• 한국구조물진단유지관리공학회 논문집
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• 제11권3호
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• pp.167-175
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• 2007

정밀한 구조물의 상태진단 혹은 안전성 평가는 비파괴 시험의 정밀성(Accuracy), 변이성(Variability) 등과 같은 여러 가지 요소에 의하여 좌우된다. 특히 비파괴 시험을 이용한 측정값과 구조물의 상태에 있어서의 불확실성(Uncertainty)은 정밀한 상태진단에 큰 영향을 미친다. 비파괴 시험을 활용함에 있어서의(간접조사) 신뢰할만한 비파괴 장비라면 현 구조물의 상태(피해면적)를 정확하게 나타낼 수 있어야 한다. 본 논문은 현재 사용이 증가되고 있는 비파괴 장비의 올바른 선택과 정확한 구조물의 안전 진단을 위하여, 비파괴장비의 성능 평가에 있어 확률적 기초를 제공한다.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 추계학술발표대회 논문집
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• pp.190-194
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• 2003

Two different types of nondestructive evaluation (NDE) techniques were employed to investigate the tensile behavior of ceramic matrix composites (CMCs). Two NDE methods, ultrasonic testing (UT) and infrared (IR) thermography, were used to assess defects and/or damage evolution before and during mechanical testing. Prior to tensile testing, a UTC-scan and a xenon flash method were performed to obtain initial defect information in light of UT C-scans and thermal diffusivity maps, respectively. An IR camera was used for in-situ monitoring of progressive damages. The IR camera measured temperature changes during tensile testing. This paper has presented the feasibility of using NDE techniques to interpret structural performance of CMCs.

• 한국신뢰성학회:학술대회논문집
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• 한국신뢰성학회 2001년도 정기학술대회
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• pp.235-238
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• 2001

It is well known that the reliability of materials of mechanical products is becoming more and more important not only for assurance of quality, but for international competition of products. In order to assure the reliability of materials or mechanical products nondestructive evaluation (NDE) techniques are playing more important roles. The existence of Internal defects in materials or mechanical parts is served as crack initiation site during the various loading condition. Historically, nondestructive evaluation (NDE) technique has been used almost exclusively for detecting microscopic discontinuities In materials or mechanical parts after they have been in service to expand the role of the NDE to include all aspects of materials production and application. Research efforts are being directed at developing and perfecting NDE techniques capable of monitoring (1) materials production processes (2) material integrity following transport, storage and fabrication and (3) the amount and rate of degradation during service. In addition, efforts are underway to develop technique capable of quantitative discontinuity sizing, permitting determination of response using fracture mechanics analysis, as well as techniques for quantitative materials characterization to replace the qualitative techniques used in the past. In this paper, the important role of NDE technology for reliability assurance of materials/mechanical parts is introduced.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 봄 학술발표회 논문집
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• pp.504-512
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• 2003

Simulation programs have been developed and used as an attempt to improve the accuracy of Non-Destructive Evaluation(NDE) techniques. The applicability of these programs is very limited, however, because it is difficult to describe the delicacy of the propagation of stress waves. To investigate the applicability of the finite element analysis for stress wave-based NDE techniques numerical simulation for Impact-Echo method and SASW method is performed. The numerical studies are performed to determine the essential parameters such as contact time of impact load, mesh size and time step size. These studies show that the choice of parameter is very important for improving the accuracy and confidence of the numerical procedure and, thereby, the applicability of the numerical analysis for stress wave-based NDE techniques

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
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• pp.803-808
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• 2001

Mathematical basis of interpretation of data from nondestructive evaluation (NDE) methods in bridge inspection is presented. In bridge inspection with NDE methods, NDE data are not assessments. NDE data must be interpreted as condition of element. Interpretation is then assessment. Correct assessments of conditions of bridge elements depend on the accuracy and variability in test data as well as on the uncertainty of correlations between attributes (what is measured) and conditions (what is sought in the inspection). Inaccuracy and variability in test data defines the qualify or NDE test. The qualify or test itself is important, but in view of condition assessment, the significance of uncertainty in correlations of attributes and conditions must be combined. NDE methods that are accurate in their measurements may still be found to be poor methods if attributes are uncertain indicators of condition of bridge elements. This paper reports mathematical presentation of inaccuracy and variability in test data and of uncertainty in correlation of attributes to element conditions with three examples of NDE methods.

• 한국구조물진단유지관리공학회 논문집
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• 제13권5호통권57호
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• pp.101-108
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• 2009

비파괴 시험을 이용한 RC 구조물의 진단에 있어서 비파괴 측정값의 적절한 해석을 통해서만 현 구조물의 상태진단이 가능하다. 보다 정확한 구조물의 상태진단은 비파괴 시험의 정밀성, 변이성 등과 같은 여러 가지 요소에 의하여 좌우된다. 특히 비파괴 시험을 이용한 측정값과 구조물의 상태에 있어서의 불확실성은 정밀한 상태진단에 큰 영향을 미친다. 본 논문은 현재 사용이 증가되고 있는 비파괴 장비의 올바른 선택과 정확한 구조물의 진단을 위하여, 비파괴 측정값의 확률적 해석법의 기초를 제공하고 있다.

