Microanalysis of supersaturated gas release based on wall-attached bubbles

Supersaturation of dissolved gases in natural water, due to spillage from high dams and other factors, may cause fish mortality. In previous experiments, the dissipation coefficient has been used to denote the degassing process of total dissolved gas(TDG) saturation. These experiments mainly analyzed supersaturated TDG dissipation from a macroscopic view. To precisely clarify the mechanism of supersaturated TDG release, this study investigated bubble adsorption at a wall surface from a microscopic view. The experiment was conducted in a Plexiglas-wall container filled with supersaturated TDG water. A model that calculates the adsorption flux of supersaturated TDG by a solid wall, and helps describe construction for a contact angle at a three-phase intersection, was developed according to Young's equation. This model was used to investigate the formation process of bubbles adsorbed on a solid polymethyl methacrylate(PMMA) surface in supersaturated TDG water. The adsorption effect of a solid wall on TDG release was analyzed based on the experimental data. The modeling results were compared with observations under different wall area conditions, and it was found that TDG release tended to increase with wall area. This study helps improve our understanding of the mechanisms of supersaturated TDG release and provides an important theoretical method for accurate calculation of the release process. The adsorption flux model of the solid wall provides mitigation measures to combat the adverse effects of TDG supersaturation,which will be beneficial to the protection of aquatic organisms in hydropower-regulated rivers.     

微波消解-分光光度法快速测定水中总磷

采用过硫酸钾-微波消解系统,以磷钼蓝分光光度法测定水中总磷,通过实验确定最佳消解及分析条件。结果表明,该方法准确、快速、简便,适于环境水样中总磷测定。     

论糖蜜稀释对煮糖的影响

糖蜜稀释在制糖企业生产当中起着举足轻重的作用,稀释的好坏程度关系到糖膏煮制的结晶率和结晶速度的提升,是制糖企业提升综合实力的重要因素.本文通过强化糖蜜稀释工作,进行不同的实验对比分析糖蜜稀释对乙、丙糖膏结晶率、煮炼时间等因素的影响,论述重视糖蜜稀释工作的重要性.     

赤砂糖中二氧化硫含量测定的不确定度分析

采用GB 5009.34-2016《食品安全国家标准食品中二氧化硫的测定》中蒸馏法对赤砂糖中二氧化硫进行测定,分析该方法不确定度来源,对不确定度各个分量进行评估.结果表明,测定赤砂糖中二氧化硫含量不确定度的主要来源为标准滴定溶液消耗的体积和重复性测量,当二氧化硫含量为0.053 g/kg时,扩展不确定度为0.0034 ...     

紫外分光光度法测定水体总氮的影响因素

本文就紫外分光光度法在测定水体总氮中易影响测定工作的几个方面做了阐述,并提出了改进意见     

全变分自适应图像去噪模型

通过分析三种主要变分去噪模型(调和、全变分以及广义全变分模型)的优缺点,提出了一种基于全变分的自适应图像去噪模型。该模型根据噪声图像的信噪比,采用高斯滤波器对图像进行预处理,克服了全变分模型引入的阶梯效应;利用图像中每一像素点的梯度信息,自适应选取去噪模型中决定扩散强弱的参数p(x,y),使接近边缘处平滑较弱,远离边缘处平滑较强。数值实验表明,本方法在去除噪声的同时保留了图像的细节信息,取得了很好的降噪性能,其峰值信噪比(PSNR)在高噪声水平下,较其他变分方法至少提高1.0dB左右。     

A novel Electro-Fenton-Like system using PW11O39Fe(III)(H2O) as an electrocatalyst for wastewater treatment

A novel Electro-Fenton-Like (EFL) system was developed using the Keggin-type iron-substituted heteropolytungstate anion PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ to substitute for Fe³⁺ in the conventional Electro-Fenton (EF) system for treatment of water polluted with organic compounds. The EFL system overcomes the drawback of low pH in conventional EF approaches and can be directly applied to neutral water treatment without any pH adjustment. Experimental results for dimethylphthalate (DMP) revealed complete degradation in <80 min in pH 6.86 solution containing 0.1 mM DMP at a potential of −0.5 V and O₂ flow rate of 60 mL min⁻¹. Total organic carbon removal of ∼56% was achieved at 120 min. Comparison with conventional EF oxidation revealed better efficiency of the present system for DMP degradation, suggesting its potential in treatment of water and wastewater with a relaxed pH requirement. The cumulative H₂O₂ concentration generated in situ at the electrode was monitored and the observed degradation rate constants k_obs were determined for different initial DMP concentrations. The ligand exchange reaction of PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ with H₂O₂ and the electron transfer resulting in hydroxyl radicals were examined using HPLC and electrochemical impedance spectroscopy. An electrocatalytic model involving inner-sphere electron transfer and a reaction mechanism for PW₁₁O₃₉Fe(III)(H₂O)⁴⁻ electrocatalytic reduction of H₂O₂ are proposed.     

Optimization of Enzymatic Process Condition for Protein Enrichment,Sugar Recovery and Digestibility Improvement of Soy Flour

Soy protein is a valuable nutritional supplement for food and animal feed. While protein constitutes ~50 % of defatted soy flour (SF), it coexists with complex carbohydrates (30–35 %) which may have anti‐nutritional effects. An enzymatic process can remove the carbohydrate and produce protein‐enriched soy products. The hydrolysate with monomerized carbohydrates is valuable fermentation feedstock. In this study, Aspergillus niger and Trichoderma reesei enzymes were compared for use in the process. Effects of pH (3.2–6.4), temperature (40–60 °C), enzyme‐to‐SF ratio (0–2 ml/g) and SF loading (150–350 g/l) were evaluated for the enzymatic conversion of SF carbohydrate to reducing sugar (Y_RS) and total soluble carbohydrate (Y_TC) in the hydrolysate. Effects of these single factors and interactions between factors were investigated. Optimal pH and temperature were similar for both enzymes: pH 4.8 and 50–51 °C for Y_TC, and pH 5.1–5.2 and 48–51 °C for Y_RS. The two enzymes also gave similar protein contents in resultant soy protein concentrates, i.e., 74–75 % with 2 ml/g enzyme broth and 150 g/l SF, which were higher than the 64–68 % protein in commercial concentrates. A. niger enzyme was significantly more effective in carbohydrate conversion, achieving Y_RS = 75 % and Y_TC = 78 % with 2 ml/g enzyme and 150 g/l SF, higher than the Y_RS (30 %) and Y_TC (64 %) obtained with T. reesei enzyme. Monomerization was essentially complete in hydrolysate produced with A. niger enzyme.     

过程控制中传感器静态性能指标的标准化研究

本文从标准化研究工作角度对目前过程控制中传感器重复性和线性度及总精度指标的确定中比较常见的几种方法进行了情况分析,指出从标准的角度提高过程控制中传感器重复性和线性度及总精度性能指标的科学合理的措施,进一步说明了标准的重要性。     

提高CCD糖液浓度测量系统精度的方法

为了实现糖液浓度的在线精密测量,在分析CCD测量原理的基础上,开发了基于ARM的糖液浓度测量系统,并分析了测量系统误差及对精度的影响;通过研究CCD信号边缘梯度特性,应用多项式插值的亚像素边缘检测算法提高了像素定位精度。实验结果表明,与传统的折光仪相比,该系统具有较高的分辨率和测量精度。