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179 results on '"Luo, K.H."'

5. Optimizing Camera Exposure Control Settings for Remote Vital Sign Measurements in Low-Light Environments

Author

Ismoil, Odinaev, Chin, Jing Wei, Luo, K.H., Ke, Zhang, So, Richard Hau Yue, Wong, Kwan Long, Ismoil, Odinaev, Chin, Jing Wei, Luo, K.H., Ke, Zhang, So, Richard Hau Yue, and Wong, Kwan Long

Abstract

Remote photoplethysmography (rPPG) is an optical technique that enables both non-invasive and efficient measurement of vital signs from facial videos. However, the quality of rPPG measurements can be adversely affected by improper camera exposure control and bad lighting conditions. In this paper, we present a systematic study of camera exposure control settings, specifically gain and exposure time, in low-light environments. Our results indicate that manual adjustment of gain and exposure time can significantly improve the quality of rPPG measurements, enabling accurate vital sign measurement even in environments with illuminance levels as low as 25 lux. Furthermore, we demonstrate that the optimal brightness range for rPPG-based vital sign measurement depends on the sensitivity of the vital sign to the shape and peaks of the rPPG signal. These findings have important practical implications for the use of rPPG in healthcare and remote monitoring applications. © 2023 IEEE.

Published
2023

6. Deep learning-based image enhancement for robust remote photoplethysmography in various illumination scenarios

Author

Chen, Shutao, Ho, Sui Kei, Chin, Jing Wei, Luo, K.H., Chan, Tsz Tai, So, Richard Hau Yue, Wong, Kwan Long, Chen, Shutao, Ho, Sui Kei, Chin, Jing Wei, Luo, K.H., Chan, Tsz Tai, So, Richard Hau Yue, and Wong, Kwan Long

Abstract

Remote photoplethysmography (rPPG) is a non-invasive and convenient approach for measuring human vital signs using a camera. However, accurate measurement can be challenging due to the different illumination of the surrounding environment. In this study, we present a deep learning-based image enhancement model (IEM) inspired by the Retinex theory to improve the robustness of rPPG signal extraction and heart rate (HR) estimation in different lighting conditions. We fine-tuned the IEM with a time-shifted negative Pearson correlation between the PPG signal ground truth and the predicted rPPG signal from a pre-trained 3D CNN (PhysNet). We evaluated our method using a publicly available dataset (BH-rPPG) of various lighting scenarios and our own private dataset. Our results demonstrate that our proposed model is generalizable and significantly improves rPPG extraction and HR estimation accuracies across a range of illumination intensities. © 2023 IEEE.

Published
2023

32. Sound generation by vortex pairing in subsonic axisymmetric jets

Author

Jiang, X., Avital, E.J., and Luo, K.H.

Subjects
Aerospace and defense industries, Business
Abstract

Direct numerical simulation (DNS) and an acoustic analogy are used to investigate the sound generation by vortex pairing in idealized subsonic axisymmetric jets. The detailed sound source structure is provided by the DNS. The acoustic analogy is based on solving the nonlinearized Lilley's third-order wave equation in the time-spare domain. A numerical algorithm for solving Lilley's equation is developed, in which the sound field is simulated simultaneously with the source field calculation. The computational domain includes both the near field and a portion of the acoustic far field. Effects of a coaxial secondary jet stream and the jet-to-ambient temperature ratio on the sound generation from an axisymmetric jet are investigated. It is shown that the sound source has a long axial distribution in the streamwise direction with the strongest source located near the end of the jet potential core where vortex pairing/merging occurs, and the radiated sound field is highly directive. It is also found that the secondary jet stream reduces the sound source size; therefore, the sound radiation from the coaxial jets is lower than that from the single jet. The hot jet simulation shows that increasing the jet-to-ambient temperature ratio leads to a smaller and weaker sound source, but does not lead to a weaker sound field. For the sound field a reasonable agreement is observed between the predictions from the axisymmetric Lilley's equation and the DNS results.

Published
2004

40. Calculation of basic sound radiation of axisymmetric jets by direct numerical simulations

Author

Avital, E.J., Sandham, N.d., Luo, K.H., and Musafir, R.E.

Subjects
Aerodynamic noise -- Measurement, Sound -- Measurement, Air jets -- Research, Atmospheric turbulence -- Research, Aerospace and defense industries, Business
Abstract

The influence of various numerical parameters on the computation of the basic radiation of sound from force laminar axisymmetric jets has been studied. Sound radiation is determined by a hybrid method where the hydrodynamic field is derived from an incompressible stream function-vorticity direct numerical simulation. The sound field is obtained from the compact Lighthill and Mohring-Kambe formulations. Ways of improving the acoustic analogies solution are also explored. The structure of the axisymmetric source of radiation has also been investigated for various Reynolds numbers.

Published
1999

50. Randomized Double-Blind, Placebo-Controlled Phase III trial Evaluating the Effect of Oral Glutamine on Radiation-Induced Oral Mucositis and Neck Dermatitis in Head and Neck Cancer Patients

Author

Lee, H.H., primary, Huang, C.J., additional, Huang, M.Y., additional, Chen, F., additional, Wang, Y.T., additional, Chen, C.H., additional, Yuan, S.S., additional, Huang, C.M., additional, Fang, P.T., additional, Luo, K.H., additional, Chuang, H.Y., additional, and Wang, Y.Y., additional

Published
2018
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