• Title/Summary/Keyword: wind power system

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High-Performance Time-Code Diversity Scheme for Shore-to-Sea Maritime Visible-Light Communication

  • Kim, Hyeongji;Sewaiwar, Atul;Chung, Yeon-Ho
    • Journal of the Optical Society of Korea
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    • v.19 no.5
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    • pp.514-520
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    • 2015
  • This paper presents a novel shore-to-sea maritime data transmission system based on time-code diversity, using visible light in maritime environments to overcome the limitations of conventional maritime wireless communications. The proposed system is primarily comprised of existing LED-based lighthouses and maritime transceivers (marine beacons, buoys, etc.), and thus is considered cost-effective in terms of implementation. We first analyze maritime visible-light communications on the basis of the unique properties of a maritime environment, i.e. sea states (wave height, wind speed, etc.), plus atmospheric turbulence, using the Pierson-Moskowitz (PM) and JONSWAP (JS) spectrum models. It is found that the JS model outperforms the PM model, and that the coverage distance depends on the LED power and sea states. To combat maritime fading conditions that significantly degrade performance and coverage distance, we propose a time-code diversity (TCD) scheme in which the delayed versions of the original data are retransmitted using orthogonal Walsh codes. This TCD scheme is found to be superior, in that it offers three orders of magnitude in terms of BER performance, compared to a conventional (non-TCD) transmission scheme. The proposed scheme is robust and efficient in overcoming the effect of impairments present in maritime environments with a BER of approximately 105and a data rate of 100 Kbps at a distance of 1 km.

The Effect of Urban and Climate Characteristics on Energy Resilience - Focusing on Blackout Time - (도시 및 기후특성이 에너지 회복력에 미치는 영향 - 정전발생시간을 중심으로 -)

  • Lee, DongSung;Moon, Tae-Hoon
    • Journal of Korea Planning Association
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    • v.54 no.4
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    • pp.122-130
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    • 2019
  • The purpose of this study is to analyze effect of climate and urban factors on energy resilience, and to explore policy alternatives to strengthen resilience of energy system. For this purpose, this study used extensive literature review on resilience studies and multiple regression analysis. In this study, blackout time was set as a dependent variable. And the independent variables were divided into climate and urban (robustness, countermeasure capacity) characteristics. As a result of the analysis, in terms of climate characteristics, maximum wind speed and cooling/heating degree-day have statistically significant impact on blackout time. With regard to urban characteristics, number of consumer, ratio of deteriorated housing and coast dummy variables have statistically significant impact on blackout time. And the ratio of government employees and road ratio were found to be the most influencing factors to shorten time taken to restore original level of electricity supply. Based on the study results, several policy suggestions to improve energy resilience were made such as continuous management of vulnerable areas and strengthening disaster response services. This study only considered engineering dimension of resilience. Further studies need to be approached on ecological & social-ecological dimension.

Battery Level Calculation and Failure Prediction Algorithm for ESS Optimization and Stable Operation (ESS 최적화 및 안정적인 운영을 위한 배터리 잔량 산출 및 고장 예측 알고리즘)

  • Joo, Jong-Yul;Lee, Young-Jae;Park, Kyoung-Wook;Oh, Jae-Chul
    • The Journal of the Korea institute of electronic communication sciences
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    • v.15 no.1
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    • pp.71-78
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    • 2020
  • In the case of power generation using renewable energy, power production may not be smooth due to the influence of the weather. The energy storage system (ESS) is used to increase the efficiency of solar and wind power generation. ESS has been continuously fired due to a lack of battery protection systems, operation management, and control system, or careless installation, leading to very big casualties and economic losses. ESS stability and battery protection system operation management technology is indispensable. In this paper, we present a battery level calculation algorithm and a failure prediction algorithm for ESS optimization and stable operation. The proposed algorithm calculates the correct battery level by accumulating the current amount in real-time when the battery is charged and discharged, and calculates the battery failure by using the voltage imbalance between battery cells. The proposed algorithms can predict the exact battery level and failure required to operate the ESS optimally. Therefore, accurate status information on ESS battery can be measured and reliably monitored to prevent large accidents.

