The AC copper loss of flat copper wire in axial flux permanent magnet (AFPM) motor can seriously affect the performance, so it cannot be ignored when optimizing the motor design. Accurate results can ...be obtained using 3-D transient field finite element (FE) to calculate AC copper loss. However, the calculation time is long, which is not conducive to the motor optimization design. In order to consider the effects of the external magnetic field, conductor arrangement mode, stator tooth-tip, skin effect, and proximity effect on AC copper loss and to balance the calculation accuracy and calculation time, the analytical calculation method and hybrid analytical calculation method are proposed. The analytical calculation method combines complex eddy current equation with the precise subdomain method, and the hybrid analytical calculation method combines three-dimensional FE with the analytical method. In order to comprehensively compare different calculation methods, the proposed methods are used to analyze the AC copper loss and motor efficiency under different conductor arrangement modes and working conditions, and the simulation verification is carried out by three-dimensional transient field. Finally, through the AC resistance experiment and prototype experiment, the accuracy of the proposed methods is verified, and the characteristics of different methods are summarized.
The research object of this paper is to investigate the mechanical behavior and develop an analytical model of the prestressed circular-section rocking steel piers with external energy-dissipating ...devices under the horizontal cyclic load. Based on the method of monolithic beam analogy under monotonic loading, the concept of generalized rotation angle and intercept strain in the pre-decompression state was introduced. The geometrical equations for the pre- and post-decompression stages are deduced. The calculation formulas for internal forces of each component and the analytical calculation method for the entire process of the rocking steel pier under horizontal cyclic loading are established in detail. To reproduce the hysteresis curve of the test, some special test conditions, such as the retraction effect of prestressed tendons and increase of the compressed area due to the vertical plates, were considered in the analytical model. The results show that the analytical method based on generalized rotation angle and intercept strain can ensure an ideal transition of the hysteresis curve of the pier in pre- and post-decompression stages. Except for the pier with particularly severe local buckling and ovalization deformation, the calculated results obtained from the proposed analytical model agrees well with the test results for the rocking steel bridge piers. The effect of prestressed tendons and the P–Δ effect on the lateral load–displacement curve of rocking steel bridge biers was further analyzed through parametric study using the proposed model. The analytical calculation method presented in this paper provides a theoretical tool for seismic design of the rocking steel pier in engineering practice. This paper provides important guidance for the establishment of seismic design method of rocking steel piers.
•to deduce the geometrical equations for the pre- and post-decompression stages of the rocking steel pier.•to establish the analytical calculation method for the entire process under horizontal cyclic loading.•to analyze the effect of prestressed tendons and the P–Δ effect on the lateral load–displacement curve.
The subject of this research paper is the evaluation of spinach's (Spinacia oleracea L.) production profitability, given that spinach is an important vegetable species for human nutrition and health. ...The research started with an overview of spinach production worldwide and in the European Union in the past ten years (2012-2021). The Statistical Office of the Republic of Serbia (SORS) does not monitor the production and yield of spinach as a separate vegetable species, so comparison between Serbia and other world countries is not possible. Therefore, the paper analyzes the values of spinach exports and imports in Serbia. In the end, the evaluation of profit and critical values is given on the example of open field spinach production by an agricultural producer in the area of AP Vojvodina, in the South Banat district. The analysis of achieved profit was made based on the calculation of spinach production for one production cycle (autumn sowing 2021/harvest 2022) on an area of 1ha. The achieved results show that the production of spinach in this district is profitable, and the financial result is positive.
Due to excellent mechanical properties, carbon fibre-reinforced plastics (CFRP) are often used for lightweight structures in the mobility sector and combined to sheet metals in order to reduce the ...weight of the structure. Due to different melting temperatures, the use of conventional thermal joining technologies is restricted. Therefore, the demand of efficient mechanical and adhesive joining technologies is increasing. In this publication, the damage behaviour of self-piercing riveted CFRP-metal joints subjected to thermal loading is analysed via computed tomography. Particular attention is paid to the residual stresses introduced in the CFRP, resulting from an interference-fit of the rivet and the laminate. It is shown, that primarily radial compressive stresses are responsible for the observed failure of the CFRP. With regard to these effects, geometric adaptions of the self-piercing rivet are carried out, which prevent damages occurring during the thermal loading. Therefore, a calculation method based on complex valued potential functions to determine stress concentrations in the composite with interference-fit bolts is used. The calculation is validated via optical 3D image-correlation. The damage reduction using the developed rivet is validated by means of micro-sections and single-lap shear tests.
