Hyunsuk Choi

Conditioning of graphene surface by CO2 cluster jet

The reduction of resistance and surface roughness obtained by CO2 cluster jet were up to 81% and 42.3% compared with pristine graphene. The shifts in Raman spectra also implied chemical doping and “mono-layerization”. Thus, CO2 cluster jet has the potential for planarization, cleaning and flattening of the graphene.

Bond Strength Deterioration of Reinforced and Prestressed Concrete Members at Reversed Cyclic Loads

The bond strength of concrete members at reversed cyclic loads is quite different from that of the concrete members at monotonic loads. Reversed cyclic loads produce a progressive bond deterioration that can lead to failure at cyclic stress levels lower than the ultimate stress at monotonic loads. In addition, the structural behavior of concrete members at dominant reversed loads reveals a dramatic reduction of energy dissipation in the hysteresis region due to a severe pinch effect. A method was proposed to predict the structural behavior of concrete members failing in bond after flexural yielding. The method takes into account the bond deterioration due to the degradation of concrete in the postyield range. To verify the bond behavior by the proposed method, predicted results were compared with the experimental data for concrete members at reversed cyclic loads, cited in the literature. Comparison of the experimental and calculated bond behavior of examined concrete members showed reasonable agreement.

Smoothing of Trajectory Data Recorded in Harsh Environments and Detection of Outlying Trajectories

The existence of an outlying trajectory, which is a trajectory that contains significant noise, can affect the quality of the movement analysis result. However, some outlying trajectories are repairable by detection and removal of noise. We propose trajectory-smoothing algorithms for automatic outlying trajectory repair, followed by application of various outlier detection algorithms to redetect outlying trajectories from among the smoothed trajectories. Our proposed approach was validated in a case study using real-life trajectories from a shipyard in South Korea.