Long-term and thermally stable superhydrophobic surfaces of carbon nanofibers

Carbon nanofibers were prepared from polyvinyl alcohol (PVA) by a simple wetting-compatible method. The surfaces of the aligned carbon nanofibers show excellent thermal- and time-stable superhydrophobicity. The average water contact angle (CA) values are about 153.1+/-2.2 degrees at room temperature, with little difference coming from experimental error. In addition, the CA of the aligned carbon nanofibers surface maintains 139.1+/-3.2 degrees after 10 months of exposure to the ambient environment. Nanostructure on the surface of carbon nanofibers and the intrinsic thermal resistance of carbon contribute to this unique surface property.     

Controlled chemical stabilization of self-assembled PS-P4VP nanostructures

Supramolecular self-assemblies in selective solvents give rise to many patterning possibilities. The diblock copolymer polystyrene-b-poly(4-vinylpyridine) (PS-P4VP) is one such polymer that self-assembles into neat nanostructures in toluene. These nanostructures once formed are highly susceptible to solvent influence. Unfortunately, for use as nanotemplates and in the synthesis of nanoparticles, the susceptibility of the films to solvents can be a problem. In this study, we present a method to stabilize the structures through chemical means in solution. We used 1,4-dibromobutane in solution to chemically crosslink the pyridine residues of each of PS-P4VP to yield a series of stable spherical aggregates. In this way, the cross-linking ratio can be precisely controlled. The solution properties were studied using dynamic light scattering and small angle X-ray scattering and the morphology of the resulting micellar film was studied using transmission electron microscopy (TEM). The size of the micelles formed was found to be dependent on the amount of cross-linking and the shape of the PS-P4VP micelles remains stable when exposed to a selective solvent for PS.     

C59XH(X=N,B)与1,3-丁二烯Diels-Alder环加成反应的区域选择性

应用半经验的AM1和密度泛函B3LYP/6-31G*方法对1,3-丁二烯与C59XH(X=N, B) Diels-Alder环加成反应的区域选择性进行理论研究, 选择一些有代表性的C59XH(X=N, B)的6—6键探讨环加成反应的机理. 1,3-丁二烯与C59NH进行的Diels-Alder反应, 随着加成位置远离C59NH的N原子, 活化能越来越低, 但都比1,3-丁二烯与C60相应反应的活化能高. 与此相反, 对于1,3-丁二烯与C59BH进行的环加成反应, 加成位置最靠近B原子的2,12/r-和2,12/f-过渡态的势垒最低, 并且比1,3-丁二烯与C60进行环加成反应的活化能约低18 kJ·mol-1, 其产物也是热力学最稳定的. 与C60相应的反应相比, C59NH和C59BH中N和B原子不同的电子性质对其邻位双键进行Diels-Alder环加成反应的活性产生了不同影响, 前者使反应活性降低, 后者使反应活性增强.     

Solvent-and catalyst-free synthesis of dihydropyrimidinthiones in one-pot under focused microwave irradiation conditions

Fifteen dihydropyrimidinthiones have been synthesized by microwave-assisted Biginelli reactions without any solvent or catalyst. The advantages of this novel protocol include the excellent yield, operational simplicity, short time and the avoidance of the use of organic solvents and catalysts.     

一氧化碳低温催化氧化

一氧化碳 (CO) 催化氧化反应因在实际生活中应用广泛而受到人们普遍关注,如激光器中微量CO的消除、封闭体系中CO的消除、汽车尾气净化以及质子交换膜燃料电池中少量CO的消除等。本文总结了近年来CO低温催化氧化研究进展,包括催化剂及其制备方法、CO氧化反应机理以及不同环境气氛对催化剂CO低温氧化性能的影响。催化剂的制备方法主要包括传统浸渍法、共沉淀法、沉积-沉淀法、溶胶-凝胶法、离子交换法、化学气相沉积法、溶剂化金属原子浸渍法等。催化剂可分为贵金属催化剂、非贵金属催化剂、以分子筛为载体的催化剂和合金催化剂等。CO氧化反应机理方面的相关报道较多,人们针对不同催化剂体系提出了各种假设。不同环境气氛对催化剂CO低温氧化性能的影响主要分为H₂O、CO₂、H₂和其它气氛等4部分进行描述。最后对该领域的发展前景进行了展望。     

嵌套网格计算的一种实用初始洞面构造方法及应用

针对结构嵌套网格计算,提出一种实用的初始洞面构造方法,成功应用于自动化嵌套网格生成过程。首先采用封闭物面作为嵌套网格"挖洞"的初始洞边界,然后通过分别给定期望的壁面距离及初始洞间距比例因子的方法进行优化,得到真正的挖洞曲面。通过对NACA4412单段翼型、30P30N三段高升力翼型等算例计算,结果表明:本文提出的方法能有效解决嵌套网格计算中初始洞边界自动构造问题,并能有效避免在近壁面区域进行流场传值,在不需要额外采用洞面优化技术的情况下解决壁面狭缝网格重叠问题,获得更优的嵌套网格流场计算结果。结合本文方法对传统嵌套网格方法进行改进,可为自动化嵌套网格生成提供有效的途径。     

一种体现发展趋势的自-互激励型多阶段信息集结方法

针对时序动态综合评价中多阶段信息集结问题,提出一种体现发展趋势的自-互激励型集结方法。首先,根据被评价对象不同的发展趋势得出不同的预测点,连接预测点得到预测线,以预测线为基准对被评价对象进行状态上的自激励;其次,依据原始评价值的大小衡量增长难度,并与增长速度结合,进行增长水平上的互激励;最后,通过算例验证方法的有效性。该集结方法从激励的视角考虑被评价对象自身的发展趋势和相对增长水平,据此对不同起点的对象实行差别化激励,充分尊重了个体发展差异。     

FCC硫转移剂MgAlCuFe复合氧化物的结构与性能：Fe和Cu含量的影响

采用共沉淀法合成MgAlCuFe水滑石前驱体,经过700 ℃焙烧 6 h 后,制备了一系列不同Fe和Cu含量的FCC硫转移剂. 利用X射线衍射、氮气吸附和X射线荧光光谱对硫转移剂的结构和组成进行了表征,采用改装的WRP-3热重天平分析了其氧化吸硫和还原脱硫的性能. 结果表明,在一定范围内调变Fe和Cu含量均可以得到结构规整的类水滑石前驱体,经过焙烧后得到MgAlCuFe-LDOs复合氧化物. 最佳的Fe和Cu含量分别为8%和1%, 其吸硫速度较快,仅 6 min 即达到吸附饱和1.57 g/g, 还原脱硫的效果也较好. 在MgAlCuFe-LDOs复合氧化物中Fe是氧化SO2和还原MgSO4的促进剂, Cu具有促进催化氧化SO2的能力.     

一类四阶差分边值问题解的存在性与临界点方法

利用临界点方法研究了一类四阶差分边值问题,分别得到了存在一个解和两个解的若干充分条件,展示了临界点理论在研究差分边值问题中的重要作用.     

Induced phase transition of BECs in optical lattices by impurity

In this work, the influence of imparity on BECs in optical lattices is investigated, and the possibility of MI-SF transition induced by impurity is verified. After the numerical calculation, the schematic phase diagram is discussed with an emphasis on the role of impurity. When n10 = n20, the phase boundaries coincide with each other; when n10 < n20 and U12 < 0, the phase boundaries do not intersect at all; when n10 < n20 and U12 > 0, the phase boundaries may or may not intersect, depending on the values of...