GOMACO摊铺机技术参数调试研究

文章结合GOMACO GP2600型水泥混凝土滑模摊铺机的特点和使用经验,阐述了GOMACO摊铺机各关键部位的技术参数调试要点及安装使用注意事项,为路面工程摊铺机的选用提供参考。     

滑模摊铺机在高寒地区施工特点

通过国道214线姜清段采用滑模摊铺机混凝土路面施工,总结高寒地区滑模混凝土路面技术、混凝土原材料及配合比的技术要求、滑模摊铺机的操作要领、混凝土路面的修补及施工中应注意的问题.     

沥青混凝土摊铺机施工工艺探讨

围绕沥青混凝土摊铺机施工作业的全过程,分析了各阶段对摊铺机的影响因素及注意事项,提出了较为科学的施工作业方法。     

美国高马科GHP2800型滑模摊铺机的使用和性能介绍

本文介绍美国GOMACO公司GHP2800滑模摊铺机的性能，及其在兴六高速公路水泥混凝土路面摊铺施工中的应用。     

摊铺机振动频率对路面结构层摊铺质量的影响分析

路面结构层的密实度和平整度是道路竣工验收的主要技术指标,而摊铺机的振动频率是影响结构层平整度和密实度的重要因素。详细阐述了沥青路面结构摊铺机的工作特点以及工作原理,并通过试验段测试分析摊铺机的振动频率对路面结构不同层位摊铺效果的影响。结果表明,摊铺机振动频率对路面结构层的平整度和密实度有较大影响,随着振动频率的增加,沥青面层的平整度下降,水泥稳定碎石基层的平整度增大,两结构层呈现相反的规律;而随着振动频率的增大,面层和基层的压实度都增大。     

水泥混凝土滑模摊铺施工技术

水泥混凝土路面施工中陆续研制开发了轨道摊铺机和滑模摊铺机等现代化大型施工机械,在路面类型上发展了钢筋混凝土路面、连续配筋混凝土路面、低噪音混凝土路面,进一步推动了水泥混凝土路面的发展.结合日南路尉许段路面四标段,介绍了水泥混凝土路面的滑模摊铺施工技术.     

沥青砼摊铺机与路面平整度

对沥青砼摊铺机的性能、操作方法和施工工艺与沥青路面平整度的关系进行了阐述.     

滑模摊铺路面混凝土配合比的设计与应用

广西兴六高速公路贵港联线水泥混凝土路面采用滑模摊铺机施工，对混凝土性能有一些特殊要求。本文介绍了滑模施工条件下混凝土配合比的设计与应用情况。     

天南海北高速路 他们为何选择中大

<正>四条历经时间验证并荣获国家级奖项的高速公路,他们的共同之处在于都选择了在水稳层施工中使用中大机械大宽度大厚度摊铺机,在面层施工中同样选择了中大机械抗离析大宽度摊铺机。中大机械摊铺机稳定可靠高效的施工保障,是四条高速公路获得国家级奖项的坚实后盾。随着我国高等级公路的发展,沥青抗离析大宽幅整体成型摊铺工艺、水稳及沥青碎石大厚度大宽度整体成型摊铺工艺、高填方路基的强力压实工艺,实现了筑路工艺质的飞跃,引领着高等级公路摊铺与压实的新时代。在这个国外大牌     

一级公路沥青路面平整度施工控制

平整度是衡量一级公路沥青路面路用性能的主要质量标准之一,也是路面品质的主要指标。本文以某工程项目为例,从原材料及混合料的质量控制、施工工艺的控制、碾压温度的控制、摊铺机与运料车辆的配合、正确使用摊铺机的微调器及仪表等方面入手,深入探讨了一级公路沥青路面平整度施工控制措施,具有一定的参考价值。     

Persistence of walking in Chile: lessons for urban sustainability

ABSTRACT

An extensive body of work from the urban planning, health, and other disciplines has documented the importance of walking to urban sustainability from health, safety, security, environmental and other perspectives. These studies come mainly from countries in North America and Europe, where the majority of the population relies on cars for transportation. Notwithstanding, in many countries in the Global South, walking remains a majority transport mode, while cars increasingly dominate the urban streetscape, but are accessible only to a minority of the population. Chile provides fertile terrain for studying this phenomenon. This article reviews current practice and recent research of walking in Chile, in light of international findings regarding walkability, equity and urban sustainability. To elaborate an overview of the depth and breadth of walking in Chile, an interdisciplinary team conducted a literature review, examined relevant case study material from experience from Chile and in particular from Santiago, and triangulated this mainly qualitative data with results from the origin-destination survey applied in Chile’s main cities, Chilean traffic safety data) and results from official transport reports of other Latin American cities [Tirachini, A. (2019). South America: The challenge of transition. In J. Stanley & D. Hensher (Eds.), A research agenda for transport policy. Northampton, MA: Edward Elgar Publishing]. Findings show that despite priority public investments that have largely prioritised infrastructure for cars, walking in Chile has remained as the majority transport mode up until today, especially for lower-middle income groups, and particularly for care-related tasks performed mainly by women. In this sense, walking in Chile has proven remarkably persistent. The importance of walking as the main transport mode, against the odds, reflects economic, cultural, and urban form determinants, which are explored in this article. Furthermore, a recent upsurge in public interest and community design initiatives to improve walking, particularly the generation of a Chilean approach to “complete streets” has emerged, opening up opportunities to challenge Chile’s version of automobility in favour of more equitable, active and public transportation modes. There is, therefore, in Chile an opportunity to prioritise the walking mode, improve infrastructure for walkers and build from preserving current high pedestrian modal shares, rather than having to reverse widespread car use, as occurs in many countries in Europe and North America. This potential is highly relevant as these conditions are similar to those in other Latin American cities and, potentially, other cities elsewhere in the Global South.     

