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排序方式: 共有526条查询结果,搜索用时 31 毫秒
51.
52.
提出了一种基于海洋流函数模型的双站高频地波雷达径向流生成矢量流算法.该算法避免了传统矢量合成法将径向流进行插值带来的误差,而且符合海洋动力学原理,生成的流场更接近实际分布.通过计算机仿真发现,流函数算法的容错、容差能力比矢量合成法更强.在径向流探测标准误差为10 cm.s-1时,新算法反演结果的均方根误差减小了约5 cm.s-1.应用到雷达实测数据中,与海流计实测结果比较表明,新算法比传统算法的平均误差减小了2 cm.s-1. 相似文献
53.
以内在碳捕集气化为背景,利用加压热重分析仪开展CaO对准东煤中温(700-750℃)水蒸气气化反应动力学特性的影响研究,采用氮气吸附仪对准东煤焦的比表面积进行测定,并对煤中不同赋存形态碱金属含量采用电感耦合等离子体发射光谱仪(ICP-OES)进行测定。结果表明,准东煤中的可溶性碱金属元素能有效催化气化反应,引入的二氧化碳吸收剂CaO与碱金属间表现出协同催化作用。水洗后的准东煤焦活性最高,添加CaO后的气化活性最好。Ca/C物质的量比对准东煤气化特性的影响研究表明,CaO的添加存在饱和量,Ca/C物质的量比为1.0较为合适。利用均相模型(HM)、缩核模型(SCM)以及修正体积模型(MVM)对反应动力学实验数据进行拟合,结果表明,修正体积模型可以较好地体现添加CaO的准东煤中温水蒸气气化反应动力学特性,由此获得反应活化能为160.90 kJ/mol。 相似文献
54.
Selective production of hydrogen by oxidative steam reforming of methanol (OSRM) was studied over Cu/SiO2 catalyst using fixed bed flow reactor. Textural and structural properties of the catalyst were analyzed by various instrumental methods. TPR analysis illustrates that the reduction temperature peak was observed between 510?K and 532?K at various copper loadings and calcination temperatures and the peaks shifted to higher temperature with increasing copper loading and calcination temperature. The XRD and XPS analysis demonstrates that the copper existed in different oxidation states at different conditions: Cu2O, Cu0, CuO and Cu(OH)2 in uncalcined sample; CuO in calcined sample: Cu2O and metallic Cu after reduction at 600?K and Cu0 and CuO after catalytic test. TEM analysis reveals that at various copper loadings, the copper particle size is in the range between 3.0?nm and 3.8?nm. The Cu particle size after catalytic test increased from 3.6 to 4.8?nm, which is due to the formation of oxides of copper as evidenced from XRD and XPS analysis. The catalytic performance at various Cu loadings shows that with increasing Cu loading from 4.7 to 17.3?wt%, the activity increases and thereafter it decreases. Effect of calcination shows that the sample calcined at 673?K exhibited high activity. The O2/CH3OH and H2O/CH3OH molar ratios play important role in reaction rate and product distribution. The optimum molar ratios of O2/CH3OH and H2O/CH3OH are 0.25 and 0.1, respectively. When the reaction temperature varied from 473 to 548?K, the methanol conversion and H2 production rate are in the range of 21.9–97.5% and 1.2–300.9?mmol?kg?1?s?1, respectively. The CO selectivity is negligible at these temperatures. Under the optimum conditions (17.3?wt%, Cu/SiO2; calcination temperature 673?K; 0.25 O2/CH3OH molar ratio, 0.5 H2O/CH3OH molar ratio and reaction temperature 548?K), the maximum hydrogen yield obtained was 2.45?mol of hydrogen per mole of methanol. The time on stream stability test showed that the Cu/SiO2 catalyst is quite stable for 48?h. 相似文献
55.
Stefania Garzoli Mijat Božović Anna Baldisserotto Manuela Sabatino Stefania Cesa Federico Pepi 《Natural product research》2018,32(11):1254-1259
A comprehensive study on essential oil samples of Foeniculum vulgare Miller from Tarquinia (Italy) is reported. A 24-h systematic steam distillation was performed on different harvested samples applying different extraction times. The GC-MS analysis of the residue outcome showed o-cymene, α-phellandrene, α-pinene and estragole as the major constituents. The predominance and continued presence of o-cymene makes this fennel oil a rather unique chemotype. An evident correlation between the antifungal activity and phenological stage is demonstrated. The most active fractions were particularly rich in estragole, as well as a significant amount of fenchone that possibly exerts some additive effect in the expression of overall antifungal potency. Pre-fruiting material produced oil particularly rich in o-cymene. With reference to the duration of the extraction, the maximum amount of oil was released within the first 3 h, whereas the reproductive phase material needed at least 6 h for the extraction. 相似文献
56.
Stoyan Stoyanov Georgi Yordanov Ceco Dushkin 《Reaction Kinetics and Catalysis Letters》2008,94(2):227-232
The effect of Ni loading on the catalytic activity of Ni/ZrO2 catalyst for methane steam reforming was investigated. The sample containing 15 wt.% Ni exhibited the highest activity as
well as stability at 600°C.
An erratum to this article is available at . 相似文献
57.
Reaction parameters influence on the catalytic performance of copper-silica aerogel in the methanol steam reforming 《燃料化学学报》2016,44(1):84-90
Steam reforming of methanol was carried out on the copper-silica aerogel catalyst.The effects of reaction temperature,feed rate,water to methanol molar ratio and carrier gas flowrate on the H_2 production rate and CO selectivity were investigated.M ethanol conversion was increased considerably in the range of about 240-300,after which it increased at a slightly lower rate.The used feed flowrate,steam to methanol molar ratio and carrier gas flowwere 1.2-9.0 m L/h,1.2-5.0 and 20-80 m L/min,respectively.Reducing the feed flowrate increased the H_2 production rate.It was found that an increase in the water to methanol ratio and decreasing the carrier gas flowrate slightly increases the H2production rate.Increasing the water to methanol ratio causes the lowest temperature in which CO formation was observed to rise,so that for the ratio of 5.0 no CO formation was detected in temperatures lower than 375℃.In all conditions,by approaching the complete conversion,increasing the main product concentration,increasing the temperature and contact time,and decreasing the steam to methanol ratio,the CO selectivity was increased.These results suggested that CO was formed as a secondary product through reverse water-gas shift reaction and did not participate in the methanol steam reforming reaction mechanism. 相似文献
58.
《Comptes Rendus Chimie》2016,19(4):433-440
In this study, an experimental plasma-chemical reactor equipped with an arc discharge water steam plasma torch was used for biomass conversion to hydrogen-rich synthesis fuels. Glycerol and crushed wood were used as biomass sources. The effects of different conversion parameters including the water steam flow rate, treated material flow rate, and plasma torch power were studied. The experimentally obtained results were compared with the model based on the thermodynamic equilibrium. Additionally, the quantification of the plasma conversion system in terms of energy efficiency and specific energy requirement was performed. It has been found that the synthesis gas can be effectively produced from the biomass using water steam plasma. 相似文献
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