离子液体添加剂[BMIM]HSO4对锌电积过程析氧反应动力学的影响

研究了1-丁基-3-甲基咪唑硫酸氢盐([BMIM]HSO₄)离子液体对锌电积过程析氧反应的影响. 研究工作借助于动电位极化, 电化学阻抗谱, 扫描电镜和X射线衍射等测试技术. 动电位极化曲线及对应的动力学参数分析表明, [BMIM]HSO₄对阳极析氧反应具有催化作用,可提高析氧反应速率常数. 电化学阻抗谱数据表明,[BMIM]HSO₄能显著降低阳极析氧电荷传递电阻,在所研究的1.85-2.10 V电位范围内添加5 mg·L^-1 [BMIM]HSO₄, 电阻值至少降低50%. 此外, 添加剂对阳极表面二次反应具有抑制作用, 其在阳极表面的吸附,阻碍了阴离子的阳极活化位点吸附过程. 电化学测试结果与长时间(120 h)阳极极化后所得阳极表面形貌和结晶取向分析结果相一致. [BMIM]HSO₄的添加能有效抑制中间产物β-PbO₂的形成,促进铅银电极表面大块且疏松多孔α-PbO₂的生成,加速阳极析氧的进行.     

增塑剂对PVA碱性聚合物电解质电化学性能的影响

通过溶解―铸膜法制备聚乙烯醇(PVA)-KOH-H2O碱性聚合物电解质膜。向聚合物中添加增塑剂丙三醇(GROL)和碳酸丙烯酯(PC)来提高离子电导率。X射线晶体衍射分析(XRD)结果表明,添加增塑剂未改变聚合物的物相结构,薄膜仍主要为不定形态。差示扫描热分析(DSC)结果显示,添加增塑剂后聚合物电解质膜的玻璃化转变温度降低,促进了电解质膜向不定形态转变。电解质膜室温离子电导率随增塑剂添加而增大,增塑剂超过一定量后离子电导率开始下降。PC对提高离子电导率的作用优于GROL。循环伏安测试结果显示,电解质膜的电化学稳定性窗口随增塑剂的添加而有所变窄,但仍显示了较好的电化学稳定性。     

Bifurcation analysis and control of chaos for a hybrid ratio-dependent three species food chain

In this paper, a hybrid ratio-dependent three species food chain model with time delay is studied by using the theory of functional differential equation and Hopf bifurcation, the condition on which positive equilibrium exists and the quality of Hopf bifurcation are given. Chaotic solutions are observed and are controlled by delay parameter. Finally, we indicate that when the delay passes through certain critical values, chaotic oscillation is converted into a stable state or a stable periodic orbit.     

Complete study on a bi-center problem for the <Emphasis Type="Italic">Z</Emphasis><Subscript>2</Subscript>-equivariant cubic vector fields

For the planar Z ₂-equivariant cubic systems having two elementary focuses, the characterization of a bi-center problem and shortened expressions of the first six Liapunov constants are completely discussed. The necessary and sufficient conditions for the existence of the bi-center are obtained. All possible first integrals are given. Under small Z ₂-equivariant cubic perturbations, the conclusion that there exist at most 12 small-amplitude limit cycles with the scheme 〈6 ∐ 6〉 is proved.     

基于犹豫模糊偏好关系FMEA方法的改进

为有效解决产品在研发过程中存在的一系列质量可靠性问题,本文提出了一种新的基于犹豫模糊偏好关系的改进FMEA方法。考虑到专家小组对不同失效模式评估时主要依据相关标准和自身经验,存在犹豫模糊不确定或自身偏好问题。本文首先对风险因子的评分标准进行犹豫模糊化,并用犹豫模糊偏好关系对失效模式的相对风险矩阵进行处理;其次,将得到的具有犹豫模糊偏好关系的综合偏好值与犹豫模糊评价信息相结合,得到改进的风险优先数,从而得出新的失效模式风险评估顺序对FMEA进行改进;最后,利用改进的FMEA模型对产品研发过程中的质量风险进行分析验证,使得风险结果更接近实际情况,进而提高研发成功率,显示该方法可行、有效。     

Bifurcations of traveling wave solutions in a coupled non-linear wave equation

By using the theory of planar dynamical systems to a coupled non-linear wave equation, the existence of solitary wave solutions and uncountably infinite, many smooth and non-smooth, periodic wave solutions is obtained. Under different parametric conditions, various sufficient conditions to guarantee the existence of the above solutions are given.     

Center and isochronous center problems for quasi analytic systems

This paper considers the problems of determining center or focus and isochronous centers for the planar quasi-analytic systems. Two recursive formulas to determine the focal values and period constants are given. The convergence of first integral near the center is proved. Using the general results to quasi-quadratic systems, the problem of the isochronous center of the origin is completely solved. This research is partially supported by the National Natural Science Foundation of China (10671179 and 10771196) and the Natural Science Foundation of Yunnan Province (2005A0092M)     

UPLC测定烟叶中的氨基酸含量

采用UPLC法测定烟叶中氨基酸的含量。Waters Acquity UPLC BEH C18色谱柱(2.1mm×100mm,1.7μm),AccQ.Tag Ultraa Eluent A及AccQ.Tag Ultraa Eluent B梯度洗脱,流速为0.7mL·min-1,波长:248nm,柱温55℃。18种氨基酸在0.0030-0.204mg/mL范围内有良好的线性关系(r0.9994),平均回收率(n=6)为98.7%。该方法10min内18种氨基酸可完全分离且具有快速、准确、重复性好的特点。     

Cusped Solitons and Loop-Solitons of Reduced Ostrovsky Equation

The qualitative theory of differential equations is applied to the Ostrovsky equation. The cusped soliton and loop-soliton solutions of the Ostrovsky equation are obtained. Asymptotic behavior of eusped soliton solutions is given. Numerical simulations are provided for cusped solitons and so-called loop-solitons of the Ostrovsky equation.     

Current reversal and mass separation of inertial Brownian motors in a two-noise ratchet

Transport of an inertial Brownian motor moving in an asymmetric periodic potential driven by an external force and correlated noises is investigated. Using the numerical algorithm, the asymptotic mean velocity (AMV) for characterizing directed transport is obtained. The effects of the external driving force f and the correlation λ between the two noises on the AMV are discussed. The results manifest: (1) the external driving force and the correlation between the two noises can lead to the phenomena like current reversal. (2) The competitions among the external driving force and the correlation between the two noises are necessary for current reversal, i.e., fλ>0. (3) Different directions of transport are found for different masses of the Brownian particles under the condition fλ>0. Therefore a theoretical study is suggested for separating Brownian particles according to their different masses in the ratchet system.