• 천문학회보
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• 제40권2호
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• pp.57.3-57.3
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• 2015

The formation of the Milky Way stellar halo is thought to be the result of merging and accretion of building blocks such as dwarf galaxies and massive globular clusters. Recently, Deason et al. (2015) suggested that the Milky Way outer halo formed mostly from big building blocks, such as dwarf spheroidal galaxies, based on the similar number ratio of blue straggler (BS) stars to blue horizontal-branch (BHB) stars. Here we demonstrate, however, that this result is seriously biased by not taking into detailed consideration on the formation mechanism of BHB stars from helium enhanced second-generation population. In particular, the high BS-to-BHB ratio observed in the outer halo fields is most likely due to a small number of BHB stars provided by GCs rather than to a large number of BS stars. This is supported by our dynamical evolution model of GCs which shows preferential removal of first generation stars in GCs. Moreover, there are sufficient number of outer halo GCs which show very high BS-to-BHB ratio. Therefore, the BS-to-BHB number ratio is not a good indicator to use in arguing that more massive dwarf galaxies are the main building blocks of the Milky Way outer halo. Several lines of evidence still suggest that GCs can contribute a signicant fraction of the outer halo stars.

• 한국통신학회논문지
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• 제22권6호
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• pp.1137-1147
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• 1997

정상 링크와 대체 링크로 구성된 스위칭소자를 갖는 RZETA망을 제안한다. RZETA망의 정상 링크로 사용되는 modified Zeat망과 대체 링크로 사용되는 다단계상호연결망은 그래프 이론에 의해 생성한다. 2개의 다단계상호연결망을 병합함으로써 RZETA망을 생성한다. modified Zeat망이 넌블럭킹되기 위한 필요충분 조건을 제시한다. 이 조건은 RZETA망의 링크나 스위칭 소자가 단일 결함이 있을 때 넌블럭킹되기 위한 충분 조건이다. 2-dilated Banyan망의 성능 분석 모델을 수정하여 RZETA망의 성능 분석을 하고 각 근원지의 입력 패킷 도착률이 1일 때 기존의 중복 경로를 갖는 망과의 성능을 비교한다.

• 한국주거학회논문집
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• 제14권3호
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• pp.147-156
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• 2003

A small apartment housings in Korea, which is built mass-product from 1980s, are dissatisfied, in spite of good condition, due to the growing living areas and changing lifestyle of the residents. Many of them confronted with slum areas and the kinds of housing stock accumulated much more in Korean contexts. For the existing small houses, it could be discuss an adaptation model to the increasing requirement standards of the house residents; wider living area, new facilities and a style of new residence. A social policy for elderly people who are handicap in physical and economical aspects, is home stay system rather than national support. But it is not easy to find the three generation family house in Korea context, specially apartment house. This paper deals with the vertical unification typology of two dwelling units to one, in order to supply three generation houses by remodel existing small apartment houses constructed by Korea National Housing Corporation. The use of convert houses into vertical expansion are expected to be a house of three generation family, it can also enhance privacy against conflictive activities in a house. And also the merging types of two dwelling units into one can be used as a device to get rid of the monotonous characteristics and gain diversity in the declining stock housing.

• 대기
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• 제25권2호
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• pp.283-294
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• 2015

For urban flash flood simulation, we need the higher resolution radar rainfall than radar rainfall of KMA, which has 10 min time and 1km spatial resolution, because the area of subbasins is almost below $1km^2$. Moreover, we have to secure the high quantitative accuracy for considering the urban hydrological model that is sensitive to rainfall input. In this study, we developed the quantitative precipitation estimation (QPE), which has 250 m spatial resolution and high accuracy using KMA AWS and SK Planet stations with Mt. Gwangdeok radar data in Seoul area. As the results, the rainfall field using KMA AWS (QPE1) is showed high smoothing effect and the rainfall field using Mt. Gwangdeok radar is lower estimated than other rainfall fields. The rainfall field using KMA AWS and SK Planet (QPE2) and conditional merged rainfall field (QPE4) has high quantitative accuracy. In addition, they have small smoothed area and well displayed the spatial variation of rainfall distribution. In particular, the quantitative accuracy of QPE4 is slightly less than QPE2, but it has been simulated well the non-homogeneity of the spatial distribution of rainfall.

• 한국경영과학회지
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• 제29권4호
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• pp.41-60
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• 2004

A stream data is a data set that is accumulated to the data storage from a data source over time continuously. The size of this data set, in many cases. becomes increasingly large over time. To mine information from this massive data. it takes much resource such as storage, memory and time. These unique characteristics of the stream data make it difficult and expensive to use this large size data accumulated over time. Otherwise. if we use only recent or part of a whole data to mine information or pattern. there can be loss of information. which may be useful. To avoid this problem. we suggest a method that efficiently accumulates information. in the form of rule sets. over time. It takes much smaller storage compared to traditional mining methods. These accumulated rule sets are used as prediction models in the future. Based on theories of ensemble approaches. combination of many prediction models. in the form of systematically merged rule sets in this study. is better than one prediction model in performance. This study uses a customer data set that predicts buying power of customers based on their information. This study tests the performance of the suggested method with the data set alone with general prediction methods and compares performances of them.

