• Journal of Korea Multimedia Society
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• v.7 no.10
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• pp.1400-1411
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• 2004

Recently, explosion of internet user requires fundamental changes on the architecture of Web service system, from single server system to clustered server system, in parallel with the effort for improving the scalability of the single internet server system. But current cluster-based server systems are dedicated to the single application, for example, One-IP server system. One-IP server system has a clustered computing node with the same function and tries to distribute each request based on the If to the clustered node evenly. In this paper, we implemented the more useful application service platform. It works on shared clustered server(back-end server) with an application server(front-end server) for a particular service. An application server provides a particular service at a low load by itself, but as the load increases, it reconfigures itself with one or more available server from the shared cluster and distributes the load on selected server evenly We used PVM for an effective management of the clustered server. We found the implemented application service platform provides more stable and scalable operation characteristics and has remarkable performance improvement on the dynamic load changes.

• KIISE Transactions on Computing Practices
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• v.23 no.10
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• pp.605-610
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• 2017

In distributed environments, dynamic partitioning is needed to resolve the load on a particular server or the load caused by communication among servers. In heterogeneous environments, existing dynamic partitioning schemes can distribute the same load to a server with a low physical performance, which results in a delayed query response time. In this paper, we propose a dynamic partitioning scheme for large RDF data in heterogeneous environments. The proposed scheme calculates the query loads with its frequency and the number of vertices used in the query for load balancing. In addition, we calculate the server loads by considering the physical performance of the servers to allocate less of a load to the servers with a smaller physical performance in a heterogeneous environment. We perform dynamic partitioning to minimize the number of edge-cuts to reduce the traffic among servers. To show the superiority of the proposed scheme, we compare it with an existing dynamic partitioning scheme through a performance evaluation.

• Journal of Broadcast Engineering
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• v.10 no.1 s.26
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• pp.83-102
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• 2005

The problem of video scheduling is analyzed in the framework of divisible load scheduling. A divisible load can be divided into any number of fractions (parts) and can be processed/computed independently on the processors in a distributed computing system/network, as there are no precedence relationships. In the video scheduling, a frame can be split into any number of fractions (tiles) and can be processed independently on the processors in the network, and then the results are collected to recompose the single processed frame. The divisible load arrives at one of the processors in the network (root processor) and the results of the computation are collected and stored in the same processor. In this problem communication delay plays an important role. Communication delay is the time to send/distribute the load fractions to other processors in the network. and the time to collect the results of computation from other processors by the root processors. The objective in this scheduling problem is that of obtaining the load fractions assigned to each processor in the network such that the processing time of the entire load is a minimum. We derive closed-form expression for the processing time by taking Into consideration the communication delay in the load distribution process and the communication delay In the result collection process. Using this closed-form expression, we also obtain the optimal number of processors that are required to solve this scheduling problem. This scheduling problem is formulated as a linear pro-gramming problem and its solution using neural network is also presented. Numerical examples are presented for ease of understanding.

• Journal of Internet Computing and Services
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• v.11 no.5
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• pp.71-80
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• 2010

The purpose of this research is to help IPTV (Internet Protocol Television) commercialization using newly produced educational contents in the area of entertainment and education which currently popular in the market. It is called, Stimulus $Tester^{TM}$, endow reaction time from the feedback of learning system, using a non-direct method, for example, a remote controller. Reaction time is the learning efficiency promotion mechanism that learner ascertain the learning condition of oneself by the time with solved questions from the solving the question in given time. Reaction time also play a key role that the learner may go through course which distribute the point to PC from Server. If this system is ready, we expect that the educational industry will gradually spread out. To verify the learning efficiency of this system, we concluded that the learning improvements, by an Internet-based and a paper-based test, of the increase by 51%, from 2.47min to 1.27min, during reaction of 7 days.

• KIISE Transactions on Computing Practices
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• v.23 no.8
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• pp.487-491
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• 2017

Open source software allows the users to freely use, copy, distribute and modify source code without any particular limitations, and this offers the advantages of low entry cost, fast and flexible development, compatibility, reliability and safety. The emergence of many useful open source projects has the advantage of achieving high levels of output with lower costs and time commitment for software development. However, this also increases the risks caused by the security vulnerabilities of the used open source software. There is still no separate process to verify security in using open source software. In this paper, we analyze the security weakness in open source and propose a secure coding scheme in adopting open source, which is known to be highly reliable from a security point of view.

