• 한국환경복원기술학회지
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• 제18권6호
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• pp.97-110
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• 2015

This study aimed to classify damaged lands, to find what are the damage factors affecting the studied area, and to present a prescription in order to provide some benefit for the restoration of Regional Ecological Network at Chungnam province. Finally we classified damaged lands from 1st to 4th damaged lands according to relative intensity of damage. The main damage factors for the First Damage Lands were humus horizon, soil hardness and plant species richness. In the Second Damage Lands, those were soil hardness, plant species richness, number of plants and dominant plant species. In the Third Damage Lands, those were humus horizon, soil hardness, plant species richness, number of plants and dominant plant species. In the Fourth Damage Lands, those were humus horizon, organic matter, soil hardness, EC, T-N content, plant species richness, number of plants and dominant plant species. In every cases, the damage of soil and vegetation was originated due to development carried out by human being. The changes in soil condition were not big enough for it to affect plant growth, however, degradation of vegetation was still severe.

• 한국해양공학회지
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• 제13권3호통권33호
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• pp.100-107
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• 1999

Due to the high temperature and pressure, the materials of pipeline in power plant are degraded by creep damage. So far, many conventional measurement techniques such as replica method, electric resistance method, adn hardness test method for creep damage have been used. Among them, the replica method has mainly been used for the inspection of components. But this technique is restricted to the applications at the surface of the objects and cannot be used to material inside. In this paper, the measuring methods of evaluation by using ultrasonic attenuation and electric resistance for the creep detection of creep damage in the form of cavities on grain boundaries or intergranular microcracks were carried out. Absolute measuring method of quantitave ultrasonic attenuation technique for 1Cr0.5Mo material degradation was analyzed for determining the creep degradation steps using life prediction formula. As a result of measurement for creep specimens, we founded that the coefficient of utrasonic attenuation was increased as the increase of creep life fracton(${phi}c$) and the decreasing rate of wlwctric resistance was also increased.

• 비파괴검사학회지
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• 제27권6호
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• pp.541-549
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• 2007

This work describes an investigation into the feasibility of using an acoustic emission (AE) technique to evaluate the integrity of a composite actuator with a PZT ceramic under electromechanical cyclic loading. AE characteristics have been analyzed in terms of the behavior of the AE count rate and signal waveform in association with the performance degradation of the composite actuator during the cyclic tests. The results showed that the fatigue cracking of the composite actuator with a PZT ceramic occurred only in the PZT ceramic layer, and that the performance degradation caused by the fatigue damage varied immensely depending on the existence of a protecting composite bottom layer. We confirmed the correlations between the fatigue damage mechanisms and AE signal types for the actuators that exhibited multiple modes of fatigue damage; transgranular micro damage, intergranular fatigue cracking, and breakdown by a short circuiting were related to a burst type signal showing a shortly rising and slowly decaying waveform with a comparably low voltage, a continuous type signal showing a gradual rising and slowly decaying waveform with a very high voltage and a burst and continuous type signal with a high voltage, respectively. Results from the present work showed that the evolution of fatigue damage in the composite actuator with a PZT ceramic can be nondestructively identified via in situ AE monitoring and microscopic observations.

• 동력기계공학회지
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• 제20권4호
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• pp.5-11
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• 2016

This study analyzed the damage to a slitting knife after cutting steel sheets. Damages to the structure were observed and wear tests were conducted. In addition, the degradation on the damaged and undamaged parts was compared with a micro Vickers hardness test. Weibull statistical analysis was carried out in order to evaluate the reliability of the micro Vickers hardness measured data. Spalling of the edge portion occurred by degradation during use over a long period. Rough parts in the specimens were caused by damage because the slitting knife was used for 1 year. The friction coefficient and wear loss at the damaged parts of the knife edge were slightly larger from shock due to repetitive cutting operation. The micro Vickers hardness followed a two-parameter Weibull probability distribution.

• Structural Engineering and Mechanics
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• 제50권2호
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• pp.231-240
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• 2014

In the present research, fatigue behavior of chopped strand mat/epoxy composites has been studied with two different techniques. First, the normalized stiffness degradation approach as a well-known model for unidirectional and laminated composites was utilized to predict the fatigue behavior of chopped strand mat/epoxy composites. Then, the capability of the fatigue damage accumulation model for chopped strand mat/epoxy composites was investigated. A series of tests has been performed at different stress levels to evaluate both models with the obtained results. The results of evaluation indicate a better correlation of the normalized stiffness degradation technique with experimental results in comparison with the fatigue damage accumulation model.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2004년도 추계학술대회 논문집
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• pp.1156-1161
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• 2004

The factors affecting the long-term design strength of geogrid for railroad reinforcement can be classified into factors on creep deformation, installation damage, temperature, chemical degradation, biological degradation. Especially, creep deformation and installation damage are considered as main factors to determine the long-term design strength of geogrid. This paper describes the results of a series of experimental study, which are carried out to assess the combined effect of installation damage and creep deformation for the long-term design strength of geogrid reinforcement. In this study, a series of field tests are carried out to assess installation damage of a various geogrids according to different fill materials, and then creep tests are conducted to assess the creep properties of both undamaged and damaged geogrids.

