• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.1-7
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• 2011

Characteristics of latitude variations of sunspots in the northern and southern hemispheres are investigated using the daily sunspot area and its latitude during the period from 1874 to 2009. Solar magnetic activity is portrayed in the form of sunspot, regions of concentrated fresh magnetic fields observed on the surface of the Sun. By defining center-of-latitude (COL) as an area-weighted latitude, we find that COL is not monotonically decreasing as commonly assumed. In fact, small humps (or short plateaus) between solar minima can be seen around every solar maxima. We also find that when the northern (southern) hemisphere is magnetically dominant, COL is positive (negative), except the solar cycle 23, which may give a hint that these two phenomena are consistently regulated by one single mechanism. As a result of periodicity analysis, we find that several significant periodicities, such as, of ~5.5, ~11, ~49, and ~167 years.

• 천문학논총
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• 제14권2호
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• pp.83-89
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• 1999

The Earth is exposed to constant outflow of the solar wind from the outer layers of the Sun, and violent transient events taking place from active regions increase the energy flux of both radiation and particles leaving the Sun. Thus the space surrounding the Earth is a highly dynamic environment that responds sensitively to changes in radiation, particles and magnetic field arriving from the Sun. Nowadays, it becomes increasingly important to understand how the physical system of Earth-space works and how the space around the Earth connects to interplanetary space. In the present paper we describe how explosive solar events, such as CME(Coronal Mass Ejection) and flares affect the Earth-space environment and how the space weather reacts to them. Practical consequences are presented to demonstrate why a broader view of Earth's environment is greatly needed to cope with modern day's inhabitation problem in a rapidly developing space age.

• 천문학회보
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• 제39권1호
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• pp.69.2-69.2
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• 2014

To estimate free magnetic energy stored in an active region is a key to the quantitative prediction of activity observed on the Sun. This energy is defined as an excess over the potential energy that is the lowest energy taken by a magnetic structure formed in the solar atmosphere including the solar corona. It is, however still difficult to derive the configuration of a coronal magnetic field only by observations, so we have to use some observable quantity to estimate free magnetic energy. Recently, by performing a coordinated series of three-dimensional magnetohydrodynamic simulations of an emerging flux tube that transfers intense magnetic flux to the solar atmosphere we have found an universal power-law relation between free magnetic energy and emerged magnetic flux, the latter of which is a possibly observed quantity. We further investigate what causes this relation through a comparison with a model of linear force-free field.

• 한국식품영양과학회지
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• 제39권8호
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• pp.1137-1142
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• 2010

함초발효액의 기능성 해명과 유용 기능성 성분 탐색연구의 일환으로 함초발효액으로부터 항산화 활성물질을 분리하여 구조해석 하였다. 함초발효액을 용매분획 하여 얻어진 용매분획물들 중 $CHCl_3$층이 높은 항산화 활성을 나타냈다. 그래서 $CHCl_3$층을 Sephadex LH-20 column chromatography의 분자체 효과 및 흡착능의 특성을 각각 이용하여 정제함으로써 2종의 항산화 활성물질을 분리하였다. 단리한 이들 화합물을 대상으로 MS 및 NMR 분석을 통하여 cirsiumaldehyde(1)와 chrysoeriol(2)로 각각 동정하였다. 이 화합물들은 $ABTS^+$ 및 DPPH radical-scavenging 활성을 나타냈으며, 화합물 2는 화합물 1에 비해 더 높은 활성을 나타냈다.

