• Journal of the Institute of Electronics Engineers of Korea SC
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• v.46 no.2
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• pp.7-14
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• 2009

In this paper we consider the problem of global finite-time stabilization for a class of uncertain nonlinear systems which include uncertainties. The uncertainties are time-varying disturbances or parameters belong to a known compact set. The proposed design method is based on backstepping and dynamic exponent scaling using an augmented dynamics, from which, a dynamic smooth feedback controller is derived. The finite-time stability of the closed-loop system and boundedness of the controller are preyed by the finite-time Lyapunov stability theory and a new notion 'degree indicator'.

• The KIPS Transactions:PartA
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• v.10A no.6
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• pp.677-684
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• 2003

Most policies of VOD services are mainly studied about server system, and make no touch on clients buffer stabilization which is the basis of guaranteeing playback quality and playing without cut off. In this paper, we proposed a skipping frame transfer policy that can sending dynamic buffer control signal to server in accordance with clients buffer state of starvation or overrun, and server transfers a skipped frame to client after receive the control signal. And through a simulation, we show the suggested policy is more efficiency on playback quality by buffer stabilization which is by preventing loss and miss for receiving frame due to grow worse client buffer state.

• The Journal of the Korea Contents Association
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• v.20 no.9
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• pp.486-493
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• 2020

The purpose of this study was to identify the effects of an exercise program for lumbar stabilization on static and dynamic balancing and gait of stroke patients. The subjects were 27 stroke patients, who were divided into an experimental group(n=14) and a control group(n=13). The exercise was conducted for 30 minutes a day, four times a week, and for six weeks. The variables included static and dynamic standing balance and gait, which were verified before and after the lumbar stabilization exercise. Using the IBM SPSS(19.0 version), data were analyzed with t-test and two-way ANOVA to validate the differences before and after the experiment and between the groups. The significance level was set at α = .05 and the results of this study are as follows. First, statistically significant differences were found in the static standing balance after the exercise (P< .05). Second, there were statistically significant differences in the dynamic standing balance after the exercise (P< .05). Third, statistically significant differences were found in the gait of the patients after the exercise (P< .05). In addition, the interactions between the two groups showed significant differences. These results suggest that stroke patients need a variety of lumbar exercises and that the lumbar stabilization exercise can improve physical treatment and health of the patients, having positive effects on their quality of life. Further studies are necessary to explore the applications of various lumber exercises.

• 한국연소학회:학술대회논문집
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• 2012.11a
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• pp.351-354
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• 2012

The characteristics of flame dynamics occurring near bluff body was experimentally investigated in a model combustor with V-gutter bluff body. Flashback occurs due to the change of pressure gradient in the combustor, and flashback distance depends on equivalent ratio. Unstable flames can be classified into three types depending on the flashback distance and structure. Re-stabilization takes place as the flame moves downstream. This process is supported by a strong vortex structure behind bluff body.

• 제어로봇시스템학회:학술대회논문집
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• 2000.10a
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• pp.533-533
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• 2000

Stabilization of piecewise-linear systems with unknown switching information is presented. The current subsystem is identified from the output, and the identified subsystem is used for the observer-based control. The stability of the overall system is proven and the performance is evaluated via a simulation.

• Journal of The Korean Society of Integrative Medicine
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• v.3 no.3
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• pp.9-16
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• 2015

Purpose : The purpose of this study was to demonstrate the effects of lumbar stabilization exercise on static and dynamic balance performance with unstable supporting surface and an even surface. Methods : The subjects of this experimental study were 30 patients among hospitalized stroke patients. They were randomly divided into two groups: unstable supporting surface group(USS; n=15) and an even surface group(ES; n=15). The lumbar stabilization exercise program for patients in two groups went through 40 minute exercise sessions three times a week for 8 weeks. To analyze the effects of a variety of supporting surface, Functional reaching test(FRT), Berg's balance scale(BBS), and Overall stability index(static balance) were measured before and after the exercise. The paired t-test was used to compare mean differences between before and after exercis and the independent t-test was used to compare mean differences between groups. Results : After 8 weeks exercise program, there were significant differences between before and after exercise in FRT, BBS, and static balance. But there were not significant differences in balance between two groups. Conclusion : This study suggest that lumbar stabilization exercise on unstable supporting surface and an even surface can improve FRT, BBS, and a static balance.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.21 no.10
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• pp.951-959
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• 2011

In this study, an OTM(on-the-move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite while moving was addressed. Since LOS(line-of-sight) of antenna should direct satellite consistently while vehicle moving to guarantee high satellite communication quality, active antenna LOS stabilization is a core technology for OTM antenna. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. In consideration of driving mechanism which consists of gear train and flexible driving shafts, a two-mass-system dynamic model coupled with vehicle motion was presented. An internal PI-control loop + outer PI-control loop structure has been suggested in order to damp the torsional vibration and stabilize control system. The classical pole-placement method was applied to design control gains. In addition, a vehicle motion compensation control beside of the feedback control loop has been suggested to improve LOS stabilization performances. The feasibility of the proposed control design was verified along with some experimental results.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.59 no.11
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• pp.2073-2082
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• 2010

The 4-th generation of mobile communication aims to realize global, fast and mobile communication service. The satellite communication charges a key role in this field. In this study, an OTM(On-The-Move) antenna which is mounted on ground vehicles and is used for mobile communication between vehicle and satellite was addressed. Since vehicles move during communication, active antenna line-of-sight stabilization is a core technology to guarantee high satellite communication quality. Stabilization of a satellite tracking antenna which consists of 2-DOF gimbals, an elevation gimbal over an azimuth gimbal, was considered in this study. Various disturbance torques such as static and dynamic mass imbalance torques, variation of moment of inertia according to elevation angle, friction torque related to vehicle motion, equivalent disturbance torque due to antenna roll motion, etc. were analyzed. As a robust stabilization control, rate feedback with sliding mode control and position feedback with proportional+integral control was suggested. To compensate antenna roll motion, a supplementary roll rate feed forward control was included beside of the feedback control loop. The feasibility of the analysis and the proposed control design were verified along with some simulation results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.11 s.104
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• pp.1303-1310
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• 2005

Stabilization error of target aiming systems mounted on moving vehicles is an important performance because the error directly affects hit Probability. In a heavy load targetaiming system, the disturbance torque comes from mass unbalance and linear acceleration is a main source of stabilization error. This study suggests an experimental design method of disturbance feedforward compensation control to improve the stabilization performance of heavy load target aiming systems. The filtered_x least square(FxLMS) algorithm is used to estimate the compensator coefficients adaptively. The proposed control is applied to a simple experimental set-up which simulates dynamic characteristics of a real target aiming system. The feasibility of the proposedtechnique is illustrated, along with results of experiments.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10a
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• pp.20-23
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• 1996

This paper deals with the flexible manipulator with rotational and translational degrees of freedom, which has an arm of time-varying length with the prismatic joint. The tracking control problem of the flexible manipulator is considered. First we design the controller of the 2-type robust servo system based on the finite horizon optimal control theory for the trajectory planned as a discontinuous velocity. Next, to reduce the tracking error, we use the method of the dynamic programming and of modifying the reference trajectory in time coordinate. The simulation results show that the dynamic modeling is adequate and that the asymptotic stabilization of the flexible manipulator is preserved in spite of nonlinear terms. The PTP control error has been reduced to zero completely, and the trajectory tracking errors are reduced sufficiently by the proposed control method.