• 한국전기전자재료학회논문지
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• 제27권11호
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• pp.736-739
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• 2014

In this paper, we propose a enhanced anti-corrosion property of the ground system by coating the CNT/PVDF composite film on it. Polymer material used for preventing the corrosion of ground system is polyvinylidene fluoride (PVDF), and conducting filler for obtaining conductivity of the composite film is multi-walled carbon nanotubes (MWCNTs). The MWCNTs were dispersed in the organic solvent of methyl ethyl ketone 2-butanone (MEK) with different concentration ratios, and the PVDF was solved in the MEK solvent with constant concentration ratio of 1 wt%. The CNT/PVDF composite solution was perpared by mixing and re-dispersing the CNT solution and the PVDF solution. Finally, the CNT/PVDF composite films were fabricated by the spray coating method using the above composite solution. Electrical conductivity, surface states, and anti-corrosion property of the CNT/PVDF composite films coated on the Cu substrate were evaluated. We found that the CNT/PVDF composite film showed relatively low resistance, hydrophobic surface state, and chemical stability. Consequently, we could improve the anti-corrosion property and maintain the electrical conductivity of the ground system by coating the CNT/PVDF composite film on it.

• 한국가스학회지
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• 제24권5호
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• pp.20-28
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• 2020

불산 누출사고 발생 시 피해영향범위 예측을 수계산, 영향평가 시뮬레이션, CFD 시뮬레이션을 활용하여서 예측하고 실제 환경영향보고서와 비교·분석하였다. 수계산은 누출원모델과 확산모델을 활용하여서 계산하였으며 영향평가 시뮬레이션은 우리나라 환경부에서 제공하는 KORA, 미국 환경부의 ALOHA, 상용화 프로그램 중 비교적 널리 사용 중인 PHAST를 사용하였고, CFD 시뮬레이션은 STAR-CMM+ 프로그램을 활용하였다. 사용자 입장에서 편리성, 신속성, 수용성, 경제성 등을 고려할 때 불산 누출사고 영향예측에 가장 적절하게 사용할 수 있는 프로그램은 ALOHA와 KORA 이었다. 아울러, 본 연구결과는 정부의 정책개발과 기업의 안전부서에서 피해영향범위 프레임워크를 선정하고 불필요한 규제, 불필요한 안전투자를 최적화하여 정부 또는 기업의 제한된 자원을 효율적으로 활용하는 데 도움이 될 것으로 기대된다.

• 한국분말재료학회지
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• 제27권2호
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• pp.119-125
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• 2020

One of the promising candidates for accident-tolerant fuel (ATF), a ceramic microcell fuel, which can be distinguished by an unusual cell-like microstructure (UO₂ grain cell surrounded by a doped oxide cell wall), is being developed. This study deals with the microstructural observation of the constituent phases and the wetting behaviors of the cell wall materials in three kinds of ceramic microcell UO₂ pellets: Si-Ti-O (STO), Si-Cr-O (SCO), and Al-Si-Ti-O (ASTO). The chemical and physical states of the cell wall materials are estimated by HSC Chemistry and confirmed by experiment to be mixtures of Si-O and Ti-O for the STO; Si-O and Cr-O for SCO; and Si-O, Ti-O, and Al-Si-O for the ASTO. From their morphology at triple junctions, UO₂ grains appear to be wet by the Si-O or Al-Si-O rather than other oxides, providing a benefit on the capture-ability of the ceramic microcell cell wall. The wetting behavior can be explained by the relationships between the interface energy and the contact angle.

• 상하수도학회지
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• 제31권6호
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• pp.551-566
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• 2017

As the modern society is rapidly developing and people become affluent in materials, many new chemical compounds in different forms of products (e.g., antibiotics, pesticides, detergents, personal care products and plastic goods) are produced, used, and disposed of to the environments. Some of them are persistently having a harmful impact on the environment and mimicking endocrine properties; in general they are present in the environment at low concentrations, so they are called organic pollutants. These organic micropollutants flow to sewage treatment plants via different routes. In this study, the generation characteristics, exposure pathways, detection levels, and environmental impacts of organic micropollutants were critically reviewed. In addition, currently available risk assessment methods and management systems for the compounds were reviewed. The United States Environmental Protection Agency (US EPA), for example, has monitored organic micropollutants and set the monitoring and management of some of the compounds as a priority. To effectively manage organic micropollutants in sewer systems, therefore, we should first monitor organic micropollutants of potential concern and then make a watch list of specific substances systematically, as described in guidelines on listing water pollutants in industrial wastewater.

