牵索挂篮在斜拉桥主梁悬臂施工的技术应用

本文结合重庆李渡长江大桥工程斜拉桥主梁挂篮悬浇施工,介绍牵索挂篮的结构特点和具体操作方法,综合说明牵索挂篮在斜拉桥悬浇施工中的技术应用。     

Microbial food web responses to light and nutrients beneath the coastal Arctic Ocean sea ice during the winter–spring transition

We measured the abundance and biomass of phototrophic and heterotrophic microbes in the upper mixed layer of the water column in ice-covered Franklin Bay, Beaufort Sea, Canada, from December 2003 to May 2004, and evaluated the influence of light and nutrients on these communities by way of a shipboard enrichment experiment. Bacterial cell concentrations showed no consistent trends throughout the sampling period, averaging (± SD) 2.4 (0.9) × 10⁸ cells L^− 1; integrated bacterial biomass for the upper mixed layer ranged from 1.33 mg C m^− 3 to 3.60 mg C m^− 3. Small cells numerically dominated the heterotrophic protist community in both winter and spring, but in terms of biomass, protists with a diameter > 10 µm generally dominated the standing stocks. Heterotrophic protist biomass integrated over the upper mixed layer ranged from 1.23 mg C m^− 3 to 6.56 mg C m^− 3. Phytoplankton biomass was low and variable, but persisted during the winter period. The standing stock of pigment-containing protists ranged from a minimum value of 0.38 mg C m^− 3 in winter to a maximal value of 6.09 mg C m^− 3 in spring and the most abundant taxa were Micromonas-like cells. These picoprasinophytes began to increase under the ice in February and their population size was positively correlated with surface irradiance. Despite the continuing presence of sea ice, phytoplankton biomass rose by more than an order of magnitude in the upper mixed layer by May. The shipboard experiment in April showed that this phototrophic increase in the community was not responsive to pulsed nutrient enrichment, with all treatments showing a strong growth response to improved irradiance conditions. Molecular (DGGE) and microscopic analyses indicated that most components of the eukaryotic community responded positively to the light treatment. These results show the persistence of a phototrophic inoculum throughout winter darkness, and the strong seasonal response by arctic microbial food webs to sub-ice irradiance in early spring.     

油料应用技术

主要介绍机械设备中常用的燃料油、润滑油、润滑脂、液压油和某些特种油的特性、牌号、分类和使用范围，以及实际工作中如何正确选用．     

基于灰色马尔科夫模型的重庆市水运货运量的预测*

通过对重庆水运发展现状的研究,根据马尔科夫理论及灰色预测模型,将灰色GM模型与马尔科夫状态转移矩阵相结合,建立了预测重庆水运货运量的灰色马尔科夫模型,并通过实际预测发现,该模型的预测精度明显高于灰色预测模型的预测结果,并预测了2011—2012年重庆市水运货运量。     

60 kg/m钢轨和60N钢轨轮轨接触几何关系对比分析

为揭示我国新研究设计的60N钢轨的轮轨接触几何关系,运用常用的迹线法,以LM型和LMA型车轮踏面为例,对60 kg/m钢轨(简称60钢轨)和60N钢轨轮轨接触几何关系及其对轨底坡和轮对摇头的适应性进行详细研究。结果表明:相比60钢轨,60N钢轨与LM型和LMA型踏面匹配时,轮轨接触点在钢轨上位于钢轨中心位置附近,同时不会在钢轨轨距角附近出现轮轨接触,且在发生轮缘接触前,60N钢轨相比60钢轨对应的等效锥度随着轮对横移量变化很小,说明60N钢轨有效的改善了轮轨接触几何关系;同60钢轨,60N钢轨对于LM型车轮踏面,当轨底坡为1/20时匹配更佳,对于LMA型车轮踏面,当轨底坡为1/40时匹配更佳,而摇头角对60钢轨和60N钢轨的影响基本一致。     

Developing metro-based accessibility: Three aspects of China’s Rail+Property practice

Populous Chinese cities have invested heavily in metro systems and planned proactively for transit-oriented development. Rail plus property (R+P) programs, where metro corporations engage in, and even orchestrate real estate development in or around rail station areas, have been recurrently reported among these cities. However, careful assessment of these programs is still rare in the existing literature. Built upon multiple R+P programs led by Shenzhen Metro Cooperation and/or Hong Kong Mass Transit Railway Cooperation, this article fathoms the rationale for R+P programs in Mainland China, the obstacles for oversea private investors’ participation and the balance between profit making and social goods supply. It finds that R+P programs serve as alternative funding sources for expensive metro projects. It decreases municipal governments’ cash flow contribution to those projects, which is mandated by the central government. In addition, local business environment for R+P projects has disadvantaged private sector participation, especially those private investors from overseas. Furthermore, public subsidy to local metro corporations is likely to persist as R+P programs have not been designed for economic value maximization; rather, they are in place because (1) they reduce the cash flow burden of the municipal government; (2) they are tasked by the municipal government to produce a considerable number of affordable public housing.     

香港“城铁一体化”开发模式对城际轨道交通可持续发展的启示

当前国内城际轨道交通的发展对以轨道交通为导向的城市综合开发提出更高的要求,针对性剖析香港铁路发展历程和成功经验,结合相关数据分析,研究"城铁一体化"综合开发模式对城际轨道交通可持续发展的作用和意义,对该模式下的财务、政策和技术层面的问题进行探讨,提出"城铁一体化"开发须在政策层面制定相应的"权益流程",实施开发建设的集约化;在运营层面体现"共赢"原则,构建"轨道交通运营+效益返还"机制;针对城市各区域发展不同步的特点,在一体化建设中采用灵活的预留机制满足分期建设的需求,最终实现轨道交通的可持续发展。     

铁路轻油类罐车卸油装置研制

根据国外大型矿区对铁路轻油类罐车装卸需求,研制一种下部卸油装置。通过分析国外下卸式卸油装置特点,确定卸油装置结构和关键部件,开展密封性试验并完成研制工作。研制并运用下卸式罐车,对解决我国轻油类罐车装卸存在的问题具有一定借鉴意义。     

Identifying preferences for public transport investments under a constrained budget

As urban areas face increasing demands for new transport infrastructure to promote a sustainable future with an increasing reality of constrained government budgets, the debate on whether we should focus on rail or bus-based investments continues unabated in many jurisdictions. Associated with the debate is an emotional (or ideological) bias by communities in favour of one mode, especially rail, which carries much sway at the political level as if there is no budget constraint. This paper presents a stated choice experiment to investigate this context as two unlabelled options described by 20 potential drivers of community preferences for improved public transport, where each choice scenario is conditioned on an estimated construction cost and a total annual transport infrastructure budget for the relevant geographical jurisdiction. This is followed by a labelling of each alternative to reveal whether the option is bus rapid transit (BRT) or light rail (LRT) and to establish whether this additional information influences preference revision. Data is collected in all eight capital cities of Australia in mid 2014. Mixed logit models with heteroscedastic conditioning in terms of the cost of the project infrastructure and whether the alternative is labelled BRT or LRT, provide new evidence on the nature and extent of community modal bias in a budget-constrained choice setting. The conclusions are twofold. On the one hand, if a fully compensatory choice rule is assumed (as is common in all previous modal comparison studies), LRT is predominantly preferred over BRT despite budgetary constraints, similarities in quality of service attributes and the opportunity to choose a greater network coverage for a given construction cost. However, when we allow for attribute non-attendance (a semi-compensatory choice rule), the modal bias is no longer a significant driver of preferences.