• Journal of the Korea Concrete Institute
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• v.20 no.3
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• pp.375-381
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• 2008

Various problems such as durability degradation may happen when extra water is added to concrete. Because of these reasons, the change of water content is managed by using rapid evaluation method of unit water content such as electric capacity method, heat drying method making use of micro wave, unit capacity mass method among various methods. Especially, in Japan, guidance for the change of water content ($\pm$ 10, 15, 20 kg/$m^3$ etc.) were regulated and used. However, it is the real situation that the guidance which were regulated in South Korea evaluate suitability only considering production and measurement error under the circumstances which are not considering the degree of durability degradation. Therefore, this study tries to investigate the influence of addition of extra water in the concrete on the durability degradation of concrete when it was added by artificial manipulation or by management error. From the test results, a guideline of the contents of extra water for the quality control is suggested with the consideration of the degree of durability degradation and the probable error resulted from the addition of extra water. The contents of extra water for tests are set as 0, 15, 25, 35 kg/$m^3$. To examine the durability degradation of concrete, freezing and thawing, carbonation, chloride penetration and compressive strength are tested.

• Current Industrial and Technological Trends in Aerospace
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• v.5 no.2
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• pp.23-32
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• 2007

헬리콥터 주 로터 시스템은 헬리콥터 전체 성능을 좌우하고, 비행특성을 결정하는 핵심 구성품이다. 주 로터 시스템은 회전하면서 추력 및 조종력을 발생시키기 때문에 동적 밸런싱을 맞추는 것도 중요한 개발단계업무 중에 하나이다. 주 로터 시스템의 개발 과정에서 헬리콥터 비행시제 장착 전에 동적 밸런스 시험, 성능시험, 안정성 시험 등을 포함하는 훨시험(whirl test)을 수행하게 된다. 이 시험 수행을 위해 제작되는 시험장치가 훨타워(whirl tower)이다. 세계 유수 헬리콥터 회사들은 주 로터 훨시험을 위한 설비인 훨타워를 보유하고 있으며, 지속적으로 성능 개량 등을 통해 최신의 기술 및 장비를 적용하여 운영하고 있다. 본 논문에서는 대표적으로 사용되고 있는 해외 헬리콥터 회사들의 훨타워의 사례를 설명하고 설비의 기능을 기술함으로써 기술적 동향에 대하여 살펴보았다. 현재 한국형헬기개발사업(KHP)에서 구축중인 다목적 의 WTTF(whirl tower test facility) 요구조건 및 설계 현황에 대해서도 기술하였다. 당 연구원의 WTTF는 한국형기동헬기(KUH)의 주 로터 훨시험 및 내구성 시험을 위해 구축되고 있다. 본 시험설비는 연구개발용 시험과 양산용 시험을 모두 수행할 수 있도록 다목적으로 개발될 예정이다. 본 설비는 기존 해외 설비와는 차별화되어 다목적 시험을 할 수 있도록 설계가 진행중이며, 2008년12월에 구축 완료 예정이다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.167-174
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• 2003

Military facilities with masonry have a great portion in the whole military facilities. But lots of them have been used for more than 20 years, the degree of deterioration of the facilities are serious. Futhermore, as insufficient budget for the facilities maintenance and poor maintenance, the performance of the aged masonry facilities have continually decreased. We suggest a structural performance assessment criteria for the military facility through literature review, interview with experts and questionnaire. The major assessment factors for the structural performance include the inclining and sinking degree of the facilities, durability of materials and resisting force of the structural members.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.5
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• pp.153-160
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• 2019

The purpose of this study was to investigate the mechanical and durability characteristics of latex-modified concrete using ultra rapid hardening cement : four types of mechanical tests including compressive strength, modulus of elasticity, flexural strength and bond strength were performed; and seven types of durability tests including resistance of concrete to chloride ion penetration, freeze-thaw resistance, scaling resistance, coefficient of thermal expansion, cracking tendency, abrasion resistance and drying shrinkage were performed. Required material performance of each test was determined in accordance with the Korea specification for repair of concrete and pavement repairing materials. The test results satisfied the required material performances, and presented a good mechanical and durability characteristics. In particularly, the materials showed early development of compressive strength, flexural strength and bond strength at 3 and 4 hours after curing. SEM photos were also taken to investigate the micro structures of the materials after chloride ion penetration test.

