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Cohort Profile: Gachon Regional Occupational Cohort Study (GROCS)
Lee, Wanhyung,Lee, Yongho,Lee, Junhyeong,Kim, Uijin,Han, Eunsun,Ham, Seunghon,Choi, Won-Jun,Kang, Seong-Kyu Occupational Safety and Health Research Institute 2022 Safety and health at work Vol.13 No.1
Background/Aims: The Gachon Regional Occupational Cohort Study (GROCS) is a large-scale longitudinal study of occupational safety and health data (covering Work Environment Monitoring, Workers' Health Surveillance, and Occupational Health Service) conducted by the Gachon University Gil Medical Center (GUGMC) in Incheon, Republic of Korea. We conducted GROCS to identify the health effects of workers' occupational risks, behavior, socioeconomic status, and life style. Methods: The GROCS includes data from Work Environment Monitoring, Workers' Health Surveillance, and Occupational Health Service. The baseline year for all data collection was 2018. Work Environment Monitoring was conducted in 240 companies located in Incheon. General Health Examination and Special Health Examination were performed on 32,725 and 9,504 workers, respectively. Occupational Health Services were provided to 16,883 workers in 171 companies. These data have been collected and operated at an external data management institution and were provided as a retrospective cohort after removing personal identification information. Results: In 2018, the total number of companies was 2,854, among which which 488 special Health Examination, 171 Work Environment Monitoring, and 240 Occupational Health Service. The proportion of companies undergoing Special Health Examination was 17.1%, the proportion of companies undergoing Work Environment Monitoring was 8.4%, and the proportion of Companies undergoing Occupational Health Service was 6.0%. Conclusion: GROCS expects researchers to utilize its useful and reliable resource for occupational health and surveillance with for academic or political purposes to lead to improved workers' health and working environment.
Charge Trap Flash structure with Feedback Field Effect Transistor for Processing in Memory
Junhyeong Lee,Misun Cha,Min-Woo Kwon 대한전자공학회 2023 Journal of semiconductor technology and science Vol.23 No.5
Recently, a memory wall has become a concern due to the increasing distance between memory and CPU in the von Neumann structure. While the CPU and logic devices operate quickly, their speed becomes irrelevant due to the slow data transfer between them. Consequently, addressing the data delay problem between the CPU and the logic elements is crucial. To tackle this issue, researchers have been exploring the Processing in Memory (PIM) technology, which enables simultaneous memory and computation. However, traditional volatile or nonvolatile memory-based PIM approaches have inherent limitations in overcoming the memory wall problem, as memory and computation are performed sequentially on separate devices. Therefore, there is a need to develop a new memory-logic device capable of performing read and operation simultaneously. In this paper, we propose a Feedback Field Effect Transistor (FBFET) with a charge trap layer that can fulfill both memory and computational roles, thus implementing an ideal Processing in Memory technology. The device features an oxide-nitride-oxide structure, where nitride is coupled to the oxide side of the FBFET. It accumulates electric charges in the floating body for memory operations and reads the data stored in the charge trap layer for logic operations. By selecting the control gate bias, the computing operation can be configured to perform AND or OR operations. This enables simultaneous memory and logical operations to take place.
Staggered swirler arrangement in two self-excited interacting swirl flames
Lee, Taesong,Lee, Jiho,Park, Junhyeong,Han, Dongsik,Kim, Kyu Tae Elsevier 2018 Combustion and flame Vol.198 No.-
<P><B>Abstract</B></P> <P>Interference of acoustic and convective disturbances controls the development of self-excited combustion oscillations of a lean-premixed swirl-stabilized flame with a central bluffbody. How this interference mechanism influences the dynamics of multiple interacting flames in a multi-nozzle environment is currently unknown. Here we present observations of a multi-nozzle system's response to staggered swirler arrangements (<I>ξ</I> <SUB>sw, 1</SUB> ≠ <I>ξ</I> <SUB>sw, 2</SUB>) as compared to non-staggered arrangements; the distance between the swirler and the flame is the dominant length scale of vortical disturbances. Our results demonstrate that a slight modification of the swirler arrangement in the streamwise direction – staggered or non-staggered – has a remarkable influence on the stability map of the whole combustion system. Phase-resolved flame imaging measurements indicate that under non-staggered conditions interacting swirl flames feature a coherent motion during a period of oscillation. By contrast, the staggered swirler combination creates significantly non-symmetric flame dynamics, disturbing the development of well-organized motion over the entire reaction zone. Flame surface modulations in the lateral direction are particularly pronounced due to the formation of non-symmetric convection delays of vortical disturbances between adjacent swirl nozzles. For a given swirler arrangement, the system's response to a wide range of combinations of mean nozzle velocities, including symmetric ( <SUB> u ¯ 1 </SUB> = <SUB> u ¯ 2 </SUB> ) and non-symmetric ( <SUB> u ¯ 1 </SUB> ≠ <SUB> u ¯ 2 </SUB> ) conditions, were explored to account for the simultaneous effects of the two convection parameters. Our data show that a major determinant of the onset of the instability is the combination of the Strouhal numbers, 〈St<SUB>1</SUB>, St<SUB>2</SUB>〉, which can be even or uneven depending on the manipulation of the convection time of each nozzle.</P>
Design and Control of High-Frequency Resonant Inverter for Wide Load Variation
Junhyeong Lee,Jung-Ik Ha 전력전자학회 2023 ICPE(ISPE)논문집 Vol.2023 No.-
The single-ended resonant inverters, such as a Class-E inverter, are suitable for tens of megahertz switching due to the soft-switching characteristics. However, maintaining the soft-switching characteristics and constant output power under wide load variation is a challenging issue in the single-ended resonant inverters. This paper proposes the design and control method to maintain the soft-switching characteristics and constant output power. The proposed method utilizes variable switching frequency, duty adjustment, and variable DC input voltage. With the proposed method, a higher power density can be achieved compared to conventional systems with a complex and bulky impedance matching network. Design methods for the series L-C filter and the Class-E inverter for wide load variation are also explained. The experimental results from 12-15 MHz, 200 W Class-E resonant inverter prototype board verify the validity of the proposed design and control method.
위협 분석 및 위험 평가(TARA) 문제점 도출 : 실제 CAN 통신 침입 사례를 중심으로
이준형(Junhyeong Lee),김태헌(Taeheon Kim),류연지(Yeonji Ryu),박세호(Seho Park),성지한(Jihan Sung),장윤정(Yunjeong Jang),주승환(Seunghwan Ju) 한국자동차공학회 2024 한국자동차공학회 부문종합 학술대회 Vol.2024 No.6
The research identifies gaps in the TARA approach when applied to sophisticated cyber-physical attack scenarios on vehicles. It calls for enhancements in the TARA methodology to accommodate complex, multi-faceted attack paths, especially as automobiles become increasingly connected and autonomous, expanding the attack surface. The study underscores the need for future research to develop a more robust, comprehensive TARA methodology that considers the evolving landscape of automotive cybersecurity threats.