application of RBI-estimation revealed that the vessel falls under the category of highly risk equipment, and there is a significant risk of both environmental and financial consequences associated with its potential failure (leakage). Such failure is anticipated to occur promptly in the area below the wear plate of the vessel's nozzle
Analysis of Lubrication Regimes for Porous Sliding Bearing
Get PDFThe purpose of this paper is to analyze the lubrication quality of porous sliding bearings, starting from the bearing model and in combination with experimental results aimed at analyzing the lubrication regimes of different working conditions. The separation between the surfaces by the lubricant layer is what determines the regime. The quality and type of lubrication regime are determined by parameters in the mathematical model including typically speed, load, motion, materials, environment, etc., which have an impact on friction. Besides those elements, important parameters such as coefficient of friction (COF) and working temperature are to be measured due to experimental investigations to detect an equilibrium working state. The self-lubrication mechanism in porous metal bearings improves their service life and lubrication processes; however, the COF still varies within a wide interval. This variability can be understood, considering that during bearing operation it operates within a broad range of lubrication regimes. Those findings are explained in the paper by using a combination of calculated parameters according to the bearing model and in combination with our own results of experimental investigations. With the obtained results for particular working conditions, the authors are trying to explain, in the form of a diagram with the limit line as an important outcome of the work, that the lubrication regime for porous metal bearings could arise from boundary lubrication (BL) close to hydrodynamic lubrication (HDL)
Mehanizam za kalibraciju sonde sa više rupica za merenje prostornog polja brzine i pritiska u ventilacionim sistemima
No full textExisting Building Renovation in the Republic of Serbia Using Green Roofs toward Fulfilment of EPBD Goals
No full textThe energy consumption in buildings is constantly rising over the last decades, besides all the efforts put in the energy efficiency and CO2 emission reduction. Increased consumption is noted especially for the cooling needs due to the climate changes and constant development of urban areas. Besides the increased energy consumption and thus the CO2 emissions, the increase of urban areas contributed to the formation of heat islands and significant increase of pollution last decades. The necessity of deep building renovation and more strict criteria for the building envelope U-values is foreseen as an imperative strategy towards fulfilment of EPBD goals. The Republic of Serbia has more than 2.2 million of buildings built before the adoption of first regulations on energy efficiency of buildings, back in 2011. Thus, the potential for final energy savings just in the term of heating needs, by thermal envelope renovation goes from 55 up to 70%, while the CO2 emission can be 50% to 65% lower depending on the type of energy efficiency measures that are implemented. Additionally, if the green roofs are introduced in the renovation as well, the energy savings in primary energy for heating and DHW increases up to 6%, while the CO2 emission decrease up to 6.5%. Besides the measurable indicators such as primary energy and CO2, a lot of studies worldwide confirmed a wide range of benefits of green roofs such as higher diversity and positive impact to pollinators, decreased pollution, possibilities of usage of green areas for recreation, lower temperatures of roofs in summer period etc.Contract number 451-03-65/2024-03/200105 from 05.02.2024
Enhanced Biogas Yield Using Co-Digestion of Food and Agricultural Waste
No full textThe increasing demand for sustainable energy sources has led to a growing interest in biogas production through anaerobic digestion of organic waste. This study explores the enhancement of biogas yield by employing co-digestion of food waste with agricultural residues. Food and agricultural waste streams are abundant and complementary in nutrient content, offering an ideal substrate blend for microbial activity and efficient methane production. Through experimental analysis, this research investigates the effect of varying food-to-agricultural waste ratios, optimizing the carbon-to-nitrogen (C/N) balance to achieve higher biogas yields. The findings demonstrate that co-digestion significantly improves methane production compared to mono-digestion, due to synergistic effects that promote a stable digestion environment and enhanced microbial performance. Optimal substrate ratios were identified, resulting in a biogas yield increase of up to 50% over traditional methods. This study provides practical insights into maximizing waste-to-energy conversion, contributing to sustainable waste management and renewable energy generation. The results underscore the potential of food and agricultural waste co-digestion as a scalable, effective approach to sustainable biogas production. Future work will examine long-term system stability and the potential for large-scale implementation
MODELLING OF THREE-DIMENSIONAL THERMAL-HYDRAULICS OF HORIZONTAL STEAM GENERATOR
No full textThe horizontal steam generators (HSGs) are applied in the VVER nuclear power plants equipped with the pressurized water reactor (PWR). The HSG transfers heat from the nuclear reactor coolant to the feedwater, which is heated and evaporated on the HSG shell side. The HSG heat transfer area is composed of the horizontal U-tube bundles connected to the hot inlet header and cold outlet header, which are both positioned vertically. The boiling feedwater flow in the large volume of the HSG shell side is self-organized in complex natural circulations loops. Experimental investigation of the two-phase flow on the HSG shell side is difficult in real operational conditions. However, sophisticated two-phase flow models enable numerical simulation and analyses of these complex conditions, and the obtained results supports design of reliable operation and nuclear power plant safety.
This paper presents a comprehensive numerical modelling approach for simulation of three-dimensional thermal-hydraulics of horizontal steam generator (HSG). The model incorporates governing equations including the continuity equations, momentum conservation equations and energy conservation equations. Two separate fluids are observed: the reactor coolant flowing through the generator tubes and the feedwater on the shell side [1]. For the shell side, a two-phase model is employed to separately account for liquid and steam phases, with closure laws utilized to fulfil governing equations. The numerical simulations are conducted using the in-house program 3D-ANA, which enables detailed analysis and visualization of flow phenomena within the steam generator. Through this approach, the complex interplay between flow dynamics, heat transfer, and phase change phenomena within the steam generator is captured with high fidelity. Results obtained from numerical simulations are verified through comparison with experimental measurements. The proposed numerical framework provides valuable insights into the complex behaviour of horizontal steam generators, facilitating the optimization of design and operational parameters to enhance efficiency and safety in nuclear power plants.
The investigation of the three-dimensional thermal-hydraulics of horizontal steam generators has yielded results indicative of notable congruence with experimental data. The calculated predictions demonstrate a high degree of similarity with observed phenomena, suggesting the reliability of the employed modelling techniques (Fig. 1). Crucially, the findings assure the operational safety of the HSG, as evidenced by the absence of local dry-outs within tube bundles and the maintenance of moderate liquid and steam phase velocities that do not lead vibration-induced instabilities (Fig. 2). These outcomes underscore the robustness of the analytical framework employed and emphasize the imperative of rigorous thermal-hydraulic assessments in ensuring the integrity and efficiency of steam generator systems