• Proceeding of KASS Symposium
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• 2008.05a
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• pp.155-158
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• 2008

As the span of spatial structure is getting longer, the law frequency of the structure makes the wind-induced response much increased. However, there are lots of hardships to establish the economical structural systems due to the fact that an relative equation between the frequency and the span of the domestic spatial structures is not existed in the stage of the basic planning design. Therefore, among the large-span structures, this paper focused on the relationship between the frequency and the span of the world-cup stadium built in 2000s. The relative equation between the frequency and span is compared with the data measured in Japan. Moreover, we are willing to provide the basic study by suggesting the summary equation in this paper.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.1
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• pp.16-22
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• 2015

As the development of Battery Energy Storage System(BESS) and the increasing of intermittent energy sources like wind power and photovoltaic, the application of BESS in load frequency control is considered as an effective method. To evaluate the effectiveness of BESS application in frequency control, we defined a governor free model of BESS to conduct dynamic simulation. Using the BESS dynamic model, we implemented the power system dynamic model including steam, gas and hydro turbine generators. In this paper we study the control performance of BESS in primary frequency control. The effect of BESS speed regulation rate and response time on governor free operation is investigated. In addition, we compared BESS from steam turbine generator in view point of frequency regulation.

• Journal of Environmental Health Sciences
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• v.13 no.2
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• pp.9-24
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• 1987

This study was conducted to measure the diurnal variation and behaviour of atmospheric mercury in an urban area by gold amalgamation and cold vapour atomic absorption spectrophotometry. The results were as follows: 1. The Hg concentration in ambient air averaged. 21.13ng/m$^3$ for 111 determinations (C.V. 78.5) in urban area and 5.91ng/m$^3$ for 140 determinations (C.V. 21.3) in suburban area. The urban area concentration was significantly higher and fluctuated more than its rural counterpart. 2. Regression analysis of the interaction between mercury concentration and other components showed a significant correlation between mercury concentration and sulfur dioxide also, TSP were found. Mercury concentration was shown to have a similar behaviour, on the whole, with other air pollutants. 3. It demonstrated a positive correlation with sunlight (UV-ray), while it had a negative response to wind speed and humidity. Its concentration showed a tendensy to increase during calm weather specifically. 4. The Hg concentration at the Mt. Dok You inland clean area ranged from 1.33ng/m$^3$ to 2.0ng/m$^3$, with a mean value of 1.63ng/m$^3$.

• Wind and Structures
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• v.22 no.3
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• pp.291-305
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• 2016

In this paper, a refined shear deformation plate theory which eliminates the use of a shear correction factor was presented for FG sandwich plates composed of FG face sheets and an isotropic homogeneous core. The theory accounts for parabolic distribution of the transverse shear strains and satisfies the zero traction boundary conditions on the surfaces of the plate. The mechanical properties of the plate are assumed to vary continuously in the thickness direction by a simple power-law distribution in terms of the volume fractions of the constituents. Based on the present refined shear deformation plate theory, the governing equations of equilibrium are derived from the principle of virtual displacements. Numerical illustrations concern buckling behavior of FG sandwiches plates with Metal-Ceramic composition. Parametric studies are performed for varying ceramic volume fraction, volume fraction profiles, Boundary condition, and length to thickness ratios. The accuracy of the present solutions is verified by comparing the obtained results with the existing solutions.

• Smart Structures and Systems
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• v.4 no.2
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• pp.247-259
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• 2008

The potential use of Cu-based shape memory alloys (SMA) in retrofitting historical monuments is investigated in this paper. This study is part of the ongoing work conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The present investigation consists of a finite element simulation, as a preliminary to an experimental study where a cantilever masonry wall, representing a part of a historical monument, is subjected to monotonic and quasi-static cyclic loadings around a horizontal axis at the base level. The wall was retrofitted with an array of copper SMA wires with different cross-sectional areas. A new model is proposed for heat-treated copper SMAs and is validated based on published experimental results. A series of nonlinear finite element analyses are then performed on the wall for the purpose of assessing the SMA device retrofitting capabilities. Simulation results show an improvement of the wall response for the case of monotonic and quasi-static cyclic loadings.

