| 1. |
- Ajeel, Raheem K., et al.
(författare)
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Comprehensive analysis of heat transfer and pressure drop in square multiple impingement jets employing innovative hybrid nanofluids
- 2024
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Ingår i: Results in Engineering (RINENG). - : Elsevier B.V.. - 2590-1230. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- This study presents a comprehensive analysis of heat transfer and pressure drop characteristics in square multiple impingement jets utilising a novel class of hybrid nanofluids. This study goes beyond the usual vertical impingement method by looking at the use of oblique impingement in a multiple impinging jet configuration with a hybrid nanofluid. Al2O3–Cu/water with different volume fractions () such as 0.1%, 0.33%, 0.75%, and 1.0% are employed as a working fluid. The purpose of the study is to clarify the impact of the jet angle (β), the jet Reynolds number (Re), extended jet height ), and different volume fraction () on the heat transfer behaviours of the curved target surface. The jet Reynolds number varies from 8000 to 24,000, and five different jet angles (β = 15 , 30°, 45°, 60°, 90 ) and three extended jet heights = 0.2H, 0.4H, and 0.6H) are adopted. Outcomes disclosed that the highest values of Re and greatly led to an increase in heat transfer rate and pressure drop of the system. It is uncovered that the heat transfer rate of binary hybrid nanofluids enhances with increasing volume fraction from for all jet angles and Re. Results also exposed that the angle of jet, which is 45°, gives a higher Nusselt number compared to other angles proposed in this study, and the maximum boost reaches 35%. Besides, despite the fact that reducing the height of the extended jet yields enhanced heat transfer rates in comparison to other methods, it concurrently results in an elevation in pressure drop. Finally, this research yielding insights that can be applied to improve the efficiency of heat transfer systems in practical applications.
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| 2. |
- Alharthai, Mohammad, et al.
(författare)
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Numerical study on enhancing shear performance of RC beams with external aluminum alloy plates bonded using steel anchors
- 2024
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 22
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Tidskriftsartikel (refereegranskat)abstract
- This article compromises a three-dimensional numerical study employing the Abaqus program to investigate the behavior of reinforced concrete (RC) beams externally strengthened in shear using aluminum alloy (AA) plates bonded utilizing steel anchors. Based on previous experimental tests, a numerical validation study was conducted in two parts. The first part modeled the interaction behavior using different bonding methods between steel plates and the surface of the RC beams, whether utilizing epoxy adhesive only, steel anchors only, or a dual system between them. The second part modeled the performance of shear-defected RC beams that externally strengthened by the AA plates using epoxy adhesive. To take into account debonding collapse due to epoxy adhesive bonding, the interaction between the AA plates and beam surface was simulated with a cohesive-damage interaction. Comparing the numerical results with previous experimental studies shows the success of the numerical model in simulating the performance of different bonding methods, as well as the behavior of the RC beams defected in shear and strengthened by the AA plates, which qualified it to study some additional variables. From the study it was found that by utilizing only epoxy adhesive, the strengthening technique using the AA plate over the entire shear span zone (AASP method) was capable of increasing the ultimate capacity of the defected beam by 104%, which represents 77% of the load of the non-defected beam. It was also demonstrated that the AA plates were susceptible to collapse by the out-of-plane buckling when bonded using the steel anchors only. By utilizing a dual system for bonding the AA plates consisting of epoxy adhesive and steel anchors, the AASP method was capable of enhancing the ultimate capacity of the defected beam by 164% and changing its failure pattern to the preferred ductile bending pattern.
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| 3. |
- Amran, Mugahed, et al.
(författare)
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Shrinkage mitigation in alkali-activated composites: A comprehensive insight into the potential applications for sustainable construction
- 2023
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 20
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Forskningsöversikt (refereegranskat)abstract
- The extant body of literature articulates a noticeable disparity in the susceptibility to cracking and concomitant material degradation between alkali-activated composites (AAC) and ordinary Portland cement (OPC), predominantly attributable to shrinkage and subsequent drying phenomena. This divergence derives from the nanoscopic porosity of AAC binders, which is substantially finer than their OPC counterparts. However, experimental research validates that the judicious incorporation of alternative cementitious materials and fibrous reinforcements enriches the shrinkage characteristics of AAC, thereby enhancing its overall structural performance. Given the crucial role of shrinkage in defining the material integrity of AAC, especially under constrained environmental conditions, an in-depth understanding of shrinkage mechanisms materializes as a necessity for conceiving efficient shrinkage-mitigating strategies. In light of the growing interest in optimizing AAC through various material integrations and methodological innovations aimed at shrinkage diminution, this scholarly review undertakes an extensive synthesis of the laboratorial investigations focused on AAC shrinkage behavior and mitigation. However, this article critically evaluates widespread strategies for shrinkage mitigation, explicating their operative mechanisms. Moreover, it is outlined gaps in the existing research paradigm, promoting for targeted scholarly endeavors to yield a more clear understanding of shrinkage dynamics and to facilitate the advancement of environmentally sustainable AAC composites. Meanwhile, this study intended to consolidate existing research on developing trends in order to gain a comprehensive understanding of the possible uses of AACs and identify viable strategies for addressing AAC shrinkages. By addressing the challenges related to micro-cracking and shrinkage, the long-term durability of AACs may be improved, leading to increased adoption of these materials as sustainable building options in the construction industry today.
