Experimental Research on the Dynamic Energy Absorbing Capacity of the Honeycomb Paperboard Filled with Polyurethane

A kind of composite buffering material was made by filling the voids of honeycomb paperboard with polyurethane. Drop tests were performed to evaluate the dynamic energy absorption capacity of the material. Based on the tests results, the mechanical behaviors of the material under low velocity dynamic impact conditions were analyzed. It was shown that the absorbed energy of the composite material varies inversely with the void diameter. The absorbed energy of the composite material is 1 - 2 times than that of honeycomb paperboard and polyurethane. The energy absorption efficiency of the composite material is better than those of honeycomb paperboard and polyurethane.     

数字化电气信息采集对继电保护可靠性的影响

数字化电气信息采集为数字化变电站乃至智能电网信息化提供直接支撑.针对电子式互感器和合并单元的特点,给出数字化电气信息采集系统的功能模块.从互感器结构、数字传输、数据验证、采样频率和系统配置方面,分析数字化电气信息采集对继电保护可靠性的影响,着重说明了数据同步对差动保护的影响.指出由于存在电子式互感器的稳定性以及网络通讯可依赖性问题,目前数字化变电站继电保护系统在很大程度上仍沿用传统保护的设计思路,有待进行深入研究和突破.     

甘蔗渣对亚甲基蓝的吸附性能实验研究

为研究甘蔗渣在处理印染废水脱色中的实际效果,以亚甲基蓝模拟废水为研究对象,考察了甘蔗渣在不同的实验条件下如吸附剂投加量、pH、振荡时间、初始质量浓度、温度等,对亚甲基蓝的吸附效果和规律.结果显示:在温度为30℃,pH为6～7,震荡时间为15 min的条件下,3 g甘蔗渣可使100 mL质量浓度为100 mg/L的亚甲基蓝的去除率达95%以上,30℃下甘蔗渣理论饱和吸附量为12.71 mg/g.甘蔗渣对亚甲基蓝的吸附过程可以用Langmuir、Freundlich、Temkin等温吸附方程和二级吸附速率方程进行很好的描述,主要表现为物理吸附.     

带有时间窗的虚拟场站接驳补货车辆路径问题

针对大区域多需求点的物流配送系统,在原有的车辆配送总费用为目标的基础上,兼顾顾客的满意度目标,建立了带有时间窗车辆路径问题的多目标最优化模型,该模型基于大小车沿途在虚拟场站接驳补货策略,节省了货车往返配送中心补货次数、距离与时间.根据该模型需要部分顾客作补货点的特点,利用K均值聚类的方法将顾客分类,采用基于分区域和极大极小策略的多目标进化算法思想进行求解,以测试题库The VRP Web中的算例进行测试分析.经由测试结果比较,相较于非接驳补货的传统VRPTW,该模型效益明显.     

门式刚架轻钢结构抗风安全性分析

为研究门式刚架轻钢结构的抗风安全性,采用风洞试验方法对我国东南沿海一轻钢厂房的表面风压进行了测试;将测得的2个最不利风向的风荷载以及按荷载规范和轻钢规程计算的风荷载分别施加于厂房的不利刚架上,采用基于板壳单元的精细有限元方法对刚架进行极限承载力的非线性分析,获得了在不同工况下刚架的抗风安全系数和风致破坏形态.通过对刚架在不同风荷载取值下的风致安全性进行了对比分析,结果显示:该刚架在轻钢规程的风荷载以及由风洞试验得到的极端风荷载作用下的安全冗余度偏低;而直接按荷载规范的风荷载(未含阵风系数)进行抗风设计可能会使承重刚架偏于不安全;通过一种简便的节点构造改进措施,可以明显提高刚架的风致安全性,并降低刚架对初始缺陷的敏感性.     

Fabrication and characteristic detection of graphene nanoelectrodes

Graphene has the advantages of high electrical conductivity, high heat conductivity, and low noise, which makes it a potential option for integrated circuits interconnection and nanoelectrodes. In this paper, we present a novel fabrication method for graphene nanoeletrodes with nanogap. First, graphene grown by chemical vapor deposition (CVD) is assembled to a chip with microelectrodes. Second, an atomic force microscopy (AFM) based mechanical cutting method is developed to cut the graphene into nanoribbons and nanoeletrodes with nanogap. Then the electronic property of a single nanodot is characterized using the garphene nanoelectrodes, demonstrating the effectiveness of the graphene nanoelectrodes. The fabricated graphene nanoeletrode pairs can be used as probes to detect single molecule in micro-environment, and show an attractive prospect for future molecular electronics applications.     

