• Transactions of the Korean Society of Automotive Engineers
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• v.18 no.6
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• pp.138-144
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• 2010

If the vibration is occurred in a large-sized bus roof, it makes people annoying and complaining the quality of a large-sized bus. So in design stage, it must be considered. To assess vibration at the roof which is equipped with air conditioner in design stage, finite element model is constructed. Computer simulation analysis and experimental method are performed. The dynamic characteristics of the large-sized bus are found by using eigenvalue method. It is related with dynamic behavior. The running conditions of a large-sized bus are velocity and road condition which followed experimental conditions. And the frequency response of a large-sized bus is well correlated with analysis result. Modal participation method is used for finding major modes at each peak. Using this method, we found that front and rear suspension system, engine mounting system and roof structure are the major reasons of the roof vibration. To reduce vibration level of roof in a large-sized bus, spring stiffness of front and rear suspension system, spring stiffness of engine mounting system and roof structure are properly combined. From this study, the vibration characteristics of the roof structure of a large-sized bus can be to a satisfactory level.

• Geomechanics and Engineering
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• v.18 no.4
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• pp.449-457
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• 2019

Physical model tests were first performed to investigate the failure pattern of multiple pillar-roof support system. It was observed in the physical model tests, pillars were design with the same mechanical parameters in model #1, cracking occurred simultaneously in panel pillars and the roof above barrier pillars. When pillars 2 to 5 lost bearing capacity, collapse of the roof supported by those pillars occurred. Physical model #2 was design with a relatively weaker pillar (pillar 3) among six pillars. It was found that the whole pillar-roof system was divided into two independent systems by a roof crack, and two pillars collapse and roof subsidence events occurred during the loading process, the first failure event was induced by the pillars failure, and the second was caused by the roof crack. Then, for a multiple pillar-roof support system, three types of failure patterns were analysed based on the condition of pillar and roof. It can be concluded that any failure of a bearing component would cause a subsidence event. However, the barrier pillar could bear the transferred load during the stress redistribution process, mitigating the propagation of collapse or cutting the roof to insulate the collapse area. Importantly, some effective methods were suggested to decrease the risk of catastrophic collapse, and the deep-hole-blasting was employed to improve the stability of the pillar and roof support system in a room and pillar mine.

• KIEAE Journal
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• v.14 no.2
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• pp.11-19
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• 2014

Building energy consumption takes up almost 25% of the total energy consumption. Therefore, diversified ways, such as improving wall and window insulation, have been considered to reduce building energy consumption. Recently, green roof system has been explored as an effective alternative for dealing with reducing heating and cooling energy, thermal island effect and improving water quality. However, recent studies regarding a green roof system have only focused on building energy reduction without considering the applied usage, location, and story of the green roof system. Therefore, this study pays attention to the heating and cooling energy in relation to the applied usage, location, and story of a green roof system for investigating its impact on energy reduction. The result of simulations show that the reduction in heating energy consumption is higher when applied to Cherwon-gun province which has a continental climate condition, compared to the city of Busan that is distinguished by its warm climate. Cooling energy saving turns out to be higher when the green roof system is applied to Busan in comparison with Cherwon. As for the applied usage or function of the building, residential space acquires the highest heating and cooling energy saving effect rather than commerce, educational or office space because of HVAC's running time based on usage. When it comes to the story of the green roof, both heating and cooling energy saving become the highest when the green roof is applied to single-storied buildings. The reason is that single story building is affected by the ground largely. Generally, the variations of heating energy consumption are larger than the cooling energy consumption. The outcome of the simulations, when a green roof system is applied, indicates that the energy consumption reduction rate is dynamically responding to the applied usage, location, and story. Therefore, these factors should be counted closely for maximizing the reduction of energy consumption through green roof systems.

• KIEAE Journal
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• v.7 no.1
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• pp.73-80
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• 2007

This paper aims to develop the diffused reflection material in order to reduce the solar absorption coefficient, and to compare the thermal properties with the different roof structure system; one is using the diffused reflection material applied the upper side of the rigid sheet waterproof system and the other is using the conventional up-side down waterproof system on the roof. For this purpose two experimental test boxes were made of same iso-panel wall and floor with different roof system. The experiment was carried out under these process; measure the surface temperature exposed solar radiation of the variation of the reflection materials(cement paste, silica, galvanized steel and titanium dioxide(TiO2)), measure and analyze the variation of the temperature distribution of the each roof system and indoor air in order to evaluate the thermal properties according to the different roof system. The result shows clearly that using the titanium dioxide(TiO2) might be more effective to reduce the solar insolation.

