二维层状GaTe的晶体结构研究

采用布里奇曼法生长出了化合物半导体GaTe,并对其晶体结构进行研究.利用X射线衍射仪对GaTe粉末和块体试样分别进行测试,确定了其晶体结构.采用透射电子显微镜对二维薄膜GaTe及二维纳米层GaTe进行观测,并结合晶体定向仪对GaTe解理面进行了定向分析.结果表明,二维薄膜GaTe及二维纳米层GaTe分别对应单斜和六方两种不同的晶体结构,并对应不同的解理面.     

土壤含盐量与电导率的高光谱反演精度对比研究

探明土壤盐渍化的高光谱遥感监测机理,对改善高光谱遥感监测精度具有重要意义。以南疆地区温宿县、和田县、拜城县的水稻土为研究对象,通过分析土样的高光谱数据和室内测定的盐分与电导率数据,研究了耕作土壤含盐量与电导率的关系,并比较了含盐量和电导率与不同光谱指标的相关性以及二者高光谱反演的精度。结果表明,南疆水稻土的含盐量与电导率的相关性较低,二者之间的关系因地区差异而有较大的变化;含盐量与反射率、一阶微分、连续统去除之间的相关性要优于电导率,特别在一些土壤盐渍化的敏感波段尤为突出;以含盐量建立的多元线性回归、主成分回归、偏最小二乘回归模型的决定系数和相对分析误差均高于电导率。研究表明高光谱信息对土壤含盐量的响应比电导率更敏感,以含盐量为监测指标的高光谱反演精度明显要优于电导率。该结果可为提高土壤盐渍化高光谱遥感监测精度提供理论依据。     

Nonlocal symmetry,optimal systems,and explicit solutions of the mKdV equation

The nonlocal symmetry of the mKdV equation is obtained from the known Lax pair; it is successfully localized to Lie point symmetries in the enlarged space by introducing suitable auxiliary dependent variables. For the closed prolongation of the nonlocal symmetry, the details of the construction for a one-dimensional optimal system are presented. Furthermore, using the associated vector fields of the obtained symmetry, we give the reductions by the one-dimensional sub-algebras and the explicit analytic interaction solutions between cnoidal waves and kink solitary waves, which provide a way to study the interactions among these types of ocean waves. For some of the interesting solutions, the figures are given to show their properties.     

Coupling Distant Spins of Surface-State Electrons by Manipulating Their Collective Vibrations

The system of electrons on liquid helium is an interesting candidate to implement quantum computation, due to the long coherence times of the qubits encoded by the electronic spins. In order to implement the quantum logic operations between the spins, we propose here a configuration, similarly to the cooled ions in a trap, to couple the distant electrons via manipulating their center of mass （CM） vibrations. First, we show that the electrons could be confined in a common harmonic oscillator potential by using an electrostatic field. Then, with a single current pulse （applied on the micro-electrode below the liquid helium） the distant electronic spins can be coupled simultaneously to the CM mode. Finally, by adiabatically eliminating the CM mode, effective interaction between the distant spins is induced for implementing the desired quantum computing.     

高精度V棱镜折射仪光机结构设计

针对传统V棱镜折射仪采用光学度盘,目视对准方式无法满足现代光学玻璃生产线以及高精度折射率测量的需求。提出一种新型的高精度基于CCD 机器视觉对准的V棱镜折射仪的总体设计方案,并对准直光管、传动机构、锁紧和微调机构以及轴角编码测角机构等主要组成部分进行了光机结构设计。在考虑空气折射率影响因素的修正公式的基础上,分析了仪器的检测误差。实验结果表明:其折射率检测精度可达 310-6,满足了高精度V棱镜折射仪的技术指标要求。     

莫桑比克摩根石的谱学特征研究

近几年摩根石凭借它独特的色彩悄然兴起。采用常规仪器测试、激光剥蚀等离子质谱(LA-ICP-MS)、紫外-可见吸收光谱(UV)、红外光谱(IR)和拉曼光谱(Raman),对产自莫桑比克的摩根石基本性质、化学成分特征、谱学性质进行了较为详细的分析。紫外-可见光谱获得样品主波长、饱和度、明度等相关颜色参数;成分测试显示样品摩根石中Li,Rb,Cs,Mn等含量较高,计算所得到的晶体化学式为Be_3.2090Al_2.0757Li_0.425Si_5.664O₁₈(Na_0.1420Cs_0.1316);红外光谱显示,摩根石的结构振动区主要在指纹区400～1 200 cm-1,其中900～1 200 cm-1为Si—O—Si环的振动区,550～900 cm-1为Be—O振动区,而450~530 cm-1为Al—O振动区。由于摩根石中的Cs元素的含量较高,而Cs为原子序数较高的元素,其存在可能令Si—O—Si环振动谱峰向低频位移。拉曼光谱显示1 065 cm-1为Si—O非桥氧伸缩面内振动,1 000 cm-1左右为Be—O的非桥氧伸缩面外振动,685 cm-1为Si—O—Si的变形面内振动,400 cm-1为O—Be—O的面外弯曲振动,在390 cm-1处为Al—O的面外变形振动,在320 cm-1处为Al—O的面外弯曲振动。     

