KZnF_3∶Eu的水热合成及其光谱性质

采用中温水热法合成了立方钙钛矿单相 KZn F3 及 KZn F3 ∶ Eu,通过 SEM观察了产物形态 ;XPS测定结果表明 ,产物含氧量不高 ;荧光光谱及 ESR谱表明 ,KZn F3 ∶ Eu体系中 Eu2 +与 Eu3 +共存 ,进一步讨论了不等价取代中的电荷补偿途径

Ce3+ -> Eu2+ energy transfer in BaLiF3 phosphor

Photoluminescence characteristics and the energy transfer between Ce3+ and Eu2+ in BaLiF3 host lattice have been investigated. A series of concentrations of Ce3+ ion with a fixed Eu2+ concentration in doubly doped BaLiF3:Ce3+,Eu2+ have been studied. According to the defects forming after Eu2+ and Ce3+ entering the host lattice, cerium ions occupy the positions of nearest neighbors of the europium ions. The energy transfer probability and critical distance are calculated. (C) 1999 Elsevier Science Ltd. All rights reserved.

(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er)的合成及晶体结构

合成了三茚基稀土配合物(η~5-C_9H_7)_3Ln·OC_4H_8(Ln=Nd、Gd、Er),经元素分析、红外光谱、水解产物核磁共振谱及质谱表征,并测得了(η~5-C_9H_7)_3Nd·OC_4H_8(1)及(η~5-C_9H_7)_3Gd·OC_4H_8(2)的晶体结构。(1)、(2)均属六方晶系,P6_3空间群,Z=2。(1)的晶体学参数为a=b=1.1843(3)nm,c=1.0304(4)nm,V=1.25165(87)nm~3,D_c=1.49g·cm~(-3),最后一致性因子R=0.049;(2)的晶体学参数a=b=1.1805(2)nm,c=1.0236(2)nm,V=1.23536(56)nm~3,D_c=1.54 g·cm~(-3),R=0.023。平均Nd-C=0.2812nm,Gd-C=0.2795nm;Nd-O=0.2557(21)nm,Gd—O=0.2459(13)nm。配合物中四氢呋喃的四个碳原子处于完全无序状态。

稀土离子4f轨道和配位体的共价行为研究

稀土离子4f轨道是否参与成键是一个引入注目的课题,多年来一直存在不同见解。一种认为不参与成键,理由是由于5s,5p壳层的屏蔽,4f轨道位于内壳层,并且到目前为止,分子轨道理论计算结果表明4f轨道不参与成键。另一种认为可以形成较弱的共价键,并发展了一种角重迭模型利角参数来研究共价行为,但是具体共价行为的数量级尚未有明确结论。我们在

Life history strategies of Calanus sinicus in the southern Yellow Sea in summer

Ecological and physiological features of the planktonic copepod Calanus sinicus in the southern Yellow Sea in summer were studied to reveal its life history strategy. From the coastal shallow waters to the central part of the southern Yellow Sea, a shift of the stage composition occurs from being dominated by the egg-nauplius stage to being dominated by the fifth copepodite (CV) stage. Most CVs reside in the Yellow Sea Cold Water Mass (YSCWM), where both temperature and food abundance are low. CVs in the YSCWM have longer body lengths, heavier body weights and higher carbon contents than those outside the YSCWM. Onboard incubations show that the development of CVs in the YSCWM is suspended. Energy conservation, development suspension and lack of diel vertical migration (DVM) behavior suggest a diapause status for the CVs in the YSCWM, although vertical distribution patterns indicate the CV individuals are not fully synchronous in physiology and development. This adaptive oversummering strategy would help C. sinicus to live through the warm and food-limited summer in the central part of the southern Yellow Sea; both low temperature and low food supply are necessary for CV to maintain the resting state in the YSCWM. Calanus sinicus exhibits different life history strategies in different regions of the southern Yellow Sea in summer.

高寒草甸不同海拔梯度下多年生黄帚橐吾的克隆生长特征

通过对多年生植物黄帚橐吾(Ligularia virgaurea)在四个不同海拔梯度下的克隆生长行为进行研究,结果表明:(1)资源水平(土壤养分)、干扰和群落性质影响间隔物(spacer)长度的变化.在第一和第四海拔梯度中(土壤养分较丰富)间隔物长度较短,而在第二和第三海拔梯度中(土壤养分较贫乏)间隔物长度较长,说明其能对资源水平和生境优劣作出反应.(2)分枝强度(branching intensity)随资源水平的增加而上升.(3)在高海拔、寒冷和资源较丰富的生境中,其生物量的投资偏向于地下部分生物量,说明黄帚橐吾的资源分配方式受到环境资源条件和群落性质的影响.

