• Title/Summary/Keyword: solar observation

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Study on the Grid-connected Photovoltaic Power System for Reducing Ripples of the PV Array Output (PV Array 출력리플 저감을 위한 계통연계형 태양광 인버터에 관한 연구)

  • Kim, H.J.;Chung, Y.H.;Lee, K.S.;Jon, Y.S.
    • Proceedings of the KIEE Conference
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    • 2007.07a
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    • pp.1211-1212
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    • 2007
  • In the PV power system, output of the PV array must contain inherent ripples due to the single-phase inverter. So, the function of maximum power point tracking to increase the output efficiency of PV system is degraded. Therefore, to overcome this problem, this paper presents a control strategy for the reducing ripples of the PV array output in grid-connected photovoltaic power system. The proposed control system consists of two loops; the maximum power point tracking loop using the perturbation and observation method is used to calculate the reference solar array terminal voltage(Vref) for reducing ripples of the PV array output and the PI control loop is used to regulate the solar array output voltage according to the Vref. The performance of proposing control strategy is analyzed by means of the PSCAD/EMTDC simulation and experiment. As a result, we may obtain the high performance of the proposed control strategy.

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SUNSPOT EVOLUTION IN THE VICINITY OF A LARGE SOLAR FLARE IN AR 6891

  • ALMLEAKY Y. M.;MALAWI A. A.;BASURAH H. M.
    • Journal of The Korean Astronomical Society
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    • v.29 no.spc1
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    • pp.317-319
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    • 1996
  • Utilizing a Calcium filter, a large two ribbon flare of an importance 2.5Xj31? was recorded at. King Abdul-Aziz University Solar Observatory (KAAUSO) at the 30th of October 1991. This chromosphenc flare observation, which is of special importance since it is rarely reported, was for a flare that occurred near the south west of the equator at the vicinity of a large sunspot group on an active region known as AR 6891. The observed foot points of this flare had a strange behavior in which the separating motion of the ribbons were not typical of most flares, rather were nearly orthogonal. In this article we present the characteristics of the main sunspot group of this active region and try to investigate its evolution and fragmentation with time. Information regarding magnetic fields and velocity fields are necessary to understand the restructuring of the magnetic field pattern and plasma motion, and hence the changes that could lead to the occurrence of such an interesting flare.

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2019 Total Solar Eclipse Expedition of KASI

  • Bong, Su-Chan;Yang, Heesu;Lee, Jae-Ok;Kim, Jinhyun;Jeon, Young-Beom;Jang, Bi-Ho;Seough, Jungjoon;Park, Young-Deuk
    • The Bulletin of The Korean Astronomical Society
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    • v.45 no.1
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    • pp.69.2-69.2
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    • 2020
  • Korea Astronomy and Space Science Institute (KASI) is developing a coronagraph to measure the coronal electron density, temperature, and speed utilizing spectral change of the K-corona around 400 nm. However, near UV light is more affected by atmospheric effect on the ground than visible light. For the total solar eclipse on July 2 2019, KASI organized an expedition team to test the possibility of the similar measurement scheme in the visible light. The observation site was in Las Flores, San Juan, Argentina. We built an imaging spectrograph using micro lenslet array and grism, named Coronal Integral Field Spectrograph (CorIFS). In addition, images of white light corona, wide field background, and all sky were taken with various camera settings. We present the preliminary results of the expedition.

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The Land Surface Temperature Distributions of Jeju Island using Landsat 7/ETM+ Data

  • Lee Byung-Gul
    • Journal of the Korean earth science society
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    • v.26 no.2
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    • pp.109-113
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    • 2005
  • In this study, the estimation of the temperature distribution of Jeju Island with coastal ocean derived from the thermal band of Landsat 7/ETM+ of January 6, 2003 was carried out. For the computation of the temperature of the island and the coastal ocean based on the thermal band, we used NASA method wiich is the 8 bit Digital Number(DN) converted into spectral radiance. The computed results showed that the land temperature variations were from 0 to 12 Celsius degrees, and a good agreement with the observation ones based on the method. However, the ocean surface temperature was not much changed ground 15 degree since the water was well mixed between the coastal and the offshore ocean. The interesting results were that the temperature distributions of the southern part(Seogwipo City) of Jeju Island were higher than those of the north one(Jeju City) by more than 2 Celsius degree at the same height although the distance between the Jeju and the Seogwipo is only about 35km in winter season. The reason was found that the solar irradiance intensity of the south part was stronger than the north one by Halla mountain in winter season only. From the results, we found that the seasonal variations of solar irradiation and the height of Mt. Halla were an important role of temperature distribution of Jeju Island.

