PTT／PP／PP-g-MAH共混材料的形态与性能研究

研究了马来酸酐接枝聚丙烯(PP-g-MAH)对聚对苯二甲酸丙二酯(PTT)/聚丙烯(PP)共混体系的形态结构和性能的影响。结果表明,PP在PTT连续相中分散均匀,粒子尺寸随着增容剂含量的增加而细化,分散相与连续相之间有较好的黏结作用,PP-g-MAH改善了PP与PTT的相容性。共混物熔体为假塑性流体,其假塑性随PP-g-MAH含量的增加而升高,熔体表观黏度从1．31 Pa·s降低到1．19 Pa·s,黏流活化能从64．5 kJ/mol降低到36．7 kJ/mol。共混物中PTT和PP可分别结晶,但结晶行为相互影响,PP-g-MAH促进了PTT在高温结晶。共混物的冲击强度随着PP-g-MAH含量的增加从14．2 kJ/m~2提高到33．5 kJ/m~2,拉伸强度在PP-g-MAH含量为5％～10％(质量分数,下同)时最大。共混物的热稳定性随着PP-g-MAH含量的增加而逐渐降低。     

线性双峰聚乙烯／低密度聚乙烯共混物的流变行为与力学性能

研究了线性双峰聚乙烯（LBPE）与低密度聚乙烯（LDPE）共混物溶体的流变行为，讨论了共混物的组成，剪切应力和剪切速率以及温度对熔体流变行为，熔体粘度的影响，测定了不同配比熔体的非牛顿指数（n)，熔体流动速率（MFR）及力学性能，为双峰聚乙烯的加工和使用提供了理论依据。     

临床血清循环miRNAs定量技术的建立

目的建立可靠的临床血清(浆)循环miRNAs定量技术。方法常规收集血清(浆)标本,mirVana PARIS试剂盒法抽提血清(浆)总RNA,采用DNaseI消化总RNA提取液,以miRNAs特异性茎-环引物引导反转录,通过TaqMan实时荧光定量PCR对U6及靶miRNAs进行检测。结果10份新鲜血浆总RNA浓度介于3.5～35.4ng/μl之间。对常规收集的400μl临床血清标本中U6、miR-16、miR-224均能实现特异扩增及定量,相应的平均Ct值约为30、25及32。6份不同留置时间血清标本总RNA浓度分别10.24和4.46ng/μl,定量PCR结果显示其中相应miR-16和miR-224的丰度却相对稳定。结论血清(浆)总RNA抽提及循环miRNAs定量切实可行。     

螺栓节点联结构件的等效优化分析

对工程中广泛使用的螺栓节点联结进行了详细分析,建立了螺栓联结节点的精细有限元模型,以刚度矩阵的误差最小为等效原则,在把节点处杆件的半刚性联接等效为杆端截面抗弯刚度下降的基础上,通过优化等效方法,得到了螺栓节点联结杆件的精细有限元模型与简化有限元模型的等效关系。     

远程控制系统在复烤厂中的应用

按照企业电控技改的原则 ,对烟叶复烤厂技改中生产线的电气控制方案进行综合分析和评价 ,以选择出最适合企业的控制形式。结合企业的实际情况 ,综合分析和评价后认为 :复烤厂电控系统适宜采用远程分站形式 ,配以标准化的编程 ,使设备控制层的程序规范化 ,便于现场设备和电控系统的维护与管理 ,提高和稳定产品的质量。     

Thermal degradation behavior and kinetic analysis of poly(L-lactide) in nitrogen and air atmosphere

The non-isothermal and isothermal degradation behaviors and kinetics of poly(L-lactide) (PLLA) were studied by using thermogravimetry analysis (TGA) in nitrogen and air atmosphere, respectively. At lower heating rate ((5–10)°C/min), PLLA starts to decompose in air at lower temperature than those in nitrogen atmosphere; however, at higher heating rate ((20–40)°C/min), the starting decomposition temperature in air are similar to those in nitrogen atmosphere, not only showing that PLLA has better thermal stability in nitrogen than in air atmosphere, but also suggesting that the faster heating rate will decrease the decomposition of PLLA in thermal processing. Whether in air or in nitrogen atmosphere, the decomposition of PLLA has only one-stage degradation with a first-order decomposed reaction, suggesting that the molecular chains of PLLA have the similar decomposed kinetics. The average apparent activation energy of non-isothermal thermal degradation (Ē_non) calculated by Ozawa theory are 231.7kJ·mol⁻¹ in air and 181.6kJ·mol⁻¹ in nitrogen; while the average apparent activation energy of isothermal degradation (Ē_iso) calculated by Flynn method are 144.0kJ·mol⁻¹ in air and 129.2kJ·mol⁻¹ in nitrogen, also suggesting that PLLA is easier to decompose in air than in nitrogen. Moreover, the decomposed products of PLLA are also investigated by using thermogravimetry-differential scanning calorimetry-mass spectrometry (TG-DSC-MS). In air atmosphere the volatilization products are more complex than those in nitrogen because the oxidation reaction occurring produces some oxides groups.     

