• Resources Recycling
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• v.25 no.3
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• pp.55-62
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• 2016

Steel structures exposed to extremely corrosive environment like marine environments and industrial area are generally manufactured by applying various protection treatment to increase their lifetime. Metal spraying is one of the protection methods to overcome some drawbacks of the widely employed technologies. Therefore, lots of research needs to be done to improve the corrosion resistance of steel structures. In this study, the corrosion resistance of steel structures was evaluated with the variation in the type and thickness of metal spray by measuring the corrosion potential and current density. As a raw material for spraying, Zn, Al and their mixture were employed to obtain coating thickness of $30{\sim}100{\mu}m$. Our data indicated that the pure zinc coating with $100{\mu}m$ showed the lowest corrosion potential. In the case of pure Al and Zn 85%-Al 15%, the corrosion potential and current density was decreased compared to pure zinc. It was found that the corrosion potential was decreased with the increase of coating thickness irrespective of the type of the coating.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.5
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• pp.618-625
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• 2018

With the passing of time, exposed concrete structures are affected by a range of environmental, chemical, and physical factors. These factors seep into the concrete and have a deleterious influence compared to the initial performance. The importance of identifying and preventing further performance degradation due to the occurrence of deterioration has been greatly emphasized. In recent years, evaluations of the target life have attracted increasing interest. During the freezing-melting effect, a part of the concrete undergoes swelling and shrinking repeatedly. At these times, chloride ions present in seawater penetrate into the concrete, and accelerate the deterioration due to the corrosion of reinforced bars in the concrete structures. For that reason, concrete structures located onshore with a freezing-melting effect are more prone to this type of deterioration than inland structures. The aim of this study was to develop a high performance mortar mixed with a mineral admixture for the durability properties of concrete structures near sea water. In addition, experimental studies were carried out on the strength and durability of mortar. The mixing ratio of the silica fume and meta kaolin was 3, 7 and 10 %, respectively. Furthermore, the ultra-fine fly ash was mixed at 5, 10, 15, and 20%. The mortar specimens prepared by mixing the admixtures were subjected to a static strength test on the 1st and 28th days of age and degradation acceleration tests, such as the chloride ion penetration resistance test, sulfuric acid resistance test, and salt resistant test, were carried out at 28 days of age. The chloride diffusion coefficient was calculated from a series of rapid chloride penetration tests, and used to estimate the life time against corrosion due to chloride ion penetration according to the KCI, ACI, and FIB codes. The life time of mortar with 10% meta kaolin was the longest with a service life of approximately 470 years according to the KCI code.

• 한국신재생에너지학회:학술대회논문집
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• 2010.06a
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• pp.131.2-131.2
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• 2010

SOFC 발전 시스템은 친환경 고효율 에너지 발전 미래 에너지기술로서 개발의 초점이 되고 있다. SOFC는 연료전지 발전 기술 중 최고효율과 최장 수명을 가지며 유일하게 기존 발전기술과 가격 경쟁이 가능한 것으로 알려지고 있다. 현재 분산 발전용으로 개발이 진행되고 있으며 향후 중앙발전, 휴대용, 가정용 및 수송용 등으로 그 시장이 확대될 것으로 예상된다. 분산 발전 SOFC 개발을 위해서는 시스템 Scale-up이 기술 확보가 관건이며 특히 스택 제조 비용의 2/3 이상을 차지하는 대면적 단전지 제조 공정 기술 개발이 필요하다. 단전지 대면적화는 원가 절감 및 성능 개선을 기대할 수 있게 하므로 분산 발전 SOFC 상용화를 위한 핵심 기술이라 할 수 있다. 그러나 기존의 국내 SOFC 연구는 시스템이나 소형 단전지 위주로 진행되어 왔으며 대면적 단전지 제조를 위한 핵심 공정 기술에 대한 연구는 취약한 상황이다. 또한 랩스케일의 소규모 연구를 뛰어넘는 양산 기술 개발에 대한 연구는 전무한 실정이다. 또한 재료 및 공정 적합성을 요구하는 대면적 SOFC 단전지의 양산 기술 개발을 위해서는 원료 분말 및 기초소재의 국산화를 통한 제조 공정 윈도우를 확대하여 제조 수율을 향상하는 것이 매우 중요하다. 본 논문에서는 그동안 포스코파워(주)에서 대면적 SOFC 단전지 양산 기술 개발을 위해 추진 중인 $400cm^2$급 대면적 SOFC 단전지의 제조 및 성능에 대한 연구 결과를 발표하고자 한다. 또한 대형 단전지 제조 공정의 재현성, 상용화 수준의 성능, 내구성 및 경제성 확보를 위한 공정 개선을 위한 포스코파워(주)의 연구 현황 및 양산 기술 확보를 위한 제조 윈도우 확보 전략에 대해 발표하고자 한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.2
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• pp.943-948
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• 2013

