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Influence of concrete compressive strength on the debonding failure of externally bonded carbon fiber reinforced polymers

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Journal of Building Pathology and Rehabilitation 2021年第1期6卷 1-15页

作者： Garcez, Mônica Regina Rohden, Abrahão Bernardo Meneghetti, Leila Cristina Gravina, Rebecca Civil Engineering Post-Graduation Program: Construction and Infrastructure Federal University of Rio Grande Do Sul Av. Osvaldo Aranha 99 7th floor room 706 Porto Alegre 90035-190 RS Brazil Environmental Engineering Post-Graduation Program Regional University of Blumenau Blumenau SC Brazil Department of Structural and Geotechnical Engineering University of São Paulo São Paulo SP Brazil Department of Civil and Infrastructure Engineering Royal Melbourne Institute of Technology Melbourne VIC Australia

This paper investigates the interactions between externally bonded FRP and high strength concrete substrate in small scale reinforced concrete beams strengthened with CFRP. The bond mechanism was assessed through beam-tests adapted from ASTM, designed to simulate normal and shear stresses induced at the FRP/concrete interface. The beams were 600 mm long, with a square 150 mm × 150 mm cross-section, two 5 mm steel reinforcing bars, 6.3 mm steel stirrups spaced 75 mm apart, one single layer of externally bonded CFRP, and concrete compressive strength of 30 MPa, 50 MPa, 80 MPa, or 90 MPa. The mechanisms of damage initiation and debonding propagation showed to be highly dependent on the load transferring and the stress redistribution after concrete cracking. The use of high concrete compressive strength affected the pre-cracking response, the stress transfer, and the overall ductility at failure, resulting in a less effective FRP strengthening scheme. For service conditions, the strains in the FRP were lower, the higher the concrete compressive strength. The FRP strains at failure were below the maximum strain level to avoid intermediate crack-induced debonding determined according to current design standards. © 2021, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

关键词： Beam test CFRP Compressive strength Concrete Debonding Intermediate crack

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Bond Behavior between Recycled Concrete Containing CDW and Different Types of Steel Bars

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Journal of Architectural Environment & Structural engineering Research 2021年第2期4卷 1-7页

作者： Carine N.S.Reis Paulo Lima Mônica B.Leite Department of Technology Post-graduation Program of Civil and Environmental EngineeringState University of Feira de SantanaBahiaBrazil

The operation of reinforced concrete structures is directly associated with the adhesion between the steel bar and the concrete,which allows the internal forces to be transferred to the reinforcement during the process of loading the structural *** modification of the concrete composition,with the introduction of recycled aggregate from construction and demolition waste(CDW),affects the steel-concrete interface and can modify the bonding stress,which is also influenced by the type and diameter of the bar *** this work,the influence of the recycled fine aggregate(RFA)and types of steel bar on the steel-concrete bond was experimentally evaluated using the pullout *** concrete and recycled concrete,with RFA replacement level of 25%,were *** types of steel rebars(i.e.,plain and deformed)with diameters of 10.0 and 16.0 mm were considered in this *** results indicate a reduction in the adhesion stress with the introduction of recycled aggregate,but this trend is influenced by the diameter of the bar *** use of ribbed bars modifies the stress bon-slip behavior,with an increase in the average bond strength,which is also observed with the reduction of the diameter of the bar.

关键词： Construction and demolition waste(CDW) Recycled concrete Steel-concrete bond behavior

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Co2 Capture Using Silica-Immobilized Dicationic Ionic Liquids with Magnetic and Non-Magnetic Properties

SSRN

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SSRN 2023年

作者： Duarte, Evandro Bernard, Franciele Dos Santos, Leonardo Moreira Polesso, Bárbara B. Duczinski, Rafael Forneck, Vitor Geshev, Julian Einloft, Sandra Post-Graduation Program in Materials Engineering and Technology Pontifical Catholic University of Rio Grande do Sul – PUC RS Brazil School of Technology Pontifical Catholic University of Rio Grande do Sul – PUC RS Brazil Institute of Physics Federal University of Rio Grande do Sul RS Porto Alegre Brazil

The need to find alternative materials to replace aqueous amine solutions for CO2 capture in post-combustion technologies is pressing. This study assesses the CO2 sorption capacity and CO2/N2 selectivity of three dicationic ionic liquids with distinct anions immobilized in commercial mesoporous silica support (SBA-15). The samples were characterized by UART-FTIR, NMR, Raman, FESEM, TEM, TGA, Magnetometry (VSM), BET and BJH. The highest CO2 sorption capacity and CO2/N2 selectivity were obtained for sample SBA@DIL_2FeCl4 [at 1 bar and 25°C;57.31 (±0.02) mg CO2/g;12.27 (±0.72)]. The results were compared to pristine SBA-15 and revealed a similar sorption capacity, indicating that the IL has no impact on the silicás CO2 sorption capacity. On the other hand, the selectivity was improved by approximately 3.8, demonstrating the ionic liquid´s affinity for the CO2 molecule. The material underwent multiple sorption/desorption cycles and proved to be stable and a promising option for use in industrial CO2 capture processes. © 2023, The Authors. All rights reserved.

