• Title/Summary/Keyword: Wind energy

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Electrical Properties of Photovoltaic cells depending on Simulated design (모의 설계에 따른 Photovoltaic cells의 전기적 특성)

  • Choi, Hyun-Min;Jeong, In-Bum;Kim, Gwi-Yeol;Kim, Tae-Wan;Hong, Jin-Woong
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • 2010.06a
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    • pp.36-36
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    • 2010
  • Currently, there are several newly developed energy resources for the future to replace petroleum resources such as hydrogen fuel cell, solar cell, wind power, and etc. Among them, solar cell has attracted a worldwide concern, because it has an enormous amount of resources. In general, a study of solar cells can be classified in to an area of bulk type and thin-film type. Inorganic solar cells based on silicon have been tremendously developed in technology and efficiency. However, since there are many lithographic steps, high processing temperature approximately $1000^{\circ}C$, and expensive raw materials, a manufacturing cost of device are nearly reaching a limit. Contrary to those disadvantages, organic solar cells can be manufactured at room temperature. Also, it has many advantages such as a low cost, easy fabrication of thin film, and possible manufacture to a large size. Because it can be made to be flexible, research and development on solar cells are actively in progress for the next generation. ever though an efficiency of the organic solar cell is low compared to that of inorganic one, a continuous study is needed. In this paper, we report optimal device structure obtained by a program simulation for design and development of highly efficient organic photovoltaic cells. we have also compared simulated results to experimental ones.

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Experimental Investigation on the Effect of Low-Speed Icing Condition to the Surface Roughness Formation (저속 결빙조건이 표면 조도 형성에 미치는 영향에 관한 실험적 연구)

  • Kang, Yu-Eop;Min, Seungin;Kim, Taeseong;Yee, Kwanjung
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.48 no.2
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    • pp.99-108
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    • 2020
  • In the field of aircraft icing prediction, surface roughness has been considered as critical factor because it enhances convective heat transfer and changes local collection efficiency. For this significance, experimental studies have been conducted to acquire the quantitative data of the formation process. Meanwhile, these experiments was conducted under low-speed condition due to the measurement difficulties. However, it has not been investigated that how the flow characteristic of low-speed will effects to the surface roughness. Therefore, the present study conducted experiment under low-speed icing condition, and analyzed the relation between surface roughness characteristics and icing condition. As an analysis method, the dominant parameters used in the previous high-speed experiments are employed, and roughness characteristics are compared. The size of roughness element was consistent with the previous known tendency, but not the smooth zone width.

Investigating the Power-Performance Prediction on an H- and Helical-type Tidal Current Turbine Using CFD Method (CFD에 의한 H 및 Helical 타입 조류발전용 터빈의 출력성능예측에 관한 연구)

  • Kim, Bum Suk
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.39 no.8
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    • pp.653-660
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    • 2015
  • In this study, we conduct power performance and load analyses of two different types of vertical-axis tidal-current turbines using the computational fluid dynamics (CFD) method. To analyze the power output and loads, we perform transient CFD simulations considering the cavitation model using ANSYS CFX. The averaged power output of an H-type rotor was 7.47 kW and 67.6 kW in normal and extreme operating conditions, respectively, which did not satisfy the initial design conditions. However, in the case of the helical-type rotor, the power output under normal and extreme conditions were close to the expected values. The cavitation, which may cause instantaneous power fluctuation, occurred repeatedly at the suction side of the rotors. In order to guarantee a more stable power supply and to prevent fatigue failure, we require a design that minimizes cavitation.

A Study on Applications of Prescriptions including Semen Arecae as a Main Component in Dongeuibogam ("동의보감(東醫寶鑑)" 중(中) 빈랑(檳榔)이 주약(主藥)으로 배오(配伍)된 방제(方劑)의 활용(活用)에 대한 고찰(考察))

  • Lim, Dai-Hwan;Jeon, Young-Kyun;Lee, Ju-Hee
    • Herbal Formula Science
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    • v.17 no.1
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    • pp.61-74
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    • 2009
  • This report describes 46 studies related to prescriptions which are mainly used Semen Arecae from Dongeuibogam. The following conclusions were reached through investigations on the prescriptions that use Semen Arecae as a main component. 19.6% of a malaria, 17.4% of an evacuation problem, recorded the largest number of clinical frequency of the prescriptions in therapeutic use when Semen Arecae was taken as a main component in prescriptions Prescriptions that utilize Semen Arecae as the main ingredient are used in the treatment of a malaria, an evacuation problem and a malignant dermatosis. they are also used for treating 11 different types of diseases. The prescriptions are compounded with Semen Arecae as a main component which can be applied to an affection by wind-cold, a heat(fire) syndrome, a cold-stroke, a phlegm-retention syndrome, a constipation induced by apoplexy, a stagnation of vital energy, an asthenia of the spleen and the stomach, a convulsion caused by improper diet, a parasitic infestation and a traumatic disease. The dosage of Semen Arecae is 2.5pun(nearly 0.94g) to 3don(nearly 11.25g), however 1don(nearly 3.75g) has been taken the most for clinical application. When Semen Arecae is combined with basic prescriptions such as Ijintang and Bulium, it applies symptoms of malaria. In addition, when Semen Arecae is combined with basic prescriptions such as Daemainhwan, Soseungkitang and Samatang, it utilizes an evacuation problem.

