• Proceedings of the Korean Institute of Building Construction Conference
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• 2021.05a
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• pp.138-139
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• 2021

The MiDF Cement Composite is a high-performance construction material with low defects that dehydrates surplus water through pressurization and minimizes air gap between particles. In other words, the performance expression of the MiDF cement complex is affected by pressurized conditions. Thus, this study analyzed the physical characteristics of MiDF cement complex according to the power and pressure of the ga-power and the time of application and intends to use it as a basic data for optimal mixing.

• Proceedings of the Plant Resources Society of Korea Conference
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• 2020.08a
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• pp.10-10
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• 2020

전 지구적으로 생물다양성의 지속적인 감소 추세에 따른 생물자원의 중요성이 증가하는 시점에서, 식물 유전자원의 종 다양성 보존과 지속가능한 이용을 위한 체계적이고 현실적인 방안 마련이 절실한 실정이다. 국내에서도 2017년에 유전자원 접근 및 이익 공유에 대한 나고야 의정서가 발효됨에 따라 식물유래 BT산업 소재의 국내 자급이 불가피해진 상황이며, 더불어 국토의 생태복원에 적합한 식물 소재 개발의 중요성이 대두되면서 자생식물의 종자 수급기반 대책은 국가적 차원에서 중대한 과제라 할 수 있다. 우리나라는 면적 대비 높은 식물 종 다양성을 보이며, 이는 종자의 휴면유형 또한 다양하고 복잡할 수 있다는 것을 의미한다. 따라서 식물유전자원으로써의 보존 및 국가 경제적 이익을 위한 종자 활용, 산업화를 위해서는 종자의 생리적 특성에 기반 한 데이터베이스의 축적과 효과적인 활용을 위한 종자 휴면유형 분류 및 적정 휴면타파 조건을 확립할 필요가 있다. 현재까지 다양한 식물종에서 종자 휴면의 하위 카테고리가 계속적으로 세부 분류되고 있으나, 아직까지 밝혀지지 않은 세부 휴면유형에 의해 많은 유용 식물자원의 활용이 제한적이다. 종자의 휴면유형은 크게 외생휴면(Exogenous dormancy)과 내생휴면(Endogenous dormancy)으로 분류되며, 국내에서는 내생휴면에 대한 연구가 주를 이루고 있다. 한편 외생휴면은 물리적 휴면(Physical dormancy), 기계적 휴면(Mechanical dormancy) 및 화학적 휴면(Chemical dormancy)으로 세부 분류되며, 기계적 휴면과 화학적 휴면은 내생휴면인 생리적 휴면(Physiological dormancy)에 포함되어야 한다는 의견도 있다. 물리적 휴면 종자에서는 water-gap 복합체의 존재 등에서 원인을 찾을 수 있으나, 발아억제 호르몬에 기인하는 화학적 휴면 및 종(과)피 또는 배유에 의한 기계적 휴면은 배의 성장잠재력과 발달에 의해 타파될 수 있다. 이와 같이 실제로 많은 식물 종에서 다양하게 존재하는 외생휴면 유형에 대해 내생휴면과는 명확히 다른 방식으로 접근되어야 하므로, 다년간의 체계적 연구를 통해 미흡한 종자생리 연구 분야를 보완하고 자생식물의 종자 활용도를 높일 수 있을 것으로 기대한다.

• Clean Technology
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• v.27 no.4
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• pp.291-296
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• 2021

