RÉSUMÉ
High-performance vector hydrophones have been gaining attention for underwater target-monitoring applications. Nevertheless, there exists the mutual constraint between sensitivity and bandwidth of a single hydrophone. To solve this problem, a four-unit array piezoelectric bionic MEMS vector hydrophone (FPVH) was developed in this paper, which has a cross-beam and a bionic fish-lateral-line-nerve-cell-cilia unit array structure. Simulation analysis and optimization in the design of the bionic microstructure have been performed by COMSOL 6.1 software to determine the structure dimensions and the lead zirconate titanate (PZT) thin film distribution. The FPVH was manufactured using MEMS technology and tested in a standing wave bucket. The results indicate that the FPVH has a sensitivity of up to -167.93 dB@1000 Hz (0 dB = 1 V/µPa), which is 12 dB higher than that of the one-unit piezoelectric MEMS vector hydrophone (OPVH). Additionally, the working bandwidth of the FPVH reaches 20 Hz~1200 Hz, exhibiting a good cosine curve with an 8-shape. This work paves a new way for the development of multi-unit piezoelectric vector hydrophones for underwater acoustic detectors.
RÉSUMÉ
In response to the growing demand for high-sensitivity accelerometers in vector hydrophones, a piezoelectric MEMS accelerometer (PMA) was proposed, which has a four-cantilever beam integrated inertial mass unit structure, with the advantages of being lightweight and highly sensitive. A theoretical energy harvesting model was established for the piezoelectric cantilever beam, and the geometric dimensions and structure of the microdevice were optimized to meet the vibration pickup conditions. The sol-gel and annealing technology was employed to prepare high-quality PZT thin films on silicon substrate, and accelerometer microdevices were manufactured by using MEMS technology. Furthermore, the MEMS accelerometer was packaged for testing on a vibration measuring platform. Test results show that the PMA has a resonant frequency of 2300 Hz. In addition, there is a good linear relationship between the input acceleration and the output voltage, with V = 8.412a - 0.212. The PMA not only has high sensitivity, but also has outstanding anti-interference ability. The accelerometer structure was integrated into a vector hydrophone for testing in a calibration system. The results show that the piezoelectric vector hydrophone (PVH) has a sensitivity of -178.99 dB@1000 Hz (0 dB = 1 V/µPa) and a bandwidth of 20~1100 Hz. Meanwhile, it exhibits a good "8" shape directivity and consistency of each channel. These results demonstrate that the piezoelectric MEMS accelerometer has excellent capabilities suitable for use in vector hydrophones.
RÉSUMÉ
BACKGROUND/AIMS: To investigate the effect of cognitive impairment and X-linked inhibitor of apoptosis protein (XIAP) on glucolipid metabolism. MATERIALS AND METHODS: ß-amyloid (Aß 1-42) was injected into the hippocampus of rats to establish a cognitive impairment model. Trans-activator of transcription (TAT)-XIAP fusion protein (the TAT-XIAP group), PBS (the model group), or XIAP antisense oligonucleotides (the ASODN group) was injected into the lateral ventricles of the rats to increase and decrease the activity of XIAP in the hippocampus. To determine the level of blood glucose and lipids, adenosine monophosphate-activated protein kinase (AMPK) expression of liver and hipppocamual neuronal apoptosis. RESULTS: The levels of FPG, TG, TC and LDL were significantly higher in the TAT-XIAP group, the model group and the ASODN group than in the blank group (P < 0.05); however, the HDL level showed no significant change in all groups of rats. The apoptosis indexes of the rat hippocampal CA1 neuron were 68.44 ± 4.31%, 13.21 ± 2.30%, 56.68 ± 4.771%, and 87.51 ± 6.63% in the model group, the blank group, the TAT-XIAP group and the ASODN group, respectively. Gastrointestinal motility was less frequent (per time unit) in the model group, the ASODN group and the TAT-XIAP group than in the blank group. Compared with the model group, gastrointestinal motility was significantly less frequent in the ASODN group and was significantly more frequent in the TAT-XIAP group. Compared with the blank group, the model group had a significantly lower gastric emptying rate and intestinal propulsive rate. Compared with the model group, the gastric emptying rate and intestinal propulsive rate were significantly lower in the ASODN group and were significantly higher in the TAT-XIAP group. Compared with the blank group, the expressions of AMPK mRNA, and AMPK protein were significantly reduced in the model group, the TAT-XIAP group, and the ASODN group. AMPK expression was significantly increased in the TAT-XIAP group and was significantly decreased in the ASODN group than in the model group. CONCLUSION: Cognitive impairment and hippocampal neuron apoptosis can cause glucose and lipids metabolic abnormalities, possibly by regulating gastrointestinal motility and AMPK expression in the liver. The changes in the function of XIAP, which is an anti-apoptotic protein in the hippocampus, may affect the metabolism of glucose and lipids.
