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Aiming at the failure of slewing bearing in a certain type of vehicle-borne radar actuator，the service life of slewing bearing is studied according to its structural characteristics and operating conditions，and a life prediction method of slewing bearing based on finite element method is obtained. Using ANSYS Workbench to analyze the simplified three-dimensional model of slewing bearing，the contact stress and fatigue life of inner and outer raceway and rolling body of slewing bearing are obtained，which improves the calculation efficiency. The accuracy of the finite element method is verified by comparing the results of the finite element method with those of the Hertz contact theory and the actual work.

The screw theory is adopted to analyze the constraint of planar mechanisms branch link on mobile platform,the redundant constraint and partial degree of freedom of mechanism is found out,and the formula of degree of freedom is modified,the mobility of planar mechanisms is researched by analyzing constraints virtual power of mechanisms branch link,which can judge whether mechanism move continuously. The effectiveness of proposed method is verified by an example of a planar instantaneous motion mechanism. Finally,taking a radar vehicle-borne array lifting mechanism as research object,the results show that the analysis method of the degree of freedom and mobility is suitable for complex planar mechanisms which contain redundant constraint.

Taking the radar vehicle- borne array lifting device as the research object,combing with the engineering practice,adopting the combination of theoretical derivation and simulation research method,an analysis method for the position error of array lifting device is proposed,and the causes and influencing factors of the position error of array lifting device are analyzed. Finally,by using MATLAB software,the simulation calculation is carried out,the position errors of array lifting device are obtained,the influence of the main parameters on the position error is analyzed,and theoretical basis for the design and control of the position accuracy of the array lifting device is provided,and the research results have some engineering significance.

Node importance is a key factor affecting the overall operation efficiency of a railway freight transportation network (RFTN) that can be measured with the indicators of Hub and PageRank. Based on complex network theory and the national railway cargo exchange data of China's provinces, this study constructs an RFTN model with the 31 provinces as the nodes and measures the values of Hub and PageRank for the 31 provinces. Then, the time evolution law of the importance of the provincial nodes is analyzed comprehensively, and, using a regression model, the influencing factors of the importance of the provincial nodes are identified. The results show the following. (1) The uneven distribution of natural resources will affect the spatial changes in the importance of RFTN nodes. The Hub values tended to cluster around the average, and the economic structure of the output-oriented provinces improved as a whole. At the same time, the PageRank values of many provinces in the central and western regions significantly increased, and those provinces exhibited more frequent exchanges of goods with other provinces and closer economic ties with other regions. (2) The traffic fixed asset investments and the population density have the most obvious influences on the importance of the provincial nodes with a positive effect. In contrast, the railway freight concentration (RFC) coefficient, geographical location (longitude and latitude), and coastal region all have negative effects on the importance of provincial nodes. The results of this study provide scientific decision-making support for the reasonable establishment and distribution of RFTN hubs in China., 1. Introduction The transportation network, which constitutes one of the three major networks (transportation, energy, and information) created by human society, lays an important foundation for the development of modern [...]