• 한국수학교육학회지시리즈A:수학교육
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• 제58권1호
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• pp.121-138
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• 2019

The purpose of this study was to analyze the trends of domestic research on mathematics teacher education in terms of the period, topics, methods, subjects, and mathematics content strands. For this purpose, a total of 220 research articles dealing with mathematics teacher education were analyzed, which have been published since 2000 by the Korean Society of Mathematics Education in the three journals: (a) The Mathematical Education; (b) Education of Primary School Mathematics; and (c) Communications of Mathematical Education. Regarding the period when the research was conducted, the number of articles on mathematics teacher education has been rapidly increased since the late 2000s. Regarding the topics, research on teacher orientation has been the most frequent topic and the studies dealing with professional development for teachers, teaching practices, or teacher knowledge tend to be popular. Regarding methods, survey and case study have been most frequently employed in studying mathematics teacher education. Regarding subjects, the main participants were in-service teachers, pre-service teachers, elementary school teachers, and secondary school teachers, respectively, who were in charge of a regular class. Finally, regarding mathematics content strands, previous studies on mathematics teacher education were not specific to mathematics content strands. Given these results, this paper closes with important implications for future research directions on mathematics teacher education in Korea.

• 한국물환경학회지
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• 제34권6호
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• pp.621-631
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• 2018

In this study, catalyst was made through incipient wetness method using palladium (Pd) as noble metal, indium (In) as secondary metal, and montmorillonite (MK10) and Al pillared montmorillonite (Al-MK10) as supporters. The nitrate reduction rate of the catalysts was measured by batch experiments where H2 gas was used as reducing agent and formic acid as pH controller. Transmission electron microscopy (TEM) equipped with energy dispersive spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS) were all used to determine the elemental distribution of Pd, In, Al, and Si on catalysts. It was observed that Al pillaring increased the Al/Si elemental composition ratio and point of zero charge of MK10, but decreased its BET specific surface area and pore volume. The nitrate reduction rate of Al-MK10 Pd/In was 2.0 ~ 2.5 times higher than that of MK10 Pd/In using artificial groundwater (GW) in ambient temperature and pressure. Nitrate reduction rates in GW were 1.2 ~ 1.7 times lower than those in distilled deionized water (DDW). Nitrate reduction rates in acidic conditions were higher than those in neutral condition in both GW and DDW. The amount of produced NH3-N over degraded NO3- at acid conditions was lower than that of neutral condition. Even though the leaching of Pd after reaction was measured in DDW it was not detected when both Al-MK10 Pd/In and MK10 Pd/In were used in GW. The modification of montmorillonite as a supporter significantly increased the reductive catalytic activities of nitrates. However, the ratio of producing ammonia by-products to degraded nitrates in ambient temperature and pressure was similar.

• 한국산학기술학회논문지
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• 제22권3호
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• pp.374-380
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• 2021

밴드 비트겐슈타인은 신해철이 이전에 결성했었던 대형 밴드 "넥스트" 이후 비교적 밴드의 형태를 갖춘 팀이다. 신해철 특유의 가사와 특정 컨셉이 돋보이는 이 앨범 또한 넥스트 앨범과 유사한 성향을 띄고 있다. 다만 샘플링과 컴퓨터음악을 바탕으로 다양한 형태의 밴드 사운드가 적절하게 융합을 이루고 있다는 점에서 그 차이점이 나타난다. 본 앨범은 300만원대의 비용으로 제작된 저예산 홈 레코딩 앨범으로 신해철은 메인보컬과 프로그래밍만 맡았고, 모든 작품들은 멤버가 함께 작업하였다. 이 앨범에서는 신해철 혼자만의 음악을 생산하기보다는 팀워크에 비중을 두어 멤버들과 공동 작업을 진행하였다. 앨범 녹음 저예산 홈 레코딩이 음악 생산에 제약이 될 수는 있었지만, 참신하고 매우 새로운 시도라는 점에서는 높이 평가받을 부분임을 틀림없는 사실이다. 음악을 창작하는 뮤지션들은 자신이 항상 선호하는 음악과 대중들이 선호하는 음악 사이에서 갈등을 초래한다. 그렇지만, 창작의 노력이 없으면 진화와 발전도 없다. 끊임없는 변화는 음악 능력을 계속해서 발전시킬 수 있으며, 이것은 한국대중음악의 발전으로 이어진다는 것은 분명한 사실이다.

