• 자원ㆍ환경경제연구
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• 제19권2호
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• pp.341-360
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• 2010

조선산업에서의 수요는 해상물동량이며 공급은 선박의 건조량이다. 따라서 해상물동량에 대한 정확한 예측은 향후 조선산업의 호 불황을 전망할 수 있는 중요한 요인이 된다. 본 연구의 목적은 해상물동량 중 가장 큰 비중을 차지하고 있는 건화물(철광석, 석탄)의 물동량을 전망하는 것이다. 철광석 물동량의 예측을 위하여 조강생산과 세계 GDP를 독립변수로, 석탄 물동량 예측을 위하여 조강생산과 세계 발전량을 독립변수로 하는 회귀식을 도출하였으며, 두 회귀식 모두 통계적으로 유의하다는 결론을 얻었다. 전망 결과, 2010년 철광석 해상물동량은 2009년 대비 5.1% 증가한 8억 9,200만 톤 수준이 될 것으로 전망되었으며, 석탄은 전년대비 6.1% 증가한 8억 2,700만 톤 수준이 될 것으로 전망되었다. 2015년까지의 중기 전망(2009~2015)은 철광석이 연평균 4.7%, 석탄이 6.1%의 증가세를 보이는 것으로 나타났다. 전체 해상물동량에서 가장 비중이 큰 두 화물의 해상물동량에 대한 예측은 향후 해운경가와 조선경기의 향방을 가늠해 볼 수 있는 중요한 정보를 제공한다는 점에서 본 연구의 의미가 있다.

• Journal of Microbiology and Biotechnology
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• 제29권8호
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• pp.1177-1183
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• 2019

Grapefruit seed extract (GSE) is a safe and effective preservative that is used widely in the food industry. However, there are few studies addressing the anti-biofilm effect of GSE. In this study, the anti-biofilm effect of GSE was investigated against biofilm-forming strains of Staphylococcus aureus and Escherichia coli. The GSE minimum inhibitory concentration (MIC) for S. aureus and E. coli were $25{\mu}g/ml$ and $250{\mu}g/ml$, respectively. To investigate biofilm inhibition and degradation effect, crystal violet assay and stainless steel were used. Biofilm formation rates of four strains (S. aureus 7, S. aureus 8, E. coli ATCC 25922, and E. coli O157:H4 FRIK 125) were 55.8%, 70.2%, 55.4%, and 20.6% at $1/2{\times}MIC$ of GSE, respectively. The degradation effect of GSE on biofilms attached to stainless steel coupons was observed (${\geq}1$ log CFU/coupon) after exposure to concentrations above the MIC for all strains and $1/2{\times}MIC$ for S. aureus 7. In addition, the specific mechanisms of this anti-biofilm effect were investigated by evaluating hydrophobicity, auto-aggregation, exopolysaccharide (EPS) production rate, and motility. Significant changes in EPS production rate and motility were observed in both S. aureus and E. coli in the presence of GSE, while changes in hydrophobicity were observed only in E. coli. No relationship was seen between auto-aggregation and biofilm formation. Therefore, our results suggest that GSE might be used as an anti-biofilm agent that is effective against S. aureus and E. coli.

• 대한금속재료학회지
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• 제50권10호
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• pp.753-761
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• 2012

The reduction behavior of low level oxides such as (T.Fe), (MnO) and ($P_2O_5$) in molten EAF slag was investigated using commercial reductants. In an air atmosphere, the slag volume increased and the reduction rate of the slag was very low due to the oxidation loss of reductants by oxygen in the air. The reduction rate of the slag was also low when a commercial reductant was used alone in an Ar gas atmosphere. The reason is probably because the material transfer through the interface between the slag and reductant is difficult due to the formation of high melting point oxide. When reductants were mixed with burnt lime in order to form low melting point reaction products, the reduction rate of the slag increased up to the range of 45-70%. By using the mixtures of reductants and burnt lime so as to form a low melting point slag at the reaction end, the reduction rate of the slag was improved up to 60-85%.

