• Proceedings of the KSRS Conference
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• 2000.04a
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• pp.131-136
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• 2000

Ocean Scanning Multi-spectral Imager (OSMI)는 다목적 실용위성 (KOMPSAT) 1호기 아리라위성에 탑재되어 1999년 12월 21일 발사된 해양 관측 기기이다. OSMI는 발사후 3년 이상 생물학적 해양지리학 연구를 위해 전세계 바다색을 관측하는 임무를 수행할 것이다. OSMI는 센서 성능의 궤도상 보정을 위해 태양광 보정과 암흑 보정을 수행한당. 태양광 보정은 궤도상에서 장기간에 걸친 해양 결상계의 노화에 따른 성능 변화 감지 및 보정에 있다. 발사 직후의 초기 태양과 보정 측정 자료는 추후 성능 변화 감지에 대한 기준이 될 뿐만아니라 발사 직후 OSMI 센서 성능 파악 및 점검에도 사용될 수 있으므로 매우 중요하다. 태양광 보정의 구조 및 광학적 특성을 분석하고 OSMI 주요 관측파 장대역별로 태양광 보정계의 출력신호량을 예측하였다. 초기 운영 기간동안 얻은 OSMI 태양광 보정계의 발사후 최초 측정 자료를 분석하고 발사전 예측 성능과 비교하였다. 이 연구는 OSMI 센서 보정 및 영상 품질 이해에 유용할 것이다.

• Nuclear industry
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• v.19 no.11 s.201
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• pp.39-46
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• 1999

국내 가동 원전의 운전 연수가 증가함에 따라 장기 사용 원전의 안전성 향상과 수명 관리 연구가 진행되고 있다. 원전 수명 관리는 발전소 운전 안전성과 성능을 유지하면서 최적 경제 시점인 최적 수명까지 발전소를 운전하기 위한 제반 기술 활동이다. 적절한 수명 관리로 원전을 최적 수명까지 운전하더라도 발전소는 노화에 의해 운전 안전성이 영향을 받거나 저하되지 않아야 한다. 발전 설비의 노화에는 실제의 기기나 구조물이 경년 열화에 의해 노화되는 물리적 노화와 설계 기술의 발달과 새로운 안전 개념의 적용으로 기존 기술이 낙후하는 비물리적 노화로 구분할 수 있다. 물리적 노화는 기기$\cdot$구조물$\cdot$계통의 물리적 상태 변화로 성능을 저하시키고, 비물리적 노화는 발전소 계통의 안전 개념$\cdot$기준$\cdot$기술이 새롭게 변화되지 않은 것이다. 본 논문에서는 물리적 노화는 수명 관리 연구, 비물리적 노화는 안전성 관리의 측면에서 검토하였고, 두 분야의 국내외 연구 현황$\cdot$개념$\cdot$추진 방법$\cdot$상호 관계 등을 살펴보고, 상호 유기적인 관계를 보완 할 수 있는 제도적 장치 도입 및 적용 방안에 대해 논하였다.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2005.06a
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• pp.211-220
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• 2005

The concrete structure is being considered for the main engineered barrier of low and intermediate level radwaste disposal facility. Concrete of low permeability can minimize infiltration of water and effectively prevent release of nuclide to ecosystem. But if concrete degrades, structural stability of disposal structure will decrease while permeability increase, resulting in increased possibility of nuclide release due to water infiltration. Therefore disposal concrete structure degradation shall be minimized to maintain capacity of nuclide isolation. The typical causes of concrete structure degradation are sulfide attack, reinforcement corrosion due to chloride attack, leaching of calcium hydroxide, alkali-aggregate reaction and repeated freezing-thawing. The common cause of these degradation processes is infiltration of water or adverse chemicals into concrete. Based on the study of these degradation characteristics and mechanisms of concrete structure, the methodology of design and service life evaluation of concrete structure as an engineered barrier are reviewed to ensure its long-term durability.

• Journal of the Korean Society of Propulsion Engineers
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• v.18 no.6
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• pp.59-67
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• 2014

Acceptance level random vibration and life firing test for development model of 1 N-class monopropellant thruster have been performed. From the results of random vibration, the natural frequency of the dual thurst module composed of 1 N-class development model thrusters was higher than the part level requirement(>100 Hz) and the structural robustness was verified. Thrust decrease of steady sate was below 7% and thrust instability was within ${\pm}5%$ in the life firing test using over 20 kg propellant throughput. The computerized tomography for catalyst bed showed a less than 7% of catalyst loss and it revealed the design appropriateness of the current thruster development model.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.05e
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• pp.40-43
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• 2003

