• 응용통계연구
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• 제15권2호
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• pp.337-354
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• 2002

본 논문에서는 오차성분이 계열상관을 갖는 불균형 랜덤모형에서 분산성분의 추정방법에 대하여 연구하였다. 분산성분에 대한 추정량으로 조건부 ANOVA(cANOVA), ML및 REML추정량등을 유도하였으며, 계열상관값과 불균형의 정도에 따른 추정량의 변동성을 추정량의 분위수를 이용하는 EQDGs플롯을 이용하여 비교하였다. 모의실험결과 cANOVA추정방법은 불균형의 정도에는 추정량값이 크게 영향을 받지 않는 것으로 나타났으나 계열상관값의 증가에 따라서는 변동성을 보이고 있다. 불균형의 정도와 계열상관값을 동시에 고려하는 경우에는 ML추정방법이 cANOVA, REML추정방법보다 변동성이 안정적으로 나타났다.

• 정보기술과데이타베이스저널
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• 제3권1호
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• pp.97-108
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• 1996

In this paper we obtain several function defined on finite partially ordered sets(posets) which may indicate constraints of comparability on sets of teams(tasks, etc.) for which evaluation is computationally simple, a relatively rare condition in graph-based algorithms. Using these functions a set of numerical coefficients and associated distributions obtained from a computer simulation of certain families of random graphs is determined. From this information estimates may be made as to the actual linearity of complicated posets. Applications of these ideas is to all areas where obtaining rankings from partial information in rational ways is relevant as in, e.g., team_, scaling_, and scheduling theory as well as in theoretical computer science. Theoretical consideration of special and desirable properties of various functions is provided permitting judgment concerning sensitivity of these functions to changes in parameters describing (finite) posets.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제7권9호
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• pp.2246-2267
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• 2013

BitTorrent is one of the most important applications in the current Internet. Despite of its interest, we still have little knowledge regarding the connectivity properties of real BitTorrent swarms. In this paper we leverage a dataset including the connectivity information of 250 real torrents and more than 150k peers to carefully study the connectivity properties of peers. The main topology parameters of the studied swarms suggest that they are significantly less resilient than random graphs. The analysis of the peer level connectivity properties reveals that peers continuously change more than half of their neighbours. Furthermore, we also find that a leecher typically keeps stable connections with a handful of neighbours with which it exchanges most of its traffic whereas seeders do not establish long-term connections with any peer so that they can homogeneously distribute chunks among leechers. Finally, we have discovered that a significant portion of the studied peers (45%) have an important locality-biased neighbourhood composition.

• 한국컴퓨터정보학회논문지
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• 제21권1호
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• pp.25-31
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• 2016

There are many methods to describe the importance of a node, centrality, in a graph. In this paper, we focus on the eigenvector centrality. In this paper, an analytical method to estimate the difference of centrality with an additional edge in a graph is proposed. In order to validate the analytical method to estimate the centrality, two problems, to decide an additional edge that maximizes the difference of all centralities of all nodes in the graph and to decide an additional edge that maximizes the centrality of a specific node, are solved using three kinds of random graphs and the results of the estimated edge and observed edge are compared. Though the estimated centrality difference is slightly different from the observed real centrality in some cases, it is shown that the proposed method is effective to estimate the centrality difference with a short running time.

• 한국수학교육학회지시리즈B:순수및응용수학
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• 제31권1호
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• pp.57-81
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• 2024

We introduce a new degree reduction method for homogeneous symmetric polynomials on binary variables that generalizes the conventional degree reduction methods on monomials introduced by Freedman and Ishikawa. We also design an degree reduction algorithm for general polynomials on binary variables, simulated on the graph coloring problem for random graphs, and compared the results with the conventional methods. The simulated results show that our new method produces reduced quadratic polynomials that contains less variables than the reduced quadratic polynomials produced by the conventional methods.

• 한국초등과학교육학회지:초등과학교육
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• 제34권1호
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• pp.86-94
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• 2015

This study is to investigate how do elementary students' eye movements appear in cognitive process that they perceive science learning materials depending on motivation system of science learning. For this study we had a random sampling of 301, 6th grade students. And we had selected 32 students through the three tests for the final; motivation system test of science learning, a learning styles test, an Edinburgh inventory for handedness test. We were analysis the cognitive process during learning tasks for the selected student using eye-tracking equipment. The results of the research are as follows: First, when students see a science learning material, we found out that SL-BAS group that has tendency searched various areas than SL-BIS group in learning task. Second, results confirmed through the data of integrational count that students looked alternately texts, images and graphs in the learning material, SL-BIS group were more than SL-BAS group on integrated count, but they had a simple and insignificant eye movement. Especially SL-BAS students showed that integrated eye movement between texts, images and graphs in the learning material, and they explored important areas of the graph compared with SL-BIS group that there was no eye movement in graph. These results may be utilized as a useful resource for designing students' learning.

