表面涂装的辐射加热

以辐射加热为主完成表面涂装的热固化,既可缩短加热时间,减少产品电能单耗,又可作到被烘工件受热均匀,提高产品质量。本文介绍了这种加热技术和方法。     

中温固化高强度环氧基体及其复合材料性能研究

本文对曾用于直升机复合材料旋翼桨叶的高强度环氧树脂基体及其复合材料性能进行了深入的研究工作。测定了单向玻璃纤维复合材料的九个工程常数和动态模量随着温度升高(20～80℃)的变化。从桨叶取样的测试数据看,Y—2复合材料的某些力学性能均优于国外同类的BO—105桨叶用复合材料。湿热老化试验表明,Y—2复合材料在45℃和90±5%湿度情况下经过3000小时老化后其强度与模量下降不到10%。对树脂基体,除了一些常规的力学性能外,还测定了四种谱图和改进了它的阻燃性能。     

波谱分析技术在淀粉研究中的应用

近年来随着对淀粉研究的深入,波谱分析技术在淀粉研究中的使用日益广泛。文中综述了近年来红外傅里叶光谱、核磁共振和紫外可见光谱这些波谱分析技术在淀粉研究中的应用。着重阐述了其在淀粉颗粒结构、糊化过程、水解程度及变性过程分析等方面的应用,为淀粉及其衍生物在不同领域的应用提供相关的信息。     

多元线性回归设计玉米须β-谷甾醇的提取

建立了玉米须β-谷甾醇测定方法及热回流提取的多元线性回归模型,实验分别考察了提取温度、时间、液固比及乙醇浓度对β-谷甾醇含量的影响,并通过多元线性回归设计了热回流提取模型。结果表明,β-谷甾醇测定方法准确可靠,可以用于玉米须中的β-谷甾醇的测定。同时乙醇提取玉米须β-谷甾醇多元线性回归模型显著,不失拟。玉米须β-谷甾醇的最佳工艺参数为提取温度45℃、时间80min、液固比25∶1、乙醇浓度75%,其中β-谷甾醇的提取率可达1.52%。     

Ultrasonic assisted enzymatic digestion (USAED) coupled with high performance liquid chromatography and electrothermal atomic absorption spectrometry as a powerful tool for total selenium and selenium species control in Se-enriched food supplements

The suitability of hyphenated USAED with HPLC separation and ET-AAS determination as a new rapid methodology for Se control in Se-enriched food supplements is demonstrated. Total Se determination and Se speciation are accomplished in a single sample treatment using low sample amounts (ca. 10 mg), and low extracting volume (1 mL). The total Se content in seven of the 10 Se-enriched supplements studied was in agreement with the values obtained after microwave pressurized acid digestion, MW, (test t, p = 0.05). The Se species studied were Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂, being some of the most common found in the 10 supplements studied. Although SeMet was the Se species expected to be present at the highest concentration in most Se-enriched food supplements, we detected it in only three of the 10 samples studied. In the other seven samples, two of them had Se(IV) as the main Se species. The other five supplements had Se species that did not match with any of the five standards selected by us. We have also systematically demonstrated that ultrasonication does not alter the following Se species: Se(IV), Se(VI), SeMet, SeMeSeCys, and SeCys₂. The new procedure can be easily adapted to more Se species and can be routinely used for Se control in Se-enriched food supplements. Concerning the supplements studied, our results suggest that stricter control on the Se content in enriched food supplements in terms of Se species will need to become mandatory.     

混凝土施工中常见几个质量问题

文章对钢筋混凝土的组成材料要求、施工技术、养护管理要求进行分析,从而达到节约资源,减少重复投资,实现工程建设的目标.     

Curing Behavior of Epoxy Resin Using Controllable Curing Agents Based on Nickel Complexes

Summary: The curing reaction kinetics and mechanism of the diglycidyl ether of bisphenol A (DGEBA) with three complexes of Ni(II) with diethylentriamine (Dien), Pyrazole (Pz) and Pyridine (Py) as ligands have been studied using differential scanning calorimetry (DSC). The curing reaction was characterized by high cure onset and peak maximum temperatures. The kinetics of the curing reaction were evaluated using the Ozawa method. The average values of activation energy for the three nickel complexes increased in the order: Dien‐based curing agent > Pz‐based curing agent > Py‐based curing agent. Three main curing mechanisms (catalytic, complex cation and free ligand polymerization path) have been proposed depending on the cure temperature. It was also shown that the cure kinetics of DGEBA with Dien‐ and Py‐based complexes could be described by the Sestak‐Berggren equation. The water absorption, chemical resistance and thermal stability of the thermosets were also studied. The results showed that the thermoset obtained with the Py‐based complex was more thermally stable than those obtained with the other two curing agents.

Activation energy versus conversion plots for the epoxy systems studied.     

DU-730紫外／可见分光光度计的应用研究

发表此文章的目的是向读者介绍一台国际先进水平的光谱仪器-美国BECKMAN（贝克曼）公司生产的DU-730紫外／可见分光光度计,它性能优良、应用广泛、操作简便,是生物医学实验室中非常实用的计量仪器。本文首先阐述了DU-750紫外／可见分光光度计的结构和原理,特别是这台仪器具有的先进的“微聚焦光束技术”。然后,介绍了仪器的各种主要技术参数,重点讨论了仪器的功能和所涉及的应用领域,包括：全波长扫描、固定波长测定、单一组分分析和蛋白质核酸的生物学测定等。最后作者为加强仪器的管理阐述了仪器的正确使用方法与维护,为正在应用这台仪器的读者提供一些有用的经验。     

Fabrication of carbon nanotube arrays for field emission and sensor devices by nanoimprint lithography

This work brings forth the idea of incorporating insulation in the resist used for ultraviolet (UV) curing nanoimprint lithography (NIL). Carbon nanotubes (CNTs) are grown in the space between two insulated resist patterns on the conductive substrate to make CNTs arrays. Two imprinting processes, soft UV curing NIL with DRPPR process and novel NIL without cured residual resist, are presented to achieve the insulation patterns. First the fabricating process is performed using a polydimethylsiloxane (PDMS) stamp. Subsequently, inductively coupled plasma (ICP) is essential to wipe off the residual resist film. To avoid the ICP process, a novel UV curing NIL is presented. Its special hard quartz stamp with chrome shelter can protect the residual resist film out of curing during the UV exposure process, and the uncured resist can be easily removed by ultrasonic vibration in organic solutions. The CNT arrays are prepared on the patterned substrates by the pyrolysis of iron phthalocyanine (FePc). Field emission experiments reveal that the turn-on field of those CNTs arrays is low to 1.3 V/um.