待定积分法     

郭文秀  朱永银  朱勇 《长江工程职业技术学院学报》2007,24(4):66-68

有几种函数乘积的积分,用传统的方法解决相当繁杂.用"待定积分法"来求这几类函数的积分,简单明了,事半功倍.  相似文献   

Deletions in the genomes of fifteen inbred mouse lines and their possible implications for fat accumulation     

Schmitt AO  Dempfle A  Brockmann GA 《Journal of Zhejiang University. Science. B》2007,8(11):777-781

Copy number variants (CNVs) are pieces of genomic DNA of 1000 base pairs or longer which occur in a given genome at a different frequency than in a reference genome. Their importance as a source for phenotypic variability has been recognized only in the last couple of years. Chromosomal deletions can be seen as a special case of CNVs where stretches of DNA are missing in certain lines when compared to the reference genome of the mouse line C57BL/6, for example. Based upon more than 8 million single nucleotide polymorphisms (SNPs) in the fifteen inbred mouse lines which were determined in a whole genome chip based resequencing project by Perlegen Sciences, we detected 20166 such long chromosomal deletions. They cover altogether between 4.4 million and 8.8 million base pairs, depending on the mouse line. Thus, their extent is comparable to that of SNPs. The chromosomal deletions were found by searching for clusters of missing values in the genotyping data by applying bioinformatics and biostatistical methods. In contrast to isolated missing values, clusters are likely the consequence of missing DNA probe rather than of a failed hybridization or deficient oligos. We analyzed these deletion sites in various ways. Twenty-two percent of these deletion sites overlap with exons; they could therefore affect a gene's functioning. The corresponding genes seem to exist in alternative forms, a phenomenon that reminds of the alternative forms of mRNA generated during gene splicing. We furthermore detected statistically significant association between hundreds of deletion sites and fat weight at the age of eight weeks.  相似文献   

创业者认知偏差对在孵企业学习的影响机制研究——基于孵化器管理情境的三阶交互模型     

唐明凤  黄皓  李凤莲 《研究与发展管理》2020,(1):169-180

孵化器有利于增加创业存活率、刺激技术创新,其内部资源利用和学习效率日益受到关注。本文以社会认知理论为基础,以成都市8家不同类型孵化器内部在孵企业为研究对象,获取184家在孵企业的调查数据,探索了孵化器管理情境下3种创业者认知偏差对在孵企业学习的具体影响机制。结果表明:过度自信负向影响在孵企业学习;过度自信与遵循小数定理存在交互作用中的拮抗作用;过度自信、控制错觉和小数定理对在孵企业学习存在三阶交互作用,即过度自信与小数定理的拮抗作用在高控制错觉时失效。本研究丰富了创业者认知偏差的研究内容,并为我国孵化器合理制订入孵标准、优化孵化绩效提供了指导和参考。  相似文献   

Kindergarten children's symbolic number comparison skills relates to 1st grade mathematics achievement: Evidence from a two-minute paper-and-pencil test     

《Learning and Instruction》2019

Basic numerical skills provide an important foundation for the learning of mathematics. Thus, it is critical that researchers and educators have access to valid and reliable ways of assessing young children's numerical skills. The purpose of this study was to evaluate the concurrent, predictive, and incremental validity of a two-minute paper-and-pencil measure of children's symbolic (Arabic numerals) and non-symbolic (dot arrays) comparison skills. A sample of kindergarten children (M_age = 5.86, N = 439) were assessed on the measure along with a number line estimation task, a measure of arithmetic, and several control measures. Results indicated that performance on the symbolic comparison task explained unique variance in children's arithmetic performance in kindergarten. Longitudinal analyses demonstrated that both symbolic comparison and number line estimation in kindergarten were independent predictors of 1st grade mathematics achievement. However, only symbolic comparison remained a unique predictor once language skills and processing speed were taken into account. These results suggest that a two-minute paper-and-pencil measure of children's symbolic number comparison is a reliable predictor of children's early mathematics performance.  相似文献   

The effect of phonological processing on mathematics performance in elementary school varies for boys and girls: Fixed-effects longitudinal analysis     

Yulia Kuzmina  Alina Ivanova  Diana Kaiky 《British Educational Research Journal》2019,45(3):640-661

Investigations into the relations between phonological processing and math performance have yielded contradictory results. These contradictions might be related to small sample sizes and/or cross-sectional designs of previous studies that limited the possibility of generalizing the findings obtained. The first goal of this study was to estimate the effect of phonological processing on number recognition and math performance during the first year of schooling, controlling for reading achievement. The second goal was to examine whether this effect varied for boys and girls. To achieve these goals, we used a large sample of first-graders (N = 3296, 49% were girls) in Russia and applied fixed effects longitudinal analysis. Participants were assessed twice, at the beginning and at the end of the first grade (mean age was 7.3 years at Time 1). The item response theory scaling procedure was used to estimate individual scores for math performance, number recognition, phonological processing and reading performance. The results revealed that phonological processing had effects on number recognition and math performance. This effect was more salient for number recognition than for math performance, probably due to the greater involvement of the retrieval strategy in number recognition tasks. The results also demonstrated that the effect of phonological processing on number recognition was stronger for girls than for boys.  相似文献   

图C_m~2×S_n与C_m~2×F_n与的gndt-染色     

刘利群  陈祥恩 《河西学院学报》2011,(2):50-53

单图G的邻点可区别的非正常全染色是指图的任意相邻两顶点的色集合都不同的全染色.所谓顶点的色集合是指顶点自身的颜色及与其关联的所有边的颜色的集合.文中讨论了笛卡儿积图C_m~2×S_n和C_m~2×F_n的邻点可区别非正常全染色,并给出了相应色数.  相似文献   

4杆汉诺塔问题     

许维美  许道云 《铜仁学院学报》2011,13(1):124-127,144

通常汉诺塔问题只考虑带3根杆,当圆盘数为n时,最佳方案的移动次数为J（n）=2^m-1。本文考虑带4杆的汉诺塔问题及其移动方案[（1-a）,a,0,0]。一个有趣的问题是：对于0〈a〈1,当口取什么值时,[（1-a）,a,0,0]-方案是最优的？实验表明：最优[（1-a）,a,0,0]-方案中,随着圆盘数n的增加,a值越大。当n≥240时,最优方案的a值稳定在0．9。  相似文献   

路与路的字典乘积图的消圈数     

沈传锦 《唐山师范学院学报》2011,33(5):20-21

探讨了路与路的字典乘积图的消圈问题。对一般的路与路,推导出它们的字典乘积图的消圈数的一个紧的下界;对一些特殊的路与路,推导出它们的字典乘积图的消圈数的准确值。  相似文献   

关于一个简单图的色数及其相邻矩阵的特征多项式     

付春娟 《唐山学院学报》2011,24(6):6-8

把图论中的着色问题同数论中的整数论相结合,并且引入代数中的矩阵、特征多项式等数学工具,在讨论图的色数为2,3的结论基础上,给出了色数为4时图的性质和相邻矩阵的特征多项式等一些基本的结论。  相似文献   

中国第三产业发展对就业的影响     

侯璐蝉 《顺德职业技术学院学报》2011,9(4):18-21

基于协整分析理论建立第三产业产值对该产业从业人数的影响函数,得到该产业产值每增减1%,对应从业人数增减0.322%的结论,通过应用时间序列分析方法预测中国2011～2012年第三产业产值分别为201 555.42亿元和237 556.34亿元,并由此估算相应的从业人员数量分别为29 731.04万人和31 819.81万人。  相似文献