• Journal of Power Electronics
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• v.11 no.2
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• pp.156-162
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• 2011

The control loop time delay caused by sampling, the zero-order-holder effect and calculations is inevitable in the digital control of dc-dc switching converters. The time delay will limit the bandwidth of the control loop and therefore degrade the transient performance of digital systems. In this paper, the quantization time delay effects with different time delay values based on a generic second-order system are analyzed. The conclusion that the bandwidth of digital control is reduced by about 20% with a one cycle delay and by 50% with two cycles of delay in comparison with no time delay is obtained. To compensate the time delay and to increase the control loop bandwidth, a duty ratio predictive control scheme based on linear extrapolation is proposed. The compensation effect and a comparison of the load variation transient response characteristics with analogy control, conventional digital control and duty ratio predictive control with different time delay values are performed on a point-of-load Buck converter by simulations and experiments. It is shown that, using the proposed technique, the control loop bandwidth can be increased by 50% for a one cycle delay and 48.2% for two cycles of delay when compared to conventional digital control. Simulations and experimental results prove the validity of the conclusion of the quantization effects of the time delay and the proposed control scheme.

• 제어로봇시스템학회:학술대회논문집
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• 1996.10b
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• pp.436-440
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• 1996

In this study, underdeveloping heavy-load driving servo control system, which are composed of controller, electro-hydraulic servo-valve, hydraulic motor, reduction gear box, turret slew bearing and turret structure, are investigated to simplify the control system. To estimate the effect of each component, modeling and simulation of linear and nonlinear system are carried out. In the first stage, to prove the reliability of performance estimation program, simulation results are compared with experimental results. In the second stage, the effect of each component of control system is evaluated and then a simplified control system is suggested.

• 유체기계공업학회:학술대회논문집
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• 2006.08a
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• pp.575-578
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• 2006

In designing smoke-control system of rescue station in train tunnel, a purpose is to prevent a disaster by proposing the jet fan operation together with smoke-control curtain in tunnel fire. This study has investigated the relationship of the Heat Release Rate(HRR) and a adequate ventilation velocity to control the fire propagation in tunnel fire, and has improved the effect of the smoke-control curtain on preventing the flow of pollutants. In this study, Computational Fluid Dynamics(CFD) simulations with ST AR-CD(ver 3.24) were carried out on predicting the fire spreading and the flow of pollutants, considering jet fan operations and effect of smoke-control curtain. Our simulation domain is the full scale model of the 'DAEGWALLYEONG' 1st tunnel. The results represent that ventilation operation can control the fire spreading and pollutants effectively to prevent a disaster.

• Journal of Institute of Control, Robotics and Systems
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• v.6 no.4
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• pp.261-267
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• 2000

In this study, a heavy-load servo-control driving system, which are composed of controller, electro-hydraulic servomechanism, hydraulic motor, reduction gearbox, turret slew bearing and turret structure, are investigated to simplify the servo-control system. To estimate the effect of each component, nonlinear modeling and simulation are carried out. In the first stage, to prove the validity of the performance estimation program, simulation results are compared with experimental results. In the second stage, the effect of each component of the control system is evaluated and then a simplified control system is suggested.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.609-614
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• 1998

A new small signal modeling of an average current mode control is proposed. In order to analyze the characteristics of the control scheme, the discrete and continuous time small signal models are derived. The derivation are mainly come from the analysis of the sampling effect presented in the current control loop. By the mathematical interpretation of practical sampler representing the sampling effect of a current control loop, the small signal models of an average current mode control can be easily derived. The instability of the current control loop, which gives rise to the subharmonic oscillation, can be identified by the proposed models. To show the usefulness of the proposed models, the simulation and experiment are carried out. The results show that the predicted results by the proposed model are much better agreed with the measured ones than that of the conventional model, even though the high gain of the compensation network of a current control loop is employed.

