An improved evaluation of the neutron background in the PandaX-Ⅱ experiment

In dark matter direct detection experiments,neutron is a serious source of background,which can mimic the dark matter-nucleus scattering signals.In this paper,we present an improved evaluation of the neutron background in the PandaX-II dark matter experiment by a novel approach.Instead of fully relying on the Monte Carlo simulation,the overall neutron background is determined from the neutron-induced high energy signals in the data.In addition,the probability of producing a dark-matter-like background per neutron is evaluated with a complete Monte Carlo generator,where the correlated emission of neutron(s)andγ(s)in the(α,n)reactions and spontaneous fissions is taken into consideration.With this method,the neutron backgrounds in the Run 9(26-ton-day)and Run 10(28-ton-day)data sets of PandaX-II are estimated to be(0.66±0.24)and(0.47±0.25)events,respectively.     

碳纳米管的可控长度拾取及导电性分析

拾取指定长度的半导体性碳纳米管对大规模制造碳纳米管场效应管具有重要意义.本文提出了一种利用原子力显微镜探针和钨针对碳纳米管进行可控长度拾取的方法并进行了碳纳米管导电性分析.在扫描电子显微镜下搭建微纳操作系统,针对切割操作过程中原子力显微镜探针、钨针和碳纳米管的接触情况进行了力学建模和拾取长度误差分析.建立了单根金属性碳纳米管、单根半导体性碳纳米管及碳纳米管束与钨针接触的电路模型,推导了接入不同性质碳纳米管后电路的电流电压特性方程.使用原子力显微镜探针对碳纳米管的空间位姿进行调整,控制钨针对碳纳米管上目标位置进行通电切割,同时获取切割电路中的电流电压数据.实验结果表明,本文提出的方法能够有效控制所拾取碳纳米管的长度,增加碳纳米管与原子力显微镜探针的水平接触长度能够减小碳纳米管形变导致的拾取长度误差,建立的电流电压特性方程能够用于分析碳纳米管的导电性.     

星载海洋激光雷达最佳工作波长分析

星载激光雷达是实现海洋垂直剖面探测的有效工具,也是目前迫切需求的海洋光学遥感手段。对星载海洋激光雷达的波长参数进行评估对保证探测有效性具有重要意义。本文从探测深度和信噪比两方面分析了星载海洋激光雷达探测全球海洋的最佳波长。利用MODIS 10个波段的水体光学特性数据,估算全球海水探测深度及相应的最优波长;并根据太阳夫琅禾费暗线特性,对信号信噪比进行优化。结果表明:在探测深度方面,最优探测波长在488 nm波段的海洋占全球海洋面积的70%左右,并且全球95%以上的海域在488 nm波段的探测深度优于0.8倍的真光层深度;在信噪比方面,相对于488 nm波段,486.134 nm夫琅禾费暗线处采用0.1 nm带宽的滤光片可以将背景光强度降低70%,相应地回波信噪比整体提升了约5.0%。就全球海洋探测来说,使用486.134 nm作为探测波长可以提高探测深度,有效抑制太阳背景光,提高信噪比,因此,486.134 nm是星载海洋激光雷达的最佳工作波长。     

关于次加泛函的一点注记

In this note we obtained a both sufficient and necessary condition there exist non-zero β′ degree abslutely homogeneous, continuous and subadditive unctionals in metric linear spaces (E, ‖·‖_β) for C < β≤β′ ≤1 . APPlying our result, a simpler proof of theorem in[1,§1] was given.     

Can (H2O) n (n = 1–2) as effective catalysts in the CH2OO + H2S reaction under tropospheric conditions?