In this paper, an end-wrapped flexible printed circuit board (FPCB) concentrated winding radial-flux slotless PMSM is proposed. Unlike the traditional slotless motor whose ends are exposed outside ...the effective core, the winding ends of this motor are wrapped within the length of the effective core, which makes full use of the winding ends and effectively improves the utilization rate of the axial magnetic field, so that the torque density is increased by 14%. In order to fully consider the end leakage effect when calculating the electromagnetic performance, a novel threedimensional semi-analytical calculation method is proposed, which can accurately calculate the magnetic field distribution at each axial position of the motor and convert it into a function, so as to improve the calculation accuracy of the electromagnetic performance. Firstly, the correction functions of PM field and armature field are constructed respectively, and the 3D semianalytical magnetic field models considering the end leakage effect are established. Secondly, the 3D semi-analytical calculation methods of the electromagnetic performances including the back EMF, electromagnetic torque and inductance are established. Then, the correctness and accuracy of the proposed 3D semianalytical methods are verified by 3D finite element method. In addition, a prototype of end-wrapped FPCB concentrated winding is developed and the correctness of the proposed 3D semianalytical method are further verified by experiments.
The method of analytical thermal calculation of dry transformers with cylindrical conductors with cast insulation and foil windings is presented. The surface and volume averaged temperatures of the ...magnetic system core and the windings are determined from the one-dimensional non-linear substitute thermal circuit of the transformer. To clarify the temperature distribution across the cross-section of the anisotropic foil winding, the solution of the boundary value problem in the form of a two-dimensional Poisson equation with heat transfer coefficients calculated from the substitute scheme is used. Calculation example of a dry transformer with a capacity of 2500 kVA is given. Numerical CFD modeling was performed to verify the calculation results. Bibl. 10, fig. 9, tab. 3.
Purpose
The dose‐averaged linear energy transfer (LETd) for intensity‐modulated proton therapy (IMPT) calculated by one‐dimensional (1D) analytical models deviates from more accurate but ...time‐consuming Monte Carlo (MC) simulations. We developed a fast hybrid three‐dimensional (3D) analytical LETd calculation that is more accurate than 1D analytical model.
Methods
We used the Geant4 MC code to generate 3D LETd distributions of monoenergetic proton beams in water for all energies and used a customized error function to fit the LETd lateral profiles at various depths to the MC simulation. The 3D LETd calculation kernel was a lookup table of these fitted coefficients, and LETd was determined directly from spot energies and voxel coordinates during analytical dose calculations. We validated our new method by comparing the calculated LETd distributions to MC results using 3D Gamma index analysis with 3%/2 mm criteria in 12 patient geometries. The significance of the improvement in Gamma index analysis passing rates over the 1D analytical model was determined using the Wilcoxon rank‐sum test.
Results
The passing rate of 3D Gamma analysis comparing LETd distributions from the hybrid 3D method and the 1D method to MC simulations was significantly improved from 94.0% ± 2.5% to 98.0% ± 1.0% (P = 0.0003). The typical time to calculate dose and LETd simultaneously using an Intel Xeon E5‐2680 2.50 GHz workstation was approximately 2.5 min.
Conclusions
Our new method significantly improved the LETd calculation accuracy compared to the 1D method while maintaining significantly shorter calculation time even comparing with the GPU‐based fast MC code.
•A model is established to calculate the load distribution among PRSM rollers.•The importance of machining error on load sharing coefficient is determined.•A load sharing coefficient prediction ...formula is proposed.
Load-carrying capacity is a critical characteristic that determines the performance of the planetary roller screw mechanism (PRSM). Until now, the relationship between the machining error and the load sharing characteristics among PRSM rollers has remained unclear, which is a challenge for the mechanism optimization. A novel analytical model considering multi-coupled machining errors is established to calculate the load distribution among the rollers, which is validated by the finite element method and available literature. Based on the experimental measurements of various machining errors, the load distribution among the rollers is analyzed in detail. By collecting data from the analytical model, a machine learning model is implemented for the first time to predict the load sharing coefficient (LSC) of the PRSM and determine the importance of each machining error on the LSC. The obtained results reveal that the importance values of the roller nominal diameter error, screw eccentricity error, and nut eccentricity error to the LSC are 19%, 34% and 47%, respectively. Accordingly, an LSC prediction formula for the PRSM accounting for various machining errors is proposed.
