Single Crystal Growth and Magnetoresistivity of Topological Semimetal CoSi

We report single crystal growth of CoSi, which has recently been recognized as a new type of topological semimetal hosting fourfold and sixfold degenerate nodes. The Shubnikov–de Haas quantum oscillation(QO) is observed on our crystals. There are two frequencies originating from almost isotropic bulk electron Fermi surfaces, in accordance with band structure calculations. The effective mass, scattering rate, and QO phase difference of the two frequencies are extracted and discussed.     

Quantum oscillation measurements in high magnetic field and ultra-low temperature

The physical properties of a solid are determined by the electrons near the Fermi energy and their low-lying excitations. Thus, it is crucially important to obtain the band structure near the Fermi energy of a material to understand many novel phenomena that occur, such as high-T_c superconductivity, density waves, and Dirac-type excitations. One important way to determine the Fermi surface topology of a material is from its quantum oscillations in an external magnetic field. In this article, we provide a brief introduction to the substation at the Synergetic Extreme Condition User Facility(SECUF),with a focus on quantum oscillation measurements, including our motivation, the structure of and the challenges in building the substation, and perspectives.     

实现均匀照度光伏聚光镜设计

为满足聚光光伏系统的聚光需求,解决传统点聚焦式聚光光伏系统中聚焦光斑不均匀、径长比过大和聚光比较小的缺点,在不增加二次匀光器件的前提下,设计了径长比小、聚焦光斑相对均匀、聚光比高的聚光光伏系统。根据几何光学柯勒照明原理、等光程原理和反射定律,通过数值求解等光程方程组获得聚光镜各个面型的轮廓曲线。利用TracePro软件对所设计的聚光系统进行光线追迹模拟,结果表明:在聚光比为725的情况下,聚焦光斑最大照度仅为太阳照度的2300倍,是点聚焦情况下的1/10左右,系统的径长比为0.3,接收角为0.72°。系统设计实现了结构紧凑,聚光性能高的设计目标,为高倍聚光光伏系统的小型化,简单化提供了一种有效的解决途径。     

露天煤矿设备运载对采空区上覆岩体稳定性分析

在平朔东露天矿开采境界内存在大量小窑采空区,对露天矿设备的运行产生极大威胁.选取以探明5-27采空区,以东露天矿常用930E型卡车和WK-35型电铲为例,应用安全系数评价方法,计算出当采空区上覆岩体存在设备运载时的安全系数,并进行稳定性分析.露天矿设备运载对采空区上覆岩体的稳定性有一定影响,当有露天矿设备作业时采空区上覆岩体安全系数K_2=0.82,易发生整体性坍塌.因此,研究露天矿采设备运载对空区上覆岩体的影响,避免出现坍塌事故,有着重要的理论意义和实用价值.     

通过Heck反应合成3-(2-羧基乙基)-1H-吡咯[2,3-b]吡啶-2-甲酸

以1H-吡咯[2,3-b]吡啶-2-甲酸乙酯为起始原料,经5步反应合成了新化合物3-(2-羧基乙基)-1H-吡咯[2,3-b]吡啶-2-甲酸,其结构经1H NMR和HR-MS表征。合成中间(E)-1-Ts-3-(3-乙氧基-3-氧代丙基-1-烯基)-1H-吡咯[2,3-b]吡啶-2-羧酸乙酯的最佳反应(Heck)条件为:无水DMF为溶剂,Pd(OAc)2为催化剂,dppf为配体,三乙胺为碱,收率88%。     

SnS2纳米材料的水热合成及光催化性质

在不同的表面活性剂和硫源的条件下,采用水热法制备了多种形貌的SnS₂纳米材料,详细讨论了反应条件对其形貌和性质的影响,并采用X射线衍射(XRD)、扫描电镜(SEM)、和BET比表面积法对制备的样品的物相、形貌和组成进行了表征,通过光催化降解罗丹明B研究了所得样品的光催化性能。结果表明：表面活性剂和硫源对产物的结构和形貌起到了重要的作用。当Sn⁴⁺与表面活性剂的物质量的比为1：1时,样品均为纯的六方相SnS₂。采用柠檬酸三钠为表面活性剂、硫脲为硫源时制得的SnS₂纳米片具有最大的比表面积,同时表现出了最优的光催化性能。     

星载张力索网天线结构混合变量的多目标优化

以纵向拉索调整力大小和可调整的纵向拉索数目为设计变量,可调整的纵向拉索数目最少和网状反射面的均方根误差最小为目标函数,应力和频率为约束条件,建立了大型空间网状可展开天线的形面调整的多目标优化数学模型,并用遗传算法进行了优化求解。优化结果表明:该方法在提高天线表面精度的同时,能有效地减少可调整的纵向拉索数目,降低了工程人员在网面调整中的繁杂劳动。并且,网面调整的总次数也远少于实际工程中的调整,对工程应用具有一定的指导意义。     

Radiation and ionization energy loss simulation for the GDHsum rule experiment in Hall-A at Jefferson Lab

The radiation and ionization energy loss are presented for single arm Monte Carlo simulation for the GDH sum rule experiment in Hall-A at the Jefferson Lab. Radiation and ionization energy loss are discussed for ¹²C elastic scattering simulation. The relative momentum ratio Δp/p and ¹²C elastic cross section are compared without and with radiative energy loss and a reasonable shape is obtained by the simulation. The total energy loss distribution is obtained, showing a Landau shape for ¹²C elastic scattering. This simulation work will give good support for radiation correction analysis of the GDH sum rule experiment.