• Journal of KIISE:Databases
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• v.37 no.1
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• pp.50-55
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• 2010

Duplicate documents in blog service system are one of causes that deteriorate both of the quality and the performance of blog searches. Unlike the WWW environment, the creation of documents is reported every time in blog service system, which makes it possible to identify the original document from its duplicate documents. Based on this observation, this paper proposes a novel method for detecting duplication documents in blog service system. This method determines whether a document is original or not at the time it is stored in the blog service system. As a result, it solves the problem of duplicate documents retrieved in the search result by keeping those documents from being stored in the index for the blog search engine. This paper also proposes three indexing methods that preserve an accuracy of previous work, Min-hashing. We show most effective indexing method via extensive experiments using real-life blog data.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.37 no.9
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• pp.11-23
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• 2000

Multicarrier DS-CDMA is an effective approach to realize wideband CDMA system in a multipath fading channel. In this paper, we propose a convolutionally-coded overlapped multicarrier DS-CDMA system, and analyze the performance with subband overlapping variation to determine the overlapping percentage showing best performance. Given a total number of subcarriers M*R, we will show that the BER variation is highly dependent on the rolloff factor P of raised-cosine chip wave-shaping filter irrespective of convolutional encoding rate I/M and repetition coding rate 1/R. We also analyze the possibility of reduction in total MUI by considering both variation of a rolloff factor (0 ($\beta$ :1) and variation of subband overlapping factor (0 ( A :2), and show that the proposed system may outperform the multicarrier DS-CDMA system in [1, 12].

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.334-340
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• 2017

Reliability is considered a particularly important design factor for systems that have critical results once a failure occurs in a system, such as trains, airplanes, and passenger ships. The reliability of the system can be improved in several ways, but in a system that requires considerable reliability, the redundancy of parts is efficient in improving the system reliability. In the case of duplicating parts to improve reliability, the kind of parts and the number of duplicating parts should be determined under the system reliability, part costs, and resources. This study examined the redundancy allocation of multi-level systems with serial structures. This paper describes the definition of a multi-system and how to optimize the kind of parts and number of duplications to maximize the system reliability. To optimize the redundancy, the cuckoo search algorithm was applied. The search procedure, the solution representation and the development of the neighborhood solution were proposed to optimize the redundancy allocation of a multi-level system. The results of numerical experiments were compared with the genetic algorithm and cuckoo search algorithm.

• Journal of the Korea Society of Computer and Information
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• v.14 no.5
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• pp.37-44
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• 2009

Recently, as the quality of multimedia data gets higher, multimedia servers require larger storage capacity and higher I/O bandwidth. In these large scale multimedia servers, the load-unbalance problem among disks due to the difference in access frequencies to multimedia objects according to their popularities significantly affects the system performance. To address this problem, many data replication schemes have been proposed. In this paper, we propose a novel data migration/replication scheme to provide better storage efficiency and performance than the dynamic data replication scheme which is typical data replication scheme employed in multimedia servers. This scheme can reduce the additional storage space required for replication, which is a major defect of replication schemes, by decreasing the number of copies per object. The scheme can also increase the number of concurrent users by increasing the caching effect due to the reduced lengths of the intervals among requests for each object.

• Proceedings of the Korean Information Science Society Conference
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• 2005.11a
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• pp.334-336
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• 2005

이동적응망(MANET: Mobile Ad-hoc Network)은 네트워크 하부 구조를 필요로 하지 않은 무선 단말들로 구성된 네트워크이다. 이러한 특성은 네트워크 단절 가능성을 높게 하기 때문에 이동단말들의 데이터 액세스률이 낮아지게 된다는 문제점을 갖는다. 이를 해결하기 위하여 이동 노드들은 데이터의 중복사본을 갖는다. 이동 노드가 갖는 중복사본은 데이터 일관성을 유지하기 위하여 별도의 중복관리 기법이 필요하다. 하지만 MANET을 구성하는 이동 노드들은 일반적으로 제한된 전력을 가지고 있고 단절될 가능성이 높기 때문에 중복 사본의 일관성 보장은 어려운 문제로 지적되고 있다. 기존에 제안된 MANET에서의 데이터 중복관리 기법은 데이터 액세스 빈도수를 계산하여 액세스률을 높이는 방법에 주안점을 두고 있고 갱신 데이터의 일관성 보장은 그 어려움 때문에 주로 판독 연산만 고려하였다. 갱신 트랜잭션을 지원하는 경우 대부분 높은 통신비용을 이유로 데이터 일관성을 보장하지 않는다. 또한 이동 노드가 다수의 서버를 통해서 갱신 연산을 실행하기 때문에 통신 오버헤드로 인하여 전력소모가 크다. 본 논문에서는 주사본 노드를 통하여 갱신을 가능하게 함으로써 데이터 일관성을 유지할 수 있는 데이터 중복 기법을 제안한다. 제안된 기법은 이동 노드들의 에너지 특성을 고려하여 더 않은 에너지를 가진 노드에게 갱신 전파 및 일관성 유지를 의뢰함으로써 상대적으로 낮은 에너지를 갖는 이동 노드의 에너지 효율을 고려하였다.

