IEC阵风作用下箱梁断面的气动特性分析

基于二维非定常不可压缩雷诺平均N-S方程和RNG k-ε湍流模型,采用CFD（computational fluid dynamics）方法对箱梁断面在IEC（international electrotechnical commission）阵风以? 5°～+ 5°攻角作用下的气动力及流场特性进行数值模拟分析,获得了IEC阵风作用过程中箱梁断面的三分力系数的总体变化特征、入口边界静压变化特性及流场内静压的顺压和逆压特性等。分析表明,IEC阵风模型比TSI（technical specifications for interoperability）阵风模型更适于桥梁气动力的数值模拟分析。     

Main‐chain smectic liquid crystalline polymer exhibiting unusually high thermal conductivity in an isotropic composite

The thermal conductivity (TC) of an isotropic composite comprising of a main‐chain smectic liquid crystalline PB‐10 polyester and 50‐μm‐sized roughly spherical magnesium oxide (MgO) particles is investigated. The increase in the composite TC with higher MgO fractions is steeper than that expected by Bruggeman's theory for the TC of a polydomain PB‐10 polyester (0.52 W m^?1 K^?1). When the filler content is larger than 30 vol %, the composite TC approaches a value that can be explained only if the polyester functions as a matrix with 1.0 W m^?1 K^?1, which is five times as high as those of isotropic common polymers (0.2 W m^?1 K^?1). Such an unusually high TC for a polymer matrix is attributed to some polymer lamellae that lie parallel to the particle surface and are stacked toward neighboring particles, thus creating effective heat paths between the particles and a continuous thermal network in a composite. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2014 , 131, 39896.     

Controlled radical polymerization with polyolefin macroinitiator: a convenient and versatile approach to polyolefin-based block and graft copolymers

This paper introduces the new synthetic methodology of polyolefin-based block and graft copolymers with polar segments [e.g., polystyrene and poly(meth)acrylates]. Various brominated polyolefins were prepared by bromination of polyolefins with N-bromosuccinimide. The resulting brominated polyolefins were able to initiate the controlled radical polymerization of polar monomers, such as methyl methacrylate, ethyl acrylate, t-butyl acrylate, styrene and 2-(dimethylamino)ethyl acrylate, using a CuBr/N,N,N′,N″,N″-pentamethyldiethylenetriamine catalyst system, leading to a variety of polyolefin-based copolymers with a different content of the corresponding polar segment. Because of the accessible synthesis of polyolefin macroinitiators, this synthetic methodology is expected to result in the preparation of a wide range of polyolefin-based block and graft copolymers.     

Flexible magnetic copolymer films with high decomposition temperature and stable dielectric properties

Two novel kinds of flexible magnetic copolymer films were prepared via copolymerization using magnetic ferrocenyl prepolymer (MFP) and poly(arylene ether nitrile)s with bisphthalonitrile functional group. Two types of poly(arylene ether nitrile)s with bisphthalonitrile functional group were used and two series of flexible magnetic copolymer film with different structure were obtained. The magnetic properties of copolymer films indicated that the films were soft magnetic. Moreover, it was also concluded that the magnetic properties of magnetic films prepared from phthalonitrile terminated poly(arylene ether nitrile)s were higher than that of magnetic films prepared from poly(arylene ether nitrile)s with pendant phthalonitriles at the same content of MFP. The results of thermogravimetry showed that the all of the copolymer films possessed high decomposition temperature. Like the magnetism, the dielectric constant and dielectric loss of films obtained from phthalonitrile terminated poly(arylene ether nitrile)s were also higher than that of films obtained from poly(arylene ether nitrile)s with pendant phthalonitriles.     

Processing of nanolitre liquid plugs for microfluidic cell-based assays

Plugs, i.e. droplets formed in a microchannel, may revolutionize microfluidic cell-based assays. This study describes a microdevice that handles nanolitre-scale liquid plugs for the preparation of various culture setups and subsequent cellular assays. An important feature of this mode of liquid operation is that the recirculation flow generated inside the plug promotes the rapid mixing of different solutions after plugs are merged, and it keeps cell suspensions homogeneous. Thus, serial dilutions of reagents and cell suspensions with different cell densities and cell types were rapidly performed using nanolitres of solution. Cells seeded through the plug processing grew well in the microdevice, and subsequent plug processing was used to detect the glucose consumption of cells and cellular responses to anticancer agents. The plug-based microdevice may provide a useful platform for cell-based assay systems in various fields, including fundamental cell biology and drug screening applications.     

Experimental study on hysteresis phenomena of shock wave structure in an over-expanded axisymmetric jet

In recent studies on two-dimensional supersonic jets, it is reported that the hysteresis phenomenon for the reflection type of shock waves in the jet flow field is occurred under the quasi-steady flow condition and this phenomenon is affected by the transitional pressure ratio between the regular reflection and Mach reflection. However, so far, there are few researches on the hysteresis phenomenon for the transition of shock waves between regular and Mach reflection in over-expanded supersonic jets and the phenomenon has not been investigated satisfactorily. Therefore, the purpose of this study is to clarify the hysteresis phenomena for the reflection type of shock wave in the over-expanded axi-symmetric supersonic jet experimentally, and to discuss the relationship between hysteresis phenomenon and rate of the change of pressure ratio with time. Furthermore, the effect of Mach number at the nozzle exit on hysteresis loop was investigated for two kinds of nozzle.     

Ziegler-Natta/茂金属复合催化剂聚合性能的研究

制备了Ziegler-Natta/茂金属复合(Z-M)催化剂,用SEM技术对其形貌进行了表征,在10L丙烯液相本体聚合模试装置上对Z-M催化剂的氢调敏感性进行了评价。通过一段丙烯本体均聚、二段乙烯-丙烯近恒温恒压气相共聚模拟Spheripol-Ⅱ工艺制备了系列聚丙烯(PP)釜内合金;考察了二段共聚时的聚合反应动力学、乙烯与丙烯配比(n(C3)∶n(C2))对PP釜内合金性能的影响。实验结果表明,在一段均聚时Z-M催化剂具有较好的氢调敏感性,得到的均聚PP粒子具有较好的流动性;在二段共聚时,Z-M催化剂能在较长的共聚时间内保持较平稳、较高的共聚活性,改变n(C3)∶n(C2)时PP釜内合金中乙丙橡胶的质量分数可调(7.19%~10.75%),熔体流动速率(10min)可调(14.0~26.5g);n(C3)∶n(C2)对合金弯曲模量的影响不大;当n(C3)∶n(C2)=1.7时制备的PP釜内合金具有最大的冲击强度(92.9J/m)。     

Ziegler-Natta/茂金属复合催化剂中茂金属组分的休眠及对聚丙烯合金性能的影响

制备出了以二醚为内给电子体的Ziegler-Natta(Z-N)催化剂及Z-N/茂金属(Z-M)复合催化剂。研究了催化剂类型(Z-N或Z-M)、休眠剂类型(苯乙烯(St)或对甲基苯乙烯(pMS))及用量对聚合过程、中间产品(均聚聚丙烯(PP))和最终产品(PP釜内合金)性能的影响,还利用扫描电子显微镜观测了PP釜内合金粒子的形貌。结果表明:St是比pMS更适宜的休眠剂;在保证使Z-M复合催化剂中茂金属组分充分休眠的前提下,应尽可能降低休眠剂的加入量;在St休眠剂存在下使用Z-M复合催化剂可制得23,-30℃抗冲击强度分别为47,5.6 kJ/m2的高刚高韧PP合金。