茂金属聚乙烯(MPE)/线性低密度聚乙烯(LLDPE)共混熔体的流变学

研究了不同比例共混的茂金属聚乙烯 (MPE)和线性低密度聚乙烯 (LLDPE)熔体的流变学行为 ,讨论了共混物组成、剪切速率和剪切应力以及温度对熔体流变曲线、熔体粘度的影响 ,为MPE的共混改性提供了理论依据。结果表明 :随着LLDPE含量的增加 ,共混熔体的粘度降低 ,转变应力和非牛顿指数减小 ,粘流活化能升高 ,MPE的流动性和加工性能得到改善。     

Studies on the rheological,phase morphologic,thermal and mechanical properties of poly(trimethylene terephthalate)/ethylene propylene diene monomer copolymer grafted with maleic anhydride/metallocene polyethylene blends

The rheological, phase morphologic, thermal and mechanical properties of poly(trimethylene terephthalate)/metallocene polyethylene (PTT/mPE) blends in the presence of ethylene propylene diene monomer copolymer grafted with maleic anhydride (EPDM-g-MAH) as compatibilizer are studied by means of a capillary rheometer, scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and thermogravimetric analyzer (TGA). Results suggest that the compatibility of PTT/mPE blends is improved greatly after the addition of a compatibilizer. The radius of the dispersed phase in the system decreases greatly when the compatibilizer is added into the blend. When the amount of compatibilizer exceeds 8 wt-%, the size of dispersed phase becomes larger again. This phenomena could be attributed to the higher viscosity of the EPDM-g-MAH phase, which is dispersed more difficulty in the PTT phase of lower viscosity, thus the mixing efficiency is apparently decreased during the melt blending process. Moreover, the melt viscosity of the blend reaches the maximal value in case of 4 wt-% compatibilizer content, above which it would decrease again. This result is associated with the generation of more and bigger dispersed phase inside the bulk phase, thus the grafting efficiency at the interface is decreased, which could result in lower viscosity. The DSC results suggest that the mPE component shows a nucleating effect, and could increase the overall degree and rate of PTT crystallization, while the addition of a compatibilizer might slightly diminish these effects. In addition, the blend with 4 wt-% compatibilizer shows the best thermal stability. Furthermore, the Izod impact strength and the tensile strength at room temperature of the blend are also markedly improved by the addition of a 4 8 wt-% compatibilizer.     

GF／PTT复合材料的力学性能和流变行为

采用扫描电子显微镜(SEM)和毛细管流变仪研究了玻璃纤维(GF)/聚对苯二甲酸丙二酯(PTT)复合材料的界面性能和流变行为。结果表明,材料断面较整齐,纤维与基体界面粘接牢固而拔出较少,表现出较强的整体承载负荷能力。部分暴露的GF表面仍附着大量树脂,说明纤维与基体间的界面粘接性能很好,GF的界面处理效果较好。复合材料熔体在剪切作用下为假塑性流体,表观黏度随剪切速率升高而下降。在相同剪切速率下,GF含量增加,非牛顿指数n增大,熔体黏度逐渐变小,且都低于纯PTT熔体黏度。粘流活化能随GF含量的增加先增加后降低。     

基于群体智慧的Web访问日志会话主题识别研究

Web访问日志中的会话(session)是指特定用户在一定时间范围内的访问行为的连续序列。会话主题(topic)是指会话中具有相同用户意图的部分。从会话中进一步识别出能体现用户意图的处理单元(topic)是进行用户访问行为分析的重要基础。目前相关工作主要集中在边界识别上,无法处理用户意图交叉情况。为了解决该问题,该文重新形式化定义了session和topic的相关概念,提出最大划分的求解任务,并设计出了基于用户群体智慧的会话主题识别算法。在使用大规模真实Web访问日志的实验中,我们的算法取得了不错的效果。