可见光敏感型纳米氮氧化钛光催化剂的制备和表征

利用高温气固相反应合成制备纳米氮氧化钛．研究制备过程中反应温度和反应时间对样品粒径和晶型的影响．采用X射线衍射、透射电子显微镜、X射线光电子能谱和紫外可见光谱等手段对样品形态结构进行表征．结果表明，纳米氮氧化钛粒径为10～30nm，平均晶粒尺寸为16nm，颗粒晶型为锐钛矿型，并且发现氮氧化钛对波长在400～500nm的可见光有明显吸收．     

纳米羟基磷灰石的制备及其吸附性能

以硝酸钙和磷酸二氢铵为原料用共沉淀法制备纳米羟基磷灰石(HA)，采用X射线衍射、透射电子显微镜、热重．差示扫描量热等手段对样品形态结构进行表征．结果表明，制备的六方晶型纳米羟基磷灰石长轴约为60nm，短轴约为20nm，粒径均匀且分散性较好．该文还研究了纳米HA对Ag^ 的吸附性能．     

短纤维石棉制备纤维状SiO2的原理与方法

对纤蛇纹石石棉的化学成分、晶体结构、形态特征和活性进行了研究,探讨了纤蛇纹石石棉制备纤维状纳米SiO2的原理,并对试验产物进行了分析.结果表明:纤蛇纹石石棉是天然产出的纳米管状材料,其内管直径为3.5～24 nm,多数小于11 nm,外管直径为16～56 nm,绝大多数在20～50 nm范围内.纯净的纤蛇纹石石棉样品的化学成分主要为SiO2、MgO和H2O ,其质量分数SiO2约为42%,MgO约为42%,结构水H2O 约为13%.纤蛇纹石具有卷管状结构,化学键特点决定了其具有很好的化学活性和可改造性,为制备纤维状纳米SiO2粉体材料创造了基础.纤蛇纹石石棉纤维经酸处理后,MgO等组分被浸取出来转变为硫酸盐,而残留下非晶质纳米SiO2纤维残骸;经后处理即可获得纤维状SiO2纳米材料.     

GaN掺杂Er~(3+)纳米颗粒的电子结构及光学性能分析

采用Material Studio软件模拟GaN掺杂稀土元素Er⁽³⁺⁾浓度在6.25%下的晶格结构,分析了掺杂GaN的光学特性,结论表明,掺杂后的GaN具有较好的发光性能.同时,实验上用氨还原法制备了3组掺杂GaN∶Er(3+)浓度在6.25%下的晶格结构,分析了掺杂GaN的光学特性,结论表明,掺杂后的GaN具有较好的发光性能.同时,实验上用氨还原法制备了3组掺杂GaN∶Er⁽³⁺⁾纳米颗粒.3组样品的X射线衍射结果均显示样品结构为六方纤锌矿结构,利用Scherrer公式,计算得到3组样品GaN∶Er(3+)纳米颗粒.3组样品的X射线衍射结果均显示样品结构为六方纤锌矿结构,利用Scherrer公式,计算得到3组样品GaN∶Er⁽³⁺⁾纳米颗粒的平均晶粒大小为25.9nm;测量了3组样品的GaN∶Er(3+)纳米颗粒的平均晶粒大小为25.9nm;测量了3组样品的GaN∶Er⁽³⁺⁾纳米颗粒的室温光致发光谱,获得了样品在可见光区(位于375(3+)纳米颗粒的室温光致发光谱,获得了样品在可见光区(位于375⁶50nm)的3个发光峰并对3组样品进行分析比较,分析了样品520nm的激发光谱.由光致发光谱得到的3条发光峰表明所制备的GaN∶Er650nm)的3个发光峰并对3组样品进行分析比较,分析了样品520nm的激发光谱.由光致发光谱得到的3条发光峰表明所制备的GaN∶Er⁽³⁺⁾具有较好的光学性能.理论和实验上确定了稀土E(3+)具有较好的光学性能.理论和实验上确定了稀土E⁽³⁺⁾离子掺杂GaN纳米颗粒的较合适的掺杂浓度为6.25%.     

