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Three-dimensional flows of Mach number 3 around a double-compression ramp with finite span have been investigated numerically. Shadowgraph visualisation images obtained in a supersonic wind tunnel are used for comparison. A three-dimensional Reynolds-averaged Navier–Stokes solver was used to obtain steady numerical solutions. Two-dimensional numerical results are also compared. Four different cases were studied: two different second ramp angles of $${30}^{\circ }$$ and $${45}^{\circ }$$ in configurations with and without sidewalls, respectively. Results showed that there is a leakage of mass and momentum fluxes heading outwards in the spanwise direction for three-dimensional cases without sidewalls. The leakage changed the flow characteristics of the shock-induced boundary layer and resulted in the discrepancy between the experimental data and two-dimensional numerical results. It is found that suppressing the flow leakage by attaching the sidewalls enhances the two-dimensionality of the experimental data for the double-compression ramp flow.

To enable the industrial application of large-area capacitive coupled plasma (CCP), we studied non-uniformity of CCP with a 450 mm electrode. The field difference is one factor that reduces plasma uniformity. This effect is increased when the electrode's area is enlarged; therefore, we designed a multi-electrode CCP to overcome this problem. We found the optimal power conditions for each electrode to provide the best uniformity. Then, we powered on only one electrode to determine the property of each electrode. Our experiments showed some diffusion issues, and these results matched the results of the previous uniformity experiments.

Damage caused by natural disasters has been increasing throughout the world due to climate change. As part of adaptation strategies, concept of vulnerability to climate change is introduced abroad to identify flood hotspots and to establish improvement measures. However, there has been very few research on vulnerability domestically. In addition, vulnerability studies conducted at a country level was also reported to be unsuitable for sub-country level. In this study, we conduct vulnerability assessment using entropy method for the Nakdong River Basin as part of domestic application. Vulnerability for present condition are first determined, and then changes in vulnerability due to climate change and large-scale river restoration project to identify their impacts. To achieve this, proxy variables that make up the vulnerability index were selected based on literature survey and data availability. Using data collected for this area, weights for proxy variables were then determined by entropy method. Finally, vulnerability was calculated and mapped for the basin. Reviewing the vulnerability maps showed that vulnerability hotspots were consistent with historical flooded areas for present condition. This suggests that the methodology employed is reasonable. The results for future scenario also showed that there were areas where vulnerability is mitigated by the large-scale river restoration project but also increased by climate change. However, the effect of the project in the future is found to be minimal because the decrease in water level by the project is offset by the increase in runoff due to climate change. The methodology presented in this study is thought to be useful in establishing the disaster prevention plan and climate-change adaptation policy by identifying hotspots.

A high-speed impedance measurement system was developed, which enables the measurement of various characteristics of CW and pulsed plasmas with time resolution of less than a microsecond. For this system, a voltage and current sensor is implemented in a printed circuit board to sense the radio frequency signals. A digital board, which has a high-speed analog to digital converter and a field-programmable gate-array, is used to calculate the impedance of the signal. The final output of impedance is measured and stored with a maximum speed of 3 Msps. This sensor system was tested in a pulsed-plasma by applying it to the point between the matching box and the plasma chamber. The experimental equipment was constructed connecting the matching box, a 13.56 MHz generator, a 2 MHz generator that produced pulsed power, and a pulse-signal generator. From the temporal behavior of the measured impedance, we were able to determine the time intervals of transient states, especially of the initial active state. This information can be used to set the pulse frequency and duty for plasma processing.