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《兰州石化职业技术学院学报》2016,(1)
建立了煤炭工业分析指标水分、灰分、挥发分与煤炭发热量间的线性回归模型,采用分位数回归估算模型系数。通过对我国新疆伊犁地区煤炭发热量分析研究,表明基于分位数估计的线性回归模型优于基于传统的最小二乘估计的线性回归模型,且预测效果优于支持向量机。 相似文献
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本文利用中国教育追踪调查数据(2014—2015),采用普通最小二乘法、分位数回归以及倾向得分匹配法,实证检验了体育锻炼对青少年认知能力的影响,结果发现:(1)利用普通最小二乘法测得经常参与体育锻炼的青少年在认知能力测试上比不经常参与的青少年高出0.149个标准分,当控制前期能力后,青少年参加体育锻炼的时间每上升1个单位值,能将认知能力提高0.049个标准分;(2)利用分位数回归发现参加体育锻炼对认知能力处于中位数上的青少年具有最强的促进作用,体育锻炼的异质性特征突出表现为“倒V”型曲线,而利用无条件分位数回归发现经常参与体育锻炼能够缩小低–高分位点上认知能力的组内差异;(3)利用Probit模型发现学校作业并非青少年参与体育锻炼的决定因素,看电视、玩网络游戏等课余活动的时间则对青少年参与体育锻炼构成了挤出关系,文化资本、人力资本以及教育期望与青少年的体育运动参与率呈正相关;(4)利用倾向得分匹配法发现体育锻炼影响认知能力的平均处理效应落入[0.095,0.117]的取值区间,而忽视选择性偏差将会高估体育锻炼的净效应。 相似文献
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数据缺失场合对数正态分布参数的渐近置信估计 总被引:1,自引:0,他引:1
利用对数正态分布的若干个样本分位数,建立线性回归模型,由获得的广义最小二乘估计的渐近正态性,得到分布参数的渐近置信估计,在样本足够大的情况下,该方法简单有效. 相似文献
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多元线性回归中自变量之间的多重共线性问题在我们实际运用中很容易产生,为了解决这个问题,常用的方法是最小二乘回归.本文以根据分析结果总结出最小二乘回归对解决这一问题的缺点的不足.而偏最小二秉回归法是最小二乘法的一种改进,在变量数目巨大的情况下,如果数据中变量的个数多,偏最小二乘回归的优点更能充分的显示出来 相似文献
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信息化社会背景下,越来越多的学生通过电子产品进行阅读.然而,已有的电子阅读对阅读素养影响的研究还不够深入,尤其是在数据的权威性、方法的妥切性和分析的精确性等方面仍有较大改进空间.本研究选取PISA2018数据库中与阅读有关的变量,运用最小二乘法建立基准回归,采用泛精确匹配技术控制选择偏误,分析不同阅读方式对学生阅读素养的影响,并采用分位数回归以及中介效应模型,探究电子阅读影响的异质性及其影响机制.研究发现:1)无论是否控制选择偏误,回归结果均说明"屏幕劣势"这一效应的确存在;2)分位数回归结果显示不同水平的学生受电子阅读的影响有明显差别;3)中介效应分析结果表明元认知策略可以发挥重要的促进和中介作用.本研究建议:合理看待电子阅读这一新兴阅读方式,灵活选择电子阅读与纸质阅读方式,充分发挥阅读元认知策略的作用,以弥补电子阅读的不足. 相似文献
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SAT(Scholastic Assessment Test)作为美国目前广为接受的大学入学考试,其公平性一直遭受质疑,尤其是在性别、种族等敏感领域。基于美国某高中学生的SAT数据,运用最小二乘估计法,建立了关于SAT考试成绩的单方程线性回归模型。回归结果显示在保持模型中其他因素不变的情况下,SAT考试的确存在性别和种族歧视,且性别对成绩的影响要大于种族对成绩的影响。最后结合2016年SAT考试的公平性改革,探究SAT的未来发展方向及对我国新高考改革的借鉴。 相似文献
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实验尝试采用近红外光谱法结合涡旋辅助液液微萃取技术,快速测定水中邻苯二甲酸二(2-乙基己基)酯(DEHP)残留.为提高检测的信噪比,使用四氯化碳作为萃取剂,不使用分散剂.近红外光谱数据采用偏最小二乘法分析,利用auto-scale对光谱进行预处理.偏最小二乘分析模型的主因子数为4,建模波段为4246.7~4424.1 cm-1.模型中RMSECV为0.3759,R2为0.9607.本实验结果显示了近红外方法结合涡旋辅助液液微萃取在分析环境水中的DEHP方面具有潜力. 相似文献
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AR(p)与指数平滑组合预测算法 总被引:1,自引:0,他引:1
本文提出一种对铜铳品位进行预测的新方法,以采集的现场数据为基础,采用系统辩识动态地建立了AR(p)模型与三次指数平滑模型,AR(p)模型要求数据对象是平衡时间序列,而三次指数平滑型的数据对象具有随机性,考虑到铜锍品位的波动性,本文将二模型按最小二乘法原理,以组合预测误差平方和为目标函数,通过使误差平方和极小化来确定两种预测方法的优化,建立了一种新的组合模型,在三种模型中其预测误差最小。 相似文献
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Sreenivasulu Reddy Mogali Ranganath Vallabhajosyula Chee Hon Ng Darren Lim Eng Tat Ang Peter Abrahams 《Anatomical sciences education》2019,12(6):664-672
In the past, medical museums played a significant role in anatomy and pathology training. The attraction of medical museums has declined recently due to the emergence of information technology and innovative medical curricula. An innovative mobile learning platform has been developed using quick response (QR) codes for the museum specimens at the Lee Kong Chain School of Medicine, Singapore. High-quality images of the potted specimens were captured and combined into an album and a video using Adobe Acrobat Pro 9 and Windows Movie Maker, respectively. Subsequently, QR codes were generated linking to PDF documents with annotations, pathology, and clinical history concerning the specimens. Quick response codes were piloted in gastrointestinal teaching module for Year 2 medical students. Survey responses were obtained from students to verify the efficacy of QR as a learning tool. The majority of students either agreed or strongly agreed that it was easy to access the information about the specimen with QR codes (4.47 ± 0.84), while 96% of students agreed that they are able to correlate the specimen with the annotated images (4.56 ± 0.56). The majority of students (78%) agreed that QR codes are useful for their learning (4.22 ± 0.87), while 75% of students felt QR codes motivate them to visit Anatomy Resource Centre. Most of the students agreed that QR codes are useful for revision of materials (4.13 ± 1.07) and independent learning (4.38 ± 0.87). These findings suggest that QR codes are not only effective for students learning but also enhance their exploration experience with the museum specimens. 相似文献
