对甲苯磺酸催化微波合成月桂酸甲酯的工艺优化

采用微波辐射加热方法,以对甲苯磺酸为催化剂合成月桂酸甲酯,考察酯化反应条件对产物收率的影响.实验结果表明,反应物甲醇、月桂酸和催化剂的投料摩尔比为n(甲醇)∶n(月桂酸)∶n(催化剂)为20∶1∶0.25,微波功率195W(30%),回流反应70min,酯化收率可达80%.产物用红外光谱,折光率进行了表征.     

2步酯化法制备棕榈酸甲酯

以棕榈酸和甲醇为原料,浓H2SO4为催化剂,采用2步酯化法制备棕榈酸甲酯.第1步反应的最佳条件为:温度为(65±2)℃,催化剂用量为棕榈酸质量的0.5%,甲醇用量为棕榈酸质量的80%,反应时间60 min,酯化率90.06%;第2步反应的最佳条件为:反应温度为(100±5)℃,甲醇流速为1.0 mL/min,反应时间为60 min,棕榈酸甲酯的酯化率为99.26%.     

2步酯化法合成肉豆蔻酸甲酯的工艺研究

以肉豆蔻酸和甲醇为原料,浓硫酸为催化剂,采用2步酯化法合成肉豆蔻酸甲酯.实验结果表明,其最佳工艺参数为:冷凝回流酯化阶段(第1阶段)甲醇的质量分数为80%,催化剂质量分数为0.5%,反应温度为(65±2)℃,反应时间为90 min,酯化率为90.03%;甲醇连续流加酯化阶段(第2阶段)甲醇流速为1.0 mL/min,反应温度为(100±5)℃,反应时间为30～60 min,最终转化率为98.19%.并采用正交法进行验证,得到的单因素实验工艺参数可靠.本实验具有反应时间短,能耗低,转化率高,工艺简单等优点.     

月桂酸甲酯的合成

本文介绍了用月桂酸、甲醇为原料，经硫酸－硫酸钠催化直接酯化合成月桂酸甲酯。     

月桂酸甘油单酯的合成

本文对以月桂酸和甘油为原料,直接酯化制备月桂酸甘油单酯的合成条件进行了试验研究,确定了最佳条件:甘油/月桂酸(摩尔比)为2.5:1,反应温度180℃,反应时间3hr,磷酸作催化剂。在此条件下,单酯收率高达99.27％。合成酯中,单酯含量达到75.34％,超过了近期化学文献报导的水平70.8％。     

二氧化硅负载磷钨酸催化合成月桂酸乙酯

以二氧化硅负载磷钨酸合成月桂酸乙酯,研究了原料量比、催化剂用量、反应温度和反应时间对产品收率的影响.实验结果表明,二氧化硅负载磷钨杂多酸是合成月桂酸乙酯的良好催化剂,在酸醇摩尔比1∶5,催化剂用量为酸质量的6.0%,反应温度90℃和反应时间4.0h的条件下,月桂酸乙酯的产率达到80%以上.     

月桂酸甲酯磺酸钠乳化剂的制备及其在丙烯酸酯乳液聚合中的应用

以月桂酸为原料、甲醇为酯化剂、氯磺酸为磺化剂,通过酯化、磺化、中和等反应制备了月桂酸甲酯磺酸钠（C12-MES）,计算和测定了亲水亲油平衡值（HLB）、临界胶束浓度（CMC）和三相点（K点）,并将其作为乳化剂应用于丙烯酸酯的乳液聚合,考察了乳化剂用量对单体转化率、乳液稳定性、乳胶粒粒径的影响。结果表明,当月桂酸甲酯与氯磺酸物质的量比为1:1.2,熟化时间60 min,且用质量分数为20%的甲醇再酯化,所得C12-MES产品色泽较浅,活性物含量能达到80%以上,其HLB值、CMC、K点分别为14.7、13.20 mmol/L（28 ℃）和0 ℃以下;以制得的C12-MES为乳化剂合成的丙烯酸酯共聚物乳液稳定,乳胶粒的粒径在100～200 nm之间,粒度分布小于0.015。     

月桂酸乙酯合成新工艺的研究

以硅藻土负载硫酸铁为催化剂,4A分子筛作脱水剂,无水乙醇作带水剂,由月桂酸和乙醇回流分水合成香料月桂酸乙酯。通过正交实验确定最佳反应条件为：酸醇摩尔比为1∶10,催化剂用量15%,回流反应12h,温度为72~80℃,酯转化率达93.8%。催化剂可重复使用2~3次。     

硫酸钛催化月桂酸乙酯的合成研究

以固体硫酸钛为催化剂、月桂酸和无水乙醇为原料,合成香料月桂酸乙酯.考察了酸醇物质的量之比,催化剂的用量,反应温度,反应时间及带水剂等因素对合成反应的影响.实验表明: 月桂酸和无水乙醇的摩尔比为1∶5,催化剂用量为反应物料总质量分数的4.5%,环己烷为带水剂, 控制反应温度为90～100℃,反应时间3.5小时的优化条件下, 月桂酸乙酯的收率可达90.7%.     

两步酯化法制备油酸甲酯的实验研究

采用油酸和甲醇为原料,浓H2SO4为催化剂,对两步酯化法制备油酸甲酯的工艺参数进行实验研究。实验结果表明两步酯化法制备油酸甲酯的最佳工艺参数为：冷凝回流循环阶段（第一阶段）甲醇用量为油酸重的80%,催化剂用量为油酸重的0.5%,反应温度为65±2℃,反应时间为60min;甲醇连续流加阶段（第二阶段）甲醇流速为1mL/min,反应温度为100±5℃,反应时间为30～60min,最优转化率为98.65%。并对最佳工艺参数采用响应面法进行优化处理。实验具有反应时间短,降酸迅速,能耗小,转化率高,工艺简单,投资成本低等优点,进一步说明两步酯化法生产生物柴油的可行性和经济性。     

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.     

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     

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.     

Wuhan University Journal of Natural Sciences TOTAL CONTENTS

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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。