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411.
Three-dimensional kinematical analyses for surface grinding of large scale substrate 总被引:1,自引:0,他引:1
Sponsored by New Energy and Industrial Technology Development Organization (NEDO) and the Ministry of Education, Science and Culture (MESC) of Japan, this project has developed an advanced machining system for 300 mm silicon wafer, using fixed abrasive instead of conventional free slurry, to provide a totally integrated solution for achieving the surface roughness Ra<1 nm (Ry<5–6 nm) and the global flatness <0.2 μm/ 300 mm. Use of state-of-the-art technologies for ultra precision machine tools has made it possible to precisely control the motion and repeatability of each cutting edge. The behavior of each grain and its effect on surface generation become analytical in 2D manner [J JSPE 68(1) (2002) 125]. Taking one step further, this paper has developed a 3D model for infeed grinding which is often used in silicon grinding systems, and mathematically described the cutting path and effects on the surface roughness and flatness. 相似文献
412.
In information technology, models are abstract devices to represent the components and functions of software applications. When a model is general and consistent, it represents a useful design tool to unambiguously describe the application. Traditional models are not suitable for the design of hypermedia systems and, therefore, specific design models and methodologies are needed. In the present article, the requirements for such models are analysed, an overview of the characteristics of the existing models for hypermedia applications is made and an abstract model fulfilling the analysed requirements is presented. The model, called Labyrinth, allows 1) the design of platform-independent hypermedia applications; 2) the categorisation, generalisation and abstraction of sparse unstructured heterogeneous information in multiple and interconnected levels; 3) the creation of personalisations (personal views) in multiuser hyperdocuments for both groups and individual users and 4) the design of advanced security mechanisms for hypermedia applications. 相似文献
413.
针对现有的生成对抗网络(GAN)伪造人脸图像检测方法在有角度及遮挡情况下存在的真实人脸误判问题,提出了一种基于深度对齐网络(DAN)的GAN伪造人脸图像检测方法。首先,基于DAN设计面部关键点提取网络,以提取真伪人脸关键点位置;然后,采用主成分分析(PCA)方法将每一组关键点映射到三维空间,从而减少冗余信息以及降低特征维度;最后,利用支持向量机(SVM)五折交叉验证对特征进行分类,并计算准确率。实验结果表明,该方法通过提高面部关键点定位准确度改善了由于定位误差引起的面部不协调问题,进而降低了真实人脸误判率。与VGG19、XceptionNet和Dlib-SVM方法相比,正脸情况下,该方法的ROC下面积(AUC)值提高了4.48到32.96个百分点,平均精度(AP)提高了4.26到33.12个百分点;有角度及遮挡人脸情况下,该方法的AUC值提高了10.56到30.75个百分点,AP提高了7.42到42.45个百分点。 相似文献
414.
415.
衡伟 《中国图象图形学报》2002,7(9):922-925
为了高质量准确地对物体多视角三维图象进行快速对齐复位,提出了一种将多个视角三维自然曲面数据精确对齐复位于同一坐标系中的新型迭代方法,该方法根据三维自然曲面的共同特性,并采用不同视角中对应曲面部分的若干单元面法向量误差最小及其对应顶点距离最小的迭代准则来进行对齐复位,同时还详细地叙述了迭代算法的过程,并讨论了提高算法速度与降低累积误差的方法,实例表明,该算法在无需约束三维数据采集过程和不额外增加三维数据采集设备及操作的情况下,不仅速度快,而且由复位后的各视角三维曲面形成的整体表面效果自然逼真。 相似文献
416.
点模式匹配对准算法的基本思想是在两个点集中各选择不共线的3个点,唯一确定一个仿射变换,该变换作用于第一个点集中的所有点,用变换后的点集与第二个点集进行比较,检验变换的正确性,但尝试所有3点组合的计算代价太大。文章基于仿射变换的最小方差的参数估计以及数值计算的稳定性,对两个点集中参与匹配的基进行筛选,来确定匹配点对,并可极大地减少计算量。 相似文献
417.
In this paper we present techniques to significantly improve the space complexity of several ordered tree comparison algorithms
without sacrificing the corresponding time complexity. We present new algorithms for computing the constrained ordered tree
edit distance and the alignment of (ordered) trees. The techniques can also be applied to other related problems. 相似文献
418.
Resources in virtual organizations are classified based on their local taxonomies. However, heterogeneity between these taxonomies is a serious problem for efficient cooperation processes (e.g., knowledge sharing and querying-based interactions). In order to overcome this problem, we propose a novel framework based on aligning the taxonomies of virtual organizations. Thereby, the best mapping between two organization taxonomies has to be discovered to maximize the summation of a set of partial similarities between concepts in the taxonomies. We can consider two levels of alignment processes; (i) intra-alignment in a virtual organization for building an organizational taxonomy and (ii) inter-alignment between organizational taxonomies. Particularly, for intra-alignment, features extracted from resources are exploited to enhance the precision of similarity measurement between concepts. For experimentation, twelve virtual organizations have been built with different local taxonomies. The proposed inter-alignment method has shown about 76% of precision and 68% of recall. Also, feature-based intra-alignment improved those performance, during resource retrieval by query transformation. In addition, we found out that alignment results are dependent on some characteristics of taxonomies (e.g., depth and number of classes). 相似文献
419.
We examine the relationship between firms’ human resources (HR) practices and their information technology (IT) practices,
focusing on the dichotomy between autonomy and control. We define facilitating HR practices as those that exhibit the following characteristics: worker autonomy, connectedness, learning, valuing individuals, trust,
and flexibility in business processes. We then characterize facilitating IT practices, which are practices that facilitate employee collaboration, autonomy, and wider access to information. We contrast these
categories of practice to traditional HR and monitoring IT, respectively. Drawing from theories of complementarities and configuration, we propose that alignment between HR and IT
strategies originates at the level of individual practices. We consider the effects of this alignment on worker performance.
We then ground our discussion in exploratory empirical and qualitative results.
相似文献
M. S. KrishnanEmail: |
420.
双语语料对齐是自然语言处理的一个重要研究课题。对双语平行语料库的研究工作主要有构建、对齐和标注等方面,其中研究不同级别的对齐技术是一个重要的中心课题,对齐不仅是进一步利用平行语料库获取一些语言知识的必要前提.也是机器翻译系统利用双语知识的重要前期处理。重点介绍典型的句子对齐方法,并总结出每种方法的优缺点,具体分析了汉维双语句子对齐的方法。 相似文献