• Structural Engineering and Mechanics
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• 제19권5호
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• pp.581-602
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• 2005

In this paper the accumulation of local damage during the cyclic loading in reinforced high-strength concrete columns is experimentally investigated. Two identical column specimens with annular cross-section and spiral reinforcement were designed and two tests, up to failure, under the action of a constant vertical concentrated force and a time-dependent concentrated horizontal force, were carried out at the LNEC shaking tables facility. Sine type signals, controlled in amplitude, frequency and time duration were used for these experiments. The concept of local damage based on local stiffness degradation is considered in detail and illustrated by experimental results. The specimens were designed and reinforced in such a way that the accumulation of damage was predicted by dominating deformations (cracking and crushing of the concrete) while the increasing of the loading values was a dominating factor of damage. It was observed that the local damage of HSC columns has exposed their anisotropic local behaviour. The damage accumulation was slightly different from the expected in accordance with the continuum damage concept, and a partial random character was observed.

• 보존과학회지
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• 제30권4호
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• pp.353-364
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• 2014

포름알데히드는 전시 수장 공간에서 농도와 발생빈도가 높아 전통직물(천연염색)에 대한 손상 개연성이 있다. 본 연구는 견, 면, 모시, 삼베의 무염색, 천연염색(적색, 황색, 청색, 흑색) 시편을 대상으로 포름알데히드 0.5, 1, 10, 100, 500ppm 농도에서의 손상, 손상농도 500ppm에서 온습도 조건에 따른 손상과 열화상태에서의 손상을 광학적, 화학적, 물리적 측정방법으로 평가하였다. 이 결과, 포름알데히드 농도 500ppm에서 일부 직물의 색차, 변퇴색등급, 포름산이온 농도, pH가 변화하였으며, 고온 고습조건($30^{\circ}C$, 80%), 고습조건($25^{\circ}C$, 80%)에서는 색차, 변퇴색등급, 포름산이온 농도가 2배 가중되었다. 그러나, 열화직물은 열화정도, 열화 생성물질로 인해 포름알데히드에 의한 손상변화가 미미하였다. 이를 통해 포름알데히드에 의한 전통직물의 손상, 손상농도, 손상가중 조건, 열화상태에서의 손상을 확인하였으며, 포름알데히드는 적색직물의 황변, 열화직물의 황변 탈색, 포름산은 전체직물의 탈색에 영향을 미치는 것으로 나타났다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 춘계학술대회논문집A
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• pp.49-54
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• 2000

Cr-Mo-V steel is widely used as a material for the turbine structural component in fossil power plants. It is well known that this material shows the various material degradation phenomenons such as temper embrittlement, carbide coarsening. and softening etc. or ins to the severe operation conditions as high temperature and high pressure. These deteriorative factors cause tile change of mechanical properties as reduction of fracture toughness. Therefor it is necessary to evaluate tile extent of degradation damage for Cr-Mo-V steel in life assessment of turbine structural components. In this paper. the electrochemical potentiokinetic reactivation(EPR) test in $50wt%-Ca(NO_3)_2$ solution is performed to develop the newly technique for degradation damage evaluation of Cr-Mo-V steel. The results obtained from the EPR test are compared with those in small punch(SP) tests recommended by semi-nondestructive testing method using miniaturized specimen. The evaluation parameters used in EPR test are tile reactivation current density$(I_R)$ and charge$(Q_{RC})$ reactivation rate$(I_R/I_{Crit},\;Q_R/Q_{Crit})$. The results suggest that $I_R/I_{Crit}$ in these parameters shows a good correlation with SP test results.

• 한국지하수토양환경학회지:지하수토양환경
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• 제22권6호
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• pp.85-93
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• 2017

In this study, the concepts of soil degradation, soil pollution and soil damage are defined, and the domestic and foreign administrative systems related to soil pollution and soil damage management are analyzed. In case of foreign countries, laws and regulations on the soil conservation and soil damage management were analyzed. In case of Korea, the present state of the legal system governing soil pollution and damage management was analyzed in each aspect. Through this study, suggestions for amendments of relevant laws were proposed by establishing policy direction for integrated management of soil pollution and soil damage. The results of this study will provide a basis for integrated management of soil pollution and damage, and it can be utilized in establishing integrated management strategy of long term soil conservation and sustaninable soil development at national level.