Improvement of Mechanical Properties and Ultraviolet Resistance of Polyethylene Pipe Materials Using High Density Polyethylene Matrix Grafted Carbon Black

In recent years, high grade high density polyethylene (HDPE) pipe materials are being more and more widely used for water and gas supply. Carbon black (CB) is usually used as an anti-UV-light reagent for pipe materials. However, homogeneous dispersion of CB in the HDPE matrix and modification of the interface has always been a great challenge. In this work, HDPE matrix grafted CB (HDPE-g-CB) was successfully prepared through HDPE radicals formation by a thermo-mechanical method and subsequent radical capture by the CB surface. The weight percentage of grafted HDPE approached 10 wt% and the modification sharply reduced the surface free energy of the CB. The SEM (scanning electron micrographs) and TEM (transmission electron microscopy) results showed that HDPE-g-CB was uniformly dispersed in the HDPE pipe materials and the domain size of the dispersed phase was remarkably decreased from that in HDPE/CB. Therefore, compared with the HDPE/CB, the mechanical properties and ultraviolet (UV) resistance of HDPE/HDPE-g-CB were significantly improved, positively influencing the expected life span of pipelines.     

高速互连设计中耦合微带线间的串扰分析

在高速互连设计电路中,耦合微带线间的串扰是影响电路性能和稳定性的主要因素.为了降低线间串扰,添加有接地过孔的防护线对减小串扰起到了很好的作用.在维持3条线(防护线和两条微带线)中两两之间的中心距不变的情况下,加大防护线的宽度,可有效减小线间的远端和近端串扰.利用FDTD方法对该结构进行模拟,给出了接地孔的有效放置方法.     

EBG结构在PDS设计中的应用研究

提出了一种利用电磁带隙(Ectromagnetic Band Gap,EBG)结构来有效抑制同步开关噪声(SSN)的方法,并应用到具体电路设计中来减小同步开关噪声.仿真结果表明,利用EBG结构来抑制同步开关噪声,可获得比传统电源分配系统设计中单纯加去耦电容更好的效果.     

A new activity phase in Hongqi brown coal liquefaction

The higher coal conversion yield is associated with the greater γ-Fe/Fe_1−x S ratio in Hongqi brown coal liquefaction. The γ-Fe species possesses higher catalytic activity than Fe_1−x S. Formation of γ-Fe species during liquefaction is related with the dispersity of iron in the coal.     

高吸湿接枝淀粉的研制与性能

本文运用回归正交的设计方法,以单体浓度、引发剂浓度、反应温度为三因子对丙烯腈、淀粉的接枝工艺进行了优化,得到并分析了接枝率、接枝效率的等高线图.同时考虑了 pH 值,淀粉的预处理对接枝工艺的影响.另外对 H-SPAN 作为卫生材料存在的吸水速率、产品状态、保水率等问题进行了分析改进.借助红外光谱图分析,表明接枝是有效的,并且皂化后产品无丙烯腈毒性。最后还报导了 H-SPAN 的一些吸水性能。     

利用数字式谐波反馈实现交流磁测量磁通波形正弦

在磁通正弦条件下进行软磁合金交流磁性测量可以获得高准确度的测量结果.利用数字式谐波反馈原理,通过对磁通波形的分析获得了磁通波形中的谐波含量,然后在电源输出端补偿与磁通波形中谐波幅值相反、相位相同的谐波,使磁通波形得到了改善.通过对硅钢样品在不同磁化程度时的测量,检验这一方法.当硅钢样品磁化为1.87T时,经谐波反馈后次级电压的波形系数也能满足国家标准的要求.     

基于多元自适应回归样条的高维岩土工程问题分析

为解决岩土工程中多元变量间的非线性相关问题,采用一种非参数回归算法——多变量自适应回归样条建立对目标参数的预测模型。该算法基于大量可靠的岩土监测数据,运用简单线性样条函数的组合对输入、输出参数进行相关性拟合,生成显性表达式,同时得到各输入参数的相对重要性。通过桩的可贯入性、地下洞室稳定性分析2个实例,对该方法进行评估。2个实例中测试集的决定性系数R~2分别为0.921和0.986,最重要的输入参数分别是桩材料的弹性模量和围岩质量,表明该方法可较精确地拟合多元输入参数与输出参数间的相关性,可用于未知响应的预测。     

Molecularly imprinted monoliths: Recent advances in the selective recognition of biomacromolecules related biomarkers

Biomarkers are significant indicators to assist the early diagnosis of diseases and assess the therapeutic response. However, due to the low abundance of biomarkers in complex biological fluids, it is highly desirable to explore efficient techniques to attain their selective recognition and capture before the detection. Molecularly imprinted monoliths integrate the high selectivity of imprinted polymers and the rapid convective mass transport of monoliths, and as a result, are promising candidates to achieve the specific enrichment of biomarkers from complex samples. This review summarizes the various imprinting approaches for the preparation of molecularly imprinted monoliths. The state-of-art advances as an effective platform for applications in the selective capture of biomacromolecules related biomarkers were also outlined.     

Synthesis,core-shell structures and properties of fluorene/polypyrrole composite

In the current study, fluorene/polypyrrole composite with the core-shell structure has been synthesized by in situ oxidative polymerization of pyrrole in the presence of fluorene. Composite was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy. Electrical performance of the composite prepared at various reaction conditions was tested. The composite has the best performance of electrical conductivity when FeCl₃–pyrrole molar ratio is equal to 3 and the reaction time is 18 h. It was found that polypyrrole could be formed on the surface of fluorene due to strong π–π interactions between the fluorene core and the polypyrrole shell.     

黄芩甙的抗氧化作用

以Ｆｅ２＋－Ｈ２Ｏ２和ＮＡＤＰＨ－Ｆｅ２＋作为氧自由基生成系统造成大鼠肝线粒体脂质过氧化,研究了黄芩甙对脂质过氧化产物丙二醛（ＭＤＡ）生成的抑制作用;以乙酰氨基酚和四氯化碳分别诱导肝脂质过氧化损伤,测定血清丙氨酸转氨酶（ｓＡＬＴ）活性、肝中超氧化物歧化酶（ＳＯＤ）活性、肝中丙二醛（ＭＤＡ）和谷胱甘肽（ＧＳＨ）含量,研究了黄芩甙对这些指标的影响．结果表明黄芩甙对大鼠肝线粒体脂质过氧化产物ＭＤＡ的生成有抑制作用,对乙酰氨基酚和四氯化碳引起的肝脂质过氧化损伤有保护作用．