Growth behavior of Cu/Al intermetallic compounds in hot‐dip aluminized copper

Hot‐dipped aluminum copper with plating auxiliary KF is introduced in this work. In this study, the intermetallic layer thickness varies with dipping temperature and time in a linear relationship. The main phases are identified to be CuAl₂ and K₃AlF₆ by means of X‐ray diffraction. The reaction equations are deduced according to the elements concentration gradient in cross section. The copper diffusion rate in liquid Al is calculated to be 1.13 × 10⁻¹² m²/s by Fick's second law in semi‐infinite solid model, and the obtained conductivity is 1.758–1.767 × 10⁻² Ω mm²/m. The results indicate that the interfacial bonding is in a good state and plating auxiliary KF aqueous solution. can significantly improve the substrate wettability. The appropriate hot‐dipping condition for the samples is 953–973 K for 4–8 s. Copyright © 2009 John Wiley & Sons, Ltd.     

Two Disparate 2‐fold Interpenetrating Frameworks Constructed from ZnII, 4,4′‐Dipyridyl Disulfide and Maleic/ Fumaric Acid

The reaction of Zn^II nitrate with maleic acid (H₂mal) / fumaric acid (H₂fum) and 4,4′‐dipyridyl disulfide (4‐pds) resulted under same conditions in two distinct interpenetrated compounds, namely [Zn(4‐dps)₂(H₂O)₂]·2Hmal ( 1 ) and [Zn(4‐dps)(fum)] ( 2 ). In 1 , Hmal anion adopts bridging mode based on hydrogen bonding, affording a 2‐fold parallel interpenetrated 3D→3D α‐Po net hydrogen‐bonded framework, in which 1D double‐stranded chains are formed, and then extended to a 3D supramolecular architecture combining second‐sphere hydrogen‐bonded interactions. For 2 , fum dianion takes on bis‐dentate bridging coordination fashion, furnishing a 2‐fold interpenetrated 2D→2D (4,4) layered coordination network, in which the tetrahedral Zn^II atoms are interlinked by 4‐dps and fum. Additionally, the compound 2 shows strong fluorescence in the solid state at room temperature.     

BaCO3和TiO2粉末混合物冲击压缩性和BaTiO3冲击合成的实验研究

 利用高能炸药爆轰驱动冲击波、狭缝扫描闪光隙高速照相技术和阻抗匹配解原理，在10~100 GPa压力范围内，测量了BaCO₃和TiO₂粉末混合物的冲击绝热数据。同时，利用轴对称柱面和平面爆轰装置，进行了该混合物样品的冲击后回收实验和回收样品的X射线衍射分析，考察BaTiO₃的冲击合成。测量出的冲击绝热数据，以冲击波压力和比容平面上的结果为例，在约30和45 GPa两个压力值时，比容发生明显跃变。冲击绝热数据与回收样品X射线衍射分析结果相结合，判断出，这两个跃变分别对应于TiO₂从锐钛矿相转变到高压β-TiO₂相，BaCO₃与TiO₂开始急剧化学反应合成出BaTiO₃并放出CO₂。此外，在压力为10 GPa左右作回收实验，其回收样品的X射线衍射分析表明TiO₂由锐钛矿相完全转变为金红石相。     

横观各向同性饱和地基上中厚圆板的非轴对称振动

研究横观各向同性饱和土地基上中厚弹性圆板的非轴对称振动问题。基于横观各向同性饱和介质Biot波动方程的一般解,按混合边值问题建立了饱和地基与弹性中厚圆板非轴对称动力相互作用的对偶积分方程,并将对偶积分方程转化为易于计算的第二类Fredholm积分方程;采用数值方法求解该积分方程。数值算例结果表明,当h/a>0.05时,饱和半空间体上中厚度圆板在不同频率下的振动特性与相应频率下的刚性板的振动特性基本相同,当h/a<0.05时,板中心的位移将随h/a的减小而增大。     

A Reusable DNA Single‐Walled Carbon‐Nanotube‐Based Fluorescent Sensor for Highly Sensitive and Selective Detection of Ag+ and Cysteine in Aqueous Solutions

