• The Journal of the Acoustical Society of Korea
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• v.16 no.5
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• pp.18-25
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• 1997

The feedforward control algorithm for active noise control exhibits high stability and performance robustness. But it has a slow convergence speed and requires a correlated reference signal. Broadband active control systems typically use feedback control in order to increase the convergence speed and to avoid the problems associated with obtaining and decoupling a suitable reference signal. However, it is well known that conventional feedback control systems have a gain-bandwidth limitation and stability problem. This paper presents the new system based on the combination of both feedforward and feedback system in order to increase the convergence speed. The proposed system uses a proposed control algorithm termed "optional-summed" algorithm in which the "optional summed reference signal" comprised of weighted sum of an original reference signal and a eror signal, is used as an input to an adaptive system. Thus, the proposed system can have faster convergence speed and better performance than either feedforward or feedback system using the Filtered-x LMS algorithm as almost equivalent complexity of computation as it. Several simulation results demonstrating the good properties of the proposed adaptive system as well as verifying the analytical results are also presented in the paper.

• Annual Conference of KIPS
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• 2002.11a
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• pp.559-562
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• 2002

LBS (Location Based Services)란 휴대폰, PDA (Personal Digital Assistant), 노트북 PC 등 위치 추적이 가능한 단말기를 휴대한 사용자의 현재 및 과거 위치 정보를 활용한 유무선 인터넷 서비스를 말한다. 최근의 이동 통신 기술의 발달과 휴대폰, PDA 등과 같은 모바일 단말의 급속한 확산으로 인하여 LBS 는 유무선 인터넷의 응용 및 위치 정보를 사용한 부가 가치 창출에 있어 핵심적인 역할을 할 것으로 예상되고 있다. 이러한 LBS 를 위해서는 단말의 위치 정보들을 저장 및 관리하고 위치 정보를 이용하여 다양한 위치 기반 서비스를 지원하는 LBS 플랫폼의 역할이 매우 중요하다. 이를 위한 LBS 플랫폼은 위치 정보의 획득. 위치 정보의 저장 및 관리, 인증 및 정보 보호 등의 사용자 관리, 대용량 위치 정보 데이터베이스의 관리 등의 기능을 제공하여야 한다. 본 논문에서는 1) 위치 기반 서비스를 위한 LBS 플랫폼으로써 사용될 수 있는 참조 시스템을 설계한다. 이를 위하여 LBS 플랫폼으로써 참조 시스템이 제공하여야 하는 기능과 각 기능의 처리 흐름을 UML 의 유스케이스(Usecase)를 사용하여 분석 및 설명한다. 또한 2) 설계된 참조 시스템을 사용하여 제공될 수 있는 서비스 시나리오를 알아본다.

• Annual Conference on Human and Language Technology
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• 2009.10a
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• pp.197-201
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• 2009

이 논문은 영어 문장에서 대명사의 참조해소 시스템을 구현한다. 대명사는 문장에서 반복되는 말 대신에 사용하는 단어이다. 반복되는 말을 선행어라고 하며 대명사는 선행어보다 간결한 형식으로 사용된다. 정보검색이나 정보추출에서 대명사를 그대로 색인하여 검색하면 정확한 정보를 추출할 수 없다. 따라서 대용어가 가리키는 개체를 정확히 파악해서 이 정보를 색인하고 검색하면 정보검색, 정보추출, 질의응답의 성능을 크게 개선할 수 있다. 이 논문에서는 CRF모델을 이용해서 이용하여 영어 문서에서 대명사 참조해결 방법을 제안하고 이를 구현한다.

• The KIPS Transactions:PartA
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• v.8A no.4
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• pp.469-478
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• 2001

In the virtual memory system, page replacement policy exerts a great influence on the performance of demand paging. There are LRU(Least Recently Used) and LFU (Least Frequently Used) as the typical replacement policies. The LRU policy performs effectively in many cases and adapts well to the changing workloads compared to other policies. It however cannot distinguish well between frequently and infrequently referenced pages. The LFU policy requires that the page with the smallest reference count be replaced. Though it considers all the references in the past, it cannot discriminate between references that occurred far back in the past and the more recent ones. Thus, it cannot adapt well to the changing workload. In this paper, we first analyze memory reference patterns of eight applications. The patterns show that the recently referenced pages or the frequently referenced pages are accessed continuously as the case may be. So it is rather hard to optimize page replacement scheme by using just one of the LRU or LFU policy. This paper makes an attempt to combine the advantages of the two policies and proposes a new page replacement policy. In the proposed policy, paging list is divided into two lists (LRU and LFU lists). By keeping the two lists in recency and reference frequency order respectively, we try to restrain the highly referenced pages in the past from being replaced by the LRU policy. Results from trace-driven simulations show that there exists points on the spectrum at which the proposed policy performs better than the previously known policies for the workloads we considered. Especially, we can see that our policy outperforms the existing ones in such applications that have reference patterns of re-accessing the frequently referenced pages in the past after some time.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2003.05a
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• pp.269-272
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• 2003

웹을 이용한 교수-학습모형인 WBI 학습을 촉진시키기 위해서 교육전문가에 의해 검증된 학습자료를 효율적으로 관리하는 시스템을 구축하고, 사용자가 원하는 문서를 추정하여 제시한다. 사용자가 참조한 문서들에 대하여 에이전트가 추가, 삭제 등을 자율적으로 하며, 참조 문서간의 유사도를 측정한다. 이 유사도를 이용하여 적합한 문서를 추정하고 제시함으로서 사용자의 불명확한 정보요구에도 적합한 문서를 제공할 수 있다. 따라서, 사용자의 정보수집을 지원하고 웹을 통한 학습환경을 개선하여 WBI 학습을 촉진시킬 수 있다.

