• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.25 no.2
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• pp.149-155
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• 2007

Mobile facility management system is a on-site management tool to collect and update various facility data. But there is a chance to make a data inconsistency between lot of concurrent workers. And facility management system requires to keep records about work log within a certain period of time. This paper describes the design and implementation of mobile facility management system, which provide efficient data synchronization mechanism using version managent technique on large facility data in concurrent work environment. And proposed system is able to keep workers update log persistently.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.2
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• pp.373-382
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• 1999

Inheritance and concurrency are the primary feature of object oriented languages, and are especially important for code re-use. They provide maximum computational power and modeling power through concurrency of objects. But, concurrent objects and inheritance have conflicting characteristics, thereby simultaneously use of them causes the problem, so called inheritance anomaly, which requires code redefinition of inherited methods to maintain integrity of objects. In this paper, to solve the inheritance anomaly problems we introduce concept of state abstraction, in which internal states of encapsulated objects are made available from a part of object's external interface. And we design inheritance interface mechanisms which methods are inherited efficiently. In our scheme, we can solve the typical inheritance anomaly problems.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.10a
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• pp.135-138
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• 2008

The existing protocol which processes sequentially synchronization has the problem where synchronization tasks which are requested subsequently from multiple client. Should be waited for a long time. In this paper, we propose a implementation of concurrent synchronization protocol that is capable of reducing the waiting time. If there are no update conflicts among different synchronization tasks, the proposed protocol synchronizes using the multi-queue based on the round-robin scheme, in order to reduce the waiting time.

• The Transactions of the Korea Information Processing Society
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• v.7 no.4
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• pp.1290-1298
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• 2000

Multimedia Systems such as VOD(Video On Demand) and MOD (Multimedia On Demand) need to support continuous media operations which are randomly called by concurrent users and require that stored media be accessed in real-tim. To satisfy such a requirements, disk arrays consisting of multiple disks are generally used as storage systems. Under the real-time environments to provide users with accessing continuous media in the parallel and concurrent manner, storage systems should be able to deal with user requests independently. In this paper, we present a new fault-tolerant continuous media storage system called PADA(PRR\ulcorner bAsed Disk Array), which is based on a PRR\ulcorner (Prime Round Robin with Grouped Parties) disk placement scheme with enhanced reliability nd load-balancing. We have compared and evaluated the storage space overhead for fault-tolerance, the reliability of diks array systems, the degree of disk load0-balancing, the demanded buffer space, the maximum number of users being capable of supporting and the fault recovery overhead for PADA, RAID 5 and Declustered storage systems. According to the results, PADA is the best among them in that PADA satisfies load-balancing more effectively and servces more user in case of arbitrary-rate retrievals.

• The Korean Journal of Applied Statistics
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• v.29 no.5
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• pp.787-806
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• 2016

Mixed-mode (MM) designs in which data are collected by different modes in one design have become increasingly popular. An MM data collection has several advantages such as reductions of coverage error, non-response and cost. However, MM designs may introduce mode effects that are confounded by selection effects and measurement effects, which can make MM data quality poor. In order to investigate mode effects, SRI implemented a concurrent mixed-mode experiment in 2014 where respondents could choose between a self-administrated Web survey and a self-administrated paper survey. This paper separately estimates selection effects and measurement effects. We found that measurement effects on some items are large.

• Journal of Communications and Networks
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• v.12 no.3
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• pp.275-284
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• 2010

The current multihome-aware protocols (like stream control transmission protocol (SCTP) or parallel TCP for concurrent multipath data transfer (CMT) are not designed for high-capacity and large-latency networks; they often have performance problems transferring large data files over shared long-distance wide area networks. It has been shown that SCTP-CMT is more sensitive to receive buffer (rbuf) constraints, and this rbuf-blocking problem causes considerable throughput loss when multiple paths are used simultaneously. In this research paper, we demonstrate the weakness of SCTP-CMT rbuf constraints, and we then identify that rbuf-blocking problem in SCTP multihoming is mostly due to its loss-based nature for detecting network congestion. We present a simulation-based performance comparison of FAST TCP versus SCTP in high-speed networks for solving a number of throughput issues. This work proposes an end-to-end transport layer protocol (i.e., FAST TCP multihoming as a reliable, delaybased, multihome-aware, and selective ACK-based transport protocol), which can transfer data between a multihomed source and destination hosts through multiple paths simultaneously. Through extensive ns-2 simulations, we show that FAST TCP multihoming achieves the desired goals under a variety of network conditions. The experimental results and survey presented in this research also provide an insight on design decisions for the future high-speed multihomed transport layer protocols.

