• Journal of Korea Spatial Information System Society
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• v.9 no.2
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• pp.13-23
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• 2007

Recently there is growing Interest in LBS(Location Based Service) requiring real-time services and the spatial main memory DBMS for efficient Telematics services. In order to optimize existing disk-based multi-dimensional Indexes of the spatial main memory DBMS in the main memory, multi-dimensional index structures have been proposed, which minimize failures in cache access by reducing the entry size. However, because the reduction of entry size requires compression based on the MBR of the parent node or the removal of redundant MBR, the cost of MBR reconstruction increases in index update and the efficiency of search is lowered in index search. Thus, to reduce the cost of MBR reconstruction, this paper proposed the RSMBR(Relative-Sized MBR) compression technique, which applies the base point of compression differently in case of broad distribution and narrow distribution. In case of broad distribution, compression is made based on the left-bottom point of the extended MBR of the parent node, and in case of narrow distribution, the whole MBR is divided into cells of the same size and compression is made based on the left-bottom point of each cell. In addition, MBR was compressed using a relative coordinate and size to reduce the cost of search in index search. Lastly, we evaluated the performance of the proposed RSMBR compression technique using real data, and proved its superiority.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.9 no.2
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• pp.13-20
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• 2009

Recently there is growing interest in LBS requiring real-time services and the spatial main memory DBMS for efficient Telematics services. In order to optimize existing disk-based spatial indexes of the spatial main memory DBMS in the main memory, spatial index structures have been proposed, which minimize failures in cache access by reducing the entry size. However, because the reduction of entry size requires compression based on the MBR of the parent node or the removal of redundant MBR, the cost of MBR reconstruction increases in index update and the efficiency of search is lowered in index search. Thus, to reduce the cost of MBR reconstruction, this paper proposed the RSMB (relative-sized MBR)compression technique, which applies the base point of compression differently in case of broad distribution and narrow distribution. In case of broad distribution, compression is made based on the left-bottom point of the extended MBR of the parent node, and in case of narrow distribution, the whole MBR is divided into cells of the same size and compression is made based on the left-bottom point of each cell. In addition, MBR was compressed using a relative coordinate and size to reduce the cost of search in index search. Lastly, we evaluated the performance of the proposed RSMBR compression technique using real data, and proved its superiority.

• Journal of the Korea Society of Computer and Information
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• v.11 no.1 s.39
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• pp.97-105
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• 2006

Over the last several years, studies on spatial index have increased in proportion to the increase in the spatial data. Most of these studies, however were on the indices based on R-tree by adding or changing some options, and there are a few studies on how to increase the search performance of the spatial data by compressing an MBR. This study was conducted in order to propose a new MBR compression scheme, SA(Semi-Approximation). The basic idea of this paper is the compression of MBRs in a spatial index. Since SA decreases the keys of MBRs, the enlargements of QMBR in half and increases the utilization of nodes, the SA heightens the overall search performance. The study analyzes mathematically the number of node accesses in a 2D space and evaluates the performance of the SA using the real data on location information. The results show that the proposed scheme has increased performance, higher than that of the pre-established schemes on compression of MBR.

• Spatial Information Research
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• v.10 no.1
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• pp.61-76
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• 2002

Mobile map services using PDA are prevailing because of the rapid developments of techniques of the internet and handhold devices recently. While the volume of spatial data is tremendous and the spatial operations are time-intensive, the PDA has small size memory and a low performance processor. Therefore, the spatial index for PDA should be small size and efficiently filter out the candidate objects of spatial operation as well. This paper proposes a spatial index far PDA called MHF(Multilevel Hashing File). The MHF has simple structure for storage efficiency and uses a hashing technique, which is direct search method, for search efficiency. This paper also designs a compression technique for MBR. which occupies almost 80% of index data in the two dimensional case. We call it HMBR. Although the HMBR technique reduces the MB\ulcorner size to almost a third, it shows good filtering efficiency because of no information loss by quantization in case of small objects that occupy a major portion. Our experimental tests show that the proposed MHF index using HMBR technique is appropriate for PDA in terms of the size of index, the Number of MBR comparisons, the filtering efficiency and the execution time of spatial operations.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.52-54
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• 2004

이동객체의 위치 정보는 데이터의 양이 방대하고, 객체의 위치가 변경될 매마다 계속적인 갱신연산이 요구되어진다. 이러한 갱신 연산에서 디스크 접근비용을 최소화하기 위해 최근 Lazy Update R-tree(LUR-tree)가 제안되었다. 그러나 디스크 기반의 색인은 검색 및 갱신 연산의 실시간 처리를 보장할 수 없기 때문에 메인 메모리에서 이동객체의 위치 정보를 유지하는 것이 필요하다. 본 논문에서는 디스크 기반의 LUR-tree를 MBR 압축을 통해 캐시에 최적화되도록 변형한 색인기법을 제안한다. MBR 압축기법은 부모 노드로의 상대적 위치로 표현된 엔트리의 MBR을 변환함수를 통해 2,4,8 바이트의 정수로 변환한다. 제안된 색인은 변환된 MBR의 크기에 따라 엔트리를 동적 할당함으로써, 상위노드에서는 키 비교 회수를 줄이고, 단말 노드로 갈수록 키 비교 횟수는 늘어나지만, 캐시 미스를 줄일 수 있다는 장점으로 인해 검색 및 갱신 성능을 전체적으로 향상시킨다

• Journal of Korea Spatial Information System Society
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• v.11 no.2
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• pp.133-142
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• 2009