• Journal of KIISE:Computer Systems and Theory
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• v.27 no.3
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• pp.324-336
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• 2000

The paper proposes an efficient buffer management scheme to enhance performance of the disk I/O system. Without any user level information, the proposed scheme automatically detects the block reference patterns of applications by associating block attributes with forward distance of a block. Based on the detected patterns, the scheme applies an appropriate replacement policy to each application. We also present a new block allocation scheme to improve the performance of buffer cache when kernel needs to allocate a cache block due to a cache miss. The allocation scheme analyzes the cache hit ratio of each application based on block reference patterns and allocates a cache block to maximize cache hit ratios of system. These all procedures are performed on-line, as well as automatically at system level. We evaluate the scheme by trace-driven simulation. Experimental results show that our scheme leads to significant improvements in hit ratios of cache blocks compared to the traditional schemes and requires low overhead.

• The Journal of the Korea Contents Association
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• v.8 no.1
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• pp.195-202
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• 2008

Reference linking based on a identification system is being widely used both domestically and overseas. National R&D information contains all information related to the R&D programs such as the output and equipment information resulting from the participant and project information. The reference linking service enables the user to freely look up output of a certain program, participant of a project, equipment information from the project or participant and all other information that originates from a R&D project without having to search for it. The reference linking service in the area of national R&D will enable the linking of heterogeneous information produced at different sources.

• The KIPS Transactions:PartD
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• v.12D no.5 s.101
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• pp.729-736
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• 2005

MND(Ministry of National Defense) has developed MND AF(Ministry of National Defense Architecture Framework) and CADM(Core Architecture Data Model) to guarantee interoperability among defense information systems. TRM(Technical Reference Model) and SP(Standard Profile) product defined in MND AF is core part of Information Technology Architecture and core element of interoperability guarantee. In this paper, we proposed a method which manages technical service and standard of TRM and SP, and developed TRM and SP management system based on the method. TRM and SP management system provides the basis for interoperability among information systems and a more efficient development and management of TRM and SP product.

• Journal of KIISE:Computer Systems and Theory
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• v.26 no.9
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• pp.1083-1095
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• 1999

최근 처리기와 입출력 시스템의 속도 차이가 점점 커짐에 따라 버퍼 캐쉬의 효율적인 관리가 더욱 중요해지고 있다. 버퍼 캐쉬는 블록 교체 정책과 선반입 정책에 의해 관리되며, 각 정책은 버퍼 캐쉬에서 블록의 가치 즉 어떤 블록이 더 가까운 미래에 참조될 것인가를 결정해야 한다. 블록의 가치는 응용들의 블록 참조 패턴의 특성에 기반하며, 블록 참조 패턴의 특성에 대한 정확한 분석은 올바른 결정을 가능하게 하여 버퍼 캐쉬의 효율을 높일 수 있다. 본 논문은 각 응용들의 블록 참조 패턴에 대한 특성을 분석하고 이를 자동으로 발견하는 기법을 제안한다. 제안된 기법은 블록의 속성과 미래 참조 거리간의 관계를 이용해 블록 참조 패턴을 발견한다. 이 기법은 2 단계 파이프라인 방법을 이용하여 온라인으로 참조 패턴을 발견할 수 있으며, 참조 패턴의 변화가 발생하면 이를 인식할 수 있다. 본 논문에서는 8개의 실제 응용 트레이스를 이용해 블록 참조 패턴의 발견을 실험하였으며, 제안된 기법이 각 응용의 블록 참조 패턴을 정확히 발견함을 확인하였다. 그리고 발견된 참조 패턴 정보를 블록 교체 정책에 적용해 보았으며, 실험 결과 기존의 대표적인 블록 교체 정책인 LRU에 비해 최대 57%까지 디스크 입출력 횟수를 줄일 수 있었다.Abstract As the speed gap between processors and disks continues to increase, the role of the buffer cache located in main memory is becoming increasingly important. The buffer cache is managed by block replacement policies and prefetching policies and each policy should decide the value of block, that is which block will be accessed in the near future. The value of block is based on the characteristics of block reference patterns of applications, hence accurate characterization of block reference patterns may improve the performance of the buffer cache. In this paper, we study the characteristics of block reference behavior of applications and propose a scheme that automatically detects the block reference patterns. The detection is made by associating block attributes of a block with the forward distance of the block. With the periodic detection using a two-stage pipeline technique, the scheme can make on-line detection of block reference patterns and monitor the changes of block reference patterns. We measured the detection capability of the proposed scheme using 8 real workload traces and found that the scheme accurately detects the block reference patterns of applications. Also, we apply the detected block reference patterns into the block replacement policy and show that replacement policies appropriate for the detected block reference patterns decreases the number of DISK I/Os by up to 57%, compared with the traditional LRU policy.

• Journal of Korea Spatial Information System Society
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• v.11 no.4
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• pp.19-27
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• 2009

Integrated Urban Spatial Information Management Platform (USIMP) is defined as an operational environment where technologies for intelligent management of urban facilities are made possible through the integration of diverse technologies such as sensors for ground and underground facilities, middleware technology, wired and wireless network, GIS-USN linkage. To make the integration of these diverse technology possible, it is imperative to have a sound reference model for the platform. This paper provides a standardized reference model for USIMP based on the RM-OPD(Reference Model for Open Distributed Processing) standard.