Characteristics of carboxymethyl cellulose synthesized in two-phase medium C6H6?C2H5OH. I. Distribution of substituent groups in the anhydroglucose unit

Carboxymethyl cellulose was synthesized in two-phase medium containing benzene, ethanol, and water. The distribution of substitution of hydroxyl group attached to C_k Carbons (k = 2, 3, and 6) in an anhydroglucose unit (AGU) was determined by ¹H-NMR method. It showed that the sequence of distribution of carboxymethyl group of the products in AGU was C₆ > C₂ > C₃; and when degree of substitution (DS) was low to 1.0, the approximate value of C₂: C₃: C₆ was 1.45: 1: 2.15. When DS was higher than 1.0 and increased, the distribution of substitution tends to identical. Through analysis of X-ray diffraction and calculation of crystallinity and interplanar distance of CMC, the principle of distribution of the substituent had been explained. The influence of benzene on distribution of substituent of CMC was also investigated. It was found that distribution of substituent of CMC prepared in medium benzene-ethanol at C₆ position was higher than that prepared in ethanol. © 1996 John Wiley & Sons, Inc.     

半逆流型磁选机在梅山选矿厂的应用

2004年梅山选矿厂在降磷弱磁作业7#系列采用半逆流型磁选机代替顺流型磁选机,试验表明,其精矿品位、金属回收率均高于6#系列,尾矿品位低于6#系列.本文分析了两种磁选机的工作原理,指出了应用中存在的问题,并提出了解决方法.     

核电厂聚乙烯管道设计方法及标准简介

随着聚乙烯管道在三门核电厂、大亚湾核电厂中的试应用成功,大量的新建核电厂及核电厂改造项目均将聚乙烯管道作为海水冷却水管道系统的首选管材,自主研制核电厂聚乙烯管技术标准迫在眉睫。本文介绍了核电聚乙烯管道的发展历史和应用现状,对比了核安全3级聚乙烯管道和非核安全相关聚乙烯管道、城市燃气与给水聚乙烯管道技术标准的设计方法及适用范围,探讨了中国目前聚乙烯管技术标准与核3级聚乙烯管道技术标准的差异与差距,为核电厂聚乙烯管道的设计制造与标准研制提供参考。     

Selective dissolution of rare-earth element carbonates in deep eutectic solvents

Dissolution in choline-chloride based deep eutectic solvents(DES) of rare earth elements(REE) from high-purity single carbonate salts of Y, La, Ce, Nd and Sm and from their multicomponent mixtures and also bastn€asite mineral was assessed with a prospect to gain an understanding on the leaching behavior of bastn€asite ores as REE source from DES suspensions. Urea, malonic acid and citric acid were used in different proportions with choline chloride in order to form deep eutectic solvents with desired viscosity and functionality. The results obtained prove promising for use insolvato-metallurgical processes in terms of selective dissolution of the higher-atomic-number(Z) rare earth elements at the expense of the lower-ZREEs and the gangue-originating metal impurities, thus initiating separation among the different REE members from the early hydrometallurgical steps.     

电厂空预器吹灰改造与研究

空预器作为我国大型火力发电厂重要组成部分,其高效、稳定的运行对于火电机组而言具有十分重大的意义.当前,我国大部分火电机组均存在空预器堵塞现象,严重影响到锅炉安全、经济运行,为此,本文基于宝庆发电公司660MW机组三分仓容克氏空预器吹灰改造展开研究,对变工况下空预器吹灰改造前后差压变化做出对比分析,以及对定工况下空预器烟...     

工业CT系统中射线源的精确定位

为了实现工业CT系统射线源的精确定位,设计了射束中心位置测试专用装置,并开发了测试程序.利用该装置对两套工业CT系统进行了测试,修正了射线源的位置,精度达到士0.1mm.结果表明,利用该装置对射线源进行定位后,获取的图像质量有明显改善,并能够降低射线源位置调节机构的设计难度.     

球形样件轮廓度工业CT精确测量方法研究

详细介绍了封闭体内球形样件轮廓度工业CT精确测量方法,在获得球体样件CT断层图像的基础上,利用CT插值方式提取球体样件的轮廓线边界系列CT值,再根据二次曲线逐次逼近拟合法获得其圆心坐标及平均半径,建立了封闭体内球形样件轮廓度及壁厚的工业CT精确测量方法,并编制了专用测量软件用于实际球形样件轮廓度的测量,比较该方法及三坐标法对不同直径、不同壁厚系列球体模拟件测量结果,在95%置信度下,测量精度达到0.05mm.     

高效液相色谱法测定食品中的酸性橙Ⅱ

建立食品中非食用色素酸性橙Ⅱ的高效液相色谱快速检测方法。样品用饱和乙腈提取,经饱和正己烷萃取除去油溶性色素及杂质,采用高效液相色谱柱分离,二极管阵列检测器(DAD)检测,结合标准物质保留时间和DAD光谱图进行定性分析,外标法定量。色谱柱为AgilentZORBAXSB-C18(150mm×4.6mm,5μm),流动相为乙腈-体积分数0.3%醋酸溶液进行梯度洗脱,检测波长为484nm,线性范围为0.01～1.0μg/mL,相关系数R2=0.9997。采用本方法对乳制品、辣椒粉、辣椒酱、卤肉制品、卤蛋、卤豆腐干6种常见基质进行验证,结果表明,HPLC-DAD测定食品中的酸性橙Ⅱ,对于1.0g样品定容至5mL、进样量为20μL时,检出限为0.05mg/kg;添加标准回收实验表明,本方法在添加水平分别为0.05、0.1、0.2mg/kg时的样品平均回收率在74.9%～100.0%之间,相对标准偏差(RSD)在1.41%～8.64%之间(n=6)。本方法准确、可靠。     

基于功效系数法的采空区稳定性判别方法研究

矿石开采后遗留下的采空区,对矿山而言始终是一种安全隐患,采空区的稳定与否关系到矿山的生产安全.本文根据矿山的实际情况,选取了5个最能充分反映采空区特征的参数作为评价指标,并基于变异系数法的客观性以及功效系数法的简单高效性,提出一种功效系数法采空区稳定性判别模型,并结合数值分析方法对某矿山7个采空区稳定性进行了判别与对比...     

Effects of Oxidation Curing of Polycarbosilane on Dielectric and Microwave Absorption Properties of PDCs‐SiC Ceramics

Polycarbosilane (PCS) was cured by oxidizing at different temperatures and pyrolyzed at 1000°C in vacuum. The dielectric properties of SiC ceramics were studied in X band. The ε′ and ε″ of SiC ceramics derived from oxidation‐curing PCS decreased to 4 and 0.35, respectively, which attribute to the decrease of free carbon content and order. SiC ceramic derived from PCS cured at 180°C showed that reflection loss was lower than ?10 dB in the frequency range from 8.2 to 11.3 GHz and the minimum value was ?26.7 dB at 9.6 GHz, which exhibits a promising prospect as microwave‐absorbing materials.