• Nuclear Engineering and Technology
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• v.47 no.4
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• pp.461-471
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• 2015

Recently, the estimation of the social cost of energy sources has been emphasized as various novel energy options become feasible in addition to conventional ones. In particular, the social cost of introducing measures to protect power-distribution systems from power-source instability and the cost of accident-risk response for various power sources must be investigated. To account for these risk factors, an integrated societal risk assessment framework, based on power-uncertainty analysis and accident-consequence analysis, is proposed. In this study, we applied the proposed framework to nuclear power plants, solar photovoltaic systems, and wind-turbine generators. The required capacity of gas-turbine power plants to be used as backup power facilities to compensate for fluctuations in the power output from the main power source was estimated based on the performance indicators of each power source. The average individual health risk per terawatt-hours (TWh) of electricity produced by each power source was quantitatively estimated by assessing accident frequency and the consequences of specific accident scenarios based on the probabilistic risk assessment methodology. This study is expected to provide insight into integrated societal risk analysis, and can be used to estimate the social cost of various power sources.

• Journal of Sensor Science and Technology
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• v.25 no.2
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• pp.116-123
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• 2016

This paper presents the fabrication and evaluation of the novel drag force type air flowmeter using MEMS technologies for the vehicle applications. To obtain the air drag force, the flowmeter utilized the curved beam structure, which was realized by the difference of residual stress between the silicon oxide layer and the silicon nitride layer. The paddle structure was applied for the maximum air drag force, and the dual-beam was adapted to prevent distortion. The basic experiments were performed in the wind tunnel, and the stable outputs were obtained. The device was applied to the internal combustion engine, and the results were compared with the HI-DS output where the convection thermal flowmeter was used as the reference sensor. The results indicated that the comparable resolutions and response times were obtained under the various engine speeds.

• New & Renewable Energy
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• v.3 no.3
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• pp.63-71
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• 2007

본 연구의 목적은 3차원 풍력터빈 블레이드 최적형상설계를 위한 실용적이고 효율적인 설계과정을 구현하는 것이다. 국내 연안의 해상풍력에 적용하기 위해서 통계적 모델을 이용하여 풍황자료를 분석하였다. 설계에 관련된 많은 수의 설계변수를 효과적으로 관리하기 위해서 설계과정은 운용조건 최적화와 블레이드 형상설계의 2단계로 구성하였다. 실험계획법에 의해 추출된 각 운용조건 설계점은 형상설계를 위한 입력 값으로 제공된다. 형상설계 단계에서는 최소에너지손실 조건과 결합된 BEMT를 이용하여 각 블레이드 단면에서의 시위길이와 피치각 분포를 최적화하였다. 블레이드 단면 익형은 NREL S830을 이용하였고, 익형의 공력성능은 XFOIL을 이용하여 예측하였다. 설계된 블레이드 형상의 성능해석을 수행하고 그 결과를 바탕으로 반응면을 구성하였다. 좀 더 나은 성능을 가진 블레이드 형상을 찾기 위해서 초기설계공간에서 확률적 방법을 이용하여 타당성 있는 설계공간까지 운용조건 설계변수를 이동시키고 구배최적화 기법을 통해 각각의 제약함수를 만족하면서 연간에너지생산량을 최대로 하는 최적블레이드 형상을 구현하였다. 제시된 최적설계과정은 풍력터빈블레이드 개발에 실용적이고 신뢰성 있는 설계툴로서 사용이 가능하다.

• 한국해양학회지
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• v.24 no.2
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• pp.96-108
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• 1989

Applying the numerical scheme developed by Semtner (1974), we investigate the circulation system in the Japan Sea in response to the air-sea interaction and the wind. In spite of blocking straits, resulting surface circulation pattern is similar to the schematic surface current chart introduced by Uda(1934) and Naganuma (1972); the northward flow along the Korean coast and the anticlockwise gyre in the northeastern part of the Japan Sea. Also the southward current flows along the Korean coast at depth of 100-200 m as similar to the North Korean Cold Current suggested by Kim and Kim (1983). And the sinking phenomenon of relatively saline water in the northeastern part of the Japan Sea is similar to the formation of the Japan Sea Proper Water.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.81-88
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• 2009

An evaluation of the structural integrity of an oceanographic buoy subjected to extreme loads was carried out in this study. Load components, such as the current, waves, and wind load, which were required for the sea's environmental conditions, were calculated precisely. A non linear finite element analysis was conducted to elucidate the structural response of the buoy under extreme environmental conditions. Based on the surface drift velocity scheme, a dynamic impact analysis was also carried out for the case of collision accidents. The proposed numerical technique would be a useful and cost effective tool for design scheme evaluation in the field of oceanographic buoys.