Recently, there has been increasing demand for advancing photocatalytic techniques that are capable of the efficient removal of organic pollutants in water. TiO₂, a representative photocatalytic material, has been commonly used as an effective photocatalyst, but it is rather expensive and an alternative is required that will fulfill the requirements of both high performing photocatalytic activities and cost-effectiveness. In this work, ZnO, which is more cost effective than TiO₂, was synthesized by using a microreactor-assisted nanomaterials (MAN) process. The process enabled a continuous production of ZnO nanoparticles (NPs) with a flower-like structure with high uniformity. In order to resolve the limited light absorption of ZnO arising from its large band gap, Ag NPs were uniformly decorated on the flower-like ZnO surface by using the MAN process. The plasmonic effect of Ag NPs led to a broadening of the absorption range toward visible wavelengths. Ag NPs also helped inhibit the electron-hole recombination by drawing electrons generated from the light absorption of the flower-like ZnO NPs. As a result, the Ag-ZnO nanocomposites showed improved photocatalytic activities compared with the flower-like ZnO NPs. The photocatalytic activities were evaluated through the degradation of methylene blue (MB) solution. Scanning electron microscopy (SEM), x-ray diffraction (XRD), and energy-dispersive x-ray spectroscopy (EDS) confirmed the successful synthesis of Ag-ZnO nanocomposites with high uniformity. Ag-ZnO nanocomposites synthesized via the MAN process offer the potential for cost-effective and scalable production of next-generation photocatalytic materials.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.28 no.3
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• pp.95-120
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• 2023

Methane (CH₄) is a key greenhouse gas in the atmosphere with 85 times greater greenhouse potent relative to carbon dioxide (CO₂). The atmospheric concentration of CH₄ is rapidly increasing due to the intensive usage of CH₄ and the thawing of the cryosphere. Additionally, with the current warming of ocean water, the dissociation of gas hydrates, an ice-like compound and the largest reservoir of CH₄ on Earth, is expected to occur, resulting in the release of CH₄ from the seafloor into the overlying water and atmosphere. Moreover, bottom water hypoxia is another concern that potentially introduces greenhouse gases into the atmosphere. With ongoing global warming and eutrophication, the size and duration of bottom water hypoxia are rapidly increasing. These low-oxygen conditions would relocate the redox zone shallower in sediment or in the water column, causing the release of CH₄ into the atmosphere and thereby intensifying global warming. However, there exists a gap in the understanding of CH₄ dynamics including its generation in relation to bottom water hypoxia. Therefore, this review article aims to understand the relationship between CH₄ and bottom water hypoxia and to draw attention to CH₄ investigation in Korea.

• The Journal of Engineering Geology
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• v.27 no.3
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• pp.331-343
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• 2017

In this study to improve stability, workability and economics of the H-Pile+Earth plate or H-Pile+Earth plate+Cutoff grouting currently in use, we had developed HCS method belonging to the retaining wall which is consisting of a combination H-Pile, Plastic Sheet Pile and Steel Square Pipe for gap maintenance and reinforcement of flexible plastic Sheet Pile, and the behavior of each member composing HCS method is investigated by three-dimensional finite element analysis. To numerically analyze the behavior of the HCS method, we have performed extensive three-dimentional finite element analysis for three kinds of plastic Sheet Pile size, two kinds of H-Pile size and three kinds of H-Pile installation interval, one kinds of Steel Square Pipe and three kinds of Steel Square Pipe installation interval. After analyzing the numerical results, we found that the combinations of $P.S.P-460{\times}131.5{\times}7t$ (PS7) and H-Pile $250{\times}250{\times}9{\times}14$ (H250), $P.S.P473{\times}133.5{\times}9t$ (PS9) and H-Pile $300{\times}200{\times}9{\times}14$ (H300) is the most economical because these combinations are considered to have a stress ratio (=applied stress/allowable stress) close to that as the stiffness of H-Pile, plastic Sheet Pile and Steel Square Pipe composite increased, the horizontal displacement of the retaining wall and the vertical displacement of the upper ground decreased. Especially, due to the arching effects caused by the difference in stiffness between H-Pile and plastic Sheet Pile, a large part of the earth pressure acting on plastic Sheet Pile caused a stress transfer to H-Pile, and the stress and displacement of plastic Sheet Pile were small. Through this study, we can confirm the behavior of each member constituting the HCS method, and based on the confirmed results of this study, it can be used to apply HCS method in reasonable, stable and economical way in the future.