• Structural Engineering and Mechanics
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• v.31 no.5
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• pp.527-544
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• 2009

In this study, the periodic seismic performance evaluation scheme is proposed using a structural health monitoring system in terms of seismic fragility. An instrumented highway bridge is used to demonstrate the evaluation procedure involving (1) measuring ambient vibration of a bridge under general vehicle loadings, (2) identifying modal parameters from the measured acceleration data by applying output-only modal identification method, (3) updating a preliminary finite element model (obtained from structural design drawings) with the identified modal parameters using real-coded genetic algorithm, (4) analyzing nonlinear response time histories of the structure under earthquake excitations, and finally (5) developing fragility curves represented by a log-normal distribution function using maximum likelihood estimation. It is found that the seismic fragility of a highway bridge can be updated using extracted modal parameters and can also be monitored further by utilizing the instrumented structural health monitoring system.

• Korean Journal of Remote Sensing
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• v.37 no.5_2
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• pp.1329-1340
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• 2021

The intertidal zone, which is a transitional zone between the ocean and the land, requires continuous monitoring as various changes occur rapidly due to artificial activity and natural disturbance. Monitoring of coastal topography changes using remote sensing method is evaluated to be effective in overcoming the limitations of intertidal zone accessibility and observing long-term topographic changes in intertidal zone. Most of the existing coastal topographic monitoring studies using remote sensing were conducted through high spatial resolution images such as Landsat and Sentinel. This study extracted the waterline using the NDWI from the GOCI-II (Geostationary Ocean Color Satellite-II) data, identified the changes in the intertidal area in Gyeonggi Bay according to various tidal heights, and examined the utility of DEM generation and topography altitude change observation over a short period of time. GOCI-II (249 scenes), Sentinel-2A/B (39 scenes), Landsat 8 OLI (7 scenes) images were obtained around Gyeonggi Bay from October 8, 2020 to August 16, 2021. If generating intertidal area DEM, Sentinel and Landsat images required at least 3 months to 1 year of data collection, but the GOCI-II satellite was able to generate intertidal area DEM in Gyeonggi Bay using only one day of data according to tidal heights, and the topography altitude was also observed through exposure frequency. When observing coastal topography changes using the GOCI-II satellite, it would be a good idea to detect topography changes early through a short cycle and to accurately interpolate and utilize insufficient spatial resolutions using multi-remote sensing data of high resolution. Based on the above results, it is expected that it will be possible to quickly provide information necessary for the latest topographic map and coastal management of the Korean Peninsula by expanding the research area and developing technologies that can be automatically analyzed and detected.

• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2014.06a
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• pp.68-69
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• 2014

At the present, ship traffic monitoring and management are focused on the harbor area and the specified coastal zone in South Korea. It, however, is required that the Jurisdictional Sea Area of South Korea is monitored from two viewpoints: Safety and Security. Through a safe sea line (transport route) over the world, it is possible to expand our ocean economical territory. As a first step, we have been in field campaigns for integrated ship monitoring on the Ieodo Ocean Research Station in November 2013 after the first test in Gyunggi Bay.

• 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.

• Proceedings of the KSRS Conference
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• 2003.11a
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• pp.981-983
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• 2003

The Remote Sensing Group of the Mines and Geosciences Bureau (MGB) has acquired SAR data of the Central Cebu Island for its research study area. The MGB is one of the proponent of DOST-NASA PACRIM II Project, which is composed of eleven (11) agencies and institutions in the Philippines, that focuses on the scientific application of radar data with the theme on hazard and natural resources management. The PACRIM II Project, being done on three-year term, is slated for completion in the year 2004. The main thrust of the project study of the MGB is the baseline environmental monitoring studies, on which the data are to be fused with some other available data from LandSAT and photogrammetry. The generated data is part of the information for the update of thematic mapping being done. The 12 ${\times}$ 60 km swath AirSAR data covers the Central Cebu Island. The highlights of conducting this research project are: Extent of Watershed Basin boundaries - identification of the tributaries that drain water supply to the metropolitan area; Monitoring of the mountain highways - identification of landslide risk prone sites as part of natural hazard monitoring on a national highway that cuts along the mountainous areas; and Coastline change assessment - monitoring the coastline activities relative to the rapid urbanization and exposure as part of coastal management. The Phase 1 of this report discusses the fusion with the ArcView generated data as baseline studies on the monitoring activities.

