燃油添加剂对汽车排放性能影响分析研究

国内对于燃油添加剂效果的分析研究较少,文章为了探讨某型燃油添加剂对在用车排放和性能的影响,依据GB18285-2005《点燃式发动机汽车排气污染物排放限值及测量方法》,针对不同行驶里程的汽车,选用双怠速法检测汽车使用某型号燃油添加剂前后的排放变化,并对油耗和动力性进行简单测评。结果表明,使用燃油添加剂和选择合适标号燃油能有效降低汽车污染物排放及油耗,对车辆使用节能减排具有较为重要意义。     

铁路隧道凸壳型防排水板通水能力研究

文章基于我国铁路隧道防排水体系的技术现状及铁路隧道防排水领域存在的主要问题,介绍了凸壳型防排水板的基本特征,并对凸壳型防排水板的等效管径、通水量等进行了理论计算和研究。结果表明:单位幅宽(隧道纵向延长米)凸壳型防排水板的最小等效管径为0.0626 m,不同工况下其通水量为376~2138 m^3/d;凸壳型防排水板的通水能力是环向盲管的18~38倍;提高凸壳型防排水板凸壳体的抗压强度是确保其通水能力的有效措施;凸壳型防排水板可全面替代传统的防水板与环向排水盲管设置。     

超声相控阵缺陷检测技术研究

为了将相控阵超声检测技术进一步推广应用,对带有人工缺陷的试件分别采用CR、超声相控阵检测技术进行检测,将检测结果进行比对,试验结果表明CR检测技术与相控阵检测技术在体积型缺陷与面积型缺陷检出率方面各具优势,应结合实际工件使用工况,确定可能出现的缺陷类型,采用合适的检测方法与检测工艺,最大限度地提高缺陷检出率.     

AC-13(改进型)沥青混合料劈裂试验研究

文章结合柳州绕城高速公路AC-13(改进型)沥青混合料矿料级配,利用SGC旋转压实机成型沥青混合料试件并进行劈裂试验,对AC-13(改进型)沥青混合料的间接抗拉强度进行评价,得出沥青混合料的空隙率、油石比、老化这些指标的变化与沥青混合料的力学特性间的密切关系。     

全球民航事故调查数据统计与分析

为探索全球民航事故的发生及调查规律,从航空安全网(ASN)采集626起事故调查数据,对事故发生季度、类型、机型等特征进行统计分析,同时对事故调查的实施机构、调查时长、各类事故调查时长等特征展开分析。结果发现:全球民航事故随运行时间的增加呈现波浪形缓慢下降;事故数量最多的前两位为冲偏出跑道和飞机失去控制,并多集中在第三季度(7-9月);波音公司各机型事故曲线整体类似,同时与空客公司各机型飞机事故曲线存在差异。民航事故调查从开始到发布报告的平均周期为26.1个月;各调查机构针对冲偏出跑道、失去控制、可控飞行撞地事故的平均调查周期分别为22.2、40.4、12.4个月。研究结果为民航事故预防政策制定及事故调查提供参考依据。     

Influences of car type class and carbon dioxide emission levels on purchases of new cars: A retrospective analysis of car purchases in Norway

The impact of socio-demographic and psychological factors on purchases of new cars is examined. Data were gathered in an online retrospective survey using a sample of 198 Norwegian households who purchased a new car in December 2010. A latent class analysis was performed to identify car type classes followed by a path analysis to investigate the determinants of the purchased car type class and the influence on the purchased car’s level of carbon dioxide emissions. The results revealed that car type class is the strongest determinant of the car’s level of CO₂ emissions. Socio-demographic factors have little impact on choice of car type class when psychological factors are controlled for. Intention to purchase an environmentally friendly car has a direct effect on the car’s CO₂ emissions.     

A meta-analysis of the impact of rail projects on land and property values

The literature on land and property values demonstrates a great deal of variability in the estimated change in values arising from rail investments. This paper conducts a meta-analysis on empirical estimates from 23 studies (102 observations) that analysed the impact of rail on land/property value changes. Variation in the estimated impacts is calculated and discussed in relation to key dimensions of study-design characteristics. The results show that a number of factors produce significant variations in the estimates. These include the type of land use, the type of rail service, the rail system life cycle maturity, the distance to stations, the geographical location, accessibility to roads, methodological characteristics, as well as whether the impacted area is land or property. On the other hand, we observe that changes in purchase price and rent values due to rail projects are statistically similar to each other, that there is no evidence of change in values over time nor due to the location of land/property within the city, and that including property characteristics and neighbourhood type in the estimation model do not change values significantly. Publication bias tests are also performed and show that although researchers tend to report both positive and negative results, they tend to be biased towards statistically significant estimates.     

