竹炭固相萃取/气相色谱-质谱联用对环境水样中16种多环芳烃的测定

以竹炭为固相萃取吸附材料,考察了其对环境水样中16种多环芳烃的吸附富集能力,采用DB-35MS弹性石英毛细管色谱柱对16种多环芳烃进行分离,气相色谱-质谱联用法对多环芳烃进行定性及定量分析.结果表明,1 000 mg竹炭作为固相萃取吸附剂,10 mL二氯甲烷作为洗脱剂,上样速率5 mL/min,水样中甲醇体积分数为15%的条件下,16种多环芳烃有较好的回收率,竹炭固相萃取柱的穿透体积大于500 mL,通过实验比较竹炭的萃取回收率优于商品化的C18固相萃取柱.16种多环芳烃的质量浓度在10 ～500 ng/L范围内与峰面积的线性关系良好(苯并(k)荧蒽,苯并(a)芘,二苯并(a,h)蒽,苯并(g,h,i)苝为25 ～500 ng/L),相关系数为0.983 6 ～0.998 4.方法的检出限为0.6 ～8.0 ng/L,实际水样的加标回收率为67% ～113%,相对标准偏差为2.1% ～11.3%.通过对白沙河河水的分析表明,该方法能够满足实际水样的测定,竹炭可以作为固相萃取材料应用于水中16种多环芳烃的分析测定.     

确定岩质边坡安全阈值的新方法

应用二维离散单元程序UDEC,以黄麦岭磷矿采场岩质边坡为例,通过分析边坡质点位移矢量的变化规律,定义了边坡的极限平衡状态和破坏状态,提出一种新的确定安全速度阈值的方法,并确定了黄麦岭磷矿采场岩质边坡的安全速度阈值。分析结果表明,新方法确定的安全阈值与现场监测确定的阈值吻合得较好。因此,应用该法来确定边坡的安全阈值是可行的。     

磁场作用下超导圆环的涡旋演化

利用Ginzburg-Landau理论模拟在外磁场作用下超导圆环的涡旋演化,讨论了外磁场、材料参数以及圆环内外径对涡旋进入超导圆环体以及涡旋达到稳定分布的影响.研究结果表明:外磁场越大,材料参数κ越大,圆环环身越宽,则超导圆环体内容纳的涡旋就越多.当磁场较小时,涡旋只由内边界进入超导体,当磁场足够大时,涡旋则先由外边界,然后再从内边界进入超导体.     

Radiation Induced Optical Absorption of Cubic Lead Fluoride Crystals and the Effect of Annealing

Transparent and colorless lead fluoride crystals with sizes of 20 × 20 × 20 （ram3） are irradiated with several doses of γ-rays from a ^60Co source. Their transmittance spectra before and after irradiation are measured, and a new parameter ΔT = Tb - Ta is defined to evaluate the irradiation damage. Three optical absorption bands peaking at 27Onto, 37Onto and 50Onto are found in the plots of AT versus wavelength, and their intensities increase with the irradiation dose. These optical absorption bands, except the one at 27Onto, can recover spontaneously with time. Thermal annealing treatment can enhance this recovery of the transmittance, while the optimum annealing temperature for different samples depends on the irradiation dose.     

广义FGM Copula的一个判定定理及应用

研究了形如C_θ(u,v)=uv θu~av~b(1-u~m)~c(1-v~n)~d的一种新型广义FGM copula中参数θ的精确取值范围．所研究的copula含盖了文献中许多特殊类型的FGM copula,具有广泛的代表性．参数θ的计算方法简单易行,改进并完善了文献中相应的结论．     

高频金融数据的标度分析

高频金融数据通常具有尖峰厚尾的非正态特征，常用稳定分布来拟合。本文采用稳定分布的性质对高频上证指数收益率的分布作了标度分析，求得特征指数为1．48，说明我们在分析证券指数分布时可以用稳定分布，而非正态分布。     

Effect of Laser Cooling on Frequency Standard of Single Ca^＋ Ion Trapped in a Radio-Frequency Paul Trap

The source of systematic frequency shift of single-ion optical frequency standard of^40 Ca^＋ ion trapped in endcap trap and laser-cooled to a few of mK is analysed and calculated. Second-order Doppler shift, Stark shift due to micromotion and thermal motion, blackbody Stark shift and ac Stark shift are calculated for the ground state and excited 3d ^2D5/2 state. The Hertz-level measurement of the optical clock frequency in a single ^40Ca^＋ ion can be performed.     

Function S-rough Sets and Their Law Characteristic

Function S-rough sets(Function Singular rough sets) are defined by R-function equivalence class which has dynamic characteristic, and a function is s law, function S-rough sets have law characteristic. Function S-rough sets has these forms: function one direction S-rough sets, function two direction S-rough sets and dual of function one direction S-rough sets. This paper presents the law characteristic of function one direction S-rough sets and puts forward the theorems of law-chain-attribute and law-belt. Function S-rough sets is s new research direction of the rough sets theory.     

大型动态规划的分解算法

An approach about large dynamic programming based on discrete linear system with a quadratic index function is proposed by importing two Lagrange multipliers.     

沪深股市相关结构分析研究

在金融市场风险分析中,对金融资产相关结构的讨论有着重要意义,从而引出对如何选取好的相关结构模型来捕捉金融资产间的相关变化规律的讨论。针对这一问题,我们用混合相关结构函数Copula对上海、深圳股票市场进行了相关分析研究,用极值分布刻画了每支股票的边缘分布,用两步估计法对Copula中的参数进行了估计。分析结果表明:混合Copula相关结构能够捕捉金融市场间相关性变化规律,比单个Copula相关结构更灵活,更能全面地反映市场间非对称变化的相关程度和模式,此方法还可以推广到对多种金融资产收益率进行相关性分析。