Technical and environmental effects of biodiesel use in local public transport

Biodiesel use in local public transport could be especially significant in improving air quality in cities. The purpose of the experiments described in this paper was to evaluate the various (10, 20 and 50%) blends of biodiesel with diesel in the context of the engine and pollution aspects. As regards the experimental use of these findings on municipal buses, these experiments were the first reference in Hungary. The ages (15–20 years) and types of buses (Ikarus-280, Ikarus-260) used in the experiments are still common vehicles in Hungarian public transport. During our measurements, there was a significant difference between the change in fuel consumption of articulated and solo buses in traffic when compared to test bench measurements. The proportion of the engine performance reduction is nearly the same as that for biodiesel share in the blends. Most pollutants were decreasing (both at idle and full rpm), but this reduction is not directly proportional to the increase of the blending percentage. However, as for CO₂, emission increase was observed in the case of idle rpm in comparison to normal diesel operation, even though this phenomenon was not due to biodiesel use, but the catalytic converter and the fact that biodiesel was used for the first time in the engine concerned.     

盐穴天然气地下储气库运行过程的关键技术问题

在具有岩盐矿床地质构造的地区,将天然气储存在地下含盐岩层内,实现在短期内提供高容量的储备,是目前各国普遍采用的方法。结合国外相关技术文献及部分研究成果,对盐穴储库运行过程的关键技术问题,主要包括:如何在运行过程减少溶腔的收敛性,防止水化物的形成,溶腔建腔过程形成的冷带和残留盐水对运行过程的影响;垫层气技术、运行的稳定性及注采循环中应注意的问题。文中分别进行了较详细的论述,为今后国内盐穴储库的运行研究提供依据和技术支持。     

An analysis of rail freight operational efficiency and mode share in the British port-hinterland container market

The growth in container shipping poses considerable challenges to efforts to reduce the negative externalities associated with freight transport. There are particular concerns about the impacts of the associated port-hinterland freight flows. Through empirical research, this paper examines trends in the operational efficiency of the British port-hinterland container rail freight market and to assess the impacts of any changes on the overall sustainability of this market. Original survey work conducted in 2007 and 2015 has allowed longitudinal and cross-sectional analysis of the characteristics of this market.The survey findings reveal that rail’s mode share of port container throughput (in TEU) has increased from 14.7% in 2007 to 16.6% in 2015 and it is likely that its share of the associated hinterland activity has also risen. Rail was carrying 25% more TEU by 2015 without an increase in train service provision. Increases in mean train capacity and mean load factor were observed, leading to growth in the mean train load from 44 TEU in 2007 to 55 TEU in 2015. This considerable improvement in operational efficiency is expected to have reduced the negative externalities per unit of transport activity associated with the rail-borne hinterland container flows, though scope is identified for further improvements in sustainability.     

频繁爆破下隧道内振动传播的数值研究

为揭示频繁爆破下隧道内振动传播衰减规律,文章以蒙华铁路段家坪隧道为工程背景,利用LS-DY NA建立了三维隧道模型,模拟分析了多次爆破下隧道内近区和中远区的振动传播规律。结果表明,质点垂向峰值振速随距离和爆破次数的增大而减小,少数振速有增大的现象;近区振动衰减较快,中远区振动衰减比近区缓慢;中远区a值比近区至少小12.5%,但整体上二者的a值随爆破作用次数的增加呈缓慢上升趋势;系数K随爆破作用次数的增加而降低,近区K值降低速率普遍大于中远区,且近区K值比中远区至少大29.1%;频繁爆破下,中远区比近区较符合萨道夫斯基经验公式。     

Application of wavelet technique to freeway incident detection

This paper presents an application of the wavelet technique to freeway incident detection because wavelet techniques have demonstrated superior performance in detecting changes in signals in electrical engineering. Unlike the existing wavelet incident detection algorithm, where the wavelet technique is utilized to denoise data before the data is input into an algorithm, this paper presents a different approach in the application of the wavelet technique to incident detection. In this approach, the features that are extracted from traffic measurements by using wavelet transformation are directly utilized in detecting changes in traffic flow. It is shown in the paper that the extracted features from traffic measurements in incident conditions are significantly different from those in normal conditions. This characteristic of the wavelet technique was used in developing the wavelet incident detection algorithm in this study. The algorithm was evaluated in comparison with the multi-layer feed-forward neural network, probabilistic neural network, radial basis function neural network, California and low-pass filtering algorithms. The test results indicate that the wavelet incident detection algorithm performs better than other algorithms, demonstrating its potential for practical application.     