广西市际机场快线发展探究

文章介绍了广西航空运输概况和机场快线开行情况,指出了广西开行市际机场快线的必要性,分析了广西开行市际机场快线存在的问题,提出了相应的发展对策,并从企业规模、车型等级、服务标准、经营方式、安全管理等方面阐述了开行市际机场快线应符合的规范与要求。     

隧道加强照明配光优化技术研究

公路隧道照明中相比中间段基本照明而言,加强照明采用传统宽光曲线照明的性价比并不高,较长照射路径反而易造成过多的光通量损耗。为此,本文采用数值模拟的方法对隧道加强照明进行仿真,对比收光型和非收(宽)光型两种配光曲线的照明计算结果,分析收光曲线的照明效能并进一步优化配置。研究结论为:加强照明收光型配光曲线比非收光型配光曲线更节能,当路面平均照度要求为1 500 lx时,非收光曲线照明需求光通量高出收光曲线照明15.8%;收光曲线照明时路面照度总均匀度并不比非收光曲线照明低;对称型收光曲线拱顶单光带布设时,横向偏0.45 m时照明效果最佳。     

A method for relating type of crash to traffic flow characteristics on urban freeways

A method is developed to determine how crash characteristics are related to traffic flow conditions at the time of occurrence. Crashes are described in terms of the type and location of the collision, the number of vehicles involved, movements of these vehicles prior to collision, and severity. Traffic flow is characterized by central tendencies and variations of traffic flow and flow/occupancy for three different lanes at the time and place of the crash. The method involves nonlinear canonical correlation applied together with cluster analyses to identify traffic flow regimes with distinctly different crash taxonomies. A case study using data for more than 1000 crashes in Southern California identified twenty-one traffic flow regimes for three different ambient conditions: dry roads during daylight (eight regimes), dry roads at night (six regimes), and wet conditions (seven regimes). Each of these regimes has a unique profile in terms of the type of crashes that are most likely to occur, and a matching of traffic flow parameters and crash characteristics reveals ways in which congestion affects highway safety.     

Heterogeneous platoon flow dispersion model based on truncated mixed simplified phase‐type distribution of travel speed

Existing research on platoon dispersion models either describe homogeneous traffic flow feature, or are in lack of analytical solutions. By analyzing the field data, the truncated mixed simplified phase‐type distribution is proved to be capable of capturing the characteristics of heterogeneous traffic flow with an excellent fitting result. In light of this, we derive a generic heterogeneous platoon dispersion model with truncated mixed simplified phase‐type of speed in the forms of integrable functions. Numerical case studies are conducted to compare the performance of the proposed model and the conventional models (i.e., the Robertson model and truncated mixed Gaussian model). The results show that the proposed model not only better captures the platoon dispersion laws of heterogeneous traffic flow, but also presents higher computational efficiency, which provides practical implications on traffic signal control. Copyright © 2017 John Wiley & Sons, Ltd.     

柱式轮廓标设计与施工技术规范探讨

文章针对施工中柱式轮廓标施工工序繁杂及稳定性较差的状况,提出柱式轮廓标设计及施工技术存在的缺陷及修改意见。     

Impact of service network topology on air transportation efficiency

Each stakeholder in the air transportation system has a different perspective on the performance efficiency metrics, making analysis of system-wide design options very difficult. This paper uses topological structures of service networks to examine trade-offs between efficiency metrics established around the passenger, airline, and air navigation service provider perspectives. The findings indicate that the scale-free type topologies are preferred under most of the metrics. However, with enough density, random topologies become more appealing with its high robustness feature and performance comparable to scale-free.     

A note on alternative matrix entry estimation techniques

Estimation of trip tables and other matrices that are subject to constraints is a common practical problem. This note reviews four common estimation methods: (1) minimization of the sum of absolute deviations, (2) the biproportional technique, (3) information minimization and (4) constrained generalized least squares (CGLS) regression. A small example illustrates their application. Computational approaches and burdens as well as implicit error structure assumptions are reviewed. The paper concludes that estimates obtained from the biproportional, information minimization and CGLS regression (with a chi-square type error distribution assumption), are likely to be similar in practice. Choice of an appropriate technique depends upon a priori assumptions of error structures, relative computational burdens and the usefulness of estimate uncertainty measures.     

