Characteristics of gaseous and particulate pollutants exhaust from logistics transportation vehicle on real-world conditions

On-road vehicle tests of three heavy duty diesel trucks were conducted by a portable emission measurement system (PEMS) in Chengdu, China. SEMTECH-ECOSTAR provided by Sensors Inc. was employed to detect gaseous emissions and MI2, an emissions measuring instrument powered by the Pegasor Particulate Sensor (PPS) was used to detect particulate emissions during the tests. The impacts of speed, acceleration and engine load on emissions were analyzed. The average nitrogen oxides (NOx) emission factors of the heavy duty diesel truck (HDDT), medium-duty diesel truck (MDDT), light duty diesel truck (LDDT) were 7.29, 5.29 and 5.53 g/km. The particulate emission factors were 0.60, 0.30 and 0.14 g/km respectively, higher than the similar reported in the previous studies. Both gaseous and particulate emission exhibit significant correlations with the change in vehicle speed, acceleration and power demand. The highest emission was generally in high VSPs and higher loads. High engine load caused by aggressive driving was the main factor of high emissions for the vehicles on real-world conditions.     

转向架撒砂装置随机振动疲劳分析与状态监测研究

转向架撒砂装置在服役过程中承受来自轮轨的随机振动激扰,其与轴箱体螺纹连接的部位可能出现松脱甚至断裂。文章一方面通过结合模态计算与模态试验对标研究,校验有限元模型,获得模态参数,并综合随机响应分析和疲劳应力评估的Dirlik模型,研究基于模态分析的随机振动疲劳分析方法;另一方面,为增加撒砂装置服役安全,研究了一种基于光纤光栅的状态监测技术,并在台架试验上进行了验证,在设计上保障了撒砂装置的服役安全。     

Development of distress condition index of asphalt pavements using LTPP data through structural equation modeling

Traditional pavement distress index such as the Pavement Condition Index (PCI) developed by U.S. Army Corps of Engineers determines coefficients of distresses based on subjective ratings. This study proposed an asphalt pavement distress condition index based on various types of distress data collected from the Long-Term Pavement Performance (LTPP) database through Structural Equation Modeling (SEM). The SEM method treated the overall distress index as a latent variable while various distresses were treated as endogenous and other influence factors such as age, layer thickness, material type, weather, environment and traffic, were exogenous observed variables. The SEM method modeled the contributions of various distresses as well as the influence of other factors on the overall pavement distress condition. Influences of age, layer thickness, material type, environment and traffic on the latent distress condition were in accordance with previous studies. Compared with previous attempts to model latent pavement condition index utilizing SEM method, more pavement condition measurements and influencing factors were included. Specifically, this study adopted the robust maximum likelihood estimator (MLR) to estimate parameters for non-normally distributed data and derived the explicit expression of latent variables with intercepts. A multiple regression prediction model was built to calculate an overall condition index utilizing those measured distress data. The established pavement distress index prediction model provided a rational estimation of weighting coefficients for each distress type. The prediction model showed that alligator cracking, longitudinal cracking in wheel path, non-wheel path longitudinal cracking, transverse cracking, block cracking, edge cracking, patch and bleeding were significant for the latent pavement distress index.     

城市轨道交通发展条件的指标体系研究

分析我国现行的城市轨道交通发展条件指标存在的问题,提出基于需求、可能及建设能力分析的城市轨道交通发展指标体系,并进行筛选。在此基础上,将城市轨道交通发展条件指标分为发展条件指标和项目建设条件指标两大类。经研究分析,确定发展条件指标为城市市区常住人口和市辖区地方财政一般预算收入2个指标,作为国家审批各城市轨道交通近期建设规划的约束性指标;项目建设条件指标包括高峰小时单向最大断面客流量、线路各期客运强度、规划建设期内地方政府资本金出资额占地方财政一般预算财政收入的比例以及全部出资额占城市维护建设财政性资金收入的比例等4个指标,作为近期项目必须上报和评估的参考标准。     

北京市公路特殊路段防撞护栏碰撞试验条件研究

现行公路规范规定护栏最高防撞能量为520 kJ,不能满足水资源保护区、水库、跨越干线铁路等特殊危险路段的安全防护需要,通过对北京市各高速公路交通流状况调查分析,对特殊路段护栏碰撞能量和碰撞试验条件进行研究,提出适合北京地区特殊防护路段护栏的碰撞试验条件为33 t重大货车以65 km/h速度、20°角碰撞护栏,碰撞能量为630 kJ,为新型高防护等级护栏的研究开发奠定基础。     

泉厦高速公路路况评价

泉州-厦门高速公路改扩建前路况差，交通堵塞严重。为了从根本上解决这一问题，对路面状况进行调查，收集历年养护资料，查明破损原因，为改扩建设计方案提供可靠的依据，同时也为类似工程提供参考。     

信息化条件下炮兵精确打击毁伤评估研究

分析了信息化条件下炮兵精确打击毁伤评估的特点与要求,并对信息化条件下炮兵精确打击毁伤评估模型进行了分析,最终得出在信息化战场上,对炮兵精确打击进行科学的毁伤评估,可以保证火力资源在作战过程中实现优化分配,对炮兵指挥提供科学的决策依据。     

隧道工程浅埋暗挖法施工要点

明确了浅埋地下工程的基础概念,阐述了浅埋暗挖法的基本原理及发展方向,指出了浅埋暗挖法的施工原则。同时对浅埋暗挖各施工方法（全断面法、台阶法、中隔墙法和交叉中隔墙法、双侧壁导坑法、双CD法及特大断面的施工方法包括中洞法、柱洞法、侧洞法和桩柱法）的施工要点,适用范围及条件,优缺点进行了介绍和比较。最后总结强调了浅埋暗挖法施工要点。     

基于液体交换的船舶破舱时域模拟

文章将船舶进水时域过程作为拟静态处理,计算出每个时刻的内外液体交换量,然后使用损失浮力法求解浮态方程计算该时刻的船舶浮态,直到进水过程终止.提出了一种适用于破口内外液体密度不同且互不相溶时计算液体交换的方法,给出了不同粘度液体的流量系数回归方程,并且针对一艘液货船破损后内外液体的交换情况进行了计算.提出的方法可以为破损船舶的救援以及防污染工作提供很大帮助.     

爆破技术在公路路基施工中的应用

在地质复杂的公路建设中需要应用爆破技术，以保证施工进度及施工质量。鉴于此，结合实际案例。对多边界条件下爆破技术进行分析，探讨爆破技术在公路路基施工中的应用，可为相关工程施工提供参考。