248 research outputs found
Variational principles, numerical schemes and bounding theorems for deformation by Nabarro-Herring creep
No full textOn the behavior of a three-dimensional fractional viscoelastic constitutive model
No full textIn this paper a three-dimensional isotropic fractional viscoelastic model is examined. It is shown that if different time scales for the volumetric and deviatoric components are assumed, the Poisson ratio is time varying function; in particular viscoelastic Poisson ratio may be obtained both increasing and decreasing with time. Moreover, it is shown that, from a theoretical point of view, one-dimensional fractional constitutive laws for normal stress and strain components are not correct to fit uniaxial experimental test, unless the time scale of deviatoric and volumetric are equal. Finally, the model is proved to satisfy correspondence principles also for the viscoelastic Poisson’s ratio and some issues about thermodynamic consistency of the model are addressed
Preparation and characterization of activated carbon fiber (ACF) from cotton woven waste
No full textIn this study, the activated carbon fibers (ACFs) were prepared using cotton woven waste as precursor. The cotton woven waste was first partly dissolved by 80% phosphoric acid and then was pre-soaked in 7.5% diammonium hydrogen phosphate solution. Finally, carbonization and activation were proceeded to get ACF. The optimum preparation conditions, including carbonization temperature, carbonization time, activation temperature and activation time, were chosen by orthogonal design. Nitrogen adsorption/desorption test was conducted to characterize the prepared ACF's pore structure. Fourier transform infrared spectroscopy (FTIR) analysis, X-ray photoelectron spectroscopy (XPS) and environmental scanning electron microscope (ESEM) were employed to characterize its chemical properties and morphology. Adsorption of oilfield wastewater was used to evaluate its adsorption properties. The results show that the prepared ACF is in the form of fiber, with the sectional diameters of 11.7 x 2.6 mu m and the surface area of 789 m(2)/g. XPS results show that carbon concentration of the prepared ACF is higher than that of the commercial ACF. When the prepared ACF dosage is 6 g/L, over 80% of COD and over 70% of chrominance can be removed after 24 h of adsorption at 18 degrees C. (C) 2014 Elsevier B.V. All rights reserved.Chemistry, PhysicalMaterials Science, Coatings & FilmsPhysics, AppliedPhysics, Condensed MatterSCI(E)[email protected]
An analytical model for the energetics of quantum dots: beyond the small slope assumption
No full text
- …
