• Journal of Astronomy and Space Sciences
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• v.36 no.2
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• pp.87-96
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• 2019

We investigate solar and lunar motions in the Seonmyeong (SM) calendar that was compiled by Xu, Ang of the Tang dynasty (A.D. 618-907) in China and used for 71 years from 822 to 892. This calendar was also used in Korea during the Goryeo dynasty (A.D. 918-1392) and in Japan for 823 years from 862 to 1684, the longest time among the three countries. Referring to historical documents of China, Korea, and Japan, we analyze the calendrical methods of calculating the daily apparent movements of the Sun and Moon in the SM calendar, which were considered their unequal motions, and compare the movements with the results of modern calculations for three periods in the Goryeo dynasty: 919, 1155, and 1392 years (i.e., the beginning, middle, and ending of the dynasty, respectively). We find that a quadratic equation was employed to obtain the daily movement of the Sun using physical quantities on the instant of each solar term, which was tabulated in its calendar book such as the Goryeosa (History of the Goryeo Dynasty). For quantitative analysis, we compute the mean absolute difference (MAD) of the daily apparent movement between the SM calendar and modern calculations and obtain 0.33, 0.30, and 0.31 arcmin for the periods of 919, 1155, and 1392 years, respectively. Meanwhile, we find relatively large MAD values in the daily movement of the Moon: 0.217, 0.284, and 0.240 degrees for each corresponding year. An interesting point is that the MAD value in the lunar motion shows the maximum in 1155 years, and is the minimum in the solar motion. In conclusion, we believe that this study will facilitate in the understanding of the SM calendar further, particularly in the calendrical methods of calculating sunrise, sunset, and eclipse times.

• Journal of Astronomy and Space Sciences
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• v.29 no.4
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• pp.329-336
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• 2012

Korea Astronomy and Space Science Institute researchers have installed and operated magnetometers at Bohyunsan Observatory to measure the Earth's magnetic field variations in South Korea. In 2007, we installed a fluxgate magnetometer (RFP-523C) to measure H, D, and Z components of the geomagnetic field. In addition, in 2009, we installed a Overhauser proton sensor to measure the absolute total magnetic field F and a three-axis magneto-impedance sensor for spectrum analysis. Currently three types of magnetometer data have been accumulated. In this paper, we use the H, D, Z components of fluxgate magnetometer data to investigate the characteristics of mid-latitude geomagnetic field variation. To remove the temporary changes in Earth's geomagnetic filed by space weather, we use the international quiet days' data only. In other words, we performed a superposed epoch analysis using five days per each month during 2008-2011. We find that daily variations of H, D, and Z shows similar tendency compared to previous results using all days. That is, H, D, Z all three components' quiet intervals terminate near the sunrise and shows maximum 2-3 hours after the culmination and the quiet interval start from near the sunset. Seasonal variations show similar dependences to the Sun. As it becomes hot season, the geomagnetic field variation's amplitude becomes large and the quiet interval becomes shortened. It is well-known that these variations are effects of Sq current system in the Earth's atmosphere. We confirm that the typical mid-latitude geomagnetic field variations due to the Sq current system by excluding all possible association with the space weather.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.53 no.4
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• pp.386-395
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• 2017

For scientific research, a number of acoustic surveys using commercial echosounders equipped in fishing vessels were conducted throughout the world; however, few studies were performed in South Korea. Hence, this research is an preliminary study for presenting the application of a sounder from a fishing vessel. The fishing operations using a pair trawler (7 Cheonghae) was conducted in the Northwest-Western sea of Jeju Island from 20 to 23 April, 2016. Substantial impulse noises and attenuated signals were eliminated by the latest algorithms. Acoustic signals were grouped into the fish aggregations and long layer-like signals. The fish aggregations appeared between 30 and 60 m, and long layer-like signals showed the diurnal vertical migration. Energetic, morphological and positional properties of the fish aggregations and layer-like signals were described. The fish aggregations appeared mainly between sunrise and sunset; however layer-like signals tended to be presented regardless of time in consideration of the time series analysis. On the basis of the consignment sales, Scomberomorus niphonius, the target species of F/V 7 Cheonghae, was the highest catch with 4,280 kg (74.6%) and might have appeared in fish aggregations and layer forms.

