• 한국측량학회지
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• 제34권4호
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• pp.357-372
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• 2016

Augustine volcano, located along the Aleutian Arc, is one of the most active volcanoes in Alaska and nearby islands, with seven eruptions occurring between 1812 and 2006. This study monitored the surface displacement before and after the most recent 2006 eruption. For analysis, we conducted a time-series analysis on data observed at the permanent GPS(Global Positioning System) observation stations in Augustine Island between 2005 and 2011. According to the surface displacement analysis results based on GPS data, the movement of the surface inflation at the average speed of 2.3 cm/year three months prior to the eruption has been clearly observed, with the post-eruption surface deflation at the speed of 1.6 cm/year. To compare surface displacements measurement by GPS observation, ENVISAT(Environmental satellite) radar satellite data were collected between 2003 and 2010 and processed the SBAS(Small Baseline Subset) method, one of the time-series analysis techniques using multiple InSAR(Interferometric Synthetic Aperture Radar) data sets. This result represents 0.97 correlation value between GPS and InSAR time-series surface displacements. This research has been completed precise surface deformation using GPS and time-series InSAR methods for a detection of precursor symptom on Augustine volcano.

• 한국측량학회지
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• 제20권4호
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• pp.415-421
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• 2002

오늘날 과학과 경제성장의 급속한 발달로 인해 많은 시설물들이 건설되어 왔다. 그중 교량은 도로의 기하구조적인 문제로 대형화되어 가는 추세이다. 그리고 현재 측량기법중 위성측량의 방법은 다양하게 실용화하고 있는 실정이다. 본 연구에서는 위성측량 기법중 RTK GPS 방법을 이용하여 종래에는 계측기로만 가능했던 교량변위를 측정하고, RTK GPS 관측값의 검증을 위해 토탈스테이션으로 검측하였다. 검증후 객체지향적 언어인 Dephi를 이용 교량경보시스템을 개발하고 적용시켜 보았다. 연구결과 0.2~8.3mm정도의 검증오차가 나타나므로 장대교량인 경우에는 실용 가능하다고 판단된다.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2022년도 봄 학술논문 발표대회
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• pp.87-88
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• 2022

For an earthquake-safe urban environment, the Republic of Korea conducts seismic performance evaluation in accordance with laws and guidelines to assign safety ratings and implement necessary management measures such as repairs and reinforcements. In the seismic performance evaluation result, structures lacking in preparation for earthquakes are prioritized and classified into measures such as repair, reinforcement, or careful observation to respond to physical risks such as earthquakes. Such repair and reinforcement work is not a one-time thing, but it is necessary to further enhance the effect through continuous follow-up observation. In this study, the location of the vertical and horizontal displacement measuring part of the construction part is displayed so that the post-construction status of the reinforcement construction part can be visually checked by identifying the problems in the process of post-monitoring in 2022 for the maintenance and reinforcement work of local governments' public facilities carried out in 2021. We propose a plan to institutionalize the installation of, inspection tools, and crack gauges at certain locations in the construction department, and to have facility managers periodically inspect and manage them with a smartphone program or the 'Facility Autonomous Safety Inspection' app.

• 한국구조물진단유지관리공학회 논문집
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• 제16권3호
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• pp.11-22
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• 2012

본 연구는 RTK-GPS (Real Time Kinematic-Global Positioning System) 측위법을 이용한 변위 계측 결과, 가속도계를 이용한 변위계측 결과, 그리고 LVDT(Linear variable differential transformer)의 변위계측 결과를 비교하여 RTK-GPS와 가속도계 센서를 구조물에 적용할 때의 문제점들을 파악하였다. 또한, 관측빈도와 측위 정확도를 향상시킨 RTK-GPS와 가속도계를 이용한 변위계측 결과를 통합 계산하여 절대변위인 LVDT와 비교를 통해 생성된 통합 변위의 정확도와 타당성을 확인하였다.

