• 제목, 요약, 키워드: Transfer function

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주기적인 선물체에 대한 Contrast Transfer Function의 수치계산 (Numerical calculation of contrast transfer function for periodic line-space patterns)

  • 김형수;전영세;이종웅;김성호
    • 한국광학회지
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    • v.9 no.6
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    • pp.396-402
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    • 1998
  • 광학계의 결상성능평가는 optical transfer function(OTF)을 측정하는 것이 표준적인 방법으로 사용되고 있다. 그러나, 대량 생산되는 광학계의 경우에서는 측정의 편리함 때문에 test pattern을 투영하여 contrast를 검사하는 방법도 많이 사용되고 있다. 본 연구에서는 회절결상이론을 사용하여 주기적 line-space pattern에 대한 contrast transfer function(CTF)을 계산하는 프로그램을 개발하고, C­계수와 Zernike 다항식으로 표현되는 3차 파면수차에 의한 광학계의 modulation transfer function (MTF)과 CTF 변화를 비교, 분석하였다.

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희박 예혼합 연소기에서 연료 조성이 화염전달함수 특성에 미치는 영향 (Effects of Fuel Composition on Flame Transfer Function in Lean Premixed Combustor)

  • 김진아;김지환;이정원;김대식
    • 한국분무공학회지
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    • v.20 no.3
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    • pp.135-140
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    • 2015
  • Flame transfer function is used to determine the relationship between flow fluctuations and heat release perturbations in a lean premixed gas turbine combustor. The characteristics of flame transfer function are known to depend greatly on flame geometries in addition to other various flow conditions. However, it is not easy to experimentally measure the flame transfer function under various actual combustor operating conditions in terms of time and cost. The current research tries to model the flame transfer function using CFD(Computational Fluid Dynamics). From the results, it is shown that the calculated steady flame geometry can be exactly captured with consideration of the wall heat transfer and radiations. Also, unsteady analysis results show the close characteristics of the flame transfer function to the measured one in both gain and phase.

Modeling of a Transfer Function for Frequency Controlled Resonant Inverters

  • Han, Mu-Ho;Lee, Chi-Hwan;Kwon, Woo-Hyun
    • Journal of Power Electronics
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    • v.9 no.4
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    • pp.567-574
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    • 2009
  • A linear transfer function for the output current control of frequency-controlled resonant inverters is proposed in this paper. The circuit of resonant inverters can be transformed into two coupled circuits through the complex phasor transform. The circuits consist of cross-coupled power sources and passive elements. The circuits are used to induce the state space equation, which is transformed into the $4^{th}$ order cross-coupled transfer function. The $4^{th}$ order cross-coupled transfer function is modeled into a $2^{nd}$ order linear transfer function based on a behavior analysis of the pole and zero locations that facilitate a simple and intuitive linear transfer function. The feasibility and validity of the proposed linear transfer function were verified by simulation and experiment.

금속벨트 CVT의 전달함수 도출과 변속비 LQG/LTR 제어 (Transfer Function Derivation and LQG/LTR Speed Ratio Control for a Metal Belt CVT)

  • 김종준;송한림;김현수
    • 한국자동차공학회논문집
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    • v.5 no.1
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    • pp.49-58
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    • 1997
  • In this paper, a transfer function was obtained for a PWM high speed solenoid valve controlled metal belt CVT system. The transfer function was defined as the ratio of speed ratio to PWM duty ratio and derived in time domain by linear regression analysis from the experimental results. The transfer function obtained showed different dynamic characteristics for the up and down shift. Also, LQG/LTR controller was designed for the CVT system using the transfer function. It is seen from the experimental results that LQG/LTR control showed good performance for the speed ratio tracking and disturbance rejection. The phase difference and relatively slow response are considered due to the inaccuracy os the transfer functions, which resulted from the inherent nonlinearities of the transmission characteristics of the metal belt CVT.

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Realization of n-th Order Voltage Transfer Function Using a Single Operational Transresistance Amplifier

  • Kilinc, Selcuk;Cam, Ugur
    • ETRI Journal
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    • v.27 no.5
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    • pp.647-650
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    • 2005
  • A new configuration to realize the most general n-th order voltage transfer function is proposed. It employs only one operational transresistance amplifier (OTRA) as the active element. In the synthesis of the transfer function, the RC:-RC decomposition technique is used. To the best of author's knowledge, this is the first topology to be used in the realization of n-th order transfer function employing single OTRA.

