• 대한화학회지
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• 제38권2호
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• pp.160-168
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• 1994

다섯자리 Schiff base의 molybdenum(Ⅴ)착물로써 [Mo(Ⅴ)O(Sal-DET)(NCS)] 와 [Mo(Ⅴ)O(Sal-DPT)(NCS)]들을 Sabat법에 의해 합성하였다. 이들 착물들의 원소분석, IR-spectrum, UV-Vis spectroscopy 및 Thermogravimetric analysis(T.G.A.)곡선으로부터 리간드 대 금속의 몰비가 1:1착물임을 확인하였다. 0.1M tetraethyl ammonium perchlorate(TEAP)지지전해질을 포함한 비수용매에서 순환 전압-전류법과 시차펄스 폴라그래피에 의한 전기화학적 측정으로부터 이들 착물들은 dimer로 형성된 후, 일전자 전이의 확전자 전이의 확산지배적인 환원과정이 다음과 같이 네단계로 진행됨을 알았다. 2Mo(Ⅴ)$\rightleftarrow^{e-}$ Mo(Ⅴ)Mo(Ⅳ) $\longrightarrow^{e-}$ 2Mo(Ⅳ), Mo(Ⅳ)$\longrightarrow^{e-}$ Mo(Ⅲ) $\longrightarrow^{e-}$ Mo(Ⅱ)

• 컴퓨터교육학회논문지
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• 제22권4호
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• pp.21-34
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• 2019

최근 2015개정 교육과정의 적용으로 소프트웨어 교육이 학교 현장에서 이루어지고 있다. 소프트웨어 교육의 목적은 컴퓨팅 사고력 신장에 있으며, 이를 위해 언플러그드 활동, 교육용 프로그래밍언어, 피지컬 컴퓨팅 등의 방법을 활용하고 있다. 이 중 언플러그드 활동과 관련된 국내 73편, 해외 85편의 연구물들을 시맨틱 네트워크 분석 기법을 활용하여 비교 분석하였다. 주제어 분석 결과 해외에서는 1998년부터, 국내에서는 2006년부터 연구가 시작되었으나, 4차 산업 혁명의 이슈와 맞물려 전 세계적으로 컴퓨팅 사고력이 미래 사회를 위한 핵심역량으로 인식되면서 국내외 모두 2016년 이후 연구가 급증하고 있음을 알 수 있었다. 국내 연구에서 소프트웨어 교육에서 활용되는 '언플러그드 활동', '로봇 활용', '교육용 프로그래밍 언어' 등의 수단적 요소에 관한 주제어가 많이 나타난 것으로 분석되었다. 언플러그드 활동이 컴퓨팅 사고력을 함양시키기 위한 방법으로 활용되어야할 것이며 이를 위해 컴퓨터 과학의 목적인 '컴퓨팅 사고력' 에 대한 고찰을 바탕으로 연구가 진행될 필요가 있다.

• 한국분말재료학회지
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• 제28권3호
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• pp.221-226
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• 2021

We fabricate the non-equiatomic high-entropy alloy (NE-HEA) Fe_49.5Mn₃₀Co₁₀Cr₁₀C_0.5 (at.%) using spark plasma sintering under various sintering conditions. Each elemental pure powder is milled by high-energy ball milling to prepare NE-HEA powder. The microstructure and mechanical properties of the sintered samples are investigated using various methods. We use the X-ray diffraction (XRD) method to investigate the microstructural characteristics. Quantitative phase analysis is performed by direct comparison of the XRD results. A tensile test is used to compare the mechanical properties of small samples. Next, electron backscatter diffraction analysis is performed to analyze the phase fraction, and the results are compared to those of XRD analysis. By combining different sintering durations and temperature conditions, we attempt to identify suitable spark plasma sintering conditions that yield mechanical properties comparable with previously reported values. The samples sintered at 900 and 1000℃ with no holding time have a tensile strength of over 1000 MPa.

