• Journal of KIISE:Databases
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• v.28 no.1
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• pp.42-47
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• 2001

실체뷰는 대량의 데이터웨어하우스에서 질의처리를 효과적으로 수행하기위한 대안으로서, 그 핵심은 각 데이터 원천에서의 데이터변화에 대응한 복합적인 뷰의 효과적인 관리 문제이다. 본 연구에서는 우선 실체뷰 관리에 관한 기존의 연구들을 일별함에 있어서 즉, 갱신의 주체문제, 갱신객체, 및 갱신시간 문제의 세가지 관점에서 본 연구의 위치를 결정한 다음, 대수적 접근법으로 복합뷰 갱신문제가 복잡해지는 원인을 규명하였다. 그 해법으로서 참조무결성을 활용한 복합 조인뷰의 갱신 알고리즘을 제안하면서, 여러 가지 참조무결성 제약조건과 트랜잭션과 관련된 자체갱신적 새로운 해법을 제시했다.

• Journal of KIISE:Software and Applications
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• v.32 no.7
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• pp.612-624
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• 2005

In this paper, we propose a surface-based registration using a gaussian weighted distance map for PET-CT brain image fusion. Our method is composed of three main steps: the extraction of feature points, the generation of gaussian weighted distance map, and the measure of similarities based on weight. First, we segment head using the inverse region growing and remove noise segmented with head using region growing-based labeling in PET and CT images, respectively. And then, we extract the feature points of the head using sharpening filter. Second, a gaussian weighted distance map is generated from the feature points in CT images. Thus it leads feature points to robustly converge on the optimal location in a large geometrical displacement. Third, weight-based cross-correlation searches for the optimal location using a gaussian weighted distance map of CT images corresponding to the feature points extracted from PET images. In our experiment, we generate software phantom dataset for evaluating accuracy and robustness of our method, and use clinical dataset for computation time and visual inspection. The accuracy test is performed by evaluating root-mean-square-error using arbitrary transformed software phantom dataset. The robustness test is evaluated whether weight-based cross-correlation achieves maximum at optimal location in software phantom dataset with a large geometrical displacement and noise. Experimental results showed that our method gives more accuracy and robust convergence than the conventional surface-based registration.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.12 no.1
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• pp.53-59
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• 1994

The purpose of this paper is to use geo-spatial information system for effective operation and management of the underground facilities. The subject area is selected and collected all of the drawing in order to get the coordinate points(tic), which become the standard of the subject area and that can be gotten by way of practising control surveying from a existing triangulation station spatial information and attribute information are classificated from obtained data. Also, after giving the code in the attribute information to make it data-based, connecting spatial information with the attribute information to overlap layer each other, and compared the positional accuracy of the data. From the results of this study, conclusions are acquired as follows; 1) To construct the Database of the spatial and attribute data, which contain all kinds of drawings in underground structures, the reservation of registers and the details of changes and so on, results in easily referencing, compiling and analyzing the reserved data in system as their own purposes. 2) It is expected that we can effectively operate and manage the situation among the underground facilities so accurately that we may obviate the safety accidents or the damages of life and property.

• 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.

• Proceedings of the Korea Database Society Conference
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• 2001.06a
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• pp.388-391
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• 2001

정보통신의 발달과 인터넷의 확산으로 정보에 대한 사용자의 욕구가 다양해졌다. 최근에는 인물을 중심으로 검색을 제공하는 웹(Web)사이트들이 등장하고 있다. 이러한 웹사이트들을 살펴보면 텍스트 위주의 서비스를 제공하거나 Hyper Link를 이용한 검색 시스템을 사용하고 있다. 특히 사이버 족보들은 단순히 자신의 위치만 검색이 가능하고 자신의 형제, 부모, 자식의 위치를 검색하기에는 불가능하다. 또한 대부분의 사이버 족보에서는 조상들의 유물이나 유적에 대하여 이미지와 부연 설명만을 제공하고 있어 후손들에게 많은 정보를 제공하고 있지 못한 실정이다. 본 논문에서는 트리 알고리즘을 도입하여 사이버 족보를 설계해 보았다. 사이버 족보 내에서 자신만이 아니라 부모, 형제, 그리고 본인의 자식까지 검색이 가능한 알고리즘을 설계하였으며 조상들의 유물과 유적에 대하여 검색이 가능하도록 설계하였다.

