• Computers and Concrete
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• v.2 no.6
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• pp.481-498
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• 2005

A wavelet based approach is proposed for structural damage detection in beams, plate and delamination of composite plates. Wavelet theory is applied here for crack identification of a beam element with a transverse on edge non-propagating open crack. Finite difference method was used for generating a general displacement equation for the cracked beam in the first example. In the second and third example, damage is detected from the deformed shape of a loaded simply supported plate applying the wavelet theory. Delamination in composite plate is identified using wavelet theory in the fourth example. The main concept used is the breaking down of the dynamic signal of a structural response into a series of local basis function called wavelets, so as to detect the special characteristics of the structure by scaling and transformation property of wavelets. In the light of the results obtained, limitations of the proposed method as well as suggestions for future work are presented. Results show great promise of wavelet approach for damage detection and structural health monitoring.

• Wind and Structures
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• v.20 no.1
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• pp.95-115
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• 2015

Wind effects on roofs are usually considered by equivalent static wind loads based on the equivalence of displacement or internal force for structural design. However, for large-span spatial structures that are prone to dynamic instability under strong winds, such equivalent static wind loads may be inapplicable. The dynamic stability of spatial structures under unsteady wind forces is therefore studied in this paper. A new concept and its corresponding method for dynamic instability-aimed equivalent static wind loads are proposed for structural engineers. The method is applied in the dynamic stability design of an actual double-layer cylindrical reticulated shell under wind actions. An experimental-numerical method is adopted to study the dynamic stability of the shell and the dynamic instability originating from critical wind velocity. The dynamic instability-aimed equivalent static wind loads of the shell are obtained.

• IEMEK Journal of Embedded Systems and Applications
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• v.9 no.4
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• pp.219-227
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• 2014

Natural disasters such as a ground collapse and a landslide have broken out due to the climate change of the Korea and the reckless expansion of cities and roads. The climate changes and the reckless urbanization have made the ground weak. Thus, it is important to keep a close eye on the highly weakened landslide and to prevent its natural disasters. In order to prevent these disasters, this paper presents a system of recognizing the road slide condition by measuring the displacements using laser scanner instrument. The previous system of monitoring the road slide has some problems as inaccurate recognition due to using only images from a camera, or expensive system such as artificial satellites and aircraft systems. To solve this problem, our proposed system uses the 3D range data from the laser scanner for measuring the accurate displacement of the road slide and optical flows from the Lucas-Kanade algorithm for recognizing the road slide in the image.

• Proceedings of the KSR Conference
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• 2006.11b
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• pp.322-327
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• 2006

Banwol bridge with steel plate girder and Pyongtaek bridge with PSC bos girder have been operated maintenance measuring system by the Seoul-Chonan of Kyongbu express railway. By analyzing the theoretical and experimental values of design load for these two bridge, the establishment of reference maintenance for measuring items was deduced from research. Two materials, steel and concrete plates, were considered as the upper structure. Actual measurement data for the behavior under speed, structural analysis results, and the presented references were analyzed and used to set up the reference establishment. The measuring items are stress(strain), displacement, dynamic acceleration, expansion movement, and dynamic frequency. The maintenance reference was established by comparing analytical and measuring values of the five items with respect to structural state class.

• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2001.10a
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• pp.71-82
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• 2001

인공위성을 이용한 범 지구 위치결정시스템인 GPS(Global Positioning System)는 수 밀리의 정밀도로 정적, 동적 위치측정이 가능한 시스템으로 교량, 건축물, 댐 등 각종 구조물의 미세한 변위를 측정하는데 이용되고 있다. 최근 국내에서도 대형구조물의 변위 측정에 GPS를 활용하려는 시도가 부분적으로 이루어지고 있으나 초보적인 단계이며 체계적인 연구가 이루어지지 못하고 있는 실정이다. 본 연구에서는 RTK(Real Time Kinematic) GPS로 구조물의 변위를 실시간 측정하고 모니터링 할 수 있는 시스템을 개발하였다. 먼저 예비실험으로 반송파의 차분에 의해서 증폭되는 수신기의 측정잡음 오차, 다중경로 오차, GDOP(Geometric Dilution of Precision)가 RTK GPS의 위치정확도에 미치는 영향을 분석하였다. 그리고, RTK GPS를 이용하여 마포대교를 관측한 결과, 수 센티미터 정도 발생하는 구조물의 변위를 3차원으로 정밀 관측할 수 있었으며, 본 연구에서 개발한 모니터링프로그램을 이용하여 구조물의 거동을 실시간으로 모니터링 할 수 있었다.

