3D image-based characterization of fluid displacement in a Berea core

Improved network flow models require the incorporation of increasingly accurate geometrical characterization of the microscale pore structure as well as greater information on fluid–fluid interaction (interfaces) at pore scales. We report on three dimensional (3D) pore scale medium characterization, absolute permeability computations for throat structures, and pore scale residual fluid distribution in a Berea core. X-ray computed microtomography combined with X-ray attenuating dopants is used to obtain 3D images of the pore network and to resolve phase distributions in the pore space.     

云顶充满度的特征分析

本文采用GMS－5红外云母，提取了一个描述云顶结构特征的参数一云顶充满度VS。结合地面观测资料，引入了云高参数DTS，得到并分析了参数VS随云高DTS的分布特征，同时还讨论了VS的天气学意义。     

Thematic mapping from remotely sensed data with neural networks: MLP, RBF and PNN based approaches

 Neural networks are attractive tools for the derivation of thematic maps from remotely sensed data. Most attention has focused on the multilayer perceptron (MLP) network but other network types are available and have different properties that may sometimes be more appropriate for some applications. Here a MLP, radial basis function (RBF) and probabilistic neural network (PNN) were used to classify remotely sensed data of an agricultural site. The accuracy of these classifications ranged from 86.25–91.25%. The accuracy of the PNN classification could be increased through the incorporation of prior probabilities of class membership but the accuracy of each classification could also be degraded by the presence of an untrained class. Post-classification analyses, however, could be used to identify potentially misclassified cases, including those belonging to an untrained class, to increase accuracy. The effect of the post-classification analysis on the accuracy of the classification derived from each of the three network types investigated differed and it is suggested that network type be selected carefully to meet the requirements of the application in-hand. Received: 23 March 2000 / Accepted: 9 July 2000     

防震减灾技术系统网络应用中的网络安全

扼要介绍计算机网络安全结构及Internet网络应用中的数据服务。国家防震减灾技术系统网络中心计算机网络的组成及安全。介绍了Internet提供的服务；网络中心与Internet的2个出口以及它提供的DNS、FTP、E－MAIL、WWW等服务。重点介绍网络中心的防火墙安全及防火墙的过滤作用。     

神经网络在镇扬大桥工程区区域稳定性评价中的应用

基于优势面区域稳定性评价理论，运用ANN优势断裂评价模型来研究镇扬大桥工程区区域稳定性，取得了较好的效果，实践表明基于ANN找寻和评价优势断裂是可行的和有效的。     

River flow mass exponents with fractal channel networks and rainfall

An important problem in hydrologic science is understanding how river flow is influenced by rainfall properties and drainage basin characteristics. In this paper we consider one approach, the use of mass exponents, in examining the relation of river flow to rainfall and the channel network, which provides the primary conduit for transport of water to the outlet in a large basin. Mass exponents, which characterize the power-law behavior of moments as a function of scale, are ideally suited for defining scaling behavior of processes that exhibit a high degree of variability or intermittency. The main result in this paper is an expression relating the mass exponent of flow resulting from an instantaneous burst of rainfall to the mass exponents of spatial rainfall and that of the network width function. Spatial rainfall is modeled as a random multiplicative cascade and the channel network as a recursive replacement tree; these fractal models reproduce certain types of self-similar behavior seen in actual rainfall and networks. It is shown that under these modeling assumptions the scaling behavior of flow mirrors that of rainfall if rainfall is highly variable in space, and on the other hand flow mirrors the structure of the network if rainfall is not so highly variable.     

Step-frequency radar applied on thin road layers

In the field of road construction and maintenance, the need for information on the thickness of very thin road layers is not satisfied by means of commercial pulse GPR, due to the inability of such devices to operate over ranges of several gigahertz. As a result, research has focused on the design of a step-frequency radar technique, able to work with very high-frequency synthetic pulses.An ultrawide band antenna, belonging to the family of Vivaldi antennas, has been developed for road applications. It has been created using stripline technology and yields a band width greater than one decade. During an initial step, this antenna was tested on various bituminous concrete samples with a network analyzer. Different parameters were studied, including band width, offset between antennas, and height and shape of the frequency-dependent pulse.A second step involved GPR dynamic measurements. A customized software program enabled recording data from the network analyzer. Several radar profiles were developed from selected road construction and maintenance test sites (e.g. the Circular Pavement Fatigue Test Track, composed of a number of known structures). Results show improved resolution when compared to a commercial impulse GPR system.     

智能CAD中图的一种表示方法

试图提出广义结点概念，并给出图的一种表示方法。该方法用邻接表法表示广义结点与邻近广义结点的关系，用向量表示法表示单一属性广义结点链。在实现方法上，不采用链接表结构，而用动态通用串结构很好地实现了图的运算操作。并举例说明在智能地ＣＡＤ中的运用。     

ALow-order Model of Two-dimensional Fluid Dynamics on the Surface of a Sphere

ＡＬｏｗ－ｏｒｄｅｒＭｏｄｅｌｏｆＴｗｏ－ｄｉｍｅｎｓｉｏｎａｌＦｌｕｉｄＤｙｎａｍｉｃｓｏｎｔｈｅＳｕｒｆａｃｅｏｆａＳｐｈｅｒｅＭｏｚｈｅｎｇＷｅｉ（ＣＲＣｆｏｒＳｏｕｔｈｅｒｎＨｅｍｉｓｐｈｅｒｅＭｅｔｅｏｒｏｌｏｇｙ，ＣＳＩＲＯＤｉｖｉｓｉｏ...     

“广义信息维”在首都圈地震中期预报中的应用

给出了“广义信息维”的计算公式和计算方法，研究了首都圈和周期地区的广义时间分维和华北地区的广义空间分维。结果表明，在该地区Ｍｓ≥５．３地震前０．５－３ａ，时间分维都有一个较明显的降维过程；空间分维也有较好的对应效果，但是存在漏现象。