• Korean Journal of Remote Sensing
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• v.30 no.6
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• pp.755-767
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• 2014

In this study, detailed air flow characteristics in an urban areas were analyzed using GIS data and a Computational Fluid Dynamics (CFD) model. For this, a building construction algorithm optimized for Geographic Information System (GIS) data with a vector format (Los Angeles region imagery acquisition consortium 2 geographic information system, LARIAC2 GIS) was used. In the LARIAC2 GIS data, building vertices were expressed as latitude and longitude. Using the model buildings constructed by the algorithm as the surface boundary data in the CFD model, we performed numerical simulations for two building-congested areas in Los Angeles using inflow information provided by California Air Resources Board. Comparing with the inflow, there was a marked difference in wind speed and direction within the target areas, which was mainly caused by the secondarily induced local circulations such as street-canyon vortices, horse-shoe vortices, and recirculation zones. In street canyons parallel to the inflow direction, wind speed increased due to a channeling effect and, in street canyons perpendicular to the inflow direction, vertically well developed vortices were induced. In front of a building, a horse-shoe vortex was developed near the surface and, behind a building, a recirculation zone was developed. Near the surface in the areas where the secondarily induced local circulations, wind speed remarkably increased. Overall, wind direction little (largely) changed at the areas where wind speed largely increased (decreased).

• Particle and aerosol research
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• v.17 no.4
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• pp.115-123
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• 2021

The emission gas from meat grilled restaurants has unpleasant odor and sticky particulate matters (PM) in form of oil mist. This affects the residents living nearby. In oder to decrease the odor and PM, electrostatic precipitators (ESP) were installed at several restaurants by support of Seoul metropolitan government and emission characteristics of PM and odor were investigated. The removal efficiency of odor and PM at before- and after-ESP was that total hydrocarbon (THC), NH₃, H₂S, acetaldehyde, butyraldehyde were not much decreased. Total suspended particles (TSP) emitted from the vent was below the value of 7 mg/m³ regardless of the concentration of before-ESP and removal efficiency was in the range of 64 ~ 86%. The ratio of PM_1.0 to PM₁₀ of emission gas was over 0.9. So it was revealed that most PM of emission gas was PM1.0. The PM concentration in the air of the street near the vent was higher than another street due to the emission gas and the PM of indoor air of restaurant grilling meats was measured very high compared to outdoor air. So it needs more powerful ventilation of indoor air.

• Proceedings of the SAREK Conference
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• 2004.11a
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• pp.33-33
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• 2004

• Journal of Korean Society of Forest Science
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• v.95 no.2
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• pp.183-187
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• 2006

This study investigated concentrations of the several air pollutants and compared antioxidative enzyme activities on Platanus occidentalis because this tree species is one of the widespread street trees in Korea. This species has been emerging the ambient air pollutants during its growing periods. The purpose of this study was to identify the relationship between air pollution on the tree species and antioxidant enzyme activities on the trees. $O_3$, $NO_2$, CO and $SO_2$ concentrations of several cities in Korea were compared for last decades. Among the air pollutants, $O_3$ and $NO_2$ concentrations in six big cities in Korea showed similar increasing trends during this period. In contrast, $SO_2$ and CO concentrations in the same cities dramatically decreased between 1994 and 2005. Platanus occidentalis trees were controlled to investigate, ascorbate peroxidase (APX) and glutathione reductase (GR) activity. Ozone exposure generally increased APX and GR activities of tree seedlings. It is a typical compensatory strategy of stressed trees.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2002.11a
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• pp.221-222
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• 2002

대기질의 예측에는 여러 가지 물리적 또는 수치적 모델링 기술이 이용되고 있다. 최근 들어 급격한 컴퓨터의 발달과 더불어 수치모델을 이용한 예측 기술이 활발히 개발 이용되고 있다. 그러나 이러한 수치 모델링 기술은 대도시 특히, 높은 건물과 그들에 의해 형성된 도심 협곡을 고려하는 경우 현재의 수치 모델이 가지고 있는 여러 가지 가정에 의해 많은 어려움을 직면하고 있는 실정이다. (중략)

• Korean Journal of Remote Sensing
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• v.38 no.6_1
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• pp.1395-1406
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• 2022

This study investigated the effects of the urban forest and street trees on flow and temperature distribution in the Daegu National Debt Redemption Movement Memorial Park. For this, we implemented tree-drag and tree-cooling parameterization schemes in a computational fluid dynamics (CFD) model and validated the simulated wind speeds, wind directions, and air temperatures against the measured ones. We used the wind speeds, wind directions, air temperatures predicted by the local data assimilation and prediction system (LDAPS) as the inflow boundary conditions. To investigate the flow and thermal characteristics in the presence of trees in the target area, we conducted numerical experiments in the absence and presence of trees. In the absence of trees, strong winds and monotonous flows were formed inside the park, because there were no obstacles inducing friction. The temperature was inversely proportional to the wind speed. In the presence of trees, the wind speeds(temperatures) were reduced by more than 40 (5)% inside the park with a high planting density due to the tree drag (cooling) effect, and those also affected the wind speeds and temperatures outside the park. Even near the roadside, the wind speeds and temperatures were generally reduced by the trees, but the wind speeds and air temperatures increased partly due to the change in the flow pattern caused by tree drag.

