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Design of Fast Steering Mirror Based on Displacement Amplification Mechanism

XIE Yong, LIU Chongfei, JIA Jianjun, DAI Jiansheng

Journal of Shanghai Jiao Tong University 2021, 55 (9): 1142-1150. DOI: 10.16183/j.cnki.jsjtu.2020.103

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According to the current situation that the deflection angle of the piezoelectric ceramics direct drive fast steering mirror (FSM) is restricted by small elongation of piezoelectric ceramics and the large deflection angle cannot be realized, a novel piezoelectric FSM is designed. A two-stage lever-type amplification mechanism is adopted to realize the amplification of small displacement of piezoelectric ceramics and a strain gauge attached to the amplification mechanism is considered as the displacement sensor. The experimental results indicate that the deflection angle of the designed FSM is larger than 50 mrad, and the closed-loop linearity is below 0.5%, which satisfies the requirements of large deflection angle and accuracy pointing for light beam.

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Impact of Continuous RESET/SET Operations on Endurance Characteristic of Phase Change Memory

WU Lei, CAI Daolin, CHEN Yifeng, LIU Yuanguang, YAN Shuai, LI Yang, YU Li, XIE Li, SONG Zhitang

Journal of Shanghai Jiao Tong University 2021, 55 (9): 1134-1141. DOI: 10.16183/j.cnki.jsjtu.2020.028

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In order to explore the effects of continuous RESET operations and continuous SET operations on the endurance characteristic of phase change memory (PCM), the endurance characteristics of PCM at different ratios of RESET-SET times are studied based on a 4Mbit PCM chip. The variation of resistance distributions of PCM after continuous RESET and continuous SET operations are measured. The endurance characteristics of PCM in RESET-only and SET-only operations are compared with the typical endurance characteristic. Besides, the causes and repair methods of failure are also discussed. Moreover, the endurance characteristics of PCM at 8 different RESET-SET ratios are compared. The research results show that continuous RESET operation has little effect on the endurance characteristic of PCM, and the endurance characteristic of PCM in the RESET-only mode is on the same order as the typical endurance characteristic. However, the continuous SET operation has a significantly destructive effect on the endurance characteristic of PCM, and the endurance characteristic of PCM in the SET-only mode is 2 orders of magnitude lower than the typical endurance characteristic. The failure process of PCM caused by continuous RESET operation is irreversible while the failure process of PCM caused by continuous SET operation can be repaired by intermittent RESET operation.

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Infrared Multispectral Radiation Temperature Measurement Based on PCA-ELM

XI Jianhui, JIANG Han, CHEN Bo, FU Li

Journal of Shanghai Jiao Tong University 2021, 55 (7): 891-898. DOI: 10.16183/j.cnki.jsjtu.2020.027

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In the case of unknown target emissivity, an infrared multispectral radiation temperature measurement method based on principal component analysis (PCA) and extreme learning machine (ELM) is established. The nonlinear mathematic model of target temperature and radiance spectrum is analyzed to find a set of initial input vectors, which include sufficient information to estimate temperature. The PCA method is used to extract the independent principle components in input vectors. This method can also reduce the input dimension for neural network. Based on ELM network, the sample data is sufficiently learned to build the target infrared temperature measurement model by PCA-ELM. The effectiveness of the proposed method is verified by using the blackbody and the coating material with unknown emissivity as test target sources.

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