模拟混凝土孔溶液中钢筋电化学噪音测量及小波分析

电化学噪音(Electrochemical Noise,ECN)测量可用于在无电信号扰动条件下检测腐蚀体系的暂态行为,获得有关腐蚀类型和腐蚀速率的信息.小波分析不需要对ECN作稳态假设,并同时具有时间分辨和频率分辨的特点,在ECN信号处理中表现出一定的优势.本工作考察了氯离子对钢筋在模拟混凝土孔溶液中电化学噪音的影响,并采用离散小波变换(DWT)及能量分布图(EDP)分析ECN信号的时间～频率特征.结果表明,在含NaCl0.0001mol/L的饱和Ca(OH)2溶液中,时间常数为16～32s的暂态占优势;在Cl-浓度更高的溶液中,去钝化趋势为主导事件,表明钢筋在SPS溶液中活化/钝化的临界Cl-浓度介于10-4～10-3mol/L.     

利用小波变换检测电化学噪声信号波形

简述了应用小波变换检测点蚀电化学噪声信号的基本原理,对在3.5％ NaCl溶液中工业纯铝发生点蚀的电化学噪声信号检测分析表明：小波变换能够提取发生点蚀的电化学噪声信号和测量系统噪声在多惊讶分辨空间中的波形特征,根据表征该特征的小波系数模极大值在不同尺度下的传播特性,可实现对点蚀电化学噪声信号波形的检测。     

基于小波变换平滑主成分分析

小波变换具有很强的信号分离能力,很容易把随机噪音从信号中分离出来,从而提高信号的信噪比。本文把小波变换引入到因子分析中,提出了基于小波变换平滑主成分分析,该算法既保留普通主成分分析的正交分解,又具备了小波变换的信号分离能力。模拟数据和实验数据的结果表明,该算法具有从低信噪比的数据中提取出有用信息,并提高信号的信噪比。迭代目标变换因子分析处理实验数据的结果表明,基于小波变换平滑主成分分析的处理结果优     

小波变换方法的比较──红外光谱数据压缩

介绍了小波变换和多分辨分析的基本理论以及常用小波变换压缩数据的3种方法:(1)只保留模糊信号;(2)全部保留模糊信号及锐化信号中的较大值;(3)保留模糊信号及锐化信号中的较大值.将紧支集小波和正交三次B-样条小波压缩4-苯乙炔基-邻苯二甲酸酐的红外光谱数据进行了对比,计算表明正交三次B-样条小波变换方法效果较好,而在全部保留模糊信号及只保留锐化信号中数值较大的系数时,压缩比大而重建光谱数据与原始光谱数据间的均方差较小.     

三种有机缓蚀剂对钢筋阻锈作用的电化学研究

应用极化曲线、电化学噪音(EN)和电化学阻抗谱(EIS)等电化学方法,检测和评价N-月桂酰肌氨酸钠、D-葡萄糖酸钠和β-甘油磷酸钠等3种缓蚀剂对钢筋在含NaC l的模拟混凝土孔溶液中电化学腐蚀行为的影响及其阻锈作用.结果表明,D-葡萄糖酸钠对钢筋具有较好的缓蚀效果,其缓蚀作用主要是通过在钢筋表面的竞争吸附和沉积而提高钢筋耐腐蚀性.     

基于小波-反向搜索及表面增强拉曼的食品中色素的光谱定性分析

使用金纳米粒子为增强因子的表面增强拉曼光谱技术,通过连续小波变换将拉曼光谱信号转化到小波空间(墨西哥帽小波作为小波基)。该步骤能够减轻信号中基线变化及随机噪音的影响并找到峰位置和最佳小波尺度系数。依据小波空间中的信息,对混合物光谱及标准谱光谱进行反向搜索得到反向搜索匹配系数(Reverse match quality,RMQ),作为判断混合物中目标成分是否存在的依据。该算法可对混合物中的目标物质进行准确定性,并已成功应用于多种食品中色素鉴定。食品中色素的检出率达到99%,且结果稳健,其效果明显优于传统的命中质量系数法(Hit quality index,HQI)。这证实了小波空间反向搜索方法是一种快速而准确的拉曼光谱定性算法。     

小波变换用于植物激素重叠色谱峰中组分的定量分析

根据小波变换将信号按频率大小分解的性质，作者提出了一种用小波变换直接提取重叠色谱峰中单一组分信息的方法，并将其应用于植物激素混和体系重叠峰的解析与定量分析。结果表明：单组分的色谱信号经小波变换分解后仍能保持原有的线性关系，用小波变换从重叠信号中提取的单一组分信息也具有良好的线性关系。     

小波变换漫反射红外光谱法测定剑麻果胶的酯化度

采用小波变换,基于漫反射红外光谱(DRIFTS)技术建立了一种快速测定剑麻果胶酯化度(DE)的分析方法.小波变换作为信号处理工具可有效消除信号失真,信噪比(SNR)由84:1增至96:1,信号基线比(SBR)由7.7:1升至8.3:1,同时提高了果胶样品测定的精确度.以不同酯化度的果胶为标准,通过傅立叶变换红外光谱仪(...     

