• Structural Engineering and Mechanics
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• v.61 no.6
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• pp.701-709
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• 2017

Seismic dissipation devices can play a crucial role in mitigating earthquake damages, loss of life and post-event repair and downtime costs. This research investigates the use of ring springs with high-force-to-volume (HF2V) dissipaters to create damage-free, recentring connections and structures. HF2V devices are passive rate-dependent extrusion-based devices with high energy absorption characteristics. Ring springs are passive energy dissipation devices with high self-centring capability to reduce the residual displacements. Dynamic behaviour of a system with nonlinear structural stiffness and supplemental hybrid damping via HF2V devices and ring spring dampers is used to investigate the design space and potential. HF2V devices are modelled with design forces equal to 5% and 10% of seismic weight and ring springs are modelled with loading stiffness values of 20% and 40% of initial structural stiffness and respective unloading stiffness of 7% and 14% of structural stiffness (equivalent to 35% of their loading stiffness). Using a suite of 20 design level earthquake ground motions, nonlinear response spectra for 8 different configurations are generated. Results show up to 50% reduction in peak displacements and greater than 80% reduction in residual displacements of augmented structure compared to the baseline structure. These gains come at a cost of a significant rise in the base shear values up to 200% mainly as a result of the force contributed by the supplemental devices.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1081-1092
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• 2014

Renewable energy is being spotlighted as the electric power generating source for the next generation. Due to an increase in renewable energy systems in the grid system, their impact on the grid has become non-negligible. Thus, many countries in the world, including Europe, present their own grid codes for grid power conversion devices. In order to experiment with these grid codes, grid fault test equipment is required. This paper proposes both equipment and a control method, which are constructed with a 7-level cascaded H-bridge converter, that are capable of generating various grid faults. In addition, the Pulse Width Modulation (PWM) method for multilevel converters is compared and analyzed. The proposed structure, the control method, and the PWM method are verified through simulation and experimental results.

• KIEAE Journal
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• v.8 no.3
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• pp.27-36
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• 2008

Urban architecture density is getting higher, and this trend is expected to continue in the future. Therefore, skyscrapers are being brought into relief as future alternative architecture beyond symbolic meaning in the aspect of demand and supply of urban space. However, skyscrapers which were newly built have many problems such as consumption of enormous amounts of energy, destruction of natural environment, and traffic jam. For this reason, environment-friendly skyscrapers based on the concept such as Green Building and Green Skyscraper started to be built around the world. However, plans or evaluation standards, which take account of the environment-friendly aspect of skyscrapers, leave much to be desired. And especially it is hard to find environment-friendly skyscrapers. Therefore, this study aims to establish the concept of environment-friendly skyscrapers that has not properly been defined, and to find realistic planning methods and practical alternatives through the analysis of the works that have brilliant ideas about environment-friendly architectural method. From the perspective of architectural planning, we did case analysis focused on site planning, form planning, elevation and floor planning, and tried to give useful ideas for high-rise architectural planning in Korea by finding practical solution focused on the active use of natural energy, saving resources, the reduction of wastes, natural architectural environment design and natural friendly system from the view of environment-friendly technological analysis.

• Journal of the Korean Solar Energy Society
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• v.24 no.2
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• pp.39-50
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• 2004

One of the challenge for successful daylighting design might be to capture sunlighting that varies in both intensity and position and to deliver the luminous flux into the inner space as deep as possible. Conventional glazing apertures allow daylight in the outer 3.5m of a perimeter spaces. More advanced daylighting technologies can extend this daylighting depth by reflecting sunlight further from the windows within a deep floor area. For this purpose, this study developed light shelves based on performance evaluation with a mock-up model that constructed recently and measured under real sky condition. All these daylighting devices have a customized geometry developed from the solar path at a given latitude and utilize unique reflecting finishing to maximize the amount of redirection and diffusion of the daylight. This paper tells that the best daylighting penetration typically can be expected from using light-colored sloped external shelves.

• Journal of the Korean Solar Energy Society
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• v.24 no.2
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• pp.25-31
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• 2004

Ventilation through air vent system in a building envelope is expected to be an effective measure to release solar radiation. An external surface of a wall absorbs solar radiation and transfers it to the air in the cavity. The warmed air gets buoyant force. So when openings are provided at the top and bottom of the cavity, the warmed air is released through the top opening and cooler outside air replaces the space in the cavity. This reduces the further heat transmission into the built environment. This natural ventilation effect seems to be steady and strong. So because of the cavity and the openings, the cooling load reduction by natural ventilation is believed to be considerable.

