• Proceedings of the Korean Society of Surveying, Geodesy, Photogrammetry, and Cartography Conference
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• 2004.04a
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• pp.113-117
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• 2004

Such social structures as bridges, buildings, dams and towers have been transformed by their own load or fundamental ground. They have been behaved by other external causes. These regular or irregular behaviors threaten to do their users safety. Therefore, to monitor the load of the structures or reaction shown by them could help to verify their behaviors. RTK GPS allows the use of a static base station and remote rover unit to allow for data collection within several seconds and in real time. It is useful for monitoring the behaviors of massive structures like bridges. In this Study, Among GPS methods, we used RTK GPS to analyze the precision of monitoring and then on the basis of it, we developed a monitoring system using RTK GPS when measured the behavior of main tower of a suspension bridge by using RTK GPS. Comparing a deviation between observation values, X axis was 1mm, Y axis was 1mm and Z axis 2.2mm. It turned out that it was possible to monitor and measure structures by RTK GPS.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.10
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• pp.41-47
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• 2008

This study aims to obtain machining characteristics during AFM (Atomic force Microscope) machining of silicon wafers and to monitor the machining states using acoustic emission. As in micro scale machining, two distinct regimes of deformation, i. e. ploughing regime and cutting regime were observed. First, the transition between the two regimes are investigated by analyzing the "pile-up" during machining. As far as in process monitoring is concerned, in the ploughing repime, no chips have been formed and related AE RMS values are relatively low, In the mean time, in the cutting regime, the RMS values are significantly higher than the ploughing regime, with apparent chip formation. From the results, we found out that the proposed scheme can be used for the monitoring of nanomachining, especially for the characterization of nanocutting mode transition.

• Journal of Magnetics
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• v.18 no.4
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• pp.473-480
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• 2013

A new concept design of electromagnetic energy harvester is proposed for powering a tire pressure monitoring sensor (TPMS). The thin coil strap is attached on the circumferential surface of a rim and a permanent magnet is placed on the brake caliper system. When the wheel rotates, the relative motion between the magnet and the coil generates electrical energy by electromagnetic induction. The generated energy is stored in a storage unit (rechargeable battery, capacitor) and used for TPMS operation and wireless signal transmission. Innovative layered design of the strap is provided for maximizing energy generation. Finite Element Method (FEM) and experiment results on the proposed design are compared to validate the proposed design; further, the method for design improvement is discussed. The proposed design is excellent in terms of durability and sustainability because it utilizes the everlasting rotary motion throughout the vehicle life and does not require material deformation.

• Proceedings of the Korean Geotechical Society Conference
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• 2008.10a
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• pp.1712-1716
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• 2008

Performance of ground improvement project using prefabricated vertical drains of condition, in which approximately 10m dredged fill overlies original soft foundation layer in the coastal area has been conducted. From field monitoring results, excessive ground settlement compared to predicted settlement in design stage developed during the following one year. In order to predict the final consolidation behavior, recalculation of consolidation settlements and back analysis using observed settlements were conducted. Field monitoring results of surface settlements were evaluated, and then corrected because large shear deformation was occurred by construction events in the early stages of consolidation. To predict the consolidation behavior, material functions and in-situ conditions from laboratory consolidation test were re-analyzed. Using these results, height of additional embankment is estimated to satisfy residual settlement limit and maintain an adequate ground elevation. The recalculated time-settlement curve has been compared to field monitoring results after additional surcharge was applied.

• International conference on construction engineering and project management
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• 2024.07a
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• pp.102-111
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• 2024

Roadbed stability is paramount in urban areas as it directly affects public safety and city operations. South Korea's major metropolis has experienced 1127 cases of ground subsidence since 2014, affecting subways, roads, railways, and construction sites. Notably, about 40% of these incidents coincide with heavy summer rainfall, while 60% resulted from utility damage, improper backfill, and groundwater fluctuations. Subsequently, roadbed instability leads to a range of cascading hazards, including sinkholes and road failures, endangering public safety and the economy. Therefore, continuous monitoring of roadbed stability and implementing proactive measures are essential for a resilient transportation infrastructure. However, terrestrial in-situ observations like GPS provide accurate surface's displacement with high temporal accuracy but limited spatial resolution. To address this issue, we used the InSAR permanent scatterer (PSInSAR) technique to process 35 Sentinel-1 SLC datasets acquired between 2017 and 2022 to monitor and prevent cascading hazards in Daejeon City, South Korea. The results revealed an average subsidence rate of -0.88mm/year with a maximum of -7.73 mm/year. Notably, the southern part of the city exhibited significant roadbed instability, with an average and maximum cumulative subsidence of -5.13 mm and -44.95 mm, respectively. The deformation data was then integrated with road geometry to develop a vulnerability map of the city, highlighting the pronounced roadbed deformation in the southern region. Time-series subsidence variations correlated with groundwater fluctuations data from 2017 to 2022, showing a decline in groundwater levels from 4.63m to 9.9m in the southern region. Furthermore, a comparison between subsidence rates and effective shear wave velocity (V_s³⁰) revealed that most subsidence events were associated with V_s³⁰ values below 420 m/sec, indicating a clear lithological influence on the spatial distribution of roadbed instability. Thus, the integrated geotechnical and hydrogeological data with PSInSAR monitoring can better understand the processes responsible for roadbed instability in areas with small-scale variations.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.6
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• pp.141-146
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• 2016

