Urban travel time reliability at different traffic conditions

The decision making of travelers for route choice and departure time choice depends on the expected travel time and its reliability. A common understanding of reliability is that it is related to several statistical properties of the travel time distribution, especially to the standard deviation of the travel time and also to the skewness. For an important corridor in Changsha (P.R. China) the travel time reliability has been evaluated and a linear model is proposed for the relationship between travel time, standard deviation, skewness, and some other traffic characteristics. Statistical analysis is done for both simulation data from a delay distribution model and for real life data from automated number plate recognition (ANPR) cameras. ANPR data give unbiased travel time data, which is more representative than probe vehicles. The relationship between the mean travel time and its standard deviation is verified with an analytical model for travel time distributions as well as with the ANPR travel times. Average travel time and the standard deviation are linearly correlated for single links as well as corridors. Other influence factors are related to skewness and travel time standard deviations, such as vehicle density and degree of saturation. Skewness appears to be less well to explain from traffic characteristics than the standard deviation is.     

锚固路堑高边坡稳定性非线性模糊评判

针对路堑高边坡锚固后的稳定性评价,基于模糊性与层次性构建锚固路堑高边坡稳定性2级模糊综合评判模型。根据不同类评价指标的取值方法及隶属度函数选取原则,建立统一的隶属度确定方法,采用三角模糊数互补判断矩阵排序方法确定权向量,以体现评价指标重要程度比较的不确定性。引入非线性模糊算子,以消除个别影响因素不利时对结果的突出影响,使评价结果能更真实地反映工程实际状况。以京新高速公路路堑高边坡稳定性评价为应用实例,验证该模型的可行性与合理性。     

Surface CO2 measurements in the English Channel and Southern Bight of North Sea using voluntary observing ships

Ships of opportunity have been used to investigate ocean–atmosphere CO₂ fluxes in the English Channel and Southern Bight of the North Sea. Continuous underway measurements of the fugacity of seawater carbon dioxide (fCO₂^sw), chlorophyll, temperature and salinity have been performed along 26 transects during the spring and autumn periods. The spatial fCO₂^sw distribution along the Channel and Southern Bight is modulated by the photosynthetic activity, temperature changes and water mixing between inputs from the North Atlantic Ocean and riverine discharges. The seasonal variability of fCO₂^sw is assessed and discussed in terms of the biology and temperature effects, these having similar impacts. The variation of fCO₂^sw shows similar interannual patterns, with lower values in spring. The annual average of air–sea CO₂ fluxes places the English Channel as neutral area of CO₂ uptake. The spring and autumn data allow differentiating between distal and proximal continental areas. The Southern Bight shows a tendency towards net CO₂ uptake on the distal continental shelf, whereas the Scheldt and Thames Plumes show a CO₂ source behaviour on the proximal continental shelves.     

基于机会约束条件下舰艇航线动态规划模型研究

从舰艇出航隐蔽性要求出发，根据舰艇在海上不同航段被敌方探测发现的概率不同，建立基于机会约束条件下动态规划航线数学模型，实现从多条航线中选择满足不被探测发现置信水平下的最短航程航线，从而为指挥员迅速选择最优航线提供辅助决策。     

浅谈城市轨道交通小号码道岔设计

小号码道岔在城市轨道交通领域占据主力市场 ,在城市轨道交通领域发挥着不可估量的作用。小号码道岔设计应结合城市轨道交通的特点 ,合理地选择未被平衡的离心加速度和线型 ,合理地计算其轨距加宽及解决自身的构造加宽问题。小号码道岔跟端应当向弹性可弯方向发展。小号码对称道岔需要重新认识并重视起来。     

梯形模糊数语言指标值的工程综合评估

采用一种折中型模糊多属性决策方法对工程中的总体方案进行评估。基于折中型模糊多属性决策方法的思想和梯形模糊数期望的计算公式,提出了梯形模糊数的相关定义和公式,给出语言多指标决策问题的折中型分析法。给出的算法使决策方法更具柔性,决策结果更加贴近于实际。最后用所提出的方法分析了1个算例。     

无控制交叉口冲突次数的计算方法

本文用概率的方法,就无控制交叉口的冲突进行了研究,提出了冲突次数的计算公式并进行了讨论。     

水下航行体通气超空泡的实验研究

为了研究超空泡的减阻效果,保证在较低流速下生成超空泡,在水洞中开展了水下航行体通气超空泡的实验研究.采用通气的方法在较低水速下(V=7-15 m/s)生成人工通气超空泡,通过改变通气率和弗洛德数,获得了不同条件下通气空泡的长度,给出了通气空泡长度与通气率及弗洛德数的经验公式.研究表明,来流速度不变时,空泡长度随通气率的增加而增加,空泡长度一定时,通气率随弗洛德数的增加而减少;重力场造成了空泡形态的严重不对称,通过比较相同空化数下自然空泡与通气空泡的长度,定量地给出了弗洛德数对通气空泡长度的影响.当Fr=43.74时,重力场对通气空泡长度的影响几乎可以忽略.     

起动机用单向离合器

详细介绍起动机用单向离合器的别称、组成、分类、功能、动作原理、常用参数、安装注意事项、品质鉴别方法、检测方法、常见故障排除方法,列举了典型故障实例,并给出了单向离合器用衬套的型号与适用车型或通用及适用起动机型号。     

残缺信息下火炮效能评估的直觉模糊群决策法

基于炮兵武器系统作战效能评估问题,在属性信息存在一定信息残缺的情况下,运用信息残缺直觉模糊多属性群决策方法,通过决策专家对不同炮兵武器的残缺效用信息值进行集结,建立属性权重求解的线性规划模型,对武器系统作战能力进行排序和择优。最后结合实例,对模型进行了检验。