• ETRI Journal
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• v.21 no.1
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• pp.55-71
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• 1999

Recently, the increased handling of on-line standards information has emerged as an important feature of information and communications technology (ICT) standardization. In order to meet market needs for on-time standards deployment, most standards organizations are actively seeking more efficient ways of standardization using electronic means in order to accelerate the standards making process. This paper suggests a virtual standard development environment designed for standards developers to carry out their standards-related activities on-line. In this paper, we outline a conceptual model of a concurrent standardization process and describe the design and implementation of an Extranet-based network system called standards information cooperative network (SICN). The system was created with a view to fostering faster standards development with functionalities such as a virtual management of networked standards developers, collaboration support tools, a workflow-based electronic signature system, and dynamic links for ready retrieval of standards information stored in a database. We conclude this paper with an introduction to the concept of a virtual standards development organization (VSDO) that supports all the features needed by the relevant standards making bodies to carry out their activities in a dynamic on-line environment.

• Journal of Communications and Networks
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• v.11 no.3
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• pp.287-296
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• 2009

Although asymptotic bounds of wireless network capacity have been heavily pursued, the answers to the following questions are still critical for network planning, protocol and architecture design: Given a three-dimensional (3D) network space with the number of active users randomly located in the space and using the wireless communication technology, what are the expected per-flow throughput, network capacity, and network transport capacity? In addition, how can the protocol parameters be tuned to enhance network performance? In this paper, we focus on the ultra wideband (UWB) based wireless personal area networks (WPANs) and provide answers to these questions, considering the salient features of UWB communications, i.e., low transmission/interference power level, accurate ranging capability, etc. Specifically, we demonstrate how to explore the spatial multiplexing gain of UWB networks by allowing appropriate concurrent transmissions. Given 3D space and the number of active users, we derive the expected number of concurrent transmissions, network capacity and transport capacity of the UWB network. The results reveal the main factors affecting network (transport) capacity, and how to determine the best protocol parameters, e.g., exclusive region size, in order to maximize the capacity. Extensive simulation results are given to validate the analytical results.

• Journal of the KSME
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• v.34 no.3
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• pp.193-204
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• 1994

병행 엔지니어링 설계 생산 시스템의 특성에 관해서 논의되었다. 시스템의 구조는 설계자와 설계 Agent (혹은 모듈)들 간에 제품설계에서 제작 . 생산에 이르는 일련의 과정을 손쉽게 처리할 수 있도록 구축되었다. 특이한 것은 중앙에 지식 베이스를 둠으로써 각 Agent들 간의 정보교환을 용이하게 하고, 또한 필요한 정보를 서로 공유함으로써 정보 간의 연관성 유지 및 상호 보완 관 계를 극대화하였다. 이 글에서는 병행 엔지니어링 시스템의 구체적인 설명을 위해 간단한 기계 조립품의 설계 제작 과정상에서 각 Agent들이 어떻게 서로 정보 교환을 하는지 보이고자 한다.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1998.10a
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• pp.623-635
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• 1998

이 논문에서 우리는 분산 실시간 소프트웨어 설계방법인 CODARTS/DA(Concurrent Design Approach for Real-Time Systems/Distributed Application)를 위한 타스크 행위 명세방법을 제안한다. 각 타스크는 CODARTS/DA 모듈들, 즉, 다수 클라이언트/서버 모듈(Multiple Client/Sever Module), 단일 클라이언트/서버 모듈(Single Client/Server Module), 그룹 통신모듈(Group Comm. Module), 우선 순위 모듈등과 통신을 수행하는데, 분산환경의 동기, 비동기 문제들을 제안한 방법으로 설계 명세할 수 있다. 또한 제안된 명세방법은 C언어와 비슷한 문법구조를 제공하므로 쉽게 문서들이 구조적 프로그램으로 변환될 수있다.