• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.7
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• pp.1561-1568
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• 2005

In client-solver environments, clients can execute applications without contact a server by storing data in its cache. To guarantee correction of applications, we need a cache consistency algorithm. Many cache consistency algorithms have been proposed, these were categorized by detection-based and avoidance-based algorithms. In this paper, we propose a new detection-based cache consistency algorithm that can reduce a burden of a client that has poor resource compare with a server Our method controls concurrency of transactions using timestamp ordering and updates a cache dynamically. In addition to we show that our method maintains a one-copy serializability.

• Proceedings of the Korean Society of Computer Information Conference
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• 2020.07a
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• pp.323-324
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• 2020

본 논문에서는 저사양 컴퓨터를 클러스터링하여 서버의 성능 향상에 관해 서술한다. 이 시스템은 다수의 컴퓨터를 하나의 클러스터로 연결하고 쿠버네티스를 활용하여 노드 간의 부하를 관리하여 컴퓨팅 시스템의 처리량을 최대화하고, 각 작업의 수행시간을 최소화한다. 또한, 이 시스템은 수행 중인 작업의 메모리 요구량과 각 노드의 부하 상태를 파악하여 작업을 동적으로 할당한다. 본 논문에서는 광학식 문자 판독(OCR)을 동작시키며 단독 서버 상태와 노드를 연결한 클러스터링 시스템과의 처리 속도를 비교하여 저사양 컴퓨터로도 효과적인 성능의 서버 구축을 할 수 있음을 보인다.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.199-201
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• 2004

유비쿼터스 컴퓨팅의 응용분야에서 거시적이고 동적인 개념을 쉽게 구현할 수 있는 플랫폼을 설계하고 구현하였다. 주위 정보를 수집하는 센서들과 이 정보들을 서버에게 보내는 PDA 그리고 여러 지역을 감지하기 위해 이동이 가능하게 하는 이동체 등으로 구성되어 있다. 응용하는 곳에 따라 이동체, 센서, 룰셋 등을 변경할 수 있도록 플랫폼을 설계하였다. 이 논문에서는 이 플랫폼의 H/W의 구성과 S/W의 구성을 살펴보고 이를 응용한 곳에 대해 설명한다. 그리고 향후 개발 방향에 대해 언급한 후 끝을 맺는다.

• The KIPS Transactions:PartD
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• v.12D no.1 s.97
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• pp.151-158
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• 2005

In order to use the existing map data base in the mobile phone, the dynamic creation technique of the radio map which will be able to be converted into the raster image and transmitted was proposed. We transferred the client module functions such as the coordinate conversion, data compression and decoding to server, and made driving of JAVA browser in the mobile phone which has the restricted resources possible for the dynamic creation of the radio map. We made the radio electronic map service possible without map data base for the mobile phone use only by performing the general work of the map at the sever. And we guaranteed the client waiting time less then the limit time by performing the filtering work of the map at the server also. After we input the keyword at the user interface for searching the region or facility, and verified the performance of the proposed technique by confirming that the raster electronic map usable at the mobile phone was created dynamically.

• Journal of KIISE:Information Networking
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• v.32 no.1
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• pp.60-67
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• 2005

A cluster consists of a collection of interconnected stand-alone computers working together and provides a high-availability solution in application area such as web services or information systems. Content-based load distribution for web server clusters uses the detailed data found in the application layer to intelligently route user requests among web servers. In this paper, we propose a content-based load distribution algorithm that considers cache hit and load information of the web servers under the web server clusters. In addition, we expand this algorithm in order to manage user requests for dynamic file. Specially, our algorithm does not keep track of any frequency of access information or try to model the contents of the caches of the web servers.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.10
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• pp.1217-1224
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• 1999

