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451.
中国铁路实现跨越式发展的资金保障包括资金筹集和资金节约两方面。一方面,铁路建设的投融资应采取政府主导的多元化投资模式,其中项目融资是实现投资主体多元化和投资方式市场化的重要途径;另一方面,应使铁路建设项目的工程寿命周期成本达到最低,关键是强本简末,严格控制投资规模以及铁路建设项目的工程造价,采取有效的工程项目管理模式。 相似文献
452.
LSPM具有良好的透水性及抵抗较大塑性和剪切变形的能力,配合横向排水管和下封层的使用,能很好地阻止路基裂缝的反射,并减少路面层间水破坏,是一种适用于基层的沥青混合料. 相似文献
453.
J. Jung J. H. Lee S. Song K. M. Chun 《International Journal of Automotive Technology》2008,9(4):423-428
Understanding the mechanism of carbon oxidation is important for the successful modeling of diesel particulate filter regeneration.
Characteristics of soot oxidation were investigated with carbon black (Printex-U). A flow reactor system that could simulate
the condition of a diesel particulate filter and diesel exhaust gas was designed. Kinetic constants were derived and the reaction
mechanisms were proposed using the experimental results and a simple reaction scheme, which approximated the overall oxidation
process in TPO as well as CTO. From the experiments, the apparent activation energy for carbon oxidation with NO2-O2-H2O was determined to be 40±2 kJ/mol, with the first order of carbon in the range of 10∼90% oxidation and a temperature range
of 250∼500°C. This value was exceedingly lower than the activation energy of NO2-O2 oxidation, which was 60±3 kJ/mol. When NO2 exists with O2 and H2O, the reaction rate increases in proportion to NO2. It increases nonlinearly with O2 or H2O concentration when the other two oxidants are fixed. 相似文献
454.
455.
拱圈喷射混凝土施工工艺及操作经验 总被引:1,自引:0,他引:1
介绍了旧桥加固改造拱圈喷射混凝土的施工经验,提出材料控制是前提,合适的喷射混凝土配合比是关键,喷射方式是重点. 相似文献
456.
To increase our understanding of the operations of traffic system, a visco‐elastic traffic model was proposed in analogy of non‐Newtonian fluid mechanics. The traffic model is based on mass and momentum conservations, and includes a constitutive relation similar to that of linear visco‐elastic fluids. The further inclusion of the elastic effect allows us to describe a high‐order traffic model more comprehensively because the use of relaxation time indicates that vehicle drivers adjust their time headway in a reasonable and safe range. The self‐organizing behaviour is described by introducing the effects of pressure and visco‐elasticity from the point of view in fluid mechanics. Both the viscosity and elasticity can be determined by using the relaxation time and the traffic sound speed. The sound speed can be approximately represented by the road operational parameters including the free‐flow speed, the jam density, and the density of saturation if the jam pressure in traffic flows is identical to the total pressure at the flow saturation point. A linear stability analysis showed that the traffic flow should be absolutely unstable for disturbances with short spatial wavelengths. There are two critical points of regime transition in traffic flows. The first point happens at the density of saturation, and the second point occurs at a density relating on the sound speed and the fundamental diagram of traffic flows. By using a triangular form flow–density relation, a numerical test based on the new model is carried out for congested traffic flows on a loop road without ramp effect. The numerical results are discussed and compared with the result of theoretical analysis and observation data of traffic flows. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
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458.
高桩码头施工中的抛石过程会对大管桩的受力产生较大的影响,这将给码头的正常使用带来隐患.模型实验用沙子模拟抛石体,用PVC管模拟大管桩,利用应变片电测技术,测量了不同工况下PVC管中的应变,并分析得出了作用在PVC管上载荷的分布规律.通过模型实验,给出了大管桩与抛石体相互作用的经验公式,并指出引起PVC管侧向弯曲的主要原因是沙子对PVC管存在侧向集中力,产生该集中力的原因是PVC管前后沙子高度差的存在.此外,通过验证实验和数值模拟,得出了与模型实验相同的结论,从而进一步证明了模型实验所得规律的正确性. 相似文献
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