• The Korean Journal of Mycology
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• v.22 no.4
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• pp.355-365
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• 1994

An extensive ssurvey was conducted on the occurrence of hyperparasites (HP) on powdery milew species in Korea during $1991{\sim}1994$ seasons. As a result, a total of 1070 materials infected with powdery mildew fungi were collected. Of these, 92 ones were infected with the HP; 6 with the unidentified HP and the rest 86 with Ampelomyces quisqualis. This showed infection of powdery mildew species with HP was common phenomenon in nature and A. quisqualis was the most common HP in Korea. To prove the hyperparasitism of A. quisqualis, 24 isolates from 32 collections in 1992 year were successfully cultured. All isolates tested were hyperparasitic to cucumber powdery mildew, Sphaerotheca fusca.

• Journal of KIISE
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• v.43 no.2
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• pp.143-151
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• 2016

Data deduplication is an important technique for cloud storage savings. These techniques are especially important for encrypted data because data deduplication over plaintext is basically vulnerable for data confidentiality. We examined encrypted data deduplication with the aid of a key issuing server and compared Convergent Encryption with a technique created by M.Bellare et al. In addition, we implemented this technique over not only Dropbox but also an open cloud storage service, Openstack Swift. We measured the performance for this technique over Dropbox and Openstack Swift. According to our results, we verified that the encrypted data deduplication technique with the aid of a key issuing server is a feasible and versatile method.

• The KIPS Transactions:PartB
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• v.12B no.2 s.98
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• pp.215-222
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• 2005

In this paper, a MetaSearch algorithm for navigational queries is presented. Previous MetaSearch algorithms focused on informational queries. They Eave a high score to an overlapped document. However, the overemphasis of overlapped documents may degrade the performance of a MetaSearch algerian for a navigational query. However, if a lot of result documents are from a certain domain or a directory, then we can assume the importance of the domain or directory. Various experiments are conducted to show the effectiveness of overlap of a domain and directory names. System results from TREC and commercial search engines are used for experiments. From the results of experiments, the overlap of documents showed the better performance for informational queries. However, the overlap of domain names and directory names showed the $10\%$ higher performance for navigational queries.

• Proceedings of the Korea Information Processing Society Conference
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• 2011.11a
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• pp.185-187
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• 2011

전통적인 가상화 기술들은 하나의 물리 머신에서 서로 다른 운영체제들을 동작시키기 위해 여러 개의 가상 머신을 제공하고 있다. 이러한 가상화 기술들은 운영체제를 소스 수정없이, 혹은 약간의 수정만으로 물리 머신에서 동작하는 것과 동일한 방식으로 동작할 수 있도록 지원하기 때문에 호스트와 게스트 간의 깊은 시멘틱 갭을 발생시킨다. 이러한 시멘틱 갭은 여러 컴퓨팅 자원에 대한 공간 중복과 접근 중복의 중요한 원인이 되고, 이러한 자원 중복은 대규모 가상화 시스템의 확장성에 제약한다. 이러한 자원 중복을 제거하기 위해 컨텐츠 기반 페이지 공유 등 다양한 연구들이 진행되어 왔지만 운영체제 수정없이 지원하는 정책으로 인한 시멘틱 갭은 여전히 제안 기법들을 제한하게 된다. 이에 우리들은 운영체제의 자원 관리 부분을 수정하여 근본적인 시멘틱 갭을 제거함으로써 메모리와 스토리지의 공간 및 접근 중복성을 제거할 수 있는 파일시스템을 제안하였다. 그리고 실험을 통해 기존의 가상 블록 장치를 사용하는 파일시스템과 비교 및 평가하여 제안 시스템이 페이지 캐시 공유 및 스토리지 접근 중복 제거에 효과적임을 입증하였다.

• Journal of Chest Surgery
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• v.33 no.11
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• pp.925-928
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• 2000

식도 중복증은 매우 희귀한 식도의 양성종양으로 증상 발현도 매우 드문 질병이다. 이 질병은 태생 6주에 소화기 내강이 상피세표의 증식으로 막히게 되고 세포벽에 공포가 생겨 점차 합쳐 장의 긴축을 따라서 길게 배열되는 과정에서, 공포가 독립적으로 나타나 다른 내강을 형성하여 발생한다. 본원 흉부 외과에서는 식도 내강으로 천공된, 식도중부 및 하부에 걸쳐 발생한 관상의 식도 중복증을 치험하였기에 문헌 고찰과 더불어 보고하는 바이다.