• The Transactions of the Korea Information Processing Society
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• v.6 no.8
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• pp.2158-2170
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• 1999

It has been required more reliable communication on processes and improvement of system performance as distributed systems using multicast protocol became widespread. In distributed environment maintaining data consistency through asynchronous execution of processes and coordinating the activities of them would occurs. This paper proposes a total ordering algorithm, TORMP, in order to resolve these problems. TORMP takes advantage of multicast protocol and uses an effective token passing method. It reduces a process delaying time before transmitting its message by multicasting a token simultaneously to every process that initiates the request of the message. Moreover, the processes receiving the token start multicasting the message at the same time, which causes to cut down the overall transmission dely. In case that one process sends a message, TORMP hardly uses the procedure of controlling for ordering. It gives fairly the right of sending messages to all processes in a group with utilizing vector clock. In TORMP, unlike other algorithms, the number of packets generated during ordering process does not depend on the number of processes.

• Journal of Korea Multimedia Society
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• v.6 no.6
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• pp.1100-1110
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• 2003

Design and implementation of remote procedure cail (RPC) resource service system based on the XML considering the request delegation between the servers are described for the resource application and efficient processing of distributed environment. For this purpose, the request information about several server, which would be used by client, is encoded into XML document based on XML-DOM and transferred to server. Server classifies the client requests using objects which can deal with the XMLL-DOM. For the request delegation between the servers, server saves the request result of client in XMLL-DOM structure without replying it immediately, and makes the client request delegated to another server in XML-DOM's request information. In addition, the resource repository are managed for resource transparency of distributed environment. As a result, resource application and processing efficiency are improved by reduction of response time caused by integration of RPC and XML-RPC services and request delegation between the servers. Extension of asynchronous and average blocking time of client were reduced and information of resource which can be used by client was offered.

• Proceedings of the Korean Information Science Society Conference
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• 2005.07a
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• pp.652-654
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• 2005

WebDAV는 웹통신 프로토콜인 HTTP/1.1의 확장으로서 인터넷을 통하여 다양한 자원의 비동기적인 협업을 지원하는 표준 프로토콜이다. CoSlide 시스템은 협업을 효과적으로 지원하기 위하여 WebDAV 프로토콜을 확장하여 개발된 협업시스템이다. CoSlide 협업시스템은 협업을 위한 가상공간을 제공하며 가상공간에 다양한 자원을 등록 및 관리할 수 있다. CoSlide 협업시스템을 활용하여 효과적인 협업을 수행하기 위한 사용자 중심의 클라이언트가 필요하다. 본 논문에서는 WebDAV 프로토콜을 이용한 협업시스템인 Coslide를 효과적으로 활용하기 위한 클라이언트 개발에 대하여 기술한다. 개발된 클라이언트는 사용자가 서버에 등록한 자원을 관리하는 기능과 팀원들 간의 상호 작용을 원활하게 지원하는 사용자 인터페이스를 제공한다. 또한 CoSlide 협업시스템을 사용하는 사용자는 새로운 작업장을 생성하고 다른 사용자를 초대할 수 있으며, 작업장에 파일을 등륵, 이동 그리고 삭제할 수 있다. 기존의 협업시스템에서 분산저작을 하는 경우 클라이언트에서 제공하는 특정 프로그램을 이용하거나, 파일을 서버로부터 내려받아 이를 수정하여 다시 등록하는 과정을 거친다. 본 클라이언트는 이러한 단점을 개선하여 CoSlide 협업시스템의 자원에 대하여 다양한 저작프로그램을 자동적으로 연결하여주며, 실시간으로 협업시스템의 자원을 갱신하여 준다. 또한 자원에 대한 일관성을 보장하기 위하여 자동 잠금기능을 제공한다. 추가적으로 사용자는 드래그앤드랍 기능을 이용하여 작업장간의 자원을 이동할 수 있다.

• The Transactions of the Korea Information Processing Society
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• v.5 no.6
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• pp.1441-1456
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• 1998

The concept of a hyperpresmtation, as an extension of a hypermedia, is the presentation in which time-varying multimedia presentations are dynamically linked together and a hyperlink's context can be changed over time at any time during a continuous presentation. Problems caused by integrating the hyperpresentation into an existing multimedia system which handles a sequential presentation only are, how to describe the hyperprcsentation, how to set up a hyperlink on a continuous media, and how to check the consistency of the synchronized presentations. In this paper. a new synchronization description method for the hyperpresentation and a method for setting a hyper link on a continuous media during" presentation are proposed after havin!; SHrvey of existing methods, The proposed method deals with only the DC value in a stream ut a DCT based compressed data for checking a condition of te link. Finally, the method for checking the consistency of mixed presentations before actual play of the hnlerpresentation is described. Proposed methods are implemented on MuX(Multimedia IO Server) where a sample scenario is tested.

