Periodica Polytechnica (Budapest University of Technology and Economics)
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Developing Low Cost Eco-friendly Restoration Mortars for Historic Lime-based Stucco and Building Materials
Get PDFIn this work, three formulations based on hydrated lime and eco-friendly additives of powdered brick, fly ash and silica fume were designed to improve repair mortars for historic lime-based stucco and building materials. The microscopic features, physical-mechanical behavior and the microstructure of the prepared mortars were evaluated before and after artificial ageing (by humidity/drying cycles and salt weathering). However, a significant mechanical enhancement was reported for the studied mixes, but the silica fume mix showed a notable failure after salt ageing. The fly ash mix revealed the highest bulk density ratio (1.172 g/cm3) compared to the lime and silica fume mixes. The silica fume mix recorded the lowest percentage of water absorption (35.56%) and apparent porosity (28.11%). Further, the silica fume mix yielded the highest dry compressive strength value (22.19 kg/cm2), with an increase reached 31% when compared to the standard lime mix. The results demonstrated that the fly ash mortar is more compatible for sustainable restoration procedures of historic lime-based structures in respect of the physical-mechanical properties
Symmetry Measure of Truss Structures with Disturbed Higher-order Symmetries
Get PDFThis paper covers aspects of quantifying the symmetry of two- and three-dimensional elastic bar-and-joint structures. The concept of symmetry as a quantitative property instead of a binary question of 'yes' or 'no' is widely accepted and thoroughly investigated, for example, in molecular physics but also in engineering sciences, mainly in chemical engineering. Similarly to most of the articles written on this topic, our method is also based on the comparison of specific metrics of the analyzed structure and a reference one, i.e., which possesses the desired (perfect) symmetry. The deviation of the analyzed (imperfect) structure from the reference structure is quantified by one scalar. The novelty in our approach is that we consider not just the relative position of the nodes but also the normal stiffness of the truss members, even for structures with higher-order, i.e., polyhedral symmetries. For both geometric and material properties to be accounted for, the eigenvalues of the stiffness matrix were chosen as metrics. The difficulty lies in finding the reference structure which will be carried out based on energy principles
Numerical Analysis of Combined Effect Hybrid Fibres and Fire Insulation on the Fire Resistance Performance of SCC Beams
Get PDFThe use of self-compacting concrete in structural members has become increasingly prevalent in various construction applications. However, these structures are susceptible to one of the most hazardous disasters, which is the fire. This paper presents a numerical investigation of the fire resistance performance of self-compacting reinforced concrete (SCC) beams, as well as a parametric study to assess the impact of hybrid fibres and fire insulation on enhancing their performance under fire conditions. The study is conducted by developing a 3D finite element (FE) model using ANSYS software, where temperatures are applied according to the ISO834 standard fire. Geometric and material nonlinearities are considered in the evaluation of the behaviour of beams under fire conditions. The developed FE model is validated by comparing the predicted results with those of the experimental tests in literature. The fire resistance performance of SCC beams was compared with that of normal strength concrete (NSC) beams. The parametric study is conducted using three types of fire insulation, namely Tyfo WR-AFP, CAFCO 300, and Carboline Type-5MD. The results showed that SCC beam has lower fire resistance performance than the NSC beam. However, the incorporation of hybrid fibres allows a 17% improvement in the fire resistance of SCC beams. The use of fire insulations has increased the fire resistance time of SCC beams, and more particularly Carboline Type-5MD insulation with an increase of 28%. The combined use of hybrid fibres and fire insulation improved the fire resistance of SCC beams by 43%
Optimized Transfer Matrix Approach for Global Buckling Analysis: Bypassing Zero Matrix Inversion
Get PDFThe transfer matrix method has two main disadvantages concerning other numerical methods: numerical instability in extreme cases and the need to calculate the inverse of the zero matrix. This paper attempts to solve the second difficulty of the transfer matrix method, widely used for the global buckling analysis of beams in all engineering fields. In particular, the transfer matrix method necessarily requires the calculation of the inverse of the zero matrix to derive the element transfer matrix, resulting in high computational costs as the number of discretizations and the size of the matrix increases. To mitigate this challenge, this paper presents a transfer matrix method that directly computes the transfer matrix without requiring the inverse of the zero matrix. The method adopts a Laplacian approach, which involves the application of Laplace transforms to the equilibrium equations and subsequent inverse Laplace transforms to express displacements and internal forces relative to the zero point of the coordinate origin significantly reducing computational costs to a minimum. Numerical applications corroborate the effectiveness and superiority of the proposed approach
Enhancing Battery Capacity Estimation Accuracy through the Neural Network Algorithm
