铱催化甲醇羰基化制乙酸循环反应的理论探究

采用密度泛函理论DFT-B3LYP方法,对铱、碘元素采用相对论校正赝势基组SDD,对C、O、H采用6-311+G(2d,p)基组,优化了各反应物、中间体和过渡态的构型特征,通过能量和振动分析证实了过渡态的真实性.理论研究了阴离子循环中铱催化甲醇羰基化制乙酸的循环反应机理.运用能量跨度模型获得了反应的动力学信息,确定了各反应的决速中间体和决速过渡态和各催化剂的能量跨度和转化频率.通过对cis-[Ir(CO)_2I_2]~-和trans-[Ir(CO)_2I_2]~-催化剂电荷密度的分析比较,得到中心金属的富电子性提高了其催化能力,以上计算结论与文献假设相符.     

In-plane current-induced magnetization reversal of Pd/CoZr/MgO magnetic multilayers

High critical current density ($> 10^{6}$ A/cm$^{2})$ is one of major obstacles to realize practical applications of the current-driven magnetization reversal devices. In this work, we successfully prepared Pd/CoZr(3.5 nm)/MgO thin films with large perpendicular magnetic anisotropy and demonstrated a way of reducing the critical current density with a low out-of-plane magnetic field in the Pd/CoZr/MgO stack. Under the assistance of an out-of-plane magnetic field, the magnetization can be fully reversed with a current density of about 10$^{4}$ A/cm$^{2}$. The magnetization reversal is attributed to the combined effect of the out-of-plane magnetic field and the current-induced spin-orbital torque. It is found that the current-driven magnetization reversal is highly relevant to the temperature owing to the varied spin-orbital torque, and the current-driven magnetization reversal will be more efficient in low-temperature range, while the magnetic field is helpful for the magnetization reversal in high-temperature range.     

超临界二氧化碳类液-类气区边界线数值分析

超临界二氧化碳(S-CO₂)因在萃取、沉淀、热力循环及化学反应等方面有着十分广阔的应用前景,逐渐成为学术界的重要研究课题.由于在近临界区,可以观察到随温度或压力变化出现大量的物性异变现象,使得各国学者对流体临界点附近区域的研究产生了浓厚兴趣.随着分子动力学模拟技术的快速发展,该技术可辅助传统实验方法用于研究近临界流体的相关物性.为确定S-CO₂在近临界区Widom线范围及类液-类气区的分子结构特征,本文通过分子动力学模拟技术结合聚类分析,研究了温度和压力范围分别在300—350 K和5.5—18.5 MPa下,CO₂密度时间序列变异系数及偏度同Widom线和类液-类气区间的关系.结果表明:S-CO₂在近临界区Widom线的确定可通过连接密度时间序列曲线变异系数极大值点来确定,Widom线沿着临界点开始延伸直到350 K时停止;S-CO₂类液区和类气区的分子分布结构可以用数密度分布的偏度来区分,偏度在类气态时为正值,在类液态时为负值,而在Widom线上达到最大值.     

WO3/PANI核壳结构反蛋白石薄膜的电致变色性能

采用连续离子层吸附法在反蛋白石结构三氧化钨(IO-WO₃)薄膜表面引入导电聚合物聚苯胺(PANI)层, 制备了独特的WO₃/PANI核壳结构反蛋白石薄膜(IO-WO₃/PANI). 探究了IO-WO₃/PANI薄膜的形貌、 组成和电化学行为. 结果表明, 当电位扫描范围为-0.6~1.0 V时, IO-WO₃/PANI复合膜在不同电压状态下会呈现出4种不同的颜色, 分别为蓝色(1.0 V)、 绿色(0.2 V)、 浅绿色(0 V)和蓝紫色(-0.6 V). 与IO-WO₃薄膜相比, IO-WO₃/PANI复合膜的电致变色性能显著提高, 其着色与退色响应时间分别为3.8和6.14 s, 变色效率(CE)值为201.1 cm²/C. 电致变色性能的改善主要归因于WO₃与PANI形成给体-受体体系和核壳反蛋白石等级孔结构, 使得离子快速扩散, 并为电荷转移反应提供更大的表面积. 研究结果表明, IO-WO₃/PANI核壳结构反蛋白石薄膜是一种潜在的多色电致变色材料, 具有广阔的应用前景.     

甲酸在Nd-Fe-WO2-4氰桥混配物修饰铂电极上的电催化氧化

首次用电沉积法制备了Nd-Fe-WO2-4氰桥混配物修饰铂电极(Nd-Fe-WO2-4/Pt),并通过SEM和XRD技术分别表征了该修饰电极的表面形貌和修饰物的晶相结构.采用循环伏安法和计时电流法研究了甲酸在该修饰电极上的电氧化行为,实验发现甲酸在修饰电极上的电催化氧化电流密度与裸铂电极相比增加了10余倍,而且CV回扫...     

基于RN和GN的两种RBF神经网络的工程造价预测模型

建立了调用NEWRB函数的正规化网络RN和基于K-means聚类的广义网络GN的两种RBF‘神经网络的工程造价预测模型,以55个厦门市工程造价案例进行实证分析.结果表明:当调用NEWRB函数构建RBF模型时,其性能主要取决于分布宽度,而基于K-means聚类的RBF神经网络主要取决于重叠系数和隐含层节点数;基于广义网络GN的RBF神经网络模型的训练效果较差,但学习速度更快、预测精度更高.     

一类微分方程系统正平衡解的存在性与全局稳定性

本文研究了一个自治的非线性微分方程系统,得到了系统正平衡点存在唯一的充分条件,通过伸缩变换法讨论了正平衡点局部稳定性,并运用构造Liapunov函数方法得到了它的全局渐近稳定性.     

“织物抗静电性能测试”综合性实验教学改革探索

静电产生的机理较为复杂,学生在理论课学习过程中很难理解和掌握,即使开展了相应的实验课,但大部分都是演示性实验或单一性实验,学习主动性差,学习效果不好.为了取得一定的学习效果,结合理论课知识点开展抗静电性能测试综合性实验显得尤为重要.本文讲述了抗静电性能测试综合性实验的教学方法,实现理论知识点与实验教学,实验内容与实验方法的全面结合,培养和提高了学生综合分析问题的能力和学习兴趣.     

Charging dynamics of a polymer due to electron irradiation： A simultaneous scattering-transport model and preliminary results

<正>We present a novel numerical model and simulate preliminarily the charging process of a polymer subjected to electron irradiation of several 10 keV.The model includes the simultaneous processes of electron scattering and ambipolar transport and the influence of a self-consistent electric field on the scattering distribution of electrons.The dynamic spatial distribution of charges is obtained and validated by existing experimental data.Our simulations show that excess negative charges are concentrated near the edge of the electron range.However,the formed region of high charge density may extend to the surface and bottom of a kapton sample,due to the effects of the electric field on electron scattering and charge transport,respectively.Charge trapping is then demonstrated to significantly influence the charge motion.The charge distribution can be extended to the bottom as the trap density decreases.Charge accumulation is therefore balanced by the appearance and increase of leakage current.Accordingly,our model and numerical simulation provide a comprehensive insight into the charging dynamics of a polymer irradiated by electrons in the complex space environment.