• Korean Journal of Remote Sensing
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• v.39 no.6_1
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• pp.1195-1210
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• 2023

Coastal debris has emerged as a salient issue due to its adverse effects on coastal aesthetics, ecological systems, and human health. In pursuit of effective countermeasures, the present study delineated the construction of a specialized image dataset for coastal debris detection and embarked on a comparative analysis between two paramount real-time object detection algorithms, YOLOv8 and RT-DETR. Rigorous assessments of robustness under multifarious conditions were instituted, subjecting the models to assorted distortion paradigms. YOLOv8 manifested a detection accuracy with a mean Average Precision (mAP) value ranging from 0.927 to 0.945 and an operational speed between 65 and 135 Frames Per Second (FPS). Conversely, RT-DETR yielded an mAP value bracket of 0.917 to 0.918 with a detection velocity spanning 40 to 53 FPS. While RT-DETR exhibited enhanced robustness against color distortions, YOLOv8 surpassed resilience under other evaluative criteria. The implications derived from this investigation are poised to furnish pivotal directives for algorithmic selection in the practical deployment of marine debris monitoring systems.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.2
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• pp.174-181
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• 2009

The present study is a preliminary attempt to effectively incorporate the environmental issue of coastal erosion into the environmental assessment process of Korea. We assess the status of the environmental assessment on coastal erosion for the previous development plans and provide potential directions for the improvement. The considerable project plans should be screened for the impact of coastal erosion, which occupies about 20% of the total project plans reviewed, and the ratio increased with project scale. In addition to screening process, most process including scoping, baseline study, impact assessment, and follow-up need to be improved. The potential directions of improvement are provided in terms of appropriate guideline development, employment of cumulative impact assessment, follow-up improvement and rearrangement of the preparation regulation of environmental assessment. Emphasis is given for follow-up process to review post-monitoring period, to employ science compensation, and to consider the establishment of relevant institution. Final suggestion is made for the establishments of comprehensive national plan to manage coastal erosion and streamlined environmental process from strategic to project levels based on the national plan.

• Smart Structures and Systems
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• v.15 no.2
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• pp.335-353
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• 2015

Previous long-term measurements of the Uldolmok tidal current power plant showed that the structure's natural frequencies fluctuate with a constant cycle-i.e., twice a day with changes in tidal height and tidal current velocity. This study aims to improve structural health monitoring (SHM) techniques for offshore structures under a harsh tidal environment like the Uldolmok Strait. In this study, lab-scale experiments on a simplified offshore structure as a lab-scale test structure were conducted in a circulating water channel to thoroughly investigate the causes of fluctuation of the natural frequencies and to validate the displacement estimation method using multimetric data fusion. To this end, the numerical study was additionally carried out on the simplified offshore structure with damage scenarios, and the corresponding change in the natural frequency was analyzed to support the experimental results. In conclusion, (1) the damage that occurred at the foundation resulted in a more significant change in natural frequencies compared with the effect of added mass; moreover, the structural system became nonlinear when the damage was severe; (2) the proposed damage index was able to indicate an approximate level of damage and the nonlinearity of the lab-scale test structure; (3) displacement estimation using data fusion was valid compared with the reference displacement using the vision-based method.

• Journal of the Korean Society for Marine Environment & Energy
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• v.15 no.2
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• pp.89-100
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• 2012

The aim of this study knows to occurrence characteristics and monthly transition of foreign marine debris by changing in the marine environment for the national marine debris monitoring areas in the west coastal area. The Jeju Island (5,112) had the highest number for foreign marine debris flowed in the coast. Many areas in the next were surveyed by Hajo Island (1,967), Imja Island (507). Plastic bottles were the most common type to 2,925 piece of the whole collection. Then, the monthly occurrence amount was concentrated in July, September. At this time, analysis results of the marine environment are as follows: The sea surface wind of southerly or southeasterly were predominated. In addition, the sea surface circulations were dominated by inflow of seawater southward along the China Coast and northward from the East China Sea.

• The Journal of the Acoustical Society of Korea
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• v.40 no.6
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• pp.537-545
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• 2021

Due to the accelerated development and transformation of coastal waters by humans, damage to marine mammals is a concern. To understand how coastal development may affect marine mammals, it is essential to determine their distribution characteristics. In this study, the appearance of finless porpoises was confirmed by passive acoustic monitoring around the Southwest offshore wind farm in July, 2020. Although there were no visual observation results of finless porpoises in the research area, the clicks measured in the offshore wind farm were verified by comparing with acoustic characteristics of the clicks measured in the area with a high detection rate. During the experimental period, clicks of finless porpoises were recorded for ten consecutive days, and Clicks per Porpoise Positive Minute (CPPM) was 40.7 clicks min-1, Porpoise Positive Minutes (PPM) was 9.7 %, Encounter duration and waiting time were 18.2 min and 94.9 min respectively. This study provides information on the appearance of them in the Southwest offshore wind farm and this result may help to monitor the impact of marine mammals from wind farm operation.