ELECTROCHEMICAL ANALYSIS USING ANGULAR POLARIZATION MODULATED ATIR SPECTROMETRY AND FLUOROMETRY

The absence of suitable in situ methods for obtaining electrical (charge-potential) and chemical information at electrode/electrolyte interfaces has represented a serious experimental incapacity in a broad range of fundamental and applied areas. This paper addresses the use of attenuated total internal reflection spectrometry and total internal fluorometry in conjunction with system modulation, both electrical cell control and spatially selective optical polarization, to probe this experimentally difficult region. Although applications of these techniques to electrolyte/solid electrode interfaces under equilibrium conditions will be described, emphasis will be given to interfacial characteization under current densities that significantly depart from equilibrium. The experimental configurations and difficulties in such measurements will also be addressed.     

THE ON-LINE CHEMICAL ANALYSIS OF SINGLE PARTICLES USING AEROSOL BEAMS AND TIME OF FLIGHT MASS SPECTROMETRY

This paper describes an on-line instrument, capable of measuring the size and chemical composition of single, aerosol particles. Possible applications include monitoring aerosol reactors and studying atmospheric chemistry. The main conclusion is that a working prototype has been built and tested. It uses a three stage vacuum system to generate an aerosol beam with a low divergence angle and a high transmittance. The pressure is reduced sufficiently to allow the application of a time-of-flight mass analyzer. The aerosol beam is probed in the analysis section by the focused beam of a low-power helium-neon laser. Every particle crossing the laser beam scatters light, which is detected by two photomultiplier tubes, mounted at angles of 45 and 90°. The signal is stored when both detectors produce a pulse simultaneously, and this event triggers the chemical analysis cycle. A pulsed Nd: YAG laser vaporizes the particle and generates ions, which are next analyzed by a time-of-flight mass spectrometer. In this way combined information on the size and the composition of the particle is obtained.     

用场解吸质谱法(FDMS)对澄清油中间相沥青组成结构的研究

用场解吸质谱（ＦＤＭＳ）对乙烯渣油中间相沥青（ＥＴＭＰ）和澄清油中间相沥青（ＤＯＭＰ）之甲苯可溶组分（ＴＳ）的组成结构进行了对比研究。通过对两种中间相沥青ＴＳ组分质谱峰的合理归属,鉴定出了主要的组成化合物系列以及各自相对应化合物的结构,分析极限大大扩大,在ＤＯＭＰ－ＴＳ中检测到的最高质量数为９９０,相应于１６个芳环的稠环芳烃分子;在ＥＴＭＰ－ＴＳ中检测到的最高质量数为９４８。相应于１５个缩合芳环的稠环芳烃分子,ＤＯＭＰ－ＴＳ含较多的迫位缩合芳环而ＥＴＭＰ－ＴＳ含较多的渺位缩合芳环,同时对中间相沥青的组成结构与其物理化学性能作了关联。     

近红外光谱法测定ABS/PC材料的共混比

使用近红外光谱仪测定不同共混比的(丙烯腈/丁二烯/苯乙烯)共聚物(ABS)/聚碳酸酯(PC)材料的近红外光谱数据,采用偏最小二乘(PLS)算法建立了测定ABS质量分数的校正模型,并对校正模型的准确性进行了验证。实际分析结果表明,该测试技术适用于ABS质量分数大于10%的ABS/PC材料中ABS质量分数的定量分析,取得了较好的分析结果。     

Performance and Durability of Membrane Electrode Assemblies Based on Radiation‐Grafted FEP‐g‐Polystyrene Membranes

Membrane electrode assemblies (MEAs) based on radiation‐grafted proton exchange membranes developed at PSI have shown encouraging performance in the past in hydrogen and methanol fuelled polymer electrolyte fuel cells. In this study, the effect of the pre‐treatment of crosslinked radiation‐grafted FEP membranes prior to lamination with the electrodes on the performance of the MEAs was investigated. Two approaches were assessed separately and in combination: (1) the impregnation of the radiation‐grafted membranes with solubilised Nafion®, and (2) the use of a swollen vs. dry membrane. It is found that the combination of coating the membrane with Nafion® ionomer and hot‐pressing the MEA with the membrane in the wet state produce the best single cell performance. In the second part of the study, the durability of an MEA, based on a radiation‐grafted FEP membrane, was investigated. The performance was stable for 4,000 h at a cell temperature of 80 °C. Then, a notable degradation of the membrane, as well as the electrode material, started to occur as a consequence of either controlled or uncontrolled start‐stop cycles of the cell. It is assumed that particular conditions, to which the cell is subjected during such an event, strongly accelerate materials degradation, which leads to the premature failure of the MEA.     

