• 자원리싸이클링
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• 제31권3호
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• pp.61-72
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• 2022

주요성분이 Sn(93.0 %)-Ag(3.26 %)-Cu(0.89 %)로 구성되는 SAC 폐무연솔더로부터 주석과 은을 회수하기 위한 전기화학적인 방법을 연구하였다. 폐무연솔더의 건식용해, 주조를 통해 제조한 작업전극을 사용하여 분극거동 조사와 정전류 전해용해를 실시하였다. 분극시험 시 활성화영역의 산화전류피크는 전해액의 황산 농도가 높아질수록 감소하였으며, 1 molL^-1 황산농도가 전해용해를 위해 가장 적절한 것으로 나타났다. 정전류 용해 시 전극표면의 부동태층인 양극슬라임이 두꺼워짐에 따라 전극전위가 지속적으로 높아졌으며, 10 mAcm^-2에서 25시간동안 지속적인 전해용해가 가능한 반면 50 mAcm^-2에서는 2.5 시간 이후부터 전극전위가 급상승하여 전해용해반응이 중단되었다. 정전류 전해용해 시 은은 양극슬라임에 농축되었으며, 전해액내 염소이온의 농도가 0.3 molL^-1인 경우 농축율이 미첨가 조건보다 12.7% 높은 94.3%를 나타내었다. 또한 염소이온의 첨가에 의해 전해액내 주석이온의 안정성을 높이고 주석의 전착전류효율을 향상시킬 수 있었다.

• 한국항해항만학회지
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• 제38권1호
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• pp.59-64
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• 2014

지구온난화로 인해 극지방의 해빙속도가 빠르게 증가하고 있으며, 이러한 환경변화로 북극항로에 대한 관심은 북극해 주변국뿐만 아니라, 먼 이웃국가들에게까지 확산되고 있다. 과거 극지역을 항해하는 선박에 대한 설계 및 운용과 관련된 선급 규칙은 주로 북극해에 인접한 러시아, 노르웨이, 핀란드에 의해서 주로 개정되어 왔다. 그러나 국제해사기구(IMO)에서는 극지해역을 운항하는 선박에 대한 안전성을 확보하기 위해, 강제규정인 극지방운항선박 안전코드(Polar Code)를 제정하기로 결정하였으며, 현재 2014년에 개발을 완료할 예정이다. 본 논문은 이러한 극지방운항선박 안전코드의 제정 현황을 파악하고, 앞으로 극지방운항선박 안전코드의 제정을 위한 우리나라의 각 기관의 역할 및 시사점 대해 분석하고자 한다.

• Current Photovoltaic Research
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• 제4권2호
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• pp.54-58
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• 2016

Laser-doped selective emitter process requires dopant source deposition, spin-on-glass, and is able to form selective emitter through SiNx layer by laser irradiation on desired locations. However, after laser doping process, the remaining dopant layer needs to be washed out. Laser-induced melting of pre-deposited impurity doping is a precise selective doping method minimizing addition of process steps. In this study, we introduce a novel scheme for fabricating highly efficient selective emitter solar cell by laser doping. During this process, laser induced damage induces front contact destabilization due to the hindrance of silver nucleation even though laser doping has a potential of commercialization with simple process concept. When the laser induced damage is effectively removed using solution etch back process, the disadvantage of laser doping was effectively removed. The devices fabricated using laser doping scheme power conversion efficiency was significantly improved about 1% abs. after removal the laser damages.

• 한국산학기술학회논문지
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• 제16권3호
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• pp.1671-1676
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• 2015

폴리-L-유산 (PLLA)/폴리-D-유산(PDLA)의 스테레오컴플렉스(SC) 특유의 결정 거동은 PLLA/PDLA의 블렌드의 특정한 용융 조건에서 나타난다. 이를 적용하여 PLA 스테레오컴플렉스를 제조하기 위해 전반적인 조성에서 PLLA와 PDLA를 블렌드 하였다. 또한 충격 강도와 열변형온도 같은 기계적 물성 및 열적 특성을 향상시키기 위해 충격보강제, 탈크와 유리섬유(GF) 등의 보강제를 첨가하였다. 그 결과로 열변형 온도가 $115^{\circ}C$ 에서 관찰 되는 조성의 복합재를 제조하였다. 더 경제적인 방법으로, PLLA와 상용화된 폴리프로필렌(PP)을 전반적인 조성에서 블렌드 하였다. 그 결과, 특정 조성에서 상용화된 PP/탈크 복합재와 ABS에 적용시킬 수 있는 물성을 나타내었다. 이러한 결과는 PP와 PLLA같은 매트릭스 수지에 유리섬유 및 충격보강제를 잘 분산시키는 것에서 기인하는 것으로 판단된다.

