• Korean Journal of Remote Sensing
• /
• v.31 no.2
• /
• pp.193-203
• /
• 2015

In this study, effects of buildings and topography on observation environment of weather stations located on mountainous terrain in metropolitan areas are investigated using a computational fluid dynamics (CFD) model. In order to investigate the characteristics of flow pattern around the weather stations, geographic information system (GIS) data are used to construct surface boundary input data of the CFD model. In order to evaluate effects of buildings and topography on wind speed and direction at three weather stations located in Deajeon, Busan, and Gwangju., target areas around the weather stations are selected and 16 cases with different inflow directions for each target area are considered. The simulated wind speed and direction at the weather stations are compared with those of inflow. As a whole, wind speed at the weather stations decreases due to drag effects of the buildings and topography in the upwind regions. This study shows that GIS data and the CFD model are successfully applicable to evaluation of observation environment for weather stations.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.40 no.5
• /
• pp.381-391
• /
• 2022

This paper is intended to find one of the prevailing deep learning models that are a type of AI (Artificial Intelligence) that helps rapidly detect damaged buildings where disasters occur. The models selected are SSD-512, RetinaNet, and YOLOv3 which are widely used in object detection in recent years. These models are based on one-stage detector networks that are suitable for rapid object detection. These are often used for object detection due to their advantages in structure and high speed but not for damaged building detection in disaster management. In this study, we first trained each of the algorithms on xBD dataset that provides the post-disaster imagery with damage classification labels. Next, the three models are quantitatively evaluated with the mAP(mean Average Precision) and the FPS (Frames Per Second). The mAP of YOLOv3 is recorded at 34.39%, and the FPS reached 46. The mAP of RetinaNet recorded 36.06%, which is 1.67% higher than YOLOv3, but the FPS is one-third of YOLOv3. SSD-512 received significantly lower values than the results of YOLOv3 on two quantitative indicators. In a disaster situation, a rapid and precise investigation of damaged buildings is essential for effective disaster response. Accordingly, it is expected that the results obtained through this study can be effectively used for the rapid response in disaster management.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.21 no.5
• /
• pp.465-474
• /
• 2008

The real-time hybrid testing method(RT-HYTEM) is a structural testing technique in which the numerical integration of the equation of motion for a numerical substructure and the physical testing for an experimental substructure are performed simultaneously in real-time. This study presents the quantitative evaluation of the seismic performance of a building structure installed with an passive and semi-active MR damper by using RT-HYTEM. The building model that was identified from the force-vibration testing results of a real-scaled 5-story building is used as the numerical substructure, and an MR damper corresponding to an experimental substructure is physically tested by using the universal testing machine(UTM). The RT-HYTEM implemented in this study is validated because the real-time hybrid testing results obtained by application of sinusoidal and earthquake excitations and the corresponding analytical results obtained by using the Bouc-Wen model as the control force of the MR damper respect to input currents were in good agreement. Also for preliminary study, some semi-active control algorithms were applied to the MR damper in order to control the structural responses optimally. Comparing between the test results of semi-active control using RT-HYTEM and numerical analysis results show that the RT-HYTEM is more resonable than numerical analysis to evaluate the performance of semi-active control algorithms.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
• /
• v.29 no.6
• /
• pp.687-695
• /
• 2011

Many internet portals provide maps with spatial information services. Recently, various images including aerial, satellite, street view, and photo-realistic 3D city models are provided as well as maps. This study suggested a method for geometric correction of the panoramic aerial images in the internet portal and 3D building modeling using information which is available in the internet. The key of this study is to obtain all necessary data easily from internet without restrictions. Practically, the ground control coordinates could be available from geo-referenced internet maps, and stereo pairs of the aerial images and close-range photographs for photo-realistic object modeling are provided by the internet service. However, the ground control points are not suitable for accurate mapping. RMSE of the plotting was about 9 meters and reduced upto 4 meters after coordinate transformation. The proposed methods would be applicable to various applications of photo-realistic object modeling which do not require high accuracy.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.17 no.5
• /
• pp.36-41
• /
• 2016

In this study, numerical analyses were used to investigate the performance of a coupling control method for the dynamic responses of adjacent buildings under multiple hazards. Numerical simulations were done using the earthquake loads of regions with strong seismicity in Los Angeles, California, and the wind loads in regions with strong winds in Charleston, North Carolina. The artificial earthquake and wind loads were made using SIMQKE and Kaimal Spectrum based on ASCE 7-10. Ten-story and twenty-story adjacent buildings were selected as example structures, and nonlinear hysteretic dampers were used to connect them. The Bouc-Wen model was used to model the nonlinear hysteretic dampers. The results show that the proposed control method could effectively reduce the dynamic responses, and the optimal control designs were different for each hazard.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.18 no.2
• /
• pp.1-15
• /
• 2015

