• Journal of the Korean earth science society
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• v.25 no.6
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• pp.418-427
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• 2004

Recently, urban planning with consideration of urban climate, represented by the concept of urban ventilation lane is widely practiced in many countries. The concept of urban ventilation lane is mainly aimed to improve the thermal comfort within urban area in summer season. It has also the aim to reduce the urban air pollution by natural cold air drainage flows which are to be intensified by a suitable alignment of buildings as well as use zonings based on scientific reasons. In this study, the prevailing wind ventilation lane of a local wind circulation and around Daegu for a typical summer days was investigated by using a numerical simulation. The transport of air pollutants by the local circulation winds was also investigated by using the numerical simulation model, the RAMS (Reasonal Atmospheric Model System).The domain of interest is the vicinity of Daegu metropolitan city (about 900 km2). The horizontal scale of the area is about 30 km. The simulations were conducted under a late spring synoptic condition with weak gradient wind and almost clear sky. From the numerical experiment, the following three conclusions were obtained: (1) The major wind passages of the local circulation wind generated by radiative cooling over the representative mountains of Daegu (Mt. Palgong and Mt. Ap) were found. The winds blow down along the valley axis over the eastern part of Daegu as a gravity flow during nighttime. (2) At the flatland, the winds blow toward the western part of Daegu through the city center. (3) As the results, the air pollutants were transported toward the western part of Daegu by the winds during nighttime.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.181-190
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• 2011

Since the radar satellite missions such as TerraSAR-X and COSMO-SkyMed were launched in 2007, the spatial resolution of spaceborne SAR(Synthetic Aperture Radar) images reaches about 1 meter at spotlight mode. In 2011, the first Korean SAR satellite, KOMPSAT-5, will be launched, operating at X-band with the highest spatial resolution of 1 m as well. The improved spatial resolution of state-of-the-art SAR sensor suggests expanding InSAR(Interferometric SAR) analysis in urban monitoring. By the way, the shadow and layover phenomena are more prominent in urban areas due to building structure because of inherent side-looking geometry of SAR system. Up to date the most conventional algorithms do not consider the return signals at the frontage of building during InSAR phase and SAR intensity simulation. In this study the new algorithm introducing multi-scattering in layover region is proposed for phase and intensity simulation, which is utilized a precise LIDAR DSM(Digital Surface Model) in urban areas. The InSAR phases simulated by the proposed method are compared with TerraSAR-X spotlight data. As a result, both InSAR phases are well matched, even in layover areas. This study will be applied to urban monitoring using high resolution SAR data, in terms of change detection and displacement monitoring at the scale of building unit.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.03a
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• pp.286-300
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• 2006

Nonlinear cross-anisotropic properties of soil is critical for exact numerical simulation. Theoretically, initial cross-anisotropic properties can be evaluated from triaxial tests with bender element tests, and nonlinear cross-anisotropic properties over initial strain level cannot be evaluated from triaxial tests. In this study, a supposed condition among nonlinear cross-anisotropic properties is suggested to calculate nonlinear cross-anisotropic properties from triaxial tests. Maximum strain and incremental strain energy are applied to combine triaxial test results and theoretical normalized shear modulus curve, respectively Based on combined results, nonlinear cross-anisotropic properties are calculated. Numerical simulation for triaxial tests Is carried out to verify the applicability of the supposed condition with calculated cross-anisotropic properties and simplified nonlinear cross-anisotropic model.

• Proceedings of the SAREK Conference
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• 2009.06a
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• pp.565-572
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• 2009

Deterioration of the outdoor thermal environment in urban areas such as heat island has become worse due to urbanization and overpopulation, etc. In this study, a new method which is coupled simulation of convection and radiation to evaluate outdoor thermal environment in urban area will be proposed. Because the solar radiation affects on outdoor thermal environment massively, therefore the radiation calculation is very important in outdoor thermal environment prediction. The coupled simulation proposed in this study can assess the outdoor thermal environment with accurate.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1433-1446
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• 2013

In this study, we proposed a methodology to develop Rating Curves for high water level using rainfall generation by the Monte Carlo Simulation (MCS) technique, optimized rainfall-runoff model, and flood routing model in an urban stream. The developed stage discharge Rating Curve based on observed data was contained flow measurement errors and uncertainties. The standard error ($S_e$) for observations was 0.056, and the random uncertainty ($2S_{mr}$) was analyzed by ${\pm}1.43%$ on average, and up to ${\pm}4.27%$. Moreover, it was found that the Rating Curve extensions by way of logarithmic and Stevens methods were overestimated to compare with the urban basin scale. Finally, we confirmed that the high water level extension by random generation of hydrological data using MCS can be reduced uncertainty of the high water level, and it will consider as a more reliable approach for high water level extension. In the near future, this results can be applied to real-time flood alert system for urban streams through construction of the high water level extension system using MCS procedures.

