• KIEAE Journal
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• 제7권4호
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• pp.141-146
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• 2007

It is necessary to guarantee the safety, serviceability and durability of reinforced concrete structures over their service life. However, concrete structures represent a decrease in their durability due to the effects of external environments according to the passage of time, and such degradation in durability can cause structural degradation in materials. In concrete structures, some degradations in durability increase the corrosion of embedded rebars and also decrease the structural performance of materials. Thus, the structural condition assessment of RC materials damaged by corrosion of rebars becomes an important factor that judges needs to apply restoration. In order to detect the damage of reinforced concrete structures, a visual inspection, a nondestructive evaluation method(NDE) and a specific loading test have been employed. However, obscurities for visual inspection and inaccessible members raise difficulty in evaluating structure condition. For these reasons, detection of location and quantification of the damage in structures via structural response have been one of the very important topics in system identification research. The main objective of this project is to develope a methodologies for the damage identification via static responses of the members damaged by durability. Six reinforced concrete beams with variables of corrosion position and corrosion width were fabricated and the damage detections of corroded RC beams were performed by the optimization and the conjugate beam methods using static deflection. In results it is proved that the conjugate beam method could predict the damage of RC members practically.

• 원예과학기술지
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• 제31권5호
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• pp.617-625
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• 2013

상록활엽 조경소재 연구개발의 일환으로써, 기후변화에 대응하여 내한성이 우수한 남부지역 상록활엽수 중에서 멀꿀과 다정큼나무에 대하여 가시적 피해, 엽록소 형광이미지, MDA(malondialdehyde) 농도 분석으로 내염성을 평가하였다. NaCl 농도가 증가함에 따라서 토양 pH는 감소하고 EC는 증가하였으며 멀꿀이 생육 중은 토양은 다정큼나무가 생육 중인 토양보다 더 강하게 영향을 받았다. 시각적 피해에서 멀꿀은 처리 후 20일에 200mM NaCl 농도 이상에서 고사하였다. 다정큼나무는 비록 400mM NaCl 농도에서 잎의 피해를 나타냈지만 실험기간 동안 모두 생존하였다. 엽록소 형광이미지에서 색상변화는 시각적 피해 결과와 강한 일관성을 보였다. NaCl 농도가 증가함에 따라서 멀꿀 잎의 적색은 유의성 있게 낮은 형광 값인 청색으로 변화하였고 변화는 가장자리에서 중앙으로 옮겨갔다. 다정큼나무의 형광이미지 반응은 NaCl 처리일이 증가할수록 잎의 가장자리에 변화가 나타났으나 여전히 실험기간 동안 적색을 나타냈다. 가장 높은 시각적 피해와 EC를 보였던 처리 후 5일에 멀꿀의 MDA 농도는 $4.56nmol{\cdot}g^{-1}$였다. 다정큼나무의 MDA 농도는 400mM NaCl 농도 처리구를 제외한 모든 처리구들에서 $1.5nmol{\cdot}g^{-1}$ 이하를 나타냈다.

• 한국공간구조학회논문집
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• 제11권2호
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• pp.55-62
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• 2011

최근 테러의 발생빈도가 증가하는 가운데 테러는 불특정 다수의 사람이 모이는 건물에서 집중적으로 발생하고 있다. 이중 고층, 초고층 빌딩에서 발생하는 테러는 막대한 피해를 발생시킨다. 이에 따른 건물의 테러피해 경감을 위한 다양한 연구가 필요하다. 본 논문에서는 비교적 수행절차가 간단하며 단기간에 실행이 가능한 Fema 455 - Rapid Visual Screening을 통해 현재 사용 중인 국내 고층 초고층 건물의 테러에 대한 위험도를 평가하여 국내 건물이 가지는 공통적인 테러 위험요소를 확인하였다. 평가결과 대상 건물은 모두 중위험도의 범위에 있다. 이는 국내 고층, 초고층 건물의 외부 환경적인 특징이 비슷한 데에 그 원인이 있었다.

