• 한국분말재료학회지
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• 제28권4호
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• pp.331-335
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• 2021

The effects of drying temperature on the microstructure of porous W fabricated by the freeze-casting process of tert-butyl alcohol slurry with WO₃ powder was investigated. Green bodies were hydrogen-reduced at 800℃ for 1 h and sintered at 1000℃ for 6 h. X-ray diffraction analysis revealed that WO₃ powders were completely converted to W without any reaction phases by hydrogen reduction. The sintered body showed pores aligned in the direction of tert-butyl alcohol growth, and the porosity and pore size decreased as the amount of WO₃ increased from 5 to 10vol%. As the drying temperature of the frozen body increased from -25℃ to -10℃, the pore size and thickness of the struts increased. The change in microstructural characteristics based on the amount of powder added and the drying temperature was explained by the growth behavior of the freezing agent and the degree of rearrangement of the solid powder during the solidification of the slurry.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.667-672
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• 2023

This study proposes polymer electrolyte membrane fuel cell (PEMFC) based cogeneration system for greenhouse heating and cooling. The main scope of this study is to examine the proposed cogeneration system's suitability for the 660 m²-class greenhouse. A 25 kW PEMFC system generates electricity for two identical air-cooled heat pumps, each with a nominal heating capacity of 70 kW and a cooling capacity of 65 kW. Heat recovered from the fuel cell supports the heat pump, supplying hot water to the greenhouse. In cooling mode, the adsorption system provides cold water to the greenhouse using recovered heat from the fuel cell. As a result, the cogeneration system satisfies both heating and cooling capability, performing 175 and 145 kW, respectively.

• 한국수소및신에너지학회논문집
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• 제35권3호
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• pp.345-351
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• 2024

The unitized regenerative fuel cell (URFC) is a method that can reduce costs and increase system simplification by unitizing a fuel cell system and a water electrolysis system. The spray method is suitable as the membrane electrode assembly (MEA) manufacturing method for URFC because it is easy to control the amount of catalyst, the size of the system is small, and economical manufacturing is possible. In this study, a numerical analysis of the effect of solution concentration on the spray method was performed to use it as basic data for the spray method to be used in MEA manufacturing. As result, as the Nafion solution concentration decreases it was found that the spray speed and the mass flow rate and the discrete phase model concentration increases and the spray range widens.

• 해양환경안전학회지
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• 제30권1호
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• pp.135-145
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• 2024

MEPC 80차 회의에서 IMO는 더욱 강화된 온실가스 감축 전략을 제시하였다. 기존의 72차 회의에서 제시하였던 초기전략보다 구체적이고 강화된 감축 전략이다. IMO는 2050년 무렵까지 국제 해운으로부터 온실가스 배출을 'Net Zero'에 도달하도록 전략을 세웠다. 이 논문에서는 대표적인 친환경 연료로 구분되는 LNG, 수소, 메탄올, 암모니아의 위험도 평가를 진행하였다. 전문가들의 설문조사를 통한 결과를 퍼지 기법을 적용하여 주관적인 모호성을 해결하였다. 또한 TOPSIS 기법을 통해서 퍼지의 긍정적인 해와 부정적인 해를 도출하였다. 이를 통해서 Vertex 방법을 이용하여 대체 연료의 근접계수 값을 최종적으로 구하여 결정하였다. 그 결과, 메탄올, LNG, 수소, 암모니아 순으로 선호하였다. 이 연구는 제안된 접근 방식이 대체 연료를 결정을 위한 집단 의사결정 방법으로 이용할 수 있음을 보여준다.

• 한국재료학회지
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• 제22권12호
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• pp.696-700
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• 2012

(Na, K) $NbO_3$ thick film was successfully achieved using a sol-gel coating process with the addition of polyvinylpyrrolidone (PVP) to a metal alkoxide solution. The transparent coating solution, mixed with Nb:PVP = 1:1 in a molar ration, was synthesized by evaporating the solvent to over 62.5 wt%. Additive PVP increased the viscosity of the solution so that the coating thickness could be enhanced. The thickness of the (Na, K) $NbO_3$ film assisted by PVP was ca. 320 nm at the time of deposition; this value is four times thicker than that of the sample fabricated without PVP. Also, due to PVP binding with the OH groups of the metal alkoxide, the condensation reaction in the film was suppressed. The crystalline size of the (Na, K) $NbO_3$ films assisted by PVP was ca. 15 nm smaller than that of the film fabricated without PVP. After the sintering process at $700^{\circ}C$, the (Na, K) $NbO_3$ films were mainly composed of randomly oriented (Na, K) $NbO_3$ phase of perovskite crystal structure, including a somewhat secondary phase of $K_2Nb_4O_{11}$. However, by adding PVP, the content of the secondary phase became quite smaller than that of the sample without PVP. It was thought that the addition of PVP might have the effect of restraining the loss of potassium and that PVP could hold metalloxane by strong hydrogen bonding before complete decomposition. Therefore, the film thickness of the (Na, K) $NbO_3$ films could be considerably advanced and made more crack-free by the addition of PVP.

