• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2003년도 한국우주과학회보 제12권2호
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• pp.81-81
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• 2003

We report the plasma blob events that were observed from KOMPSAT-1 (2250 LT, 685-km altitude) and from DMSP F15 (2130 LT,840-km altitude) in the low-latitude ionosphere. The global distribution of blobs showed a season-longitudinal dependence similar to the distribution of the equatorial plasma bubbles, although they were observed along the ${\pm}$15 dip latitudes. The blobs drifted upward relative to the ambient plasmas, and the electron temperatures and H+ proportions were lower within the blobs compared to those in the background. These characteristics of the plasma blobs are very similar to the characteristics of the equatorial plasma bubbles. Then, we suggest that the blobs were originated from the lower altitudes by the mechanism that drives an upward drift of the plasma bubbles. The blob events did not occur in a correlated way with the magnetic activity or daily variation of the solar activity.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2008년도 한국우주과학회보 제17권2호
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• pp.24.3-24.3
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• 2008

The signals transmitted from satellites of Global Navigation Satellite System (GNSS) interact with the plasma of the ionosphere. To study the impact of the ionospheric plasma on GNSS applications a comprehensive knowledge of the ionosphere is required. Especially the correct measurement of the ionosphere such as the peak height of the F2 layer peak electron density (hmF2) is important for the GNSS ionospheric model. Anyang ionosonde station ($37.39^{\circ}N$, $126.95^{\circ}E$) has been operating from October 2000 and the accumulated data for 8 years may allow us to obtain climatological characteristics of middle latitude ionospheric F region for GNSS application. We analyzed the variations of the hmF2 and NmF2 over Anyang station for different conditions of solar activity, geomagnetic activity, season, and local time, and we compared our results with the IRI model.

• Journal of Astronomy and Space Sciences
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• 제16권1호
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• pp.53-60
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• 1999

태양에 의한 위성전파교란으로 인해 통신이 두절되는 태양간섭 현상(Sun Transit Outage)을 예측해 보았다. 지금까지의 연구는 주로 정지위성의 경우에 국한되었고, 태양모델도 흑점 극소기때의 태양을 가정한 경우가 대부분이었다. 본 연구에서는 정지위성의 경우뿐 아니라 최근에 그 수요가 급증하고 있는 비 정지위성의 경우에도 그 발생가능성을 예측해 보았다. 특히 11년 주기의 태양표면에서의 활동 변화를 고려하여 태양 간섭현상을 보다 정확히 예측해 보았으며 그 영향을 하향링크의 주파수에 따라 알아보았다. 또한 연구 결과를 실제 운용되고 있는 무궁화위성 시스템에 적용시켜보았다.

• Journal of Plant Biology
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• 제34권3호
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• pp.215-221
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• 1991

Photoxynthetic properties of polyvinylalcohol (PVA)-immobilized chloroplast especially regarded to stability of photosynthetic electron transport and the fluorescence induction pattern were studied. When isolated spinach chloroplasts were immobilized with PVA, it showed good preservation of photosynthetic electron transport activity, especially PS II activity, during storage at -15$^{\circ}C$, 4$^{\circ}C$ and 2$0^{\circ}C$. And immobilized chloroplasts revealed similar thermostability of whole chain electron transport to free chloroplsts. And the absorption peak of red band of chloroplasts showed the blue-shift of 2-4 nm after immobilization. Fv/Fm ratio of chlorophyll fluorescence slightly decreased after immobilization. White light pulse after continuous light do not induced the additional fluorescence rise. This means chlorophyll fluorescence at room temperature reached to Fmax under continuous light in the immobilized chloroplasts. It seems that PVA may be a good candidate for immobilization matrix for the preservation of photosynthetic function of thylakoids and for the continuous use of chloroplast membranes of higher plants for solar energy storage and conversion.

