• Proceedings of the Korea Water Resources Association Conference
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• 2019.05a
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• pp.233-233
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• 2019

본 연구에서는 3형식 다공성 인공어초의 국부세굴 발생에 따른 인공어초의 안정성 검토를 위하여 3차원 수치모형인 FLOW-3D의 Sediment 모듈을 적용하여 분석을 실시하였다. 실험파랑 설정을 위하여 인공어초 설치 예정지인 서해 대상해역(대청도, 연평도 인근)의 100년 빈도 설계파랑을 적용하였으며, Bretschneider-Mitsuyasu 스펙트럼 기법을 통하여 파랑을 재현하였다. 원형상격자 조건은 최대 0.1m~2.0m에 해당하며, 수치모형실험 해석 시간을 고려하여 입사파랑의 진행방향으로 인공어초의 1/2 폭에 해당하는 X축(190개), Y축(80개), Z축(110~180개) 영역에 대한 격자조건 설정하고 분석을 실시하였다. 분석은 인공어초 하중에 따른 동적 거동을 반영하는 FSI(Flood Structure Interaction)기법을 적용하였으며, 분석결과 인공어초 구조물 하단의 돌출부분에서 세굴발생이 확인되었으며, 최대세굴심은 3형식 인공어초의 규격 및 단위체적당 중량이 클수록 높게 발생하였다.

• Proceedings of the Korean Nuclear Society Conference
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• 1997.05b
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• pp.256-261
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• 1997

국내 원전의 사용후핵연료를 경제적으로 수송할 수 있는 대형 수송용기의 국내개발을 위하여 10년의 냉각기간을 갖는 28다발의 PWR 사용후핵연료를 수송할 수 있도록 기본 설계기준을 설정하였다. 이 대형 수송용기에 대하여 개념설계로부터 결정된 차폐두께와 칫수를 기준으로 기본구조를 결정하고 정상수송조건 및 가상사고 조건에 대한 구조해석을 수행하였다. 대형 수송용기는 내부에 많은 양의 PWR 사용후핵연료를 담고 있으므로 이들 핵연료의 중량은 구조설계에 큰 영향을 미치게 된다. 본 연구의 목적은 28다발의 PWR 핵연료를 담은 대형 수송용기가 9m 높이에서 자유낙하하여 충돌사고를 일으켰을 때의 안전성을 파악하기 위한 것이다. 수송용기가 충돌시 충격면에 발생하는 충격력으로 인한 충격완충체의 변형과 충격흡수, 수송용기에 발생하는 응력, 가속도, 충돌력 등의 동적거동을 파악하여 안전성을 입증하였다.

• Prospectives of Industrial Chemistry
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• v.23 no.1
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• pp.18-29
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• 2020

배터리 구동 기기의 사용이 계속적으로 증가하고 첨단화, 다기능화, 융합화가 되면서 고에너지 밀도 배터리에 대한 수요는 지속적으로 증가하고 있다. 배터리의 에너지 밀도를 높이는 여러 가지 전략 중에서 활물질 코팅 두께를 늘려 에너지를 저장하지 않는 집전체와 분리막의 사용량을 줄이고 배터리의 중량, 부피, 그리고 가격을 동시에 줄이는 전략은 간단하면서도 매우 효율적인 방법이다. 하지만 기존 전극 제작 방법으로 후막 전극을 제작할 경우 전극 제작 자체가 쉽지 않고 만들었다고 해도 전자와 이온의 두께 방향 이동 지연으로 인해 전극의 전기화학 특성이 좋지 않다. 이러한 문제점을 극복하고자 이차 전지용 첨단 후막 전극에 대한 연구가 활발하게 진행되고 있다. 본 기고문에서는 이차 전지용 후막 전극의 구조, 제조방법, 전기화학 특성에 관한 연구동향을 소개하고자 한다.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.1
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• pp.25-35
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• 2018

This study presents microstructural characteristics and strength properties of alkali-activated kaolin(K)-fly ash(FA) blends binders. The compressive strength, X-ray diffraction(XRD), thermogravimetric(TG) analysis and SEM/EDS were measured for hardened samples. The results were shown that all the samples had developed the compressive strength over time, regardless of replacement levels of K. It was found that when the amount of K increased, the strengths of samples decreased. In XRD result, no new crystalline phases were observed in all the hardened samples other than the crystalline components of raw FA and K, whereas TG analysis showed that N-A-S-H gel was formed as a reaction product in all the samples. Samples did not have the typical microstructure of dense, and there is little significant difference between the microstructures of the samples despite the differences in the strength testing results with replacement ratios of K. This study showed that the strength of sample was larger for lower Si/Al ratio of reaction product formed in sample. According to the correlation between Si/Al ratio and strength in this study, it is expected that if a chemical additive is used for lowering the Si/Al ratio of reaction product(i.e., increasing the $Al_2O_3$ solubility) in alkali-activated K-FA blends binders, strength improvement in K-FA blends binders could be achieved.

