表面微观形貌的MOTIF参数计算

对MOTIF参数的基本概念、意义及算法作了介绍，并在精密加工试件上进行了实验。     

医学超声图像的特征提取方法初探

本文在分析了医学超声图像特殊性的基础上,构建了基于灰度共生矩阵的四个纹理特征描述算子,对正常肝和非正常肝的超声图像进行了特征提取。MATLAB仿真实验结果验证了该算法的有效性。     

飞机蒙皮铝合金超声辅助搅拌摩擦焊试验分析

针对飞机蒙皮对接时,因搅拌摩擦焊(FSW)工艺窗口狭窄易致底部虚焊、弱连接等缺陷问题,为了探索更适合大飞机蒙皮长程稳定焊接的新方法,设计了超声辅助搅拌摩擦焊(UAFSW)与FSW的蒙皮连接对比试验,采用1.8 mm厚度的2524-T3铝合金进行了同种工艺条件下的UAFSW与FSW焊接,对表面成形良好、内部无缺陷的FSW与UAFSW焊缝,进行了拉伸、金相、扫描电镜观察等对比分析试验。结果表明,与FSW焊缝相比,UAFSW焊缝缺陷率明显降低,工艺窗口扩大;UAFSW焊缝表面纹理更细密,层叠现象消失;UAFSW焊缝的平均抗拉强度略高于FSW焊缝,达到母材强度的90.7%;UAFSW焊缝的平均延伸率则比FSW焊缝高20%左右。研究发现,超声的加入使UAFSW焊缝微观组织更细更均匀,晶粒尺寸变细小,且晶粒沿轧制方向的规律性被打乱,呈现无明显方向的杂序排列。     

核空间聚类在图像纹理分类中的简化算法

模糊c均值聚类已广泛应用于模糊模式识别领域,但对于线性不可分数据并不适用.在核方法中通过将输入数据经过非线性映射投影到高维特征空间来解决非线性分类的问题.将传统的模糊c均值聚类算法应用于核空间中,对线性不可分的样本进行了核空间聚类的分类实验,得到了正确的分类结果.由于图像分类中分类样本(对应图像像素)数目庞大,造成了核空间聚类算法中特征距离的计算量过大.因此,在核空间聚类的基础上,提出了对图像先进行过分割,再对过分割的图像块进行核空间聚类的方法,大大降低了高维空间特征距离计算的运算成本,并取得了良好的分类效果.      

SAR图像识别提取与选择特征

阐述了SAR图像在模式识别中特征提取与选择的概念、任务和基本原则,结合国内外图像特征提取与选择的最新研究动态,介绍了在SAR图像目标识别中普遍采用的一些特征提取与选择方法,并对提取纹理特征采用的灰值共生矩阵及其统计量进行了研究。     

Al-Cu-Li系合金热轧板材组织、性能和织构的研究

研究了 Al-Cu-Li-( Mn) -( Zr)合金热轧板在 T8态下的显微组织、性能和织构情况。发现因合金的成分不同 ,T8处理对它们造成的影响也不同。其原因主要是由于 Mn、Zr对合金内部的再结晶过程产生了不同的影响。对热轧板的织构和性能测试结果表明 ,晶体学织构与材料的各向异性之间存在着对应关系 ,材料的塑性各向异性比强度各向异性更为严重 ,Mn可以作为控制合金织构和各向异性的重要合金化元素     

Object-based representations of spatial images

Object based representations of image data enable new content-related functionalities while facilitating management of large image databases. Developing such representations for multi-date and multi-spectral images is one of the objectives of the second phase of the Alexandria Digital Library (ADL) project at UCSB. Image segmentation and image registration are two of the main issues that are to be addressed in creating localized image representations. We present in this paper some of the recent and current work by the ADL's image processing group on robust image segmentation, registration, and the use of image texture for content representation. Built upon these technologies are techniques for managing large repositories of data. A texture thesaurus assists in creating a semantic classification of image regions. An object-based representation is proposed to facilitate data storage, retrieval, analysis, and navigation.     

热处理对挤压态 Mg -8Er 合金组织性能的影响

对挤压态 Mg -8Er 合金在再结晶热处理过程中组织、织构的演变以及相应的力学行为进行了系统表征,在此基础上分析了塑性变形机理。结果表明,挤压态 Mg -8Er 合金在500℃条件下退火时,随着保温时间的延长,再结晶组织的逐渐形成,织构出现明显的随机化,织构强度也显著弱化,合金的室温塑性也随之提高。热处理态 Mg -8Er 合金的塑性大小主要取决于再结晶程度的大小。再结晶程度高的合金织构也更加随机化,从而获得高塑性。     

Development and testing of a statistical texture model for land cover classification of the Black Sea region with MODIS imagery

A statistical model is proposed for analysis of the texture of land cover types for global and regional land cover classification by using texture features extracted by multiresolution image analysis techniques. It consists of four novel indices representing second-order texture, which are calculated after wavelet decomposition of an image and after texture extraction by a new approach that makes use of a four-pixel texture unit. The model was applied to four satellite images of the Black Sea region, obtained by Terra/MODIS and Aqua/MODIS at different spatial resolution. In single texture classification experiments, we used 15 subimages (50 × 50 pixels) of the selected classes of land covers that are present in the satellite images studied. These subimages were subjected to one-level and two-level decompositions by using orthonormal spline and Gabor-like spline wavelets. The texture indices were calculated and used as feature vectors in the supervised classification system with neural networks. The testing of the model was based on the use of two kinds of widely accepted statistical texture quantities: five texture features determined by the co-occurrence matrix (angular second moment, contrast, correlation, inverse difference moment, entropy), and four statistical texture features determined after the wavelet transformation (mean, standard deviation, energy, entropy). The supervised neural network classification was performed and the discrimination ability of the proposed texture indices was found comparable with that for the sets of five GLCM texture features and four wavelet-based texture features. The results obtained from the neural network classifier showed that the proposed texture model yielded an accuracy of 92.86% on average after orthonormal wavelet decomposition and 100% after Gabor-like wavelet decomposition for texture classification of the examined land cover types on satellite images.     

圆柱形微凹坑表面织构对流体动压润滑性能的影响

通过建立具有规则田往形微凹坑分布的表面织构流体动压润滑模型,分析了微凹坑几何参数及微凹坑分布形式对流体动压润滑性能的影响.研究结果表明:在微凹坑直径及深径比不变时,存在最优的微凹坑面积率,约为30%;在微凹坑分布密度不变时,存在最优的深径比,约为0.027.在此最优微凹坑面积率及深径比下,本文创新性地通过优化微凹坑的分布形式,进一步提高了润滑膜承载力21.7%.研究结果对进一步的研究工作提供了理论依据,具有指导意义.