微波/电热板组合消解-电感耦合等离子体质谱(ICP-MS)法测定土壤中重金属元素

为提高土壤检测的重金属得率,采用了微波消解/电热板组合预处理-电感耦合等离子体质谱法(ICP-MS)测定土壤重金属含量。分析了硝酸(HNO3)、氢氟酸(HF)、高氯酸(HClO4)和盐酸(HCl)组合消解液及赶酸温度对土壤预处理影响。结果显示：在硝酸和盐酸混合消解液中,硝酸占比越高,铬(Cr)、钴(Co)、铜(Cu)、镉(Cd)得率更高;消解液体系中加入氢氟酸可使消解更加彻底,提高铬与铜的得率。最优预处理消解条件为硝酸 6ml+ 氢氟酸 2ml消解液组合进行微波消解,1ml 高氯酸于155℃电热板上赶酸。经土壤标准样品GBW07401(GSS-1)和GBW07452(GSS-23)实际应用,预处理条件优化后测试准确度和稳定性均显著提高。此外使用元素铑(Rh)作为内标物时,其方法稳定性和准确性高于内标物钪(Sc)和锗(Ge)。可为相关国家土壤重金属测定标准的修制订提供方法学参考。     

蛇笼型螯合树脂的合成及性能研究Ⅱ·CMC/B-62/TETA体系

以羧甲基纤维素（ＣＭＣ）、甘油环氧树脂（Ｂ－６２）及三乙烯四胺（ＴＥＴＡ）为基本原料,经脱水交联合成了一种ＣＭＣ的蛇／ＴＥＴＡ交联Ｂ－６２树脂为笼的新型弱酸弱碱型蛇笼树脂。研究了该树脂在不同溶剂中的溶胀性能及对Ｃｕ＾２＋、Ｎｉ＾２＋、Ｐｂ＾２＋的吸附量、吸附动力学、等温吸附过程等静态吸附。同时研究了ｐＨ值等因素对吸附性能的影响。实验结果表明,该树脂在所有溶剂中只溶胀而不流失;其对上述三种金属离子的     

鞅的自正则指数不等式

本文讨论了局部平方可积鞅,给出了Delyon不等式的推广形式. 这个结果对于建立鞅的自正则指数不等式有一定的意义. 本文还讨论了线性回归的一个应用.     

Circuit-field coupled finite element analysis method for an electromagnetic acoustic transducer under pulsed voltage excitation

This paper presents an analytical method for electromagnetic acoustic transducers (EMATs) under voltage excitation and considers the non-uniform distribution of the biased magnetic field. A complete model of EMATs including the non-uniform biased magnetic field, a pulsed eddy current field and the acoustic field is built up. The pulsed voltage excitation is transformed to the frequency domain by fast Fourier transformation (FFT). In terms of the time harmonic field equations of the EMAT system, the impedances of the coils under different frequencies are calculated according to the circuit-field coupling method and Poynting’s theorem. Then the currents under different frequencies are calculated according to Ohm’s law and the pulsed current excitation is obtained by inverse fast Fourier transformation (IFFT). Lastly, the sequentially coupled finite element method (FEM) is used to calculate the Lorentz force in the EMATs under the current excitation. An actual EMAT with a two-layer two-bundle printed circuit board (PCB) coil, a rectangular permanent magnet and an aluminium specimen is analysed. The coil impedances and the pulsed current are calculated and compared with the experimental results. Their agreement verified the validity of the proposed method. Further- more, the influences of lift-off distances and the non-uniform static magnetic field on the Lorentz force under pulsed voltage excitation are studied.