Storage space allocation in container terminals

Container terminals are essential intermodal interfaces in the global transportation network. Efficient container handling at terminals is important in reducing transportation costs and keeping shipping schedules. In this paper, we study the storage space allocation problem in the storage yards of terminals. This problem is related to all the resources in terminal operations, including quay cranes, yard cranes, storage space, and internal trucks. We solve the problem using a rolling-horizon approach. For each planning horizon, the problem is decomposed into two levels and each level is formulated as a mathematical programming model. At the first level, the total number of containers to be placed in each storage block in each time period of the planning horizon is set to balance two types of workloads among blocks. The second level determines the number of containers associated with each vessel that constitutes the total number of containers in each block in each period, in order to minimize the total distance to transport the containers between their storage blocks and the vessel berthing locations. Numerical runs show that with short computation time the method significantly reduces the workload imbalance in the yard, avoiding possible bottlenecks in terminal operations.     

重庆市内河航运危化品应急处置技术研究

近年来,重庆市逐步建成了沿江化工产业带,内河航道运输成为重庆市危化品运输的重要方式之一。为提升重庆市内河航运危化品安全,本文分析了重庆市内河航运危化品的种类,阐述了重庆市内河航运危化品典型事故案例,指出了重庆市内河航运危化品运输存在的问题,研究了相应的处置技术,从政府和企业角度提出了重庆市内河航运危化品应急处置的对策与建议。     

Structural changes in commuting in the Toronto region 1971–1981

Changes in the commuting structure of the Toronto CMA are examined using 1971 and 1981 census journey to work data. There have been important changes in household structure, the employment base and the associated location decisions which in turn have created significant changes in commuting structure. The proportions of one‐ and two‐person households increased sharply over the decade and many of these smaller‐sized, high occupational status households were located in the older inner residential areas. The bulk of the larger‐sized households continued to be located on the developing fringe where housing prices are much lower. The structure of the employment base shifted over the decade with a reduction in the proportion of manufacturing jobs and growths in the proportions of jobs in finance and services, with the bulk of these office‐based jobs located in the Yonge Street transit corridor. Job growth in the suburbs was dominated by employment in manufacturing, transportation, trade and services. The addition of some 100000 jobs in the Yonge Street corridor resulted in strong commuting growth from the inner suburbs as well as from the newly developing outer suburbs. About half of the labour force living in the outer suburbs in the decade found local jobs, with the remainder of the labour force commuting to jobs in Metropolitan Toronto, principally along the high‐mobility transit and freeway corridors.     

Intrapersonal variability in daily urban travel behavior: Some additional evidence

Researchers have used multiday travel data sets recently to examine day-to-day variability in travel behavior. This work has shown that there is considerable day-to-day variation in individuals' urban travel behavior in terms of such indicators of behavior as trip frequency, trip chaining, departure time from home, and route choice. These previous studies have also shown that there are a number of important implications of the observed day-to-day variability in travel behavior. For example, it has been shown that it may be possible to improve model parameter estimation precision, without increasing the cost of data collection, by drawing a multiday sample (rather than a single day sample) of traveler behavior, if there is considerable day-to-day variability in the phenomenon being modeled. This paper examines day-to-day variability in urban travel using a three-day travel data set collected recently in Seattle, WA. This research replicates and extends previous work dealing with day-to-day variability in trip-making behavior that was conducted with data collected in Reading, England, in the early 1970s. The present research extends the earlier work by examining day-to-day variations in trip chaining and daily travel time in addition to the variation in trip generation rates. Further, the present paper examines day-to-day variations in travel across the members of two-person households. This paper finds considerable day-to-day variability in the trip frequency, trip chaining and daily travel time of the sample persons and concludes that, in terms of trip frequency, the level of day-to-day variability is very comparable to that observed previously with a data set collected almost 20 years earlier in Reading, England. The paper also finds that day-to-day variability in daily travel time is similar in magnitude to that in daily trip rates. The analysis shows that the level of day-to-day variability is about the same for home-based and non-homebased trips, thus indicating that day-to-day variability in total trip-making is attributable to variation in both home-based and non-home-based trips. Day-to-day variability in the travel behaviors of members of two-person households was also found to be substantial.     

含蜡热油管道清管过程的卡堵风险分析

现场清管作业时,清管器经常被卡堵,严重时会影响生产.因此,为降低热油管道清管过程中的卡堵风险,根据清管器在含蜡热油管道中的受力情况和运行规律,结合输油管道的现场运行管理经验,分析含蜡热油管道清管过程可能遇到的卡堵,对此提出可靠的应对措施,以杜绝含蜡热油管道周期性清管中各种事故的发生,保证热油管道清管工作的安全进行,为今...     

