• 전기학회논문지
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• 제66권1호
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• pp.203-210
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• 2017

In this paper, we propose a electrical/mechanical method to effectively diagnose the local deterioration of a 10m long power shielded twist pair cable defined by the American Wire Gauge (AWG) 14 specification using electrical/mechanical methods. The rapid deterioration of the cable proceeded by using the heating furnace, which is based on the Arrhenius equations proceeds from 0 to 35 years with the deteriorated equivalent model. In this paper, we introduce a method to diagnose the characteristics of locally deteriorated cable by using $S_{21}$ phase and frequency change rate measured by vector network analyzer which is the electrical diagnostic method. The measured $S_{21}$ phase and rate of change of frequency show a constant correlation with the number of years of locally deteriorated cable, thus it can be useful for diagnosing deteriorated cables. The change of modulus due to deterioration was measured by a modulus measuring device, which is defined by the ratio of deformation from the force externally applied to the cable, and the rate of modulus change also shows a constant correlation with the number of years of locally deteriorated cable. Finally, By combining the advantages of electrical/mechanical diagnostic methods, we can efficiently diagnose the local deterioration in the power shielded cable.

• 한국분말야금학회:학술대회논문집
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• 한국분말야금학회 2006년도 Extended Abstracts of 2006 POWDER METALLURGY World Congress Part 1
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• pp.297-298
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• 2006

Free-machining agent 'KSX' contains complex calcium oxide is developed. The effect of admix ratio of KSX on mechanical properties and machinability with two different cutting speeds is reported. KSX displays improved machinability without deterioration of mechanical properties up to 0.3mass% addition. It was observed that KSX is effective with a small addition of 0.1mass% at slower cutting speed, and increased of admix ratio is effective at faster cutting speed.

• 한국건축시공학회지
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• 제4권1호
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• pp.119-126
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• 2004

Generally, reinforced concrete is one of the most commonly used structural materials and it prevents corrosion of steel bar by high pH of interior, But, as time elapsed, reinforced concrete structure become deteriorated by many of combined deterioration factors and environmental conditions. And, there are large number of deteriorate mechanism of the reinforced concrete structure and it acts complexly. It is recognized that steel bar corrosion is the main distress behind the present concern regarding concrete durability. In this study, to institute combined deterioration environments, established acceleration condition and cycle for combined deterioration environments has a resemblance to environments which are real structures placed. After that to confirm corrosion properties of reinforced concrete due to permeability with covering depth and types of surface cover under combined deterioration environments, measured carbonation velocity coefficients, chloride ion diffusion coefficients, water absorption coefficients, air permeability coefficients and electric potential, corrosion area ratio, weight reduction, corrosion velocity of steel bar. The results showed that an increase in age also decrease carbonation velocity coefficients, increase Chloride ion diffusion coefficients and increases water absorption coefficients. As well, an increase in age also increases corrosion of steel bar. Data on the development of corrosion velocity of steel bar with types of surface cover made with none, organic B, organic A, inorganic B, and inorganic A is shown. As well, permeability and corrosion velocity of steel bar with covering depth is superior to 10mm than 20mm. And it is confirmed permeability and corrosion properties of steel bar are closely related.

• 농업과학연구
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• 제49권2호
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• pp.367-377
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• 2022

The purpose of this study was to analyze the deterioration of trail conditions and to obtain information for desirable maintenance and restoration of a trail in Deogyusan National Park. The physical characteristics of a trail were surveyed at a total of 412 sites over 79.8 km length. The average trail degree and width were found to be 14.31° and 1.60 m, respectively, while the average bare trail width was 1.40 m and the average maxim trail depth was 5.66 cm. Major deterioration types of trail were trail deepening (36.6%), rock exposure (33.9%), and root exposure (12.5%) in order of frequency. Deterioration classes of the trail were 0.626 km (0.8%), 3.110 km (3.9%) and 8.935 km (11.2%) for heavily, moderately, and lightly deteriorated, respectively, with a deterioration rate of 12.671 km (15.9%). Compared to other national parks, the ratio damaged trail to the total trail was 15.9%, which is slightly higher than other, including Jirisan National Park 9.6% (2019), Bukhansan National Park 13.6% (2019), Sokrisan National Park 11.7% (2019), Chiaksan National Park 12.3% (2015), and Woraksan National Park 10.5% (2015). The section of trail in Deokyusan National Park where the damage grade is analyzed as "Heavy" should therefore be restored in consideration of the field conditions. In particular, the damage status of the trail is expected to be greatly improved when the trail surface maintenance level is restored.

• 한국구조물진단유지관리공학회 논문집
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• 제16권6호
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• pp.82-92
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• 2012

본 연구에서는 콘크리트 교량 바닥판의 열화를 비파괴시험인 지표투과레이더(GPR)를 이용하여 평가하는 방법을 개발하였다. 콘크리트 교량 바닥판의 유전 상수를 계산하기 위하여 비접촉식 GPR 안테나를 이용하여 2층 구조체에 적용할 수 있는 확장형 공통중간점 방법을 개발하였다. 콘크리트 교량 바닥판의 열화 깊이와 열화 상태는 콘크리트 교량 바닥판의 유전 상수와 표면대비 평균 유전상수비를 이용하여 평가하였다. 제안된 방법을 검증하기 위하여 GPR 현장 시험을 공용수명이 오래된 콘크리트 교량에서 실시하였다. 시험 결과 새로 제안된 방법을 이용하여 추정된 두께와 열화 깊이가 어느 정도 신뢰성을 가지는 것으로 나타났다.

