• Journal of KIISE:Computer Systems and Theory
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• v.33 no.8
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• pp.536-546
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• 2006

Painterly animation is a method that expresses painterly images with a hand-painted appearance from a video, and the most crucial element for it is the temporal coherence of brush strokes between frames. A motion map is proposed in this paper as a solution to the issue of maintaining the temporal coherence in the brush strokes between the frames. A motion map is the region that frame-to-frame motions have occurred. Namely, this map refers to the region frame-to-frame edges move by the motion information with the motion occurred edges as a starting point. In this paper, we employ the optical flow method and block-based method to estimate the motion information. The method that yielded the biggest PSNR using the motion information (the directions and magnitudes) acquired by various methods of motion estimation has been chosen as the final motion information to form a motion map. The created motion map determine the part of the frame that should be re-painted. In order to express painterly images with a hand- painted appearance and maintain the temporal coherence of brush strokes, the motion information was applied to only the strong edges that determine the directions of the brush strokes. Also, this paper seek to reduce the flickering phenomenon between the frames by using the multiple exposure method and the difference map created by the difference between images of the source and the canvas. Maintenance of the coherence in the direction of the brush strokes was also attempted by a local gradient interpolation to maintain the structural coherence.

• Journal of KIISE:Databases
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• v.31 no.2
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• pp.140-149
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• 2004

Data broadcast has received much attention as a very efficient method for disseminating data items in mobile environment with large number of mobile clients. In this approach, a database server periodically and continuously broadcasts data items through wireless channels and clients perform read-only transactions by accessing necessary data items from the air. While broadcasting, the server must also process update transactions on the database, which raises an obstacle for client's accessing consistent data. In this research, we propose a new algorithm SCDSC(Serialization Checking with DirtySet on Commit) which is an alternative for solving the concurrency control problem efficiently. The SCDSC is a kind of optimistic concurrency control in that a client checks the consistency of data using a DirtySet as a part of data broadcast when it commits its transaction. In each broadcast cycle, the server updates and disseminates the DirtySet with newly changed data items for last few cycles in the sliding window approach. We perform an analysis and a simulation study to evaluate the performance of our SCDSC algorithm in terms of data consistency and data currency.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.4
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• pp.73-80
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• 2016

Multiplayer Online Games(MOG) using the Internet are typically organized based on a CS(client-server) or P2P(peer-to-peer) architecture. We then propose a method that combines a P2P architecture with a CS architecture in order to utilize their advantages. Most MOGs use a primary-copy replication approach that provides strong consistency control over an object. For each object and character there exists an authoritative copy, called primary copy and all other copies are secondary copies or replicas. Any update to the object has to be first performed on the primary copy. In the proposed hybrid architecture, primary copies may reside on the server or be held by clients. In this architecture, load balancing between a server and clients can be achieved by reducing the number of objects maintained by the server. Games consist of various types of actions with different consistency requirements. A multi-level approach to game consistency is sensible as it provides the best trade-off between consistency and performance. The performance for the hybrid game architecture with the primary-copy model is evaluated through simulation experiments and analysis in this paper.

• Journal of KIISE:Databases
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• v.32 no.6
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• pp.616-627
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• 2005

In the shared storage file system, systems can directly access the shared storage device through specialized data-only subnetwork unlike in the network attached file server system. In this shared-storage architecture, data consistency is maintained by some designated set of lock servers which use control network to send and receive the lock information. Furthermore, lease mechanism is introduced to cope with the control network failure. But when the control network is partitioned, participating systems can no longer make progress after the lease term expires until the network recovers. This paper addresses this limitation and proposes a method that allows partitioned systems to make progress under the partition of control network. The proposed method works in a manner that each participating system is rotationally given a predefined lease term periodically. It is also shown that the proposed mechanism always preserves data consistency.

• Proceedings of the Korea Contents Association Conference
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• 2003.11a
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• pp.234-244
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• 2003

In distributed file-systems, cooperative caching algorithm which owns the data cached at each node jointly is used to reduce an expense of disk access. Cooperative caching algorithm is the method that increases a cache hit-ratio and decrease a disk access as it holds the cache information of distributed systems in common and makes cache larger virtually. Recently, several cooperative caching algorithms decrease the message costs by using approximate information of the cache and increase the cache hit-ratio by using local and global cache fields dynamically. And they have an advantage that increases the whole field hit-ratio by sending a replaced block to the idel node on cache replacement in order to maintain the replaced block in the cache field. However the wrong approximate information deteriorates the performance, the concistency maintenance goes to great expense to exchange messeges and the cost that manages Age-information of each node to choose the idle node increases. In this thesis, we propose a cooperative cache algorithm that maintains correct cache information, minimizes the maintance cost for consistency and the management cost for cache Age-information. Also, we show the superiority of our algorithm through the performance evaluation.

