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CSI-based human sensing using model-based approaches: a survey
Zhengjie Wang,Zehua Huang,Chengming Zhang,Wenwen Dou,Yinjing Guo,Da Chen 한국CDE학회 2021 Journal of computational design and engineering Vol.8 No.2
Currently, human sensing draws much attention in the field of ubiquitous computing, and human sensing based on WiFi CSI (channel state information) becomes a hot research topic due to the easy deployment and availability of WiFi devices. Although various human sensing applications based on the CSI signal model are emerging, the model-based approach has not been studied thoroughly. This paper provides a comprehensive survey of the latest model-based human sensing methods and their applications. First, the CSI signal and framework of model-based human sensing methods are introduced. Then, related models and fundamental signal preprocessing techniques are described. Next, typical human sensing applications are investigated, and the crucial characteristics are summarized. Finally, the advantages, limitations, and future research trends of model-based human sensing methods are concluded in this paper.
Yin Li,Keyu Zhang,Zhengjie Chen,Yunke Wang,Li Wang,Feng Liang,Yaochun Yao 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2020 NANO Vol.15 No.02
The olivine LiFePO4 with various morphologies and different growth lattice planes was prepared by a controllable hydrothermal method with changing precursor concentration and using phytic acid as phosphorus source. The microstructure, crystal orientation and electrochemical performance of the prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM) and charge–discharge tests. The results show that the morphologies of all samples change from spindle-like to hierarchical plate-like and then to long plate-like shape, and the main exposed facets transform from (100) to (001). This indicates that the precursor concentration and phytic acid play important roles in exposing facets and controlling the morphology of LiFePO4. In order to illustrate these phenomena, a reasonable assembly process is provided and the formation is explained. Li ion diffusion coefficient along [100] and [001] directions was calculated by using electrochemical impedance spectroscopy (EIS). The results show that the diffusion coefficient of (100) facet is higher than that of (001) facet, indicating a good electrochemical performance for (100) facet. In addition, the capacity test is carried out, which also confirms the above results. With the precursor concentration of 0.5 M, the obtained LiFePO4 with self-assembled hierarchical structure, smaller size and (100) facet shows the best electrochemical performance: 162.1 mAh/g at 0.1C and 112.4 mAh/g at 10 C. Using phytic acid as phosphorus source and controlling precursor concentration to prepare high performance LiFePO4 open up a new prospect for the production of cathode materials for lithium ion batteries.
Jia, Xiangling,Zhang, Chen,Liu, Juanjuan,Lv, Wei,Wang, Da-Wei,Tao, Ying,Li, Zhengjie,Zheng, Xiaoyu,Yu, Jong-Sung,Yang, Quan-Hong The Royal Society of Chemistry 2016 Nanoscale Vol.8 No.8
<P>A controllable drying strategy is proposed for the precise and non-destructive control over the structure of a 3D graphene assembly. Such an assembly is used as a model carbon material to investigate the pore structure-dependent shuttle effect and cycling performance of the cathode of a Li-S battery.</P>