基于数据拟合分析坡面土壤侵蚀的临界坡度

通过不同雨强、坡度的多段模拟降雨实验,将坡度与坡面侵蚀模数进行二次多项式拟合,求得不同条件下坡面侵蚀的临界坡度.实验结果表明,临界坡度会随着雨强、降雨历时的变化而产生规律性变化.雨强越大,临界坡度越大,对坡面侵蚀临界坡度的影响越强烈;降雨历时增加,坡面侵蚀的临界坡度也随之增大,雨强越大,临界坡度增速越快,且增速拐点出现越早.在坡面侵蚀初期,坡度增加加强了坡面径流对坡面泥沙的搬运作用,减弱了坡面的溅蚀作用,使得在一定坡度范围内坡度大的坡面细沟侵蚀开始时间晚于坡度小的坡面,这是临界坡度产生的原因之一.随着坡面侵蚀过程的发展,坡面侵蚀主要发生于细沟的边缘、侧壁和底部,不同坡度坡面单位时间内的侵蚀模数差值减少且趋于稳定,坡度对于侵蚀模数的影响逐渐减小,临界坡度逐渐消失.该研究可为完善黄土区的土壤侵蚀机理提供理论依据.     

雨量感应自动升降防雨帘的开发研究

介绍了一种雨量感应自动升降防雨帘装置,主要由卷轴及防雨卷帘、电动机及传动装置、雨量信号检测及控制系统等组成,实现了窗户用防雨帘的自动升降.讨论了这种防雨帘装置的总体结构和传动方式,特别是手动、遥控和自动控制系统的工作原理以及设计方法.     

The Invisible Hand of Rain in Spending: Effect of Rainfall‐Driven Agricultural Income on Per Capita Expenditure in Ghana

This paper uses a nationally representative household pseudo‐panel dataset for Ghana, a rain‐fed agriculture economy, to investigate whether there is a positive relationship between rainfall‐driven agricultural income and household per capita expenditure. By using the Two Stage Least Squares Instrumental Variable (2SLS‐IV) estimator, it is found that a fall in rainfall‐driven agricultural income leads to a decrease in per capita expenditure. The results show that the gender and the locality of the household head matter in the response of per capita expenditures to rainfall‐driven agricultural income. Female‐headed and rural households are more vulnerable to rainfall‐driven agricultural income changes. The expenditure disaggregation indicates that female‐headed households significantly reduce per capita non‐food expenditure in times of rainfall‐induced agricultural income decrease whilst the response of male‐headed households focuses more on reducing per capita food and remittance expenditures.     

基于改进可拓理论-有效降雨耦合模型的库岸滑坡稳定性动态评价

库区滑坡稳定性问题是水利水电工程中研究的关键问题之一，影响滑坡稳定性的指标具有差异性、时变性，传统方法难以实现稳定性的动态评价。通过改进可拓理论，建立多层次、多变量的滑坡稳定性动态评价模型，引入有效降雨模型替代日降雨量模型，采用差异系数替代传统CRITIC法标准差，建立基于关联函数矩阵的动态权重计算方法。通过对羊曲水电站库区内某滑坡体地表宏观变形、实时监测数据分析，证明了有效降雨模型的适用性，定义了有效降雨作用期，最终将改进可拓理论与有效降雨模型联用对该滑坡体进行稳定性动态评价，研究结果与监测数据表明规律具有较好的一致性，证明提出的方法具有可靠性及准确性。此外，构建的模型可以快速分析现场实时数据，实现随时间、环境变化的滑坡稳定性状态的动态评价，为滑坡体防治工作提供了一种客观准确的分析方法。     

The dynamic effects of monsoon rainfall shocks on agricultural yield,wages, and food prices in India*

This paper shows that, first, the effects of monsoon rainfall shocks on agricultural yield in India are highly asymmetric: yield falls strongly after droughts, whereas excessive rainfall has only little effects. Second, our key novel finding is that the short-lived yield loss after a widespread drought elicits a persistent decline (increase) in wages (food prices), which lasts for up to five years. Third, affiliation to the same National Sample Survey region (and thus to the same state) seems to be a key determinant of internal migration, whereas distance appears more relevant for food arbitrage trading.     

降水资源的高效利用---沧州市 农业持续发展的战略选择

文章在分析沧州市农业干旱缺水基本状况的基础上,论述了该地区充分利用降水资源的重要性,总结了沧州市两大节水种植小麦模式。从长远看,继续走依靠超采大量地下水来发展农业生产的路子会越来越艰难。因此,建议采用各种农业技术,提高降水资源利用率,有可能成为解决沧州市农业缺水问题的主要途径。