• 전자공학회논문지A
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• 제32A권8호
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• pp.1-10
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• 1995

We have analyzed the reliability of failure models in circuit-switched networks. These models are grid topology circuit-switched networks, and each node transmits a packet to a destination node using a Flooding routing method. We have assumed that the failure of each link and node is independent. We have considered two method to analyze reliability in these models : The Karnaugh Map method and joint probability method. In this two method, we have analyzed the reliability in a small grid topology circuit switched network by a joint probability method, and comared analytic results with simulated ones. For a large grid enormous. So, we have evaluated the reliability of the network by computer simulation techniques. As results, we have found that the analytic results are very close to simulated ones in a small grid topology circuit switched network. And, we have found that network reliability decreases exponentially, according to increment of link or node failure, and network reliability is almost linearly decreased according to increment of the number of links, by which call has passed. Finally, we have found an interesting result that nodes in a center of the network are superior to the other nodes from the reliability point of view.

• 대한전기학회논문지:전력기술부문A
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• 제49권7호
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• pp.313-322
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• 2000

This paper presents optimal placement of minimal set of Phasor Measurement Units (PMU's) and observability analysis of the network with PMU's. In order to find a observable system, a symbolic method which directly assigns an appropriate symbol for measurement or pseudo-measurement to every entry of node-branch incidence matrix is proposed. It is much simpler and easier to analyze the observability of the network with PMU's than the conventional ones. For the optimal PMU placement problem, two approaches which are based on a modified Simulated-Annealing (SA) method and a Direct Combination method are proposed. Some case studies with IEEE sample system are made to show the performance of the proposed methods are almost alike and more effective than the conventional simulated-annealing method. It is also shown that the Direct Combination method is more effective than the modified simulated-annealing one in the sense of computation burden. The results of this study showed also that the accuracy of power system estimation and system observability can be improved the proposed PMU placements.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.275-280
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• 2011

Due to high-speed of trains, the track deformation increases rapidly and may lead to track irregularities causing the track stability problem. To secure the track stability, the continual inspection on track irregularities is required. The paper presents a methodology for identifying track irregularity using the NARX neural network considering non-linearity in the train structural system. A simulation study has been carried out to examine the proposed method. Acceleration time history data measured at a bogie were re-sampled to every 0.25m track irregularity. In the simulation study, two sets of measured data were simulated. The second data set was obtained by a train with 10% more mass than the one for the first data set. The first set of simulated data was used to train the series-parallel mode of NARX neural network. Then, the track irregularities at the second time period are identified by using the measured acceleration data. The closeness of the identified track irregularity to the actual one is evaluated by PSD and RMSE.

• 한국정보통신학회논문지
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• 제3권2호
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• pp.397-402
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• 1999

본 논문에서는 모형 헬리콥터의 동적방정식을 유도하고 이 헬리콥터의 자세를 제어하기 위해서 신경망을 이용한 제어법을 제안하였다. 신경망의 결합계수들은 제어계의 출력과 기준시간의 오차를 최소화하도록 조종된다. 제안한 제어기의 이득은 신경망의 역전파 알고리즘에 의해서 자동적으로 조정된다. MATLAB을 이용한 시뮬레이션 결과를 제시하였다.

• 한국생산제조학회지
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• 제24권1호
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• pp.63-68
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• 2015

Pattern layout design is very important to the automation of apparel industry. Until now, the genetic algorithm and Tabu search method have been applied to layout design automation. With the genetic algorithm and Tabu search method, the obtained values are not always consistent depending on the initial conditions, number of iterations, and scheduling. In addition, the selection of various parameters for these methods is not easy. This paper presents a hybrid search method that uses a neural network and simulated annealing to solve these problems. The layout of pattern elements was optimized to verify the potential application of the suggested method to apparel pattern layout design.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 1999년도 추계종합학술대회 논문집
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• pp.841-844
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• 1999

The interference situation from NGSO/FSS network to GSO/FSS network is more complicated than the situation between GSO networks because of the time varying orbital characteristics of NGSO systems. In this paper, the interference characteristics for several types of hand-over strategies are simulated and it is shown that the results should be useful in practical coordination of inter-network interference.

