• Transactions of the Korean Society of Mechanical Engineers B
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• v.35 no.1
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• pp.1-8
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• 2011

An analytical study on the flow resistance of tree-shaped channel-flow architectures was carried out based on the principle of the constructal law; the evolutionary increase in the access to currents that flow through the channels with improvements in the flow configurations were studied in a square domain using two diameters. Two types of tree-shaped configurations were optimized. The minimized global flow resistance decreased steadily as the system size $N^2$ increased. From the two channel configurations, the one that resulted in better pressure drop was selected. Further, it was shown that the system performance can be enhanced by adopting the second tree-shaped configurations when the system size is greater than $18^2$.

• The Transactions of the Korea Information Processing Society
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• v.7 no.12
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• pp.3952-3963
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• 2000

This paper considers the WRA(Wavelength and Houting Assignment) problem on all-optical tree networks using WDM(Wavelength Division Multiplexing). Each link between a pair of request nodes on all optical networks is assigned different wavelengths because of technical constraint. On the basis of this, we give an polynomial time algorithm to assign wavelengths to the all patbs of a arbitrary tree network using divide and conquer method. The time complexity of this algorithm is O(Q. R), in which Q is the request nodes for all to'all communication in a tree topology and U is the maximum number of wavelength. Also we implemented our algorithm using C in Pentium II 233MHz and analyzed performance results.

• Journal of KIISE:Information Networking
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• v.28 no.2
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• pp.229-235
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• 2001

With the explosive popularity of the World Wide Web, the low penonnance of network often leads web clients to wait a long time for web server's response. To resolve this problem, web caching (proxy) has been considered as the most efficient technique for web server to handle this problem. The placement of web proxy is critical to the overall penonnance, and Li et al. showed the optimal placement of proxies for a web server in the internet with the linear and tree topology when the number of proxies, ]M, is given [4, 5]. They focused on minimizing the over all access time. However, it is also considerable for target web server to minimize the total number of proxies while each proxy server guarantees not to exceed certain res(Xlnse time for each request from its clients. In this paper, we consider the problem of finding the optimal number and placement of web proxies with the lin~ar and tree topology under the given threshold cost for delay time.

• Journal of the Korean Society for information Management
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• v.24 no.2
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• pp.71-87
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• 2007

With the rapid change of the Web and E-transaction application, the search interface is providing more powerful search and visualization methods, while offering smoother integration of technology with task. Especially, visualization techniques for long menu-lists are applied in retrieval system with the goal of improving performance in user's ability to select one item from a long list. In order to review visualization techniques appropriate to the types of users and data set, this study compared the five visualization browsers such as the Tree-structured menu, the Table-of-contents menu, the Roll-over menu, the Click menu, and Fisheye menu. The result of general analyses shows that among the hierarchical methods, the experienced group prefers the Table-of-contents method menu, whereas the novice's group prefers the Tree-structure method menu. Among the linear methods, the two groups prefer the Roll-over menu. The Roll-over menu is most preferred among the five browsers by the two groups.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.2
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• pp.1-14
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• 2019

Since most documents used in web, XML, office applications are tree-structured, diff, merge, and version control for tree-structured documents in multi-user environments are crucial tasks. However research on edit scripts which is a basis for them is in primitive stage. In this paper, we present a document model for understanding the change of tree-structured documents as edit scripts are executed, and propose a method of switching adjacent edit operations on tree-structured documents based on the analysis of the effects of edit operations. Mostly, edit scripts which are produced as the results of diff on tree-structured documents only consist of basic operations such as update, insert, delete. However, when move and copy are included in edit scripts, because of the characteristics of their complex operation, it is often that edit scripts are generated to execute in two passes. In this paper, using the proposed method of switching edit operations, we present an algorithm of transforming the edit scripts of X-treeESgen, which are designed to execute in two passes, into the ones that can be executed in one pass.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.451-463
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• 2003