The addition reaction of CH₂OO?+?H₂S → HSCH₂OOH without and with catalyst X (X?=?H₂O and (H₂O)₂) has been investigated by CCSD(T)-F12a/VTZ-F12//B3LYP/aug-cc-pVTZ method and canonical variational transition state theory with small curvature tunneling correction. When H₂O was introduced in the CH₂OO?+?H₂S reaction, it not only acts as a catalyst for producing HSCH₂OOH, but also plays as a reactant to forming HOCH₂OOH. The formation channel of HSCH₂OOH is more important than the formation channel of HOCH₂OOH with its calculated rate constant larger by 11.0–43.2 times within the temperature 280–320?K. Then, (H₂O)₂ catalysed CH₂OO?+?H₂S → HSCH₂OOH reaction has been taken into account with its rate lower 1.9–4.2 times than the reaction of CH₂OO?+?H₂S → HSCH₂OOH with water. Also, CH₂OO?+?H₂S with H₂O cannot compete with the CH₂OO?+?H₂S reaction without water. This is different from CH₂OO?+?(H₂O)₂ reaction, which is about 4 orders of magnitude larger than the rate constant for CH₂OO?+?H₂O reaction. Such discrepancy is possible because C(CH₂OO)···O(H₂O) interaction has been enhanced more obviously by H₂O as compared to that of C(CH₂OO)···O(H₂S) interaction.     

基于PLC 的中央空调制冷系统变频控制研究

针对现有中央空调系统能源消耗严重的现状,基于可编程逻辑控制器(Programmable Logic Controller,PLC)对中央空调系统进行变流量节能改造。分析改造后中央空调系统的结构组成和变频运行原理,并提出适用于冷冻水泵和冷却水泵的分段速温差控制和PID温差控制设计方案。控制硬件选用三菱FX3U系列PLC和台达VFD-EL变频器,软件选用GX Work2编程软件及力控组态软件。将控制方案进行实验验证,实验结果表明,所设计的两种控制策略不仅跟随系统末端负荷变化快速达到稳定运行状态,提高运行能效比,而且节能效果显著,节能率分别为40.2%和48.7%。     

十二烷基苯磺酸钠对2代2一苯骄唆邃偶氮)一5一二甲氨基苯甲酸与镍反应影响的研究

本义刊通过虑法研究了Ni( g )-BTPiMB一S3}BS沐系的热力学性质.同时利用光度法肝尤了‘i};,}}7 fi勺\3性i }Tl }讨沦了表面活I剂与各组份之间的作用情况,结果丧明,胶束对显色泛:,;r约“催化”作用,实质土是由胶束对过鼠试剂的“富集”作用引起,BTAMB几乎不波SDBS富集,故体系中观察不到这种崔化作用,并且在通常所涉及的表面活性剂用量范围勺,不序在过量胶束使显色沐系魁色的议电,这与通常的表面活性刘}.f3敏沐系相比,有其特殊之处.     

位标器动平衡测试系统中的相位测量方法研究

提出了一种相位测量方法,该方法可以准确检测从位标器陀螺仪输出的钟形光电脉冲信号峰值点的位置并以其为时间基准点进行相位测量,并可判断被测两信号之间的时间间隔以及超前滞后关系.针对在现场中的干扰因素,提出了相应的解决措施.该方法电路简单;测量速度快;精度高;可靠性好.     

Faraday镜预转角对FMOCT输出光偏振态的影响

通过计算机仿真,运用琼斯矩阵理论分析了Faraday镜预转角对法拉第镜式光学电流互感器输出光偏振态的影响.实验测量了Faraday镜实际预转角的大小,测量了外磁场的改变对Faraday镜预转角的影响.外磁场的存在和变化使Faraday镜预转角偏离初始值,并使系统输出光由理想状态下的线偏振光退化成椭圆偏振光,并引起法拉第镜式光学电流互感器工作灵敏度和稳定性的下降.提出了用电磁屏蔽解决外界磁场影响的方法.     

塑料闪烁体的辐照特性

利用⁶⁰Co放射源分别对3种塑料闪烁体(BC-408, EJ-200, BC-404)进行辐照损伤研究, 比较辐照前后的透射谱、发射谱及光产额的变化, 发现3种闪烁体在低剂量具有较好的抗辐照性能; 当照射剂量超过1.44×10⁴Gy时,透射谱明显变坏, 光输出减少很严重, 但发射谱却保持不变.