小波变换与分析化学信号处理

介绍了小波变换的基本理论并对小波变换的常用算法和应用进行了评述。由于小波变换的时2频局部化性质, 使其成为信号处理的强有力工具。在分析化学领域中, 小波变换在流动注射分析、伏安分析、高效液相色谱、红外光谱、质谱、核磁共振谱、可见-紫外光谱、光声光谱、扩展X-射线吸收精细结构(EXAFS) 谱等分析化学信号的平滑滤噪、数据压缩、重叠信号解析等方面都有成功的应用。     

小波变换用于近红外光谱性质分析

以汽油研究法辛烷值分析为例,研究了小波变换在近红外光谱分析中的应用。对近红外光谱的小波特性、小波变换参数以及变量提取方法进行了详细研究。研究结果表明：光谱噪音、有用信息和背景分别分布在小波高、中和低频区域;母小波函数对性质分析结果影响很大;小波变换可以同时扣除光谱背景、去除噪音和压缩变量,具有运算速度快、分析精度高以及无需去噪后处理等优点,在近红外光谱分析中具有很好的应用前景。     

Online Monitoring of the Atmospheric Corrosion of Aluminium Alloys Using Electrochemical Noise Technique

In this work, an electrochemical system based on electrochemical noise (EN) technique for online detection and monitoring of atmospheric corrosion of LY12CZ aluminium alloys has been established. A detecting probe and a monitoring instrument with a software have been developed to perform the electrochemical noise measurements with zero resistance ammeter (ZRA) mode. Experimental results show that the atmospheric corrosion behaviour of aluminium could be effectively detected and monitored by the analysis of the electrochemical potential and current noise, also by the noise resistance variation.     

Wavelet Derivative: Application in Multicomponent Analysis of Electrochemical Signals

The wavelet derivative was developed for resolving overlapped signals in electrochemical analysis. It has been shown that the wavelet derivative could be used as an effective tool in resolution enhancement of the electrochemical signals. Since signal‐to‐noise ratio (SNR) does not degrade significantly at high order derivatives, the wavelet derivative is much better than the conventional numerical derivative in resolving practical signals with low SNR, particularly in the case when the overlapped degree of complex is high and high order derivatives are required for the further resolution enhancement. In this article, applications of the wavelet derivative in the voltammetric determination of small mounts of substances in the presence of large mounts of potentially interfering species are presented, and the advantages of this technique are discussed as well.     

核酸等温扩增技术在电化学生物传感器中的应用

生物分子检测在临床诊断、基因治疗、基因突变分析等方面变得日益重要,因而,建立简单、快速、灵敏的检测方法具有重要意义。近年,电化学生物传感器因其简单、便携、易操作、成本低等优势在生物分子检测的研究中备受关注。为了提高检测方法的灵敏度,不同的核酸等温扩增技术被应用于电化学生物传感器的构建中。本文简单介绍了电化学生物传感器的工作原理,着重综述了几种主要应用于电化学传感器中的核酸等温扩增技术,同时比较了各方法的优缺点。     

Analysis of large experimental datasets in electrochemical impedance spectroscopy

An approach for the analysis of large experimental datasets in electrochemical impedance spectroscopy (EIS) has been developed. The approach uses the idea of successive Bayesian estimation and splits the multidimensional EIS datasets into parts with reduced dimensionality. Afterwards, estimation of the parameters of the EIS-models is performed successively, from one part to another, using complex nonlinear least squares (CNLS) method. The results obtained on the previous step are used as a priori values (in the Bayesian form) for the analysis of the next part. To provide high stability of the sequential CNLS minimisation procedure, a new hybrid algorithm has been developed. This algorithm fits the datasets of reduced dimensionality to the selected EIS models, provides high stability of the fitting and allows semi-automatic data analysis on a reasonable timescale. The hybrid algorithm consists of two stages in which different zero-order optimisation strategies are used, reducing both the computational time and the probability to overlook the global optimum. The performance of the developed approach has been evaluated using (i) simulated large EIS dataset which represents a possible output of a scanning electrochemical impedance microscopy experiments, and (ii) experimental dataset, where EIS spectra were acquired as a function of the electrode potential and time. The developed data analysis strategy showed promise and can be further extended to other electroanalytical EIS applications which require multidimensional data analysis.     

