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.
With more and more applications of DC microgrids in power systems, reasonable control methods need to be adopted so that DC microgrids can be connected to large power grids in a friendly manner. Most DC microgrids use power electronic converters to achieve grid-connected and electrical energy transmission. The access of a large number of power electronic converters has a great impact on the stability of the power system.The Virtual Synchronous Generator (VSG) solves the disadvantages of low damping and small inertia of the DC microgrid, but ignores the effects of harmonics on the grid.Firstly, the excitation regulator and power frequency regulator are analyzed to establish a mathematical model; Secondly, the network-side RL filter circuit is designed and the parameters are given. The harmonics of the network before and after the filtering are analyzed and the ideal network is realized. Finally, a simulation model is established in MATLAB, and the correctness of the proposed method is verified by simulation.
This study analysis the basic characteristics of the smart grid,provides the process of smart grid construction in electric power engineering technology application strategy,puts forward the key points for the smart grid construction process in the specific application of electric power engineering technology.
Accurate measurement of pumping unit balance is of great significance for ensuring stable and efficient operation of oil fields.Currently,several conventional balance measurement methods in oil fields have disadvantages such as complex operation,large errors,and inconvenient equipment to carry.For this purpose,the paper developed a portable balance tester,which has a small volume,simple wiring,and is convenient to carry.The system is divided into two modules:the main module and the slave module.The main module uses a high-performance microprocessor as the control core,and uses a single-phase electric energy metering strategy to measure the power consumption of the three-phase drive motor on the up and down strokes of the pumping unit.The slave module detects the upper and lower dead center positions of the pumping unit's rod through an acceleration sensor.The signal transmission between the host and the slave is carried out through wireless modules to avoid wired transmission affecting the safety of oilfield production and operation,thus achieving accurate and convenient measurement of the balance degree of the pumping unit.
Taking the construction of a certain highway roadbed project in Guangxi as an example,this paper deeply explored the slope construction platform technology and temporary retaining wall construction technology that affect roadbed construction.This project research adopt a new type of integral movable slope construction platform and an efficient array type cable-stayed pile retaining wall.Then a detailed explanation was provided from the following aspects,including the research purpose,construction device structure composition,construction technology and efficacy comparison analysis.The adoption of these two construction techniques had significantly accelerated the progress of the project,saved the construction period,and improved the efficiency of the project.This type of construction technology has few engineering examples in China,which certains reference significance.
The iron in vanadium titanium magnetite ore in Panxi region of China has low quality,co-associated elements and is difficult to utilize.In the process of smelting pig iron in blast furnace,a large number of by-products of high titanium slag are produced,resulting in a large amount of waste of land resources and serious pollution of air and soil.In this study,high titanium slag sand was used to completely replace natural aggregate to prepare ultra-high performance concrete.The results showed that there was an optimal amount of steel fiber and cementitious material for high titanium slag ultra-high performance concrete.When the volume fraction of steel fiber was 1.5%and the cementitious material was 789kg/m3,the mechanical properties reached the best,with compressive strength and flexural strength of 158.6MPa and 36.8MPa,respectively.
The IoT structure deformation automatic monitoring system is developed by using the IoT technology.The system is mainly composed of sensor data acquisition and forwarding node,data forwarding IoT base station,data forwarding middle platform,and front-end software.At the same time,the advantages of IoT structure deformation monitoring system over traditional automatic monitoring methods are introduced.In response to the construction monitoring requirements of a large-span steel truss during the prestressing and unloading stages,the IoT structural deformation automation monitoring system was used to monitor the strain,deflection,and environmental temperature of the steel truss in real-time.The conclusion is that the real-time monitoring data obtained by the system can accurately reflect the stress characteristics of the steel truss at different construction stages,providing data support for the adjustment of the next construction process,Improved the safety of steel truss construction.
The original construction plan for the outer containment of the Hualong No.1 reactor building was to install scaffolding as a concrete template support at the top of the inner containment.The development period of this plan was long and the construction operation was difficult.After research by technical personnel,a steel template plan for the construction of the outer shell dome was proposed.This article analyzes the impact of the steel template plan on the cost.The application of steel formwork has shortened the construction period and improved construction safety,which is of great significance for the research and improvement of Hualong's subsequent models.
