农田土壤水分和盐分空间分布的指示克立格分析评价

运用非参数地质统计学的多元指示克立格法,结合单元指示克立格法,对黄河河套灌区55hm2的盐渍化土地上两个比较关键时期的土壤水分和盐分进行空间分布的分析,给出了同一时期土壤水盐和不同时期土壤盐分满足一定标准的综合概率图,并借助该案例详细介绍了多元指示克立格的原理、步骤及应用范围。指示克立格方法为不同尺度(从农田到区域)上水土资源质量的评价提供了新的方法,能为水土资源的现代决策管理提供指导。     

最大熵时域逆散射层析成像的研究

用最大熵求解二维时域逆散射问题的层析成像算法反演井间、ＶＳＰ和ＳＲＰ中的二维介质波速分布。首先给出时域散射场与介质扰动的关系式，然后，应用最大熵剑桥算法从所有满足时域散射数据的模型中挑选图像熵最大的模型作为反演结果，并给出了该算法的实现步骤。数值试验的结果表明，本文算法用于反演含噪声，不完全的时域波场数据时，十分有效。     

自适应混合遗传算法在基坑支护结构优化中的实现

采用遗传算法对基坑支护结构进行优化设计,针对其早熟现象和局部搜索能力差的缺点改进遗传算法。使用自适应策略改进交叉算子与变异算子,在进化后期采用与位爬山法结合的混合遗传算法增强GA的局部搜索能力。对基坑支护结构建立优化设计数学模型,编制了基于遗传算法的基坑优化设计程序。通过实例分析,验证了改进策略的正确性。     

A Novel Method for Real-Time Monitoring of Channel Siltation Based on Bistatic Scattering Theory

Monitoring the thickness changes of channel siltation is paramount in safeguarding navigation and guiding dredging.This paper presents a novel method for realizing the field monitoring of channel siltation in real time.The method is based on the bistatic scattering theory and concerned more with the receiving and processing of multipath signal at high-frequency and small grazing angle.By use of the multipath propagation structure of underwater acoustic channel,the method obtains the silt thickness by calculating the relative time delay of acoustic signals between the direct and the shortest bottom reflected paths.Bistatic transducer pairs are employed to transmit and receive the acoustic signals,and the GPS time synchronization technology is introduced to synchronize the transmitter and receiver.The WRELAX (Weighted Fourier transform and RELAX) algorithm is used to obtain the high resolution estimation of multipath time delay.To examine the feasibility of the presented method and the accuracy and precision of the developed system,a series of sea trials are conducted in the southwest coast area of Dalian City,north of the Yellow Sea.The experimental results are compared with that using high-resolution dual echo sounder HydroBoxTM,and the uncertainty is smaller than ±0.06 m.Compared with the existing means for measuring the silt thickness,the present method is innovative,and the system is stable,efficient and provides a better real-time performance.It especially suits monitoring the narrow channel with rapid changes of siltation.     

QGIS在地理项目式学习中的应用探索——以"衢州人口分布与地形关系的定量分析"为例

随着科学技术的发展,学生学习的方式和获取知识的途径发生了改变.地理信息技术作为地理重要的研究工具,不应该再停留在纸面概念的学习,应该成为学生解决地理问题的工具.本文分析了QGIS在地理项目式学习中的适用性,以定量分析人口分布与地形关系为例,探索QGIS在地理项目式学习活动中的应用.