• Korean Chemical Engineering Research
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• v.61 no.3
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• pp.362-367
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• 2023

Recently, research and development of proton exchange membrane fuel cells (PEMFC) membranes are progressing in the direction of thinning to reduce prices and improve performance. Demand for hydrogen-powered vehicles for commercial vehicles is also increasing, and their durability should be five times greater than those for passenger vehicles. Despite the thinning of the membranes, the durability of the membranes must be increased five times, so the improvement of the durability of the membranes has become more important. Since the acceleration durability evaluation time also needs to be shortened, the protocol using oxygen instead of air in the existing protocol was applied to a 10 ㎛ thin membrane to evaluate durability. The accelerated durability test (Open circuit voltage holding) was terminated at 720 hours. If the air-based department of energy (DOE) protocol was used, a lifespan of 450,000 km of driving hours would be expected, with a durability of about 1,500 hours. During the chemical durability evaluation, the active area of the electrode decreased by 51%, suggesting that catalyst degradation had an effect on membrane durability. Reducing the catalyst degradation rate is expected to increase membrane durability.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.11a
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• pp.204-207
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• 2002

주로 터널 등에 사용되는 숏크리트는 콘크리트와 달리 높은 압력으로 뿜어붙이기 때문에 콘크리트와 다른 역학적 특성이 보이게 된다. 그러나 국내에서는 이러한 숏크리트의 중요한 역학적 특성인 내구성능에 관한 실험이 미미한 실정으로 본 연구에서는 숏크리트 장비를 이용하여 실험시편을 급결제의 종류, 혼화제의 종류, 혼화재(실리카흄, 고로슬래그, 플라이애쉬)의 종류 등에 따라 제작하여 강도실험(28일 및 56일 압축강도, 28일 휨강도, 56일 할렬인장강도), 동결융해실험, 내투수성실험, 중성화실험 등의 폭 넓은 실험을 통해 고성능 숏크리트의 전반적인 내구특성을 규명할 수 있었다.(중략)

• Journal of rehabilitation welfare engineering & assistive technology
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• v.5 no.1
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• pp.11-15
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• 2011

This paper propose the test method for a performance of the myoelectric hand prosthesis(MHP) controlled according to the myoelectric signal generated in the human muscle. The MHP consists of a mechanical hand, a surface myoelectric sensor(SMES) for a measuring myoelectric signal, a control system and a charging battery. The two commercialized MHP is tested for the grip endurance property. The test results is not difference a noise and a grip force. The proposed test method is proved the reliability of MHP by the endurance test.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.2
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• pp.112-117
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• 2009

The new suspension, called ISU(In-arm suspension system) was developed for Infantry Fighting Vehicle. During vehicle field test, early failure of ISU's sealing system was occurred after driving the paved road. From the failure analysis, ISU's displacement data was obtained. In analysis of PSD data, track induced vibration which has high frequency and small amplitude characteristics, was dominant. Such track vibration would result in early seal failure because of friction increase and lack of lubrication. To simulate track vibration environment in laboratory, seals were tested under the condition of 20Hz, ${\pm}1$, ${\pm}2mm$ amplitude. The same type of seal failure occurred in vehicle test, was reproduced in the lab test under ${\pm}1mm$ amplitude. From the test results, the durability of improved seal was increased by 2.5 times compared with the previous one.

• Magazine of the Korea Concrete Institute
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• v.11 no.3
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• pp.70-84
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• 1999

HPC를 사용한 장기수명 바닥판 콘크리트의 시공에 관한 4가지 접근방법을 제시하였다. Nebraska, New Hampshire, Texas 그리고 Virginia 등 4개주의 프로젝트에서 보면 아래와 같이 여러 가지 유사성을 알 수 있었다. $\cdot$ HPC의 사용은 장기 수명의 교량 바닥판을 건설하기 때문에 life cycle cost와 유지관리비의 감소가 예상된다. $\cdot$ 교량 바닥판에 대한 HPC의 중요성은 더 큰 강도보다는 내구성과 시공성을 일관성있게 양호하게 개선한다는 것이다. $\cdot$ 그 지역의 재료와 기존의 방법을 가능한 최대한 범위로 사용한다. $\cdot$ 많은 실험실 및 현장 시험 배합표가 개발되었고 배합되었다. 성능 특성은 혼합 재료의 형태, 상품 및 배합에 따라 다르게 나타났다. $\cdot$ 향상된 성질을 갖는 균일하고 일관성 있는 제품의 사용에 덧붙여 적절한 시공 기술은 장기 수명의 콘크리트 구조물을 위해서는 필수적이다. $\cdot$ 알카리-골재 반응을 갖고 있는 지역이나 높은 황산염을 갖고 있는 지역과 같이 특별한 문제점이 예상되는 지역에서는 화학적 내구성을 검토하기 위해 별도의 실험이 필요하다. $\cdot$ 현장에서 소요의 성능특성을 얻기 위해서는 시작부터 모든 분야 사이의 원활한 의견 교환과 협력이 요구된다.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2005.05a
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• pp.29-32
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• 2005

It is recognised that a permeability waterproof agent have been extensively used for concrete, in these days. In present paper shows effective practical scheme of a permeability waterproof agent in construction market that is to develope durability of concrete structure as apply to job site through the examination physical and chemical property of a permeability waterproof agent. It is indentified that can be maintain waterproofing performance, moreover it makes satisfactory result of permeation resistance as applying siliceous waterproof agent.