The low-temperature plasticity of aluminum nitride (AlN) is determined by the interaction between edge and screw dislocations. However, the motion of screw dislocations and their glide mechanisms have not been evaluated. In this study, the motion of a ⟨0001⟩{11̅00} screw dislocation in a single crystal of AlN is explored by molecular dynamics simulations using LAMMPS software with the Stillinger–Weber (SW) potential. Four modes of thermally activated motion are observed under different conditions of temperature and stress: double kinks, Shockley partials, self-pinning, and debris and dislocation loops. The mobilities of a ⟨0001⟩{11̅00} screw dislocation and a 1/3⟨112̅0⟩{11̅00} edge dislocation are compared under various conditions. Our results show that the mobilities of the ⟨0001⟩{11̅00} screw and 1/3⟨112̅0⟩{11̅00} edge dislocations are quite low at T < 600 K. The ⟨0001⟩{11̅00} screw dislocation moves faster at 900 < T < 1500 K and seems less dependent on the temperature than does the 1/3⟨112̅0⟩{11̅00} edge dislocation at 1200 < T < 2200 K. However, the opposite phenomenon is observed at higher temperatures. The mobility of the ⟨0001⟩{11̅00} screw dislocation is slightly lower than that of the 1/3⟨112̅0⟩{11̅00} edge dislocation at T > 1800 K, although the mobility difference can reach several orders of magnitude at 900 < T < 1200 K due to different Peierls barriers.

Peierls stress

10.1021/acs.cgd.1c00428

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Behavior for Inertial Lift on Elastic Particles in Micro-channel

Journal of Mechanical Engineering (2015)

Qikun Wang

摘要: 建立一个简单模型以描述球状颗粒弹性变形特征,并根据"运动相对性原理",提出一种描述弹性颗粒准定常运动的数值计算方法,据此研究在方形截面微通道层流场中,弹性球状颗粒所受惯性升力的空间分布特征,揭示了颗粒的弹性变形对惯性升力的影响特点。研究结果表明:弹性颗粒在低Re数通道内运动时,仍存在稳定的横向聚集位置。与对应刚性颗粒相比,弹性颗粒的聚集位置更靠近通道中心,且随颗粒弹性的增加,其聚集位置会向通道中心偏移;弹性颗粒所受惯性升力的空间分布特征与刚性颗粒相似,但颗粒弹性变形会额外产生一个附加升力。这个附加升力的方向始终指向通道中心且随弹性颗粒变形幅度的增加而增大;弹性颗粒所受的惯性升力由"切应力分量"与"压力分量"构成,然而后者是诱发弹性颗粒产生惯性聚集运动的力学成因。

Lift (data mining)

10.3901/jme.2015.14.160

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A new method for energizing multi-radiofrequency ion trap electrodes with adjustable amplitude and identical phase maintenance

Research Square (Research Square) (2023)

Qikun Wang Wang Zhao Xu Wang

Abstract A helical resonator with a certain resonant frequency and a high-quality factor (Q-factor)[1] is critical for an ion trap system, which results in a larger trap depth, longer trap time, and lower RF noise. Here we propose a new method for energizing amplitude-adjustable multiple RF ion trap electrodes. By dividing the output of the helical resonator into multiple circuits and simultaneously energizing the ion trap multi-RF electrodes, each circuit is composed of capacitors connected in series, and the desired amplitude is applied to the ion trap RF electrodes using capacitive voltage dividing. In contrast, the capacitance of the multi-RF capacitors connected in series is determined by three constraints. Different voltages for each circuit are realized while keeping the phase consistent. To demonstrate our proposed method in experiments, we first determine that the theory is feasible through circuit simulations and then confirm the method’s validity by comparing the measured results with the analog simulations. Our method can be applied to the ion trap structure of multiplexed RF electrodes, which contributes to the realization of ion traps for multiplexed RF electrodes.

Trap (plumbing)

10.21203/rs.3.rs-3357859/v1

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