• Title, Summary, Keyword: transfer function

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

  • 김형수;전영세;이종웅;김성호
    • Korean Journal of Optics and Photonics
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    • v.9 no.6
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    • pp.396-402
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    • 1998
  • The measurement of OTF(optical transfer function) is used for evalution of imaging performance of optical system as a standard method. In the mass-production, the contrast measurement of projected patterns is also popular because of its simplicity. In this study, a computer program which evaluates the CTF(contrast transfer function) of optical system for periodic line-space patterns is developed by using the diffraction imaging theory. The MTF(modulation transfer function) and CTF of an aberrated system are evaluated and analyzed for the third order aberrations expressed by the C-coefficients and the Zemike polynomials.

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

  • Kim, Jinah;Kim, Jihwan;Lee, Jeongwon;Kim, Daesik
    • Journal of ILASS-Korea
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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.

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

  • 김종준;송한림;김현수
    • Transactions of the Korean Society of Automotive Engineers
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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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A Study of the Flame Transfer Function Characteristics using Cold-flow Transfer Function in a Partially Premixed Model Gas Turbine Combustor (부분 예혼합 가스터빈 연소기에서의 비연소 전달함수 계측으로부터의 화염전달함수 특성 파악)

  • Joo, Seongpil;Kim, Seongheon;Yoon, Jisu;Yoh, Jai-ick;Yoon, Youngbin
    • Journal of the Korean Society of Propulsion Engineers
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    • v.21 no.5
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    • pp.54-60
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    • 2017
  • In order to identify the characteristics of the flame transfer function gain, cold-flow transfer function was introduced, which is the part of the combustion instability research. Nitrogen and carbon dioxide was used to obtain the cold-flow transfer function and input/output variables was measured by hot wire anemometry. Density and fluid flow rate affect the cold-flow transfer function gain and peak frequency. In addition, acoustic resonance frequency affects the peak frequency of gain in the fuel feeding line.

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

  • Nam, Jinhyun;Nam, Doohee
    • The Journal of The Institute of Internet, Broadcasting and Communication
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    • v.14 no.4
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    • pp.107-112
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    • 2014
  • This Study is Transfer function optimization plan of volume rendering of multi user environment. Each volume data, for appropriate transfer function, they should be adjusted parameter many times. To prevent this, we propose transfer function optimization plan using crowd sourcing. In multi user environment, we use weight value for reliability level for each user. Because transfer function parameter used previous users is provided next users, they can be used effectively optimized transfer function and can reduce attempts.

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.

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

  • Cho, Ju-Hyeong;Baek, Seung-Wook
    • Transactions of the Korean Society of Mechanical Engineers B
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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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