Get PDFAccurate estimation of battery metrics, such as state of health (SOH), is crucial for effective battery management systems (BMS) due to capacity degradation over time. This paper proposes a methodology to enhance battery capacity estimation accuracy by addressing uncertainties related to state of charge (SOC) estimation and measurement. The methodology employs the Neural Network Algorithm (NNA), an optimization algorithm inspired by artificial neural networks (ANNs). The NNA generates an initial population of pattern solutions and iteratively updates them using a weight matrix, bias operator, and transfer function operator. By combining the advantages of ANNs and optimization techniques, the NNA aims to find an optimal solution considering interdependent variables and incorporating global and local feedbacks. Leveraging the capabilities of the NNA, our objective is to identify the candidate that minimizes a specified cost function, ensuring up-to-date cell capacity through a memory forgetting factor. The algorithm's precision was validated using NASA's Prognostic Data, demonstrating outstanding performance by surpassing two aggressive algorithms in terms of accuracy. In the most severe case scenario, the algorithm achieved a peak error of less than 0.4%. Furthermore, the algorithm consistently demonstrated predictive performance measures that were superior to those of the compared algorithms
Quantifying the Tip Leakage Vortex Wandering in a Low-Speed Axial Flow Fan via URANS Simulation
Get PDFThe tip leakage vortex is a dominant noise and aerodynamic loss source of low-speed axial flow fans. The tip leakage vortex often has an unsteady behavior, like the periodic motion of the vortex core: the so-called vortex wandering. This periodic vortex wandering results in additional noise, aerodynamic loss, and an oscillation in the moment acting on the blading, which causes an unfavorable vibration of the rotor. In the research campaigns focusing on vortex wandering, complicated measurement techniques (PIV) or high-fidelity but computationally costly simulations are commonly used. The present paper aims to introduce a relatively cost-effective unsteady Reynolds-averaged Navier-Stokes simulation-based investigation method of vortex wandering. The capabilities of the proposed technique are presented through a low-speed axial flow fan case study
Miniportrék az augusztus 20-a alkalmából kitüntetett könyvtárosokról
No full textAugusztus 20-a alkalmából több könyvtároskolléga is állami elismerésben részesült. Az alábbiakban röviden ismertetjük az életútjukat, valamint „mini interjúk” formájában arról kérdezzük a kitüntetetteket, hogy miért választották ezt a pályát, mit jelent számukra a könyvtárosság, és hogyan látják a szakma jövőjét
RETRACTED: Geometric Parameter Optimization of Switched Reluctance Machines for Renewable Energy Applications using Finite Element Analysis
Get PDFPAPER RETRACTED April 26, 2024, by the general editor of Periodica Polytechnica, because of the authors' incidental double submission of Touati, Z., Araújo, R. E., Mahmoud, I., Khedher, A. "Analysis of Skewing Effects on Radial Force for Different Topologies of Switched Reluctance machines: 6/4 SRM, 8/6 SRM, and 12/8 SRM", U.Porto Journal of Engineering, 9(1), pp. 55–71, 2023.https://doi.org/10.24840/2183-6493_009-001_00113
The Effect of GSI and mi on the Stability of 3D Twin Tunnel in Limestone
Get PDFThe Generalised Hoek-Brown (GHB) failure criterion is one of the most used criteria to study the behaviour of the rocks; affected parameters of the Hoek-Brown equation are Geological Strength Index (GSI), intact rock constant (mi), and Disturbance factor (D). GSI is one of the rock classification systems used to evaluate jointed rocks. In light of this equation, this paper studies the stability of unsupported twin tunnels in a weak rock by changing the mentioned parameters (GSI, mi) to find the relation between the stability and these parameters under different distances between the centres of the tunnels (L). The tunnels have a circular cross-section with a diameter (B), and they have been modelled in three dimensions using Rocscience software package (RS3). The results showed that the stability of the tunnels, which was represented by the strength reduction factor (SRF), increased as a result of increasing L/B or GSI in the studied range; for mi , the modelling results showed that the SRF value increased while mi value was increased
A Genetic Algorithm-based Decision Framework to Incorporate Climate Impact on Pavement Maintenance Planning
Get PDFA recent trend of increase in the vulnerable behavior of roads to potential climate events is observed worldwide. However, a few studies conducted incorporate climate impact into road maintenance and rehabilitation. To address this, a genetic algorithm (GA) based optimization approach is proposed in this study with a climate risk index (CRI) in terms of criticality of roads, probability of occurrence of a climate event, and existing severity level of pavement. Criticality is defined by road functional class, availability of alternative routes and land use. Probability is determined by historical events and topography, while severity is defined by existing pavement condition. The CRI is incorporated as a generic constraint to the GA-based optimization model to maximize the average network condition under a given budget. To demonstrate this, a case study is conducted using twenty roads in different climatic conditions in Sri Lanka. The results show that in 25% and 50% of required total budget conditions there is a clear separation between priority roads IRI and non-priority roads IRI due to the generic constraint. This is an indication that the optimization model effectively prioritizes roads when there is a budget constraint. This concludes that the proposed approach can be utilized to make the most of the available budget for road maintenance by prioritizing roads that are highly vulnerable to climate events without compromising the overall network condition. Further, the proposed maintenance optimization approach can be extended to long term maintenance planning economically for developing countries