• English Language & Literature Teaching
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• v.17 no.4
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• pp.207-227
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• 2011

This paper investigates how two different modes of feedback (selective vs. comprehensive) affect selected students' writing development in terms of three different types of measurement (accuracy, fluency, and complexity). 139 university students participated in the study, and 278 writing samples were analyzed. The results of the study indicate that participants who received selective feedback wrote more accurately and fluently than their counterparts. However, in terms of complexity, both selective and comprehensive groups showed no sign of improvement in semester-based investigations. The results of this study support Skehan's (2009) theory of trade-off effects, suggesting that 'natural' tension exists between accuracy and complexity when resources are limited. Moreover, this finding contrasts with the theory of Cognition Hypothesis, which proposes that task complexity will be associated with increases in complexity and accuracy. In the study, selected participants (N=21) strongly nominated their error sources as unfamiliarity toward using key words, usage, transition, and sentence types. This study not only contributes to the accumulation of our current knowledge in the related area of theory, but offers educational implications for those who are dealing with intermediate-level students when deciding what particular teaching content should constitute a priority within a limited instructional period.

• Journal of the Korean Society for Railway
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• v.9 no.5 s.36
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• pp.569-576
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• 2006

Recently, many Korean firms have been adopting $360^{\circ}$ Degree Feedback System as a way of adapting to the environmental changes in business world. The reason is that the traditional top-down way of personnel evaluation pattern can not but have many limits in this turbulent changing environment. The main purpose of this article is to depict some aspects of $360^{\circ}$ Degree Feedback System including its current status quo, its positive and negative side, and the effective ways of its improvement focusing on the railway-related "A firm".

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.271-273
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• 2002

Switching power supply are widely used in many industrial field. Power factor correction(PFC) has become an increasingly necessary feature in new power supply designs. The power factor correction circuit using boost converter used in input of power source is studied in this paper. In a boost power factor correction circuit there are two feedback control loops, which are a current feedback loop and a voltage feedback loop. In this paper, it is analyzed regulation performance of output voltage and compensator to improve of transient response that presented at continuous conduction mode(CCM) of boost PFC circuit. The validity of designed boost PFC circuit is confirmed by simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2007.07a
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• pp.1650-1651
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• 2007

This paper presents a novel nonlinear speed control strategy for induction motor utilizing exact feedback linearization with states feedback. The speed and flux control loops utilize nonlinear feedback which eliminates the need for tuning, while ordinary proportional-integral controllers are used to control the stator current of d-axis the speed. The control scheme is derived in rotor field coordinates and employs an appropriate estimator for estimation of the rotor flux angle, flux magnitude.

• International conference on construction engineering and project management
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• 2005.10a
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• pp.836-840
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• 2005

This research investigates the feasibility of Web technology as a means of delivering facility information for better support facility operation and maintenance. Our research proposes a Web-based feedback system as a pragmatic solution to the limitations of current FM (Facility Management) processes. In practice work orders and records are often misplaced resulting in lower efficiency and customer satisfaction. This may be overcome by a system that states information digitally and provides a Web-based interface. The interface could allow customers to report facility problems, trace their work order in progress, view schedules for maintenance and provide feedback for service online. The benefit for a FM department is that it can receive feedback on performance which would improve the quality of service and build a record of practical experiences.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.43 no.2
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• pp.215-225
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• 1994

In this paper, a performance evaluation of different current regulators for induction motor drive systems fed by IGBT inverter is presented. The twoparts of current regulation are considered : current error compensation part, voltage modulation part. The characteristics of hysteresis, synchronous PI, decoupled PI, predictive, deadbeat and stage feedback controllers are analyzed and the steady-state performances and transient responses of current regulation are well compared through the simulation and experimental results.

• The Transactions of the Korean Institute of Power Electronics
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• v.11 no.5
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• pp.404-408
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• 2006

This paper presents an anti-windup gain selection method for a complex vector synchronous frame PI current controller. The complex vector PI current controller is more robust to the parameter variation than the state feedback decoupling PI current controller. The complex vector PI current controller also includes an integral term, which can results in windup problem when the controller is saturated due to physical limitation of the system. Furthermore, even an anti-windup is utilized, inappropriate gain can deteriorate the performance of the current controller. Therefore, appropriate anti-windup gain selection method for a complex vector current controller has been proposed based on the mathematical description of the current control system. The superior performance of the current control system with the proposed anti-windup gain has been verified by the experimental results.

• The Journal of Korean Association of Computer Education
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• v.5 no.3
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• pp.59-67
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• 2002

In this study, we have designed and established a formative evaluation system which provides the web-based corrective feedback in the current situation that the importance of feedback as well as the formative evaluation is getting highlighted in the course of learning and instruction. This system is composed of three types of corrective feedback. The first one is the informations providing feedback by stage. It provides the explanations or the correct answers-related informations for the wrong answered questions by stage and directly. The second one is the error corrective feedback, which provides the informations about the reasons of the errors on each wrong answered question so that the learner can correct his errors. Lastly, the corrective feedback by the accumulated marks shows the learner's total marks and their wrong answered questions to enable the learner to learn for themselves. We analyzed how these three corrective feedback effects on the learning achievement after applying them to learners, and testified the type of the most effective corrective feedback in enhancing the degree of learning achievement.

• Current Optics and Photonics
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• v.4 no.5
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• pp.434-440
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• 2020

Based on single-mode rate equations, we present an improved equivalent-circuit model for distributed-feedback (DFB) lasers that accounts for the effects of parasitic parameters and nonradiative recombination. This equivalent-circuit model is composed of a parasitic circuit, an electrical circuit, an optical circuit, and a phase circuit, modeling the circuit equations transformed from the rate equations. The validity of the proposed circuit model is verified by comparing simulation results to measured results. The results show that the slope efficiency and threshold current of the model are 0.22 W/A and 13 mA respectively. It is also shown that increasing bias current results in the increase of the relaxation-oscillation frequency. Moreover, we show that the larger the bias current, the lower the frequency chirp, increasing the possibility of extending the transmission distance of an optical-fiber communication system. The results indicate that the proposed circuit model can accurately predict a DFB laser's static and dynamic characteristics.

• Proceedings of the KIEE Conference
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• 2007.10c
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• pp.144-146
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• 2007

High frequency voltage signal injection have been widely used but they have some problems like over current protection. High frequency current signal injection and feedback control are more stable than voltage signal injection. In this paper, high frequency current controller for self-sensing and parameter estimation of induction motors is presented.