• Nuclear Engineering and Technology
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• 제46권3호
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• pp.363-372
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• 2014

In this study, we proposed a newly designed sulfuric acid transfer system for the sulfur-iodine (SI) thermochemical cycle. The proposed sulfuric acid transfer system was evaluated using a computational fluid dynamics (CFD) analysis for investigating thermodynamic/hydrodynamic characteristics and material properties. This analysis was conducted to obtain reliable continuous operation parameters; in particular, a thermal analysis was performed on the bellows box and bellows at amplitudes and various frequencies (0.1, 0.5, and 1.0 Hz). However, the high temperatures and strongly corrosive operating conditions of the current sulfuric acid system present challenges with respect to the structural materials of the transfer system. To resolve this issue, we designed a novel transfer system using polytetrafluoroethylene (PTFE, $Teflon^{(R)}$) as a bellows material for the transfer of sulfuric acid. We also carried out a CFD analysis of the design. The CFD results indicated that the maximum applicable temperature of PTFE is about 533 K ($260^{\circ}C$), even though its melting point is around 600 K. This result implies that the PTFE is a potential material for the sulfuric acid transfer system. The CFD simulations also confirmed that the sulfuric acid transfer system was designed properly for this particular investigation.

• 한국수소및신에너지학회논문집
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• 제8권3호
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• pp.137-141
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• 1997

The effects of Ag addition to Zr-based hydrogen storage alloys ($Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$, $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$ and $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Fe_{0.1}$) on the electrode properties were examined. Ag-free and Ag-added Ze-based alloys were prepared by arc melting, crushed mechanically, and subjected to the electrochemical measurement. In $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy, 0.08 wt% Ag addition to the alloy improved the activation rate. Also Ag addition improved both activation property and discharge capacity in $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.3}Cr_{0.1}$. For these Ag-added alloys, discharge capacities with the change of charge-discharge current density(10mA, 15mA and 30mA) are almost constant. Showing very high rate capability, discharge capacity of $Zr_{0.6}Ti_{0.4}V_{0.4}Ni_{1.2}Mn_{0.3}Fe_{0.1}$ alloy increased by Ag addition to the alloy. When the amount of Ag addition in $Zr_{0.7}Ti_{0.3}V_{0.4}Ni_{1.2}Mn_{0.4}$ alloy increased too much, the electrode properties became worse. Unveiling mechanism of effect of Ag addition is now progressing in our laboratory.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 하계학술대회 논문집 C
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• pp.1378-1380
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• 2001

Ohmic contacts have been fabricated on p-type 4H-SiC using Pt/Ti. Low resistivitf Ohmic contacts of Pt/Ti to p-type 4H-SiC were investigated. Specific contact resistances were measured using the transmission line model method, and the physical properties of the contacts were examined using x-ray diffraction, scanning electron microscopy. Ohmic behavior with linear current-voltage characteristics was observed following anneals at $900^{\circ}C$ for 90sec at a pressure of $3.4{\times}10^{-5}$ Torr. The Pt/Si/Ti films was measured lower value of the specific contact resistance by the annealing process, and the contact resistances were improved more than one order compared to Ti contact the annealed sample. Scanning electron microscopy shows that the Pt layer effectively reduce the oxidation of Ti films. And results are obtained as $4.6{\times}10^{-4}$ ohm/$cm^2$ for a Pt/Ti metal structure after a vacuum annealing at $900^{\circ}C$ for 90sec. Titanium has a relatively high melting point, thus Ti-based metal contacts were attempted in this study.

