To analyze the impact of complex external vibration interference on the pantograph-catenary system,the research is conducted on the problems of pantograph detachment caused by contact force reduction due to mechanical vibration,as well as the instability of current transmission caused by parameter imbalance in the coupling model.A neural network-based finite element control strategy is applied to the overall coupling modeling of the pantograph-catenary system.A matching model based on dynamic pantograph adjustment is established,and a neural network prediction theory is used for autonomous error parameters correction and fitting.The experimental and simulation results show that there is a nonlinear relationship between the output of the pantograph and the vibration intensity,both the vertical contact force arc and horizontal sliding friction caused by mechanical vibration meet the requirements for autonomous correction of pantograph parameters,and after error adjustment,the train can maintain good current transmission and stability.
In this paper, we consider a Galton-Watson process with immigration. Pick $i(\ge2)$ individuals randomly without replacement from the $n$-th generation and trace their lines of descent back in time till they coalesce into $1$ individual in a certain generation, which we denote by $X_{i,1}^n$ and is called the coalescence time. We give the probability distribution of $X_{i,1}^n$ in terms of the probability generating functions of both the offspring distribution and the immigration law.
为了转变国内中小规模肉羊养殖企业(场)生产方式,向广大肉羊养殖户推介基于循环经济的"草–羊–蚓–鱼–禽–菌"新型生态循环种养模式及关键技术.结果表明:种植牧草与饲用甜高粱等养羊,利用羊粪养殖蚯蚓,应用层叠式新型生态堆肥腐熟羊粪,运用羊粪与蚯蚓粪木盒法进行平菇栽培等技术,在实现羊粪资源循环利用的同时,可有效促进农业转型升级,实现农民增产增收,提高养殖生态综合效益."草–羊–蚓–鱼–禽–菌"新型生态循环种养模式及上述关键技术具有科学性、可行性和推广性,对指导和解决当前及今后国内中小规模肉羊健康养殖相关技术问题,降低养殖成本与养殖风险具有重要的示范与指导意义.
基于单天线相位的UHF RFID,采用双标签的定位方法,对室内定位算法进行了研究,结果表明:待定位目标边长距离在超过高频载波信号波长的情况下,有2个间距为1/2载波波长的无源标签附着于特定目标上.仿真表明:在三条路径、两条路径情况下,两步测距可估计平均定位误差;两步测距(副载波)方法也可估计平均定位误差;但两步测距(副载波)方法基于双标签定位中,无法确保阅读器与2个标签间距离大小关系.在三条路径、两条路径情况下,两步测距(副载波)方法误判率分别为17.45％、17.82％,两步测距(载波)方法误判率均为0,故两步测距(载波)方法可将定位误差降低,确保物品登记准确性.
采用水热法分别制备了ZnO/CdS、BiVO4/g-C3N4两种可见光响应光催化剂,针对光催化降解致癌物罗丹明B进行了实验研究.通过X射线粉末衍射表征,发现在温和条件下成功合成了光催化材料.其中,随着ZnO的掺杂,CdS的结晶度下降,粒径尺寸变小.紫外可见漫反射表明两种催化材料具有可见光吸收能力.质量比为1︰5的ZnO/CdS和80℃下制备的BiVO4/g-C3N4有最高的降解率,降解反应符合一级动力学过程.