Analysis of Mammalian Cell Cytoplasm with Electrophoresis in Nanometer Inner Diameter Capillaries

Capillary electrophoresis in 770 nanometer inner diameter capillaries coupled to electrochemical detection with an etched electrode matching an etched capillary (etched electrochemical detection) has been used with ultrasmall sampling to inject subcellular samples from intact single mammalian cells. Separations of cytoplasmic samples taken from rat pheochromocytoma cells have been achieved. As little as 8% of the total volume of a single cell has been sampled and analyzed. Dopamine has been identified and quantified in these PC12 cells using this technique. The average cytoplasmic level of dopamine in rat pheochromocytoma cells has been determined to be 240 ± 60 μM. The use of electrophoresis in 770 nanometer inner diameter capillaries with electrochemical detection to monitor cytoplasmic neurotransmitters at the single cell level can provide information about complex cellular functions such as neurotransmitter storage and synthesis.     

集成因子分析与卡尔曼滤波的计算光度分析方法

通过将因子分析与卡尔曼滤波法集成,提出一种多元光度分析新算法。该法运用因子分析法提取多组分化学体系量测数据矩阵中的因子构建卡尔曼滤波校正模型,以克服卡尔曼滤波法依赖于纯物质光谱建模的内在局限性。数值仿真及分析实验结果均表明,该法能获得准确可靠的计算分析结果,是一种有效的计算光度分析新算法。     

动力学体系二维数据的秩分析及其应用

详细论证了动力学体系中存在的多种共线性情况,以及在此情况下二维数据阵的秩与独立反应数及组分数的关系.分析了通过增秩这一方式来判断体系组分数的条件.讨论了反应间存在物质交换对数据阵秩的影响.建立起一套通过秩分析判断未知动力学体系中存在的反应组分数、独立反应数以及可能反应机理的方法.将秩分析技术应用到聚苯胺与质子酸反应,初步分析了该体系存在的多种吸光性结构及结构变化.确定了[H＋]=0.01～0.1 mol•L－1范围内,聚苯胺与质子酸反应存在一个三结构两步互变过程.     

Recent Advances in Real-Time Analysis of Electrochemical Reactions by Electrochemical Mass Spectrometry†

Electrochemical mass spectrometry (EC-MS) is a powerful tool to capture and analyze the intermediates and products during electrochemical reactions. This hyphenated technique combines electrochemistry with mass spectrometry using specific apparatuses, which helps researchers study mechanisms of redox reactions by in situ detecting chemical composition changes. Recently, various EC-MS methods have been applied in a series of electrochemical reactions to reveal the mechanisms, mainly in the areas of electrochemical sensors, organic electrochemistry, and electrocatalysis. In this review, we intend to summarize the recent advances in real-time analysis of different types of electrochemical reactions by EC-MS and offer an outlook on the perspectives in these areas.      

一种含二茂铁基的多枝状分子的合成、表征及其性质研究

采用新的方法合成了一种二茂铁衍生物——均三（二茂铁乙烯基）苯，通过元素分析、红外光谱、核磁共振氢谱、质谱、紫外可见光谱等对其进行了表征。用循环伏安法对其电化学性质进行了初步研究，用Z-扫描技术测试了它的非线性光学性能。结果表明，该化合物具有良好的电化学及非线性光学性质。     

Electrochemical Detection of Gunshot Residue for Forensic Analysis: A Review

Current demands for detection of Gunshot Residue (GSR) require a reliable and rapid decentralized detection system with high sensitivity and specificity. This article reviews the use of electrochemical devices for GSR detection over the last 35 years and highlights recent advances associated with the demands of GSR field detection such as portability, speed, cost and power. Anodic stripping voltammetry (ASV) has been widely implemented for the detection of the metallic components of GSR at a variety of working electrodes. Efforts toward the detection of the organic components of GSR have also been reported using cyclic‐ and square‐wave voltammetry. The simultaneous detection of both organic and inorganic GSR constituents has recently been examined to increase the overall information content in a single voltammetric scan. As well as this, exploitation of screen‐printing fabrication allows replacement of conventional electrochemical cells with easy‐to‐use sensor strips Sampling methods for electrochemical GSR analysis are also advancing from acid washes or swabs to simpler abrasive methods which integrate sampling and analysis obviating the need for intermediate processing steps. The latest direction of electrochemical detection of GSR involves chemometric treatment to evaluate data allowing for more objective conclusions and increasing the automation of the system. These advances indicate great promise for investigating firearm‐related crimes, and bring significant changes to the detection of GSR making electroanalysis a powerful tool for decentralized forensic analysis.