基于组合预测模型的世界海运周转量预测分析

世界海运周转量是衡量未来航运市场运力需求的直接体现,在确定航运市场和船舶市场的发展趋势方面具有关键作用。针对世界海运周转量受到众多复杂因素影响的现实,基于传统的单个预测方法,分别采用时间序列、灰色系统、神经网络方法对世界海运周转量进行预测,然后再对单个预测方法进行加权组合,建立组合预测模型进行海运周转量的预测,预测结果表明:组合预测模型能够得到更加可靠的结果。     

Thermal Model for Square Lithium-ion Battery Pack

首先通过最小二乘法对方形锂离子电池组中单体电池的比热容、流道材料的导热系数和自然冷却条件下的综合换热系数进行了估计;然后根据热边界层理论确定了强制冷却条件下电池冷却流道表面局部综合换热系数的计算式;最后根据电池组的结构特点和冷却方式,建立了电池组的一维瞬态传热模型.该模型能根据电池组当前的环境温度、运行负荷、冷却强度和初始荷电状态实时预测电池组中各单体电池的运行温度.在Arbin试验台架上测量了144V/8A·h方形锂离子电池组在不同运行工况下单体电池的温度分布,并与模型仿真结果进行了对比,结果表明模型仿真的最大误差不超过1℃,满足混合动力系统性能仿真和电池组管理策略优化的精度要求.     

燃料电池发动机空气过滤器的实验与仿真

基于FLUENT软件,通过用户自定义函数(UDF)给定滤芯吸附SO2的约束条件,对过滤器的流体力学及化学吸附特性进行了仿真;仿真得到的SO2穿透曲线与实验结果吻合较好,所建模型能可靠地预测滤芯使用寿命.在此基础上对过滤器结构进行改进,结果表明,通过在化学滤芯上增加导流板可改善吸附层出现“死区”、“短路”的现象,从而提高滤芯的性能和使用寿命.     

新型变截面双空腔吸声结构设计探讨

为改变高速公路交通噪声的严重污染现状,设计一种新型变截面双空腔吸声结构,其是由金属吸声板、前部变截面空腔、中间吸声隔层、后部空腔、背部隔声板5大部分构成。由混响室吸声系数的测定试验可知,该吸声结构在250～1 000 Hz中低频段的吸声系数均在0.65以上,总体降噪系数均大于0.60,较传统吸声结构,其吸声降噪效果有显著提升。     

Brazil’s new vehicle front impact safety standards — ABNT NBR 15300-1 & ABNT NBR 15300-2 or ABNT NBR 15300-3: Is the manufacturerer choice the safest for the passenger?

To increase car passenger safety, the Brazilian National Traffic Council (CONTRAN) released Resolution 221, which defines the maximum passenger and driver biomechanical criteria in the event of a vehicle frontal impact. The vehicle maximum allowed biomechanical injury criteria will be enforced from January 2012 for new vehicles and in January 2014 for vehicles in production before January 2014. To standardize the test method to measure the driver and front passenger injury values in a frontal crash, Resolution 221 states that the tests must be performed according to the ABNT NBR 15300-1 standard, followed by the ABNT NBR 15300-2 standard or the ABNT NBR 15300-3 standard. The use of ABNT NBR 15300-2 or ABNT NBR 15300-3 standards is a free choice for the manufacturer of the vehicle. The ABNT NBR 15300-1 + 15300-2 test is similar to the FMVSS 208 standard in the United States in terms of its vehicle frontal impact test perpendicular to a rigid barrier with the use of seat belts by male model dummies. The test according to ABNT NBR 15300-1 + 15300-3 follows the European ECE R94 and 96/79/EC standards. However, ABNT NBR 15300-2 focuses on occupant protection during vehicle deceleration rather than occupant protection during vehicle deformation in a crash test. ABNT NBR 15300-3 tests occupant protection during vehicle deformation more than it tests occupant protection during vehicle deceleration. Therefore, this paper aims to show the types of test results produced by the ABNT NBR 15300-2 and ABNT NBR 15300-3 standards and their differences concerning occupant protection verification and discuss the manufacturer??s freedom of choice.     