关键词： Carbon dioxide

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Information Gain applied to reduce model-building time in decision-tree-based intrusion detection system

Information Gain applied to reduce model-building time in de...

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Iberian Conference on Information Systems and Technologies (CISTI)

作者： Moisé s S. De Sousa Carlos Eduardo Lacerda Veiga Robson De O. Albuquerque William F. Giozza Professional Post-Graduation Program in Electrical Engineering&#x2013 PPEE&#x2013 Electrical Engineering Department Faculty of Technology University of Bras&#x00ED lia (UnB) Bras&#x00ED lia Brazil Advocacia-Geral da Uni&#x00E3 o Bras&#x00ED

Due to the large amount of sensitive data generated by websites, it is possible to understand the progress of attacks to their databases. This work proposes an intrusion detection system based on data mining and machine learning techniques to detect and mitigate the damage caused by these attacks. It adopts the Information Gain method of selecting attributes in order to reduce the model-building time without affecting the classification performance. Using the CIC-IDS 2017 dataset, this work shows how different decision tree algorithms (Random Forest and J48 Algorithm) behave even if they receive equal parameters and data. Using Information Gain to select attributes, the proposed system achieves a processing time reduction of up to 90%.

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Revolutionary valorization of carbon dioxide into dimethyl carbonate is catalyzed by sodium chloride: cheap, clean, one-pot, and water-free synthesis

arXiv

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arXiv 2023年

作者： Chaban, Vitaly V. Andreeva, Nadezhda A. Santos, Leonardo Moreira dos Einloft, Sandra Yerevan State University Yerevan0025 Armenia Peter the Great St. Petersburg Polytechnic University Saint Petersburg Russia School of Technology Pontifical Catholic University of Rio Grande do Sul - PUCRS Porto Alegre Brazil Post-Graduation Program in Materials Engineering and Technology School of Technology Pontifical Catholic University of Rio Grande do Sul – PUCRS Brazil

The robust valorization of carbon dioxide (CO2) stays at the center of sustainable development. Since CO2 represents a low-energy compound, its transformation into commercially coveted products is cumbersome. In the present work, we report a revolutionary method to obtain dimethyl carbonate (DMC) out of methanol (CH3OH) and CO2 catalyzed by sodium chloride (NaCl) and similar inorganic salts. The computational exploration revealed a mechanism of favorable catalysis, which was subsequently confirmed experimentally. Unlike all competitive syntheses of DMC, the new one does not produce water and, therefore, the hydrolysis of a carbonate does not occur. No dehydrating agents are necessary. The employed catalyst is cheap and permanently exists in the same phase with the reactants and products. The action of NaCl was compared to those of other alkali metal salts, LiI, LiCl, and KI, and competitive performances were recorded. The experimentally obtained result outperforms most competing technologies according to the DMC yield, 19% with molecular sieves and 17% without molecular sieves. All existing competitors are excelled by the simplicity and cleanness of the synthesis. The reported advance substantially simplifies the synthesis of linear organic carbonates and robustly valorizes CO2 © 2023, CC BY.

关键词： Methanol

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A mini-review on plasticrusts: occurrence, current trends, potential threats, and recommendations for coastal sustainability

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Environmental Monitoring and Assessment 2024年第2期196卷 137-137页

作者： Nguyen, Minh-Ky Rakib, Md. Refat Jahan Nguyen, Hoang-Lam Lin, Chitsan Malafaia, Guilherme Idris, Abubakr M. Faculty of Environment and Natural Resources Nong Lam University of Ho Chi Minh City Hamlet 6 Linh Trung Ward Thu Duc City Ho Chi Minh City700000 Viet Nam Ph.D. Program in Maritime Science and Technology National Kaohsiung University of Science and Technology Kaohsiung81157 Taiwan Department of Fisheries and Marine Science Faculty of Science Noakhali Science and Technology University Sonapur Noakhali3814 Bangladesh Department of Civil Engineering McGill University Montreal Canada Department of Marine Environmental Engineering National Kaohsiung University of Science and Technology Kaohsiung81157 Taiwan Post-Graduation Program in Ecology Conservation and Biodiversity Federal University of Uberlândia MG Uberlândia Brazil Post-Graduation Program in Biotechnology and Biodiversity Federal University of Goiás GO Goiânia Brazil Post-Graduation Program in Conservation of Cerrado Natural Resources Goiano Federal Institute GO Urutaí Brazil Department of Chemistry College of Science King Khalid University Abha62529 Saudi Arabia King Khalid University Abha62529 Saudi Arabia