• 대한화학회지
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• 제29권5호
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• pp.510-515
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• 1985

진한 메탄설폰산(약10M)에서 초록색의 $MoO_{(aq)}^{3+}$는 진한 초록색의 이합체인$Mo_2O_2(OH)_{2(aq)}^{4+}$를 생성한다. 또한 이러한 진한 초록색은 15-16M의 메탄설폰산에서 존재하는 $MoO_{(aq)}^{3+}$용액에 물을 가하면 나타나며 15M의 메탄설폰산에서 단위체의 몰흡광계수는 415nm에서 약 20이다. 속도 상수는 이 실험조건하에서 아쿠오몰리브덴(V)와 수소이온농도에 의존하지 않는다. $Mo_2O_2(OH)_{2(aq)}^{4+}$의 수산화이온은 HPTS 약 6M, $CH_3SO_3H$는 10M이하에서 탈수소화반응이 일어난다. 마지막 생성물의 말단산소와 다리산소의 구조는 (*image) 단위를 가진 것으로 확인되었다.

• 한국수산과학회지
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• 제42권6호
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• pp.545-554
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• 2009

This study was conducted to develop and characterize of a high quality salted mackerel using enzymatic extracts of Ecklonia cava (EEC). In this study, potential antioxidative properties of EEC were evaluated by DPPH free radical scavenging activity, hydrogen peroxide scavenging activity, peroxide value, and fatty acid composition, and the antimicrobial properties were also measured by analysis for volatile basic nitrogen, pH, viable cells, Eschericia coli and biogenic amine. Compared to EEC-untreated salted mackerel, the salted mackerel with EEC was superior in antioxidative properties, while was negligible in the difference of antimicrobial properties. These results suggested that the high quality salted mackerel with antioxidative activity could be developed by treatment of EEC.

• 멤브레인
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• 제24권3호
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• pp.177-184
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• 2014

본 연구에서 고투과도를 갖는 실리카 분리막은 콜로이달 실리카 졸과 고분자형 실리카 졸 두 가지를 DRFF법과 SRFF법으로 다공성 금속 지지체 위에 코팅하여 제조되었다. 실리카 졸은 졸-겔법으로 테트라에톡시실란(TEOS)에 의하여 제조되었고, 각각의 졸은 동적광산란법(DLS), 전계방사 주사전자현미경(FE-SEM), 질소 흡착법 등을 이용하여 그 특성을 평가하였다. 다공성 금속 지지체위에 콜로이달 실리카 졸로 중간층을 형성하여 치밀한 구조의 실리카 층을 형성한 후 그 위에 분리층으로 고분자형 실리카 졸을 코팅하여 핀홀을 줄이는 방법으로 기체분리용 분리막을 제조하였다. FE-SEM으로 분리막의 코팅 층을 분석한 결과 분리층은 중간층보다 침밀한 구조를 가지고 있음을 확인하였고 기체투과 결과 수소 투과도 $(6.63-9.21){\times}10^{-5}mol{\cdot}m^{-2}{\cdot}s^{-1}{\cdot}Pa^{-1}$ 분포를 보였다.

• Bulletin of the Korean Chemical Society
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• 제34권11호
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• pp.3399-3404
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• 2013

A new accepter unit, pyrrolo[3,2-b]pyrrole-2,5-dione, was prepared and utilized for the synthesis of the conjugated polymers containing electron donor-acceptor pair for OPVs. Pyrrolo[3,2-b]pyrrole-2,5-dione unit, regioisomer of the known pyrrolo[3,4-c]pyrrole-1,4-dione, is originated from the structure of stable synthetic pigment. The new conjugated polymers with 1,4-diphenylpyrrolo[3,2-b]pyrrole-2,5-dione, thiophene and carbazole were synthesized using Suzuki polymerization to generate P1 and P2. The solid films of P1 and P2 show absorption bands with maximum peaks at about 377, 554 and 374, 542 nm and the absorption onsets at 670 and 674 nm, corresponding to band gaps of 1.85 and 1.84 eV, respectively. To improve the hole mobility of the polymer with 1,4-bis(4-butylphenyl)-pyrrolo[3,2-b]-pyrrole-2,5-dione unit, which was previously reported by us, the butyl group at the 4-positions of the N-substituted phenyl group was substituted with hydrogen and methyl group. The field-effect hole mobility of P2 is $9.6{\times}10^{-5}cm^2/Vs$. The device with $P2:PC_{71}BM$ (1:2) showed $V_{OC}$ value of 0.84 V, $J_{SC}$ value of 5.10 $mA/cm^2$, and FF of 0.33, giving PCE of 1.42%.

• 한국산학기술학회논문지
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• 제16권9호
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• pp.6411-6418
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• 2015

기후변화 및 환경오염에 대응하기 위해 신재생에너지 정책 연구가 증가하고 있다. 신재생에너지는 녹색산업과 녹색기술로 대표되는 새로운 성장 동력 기술이다. 현재 우리나라는 태양광, 풍력, 수소연료전지 등 3대 전략부분에 신재생에너지 보급 및 기술개발사업에 대한 투자가 이루어지고 있지만 아직은 초기 단계로, 연구 방향 및 투자 분야에 대한 불확실성을 줄이는 것이 무엇보다도 시급한 실정이다. 따라서 본 연구는 빅데이터(big data) 분석방법 중 텍스트 마이닝(Text mining method)과 토픽 모델링 기법(multinominal topic model)을 신재생에너지와 관련된 최근 10년간의 우리나라 언론기사에 적용하여 국가 정책의 핵심이슈 및 세계적인 연구 트렌드를 분석하고, 성장 가능성이 있는 신재생에너지 분야를 예측하였다. 정보통신기술을 바탕으로 한 연구결과는 신재생에너지 분야에 활발히 적용될 것으로 예측된다.