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Robert Lee Mayes Jennifer Harris Forrester Jennifer Schuttlefield Christus Franziska Isabel Peterson Rachel Bonilla Nissa Yestness 《International Journal of Science Education》2013,35(4):635-658
The ability of middle and high school students to reason quantitatively within the context of environmental science was investigated. A quantitative reasoning (QR) learning progression was created with three progress variables: quantification act, quantitative interpretation, and quantitative modeling. An iterative research design was used as it is the standard method for the development of learning progressions. The learning progression was informed by interviews of 39 middle and high school students from 5 schools in the Western USA using QR assessments. To inform the lower anchor, intermediate levels, and upper anchor of achievement for the QR learning progression, an extensive review of the literature on QR was conducted. A learning progression framework was then hypothesized. To confirm the framework, three QR assessments within the context of environmental literacy were constructed. The interviews were conducted using these QR assessments. The results indicated that students do not actively engage in quantitative discourse without prompting and display a low level of QR ability. There were no consistent increases on the QR learning progression either across grade levels or across scales of micro/atomic, macro, and landscape. 相似文献
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QR码作为二维码中的一种,具有容量大、可靠性高等优势。伴随手机图书馆的逐步建设,QR码与短信、手机网站等结合,广泛应用于书目联机查询系统(OPAC)、研读间预约等场景,促使图书馆服务的时空、方式得到拓展和延伸。简要介绍QR码的基本情况后,针对目前手机图书馆中QR码的几种具体应用形式进行分析,并指出该技术在图书馆推广过程中需要注意的问题。随着3G时代的到来、智能手机的普及,QR码在图书馆服务中将发挥更大的作用。 相似文献
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蒋尔雄 《上海大学学报(英文版)》2004,8(4):369-377
QL(QR) method is an efficient method to find eigenvalues of a matrix. Especially we use QL(QR) method to find eigenvalues of a symmetric tridiagonal matrix. In this case it only costs O( n^2) flops, to find all eigenvalues. So it is one of the most efficient method for symmetric tridiagonal matrices. Many experts have researched it. Even the method is mature, it still has many problems need to be researched. We put forward five problems here. They are: (1) Convergence and convergence rate; (2) The convergence of diagonal elements; (3) Shift designed to produce the eigenvalues in monotone order; (4) QL algorithm with multi-shift; (5) Error bound. We intoduce our works on these problems, some of them were published and some are new. 相似文献
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The authors argue that skills in quantitative literacy (QL) and quantitative reasoning (QR) augment students’ communicative effectiveness. This article offers a pedagogical framework and model for how QR can be productively interwoven with the rhetorical know-how of technical writing pedagogy. The authors describe their course redesign, present preliminary assessment data, and conclude by highlighting some implications not only for student learning, but also for the QL movement itself. 相似文献
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针对模糊、光照不均情况下获得的低质量QR码难以识别的问题,设计一种低质量QR码识别算法,包括加权平均值法灰度化、中值滤波算法降噪、二值化、基于位置探测图形定位、基于透视变换法的旋转矫正,以及基于Zbar开源库的译码算法等。重点研究针对模糊、光照不均QR码图像的二值化算法,提出一种基于Bernsen算法思想的改进算法,将全局阈值引入该算法中,实现对图像的二值化处理。在VS2010环境下基于Opencv2.4.9图像处理库对识别算法进行验证,结果表明,通过该算法得到的QR码图像完整且噪声少,有效克服了低质量QR码的影响,提高了图像识别率,具有一定的实用性。 相似文献
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借助移动互联时代以智能手机为代表的便携式移动学习终端和二维码技术,教师利用二维码能够在课前将微课等资源推送给学生,方便学生高效自主地学习,还能随时掌握课前检测数据的汇总结果,增强后续教学的针对性。本文以《爱莲说》一课为例,介绍了二维码在初中文言文教学各环节的应用,在此基础上讨论二维码的教学功能,并对基础教育中学生使用手机的现象进行反思。 相似文献