• 한국공작기계학회논문집
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• 제12권5호
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• pp.1-7
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• 2003

In order to predict vibrations occurred during end-milling processes, the cutting dynamics was modelled by using neural network and combined with structural dynamics by considering dynamic cutting state. Specific cutting force constants of the cutting dynamics model were obtained by averaging cutting forces. Tool diameter, cutting speed, fled, axial and radial depth of cut were considered as machining factors in neural network model of cutting dynamics. Cutting farces by test and by neural network simulation were compared and the vibration displacement during end-milling was simulated.

• 한국통신학회논문지
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• 제32권5B호
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• pp.277-285
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• 2007

본 논문에서는 2003년 국내 뿐만 아니라 전세계의 인터넷망에서의 심각한 소통장애를 일으켰던 슬래머 웜 보안공격의 전파과정에 대한 새로운 통신망 모델을 제시하고 NS-2를 이용한 시뮬레이터를 구현하여 웜 보안공격에 의한 전파과정을 분석하였다. 기존 DN-AN모델을 Abstract network-Abstract network(AN-AN)모델로 추상화함으로써 국내 뿐만 아니라 전 세계의 수많은 호스트를 대상으로 한 대규모 인터넷망에 대하여 최초의 웜 패킷이 국내의 인터넷 국제관문국으로 유입된 시점부터 국내의 망이 포화되는 전 과정을 시간대별로 분석할 수 있는 NS-2용 시뮬레이터를 구현하였다. 또한 구현된 시뮬레이터는 감염된 국내의 호스트에 의해 국외의 호스트를 감염시키는 과정도 분석 가능하였다. 시뮬레이션 결과 290초만에 8,848개의 국내 호스트가 감염되었고, 308초만에 66,152개의 국외 호스트가 감염되었다. 또한 공격시 수행되는 웜 감염 전파과정에 의해 국내로 유입되거나 국외로 유출되는 웜 감염패킷들은 국제관문국에서 각각 154초와 135초내에 포화됨을 알 수 있었다.

• 시스템엔지니어링학술지
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• 제12권2호
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• pp.101-114
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• 2016

A model-based systems engineering (MBSE) approach to implementing hardware-based network cybersecurity controls for APR1400 non-safety data network is presented in this work. The proposed design was developed by implementing packet filtering and deep packet inspection functions to control the unauthorized traffic and malicious contents. Denial-of-Service (DoS) attack was considered as a potential cybersecurity issue that may threaten the data availability and integrity of DCS gateway servers. Logical design architecture was developed to simulate the behavior of functions flow. HDL-based physical architecture was modelled and simulated using Xilinx ISE software to verify the design functionality. For effective modelling process, enhanced function flow block diagrams (EFFBDs) and schematic design based on FPGA technology were together developed and simulated to verify the performance and functional requirements of network security controls. Both logical and physical design architectures verified that hardware-based cybersecurity controls are capable to maintain the data availability and integrity. Further works focus on implementing the schematic design to an FPGA platform to accomplish the design verification and validation processes.

• 정보처리학회논문지A
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• 제18A권6호
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• pp.281-292
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• 2011

본 논문에서는 NS - 2 시뮬레이션 소프트웨어를 적용하여 AMI 네트워크 환경의 네트웍 시뮬레이터를 설계 및 구현하였다. 데이터의 처리 시간, 네트웍 프로토콜 그리고 시스템 성능 등과 같은 다양하고 제한된 AMI 운영 환경에서 최적의 AMI 네트웍 구성을 구현하기 위하여 시뮬레이션 될 것이다. 따라서 본 AMI 네트웍 시뮬레이터는 실제 네트웍과 장비와 최대한 비슷한 환경에서 운영될 수 있도록 구현되었다. 본 시스템의 개발로 앞으로 AMI 네트웍 시뮬레이터는 유틸리티의 AMI 본격 전개시 AMI 운영 네트웍 설계에 적용됨으로써, 운영 자원의 낭비를 줄이고 AMI 운영의 효율성을 극대화 할 수 있을 것으로 기대한다.