Sensor for oxygen evaluation in concrete

This paper includes results from a research work carried out for developing and optimising a sensor to measure the limiting current of oxygen reduction in concrete.Platinum, stainless steel and carbon steel materials were tested as working electrodes in saturated Ca(OH)₂ solution. Linear correlations were obtained between the limiting currents of oxygen reduction and the oxygen concentration in solution.The measurements of the limiting current density due to oxygen reduction have been made in concrete specimens with a sensor consisting of platinum and stainless steel, as working electrodes, graphite, as a counter electrode, and activated titanium, as a reference electrode, under different conditions of water and oxygen accessibility to the concrete. The results show that this sensor detects oxygen content variations in the interstitial solution of the concrete, providing qualitative information about the evolution of oxygen availability in concrete.     

金橙G为电化学探针测定DNA的研究

在pH5.0的Britton-Robinson(B-R)缓冲溶液中,用电化学方法研究了金橙G(OG)与脱氧核糖核酸(DNA)的结合反应。OG在-0.62V处有一个灵敏的示差脉冲伏安还原峰;当在溶液中加入DNA后,随着DNA浓度的增大,OG的峰电流减小而峰电位不发生变化。峰电流的减小主要是由于溶液中DNA与OG相互结合生成了生物超分子复合物。在最佳条件下,峰电流的降低与DNA的浓度在1.0-15.0mg/L范围内呈良好的线性关系,检出限为0.35mg/L。该方法用于合成样品中DNA的测定,具有较好的回收率和选择性。     

Hall MHD and Electron Inertia Effects in Current Sheet Formation at a Magnetic Neutral Line

An exact self-similar solution is used to investigate current sheet formation at a magnetic neutral line in incompressible Hall magnetohydrodynamics. The collapse to a current sheet is modelled as a finite-time singularity in the solution for electric current density at the neutral line. We establish that a finite-time collapse to the current sheet can occur in Hall magnetohydrodynamics, and we find a criterion for the finite-time singularity in terms of the initial conditions. We derive an asymptotic solution for the singularity formation and a formula for the singularity formation time. The analytical results are illustrated by numerical solutions, and we also investigate an alternative similarity reduction. Finally, we generalise our solution to incorporate resistive, viscous and electron inertia terms.     

Aqueous Cr(VI) reduction by electrodeposited zero-valent iron at neutral pH: acceleration by organic matters

This work investigated the effect of co-existing organic matters on aqueous Cr(VI) reduction by electrodeposited zero-valent iron (ED Fe(0)) at neutral pH. The ED Fe(0) prepared in a solution containing mixture of saccharin, L-ascorbic acid and sodium dodecyl sulfate showed higher activity in reducing the aqueous Cr(VI) at neutral pH than that prepared without any organic presence. XRD and SEM indicated that the structure of ED Fe(0) was significantly improved to nano-scale by the presence of organic mixture in the preparation solution. Further, the ED Fe(0) activity in the Cr(VI) reduction at neutral pH was increased by the co-existence of citric acid or oxalic acid in the chromate solution. Electrochemical impedance spectroscopy (EIS) demonstrated that the corrosive current increased with the concentration of organic matter in the reaction solution. With the co-existing organic matters in the preparation solution, the ED Fe(0) corroded more rapidly due to its nano-size, thus the Cr(VI) reduction by the ferrous iron was accelerated. With the co-existing organic matters in the reaction solution, the Cr(VI) reduction was accelerated by a Fe(II) complex as the main electron donor, and a prevention of the passivation due to the Fe(III) and Cr(III) complexes also accelerated the Cr(VI) reduction.     