• 한국진공학회지
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• 제11권1호
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• pp.22-27
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• 2002

Reactive sputtering 방법으로 증착된 tungsten nitride ($(WN_x)$) 박막에 대해 $N_2$ 유량비 변화에 따르는 구조, 화학결합, 그리고 비저항 값의 변화를 조사하였다. $(WN_x)$ 박막 증착시 $N_2$ 유량비를 20%, 40%, 60%로 늘려감에 따라 그 구조는 각각 bcc $\beta$-W상, 비정질상, 그리고 fcc W$_2$N상으로 변화하였으며, 비정질상이 형성되었을 때 박막 표면이 가장 평탄하였다. $(WN_x)$ 박막이 공기 중에 노출된 경우, 모든 시료 표면에서 $WO_3$ 산화물이 형성되었으며, $N_2$유량비가 증가할수록 $(WN_x)$ 박막내 N의 조성비가 증가하였고, W $4f_{7/2}$ peak가 높은 binding energy 쪽으로 이동하였다. 하지만 시료표면을 $Ar^+$ 이온으로 etching한 후에는 WNx 박막 표면이 비정질화되기 때문에 N의 조성비가 변화함에도 불구하고 $W4f_{7/2}$ / peak가 거의 변화하지 않았다. 박막의 비저항 값은 $N_2$ 유량비가 증가함에 따라 증가하였다.

• 멤브레인
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• 제26권4호
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• pp.291-300
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• 2016

분리막(Separation membrane)을 이용하여 기체 또는 액체상태로 존재하는 분자들을 선택적으로 분리하는 기술은 화학, 생물, 제약, 석유화학 등의 산업에서 매우 다양하게 응용되고 있으며 산업적으로 매우 큰 비중을 차지하고 있다. Anodic aluminum oxide (AAO) 막은 nanochannel의 직경, nanochannel 간의 거리 및 원통형 nanochannel의 길이 등을 정밀하게 조절할 수 있어 AAO 막을 이용하여 혼합분자를 효과적으로 분리하려는 다양한 연구가 진행되고 있다. 본 연구에서는 양 말단이 열려있어 through-hole 구조로 다양한 직경의 nanochannel을 가지는 AAO 막을 제작하였으며, 이것을 이용하여 용매에 녹아있는 고분자 사슬의 수력학적 부피에 따른 선택적 투과를 관찰하였다. Nanochannel을 투과한 고분자 사슬의 회전반지름과 nanochannel의 직경 사이에 정량적인 관계가 있음을 확인하였다. 또한 AAO 막의 nanochannel을 흐르는 고분자 용액의 유동률(flow rate)이 Hagen-Poiseuille 관계식으로 정확하게 설명될 수 있음을 확인하여 AAO 내에 존재하는 원통형태의 nanochannel 내에서 흐르는 용액의 나노흐름(nanoflow)에 대한 이론적 해석이 가능함을 증명하였다.

• 한국정보통신학회논문지
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• 제21권4호
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• pp.698-707
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• 2017

본 논문에서 이동로봇의 기준궤적추적제어를 위한 예측제어방법을 다룬다. 예측제어는 예측모델을 사용하여 기준궤적과 시스템 상태 간의 미래오차들을 최소화시키는 효과적인 제어방법으로 알려져 있으나, 실시간 계산량이 너무 많아 화공정 플랜트와 같이 매우 느린 시스템에 한정되어 적용되었다. 근래에는 컴퓨터 기술 발달로 고속계산이 가능하여 이동로봇과 같은 빠른 시스템에도 예측제어방법이 도입되고 있다. 그런데 예측제어기에서 제어성능과 관계된 제어 파라미터들이 있는데 임의로 지정되어 최적화되지 못하였다. 본 논문에서 이동로봇 예측제어기 성능 개선을 위해 관련 제어 파라미터들을 유전알고리즘으로 최적화시켰고 모의실험을 통해 제어성능이 개선됨을 확인하였다.

