盐湖卤水氨法制备氢氧化镁工艺探究

以青海察尔汗盐湖卤水为原料,以氨水为沉淀剂,采用直接沉淀法制备了粒径分布均匀、分散性良好的微米级球状氢氧化镁。考察了反应温度、陈化时间、氨水加入量、沉淀剂滴加速度等工艺条件对氢氧化镁结晶及产率的影响,并通过正交试验设计优化实验条件。采用SEM分析手段对产品的粒径分布、形貌等进行了表征。结果表明,当反应温度为60℃、陈化时间为150 min、氨水加入量40 mL、沉淀剂滴加速度为6 mL/min时,制备的氢氧化镁晶体粒度均匀,结构清晰,分散性好,产率较高,产品平均粒径为20μm。该工艺条件为制备微米级球状氢氧化镁晶体提供了科学依据。     

纳米氢氧化镁晶体阻燃剂的制备及其性质

以氯化镁、硫酸镁及氢氧化钠为原料,采用水热法制备了尺寸在50nm左右的氢氧化镁纳米晶。用XRD、TEM、BET等对纳米晶的化学成分、大小、结构及表面积大小进行了表征。采用TG、DSC对产品的热学性质进行了研究,结果表明:作为阻燃剂,纳米晶氢氧化镁具有比常规微米级氢氧化镁更为优越的热学性质。对影响纳米晶尺寸的因素及应用于阻燃剂的可行性进行了分析。     

氢氧化镁循环反应法制取硝酸钾研究

介绍了硝酸、氯化钾与氨为原料制取硝酸钾与氯化铵新工艺.利用氢氧化镁为反应中间物,先将硝酸、氢氧化镁与氯化钾混合,反应后溶液通过冷却结晶、分离、干燥等操作制得硝酸钾.母液中通入氨,反应生成氢氧化镁沉淀与氯化铵溶液,氢氧化镁沉淀经过滤分离后返回与硝酸与氯化钾一起循环反应,氯化铵溶液经蒸发浓缩、冷却结晶、分离得氯化铵.     

几种因素对氢氧化镁料浆过滤性能影响的研究

以氯化镁为原料,以氢氧化钠为沉淀剂,采用加入氢氧化镁晶种的方法制备氢氧化镁。研究了晶种系数、反应温度、反应时间对料浆过滤性能的影响,并通过正交试验找到了最佳反应条件。对探索氢氧化钠法制备氢氧化镁有一定的参考意义。     

SO2-4对电沉积法制备氢氧化镁的影响

以海绵钛副产品氯化镁为原料,采用水溶液电沉积法制备氢氧化镁时,氢氧化镁团聚严重,且在极板上脱落困难.通过向电解液中加入适量SO^2-₄来优化氢氧化镁分散性,可有效解决氢氧化镁团聚严重的问题.探究了SO^2-₄对氢氧化镁脱落性能、产物形貌及生长方式的影响.结果表明:SO^2-₄的质量浓度对氢氧化镁初始脱落时间影响较大,SO^2-₄的质量浓度为0.45g/L时,氢氧化镁性能最佳,初始脱落时间最短约 10min;氢氧化镁在极板上结晶长大时,生长方式为层岛复合生长模式,同时发现添加SO^2-₄后,能够诱导氢氧化镁以阶梯状的方式生长.     

氢氧化镁填充量对聚丙烯阻燃性能的研究

以氢氧化镁为阻燃剂,硅烷偶联剂为改性剂,不同填充量的氢氧化镁加入到聚丙烯中所得的复合材料的阻燃和力学性能。结果表明,随着氢氧化镁填充量的增加,复合体系的阻燃性能逐渐提高,但随着氢氧化镁添加量的增多,聚丙烯的力学性能,如拉伸强度,冲击强度,都会有明显的下降。所以综合各因素考虑,氢氧化镁添加量为100份时最适宜。     

氢氧化镁基有机无机复合阻燃剂的制备

以Mg(NO)2·6H2O和氨水为原料,用直接沉淀法制备了纳米氢氧化镁,讨论了使用不同表面活性剂及其用量对纳米氢氧化镁的分散效果。同时,还进行了在氢氧化镁表面包覆有机阻燃剂THPC的研究,并采用SEM、TEM、FTIR、Zeta电位和热分析等手段,对包覆前后的氢氧化镁进行表征。实验结果表明,在氢氧化镁表面存在THPC有机包覆层。     

浆状氢氧化镁制备

料浆状氢氧化镁是环境友好的水处理剂,广泛用作酸的中和剂,沉淀重金属离子,脱除二氧化硫。以唐山南堡盐场的卤水为原料,以氨水为沉淀剂制备了料浆状氢氧化镁,通过试验确定了卤水氨法沉镁制备氢氧化镁的最佳工艺条件。研究了分散剂的种类、加入量对料浆状氢氧化镁性能的影响,并通过实验确定了制备浆状氢氧化镁聚分散剂环氧琥珀酸合成条件和最佳配比。浆状氢氧化镁最佳分散剂配比为：偏硅酸钠加入量0．3％,烷基酚聚氧乙烯醚溶液加入量2．4％,聚环氧琥珀酸的加入量为0．7％。在该条件下制备出的产品放置三周不分层,且具有很好的流动性。     

氨基乙酸辅助化学液相沉积制备花状氢氧化镁

以金属镁片为前驱体,用氨基乙酸辅助化学液相沉积方法在室温下合成具有三维花状形貌的氢氧化镁纳米结构,并用X-射线衍射（XRD）、扫描电镜（SEM）、红外光谱（IR）和热分析技术对氢氧化镁样品进行表征。结果表明三维花状形貌的氢氧化镁是由氢氧化镁纳米薄片组装而成,并具有高的纯度。初步分析氨基乙酸辅助化学液相沉积法制备花状氢氧化镁的可能机理。这种方法具有反应条件温和、方便等特点,并可以应用于制备其它不同形貌的金属氢氧化物或氧化物。     

盐湖卤水制备棒状氢氧化镁

以卤水浓缩结晶得到的水氯镁石为原料,采用两步法制备棒状氢氧化镁,即先用氨法制备纤维状碱式氯化镁(Mg3Cl(OH)5·4H2O)前驱体,再将前驱体用烧碱转化为棒状氢氧化镁。探讨Mg2+浓度、反应时间、陈化时间对前驱体成分和形貌的影响。在碱式氯化镁转化为氢氧化镁的过程中,探讨反应溶剂的组成与反应温度对氢氧化镁形貌的影响。研究结果表明:只有Mg2+浓度大于3.0 mol/L时才能得到碱式氯化镁,Mg2+浓度小于3.0 mol/L时只能得到氢氧化镁;随着反应时间的增加,前驱体部分转化为氢氧化镁;随着陈化时间的延长,前驱体结晶趋于完善,粒子表面更加光滑规则,长径比由8.3增加到35.6;溶剂组成对氢氧化镁的形貌影响显著,在纯水体系中,氢氧化镁团聚严重,棒状颗粒少,在乙醇体系中,氢氧化镁分散性好,表面光滑,棒状粒子产率高。在乙醇体系中,40℃反应1 h,得到长径比大于25.0,纯度达99.8%以上的棒状氢氧化镁。     

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。