1,359,835 research outputs found
Interoperability between BIM and FEM for vibration-based model updating of a pedestrian bridge
No full textFinite Element Model (FEM) updating is the procedure of minimizing errors between the experimental measurements and response simulated by FEMs. It can lead to more accurate and representative models useful to perform forecast analysis or detect initial damage thresholds for structures and infrastructure. The paper investigates the potentialities to carry out an automatic model updating through the interoperability between FEMs, Building Information Modeling (BIM), and experimentally vibration-based information. Indeed, these latter possess details and data (geometrical or mechanical) that could be automatically transferred in a numerical environment for structural modeling. The ability of this exchange is assessed by a methodology applied to a pedestrian walkway. The first path utilizes the geometrical data coming from a BIM model of the walkway to achieve three different levels of meshing. Consequently, three accurate finite element modeling have been pursued based on the achieved discretization. For each model, the accuracy and cost analysis has been evaluated considering the minimal distance between the main experimental modal parameters, identified from output-only dynamic tests, and the numerical ones, obtained after manual model updating. Additionally, a second path attempts to realize an automatic model updating through a simplified representative numerical system of the walkway implemented in Matlab. To this end, first, an opportune algorithm has been developed capable of processing the data and information from both BIM and experimental identification. Second, once the numerical model is realized, the potentiality of a modified Particle Swarm Optimization for improving the structural representativeness has been assessed. In particular, the usefulness of this approach could be related to a smart management system of the structures and infrastructure through a corresponding digital twin model
Process-induced microstructural variations in laser powder bed fusion of novel titanium alloys: A comprehensive study on volumetric energy density and alloying effects
No full textThis study explores the effect of in-situ alloying and volumetric energy density (VED) on the microstructure of Laser Powder Bed Fusion (L-PBF) fabricated Ti alloys. Pure Ti, Ti–5Cu, and Ti–5Cu–1Si (wt%) samples were printed using elemental powders with varying VEDs. This study investigates the influence of VED and Cu/Si additions on the growth restriction factor (Q) and columnar-to-equiaxed transition of the β phase. Pure Ti samples exhibited coarse, prior columnar β grains with an average diameter of 106 μm, and a grain shape factor greater than 3.0. In contrast, both Ti–Cu and Ti–Cu–Si samples displayed a significant fraction of equiaxed prior β grains with a near-spherical morphology. Additionally, Cu/Si addition refined the prior β columnar grains, reducing their average diameter to 37 μm and 25 μm in Ti–Cu and Ti–Cu–Si, respectively. Furthermore, the study reveals a strong dependence of microstructure on VED in the Ti–5Cu–1Si alloy. Higher VED promotes a more uniform distribution of solute elements and a lower thermal gradient, resulting in finer equiaxed β grains with an average diameter of 4.9 μm, compared to samples printed at lower VEDs. The addition of Cu and Si also significantly refined the lath-like α phase and decreased the c/a ratio of the Ti HCP lattice, introducing lattice microstrains in the Ti–Cu and Ti–Cu–Si alloys. These findings demonstrate the potential of in-situ alloying and VED optimization for tailoring microstructures in novel Ti alloys fabricated via L-PBF, paving the way for achieving superior mechanical properties
Ni-based water photocatalysts for hydrogen evolution, and physical mechanism behind photocatalysis
No full textAbstract
This doctoral thesis is dedicated to the exploration and enhancement of Nibased water photocatalysts, with a focus on their potential for efficient hydrogen evolution and unraveling the underlying physical mechanisms governing photocatalysis. The primary focus is on the utilization of commercial Ni@NiO/NiCO3 with varied sizes, subjected to vacuum annealing thermal treatment to enhance their photocatalytic properties. Additionally, the incorporation of Ag as a buffer element, facilitates the attachment of Ni to multilayered MoS2, resulting in the formation of a MoS2 -Ag-Ni ternary composite. Furthermore, the synthesis of hierarchical Nickel carbonate hydroxide via the hydrothermal method is investigated. A comprehensive characterization of the synthesized materials is carried out using various microscopic techniques (SEM, TEM, HRTEM, etc.) and spectroscopic tools (UV-vis, XPS, XRD, EDS, etc.) to provide detailed insights into the structural and chemical composition of the materials. The synthesized materials are then subjected to photocatalytic water splitting experiments, wherein hydrogen production under visible light irradiation is investigated. The outcomes of this research not only contribute to the advancement of Ni-based photo catalysts but also enhance our understanding of the complicated interplay between material structures and their photocatalytic performance. Original papers Talebi, P., Singh, H., Rani, E., Huttula, M., & Cao, W. (2021). Surface plasmon-driven