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The Analysis of Terrain Height Variance Spectra over the Korean Mountain Region and Its Impact on Mesoscale Model Simulation (한반도 산악 지역의 지형분산 스펙트럼과 중규모 수치모의에서의 효과 분석)

  • An, Gwang-Deuk;Lee, Yong-Hui;Jang, Dong-Eon;Jo, Cheon-Ho
    • Atmosphere
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    • v.16 no.4
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    • pp.359-370
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    • 2006
  • Terrain height variance spectra for the Korean mountain region are calculated in order to determine an adequate grid size required to resolve terrain forcing on mesoscale model simulation. One-dimensional spectral analysis is applied to specifically the central-eastern part of the Korean mountain region, where topographical-scale forcing has an important effect on mesoscale atmospheric flow. It is found that the terrain height variance spectra in this mountain region has a wavelength dependence with the power law exponents of 1.5 at the wavelength near 30 km, but this dependence is steeply changed to 2.5 at the wavelength less than 30 km. For the adequate horizontal grid size selection on mesoscale simulation two-dimensional terrain height spectral analysis is also performed. There is no directionality within 50% of spectral energy region, so one-dimensional spectral analysis can be reasonably applied to the Korea Peninsula. According to the spectral analysis of terrain height variance, the finer grid size which is higher than 6 km is required to resolve a 90% of terrain variance in this region. Numerical simulation using WRF (Weather Research and Forecasting Model) was performed to evaluate the effect of different terrain resolution in accordance with the result of spectral analysis. The simulated results were quantitatively compared to observations and there was a significant improvement in the wind prediction across the mountain region as the grid space decreased from 18 km to 2 km. The results will provide useful guidance of grid size selection on mesoscale topographical simulation over the Korean mountain region.

Analysis of Heat Transfer Characteristics in Response to Water Flow Rate and Temperature in Greenhouses with Water Curtain System (수막하우스의 유량 및 수온에 따른 열전달 특성 분석)

  • Kim, Hyung-Kweon;Kim, Seoung-Hee;Kwon, Jin-Kyeong
    • Journal of Bio-Environment Control
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    • v.25 no.4
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    • pp.270-276
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    • 2016
  • This study analysed overall heat transfer coefficient, heat transmission, and rate of indoor air heating provided by water curtain in order to determine the heat transfer characteristic of double-layered greenhouse equipped with a water curtain system. The air temperatures between the inner and outer layers were determined by the water flow rate and inlet water temperature. Higher water flow rate and inlet water temperature resulted in the increased overall heat transfer coefficient between indoor greenhouse air and water curtain. However, it was found that with higher levels of water flow rate and inlet water temperature, indoor overall heat transfer coefficient was converged about $10W{\cdot}m^{-2}{\cdot}^oC^{-1}$. The low correlation of overall heat transfer coefficient between water curtain and air within double layers was likely because the combination of greenhouse shape, wind speed and outdoor air temperature as well as water curtain affected the heat transfer characteristics. As water flow rate and inlet water temperature increased, the heat transferred into the greenhouse by water curtain also tend to rise. However it was demonstrated that the rate of heat transmission from water curtain into greenhouse with water curtain system using underground water was accounted for 22% to 28% for total heat lost by water curtain. The results of this study which quantify heat transfer coefficient and net heat transfer from water curtain may be a good reference for economical design of water curtain system.

