一种无需重新建模的特征编辑算法

介绍了一种对引用特征进行动态修改的编辑算法,这种算法基于Ｂ－Ｒｅｐ／ＣＳＧ混合表示的特征模型,可以保证存储在模型中的产品信息在特征修改操作完成后不会丢失,并且可以方便地实现修改过程中的约束驱动;提出了广义操作链表的概念和构造方法,实现了对造型操作的详细跟踪;利用索引表方法解决了广义操作链表对造型操作过程跟踪信息量过大的问题。本文所提出的算法已成功地应用在一个特征造型原型系统中     

弧面分度凸轮机构传动系统动态响应的实验研究

对弧面分度凸轮机构传动系统的动态特性进行了测试,初步研究了该系统的某些动态响应特性,为该传动系统的理论研究提供了实验数据．     

新型球面包络蜗杆分度凸轮机构的研究

在总结分析传统弧面分度凸轮机构和平面、柱面包络蜗杆分度凸轮机构的基础上,提出了一种球面包络蜗杆分度凸轮、钢球、嵌装钢球的分度盘三体式结构的新型球面包络蜗杆分度凸轮机构;介绍了其结构形式,推导了分度盘上球面齿廓方程、啮合方程、球面包络蜗杆分度凸轮廓面方程,最后指出了这种新型球面包络蜗杆分度凸轮机构优良的结构特性     

平面凸轮齿轮型分度(间歇)机构的设计

导出了平面凸轮齿轮型间歇机构有关结构尺寸的求解式,给出了合理的产品系列及其数据．     

Distortion-free predictive streaming time-series matching

Efficient processing of streaming time-series generated by remote sensors and mobile devices has become an important research area. As in traditional time-series applications, similarity matching on streaming time-series is also an essential research issue. To obtain more accurate similarity search results in many time-series applications, preprocessing is performed on the time-series before they are compared. The preprocessing removes distortions such as offset translation, amplitude scaling, linear trends, and noise inherent in time-series. In this paper, we propose an algorithm for distortion-free predictive streaming time-series matching. Similarity matching on streaming time-series is saliently different from traditional time-series in that it is not feasible to directly apply the traditional algorithms for streaming time-series. Our algorithm is distortion-free in the sense that it performs preprocessing on streaming time-series to remove offset translation and amplitude scaling distortions at the same time. Our algorithm is also predictive, since it performs streaming time-series matching against the predicted most recent subsequences in the near future, and thus improves search performance. To the best of our knowledge, no streaming time-series matching algorithm currently performs preprocessing and predicts future search results simultaneously.     

DMP-tree: A dynamic M-way prefix tree data structure for strings matching

We propose DMP-tree, a dynamic M-way prefix tree, data structure for the string matching problem in general and prefix matching in particular. DMP-tree has been initially devised for fast and efficiently handling prefix matching which constitutes the building block of some applications in the computer realm and related area. It is assumed there are strings of an alphabet Σ which are ordered. The data strings can have different lengths and some of them can be prefixes of others. Two well known applications of prefix matching are layers 3 and 4 switching in TCP/IP protocols. In layer 3 switching, routers forward an IP packet by checking its destination address and finding the longest matching prefix from a database. In layer 4 switching, the source and destination addresses are used to classify packets for differentiated service and Quality of Services (QoS). DMP-tree is a superset of B-tree. When none of the data strings are a prefix of each other, DMP-tree is the same as B-tree. In DMP-tree, no data string can be in a higher level than another data string which is its prefix. This requires a special procedure for node splitting. Indeed, node splitting differentiates DMP-tree from B-tree. The proposed data structure is simple, well defined, easy to implement in hardware or software and efficient in terms of memory usages and search time compared to other data structures proposed for prefix matching. We have implemented DMP-tree and the experimental results for simulated IP prefixes from the {0, 1} character set show an average search time of for a large number of N, number of data elements, when the internal node branching factor M is big enough (?5).     

面向高维数据集的近邻顺序查询方法

对顺序索引方法进行了研究,提出一种基于向量近似的高维顺序索引结构,该结构顺序访问部分文件就能完成k近邻查询。在查询过程中依据投影值来终止查询过程,依据距离来排除不匹配的数据。为进一步降低数据访问率,采用椭圆体聚类算法对数据集进行划分。新索引结构支持以多个顺序访问过程完成k近邻查询,能够同时降低查询过程中的I/O开销和CPU开销。在大型高维图像特征库上的实验表明,新的高维索引结构的查询性能优于其他高维索引方法。     

一种基于空间索引技术的全局光照快速绘制算法

在研究分析各种光照模型算法的基础上,提出一个基于对场景空间规则划分索引及建立光粒子空间分布,并以此进行全局光照计算的模型,其中包括提出一种从光源自适应地发射光粒子的模式和基于空间分割索引传播存储光粒子的技术,以及从视点出发的空间索引定位光粒子的收集显示方案.在算法实现的过程中,由于采用了场景空间规则划分的有序索引、对光...     

基于引文相关性排序的科技论文检索方法

为了实现学术主题相关的科技论文检索,提出了一种基于引文相关性排序的科技论文检索方法。自动抽取科技论文的结构信息,获得论文的标题、摘要、关键词和引文;根据引文与标题的相关性,评价引文的重要性,用引文的评价得分修正引文向量特征项的权重,构造引文的词项-文档关联矩阵,并利用奇异值分解方法构造引文的潜在语义空间,计算查询论文与文档库中论文的引文语义相关性;采用信息增益方法确定了引文相关性阈值,将引文相关性超过阈值的科技论文作为检索结果返回。实验结果表明,提出的检索方法的准确率、召回率、综合性能均高于基于概括性信息(标题、摘要、关键词)的检索方法。     

视频镜头分割方法综述

视频序列的镜头分割亦称镜头变化检测是视频检索中的关键技术之一.对五种常用的视频分割算法作了综述,包括像素法、直方图法、X2直方图法、X2直方图分块法、边缘轮廓变化率法,并详细介绍了各种算法中的帧差异值的计算以及介绍了了他们的优缺点,并且通过实验分析对各种算法进行了比较,五种算法的优缺点实验中得到了很好的体现.