纳米硫化镉在对氨基苯硫酚自组装单层修饰金电极上的电化学合成

采用电流脉冲法在自组装了对氨基苯硫酚单层的金电极(PATP/Au)上电沉积硫化镉(CdS)纳米薄膜,运用扫描电子显微镜(SEM)和X射线衍射谱(XRD)对其形貌和结构进行了表征,发现得到的是垂直基底生长的CdS纳米棒有序阵列.研究电沉积中电流脉冲参数的影响时发现:随着电流脉冲宽度增大,CdS纳米棒的尺寸增大,有序性降低;脉冲幅度增大,则纳米棒尺寸增大,覆盖度也随之增大.因此通过调节脉冲宽度和脉冲幅度,可对所制备的CdS纳米薄膜的形貌和尺寸进行调控.运用循环伏安法和计时电位法对电沉积机理进行了探究.根据实验结果我们认为Au电极自组装PATP单分子层后,PATP分子中的-NH2与溶液中Cd2+相互作用,使沉积时的电子通过表面的PATP分子链进行传递.并进一步提出纳米CdS在PATP/Au电极上电化学合成的生长机理.     

模拟混凝土孔隙液中D-葡萄糖酸钠复合缓蚀剂对钢筋的阻锈作用

应用电化学技术, 结合扫描电子显微镜(SEM)观测, 研究D-葡萄糖酸钠、钼酸钠和硫脲三组分复合缓蚀剂对模拟混凝土孔隙液中钢筋腐蚀行为的影响及其阻锈作用. 结果表明: 在含3.5% (w) NaCl的模拟混凝土孔隙液中, 复合缓蚀剂具有协同效应, 对钢筋有良好的阻锈作用. 当D-葡萄糖酸钠、钼酸钠和硫脲浓度分别为750、250和500 mg·L^-1时, 对钢筋的缓蚀效率可达到94.5%. 应用软硬酸碱(HSAB)理论分析缓蚀机理, 可认为三组分复合缓蚀剂在钢筋表面共同形成保护膜而阻止钢筋的腐蚀.     

Analysis of the effects of the global financial crisis on the Turkish economy, using hierarchical methods

We have analyzed the topology of 50 important Turkish companies for the period 2006-2010 using the concept of hierarchical methods (the minimal spanning tree (MST) and hierarchical tree (HT)). We investigated the statistical reliability of links between companies in the MST by using the bootstrap technique. We also used the average linkage cluster analysis (ALCA) technique to observe the cluster structures much better. The MST and HT are known as useful tools to perceive and detect global structure, taxonomy, and hierarchy in financial data. We obtained four clusters of companies according to their proximity. We also observed that the Banks and Holdings cluster always forms in the centre of the MSTs for the periods 2006-2007, 2008, and 2009-2010. The clusters match nicely with their common production activities or their strong interrelationship. The effects of the Automobile sector increased after the global financial crisis due to the temporary incentives provided by the Turkish government. We find that Turkish companies were not very affected by the global financial crisis.     

Influence of substrate temperature and Cobalt concentration on structural and optical properties of ZnO thin films prepared by Ultrasonic spray technique

Pure and Cobalt doped zinc oxide were deposited on glass substrate by Ultrasonic spray method. Zinc acetate dehydrate, Cobalt chloride, 4-methoxyethanol and monoethanolamine were used as a starting materials, dopant source, solvent and stabilizer, respectively. The ZnO samples and ZnO:Co with Cobalt concentration of 2 wt.% were deposited at 300, 350 and 400 °C. The effects of substrate temperature and presence of Co as doping element on the structural, electrical and optical properties were examined. Both pure and Co doped ZnO samples are (0 0 2) preferentially oriented. The X-ray diffraction results indicate that the samples have polycrystalline nature and hexagonal wurtzite structure with the maximum average crystallite size of ZnO and ZnO:Co were 33.28 and 55.46 nm. An increase in the substrate temperature and presence doping the crystallinity of the thin films increased. The optical transmittance spectra showed transmittance higher than 80% within the visible wavelength region. The band gap energy of the thin films increased after doping from 3.25 to 3.36 eV at 350 °C.     

Regularity for nonlinear elliptic systems with dini coefficients under natural growth condition for the case: 1 < m < 2

In this article, we consider interior regularity for weak solutions to nonlinear elliptic systems of divergence type with Dini continuous coefficients under natural growth condition for the case 1 < m < 2. All estimates in the case of m ≥ 2 is no longer suitable, and we can't obtain the Caccioppoli's second inequality by using these techniques developed in the case of m ≥ 2. But the Caccioppoli's second inequality is the key to use A-harmonic approximation method. Thus, we adopt another technique introduced by Acerbi and Fcsco to overcome the difficulty and we also overcome those difficulties due to Dini condition. And then we apply the A-harmonic approximation method to prove partial regularity of weak solutions.     

Noisy image segmentation based on nonlinear diffusion equation model

This paper addresses the segmentation problem in noisy image based on nonlinear diffusion equation model and proposes a new adaptive segmentation model based on gray-level image segmentation model. This model also can be extended to the vector value image segmentation. By virtue of the prior information of regions and boundary of image, a framework is established to construct different segmentation models using different probability density functions. A segmentation model exploiting Gauss probability density function is given in this paper. An efficient and unconditional stable algorithm based on locally one-dimensional (LOD) scheme is developed and it is used to segment the gray image and the vector values image. Comparing with existing classical models, the proposed approach gives the best performance.     

Minimum flow problem on network flows with time-varying bounds

In this paper, we consider the minimum flow problem on network flows in which the lower arc capacities vary with time. We will show that this problem for set {0, 1, … , T} of time points can be solved by at most n minimum flow computations, by combining of preflow-pull algorithm and reoptimization techniques (no matter how many values of T are given). Running time of the presented algorithm is O(n²m).     

Coupling particle sets of contours and streamline methods for solving convection problems

In this work a particle sets of contours method is coupled with a streamline technique in order to obtain accurate approximations of transport problems. A modified streamline technique is proposed and several bench tests arising in the field of porous media are then simulated to validate the new method.     

Optical band gap and conductivity measurements of polypyrrole-chitosan composite thin films

Electrical conductivity and optical properties of polypyrrole-chitosan（PPy-CHI） conducting polymer composites have been investigated to determine the optical transition characteristics and energy band gap of composite films.The two electrode method and I-V characteristic technique were used to measure the conductivity of the PPy-CHI thin films,and the optical band gap was obtained from their ultraviolet absorption edges.Depending upon experimental parameter,the optical band gap（E_g） was found within 1.30-2.32 eV as estimated from optical absorption data.The band gap of the composite films decreased as the CHI content increased.The room temperature electrical conductivity of PPy-CHI thin films was found in the range of 5.84×10^-7-15.25×10^-7 S·cm^-1 depending on the chitosan content.The thermogravimetry analysis（TGA） showed that the CHI can improve the thermal stability of PPy-CHI composite films.     

一种主动浮标阵的定位解算方法仿真分析

在研究单枚主动定向浮标定位原理的基础上,推导出一种利用最小二乘法解算多枚浮标的定位结果的方法,并针对圆阵就阵元个数、圆阵半径以及测距误差对该解算方法的性能影响进行了数值仿真分析。仿真结果表明,该算法在测向均方误差较大或者目标在距离圆内的情况下,性能远优于单枚主动定向浮标;圆阵半径2 km左右,阵元个数在6左右时,该解算方法的性能达到最佳。此外,该解算算法很容易被扩展至三维定位问题,因此有一定的理论和应用价值。