• The Bulletin of The Korean Astronomical Society
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• v.37 no.2
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• pp.87.1-87.1
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• 2012

The fraction of blue galaxies in clusters is found to dramatically increase with redshift. This trend has been known as the Butcher-Oemler (B-O) effect which implies a significant evolution among the cluster galaxy population with time. It has been proposed that the blue galaxies in B-O clusters are at their last stage of star formation, probably using up the gas, which then might have evolved into red and passive cluster galaxies as found in the Local Universe. To test this hypothesis and ultimately to understand the evolution of cluster galaxy population as a function of redshift, we have embarked a multi-wavelength study of two carefully selected galaxy clusters at z~0.2 where the B-O effect becomes first noticeable. In this talk, I will introduce the Blind Ultra-deep Distant HI Environmental Survey (BUDHIES) on those two clusters and relevant multi-wavelength observations. Also, I will present the preliminary results of our recent Nobeyama CO observations of two galaxies selected among the BUHDIES sample.

• Bulletin of the Korean Space Science Society
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• 2006.04a
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• pp.62-62
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• 2006

• Journal of the Korean Magnetics Society
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• v.11 no.2
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• pp.63-71
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• 2001

The effects of an Ag seed layer on the magnetic properties and the microstructural evolution of SmCo/Cr thin films deposited on glass substrates were investigated. Coercivity of the films is 2.0 kOe when the thickness of Ag seed layer was 1nm thick, but it increased to 2.7 kOe when the Ag seed layer thickness is 3 nm. The increase of coercivity for film with 3 nm-thick Ag is due to roughness of Cr and grain size of Cr by the Ag microbumps. Ar partial pressure influenced on the formation of Ag microbumps, for example, they were formed at 5 mTorr when Ag thickness was 1 nm. The mechanism of magnetization reversal of the SmCo films changed from domain wall motion to domain rotation as the Ag inserted. This was thought to be due to inhibition of domain wall motion by the reduction of Cr grain size and the increase of roughness.

• Korean Journal of Materials Research
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• v.33 no.10
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• pp.377-384
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• 2023

Exploring earth-abundant, highly effective and stable electrocatalysts for electrochemical water splitting is urgent and essential to the development of hydrogen (H₂) energy technology. Iron-cobalt layered double hydroxide (FeCo-LDH) has been widely used as an electrocatalystfor OER due to its facile synthesis, tunable components, and low cost. However, LDH synthesized by the traditional hydrothermal method tends to easily agglomerate, resulting in an unstable structure that can change or dissolve in an alkaline solution. Therefore, studying the real active phase is highly significant in the design of electrochemical electrode materials. Here, metal-organic frameworks (MOFs) are used as template precursors to derive FeCo-LDH from different iron sources. Iron salts with different anions have a significant impact on the morphology and charge transfer properties of the resulting materials. FeCo-LDH synthesized from iron sulfate solution (FeCo-LDH-SO₄) exhibits a hybrid structure of nanosheets and nanowires, quite different from other electrocatalysts that were synthesized from iron chloride and iron nitrate solutions. The final FeCo-LDH-SO₄ had an overpotential of 247 mV with a low Tafel-slope of 60.6 mV dec^-1 at a current density of 10 mA cm^-2 and delivered a long-term stability of 40 h for the OER. This work provides an innovative and feasible strategy to construct efficient electrocatalysts.

• Journal of the Korea Society of Computer and Information
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• v.26 no.9
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• pp.27-35
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• 2021

Artificial life is used in various fields of applied science by evaluating natural life-related systems, their processes, and evolution. Research has been actively conducted to evolve physical body design and behavioral control strategies for the dynamic activities of these artificial life forms. However, since co-evolution of shapes and neural networks is difficult, artificial life with optimized movements has only one movement in one form and most do not consider the environmental conditions around it. In this paper, artificial life that co-evolve bodies and neural networks using predator-prey models have environmental adaptive movements. The predator-prey hierarchy is then extended to the top-level predator, medium predator, prey three stages to determine the stability of the simulation according to initial population density and correlate between body evolution and population dynamics.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.293-303
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• 2016

Analysis of bargaining games utilizing evolutionary computation in recent years has dealt with important issues in the field of game theory. In this paper, we investigated interaction and coevolution process among heterogeneous artificial agents using evolutionary computation in the bargaining game. We present three kinds of evolving-strategic agents participating in the bargaining games; genetic algorithms (GA), particle swarm optimization (PSO) and differential evolution (DE). The co-evolutionary processes among three kinds of artificial agents which are GA-agent, PSO-agent, and DE-agent are tested to observe which EC-agent shows the best performance in the bargaining game. The simulation results show that a PSO-agent is better than a GA-agent and a DE-agent, and that a GA-agent is better than a DE-agent with respect to co-evolution in bargaining game. In order to understand why a PSO-agent is the best among three kinds of artificial agents in the bargaining game, we observed the strategies of artificial agents after completion of game. The results indicated that the PSO-agent evolves in direction of the strategy to gain as much as possible at the risk of gaining no property upon failure of the transaction, while the GA-agent and the DE-agent evolve in direction of the strategy to accomplish the transaction regardless of the quantity.