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부분 예혼합 가스터빈 연소기에서의 비연소 전달함수 계측으로부터의 화염전달함수 특성 파악 (A Study of the Flame Transfer Function Characteristics using Cold-flow Transfer Function in a Partially Premixed Model Gas Turbine Combustor)

  • 주성필;김성헌;윤지수;여재익;윤영빈
    • 한국추진공학회지
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    • v.21 no.5
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    • pp.54-60
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    • 2017
  • 연소불안정 연구의 일환인 화염전달함수에서 나타나는 gain의 특성을 파악하기 위하여 비연소상태에서의 전달함수를 도입하여 화염전달함수에서의 특성과 비연소전달함수의 특성에 대한 원인을 파악하고자 하였다. 비연소 전달함수를 획득하기 위하여 질소와 이산화탄소를 활용하였으며, 입력값과 출력값을 계측하기 위하여 열선풍속계를 이용하였다. 비연소 전달함수에서의 gain과 주파수의 peak는 비활성기체의 밀도와 유량에 대하여 영향을 받는 것을 확인하였다. 또한 연료공급라인에서의 음향학적 공진주파수가 peak 주파수에 영향을 주는 것을 확인하였다.

크라우드 소싱을 이용한 변환함수 최적화 (Transfer Function Optimization Using Crowd Sourcing)

  • 남진현;남두희
    • 한국인터넷방송통신학회논문지
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    • v.14 no.4
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    • pp.107-112
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    • 2014
  • 본 연구에서는 다중 사용자 환경의 볼륨 가시화(Volume Rendering)에서 변환 함수(Transfer Function)의 최적화 방안을 연구한다. 볼륨 데이터에 따라 필요한 변환 함수의 형태가 다르기 때문에 여러 번의 시행착오를 겪어야 필요한 변환 함수를 얻을 수 있는데, 이를 방지하기 위해 크라우드 소싱 기법을 이용하여 변환 함수의 파라미터를 최적화 하는 방안을 제안한다. 다중 사용자 환경에서 각 사용자마다 신뢰도에 따른 레벨을 지정하여 가중치로 사용한다. 이전 사용자가 사용했던 변환 함수 파라미터는 가중치만큼 다음 사용자에게 제공되기 때문에 다음 사용자는 변환 함수의 최적 파라미터를 찾기 위한 시도횟수를 줄일 수 있다.

Automatic Contrast Enhancement by Transfer Function Modification

  • Bae, Tae Wuk;Ahn, Sang Ho;Altunbasak, Yucel
    • ETRI Journal
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    • v.39 no.1
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    • pp.76-86
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    • 2017
  • In this study, we propose an automatic contrast enhancement method based on transfer function modification (TFM) by histogram equalization. Previous histogram-based global contrast enhancement techniques employ histogram modification, whereas we propose a direct TFM technique that considers the mean brightness of an image during contrast enhancement. The mean point shifting method using a transfer function is proposed to preserve the mean brightness of an image. In addition, the linearization of transfer function technique, which has a histogram flattening effect, is designed to reduce visual artifacts. An attenuation factor is automatically determined using the maximum value of the probability density function in an image to control its rate of contrast. A new quantitative measurement method called sparsity of a histogram is proposed to obtain a better objective comparison relative to previous global contrast enhancement methods. According to our experimental results, we demonstrated the performance of our proposed method based on generalized measures and the newly proposed measurement.

유동 섭동에 의한 난류예혼합화염의 열발생 모델에 관한 연구 (A Heat Release Model of Turbulent Premixed Flame Response to Acoustic Perturbations)

  • 조주형;백승욱
    • 대한기계학회논문집B
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    • v.32 no.6
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    • pp.413-420
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    • 2008
  • The unsteady heat release characteristics play a significant role in combustion instabilities observed in low emissions gas turbine combustors. Such combustion instabilities are often caused by coupling mechanisms between unsteady heat release rates and acoustic perturbations. A generalized model of the turbulent flame response to acoustic perturbations is analytically formulated by considering a distributed heat release along a curved mean flame front and using the flame's kinematic model that incorporates the turbulent flame development. The effects of the development of flame speed on the flame transfer functions are examined by calculating the transfer functions with a constant or developing flame speed. The flame transfer function due to velocity fluctuation shows that, when a developing flame speed is used, the transfer function magnitude decreases faster with Strouhal number than the results with a constant flame speed at low Strouhal numbers. The flame transfer function due to mixture ratio fluctuation, however, exhibits the opposite results: the transfer function magnitude with a developing flame speed increases faster than that with a constant flame speed at low Strouhal numbers. Oscillatory behaviors of both transfer function magnitudes are shown to be damped when a developing flame speed is used. Both transfer functions also show similar behaviors in the phase characteristics: The phases of both transfer functions with a developing flame speed increase more rapidly than those with a constant flame speed.

Order identification of transfer function-noise model

  • Park, Seongju;Bae, Hankyung;Huh, Kyungmoo
    • 제어로봇시스템학회:학술대회논문집
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    • pp.164-169
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    • 1992
  • Classical methods for estimating transfer function models have not always been successful. A statistic approach to the identification of transfer function models which is corrupted by disturbances or noise is presented. The estimated impulse response is obtained from the autocorrelation function and cross correlation function between the measured input and output. Several data analysis tools such as R- , S- and GPAC array for the estimated impulse response give us pretty clear information on the order of transfer function models.

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