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。     

基于径向基函数网络的社会消费品总额预测模型

利用BP、RBF神经网络自适应学习法模型,对社会消费品总额进行了预测和研究,结果表明用RBF网络自适应学习法所建立的模型经过训练后,可得到较精确的预测结果,并具有较强的应用性。     

频谱分析的一类新算法

本文指出可替代ＦＦＩ法的一类频谱分析新算法，它们以功率谱形式给出，文中给出一个构造算创并与同类算法作了比较。     

THE CHANGES OF CHILDREN′S BEHAVIOR PROBLEMS IN XI′AN DURING FIVE YEARS FROM 1988 TO 1993

ＢｙｕｓｉｎｇＣＢＣＬ（ＣｈｉｌｄＢｅｈａｖｉｏｒＣｈｅｃｋｌｉｓｔ）ｏｆＸｉ′ａｎｎｏｒｍ，ｔｈｅｃｈｉｌｄｒｅｎ＇ｓｂｅｈａｖｉｏｒｐｒｏｂｌｅｍｓｉｎＸｉ′ａｎｈａｖｅｂｅｅｎｉｎｖｅｓｔｉｇａｔｅｄａｎｄｃｏｍｐａｒｅｄｗｉｔｈｔｈｅｒｅｓｕｌｔｓｏｂｔａｉｎｅｄｂｅｆｏｒｅ１９９３，ｔｈｅｐｏｓｉｔｉｖｅｒｅｓｕｌｔｓｐｒｏｖｉｄｅｓｃｉｅｎｔｉｆｉｃｂａｓｉｓｆｏｒｄｉａｇｎｏｓｉｓａｎｄｒｅｆｅｒｅｎｃｅｆｏｒｔｅａｃｈｅｒｓ．ＭＡＴＥＲＩＡＬＳＡＮＤＭＥＴＨＯＤＳＴｈｅｐｕｐｉｌ…     

Transportation agencies experiences with decision support systems for airport ground access planning

This article reports on a field investigation into the ways that transportation agencies use quantitative and qualitative information for making strategic decisions regarding airport ground access. The study analyzes the value of this information for planning airport ground access improvements at seven major international airport sites.The major finding of the research is that quantitative modeling for strategic decision support is very difficult, costly and time consuming. Modelers are confident that the models are accurate and reliable but executives generally lack confidence in the results. Transportation officials believe that the information supplied is flawed by a number of defects that minimize its value for strategic decision makers. The information defects described in this article provide an analysis of the structural difficulty of using quantitative modeling for transportation problems of strategic importance. To date, qualitative information is not frequently used, but some transportation agencies are considering its application to designing transportation services. Although this study is limited to airport ground access, the authors feel that this evidence, in conjunction with the evidence from other studies in the transportation area, dictates a need for wariness in the development of decision support systems for transportation planners. Developers of decision support systems for transportation planners must be aware of modeling costs and defects and consider how to improve the timeliness, relevance and credibility of information quantitative models provide transportation executives. Fundamentally it is important to recognize that decision makers tend, either singularly or in concert with other individuals or groups, to be the champions of a long-term vision for the community. When modeling produces inconsistent or wide ranging results that contradict their position, decision makers may not only discard modeling activities, but lose confidence in the models altogether. As a consequence, transportation planners are faced with the challenge of how to improve quantitative modeling. The most reliable and effective means for improvement is incorporation of qualitative techniques which provide greater understanding of customer perceptions and human behavior.     

基于时间序列法的舰船运动预报实验研究

采用线性自回归AR模型、具有首前波观测量的ARMA模型以及非线性自回归NAR模型三种方法分别对舰船运动进行预报,将得到的预报结果与实验测量结果进行验证比较,并对最佳预报模式进行讨论.     

全长粘结岩锚抗拔受力特性

根据锚杆与锚固浆之间界面耦合机理,分析了岩锚抗拔状态下界面剪应力的分布特征。基于变形协调得出小荷载情况下界面剪应力随离锚固受力点距离的增大成指数衰减,并随荷载增加,界面出现4个变形段,分离段和残余变形段随着塑性区开展产生非耦应力向远端传递。耦合区界面剪应力分布与小荷载情况不同,其相关模量参数可采用综合折减系数表示。同时,提出了单孔多锚杆受力剪应力衰减模型,并通过试验证示了现场锚杆在荷载逐级加大时,剪应力峰值强度的变化规律。     

混合交通流参数之间关系模型标定

提出了混合交通流参数之间关系模型的标定和超车换道率的计算方法,采用广深高速公路、广佛高速公路和沪宁高速公路的实测数据对模型进行了验证,并计算了各数据点的超车换道率.结果表明,流量、密度数据的相关系数都接近1,超车换道率介于-1和1之间.