A case study in engineering model validation using new wavelet‐based methods

Simulation model validation is an important part of simulation development and use. An emerging challenge is the examination of functional data systems and the validation of the simulations built to represent them. While validation methods do exist, there is a gap in the engineering and statistical approaches used for functional model validation. This case study demonstrates the use of recently developed methods based on the use of wavelets to bridge the engineering‐statistical gap in functional simulation model validation. Two methods are used to provide insight regarding model validity, and a third method is used to identify areas of system‐simulation disagreement when model validity fails to hold.     

Evolution of stress and morphology in thermal barrier coatings

Residual stress in the thermally grown oxide (TGO) in thermal barrier coatings (TBCs) was measured by photoluminescence piezospectroscopy (PLPS) and stress maps created to track local stress changes as a function of thermal cycling. The local stress images were observed to be correlated with morphological features on the metal surface that were purposely introduced during specimen preparation. Local stress relaxation and morphological evolution with thermal cycling were studied using the stress maps combined by post-mortem SEM examination. It was found that the morphology in the specimen having an initial polished surface was quite stable, while that in the specimen with a rough surface was unstable. The average residual stress in the specimen with the unstable morphology decreased with thermal cycling and it eventually failed along TGO/YSZ interface. The specimen with stable morphology maintained a high TGO stress throughout the thermal cycling process and failed along TGO/bond coat interface. The rough surface was also found to give rise to the formation of transition alumina (θ-Al₂O₃) in the TGO which was correlated with a reduced TGO stress.     

基于FastICA的低信噪比下L-PLC语音的间断传输

在低压电力线通信（L-PLC）中,多径衰减和信道背景噪声大的问题不可忽视,为此提出了一种基于快速独立分量分析（FastICA）的L-PLC间断传输提升抗干扰能力的方法。在建立L-PLC信道噪声模型的基础上,利用FastICA对强噪声干扰的语音信号进行去噪处理,并对处理后的信号进行话音活性检测,最终获得满足质量要求的语音段。Matlab仿真实验结果表明,在低信噪比环境下,该方法成功实现了有条件的语音信号间断传输,并在一定程度上提高了语音传输质量。     

基于锁相混频原理的高精度激光外差干涉信号的处理方法研究

利用锁相环实现拍频转换,将高频干涉拍频信号降频至1.0 kHz,通过填脉冲式测相方法获得被测相位差.实验结果表明利用该方法在拍频转换后易于获得0.078°的高精度相位差,而且该方法具有实现电路简单、频率稳定性高和相位跟踪稳定的优点.