• Wind and Structures
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• v.31 no.2
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• pp.165-183
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• 2020

The first step of performance-based design for transmission lines is the determination of wind fields as well as wind loads, which are largely depending on local wind climate and the surrounding terrain. Wind fields in a mountainous area are very different with that in a flat terrain. This paper firstly investigated both mean and fluctuating wind characteristics of a typical mountainous wind field by wind tunnel tests and computational fluid dynamics (CFD). The speedup effects of mean wind and specific turbulence properties, i.e., turbulence intensity, power spectral density (PSD) and coherence function, are highlighted. Then a hybrid simulation framework for generating three dimensional (3D) wind velocity field in the mountainous area was proposed by combining the CFD and proper orthogonal decomposition (POD) method given the properties of the target turbulence field. Finally, a practical 220 kV transmission line was employed to demonstrate the effectiveness of the proposed wind field generation framework and its role in the performance-based design. It was found that the terrain-induce turbulence effects dominate the performance-based structural design of transmission lines running through the mountainous area.

• Wind and Structures
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• v.30 no.6
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• pp.649-662
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• 2020

The existence of a dam has potential effects on the surrounding wind environment especially when it is located in mountainous areas. In this situation, the long-span bridge over the reservoir can easily be exposed to non-uniform incoming flows, affecting its wind-resistance performance. This paper presents a study on the aerostatic stability of such a bridge. Wind tunnel tests were first carried out to investigate the wind environment above a mountainous reservoir. The results show that the angle of attack and the wind speed along the bridge axis show obvious non-uniform characteristics, which is related to the inflow direction. When winds come from the south where the river is winding, the angle of attack varies along the span direction significantly. The finite element model for the bridge was established using ANSYS software, and effects of non-uniform wind loads on the aerostatic stability were computed. Non-uniform angle of attack and wind speed are unfavorable to the aerostatic stability of the bridge, especially the former. When the combined action of non-uniform angle of attack and wind speed is considered, the critical wind speed of aerostatic instability is further reduced. Moreover, the aerostatic stability of the bridge is closely related to the dam height.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.493-495
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• 2010

A three-dimensional flow simulation is performed to investigate the flow field in the ski resort on complex terrain. The present paper aims to study the wind effects of mountainous terrain on the gondola safety. Strong wind happens in the ski resort on the mountain by complex terrain and it causes the dangerous accident of gondola. A digital map around the ski resort area is used to model the actual complex terrain for a 3-D analysis domain. Wind direction and speed to be used as a boundary condition are taken from local meteorological reports. The numerical results show details of the velocity distribution around a ski resort. From the results, we can suggest the modification of the installation of gondola for the safety due to strong wind.

• Wind and Structures
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• v.7 no.5
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• pp.345-357
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• 2004

In the 1990s, four strong typhoons hit the Kyushu area of Japan and inflicted severe damage on power transmission facilities, houses, and so on. Maximum gust speeds exceeding 60 m/s were recorded in central Kyushu. Although the wind speeds were very high, the gust factors were over 2.0. No meteorological stations are located in mountainous areas, creating a deficiency of meteorological station data in the area where the towers were damaged. Since 1995 the authors have operated a network for wind measurement, NeWMeK, that measures wind speed and direction, covering these mountainous areas, segmenting the Kyushu area into high density arrays. Maximum gusts exceeding 70 m/s were measured at several NeWMeK sites when Typhoon Bart (1999) approached. The gust factors varied widely in southerly winds. The mean wind speeds increased due to effects of the local terrain, thus further increasing gust speeds.

• Journal of Environmental Science International
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• v.6 no.4
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• pp.359-367
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• 1997

The Characteristics of atmospheric flow and dispersion of air pollutants in the mountainous coastal area were studied using three-dimensional model by the combination of land/sea breezes and transport. It was then applied to Pusan city. As the urban area considered In this study is located in a mountainous coastal area, the atmospheric flow is strongly affected by the land/sea breezes and mountain/valley winds. The typical effects of land/sea breezes on the dispersion and the characteristics of pollutants movement in the region were analysed. The model has been proved to be an useful tool to prodict real time air pollutants transport as shown by the results of application studies In Pusan, Korea which Is an urbanized coastal area with mountainous topography. It was found that the pollutants are differently transported and concentrated as going Inland by the Influence of the sea breeze with topographic changes. By comparing the pollutants concentrations of the stimulated results with those of the observational results, It is shown that stimulated results in this study are in qualitative agreement with observational ones.

