• Proceedings of the KIEE Conference
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• 1995.07b
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• pp.710-713
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• 1995

Hopfield networks have been applied to the problem of linear system identification. In this paper, Hopfield network based parameter identification scheme of non-linear dynamic systems is proposed. Simulation results demonstrate that Hopfield network can be used effectively for the identification of non-linear systems assuming that the system states and their time derivatives are available. Therefore, the proposed scheme can be applied in fault detection and isolation(FDI) and adaptive control of non-linear systems where the Hopfield networks perform on-line identification of system parameters.

• International Journal of Aeronautical and Space Sciences
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• v.18 no.3
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• pp.535-544
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• 2017

In-flight aircraft engine performance estimation is one of the key techniques for advanced intelligent engine control and in-flight fault detection, isolation and accommodation. This paper detailed the current performance degradation estimation methods, and an improved hybrid Kalman filter via velocity-based LPV (VLPV) framework for these needs is proposed in this paper. Composed of a nonlinear on-board model (NOBM) and VLPV, the filter shows a hybrid architecture. The outputs of NOBM are used for the baseline of the VLPV Kalman filter, while the system performance degradation factors on-line estimated by the measured real system output deviations are fed back to the NOBM for its updating. In addition, the setting of the process and measurement noise covariance matrices' values are also discussed. By applying it to a commercial turbofan engine, simulation results show the efficiency.

• Proceedings of the Korea Information Processing Society Conference
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• 2010.11a
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• pp.1714-1717
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• 2010

디바이스 드라이버는 커널의 대부분을 차지하기 때문에 디바이스 드라이버에 문제가 발생하면 시스템에 심각한 영향을 미치게 된다. 따라서 디바이스 드라이버의 고장 분리 기술은 운영체제의 신뢰도 향상을 위해서 매우 중요하다. 동적 코드 변환 기법(Binary Translation)은 기계어 코드의 수준에서 기존의 디바이스 드라이버의 명령어 집합을 다른 명령어 집합으로 변환하여 실행하도록 하는 기법이다. 이 기법을 통해 우리는 각 명령어의 변환 과정에서 디바이스 드라이버의 모든 행위를 감시할 수 있다. 따라서 동적 코드 변환기법은 디바이스 드라이버의 고장을 분리하며 악의적인 메모리 접근을 제한하는 장점을 가지고 있다. 또한 커널 코드의 수정과 디바이스 드라이버의 수정이 요구되지 않는다. 이 논문에서 우리는 동적 코드 변환 기법을 설계하고 구현하였다. 그리고 동적 코드변환 기법을 이용한 몇 가지 실험을 통해, 디바이스 드라이버를 수행 시 발생하는 오버헤드와 고장 분리 가능 여부를 평가해 보았다.

• Earthquakes and Structures
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• v.23 no.2
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• pp.207-219
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• 2022

Seismic response control has always been a grave concern with the damage and collapse of many buildings during the past earthquakes. While there are several existing techniques like base isolation, viscous damper, moment-resisting beam-column connections, tuned mass damper, etc., many of these are succumbing to either of large displacement, near-fault, and long-period earthquakes. Keeping this viewpoint, extensive research on the application of smart materials for seismic response control of buildings was attempted during the last decade. Shape Memory Alloy (SMA) with its unique properties of superelasticity and shape memory effect is one of the smart materials used for seismic control of buildings. In this paper, an exhaustive review has been compiled on the seismic control applications of SMA in buildings. Unique properties of SMA are discussed in detail and different phases of SMA along with crystal characteristics are illustrated. Consequently, various seismic control applications of SMA are discussed in terms of performance and compared with prevalent base isolators, bracings, beam-column connections, and tuned mass damper systems.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.5
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• pp.1025-1037
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• 2015

Flexible base isolation bearings that separate superstructure from ground have been widely used in the construction field because they make a significant contribution to increasing the fundamental period of the structure, thereby decreasing response acceleration transmitted into the superstructure. However, the established bearing devices installed to uphold the whole building give rise to some problems involved with failure and collapse due to lack of the capacity as modern structures are getting more massive and higher. Therefore, this study suggests new isolation bearings assembled with additional restrainers enabled to reinforcing and recentering, and then evaluates their performance to withstand the seismic load. The superelastic shape memory alloy (SMA) bars are installed into the conventional lead-rubber bearing (LRB) devices in order to provide recentering forces. These new systems are modeled as component spring models for the purpose of conducting nonlinear dynamic analyses with near fault ground motion data. The LRB devices with steel bars are also designed and analyzed to compare their responses with those of new systems. After numerical analyses, ultimate strength, maximum displacement, permanent deformation, and recentering ratio are compared to each model with an aim to investigate which base isolation models are superior. It can be shown that LRB models with superelastic SMA bars are superior to other models compared to each other in terms of seismic resistance and recentering effect.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.13 no.3
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• pp.288-300
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• 2002