The cantilever pouring construction technology is often used in the construction of the main girder of the extradosed cable-stayed bridge.During the construction of the 0#block,it is necessary to set up the support and set up the temporary consolidation to resist the tensile stress caused by the unbalanced bending moment during the construction of the main girder.In order to ensure the safety of the cantilever construction,both of them must be designed and checked.Based on the Liulv Yongjiang Bridge,this paper comprehensively expounds the design and calculation points of the support and the temporary consolidation structure.The steel tube-steel support and the external temporary consolidation composite support system are used to construct the 0#block.The stress distribution of the support in different construction stages is analyzed by finite element software.Based on the rigid double fulcrum model,the compressive bearing capacity and anti-overturning ability of the temporary consolidation structure under the maximum cantilever state are calculated,which provides a reference for similar structural design in the future.
In this paper,through literature reading and expert interviews,28 factors affecting the development of green buildings in Sichuan Province were identified and screened,and they were classified as 6 key influencing factors.The sample data were obtained by questionnaire survey.The factor analysis method was used to test the reliability and validity of the sample data with the help of SPSS.According to the calculation formula of the importance index,the importance ranking of the influencing factors was determined.The results show that the key factor that has the greatest impact on the development of green buildings in Sichuan Province is economic factors.
In order to relax the flexibility and reduce the investment,this paper allows regional integrated energy system to exceed the limit slightly in a short time.Firstly,the security constraints of the system are relaxed by chance constraints.Secondly,based on constraint relaxation,a system planning model considering the optimal economy is established.Then,auxiliary variables and indicator function are introduced to transform nonlinear constraints into linear constraints.Finally,a system composed of IEEE33-node power grid and 11-node natural gas network is taken as an example to verify the accuracy and effectiveness of the model proposed in this paper.
Taking a typical soil slope as the research object,Flac3D software is used to carry out stability calculation to analyse the deformation and damage mechanism of the landslide,and combined with the monitoring data to verify the reliability of the numerical analysis results.The results of stability calculation and analysis show that the slope has a small displacement and is in a stable state under natural condition,and the displacement of the slope increases significantly and the stability coefficient decreases under heavy rain condition,which makes the slope unstable.Comparison of the numerical simulation results with the on-site monitoring data shows that the numerical simulation results are in good agreement with the on-site monitoring data.The results of numerical simulation analysis of the slope provide a basis for its slope management and prevention.
Regarding the calculation of earthwork quantities,there are currently mainly grid method,contour method,average section method,DTM method,etc.The article first explores the computational accuracy of each method from a theoretical perspective.Through examples,it is demonstrated that using the triangular prism method can obtain accurate values,while using the square prism method may not necessarily result in accurate values,even if the corners of the natural ground grid are coplanar.At the practical operational level,the scope of application of each method was explored.Compared to other methods,the DTM method based on triangular prism volume calculation has relatively higher accuracy and wider applicability.
With the development of China′s economy,people′s living standards have been greatly improved,and their requirements for living conditions have increased from mere quantity to both quantity and quality.However,the continuous improvement of urbanization level leads to the increase of human settlement density,and therefore the demand for good sound insulation is more prominent.In this research,we selected six representative floor data from the inspection examples over the past year for analysis.We got four key findings.First,the structure of the elastomer wrapped around the rigid body is beneficial to decrease the impact sound.Second,the size of the receiving chamber volume will significantly affect the results of the test.Third,increasing the thickness of each structural layer can reduce the impact sound.Fourth,it is necessary to apply sound insulation measures instead of only increase the thickness of the material to reach the requirement score of the"Green Building Evaluation Standard".
Traffic demand data is an important basic data for traffic control and travel guidance.Optimizing the original traffic demand data can improve the accuracy of traffic state discrimination and prediction.This article selects high-precision coil traffic volume data and uses genetic algorithm to optimize the original traffic travel data.Through the example calculation and analysis of RFID collected vehicle data in a certain road network in Nanjing,it is shown that the optimization model and algorithm have a good effect on improving the amount of travel volume data.The optimized travel volume data can be used as prior data for traffic demand prediction,or directly as decision support for traffic status discrimination and early warning.
