Ko Keun Kim

Hongjun Jeong, Minji Kim, Heesoo Jung, Ko Keun Kim, Hogun Park. Findings of the Association for Computational Linguistics: ACL 2025. 2025.

Respiratory rate (RR) is a vital indicator for assessing the bodily functions and health status of patients. RR is a prominent parameter in the field of biomedical signal processing and is strongly associated with other vital signs such as blood pressure, heart rate, and heart rate variability. Various physiological signals, such as photoplethysmogram (PPG) signals, are used to extract respiratory information. RR is also estimated by detecting peak patterns and cycles in the signals through signal processing and deep-learning approaches. In this study, we propose an end-to-end RR estimation approach based on a third-generation artificial neural network model—spiking neural network. The proposed model employs PPG segments as inputs, and directly converts them into sequential spike events. This design aims to reduce information loss during the conversion of the input data into spike events. In addition, we use feedback-based integrate-and-fire neurons as the activation functions, which effectively transmit temporal information. The network is evaluated using the BIDMC respiratory dataset with three different window sizes (16, 32, and 64 s). The proposed model achieves mean absolute errors of 1.37 ± 0.04, 1.23 ± 0.03, and 1.15 ± 0.07 for the 16, 32, and 64 s window sizes, respectively. Furthermore, it demonstrates superior energy efficiency compared with other deep learning models. This study demonstrates the potential of the spiking neural networks for RR monitoring, offering a novel approach for RR estimation from the PPG signal.

Numerical reasoning is an essential task for supporting machine learning applications, such as recommendation and information retrieval. The reasoning task aims to compare two items and infer new facts (e.g., is taller than) by leveraging existing relational information and numerical attributes (e.g., the height of an entity) in knowledge graphs. However, most existing methods rely on leveraging attribute encoders or additional loss functions to predict numerical relations. Therefore, the prediction performance is often not robust in cases when attributes are sparsely observed. In this paper, we propose a Relation-AAware attribute representation learning-based Knowledge Graph Embedding method for numerical reasoning tasks, which we call RAKGE. RAKGE incorporates a newly proposed attribute representation learning mechanism, which can leverage the association between relations and their corresponding numerical attributes. In addition, we introduce a robust self-supervised learning method to generate unseen positive and negative examples, thereby making our approach more reliable when numerical attributes are sparsely available. In the evaluation of three real-world datasets, our proposed model outperformed state-of-the-art methods, achieving an improvement of up to 65.1% in [email protected] and up to 52.6% in MRR compared to the best competitor. Our implementation code is available at https://github.com/learndatalab/RAKGE.

Recently, the interest in biometric authentication based on electrocardiograms (ECGs) has increased. Nevertheless, the ECG signal of a person may vary according to factors such as the emotional or physical state, thus hindering authentication. We propose an adaptive ECG-based authentication method that performs incremental learning to identify ECG signals from a subject under a variety of measurement conditions. An incremental support vector machine (SVM) is adopted for authentication implementing incremental learning. We collected ECG signals from 11 subjects during 10 min over six days and used the data from days 1 to 5 for incremental learning, and those from day 6 for testing. The authentication results show that the proposed system consistently reduces the false acceptance rate from 6.49% to 4.39% and increases the true acceptance rate from 61.32% to 87.61% per single ECG wave after incremental learning using data from the five days. In addition, the authentication results tested using data obtained a day after the latest training show the false acceptance rate being within reliable range (3.5–5.33%) and improvement of the true acceptance rate (70.05–87.61%) over five days.