• 정보처리학회논문지A
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• 제12A권5호
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• pp.427-432
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• 2005

웹 클러스터 시스템에서 사용자들의 접속 요구를 효율적으로 real 서버에 분산시키기 위하여 기존의 부하분산 알고리즘들과 현재 많이 사용중인 WLC(Weighted Least Connection) 알고리즘에 대하여 연구하였다. 이 부하분산 알고리즘들은 서버들의 부정확한 부하상태 파악과 파악 시점에 문제가 있어 서버들 간에 부하 불균형이 발생함으로써 효율성이 저하된다. 본 연구에서는 사용자의 접속 요청 시 broadcasting RPC(Remote Procedure Call)를 이용하여 서버들의 다양한 부하상태를 실시간으로 파악하여 부하를 분산하는 알고리즘을 제안하고, prototype을 구현하여 성능을 실험하였다. 실험 결과, real 서버 간 부하 불균형 현상이 기존 방법에 비하여 크게 향상되었고, 응답시간이 단축되는 효과로 웹 클러스터 시스템의 성능이 향상되었다.

• 천문학회보
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• 제38권1호
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• pp.58.2-58.2
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• 2013

We present a photometric study of the globular clusters (GCs) in the giant elliptical galaxy M86 in the Virgo Cluster, using the Washington $CT_1$ images taken at the KPNO 4 m telescope. The color distribution of the GCs in M86 is bimodal. The radial number density profile of the blue GCs decreases more slowly as the galactocentric distance increases than that of the red GCs. The density profile of the red GCs is similar to the surface brightness profile of M86 stellar halo. The blue GCs have a roughly circular spatial distribution, while the red GCs have a spatial distribution somewhat elongated, which is consistent with the distribution of the galaxy stellar light. M86 GCs have the negative radial color gradient because the number ratio of the blue GCs to the red GCs increases as galactocentric radius increases. The mean color of the red GCs is similar to that of the stellar halo. The bright blue GCs in the outer region of M86 reveal a blue tilt that the mean colors of the blue GCs get redder as they get brighter. We discuss these results in comparison with other giant elliptical galaxies in the Virgo Cluster.

• Communications for Statistical Applications and Methods
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• 제22권3호
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• pp.265-276
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• 2015

In this paper, we propose hierarchical cluster analysis and multidimensional scaling for joint distribution valued data. Information technology is increasing the necessity of statistical methods for large and complex data. Symbolic Data Analysis (SDA) is an attractive framework for the data. In SDA, target objects are typically represented by aggregated data. Most methods on SDA deal with objects represented as intervals and histograms. However, those methods cannot consider information among variables including correlation. In addition, objects represented as a joint distribution can contain information among variables. Therefore, we focus on methods for joint distribution valued data. We expanded the two well-known exploratory methods using the dissimilarities adopted Hall Type relative projection index among joint distribution valued data. We show a simulation study and an actual example of proposed methods.

• 대한전기학회논문지:전력기술부문A
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• 제53권10호
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• pp.556-564
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• 2004

This paper presents an application of parallel Genetic Algorithm-Tabu Search(GA-TS) algorithm to search an optimal solution of a reconfiguration in distribution system. The aim of the reconfiguration of distribution systems is to determine switch position to be opened for loss minimization in the radial distribution systems, which is a discrete optimization problem. This problem has many constraints and very difficult to solve the optimal switch position because it has many local minima. This paper develops parallel GA-TS algorithm for reconfiguration of distribution systems. In parallel GA-TS, GA operators are executed for each processor. To prevent solution of low fitness from appearing in the next generation, strings below the average fitness are saved in the tabu list. If best fitness of the GA is not changed for several generations, TS operators are executed for the upper 10% of the population to enhance the local searching capabilities. With migration operation, best string of each node is transferred to the neighboring node aster predetermined iterations are executed. For parallel computing, we developed a PC-cluster system consisting of 8 PCs. Each PC employs the 2 GHz Pentium Ⅳ CPU and is connected with others through ethernet switch based fast ethernet. To show the usefulness of the proposed method, developed algorithm has been tested and compared on a distribution systems in the reference paper. From the simulation results, we can find that the proposed algorithm is efficient and robust for the reconfiguration of distribution system in terms of the solution qualify. speedup. efficiency and computation time.

