高速铁路轨道的波阻抗及影响因素研究

高速铁路轨道在雷击或故障冲击电流作用下会产生暂态冲击过电压,该过电压的大小由轨道的波阻抗决定。通过建立高速铁路线路的仿真模型,分析直角冲击波在轨道上的传播与折反射过程,提出轨道的波阻抗的计算方法,研究钢轨类型、土壤电阻率、钢轨对地过渡电阻对波阻抗的影响。结果表明:P60型轨道波阻抗数值为235. 55Ω;轨道的波阻抗主要受钢轨类型和土壤电阻率的影响,高速铁路轨道的波阻抗在在210～250Ω变化;在高速铁路轨道仿真模型中,线路末端电阻等于波阻抗时,可以有效地消除折反射对仿真结果的影响,末端电阻的取值不需要考虑钢轨地过渡电阻的影响。研究给出高速铁路轨道波阻抗的范围及仿真模型中末端电阻的取值方法,可以为轨道过电压计算、分析与仿真提供理论与方法参考。     

Estimation of extreme significant wave heights and the associated uncertainties: A case study using NORA10 hindcast data for the Barents Sea

The reliability of an offshore structure is dependent on its response to the extreme wave climate; therefore, an adequate knowledge of the wave climate at a location is a prerequisite during design as well as in marine operations. This study aims to contribute to the knowledge of the extreme wave climate in the Norwegian Sector of the Barents Sea, using wave hindcast datasets from the Norwegian Reanalysis 10 km (NORA10) database for four locations.We have considered three commonly used methods for the estimation of extreme wave heights, that is, the initial distribution method, the peak over threshold method, and the annual maxima method. The parametric bootstrap concept is considered in the estimation of the epistemic uncertainty related to sample size. The estimated 100-year significant wave heights obtained from the three methods differ, and the degree of variability in the estimates varies, depending on the dataset. The epistemic uncertainty due to sample size is wider when considering the annual maxima method.The estimates obtained from the three methods show the importance of considering different methods and their associated uncertainties when estimating extreme wave values for design. While it is difficult to single out the best method among the three, the estimated values give knowledge of the possible range of the extreme significant wave heights at the locations. Generally, the datasets considered in this study suggest that the wave climate is less harsh further north compared to the southern region of the Barents Sea. The datasets do not suggest any temporal trends in the historical significant wave heights at any of the locations.     

Are French millenials less car-oriented? Literature review and empirical findings

Generation effects play a key role in shaping long-term trends in travel behaviors. Though cohorts born until the 1970s have been increasingly car-focused, a reversal of this trend was noticed among the millenials. Determining whether this break-in-trend resulted from changes in living conditions and economic difficulties, or demonstrates a shift in attitudes away from the car, is critical to future travel trends. We bring a contribution to this debate in the French context, through a literature review followed by empirical findings, using the French Base of Local Household Travel Surveys. Through age-cohort analysis, we find evidence of changing travel patterns among the millenials, taking the form of a shift from driving to transit, along with a decline of car ownership. However, travel attitudes of the millenials play little role, as they do not differ substantially from their elders. Besides, we show that generation effects disappear once a large number of structural factors are controlled for. It looks like the main driver of change in travel behaviors comes from a shift in residential patterns, in relation with longer studies and a delayed entrance into the workforce, and possibly because of increasing work pressure, degraded transport conditions and changes in residential attitudes and desired lifestyles. In the end, these assumptions should be further explored, along with complementary research tracks, including the role of economic factors, the effects of learning experience, as well as heterogeneity in travel patterns, in relation with issues of social and spatial equity.     

A traffic-condition-based route guidance strategy for a single destination road network

Most of existing route guidance strategies achieves user optimal equilibrium by comparing travel time. Measuring travel time, however, might be uneasy on an urban road network. To contend with the issue, the paper mainly considers easily obtained inflow and outflow of a link and road capacity as input, and proposes a route guidance strategy for a single destination road network based on the determination of free-flow or congested conditions on alternative routes. An extended strategy for a complex network and a feedback approximation for avoiding forecast are further explored. Weaknesses of the strategy are also explicitly analyzed. To test the strategy, simulation investigations are conducted on two networks with multiple parallel routes. The results indicate that the strategy is able to provide stable splitting rates and to approximate user optimal equilibrium in different conditions, in particular when traffic demand is high. This strategy has potential to be applied in an urban road network due to its simplicity and easily obtained input data. The strategy is also applicable for single destination if some alternatives and similar routes are available.     

关于公交停靠站影响区范围的研究

随着城市公共交通系统的发展,公交停靠站对道路交通流的影响已逐渐引起人们的注意。分析公交停靠站的影响首先应该对停靠站的影响区范围进行界定。在分析前人研究成果的基础上,基于交通波理论,按考虑超车与否,分析公交停靠站的影响区范围长度,得到不同交通流密度条件下公交停靠站影响区长度的计算公式。     

浮摆式波浪发电平台系泊系统设计

针对一台自行设计的浮摆式波浪发电平台的运动特点与采能方式,对其系泊系统进行设计。系泊型式为"平台—连接缆—浮筒—锚链—锚"的悬链线单点浮筒系泊。以试验海域海况参数为依据,计算系统载荷,并采用准静力分析法对系泊系统各构件进行选型设计。设计的连接缆为钢丝绳,浮筒为圆柱型钢制浮筒,锚链为二级有档锚链,作业锚为AC-14锚。经检验,设计的系统符合安全要求和平台稳定性需求。     

田湾核电站扩建工程取水明渠导流堤优化设计

取水工程为核电厂重要构筑物,按照较高的核电标准设计往往断面较大,在保证取水安全的前提下,分析不同工程的使用要求,有针对性的的进行优化设计,可降低工程造价。以田湾核电取水工程为例,分析优化设计过程,供类似工程参考。     

小水线面双体船波浪载荷研究

摘要：针对某大型小水线面双体船,进行波浪载荷直接计算。根据规则波中波浪载荷RAO特性和其波浪载荷的长期预报结果,确定该船的设计载荷。并将该设计载荷与CCS《小水线面双体船指南》中设计载荷进行对比和分析,指出规范对于大尺度大排水量小水线面双体船波浪载荷计算的局限性。同时,由该船波浪载荷长期值沿船长和船宽的分布,分析其波浪载荷的分布规律,为工程中大排水量小水线面双体船的结构设计和加载提供参考。     

CSR-H与CSR强度评估载荷的对比研究

对CSR-H 与CSR用于强度分析的载荷变化进行分析,对各载荷分量的包络值以及应用于等效设计波中的船体梁波浪弯矩、波浪剪力和外部海水压力、加速度等载荷分量的大小进行比较。分析货油舱、干散货舱、压载舱典型位置处的内部压力变化,并对载荷变化可能引起的结构要求变化进行分析和概括。