Recently, with the advance of wireless internet and the frequent use of mobile devices, demand for LBS(Location Based Service) is increasing, and research is required on spatial indexes for the storage and maintenance of spatial data to provide efficient LBS in mobile device environments. In addition, the use of flash memory as an auxiliary storage device is increasing in order to store large spatial data in a mobile terminal with small storage space. However, the application of existing spatial indexes to flash-memory lowers index performance due to the frequent updates of nodes. To solve this problem, research is being conducted on flash-memory based spatial indexes, but the efficiency of such spatial indexes is lowered by low utilization of buffer and flash-memory space. Accordingly, in order to solve problems in existing flash-memory based spatial indexes, this paper proposed FR-Tree (Flash-Memory based R-Tree) that uses the node compression technique and the delayed write operation technique. The node compression technique of FR-Tree increased the utilization of flash-memory space by compressing MBR(Minimum Bounding Rectangle) of spatial data using relative coordinates and MBR size. And, the delayed write operation technique reduced the number of write operations in flash memory by storing spatial data in the buffer temporarily and reflecting them in flash memory at once instead of reflecting the insert, update and delete of spatial data in flash-memory for each operation. Especially, the utilization of buffer space was enhanced by preventing the redundant storage of the same spatial data in the buffer. Finally, we perform ed various performance evaluations and proved the superiority of FR-Tree to the existing spatial indexes.

• Journal of KIISE:Databases
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• v.31 no.4
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• pp.384-394
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• 2004

Recently, to relieve the performance degradation caused by the bottleneck between CPU and main memory, cache conscious multi-dimensional index structures have been proposed. The ultimate goal of them is to reduce the space for entries so as to widen index trees and minimize the number of cache misses. The existing index structures can be classified into two approaches according to their entry reduction methods. One approach is to compress MBR keys by quantizing coordinate values to the fixed number of bits. The other approach is to store only the sides of minimum bounding regions (MBRs) that are different from their parents partially. In this paper, we propose a new index structure that exploits the properties of the both techniques. Then, we investigate the existing multi-dimensional index structures for main memory database system through experiments under the various work loads. We perform various experiments to show that our approach outperforms others.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.1-3
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• 2003

최근 중앙처리장치와 주기억장치간의 병목 현상에 의한 성능 저하를 극복하기 위해 캐시를 고려한 색인 구조들이 제안되었다. 이런 색인 구조들의 궁극적인 목표는 엔트리 크기를 줄여 팬-아웃(fan-out)을 증가시키고, 캐시 접근 실패를 최소화하여 시스템의 성능을 높이는 것이다. 엔트리의 크기를 줄이는 기법에 따라 기존의 색인 구조들을 두 가지로 구분할 수 있다. 하나는 좌표 값을 고정된 비트로 양자화 함으로써, MBR 키를 압축하는 것이다. 또 다른 하나는 MBR들의 각 좌표 값 중에 그들의 부모 MBR과 같지 않은 좌표 값만을 저장하는 것이다. 본 논문에서는 두 기법의 특성들을 적절히 합한 새로운 색인 구조를 제안하고, 기존에 제시된 두 접근법을 따르는 주기억장치 상주형 다차원 색인 구조를 다양한 환경에서 성능 평가한다. 또한, 기존의 색인 구조와 비교를 통해 제안하는 색인 구조의 우수성을 보인다.

• Membrane Journal
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• v.21 no.4
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• pp.360-366
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• 2011

The effect of cross-flow velocity and transmembrane pressure (TMP) on membrane fouling was observed from pilot-scale operation of thermophilic anaerobic membrane bioreactor (AnMBR) treating food waste leachate. It was found that fouling rate was reduced significantly as cross-flow velocity increased at constant TMP mode of operation while this effectiveness was more pronounced at lower TMP. Higher TMP resulted in less permeable fouling layer possibly due to compressibility of foulant material on membrane surface. Particle sizes of membrane concentrate ranged from 10 to $100{\mu}m$, implying that shear-induced diffusion enhance back transport of these particle sizes away from the membrane effectively. From the continuous operation of AnMBR, it was confirmed that shear rate played an important role in the reduction of membrane fouling. Membrane autopsy works at the end of operation of AnMBR showed clearly that both organic and inorganic fouling were significant on membrane surface. Surface shear by cross-flow velocity was expected to be less effective to remove irreversible fouling which can be mainly caused by the adsorption of organic colloidal materials into membrane pores.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10b
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• pp.73-75
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• 2004

최근에 무선 인터넷과 이동 컴퓨팅 기술이 발전하고, 휴대 전화, PDA와 같은 이동 단말기가 보편화됨에 따라 사용자의 위치 정보를 활용하는 위치 기반 서비스(LBS: Location Based Service)가 다양한 분야에서 제공되고 있다. 모바일 환경에서 위치 기반 서비스를 제공하기 위해서는 모바일 장치에서 대용량의 공간 데이타를 신속하게 처리하고 효과적으로 관리하기 위한 공간 MMDBMS(Main Memory Database Management System)가 필요하다. 이에 본 논문에서는 기존의 PC용 MMDBMS인 HSQLDB를 확장하여 모바일 장치에서 공간 데이타를 효율적으로 관리할 수 있는 공간 MMDBMS를 설계 및 구현하였다. 공간 MMDBMS는 OGC의 공간 데이타 모델을 따르며, 공간 데이타 특성에 적합한 압축 기법인 산술 코딩 기법을 제공하고, 모바일 장치에 적합한 MBR 압축 및 해슁 기법을 이용한 공간 인덱스를 지원한다. 그리고, 모바일 장치의 낮은 성능의 프로세서에서 공간 데이타 디스플레이 기능을 제공하고, 모바일 장치와 디스크 기반 GIS인 ZEUS 사이에서 공간 데이타 import/export의 성능 향상을 위한 데이타 캐쉬 기능을 지원한다.