• Journal of Korea Society of Industrial Information Systems
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• v.4 no.4
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• pp.88-93
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• 1999

Several Iterative methods are considered, Gram-Schmidt algerian for thin orthogonalization and Lanczos methodfor a few extreme eigenvalues. For these methods, a variants of method is derived for which only one synchronization point per on iteration is required; that is one global communication in a message passing distributed-memory machine per one iteration is required The variant is called restructured method, and restructured method has better parallel properties to the conventional method.

• The Journal of Bigdata
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• v.7 no.1
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• pp.1-14
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• 2022

The proof-of-work consensus algorithm used by most blockchains is causing a massive waste of computing resources in the form of mining. A useful proof-of-work consensus algorithm has been studied to reduce the waste of computing resources in proof-of-work, but there are still resource waste and mining centralization problems when creating blocks. In this paper, the problem of resource waste in block generation was solved by replacing the relatively inefficient computation process for block generation with distributed artificial intelligence model learning. In addition, by providing fair rewards to nodes participating in the learning process, nodes with weak computing power were motivated to participate, and performance similar to the existing centralized AI learning method was maintained. To show the validity of the proposed methodology, we implemented a blockchain network capable of distributed AI learning and experimented with reward distribution through resource verification, and compared the results of the existing centralized learning method and the blockchain distributed AI learning method. In addition, as a future study, the thesis was concluded by suggesting problems and development directions that may occur when expanding the blockchain main network and artificial intelligence model.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.12 no.6
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• pp.33-42
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• 2012

Rapid evolution of wired and wireless technologies results in various types of embedded systems, and the software to be embedded into those devices now needs the flexibility rather than the fixedness which was well-known property for the embedded software in the past. Mobile agent is one of the useful distributed technologies of reducing network load and latency because of its disconnected operations and high asynchrony. In this paper, a component-based mobile agent framework, called EmHUMAN, is designed and implemented for structural embedding into the devices showing different functions and resource constraints. It consists of 3 layers of components. Based on those components, a structural embedding, considering resource constraints of required functions, amount of storage space, computing power, network bandwidth, ${\ldots} $ etc can be performed. The components in each layer can be extended with addition of new components, removing some components and modifying components. EmHUMAN plays the role of a framework for developing mobile agent based distributed systems. It is also a mobile agent system by itself. EmHUMAN provides several utilities as built-in API's, and thus high effectiveness in programming mobile agents can be achieved.

• Journal of KIISE:Computing Practices and Letters
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• v.15 no.1
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• pp.29-37
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• 2009

Recently, message based data transmission plays an important role in modem computing systems. Especially JMS(Java Message Service) is one of the most popular messaging platform. However, because of its characteristics for maintaining reliability, if we want to use it for transmission of large scale messages in a distributed Internet environment by using a WAN connection which may not be robust enough, we need to employ a different method to minimize total transmission time of messages. We found the fact that the total time of message transmission heavily depends on size of a message. In order to achieve the ideal size of a message, we develope a novel mechanism and a system which finds the ideal size of a message and automatical1y control JMS applications for minimizing transmission time. Finally, we test the proposed mechanism and system using real-data in order to prove advantages and compared with the naive mechanism. As a conclusion, we showed that our proposed mechanism and system provide an effective way to reduce transmission time of large scale messages in distributed environment.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.9
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• pp.1582-1589
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• 2006

A lock mechanism is essential for synchronization on the multiprocessor systems. The conventional queuing lock has two bus traffics that are the initial and retry of the lock-read. %is paper proposes the new locking protocol, called WPV (Waiting Processor Variable) lock mechanism, which has only one lock-read bus traffic command. The WPV mechanism accesses the shared data in the initial lock-read phase that is held in the pipelined protocol until the shared data is transferred. The nv mechanism also uses the cache state lock mechanism to reduce the locking overhead and guarantees the FIFO lock operations in the multiple lock contentions. In this paper, we also derive the analytical model of WPV lock mechanism as well as conventional memory and cache queuing lock mechanisms. The simulation results on the WPV lock mechanism show that about 50% of access time is reduced comparing with the conventional queuing lock mechanism.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.6
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• pp.569-576
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• 2011

This paper proposes a new dead time compensation method for a PWM inverter. Recently, PWM inverters are extensively used for industry applications, such as ac motor drives, distributed grid-connected systems and a static synchronous compensator (STATCOM). Nonlinear characteristics of the switch and the inverter dead time cause a current distortion and deterioration of power quality. The dominant harmonics in the output current are the $5^{th}$ and $7^{th}$ harmonics in the stationary frame, and the $6^{th}$ harmonics in the synchronous rotating frame. In this paper, a resonant controller which compensates the $6^{th}$ harmonics in the synchronous rotating frame is proposed. This method does not require any off-line experimental measurements, additional hardware and complicated mathematical computations. Furthermore, the proposed method is easy to implement and does not cause any stability problem.