• 한국태양에너지학회:학술대회논문집
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• 2008.11a
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• pp.190-195
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• 2008

The objective of this research is to determine overall heat transfer coefficients (K-value) of exterior wall, floor, and roof of Nakseonjae, a Korean traditional residence via field measurement of transient heat flow and temperature difference across each envelope component. Heat flow sensors and T-type thermocouple were attached on the internal and the external surface of each building component, and real-time measurement data were collected for the three consecutive summer days. The K-values determined in this research showed good agreement with other results from open literature. Peak and annual thermal loads of the traditional residence estimated by a commercial energy simulation program were compared with those for a current apartment house. The traditional house showed lower annual cooling load than that of the current building. It may caused by the fact that the traditional building has less air-tight envelopes and no fenestration passing direct solar radiation into the space.

• Journal of the Korean Society for Geothermal and Hydrothermal Energy
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• v.15 no.4
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• pp.46-54
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• 2019

In this study, the performance of a shell and tube heat exchanger (STHE) and welded plate heat exchanger (WPHE) was measured experimentally. The pass numbers of the STHE was changed by 1, 2 and 4. As a result, the WPHE showed 2.1 times higher heat exchange capacity than that of the STHE. In case of pressure drop, the STHE with 1 and 2 pass number has a lower pressure drop than the WPHE, while the STHE with 4 pass presented higher pressure drop than the WPHE. The performance index considering the heat exchange capacity and pump consumption power, showed in oder of STHE_Pass1 > STHE_Pass2 > W PHE > STHE_Pass4 under the same flow rate. Therefore, when the WPHE was designed optimally under same operating condition with STHE, the maintenance fee and space can be reduced effectively by using the WPHE.

• KIEAE Journal
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• v.11 no.1
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• pp.15-20
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• 2011

Computer simulation of buildings and solar energy systems is being used increasingly in energy assessments and design. For the six locations (Seoul, Incheon, Daejeon, Deagu, Gwangju and Busan) in South Korea where the global hourly solar irradiation (GHSI) is currently measured, GHSI was calculated using a comparatively simple cloud cover radiation model (CRM) and sunshine fraction radiation model (SFRM). The result was that the measured and calculated values of GHSI were similar for the six regions. Results of cloud cover and sunshine fraction models have been compared with the measured data using the coefficient of determination (R2), root-mean-square error (RMSE) and mean bias error (MBE). The strength of correlation R2 varied within similar ranges: 0.886-0.914 for CRM and 0.908-0.934 for SFRM. Average MBE for the CRM and SFRM were 6.67 and 14.02 W/m2, respectively, and average RMSE 104.36 and 92.15 W/m2. This showed that SFRM was slightly accurate and used many regions as compared to CRM for prediction of GHSI.

• Journal of the Korean Institute of Rural Architecture
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• v.17 no.1
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• pp.9-18
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• 2015

The purpose of this study is to analyze the usage of eco-friendly elements in Korean traditional architecture to evaluate Hanok(Unjoru and Jinwondang) according to Green Building Certification Criteria(G-SEED). The results of this study were as follows; Unjoru and Jinwondang was not enough to obtain certification points. From Site usage and Traffic category, Jinwondang gets more points than Unjoru. It's because Jinwondang is located in downtown Seoul, so it gets more points of traffic and neighborhood facility. From Energy and Environmental Pollution category, Jinwondang gets more points of energy performance than Unjoru, too. It's because Jinwondang secured insulation performance of wall and windows using insulator and glass. From Resources category, Unjoru gets more points than Jinwondang. It shows that modern Hanok was limited using natural resources. From Ecological Environments category, Jinwondang is located urban area, it's difficult to secure the open space, so Unjoru gets more points than Jinwondang. If Modern Honok installs a system that can getting point and secure insulation performance, it will be certificated according to G-SEED.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.241-247
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• 2005

This paper deals with the operation of a flywheel energy storage UPS. The UPS has good features such as long life-time, improved efficiency, no environmental problems, reduced size and space, and low maintenance cost compared with the conventional UPS using battery. The operating principle of the UPS is analysed in each mode including voltage compensation as well as uninterruptible power supply. Especially, the tracking characteristic of the disturbed phase of the source voltage after outage is analysed. The usefulness of the system is proved through simulations and experiments.