• Proceedings of the KSME Conference
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• 2002.08a
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• pp.259-262
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• 2002

Application of combustion stabilization devices such as baffle and acoustic cavity to liquid propellant rocket engine is investigated to suppress high-frequency combustion instability, i.e., acoustic instability. First, these damping devices are designed based on linear damping theory. As a principal design parameter, damping factor is considered and calculated numerically in the chambers with various specifications of these devices. Next, the unbaffled chambers with/without acoustic cavities are tested experimentally for several operating conditions. The unbaffled chamber shows the specific stability characteristics depending on the operating condition and has small dynamic stability margin. The most hazardous frequency is clearly identified through Fast Fourier Transform. As a result, the acoustic cavity with the present design has little stabilization effect in this specific chamber. Finally, stability rating tests are conducted with the baffled chamber, where evident combustion stabilization is observed, which indicates sufficient damping effect. Thrust loss caused by baffle installation is about $2{\%}$.

• Journal of the Korean Society for Precision Engineering
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• v.9 no.3
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• pp.102-109
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• 1992

The heavy vibrations of vehicles on the severe off-road environment degenerate the stabilization proformance of the gunner primary sight. To improve the stabilization performance, the dynamic equations of the gunner primary sight were derived, and the stabilization systems were designed using VSC methods. The performances were compared with the Lead/Lag scheme. In the nonlinear simulation including real disturb ances and couloumb friction, it is shown that the VSC methods exhibit more effective stabilization.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.15 no.1
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• pp.102-108
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• 2016

A flying drone generates vibrations in a great variety of frequencies, and it requires a gimbal system stabilization loop design in order to obtain clean and accurate image from the camera attached to the drone under this environment. The gimbal system for drone comprises the structure that supports the camera module and the stabilization loop which follows the precise angle while blocking the vibration from outside. This study developed a dynamic model for one axis for the stabilization loop design of a gimbal system for drones and applied classical PID controller and intelligent PID controller. The Stabilization loop design was developed by using MATLAB/Simulink and compared the performance of each controller through simulation. Especially, the intelligent PID controller can be designed almost without the dynamic model and it demonstrates that the angle can be followed without readjusting the parameters of the controller even when the characteristics of the model changes.

• PNF and Movement
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• v.22 no.2
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• pp.201-211
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• 2024

Purpose: This study aimed to evaluate the effects of trunk stabilization exercises using a Reformer on trunk control, balance ability, and gait function in chronic stroke patients. Methods: The participants were 24 chronic stroke patients, randomly divided into two groups: trunk stabilization exercise using the Reformer group (TS-R, n = 12) and general trunk stabilization exercise group (GT-E, n = 12). Assessment methods included the Trunk Impairment Scale for trunk control, the AMTI force platform for static balance, the Timed Up and Go test for dynamic balance, and the Dynamic Gait Index for gait function. Assessments were conducted before and after the intervention. The intervention for the TS-R group consisted of bridging exercises using a Reformer, while the GT-E group performed bridging exercises on a mat. All interventions were performed for 17 minutes per session, five times a week, for a total of 20 sessions over four weeks. Statistical analysis was performed using repeated-measures ANOVA to analyze the interaction between groups and time. Results: The results of the repeated measures ANOVA indicated a significant interaction between the groups and time. The TS-R group showed statistically significant differences in all variables before and after the intervention. In contrast, the GT-E group did not show statistically significant differences in any variables before and after the intervention. Conclusion: The findings of this study suggest that trunk stabilization exercises using a reformer are effective in improving trunk control, balance ability, and gait function in chronic stroke patients.

• JSTS:Journal of Semiconductor Technology and Science
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• v.10 no.4
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• pp.276-281
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• 2010

A 2.5 V feed-forward second-order deltasigma modulator for audio application is presented. A 9-level quantizer with a tree-structured dynamic element matching (DEM) was employed to improve the linearity by shaping the distortion resulted from the capacitor mismatch of the feedback digital-toanalog converter (DAC). A chopper stabilization technique (CHS) is used to reduce the flicker noise in the first integrator. The prototype delta-sigma analogto-digital converter (ADC) implemented in a 65 nm 1P8M CMOS process occupies 0.747 $mm^2$ and achieves 109.1 dB dynamic range (DR), 85.4 dB signal-to-noise ratio (SNR) in a 24 kHz audio signal bandwidth, while consuming 14.75 mW from a 2.5 V supply.