• Journal of Computing Science and Engineering
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• 제2권3호
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• pp.249-273
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• 2008

Epidemic protocols have two fundamental assumptions. One is the availability of a mechanism that provides each node with a set of log(N) (fanout) nodes to gossip with at each cycle. The other is that the network size N is known to all member nodes. While it may be trivial to support these assumptions in small systems, it is a challenge to realize them in large open dynamic systems, such as peer-to-peer (P2P) systems. Technically, since the most fundamental parameter of epidemic protocols is log(N), without knowing the system size, the protocols will be limited. Further, since the network churn, frequently observed in P2P systems, causes rapid membership changes, providing a different set of log(N) at each cycle is a difficult problem. In order to support the assumptions, the fanout nodes should be selected randomly and uniformly from the entire membership. This paper investigates one possible solution which addresses both problems; providing at each cycle a different set of log(N) nodes selected randomly and uniformly from the entire network under churn, and estimating the dynamic network size in the number of nodes. This solution improves the previously developed distributed algorithm called Shuffle to deal with churn, and utilizes the Shuffle infrastructure to estimate the dynamic network size. The effectiveness of the proposed solution is evaluated by simulation. According to the simulation results, the proposed algorithms successfully handle network churn in providing random log(N0 fanout nodes, and practically and accurately estimate the network size. Overall, this work provides insights in designing epidemic protocols for large scale open dynamic systems, where the protocols behave autonomically.

• 한국통신학회논문지
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• 제30권7B호
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• pp.417-426
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• 2005

경로설정 및 파장할당(RWA: Routing and Wavelength Assignment) 문제는 파장 분할 다중화 기술에 기반한 차세대 광 인터넷 백본망에서 주목되는 기술중의 하나이다. 이러한 광 인터넷 망에서 연결요구에 대해 최적의 경로를 선택하여 선택된 경로에 효율적으로 파장을 할당하는 RWA문제는 매우 중요하다. 본 논문에서는 경로 충돌 그래프 개념과 송신노드-수신노드 간의 MAX_EDP(Maximum Edge Disjoint Paths: 최대 링크 비 중복 경로) 알고리즘을 이용한 효율적인 알고리즘을 제안한다. 또한, 이에 대한 모의실험을 통해 제안한 방법과 기존의 BGAforEDP 알고리즘과의 성능분석을 통해 효율성을 검증한다. 모의 실험결과 제안된 방식이 기존의 방식보다 고정된 네트워크 토폴로지(NSFNET)에서는 최대 20$\%$, 랜덤 토폴로지에서는 최대 32$\%$정도의 성능향상을 보인다.

• 유통과학연구
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• 제17권2호
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• pp.25-34
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• 2019

Purpose - This research strives to analyze and investigate customers' perception of the dimensions of service quality at retails in Makassar Municipality of Indonesia Country. This research tries to present its results empirically, which might be helpful to prepare a strategy to improve the service quality at retail companies. Research design, data, and methodology - The research uses Parasuraman's in 1985 unmodified SERVQUAL approach. This research is conducted using a questionnaire by purposive random sampling with 150 housewives customers who are met while they are shopping. The object of the study included several retail companies such as Alfa Mart, Alfa Midi, and Indomart operating in Makassar, Indonesia, which has been serving in 2017. Analysis was conducted by quantitative descriptive analysis, measurement of variable dimensions on the questionnaire using a Likert scale, and using cartecius graph and quadrant graphs to determine the gap size of each variable. Result - This research finds that the tangible and empathy dimensions such as product layout and lighting condition should be prioritized, and the empathy dimension whose gap value is too prominent such us peak load time condition and problem-solving adjustment. Conclusion - The second priority is responsiveness dimensions, and the last priority is reliability and assurance dimensions.

• Journal of Communications and Networks
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• 제11권1호
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• pp.47-56
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• 2009

We investigate the connectivity of fading wireless ad-hoc networks with a pair of novel connectivity metrics. Our first metric looks at the problem of connectivity relying on the outage capacity of MIMO channels. Our second metric relies on a probabilistic treatment of the symbol error rates for such channels. We relate both capacity and symbol error rates to the characteristics of the underlying communication system such as antenna configuration, modulation, coding, and signal strength measured in terms of signal-to-interference-noise-ratio. For each metric of connectivity, we also provide a simplified treatment in the case of ergodic fading channels. In each case, we assume a pair of nodes are connected if their bi-directional measure of connectivity is better than a given threshold. Our analysis relies on the central limit theorem to approximate the distribution of the combined undesired signal affecting each link of an ad-hoc network as Gaussian. Supported by our simulation results, our analysis shows that (1) a measure of connectivity purely based on signal strength is not capable of accurately capturing the connectivity phenomenon, and (2) employing multiple antenna mobile nodes improves the connectivity of fading ad-hoc networks.