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Insu Paek,백순근,Mark Wilson 서울대학교 교육연구소 2012 Asia Pacific Education Review Vol.13 No.3
In this study, repeated measures item response data from an English language proficiency (ELP) test administered over 2 years were analyzed by item response theory-based approaches to model change over time. First, change over time was modeled by an item side change approach where change was parameterized at the item level. Second, more importantly, this study introduced and demonstrated an application of an interaction model for change, which overcomes a limitation of the item side change approach by allowing interaction effects between persons and item side change parameters. The results showed that student changes in the ELP data used in this study should be modeled for the three sub-content areas and that modeling interaction for change was necessary.
김석현(Kim Seockhyun),백인수(Paek Insu),김재철(Kim Jaecheol) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-
This paper investigates the sound insulation performance of the fiber sandwich panels for a tilting train. Due to the high strength and low mass, fiber sandwich panels are widely used for aircraft structures, railway vehicle structures. These fiber sandwich panels show orthotropic behavior because of the fiber"s structural characteristics. This orthotropy often reduces the critical frequency and makes negative effect on the sound insulation performance. In this study, transmission loss of the fiber panels is analyzed based on the equivalent orthotropic plate model. An analysis program is developed to calculate the transmission loss of the fiber sandwich panels. Using the program, the coincidence frequency ranges and their effects on the transmission loss are investigated.
Feedforward Pitch Control Using Wind Speed Estimation
Yoonsu Nam,Jeonggi Kim,Insu Paek,Young-Hwan Moon,Seog-Joo Kim,Dong-Joon Kim 전력전자학회 2011 JOURNAL OF POWER ELECTRONICS Vol.11 No.2
The dynamic response of a multi-MW wind turbine to a sudden change in wind speed is usually slow, because of the slow pitch control system. This could cause a large excursion of the rotor speed and an output power over the rated. A feedforward pitch control can be applied to minimize the fluctuations of these parameters. This paper introduces the complete design steps for a feedforward pitch controller, which consist of three stages, i.e. the aerodynamic torque estimation, the 3-dimensional lookup table for the wind seed estimation, and the calculation of the feedforward pitch amount. The effectiveness of the feedforward control is verified through numerical simulations of a multi-MW wind turbine.