The electric vehicles (EVs) have been helping to alleviate the pressure of the world energy crisis. However, the insulation of EVs driving motors usually suffers from the electrical stress caused by partial discharge (PD) during the operation. Aramid paper in the stator can reduce the incidence of electrical degradation. In this context, PD characteristics, topography and chemical groups changes of Aramid paper under AC and repetitive nanosecond impulse voltages were compared. The results illustrated that the increase of ambient temperature will promote the activity of PD under AC voltage. The PD magnitude under nanosecond impulse voltage is almost 100-fold that under AC voltage. PD caused by nanosecond impulse voltage leads to more severe destroy of chemical groups and higher roughness. This investigation offers an important reference for exploring the electrical aging of Aramid paper for the slot of stator in EVs motor.

As a new type of semiconductor processing technology, nanoimprint lithography has attracted growing attention in recent years because of its low cost, high yield, simple process and good fidelity. In order to improve the fidelity of patterning, a novel method, direct metallic pattern nanoimprinting with a pseudoplastic metal nanoparticle fluid as the transfer medium, is proposed and studied. Demolding, which has a great impact on the integrity and fidelity of patterning, is a critical step in nanoimprint lithography.Through the analysis of key parameters, which affect patterning integrity at the initial time of demolding, analytic expressions of the forces acting on the microstructure, e.g., adhesion force, internal force, friction force and other related parameters, as well as the effects of the friction coefficient, the Hamaker constant, the aspect ratios of the patterning, and the size of the metal nanoparticles on the integrity of patterning are obtained and analyzed. In the case of the absence of a bottom fracture in demolding, the analysis results have important guiding significance for the optimization of the parameters set in demolding process.

Driven by the development of internet technology, higher requirements on information materials and data storage devices were demanded. To improve the work efficiency and performance of the new generation of information materials and data storage devices, the magnetoelectric (ME) coupling and storage mechanism of magnetoelectric composites deserve more attention. Here, we explored the influence of applied magnetic fields on the output voltage on a metal–insulation–metal (MIM) sandwich composite for realizing the magnetoelectric memory by experiments and modeling. It is found that the DC magnetic field ( H dc ) and the output voltage of the polyvinylidene fluoride film are linearly correlated. At a frequency of 1 kHz, the magnetoelectric voltage coefficient is 60.71 mV cm –1 Oe –1 , which is evidently larger than that of other film materials. From this work, we can conclude that the MIM sandwich composite could generate higher magnetoelectric voltage under the AC magnetic field ( H ac ) with higher frequency, which could be used as the magnetoelectric memory device, and provides significant support for improving the performance of magnetoelectric memory devices and the whole internet system.

Soft magnetic composite (SMC) is composed of ferromagnetic particles surrounded by an electrical insulation layer. The unique structure of SMC makes it difficult to calculate the eddy current loss of SMC. In addition, the temperature rise in the working condition affects the magnetic properties of the material, which makes it necessary to consider the temperature effect in the process of core loss prediction. In this paper, a magnetic property test platform that considers the influence of temperature is established. The core losses of the SMC ring sample were measured at 20-100 °C , and the experimental results show that core loss decreases as the temperature increases. Then, based on the method of using the SMC model to calculate the core loss, the effect of temperature increase on hysteresis loss and eddy current loss was analyzed, and the existing model was improved to consider the effect of temperature on the core loss. Finally, the measured core losses at different temperatures were compared with the calculated ones, and it is shown that the improved model considering the influence of temperature agreed well with the experimental results, which improves the accuracy and convenience of core loss calculation for the electromagnetic device with SMC cores.

In this paper, a single target fitting optimization model for parameter calibration of CT system was built based on the least square principle in combination with the attenuation rule of X-ray in media and the related theory of Radon transform. Applying this model to problem A of CUMCM in 2017, based on the method of grouping optimization, we applied genetic algorithm to solve the rotation center point and the spacing of detection units. The results obtained almost converge to the same value. Then under the calibrated CT system parameters, combined with the relevant theory of CT image reconstruction, we applied Fourier transform and Fourier Slice theorem to build a image reconstruction model of filtered back-projection. Based on the information received by the detector unit, the absorption rate information on every location was obtained, and the location as well as the shape of the medium on the tray were constructed. Finally, through the image reconstruction and comparison of the original data, the feasibility of the model is verified.