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| 4. |
- Arnesen, Marcus, et al.
(författare)
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A comparative study of constitutive models for EPS foam under combined compression and shear impact loading for helmet applications
- 2024
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Ingår i: Results in Engineering (RINENG). - : Elsevier BV. - 2590-1230. ; 23
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Tidskriftsartikel (refereegranskat)abstract
- Virtual testing of helmets using finite element (FE) analysis can be a valuable tool during product development. Still, its usefulness is limited by the quality of the constitutive model of the energy-absorbing material, usually foam. Built-in constitutive models in commercial FE software are developed for traditional linear compression loading. However, modern oblique test methods load the foam in combined compression and shear. Therefore, we aim to evaluate to what extent built-in constitutive models in commercial FE software can represent Expanded Polystyrene (EPS) foam during combined compression and shear loading (CCSL). EPS foam is tested experimentally in a newly developed test rig for CCSL (V-test). The response is compared against the simulation using three different constitutive models available in LS-DYNA (M83, M126, and M181). The models are assessed by their ability to capture the correct response, focusing on how well the continuum models can capture the phenomenological events seen in the experiments. The results show that the models perform well in compression, as expected. However, we point out limitations in the shear response and significant limitations in the unloading response, both important for oblique helmet testing. Due to these limitations, we conclude that the existing models are inadequate for accurately simulating oblique helmet impacts. There is a clear need to develop and implement new constitutive models focused on capturing CCSL including the unloading. Additionally, frictional sliding was found to substantially influence the measured response in the V-test method. Minimizing interface sliding is therefore critical for isolating the material behavior.
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| 5. |
- Awoyera, Paul O., et al.
(författare)
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Structural performance of fire-damaged concrete beams retrofitted using bamboo fiber laminates
- 2024
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 21
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Tidskriftsartikel (refereegranskat)abstract
- Fire-induced damage is a serious threat to the structural integrity of reinforced concrete (RC) beams, necessitating an effective retrofitting strategy to restore and improve their performance. This study investigates the structural performance of fire-damaged RC beams retrofitted with bamboo fiber laminates. A comprehensive analysis was performed, incorporating degradation rules to quantify the effect of temperature on both the load-carrying capacity and ultimate deflection of the RC beams. Eight conventionally designed and reinforced RC beams were tested, with two serving as controls. The remaining six beams were tested in pairs at three different temperatures (400 ◦C, 600 ◦C, and 800 ◦C) for 2-h exposure, with one beam featuring the bamboo fiber laminates in each pair. The bamboo fiber laminates enhanced the load-carrying capacity and deflection of the fire-damaged beams when subjected to incremental loading until failure. The deflection was improved by 48.78% at 400 ◦C, restoring the load-carrying capacity to control levels. The load-carrying capacity was increased by 29.5% at 600 ◦C, while the deflection was restored by 39.37%. The load-carrying capacity was enhanced by 37% at 800 ◦C, while the deflection was improved by 4.83%. According to the findings, bamboo fiber laminate is a viable alternative to synthetic fibers for retrofitting fire-damaged beams.
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| 6. |
- Cehlin, Mathias, Doktor, 1974-, et al.
(författare)
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Towards benchmarking of urban air quality based on homogenous surface emission
- 2023
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 20
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Tidskriftsartikel (refereegranskat)abstract
- Here, it is presented a possible methodology and experimental model for benchmarking of air quality in cities. The concept behind the methodology is that a city’s inherent structure affects the potential for contaminant removal due to the resistance it poses to inflow. The approach is based on homogenous emission across the street surface network, representing a worst-case situation. Different levels of complexity can be used for benchmarking, making it valuable for evaluating different layouts. Additionally, an urban ventilation index suitable for these kinds of experimental studies has been suggested.
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| 7. |
- Chanda Nagarajan, Pratheeba, 1978, et al.
(författare)
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Turbulent uniformity fluctuations in automotive catalysts – A RANS vs DES assessment
- 2022
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Ingår i: Results in Engineering. - : Elsevier BV. - 2590-1230. ; 16
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Tidskriftsartikel (refereegranskat)abstract
- Attaining sufficient flow uniformity in catalytic aftertreatment systems is a major challenge for the automotive industry. Computational fluid dynamics (CFD) simulations offer means of analyzing and quantifying this flow uniformity in silico. In this work, predictions from numerical simulations of flow uniformity obtained using a conventional steady-state Reynolds-Averaged Navier-Stokes (RANS) approach are contrasted against comprehensive Detached Eddy Simulations (DES) where the large-scale turbulence is resolved in space and time. It is shown that the DES approach provides access to data on flow uniformity fluctuations that could be significant for the catalyst light-off behavior. However, the computational cost of the DES is approximately three orders of magnitude larger than that of the corresponding RANS simulation.
