Turbulence Statistics Inside and Over Forest: Influence on Footprint Prediction

Observations of wind statistics within and above a Scots pine forest are comparedwith those predicted from an analytical second-order closure model. The roughnesssublayer (RSL) effects, and the influence of stability on similarity functions, arestudied using observations. The commonly accepted forms of similarity functionsdescribe the influence of diabatic effects above the RSL well. According to earlierstudies they are expected also to apply within the RSL. As an exception, the averagewind speed normalised with friction velocity was found to be invariant with stabilityclose to the canopy top under unstable conditions. Lagrangian stochastic trajectorysimulations were used to evaluate the influence of canopy turbulence profiles onfootprint prediction. The main uncertainty was found to arise from parameterisationof the random forcing term in the Lagrangian velocity equation. The influence ofdiabatic conditions was studied, and it was found that thermal stability affectssignificantly the footprint function above the forest canopy, but significantuncertainty exists because of uncertainties in the formulation of stability functions.     

磁场重联中离子轨道的混合模拟研究

在使用2.5维混合模拟方法研究了Petschek模型稳态驱动磁场 重联演化的基础上， 本文考察了计算域内各典型区域中粒子分布函数的变化，描绘了重联区不同位置几种类型的 非Maxwell分布函数. 结果表明，磁场重联会将重联区少部分粒子加速到很高的能量，不同 加速程度的粒子将形成球壳状的速度分布. 粒子的轨道特征表明，在重联区中出流的粒子， 有一部分被磁镜捕获，其回旋半径大于重联区宽度，并构成整个流体速度的低速部分. 另外 ，在X中性点附近进入重联区的粒子沿磁力线向出流区以三种形式漂移，分别为：沿磁力线 逃逸、捕获在磁镜中随流体运动、横越磁力线漂移，其比例分别约为70%，20%和10%。     

截渗墙(防渗墙)质量检测技术研究进展

截渗墙是堤坝整治的重要手段，但由于截渗墙施工质量不易控制，并且具有隐蔽性等特点，截渗墙的质量检测非常重要且存在不小的难度。本文首先简要介绍了近年来得到研究与实践的一些截渗墙质量检测技术，并对各种检测技术的特点进行了分析，最后推荐了截渗墙(防渗墙)质量检测的技术方案。     

地震层析成像在水利水电工程地质勘察中的应用

水利水电工程地质勘察是水利水电工程建设中的基础工作。地震层析成像技术作为一种新的物探方法，通过工程中孔，碉间地质条件的探测，进而评价大坝建筑物的工程地质条件是一种有效的手段。本文介绍了乌江构皮滩水利枢纽的应用效果。     

时间剖面上小断层的计算机自动检测

煤田地震勘探一直探寻着对小断层的自动检测方法，因受各种因素的影响，至今尚无良策。本文介绍了多元地震参数的模式识别方法，并通过模型及实测资料成功地检测到１０ｍ以下小断层。     

数据采集中特征点粗差定位方法的探讨

本文分析了特征点应满足的几种条件，给出了一次范围最小（Ｌ１）法，最小二乘法以及粗差探测法进行特征点粗差定位方法，并以模拟实例为例对它们进行了比较，得出了一些有意义的结论。     

地质雷达在隧道检测中的应用

隧道施工完成后用常规方法很难对衬砌质量做出系统评价，地质雷达利用超高频脉冲电磁波探测目标介质的介电常数，很容易掌握砼衬砌结构的厚度、衬砌周围回填及空隙情况，围岩断层裂隙构造情况等，为工程技术评价提供依据。文章以实例，介绍了利用地质雷达对隧道进行检测所使用的仪器、工作参数及地质雷达资料处理解释步骤，并通过对几幅典型雷达图像进行分析介绍了不同异常结构在雷达剖面上的反映。     

近间距并行管线探测方法的效果对比

介绍了管线探测的几种方法,结合实例,对近间距并行管线的几种探测方法的效果进行了比较。     

Applicability of a Backprojection Algorithm to Reconstruct Images of Subsurface Horizontal Planes for Laboratory Experiments in Electrical Resistance Tomography

This paper describes the use of a backprojection algorithm to reconstruct subsurface images of the electrical resistivity in horizontal planes parallel to the surface. The algorithm can be applied to detect buried objects such as tanks or pipes and possible leakages from them. Two imaging strategies are compared: juxtaposition of vertical planes, and 3D reconstruction from the sensitivity matrix corresponding to the entire volume whose surface is explored. The electrode arrays used for voltage measurement are the dipole–dipole array and a modified Schlumberger array. A personal computer controls current injection, electrode switching, and voltage detection. The system injects 1 kHz, 20 V peak-to-peak square waveforms, thus avoiding electrode polarization effects. Experimental laboratory measurements show that the algorithm detects localized objects such as an insulating sphere and a conductive cylinder immersed in water. Furthermore, covering half of the cylinder by a rubber sleeve to simulate a nonconductive leak, yields a distinct image for the leak. The backprojection algorithm does not need any regularization parameter and it is very fast in inverting the sensitivity matrix because it approximates the inverse matrix by its transposed. The dipole–dipole array usually yields a lower overall pixel error than the modified Schlumberger array but both allow the detection of simulated underground leaks.