• Smart Structures and Systems
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• 제31권4호
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• pp.393-407
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• 2023

To assess structural condition in a non-destructive manner, computer vision-based structural health monitoring (SHM) has become a focus. Compared to traditional contact-type sensors, the advantages of computer vision-based measurement systems include lower installation costs and broader measurement areas. In this study, we propose a novel computer vision-based vibration measurement and coarse-to-fine damage assessment method for truss bridges. First, a deep learning model FairMOT is introduced to track the regions of interest (ROIs) that include joints to enhance the automation performance compared with traditional target tracking algorithms. To calculate the displacement of the tracked ROIs accurately, a normalized cross-correlation method is adopted to fine-tune the offset, while the Harris corner matching is utilized to correct the vibration displacement errors caused by the non-parallel between the truss plane and the image plane. Then, based on the advantages of the stochastic damage locating vector (SDLV) and Bayesian inference-based stochastic model updating (BI-SMU), they are combined to achieve the coarse-to-fine localization of the truss bridge's damaged elements. Finally, the severity quantification of the damaged components is performed by the BI-SMU. The experiment results show that the proposed method can accurately recognize the vibration displacement and evaluate the structural damage.

• 보존과학연구
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• 통권31호
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• pp.121-130
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• 2010

Wooden structures in Korea are usually damaged by some insects such as termites, wasps, cigarette beetles, powder-post beetles. Especially, the termites inhabiting in Korea are the subterranean termites, Reticulitermes speratus kyushuensis Morimoto, that make colonies in underground, therefore it is difficult to predict and control substantial infestations in advance. Accordingly, to enable inspectors to locate the termite infestations before the extensive damage occurs, the pest management industry has begun using several elaborate tools and making the various effect to inspect areas hard to access through a visual inspection. Recently detector dogs were adopted as one of those tools. Detector dogs are useful for locating subterranean termites because they use their acute olfaction rather than vision. We also have used detector dogs to locate termites and investigated 270 buildings from 31 sites since 2007. According to the results, while 144 buildings (53.4%) were in good condition with no damage by termites, 80 buildings (29.6%) were found out to be damaged by termites through visual inspection and detector dog. So it is expected to control termites according to the conservation status if detector dogs are well trained to discriminate live termites from fecal pellets by termites.

• 비파괴검사학회지
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• 제30권6호
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• pp.521-526
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• 2010

Gas transmission pipelines are often inspected and monitored using the magnetic flux leakage method. An inspection vehicle known as a "pig" is launched into the pipeline and conveyed along the pipe by the pressure of natural gas. The pig contains a magnetizer, an array of sensors and a microprocessor-based data acquisition system for logging data. This paper describes magnetic flux leakage (MFL) signal processing used for detecting mechanical damages during an in-line inspection. The overall approach employs noise removal and clustering technique. The proposed method is computationally efficient and can easily be implemented. Results are presented and verified by field tests from an application of the signal processing.

• 한국산림과학회지
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• 제97권6호
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• pp.656-660
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• 2008

본 연구는 숲가꾸기 작업을 위하여 개설된 작업로를 대상으로 노면피해에 영향을 미치는 요인을 평가하여 작업로 노면의 피해예방을 위한 적정 시설기준의 기초자료를 제공하고자 실시하였다. 작업로 노면피해에 영향을 크게 미치는 요인은 시설위치, 종단기울기, 겉보기토질, 산지사면형상, 노폭의 순으로 나타났다. 따라서 종단기울기, 노폭 등 도로 구조적인 요인과 시설위치, 산지사면형상 등 입지적 요인 그리고 겉보기 토질과 같은 도로 구성물질이 노면 피해 발생과 밀접한 연관이 있는 것으로 나타났다. 또한 작업로의 피해발생은 계곡부, 종단기울기 24%이상, 마사토 토질, 요형사면, 노폭 3.0 m이상에서 심한 것으로 나타났고, 안정성은 능선부, 종단기울기 4~24%, 토사지역, 직선형(-)사면, 노폭 3.0 m이하에서 큰 것으로 나타났다. 수량화II류의 판별식의 판별적중률은 79.4%로 상당히 양호한 값으로 나타나 작업로 노면의 양부판정에 활용이 가능할 것으로 사료된다.

• 비파괴검사학회지
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• 제36권5호
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• pp.391-398
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• 2016

음향방출기법은 구조물에 존재하는 손상 및 손상 메커니즘을 규명하는 가장 유효한 비파괴검사 수단으로 널리 이용되고 있다. 그러나 기존의 손상위치표정 기법은 탄성파 전파 속도에 크게 의존하는 기법의 한계에 의하여 복합재료 또는 이종의 재료로 구성된 구조물에서의 손상을 탐지하기 어려운 한계점을 가지고 있다. 최근 다양한 분야에서 사용되고 있는 압축천연가스(CNG) 저장용기는 무게와 강성의 효율을 위하여 복합재료를 사용하여 외부를 보강하는 새로운 형태의 구조를 사용하고 있다. 이러한 다층 복합소재의 사용으로 기존의 손상탐지기법으로는 저장용기의 외부에서 가해지는 충격 혹은 결함에 의한 저장탱크에 발생한 손상의 측정이 매우 어렵게 되었다. 이러한 한계를 극복하기 위하여 본 연구에서는 선행연구를 통하여 개발된 에너지 기반 contour D/B map 기법을 이용하여 4 가지 형식의 CNG 저장탱크에 발생한 외부 충격 신호의 손상 위치를 측정하였다. 각각의 형식의 저장탱크에서 측정된 손상 위치 결과를 비교 분석하여 새로운 기법의 측정 성능을 알아보았다.

