Properties of Phase-Separated, Super-Oxygenated La2−x Sr x CuO4+y

We review a series of experiments that have established that super-oxygenated La_2−x Sr _x CuO_4+y phase-separates at low temperature into large magnetic and superconducting regions, driven by the physics of the doped holes themselves. Magnetization studies of trapped flux indicate that the large phase-separated magnetic and superconducting regions develop from nanoscale regions of charge inhomogeneity present in Sr-doped La₂CuO₄ and other more commonly studied cuprates. Neutron studies of the elastic magnetic diffraction show that the peak intensity grows with applied field as in La_2−x Sr _x CuO₄. However, the magnitude of the increase varies widely and is not well accounted for by current theory.     

Numerical gradient methods for flux identification in a system of conservation laws

The identification of the flux for a system of conservation laws is studied from a numerical point of view, on the specific example of chromatography. Different strategies to compute the exact gradient of the discretized optimization problem are developed and compared. Numerical evidence of the convergence of the method is also given in the scalar and binary case. Finally a ternary mixture with real experimental data is studied and the identified isotherm is compared with results obtained by chemical engineers.     

河口泥沙通量研究综述

河口泥沙通量的研究既是与全球变化研究有关的理论课题，也是与河口工程、经济生活关系密切的现实课题，本文系统地介绍了国内外关于河口泥沙通量研究的进展。泥沙通量研究多采用水文统计、机制分解、数学模型的方法进行，水文统计和机制分解无法达到预报的高度，相比之下，数学模型的优点很多，但由于河口海岸地区的泥沙运动规律复杂，其物理机制尚不完全清楚，阻碍了河口泥沙数学模型的发展。在深入分析基础上，文章就今后的河口泥沙通量研究工作提出了建议。     

RO membrane solute rejection behavior at the initial stage ofcolloidal fouling

This study investigated the rejection of salt and inert organic compounds by reverse osmosis membranes during the initial stage of colloidal fouling. Results of laboratory-scale experiments showed that colloidal fouling caused a marked decrease in flux, salt rejection and rejection of organics with molecular weight (MW) smaller than about 100 g/mol. Removal of neutrally charged organics was mainly by size or steric exclusion. Rejection of xylose, which has MW >100 g/mol, was not affected much by colloidal fouling. The decrease in salt and low MW organic rejections during the initial stage of colloidal fouling was attributed to cake-enhanced concentration polarization, whereby the colloidal cake layer hindered back diffusion of solutes from the membrane surface to the bulk solution, resulting in higher solute concentration gradient across the membrane. At higher channel wall shear rate, the rates of colloidal deposition, flux decline, decrease in salt rejection, and decrease in low MW organic rejection were lower.     

高铝质陶瓷焊补技术开发

根据陶瓷焊补料配制的工艺要求,通过对高铝质焊补料耐火原料的精心选择及其颗粒配比和燃料量的科学测算,用较少的焊补试验,经目测和理化指标测定,找出比较合适的组成配方,使其形成的焊补体各项性能指标接近或超过原炉衬高铝砖的性能指标,达到实际应用的技术要求.     

滑板式调节阀流场的数值模拟及性能预测

针对新型滑板式调节阀产品模型,采用基于各向同性涡黏性理论的k-ε双方程模型求解,获得了阀门内部流场不同开度下的压力场和速度场,预测了阀门出现空化现象的位置,建立了阀门的流量特性曲线和流阻特性曲线。通过研究发现,滑板式调节阀流通能力强,具有线性流量调节功能;阀门在小开度情况下,内部流场紊乱,存在大尺度的漩涡;仿真结果可为此类新型阀门的开发与优化提供了依据。     

Flux enhancement of thin film composite RO membrane by controlled chlorine treatment

A major stumbling block in polyamide thin film composite RO membrane performance is its incompatibility with chlorine and oxidizing agents. The amide bond of the membrane is highly vulnerable to chlorine attack. Two reactions are possible with chlorine exposure i.e. N-H bond chlorination and/or aromatic ring chlorination. In this way, chlorine may cause degradation/modification in the membrane leading to deterioration in performance.However, low concentration of chlorine up to a certain time may give synergistic effect on membrane and improve its performance. Chlorine solution, if exposed to membrane for certain time gives enhancement in trans-membrane flux of the membrane.The same solution if exposed for more time deteriorates ultra-thin polyamide layer of TFC membrane. Conspicuously, the membrane with poor salt rejection and flux benefited more as compared to the membrane with better performance. In the present study, membranes with different salt rejection and flux were taken and exposed to the inorganic chlorine solution. The inorganic chlorine solutions were made by dissolving sodium hypochlorite in pH buffer. The different solutions were made by varying pH to investigate the pH dependence. The membrane samples were kept in solution for different time durations. The exposure time was monitored and the exposure level was taken in terms of ppm h (ppm chlorine solution exposed to membrane for a fixed time in h). With the same chlorine concentration, effect of varying pH was studied. Spiral wound TFC membrane modules were also subjected to chlorine solution to study its effect.     

Dissolution behavior of spent MgO–C refractory in the CaO–SiO2–FeO slag system as a steelmaking flux

A large amount of spent MgO–C refractory is generated in steel plant every year. Because of the similarities in chemical and mineralogical composition of slag formers and MgO–C refractory, it is possible to reuse the spent MgO–C refractory as a steelmaking flux. To achieve this goal, it should promote the dissolution of MgO–C refractory during slag forming. In this study, the effect of slag composition on the dissolution behavior of spent MgO–C refractory in the CaO–SiO₂–FeO slag system and the dissolution kinetics were investigated. It showed that the dissolution rate of MgO–C refractory was controlled by surface chemical reaction. The dissolution of MgO–C refractory led to an increase in the MgO content in slag while the FeO content decreased because the graphite in refractory was oxidized by FeO. Increasing temperature significantly promoted the dissolution of MgO–C refractory. The MgO–C refractory was readily dissolved in the low-basicity slag. A higher FeO content in slag was beneficial for the oxidation of graphite in refractory, resulting in better dissolution. The dissolution thickness of MgO–C refractory could exceed 4.0 mm under these conditions and its dissolution supplied some MgO to slag.     

超滤法提取蛋清溶菌酶

对蛋清料液进行前处理:采用磷酸盐缓冲液稀释10倍,在24MPa压力下均质;对超滤工艺进行了研究,采用截留相对分子质量为30000的聚醚砜(PES)膜进行超滤;溶菌酶制品活力为14610U/mg.     

Flux modification for AC-TIG braze welding of aluminium to stainless steel

A modified flux consisting of KAlF₄ and aluminium powder was developed for AC-TIG braze welding of aluminium to stainless steel. By employing the flux, the arc instability and wetting angle was decreased significantly, and therefore a good joint shape was obtained. The wetting and spreading behaviour as well as the action mechanism of the flux were changed. Microstructure analysis suggested that the intermetallic compound (IMC) thickness increased obviously when the addition percentage of aluminium powder in the flux exceeded 40 wt-%. Results of tensile tests illustrated that a significant improvement in mechanical properties of the butt joint was obtained with the modified flux, and tensile strength increased from 125 to 170 MPa in maximum. Relationships between aluminium powder content in the flux and wetting angle, IMC thickness as well as tensile strength were established. Results indicated that the joint strength was affected both by weld shape and IMC thickness.