基于神经网络的河道浅滩演变预测模型

河道浅滩演变是一个复杂的非线性动力学过程, 作者借助神经网络处理非线性问题的优势, 在分析影响河道浅滩演变因素的基础上, 建立了预测河道浅淮演变的BP网络模型, 并对模型中的输入因子和样本的提取进行了探讨. 以闽江竹岐至侯官河段为实例,用“试控法”给出了BP网络模型的建模方案, 用正交设计原理选取相应的训练样本集, 利用该样本集对网络进行学习和训练, 并用训练好的BP网络模型预测浅滩上年内最小水深和年平均淤积厚度. 计算结果表明: 模型预测结果与实际值吻合良好. 这为河道浅滩演变预测研究提供了新方法.     

Extension of the QUASAR River-Water Quality Model to Unsteady Flow Conditions

A modification of the well-known water-quality model 'quality simulation along river systems'(QUASAR) is presented in order to extend its ability, so that it may be considered applicable under unsteady-flow conditions. An aggregated dead-zone travel-time parameter, based on (a) the kinematic wave velocity (celerity) of the flow wave and (b) the behaviour of the solute within so-called 'dead zones', has been incorporated into the existing model formulation. This extends the current continuously-stirred tank reactor-based model process to account for the behaviour of solute under unsteady-flow conditions. The enhanced water-quality model has been validated by application to the Colorado River.     

数值地形图的生成及其水文地貌特征评价

数值地形图(DEM)是利用地理信息系统(GIS)进行流域水文模拟的基础, 其精度直接影响模拟结果在没有现成的数值地形图时, 应用人员往往利用传统的地形图来生成它. 本文分别采用Arc/Info地理信息系统软件提供的哈奇逊法和不规则三角网五次插值法, 对一个实验流域的高程取样点进行插值, 生成了4种不同的数值地形图, 从凹洼分布、流域界定、河网提取、地面坡度和地形指数、以及地面径流汇成等方面, 对它们的水文地貌精度进行了比较. 结果表明, 两种方法都能生成由高程点群所反映的地形, 然而由于哈奇逊法能够结合流域的河网结构及其具有物理基础的水文地貌加强法来处理凹洼问题, 因此大大地提高了其所生成的流域数值地形图水文地貌特征精度.     

éditorial.

This issue begins with an invited paper by Ronald Melzack, continuing the "Distinguished Contribution Series" begun in 1990 by my predecessor, Gordon Winocur. Professor Melzack is known world-wide for his research on pain. In 1965, together with Patrick Wall, he proposed the gate control theory, an entirely new conception of pain. For the first time, there was an explicit physiological model emphasizing the role played by the brain as well as by the spinal cord, leading to a new integration of psychological and physiological contributions to pain, as well as to new avenues for the control of pain. This theory has been highly influential, as a quick look in virtually any textbook in biology or medicine will confirm. Professor Melzack's continuing development of his ideas is presented with remarkable clarity in his books and in his many journal articles. It is, therefore, especially exciting for CJEP to be the first to publish a sketch of his new neuromatrix theory. When the book developing this theory is published, it too will no doubt have an immediate and major impact. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A novel laboratory bench for practical evaluation of catalysts useful for simultaneous conversion of NOx and soot in diesel exhaust

This study deals with the development of a laboratory bench for the practical evaluation of catalysts that are useful for the direct conversion of NO_x and soot in the exhaust of diesel engines. The employed model exhaust is generated by using a diffusion burner with additionally dosing some gaseous components to the burner gas to obtain a realistic feed composition. The produced soot is extensively characterized by employing thermogravimetry, transmission electron microscopy, N₂ physisorption and temperature programmed techniques. The results of the different characterization methods show that the present soot is suitable for the intended catalytic investigations. The simultaneous conversion of NO_x and soot is examined like in practice, i.e. the soot is separated from the tail gas by a diesel particulate filter (DPF) that is coated with the catalyst. The deposited soot is then catalytically converted by NO_x and O₂ to form N₂ and CO₂. The conversions of NO_x and soot are measured by exclusively applying gas analysers, whereby a special experimental procedure is developed to determine the soot removal. Hence, additional soot related analytics are not required. To show the suitability of the constructed bench a Pt/Fe₂O₃/β-zeolite sample is taken as test catalyst that is reported to be very active in NO_x/soot reaction. The measurements performed with and without catalyst clearly show the effect of the used sample in simultaneous NO_x/soot conversion. We therefore consider the constructed laboratory bench to be a useful tool for testing and ranking catalytic materials.     

新型细粒煤分选设备的研究及应用

提出了一种新的细粒煤分选设备,主要介绍了它的结构模型、数学模型、动力学分析以及在贵州老屋基、孝义东兴、山西五阳、黑龙江七台河矿务局等洗煤厂中在煤泥脱水回收作业中的应用,取得了较好的效果。尤其用于简易选煤厂,从煤泥水中回收低灰精煤,既解决了环保污染问题,又取得了较高的经济效益,因而倍受欢迎。     

循环荷载作用下饱和黏性土的弹塑性双面模型

基于作者新近提出的一种混合塑性硬化准则和临界状态土力学理论建立了一个三维形式表述的适于饱和黏性土的弹塑性双面模型,此硬化准则是著名的M asing方法在三维应力空间中的推广。该模型的二维形式已采用饱和黏性土样室内动态三轴不排水剪切试验的结果进行了验证并已在另文发表。本文所建的三维弹塑性动本构模型与一个半经验的孔隙水压力增长模式相结合,通过有限元程序ABAQUS*对一个循环荷载作用下的条形基础下部地基土层内的位移、应力分布和超孔隙水压力随时间的变化进行了分析,计算结果表明模型预测的地基土的力学响应是符合实际的。     

网上协作学习模式研究

主要针对网上协作学习的基本模式、实现方式和存在的问题进行了初步研究。     

Simulation of cup-cone fracture using the cohesive model

The cohesive model is used for the prediction of the crack path during stable crack extension in ductile materials. The problem of crack-path deviation is investigated by means of simulation of crack propagation in a round tensile bar. The respective phenomenon is known as cup-cone fracture. It is shown that the model is able to predict the failure mechanism, which consists of normal fracture in the center and combined normal/shear fracture in the so-called “shear lips” at the specimen’s rim. The damage evolution and crack path predicted by the model are presented. The effect of the normal and shear failure parameters on the crack-deflection point and several aspects of the finite element mesh are discussed.     

基于移动端多天线系统的无线衰落信道模型

根据当前无线移动通信对多天线移动接收端性能仿真的要求，讨论并建立了适于空时信号处理的移动端矢量信道模型。通过分析无线移动信道特点。研究了影响接收信号幅度相位的诸多因素，建立了相应的数学模型。并对随机参数选取进行了探讨。其中考虑到移动端接收信号到达角扩散的特点，采用GBSB椭圆模型产生了适于移动端接收信号仿真的随机角度，改进了一种瑞利衰落生成算法。最后信道的数值仿真结果符合理论和经验。同时，通过TD-SCDMA系统链路级仿真，也证明了该信道模型的有效性。