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Jaehyuk Kang,Mal-Soon Lee,Hyojoo Kim,Wooyong Um 한국방사성폐기물학회 2023 한국방사성폐기물학회 학술논문요약집 Vol.21 No.2
Radioactive iodine released from nuclear power plants has been recognized to pose significant risks and environmental hazards. In response to these challenges, extensive investigations into iodine sorbents have been conducted with a particular focus on the utilization of layered double hydroxides (LDH) as a promising candidate. Herein, we have focused on the investigation of LDH materials featuring diverse transition metals for their synthesis, with specific emphasis on CoAl LDH for its proficiency in removing iodine species, particularly IO3 –. Nevertheless, a comprehensive understanding of the removal mechanisms employed by these LDH materials remained elusive. Hence, the primary aim of this study is to elucidate the intricacies of the removal mechanisms through sorption tests, spectroscopic techniques, and theoretical chemistry analyses, subsequently contrasting the experimental outcomes with computational results. For the experimental facet, the synthesis of CoAl LDH was conducted utilizing 0.15 mol L?1 of Co(NO3)2?6H2O and 0.06 mol L?1 of Al(NO3)3?9H2O to attain a molar ratio (M2+:M3+) of 2.5:1. Subsequently, pH-dependent IO3 – sorption tests were carried out, coupled with X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) spectroscopy, facilitating the elucidation and discourse of the removal mechanism. The theoretical chemistry in this research harnessed ab initio molecular dynamics (AIMD) simulations for structural modeling, atomic density profiles, radial distribution function, analysis of oxide species, and MD-EXAFS spectrum analysis. In summary, this study aims to elucidate iodine removal mechanisms using diverse experimental results, culminating in the revelation that ion-exchange with NO3 – present in the interlayer predominates as the principal mechanism for IO3 – removal. Notably, a distinct spectral feature at approximately 33,190 eV emerged, defying identification through XANES and EXAFS analyses conducted under experimental conditions. In the AIMD simulations, meticulous scrutiny of individual iodine atoms uncovered the prevalence of I?O and I?O?H molecular species, marked by interactions between O and H atoms, with a coordination number of I?O = ~3. This transformation was primarily instigated by proton hopping. As a result, the comparative investigation reveals the dominance of IO3 – intercalation in the CoAl LDH material with the potential to undergo a transformation to the I?O?H molecule upon interaction with protons.
MMORPG에서 GFG 쇠퇴를 위한 현금거래 구매자 탐지 방안에 관한 연구
강성욱(Sung Wook Kang),이진(Jin Lee),이재혁(Jaehyuk Lee),김휘강(Huy Kang Kim) 한국정보보호학회 2015 정보보호학회논문지 Vol.25 No.4
온라인 게임의 인기가 증가하면서 희소성 있는 재화를 현금으로 바꾸는 RMT (Real Money Trade) 유저들이 증가하였고 이를 전문적으로 이용하는 게임 내 범죄 집단인 GFG (Gold Farming Group)이 나타났다. GFG는 게임재화를 수집하기 위해서 다수의 봇 계정이 필요한데, 이를 위해 명의 도용, 개인정보 유출 문제를 발생시키게 된다. 또한 현금거래를 유발시켜 게임 내 경제의 형평성을 파괴하고, 계정 도용, 아이템 탈취를 유발 시킨다. 따라서 GFG를 제거 및 차단하는 일은 사회적, 게임 내 관점에서 중요한 문제이다. 본 논문은 기존의 판매자 관점의 탐지가 아닌 수요공급의 원칙에 따라 현금거래 구매자를 탐지하는 근본적인 방안을 제시하였다. 실제 게임 데이터를 분석하여 두 가지의 RMT 형태를 발견하였고, 구매자 탐지의 재현율이 98% 이상을 보일 수 있었다. As the rise in popularity of online games, the users start exchanging rare items for real money. As RMT (Real Money Trade) is prevalent, GFG (Gold Farming Group) who abuse RMT shows up. GFG causes social problems such as identity theft, privacy leaks. Because they needs many bot characters to gather game items. In addition, GFG induce RMT that makes in-game problems such as a destroying game economy, account hacking. Therefore, It is very important work to collapse GFG at the perspective of social and in-game. In this paper, we proposed a fundamental method for detecting RMT buyers for the collapse of GFG at the perspective of buyer by Law of Demand and Supply. We found two type of RMT by analyzing actual game data and detected RMT buyers with high recall ratio of 98% by ruled-based detection.
