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Terahertz conductivity of high-quality indium films deposited using a substrate cooling method
Choi Geunchang,Choi Dong-Hwan,Ryeom Junho,Park Dae Young,Kim Wu-Sin,Kim Ju-Jin,Bahk Young-Mi,Jeong Mun Seok 한국물리학회 2023 Current Applied Physics Vol.52 No.-
High-quality indium thin films were fabricated by substrate cooling method during the metal deposition. The cooling effect reduced the threshold thickness for insulator-to-metal transition, which originates from the interconnections between the indium nano-islands. The complex conductivities of the films were measured by terahertz time-domain spectroscopy. We showed that the conductivity of the indium films prepared by substrate cooling were ~10 times higher than that deposited at room temperature, even though thickness of the former was lower than that of the latter film. Our results suggest that substrate cooling is promising for the applications of metal thin films and contacts.
Junho Choi,Chongsoo Cheung,Dongkwan Lee J-INSTITUTE 2021 International Journal of Human & Disaster Vol.6 No.4
Purpose: Framework act on the management of disasters and safety is the highest law covering disasters and safety in South Korea. Disaster management infrastructure has been expanded through the enactment and revision of the Framework act on the management of disasters and safety. However, there is still a high awareness that disaster management should be led by the administration. In the modern society, where self-help is emphasized above all else in the event of a disaster, it is difficult to expect effective disaster response through administrative initiative alone. This study intends to review measures to improve Framework act on the management of disasters and safety through evacuation that enables the primary victims, the residents, to respond to disasters most effectively. Method: The items such as enhancement of disaster site response capacity and emphasis on the role of local governments in disaster and safety management , which were newly revised in 2015, were reviewed. The problems of the current Disaster Safety Act were reviewed from three perspectives: Incomplete disaster prevention administration in case of a disaster , Various aspects of local residents for evacuation , and Insufficient structure of public-private cooperative system for evacuation . Results: First, it is necessary to recognize the incompleteness of disaster prevention administration during a disaster. Rather than increasing dependence on the administration, improvement should be made with the direction of how the residents can increase their independence and self-reliance. Second, the evacuation order should be improved to be ‘situational information’ that informs residents that they are in a situation that makes them think of evacuation, rather than ‘action directive type’. Third, the Framework act on the management of disasters and safety should stipulate in detail the establishment and reinforcement of public-private cooperation networks that utilize the capabilities of residents. Conclusion: For effective evacuation in the event of a large-scale disaster, the response capacity between various actors in the local community must be quickly aggregated. In addition, through improvement of the Disaster Safety Act in the future, the evacuation plan should start with reestablishing the relationship between the administration and residents. Residents should be aware of their own role for evacuation, and the administration should have a system that can support it as much as possible.
Junho Choi,Dongkwan Lee,Chongsoo Cheung J-INSTITUTE 2021 International Journal of Human & Disaster Vol.6 No.1
Purpose: In line with the global transition to a hydrogen society, Korea is accelerating the vitalization of the hydrogen economy through relevant plans and strategies. In order to revitalize the hydrogen economy, it is necessary to add hydrogen-related matters to the National Infrastructure Protection Plan(NIPP) and to promote continuous stability for the national-level hydrogen infrastructure. This study aims to present direction from a long-term perspective for the addition of NIPP to hydrogen infrastructure. Method: This study reviews and recognizes the importance of efficient construction strategies for hydrogen society. As an example, we analyze the case of Japan, which established a basic plan for hydrogen society before Korea. The factors for realizing the plan were analyzed by categorizing the contents into flexibility, adaptability, and reliability. Results: We were able to find some implications through the case study. First, It is important to seek inter-national cooperation for hydrogen supply and to respond flexibly to ensure that the plan is not disrupted in order to realize a hydrogen society and to secure safety. Second, it is necessary to regularly revise and implement the roadmap over time so that the plan can adapt well to time. Thirdly, In order to reinforce the credibility of the plan, a risk communication plan to enhance Local Acceptance should be devised. Conclusion: Korea cannot achieve empirical results simply by reducing carbon emissions and building an eco-friendly hydrogen society. It is important to discover demand and monitor hydrogen-related infrastructure integrally with potential stakeholders. In addition, social acceptance, including the central government, local governments, and private businesses, is essential to improve the public's awareness and understanding of hy-drogen society and to strategically rearrange hydrogen infrastructure. The establishment of the NIPP with the addition of hydrogen social infrastructure will contribute to raising national interest and increasing public con-fidence in hydrogen safety.
Range-only Relative Position Estimation for Multi-UAV
Junho Choi,Eungchang Lee,Myeongwoo Jeong,Duckyu Choi,Hyun Myung 제어로봇시스템학회 2022 제어로봇시스템학회 국제학술대회 논문집 Vol.2022 No.11
Although a UAV itself is adaptable to variety of tasks, its low payload and short flight time limit its usage. As a way to overcome the limitations of a UAV, a multi-UAV system is being researched. In order to utilize the Multi-UAV system, it is essential to estimate the relative position of each UAV. In this paper, a relative position estimation method is proposed that requires only range measurements from each pair of UAV combinations. The positions of UAVs are estimated by minimizing the difference between the range measurements and the distance values which are calculated from each pair of estimated positions of UAVs. The performance of the proposed method is verified by five UAVs flight simulation. The range data are generated from the ground-truth positions of five UAVs and Gaussian noise added range data are used for the experiments.
Compact Circularly Polarized Microstrip Antennas Using EM Coupled Loop Resonators
CHOI, Junho,PYO, Seongmin,HAN, Sang-Min,KIM, Young-Sik The Institute of Electronics, Information and Comm 2010 IEICE TRANSACTIONS ON COMMUNICATIONS - Vol.93 No.10
<P>In this letter, compact loop resonator type circular polarization (CP) antennas with a square ring and an X-shaped meander loop are presented. Both antennas are fed to a microstrip line with electromagnetic coupling. By adjusting the gap and length of a coupled microstrip line, the magnitude and phase conditions of two orthogonal modes for CP can be determined. The proposed antennas show good axial ratios and also good agreements between experimented and simulated results.</P>