红水河滚装运输方式价值研究

文章针对红水河运输需求大与通航设施能力小的矛盾。提出新型的滚装运输方式，介绍了滚装运输的线路、车型、船型选择方法。并通过与公路、铁路等运输方式在运价、运能及资源综合利用率方面的比较，论述了滚装运输方式的经济价值和社会价值。     

Categorization of the lane change decision process on freeways

Traffic operations for new road layouts are often simulated using microscopic traffic simulation packages. These traffic simulation packages usually simulate traffic on freeways by a combination of a car-following model and a lane change model. The car-following models have gained attention of researchers and are well calibrated versus data. The proposed lane change models are often representations of assumed reasonable behavior, not necessarily corresponding to reality. The current simulation packages apply solely one specific type of model for car-following or lane changing for all vehicles during the simulation. This paper investigates the decision process of lane changing maneuvers for a variety of drivers based on a two-stage test-drive. Participants are asked to take a drive on a freeway in the Netherlands in a camera-equipped vehicle. Afterwards, the drivers are asked to comment on their choices related to lane and speed choice, while watching the video. This paper reveals that different drivers have completely different strategies to choose lanes, and the choices to change lane are related to their speed choice. Four distinct strategies are empirically found. These strategies differ not only in parameter values, as is currently being modeled in most simulation packages, but also in their reasoning. Most remarkably, all drivers perceive their strategy as an obvious behavior and expect all other drivers to drive in a similar way. In addition to the interviews of the participants in the test-drive, 11 people who did not take part in the experiment were interviewed and questioned on lane change decisions. Moreover, the findings of this study have been presented to various groups of audience with different backgrounds (about 150 people). Their comments and feedback on the derived driving strategies have added some value to this study. The findings in this paper form a starting point for developing a novel lane change model which considers four different driving strategies among the drivers on freeway. This is a significant contribution in the area of driving behavior modeling, since the existing microscopic simulators consider only one type of lane change models for all drivers during the simulation. This could lead to significant changes in the way lane changes on freeways are modeled.     

Highway traffic noise effects on land price in an urban area

The study evaluates the monetary effect of traffic noise on property values in Seoul, Korea. Hedonic price models are estimated using the zone-based data that includes traffic noise levels, official land price, land use classification, distance to roadways, type of nearby roadway facilities, and traffic characteristics. It is found that a 1% increase in traffic noise associated with a 1.3% decline in land price. Based on this, the annual cost per kilometer due to traffic noise is about $347 thousand.     

Multi-day activity-travel pattern sampling based on single-day data

Although it is important to consider multi-day activities in transportation planning, multi-day activity-travel data are expensive to acquire and therefore rarely available. In this study, we propose to generate multi-day activity-travel data through sampling from readily available single-day household travel survey data. A key observation we make is that the distribution of interpersonal variability in single-day travel activity datasets is similar to the distribution of intrapersonal variability in multi-day. Thus, interpersonal variability observed in cross-sectional single-day data of a group of people can be used to generate the day-to-day intrapersonal variability. The proposed sampling method is based on activity-travel pattern type clustering, travel distance and variability distribution to extract such information from single-day data. Validation and stability tests of the proposed sampling methods are presented.     

泥水平衡盾构穿越富水砂砾层施工技术研究

文章依托沈阳地铁十号线11标长青桥站—浑南大道工程,该工程区间全长1.6 km,采用?6240 mm泥水平衡盾构施工,穿越段以富水砂砾层为主,最大粒径110 mm,在施工过程中,通过优化调整刀盘的合理选型和泥浆参数,有效地减少了刀盘的磨损,全程未更换刀具。研究表明:通过分析盾构设计阶段刀盘的选型配置和隧道贯通后刀具的磨损情况,提出了一套有针对性的泥水盾构刀盘配置;通过分析施工掘进参数可知,提高泥浆粘度虽然可以增加泥浆支护效果,但易在盾构刀盘的正面形成泥饼,导致正面砾石无法顺利进入土舱内,进而造成扭矩及推力的异常;通过分析不同粘度、比重下盾构机扭矩及推力的变化,总结了富水砂砾层中泥浆参数的合理指标,对今后类似工程的施工具有借鉴意义。     

Understanding travellers’ preferences for different types of trip destination based on mobile internet usage data

New mobility data sources like mobile phone traces have been shown to reveal individuals’ movements in space and time. However, socioeconomic attributes of travellers are missing in those data. Consequently, it is not possible to partition the population and have an in-depth understanding of the socio-demographic factors influencing travel behaviour. Aiming at filling this gap, we use mobile internet usage behaviour, including one’s preferred type of website and application (app) visited through mobile internet as well as the level of usage frequency, as a distinguishing element between different population segments. We compare the travel behaviour of each segment in terms of the preference for types of trip destinations. The point of interest (POI) data are used to cluster grid cells of a city according to the main function of a grid cell, serving as a reference to determine the type of trip destination. The method is tested for the city of Shanghai, China, by using a special mobile phone dataset that includes not only the spatial-temporal traces but also the mobile internet usage behaviour of the same users. We identify statistically significant relationships between a traveller’s favourite category of mobile internet content and more frequent types of trip destinations that he/she visits. For example, compared to others, people whose favourite type of app/website is in the “tourism” category significantly preferred to visit touristy areas. Moreover, users with different levels of internet usage intensity show different preferences for types of destinations as well. We found that people who used mobile internet more intensively were more likely to visit more commercial areas, and people who used it less preferred to have activities in predominantly residential areas.