Ranking the substantive problems in the Dutch Cost–Benefit Analysis practice

This paper investigates the perceptions of key participants in the Dutch Cost–Benefit Analysis (CBA) practice regarding substantive problems when appraising spatial-infrastructure projects with CBA. Two research methods were applied. Firstly, 86 key participants in the Dutch CBA practice were interviewed in-depth in order to obtain an overview and a ranking of perceived substantive problems with CBA in the Netherlands. Secondly, the people interviewed were also asked to fill in a written questionnaire in which they were asked to rank the substantive problems once again, in order to improve the validity of the ranking; 74 of the participants completed this questionnaire. The most important conclusions of this paper are, firstly, that key participants in the Dutch CBA practice consider ‘problems with the estimation of the non-monetized project effects’ as the most important substantive problem cluster and ‘problems with monetizing project effects’ as the second most important substantive problem cluster. Secondly, key participants in the Dutch CBA practice consider the ‘problem analysis’ in a CBA to be a very important substantive problem. Thirdly, there is, in a broad sense, consensus among the different groups in the Dutch CBA practice concerning their perception of the seriousness of problem clusters and the way they rank the problem clusters. Fourthly, a large part of the substantive problems mentioned by the key participants in the Dutch CBA practice are non-specific CBA problems.     

北京轨道交通房山线与中心城线网衔接方案研究

北京轨道交通房山线近期是市郊线,远期有可能提升为市域线。如何处理好近、远期线路功能的转换,是房山线线路设计的重点。从线路可达性、换乘便利性、投资经济性、工程可实施性、功能转换灵活性等方面,对房山线与北京中心城线网衔接方案展开探讨,从而推荐近远结合的综合最优方案。     

喀斯特地貌地区高速公路建设安全管理研究

文章基于喀斯特地貌地区高速公路建设的特点,分析了喀斯特地貌高速公路建设过程中普遍存在的安全问题,提出加强喀斯特地貌地区高速公路建设安全管理工作的思路,并介绍了地处喀斯特地貌地区的广西河池至都安高速公路工程安全管理工作经验。     

The design of interurban bus networks in city centers

This paper proposes a bilevel formulation for solving the Bus Network Design Problem (BNDP) of interurban services entering a major city. It is focused in interurban services because it is a growing problem in most of major cities, yet new in the literature. The layout of interurban bus routes and the locations of transfer stations in the main city are the key factors to provide a competitive public transportation service to commuters in a metropolitan area. The number of commuters in huge urban concentrations is growing due to the difficulties of living near the city center. The objective function of the first level is defined with the aim of reducing user and agency costs. In the second level the performance of users is addressed. Furthermore, a local search method based on the Tabu Search algorithm was carried out to guide the exploration in the solution domain. The results obtained in a set of test problems have demonstrated that the restart parameters of the algorithm play a significant role in the efficiency of the algorithm. Finally, implementation in the large network of Barcelona (Spain) reduces the total cost by 5% with regard to the present situation.     

Energy use in passenger transport in OECD countries: Changes since 1970

This paper analyzes some of the changes that took place in the structure of energy use for passenger travel in industrialized countries. Data is presented on energy use and travel activity for the four major modes of travel — automobile, bus, rail and air — for eight OECD countries: the United States, Japan, the United Kingdom, West Germany, France, Italy, Sweden, and Norway. We use the Laspeyres and Divisia indices to analyze the causes of the change in energy use between 1970 and 1987. The total change in energy use for travel is explained by changes in domestic passenger transport volumes, the mix of modes of travel, and the energy intensities of each mode. We have found two important effects that have a fundamental impact on energy use for travel since 1970. First, shifts among modes of transport towards more energy-intensive ones and large increases in volumes of travel (measured in passenger-kilometers) increased energy use for travel in many OECD countries, often more rapidly than the overall growth in GDP. Second, energy intensities, measured in mJ/passenger-kilometer, of passenger transport fell only in a few countries between 1970 and 1987. Even though individual automobiles have become more energy-efficient, greater size, power, and weight, worsening traffic conditions in Japan and Europe, and fewer people in cars restrained or even offset efficiency improvements. Particularly notable are the increases in intensities in Japan and Germany. The most important exception to this trend was the United States, but the intensities of land-based travel remain higher there than in most other countries. These findings lead to a pessimistic outlook for future energy use for travel. After all, if little or no energy was saved during the decades of high fuel prices, what can be expected in the 1990s?     