3D Visualisation of PEMFC Electrode Structures Using FIB Nanotomography

It is well known that the electrode structure of a PEMFC has a huge influence on the water management and thereby on the cell performance. In this work, two MEAs – one prepared by an airbrushing technique and the other by a novel fast spray coating technique (multilayered MEA) – were analysed with respect to porosity, pore size distribution, tortuosity and their electrochemical performance. FIB nanotomography with following 3D reconstruction, SEM investigation on ultramicrotomic thin‐sections, and single cell tests were performed on these MEAs. The results show a higher porosity and lower pore size for the multilayered MEA. The multilayered MEA reaches a Pt utilisation of 1,962 mW mg^–1 and a peak power density of 210 mW cm^–2, whereas the airbrushed MEA only provides a Pt utilisation of 879 mW mg^–1 and a peak power density of 218 mW cm^–2. The Pt utilisation calculations showed in combination with the structural characterisations that a homogeneous pore structure and Pt distribution provide an advantage with regard to performance and efficiency of the PEMFC. Furthermore, the multilayered MEA may offer an advantage over the airbrushed MEA in its long term stability, which was observed in preliminary tests.     

巯基纸富集-X射线荧光光谱测定氧化锌中的砷

在1mol／LHCl介质中，砷（Ⅲ）被巯基纸吸附和富集，制成薄样后，用X射线荧光光谱（XRF）测定.方法的检出限为0．20μg，线性范围为0.20－100μg.     

METHODS FOR AROMATIC AND HETEROCYCLIC AMINE CARCINOGEN-DNA ADDUCT ANALYSIS BY LIQUID CHROMATOGRAPHY-TANDEM MASS SPECTROMETRY

Xenobiotic-DNA adducts are used as biomarkers to assess the genotoxic effects of carcinogens. Rats were dosed with 4-aminobiphenyl (4-ABP), 2-amino-3,8-dimethylimidazo[4,5-f]quinoxaline (MeIQx), or 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP). DNA was isolated from the colons of vehicle and carcinogen-treated rats and digested using different nucleases and alkaline phosphatase. Deoxyribonucleoside adducts were quantified by capillary liquid chromatography-tandem mass spectrometry (LC-MS/MS) using isotope dilution methods with deuterated internal standards. Major adducts were those bound to the C8 position of deoxyguanosine. 3′- and 5′- Exonucleases were the most efficient nucleases at isolating dG-C8-ABP adducts. However, bulky adducts such as dG-C8-MeIQx and dG-C8-PhIP were better isolated using nuclease P1 rather than a combination of micrococcal nuclease and spleen phosphodiesterase. The use of DNase I enhanced the detection of all three adducts. We describe LC-MS/MS methods for DNA adduct detection and support the testing of different nucleases that increase DNA digestion efficiency and make available more DNA adducts for detection.     

Thermo‐Mechanical Response of Fuel Cell Electrodes: Constitutive Model and Application in Studying the Structural Response of Polymer Electrolyte Fuel Cell

The characterization of the mechanical properties of fuel cell electrodes through the experimental techniques is a complex task due to the low thickness, constituents' heterogeneous composition, and fragile nature of the film. We present a preliminary investigation on the thermomechanical response of fuel cell catalyst layer (CL) obtained through the numerical experiment. Since the Nafion ionomer is one of the constituents' of the CL, a modified micromechanically motivated viscoplastic model is adopted to characterize the Nafion ionomer in terms of reduced density factor to account for the void content. The catalyst agglomerates are taken as inclusions in the ionomer matrix to form a composite unit which is used to plot the true stress–true strain response. Practicality of this work is tested by implementing the electrode layer as a separate component in the single fuel cell unit cell model. A remarkable difference in the magnitude of stress levels in the membrane is observed under thermal and hydrated conditions with the presence and absence of electrode layer in the simulation domain. The present work will assist in improved understanding of the localized stress distribution in the membrane, which is essential to understand its mechanical endurance.     

粉煤灰制黑陶关键技术及分析

本文介绍了粉煤灰制黑陶的关键技术，提出了合理的配方组成、泥浆工艺参数及合理的烧成制度。     

MACROPORE SIZE ANALYSIS USING DIGITAL IMAGE PROCESSING AND A STEREOLOGICAL MODEL

An analytical method employing digital image processing and a stereological model is developed and applied to macropore structure characterization. Digital images of porous particle cross-sections are collected and analyzed on an image processor to identify the two-dimensional pore profiles and to obtain the distribution for the equivalent radii of pore sections. A stereological model with improved numerical integration, approximation and data smoothing features is developed to unfold the size distribution of the three-dimensional pores from the two-dimensional data. The method is used to characterize the macropore structure of coal-derived chars. Presented results establish that the developed technique can quantify features of the macropore structure of chars that cannot be identified by indirect analytical methods.     

化学修饰碳糊电极对环境水样中微量铅、镉离子的连续电化学测定

报道了用8-羟基喹啉作碳糊电极的修饰剂,测定环境体系中微量铅、镉离子的电化学方法.该电极在KNO3(pH=4.0)中,用吸附溶出伏安法测定Pb2+、Cd2+,在-0.56V(vs,SCE)和-0.84V处有灵敏溶出峰,峰电流与铅的浓度在(3.0×10-8～4.5×10-6)mol/L的范围内呈良好的线性关系,与镉的浓度在(4.0×10-8～3.5×10-6)mol/L的范围内呈良好的线性关系,该方法用于水样中铅、镉的测定,检出限为3.0×10-9mol/L(Pb2+)和5.0×10-9mol/L(Cd2+).     

MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS

In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.     

MODELING AND PREDICTIVE CONTROL OF MIMO NONLINEAR SYSTEMS USING WIENER-LAGUERRE MODELS

In this work, a Weiner-type nonlinear black box model was developed for capturing dynamics of open loop stable MIMO nonlinear systems with deterministic inputs. The linear dynamic component of the model was parameterized using orthogonal Laguerre filters while the nonlinear state output map was constructed either using quadratic polynomial functions or artificial neural networks. The properties of the resulting model, such as open loop stability and steady-state behavior, are discussed in detail. The identified Weiner-Laguerre model was further used to formulate a nonlinear model predictive control (NMPC) scheme. The efficacy of the proposed modeling and control scheme was demonstrated using two benchmark control problems: (a) a simulation study involving control of a continuously operated fermenter at its optimum (singular) operating point and (b) experimental verification involving control of pH at the critical point of a neutralization process. It was observed that the proposed Weiner-Laguerre model is able to capture both the dynamic and steady-state characteristics of the continuous fermenter as well as the neutralization process reasonably accurately over wide operating ranges. The proposed NMPC scheme achieved a smooth transition from a suboptimal operating point to the optimum (singular) operating point of the fermenter without causing large variation in manipulated inputs. The proposed NMPC scheme was also found to be robust in the face of moderate perturbation in the unmeasured disturbances. In the case of experimental verification using the neutralization process, the proposed control scheme was found to achieve much faster transition to a set point close to the critical point when compared to a conventional gain-scheduled PID controller.     

基于动力有限元分析和神经网络技术的含分层复合材料层合板的损伤诊断

本文基于作者提出的含层间分层损伤层合板的动力有限元分析模型和方法,计算了分层长度和位置对含层间分层损伤层合板结构的固有频率的影响,然后应用MATLAB的神经网络工具箱建立了人工神经网络,通过典型结构的仿真结果比较,证明了采用有限元动力分析和BP网络技术相结合的方法是一种可用于复合材料层合板的分层损伤诊断的有效方法.     

基于响应曲面法的自动铺放工艺参数分析与优化

通过对自动铺带(Automated tape laying,ATL)成型工艺的分析,提出了一种新的铺放质量评分标准。采用响应曲面法(Response surface methodology,RSM)设计了铺放工艺参数优化实验,分析了热风温度、铺放压力和铺放速度各工艺参数及其交互作用对铺放质量的影响,建立了各工艺参数与铺放质量的二次多项式回归方程的预测模型。根据回归方程求得了最佳铺放质量下的工艺参数,以及可接受铺放质量下的最大铺放速度时的工艺条件,为自动铺带工艺参数的控制提供了参考。     

A NEW APPROACH TO DECENTRALISED PROCESS CONTROL USING PASSIVITY AND SECTOR STABILITY CONDITIONS

A new robust decentralised process control strategy based on the sector stability theorem is proposed in this paper. The interaction between sub-systems is measured by a revised passivity index, which is used in the development of a new stability condition for decentralised control. The controller synthesis method is developed to satisfy the stability condition and H_∞ performance specification. The decentralised control of a boiler furnace is studied as an application example.     

MEASUREMENT AND ANALYSIS OF MOISTURE CHANGES IN AGRICULTURAL PRODUCTS USING FFT NOISE IMPEDANCE SPECTROSCOPY

ABSTRACT

Macroscopically, cellular foods including agricultural products are regarded as the electrical systems in which cell membranes isolate intracellular electrolytes from extracellular electrolytes. Moisture movement in the materials during drying causes the changes in moisture of the intracellular and extracellular electrolytes. Therefore, the moisture movements can be detected by an electrical measurement

The authors measured the impedance of carrot roots during drying by a FFT (fast Fourier transform) noise impedance method at frequency of 40 Hz to 100 kHz. The equivalent circuit model agreed with the measured impedance. The parameters in the model were determined as the intracellular and extracellular resistances and membrane capacitance

As a result, it was found that the increase in the extracellular resistance showed a good correlation with a decrease in moisture content between 200 and 400% d.b (dry basis) and that the membrane capacitance had the maximum near the second critical moisture content. It was concluded that the FFT noise impedance method was applicable to the moislure measurement of agricultural products during drying.     

辊道窑温度监控系统分析与展望

对现有主要的辊道窑温度监控系统作了概括，分析了其构建原理和特点及其应用情况。指出分布式温度监控系统是当前发展的主流，基于现场总线的辊道窑温度监控系统是未来的发展方向，提出了利用工控组态软件和通用计算机开发辊道窑温度监控系统的新思路。     

DCS和PLC控制系统升级改造分析

总结和分析大型化工装置DCS和PLC的改造升级过程,结合合成氨、尿素装置的经验,分析改造中注意事项和难点,提出解决问题的办法,并进一步评价改造效果。