In this study, the characteristics of polymer-modified mortar which include UM resin, eco-friendly resin, was studied for improving the durability of concrete. UM and cement mortar were mixed with a certain percentage. Eco-friendly UM resin polymer-modified mortar was evaluated by compressive strength, splitting tensile strength, flexural strength, water absorption and chemical resistance experiments. The characteristics of eco-friendly UM resin polymer-modified mortar were evaluated by experiments. Performance of compressive strength and splitting tensile strength were decreasing. On the other hand, performance of flexural strength, water absorption and chemical resistance were increasing. Eco-friendly UM resin polymer-modified mortar reinforced concrete durability performance is excellent.

• Journal of the Korea Institute of Military Science and Technology
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• v.1 no.1
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• pp.154-165
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• 1998

In this paper, the mongrel singular element with 6 node triangle and 8 node quadrilateral element with J-integral are developed and applied to the various plane crack problems for the isotropic material. The convergence nature is excellent for various crack size with even coarse mesh using the direct method. But the results of the mongrel element with J-integral are worse than the former's ones. Fracture tests were conducted on precracked CT specimens. Results show that, for 7075-T6 aluminum wing spar materials, the fracture toughness is 31.06 ksi.inch $\frac{1}{2}$ in the L-T direction.

• Composites Research
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• v.30 no.6
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• pp.399-405
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• 2017

We manufactured the long fiber-reinforced thermoplastic prototype of under cover using in-line compounding technology, and investigated the formability, mechanical properties and durability of the prototype of under cover. We manufactured the injection mold for the prototype through injection molding analysis and consideration of weight reduction. We investigated the formability of the prototype by evaluating the residual length and dispersion of fiber, and also tested the mechanical properties such as flexural strength, stiffness and impact strength. We investigated the durability of the prototype by the Key-Life Test(KLT) method which is generally used for the automotive interior parts.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.8 no.5
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• pp.1173-1178
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• 2007

A laboratory investigation is conducted to characterize and quantity fatigue life of continuously reinforced concrete pavement with initial cracks. Four specimens scaled were made based on results of finite-element analyses and stress-strain curve comparisons. Static tests were firstly performed to obtain magnitudes of static failure loads and to predict crack patterns before fatigue tests. The fatigue lives measured in the study were compared based on the initial crack spacing. The comparison indicates that the fatigue lives of most specimens increases with increasing the initial crack spacing. The results obtained in the study can be used for maintenance and retrofit of the continuously reinforced concrete pavements.

