中国北方坡面灌木建植方法研究

坡面生态修复成败的关键在于能否在坡面建植出稳定的植物群落,而坡面植物群落稳定性很大程度又取决于灌木的生长情况,因此灌木的建植方法将决定坡面生态修复工作的成败。文章对我国北方坡面灌木建植方法进行分类梳理,并结合工程经验分析各种坡面灌木建植方法的优缺点,力求为坡面生态修复工程实践提供有益的工程参照和技术指导。     

植筋技术在港口工程中的应用

通过对植筋锚固技术的理论分析,系统地提出了植筋锚固的破坏形式、工程经验公式及施工操作的要点,并结合现场试验与检测说明植筋技术在港口工程上的发展应用。     

应用反射波法检测水泥搅拌桩的方法探讨

对水泥搅拌桩反射波法的检测原理进行了讨论，在此基础上，进一步对检测中激振方式、传感器设置以及检测时间的选择进行了探讨，并给出了波形曲线分析和处理的一般方法。     

Inhomogeneous cellular automata modeling for mixed traffic with cars and motorcycles

This paper develops inhomogeneous cellular automata models to elucidate the interacting movements of cars and motorcycles in mixed traffic contexts. The car and motorcycle are represented by non‐identical particle sizes that respectively occupy 6×2 and 2×1 cell units, each of which is 1.25×1.25 meters. Based on the field survey, we establish deterministic cellular automata (CA) rules to govern the particle movements in a two‐dimensional space. The instantaneous positions and speeds for all particles are updated in parallel per second accordingly. The deterministic CA models have been validated by another set of field observed data. To account for the deviations of particles' maximum speeds, we further modify the models with stochastic CA rules. The relationships between flow, cell occupancy (a proxy of density) and speed under different traffic mixtures and road (lane) widths are then elaborated.     

A continuous-flow-intersection-lite design and traffic control for oversaturated bottleneck intersections

Oversaturation has become a severe problem for urban intersections, especially the bottleneck intersections that cause queue spillover and network gridlock. Further improvement of oversaturated arterial traffic using traditional mitigation strategies, which aim to improve intersection capacity by merely adjusting signal control parameters, becomes challenging since exiting strategies may (or already) have reached their “theoretical” limits of optimum. Under such circumstance, several novel unconventional intersection designs, including the well-recognized continuous flow intersection (CFI) design, are originated to improve the capacity at bottleneck intersections. However, the requirement of installing extra sub-intersections in a CFI design would increase vehicular stops and, more critically, is unacceptable in tight urban areas with closed spaced intersections. To address these issues, this research proposes a simplified continuous flow intersection (called CFI-Lite) design that is ideal for arterials with short links. It benefits from the CFI concept to enable simultaneous move of left-turn and through traffic at bottleneck intersections, but does not need installation of sub-intersections. Instead, the upstream intersection is utilized to allocate left-turn traffic to the displaced left-turn lane. It is found that the CFI-Lite design performs superiorly to the conventional design and regular CFI design in terms of bottleneck capacity. Pareto capacity improvement for every traffic stream in an arterial system can be achieved under effortless conditions. Case study using data collected at Foothill Blvd in Los Angeles, CA, shows that the new design is beneficial in more than 90% of the 408 studied cycles. The testing also shows that the average improvements of green bandwidths for the synchronized phases are significant.     

蒸汽动力系统在不同工况下的凝水分配协调性分析

[目的]为满足蒸汽动力系统在不同工况下的使用要求,需开展凝水分配协调性分析和管路优化设计。[方法]基于Flowmaster仿真计算软件,建立凝水系统的管网仿真模型,分析低工况和高工况下的凝水系统压力和流量分配情况,并相应提出降低水柜安装高度和调整系统管路连接方式这2种优化设计方案。[结果]计算结果表明:在低工况下,当凝水系统中节流阀开度30%、循环阀开度45%时,储水量最大为0.128(归一化处理结果),当节流阀开度小于13%时,凝水系统将无法实现储水功能;在高工况下,当凝水系统中节流阀开度90%、循环阀开度18%时,储水量最大为0.404,且凝水系统的分配协调性更好;2种优化设计方案均可有效改善低工况下凝水系统的分配协调性。[结论]研究成果可为实船凝水系统的管路优化设计提供参考。     

ATIS影响下的混合随机用户均衡交通分配模型研究

在考虑信息对出行者路径选择行为影响的基础上,基于路网混合随机用户均衡建模理论,建立了ATIS影响下的混合随机用户均衡交通分配模型,证明了该数学规划模型解的等价性,设计了求解算法,并利用算例进行了计算分析.     

四边形杂交／混合轴对称有限元列式

本文建立了—8—节点四边形轴对称杂交/混合有限单元。该单元不含多余机动模式,无伪剪切现象,能通过补片试验。本单元的各项应力表达式由一次线性完备的应力参数组成,它对坐标取向、单元网格歪斜以及节点编号顺序皆不敏感。数值算例表明,这一单元具有优异的计算精度。     

混合交通流的动力学模型

引入超车换道流量，建立了混合交通流的连续性方程；通过对交通流参数的微分变换,建立了混合交通流的运动微分方程．连续性方程和运动微分方程构成了混合交通流的动力学模型．将模型应用于无超车换道交通流，求出了流量和密度之间的关系．结果表明在低密度段模型与实测数据吻合．     

12—节点杂交／混合Reissner—Mindlin板单元

按杂交/混合有限元方法,根据Reissner-Mindlin板理论,建立了12-节点C~0类板弯曲单元HP 12。数值研究表明,HP 12不含多余机动模式,当趋于薄板极限时,不出现“自锁”,且弯矩与位移响应良好。本文还指出了CH 1单元含有多余机动模式的原因。