• Proceedings of the Korean Geotechical Society Conference
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• 2001.06a
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• pp.45-54
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• 2001

In this study, slope stability analysis of LCRS(Leachate Collection Removel System) in waste landfill was peformed by large scale field test. Geocomat is new type of geocomposite product. Gecomat is a sort of Geocomposite product. It is composed of nonwoven geotextiles, woven geotextile, and geonet. Large scale field tests were performed on the slope of different two LCRSsections with static loading condition. One is LCRS section witch consist of GCL, HDPE and Geocomat, another is GCL, HDPE, and woven type geocomposite. The behavior of geosynthetics lined slope was monitored by incorporating instrumentation including vertical soil pressure meter, settlement plate, strain gauges, potential meter, displacement pin.. Based on the field monitoring, the Geocomat LCRS section is less sliding than the conventional geocomposite LCRS section.

• Proceedings of the KSR Conference
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• 2008.11b
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• pp.789-795
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• 2008

Slope stability is affected by various factors. For safety management of slopes, monitoring systems have been widely constructed along railway lines. The representative data from the systems are variations of ground profile such like ground water level and pore water pressure etc. and direct displacement measured by ground clinometer and tension wire sensor. Slopes are mainly effected by rainfall and rainfall causes the decrease of factor of safety(FOS). Because FOS varies linearly by the variation of ground water level and pore pressure, it has a weak point that could not define the time and proper warning sign to secure the safety of the train. In this study, alternative of FOS such as reliability index and probability of failure is applied to slope stability analysis introducing the reliability concept. FOS, reliability index, probability of failure and velocity of probability of failure of the slopes by variation of ground water level are investigated for setting up the specification of safety management of slopes. By executing case study of a slope(ILLO-IMSUNGLI), it is showed to be applied to specification of safety management.

• Journal of Dental Anesthesia and Pain Medicine
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• v.19 no.4
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• pp.235-238
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• 2019

Corticobasal degeneration (CBD) is a rare neurodegenerative disease characterized by dystonia, cognitive deficits, and an asymmetric akinetic-rigid syndrome. Little information is available regarding anesthetic management for CBD patients. Our patient was a 55-year-old man with CBD complicated by central sleep apnea (CSA). Due to the risk of perioperative breathing instability associated with anesthetic use, a laryngeal mask airway was used during anesthesia with propofol. Spontaneous respiration was stable under general anesthesia. However, respiratory depression occurred following surgery, necessitating insertion of a nasopharyngeal airway. Since no respiratory depression had occurred during maintenance of the airway using the laryngeal mask, we suspected an upper airway obstruction caused by displacement of the tongue due to residual propofol. Residual anesthetics may cause postoperative respiratory depression in patients with CBD. Therefore, continuous postoperative monitoring of $SpO_2$ and preparations to support postoperative ventilation are necessary.

• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.149-156
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• 1995

This paper presents the surface profile of machined workpiece in face milling operation. The roughness model of feed direction is considered the cutting condition, the profile and run-out of inserts. For the dynamic model the cutting system can be modeled as avibratory system. The dynamic model of surface roughness is considered the relative displacements between tool and work- piece which can be obtained from the cutting system. These model can predict various surface roughnesses. i.e. maximum and arithmetic mean surface ruughnesses. Therefore, the developed model can be used for the monitoring of surface roughness.

• Proceedings of the Korean Society of Computer Information Conference
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• 2023.07a
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• pp.107-108
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• 2023

본 논문에서는 교량의 변위를 IoT 장치를 이용하여 실시간 측정하고 추출된 데이터를 이용하여 교량의 이상징후를 AI 기반으로 진단 및 모니터링 하는 방법을 제안한다. AI 모델 학습 학습을 위해서 비정상 상태의 교량이 필요하지만, 실제 교량에 인위적으로 비정상 상태를 만들 수 없으므로, 탄성 받침을 이용하여 모의 교량을 제작하였다. 탄성 받침을 이용하여 제작에 반영 및 모의교량에 적합한 모의 차량도 제작하여 정상적 데이터와 비정상적 데이터를 수집하였다. 수집된 데이터를 전처리 과정을 통해 AI 분석을 통해 교량의 이상 징후를 진단 및 모니터링하였으며, 제안 모델을 실험한 결과 96.7%의 정확도가 도출되었다.