Study on soil water characteristics of tobacco fields based on canonical correlation analysis

In order to identify the principal factors influencing soil water characteristics (SWC) and evaluate SWC effectively, the multivariate-statistical canonical correlation analysis (CCA) method was used to study and analyze the correlation between SWC and soil physical and chemical properties. Twenty-two soil samples were taken from 11 main tobacco-growing areas in Guizhou Province in China and the soil water characteristic curves (SWCC) and basic physical and chemical properties of the soil samples were determined. The results show that: (1) The soil bulk density, soil total porosity and soil capillary porosity have significant effects on SWC of tobacco fiels. Bulk density and total porosity are positively correlated with soil water retention characteristics (SWRC), and soil capillary porosity is positively correlated with soil water supply characteristics (SWSC). (2) Soil samples from different soil layers at the same soil sampling point show similarity or consistency in SWC. Inadequate soil water supply capability and imbalance between SWRC and SWSC are problems of tobacco soil. (3) The SWC of loamy clay are generally superior to those of silty clay loam.     

雨雾淞导线覆冰理论模型数值模拟研究

导线覆冰的理论模型及数值模拟是研究覆冰过程机理的必要手段。 本文基于国际公认的导线覆冰理论模型框架,采用合理的覆冰过程物理参数化方法,构建了一套完整的数值计算方案,并利用其对雨雾淞导线覆冰过程进行了数值模拟研究,探讨了雨凇、雾淞及雨雾凇混合覆冰过程的机理及其演变特征。数值模拟结果表明：雾凇覆冰过程的增长曲线呈对数曲线变化特征,覆冰在开始阶段增长很快而随时间逐渐变慢; 而雨淞覆冰则随时间持续增长,且覆冰质量增长比覆冰厚度增长更为明显; 雨雾淞混合覆冰状态下覆冰的增长与单纯雨淞或雾凇覆冰的增长曲线均不同,由于干、湿覆冰机制的转换使覆冰增长过程呈现复杂的变化,而开始阶段无论是雨淞覆冰还是雾凇覆冰都可能表现出明显的湿增长特征。本文的研究结果揭示了雨雾凇导线覆冰过程的机理及其演变特征,具有较大的理论参考价值。     

ANALYSIS OF WATER QUALITY IN SHALLOW LAKES WITH A TWO-DIMENSIONAL FLOW-SEDIMENT MODEL

The governing equation for sediment pollutions was derived based on the turbulent diffusion of pollutants in shallow lakes. Coupled with shallow water equations, a depth-averaged 2-D flow and water quality model was developed. By means of the conservation law, a proposed differential equation for the change of sediment pollutants was linked to the 2-D equations. Under the framework of the finite volume method, the Osher approximate Riemann solver was employed to solve the equations. An analytical resolution was used to examine the model capabilities. Simulated results matched the exact solutions especially well. As an example, the simulation of CODMn in the Wuli Lake, a part of the Taihu lake, was conducted, which led to reasonable results. This study provides a new approach and a practical tool for the simulation of flow and water quality in shallow lakes.     

贵州烤烟大田期可用日数与利用分析

为了进行烤烟合理布局和制订生产技术措施,利用贵州 84 个气象站点 1961-2010 年逐日温度资料,在 GIS 平台下推算并定点读取各乡(镇)起点温度和终止温度,确定贵州烤烟大田期的可利用日数。结果发现,贵州烤烟大田期可用日数各地差异很大,随着海拔高度的增加,烤烟大田期可利用日数不断减少。按照时限长短、分布地域、气候特点将贵州烤烟大田期可利用日数划分为4 个类型区。除海拔2000 m以上地区外,其余地区大田期可利用日数均能保证烤烟的正常生长。根据各类型区的可利用日数和气候特点,提出了不同类型区的利用方式和技术要求,并对各类型区的移栽期和采收结束期提出了旬期安排建议。     

导线覆冰厚度线径订正系数的理论计算分析

合理的设计冰厚可在保障电网抵御覆冰灾害能力的同时大大降低电网工程的整体造价,因此输电线路冰厚线径订正系数的正确计算具有重要的工程应用价值。本文基于量纲分析提出了一个导线覆冰碰撞率的简化计算公式,并结合雨雾凇导线覆冰理论模型导出了冰厚线径订正系数的理论计算方法,其结果与有关实验研究结果相符并优于最新行业标准(DL/T5158-2012)推荐的方法。进一步利用该方法从理论上计算分析了不同覆冰类型冰厚线径订正系数及其差异,结果表明：雾凇覆冰情况下冰厚线径订正系数随导线直径增大而减小,雨凇覆冰情况下冰厚线径订正系数随导线直径增大而增大,而模拟雨雾凇混合覆冰情况下的线径订正系数介于前两者之间。由于具有较完整的理论基础并能够考虑不同的覆冰类型和气象条件,该方法具有较好的理论普适性,对电力线路防冰设计具有较大的应用参考价值。