• KSII Transactions on Internet and Information Systems (TIIS)
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• v.9 no.7
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• pp.2599-2613
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• 2015

Multi-index hashing (MIH) is the state-of-the-art method for indexing binary codes, as it di-vides long codes into substrings and builds multiple hash tables. However, MIH is based on the dataset codes uniform distribution assumption, and will lose efficiency in dealing with non-uniformly distributed codes. Besides, there are lots of results sharing the same Hamming distance to a query, which makes the distance measure ambiguous. In this paper, we propose a data-oriented multi-index hashing method (DOMIH). We first compute the covariance ma-trix of bits and learn adaptive projection vector for each binary substring. Instead of using substrings as direct indices into hash tables, we project them with corresponding projection vectors to generate new indices. With adaptive projection, the indices in each hash table are near uniformly distributed. Then with covariance matrix, we propose a ranking method for the binary codes. By assigning different bit-level weights to different bits, the returned bina-ry codes are ranked at a finer-grained binary code level. Experiments conducted on reference large scale datasets show that compared to MIH the time performance of DOMIH can be improved by 36.9%-87.4%, and the search accuracy can be improved by 22.2%. To pinpoint the potential of DOMIH, we further use near-duplicate image retrieval as examples to show the applications and the good performance of our method.

• Journal of Korea Multimedia Society
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• v.13 no.10
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• pp.1534-1546
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• 2010

In sensor network systems, various hierarchical clustering schemes have been proposed in order to efficiently maintain the energy consumption of sensor nodes. Most of these schemes, however, are hardly applicable in practice since these schemes might produce unbalanced clusters or randomly distributed clusters without taking into account of the distribution of sensor nodes. To overcome the limitations of such hierarchical clustering schemes, we propose a novel scheme called CSM(Clustering using Split & Merge algorithm), which exploits node split and merge algorithm of tree-based indexing structures to efficiently construct clusters. Our extensive performance studies show that the CSM constructs highly balanced clustering in a energy efficient way and achieves higher performance up to 1.6 times than the previous clustering schemes, under various operational conditions.

• Journal of Digital Contents Society
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• v.15 no.4
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• pp.527-532
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• 2014

Recently, due to the proliferation of mobile smart devices, the inovation of bigdata, which analyzes and processes massive data collected from various sensors implaned in smart devices, expands to LBSs. Many location prediction techniques for moving objects have been studied in literature. However, as the majority of studies perform location prediction which depends on specific applications, they hardly reflect the technical requirements of next-generation spatio-temporal information services. Therefore, this paper proposes the design of general-purpose distributed moving object prediction query processing framework that is capable of performing primitive and various types of queries effectively based on massive spatio-temporal data of moving objects in real-world space networks.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.7
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• pp.718-722
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• 2008

Ontology plays an important role of the Semantic Web to describe meaning and reasoning of resources. Ontology has more rich expressive power through OWL that is a next standard representation language recommended by W3C. As the Semantic Web is widely known, an amount of information resources on the Web is growing rapidly and the related information resources are placed in distributed systems on the Web. So, for providing seamless services without the awareness of far distance, efficient management of the distributed information resources is required. Especially, sear ching fast for local repositories that include data related to user's queries is important to the performance of systems in the distributed environment. In this paper, first, we propose an index structure to search local repositories related to queries in the distributed Semantic Web. Second, we propose a query rewriting strategy to extend given user's query using various expression of OWL. Through the proposed index and query strategy, we can utilize various expressions of OWL and find local repositories related to all query patterns on the Semantic Web.

• Journal of KIISE
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• v.42 no.12
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• pp.1474-1479
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• 2015

With mobile devices showing marked improvement in performance in the age of the Internet of Things (IoT), there is demand for rapid processing of the extensive amount of multimedia big data. However, because research on image searching is focused mainly on increasing accuracy despite environmental changes, the development of fast processing of high-resolution multimedia data queries is slow and inefficient. Hence, we suggest a new distributed image search algorithm that ensures both high accuracy and rapid response by using feature extraction of distributed images based on MapReduce, and solves the problem of memory scalability based on BIRCH indexing. In addition, we conducted an experiment on the accuracy, processing time, and scalability of this algorithm to confirm its excellent performance.