• Bulletin of the Korean Chemical Society
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• 제6권5호
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• pp.287-291
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• 1985

The addition of poly(styrenesulfonate) (PSS) to $Ru(bpy)_3^{2+}$ solutions shifted the emission peak by 3 nm to red, and increased emission intensity by 1.8 times. By contrast, poly(vinylsulfonate) (PVS) had little effect on the fluorescence spectrum. The effects of PSS on the spectral properties of $Ru(bpy)_3^{2+}$, were attributed to the presence of a hydrophobic phenyl group in PSS, which interact with $Ru(bpy)_3^{2+}$ by, at least in part, hydrophobic effect. The binding constant of $Ru(bpy)_3^{2+}$ to PSS in 0.1 M NaCl was $6{\times}10^4\;M^{-1}$, and this value was about $10^3$ times higher than those of methyl viologen ($MV^{2+}$) and $Cu^{2+}$. The Stern-Volmer constants of emission quenching of $Ru(bpy)_3^{2+}$ by $MV^{2+}$ and $Cu^{2+}$ in 0.1 M NaCl solutions were 426 and 40 $M^{-1}$, which correspond to second order rate constants($k_q$) of $1.1{\times}10^9\;and\; 1.0{\times}10^8\;M^{-1}s^{-1}$, respectively. The presence of PSS enhanced $K_{SV's}\;by\;{\sim}50$ times, whereas PVS increased the values only 1-4 times. The large enhancing effect of PSS, despite of lower charge density than PVS, was explained in terms of longer life-time of photoexcited $Ru(bpy)_3^{2+}$ bound to PSS and strong association of $Ru(bpy)_3^{2+}$ to PSS due to a specific interaction involving hydrophobic effect. The variation of $K_{SV's}$ on the concentrations of PVS and PSS were also investigated for $Ru(bpy)_3^{2+}-MV^{2+}\;and \;Ru(bpy)_3^{2+}-Cu^{2+}$ photoredox systems.

• 문화기술의 융합
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• 제7권1호
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• pp.42-48
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• 2021

본 연구는 다문화사회의 미래를 담당해야 하는 대학생들을 대상으로 우리 사회가 다문화사회를 준비하면서 필수적으로 요구되는 우리의 인식을 점검하고 구체적으로 무엇이 어떻게 변화해야 하는지 그 방법을 제안해 보고자 시도되었다. 2018년과 2019년 매 학기 1회씩 4번에 걸쳐 동일 교양 교과를 수강하는 대학생들을 대상으로 설문조사를 실시하였으며, 불충분한 설문 6부를 제외하고 총 299부의 설문자료를 활용하여 결과를 분석하였다. 분석 결과, 이주민에 대해 연령이 낮거나 외국 경험이 없는 경우 부정적인 이미지를 가지는 것으로 나타났다. 이주민에 대한 인식형성 요인에서는 사회적 거리감과 인지적 유연성에 있어서 연령이 높은 경우 이주민에 대해 더 친밀하게 느끼지만 사회문제에 대한 걱정이 많은 것으로 나타났다. 마지막으로 이주민에 대한 한국인 인정조건에 있어서는 사회복지학 전공자가 혼합된 전공자들에 비해 훨씬 더 많은 항목에서 이주민을 한국인으로 인정하는 조건들에 동의하고 있음을 알 수 있다. 이러한 결과를 바탕으로 다문화사회를 이끌어가기 위해 준비해야 하는 대학생들에게 적용할 수 있는 몇 가지 실천적 방법들을 제안하였다.

• Journal of Electrochemical Science and Technology
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• 제12권3호
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• pp.346-357
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• 2021

In recent years, supercapacitors have been developed rapidly as a rechargeable energy storage device. And the performance of supercapacitors is depending on electrode materials, the preparation method and performance of electrode materials have become the primary goal of scientific development. This study synthesizes Co₃O₄@MnO₂@PPy cathode material with porous pattern core-shell structure by hydrothermal method and electrodeposition. The result samples are characterized by X-ray diffraction transmission/scanning electron microscope, and X-ray photoelectron spectroscopy. Electrochemical evaluation reveals that electrochemical performance is significantly enhanced by PPy depositing. The specific capacitance of Co₃O₄@MnO₂@PPy is 977 F g^-1 at 1 A g^-1, the capacitance retention rate of 105%. Furthermore, the electrochemical performance of Co₃O₄@MnO₂@PPy//AC asymmetric supercapacitor assembles with AC as the negative electrode material is significantly better than that of MnO₂//AC and Co₃O₄@MnO₂//AC. The capacity of Co₃O₄@MnO₂@PPy//AC is 102.78 F g^-1. The capacity retention rate is still 120% for 5000 charge-discharge cycles.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.246-256
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• 2021

