苏丹红Ⅰ在壳聚糖-氧化石墨烯自组装膜修饰玻碳电极上的电化学行为及其测定

制备了壳聚糖-氧化石墨烯自组装膜修饰玻碳电极(CS-GO/GC),并用电化学阻抗法进行表征,研究了苏丹红Ⅰ在该修饰电极上的电化学行为。实验结果表明,苏丹红Ⅰ在该修饰电极上出现了1个氧化峰,为不可逆电化学反应。在50～250 mV.s-1扫速范围内,氧化峰电流与扫速呈线性关系,该电极过程受吸附控制,苏丹红Ⅰ在修饰电极上的电子转移数和质子数均为1,扩散系数为1.70×10-6cm2.s-1。采用差分脉冲伏安法对苏丹红Ⅰ进行测定,结果表明,苏丹红Ⅰ浓度与其氧化峰电流在6.0×10-8～5.0×10-6mol/L范围内呈良好的线性关系,相关系数为0.995,检出限为4.45×10-8mol/L。该修饰电极具有良好的重现性和稳定性,可简便、快捷、灵敏地检测咸鸭蛋黄中苏丹红Ⅰ的含量。     

Half-metallicity and magnetism of the quaternary inverse full-Heusler alloy Ti<Subscript>2-x</Subscript>M<Subscript>x</Subscript>CoAl (M = Nb,V) from the first-principles calculations

Using the first-principles calculations based on density functional theory, we investigate the more d-electrons doping effects on the electronic structure and magnetism of the parent inverse Heusler alloy Ti₂CoAl by the substitution of Nb and V atoms for Ti(A) and Ti(B) atoms locating at the two inequivalent sublattices. The Ti₂CoAl is half-metallic with Fermi level near the top of the minority-spin valence band and hence its spin-polarization is easily reduced by the spin-flip excitation. Our total energy calculations show that the V/Nb doping at the Ti(A)/Ti(B) site is energetically favorable compared with the Ti(B)/T(A) site due to the lower total energy. Our band structure calculations indicate that for the V doped compounds, half-metallicity can be well retained regardless of doping sites and percentages except for the case of Ti(A)-site doping with x = 1, while for Nb doped compounds, the half-metallicity persists only in Ti(B)-site doping with different percentages. For the doped compounds with half-metallicity, the Fermi level shifts from the top of minority-spin valence band to the bottom of minority-spin conduction band with increasing content of x, and typically, the doped compounds (V in Ti(A) and Ti(B) sites at x = 0.75 and 0.5, respectively; Nb in Ti(B) site at x = 0.5), whose Fermi levels are adjusted to the expected positions to effectively inhibit the spin-flip excitation are promising candidates for spintronics applications.     

A study on excited states dipole moments of 9,9′-bianthryl

The influence of an external electric field on the fluorescence intensity of 9,9′-bianthryl in non-polar and medium polar solvents and solvent mixtures is studied experimentally. The results show that the single fluorescence band observed in these solvents is not due to a homogeneous transition between two states.     

Spectroscopic studies on quantum dots of PbI2

We report the preparation of PbI₂ clusters of sizes less than 30 Å by colloidal routes and characterization by optical absorption spectra. We show that the blue-shifted absorption spectra are not due to the presence of I⁻₃ ions, as suggested previously, but are characteristic of the clusters present. We also show that similar sized clusters form, though sparingly, on dissolving bulk PbI₂ in the solvents. We establish that the stability of a large concentration of these clusters in the colloidal process is due to the presence of excess iodine ions attached to the microcrystallites.     

Atomic disorder and magnetism in Fe2TiSn alloy

An effect of local atomic disorder on the electronic structure and magnetic moments in Fe₂TiSn is studied. The band structure is calculated by the spin-polarised tight-binding linearised muffin tin orbital (TB LMTO). We found that the Fe₂TiSn alloy in which Fe occupy two FCC sublattices in L2₁-type structure is paramagnetic. The substitution of Fe atoms onto titanium or tin positions leads to an increase of the magnetic moment.     

