• Convergence Security Journal
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• v.7 no.2
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• pp.73-80
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• 2007

The fact that since Internet has been spreaded widely to people, Many security problems also have been grown too much. Due to sudden growth, administrator's responsibility for secure network and services has been growing more and more. This paper represents how to prevent account which didn't use for long period on multi domains environment using service log analysis. hence administrator can find security hole on systems and can dealing with it. The Service Log Analyzer is that loading log file which are written by each service and analyzing them. as a result it makes a list named Used User List contains a number of account names which uses specific services. When the time has come - means cron job schedule time, User Usage Shifter is the next runner. it's mission is finding the person who didn't used service for a specific period of time. Then modifying the expire day of the account information.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.25 no.1A
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• pp.132-141
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• 2000

In this paper, we proposed the MAC protocol of APON supporting multi-class traffic such as CBBUVBR, ABR, UBR, to guarantee the required QoS of each service. For this, we analyze the performance of variousrequest mechanisms and employee the different request mechanism for each traffic classes. Upstream anddownstream frame structures to minimize transmission overhead are proposed based on our request mechanism.The proposed MAC protocol applies the different priority to permit distribution process. CBBWBR traffic, withthe stringent requirements on CDV or delay, is allocated prior to any other class. ABR traffic, which hasnon-strict CDV or delay criteria, uses flexibly the available bandwidth but ensures a minimum cell rate (MCR).UBR traffic is allocated with lowest priority for the remaining capacity. The performance of proposed protocol isevaluated in terms of transfer delay and 1-point CDV with various offered load. The result of simulation showsthat the proposed protocol guarantees the required QoS of the corresponding category, while making use of theavailable resources in both an efficient and dynamical way.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.3
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• pp.664-674
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• 1996

In high speed multi-wavelength networks, retransmission overhead due to desination conflict or control packet collision is one factor of performance degration because signal prpagation delay is much larger than the transmission time of data packet. In this paper, an efficient WDMA protocol with a collision avoidance mechanism is proposed for high speed WDM single-hop network with a passive star topology. In proposed protocol, each node has cource queues and routing table to store souting informatio. This architecture makes is possible to avoid any kind of collision when a node reserves the channel to transmit a data packet. High system thoughput and channel utilization can be achieved by proposed protocol since there are no discarded packets caused by any collision at transmission time. The performance of proposed protocol is evaluated in term of throughput and delay with variations in offered load. Simulation results show that the proposed protocol has superior performance to convertional protocols under nonuniform traffic as well as uniform traffic.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.39B no.10
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• pp.645-653
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• 2014

Recently, the ocean field researches such as offshore plant, ocean survey and underwater monitoring systems are garnering the attention from both academy and industry. However, the communication in underwater environment is very difficult because of the unique irregular features in water. This is the reason that the application of terrestrial protocols to the water environment is not proper. This paper proposes a routing algorithm that can enhance communication reliability by utilizing channel properties in underwater environment. We address two problems that lead to the poor communication performance, signal attenuation and multi-path problem in water. Overcoming these problems, the proposed algorithm ensures high packet delivery ratio and low transmission delay. Also, this paper evaluates the performance through simulation.

• Journal of Internet Computing and Services
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• v.2 no.4
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• pp.41-53
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• 2001

Multi-distributed web cluster model built for high availability E-Business model exposes internal system nodes on its structural characteristics and has a potential that normal job performance is impossible due to the intentional prevention and attack by an illegal third party. Therefore, the security system which protects the structured system nodes and can correspond to the outflow of information from illegal users and unfair service requirements effectively is needed. Therefore the suggested distributed invasion detection system is the technology which detects the illegal requirement or resource access of system node distributed on open network through organic control between SC-Agents based on the shared memory of SC-Server. Distributed invasion detection system performs the examination of job requirement packet using Detection Agent primarily for detecting illegal invasion, observes the job process through monitoring agent when job is progressed and then judges the invasion through close cooperative works with other system nodes when there is access or demand of resource not permitted.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2013.10a
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• pp.1055-1057
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• 2013