• Journal of Astronomy and Space Sciences
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• 제31권4호
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• pp.325-333
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• 2014

We are motivated by both the accumulating evidence for the connection of solar variability to the chemistry of nitrogen oxide in the atmosphere and recent finding that the Galactic cosmic-ray (GCR) influx is associated with the solar north-south asymmetry. We have analyzed the measured pH in precipitation over the 109 stations distributed in the United States. We have found that data of pH in precipitation as a whole appear to be marginally anti-correlated with the solar asymmetry. That is, rain seems to become less acidic when the southern hemisphere of the Sun is more active. The acidity of rain is also found to be correlated with the atmospheric temperature, while not to be correlated with solar activity itself. We have carried on the analysis with two subsamples in which stations located in the east and in the west. We find that the pH data derived from the eastern stations which are possibly polluted by sulfur oxides and nitrogen oxides are not correlated with the solar asymmetry, but with the temperature. On the contrary, the pH data obtained from the western stations are found to be marginally anti-correlated with the solar asymmetry. In addition, the pH data obtained from the western stations are found to be correlated with the solar UV radiation. We conclude by briefly pointing out that a role of the solar asymmetry in the process of acidification of rain is to be further examined particularly when the level of pollution by sulfur oxides and nitrogen oxides is low.

• 한국표면공학회:학술대회논문집
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• 한국표면공학회 2014년도 추계학술대회 논문집
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• pp.264-265
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• 2014

This Paper reports the photocatalytic activity of $g-C_3N_4/NaTaO_3$ hybrid composite photocatalysts synthesized by ball-mill method. The $g-C_3N_4$ and $NaTaO_3$ were individually prepared by Solid state reaction and microwave hydrothermal process, respectively. The $g-C_3N_4/NaTaO_3$ composite showed the enhanced photocatalytic activity for degradation of rhodamine B dye (Rh. B) under simulated solar light irradiation. The results revealed that the band-gap energy absorption edge of hybrid composite samples was shifted to a longer wavelength as compared to $NaTaO_3$ and the 50 wt% $g-C_3N_4/NaTaO_3$ hybrid composite exhibited the highest percentage (99.6 %) of degradation of Rh. B and the highest reaction rate constant ($0.013min^{-1}$) in 4 h which could be attributed to the enhanced absorption of the hybrid composite photocatalyst in the UV-Vis region. Hence, these results suggest that the $g-C_3N_4/NaTaO_3$ hybrid composite exhibits enhanced photocatalytic activity for the degradation of rhodamine B under simulated solar light irradiation in comparison to the commercial $NaTaO_3$.

• Journal of Astronomy and Space Sciences
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• 제14권1호
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• pp.94-108
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• 1997

열권 상부의 온도는 일반적으로 태양 활동에 따라 변화하며, 특히 고위도 지역에서는 지자기 활동에 의해서도 크게 변화된다. 본 연구에서는 장기간에 걸쳐 관측된 열권 온도를 이용하여 태양 활동 지수 및 지자기 활동 지수와의 상관 관계를 정량적으로 분석하였다. 본 연구에서 사용된 온도 자료는 미시간 대학에서 운용하고 있는 그린랜드의 두 관측소인 Thule Air Base(76.6$^{\circ}$N, 68.4$^{\circ}$W, Λ = 86$^{\circ}$)와 Strømfjord (67.0$^{\circ}$N,50.9$^{\circ}$W, Λ - 74$^{\circ}$)에서 측정된 것으로 두 곳 모두 지리적 뿐만 아니라 지자기적으로도 고위도 지역에 위치하고 있다. 자료는 페브리-페로 간섭계를 이용하여 6300 $\AA$ 대기광을 관측한 것이며 관측기간은 Thule Air Base 관측소는 1986~1991년, Søndre Strømfjord 관측소는 1986~1994년이다. 본 연구에서 얻어진 분석 결과는 다음과 같다. (1)Thule 지역의 관측 온도와 태양 활동 지수와의 상관 관계는 3$\leq$Kp$\leq$4에서 가장 높게 나타나며 Søndre Strøfjord 지역의 상관 관계는 Kp 지수가 커질수록 증가함을 보인다. (2) 전반적인 온도는 고위도 지역인 Thule 지역에서 높지만, 태양 활동 지수 변화에 따른 온도 변화의 증가율은 Søndre Strømfjord 지역에서 더 크게 나타났다. (3) 겨울철 Thule 지역의 하루 온도 변화는 13-14 LT(LT=UT-4) 부근에 최대 온도를 가진 일일 주기(24hrs) 변화를 보이지만, 태양 활동이 미약한 경우에는 반일 주기 (12 hrs) 변화가 우세하게 나타났다. (4) 고층 대기분야에서 통용되는 MSIS86 모델과 VSH 모델은 여기서 분석된 관측치에 비해 전반적으로 낮은 온도를 예측하고 있으며, 이러한 차이는 특히 태양 활동이 증가함에 따라 더욱 심해짐을 보였다. 따라서 보다 많은 관측 자료를 이용한 새로운 열권 모델의 개발이 시급하다고 생각된다.

