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排序方式: 共有1718条查询结果,搜索用时 62 毫秒
51.
Samer Aouad Cedric Gennequin Mary Mrad Haingomalala Lucette Tidahy Jane Estephane Antoine Aboukaïs Edmond Abi‐Aad 《国际能源研究杂志》2016,40(9):1287-1292
The wet impregnation method was used to prepare different ruthenium promoted Ce–Al catalysts. These catalysts were used in the steam reforming of methanol reaction (SRM). The effects of the reaction temperature (200–400 C) and the catalyst composition were studied for optimization reasons. The steam to methanol molar ratio was kept constant (S/M = 2). The promotion of cerium/aluminum oxides with Ru enhanced their catalytic activity. The catalytic test results showed that the Ru/Ce combination was the most beneficial. The synergy between Ru and cerium oxide led to the formation of active sites with excellent redox properties. For high active phase content, the 5 RuCe catalyst exhibited the highest hydrogen production amount with no CO formation. This catalyst was kept under stream for 5 days at 400 C, and no significant deactivation was observed. Copyright © 2016 John Wiley & Sons, Ltd. 相似文献
52.
Jane M. Watson Ben A. Kelly 《Canadian Journal of Science, Mathematics, & Technology Education》2013,13(2):145-166
Abstract: A task adapted from one used by Tversky and Kahneman (1971) was used in an interview or questionnaire context with 122 students from Grade 3 to Grade 13. Two questions assessed student understanding of the relationship of a sample to a population and of the expected value of the arithmetic mean, with and without information on a single value from the sample. Combining responses to the two questions, increasingly complex hierarchical sequences were identified in the observed responses in relation to the expected value of the means, an expectation variable, and in relation to the degree that ideas about variation were used to support judgements, a variation variable. Using data from another task performed by 68 of the students, responses were associated with the observed development of understanding of sampling more generally, a basic sampling variable. Overall, the associations of levels of response among the variables was not strong, suggesting more explicit discussion of sampling issues is required in classrooms. 相似文献
53.
Brandon J. Hathaway Jane H. Davidson 《International Journal of Hydrogen Energy》2021,46(29):15257-15267
High efficiency solar steam gasification of biomass is carried out in a prototype molten salt reactor for solar-only and solar-autothermal hybrid operation. Previous demonstration of the prototype 3-kW solar gasifier for steam gasification of cellulose at stoichiometric conditions demonstrated thermal efficiency of 44% during continuous operation at 1200 K. The present work expands the range of operating conditions to consider two challenges. Hybridization between solar and autothermal modes of operation is accomplished by adding oxygen directly to the reactor. Control of the H2:CO ratio of the product gas is accomplished through in-situ steam shifting. Hybridization stabilized temperatures for variations in radiative input as large as a 30% reduction in power, corresponding to conditions where both sensible and chemical heat demands for the process were fully met by exothermic heat release with no significant challenges. Peak efficiencies and carbon conversion values observed are 45% and 99.5% respectively. The resulting product gas stream composition was shifted from a hydrogen and carbon monoxide ratio of 1:1 with stoichiometric steam delivery to a ratio of 1.7:1 with steam at nine times the stoichiometric amount, only slightly lower than equilibrium predictions. The results demonstrate very favorable attributes for the molten salt reactor in a continuous fuel production process. 相似文献
54.
A composite membrane composed of a sulfonated diblock copolymer (SDBC) based on poly(ether ether ketone) blocks copolymerized with partially fluorinated poly(arylene ether sulfone) and sulfonated carbon nanotubes (SCNTs) was fabricated by simple solution casting. Addition of the SCNT filler enhanced the water absorption and proton conductivity of membranes because of the increased per‐cluster volume of sulfonic acid groups, at the same time reinforced the membranes' thermal and mechanical properties. The SDBC/SCNT‐1.5 membrane exhibited the most improved physicochemical properties among all materials. It obtained a proton conductivity of 10.1 mS/cm at 120°C under 20% relative humidity (RH) which was 2.6 times more improved than the pristine membrane (3.9 mS/cm). Moreover, the single cell performance of the SDBC/SCNT‐1.5 membrane at 60°C and 60% RH at ambient pressure exhibited a peak power density of 171 mW/cm2 at a load current density of 378 mA/cm2, while the pristine membrane exhibited 119 mW/cm2 at a load current density of 294 mA/cm2. Overall, the composite membrane exhibited very promising characteristics to be used as polymer electrolyte membrane in fuel cells operated at intermediate RH. 相似文献
55.
