• Journal of Information Processing Systems
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• v.6 no.4
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• pp.575-596
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• 2010

Video-on-Demand services are increasing rapidly nowadays. The load on servers can be very high, even exceeding their capacity. For popular contents, we can use a Periodic Broadcast (PB) strategy using multicast to serve all clients. Recent development of PB uses multiple channels broadcasting for segments of movies in certain patterns, so that users only need to wait for a small segment to start the service. However, users need higher download capacity to download multiple segments at a time. In order to compensate for this, a proxy server can help to reduce download bandwidth requirements by holding some segments for a certain time. This research will focus on more recent PB schemes that couldn't be covered by previous Proxy-Assisted Periodic Broadcast strategies.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.532-534
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• 2004

단일서버 시스템에서 응용간 자원의 공정한 분배는 GPS(Generalized Processor Sharing)을 통친 실현될 수 있다. 그러나 다중서버시스템에서 GPS를 적용한다면, 각 서버 내에서의 공정성은 보장해 주지만, 시스템 관점에서의 공정성은 더 이상 보장되지 않는다. 본 논문에서는 멀티서버 시스템에서 시스템 관점에서의 공정성 보장을 위한 기법을 제시한다. 이 기법은 시스템에서 발생하는 각 서버의 잔여용량을 응용간 공정하게 분배하는 모델과 모델을 참조하여 실행하는 실제 스케줄링 알고리즘으로 구성된다 모델에서는 긴 시간동안 각 서버에서 발생하는 잔여용량의 사용을 관측하여, 향후 각 응용의 요청들에게 제공할 잔여용량 분배를 결정한다. 스케줄링 알고리즘은 모델에 의해 결정된 잔털용량 분배를 실제 각 응용들이 제대로 가져갈 수 있도록 제어한다. 실제 모델을 참조하여 공정 잔여용량 분배를 수행하는 스케줄링 알고리즘의 동작은 시뮬레이션을 통해 검증하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.1262-1265
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• 2007

인터넷 및 디바이스의 발달과 유비쿼터스 환경이 도래함에 따라 모바일 디바이스를 이용하여 서비스를 제공받고자 하는 수요는 급속도로 증가하고 있다. 유비쿼터스 환경에서 모바일 디바이스가 이기종 네트워크로 이동하여 언제, 어디서, 누구에게나 끊김없는 서비스를 제공하기 위해서는 이기종 네트워크간의 통신 및 디바이스간의 데이터 통신이 가능해야 한다. 그러나 동종 네트워크에서의 보안 기술 및 통신 기술로는 이기종 네트워크에 적용했을 때 확장성 및 안전성에 많은 문제가 따른다. 따라서 이기종 네트워크 로밍 환경에서 안전하고 효율적인 인증 메커니즘을 제안하였다.

• Proceedings of the Korea Information Processing Society Conference
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• 2007.11a
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• pp.878-879
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• 2007

유비쿼터스 환경에서 서로 상이한 시스템들이 네트워크로 연결되어 각 시스템 간의 상호작용과 시스템 모니터링의 문제가 대두되고 있다. 구조가 상이한 시스템을 제어하기 위해서 해당 시스템의 인터페이스 정보와 인터페이스의 구현 기술이 필요하다. 본 연구에서는 제어 대상인 기기의 프로필 정보를 이용하여 인터페이스 정보를 획득하고 코드 생성 자동화를 통하여 상이한 시스템 간의 효율적 상호작용 메커니즘을 제공한다. 인터페이스 정보가 포함된 프로필을 통해 제어 스텁 코드를 생성함으로써 코드 생성 자동화를 수행하여 상이한 시스템 간에 이루어지는 상호작용의 한계를 해결한다.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.3
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• pp.140-148
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• 2009

Recent advances in communication and multimedia technologies make it possible to provide video-on-demand(VOD) services and people can access video servers over the Internet at any time using their electronic devices, such as PDA, mobile phone and digital TV. Each device has different processing capabilities, energy budgets, display sizes and network connectivities. To support such diverse devices, multiple versions of videos are needed to meet users' requests. In general cases, VOD servers cannot store all the versions of videos due to the storage limitation. When a device requests a stored version, the server can send the appropriate version immediately, but when the requested version is not stored, the server first converts some stored version to the requested version, and then sends it to the client. We call this conversion process transcoding. If transcoding occurs frequently in a VOD server, the CPU resource of the server becomes insufficient to response to clients. Thus, to admit as many requests as possible, we need to maximize the CPU availability. In this paper, we propose a new algorithm to select versions from those stored on disk using a branch and bound technique to maximize the CPU availability. We also explore the impact of these storage management policies on streaming to heterogeneous users.

