• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1833-1839
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• 2011

In this study, Global Gravitational Model EGM2008, EGM96 and 16,786 gravity points measured on land were compared and analyzed. On the assumption that land gravity data is most accurate, the correlation coefficient, differences, MSE and difference variance along the height were computed between land gravity data and EGM2008, EG96. The correlation coefficient, land gravity data and EGM2008, was computed most largely with 0.824 and the correlation coefficient with EGM96 was computed with 0.538. The standard deviation of differences between land gravity and EGM2008, EGM96 were 13.196 magl, 18.685 mgal respectively. Also the difference variance scope of EGM2008 was smaller than EGM96. There was no large variance of free-air anomaly differences between land gravity data and EGM2008 along the height however free-air anomaly differences with EGM96 varied along the height changes. Consequently EGM2008 nicely expresses Korea gravity field more than EGM96.

• Journal of Astronomy and Space Sciences
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• v.23 no.2
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• pp.127-134
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• 2006

Variation of the Local Time of Ascending Node (LTAN) has been analysed according to initial inclinations when the altitude of Sun-synchronous satellite is continuously decreased due to the atmospheric drag. Orbit predictions of 3 years have been performed with the satellite of 500 km altitude when the initial LTAN were set to 06:00, 09:00, 12:00, 15:00, and 18:00. Different profiles of the inclination and LTAN have been obtained according to the satellite altitude decay and initial LTAN value. Using the profiles of the inclination and LTAN, initial orbital elements can be derived for minimizing the LTAN variations during the mission life time of the sun-synchronous satellite without any on-board thrusters for orbit maneuvers.

• Korean Journal of Environmental Biology
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• v.38 no.4
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• pp.594-602
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• 2020

This study investigated the effect of geography and altitude on epigeic spider communities in rice field levees in Jeollabuk-do. Spider communities in the mountainous and plain areas were compared to determine the effect of geography on the cultivation periods. The effect of altitude was compared between the Jeongeup and Jangsu areas during non-cultivation periods. Analysis using nMDS (non-metric multidimensional scaling), MRPP (multiple response permutation procedure), and ANOSIM (analysis of similarity) revealed differences in spider community structures between the two types of study areas. Lycosidae predominated at the family level, and its abundance was greater in the mountainous area than in the plains area. The total abundance did not differ between the two areas with different altitudes, but the abundance of three Pardosa species was greater at lower altitudes than at higher altitudes. Geography and altitude had a minimal effect on species richness and diversity indices at the community level. However, several Lycosidae species showed species-specific responses to both geography and altitude in the rice fields.

• 한국신재생에너지학회:학술대회논문집
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• 2008.05a
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• pp.564-567
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• 2008

산소분압은 연료전지의 성능을 좌우하는 주요한 인자이다. 실생활에서 공기 중 산소농도는 21%이지만 차량이 많은 도심지역에서는 약 20%, 환기시설이 낙후한 지하주차장은 약 18%까지 산소농도가 감소한다. 높은 고도에서 산소농도는21%이지만 산소분압이 낮아져 연료전지자동차의 효율이 감소하는 영향이 발생될 수 있다. 농도에 따른 연료전지의 성능곡선 결과를 empirical equation에 적용하여 연료전지 자동차의 운전환경에 속하는 산소농도 18$\sim$23% 범위와 고도 0$\sim$4,000 m 범위에서 연료전지의 성능변화를 분석하였다. 공기공급량(SR)이 2일 경우 산소농도에 따른 성능변화를 비교한 결과 산소농도 18%인 성능은 산소농도 21%에 비하여 10%이상 감소하였으며 산소농도 21%를 기준으로 공기공급량이 2인 유량으로 공급할 때 산소농도가 18%까지 낮아질 경우 산소농도 21%에 비하여 22%이상 성능이 감소하는 결과가 나타났다. 고도가 4,000 m인 경우 산소분압은 약 13 kPa까지 낮아지고 이로 인하여 연료전지 성능은 약 25%까지 감소하는 것으로 나타났다.

• Korean Journal of Remote Sensing
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• v.18 no.2
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• pp.91-96
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• 2002

The performance characteristics of a satellite imager using a Time Delay and Integration(TDI) Charge Coupled Device (CCD) with fixed integration time is investigated for the variation of satellite altitude and tilt angle. In consequence of the investigation TDI synchronization using tilt imaging is proposed as a solution to compensate geometric performance degradation due to altitude decrease. The tilt angle optimized for the TDI synchronization at decreased altitude is presented. This result can be used for a TDI CCD imager with variable integration time in a certain range as well.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.22 no.2
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• pp.102-108
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• 1989

The effects of n 3 polyunsaturated fatty acid (PUFA) on protein and phospholipid con-tents, and cholesterol level were studied in rats fed with diets of different fat composition. Body weights of fish oil groups were decreased to $11.1\%\~14.4\%$ compared with lard group (control), and also $16.4\%\~23.3\%$ compared with corn oil group, respectively. Protein contents of $\omega3$ PUFA and sardine oil groups in liver were increased to $6.78\%\~8.51\%$ compared with control group, but were no significant difference in brain and serum. $\omega3$ PUFA and sardine oil slightly repressed the phospholipid in microsome of liver. Moreover they effectively reduced the serum cholesterol levels compared with control group.

