Young Gyu Choi
Korea National University of Transportation
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Publication
Featured researches published by Young Gyu Choi.
Modelling and Simulation in Materials Science and Engineering | 2009
Jeong Won Kang; Jun Ha Lee; Ki-Sub Kim; Young Gyu Choi
We investigated the characteristics of a capacitive nano-accelerometer based on a telescoping carbon nanotube by means of classical molecular dynamics simulations. The position of the telescoping nanotube was controlled by an externally applied force, and feedback sensing was based on the capacitance change. The capacitance variations, which were almost linearly proportional to the applied acceleration, were monitored within an error tolerance.
Molecular Simulation | 2008
Jeong Won Kang; Young Gyu Choi; Jun Ha Lee; Oh Kuen Kwon; Ho Jung Hwang
Pure carbon nanotube (CNT) oscillators are compared to the corresponding CNT oscillators encapsulating copper nanowires (Cu@CNTs) by molecular dynamics simulations. The classical oscillation theory provides a fairly good estimate of the mass dependence of the operating frequency when the CNT surface is not deformed by the Cu nanowire. The structural deformations of the CNT induced by the encapsulated copper nanowire have a greater effect on the oscillation frequency than the mass of the copper nanowire. The excess forces of the Cu@CNT oscillator are slightly higher than those of the CNT oscillator and the excess van der Waals forces induced by the inter-wall interactions are 17 times higher than the excess forces induced by the Cu nanowire–CNT interactions.
Journal of Physics: Condensed Matter | 2009
Jeong Won Kang; Young Gyu Choi; Younghoon Kim; Qing Jiang; Oh Kuen Kwon; Ho Jung Hwang
Analysis of vibrational characteristics of cantilevered double-walled carbon nanotube (DWCNT) resonators is carried out based on classical molecular dynamics simulation. Vibrational frequencies of DWCNTs are less than those of single-walled carbon nanotubes (SWCNTs) with the same length and the same diameter because of van der Waals intertube interaction. For DWCNTs with short outer walls, the resonance frequency initially increases with increasing outer nanotube length and then decreases after a peak, and thus the result can be modeled by a Gaussian distribution. The frequency of DWCNT resonators with short outer walls is a maximum when the length of the outer wall is about 72.5% of the length of the inner wall.
Molecular Simulation | 2010
Jeong Won Kang; Ki Ryang Byun; Oh Kuen Kwon; Young Gyu Choi; Ho Jung Hwang
The schematics of a gigahertz-range tuner is addressed as an application of a telescoping multi-walled carbon nanotube (CNT) that can be used repeatedly, and its dynamic operation is investigated via classical molecular dynamics simulations based on a (5,5)(10,10) double-walled CNT. Fine control of the telescoped length of the double-walled CNT enables its resonance frequency to be matched to one of the signal frequencies, and the telescoped nanotube can be tuned to its resonance frequency for use as a component of a bandpass filter.
Molecular Simulation | 2009
Jeong Won Kang; Young Gyu Choi; Jun-Ha Lee; Sun Hwa Lee; Hyun Jung Oh
We investigated vacancy-assisted self-diffusion in germanium by means of kinetic lattice Monte Carlo (KLMC) simulations below the melting temperature, for a vacancy concentration of 1 × 1018/cm3. At higher temperatures, fewer clusters formed, but there was less variation in the number of clusters than at lower temperatures as the time increased. Equilibrium diffusivities in the clustering region were 102 lower than those of free vacancies in the initial stage of KLMC simulations. They were expressed according to three temperature regimes: 6.5 × 10− 4 exp(–0.35/k B T) cm2/s at temperatures above 1100 K, 5.2 × 105 exp(–2.32/k B T) cm2/s at temperatures of 900–1100 K and 6.0 × 0–7 exp(–0.19/k B T) cm2/s at temperatures below 900 K. The effective mean migration energy, 1.1 eV, closely coincided with that of the 1.0–1.2 eV in experiments and was very different from the migration energy of the free vacancy.
Proceedings of SPIE, the International Society for Optical Engineering | 2008
Jeong Won Kang; Young Gyu Choi; Gi Han Ryu; Chung Sang Won
We investigated a linear carbon nanotube motor serving as the key building block for nanoscale motion control by using molecular dynamics simulations. This linear nanomotor, is based on the electrostatically telescoping multi-walled carbon-nanotube with ultralow intershell sliding friction, is controlled by the gate potential with the capacitance feedback sensing. The resonant harmonic peaks are induced by the interference between the driving frequencies and its self-frequency. The temperature is very important factor to operate this nanomotor.
Proceedings of SPIE, the International Society for Optical Engineering | 2008
Jeong Won Kang; Chung Sang Won; Young Gyu Choi
We investigated a carbon nanotube (CNT) oscillator controlled by the thermal gas expansion using classical molecular dynamics simulations. When the temperature rapidly increased, the force on the CNT oscillator induced by the thermal gas expansion rapidly increased and pushed out the CNT oscillator. As the CNT oscillator extruded from the outer nanotube, the suction force on the CNT oscillator increased by the excess van der Waals vdW energy. When the CNT oscillator reached at the maximum extrusion point, the CNT oscillator was encapsulated into the outer nanotube by the suction force. Therefore, the CNT oscillator could be oscillated by both the gas expansion and the excess vdW interaction. As the temperature increased, the amplitude of the CNT oscillator increased. At the high temperatures, the CNT oscillator escaped from the outer nanotube, because the force on the CNT oscillator due to the thermal gas expansion was higher than the suction force due to the excess vdW energy. By the appropriate temperature controls, such as the maximum temperature, the heating rate, and the cooling rate, the CNT oscillator could be operated.
Proceedings of SPIE, the International Society for Optical Engineering | 2008
Jeong Won Kang; Gi Han Ryu; Chung Sang Won; Young Gyu Choi
The coupled oscillation of multi-walled CNT oscillators consisting of (5n,5n) CNTs was investigated by molecular dynamics simulations. The oscillation feature of the CNT oscillators can not be described by a continuum theory. All walls of the multi-walled CNT are oscillated due to the interwall coupling. The frequencies of the multi-walled CNT oscillators are higher than those of the double-walled CNT oscillators. In spire of the different core CNT, the frequency peaks due to the interwall coupling are similar to each other as the number of walls increases. This reason is that the interwall coupling effects increase as the number of walls increases.
Solid State Communications | 2009
Jeong Won Kang; Oh Kuen Kwon; Jun Ha Lee; Young Gyu Choi; Ho Jung Hwang
Physica E-low-dimensional Systems & Nanostructures | 2010
Jeong Won Kang; Ki-Sub Kim; Ki Ryang Byun; Eu-Seok Kang; Jun-Ha Lee; Oh Kuen Kwon; Young Gyu Choi; Ho Jung Hwang