Status of CSNS H- ion source

A new H^- ion source has been installed successfully and will be used to serve the China Spallation Neutron Source (CSNS). In this paper, we report various components of the ion source, including the discharge chamber, temperature, cooling system, extraction electrodes, analyzing magnet, remote control system and so on. Compared to the previous experimental ion source, some improvements have been made to make the ion source more compact and convenient. In the present arrangement, the Penning field is generated by a pair of pole tip extensions on the 90° analyzing magnet instead of by a separate circuit. For the remote control system, F3RP61-2L is applied to the accelerator online control system for the first time. In the running of the ion source, a stable pulse H^- beam with a current of 50 mA at an energy of 50 keV is produced. The extraction frequency and pulse width is 25 Hz and 500 μs, respectively. Furthermore, an emittance scanner has been installed and measurements are in progress.     

上海股票市场收益率分布研究

股票市场的收益率从分布的角度看,并不服从标准的正态分布,而是呈现出一种"尖峰、厚尾"的特征。本文对上海股票市场进行分析,采用几种方法对股指对数收益率进行正态分布检验,发现收益率更加接近于一种混合正态分布,本文利用混合辨析的思想得到了收益率分布的具体形式。     

基于化学模式识别技术的枳实HPLC定量指纹图谱研究

建立了枳实的高效液相色谱(HPLC)指纹图谱分析方法.色谱柱为Tnature-ACCHROM C18色谱柱(4.6 mmx250 mm,5 μm);以乙腈-0.5％甲酸水溶液为流动相进行梯度洗脱,结合液相色谱-四极杆飞行时间质谱(HPLC-QTOF-MS)联用技术对枳实指纹图谱中的共有峰进行鉴定;采用相似度评价、聚类分...     

空间非均匀激光场驱动的原子非次序双电离

利用三维经典系综模型,研究空间非均匀激光场驱动的氙原子非次序双电离,并对比了空间均匀激光场的情况.结果显示,波长较短时,空间非均匀激光场与空间均匀激光场的非次序双电离的产率较为相近.随着波长的增大,较高激光强度时空间非均匀激光场下非次序双电离受到越来越明显的抑制.相比于空间均匀激光场,空间非均匀激光场下非次序双电离两电子的末态发射角表现出更强烈的关联特性,特别在较大的激光波长下,两电子的末态发射角几乎全部集中在0°附近,这意味着两电子往往是平行发射到相同方向.此外,波长由近红外增大到中红外时,空间非均匀激光场下非次序双电离的有效再碰撞均由第1个电子的第1次返回主导,而空间均匀激光场下则呈现由第1次返回主导到第2次返回主导的转变.进一步,通过反演分析非次序双电离的经典轨迹,揭示了空间非均匀激光场下关联电子超快动力学过程的更多细节.     

热释电双波长光纤测温仪的精度分析

在介绍一种利用钽酸锂热释电探测器实现的实用化双波长光纤测温仪的基础上,着重讨论了反射辐射、探测器周围环境的热辐射、仪器工作波长的带宽,以及光路中选择性吸收气体的光谱吸收等多种因素对仪器测温精度的影响,并提出了相应的抑制措施。实验表明,采取相应的抗干扰措施后,在系统要求的测温范围400—1360℃内,其测温精度符合设计要求。     

Synthesis of Covalently-linked Linear Donor-Acceptor Copolymers Containing Porphyrins and Oligothiophenes

The construction of macro-molecular system containing multiple redox centers or photosensitizers is aimportant subject in the design of molecular electronidevices.1,2 For such objectives, systematization of donor-redox center-acceptor triad molecules into largmolecular systems is one of the most feasible approaches, because the exquisite incorporation of thphotosensitizers and suitable electron donors and/oacceptors into a polymeric chain is useful for varioumolecular electronic systems.3-5 Th…     

美式看跌期权定价的一种混合数值方法

本文对美式看跌期权的定价提供了一种新的混合数值方法,即快速傅里叶变换法加龙格-库塔法.首先将美式看跌期权价格所满足的Black-Scholes微分方程定解问题转化为一个标准的抛物型初、边值问题,然后通过傅里叶变换,使之转换为一个不带股价变量的常微分方程初值问题,再利用龙格-库塔法对其进行数值求解.数值实验表明,本文算法是一种快速的高精度的算法.     

用密度泛函理论研究氮化硅新相的电子结构、光学性质和相变

运用第一性原理赝势方法,对氮化硅新相(六方Pˉ6和Pˉ6′相)的电子结构、光学性质和相变过程进行分析,研究能带结构、介电函数谱、反射谱和能量损失函数的变化机理.研究发现,β→Pˉ6→δ相变是可行的,在室温下β→Pˉ6和Pˉ6→δ相变的临界压强分别为42.9和47.7 GPa;相界的斜率为正值表明Pˉ6→δ相变过程伴随着晶胞体积的塌缩;Pˉ6和Pˉ6′相分别属于直接带隙和间接带隙半导体,能隙宽度分别为4.98和4.01 eV;得到了两相的零频介电常数;反射谱表明,两相的强反射峰均位于真空紫外线区域,因此可以用作紫外光屏蔽或紫外探测材料;在可见光区域,两相表现为近似透明.     

Phase transition, structural and thermodynamic properties of Mg2Si polymorphs

The plane-wave pseudo-potential method within the framework of first principles is used to investigate the structural and elastic properties of Mg 2 Si in its intermediate pressure(Pnma) and high pressure phases(P 6 3 /mmc).The lattice constants,the band structures.The bulk moduli of the Mg 2 Si polymorphs are presented and discussed.The phase transition from anti-cotunnite to Ni 2 In-type Mg 2 Si is successfully reproduced using a vibrational Debye-like model.The phase boundary can be described as P = 24.02994 + 3.93 × 10 3 T 4.66816 × 10 5 T 2 2.2501 × 10 9 T 3 + 2.33786 × 10 11 T 4.To complete the fundamental characteristics of these polymorphs we have analysed thermodynamic properties,such as thermal expansion and heat capacity,in a pressure range of 0-40 GPa and a temperature range of 0-1300 K.The obtained results tend to support the available experimental data and other theoretical results.Therefore,the present results indicate that the combination of first principles and a vibrational Debye-like model is an efficient scheme to simulate the high temperature behaviours of Mg 2 Si.     

股票期权VaR的一种计算方法

本文提出一种运用Laplace分布来计算股票期权VaR的新方法.首先对股票价格的运动规律进行理论和实证分析,表明利用Laplace分布来来拟合股票的对数收益率是合理的,然后在此基础上推导了股票期权VaR的计算公式,最后给出了算例.