• Journal of Korean Society for Geospatial Information Science
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• v.5 no.2 s.10
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• pp.193-205
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• 1997

It is required for multi-users to share massive mapping data effectively that distributed data model in the Client-Server environment is developed for the replication consistency. The existing model is not effective to the long transaction just like a mapping system, since it does not account lot consistency between GUI screen and database replications even though it emphasizes on the replication consistency. The performance of concurrency control is very important for those long transactions, especially the mapping systems. This model is to support consistency between GUI screen and replicas using display locks. It suggests consistency model improving process performance by modifying memory consistency model and optimistic concurrency control for mapping data's characteristics.

• Proceedings of the Korean Information Science Society Conference
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• 2003.10b
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• pp.706-708
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• 2003

컴퓨터 게임, 지리정보시스템(GIS), 가상현실 분야등에서 환경표현의 기반이 되는 지형의 렌더링 기술은 매우 중요하다. 하지만 지형정보는 일반적으로 방대한 양의 데이터로 구성되어 처리가 쉽지 않다. 지형렌더링을 수행하기 위한 여러가지 기법들 중에 쿼드트리 구조를 기반으로한 연속적 상세단계기법이 있다. 본 논문에서는 쿼드트리 기반의 연속적 상세단계에서 시각 절두체 내에서 렌더링되는 삼각형의 개수를 조절하여 프레임율을 일정하게 유지하는 기법을 제안한다. 이 방법은 인접 프레임간의 일관성을 이용하여 최근 프레임에 가중치를 줌으로써 삼각형의 개수가 급격하게 변하는 것을 막는다.

• Journal of KIISE:Databases
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• v.29 no.6
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• pp.477-491
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• 2002

The broadcast environment has asymmetric communication aspect that is typically much greater communication bandwidth available from server to clients than in the opposite direction. In addition, mobile computing systems generate mostly read-only transactions from mobile clients for retrieving different types of information such as stock data, traffic information and news updates. Since previous concurrency control protocols, however, do not consider such a particular characteristics, the performance degradation occurs when previous schemes are applied to the broadcast environment. In this paper, we propose optimistic concurrency control based on timestamp interval for broadcast environment. The following requirements are satisfied by adapting weak consistency that is the appropriate correctness criterion of read-only transactions: (1) the mutual consistency of data maintained by the server and read by clients (2) the currency of data read by clients. We also adopt the timestamp Interval protocol to check the weak consistency efficiently. As a result, we improved a performance by reducing unnecessary aborts and restarts of read-only transactions caused when global serializability was adopted.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.05a
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• pp.53-56
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• 2007

CAD와 같이 계산위주의 응용을 지원하기 위해 개발된 초기의 객체지향 데이터베이스 시스템은 클라이언트에서 자료의 요구와 처리를 허용하는 자료 탑재방식이다. 이 방식은 클라이언트 워크스테이션에서 수행되는 작업의 대부분을 수행할 수 있는 지역 DBMS를 허용한다. 클라이언트 워크스테이션에서 자료와 잠금을 캐싱하는 것은 클라이언트-서버 데이터베이스 시스템의 성능 향상을 위한 중요한 기술이다. 이 논문에서는 클라이언트 워크스테이션이 자신의 지역 데이터베이스를 유지하면서 회피 또는 탐지 기반의 캐시일관성 유지 알고리즘들의 성능을 평가할 수 있도록 하는 클라이언트 워크스테이션을 모델링하고 구현하였다. 이 시스템은 3개의 클라이언트로 구성되고, 각 지역 동시성 제어 기법으로는 2PL을 사용하였다. 이 모델은 멀티데이터베이스 시스템 환경으로 확장 가능하다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.30-32
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• 2000

최근 메타데이타의 주요 논쟁점으로 메타데이타의 표준화 문제가 등장하고 있다. 새로운 표준화 방향으로 인한 메타데이타의 확장성은 기존 메타데이타 관리 기법의 변화를 요구하게 되었다. 즉, 사용자의 질의에 대한 신속한 정보 제공과 동적인 자료의 일관성 있는 저장과 유지방 안을 필요로 한다. 이에 본 논문에서는 디지털 라이브러리 환경에서 메타데이타 속성을 정의하고, 이러한 요구사항을 만족하는 병행수행 제어 기법인 2VL(Two Version using the Latch)을 제안한다. 2VL은 래치를 사용하여 2버전을 유지함으로써 판독과 기록 연산간의 충돌로 인한 지연을 최소화하며 판독 연산에 있어서의 빠른 응답시간과 높은 최근성 반영율을 보인다.