Copper–4,4′-dipyridyl coordination compound as solid reagent for spectrophotometric determination of reducing sugar employing a multicommutation approach

In this work a multicommuted flow system employing copper–4,4′- dipyridyl coordination compound as the solid-phase reagent for the spectrophotometric determination of reducing sugar was developed. The coordination compound was synthesized through a reaction of the 4,4′-dipyridyl and copper (II) nitrate, under hydrothermal conditions. The complex was characterized by infrared spectroscopy (FTIR), power X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and thermogravimetric analysis (TGA). Based on the characterization, a multicommuted spectrophotometric procedure for the determination of reducing sugar using copper (II) complex as solid reagent is proposed. The proposed method was based on the redox reaction between a monosaccharide, such as fructose and glucose (reducing sugar) and Cu(II). This reaction, mediated in an alkaline medium, produces a yellow compound that can be determined by absorption electronic spectroscopy (λ_ABS = 420 nm). Under optimum experimental conditions, a linear response ranging from 1.0 to 20.0 g L⁻¹ (R = 0.9978 and n = 5), a detection (3σ criterion) and quantification (10σ criterion) limit estimated at 0.23 and 0.75 g L⁻¹, respectively, a standard deviation relative of 4.7% (n = 7), for a reference solution of 10.0 g L⁻¹ reducing sugar, and a sampling rate of 75 determinations per hour were achieved. The proposed system was applied to the determination of reducing sugars in coconut water and juices. The analysis of ten samples and the application of the t-test to the results found, and those obtained using reference procedures (AOAC), provided no significant differences at a 95% confidence level. This system enabled the analysis of reducing sugar with ease and simplicity, providing a significant economy of the solid reagent (600 μg per determination) and reducing effluent generation.     

光伏系统用于漏电流测量的霍尔闭环传感器设计

基于闭环磁通门技术的传感器广泛应用在测量大电流中的小剩余电流以及噪声共模电流。这类传感器的精度以及对大电流的隔离能力使之成为漏电流检测的最优方案,但通常缺点是成本昂贵且体积庞大。本文介绍了一种新型小尺寸且利用霍尔闭环技术对太阳能系统中的漏电流进行测量的传感器:新一代的LDSR产品。     

Physical properties and microstructures of residual carbon and slag particles present in fine slag from entrained-flow coal gasification

Fine slag (FS) consists of residual carbon (RC) and slag particles (SP). This paper studies the characteristics of SP and RC separately. SP contain a little of pores and mainly consist of spherical particles most of which are solids. RC have a higher pore surface, more continuous and complete pore structure. The chemical structure of inorganic minerals in SP has the following characteristics: According to nuclear magnetic resonance results, the amounts of network structure Q₄ and Q₃ are more than that of chain structure Q₂ and Q₁. The 4-coordinated aluminum consists of 74% and the octahedral coordination (Al(VI)) takes up only 11%. SP is a heterogeneous material which contain not only inorganic minerals but also organic carbon. C atom associated in chemical way with the inorganic matter within SP matrix. The predominant groups of organic carbon within SP matrix are C-C and C-O. C-O groups organically bound with inorganic elements in SP forming C-O-M (M: inorganic elements) bands. The predominant components in RC are C-C and C-O.     

Context-driven mean residual life estimation of mining machinery

Maintenance is crucial to ensure production/output and customer satisfaction in the mining sector. The cost of maintenance of mechanised and automated mining systems is very high, necessitating efforts to enhance the effectiveness of maintenance systems and organisation. For effective maintenance planning, it is important to have a good understanding of the reliability and availability characteristics of the systems. Determining the Mean Residual Life (MRL) of systems allows organisations to more effectively plan maintenance tasks. In this paper, we use a statistical approach to estimate MRL and consider a Weibull proportional hazard model (PHM) with time-independent covariates to model the hazard function so that the operating environment could be integrated into the reliability analysis. The paper explains our methods for calculating the conditional reliability function and computing the MRL as a function of the current conditions. The model is verified and validated using data from the hydraulic system of LHD equipment in a Swedish mine. The results are useful to estimate the remaining useful life of such systems; the method can be used for maintenance planning, helping to control unplanned stoppages of highly mechanised and automated systems.     

Lab scale optimization of various factors for photocatalytic hydrogen generation over low cost Cu0.02Ti0.98O2-δ photocatalyst under UV/Visible irradiation and sunlight

