• 산업기술연구
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• 제27권A호
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• pp.131-139
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• 2007

The recent advance in wireless network technologies has enabled the streaming media service on the mobile devices such as PDAs and cellular phones. Since the wireless network has low bandwidth channels and mobile devices are actually composed of limited hardware specifications, the transcoding technology is needed to adapt streaming media to given mobile devices. Futhermore owing to the diversity of bandwidth in the wireless network by reason of mobile users' movements and environments, it is difficult to provide stable QoS. In this paper, the autonomic multimedia transcoding system is proposed in order for users to provide network adaptive QoS. Our proposed system is based on the estimation of available bandwidth in wireless network for seamless multimedia streaming service. The proposed system is designed and implemented for various mobile clients. In experiments, we evaluate its seamless multimedia streaming and the adaptation transcoding bit rate according to the changes of bandwidth in wireless network.

• Industrial Engineering and Management Systems
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• 제15권1호
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• pp.19-31
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• 2016

A design method of the network for automated transporters mounted on rails is addressed for automated container terminals. In the network design, the flow directions of some path segments as well as routes of transporters for each flow requirement must be determined, while the total transportation and waiting times are minimized. This study considers, for the design of the network, the waiting times of the transporters during the travel on path segments, intersections, transfer points below the quay crane (QC), and transfer points at the storage yard. An algorithm, which is the combination of a modified Dijkstra's algorithm for finding the shortest time path and a queuing theory for calculating the waiting times during the travel, is proposed. The proposed algorithm can solve the problem in a short time, which can be used in practice. Numerical experiments showed that the proposed algorithm gives solutions better than several simple rules. It was also shown that the proposed algorithm provides satisfactory solutions in a reasonable time with only average 7.22% gap in its travel time from those by a genetic algorithm which needs too long computational time. The performance of the algorithm is tested and analyzed for various parameters.

• 산업경영시스템학회지
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• 제41권1호
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• pp.84-93
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• 2018

In this paper, we propose an Elman recurrent neural network to predict and analyze a time series of power energy consumption. To this end, we consider the volatility of the time series and apply the sample variance and the detrended fluctuation analyses to the volatilities. We demonstrate that there exists a correlation in the time series of the volatilities, which suggests that the power consumption time series contain a non-negligible amount of the non-linear correlation. Based on this finding, we adopt the Elman recurrent neural network as the model for the prediction of the power consumption. As the simplest form of the recurrent network, the Elman network is designed to learn sequential or time-varying pattern and could predict learned series of values. The Elman network has a layer of "context units" in addition to a standard feedforward network. By adjusting two parameters in the model and performing the cross validation, we demonstrated that the proposed model predicts the power consumption with the relative errors and the average errors in the range of 2%~5% and 3kWh~8kWh, respectively. To further confirm the experimental results, we performed two types of the cross validations designed for the time series data. We also support the validity of the model by analyzing the multi-step forecasting. We found that the prediction errors tend to be saturated although they increase as the prediction time step increases. The results of this study can be used to the energy management system in terms of the effective control of the cross usage of the electric and the gas energies.

• 한국산학기술학회논문지
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• 제21권10호
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• pp.106-114
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• 2020

4차 산업혁명 시대의 핵심 인프라로 자리 매김하는 IP(Internet Protocol) 네트워크 시스템을 실제 구축, 시험 및 운영하면서 공부한 내용을 확인하고 이해하는 것은 네트워크 입문자들에게 매우 중요하다. IP 네트워크 시스템은 인터넷 계층 이하의 기능을 담당하는 IP 네트워크 자체와 DNS, DHCP, email 및 WWW로 기본적인 네트워크 서비스를 제공하는 기본 네트워크 시스템, 그리고 VoIP와 같은 응용 서비스 시스템으로 구성된다. 본 논문에서는 공개 소프트웨어 기반의 최소한의 네트워크 형상으로 IP 네트워크 시스템의 제반 기능을 실습해볼 수 있는 플랫폼을 제안하고, 실습 시나리오와 결과를 제시한다. 그리고 ns(network simulator)에 IP 주소 할당과 라우팅 테이블 관리 기능을 추가하여 테이블 기반 데이터그램 라우팅 기법을 사전 학습할 수 있도록 하였다. 본 연구에서 제안된 실습 플랫폼으로 별도의 장비와 비용 부담 없이 개인용 컴퓨터에서 간편하게 실습을 수행할 수 있어 네트워크 입문자에게 유용하리라 기대된다.

