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Yini Chen,Changping Li,Shuang Li,Moran Xu,Lei Huang,Shujian Li,Pengnan Li,Xinyi Qiu,Tae Jo Ko 한국정밀공학회 2023 International Journal of Precision Engineering and Vol.24 No.3
Electric discharge machining (EDM) is used widely in machining titanium alloys, but the modified layer formed can weaken the mechanical properties of the parts. The present study examined the formation of craters and the evolution of the modified layer (melting layer + heat-affected layer) in RC-type EDM using a fluid–solid coupled temperature field model. This model adopts the level set method to track the liquid–solid two-phase and the driving force equation to control the recoil pressure. The results showed that the discharge energy has a significant effect on the formation of the modified layer. The formation of the modified layer showed phased characteristics with time. The variation law and formation mechanism of the modified layer are described in detail. A verification experiment showed that the diameter and depth of the crater were in good agreement with the simulation results. These results can provide an important reference for EDM to formulate the machining parameters.
Electron transport properties of Y-type zigzag branched carbon nanotubes
MaoSheng Ye,HangKong, OuYang,YiNi Lin,Quan Ynag,QingYang Xu,Tao Chen,LiNing Sun,Li Ma Techno-Press 2023 Advances in nano research Vol.15 No.3
The electron transport properties of Y-type zigzag branched carbon nanotubes (CNTs) are of great significance for micro and nano carbon-based electronic devices and their interconnection. Based on the semi-empirical method combining tight-binding density functional theory and non-equilibrium Green's function, the electron transport properties between the branches of Y-type zigzag branched CNT are studied. The results show that the drain-source current of semiconducting Y-type zigzag branched CNT (8, 0)-(4, 0)-(4, 0) is cut-off and not affected by the gate voltage in a bias voltage range [-0.5 V, 0.5 V]. The current presents a nonlinear change in a bias voltage range [-1.5 V, -0.5 V] and [0.5 V, 1.5 V]. The tangent slope of the current-voltage curve can be changed by the gate voltage to realize the regulation of the current. The regulation effect under negative bias voltage is more significant. For the larger diameter semiconducting Y-type zigzag branched CNT (10, 0)-(5, 0)-(5, 0), only the value of drain-source current increases due to the larger diameter. For metallic Y-type zigzag branched CNT (12, 0)-(6, 0)-(6, 0), the drain-source current presents a linear change in a bias voltage range [-1.5 V, 1.5 V] and is symmetrical about (0, 0). The slope of current-voltage line can be changed by the gate voltage to realize the regulation of the current. For three kinds of Y-type zigzag branched CNT with different diameters and different conductivity, the current-voltage curve trend changes from decline to rise when the branch of drain-source is exchanged. The current regulation effect of semiconducting Y-type zigzag branched CNT under negative bias voltage is also more significant.