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91.
Solution annealed and water quenched duplex and super duplex stainless steels are thermodynamically metastable systems at room temperature.These systems do not migrate spontaneously to a thermodynamically stable condition because an energy barrier separates the metastable and stable states. However, any heat input they receive, for example through isothermal treatment or through prolonged exposure to a voltaic arc in the welding process, cause them to reach a condition of stable equilibrium which, for super duplex stainless steels, means precipitation of intermetallic and carbide phases. These phases include the sigma phase, which is easily identified from its morphology, and its influence on the material's impact strength.The purpose of this work was to ascertain how 2-hour isothermal heat treatments at 920 °C and 980 °C affect the microstructure of ASTM A890/A890M GR 6A super duplex stainless steel. The sigma phase morphologies were found to be influenced by these two aging temperatures, with the material showing a predominantly lacy microstructure when heat treated at 920 °C and block-shaped when heat treated at 980 °C. 相似文献
92.
93.
Leandro C. Silva Valéria V. Murata Carla E. Hori Adilson J. Assis 《Optimization and Engineering》2010,11(3):441-458
In this work three mathematical models for methane steam reforming in membrane reactors were developed. The first one is a
steady state, non isothermal, non isobaric and one dimensional model derived from material and energy balances and validated
using experimental data from the literature. It is referred as full model. The influence of two different intrinsic kinetics
available, as well as, the influence of five important parameters on methane conversion (XCH4_{\mathrm{CH}_{4}}) and hydrogen recovery (YH2_{\mathrm{H}_{2}}) were parametrically evaluated through simulations. The second model, referred as meta-model, was obtained though the response
surface technique. This meta-model was included into a constrained optimization problem solved using NPSOL. The third model,
referred as a simplified model, takes into account only mass balances from the full model. Using this model, a gradient based
method (DIRCOL) was used to perform the optimization of the sum of methane conversion and hydrogen recovery. High methane
conversions and hydrogen recoveries were reached through these methodologies. 相似文献
94.
Aline T. PERES Maria A. DALBONI Maria E. CANZIANI Silvia R. MANFREDI Jose Tarcisio G. CARVALHO Marcelo C. BATISTA Lilian CUPPARI Aluisio B. CARVALHO Rosa M. A. MOYSES Nadia GUIMARÃES Vanda JORGETTI Maria C. ANDREOLI Sergio A. DRAIBE Miguel CENDOROGLO 《Hemodialysis international. International Symposium on Home Hemodialysis》2009,13(3):271-277
It has been suggested that phosphate binders may reduce the inflammatory state of hemodialysis (HD) patients. However, it is not clear whether it has any effect on oxidative stress. The objective of this study was to evaluate the effect of sevelamer hydrochloride (SH) and calcium acetate (CA) on oxidative stress and inflammation markers in HD patients. Hemodialysis patients were randomly assigned to therapy with SH (n=17) or CA (n=14) for 1 year. Before the initiation of therapy (baseline) and at 12 months, we measured in vitro reactive oxygen species (ROS) production by stimulated and unstimulated polymorphonuclear neutrophils and serum levels of tumor necrosis factor α, interleukin-10, C-reactive protein, and albumin. There was a significant reduction of spontaneous ROS production in both groups after 12 months of therapy. There was a significant decrease of Staphylococcus aureus stimulated ROS production in the SH group. There was a significant increase in albumin serum levels only in the SH group. In the SH group, there was also a decrease in the serum levels of tumor necrosis factor α and C-reactive protein. Our results suggest that compared with CA treatment, SH may lead to a reduction in oxidative stress and inflammation. Therefore, it is possible that phosphate binders exert pleiotropic effects on oxidative stress and inflammation, which could contribute toward decreasing endothelial injury in patients in HD. 相似文献
95.
João Felipe G. Oliveira Izabelly Larissa Lucena Rosana M. Alves Saboya Marcelo L. Rodrigues Antonio Eurico B. Torres Fabiano A. Narciso Fernandes Célio L. Cavalcante Expedito José S. Parente 《Renewable Energy》2010,35(11):2581-2584
The production of biodiesel by esterification with ethanol using waste oil generated in the refining of coconut oil was investigated in this study. The reaction was performed with and without adsorption of water in order to verify the effect of removing water on the reaction conversion. Methanol was also evaluated as an esterification agent. For both ethanol and methanol, conversions over 99% mol were observed. Simultaneous water adsorption allowed the use of lower alcohol/oil molar ratios thus enabling better economics to a possible industrial process. 相似文献
96.
Marcelo A. V. Souza Luiz Claudio de Santa Maria Marcos A. S. Costa Wang S. Hui Luciana C. Costa Hiram C. Araujo Filho Sandro C. Amico 《Polymer Bulletin》2011,67(2):237-249
Phosphinic-derivative poly(styrene-co-divinylbenzene)-based on PS–DVB copolymers with different porosity degrees have been
prepared by aromatic electrophilic substitution reaction using PCl3/AlCl3 followed by base-promoted hydrolysis. The phosphorylation reaction was analyzed by infra-red spectroscopy (FTIR), scanning
electron microscopy (SEM), and thermogravimetry (TG/DTG). In addition, the phosphorous content of the phosphorylated copolymers
was determined by spectrophotometry using the method based on sodium molybdate reactant so that the extension of that modification
could be assessed. The performance of the phosphorylated resins in the extraction of Pb2+ from aqueous solutions in a batch system was also evaluated. The Pb2+ content was determined by atomic absorption spectrometry (AAS). These materials presented excellent extraction capacity under
the contact time of 30 min and pH 6. 相似文献
97.
The objective of this paper is to present an extension of a simplified reaction kinetics model that, combined with a thermo-mechanical closure, entails a full-generalized turbulent combustion model for flow in porous media. In this model, one explicitly considers the intra-pore levels of turbulent kinetic energy. Transport equations are written in their time-and-volume-averaged form and a volume-based statistical turbulence model is applied to simulate turbulence generation due to the porous matrix. The rate of fuel consumption is described by an Arrhenius expression involving the product of the fuel and oxidant mass fractions. These mass fractions are double decomposed in time and space and, after applying simultaneous time-and-volume integration operations to them, distinct terms arise, which are here associated with the mechanisms of dispersion and turbulence. Modeling of these extra terms remains an open question and the derivations herein might motivate further development of models for turbulent combustion in porous media. 相似文献
98.
99.
This paper investigates the problem of ??∞ filtering for a class of uncertain Markovian jump linear systems. The uncertainty is assumed to be norm‐bounded and appears in all the matrices of the system state‐space model, including the coefficient matrices of the noise signals. It is also assumed that the jumping parameter is available. We develop a methodology for designing a Markovian jump linear filter that ensures a prescribed bound on the ??2‐induced gain from the noise signals to the estimation error, irrespective of the uncertainty. The proposed design is given in terms of linear matrix inequalities. Copyright © 2002 John Wiley & Sons, Ltd. 相似文献
100.
de Assis MA Destro MT Franco BD Landgraf M 《International journal of food microbiology》2000,62(1-2):161-164
The incidence of Salmonella spp., Listeria spp. and Listeria monocytogenes in horsemeat for human consumption was investigated. One-hundred and twenty-one samples of frozen horsemeat collected from two Brazilian abattoirs were analysed over a period of 1 year. Twenty-two samples (18.2%) were positive for Listeria spp. with nine (7.4%) containing L. monocytogenes. None of the samples harbored Salmonella spp. 相似文献