Mesospheric Temperatures over Apache Point Observatory (32°N, 105°W) Derived from Sloan Digital Sky Survey Spectra

  • Kim, Gawon;Kim, Yong Ha;Lee, Young Sun
    • Journal of Astronomy and Space Sciences
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    • v.34 no.2
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    • pp.119-125
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    • 2017
  • We retrieved rotational temperatures from emission lines of the OH airglow (8-3) band in the sky spectra of the Sloan digital sky survey (SDSS) for the period 2000-2014, as part of the astronomical observation project conducted at the Apache Point observatory ($32^{\circ}N$, $105^{\circ}W$). The SDSS temperatures show a typical seasonal variation of mesospheric temperature: low in summer and high in winter. We find that the temperatures respond to solar activity by as much as $1.2K{\pm}0.8K$ per 100 solar flux units, which is consistent with other studies in mid-latitude regions. After the seasonal variation and solar response were subtracted, the SDSS temperature is fairly constant over the 15 year period, unlike cooling trends suggested by some studies. This temperature analysis using SDSS spectra is a unique contribution to the global monitoring of climate change because the SDSS project was established for astronomical purposes and is independent from climate studies. The SDSS temperatures are also compared with mesospheric temperatures measured by the microwave limb sounder (MLS) instrument on board the Aura satellite and the differences are discussed.

THE RELATIVE SUNSPOT NUMBERS FROM 1987 TO 2002 (1987-2002년 태양흑점 관측자료 분석)

  • Kim, K.S.;Cho, K.S.;Park, Y.D.;Moon, Y.J.;Kim, Y.H.;Sim, K.J.
    • Publications of The Korean Astronomical Society
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    • v.18 no.1
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    • pp.25-35
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    • 2003
  • In this paper, we have re-examined the relative sunspot numbers from June 1987 to December 2002 observed at Korea Astronomy Observatory. For this we determined conversion factors (K) for each year data to derive the relative sunspot numbers. The estimated conversion factor ranges from 0.57 to 1.09 and has a trend to decrease with time, which seem to depend on the several effects such as observational system, observation methods, and experience of an observer. Our analysis shows that the newly-determined relative sunspot numbers are in much better agreements with the international sunspot numbers than the previously-determined ones in which the conversion factors were determined only four times. This result implies that we should determine the conversion factor for each year data. From these investigations, we also identified one and half solar cycles form our relative sunspot number.

FISS and SDO Observation of a Brightening Event Near a Pore

  • Kang, Juhyeong;Chae, Jongchul
    • The Bulletin of The Korean Astronomical Society
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    • v.42 no.2
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    • pp.61.2-61.2
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    • 2017
  • We report a fine scale transient brightening event near a pore boundary with the Fast Imaging Solar Spectrograph (FISS) of the 1.6m Goode Solar Telescope (GST), the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO), and Helioseismic and Magnetic Imager (HMI) aboard SDO. The event appears in all AIA extreme ultraviolet bands, also in the two FISS lines, $H{\alpha}$ and Ca II $8542{\AA}$, and lasted for a minute. The brightening occurred at a footpoint of a loop. The conjugate brightening occurred at the other foot point outside the FISS field of view. The brightening near the pore exhibit a redshift of 4.3 km s-1 in the $H{\alpha}$ and about 2.3 km s-1 in Ca II line. Differential emission measure derived from 6 AIA EUV passbands and cloud model fitting of the two FISS lines indicate the temperature increase of between 10,000 and 20 MK at the main event. After the brightening, the upward mass motion appears in the AIA images. We discuss the physical implication of this brightening in the context of magnetic reconnection and coronal heating.