离子膜原电池法还原钛液中的三价铁

提出了离子膜原电池法还原钛液中的Fe^3 新方法。原电池的正极由铅（或铜）电极和钛液组成,负极电铁电极和酸性FeSO4溶液组成,离子交换膜作为正负两极间的隔膜,利用原电池的放电过程还原钛液中的Fe^3 。并详细地考察了温度、溶液电解液流速、膜面积等因素对还原速度的影响,实验结果表明,膜电流密度最大可达100A/m^2以上。     

Nonlinear model order reduction based on local reduced‐order bases

A new approach for the dimensional reduction via projection of nonlinear computational models based on the concept of local reduced‐order bases is presented. It is particularly suited for problems characterized by different physical regimes, parameter variations, or moving features such as discontinuities and fronts. Instead of approximating the solution of interest in a fixed lower‐dimensional subspace of global basis vectors, the proposed model order reduction method approximates this solution in a lower‐dimensional subspace generated by most appropriate local basis vectors. To this effect, the solution space is partitioned into subregions, and a local reduced‐order basis is constructed and assigned to each subregion offline. During the incremental solution online of the reduced problem, a local basis is chosen according to the subregion of the solution space where the current high‐dimensional solution lies. This is achievable in real time because the computational complexity of the selection algorithm scales with the dimension of the lower‐dimensional solution space. Because it is also applicable to the process of hyper reduction, the proposed method for nonlinear model order reduction is computationally efficient. Its potential for achieving large speedups while maintaining good accuracy is demonstrated for two nonlinear computational fluid and fluid‐structure‐electric interaction problems. Copyright © 2012 John Wiley & Sons, Ltd.     

电化学还原法制备氧化铅纳米棒

本文介绍一种用电化学还原法制备氧化铅纳米棒的简单方法.实验中所用的电解液是混有氧氯化锆和三氯化钛的硝酸铅溶液,采用不锈钢片作为阴极和基底.在室温下,由直流电源供电,通过控制输出电流的大小在不锈钢片基底上沉积产物.氧化铅纳米棒的产生与电流密度有关,通过讨论,得出生成氧化铅纳米棒的最佳电流密度大小.用SEM、TEM、EDS和XRD对产物进行了表征.研究结果表明,所制备的氧化铅纳米棒是单晶结构.     

Properties of ultrafine copper-containing powders prepared by a sonoelectrochemical method

In this paper, we analyze the factors that influence the particle size and morphology of copper powders prepared by electrodeposition from solution at increased current densities (0.5–1.0 A/cm²) under ultrasonication (sonoelectrochemical method). The cathode current density and current pulse duration are shown to have the most significant effect on the particle size of the powders. Reducing the current density and pulse duration leads to a reduction in particle size. Our results demonstrate that the method allows one to obtain copper powders with an average particle size of 100 nm exhibiting high antibacterial activity and capable of suppressing the growth of pathogenic bacteria.     

Immunoassay of the MRSA-related toxic protein, leukocidin, with scanning electrochemical microscopy

Scanning electrochemical microscopy (SECM) was applied to the immunoassay of leukocidin, which is a toxic protein produced by methicillin-resistant Staphylococcus aureus (MRSA), with the intention of developing and early diagnostic for MRSA infection. An antibody-chip for leukocidin was prepared by self-assembling of anti-leukocidin on a protein A-coated glass substrate. A sample solution containing leukocidin was spotted onto the antibody-chip, followed by labeling with horseradish peroxidase (HRP) via a sandwich method. The reduction current of the oxidized form of ferrocenylmethanol generated by the HRP reaction was monitored to view SECM images of the spot of captured leukocidin. The amplitude of reduction current depended on the concentrations of sample solutions used for making spots. This SECM-based immunoassay detects as low as 5.25 pg mL(-1) leukocidin.     

Evaluating capacity change and setup time reduction in a capacity-constrained,joint lot sizing situation

We develop a simple decision model which can be used for determining the optimum levels of order quantity, order cycle, and capacity change for a capacity-constrained, single-stage joint lot sizing/scheduling (JLS) situation. The model solution (i.e., capacity change) can also be converted into an equivalent setup time reduction. Thus, the model can be used to evaluate the effectiveness of capacity change and setup reduction alternatives. Therefore, the proposed model extends the capability for analysis over that of current JLS approaches.     

