二次函数图象平移规律的猜想与探索

<正>初三我们学习了二次函数．在研究二次函数图象的平移时,我们通过将一般式y=ax2+bx+c转换为顶点式y=a (x-h)²+k来研究左右平移时的变化规律．最后,我们得出研究结论:y=a (x-h)²+k的图象是由y=ax2的图象向右平移h个单位得到的．     

离子液体-基质固相分散-超声雾化-固相萃取结合高效液相色谱法检测人参中三嗪类除草剂

采用固载1-甲基-3己基咪唑六氟磷酸([C6MIM][PF6])的硅胶作为基质固相分散剂,与超声雾化提取及C18固相萃取相结合,对人参提取物进行提取和净化;采用高效液相色谱法,建立了人参中5种三嗪类除草剂的检测方法.样品前处理的最优条件为:300 mg人参粉末与150 mg硅胶([C6MIM][PF6]含量2.0 mmol/g)研磨5 min,以20.0 mL去离子水(pH 7,含1.0％ NaCl)超声雾化提取10 min,再以5.0 mL乙腈洗脱萃取小柱(300 mg C18).实验结果表明,目标物的检出限为0.020～0.035 g/g,线性相关系数r2≥0.9992,实际样品加标回收率为78.2％～95.4％,相对标准偏差为3.5％ ～6.0％.本方法快速高效、净化效果好、提取率高,为中药中农药残留的检测提供了新的样品前处理方法.     

Microstructural,magnetic and dielectric performance of rare earth ion (Sm3+)-doped MgCd ferrites

The combined effects of Sm$^{3+}$ substitution together with the addition of 3 wt% Bi$_{2}$O$_{3}$ endow MgCd ferrites with excellent magnetic permeability and dielectric permittivity. Various concentrations of Sm$^{3+}$ ($x = 0$, 0.03, 0.06, 0.09, 0.12 and 0.15) were employed to modify the permeability ($\mu'$) and permittivity ($\varepsilon'$) of the MgCd ferrites. X-ray diffraction, scanning electron microscopy (SEM), vibrating sample magnetometry and vector network analysis techniques were used to characterize the samples. The measurement results reveal that the ferrites processed a saturation magnetization of up to 36.8 emu/g and coercivity of up to 29.2 Oe via the conventional solid-state reaction method. The surface morphology SEM confirms that with increasing Sm$^{3+}$ concentration, the grain shape changes from a polygon to a circle. Moreover, the dielectric permittivity can reach a value of 23. The excellent properties obtained in Sm$^{3+}$-substituted Mg ferrites suggest that they could be promising candidates for modern high-frequency antenna substrates or multilayer devices.