• Journal of Korea Multimedia Society
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• v.11 no.2
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• pp.247-256
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• 2008

Recently, natural disasters like flooding damages have frequently occurred as to typhoons and local downpours affected by the climate changes. Many researches have actively been studied in analysing runoff models, the verification of their parameters, and the inflow on surfaces in order to lessen the damages. However, much time and effort needs in generating input files of the models in most current researches. Therefore, in this paper we develop a system for generating a simulation input data automatically. This system is connected to the EPA-SWMM based on the spatial data in the UIS systems and consists the simulation module for analysing urban flooding and the SWMM simulator module. Also, we construct a prototype using a range of regular inundation to generate a simulation input file. This system gives advantages showing inundation areas based on the map viewer as well as lessening errors of input data and simulation time.

• Journal of the Korean Institute of Landscape Architecture
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• v.35 no.6
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• pp.74-83
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• 2008

As urban residents' standard of living has recently risen, efforts to improve urban landscapes have increased. It is very important to manage streetscapes to improve the urban landscape because they are one of the essential elements in city construction and urban landscaping. This study focuses on the indicators that manage streetscapes more accurately and realistically. To achieve this purpose, this study used dynamic simulations considering shape and layout of buildings, the primary factors in streetscapes. This study can be summarized as follows: 1. Two indicators to manage streetscape were investigated in previous studies: one to increase visual openness and the other to reduce visual overstimulation. These indicators had high correlation with scenic beauty. Therefore, increasing openness and reducing overstimulation are essential to improve streetscapes. 2. Two household tower type buildings should be arranged along roadsides to increase openness and scenic beauty. However, low tower buildings with two household are not suitable along roadsides because they create monotony and intervals are needed between buildings. 3. To increase openness, the angled arrangement of buildings is suggested $75^{\circ}{\sim}90^{\circ}(105^{\circ}{\sim}135^{\circ})$ for low buildings, $30^{\circ}{\sim}45^{\circ}(135^{\circ}{\sim}150^{\circ})$ for mid-sized buildings, and $75^{\circ}{\sim}90^{\circ}(105^{\circ}{\sim}135^{\circ})$ for high buildings. 4. To reduce overstimulation, the height and setback control regulations should be at an angle of less than $45^{\circ}$. This study suggests more accurate management guidelines by organizing the indicators that could effectively manage streetscapes and by overcoming limitations of reality shown in a static simulation.

• Journal of Korea Water Resources Association
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• v.39 no.5 s.166
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• pp.441-452
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• 2006

Recently the natural damage associated with flood disaster has been dramatically increased. Especially, inundation in the urban area causes serious damage to people and assets because of the concentration of infrastructure and population growth. The purpose of this study is to develop a new urban inundation model combining a storm sewer system model and a 2D overland-flow model for the estimation inundation depth In urban area caused by the surcharge of storm sewers. The movement of water in the studied urban watershed is characterized by two components, namely, the storm sewer flow component and the surcharge-induced inundation component. The model was applied to Goonja and Jangan catchments. Inundated depths were presented to demonstrate model simulation results. The simulation results can help the authority decide preventing flood damages by redesigning and enlarging the capacities of storm sewer systems in the inundation-prone areas. The model can also be applied to make the potential inundation area map and establish flood-mitigation measures as a part of the decision support system for flood control authority.

• Journal of Wetlands Research
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• v.21 no.4
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• pp.298-304
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• 2019

In this paper, the analytical method to derive wind fragility for urban street tree in Korea was shown. Monte Carlo Simulation method was used to determine the probability of failure for urban street tree. This probability result was used to determine wind fragility parameters for four types of tree based on the study of street tree species in urban area in Daegu, Korea. Wind fragility for street tree was presented in terms of median capacity and standard deviation of the natural logarithm of the capacity. Results showed that the dominant factor affecting the probability of failure of tree under wind load was their diameter. Moreover, amongst the four types of tree chosen, the tree with height 7m and diameter 35cm had the lowest probability of failure under wind loading, whereas the tree with height 8m and diameter 30cm could resist the least wind loading. The median failure wind speed for urban street tree with height 7m were 43.8m/s and 50.6m/s for diameter 30cm and 35cm, respectively. Also, for tree with height 8m, their median failure wind speeds were 38.7m/s and 45.4m/s for tree with diameter 30cm and 35cm, respectively.

• Journal of Soil and Groundwater Environment
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• v.10 no.3
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• pp.24-31
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• 2005

This study presents a contaminant transport model suitable for a 2-dimensional heterogeneous aquifer with multiple contaminant sources. It uses a streamline simulation, which transforms a multi-dimensional problem into multiple 1dimensional problems. It runs flow simulation, streamline tracking, and calculation of contaminant concentrations by turns. The model is verificated with a Visual MODFLOW by comparing contaminant concentration distributions and breakthrough curves at an observation well. Due to its fast simulation, it can be applied to time consuming simulations such as in a fine-grided aquifer, an inverse modeling and other applications.