• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.04b
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• pp.47-47
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• 2009

The formation of variable one-dimensional structures including core/shell structure is of particular significance with respect to potential applications for thermoelectric devices with the enhanced figure of merit ($ZT=S2{\sigma}T/{\kappa}$). We report the fabrication of Bi-Te core/shell nanowire based on a novel stress induced method. Fig. 1 schematically shows the nanowire fabrication process. Bi nanowires are grown on the Si substrate by the stress-induced method, and then Te is evaporated on the Bi nanowires. Fig. 2 is a transmission electron microscopy image clearly showing a core/shell structure for which effective phonon scattering and quantum confinement effect are expected. Electrical conductivity of the core/shell nanowire was measured at the temperatures from 4K to 300K, respectively. Our results demonstrate that Bi-Te core/shell nanowire can be grown successfully by the stress-induced method. Based on the result of electrical transport measurement and characteristic morphology of rough surface, Seebeck coefficient and thermal conductivity of Bi-Te core/shell nanowires are presented.

• Journal of the Korea Society of Computer and Information
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• v.24 no.1
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• pp.197-206
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• 2019

The purpose of this study is to develop and validate a model for diagnosing core competencies at the higher education level. Based on literature reviews, a potential model for core competencies at university was suggested. A tool for validating the model was composed of 24 items, which were delivered to 226 professors and administrative staffs, 730 students, and 134 graduates & external industrial experts. Five constructs (core competencies) were extracted from the data collected among professors and administrative staff responding to the importance of the items. The results of importance and performance surveys on core competencies with students were respectively 3.28 to 3.66 and 2.68 to 3.28 (4-point Likert scale). Statistical differences between importance level and performance level were found in all the sub-categories of core competencies. Borich priority determination formula and Locus for Focus Model were used for the determination of the priority of needs. Importance survey among graduates and external experts showed that the mean of each items ranged from 2.80 to 3.76 (4-point Likert scale). The overall results of the analyses suggest that the final model is appropriate for measuring the core competencies.

• Biomolecules & Therapeutics
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• v.21 no.2
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• pp.97-106
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• 2013

Chronic hepatitis C virus (HCV) infection is responsible for the development of liver cirrhosis and hepatocellular carcinoma. HCV core protein plays not only a structural role in the virion morphogenesis by encapsidating a virus RNA genome but also a non-structural role in HCV-induced pathogenesis by blocking innate immunity. Especially, it has been shown to regulate JAK-STAT signaling pathway through its direct interaction with Janus kinase (JAK) via its proline-rich JAK-binding motif ($^{79}{\underline{P}}GY{\underline{P}}WP^{84}$). However, little is known about the physiological significance of this HCV core-JAK association in the context of the virus life cycle. In order to gain an insight, a mutant HCV genome (J6/JFH1-79A82A) was constructed to express the mutant core with a defective JAK-binding motif ($^{79}{\underline{A}}GY{\underline{A}}WP^{84}$) using an HCV genotype 2a infectious clone (J6/JFH1). When this mutant HCV genome was introduced into hepatocarcinoma cells, it was found to be severely impaired in its ability to produce infectious viruses in spite of its robust RNA genome replication. Taken together, all these results suggest an essential requirement of HCV core-JAK protein interaction for efficient production of infectious viruses and the potential of using core-JAK blockers as a new anti-HCV therapy.

• JSTS:Journal of Semiconductor Technology and Science
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• v.12 no.3
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• pp.297-312
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• 2012

For future multi-core processors, 3D integration is regarded as one of the most promising techniques since it improves performance and reduces power consumption by decreasing global wire length. However, 3D integration causes serious thermal problems since the closer proximity of heat generating dies makes existing thermal hotspots more severe. Conventional air cooling schemes are not enough for 3D multi-core processors due to the limit of the heat dissipation capability. Without more efficient cooling methods such as liquid cooling, the performance of 3D multi-core processors should be degraded by dynamic thermal management. In this paper, we examine the architectural impact of cooling methods on the 3D multi-core processor to find potential benefits of liquid cooling. We first investigate the thermal behavior and compare the performance of two different cooling schemes. We also evaluate the leakage power consumption and lifetime reliability depending on the temperature in the 3D multi-core processor.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.183.1-183.1
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• 2016

Due to the latest research trend toward wearable energy devices, transparent and stretchable supercapacitors which can sustain their performance even under physical deformation have steadily attracted huge attention. Despite the Ag NW is the most promising candidate for fabrication of transparent and stretchable electronics, the electrochemical instability interrupts its application to development of the energy device. Here, we introduce a transparent and highly stretchable supercapacitor made by Au-Ag core shell NW network percolation electrode. The Au-Ag core shell NW synthesized by a simple solution process not only shows excellent electrical conductivity but also greatly enhanced chemical and electrochemical stability compare to pristine Ag NW. These outstanding properties of the Au-Ag core shell NW are attributed both to the core Ag NW and the Au protecting sheath layer. The proposed Au-Ag core shell NW based supercapacitor exhibits optical transmittance with outstanding mechanical stability withstanding 60% strain without any decrease of the performance. The supercapacitors connected in series are charged and discharged stable in 30% strain turning on a red LED. These notable results demonstrate the potential of the Au-Ag core shell NW as a strong candidate for development of wearable energy devices.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.11a
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• pp.15-16
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• 2023

In this paper, we aimed to develop a new method for diagnosing the depth of neutralization in architectural and civil engineering structures using the core drilling method, which combines the speed of drilling with the accuracy of core ringing. When compared to the drilling method, the core drilling method showed a lower measurement deviation of 1-2mm (7.6%) in confirming the depth of neutralization. This is believed to be a result of potential interference during the sample collection process in the drilling method, where the drill may pass through aggregates, leading to overestimation, as indicated in previous studies. The rapid evaluation of neutralization using the core drilling method serves as an alternative to address the issues associated with both drilling and core ringing methods in diagnosing the depth of neutralization. It offers a solution to the inaccuracy caused by coarse aggregates and the cumbersome post-processing steps required for neutralization diagnosis. Our proposed technique aims to provide an accurate and expedited diagnosis of neutralization depth without the need for additional processes.

