• Journal of Advanced Navigation Technology
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• v.13 no.6
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• pp.943-949
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• 2009

In this paper, the 5.9GHz WAVE(Wireless Access in Vehicular Environments) channel modeling is used by the Jakes channel model for the suitability of the fast wireless channel fluctuation. The performance analysed the fading signal constellation and the spectrum in the IEEE 802.11p spectrum mask, the Doppler effect, the modulation scheme. In addition, the vehicular speed, exactly the performance analysis the WAVE communication systems follow the Doppler effect.

• New & Renewable Energy
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• v.10 no.1
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• pp.41-49
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• 2014

For a proper valuation of wind power project, it is necessary to consider volatilities of key parameters such as annual energy production, electricity sales price, and long term interest rate. Real option methodology allows to calculate option values of these parameters. Volatilities to be considered in wind project valuation are 1) annual energy production (AEP) estimation due to meteorological variation and estimation errors in wind speed distribution, 2) changes in system marginal price (SMP), and 3) interest rate fluctuation of project financing which provides refinancing option to be exercised during a loan tenor for commercial scale projects. Real option valuation turns out to be more than half of the sales value based on a case study for a FIT scheme wind project that was sold to a financial investor.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1997.04a
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• pp.241-246
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• 1997

Corrugation of railway track can be caused by the various dynamic behaviors of traveling wheels and track. In this paper, the coupled vibrations of traveling wheel and railway track are analyzed as the cause of corrugations. To analyze the coupled vibration, the track supported by the sleepers and the traveling wheels are identified to the elastically supported infinite beam and the spring-mass system which runs at constant speed. The Hertzian contact spring is considered between the infinite beam and spring-mass system. The dynamic responses of elastically supported infinite beam and spring-mass system are calculated. The cause and development of rail corrugation are discussed in the view point of contact force fluctuation affected by the elastic supports and the corrugated surface profile on the track. By the obtained results, the possibilities of resonance are checked between the excitation by the corrugated surface profile and the natural frequency of contact spring-mass system. It may be thought to a development of railway corrugation.

• Lingua Humanitatis
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• v.5
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• pp.293-310
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• 2003

This study starts with a remark on the frequent usage of the term 'generation culture' in the explanations of cultural change. The term 'generation culture' itself does have neither a clear meaning nor any academic consensus for its operational definition yet. Depending on intuitions or common senses, in most cases, of everyday lift experience, the tends to designate the co-existence of different cultural layers as composing subsystems of a little broader Korean cultural trend. I tried here to analyze different positions and perspectives in the employment of this term, sometimes with strategic intentions of each social groups. Economic or political positions, for example, are intertwined with the quest of identification concerning 'we' and 'other' grouping dynamics in the Age of Globalization, which accelerates the speed of cultural re-territorialization. And the role of consumption activity as a kind of cultural indication has gained more weight in that process. This analysis will remind us, also, of the post-modem society's assumption about the space-and-time in transition, and its fluctuation.

• Journal of Power System Engineering
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• v.14 no.6
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• pp.89-95
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• 2010

This paper deals with design method of proportional-integral(PI) and feedforward controller for obtaining precise temperature and high energy efficiency of oil cooler system in machine tools. The compressor's speed and opening angle of an electronic expansion valve are controlled to keep reference value of temperature at oil outlet and superheat of an evaporator. Especially, the feedforward controller is added to suppress temperature fluctuation under abrupt disturbances. Through some experiments, the suggested method can control the target temperature within steady state error of ${\pm}0.l^{\circ}C$ and maximum overshoot $0.2^{\circ}C$ under abrupt disturbances.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.3
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• pp.180-187
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• 2016

As distinct from a slender body, the separation of the boundary layer on a bluff body give rise to complex wakes in which various kinds of vortices form, develop and interact with each other. In this paper, we investigate cavitation wake field behind wedge shaped two-dimensional fin models. Eight different models are tested at the Chungnam National University Cavitation Tunnel (CNU-CT). First, we measure wake cavity shapes and compare with numerical results, which shows the good agreement with each other. In addition, we demonstrate that wake flow characteristics of the control fin are clearly identified by the correlation analysis of high-speed camera images and pressure fluctuation measurements.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.342-352
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• 2003

Idle NVH characteristics are one of the most important aspects among the vehicle performances. Vehicle developers are devoted to improve vehicle interior noise and steering wheel and seat vibrations. In order to improve the idle quality, noise and vibration transfer path should be carefully evaluated. Also, effects of various components related to the idle performance should be confirmed. A general procedure for improving the idle qualify is described in detail. The relationship among cylinder pressure characteristics, crankshaft rotational speed variation, and vehicle vibrations is also investigated. Influences of drive shaft, torque converter, air conditioning system, vehicle structure including engine mount system, and idle control parameters on the vehicle idle quality are studied. Weak points of typical vehicles on the idle qualify are identified. Some of improvement measures are proposed and verified.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.3 no.3
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• pp.617-626
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• 1999

For the purpose of high speed and reliable data transmission through the frequency response variation channel by load fluctuation, we present CSK signal transmission characteristics by computer simulation. Also using the simple structure of Roll-off filter at the CSK receiving system, the exact synchronization tracking and data detection without error at the worst case of S/I=2 and S/N=2 were achieved.

• Proceedings of the KIPE Conference
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• 2013.07a
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• pp.491-492
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• 2013

본 연구는 STATCOM을 이용하여 고속철도 급전 계통의 전압 변화를 보상하는 기법에 관한 것이다. 기존의 PI 제어기를 이용한 제어기법를 대신하여 본 연구에서는 퍼지제어기(FLC) 적용을 제안하며, 퍼지제어기와 PI제어기의 제어결과를 비교한다. 퍼지제어기를 통해 내부 파라미터 변동이나 외부의 환경 변화 등 계통의 변화시에 정상상태 편차, 정상상태 도달 시간 등을 최소화 시킬 수 있음을 보인다.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.22 no.2
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• pp.153-161
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• 1998

This study describes the results of the analysis of measured rotating stall signal in a centrifugal compressor with vaneless diffuser. Unsteady flow and rotating stall in vaneless diffuser were investigated by measuring of unsteady velocity fluctuation using hot-wire anemometer. Experiments were carried out in several impeller rotating speeds, at different radius ratios. Single hot -wire was used to study the characteristics of rotating stall. As a result, the abrupt rotating stall was detected at all measured impeller rotating speeds and the several flow coefficients which are less than 0.16. The number of the stall cell was one at all measured rotational speeds, and the rotating direction was the same as that of the impeller. As the flow rate decreased, the profile of the phase averaged radial velocity component with time changed from a sawtooth to a sine wave.