输水管线大口径钢顶管施工技术措施

输水管线大口径长距离钢顶管施工中,技术措施的正确运用对保证质量安全、降低施工风险具有重大意义.该文从青草沙严桥支线DN3600双线钢顶管施工实践出发,介绍大口径钢顶管施工工艺中的几个问题和采取的对策,以期与同行进行交流和探讨.     

尼龙6弹性体的合成

以ε－己内酰胺（CL）的水解开环聚合法为合成路线，采用正交试验法求得了较佳基本配方与反应条件；聚醚选用PTMG1000，催化剂选有亚磷酸三苯酯，抗氧化剂和Irganox1098，适宜的反应温度为250－260℃，适宜的开环反应时间为2－3h，预缩聚0.5-1h，后缩聚0.5-2h。在此条件下，不存在反应体系相容性问题，可以合成出颜色浅，摩尔质量较高的N6型尼龙6弹性体（TPAE）树脂。通过对比试验，发现在适宜反应温度和开环反应时间下，采用对苯二甲酸作原料能显著提高CL的转化率。     

新型曼尼希碱的合成及缓蚀性能评价

针对炼油厂常减压塔塔顶冷凝系统存在的腐蚀问题,研制出以肉桂醛、苯乙酮、环己胺为原料合成的一种新型曼尼希碱缓蚀剂。采用静态失重法,在HCl-H2S-H2O型腐蚀环境下进行缓蚀性能评价,确定了最佳合成条件：n（醛）∶n（胺）∶n（酮）=5∶6∶5,合成反应温度65℃,反应时间5h。对最佳条件下合成的缓蚀剂加入量、腐蚀环境温度、腐蚀时间进行了综合评价,结果表明温度在60～90℃,腐蚀时间在6h,加入φ（曼尼希碱）=0.9%,都展现了很好的缓蚀性能。     

Novel bioresorbable hydrogels prepared from chitosan‐graft‐polylactide copolymers

A series of biodegradable chitosan‐graft‐polylactide (CS‐g‐PLA) copolymers were prepared by grafting of poly(L ‐lactide) (PLLA) or poly(D ‐lactide) (PDLA) precursor to the backbone of chitosan using N,N′‐carbonyldiimidazole as coupling agent. The composition of the copolymers was varied by adjusting the chain length of PLA as well as the ratio of chitosan to PLA. The copolymers synthesized via this ‘graft‐onto’ method present interesting properties as shown by NMR and infrared spectroscopy, gel permeation chromatography and solubility tests. Hydrogels were prepared by mixing water‐soluble CS‐g‐PLLA and CS‐g‐PDLA solutions. Gelation was assigned to stereocomplexation between PLLA and PDLA blocks as evidenced by differential scanning calorimetry and wide‐angle X‐ray diffraction measurements. Thymopentin (TP5) was taken as a model drug to evaluate the potential of these CS‐g‐PLA hydrogels as drug carriers. An initial burst and a final release up to 82% of TP5 were observed from high‐performance liquid chromatography analysis. Copyright © 2011 Society of Chemical Industry     

蒙脱土改性环氧树脂及其复合材料性能研究

以蒙脱土(MMT)作为EP(环氧树脂)的改性剂制备EP/MMT纳米复合材料。考察了MMT含量对EP/MMT体系的凝胶时间、黏度和力学性能等影响。结果表明:MMT的加入明显缩短了EP体系的凝胶时间,并显著缩短了EP体系达到高黏度的时间;当w(MMT)=4%时,EP/MMT纳米复合材料的力学性能相对最好,其浇铸体的拉伸强度、弯曲强度和冲击强度分别为85 MPa、140 MPa和35 kJ/m2,其复合材料的拉伸强度和弯曲强度分别为160 MPa和200 MPa。     

纳米二氧化硅对碱矿渣水泥泛碱的影响

碱矿渣水泥因具有能耗低、二氧化碳排放低、性能优越等优点成为近年来建筑材料领域的研究热点.但其泛碱现象,影响了碱矿渣水泥的实际应用.本文旨在将纳米二氧化硅掺入碱矿渣水泥中,抑制其泛碱.研究了纳米二氧化硅掺入方式对碱矿渣水泥抗压强度和泛碱的影响,利用扫描电镜(SEM)、水化热测定、汞压入法(MIP)等技术分析了纳米二氧化硅对碱矿渣水泥泛碱的抑制机理.结果表明,纳米二氧化硅最佳掺入方式为超声分散.此外,掺加纳米二氧化硅可有效促进碱矿渣水泥的水化进程及水化程度,改善碱矿渣水泥硬化浆体微观结构,优化碱矿渣水泥硬化浆体的孔径尺寸分布,提高硬化浆体密实度,增加碱矿渣水泥的抗压强度,从而有效抑制碱矿渣水泥泛碱.     

A Student's t-based density peaks clustering with superpixel segmentation (tDPCSS) method for image color clustering

Image color clustering is a basic technique in image processing and computer vision, which is often applied in image segmentation, color transfer, contrast enhancement, object detection, skin color capture, and so forth. Various clustering algorithms have been employed for image color clustering in recent years. However, most of the algorithms require a large amount of memory or a predetermined number of clusters. In addition, some of the existing algorithms are sensitive to the parameter configurations. In order to tackle the above problems, we propose an image color clustering method named Student's t-based density peaks clustering with superpixel segmentation (tDPCSS), which can automatically obtain clustering results, without requiring a large amount of memory, and is not dependent on the parameters of the algorithm or the number of clusters. In tDPCSS, superpixels are obtained based on automatic and constrained simple non-iterative clustering, to automatically decrease the image data volume. A Student's t kernel function and a cluster center selection method are adopted to eliminate the dependence of the density peak clustering on parameters and the number of clusters, respectively. The experiments undertaken in this study confirmed that the proposed approach outperforms k-means, fuzzy c-means, mean-shift clustering, and density peak clustering with superpixel segmentation in the accuracy of the cluster centers and the validity of the clustering results.     

Phase transitions and glass transition in a hyperquenched silica‐alumina glass

We investigate phase transitions, glass transition, and dynamic behavior in the hyperquenched 69SiO₂–31Al₂O₃ (mol%) glass (SA glass). Upon reheating, the SA glass exhibits a series of thermal responses. Subsequent to the sub‐T_g enthalpy release, the glass undergoes a large jump in isobaric heat capacity (ΔC_p) during glass transition, implying the fragile nature of the SA glass. The mullite starts to form before the end of glass transition, indicating that the SA glass is extremely unstable against crystallization. After the mullite formation, the remaining glass phase exhibits an increased T_g and a suppressed ΔC_p. The formation of cristobalite at 1553 K indicates the dominance of silica in the remaining glass matrix. The cristobalite gradually re‐melts as the isothermal heat‐treatment temperature is raised from 1823 to 1853 K, which is well below the melting point of cristobalite, while the amount of the mullite remains unchanged.     

The application of a three dimensional CNT-sponge as the counter electrode for dye-sensitized solar cells

A sponge-like three dimensional carbon nanotube (CNT) framework has been applied as the counter electrode for a dye-sensitized solar cell (DSC). The CNT-sponge shows high catalytic activity to the counter electrode reduction reactions of I^?/I₃^? redox couple and a photoelectric conversion efficiency of 6.21% has been achieved. Compared with previous carbon-based counter electrode materials for DSCs, the CNT sponge retains highly flexibility and good mechanical strength. Its soft structure makes it possible to directly transfer it onto a substrate to make DSC devices.