Unmanned Surface Vehicle Thruster Fault Diagnosis via Vibration Signal Wavelet Transform and Vision Transformer under Varying Rotational Speed Conditions.

Among unmanned surface vehicle (USV) components, underwater thrusters are pivotal in their mission execution integrity. Yet, these thrusters directly interact with marine environments, making them perpetually susceptible to malfunctions. To diagnose thruster faults, a non-invasive and cost-effective vibration-based methodology that does not require altering existing systems is employed. However, the vibration data collected within the hull is influenced by propeller-fluid interactions, hull damping, and structural resonant frequencies, resulting in noise and unpredictability. Furthermore, to differentiate faults not only at fixed rotational speeds but also over the entire range of a thruster's rotational speeds, traditional frequency analysis based on the Fourier transform cannot be utilized. Hence, Continuous Wavelet Transform (CWT), known for attributions encapsulating physical characteristics in both time-frequency domain nuances, was applied to address these complications and transform vibration data into a scalogram. CWT results are diagnosed using a Vision Transformer (ViT) classifier known for its global context awareness in image processing. The effectiveness of this diagnosis approach was verified through experiments using a USV designed for field experiments. Seven cases with different fault types and severity were diagnosed and yielded average accuracy of 0.9855 and 0.9908 at different vibration points, respectively.

Tissue transglutaminase-induced down-regulation of matrix metalloproteinase-9.

Tissue transglutaminase (TGase 2) has been reported to have multiple functions in addition to its function as a biological adhesive. To identify its roles, we investigated the effects of TGase 2 on gelatinase activity. The MMP-9 activity of certain cell lines was significantly inhibited with retinoic acid treatment, and this effect was reversed in the presence of a TGase 2 inhibitor. Furthermore, TGase 2 overexpression reduced the MMP-9 protein expression levels and inhibited its activity in both culture media and cell lysate. The decreased mRNA levels of MMP-9 and the results of a promoter assay revealed that TGase 2 may be involved in MMP-9 transcription. Further, data obtained in an immunoprecipitation assay and an electrophoretic mobility shift assay demonstrated that TGase 2 binds to c-Jun and suppresses its binding activity toward AP-1. These results suggest that TGase 2 inhibits MMP-9 via downregulation of MMP-9 transcription activity by blocking the binding of the Jun-fos complex to an AP-1 site.