• 한국기계가공학회지
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• 제19권11호
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• pp.29-34
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• 2020

In this study, a sensitivity formulation was applied to analyze the dynamic response due to the effect of the excitation force for the undamped vibration of the cantilever beam. The theoretically fundamental formulations were derived considering an eigenvalue problem and its modal analysis to govern the second order algebraic differential equation in terms of the change in the modal coordinate with respect to the design parameters. A representative physical quantity pertaining to the dynamic response, that is, the rate of change in the dynamic displacement, was observed by changing the design variables, such as the cross-sectional area of the beam. The numerical results were obtained at various locations, considering the application of the external forces and observation of the dynamic displacement. When the detection position was closer to the free end of the cantilever beam, the sensitivity of the dynamic displacement was higher, as predicted through the oscillating motion of the beam. The presented findings can provide guidance to compute the dynamic sensitivity for a flexibly connected structure under dynamic excitations.

• 대한원격탐사학회지
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• 제40권2호
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• pp.141-150
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• 2024

Ground subsidence in urban areas is mainly caused by anthropogenic factors such as excessive groundwater extraction and underground infrastructure development in the subsurface composed of soft materials. Global Navigation Satellite System data with high temporal resolution have been widely used to measure surface displacements accurately. However, these point-based terrestrial measurements with the low spatial resolution are somewhat limited in observing two-dimensional continuous surface displacements over large areas. The synthetic aperture radar interferometry (InSAR) technique can construct relatively high spatial resolution surface displacement information with accuracy ranging from millimeters to centimeters. Although constellation operations of SAR satellites have improved the revisit cycle, the temporal resolution of space-based observations is still low compared to in-situ observations. In this study, we evaluate the extraction of a time-series of surface displacement in Incheon Metropolitan City, South Korea, using the small baseline subset technique implemented using the commercial software, Gamma. For this purpose, 24 COSMO-SkyMed X-band SAR observations were collected from July 12, 2011, to August 27, 2012. The time-series surface displacement results were improved by reducing random phase noise, correcting residual phase due to satellite orbit errors, and mitigating nonlinear atmospheric phase artifacts. The perpendicular baseline of the collected COSMO-SkyMed SAR images was set to approximately 2-300 m. The surface displacement related to the ground subsidence was detected approximately 1 cm annually around a few Incheon Subway Line 2 route stations. The sufficient coherence indicates that the satellite orbit has been precisely managed for the interferometric processing.

• 한국지하수토양환경학회지:지하수토양환경
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• 제23권1호
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• pp.1-13
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• 2018

A series of experiments using transparent micromodels with an artificial pore network etched on glass plates was performed to investigate the effects of flow rate on the migration and distribution of resident wetting porewater (deionized water) and injecting non-wetting fluid (n-hexane). Multicolored images transformed from real RGB images were used to distinguish n-hexane from porewater and pore structure. Hexane flooding followed by immiscible displacement with porewater, migration through capillary fingering, preferential flow and bypassing were observed during injection experiments. The areal displacement efficiency increases as the injection of n-hexane continues until the equilibrium reaches. Experimental results showed that the areal displacement efficiency at equilibrium increases as the flow rate increases. Close observation reveals that preferential flowpaths through larger pore bodies and throats and clusters of entrapped porewater were frequently created at lower flow rate. At higher flow rate, randomly oriented forward and lateral flowpaths of n-hexane displaces more porewater at an efficiency close to stable displacement. It may resulted from that the pore pressure of n-hexane, at higher flow rate, increases fast enough to overcome capillary pressure acting on smaller pore throats as well larger ones. Experimental results in this study may provide fundamental information on migration and distribution of immiscible fluids in subsurface porous media.