• Safety and Health at Work
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• 제8권3호
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• pp.237-245
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• 2017

Background: Solar furnaces are used worldwide to conduct experiments to demonstrate the feasibility of solar-chemical processes with the aid of concentrated sunlight, or to qualify high temperature-resistant components. In recent years, high-flux solar simulators (HFSSs) based on short-arc xenon lamps are more frequently used. The emitted spectrum is very similar to natural sunlight but with dangerous portions of ultraviolet light as well. Due to special benefits of solar simulators the increase of construction activity for HFSS can be observed worldwide. Hence, it is quite important to protect employees against serious injuries caused by ultraviolet radiation (UVR) in a range of 100 nm to 400 nm. Methods: The UV measurements were made at the German Aerospace Center (DLR), Cologne and Paul-Scherrer-Institute (PSI), Switzerland, during normal operations of the HFSS, with a high-precision UV-A/B radiometer using different experiment setups at different power levels. Thus, the measurement results represent UV emissions which are typical when operating a HFSS. Therefore, the biological effects on people exposed to UVR was investigated systematically to identify the existing hazard potential. Results: It should be noted that the permissible workplace exposure limits for UV emissions significantly exceeded after a few seconds. One critical value was strongly exceeded by a factor of 770. Conclusion: The prevention of emissions must first and foremost be carried out by structural measures. Furthermore, unambiguous protocols have to be defined and compliance must be monitored. For short-term activities in the hazard area, measures for the protection of eyes and skin must be taken.

• Preventive Nutrition and Food Science
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• 제22권2호
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• pp.149-155
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• 2017

The effects of Korean solar salt on an azoxymethane (AOM)/dextran sodium sulfate (DSS)-induced colon cancer C57BL/6 mouse model were studied. Korean solar salt samples (SS-S, solar salt from S salt field; SS-Yb, solar salt from Yb salt field), nine-time-baked bamboo salt (BS-9x, made from SS-Yb), purified salt (PS), and SS-G (solar salt from $Gu\acute{e}rande$, France) were orally administered at a concentration of 1% during AOM/DSS colon cancer induction, and compared for their protective effects during colon carcinogenesis in C57BL/6 mice. SS-S and SS-Yb suppressed colon length shortening and tumor counts in mouse colons. Histological evaluation by hematoxylin and eosin staining also revealed suppression of tumorigenesis by SS-S. Conversely, PS and SS-G did not show a similar suppressive efficacy as Korean solar salt. SS-S and SS-Yb promoted colon mRNA expression of an apoptosis-related factor and cell-cycle-related gene and suppressed pro-inflammatory factor. SS-Yb baked into BS-9x further promoted these anti-carcinogenic efficacies. Taken together, the results indicate that Korean solar salt, especially SS-S and SS-Yb, exhibited anti-cancer activity by modulating apoptosis- and inflammation-related gene expression during colon carcinogenesis in mice, and bamboo salt baked from SS-Yb showed enhanced anti-cancer functionality.

• Journal of Astronomy and Space Sciences
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• 제24권2호
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• pp.119-124
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• 2007

The relation between substorm occurrences and HILDCAA events has been an issue. We have studied the association of particle injections with substorm onsets during HILDCAA intervals for the first half of year 2003. The examination of aurora images observed by IMAGE spacecraft and electron flux data measured by LANL satellites exhibits a close association of repetitive particle injections with substorm activity. We also find that HILDCAA events can occur equally frequently during slow speed solar wind streams as long as the interplanetary magnetic field exhibits Alfvenic wave feature.