基于存活概率的动态车龄分布模型

城市车辆的年龄组成(简称车龄分布)是体现城市车辆老化程度和确定车辆报废年限的重要指标。目前已有的车龄分布算法要求数据量大,在我国大部分城市很难得到完整的数据。笔者提出一种符合威布尔分布的车辆存活概率算法。该算法根据车辆保有量数据和报废车辆总数(或新车数据)推导出各年的车龄分布,且能够动态预测将来年份的车龄分布。同时,利用北京市小客数据对算法进行了实例应用,证明该法的实用可行性。由于该算法所需数据量小,计算简便,特别适用于我国在用车统计不完备的地区,利用该算法根据有限的数据来推导出当地的车龄分布,具有通用性。该算法的有效性检验和敏感度分析需进一步研究。     

车辆碰撞特性的数值仿真及试验研究

运用显式动态有限元方法建立了某车辆的有限元模型 ,按照国家标准对整车进行了正面碰撞仿真计算和实车正面碰撞试验。通过仿真计算和实验的对比分析 ,其结果表明 :仿真计算的变形结果和试验吻合较好 ,车身上一些主要部位的加速度曲线在趋势上也基本吻合 ,说明运用有限元法进行车辆的仿真切实可行。分析结果为车辆的安全性设计提供了参考依据。     

Characteristics and anthropogenic sources of carbonyl sulfide in Beijing

Atmosphericmixing ratios of carbonyl sulfide (COS) in Beijingwere intensivelymeasured from March 2011 to June 2013. COS mixing ratios exhibited distinct seasonal variation, with a maximumaverage value of 849 ± 477 pptv in winter and a minimal value of 372 ± 115 pptv in summer. The seasonal variation of COS was mainly ascribed to the combined effects of vegetation uptake and anthropogenic emissions. Two types of significant linear correlations (R² > 0.66) were found between COS and CO during the periods from May to June and from October to March, with slopes (ΔCOS/ΔCO) of 0.72 and 0.14 pptv/ppbv, respectively. Based on the emission ratios of COS/CO from various sources, the dominant anthropogenic sources of COS in Beijing were found to be vehicle tire wear in summer and coal burning in winter. The total anthropogenic emission of COS in Beijing was roughly estimated as 0.53 ± 0.02 Gg/year based on the local CO emission inventory and the ΔCOS/ΔCO ratios.     

Buses retrofitting with diesel particle filters: Real-world fuel economy and roadworthiness test considerations

Retrofitting older vehicles with diesel particulate filter(DPF) is a cost-effective measure to quickly and efficiently reduce particulate matter emissions. This study experimentally analyzes real-world performance of buses retrofitted with CRT DPFs. 18 in-use Euro III technology urban and intercity buses were investigated for a period of 12 months. The influence of the DPF and of the vehicle natural aging on buses fuel economy are analyzed and discussed. While the effect of natural deterioration is about 1.2%–1.3%, DPF contribution to fuel economy penalty is found to be 0.6% to 1.8%, depending on the bus type. DPF filtration efficiency is analyzed throughout the study and found to be in average 96% in the size range of 23–560 nm. Four different load and non-load engine operating modes are investigated on their appropriateness for roadworthiness tests. High idle is found to be the most suitable regime for PN diagnostics considering particle number filtration efficiency.     

Characteristics of the pollutant emissions in a tunnel of Shanghai on a weekday

Tunnel displays a typical semi-closed environment, and multitudes of the pollutants tend to accumulate. The samples of gaseous pollutants and particulate matter(PM) were collected from the Xiangyin tunnel at Shanghai to investigate the characteristics of the pollutant emissions. The results indicated that both gaseous pollutants and PM exhibited much higher concentrations during the rush hours in the morning and at night due to vehicle emission. Two peaks of the PM concentration were observed in the scope of 0.7‐1.1 and 3.3–4.7 μm, accounting for 14.6% and 20.3% of the total concentrations, respectively.Organic matter(OM), EC, and many water-soluble ions were markedly higher at the rush hours in the morning than those at night, implicating comprehensive effects of vehicle types and traffic volume. The particle number concentrations exhibited two peaks at Aitken mode(25 nm and 100 nm) and accumulation mode(600 nm), while the particle volume concentration displayed high values at the accumulation mode(100–500 nm) and coarse mode(2.5–4.0 μm). The peak around 100 nm was detected in the morning rush hours, but it diminished with the decrease of the traffic volume. Individual-particle analysis revealed that main particles in the tunnel were Fe-rich particles, K-rich particles, mineral particles,Ca–S rich particles and Al–Si particles. The particles collected at the rush hours displayed marked different morphologies, element concentrations and particle sizes compared to the ones collected at the non-rush period. The data presented herein could shed a light on the feature of vehicle emissions.     