Changes in travel mode use after residential relocation: a contribution to mobility biographies

In recent years, a growing body of research has been emerging that focuses on changes in travel behaviour over an individual’s life course. It has been labelled the ‘mobility biographies approach’ and highlights changes in travelling induced by key events and experiences in an individual’s life course. In this context residential relocation plays an important role. This paper examines changes in travel mode use after residential relocations using structural equation modelling. It draws on retrospectively recorded empirical data collected in the region of Cologne. The findings show that relocations and associated changes in the built environment induce significant changes in car ownership and travel mode use and thus may be regarded as key events in an individual’s mobility biography. Changes in levels of satisfaction with attributes of the built environment have a significant impact in this context as well. The causal direction of the changes fulfils expectations: suburbanisation is followed by increases in car use and decreases in public transport use, bicycle use and walking. The opposite is true for relocations into the city. In addition, changes in household structure that tend to go along with relocation have significant effects. The findings provide further evidence for the built environment having a causal impact on mode use: modal changes temporally follow changes in the built environment and thus appear to be adjustments to the new spatial setting.     

Organizational effects of experience from accidents. Learning in the aftermath of the Tretten and Åsta train accidents

This article explores possible signs on learning in organizations following two major railway accidents in Norway, the Tretten accident in 1975 and the Åsta accident in 2000. These are the most serious railway accidents to have occurred in the past decades and both involved collisions on a single track system. The two events have been analyzed and compared in order to investigate possible learning effects and possible differences in learning given the 25-year span between them. The study is based on the analysis of selected documents related to the accidents in general and the narrative components in the documentation related to learning in particular.Our findings indicate that learning from these events was not expressed as an explicit goal in the aftermath. Learning in these cases seems to be linked for a large part to a change in measures, technical, operational and organizational, but we have not observed any managed confirmation or comprehension processes. The Tretten accident report suggests that the possibility of human error should be mitigated through the implementation of technological barriers, while it omits all other elaborations and risk reducing measures. The Åsta accident report recommended that the work to introduce modern safety management principles that had already been initiated before the accident should be continued. Neither of the accidents yielded any new insights and the knowledge brought forward was merely perceived as confirmation of already-agreed changes.     

油气长输管道壁厚计算及选用

在油气长输管道设计中,管道的壁厚设计计算和选取直接影响到管道输送安全和工程投资.针对油气长输管道壁厚计算因输送介质不同、输送温度不同、输送压力不同及处于不同地段而产生的差异,归纳总结出油气长输管道普通线路段、穿跨越段和站场部分管道壁厚计算方法,也总结出了在管道壁厚的选取中需要注意的问题及应用的规范.     

Environmentally appraising different pavement and construction scenarios: A comparative analysis for a typical local road

The aim of this work is to carry out a comparative analysis of environmental impacts for different scenarios of a typical local road. Life Cycle Assessment (LCA) is the modeling tool used to quantify and characterize comparative environmental impacts. In carrying out this specific application of the LCA, different road construction techniques were considered with regards to the whole structure and compared in order to identify the best alternative in terms of environmental sustainability.So far, in fact, typical LCA frameworks of roads have focused on recycled materials for pavement layers only, thus neglecting study of the materials used in the embankment or in the subgrade. In this study, these materials were included too, in order to prove the environmental benefit of using a sustainable technique such as in situ stabilization of fine soils with lime (typically dumped clayey soils) in order to reduce the need for virgin material for embankment and subgrade construction.When using different percentages of recycled materials (such as reclaimed asphalt pavement – RAP) in the bituminous layer or in the foundation, the analysis of the functional unit studied shows a significant reduction of energy consumption and pollutant emissions mainly due to transportation of materials involved, in this way increasing the environmental performance of the road.Another important consideration is that the use of fine soils stabilized with lime “in situ”, instead of dumping it, not only is a good technical solution for improving soil mechanical properties, but it also produces a reduction of energy consumption and of pollutant emissions. It is noticeable that this technique results in a significant reduction of pollutant emissions due the transportation of involved materials, increasing the environmental performance of the road.     

Value of travel time reliability: A review of current evidence

Travel time reliability is a fundamental factor in travel behavior. It represents the temporal uncertainty experienced by travelers in their movement between any two nodes in a network. The importance of the time reliability depends on the penalties incurred by the travelers. In road networks, travelers consider the existence of a trip travel time uncertainty in different choice situations (departure time, route, mode, and others). In this paper, a systematic review of the current state of research in travel time reliability, and more explicitly in the value of travel time reliability is presented. Moreover, a meta-analysis is performed in order to determine the reasons behind the discrepancy among the reliability estimates.