Well-to-wheel costs,primary energy demand,and greenhouse gas emissions for the production and operation of conventional and alternative vehicles

This study provides a comprehensive comparison of well-to-wheel (WTW) energy demand, WTW GHG emissions, and costs for conventional ICE and alternative passenger car powertrains, including full electric, hybrid, and fuel cell powertrains. Vehicle production, operation, maintenance, and disposal are considered, along with a range of hydrogen production processes, electricity mixes, ICE fuels, and battery types. Results are determined based on a reference vehicle, powertrain efficiencies, life cycle inventory data, and cost estimations. Powertrain performance is measured against a gasoline ICE vehicle. Energy carrier and battery production are found to be the largest contributors to WTW energy demand, GHG emissions, and costs; however, electric powertrain performance is highly sensitive to battery specific energy. ICE and full hybrid vehicles using alternative fuels to gasoline, and fuel cell vehicles using natural gas hydrogen production pathways, are the only powertrains which demonstrate reductions in all three evaluation categories simultaneously (i.e., WTW energy demand, emissions, and costs). Overall, however, WTW emission reductions depend more on the energy carrier production pathway than on the powertrain; hence, alternative energy carriers to gasoline for an ICE-based fleet (including hybrids) should be emphasized from a policy perspective in the short-term. This will ease the transition towards a low-emission fleet in Switzerland.     

Multilevel analysis of daily time use and time allocation to activity types accounting for complex covariance structures using correlated random effects

In this paper multilevel analysis is used to study individual choices of time allocation to maintenance, subsistence, leisure, and travel time exploiting the nested data hierarchy of households, persons, and occasions of measurement. The multilevel models in this paper examine the joint and multivariate correlation structure of four dependent variables in a cross-sectional and longitudinal way. In this way, observed and unobserved heterogeneity are estimated using random effects at the household, person, and temporal levels. In addition, random coefficients associated with explanatory variables are also estimated and correlated with these random effects. Using the wide spectrum of options offered by multilevel models to account for individual and group heterogeneity, complex interdependencies among individuals within their households, within themselves over time, and within themselves but across different indicators of behavior, are analyzed. Findings in this analysis include large variance contribution by each level considered, clear evidence of non-linear dynamic behavior in time-allocation, different trajectories of change in time allocation for each of the four dependent variables used, and lack of symmetry in change over time characterized by different trajectories in the longitudinal evolution of each dependent variable. In addition, the multivariate correlation structure among the four dependent variables is different at each of the three levels of analysis.     

Optimizing sustainable feeder bus operation considering realistic networks and heterogeneous demand

A mathematical model is developed to optimize social and fiscal sustainable operation of a feeder bus system considering realistic network and heterogeneous demand. The objective total profit is a nonlinear, mixed integer function, which is maximized by optimizing the number of stops, headway, and fare. The stops are located which maximize the ridership. The demand elasticity for the bus service is dependent on passengers' access distance, wait time, in‐vehicle time, and fare. An optimization algorithm is developed to search for the optimal solution that maximizes the profit. The modeling approach is applied to planning a bus transit system within Woodbridge, New Jersey. Copyright © 2011 John Wiley & Sons, Ltd.     

Real-world gaseous and particle emissions of a Bi-fuel gasoline/CNG Euro 6 passenger car

The objective of the present study is the assessment of the environmental impact of a bivalent (bi-fuel) vehicle, running either on gasoline or compressed natural gas (CNG). To that aim, a Euro 6 passenger car was tested under various real-world driving conditions. In order to cover the full range of conventional powertrains currently in the market, the tests were also repeated on a Euro 6 diesel passenger car. Both cars were driven in two routes, the first complying with the regulation limits and the second going beyond them. Carbon monoxide (CO), nitrogen oxides (NO_x) and particle number (PN) emissions were recorded using a Portable Emissions Measurement System (PEMS). Apart from the aggregated emission levels, in g/km, the exact emission location along the route was also assessed. Natural gas proved beneficial for CO and PN emissions, the level of which always remained below the respective legislation limits. On the other hand, under the dynamic driving conditions with gasoline, the relevant limits were exceeded. Cold start, occurring at the beginning of the urban part, and motorway driving were identified as major contributors to total emissions, especially in gasoline mode. However, the application of natural gas was associated with a penalty in NO_x emissions, which were significantly increased as compared to gasoline. Local peaks within the urban part were identified in CNG mode. In any case, the diesel vehicle was by far the highest NO_x emitter.     

