铁路10kV配电所改造设计若干问题探讨

铁路配电所是铁路电力供电系统的主要组成部分,既有配电所改造设计与新建配电所设计有着明显的不同,需要满足技术先进性、设备可靠性以及经济性,而且还要解决现有设备在运行过程中的问题.本文对铁路10 kV配电所改造设计中遇到的问题进行分析与讨论,并提出设计应采用的策略.     

不同方法对南黄海重现波高计算值的影响

采用SWAN波浪模型对江苏南黄海地区1979~2018年共40 a的波况进行模拟及验证,将模拟结果与实测资料进行比对,吻合良好。百年重现波高分布通过基于年极值和月极值的广义极值分布函数(GEV)和超阈值取值方法(POT)的广义帕累托分布模型(GP)计算得出。计算结果表明,不同方法的计算结果在辐射沙洲北部地区差别最大,采用月极值所得重现波高偏小,采用年极值计算的重现波高在辐射沙洲南北外围地区最大,其余地区则以POT方法为大值。在分别采用不同数据长度计算重现波高的试验中得出,取月极值的GEV分布计算结果对时间跨度的改变不敏感,而取年极值受之影响最大,POT方法介于两者之间。     

断级滑行艇水动力特性的初步计算研究

利用数值手段对二维断级滑行艇模型的绕流场进行模拟,并针对不同攻角及断级高度的模型进行对比计算。不同模型的计算结果具有明显差异性,能较好表现出模型参数的变化对模型水动力特性的影响。分析断级的作用机理,并论述断级后脱体涡的强度和范围以及模型参数不同而引起的滑行面压力分布的差异。     

Measuring transport related CO2 emissions induced by online and brick-and-mortar retailing

We develop a method for empirically measuring the difference in transport related carbon footprint between traditional and online retailing (“e-tailing”) from entry point to a geographical area to consumer residence. The method only requires data on the locations of brick-and-mortar stores, online delivery points, and residences of the region’s population, and on the goods transportation networks in the studied region. Such data are readily available in most countries. The method has been evaluated using data from the Dalecarlia region in Sweden, and is shown to be robust to all assumptions made. In our empirical example, the results indicate that the average distance from consumer residence to a brick-and-mortar retailer is 48.54 km in the studied region, while the average distance to an online delivery point is 6.7 km. The results also indicate that e-tailing increases the average distance traveled from the regional entry point to the delivery point from 47.15 km for a brick-and-mortar store to 122.75 km for the online delivery points. However, as professional carriers transport the products in bulk to stores or online delivery points, which is more efficient than consumers’ transporting the products to their residences, the results indicate that consumers switching from traditional to e-tailing on average reduce their transport CO₂ footprints by 84% when buying standard consumer electronics products.     

基于坐垫体压分布的驾驶员生理状态识别方法

提出一种基于坐垫体压分布识别长途驾驶过程中驾驶员生理状态的方法.开展长途驾驶模拟试验,采集9名被试者在驾驶过程中的坐垫体压分布数据,提取82维分类特征,再采用序列浮动前向选择算法从中选出55维最优特征子空间.试验结果表明,该方法能准确识别驾驶员生理状态,贝叶斯分类正确率可达93.37％.     

Brake light cellular automaton model with advanced randomization for traffic breakdown

Traffic breakdown is one of the most important empirical phenomena in traffic flow theory. Unfortunately, it cannot be simulated by many traffic flow models. In order to clarify its mechanism, the new brake light cellular automaton model has been proposed. Comparing with previous brake light models, three different aspects have been considered: (i) drivers tend to take large decelerations if the time gap is smaller than the safe time gap and the leading vehicle’s brake light is on; (ii) the brake light rule is set according to the reality; (iii) the randomization rule is put forward before the acceleration rule to weaken the impact of brake light on driving behaviors. Analyses show that the new model can explain the mechanism of traffic breakdown and the failures of other brake light models. Simulations confirm that all empirical features of traffic breakdown are successfully reproduced. At last, brake light models are calibrated and validated by the I-80 empirical data provided by NGSIM. Results show that the performance of the new model is the best and models in the three-phase theory are not necessarily better than models in the fundamental diagram approach and vice versa, at least for the brake light models.     

基于Ecotect的T型交叉路口布灯方式仿真分析

为研究灯具布置对T型交叉口的照明影响,通过采用照明仿真软件对T型交叉口的交错式、对称式及中心对称式3种布灯方案进行仿真模拟分析,得到了不同布灯方式下的照明强度。结果表明:在相同灯具及条件下,交错式布灯方案最优,但道路终端灯光光强设置需偏大;对称式方案效果次之,交叉口中心位置照度低;中心对称式集中照明效果最好,但相比交错式及对称试其经济能耗最大。通过照明仿真模拟分析,有效验证了交错式布灯方案在T型交叉口照明设计中的优越性。     

Bi-objective routing problem with asymmetrical travel time distributions

Recent studies have confirmed that travelers consider travel time reliability in addition to average travel time when making route choice decisions. In this study, we develop a bi-objective routing model that seeks to simultaneously optimize the average travel time and travel time reliability. The semi-standard deviation (SSD) is chosen as the reliability measure because it reflects travelers' concerns over longer travel time better than the commonly used standard deviation. The Pareto-optimal solutions to the bi-objective model are found by using an improved strength Pareto evolutionary algorithm. Tests on a real-world urban network with field measured travel time data have demonstrated good performance of the algorithm in the aspects, such as computational efficiency, quick convergence, and closeness to the global Pareto-optimal. Overall, the bi-objective routing model generates reasonable path recommendations. The SSD-based model is sensitive to the asymmetry of travel time distribution and tends to avoid paths with excessively long delays. This would be particularly helpful to those users placing high values on travel time reliability.     

沉管隧道横向地基刚度分布模式初探

为解决沉管结构横向设计计算中的地基刚度取值问题,基于HS本构模型,通过理论推导研究地基刚度随应力水平的变化关系,得出沉管隧道横向地基刚度分布的近似解析解。结果表明： 1)沉管横向地基刚度分布模式与地基初始刚度、结构刚度、地基应力水平和上部荷载有关; 2)在软弱地基情况下,沉管横向地基刚度为W形分布模式; 坚硬地基情况下,底板跨中可能会与地基发生局部脱开,脱开段地基刚度为水平分布; 3)通过算例分析,地基刚度分布近似解析解与数值模拟结果能够较好地吻合,可为沉管结构计算提供依据。     

高速布置型船舶的风帆设计及综合效能分析

针对国内研究较少的高速布置型船舶的风帆助航问题,基于船舶特点及风帆升阻力特性选定了帆型,设计了一套风帆加装方案。在结合历史气象统计数据的基础上,对风帆长期综合效能进行了分析。以一艘大连-烟台航线上高速客滚船为例,结合实船统计得到的此航线上的历史风场资源时空分布,对该船加帆后长期综合效能进行了计算,结果表明,所设计的风帆可较为显著地降低耗能并减少温室气体排放,具有良好的推广应用前景。