Geotechnial engineering projects that requires excavation activity can cause massive ground deformation and this can damage adjacent structures. Depending on the engineering characteristics of ground material and the excavation depth, the ground movement is various. To overcome this issue, the ground deformation is monitored by multiple sensors. Typically, an inclinometer is installed behind the support wall. In this paper, we present an adaptive duty-cycling control mechanism using wireless sensors for monitoring ground deformation in excavations. The proposed mechanism dynamically adjusts the sleep time based on the urgency degree of sensed data from inclinometer. Through analytical evaluation of expected latency time, we confirm our adaptive duty-cycling mechanism has lower latency compared with periodic duty-cycling mechanism under variable conditions.

• Korean Journal of Remote Sensing
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• v.33 no.1
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• pp.37-46
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• 2017

Sinabung volcano in Indonesia was formed due to the subduction between the Eurasian and Indo-Australian plates along the Pacific Ring of Fire. After being dormant for about 400 years, Sinabung volcano erupted on the 29th of August, 2010 and most recently on the 1st of November, 2016. We measured the deformation of Sinabung volcano using Advanced Land Observing Satellite/Phased Array type L-band Synthetic Aperture Radar(ALOS/PALSAR) interferometric synthetic aperture radar(InSAR) images acquired from February 2007 to January 2011. Based on multi-temporal InSAR processing, we mapped the ground surface deformation before, during, and after the 2010 eruption with time-series InSAR technique. During the 3 years before the 2010 eruption, the volcano inflated at an average rate of ~1.7 cm/yr with a markedly higher rate of 6.6 cm/yr during the 6 months prior to the 2010 eruption. The inflation was constrained to the top of the volcano. From the 2010 eruption to January 2011,the volcano subsided by approximately 3 cm (~6 cm/yr). We interpreted that the inflation was due to magma accumulation in a shallow reservoir beneath Sinabung. The deflation was attributed to magma withdrawal from the shallow reservoir during the eruption as well as thermo-elastic compaction of erupted material. This result demonstrates once again the utility of InSAR for volcano monitoring.

• Journal of the Korean Geotechnical Society
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• v.19 no.6
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• pp.189-206
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• 2003

During tunnel excavation in urban area a systematic monitoring is important for the purpose of determination of support type and quantity, as well as for the control of stability of both surface structures and the tunnel itself due to the frequently, and in many cases, abruptly changing ground condition. In Austria absolute displacement monitoring methods have replaced relative displacement measurements by geodetic methods to a large extent. Prompt detection of weak ground ahead of the tunnel face as well as better adjustment of excavation and support to the geotechnical conditions is possible with the help of the improved methods of data evaluation on sites. Deformation response of the ground to excavation starts ahead of the tunnel face, therefore, the deformation and state of the tunnel advance core is the key factor of the whole deformation process after excavation. In other words, the rigidity and state of the advance core play a determining role in the stability of both surface structures and the tunnel itself. This paper presents the results from detailed three-dimensional numerical studies, exploring vertical displacements, vector orientations and extrusions on tunnel face during the progressive advancement for the shallow tunnel in various geotechnical conditions.

• Journal of the Korean Society for Nondestructive Testing
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• v.22 no.1
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• pp.22-31
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• 2002

A Safety Monitoring System using a laser and 2-D arrayed photo sensors is developed. To monitor of the deformation and small rotation of structure the developed optical system using 2-D photo sensor array was used to detect the variation of optical orbit of laser which was induced by deformation of the structure. Also, an operating program to manage the system and an algorithm for the data acquisition and the database are introduced. In this study, we demonstrated the capabilities of this system by laboratory experiments before applying the system to the field.

• Journal of the Korea institute for structural maintenance and inspection
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• v.13 no.5 s.57
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• pp.93-100
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• 2009

This study presents reasonable relationships to estimate the deformation based on beam mechanism analysis and TDR(Time Domain Reflectometry) data. To declar the length points of co-axial cable installed in civil structure, Nano material ($BaTiO_3$ powders and silver mixture) is used on co-axial cables. From the laboratory test, nano material could make the correct information about attached cable points on beam, and TDR sensor system and Fourier series (data filter) found out the deformation of beam. Therefore it is concluded that the correct deformed information of beam were acquired by Nano-TDR and Fourier filter, they are much more effective to apply at health monitoring system in civil structure compared to conventional TDR or Fiber Optic Sensor (FOS) systems.