A cognitive framework to plan for the future of transportation

ABSTRACT

Automated, connected, electrified, and shared mobility will be cornerstones of the transportation future. Research to quantify the potential benefits and drawbacks of practice, and to identify barriers to adoption, is the first step in any strategic plan for their adoption. However, uncertainties, complexity, interdependence, and the multidisciplinary nature of emerging transportation technologies make it difficult to organize and identify focused research. The contribution of this work is a cognitive framework to help planners and policymakers organize broad topics, reveal challenges, discover ideas for solutions, quantify potential impacts, and identify implications to guide preparation strategies. The authors provide example cognitive frameworks for connected, automated, and electrified vehicles.     

国外铁路运营安全效益评价现状及启示

铁路运输在国民经济运行中发挥着重要作用,各国铁路公司都非常重视对铁路运营、安全、效益的管理及评价。国外铁路经过两个世纪的发展,积累了丰富经验,通过分析美国、日本、欧洲等国家和地区的普速、高速铁路,在运营效率评价、运营安全评价、服务质量评价、经营效益评价、安全保障法律法规建设和第三方评价机构发展等方面的现状,从客户服务质量评价、安全评价标准体系建立、效率效益导向的经营效益评价机制建设、第三方专业评价机构发展等维度,总结对我国高速铁路运营安全效益评价的经验借鉴及启示。     

Travel-based multitasking: review of the role of digital activities and connectivity

ABSTRACT

Travel-based multitasking, also referred to as travel time use, is now a well-established concept, whose existence is supported by the technological trajectories, with mobile information and communication technologies (ICT) and vehicle automation working together to allow travel time to be more productive and enjoyable. Despite existence of reviews of travel-time multitasking studies, the systematic overview of the role digital activities, i.e. those that necessarily require modern ICT equipment to participate, has been limited, often wrapped under the umbrella term “use of ICT”, potentially obscuring their complexity and sophistication. Similarly, the role of connectivity and its attributes, e.g. speed (bandwidth), reliability, price, ease of use, data allowance or security, deserves a more systematic overview given its key role in enabling digital online activities and hence the travel-based multitasking options. This paper provides a review of 77 empirical travel-based multitasking-studies that explored the role of digital activities or connectivity. In particular, the review discusses the existing typologies of digital activities, dividing them into hardware-centric, function-centric or a combination of both (mixed). Subsequently, key contributions are discussed with respect to the treatment of digital activities and connectivity and its attributes. Based on the review, it is possible to observe that the existing studies have looked only at a handful of rather restricted online activities that do not sufficiently capture the sophistication with which individuals interact with the virtual world nowadays. Furthermore, the role of connectivity, although deeply embedded in the “C” of the “ICT” concept, has not been looked at or modelled in any detail in studies related to travel time use or its quality. This existing shortcoming might have resulted in an insufficient understanding of the mechanisms driving travel time use, the associated experience indicators of customer satisfaction, productivity or the consequences for relative attractiveness of transport modes. All of these considerations remain, however, crucial for designing, appraising and operating transport infrastructure and services that are able to take the advantage of lifestyle digitisation to meet the increasing customer needs while also delivering broader economic, social benefits and possibly also environmental benefits.     

Crowding in public transport systems: Effects on users,operation and implications for the estimation of demand

The effects of high passenger density at bus stops, at rail stations, inside buses and trains are diverse. This paper examines the multiple dimensions of passenger crowding related to public transport demand, supply and operations, including effects on operating speed, waiting time, travel time reliability, passengers’ wellbeing, valuation of waiting and in-vehicle time savings, route and bus choice, and optimal levels of frequency, vehicle size and fare. Secondly, crowding externalities are estimated for rail and bus services in Sydney, in order to show the impact of crowding on the estimated value of in-vehicle time savings and demand prediction. Using Multinomial Logit (MNL) and Error Components (EC) models, we show that alternative assumptions concerning the threshold load factor that triggers a crowding externality effect do have an influence on the value of travel time (VTTS) for low occupancy levels (all passengers sitting); however, for high occupancy levels, alternative crowding models estimate similar VTTS. Importantly, if demand for a public transport service is estimated without explicit consideration of crowding as a source of disutility for passengers, demand will be overestimated if the service is designed to have a number of standees beyond a threshold, as analytically shown using a MNL choice model. More research is needed to explore if these findings hold with more complex choice models and in other contexts.     

北欧公路印象与启示

以人为本、尊重自然、适用完善是北欧公路的鲜明特点。本文介绍了北欧公路在总体设计、路线、路基路面、排水、桥遂、交通工程及服务设施、运营管理等方面的具体做法,并结合我国公路的现状提出了一些思路。