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.     

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.     

Unique Charge Storage Characteristics of FEP//THV//FEP Sandwich Electret Membrane Polarized by Thermally Charging Technology

Nowadays, electrets have been widely applied in acoustic electric sensors such as microphones and other actuators due to its lasting and stable electrostatic field. Recently, research has focus on the application of micro-electro-mechanical systems （MEMS）, especially on electret generator for energy harvesting,where vibration energy can be changed into electrical energy by relative displacement between two electret layers when vibrating. Many kinds of configurations for the electret generator have been proposed, in which the theoretical power output is proportional to the surface charge density of the electret. Therefore, it is crucial to develop a new novel electret with an extremely high surface charge density and long-term stability for electret generators with large power output.     

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．     

高考专题复习系列讲座——集合与简易逻辑

[考试内容及考试要求]。考试内容：集合，子集，补集，交集，并集，逻辑联结诃，四种命题，充要条件．     

用Бернштейн多项式通近 可微函数的渐近表达

本文研究用BepaiuTefta多项式逼近可微函数·改进了现有结果，建立了一个含有点态因子的渐近等式;     

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.