• Journal of the Korean Geographical Society
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• v.41 no.4 s.115
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• pp.435-456
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• 2006

This study examines the long-term spatial patterns and recent trends of seasonal onsets and durations defined by daily temperatures in South Korea for the period 1973-2004. Spatially, spring and winter onset dates show approximately 44 day and 63 day maximum difference respectively between south and north (Seongsanpo to Daegwallryeong) attributable to the impacts of latitudes and altitudes. In contrast, summer onset, which is more affected by proximity to oceans and altitudes than by latitudes, begins earlier in interior low elevated areas than in the coastal areas but earliest at higher latitudes than Jeiu Island. Five climatic types regarding the seasonal cycles in South Korea are spatially clustered according to the combination of longer seasonal durations. As a reflection of recent climate changes on seasonal cycles in South Korea, winter duration was shortened by 10 days during the post-1988 period due to a late winter onset of 4 days and an early spring onset of 6 days. The winter reduction began in the southern regions of the Korean Peninsula in the mid-1980s and spread northward during the 1990s period, ultimately appearing everywhere. In urbanized cities, where much of the surface is covered with asphalt or concrete, the winter reduction was intensified and summer duration was locally incremented. The reduced winter duration in recent decades shows significant teleconnections with variations of geopotential height (925hPa) in the eastern Arctic region ($0-90^{\circ}E$, $65-85^{\circ}N$) during the cold season. The reduction in winter duration in South Korea agrees with results in overall global warming trends as a climate change signal.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.10
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• pp.844-854
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• 2017

The Expansion-Deflection(E-D) nozzle is a nozzle that has a performance gain through the altitude compensation effect by changing the effective area within the nozzle according to the altitude. An E-D nozzle has been known to reduce the length of the nozzle and achieve the payload gain of the launch vehicle. Due to the potential advantages of an E-D nozzle, related research has been carried out in the United Kingdom, Germany, Australia and Europe etc. In the UK, the flow characteristics of the E-D nozzle and the performance comparison with the dual-bell nozzle which is altitude compensation nozzle were studied. In order to understand the transition characteristics of the E-D nozzle in DLR, the transition characteristics according to the nozzle pressure ratio change were analyzed. In Europe, numerical study using the E-D nozzle concept on upper stage of the launch vehicle Ariane 5 ESC-B was carried out to confirm the possibility of payload gain according to the nozzle length reduction. In this paper, research trends of an E-D nozzle performed outside the country are classified and analyzed according to their characteristics and utilized as basic data of E-D nozzle research in the future.

• Korean Journal of Remote Sensing
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• v.34 no.2_1
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• pp.249-265
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• 2018

The Korea Meteorological Administration has been operating wind profiler at 9 stations since the year of 2007. Among these stations, Bukgangneung is the only one that produces regularly both rawinsonde and wind profiler wind measurements at the same time. In this study, wind profiler measurements were compared with rawinsonde wind at Bukgangneung. Unlike most other studies which have used the temporal measurements for several days in summer season, in this study the routine rawinsonde measurments during almost one year (2016) were employed for the accuracy test of the wind. The monthly mean maximum observation height in Bukgangneung shows a large seasonal variation; it was relatively high in summer (4,310 m in July) and low in winter (2,130 m in December). The vertical observation rates at the altitude above these heights were less than 50%. The monthly and vertical wind comparison between rawinsonde and wind profiler shows that absolute bias and RMSE of zonal and meridional wind velocity are mostly less than 1 m/s and less than 2 m/s, respectively. In winter season the RMSE of wind velocity increased to 2~3 m/s. However, at some high altitudes and certain months, large errors were found. It is shown that these errors were related with very weak wind (less than 1 m/s) of wind profiler at 3,500~4,000 m from January to May and dramatic changes of wind the height of 1,500~2,500 m for in April. For Snow events the errors were lower than those for the winter season and for the heavy rain events the errors increased to 3~4 m/s at the height of 4~5 km.

• Korean Journal of Environment and Ecology
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• v.35 no.1
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• pp.37-47
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• 2021

This study carried out the plant sociological survey of Abies nephrolepis forest in Mt. Seorak, which is in danger of deterioration due to the accelerated climate change. We examined seventy quadrats obtained from the survey and used the TWINSPAN technique to classify communities. We then performed the DCA method for the sequence analysis and analyzed the characteristics of each community. A. nephrolepis forest of Mt. Seorak is composed of four communities (A. nephrolepis-Lonicera caerulea var. edulis community, A. nephrolepis-Acer komarovii community, A. nephrolepis-Ac. pseudosieboldianum community, and A. nephrolepis-Betula costata community). Each community showed a different distribution according to location because different microenvironments are formed depending on location such as altitude and slope direction, resulting in different species composition. Each community showed differences in environmental characteristics such as altitude, rock ratio, soil characteristics, and litter layer thickness. As a result, there were significant differences between communities in the number of species and individuals, coverage, tree size, and species diversity, as well as differences in species composition. The A. nephrolepis-L. caerulea var. edulis and A. nephrolepis-Ac. komarovii communities were located in high altitude with high rock ratios and had little development of tree layer. On the other hand, the A. nephrolepis-Ac. pseudosieboldianum and A. nephrolepis-B. costata communities were relatively in low altitude with high soil ratio and had the development of tree layer with high species diversity.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.799-810
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• 2003