• 대기
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• 제25권3호
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• pp.389-405
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• 2015

In this study, the occurrence circumstances of 3 cases (12 Jan 2006, 11 Jan 2008, 22 Feb 2009) when the freezing rain was observed at more than two observatories in a day with more than three times each observatory, were investigated. Following the advanced study about the same cases, we have tried to find more delicate differences in using the Korea Local Analysis and Prediction System (KLAPS; 5 km reanalysis data) that has the smallest grid scale at current situation. As results, three common characteristics are found: (1) Just before the occurrence of the freezing rain, the wind direction was consistently continuous and the wind speed was constant or gradually increased for at least 3 hr more. (2) Surface air temperature (Relative humidity) was respectively $3.08^{\circ}C$ (28.76%), $0.47^{\circ}C$ (50.07%) and $-3.60^{\circ}C$ (71.07%) 3 hr ago to break out the freezing rain. It means the freezing rain occurs in a wide range of atmospheric environments. However, the closer it got to the occurrence time of the freezing rain, the closer the surface air temperature was to $0^{\circ}C$, and the bigger the humidity of the surface air was. (3) The liquid precipitation formed in the upper atmosphere, met a cold advection bellower than 950 hPa level and suspected to be changed to the super-cooled condition.

• Nuclear Engineering and Technology
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• 제52권2호
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• pp.248-257
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• 2020

This study presents an initial design for a novel system consisting in a coupled nuclear reactor and a phase change material-based thermal energy storage (TES) component, which acts as a buffer and regulator of heat transfer between the primary and secondary loops. The goal of this concept is to enhance the capacity factor of nuclear power plants (NPPs) in the case of high integration of renewable energy sources into the electric grid. Hence, this system could support in elevating the economics of NPPs in current competitive markets, especially with subsidized solar and wind energy sources, and relatively low oil and gas prices. Furthermore, utilizing a prismatic-core advanced high temperature reactor (PAHTR) cooled by a molten salt with a high melting point, have the potential in increasing the system efficiency due to its high operating temperature, and providing the baseline requirements for coupling other process heat applications. The present research studies the neutronics and thermal hydraulics (TH) of the PAHTR as well as TH calculations for the TES which consists of 300 blocks with a total heat storage capacity of 150 MWd. SERPENT Monte Carlo and MCNP5 codes carried out the neutronics analysis of the PAHTR which is sized to have a 5-year refueling cycle and rated power of 300 MW_th. The PAHTR has 10 metric tons of heavy metal with 19.75 wt% enriched UO₂ TRISO fuel, a hot clean excess reactivity and shutdown margin of $33.70 and -$115.68; respectively, negative temperature feedback coefficients, and an axial flux peaking factor of 1.68. Star-CCM + code predicted the correct convective heat transfer coefficient variations for both the reactor and the storage. TH analysis results show that the flow in the primary loop (in the reactor and TES) remains in the developing mixed convection regime while it reaches a fully developed flow in the secondary loop.

• 한국환경농학회:학술대회논문집
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• 한국환경농학회 2009년도 정기총회 및 국제심포지엄
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• pp.228-239
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• 2009

The observations on climate change show a clear increase in the temperature of the Earth's surface and the oceans, a reduction in the land snow cover, and melting of the sea ice and glaciers. The effects of climate change are likely to include more variable weather, heat waves, increased mean temperature, rains, flooding and droughts. The threat of climate change and global warming on human and animal health is now recognized as a global issue. This presentation is described an overview of the latest scientific knowledge on the impact of climate change on zoonotic diseases. Climate strongly affects agriculture and livestock production and influences animal diseases, vectors and pathogens, and their habitat. Global warming are likely to change the temporal and geographical distribution of infectious diseases, including those that are vector-borne such as West Nile fever, Rift Valley fever, Japanese encephalitis, bluetongue, malaria and visceral leishmaniasis, and other diarrheal diseases. The distribution and prevalence of vector-borne diseases may be the most significant effect of climate change. The impact of climate change on the emergence and re-emergence of animal diseases has been confirmed by a majority of countries. Emerging zoonotic diseases are increasingly recognized as a global and regional issue with potential serious human health and economic impacts and their current upward trends are likely to continue. Coordinated international responses are therefore essential across veterinary and human health sectors, regions and countries to control and prevent emerging zoonoses. A new early warning and alert systems is developing and introducing for enhancing surveillance and response to zoonotic diseases. And international networks that include public health, research, medical and veterinary laboratories working with zoonotic pathogens should be established and strengthened. Facing this challenging future, the long-term strategies for zoonotic diseases that may be affected by climate change is need for better prevention and control measures in susceptible livestock, wildlife and vectors in Korea. In conclusion, strengthening global, regional and national early warning systems is extremely important, as are coordinated research programmes and subsequent prevention and control measures, and need for the global surveillance network essential for early detection of zoonotic diseases.