Induced modi fi cations in the properties of Sr doped BiFeO3 multiferr oics

Multiferroics exhibit unique combination of ferroic properties,simultaneously.For instance,in BiFeO3,magnetic and electric properties co-exist.In this work,BiFeO3 and Sr-doped BiFeO3 samples with general formula,Bi1-x Srx FeO3(x=0.00,0.05,0.10,0.20,and 0.30) were synthesized by sol-gel auto-combustion technique,in order to investigate these ferroic properties.The samples were confrmed to have perovskite type rhombohedral structure,characteristic of BiFeO3.A dilute phase of Bi2Fe4O9was also found in all the Sr-doped samples.The micrographs of the palletized samples revealed that minutely doped Sr might not have any effect on the morphology of the samples.Frequency dependent dielectric measurements were carried out at room temperature for all the samples from 100 Hz to 1 MHz.The dielectric constant of un-doped sample at low frequency was 52 which decreased with increasing Sr doping.An enhancement of magnetic properties was observed with increasing the Sr contents.Pure BiFeO3 material was observed to have the least value of remanent magnetization.As the Sr2+ tions were doped in BiFeO3,its magnetization and remanence were increased to 0.867 emu/g and 0.175 emu/g,respectively,at x=0.30.     

连续小波变换HATR—FTIR分析应用于中药枸杞子与同属非正品鉴别的研究

采用水平衰减全反射傅立叶变换红外光谱（HATR—FTIR）法直接测定了枸杞子与同属非正品的HA—TR-FTIR谱图,应用主成分分析法确定出所有区域的信息负荷量,在1750-750cm^-1采用Morlet小波函数对枸杞子及其非正品的HATR-FTIR谱图进行了一维连续小波变换。结果发现,傅立叶变换红外光谱与连续小波变换分析相结合在中药材枸杞子与非正品的鉴别中具有应用价值,方法简便、快速、准确,而且不需制备样品。     

有序介孔分子筛的生物大分子固定化研究

利用介孔材料孔径和生物大分子的尺寸相当的特点,采用有序介孔分子筛SBA-15为载体实现对血红蛋白（Hb）和葡萄糖氧化酶（GOx）的固载,并考察其生物活性．紫外可见光谱和红外吸收光谱表明：以介孔分子筛SBA-15作为固定载体可以有效地吸附血红蛋白和葡萄糖氧化酶,且在吸附过程中很好的保持了蛋白质的天然二级结构．     

基于元搜索引擎技术的科研项目信息服务系统

本文针对信息技术这一特定领域,提出了一个通过元搜索引擎向特定用户群体一高校教师提供科研项目信息服务的系统,使其可以使用基于关键词的检索、目录式检索以及信息推送服务。该系统通过元搜索引擎提供统一的访问服务,同时利用用户检索行为信息动态反馈其兴趣主题并调整文档聚类结果．因此可有效提高项目信息检索的查准和查全率,更好地帮助用户快速检索到所需的科研项目信息。     

基于有序树的广义表运算算法设计

通过分析与研究广义表与有序树之间的关系和性质,并在相关文献对广义表的研究基础上,提出了基于有序树的广义表表头、表尾、长度和深度的定义,并根据有序树的二叉链表表示法对以上定义进行算法设计.     

Influence of stacking fault energy on formation of long period stacking ordered structures in Mg ? Zn? Y ? Zr alloys

The influence of alloying elements on the stacking fault energy (SFE) of Mg ? Y? Zn? Zr alloys was calculated by using first-principles, and the microstructure of as-cast Mg-1.05Y-0 .79Zn-0.07Zr (mole fraction, %) alloy prepared by conventional casting was investigated by SEM, TEM and HRTEM. The block-like long period stacking orde red (LPSO) phase, the lamellar LPSO phase and stacking faults were observed simulta neously and the lamellar LPSO structure an d stacking faults were both formed on (0001)α-Mg habit plane and grown or extended along [010-1]α-Mg direction. The calculation results by the first-principles showed that the addition of Y can sharply decrease the stacking fault energy of the Mg? Zn?Y? Zr alloy, while Zn slightly increases the stacking fault energy of the alloy. The influence of stacking fault energy on the formation of LPSO was di scussed. It shows that LPSO may nucleate directly through stacking faults and the lower stacking fault energy was in favor of formation of LPSO.     

BCI-代数的加法序半群的理想

说明了一般BCI-代数(X,*,0)的加法半群是序半群,讨论了它作为序半群的理想和核的性质,并由此刻画了BCK-代数和p-半单BCI-代数.     

First-principles study of the interactions of hydrogen with low-index surfaces of PdCu ordered alloy

PdCu catalysts play a key role in several hydrogen-involved processes. Among these reactions, the interaction of hydrogen with PdCu essentially determines the catalytic performance. However, the response of PdCu to surrounding hydrogen has been poorly investigated, especially for specific facets of PdCu at different environment. In this work, taking temperature and hydrogen pressure into account, we studied the hydrogen-surface interactions for four low-index surfaces of PdCu through first-principles calculations. It was found that H-PdCu adsorption strong relies on the facets, hydrogen coverage, and reaction environment (temperature and H-pressure). Our work highlights the importance of the environment on the nature of catalyst surfaces and reactions and offers a plausible way to investigate the interactions between gas and the surfaces of nanocatalysts in real reactions.     

超临界流体技术制备有序材料研究进展

超临界流体由于其特殊的性质, 是制备在纳米及微米尺度范围有序结构的一种良好的溶剂, 其中包含超临界二氧化碳. 超临界流体根据其特殊性, 可扩展“自上而下”的方法, 包括沉积法、清洁法、刻蚀法和表面修饰法, 从而达到最精细的雕琢. 当采用“自下而上”的方法时, 由于二氧化碳分子与聚合物的相互作用, 尤其是与嵌段共聚物模板的作用, 可促使完全的结构精细化, 因此超临界流体中纳米粒子和纳米线的合成近年来发展迅速, 由此制备的有序结构材料在微电子、探测技术、能量转换等领域显示了令人欣喜的应用前景. 本文就有关领域, 对超临界流体技术的基础及其应用进行了评述.     

K-最近邻分类技术的新发展与技术改进

K-最近邻算法是数据挖掘分类方法中最常用的算法之一.在很多实际问题上都有应用.本文对近年来基于K-最近邻算法的各种改进技术进行了分析.从速度提高和准确度提高两个方面给予了归纳.