Hydrologic models generally require land surface analysis to different topographic parameters defined as direct or indirect input variables to the model. Specially GIS supply the these parameters from digital data set of land surface The sensitivity analysis to DEM(Digital Elevation Model) resolution and the threshold area are of GIS extracted digital data set applied GIUH(Geomorphological Instantaneous Unit Hydrograph)model is investigated. Also it is compared the responses of GIUH model as input data of stream networks from digital data set(blue line) of NGIS and those extracted from DEM of various grid sizes. The results shows that the GIUH model is significantly affected by the DEM resolution and threshold area. According to the results, DEM grid size is suitable from 25m to 50m. Also threshold area is in the range of 30%∼50% for exceedance probability.

• Journal of the Korean association of regional geographers
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• v.10 no.3
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• pp.667-681
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• 2004

This research is aimed to investigate the relationship of the effective wind velocity and the morphological change in coastal dune at Sindu-ri in Korea. Sediment flux was estimated by the measurement of elevation change along eight transects deployed in the study area from July 1999 to July 2000. The results of this study indicated that. first. based on the occurrence of morphological change and winds effective for sand movement. two distinct seasons were identified: a season of deposition and that of erosion. During the depositional season, spanning from November to April, effective winds were dominant and sand accumulation occurred mainly in foredunes and sequentially in dune plains. During the erosional season, from May through October, volume change was small and erosion or sand loss occurred mostly at the dunefoot of foredunes. Secondly, the research revealed that the sediment budget of Sindu coastal dune turned out to be surplus on the whole, but there are some regional differences. Deficit budgets were observed partly in secondary dunes. The utmost northern part of Sindu coastal dune was provided with abundant sand, whereas the central and northern parts were poorly supplied.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.10
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• pp.1345-1352
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• 2021

Most of weather radar systems are used to monitor the whole weather situation for the very wide and medium-to-long range area. However, as the likelihood of occurrence of the local weather hazards is increased in recent days, it is very important to detect these wether phenomena with a local weather radar. For this purpose, it is necessary to detect the fast varying low altitude weather conditions and the effect of the ground surface clutter is more evident. Therefore, in this paper, the newly suggested method is explained and analyzed for detection of weather hazards such as the gust and wind shear using the fluctuation of wind velocities and the gradient of wind velocities among range cells. It is shown that the suggested method can be used efficiently in the future for faster detection of weather change through the simple algorithm implementation and also the effect of the ground clutter can be minimized in the detection procedure.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.04b
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• pp.462-467
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• 1994

최근의 생산 시스템은 가공부품의 변화와 생산롯트의 변화에 유연하게 대처하며 동시에 높은 생산성을 가질 수 있 는 FMS, FMC, CIM와 같은 고도로 자동화된 유연생산 시스템으로나아가고있다. 본 연구에서는 실제상품화가 가능한 지능형 전류 감시장치를 개발하는 것을 그 목적으로 하였으며 인텔8096 단일칩 콘트롤러를 이용하여 이를 실현하였다. 개발된 장치의 성능 평가를 위해드릴가공에 적용하였다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 1998.05a
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• pp.107-112
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• 1998

사회가 점점 고도화, 다양화, 고속화 하여가는 것과 비례하여 화재에 대한 위험성도 증대하며 일단 화재가 발생하면 그 피해 역시 막대하게 커지고 있습니다. 인간의 생활수준이 의식주를 해결하기에 급급하던 수준을 벗어나면, 즉 소득수준이 높아지면 "우선 살아야 한다"는 의식에서 "어떻게 잘 살 것인가"하는 방향으로 의식의 변화가 일어난다고 합니다. 인명을 존중하고, 생활환경 도시환경 노동환경에 있어서의 안전방재에 대한 의식도 높아진다는 것입니다. 일반적으로 그 의식의 변화는 일인당 국민소득 약 만불($10.000.-)전후에서 일어난다고 합니다. 이와 같은 사회배경을 바탕으로 섬유재료에 있어서도 보다 난연 또는 내열소재를 필요로 하게 되었습니다. (중략)

• Journal of the Korean Professional Engineers Association
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• v.32 no.2
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• pp.59-65
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• 1999

21세기는 고령화사회, 국제화사회, 성숙사회 등 여러 가지 단면으로 잡아 볼 수 있다. 사회는 "마음의 풍부함" 또는 "여유"를 구하며, 그곳에서는 넓은 의미에서의 휴먼네트워크가 중요하게 된다. 이와 같은 휴먼네트워크를 떠받치는 수단으로서, 사회의 정보화, 더욱이 통신이 수행해야 할 역할은 점점 큰 것으로 된다. 전자공학, 정보공학의 진보와 잘 어울려서 통신 네트워크의 고도화가 진보하여 정보슈퍼하이웨이의 구축 또는 VOD(Video On DEMAND)등 멀티미디어통신서비스가 진전하여 네트워크형 산업구조, 사회구조가 형성되어 간다. 이와 같이 산업이나 사회로 통신기술의 전개·침투가 착착 진행하여 그것에 수반하여 통신을 질적으로도 산업구조적으로도 크게 변화해 간다.