一种基于DTW改进的轨迹相似度算法

针对传统的轨迹相似度计算方法无法区分现实采集到的轨迹中由噪声带来的差异和真实的不相似部分的问题，基于动态时间规整（dynamic time warping,简称DTW）算法，提出了一种改进的轨迹相似度的计算方法。并对最后的结果进行了归一化处理，便于人们直观理解，同时也可用于对多对轨迹之间的相似性进行排序，从而可以在数据挖掘的相关应用中得到有效利用，同时对计算过程也进行了优化。在现实采集到的数据上的测试表明这种方法对噪声和异常点是鲁棒的，对轨迹的采样频率等参数没有任何要求，而且可以适用于仅获得轨迹的部分片段的情况，并且在区分轨迹的相似和不相似部分方面较之前的方法准确度有了很大提升，即使轨迹的采样较为稀疏的前提下依然如此。     

Effect of deposition path of electron beam freeform fabrication on residual stress and deformation of deposited parts

The present work focused on the effect of deposition path on the transient temperature distribution, heat transfer, residual deformation and residual stress of a rectangular solid deposited by electron beam freeform fabrication technology. To achieve this aim, three representative deposition paths were involved to produce rectangular solid by electron beam freeform fabrication technology. Thermal-mechanical decoupling simulations were carried out with respect to three different deposition paths. Both of the experimental and simulation results showed that a shorter deposition track can remarkably reduce the residual stress and warping. After separating the deposition area into small segments, remarkable local bulges were formed near the conjunction lines, and overheating was prone to occur at the turning points of the conjunction lines. The present work is helpful to the selection of deposition path for additive manufacturing process.