公路隧道通风CO、烟雾基准排放量折减率研究

针对公路隧道通风设计环节需风量计算是整个设计的基本依据,而计算中CO及烟雾基准排放量折减率的取值对远期需风量影响很大这一特点,列举分析机动车排放污染物组成、欧盟汽车排放标准限制值以及PIARC对机动车的排放规定,得出我国汽车排放标准沿袭欧盟法规的进度和实施现行排放标准的4个阶段时间划分。通过对CO、烟雾年折减系数取值以及CO、烟雾基准排放量折减的分析,结合国内严格的排放限制无论从国内外环保要求,还是汽车工业技术的发展进步以及法律法规的规定,目前我国《公路隧道通风照明设计规范》所规定的1%~2%年折减率均是偏于保守的,在实际隧道通风设计中应综合分析,因"隧"制宜,将需风量在保证运营安全的情况下控制在合理的范围内。     

基于三点弯曲试验的ATB-25弯拉特性的研究

通过沥青稳定碎石基层ATB-25沥青混合料的三点弯曲试验,研究了温度及加载速率对弯拉强度、弯拉应变及弯曲劲度模量的影响规律。在较大试验温度范围内,施加两组加载速率对ATB-25沥青混合料小梁试件的弯拉特性进行试验研究。结果表明:高加载速率条件下试件破坏的弯拉强度大于低加载速率下的弯拉强度;温度越高,高低荷载速率之间的弯拉强度差别越大。低荷载速率条件下的弯拉应变约为高荷载速率下的1.5~2.5倍,且在温度低于25℃时,小梁试件的弯拉应变与温度之间有较好的指数变化规律。同时,其弯曲劲度模量与温度之间也呈现良好的指数关系。对比分析了高低荷载速率条件下的指数回归方程参数,表明了低荷载速率条件下的ATB-25沥青混合料表现出较佳的抗裂性能。通过对小梁试件破坏前的弯曲应变能的计算,可得知其在常温域(15℃)附近具有最大的弯曲应变能。     

基于Gram-Schmidt正交化法的串行干扰消除算法

基于Gram-Schmidt正交化法,提出了一种改进的串行干扰消除算法.不同于传统的串行干扰消除算法,该算法运用Gram-Schmidt正交化法,通过扩频序列获取正交序列作为最优解扩码,使得检测器每一级最强用户的解扩码与其他用户的扩频码所张的子空间正交,从而实现对多址干扰的完全抑制.给出了具有幅度失配的系统误码率近似公式,讨论了幅度失配对检测性能的影响.仿真结果表明,改进算法能有效抑制CDMA系统中的多址干扰,改善系统性能.     

Probe vehicle lane identification for queue length estimation at intersections

Vehicles instrumented with Global Positioning Systems, also known as GPS probe vehicles, have become increasingly popular for collecting traffic flow data. Previous studies have explored the probe vehicle data for estimating speeds and travel time; however, there is very limited research on predicting queue dynamics from such data. In this research, a methodology was developed for identifying the lane position of the GPS-instrumented vehicles when they are standing in the queue at signalized intersections with multiple lanes, particularly in the case of unequal queue. Various supervised and unsupervised clustering methods were tested on data generated from a microsimulation model. Among the tested methods, the Optimal Bayes Rule that utilizes probability density functions estimated using bivariate statistical mixture models was found to be effective in identifying the lanes. The methodology for lane identification was tested for queue length estimation. This research confirms that the lane identification is an important step required prior to the queue length estimation. The accuracies of the models for lane identification and queue length estimation were evaluated at varying levels of demand and probe vehicle market penetrations. In general, as the market penetration increases, the accuracy improves as expected. The result shows that 40% market penetration rate is adequate to reach about 90% accuracy.     

基于RBF网络的醋酸乙烯聚合率软测量研究

针对目前聚乙烯醇生产过程中醋酸乙烯（VAC）聚合率难以在线检测的情况,提出利用RBF神经网络建立VAC聚合率软测量模型,并运用大量实测数据对RBF神经网络进行了训练和仿真．仿真结果表明该方法是有效的,所建模型具有较高的精度和良好的泛化能力．     

浅谈混凝土及砂浆中掺加粉煤灰技术的应用

在点岱沟至南坪工业广场铁路专用线工程中,由于混凝土及浆砌片石量比较大,通过在混凝土和砂浆中适量掺加粉煤灰取得了较好的经济效果.     