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High altitude powered lighter-than-air vehicle as remote sensing platform

  • Onda, Masahiko
    • 제어로봇시스템학회:학술대회논문집
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    • 1990.10b
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    • pp.1361-1364
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    • 1990
  • In order to tackle global environmental problems such as destruction of the ozone layer or climatic changes due to atmospheric temperature increase, the acquisition of plentiful and precise data is necessary. Therefore, a means of conducting long-lasting high-resolution measurements over broad areas is required. A feasibility study has been made on a high altitude (20km), super-pressured helium-filled PLTA (Powered Ligher-than-Air) vehicle as an ideal platform for environmental observation. It has a long service life and carries a larger payload than an artificial satellite. This PLTA platform uses an electric propulsion system to maintain position in space against wind currents. The thruster is driven by solar power acquired from solar cells. For night use, solar energy is stored in regenerative fuel cells. This study focuses on energy balance and structural analysis of the hull and platform. The platform is capable of conducting high resolution remote sensing as well as having the capability to serve as a telecommunications relay. The platform could replace a number of ground-based telecommunications relay facilities, guaranteeing sufficient radio frequency intensity to secure good quality telecommunication transmittal. The altitude at which the platform resides has the lowest wind flow in the lower stratosphere, and permits viewing from the ground within a 1,000km range. Because this altitude is much lower than that required of an artificial satellite, the measuring resolution is a couple of thousand times higher than with artificial satellites. The platform can also be used to chase typhoons and observe them from their sources in tropical regions.

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A Study of Historical Seasonal Subdivision System and Modern Definitional Issue of Meteorological Seasons (전통시대 절후법과 기후표 고찰에 따른 현대 '기상계절'과 '새로운 기후표'의 제안)

  • Kim, Il-Gwon
    • Atmosphere
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    • v.26 no.1
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    • pp.185-192
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    • 2016
  • In this paper, I studied about historical seasonal subdivision system and a theory of traditional monthly order, which was used for so long from Koryo dynasty to the late of Choseon dynasty in Korean histoy. Especially, I took note of the fact that there used the table of solar terms and meteorological observation what we called the table of Kihoo-pyo in the historical Sunmyung-calendar and the Soosi-calendar during the Koryo dynasty. This table of Kihoo was developed for explaining meteorological change during a year at that time. Here are largely four elements related meteorological nature : the first is the list of 24 solar terms, and the second is 12 monthly seasonal terms and 12 monthly central terms, the third is about four right hexagon based I-ching, the fourth is 72 meteorological observations called 72-hoo. Among them, the 72-hoo system is important to know how premodern people observed natural materials including animals and plants, weather, climate about meteorological phenomena according to the seasonal change or solar terms' change during a year. I argued in this article to need developing modern new table of Kihoo system like that, in order to show common people to recognize annual meteorological change more easy and clear. I also argued to need a distinct definition of meteorological seasons from a view point of modern meteorology.

Performance and Stability Enhancement of Organic Solar Cells by Surface Treatment Processes of Transparent Electrodes (표면 전처리 공정에 따른 투명전극 계면 특성 변화와 유기 태양전지 성능 및 안정성 향상)

  • Lee, Kwan-Yong;Kim, Do-Hyun;Park, Sun-Joo;Kim, Young-Joo
    • Transactions of the Society of Information Storage Systems
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    • v.9 no.2
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    • pp.42-47
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    • 2013
  • In this study, we have experimentally analyzed how the surface properties of transparent electrode layer influence the photovoltaic performance of bulk heterojunction organic solar cell by the contact angle measurement and X-ray photoelectron spectroscopy(XPS) observation. As a result, the power conversion efficiency of test devices improved from 0.64% to 1.83% and 2.15% by UV-ozone exposure and $O_2$ plasma treatment, respectively. Thus, we conclude that the surface activation process is very important for better performance and stability in addition to the cleaning process of carbonate residue on the surface.