Quantile regression is gradually emerging as a powerful tool for estimating models of conditional quantile functions, and therefore research in this area has vastly increased in the past two decades. This paper, with ...Quantile regression is gradually emerging as a powerful tool for estimating models of conditional quantile functions, and therefore research in this area has vastly increased in the past two decades. This paper, with the quantile regression technique, is the first comprehensive longitudinal study on mathematics participation data collected in Alberta, Canada. The major advantage of longitudinal study is its capability to separate the so-called cohort and age effects in the context of population studies. One aim of this paper is to study whether the family background factors alter performance on the mathematical achievement of the strongest students in the same way as that of weaker students based on the large longitudinal sample of 2000, 2001 and 2002 mathematics participation longitudinal data set. The interesting findings suggest that there may be differential family background factor effects at different points in the mathematical achievement conditional distribution.展开更多
The Songnen Plain lying in the central part of the Northeast China Plain covers an area of about 170 000 km2. There are vast patches of saline land, which are still in the process of enlargement. The spread of saline ...The Songnen Plain lying in the central part of the Northeast China Plain covers an area of about 170 000 km2. There are vast patches of saline land, which are still in the process of enlargement. The spread of saline land has already caused the worsening of ecoenvironment and hindered agricultural development in the region. The paper analyses background factors of natural environment that caused the spread of saline land according to the information of Landsat TM images. The result shows that among the three kinds of lakes the fault lake is the background factor of natural environment that causes the spread of saline land under arid conditions. Its lakebeach meadows could not recover from the excessive utilization in farming and stockraising. The proposed countermeasures to prevent and control the spread of saline land serve as biological steps or water conservancy facilities to protect the lakebeach meadows of the fault lakes from being artificial excessively utilized.展开更多
针对机器学习在流量异常检测中存在特征选择依赖经验、易受离群点影响导致鲁棒性差等问题,基于因素空间理论的“背景关系-背景分布-背景基”体系提出一种流量异常检测的基点分类方法。首先,数据预处理阶段使用KNN离群点检测算法去除数...针对机器学习在流量异常检测中存在特征选择依赖经验、易受离群点影响导致鲁棒性差等问题,基于因素空间理论的“背景关系-背景分布-背景基”体系提出一种流量异常检测的基点分类方法。首先,数据预处理阶段使用KNN离群点检测算法去除数据中的离群点,降低异常点对后续背景基提取的影响。其次,使用mRMR算法对数据特征进行排序,选择对分类最具影响力的特征标注为类别区分特征。然后,以内点判别法为理论基础优化背景基提取算法,提取训练数据中不同类别数据的背景基,得到各类别的单位认知包。最后,以单位认知包为核心构造基点分类算法(fundamental point classification algorithm,FPCA)实现异常流量的精准二分类。在NSL-KDD数据集上对所提方法的二分类实验准确率和F1-score分别达到92.48%和92.18%,检测性能优于同类型的其他机器学习方法。在CICIDS2017场景数据集上的测试进一步验证了所提方法在实际应用中的可行性。展开更多
With the proposal of Internet-based CET,more emphasis need be attached to listening skill.In order to improve stu dents' listening skill,linguistic knowledge,psychological factors and cultural background knowledge...With the proposal of Internet-based CET,more emphasis need be attached to listening skill.In order to improve stu dents' listening skill,linguistic knowledge,psychological factors and cultural background knowledge,as three key factors affect ing Chinese ESL students,have been analyzed and the improving solutions have been suggested.展开更多
In 152 primary liver cancer (PLC)cases and 1: 1 matched controls, risk factors for PLC as well as relevent pedigree data were investigated. The results showed that in relatives of cases,PLC accumulative mortality was ...In 152 primary liver cancer (PLC)cases and 1: 1 matched controls, risk factors for PLC as well as relevent pedigree data were investigated. The results showed that in relatives of cases,PLC accumulative mortality was much higher than that in those of controls (0. 46% vs. 0. 07%, P< 0. 001 ). Of the cases, the rate in consanguineous relatives was 0. 55 %, but in non-consanguineous relatives it was 0. 08 % (P< 0. 01 ); and with alienating of consanguinity a regularly downward gradient of the rate could be observed ; in addition, an independent effect of inheritance remained significant when environmental factors were controlled by Logistic regression and stratification skill. And with an inheritance background, the role of some environmental factors as HBV infection, psychic trauma was reinforced significantly. These results provided further evidence for understanding the association between inheritance and PLC.展开更多