• Smart Structures and Systems
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• 제22권5호
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• pp.509-525
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• 2018

Sensors and systems in Civionics technology play an important role for continuously facilitating real-time structure monitoring systems by detecting and locating damage to or degradation of structures. An advanced materials, design processes, long-term sensing ability of sensors, electromagnetic interference, sensor placement techniques, data acquisition and computation, temperature, harsh environments, and energy consumption are important issues related to sensors for structural health monitoring (SHM). This paper provides a comprehensive survey of various sensor technologies, sensor classes and sensor networks in Civionics research for existing SHM systems. The detailed classification of sensor categories, applications, networking features, ranges, sizes and energy consumptions are investigated, summarized, and tabulated along with corresponding key references. The current challenges facing typical sensors in Civionics research are illustrated with a brief discussion on the progress of SHM in future applications. The purpose of this review is to discuss all the types of sensors and systems used in SHM research to provide a sufficient background on the challenges and problems in optimizing design techniques and understanding infrastructure performance, behavior and current condition. It is observed that the most important factors determining the quality of sensors and systems and their reliability are the long-term sensing ability, data rate, types of processors, size, power consumption, operation frequency, etc. This review will hopefully lead to increased efforts toward the development of low-powered, highly efficient, high data rate, reliable sensors and systems for SHM.

• Maxillofacial Plastic and Reconstructive Surgery
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• 제32권6호
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• pp.567-572
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• 2010

Intraoperative breakage of instruments can be occurred unexpectedly. To prevent damage of neighboring important anatomic structures and consequent complications, broken instruments should be removed as soon as possible. There have been several methods to remove broken instruments. One of them is the Carm fluoroscopy which is commonly used for locating metal foreign bodies. However, its application for removal of broken instruments in the oral and maxillofacial area is not common. In our experiences with the removal of two broken instruments in mandibular area, the newly developed dental mini C-arm was used to find broken instrument in soft tissue, because it gives real-time in situ information for the intraoperative location. We report two cases with broken instruments, a broken dental needle in the pterygomandibular space and a broken straight bur in the mandibular angle area. They were identified and could be removed safely using a dental mini C-arm.

• 한국지반공학회지:지반
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• 제7권2호
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• pp.27-40
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• 1991

동아대학교 승학캠퍼스는 산지를 굴착하여 약 10년 전부터 연차적으로 건설되어 왔다. 1989년 8월에 내린 200mm16ay이상의 집중호우로 인한 지하수 및 산사태로써 건물, 사면, 미로 등 많은 피해를 입었다. 이 피해의 원인조사 및 보완대책을 위하여 현황 및 50m 격자형 위치측량, 예비조사, 야외간이 측량법, 지구 물리학적 탐사법, 시추조사 및 흙의 특성시험 등이 수행되었다. 이러한 조사결과를 바탕으로 피해의 원인 및 예측을 수행하였으며 수평배수공법, 위험한 노출암괴의 제거, 지하배수를 겸한 옹벽설치, 붕적층의 제거 및 격자형 블록에 의한 사면안정공법 등좌 보완대책이 수립되었다.

• 한국분말재료학회지
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• 제1권2호
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• pp.159-166
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• 1994

The variation of the microstructures and the mechanical properties with varying vacuum hot pressing temperature and pressure was investigated in PyM processed 20 vol%) SiCw/ 2124Al composites. As increasing the vacuum hot pressing temperature, the aspect ratio of whiskers and density of composites increased due to the softening of 2124Al matrix with the increased amount of liquid phase. The tensile strength of composite increased with increasing vacuum hot pressing temperature up to $570^{\circ}C$ and became saturated above $570^{\circ}C$, To attain the high densification of composites above 99%, the vacuum hot pressing pressure was needed to be above 70 MPa. However, the higher vacuum hot pressing pressure above 70 MPa was not effective to increase the tensile strength due to the reduced aspect ratio of SiC whiskers from damage of whiskers during vacuum hot pressing. A phenomenological equation to predict the tensile strength of $SiC_w$/2124AI composite was proposed as a function including two microstructural parameters, i.e. density of composites and aspect ratio of whiskers. The tensile strength of $SiC_w$/2124AI were found more sensitive to the porosity than other P/M materials due to the higher stress concentration and reduced load transfer efficiency by the pores locating at whisker/matrix interfaces.

• 대한전기학회논문지:전력기술부문A
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• 제51권7호
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• pp.349-361
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• 2002

Occasionally, equipment in a distribution system fails due to damage from weather, vandalism, or other causes. Failures and unexpected events do not always occur as and where expected. Therefore, a good contingency plan, multi-zone or otherwise, provides flexibility by locating switches at various strategic locations so that parts of a feeder can be picked up in the event of line outages at various places. It is possible to create feeder system layout that achieve remarkable contingency support economics, even as their normal peak loading levels approach thermal capacity, by utilizing six, seven, or even nine switchable zones per feeder. But many switchable zones per feeder are of questionable practicality and effectiveness, because of the complexity and time required for the switching operation. In practice, a zonal scheme with between three and four zones will usually provide complete contingency backup for all feeders. Line switches have both capital and maintenance costs, the planning for multi-zonal schemes is considerably more difficult than or loop or single-zone systems, and the required switching operations required during contingencies take more time. But multi-zonal schemes are used because these costs come to far less than the cost of additional capacity required for loop or single-zone. In this paper, we present the optimal number of switchable zones per feeder in Kora distribution system.