• 대한토목학회논문집
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• 제11권1호
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• pp.9-16
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• 1991

콘크리트는 고응력 범위에서 적은 반복횟수에 의해서도 파괴에 도달할 수 있고 소성 변형에 의한 콘크리트 손상이 심각하다. 본 연구에서는 반복하중하에서의 콘크리트의 손상과정에 관하여 실험적으로 연구하였고 에너지개념에 의한 소상모델을 개발하였다. 실험은 일축압축상태의 무근콘크리트에 대해서 변위제어상태하에서 수행하였다. 콘크리트의 파괴시점은 잔여강도가 존재하지 않은 상태까지로 가정하였고, 손상도는 실험적으로 파괴시까지 구해진 에너지 발산량과 주어진 횟수의 반복하중에 의한 에너지 발산량의 비로 정의하였다. 고응력 범위에서 손상도는 변형량의 비선형함수로 누적되며, 손상비율은 초기에 높고 파괴상태에 가까울수록 점차적으로 감소하였다.

• 대한토목학회논문집
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• 제32권6C호
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• pp.305-314
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• 2012

본 연구에서는 미소파괴음을 활용하여 한국 원자력 연구원 지하처분연구시설에서 채취한 화강암의 손상도를 정량적으로 평가하였다. 해석결과 균열손상기준은 균열개시, 균열손상응력은 일축압축강도의 약 48%, 72%이며 균열손상기준에 따른 암석의 손상은 시료에 가해지는 응력이 균열손상응력을 초과하면서부터 0.06에서 일축압축강도의 80%, 90%에서는 0.34, 0.60로 급격히 증가하였다. 이는 축 방향 변형계수를 활용한 손상도 결과와 유사하여 단순회귀분석 결과 두 기법의 상관관계는 0.90로 상관성은 매우 높은 것으로 나타났다. 이에 미소파괴음 에너지를 활용한 손상도 결과와 모어-쿨롱 파괴규준을 이용하여 응력수준에 따른 축 방향 변형계수, 암석의 강도, 점착력, 내부마찰각 변화를 분석한 결과 균열손상응력 이전까지는 원결과보다 각각 6%, 12%, 7%, 3% 감소하였지만 일축압축강도의 90%수준에서는 69%, 72%, 62%, 24%로 감소의 기울기는 급격히 증가하였다.

• Annals of Laboratory Medicine
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• 제38권6호
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• pp.524-529
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• 2018

Background: An increase in neutrophil gelatinase-associated lipocalin (NGAL) indicates tubular injury. Diabetic nephropathy causes typical changes in the kidney, characterized by glomerulosclerosis and eventual tubular damage. We validated the usefulness of plasma NGAL (pNGAL) as a biomarker of tubular damage in patients with diabetic nephropathy. Methods: We included 376 patients with diabetes mellitus (260 patients with chronic renal insufficiency who had not received hemodialysis and 116 hemodialyzed due to diabetic nephropathy) and 24 healthy controls. Patients with chronic renal insufficiency were divided into three groups according to urinary albumin excretion (UAE) levels. pNGAL levels were measured using the Triage NGAL test (Alere, San Diego, CA, USA) and were compared between groups. We also examined whether pNGAL level was related to the degree of albuminuria and cystatin C-based glomerular filtration rate (GFR). Results: Mean pNGAL levels of the healthy controls, chronic renal insufficiency patients with diabetes mellitus, and hemodialyzed patients were $61.9{\pm}5.3ng/mL$, $93.4{\pm}71.8ng/mL$, and $1,536.9{\pm}554.9ng/mL$, respectively. pNGAL level increased significantly in patients with severe albuminuria (P <0.001) and had a moderate correlation with the degree of albuminuria (r=0.467; P <0.001) and GFR (r=0.519; P <0.001). Multivariate regression analysis showed that the pNGAL level was associated with tubular damage independent of patient age, sex, and GFR. Conclusions: pNGAL level independently reflects the degree of tubular damage in patients with diabetic nephropathy. Measurement of pNGAL, combined with UAE, would enable simultaneous, highly reliable assessments of tubular damage for such patients.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1990년도 가을 학술발표회 논문집
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• pp.45-50
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• 1990

This study develops practical models and methods for the assessment of safety and capacity rating of existing P.C. girder bridges based on the reliability methods. One of the main objectives of the study is to propose a practical but realistic limit state model for safety assessment and LRFR rating criteria, which explicitly incorporates the degree of deterioration and damage as well as actual condition of P.C. girder bridges in terms of the damage factor and the response ratio. The damage factor proposed in the paper is defined as the ratio of the current estimated stiffness to the intact base-line stiffness of a member. Based on the observation and the results of applications to existing bridges, it may be concluded that the proposed methods for the assessment and capacity rating models, which explicitly account for the uncertainties and effects of degree of deterioration or damage, provide more realistic and consistent safety-assessment and capacity rating.

• Computers and Concrete
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• 제12권1호
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• pp.65-77
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• 2013

This paper examines the dynamic response of an arch dam subjected to blast loading. A damage model is developed for three dimensional analysis of arch dams. The modified Drucker-Prager criterion is adopted as the failure criteria of the damage evolution in concrete. Then, Xiluodu arch dam serves as an example to simulate the failure behaviors of structures with the proposed model. The results obtained using the proposed model can reveal the reliability degree of the safe operation level of the high arch dam system as well as the degree of potential failure, providing a reliable basis for risk assessment and risk control.