• Spatial Information Research
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• v.2 no.1
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• pp.93-101
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• 1994

A river space means the river related environments such as rIver and floodplain. Because river space data include two-dimensional and three¬dimensional characters. geographic informat ion system is an effect ive tool to manage the data. The objective of this study is to construct the pilot system called RSDB '93 and to simulate the system in practical aspects. The local area for the study was limited about 12km from Jamsil cheolgyo to Dongjak daegyo of the Han River. PC ARC/INFO was selected which can be used on PC 386DX. The Graphic data in an establ ished database contain river layer. floodplain layer. road layer. profile site and hydraulic structure site8 layer. Attributes include water prof i Ie. ut i I i ty status. ecological data. landmark data. hyd¬rology data. water quality data. aerial photo and other photos. RSDB '93 is a system presenting the potentials for the effective river space management which can be applied to all the domestic rivers.

• Journal of KIISE:Databases
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• v.37 no.1
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• pp.22-32
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• 2010

Location-based services have been expanded rapidly in local and overseas markets due to technological advances and increasing applications of wireless internet. Various researches have been made to manage efficiently the location information of moving objects. A basic location-based alert service provides alerting messages automatically when either entering or leaving a specific location and it is expected to become one of the most important location-based services. Location-based alert services require a location polling method to acquire current locations for a large number of moving objects. However, a simple periodical location polling method causes severe system overload because a system should keep updating location information of the moving objects ceaselessly. Most location polling algorithms for location-based alerting services are not suitable for mobile users with dynamic and unsteady moving patterns. In this paper, we propose an improved location polling algorithm for location-based alerting services to reduce the amount of location information acquisition and therefore, to decrease the system load. Various experiments show that the proposed algorithm outperforms other algorithms.

• Journal of KIISE:Computing Practices and Letters
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• v.14 no.3
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• pp.266-270
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• 2008

Bluetooth technology provides a way to connect and exchange information between personal devices over a secure and short-range radio frequency without any authentication infrastructures. For this infrastructure-less feature, Bluetooth has several problems which could not occur in other network, and among them location tracking attacks is essential problem which should be solved. In this paper, we introduce the location tracking attack and propose an anonymous connection protocol against it. We also perform security analysis based on possible scenarios of this attack, and estimate both execution time and memory spaces of our scheme and existing methods.

• Journal of KIISE:Information Networking
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• v.34 no.5
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• pp.328-339
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• 2007

Conventional topology-based routing protocols are not suitable for inter-vehicular communication, where frequent route updates are necessary due to continuous and abrupt changes in network topology Position-based routing protocols are widely accepted to better serve their purpose in such a scenario as they do not require path discovery or maintenance. However they have to deal with the overhead of the location service and inaccurate position information. This paper proposes the MMFP (Multi-hop MAC Forwarding Protocol) for inter-vehicle communication that relies on reachability information collected from received packets in making a forwarding decision without path discovery. The MMFP is designed as an extension to the IEEE 802.11 MAC layer to ensure accuracy in its time-critical operations. This paper also presents some simulation results that demonstrate the superior performance of the MMFP over AODV in a realistic inter-vehicular communication.

• The Journal of the Acoustical Society of Korea
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• v.19 no.5
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• pp.13-19
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• 2000

The blind segmentation method, which segments input speech data into recognition unit without any prior knowledge, plays an important role in continuous speech recognition system and corpus generation. As no prior knowledge is required, this method is rather simple to implement, but in general, it suffers from bad performance when compared to the knowledge-based segmentation method. In this paper, we introduce a method to improve the performance of a blind segmentation of Korean continuous speech by postprocessing the segment boundaries obtained from the blind segmentation. In the preprocessing stage, the candidate boundaries are extracted by a clustering technique based on the GLR(generalized likelihood ratio) distance measure. In the postprocessing stage, the final phoneme boundaries are selected from the candidates by utilizing a simple a priori knowledge on the syllabic structure of Korean, i.e., the maximum number of phonemes between any consecutive nuclei is limited. The experimental result was rather promising : the proposed method yields 25% reduction of insertion error rate compared that of the blind segmentation alone.