Plasticrusts manifest as a coating on intertidal rocks due to environmental exposure. They refer to crushed plastic debris that blankets rocks found along intertidal shorelines. This study significantly contributes to a better understanding of the occurrence of these novel plastic formations, shedding light on their potential pathways of formation during the Anthropocene era. The research provides comprehensive insights into the composition, origins, challenges, and effective management strategies for removing coastal plastic litter. The findings of this investigation offer valuable evidence regarding the formation and impact of these recently discovered plastic items in coastal regions, prompting discussions about their formation processes and their effects on the marine ecosystem. Recognizing that these newly emerged plastic litter pose a considerable threat to the marine environment is crucial. With their emergence, we face an environmental challenge, especially concerning the health of coastal ecosystems. Plasticrusts, when degraded, can release microplastics (MPs) and nanoparticles (NPs) into the surrounding environment. These micro- and nano-sized plastic particles pose significant ecological risks as they persist in ecosystems, potentially harming wildlife and entering the food chain, causing widespread environmental contamination. Significantly, it outlines strategies to minimize the impact of this emerging plastic debris and its source. © 2024, The Author(s), under exclusive licence to Springer Nature Switzerland AG.

关键词： Ecosystems

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Growth of Wafer-Scale Single-Crystal 2D Semiconducting Transition Metal Dichalcogenide Monolayers

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Advanced Science 2024年第11期11卷 e2307839页

作者： Singh, Jitendra Astarini, Nadiya Ayu Tsai, Meng-Lin Venkatesan, Manikandan Kuo, Chi-Ching Yang, Chan-Shan Yen, Hung-Wei Department of Materials Science and Engineering National Taiwan University of Science and Technology Taipei City106335 Taiwan Department of Physics Udit Narayan Post Graduate College Padrauna Uttar Pradesh Kushinagar274304 India Department of Molecular Science and Engineering Institute of Organic and Polymeric Materials National Taipei University of Technology Taipei City106344 Taiwan Institute and Undergraduate Program of Electro-Optical Engineering National Taiwan Normal University Taipei City11677 Taiwan Department of Materials Science and Engineering National Taiwan University Taipei City106319 Taiwan

Due to extraordinary electronic and optoelectronic properties, large-scale single-crystal two-dimensional (2D) semiconducting transition metal dichalcogenide (TMD) monolayers have gained significant interest in the development of profit-making cutting-edge nano and atomic-scale devices. To explore the remarkable properties of single-crystal 2D monolayers, many strategies are proposed to achieve ultra-thin functional devices. Despite substantial attempts, the controllable growth of high-quality single-crystal 2D monolayer still needs to be improved. The quality of the 2D monolayer strongly depends on the underlying substrates primarily responsible for the formation of grain boundaries during the growth process. To restrain the grain boundaries, the epitaxial growth process plays a crucial role and becomes ideal if an appropriate single crystal substrate is selected. Therefore, this perspective focuses on the latest advances in the growth of large-scale single-crystal 2D TMD monolayers in the light of enhancing their industrial applicability. In the end, recent progress and challenges of 2D TMD materials for various potential applications are highlighted. © 2023 The Authors. Advanced Science published by Wiley-VCH GmbH.

关键词： Single crystals

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Study of Machine Learning Techniques for Damage Identification in a Beam 10th

Study of Machine Learning Techniques for Damage Identifica...

