A framework to evaluate policy options for supporting electric vehicles in urban freight transport

Electric vehicles (EVs) are considered as a feasible alternative to traditional vehicles. Few studies have addressed the impacts of policies supporting EVs in urban freight transport. To cast light on this topic, we established a framework combining an optimization model with economic analysis to determine the optimal behavior of an individual delivery service provider company and social impacts (e.g., externalities and welfare) in response to policies designed to support EVs, such as purchase subsidy, limited access (zone fee) to congestion/low-emission zones with exemptions for EVs, and vehicle taxes with exemptions for EVs. Numerical experiments showed that the zone fee can increase the company’s total logistics costs but improve the social welfare. It greatly reduced the external cost inside the congestion/low-emission zone with a high population, dense pollution, and heavy traffic. The vehicle taxes and subsidy were found to have the same influence on the company and society, although they have different effects with low tax/subsidy rates because their different effects on vehicle routing plans. Finally, we performed a sensitivity analysis. Local factors at the company and city levels (e.g., types of vehicle and transport network) are also important to designing efficient policies for urban logistics that support EVs.     

Time-dependent drivers’ merging behavior model in work zone merging areas

This study investigates the drivers’ merging behavior in work zone merging areas during the entire merging implementation period from the time of starting a merging maneuver to that of completing the maneuver. With the actual work zone merging traffic data, we propose a time-dependent logistic regression model considering the possible time-varying effects of influencing factors, and a standard logistic regression model for the purpose of model comparison. Model comparison results show that the time-dependent model performs better than the standard model because the former can provide higher prediction accuracy. The time-dependent model results show that seven factors exhibit time-varying effects on the drivers’ merging behavior, including merging vehicle speed, through lane lead vehicle speed and through lane lag vehicle speed, longitudinal gap between the merging and lead vehicles, longitudinal gap between the merging and through lane lead vehicles, types of through lane lead and through lane lag vehicles. Interestingly, both the through lane lead vehicle speed and the through lane lag vehicle speed are found to exhibit heterogeneous effects at different times of the merging implementation period. One important finding from this study is that the merging vehicle has a decreasing willingness to take the choice of “complete a merging maneuver” as the elapsed time increases if the through lane lead vehicle is a heavy vehicle.     

冰区船舶操纵

本文详细分析了船舶在冰区航行时靠离码头，冰流中锚泊，冰中救助等冰区船舶操纵特殊情况，并总结经验。其对船舶在冰区安全航行具有很好指导意义。     

Microbial community structure in the marginal ice zone of the Bellingshausen Sea

Phytoplankton, bacteria and microzooplankton were investigated on a transect in the Bellingshausen Sea during the ice melt period in November–December 1992. The transect along the 85°W meridian comprised seven stations that progressed from solid pack-ice (70°S), through melting ice into open water (67°S). The abundance, biomass and taxonomic composition were determined for each component of the microbial community. The phytoplankton was mostly dominated by diatoms, particularly small (<20 μm) species. Diatom abundance ranged from 66 000 cells l⁻¹ under the ice to 410 000 cells l⁻¹ in open water. Phytoplankton biomass varied from <1 to 167 mg C m⁻³, with diatoms comprising 89–95% of the total biomass in open water and autotrophic nanoflagellates comprising 57% under the ice. The standing stocks of autotrophs in the mixed layer ranged from 95 mg C m⁻² under the pack-ice to 9478 mg C m⁻² in open waters. Bacterial abundance in ice-covered and open water stations varied from 1.1 to 5.5×10⁸ cells l⁻¹. Bacterial biomass ranged from 2.4 mg C m⁻³ under pack-ice to an average of 14 mg C m⁻³ in open water. The microzooplankton consisted mainly of aloricate oligotrich ciliates and heterotrophic dinoflagellates and these were most abundant in open waters. Their biomass varied between 0.2 and 54 mg C m⁻³ with a minimum at depth under the ice and maximum in open surface waters. Microheterotrophic standing stocks varied between 396 mg C m⁻² under pack-ice and 3677 mg C m⁻² in the open waters. The standing stocks of the total microbial community increased consistently from 491 mg C m⁻² at the ice station to 13 155 mg C m⁻² in open waters, reflecting the productive response of the community to ice-melt. The composition of the microbial community also shifted markedly from one dominated by heterotrophs (82% of microbial stocks) at the ice station to one dominated by autotrophs (73% of microbial stocks) in the open water. Our estimates suggest that the microbial community comprised >100% of the total particulate organic carbon (POC) under the ice and 62–66% of the measured POC in the open waters.     

