Overview of runaway current suppression and dissipation on J-TEXT tokamak

The main works on disruption mitigation including suppression and mitigation of runaway current on the J-TEXT tokamak are summarized in this paper. Two strategies for the mitigation of runaway electron (RE) beams are applied in experiments. The first strategy enables the REs to be completely suppressed by means of supersonic molecular beam injection and resonant magnetic perturbation which can enhance RE loss, magnetic energy transfer which can reduce the electric field, and secondary massive gas injection (MGI) which can increase the collisional damping. For the second strategy, the runaway current is allowed to form but should be dissipated or soft landed within tolerance. It is observed that the runaway current can be significantly dissipated by MGI, and the dissipation rate increases with the injected impurity particle number and eventually stabilizes at 28 MA s−1. The dissipation rate of the runaway current can be up to 3 MA s−1 by ohmic field. Shattered pellet injection has been chosen as the main disruption mitigation method, which has the capability of injecting material deeper into the plasma for higher density assimilation when compared to MGI. Moreover, simulation works show that the RE seeds in the plasma are strongly influenced under different phases and sizes of 2/1 mode locked islands during thermal quench. The robust runaway suppression and runaway current dissipation provide an important insight on the disruption mitigation for future large tokamaks.     

正火终冷温度对U26Mn2Si2CrNiMo贝氏体奥氏体钢力学性能的影响

通过力学性能测试及OM、SEM、EBSD、XRD显微组织分析，研究了正火终冷温度对U26Mn2Si2CrNiMo贝氏体奥氏体钢力学性能的影响。结果表明，当正火终冷温度为330℃时，其屈服强度达到1 246 MPa,抗拉强度达到1 335 MPa,伸长率为14.4%,室温冲击功为84 J,-40℃低温冲击功为38 J。随着正火终冷温度的降低，其屈服强度有所降低，但是抗拉强度增加，同时其伸长率和冲击功均逐渐降低。随正火终冷温度的降低，残余奥氏体体积分数逐渐降低，大角度晶界比例增加，残余奥氏体的取向稳定性和机械稳定性均降低，当温度降低至300℃时，残余奥氏体消失。同时低的正火终冷温度将增大贝氏体铁素体间的应变梯度，晶界失去了对裂纹扩展的阻碍作用，这些因素的协同作用导致综合力学性能的降低。     

基于球面波的非平稳性MIMO信道建模

提出了一种新的无线通信物理信道模型，可用于研究多输入多输出(Multiple-Input Multiple-Output, MIMO)系统中天线与传播信道之间的相互作用。利用球矢量波系数展开、天线散射矩阵和非平稳性建模，推导出了信道矩阵的扩展形式。引入了剥离天线影响的信道矩阵，并将其协方差统计量表示为共极化分量和交叉极化分量的双边功率角谱(Double-Directional Power-Angular Spectrum, DD-PAS)的函数。模型对于研究指定传播信道中天线设计具有重要价值，对MIMO系统在典型的传播环境中的应用进行了仿真分析，验证了所提出信道的准确性，结果表明提出的模型可以用于未来无线通信系统建设中。     

基于微透镜阵列的大面积LED阵列光源匀化方法

LED阵列光源凭借其高亮度、长寿命及节能环保等独特优点广泛应用于医学、微纳加工、光学成像等领域，但其匀化系统存在光线准直难、可实现的照明光斑面积小等问题，难以在需要均匀照明的光学领域当中得到广泛应用。针对这一问题，提出了一种基于微透镜阵列的大面积LED阵列光源匀化方法。首先通过矩阵光学及近轴光学理论进行理论分析，然后利用lighttools软件进行系统设计及仿真实验，最终在像面上实现了大面积的均匀光斑。相较于以往最多可实现50 mm×50 mm的匀化光斑，该匀化系统可做到104 mm×104 mm、均匀度为87.375%的大面积规则的均匀光斑，该方法对医学、红外夜视、投影显示、航空照明领域等需要大面积均匀照明的系统有着重要意义。