• Proceedings of the KIEE Conference
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• 2000.07d
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• pp.2799-2801
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• 2000

Robust control for DC motor is needed according to the highest precision of industrial automation. However, when a motor control system with PID controller has an effect of load disturbance, it is very difficult to guarantee the robustness of control system. In this paper, PID-Expert hybrid control method for motor control system as a compensation method solving this problem is presented. If PID control system is stable, the Expert controller is idle. if the error hits the boundary of the constraint. the Expert controller begins operation to force the error back to the constraint set. The disturbance effect decrease remarkably, robust speed control of DC motor using PID-Expert Hybrid controller is demonstrated by the simulation.

• Asia Marketing Journal
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• v.26 no.3
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• pp.156-169
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• 2024

This study leverages group-based control theory to explore how fresh starts reinvigorate consumers with low motivation to engage in collective environmental efforts. Typically, individuals with low control over their circumstances show less inclination toward collective goals. However, fresh starts can enhance the influence of perceived control on collective environmental engagement, with global identity mediating this relationship. This hypothesis was supported by two empirical studies. The first study analyzed data from 10,430 corporate participants in an energy-saving initiative, revealing that smaller organizations, which likely experience lower levels of control, made substantial energy-saving efforts early in the year, although this effect diminished over time. The second study of 108 college students found that a fresh start mindset and desire for control, mediated by global identity, enhance environmentally responsible behaviors. These findings suggest that fresh starts can effectively connect control perceptions with proactive environmental actions, underscoring their potential to foster collective environmental efforts.

• Journal of Korean Academy of Nursing
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• v.35 no.1
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• pp.56-64
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• 2005

Purpose: The purpose of this study was to verify the effect of aromatherapy massage on constipation in the elderly. Method: This study for 10 day, employed a randomized control group pretest-posttest design. The experimental group received abdominal massage using essential oils with Rosemary, Lemon, and Peppermint, and the control group received a placebo massage. To evaluate the effect of aromatherapy, the degree of constipation was measured using the CAS (constipation assessment scale) and the number of bowel movements per week. Data was analyzed by repeated measures of ANOVA using the SPSS program. Result: The score of CAS of the experimental group was significantly lower than that of the control group. In addition the average number of bowel movements in the experimental group was higher than that of the control group. The effect of aromatherapy lasted 2 weeks after treatment, while the placebo effect lasted 7~10 days after treatment. Conclusion: The finding of this study showed that aromatherapy helps relieve constipation in the elderly.

• Journal of the Korean Society of Physical Medicine
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• v.7 no.4
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• pp.493-500
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• 2012

PURPOSE: The purpose of this study was to investigate effect of self-controlled feedback on proprioception in elbow flexion. METHODS: Thirty young adult volunteered to participate and were randomly assigned to one of three groups (self-controlled, yoked, control). Power and velocity in elbow flexion was measured by PRIMUS RS (BTE Tech., Hanover, U.S.A). Statistical analysis was used multivariate ANOVA to know effect of self-controlled feedback on proprioception in elbow flexion. Post hoc was used Scheffe. RESULTS: In acquisition phase to practice effect, variable errors in self-controlled group was significantly low scored more than yoked and control group. In retention phase to learning effect, variable errors in self-controlled group was significantly low scored more than yoked and control group. CONCLUSION: Self-controlled feedback was more effective on movement control when the learner could make a decision about receiving feedback after the trial. This seems to support the view that self-controlled feedback benefits learning, because learners can make a decision about feedback based on their performance on a given trial.

• Journal of Environmental Science International
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• v.30 no.12
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• pp.993-1003
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• 2021

It is known that the effect of traditional agricultural techniques of burning farmland such as paddy fields and fields gradually declines and affects both the fauna and flora of the rice paddy as well as pests. Therefore, in this study, a study was conducted to investigate the effects of burning rice paddy fields and rice paddy fields levee on the control effect of winter pests inhabiting agricultural land and the amount of pests generated and damaged during the growing season. As a result of this study, the pest control effect of incineration reduces not only the density of pests, but also beneficial insects (natural enemies) and non-reptiles. It is judged that burning has a very low insect control effect. It is expected to be used as basic data to create a sustainable agricultural environment, such as minimizing various negative effects such as pest control effects, wildfires, and air pollution caused by incineration, and suppressing unnecessary incineration and fine dust generation.