이동 호스트들의 위치 정보를 관리하는 것은 이동 컴퓨터 시스템에서 중요한 문제이다. 이동 호스트가 이동할 때 위치 수정과 위치 탐색간에는 상반관계가 존재한다. 본 논문에서는 위치 서버를 이용한 간단한 quorum 기반 분산 동적 위치 관리 방법을 제안한다. 이 방법에서는 이동 호스트들의 위치 정보가 모든 위치 레지스터가 아닌 위치 레지스터들의 부분집합에서 효율적으로 관리되기 때문에 위치 수정 비용과 위치 탐색 비용이 감소된다. 그리고 위치 레지스터들의 부분집합은 동적으로 변하고, 각 위치 서버의 부하는 이동 호스트에 대한 질의율을 고려하므로 균등해진다. 제안된 알고리즘의 성능은 위치 수정비용과 위치 탐색비용의 전체비용으로 평가되었고, Prakash의 알고리즘과 비교되었다.Abstract Managing location information of mobile hosts is an important issue in mobile computing systems. There is a trade-off between location update and search, when a mobile host moves. This paper proposes a simple quorum-based distributed dynamic location management method using location registers. The cost of location updates and searches is reduced by our method because the location information of mobile hosts is managed efficiently in a subset of location registers instead of in all location registers. In our method, the subset of location registers is dynamically changed, and the load of each location register is balanced by considering query rate for mobile hosts. The performance of proposed algorithm is evaluated in terms of the total cost of a location update and a location search, and is compared with Prakash's algorithm.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10c
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• pp.409-411
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• 2004

최근에 많은 기업들은 XML 메시지 기반의 분산 환경에서 이기종 간의 표준으로 자리잡고 있는 웹 서비스를 도입하여 B2C 뿐만 아니라 B2B에 거쳐서 기업과 기업간 동적인 비즈니스를 수행하고 있다. 하지만, 웹 서비스의 도입이 성공적으로 이루어지기 위해서는 차별화된 서비스 품질을 보장해 주어야 한다. 현재 대부분의 웹 서비스에서는 메시지에 대하여 차별화를 두고 있지 않으며, 기존의 웹 서버들은 웹 서비스 제공자와 사용자간에 체결된 서비스 수준 계약에 대한 품질 요소들을 적절하게 반영하지 못하고 있다. 본 논문에서는 차별화 서비스에 사용되는 응용 수준에서의 적합한 품질 요소를 분석하고, 이러한 품질 요소를 이용하여 웹 서비스 메시지를 처리하는 프로세스에 대하여 서비스 수준 계약을 최대한으로 만족시키기 위하여 동적으로 우선순위를 할당할 수 있는 스케줄링 기법을 제안한다.

• The KIPS Transactions:PartA
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• v.9A no.2
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• pp.137-146
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• 2002

In VOD server, in order to guarantee playback of continuous media, such as video, without hiccups for multiusers, the server has to manage its buffer sophisticatedly by prefeching a part of the data into the buffer As the continuous media data buffered by one user can be used again by the others, the number of disk accesses is reduced and then the latency time far the users is also reduced. In this paper, we propose a new buffer management technique for continuous media in VOD server. Our basic algorithm partitions the buffer into groups and then a group of buffer which has the lowest utilization is chosen and partitioned again for a new user. The basic algorithm is extended for supporting multiple streams and clip data and for providing VCR functions. Our proposed technique is able to increase in the number of concurrent users as increasing the utilization of the buffer and to minimize the average waiting time for multiuser accesses as the bandwidth of storage is slowly reached to the limit. In the simulation study for comparing the performance of our technique with that of the existing techniques, we show that the average waiting time is reduced mere than 50% and the number of concurrent users increases by 1 ∼5% as compared with those of the exiting techniques.

• Journal of Korea Spatial Information System Society
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• v.6 no.1 s.11
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• pp.87-100
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• 2004

When spatial data which a user requests are stored various data servers in web mapping environment, it is necessary to access one more map servers to gain data and then integrate them. This paper designs and implements a fusion map server for web mapping. The proposed fusion map server has three characteristics. First, it has customizing metadata which reflect various user's requests. Second, it provides fusion services which integrate spatial and non-spatial data. Last, it uses the dynamic liking method to support the fusion services efficiently. We design and implement a publisher client, a map server and a fusion map server for proposed map server.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.08a
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• pp.87-90
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• 2008

Dynamic Heuristic(DH) is not fixed data and is dynamically modified using transferred real time road data from server In this paper, we propose path-finding algorithm with Maximum Speed Dynamic Heuristic (DH-MAX) and do an experiment. The DH-MAX is to be used the highest speed as DH, in real map divided by same sire. And proposed algorithm searches path using the priority searching only of the fixed data, but also the highest speed with real time information. In the performance test, the quality of path is enhanced but the cost of searching is increased than $A^*$ algorithm.