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| 8. |
- Dehsorkhi, Soha, et al.
(författare)
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Low turn-on voltage of doped organic light emitting diodes based on food dyes
- 2020
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Ingår i: Results in Engineering. - : Elsevier. - 2590-1230. ; 5, s. 1-10
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Tidskriftsartikel (refereegranskat)abstract
- Three derivatives of food azo dye were investigated (Dyes 1, 2 and 4) by theoretical and experimental tools. Photophysical properties, based on theoretical estimations, experimental evaluations, electrochemical and photoelectrical properties were discussed. The compounds exhibited efficient emission of solid state with maximum fluorescence intensity at the range of 517–646 nm and PLQY (photoluminescence quantum yield) values at the range of 9–17% in non-doped solid state and 13–39% in doped solid state. In this study 90 wt percent of PBD (2-(4-tert-Butylphenyl)-5-(4-biphenylyl)-1,3,4-oxadiazole) have been used as the electron transporting host who derived balanced charge carrier transport for high internal and external efficiency of OLEDs (organic light emitting diodes). Ionization potential for compounds was found to be comparable (5.85 and 6.18 eV) by photoelectron emission spectrometry. According to the fabrication of devices for gaining charge mobility the layers of the dyes showed properties as a bipolar charge transporting with balanced hole and electron mobility and the values reaching to 1.27 × 10−4 cm2/Vs and 1.09 × 10−4 cm2/Vs respectively at high electric fields. Furthermore, OLEDs consist of azo dyes as an emitter layer fabricated by PVD (physical evaporation deposition) method and the maximum values of the best device showed, consist of, the low turn on voltage of 2.69 V and values of brightness, current efficiency, power efficiency, EQE (external quantum efficiency) 16432.40 cd/m2, 8.20 cd/A, 6.95 lm/w, 4.89% respectively.
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| 9. |
- Duryodhana, D., et al.
(författare)
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Buckling and free vibrations behaviour through differential quadrature method for foamed composites
- 2023
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Ingår i: Results in Engineering (RINENG). - : Elsevier BV. - 2590-1230. ; 17
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Tidskriftsartikel (refereegranskat)abstract
- The current work focuses on predicting the buckling and free vibration frequencies (fn) of cenosphere reinforced epoxy based syntactic foam beam under varying loads. Critical buckling loads (Ncr) and fn are predicted using the differential quadrature method (DQM). Ncr and fn have been calculated for beams of varying cenosphere volume fractions subjected to axial load under clamped-clamped (CC), clamped-simply (CS), simply-simply (SS), and clamped-free (CF) boundary conditions (BC′s). Upon increasing the cenosphere volume fraction, Ncr and fn of syntactic foam composites increases. These numerical outcomes are compared with the theoretical values evaluated through the Euler-Bernoulli hypothesis and further compared with experimental outcomes. Results are observed to be in precise agreement. The results of the DQM numerical analysis are given out for the different BC′s, aspect ratios, cenosphere volume fractions, and varying loads. It is perceived that depending on the BC′s, the type of axial varying loads and aspect ratios has a substantial effect on the Ncr and fn behaviour of the syntactic foam beams. A comparative study of the obtained results showed that the beam subjected to parabolic load under CC boundary conditions exhibited a higher buckling load. © 2023 The Authors
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| 10. |
- Forsberg, Samuel, et al.
(författare)
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Resilience to extreme storm conditions : A comparative study of two power systems with varying dependencies on offshore wind
- 2024
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Ingår i: Results in Engineering (RINENG). - : Elsevier. - 2590-1230. ; 23
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Tidskriftsartikel (refereegranskat)abstract
- In the next decades, the dependencies on power production from renewable energy sources are expected to increase dramatically. A transition towards large-scale offshore wind farms together with an increased electrification of the industry and transportation sectors introduces new vulnerabilities to society. Further, extreme weather events are expected to increase in intensity and frequency, driven by climate change. However, there are significant knowledge gaps concerning the impacts of severe weather conditions on the resilience of power systems with large dependencies on offshore wind. In the present study, a comparison between two different power systems’ resilience to historical extreme storm conditions has been conducted. The power systems are the IEEE39-bus New England model and the Great Britain model. The results show significant differences between the two power systems, which underlying reasons are analysed and explained. With an offshore wind penetration level of 30 %, the New England model stays intact in terms of connected load. When increasing the penetration level to 40 %, about 10 % of the total connected load gets disconnected, whereas about 33 % of the load gets disconnected with a penetration level of 50 %. The Great Britain model stays intact in terms of connected load with a penetration level of at least 49 %.
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