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101.
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The objective of this analysis is to examine the influence of the moisture in the porosity measurement by means of thermal non-destructive test and ultrasound techniques. It is possible to determine the concrete durability by the calculation of its porosity. Porosity is determined in an indirect way, measuring mortar diffusivity by means of active thermography. Using ultrasound techniques, the porosity is related with the ultrasonic propagation of velocity. The diffusivity has been calculated using the W.J. Parker equation. In the ultrasound technique, using the pulse transmission method, ultrasonic propagation velocity was measured as a function of the water content. The conclusions express the correlation between both methods. 相似文献
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Karla Calfumán María Jesus Aguirre Diego Villagra Claudia Yañez Carmen Arévalo Betty Matsuhiro Leonora Mendoza Mauricio Isaacs 《Journal of Solid State Electrochemistry》2010,14(6):1065-1072
In this work, the modification of a glassy carbon electrode with tetraruthenated porphyrins electrostatically assembled onto
a Nafion film, previously adsorbed on the electrode surface, is reported. This modified electrode was characterized by scanning
electron microscopy–energy-dispersive X-ray, Raman spectroscopy, UV-Vis spectroelectrochemistry, and cyclic voltammetry. The
Nafion film onto the glassy carbon electrode shows a smooth disposition; when the tetraruthenated porphyrin is incorporated
on the Nafion film, the complex is adsorbed in a homogeneous way. The modified electrode catalyzes HSO3− oxidation in water–ethanol solutions and shows an enhanced stability compared with the electrode modified with the dip coating
method. Rotating disk electrode experiments showed a kinetic limitation to the electron transfer controlled by charge propagation
in the film. I/E curves show a Tafel slope of 120 mV/decade corresponding to a first electron-transfer reaction, depending on the potential,
as the determining step. Spectroelectrochemical experiments demonstrated that Ru(II) is the active site for the electrocatalysis. 相似文献
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The palladium-catalyzed arylation of aryl bromides can be carried out in the presence of bidentate phosphines, such as dppm, dppe, dppf, and Xantphos under mild conditions. The experimental results and the DFT calculations fully support for this reaction a mechanism proceeding by an intermolecular proton abstraction. 相似文献
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In recent years, significant research in the field of electrochemistry was developed. The performance of electrical devices, depending on the processes of the electrolytes, was described and the physical origin of each parameter was established. However, the influence of the irregularity of the electrodes was not a subject of study and only recently this problem became relevant in the viewpoint of fractional calculus. This paper describes an electrolytic process in the perspective of fractional order capacitors. In this line of thought, are developed several experiments for measuring the electrical impedance of the devices. The results are analyzed through the frequency response, revealing capacitances of fractional order that can constitute an alternative to the classical integer order elements. Fractional order electric circuits are used to model and study the performance of the electrolyte processes. 相似文献