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Luís Simões da Silva,Trayana Tankova,Carlos Rebelo 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.1
This paper presents the safety assessment of Eurocode 3—part 1-1 (Eurocode in EN 1993-1-1, Eurocode 3: design of steel structures—part 1-1: general rules and rules for buildings, CEN, Brussels, 2005) rules for hot-rolled members with I and H cross-sections loaded in bending and compression. The safety assessment follows the recommendations of Annex D of EN 1990 (Eurocode in EN 1990, Eurocode—basis of structural design, CEN, Brussels, 2002). It is based on a large number (11,345) of numerical simulations (GMNIA) covering various relevant parameters. The assessment aimed at the justifi cation of the partial factors to be used in the design of members under bending and compression as part of the ongoing process of revision of Eurocode 3—part 1-1. For that, it covered the application of the interaction factors given in Annex B/Method 2 of the current version of Eurocode 3—part 1-1 which will be the only method in the future version of Eurocode 3. In addition, the interaction factors were applied with the new buckling curves for lateral-torsional buckling, as they will appear in the new version. The assessment showed consistent results across the subsets considered with low variability and partial factors generally lower than 1.0. Finally, the γ M * values are compared for fl exural buckling of columns, lateral-torsional buckling of beams with the results obtained for beam-columns considering f y , cross-section geometry and E as random variables, using the same statistical characterization of the random variables. It is observed that the partial factors obtained beam-columns are lower than those obtained for columns and beams. In conclusion, based on combination of the results obtained it was possible to recommend a global value of γ M1 = 1.0.
Behaviour of flush end-plate beam-to-column joints under bending and axial force
Luís Simões da Silva,Luciano R. O. de Lima,Pedro C. G. da S. Vellasco,Sebastião A. L. de Andrade 국제구조공학회 2004 Steel and Composite Structures, An International J Vol.4 No.2
Steel beam-to-column joints are often subjected to a combination of bending and axial forces. The level of axial forces in the joint may be significant, typical of pitched-roof portal frames, sway frames or frames with incomplete floors. Current specifications for steel joints do not take into account the presence of axial forces (tension and/or compression) in the joints. A single empirical limitation of 10% of the beam’s plastic axial capacity is the only enforced provision in Annex J of Eurocode 3. The objective of the present paper is to describe some experimental and numerical work carried out at the University of Coimbra to try to extend the philosophy of the component method to deal with the combined action bending moment and axial force.
Behaviour of steel joints under fire loading
Luís Simões da Silva,Aldina Santiago,Paulo Vila Real,David Moore 국제구조공학회 2005 Steel and Composite Structures, An International J Vol.5 No.6
This paper presents a state-of-the-art on the behaviour of steel joints under fire loading and some recent developments in this field, currently being carried out by the authors. Firstly, a review of the experimental research work on steel joints is presented, subdivided into isolated member tests, sub-structure tests and tests on complete building structures. Special emphasis is placed on the seventh Cardington test, carried out by the authors within a collaborative research project led by the Czech Technical University in Prague. Secondly, a brief review of various temperature distributions within a joint is presented, followed by a discussion of the behaviour of isolated joints at elevated temperature, focussing on failure modes and analytical procedures for predicting the moment-rotation behaviour of joints at elevated temperature. Finally, a description of the coupled behaviour of joints as part of complete structures is presented, describing previous work and investigations on real fire (including heating and cooling phases) currently being carried out by the authors.
