No abstract

Bearings play an important role in the industrial system. Among all kinds of diagnosis methods, empirical wavelet transform has been widely used for its characteristic of separating empirical modes from the spectrum. Although the empirical wavelet transform restrains the mode aliasing of extracting modal functions from the time domain, it runs slowly and separates a large number of invalid components. In this paper, an adaptive and fast empirical wavelet transform method is proposed. The method extracts the first feature cluster in the Fourier transform of the spectrum to reconstruct the trend spectrum. The minimum points are regarded as the initial boundaries. The key spectral negentropy is proposed to extract the frequency band which may contain main information. This method reduces the number of invalid components and computation time by filtering components before reconstruction. The simulation signal proves that the proposed method is effective and the proposed key spectral negentropy has stronger anti-noise ability than kurtosis. The experimental signals show that the method can successfully extract the fault features of inner or outer rings of bearings, and is suitable for the diagnosis of composite faults. INDEX TERMS Empirical wavelet transform, spectral negentropy, spectral segmentation, trend spectrum, rolling bearing fault diagnosis.

SUMMARY Stem strength is an important agronomic trait affecting plant lodging, and plays an essential role in the quality and yield of plants. Thickened secondary cell walls in stems provide mechanical strength that allows plants to stand upright, but the regulatory mechanism of secondary cell wall thickening and stem strength in cut flowers remains unclear. In this study, first, a total of 11 non‐redundant Paeonia lactiflora R2R3‐MYBs related to stem strength were identified and isolated from cut‐flower herbaceous peony, among which PlMYB43, PlMYB83 and PlMYB103 were the most upregulated differentially expressed genes. Then, the expression characteristics revealed that these three R2R3‐MYBs were specifically expressed in stems and acted as transcriptional activators. Next, biological function verification showed that these P. lactiflora R2R3‐MYBs positively regulated stem strength, secondary cell wall thickness and lignin deposition. Furthermore, yeast‐one‐hybrid and dual luciferase reporter assays demonstrated that they could bind to the promoter of caffeic acid O‐methyltransferase gene (PlCOMT2) and/or laccase gene (PlLAC4), two key genes involved in lignin biosynthesis. In addition, the function of PlLAC4 in increasing lignin deposition was confirmed by virus‐induced gene silencing and overexpression. Moreover, PlMYB83 could also act as a transcriptional activator of PlMYB43. The findings of the study propose a regulatory network of R2R3‐MYBs modulating lignin biosynthesis and secondary cell wall thickening for improving stem lodging resistance, and provide a resource for molecular genetic engineering breeding of cut flowers.

No abstract

The safety, performance, and lifetime of lithium-ion cells are critical for the acceptance of electric vehicles (EVs), but non-destructively evaluating cell quality issues is not easy. In recent studies, batterie's deformation measurement by optical methods is a promising candidate for detecting a possible local failure originating from mechanical and current inhomogeneities or potential gradients. However, the existing measurement techniques, such as laser scanning and digital image correlation, cannot achieve high-precision deformation measurement up to submicron. In this study, a temporal electronic speckle pattern interferometry (ESPI) is proposed to acquire out-of-plane deformation of both surfaces of a commercial Li-ion polymer battery simultaneously. Various data processing techniques, such as the Fourier and windowed Fourier transform(WFT) methods, are applied in temporal and spatial domains to extract the out-ofdisplacement during the battery charging process. High-precision deformation of both surfaces can be obtained during the charging process. The result shows that temporal ESPI can be a helpful tool to offer high-precision data for optimizing the Li-ion batteries model.

This study proposes a method to measure vibration mode shape on beam structures by using the elastic mechanoluminescent (EML) material SrAl2O4: Eu2+. The EML phenomenon has attracted interest due to its potential for application to strain distribution, crack visualization, and structural health monitoring. In this Letter, the relationship between the distribution of luminous intensity and the vibration mode shape of beam structures is explored and is found to be quadratic. A comparison between the results of experiments and simulations shows that the proposed method can measure a structure's vibration mode shape. The study also shows that experimental parameters, such as the exposure time of the camera and the amplitude of excitation, do not affect the validity of this method. The robustness and convenience of the proposed method make it a more efficient technique than prevalent electrical or optical vibrational methods of analysis.

Vibration measurement, particularly mode shape measurement, is an important aspect of structural dynamic analysis since it can validate finite element or analytical vibration models. Scanning laser Doppler vibrometry (LDV) and high-speed digital image correlation have become dominant methods for experimental mode shape measurement. However, these methods have high equipment costs and several disadvantages regarding spatial or temporal performance. This paper proposes a laser Doppler vibrometer induced stroboscopic digital image correction for non-contact mode shape and operational deflection shape measurement. Our results verify that single-point LDV and normal rate cameras can be used obtain high spatial resolution mode shape and operational deflection shape. Measurement frequency range is much higher than the camera capturing rate. We also show that the proposed approach coincides well with time-averaged electronic speckle pattern interferometry.

The laser speckle correlation method has found widespread application for obtaining information from vibrating objects. However, the resolution and accuracy of the laser speckle correlation method as they relate to the defocusing degree have not been analyzed sufficiently. Furthermore, the possible methods for speckle pattern quality assessment and enhancement have not been studied. In this study, the resolution and accuracy of the laser speckle correlation method are analyzed, and it is found that they are affected by the defocusing degree and speckle pattern quality, respectively. A new speckle pattern quality criterion combining the mean intensity gradient and frequency spectrum was proposed, called CMZ. The quality of the speckle pattern is higher when the CMZ is closer to zero. The proposed criterion was verified by simulated speckle patterns and real speckle patterns with different speckle sizes, densities, and gray contrasts. In the experimental setup stage, a suitable defocusing degree can be selected based on the resolution requirement and optimal speckle size, and other experimental parameters can be determined according to the CMZ criterion. Rotation and vibration experiments verified the effectiveness of the laser speckle correlation method and confirmed the reliability of the experiment preparation based on proposed CMZ criterion.