Periodica Polytechnica (Budapest University of Technology and Economics)
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Gas Phase Membrane Bioreactors
Get PDFThis mini review aims to introduce the gas phase membrane bioreactors (GPMBR). These systems can be considered as a combination of membrane contactors and bioprocesses. Constructions, features, and operations of these structures are described, moreover examples are given for their application possibilities, comparison to conventional processes is presented, advantages, limitations and perspectives are discussed
Façade Fire Separation Distances: A Critical Overview and Further Investigations
Get PDFBy the second half of the 20th century, the protection of building façades against fire spread became a considerable challenge in fire safety engineering. In the 1950s, several theoretical and experimental research projects were launched simultaneously, in order to determine the size of the separation distance which can stop the opening-to-opening façade fire propagation. In spite of the fact that the first major studies have already elucidated several limitations in connection with this approach, different separation distances are still widely used, without their practical objective and actual effectiveness having been clarified. This paper briefly summarizes the relevant conclusions of the research to date, explains the original protection objectives and highlights the shortcomings of the existing regulations. With the use of a numerical model based on the standard Hungarian façade fire testing method, the study presents some potential new opportunities for improving both our test methods and regulations
Social Resilience in Central-Eastern Europe: Comparing Bucharest Nine and Ukraine
Get PDFThis article examines social resilience among the Bucharest Nine (B9) countries and Ukraine amidst the intricate geopolitical landscape of Eastern Europe. It explores various aspects of social resilience, such as political structures, economic robustness, defence capabilities, social unity, and cultural identity, while also taking into account the influence of historical legacies, contemporary policies, and societal perceptions. The study constructs an integrated index of social resilience, amalgamating economic, political, social, and environmental parameters, thereby filling a critical void in the existing literature by providing a holistic understanding of a nation's social resilience. Key findings highlight divergent levels of social resilience among these nations, shown to be influenced by institutional trust, economic inclusivity, and environmental sustainability. Estonia emerges as the most resilient country with a "sufficient" level, while others like Hungary, Romania, and Ukraine fall within the "medium" resilience category. None of the research countries exhibited "high" or "low" level of social resilience. Consideration of the practical implications underlines the necessity for targeted strategies in bolstering institutional trust, economic inclusivity, environmental sustainability, and social cohesion. By offering a multi-dimensional viewpoint, this study can inform policy formulation, enhancing nations' capacities to navigate regional complexities and uphold societal integrity and national stability. Limitations such as the dynamic nature of social resilience factors and challenges in data availability, particularly in war-affected regions like Ukraine, are acknowledged. The study advocates for future research focusing on longitudinal studies and the influence of digital transformation and innovation on social resilience
Effects of Non-traditional Additives on the Early Strength of a Lean Clay Soil Stabilized by Compound Calcium-based Stabilizer
Get PDFSoil stabilization is a widely used technique in civil engineering to enhance the engineering properties of fine-grained soils. Traditional calcium-based stabilizers, such as cement, lime (L), and fly ash (FA), are most commonly used due to their availability and proven effectiveness. However, these stabilizers often exhibit slow early strength development. To address this challenge, the present study explores the potential of non-traditional additives to improve early strength in stabilized soils. A range of additives, including two nano-materials, six soluble sodium and calcium salts, five soluble iron and aluminum salts, and cationic polyacrylamide (CPAM), were incorporated into a lean clay soil stabilized with a compound calcium-based stabilizer composed of cement, L, and FA. The 7-day unconfined compressive strength (UCS) was used as the primary performance indicator. The results indicated that within the tested dosage ranges, the two nano-materials, most soluble iron and aluminum salts, and CPAM had minimal or even adverse effects on early strength development. In contrast, specific combinations of soluble sodium salts significantly enhanced early strength. For example, a combination of 0.05% sodium carbonate with 0.05% sodium silicate, and 0.05% sodium sulfate with 0.05% sodium silicate, resulted in strength increases of 34.5% and 33.6%, respectively. Additionally, the standalone addition of 0.5% water glass led to a 32.2% improvement in strength
Experimental Investigation on the Dynamic Characteristics of Representative Sand and Clay in the Beijing Region