Recently, there have been various research efforts to develop strategies for accelerating OLAP operations on huge amounts of spatio-temporal data. Most of the work is based on multi-tree structures which consist of a single R-tree variant for spatial dimension and numerous B-trees for temporal dimension. The multi~tree based frameworks, however, are hardly applicable to spatio-temporal OLAP in practice, due mainly to high management cost and low query efficiency. To overcome the limitations of such multi-tree based frameworks, we propose a new approach called Hilbert Cube(H-Cube), which employs fractals in order to impose a total-order on cells. In addition, the H-Cube takes advantage of the traditional Prefix-sum approach to improve Query efficiency significantly. The H-Cube partitions an embedding space into a set of cells which are clustered on disk by Hilbert ordering, and then composes a cube by arranging the grid cells in a chronological order. The H-Cube refines cells adaptively to handle regional data skew, which may change its locations over time. The H-Cube is an adaptive, total-ordered and prefix-summed cube for spatio-temporal data warehouses. Our approach focuses on indexing dynamic point objects in static spatial dimensions. Through the extensive performance studies, we observed that The H-Cube consumed at most 20% of the space required by multi-tree based frameworks, and achieved higher query performance compared with multi-tree structures.

• Proceedings of the Korean Institute of Communication Sciences Conference
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• 2006.07a
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• pp.602-602
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• 2006

• Journal of Korean Society for Geospatial Information Science
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• v.2 no.2 s.4
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• pp.43-53
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• 1994

GSIS(geo-spatial information system), particularly when utilized in hazard management decision, is one of hazard analysis tool. Data of GSIS input from digitizing or scanning of map or aerial photos. This paper focuses upon the hazard prediction in GSIS and RS analysis to assess map, aerialphotos, satellite imagery and soil map. This study found computation of hazard area analysis. the results is formed as raster data model of quadtree. Authors knew more accurate results of overlay. This paper shows building up integrated data base as well as search of hazard area in aerial photographs.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.4 no.2
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• pp.407-416
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• 2000

Adaptive digital filtering and noise cancelling technique using a tree structured filter bank are presented to reduce a undesirable aliasing due to the decimation of filtered output and improve the performance in terms of mean-square error and the convergence speed using a aliasing canceller. A signal is split into two subband by analysis filter bank and decimated by decimator and reconstructed by interpolation technique and synthesis filter bank. A variable step-size LMS algorithm is used to improve the convergence speed in case of existing the measurement noise in desired input of filter. It is shown by computer simulation that the proposed subband structure in this paper is superior to conventional subband filter structure in terms of mean-square error and convergence speed.

• Proceedings of the Korean Information Science Society Conference
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• 2008.06c
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• pp.391-396
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• 2008

유비쿼터스 컴퓨팅의 목표 중 하나는 사용자의 직접적이거나 은연중에 내포된 요청에 따라 적절한 서비스를 제공하는 것이다. 최근에는 사용자의 다양한 요청에 보다 유연하게 대응할 수 있는 연구가 이루어지고 있으며 그 중 단일서비스의 조합을 통해 복합서비스를 제공할 수 있는 서비스 컴포지션(Service Composition)이 주목을 받고 있다. 하지만 기존 연구들은 늦은 처리속도로 인해 실시간 상황인식 서비스에서 빠른 응답을 바라는 사용자의 요구사항을 만족시키기 어렵다. 또한 사례기반추론은 사례기저에 쌓인 사례의 수가 늘어감에 따라 속도가 저하되는 단점이 있다. 이러한 단점을 최소화 하기 위하여 클러스터링 기법이 사용되고 있다. 그러나 클러스터링 기법은 사례기저의 수를 줄여가면서 속도를 유지하기 때문에 기존의 사례가 다시 발생하였을 경우에도 새로운 문제로 인식하게 되는 문제를 가지고 있다. 이러한 문제점을 해결하기 위해서 본 논문에서는 사례기저의 수를 유지하면서 사례기저의 수치화 및 트리구조 관리를 이용하여 기존방법보다 빠른 서비스 컴포지션을 구현하는 방법을 제안한다. 그리고 기존의 서비스 컴포지션 기법과 비교 분석을 통하여 제안하는 기법의 유효함을 확인하였다.