• Journal of KIISE:Computer Systems and Theory
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• v.28 no.9
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• pp.434-441
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• 2001

The concept of network memory was introduced for the efficient exploitation of main memory in a cluster. Network memory can be used to speed up applications that frequently access large amount of disk data. In this paper, we present a memory a management algorithm that does not require prior knowledge of access patterns and that is practical to implement under the web server cluster, In addition, our scheme has a good user response time for various access distributions of web documents. Through a detailed simulation, we evaluate the performance of our memory managment algorithms.

• The KIPS Transactions:PartA
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• v.14A no.1 s.105
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• pp.63-72
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• 2007

This paper introduces a load-balancing algorithm focusing on distributing web requests evenly into the web cluster servers. The load-balancing algorithms based on conventional periodic load-information update mechanism are not suitable for dynamic page applications, which are common in Cyber Foraging services, due to the problems caused by periodic synchronized load-information updating and the difficulties of work load estimation caused by embedded executing scripts of dynamic pages. Update-on-Finish algorithm solves this problem by using non-periodic load-update mechanism, and the web switch knows the servers' real load information only after their reporting and then distributes new loads according to the new load-information table, however it results in much communication overhead. Our proposed mechanism improve update-on-finish algorithm by using K-Percents-Finish mechanism and thus largely reduce the communication overhead. Furthermore, we consider the different capabilities of servers with a threshold Ti value and propose a load-balancing algorithm for servers with various capabilities. Simulation results show that the proposed K-Percents-Finish Reporting mechanism can at least reduce 50% communication overhead than update-on-finish approach while sustaining better load balancing performance than periodic mechanisms in related work.

• Journal of KIISE:Computing Practices and Letters
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• v.8 no.6
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• pp.639-646
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• 2002

In this paper, we discuss the system configuration and the design issues of CATS-i, a set of installation and administration tools for Linux cluster systems. CATS-i enables users to manage cluster systems easily, quickly, and safety. It integrates many functions, ranging from installing operating systems and applications to real-time monitoring and management of various important resources. In addition, batch job submission and management are included. These functions support a single system image. Finally, a powerful graphic user interface based on Java lets users quickly understand the cluster status and conveniently use the CATS-i on the Web.

• Educational Technology International
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• v.18 no.2
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• pp.193-213
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• 2017

This study aimed to explore online learning profiles of in-service teachers in South Korea, focusing on video lecture and discussion activities. A total of 269 teachers took an online professional development course for 14 days, using an online learning platform from which web log data were collected. The data showed the frequency of participation and the initial participation time, which was closely related to procrastinating behaviors. A cluster analysis revealed three online learning profiles of in-service teachers: procrastinating (n=42), passive interaction (n=136), and active learning (n=91) clusters. The active learning cluster showed high-level participation in both video lecture and discussion activities from the beginning of the online course, whereas the procrastinating cluster was seldom engaged in learning activities for the first half of the learning period. The passive interaction cluster was actively engaged in watching video lectures from the beginning of the online course but passively participated in discussion activities. As a result, the active learning cluster outperformed the passive interaction cluster in learning achievements. The findings were discussed in regard to how to improve online learning environments through considering online learning profiles of in-service teachers.

• Journal of Korea Multimedia Society
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• v.21 no.2
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• pp.199-209
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• 2018

Recently, services provided to consumers are increasingly being combined with big data such as low-priced shopping, customized advertisement, and product recommendation. With the increasing importance of big data, the web crawler that collects data from the web has also become important. However, there are two problems with existing web crawlers. First, if the URL is hidden from the link, it can not be accessed by the URL. The second is the inefficiency of fetching more data than the user wants. Therefore, in this paper, through the Casper.js which can control the DOM in the headless brwoser, DOM event is generated by accessing the URL to the hidden link. We also propose an intelligent web crawler system that allows users to make steps to fine-tune both Structured and unstructured data to bring only the data they want. Finally, we show the superiority of the proposed crawler system through the performance evaluation results of the existing web crawler and the proposed web crawler.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.12
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• pp.708-713
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• 2003

For many years clustered heterogeneous web server architecture has been formed on the internet because the explosive internet services and the various quality of requests. The critical point in cluster environment is the mapping schemes of request to server. and recently this is the main issue of internet architecture. The topic of previous mapping methods is to assign equal loads to servers in cluster using the number of requests. But recent growth of various services makes it hard to depend on simple load balancing to satisfy appropriate latency. So mapping based on requested content to decrease response time and to increase cache hit rates on entire servers - so called “content-based” mapping is highly valuated on the internet recently. This paper proposes Prioritized Highest Random Weight mapping(PHRW mapping) that improves content-based mapping to properly fit in the heterogeneous environment. This mapping scheme that assigns requests to the servers with priority, is very effective on heterogeneous web server cluster, especially effective on decreasing latency of reactive data service which has limit on latency. This paper have proved through algorithm and simulation that proposed PHRW mapping show higher-performance by decrease in latency.