• Journal of Korean Medical classics
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• v.9
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• pp.654-699
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• 1996

By studying Hwang Jae Nae Kyung(黃帝內經)'s O Haeng Kui Ryoo(五行歸類) in view of Chinese-Ancient-Thought like Chun In Hap Il Lon(天人合一論). Um Yang O Hang Lon(陰陽五行論). The theory of the month's age the conclusion is reached as follows 1. Chun In Hap Il Lon(天人合一論) means naturally men and nature consist of one energy to counteract each other and then developed to be concidered that the change of men and nature is same one;that is the basic thought of Hwang Jae Nae Kyung(黃帝內經) 2. Um Yang(陰陽) stands originally for the bright and the dark by sunrise or sunset. Ju Yuk Gye Sa Jun(周易繫辭傳) ahs considered Um Yang(陰陽) as the energy to explain changes of nature. O Haeng(五行) meaned originally five necessary materials or stuffs for living and then Chu Yun(鄒衍) has considered the difference between five powers in the nature through the combination with thought of O Haeng(五行). Hwang Jae Nae Kyung(黃帝內經) writes in the viewpoint of Um Yang O Haeng(陰陽五行) to analyze the changes of men and nature effectively. 3. O Haeng Kui Ryoo(五行歸類) is originated from Sang Su Hong Bum(尙書洪範) and its concrete examples are found in Kwan Ja(管子) and Yu SSi Chun Chu(呂氏春秋). O Haeng Kui Ryoo(五行歸類) in Hwang Jae Nae Kyung(黃帝內經) is widly affected by Kwan Ja O Haeng(管子五行) and adopts the opinion of Kum Mun Kyung Hak(今文經學) because of the background of times and medical physiology. 4. Hwang Jae Nae Kyung(黃帝內經) thinks that O Haeng(五行) means Mok(木) is the energy of being born, Hwa(火) growing-up, Kum(金) accumulating, Su(水) concluding, To(土) devoloping. O Haeng Kui Ryoo(五行歸類) in the heaven and the earth is classified by the property of O Haeng(五行). 5. O Haeng Kui Ryoo(五行歸類) in men can be explained so rationally with the property of O Haeng(五行) and the thery of an organism studied.

• Korean Journal of Agricultural and Forest Meteorology
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• v.3 no.4
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• pp.206-214
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• 2001

Cooling rate shows the highest as about 0.7$^{\circ}C$/hr on spring season and the lowest as about 0.3$^{\circ}C$/hr on september at plain place. The correlation coefficient between net radiation and cooling rate from sunrise to sunset was 0.63$^{**}$, It became higher to 0.90$^{**}$ when the wind speed decreased lower than 0.5 m/sec, and it decreased as the wind speed increased. On a clear and calm day, cooling rates were observed as 1.4$^{\circ}C$/hr on the plain (site 1, 2, 3), 1.2$^{\circ}C$/hr on the slope (site 4, 5) and 0.6$^{\circ}C$/hr on the top of mountain (site 6). In condition of the wind speed is 1.2~2 m/sec on a clear and calm day and the temperature on the top of mountain is lower than that of slope and plain, the temperature on the slope (site 4,5) was increased unlike our expectation.ion.

• Atmosphere
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• v.29 no.5
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• pp.537-550
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• 2019

To analyze the observation environment of solar radiation stations operated by the Korea Meteorological Administration (KMA), we analyzed the skyline, Sky View Factor (SVF), and solar radiation due to the surrounding topography and artificial structures using a Digital Elevation Model (DEM), 3D camera, and solar radiation model. Solar energy shielding of 25 km around the station was analyzed using 10 m resolution DEM data and the skyline elevation and SVF were analyzed by the surrounding environment using the image captured by the 3D camera. The solar radiation model was used to assess the contribution of the environment to solar radiation. Because the skyline elevation retrieved from the DEM is different from the actual environment, it is compared with the results obtained from the 3D camera. From the skyline and SVF calculations, it was observed that some stations were shielded by the surrounding environment at sunrise and sunset. The topographic effect of 3D camera is therefore more than 20 times higher than that of DEM throughout the year for monthly accumulated solar radiation. Due to relatively low solar radiation in winter, the solar radiation shielding is large in winter. Also, for the annual accumulated solar radiation, the difference of the global solar radiation calculated using the 3D camera was 176.70 MJ (solar radiation with 7 days; suppose daily accumulated solar radiation 26 MJ) on an average and a maximum of 439.90 MJ (solar radiation with 17.5 days).