Here we report a reusable DNA single‐walled carbon nanotube (SWNT)‐based fluorescent sensor for highly sensitive and selective detection of Ag⁺ and cysteine (Cys) in aqueous solution. SWNTs can effectively quench the fluorescence of dye‐labeled single‐stranded DNA due to their strong π–π stacking interactions. However, upon incubation with Ag⁺, Ag⁺ can induce stable duplex formation mediated by C–Ag⁺–C (C=cytosine) coordination chemistry, which has been further confirmed by DNA melting studies. This weakens the interactions between DNA and SWNTs, and thus activates the sensor fluorescence. On the other hand, because Cys is a strong Ag⁺ binder, it can remove Ag⁺ from C–Ag⁺–C base pairs and deactivates the sensor fluorescence by rewrapping the dye‐labeled oligonucleotides around the SWNT. In this way, the fluorescence signal‐on and signal‐off of a DNA/SWNT sensor can be used to detect aqueous Ag⁺ and Cys, respectively. This sensing platform exhibits high sensitivity and selectivity toward Ag⁺ and Cys versus other metal ions and the other 19 natural amino acids, with a limit of detection of 1 nM for Ag⁺ and 9.5 nM for Cys. Based on these results, we have constructed a reusable fluorescent sensor by using the covalent‐linked SWNT–DNA conjugates according to the same sensing mechanism. There is no report on the use of SWNT–DNA assays for the detection of Ag⁺ and Cys. This assay is simple, effective, and reusable, and can in principle be used to detect other metal ions by substituting C–C base pairs with other native or artificial bases that selectively bind to other metal ions.     

仪器分析课程教学实践

在仪器分析课程的教学实践中,采取加强绪论课教学,引入仪器分析发展史,运用生活化的形象描述及比喻,以及充分利用多媒体教学手段4种方法,培养和激发学生学习兴趣。     

Geometric conservation law and applications to high-order finite difference schemes with stationary grids

The geometric conservation law (GCL) includes the volume conservation law (VCL) and the surface conservation law (SCL). Though the VCL is widely discussed for time-depending grids, in the cases of stationary grids the SCL also works as a very important role for high-order accurate numerical simulations. The SCL is usually not satisfied on discretized grid meshes because of discretization errors, and the violation of the SCL can lead to numerical instabilities especially when high-order schemes are applied. In order to fulfill the SCL in high-order finite difference schemes, a conservative metric method (CMM) is presented. This method is achieved by computing grid metric derivatives through a conservative form with the same scheme applied for fluxes. The CMM is proven to be a sufficient condition for the SCL, and can ensure the SCL for interior schemes as well as boundary and near boundary schemes. Though the first-level difference operators δ₃ have no effects on the SCL, no extra errors can be introduced as δ₃ = δ₂. The generally used high-order finite difference schemes are categorized as central schemes (CS) and upwind schemes (UPW) based on the difference operator δ₁ which are used to solve the governing equations. The CMM can be applied to CS and is difficult to be satisfied by UPW. Thus, it is critical to select the difference operator δ₁ to reduce the SCL-related errors. Numerical tests based on WCNS-E-5 show that the SCL plays a very important role in ensuring free-stream conservation, suppressing numerical oscillations, and enhancing the robustness of the high-order scheme in complex grids.     

融合形态学连通域和CV模型的民族服饰图案纹样元素分割方法

对民族服饰图案进行自动分割以提取图案纹样元素,是民族服饰图案素材库构建急需解决的难题。通过融合形态学连通域标记和CV模型（MCC-CV）,提出了一种民族服饰图案自动分割方法,首先对民族服饰图案进行预处理,然后采用形态学连通域标记算法获得待分割目标的位置和大致轮廓信息,对CV模型进行初始化,最后通过CV模型对不同分割目标进行边缘追踪,以实现民族服饰图案纹样元素的自动分割。实验表明,融合形态学连通域和CV模型的民族服饰图案纹样元素自动分割方法在边界召回率（BR）为0.5时,分割准确率为60%,与其他自动分割算法相比,该算法更为有效,满足了民族服饰图案素材库建设对图案纹样元素分割的基本要求。     

饮料中4种人工合成甜昧剂同时测定的超高效液相色谱快速检测方法

建立了采用超高效液相色谱同时测定饮料中4种甜味剂(安赛蜜、糖精钠、甜味素、纽甜)的方法.样品经简单的预处理后,通过ACQUITY UPLCTM BEH C18色谱柱分离,以乙腈-20 mmol/L磷酸二氢钠水溶液为流动相进行梯度洗脱,于220 nm波长下紫外检测.一次进样分析仅需6 min.4种甜味剂在0.5～20.0 mg/L范围内的线性关系良好,在加标水平为1,10和20 mg/L时,被测物的回收率为80.5%～95.2%,相对标准偏差为0.50%～8.7%.