• Journal of Mechanical Science and Technology
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• v.17 no.12
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• pp.1844-1854
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• 2003

This paper discusses details of modeling and robust control of an AMB (active magnetic bearing) spindle, and part I presents a modeling and validation process of the AMB spindle. There are many components in AMB spindle : electromagnetic actuator, sensor, rotor, power amplifier and digital controller. If each component is carefully modeled and evaluated, the components have tight structured uncertainty bounds and achievable performance of the system increases. However, since some unknown dynamics may exist and the augmented plant could show some discrepancy with the real plant, the validation of the augmented plant is needed through measuring overall frequency responses of the actual plant. In addition, it is necessary to combine several components and identify them with a reduced order model. First, all components of the AMB spindle are carefully modeled and identified based on experimental data, which also render valuable information in quantifying structured uncertainties. Since sensors, power amplifiers and discretization dynamics can be considered as time delay components, such dynamics are combined and identified with a reduced order. Then, frequency responses of the open-loop plant are measured through closed-loop experiments to validate the augmented plant. The whole modeling process gives an accurate nominal model of a low order for the robust control design.

• Smart Structures and Systems
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• v.18 no.4
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• pp.801-818
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• 2016

To estimate structural displacement, a visually servoed paired structured light system (ViSP) was proposed in previous studies. The ViSP is composed of two sides facing each other, each with one or two laser pointers, a 2-DOF manipulator, a camera, and a screen. By calculating the positions of the laser beams projected onto the screens and rotation angles of the manipulators, relative 6-DOF displacement between two sides can be estimated. Although the performance of the system has been verified through various simulations and experimental tests, it has a limitation that the accuracy of the displacement measurement depends on the alignment of the laser pointers. In deriving the kinematic equation of the ViSP, the laser pointers were assumed to be installed perfectly normal to the same side screen. In reality, however, this is very difficult to achieve due to installation errors. In other words, the pose of laser pointers should be calibrated carefully before measuring the displacement. To calibrate the initial pose of the laser pointers, a specially designed jig device is made and employed. Experimental tests have been performed to validate the performance of the proposed calibration method and the results show that the estimated displacement with the initial pose calibration increases the accuracy of the 6-DOF displacement estimation.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.35S no.6
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• pp.156-163
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• 1998

The ATM network provides ATM CES(Circuit Emulation Services) with AAL1 for CBR(constant bit rate) services such as telephone speech. In this study, quality assessment of telephone speech with CES over ATM was performed and discussed. For this, interoperability between ATM network and structured/unstructured DS1 link was modeled for simulation. And for qualiy assessment of telephone speech, SNR and MOS were used as an objective and a subjective measure, respectively. Experimental results have shown that MOS score 4 as well as SNR 30dB could be obtained at CLR of $10^{-3}$ or below for speech signal.

• Journal of Welding and Joining
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• v.32 no.3
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• pp.89-94
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• 2014

AISI 304 austenitic stainless steel is widely used for LNG pipes for LNG transmission thanks to its good metallurgical and mechanical properties. In the present research, impact toughness of a gas tungsten arc welded AISI 304 stainless steel pipe was evaluated between room and liquid nitrogen ($-196^{\circ}C$) test temperatures. In addition, a comparative study was made of the fracture behavior of FCC crystal structured stainless steel weldments and BCC crystal structured mild steels(A-grade and SS400). The results showed a slight decrease in the impact energy of the AISI 304 base metal, heat affected zone(HAZ), and welded zone with decreasing test temperature. In addition, the welded metal has the highest absorbed impact energy, followed by HAZ and the base metal.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.331-334
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• 2006

This paper deals with the ways how the AUV is composed of sub-modules to be fault-tolerant during the mission. The emergency situations can be classified into several parts according to the zones where the situations take place - sensor zone, actuator zone, interpreter zone, and communication zone. This paper explains how each element of emergency situation is detected, contained and treated, and as a result, introduce the modular structured AUV controller for the autonomous cruising.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.35-40
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• 2006

Ultrasonic cold forging technology (UCFT) utilizing ultrasonic vibration energy is a method to induce severe plastic deformation to a material surface, therefore the structure of the material surface becomes a nano-crystal structure from the surface to a certain depth. It improves the mechanical properties; hardness, compressive residual stress, wear and fatigue characteristics. Applying UCFT to a rolling process in the steel industry is introduced in this study. First, the UCFT specimens of a tool steel (SKD-61/equivalent H13) are prepared and tested to verify the effects of the UCFT in a variety of mechanical properties, the UCFT is applied to the trimming knives in a cold rolling process. It has been determined that UCFT improves the mechanical properties effectively and becomes a practical method to improve productivity and reliability by about two times compared with the conventionally treated tooling in the trimming process in a cold rolling line.