Routers currently used in homes and institutions have a function of multiple computers to connect to the Internet with a single IP address. It is possible only through setting or establishing a separate operation in a used PC or server to function as a web/printer server, web hard, and P2P. In this paper, by utilizing the OpenWRT Linux-based through the construction of the Web server through a router OpenWRT of (Open Wireless Router) base, to build a server simple compact, low power consumption, low cost, to operate by reliability to provide Internet telephony and multimedia services high securely over the server security, which is based on the setting of policy and various firewall at the same time the configuration of the network utilizing OpenWRT router that can be enhanced, to construct a Web server through a router multi functional can receive the provision of services using the program PC and mobile APP.

• Korean Journal of Optics and Photonics
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• v.6 no.4
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• pp.379-384
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• 1995

In order to construct B-ISDN, it is inevitable to introduce optical fiber of low loss and wide bandwidth. Coincidently, high count optical fiber cable is solely important to form optical subscriber network. The best structure of high count optical fiber cable to achieve multi-splicing as well as high density at the same time is the one of taking optical ribbon as a unit of accomodation. However, since optical ribbon has its own width. optical loss due to length difference during the bending of ribbon cable unit occurs in relatively easy way. Therefore, care should be taken during its manufacturing and storage. In t\1::; paper, strain, bending radius and lateral pressure of each fiber in ribbon due to the bending of ribbon cable unit are caculated theoretically. Hence, we have measured optical loss of each fiber as function of unit bending radius, when we bent the ribbon cable unit on the various reel. We found that the result accords well with the theoretical analysis. The result shows the importance to determine proper radius of reel used in ribbon cable manufacturing and storage. orage.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.33 no.7B
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• pp.469-476
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• 2008

In this paper we analyze the packet interference probability and the aggregated throughput of a WPAN in which a number of Bluetooth piconets share the ISM band with WLANS. Using an Adaptive Frequency Hopping algorithm, when the AFH is employed, the number of hops available to the Bluetooth piconets varies depending on the number of independent WLANs within the piconet's radio range. Using a packet collision model in a piconet cluster, we give an analysis of the packet interference probability and the aggregated throughput as a function of the available hops for the AFH algorithm. We also present an analytical model of packet interference with multi-path fading channel in a cluster of piconets. Through analysis, we obtain the packet collision probability and aggregated throughput assuming capture effect. Numerical examples are given to demonstrate the effect of various Parameters such as capture ratio, Rice factor and cluster size on the system performance.

• Journal of the Korean Institute of Intelligent Systems
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• v.24 no.1
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• pp.71-77
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• 2014

In this paper, we propose an improved numeric character recognition method which can recognize numeric characters well under low-illuminated and shade-illuminated environment. The LN(Local Normalization) preprocessing method is used in order to enhance low-illuminated and shade-illuminated image quality. The reading area is detected using line segment information extracted from the illumination-normalized meter images, and then the three-phase procedures are performed for segmentation of numeric characters in the reading area. Finally, an efficient hybrid classifier is used to classify the segmented numeric characters. The proposed numeric character classifier is a combination of multi-layered feedforward neural network and template matching module. Robust heuristic rules are applied to classify the numeric characters. Experiments using meter image database were conducted. Meter image database was made using various kinds of meters under low-illuminated and shade-illuminated environment. The experimental results indicates the superiority of the proposed numeric character recognition method.

• The Journal of the Convergence on Culture Technology
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• v.6 no.2
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• pp.521-527
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• 2020

Quantum-dot cellular automata (QCA) is a technology that attracts attention as a next-generation digital circuit design technology, and several digital circuits have been proposed in the QCA environment. Content-addressable memory (CAM) is a storage device that conducts a search based on information stored therein and provides fast speed in a special process such as network switching. Existing CAM cell circuits proposed in the QCA environment have a disadvantage in that a required area and energy dissipation are large. The CAM cell is composed of a memory unit that stores information and a match unit that determines whether or not the search is successful, and this study proposes an improved QCA CAM cell by designing the memory unit in a multi-layer structure. The proposed circuit uses simulation to verify the operation and compares and analyzes with the existing circuit.