• Journal of the Korean Society for Railway
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• v.14 no.5
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• pp.425-432
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• 2011

Concrete was identified as the significant GHG emission source resulting from a GHG emission analysis of railway infrastructure. An environmental assessment method (life cycle assessment; LCA) and low carbon railway infrastructure design strategy development method (ECODESISGN PILOT) were applied to develop low carbon railway infrastructure design strategies. The railway infrastructure was analyzed as a raw material intensive industry emitting large amount of greenhouse gas (GHG) at its construction stage. Therefore, in this study, it is analyzed that current status of GHG emission at its construction stage, and a method reducing GHG emission of railway infrastructure is proposed. In this study, eco-concrete, concrete aging prevention agent and a low carbon railway route decision method based on a need of low carbon railway infrastructure construction technology application for green railway development were considered.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.342-342
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• 2007

원자층 증착(Atomic Layer Deposition: ALD) 방법은 반응물질들을 펄스형태로 챔버에 공급하여 기판 표면에 반응물질의 표면 포화반응에 의한 화학적 흡착과 탈착을 이용한 박막증착기술이다. ALD법은 박막의 조성 정밀제어가 쉽고, 파티클 발생이 없으며, 대면적의 박막 증착시 균일성이 우수하고, 박막 두께의 정밀 조절이 용이한 장점이 있다. 원자층 증착 공정에서 짧은 시간 안에 소스를 충분히 공급하기 위한 방법으로는 소스 온도를 증가시켜 전구체의 증기압을 높여 반응기로의 유입량을 증가시키는 방법, 전구체의 공급시간을 늘리는 방법 등을 들 수 있다. 그러나 전구체 온도를 상승시키는 경우, 공정 조건의 변화가 요구되며 전구체의 변질에 의하여 형성된 막이 의도하는 막 특성을 만족시키지 못하게 되는 문제점이 발생될 우려가 있다. 그리고 전구체를 충분히 공급하기 위하여 전구체의 공급시간을 늘이는 방법을 사용하면, 원하는 두께의 막을 형성하기 위하여 소요되는 공정시간이 증가된다. 이를 해결하기 위해 수송가스를 이용한 버블러 형태의 전구체 공급 장치를 사용하지만 이 또한 전구체의 수명을 단축시키는 단점을 가지고 있다. 본 논문에서는 위의 문제점을 극복할 수 있는 새로운 개념의 수송가스 도움 전구체 공급 장치를 소개한다. 본 연구에서 사용된 수송가스 도움 전구체 공급 장치를 가지는 ALD 장비는 Lucida-D200 (NCD Technology사)이며 기판으로는 8인치 실리콘 웨이퍼를 사용하였으며 (TEMA)Zr을 사용하여 ZrO2 박막을 성장하였다. 수송가스 도움 전구체 공급 장치를 사용한 경우, 그렇지 않은 경우 보다 $30^{\circ}C$ 이상 전구체 온도를 낮출 수 있으며, 또한 증착 속도를 약 2배정도 증가시킬 수 있었다. 이들 박막들은 XRD, XPS, AFM 등을 이용하여 결정구조, 결합에너지, 표면 거칠기 등의 특성을 관찰하였다. 그리고 C-V, I-V 측정을 이용해 정전용량, 유전율, 누설전류 등의 전기적 특성을 평가하였다.

• Korean Journal of Metals and Materials
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• v.47 no.12
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• pp.834-841
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• 2009

A study on the welding of electrogalvanized TRIP (Transformation-Induced Plasticity) steels was done to compare the life of the electrode and the alloying phenomena on the electrode tip surface using singlephase AC and inverter-DC resistance welding processes. A longer life of the electrode (>200 welds) was achieved using the inverter-DC welding process. The tensile shear strength was higher in the electrode life test when welded with the inverter DC welding machine it maintained a higher value even when the welding nugget diameter was smaller than specified. When spot-welding was conducted using the single-phase AC welding process, a higher wear rate of the electrode was observed compared to that with the inverter-DC process. An alloying layer used to determine the rate of electrode growth showed differences in the metallurgical features of the surface alloying and Zn penetration depending on whether the single-phase AC process or the inverter-DC welding process was used. Moreover, changes in the dynamic resistance during the electrode life test were correlated with the electrode wear (or growth) rate.