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Cardiac Autonomic Modulation during on-Call Duty under Working Hours Restriction
(2020-02-01)
Chien, Jien-Wen
;
Chen, Chung-Yen
;
Lin, Sheng-Hsuan
;
Lin, Shih-Wen
;
Lin, Yu-Hsuan
Background: Medical residency is a time of high stress and long working hours, which increase the risk of cardiovascular disease. This study aimed to investigate the autonomic modulation of resident physicians throughout the on-call duty cycle. Methods: Spectral analysis of heart rate variability (HRV) was used to compute cardiac parasympathetic modulation (high-frequency power, HF) and cardiac sympathetic modulation (normalized low-frequency power, LF%, and the ratio of LF and HF, LF/HF) of 18 residents for a consecutive 4-day cycle. Results: Male residents show reduced cardiac sympathetic modulation (i.e., higher LF/HF and LF%) than the female interns. Medical residents' cardiac parasympathetic modulation (i.e., HF) significantly increased on the first and the second post-call day compared with the pre-call day. In contrast, LF% was significantly decreased on the first and the second post-call day compared with the pre-call day. Similarly, LF/HF was significantly decreased on the second post-call day compared with the pre-call day. LF/HF significantly decreased on the first post-call day and on the second post-call day from on-call duty. Conclusion: The guideline that limits workweeks to 80 h and shifts to 28 h resulted in reduced sympathetic modulation and increased parasympathetic modulation during the two days following on-call duty.
Comparison of thresholding schemes for visible light communication using mobile-phone image sensor
(2016-02-08)
Liu, Yang
;
Chow, Chi-Wai
;
Liang, Kevin
;
Chen, Hung-Yu
;
Hsu, Chin-Wei
Based on the rolling shutter effect of the complementary metal-oxide-semiconductor (CMOS) image sensor, bright and dark fringes can be observed in each received frame. By demodulating the bright and dark fringes, the visible light communication (VLC) data logic can be retrieved. However, demodulating the bright and dark fringes is challenging as there is a high data fluctuation and large extinction ratio (ER) variation in each frame due. Hence proper thresholding scheme is needed. In this work, we propose and compare experimentally three thresholding schemes; including third-order polynomial curve fitting, iterative scheme and quick adaptive scheme. The evaluation of these three thresholding schemes is performed. (C) 2016 Optical Society of America
Visible light communication using mobile-phone camera with data rate higher than frame rate
(2015-10-05)
Chow, Chi-Wai
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
光電工程學系
;
光電工程研究所
Complementary Metal-Oxide-Semiconductor (CMOS) image sensors are widely used in mobile-phone and cameras. Hence, it is attractive if these image sensors can be used as the visible light communication (VLC) receivers (Rxs). However, using these CMOS image sensors are challenging. In this work, we propose and demonstrate a VLC link using mobile-phone camera with data rate higher than frame rate of the CMOS image sensor. We first discuss and analyze the features of using CMOS image sensor as VLC Rx, including the rolling shutter effect, overlapping of exposure time of each row of pixels, frame-to-frame processing time gap, and also the image sensor "blooming" effect. Then, we describe the procedure of synchronization and demodulation. This includes file format conversion, grayscale conversion, column matrix selection avoiding blooming, polynomial fitting for threshold location. Finally, the evaluation of bit-error-rate (BER) is performed satisfying the forward error correction (FEC) limit. (C)2015 Optical Society of America
Enhancement of Signal Performance in LED Visible Light Communications Using Mobile Phone Camera
(2015-10-01)
Chow, Chi-Wai
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
光電工程學系
;
光電工程研究所
Visible light communication (VLC) is attractive as a supplementary method for future fifth-generation (5G) wireless communication owing to the shortage of radio-frequency bandwidth in conventional wireless communications. The VLC systems reported in the literature are mainly based on PIN receivers (Rxs). It is highly desirable if these VLC signals can be detected by using built-in complementary metal-oxide-semiconductor (CMOS) cameras as Rxs to provide flexible and low-cost wireless communications. However, using the CMOS camera is challenging. In this paper, we propose and demonstrate a VLC link using a CMOS mobile phone camera as Rx. By using the rolling shutter effect of the CMOS sensor, the VLC data rate can be significantly enhanced. We first use a second-order polynomial fitting to mitigate the "blooming effect" (saturation of pixels) of the CMOS sensor. In order to extend the VLC transmission distance and mitigate the influence of the background noise, we also propose and demonstrate using histogram equalization and Sobel filter to enhance VLC signal performance. Finally, a third-order polynomial fitting is used to define the threshold. The experimental results show that significant improvement of bit error rate (BER) for about an order of magnitude under different illuminances can be achieved.
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
;
Liang, Kevin
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
Chow, Chi-Wai
We demonstrate using solar cell as optical receiver (Rx) for visible light communication (VLC). The solar cell is low cost and can convert the VLC optical signal into electrical signal without external power supply. As the response of the solar cell is very limited; we also propose and demonstrate using predistortion to significantly enhance the response of the solar cell Rx. A VLC capacity of 0.4 Mbit/s at bit-error-rate (BER) of 10(-9) under wireless transmission distance of 75 cm; and a capacity of 0.3 Mbit/s at BER of 10-9 under wireless transmission distance of 125 cm can be achieved.
Passive Optical Receiver for Visible Light Communication (VLC)
(2015-01-01)
Chen, Hung-Yu
;
Liang, Kevin
;
Chen, Chung-Yen
;
Chen, Shih-Hao
;
Chow, Chi-Wai
We demonstrate using solar cell as optical receiver (Rx) for visible light communication (VLC). The solar cell is low cost and can convert the VLC optical signal into electrical signal without external power supply. As the response of the solar cell is very limited; we also propose and demonstrate using pre-distortion to significantly enhance the response of the solar cell Rx. A VLC capacity of 0.4 Mbit/s at bit-error-rate (BER) of 10(-9) under wireless transmission distance of 75 cm; and a capacity of 0.3 Mbit/s at BER of 10(-9) under wireless transmission distance of 125 cm can be achieved.
Secure communication zone for white-light LED visible light communication
(2015-06-01)
Chow, Chi-Wai
;
Liu, Yang
;
Yeh, Chien-Hung
;
Chen, Chung-Yen
;
Lin, Chao-Nan
As visible light communication (VLC) can be one of the promising wireless communication technologies in the future, improving the transmission security in VLC is highly desirable. We propose and demonstrate a secure VLC system using data superposition of different light emitting diodes (LEDs). The eavesdroppers can receive similar illumination but cannot obtain enough signal-to-noise ratio (SNR) for communication. The channel model and simulation parameters are presented. Analysis of the secure VLC zone forming using practical in-home scenarios is also discussed, showing the flexibly control the size and shift of secure VLC zone. A proof-of-concept experiment is performed, and there is a good match in trend between the experimental and simulation results. (C) 2015 Elsevier B.V. All rights reserved.

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