公路隧道通风需风量计算中车密度系数的讨论

对《公路隧道通风照明设计规范》(JTJ 026.1—1999)中的车密度系数进行讨论,推导了不同情况下,机动车在隧道内行驶路程的表达式;证明了一定交通量下的机动车在隧道内行驶路程与车密度无关,即交通量一定时公路隧道通风需风量与车密度与无关。又讨论了交通量与车速的关系,指出车密度系数实际上是对不同速度交通量的修正,所以此系数的意义和取值需要重新考虑。     

Correlations between industrial demands (direct and total) for communications and transportation in the U.S. economy 1947–1997

Using input–output (I–O) accounts provided by the U.S. Department of Commerce, this study investigates the aggregate relationships between the transportation and communications inputs demanded (directly and in total) by all industries in the U.S., and compares the results across time. We analyzed five pairs of Spearman correlations of transportation and communications demands (utilities, manufacturing, and overall) using the direct and total coefficient tables from the ten benchmark input–output years spanning 1947 to 1997. To correctly represent the overall economy-wide relationship, each industry (direct table) or commodity (total table) in the correlation was weighted proportionately to the monetary value of its contribution to the U.S. economy. In the analysis using direct I–O coefficients, we found a pattern of predominant complementarity between transportation and communications manufacturing, and substitution between transportation and communications utilities. There are intriguing indications, however, of a shift from substitution to complementarity in the latter case, beginning around 1987. In the analysis using total I–O coefficients, we found a pattern of complementarity for all years between transportation and communications manufacturing, and a pattern changing from substitution to complementarity for the remaining four pairs (transportation manufacturing and communications utilities; transportation utilities and communications manufacturing; the utilities pair; and the overall pair). Thus, from the industrial perspective (which constitutes a sizable proportion of the total demand for communications and transportation), it is not realistic in modern times to expect telecommunications to substitute for travel. Nevertheless, further research is needed into the specific causes of the observed shift from substitution to complementarity, and current trends should continue to be monitored for any changes.

广义疲劳裂纹扩展模型在单一过载疲劳问题中的应用

对于复杂载荷作用下的船舶及海洋工程结构物,至今仍没有一个统一的疲劳寿命预报模型能够很好地解释载荷次序效应的影响.单峰过载下的疲劳裂纹扩展问题是研究变幅载荷疲劳问题的基础,伴随单峰过载将出现疲劳裂纹扩展迟滞现象.课题组所提出的广义疲劳裂纹扩展模型能够定量地预报出过载迟滞这一现象,通过确定过载参数β的大小,能够有效地衡量出过载迟滞的程度.在此基础上,文章将广义的疲劳裂纹扩展模型进行了进一步的修正,通过引入一个幂指数项,使得模型能够更好地反映出过载后疲劳裂纹扩展速率由迟滞的最低点逐渐恢复到过载前的水平.文中将课题组所发展的广义疲劳裂纹扩展率模型应用于实际的单峰过载疲劳问题中,并引用铝合金D16Cz的单峰过载试验数据与模型预报结果进行了比较,结果发现,经修正的广义疲劳裂纹扩展模型能够更好地反映出单峰过载后的疲劳裂纹扩展情况.     

组合涡诱导结构对某型燃烧室性能影响的分析

为解决某型燃气轮机间冷改造后环形燃烧室在高容热强度下燃烧效果不理想的问题,提出组合涡诱导结构,并通过数值模拟,研究该结构中的主要结构参数(波瓣高宽比、波瓣数和波瓣长度)对燃烧室性能的影响规律.结果表明:1)组合涡诱导结构可以明显改善高容热强度下的燃烧性能,具有较好的应用前景;2)随着高宽比的增加,燃烧效率逐渐降低,总压损失系数基本保持不变;3)随着波瓣数的增加,总压损失系数、出口平均温度和NOx排放均逐渐增大;4)随波瓣长度的增加,燃烧效率、NOx排放和出口平均温度均逐渐增大,总压损失基本保持不变.上述结论可为后续该型号燃气轮机燃烧室的数值计算和设计提供参考.