• 한국경영과학회지
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• 제25권3호
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• pp.81-89
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• 2000

The real-time multicast problem is to construct a multicast tree starting from a source node and including multiple destination nodes and that has minimum network cost with delay constraints. It is known that to find a tree of the minimum network cost is the Steiner Tree problem which is NP-complete. In this paper, we propose a genetic algorithm to solve the multicast tree with minimum network cost and the delay constraints. The computational results obtained by comparing an existing algorithm. Kompella algorithm, and the proposed algorithm show that our algorithm tends to find lower network cost on the average than Kompella algorithm does.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2002년도 춘계학술대회 논문집
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• pp.561-564
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• 2002

With Rapid Prototyping system, the efficient packing in a fixed work volume reduces build time when multiple parts are built in a process. In this paper, an efficient and rapid packing algorithm is developed for SLS system that has cylindrical workspace. A genetic algorithm is implemented to place as many part as possible in a vat. For fast computation, a collision detection algorithm "k-DOPs Tree" is implemented.

• 한국정보과학회논문지:소프트웨어및응용
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• 제32권4호
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• pp.268-276
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• 2005

본 논문은 최적 통신 걸침 나무 문제(Optimum Communication Spanning Tree Problem OCST)를 다룬다. 일반적으로, OCST문제는 WP-hard 문제로 알려져 있으며 최근에 Papadimitriou 와 Yannakakis에 의해서 MAX SNP-hard로 밝혀졌다. 그럼에도 불구하고 OCST 문제를 해결하기 위한 기존의 주된 접근법은 polynomial time 알고리즘들 이었다. 본 논문에서는 OCST 문제를 해결하기 위한 진화 알고리즘을 소개한다. 특히, 진화 알고리즘을 어떤 문제에 적용할 때 가장 우선적으로 고려되어야 하는 사항은 해를 어떻게 표현할 것인가 하는 표현법(representation)에 관한 것이다. 따라서 본 논문에서는 기존에 차수 제약 걸침 나무 문제를 해결하기 위해 제안한 표현법의 단점을 개선하는 새로운 표현법을 제안하고 이 표현법을 이용해서 트리(tree)를 만들어 내는 decoding 방법 또한 소개한다. 그리고 제안하는 해 표현법에 맞는 유전 연산자를 찾기 위해 네트워크의 정보 및 부모세대가 지닌 유전 정보를 이용하는 3가지 방법을 실험하였다. 결론적으로, 다양한 실험을 통해서 제안하는 방법이 기존의 방법에 비해 우수한 결과를 보여 준다는 것을 확인할 수 있었다.

• ETRI Journal
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• 제22권1호
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• pp.30-37
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• 2000

Existing tree construction mechanisms are classified into source-based trees and center-based trees. The source-based trees produce a source-rooted tree with a low delay. However, for the applications with multiple senders, the management overheads for routing tables and resource reservations are too high. The center-based trees are easy to implement and manage, but a priori configuration of candidate center nodes is required, and the optimization mature such as tree cost and delay is not considered. In this paper, we propose a new multicast tree building algorithm. The proposal algorithm basically builds a non-center based shared tree. In particular, any center node is not pre-configured. In the purposed algorithm, a multicast node among current tree nodes is suitably assigned to each incoming user: Such a node is selected in a fashion that tree cost and the maximum end-to-end delay on the tree are jointly minimized. The existing and proposed algorithms are compared by experiments. In the simulation results, it is shown that the proposed algorithm approximately provides the cost saving of 30% and the delay saving of 10%, compared to the existing approaches. In conclusion, we see that the cost and delay aspects for multicast trees can be improved at the cost of additional computations.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3219-3236
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• 2012

A tree routing structure is often adopted for many-to-one data gathering and aggregation in sensor networks. For real-time scenarios, considering lossy wireless links, it is an important issue how to construct a maximum-lifetime data gathering tree with delay constraint. In this work, we study the problem of lifetime-preserving and delay-constrained tree construction in unreliable sensor networks. We prove that the problem is NP-complete. A greedy approximation algorithm is proposed. We use expected transmissions count (ETX) as the link quality indicator, as well as a measure of delay. Our algorithm starts from an arbitrary least ETX tree, and iteratively adjusts the hierarchy of the tree to reduce the load on bottleneck nodes by pruning and grafting its sub-tree. The complexity of the proposed algorithm is $O(N^4)$. Finally, extensive simulations are carried out to verify our approach. Simulation results show that our algorithm provides longer lifetime in various situations compared to existing data gathering schemes.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권12호
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• pp.3117-3132
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• 2012