• 한국통신학회논문지
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• 제33권7B호
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• pp.528-537
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• 2008

본 논문은 NoC 시스템에서 수행되는 멀티미디어 application에서 deadlock과 패킷 drop율을 최소화하기 위한 hybrid 구조의 네트워크 토폴로지와 job distribution 알고리듬을 제안한다. 제안된 NoC 시스템은 멀티미디어 application에 따라 패킷 drop율이 최소화될 수 있는 네트워크 토폴로지를 적용하여 sub-cluster에 배정하고, 수행되는 application은 sub-cluster 내의 네트워크 상황을 고려하여 동적 round-robin 방식의 스케줄링을 수행한다. 본 연구에서는 hybrid 네트워크 토폴로지와 동적인 job distribution을 통해 네트워크에 발생하는 트래픽을 분산시킴으로써 패킷 deadlock과 패킷 drop율을 최소화하는 알고리듬을 제시하였다. 제안된 시스템의 성능을 검증하기 위해 임베디드 시스템에서 사용되는 멀티미디어 application 중 MPEG4 동영상 재생, MPEG1 audio layer-3(MP3) 재생, GPS 위치 계산, OFDM 복조를 대상으로 실험하였다. 실험결과 제안된 job distribution 알고리듬에 적용된 시스템은 기존의 APSRA 알고리듬에 비해 패킷 drop율이 평균 13% 감소하고 면적은 2.7% 증가하였다. 또한 deadlock 감소의 비교 대상으로 흔히 사용되는 XY 알고리듬을 본 구조에 맞게 변경한 알고리듬에 대해 패킷 drop율은 평균 23.9% 감소하고 면적은 3.0% 증가하였다.

• KIEE International Transactions on Power Engineering
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• 제5A권2호
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• pp.116-124
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• 2005

This paper presents an application of the parallel Genetic Algorithm-Tabu Search (GA- TS) algorithm, and that is to search for an optimal solution of a reconfiguration in distribution systems. The aim of the reconfiguration of distribution systems is to determine the appropriate switch position to be opened for loss minimization in radial distribution systems, which is a discrete optimization problem. This problem has many constraints and it is very difficult to solve the optimal switch position because of its numerous local minima. This paper develops a parallel GA- TS algorithm for the reconfiguration of distribution systems. In parallel GA-TS, GA operators are executed for each processor. To prevent solution of low fitness from appearing in the next generation, strings below the average fitness are saved in the tabu list. If best fitness of the GA is not changed for several generations, TS operators are executed for the upper 10$\%$ of the population to enhance the local searching capabilities. With migration operation, the best string of each node is transferred to the neighboring node after predetermined iterations are executed. For parallel computing, we developed a PC-cluster system consisting of 8 PCs. Each PC employs the 2 GHz Pentium IV CPU and is connected with others through switch based rapid Ethernet. To demonstrate the usefulness of the proposed method, the developed algorithm was tested and is compared to a distribution system in the reference paper From the simulation results, we can find that the proposed algorithm is efficient and robust for the reconfiguration of distribution system in terms of the solution quality, speedup, efficiency, and computation time.