一个数控自动编程系统的自然语言接口

本文简要介绍了一个数控自动编程专家系统的自然语言接口的实现.该自然语言接口是以我们研制的数控自动编程专家系统为背景,运行在 SUN3/4 工作站的 UNIX 下和 IBM/AT 机的 DOS 下,用 C语言编程.该自然语言接口由词法分析、句法分析、语义语用分析、目标生成和图形仿真五个模块及相应的知识库构成.该接口能够接受数控编程系统所需的对工件的英语自然语言描述并处理一些比较简单的英语语言现象.

地理信息系统支持下的滑坡灾害空间分析预测-以云南小江流域为例

As a typical geological and environmental hazard, landslide has been causing more and more property and life losses. However, to predict its accurate occurring time is very difficult or even impossible due to landslide's complex nature. It has been realized that it is not a good solution to spend a lot of money to treat with and prevent landslide. The research trend is to study landslide's spatial distribution and predict its potential hazard zone under certain region and certain conditions. GIS(Geographical Information System) is a power tools for data management, spatial analysis based on reasonable spatial models and visualization. It is new and potential study field to do landslide hazard analysis and prediction based on GIS. This paper systematically studies the theory and methods for GIS based landslide hazard analysis. On the basis of project "Mountainous hazard study-landslide and debris flows" supported by Chinese Academy of Sciences and the former study foundation, this paper carries out model research, application, verification and model result analysis. The occurrence of landslide has its triggering factors. Landslide has its special landform and topographical feature which can be identify from field work and remote sensing image (aerial photo). Historical record of landslide is the key to predict the future behaviors of landslide. These are bases for landslide spatial data base construction. Based on the plenty of literatures reviews, the concept framework of model integration and unit combinations is formed. Two types of model, CF multiple regression model and landslide stability and hydrological distribution coupled model are bought forward. CF multiple regression model comes form statistics and possibility theory based on data. Data itself contains the uncertainty and random nature of landslide hazard, so it can be seen as a good method to study and understand landslide's complex feature and mechanics. CF multiple regression model integrates CF (landslide Certainty Factor) and multiple regression prediction model. CF can easily treat with the problems of data quantifying and combination of heteroecious data types. The combination of CF can assist to determine key landslide triggering factors which are then inputted into multiple regression model. CF regression model can provide better prediction results than traditional model. The process of landslide can be described and modeled by suitable physical and mechanical model. Landslide stability and hydrological distribution coupled model is such a physical deterministic model that can be easily used for landslide hazard analysis and prediction. It couples the general limit equilibrium method and hydrological distribution model based on DEM, and can be used as a effective approach to predict the occurrence of landslide under different precipitation conditions as well as landslide mechanics research. It can not only explain pre-existed landslides, but also predict the potential hazard region with environmental conditions changes. Finally, this paper carries out landslide hazard analysis and prediction in Yunnan Xiaojiang watershed, including landslide hazard sensitivity analysis and regression prediction model based on selected key factors, determining the relationship between landslide occurrence possibility and triggering factors. The result of landslide hazard analysis and prediction by coupled model is discussed in details. On the basis of model verification and validation, the modeling results are showing high accuracy and good applying potential in landslide research.

菲和萘的非线性吸附过程研究

分配模型认为疏水性有机物在土壤上的吸附过程是一种分配的过程[1,2],平衡分配系数与土壤有机碳的含量存在线性相关关系.Weber和Huang[3,4]提出土壤吸附有机污染物的三端员模式.认为无机矿物表面和无定形有机质对有机污染物的吸附以相分配为主,而凝聚态有机质对有机污染物吸附则表现为非线性的.Pignatello和Xing[5,6]指出双模式吸附模型可将土壤有机质分为溶解相和孔隙填充相两个部分;认为有机污染物在溶解相上的吸附是一个分配过程,而在孔隙填充相中的吸附则服从兰格缪尔吸附等温模型,表现为非线性.可以肯定土壤有机质是引起疏水性有机物非线性吸附过程的主要组分.因此,本研究利用现代分析方法表征土壤有机质的化学组成和结构;定量研究多环芳技烃化合物菲和萘在吸附剂上的等温吸附过程;探讨疏水性有机污染物的非线性等温吸附与吸附剂中有机质化学组成和结构之间的关系.