Physical modelling of solute transport in porous media: evaluation of an imaging technique using UV excited fluorescent dye

The development and evaluation of a 2-dimensional physical model, which is designed to assist in the characterisation of complex solute transport problems in porous media, is described. The laboratory model is a transparent 2-dimensional porous media of nominal thickness and uses a non-invasive imaging technique in conjunction with a fluorescent dye tracer (sodium fluorescein) to monitor solute movements. Under ultraviolet (UV) illumination the dye emits visible light which is imaged by a CCD (Charge Coupled Device) camera. The image is processed to estimate the 2-dimensional distribution of tracer concentrations. The system can successfully model a simple contaminant plume within a homogenous porous matrix constructed from glass beads (60-100 microm). Experimental results show that transverse dispersion coefficient was 3.9 x 10(-10) m2/s when sodium fluorescein transported in porous matrix with a walter velocity of 5.71 x 10(-6) m/s. The low transverse dispersion coefficient suggests that the molecular diffusion of solute cannot be neglected under low velocity of the water. The advantages of using UV rather than an ordinary light system are a reduction in noise and experimental errors. Errors due to light dispersion within the model are shown to be negligible for the current model. Since contaminant with aromatic rings are usually fluorescent and biological samples can be labelled by fluorescent dye, this imaging technique using UV excited fluorescent dye will be used to investigate biodegradation process in porous media.     

硅质碎屑陆坡和坡麓沉积体系的相组成,地层结构及分类

水下陆坡和坡麓沉积体系是大多数海相和许多湖相盆地充填的主要组成部分，它们构成了泊气勘探和开发的主要目标，陆坡体系包括７种基本岩相单元（１）浊沉河道充填体；（２）浊积朵体，（３）席状浊积体；（４）滑动，坍塌和碎屑流作用的形成的席状，朵状和舌状体；（５）细粒浊积充填和席状体；（６）等深流漂积物；（７）半远洋的披覆和充填物。所供应的沉积物粒度是河道和朵体形态，以及坍塌和碎屑流沉积的规模及其重要性的主要控     

“小”肚能容天下事——CF存储卡选购点滴

在刚接触数码相机的用户看来，购买CF卡只需考虑品牌和容量即可，事实真的如此简单？     

对多目标,多背景分类的多传感器融合算法

介绍将输入（数据或图像）分类（目标，背景）的多传感器融合算法，该算法形成许多群，并且自动排队，分群是基于一组输入的统计特性做的，这种算法执行一种分群算法，极类似简单顺序首项分群算法ＣａｒｐｅｎｔｅｒＧｒｏｓｓｂｅｒｙ网算法（ＣＧＮＡ）。该算法在以下方面不同于ＣＧＮＡ，（１）数据输入和数据指针可以取实值；（２）它有自适应选择群集数的机理；（３）它有一个自适应的门限，分析了门限选择的问题，并且证明了该     

压裂液损耗的试验室研究

本文描述了实验室条件下普通水力压缩液的过滤特性。文中介绍了滤饼阻力概念，还应用粘弹元素理论对观察到的现象进行了解释。通过本项研究我们得出了滤饼滤失系数与聚合物用量之间的关系．还得出了在特定温度、特定压差及特定聚合物用量条件下滤饼滤失特性预测模型。我们可以将这—研究成果用于任一稳固模型中，解释水力压裂期间压裂液的滤失情况。     

CT dosimetry computer codes: their influence on radiation dose estimates and the necessity for their revision under new ICRP radiation protection standards

Computed tomography (CT) dosimetry computer codes have been most commonly used due to their user friendliness, but with little consideration for potential uncertainty in estimated organ dose and their underlying limitations. Generally, radiation doses calculated with different CT dosimetry computer codes were comparable, although relatively large differences were observed for some specific organs or tissues. The largest difference in radiation doses calculated using different computer codes was observed for Siemens Sensation CT scanners. Radiation doses varied with patient age and sex. Younger patients and adult females receive a higher radiation dose in general than adult males for the same CT technique factors. There are a number of limitations of current CT dosimetry computer codes. These include unrealistic modelling of the human anatomy, a limited number of organs and tissues for dose calculation, inability to alter patient height and weight, and non-applicability to new CT technologies. Therefore, further studies are needed to overcome these limitations and to improve CT dosimetry.