基金Supported by the National Natural Science Foundation of China (No. 10431010) Education Ministry Key Project (No. 05JJD910001) +1 种基金 National Philosophy and Social Science Foundation grant (No. 07BTJ002) 2006 New Century Excellent Talent Program and Funds supported by Renmin University of China (No. 2006031611)
文摘Quantile regression is gradually emerging as a powerful tool for estimating models of conditional quantile functions, and therefore research in this area has vastly increased in the past two decades. This paper, with the quantile regression technique, is the first comprehensive longitudinal study on mathematics participation data collected in Alberta, Canada. The major advantage of longitudinal study is its capability to separate the so-called cohort and age effects in the context of population studies. One aim of this paper is to study whether the family background factors alter performance on the mathematical achievement of the strongest students in the same way as that of weaker students based on the large longitudinal sample of 2000, 2001 and 2002 mathematics participation longitudinal data set. The interesting findings suggest that there may be differential family background factor effects at different points in the mathematical achievement conditional distribution.
文摘The Songnen Plain lying in the central part of the Northeast China Plain covers an area of about 170 000 km2. There are vast patches of saline land, which are still in the process of enlargement. The spread of saline land has already caused the worsening of ecoenvironment and hindered agricultural development in the region. The paper analyses background factors of natural environment that caused the spread of saline land according to the information of Landsat TM images. The result shows that among the three kinds of lakes the fault lake is the background factor of natural environment that causes the spread of saline land under arid conditions. Its lakebeach meadows could not recover from the excessive utilization in farming and stockraising. The proposed countermeasures to prevent and control the spread of saline land serve as biological steps or water conservancy facilities to protect the lakebeach meadows of the fault lakes from being artificial excessively utilized.
文摘针对机器学习在流量异常检测中存在特征选择依赖经验、易受离群点影响导致鲁棒性差等问题,基于因素空间理论的“背景关系-背景分布-背景基”体系提出一种流量异常检测的基点分类方法。首先,数据预处理阶段使用KNN离群点检测算法去除数据中的离群点,降低异常点对后续背景基提取的影响。其次,使用mRMR算法对数据特征进行排序,选择对分类最具影响力的特征标注为类别区分特征。然后,以内点判别法为理论基础优化背景基提取算法,提取训练数据中不同类别数据的背景基,得到各类别的单位认知包。最后,以单位认知包为核心构造基点分类算法(fundamental point classification algorithm,FPCA)实现异常流量的精准二分类。在NSL-KDD数据集上对所提方法的二分类实验准确率和F1-score分别达到92.48%和92.18%,检测性能优于同类型的其他机器学习方法。在CICIDS2017场景数据集上的测试进一步验证了所提方法在实际应用中的可行性。
文摘With the proposal of Internet-based CET,more emphasis need be attached to listening skill.In order to improve stu dents' listening skill,linguistic knowledge,psychological factors and cultural background knowledge,as three key factors affect ing Chinese ESL students,have been analyzed and the improving solutions have been suggested.
文摘In 152 primary liver cancer (PLC)cases and 1: 1 matched controls, risk factors for PLC as well as relevent pedigree data were investigated. The results showed that in relatives of cases,PLC accumulative mortality was much higher than that in those of controls (0. 46% vs. 0. 07%, P< 0. 001 ). Of the cases, the rate in consanguineous relatives was 0. 55 %, but in non-consanguineous relatives it was 0. 08 % (P< 0. 01 ); and with alienating of consanguinity a regularly downward gradient of the rate could be observed ; in addition, an independent effect of inheritance remained significant when environmental factors were controlled by Logistic regression and stratification skill. And with an inheritance background, the role of some environmental factors as HBV infection, psychic trauma was reinforced significantly. These results provided further evidence for understanding the association between inheritance and PLC.