Continuous Monitoring System for Invasive Alien Plant Pests
Jaehyuk Choi,Yang-Sup Bae,Heechan Kang 한국응용곤충학회 2018 한국응용곤충학회 학술대회논문집 Vol.2018 No.04
In recent decades, introduction of the alien plant pests into Korea was dramatically increased and the role of plant quarantine became more important than ever. At the same time, early detection of the introduced population of the alien pests is critical for protection of their spread. However, continuous monitoring for their distribution or spread has not been performed yet in Korea. Present monitoring systems in Korea is not unified but sectored according to three institutes. There are some limitations in managing human resources, executing budgets, and collecting information among them, resuling in delayed responses to the introduced alien pests. Our study focused on 1) constructing nation-wide continuous monitoring system, 2) developing a decision flow chart for evaluating risks, 3) performing the benefits and costs analysis. Continuous monitoring will clarify overall distribution of alien pests, support government’s quarantine negotiation, and enable early detection of alien pests. Furthermore, the system will provide scientific data management and early responses to invasion of alien pests.
Performance Trade-Offs in Using NVRAM Write Buffer for Flash Memory-Based Storage Devices
Sooyong Kang,Sungmin Park,Hoyoung Jung,Hyoki Shim,Jaehyuk Cha IEEE 2009 IEEE Transactions on Computers Vol.58 No.6
<P>While NAND flash memory is used in a variety of end-user devices, it has a few disadvantages, such as asymmetric speed of read and write operations, inability to in-place updates, among others. To overcome these problems, various flash-aware strategies have been suggested in terms of buffer cache, file system, FTL, and others. Also, the recent development of next-generation nonvolatile memory types such as MRAM, FeRAM, and PRAM provide higher commercial value to non-volatile RAM (NVRAM). At today's prices, however, they are not yet cost-effective. In this paper, we suggest the utilization of small-sized, next-generation NVRAM as a write buffer to improve the .overall performance of NAND flash memory-based storage systems. We propose various block-based NVRAM write buffer management policies and evaluate the performance improvement of NAND flash memory-based storage systems under each policy. Also, we propose a novel write buffer-aware flash translation layer algorithm, optimistic FTL, which is designed to harmonize well with NVRAM write buffers. Simulation results show that the proposed buffer management policies outperform the traditional page-based LRU algorithm and the proposed optimistic FTL outperforms previous log block-based FTL algorithms, such as BAST and FAST.</P>
Defects on the Surface of Ti-Doped MgAl <sub>2</sub> O <sub>4</sub> Nanophosphor
Lim, Jaehyuk,Kim, Yongseon,Kim, Sungdae,Kim, Youngwoon,Kang, Shinhoo Springer US 2017 NANOSCALE RESEARCH LETTERS Vol.12 No.1
<P>Ti-doped nano MgAl<SUB>2</SUB>O<SUB>4</SUB> for white emission was synthesized by combustion method. Extrinsic Schottky defects, Al vacancies and Ti<SUP>4+</SUP> dopant in Al sites, which are considered to be responsible for bluish-white emission, were observed by STEM on the surface of Ti-doped nano MgAl<SUB>2</SUB>O<SUB>4</SUB> powder. The stabilities of the Schottky defect associates, (Ti<SUB>Al</SUB><SUP>·</SUP>–V<SUB>Al</SUB>′′′)′′, were demonstrated by DFT calculation. The emission behavior was interpreted with these results.</P>