• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.4
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• pp.660-666
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• 1998

We discussed structure, energy state, characteristics of thermal stability, and electrochemical properties of Li-GFICs, Li-PCICs, and Li-AGICs during the intercalation process. According to X-ray diffraction patterns, we observed phase of stage 2 mainly from Li-GFICs, while stage 1 phase as well as stage 2 from Li-PCICs. For the structure of Li-AGICs, stage 1 phase was dominant, but it was not possible to obtain pure stage 1 compound probably due to structural characteristics of artificial graphite. We measured energy state of the compounds to stage stability, and revealed that Li-AGICs and Li-GFICs were in more stable state than Li-PCICs. Therefore, those two compounds could be excellent candidate for energy reserve material. From the study of thermal degradation, Li-GFICs showed strong exothermic reaction at around 300 and $400^{\circ}C$. In the study of thermal stability of Li-AGIC at various temperatures, we observed that lithium was not completely deintercalated and high stage was maintained even at high temperature. In the case of charge, discharge, and electrochemical studies, Li-GFICs showed the best results.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.29 no.4
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• pp.160-166
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• 2019

Cerium oxide ($CeO_2$, often called as Ceria) is one of the valuable rare earth oxide materials, which has been widely used for high temperature applications such as solid oxide fuel cells, automotive three-way catalysts and oxygen storage capacity. Considering those application, it is important to improve high redox and thermal stability with high surface morphology because the high surface area of $CeO_2$ could improve the catalytic reactivity at high temperature conditions. Herein we successfully fabricated hierarchical flower-like $CeO_2$ deposited via controlling pathway of precipitation reaction to supply carbonate ion lead to the flower-like morphology. The hexagonal lattice system of precipitated precursor shows better thermal stability then orthorhombic one during thermal cycling condition.

• Journal of the Korean Society for Railway
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• v.19 no.6
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• pp.717-726
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• 2016

Emergency tracks are necessary in case a broken down train evacuates, a train needs to make way for a faster train behind it, or a train suddenly stops and following trains must avoid colliding with it. Magnetic Levitated (maglev) Trains can change track to enter an emergency track using a segmented switch or a traverse switch. On a traverse switch, a train can change its track when the part of the track that the train is on moves to the other track. Currently manufactured Maglev trains have two bodies and the total length is 25 meters. If a traverse switch is used, it will only require 30 meters of track to move the train to the other track, so, when it comes to efficiency of costs and space, the traverse switch surpasses the articulated switch. Therefore, in this paper, an optimized design to secure structural safety and weight lightening is suggested. To achieve these results, the heights of the piled concrete and girders which are both placed on the top of the traverse switch, are set as design variables. The Finite Element Method (FEM), in application of kriging and in the design of the experiments (DOE), is used. Maximum stress, deformation, and structural weight are compared with the results, and through this process structural safety and weight lightening is proven.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.133-138
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• 2003

As concrete structures are heated, thermal strain can be developed. Because of the boundary conditions, the thermal stress may be arisen. Thermal strain and temperature were measured simultaneously using an optical fiber sensor. Fiber Bragg Grating Sensor(FBG sensor) was used in the measurement. Because it can measure the strains more than two points with one line, it was possible to measure both thermal strain and temperature with one line. To compare data measured by FBG sensor, strain and temperature were measured using strain gauge and thermocouple. The FBG sensor could measure the strain under the temperature greater than $60^{\circ}C$ but strain gauge couldn't. Both the FBG temperature sensor and thermocouple could measure the temperature and the results are related each other linearly.

