Sang-Hyun Lee

Prof. Dr. Sang-Hyun Lee

Department of Computer Engineering, Honam University, Gwangju 62399, Korea

Research Focus & Metrics

Academic Career Length

7Years (2020-Present)

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

Representative Publications

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9 September 2024 in Applied Sciences
Verified
Journal Article
Open access
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SKSang-Bum Kim
Sang-Bum Kim
Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
This study proposes a deep learning-based long short-term memory (LSTM) model to predict the state of charge (SOC) of lithium-ion batteries. The purpose of the research is to accurately model the complex nonlinear behavior that occurs during the charging and discharging processes of batteries to predict the SOC. The LSTM model was trained using battery data collected under various temperature and load conditions. To evaluate the performance of the artificial intelligence model, measurement data from the CS2 lithium-ion battery provided by the University of Maryland College of Engineering was utilized. The LSTM model excels in learning long-term dependencies from sequence data, effectively modeling temporal patterns in battery data. The study trained the LSTM model based on battery data collected from various charge and discharge cycles and evaluated the model’s performance by epoch to determine the optimal configuration. The proposed model demonstrated high SOC estimation accuracy for various charging and discharging profiles. As training progressed, the model’s predictive performance improved, with the predicted SOC moving from 14.8400% at epoch 10 to 12.4968% at epoch 60, approaching the actual SOC value of 13.5441%. Simultaneously, the mean absolute error (MAE) and root mean squared error (RMSE) decreased from 0.9185% and 1.3009% at epoch 10 to 0.2333% and 0.5682% at epoch 60, respectively, indicating continuous improvement in predictive performance. In conclusion, this study demonstrates the effectiveness of the LSTM model for predicting the SOC of lithium-ion batteries and its potential to enhance the performance of battery management systems.

1 January 2022 in Computers, Materials & Continua
Verified
Journal Article
Open access
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MLMan-Ting Li
Man-Ting Li
Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
This study aims to detect and prevent greening disease in citrus trees using a deep neural network. The process of collecting data on citrus greening disease is very difficult because the vector pests are too small. In this paper, since the amount of data collected for deep learning is insufficient, we intend to use the efficient feature extraction function of the neural network based on the Transformer algorithm. We want to use the Cascade Region-based Convolutional Neural Networks (Cascade R-CNN) Swin model, which is a mixture of the transformer model and Cascade R-CNN model to detect greening disease occurring in citrus. In this paper, we try to improve model safety by establishing a linear relationship between samples using Mixup and Cutmix algorithms, which are image processing-based data augmentation techniques. In addition, by using the ImageNet dataset, transfer learning, and stochastic weight averaging (SWA) methods, more accuracy can be obtained. This study compared the Faster Region-based Convolutional Neural Networks Residual Network101 (Faster R-CNN ResNet101) model, Cascade Region-based Convolutional Neural Networks Residual Network101 (Cascade R-CNN-ResNet101) model, and Cascade R-CNN Swin Model. As a result, the Faster R-CNN ResNet101 model came out as Average Precision (AP) (Intersection over Union (IoU)=0.5): 88.2%, AP(IoU = 0.75): 62.8%, Recall: 68.2%, and the Cascade R-CNN ResNet101 model was AP(IoU = 0.5): 91.5%, AP (IoU = 0.75): 67.2%, Recall: 73.1%. Alternatively, the Cascade R-CNN Swin Model showed AP (IoU = 0.5): 94.9%, AP (IoU = 0.75): 79.8% and Recall: 76.5%. Thus, the Cascade R-CNN Swin Model showed the best results for detecting citrus greening disease.