Physicochemical properties of a calcium aluminate cement containing nanoparticles of zinc oxide
da Rosa Amanda Freitas,Amaral Thuany Schmitz,Paz Dotto Maria Eduarda,Goulart Taynara Santos,Rossetto Hebert Luís,Bortoluzzi Eduardo Antunes,Teixeira Cleonice da Silveira,Garcia Lucas da Fonseca Robert 대한치과보존학회 2023 Restorative Dentistry & Endodontics Vol.48 No.1
Objectives This study evaluated the effect of different nanoparticulated zinc oxide (nano-ZnO) and conventional-ZnO ratios on the physicochemical properties of calcium aluminate cement (CAC). Materials and Methods The conventional-ZnO and nano-ZnO were added to the cement powder in the following proportions: G1 (20% conventional-ZnO), G2 (15% conventional-ZnO + 5% nano-ZnO), G3 (12% conventional-ZnO + 3% nano-ZnO) and G4 (10% conventional-ZnO + 5% nano-ZnO). The radiopacity (Rad), setting time (Set), dimensional change (Dc), solubility (Sol), compressive strength (Cst), and pH were evaluated. The nano-ZnO and CAC containing conventional-ZnO were also assessed using scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. Radiopacity data were analyzed by the 1-way analysis of variance (ANOVA) and Bonferroni tests (p < 0.05). The data of the other properties were analyzed by the ANOVA, Tukey, and Fisher tests (p < 0.05). Results The nano-ZnO and CAC containing conventional-ZnO powders presented particles with few impurities and nanometric and micrometric sizes, respectively. G1 had the highest Rad mean value (p < 0.05). When compared to G1, groups containing nano-ZnO had a significant reduction in the Set (p < 0.05) and lower values of Dc at 24 hours (p < 0.05). The Cst was higher for G4, with a significant difference for the other groups (p < 0.05). The Sol did not present significant differences among groups (p > 0.05). Conclusions The addition of nano-ZnO to CAC improved its dimensional change, setting time, and compressive strength, which may be promising for the clinical performance of this cement.
Preparation of magnetic activated carbon-chitosan nanocomposite for crystal violet adsorption
Ferda Civan Çavuşoğlu,Seher Akan,Ezgi Aleyna Arı,Ezgi Çetinkaya,Elif Çolak,Gamze Nur Daştan,Semina Deniz,Damla Erdem,Melda Köksal,Sevgi Korkmaz,Nursena Onsekiz,Betül Oruçoğlu,Didem Özkaya,Hamdi Buğra 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.11
Magnetic, cheap and versatile adsorbents were developed for crystal violet (CV) adsorption in this study. These adsorbents are magnetic activated carbon (AC-Fe3O4) and chitosan grafted magnetic activated carbon (Chitosan- AC-Fe3O4). Fe3O4 and chitosan were also used for adsorption. X-ray diffraction (XRD), scanning electron microscopy (SEM), vibrating sample magnetometer (VSM), zeta potential analysis and Fourier transform infrared spectroscopy (FTIR) methods were used for characterization of adsorbents. Adsorption parameters for CV were investigated. Raw chitosan and Fe3O4 were also used for CV adsorption to compare the results of composites. The chosen adsorption parameters are amount of adsorbent, contact time, initial CV concentration, and temperature. The equilibrium period was observed to be very short for chitosan and Fe3O4 nanoparticles. The adsorption efficiencies of these adsorbents are very low. AC-Fe3O4 and AC-Fe3O4-Chitosan nanoparticles reached equilibrium at 80min. The all adsorbent-CV systems followed pseudo second-order kinetic model. AC-Fe3O4 and AC-Fe3O4-Chitosan composites suited non-linear Freundlich isotherm for all temperatures (298, 308 and 318 K). Regeneration of adsorbents was also investigated. 1M of acetic acid and 0.1M of NaOH solutions were tested. Acetic acid solution desorbed CV better than NaOH solution at 6 hours.
