共查询到20条相似文献，搜索用时 19 毫秒
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为了论证暴雨选样间的频率转换的合理性和可行性,以及合理的频率转换模型,对福建省9个市49座城镇雨量观测站实测的资料进行分析计算,以离差绝对值和、离差平方和以及Nash-Sutcliffe作为误差评定标准,分别计算各自的暴雨设计值的离差绝对值和、离差平方和和NSE值。最后分别计算49个站点不同历时离差绝对值和平均值、离差平方和平均值以及NSE值平均值。计算结果表明:P-Ⅲ型分布是短历时暴雨最佳拟合线型,配合模型2,可以作为福建省城市暴雨频率转换关系式。 相似文献
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刘小明 《赣南师范学院学报》1987,(Z1)
非线性问题经数学代换后转化为线性问题进行一元线性回归时,用加权最小二乘法比用等权(单位权)最小二乘法更有益,所得残差要更小。在此结合几个具体实例进行了一般的讨论。 相似文献
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4k个连续正整数平方和中的素数方幂 总被引：2，自引：0，他引：2
陈荣基 《黄冈师范学院学报》2001,21(5):1-2
证明了：4k(k为正整数）个连续正整数的平方和不是素数或素数方幂。 相似文献
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定义了一种基于正交相遇平衡区组设计(或者广义正交表)的统计模型,给出了二次型统计量及数据的平方和分解,在此基础上进行了方差分析研究,最后,给出了广义正交表的应用实例. 相似文献
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《The Journal of educational research》2012,105(4):184-186
AbstractThe distribution of inter-test sums of squares for 7,021 freshmen was found to be markedly skewed positively. Formens high variability was usually due to a relatively lower English score; for women, a lower mathematics score. The “high-variables” (sum of squares 100 or more) had higher variances on each of the tests than did the “low-variables.” High-variable men were most likely to have mathematics as their highest score and social studies as lowest; for women, high social studies and low mathematics was the most likely combination. For men, the numbers of “high- variables” majoring In mathematics and “low-variables” in English were disproportionately high. Fathers of high- variable men had an education that was either higher or lower than the modal level for all the fathers. 相似文献
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Item discrimination for instruments used to measure characteristics by means of group responses is stressed. It is argued that a percentage of the total sum of squares which is due to groups can appropriately be used as an index of item discrimination. 相似文献
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The aim of this article is to explicitly compute the number of generalized magic squares of order 3. Counting functions for (generalized) magic squares of order n with fixed line sum r is known to be a polynomial function in r over ? of degree (n?1)2. For higher values of n, it is quite difficult to explicitly write down such counting functions. 相似文献
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从中国的实际情况和人口增长的特点出发,建立中国人口增长的数学模型,并由此对中国人口增长的中短期和长期趋势做出预测,同时采用相对误差准则和残差平方和准则对预测的数据进行了分析. 相似文献
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符君健 《南阳师范学院学报》2003,2(11):98-100
汉字书体的演化经过了篆、隶、楷、行这几个大的阶段,对各种书体的形态结构进行概括、归纳,就可发现,汉字本身的形态结构并不是纯粹方形的,而是一种外(椭)圆内方形的结构,这种“外圆内方”是华夏民族“天圆地方”的传统思想以及人们的普遍审美标准所形成的。因此称汉字为方块字是不准确的,而称之为“外圆内方字”则更能说明汉字的文化内涵和结构特征。由汉字的方圆性所发明的符合面积黄金分割的“方圆格”,对习练者书写规范汉字,缩短习字时间,提高习字水平,将起到积极的推动作用。 相似文献
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In this article, the degrees of freedom of the sample variance are simulated by using the Visual Basic for Applications of Microsoft Excel 2010. The simulation file dynamically displays why the sample variance should be calculated by dividing the sum of squared deviations by n‐1 rather than n, which is helpful for students to grasp the meaning of degrees of freedom. 相似文献
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This paper probes into the feasibility of equilibrating pressure of water distribution network through using auto-control valves in theory and in the economy. An optimal valve control model is designed to minimize the sum of squares of residual pressure in the network. Such an analog simulation has been performed on the year 2003 programming network of a certain littoral district in North China, through which this paper confirms that it is feasible to equilibrate pressure with auto-control valves in theory. The research work has brought about a discovery of applicable conditions of valves in economic feasibility, which avoids a great economic loss due to the wild use of auto-control valve. In addition, simulated annealing algorithm is applied to optimize valve settings and shown to identify global optimum or near-optimum. 相似文献
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ABSTRACTThis paper estimates the relative effectiveness of private and public primary schools in Kenya using data from 4,433 Grade 6 schoolchildren. Using ordinary least squares as a baseline model, we use the proportion of private schools in a district as an instrument in a Heckman two-stage correction framework, as well as propensity score matching models to correct for selection bias. There is a positive private school effect across all models. In the corrected models, we find that private school pupils outperform their public school counterparts by between .24 and .52 standard deviations. 相似文献
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在当今西方经济学至少是所谓的"高级"西方经济理论中,数学已经成为阐述理论内容的基本要素或者说是通用语言.线性回归模型是最常用的经济计量模型,用于研究风险、保险、资产组合等经济问题,也可以用作经济预测.本文研究了线性回归模型中的参数估计问题,运用最小二乘法进行参数估计的数学分析基础.最小二乘法只是使用了函数的稳定点而没有运用数学分析的极值理论里的第一充分条件和第二充分条件,本文讨论最小二乘法的估计参数方法和数学分析的极值理论的方法是等价的. 相似文献
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This study interconnects developmental psychology of fair and moral behavior with economic game theory. One hundred eighty-nine 9- to 17-year-old students shared a sum of money as individuals and groups with another anonymous group (dictator game). Individual allocations did not differ by age but did by gender and were predicted by participants' preferences for fair allocations. Group decision making followed a majority process. Level of moral reasoning did not predict individual offers, but group members with a higher moral reasoning ability were more influential during group negotiations and in influencing group outcomes. The youngest participants justified offers more frequently by referring to simple distribution principles. Older participants employed more complex reasons to justify deviations from allocation principles. 相似文献
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以1992-2012年的安徽省城镇居民人均消费支出的数据,运用多元回归与时间序列结合的模型预测、ARIMA模型预测和灰色预测三种单项预测方法,以预测的误差平方和最小为准则,建立IOWA组合预测模型,并以安徽省城镇人均消费支出为例进行实证分析,发现组合预测模型在整体上都优于每一单项预测方法,对我国居民消费支出预测和研究城镇居民人均消费具有重大意义。 相似文献
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汪朝晖 《南宁师范高等专科学校学报》2008,25(1):138-139
讨论了线性回归模型中未知参数最小二乘估计的改进,引入了一种估计的相对效率,证明了广义根方估计比狭义根方估计的效率较高。 相似文献
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基于小波分解频带能量特征和BP神经网络的方法识别油浸式变压器短路故障。利用电弧光信号进行油浸式变压器短路故障诊断,对不同工况下的光信号进行多分辨率分析的四层小波分解,选择合适的重构小波系数,提取特征频带。对提取出的特征频带的小波系数作平方和归一化处理,求出每个特征频带的能量,作为特征参数输入到BP神经网络模型中进行训练和故障识别。 相似文献