Large eddy simulation and proper orthogonal decomposition analysis of turbulent flows in a direct injection spark ignition engine: Cyclic variation and effect of valve lift

Large eddy simulation(LES)is used to calculate the in-cylinder turbulent flow field in a direct injection spark ignition(DISI)engine.The computations are carried out for three different maximum valve lifts(MVL)and throughout 100 consecutive engine cycles.The simulated results as well as corresponding particle image velocimetry(PIV)measurement database are analyzed by the proper orthogonal decomposition(POD)method.Through a new developed POD quadruple decomposition the instantaneous in-cylinder flow fields are decomposed into four parts,named mean field,coherent field,transition field and turbulent field,respectively.Then the in-cylinder turbulent flow characteristics and cycle-to-cycle variations(CCV)are studied separately upon the four part flow fields.Results indicate that each part exhibits its specific characteristics and has close connection with others.The mean part contains more than 50%of the total kinetic energy and the energy cascade phenomenon occurs among the four part fields;the coherent field part possesses the highest CCV level which dominates CCV of the bulk flow.In addition,it is observed that a change in MVL affects significantly the in-cylinder flow behavior including CCV,especially for the coherent part.Furthermore,the POD analysis demonstrates that at least 25 sample cycles for the mean velocity and 50 sample cycles for the RMS velocity are necessary for obtaining converged and correct results in CCV.     

The effect of MWCNTs on the performance of α-sexithiophene OTFT device and its gas-sensing property

In this paper,bottom contact organic thin-film transistor(OTFT)gas sensors were prepared.Silicon dioxide(SiO2)and titanium/aurum(Ti/Au)were used as the insulating layer and the electrode for the device,respectively.The multi-walled carbon nanotubes(MWCNTs)/α-sexithiophene(α-6T)bilayer films were used as the active layer,andα-6T single layer sensitive film was also prepared for comparison purpose.The electrical and trace NO2-sening properties of these two OTFT gas sensors were tested and analyzed.The results showed that,the OTFT device based on MWCNTs/α-6T bilayer had obviously better electrical properties,better stabilities and higher NO2-sening response values than the device withα-6T single layer,in which both the carrier mobility(μ)and on/off current ratio enhanced two order of magnitude.The improved performance of bilayer OTFT can be explained that MWCNTs acted as highly conducting bridges connecting the crystalline terraces in theα-6T film.Threshold voltage(VT),carrier mobility,on/off current ratio and grid current which showed extremely similar variation trend as source-drain current,were optional parameters to reveal the gas-sensing characteristic of OTFT gas sensors.Morphology analysis showed that the special feature of MWCNTs had certain influence on the gas-sensing properties.     

CATIA-FLAC 3D耦合建模方法及其应用

针对FLAC3D面向复杂的地质模型建模存在的技术困难和不足,提出CATIA-FLAC3D耦合建模新方法.先利用CATIA强大的三维地质体建模功能进行三维地质建模,再利用其有限元模块对地质体进行网格划分;基于对两类软件中单元、节点数据关系的差异分析,应用Visual Basic语言编写CATIA-FLAC3D接口程序,实现了将CATIA环境下建模生成的单元、节点信息导入FLAC3D.以某已建成偏压隧道工程为例,验证了CATIA-FLAC3D耦合建模方法的可行性和有效性,为FLAC3D构建三维复杂工程模型提供了新的思路.     

基于改进APF的无人机编队航迹规划

传统APF应用于航迹规划存在不可达性、局部极小点、震荡等问题,文章提出了改进的APF模型,它的核心内容有:使用改进斥力势场函数,考虑无人机与目标的相对距离,确保目标点为整个势场的全局最小点,解决了威胁与目标点过近导致的目标不可达问题;使用随机波动法,解决了无人机陷入局部最小点而导致的规划失败问题;考虑传统势场法的震荡问题,提出障碍物联通法。同时,使用APF进行编队控制,保持紧密编队下的无人机编队距离。仿真结果表明,利用这种方法很好地实现了无人机编队的航迹规划。