TiSiW1240/TiO2催化合成抗氧化剂没食子酸丙酯的研究

以TiSiW12O40/TiO2为催化剂,用没食子酸与正丙醇直接酯化合成了抗氧化剂没食子酸丙酯(PG),通过正交试验确定了醇酸物质的量比、催化剂用量、反应时间对PG收率的影响.得到的最佳工艺条件为:醇酸物质的量比为8:1,催化剂用量为没食子酸质量的2%,反应时间为3 h,PG的收率可达95.1%.实验表明,该催化剂用于合成PG具有极好的催化活性和重复使用性.     

TiSiW_(12)O_(40)/TiO_2催化合成抗氧化剂没食子酸丙酯的研究

以TiSiW12O40/TiO2为催化剂,用没食子酸与正丙醇直接酯化合成了抗氧化剂没食子酸丙酯(PG),通过正交试验确定了醇酸物质的量比、催化剂用量、反应时间对PG收率的影响.得到的最佳工艺条件为:醇酸物质的量比为8∶1,催化剂用量为没食子酸质量的2%,反应时间为3 h,PG的收率可达95.1%.实验表明,该催化剂用于合成PG具有极好的催化活性和重复使用性.     

硫酸镍催化合成乙酸丁酯

以硫酸镍为催化剂合成乙酸丁酯,考察了催化剂用量、醇酸物质的量比、反应时间及催化剂重复使用次数等因素对酯化率的影响。结果表明硫酸镍具有催化活性高,易分离回收,重复使用性良好,无废液排放等优点;在最佳反应条件下,酯化率为94.8%。     

难溶钨硅酸盐催化合成柠檬酸三丁酯

合成了钨硅酸三乙醇铵盐并用于柠檬酸三丁酯的催化合成，考察了催化剂用量、醇酸的物质的量比、反应时间对酯化率的影响，结果表明，该催化剂具有较高的催化活性，易回收，可重复使用5次以上。     

硫酸氢钠催化合成乙酸异戊酯

以乙酸和异戊酸为原料,采用硫酸氢钠为催化剂合成了乙酸异戊酯.当反应时间为1h,醇酸物质的量比为1∶3,催化剂用量为醇酸总量的3.0%,反应温度为130～135℃,酯的产率可达85%以上.     

正丁基吡啶硫酸氢盐离子液体催化合成棕榈酸甲酯的试验研究

采用正丁基吡啶硫酸氢盐离子液体为催化剂,对棕榈酸和甲醇催化酯化合成棕榈酸甲酯的影响因素进行了研究.试验结果表明:棕榈酸物质的量比为50∶1、反应温度为70℃、催化剂用量为6%和反应时间为110 min时酯化率最高,在此基础上进行了正交试验极差分析,各因素对反应酯化率的影响主次顺序为:催化剂用量>反应时间>反应温度>醇酸摩尔比,反应的最佳条件是:催化剂用量为8%,反应时间为130 min,反应温度为70℃,醇酸物质的量比为50∶1,在此最优条件下进行验证试验,通过验证试验可测得酯化率为98.63%.根据试验数据进行方差分析表明,反应时间、反应温度、醇酸摩尔比和催化剂用量4个因素的水平变化对酯化率均无显著影响.     

微波辐射纳米固体超强酸催化合成尼泊金庚酯

以纳米固体超强酸SO42-/ZrO2为催化剂,以对羟基苯甲酸和正庚醇为原料,在微波辐射下合成了尼泊金庚酯。讨论了微波功率、微波辐射时间、催化剂用量、醇酸物质的量比等对合成尼泊金庚酯产率的影响。结果表明,微波功率450 W、微波辐射30 min、醇酸物质的量比3.0∶1、催化剂用量为酸质量的1.5%,尼泊金庚酯的产率可达96.0%。同时,考查了催化剂的重复使用性。     

催化剂 WO3/TiO2的制备及催化合成乙酸正丁酯

制备了催化剂WO3/TiO2,研究了该催化剂在乙酸正丁酯合成中的催化性能.实验结果表明:当醇酸的物质的量比为1∶1.1,反应时间为120 min,催化剂用量为0.6g,反应温度为130℃时,酯化率达到最大值83.6%.该催化剂有良好的循环使用性.     

六水合三氯化铝催化合成己二酸二甲酯

以己二酸和甲醇为原料,六水合三氯化铝为催化剂合成己二酸二甲酯,通过正交实验考察了催化剂用量、醇酸摩尔比、反应时间和反应温度等因素对酯化反应的影响,确定了六水合三氯化铝为催化剂催化酯化的最佳条件:己二酸的物质的量为0.05mol,醇酸摩尔比为8∶1,催化剂用量为1.0s,反应时间为2.5小时,反应温度为100℃.     

H3PW12O40/SiO2催化合成季戊四醇四庚酸酯的研究

以正硅酸乙酯为硅源，采用溶胶-凝胶法制备硅载磷钨酸催化合成了季戊四醇四庚酸酯．考察了催化剂用量、醇酸摩尔比、反应温度、反应时间以及催化剂重复使用对酯含量的影响．实验表明，在催化剂用量(质量分数)为总体系的2％、醇酸摩尔比1：6、反应温度120℃～200℃、反应时间4h的条件下，酯化率可达96％以上，且催化剂重复使用效果好．     

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.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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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.     

An Affordable Accurate Evaluation of the Binding Conformations Predicted by Molecular Docking Studies in Bio-System

正Recently,docking has been widely used to predict the binding-modes of protein-inhibitors,when the crystal complexes structure was absent.Most docking algorithms are able to generate a large number of probable conformations,it,however,is difficult to effectively evaluate these docking poses and identify the most reasonable bindingmode.In the present study,on the basis of the crystallographic data of human 3-hydroxy-3-methylglutaryl coenzyme     

WIMAX与WI-FI技术分析及联合组网

介绍了WiMAX与Wi-Fi两种无线宽带接入技术,并对两者之间的关系及相互之间的影响做了对比及分析,并对WiMAX的关键技术进行了详细说明,最后对两者的联合组网方式做了简单的探讨。