Get PDFIn order to gain a more accurate understanding of the dynamic characteristics of soil, vibration triaxial tests were conducted on representative sand and clay samples from the Beijing area. The study investigated the influence of varying loading frequencies, cyclic stress ratios, and confining pressures on soil strength and liquefaction resistance, while also analyzing changes in shear modulus and damping ratio. The dynamic shear modulus of both sand and clay decreases with increasing shear strain, with higher confining pressures resulting in larger shear moduli. For sand, the damping ratio decreases as shear strain increases; however, for clay it initially increases before decreasing. Overall, clay exhibits a larger dynamic shear modulus but smaller damping ratio compared to sand. The number of cycles experienced by both sand and clay samples decreases with increasing confining pressure or deviational stress. As loading frequency increases, the number of cycles gradually rises for sand samples but first increases then decreases for clay samples. The damping ratio of sand gradually declines with an increase in cycle count while that of clay remains relatively stable. The variations observed in shear modulus and damping ratio are influenced by factors such as loading frequency, confining pressure, and deviating stress
Chaos-based Swarm Intelligence Algorithms for Optimal Design of Truss Structures
Get PDFThe incorporation of chaos functions into metaheuristic algorithms leads to significant progress in the results of optimal design of truss structures. Chaos functions, by forming chaotic mutations, create the necessary conditions to create a balance between exploration and exploitation. With this balance, the algorithm is saved from premature convergence and, by forming chaotic series, a jump from local optima to global optima is achieved. In this research, chaos functions are formed in the basic steps of three meta-heuristic swarm intelligence algorithms and three new chaos algorithms. These algorithms include the Chaotic Grey Wolf Optimizer (CGWO), the Chaotic Crow Search Algorithm (CCSA), and the Chaotic Cyclical Parthenogenesis Algorithm (CCPA). To improve the optimization results, three different scenarios are examined and the chaotic results are compared with the standard case. In these scenarios, chaos series replace the exploration, exploitation, or both stages simultaneously
Sustainable Use of Sugarcane Bagasse Ash in Fly Ash-based Geopolymers: Implications for Compressive Strength and Shrinkage
Get PDFGeopolymers are synthesized through the reaction between alkaline activator solutions and aluminosilicate-rich precursors, offering an alternative to Portland cement for sustainable construction. Sugarcane bagasse ash (SCBA), an agricultural byproduct rich in SiO2, presents potential for incorporation into fly ash (FA)-based geopolymer systems. While SCBA has been explored for environmental benefits, limited studies have evaluated the combined influence of SCBA and alkaline activator solutions on hardening behavior. This study investigated the effects of SCBA content (0%, 10%, 20%, 30% by mass), NaOH concentration (8M, 12M, 16M), and liquid-to-solid (L/S) ratio (0.2, 0.4, 0.6) using 36 geopolymer paste mixtures. SCBA was processed by drying, sieving to 149 µm, and calcining at 700 °C for 2 hours. Specimens were cured at 90°C for 24 hours, followed by ambient curing. Bulk density, apparent porosity, water absorption, compressive strength, and shrinkage were evaluated. Results showed that SCBA content and L/S ratio strongly affected compressive strength and shrinkage. The mixture containing 10% SCBA, NaOH 12M, and L/S = 0.4 achieved the highest compressive strength (47.65 MPa at 90 days), along with reduced porosity and water absorption. In contrast, SCBA replacement above 20% resulted in decreased strength and increased shrinkage. The results indicate the potential of SCBA as a partial FA replacement to promote sustainable construction materials
Revenue Alterations of Shared Automated Mobility Services Integrated into Mobility as a Service
Get PDFThe concept of mobility as a service (MaaS) is integrating mobility services and offering them to users via a single means. The introduction of shared autonomous vehicles (SAVs) and adaptation of revenue models must be tackled in the MaaS concept. As the scientific basis for this is incomplete, we forecasted the alterations in the revenue of SAVs after the integration into MaaS. We analyzed the existing revenue models used by shared mobility services and MaaS, and used a revenue model framework (RMF) to explore the possible sources of revenue. Our methodology contains the before-and-after analysis and considers the MaaS integration levels. The main findings indicate that MaaS takes over revenue sources from mobility service providers as the integration levels increase. Also, the commission paid to MaaS is a new cost for mobility service providers. Then, integrating SAVs into MaaS is beneficial if the revenue increase caused by number of trips outweighs the loss generated by the responsibilities taken by MaaS. Finally, the door-to-door SAV services exist in all integration levels, but feeder is only present at level 3. MaaS operators and SAV mobility service providers can use our findings during negotiations of contracts, and the integration process can be accelerated