Application of chronopotentiometry and derivative chronopotentiometry with an alternating current to the study of a slow charge transfer in a surface confined redox system

General analytical expressions for the potential-time (E-t) and derivative-potential ((dt/dE)-E) curves of a electroactive monolayer exhibiting a quasi-reversible behaviour, corresponding to the application of an alternating current time function of the form I(t) = I₀ cos(ωt), are presented. The use of this programmed current gives rise to singular and characteristic electrochemical responses. The alternating current also allows to obtain cathodic or both anodic and cathodic responses depending on whether the depletion of the adsorbed species was complete or not, and without using more than one applied current. Moreover, in this last case, it is possible to distinguish a reversible or an irreversible process by means of a simple visualisation of the E-t or (dt/dE)-E curves. Easy methods for estimating thermodynamic and kinetic parameters of the electroactive film are proposed and experimentally tested and compared with those previously obtained by using Cyclic Voltammetry.     

缓释／控释包膜肥料的研究现状与发展

缓释腔释包膜肥料具有重要的经济效益和生态效益,因而成为目前肥料研究与发展的热点之一.简述了缓释腔释肥料的特点和分类,回顾了国内外缓释/控释包膜肥料发展和研究现状,总结了其养分释放机理和养分释放影响因素,论述了其发展前景,并分析了进一步研究和开发的方向.     

Batch process fault detection and identification based on discriminant global preserving kernel slow feature analysis

As an attractive nonlinear dynamic data analysis tool, global preserving kernel slow feature analysis (GKSFA) has achieved great success in extracting the high nonlinearity and inherently time-varying dynamics of batch process. However, GKSFA is an unsupervised feature extraction method and lacks the ability to utilize batch process class label information, which may not offer the most effective means for dealing with batch process monitoring. To overcome this problem, we propose a novel batch process monitoring method based on the modified GKSFA, referred to as discriminant global preserving kernel slow feature analysis (DGKSFA), by closely integrating discriminant analysis and GKSFA. The proposed DGKSFA method can extract discriminant feature of batch process as well as preserve global and local geometrical structure information of observed data. For the purpose of fault detection, a monitoring statistic is constructed based on the distance between the optimal kernel feature vectors of test data and normal data. To tackle the challenging issue of nonlinear fault variable identification, a new nonlinear contribution plot method is also developed to help identifying the fault variable after a fault is detected, which is derived from the idea of variable pseudo-sample trajectory projection in DGKSFA nonlinear biplot. Simulation results conducted on a numerical nonlinear dynamic system and the benchmark fed-batch penicillin fermentation process demonstrate that the proposed process monitoring and fault diagnosis approach can effectively detect fault and distinguish fault variables from normal variables.     

低温热处理对鲕状赤铁矿助磨效果的试验研究

采用SRJX4-13型箱式电阻炉对鲕状赤铁矿进行低温热处理,从磨矿细度,平均粒度,孔隙率以及磨矿能耗几个方面,考察了低温热处理对鲕状赤铁矿的助磨效果。研究结果表明,矿石在400℃的温度下热处理90min,水淬冷却,孔隙率由3.6901%提高到4.0816%,磨矿产品-0.038mm含量由50.25%增大到60.88%;平均粒径由68.72μm减小为36.57μm;达到相同的磨矿细度,经热处理后的矿石所需要的磨矿时间更短。由此可知,低温热处理改善了鲕状赤铁矿的细磨效果,一定程度上降低了磨矿的能耗,对矿石的细磨起到了一定的辅助作用。     

Evaluation of SCC susceptibility of supermartensitic stainless steel using slow strain rate tests

Abstract

The susceptibility to chloride stress corrosion cracking (Cl-SCC) of supermartensitic stainless steel (SMSS) was evaluated at different temperatures through slow strain rate tests. In order to evaluate the Cl-SCC susceptibility the reduction in area and the time to failure ratio were considered. It is clear that all specimens tested in the chloride solution exhibited a generally high resistance to chloride SCC. However, according to the slow strain rate tests results, at lower temperature (5°C) the susceptibility to Cl-SCC increases compared to the other temperatures studied; also an increase in the corrosion rate was observed as the temperature decreased according to electrochemical impedance spectroscopy measurement. The corrosion mechanism observed on the material under dynamic stress was a combination of high activation resistivity with a diffusive process on the metallic interface given by a thin film from a protector layer of chromium oxides. This mechanism generates a high corrosion resistance and therefore good performance to chloride induced SCC.     

复凝聚法制备明胶/ES香精微胶囊

以古龙香精为芯材,明胶和柔软剂二硬脂酰胺乙基环氧丙基醋酸铵(ES)为壁材,在搅拌条件下,通过复凝聚方法制备了香精微胶囊。探讨了戊二醛用量、ES与明胶质量比及ES的质量分数对香精微胶囊形态的影响。用TEM、SEM和激光粒度分析仪对香精胶囊的粒子尺寸及分布、形态进行了表征。结果表明,戊二醛用量为明胶质量的2.2倍、ES与明胶质量比为1:0.3、ES的质量分数为1.5%时所制备的香精微胶囊形态规整、粒径分布较窄、干态粒径小于1μm。所制备的香精微胶囊具有良好的缓释性能,80℃烘干7 h仍然具有较高的香精残余量。所制备的香精微胶囊的载香量为41.1%,包埋率高达95.3%。     

延长混凝土工程寿命的简易途径

古代混凝土工程之所以耐久,除了它的化学组成和现代混凝土有所不同外,古代混凝土强度低、施工进度慢也是成就耐久的原因之一。现代混凝土工程短命的主要原因是施工进度过快。由于赶工期使许多工序被简化,使混凝土体内原始互不相通的微裂缝和微空隙数量增加、提前连通并延伸到混凝土表面,使大气中的冷热、干湿循环进入混凝土体内和钢筋表面,从...     

大都市低碳交通策略的国际案例比较分析

本文从城市交通规划和城市交通政策作为切入点,旨在探索国内外大都市的低碳交通策略.通过对12个国际大都市在推行低碳交通方面的实践经验总结归纳出当前大都市交通的五种低碳化策略,并对每一类策略的利弊和适用条件进行分析.在此基础上,提出在规划战略层面探索城市土地利用与交通一体规划策略,在实施层面构建公共交通和慢行交通并重的缘色出行结构,在管理层面完善交通需求管理体系应是现阶段我国大都市主要的低碳交通策略.     

南京市鼓楼片区慢行单元规划

慢行交通主要包括步行和自行车交通,在中短距离出行中具有一定的优势。针对慢行交通中的系统缺乏、设施配套不足和场所缺乏等问题,南京市鼓楼片区慢行单元规划通过打造自然休闲慢行单元、轨道交通接驳单元、历史文化慢行单元、商业活力慢行单元和人文高校慢行单元,并以慢行路线将各个单元串联起来,构建起较完整的慢行交通系统,进而推动片区整体系统的健康发展。     

CRTSⅢ型轨道板气液联动同步放张器的优化与改进

基于气液联动同步放张器在实际运用中出现的新型放张工艺要求,深入了解现场钢筋放张工艺和放张器实际使用时出现的问题,进行针对性的完善和改进。优化其结构尺寸,克服钢筋或放张器断裂现象;严格控制液压油流过环形间隙的流量和时间,实现缓慢动态同步放张;设计回油单向阀,达到油液迅速自动复位的目的。优化和完善了气液联动同步放张器,并以有限元分析数据为参考,证实了放张器的可行性。