Experimental study on the effect of cyclic preloading on the resistance to liquefaction of saturated loose sand under wave loading

By using the soil static and dynamic universal triaxial and torsional shear apparatus, a series of combined cyclic shear tests are performed to simulate the rotation in the principal stress direction induced by ocean wave. The tests include the cyclic preloading tests and liquefaction tests in the second loading on saturated loose sand with a relative density of 30%. The all tests are consolidated under isotropic condition. The effect of the cyclic preloading on the resistance to liquefaction of saturated loose sands under the condition of continuous rotation in the principal stress direction is investigated. Experimental data indicate that the void ratio of saturated sands has a negligible reduction after cyclic preloading. With the increase of the intensity of cyclic preloading (in the amplitude and in the number of cycles), the resistance to liquefaction in the second loading is increased continuously under the condition that the liquefaction does not occur during the cyclic preloading. The reason is that the construction of more stable structure due to the uniformity of the void and the better interlocking of the particles when the cyclic preloading is applied to the saturated sand.     

基于SOC-OCV优化曲线与EKF的锂离子电池荷电状态全局估计

SOC-OCV曲线是锂离子电池状态估计的基础.针对传统HPPC测试法在非测试点不能描述电池非线性特性和小电流恒流放电法得到的OCV曲线精度不足等问题,提出一种基于粒子群优化算法的OCV曲线优化方法.该方法将小电流恒流放电得到的OCV曲线进行平移,以平移曲线在测试点与HPPC测试得到的OCV值之间的误差和最小为优化目标,...     

直接边界元法时域全非线性兴波计算

文章在时域中采用直接边界元的方法计算模拟了以稳定航速运动的近水面潜体全非线性兴波现象.从格林定理出发,在边界面上布置Rankine源和偶极子,采用时间步进的方法计算模拟潜体近自由面运动的兴波现象.每个时步自由面上的势和节点位置采用全非线性拉格朗日自由面边界条件求解,重新生成自由面网格准备下一个时步计算的初始条件.文中给出了数值计算的结果并与试验和线性计算的结果相比,证实了该方法是可靠的,并可以利用该方法建立数值波浪水池.     

杭衢铁路新安江至金千货场段线路方案优化

杭衢铁路位于浙江省西部建德市和衢州市境内,是长三角城际路网的重要组成部分,是沪昆铁路杭衢段的辅助通路.本文从保护自然景观、节省工程投资的角度考虑,对杭衢铁路新安江特大桥线路纵断面方案进行了优化;在与行车速度相匹配的前提下,结合满足轨温调节器设置的平面条件、绕避居民回迁区以避免二次拆迁等因素,对杭衢铁路新安江至金千货场段...     

基于区块链技术的船舶污染物跟踪追溯应用研究

随着我们国家从海洋大国走向海洋强国,航运规模持续提升,船舶对海洋造成的污染问题也日益凸显.目前,船舶污染物大多送岸处理,水岸双方对船舶污染物接收、转运、处置的监管方式方法比较陈旧,衔接不畅,存在二次污染的可能性.区块链技术的出现,可以更好地解决船舶污染物监管问题,能够如实、准确反映船舶不同种类污染物的产生数量、转移去向...     

武汉轨道交通4号线二期工程换乘站方案研究

研究目的:武汉市轨道交通4号线二期工程穿越武汉主城区,与线网规划中的多条地铁线路进行换乘。由于经过的城市区域尚处于开发时期,地铁工程多处与规划或在建的市政工程协调。本文通过对武汉轨道交通4号线二期工程换乘车站方案的介绍,论述了各个换乘车站的控制因素及方案形成的过程,以及方案形成过程中与规划的市政工程协调关系,以工程可实施性和乘客的换乘便捷为出发点,兼顾城市发展规划的需要,为换乘车站设计提出清晰的思路。研究结论:(1)地铁换乘车站设计除了在满足换乘功能外,还要与密切的相关市政工程同期设计、同期实施,应从城市发展的高度统筹协调处理;(2)处于开发阶段的城市区域可利用地铁建设的契机,完善强化城市地下空间的建设,使得区域性的交通组织得到相应的改善。     

既有混凝土梁桥抗震性能评价

针对既有混凝土梁桥抗震性能评价尚无规范可循的现状,结合正在实行的《公路桥梁抗震设计细则》（JTG／T B02－01－2008）以及《公路桥梁抗震性能评价细则》（征求意见稿）,对相关规定对比分析,明确既有混凝土梁桥抗震性能评价方法。根据桥梁的重要程度、建造年代、设计标准等确定抗震性能目标;对桥梁进行调研,针对构造措施、构造细节等进行一级评价;对关键构件进行详细的抗震能力评价,依据结构形式、材料实际强度等,对其整体抗震性能进行二级评价;综合评价结果,针对存在的问题提出解决建议。将该方法应用于京沪高速公路某混凝土梁桥,得出该桥总体抗震性能不满足要求,建议优化支座布置方式及更改支座型号,或采取减隔震措施。应用实例验证该评价方法思路清晰、步骤明确、便于应用。     

京杭运河二通道方案研究及工程措施分析

阐述京杭运河与钱塘江沟通的第二通道工程线位方案的研究,并对八堡出口的通航条件作了深入的分析,提出八堡出口是目前钱塘江三堡船闸下游的最优出口,分析了八堡出口的河床演变规律及控制因素,在对历年资料进行综合分析、模型试验及专题研究的基础上,提出了八堡出口的工程整治措施,为京杭运河二通道工程的顺利实施奠定了良好的基础。     

不连续导电模式功率因数校正电路二次谐波的分析与抑制

基于Buck变换器的有源功率因数校正电路可直接实现功率因数校正和降压功能,但会在输出电压中产生较大的二次谐波电压,本文就两种降低二次谐波电压的方法-增大输出电压反馈的带宽和串联补偿技术进行了比较,结果表明串联补偿技术能够有效降低二次谐波电压,而且输入电流能够很好地跟踪输入电压且无畸变,保持较高的功率因数。     

A consumer-oriented total cost of ownership model for different vehicle types in Germany

In Germany, market penetration by alternative powertrains has been generally processing at a slow pace. Therefore, reaching the 2020 target of one million registered electric vehicles (EVs) is a major challenge. We analyze the German market by advancing and refining existing consumer-oriented total cost of ownership (TCO_C) models and demonstrate the validity of our model by comparing the cost-efficiency of EVs and internal combustion engine vehicles (ICEVs) including the battery resale value for second use and second life. The TCO_C model was calculated for the ten most frequently registered battery electric vehicles (BEVs) and hybrid electric vehicles (HEVs) and compared with ICEVs in the same vehicle segments. The results are further validated through applying three typical annual mileage driver profiles and by Monte Carlo simulations under various scenarios. Results reveal that only a few BEVs and HEVs are economical without subsidies when compared with ICEVs in all considered scenarios. The subsidies only barely change the results. The mini and the medium vehicle segment remain uneconomical in all tested scenarios. Overall, we conclude that subsidies support the competitiveness of BEVs, but fail to lead to favorable TCO_C within several vehicle segments and several tested annual mileages.