• International Journal of Computer Science & Network Security
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• 제21권1호
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• pp.6-11
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• 2021

Routing protocols play a pivotal role in the energy management and lifespan of any Wireless Sensor Network. Lower network lifetime has been one of the biggest concerns in LEACH protocol due to dead nodes. The LEACH protocol suffers from uneven energy distribution problem due to random selection of a cluster head. The cluster head has much greater responsibility compared to other non- cluster head nodes and consumes greater energy for its roles. This results in early dead nodes due to energy lost for the role of cluster- head. This study proposes an approach to balance the energy consumption of the LEACH protocol by using a semi-deterministic opportunity coefficient to select the cluster head. This is calculated in each node with the battery energy level and node ID. Ultimately, based on the opportunity cost, cluster head will be selected and broadcasted for which other nodes with higher opportunity cost will agree. It minimizes the chances of nodes with lower battery level being elected as cluster head. Our simulation experiments demonstrate that cluster heads chosen using our proposed algorithm perform better than those using the legacy LEACH protocol.

• 한국경제지리학회지
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• 제26권3호
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• pp.202-222
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• 2023

본 연구는 서울의 영화산업과 방송산업 공간분포를 분석하고 집적지 변화에 작용하는 산업 성장과 도시 특성에 주목하여 서울 영상산업 클러스터의 공간적 특성을 파악하고자 한다. 1994년, 2004년, 2014년, 2021년의 서울시 사업체 조사를 분석자료로, 산업의 성장을 확인하고 공간적 자기상관성 분석(Moran's I와 LISA분석)을 수행해 영상산업의 공간분포와 집적지 변화를 확인했다. 또한 현직 종사자 인터뷰의 질적자료 수집과 분석으로 영상산업의 현황과 집적지 형성 요인 등을 파악하여 종합적인 분석을 시도했다. 분석 결과 영화산업과 방송산업 집적지는 서울에 분산되어 다핵형태로 성장하고 있다. 1994년에 영화산업 집적지는 충무로와 강남, 방송산업은 여의도로 집적지 구분이 뚜렷했던 반면, 2021년에는 마포와 강남이 영화산업과 방송산업의 공통 집적지로 나타났다. 그 외 여의도, 강서-영등포 일대의 방송산업 집적지와 성수 일대의 영화산업 집적지가 확인되었다. 끝으로 본 연구에서는 서울의 영상산업 성장과 공간적 분포 변화에 작용한 요인들을 영상산업의 특성과 도시환경의 변화와 연관시켜 제시하였다.

• 천문학회지
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• 제35권2호
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• pp.87-95
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• 2002

We have conducted VI CCD photometry of the open cluster NGC 6819 in order to understand the effects of dynamical evolution in old open clusters. Our photometry covers 18' $\times$ 18' on the sky, centered on the cluster, which seems to cover the whole cluster field. Our photometry reaches down to V $\approx$ 20.5, which allows us to analyze the luminosity function and spatial distribution of stars brighter than Mv $\approx$ 8.5. There is a clear evidence for mass segregation in NGC 6819, i.e., the giants and upper main-sequence stars are concentrated in the inner regions, whereas the lower main-sequence stars distribute almost uniformly throughout the cluster. The luminosity function of the main-sequence stars of NGC 6819 is almost flat. The flat luminosity function indicates that a large number of low mass stars has escaped from the cluster unless its initial mass function is much different from the Salpeter type (${\phi}(m){\propto} m^{-(1+x)},x = 1.35$).

• 천문학회보
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• 제43권1호
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• pp.60.3-61
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• 2018

Abell 115 is a renowned cluster merger at z=0.197. It exhibits an asymmetric X-ray distribution with cometary tails and a megaparsec-sized radio relic stretching in the northeastern direction from the core of the northern cluster. Many observations have concluded that this cluster merger has a large impact parameter, but there has been no numerical analysis on the structure of Abell 115. In this study, we simulate Abell 115 with Gadget2 N-body/SPH code to reproduce the X-ray and weak lensing features of Abell 115. We find a new plausible merger scenario of Abell 115, wherein the northern cluster is currently in an outgoing phase. The predicted X-ray emission has a similar morphology to the observed tail of the northern cluster. However, in order to reproduce the observed line-of-sight velocity and projected distance while maintaining the two systems gravitationally bound, the system should possess a large projection angle, which makes the shock look considerably more diffused than the observed radio relic.