• Earthquakes and Structures
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• v.21 no.5
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• pp.515-530
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• 2021

In a tall reinforced concrete (RC) core wall system subjected to strong ground motions, inelastic behavior near the base as well as mid-height of the wall is possible. Generally, the formation of plastic hinge in a core wall system may lead to extensive damage and significant repairing cost. A new configuration of core structures consisting of buckling restrained braced frames (BRBFs) and RC walls is an interesting idea in tall building seismic design. This concept can be used in the plan configuration of tall core wall systems. In this study, tall buildings with different configurations of combined core systems were designed and analyzed. Nonlinear time history analysis at severe earthquake level was performed and the results were compared for different configurations. The results demonstrate that using enough BRBFs can reduce the large curvature ductility demand at the base and mid-height of RC core wall systems and also can reduce the maximum inter-story drift ratio. For a better investigation of the structural behavior, the probabilistic approach can lead to in-depth insight. Therefore, incremental dynamic analysis (IDA) curves were calculated to assess the performance. Fragility curves at different limit states were then extracted and compared. Mean IDA curves demonstrate better behavior for a combined system, compared with conventional RC core wall systems. Collapse margin ratio for a RC core wall only system and RC core with enough BRBFs were almost 1.05 and 1.92 respectively. Therefore, it appears that using one RC core wall combined with enough BRBF core is an effective idea to achieve more confidence against tall building collapse and the results demonstrated the potential of the proposed system.

• Nuclear Engineering and Technology
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• v.41 no.5
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• pp.575-602
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• 2009

In the wake of the Three Mile Island accident, vigorous research efforts were initiated to acquire a basic knowledge of the progression and consequences of accidents that involve a substantial degree of core degradation and melting. The primary emphasis of this research was placed on containment integrity, with: i) hydrogen combustion-detonation, ii) steam explosion, iii) direct containment heating (DCH), and iv) melt attack on the BWR Mark-I containment shell identified as energetic processes that could lead to early containment failure (i.e., within the first 24 hours of the accident). Should the core melt fail the reactor vessel, then non-condensable gas production from Molten Core-Concrete Interaction (MCCI) was identified as a mechanism that could fail the containment by pressurization over the long term. One signification question that arose as part of this investigation was the effectiveness of water in terminating an MCCI by flooding the interacting masses from above, thereby quenching the molten core debris and rendering it permanently coolable. Successful quenching of the core melt would prevent basemat melt through, as well as continued containment pressurization by non-condensable gas production, and so the accident progression would be successfully terminated without release of radioactivity to the environment. Based on these potential merits, ex-vessel corium coolability has been the focus of extensive research over the last 20 years as a potential accident management strategy for current plants. In addition, outcomes from this research have impacted the accident management strategies for the Gen III+LWR plant designs that are currently being deployed around the world. This paper provides: i) an historical overview of corium coolability research, ii) summarizes the current status of research in this area, and iii) highlights trends in severe accident management strategies that have evolved based on the findings from this work.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.5
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• pp.860-865
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• 2010

When a circuit breaker is opened, a large capacitance around the buses, the circuit breaker and the potential transformer (PT) might cause PT ferroresonance. During PT ferroresonance, the iron core repeats saturation and unsaturation even though the supplied voltage is a rated voltage. This paper describes an analytical analysis of PT ferroresonance in the transient-state. To analyze ferroresonance analytically, the iron core is modelled by a simplified two-segment core model in this paper. Thus, a nonlinear ordinary differential equation (ODE) for the flux linkage is changed into a linear ODE with constant coefficients, which enables an analytical analysis. In this simplified model, each state, which is either saturated or unsaturated state, corresponds to one of the three modes, i.e. overdamping, critical damping and underdamping. The flux linkage and the voltage in each state are obtained analytically by solving the linear ODE with constant coefficients. The proposed transient analysis is effective in the more understanding of ferroresonance and thus can be used to design a ferroresonance prevention or suppression circuit of a PT.

• Nuclear Engineering and Technology
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• v.56 no.3
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• pp.873-879
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• 2024

A sodium-cooled fast reactor (SFR) core has a potential of prompt criticality due to a change of core material distribution during a severe accident, and the resultant energy release has been one of the safety issues of SFRs. In this study, the safety assessment of an unprotected loss-of-flow (ULOF) in a small SFR (SSFR) has been performed using the SIMMER-IV computer code, which couples the models of space- and time-dependent neutronics and multi-component, multi-field thermal hydraulics in three dimensions. The code, therefore, is applicable to the simulations of transient behaviors of extended disrupted core material motion and its reactivity effects during the transition phase (TP) of ULOF, including a potential of prompt-criticality power excursions driven by fuel compaction. Several conservative assumptions are used in the TP analysis by SIMMER-IV. It was found out that one of the important mechanisms that drives the reactivity-inserting fuel motion was sodium vapor pressure resulted from a fuel-coolant interaction (FCI), which itself was non-energetic local phenomenon. The uncertainties relating to FCI is also evaluated in much conservative way in the sensitivity analysis. From this study, the ULOF characteristics in an SSFR have been understood. Occurrence of recriticality events under conservative assumptions are plausible, but their energy releases are limited.