• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.3B
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• pp.305-313
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• 2004

Group multicast refers to the kind of multicast in which every member of a group is allowed to transmit data to the group. The goal of routing algorithms for group multicast is to construct a set of low cost multicast trees including all the group members with QoS (e.g., bandwidth) constraint. There have been several algorithms proposed: source tree and shared tree approaches. However, the latter approach has a low success rate in constructing a shared multicast tree, and the former approach suffers from high control overhead and low scalability as stoup size increases. In this paper, we present a heuristic algorithm which varies the number of multicast trees according to the network load. The simulation results show not only that our algorithm outperforms the shared tree approach in terms of the success rate, but also that it has lower control overhead than the source tree approach while guaranteeing the same success rate.

• Journal of KIISE:Databases
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• v.32 no.3
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• pp.285-296
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• 2005

In mobile distributed systems the data on the air can be accessed by a lot of mobile clients. And, we need an indexing scheme in order to energy-efficiently access the data on the wireless broadcast stream. In conventional indexing schemes, they use the values of primary key attributes and construct tree-structured index. Therefore, the conventional indexing schemes do not support content-based retrieval queries such as partial-match queries. In this paper we propose an indexing scheme, called B2V-Tree, which supports partial match queries on wireless broadcast data stream. For this purpose, we construct a tree-structured index which is composed of bit-vectors, where the bit-vectors are generated from data records through multi-attribute hashing.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.36 no.4B
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• pp.346-353
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• 2011

Routing schemes that service applications with various delay times, maintaining the long network life time are required in wireless sensor & actor networks. However, it is known that network lifetime and hop count of trees used in routing methods have the tradeoff between them. In this paper, we propose a Pareto Ant Colony Optimization algorithm to find the Pareto tree set such that it optimizes these both tradeoff objectives. As it enables applications which have different delay times to select appropriate routing trees, not only satisfies the requirements of various multiple applications but also guarantees long network lifetime. We show that the Pareto tree set found by proposed algorithm consists of trees that are closer to the Pareto optimal points in terms of hop count and network lifetime than minimum spanning tree which is a representative routing tree.

• Journal of Advanced Navigation Technology
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• v.20 no.6
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• pp.625-630
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• 2016

Recently, various types of image contents are being produced, and interest in copyright protection technology is increasing. In this paper, we propose an image encryption technology for color images. This technique divides the image into RGB color components and then performs quad-tree decomposition based on the edge of image. After the quad-tree partitioning, encryption is performed on the selected blocks. Encryption is performed on color components to measure encryption efficiency, and encryption efficiency is measured even after reconstitution into a color image. The encryption efficiency uses a visual measurement method and an objective image quality evaluation method. The PSNR values were measured as 7~10 dB for color difference components and 16~19 dB for color images. The proposed image encryption technology will be used to protect copyright of various digital image contents in the future.

• Proceedings of the Korea Multimedia Society Conference
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• 2003.11a
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• pp.388-391
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• 2003

대규모의 대용량 파일 시스템에서 전통적인 파일 시스템인 UNIK와 같은 디렉토리 구조를 갖게 되면, 파일 탐색 시 순차 검색으로 인해 많은 시간이 걸리게 된다. 이러한 문제를 해결하고자, 본 논문에서는 파일의 수를 고려하여 파일의 수가 적을 때는 inode 블록에 디렉토리 엔트리를 함께 저장하고, 파일의 수가 많아져 inode 블록에서 오버플로우가 발생하면 선형 해싱(Linear Hashing)을 이용하여 디렉토리 엔트리를 저장하고자 한다 선형 해싱 디렉토리 구조의 설계 및 구현에 대해서 설명하고, 일반적으로 대용량 파일 시스템에서 많이 사용되는 B+ 트리 디렉토리 구조와 성능을 비교 분석한다.