• 대한본초학회지
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• 제33권6호
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• pp.87-92
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• 2018

Objectives: The aim of the study was to analyze the constituents of Pyrolusitum, which was used to eliminate static blood and inflammation, to establish the basis of clinical application. Methods: Qualitative analysis was performed by X-Ray Diffraction (XRD) using the sample as a powder, and the elemental content of granular sample was measured by X-Ray Fluorescence (XRF). 1 M hydrochloric acid and 5% sodium hydroxide aqueous solution were added to observe the changing shape, respectively. Results: Qualitative analysis by XRD revealed that the Pyrolusitum samples used in the study contained quarts and kaolinite. Quantitative analysis by XRF revealed that the manganese content in the samples used in the study was 6.16% on average, while iron was contained the highest amount of 22.99%. The minor constituents include 1.08% of titanium, 0.30% of barium, 0.18% of lead, 0.06% of zirconium, 0.05% of chromium, 0.04% of zinc, 0.03% of cadnium, 0.02% of nickel, 0.01% of arsenic, 0.01% of copper, 0.01% of rubidium, 0.01% of strontium, 0.00% of molybdenum, respectively. And cobalt, which is reported to be a constituent of Pyrolusitum, was not detected at all in the samples of the study. Pyrolusitum was dissolved in dark brown when it was put into 1 M hydrochlorid acid, and there was brown precipitate when sodium hydroxide solution was added to Pyrolusitum and stirred. Conclusions: It was found that manganese and iron were the major constituents of Pyrolusitum, and it could be identified by using concentrated hydrochloric acid and sodium hydroxide solution.

• 분석과학
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• 제21권2호
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• pp.109-116
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• 2008

1%, 2%, 6% 및 12%의 가교도를 가진 스틸렌(제4류 위험물) 디비닐벤젠 공중합체에 1-aza-18-crown-6 거대고리 리간드를 치환반응으로 결합시켜 수지들을 합성하였다. 이들 수지의 합성은 염소 함량, 원소 분석, 열중량 분석, 전자 현미경, 그리고 IR-스펙트럼으로 확인하였다. 수지 흡착제에 의한 우라늄 이온의 흡착에 미치는 pH, 시간, 수지의 가교도 그리고 용매의 유전상수에 따른 영향들을 조사하였다. 우라늄 이온은 pH 3 이상에서 큰 흡착율을 보였으며, 금속 이온들의 흡착 평형은 2 시간 정도였다. 한편, 에탄올 용매에서 수지에 대한 흡착 선택성은 $UO{_2}^{2+}$ > $Zn^{2+}$ > $Lu^{3+}$ 이온이었고, 우라늄 이온의 흡착력은 1%, 2%, 6% 및 12%의 가교도 순 이었으며, 용매의 유전상수 크기에 반비례하였다.

• Bulletin of the Korean Chemical Society
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• 제35권11호
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• pp.3289-3293
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• 2014

Femtosecond laser ablation (fs LA) was used in this study to identify pollution by heavy metals and the distribution of elemental nutrients at different rice milling ratios. Polished rice (degrees of milling of 3, 5, 7, 9, and 11) was collected from major Korean supermarkets and one sample thereof was selected. An internal quality control experiment was conducted using a rice flour certified reference material from the Korea Research Institute of Standards and Science (KRISS CRM) for the evaluation of the efficacy. To assess the effectiveness of the analysis method, the reliability was validated using a food analysis performance assessment scheme (FAPAS), with chili powder serving as an external quality control. The results of the analysis of the inorganic elements Ti, Ca, Al, Fe and Mn in white and brown rice with degrees of milling of 3, 5, 7, 9 and 11 using ICP-MS, ICP-OES and AAS revealed contents of 0.40, 49.2, 2.43, 5.36 and 10.3 mg/kg in white rice and 0.59, 78.0, 7.52, 11.0 and 18.5 mg/kg in brown rice, respectively. Among the elements, there were remarkable differences in the measured contents. By comparing the contents of the elements at different degrees of milling, Ti, Co, As, Ca, Al, Cu, Fe, and Mn were determined to be distributed on the surface of the rice grains, whereas the contents of Cd and Pb increased toward the center of the rice grains, and Si was evenly distributed. After the quantitative analysis of rice samples polished to different degrees of milling, Ca and Al, which were contained in large amounts, and Si were analyzed with specificity by fs LA. The results show that Ca and Al were distributed in the rice husk (protective covering of rice) and Si was distributed in all parts of the rice.

