Cluster Observation of Eelectrostatic Solitary Waves around Magnetic Null Point in Thin Current Sheet

Electrostatic solitary waves （ESWs） are observed in the vicinity of the magnetic null of the widely studied magnetic reconnection taking place at the near-earth tail when current sheet becomes dramatic thinning during substorm time on 1 October 2001. We use the Imada method for the 2-D reconnection model and study the characteristics of ESWs near the X-line region and the magnetic null points. The result shows that the amplitude of the observed ESWs in the vicinity of X-line region ranges from 0.1mV/m to 5mV/m, and the amplitude is larger near the magnetic null points. The generation mechanism and the role of ESWs associated with magnetic reconnection are also discussed.     

Interest-Driven Model for Human Dynamics

Empirical observations indicate that the interevent time distribution of human actions exhibits heavy-tailed features. The queuing model based on task priorities is to some extent successful in explaining the origin of such heavy tails, however, it cannot explain all the temporal statistics of human behavior especially for the daily entertainments. We propose an interest-driven model, which can reproduce the power-law distribution of interevent time. The exponent can be analytically obtained and is in good accordance with the simulations. This model well explains the observed relationship between activities and power-law exponents, as reported recently for web-based behavior and the instant message communications.     

Narrow Linewidth Tm^3＋-Doped Large Core Fiber Laser Based on a Femtosecond Written Fiber Bragg Grating

A diode laser （LD） clad-pumped narrow linewidth all-fiber Tm^3＋-doped fiber laser is reported with a maximal output power of 27W at 1.947μm. By successively splicing an LD pigtail fiber, a single-mode Tm^3＋-doped fiber, and a multi-mode Tm^3＋-doped fiber, the fiber laser has 70pm narrow linewidth output, and a high slope efficiency of nearly 47.5% with respect to the launched pump power. The high reflectivity fiber Bragg gratings, which are directly written into the single-mode Tm^3＋-doped fiber core by the 800nm femtosecond pulsed laser, act as the high reflectivity coupler. The output laser has diffraction-limited beam quality with a factor M^2 of 1.29, when the output laser power is nearly 27W.     

Rb与H_2的反应碰撞:Rb(6~2D)+H_2→RbH+H

在样品池条件下,应用脉冲激光的泵浦-检测技术,研究了Rb(6~2D)激发态原子与H_2反应碰撞生成的RbH分子的振转能级的布居数密度分布及平均转动能、振动能、平动能的相对比值.发现RbH(X~1∑~+)只有v=0,1上有布居.转动带分布轮廓与池温下的统计分布接近,得到RbH的Boltzmann转动温度稍低于池温,而振动温度高.v=1和v=0上的布居数之比约为0.69,从而得到RbH(X~1∑~+)上平均转动能和平均振动能,由反应的有效能得到平均平动能,这三种能量的相对比值f_R:f_V:     

利用光栅光谱仪研究乙醇汽油溶液的吸收特性

利用WGD-8A型多功能光栅光谱仪测量了不同汽油体积含量的乙醇汽油溶液对波长为300.0～430.0 nm光的吸收光谱,分析了乙醇汽油吸光度和汽油浓度的关系,在稀溶液吸光度的朗伯-比尔定律基础上,进一步研究了2种高浓度混合溶液吸光度的计算方法,并得出了入射光波长为377.0,382.0,391.5,410.9 nm时乙醇汽油的吸光度与汽油体积浓度的关系式.     

基于经验模态分解的高光谱遥感数据去噪方法

经验模态分解(EMD)是一种新的时频分析方法,经EMD分解后的各个固有模态函数(IMF)突出了原始信号的局部特征,从而可以区分噪声和有用信号。基于此,结合高光谱遥感数据的光谱变化特征,提出了一种基于经验模态分解的高光谱遥感数据去噪方法。通过对理论数据的实验表明,数据中的噪声无论是高斯分布还是均匀分布,数据经EMD分解后,噪声都主要集中在前几个特定的IMF,对相应的IMF进行滤波处理后并与其他IMF分量进行重构就可得到去噪信号,与小波去噪结果相比较,这种方法效果更好。最后把该去噪方法应用于野外实测的油膜高光谱数据去噪,实验结果表明,该方法能准确、有效地去除高光谱遥感数据的噪声。     

进口锆英砂放射性γ能谱分析

利用γ能谱分析技术对2个产地共17个进口锆英砂样品中的放射性核素226Ra、232Th和40K进行了定量分析,并提出了一种新的样品自吸收修正方法。结果:产地1样品中226Ra的比活度均值为2399.75Bq/kg,232Th的比活度均值为422.72Bq/kg;产地2样品中226Ra的比活度均值为1852.91Bq/kg,232Th的比活度均值为455.45Bq/kg;2个产地样品中40K的比活度均很低。研究表明,锆英砂样品中放射性主要来源是226Ra、232Th。两产地样品中232Th的放射性比活度相差较小,而226Ra的放射性比活度差别明显。同一产地样品中放射性核素比活度也存在较大差异。样品自吸收对分析结果的影响可达10%—30%,须进行自吸收修正。     

用于测量熔合反应的静电偏转板介绍

An electrostatic deflector for separating the fusion evaporation residues from the beam-like products in heavy ion reactions was installed. The evaporation residue separation and identification with the electrostatic deflector setup was tested with the reaction ^32S＋^96Zr at several energies. The fusion evaporation residues and the beam-like particles were well separated after the electrical separation and the experimental fusion cross section obtained from the angular distribution is in good agreement with the calculated value well above the Coulomb barrier. This confirms the reliability of the setup.     

Dipole bands in nucleus ~(139)Pm

High-spin states in nucleus 139Pm have been studied using the reaction 116Cd(27Al,4n)139Pm.Two dipole cascades have been found.Spin and parity assignments were based on the Directional Correlation of Oriented Nuclei(DCO) ratios and systematic behavior in neighboring odd-proton nuclei.The level structures of 139Pm are compared with those of the N =78 isotone 141Eu in which two dipole bands have been confirmed as magnetic rotational bands.The close similarity between them suggests that the dipole bands in 139...     

反射转镜式干涉光谱仪光程差非线性修正方法比较

介绍了反射转镜式干涉光谱仪的原理。转镜的转动会导致光程差存在非线性问题,是转镜式干涉光谱仪普遍存在的问题。由于光程差的非线性会导致反演光谱的严重失真,因此需要对其进行修正处理。对非线性修正问题,目前常用的有光程差替换法、干涉图二次采样法和NUFFT法。实验结果证明,NUFFT法和光程差替换法运算精度较高,相对偏差优于0.13%,NUFFT法精度又略高于光程差替换法;在运行效率上,NUFFT法运行速度最快,其次为光程差替换法。由于干涉图本身是一个剧变信号(特别是在零光程差附近),不适合进行多项式拟合,所以干涉图二次采样法运算精度最低,另外,由于干涉图二次采样法需要做分段拟合运算,所以运行效率也最低,从而可以认为NUFFT方法是目前最适用于反射转镜式干涉光谱仪非线性采样误差修正的方法。