• International Journal of Control, Automation, and Systems
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• v.5 no.2
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• pp.138-146
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• 2007

The analysis and design method for achieving robust stabilization of Decentralized Dynamic Surface Control (DDSC) is presented for a class of interconnected nonlinear systems. While a centralized design approach of DSC was developed in [1], the decentralized approach to deal with large-scale interconnected systems is proposed under the assumption that interconnected functions among subsystems are unknown but bounded. To provide a closed-loop form with provable stability properties, augmented error dynamics for N nonlinear subsystems with DDSC are derived. Then, the reachable set for errors of the closed-loop systems will be approximated numerically in the form of an ellipsoid in the framework of convex optimization. Finally, a numerical algorithm to calculate the $L_2$ gain of the augmented error dynamics is presented.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.337-340
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• 2004

Stabilizing systems with Gyroscope are extensively used in various tracking devices for attaining the system's objective. Because of putting performance first in importance of system and focusing on specification of parts, designers are sometimes passing over the dynamic characteristics of system in vibrating condition. In this paper, we were dealing with unstable stabilizing control due to coincidence of stabilization platform natural frequency and that of Gyroscope used for sensing rate. For solving this problem, statics and dynamic test of silicon rubber with 3 different hardness were performed and similar stabilizing system was adopted to prove reasonability of rubber choice and static pre-strain.

• Journal of The Korean Society of Integrative Medicine
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• v.12 no.3
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• pp.49-59
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• 2024

Purpose : Chronic ankle instability (CAI) can impair strength and balance, leading to activity limitations and restricted participation. Traditionally, ankle stabilization exercises have been applied, and more recently, the effects of hip muscle exercises have been studied. The purpose of this study was to determine the immediate effects of hip exercises (HE) and ankle stabilization exercises (ASE) on dynamic balance, performance and ankle function in subjects with CAI. We also compared the difference in effectiveness between HE and ASE. Methods : A total of 34 subjects with CAI participated, ane were randomly divided into two groups: the HE group and the ASE group. The HE group performed a program consisting of exercises above 70 % MVIC, while the ASE group performed a traditional ankle stabilization exercise program. The subjects in each group completed their respective exercise program for a total of 30 minutes once a day and were assessed before and after the intervention. Dynamic balance was assessed using the Y-balance test (YBT). Performance was assessed using the hop for distance test (HDT), and side-hop test (SHT). Ankle function was assessed using foot and ankle ability measure (FAAM) questionnaires. Results : YBT, HDT, and FAAM values increased significantly in both groups after the intervention (p<.05), and there was no significant difference between the groups. SHT values decreased significantly in both groups after the intervention (p<.05), and there was no significant difference between the groups. Conclusion : Although no significant superiority was observed between HE and ASE in this study, both exercise programs were effective in improving dynamic balance, performance, and ankle function in subjects with CAI. These findings suggest that both HE and ASE can be suitable interventions for CAI, highlighting the need for individualized treatment plans. Future research is warranted to explore the long-term effects of exercise programs on CAI subjects of different ages and occupational characteristics.

• Biomaterials and Biomechanics in Bioengineering
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• v.2 no.4
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• pp.237-248
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• 2015

"Dynamic stabilization" systems have been developed in recent years to treat degenerative disorders of the spinal column. In contrast to arthrodesis (fusion), the aim here is to conserve intervertebral mobility to maximize comfort. When developing innovative concepts, many mechanical tests need to be carried out in order to validate the different technological solutions. The present study focuses on the B Dyn$^{(R)}$ "dynamic stabilization" device (S14$^{(R)}$ Implants, Pessac, France), the aim being to optimize the choice of polymer material used for one of the implant's components. The device allows mobility but also limit the range of movement. The stiffness of the ring remains a key design factor, which has to be optimized. Phase one consisted of static tests on the implant, as a result of which a polyurethane (PU) was selected, material no.2 of the five elastomers tested. In phase two, dynamic tests were carried out. The fatigue resistance of the B Dyn$^{(R)}$ system was tested over five million cycles with the properties of the polymer elements being measured using dynamic mechanical analysis (DMA) after every million cycles. This analysis demonstrated changes in stiffness and in the damping factor which guided the choice of elastomer for the B Dyn$^{(R)}$ implant.

• ETRI Journal
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• v.39 no.2
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• pp.292-299
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• 2017

We propose pulse-mode dynamic $R_on$ measurement as a method for analyzing the effect of stress on large-scale high-power AlGaN/GaN HFETs. The measurements were carried out under the soft-switching condition (zero-voltage switching) and aimed to minimize the self-heating problem that exists with the conventional hard-switching measurement. The dynamic $R_on$ of the fabricated AlGaN/GaN MIS-HFETs was measured under different stabilization time conditions. To do so, the drain-gate bias is set to zero after applying the off-state stress. As the stabilization time increased from $ 0.1{\mu}s$ to 100 ms, the dynamic $R_on$ decreased from $160\Omega$ to $2\Omega$. This method will be useful in developing high-performance GaN power FETs suitable for use in high-efficiency converter/inverter topology design.