Synthesis and characterization of poly(arylene ether ketone)s bearing pendant sulfonic acid groups for proton exchange membrane materials

A bisphenol monomer (2,5‐dimethoxy)phenylhydroquinone was prepared and further polymerized to obtain poly(arylene ether ketone) copolymers containing methoxy groups. After demethylation and sulfobutylation, a series of novel poly(arylene ether ketone)s bearing pendant sulfonic acid group (SPAEKs) with different sulfonation content were obtained. The chemical structures of all the copolymers were analyzed by ¹H NMR and ¹³C NMR spectra. Flexible and tough membranes with reasonably good mechanical properties were prepared. The resulting side‐chain‐type SPAEK membranes showed good dimensional stability, and their water uptake and swelling ratio were lower than those of conventional main‐chain‐type SPAEK membranes with similar ion exchange capacity. Proton conductivities of these side‐chain‐type sulfonated copolymers were higher than 0.01 S/cm and increased gradually with increasing temperature. Their methanol permeability values were in the range of 1.97 × 10^?7–5.81 × 10^?7 cm²/s, which were much lower than that of Nafion 117. A combination of suitable proton conductivities, low water uptake, low swelling ratio, and high methanol resistance for these side‐chain‐type SPAEK films indicated that they may be good candidate material for proton exchange membrane in fuel cell applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Conditions based on conditional moments for max-stable limit laws

Let X ₁, X ₂, ...X _n be independent and identically distributed random variables with common distribution function F. Necessary and sufficient conditions for F to belong to the domains of attraction of Φ _α and Ψ _α are derived in terms of conditional moments.      

Microfibrous entrapped ZnO-CaO/Al2O3 for high efficiency hydrogen production via methanol steam reforming

Sinter-locked microfibrous networks consisting of ～3 vol.% of 8 μm (din.) nickel microfibers have been utilized to entrap ～30 vol.% of 100-200 μm din.porous Al2O3.ZnO and CaO were then highly dispersed onto the pore surface of entrapped Al2O3 by the incipient wetness impregnation method.Due to the unique combination of surface area,pore size/particle size,thermal conductivity,and void volume,the resulting microfibrous catalyst composites provided significant improvement of catalytic bed reactivity and utilization efficiency when used in methanol steam reforming.Roughly 260 mL/min of reformate,comprising ＞70% H2,＜5% CO and trace CH4,with ＞97% methanol conversion,could be produced in a 1 cm3 bed volume of our novel micro fibrous entrapped ZnO-CaO/Al2O3 catalyst composite at 470 ℃ with a high weight hourly space velocity (WHSV) of 15 h-1 using steam/methanol ( 1.3/1 ) mixture as feedstock.Compared to a packed bed of 100-200 μm ZnO-CaO/Al2O3,our composite bed provided a doubling of the reactor throughput with a halving of catalyst usage.     

大孔阳离子交换树脂分离纯化Zwittermicin A

以抑菌圈为指标,通过离子交换法对双效菌素Zwittermicin A进行了分离纯化,并研究其抑菌活性。首先通过静态法比较D151、D113、D001-cc 3种大孔阳离子交换树脂吸附效果,结果表明,D151对ZwittermicinA分离纯化效果最好。利用单因素轮换法,确定了ZwittermicinA的最佳纯化工艺为:上柱样品的最佳pH=7;第1次冲洗液NH4H2PO4的最适浓度为5mmol/L;第2次冲洗液CH3COONH4的最适浓度为30mmol/L;1mol/L氨水洗脱液的最少用量为12.7mL/cm3树脂;Zwittermicin A的总收率达90%以上。利用红外光谱仪对D151树脂的吸附前后进行了分析。     

无限长湍流相位屏产生方法

在考虑时间特性的激光大气湍流数值模拟中,构造满足要求的湍流相位屏对大气湍流的模拟尤为重要,为此提出基于多点预测的相位协方差插值方法产生湍流相位屏,由多个已知点的相位值对新插值点的相位值进行预测,推导出了插值点的预测矩阵及其残余方差的表达式,并对插值后生成的相位屏的空间统计特性进行了验证。数值模拟结果表明:该方法产生的湍流相位屏与大气湍流的统计特性符合得较好,随着用于预测的已知点数的增加,模拟生成的湍流相位屏的精度提高,并可以进行连续插值生成无限长的湍流相位屏。     

关于几类2阶ai-半环生成的簇的研究

借助半环的格林关系研究了由所有2阶ai-半环生成的半环簇S2的一些子簇．其次,定义了与S2中半环的元素相关的同余关系,并揭示了同余关系之间的联系．     

一类平坦半环生成的簇

平坦半环是一类重要的加法幂等元半环,它在半环簇理论的研究中扮演着重要的角色.主要研究了次直不可约的平坦半环,以及一类平坦半环生成的簇.给出了次直不可约的nil-平坦半环的等价刻画,证明了当n小于4时,平坦半环S(x1x2…xn)均是有限基底的.