The tree topology in multicast systems has high transmission efficiency, low latency, but poor resilience to node failures. In our work, some nodes are selected as backbone nodes to construct a tree-like core overlay. Backbone nodes are reliable enough and have strong upload capacity as well, which is helpful to overcome the shortcomings of tree topology. The core overlay is organized into a spanning tree while the whole overlay is of mesh-like topology. This paper focuses on improving the performance of the application-layer multicast overlay by optimizing the core overlay which is periodically adjusted with the proposed optimization algorithm. Our approach is to construct the overlay tree based on the out-degree weighted reliability where the reliability of a node is weighted by its upload bandwidth (out-degree). There is no illegal solution during the evolution which ensures the evolution efficiency. Simulation results show that the proposed approach greatly enhances the reliability of the tree-like core overlay systems and achieves shorter delay simultaneously. Its reliability performance is better than the reliability-first algorithm and its delay is very close to that of the degree-first algorithm. The complexity of the proposed algorithm is acceptable for application. Therefore the proposed approach is efficient for the topology optimization of a real multicast overlay.

• JSTS:Journal of Semiconductor Technology and Science
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• 제17권1호
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• pp.86-93
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• 2017

In this paper, we propose a novel defect detection method using component tree representations of scanning electron microscopy (SEM) images. The component tree contains rich information about the topological structure of images such as the stiffness of intensity changes, area, and volume of the lobes. This information can be used effectively in detecting suspicious defect areas. A quasi-linear algorithm is available for constructing the component tree and computing these attributes. In this paper, we modify the original component tree algorithm to be suitable for our defect detection application. First, we exclude pixels that are near the ground level during the initial stage of component tree construction. Next, we detect significant lobes based on multiple attributes and edge information. Our experiments performed with actual SEM wafer images show promising results. For a $1000{\times}1000$ image, the proposed algorithm performed the whole process in 1.36 seconds.

• 융합신호처리학회논문지
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• 제11권1호
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• pp.19-25
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• 2010

본 논문에서는 쿼드트리 알고리즘을 이용한 디지털 워터마킹의 성능평가를 수행하였다. 제안한 알고리즘은 웨이블렛 영역에서 퀴드트리 알고리즘을 이용하여 워터마크의 중요계수를 선택하였고, Cox의 알고리즘을 이용하여 워터마크를 삽입하였다. 제안한 알고리즘의 성능 평가를 위한 시뮬레이션은 웨이블렛 영역에서 쿼드트리 알고리즘의 효과, DWT 변환 레벨과 대역(HH, LH, HL)에 따른 워터마킹 효과, 그리고 최저주파수 대역(LL)의 워터마킹 효과에 대하여 수행하였다. 시뮬레이션 결과에서 퀴드트리 알고리즘을 이용한 워터마킹은 고정된 대역의 중요계수에 워터마크를 삽입한 방법과 비교하여 향상된 결과를 보였고, 6 레벨 DWT에서 HH, HL LH 대역에 동시에 워터마크를 삽입하였을 경우에 가장 좋은 결과를 보였다. 또한, 전체 워터마크 중 30~60%를 LL 대역에 삽입하였을 경우에 PSNR 성능은 1~3dB 정도 떨어지나 추출한 워터마크의 상관도 값은 향상된 결과를 보였다.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.889-898
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• 2013

The shortest-path searching algorithm must not only find a global solution to the destination, but also solve a turn penalty problem (TPP) in an urban road transportation network (URTN). Although the Dijkstra algorithm (DA) as a representative node-based algorithm secures a global solution to the shortest path search (SPS) in the URTN by visiting all the possible paths to the destination, the DA does not solve the TPP and the slow execution speed problem (SEP) because it must search for the temporary minimum cost node. Potts and Oliver solved the TPP by modifying the visiting unit from a node to the link type of a tree-building algorithm like the DA. The Multi Tree Building Algorithm (MTBA), classified as a representative Link Based Algorithm (LBA), does not extricate the SEP because the MTBA must search many of the origin and destination links as well as the candidate links in order to find the SPS. In this paper, we propose a new Link-Based Single Tree Building Algorithm in order to reduce the SEP of the MTBA by applying the breaking rule to the LBA and also prove its usefulness by comparing the proposed with other algorithms such as the node-based DA and the link-based MTBA for the error rates and execution speeds.

• Management Science and Financial Engineering
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• 제20권1호
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• pp.17-19
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• 2014

In this paper, we consider an interesting variant of the inverse minimum traveling salesman problem. Given an instance (G, w) of the minimum traveling salesman problem defined on a metric space, we fix a specified Hamiltonian cycle $HC_0$. The task is then to adjust the edge cost vector w to w' so that the new cost vector w' satisfies the triangle inequality condition and $HC_0$ can be returned by the minimum spanning tree algorithm in the TSP-instance defined with w'. The objective is to minimize the total deviation between the original and the new cost vectors with respect to the $L_1$-norm. We call this problem the inverse metric traveling salesman problem against the minimum spanning tree algorithm and show that it is closely related to the inverse metric spanning tree problem.