• Journal of the Korean Society of Propulsion Engineers
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• v.10 no.4
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• pp.69-76
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• 2006

Elastic-viscoplastic structural analysis has been performed for regenerative cooling chamber of liquid rocket thrust chamber using Bodner-Partom visco-plastic model. Strain rate test was conducted for a copper alloy at various temperatures in order to get material constants of visco-plastic model used in the structural analysis. Material constants of visco-plastic model were obtained from strain rate test results and visco-plastic model was incorporated into finite element program, Marc, by means of a user subroutine. The structural analysis results indicated that the deformation of cooling channel is mostly caused by thermal loading rather than pressure loading and confirmed structural stability of the cooling channel under the operating condition.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.12
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• pp.109-116
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• 2005

Elastic-plastic structural analysis for regenerative cooling chamber of liquid rocket thrust chamber is performed. Uniaxial tension test is also conducted for the copper alloy in order to get material data necessary for the structure analysis. The results of uniaxial tension test reveal that copper alloy become ductile after brazing process and flow stress becomes lower as temperature becomes higher. As a result of structural analysis using the material data, the deformation of cooling channel is more increased by thermal load than by internal pressure of cooling fluid. Therefore, the results of analysis show that structural stability and cooling performance of combustion thrust chamber which is designed to endure mechanical load and minimized a channel thickness are improved by decreased thermal load as possible.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.7 no.4
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• pp.76-81
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• 2008

A cryogenic butterfly valve is used to transfer the liquefied natural gas (LNG) which temperature is $-162^{\circ}C$. This valve is core part in the piping system using LNG. This paper performed coupling analysis using FEM to evaluate safety of cryogenic butterfly valve. Flow analysis is calculated numerically the CAE and CFD methods are useful to predict the thermal matter and the inner flow field of the valve. Thermal analysis and structural analysis used ANSYS Workbench.

• Journal of the Korean Society of Propulsion Engineers
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• v.22 no.6
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• pp.126-133
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• 2018

A liquid rocket engine experiences various static loads in flight, such as high pressures due to propellents, thrust and thermal loads due to cryogenic liquid oxygen and combustion gas with extreme vibration. During the engine development stage, structural analyses and investigation on the strain measured from ground firing tests are necessary for determining the structural reliability of the engine. In this study, the strain characteristics, obtained from the ground firing tests of a 75 tonf-class engine, were analyzed.

• Journal of the Korean Geosynthetics Society
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• v.13 no.4
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• pp.45-56
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• 2014

Frozen ground in cold region consists of an upper active layer and lower permafrost which is permanently frozen land. During the summer season, the air temperature is high enough to make the frozen ground melt, which causes the reduction of soil strength and thaw settlement. These phenomena result in structural instability, so it is necessary to apply frozen ground stability techniques. Thermosyphon is a closed natural two-phase convection device to maintain the ground temperature below $0^{\circ}C$ by extracting heat from the ground and discharges it into the atmosphere. Experimental and numerical investigation has been performed to estimate the effect of the refrigerant filling ratio in thermosyphon using R-134a refrigerant and the thermal conductance of the thermosyphon.

• Proceedings of the Membrane Society of Korea Conference
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• 1995.04a
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• pp.58-59
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• 1995

기체 분리용 무기분리막은 고분자막과 비교하여 열 및 구조적 안정성이 우수하므로, 석탄가스화반응 혼합기체중의 기체분리 등 고온 또는 고압공정에 적합한 분리방법으로서 주목되고 있다. 기체의 분리를 위한 무기재료막은 크게 다공성막과 비다공성막으로 나눌 수 있으며, 이 중 비기공 성막의 경우 높은 선택도를 가지나 투과도가 낮아 경제성이 떨어지는 것으로 평가되고 있다. 한편, 기존의 다공성막의 경우 투과도는 높으나 기체의 분리가 혼합기체중 각 기체의 분자량의 차이에 의존하는 Knudsen 확산에 제한되는 낮은 선택도를 갖는 단점이 있다. 따라서 다공성막의 기공을 특정기체의 선택도가 우수한 촉매물질등으로 개선하여 비기공성막에 비해 우수한 투과도를 갖고, 기공성막에 비해 향상된 선택도를 보이는 복합막의 연구가 활발히 추진되고 이\ulcorner. 본 연구는 솔젤법에 의해 제조된 팔라듐 함침 알루미나 지지막의 기공을 침투$\cdot$증착(Soaking and Vapor-deposition)법에 의해 개선하여 기체의 투과도를 높게 유지하면서 수소의 선택성을 향상시키는 것을 목적으로 하였다.