• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.10a
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• pp.426-431
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• 1997

In this paper, a sensorless realization method is proposed for the magnetic levitation system. Also we design the robust servo controller which based on the two degree-of-freedom-control theory and H$\sub$.inf./ control theory for the system. From time responses, we confirm that the proposed sensorless method can be applied the magnetic levitation system. Also the designed controller has the good disturbance rejection and the reference tracking performance.

• Journal of the Institute of Convergence Signal Processing
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• v.2 no.3
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• pp.57-64
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• 2001

This paper propose a robust control method to achieve a desired system performance in spite of system uncertainty and disturbance uncertainty. The procedures of the robust controller based on QFT(Quantitative Feedback Theory) make template, bound and loop shaping which are considered by system parameter variations and performance specifications. To prove the efficiency, the designed controller is applied for an inverted pendulum which is so sensitive to the parameter variation and has a highly nonlinear and unstable characteristics. It is shown that the simulation and experimental results from the proposed controller are efficient in robustness of parameter variation and disturbance.

• Asia pacific journal of information systems
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• v.25 no.3
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• pp.500-518
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• 2015

The present research aims to identify the relationship between trust and distrust in an online business environment. To clarify the concepts, cognitive-affective personality system theory was introduced, through which five types of psychological units were proposed. In developing the research model based on the theory, technical effectiveness of the system and content truthfulness of the website were selected as two key stimuli for the coding process of online users. Trust and distrust were selected as mediating factors that generate consequent behaviors. Finally, purchase intention served as a final dependent variable. Assuming that trust and distrust emerge in psychologically different stages, this study hypothesized the mutual causal relationship between trust and distrust, indicating that the relationship will be determined by their contextual emphasis on each dimension. To validate, a survey was conducted with 307 online shopping mall users. Results show that stimuli were more significantly associated with trust. Trust is therefore a more cognitive construct than distrust, and the path from trust to distrust is stronger than that from distrust to trust. This finding implies that the cognitive aspect of trust is stronger than that of distrust. Distrust is rather more affectively emerging than trust.

• Proceedings of the Korea Institute of Convergence Signal Processing
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• 2001.06a
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• pp.129-132
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• 2001

she purpose of this paper is to propose an approach to suppress the vibration of three-mass inertia system based on the LMI theory. and confirm its validity through simulations under the condition of parameter variation. First, the existing $H_{\infty}$ servo problem is modified to a structure to which the LMI theory can be applied by virtue of the interval model principle. By adopting this structure, we can divide given specifications fur the vibration suppression problem into $H_2$and $H_{\infty}$ performance criteria. The results of simulation for the three-mass inertia system show that the proposed design approach is quite effective.

• Journal of the Korean Society for Library and Information Science
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• v.21
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• pp.249-290
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• 1991

Theoretical developments in the information retrieval have offered a number of alternatives to traditional Boolean retrieval. Probability theory and fuzzy set theory have played prominent roles here. Fuzzy set theory is an attempt to generalize traditional set theory by permitting partial membership in a set and this means recognizing different degrees to which a document can match a request. In this study, an experimentation of a document retrieval system using the fuzzy relation matrix of the keywords is described and the results are offered. The queries composed of keywords and Boolean operaters AND, OR, NOT were processed in the retrieval method, and the method was implemented on the PC of 32bit level (30 MHz) in an experimental system. The measurement of the recall ratio and precision ratio verified the effectiveness of the proposed fuzzy relation matrix of keywords and retrieval method. Compared to traditional crisp method in the same document database, the recall ratio increased $10\%$ high although the precision ratio decreased slightly. The problems, in this experiment, to be resolved are first, the design of the automatic data input and fuzzy indexing modules, through which the system . can have the ability of competition and usefulness. Second, devising a systematic procedure for assigning fuzzy weights to keywords in documents and in queries.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.12 no.3
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• pp.129-139
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• 2002

As internet expands, the possibility of attack through the network is increasing. So we need the technology which can detect the attack to the system or the network spontaneously. The purpose of this paper proposes the system to detect intrusion automatically using the Adaptive Resonance Theory2(ART2) which is one of artificial neural network The parameters of the system was tunned by ART2 algorithm using a lot of normal packets and various attack packets which were intentionally generated by attack tools. The results were compared and analyzed with conventional methods.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.301-307
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• 2005

In this study, simplified whirl flutter analyses using quasisteady aerodynamic theory have been performed for a 2-DOF tilt-rotor system with both pitch and yaw motions of a rotor-nacelle. The present dynamic system consists of the rotor (propeller), forming the gyroscopic and aerodynamic element, supported horizontally by a pylon that is pivoted at some wing attachment point. Several design parameters (or rotor-nacelle system are considered and the effect of whirl flutter stability are also investigated for various design parameters.

• Proceedings of the KIEE Conference
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• 2001.05a
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• pp.17-19
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• 2001

In this paper, eigenvalue perturbation theory and its applications for the augmented system matrix are described. This theory is quite useful in the cases where any change in a system parameter results in signifiant changes to most of the elements of the augmented matrix or where the forming of sensitivity matrix so complicate. And AMEP(augmented matrix eigenvalue perturbation) for the excitation system parameters are computed for analysis of small signal stability of KEPCO 215-machine 791-bus system.

• Journal of the Korea Society for Simulation
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• v.9 no.1
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• pp.55-66
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• 2000

This paper deals with complex system theory to describe land combat situation using EINSTein (Enhanced ISAAC Neural Simulation Tool) simulation model. Many studies have shown that existing Lanchester equations used in most wargame models does not describe changes of combat units, real land warfare situation and qualitative factors in combat. Future warfare will be a non-linear combat with various weapon system and complex combat units. EINSTein models is an agent-based simulation tool using complex system theory. We have compared and tested land combat results with Lanchester models and EINSTein models. The results have shown that EINSTein model has a possibility to apply and analyze land warfare more properly than Lanchester models.

• Korean System Dynamics Review
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• v.5 no.1
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• pp.5-33
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• 2004

This study explores how agents would make decisions responding to control mechanism in contractual relationship of their firm. Focusing on agent's averse behavior against control, system dynamics model for agent's opportunistic behavior is developed in view of agent theory and control theory. This SD model shows that control mechanism by contracts doesn't always play a positive role on corporate decision-making process and Control, especially in the over-controlled contracts, often makes a paradox accelerating agent's opportunistic behavior unexpectedly. This paradox provides us both theoretical and practical implications for the relationship between control mechanism and autonomous behavior for sustainable corporate management.