Effect of oxygen addition on the hydrogen production from ethanol steam reforming in a Pd–Ag membrane reactor

In this communication, a porous stainless steel (PSS) tube was electrolessly plated into Pd–Ag membrane reactor which was used for separating hydrogen produced in an ethanol steam reforming reaction with the addition of oxygen, which has not been reported before. Palladium and silver were deposited on porous stainless steel tube via the sequential electroless plating procedure with an overall film thickness of 20 μm and Pd/Ag weight ratio of 78/22. Ethanol–water mixture (n_water/n_ethanol = 1 or 3) and oxygen (n_oxygen/n_ethanol = 0.2 or 0.7) were fed concurrently into the membrane reactor packed with MDC-3. The reaction temperatures were set at 593–723 K and the pressures 3–10 atm. The effect of oxygen addition plays a vital role on the ethanol steam reforming reaction, especially for the Pd–Ag membrane reactor in which a higher flux of hydrogen is required. If oxygen in the feed is not sufficient, it would be possible that steam reforming reaction prevails. Inversely, high O₂ addition will shift the reaction scenario to be partial oxidation dominating, and selectivity of CO₂ increases with increasing oxygen feed. At high pressure, autothermal reaction of ethanol would be easily reached.     

Novel designed polymer–acyclovir conjugates with linker‐controlled drug release and hepatoma cell targeting

To develop designed polymer–drug conjugates, where the rate of drug liberation and hepatoma cell targeting function could be rationally and widely controlled, we facilely synthesized a series of novel, galactose‐functionalized polymer–acyclovir conjugates with different linkers and first reported the effect of the linker structure including the type of acyclovir‐linked bond (an ester bond or an amide bond) and relative length of the linker between acyclovir and the polymer main chain on release rate and targeting ability of conjugates. In vitro release studies showed that the cumulative released acyclovir from these polymer–acyclovir conjugates was between 24 and 65% in pH 1.2 glycine solution after 7 days. The ester bond more easily underwent hydrolysis than the amide bond. The longer the relative linker length was, the faster the acyclovir was released. The cell recognition experiments visualized using confocal laser scanning microscopy exhibited that the resultant galactose‐functionalized polymer–acyclovir conjugates had evident targeting to hepG2 cells, and targeting ability was also in connection with the relative length of linker. By choosing appropriate linker, cellular internalization of acyclovir could be well achieved. We consider these results to be helpful for the design of multifunctional polymeric prodrugs, in which the required release rate and targeting ability could be rationally controlled by predetermined molecular architecture. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 117–126, 2008     

Preparation of polybenzoxazole fibers via electrospinning and postspun thermal cyclization of polyhydroxyamide

Polybenzoxazole (PBO) fibers with a submicron diameter were successfully prepared by electrospinning its precursor, polyhydroxyamide (PHA), solutions to obtain the PHA fibers first, followed by appropriate thermal treatments for cyclization reaction. BisAPAF‐IC PHA with two different molecular weights (MWs) were synthesized from a low temperature polymerization of 2,2′‐bis(3‐amino‐4‐hydroxyphenyl) hexafluoropropane (BisAPAF) and isophthaloyl chloride (IC). Using dimethylacetamide (DMAc) and tetrahydrofuran (THF), solvent effects on the electrospinnability of PHA solutions were investigated. For balancing the solution properties, it was found that DMAc/THF mixture with a weight ratio of 1/9 was the best cosolvent to prepare smooth PHA fibers; uniform PHA fibers with a diameter of 325–720 nm were obtained by using 20 wt % PHA/(DMAc/THF) solutions. For a fixed PHA concentration, solutions with a lower MW of PHA yielded thinner electrospun fibers under the same electrospinning condition. After obtaining the electrospun BisAPAF‐IC PHA fibers, subsequent thermal cyclization up to 350 °C produced the corresponding thermally stable BisAPAF‐IC PBO fibers with a diameter of 305–645 nm. The structure of the precursor fibers and the fully cyclized fibers were characterized by FTIR. For the cyclized BisAPAF‐IC PBO fibers, thermogravimetric analysis showed a 5% weight loss temperature at 523 °C in nitrogen atmosphere. The interconnected fiber structure in the BisAPAF‐IC PBO fiber mats was irrelevant to the curing process, but resulted from the jet merging during the whipping process as revealed by the high speed camera images. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 8159–8169, 2008     

无水肼水含量标准物质分装技术研究

为寻找高效、安全、少污染的无水肼水含量标准物质分装方法,对无水肼水含量标准物质的灌装技术和封口技术进行了分析,比较了3种封口技术的优缺点,对压制封口垫片与无水肼的相容性及渗透情况进行了试验。综合考虑无水肼的特殊性、分装过程的安全性、密封性、实用性等,确定采用压制封口技术,使用M242橡胶材料作为垫片。     

吸流管道动力学模型的研究现状与展望

围绕吸流管道的稳定性与振动问题,对近年来的主要研究工作加以综述并提出预测,其中包括运动方程的归纳与讨论、管道自由端口处的流固耦合理论、定常流速下吸流管道的稳定性机理以及今后值得进一步研究的某些问题.     

THE BLOW-UP PROPERTIES OF SOLUTIONS TO A PARABOLIC SYSTEM WITH LOCALIZED NONLINEAR REACTIONS

1IntroductionThispaperisconcernedwithpositivesolutionOfthesemilinearheatequationswithlocalizedreactionssubjecttoeitherinitialconditions(Cauchyproblem)ortheinitialandboundary-value(DirichletorNeumanntype)conditionswherenisaboundeddomaininRe,icEO.Equations(1.1)canbethoughtofasamodeltodescribesomephysicalphenomena(heatpropagation,chemicalreaction)inwhichthenonlinearreactionsinadynndcalsystemtakesplaceonlyatasinglesite.InthesequelforconvenienceweshallsamplycalltheCauchy,initial-Direchlet,orini…     

基于广义动态因子模型的中国出口周期分析与预测

研究出口周期的景气循环对于进一步扩大出口及推动整个国民经济的发展具有重要的意义.基于传统的先行指标体系和SW景气指数方法能够为出口周期的监测和预警提供参考,而近年来逐渐完善的广义动态因子模型基于频域分析方法,在处理高维数据方面比前两种方法更具有优势,同时该方法在拐点的探测方面也具有重要的作用.作者首先对三种指数构建方法进行了理论上的介绍;其次,分别运用三种方法构建了中国出口增长循环的一致及先行指数;最后,对三种方法在中国出口周期分析上的表现进行了比较与评价,得出了一些重要的结论.     

Spaces of type BLO on non-homogeneous metric measure

Let (, d, μ) be a metric measure space satisfying the so-called upper doubling condition and the geometrically doubling condition. In this paper, we introduce the space RBLO(μ) and prove that it is a subset of the known space RBMO(μ) in this context. Moreover, we establish several useful characterizations for the space RBLO(μ). As an application, we obtain the boundedness of the maximal Calderón-Zygmund operators from L ^∞(μ) to RBLO(μ).     

A numerical solution to nonlinear multi‐point boundary value problems in the reproducing kernel space

In this paper, a new numerical algorithm is provided to solve nonlinear multi‐point boundary value problems in a very favorable reproducing kernel space, which satisfies all complex boundary conditions. Its reproducing kernel function is discussed in detail. The theorem proves that the approximate solution and its first‐ and second‐order derivatives all converge uniformly. The numerical experiments show that the algorithm is quite accurate and efficient for solving nonlinear multi‐point boundary value problems. Copyright © 2010 John Wiley & Sons, Ltd.