• 한국정보처리학회논문지
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• 제7권11호
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• pp.3445-3461
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• 2000

많은 종류의 침입탐지시스템들이 국내외에서 만들어졌으나 이러한 시스템들을 평가할 수 있는 방법론에 대한 연구는 아직 미흡한 상태이다. 이와 같은 상황을 인지하여 본 논문에서는 침입탐지시스템들을 평가할 수 있는 여러 가지 기준 중에서 가장 중요하다고 생각되는 침입탐지시스템 성능 및 안전성 측면에 대해 평가 초점을 맞추어 이에 대한 방법론을 제시하려한다. 기존 침입탐지시스템 성능 측면 평가 관련 연구에서는 주로 오용행위에 대해 평가를 실시하였으며 이에 대한 탐지 능력을 측정하는데 초점을 맞춘 반면 비정상행위 대해서는 현재 자세한 평가 방법론을 제시하고 있지 않은 상황이다. 안전성 평가의 경우 오프라인 방법론상에서는 적용하기 어려우며 기존 온라인 방법론에서는 아직 평가 방법이 제시되고 있지 않은 실정이다. 본 논문에서는 비정상행위의 체계적인 분류와 이를 기반으로 한 비정상행위 생성 방법 제시를 통해 오용행위 탐지시스템과 더불어 비정상행위 탐지시스템에 대해서도 평가 방법을 제시하고자 하며 또한 침입탐지시스템의 안전성을 위해할 수 있는 요소들을 파악하여 이를 기반으로 한 안전성 측면 평가 방법도 같이 제시한다.

• Structural Engineering and Mechanics
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• 제16권3호
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• pp.327-340
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• 2003

Variations in system parameters due to uncertainties of parameters may result in system performance deterioration and create system internal stability problems. Uncertainties in structural modeling of structures are often considered to ensure that the control system is robust with respect to response errors. So the uncertain concept plays an important role in the analysis and design of the engineering structures. In this paper, the active control of the intelligent structures with the uncertainties is studied and a new method for analyzing the robustness of systems with the uncertainties is presented. Firstly, the system with uncertain parameters is considered as the perturbation of the system with deterministic parameters. Secondly, the feedback control law is designed on the basis of deterministic system. Thirdly, perturbation analysis and robustness analysis of intelligent structures with uncertainties are discussed when the feedback control law is applied to the original system and perturbed system. Combining the convex model of uncertainties with the finite element method, the analysis theory of the robustness of intelligent structures with the uncertainties can be developed. The description and computation of the robustness of intelligent structures with uncertain parameters is obtained. Finally, a numerical example of the application of the present method is given to show the validity of the method.

• KSII Transactions on Internet and Information Systems (TIIS)
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• 제6권5호
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• pp.1333-1353
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• 2012

The robustness of a network is usually measured by error tolerance and attack vulnerability. Significant research effort has been devoted to determining the network design with optimal robustness. However, little attention has been paid to the problem of how to improve the robustness of existing networks. In this paper, we investigate how to optimize attack tolerance and communication efficiency of an existing network under the limited link addition. A survival fitness metric is defined to measure both the attack tolerance and the communication efficiency of the network. We show that network topology reconfiguration optimization with limited link addition (NTRLA) problem is NP-hard. Two approximate solution methods are developed. First, we present a degree-fitness parameter to guide degree-based link addition method. Second, a preferential configuration node-protecting cycle (PCNC) method is developed to do trade-off between network robustness and efficiency. The performance of PCNC method is demonstrated by numerical experiments.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2003년도 ICCAS
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• pp.903-908
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• 2003

In this paper, we present an observer-based robust controller which achieves not only robust stability but also an performance robustness for linear uncertain discrete-time systems. The performance robustness means that comparing the transient behavior of the uncertain system with a desired one generated by the nominal system, the deterioration of control performance (i.e. the error between the real response and the desired one) is suppressed without excessive control input. The control law consists of a state feedback law for the nominal system and a compensation input given by a feedback form of an estimated error signal. In this paper, we show that conditions for the existence of the observer-based controller are given in terms of linear matrix inequalities (LMIs). Finally, a numerical example is given to illustrate the proposed technique.