10 August 2023 in Applied Sciences
Verified
Journal Article
Open access
PDF file
Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
Lithium-ion batteries are widely used in electric vehicles, smartphones, and energy storage devices due to their high power and light weight. The goal of this study is to predict the remaining capacity of a lithium-ion battery and evaluate its performance through three machine learning models: linear regression, decision tree, and random forest, and two deep learning models: neural network and ensemble model. Mean squared error (MSE), mean absolute error (MAE), coefficient of determination (R-squared), and root mean squared error (RMSE) were used to measure prediction accuracy. For the evaluation of the artificial intelligence model, the dataset was downloaded and integrated with measurement data of the CS2 lithium-ion battery provided by the University of Maryland College of Engineering. As a result of the study, the RMSE of the linear regression model was 0.045, the decision tree model was 0.038, the random forest model was 0.034, the neural network model was 0.032, and the ensemble model was 0.030. According to the measured values, the ensemble model showed the best predictive performance, followed by the neural network model. Decision tree and random forest models also showed very good performance, and the linear regression model showed relatively poor predictive performance compared to the other models.

30 July 2020 in Applied Sciences
Verified
Journal Article
Open access
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SKSangbum Kim
Sangbum Kim
Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
In this paper, we propose an intelligent battery control system that incorporates an active balancing technique and a fuzzy controller to manage and extend the life of an agricultural drone battery efficiently. The control system includes the following key features: A battery pack balancing algorithm based on a bidirectional DC/DC converter; a cell balancing system to prevent overcharge/discharge and ensure equal control of the cell voltages; and a monitoring system and wireless link to track the real-time status of the battery, temperature, and acceleration while the drone is in operation. Each battery pack consists of six lithium polymer batteries, one fuzzy controller per cell, and supports active balancing using the developed balancing technique. The capacity of each of the battery packs in the system is 11,000 mAh, and two can be combined to provide a total capacity of 22,000 mAh.

6 August 2024 in Applied Sciences
Verified
Journal Article
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Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
MOMyeong-Hoon Oh
Myeong-Hoon Oh
Modern aquaculture utilizes computer vision technology to analyze underwater images of fish, contributing to optimized water quality and improved production efficiency. The purpose of this study is to efficiently perform underwater fish detection and tracking using multi-object tracking (MOT) technology. To achieve this, the FairMOT model was employed to simultaneously implement pixel-level object detection and re-identification (Re-ID) functions, comparing two backbone models: FairMOT+YOLOv5s and FairMOT+DLA-34. The study constructed a dataset targeting the popular black porgy in Korean aquaculture, using underwater video data from five different environments collected from the internet. During the training process, the FairMOT+YOLOv5s model rapidly reduced train loss and demonstrated stable performance. The FairMOT+DLA-34 model showed better results in ID tracking performance, with an accuracy of 44.1%, an IDF1 of 11.0%, an MOTP of 0.393, and an IDSW of 1. In contrast, the FairMOT+YOLOv5s model recorded an accuracy of 43.8%, an IDF1 of 14.6%, an MOTP of 0.400, and an IDSW of 10. The results of this study indicate that the FairMOT+YOLOv5s model demonstrated higher IDF1 and MOTP scores compared to the FairMOT+DLA-34 model, while the FairMOT+DLA-34 model showed superior performance in ID tracking accuracy and had fewer ID switches.

31 August 2020 in Applied Sciences
Verified
Journal Article
Open access
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CYChulseung Yang
Chulseung Yang
Giwon KuGiwon Ku
Giwon Ku
JLJeong Gi Lee
Jeong Gi Lee
Sang-Hyun LeeSang-Hyun Lee
Sang-Hyun Lee
This paper presents an interval-based LDA (Linear Discriminant Analysis) algorithm for individual verification using ECG (Electrocardiogram). In this algorithm, at first, unwanted noise and power-line interference are removed from the ECG signal. Then, the autocorrelation profile (ACP) of the ECG signal, which is a mathematical representation of the degree of similarity between a given time series and a lagged version of itself over successive time intervals, is calculated. Finally, the interval-based LDA algorithm is applied to extract unique individual feature vectors that represent distance and angle characteristics on short ACP segments. These feature vectors are used during the processes of enrollment and verification of individual identification. To validate our algorithm, we conducted experiments using the MIT-BIH ECG and achieved EERs (Equal Error Rate) of 0.143%, showing that the proposed algorithm is practically effective and robust in verifying the individual’s identity.