Design of a soft switching bidirectional DC-DC power converter for ultracapacitor-battery interfaces

One solution to the low specific power of hybrid electric vehicular batteries is a hybrid energy storage system (HESS) that takes advantage of the high specific power performance of ultra-capacitors. The design of a type of zero current transition (ZCT) soft switching bidirectional direct current-direct current (DC-DC) power converter that can be used as an ultra-capacitor-battery interface in an active parallel schema of a HESS is described. The circuit operation of the ZCT DC-DC power converter is depicted in detail. The HESS controller is designed as a two-layered hierarchical control structure: the first layer is responsible for working mode control of the HESS, and the second layer is responsible for DC-DC power converter control in which a fuzzy logic PID algorithmis employed. Simulation results indicate that this design is a potential solution to the problem of the low specific power of batteries, especially for regenerative braking and electric motor assist. The proposed active parallel schema with ZCT exhibits a significant advantage in power and energy decoupling. HESS with ZCT achieves better efficiency compared to the battery only operation. The experimental results validates the idea that the ultra-capacitor cooperates with the battery in acceleration mode.     

Fuzzy adaptive sliding mode controller for an air spring active suspension

A fuzzy adaptive sliding mode controller for an air spring active suspension system is developed. Due to nonlinearity, preload-dependent spring force and parameter uncertainty in the air spring, it is difficult to control the suspension system. To achieve the desired performance, a fuzzy adaptive sliding mode controller (FASMC) is designed to improve the passenger comfort and the manipulability of the vehicle. The fuzzy adaptive system handles the nonlinearity and uncertainty of the air suspension. A normal linear suspension model with an optimal state feedback control is designed as the reference model. The simulation results show that this control scheme more effectively and robustly isolates vibrations of the vehicle body than the conventional sliding mode controller (CSMC).     

管线钢X70-L245对接接头焊接工艺研究

针对不同强度级别的管线钢X70和L245对接的焊接工艺进行了研究。通过碳当量计算和金相组织观察,分析了钢材焊接性;确定出预热和层间温度;选择了焊接材料;并进行了坡口设计。同时根据Q/SYXQ18—2002和XQ-CS-JX-SPE-0010标准对所制定的焊接工艺进行了评定。经评定,管口外观检查和射线检测合格,金相组织、拉伸试验、冲击试验等各项性能指标优良。按照该工艺施工的焊接接头质量合格,完全满足施工的技术要求。     

高速道岔尖轨点云的复合拼接及数据处理优化

为实现高速铁路尖轨磨耗的高效检测,结合高速尖轨的检测需求及其几何特征,提出了基于距离编码器的复合拼接方法.该方法将距离信息融合到点云拼接中,提高了检测系统的自动化程度.在计算点特征直方图（point feature histograms,PFH）的过程中,引入OpenCL（open computing language）异构加速模型调整点云的数据结构,发挥GPU的并行处理优势获得了更快的数据处理速度.利用实际尖轨开展磨耗检测实验,证明了针对高速尖轨的结构光检测系统有效可行.经过点云拼接和点云扫描数据处理的优化,系统的整体检测效率获得了70%左右的提升.      

板边离缝对CRTS III型轨道-路基动力特性的影响

为了研究板边离缝对高速铁路基础结构动力特性的影响,利用CRTS III型板式轨道-路基全尺寸试验模型开展了落轴试验,实测了轨道板与自密实充填层一侧界面处离缝的几何分布,并利用ANSYS/LS-DYNA有限元软件建立了相应的动力有限元分析模型,分析了板边离缝对轨道和路基结构冲击动力特性的影响规律,并利用相应的试验结果对数值结果进行了对比验证. 研究结果表明:轨道板和自密实层界面处单侧离缝的平均宽度和平均高度分别为28.18 cm和2.15 mm;板边离缝宽度对基础结构动力特性的影响要大于离缝高度;在0～800 mm的范围内,随着离缝宽度的增加,轨道和路基位移以及钢轨加速度、轨道板加速度和基床底层加速度都持续增加,其中轨道板的位移和加速度的增幅均为最大,分别为56.8%和143.3%,充填层、支承层和基床表层的垂向加速度随离缝宽度的增加先增大后减小,当离缝尖端扩展至钢轨正下方附近时达到最大值;在0～3 mm的范围内,轨道和路基垂向位移与加速度均随离缝高度的增大而略微增加,最大增幅分别为8%和12%;越靠近离缝界面层面,离缝高度对其冲击动力特性的影响也越显著.