Effect of external surface of HZSM-5 zeolite on product distribution in the conversion of methanol to hydrocarbons

The external surface of HZSM-5 zeolite was passivated by liquid siliceous deposition and by acidic sites poisoning with lepidine, respectively. Then methanol-to-hydrocarbons （MTH） reaction was investigated over the above as-prepared catalysts and the dissoluble coke on these used catalysts was analyzed by GC-MS, to study the role of the external surface of HZSM-5 in the catalytic reaction. Comparison with the experi- mental results based on parent ZSM-5 showed that the product distribution of MTH reaction was obviously influenced by the external surface. Evidences were listed as follows： （1） the final product on parent HZSM-5 showed higher aromatic selectivity, lower olefin selectivity, lower ra- tio of C2/C3＋ aliphatics and higher ratio of C3/C4＋ aliphatics than the reaction mixture produced by the sole catalysis of acidic sites in HZSM-5 channel; （2） a little of pentamethylbenzene and hexamethylbenzene in the product on parent HZSM-5, was produced via multi-methylation of methylbenzene on the external surface. The above conclusion may also be suitable for MTH reaction over other zeolites with 10-ring channel.     

Quantum variance for Hecke eigenforms

We calculate the quantum variance for the modular surface. This variance, introduced by S. Zelditch, describes the fluctuations of a quantum observable. The resulting quadratic form is then compared with the classical variance. The expectation that these two coincide only becomes true after inserting certain subtle arithmetic factors, specifically the central values of corresponding L-functions. It is the off-diagonal terms in the analysis that are responsible for the rich arithmetic structure arising from the diagonalization of the quantum variance.     

Ambrosetti-Prodi问题-常微分方程组情形

本文研究常微分方程组情形的Ambrosetti-Prodi型问题.在非线性项超线性,凸性等条件下,得出随着参数的变化,问题无解,有唯一解,至少有两解的结论.     

镀锡薄板单位面积镀锡量新的测定方法—贝尔德直读光谱仪分析技术的开发

本文利用贝尔德公司生产的ＳＶ－１０００型（ＤＶ－４）直读光谱仪测定镀锡薄板单位面积镀锡量，开拓了光电光谱仪在镀层领域的应用，通过选用基体铁元素作内标，在适宜的激发条件下获得锡元素涨强比与镀锡量间的线性关系。选择合适条件，解决了薄板易击穿，内标元素光强值稳定性等技术关键，采用容量法制作一套不同镀锡量的标准镀锡薄板，绘制校准曲线，建立了光电光谱分析测定镀锡薄板单位面积镀锡量的方法。方法精度ＲＳＤ小于５     

重离子加速器冷却储存环高频腔体设计

 通过二维高频电磁场的计算，设计了兰州重离子加速器冷却储存环（HIRFL–CSR）的铁氧体加载腔，给出了高频系统主要参数及加速电场的分布。     

一种求解扩散方程的混合格式

本文提出了一种求解扩散方程的新型混合格式，具有明显的并行性，很高的精度与稳定性．文中给出了一数值例子，其在一具有五个ｔｒａｎｓｐｕｔｅｒ的并行机上的并行加速达３．５．     

微铂电极的预处理方法

本文推荐采用超声波清洗法对微铂电极进行预处理。这种预处理方法可确保微铂电极不受损伤,并可获得重现性良好的测试结果。     

A simple yet highly selective colorimetric sensor for cyanide anion in an aqueous environment

The nucleophilic nature of cyanide is used to create a simple, sensitive, and highly effective sensor, 2-(trifluoroacetylamino)anthraquinone (2-TFAQ), for the easy "naked-eye" detection of very low concentrations of cyanide in an aqueous environment.