Periodica Polytechnica (Budapest University of Technology and Economics)
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The Effect of Torsional Rigidity and Approximations in Analytical Solutions for the Critical Moment of Beams Considering Prebuckling Deflections
Full text linkSolutions for the critical moment of lateral-torsional buckling of beams commonly used in design codes, are based on initially straight undeflected beams. However, studies indicate that when the weak-to-strong moment of inertia ratio is sufficiently high, prebuckling deformations can significantly impact critical loads. The proposed formulae in the literature often vary, and discussions on the effect of torsional rigidity are limited, with most studies focusing on open sections. This study provides a comprehensive review of the problem and relevant literature, exploring variations and simplifications used to derive closed-form solutions for the critical moment, while accounting for prebuckling deformations through the energy method. Several variations of the critical moment formula are presented and compared, with a detailed investigation into the influence of torsional rigidity. Prebuckling deformations were confirmed to have a significant effect on the critical moment for specific sections, and the conditions for appropriate simplifications were identified. Additionally, torsional rigidity was found to exert a non-negligible influence, with closed sections demonstrating a greater effect of prebuckling deformations
Long-term Effects of Munisipal Solid Waste Leachate on Soil Geotechnical Properties
Full text linkThis study investigates the long-term effects of landfill leachate contamination on soil hydraulic conductivity and shear strength parameters over a 12-month period, addressing the current lack of comprehensive long-term experimental data in this field. Laboratory permeability tests and direct shear tests were performed on sandy clayey silt samples contaminated with leachate at concentrations ranging from 5% to 25%. Microstructural and mineralogical analyses were conducted using SEM and XRD to identify the mechanisms behind observed changes. The results identify a critical threshold at 15% contamination where soil behavior transitions from granular to cohesive characteristics, marked by significant changes in both hydraulic and mechanical properties. Hydraulic conductivity increases at low contamination levels but decreases significantly at higher levels, while friction angle shows an immediate reduction from 36.5° to 31-31.5° and cohesion exhibits a three-phase evolution pattern, reaching peak increases of 151.5% at 15% contamination. The hydraulic conductivity changes are controlled by contamination level rather than exposure time, maintaining stable values throughout the testing period, whereas shear strength parameters demonstrate more complex temporal evolution patterns. These findings provide essential parameters for landfill design and stability assessment, demonstrating how leachate concentration affects long-term soil behavior through mineral formation and structural modification
Freedom Monument, Malta: The Golgotha Metaphor and the Intriguing Concept Design Sketch
Full text linkFreedom Monument marks Jum il-Ħelsien, the last day when Malta served as a military base for a foreign nation. It was, for Malta's then-Prime Minister Dom Mintoff, a profoundly significant and moving event. As stated by the sculptor Anton Agius, the realised design was Mintoff's creation rather than his. Its location is L-Għolja tal-Ħelsien, which freely translated means Freedom Hill, a man-made hillock located along the Birgu waterfront, just in front of the Parish Church. This church has strong associations with the main previous occupying power, the Military Hospitaller Order of St John. This article 1. addresses the author's proposal that Golgotha is a suitable metaphor through which to read Freedom Hill, and 2. asks whether an atypical concept sketch among the many submitted by Agius could possibly be Mintoff's own design. With respect to the former, it is argued that Freedom Monument is Mintoff's iconic statement about the history of Malta in visual form and, given that his perception that Malta's road to total freedom from foreign rule was strenuous, Golgotha is a fitting metaphor. With respect to the latter question, although there is a change in medium and style, this concept design sketch does recall an earlier one. It is a fine monumental interpretation of the event quite remote from Mintoff's idea of four figures on an artificial mound. Stylistically, the sketch is a mature artistic expression; it is unlikely to have been drawn by Mintoff and more likely to have been created by Agius
Exergy Analysis of Thermal Systems in a Paper Production Factory
