Attrition resistant catalyst for dimethyl ether synthesis in fluidized-bed reactor   总被引：1，自引：0，他引：1  

Li-hua Teng 《浙江大学学报(A卷英文版)》2008,9(9):1288-1295

Fluidized-bed reactor is a candidate for dimethyl ether （DME） synthesis from syngas because of its excellent heat removal capability. In order to improve the attrition resistance of catalyst, an amount of silica sol as binder was added to the catalyst composed of methanol synthesis component CuO/ZnO/Al2O3 and methanol dehydration component HZSM-5, which was prepared by coprecipitation and shaped by spray drying to get spherical particles. The effect of silica sol on the catalytic activity was investigated in a fixed-bed flow microreactor. Based on the experiment results, silica sol in the range of 0-20wt% had small effect on the catalytic activity. Generally, the CO conversion and DME yield decreased with the increase in concentration of silica sol, while the attrition resistance of catalysts increased with increasing silica sol, indicating that it was feasible to improve the attrition resistance without greatly sacrificing the activity of catalyst. In addition, the characterizations of catalysts were carried out using Brunauer-Emmett-Teller （BET）, X-ray powder diffraction （XRD） and temperature programmed reduction （TPR）.  相似文献   

Pathways from parental stimulation of children’s curiosity to high school science course accomplishments and science career interest and skill     

Adele Eskeles Gottfried  Kathleen Suzanne Johnson Preston  Allen W. Gottfried  Pamella H. Oliver  Danielle E. Delany  Sirena M. Ibrahim 《International Journal of Science Education》2016,38(12):1972-1995

Curiosity is fundamental to scientific inquiry and pursuance. Parents are important in encouraging children’s involvement in science. This longitudinal study examined pathways from parental stimulation of children’s curiosity per se to their science acquisition (SA). A latent variable of SA was indicated by the inter-related variables of high school science course accomplishments, career interest, and skill. A conceptual model investigated parental stimulation of children’s curiosity as related to SA via science intrinsic motivation and science achievement. The Fullerton Longitudinal Study provided data spanning school entry through high school (N?=?118). Parental stimulation of curiosity at age 8 years comprised exposing children to new experiences, promoting curiosity, encouraging asking questions, and taking children to a museum. Intrinsic motivation was measured at ages 9, 10, and 13 years, and achievement at ages 9, 10, and 11 years. Structural equation modelling was used for analyses. Controlling for socio-economic status, parental stimulation of curiosity bore positive and significant relations to science intrinsic motivation and achievement, which in turn related to SA. Gender neither related to stimulation of curiosity nor contributed to the model. Findings highlight the importance of parental stimulation of children’s curiosity in facilitating trajectories into science, and relevance to science education is discussed.  相似文献   

Optimization of conditions for supercritical fluid extraction of flavonoids from hops (Humulus lupulus L.)     

He GQ  Xiong HP  Chen QH  Ruan H  Wang ZY  Traoré L 《Journal of Zhejiang University. Science. B》2005,6(10):999-1004

Waste hops are good sources of flavonoids. Extraction of flavonoids from waste hops (SC-CO₂ extracted hops) using supercritical fluids technology was investigated. Various temperatures, pressures and concentrations of ethanol (modifier) and the ratio (w/w) of solvent to material were tested in this study. The results of single factor and orthogonal experiments showed that at 50°C, 25 MPa, the ratio of solvent to material (50%), ethanol concentration (80%) resulted in maximum extraction yield flavonoids (7.8 mg/g). HPLC-MS analysis of the extracts indicated that flavonoids obtained were xanthohumol, the principal prenylflavonoid in hops. Project (No. Y304203) supported by the Natural Science Foundation of Zhejiang Province, China  相似文献   

新出土简帛佚籍与中国教育史研究     

米靖 《教育研究》2003,(3)

半个多世纪以来 ,简帛佚籍不断出土问世 ,其中包含有不少重要的教育史料 ,这些史料给中国教育史研究提供了新的内容和领域 :第一 ,有望促成《老子》一书现其历史真面目 ,并使先秦黄老道家学派的著作与思想体系渐趋明朗 ,从而极大地推动关于先秦道家教育思想体系的确立与完善 ;第二 ,极大地丰富了研究孔子及其后学八派教育思想的史料 ,使加深对孔子教育思想的认识 ,弥补从孔子到孟子之间儒家教育思想长期存在的研究空白成为可能 ;第三 ,对于明确先秦两汉经学教育的细节有着举足轻重的作用 ;第四 ,重要字书《仓颉篇》的出土 ,为研究秦汉语文教育提供了极其重要的文献  相似文献   

Dimensionality and reliability of a screening instrument for students at-risk of dropping out from Higher Education     

