• Journal of KIISE:Computing Practices and Letters
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• v.14 no.6
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• pp.567-581
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• 2008

As the size of the web is growing explosively, search engines are becoming increasingly important as the primary means to retrieve information from the Internet. A search engine periodically downloads web pages and stores them in the database to provide readers with up-to-date search results. The web crawler is a program that downloads and stores web pages for this purpose. A large-scale search engines uses a parallel web crawler to retrieve the collection of web pages maximizing the download rate. However, the service architecture or experimental analysis of parallel web crawlers has not been fully discussed in the literature. In this paper, we propose an architecture of the parallel web crawler and discuss implementation issues in detail. The proposed parallel web crawler is based on the coordinator/agent model using multiple machines to download web pages in parallel. The coordinator/agent model consists of multiple agent machines to collect web pages and a single coordinator machine to manage them. The parallel web crawler consists of three components: a crawling module for collecting web pages, a converting module for transforming the web pages into a database-friendly format, a ranking module for rating web pages based on their relative importance. We explain each component of the parallel web crawler and implementation methods in detail. Finally, we conduct extensive experiments to analyze the effectiveness of the parallel web crawler. The experimental results clarify the merit of our architecture in that the proposed parallel web crawler is scalable to the number of web pages to crawl and the number of machines used.

• Proceedings of the Korea Information Processing Society Conference
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• 2001.10b
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• pp.969-972
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• 2001

컴퓨터망의 확대 및 컴퓨터 이용의 증가에 따른 부작용으로 컴퓨터 보안 문제가 중요하게 대두되고 있다. 이에 따라 침입자들로부터 침입을 줄이기 위한 침입탐지 시스템에 관한 연구가 활발히 논의 되고 있다. 본 논문에서 IDS 모델들의 소개와 새로운 IDS의 모델을 제시하고 단위 침입 행동별로 학습된 모니터링 프로세서에서 전송되는 사용자 위협 메시지에 대한 처리를 담당하는 조정자 에이전트 시스템을 설계하고자 한다. 본 논문에 제안된 조정자는 안정화된 메시지 처리 문제 뿐 아니라 기존 모델의 에이전트간 협력 작업에 의해 처리되었던 침입판단 기능 및 모니터링 프로세서들의 관리 기능 또한 수행하도록 한다. 그리고 시스템의 유연성 및 확장성 향상을 하도록 하였다.

• Proceedings of the Korean Information Science Society Conference
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• 2000.10a
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• pp.566-568
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• 2000

급격한 통신의 발달은 분산시스템의 메시지 전달 환경을 FIFO 뿐만 아니라, 인과적 순서로도 가능케 한다. 낙관적 메시지 로깅 기법은 프로세스의 결함을 저비용으로 회복할 수 있다. 기존의 낙관적 메시지 로깅기법은 인과적 메시기 전달 순서를 보장해주는 환경에 적용되었을 때, 회복과정시 각 프로세스가 전체 프로세스에게 회복메시지를 브로드캐스팅함으로써 불필요한 오버헤드를 가진다. 그러나 제안하는 알고리즘은 회복과정을 시작하고 종료하는 시점에서 조정자 프로세스만 전체 프로세스에게 회복메시지를 브로드캐스팅함으로써 이러한 오버헤드를 줄일 수 있다. 즉, 조정자 프로세스가 아닌 프로세스는 정상수행시 유지하고 있는 상태정보에 기반하여 자신과 의존성이 존재하는 프로세스에게만 회복메시지를 선택적으로 멀티캐스팅함으로써 회복과정시 필요한 메시지의 수를 줄이고 전체적인 회복비용을 감소시킨다.

• Proceedings of the KOSOMBE Conference
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• v.1996 no.11
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• pp.29-32
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• 1996

기존의 안과 진단 및 치료 기기의 안구 고정장치는 진단 및 치료에 있어서 피검사자와 검사자에 사이에 충분한 협조가 되지 않을 경우 진단의 비효율성과 치료의 안정성등의 문제가 발생하고있다. 따라서 이러한 문제를 보완하기 위하여 SLO의 전면 세극등을 소형의 반사경으로 대치하고 표시등을 후면의 먼거리에 수직으로 배열시켜서 피검사자에게 적당한 높이의 고정등을 선택하게하여 수직방향의 안구 위치를 고정시키고 SLO(Scanning Laser Ophthalmoscope)의 좌우 회전기능으로 표적의 수평방향을 근절시킨 후에 검사자의 조작으로 원격조정되는 서보장치를 이용하여 다시 반사경을 전방향으로 미세하게 회전되게하여 정확한 위치로 안구를 이동시키게 하는 원격조정 표적 추적장치를 개발하였다. 이에 따라 피검사자는 거울에 비친 먼거리의 허상을 보게 되어 세극등을 이용한 근접주사방식의 단점인 안구의 축동, 폭주등으로 인한 환자의 눈의 피로를 최소화하면서 피검사자의 안구를 검사자가 원하는 위치로 고정시킬 수 있게 함으로써 임상실험에서 안과 진단의 정확성과 관리도를 높이고 치료의 효율성과 안전성을 증가시킬 수 있는 원격조정 추적장치로써의 성능을 확인하였다.