共沉淀法制备LaPO4：Ce，Tb纳米棒及其发光性能

采用共沉淀法合成了LaPO4：Ce,Tb纳米棒,利用XRD和SEM分别测试了样品的物相结构及形貌,用荧光光谱仪测试了样品的激发光谱和发射光谱,研究了不同Ce^3＋含量对LaPO4：Cex,Tb0.06纳米棒发光性能的影响。结果表明：LaPO4：Ce,Tb样品为独居石结构,属于单斜相;样品呈棒状,其长度为100～1000nm,宽度为11～82nm;LaPO4：Ce,Tb纳米棒的最强发射波长为544nm。     

多臂CdS纳米棒的合成、表征及修饰

以二乙基二硫代氨基甲酸镉为单一前驱体,在油胺介质中裂解,得到多臂状CdS纳米棒.研究了前体中Cd/S配比和裂解时间对CdS纳米棒光学性能的影响.实验结果表明,该方法合成的CdS纳米棒为六方晶态结构,直径约为5 nm,臂长为36 nm左右,其耐光漂白性好,在最佳条件下量子产率可达2O%.分别用透射电镜、高分辨透射电镜、紫外-可见吸收光谱、荧光光谱对样品的结构形态和光学特性进行了表征.同时,采用二巯基辛酸为修饰剂,得到了性能优良的水溶性CdS纳米棒.     

溶胶-凝胶法制备FePt纳米颗粒及其性质研究

通过溶胶-凝胶法制备了L10相FePt纳米颗粒,并利用X射线衍射(XRD)、振动样品磁强计(VSM)、透射电子显微镜(TEM)等测试手段对所制备的样品进行了结构和磁性表征.XRD及TEM分析表明,700℃所制备的FePt纳米颗粒为面心四方(FCT)结构,颗粒形状为球形且分散性较好,晶粒尺寸约为12 nm.磁性测试结果表明,L10相的FePt纳米颗粒室温下具有铁磁性,其矫顽力为1 887 Oe.     

超声化学制备ZnO单分散纳米球及光学性能

以Zn（CH3COO）2.2H2O为锌源、三乙醇胺（TEA）为碱源,通过无模板超声化学技术制得了大面积单分散的纳米ZnO多孔球和实心球.产品用XRD、FESEM、IR、UV-vis吸收光谱和光致发光光谱对所制得的ZnO样品进行了结构、形貌和光学性质的测试.通过调控TEA浓度,可获得由20～25 nm的粒子组装成的ZnO多孔球和实心球,多孔球的直径为120～260 nm,实心球的直径为200～340 nm.对球形ZnO纳米结构的生长过程进行了探讨.     

利用电石渣制备纳米碳酸钙的研究

以电石渣为原料 ,制备纳米碳酸钙 .研究制备过程中原料浓度、气体浓度、气体流速、反应温度、搅拌速度、添加剂用量等对产品粒径及晶型的影响 .采用 TEM、XRD等手段对颗粒形态与结构进行表征 ,纳米碳酸钙平均颗粒粒径约 5 0 nm,晶粒平均尺寸约 30 nm,为方解石型 .     

导电聚苯胺不同纳米结构的制备

分别以纤维状材料(如H3PW12O40/PVA纤维、头发丝、涤纶丝、玻璃丝、细铜丝)、环状材料(如细铜丝环、头发丝环)以及膜状材料(如保鲜膜)等为模板,以杂多酸H3PW12O40为掺杂剂,过二硫酸铵为氧化剂,制备了具有不同纳米结构的多酸掺杂聚苯胺材料.采用红外光谱和扫描电镜对聚苯胺进行了结构和形态表征.结果表明:模板形态对聚苯胺纳米结构有较大的影响,纤维状模板导致聚苯胺具有纳米棒结构,直径在300～400 nm之间;环状模板导致聚苯胺具有微米球结构,直径在1 000～3 000 nm之间;膜状模板导致聚苯胺具有片状结构.所得材料的电导率均大于0.1 S/cm.     

