硅酸钠表面施胶改善纸张防水性能的机理探讨

分别利用硅酸钠、硅酸钠与淀粉复配进行纸张表面施胶,表面施胶体系中有机硅油用量控制为3%(相对于硅酸钠绝干质量);探讨了施胶量和施胶体系对纸张孔隙率、纸张平均孔径、表面平滑度、Cobb30值和表面接触角的影响;依据毛细管现象公式,探讨及分析了表面施胶纸张的防水机理;利用扫描电镜(SEM)观察分析了表面施胶纸张的表面形貌。结果表明,硅酸钠-淀粉复配体系中,淀粉最佳用量为33%;随着表面施胶体系施胶量的增加,表面施胶纸张的孔隙率和平均孔径均下降;经硅酸钠和硅酸钠-淀粉复配表面施胶后,纸张的表面接触角较原纸大幅提高且硅酸钠-淀粉复配体系对纸张抗水性的改善效果优于硅酸钠。此外,研究还发现,纸张平均孔径的降低、表面接触角的增加及胶层在纸张表面的覆盖是硅酸盐及其复配体系表面施胶纸张产生抗水性的主要原因。     

胡椒粉中胡椒碱两种测定方法的比较

本文采用了无水乙醇回流法及无水乙醇超声提取法两种处理方法后分别利用液相色谱仪、紫外分光光度法两种检测方法检测胡椒粉中的胡椒碱含量,通过比较确定了超声提取加液相色谱法是一种适宜实验室推广的方便、高效、准确的检测方法。     

Optimal operation of an integrated bioreaction–crystallization process for continuous production of calcium gluconate using external loop airlift columns

A kinetic model was proposed to optimize the integrated bioreaction–crystallization process newly developed for production of calcium gluconate crystals using external loop airlift columns. The optimal operating conditions in the bioreactor were determined using an objective function defined to maximize the productivity as well as to minimize biocatalyst loss. The optimization of the crystallizer was carried out by matching the crystallization rate to the optimal production rate in the bioreactor because the bioreaction was found to be the rate controlling process. The calcium gluconate productivity under the optimal conditions of the integrated process was obtained by the simulation based on the process model. The productivity of the proposed process was found to be comparable to that of the current batch fermentation process.     

多余约束横梁直线振动筛的设计与分析

针对振动筛在使用过程中容易发生侧板撕裂及横梁断裂等问题,设计了新型多余约束横梁直线振动筛。并分析了振动筛的动力学特性,得出改进横梁后的筛体变形变小,筛体整体刚度增加。     

青霉菌B01 产菊粉酶特性的研究及菊粉酶系分析

研究了pH 值、温度、底物浓度、金属离子对青霉菌(Penicillium sp.)B01 所产胞外菊粉酶活性的影响以及酶活随反应时间的变化情况。结果表明,pH4.6 时菊粉酶活力最大,最适反应温度是55℃。在pH3.6～5.4 的范围内,60℃以下酶活较稳定。Ca2+ 对菊粉酶有激活作用,而Cu2+ 对其活性强烈抑制。采用活性聚丙烯酰胺凝胶电泳法(PAGE)对该酶粗液进行蛋白质分析,获得较清晰的6 条蛋白谱带;2,3,5- 氯化三苯基四氮唑(TTC)活性染色结果显示,只有3 条谱带表现为具有菊粉酶活性。对酶解产物用薄层层析(TLC)和高效液相色谱(HPLC)法的分析结果,进一步证实这3 条谱带具有菊粉酶活性,并确定其主要为外切型菊粉酶,产物主要为果糖。     

溶剂极性对2-溴异丁酰溴修饰凹凸棒石粘土效果的影响

研究了溶剂的极性对2-溴异丁酰溴修饰凹凸棒石粘土效果的影响。流变学测试结果表明,凹凸棒石粘土和2-溴异丁酰溴间的作用受溶剂极性的影响,在极性较大的环氧丙烷和环氧己烷中2-溴异丁酰溴修饰凹凸棒石粘土效果优于极性较小的正辛烷溶剂。     

Green emission from Cr,Dy co-doped sol–gel SiO2 glasses

Silica glasses singly doped and co-doped with Cr ions and Dy ions have been prepared by sol–gel method and their photoluminescence (PL) properties have been studied. The emission spectrum of Dy singly doped sample shows a band around 450 nm with a shoulder band around 480 nm, Cr singly doped sample consists of three bands around 450, 530 and 620 nm, and Cr, Dy co-doped samples show two bands around 450 and 530 nm. The relative PL intensity of the green emission at 530 nm in co-doped samples increases greatly compared with the singly doped. These two bands at 450 and 530 nm are respectively assigned to the defects in silica network and a complex luminescence centers associated with Cr ions. The quenching effect of metal ions and energy transfer process could be responsible for the change of PL properties in the co-doped samples.     

原子荧光法测定工业硫酸中砷含量

采用HG—AFS法对工业硫酸中的砷含量的测定方法进行了研究,对优化HG—AFS法的测定条件进行了探讨。本方法枪出限为0．022ug/L,试样的加标回收率范围为92．2％～106．3％。测定过程中体系的酸度对测定结果有一定的影响,砷的荧光强度随着酸度的增加而增大,当体系酸度在5％左右时,测定结果相对稳定。结果表明,本实验方法具有检出限低、精密度和准确度高、操作简捷等特点。     

Effect of clay and PEO-PPO-PEO block copolymer on the microstructure and properties of cyanate ester/epoxy composite

In this study, processing, morphology and properties of poly (ethylene oxide)-block-poly (propylene oxide)-block-poly (ethylene oxide) (PEO-PPO-PEO) triblock copolymer and clay modified cyanate ester/epoxy hybrid nanocomposites were investigated. The PEO-PPO-PEO triblock copolymer preferentially reaction-induced microphase separate into spherical micelles in the cyanate ester/epoxy matrix. PEO-PPO-PEO was used as both nanostructuring agent for cyanate ester/epoxy blended resin and thus the predominantly intercalated and few exfoliated platelets of were also observed with clay, which successfully reduced the brittleness of the cyanate ester/epoxy blended resin increasing the toughness of designed materials. The stiffness and heat resistance of the neat BCE/EP resin could be retained in the BCE/EP/F68/clay hybrid nanocomposites. The optimum property enhancement was observed in the hybrid nanocomposites containing 5 wt% PEO-PPO-PEO and 3 wt% clay. The thermo/mechanical properties of the hybrid nanocomposites depend on microstructure, dispersion state and the ratio between organic and inorganic modifiers content.     

电流驱动共模模型对辐射噪声预估及校准研究

开阔场测试、电波暗室测试和近场测量是目前用于测量辐射电磁噪声的主要手段,但是考虑到成本原因,对辐射噪声的预估往往采用近场测量．美国克莱姆森大学的Hubing教授提出的电流驱动共模模型可以对辐射噪声进行预估．如加之方差的拟合校准,可以对数据进行补偿．结果证明了以上方法可以为进一步改进辐射电磁干扰预估方法提供借鉴．