• 콘크리트학회지
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• 제6권2호
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• pp.129-137
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• 1994

해양환경하에 있는 콘크리트 구조물의 열화를 알아보고 철근의 부식 정도를 추정하기 위한 연구내용으로서 콘크리트 중에 철근을 묻은 공시체를 제작하여 간만의 차가 있는 해변에 1년 동안 노출시킨 상태로 시험을 실시 하여 콘크리트 중의 가용성 염분량, 철근의 자연전위값 및 철근의 부식정도에 대하여 고찰하였다. 본 연구 결과 콘크리트 중의 가용성 염분량은 물-시멘트비가 낮을수록, 혼화재를 혼입할 경우 적게 나타났으며 가용성 염분량이 클수록 철근의 부식이 크게 나타났다. 철근 부식의 정도가 심할수록 자연전위값이 감소하였으며 자연전위와 부식면적율과는 상관관계가 있음을 알 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제14권2호
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• pp.171-175
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• 2010

본 연구는 동결융해, 염해 및 중성화가 복합적으로 작용하는 콘크리트 구조물의 내구성능을 평가하기 위하여 일반강도 콘크리트를 대상으로 동결수를 달리하여 동결융해 시험을 실시함으로서 염해와 동결융해 복합작용에 의한 콘크리트의 열화를 평가하였고, 염해, 동결융해 및 중성화의 세가지 열화가 복합적으로 발생되는 복합열화에 대해서는 적절한 평가방법이 부재하여 동결수에 따른 동결융해 시험 후의 시험체에 대하여 중성화 촉진시험을 실시함으로서 복합열화에 의한 콘크리트 내구성능 저하 특성을 평가하고자 하였다. 본 연구를 통하여 동결수의 종류나 물-결합재비 수준과 무관하게 고로슬래그미분말을 사용한 배합의 경우 염해와 동결융해가 동시에 복합적으로 발생되는 환경에서도 우수한 저항성능을 보이는 결과를 나타내므로 동결융해를 포함한 복합열화 환경에서 충분한 내구성 확보를 위해서는 최소한의 설계기준강도의 확보와 고로슬래그미분말 등 적절한 시멘트 결합재의 선정이 무엇보다 중요하다는 결론을 얻었다.

• 유체기계공업학회:학술대회논문집
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• 유체기계공업학회 2006년 제4회 한국유체공학학술대회 논문집
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• pp.509-512
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• 2006

The propellant mixture ratio of gas generator changes when thrust control valve operate to change LRE thrust level. The mixture ratio change of gas generator result in gas temperature change and failure of turbine blade or deterioration of LRE specific impulse. The mixture ratio stabilizer has been developed to maintain propellant mixture ratio of gas generator. This article deals with design and static/dynamic characteristic of stabilizer. Also gas generator system simulation test has shown that the stabilizer can maintain propellant mixture ratio effectively within tolerable range.

• 콘크리트학회논문집
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• 제23권4호
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• pp.431-440
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• 2011

콘크리트 구조물은 화재에 노출시 고온에 의해 내부 구조가 변화하며 보유하고 있는 강도와 변형 성능이 저하되어 최종적으로 수명이 단축하게 된다. 그 성능 저하 수준은 도달된 온도, 고온에 노출된 시간, 콘크리트의 배합, 골재의 특성 및 콘크리트 자체의 특성 등에 의해 결정된다. 이 연구는 물시멘트비, 잔골재율 및 굵은 골재의 최대 크기등의 변수에 대한 초고강도 콘크리트의 열적 거동을 평가하기 위해 실시되었다. 상온 및 $500^{\circ}C$의 온도에 대하여 초음파 속도, 동탄성 계수, 정탄성 계수 및 압축강도 시험은 ${\varnothing}100{\times}200\;mm$ 원주형 콘크리트 시험체를 사용하여 실시되었다. 결과로서 $500^{\circ}C$의 온도에서 가열된 초고강도 콘크리트의 잔존 역학적 특성은 물결합재비, 잔골재율 및 굵은 골재 최대 치수의 변화에 영향을 받는 것으로 나타났다.

• KIEAE Journal
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• 제14권2호
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• pp.69-75
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• 2014

Building has been deteriorated over the year after construction. The deterioration has caused to hinder the living condition and to decrease the building value. Thus, it is important to prevent or delay the building deterioration as well as to proceed the maintenance. The long-term repair program for the apartment in Korea plays a key role to make the repair plan after construction and to assure the function decent. This is not flexible to the change of the material and component because the program is provided by the Korean-law. Many items are omitted in the long-term program so that the maintenance experts face many difficulties to make a repair plan. In this paper, it aimed at providing the repair cycle and repair ratio according to the repair scope, which are not provided in the current program. This study shows that the repair ratio is presented with quartile range in 25%, 50%, 75% and 100%. This has an advantage to take an overall look in repair items. Under this presentation of the repair ratio, each item has a unique repair value. Second, the repair scope is divided into partly repair, fully repair, partly alteration and fully alteration. If a fully repair has a repair ratio close to 100%, it would mean that a fully repair is a fully alteration. Third, the short repair cycle means that it requires to maintain the function or performance of the components in a short term.