• 한국재료학회지
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• 제13권3호
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• pp.169-173
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• 2003

W-Cu composite powders can be prepared by mechanochemical process, where the $WO_3$-CuO composite powders were mechanically synthesized from the elemental oxide powders and subsequently reduced to W-Cu composite powders. In the present work, reduction behavior of$ WO_3$-CuO composite powders that were synthesized at different milling time was examined in terms of hygrometric analysis. In case of $WO_3$-CuO ball-milled for 20 h, the reaction temperature of CuO\longrightarrowCu became lower than in case of 1 h. Also, the reaction of $WO_3$\longrightarrow$WO_{2.9-2.72}$ and $WO_{2.9-2.72}$ \longrightarrow$WO_2$were shifted to lower temperatures and the peaks were changed to much sharper shape. While the reaction of $WO_2$\longrightarrowW in case of ball-milling for 20 h started at lower temperature, the peak temperature was the same as in 1 h ball-milling. The reduced W particle size was somewhat finer fer 20 h ball-milling. It was considered that the refinement of oxide particles caused by ball-milling process leads to such a change in the reduction behavior.

• 한국대기환경학회지
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• 제30권4호
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• pp.301-310
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• 2014

Country-specific data for net calorific values and carbon emission factors requires for a higher tier estimate of greenhouse gas emissions in the energy sector. The objective of this study is to develop country-specific net calorific values and carbon emission factors for petroleum energy produced in Korea. Calorific values and carbon contents of the fuels were measured using the oxygen bomb calorimeter method and the CHN elemental analysis method, respectively. Sulfur and hydrogen contents, which were used to calculate the net calorific value, were also measured and then net calorific values and carbon emission factors were determined based on the measurement results. The net calorific values and carbon emission factors determined for the petroleum produced in Korea 2012 and 2013 were compared to those in the 2006 IPCC Guidelines. Most of the values were different compared with the default values of the 2006 IPCC Guidelines although those were placed within their upper and lower limits. Time series analysis results showed inconsistent seasonal variation for the net calorific values and carbon emission factors.

• 한국염색가공학회지
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• 제28권2호
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• pp.57-62
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• 2016

We have synthesized five novel phthaloperinone dyes via a condensation reaction to be applied as yellow colorants for liquid crystal display(LCD) color filters. The reaction between 1,8-naphthalic anhydride(1a), 4-chloro-1,8-naphthalic anhydride(1b), 4-bromo-1,8-naphthalic anhydride(1c), 3-nitro-1,8-naphthalic anhydride(1d), 4-nitro-1,8-naphthalic anhydride(1e) and 1,2-diaminoanthraquinone(2) proceeded readily giving a product in 72-88% yields. The synthesized dyes were characterized by UV-Vis, mass spectrometry and elemental analysis. The spectral properties and thermal stability of the dyes were examined. The dyes absorb at around 400-450nm. All five dyes showed satisfactory thermal stability: the dyes retain 99-100% of its original weight at $300^{\circ}C$, 98-100% at $350^{\circ}C$, 92-98% at $400^{\circ}C$, and 84-92% at $450^{\circ}C$. We have quantitatively evaluated the reaction mechanism and reactivity of dye molecules by means of Pariser-Parr-Pople Molecular Orbital Method(PPP-MO).

• 대한화학회지
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• 제56권1호
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• pp.62-67
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• 2012

A series of homo binuclear complexs of the type $[M_2(L/L^')(NO_3)n].mH_2O$, [where $M=U{O_2}^{2+},\;Th^{4+},\;ZrO^{2+}$] and $[(VO)_2(L/L^')(SO_4)_2]{\cdot}2H_2O$, L=1,5,6,9,12,15,16,20 octaaza-7,813,14-tetraphenyl-2,4,17,19-tetramethyl-1,4,6,8,12,14,16,19-docosaoctene (OTTDO) or L'=10:11;21:22-dibenzo-1,5,6,9,12,15,16,20-octaaza-7,813,14-tetraphenyl-2,4,17,19-tetramethyl-1,4,6,8,12,14,16,19-docosaoctene (DOTTOT), n=4 for $U{O_2}^{2+}$, $ZrO^{2+}$ n=8 for $Th^{4+}$ m=1,2,3 respectively, have been synthesized in template method from ethylenediamine/orthophenylene diamine, benzil monohydrazone and acetyl acetone and characterized on the basis of elemental analysis, thermal analysis, molar conductivity, magnetic moment, electronic, infrared, $^1H$-NMR studies. The results indicate that the VO(IV) ion is penta co-ordinated yielding paramagnetic complexes; $UO_2(VI)$, ZrO(IV) ions are hexa co-ordinated where as Th(IV) ion is octa co-ordinated yielding diamagnetic complexes of above composition. The fungi toxicity of the ZrO(IV) and VO(IV) complexes against some fungal pathogen has been studied.