Mo,Cu-doped CeO₂ (CMCuO) nanopowders were synthesized by the nitrate-fuel combustion method aiming to improve the electrical and electrochemical properties of its Mo-doped CeO₂ (CMO) parent by the addition of copper. An electrical conductivity of ca. 1.22·10^-2 S cm^-1 was measured in air at 800℃ for CMCuO, which is nearly 10 times higher than that reported for CMO. This increase was associated with the inclusion of copper into the crystal lattice of ceria and the presence of Cu and Cu₂O as secondary phases in the CMCuO structure, which also could explain the increase in the charge transfer activities of the CMCuO based anode for the hydrogen and carbon monoxide electro-oxidation processes compared to the CMO based anode. A maximum power density of ca. 120 mW cm^-2 was measured using a CMCuO based anode in a solid oxide fuel cell (SOFC) with YSZ electrolyte and LSM-YSZ cathode operating at 800℃ with humidified syngas as fuel, which is comparable to the power output reported for other SOFCs with anodes containing copper. An increase in the area specific resistance of the SOFC was observed after ca. 10 hours of operation under cycling open circuit voltage and polarization conditions, which was attributed to the anode delamination caused by the reduction of the Cu₂O secondary phase contained in its microstructure. Therefore, the addition of a more electroactive phase for hydrogen oxidation is suggested to confer long-term stability to the CMCuO based anode.

• Journal of Information Science Theory and Practice
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• 제11권1호
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• pp.14-30
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• 2023

The purpose of this study is to compare research trends in the information and communication technology (ICT) field between North and South Korea and analyze the differences by using data mining. Frequency analysis, clustering, and network analysis were performed using keywords from seven South Korean and two North Korean ICT academic journals published for five years (2015-2019). In the case of South Korea (S. Korea), the frequency of research on image processing and wireless communication was high at 16.7% and 16.3%, respectively. North Korea (N. Korea) had a high frequency of research, in the order of 18.2% for image processing, 16.9% for computer/Internet applications/security, and 16.4% for industrial technology. N. Korea's natural language processing (NLP) sector was 11.9%, far higher than S. Korea's 0.7 percent. Student education is a unique subject that is not clustered in S. Korea. In order to promote exchanges between the two Koreas in the ICT field, the following specific policies are proposed. Joint research will be easily possible in the image processing sector, with the highest research rate in both Koreas. Technical cooperation of medical images is required. If S. Korea's high-quality image source is provided free of charge to N. Korea, research materials can be enriched. In the field of NLP, it calls for proposing exchanges such as holding a Korean language information conference, developing a Korean computer operating system. The field of student education encourages support for remote education contents and management know-how, as well as joint research on student remote evaluation.

• Journal of Electrochemical Science and Technology
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• 제13권4호
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• pp.472-478
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• 2022

Solar energy harvesting is practiced by various nations for the purpose of energy security and environment preservation in order to reduce overdependence on oil. Converting solar energy into electrical energy through Photovoltaic (PV) module can take place either in on-grid or off-grid applications. In recent time Lithium battery is exhibiting its presence in on-grid applications but its role in off-grid application is rarely discussed in the literature. The preliminary capacity and Peukert's study indicated that the battery quality is good and can be subjected for life cycle test. The capacity of the battery was 10.82 Ah at 1 A discharge current and the slope of 1.0117 in the Peukert's study indicated the reaction is very fast and independent on rate of discharge. In this study Lithium Iron Phosphate battery (LFP) after initial characterization was subjected to life cycle test which is specific to solar off-grid application as defined in IEC standard. The battery has delivered just 6 endurance units at room temperature before its capacity reached 75% of rated value. The low life of LFP battery in off-grid application is discussed based on State of Charge (SOC) operating window. The battery was operated both in high and low SOC's in off-grid application and both are detrimental to life of lithium battery. High SOC operation resulted in cell-to-cell variation and low SOC operation resulted in lithium plating on negative electrode. It is suggested that to make it more suitable for off-grid applications the battery by default has to be overdesigned by nearly 40% of its rated capacity.

• 한국표면공학회지
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• 제56권1호
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• pp.104-114
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• 2023

Three dimensional (3D) porous structures consisting of Cu@CoO core-shell-type nano-dendrites were synthesized and tested as the anode materials in lithium secondary batteries. For this purpose, first, the 3D porous films comprising Cu@Co core-shell-type nano-dendrites with various thicknesses were fabricated through the electrochemical co-deposition of Cu and Co. Then the Co shells were selectively anodized to form Co hydroxides, which was finally dehydrated to get Cu@CoO nanodendrites. The resulting electrodes exhibited very high reversible specific capacity almost 1.4~2.4 times the theoretical capacity of commercial graphite, and excellent capacity retention (~90%@50^th cycle) as compared with those of the existing transition metal oxides. From the analysis of the cumulative irreversible capacity and morphology change during charge/discharge cycling, it proved that the excellent capacity retention was attributed to the unique structural feature of our core-shell structure where only the thin CoO shell participates in the lithium storage. In addition, our electrodes showed a superb rate performance (70.5%@10.8 C-rate), most likely due to the open porous structure of 3D films, large surface area thanks to the dendritic structure, and fast electron transport through Cu core network.