• Journal of KIISE:Information Networking
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• v.31 no.1
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• pp.91-100
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• 2004

This paper presents a receiver-driven TCP flow control mechanism, which is adaptive to the wireless condition, for memory constrained mobile receiver. A receiver-driven TCP flow control is, in general, achieved by adjusting the size of advertised window at the receiver. The proposed method constantly measures at the receiver both the available wireless bandwidth and the packet round-trip time. Depending on the measured values, the receiver adjusts appropriately the size of advertised window. Constrained by the adjusted window which reflects the current state of the wireless network, the sender achieves an improved TCP throughput as well as the reduced round-trip packet delay. Its implementation only affects the protocol stack at the receiver and hence neither the sender nor the router are required to be modified. The mechanism has been implemented in real environments. The experimental results show that in CDMA2000 1x networks the TCP throughput of the proposed method has improved about 5 times over the conventional method when the receiver's buffer size is limited to 2896 bytes. Also, with 64Kbytes of buffer site, the packet round-trip time of the proposed method has been reduced in half, compared the case with the conventional method.

• Journal of Environmental Policy
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• v.6 no.4
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• pp.103-127
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• 2007

This study presents the political economics models to explore the political landscape of special interest groups influencing the government's decision making process for implementing international environmental standard. Starting with the popular menu-auction types of lobbying frameworks in the literature, the study extends its scope of research to multi-principal and multi-agency based international interest group politics and its hybrid case in order to bring the interaction of the relevant interest politics to the fore. Within a specific factor model of international trade between 2 small open economies, we compare the political equilibrium environmental standards in different institutional frameworks which can be feasible in the sense of recently growing role of environmental interest group. Although the conventional finding suggests that cooperative bargaining between the two countries can attain the globally optimal level of the standard, the paper rather explains that the cooperation between the national interest groups and the hybrid case also generate the stricter standard then national interest politics usually do.

• The Journal of the Korea Contents Association
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• v.11 no.2
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• pp.126-134
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• 2011

Recently, many researchers are interested in using join queries to correlate sensor readings stored in different regions. In the conventional algorithm, the preliminary join coordinator collects the synopsis from sensor nodes and determines a set of sensor readings that are required for processing the join query. Then, the base station collects only a part of sensor readings instead of whole readings and performs the final join process. However, it has a problem that incurs communication overhead for processing the preliminary join. In this paper, we propose a novel energy-efficient in-network join scheme that solves such a problem. The proposed scheme determines a preliminary join coordinator located to minimize the communication cost for the preliminary join. The coordinator prunes data that do not contribute to the join result and performs the compression of sensor readings in the early stage of the join processing. Therefore, the base station just collects a part of compressed sensor readings with the decompression table and determines the join result from them. In the result, the proposed scheme reduces communication costs for the preliminary join processing and prolongs the network lifetime.

• Asia-pacific Journal of Multimedia Services Convergent with Art, Humanities, and Sociology
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• v.9 no.7
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• pp.175-185
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• 2019

In order for learners with different characteristics to reach meaningful learning, the curriculum - class-assessment must be integrated. In this study, we classified the integration into three aspects: content compatibility, operator convergence, and institutional connectivity, and looked at the status of unifying special classes in general schools from each perspective. As a result of the study, in terms of content suitability, adjustment of the curriculum to those subject to special education-professorial revision-assessment adjustment was not performed well except for subjects where individualization professors were conducted. From an actor's perspective, the ambiguity of the roles of general and special teachers resulted in the inability of curriculum coordinators, educators, evaluators and others to agree or even minimal consultations. In terms of institutional linkage, the authority and role of curriculum coordination, professorial revision, and assessment coordination were unclear except for subjects where individualization professors were conducted. As an alternative to discuss and remedy these problems, it proposed increasing awareness of individualized education, compulsory consultation and institutional readjustment.

• Journal of KIISE:Information Networking
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• v.27 no.1
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• pp.58-67
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• 2000

The paper presents a representative-based feedback mechanism and rate adaptation policy for congestion control in multicast traffic for multimedia applications. In multicast congestion control, feedback implosion occurs as many receivers send feedback to a sender. We propose to use representatives to avoid the feedback implosion. In our scheme, receivers feedback packet loss information periodically and a sender adapts the sending rate based on the information collected through a hierarchy of representatives. A representative is selected in each region and roles as a filter to decrease the number of feedbacks. The simulation results show that the proposed scheme solves the feedback implosion problem and well adapts in a congested situation.

• International Area Studies Review
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• v.16 no.1
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• pp.303-325
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• 2012

This paper is to provide an analysis on the European Globalisation Adjustment Fund(EGF) program and the study of European Member State. Established in December 2006, the EGF was originally intended to help workers who were affected by redundancies resulting from globalisation. The EGF at present also provides support to workers who were made redundant as a direct result of the global financial and economic crisis. In general, EGF measures are defined as assistance actions for job search, training, upskilling, outplacement, business start-up, etc. The paper focuses on the cases implemented by EGF for redundant workers harmed by globalisation and by a direct result of the global financial & economic crisis, and also focuses on the statistical portrait of the EGF 2007-2011. In addition, the paper provides criteria & implications of the EGF in the changing international economy. Finally, we could learn the importance of the EGF program through the analysis in this paper. With criteria & implications of the EGF program, the effective application to keep workers in employment or help them back into jobs would help us get over difficulties.