We have demonstrated earlier that maximum H₂ generated @ 1.167 l/h/m² over Cu_0.02Ti_0.98O_2-δ photocatalyst with apparent quantum efficiency, AQE of 7.5% and solar fuel efficiency, SFE of 3.9% under sunlight. With an aim to scale-up the solar photocatalytic hydrogen process to pilot plant, optimization studies at lab scale as well as in upscaled photoreactors were performed over Cu_0.02Ti_0.98O_2-δ, photocatalyst under UV/visible and sunlight. Cu_0.02Ti_0.98O_2-δ was synthesized by facile sol-gel route and characterized by relevant techniques. Several operational parameters were investigated in order to finalize the conditions which are most favourable for photocatalytic hydrogen yield. Factors such as photocatalyst loadings, v/v concentration of sacrificial reagent, replacement of methanol by industrial waste glycerol, role of different configuration of light source with reactor, effect of stirring during the photocatalytic reaction, effect of fluctuations of solar flux at hourly basis, illumination area on hydrogen yield were studied. Contribution of each factor in determining the hydrogen yield was quantified. Relative standard deviation in hydrogen yield as a function of each factor was estimated. Our findings suggest that in addition to catalyst loadings and sacrificial reagent, improved dispersion of photocatalyst obtained by stirring the reaction mixture in horizontal geometry resulted in enhanced H₂ yield. Hydrogen yield obtained at lab scale can be appropriately extrapolated with respect to illumination area instead of weight of photocatalyst. A relative standard deviation (RSD) of ± 3.82% and ± 4.53% in H₂ yield was calculated for sunny and cloudy days in time zone of 10.30–16.30 h IST. Deviation of H₂ yield was more on cloudy days and beyond 16:30 h. These studies have provided a daily window of 11:00–15:00 h to be utilized throughout the year for a commercial scaled up process, prohibiting the illumination during less productive hours of the day for shaping the improved economics of solar hydrogen generation. Our results obtained at lab scale would be useful to perform sunlight driven scaled –up photocatalytic process using low cost visible light efficient photocatalyst, Cu_0.02Ti_0.98O_2-δ.     

Residual Stress Removal Under Pulsed Electric Current

The effect of a pulsed electric current on the residual stress evolution of metal materials has been investigated.It was found that the surface and internal residual stresses in the as-quenched samples were reduced dramatically by electropulsing.A large number of experimental data show that the residual stress reduction is proportional to the initial residual stress and related to the material properties and electropulsing parameters.Under the combined actions of drift electrons,Joule heating,and residual stress,the dislocation mobility was enhanced,resulting in plastic strain and the decrease in residual stress.Drift electrons played a unique role in the electropulsing treatment,acting as an additional force pushing dislocations forward.The dislocations ultimately accumulated at a grain boundary,forming a parallel arrangement.Finally,the phenomenological equation of the residual stress evolution under electropulsing was derived from the experimental data.     

锤击法在消除熔丝积材残余应力中的研究进展

锤击法在熔丝积材残余应力消除中具有非常重要的研究价值和学术意义。近年来该方法日趋完善,现已成为消除熔丝积材残余应力的重要方法之一。本文概括综述了消除残余应力的方法,并着重分析了锤击法消除残余应力的国内外研究现状和最新进展。希望能给相关工作者提供参考。     

Optimized etching of porcelain and polycrystalline alumina with a glass phase

Chemical and thermal etching techniques are commonly used in ceramography to enhance microstructural features. While thermal etching works well for high purity ceramic systems, this technique may not be appropriate where glass is present. Porcelain and industrial alumina both contain a glass phase, typically 40?60 vol% and 4?30 vol%, respectively, and these glass chemistries are proposed to be similar. Chemical etching of porcelain is common, but the images published in the literature are frequently over-etched. When glass is present in the grain boundaries of alumina, thermal etching can cause the glass to disappear or to recrystallize, obscuring the microstructure. Because of this, it is proposed that both chemical and thermal etching are necessary to prepare an industrial alumina microstructure for grain size measurements. In addition, it was observed that chemical etching is sensitive to the residual stress in the glass phase, becoming more aggressive when there is residual tension in the glass.     

某铜矿浮选药剂用量优化及技术应用探讨

湖北某铜矿浮选在常规加药条件下，前两槽不能有效形成泡沫层，浮选液面经常出现“翻花”现象，以致选矿指标波动大，起泡剂用量大幅上升，因此开展了浮选试验研究。试验结果表明，在总药量不变的情况下，适当降低粗选捕收剂用量，使有用矿物有序上浮，有效改善了浮选泡沫层的稳定性。在生产现场应用后，浮选现场泡沫稳定，层次感分明，彻底解决了浮选前两槽不起泡、翻花等问题，选铜回收率提高0.69%，起泡剂单耗降低18g/t，取得较好的应用效果。     

On the machining induced residual stresses in IN718 nickel-based alloy: Experiments and predictions with finite element simulation

Residual stresses after machining processes on nickel-based super alloys is of great interest to industry in controlling surface integrity of the manufactured critical structural components. Therefore, this work is concerned with machining induced residual stresses and predictions with 3-D Finite Element (FE) based simulations for nickel-based alloy IN718. The main methods of measuring residual stresses including diffraction techniques have been reviewed. The prediction of machining induced stresses using 3-D FE simulations and comparison of experimentally measured residual stresses for machining of IN718 have been investigated. The influence of material flow stress and friction parameters employed in FE simulations on the machining induced stress predictions have been also explored. The results indicate that the stress predictions have significant variations with respect to the FE simulation model and these variations can be captured and the resultant surface integrity can be better represented in an interval. Therefore, predicted residual stresses at each depth location are given in an interval with an average and standard deviation.