• Proceedings of the KSR Conference
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• 2007.11a
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• pp.913-916
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• 2007

In this paper, the possibility of time reversal phenomenon was investigated in damage detection of structure. In conventional lamb wave techniques, damage is identified by comparing the measured data (baseline signals) and the current data. But this method can lead to high false signal in the intact condition of structures due to environmental conditions of the structures. So in this studying, we investigate the possibility of damage detection in the aluminum plate using the time reversal phenomenon of lamb waves.

• Proceedings of the KSR Conference
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• 2008.06a
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• pp.2066-2072
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• 2008

The time reversal was investigated for direct root between PZT and PZT, but in case of a circular PZT, lamb wave moves not only along the direct root but also another roots. The center frequency of lamb wave is kept when the lamb waves are reflected from damage. This paper presents experimental and theoretical results for the new structural health monitoring method by above features of lamb wave, and we can increase accuracy of the new structural health monitoring method by using STFT(Short Time Fourier Transform).

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.315-318
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• 2011

본 논문에서는 구조물 연결부의 실시간 손상 검색을 통해 이상이 감지되었을 경우 자가치유까지 가능한 지능형 볼트접합부 시스템에 관한 실험적 연구결과가 제시되었다. 지능형 센서인 PZT센서의 전기-역학적 커플링 특성을 이용한 전기역학적 임피던스 기반의 구조물 건전성 평가 방법이 사용되었다. 전기역학적 임피던스의 측정을 통한 계측값을 베이스라인 값과 비교하는 손상 평가를 통해 구조물 볼트접합부의 볼트풀림 손상을 진단하고, 손상은 손상지수 RMSD를 통하여 정량화되었다. 볼트접합부의 손상이 감지되었을 경우 형상기억합금(SMA) 와셔에 부착되어있는 히팅 필름에 전원을 가함으로써 형상기억합금에 열을 가하고, 가열된 형상기억합금 와셔는 축방향으로 팽창을 함으로써 잃었던 볼트의 토크력을 회복시켜주었다. 실험 결과, 제안된 전기역학적 임피던스 기반의 구조물 건전성 평가기법과 형상기억합금 와셔 기반의 볼트접합부 자가치유 시스템의 성능 평가와 검증이 이루어졌다.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.6
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• pp.550-557
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• 2008

Delamination damage at a bolt hole in a composite stiffened panel was detected using a built-in piezoelectric active sensor array. Various signal processing techniques were used to detect an invisible small scale delamination around a fastener hole due to localized transverse loading. A built-in piezoelectric sensor array was used to generate diagnostic signals and to measure response signals. Then, the response signals were processed to extract damage-sensitive features. Damage indexes were calculated to estimate the severity and location of the damage from the features.

• Tuberculosis and Respiratory Diseases
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• v.66 no.3
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• pp.241-245
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• 2009

Traumatic diaphragmatic rupture is uncommon, but requires a prompt diagnosis and repair. Diaphragmatic injury is most commonly associated with automobile accidents. The diagnosis is difficult and may be delayed because there are no specific symptoms, signs, or radiographic studies that are pathognomic for diaphragmatic injury. The most important factor in the diagnosis is a high suspicion and the use of proper diagnostic studies. We report a case involving the delayed presentation of diaphragmatic rupture in a 54 year old man, requiring surgical repair 12 days following multiple blunt trauma. It should be noted that early recognition for diaphragmatic injury is important in patients with multiple trauma to avoid the potential fatal complications.

• Journal of KSNVE
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• v.8 no.4
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• pp.723-732
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• 1998

원자력 발전소에서 운전되고 있는 원자로 냉각재 펌프는 대형 수직 펌프로서 증기 발생기로부터 원자로에 냉각재를 순환시키는 중요한 역할을 담당하고 있다. 원자로 냉각재 펌프는 운전 조건 및 각종 결함에 따라 진동, 열적 변형, 마모 등의 비정상 상태에서 운전될 수 있으며, 이로 인한 발전소 신뢰성 저하의 원인이 된다. 따라서 이 펌프의 감시 및 진단에 대한 연구가 계속되어 왔으며 각종 시스템이 설치 운용되고 있다. 그러나 미국내의 거의 모든 냉각재 펌프 감시 시스템은 펌프의 고진동 여부만을 나타내며 진동의 원인을 진단하기 어렵다. 본 연구에서는 최근까지 주로 발생되었던 미국내 원자로 냉각재 펌프의 문제점을 분석하고 이들의 원인별 진동 특성을 지식베이스화 하였으며, 진단시스템 개발을 위한 알고리즘을 제안하였다.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.218-219
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• 2010

유도 전동기의 편심 고장은 베어링 손상 등으로 발생되며, 심해질 경우 고정자와 회전자간의 접촉으로 전동기 파괴를 일으킨다. 이를 진단하는 대표적인 방법으로 온라인 전류 스펙트럼 분석법(Motor Current Signature Analysis, MCSA)이 있으나 전동기 정보의 필요, 부하에 영향을 받는 등의 문제점이 있다. 본 논문에서는 유도 전동기의 편심을 오프라인으로 진단하는 새로운 방법을 제안한다. 유도 전동기의 회전자의 위치를 변경하며 고정자 권선으로부터 관측된 임피던스 값으로 편심을 진단한다. 제안된 방법은 온라인 진단 후 정확한 편심 고장 여부를 확인하는데 사용될 수 있으며, 7.5마력 유도전동기의 정적, 동적, 복합 편심에 대한 실험을 통해 증명되었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.1
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• pp.19-32
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• 2024

An investigation into the detailed safety diagnosis report indicates that domestic highway bridges mainly suffer from defects, deterioration, and damage due to physical forces. In particular, deterioration is an inevitable damage that occurs due to various environmental and external factors over time. In particular, bridge deck is very vulnerable to cracks, which occur along with various types of damages such as rebar corrosion and surface delamination. Thus, this study evaluates a correlation between heterogeneous damage and deterioration environment and then identifies the main causes of such heterogeneous damage. After all, a bridge heterogeneous damage prediction model was developed using random forests to determine the top five factors contributing to the occurrence of the heterogeneous damage. The results of the study would serve as a basic data for estimating bridge maintenance and budget.

• The Journal of Korean Orthopaedic Ultrasound Society
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• v.8 no.1
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• pp.26-30
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• 2015

There are many traumatic foot and ankle problems in orthopaedic fields. Though it is not life-threatening problems, a delay in accurate diagnosis and treatments can danger limb function and therefore correct diagnosis can prevent long-term complications. Achilles tendon rupture is relatively common injury for active sports people. Ultrasonography is cost-effective, irradiation -free, effective for evaluation of soft tissues and dynamic analysis. It has been growing importance in Achilles tendon rupture. Ultrasonography is a diagnostic tool in Achilles tendon rupture. Physical examination and patient history is needed to diagnose Achilles tendon without image, but it is missed up by 20% in private clinic. Discontinuity of normal fibrillar architecture seen on an ultrasonographic image is diagnostic for Achilles tendon rupture, and can be accentuated by the performance of dorsi-flexion and plantar flexion, while observing in real time. And ultrasonography is a reliable method for serial observation after surgical treatment or conservative treatment.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.113-120
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• 2005

The purpose of this study is to suggest a method of concrete safety inspection management system for safety inspection. this research investigates the process of building safety inspection with IDEF0(Integration DEFinition) process modeling method, focusing on concrete durability inspection, and then suggests a data management system, which allows user communications between site and related unit with RDBMS(Relational Database Management System). The suggested system is expected to provide more efficient data sharing tools and consequently improve safety inspection's quality.