• Journal of KIISE:Computer Systems and Theory
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• v.29 no.10
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• pp.582-588
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• 2002

Scalable displays generate large and high resolution images and provide an immersive environment. Recently, scalable displays are built on the networked clusters of PCs, each of which has a fast graphics accelerator, memory, CPU, and storage. However, the distributed rendering on clusters is a network bound work because of limited network bandwidth. In this paper, we present a new algorithm for reducing the network bandwidth and implement it with a conventional distributed rendering system. This paper describes the algorithm called geometry tracking that avoids the redundant geometry transmission by indexing geometry data. The experimental results show that our algorithm reduces the network bandwidth up to 42%.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10c
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• pp.45-50
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• 2006

정보의 단순한 연결뿐만 아니라 의미적인 연결 관계를 표현하는 시맨틱 웹에서 RDF와 RDFS만으로는 정보간의 다양한 의미적 관계를 나타내기가 힘들다. 따라서 정보간의 의미적 관계를 보다 명확하게 필요로 하는 분산 환경에서는 시맨틱 웹 언어의 표준으로 인식되고 있는 OWL로 표현된 시맨틱 웹 데이터를 위한 저장 구조가 필요하다. 따라서 본 논문에서는 분산 환경을 고려하여 OWL이 표현하는 다양한 의미적 관계를 이용한 질의 처리를 지원하는 저장 구조를 제안한다. 그리고 OWL에 정의된 클래스 간의 계층 관계를 이용한 질의의 효율적인 처리를 위한 인덱스 구조와 처리 전략을 제안한다.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06a
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• pp.29-32
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• 2011

최근 GPS를 탑재한 스마트 기기의 보급으로 인해 사용자의 위치 정보를 이용한 위치기반서비스(LBS)가 많은 관심 속에 급속도로 성장하고 있다. 대부분의 위치기반서비스는 사용자의 위치를 바탕으로 주변의 유용한 정보를 제공하고 있으며 이러한 사용자 주변의 유용한 정보를 효율적으로 검색하기 위해서는 공간 데이터에 대한 색인 기법이 필요하다. 그러나 기존 공간 색인은 대부분 중앙 집중식 환경에서 연구가 진행되었고 분산 스토리지 환경에 대한 연구는 미흡하다. 따라서 본 연구는 서비스 성장과 더불어 서비스 영역이 확대됨에 따른 대용량 공간 데이터 환경에서 효율적인 공간 데이터 검색을 지원하는 그리드 기반 분산 색인 기법을 제안한다.

• Proceedings of the KIEE Conference
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• 1987.07b
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• pp.1540-1542
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• 1987

This paper describes a special-purpose schematic editor program which is appropriate for Top-Down methodology of hierarchical logic design. The data structure which has capability to be shared with multi-level logic simulator is developed. For the purpose of efficient search, a new indexing method is designed. That is exponentially distributed one dimentional bin based on probability of presence of graphic elements.

• Journal of the Korea Computer Industry Society
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• v.5 no.2
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• pp.293-300
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• 2004

In this paper, we devise both methods supporting interactive VCR-like functions for MPEG stream and minimizing the storage space. Specifically, we proposed both methods to efficiently stripe MPEG stream into multiple disks, and an access strategy to retrieve the distributed streams over the disks. To accurately locate the streams to be referred to, we introduce a table indexing the location. When client request Fast Forward(FF)/Fast Backward(FB), VOD(Video on Demand) server refer to this index table supporting FF/FB functions. Experimental result shows that the proposed method can reduce the additional storage space needed when VOD server services FF/FB functions.