• 한국가금학회지
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• 제44권1호
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• pp.11-18
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• 2017

본 연구는 국내 산란계 동물복지 인증농가의 사육시설 및 사육형태에 따른 기초 사료를 수집하기 위해 수행하였다. 조사를 위하여 동물복지 인증을 받은 64농가에 설문지를 발송하였으며, 이 중 20농가(31.3%)에서 설문지가 회수되었다. 20농가의 사육시설별 현황은 보온덮개계사, 자연농법계사, 판넬철골조계사가 각각 4농가(20%), 7농가(35%), 9농가(45%)였으며, 사육밀도별 현황은 2~3수/$m^2$ 2농가, 4~5수/$m^2$ 10농가, 6~7수/$m^2$ 8농가였다. 사육형태별 현황은 평사 14농가(70%), 방사 3농가(15%), 평사+방사 3농가(15%)였다. 보온덮개계사와 자연농법계사의 사육밀도는 대부분의 농가에서 4~6수/$m^2$ 로 사육하였고, 판넬철골조계사는 9농가 중 7농가에서 6~7수/$m^2$로 사육하였다. 사료섭취량은 20농가 중 11농가(55%)에서 120~130 g을 섭취하였으며, 보온덮개, 자연농법, 판넬철골조계사의 농가 수가 각각 3농가(15%), 3농가(15%), 5농가(25%)이었다. 사육시설별 산란피크는 보통 24~28주령이었고, 산란율 80% 이상의 농가는 보온덮개 75%, 자연농법 56.2%, 판넬철골조계사 67%이었다. 호흡기 질병 발병률이 55%로 가장 높았으며, 보온덮개계사 75%, 자연농법계사 70%, 판넬철골조계사 33%가 발병하였다. 대장균증은 판넬철골조계사에서만 나타났으며, 발병률은 44%였다. 동물복지 인증을 받은 계란(특히 판넬철골조계사) 중 70%가 대형마트나 지역판매장으로 유통되었다. 사육형태에 따른 계란가격은 평사 14농가 중 6농가(42.9%)가 계란 1개당 200~250원으로 계산되었다. 이런 결과들은 현재 동물복지 인증농가의 생산실태를 보여주고 있다.

• 에너지공학
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• 제18권1호
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• pp.49-55
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• 2009

금속의 수소취화는 수소를 사용하는 설비의 안전성을 위협하는 중요한 문제이므로, 수소 환경에서 금속의 취화평가법에 관한 연구의 필요성이 요구되고 있다. 수소사회를 대비하기 위하여 대용량의 수소공급방법에 관한 연구가 진행되고 있는데, 기존의 천연가스 배관을 통한 공급방안이 검토되고 있다. 본 연구에서는 배관 내부에 수소혼합가스가 흐르면 배관모재부 및 용접부의 손상이 우려되므로, 국내에 건설되어 운용되고 있는 X65 천연가스 배관의 모재부를 대상으로 수소취화 거동에 대하여 연구하였다. 재료의 수소침투는 전기분극법을 사용하였으며 강도평가에는 소형펀치시험법을 사용하였다. 수소장입량의 증가에 따라서 금속의 강도가 저하되는 현상이 발견되는 재료도 있으나, 본 연구에 사용한 X65강의 모재부에서 수소취화의 영향은 거의 나타나지 않았으므로 수소영향에 의한 X65강 모재부의 강도저하는 발생하지 않는 것으로 판단된다. 또한 소형펀치시험을 이용함으로써 금속재료의 수소취화에 의한 기계적 강도변화를 평가할 수 있었다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2004년도 ICCAS
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• pp.1953-1957
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• 2004

The machine vision has been applied to a number of industrial applications for quality control and automations to improve the manufacturing processes. In this paper, the automation system using the machine vision is developed, which is applicable to the marking process in a steel production process line. The working environment is very harsh to workers so that the automatic system in the steel industry is required increasingly. The developed automatic marking system consists of several mechanical and electrical elements such as the laser position detecting sensor system for a structured laser beam which is projected to the billet in order to detect the geometry of the billet. An image processing algorithm has been developed to percept the two center positions of a camera and a billet, respectively, and to align two centers. A series of experiments has been conducted to investigate the performance of the proposed algorithm. The results show that two centers of the camera and the billet could be detected very well and differences between two center positions could be also decreased via the proposed tracking algorithm.

