Papers by Keyword: Effect of Temperature

Abstract: The monitoring of dynamic parameters of slender bridge structures is becoming of particular interest in terms of their possible use in determining their structural condition, or possibly as one of the parameters for their long-term monitoring. The method for monitoring dynamic parameters is relatively new and practically unexplored. First of all, it is necessary to find out with certainty how the dynamic parameters of slender bridge structures change, for example, with changes in temperature, the magnitude of the prestressing force, or how they change with changes in discontinuous mass (e.g. overlaying or stripping of pavement layers). The paper summarizes the important aspects that can affect the modal parameters - natural frequencies and their shapes. The above listed influences and their impact on the structure were investigated on real structures formed by stress ribbon.

Abstract: Activated carbon was prepared from palm shell by pyrolysis followed by K2CO3 assisted microwave heating. Effects of temperature on adsorption capability and kinetics of the sorbent towards CO2 adsorption was also studied. The results indicated that, the amount CO2 adsorbed decrease as the adsorption temperature increases. The kinetic data were obtained using a static volumetric method at 303.15, 343.15, 378.15, and 443.15 K and at pressures up to 4 bar. The kinetics of CO2 adsorption on the activated carbons was examined using the pseudofirst-order equation and pseudosecond-order equations. Weber and Morris intraparticle diffusion model was applied to examine the mechanism of the adsorption system. Lowest CO2 uptake recorded was 0.3 mmol/g at 443.15 K and 0.5 bar while the highest was 7.45mmol/g obtained at 303.15 K and 4 bar. The kinetics followed pseudosecond-order model. Pore diffusion is not the sole rate diffusion mechanism.

Abstract: ZnO nanostructures were synthesized by thermal evaporation method using Zn metal plate in air. The Zn metal plates were frozen at -10 C, before into the furnace at a temperature ranging from 300 to 420 C for 15 minutes. The ZnO nanostructures were characterized by X-ray diffraction, XRD and field emission scanning electron microscopy( FE-SEM) and X-ray diffraction( XRD) pattern showed the crystal nanostructure of ZnO. FE-SEM images indicated that the nanowires were depended on temperatures. The diameter of ZnO nanowires werevaried from 50 nm to 70 nm and length of several 100 micrometers.

Abstract: The formic acid oxidation on Pt/Ru nanoparticles in acid solution over the temperature range 298-333 K has been studied by thin-film rotating disk method (RDE). Transmission electron microscopy in combination with scanning tunneling microscopy was used to determine the size (4.3 ± 0.3 nm) and shape (cuboctahedral) of the particles. Kinetic analysis revealed that at elevated temperatures (313 K, 333 K) the reaction rate is much higher than at room temperature (295 K), indicating that formic acid oxidation on supported Pt/Ru catalyst is a highly activated process. Based on experimental kinetic parameters we propose that the HCOOH oxidation on the PtRu alloy most likely follows a dual pathway, but the branching ratio is still very high, i.e. Pt-like. The principal effect of opening the dehydration channel at steady-state (via the presence of Ru in the surface) is to lower the coverage of COads on Pt sites and permit the dehydrogenation path to increase in rate.