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10th International Conference on Wave Mechanics and Vibrations, WMVC 2022

作者： da Silva Coelho, Jefferson de Sousa, Amanda Aryda Silva Rodrigues Machado, Marcela Rodrigues Dutkiewicz, Maciej Department of Mechanical Engineering University of Brasília Campus Universitário Darcy Ribeiro Faculdade de Tecnologia - Asa Norte DF Brasília Brazil Post-Graduate Program - Integrity of Engineering Materials University of Brasília Campus Universitário Darcy Ribeiro Faculdade de Tecnologia - Asa Norte DF Brasília70910-900 Brazil Faculty of Civil Environmental Engineering and Architecture University of Science and Technology Bydgoszcz85-796 Poland

ISBN: (纸本)9783031157578

Damage is defined as any change to the material, geometry or boundary condition that can modify the structure’s properties or response. In the past, damage identification was performed through periodical inspection, non-destructive testing/non-destructive evaluation, or visual observation. Structural health monitoring (SHM) has emerged to transition from offline damage identification to near real-time and online damage assessment. Hence, SHM is a damage detection strategy to monitor a structure for a period using a series of continuous measurement devices, which then collect the system’s characteristics and subsequently perform statistical analysis to assess the current circumstances and health of the structure. One of the first steps for the study of SHM is damage detection followed by monitoring. Machine Learning (ML) techniques can be used to develop viable algorithms to make potential predictions. ML algorithms are therefore providing the tools needed to enhance the capabilities of SHM systems and provide intelligent solutions to past challenges. Preliminary studies have reviewed that the extension of ML into SHM has dramatically increased the system’s capabilities, providing innovative solutions to different research challenges. This work conducts a study of the use of ML to identify damage in a beam and discuss the challenge of usage, performance and implementation of each technique. © 2023, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Decision trees

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A Critical Review on Cryopreservation of Cells Technics: Thermal Aspects 6th

A Critical Review on Cryopreservation of Cells Technics: The...

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6th Multiphase Flow Journey, JEM 2021

作者： Steffenon, Guilherme D. Copetti, Jacqueline B. de Oliveira, Jeferson D. Macagnan, Mario H. Cardoso, Elaine M. the University of Vale do Rio dos Sinos Mechanical Engineering Graduate Program LETEF Laboratory of Thermal and Fluid Dynamic Studies Unisinos Avenue 950 RS São Leopoldo93022-750 Brazil FSG—University Center Center of Innovation and Technology Department of Mechanical Engineering Os Dezoito do Forte 2366 RS Caxias do Sul95020-472 Brazil UNESP—São Paulo State University Post-Graduation Program in Mechanical Engineering Brasil Avenue 56 SP Ilha Solteira15385-000 Brazil

ISBN: (纸本)9783030934552

The studies carried out in the area of cell preservation have been of significant importance in recent years. This process, known as cryopreservation, has been used for decades and aims to preserve various cellular materials at cryogenic temperatures. Different methods allow cryopreservation, where the best known are the slow freezing and vitrification processes. Regardless of the process, it is necessary to use cryoprotective agents (CPAs) in conjunction with the cells to avoid possible cell damage during cryopreservation. Regarding the methods, they differ in their cooling rates and the concentration of CPAs used. According to some studies, the method that has been most studied is that of vitrification, which seeks to increase the cooling rate, reaching values above 20,000 ∘ C/min. Evaporation by a thin film of liquid nitrogen is one of the methods of vitrification, which uses a microstructure with a finned or porous surface for evaporation, and in these conditions cooling rates of up to 150,000 ∘ C/min were found, which shows a significant advance and alternative for cell cryopreservation. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Cryopreservation Slow freezing Thin film evaporation Vitrification

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Investigation of Vorticity Fields During Two-Phase Flow in Flow Boiling 6th

Investigation of Vorticity Fields During Two-Phase Flow in F...

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6th Multiphase Flow Journey, JEM 2021

作者： de Oliveira, Jeferson D. Copetti, Jacqueline B. Cardoso, Elaine M. FSG-University Center Center of Innovation and Technology Department of Mechanical Engineering Os Dezoito do Forte 2366 RS Caxias do Sul95020-472 Brazil The University of Vale do Rio dos Sinos Mechanical Engineering Graduate Program LETEF Laboratory of Thermal and Fluid Dynamic Studies Unisinos Avenue 950 RS São Leopoldo93022-750 Brazil UNESP—São Paulo State University Post-Graduation Program in Mechanical Engineering Av. Brasil 56 SP Ilha Solteira15385-000 Brazil

ISBN: (纸本)9783030934552

Flow patterns are found in many processes involving multiphase flows in the industry. This experimental investigation focuses on the behavior of the vorticity fields found in the liquid-vapor interface during flow boiling of R-600a with heat flux varying from 5 to 20 kW/m 2 and fixed mass flux of 890 kg/(m 2 s) at a saturation temperature of 17 ∘ C. Tests were performed in a horizontal tube with 1.0 mm ID. Four different flow patterns were identified based on images, and the vorticity fields were investigated using an optical flow method. © 2022, The Author(s), under exclusive license to Springer Nature Switzerland AG.

关键词： Flow boiling Flow patterns Optical flow Vorticity

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