Urban flooding threatens human beings and facilities with chemical and physical hazards since the beginning of human civilization. Recent studies have emphasized the integration of data and models for effective urban flood inundation modeling. However, the model set-up process is tend to be time consuming and to require a high level of data processing skill. Furthermore, in spite of the use of high resolution grid data, inundation depth and velocity are varied with building treatment methods in 2-D inundation model, because undesirable grids are generated and resulted in the reliability decline of the simulation results. Thus, it requires building generalization process or enhancing building orthogonality to minimize the distortion of building before converting building footprint into grid data. This study aims to develop building generalization method for 2-dimensional inundation analysis to enhance the model reliability, and to investigate the effect of building generalization method on urban inundation in terms of geographical engineering and hydraulic engineering. As a result to improve the reliability of 2-dimensional inundation analysis, the building generalization method developed in this study should be adapted using Digital Building Model(DBM) before model implementation in urban area. The proposed building generalization sequence was aggregation-simplification, and the threshold of the each method should be determined by considering spatial characteristics, which should not exceed the summation of building gap average and standard deviation.

• Korean Journal of Remote Sensing
• /
• v.36 no.6_3
• /
• pp.1653-1667
• /
• 2020

In this study, we coupled a computation fluid dynamics (CFD) model to the local data assimilation and prediction system (LDAPS), a current operational numerical weather prediction model of the Korea Meteorological Administration. We investigated the characteristics of fine particulate matter (PM2.5) distributions in a building-congested district. To analyze the effects of road emission on the PM2.5 concentrations, we calculated road emissions based on the monthly, daily, and hourly emission factors and the total amount of PM2.5 emissions established from the Clean Air Policy Support System (CAPSS) of the Ministry of Environment. We validated the simulated PM2.5 concentrations against those measured at the PKNU-AQ Sensor stations. In the cases of no road emission, the LDAPS-CFD model underestimated the PM2.5 concentrations measured at the PKNU-AQ Sensor stations. The LDAPS-CFD model improved the PM2.5 concentration predictions by considering road emission. At 07 and 19 LST on 22 June 2020, the southerly wind was dominant at the target area. The PM2.5 distribution at 07 LST were similar to that at 19 LST. The simulated PM2.5 concentrations were significantly affected by the road emissions at the roadside but not significantly at the building roof. In the road-emission case, the PM2.5 concentration was high at the north (wind speeds were weak) and west roads (a long street canyon). The PM2.5 concentration was low in the east road where the building density was relatively low.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
• /
• 2011.11a
• /
• pp.139-142
• /
• 2011

오픈 소스인 FDS(fire dynamic simulator)는 건물, 터널내의 화재나 연기, 열기류의 거동을 연구하기 위하여 국내외적으로 광범위하게 이용되고 있다. 소스코드 또한 공개 되어 있어 그 활용범위가 더욱 넓어지고 있다. 대부분의 기본적인 화재, 방재 해석을 위한 모델들을 제공하고 있으나 이를 더욱 발전시키고 새로운 알고리즘의 적용하기 위해서는 이러한 모델의 구조를 잘 이해할 필요가 있다. 본 연구에서는 이러한 FDS모델을 더욱 확장하기 위한 일환으로 현 FDS의 기본적인 구조를 검증모델(verification)을 이용하여 파악하고 이를 향후 소스코드를 확장할 수 있는 근간으로 삼고자 한다.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.28 no.5A
• /
• pp.685-690
• /
• 2008

Recently, as large structures become lighter and more flexible, the necessity of structural control for reducing excessive displacement and acceleration due to seismic excitation is increased. As a means to minimize seismic damages, various base isolation systems are adopted or considered for adoption. In this study, a base isolation system using hysteretic damper is shown to effectively protect structures against earthquakes. A mechanical model is determined that can effectively portray the behavior of a typical E-shape device. Comparison with experimental results for a hysteretic damper indicates that the model is accurate over a wide range of operating conditions and adequate for analysis. The seismic performance of hysteretic dampers are studied and compared with the conventional systems as a base isolation system. A five-story building is modeled and the seismic performance of the systems subjected to three different earthquake is compared. The results show that the hysteretic damper system can provide superior protection than the other systems for a wide range of ground motions.

• Korean Journal of Remote Sensing
• /
• v.36 no.2_1
• /
• pp.139-153
• /
• 2020

Using a computationalfluid dynamics(CFD) model, thisstudy evaluated the representativeness of an air quality monitoring system (AQMS) in an urban area and presented a methodology to determine the suitable AQMS locations for specific purposes. For this, we selected a 1.6 km × 1.6 km area around the Eunpyeong-gu AQMS (AQMS 111181) as a target area. We conducted simulationsfor two emission scenarios (scenario one: air pollutants transported from inflow boundaries, scenario two: air pollutants emitted from roads). Urban airflows were markedly influenced by mountainous terrain located in the northeast and southeast of the target area, and complicated airflow patterns occurred around the buildings. The distributions of air pollutants were dependent on the terrain (mountain) in scenario one, but the road location and building height in scenario 2. We evaluated whether the AQMS could represent the air quality in the target area based on the simulations for two scenarios. The concentrations simulated at the AQMS were similar in magnitude to the layer mean concentrations, which indicated good representativeness for the air quality in the target area. We also suggested which locations were suitable for different measurement purposes (hot spots, clean zones, average zones, shelter zones, equi-background zones).