Yuyan Liu

Dr. Yuyan Liu


Research Focus & Metrics

Academic Career Length

4Years (2023-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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18 October 2023 in Remote Sensing
Verified
Journal Article
Open access
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XLXuqing Li
Xuqing Li
XWXiaodan Wang
Xiaodan Wang
JWJianjun Wu
Jianjun Wu
WLWei Luo
Wei Luo
LTLingwen Tian
Lingwen Tian
WZWenlong Zhang
Wenlong Zhang
The North China Plain is an important area for agricultural economic development in China. But water shortages, severe groundwater over-exploitation and drought problems make it difficult to exercise the topographic resource advantages of the plain. Therefore, the precise monitoring of soil moisture is of great significance for the rational use of water resources. Soil characteristics vary in natural farmland ecosystems, crops are constrained by multiple compound stresses and the precise extraction of soil moisture stress is a difficult and critical problem. The long time series was decomposed via complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN) to obtain different intrinsic mode function (IMF) components, and the statistical descriptors of each component were calculated to realize the precise discrimination of soil moisture stress. A quantitative evaluation model of soil moisture was established, and the different noise addition ratios and modeling types were set respectively to investigate the optimal inversion model. The results showed that: (1) The reconstruction error of the CEEMDAN was small and almost 0; it had a high reconstruction accuracy and was more suitable for the decomposition of the long time series. The first two components, IMF1 and IMF2, were soil moisture stress subsequences, and it could effectively reflect the moisture stress situation. (2) The inversion model performed well when ε was 0.05 and the model type was quadratic, with a coefficient of determination R2 of 0.98, which gave a better fit and less error. (3) The overall soil moisture content in the study area was low, basically in the range of 6.9% to 15.7%, with the central part, especially the south-central part, being the most affected by soil moisture stress, and the overall impact of soil moisture stress showed a decreasing trend from February to May. The utilization of CEEMDAN further enhances the accuracy of soil moisture inversion in agricultural fields, realizing the effective application of remote sensing observation technology and time-frequency analysis technology in the field of soil moisture research.

24 February 2025 in Agriculture
Verified
Journal Article
Open access
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DCDongxuan Cao
Dongxuan Cao
WLWei Luo
Wei Luo
RTRuiyin Tang
Ruiyin Tang
YLYuyan Liu
Yuyan Liu
JZJiasen Zhao
Jiasen Zhao
LYLihua Yuan
Lihua Yuan
Accurately detecting apple fruit can crucially assist in estimating the fruit yield in apple orchards in complex scenarios. In such environments, the factors of density, leaf occlusion, and fruit overlap can affect the detection and counting accuracy. This paper proposes an improved YOLOv7-Tiny-PDE network model based on the YOLOv7-Tiny model to detect and count apples from data collected by drones, considering various occlusion and lighting conditions. First, within the backbone network, we replaced the simplified efficient layer aggregation network (ELAN) with partial convolution (PConv), reducing the network parameters and computational redundancy while maintaining the detection accuracy. Second, in the neck network, we used a dynamic detection head to replace the original detection head, effectively suppressing the background interference and capturing the background information more comprehensively, thus enhancing the detection accuracy for occluded targets and improving the fruit feature extraction. To further optimize the model, we replaced the boundary box loss function from CIOU to EIOU. For fruit counting across video frames in complex occlusion scenes, we integrated the improved model with the DeepSort tracking algorithm based on Kalman filtering and motion trajectory prediction with a cascading matching algorithm. According to experimental results, compared with the baseline YOLOv7-Tiny, the improved model reduced the total parameters by 22.2% and computation complexity by 18.3%. Additionally, in data testing, the p-value improved by 0.5%; the R-value rose by 2.7%; the mAP and F1 scores rose by 4% and 1.7%, respectively; and the MOTA value improved by 2%. The improved model is more lightweight and can preserve a high detection accuracy well, and hence, it can be applied to detection and counting tasks in complex orchards and provides a new solution for fruit yield estimation using lightweight devices.

5 December 2023 in ISPRS Annals of the Photogrammetry, Remote Sensing and Spatial Information Sciences
Verified
Journal Article
Open access
PDF file
JLJ. Li
J. Li
YLYuyan Liu
Yuyan Liu
Changfeng JingChangfeng Jing
Changfeng Jing
YFY. Feng
Y. Feng
Geoparks contain various geological relics and peculiar geological landscapes, which have good ornamental value and are non-renewable precious wealth. Today, with the deterioration of the natural environment and the impact of human activities, the geopark has been destroyed to a certain extent, but the current research methods on the geopark are still mostly traditional propaganda methods with a single method. This study takes the geoparks in Southwest China as the research object, establishes a geopark management system, realizes the display, query, statistical rendering, distribution analysis and impact factor analysis of geoparks in the region, not only intuitively reflects the distribution of geoparks, The GIS analysis method is also introduced to explore the regularity of their distribution and the factors affecting the distribution, so as to provide reference for the protection, planning and construction of subsequent geoparks.