Full text linkCombined cycle power plants have an important effect in the energy production sector today. In this study, the natural gas cycle power plant that meets the electrical and thermal energy needs of Hayat Paper Factory established in Çorum is discussed from a thermodynamic perspective. The facility consists of a gas turbine, a heat recovery steam generator (HRSG) directly connected to the gas turbine exhaust, and units used in paper production. In the study, energy and exergy analyzes of gas turbine, HRSG and pulp cylinders were examined. As a result of these energy analyses, waste energy was determined. This is calculated to reuse waste energy and increase the energy efficiency of industrial production facilities. Outdoor air temperatures, pressure ratio of the gas turbine compressor and electrical energy efficiency were determined as 9.1 °C, 14.7% and 30%, respectively. In the production facility, the saturated steam need of the process is met by HRSG and the overall efficiency of the system is approximately 42.6%. The resulting steam is used in paper production systems. The 3094.85 kW exergy coming out of the HRSG is lost in total in the pipes and connection valves until it reaches the paper drying cylinders. Preventing these energy losses will increase the energy efficiency of the facility
Economical Camera-based Measuring Scheme for Roundabout Traffic
Full text linkCounting the turning movements in a four-leg roundabout is a challenging task and often executed by vehicle recognition and tracking on traffic videos. In order to obtain accurately all the 12 flow values of the origin-destination (O-D) matrix we need to measure arbitrary chosen 12 linearly independent flow values. However, the larger the area to be observed the more cameras are needed because the good pixel resolution of the vehicles and the proper camera inclination angles are essential. Here we propose a novel measuring scheme, which observes only two roundabout legs instead of observing all the four, as a result obtaining all the 12 flow values requires a reduced number of cameras. The directly measured flow values and the mathematical method of determining the O-D matrix are given in details
Intensification of Hydrolysis Treatment of Waste Plantain Peels Using Ultrasonic Waves for Enhanced Production of Reducing Sugars and Bioethanol
Full text linkThis work focuses on enhancing hydrolysis and bioethanol production from waste plantain peels by using ultrasound acoustic cavitation, comparing its effectiveness to that of hot-acid hydrolysis (HAH) and enzymatic hydrolysis (EH). Statistical response surface methodology (RSM) was employed to examine the enhancement of ultrasonic aided-dilute acid hydrolysis (UADAH) and HAH parameters for the extraction of reducing sugars. The highest reducing sugar yield was obtained as 166.89 ± 0.75 mg/g, 115.03 ± 0.87 mg/g and 131.04 ± 0.29 mg/g from UADAH, HAH and EH respectively. Ultrasound cavitation enhanced the reducing sugar yield with a shorter processing time of 46 min. Notably, the processing time required for UADAH method was reduced threefold and twenty-fold compared to that of HAH and EH, respectively. Also, the UADAH process resulted in a maximum bioethanol yield of 76%. Therefore, ultrasonic irradiation is a promising technology for 2G biofuel production from waste plantain peels owing to its effectiveness in attaining maximum yield within a shorter processing time and with minimal solvent usage
Comprehensive Review of Classes F and C Fly Ash Effects on Clayey Soils: Geotechnical Predictive Correlations
Full text linkFly ash, a by-product of coal combustion, enhances the geotechnical properties of soil, primarily through its two types: class F and class C, known for their pozzolanic and cementitious properties, respectively. Numerous studies have explored the benefits of both types of fly ash in stabilizing problematic expansive soils, which are characterized by weak strength, high compressibility, and significant volume changes that can damage infrastructure. However, direct comparisons between class F and class C fly ashes in improving expansive soils are limited. This study aims to fill this gap by conducting a critical review of research from the past 20 years, focusing on the impact of class F and class C fly ashes on the geotechnical properties of expansive clayey soils. Key parameters examined include Atterberg limits, free swell, unconfined compressive strength (UCS), and California bearing ratio (CBR). The findings indicate that both fly ash types reduce liquid limits and plasticity indices of clayey soils, with class C fly ash showing more pronounced effects. Additionally, class C fly ash significantly reduces soil swelling and enhances UCS and CBR, especially due to its higher CaO content. The study provides novel formulas to aid future researchers in predicting the behavior and performance of clayey soils stabilized with these specific fly ash types, offering a comprehensive examination of their geotechnical parameters
Research on the Torsional Mechanical Properties of Concrete Beams Reinforced with Carbon Fiber Reinforced Polymer and Angle Steel Combination