• The KIPS Transactions:PartB
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• v.9B no.6
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• pp.827-834
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• 2002

In this paper, we proposed the formation of Korean-Roman alphabet notation conversion table for the generation of Korean-Roman alphabet notation that also meets revised Roman alphabet notation. Introduced a mathematical analyzing method of the natural language which used a petrinet model so that a base of Roman alphabet notation analyzed standard pronunciation and Roman alphabet notation to work mathematically. It display the practical example through a petrinet modeling of a plan and Roman alphabet notation to create a Korean Roman alphabet notation conversion table with the method of the analysis that used a petrinet model, and present a mathematical modeling plan and application method of Korean. We developed application program based on window in order to verify a created Korean-Roman alphabet notation conversion table, and compared the result of an application program with Roman alphabet notation of an Roman alphabet notation example dictionary.

• Proceedings of the Korea Information Processing Society Conference
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• 2006.11a
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• pp.345-348
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• 2006

경로 질의는 XML에서 가장 일반적으로 사용되는 질의이며, 기존에 경로 질의를 효율적으로 처리하기 위한 다양한 색인 기법들이 연구되었다. 최근에는 suffix 트리를 사용하는 구조 조인 기법들이 제안되어 경로 질의 성능을 향상시키고 있다. ViST는 가장 대표적인 구조 조인 기법으로 XML 문서에 대한 검색 시간을 줄이기 위해 suffix 트리와 $B^{+)$ 트리를 사용한다. 하지만, ViST는 suffix 트리에 최적화 되지 못한 번호 부여 기법을 사용함으로써, 질의 처리 시 불필요한 조인과 디스크 접근이 야기된다. 이와 같은 문제들은 경로 질의 성능을 급격히 감소시킨다. 따라서 본 논문에서는 ViST의 문제들을 해결하기 위한 새로운 색인 구조를 제안하다. 제안하는 색인 구조는 suffix 트리를 사용하는 구조 조인 기법의 성능을 향상시키기 위해서 최적화된 번호 부여 기법과 상향식 질외 처리 기법을 사용한다. 본 논문의 성능 평가에서는 제안하는 색인 구조를 ViST와 비교하여, 제안하는 색인 구조가 와일드-카드('$^{\ast}$와 '//')를 포함하는 다양한 단일 경로 질의와 분기 질의에 대해 향상된 성능을 나타냄을 보인다.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10a
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• pp.263-266
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• 2001

인터넷 상의 문서양이 기하급수적으로 증가하면서 검색엔진의 성능평가가 대두되고 있다. 이를 위해 검색엔진 인덱스 모듈부분의 좋은 성능이 요구되는데 빠른 대용량 역파일 구성을 위한 알고리즘을 사용하게 되면 인덱스 속도를 향상시킬 수 있다. 그러나, 병렬처리가 되지 않는 문헌벡터화일 제작시 트리검색 모듈에서 병목 현상이 발생하게 된다. 본 논문에서는 병목현상이 발생하는 트리를 병렬로 접근함으로써 시스템의 병목현상을 해소하고 인덱스 시스템의 전체적인 성능을 개선찬 수 있는 방안을 연구한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.11B
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• pp.991-1000
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• 2004

This paper presents an application layer multicast tree constructing algorithm to minimize the average time delay from the sender to end-systems for the effective real-time media delivery. Simultaneously, the proposed algorithm takes into account the computing power and the network condition of each end-system as a control variable and thus avoids the undesirable case that loads are concentrated to only several end-systems. The multicast tree is constructed by clustering technique and modified Dijkstra's algorithm in two steps, i.e. tree among proxy-senders and tree in each cluster. By the experimental results, we show that the proposed algorithm can provide an effective solution.

• Korean Journal of Crystallography
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• v.5 no.1
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• pp.14-19
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• 1994

Tlifluoromethyltriphenyl-1,2,4-tioxolane(C2IHlsF303)is triclinic, space group P1 with a=10.477(1), b= 11.056(1), c=9.917(3) A, a=104.7(1), B=122.7(1), r=63.9(1), Z=2, V=867.9(3) A3, Dc=1.43 g/cm3, λ(Mo Ka)=0.71069 A, μ=0.0116 cm-1,F(000)=384, and R=0.067 for 1713 unique observed reflections with I > 1.0 o(I). The structure was solved by direct methods and refined by fall-matrix least-squares refinement with the fixed C-H bond lengths at 0.96 A. Two phenyl rings((2) and (3)) that have the dihydral angle of 106.0°.