• 한국우주과학회:학술대회논문집(한국우주과학회보)
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• 한국우주과학회 2009년도 한국우주과학회보 제18권2호
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• pp.26.1-26.1
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• 2009

Many solar, interplanetary and geomagnetic activity parameters have 11-year cycle on the average in sync with solar sunspot number. The galactic cosmic ray (GCR) intensity measured by ground Neutron Monitor (NM) is one of those parameters showing the unprecedented activity levels in the current solar minimum (2008-2009) of solar cycles 23/24. We defined abnormality as the ratio of deviation from long term mean over mean amplitude of solar cycle change. The abnormality distribution map was drawn using all the data of NM stations available online. The implications of those unprecedented levels of GCR intensities of different cutoff rigidities will be discussed.

• Journal of Astronomy and Space Sciences
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• 제38권1호
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• pp.23-29
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• 2021

Utilizing a new version of the sunspot number and group sunspot number dataset available since 2015, we have statistically studied the relationship between solar activity parameters describing solar cycles and the slope of the linear relationship between the monthly sunspot numbers and the monthly number of active days in percentage (AD). As an effort of evaluating possibilities in use of the number of active days to predict solar activity, it is worthwhile to revisit and extend the analysis performed earlier. In calculating the Pearson's linear correlation coefficient r, the Spearman's rank-order correlation coefficient rs, and the Kendall's τ coefficient with the rejection probability, we have calculated the slope for a given solar cycle in three different ways, namely, by counting the spotless day that occurred during the ascending phase and the descending phase of the solar cycle separately, and during the period corresponding to solar minimum ± 2 years as well. We have found that the maximum solar sunspot number of a given solar cycle and the duration of the ascending phase are hardly correlated with the slope of a linear function of the monthly sunspot numbers and AD. On the other hand, the duration of a solar cycle is found to be marginally correlated with the slope with the rejection probabilities less than a couple of percent. We have also attempted to compare the relation of the monthly sunspot numbers with AD for the even and odd solar cycles. It is inconclusive, however, that the slopes of the linear relationship between the monthly group numbers and AD are subject to the even and odd solar cycles.

• Journal of Positioning, Navigation, and Timing
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• 제5권2호
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• pp.87-96
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• 2016

The ionospheric error, which is one of many error elements considered during the Global Navigation Satellite System (GNSS) positioning, is hard to be predicted due to the influence of geomagnetic activity and irregular solar activities. Thus, the present study analyzed a change pattern in the ionosphere through Global Ionosphere Map (GIM) data for 12 years from 2003 to 2014 and a variation in the Slant Total Electron Content (STEC) between Sinuiju and Busan which was the longest range in the southeastern direction of the Korean Peninsula. The variation in the STEC verified the diurnal, annual, and solar cycle variations due to the influence of solar activity. The diurnal variation was characterized that the variation in the STEC started to increase from 6-7 am and reached the maximum at 13-14 pm followed by being decreased. The seasonal variation was characterized that the variation in the STEC was high in spring and autumn whereas it was low in summer and winter. The solar cycle variation revealed that the variation in the STEC increased during solar maximum and decreased during solar minimum. The variation in the STEC was up to 20 Total Electron Content Unit (TECU) during the solar minimum and up to 60 TECU during solar maximum.

• 설비공학논문집
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• 제1권1호
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• pp.46-54
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• 1989

The purpose of this study is to obtain the dynamic characteristics of an absorption refrigerator powered by solar energy by experiments. Since the absorption refrigerator power by solar energy should have the characteristics which is suitable for the intermittence and rarity of solar energy, not only the characteristics of the steady state operations but also the partial load and the transient operations should be considered. The minimum available temperature of the storage tank should be known, and the absorption refrigerator can be suitably selected for air-conditioning systems. In this study, the experimental data of the transient state for on-off and warming-up operations has been obtained. Also the experiments are performed which test the minimum available temperature of the storage tank. The results show that it takes 1 hour to get to the steady state of the absorption refrigerator, and the minimum available temperature of the storage tank is about $68^{\circ}C$, and show that in the partial load operations the performance of the absorption refrigerator is improved by applying the modified control method to on-off operations.

• 한국태양에너지학회 논문집
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• 제25권4호
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• pp.119-123
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• 2005

The main purpose of this study is to define an optimum slope of the roof that demands minimum cooling load of the building, when the roof is affected by the solar and wind energy. Two different roof shapes were chosen: hip, gabled. The cooling load of building having those roof shapes was calculated through the computer simulation, using DOE program. For the simulation, the angle of the roof and angle of the orientation was changed. In the conclusion of this paper, an optimum slope of the roof which causes minimize cooling load is presented according to the roof shape and orientation. The result of this study could provide a practical design guideline for determining the roof angle for various climatic conditions.