• Economic and Environmental Geology
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• v.48 no.6
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• pp.451-465
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• 2015

The free-air anomalies are computed using a data set from various types of gravity measurements in the Korean Peninsula area. The gravity values extracted from the Earth Gravitational Model 2008 are used in the surrounding region. The upward continuation technique suggested by Dragomir is used in the computation of the external free-air anomalies at various altitudes. The integration radius 10 times the altitude is used in order to keep the accuracy of results and computational resources. The direct geodesic formula developed by Bowring is employed in integration. At the 1-km altitude, the free-air anomalies vary from -41.315 to 189.327 mgal with the standard deviation of 22.612 mgal. At the 3-km altitude, they vary from -36.478 to 156.209 mgal with the standard deviation of 20.641 mgal. At the 1,000-km altitude, they vary from 3.170 to 5.864 mgal with the standard deviation of 0.670 mgal. The predicted free-air anomalies at 3-km altitude are compared to the published free-air anomalies reduced from the airborne gravity measurements at the same altitude. The rms difference is 3.88 mgal. Considering the reported 2.21-mgal airborne gravity cross-over accuracy, this rms difference is not serious. Possible causes in the difference appear to be external free-air anomaly simulation errors in this work and/or the gravity reduction errors of the other. The external gravity field is predicted by adding the external free-air anomaly to the normal gravity computed using the closed form formula for the gravity above and below the surface of the ellipsoid. The predicted external gravity field in this work is expected to reasonably present the real external gravity field. This work seems to be the first structured research on the external free-air anomaly in the Korean Peninsula area, and the external gravity field can be used to improve the accuracy of the inertial navigation system.

• Korean Journal of Ecology and Environment
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• v.50 no.4
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• pp.381-402
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• 2017

In order to investigate distribution of vascular plants along elevational gradient in the Nodong valley of Gyebangsan, vascular plants of eight sections with 100-meter-high were surveyed from the Auto-camping site (800 m) to the top of a mountain (1,577 m). There were a total of 382 taxa: 89 families, 234 genera, 339 species, 7 subspecies, 34 varieties, and 2 forms. As a result of analyzing the pattern of species richness, it showed a reversed hump-shaped with minimum richness at mid-high elevation. As a result of analyzing habitat affinity types, the proportion of forest species increased with increasing elevation. But, the ruderal species decreased with increasing elevation, and then increased at the top of a mountain. As for the proportion of life forms, the annual herbs gradually decreased with increasing elevation, but it did not appear between 1,300 m and 1,500 m and then increased at the top of a mountain. The trees gradually increased with elevation and decreased from 1,300~1,400 m. The vascular plants divided into four groups by using DCA. The arrangement of each stands was arranged in order from right to left on the I axis according to the elevation. The distribution of vascular plants is determined by their own optimal ranges of vegetation. Also, rise in temperature due to climate change affects the distribution of vascular plants, composition, and diversity. Therefore, continuous monitoring is necessary to confirm ecological and environmental characteristics of vegetation, distribution ranges, changes of habitat. Furthermore, plans for conservation and management based on these data should be prepared according to climate change.

• Korean Journal of Remote Sensing
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• v.22 no.6
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• pp.519-531
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• 2006

Sea surface height (SSH) around fe Korean Peninsula was investigated as a rising rate of $3.89mm\;yr^{-1}$ on the average from 1993 to 2005, which is 1.3 times higher rising rate, compared to the world ocean. In the present study, to investigate SSH changes in regional sections of the East Sea, the Yellow Sea, the South Sea, and the Korea Strait, DT-MSLA (Delayed Time-Maps of Sea Level Anomalies) with multi-satellite data (Topex/Poseidon, Jason-1, ERS, Envisat), provided by AVISO (Archiving, Validation and Interpretation of Satellite Oceanographic data), was used. The periodicity in interannual variability was dominant for $4\sim5$ year in summer, and 3 year in winter as well as an increasing trend. The amplitude and phase for the annual and semi-annual mode in SSH and SST were investigated with harmonic analysis. The geographical distribution of amplitudes for comparison of SSH and SST are slightly reverse in southwest-northeast tilted direction. The monthly SST and SSH is highly correlated correlation coefficient about 0.7 with lag of one or two months over the East Sea and the South Sea during June-August. These results suggest that the Kuroshio stream is dominant during summer over these regions.

• KDI Journal of Economic Policy
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• v.16 no.3
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• pp.147-178
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• 1994

우리나라 경제(經濟)는 1960년대초 이후 거의 지속적(持續的)인 고도성장(高度成長)을 이룩하여 왔다. 이와 같은 고도성장(高度成長)이 가능하였던 원인(原因)으로서는 1960년대초 이후 수출주도형(輸出主導型) 공업화정책(工業化政策)의 계속적이고 성공적인 추진을 들 수 있으며, 또한 정치적(政治的), 사회(社會) 경제적(經濟的) 여건과 요인들도 고도성장(高度成長)에 기여(寄與)했을 것이다. 본고(本稿)는 인적(人的) 및 물적(物的) 부존자원조건(賦存資源條件)과 그에 따른 자원(資源)의 배분(配分) 및 생산성변화(生産性變化)등과 관련된 우리나라 경제성장요인별(經濟成長要因別) 기여도(寄與度)를 Edward F. Denison의 접근방법에 의해서 추정했으며 1963~92년간을 분석대상으로 하였다. 이 접근방법으로 추정한 1963~82년간에 대한 Kim and Park(1985) 의 측정결과를 수정발표된 국민계정자료(國民計定資料)에 의해서 1972년부터 수정하고 1992년까지 연장추정하였다. 추정결과는, 과거 우리나라의 고도성장요인(高度成長要因)이 구체적으로 무엇이었던가 하는 문제에 대한 해답과, 선진국가(先進國家)의 성장요인(成長要因)과의 비교분석을 통하여 일반적(一般的)인 경제성장과정(經濟成長過程)의 보다 확실한 이해를 위한 자료로서, 또는 우리나라의 장내(將來) 성장잠재력(成長潛在力)을 전망(展望)하는 데 유용한 자료로서 이용될 수 있을 것으로 기대한다.