• Journal of Korean Society of Forest Science
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• v.97 no.3
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• pp.340-347
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• 2008

This study investigates the conceptional structure between festival service quality, visitor's satisfaction, loyalty and festival effects in the Juwangsan Sudalrae mountainous local festival. In order to analyze the structural equation model the paper employed the LISREL (linear structural relationships) approach, covariance structural equation model. Data of 445 visitors were collected from the Juwangsan Sudalrae festival in 2008. Research findings showed that experience, facility and service are positively related to visitors' satisfaction. In addition, visitors' satisfaction is related to loyalty and festival effects. One of the major research findings is that the festival service most affects visitors' satisfaction. This implies that the host of mountainous local festival must put great emphasis on organizing hospitality and festival information. This will lead the festival to a great success and ultimately bring positive impacts to the mountainous residents.

• Proceedings of the KSRS Conference
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• 2004.10a
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• pp.537-540
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• 2004

Space-borne multi-sensor data could provide fire scar and bum severity mapping. This paper will present detail mapping of burnt areas in Cheongyange Yesan of Korea with ETM+ image. Burn severity map based on ETM+ image was found to be affected by strong topographic illumination effects in mountainous forest area. Topographic effect is a factor which causes errors in classification of high spatial resolution image like IKONOS image. Minnaert constants J( in each band of ETM+ image is derived for reduction of mountainous terrain effects. Finally, this paper computes quantitative analysis of forest fire damage by each forest types.

• Wind and Structures
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• v.32 no.5
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• pp.423-437
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• 2021

Aerodynamic measures have been widely used for improving the flutter stability of long-span bridges, and this paper focuses their windproof ability to improve the wind environment for vehicles. The whole wind environment around a long-span bridge located in high altitude mountainous areas is first studied. The local wind environment above the deck is then focused by two perspectives. One is the windproof effects of aerodynamic measures, and the other is whether the bridge with aerodynamic measures meets the requirement of flutter stability after installing extra wind barriers in the future. Furthermore, the effects of different wind barriers are analyzed. Results show that aerodynamic measures exert potential effects on the local wind environment, as the vertical stabilizer obviously reduces wind velocities behind it while the closed central slot has limited effects. The suggested aerodynamic measures have the ability to offset the adverse effect of the wind barrier on the flutter stability of the bridge. Behind the wind barrier, wind velocities decrease in general, but in some places incoming flow has to pass through the deck with higher velocities due to the increase in blockage ratio. Further comparison shows that the wind barrier with four bars is optimal.

• Journal of the Korean earth science society
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• v.25 no.8
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• pp.784-798
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• 2004

Microscale wind fields were simulated by MUKLIMO at the Naro Space Center, where complicated mountainous terrain and trees exist. In order to test the model's sensitivity with the effects of terrain and trees, experimental simulations were conducted under the various initial conditions. The experiments showed that the effects of trees were more significant on flat surfaces than on mountain cliffs. Based on the results, an actual 10 m level microscale wind field was simulated at the Naro Space Center, which has complicated mountainous terrain. Simulations of wind fields before and after the construction of the launching site were also conducted. It was found that MUKLIMO was of the mesoscale wind fields at the Naro Space Center.

• Journal of Wetlands Research
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• v.16 no.1
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• pp.113-124
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• 2014

The observed rainfall may be different along with the altitude of rain gauge, resulting in the fact that the characteristics of rainfall events occurred in urban or mountainous areas are different. Due to the mountainous effects, in higher altitude, the uncertainty involved in the rainfall observation gets higher so that the density of rain gauges should be more dense. Basically, a methodology for the rain gauge network evaluation, considering this altitude effect of rain gauges can account for the mountainous effects and becomes an important step for forecasting flash flood and calibrating of the radar rainfall. For this reason, in this study, we suggest a methodology for rain gauge network evaluation with consideration of the rain gauge's altitude. To explore the density of rain gauges at each level of altitude, the Equal-Altitude-Ratio of the density of rain gauges, which is based on the fixed amount of elevation and the Equal-Area-Ratio of the density of rain gauges, which is based on the fixed amount of basin area are designed. After these two methods are applied to a real watershed, it is found that the Equal-Area-Ratio generates better results for evaluation of a rain gauge network with consideration of rain gauge's altitude than the Equal-Altitude-Ratio does. In addition, for comparison between the soundness of rain gauge networks in other watersheds, the Coefficient of Variation (CV) of the rain gauge density by the Equal-Area-Ratio is served as the index for the evenness of the distribution of the rain gauge's altitude. The suggested method is applied to the five large watersheds in Korea and it is found that rain gauges installed in a watershed having less value of the CV shows more evenly distributed than the ones in a watershed having higher value of the CV.