• 대한토목학회논문집
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• 제28권6A호
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• pp.873-880
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• 2008

구조물의 열화 또는 손상상태 점검 시 정기적인 외관조사는 매우 중요한 역할을 담당한다. 이때 실시되는 외관조사는 주로 조사자의 스케치나 일반 카메라를 이용한 사진촬영에 의해 이루어지고 있다. 이럴 경우, 조사에 많은 노력과 시간이 소요된다. 따라서 본 연구에서는 보다 효율적이고 효과적인 조사를 위하여, 터널 외관상의 결함을 자동인식 할 수 있는 시스템을 개발하고자 한다. 이 과정에서 결함 손상인식을 위한 화상처리기술과 데이터 관리 및 분석 시스템이 중점적으로 개발 응용되었다. 이를 통해 콘크리트의 균열, 누수, 백화, 박리, 박락, 손상 등의 결함을 인식하여 데이터를 획득하고, 지속적이고 체계적인 데이터 관리시스템을 구축하여, 터널의 안전성 확보, 기능성 유지, 수명연장 등의 효과를 얻고자 한다.

• Geomechanics and Engineering
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• 제17권1호
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• pp.81-95
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• 2019

Due to the importance of soil reinforcement using geotextiles in geotechnical engineering, study and investigation into long-term performance, design life and survivability of geotextiles, especially due to installation damage are necessary and will affect their economy. During installation, spreading and compaction of backfill materials, geotextiles may encounter severe stresses which can be higher than they will experience in-service. This paper aims to investigate the installation damage of geotextiles, in order to obtain a good approach to the estimation of the material's strength reduction factor. A series of full-scale tests were conducted to simulate the installation process. The study includes four deliberately poorly-graded backfill materials, two kinds of subgrades with different CBR values, three nonwoven needle-punched geotextiles of classes 1, 2 and 3 (according to AASHTO M288-08) and two different relative densities for the backfill materials. Also, to determine how well or how poorly the geotextiles tolerated the imposed construction stresses, grab tensile tests and visual inspections were carried out on geotextile specimens (before and after installation). Visual inspections of the geotextiles revealed sedimentation of fine-grained particles in all specimens and local stretching of geotextiles by larger soil particles which exerted some damage. A regression model is proposed to reliably predict the installation damage reduction factor. The results, obtained by grab tensile tests and via the proposed models, indicated that the strength reduction factor due to installation damage was reduced as the median grain size and relative density of the backfill decreases, stress transferred to the geotextiles' level decreases and as the as-received grab tensile strength of geotextile and the subgrades' CBR value increase.

• 한국복합재료학회:학술대회논문집
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• 한국복합재료학회 2003년도 춘계학술발표대회 논문집
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• pp.125-128
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• 2003

Low-velocity impact damage is a major concern in the design of structures made of composite materials, because impact damage is hidden inside and cannot be detected by visual inspection. The piezoelectric thin film sensor can be used to detect variations in structural and material properties for structural health monitoring. In this paper, the PVDF and PZT sensors were used for monitoring impact damage initiation in Gr/Ep composite panel to illustrate this potential benefit. A series of impact test at various impact energy by changing impact mass and height is performed on the instrumented drop weight impact tester. The wavelet transform(WT) is used to decompose the piezoelectric sensor signals in this study. Test results show that the particular waveform of sensor signals implying the damage initiation and development are detected above the damage initiation impact energy. And it is found that both PZT and PVDF sensors can be used to detect the impact damage.

• Structural Engineering and Mechanics
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• 제41권4호
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• pp.539-558
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• 2012

The diagnosis of bridge serviceability is carried out by a combination of in-situ visual inspection, static and dynamic loading tests and analyses. Structural health monitoring (SHM) using information technology and sensors is increasingly being used for providing a better estimate of structural performance characteristics rather than above traditional methods. Because the mechanical behavior of bridges with various kinds of damage can not be made clear, it is very difficult to estimate both the damage mode and degree of damage of existing bridges. In this paper, the sensitivity of both static and dynamic behaviors of bridges are studied as a measure of damage assessment through experiments on model bridges induced with some specified artificial damages. And, a method of damage assessment of bridges based on those behaviors is discussed in detail. Finally, based on the results, a possible application for structural health monitoring systems for existing bridges is also discussed.

