• Smart Structures and Systems
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• 제26권2호
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• pp.175-184
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• 2020

Conventional Monte Carlo simulation-based methods for seismic risk assessment of water networks often require excessive computational time costs due to the hydraulic analysis. In this study, an Artificial Neural Network-based surrogate model was proposed to efficiently evaluate the flow-based system reliability of water distribution networks. The surrogate model was constructed with appropriate training parameters through trial-and-error procedures. Furthermore, a deep neural network with hidden layers and neurons was composed for the high-dimensional network. For network training, the input of the neural network was defined as the damage states of the k-dimensional network facilities, and the output was defined as the network system performance. To generate training data, random sampling was performed between earthquake magnitudes of 5.0 and 7.5, and hydraulic analyses were conducted to evaluate network performance. For a hydraulic simulation, EPANET-based MATLAB code was developed, and a pressure-driven analysis approach was adopted to represent an unsteady-state network. To demonstrate the constructed surrogate model, the actual water distribution network of A-city, South Korea, was adopted, and the network map was reconstructed from the geographic information system data. The surrogate model was able to predict network performance within a 3% relative error at trained epicenters in drastically reduced time. In addition, the accuracy of the surrogate model was estimated to within 3% relative error (5% for network performance lower than 0.2) at different epicenters to verify the robustness of the epicenter location. Therefore, it is concluded that ANN-based surrogate model can be utilized as an alternative model for efficient seismic risk assessment to within 5% of relative error.

• 한국인터넷방송통신학회논문지
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• 제12권3호
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• pp.201-207
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• 2012

RAM 기반 신경망은 2진 신경망(Binary Neural Network, BNN)에 복수개의 정보 저장 비트를 두어 교육의 반복 횟수를 누적하도록 구성된 가중치를 가지지 않는(weightless) 신경회로망으로서 한 번의 교육만으로 학습이 이루어지는 효율성이 뛰어난 신경회로망이다. 지도 학습에 기반을 둔 RAM 기반 신경망은 패턴 인식 분야에는 우수한 성능을 보이는 반면, 비지도 학습에 의해 패턴을 구분해야 하는 범주화 연구에는 적합하지 않은 모델로 분류된다. 본 논문에서는 비지도 학습 알고리즘을 제안하여 RAM 기반 신경망으로 패턴 범주화를 수행한다. 제안된 비지도 학습 알고리즘에 의해 RAM 기반 신경망은 입력 패턴에 따라 자율 학습하여 스스로 범주를 생성할 수 있으며, 이를 통해 RAM 기반 신경망이 지도 학습과 비지도 학습이 모두 가능한 복합 모델임을 증명한다. 실험에 사용한 학습 패턴으로는 0에서 9까지의 오프라인 필기체 숫자로 구성된 MNIST 데이터베이스를 사용하였다.

• Journal of Information Technology Applications and Management
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• 제14권4호
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• pp.121-138
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• 2007

This study proposes a method to improve network security systems based on critical success factors for systems development. To accomplish the research objective, the study analyzes required functions of network security systems and reviews existing methods to improve network security systems. Based on the analyses and literature review, critical success factors for development of network security systems are identified and a new method to improve network security systems based on the critical success factors is proposed. The proposed method to improve network security systems is based on utilizing multi-core processors. A prototype is developed and validated. This study will provide a good case in the network security area where research incorporating both engineering and management disciplines lacks.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제11권1호
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• pp.193-214
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• 2017

In this paper, we study the problem of network utility maximization in a CSMA based multi-hop wireless network. Existing work in this aspect typically adopted continuous time Markov model for performance modelling, which fails to consider the channel conflict impact in actual CSMA networks. To maximize the utility of a CSMA based wireless network with channel conflict, in this paper, we first model its weighted network capacity (i.e., network capacity weighted by link queue length) and then propose a distributed link scheduling algorithm, called CSMA based Maximal-Weight Scheduling (C-MWS), to maximize the weighted network capacity. We derive the upper and lower bounds of network utility based on C-MWS. The derived bounds can help us to tune the C-MWS parameters for C-MWS to work in a distributed wireless network. Simulation results show that the joint optimization based on C-MWS can achieve near-optimal network utility when appropriate algorithm parameters are chosen and also show that the derived utility upper bound is very tight.

• International Journal of Computer Science & Network Security
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• 제22권12호
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• pp.212-216
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• 2022

Space based constellation network is a kind of ad hoc network in which users are self-organized without center node. In space based constellation network, users are allowed to enter or leave the network at any given time. Thus, the number of active users is an unknown and time-varying parameter, and the performance of the network depends on how accurately this parameter is estimated. The so-called problem of active user identification, which consists of determining the number and identities of users transmitting in space based constellation network is discussed and a novel active user identification method is proposed in this paper. Active user identification code generated by transmitter address code and receiver address code is used to spread spectrum. Subspace-based method is used to process received signal and judgment model is established to identify active users according to the processing results. The proposed method is simulated under AWGN channel, Rician channel and Rayleigh channel respectively. Numerical results indicate that the proposed method obtains at least 1.16dB E_b/N₀ gains compared with reference methods when miss alarm rate reaches 10^-3.