• 한국작물학회지
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• 제32권3호
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• pp.302-309
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• 1987

벼 품종의 잎집무늬마름병에 대한 저항성 정도를 성묘기에 검정하여 이 병에 대한 저항성원을 선발할 목적으로 1984년 30품종, '85년 40품종, 그리고 '86년에 100품종을 공시, 보통기에 다비, 밀식재배하여 병원구을 접종하였다. 1984년에는 2개의 균주를 접종하였으며 '85년에는 만기재배하에서의 검정을 별도로 수행하였기 때문에 3년간에 걸친 보통기 재배하에서의 검정을 합하여 총 5회의 실험이 이루어 졌다. 공시한 각 품종의 출수 25일 후에 조사한 피해도를 기준으로 하여 품종간 저항성차이를 구분한 결과를 요약하면 다음과 같다. 1. 3년간에 걸친 5회의 실험에서 모두 공시품종간 피해도의 차이는 확실하였으며 어느 경우에나 피해도의 유전분산이 환경분산보다 훨씬 큰 값을 보였다. 2. 2∼3년간 계속해서 공시되었던 품종들의 피해도는 년차간 그리고 재배시기간에 정의 상관관계가 인정되었다. 3. 1984년을 제외하고는 공시한 벼 품종의 출수기와 피해도 간에 부의 상관관계가 인정되고 있어 출수기가 늦은 품종군은 피해도의 평균치도 낮고 품종간 변이폭도 좁았다. 4. 자연포장에서 잎집무늬마름병에 대한 저항성 검정은 비슷한 출수기를 가진 품종들끼리 피해도가 비교되어야 하며 만생종 및 극만생종은 별도의 조건에서 재배, 접종 및 피해도 조사가 이루어져야한다. 5. 국내육성종 중에서 가야벼는 조생종에 속하면서도 3년간 5회의 검정실험에서, 그리고 SR9713- 54- 3은 중대종이면서 2년간 3회의 검정실험에서 비교적 낮은 피해도 값을 보여 이 두 품종은 잎집무늬마름병에 대하여 안정적인 중도저항성(MR)을 보여 주었다.

• 한국작물학회지
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• 제26권3호
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• pp.219-225
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• 1981

Strong wind of 6.5m/s from electric fan was applied to rice at heading stage to find out the nature of wind damage to panicle. Damaged panicles caused by typhoon were sampled out of field to measure the yield and milling components. Wind-treated glumes were developed into two forms, fertile and sterile, and each of them showed all degree of glume discoloration. The number of fertile grains were higher than sterile grains in a damaged panicle. Averagesdegree of glume discoloration was higher in not flowered glume than in flowered glume. The more recently flowered glumes resulted the higher degree of discoloration among flowered glume. The percent of sterile grain to total number of grains was the highest at stage of just flowering. The glume discoloration representing wind damage at heading state advanced in degree in ten days after treatment compared to that just after treatment. Grain length and grain width were decreased with the increased degree of glume discoloration, while grain thickness was not changed greatly. Chalkiness was a little higher in damaged grain than in normal grain without definite trends by degree of discoloration. Ripening ratio, 1000 grain weight and yield decreased with increased degree of glume discoloration in damaged panicle by typhoon. Decreasing order in yield was white rice, rough rice and brown rice. Ratio of brown rice to rough rice increased, white rice to brown rice decreased, and milling recovery was not changed greatly with increased degree of 히ume discoloration.

• Earthquakes and Structures
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• 제3권3_4호
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• pp.413-434
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• 2012

This paper presents a displacement-based seismic design method with damage control, in which the targets for the considered performance level are set as displacements and a damage distribution is proposed by the designer. The method is based on concepts of basic structural dynamics and of a reference single degree of freedom system associated to the fundamental mode with a bilinear behaviour. Based on the characteristics of this behaviour curve and on the requirements of modal spectral analysis, the stiffness and strength of the structural elements of the structure satisfying the target design displacement are calculated. The formulation of this method is presented together with the formulations of two other existing methods currently considered of practical interest. To illustrate the application of the proposed method, 5 reinforced concrete plane frames: 8, 17 and 25 storey regular, and 8 and 12 storey irregular in elevation. All frames are designed for a seismic demand defined by single earthquake record in order to compare the performances and damage distributions used as design targets with the corresponding results of the nonlinear step by step analyses of the designed structures subjected to the same seismic demand. The performances and damage distributions calculated with these analyses show a good agreement with those postulated as targets.

• 한국측량학회:학술대회논문집
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• 한국측량학회 2007년도 춘계학술발표회 논문집
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• pp.211-214
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• 2007

After the forest fire, as access is not easy, forest damage degree are determined with Landsat TM image rather than visual inspection. Therefore in this study, damaged areas are extracted with factor analysis and cluster analysis. Second factor analysis was performed for areas suspicious as forest fire damage areas to evaluate accuracy after separating into strong, medium and light forest fire areas.

• 한국표면공학회지
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• 제50권4호
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• pp.251-258
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• 2017

This study was carried out with solution temperature variables of $75^{\circ}C$ and $90^{\circ}C$ for STS 304, which is a nuclear equipment material, in order to determine the corrosion damage behavior in chemical decontamination process using permanganic acid and oxalic acid. Then electrochemical polarization experiment, weight loss measurement, surface morphology observation and surface damage depth were measured every cycle of the decontamination process to analyze the degree of corrosion damage. As a result, the corrosion current density, weight loss, and surface damage increased as the decontamination process cycle increased, and the corrosion damage of STS 304 tended to increase. Few ${\mu}m$ pitting damage was observed on the surface observation. In 5 cycle, the elongated wormhole-type pitting damage appeared, leading to relatively large surface damage. However, there was no significant difference in the degree of surface damage resulting from the increase in the temperature of the chemical decontamination solution.