Full text linkConcrete beams are often subjected to torsion in the actual project, paste carbon fiber reinforced polymer and wrapped angle is commonly used in the actual project of the two concrete beam reinforcement methods, the use of carbon fiber reinforced polymer and angle for the combination of reinforcement, can be combined with the advantages of the two materials in the improvement of the structural mechanical properties, so that concrete beams can be reinforced to form a combination of superior performance of the structure, the concrete beams subjected to torsion beams for the combination of reinforcement is currently still At present, the combined reinforcement of concrete beams subjected to torsion is rarely involved. In this paper, for the carbon fiber reinforced polymer and angle steel combination of reinforced concrete torsion beams, designed 18 numerical specimens, its torsional stiffness and bearing capacity research, to determine the combination of torsional reinforced concrete beams of the main factors affecting the optimal combination of ratios, and to give the combination of reinforced concrete torsion beams torsional bearing capacity calculation formula. The research results show that the carbon fiber material and the splicing plate can form effective constraints on the concrete torsion beams, and the combined reinforcement method has a significant effect on the torsional load capacity, torsional stiffness and ductility enhancement of the reinforced concrete beams compared with the single reinforcement. The research results can provide technical support for the design and construction of combined reinforcement of concrete torsion columns
The Utilization of Coal Bottom Ash as a Natural Sand Replacement in Mortar Containing Fly Ash
Full text linkThe substantial generation of waste ashes from coal thermal power plants (CTP), particularly fly ash (FA) and bottom ash (BA), poses significant environmental challenges; meanwhile, the exhaustion of natural river sand for the construction industry is more serious. The study aims to explore the use of BA as a sand replacement and FA as a partial cement substitute in mortar production, focusing on sustainability. In this research, FA and cement served as binder materials, with FA comprising 15% of the total binder mass. BA was incorporated as a fine aggregate, replacing sand at varying levels of 0%, 25%, 50%, 75%, and 100% by weight. The study assessed the effects of BA substitution on the mortar's compressive strength (CS), ultrasonic pulse velocity (UPV), water absorption (WA), thermal conductivity (TC), and resistance to sulfate attack. Additionally, scanning electron microscopy (SEM) was utilized to analyze the mortar's microstructure. Results indicate that substituting sand with BA negatively impacted all tested properties. As BA content increased, CS, UPV, and TC of mortar samples decreased, while WA and sulfate expansion increased markedly. At 56 days, the mortar samples exhibited CS values ranging from 20.6 to 57.0 MPa, UPV values from 3395 to 4203 m/s, WA values from 5.58% to 18.70%, and TC values from 0.89 to 1.73 W/m·K. Furthermore, the control mortar demonstrated a length change of 0.0218% due to sulfate attack, whereas the length changes for specimens with 25%, 50%, 75%, and 100% BA replacement were approximately 68.8%, 96.3%, 155.0%, and 162.4% higher, respectively
Mathematical Remodeling: Hierarchical Sensitivity Analysis Approach Based on Analysis of Finite Fluctuations
Full text linkTo make the process of evaluating complicated hierarchical systems more tractable, it is beneficial to represent them through models derived from a unified class of frameworks that are conducive to subsequent analytical endeavors. This method of interchanging the original model with ones from predetermined categories possessing desirable characteristics is referred to as Mathematical Remodeling. Among remodeling classes there can be mentioned Neural Networks as structures being universal approximators and which are acceptable to be analyzed. The question related to the importance of model inputs (Sensitivity Analysis) has a great practical meaning, for example, this information can be used for model reduction, control of the system, etc. There are a wide variety of methods of Sensitivity Analysis, which can be classified both by the mathematical approaches used and by the types of models to which they are relevant. However, there are almost no unified approaches to assessing sensitivity in the case of hierarchical systems. The paper introduces the approach to estimate sensitivity measures for hierarchical system obtained by applying remodeling concept. The proposed method is based on Analysis of Finite Fluctuations built on the Lagrange mean value theorem. The proposed approach provides both end-to-end analysis (investigation of the influence of inputs of sub-systems on the output of the main system) and analysis of the components of the hierarchical system. The paper also contains a numerical example which demonstrates the ability of the proposed approach to deliver sensitivity measures of hierarchical system