Papers by Author: Yong Jae Kim

Abstract: A four-dimensional digital speckle tomography has been developed to analyze an initial helium jet flow. Speckle movements from refraction of a laser beam have been captured by multiple high-speed cameras simultaneously because a shape of a nozzle for the jet flow is asymmetric and the initial jet flow is fast and unsteady. A cross-correlation tracking method has been used to obtain the speckle displacements between no flow and helium jet flow from an asymmetric nozzle controlled by a solenoid valve. The measured speckle movements have been transferred to deflection angles of laser rays to calculate density gradients. The four-dimensional density fields for the high-speed and initial helium jet flow have been reconstructed from the deflection angles by a developed real-time tomography method.

Abstract: We propose to use electrostatic drop-on-demand devices, with precise metering and accurate delivery capabilities, to manipulate single-walled carbon nanotubes suspended in solution. The conductivity of the solution increases significantly by the addition of anionic surfactants and nanotubes, generating favorable conditions for electrostatic ejection. This technique could find applications, combined with chemical functionalization, in the fabrication of carbon nanotube field emission devices as well as electronic circuits. hanseoko@yurim.skku.ac.kr

Abstract: Velocity and density distributions of a high-speed and initial CO2 jet flow have been analyzed simultaneously by a developed three-dimensional digital speckle tomography and a particle image velocimetry (PIV). Three high-speed cameras have been used for the tomography and the PIV since a shape of a nozzle for the jet flow is asymmetric and the initial flow is fast and unsteady. The speckle movements between no flow and CO2 jet flow have been obtained by a cross-correlation tracking method so that those distances can be transferred to deflection angles of laser rays for density gradients. The three-dimensional density fields for the high-speed CO2 jet flow have been reconstructed from the deflection angles by the real-time tomography method, and the two-dimensional velocity fields have been calculated by the PIV method simultaneously.