• 한국지능시스템학회논문지
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• 제14권2호
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• pp.247-252
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• 2004

In this paper are proposed 2nd-order PD-type iterative learning control algorithms for linear continuous-time system and linear discrete-time system. In contrast to conventional methods, the proposed learning algorithms are constructed based on both time-domain performance and iteration-domain performance. The convergence of the proposed learning algorithms is proved. Also, it is shown that the proposed method has robustness in the presence of external disturbances and the convergence accuracy can be improved. A numerical example is provided to show the effectiveness of the proposed algorithms.

• 대한기계학회논문집A
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• 제26권9호
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• pp.1859-1865
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• 2002

In the conventional sliding mode control technique, a priori knowledge of the bound of external disturbances or/and parameter uncertainties is required to assure control robustness. This, however, may not be easy to obtain in practical situation. This work presents a novel methodology, a sliding mode controller with perturbation estimator, which offers a robust control performance without a priori knowledge about the perturbations (disturbances and parameter uncertainties). The proposed technique is featured by an integrated average value of the imposed perturbation over a certain sampling period. In order to demonstrate the effectiveness of the proposed methodology, a two-link robotic system is adopted and its position control performance is evaluated. In addition, a comparative work between the conventional technique and the proposed one is undertaken.

• Journal of Mechanical Science and Technology
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• 제16권3호
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• pp.283-291
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• 2002

The paper demonstrates the tracking performance of a sliding horizon feedback/feedforward preview optimal control when applied to a hydraulic motion simulator which has been built to provide a means of replicating the actual ride dynamics of an automobile seat/human system. The design was developed by solving an ordinary differential equation problem instead of a Ricatti equation. Simulation results indicate that the proposed technique has good performance improvement in phase tracking when compared to the classical design methods. It is also found that the controller can be adjusted more easily for robustness due to more tuning parameters.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2003년도 컴퓨터소사이어티 추계학술대회논문집
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• pp.7-10
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• 2003

In this paper, we present a new echo kernel, which is a modification of polar echo kernel. to improve the detection performance and robustness against attacks. Polar echo kernel may take advantage of large detection margin from the polarity of inserted echo signal, but its poor frequency response in low frequency band degrades sound quality. To solve this problem, we applied bipolar echo pulses to the polar echo kernel. Using the proposed echo kernel the distributions of autocepstrum peaks fur data ‘0’ and ‘1’ are located more distant and improvement of detection performance is achieved. It also makes the low frequency band flat so that the timbre difference in the polar echo kernel can be removed to reproduce the imperceptible sound qualify. Informal listening tests as well as robustness test against attacks were performed to evaluate the proposed echo kernel. Experimental results demonstrated the superiority of the proposed echo kernel to both conventional unipolar and polar echo kernels

• Smart Structures and Systems
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• 제19권4호
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• pp.383-391
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• 2017

In this paper, we investigate the impacts of network topology on the performance of a distributed estimation algorithm, namely combine-then-adaptive (CTA) diffusion LMS, based on the data with or without the assumptions of temporal and spatial independence with noisy links. The study covers different network models, including the regular, small-world, random and scale-free whose the performance is analyzed according to the mean stability, mean-square errors, communication cost (link density) and robustness. Simulation results show that the noisy links do not cause divergence in the networks. Also, among the networks, the scale free network (heterogeneous) has the best performance in the steady state of the mean square deviation (MSD) while the regular is the worst case. The robustness of the networks against the issues like node failure and noisier node conditions is discussed as well as providing some guidelines on the design of a network in real condition such that the qualities of estimations are optimized.

• Journal of Power Electronics
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• 제17권4호
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• pp.983-990
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• 2017

This paper proposes a model predictive control based on the discrete Lyapunov function to improve the performance of power electronic converters. The proposed control technique, based on the finite control set model predictive control (FCS-MPC), defines a cost function for the control law which is determined under the Lyapunov stability theorem with a control error compensation. The steady state and dynamic performance of the proposed control strategy has been tested under a single phase AC/DC voltage source rectifier (S-VSR). Experimental results demonstrate that the proposed control strategy not only offers global stability and good robustness but also leads to a high quality sinusoidal current with a reasonably low total harmonic distortion (THD) and a fast dynamic response under linear loads.