• 천문학회지
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• 제54권4호
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• pp.129-137
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• 2021

It has been established that the acoustic mode parameters of the Sun and Sun-like stars vary over activity cycles. Since the observed variations are not consistent with an activity-related origin, even Sun-like stars showing out-of-phase changes of mode frequencies and amplitudes need to be carefully studied using other observational quantities. In order to test whether the presumed relations between the global seismic parameters are a signature of the stellar activity cycle, we analyze the photometric light curve of HD 49933 for which the first direct detection of an asteroseismic signature for activity-induced variations in a Sun-like star was made, using observations by the CoRoT space telescope. We find that the amplitude of the envelope significantly anti-correlates with both the maximum frequency of the envelope and the width of the envelope unless superflare-like events completely contaminate the light curve. However, even though the photometric proxy for stellar magnetic activity appears to show relations with the global asteroseismic parameters, they are statistically insignificant. Therefore, we conclude that the global asteroseismic parameters can be utilized in cross-checking asteroseismic detections of activity-related variations in Sun-like stars, and that it is probably less secure and effective to construct a photometric magnetic activity proxy to indirectly correlate the global asteroseismic parameters. Finally, we seismically estimate the mass of HD 49933 based on our determination of the large separation of HD 49933 with evolutionary tracks computed by the MESA code and find a value of about 1.2M_☉ and a sub-solar metallicity of Z = 0.008, which agrees with the current consensus and with asteroseismic and non-asteroseismic data.

• 천문학회보
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• 제42권2호
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• pp.83.1-83.1
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• 2017

SDO/AIA와 STEREO/EUVI 두 태양 관측 위성의 193 파장에서의 실시간 영상 이미지를 이용하여 Stonyhurst Heliographic Map을 작성하고 각각의 위성 데이터 분석으로부터 얻어진 결과들을 종합적으로 재구성하여 태양 전면 및 후면의 활동 영역들을 동시에 표출하는 태양 활동성 지도 (Solar Activity Monitoring Map)를 작성하는 프로그램을 제작하였다. 태양 활동성 지도를 이용하여 태양 후면에서의 극자외선 밝기 분포를 경도에 따라 등간격으로 나눈 후 각 지역에서 얻은 극자외선량을 실시간으로 갱신하며 그래프를 작성하는 프로그램도 함께 제작하고 그로부터 태양 후면 영역의 활동성이 향후 지구에 어떠한 방식으로 영향을 미칠 것인지 사전에 예측 가능하도록 하였다. 또한 태양 후면에서 발생하는 활동 영역 (Active Region) 및 코로나홀들을 자동적으로 탐지한 후 실시간으로 변화 정도를 추적 및 기록하는 프로그램도 제작하였다. 태양 활동성 지도는 193 파장에서 뿐만 아니라 두 위성이 공유하는 세 개의 동일 혹은 유사한 파장대 (171,211,304)에서 얻어진 데이터들도 함께 이용하여 각 파장대에서 독립적으로 작성하였는데 이로 인해 각각의 에너지 영역의 특성에 해당하는 태양 활동성을 동시에 표출하는 것이 가능하게 되었다. 이러한 프로그램을 이용하여 태양 후면에서의 활동 영역의 발생 및 변화를 사전에 인식하고 그들이 태양 전면으로 나타나기 전에 대비할 수 있는 예보 장치가 마련되었다. 본 연구들과 더불어 극자외선 영역에서의 태양 활동성 조사로부터 플레어의 발생을 예측할 수 있을 것인지의 가능성 여부를 타진하기 위해 과거 극자외선 관측에서 얻어진 활동 영역들의 데이터와 연 X-선 관측으로부터 기록된 플레어 발생 여부의 상관관계를 조사하는 연구가 현재 진행 중이다. 이러한 연구로부터 긍정적인 결과가 도출되는 경우 극자외선 영역에서의 관측 데이터를 이용하여 플레어 발생 가능성을 예측하는 새로운 방법을 제시하는 것이 가능해질 것이다.

