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With the characteristics of wear resistance， corrosion resistance， improved biocompatibility and antibacterial properties， the micropits array structure has been widely used.femtosecond laser has unique advantages in high-quality micro pit processing， because of its unique ultra-fast processing effect.In this work， Random Forest Regression (RFR) algorithm and Artificial Neural Network (ANN) algorithm were applied to predict the geometry and quality of micro-pit arrays processed by femtosecond laser.Additionally， the effects of laser processing parameters on the diameter， depth and surface roughness (Ra) of micro-pits were analyzed.The predictive capabilities of the RFR and ANN models were evaluated through the root mean square error， coefficient of determination and mean absolute error.Results showed that the overall prediction accuracy of ANN model was slightly higher than RFR model.The R2 for ANN model was 0.81.For diameter， depth and surface roughness， the R2 was 0.67， 0.79 and 0.85， respectively.Data augmentation method was applied to augment the dataset， and the ANN model prediction accuracy was further improved after data augmentation.The overall R2 increased to 0.91.The R2 for diameter， depth and surface roughness was 0.81， 0.91 and 0.95， respectively.In general， the ANN model had better prediction performance than Random Forest in predicting micro pit arrays processed by femtosecond laser processing.As the amount of data increased， this advantage became more obvious， which further verified the potential of the ANN model.

In this work, we investigated the magnetic annihilation and reconnection and the resulted hot electron acceleration driven by double-beam intense laser pulses in two-layer near critical density (NCD) plasma target. The results are obtained by performing two-dimensional (2D) particle-in-cell (PIC) simulations. It is found that a quasi-mono-energetic peak can be formed in the energy spectrum of electrons accelerated by the process of magnetic field annihilation (MA) at cutoff energy. Electron spectra feature depends on the length of the second low-density layer. This suggests that the process of relativistic magnetic annihilation may be controlled in experiments by target design. [ABSTRACT FROM AUTHOR]

TA15 pre-alloyed powder chosen in this paper is made by plasma rotating electrode method. The powders were used to prepare fully dense TA15 alloy ingots by the means of hot isostatic pressing(HIP) forming technology. The optimum parameter of the HIP process is 900°C /120MPa/3h. After the process of hot isostatic pressing, the powders were pressed into a fully dense ingot. An optital microscope was used to observe the microstructure of the ingot specimen and its formation mechanism was analysized. The microstructure of the TA15 alloy prepared by hot isostatic pressing of pre-alloyed powder is composed of fine α-equiaxed grains along lamellar colony boundaries. The mechanical properties exceed that of the casting level, which is close to the forging level. A typical TA15 alloy component was finally produced by HIP-PM process.