• Title/Summary/Keyword: 68 generation

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Evaluation of Effects of Real Joint-Operation of Multi-purpose Dams (다목적댐군의 실제 연계운영 효과 평가)

  • Kang, Min-Goo;Lee, Gwang-Man;Cha, Hyung-Sun
    • Journal of Korea Water Resources Association
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    • v.40 no.2 s.175
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    • pp.101-112
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    • 2007
  • In this study, a methodology was developed to evaluate the effects produced in the event of joint-operation of dams from the viewpoint of water use. It was applied to evaluating the actual results of dam operation in the Han River basin. In order to evaluate the effects of real joint-operation in terms of water supply and flow conditions, the methodology used the satisfaction rate of water requirement and the stability of flow conditions at the evaluation site as indicator. In order to evaluate the effects of joint-operation in terms of power generation, the total power generation produced by dams was used as evaluation indicator. Actual operation results were evaluated by comparison of evaluation indicators relating to single dam operation by which the notified mont of water was supplied, as well as to optimization models. Results of actual joint-operation of the Han River basin, from 2001 to 2004, were compared yearly with results from single operation and optimization model; in terms of water supply, the satisfaction ratio of water requirement stood at $94.36{\sim}99.68%$ for single operation, $97.16{\sim}99.90%$ for actual joint-operation, and 100.0 % for optimization model for all four years. The stability of flow condition was evaluated by the coefficient of river regime and coefficient of flow conditions definitely, indicating that flow conditions were more stable in case of actual operation and optimization models than in case of single operation. The actual total power generation was compared with that generated by other operation rules, indicating that the optimization model increased the power generation by $-3.47{\sim}6.54%$ compared with the actual total power generation, and that the single operation decreased the power generation amount by $12.68{\sim}38.94%$ compared with the actual total power generation.

3-Phase Single Stage AC-DC Converter for Small Wind Turbine System (소형풍력발전을 위한 3상 단일전력단 교류-직류 컨버터)

  • Yu-Jin Moon;Beom-Su Park;Sang-Kyu Kim;Eun-Soo Kim;Deok-Jin Lim
    • The Transactions of the Korean Institute of Power Electronics
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    • v.28 no.1
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    • pp.68-75
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    • 2023
  • This paper proposes a three-phase single-stage AC-DC converter for the small wind generation system. Input power factor improvement and insulated output can be implemented with the proposed three-phase single-stage AC-DC converter under the wide power generation voltage (80-260 Vac) and frequency (10-42 Hz) in a small wind power generation (WPG) system. The proposed converter is also capable of zero-voltage switching in the primary-side switches and zero-current switching in the secondary-side diodes by phase-shift control at a fixed switching frequency. In addition, it is possible to control a wide output voltage (Vo: 39 VDC-60 VDC) by varying the link voltage and improving the input power factor (PF) and the total harmonic distortion factor (THDi). Simulation and experimental results verified the validity of the proposed converter.

Heat Generation Model of Angular Contact Ball Bearing with Oil-Air Lubrication

  • Na, Hee-Hyeong;Rhim, Yoon-Chul
    • KSTLE International Journal
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    • v.1 no.1
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    • pp.63-68
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    • 2000
  • Angular contact ball bearings are mainly used in the spindle, which requires high speed and stiffness. The heat generation is studied by experiments and simulations using a pair of angular contact ball bearings. The temperature variation of inner and outer races and the temperature increment distribution are measured by using thermocouples for the rotational speed, preload, viscosity of lubricant. The measured values from experiments are used to estimate the heat conduction rate. The method of oil-air lubrication is used for the experiment. The amount of conduction heat transfer to the test spindle and the convection heat transfer coefficients long the spindle are computed by using inverse method with temperature increment distribution. Total heat generation rate is estimated with the heat partition rate which is calculated from temperatures of inner and outer races. In addition, the empirical factor of oil-air lubrication method for Palmgren's heat generation model is suggested. The empirical friction coefficients, which are obtained from the experiments, depend on the preload condition, and can give us more accurate estimation of the heat generation in ball bearings.

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Characteristic Mass Function of First Generation of Stars Investigated by Extremely Metal-Poor ([Fe/H] < -3.0) Stars

  • Cheon, Sehwan;Lee, Young Sun
    • The Bulletin of The Korean Astronomical Society
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    • v.44 no.1
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    • pp.68.3-68.3
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    • 2019
  • Even though the initial mass function (IMF) of the first generation of stars played important roles in reionization of the universe, subsequent star formation, and chemical enrichment of the universe, it is still very uncertain. In this study, among the several indirect ways of estimating the IMF of the population III (Pop III) stars, we make use of extremely metal-poor (EMP; [Fe/H] < -3.0) stars in the Milky Way, in order to infer the characteristic mass range of Pop III stars. As the progenitors of many of the EMP stars are known to be Pop III stars, we attempt to construct the characteristic mass range of the progenitors (e.g., Pop III stars) of the EMP stares by comparing their observed abundance pattern of various chemical elements with chemical yields from supernova models.

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Characteristics of Ion Wind Generation According to Application of Acceleration Electrodes (가속전극의 적용에 따른 이온풍 발생 특성)

  • Kim, Chol-Gyu;Jang, Kyeong-Min;Kim, Jin-Gyu
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.68 no.5
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    • pp.656-661
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    • 2019
  • Currently, the devices to generate ion winds in air are mainly composed of corona electrodes and induction(ground) electrodes, of which the corona electrodes mainly use needles or wires as electrodes and the induction electrodes use plate electrodes of ring or mesh type. Ion winds can be effectively generated through a diverse combination of corona electrodes and induction electrodes mentioned above. However, only changing the form and structure of corona electrodes and induction electrodes has a limit in raising the speed of ion winds. This paper conducted a study on the characteristics of ion wind generation by additionally installing acceleration electrodes in addition to corona electrodes and induction electrodes to increase the speed of ion winds.

Calculating the Benefit of Distributed Combined Heat Power Generators from Avoiding a Transmission Expansion Cost by Solving a Mixed Integer Linear Programming (혼합 정수 선형 계획법 기반의 최적 경제 급전을 활용한 분산형 열병합 발전원의 송전선로 건설비용 회피 편익계산)

  • Kwon, Wook Hyun;Park, Yong-Gi;Roh, Jae Hyung;Park, Jong-Bae;Lee, Duehee
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.68 no.4
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    • pp.513-522
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    • 2019
  • We calculate the benefit of distributed combined heat power generators from avoiding a transmission expansion cost by building distributed generators near electricity demand centers. We determine a transmission expansion plan by solving a mixed integer linear problem, where we modify capacities of existing transmission lines and build new transmission lines. We calculate the benefit by comparing the sum of generation and transmission expansion costs with or without distributed generators through two simulation frames. In the first frame, for the current demand, we substitute existing distributed generators for non-distributed generators and measure an additional cost to balance the generation and demand. In the second frame, for increased future demand, we compare the cost to invest only in distributed generators to the cost to invest only in non-distributed generators. As a result, we show that the distributed generators have at least 5.8 won/kWh of the benefit from avoiding the transmission expansion cost.