• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.5B no.3
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• pp.215-223
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• 2005

An electrical machine for a high-speed flywheel for energy storage in large hybrid electric vehicles is described. Design choices for the machine are motivated: it is a radial-flux external-rotor permanent-magnet synchronous machine without slots in the stator iron and with a shielding cylinder. An analytical model of the machine is briefly introduced whereafter optimization of the machine is discussed. Three optimization criteria were chosen: (1) torque; (2) total stator losses and (3) induced eddy current loss on the rotor. The influence of the following optimization variables on these criteria is investigated: (1) permanent-magnet array; (2) winding distribution and (3) machine geometry. The paper shows that an analytical model of the machine is very useful in optimization.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2000.04a
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• pp.435-442
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• 2000

In this thesis the dynamic behavior of the vehicles is analyzed while the track is subjected to lateral vibration due to earthquakes. A computer program is developed which can simulate dynamic responses of vehicles subjected to earthquake loading. The analysis considers two types of two types of vehicles : I. e. a 2-axle vehicle with 13 DOF's an da power car of K-TGV with 38 DOF's It can also consider the interaction with substructures such as tracks and bridges. El Centro record is considered as earthquake loading. The creep force module developed in this study is verified and the results of this study are compared with those of others. Furthermore he running safety of high-speed railway vehicles(K-TGV) subjected to earthquake loading is studied. Based on the results of this study the running safety of the K-TGV can be confirmed against el centro earthquake.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.1888-1893
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• 2011

Considering the dynamic performance and stability of railroad vehicles has begun to grab the attention because of developing the high speed train recently. A development based on an analysis of dynamics and verification has to be required to study the stability of vehicle performance. Several ways of analysis were using the look-up table to apply the wheel-rail contact characteristics quickly, whereas there is a constraint of the wheelset lateral displacement. In this study, an development of searching the wheel-rail contact position has been provided. The 2-point contact between wheel and rail during the driving condition can be calculated by numerical analysis. Moreover, a reliability is verified by comparing the result with a commercial program.

• Proceedings of the KSR Conference
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• 2011.10a
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• pp.2949-2951
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• 2011

It is expected that domestic railway vehicle operation companies may be subjected to GHG emission reduction when GHG emission system is enforced. This study aimed that reviewing on GHG emission system such as CDM, VCS and KCER, and analysing availability of GHG emission credit acquisition for railroad transportation sector. In order to estimate GHG emission credit, a GHG emission estimation methodology should be developed, which includes GHG emission baseline estimation and GHG emission monitoring method, MRV method and etc. Modal shift project, high speed train technology, straight lining project, mass transportation technology, operation optimization tehcnology and etc. may produce GHG emission credit.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.289-295
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• 2013

It is important to know exact values of Interior Permanent Magnet Synchronous Motors(IPMSM)' parameters such as stator resistance and inductance in order to have their high performance. This paper proposes a novel motor parameter(stator resistance, d&q axis inductance) estimation algorithm for IPMSM. The proposed estimation method utilizes back-EMF equations and model reference adaptive system(MRAS). The algorithm using back-EMF estimates d and q axis inductances in the constant torque region, and the stator resistance is estimated by using MRAS with the estimated inductance regardless of speed regions. The validity of the proposed algorithm is verified by simulations and experiments.

• Tribology and Lubricants
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• v.29 no.5
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• pp.318-323
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• 2013

Overheating in electrical motors results in detrimental effects such as degradation of the insulation materials, demagnetization of magnets, increases in Joule losses, and decreases in motor efficiency and lifetime. Thus, it is important to find ways to dissipate heat from the motor and to keep the motor operating at its most efficient temperature. In this study, a new design to guide air flow through a given brushless direct current (BLDC) motor is developed and the design is analyzed, specifically by using computational fluid dynamics (CFD) simulations. The results showed that the temperature distribution in the three proposed models is lower than that in the original model, although the speed of the cooling fan in the original model reaches a very high value of $15{\times}10^3$ rpm. The results also showed that CFD can be effectively used to simulate the heat transfer of BLDC motors.

• English Language & Literature Teaching
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• v.12 no.1
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• pp.103-129
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• 2006

This paper presents a case study of the effectiveness of debate class in promoting speaking skills of advanced learners. The researcher adopted English debate techniques in an English speaking class during four-week teacher training program and investigated how teachers responded to the new technique. Forty-five middle and high school teachers participated in the study and classroom observation, pre-survey, post-survey, and focus group interviews were used as the major research methods. The teacher pre-survey results presented that teachers prefer a conversation class where they can directly acquire proper sentence patterns and speaking strategies rather than spend time in performing communicative events. The results of the focus group interview and post-survey confirmed that a debate class can meet this specific teachers' needs. Most teachers responded positively to the debate classes since: 1) debate techniques are relatively new ideas to Korean teachers; 2) debate techniques require speed and accuracy in speech; thus teachers could learn to present their ideas logically and efficiently in a limited time through repeated argument exercises. The study result implies that debate technique can be an effective vehicle in an EFL context to promote advanced learners' logical thinking skills and logical English sentence structures.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.121-122
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• 2016

본 논문에서는 중 고속 자기부상열차용 선형 유도전동기에서 나타나는 단부효과를 고려하여 중 고속 운전을 할 수 있는 제어 알고리즘을 제안한다. 선형 유도전동기에서 나타나는 단부효과를 수식적으로 분석하여 선형 유도전동기 시뮬레이션 모델을 구성하였으며, 단부효과의 영향을 보상하여 제어를 함으로서 선형 유도전동기 적합한 제어 알고리즘을 구성하여 시뮬레이션을 통하여 검증하였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.17 no.5
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• pp.7-15
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• 2009

This paper introduces a new variable valve actuation mechanism with movable second cam center. Valve lift and open duration can be continuously varied according to engine speed and load conditions. A new method to analyze the kinematic relations between the first and second cam profiles and valve motion are also introduced. Because of rocker motion of the second cam, conventional motion conversion program could not be used in this problem. An example shows continuous variations of valve motion and adequate ramp incorporation throughout all valve lift modes. Valve acceleration profile at the high lift mode is similar to that of conventional valvetrains. Contact geometry analysis of the mechanism gives basic information on the load conditions between the components.

• International Journal of Automotive Technology
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• v.6 no.6
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• pp.635-641
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• 2005

This paper presents an ASF (Aluminum Space Frame) BIW (Body in White) optimal design, which minimizes weight and satisfies multidisciplinary constraints such as static stiffness, vibration characteristics, low-/high-speed crash, and occupant safety. As only one cycle CPU time for all the analyses is 12 hours, the ASF design having 11-design variable is a large scaled problem. In this study, ISCD-II and conservative least square fitting method were used for efficient RSM modeling. Likewise, the ALM method was used to solve the approximate optimization problem. The approximate optimum was sequentially added to remodel the RSM. The proposed optimization method uses only 20 analyses to solve the 11-design variable problem. Moreover, the optimal design can achieve $15.6\%$ weight reduction while satisfying all the multidisciplinary design constraints.