玻璃微珠折射率测定

提出了一种测量直径小于1mm的玻璃珠折射率的新技术,其精度可达10-4,比常规的浸液法测量方便而又精确.     

基于生态足迹的格网化生态承载力评价——以衡水市为例

针对行政单元生态承载力评价不能精细反映区域内部生态状况的差异和局部细节特征的问题,难以满足精细管控生态承载力的需要,本文提出了格网化生态承载力评价方法。基于生态足迹模型,结合人口空间分布模型,借助GIS空间分析技术,从格网角度对生态足迹和生态承载力进行定量估算与空间格局分析,并以衡水市为例进行试验验证。结果表明,格网尺度生态承载力评价方法与区域生态承载力评价方法相比更符合真实情况。从格网尺度看,衡水市生态足迹分布圈层特点,生态承载力呈离散分布特征。生态赤字状况表现出明显的异质性,沿滏东排河和滏阳河两侧呈条带状分布。衡水市大部分地区处于生态赤字临界状态,生态状况亟须得到保护。     

绵阳市涪城区近十年土地利用动态监测及分析

近年来绵阳市土地利用变化现象表现十分明显,但缺乏比较深入的研究。本文根据绵阳市涪城区2000年和2010年的土地利用变化动态监测数据,利用CA-Markov模型对2020年的土地利用空间格局进行预测,并对引起该区土地利用变化的驱动力进行分析。     

基于车载激光雷达的行道树提取研究

对车载激光雷达点云数据进行研究,提出了一种分层投影的方法提取行道树,该方法对点云数据进行分层投影,利用不同高程点云投影后表现出的不同特征,采用面向对象的方法对行道树进行提取,最后叠加分析得到行道树点云。实验证明,该方法能够比较完整的提取出行道树点云。     

Active X控件在计算机辅助设计中的应用初探

以具体实例探讨了ActiveX控件在计算机辅助设计中的应用，给出了部分源代码。对这种新的设计思想作了概念性的剖析与展望。     

平衡施肥对棉麦套作中小麦生长发育的影响

根据田间区试结果,分析了有机肥与氮磷钾化肥配施对棉麦套作中小麦生物产量和经济产量的构成因素、养分含量及吸收量的影响,结果表明:有机肥与化肥配施能显著提高小麦的生物产量和经济产量,且以中肥最为适宜;增施氮磷钾肥能提高小麦各生育期养分含量和吸收积累量,并且还能增加旗叶的叶面积和叶绿素含量.小麦营养生殖并重时期(拔节至孕穗期),对养分的需求量大,此时土壤中足够的养分,可为小麦高产优质奠定营养基础,此期也是小麦平衡施肥的关键时期.     

Stability of richterite50-tremolite50 solid solution at high pressures and possible presence of sodium calcic amphibole under upper mantle conditions

High pressure experiments have been made on the stability of richterite₅₀-tremolite₅₀ solid solution by the piston-cylinder type high pressure apparatus in the pressure range from 15 to 40 kb, at temperatures from 700 to 1150°C. This amphibole is stable up to 40 kb at 700°C, and the breakdown pressure gradually decreases with increasing temperatures. It is suggested that this amphibole, on the basis of high pressure experiments, may occur in the upper mantle.     

On the Distance Function Between Two Keplerian Elliptic Orbits

The problem of finding critical points of the distance function between two Keplerian elliptic orbits is reduced to the determination of all real roots of a trigonometric polynomial of degree 8. The coefficients of the polynomial are rational functions of orbital parameters. Using computer algebra methods we show that a polynomial of a smaller degree with such properties does not exist. This fact shows that our result cannot be improved and it allows us to construct an optimal algorithm to find the minimal distance between two Keplerian orbits. This revised version was published online in July 2006 with corrections to the Cover Date.     

Non-symmetrical levee breaching processes in a channel bend due to overtopping

A series of experiments were done to reveal the overtopping breaching process of non-cohesive and cohesive levees in a U-bend flume. The flood hydrograph and breaching geometry were measured and analyzed in detail. The results show that the levee breaching processes can be briefly divided into four stages: slope erosion, longitudinal headward gully-cutting, lateral erosion, and relative stabilization. For non-cohesive levees, non-symmetrical lateral development of the breach occurs throughout the four stages, and the final non-symmetrical coefficient is approximately 2.2–2.6. Larger flow discharge or higher water level can accelerate the breaching process, while coarser sands tend to accelerate the process initially but depress the process at the end. The fluvial erosion rate of a non-cohesive breach shows a power-function relation with the excess wall shear stress. For cohesive levees, a plateau forms in the breach partially blocking the flow in the first two stages. The breach flow is approximately perpendicular to the levee body, and, thus, the erosion rates of the two breach sides are almost the same. Non-symmetrical lateral development mainly occurs in the third stage when the deep gully forms. The final non-symmetrical coefficient is approximately 2.7–3.3. It is expected that these findings can provide a valuable experimental dataset and a theoretical basis for breach closure and flood alleviation.