• Corrosion Science and Technology
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• 제18권6호
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• pp.258-266
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• 2019

The objective of this study was to evaluate corrosion resistance of additive manufactured 316L stainless steel and alloy 625 powders widely used in corrosion resistance alloys of marine industry in comparison with cast alloys. Directed Energy Deposition (DED) method was used in this work for sample production. DED parameter adjustment was also studied for optimum manufacturing and for minimizing the influence of defects on corrosion property. Additive manufactured alloys showed lower corrosion resistance in seawater compared to cast alloys. The reason for the degradation of anti-corrosion property was speculated to be due to loss of microstructural integrity intrinsic to the additive manufacturing process. Application of heat treatment with various conditions after DED was attempted. The effect of heat treatments was analyzed with a microstructure study. It was found that 316L and alloy 625 produced by the DED process could recover their expected corrosion resistance when heat treated at 1200 ℃.

• 한국생산제조학회지
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• 제19권1호
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• pp.108-113
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• 2010

Decreasing products lifecycles and increasing consumers desires for quality and design make the automotive industries try to reduce time for developing new designs. In order to reduce developing time, I have designed head lamps, which are really important to have an effect on brand identities and images, using layers concept that is one of the international automotive design trends by alias and photoshop, and produced prototype by RP. To assemble the produced prototype to the body and manufacture the frame to exterior modelling efficiently, I have studied on joining dissimilar materials of aluminum alloy that can make the prototype lighter and stainless steel, which is good for corrosion resistance by using laser beam. These materials were welded for finding the optimum joining condition and evaluating the soundness of joining zone. The joining was performed under the condition of laser power 500, 550, 575, 600W and 11~14Hz. In this study, the suitable joining condition between aluminum alloy (Al 2024) and stainless steel (STS 304) can be obtained at the laser power 575W and frequency 12Hz.

• 한국정밀공학회지
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• 제33권6호
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• pp.477-483
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• 2016

The spring-back and bow phenomenon in the roll forming process are important factors regarding the accuracy of evaluation of production goods. The purpose of this study was to determine the influence of spring-back and bow phenomenon according to the main variables (forming velocity and roll gap). The material of the forming sheet was high tension steel (SPFH 590), which has been used commonly in recent years. In order to accurately measure the spring-back and bow phenomenon, the forming sheet was formed into a V-shape. The study was applied to OFAT (One Factor at a Time) experimentation, with respect to the experimental variables (the forming speed and the roll gap). In the experimental results, the forming speed had a small influence on the spring-back and bow phenomenon. However, the roll gap had a greater influence on the springback and the bow phenomenon, as opposed to the forming speed.

• 한국해양공학회지
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• 제28권1호
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• pp.85-92
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• 2014

Offshore fields are increasingly important for the development of offshore resources due to the growing energy needs. However, an offshore field for oil and gas production has difficult development conditions, e.g., high temperature, high pressure, sweet/sour compositions of fluids, etc. Corrosion is one of the biggest issues for offshore pipeline engineering. In this study, a Corrosion Resistant Alloy (CRA) pipe for corrosion prevention was investigated through its global demand and trends, and three types of CRA pipelines were introduced with detailed explanations. The usefulness of CRA was also evaluated in comparison to a carbon steel pipeline in terms of the structural strength, cost, and other factors. Offshore pipeline engineering, including mechanical design and verification of the results through an installation analysis based on numerical software, was performed for the carbon steel type and solid CRA type. The results obtained from this study will be useful data for CRA pipeline designers and researchers.