• 대한교통학회지
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• 제23권5호
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• pp.169-176
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• 2005

고속도로 합류부의 반복정체는 모든 이의 일상이지만 정체가 발생한 이후에 마땅히 시도할 대책이 없는 것이 작금의 현실이다. 본 연구는 접속부에 혼잡이 발생한 후 상황에 따라 가속차로 길이를 동적으로 제어하여 본선에 대한 상대적인 우월성을 억제함으로써 혼잡구간의 정체를 저감시키는 기법을 제안하고 있다. 가속차로의 동적 제어가 미치는 교통영향 분석을 위해서 car-following 이론에 토대를 둔 미시 모형인 CORSIM을 사용하였으며, 본선의 수요는 LOS D/E로 유지하는 가운데 연결로 수요를 변화시킴으로서 접속부의 혼잡을 점진적으로 연출하고 본선과 가속차로의 운영속도가 역전되는 시점에 가속차로의 유효길이를 축소하는 기능을 구현하였다. 동적 제어의 대상이 되는 가속차로 길이는 세 가지로 제한하였으며 평가척도는 통행시간과 통과교통량으로 하였다. 또 경부고속도로에 신갈 JC서의 유사 운영 결과와 비교를 통해 모의실험 결과를 뒷받침하였다.

• 전기학회논문지
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• 제64권2호
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• pp.315-323
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• 2015

Nowadays, it is expected that mobility loads such as electric railways and electric vehicles will be penetrated gradually and affect on the power system stability by their load characteristics. Various researches have been carried out about electric vehicles for the recent decade though the load of electric railway could be forecasted because of the specified path and timetable, is a field with a long historic background. Some precise 5th polynomial equations are required to analyze the power system stability considering mobility load to be increased in the immediate future while the electric railway dispatching simulator uses load models with constant power and constant impedance for the system analysis. In this paper, seasonal urban railway load models are established as the form of 5th polynomial equations and substation load modeling methods are proposed merging railway station load models and general load models. Additionally, load management effects by the load modeling are confirmed through the case studies, in which seasonal load models are developed for Seoul Subway Line No. 2, Gyeongui Line and Airport Railroad and the substation load change is analyzed according to the railway load change.

• 천문학회보
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• 제37권1호
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• pp.40.1-40.1
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• 2012

In the hierarchical universe, galaxy merger is predicted to be frequent, and thus it is an important element for understanding galaxy evolution. In particular, star formation is greatly enhanced during the merger. The aim of this study is to understand the position and rate change of star formation caused by equal-mass edge-on mergers. We use the GADGET2- N-body/SPH code, and fully consider gas cooling, star formation, and supernova feedback. We show the star formation rate (SFR), and the magnitude and color evolution of the merger remnants for 18 different configurations varying orbit elements and inclinations of host galaxies against orbit planes. Then we construct the mock images of the remnants and investigate on how equal-mass galaxy merger affects the SFR and color/magnitude evolution while considering dust reddening. We conclude that over 90% mass of SF in equal-mass merger is in the central region. SF in tidal feature involves a small fraction of new stars and thus is difficult to detect unless deep imaging is performed. Around 55 ${\pm}$ 5 percent of gas turns into stars until the final coalescence which typically corresponds to 0.8, 1.2, and 2.5 Gyr for direct, parabolic, and elliptical orbit, respectively. This result is roughly consistent with Cox et al. 2000. We plan to implement this result into semi-analytic model of galaxy formation. Caveats and future work on merging conditions are discussed.

• 한국전산유체공학회지
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• 제17권3호
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• pp.33-38
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• 2012

The droplet ejection behavior from drop-on-demand printhead are investigated numerically for Newtonian and shear-thinning fluid. The numerical simulation is performed using a volume-of-fluid model. In this study, we compare the printable range in terms of Z number and pinch-off time for Newtonian and shear-thinning fluids. The printability range are found to be 1.08 $$\leq_-$$ Z $$\leq_-$$ 12.9 for Newtonian fluid and 0.8 $$\leq_-$$ Z $$\leq_-$$ 12.9 for shear-thinning fluid. However, air entrainment is observed during merging of primary and satellite droplet within the printability range. The pinch-off time of the shear-thinning fluid is apparently shorter compared to the corresponding Newtonian fluid due to shear-thinning effects and the differences in the pinch-off time is enlarged significantly when the capillary number is larger than 0.5.

• 대한공간정보학회지
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• 제5권2호
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• pp.207-220
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• 1997

본 연구에서는 항공사진과 지형공간정보체계를 이용하여 수치영상지도를 제작하기 위한 효율적 방안을 고찰하고, 저가의 개인용 컴퓨터시스템을 기본으로 하는 지형공간정보체계를 이용하여 수치항공사진 영상과 수치지형도를 중첩함으로써, 지형판독성과 활용성이 높은 수치영상지도를 제작하는 실험적 방안을 연구한다. 이를 위하여 지상좌표의 결정, 수치영상처리, 수치표고모형의 생성에 대하여 고찰한 다음, 수치영상지도제작에 필요한 영상자료 입출력, 수치편위미분수정, 항공사진을 이용한 정사투영상의 생성에 관련된 방법을 고찰하고, 수치영상지도를 실험제작하여 그 활용방안을 제시하였다.