Multivariate statistical analysis for the surface water quality of the Luan River, China

In order to analyze the characteristics of surface water resource quality for the reconstruction of old water treatment plant, multivariate statistical techniques such as cluster analysis and factor analysis were applied to the data of Yuqiao Reservoir-- surface water resource of the Luan River, China. The results of cluster analysis demonstrate that the months of one year were divided into 3 groups and the characteristic of clusters was agreed with the seasonal characteristics in North China. Three factors were derived from the complicated set using factor analysis. Factor 1 included turbidity and chlorophyll, which seemed to be related to the anthropogenic activities; factor 2 included alkaline and hardness, which were related to the natural characteristic of surface water; and factor 3 included Cl and NO2-N affected by mineral and agricultural activities. The sinusoidal shape of the score plots of the three factors shows that the temporal variations caused by natural and human factors are linked to seasonality.     

松散结构砂砾基层的应用技术

根据广西沿海地区钦州、防城、北海历年在沥青路面基层中大量使用砂砾结构的实际情况和使用经验、施工方法等加以总结,合理利用这一结构可有效使用当地材料,降低工程造价,发挥良好的经济效益和社会效益,这种经验应总结提高和继续推广.     

Hierarchical planning for a surface mounting machine placement

For a surface mounting machine(SMM)in printed circuit board(PCB)assembly line,there are four problems,e.g. CAD data conversion,nozzle selection,feeder assignment and placement sequence determination. A hierarchical planning for them to maximize the throughput rate of an SMM is presented here. To minimize set-up time,a CAD data conversion system was first applied that could automatically generate the data for machine placement from CAD design data files. Then an effective nozzle selection approach was implemented to minimize the time of nozzle changing. And then,to minimize picking time,an algorithm for feeder assignment was used to make picking multiple components simultaneously as much as possible. Finally,in order to shorten pick-and-place time,a heuristic algorithm was used to determine optimal component placement sequence according to the decided feeder positions. Experiments were conducted on a four head SMM.The experimental results were used to analyse the assembly line performance.     

Improvement of enamel bond strengths for conventional and resin-modified glass ionomers: acid-etching vs. conditioning

Objective:This study deals with the effect of phosphoric acid etching and conditioning on enamel micro-tensile bond strengths(μTBSs)of conventional and resin-modified glass ionomer cements(GICs/RMGICs).Methods:Forty-eight bovine incisors were prepared into rectangular blocks.Highly-polished labial enamel surfaces were either acid-etched,conditioned with liquids of cements,or not further treated(control).Subsequently,two matching pre-treated enamel surfaces were cemented together with one of four cements[two GICs:Fuji I(GC),Ketac Cem Easymix(3M ESPE);two RMGICs:Fuji Plus(GC),RelyX Luting(3M ESPE)]in preparation forμTBS tests.Pre-treated enamel surfaces and cement-enamel interfaces were analyzed by scanning electron microscopy(SEM).Results:Phosphoric acid etching significantly increased the enamelμTBS of GICs/RMGICs.Conditioning with the liquids of the cements produced significantly weaker or equivalent enamelμTBS compared to the control.Regardless of etching,RMGICs yielded stronger enamelμTBS than GICs.A visible hybrid layer was found at certain enamelcement interfaces of the etched enamels.Conclusions:Phosphoric acid etching significantly increased the enamelμTBSs of GICs/RMGICs.Phosphoric acid etching should be recommended to etch the enamel margins before the cementation of the prostheses such as inlays and onlays,using GICs/RMGICs to improve the bond strengths.RMGICs provided stronger enamel bond strength than GICs and conditioning did not increase enamel bond strength.     

Yellowing of Oil-Based Paints

Summary

The cause of yellowing of oil-based paints has been investigated by analysing drying oils simultaneously by iodometry (to determine the degree of oxidation) and by colorimetry. It was found that yellowing of drying oils can be attributed to co-oxidation reactions of contaminants. Yellowing level is closely related to the extent of drying and appears to be unaffected by increase in temperature, the addition of driers, or linolenate content.     

"普通话水平测试"中的普通话语调刍议

人们对“普通话水平测试”中的普通话语调把握存在太多不确定因素。本文试图从阐述汉语声调变调的必然性和或然性出发，阐明声调与语调之间的复杂关系。声调与语调同时并存，两者的关系是音阶叠加的“代数和”，而不是“调形叠加”的“代数和”。声调受语调调节，语调通过声调得以实现。从而帮助人们了解一些随语语调规律，以便更有效地学习普通话，减少“普通话水平测试”普通话语调偏误。     

银川平原水资源优化配置研究

该文在对银川平原水资源分布特点、开发利用现状及存在问题分析的基础上,以区域发展、生态环境保护和水资源可持续利用为依据,利用系统分析原理,建立了银川平原水资源优化配置模型,运用模型对区内工农业、生态环境用水以及地表水与地下水联合开发的合理配置进行了分析研究.结果表明:在满足不同水平年工农业及生态用水情况下,优化的地表水与地下水合理配水比例是:对盐渍化比较严重地区在实施地表水与地下水联合开发中,地下水开采所占比例大约在40%～55%之间;盐渍化中等地区,地下水开采占比例大约在35%～40%;盐渍化程度较弱地区地下水开采所占比例小于35%.这一结果有利于调控地下水位,体现了地表水与地下水联合开发的原则,节约了水资源,为区内水资源宏观开发利用与生态环境改善提供了科学依据.     

基于可视化语言的图像表面控制

许多复杂的图像处理需要结合其他的图像处理算法才能实现,因此,主要介绍了计算机图像处理中的图像草稿效果算法,并在该算法的基础上利用VB6.0语言所提供的图像处理功能实现了图像表面的草稿效果。     

表面肌电信号分析评价肌肉疲劳的有效性和敏感性

目的:测定和分析应用表面肌电信号分析指标评价肌肉疲劳的有效性和敏感性,方法:选取健康无专业运动男、女大学生各10名,进行3个膝关节角度(90°、60°和30°)×3个运动负荷(40％MVC、60％MVC和80％ MVC)共9次静力性等长疲劳实验,同步记录sEMG信号并进行线性和非线性信号处理.结果:sEMG信号分析指标表现出单调性变化,且采样序列线性拟合具有显著性.膝关节角度、运动负荷和性别对各指标的变化率有显著影响.结论:应用非线性分析指标评价肌肉疲劳具有很好的敏感性.     

如何对表面贴装印刷电路板(SMT PCB)进行缺陷检查

在最近十年,伴随着表面贴装印刷电路板生产自动化程度的飞速发展,对其相应的质量缺陷检查也提出了更高的要求,从简单的摄像系统到复杂的“3-D”X光检测系统,自动光学检测系统大量被各生产厂家采用。本文从表面贴装印刷电路板的缺陷分析和缺陷种类及缺陷检查过程各方面分析了自动光学检测系统的应用。