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Molecular Dynamics Simulation for Grain Boundary Deformation under Tensile Loading Condition

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Journal of Materials Science & Technology 2001年第1期17卷 145-146页

作者： kim, YS Choi, DY won, SY Kyungpook Natl Univ Dept Mech Engn Taegu South Korea Kyungpook Natl Univ Grad Sch Mech Engn Taegu South Korea

In this study, MD simulations have been performed to observe the behavior of a grain boundary in an alpha -Fe plate under 2-dimensional loading. In MD simulation, the acceleration of every molecule can be achieved from the potential energy and the force interacting between each molecule, and the integration of the motion equation by using Verlet method gives the displacement of each molecule. Initially, four alpha -Fe rectangular plates having different misorientation angles of grain boundary were modeled by using the Johnson potential and Morse potential. We compared the potential energy of the grain boundary system with that of the perfect structure model. Also, we could obtain the width of the grain boundary by investigating the local potential energy distribution. The tensile loading for each grain boundary models was applied and the behavior of grain boundary was studied. From this study it was clarified that in the case using Johnson potential, the obvious fracture mechanism occurs along the grain boundary, in the case of Morse potential, the diffusion of the grain boundary appears instead of the grain boundary fracture.

关键词： Simulation Molecular Dynamics Simulation for Grain Boundary Deformation under Tensile Loading Condition

Nanostructure and corrosion behaviors of nanotube formed Ti-Zr alloy

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中国有色金属学会会刊：英文版 2009年第4期19卷 1005-1008页

作者： won-Gi kim Han-Cheol CHOE Department of Dental Materials & Research Center of Nano-Interface Activation for Biomaterials College of DentistryChosun University

In order to investigate the nanostructures and corrosion behaviors of Ti-Zr alloys,nanotube formed Ti-Zr(10%,20%,30% and 40% in mass fraction) alloys were prepared by arc melting and the condition of controlling nanostructure was at 1 000 ℃ for 24 h in argon atmosphere;formation of nanotubes was conducted by anodizing a Ti-Zr alloy in H3PO4 electrolyte with a small amount of fluoride ions at room *** corrosion properties of specimens were examined through potentiodynamic test(potential range of -1 500-2 000 mV) in 0.9% NaCl solution by using *** of the alloys were observed by optical microscope(OM),field emission scanning electron microscope(FE-SEM) and X-ray diffractometer(XRD).Diameter of nanotube does not depend on Zr content,but interspace of nanotube predominantly depends on Zr content,which confirms that ZrO2 oxides play a role to increase the interspace of nanotube formed on the surface.

关键词：钛锆合金纳米结构腐蚀行为扫描电子显微镜 NaCl溶液阳极氧化光学显微镜 X射线衍射

Local Meteorological and Synoptic Characteristics of Fogs Formed over Incheon International Airport in the West Coast of Korea

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Advances in Atmospheric Sciences 2010年第4期27卷 761-776页

作者： Chang ki kim Seong Soo YUM Department of Atmospheric Sciences Yonsei University 134 Shinchon-dong Seodaemun-gu Seoul 120-749 Korea

Fogs observed over Incheon international airport （IIA） in the west coast of Korea from January 2002 to August 2006 are classified into categories of coastal fog, cold sea fog, and warm sea fog based on the areal extent of the fogs and the difference between the air temperature （T ） and the SST, i.e., cold sea fog if TSST = T -SST 〉 0~0C and warm sea fog if TSST 〈 0~0C. The numbers of coastal, cold, and warm sea fog cases are 64, 26, and 9. Coastal fogs form most frequently in winter, while cold sea fogs occur mostly in summer and warm sea fogs are observed from January to May but not in November and December. On average the air gets colder by 1.6~0C during the three hours leading up to the coastal fog formation, and an additional cooling of 1.1~0C occurs during the fog. The change in the dew point temperature （T_d） is minimal except during the fog （0.6~0C）. Decreases in T for the cold and warm sea fogs are relatively smaller. The average Td is higher than SST during the cold sea fog periods but this T_d is more than 4~0C higher than that for the corresponding non-fog days, suggesting that cold sea fogs be formed by the cooling of already humid air （i.e., T_d〉SST）. Increases of T_d are significant during the warm sea fog periods （1.4~0C）, implying that effcient moisture supply is essential to warm sea fog formation. Four major synoptic patterns are identified in association with the observed fogs. The most frequent is a north Pacific high that accounts for 38% of cases. Surface or upper inversions are present in 77%, 69%, and 81% of the fog periods for coastal, cold, and warm sea fogs, respectively.

