纵横码比较优势分析及推广应用策略的制订

纵横码具有数字编码、规则简单、易学易记、词组丰富等特点,在香港、江苏、浙江、上海等地得到一定规模的推广.深入分析了纵横码的潜在优势,探讨了进一步推广应用的策略,以及在推广过程中所应采取的措施.     

Fe对NaNbO3的晶格掺杂和同步异质结改性及其光催化性能

运用溶剂热法及继之的高温晶化法制备钙钛矿结构NaNbO₃,并在此基础上同步获得了NaNbO₃晶格内Fe³⁺的掺杂和NaNbO₃晶格外α-Fe₂O₃的异质结复合.观察到了同步改性NaNbO₃对水体罗丹明B（RhB）光催化降解效率的显著提升,最适Fe含量的改性NaNbO₃对罗丹明B 1 h内的降解率可达95%,表观一级动力学速率常数为改性前NaNbO₃的近7倍.运用X射线衍射（XRD）、扫描电子显微（SEM）、X光电子能谱（XPS）、光致发光（PL）光谱、低温N₂吸附-脱附（BET法）,电子自旋共振光谱（ESR）,紫外-可见漫反射光谱（DRS）及光致电流检测等表征和测量探明改性体系的组成及结构,并表明Fe³⁺对Nb⁵⁺的掺杂取代可通过杂质能级形成、电子和空穴捕获以及溶氧吸附的促进从而有利于对罗丹明B的光催化降解;适量α-Fe₂O₃晶格外复合改性NaNbO₃可通过NaNbO₃与α-Fe₂O₃异质结间电子的跃迁和流动提高复合催化剂的光量子效率.Fe对NaNbO₃晶格内外改性促活的实质可能在于光生载流子迁移的促进和对其复合的抑制.     

线代教学中如何发挥例题的作用

由同济大学编《线性代数》的一个典型例题入手,拓展到多个典型例题,引导学生步步深入,得到行列式计算的解题方法,提高学生分析问题,综合问题,解决问题的能力．     

Stochastic modelling of household behaviour before,during and after a consumer price promotion

A stochastic model is developed to study household behaviour with regard to purchase quantity, brand choice and purchase timing before, during and after a price change and a price promotion such as price-offs and price-cuts. The basic assumption of the model is that price promotion and levels of consumer inventory influence a household's purchase-timing and brand-switching decisions. The model incorporates market segments and brand switching on aggregated demand for the brands by the use of multivariate Markov processes. A transient stochastic model is employed to analyse the dynamic process of household behaviour before, during, and after a price promotion. The interpurchase time that is derived from the model does not require any assumptions and is not independently, identically distributed. An empirical analysis using the Information Resources Incorporated cracker data indicated that (1) price promotion does affect household purchase of the brand and (2) households with larger family size tend to purchase promoted items. We conjecture that households with larger family size take advantage of the lower price of the promoted brands while smaller households tend to remain loyal to one brand.     

水促进的氯化钌催化α-蒎烯加氢反应

考察了水促进的RuCl3催化α-蒎烯加氢反应.结果表明,同传统催化剂或无水RuCl3相比,水对α-蒎烯加氢反应具有明显的促进作用,可显著提高蒎烷选择性及产物中蒎烷顺反比,且容易实现产物的分离及催化剂的循环使用.在RuCl3·3H2O用量1.8mg,α-蒎烯2.5g,m(H2O):m(a-蒎烯)=4:1下,160℃,5M...     

固体酸催化烷基化反应中微量氟化氢反应助剂的作用 Ⅰ.助剂对反应的促进效应

 研究了负载型杂多酸催化剂20%H3PW12O40/SiO2催化的异丁烷与丁烯的烷基化反应. 发现当在反应物料中加入0.0192%(质量分数)含强电负性元素F的反应助剂HF后,在超临界烷基化反应条件下（137 ℃和5.0 MPa）,反应产物烷基化汽油中C8烷烃的含量和目的产物三甲基戊烷的收率均大幅度提高,三甲基戊烷与二甲基己烷的摩尔比值提高了一倍以上. 这是一个重要和有趣的实验现象,它说明微量HF反应助剂可大幅度提高固体酸催化剂对烷基化反应的选择性. 我们把微量反应助剂在固体酸催化烷基化反应中的这种特殊作用称为对烷基化反应的促进效应,这种促进效应已经在我们实验室中被反复证实.