• Journal of Korean Neurosurgical Society
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• 제48권6호
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• pp.506-517
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• 2010

Objective : We investigated whether Disability Evaluation (DE) situations influence patients' neuropsychological test performances and psychopathological characteristics and which variable play a role to establish an explanation model using statistical analysis. Methods : Patients were 536 (56.6%) brain-injured persons who met inclusion and exclusion criteria, classified into the DE group (DE; n = 300, 56.0%) and the non-DE group (NDE; n = 236, 44.0%) according to the neuropsychological testing's purpose. Next, we classified DE subjects into DE cluster 1 (DEC1; 91, 17.0%), DE cluster 2 (DEC2; 125; 23.3%), and DE cluster 3 (DEC3; 84, 15.7%) via two-step cluster analysis, to specify DE characteristics. All patients completed the K-WAIS, K-MAS, K-BNT, SCL-90-R, and MMPI. Results : In comparisons between DE and NDE, the DE group showed lower intelligence quotients and more severe psychopathologic symptoms, as evaluated by the SCL-90-R and MMPI, than the NDE group did. When comparing the intelligence among the DE groups and NDE group, DEC1 group performed worst on intelligence and memory and had most severe psychopathologic symptoms than the NDE group did. The DEC2 group showed modest performance increase over the DEC1 and DEC3, similar to the NDE group. Paradoxically, the DEC3 group performed better than the NDE group did on all variables. Conclusion : The DE group showed minimal "faking bad" patterns. When we divided the DE group into three groups, the DEC1 group showed typical malingering patterns, the DEC2 group showed passive malingering patterns, and the DEC3 group suggested denial of symptoms and resistance to treatment.

• 비파괴검사학회지
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• 제34권4호
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• pp.305-310
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• 2014

본 고에서는 미세 이물질이 삽입된 볼베어링에 대하여 비파괴평가를 제안하였다. 비파괴평가 연구로서 동적인 하중조건하 회전체의 동작에 따른 고장 진단을 위해 비접촉식 정량화된 적외선 열화상 기법을 적용하였다. 이로부터 볼베어링에 대한 적정 체결조건을 설정하였고 고장 상태감시에 대한 수동형 열화상시험을 수행하였다. 본 연구로부터, 적외선 열화상 시험은 조기의 결함 진단을 평가하기 위해 정상 및 이물질이 삽입된 시편들로부터의 온도 프로파일링을 비교, 분석되었다. 연구의 비파괴검사 평가의 결과로써, 고장에 이르는 이상단계에 따른 볼베어링의 온도 특성이 정량적으로 분석되었다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회A
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• pp.250-255
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• 2007

Steam generator tubes play an important role in safety because they constitute one of the primary barriers between the radioactive and non-radioactive sides of the nuclear power plant. For this reason, the integrity of the tubes is essential in minimizing the leakage possibility of radioactive water. The integrity of the tubes is evaluated based on NDE (non-destructive evaluation) inspection results. Especially ECT (eddy current test) method is usually used for detecting the flaws in steam generator tubes. However, detection capacity of the NDE is not perfect and all of the "real flaws" which actually existing in steam generator tunes is not known by NDE results. Therefore reliability of NDE system is one of the essential parts in assessing the integrity of steam generators. In this study POD (probability of detection) of ECT system for ODSCC in steam generator tubes is evaluated using multivariate logistic regression. The cracked tube specimens are made using the withdrawn steam generator tubes. Therefore the cracks are not artificial but real. Using the multivariate logistic regression method, continuous POD surfaces are evaluated from hit (detection) and miss (no detection) binary data obtained from destructive and non-destructive evaluation of the cracked tubes. Length and depth of cracks are considered in multivariate logistic regression and their effects on detection capacity are evaluated.

• Coupled systems mechanics
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• 제1권4호
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• pp.297-309
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• 2012

As a result of the medium coupling, propagation characteristics of ultrasonic waves guided by a multi-phase medium can be different from those in a homogeneous system. This phenomenon becomes prominent for a medium consisting of phases with considerably distinct material and physical properties (e.g., submerged structures or human bones covered with soft tissues). In this study, the coupling effect arising from both fluid and soft tissues on wave propagation in engineering structures and human bone phantoms, respectively, was explored and calibrated quantitatively, with a purpose of enhancing the precision of ultrasonic-wave-based non-destructive evaluation (NDE) and clinical quantitative ultrasound (QUS). Calibration results were used to rectify conventional NDE during evaluation of corrosion in a submerged aluminium plate, and QUS during prediction of simulated healing status of a mimicked bone fracture. The results demonstrated that with the coupling effect being appropriately taken into account, the precision of NDE and QUS could be improved.