大尺寸图片的复制粘贴检测*

针对目前图像复制粘贴检测算法有时间复杂度高、当图像中有光滑区域时错检率大的缺点,将图像角点区域及其八方向邻接圆形区域作为伪造检测区域,提取每个检测区域的矩特征后用k-d树进行排序,并通过比较每个区域矩特征的相似性来定位伪造复制区域.该算法效率高,且对经过旋转、添加噪声、模糊、JPEG压缩等后处理的复制粘贴伪造图像检测效果很好.     

基于直觉模糊推理的网络舆情预警方法*

为解决网络舆情预警等级问题,提出了一种基于直觉模糊推理的网络舆情预警方法。借鉴战场态势分析思想,对网络舆情态势分析的原理进行了阐述,选取了适合计算机实现的七个网络舆情态势分析模式对预警等级进行判断。选择七个舆情话题进行实验,实验结果表明,该方法能够准确地估计出威胁等级,符合专家经验判断,说明该方法是可行的。     

倾斜疲劳裂纹在混合型应力下张开及滑移特性

对于存在裂纹的机械零件或者构件,它很有可能会受到来自不同方向的作用力, 因此有必要研究裂纹在混合型应力条件下的传播特性. 该文使用具有不同倾斜角度的裂纹--这些裂纹是在应力比R=0的Ⅰ型循环应力下制作的,通过测量裂纹的开口方向和滑移方向的位移量,计算了裂纹端部Ⅰ型应力强度因子(KⅠ)mes和Ⅱ型应力强度因子(KⅡ)mes.裂纹的倾斜角度是指载荷方向与裂纹间的夹角.结果表明,对于存在压缩残余应力的疲劳裂纹,当倾斜角度较大,即β=60°时,应力强度因子的实验值(KⅠ)mes小于理论计算值(KⅠ),但此时实验值(KⅡ)mes与理论值(KⅡ)基本一致.另一方面,对于倾斜角度较小β=45°的疲劳裂纹,其(KⅠ)mes减少的同时,由于裂纹上下表面相互接触,从而导致(KⅡ)mes同时下降.     

Study on the characteristics of erbium-doped waveguide ring laser

A theoretical model of the erbium-doped waveguide ring laser is established according to the theory of erbium-doped waveguide amplifier and the transmission matrix of waveguide directional coupler. The influence of bend radius, coupling coefficient and doped erbium ion concentration on the characteristics of waveguide ring laser is investigated. It is shown that due to the co-action of waveguide bend loss and other relevant loss there is an optimal bend radius which can provide simultaneously low threshold pumping power and high laser light output power. As one part of the resonator’s loss, the laser light coupling coefficient of directional coupler has an impact on the laser property. The analysis indicates that the laser achieves the high output power when the coupling coefficient is about 0.2. The threshold pumping power is the minimum when the doped erbium ion concentration is 0.85×10²⁶ m⁻³. Increasing the concentration of doped erbium ions will enhance the output power of laser light as long as the concentration doesn’t introduce remarkable up-conversion effect. The results give a good theoretical basis for the design and fabrication of erbium-doped waveguide ring laser devices. Supported by the National Natural Science Foundation of China (Grant No. 60807015), the Specialized Research Fund for the Doctoral Program of Higher Education (Grant No. 200801411037), the Young Teacher Cultivation Foundation of Dalian University of Technology (Grant No. 893210) and Doctor Start-up Foundation of Dalian University of Technology (Grant No. 893322)     

Growth of Ag nanocrystals on multiwalled carbon nanotubes and Ag-carbon nanotube interaction

The experimental investigations on the interaction between Ag-nanocrystal particles (Ag-NCPs) and carbon nanotubes (CNTs) in Ag-nanocrystal particles/carbon nanotubes (Ag-NCPs/CNTs) hybrid structures were reported. The growth of Ag-NCPs on multiwalled carbon nanotubes (MWCNTs) was carried out by thermal evaporation deposition. High-resolution transmission electron microscopy and X-ray diffraction analyses revealed that Ag-NCPs had the crystal lattice feature of face-centered cube (fcc). The growth of Ag-NCPs on MWCNTs induced the cross-section deformation of MWCNT. The experimental results also showed that the synthesized Ag-NCPs/CNTs hybrid structure appeared as quasi-one dimensional nanowires containing the Ag-NCP/CNT hetero-junction. There was local cross-section deformation on MWCNTs at the interface of hetero-junction. These results involve the important topic about fundamental and practical studies for structure of MNCPs on CNTs and also find clues to further research of Ag nanocrystal growing on MWCNTs and related Ag-CNT interaction.     

SMA-5应力吸收层在旧水泥路面加铺改造中的应用研究

为减少和延缓旧水泥板沥青加铺层反射裂缝的产生,在分析研究各种夹层材料应用效果和SMA-5作为应力吸收层性能要求的基础上,设计了SMA-5应力吸收层的配合比,采用搓揉成型的方法改进了马歇尔试件,并对SMA-5沥青混合料的各项路用性能进行了试验研究,且成功的铺筑了试验路.结果表明:SMA-5沥青混合料可以作为夹层材料,并起到了很好的应力吸收效果.此项研究成果对于旧水泥混凝土路面加铺改造具有重要的工程实用价值,SMA-5应力吸收层具有广阔的应用前景.     

正负关联规则挖掘

针对传统的关联规则数据挖掘的支持度-置信度框架存在很多缺陷,同时研究正负关联规则时可能产生很多问题的情况,阐述了在正负关联规则挖掘中,如何利用允许用户指定多重最小支持度来反应数据库中项的性质和它们各种各样的频率,并通过设置相关度提高挖掘效率.实验结果显示该方法是有效的.     

基于视频帧的彩色水印嵌入算法研究

为了增强水印的内容认证性,提出了视频帧中嵌入彩色水印的算法.先分别选取I帧的单色通道做DCT变换,分块后提取奇异值,将彩色水印的对应通道层做DWT变换,对低频区域置乱后提取奇异值,再将水印奇异值嵌入到载体奇异值中,然后由三色通道合成水印视频图像.最后进行了攻击实验,实验结果表明,该算法具有较好的水印提取能力和一定的鲁棒性.     

聚羧酸系减水剂对水泥水化过程的影响

研究了以聚乙二醇800、丙烯酸、顺酐、烯丙基磺酸钠、丙烯酸羟乙酯为原料合成的聚羧酸系XYZ18减水剂对水泥水化过程及微观结构的影响.结果表明,XYZ系减水剂具有缓凝特性,能减少并延缓水泥水化放热;使水泥早期微小晶体大量生长并填充孔隙,气孔细化且分布更加合理,晶体向外伸长使水泥粒子相互搭接而形成网络结构,提高了水泥石的密实性.     

利用干扰提高容量的低复杂度预编码方法

在接收用户配置单天线的多输入多输出广播系统(MIMO BC)中,提出了一种利用干扰提高系