• Journal of Korean Tunnelling and Underground Space Association
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• v.9 no.3
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• pp.299-307
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• 2007

In this study, a new concept for simulating a physical damage of tunnel shotcrete lining due to a long-term chemical deterioration has been proposed. It is known that the damage takes place mainly by internal cracks, reduction of stiffness and strength, which results mainly from volume expansion of the lining and corrosion of cement materials, respectively. This damage mechanism of shotcrete lining appears similar in most kinds of chemical reactions in tunnels. Therefore, the mechanical deterioration mechanism induced by a series of chemical reactions was generalized in this study and mathematically formulated in the framework of thermodynamics. The numerical model was implemented to a 3D finite element code, which can be used to simulate behaviour of tunnel structures undergoing external loads as well as chemical deterioration in time. A number of illustrative examples were given to show a feasibility of the model in tunnel designs.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2009.11a
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• pp.483-484
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• 2009

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.4
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• pp.61-68
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• 2017

Bridge decks are members that rapidly deteriorated due to various environmental factors such as heavy vehicle and deicing salt, etc. As the lifespan of bridges built in Korea increases, it is expected that the demand for replacing the deteriorated bridge decks will increase. In other countries, Accelerated Bridge Construction technology using precast decks is already actively being used as a countermeasure for replacement demand of deteriorated bridge decks. In this study, bridge decks deterioration models are proposed by collecting and analysing the condition index data of domestic bridge decks. Also, the future replacement demands of deteriorated bridge decks in terms of replacement time and replacement scale are predicted.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.16 no.4
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• pp.173-179
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• 2023

This paper analyzes the time-dependent dielectric breakdown(TDDB) degradation mechanism for each stress region of Peri devices manufactured by 4th generation VNAND process, and presents a complementary lifetime prediction model that improves speed and accuracy in a wider reliability evaluation region compared to the conventional model presented. SiON dielectric nMOSFETs were measured 10 times each under 5 constant voltage stress(CVS) conditions. The analysis of stress-induced leakage current(SILC) confirmed the significance of the field-based degradation mechanism in the low electric field region and the current-based degradation mechanism in the high field region. Time-to-failure(TF) was extracted from Weibull distribution to ascertain the lifetime prediction limitations of the conventional E-model and 1/E-model, and a parallel complementary model including both electric field and current based degradation mechanisms was proposed by extracting and combining the thermal bond breakage rate constant(k) of each model. Finally, when predicting the lifetime of the measured TDDB data, the proposed complementary model predicts lifetime faster and more accurately, even in the wider electric field region, compared to the conventional E-model and 1/E-model.

• Proceedings of the Materials Research Society of Korea Conference
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• 2012.05a
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• pp.100.1-100.1
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• 2012

태양전지 모듈의 25년 이상 장기간 정상 발전을 위해 태양전지 모듈을 구성하는 부품 소재의 장기 열화메커니즘 연구가 중요시되고 있다. 결정질 및 박막 태양전지 모듈 내 셀을 보호하기 위한 봉지재(Encapsulation)로 다양한 폴리머 재료가 적용되고 있다. 봉지재 부품으로 적용되고 있는 에틸렌 비닐 아세테이트(Ethylene Vinyl Acetate, EVA)는 장기 열화특성 및 내구성 개선 연구가 중요하다. 따라서 EVA를 가속열화하여 열화메커니즘 분석과 25년 보증 내구성을 보유하고 있는지 연구가 필요하다. 본 연구에서는 EVA의 Ultraviolet(UV), 온도 복합 환경스트레스 조건을 적용한 가속시험을 수행하고 장기 열화메커니즘을 분석하였다. 수명 및 손상모델을 이용하여 실환경에서 변화하는 UV와 온도를 일정한 값으로 나타낼 수 있는 UV/온도 가속조건을 설계하였다. 이를 통해 UV/온도 가속조건을 설정하였고 1년 및 25년 동안 EVA에 인가되는 stress와 유사한 양을 인가할 수 있는 시험시간을 결정하였다. 시험 후 전자현미경, AFM, FT-IR, TGA, DSC 등의 분석을 통해 열화메커니즘을 도출하였다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.665-668
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• 2011