• Journal of the Korean Wood Science and Technology
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• v.28 no.1
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• pp.65-70
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• 2000

Ergosterol is an indicator chemical of fungi and involves in fungal cell growth as a major component in fungal cell membranes. Thus, this chemical can be used to estimate live fungal biomass within various solid substrates. Ergosterol content in liquid culture of Lentinula edodes had a linear relationship (r=0.98) with the hyphal mass of the fungus. This chemical content differed depending on the fungal strains, age of culture and water content levels of sawdust substrate. Ergosterol content was 0.13% in the 10 weeks old liquid culture while it was 0.10% in 20 weeks old one. The chemical content in the sawdust cultures of the fungus varied 0.015% to 0.042% depending upon strains and water content levels within sawdust substrate. Ergosterol content in the culture of a L. edodes strain, Sanrim 4, was higher by $20{\mu}g$ to $140{\mu}g$/g dry substrate than those of strains, Mok-H and Sanrim 6. And the chemical contents in the sawdust cultures with 125% or 175% water, 297 to 425 ${\mu}g$/g dry substrate, were higher than those with 75% or 225% water, 148 to $286{\mu}g$/g dry substrate. We conclude that ergosterol analysis can estimate the fungal biomass within solid substrate such as logs and sawdust.

• Fire Science and Engineering
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• v.25 no.6
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• pp.89-97
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• 2011

This study is for evaluating the fire resistance performance (1~2 h) of the RC Structure void slab using the Lightweight Hollow Sphere, which can reduce the unnecessary dynamic part of removing the central concrete. For this experiment, we set up depth of concrete cover, live load, and span length as the factors. The result comes out with all the slabs under those conditions can ensure the goal fire resistance performance (120 min). And among these factors, the resisting capability changes more sensitively with the live load rather than the thickness of cover. And the shorter span length could assure the better the fire resistance performance. The result observing the character in high temperature of the Lightweight Hollow Sphere which does not used as existing RC structure slab, a delay section in temperature change is occurred due to the Glass Transition in $100^{\circ}C$. And heat transfer by conduction does not occur at lightweight hollow sphere because the polystyrene in EPS (Expanded Polystyrene) melts point in $185^{\circ}C$. Therefore temperature at lightweight hollow sphere is lower than the concrete and rebar.

• Journal of the Korean Society of Propulsion Engineers
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• v.21 no.6
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• pp.64-72
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• 2017

The longitudinal dynamic instability which can occur in the fueling process of a space launch vehicle is called pogo. It is caused by coupling between the fuselage and propulsion system and they would be formed as a closed-loop system. so that the amplitude of the response may increase or decrease. In this paper, a mathematical model which is applicable to the systematic pogo analysis of a general launch vehicle is developed for an example of space shuttle. The formulations are composed of the linearized second-order differential equation for the propulsion system, and of the pressure, weight displacement, and generalized displacement. Those are important parameters for pogo analysis, are derived through eigenvalue analysis. By the formulation suggested in this paper, it is expected that mathematical modeling method of the pogo system can be obtained and systematic pogo stability analysis for any launch vehicle will be enabled.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4D
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• pp.377-386
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• 2010

This study was conducted to find out the characteristics of the expanded road embankment constructed by the lightweight air-mixed soil (slurry density $10kN/m^3$) for a short-term without any ground improvement. Compression strength, capillary rise height of the lightweight air-mixed soil and settlement behavior of soft ground were studied. Compression strengths of the specimens sampled at the site after 1 and 5 months of construction were all satisfied the required strength 500 kPa. However, it was not convinced the homogeneity construction, because the values of strength were depending on the sampled location. Also, strength difference between laboratory and site specimens were found about 19%, and thus it should be considered for mixing design. Capillary rise reached about 20 cm for 70 hours because of a numerous tiny pores existed inside the lightweight air-mixed soil. Relationship between settlement and time of the soft ground placed underneath the expanded embankment was estimated by using the measured data and back analysis technique. The current average consolidation ratio and the final settlement after 120 months later were estimated about 32% and 4.5cm, respectively. This settlement is much less value than the allowable settlement 10cm for this structure.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2004.11a
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• pp.311-316
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• 2004

LMTT (Linear Motor-based Transfer Technology) is a horizontal transfer system for the yard automation. which has been proposed to take the place qf AGV (Automated Guided Vehicle) in the maritime container terminal. the system is based on PMLSM (Permanent Magnetic Linear Synchronous Motor) that consists of stator modules on the rail and shuttle mr. It is desirable to reduce the weight of LMTT in order to control the electronic devices with minimum energy. In this research structural optimization for a mover of shuttle mr is performed to minimize the weight satisfying design criteria the objective function is set up as weight. On the contrary, design variable is considered as transverse, longitudinal and wheel beam's thickness and shape variable determining the dimension toward high direction and the constraints are the stresses.

• Journal of the Korea Concrete Institute
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• v.26 no.1
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• pp.35-46
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• 2014

Two types of cast-in-place concrete-filled hollow PC (HPC1, HPC2) columns were developed to reduce lifting load of heavy-weight PC columns and to improve the structural integrity of joints. To form the hollow PC columns, a couple of prefabricated PC panels was used for HPC1, and special hoops were used for HPC2. Lateral pressure of wet concrete on PC faces was measured while placing the concrete inside the columns. To evaluate the seismic resistance, full scale specimens of two HPC columns and a conventional RC column were tested under combined axial compression and lateral cyclic loading. The test results showed that the structural performance of the proposed HPC columns such as intial stiffness, maximum strength, and displacement ductility was comparable to that of the conventional RC column, but the energy dissipation of HPC2 slightly decreased after rebar-buckling. However, all the test specimens satisfied the energy dissipation requirement specified in ACI 374.