Enhanced photocatalytic activity of TiO2 nano-structured thin film with a silver hierarchical configuration

TiO₂ sol-gels with various Ag/TiO₂ molar ratios from 0 to 0.9% were used to fabricate silver-modified nano-structured TiO₂ thin films using a layer-by-layer dip-coating (LLDC) technique. This technique allows obtaining TiO₂ nano-structured thin films with a silver hierarchical configuration. The coating of pure TiO₂ sol-gel and Ag-modified sol-gel was marked as T and A, respectively. According to the coating order and the nature of the TiO₂ sol-gel, four types of the TiO₂ thin films were constructed, and marked as AT (bottom layer was Ag modified, surface layer was pure TiO₂), TA (bottom layer was pure TiO₂, surface layer was Ag modified), TT (pure TiO₂ thin film) and AA (TiO₂ thin film was uniformly Ag modified). These thin films were characterized by means of linear sweep voltammetry (LSV), X-ray diffraction (XRD), scanning electron microscopy (SEM), electrochemical impedance spectroscopy and transient photocurrent (I_ph). LSV confirmed the existence of Ag⁰ state in the TiO₂ thin film. SEM and XRD experiments indicated that the sizes of the TiO₂ nanoparticles of the resulting films were in the order of TT > AT > TA > AA, suggesting the gradient Ag distribution in the films. The SEM and XRD results also confirmed that Ag had an inhibition effect on the size growth of anatase nanoparticles. Photocatalytic activities of the resulting thin films were also evaluated in the photocatalytic degradation process of methyl orange. The preliminary results demonstrated the sequence of the photocatalytic activity of the resulting films was AT > TA > AA > TT. This suggested that the silver hierarchical configuration can be used to improve the photocatalytic activity of TiO₂ thin film.     

大学物理实验教学改革的实践与探索

对我校大学物理实验教学存在的弊端进行了分析,指出了大学物理实验教学改革的思路、内容和方法,并付诸实践,取得了较好的效果.     

单脉冲加载的Hopkinson压杆实验中预留缝隙确定方法的研究

 在传统Hopkinson压杆实验中,反射拉伸波在入射杆的撞击端反射形成压缩波,导致实验过程中对试样进行了多次加载,单脉冲加载的Hopkinson压杆实验技术解决了该问题。详细总结了单脉冲加载的Hopkinson压杆实验技术原理,给出了法兰盘与质量块间预留缝隙的计算方法,分析了预留缝隙不同大小对实验结果的影响。建立了一套单脉冲加载的Hopkinson压杆实验装置,并利用高速摄影验证了实验技术的可靠性。     

利用图像处理实现平面工作台三自由度位移的同步检测

为了实现平面工作台三自由度位移的同步检测 ,研制了图像处理位移检测系统。以CCD相机为核心 ,结合显微镜放大、图像采集和图像处理构成检测系统。图像处理软件用VC编制 ,计算并绘制了工作台三自由度位移随时间的变化关系 ,以及工作台在平面内的运动轨迹。系统的位移检测不受工作台大幅转动的影响。检测系统达到了亚像素级的位移分辨率。选择合适的显微镜放大倍率 ,可使检测系统既有较高的位移分辨率 ,又有一定的位移检测范围     

Bayes minimax estimation of multiple Poisson parameters

For the p-variate Poisson mean, under the sum of weighted squared error losses, weights being reciprocals of variances, a class of proper Bayes minimax estimates dominating the usual estimate, namely the sample mean is produced. An example is given to illustrate this. The interrelation of our results with those of Clevenson and Zidek is pointed out.     

Protocol Challenges for On-the-Job Voice Dosimetry of Teachers in the United States and Finland

The occupational voice use of teachers has been an important research topic over the last 10 years. However, data collection on vocal loading in teachers at and away from the workplace poses significant challenges to the research protocol. The challenges include recruitment of subjects, voice data collection on the job, and subject compliance and retention. The present article offers recommendations for coping with these protocol difficulties. The recommendations are based on the authors' experiences with long-term, on-the-job voice dosimetry of large subject groups of teachers in the United States and Finland.     

The Approximate Runge-Kutta Computational Process

Implicit Runge-Kutta methods are efficient for solving stiff ODEs and DAEs. To bridge the gap between their theoretical analysis and practical implementation, we introduce the notion of the (, K)-approximate Runge- Kutta process to account for inevitable iteration errors. We prove iteration error bounds uniform with respect to stiffness, and investigate stage derivative reuse for methods having a first explicit stage. The latter technique may result in significant performance gains, also when such methods are used as error estimators. Previous computational heuristics can therefore be replaced by a consistent approach supported by theoretical analysis. The approximate but well-defined computational process is evaluated using approved test problems.     

On the Starting Algorithms for Fully Implicit Runge-Kutta Methods

This paper is concerned with the behavior of starting algorithms to solve the algebraic equations of stages arising when fully implicit Runge-Kutta methods are applied to stiff initial value problems. The classical Lagrange extrapolation of the internal stages of the preceding step and some variants thereof that do not require any additional cost are analyzed. To study the order of the starting algorithms we consider three different approaches. First we analyze the classical order through the theory of Butcher's series, second we derive the order on the Prothero and Robinson model and finally we study the stiff order for a general class of dissipative problems. A detailed study of the orders of some starting algorithms for Gauss, Radau IA-IIA, Lobatto IIIA-C methods is also carried out. Finally, to compare the most relevant starting algorithms studied here, some numerical experiments on well known nonlinear stiff problems are presented.     

纳秒脉冲电压同轴电场下有机玻璃和尼龙的闪络特性

利用基于SOS的SPG200高压脉冲功率装置研究了有机玻璃(PMMA)和尼龙1010在变压器油中的闪络特性。研究结果表明:闪络电压随内电极直径增加近似指数增加，随闪络距离延长近似线性增加，相应的击穿时延也近似线性增加。受实验条件的影响，有机玻璃和尼龙1010的闪络性能略有差异。同轴径向电场降落集中在内电极表面附近一定径向距离内，同轴电场下的闪络电压主要由内电极表面电场与径向电场分布的均匀程度决定。增加内电极直径和延长闪络距离都可以提高闪络电压，而增加内电极直径的效果更显著。