Study of the electrochemical oxidation and reduction of C.I. Reactive Orange 4 in sodium sulphate alkaline solutions

Synthetic solutions of hydrolysed C.I. Reactive Orange 4, a monoazo textile dye commercially named Procion Orange MX-2R (PMX2R) and colour index number C.I. 18260, was exposed to electrochemical treatment under galvanostatic conditions and Na₂SO₄ as electrolyte. The influence of the electrochemical process as well as the applied current density was evaluated. Ti/SnO₂–Sb–Pt and stainless steel electrodes were used as anode and cathode, respectively, and the intermediates generated on the cathode during electrochemical reduction were investigated. Aliquots of the solutions treated were analysed by UV–visible and FTIR-ATR spectroscopy confirming the presence of aromatic structures in solution when an electro-reduction was carried out. Electro-oxidation degraded both the azo group and aromatic structures. HPLC measures revealed that all processes followed pseudo-first order kinetics and decolourisation rates showed a considerable dependency on the applied current density. CV experiments and XPS analyses were carried out to study the behaviour of both PMX2R and intermediates and to analyse the state of the cathode after the electrochemical reduction, respectively. It was observed the presence of a main intermediate in solution after an electrochemical reduction whose chemical structure is similar to 2-amino-1,5-naphthalenedisulphonic acid. Moreover, the analysis of the cathode surface after electrochemical reduction reveals the presence of a coating layer with organic nature.     

Board sequencing and component loading problem for a single machine in PCB assembly planning

Most current research sequentially solves the board sequencing and component-loading problem for a single machine in printed circuit board (PCB) assembly. The board sequence is first determined. The component-loading order is then established. In addition, other current approaches are used to solve the problem based on the upper bound on component changeovers between two jobs. However, consideration of current magazine status could be a source for total set-up time reduction. In this paper, a new approach is developed to establish board sequence and component-loading order simultaneously. Each board sequence position and component-loading order are obtained together from the process of current set-up determination. The obtained solution is then improved further by the combination of bias and random search processes. Some experiments are tested to confirm theoretical judgement.     

Electrodeposited Cu-Stabilization Layer for High-Temperature Superconducting Coated Conductors

We have developed a nonaqueous-based process for electrodepositing a Cu-stabilization layer on a YBCO superconductor tape. Conventional approaches to electroplating Cu layers use a cyanide-based solution to prevent uncontrolled hydrogen evolution from the aqueous-based solution; these are very reactive with the superconductor layer, and thus destroy its critical-current capability when plated directly onto high-temperature superconductor (HTS) tape. It has been found that a capping layer at least 1 micron thick is needed between the superconductor and stabilizer layers to avoid such a reaction and the subsequent reduction in the critical-current capability of the superconductor layer. In contrast, the nonaqueous electroplating solution is nonreactive to the HTS layer, allowing the Ag capping layer to be thinner. We demonstrated that direct Cu plating on YBCO tapes using a nonaqueous solvent does not destroy the superconducting YBCO layer. The superconducting current capabilities of these tapes were measured by noncontact magnetic measurements. Contact current?Cvoltage (I?CV) measurements required a 0.1-micron-thick Ag capping layer on YBCO tapes, which is sufficient for subsequent Cu plating from the non-aqueous solvent.     

在NaCl溶液中Cu-Zn-Al形状记忆合金的电化学行为研究

在NaCl溶液中对Cu-Zn-Al形状记忆合金的电化学行为进行了研究，结果表明，在NaCl溶液中Cu-Zn-Al形状记忆合金发生脱锌腐蚀，腐蚀表面主要由CuZn相组成，Cu-Zn-Al形状记忆合金随NaCl浓度增加，PH值降低，环境温度升高，阳极活性电流密度增大，电化学溶解敏感性增强，表面分析结果表明，Cl离子参与了电化学溶解历程，即促进了CuCl2的阴极还原反应，从而导致Cu-Zn-Al形状记忆合金的脱锌腐蚀。     

