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Governing Factor (governing + factor)

Distribution by Scientific Domains
Engineering50%

Selected Abstracts

Residual compressive behavior of alkali-activated concrete exposed to elevated temperatures

FIRE AND MATERIALS, Issue 1 2009
Maurice Guerrieri
Abstract This paper reports the effect of elevated temperature exposures, up to 1200°C , on the residual compressive strengths of alkali-activated slag concrete (AASC) activated by sodium silicate and hydrated lime; such temperatures can occur in a fire. The strength performance of AASC in the temperature range of 400,800°C was similar to ordinary Portland cement concrete and blended slag cement concrete, despite the finding that the AASC did not contain Ca(OH)2 , which contributes to the strength deterioration at elevated temperatures for Ordinary Portland Cement and blended slag cement concretes. Dilatometry studies showed that the alkali-activated slag (AAS) paste had significantly higher thermal shrinkage than the other pastes while the basalt aggregate gradually expanded. This led to a higher thermal incompatibility between the AAS paste and aggregate compared with the other concretes. This is likely to be the governing factor behind the strength loss of AASC at elevated temperatures. Copyright © 2008 John Wiley & Sons, Ltd. [source]

Gas permeation related to the moisture sorption in films of glassy hydrophilic polymers

JOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010
F.L. Laksmana
Abstract The purpose of this article is to elucidate the effect of integral sorption of moisture on gas permeation in glassy hydrophilic polymers. The oxygen and the simultaneous moisture sorption into various hydroxypropyl methylcellulose (HPMC) films were measured under a wide range of relative humidities using sorption analyzer equipment. Correspondingly, the oxygen permeability at different ambient conditions was measured using an oxygen detector. The solubility of oxygen in the HPMC film was found to be affected by the amount of water and therefore by the water state. At low moisture content, the water molecules are present as bound water, which promotes the sorption of oxygen in the HPMC films. At moisture content higher than 5%, water clusters are rapidly formed, which increase the affinity of HPMC polymer towards water rather than towards oxygen molecules, resulting in a decrease of oxygen solubility in the polymer. This was found to be the governing factor for the reduction in the oxygen permeability in glassy HPMC films at high water activity. This proposes a specific interaction between moisture sorption and oxygen transport in coating films like HPMC, which is of important aspect in the coating design and formulation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source]

Development and experimental validation of a conceptual model for biotrickling filtration of H2S

ENVIRONMENTAL PROGRESS & SUSTAINABLE ENERGY, Issue 2 2003
Seongyup Kim
A dynamic model that describes the behavior of high-performance hydrogen sulfide (H2S)-degrading biotrickling filters for odor control was developed. The model attempts to accurately describe pollutant mass transfer in the biotrickling filter, i.e., external mass transfer resistances, and both direct gas-biofilm and gas-liquid-biofilm mass transfer were considered. In order to calibrate the model, an innovative differential biotrickling filter was constructed in which the effect of air velocity on the removal of H2S could be studied. Model outputs were compared with experimental data to determine the sensitivity of the system to selected parameters. At low H2S concentration, diffusion of H2S within the biofilm, and biofilm thickness were the major governing factors among nine considered model parameters. At higher H2S concentrations and lower air flow rates, external mass transfer played a very important role. This new finding, confirmed experimentally, has important implications, as it proves that the performance limit of H2S degrading biotrickling filters has not yet been reached. [source]

Kinetic limitations of a bioelectrochemical electrode using carbon nanotube-attached glucose oxidase for biofuel cells

BIOTECHNOLOGY & BIOENGINEERING, Issue 6 2009
Xueyan Zhao
Abstract Carbon nanotubes (CNTs) have been used for various bioelectrochemical applications, presumably for substantial improvement in performance. However, often only moderate results observed, with many governing factors have been considered and suggested yet without much systematic evaluation and verification. In this study, CNT-supported glucose oxidase (CNT,GOx) was examined in the presence of 1,4-benzoquinone (BQ). The intrinsic Michaelis parameters of the reaction catalyzed by CNT,GOx were found very close to those of native GOx. However, the Nafion entrapment of CNT,GOx for an electrode resulted in a much lower activity due to the limited availability of the embedded enzyme. Interestingly, kinetic studies revealed that the biofuel cell employing such an enzyme electrode only generated a power density equivalent to <40% of the reaction capability of the enzyme on electrode. It appeared to us that factors such as electron and proton transfer resistances can be more overwhelming than the heterogeneous reaction kinetics in limiting the power generation of such biofuel cells. Biotechnol. Bioeng. 2009; 104: 1068,1074. © 2009 Wiley Periodicals, Inc. [source]