《Studies in Educational Evaluation》2021

Dropout stems from a complex, gradual process of decision-making in which the demands and benefits of university attendance are weighed. Early identification of at-risk students benefits from quick and large-scale screening instruments. This study presents the dimensionality of a screening instrument for students at risk of dropping out of Higher Education, integrating three scales: Academic Exhaustion, Satisfaction with Education and Dropout Intention. A sample of 611 first-year university students was considered in the statistical analysis. The results demonstrate evidence of internal and external validity as well as the reliability of the screening instrument scores. The differences in correlation coefficients between these three scales and the students’ intentions of completing the course and completing their education at their university, evaluated at two different points during the first semester, suggest that dropout analysis requires collecting information throughout the process of adjustment to higher education.  相似文献   

“Commenting on your work is a waste of time only!”: An appraisal-based study of evaluative language in supervisory feedback     

《Studies in Educational Evaluation》2021

Research on supervisory feedback on master’s theses, especially attitudinal stances conveyed in such feedback, is thin on the ground. Students’ construal of their supervisors’ attitudes, however, can have a profound impact on their engagement with supervisory feedback. Drawing on the appraisal framework, which characterizes attitudinal meanings in terms of affect (i.e., emotional responses), judgement (i.e., normative evaluation of human behaviors) and appreciation (i.e., aesthetically-/socially-based evaluation of objects and products), this study examined Nepalese supervisors’ attitudinal stances communicated in written comments on master’s thesis drafts (n = 76) submitted by English-as-a-foreign-language students and oral feedback on proposal and thesis defences (n = 89). Quantitative analyses revealed that while instances of appreciation dominated in the supervisors’ use of evaluative language, judgements were also frequent, with affective responses trailing far behind. In both the oral feedback and written comments, significant disciplinary variations were observed for certain types of judgment and appreciation. These findings are discussed in terms of disciplinary culture and the potential impact of the attitudinal stances on students’ learning. Implications are derived for the productive framing of supervisory feedback to facilitate students’ feedback uptake.  相似文献   

The role of academic competences and learning processes in predicting Bachelor’s and Master’s thesis grades     

《Studies in Educational Evaluation》2021

Writing an academic thesis is an important and complex task and the thesis grade should reflect students’ academic competences. The present study aims, firstly, at exploring how Bachelor’s and Master’s students self-evaluate their academic competences and approaches to learning and whether their evaluations differ from each other. In addition, the study aims at investigating how academic competences and approaches to learning are related to the thesis grades of Bachelor’s and Master’s students. The data consisted of 1 019 Bachelor's and Master’s students, all of whom completed an electronic questionnaire at the time of their graduation. The results imply that Bachelor’s students already possess a considerable number of academic competences. It seems that students’ organising skills should be supported, especially in the Bachelor phase. Finally, the present study raises the question of what the thesis grade actually measures if its relations to both learning processes and academic competences are questionable.  相似文献   

Connecting feedback to self-efficacy: Receiving and providing peer feedback in teacher education     

《Studies in Educational Evaluation》2021

Feedback can play a vital role in fostering teacher self-efficacy. Social comparisons and feedback valence (positive vs. negative feedback) are assumed to have a large impact on self-efficacy. Therefore, how pre-service teachers perceive social comparisons and feedback valence in peer feedback and the extent to which pre-service teachers (bachelor/master students) and teacher trainers incorporate comments that can have an impact on self-efficacy into their peer feedback merit investigation. Two studies were conducted. The first showed that peer feedback consisting of a social comparison and with positive feedback valence resulted in greater willingness to improve and positive affect. The second study revealed that teacher trainers’ feedback was more specific, whereas bachelor students’ feedback contained more social comparisons than did master students’ and teacher trainers’. Future research and practical implications are discussed.  相似文献   

A scoping review on the notions of Assessment as Learning (AaL), Assessment for Learning (AfL), and Assessment of Learning (AoL)     

《Studies in Educational Evaluation》2021

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Teacher support and academic engagement among EFL learners: The role of positive academic emotions     

《Studies in Educational Evaluation》2021

Academic engagement and teacher support, as two important factors in education, have been largely neglected in the research literature of English as a Foreign Language (EFL) and applied linguistics. Given the facilitative role of positive emotions in learning processes, this study aimed to examine their mediating role in the relationship between teacher support and academic engagement among Iranian EFL learners. The participants were 435 EFL freshmen randomly selected via multi-stage cluster sampling. The data were collected through previously validated measures. The results of structural equation modelling showed that perceived teacher support could directly and positively affect academic engagement. Additionally, positive emotions mediated the relationship between teacher support and academic engagement. Finally, some important implications and suggestions for further research are presented.  相似文献