Electrochemical reduction of nitrobenzene at carbon nanotube electrode

The electrochemical behaviors of nitrobenzene at a pyrolytic graphite electrode modified with carbon nanotubes (CNTs) were studied using cyclic voltammetry and constant-potential electrolysis technique, and the CNT-modified electrode was characterized with Fourier transform infrared spectroscopy (FTIR), high resolution transmission electron microscopy (HRTEM) and scanning electron microscopy (SEM) measurements. A CNT-modified packed-bed flow reactor was also constructed for electrocatalytic reduction of nitrobenzene. The results showed that CNTs exhibited high activity for nitrobenzene reduction to aniline and the electrochemical reduction of nitrobenzene at CNT-modified electrode followed the pathway of nitrobenzene-->phenylhydroxylamine-->aniline. CNTs had been functionalized with profuse carboxylic group and other oxygen-containing groups, became open with some lacuna on the wall, and were distributed symmetrically on the electrode with forming a three-dimensional layer, resulting in the high catalytic-activity for nitrobenzene reduction to aniline. The removal of nitrobenzene was over 95% with electrolysis for 50 min at -1.20 V in pH 5 solution using the CNT-modified packed-bed flow reactor, and no other product was obtained except aniline. The removal of nitrobenzene was over 95% with electrolysis for 80 min at -1.20 V in pH 7 solution and was 87% with electrolysis for 120 min in pH 9 solution. A little phenylhydroxylamine besides aniline was obtained during the initial electrolysis stage, and then all reduced to aniline. The average current efficiency at pH 5, 7 and 9 was 46, 51 and 63%, respectively. The electrolysis products were mineralized easily through aerobiotic biodegradation.     

A concept for immobilizing catalytic complexes on electrodes: cubic phase layers for carbon dioxide sensing

Liquid crystalline cubic phases formed with monoolein and Myverol have been used as matrixes to host a catalytic complex of nickel(II) and 1-hexadecyl-1,4,8,11-tetraazacyclotetradecane for the reduction of carbon dioxide. The structures of the cubic phases, both with and without the catalyst, were established using small-angle X-ray scattering. The catalytic reduction of carbon dioxide was performed using thin mercury film and glassy carbon electrodes modified with cubic phases containing the catalyst. The linear dependence of the catalytic reduction current on the carbon dioxide concentration allowed use of the modified electrodes as sensing devices both in solution and in the gas phase. The high reproducibility of the measurements makes this method of monitoring carbon dioxide levels attractive compared to other methods based on modified electrodes.     

Effect of hydrogen charging on the mechanical properties of medium strength aluminium alloys 2091 and 2014

Cathodic hydrogen charging in 3·5% NaCl solution altered the mechanical properties of 2091-T351 (Al-Cu-Li-Mg-Zr) determined by a slow (10⁻³/s) strain rate tensile testing technique. UTS and YS decreased in the case of 2091-T351 and 2014-T6(Al-Cu-Mn-Si-Mg) with increase in charging current density. Elongation showed a decrease with increase in charging current density for both the alloys. However, elongation occurring throughout the gauge length in uncharged specimens changed over to localized deformation, thus increasing the reduction in area in charged specimens. A transition in fracture mode from surface (brittle) to the core (ductile) was observed. The presence of hydrogen increased the hardness, mostly indicative of solution strengthening and it decreased with depth confirming the existence of hydrogen concentration gradient. The effects were similar in 2014-T6, but to a slightly smaller extent.     

Photoelectric Emission Measurements of Temperature. Effective Wavelength

A method is proposed for determining the effective wavelength by numerical solution of an integral equation for the case of energy analysis of photoelectrons in a retarding field. With use of an FÉU-175M as a temperature sensor and temperature measurement according to dispersion of previously accelerated photoelectrons in the field of an electrostatic lens, values of the effective wavelength lie within the region of values corresponding approximately to a twofold reduction of the retarding field photoelectric current that follows from calculation based on the empirical equation.     

Precise and rapid size selection and targeted deposition of nanoparticle populations using CO2 gas expanded liquids

This paper demonstrates the rapid and precise size selection of nanoparticle populations using the pressure tunable solvent properties of CO2-expanded liquids. Specifically, by pressurizing and expanding a single organic solution with carbon dioxide gas, ligand-stabilized silver particles of desired mean size were size selectively precipitated at desired locations. Compared to current techniques, this CO2-expanded liquid approach provides for faster and more efficient particle size separation, reduction in organic solvent usage, and pressure tunable size selection.     

Column design for electrochemically modulated liquid chromatography

A new column design for electrochemically modulated liquid chromatography (EMLC) is presented. The principal attribute of the new design is the enhancement of the control over the potential applied to the stationary phase by the reduction of the background current and solution resistance. The enhancement is demonstrated through a series of comparisons of the electrochemical performance of the new and the earlier column designs. This enhancement, as shown using mixtures of aromatic sulfonates, translates to an improvement in the capability of EMLC as a separation technique.