• Annual Conference on Human and Language Technology
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• 1998.10c
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• pp.419-424
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• 1998

본 논문에서는 단어들의 분포적 특성을 이용하여 자동으로 단어를 군집화(clustering) 하는 기법을 제시한다. 제안된 군집화 기법에서는 단어들 사이의 거리(distance)를 가상 공간상에 있는 두 단어의 평균점에 대한 불일치의 합(total divergence to the average)으로 측정하며 군집화 알고리즘으로는 최소 신장 트리(minimal spanning tree)를 이용한다. 본 논문에서는 이 기법에 대해 두 가지 실험을 수행한다. 첫 번째 실험은 코퍼스에서 상위 출현 빈도를 가지는 약 1,200 개의 명사들을 의미에 따라 군집화 하는 것이며 두 번째 실험은 이 논문에서 제시한 자동 군집화 방법의 성능을 객관적으로 평가하기 위한 것으로 가상 단어(pseudo word)에 대한 군집화이다. 실험 결과 이 방법은 가상 단어에 대해 약 91%의 군집화 정확도와(clustering precision)와 약 81%의 군집 순수도(cluster purity)를 나타내었다. 한편 두 번째 실험에서는 평균점에 대한 불일치의 합을 이용한 거리 측정에서 나타나는 문제점을 보완한 거리 측정 방법을 제시하였으며 이를 이용하여 가상 단어 군집화를 수행한 결과 군집화 정확도와 군집 순수도가 각각 약 96% 및 95%로 향상되었다.

• 제어로봇시스템학회:학술대회논문집
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• 2005.06a
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• pp.1039-1043
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• 2005

Despite the many significant advances made in robot architecture, the basic approaches are deliberative and reactive methods. They are quite different in recognizing outer environment and inner operating mechanism. For this reason, they have almost opposite characteristics. Later, researchers integrate these two approaches into hybrid architecture. In such architecture, Reactive module also called low-level motion control module have advantage in real-time reacting and sensing outer environment; Deliberative module also called high-level task planning module is good at planning task using world knowledge, reasoning and intelligent computing. This paper presents a framework of the integrated planning and control for mobile robot navigation. Unlike the existing hybrid architecture, it learns topological map from the world map by using MST (Minimum Spanning Tree)-based SOFM (Self-Organizing Feature Map) algorithm. High-level planning module plans simple tasks to low-level control module and low-level control module feedbacks the environment information to high-level planning module. This method allows for a tight integration between high-level and low-level modules, which provide real-time performance and strong adaptability and reactivity to outer environment and its unforeseen changes. This proposed framework is verified by simulation.

• Land and Housing Review
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• v.10 no.1
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• pp.9-18
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• 2019

This study examined the dynamic change in the co-movement between the house price rates with the network methods of Mantegna (1999). First, Capital area and non-capital area form independent clusters which have the heterogeneous co-movement pattern. In other words, Capital and non-capital areas have low connectivity in the housing market. Also, if the co-movement between capital areas have been strengthened, the co-movement between non-capital areas have been weakened. The results of the dynamic analysis show that the degree of the co-movement in the housing market is continuously increased. The members of the co-movement group in the capital area are strongly steadied by all periods. However, the members in the non-capital area have been changed according to the period. Accordingly, it is necessary to establish policies based on various information for the housing market of the non-capital area rather than policies targeting the capital area. In addition, Apartments in Korea are more likely to be used as investment or speculative assets than other types of houses. It has been confirmed that this is Gangbuk, which is locatied in the northern part of Seoul, appears to be a region where the Spillover Effects of price fluctuation can be triggered in the housing and apartment market. However, the housing market in Gangnam, which is locatied in the southern part of Seoul, was divided into low systematic risk.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.11 no.4
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• pp.1911-1930
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• 2017

Overlay routing has emerged as a promising approach to improve reliability and efficiency of the Internet. The key to overlay routing is the placement and maintenance of the overlay infrastructure, especially, the selection and placement of key relay nodes. Spurred by the observation that a few relay nodes with high betweenness centrality can provide more optimal routes for a large number of node pairs, we propose a resilient routing overlay network construction method by introducing Super-Relay nodes. In detail, we present the K-Minimum Spanning Tree with Super-Relay nodes algorithm (SR-KMST), in which we focus on the selection and connection of Super-Relay nodes to optimize the routing quality in a resilient and scalable manner. For the simultaneous path failures between the default physical path and the overlay backup path, we also address the selection of recovery path. The objective is to select a proper one-hop recovery path with minimum cost in path probing and measurement. Simulations based on a real ISP network and a synthetic Internet topology show that our approach can provide high-quality overlay routing service, while achieving good robustness.

• Proceedings of the Korean Information Science Society Conference
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• 2000.04b
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• pp.511-513
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• 2000

