基于“门到门”运输的铁路物流“库存-运输”模型研究

我国铁路货运改革提出了"门到门"运输的发展模式,给铁路物流企业提出了新的要求和挑战。对于铁路货运来讲,这是改变体制、面向竞争、融入市场的良好发展契机。铁路物流企业将来要更多的承担全程物流的任务,因此,如何在具有"效益悖反"的库存和运输之间获得整体最优的运输模式成为亟待解决的问题。本文分析了铁路物流系统中的库存和运输费用,用时间因素反映二者的效益悖反关系,建立了以铁路运输为主导、联合多种运输方式实现"门到门"运输的库存-运输整体最优模型,提出求解模型的模拟退火算法,并对一算例进行简单分析,最后基于模型为铁路物流企业的发展提供针对性建议。     

面向“离位”儿童乘员的常开式安全气囊优化设计

儿童乘坐校车时常呈现多种"离位"坐姿,有必要开展多种儿童坐姿下,常开式安全气囊的优化设计研究,明确12岁儿童的损伤阈值。为此构建并验证校车的仿真模型,搭建校车和常开式安全气囊的耦合模型。选取躺卧坐姿、右倾坐姿作为12岁儿童乘员的典型"离位"坐姿,并针对正常坐姿、躺卧坐姿和右倾坐姿,以加权伤害指标为优化目标,基于响应面代理模型和改进型NSGA-Ⅱ算法,权衡确定常开式安全气囊的主要设计参数的最优配置为:泄气阀开度199.73%、泄气阀开启压力1.1628×105Pa、安装点高度0.362 8 m和中部拉带长度0.315 2 m。结果表明:3种儿童坐姿下,具备最优配置的常开式安全气囊能够最大限度地提升12岁儿童乘员的安全性。     

Field data observations for monitoring the impact of typhoon “In-fa” on dynamic performances of mono-pile offshore wind turbines: A novel systematic study

For offshore structures such as offshore wind turbines (OWT), typhoon is usually considered one of the most critical threats to structural safety performances and service life due to its heavy wind, wave, and even coexisted storm surge. Meanwhile, it is challenging to obtain the systematic data from the environmental conditions, structural dynamic vibrations and the SCADA record, when typhoon passes by the offshore wind farm. Taking into account these situations, a real-time multi-source monitoring system enabling the investigation of the typhoon impact on the performances of OWT, has been firstly established and implemented to a 4.0 MW mono-pile OWT in Rudong, Jiangsu, China. One of the major contributions in this work is to develop the monitoring system using a unique environment of real-world data that has been synchronously obtained from waves, winds, vibrational accelerations, inclinations of towers and SCADA data during the typhoon “In-fa” passing by the wind farm, and provide the scientific community with the underlying standards and technical recommendations. To investigate the influence caused by “In-fa”, comparison results of the measured data in the range of June to August have been analysed. It is worth noting that two conclusions have been obtained: (1) the region near the nacelle is not always the most critical vibrational area. Actually, the change of the maximum structural response in the position under different external loads should be applied to effectively evaluate the structural safety; (2) the measured accelerations exhibit an obvious decay process in the presence of the turbine rotor-stop, but not the yaw rigid-body motion. This observation promotes the accurate identification of modal parameters for the long-term monitoring. Consequently, these valuable findings to facilitate the assessment of structural operational conditions have been developed into two guide-lines. All the data and analyses presented in this paper provide a valuable insight into the design, energy efficiency, safety monitoring and damage diagnosis of OWT structures.