In this paper, a novel method of equalization of RF transceivers is suggested for MIMO(Multiple Input Multiple Output) antenna actively studied for high speed data transmission in the recent IMT-2000 system. The core of suggestion is in equalizing the transfer characteristics of multiple transceivers using feedback and memory during the predefined calibration time. This makes it possible to weight the signals in the intermediate frequency, which is easier in the application of recently developed DoA(Direction of Arrival) algorithms. In addition, the time varying optimum cell formation according to traffic is feasible by antenna beam-forming based on the DoA information. The suggested method of equalizing multiple transceivers are successfully verified using envelope simulation. two outputs. This paper is concerned with the diagnosis of multiple crosstalk-faults in OSM. As the network size becomes larger in these days, the convent.
nal diagnosis methods based on tests and simulation be.
me inefficient, or even more impractical. We propose a simple and easily implementable alg？ithm for detection and isolation of the multiple crosstalk-faults in OSM. Specifically, we develop an algorithm for isolation of the source fault in switc.
ng elements whenever the multiple crosstalk-faults are.
etected in OSM. The proposed algorithm is illustrated by an example of 16$\times$16 OSM.

• Journal of the Korean Institute of Intelligent Systems
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• v.10 no.2
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• pp.94-102
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• 2000

This paper presents a new FDI scheme based on dynamic fuzzy model(DFM) for the unknown nonlinear system, which can detect and isolate process faults continuously over all ranges of operating condition. The dynamic behavior of a nonlinear process is represented by a set of local linear models. The parameters of the DFM are identified by an on-line methods. The residual vector of the FDI system is consisted of the parameter deviations from nominal model and the set of grade of membership values indicating the operating condition of the nonlinear process. The detection and isolation of faults are performed via a neural network classifier that are learned the relationship between the residual vector and fault type. We apply the proposed FDI scheme to the FDI system design for a two-tank system and show the usefulness of the proposed scheme.

• Proceedings of the Korean Information Science Society Conference
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• 2011.06b
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• pp.401-404
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• 2011

운영체제와 같은 대규모 프로그램은 확장을 용이하게 하기 위해 장치 드라이버를 모듈 구조를 통해 동작시킨다. 그러나 이러한 드라이버 모듈은 커널과 분리되어 개발되기 때문에 상대적인 취약성을 가지고 있다. 이러한 취약성으로 인해 발생한 고장은 드라이버뿐만 아니라 커널 전체에 오류를 야기해 시스템의 안정성을 저하시키는 요인이 된다. 이러한 문제를 해결하기 위해 안전하지 않은 드라이버를 커널로부터 격리하고자 하는 논의가 진행되었고, 이후 많은 연구를 통해 여러 가지 접근 방식을 통한 해결방법이 제안되었다. 그러나 기존의 방법은 드라이버 소스코드의 수정이 필요하거나 드라이버 요청에 대한 응답속도가 매우 느린 현실적인 제약이 있었다. 본 논문에서는 기존방법의 한계를 극복하는 동적 컴파일러를 이용한 고장 분리 기법을 제안한다. 본 제안 기법은 기존 드라이버를 그대로 사용가능하며 기존 기법의 분리 정책을 모두 적용할 수 있다. 리눅스 커널에 본 제안기법을 적용하여 동적 컴파일러의 성능을 측정하고 본 제안 기법의 특성을 기존 기법과 비교함으로써 본 제안기법이 매우 적은 부하만으로 장치 드라이버의 고장 분리가 가능함을 확인하였다.

• Journal of KIISE:Computer Systems and Theory
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• v.36 no.3
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• pp.181-190
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• 2009

Module is an object file that can be loaded into operating system dynamically and has complete privileged access to all resources in kernel. Therefore trivial misuses in a module may cause critical system halts or deadlock situations. In this paper, we propose Kernel Resource Protector(KRP) scheme to reduce the various problems caused by module. KRP provides protections of a variety of kernel resources such as memory, major number and work queue resource. We implement the scheme onto linux kernel 2.6.18, and experimental results show that our scheme can protect kernel resources effectively.

• The Transactions of the Korean Institute of Electrical Engineers A
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• v.55 no.2
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• pp.62-66
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• 2006

We investigated the characteristics of the hybrid-type superconducting fault current limiter (SFCL) by the number of secondary windings. The SFCL consists of a transformer, which has a primary winding and several secondary windings with serially connected $YB_{a2}Cu_{3}O_{7}$ films. In order to increase the capacity. of the SFCL, the serial connection between each current limiting unit is necessary. Resistive-type SFCL has a difficulty in quenching simultaneously between the units due to slight differences of their critical current densities. The hybrid-type SFCL could achieve the simultaneous quenching through the electrical isolation and the mutual flux linkage among the units. We confirmed that the capacity of the SFCL could be increased effectively through the simultaneous quenching among the units. In addition, the power burden of the system could be reduced by adjusting the number of secondary windings. We will investigate the method to increase the capacity through serial and Parallel connections among current limiting units.