十二烷基键合氧化锆填充电色谱柱的研究

以十二烷基键合氧化锆(C12-ZrO2)作为固定相,制备了填充毛细管电色谱(CEC)柱,较为系统地研究了流动相条件对电渗流的影响、填充CEC柱的稳定性、碱性与中性化合物的保留与流动相pH值和有机溶剂含量的关系。C12-ZrO2固定相填充CEC柱在pH3～11．7范围内具有极好的稳定性;利用磷酸盐与氧化锆表面之间较强的相互作用,能够有效解决传统硅胶键合烷基固定相在有机溶剂含量低的流动相条件下不稳定的问题;同时吸附磷酸盐的固定相表面使得在更宽的流动相pH值范围内CEC柱有足够的电渗流,进一步拓宽CEC的应用领域。     

火焰原子吸收法测定储氢镁合金中高含量钠

建立火焰原子吸收分光光度计测定储氢镁合金中高含量钠的方法。样品经盐酸溶解后,采用火焰原子吸收光谱计测定储氢镁合金中的钠。通过调整燃烧器的角度,选择钠的次灵敏吸收谱线降低测量灵敏度,可消除高倍数稀释造成的误差,提高了测量准确度。方法线性范围为0.001 5%~0.60%,检出限为0.001 5%。4个标准镁合金样品钠含量测定结果均在允许范围内,相对标准偏差为2.04%~3.45%(n=8)。该法适用于镁合金中高含量钠的测定。     

弱阴离子交换硅胶整体柱的制备及其电色谱性能

采用溶胶-凝胶法,结合超分子模板技术,制备了一类新型有机-无机杂化硅胶离子交换整体柱。采用扫描电镜对整体柱的微观结构加以表征,证实孔结构均匀。将制备的弱阴离子交换整体柱应用于9种有机酸的分离,获得最高19万塔板数／米的柱效。探讨了pH值和有机改性剂浓度对分离的影响。     

Trigonometrically fitted two-derivative Runge-Kutta methods for solving oscillatory differential equations

Explicit trigonometrically fitted two-derivative Runge-Kutta (TFTDRK) methods solving second-order differential equations with oscillatory solutions are constructed. When the second derivative is available, TDRK methods can attain one algebraic order higher than Runge-Kutta methods of the same number of stages. TFTDRK methods have the favorable feature that they integrate exactly first-order systems whose solutions are linear combinations of functions from the set $\{\exp ({\rm i}\omega x),\exp (-{\rm i}\omega x)\}$ or equivalently the set $\{\cos (\omega x),\sin (\omega x)\}$ with $\omega >0$ the principal frequency of the problem. Four practical TFTDRK methods are constructed. Numerical stability and phase properties of the new methods are examined. Numerical results are reported to show the robustness and competence of the new methods compared with some highly efficient methods in the recent literature.     

Promoting Surface Electric Conductivity for High-Rate LiCoO2

The cathode materials work as the host framework for both Li⁺ diffusion and electron transport in Li-ion batteries. The Li⁺ diffusion property is always the research focus, while the electron transport property is less studied. Herein, we propose a unique strategy to elevate the rate performance through promoting the surface electric conductivity. Specifically, a disordered rock-salt phase was coherently constructed at the surface of LiCoO₂, promoting the surface electric conductivity by over one magnitude. It increased the effective voltage (V_eff) imposed in the bulk, thus driving more Li⁺ extraction/insertion and making LiCoO₂ exhibit superior rate capability (154 mAh g⁻¹ at 10 C), and excellent cycling performance (93 % after 1000 cycles at 10 C). The universality of this strategy was confirmed by another surface design and a simulation. Our findings provide a new angle for developing high-rate cathode materials by tuning the surface electron transport property.     

酱油中3-氯-1，2-丙二醇检测实验室间比对分析

介绍了由中国计量科学研究院化学所负责实施的酱油中3-氯-1,2-丙二醇检测实验室间比对情况,并针对该项目的检测方法、标准物质选择、前处理方法等进行了技术分析。21家参加比对实验室对样品l检测结果满意率85．7％,样品2结果满意率100％。建议实验人员在检测中可通过空白加标或应用质控样品等手段提高检测结果的准确度。     

线性离散不确定时滞系统滞后相关H∞鲁棒控制

基于Lyapunov泛函方法,对存在状态时滞的线性离散不确定系统,给出了滞后相关型无记忆H∞状态反控制器设计方案,通过求解相应的线性矩阵不等式即可求得满足设计要求的控制器．     

Dynamic behaviors of a delayed HIV model with stage-structure

Inspired by a simulation specific to a delayed HIV model with stage-structure, some dynamic behaviors are studied in this paper, including global stability of disease-free equilibrium and local Hopf bifurcation when taking the delay as a parameter. The corresponding characteristic equation is a transcendental equation, with the parameters delay-dependent, thus we use the conventional analysis introduced by Beretta and Kuang to obtain sufficient conditions to the existence of Hopf bifurcation. Then some properties of Hopf bifurcation such as direction, stability and period are determined, and several examples illustrate our results.