排序方式: 共有11条查询结果,搜索用时 31 毫秒
1.
2.
在磨削加工过程中,加工刀具即砂轮会发生钝化现象,砂轮表面磨损影响加工精度和工件质量,需要及时检测并修整。磨粒的塑性变形、破碎、断裂等会产生声发射信号,能够作为精确识别砂轮钝化状态的依据,且不易被噪声干扰,因此提出一种基于变分模态分解(Variational Mode Decomposition,VMD)和概率神经网络(Probabilistic Neural Network,PNN)的砂轮钝化声发射检测方法。VMD可以将原始信号分解为多个本征模态函数(Intrinsic Mode Function,IMF)分量,筛选其中峭度较大的分量重构即得到声发射信号。声发射检测的关键是特征参数的选取,在相关研究基础上本文提出了声发射包络能量占比作为一个重要的特征参数,并选取了共5种特征参数,构建出5维特征向量数据集,输入到PNN中进行训练,经过测试识别准确度达到94.5%。该方法建立了声发射信号特征参数与砂轮不同钝化状态的关系,能够对砂轮严重钝化状态给出准确预警,具有实际应用价值。文章比较了声发射信号不同特征参数用于识别砂轮钝化状态的准确度,对特征参数的选用具有参考意义。 相似文献
3.
4.
5.
6.
7.
8.
Lanthanide-containing liquid crystals exhibiting smectic A phase close to room temperature were obtained. Photoacoustic (PA) spectroscopy was used to study the spectral properties and phase transitions of liquid crystalline metal complexes. It was found that PA intensity of the ligand had a relationship with the probability of nonradiative transitions, which increased in the order of Eu(tta)3L2〈La(tta)3L2〈 Tb(tta)3L2〈Er(tta)3L2. The relaxation processes of the complexes were studied in depth from two aspects: radiative and non-radiative processes, combining with their fluorescence spectra. Phase transitions of europium(m) and erbium(m) complexes, in the temperature range of 383-358 K, could be clearly monitored by both PA amplitude and PA phase signals. As the temperature crossed the transition point, PA amplitude showed a minimum and PA phase a maximum. The results indicated that PA technique could serve as a new tool for investigating the physicochemical properties of liquid crystals containing metal ions. 相似文献
9.
10.