多年冻土路基工程技术探索与实践

简要总结了自上世纪六七十年代以来青藏铁路多年冻土路基工程技术探索与实践过程,认为青藏铁路多年冻土路基设计应以冻土地基稳定为核心,依据冻土年平均地温、含冰量、不良冻土现象及水文地质等,考虑全球气温升高及其他因素的影响,以科学试验为指导,采取主动保护冻土的措施动态设计,为列车快速通过高原提供技术保证。     

青藏高原东部香日德—花石峡公路工程多年冻土分布特征分析

研究目的:拟建香日德—花石峡公路位于青海省境内,全长156.61 km,起点在香日德与G109线连接,终点至花石峡与G214线国道连接。其中K 88+200~K 156+610段长68.41 km,大部分海拔4 000 m以上,最高在挝卓依垭口,海拔4 445.647 m;本段线路位于青藏高原东部,多年冻土发育的边缘地带,本文通过勘察资料分析,得出沿线多年冻土分布特征并分析其变化规律。研究结论:通过对本段线路的勘察资料分析表明:本段多年冻土和海拔高度有很好的相关性,主要分布在挝卓依垭山垭口前后海拔4 200 m以上路段,局部海拔在4 000~4 200 m湖相沉积细粒土地段存在残余多年冻土。沿线整段多年冻土处于退化状态,且北坡较南坡年平均低温低,南坡多年冻土退化严重。     

贵广线天平山隧道软岩变形分析

研究目的:软岩变形预测及监测是铁路工程地质中一项复杂而又重要的工作,寻求一种有效的预测及监测方法具有重要的意义。研究结论:针对天平山隧道的软岩变形问题,勘察阶段已经有了较为充分的认识,并为此开展了综合勘探,从岩性、构造、地应力等方面对隧道开挖所经受的变形范围及程度进行了详细的分析。从目前开挖情况看,2号斜井及相应正洞穿过下朝塘断裂带变形预测较为合理,而页岩为主夹炭质页岩段的变形预测还有待开挖对比。     

混凝土水化热对寒区隧道围岩融化及回冻过程的影响

混凝土水化热是导致围岩融化的主要热量来源之一,不同水化热放热方程(不同放热速率)对结果影响较大。本文以昆仑山隧道为例,利用有限单元法计算考虑混凝土水化热及其放热过程和不考虑水化热的隧道围岩融化回冻过程,分析水化热对围岩融化、回冻过程的影响。2种工况计算中均考虑施工过程、隧道衬砌内缘温度变化、防水隔热保温层、入模温度、相变等因素。结果表明:在寒区隧道围岩施工过程中,混凝土水化热增加了围岩的最大融化深度,同时使围岩温度升高;考虑混凝土水化热影响寒区隧道围岩回冻时间比不考虑水化热情况晚1年。     

高地应力断层破碎带衬砌力学特性对比与分析

以高地应力区某穿越断层破碎带隧道为工程依托,通过三维数值模拟来分析随着掌子面推进过程中的围岩空间应力场的状态及其变化趋势。首先,根据弹性衬砌模型计算结果判断衬砌结构是否还处于弹性状态;其次,按照弹塑性衬砌模型进行某穿越高地应力断层破碎带隧道三维数值模拟。计算结果表明:高地应力区穿越断层破碎带隧道三维数值模拟应该采用弹塑性衬砌结构;弹性计算模型与摩尔—伦计算模型分别计算所得衬砌结构关键点位移量差别较大,弹性衬砌模型计算得到关键点位移均小于摩尔—库伦衬砌模型所得到的量值,且约为摩尔—库伦模型计算所得量值的50%;拱顶和拱腰主应力波动范围在掌子面通过z=-50 m平面前0.5B(B为隧道宽度)和通过后1.5B范围,墙脚主应力波动范围在掌子面通过前1B和通过后0.5B范围;弹塑性衬砌计算的主应力较弹性衬砌计算的主应力大;揭示了某穿越高地应力断层破碎带隧道衬砌的破坏形式与潜在破坏面。     

故障模式下通过CBTC控区边界的分析

CBTC(基于通信的列车控制)系统普遍采用分布式的移动授权管理架构,不同的移动授权单元控制不同的控区。介绍了正常模式下通信列车通过控区边界的过程,逐一分析了非通信列车在接车控区MAU(移动授权单元)发生故障、发车控区MAU发生故障及两个连续控区MAU均发生故障模式下的系统反应;并论述了在分布式移动授权管理架构运用过程中涉及到的跨控区列车运行的管理问题,最终提出相应的系统解决方案。