关键词： costal fogs sea fogs west coast of Korea meteorological and synoptic characteristics

Ransomware Classification Framework Using the Behavioral Performance Visualization of Execution Objects

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Computers, Materials & Continua 2022年第8期72卷 3401-3424页

作者： Jun-Seob kim ki-Woong Park Department of Computer and Information Security and Convergence Engineering for Intelligent DroneSejong UniversitySeoul05006Korea

A ransomware attack that interrupted the operation of Colonial Pipeline(a large *** pipeline company),showed that security threats by malware have become serious enough to affect industries and social infrastructure rather than individuals *** agents and characteristics of attacks should be identified,and appropriate strategies should be established accordingly in order to respond to such *** this purpose,the first task that must be performed is malware *** creators are well aware of this and apply various concealment and avoidance techniques,making it difficult to classify *** study focuses on new features and classification techniques to overcome these *** propose a behavioral performance visualization method using utilization patterns of system resources,such as the central processing unit,memory,and input/output,that are commonly used in performance analysis or tuning of *** extracted the usage patterns of the system resources for ransomware to performbehavioral performance *** results of the classification performance evaluation using the visualization results indicate an accuracy of at least 98.94%with a 3.69%loss ***,we designed and implemented a framework to perform the entire process—from data extraction to behavioral performance visualization and classification performance measurement—that is expected to contribute to related studies in the future.

关键词： Behavioral performance visualization ransomware malware classification

Computed tomography coronary angiography after excluding myocardial infarction:high-sensitivity troponin versus risk score-guided approach

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World Journal of Emergency Medicine 2023年第6期14卷 428-433页

作者： won Jae Yoo Shin Ahn Bora Chae won Young kim Department of Emergency Medicine Asan Medical CenterUniversity of Ulsan College of MedicineSeoul 05505Republicof Korea

BACKGROUND:Patients with suspected acute coronary syndrome (ACS) in whom myocardial infarction has been ruled out are still at risk of having obstructive coronary artery disease (CAD).This rate is higher among patients with intermediate high-sensitivity troponin I (hsTnI) concentrations (5 ng/L to 99th percentile) than low concentrations (<5 ng/L).Therefore,an intermediate concentration has been suggested as a candidate for downstream investigation with computed tomography coronary angiography(CTCA).We tried to compare the HEART score-guided ***-guided approach for identifying obstructive ***:From a prospective cohort study of patients presenting to the emergency department with suspected ACS,433 patients without elevated hsTnI who also underwent CTCA were selected and *** performances of hsTnI concentration and HEART score were compared using sensitivity,specificity,positive predictive value (PPV),and negative predictive value (NPV).RESULTS:Overall,120 (27.7%) patients had obstructive *** with intermediate hsTnI concentrations were more likely to have obstructive CAD than those with low hsTnI concentrations(40.0%vs.18.1%);patients with non-low-risk HEART scores (≥4 points) were also more likely to have obstructive CAD than those with low-risk scores (0 to 3 points)(41.0%vs.7.6%).The HEART score had higher sensitivity and NPV for detecting obstructive CAD in each classification than hsTnI concentration (sensitivity:89.2%vs.63.3%;NPV:92.4%vs.81.9%,respectively).CONCLUSION:After excluding myocardial infarction in patients with suspected ACS,adding the HEART score for selecting candidates for CTCA could improve patient risk stratification more accurately than relying on hsTnI concentration.

关键词： Chest pain Coronary artery disease Acute coronary syndrome Troponin HEART score

N-doped carbon-embedded TiN nanowires as a multifunctional separator for Li–S batteries with enhanced rate capability and cycle stability

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Journal of Energy Chemistry 2021年第6期30卷 10-18,I0001页

作者： Yoongon kim Yuseong Noh Jaejin Bae Hyunwoo Ahn Minho kim won Bae kim Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)77 Cheongam-roNam-guPohang 37673South Korea

Lithium-sulfur(Li-S)batteries have attracted considerable attention as next-generation energy storage devices owing to their high theoretical specific capacity and ***,the commercialization of Li-S batteries is hindered by critical issues,including the migration of the dissolved lithium polysulfides(LiPSs)from the sulfur electrode to the lithium metal anode,resulting in poor cycling ***,we report a multifunctional interlayer configured with an N-doped carbon framework and titanium nitride nanowires on a polypropylene separator(NC/TiN NWs@PP)to suppress the polysulfide shuttling ***/TiN NWs@PP can be obtained by electrospinning and the subsequent scalable solution-based vacuum *** one-dimensional structure of the TiN NWs can shorten the Li-ion diffusion distance with large electrode/electrolyte ***,the N-doped carbon framework in the NWs enables facile electron transportation and allows the suppression of the shuttle effect to improve the electrochemical reaction *** Li-S battery with a NC/TiN NWs@PP separator exhibited enhanced cycling stability and rate capability,indicating that this could be a new research direction for Li-S batteries.