전기방전에 대한 shed 재료의 열화내성과 우수한 발수성의 장기간 유지특성은 폴리머 애자의 장기성능에 있어서 가장 중요한 인자들이다. 애자 제조시 무결점 성형성 또한 중요한데 열화내성을 확보하기 위해 다량의 ATH의 첨가가 수반되기 때문에 적절한 process oil의 사용이 불가피하다. 사용하는 오일의 종류와 량에 따라 옥외절연물의 장기성능에 영향을 주는 표면발수성이나 방전내성은 크게 차이가 나는 것으로 밝혀지고 있다. 본 논문에서는 화학적 구조와 정도가 다른 몇 가지 실리콘 fluid들을 실리콘 고무에 처방하여 기본물성과 초고압 옥외절연물의 shed 재료로서 장기성능에 영향을 주는 방전열화내성과 표면발수성의 회복특성을 평가하였다. 실리콘 고무의 무결점 사출성형에 가소도가 중요한데 동일한 무기물 첨가조건에서 유사한 가소도를 갖게 하는데 필요한 량은 fluid들의 종류에 따라서 상당한 차이가 있었다. 특히 PDMS는 점도는 낮지만 분자량이 커서 많은 량이 첨가되어 기계적 특성저하가 크게 일어났다. 코로나 처리후 발수성 회복특성은 fluid들의 분자크기와 반응기의 종류에 따라 상당히 영향을 받았으며 분자가 클수록 초기회복속도는 다소 느려도 최종의 상시발수성은 다소 높게 유지되었으며 2일 이내에 거의 초기 접촉각으로 회복되었다. 내아크성은 무게손실이 적을수록 오차범위도 작은 안정된 특성을 보였으며 fluid들의 종류에 따른 무게손실의 차이는 크지 않았다. 트래킹 방전에 의한 무게 감소는 fluid의 분자가 크면서 페닐기를 가진 fluid들이 첨가된 고무가 우수한 특성을 보였다.

• Journal of the Korean Geosynthetics Society
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• v.4 no.1
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• pp.7-15
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• 2005

In recent years, the geotextile tubes filled with dredged material have been used in dike and breakwater construction for a number of projects around the world, and their use in this field is growing very fast. One of the most attractive advantages of geotextile tube technology is can be use the in-situ filling materials by hydraulic pumping, it can be also established lower costs and fast construction than other technology. Geotextiles form one of the two largest groups of geosynthetics and it is commonly made by two major types of polymer material(Polypropylene, Polyester). The objective of this paper is to examine several issues associated with drainage function and feasibility of geotextile tube structure such as filtering efficiency, dewatering efficiency, and filling process with polymer materials. Based on the laboratory filtering test and in-situ tests, polypropylene goetextile is more effective for drainage function of geotextile tube technology.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.111-114
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• 2010

MOV(Main Oxidizer shut-off Valves) control the combustion of launch vehicle systems by the supply and the isolation of liquid oxygen to a main combustion chamber in launch vehicle systems. Moreover, the MOV should secure a constant flow rate of liquid oxygen for combustion instability in the steady operational state. To modify the middle flange and rip of inlet valve design by Computer Aided Structural Analysis for improvement of EM core functions. In result, it has been verified to improve performance of EM by tests.

• International Journal of Highway Engineering
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• v.13 no.3
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• pp.65-73
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• 2011

Recently, researches to introduce the performance warranty contract are in progress for quality improvement of road pavements. The performance warranty contract is a type of contract in which contractors guarantee to maintain certain level of performance during a period from completion of construction. The contract use in Europe and the U.S is being increased because it has been known to contribute to improvement of structure quality, reduction of life cycle cost, development of construction techniques, and etc. The research on performance indicators, threshold values, and warranty durations is essential to effectively introduce the contract in Korea. In this study, literatures on the performance warranty contract for concrete pavements of the Minnesota, Indiana, and Florida of the U.S. were reviewed. Major distresses influencing the pavement performance were investigated and analyzed in the jointed concrete pavement sections of 21 Korean expressway routes to be compared to the performance indicators, threshold values, and warranty durations of the states. More accurate comparison is expected by investigation in planned sections for a long time.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.737-740
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• 2008

When UHSFRC is applied to structures, it can be expected that it shows excellent performance in a point of constructability and load capacity. However, its rich mix can cause some problems concerning the long-term behavior such as shrinkage and creep. Therefore it is inevitably needed to investigate its long-term behavior in order to apply it to structures safely. This study is dealing with the drying shrinkage of UHSFRC. UHSFRC shows relatively fast drying shrinkage in the early exposed ages and slow moisture diffusion caused by compact microstructure of the material. It was found that The KCI model to predict the drying shrinkage did not properly represent these properties of UHSFRC. therefore a modified drying shrinkage model applicable to UHSFRC, which has different shrinkage properties from that of normal concrete, was proposed

• Journal of the Korea Concrete Institute
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• v.14 no.3
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• pp.382-391
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• 2002

This study is devoted to the problems of thermal and shrinkage stresses in order to avoid cracking at early ages. The early-age damage induced by volume change has great influence on the long-term structural performance of the concrete structures such as its durability and serviceability To solve this complex problem, the computer programs for analysis of thermal and shrinkage stresses were developed. In these procedures, numerous material models are needed and the realistic numerical models have been developed and validated by comparison with relevant experimental results in order to solve practical problems. A framework has been established for formulation of material models and analysis with 3-D finite element method. After the analysis of the temperature, moisture and degree of hydration field in hardening concrete structure, the stress development is determined by incremental structural formulation derived from the principle of virtual work. In this study, the stress development is related to thermal and shrinkage deformation, and resulting stress relaxation due to the effect of early-age creep. From the experimental and numerical results it is found that the early-age creep p)ays important role in evaluating the accurate stress state. The developed analysis program can be efficiently utilized as a useful tool to evaluate the thermal and shrinkage stresses and to find measures for avoiding detrimental cracking of concrete structures at early ages.