Position and Attitude Control System Design of Magnetic Suspension and Balance System for Wind Tunnel Test using Iterative Feedback Tuning and L1 Adaptive Control Scheme (IFT와 L1 적응제어기법을 이용한 풍동실험용 자기부상 비접촉식 밸런스의 제어시스템 설계)

  • Lee, Dong-Kyu
    • Journal of Aerospace System Engineering
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    • v.11 no.5
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    • pp.28-35
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    • 2017
  • Magnetic Suspension and Balance System (MSBS) demonstrates the capacity to levitate an experimental model absent any mechanical contact using magnetic forces and moments. It allows precise control of position and attitude of the model, and measures external forces and moments acting on the model. For the purpose of acquisition of reliable experimental results under stable and safe conditions, the performance and robustness of the position and attitude control system of MSBS needs to be improved. To this end, Iterative Feedback Tuning (IFT) and L1 adaptive output feedback algorithm were employed to automatically increase command following performance and to ensure robust operation of MSBS with failure of electric power supply. The applicability was validated using computational simulation.

Characteristics of regional scale atmospheric dispersion around Ki-Jang research reactor using the Lagrangian Gaussian puff dispersion model

  • Choi, Geun-Sik;Lim, Jong-Myoung;Lim, Kyo-Sun Sunny;Kim, Ki-Hyun;Lee, Jin-Hong
    • Nuclear Engineering and Technology
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    • v.50 no.1
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    • pp.68-79
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    • 2018
  • The Ki-Jang research reactor (KJRR), a new research reactor in Korea, is being planned to fulfill multiple purposes. In this study, as an assessment of the environmental radiological impact, we characterized the atmospheric dispersion and deposition of radioactive materials released by an unexpected incident at KJRR using the weather research and forecasting-mesoscale model interface program-California Puff (WRF-MMIF-CALPUFF) model system. Based on the reproduced three-dimensional gridded meteorological data obtained during a 1-year period using WRF, the overall meteorological data predicted by WRF were in agreement with the observed data, while the predicted wind speed data were slightly overestimated at all stations. Based on the CALPUFF simulation of atmospheric dispersion (χ/Q) and deposition (D/Q) factors, relatively heavier contamination in the vicinity of KJRR was observed, and the prevailing land breeze wind in the study area resulted in relatively higher concentration and deposition in the off-shore area sectors. We also compared the dispersion characteristics between the PAVAN (atmospheric dispersion of radioactive release from nuclear power plants) and CALPUFF models. Finally, the meteorological conditions and possibility of high doses of radiation for relatively higher hourly χ/Q cases were examined at specific discrete receptors.

The Kwinana Shoreline Fumigation Experiment in Western Australia, Australia

  • Yoon, I.H.;Sawford, B.L;Manins, P.C.
    • Proceedings of the Korean Environmental Sciences Society Conference
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    • 1996.04a
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    • pp.22-22
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    • 1996
  • ;The Kwinana Shoreline Fumigation Experiment(KSFE) took place in Fremantle, WA, Australia between 23 January and 8 February, 1995. All measurement systems performed to expectation. The CSIRO DAR(Division of Atmospheric Research) LIDAR measured plume sections from near the Kwinana Power Station(KPS) stacks to up to about 5 km downstream. It also measured boundary layer aerosols and the structure of the boundary layer on some occasions. Both stages A and C of KPS were used as tracers at different times. Radiosonde and double theodolite sounding systems measured temperature, humidity, air pressure and wind structure at the coast(Woodman Point) and at the inland(ALCOA residue dump) site at intervals of roughly two hours. These were supplemented by mid afternoon soundings(radiosonde and single theodolite) by Department of Environmental Protection(DEP) at Swanbourne. The Flinders aircraft measured wind, turbulence and temperature structure of the atmospheric boundary layer, concentrations of C02,03,S02andNOx in the smoke plumes and surface radiation over both land and sea. CSIRO DCET(Division of Coal and Energy Technology) vehicle successfully interceptde many smoke plumes and using a range of tracers will be able to identify the various sources much of the time. Routine data from the DEP and Kwinana Industrial Council(KIC) air quality monitoring networks were also automatically logged. Murdoch University measured surface heat flux at Hope Valldy monitoring station and also at Wattleup monitoring station for the last five days. The heart of the LIDAR system is a Neodymium-doped Yttrium-aluminumgarnet(Nd:Y AG) laser operating at a fundamental wavelength of 1064 nm, with harmonics fo 532 nm and 355 nm. A small fraction of the laser beam is scattered back to the LIDAR, collected by a telescope and detedted by a photomultiplier tube. The intensity of the signal as a function of time is a measure of the particle concentration as a function of distance along the line of the laser shot. The results of nine days special field observations are summarized in detail.etail.

