市场集中度与道路运输集约化经营

针对我国道路运输市场发展现状,从产业经济学理论出发,借鉴发达国家道路运输发展成功经验,系统分析我国道路运输市场结构及其存在的问题,通过论述市场集中度与道路运输集约化经营之间的关系,提出通过以提高道路运输市场集中度为核心和积极培植大型骨干企业、强化道路运输网络化经营、加大运输组织结构优化和提高产业科技水平等措施,来有效推动道路运输集约化经营。     

连云港外海含沙量推求及航道回淤预测

目前国内在研究淤泥质海岸航道回淤时,通常仅有近岸含沙量的实测资料,而外海含沙量较难获得。为此,建议可以利用实测的航道淤积、近岸含沙量等资料,根据刘家驹的航道回淤计算公式,近岸率定淤积系数,反推外海泥沙含量,据此进行航道回淤预测。经过连云港7万吨级进港航道验证,计算的航道回淤与实测值吻合较好,在此基础上,对拟建的连云港15万吨级航道回淤进行了预测。研究结果表明,所提出的方法切实可行,计算结果合理可信,可以作为相似条件下航道泥沙回淤计算的参考。     

京沪线接触网集中修模式的探讨

接触网设备是铁路重要行车设备之一,对铁路运输的安全和畅通起着重要作用.本文通过京沪线接触网集中修试点情况,探讨接触网检修模式,提出了实施集中修既可以提高设备检修效率、节约检修成本,快速改善设备质量,又能减少运输损失.     

大跨度公路隧道交叉分岔段施工方案研究

由于支隧道的存在，交叉段结构受力复杂，围岩应力高度集中，给施工带来很大困难。为获得交叉段合理施工方案，以四川雅砻江官地水电站内交通工程——隧道交叉段实态建模，进行5种可能方案的三维施工数值研究。结果表明，每种方案中交叉段围岩的竖向位移和应力集中程度均较其他部位高20％以上；开挖后立即支护或分部开挖，可明显降低交叉部围岩的应力集中程度；对交叉部控制截面进行线型优化，可改善裸洞受力情况。研究结论对设计、施工交叉隧道有一定指导意义。     

静电除尘装置在公路隧道通风中的使用条件研究

隧道通风需风量的确定是取CO浓度指标和烟雾指标计算出来的较大者作为需风量。如果是烟雾浓度指标的需风量大于CO指标需风量,则静电除尘装置的使用可以降低隧道内的需风量,从而提高了运行的经济性。在不同的坡度和车速下,机动车的CO和烟雾的排放特性会发生变化。研究了在不同的坡度和车速下,静电除尘装置基本使用条件的确定。研究成果可用于隧道通风设计与研究中。     

On particulate emissions from moving trains in a tunnel environment

Increasing attention is being paid to airborne particles in railway environments because of their potential to adversely affect health. In this study, we investigate the contribution of moving trains to both the concentration and size distribution of particles in tunnel environments. Real-time measurements were taken with high time-resolution instruments at a railway station platform in a tunnel in Stockholm in January 2013. The results show that individual trains stopping and starting at the platform substantially elevate the particulate concentrations with a mobility diameter greater than 100 nm. Two size modes of the particulate number concentrations were obtained. A mode of around 170 nm occurs when a train moves, while the other mode peaks at about 30 nm when there is no train in the station. By using principal component analysis (PCA), three contributing sources were identified on the basis of the classification of the sizes of the particles, namely railway-related mechanical wear, suspension due to the movement of trains and sparking of electric-powered components. It is concluded that the particulate matter released by individual moving trains is a key contributor to fine particles (100–500 nm) on the railway platform in a tunnel.     

Port system evolution – the emergence of second-tier hubs

Some evidence has emerged of second-tier hubs inserting themselves between hubs and feeder ports, producing a new hierarchy of port networks. This article aims to establish the dynamics of this process based on illustrative cases in Asia, South America, and Europe. Findings reveal spatial factors to include a cluster of small ports with minimal sailing distance within a given range, suitable channel and berth depth, and ideally high capacity inland links. From the economic perspective, demand-side factors include a local captive market and aggregated demand to be captured from other ports, while supply-side factors include diseconomies of scale at traditional hubs, an increase in direct services, an increase in large feeder vessels calling from first-tier hubs which are then transhipped to smaller feeders for serving local ports, and an increase in overland servicing of local smaller ports. From a strategic perspective, vertical and horizontal integration in the shipping sector has produced extensive network economies, whereby shipping lines look to create group-specific port hierarchies, enhanced in the presence of aggressive management strategies and supportive policies. This finding suggests that proactive port stakeholders can in certain circumstances seize the opportunity to capture this role within their port range.     

合力打造铁路给水排水行业快速发展的新局面

根据铁路跨越式发展对给水排水行业带来的新课题 ,提出了给水排水行业快速发展的总体思路和主要内涵 ,说明了行业加速实现装备现代化的建设要求 ,分析了生产布局调整的意义和前景。号召大家齐心协力 ,奋发进取     

Surface chlorophyll in the Black Sea over 1978–1986 derived from satellite and in situ data

Absolute values of chlorophyll a concentration and its spatial and seasonal variations in the Black Sea were assessed by using satellite CZCS and in situ data. Since the satellite CZCS had operated for the 1978–1986 period, CZCS data was used for assessing the past state of the Black Sea just before the onset of drastic changes observed in late 1980s. The approach used for the calculation of the absolute values of chlorophyll a concentration from CZCS data was based on the direct comparison of in situ chlorophyll a data and those of CZCS and by applying the algorithm developed for the transformation of CZCS data into chlorophyll a values. CZCS Level 2 data related with pigment concentration having a spatial resolution of 1 km at nadir were used. The daily Level 3 files were derived by binning Level 2 values into 4-km grid cells and the monthly and seasonal Level 3 files were created by averaging the daily Level 3 files over the corresponding period. In situ chlorophyll a data were obtained by spectrophotometric and fluorometric methods in 15 scientific cruises over the 1978–1986 period. Total number of ship-measured data used for the comparison with those CZCS values was 590.Chlorophyll a concentration (Chl) was derived from CZCS values (C) with regression equations Chl=kC; the coefficient of transformation k was calculated from six different data sets by taking into account distinctions between subregions and seasons. The reasons for difference in the k values have been analyzed.Statistical comparison of the chlorophyll a values measured in situ and those derived from CZCS data was based on log-transformed data and gave the following results: regression SLOPE=0.842, regression INTERCEPT=−0.081, coefficient of determination (R²)=0.806, root–mean–square ERROR=0.195. The mean monthly chlorophyll a distributions derived from CZCS data over 1978–1986 have been constructed and the mean seasonal chlorophyll a values in different regions have been calculated and analyzed. The significant difference in chlorophyll concentration between the western shelf regions and the open part of the Black Sea has been demonstrated, especially in warm season. At almost all seasons, the highest chlorophyll concentration is observed in the western interior shelf region which is under strong influence of Danube. The summer mean chlorophyll concentration in this region is 18 times higher than that in the open parts and about nine times higher than in the eastern shelf region. The greatest seasonal variations are observed in the open part of the Black Sea: chlorophyll concentration in cold season is four to six times higher than in summer and three to five times higher than in April and October. To the contrary, in the western interior shelf regions, the concentration is higher in May–October (about twice than that in November–March). Seasonal variations in the western outer shelf regions are smoothed out as compared with both the western interior shelf and the open regions.     

青藏铁路客车供氧系统

简要介绍了青藏铁路客车供氧系统的组成及工作过程,针对其使用情况,指出了青藏铁路客车供氧系统在运用中的注意事项。