激光超声信号去噪方法的研究

针对激光超声信号信噪比低的问题,分析了干扰噪声的特点,设计了基于数字平均和小波分析相结合的数据采集与处理系统。利用外部同步触发技术,间隔采集若干次激光超声信号,将各次采样信号相加平均,最后选择合适的小波基、分解层数和阈值方法,对数字平均后的信号进一步进行小波去噪处理。实验结果表明,该方法能够有效去除信号中的干扰噪声,提高信号的信噪比(SNR)。     

多孔钛磷灰石的制备及其对乙醛的催化降解性能

以多孔CaCO3为模板,采用共沉淀的方法制备了蜂窝型多孔状钛取代的羟基磷灰石(TiHA).采用扫描电子显微镜(SEM)、能谱(EDS)、X射线衍射(XRD)、比表面积分析仪(BET)、紫外-可见漫反射分光光度计(Uv-vis)对多孔TiHA的形貌、结构、元素成分、孔隙率、孔径、紫外可见光响应性进行了测定;以有机污染物代表乙醛为对象,研究了多孔TiHA对乙醛的吸附和催化降解性能,考察了TiHA中钙和钛离子的比例对其吸附和催化性能的影响,提出了催化降解路径和机理.制备的多孔TiHA呈蜂窝型多孔结构,具有羟基磷灰石的基本元素和特征衍射峰,其结晶性比非孔状的TiHA变弱;禁带宽度比TiO2更小;多孔TiHA比表面积为TiHA的1.7倍,有助于提高其表面吸附位点和催化活性,表现出具有更优异的吸附和催化降解性能,对乙醛的吸附率12 h可达82.8;,光催化降解效率120 min达85.8;;钙钛离子比为10:1时,多孔TiHA对乙醛的吸附能力最强;钙钛比为10:5时,催化降解效率最高,并且具有良好的稳定性.催化降解过程是羟基、空穴、超氧自由基共同作用的结果.     

基于离散点和法矢的曲线重构算法

This paper presents a curve reconstruction algorithm based on discrete data points and normal vectors using B-splines.The proposed algorithm has been improved in three steps:parameterization of the discrete data points with tangent vectors,the B-spline knot vector determination by the selected dominant points based on normal vectors,and the determination of the weight to balancing the two errors of the data points and normal vectors in fitting model.Therefore,we transform the B-spline fitting problem into three sub-problems,and can obtain the B-spline curve adaptively.Compared with the usual fitting method which is based on dominant points selected only by data points,the B-spline curves reconstructed by our approach can retain better geometric shape of the original curves when the given data set contains high strength noises.