Ni-P-PTFE复合化学沉积的研究

研究了PTFE添加量及热处理温度对镀层性能的影响,研究结果表明:使用阳离子与非离子混合表面活性剂对PTFE微粒进行预处理,可提高PTFE在镀液中的润湿和分散能力,使之较易与镍离子一起共沉积;经高温热处理后的复合镀层的硬度及耐磨性有明显提高,且其耐磨性优于一般Ni-P镀层。X射线衍射实验结果证明:镀层硬度的提高是热处理使复合镀层晶化所致。     

Ni-SiC复合镀层的制备及耐蚀性研究

用电沉积法在碳钢表面制备Ni-SiC复合镀层.考察镀液中SiC的质量浓度,阴极电流密度,施镀温度和搅拌速度等工艺参数对复合镀层耐蚀性的影响,通过扫描电子显微镜、X射线衍射仪和电化学工作站分别对镀层的表观形貌、组成和耐蚀性进行测定.结果表明,复合镀层的表面平整致密,由金属Ni和SiC颗粒组成;对比碳钢基体和镍镀层,复合镀层的耐蚀性能最佳.     

Fe2+浓度对20号钢表面电镀Fe-Ni合金镀层的影响

采用电沉积技术在20号钢表面制备了Fe--Ni合金层,考察了镀液中Fe2+浓度对合金镀层沉积速度、镀层成分、相结构、镀层显微硬度和耐蚀性的影响规律,并探讨了耐蚀机理.实验结果表明:电镀Fe--Ni合金可获得纳米晶结构,随镀液中Fe2+浓度增加,镀层中含铁量增大;镀层显微硬度的变化与Fe原子在Ni晶格中有序固溶程度有关;Fe--Ni合金镀层的耐蚀性均优于20号钢,当镀液Fe2+浓度为0.01 mo.lL-1时,获得镀层具有最佳的耐蚀性.随镀层中铁含量增加,具有钝化特性的高含Ni的Fe--Ni相含量减少,耐蚀性下降,但该相纳米结构显著细化,加速钝化可提高耐蚀性,这一对矛盾导致镀层耐蚀性与铁含量间没有明显的变化规律.高孔隙率也是耐蚀性下降的原因之一.     

镍-磷-纳米SiO2化学复合镀层耐腐蚀特性研究

研究了镍-磷-纳米SiO2化学复合镀层的机理，用SEM和XRD等技术分析了，复合镀层的微观结构，比较了传统的化学镀镍-磷层和纳米复合镀层的沉积速度和耐蚀性，结果表明，纳米SiO2颗粒的引入加快了化学镀层的沉积速度，在同等条件下可降低化学镀的反应温度，镀层在酸、碱、盐水溶液中表现出了良好的耐蚀性能。     

稀土铈添加对Ni-Co-P化学镀层组织及耐蚀性的影响

探讨了稀土元素铈对化学镀Ni—Co—P镀层组织及耐蚀性的影响．结果表明,在化学镀Ni—Co—P基础液中添加适量稀土元素,可以改善镀液稳定性,提高沉积速度,细化镀层晶粒,降低合金镀层在5%NaCl溶液中的腐蚀电流,从而提高镀层的耐蚀性。     

化学镀镍硼合金镀层组织形态及其形成机制

基于化学镀镍硼合金镀层的组织形态和成分、结构．探讨了镍硼合金镀层的沉积规律．分析表明，镀层在侧向和纵向上的相对沉积速度快慢是影响镀层组织形态的关键因素．柱状组织的形成原因是由于纵向沉积速度相对较快，该组织镀层含镍量相对较高，结构是非晶晶态混合结构；圆粒状组织是在侧向、纵向沉积速度较接近的条件下形成的，其成分中硼的含量相对较高，镀层结构趋于完全非晶态．     

稀土氧化钐对直流电沉积纳米镍铁合金箔的影响

利用直流电沉积的方法,在硫酸盐体系中制备纳米晶Ni-Fe合金镀层,研究在镀液中添加不同量的稀土氧化钐对镍铁合金箔镀层的影响.结果表明:添加氧化钐后镀层结晶细致,结构紧密,光亮度增加,添加氧化钐后并没有改变Ni-Fe合金箔的镀层结构,但使Ni-Fe合金箔的沉积速率下降,镀层的显微硬度增加;镀层中铁含量随着氧化钐含量的增加而逐渐降低,镀层耐蚀性得到提高.     

Ni-TiO2纳米复合电镀层的制备与性能研究

用电镀的方法制备出了Ni-TiO2纳米复合电镀层,讨论了表面活性剂、阴极电流密度、搅拌速率等对复合镀层硬度的影响,并分析了纳米TiO2的加入对复合镀层硬度、耐蚀性的影响情况.结果表明,与纯镍镀层相比,NI-纳米TiO2复合电镀层的硬度可提高90～190HV;添加阳离子表面活性剂分散纳米TiO2所得复合镀层硬度最高,说明阳离子表面活性剂有利于纳米TiO2-Ni复合电沉积.浸泡试验表明,在硝酸溶液中复合镀层的腐蚀速率高于纯镍镀层的腐蚀速率,但远低于未镀覆钢板的腐蚀速率,极化曲线表明,与纯镍镀层相比,复合镀层的自腐蚀电位没有显著提高.说明在复合镀层中添加纳米TiO2不能改善其耐蚀性.     

超声波化学镀镍工艺

采用超声波化学镀镍工艺，研究了有机聚合物薄膜上化学镀镍过程中温度、镀液成分对沉积速度及镀层情况的影响．采用SEM观测镀层表面形态、厚度，通过EDS测定镀层的镍磷含量，并用XRD分析了镀层的微观结构．     

H3PO3体系中镍磷非晶态合金及其耐蚀性能

用恒电流沉积、腐蚀电位和极化电阻等方法研究了H3PO3体系中Ni-P合金的电沉积及其镀层的腐蚀性能,用XRD、XPS、SEM检测了镀层的晶形、组成和表面形貌,探讨了沉积条件对镀层耐蚀性能的影响。研究结果表明：在H3PO3体系中得到的Ni-P合金镀层同样具有较强的耐蚀性,当镀层中磷的含量达7％时,晶形转为非晶态,镀层中含磷量越大,耐蚀性越好。     

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。