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Risk-informed Emergency Response Training for Backdraft in Nuclear Power Plants
Mihyun Kim,Wonkook Kim,Hongki Kim,Jungman Kim,Sunhong Yoon,Jangwon Choi,Heemoon Kim 한국화재소방학회 2023 International Journal of Fire Science and Engineer Vol.37 No.3
Research has been conducted for developing fire evacuation and response training programs for nuclear power plant (NPP) application. Among numerous fire scenarios that may occur in an NPP environment, three different points of origin for a fire were selected for the program based on a risk-informed approach: switchgear room, main control room, and safety injection pump room. Fire outcomes were predicted for these scenarios via numerical modeling and the results were incorporated into the newly developed fire evacuation and response training program for the APR1400, Korea’s next-generation NPP model. The switchgear room fire scenario was found to have the most potential for backdraft to occur during manual fire response following automatic gaseous fire suppression system activation. The emergency response manual does discuss this possible backdraft occurrence; however, the guidance to avoid injuries is qualitative, such as to be cautious of backdrafts and wait a sufficient amount of time after opening a door before entering the. In this study, backdraft phenomenon that may occur from a switchgear room fire was numerically examined using the recent version of the Fire Dynamics Simulator to develop an appropriate timeline to be implemented in the fire evacuation and response training program. Based on the findings, the following guidance is provided: (1) backdraft can only occur when the fire originates in the space near the door; (2) wait at least 10 minutes after opening the door before entering the room; (3) watch for rapid smoke production, as this may be an antecedent phenomenon of backdraft; and (4) when smoke production increases rapidly, leave the room as soon as possible to avoid being caught within the deflagrating flames from a backdraft.
A Design and Implementation of Energy-Aware Resilience Architecture for Mobile Edge Cloud
JangWon Lee,YoungHan Kim,Dooho Keum,Gyu-min Lee,Suil Kim,Myoung-hun Han 한국통신학회 2024 韓國通信學會論文誌 Vol.49 No.8
In In edge-cloud environments, mobile nodes face significant challenges due to their mobility and the distributed nature of the environment. The unstable communication links between mobile nodes and the cloud often lead to frequent disruptions in connectivity, posing obstacles to seamless operation and service delivery. Effective energy management strategies are crucial to address these challenges and ensure the long-term viability of mobile nodes. In this paper, we propose an architecture for energy-aware resilience in edge-cloud environments for a standalone mobile node in an edge-cloud environment that can operate seamlessly in the connection disruption from the cloud. Our architecture leverages machine learning-based energy consumption prediction techniques to forecast energy consumption patterns while considering dynamic network conditions. In addition, we propose a threshold-based control policy for autonomous node resilience, enabling mobile nodes to adaptively adjust their operations in response to fluctuating energy levels and network conditions of edge environments. Through proactive energy management strategies, such as workload autoscaling with energy awareness, we aim to minimize energy consumption and maximize node survival time, particularly under constrained conditions. Experimental evaluations demonstrate the efficiency of our proposed approach in extending node longevity and ensuring reliable operation in dynamic and resource-constrained edge-cloud environments.