• 대한치과교정학회지
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• 제40권6호
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• pp.398-410
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• 2010

관절원반변위가 있는 여자 환자 중 초진 시와 일정 시간이 지난 기간 동안 교정 치료를 비롯한 교합에 변화를 줄만한 치료를 받지 않은 여성 환자를 대상으로 두 시기의 측모두부계측방사선 사진을 비교하여 골격 및 치성 변화를 관찰할 목적으로 시행되었다. 1996년 1월부터 2006년 12월 사이에 서울대학교 치과병원 치과교정과에 내원한 여자 환자 중 MRI를 촬영하여 관절원반변위가 있는 환자를 선별하였으며, 총 25명의 환자를 대상으로 연구를 하였다. 초진(T1) 시의 환자의 평균 연령(표준편차)은 18.1세(3.5세)이며 연령의 범위는 14.2 - 25.8세이고, 재진(T2)시 평균 연평(표준편차)은 21.1세(3.5세)이며 연령의 범위는 16.2 - 28.0세였다. 또한 평균 관잘 기간(표준편차)은 3.0년 (1.9년)이었고 범위는 7개월부터 6.7년이었다. 초진(T1), 재진(T2) 시와 두 기간 사이 변화량에 대한 각 변수의 기술 통계량을 계산하였다. 이상의 결과로부터 다음과 같은 결론을 얻었다. MRI로 관절원반변위를 진단받은 환자 중 교정치료나 악관절 치료 등 교합에 변화를 줄 만한 치료를 받지 않은 환자의 약 64%에서 하악골의 골격적인 변화가 나타났다. L1 to Mandibular plane은 0.8 mm 유의성 있게 증가하였다 (p < 0.01). 그러나 이를 제외한 나머지 치성 계측 항목인 전치돌출도, 전치피개도 및 U1 to Palatal plane (mm)의 변화는 유의성이 없었다. 변화의 방향은 주로 하악의 후하방회전이었고, 그 비율은 FMA가 $1^{\circ}$ 증가 시 SNB는 약 $0.43^{\circ}$ 감소하는 정도였다 (Spearman's rho = -0.660, p < 0.01). 일부 환자들은 수평적인 하악골의 후방 양상 이동을 보이기도 하였다.

• 한국산업융합학회 논문집
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• 제20권2호
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• pp.125-132
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• 2017

The slope of the road in the forest area has a characteristic of steep slope, so natural disasters such as slope collapse occur. The slope displacement observation technique according to landslide is being studied as a method to observe a wide area and a method to observe a small area. This is a study on high-precision digital map generation using ground LiDAR. It is possible to create a high - precision digital map by minimizing the US side using the 3D LiDAR in the steep slope area where the GPS and Total Station measurement are difficult in the maintenance of the danger slope area. It is difficult to objectively evaluate whether the contour lines generated by LiDAR are correct and it is considered necessary to construct a test bed for this purpose. Based on this study, if terrain changes such as landslides occur in the future, it will be useful for measuring slope displacement.

• Geomechanics and Engineering
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• 제12권6호
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• pp.919-933
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• 2017

A series of Brazilian tests under diameter compression for disc specimens was carried out to investigate the strength and failure behavior by using acoustic emission (AE) and photography monitoring technique. On the basis of experimental results, load-displacement curves, AE counts, real-time crack evolution process, failure modes and strength property of granite specimens containing two pre-existing holes were analyzed in detail. Two typical types of load-displacement curves are identified, i.e., sudden instability (type I) and progressive failure (type II). In accordance with the two types of load-displacement curves, the AE events also have different responses. The present experiments on disc specimens containing two pre-existing holes under Brazilian test reveal four distinct failure modes, including diametrical splitting failure mode (mode I), one crack coalescence failure mode (mode II), two crack coalescences failure mode (mode III) and no crack coalescence failure mode (mode IV). Compared with intact granite specimen, the disc specimen containing two holes fails with lower strength, which is closely related to the bridge angle. The failure strength of pre-holed specimen first decreases and then increases with the bridge angle. Finally, a preliminary interpretation was proposed to explain the strength evolution law of granite specimen containing two holes based on the microscopic observation of fracture plane.