PaP Smear 테스트는 자궁 경부암 진단에 가장 효율적인 방법으로 알려져 있다. 그러나 이 방법은 높은 위 음성률(false negative error, 15~50%)을 나타내고 있다. 이런 큰 오류율은 주로 다량의 세포 검사에 기인하여, 자동화 시스템의 개발이 절실히 요구되고 있다. 본 논문은 자궁 경부암의 특징인 군집을 이루는 암세포를 인식할 수 있는 시스템을 제안한다. 시스템은 두 부분으로 나누어진다. 첫 단계에서는 저 배율(100배)에서 간단한 영상처리와 최소 근접 트리(Minimum Spanning Tree)를 통해 군집을 이루는 세포를 찾는다. 두 번째 단계서는 고 배율(400배)로 확대하여 군집 세포들로부터 여러 가지 특징을 추출한 후 KNN(k-Neighbor) 방법을 통해 인식하는 단계이다. 50개의 영상 (640X 480, RGB True Color 25 개의 100배 영상 , 25개의 400배 영상)이 실험에 사용되었다. 한 영상을 처리하는데 약 3초 (2.984초) 소요되었으며, 이는 region growing(20초)나 split and merge(58초) 방법 보다 덜 소요되었다. 100배 영상에서 정상과 비정상의 두 그룹으로 나누었을 경우에는 96%의 높은 인식율을 나타내었으나 비정상을 다시 5개의 그룹으로 나누었을 때는 45%로 나타내었다. 이는 영역 추출(segmentation) 단계에서 오류와 트레이닝 데이터의 비정확성에 기인한다. 400배 영상에서는 각각 92%와 30%로 나타내었다. 이는 영역추출 단계에서 사용한 Watershed 방법의 오류로 기인한 것으로 본다.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.4 no.5
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• pp.799-818
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• 2010

In traditional unstructured P2P file sharing network, each peer establishes connections with a certain number of randomly chosen other peers. This would lead to redundant traffic and P2P network partition in mobile ad hoc network (MANET). We propose an approach to construct an efficient unstructured P2P overlay over MANET using underlying cluster-based routing (CBRP). One of the peers in the P2P network is used as a root-peer to connect all peers. Each peer maintains connection with physically closer peers such that it can reach the root-peer. The peer constructs a minimum-spanning tree consisting of itself, its directly connected neighbor peers and 2-hop away neighbor peers to remove far away redundant links and to build an overlay closer to the physical network. Due to on-demand nature of inter-cluster routing of CBRP, the positioning algorithm for MANET is used to retrieve the file by a peer from the source peer via shorter path in the physical network. We can show by simulation that our approach performs better in comparison with the existing approach.

• Journal of Communications and Networks
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• v.13 no.1
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• pp.17-25
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• 2011

A convergecast is a popular routing scheme in wireless sensor networks (WSNs) in which every sensor node periodically forwards measured data along configured routing paths to a base station (BS). Prolonging lifetimes in energy-limited WSNs is an important issue because the lifetime of a WSN influences on its quality and price. Low-energy adaptive clustering hierarchy (LEACH) was the first attempt at solving this lifetime problem in convergecast WSNs, and it was followed by other solutions including power efficient gathering in sensor information systems (PEGASIS) and power efficient data gathering and aggregation protocol (PEDAP). Our solution-chain routing with even energy consumption (CREEC)-solves this problem by achieving longer average lifetimes using two strategies: i) Maximizing the fairness of energy distribution at every sensor node and ii) running a feedback mechanism that utilizes a preliminary simulation of energy consumption to save energy for depleted Sensor nodes. Simulation results confirm that CREEC outperforms all previous solutions such as LEACH, PEGASIS, PEDAP, and PEDAP-power aware (PA) with respect to the first node death and the average lifetime. CREEC performs very well at all WSN sizes, BS distances and battery capacities with an increased convergecast delay.

• Journal of Communications and Networks
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• v.6 no.1
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• pp.46-59
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• 2004

In this paper, we present two algorithms for efficiently aggregating link state information needed for quality-of-service (QoS) routing. In these algorithms, each edge node in a group is mapped onto a node of a shufflenet or a node of a de Bruijn graph. By this mapping, the number of links for which state information is maintained becomes aN (a is an integer, N is the number of edge nodes) which is significantly smaller than N2 in the full-mesh approach. Our algorithms also can support asymmetric link state parameters which are common in practice, while many previous algorithms such as the spanning tree approach can be applied only to networks with symmetric link state parameters. Experimental results show that the performance of our shufflenet algorithm is close to that of the full-mesh approach in terms of the accuracy of bandwidth and delay information, with only a much smaller amount of information. On the other hand, although it is not as good as the shufflenet approach, the de Bruijn algorithm also performs far better than the star approach which is one of the most widely accepted schemes. The de Bruijn algorithm needs smaller computational complexity than most previous algorithms for asymmetric networks, including the shufflenet algorithm.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• v.9 no.2
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• pp.123-126
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• 2005

STP gets to have different network performance, depending on the configuration method of topology. Accordingly, for efficient network environment, it is necessary to make the optimum topology. This paper proposed a way to make the optimum topology for construction of efficient network among switches on ethernet: the optimum topology was made by calculating the time the switches in the same domain receive the frame transmitted from the root switch, using a mathematical model. And it analyzed the performance of the topology depending on the location of the root switch. As a result of analyzing the performance, this study came to the conclusion that it would be effective to locate the root switch in the center of the square network.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10a
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• pp.196-198
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• 2003

Virtually every digital signal processors(DSPs) support on-chip multi- memory banks that allow the processor to access multiple words of data from memory in a single instruction cycle. Also, all existing fixed-point DSPs have irregular architecture of heterogeneous register which contains multiple register files that are distributed and dedicated to different sets of instructions. Although there have been several studies conducted to efficiently assign data to multi-memory banks, most of them assumed processors with relatively simple, homogeneous general-purpose resisters. Therefore, several vendor-provided compilers fer DSPs were unable to efficiently assign data to multiple data memory banks. thereby often failing to generate highly optimized code fer their machines. This paper presents an algorithm that helps the compiler to efficiently assign data to multi- memory banks. Our algorithm differs from previous work in that it assigns variables to memory banks in separate, decoupled code generation phases, instead of a single, tightly-coupled phase. The experimental results have revealed that our decoupled algorithm greatly simplifies our code generation process; thus our compiler runs extremely fast, yet generates target code that is comparable In quality to the code generated by a coupled approach