• KIEAE Journal
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• v.17 no.1
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• pp.49-54
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• 2017

Purpose: Temperature in urban areas increase much more than suburban areas and it is called urban heat island (UHI) phenomenon. There are several solutions to control UHI phenomenon such as green roof system, water space construction, and cool roof system. However, application of green roof system and cool roof system to some of the buildings which compose the city has a critical limit. Therefore, in order to diminish the temperature rising and UHI phenomenon due to climate change of the city, it needs to approach from the viewpoint of site or city, rather than the viewpoint of individual buildings. This study is aims at analyzing UHI phenomenon by characteristics of surface materials and suggesting the solutions to reduce UHI phenomenon by types of complex. Method: Literature reviews were conducted to analyze the cause, mitigating plan, and recent trends of UHI phenomenon. For the simulation analysis, the type of complex was classified 3 representative complex. Based on measured reflectivity, simulation about UHI phenomenon was conducted by setting 4 strategies; albedo of roof, road pavement, green roof system, and vegetating around buildings. Result: As the results of simulating the UHI reduction factor by types of complex, it showed that the effect of temperature reduction on the building roof layer is more effective than adjusting the reflectivity of buildings such as green roof system, planting near the buildings in both the detached house complex, apartment complex, and commercial complex.

• KIEAE Journal
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• v.9 no.6
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• pp.51-56
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• 2009

The most important advantages of atrium buildings are to allow the abundant natural lighting and outside views. However, the abundant lighting frequently causes to increase a cooling load in summer. The roof watering systems are useful to reduce the cooling load and save the energy. This study aims to investigate the effects of the roof watering system in atrium through the scaled model experiments. For the study, the 1/20 scaled model was made and tests were performed under the clear sky conditions through August 24 to september 7 in 2008. The model size was $45{\times}45{\times}60(cm)$ and depth of roof water was 3(cm). As results, the thermal effects of two types of atrium(roof opening, and roof and front opening,) were evaluated through the experimental points and conditions. It is expected to use the results for the next research to develop the practical roof watering systems for atrium.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.10
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• pp.109-115
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• 2011

Apartments covered with a metal roof made from galvalume steel are prevailing due to their economic and technical advantages. The metal roof, however, has disadvantages in terms of the installation of air-termination system on it because of the slip thickness of the metal roof. In this paper, the impacts of the lightning current to a metal roof were verified experimentally with a short lightning impulse current (10/350[${\mu}s$]). Also, we developed various supporters of air-termination conductor for the metal roof and verified their excellent workability and economical strength through field application test.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.5
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• pp.56-62
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• 2010

This paper presents the development process of roof carrier assembly using a one side release system for a vehicle. An RV(Recreational Vehicle) or SUV(Sports Utility Vehicle) has a roof carrier system on an upper surface of a roof panel for loading large or long size baggage. Such a roof carrier system is comprised of a roof rack longitudinally mounted on a roof panel and cross bar perpendicularly installed in the horizontal direction. Several locking mechanisms used in most vehicle roof carrier systems are composed with both side releasable locking ones. The obvious drawback to this arrangement is that when the user desires to reposition the cross bar, first one of the locking members must be unlocked and then the user must walk around to the opposite side of the vehicle to unlock the other member. In this paper, we proposed a newly locking mechanism, which allows a user simultaneously place both locking members of the roof carrier in locked and unlocked positions. In order to estimate design compatibility, structural and modal analysis is performed. Furthermore, a prototype based on the proposed design has been made, and then durability test carried out. From the simulation and experimental results, the proposed roof carrier system is proved effective and safe.

• International conference on construction engineering and project management
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• 2013.01a
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• pp.300-303
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• 2013

On BIPV systems, especially roof-top PV systems, the power generation is easier to be reduced due to the shades of facilities nearby, or roof itself. To secure profitability of roof-top PV systems, the optimal design of solar arrays through the precise shading analysis is an important item of design considerations. In this paper, an optimization system for array design of roof-top PVs is to be developed using three-dimensional Geospatial Information System(GIS). The profitability of income and expense is considered through the shading analysis of entire roofs. By applying the system to project for validation, the adequacy and the improvement of NPV of the system were verified compared to expert's design. The system has significance by reason that PV modules are placed through rules established with expert knowledge and geometric rules were applied to reflect the constructability and maintainability.

• Journal of Korean Society of Water and Wastewater
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• v.29 no.2
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• pp.165-169
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• 2015

Green roofs are gaining much interest in many cities around the world due to its multi-purpose effects of water conservation, flood mitigation and aesthetic benefits. However it may cause additional water demand to maintain green plants, which may intensify the current and future water shortage problems. While ordinary concrete roofs and normal green roof drains off rain water, concave green roof system can retain rain water because of its water holding capability. In this study, the water conservation effect of concave green roof was compared to normal roof on #35 building in Seoul National University, Seoul, Korea. For seven rainfall events the amount of stored rainwater and runoff were measured and proved water conservation effect of the concave green roof system. The concave green roof system of which area is 140m2 showed effect of water conservation from 1.8ton to 7.2ton and the most influence factors on water conservation in green roof are rainfall and antecedent day. If this concave green roof is applied to many buildings in the cities, it is expected as a way to water conservation through rainfall storage.