photocatalytic activity of Ni@NiO/NiCO3 core–shell nanostructures. RSC Advances, 11(5), 2733–2743. https://doi.org/10.1039/D0RA09666K. https://doi.org/10.1039/D0RA09666K Self-archived version Talebi, P., Kistanov, A. A., Rani, E., Singh, H., Pankratov, V., Pankratova, V., King, G., Huttula, M., & Cao, W. (2022). Unveiling the role of carbonate in nickel-based plasmonic core@shell hybrid nanostructure for photocatalytic water splitting. Applied Energy, 322, 119461. https://doi.org/10.1016/j.apenergy.2022.119461. https://doi.org/10.1016/j.apenergy.2022.119461 Self-archived version Talebi, P., Rani, E., Niu, Y., Zakharov, A., & Cao, W. (2023). Spectromicroscopic determinations of chemical environments of Ni in MoS2‐Ag‐Ni ternary systems. X-Ray Spectrometry, 52(1), 38–45. https://doi.org/10.1002/xrs.3314. https://doi.org/10.1002/xrs.3314 Talebi, P., Greco, R., Yamamoto, T., Zeynali, M., Asgharizadeh, S., & Cao, W. (2024). Hierarchical nickel carbonate hydroxide nanostructures for photocatalytic hydrogen evolution from water splitting. Materials Advances, 5(7), 2968–2973. https://doi.org/10.1039/D3MA00977G. https://doi.org/10.1039/D3MA00977G Self-archived version Osajulkaisut Talebi, P., Singh, H., Rani, E., Huttula, M., & Cao, W. (2021). Surface plasmon-driven photocatalytic activity of Ni@NiO/NiCO3 core–shell nanostructures. RSC Advances, 11(5), 2733–2743. https://doi.org/10.1039/D0RA09666K. https://doi.org/10.1039/D0RA09666K Rinnakkaistallennettu versio Talebi, P., Kistanov, A. A., Rani, E., Singh, H., Pankratov, V., Pankratova, V., King, G., Huttula, M., & Cao, W. (2022). Unveiling the role of carbonate in nickel-based plasmonic core@shell hybrid nanostructure for photocatalytic water splitting. Applied Energy, 322, 119461. https://doi.org/10.1016/j.apenergy.2022.119461. https://doi.org/10.1016/j.apenergy.2022.119461 Rinnakkaistallennettu versio Talebi, P., Rani, E., Niu, Y., Zakharov, A., & Cao, W. (2023). Spectromicroscopic determinations of chemical environments of Ni in MoS2‐Ag‐Ni ternary systems. X-Ray Spectrometry, 52(1), 38–45. https://doi.org/10.1002/xrs.3314. https://doi.org/10.1002/xrs.3314 Talebi, P., Greco, R., Yamamoto, T., Zeynali, M., Asgharizadeh, S., & Cao, W. (2024). Hierarchical nickel carbonate hydroxide nanostructures for photocatalytic hydrogen evolution from water splitting. Materials Advances, 5(7), 2968–2973. https://doi.org/10.1039/D3MA00977G. https://doi.org/10.1039/D3MA00977G Rinnakkaistallennettu versio Academic Dissertation to be presented with the assent of the Faculty of Science, University of Oulu, Finland for public discussion in the Auditorium L5, on June 13th, 2024, at 12 o’clock (EEST) noon.Abstract
This doctoral thesis is dedicated to the exploration and enhancement of Nibased water photocatalysts, with a focus on their potential for efficient hydrogen evolution and unraveling the underlying physical mechanisms governing photocatalysis. The primary focus is on the utilization of commercial Ni@NiO/NiCO3 with varied sizes, subjected to vacuum annealing thermal treatment to enhance their photocatalytic properties. Additionally, the incorporation of Ag as a buffer element, facilitates the attachment of Ni to multilayered MoS2, resulting in the formation of a MoS2 -Ag-Ni ternary composite. Furthermore, the synthesis of hierarchical Nickel carbonate hydroxide via the hydrothermal method is investigated. A comprehensive characterization of the synthesized materials is carried out using various microscopic techniques (SEM, TEM, HRTEM, etc.) and spectroscopic tools (UV-vis, XPS, XRD, EDS, etc.) to provide detailed insights into the structural and chemical composition of the materials. The synthesized materials are then subjected to photocatalytic water splitting experiments, wherein hydrogen production under visible light irradiation is investigated. The outcomes of this research not only contribute to the advancement of Ni-based photo catalysts but also enhance our understanding of the complicated interplay between material structures and their photocatalytic performance
Effect of In-Situ Alloying with Si on the Microstructure of a Novel Ti-5Cu Alloy Manufactured by Laser Powder Bed Fusion
No full textThe present work aims to explore the influence of Si addition on the microstructure of a novel Ti-5Cu alloy produced by the Laser Powder Bed Fusion (L-PBF) technique, under an in-situ alloying strategy. For this purpose, Ti–5Cu and Ti–5Cu–1Si samples were manufactured under the same volumetric energy density (VED), i.e., 50.26 J/mm3. The findings revealed that incorporating 1 wt% Si into the Ti-5Cu alloy converted the prior β columnar and equiaxed grains with an average size of 41 μm and 22 μm, respectively, to finer equiaxed prior β grains within the Ti-5Cu-1Si microstructure, which featured with an average size of about 8 μm. Greater tendency for columnar to equiaxed transition and a notable grain refinement with Si addition were linked to a greater constitutional supercooling zone created by the rejection of Si solute atoms in front of the solidification front. Comparison of the solidification ranges for Ti-5wt%Cu and Ti-1wt%Si alloys plotted by PANDAT software revealed that Si has a more severe impact on the solidification range than Cu, making it a potentially better option for inducing columnar to equiaxed transition. Incorporating 1% Si to the Ti-5Cu alloy increased the growth restriction factor from 35 to 60 K, resulting in an almost 3-fold reduction in grain size. Addition of Si to the Ti-5Cu alloy also significantly refined the average length of α lath from about 4 μm to about 1.7 μm in the microstructure of Ti–Cu–Si alloys