Jane Roche Zephirin Mouloungui Muriel Cerny Othmane Merah 《International Journal of Food Science & Technology》2016,51(8):1820-1826
This study was carried out to compare the kinetic accumulation of bioactive lipids during seed development in three oil crops rapeseed, sunflower and woad. Field experiments were conducted under organic conditions during 3 years. After flowering, seeds were collected each 4–5 days until harvest. The three species differed by the quantity and quality of both fatty acids and sterols. Higher levels of phytosterols and fatty acids were reached between 20 and 40 days after flowering (DAF) in sunflower, 40 and 60 DAF in rapeseed and 25 and 45 DAF for woad. The modification of lipid composition during the grain filling depends on species. Knowledge of the composition and accumulation of fatty acids and phytosterols in sunflower, rapeseed and woad seeds would assist in efforts to achieve industrial applications. These seeds may give an interesting source of bioactive lipids. 相似文献
56.
Jane H. Fujiyama-Novak Amrita Mukherjee Ganesh Rahul Bhimanapati Chethan Kumar Gaddam Randy L. Vander Wal Benjamin Ward 《Combustion and Flame》2012,159(3):1160-1164
In this study the main objective was to develop and demonstrate a glow discharge microplasma coupled to a miniature spectrometer for detection of fire signatures from pyrolyzing and burning spacecraft materials. Our experimental results demonstrate that combustion-produced carbonaceous aerosols can serve to identify the burning materials. Demonstrating versatility for chemistry analysis, the plasma detector could differentiate carbonaceous aerosols with different C/H ratios and distinguish inorganic samples such as salts and metal oxides from carbonaceous aerosols. In addition, in situ analysis of aerosol samples validated the microplasma’s analytical utility by linearity of its optical emission intensity with aerosol elemental composition. 相似文献
57.
58.
There has been growing interest in the use of urban agriculture to address food insecurity and poverty in Cape Town. This reflects debates on urban agriculture in the global south. In the north, growing food in cities has been tended to be framed in terms of its social benefits. This paper investigates the perceived benefits of urban agriculture in projects in Seawinds and Vrygrond in Cape Town. Using the concept of metabolic rift is argues for connections between northern and southern constructions of urban agriculture. This approach enables connections to be seen between the practice in seemingly different areas without losing the local context. The paper argues that by using this integrated approach, projects may be more sustainable and ultimately provide both clearer social and economic benefits. 相似文献
59.
Bridger Emma K.; Herron Jane E.; Elward Rachael L.; Wilding Edward L. 《Canadian Metallurgical Quarterly》2009,35(5):1175
Processes engaged when information is encoded into memory are an important determinant of whether that information will be recovered subsequently. Also influential, however, are processes engaged at the time of retrieval, and these were investigated here by using event-related potentials (ERPs) to measure a specific class of retrieval operations. These operations were revealed by contrasts between ERPs elicited by new (unstudied) test items in distinct tasks, the assumption being that these contrasts index operations that are engaged in service of retrieval and that vary according to the demands of different retrieval tasks. Specific functional accounts of this class of retrieval processing operations assume that they influence the accuracy of memory judgments, and this experiment was designed to test for the first time whether this is in fact the case. Toward this end, participants completed 2 retrieval tasks while ERPs were acquired, and the extent to which processes were engaged differentially across tasks in service of retrieval was operationalized as the magnitude of the differences between the new-item ERPs that were elicited. This measure correlated positively with response accuracy on the tasks, which provides strong evidence that this class of retrieval processing operations benefits the accuracy of memory judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
60.