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针对现有陶瓷制品敲击声波信号特征提取方法中提取的特征代表性降低的问题,该文提出结合最大重叠离散小波包变换(MODWPT)和时频分帧能量熵的特征提取方法。首先采用MODWPT将信号分解为4层,再对每个节点的子信号分帧后计算各个节点的时频分帧能量熵,然后根据能量分布特征选择了前6个节点的时频分帧能量熵特征,最后构建随机森林分类器完成识别。将该方法和MODWPT时频分段能量熵、MODWPT归一化能量特征两种方法进行比较。实验结果表明,相比MODWPT时频分段能量熵、MODWPT归一化能量两种特征提取方法,MODWPT时频分帧能量熵能提升特征的代表性,具有更优的陶瓷制品敲击声波信号特征识别性能,其识别的F1值达到了98.46%,相比上述两种方法分别提升F1值3.22%、1.86%。 相似文献
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间隔靶对射流侵彻影响的数值模拟和实验研究 总被引:3,自引:0,他引:3
对某聚能装药射流侵彻靶板的过程进行了数值模拟 ,得出其碰撞点附近应力分布与传统理论相符 ,侵彻深度与实验结果及工程计算结果基本相符 ;分别对该聚能装药侵彻连续靶和间隔靶的过程进行了数值模拟 ,数值模拟结果显示间隔靶的侵彻深度明显低于连续靶的侵彻深度 ,这说明侵彻开坑阶段的能耗侵深比远大于准定常阶段。为了验证间隔靶对射流侵彻的影响 ,用另一聚能装药分别对连续靶和间隔靶进行了侵彻实验 ,并排除了炸高的影响。实验结果也表明 ,间隔靶对射流侵彻的确存在着不利影响。还结合数值模拟及实验结果对传统的侵彻公式进行了修正。 相似文献
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Research on the boron contamination at the p/i interface of microcrystalline silicon solar cells deposited in a single PECVD chamber 下载免费PDF全文
This paper studies boron contamination at the interface between the p and i layers of μc-Si:H solar cells deposited in a single-chamber PECVD system. The boron depth profile in the i layer was measured by Secondary Ion Mass Spectroscopy. It is found that the mixed-phase μc-Si:H materials with 40% crystalline volume fraction is easy to be affected by the residual boron in the reactor. The experimental results showed that a 500-nm thick μc-Si:H covering layer or a 30-seconds of hydrogen plasma treatment can effectively reduce the boron contamination at the p/i interface. However, from viewpoint of cost reduction, the hydrogen plasma treatment is desirable for solar cell manufacture because the substrate is not moved during the hydrogen plasma treatment. 相似文献
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We propose a new type of Y-branch power splitter and beam expander with scales of microns in two- dimensional (2D) photonic crystals (PCs) by drilling air holes in a silicon slice. Its functionality and performance are numerically investigated and simulated by finite-difference time-domain (FDTD) method. Simulation results show that the splitter can split a TE polarized light beam into two parallel sub-beams and the distance between them is tunable by changing the parameters of the splitter, while the expander can expand a narrow beam into a wider one, which is realized in an integrated optical circuit. The proposed device is based on the avoiding of anomalous reflection effect and the coupling transmission of defect modes of the interfaces. 相似文献
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使用光发射谱(OES)对甚高频等离子增强化学气相沉积(VHF-PECVD)技术沉积硅薄膜时的等离子体发光基团的空间分布进行了在线监测和研究. 研究表明:等离子体的不同发光基团都存在着一个中间强度较大的区域和两边电极附近的暗区;增大硅烷浓度和提高辉光功率都会增大SiH*峰强度;硼烷的加入,使得SiH*和Hα*峰强度增大,但硼烷流量变化的影响很小;硼烷流量增大,材料的晶化率下降,而I[Hα*]关键词:
甚高频等离子增强化学气相沉积
等离子体
发光基团
空间分布 相似文献