• 한국자동차공학회논문집
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• 제14권5호
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• pp.47-57
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• 2006

This paper presents a network-based traction control system(TCS), where several electric control units (ECUs) are connected by a controller area network(CAN) communication system. The control system consists of four ECUs: the electricthrottle controller, the transmission controller, the engine controller and the traction controller. In order to validate the traction control algorithm of the network-based TCS and evaluate its performance, a Hardware-In-the-Loop Simulation(HILS) environment was developed. Herein we propose a new concept of the HILS environment called the network-based HILS(Net-HILS) for the development and validation of network-based control systems which include smart sensors or actuators. In this study, we report that we have designed a network-based TCS, validated its algorithm and evaluated its performance using Net-HILS.

• Smart Structures and Systems
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• 제32권1호
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• pp.49-59
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• 2023

A bridge transportation network supplies products from various source nodes to destination nodes through bridge structures in a target region. However, recent frequent earthquakes have caused damage to bridge structures, resulting in extreme direct damage to the target area as well as indirect damage to other lifeline structures. Therefore, in this study, a surrogate model-based comprehensive framework to estimate the seismic resilience of bridge transportation networks is proposed. For this purpose, total system travel time (TSTT) is introduced for accurate performance indicator of the bridge transportation network, and an artificial neural network (ANN)-based surrogate model is constructed to reduce traffic analysis time for high-dimensional TSTT computation. The proposed framework includes procedures for constructing an ANN-based surrogate model to accelerate network performance computation, as well as conventional procedures such as direct Monte Carlo simulation (MCS) calculation and bridge restoration calculation. To demonstrate the proposed framework, Pohang bridge transportation network is reconstructed based on geographic information system (GIS) data, and an ANN model is constructed with the damage states of the transportation network and TSTT using the representative earthquake epicenter in the target area. For obtaining the seismic resilience curve of the Pohang region, five epicenters are considered, with earthquake magnitudes 6.0 to 8.0, and the direct and indirect damages of the bridge transportation network are evaluated. Thus, it is concluded that the proposed surrogate model-based framework can efficiently evaluate the seismic resilience of a high-dimensional bridge transportation network, and also it can be used for decision-making to minimize damage.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.1051-1055
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• 2003

Policies are collections of general principles specifying the desired behavior and state of a system. Network management is mainly carried out by following policies about the behavior of the resources in the network. Policy-based (PB) network management supports to manage distributed system in a flexible and dynamic way. This paper focuses on configuration management based on Internet Engineering Task Force (IETF) standards. Network security approaches include the usage of intrusion detection system to detect the intrusion, building firewall to protect the internal systems and network. This paper presents how the policy-based framework is collaborated among the network security systems (intrusion detection system, firewall) and intrusion detection systems are cooperated to detect the intrusions.

• 컴퓨터교육학회논문지
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• 제6권3호
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• pp.57-64
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• 2003

이미 SNMP를 기반으로 하는 망 관리 장치가 구현되어 있는 상황에서 OSI망을 기반으로 하는 시스템들로 구성된 망을 추가적으로 관리하고자 하면 새로운 망 관리 시스템을 개발해야 하는 것이 일반적이다. 그리고 OSI망을 기반으로 하는 통신망으로 구축된 시스템들을 관리하기 위해서는 CMIP을 사용하는 것이 표준으로 제시되어 왔다. 추가된 OSI망 요소들을 수용하기 위해, 새로운 망 관리 시스템을 개발하는 것은 개발비용과 기간을 고려하연 매우 비효율적이다. 따라서 본 연구에서는 기존의 SNMP 기반의 망 관리 장치에서 망 인터페이스만을 변경하여 추가적인 OSI 망을 관리하는 시스템을 구축하는 방안과 구현방법을 제시하고자 한다.

• ETRI Journal
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• 제27권5호
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• pp.497-503
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• 2005

In this paper, we present a performance analysis for an MPEG-4 video codec based on the on-chip network communication architecture. The existing on-chip buses of system-on-a-chip (SoC) have some limitation on data traffic bandwidth since a large number of silicon IPs share the bus. An on-chip network is introduced to solve the problem of on-chip buses, in which the concept of a computer network is applied to the communication architecture of SoC. We compared the performance of the MPEG-4 video codec based on the on-chip network and Advanced Micro-controller Bus Architecture (AMBA) on-chip bus. Experimental results show that the performance of the MPEG-4 video codec based on the on-chip network is improved over 50% compared to the design based on a multi-layer AMBA bus.