Optimal variables of TMDs for multi-mode buffeting control of long-span bridges

  • Chen, S.R.;Cai, C.S.;Gu, M.;Chang, C.C.
    • Wind and Structures
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    • v.6 no.5
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    • pp.387-402
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    • 2003
  • In the past decades, much effort has been made towards the study of single-mode-based vibration controls with dynamic energy absorbers such as single or multiple Tuned Mass Dampers(TMDs). With the increase of bridge span length and the tendency of the bridge cross-section being more slender and streamlined, multi-mode coupled vibrations as well as their controls have become very important for large bridges susceptible to strong winds. As a simple but effective device, the TMD system especially the semi-active one has become a promising option for such coupled vibration controls. However, despite various studies of optimal controls of single-mode-based vibrations with TMDs, research on the corresponding controls of the multi-mode coupled vibrations is very rare so far. For the development of a semi-active control strategy to suppress the multi-mode coupled vibrations, a comprehensive parametric analysis on the optimal variables of this control is substantial. In the present study, a multi-mode control strategy named "three-row" TMD system is discussed and the general numerical equations are developed at first. Then a parametric study on the optimal control variables for the "three-row" TMD system is conducted for a prototype Humen Suspension Bridge, through which some useful information and a better understanding of the optimal control variables to suppress the coupled vibrations are obtained. This information lays a foundation for the design of semi-active control.

Analysis of Saturation Flow Rate on Interrupted Flow During Rainfall (강우시 단속류 포화교통류율 변화 분석)

  • Kim, Bongseok;Roh, Chang-Gyun;Son, Bongsoo
    • Journal of Korean Society of Transportation
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    • v.33 no.1
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    • pp.90-99
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    • 2015
  • The climate of Korea has clear rainy and dry season due to seasonal wind. In general, The rainy season in Korea is from early summer through to early fall. And precipitation accounted for more than half of the total annual rainfall in this period. This study is aiming to analysis of variation in saturation flow rate at signalized intersection during rainfall. The range of spatial is urban signalized intersections in Seoul and temporal is rainfall or ideal condition in daylight. Traffic data are collected through CCTV of Seoul Metropolitan Police Agency, and on-site video recordings directly. Weather condition data are collected from the Korea Meteorological Administration. In addition, the value of saturation headway and saturation flow rate, in rainfall condition, are derived through video frame analysis. As a results of analysis, decrease of saturation flow rate and increase of saturation headway during rainfall were confirmed by comparison with non-rainfall. The higher rainfall rate is, the more decreased saturation flow rate at the intersections. Rainfall rate is divided three area by the results of statistical test, and saturation flow rate decrease 7%, 17%, 21%, respectively.

Structural Behavior of Steel Brace Strengthened with Non-welded Buckling Restraint Casing (무용접 좌굴방지재로 보강한 철골 가새의 구조거동)

  • Kim, Sun Hee;Moon, Ji Young;Choi, Sung Mo
    • Journal of Korean Society of Steel Construction
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    • v.27 no.2
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    • pp.207-217
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    • 2015
  • A concentrically braced steel frame is a very efficient structural system because it requires relatively smaller amount of materials to resist lateral forces. However, primarily developed as a structural system to resist wind loads based on an assumption that the structure behaves elastically, a concentrically braced frame possibly experiences the deterioration in energy dissipation after brace buckling and the brittle failure of braces and connections when earthquake loads cause inelastic behavior. Consequently, plastic deformation is concentrated in the floor where brace buckling occurs first, which can lead to the rupture of the structure. This study suggests reinforcing H-shaped braces with non-welded cold-formed stiffeners to restrain flexure and buckling and resist tensile force and compressive force equally.

Sustainability Evaluation for Shellfish Production in Gamak Bay Based on the Systems Ecology 1. EMERGY Evaluation for Shellfish Production in Gamak Bay (시스템 생태학적 접근법에 의한 가막만 패류생산의 지속성 평가 1. 가막만 패류양식의 에머지 평가)

  • Oh, Hyun-Taik;Lee, Suk-Mo;Lee, Won-Chan;Jung, Rae-Hong;Hong, Suk-Jin;Kim, Nam-Kook;Tilburg, Charles
    • Journal of Environmental Science International
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    • v.17 no.8
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    • pp.841-856
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    • 2008
  • This research outlines a new method for evaluation of shellfish production in Gamak Bay based on the concept of EMERGY. Better understanding of those environmental factors influencing oyster production and the management of oyster stocks requires the ability to assess the real value of environmental sources such as solar energy, river, tide, wave, wind, and other physical mechanisms. In this research, EMERGY flows from environment sources were 76% for shellfish aquaculture in Gamak Bay. EMERGY yield ratio, Environmental Loading Ratio, and Sustainability Index were 4.26, 0.31 and 13.89, respectively. Using the Emergy evaluation data, the predicted maximum shellfish aquaculture production in Gamak Bay and the FDA (Food and Drug Administration, U.S.) designated area in Gamak Bay were 10,845 ton/y and 7,548 ton/yr, respectively. Since the predicted shellfish production was approximately 1.3 times more than produced shellfish production in 2005, the carrying capacity of Gamak Bay is estimated to be 1.3 times more than the present oyster production.