An Index mechanism for multi-scale view in spatial databases

There are numerous geometric objects stored in the spatial databases. An importance function in a spatial database is that users can browse the geometric objects as a map efficiently. Thus the spatial database should display the geometric objects users concern about swiftly onto the display window. This process includes two operations:retrieve data from database and then draw them onto screen. Accordingly, to improve the efficiency, we should try to reduce time of both retrieving object and displaying them. The former can be achieved with the aid of spatial index such as R-tree, the latter require to simplify the objects. Simplification means that objects are shown with sufficient but not with unnecessary detail which depend on the scale of browse. So the major problem is how to retrieve data at different detail level efficiently. This paper introduces the implementation of a multi-scale index in the spatial database SISP (Spatial Information Shared Platform) which is generalized from R-tree. The difference between the generalization and the R-tree lies on two facets: One is that every node and geometric object in the generalization is assigned with a importance value which denote the importance of them, and every vertex in the objects are assigned with a importance value,too. The importance value can be use to decide which data should be retrieve from disk in a query. The other difference is that geometric objects in the generalization are divided into one or more sub-blocks, and vertexes are total ordered by their importance value. With the help of the generalized R-tree, one can easily retrieve data at different detail levels.Some experiments are performed on real-life data to evaluate the performance of solutions that separately use normal spatial index and multi-scale spatial index. The results show that the solution using multi-scale index in SISP is satisfying.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

<正>~~     

Advances in broadband wireless communications under high-mobility scenarios

Future mobile communication systems aim at providing very high data transmission rates, even in high-mobility scenarios such as high-speed wheel-track trains, maglev trains, highway vehicles, airplanes, guided missiles or spacecraft. A particularly important commercial application is the strong and increasing worldwide demand for high- speed broadband wireless communications （up to 574.8 km/ h test speeds or 380 km/h commercial speeds） in railways, providing data, voice and video services for applications such as onboard entertainment services to passengers, train control, train dispatch, train sensor status handling and sur- veillance. In such high-mobility scenarios, there are a number of communication challenges, including fast hand- over, location updating, high-speed channel modeling, estimation and equalization, anti-Doppler spreading tech- niques, fast power control, and dedicated network architec- ture. Because signal transmission in very high-speed scenarios will inevitably experience serious deterioration, it is imperative to develop key broadband mobile communi- cation techniques for such high-speed vehicles.     

Perspherical Approaches for Electrons in Atoms and Charged Excitons in Quantum Wells

Instead of following Fock’s expansion,we solve the Schrodinger equation for some quantum mechanical manybody systems such as electrons in atoms and charged excitons in quantum wells in a similar way in hyperspherical coordinates by expanding the wave functions into orthonormal complete basis sets of the hyperspherical hannonics(HHs)of hyperangles and generalized Laguerre polynomials(GLPs)of the hyperradius.This leads the equation to     

Scale-based spatial data model for GIS

Being the primary media of geographical information and the elementary objects manipulated, almost all of maps adopt the layer-based model to represent geographic information in the existent GIS. However, it is difficult to extend the map represented in layer-based model. Furthermore, in Web-Based GIS, It is slow to transmit the spatial data for map viewing. In this paper, for solving the questions above, we have proposed a new method for representing the spatial data. That is scale-based model. In this model we represent maps in three levels: scale-view, block, and spatial object, and organize the maps in a set of map layers, named Scale-View, which associates some given scales.Lastly, a prototype Web-Based GIS using the proposed spatial data representation is described briefly.     

英文诗歌中的喻类修辞

为了有助于提高英文爱好者的个人情操、文化素养和学习兴趣,以及专业人员对英语学习和研究进行多途径的探索,本文通过一些精选诗歌的引证和分析,着重论述了喻类修辞法在英文诗歌中的运用其及效果。     

Man Is Unable to Change the Miserable Life——Analysis of the Arrangement of Four Characters in The Glass Menagerie

Tennessee Williams is considered as one of the most important American playwrights since World War II.The Glass Menagerie is his first successful drama,which describes a tragic situation of family and means to say that Man is unable to change the miserable life,no matter whatever means he try,This essay focuses on the analysis of the arrangement of the four main characters:Laura.Amanda,Jim and Tom to reveal the theme.Laura is fragile.Amanda is brave.Jim is vital.Tom is sensible.And all of them develop and try the different means to struggle against life,but fail tragically.With the evidence,the paper comes to conclusion naturally that Man is unable to change the miserable life,and he dooms to fail.     

Characterization of root-nodulating bacteria on Retama raetam in arid Tunisian soils

The aim of this study is to investigate the diversity of Retama raetam root-nodule bacteria isolated from arid regions of Tunisia. Twelve isolates, chosen as representative for different 16S rRNA gene patterns, were characterized by 16S rRNA gene sequencing and phenotypic analysis. Isolates were assigned to Sinorhizobium, Rhizobium and Agrobacterium. Symbiotic properties of Sinorhizobium and Rhizobium isolates showed a large diversity in their capacity to infect their host plant and fix atmospheric nitrogen. Strain RK 22 identified as Rhizobium was the most effective isolate.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。