철근콘크리트 구조물은 타설 후 시간이 경과함에 따라 물리적인 요인과 화학적인 요인으로 인하여 열화가 발생한다. 열화를 고려한 구조해석에서 모든 열화 관련 변수를 고려하는 것은 비효율적이다. 따라서 구조물의 거동과 밀접한 관련이 있는 중요열화변수를 정의하는 것이 필요하다. 본 연구에서는 철근콘크리트 전단벽의 경년열화 해석시 중요변수를 고려하기 위하여 민감도해석을 수행하였다. 해석결과에 의하면 재료의 경화와 관련한 변수들이 열화와 관련한 변수들보다 지진응답이 민감하게 나타났다. 해석모델의 낮은 철근비로 인하여 콘크리트의 탈락에 의한 지진응답의 변화보다 철근의 단면손실에 의한 지진응답의 변화가 크게 나타났다. 만약 원전과 같이 철근비가 높은 전단벽에서는 철근의 단면손실도 지진응답에 대한 중요변수가 될 수 있을 것으로 사료된다.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.12
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• pp.525-534
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• 2023

Gas leak detection system is a key to minimize the loss of life due to the explosiveness and toxicity of gas. Most of the leak detection systems detect by gas sensors or thermal imaging cameras. To improve the performance of gas leak detection system using single-modal methods, the paper propose multimodal approach to gas sensor data and thermal camera data in developing a gas type identification model. MultimodalGasData, a multimodal open-dataset, is used to compare the performance of the four models developed through multimodal approach to gas sensors and thermal cameras with existing models. As a result, 1D CNN and GasNet models show the highest performance of 96.3% and 96.4%. The performance of the combined early fusion model of 1D CNN and GasNet reached 99.3%, 3.3% higher than the existing model. We hoped that further damage caused by gas leaks can be minimized through the gas leak detection system proposed in the study.

• Proceedings of the KIPE Conference
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• 2020.08a
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• pp.377-378
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• 2020

본 논문에서는 열화에 따른 하이브리드 차량의 연비 특성을 분석하기 위해 시뮬레이션을 통한 연구를 진행하였다. 전기적 특성 실험 기반으로 배터리 내부 파라미터가 열화에 어떤 영향을 미치는지 분석을 하고 이를 기반으로 하이브리드 차량모델을 통해 시뮬레이션을 진행하였다. 분석 결과를 통해 배터리 열화 상태에 따른 State-Of-Charge (SOC) 및 연비효율 그래프의 변화 추이를 비교하였다.

• The Journal of the Convergence on Culture Technology
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• v.8 no.3
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• pp.239-244
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• 2022

In this study, the key parameters affecting the deterioration of each track type were derived based on field inspections and laboratory tests. The existing track deterioration model was limited to the ballasted tracks, and the deterioration evaluation of concrete tracks was insufficient. In this study, the laboratory test was performed to evaluate the performance and condition of track components to derive the deterioration factors reflecting the characteristics of various track structures. In addition, through analysis of track maintenance history data, parameters affecting track deterioration and maintenance were derived. The key parameters for presenting a track deterioration model based on the track performance of ballasted and concrete tracks through field inspection, track maintenance history data analysis, and performance test of track components using on-site specimens were identified as track support stiffness, Ballast gravel, track settlement and Resilience pad were presented.

• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.1
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• pp.45-50
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• 2002

Use of a phenomenological model, developed far prediction of catalytic deactivation, is demonstrated in comparing harshness of different driving cycles that are currently used to rapidly age catalytic converters on engine test benches. The model shows that seemingly equivalent driving cycles cause the catalytic converters to reach significantly different levels of deactivation. The comparison of the model prediction with the limited vehicle data seems encouraging despite the simplicity of the model at the current stage of its infancy.