• Korean Journal of Ichthyology
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• v.31 no.1
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• pp.54-61
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• 2019

A study on the diel activities and feeding habits of Pseudobagrus brevicorpus living in the Daegacheon Stream of Nakdonggang River was conducted in September 2017. Diel activity took place during the night, just after sunset and just before sunrise. Pseudobagrus brevicorpus swam in the middle depths, and when they found prey organisms, approached and consumed them immediately. Fish were divided by age into three groups. Prey organisms whose index of relative importance in the stomach contents exceeded 1% belonged to the orders Ephemeroptera (80.8%), Diptera (8.6%), and Trichoptera (8.5%). An index of relative importance by age showed that the Ephemeroptera are very important prey organisms, and the sizes of prey organisms increase with fish growth.

• Journal of Information Management
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• v.42 no.2
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• pp.103-120
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• 2011

The astronomical data obtained by observations of celestial objects movements are useful in our daily life. These data - such as 1) sunrise and sunset data, 2) data transformation between lunar calendar and solar calendar, 3) solar eclipse and lunar eclipse data, and 4) sun's altitude and azimuth data - were used to important things in the agricultural society and ancient kingdom. In the modern society, these data have been used continuously for the legal disputes, construction of buildings and the other areas. This is a good example of pure science data using directly in our life. However there are difficulties to public service because all the data were printed as an Almanac. Using MySQL, we constructed web-based service system which makes to use them easily. This database system was made for the quick search using the calculated orbital data of celestial bodies.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.10 no.3
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• pp.16-24
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• 2011

The vehicle electronic control system is being developed as the legal and social demand for ensuring driver's safety is rising. The various Driver Assistance Systems with various sensors such as radars, camera, and lasers are in practical use because of the falling price of hardware and the high performance of sensor and processer. In the preceding study of this research, the program was developed to recognize the experiment vehicle's driving lane and the cars nearby or approaching the experiment vehicle throughout the images taken by CCD camera. In addition, the 'dangerous driving analysis program' which is Vision System basis was developed to analyze the cause and consequence of dangerous driving. However, the Vision system developed in the previous studyhad poor recognition rate of lane and vehicles at the time of passing a tunnel, sunrise, or sunset. Therefore, through mounting the brightness response algorithm to the Vision System, the present study is aimed to analyze the causes of driver's dangerous driving clearly by improving the recognition rate of lane and vehicle, regardless of when and where it is.

• Journal of the Korean Solar Energy Society
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• v.32 no.5
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• pp.41-51
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• 2012

Heliostat field is the most important subsystem in the tower type solar thermal power plant since its optical performance affects the total system efficiency most significantly while the construction cost of it is the major part of total construction cost in such a power plant. Thus a well designed heliostat field to maximize the optical efficiency as well as to minimize the land usage is very important. This work presents methodology, procedures and result of heliostat filed design for 200kW solar thermal power plant built recently in Daegu, Korea. A $2{\times}2(m)$ rectangular shaped receiver located at 43(m) high and tilted $28^{\circ}$ toward heliostat field, 450 of heliostats of which the reflective surface is formed by 4 of $1{\times}1(m)$ flat plate mirror facet, and the land area having about $140{\times}120(m)$ size are used to form the heliostat field. A procedure to deploy 450 heliostats in radial staggered nonblocking formation is developed. Also the procedures to compute the cosine effect, intercept ratio, blocking and shading ratio in the field are developed. Finally the heliostat filed is designed by finding the optimal radial distance and azimuthal spacing in radial staggered nonblocking formation such that the designed heliostat field optical efficiency could be maximized. The designed heliostat field has 77% of annual average optical efficiency, which is obtained by annually averaging the optical efficiencies computed between the time of where sun elevation angle becomes $10^{\circ}$ after sunrise and the time of where sun elevation angle becomes $10^{\circ}$ before sunset in each day.