The Doubly Salient Electromagnetic Motor (DSEM) has a promising application prospect in fields such as new energy vehicles. However, the field windings of DSEM brings high copper loss, and traditional converter topologies and control methods limit the improvement of motor efficiency. In this paper, to improve the efficiency of a four-phase 8/6 pole DSEM, a current coordinated control strategy based on five-leg converter is proposed. This strategy achieves coordinated control of the DSEM positive and negative phase currents and field current by controlling the five-leg switches. Based on the working principles of the converter, the relationship between phase current, field current, and average electromagnetic torque is established through magnetic co-energy. The minimum copper loss current combination is obtained using the Lagrange multiplier method, and a speed closed-loop control is established. Simulation results show that compared with the conventional symmetrical current control, the motor efficiency increases 2.8
The Ji'nan Henglong Plaza(Quancheng Plaza)project is a complex building with a large basement without seams and multiple towers together.The design adopts a raft foundation,and seismic joints are set in different parts of the upper structure,making the upper structure units simpler and more regular Structural calculations show that the structural modes,inter-story displacement angles,and bearing capacity all meet the code requirements.It is also recommended to use GPZ basin type rubber isolation bearings for weak connection treatment when connecting the steel structure bridge connecting the left and right towers to the main structure.The analysis of similar projects has high reference value.
The X2 plot of Shanghai Pudong Lujiazui Financial and Trade Zone is invested and constructed by Shanghai Xinlu Real Estate Co.,Ltd.The entire project covers an area of 64,406 square meters,with a total above ground construction area of 355,000 square meters.The project includes two multifunctional super high-rise towers,the North Tower and the South Tower,a North Tower,and a three story commercial podium.The tower is designed to serve as an office building,hotel,and apartment style hotel.The architectural plan and vertical layout of the two towers are similar.The vertical bearing capacity calculation,horizontal load calculation,bottom plate shear resistance calculation,bottom plate impact shear resistance calculation,and settlement calculation of the project were carried out by using the high-precision finite element analysis program for settlement and internal force calculation of high-rise building pile raft and pile box bottom plate developed by East China Institute-PWMI.At the same time,the bored pile is treated with post grouting at the bottom of the pile.The analysis of similar projects has high reference value.
This paper proposes an improved traffic sign object detection algorithm based on YOLOv5,aiming to improve the accuracy of small object detection and reduce the missing detection rate.By introducing the attention mechanism CBMA and the weighted feature fusion network BiFPN,meanwhile,the SIoU loss function is adopted to enhance the model accuracy.Experimental results show that this algorithm achieves a mAP of 93.6%on the CCTSDB dataset,an improvement of 6%compared to the original algorithm.Especially for small object detection tasks at medium to long distances,the algorithm achieves a detection speed of 63.13 FPS,significantly improving the effectiveness of the original model and meeting real-time requirements.
Aiming at the difficult problem of soft rock roadway support in deep mine, the support mode of "truss anchor beam" is proposed, and the support mode technology of truss anchor beam in deep soft rock roadway driving is studied by FLAC simulation software. Combined with the measured displacement of coal and rock around underground roadway under this support mode, it is concluded that the truss anchor beam support mode can introduce the high stress of shallow coal and rock around roadway into deep area, thus effectively controlling the deformation of coal and rock around roadway and ensuring safe and efficient production of mine.
