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河沾线管输原油黏度大,凝固点高,管输困难,为解决此问题,进行了河沾线应用BEM-5P流动性改进剂对原油具有较好的降凝,降黏效果,运行温度40℃以上时降黏幅度约20%;30℃和25℃的降黏幅度可达46.3A%和68.9%;全线降凝幅度为12-14℃。另外,BEM-5剂具有很好的分散性,对河沾线原油具有良好的改性效果。加剂后可降低管道的运行温度,增加运行的性,并取得了一定的经济效益。 相似文献
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高含蜡原油降凝减阻方法 总被引:1,自引:1,他引:0
以青海原油为例,对高含蜡低胶质沥青质原油的降凝减阻方法进行了研究。研究表明:高含蜡低胶质沥青质原油,蜡晶多且大,在低温时能够形成可逆网状结构,热处理温度高,处理效果差,而且处理温度选择不当还会使原油的低温流动性恶化。采用降凝剂降凝减阻效果明显优于热处理。加剂处理原油的物性受加热历史和强剪切速率影响很大,多次重复低温加热或在析蜡高峰进行强剪切,会严重影响加剂原油的低温流动性。由于高合蜡低胶质原油组分的影响,降凝剂的降凝作用还不够理想,需要进一步研究。 相似文献
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稠油掺稀后混油黏度计算方法的研究 总被引:1,自引:0,他引:1
稀释输送是传统的稠油降黏输送方法,因其工艺简单,降黏效果在管输过程中较稳定,一直在国内外得到广泛应用。但稠油中加入稀油后其混油黏度又是一个难点,混油黏温数据是摩阻计算的重要参数,是输油管道设计和运行管理的重要参数,其准确性对水力计算结果至关重要。对混合原油的黏度计算,国内外学者提出了不少经验公式、半经验公式以及计算图表,且大多是利用实验数据通过线性回归得到的,每种模型都有一定的适用范围。通过对Cragoe模型进行修正,得出稠油掺入稀油黏度计算需分段选择模型的结论。 相似文献
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原油顺序输送的现状与展望 总被引:2,自引:0,他引:2
通过对国内外现有油品顺序输送管道的发展情况的了解,以及对国内外油品顺序输送中的混油机理、界面检测、界面隔离、减少混油措施等现有技术进行总结,对国产原油-进口原油顺序输送所应解决的问题进行了阐述,最后提出对顺序输送技术的展望,并提出应该急需研究的油品顺序输送所应注意的相关技术问题。 相似文献
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Ingmar Andrasson 《先进运输杂志》1998,32(1):23-34
A survey of research and development in advanced transit has been made by Chalmers University of Technology in Gothenburg in cooperation with Trans21 in Boston. Summary findings are reported for fourteen academic research programs and ten development programs for PRT. An earlier version of this paper was presented at the International Conference of PRT and other Emerging Systems held in Minneapolis in 1996. 相似文献
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AbstractDespite a concentration of container traffic in the southeast of the UK over the last few decades, regional ports are attempting new development strategies to capture or retain specific traffic segments. These include intra-European short-sea traffic and a potentially increasing feeder market. These trends are reflected in the movement of different container types, which result in a number of planning challenges related to changing infrastructural and operational requirements. This paper uses highly disaggregated data on container type movements to address three issues that can inform these planning challenges. First, the imbalance of trade resulting in empty container repositioning; second, the requirement for gauge-cleared rail routes to cater for the increasing proportion of high-cube containers; and third, the specialisation of European short-sea traffic at secondary UK ports. The results reveal the disproportionate repositioning of empty containers at Scottish ports and the importance of 45?ft, high-cube and pallet-wide containers at regional ports, highlighting their focus on intra-European short-sea traffic and raising difficulties relating to their lower quality of landside infrastructure (particularly rail) in comparison to the large south-eastern ports. The potential repercussions on hinterland infrastructure development raise questions about both public and private sector responses to regional port development. 相似文献
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This research examines the problem of route bus specification and vehicle manufacturability. In order for bus operators to provide transport services, a range of vehicle configurations must be available from bus manufacturers, generating variety which has a negative impact on the manufacturing process. Larger part inventories, uncontrolled labour tasks and more troublesome maintenance are known impacts of this variety. This research identifies the functional necessities in route bus interior design and reduces the problems in bus manufacture and operation caused by specification diversity by proposing a modularised system of bus design. In particular, it makes recommendations as to how bus configuration should be carried out, ensuring an optimum mix of operational and manufacturing needs:
- 1.Determine user needs before the bus specification process.
- 2.Designs to be developed by the manufacturer in response to user needs.
- 3.This design should be standardised where possible, as suggested by the user needs.
