基于西门子802D系统的磨床数控化改造

介绍利用西门子公司的数控设备SINUMERIK 802D数控系统对SS-13缓进磨床进行数控改造的方案以及设计内容.     

纳米TiO2涂料在潜艇空气净化中的应用可能性

将具有独特光催化特性的纳米TiO2添加在涂料中可制成具有催化性能的功能型涂料。结合潜艇舱室的实际情况,分别讨论了纳米TiO2涂料在不同初始浓度、光强、湿度、温度、风速等条件下的催化效率,说明了将纳米TiO2涂料应用在潜艇上可以有效地起到催化分解有害气体的作用。同时提出了未来应用中可能出现的问题,并给出了部分解决方法。     

Application of time-variant predictive control to modelling driver steering skill

The paper addresses the need for improved mathematical models of human steering control. A multiple-model structure for a driver's internal model of a nonlinear vehicle is proposed. The multiple-model structure potentially offers a straightforward way to represent a range of driver expertise. The internal model is combined with a model predictive steering controller. The controller generates a steering command through the minimisation of a cost function involving vehicle path error. A study of the controller performance during an aggressive, nonlinear steering manoeuvre is provided. Analysis of the controller performance reveals a reduction in the closed-loop controller bandwidth with increasing tyre saturation and fixed controller gains. A parameter study demonstrates that increasing the multiple-model density, increasing the weights on the path error, and increasing the controller knowledge range all improved the path following accuracy of the controller.     

EVS耦合地层-岩性三维地质建模方法在南宁地铁工程中的应用

为解决地质建模软件Earth Volumetric Studio（EVS）存在的地层建模方法无法对钻孔揭露地层比较复杂的情形进行层序划分，岩性建模方法无法生成连续光滑的层间界面等问题，以南宁市轨道交通3号线青秀山站至博艺路站区间段为研究对象，提出一种同时具有表达复杂透镜体和清晰的地质层面能力的EVS地层-岩性建模方法。通过工程实例将该方法分别与地层建模和岩性建模方法进行对比分析和交叉验证计算，结果表明采用地层-岩性建模方法建立的模型比单独使用地层模型和岩性模型更能反映实际的地质情况，且模型具有更高的精度，模型的相对误差和均方根误差较地层建模方法明显降低。     

基于期望熵的人才流动模型及其选择

Shannon熵可以表示模型不稳定性。本文提出了期望熵的概念并在此基础上建立了人才流动模型。本文还讨论了该模型的选择，并通过抽样调查进行了验证。     

Lead emission rates from gasoline engines—a legislative and in‐use emission rate study of U.K. and U.S. to 1990

Concern for reduction in air‐borne lead emission from passenger cars is focussed on both the legislative and practical steps in reducing lead in gasoline. The historical trends and projections to 1990 of present U.S. and U.K. policies are examined in terms of a baseline passenger car lead emission rate, g.km^‐1. It is likely that should the U.K. adopt a lead‐free petrol the decrease in lead emissions will only partially parallel the present U.S. experience from a start‐up date typically post 1990. The U.S. gasoline pool philosophy has permitted lead levels in gasoline to remain high; a pitfall which the U.K./EEC should avoid.     

DP盖帽混凝土本构模型二次开发及边坡加固工程应用

基于有限元计算软件的二次开发技术,提出一种新型的DP盖帽混凝土本构模型,并结合某边坡置换洞加固工程实例,建立其边坡潜在滑块三维有限元模型,分别采用DP模型与DP盖帽模型分析置换洞的弹塑性破坏程度,对比分析评价其加固效应。研究发现:新开发的DP盖帽模型可成功应用于软件计算中;采用DP模型计算所得安全系数约1.45,采用DP盖帽模型计算所得安全系数约1.41,说明在置换洞加固后存在部分双轴压坏和少量三轴压坏情况,且证明DP盖帽模型能够比DP模型更为精准地考虑混凝土破坏情况,可以为类似工程提供参考依据。     

干湿交替条件下膨胀围岩隧道的力学性态研究

以广西南宁膨胀土为围岩材料,制作室内膨胀围岩隧道物理模型。通过对隧道模型进行干湿循环试验,得出围岩在吸水及失水条件下的围岩应力-时间关系曲线及衬砌应变-时间关系曲线。试验认为在吸水过程中大部分测点的围岩压力都经历了增长、减小、不同速率的再增长3个阶段。衬砌变形则经历缓慢增长、急剧增长、急剧减小、微增长4个阶段;在失水过程中,从整体上可以将围岩压力变化分为两部分,即围岩失水收缩致使衬砌和围岩的接触压力下降导致围岩应力值减小以及土体收缩产生收缩应力导致应力监测值增大。并分析这种变化规律的形成机理,证明时间效应和空间效应的存在。为今后膨胀围岩隧道的结构设计和施工优化提供一定的理论参考。     

A new estimation approach for the multiple discrete–continuous probit (MDCP) choice model

This paper develops a blueprint (complete with matrix notation) to apply Bhat’s (2011) Maximum Approximate Composite Marginal Likelihood (MACML) inference approach for the estimation of cross-sectional as well as panel multiple discrete–continuous probit (MDCP) models. A simulation exercise is undertaken to evaluate the ability of the proposed approach to recover parameters from a cross-sectional MDCP model. The results show that the MACML approach does very well in recovering parameters, as well as appears to accurately capture the curvature of the Hessian of the log-likelihood function. The paper also demonstrates the application of the proposed approach through a study of individuals’ recreational (i.e., long distance leisure) choice among alternative destination locations and the number of trips to each recreational destination location, using data drawn from the 2004 to 2005 Michigan statewide household travel survey.     

动力湿化作用下粗粒土高路堤渗流场时空演化模型试验

为了研究动力湿化作用下渗流水在粗粒土高路堤内的迁移特性，自主研发设计制作一种室内喷洒降雨装置及车辆动力荷载模拟装置，开展动力湿化作用下粗粒土高路堤渗流场时空演化模型试验，从时间和空间2个角度描述渗流水在路堤内的迁移特性，然后根据模型试验结果，建立粗粒土渗流场时空演化机制，揭示动力湿化作用下的粗粒土高路堤边坡渐变失稳发育机理。研究结果表明：基于相似理论，开展粗粒土高路堤渗流场时空演化模型试验可以较为真实地反映粗粒土高路堤在动力湿化作用下渗流水的迁移特性；动力湿化作用下，湿润锋首先在路堤边坡表面形成，并逐渐从边坡表面向内部拓展，在坡顶处的拓展速率较小，坡脚处的拓展速率较大；受湿润锋演变规律的影响，路堤边坡监测点负孔隙水压力逐渐减小，体积含水率逐渐增大，坡前应力逐渐增加，位于坡脚浅层区域的应力增加速度较快；依据渗流水的迁移规律，将渗流影响范围内的土体自上而下分为浅层暂态饱和区、渗流水填充区及渗流水湿润区；在动力湿化作用下，粗粒土高路堤边坡将逐渐产生沿坡脚深层滑移的渐变趋势。