Kim, Mac,Kang, Tae-Woon,Kim, Sung Hyun,Jung, Eui Hyuk,Park, Helen Hejin,Seo, Jangwon,Lee, Sang-Jin Elsevier 2019 Solar energy materials and solar cells Vol.191 No.-
<P><B>Abstract</B></P> <P>Optical films with antireflective and self-cleaning surfaces have much potential for applications in solar cells, architectural glasses, and outdoor displays. Here we demonstrate the fabrication of novel self-cleaning antireflection (AR) thin films by depositing plasma-polymerized fluorocarbon (PPFC) which is fluorinated polymer consisting carbon and fluorine formed under plasma environment on Nb<SUB>2</SUB>O<SUB>5</SUB>/SiO<SUB>2</SUB>/Nb<SUB>2</SUB>O<SUB>5</SUB> (NSN) trilayers using mid-range frequency power source in a continuous roll-to-roll sputtering system. The reflectance of PPFC/NSN films with a PPFC thickness of 70 nm was 1.71% at a wavelength of 528 nm, and the PPFC/NSN films showed low reflectance in a wide range in the visible region. The PPFC/NSN AR films exhibited a water-repelling surface with water contact angle of 105° after the application of a top fluorocarbon layer with low surface energy. We tested and confirmed the AR and self-cleaning functions of the PPFC/NSN films through the incorporation to perovskite solar cells (PSC). The short-circuit current density and power conversion efficiency of PPFC/NSN/HC-PET/PSC were 20.6 mA cm<SUP>−2</SUP> and 17%. By attaching a self-cleaning AR films to both side of PSC, photocurrent collection of the device was improved and applicability of protective films to PSC was demonstrated.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A self-cleaning antireflection quadrilayered thin film was fabricated by R2R sputtering. </LI> <LI> Plasma-polymerized fluorocarbon with low surface energy was applied as the top layer. </LI> <LI> The reflectance of antireflection film was reduced to 1.71% in the visible region. </LI> <LI> The antireflection film showed water-repellent surface above 100° of water contact angle. </LI> <LI> By attaching antireflection film to the PSCs, the photocurrent collection was improved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
A Design and Implementation of a Self-Managed Kubernetes Mobile Edge Cluster
JangWon Lee,YoungHan Kim,Dooho Keum,Gyu-min Lee,Suil Kim,Myoung-hun Han 한국통신학회 2024 韓國通信學會論文誌 Vol.49 No.8
In recent years, edge computing has acquired a significant interest in developing and deploying applications by bringing computational resources close to the data source, improving the quality of application experience, and optimizing system resource usage. Edge node deployment strategies in existing studies suppose that once edge nodes are registered in an edge computing system, they will permanently operate with high availability. However, deploying the orchestration solutions in edge computing environments is challenging because of the mobility of edge nodes (mobile nodes) and low availability due to energy limitations and network unstable. To solve this problem, we propose a standalone management structure for deploying mobile nodes in an edge-cloud computing environment that enables mobility support in a Kubernetes-based Edge-Cloud infrastructure. We develop self-managed mobile edge nodes constructed as standalone nodes, ensuring workloads continue operating even when the connection between the mobile node and the cloud is interrupted. Additionally, we consider an energy-aware deployment strategy through energy monitoring and workload scaling schemes at the self-managed mobile node. In this paper, we also implement the proposed architecture on the infrastructure built and established by OpenStack and KubeEdge open-source projects. Measurements show the feasibility of the proposed architecture in deploying mobile nodes that operate independently.
Microstructural evolution of chemically vapor-deposited tantalum carbide at elevated temperatu
Jangwon Han,SangMin Jeong,Ji Yeon Park,Hyun-Geun Lee,Weon-Ju Kim,Chan Park,Daejong Kim 한양대학교 청정에너지연구소 2022 Journal of Ceramic Processing Research Vol.23 No.6
Tantalum carbide (TaC), one of the ultra-high temperature ceramics, was chemically vapor-deposited at 1100 - 1300 oC in a TaCl5-C3H6-H2 system. Microstructural evolution of TaC was evaluated after heat treatment at 1850 oC for 4 hours. Various tantalum carbides with different orientation and microstructure were obtained depending on the deposition temperature andthe position. Crystallophic preferred orientation of the TaC changed from highly oriented (111) and (200), to random texture, as deposition temperatures increase. The continuous feed of TaCl4 powders using screw-driven feeder led to the fluctuation of TaCl4 partial pressure during the deposition process, resulted in a low crystallinity and formation of micropores. A dense TaC was only obtained at the high partial pressure of TaCl5. Heat treatment dramatically enhanced crystallinity but micropores were coalesced into large pores along grain boundaries. The influence of crystallophic orientation and microstructure on microstructural evolution and hardness during heat treatment were investigated.