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Your search keyword '"Jongwook, Lee"' showing total 3 results
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3 results on '"Jongwook, Lee"'

1. In situhydrogenation of visible a-SiC:H-based p - i - n type thin-film light-emitting diodes using the photochemical vapour deposition method

Author

Jongwook Lee and Koeng Su Lim

Subjects
Chemistry, Analytical chemistry, Substrate (electronics), Electroluminescence, Condensed Matter Physics, Photochemistry, Electronic, Optical and Magnetic Materials, law.invention, law, Materials Chemistry, Ultraviolet light, Irradiation, Electrical and Electronic Engineering, Thin film, Layer (electronics), Deposition (law), Light-emitting diode
Abstract

The effects of in situ hydrogenation on the performance of visible a-SiC:H-based p - i - n type thin-film light-emitting diodes (TFLEDs) have been investigated. The TFLEDs were fabricated with a photochemical vapour deposition method. In the process of TFLED fabrication, with a stream of of 50 sccm and ultraviolet light irradiation at a substrate temperature of and a process pressure of 0.3 Torr for 30 min, in situ hydrogenation was performed at the base of a p layer with various thicknesses of i-a-SiC:H layers (0, 10, 20 and 30 nm). It was found that the performance of visible TFLEDs was dramatically improved by in situ hydrogenation. With in situ hydrogenation after deposition of the 30 nm thick luminescently active i-a-SiC:H layer, the threshold voltage was decreased by about 2 V, the electroluminescence peak shifted from 680 nm to 625 nm and the brightness increased from to .

Published
1996

2. Hydrogenation Time Dependence of a-SiC:H-Based P-I-N Thin Film Visible Light-Emitting Diode Characteristics

Author

Jongwook Lee and Koeng Su Lim

Subjects
Brightness, Wavelength, Chemistry, General Engineering, Visible range, Analytical chemistry, General Physics and Astronomy, Thin film, Visible spectrum, Diode, Threshold voltage
Abstract

The hydrogenation time dependence of hydrogenation effects on the performance of a-SiC:H-based p-i-n thin film light-emitting diodes (TFLEDs) in the visible range has been investigated. It was found that hydrogenation markedly improved the device performance, and that increasing the hydrogenation time beyond a saturation point degraded the device performance; that is, as compared with the performance of a TFLED hydrogenated for a short time (∼15 min), the threshold voltage increased slightly, the EL peak shifted towards a longer wavelength, and the brightness decreased. In particular, after hydrogenation for 45 min, the brightness decreased to 15 cd/m2.

Published
1996

3. Data mining investigation of the association between a limb ballistocardiogram and blood pressure.

Author

Peyman Yousefian, Sungtae Shin, Azin Mousavi, Chang-Sei Kim, Ramakrishna Mukkamala, Dae-Geun Jang, Byung-Hoon Ko, Jongwook Lee, Ui Kun Kwon, Youn Ho Kim, and Jin-Oh Hahn

Subjects
BALLISTOCARDIOGRAPHY, BLOOD pressure, DIASTOLE (Cardiac cycle), MICROELECTROMECHANICAL systems, ACCELEROMETERS, DATA mining
Abstract

Objective: To investigate the association between a limb ballistocardiogram (BCG) and blood pressure (BP) based on data mining. Approach: During four BP-perturbing interventions, the BCG and reference BP were measured from 23 young, healthy volunteers using a custom-manufactured wristband equipped with a MEMS accelerometer and a commercial continuous BP measurement device. Both timing and amplitude features in the wrist BCG waveform were extracted, and significant features predictive of diastolic (DP) and systolic (SP) BP were selected using stepwise linear regression analysis. The selected features were further compressed using principal component analysis to yield a small set of DP and SP predictors. The association between the predictors thus obtained and BP was investigated by multivariate linear regression analysis. Main results: The predictors exhibited a meaningful association with BP. When three most significant predictors were used for DP and SP, a correlation coefficient of r  =  0.75  ±  0.03 (DP) and r  =  0.75  ±  0.03 (SP), a root-mean-squared error (RMSE) of 7.4  ±  0.6 mmHg (DP) and 10.3  ±  0.8 mmHg (SP), and a mean absolute error (MAE) of 6.0  ±  0.5 mmHg (DP) and 8.3  ±  0.7 mmHg (SP) were obtained across all interventions (mean  ±  SE). The association was consistent in all the individual interventions (r  ⩾  0.68, RMSE  ⩽  5.7 mmHg, and MAE  ⩽  4.5 mmHg for DP as well as r  ⩾  0.61, RMSE  ⩽  7.9 mmHg, and MAE  ⩽  6.4 mmHg for SP on the average). The minimum number of requisite predictors for robust yet practically realistic BP monitoring appeared to be three. The association between predictors and BP was maintained even under regularized calibration (r  =  0.63  ±  0.05, RMSE  =  9.3  ±  0.8 mmHg, and MAE  =  7.6  ±  0.7 mmHg for DP as well as r  =  0.60  ±  0.05, RMSE  =  14.7  ±  1.4 mmHg, and MAE  =  11.9  ±  1.1 mmHg for SP (mean  ±  SE)). The requisite predictors for DP and SP were distinct from each other. Significance: The results of this study may provide a viable basis for ultra-convenient BP monitoring based on a limb BCG alone. [ABSTRACT FROM AUTHOR]

Published
2018
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