• Journal of Digital Convergence
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• v.17 no.11
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• pp.395-407
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• 2019

This study attempted to verify the structural model of the effects of stress, self-efficacy, and self-control on smartphone addiction in University students. The subjects of this study were 440 University students in G and P city. Results, First the most influential variables on smartphone addiction were self-control, followed by stress, and two variables explained explanation about smartphone addiction in 34%. Second, self-efficacy had a positive effect on self-control and stress had a negative effect. Both variables had an indirect effect on smartphone addiction through self-control. In groups less than 4 hours and above, there was a partial regulation effect because of differences between groups in the smartphone addiction pathway coefficients of stress and self-efficacy. Therefore, in order to reduce smartphone addiction, it is important to find ways to reduce stress and increase self-control and self-efficacy, and necessary to develop various programs and tailor educational interventions for each individual situation.

• Korean journal of applied entomology
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• v.61 no.2
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• pp.293-297
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• 2022

Korean thistle (Cirsium setidens Nakai), also called Gondre, is an edible perennial herbaceous plant. A new occurrence of aphids has been confirmed on Korean thistle, which is expected to damage crops. The control effect of organic materials was tested to develop an eco-friendly control method for aphid. Pyrethrins+paraffinic oils exhibited a 98% control effect, pyrethrins+matrine+pyroligneous acid showed a 95% control effect, and azadirachtin+rotenone was found to have a 75% control effect. Pyrethrins appear to be the most effective; no damage (phytotoxticity) was caused with organic materials spraying.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.103-104
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• 2007

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.411-413
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• 2005

This paper proposes a modeling of wind turbine simulator which includes the dynamic characteristics such as pitch angle control, torsional vibration, and tower effect. Simulation results using PSCAD are provided to show the wind turbine simulator performance.

• Journal of the Korean Society for Precision Engineering
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• v.16 no.5 s.98
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• pp.58-65
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• 1999

A magnetic levitation system requires a robustness to overcome a dynamic instability due to disturbances. In this paper a robust controller for a magnetically levitated fine manipulator is presented. The proposed controller consists of following two parts: a model reference controller and an $H_{\infty}$ controller. First, the model reference control stabilizes the motion of the manipulator. Then, the motion of the manipulator follows that of the reference model. Second, the $H_{\infty}$ control minimizes errors generated from the model reference control due to noise and disturbance since the $H_{\infty}$ control is a kind of robust control. The experiments of position control and tracking control are carried out by use of the proposed controller under the conditions of free disturbances and forced disturbances. Also, the experiments using PID controller are carried out under the same conditions. The results from above two controllers are compared to investigate the control performances. As the results, it is observed that the proposed controller has similar position accuracy but better tracking performances comparing to the PID controller as well as good disturbance rejection effect due to the robust characteristics of the controller. In conclusion. it is verified that the proposed controller has the simple control structure, the good tracking performances and good disturbance rejection effect due to the robust characteristics of the controller.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2004.10a
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• pp.291-294
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• 2004

Many researches have been focused on optimal designs of a pole shape in order to reduce cogging torques, which are generated between permanent magnets and slots. In this paper, an adaptive controller is proposed for reducing the effect of cogging torques in servo motors. The controller stabilizes the control system and shows an excellent trajectory tracking performance compared to the conventional PD controller.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.155-158
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• 1999

In the high speed range for Vector control of Synchronous Reluctance Motor, the effect of iron loss and the cross-coupling of dq axis currents is dependent on the increase of the operating frequency can not be negligible. In this paper, we propose a decupling Vector control of dq axis current that the effect of iron loss is eliminated, and confirm that through simulation results.

• 제어로봇시스템학회:학술대회논문집
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• 1992.10a
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• pp.981-986
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• 1992

In order to implement the digital PID control algorithm, it is necessary to consider the effect of the finite word length(FWL). In this paper, we show the FWL effect in the digital PID controllers. The conception analyse the effects of the signal quantization error in the digital PID algorithm and the coefficient wordlength determined from performance criteria with the statistical wordlength concept. Throughout this paper, it is dealt with the type of controller structure based delta operator the delta operator has such advantages are superior rounfoff noise perfoff noise performance, more accurate coefficient repersentation, and less sensitive control law.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.17 no.31
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• pp.33-42
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• 1994

This paper aims to analyse and appraise the effect of human performance to the variation of quality through constructing the dynamic recursive control model considering the human factor in a single production system. The model studied in this paper has a great advance from the point of combinating three technologies(quality control, automatic control theory, human engineering) and can also be expanded in several applications.

• Plant Resources
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• v.7 no.2
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• pp.110-115
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• 2004

This study was conducted to evaluate the effect of herbicides on weed control, growth characteristics and yield in flax, after direct seeding it to the field, the herbicides treated had no effect on the emergence period. The major weeds were decreased some what more with mecoprop-wp, herbicide than the other herbicides and by hand weeding. Mecoprop-wp and simazin-wp were had no injury but sethoxydim-EC and 2.4-D-wp were slighthy harmful for the flax with recommended concentration, On the other hand, all herbicides were harmful in the double dosage level