Development of the liquid level meters for the PandaX dark matter detector

The two-phase xenon detector is at the frontier of dark matter direct search. This kind of detector uses liquid xenon as the sensitive target and is operated in two-phase (liquid/gas) mode, where the liquid level needs to be monitored and controlled in sub-millimeter precision. In this paper, we present a detailed design and study of two kinds of level meters for the PandaX dark matter detector. The long level meter is used to monitor the overall liquid level while short level meters are used to monitor the inclination of the detector. These level meters are cylindrical capacitors that are custom-made from two concentric metal tubes. Their capacitance values are read out by a universal transducer interface chip and are recorded by the PandaX slow control system. We present the developments that lead to level meters with long-term stability and sub-millimeter precision. Fluctuations (standard deviations) of less than 0.02 mm for the short level meters and less than 0.2 mm for the long level meter were achieved during a few days of test operation.     

金纳米颗粒光散射提高InAs单量子点荧光提取效率

采用光学方法确定InAs/GaAs单量子点在样品外延面上的位置坐标, 利用AlAs牺牲层把含有量子点的GaAs层剥离并放置在含有金纳米颗粒或平整金膜上, 研究量子点周围环境不同对量子点自发辐射寿命及发光提取效率的影响. 实验结果显示, 剥离前后量子点发光寿命的变化小于13%, 含有金纳米颗粒的量子点发光强度是剥离前的7倍, 含有金属薄膜的量子点发光强度是剥离前的2倍. 分析表明在金纳米颗粒膜上的量子点荧光强度的增加主要来自于金纳米颗粒对量子点荧光的散射效应, 从而提高量子点发光的提取效率.     

离子液体-静态顶空气相色谱法检测十滴水中的樟脑和桉油精

建立了以离子液体(ILs)为顶空溶剂的静态顶空气相色谱法,并用于十滴水中樟脑和桉油精的含量测定。采用1-癸基-3-甲基四氟硼酸盐([Demim][BF4])作为顶空溶剂,于恒温箱中140℃静态平衡30 min后,手动抽取顶空气体1 mL,供气相色谱仪分析。采用TM-5毛细管柱,FID检测器,程序升温。樟脑和桉油精与其它成分分离度良好,加样回收率在95.1%～98.2%范围内,RSD低于2.2%。樟脑和桉油精浓度分别在32.0～511 mg/L(r=0.9994),5.28～84.4 mg/L(r=0.9990)范围内线性关系良好。本方法样品前处理简单,无污染,结果准确,为中药制剂中高沸点挥发性成分的含量测定提供了一种新手段。     

面向能源领域的石墨烯研究

化石能源枯竭以及地球环境污染已经成为并且在未来相当长一段时期内都将是人类面临的最严峻的危机之一.因此,寻找清洁的替代能源形式、有效的能量存储方式以及高效的能源利用途径是目前科学研究的热点.自从其高质量样品被制备和研究以来,石墨烯一直吸引着全世界科研工作者的兴趣;它的一系列独特的物理化学性质,为其在能源领域的应用提供了无限前景.本文对石墨烯在能源领域的最新研究进展以及其工业化应用作了简要综述,具体内容包括石墨烯材料在以下领域的应用：能源储存器件类,如超级电容器和锂离子电池;能源转化装置类,如燃料电池和太阳能电池.     

氰根桥联CrⅢ-CrⅡ一维配合物{[Cu(cyclam)] [Cr(bpb)(CN)2]2·2H2O}n的合成、结构与磁性

基于构筑单元K[Cr(bpb)(CN)₂] 和[Cu(cyclam)] (ClO₄)合成了一个氰根桥联的Cr^Ⅲ-Cr^Ⅱ一维化合物{[Cu(cyclam)] [Cr(bpb)(CN)₂]₂·2H₂O}_n[cyclam=1,4,8,11-四氮杂环十四烷;bpb^2-=1,2-二(2-吡啶甲酰胺基)苯] (1),并通过X-衍射单晶分析表征其结构特征.结果表明:化合物1是由氰根桥联的2种不同金属组成的聚合物,其结构属于三斜晶系, P1空间群,a=0.9667 3(19) nm,b=1.345 1(3) nm,c=1.382 0(3) nm,α=77.12(3)°,β=76.93(3)°,γ=82.02(3)°,V=1.699 1(6) nm³,Z=2,D_c=1.567 g·cm^-3,μ=1.086 mm^-1,F(000)=828,R₁=0.0413,wR₂=0.1200.磁性研究表明:配合物1中的Cr^Ⅲ离子和Cr^Ⅱ离子之间存在弱的铁磁耦合作用.     

注重统计思想的现代工科概率统计教学方法

指出了工科概率统计教学中长期存在而又被忽视的一个问题,即学生的统计计算能力有余而对于统计思想、统计方法的理解与使用不足.并尝试着提出了注重统计思想的现代统计教学方法.     

场向传播的内磁层哨声波对辐射带高能电子的共振扩散

基于高斯分布的哨声波谱密度分布、偶极子背景磁场模型以及建立在卫星观测数据基础上的半经验电子密度纬度分布模型,对于等离子体层顶以外区域(4≤L≤7),计算了准线性当地及弹跳平均电子共振扩散系数,并估算了与磁层哨声波回旋共振导致的辐射带电子损失及加速时间尺度.结果表明,波粒共振相互作用区域取决于电子能量、波谱分布、电子赤道抛射角以及当地电子密度及背景磁场.哨声波共振频率除了与以上5个参量有关外,还与地磁纬度有关.赤道哨声波主要影响较低能量辐射带电子的加速,中高纬度哨声波主要作用于较高能量辐射带电 关键词： 共振波粒相互作用 地球辐射带 哨声波 回旋共振加速及散射沉降     

超声调制光法测量弱散射液体的声速

本文介绍一种利用超声调制光波现象测量超声波在弱散射液中传输速度的方法。     

Generation of GHZ state and cluster state with atomic ensembles via the dipole-blockade mechanism

This paper proposes scalable schemes to generate the Greenberger-Horne-Zeilinger (GHZ) state and the cluster state with atomic ensembles via the dipole blockade mechanism on an atom chip, where the qubit is not carried by a single atom but an atomic ensemble. In the protocols, multiqubit entangled states are determinately prepared. Needlessness for single-photon source further decreases the complexity of the experiment. Based on the present laboratory technique, the schemes may be realized. The achieved results reveal a prospect for large-scale quantum communication and quantum computation.     

Characteristics of a Novel Water Plasma Torch

Relying on heat generated by plasma arc heating liquid water into steam as a swirl gas, a water plasma torch has the distinctive steam generation structure, which has various applications such as in the treatment of organic waste and hydrogen production for fuel cells in future vehicles. The operational features of the water plasma torch and water phase change process in the discharge chamber are investigated based on the temporal evolution of the voltage and current. The optical emission spectrum measurement shows that the water molecule in the plasma is decomposed into 14, OH and O radicals. As the electrodes do not require water-cooling, the thermal efficiency of the torch is very high, which is confirmed by analytical calculation and experimental measurement.