R290在家用空调中替代R22的实验研究     

刘丽刚 《顺德职业技术学院学报》2007,5(4):26-28

为探索R290作为制冷剂在家用空调中应用的可行性,在相同型号的空调器中进行了R290与R22的性能对比实验。结果表明:家用空调器不仅可以用R290替代R22,而且还有环保和节能的效果,能效比可提高10.26%～19.53%。  相似文献   

中美数学思维观的比较研究     

杜英芳 《天津师范大学学报(基础教育版)》2011,12(1):59-61

中美两国数学教育界对学生数学思维的发展都非常重视。我国学者从形象思维、抽象思维、直觉思维等角度对之进行研究和探索;美国学者从儿童生活实际出发,认为学生数学思维包括：匹配与区分、分类、排序、顺序、建模。在论述思维发展时,都结合学生的实际,以案例的方式进行描述。两国在研究的逻辑方法上存在显著差异。我国研究体现出从一般到特殊的特点,而美国的研究则体现出从特殊到一般的特点。比较两国的研究,吸取各自所长,有利于促进我国基础教育数学课程改革的健康发展。  相似文献   

Do tuition fees affect enrollment behavior? Evidence from a ‘natural experiment’ in Germany     

Malte Hübner 《Economics of Education Review》2012

This paper uses the introduction of tuition fees in seven of the sixteen German states in 2007 as a natural experiment to identify the effects of tuition prices on enrollment probabilities. Based on information on enrollment decisions of the entire population of high-school graduates between 2002 and 2008, I find a negative effect of tuition fees on enrollment behavior. The effect is larger than in existing studies for European countries, but of a similar magnitude as effects identified with U.S. data. A potential spill-over effect of the policy intervention to the comparison group is accounted for by using the estimation results to calibrate a structural model of the enrollment decision.  相似文献   

分光光度法直接测定饮料中的柠檬黄和胭脂红     

《雁北师范学院学报》2007,23(3):22-24

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Differential effects of norm-referenced and self-referenced feedback on performance expectancies,attributions, and motivation     

Wendy McColskey  Mark R. Leary 《Contemporary educational psychology》1985,10(3):275-284

When feedback is provided to students in a norm-referenced manner that compares the individual's performance to that of others, people who perform poorly tend to attribute their failures to lack of ability, expect to perform poorly in the future, and demonstrate decreased motivation on subsequent tasks. The present study examined the hypothesis that the deleterious effects of failure might be attenuated when failure is expressed in self-referenced terms—relative to the individual's known level of ability as assessed by other measures. In this study, subjects received feedback indicating that they did well or poorly on an anagram test, and this feedback was described as either norm-referenced (comparing the individual's performance to that of others) or as self-referenced (comparing performance to other measures of the individual's ability). As predicted, compared to norm-referenced failure, self referenced feedback resulted in higher expectancies regarding future performance and increased attributions to effort. Contrary to expectations, attributions to ability were not affected. The implications of the results for the structure of academic feedback are discussed.  相似文献   

Diplomatic Shock and Awe: Moving,Sometimes Speaking,Islamic Sculptures     

T.M.P. Duggan 《Al-Masaq: Islam & the Medieval Mediterranean》2009,21(3):229-267

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In search of the keyword method/vocabulary comprehension link     

Joel R. Levin  Beverly J. Dretzke  Michael Pressley  Julia E. McGivern 《Contemporary educational psychology》1985,10(3):220-227

Previous research has indicated that the keyword method of vocabulary learning facilitates students' performance not just on simple tests of definition recall, but on comprehension-demanding tasks as well. The present study was conducted to determine whether the “comprehension” finding could be accounted for by keyword subjects' superior definition recall per se. The results generally supported that conclusion: When conditions and subjects within conditions were equated with respect to their initial levels of definition recall, the comprehension advantage of keyword subjects disappeared.  相似文献   

Reflections on R2     

S. J. DAY 《Teaching Statistics》1985,7(1):11-12

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基于投入产出分析的广西R&D产业发展研究     

戎陆庆  ;欧阳浩  ;韦克脉 《柳州师专学报》2014,(3):56-60

R&D产业对国民经济发展具有重大意义。本文依据广西最新投入产出表实证分析了研发产业与其它产业间的前后向直接关联度、前后向完全关联度、影响力系数、感应度系数、生产诱导系数及依赖度系数,并在此基础上阐述了它们之间直接与间接联系,最后提出了发展广西R&D产业的可行性建议。  相似文献   

基于NDVI的内蒙古植被动态变化分析     

曹建军 《南京晓庄学院学报》2014,(6):97-104

植被对于生态环境变化的反应是较为敏感的,研究植被动态变化对生态环境的保护和生态预警有很大的意义.基于SPOT/VEGETATION NDVI数据,该文获得了内蒙古的空间NDVI分布,分析了自1998年至2008年之间NDVI的变化趋势.并由最大值合成法（MVC）,Mann-Kendall检验和Rescaled范围（R/S）分析计算出NDVI时间序列的赫斯特指数.此外,通过叠加分析对研究区域NDVI的未来变化趋势进行判断.主要的研究结果包括：第一,1998年到2008年间,内蒙古的植被变化总体上是稳定的,但数据显示10.16%的植被有显著减少的趋势,它们属于脆弱的草原植被;其次,在空间分布方面,NDVI时间序列存在一定规律,赫斯特指数在西部高,东部低;第三,在低植被覆盖区存在植被减少的现象.其中9.58%的土地开始衰退,这些土壤急切的需要植被的保护和综合的管理.没有人类的干预,这些土地将会出现荒漠化.  相似文献