• Geomechanics and Engineering
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• v.17 no.6
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• pp.573-581
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• 2019

Excavation of underground cavern and shaft was proposed for the construction of a ventilation facility in an urban area. A shaft connects the street-level air plenum to an underground cavern, which extends down approximately 46 m below the street surface. At the project site, the rock mass was relatively strong and well-defined joint sets were present. A kinematic block stability analysis was first performed to estimate the required reinforcement system. Then a 3-D discontinuum numerical analysis was conducted to evaluate the capacity of the initial support and the overall stability of the required excavation, followed by a 3-D continuum numerical analysis to complement the calculated result. This paper illustrates the application of detailed numerical analyses to the design of the required initial support system for the stability of underground hard rock mining at a relatively shallow depth.

• Korean Journal of Remote Sensing
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• v.33 no.6_2
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• pp.1151-1157
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• 2017

Street Trees is an important object for urban environment improvement. Especially the height of the trees needs to be precisely measured as a factor that greatly influences the removal of air pollutants in the Urban Street Canyons. In this study, we extracted the height of the tree based on the stereo image using the precisely adjusted UAV Images of the target area. The adjustment of UAV image was applied photogrammetric SfM (Structure from motion) based on the collinear condition. We measured the height of the trees on the Street Canyon using stereoscopic vision on stereo plotting system. We also acquired the height of the building adjacent to the street trees and the average height of the road surface was calculated for accurate measurement of the height of each object. Through the visual analysis with the plotting operation system, it was possible to measure height of the tree and to calculate the relative height difference value with building quickly. This means that the height of buildings and trees can be calculated without making a 3D point cloud of UAV and it has the advantage of being able to utilize non-experts. In the future, further studies for semiautomatic/automation of this technique should be performed. The development and research of these technologies is expected to help to understand the current status of environmental policies and roadside trees in urban areas.

• Journal of Environmental Health Sciences
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• v.30 no.3
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• pp.293-299
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• 2004

Traffic represents one of the largest sources of primary air pollutants in urban area. As a consequence, numerous abatement strategies are being pursued to decrease the ambient concentration of pollutants. A characteristics of most of the these strategies is a requirement for accurate data on both the quantity and spatial distribution of emissions to air in the form of an atmospheric emission inventory database. In the case of traffic pollution, such an inventory must be compiled using activity statistics and emission factors for vehicle types. The majority of inventories are compiled using passive data from either surveys or transportation models and by their very nature tend to be out-of-date by the time they are compiled. The study of current trends is towards integrating urban traffic control systems and assessments of the environmental effects of motor vehicles. In this study, a model of vehicle emission calculation by using real-time traffic data was studied. Traffic data, which are required on a street-by-street basis, is obtained from induction loops of traffic control system. It is possible that characteristics of hourly air pollutants emission rates is obtained from hourly traffic volume and speed. An emission rates model is allocated with a high resolution space by using geographic information system (GIS). Vehicle emission model was developed with a high resolution spatial, gridded and hourly emission rates.

• Proceedings of the Korea Air Pollution Research Association Conference
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• 2003.05b
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• pp.165-166
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• 2003

도심 도로변의 대기질은 주변의 고층 건물로 인한 거리 협곡으로 인하여 도시의 대기질에서 가장 빈번하게 기준을 초과하는 지역이다. 대부분의 대도시에서 고층 빌딩으로 구성된 도심 거리 협곡(urban street canyon)의 자동차에서 배출되는 대기오염물질은 운전자, 보행자, 도로변 작업자, 자동차 승객 등의 건강에 직접적으로 영향을 미칠 수 있다. 자동차 대기오염물질은 지표면에서 발생되기 때문에 거리 협곡은 배출원 인근의 대기오염물질 확산에 중요한 영향을 준다. 우선적으로, 거리 협곡은 협곡 상공에서 수직적인 혼합을 유도하게 된다. 둘째로, 거리 협곡의 형성은 협곡의 지형적 또는 물리적 경계 내의 오염물질을 정체시키게 되어, 협곡 상공으로 공기가 자유롭게 이동하여 오염물질을 수송하는 것을 지체시키는 경향이 있다. (중략)