- 4.Where user needs dictate product variations, apply a mass customisation approach to accommodate these needs.
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In the next few years, exciting developments in the field of freight transport are likely to occur. The Channel Tunnel will be perceived as giving railways much greater distance of operation, compared to the current train ferry to/from Great Britain. The further development of swap-body technology will allow easier modal transfer and the creation, in 1992, of a single market in Europe will transform the pattern of trade. All of these are likely to have significant impacts on modal choice, and hence modal split, in freight transport. Reappraisal by many firms of the modes of transport used is likely but will it result in a net transfer of freight from road to rail and, if so, to what extent? To answer such questions, an accurate and reliable method of predicting modal split is required. Research in the past has concentrated on the development of modal split models based on generalised costs. These fail to explain adequately the prevalence of road freight in the UK. From surveys of freight managers within industry, it is clear that models to date rely too heavily on the economic cost factor and too little on behavioural factors (Jeffs 1985). This paper derives from a recent study of freight transport modal choice from the standpoint of the transport decision-maker within the firm. It attempts to shed light on the actual parameters which should be incorporated into a modal split model. Many variables appear to exert an influence on modal choice decision-making process. However, it is possible to categorise them into six main groups, namely: customer-requirements; product-characteristics; company structure/organisation; government interventions; available transport facilities; and perceptions of the decision-maker him/herself. It is the interactions and inter-relationships between these which ultimately determine freight modal split. This study has shown that the relationship between the outcome of the transport decision process and the values of particular determinants of modal split is not straight-forward, due to the complexity and variety of interactions involved. Perhaps one of the main reasons for researchers' failure hitherto to develop a successful modal-split model has been the preoccupation with techniques that rely on the development of common metric (e.g. generalised cost), which has led to the exclusion of some important explanatory variables along quite different dimensions. Another important issue concerns the appropriate level of aggregation. In order not to reduce the explanatory power of the key variables, it is important to work at a disaggregate level, although this does make substantial demands on data. The use of factor analysis enables both the aggregation of information without loss of behavioural reality and the specification of variables in terms of a common metric. In conclusion, freight transport has usually been examined within too narrow a framework. It must be placed firmly within the context of the total industrial process. The demand for freight transport is directly influenced by the level, composition and geographical distribution of production and consumption activities. Freight flows are complex and so it is highly unlikely that a universal mode-choice model can ever be developed. Future research should, therefore, be directed towards developing partial models in response to specific needs of those involved in decision-taking in the freight sector. 相似文献
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管道风险分析指数评分法中重要步骤之一就是确定影响管道事故因素的权重,各个管道风险因素在整个管道事故中所占的权重是不相同的。针对目前管道风险分析指数评分法基本假设之一(各因素的分值范围都是0~100分),为了更加客观、准确、合理地反映各个风险因素对于管道事故的影响程度,提出并论述了依据层次分析法的数学逻辑性进行综合计算得出管道风险因素的权重,然后对评分法中各个因素的最高分值,根据其权重不同进行相应调整,从而增强评价者对风险因素的认识和评判能力,提高管道风险评价结果的准确性。 相似文献
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The concept of accessibility has acquired numerous meanings along multiple dimensions during the century of its evolution. This essay argues for the salience of two dimensions: application-based and definition-based. In its application, accessibility has incorporated positive and normative dimensions which have varied in prominence over time. In its definition, accessibility has varied between a mode of evaluation incorporating measured mobility and proximity, on the one hand, and a predefined market basket of urbanist improvements to transportation and land use systems, on the other. Advocates of the accessibility shift should emphasize both the measured approach to accessibility and accessibility’s normative side. 相似文献
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Nicholas B. Taylor 《运输规划与技术》2018,41(1):37-57
ABSTRACTPredicting the risk of traffic demands and delays exceeding critical limits at road junctions, airports, hospitals, etc., requires knowing how both mean and variance of queue size vary over time. Microscopic simulation can explore variability but is computationally demanding and gives only sample results. A computationally efficient approximation to the mean is used in many modelling tools, but only empirical extensions for variance in particular situations have been available. The paper derives theoretical formulae for time-dependent and equilibrium variance, believed to be novel and to apply generally to queues covered by the Pollaczek–Khinchin mean formula, and offering possible structural insights. These are applied in an extended approximation giving mutually consistent mean and variance estimates with improved accuracy. Tests on oversaturated peak demand cases are compared with Markov probabilistic simulation, demonstrating accuracy (R2?>?0.99) for typical random, priority-like (M/M/1) and traffic-signal-like (M/D/1) queues. Implications for risk analysis, planning and policy are considered. 相似文献