关键词： Li-S battery Shuttle effect Interlayer Separator TiN N-doped carbon 1D Nanowire

Electrochemical and electronic properties of nitrogen doped fullerene and its derivatives for lithium-ion battery applications

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Journal of Energy Chemistry 2018年第2期27卷 528-534页

作者： Parveen Sood ki Chul kim Seung Soon Jang School of Materials Science and Engineering Georgia Institute of Technology Atlanta CA 30332-0245. USA Department of Chemical Engineering Konkuk University Seoul 05029 Republic of Korea Institute for Electronics and Nonotechnology Georgia Institute of Technology Atlanta GA 30332-0245 USA Parker H. Petit Institute for Bioengineering and Bioscience Georgia Institute of Technology Atlanta GA 30332-0245 USA

We have studied the redox potentials and electronic properties of C60 and C59N using density functional theory method. It is found that doping C60 with one nitrogen atom results in a slight increase in redox potential. Next, we have also studied C59N functionalized with various redox-active oxygen containing functional groups and strongly electron withdrawing functional groups. It is found that the intrinsic electronic structure of the molecule is the major determinant of the redox potential. Our DFT calculations show that the electron affinity to redox potential of functionalized C59N is correlated with the LUMO of the systems very well. This is the first systematic study on the redox properties and electronic structures of N-doped C60 systems.

关键词： DFT Redox potential C60 Doping Li-ion battery

PIR-based data integrity verification method in sensor network

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Journal of Central South University 2014年第10期21卷 3883-3888页

作者： Yong-ki kim Kwangnam Choi Jaesoo kim JungHo Seok Korea Institute of Science and Technology Information 245 DaehangnoYuseong Daejeon 305-806 Korea

Since a sensor node handles wireless communication in data transmission and reception and is installed in poor environment, it is easily exposed to certain attacks such as data transformation and sniffing. Therefore, it is necessary to verify data integrity to properly respond to an adversary's ill-intentioned data modification. In sensor network environment, the data integrity verification method verifies the final data only, requesting multiple communications. An energy-efficient private information retrieval(PIR)-based data integrity verification method is proposed. Because the proposed method verifies the integrity of data between parent and child nodes, it is more efficient than the existing method which verifies data integrity after receiving data from the entire network or in a cluster. Since the number of messages for verification is reduced, in addition, energy could be used more efficiently. Lastly, the excellence of the proposed method is verified through performance evaluation.

关键词： data integrity verification private information retrieval sensor network

Airborne bioaerosols and their impact on human health

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Journal of Environmental Sciences 2018年第5期30卷 23-35页

作者： ki-Hyun kim Ehsanul Kabir Shamin Ara Jahan Department of Civil and Environmental Engineering Hanyang UniversitySeoul 04763Republic of Korea Department of Farm Power&MachineryBangladesh Agricultural UniversityMymensinghBangladesh BRAC Clinic DhakaBangladesh

Bioaerosols consist of aerosols originated biologically such as metabolites, toxins, or fragments of microorganisms that are present ubiquitously in the environment. International interests in bioaerosols have increased rapidly to broaden the pool of knowledge on their identification,quantification, distribution, and health impacts（e.g., infectious and respiratory diseases,allergies, and cancer）. However, risk assessment of bioaerosols based on conventional culture methods has been hampered further by several factors such as：（1） the complexity of microorganisms or derivatives to be investigated;（2） the purpose, techniques, and locations of sampling; and（3） the lack of valid quantitative criteria（e.g., exposure standards and dose/effect relationships）. Although exposure to some microbes is considered to be beneficial for health,more research is needed to properly assess their potential health hazards including inter-individual susceptibility, interactions with non-biological agents, and many proven/unproven health effects（e.g., atopy and atopic diseases）.

关键词： Health effect Exposure Infectious diseases Respiratory diseases Cancer Guideline