秧龄、播量、密度和氮肥运筹对"新两优6号"产量的影响

采用四因素三水平正交试验研究了秧龄、播量、密度和氮肥运筹对杂交中稻"新两优6号"产量的影响.结果表明:秧龄、播量、密度和氮肥运筹对水稻产量均有一定程度的影响,对产量影响程度依次为栽插密度 (B)＞秧龄 (D) ＞氮肥运筹 (A) ＞播种量 (C).本试验四因子的最优组合为A2B1C3D2,产量为15208.50kg /hm2.     

Flexible sample selection strategies for transfer learning in ranking

Ranking is a central component in information retrieval systems; as such, many machine learning methods for building rankers have been developed in recent years. An open problem is transfer learning, i.e. how labeled training data from one domain/market can be used to build rankers for another. We propose a flexible transfer learning strategy based on sample selection. Source domain training samples are selected if the functional relationship between features and labels do not deviate much from that of the target domain. This is achieved through a novel application of recent advances from density ratio estimation. The approach is flexible, scalable, and modular. It allows many existing supervised rankers to be adapted to the transfer learning setting. Results on two datasets (Yahoo’s Learning to Rank Challenge and Microsoft’s LETOR data) show that the proposed method gives robust improvements.     

跨部门组织社会网络结构比较研究及其管理启示

在回顾组织社会网络结构理论研究的基础上,结合分析六家公司案例数据,从群体密度、群体中心性和群体中介性三个网络结构指标角度,对比研究组织内跨部门咨询网络和情报网络结构的差异性。研究发现:咨询网络的密度比情报网络的密度低,而在群体中心性和群体中介性方面,咨询网络比情报网络高。最后,针对这一结论对理解组织内部工作信息传递、组织沟通和知识管理等的作用和启示进行了探讨。     

《概率论》教学中的四个重点

《概率论与数理统计》是一门研究随机现象统计规律性的学科,其应用非常广泛。文中就教师在《概率论》教学中容易忽视的四个方面的知识点加以叙述。     

表面张力系数实验的应用研究

应用拉脱法测量了食盐和白糖溶液的表面张力系数,发现：盐溶液的表面张力系数随着溶液密度的增大而增大,糖溶液的表面张力系数随着浓度的增大而减小。测量了自来水与纯净水在不同环境温度下的表面张力系数,验证了液体表面张力系数随着温度的升高而降低的物理规律。     

液体互扩散速率的初步研究

实验研究了常温常压条件下,给定浓度的墨水溶液在竖直方向上、在不同密度的盐溶液中的扩散情况.研究发现:(1)盐溶液密度较小时,墨水的扩散速率随着盐溶液液柱的下降呈现增加的趋势,当密度增大到一定程度时,墨水溶液的扩散速率与盐溶液液柱的深度不存在相关关系.(2)在相同的温度下,墨水溶液的平均扩散速率随盐溶液密度的增加呈现指数下降规律;不同温度下,规律趋势相同.说明液体扩散质在扩散过程中受到溶液中微粒的阻碍作用力与溶液的密度成增函数关系.     

Individual effects on biomechanical variables during landing in tennis shoes with varying midsole density

The aim of this study was to determine whether individuals responded uniquely to three different pairs of tennis shoes that differed only in midsole hardness. Kinematic and kinetic data were collected while the subjects (n = 3) performed a stereotyped lateral movement wearing each of the three pairs of tennis shoes. The results were analysed statistically for each subject separately. Variables were identified as discriminators between shoes for individual subjects based upon the results of separate discriminant analyses. After these analyses, a multivariate analysis of variance (MANOVA) was used for each subject to determine whether the discriminator variables differed significantly between shoes. A scoring system was devised that used the results of the MANOVA to assign scores to shoes for each variable. Cumulative scores for shoes (for each subject) were compared to determine which shoe was best for a subject. The results indicated that each subject responded uniquely to the shoes, and each demonstrated a preference for a particular pair of shoes. A need for single-subject designs exists when evaluating variations in athletic shoes.     

退耕还湖后菜子湖湿地土壤剖面有机碳分布变化

退耕还湖是我国长江中下游地区湿地生态恢复的重要举措,土壤有机碳是评价湿地生态功能恢复的重要组成部分。本文选取菜子湖区不同退耕年限(2、5、8、10、20a)和退耕后不同植被群落(苔草、芦苇和酸模)湿地土壤为研究对象,揭示退耕还湖后退耕年限和植被类型对湿地土壤有机碳恢复的影响。结果表明:随退耕年限的增加,湿地土壤有机碳含量逐渐增加,但土壤有机碳密度随退耕年限增加呈"升高―降低―升高"的趋势,总体比油菜地高出61.5%~82.3%;不同植被类型下土壤剖面(0~55 cm)有机碳含量表现为:芦苇(8.90g/kg)苔草(8.84g/kg)酸模(5.84g/kg),芦苇土壤剖面有机碳含量随土层深度增加而变化幅度小于苔草和酸模;不同植被类型下土壤剖面(0~55 cm)有机碳密度呈现出芦苇(7.92 kg/m2)苔草(7.42 kg/m2)酸模(5.01 kg/m2)。结果分析表明退耕还湖后菜子湖湿地植被恢复和理化性质变化促进土壤有机碳含量及其密度变化,而苔草、芦苇和酸模土壤剖面土壤有机碳恢复不一致,芦苇对土壤剖面有机碳密度提升能力最强。     

黑龙江省不同运动训练水平大学生身体成分和骨密度的比较研究

采用文献资料法、实验测试法和数理统计法,对黑龙江省普通本科院校与体育院校大学生的身体成分和骨密度进行测试,以期找到某种规律,为科学健身、合理的饮食生活规律提供理论指导,充实大学生身体成分和骨密度的实验研究。结果显示,体育运动降低体脂含量（P〈0.05）,增加瘦体重、肌肉和蛋白质含量（P〈0.05）,中等强度的运动提高骨密度（P〈0.05）,且不同训练水平之间存在明显差异,这种差异主要与课程设置、运动训练内容以及生活方式等因素有关,指出适当的运动可以有效的改善身体成分和骨密度,而运动强度过大反而会降低骨密度的含量。     

线性介质中伴随电磁场存在而附加的自由能密度

本文证明了在线性介质中,通常所说的电磁场能量密度的表示式w=1/2((?)·(?)+(?)·(?))。实质上是所考虑系统的自由能密度的增量。