Estimation and validation of PM2.5/PM10 exhaust and non-exhaust emission factors for practical street pollution modelling

In order to carry out efficient traffic and air quality management, validated models and PM emission estimates are needed. This paper compares current available emission factor estimates for PM₁₀ and PM_2.5 from emission databases and different emission models, and validates these against eight high quality street pollution measurements in Denmark, Sweden, Germany, Finland and Austria.The data sets show large variation of the PM concentration and emission factors with season and with location. Consistently at all roads the PM₁₀ and PM_2.5 emission factors are lower in the summer month than the rest of the year. For example, PM₁₀ emission factors are in average 5–45% lower during the month 6–10 compared to the annual average.The range of observed total emission factors (including non-exhaust emissions) for the different sites during summer conditions are 80–130 mg km⁻¹ for PM₁₀, 30–60 mg km⁻¹ for PM_2.5 and 20–50 mg km⁻¹ for the exhaust emissions.We present two different strategies regarding modelling of PM emissions: (1) For Nordic conditions with strong seasonal variations due to studded tyres and the use of sand/salt as anti-skid treatment a time varying emission model is needed. An empirical model accounting for these Nordic conditions was previously developed in Sweden. (2) For other roads with a less pronounced seasonal variation (e.g. in Denmark, Germany, Austria) methods using a constant emission factor maybe appropriate. Two models are presented here.Further, we apply the different emission models to data sets outside the original countries. For example, we apply the “Swedish” model for two streets without studded tyre usage and the “German” model for Nordic data sets. The “Swedish” empirical model performs best for streets with studded tyre use, but was not able to improve the correlation versus measurements in comparison to using constant emission factors for the Danish side. The “German” method performed well for the streets without clear seasonal variation and reproduces the summer conditions for streets with pronounced seasonal variation. However, the seasonal variation of PM emission factors can be important even for countries not using studded tyres, e.g. in areas with cold weather and snow events using sand and de-icing materials. Here a constant emission factor probably will under-estimate the 90-percentiles and therefore a time varying emission model need to be used or developed for such areas.All emission factor models consistently indicate that a large part (about 50–85% depending on the location) of the total PM₁₀ emissions originates from non-exhaust emissions. This implies that reduction measures for the exhaust part of the vehicle emissions will only have a limited effect on ambient PM₁₀ levels.     

机动车尾气控制策略效益综合评价指标体系

针对当前国内外缺乏系统的尾气控制策略效益评价方法,本文建立了微观、中观、宏观三个层次的尾气控制策略效益综合评价指标体系,分别从环境效益和经济效益两方面对静态、动态及综合尾气控制策略的效益进行评价,该指标体系的建立对于尾气控制策略效益分析具有一定的理论及实践意义。     

气浮-水解酸化-高效接触氧化工艺处理汽车废水

对某汽车公司的废水处理系统进行了改造,采用气浮-水解酸化-高效接触氧化工艺对其废水进行了处理,在水解酸化池中使用生物微电解填料,在接触氧化池内使用LK40弹性立体网状生物亲和性组合填料.经该体系处理后,出水水质为pH=6～9、SS＜60mg/L、CODCr＜90mg/L、BOD5＜20mg/L、石油类＜5mg/L,达到DB44/26-2001中一级标准,其处理费用为1.91元/m3.     

系留气球垂直观测平台的构建与应用

利用1 600 m~3车载系留气球,构建大气复合型污染垂直观测平台。利用该平台对近地大气边界层的多种气象要素、多种污染物浓度水平及其物理化学特性进行高分辨的垂直测量,用以研究大气边界层的形成和演变及大气污染物垂直分布和变化特征、大气光化学过程的垂直变化以及污染物的区域输送。该平台以0.5 m/s的速度进行升降,于2013年12月在上海成功应用于大气污染垂直观测,观测中共获取大气污染物有效廓线50余组。利用观测数据,初步探索上海近地层复合型大气污染的生消机制及大气污染物垂直分布特征,为上海市空气污染预警和防控对策机制的制定提供技术支撑。     

The effects of daylight saving time on vehicle crashes in Minnesota

Introduction: Daylight saving time (DST), implemented as an energy saving policy, impacts many other aspects of life; one is road safety. Based on vehicle crash data in Minnesota from 2001 to 2007, this paper evaluates long- and short-term effects of DST on daily vehicle crashes. Method: To provide evidence to explain the causes of more/fewer crashes in DST, we examine the impact of DST on crashes in four periods of a day: 3 a.m.-9 a.m., 9 a.m.-3 p.m., 3 p.m.-9 p.m., 9 p.m.-midnight. The effects of risk and exposure to traffic are also separated. Our statistical models not only include weather conditions and dummy variables for days in DST as independent variables, but also consider traffic volumes on major roads in different periods of a day. Our major finding is that the short-term effect of DST on crashes on the morning of the first DST is not statistically significant. Moreover, it is interesting to notice that while DST per se is associated with fewer crashes during dusk, this is in part offset because it is also associated with more traffic on roads (and hence more crashes). Our path analysis shows that overall DST reduces crashes. Impact on industry: Daylight saving time can lead to fewer crashes on roads by providing better visibility for drivers.