• KIEAE Journal
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• 제5권3호
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• pp.33-40
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• 2005

The existing building code regulates the minimum distance between buildings and the minimum required sunshine hours for winter solstice to ensure the right to light. Especially, the minimum sunshine hours have been guaranteed by the constitution after the right for the people to live in a healthy and comfortable environment was established. However, the existing regulation on the sunshine hours only considers the duration of sunshine hours, but ignores the minimum amount of sunlight. Therefore, the calculated sunshine hours are not coincident with the hours occupants actually feel. Therefore, the purpose of this study is to investigate the effect of solar incident angle on interior illuminance distribution, which will be used to propose a new code on the minimum sunshine hours and levels.

• Journal of Astronomy and Space Sciences
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• 제32권4호
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• pp.297-304
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• 2015

In this study, we documented the midlatitude F2-layer response to five strong geomagnetic storms with minimum Dst < -150 nT that occurred in solar minimum years using hourly values of the F2-layer critical frequency (foF2) from four ionosondes located in different hemispheres. The results were very limited, but they illustrated some peculiarities in the behavior of the F2-layer storm. During equinox, the characteristic ionospheric disturbance patterns over the Japanese station Wakkanai in the Northern Hemisphere and the Australian station Mundaring in the Southern Hemisphere were consistent with the well-known scenario by $Pr{\ddot{o}}lss$ (1993); however, during a December solstice magnetic storm, both stations did not observe any noticeable positive ionospheric disturbances. Over the "near-pole" European ionosonde, clear positive ionospheric storms were not observed during the events, but the "far-from-pole" Southern Hemisphere station Port Stanley showed prominent enhancements in F2-layer peak electron density in all magnetic storms except one. No event produced noticeable nighttime enhancements in foF2 over all four ionosondes.

• 한국환경과학회지
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• 제20권8호
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• pp.1041-1048
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• 2011

The purpose of this study was to analyze the effects on meteorological variables in Seoul, Busan and Jeju during the partial solar eclipse event of 22 July 2009 in Korea. Solar irradiance decreased 16 and 19 minutes after eclipse in Seoul and Busan, and 6 minutes before eclipse in Jeju. Minimum solar irradiance occurred 7 and 3 minutes after maximum eclipse in Seoul and Busan, respectively, and 8 minutes before maximum eclipse in Jeju. Solar irradiance began to increase after maximum eclipse in Seoul and Busan, and recovered to the original state as eclipse ended. On the other hand, recovery of solar irradiance after maximum eclipse in Jeju was slower than those of two cities. Temperature drop due to partial solar eclipse were $0.7^{\circ}C$, $4.0^{\circ}C$, $1.5^{\circ}C$ in Seoul, Busan, and Jeju, respectively, and time needed to arrive minimum temperature from maximum eclipse were each 12, 32, 30 minutes, respectively. Change of relative humidity during partial solar eclipse were 2.6%, 17.4%, 12.3% in Seoul, Busan, and Jeju, respectively. Temperature drop turned out to be sharper as altitude increases. Wind speed decreased by each about 1.1 m/s, 3.4 ms/s, 1.4 ms/s due to partial solar eclipse in Seoul, Busan, and Jeju. Soil temperature of 5 cm equally decreased by $0.2^{\circ}C$ in Seoul and Busan, soil temperature of 10 cm maintained almost constant, and soil temperature of 20 cm was hardly affected by eclipse.

• Nuclear Engineering and Technology
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• 제4권3호
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• pp.194-202
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• 1972

방사성 폐액처리에서 나오는 방사성 Sludge의 Solar energy에 의한 고화 처리방법은 가장 효과적이고 경제적인 처리방법의 하나이다. 본연구를 통해서 Sludge의 고화처리는 3月부터 8月사이가 가장 적정기이고, 또 Mass-transfer방법에 의해 증발량 추정에 대한 실험식을 유도하였다.

• 한국태양에너지학회 논문집
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• 제27권3호
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• pp.45-54
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• 2007

For a conventional natural-circulation type solar water heater, the pressure head is limited by the height between the storage tank and hot water tap. Therefore, it is difficult to provide sufficient hot water flow rate for general usage. This study deals with a design modification of the storage tank to utilize the tap-water pressure to increase hot-water supply Based on fluid dynamic and heat transfer theories, a series of modeling and simulation is conducted to achieve practical design requirements. An experimental setup is built and tested and the results are compared with theoretical simulation model. The storage tank capacity is 240 l and the outer diameter of piping was 15 mm. Number of tube turns tested are 5, 10, and 15. Starting with initial storage tank temperature of $80^{\circ}C$, the temperature variation of the supply hot water is investigated against time, while maintaining minimum flow rate of 10 1/min. Typical results show that the hot water supply of minimum $30^{\circ}C$ can be maintained for 34 min with tap-water supply pressure of 2.5 atm, The relative errors between modeling and experiments coincide well within 10% in most cases.