• Journal of Powder Materials
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• v.25 no.1
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• pp.60-68
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• 2018

The design and fabrication of photoelectrochemical (PEC) electrodes for efficient water splitting is important for developing a sustainable hydrogen evolution system. Among various development approaches for PEC electrodes, the chemical vapor deposition method of atomic layer deposition (ALD), based on self-limiting surface reactions, has attracted attention because it allows precise thickness and composition control as well as conformal coating on various substrates. In this study, recent research progress in improving PEC performance using ALD coating methods is discussed, including 3D and heterojunction-structured PEC electrodes, ALD coatings of noble metals, and the use of sulfide materials as co-catalysts. The enhanced long-term stability of PEC cells by ALD-deposited protecting layers is also reviewed. ALD provides multiple routes to develop improved hydrogen evolution PEC cells.

• Ceramist
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• v.22 no.2
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• pp.182-188
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• 2019

Alternative energy sources to the systems using hydrocarbon fuels have been actively developed due to exhaustion of fossil fuels and issue of global warming by CO₂. Fuel cells have attracted great attentions to solve these issues as electricity can be produced with product of clean H₂O by using H₂-O₂ as a fuel. Besides, using reverse reactions make it possible to produce H₂ and O₂ gas from electrolysis of water. There are various fuel cells systems depending on the types of electrolyte, and in this mini-reviews, the main aim is to focus on perovskite oxides as a catalyst for oxygen-evolution reactions in alkaline electrolysis and its potential to application of alkaline electrolysis systems.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2002.04a
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• pp.199-202
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• 2002

Many methods have been developed for the remediation of contaminated soil and groundwater. Among those technologies, in-situ bioremediation is most likely to be cost-effective method for petroleum hydrocarbon contamination. But the in-situ bioremediation can require more time to remediate hydrocarbon-contaminated soil and groundwater than other methods. Therefore we intended to save time of in-situ bioremediation using a biological additive to activate indigenous microbes in soil. The additive, 'Inipol EAP 22' stimulates the growth of specific flora, significantly accelerating the speed at which hydrocarbons are biodegraded. And it hans been tested in accordance with protocol approved by the USEPA and is registered on the National Contingency Plan Product Schedule List. In the experiment, three soil samples contaminated with fuel oil were prepared in the same concentration. Inipol EAP 22 was not added to one sample and was added to the other two samples with 5% and 10% of hydrocarbon by weight respectively. And $CO_2$gas derived from bacterial respiration was analyzed in each samples for 15 days. As a result, 145% and 153% of $CO_2$ evolution (microbial respiration) against the sample without 'Inipol EAP 22' occurred in samples with 'Inipol EAP 22' addition of 5% and 10%, respectively

• Geomechanics and Engineering
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• v.20 no.2
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• pp.165-174
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• 2020

The enzyme-induced carbonate precipitation (EICP) method has been investigated to improve the hydro-mechanical properties of natural soil deposits. This study was conducted to explore the stiffness evolution during various stress scenarios. First, the optimal concentration of urea, CaCl₂, and urease for the maximum efficiency of calcite precipitation was identified. The results show that the optimal recipe is 0.5 g/L and 0.9 g/L of urease for 0.5 M CaCl₂ and 1 M CaCl₂ solutions with a urea-CaCl₂ molar ratio of 1.5. The shear stiffness of EICP-treated sands remains constant up to debonding stresses, and further loading induces the reduction of S-wave velocity. It was also found that the debonding stress at which stiffness loss occurs depends on the void ratio, not on cementation solution. Repeated loading-unloading deteriorates the bonding quality, thereby reducing the debonding stress. Scanning electron microscopy and X-ray images reveal that higher concentrations of CaCl₂ solution facilitate heterogeneous nucleation to form larger CaCO₃ nodules and 11-12 % of CaCO₃ forms at the interparticle contact as the main contributor to the evolution of shear stiffness.