高锰酸钾-甲醛-荧光素-没食子酸丙酯化学发光体系的研究

高锰酸钾-甲醛-荧光素-没食子酸丙酯在酸性介质中有较好的发光特性,在最佳实验条件下,当没食子酸丙酯溶液浓度在8.0×10-6～2.0×10-3g/L范围内与化学发光强度有良好的线性关系(r=0.9960),对1.0×10-3g/L的没食子酸丙酯溶液平行测定11次,RSD为1.9%,检出限为5.6×10-6g/L。该法用于食用调和油中没食子酸丙酯的测定,结果令人满意。     

水热法制备纳米MnO2及其赝电容性能研究

本文K2S2O8作氧化剂,以MnSO4为锰源,于120℃不同水热反应时间下制备得到不同形貌的纳米MnO2,用X射线衍射(XRD)和扫描电镜(SEM)对样品的结构与形貌进行表征。采用循环伏安法、交流阻抗和恒流充放电技术对纳米MnO2赝电容性能进行测试。结果表明,随着反应时间的增加,纳米MnO2形貌由海胆结构转变为纳米线,水热处理12 h时纳米MnO2比电容为282 F.g-1,水热处理时间延长至24 h时比电容下降为161 F.g-1,继续反应至36 h比电容又上升为203 F.g-1。     

约束粒子群算法求解自融资投资组合模型研究

在马克维茨投资组合的均值-方差模型框架下,给出限制投资数量的自融资投资组合优化模型.在金融市场上有广泛应用,为了有效地求解此类问题的最优解,采用一种基于广义学习策略的约束粒子群算法(CPSO).CPSO算法具有广义的学习策略,极大地提升了种群的多样性,进而提升种群跳出局部最优解的能力.在基准函数测试中,结果显示CPSO算法有较好的运行结果.在自融资投资组合优化模型上,优化结果表明CPSO算法是可行的,有效的,并有较好的优化结果.     

改进的粒子群算法及在CVaR模型中的应用

为了求解带有条件风险价值(CVaR)约束的均值-方差模型,提出一种基于广义学习和柯西变异的粒子群算法(CCPSO).在CCPSO算法中,为了提升种群跳出局部最优解的能力,引入一种广义学习策略,提升粒子向最优解飞行的概率;并引入一种动态变异概率,对粒子自身最优位置进行柯西变异,更好地引导种群的飞行;最后,根据全局最优粒子的运行状况,每间隔若干代对其进行变异,以产生全局新的领导者.在基准函数测试中,结果显示CCPSO算法有较好的运行结果.在CVaR模型投资组合优化中,与其它算法相比,CCPSO算法所获结果是有效的,并且优于其它算法.     

基于SVD的超精密工件自寻位加工算法能力评价

为进一步改善超精密表面修形的最终精度、效率与成本,优化超精密自寻位加工的工艺方向与工艺决策过程, 开展了对超精密工件的自寻位加工算法点云融合过程的定量评价研究,提出了基于SVD的自寻位加工算法能力评价方法。首先基于运动学方法建立了点云融合的矩阵表示,分别对平动、转动、复合运动等情况建立了自寻位结果的转换矩阵表示,获得自寻位点云融合转换矩阵;进而对转换矩阵进行奇异值分解得到转换矩阵的奇异值列表;最后将列表中最大奇异值用以表征自寻位加工算法的能力。通过对某型超精密叶片在平动、转动和复合运动、共计1078组自由放置状态进行分析,发现所提出的评价指标在独立平动和独立转动两种任意放置情况下能够正确地表征自寻位加工算法的工艺能力。对于独立平动情况,自寻位加工算法能够正常定位加工,其最大奇异值也与预设偏差较小;对于独立转动情况,当旋转角度小于45°时,均能够正确地进行自寻位加工,最大奇异值差值也趋近于零,旋转角度超过45°时,算法的自寻位加工能力恶化,这一特性能够被所提指标正确捕捉。对于由平动和转动构成的复合运动而言,所提指标显示约35%的情况能够正确进行自寻位加工,其余情况无法进行正确的自寻位加工。结果表明本文所提方法建立的指标能够正确表征自寻位加工算法能力。