Instantaneous Brain-to-Heart Functional Assessment using Inhomogeneous Point-process Models: a Proof of Concept Study
No full textWe introduce a new computational model for estimating the directional brain-heart interplay (BHI) in an instantaneous fashion using inhomogeneous point processes. Brain dynamics is considered as the exogenous input to a bivariate model predicting the first-order moment of an inverse-Gaussian function characterizing heartbeat dynamics continuously. Transfer entropy using brain- and heartbeat-related parameters finally quantifies the functional interplay from the brain to the heart. Here, we preliminarily evaluate our framework by studying heart rate variability (HRV) and electroencephalographic (EEG) series from 12 healthy subjects undergoing a cold-pressor test. Results suggest that cortical dynamics regulates heartbeat with specific time delays in the 30-60s and 90-120s ranges
Species diversity and community structure of braconid wasps (Hymenoptera) in two ecological hotspots of Iran: implication for conservation
No full text<p><span><span>Species diversity and community structure of braconid wasps (Hymenoptera) <a name="_Hlk115346465"></a>in two ecological hotspots of <a name="_Hlk115825047"></a><span>Iran</span>: implication for conservation </span></span></p>
<p><span>Parisa Abdoli<sup>1</sup>, Ali Asghar Talebi<sup>1</sup></span><a title="" href="#_ftn1" name="_ftnref1"><sup><span><span>*</span></span></sup></a><span>, Nickolas G. Kavallieratos<sup>2</sup>, Samira Farahani<sup>3­</sup> and Rasoul Khosravi<sup>4</sup> </span></p>
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<p><span>1. Department of Entomology, Faculty of Agriculture, Tarbiat Modares University, Tehran, I.R. Iran. <a name="_Hlk533412392"></a>[email protected]; [email protected]</span></p>
<p><span>2. Laboratory of Agricultural Zoology and Entomology, Department of Crop Science, Agricultural University of Athens; 75 Iera Odos <span> </span>str., 11855 Athens, Attica, Greece. </span><span>[email protected]</span></p>
<p><span>3. Research Institute of Forests and Rangelands, Agricultural Research Education and Extension Organization (AREEO), Tehran, I. R. Iran.<span> </span></span><a href="mailto:[email protected]"><span>[email protected]</span></a></p>
<p><span><span>4. Department of Natural Resources and Environmental Engineering, College of Agriculture, Shiraz University, Shiraz, Iran, [email protected]</span></span></p>
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<p><a title="" href="#_ftnref1" name="_ftn1"><span><span><span>*</span></span></span></a><span> </span>Correspondence<span>. E-mail: [email protected]</span></p>
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The recovery of rare earth metals from WEEE leaching solution via liquid-liquid extraction
No full textThe recovery of rare earth metals (REMs) from end-of-life products, such as Waste Electrical and Electronic Equipment (WEEE), is drawing great attention as an attractive strategy for promoting the sustainable development. The hydrometallurgical technique of solvent extraction has been reported to be one of the most interesting method to recover REMs. However, when applied to WEEE, this process is challenged by the heterogeneous composition of electronic waste, completely different from other solid matrices, and it still has much rooms of improvements. This study investigated the extraction, stripping and recovery of REMs from a WEEE leaching solution using Versatic 10 as carrier in the organic phase and oxalic acid as stripping agent. A factorial design was carried out to evaluate the simultaneous effects of factors as the feed phase pH and the concentrations of both extractant and organic phase modifier in the extraction process. Cerium, lanthanum and yttrium were extracted at high percentages using 200 mM of Versatic 10, loaded by 100 mM of TBP in kerosene at pH 7. Moreover, 750 mM of oxalic acid successfully stripped and recovered 7.63 and 13.82 mg/kg of lanthanum and yttrium, respectively
Internationalization of SMEs and Organizational Factors in Emerging Economies: High –Tech Industry of Iran
No full textSMEs as an engine of growth play an important role in emerging economies for poverty
reduction, the role which has attracted the attention of scholars in recent years. This study
explores the effect of firm characteristics, resources and top management team (TMT)
characteristics on the internationalization of SMEs. According to our conceptual model, we
assumed that firm resources mediate the link between international performance of SMEs and
characteristics of firms and of TMT. To test our model, we asked top managers of international
SMEs in Iran ICT sector to fill in a questionnaire. The data was analyzed through structural
equation modeling which leads us to codifying a causal model accordingly. The findings show a
direct and indirect positive effect of TMT characteristics on internationalization of SMEs,
however, it indicates that indirect effect of firm characteristics is not significant. Finally, a set of
guidelines are proposed for internationalization of SMEs in emerging economies
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