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61.
A design model is a necessary tool to understand the gas transport phenomena that occurs in a tubular solid oxide fuel cell (SOFC). This paper describes a computational model, which studies the gas flow through an anode-supported tubular SOFC and the subsequent diffusion of gas through its porous anode. The model is a numerical solution for the gas flow through a plug flow reactor with a diffusion layer, which includes the activation, ohmic, and concentration polarizations. Gas diffusion is modeled using the dusty-gas equations which include Knudsen diffusion. Mercury intrusion porosimetry (MIP) is used to experimentally determine micro-structural parameters such as porosity, tortuosity and effective diffusion coefficients, which are used in the diffusion equations for the porous anode layer. It was found that diffusion in the anode plays a key role in the performance of a tubular SOFC. The concentration gradient of hydrogen and water results in a lower concentration of hydrogen and a higher concentration of water at the reactive triple phase boundary (TPB) than in the fuel stream which both lead to a lower cell voltage. The gas diffusion determines the limiting current density of the cell where a higher concentration drop of hydrogen results in a lower limiting current density. The model validates well with experimental data and is used to improve micro-tubular solid oxide fuel cell designs. 相似文献
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63.
Samuel J. Moseley Christine A. Allen Nicholas Costin Richard Kelley Caroline Kilbourne Timothy Miller 《Journal of Low Temperature Physics》2008,151(1-2):418-423
We have developed an automated die-scale process for the attachment of X-ray absorbers onto microcalorimeters. Here, we describe
the process for the production of absorber tiles on a handle wafer, their attachment to the microcalorimeter, and the removal
of the supporting handle wafer. The process is shown to be a robust path to large format arrays of microcalorimeters.
相似文献
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65.
Hecham Elhamri Larbi Idrissi Marina Coquery Sabine Azemard Abdellah El Abidi Mohamed Benlemlih Mohamed Saghi Francesco Cubadda 《Food Additives & Contaminants》2007,24(11):1236-1246
Coastal populations with high seafood consumption in the Mediterranean have a significant exposure to dietary methylmercury, and areas where environmental mercury pollution is an issue due to industrial activities are of special concern. The study was undertaken with the aim of assessing methylmercury exposure through fish consumption in a community of north Morocco and characterizing the relevant health risk. Concentrations of total mercury were determined in human hair, a biomarker of methylmercury exposure, and in locally consumed fish by cold vapour atomic absorption spectrophotometry. Based on consumption frequencies reported by the 108 subjects included in the study the weekly intake of methylmercury was estimated and biomarker data were evaluated in relation to the estimated intake and the sociodemographic characteristics of the population. Multiple regression analysis was employed for the interpretation of hair mercury data in relation to fish consumption frequency, gender and the age of individuals. Mercury concentrations in hair ranged from 0.22 to 9.56 µg g-1 (geometric mean = 1.79 µg g-1) and were closely related to fish intake. Fisherman and their families consumed fish three to five times per week and were the most exposed population subgroup. A high proportion of women of child-bearing age (50%) had relatively high levels of mercury in their hair (3.08-7.88 µg g-1). 相似文献
66.
Total mercury, cadmium and lead concentrations were measured in black scabbard fish (Aphanopus carbo), caught off Madeira and the Azores archipelagos (Portugal). The metal contents were expressed in mg kg−1 wet weight. The mean mercury levels in liver were 4.50 and 2.37 whereas, in skin, such values were 0.59 and 0.36 (Madeira and Azores, respectively). On average, the muscle content was around 0.9 in fish from both areas. Cadmium maximum levels in muscle and skin were found in Azores samples (0.09 and 0.11, respectively). Mean lead contents in all samples were always below than 0.10. In general, the results obtained did not allow the establishment of any relationship between metal accumulation and fish weight or length. According to the permissible WHO and FAO levels, these results, suggest that this species does not represent a risk for human consumption if the liver is excluded and the edible part consumed with moderation. 相似文献
67.
汞是天然气中常见的有毒有害气体。根据国内外研究现状,阐述了天然气中汞对天然气采、储、运设备及对人体的危害,讨论了汞的烃源岩和岩浆热液2种成因模式;利用汞同位素分馏特征来鉴别煤型气和油型气的成因,认为煤型气表现为负的汞非质量分馏特征,而油型气表现为正的汞非质量分馏特征;提出了高汞天然气的富集条件,主要与烃源岩中汞含量、热力条件和岩浆热液的活动有关;介绍了天然气中汞的实验室测定和现场检测方法与仪器。针对化学吸附法、溶液吸收法、低温分离技术、阴离子树脂和膜分离5种天然气脱汞技术进行了对比分析,指出载硫活性炭吸附是目前使用最广泛的脱汞技术。 相似文献
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69.
用分光光度法测定烟草中的汞 总被引:5,自引:3,他引:5
研究了对 -磺酸基苯基亚甲基若丹宁 (SBDR)与汞离子 (Hg2 +)的显色反应。在pH为 4 .0的HAc NaAc缓冲介质中和吐温 - 80存在下 ,SBDR与Hg2 +反应生成稳定的络合物 ,通过WatersSep Park C18固相萃取小柱萃取和无水乙醇洗脱后 ,用分光光度计测定洗脱液在λmax=5 2 0nm处的吸光度。体系ε=1.2 1× 10 5L·mol-1·cm-1,Hg2 +含量在 0 .0 1~ 1.5 μg mL内此溶液的吸光度与Hg2 +浓度的关系符合比尔定律。用该法测定了几种烟叶中的汞含量 相似文献
70.
《International Journal of Hydrogen Energy》2020,45(16):10189-10198
Precipitation of Cr-rich carbides, diffusible hydrogen content and heterogeneous microstructure formation across the weldments makes heat-affected zone (HAZ) susceptible to intergranular cracking and makes weldability of creep strength enhanced ferritic (CSEF) Grade P92 steel a critical issue. In the present research work, the Granjon implant test and mercury method (for diffusible hydrogen measurement) have been performed on Grade P92 steel welded specimens to study the effect of welding parameters on diffusible hydrogen levels and their subsequent effect on hydrogen-assisted cracking (HAC). The weld metal was deposited by a shielded metal arc welding process on Grade P92 steel samples using P92 matching filler. The three different welding conditions are used to measure the diffusible hydrogen level in the deposited metal. Granjon implant test was performed to evaluate HAZ HAC susceptibility with similar welding conditions which were used in the mercury method. Lower critical stress (LCS) was also evaluated using the Granjon implant test. The higher susceptibility of CSEF Grade P92 steel welded plate towards HAZ HAC was noticed in case of lower heat input or higher diffusible hydrogen content. However, by considering LCS, fracture mode and diffusible hydrogen content, the weld deposited using the highest heat input (condition III) offers great resistance to HAZ HAC. 相似文献