• International Journal of Internet, Broadcasting and Communication
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• v.4 no.1
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• pp.13-17
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• 2012

Indexing allows converting raw document collection into easily searchable representation. Web searching by Google or Yahoo provides subsecond response time which is made possible by efficient indexing of web-pages over the entire Web. Indexing process gets challenging when the scale gets bigger. Parallel techniques, such as MapReduce framework can assist in efficient large-scale indexing process. In this paper we propose PDFindexer, system for indexing scientific papers in PDF using MapReduce programming model. Unlike Web search engines, our target domain is scientific papers, which has pre-defined structure, such as title, abstract, sections, references. Our proposed system enables parsing scientific papers in PDF recreating their structure and performing efficient distributed indexing with MapReduce framework in a cluster of nodes. We provide the overview of the system, their components and interactions among them. We discuss some issues related with the design of the system and usage of MapReduce in parsing and indexing of large document collection.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.15 no.5
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• pp.1708-1727
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• 2021

In the advent of the twenty-first century, human beings began to closely interact with technology. Today, technology is developing, and as a result, the world wide web (www) has a very important place on the Internet and the significant task is fulfilled by Web services. A lot of Web services are available on the Internet and, therefore, it is difficult to find matching Web services among the available Web services. The recommendation systems can help in fixing this problem. In this paper, our observation was based on the recommended method such as the collaborative filtering (CF) technique which faces some failure from the data sparsity and the cold-start problems. To overcome these problems, we first applied an ontology-based clustering and then the k-nearest neighbor (KNN) algorithm for each separate cluster group that effectively increased the data density using the past user interests. Then, user ratings were predicted based on the model-based approach, such as singular value decomposition (SVD) and the predictions used for the recommendation. The evaluation results showed that our proposed approach has a less prediction error rate with high accuracy after analyzing the existing recommendation methods.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 2007.11a
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• pp.899-904
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• 2007

Process management techniques are highly important in the construction industry. However, indicators or details of assessment which will show process management and its performance are still very insufficient. In particular, it is true that local corporations or small and medium sized companies suffer more difficulties than ones in metropolitan areas. Therefore, it is necessary to prepare a flexible process management and performance assessment system suited to field situations. This study identified problems of local small and medium sized companies, implemented a process and performance management system using the Lean concept, and systemized a web-based system. Also, the study proposed operational strategies so that small and medium construction companies may access and use the system easily. This will ensure the competitiveness of local small and medium sized companies, will pursue visible outcomes such as construction period reduction and construction cost reduction, and will be utilized as data related to performance assessment both during construction progress and after construction.

• Proceedings of the Korean Information Science Society Conference
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• 2004.10a
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• pp.64-66
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• 2004

현재까지 대부분의 클러스터들은 웹 서비스를 지원하지 않고 있다. 하지만 웹 서비스를 사용하면 서비스 사이의 상호 의존성을 최소한으로 줄일 수 있다 그리고 프로토콜에 얽매이지 않기 때문에 코드 재활용 성 및 확장성이 높아진다는 장정이 있다. 또한 서비스간에는 개발 언어에 상관없이 서비스 개발이 가능하며 이렇게 개발된 서비스간의 통합 역시 용이하기 때문에 클러스터를 구축하는 비용을 줄일 수 있다. 더욱이 클러스터를 윈도우 환경으로 구축할 경우에는 다양한 GUI 도구들과 않은 어플리케이션을 사용할 수 있어서 리눅스를 기반으로 클러스터를 구축할 때 보다 좀 더 쉽게 클러스터를 구축할 수 있다. 따라서 본 논문에서는 윈도우 환경의 컴퓨터들을 서로 연결하여 클러스터를 만들고 웹 서비스를 통하여 작업을 스케쥴링할 수 있는 클러스터 작업 스케쥴러를 설계하고자 한다. 본 논문에서 설계한 클러스터 작업 스케쥴러는 크게 SchedulingClient ClusterJobScheduler와 ResourceManager 3 부분으로 나누어진다. SchedulingClient는 사용자의 작업 정보를 입력받는 사용자용 어플리케이션이고 ClusterJobScheduler는 사용자의 작업 정보를 큐에 저장하고, 스궤쥴링하며, 작업의 결과를 사용자에게 전달하는 웹 서비스 어플리케이션이다. 그리고 ResourceManager는 클러스터를 구성하는 컴퓨터를 관리하는 기능을 한다.