• 전력전자학회논문지
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• 제17권6호
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• pp.553-561
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• 2012

Existing energy sources convert chemical energy into mechanical energy, while fuel cell directly generates electricity through an electrochemical reaction between hydrogen and oxygen. Therefore, it has a lot of strong points such as high efficiency, zero emission, and etc. In addition, with the development of hydrogen preservation technique, some companies have been researching and releasing portable fuel cell power packs for specific applications like military equipment, automobile, and so on. However, there are some drawbacks to the fuel cell, high cost and slow dynamic response. In order to compensate these weak points, auxiliary energy storages could be applied to the fuel cell system. In this paper, the optimum structure for a 150W portable fuel cell power pack with a battery pack is selected considering the specification of the system, and the design process of main parts is described in detail. Here, main objectives are compact size, simple control, high efficiency, and low cost. Then, an automatic mode change algorithm, which converts the operating mode depending on the states of fuel cell stack, battery pack, and load, is introduced. Finally, performance of the designed prototype using the automatic mode change control is verified through experiments.

• ETRI Journal
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• 제38권2호
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• pp.265-271
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• 2016

We analyzed the interface characteristics of Zn-based thin-film buffer layers formed by a sulfur thermal cracker on a $Cu(In,Ga)Se_2$ (CIGS) light-absorber layer. The analyzed Zn-based thin-film buffer layers are processed by a proposed method comprising two processes - Zn-sputtering and cracker-sulfurization. The processed buffer layers are then suitable to be used in the fabrication of highly efficient CIGS solar cells. Among the various Zn-based film thicknesses, an 8 nm-thick Zn-based film shows the highest power conversion efficiency for a solar cell. The band alignment of the buffer/CIGS was investigated by measuring the band-gap energies and valence band levels across the depth direction. The conduction band difference between the near surface and interface in the buffer layer enables an efficient electron transport across the junction. We found the origin of the energy band structure by observing the chemical states. The fabricated buffer/CIGS layers have a structurally and chemically distinct interface with little elemental inter-diffusion.

• 한국수산과학회지
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• 제46권5호
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• pp.626-637
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• 2013

We measured the grain size, ignition loss (IL), chemical oxygen demand (COD), acid volatile sulfide (AVS) and trace metals (Al, Fe, Cu, Pb, Zn, Cd, Cr, Mn, Hg, and As) of intertidal surface sediment collected from 11 islands (62 stations) in the southern region of Jeollanam Province. The objective of this research was to evaluate the organic matter and trace metals contaminations of sediments from coastal island tidal flats. Surface sediment texture was characterized as follows: mud, sandy silt, muddy sand, and slightly gravelly sand facies. The finer sediments are mainly dominated in the northern part of each island. The concentrations of IL, COD, AVS and some trace metals (Al, Fe, Zn, Cr, Cu, and Hg) were higher in the northwestern part of Wan Island and the area between Gogeum and Sinji Islands, and were associated with relatively finer sediment, as compared to other locations. The concentrations of Mn, Pb, Cd, and As were higher in the northwestern and southeastern parts of Geoguem and Pyungil Islands, but were not correlated with mean grain size. Based on sediment quality guidelines (SQGs), the concentrations of trace metals were lower than the values of effect range low (ERL), used in United States, and threshold effects level (TEL), used in Korea, with exception of As. Similarly, the intertidal sediments were moderately contaminated with As, based on the the enrichment factor (EF) and the geoaccumulation index ($I_{geo}$). The high concentration of As in intertidal sediments from this study region may be due to the input of naturally or artificially contaminated submarine groundwater, contaminated waste from seaweed aquaculture operations and/or land-based seaweed processing facilities. Further studies are needed to identify the sources of As in this study region, and to determine the effects of As contamination on coastal ecosystem.