• 한국전자통신학회논문지
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• 제9권1호
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• pp.137-142
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• 2014

산업제어시스템(Industrial Control System)은 전력, 가스, 수도, 하수, 오일 및 교통시스템과 같은 국가주요기반시설 및 산업분야에서 원거리에 산재된 시스템의 효과적인 원격모니터링 및 제어를 위해 필수적으로 사용되는 컴퓨터 기반의 시스템을 말한다. 고도로 발전된 IT 및 네트워크 관련 기술들이 산업제어시스템에 적용되어 효율성을 높이는 장점이 있지만, 일반적인 IT 환경에서의 각종 정보시스템이 가지는 사이버보안 취약성 및 사고의 가능성이 증대되는 단점을 가지게 되었다. 산업제어시스템에서 통상적으로 발견되는 취약점은 우선순위, 발생빈도 및 영향의 심각성들과는 무관하게 정책 및 절차, 플랫폼 및 네트워크 등으로 분류된다. 이러한 취약점들은 첫째, 패스워드의 강제 사용등과 같은 보안 정책 및 절차를 적용함으로서 취약점을 경감 시킬 수 있다. 둘째로, 운영체제 및 응용프로그램의 패치 적용, 물리적인 접근제어, 보안프로그램 사용등과 같은 다양한 보안통제를 적용함으로서 취약점을 경감 및 완화 시킬 수 있다. 셋째로, 심층방호개념의 네트워크 설계, 네트워크 통신의 암호화, 네트워크 트래픽 제한, 네트워크 장비에 대한 물리적 접근제어 방법 등과 같은 다양한 보안통제를 적용함으로서 취약점을 제거하거나 완화 시킬 수 있다.

• International Journal of Precision Engineering and Manufacturing
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• 제3권3호
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• pp.12-20
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• 2002

As numerous sensors and actuators are used in many automated systems, various industrial networks are adopted for real-time distributed control. In order to take advantages of the networking, however, the network implementation should be carefully designed to satisfy real-time requirements considering network induced delays. This paper presents an implementation scheme of a networked control system via Profibus-DP network fur real-time distributed control. More specifically, the effect of the network induced delay on the control performance is evaluated on a Profibus-DP testbed. Also, two conventional PID gain tuning methods are slightly modified fur fouling controllers fur the networked control system. With appropriate choices for gains, it is shown that the networked control system can perform almost as well as the traditional control system.

• 산업공학
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• 제20권4호
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• pp.427-437
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• 2007

As increasing the Internet traffic, many researches on access network are reported for end-to-end highspeed broadband network, where E-PON (Ethernet-Passive Optical Network) is one of reasonable candidates for the network with respect to cost and bandwidth utilization. For the high-speed access network, E-PON needs an efficient bandwidth allocation method. This paper describes a WFBA (Water-Filling Bandwidth Allocation) algorithm for the efficient bandwidth allocation with various simulation test. Based upon the simulation test, we suggest several ways to improve performance of E-PON.

• 산업경영시스템학회지
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• 제21권45호
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• pp.181-191
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• 1998

The purpose of this paper is to develop an efficient algorithm for determining the most vital arcs in a weighted network and implement its algorithm on GIS. The most vital arcs in a weighted network of GIS is that arc whose removal from the network results in the greatest increase in shortest distance between two specified nodes. These studies are well applied to a situation where a logistics or communications network is broken by unexpected accidents. Because a user of the system wants to know which arcs are most vital to him so that he can reinforce them against unexpected accidents. We first present an algorithm to find the most vital arcs in a weighted network, then show that how its algorithm can be applied to a geo-spatial network.

• 한국산업정보학회논문지
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• 제9권1호
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• pp.1-6
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• 2004

광 인터넷 네트워크는 WDM(Wavelength Division Multiplexing) 링크를 사용하여 연결 기반의 서비스를 제공하여야 하는 특성을 가지기 때문에 IP 네트워크의 제어 평면을 광 인터넷 네트워크에 적합하게 확장해야 한다. 본 논문에서는 광 인터넷 네트워크를 위해 기존의 라우팅 프로토콜과 시그널링 프로토콜이 어떻게 확장되는지를 살펴보고, 광 인터넷 네트워크 노드가 자동 구성될 수 있는 오버레이 형태의 네트워크 구조를 제시한다.

• 대한산업공학회지
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• 제40권1호
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• pp.1-7
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• 2014

We consider a human contact social network that has connections through cellphone addresses. To construct such a social network, we use real call records provided by a large carrier, and connect to each other if there exists a call record between any two cellphone users. Due to its huge amount of data, we down-sample it in a way that the smallest-degree nodes are removed, in turn, from the network. For a moderate size of the networks we show that the degree distribution of the network follows a power-law distribution via linear regression analysis, implying the so-called scale-free property. We finally suggest some alternative measures to analyze a social network.