• The Journal of Korean Physical Therapy
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• 제31권2호
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• pp.67-75
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• 2019

Purpose: Patients with brain damage suffer from limitations in performing the activities of daily living (ADL) because of their motor function and visual perception impairment. The aim of this study was to help improve the motor function and visual perception ability of patients with brain damage by providing them with virtual reality-based contents. The usability results of the patients and specialists group were also evaluated. Methods: The ADL contents consisted of living room, kitchen, veranda, and convenience store, similar to a real home environment, and these were organized by a rehabilitation specialist (e.g., neurologist, physiotherapist, and occupational therapist). The contents consisted of tasks, such as turning on the living room lights, organizing the drawers, organizing the kitchen, watering the plants on the veranda, and buying products at convenience stores. To evaluate the usability of the virtual reality-based visual cognitive rehabilitation service, general elderly subjects (n=11), stroke patients (n=7), stroke patients with visual impairment (n=4), and rehabilitation specialists (n=11) were selected. The questionnaires were distributed to the subjects who were using the service, and the subjective satisfaction of individual users was obtained as data. The data were analyzed using SPSS 21.0 software. The general characteristics of the users and the evaluation scores of the experts were analyzed using descriptive statistics. Results: The usability test result of this study showed that the mean value of the questionnaire related to content understanding and difficulty was high, between 4-5 points. Conclusion: The virtual reality rehabilitation service of this study is an efficient service that can improve the function, interest, and motivation of stroke patients.

• 한국산학기술학회논문지
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• 제19권11호
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• pp.421-425
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• 2018

본 메탄올은 공업용 용매로 흔히 사용되는 무색의 휘발성, 유독성 액체이다. 메탄올 중독에 의해서 시각 장애는 흔히 나타나는 증상 및 후유증의 하나지만, 흡입으로 인한 중독에서는 잘 나타나지 않는 것으로 알려져 있다. 그렇기 때문에 메탄올을 흡인한 이후에 시력저하가 생긴 증례는 잘 발표되어 있지 않다. 우리는 산업장에서 호흡기를 통해서 메탄올이 흡입된 이후에 시력손실이 발생한 케이스를 보고하고자 한다. 한국의 한 휴대폰 공장에서 일하던 28세 여자환자가 의식저하로 응급실로 내원하였다. 그녀는 이틀 전부터 시야가 흐릿하게 보였지만 대수롭지 않게 여겨 따로 병원을 찾아가지 않았고, 의식저하가 발생하여서야 병원에 오게 되었다. 내원시 환자는 글래스고혼수척도 9점의 의식저하를 보였으며, 혈액 검사 결과 심한 대사성 산증을 보이고 있었다. 중환자실에 입원하여 응급 투석을 비롯하여 메탄올 중독에 대한 치료를 시행하였다. 치료 후 의식이 회복되어 퇴원할 수 있었으나, 6개월 후까지 재활치료를 받고 있으며, 영구적으로 시력저하가 남았다. 흡입을 통해서도 메탄올 중독이 발생 할 수 있으며, 이는 초기에 알아차리기가 쉽지 않다. 하지만 메탄올 중독의 치료는 시간과의 싸움이며, 초기에 빠르게 치료해야 예후가 좋다. 그러므로 흡입에 의한 중독 가능성을 항상 염두에 두어야 하며, 의심시에는 빠르게 치료를 해야만 한다.

• Smart Structures and Systems
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• 제31권6호
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• pp.573-583
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• 2023

Although unmanned aerial vehicles have been used to overcome the limited accessibility of human-based visual inspection, unresolved issues still remain. Onsite inspectors face difficulty finding previously detected damage locations and tracking their status onsite. For example, an inspector still marks the damage location on a target structure with chalk or drawings while comparing the current status of existing damages to their previous status, as documented onsite. In this study, an augmented-reality-based structural inspection system with onsite damage information marking was developed to enhance the convenience of inspectors. The developed system detects structural damage, creates a holographic marker with damage information on the actual physical damage, and displays the marker onsite via an augmented reality headset. Because inspectors can view a marker with damage information in real time on the display, they can easily identify where the previous damage has occurred and whether the size of the damage is increasing. The performance of the developed system was validated through a field test, demonstrating that the system can enhance convenience by accelerating the inspector's essential tasks such as detecting damages, measuring their size, manually recording their information, and locating previous damages.