Yalan Li

Feb 29, 2024 | onlinelibrary.wiley.com | Xinxin Ma |Yalan Li |Ichiro Iwasaki

1 INTRODUCTION The household registration (hukou) system is a unique institution in contemporary China that has been in place since 1958. The imbalance in social resource allocation between urban and rural residents based on the hukou system has segmented China into a dual society structure (Cai, 2016). During the institutional transition period (after 1978), the Chinese government carried out market-oriented reforms and gradually deregulated the hukou system.

Oct 30, 2023 | mdpi.com | Yalan Li |Jing Yuan |Jie J. Cao |Yaohui Liu

1. IntroductionLightning-generated whistler waves have abundant access to the topside ionosphere, even close to the magnetic equator. They propagate with different group velocities depending on the frequency; that is, signals at lower frequencies arrive later than those at higher frequencies. Additionally, they present as an L-shape in the time–frequency diagram [1], as shown in Figure 1.

Aug 16, 2023 | mdpi.com | Ying Han |Yalan Li |Jing Yuan |Jianping Huang

4. Experimental Setup and Results Analysis 4.1. Experimental EnvironmentFor this experiment, MATLAB 2020 was used to generate spectrograms. Python 3.7 was used with the OpenCV and Scikit-learn libraries for feature extraction and clustering algorithms. This implementation enabled automatic recognition of electromagnetic pulse sequence signals. 4.2. Experimental DataThe experimental data used in this study were obtained from VLF waveform data collected by the CSES EFD from 2019 to 2020.