• Journal of Institute of Control, Robotics and Systems
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• v.21 no.1
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• pp.34-39
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• 2015

In this paper, a finite impulse response (FIR) filter is proposed for discrete-time nonlinear systems. The proposed filter is designed by combining the estimate of the perturbation state and nominal state. The perturbation state is estimated by adapting the optimal time-varying FIR filter for the linearized perturbation model and the nominal state is directly obtained from the nonlinear nominal trajectory model. Since the FIR structured estimators use the finite horizon information on the most recent time interval, the proposed extended FIR filter satisfies the bounded input/bounded output (BIBO) stability, which can't be obtained from infinite impulse response (IIR) estimators. Thus, it can be expected that the proposed extended FIR filter is more robust than IIR structured estimators such as an extended Kalman filter for the round-of errors and the uncertainties from unknown initial states and uncertain system model parameters. The simulation results show that the proposed filter has better performance than the extended Kalman filter (EKF) in both robustness and fast convergency.

• Journal of the Institute of Electronics Engineers of Korea TE
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• v.37 no.2
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• pp.12-16
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• 2000

The electrical characteristics of n-channel LDD structured poly-Si TFT's have been systematically investigated. It have been found that the LDD regions act as the effect of series resistance and reducing the electric field. Kink effect is disappeared and off current is greatly reduced, while on current is slightly reduced. On/off current ratio graph shows that LDD device's switching characteristic is better than that of conventional device. As a result of study, it is concluded that the effect of electric field's reduction is more dominant than that of series resistance.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.49 no.1
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• pp.53-58
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• 2012

With a game-theoretic view, p-persistence slotted ALOHA is structured as a non-cooperative game, in which a Nash equilibrium is sought to provide a value for the probability of attempting to deliver a packet. An expression of Nash equilibrium necessarily includes the number of active outer stations, which is hardly available in many practical applications. In this paper, we thus propose a Bayesian scheme of predicting the number of active outer stations prior to deciding whether to attempt to deliver a packet or not. Despite only requiring the minimal information that an outer station is genetically able to acquire by itself, the Bayesian scheme demonstrates the competitive predicting performance against a method which depends on heavy information.

• Korean Journal of Health Education and Promotion
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• v.21 no.3
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• pp.151-177
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• 2004

Recently, the educational community has attempted to implement the theory of multiple intelligences. In approaching multiple intelligences, teachers have applied the same structural approach which has been so successful with cooperative learning. Cooperative learning is easy to learn and implement, fun for teachers and students, and produce profoundly positive outcomes along a remarkable number of dimensions. Different structures are designed for different outcomes, including enhanced mastery of subject matter, improved thinking skills, team building, class building, development of social character and social skills, communication skills, classroom management, classroom discipline, and development of and engagement of each of the multiple intelligences. Cooperative learning is becoming an increasingly popular teaching strategy. In this study, it is aimed to clarify the application of cooperative learning in health education. Cooperative Learning in health education enhances student learning by: 1) providing a shared cognitive set of information between students, 2) motivating students to learn the material, 3) ensuring that students construct their own health knowledge, 4) providing formative feedback, 5) developing social and health group skills necessary for success outside the classroom, and 6) promoting positive interaction between members of different cultural and socio-economic groups. Cooperative Learning structures and techniques in health education are following. Flash Card, Focused Listing, Structured Problem-solving, Paired Annotations, Structured Learning Team Group Roles, Send-A-Problem, Value Line, Uncommon Commonalities, Team Expectations, Double Entry Journal, Guided Reciprocal Peer Questioning, What if. Because the purpose of health education is the practice, therefore health specialists have to guide powerful and effective teaching method The application of cooperative learning in health education may improve its effectiveness.