• Journal of the Korea Convergence Society
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• v.7 no.5
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• pp.15-21
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• 2016

Recently the degree of integration of processor and developed rapidly. However, clock speed is not increased, a situation that increases the number of cores in the processor. In this paper, we analyze the performance of a typical Intel Xeon Phi of many core process used for the current operation accelerate. Utilizing the Quantum ESPRESSO, which was calculated using the FFTW library. By varying the number of ranks in MPI when running the benchmarks the performance Xeon Phi. The result shows a good performance in the handling of four job on one physical core. However, four or more to expand the number of MPI Rank is degraded. Through this convergence it was found to improve the performance of Quantum ESPRESSO. It is possible to check the hardware characteristics of the Xeon Phi.

• Journal of KIISE:Computing Practices and Letters
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• v.16 no.3
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• pp.341-345
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• 2010

WMN is one of efficient solutions to provide Internet services for users by forming wireless backbone networks with wireless links. The dominant technology for WMNs is the IEEE 802.11, which provides multi-channel and multi-rate capabilities. One of important issues in WMNs is the network capacity and it is essential to design a multi-channel protocol that leverages the network capacity. However, when wireless links that use different data rates operate on the common channel, the performance of high-rate links is severely degraded by the presence of the low-rate links, which is often referred as performance anomaly. In this paper, we propose a Tree-based Channel Assignment (TreeCA) protocol to mitigate the performance anomaly problem by distributing data rates over multiple channels. TreeCA performs channel assignments based on the tree WMN architecture to accommodate the Internet traffics efficiently. Parent nodes on the tree distribute their child nodes over multiple channels so that the performance anomaly is reduced. Through simulations, we observed that the proposed TreeCA outperforms the existing multi-channel protocols for WMNs.

• KIISE Transactions on Computing Practices
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• v.22 no.12
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• pp.632-645
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• 2016

The enterprise environment, various interface systems are utilized for business processes and for exchange of messages. In the interface communication environment, as business complexity increases, the interface system is connected with numerous systems. With increasing number of linked systems, there is a proportional increase in the workforce, leading to a rise in numerous risks (inconsistency of information, non-compliance with standards, etc.). To solve the problem, we propose a system for managing and centralizing information of the message based interface system. The proposed system enables information integration management, message information distribution, standard code generation, risk management and risk evasion. Using the proposed system, the in development environment user can prevent inconsistent information, analyze risk, avoid risk, distribute information automatically and create a standard code. Ultimately, there is an increase in user productivity and it is possible to evade the risks involved.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.2
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• pp.225-233
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• 2000

Local Number Portability (LNP), an Intelligent Network (IN) service, provides the ability to retain existing telephone numbers when switching from one telecommunications carrier to another, from one region to another, or from one service to another. Local Number Portability (LNP), an Intelligent Network (IN) service, provides the ability to retain existing telephone numbers when switching from one telecommunications carrier to another, from one region to another, or from one service to another. LNP is a key service for increasing competition in the local telephone marketplace. Many countries are now establishing detailed rules for ensuring competition between network operators. Because many major carriers will deploy their own LNP databases, a single access point must be provided to effectively manage and distribute updates to the common regional LNP database. This is called Number Portability Administration Center (NPAC). Recently, CORBA is being accepted as one of the key technologies for developing distributed application systems. To use CORBA for managing IN services, several standard organizations are working towards the integration of IN, TMN and CORBA. In this paper, we present our work on applying the TMN and CORBA technology for the service management of LNP. We first propose a CORBA-based LNP service management system architecture, We then present the design and implementation of a LNP service management system using CORBA.

• KIISE Transactions on Computing Practices
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• v.22 no.2
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• pp.101-106
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• 2016

A femtocell network has been attracting attention as a promising solution for providing high data rate transmission over the conventional cellular network in an indoor environment. In this paper, we propose a distributed power control algorithm considering both indoor coverage and data load balancing in the femtocell network. As data traffic varies by time and location according to user distribution, each femto base station suffers from an unbalanced data load, which may degrade network performance. To distribute the data load, the base stations are required to adjust their transmission power dynamically. Since there are a number of base stations in practice, we propose a distributed power control algorithm. In addition, we propose the simple algorithm to detect the faulty base station and to recover coverage. We also explain how to insert a new base station into a deployed network. We present the simulation results to evaluate the proposed algorithms.