• The KIPS Transactions:PartC
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• v.10C no.5
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• pp.565-574
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• 2003

This paper implements an intrusion detection message exchange protocol library (IDMEPL) for SDMS-RTIR, which Korea Information Security Agency (KISA) has developed to hierarchically detect and respond to network vulnerability scan attacks. The IDMEPL, based on the IDMEF and the IAP of the IDWG, enables SDMS-RTIR to interact with other intrusion detection systems (IDS) in realtime, and supports the TLS protocol to prevent security threats in exchanging messages between its server and its agents. Especially, with the protocol selection stage, the IDMEPL can support various protocols such as the IDXP besides the IAP. Furthermore, it can allow for agents to choose an appropriate security protocol for their own network, achieving security stronger than mutual authentication. With the IDMEPL, SDMS-RTIR can receive massive intrusion detection messages from heterogeneous IDSes in large-scale networks and analyze them.

• Journal of KIISE:Databases
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• v.30 no.5
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• pp.464-475
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• 2003

few sample objects and compressed histogram information of image databases. The histogram information is used to estimate the selectivity of spherical range queries and a small number of sample objects is used to compensate the selectivity error due to the difference of the similarity measures between meta server and local image databases. An extensive experiment on a large number of image data demonstrates that our proposed method performs well in the distributed heterogeneous environment.

• The KIPS Transactions:PartD
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• v.10D no.2
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• pp.327-336
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• 2003

Recently the rapid growth of Internet and the construction of high speed networks make many kinds of multimedia services possible. But most of current multimedia services are designed being by client/server model, which incurs high load of central server. In order to solve this problem, we propose a peer-to-peer network-based discovery mechanism for multimedia services. In the proposed scheme, mobile agents that have autonomy and mobility are used to search the location of resources. Use of mobile agents can solve the loss problem of the search result that occurs when the network is unsettled in pure peer-to-peer network. It also supports interoperability in heterogeneous system environments. In the proposed scheme, each host maintains the location information of resources which are locally requested or recently requested by other hosts. So, the proposed scheme has faster response time than the pre-existing mechanisms in pure peer-to-peer network environments.

• Journal of Korea Multimedia Society
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• v.9 no.10
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• pp.1361-1370
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• 2006

Recently fast innovation of Internet technology causes lot of application to change into web application and requirement for the inter-operable communication among various systems are increased rapidly. These trends are part of changes which is caused by ubiquitous world and it is just beginning of huge waves that is required to fit and change under the ubiquitous environments. This thesis is focused on the Design and Implementation of Layer Structured Components which can be interfaced effectively for the Material Management System under the Heterogeneous Client Server Environments. The key points to do that kinds of affairs are using XML web services that can communicate thru systems and also using independent layered components for the enforcement of reusability and inter-operability. For the various type of testing of implementation, we used RFID System, PDA, Desktop Systems and confirmed the normal operation without concerning the type of client system and platforms. The Components proposed in this thesis could be reused effectively in case of developing similar applications.

• The KIPS Transactions:PartD
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• v.10D no.1
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• pp.143-152
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• 2003

XML and Web Services draw a lot of attention as standard technologies for data exchange and integration among heterogeneous platforms XML/A, which supports such technologies, is a SOAP based XML APl that facilitates data exchange between a client application and a data analysis engine through the Internet. The fact that the XML format is used for data exchange makes XML/A to be platform-independent. However. client application developers have to go through a tedious Job of treating the same type of XML documents fur downloading data from the server. Also, an XML query language is needed for extracting data from the XML documents sent by the server. In this paper, we present a high level client OLAP API, called DXML, for the client application developers in the windows environment to easily use the OLAP services of XML/A. XMLMD consists of properties and methods needed for OLAP application development. XMLMD is to XML/A what ADOMD is to OLEDB for OLAP. We also present a web OLAP cube browser that is developed using XMLMD. The browser display's data in various formats such as XML, HTML, Excel, and graph.