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10,401 results on '"Zhang Fei"'

172. Quality assurance test and Failure Analysis of SiPM Arrays of GECAM Satellites

Author

Zhang, D. L., Gao, M., Sun, X. L., Li, X. Q., An, Z. H., Wen, X. Y., Cai, C., Chang, Z., Chen, G., Chen, C., Du, Y. Y., Gao, R., Gong, K., Guo, D. Y., He, J. J., Hou, D. J., Li, Y. G., Li, C. Y., Li, G., Li, L., Li, X. F., Li, M. S., Liang, X. H., Liu, X. J., Liu, Y. Q., Lu, F. J., Lu, H., Meng, B., Peng, W. X., Shi, F., Wang, H., Wang, J. Z., Wang, Y. S., Wang, H. Z., Wen, X., Xiao, S., Xiong, S. L., Xu, Y. B., Xu, Y. P., Yang, S., Yang, J. W., Zhang, Fan., Zhang, S. N., Zhang, C. Y., Zhang, C. M., Zhang, Fei, Zhao, X. Y., and Zhou, X.

Subjects
Physics - Instrumentation and Detectors
Abstract

The Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) satellite consists of two small satellites. Each GECAM payload contains 25 gamma ray detectors (GRD) and 8 charged particle detectors (CPD). GRD is the main detector which can detect gamma-rays and particles and localize the Gamma-Ray Bursts (GRB),while CPD is used to help GRD to discriminate gamma-ray bursts and charged particle bursts. The GRD makes use of lanthanum bromide (LaBr3) crystal readout by SiPM. As the all available SiPM devices belong to commercial grade, quality assurance tests need to be performed in accordance with the aerospace specifications. In this paper, we present the results of quality assurance tests, especially a detailed mechanism analysis of failed devices during the development of GECAM. This paper also summarizes the application experience of commercial-grade SiPM devices in aerospace payloads, and provides suggestions for forthcoming SiPM space applications., Comment: 13 pages, 23 figures

Published
2021

189. Complementary Patch for Weakly Supervised Semantic Segmentation

Author

Zhang, Fei, Gu, Chaochen, Zhang, Chenyue, and Dai, Yuchao

Subjects
Computer Science - Computer Vision and Pattern Recognition
Abstract

Weakly Supervised Semantic Segmentation (WSSS) based on image-level labels has been greatly advanced by exploiting the outputs of Class Activation Map (CAM) to generate the pseudo labels for semantic segmentation. However, CAM merely discovers seeds from a small number of regions, which may be insufficient to serve as pseudo masks for semantic segmentation. In this paper, we formulate the expansion of object regions in CAM as an increase in information. From the perspective of information theory, we propose a novel Complementary Patch (CP) Representation and prove that the information of the sum of the CAMs by a pair of input images with complementary hidden (patched) parts, namely CP Pair, is greater than or equal to the information of the baseline CAM. Therefore, a CAM with more information related to object seeds can be obtained by narrowing down the gap between the sum of CAMs generated by the CP Pair and the original CAM. We propose a CP Network (CPN) implemented by a triplet network and three regularization functions. To further improve the quality of the CAMs, we propose a Pixel-Region Correlation Module (PRCM) to augment the contextual information by using object-region relations between the feature maps and the CAMs. Experimental results on the PASCAL VOC 2012 datasets show that our proposed method achieves a new state-of-the-art in WSSS, validating the effectiveness of our CP Representation and CPN., Comment: 10 pages, accepted in ICCV2021

Published
2021

190. Superior Photo-carrier Diffusion Dynamics in Organic-inorganic Hybrid Perovskites Revealed by Spatiotemporal Conductivity Imaging

Author

Ma, Xuejian, Zhang, Fei, Chu, Zhaodong, Hao, Ji, Chen, Xihan, Quan, Jiamin, Huang, Zhiyuan, Wang, Xiaoming, Li, Xiaoqin, Yan, Yanfa, Zhu, Kai, and Lai, Keji

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics, Condensed Matter - Materials Science, Physics - Applied Physics, Physics - Optics
Abstract

The outstanding performance of organic-inorganic metal trihalide solar cells benefits from the exceptional photo-physical properties of both electrons and holes in the material. Here, we directly probe the free-carrier dynamics in Cs-doped FAPbI3 thin films by spatiotemporal photoconductivity imaging. Using charge transport layers to selectively quench one type of carriers, we show that the two relaxation times on the order of 1 microsecond and 10 microseconds correspond to the lifetimes of electrons and holes in FACsPbI3, respectively. Strikingly, the diffusion mapping indicates that the difference in electron/hole lifetimes is largely compensated by their disparate mobility. Consequently, the long diffusion lengths (3 ~ 5 micrometers) of both carriers are comparable to each other, a feature closely related to the unique charge trapping and de-trapping processes in hybrid trihalide perovskites. Our results unveil the origin of superior diffusion dynamics in this material, crucially important for solar-cell applications.

Published
2021
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191. An Improved Algorithm of Robot Path Planning in Complex Environment Based on Double DQN

Author

Zhang, Fei, Gu, Chaochen, and Yang, Feng

Subjects
Computer Science - Robotics, Computer Science - Artificial Intelligence
Abstract

Deep Q Network (DQN) has several limitations when applied in planning a path in environment with a number of dilemmas according to our experiment. The reward function may be hard to model, and successful experience transitions are difficult to find in experience replay. In this context, this paper proposes an improved Double DQN (DDQN) to solve the problem by reference to A* and Rapidly-Exploring Random Tree (RRT). In order to achieve the rich experiments in experience replay, the initialization of robot in each training round is redefined based on RRT strategy. In addition, reward for the free positions is specially designed to accelerate the learning process according to the definition of position cost in A*. The simulation experimental results validate the efficiency of the improved DDQN, and robot could successfully learn the ability of obstacle avoidance and optimal path planning in which DQN or DDQN has no effect., Comment: Accepted in International Conference on Guidance, Navigation and Control,2020

Published
2021

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