基于EEMs及PARAFAC的洪湖、东湖与梁子湖CDOM组成特征分析

国内外关于长江中下游地区如洪湖、东湖及梁子湖等大中型浅水湖泊DOM组成特征的分析较少,本文基于2007年9月—10月洪湖、东湖与梁子湖34个站点野外实地采样数据,运用三维荧光图谱(EEMs)与平行因子分析(PARAFAC)模型,着重分析了三个湖泊CDOM吸收荧光特性及组成特征。结果表明,CDOM在350 nm处吸收系数a(350)在三个湖泊表现为洪湖极显著高于东湖与梁子湖(p<0.001);三个湖泊CDOM光谱斜率S_280～500与a(350)呈极显著负相关(R2=0.781, p<0.001)且洪湖S_280～500值极显著低于东湖与梁子湖(p<0.01);光谱斜率比值S_R值也表现为洪湖显著低于东湖与梁子湖(p<0.05)。PARAFAC模型解析得到两个类腐殖质组分(C1, C2),两个类蛋白质组分(C3,C4),其中组分C1与C2呈极显著正相关(R2=0.884,p<0.001),组分C3与C4亦为极显著正相关(R2=0.677,p<0.001),这表明三个湖泊CDOM组分C1与C2,C3与C4来源相似,然而统计结果并未发现四个荧光组分与DOC及Chl-a浓度之间存在任何显著性相关关系。三个湖泊荧光指数FI₂₅₅(HIX),FI₂₆₅,FI₃₁₀(BIX)与FI₃₇₀值均表现为东湖显著高于梁子湖(p<0.05),极显著高于洪湖(p<0.01),这意味着东湖富营养化程度高于洪湖与梁子湖。     

Effect of magnetic field decay on the chemical heating of cooling neutron stars

The effect of magnetic field decay on the chemical heating and thermal evolution of neutron stars is discussed in this paper. Our main goal is to study how the chemical heating mechanism and thermal evolution are changed by the field decay and how the magnetic field decay is modified by the thermal evolution. We compare stars cooling with chemical heating with one without chemical heating and find that the decay of the magnetic field is delayed significantly by the chemical heating. We find that the effect of chemical heating has been suppressed through the decaying magnetic field by the spin-down of the stars at a later stage. Compared with typical chemical heating, we find the decay of the magnetic field can even cause the surface temperature to turn down at an older age. When we discuss the cooling of neutron stars, we should consider the coupling effect of the magnetic field and the rotational evolution of neutron stars on the heating mechanisms.     

适用于测量大气气溶胶吸收系数的光声光谱系统的研究

外部噪声和环境温湿度变化对光声池性能的影响是光声光谱技术在实际大气气溶胶吸收测量应用中遇到的主要问题。详细分析了环境温湿度变化引起的共振频率漂移对光声信号的影响,提出了抑制流动噪声和采样泵振动噪声的方法,研制完成了一套测量大气气溶胶吸收的光声光谱系统,探测极限为1.4×10-8 W·cm-1·Hz-1/2。利用NO₂气体在532 nm的吸收对光声池进行了标定,并对实际大气气溶胶的吸收特性进行了测量,结果表明光声光谱测量系统可以满足自然悬浮状态下的气溶胶吸收系数的实时测量。     

Overview on neutrinos and the Daya Bay experiment

Neutrinos are elementary particles in the Standard Model. Neutrino oscillation is a quantum mechanical phenomenon beyond the Standard Model. Neutrino oscillation can be described by two independent mass-squared differences Δm ₂₁ ² , Δm ₃₁ ² (or Δm ₃₂ ² ) and a 3 × 3 unitary matrix, containing three mixing angles θ ₁₂, θ ₂₃, θ ₁₃, and one charge-parity (CP) phase. θ ₁₂ is about 34° and determined by solar neutrino experiments and the reactor neutrino experiment KamLAND. θ ₂₃ is about 45° and determined by atmospheric neutrino experiments and accelerator neutrino experiments. θ ₁₃ can be measured by either accelerator or reactor neutrino experiments. On Mar. 8, 2012, the Daya Bay Reactor Neutrino Experiment reported the first observation of non-zero θ ₁₃ with 5.2 standard deviations. In June, with 2.5× previous data, Daya Bay improved the measurement of sin²2θ ₁₃ = 0.089 ± 0.010(stat) ± 0.005(syst).