• Rapid Communication in Photoscience
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• 제2권2호
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• pp.42-45
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• 2013

Natural photosynthesis utilizes solar energy to convert carbon dioxide and water to energy-rich carbohydrates. Substantial use of sunlight to meet world energy demands requires energy storage in useful fuels via chemical bonds because sunlight is intermittent. Artificial photosynthesis research focuses the fundamental natural process to design solar energy conversion systems. Nicotinamide adenine dinucleotide ($NAD^+$) and $NADP^+$ are ubiquitous as electron transporters in biological systems. Enzymatic, chemical, and electrochemical methods have been reported for NADH regeneration. As photochemical systems, visible light-driven catalytic activity of NADH regeneration was carried out using platinum nanoparticles, molecular rhodium and cobalt complexes in the presence of triethanolamine as a sacrificial electron donor. Pt nanoparticles showed photochemical NADH regeneration activity without additional visible light collector molecules, demonstrating that both photoactivating and catalytic activities exist together in Pt nanoparticles. The NADH regeneration of the Pt nanoparticle system was not interfered with the reduction of $O_2$. Molecular cobalt complexes containing dimethylglyoxime ligands also transfer their hydrides to $NAD^+$ with photoactivation of eosin Y in the presence of TEOA. In this photocatalytic reaction, the $NAD^+$ reduction process competed with a proton reduction.

• 한국태양에너지학회 논문집
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• 제34권5호
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• pp.73-80
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• 2014

This study introduces and analyzes the geothermal energy availability in Non-active volcanic region. Jeju island in Korea is situated in non-active volcanic region. The island is composed of rock with high pore and clinker, scoria geological layer formed by volcanic activity about two million ago. Volcanic geological layers with porous characteristics have air, vapor, water and a underground structure through which air or water can move easily. For this reason, it is probable that the mechanism of energy acquisition is by convective heat transfer. For this presumption, the availability of underground air as energy source has been studied here through theoretical analysis and experimental data. The energy output of our system ranged from 2,485,076 kJ/day to 4,060,978 kJ/day monitored using variable velocity air flow controller. Our system has capability to be a reliable energy source irrespective of environmental changes. Consequently, underground air can be utilized for energy source and provide the optimal design of heating/cooling system.

• 천문학회보
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• 제41권1호
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• pp.54.2-54.2
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• 2016

Korea Microlensing Telescope Network (KMTNet) is the first optical survey system of its kind in a way that three KMTNet observatories are longitudinally well-separated, and thus have the benefit of 24-hour continuous monitoring of the southern sky. The wide-field and round-the-clock operation capabilities of this network facility are ideal for survey and the physical characterization of small Solar System bodies. We obtain their orbits, absolute magnitudes (H), three dimensional shape models, spin periods and spin states, activity levels based on the time-series broadband photometry. Their approximate surface mineralogy is also identified using colors and band slopes. The automated observation scheduler, the data pipeline, the dedicated computing facility, related research activity and the team members are collectively called 'DEEP-South' (DEep Ecliptic Patrol of Southern sky). DEEP-South observation is being made during the off-season for exoplanet search, yet part of the telescope time is shared in the period between when the Galactic bulge rises early in the morning and sets early in the evening. We present here the observation mode, strategy, software, test runs, early results, and the future plan of DEEP-South.

• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2010년도 한국우주과학회보 제19권1호
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• pp.30.3-31
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• 2010

We performed a comprehensive comparison between GPS Global Ionosphere Map (GIM) and TOPEX/Jason (T-J) TEC data for the periods of 1998~2009 in order to assess the performance of GIM over the global ocean where the GPS ground stations are very sparse. Using the GIM model constructed by CODE at University of Bern, the GIM TEC values were obtained along the T-J satellite orbit at the locations and times of the measurements and then binned into various geophysical conditions for direct comparison with the T-J TECs. On the whole, the GIM model was able to reproduce the spatial and temporal variations of the global ionosphere as well as the seasonal variations. However, the GIM model was not accurate enough to represent the well-known ionospheric structures such as the equatorial anomaly, the Weddell Sea Anomaly, and the longitudinal wave structure. Furthermore, there seems to be a fundamental limitation of the model showing the unexpected negative differences (i.e., GPS < T-J) in the northern high latitude and the southern middle and high latitude regions. The positive relative differences (i.e., GIM > T-J) at night represent the plasmaspheric contribution to GPS TEC, which is maximized, reaching up to 100% of the corresponding T-J TEC values in the early morning sector. In particular, the relative differences decreased with increasing solar activity and this may indicate that the plasmaspheric contribution to the maintenance of the nighttime ionosphere does not increase with solar activity, which is different from what we normally anticipate. Among these results, the plasmaspheric contribution to the ionospheric GPS TEC will be presented in this talk and the rest of it will presented in the companion paper (poster presentation).