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Operational modal analysis of Canton Tower by a fast frequency domain Bayesian method

  • Zhang, Feng-Liang;Ni, Yi-Qing;Ni, Yan-Chun;Wang, You-Wu
    • Smart Structures and Systems
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    • v.17 no.2
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    • pp.209-230
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    • 2016
  • The Canton Tower is a high-rise slender structure with a height of 610 m. A structural health monitoring system has been instrumented on the structure, by which data is continuously monitored. This paper presents an investigation on the identified modal properties of the Canton Tower using ambient vibration data collected during a whole day (24 hours). A recently developed Fast Bayesian FFT method is utilized for operational modal analysis on the basis of the measured acceleration data. The approach views modal identification as an inference problem where probability is used as a measure for the relative plausibility of outcomes given a model of the structure and measured data. Focusing on the first several modes, the modal properties of this supertall slender structure are identified on non-overlapping time windows during the whole day under normal wind speed. With the identified modal parameters and the associated posterior uncertainty, the distribution of the modal parameters in the future is predicted and assessed. By defining the modal root-mean-square value in terms of the power spectral density of modal force identified, the identified natural frequencies and damping ratios versus the vibration amplitude are investigated with the associated posterior uncertainty considered. Meanwhile, the correlations between modal parameters and temperature, modal parameters and wind speed are studied. For comparison purpose, the frequency domain decomposition (FDD) method is also utilized to identify the modal parameters. The identified results obtained by the Bayesian method, the FDD method and a finite element model are compared and discussed.

A Study on Solar Panel Installation Angles for Stratospheric Platform Airship Power Systems (성층권 비행선 전원공급용 태양전지의 부착각도에 관한 연구)

  • Kim, Hyoung-Jin;Lee, Chang-Ho;Yang, Soo-Seok
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.30 no.8
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    • pp.148-155
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    • 2002
  • A study on the installation angle of solar panels is conducted as a conceptual study on solar-RFC(regenerative fuel cell) system for stratospheric airships. The airship heads for the west in winter days and the east in summer days according to wind directions. Considering this, it is found that when the solar panel is installed with the center angle of 30 degree the energy output of solar panels is maximized on winter solstice and satisfies the required energy of summer days as well. Although with the optimized solar panel installation angle, efficiency of the regenerative power system needs be improved to 47% to provide required energy of a 170m-long airship. And the required amount of efficiency improvement decreases as the airship size increases.

A Study on the Limit of Anchor Dragging for Ship at Anchor( I ) (묘박 중인 선박의 주묘 한계에 관한 연구( I ))

  • Lee, Yun-Sok;Jung, Yun-Chul;Kim, Se-Won;Yun, Jong-Hwui;Bae, Suk-Han;Nguyen, Phung-Hung
    • Proceedings of the Korean Institute of Navigation and Port Research Conference
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    • v.29 no.1
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    • pp.165-171
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    • 2005
  • When typhoon approaches, ship normally drops her anchor at proper anchorage for sheltering. If an anchoring ship is under the influence of typhoon, she can keep her position when the external force and counter force is balanced. Where, external force is induced by wind, wave and tidal currents while counter force is induced by holding power of anchor/chain and thrust force of main engine. In this study, authors presented a method to analyze theoretically the limit of external force for the ship to keep her position without being dragged and, to check the validity of method, applied this to the ship which had been anchored in Jinhae Bay when the typhoon MAEMI passed on September 2003.

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Operating Characteristics of Protection Coordination Devices in Distribution System interconnected with Distributed Generation (분산전원이 연계된 배전계통에서 보호협조기기의 운용특성에 관한 연구)

  • Kim, So-Hee;Ji, Seong-Ho;Kim, Sun-Young;Rho, Dae-Seok
    • Journal of the Korea Convergence Society
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    • v.2 no.2
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    • pp.35-45
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    • 2011
  • Recently, with the increasement of the interest about global warming, pollutions, and so on, a number of distributed generations(DGs) such as photovoltaic(PV) and wind power(WP), are interconnected with distribution systems. However, installing of DGs makes power flow changes such as directions, one-direction to bi-direction, and increasing/decreasing of fault current. Therefore, it may cause the critical problems. This paper proposes an evaluation algorithm for bi-directional protection coordination and presents an evaluation system for protection coordination based on this algorithm. Additionally, the result shows that the existing method may cause critical problems, and also the effectiveness of proposed method is verified.