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RISS 인기검색어
- 검색키워드
- 저자 : A. F. Gouveia (검색결과 3 건)
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A. Ventura-Gouveia,Joaquim A.O. Barros,Álvaro F.M. Azevedo 사단법인 한국계산역학회 2011 Computers and Concrete, An International Journal Vol.8 No.6
The capability of a multi-directional fixed smeared crack constitutive model to simulate the flexural/punching failure modes of fiber reinforced concrete (FRC) laminar structures is discussed. The constitutive model is implemented in a computer program based on the finite element method, where the FRC laminar structures were simulated according to the Reissner-Mindlin shell theory. The shell is discretized into layers for the simulation of the membrane, bending and out-of-plane shear nonlinear behavior. A stress-strain softening diagram is proposed to reproduce, after crack initiation, the evolution of the normal crack component. The in-plane shear crack component is obtained using the concept of shear retention factor, defined by a crack-strain dependent law. To capture the punching failure mode, a softening diagram is proposed to simulate the decrease of the out-of-plane shear stress components with the increase of the corresponding shear strain components, after crack initiation. With this relatively simple approach, accurate predictions of the behavior of FRC structures failing in bending and in shear can be obtained. To assess the predictive performance of the model, a punching experimental test of a module of a façade panel fabricated with steel fiber reinforced self-compacting concrete is numerically simulated. The influence of some parameters defining the softening diagrams is discussed.
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Marcos G.S. Gouveia,Maria A. Xavier,Andre´ S. Barreto,Daniel P. Gelain,Joa˜o P.A. Santos,Adriano A.S. Arau´jo,Francilene A. Silva,Jullyana S. Quintans,Maria F. Agra,Analu´cia G.S. Cabral,Josean F. Tav 한국식품영양과학회 2011 Journal of medicinal food Vol.14 No.11
The antioxidant, antinociceptive, and anti-inflammatory activities of the ethanolic extract from leaves of Combretum duarteanum (EEC) were assessed in rodents through in vitro tests. The antioxidant activity was investigated by using thiobarbituric acid reactive species (TBARS), hydroxyl radical–scavenging, and scavenging activity of nitric oxide assays. The antinociceptive activity was investigated by using acetic acid–induced writhing, formalin, and hot-plate tests in mice. The anti-inflammatory activity was assessed in rats by using the carrageenan-induced hind-paw edema test and arachidonic acid–induced paw edema test. EEC possesses a strong antioxidant potential according to the TBARS, nitric oxide, and hydroxyl radical–scavenging assays; it also presented scavenger activity in all in vitro tests. After intraperitoneal injection, EEC (100, 200, and 400 mg/kg) significantly reduced the number of writhes (38.1%, 90.6%, and 97.8%, respectively) in a writhing test and the number of paw licks during phase 1 (30.5% and 69.5%, higher doses) and phase 2 (38.1%, 90.6%, and 97.8%, all doses) of a formalin test when compared with the control group. Naloxone (1.5 mg/kg, intraperitoneally) antagonized the antinociceptive action of EEC (400 mg/kg), and this finding suggests participation of the opioid system. Administration of 200 and 400 mg/kg (intraperitoneally) of EEC exhibited an anti-inflammatory activity in the carrageenin test, which was based on interference with prostaglandin synthesis. This finding was confirmed by the arachidonic acid test. Together, these results indicate that properties of EEC might be further explored in the search for newer tools to treat painful inflammatory conditions, including those related to pro-oxidant states.
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R. C. Silva,A. F. Gouveia,J. C. Sczancoski,R. S. Santos,J. L. S. Sá,E. Longo,L. S. Cavalcante 대한금속·재료학회 2019 ELECTRONIC MATERIALS LETTERS Vol.15 No.5
This letter reports the synthesis of RuO2nanocrystals by the anionic surfactant-assisted hydrothermal method at 90 °C for24 h followed by heat treatment at 500 °C for 1 h. These crystals were structurally characterized by means of X-ray diffraction(XRD) and Rietveld refinement analysis. Field emission scanning electron microscopy (FE-SEM) was employed to observethe morphological features these crystals. The optical behavior was investigated by ultraviolet–visible (UV–Vis) spectroscopy. First-principles quantum mechanical calculations based on the density functional theory at the B3LYP level wereemployed to obtain the electronic band structure and density of states. For electrochemical behavior, the supercapacitorproperties of RuO2crystals were investigated by cyclic voltammetry. XRD patterns and Rietveld refinement data indicatethat RuO2crystals have a rutile-type tetragonal structure. FE-SEM images showed the presence of sphere-like RuO2crystalswith an average crystal sized at around 19.13 nm. The experimental band gap energy (Egap[exp]) was estimated at 2.60 eV byusing UV–Vis spectroscopy, while the theoretical calculations indicate an Egap[theo] at 1.92 eV. These calculations revealed aband structure predominantly composed of O 2p orbitals (valence band) and Ru 4d orbitals (conduction band). The specificcapacitance measured for RuO2film was 193 F g−1 at 5 mV s−1 in an electrode with 0.5 mg of electroactive material in 1 MNa2SO4solution.
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