Endovascular treatment of residual or recurrent intracranial aneurysms after surgical clipping
da Silva Júnior Nilton Rocha,Trivelato Felipe Padovani,Nakiri Guilherme Seizem,Rezende Marco Túlio Salles,de Castro-Afonso Luís Henrique,Abud Thiago Giansante,Vanzin José Ricardo,Manzato Luciano Bambi 대한뇌혈관외과학회 2021 Journal of Cerebrovascular and Endovascular Neuros Vol.23 No.3
Objective Total aneurysm occlusion is crucial for the prevention of rebleeding of a ruptured aneurysm or to avoid rupture of an unruptured lesion. Both surgical and endovascular embolization fail to achieve complete aneurysm occlusion in all the cases. The objective of the study was to establish the safety and efficacy of endovascular treatment for previously clipped residual or recurrent aneurysms. Methods This was an observational, retrospective study of patients harboring incompletely occluded intracranial aneurysms after clipping who underwent endovascular treatment. Patients were treated using 4 different techniques: (1) simple coiling, (2) balloon remodeling, (3) stent-assisted coiling, and (4) flow diversion. Analyses were performed to identify predictors of total aneurysm occlusion, recanalization and complications. Results Between May 2010 and September 2018, 70 patients harboring incompletely occluded intracranial aneurysms after clipping met the inclusion criteria in 5 centers. The mean residual aneurysm size was 7.5 mm. Fifty-nine aneurysms were unruptured. Total aneurysm occlusion was achieved in 75.3% of the aneurysms after 1 year. All aneurysms treated with flow diversion revealed complete occlusion according to control angiography. Recanalization was observed in 14.5%. Permanent morbidity and mortality occurred in 2.9% and 1.4% of the patients, respectively. Conclusions Endovascular treatment of recurrent or residual aneurysms after surgical clipping was safe and efficacious. Flow diversion seems to be associated with better anatomical results. A more rigid study, a larger group of patients, and long-term follow-up are required to provide stronger conclusions about the best approach for residual clipped aneurysms.
Eduardo Luís Menezes de Almeida,Eduard J. Kerkhoven,Wendel Batista da Silveira 한국생물공학회 2024 Biotechnology and Bioprocess Engineering Vol.29 No.1
Non-conventional yeasts are promising cell factories to produce lipids and oleochemicals, metabolites of industrial interest ( e.g ., organics acids, esters, and alcohols), and enzymes. They can also use diff erent agro-industrial by-products as substrates within the context of a circular economy. Some of these yeasts can also comprise economic and health burdens as pathogens. Genome-scale metabolic models (GEMs), networks reconstructed based on the genomic and metabolic information of one or more organisms, are great tools to understand metabolic functions and landscapes, as well as propose engineering targets to improve metabolite production or propose novel drug targets. Previous reviews on yeast GEMs have mainly focused on the history and the evaluation of Saccharomyces cerevisiae modeling paradigms or the accessibility and usability of yeast GEMs. However, they did not describe the reconstruction strategies, limitations, validations, challenges, and research gaps of non-conventional yeast GEMs. Herein, we focused on the reconstruction of available non- Saccharomyces GEMs, their validation, underscoring the physiological insights, as well as the identifi cation of both metabolic engineering and drug targets. We also discuss the challenges and knowledge gaps and propose strategies to boost their use and novel reconstructions.
On the rate of convergence of uniform approximations for sequences of distribution functions
João Lita da Silva,Luís Pedro Ramos 한국통계학회 2014 Journal of the Korean Statistical Society Vol.43 No.1
In this paper, we develop uniform bounds for the sequence of distribution functions ofg(Vn + μn), where g is some smooth function, {Vn, n ≥ 1} is a sequence of identicallydistributed random variables with common distribution having a bounded derivative and{μn} are constants such that μn → ∞. These bounds allow us to identify a suitablesequence of random variables which is asymptotically of the same type of g(Vn + μn)showing that the rate of convergence for these uniform approximations depends on theratio of the second derivative to the first derivative of g. The corresponding generalizationto the multivariate case is also analyzed. An application of our results to the STATIS-ACTmethod is provided in the final section.
Pedro Nogueiro,Luís Simões da Silva,Rita Bento,Rui Simões 국제구조공학회 2009 Steel and Composite Structures, An International J Vol.9 No.1
Composite joints, considering the composite action of steel and concrete, exhibit, in general, high strength and high ductility. As a consequence, the use of this type of joint has been increasing in many countries, especially in those that are located in earthquake-prone regions. In this paper, a hysteretic model with pinching is presented that is able to reproduce the cyclic response of steel and composite joints. Secondly, the computer implementation and adaptation of the model in a spring element within the computer code. Seismosoft is described. The model is subsequently calibrated using a series of experimental test results for composite joints subjected to cyclic loading. Finally, typical parameters for the various joint configurations are proposed.