Linear alkylbenzene

Linear alkylbenzene (LAB) was introduced in the mid-1960s as a raw material for cleaning products. Since then, continuing and explosive research on its biodegradation and on its environmental and human toxicity has been performed. The efficiency of linear alkylbenzene sulfonate as surfactant is clearly established, and it is one of the safest and most cost-effective products in widespread commercial use. The aim of the present paper is to survey the most important developments and understandings of the chemistry of LAB production and of its physical and environmental properties. The expected consequence of this analytical survey is to envisage the continuous challenges for the detergents industry in catalytic production of LAB, better control of selectivity, replacement of corrosive and mineral liquid acid catalyst by heterogeneous acid catalyst and the maintenance of competitiveness of LAB with respect to natural alcohols.     

Cometabolic transformation of linear alkylbenzenesulphonates by methanotrophs

Cometabolic transformation of commercial linear alkylbenzenesulphonates (LAS) and pure congeners of 2-[4-(sulphophenyl)]nonan (2C₉LAS) and 2-[4-(sulphophenyl)]decan (2C₁₀LAS) was studied by using a mixed methanotrophic-heterotrophic culture MM1 and a pure culture of type II methanotroph (strain CSC1), isolated from culture MM1. Cultures were grown in shake flasks under conditions promoting expression of the soluble methane monooxygenase (sMMO). Both the mixed culture MM1 and the pure culture CSC1 were capable of transforming LAS with or without methane as the natural substrate. Experiments performed without methane (resting cells) showed faster cometabolic transformation of LAS congeners with longer alkyl side-chains. Both 2C₉LAS and 2C₁₀LAS congeners were transformed significantly faster at 30°C, although the optimum temperature for the growth of mixed culture MM1 was 20°C. Simultaneous methane oxidation and LAS transformation, and their mutual competitive inhibition, indicated the involvement of the MMO enzyme system and possible methanotrophic activity in the initiation of cometabolic LAS transformation. The capability of two heterotrophic species to transform sulphophenyldecanoic acid suggests possible heterotrophic activity in further LAS transformation (β-oxidation). Faster LAS transformation by mixed culture MM1 than by pure culture CSC1 suggested that methanotrophic-heterotrophic interactions are important for transformation of the complex LAS molecule.     

混凝土排水管道工程闭气检验简介

简要介绍排水管道闭气检验的特点、闭气检验标准的试验原理、闭气检验的操作步骤及应用现状。     

浅谈水泥混凝土路面的防滑性能及原材料和施工工艺对其影响

应用各种施工工艺,改善和提高了水泥混凝土路面的防滑性能;探讨了原材料对防滑性能的影响。特别详细说明了(机械)刻槽工艺显著的路面防滑效果。     

Imaging the Detergency of Single Cotton Fibers with Confocal Microscopy: the Effect of Surfactants and Lipases

Detergency mechanisms of lipids from single cotton fibers were visualized by means of confocal laser scanning microscopy (CLSM). Fibers were soiled with different types of lipids: olive oil, lard and tri-C₁₀, and subsequently stained with the fluorescent probe Nile Red. A surfactant composition of 300 μM C₁₂E₆/LAS (1:2 mol%) was used to mimic the surfactants used in a common washing solution. It was evident from the captured image series that the different kinds of soiling were removed by different mechanisms by the surfactants, depending on the fluidity of the lipid. Roll-up was the main mechanism when removing olive oil, whereas emulsification (necking) and/or solubilization were observed in the removal of lard and tri-C₁₀. Only 20–25% of the olive oil remained after treatment with surfactants, which was much less compared to the solid fats where roughly 50% remained at end of treatment. The effect of adding lipases to the detergent formulation was clearly seen, both by an apparently higher rate of removal of olive oil but also using double injection when removing lard. A first injection of only surfactants removed a certain part of the lard as emulsion droplets stuck onto the fiber. A second injection of both lipases and surfactants was able to remove some of the preformed emulsion particles and reduce the overall remaining lard content on the cotton fiber.

在氢环境中16Mng钢的短裂纹低频疲劳特性

研究了在氢环境中１６Ｍｎｇ钢的低频短裂纹扩展规律。应用弹塑性断裂力学和△Ｊ参数,用ｄａ／ｄＮ＝Ｃ（△Ｊ）ｎ计算裂纹的扩散速率。结果表明ｄａ／ｄＮ～△Ｊ关系曲线分三个阶段;并得到了在氢环境中裂纹扩展的门槛值△Ｊ（ｔｈ）。用金相法考察了裂纹扩展的途径。     

神经网络模型与时差方法结合预报铁水硅含量

针对以ＢＰ算法为代表的监督学习神经网络在直接多步预测中不能渐进计算的问题,建立了一个三层简单反馈递归的神经网络模型,提出了将神经网络模型与时差方法相结合在高炉铁水硅含量预报中应用的策略。结合现场采集的实时数据进行实验,并与采用ＡＲＭＡＸ模型的预测结果相比较,具有较高的命中率。     

反对称铺设的单曲率椭圆形壳结构双稳态性能研究

通过垂直于圆柱壳方向的圆柱截取反对称铺设的双稳态圆柱壳结构的方法,可得到一种新型 的单曲率椭圆形双稳态壳结构,此结构具有伸展和卷曲两种稳定状态．通过最小势能原理对双稳态 椭圆形壳结构进行理论研究,得到其卷曲半径理论解,并与有限元模拟结果进行对比来研究不同参 数,包括截取半径、圆柱壳的初始半径、铺设层数和铺设角度等对椭圆形壳结构的双稳态特性的影 响．在研究双稳态椭圆形壳结构的过程中,通过对截取半径、圆柱壳的初始半径、铺设层数和铺设角 度等参数的不同设计,可以得到其不同的双稳态形状,可指导新型的双稳态椭圆形壳结构的制备及 应用．     

机械振打除灰中煤灰颗粒脱落的实验研究

为了探究煤灰颗粒从金属板上脱落的影响因数,自建实验平台,记录了煤灰颗粒振打脱落过程以及每次振打中煤灰脱落质量,探究了机械振打除灰中振打敲击力大小对振打除灰的影响,以及不同煤灰厚度对最小有效振打力的影响. 结果显示,在振打冲击金属板时,煤灰颗粒脱落存在“分层现象”和“分阶段现象”,而且随着振打力的增加各阶段之间的分界越模糊;煤灰颗粒脱落的质量向前几次振打冲击集中;煤灰的厚度越大,最小有效振打力越小,当煤灰厚度为１ ｍｍ、２ ｍｍ、３ ｍｍ和４ ｍｍ时,最小有效振打力分别为６５．３ Ｎ、３６．９ Ｎ、２５．９ Ｎ和１７．０ Ｎ.     

纸币清分系统中光电图像实时采集方法

纸币图像实时采集是纸币清分系统自动化工作的首要任务．利用现场可编程门阵列并行控制技术,实现了纸币图像光电转换、模数转换、数据缓存等功能,为纸币清分系统实现真伪辨别、纸币分类、残币识别、冠字号提取等功能提供实时清晰的纸币图像数据．选用三段式多光源接触式图像传感器采集纸币的光感电压信号,经过模数转换电路,每行三段数据同时拼接成一行,每张纸币采集５００行,组成一幅完整的纸币图像送到高速存储器进行缓存．经仿真分析与实验板验证,采用本系统进行纸币图像采集可以实现1 min采集约１　３８２张纸币图像,具有很好的实时采集效果．