• 제어로봇시스템학회논문지
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• 제8권8호
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• pp.649-654
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• 2002

The essential philosophy of the QFT(Quantitative Feedback Theory) is that a suitable controller can be found by loop shaping a nominal loop transfer function such that the frequency response of this function does not violate the QFT bounds. The loop shaping synthesis involves the identification of a structure and its specialization by means of the parameter optimization. This paper presents an optimization algorithm to estimate the controller parameters from the frequency transfer function synthesis using the TLS(Total Least Squares) in the QFT loop shaping procedure. The proposed method identifies the parameter vector of the robust controller from an overdetermined linear system developed from rearranging the two dimensional system matrices and output vectors obtained from the QFT bounds. The feasibility of the suggested algorithm is illustrated with an example.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2010년도 춘계학술대회 논문집
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• pp.1444-1451
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• 2010

This paper aims for proposed the deflection limit on vibration serviceability of high-speed railway bridges considering the exposed time duration when a train passes a railway bridge. For this purpose, bridge-train transfer function was derived and bridge-train interaction analysis was performed by using the derived function. The vertical acceleration signals of passenger cars obtained from bridge-train interaction analysis were compared with them from the bridge-train transfer function by moving constant force analysis. Therefore it was estimated possible to induce the comfort deflection limit of railway bridge by using bridge-train transfer function. The deflections by moving force of single span bridge and continuous bridge were assumed as sine and haversine wave. The deflection limit on vibration serviceability of high-speed railway bridges considering the exposed time duration can be expanded using bridge-train transfer function and bridge comfort limit considering serviceability due to bridge vibration. And it was compared to other allowable deflection limits of railway bridge design specifications.

• Journal of the Optical Society of Korea
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• 제10권4호
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• pp.169-173
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• 2006

This paper describes an efficient optimal design method for an arrayed waveguide grating (AWG) having MMI coupler with flattened transfer function. The objective function is the norm of the difference between calculated and target spectra. To analyze the AWG transfer function, the Fresnel-Kirchhof diffraction formula was employed and the design variable was optical path difference of each array waveguide. The (1+1) Evolution Strategy was applied to an eight-channel coarse wavelength division multiplexing (CWDM) AWG as the optimization tool. For obtaining a broadened spectrum, we use a MMI coupler and the variation in optical path difference at each array waveguide changes the shape of the transfer function to obtain the optimal spectrum shape.

• Journal of the Optical Society of Korea
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• 제10권1호
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• pp.33-36
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• 2006

This paper describes an efficient optimal design method for an arrayed waveguide grating (AWG) with flattened transfer function. The objective function is the norm of the difference between calculated and target spectra. To analyze the AWG transfer function, the Fresnel-Kirchhof diffraction formula was employed and the design variable was optical path difference of each array waveguide. The (1+1) Evolution Strategy was applied to an eight-channel coarse wavelength division multiplexing (CWDM) AWG as the optimization tool. The optimized transfer function will considerably improve the system performance.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2009년도 춘계학술대회 논문집 특별세미나,특별/일반세션
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• pp.359-366
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• 2009

This paper aims for analyzing the vibration serviceability of train by simply expressing its vertical vibration when it passes a railway bridge. For this purpose, bridge-train transfer function was derived and bridge-train interaction analysis was performed by using the derived function. The bridge-train transfer function was developed with the assumption that train is a single mass-spring system, and bridge-train interaction analysis was performed on simple beams of KTX passenger car. The vertical acceleration signals of passenger cars obtained from bridge-train interaction analysis were compared with them of cars obtained from the bridge-train transfer function. As a result, it could be estimated to express the vertical vibration inside the passenger car required for vibration serviceability evaluation by using the vertical vibration of bridges obtained from moving load analysis. Therefore, it may be possible to evaluate the vibration serviceability of railway bridges considering bridge-train interaction effect.

• Nuclear Engineering and Technology
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• 제46권2호
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• pp.195-206
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• 2014

Heat transfer characteristics in a narrow rectangular channel are experimentally investigated for upward and downward flows. The experimental data obtained are compared with existing data and predictions by many correlations. Based on the observations, there are differences from others: (1) there are no different heat transfer characteristics between upward and downward flows, (2) most of the existing correlations under-estimate heat transfer characteristics, and (3) existing correlations do not predict the high heat transfer in the entrance region for a wide range of Re. In addition, there are a few heat transfer correlations applicable to narrow rectangular channels. Therefore, a new set of correlations is proposed with and without consideration of the entrance region. Without consideration of the entrance region, heat transfer characteristics are expressed as a function of Re and Pr for turbulent flows, and as a function of Gz for laminar flows. The correlation proposed for turbulent and laminar flows has errors of ${\pm}18.25$ and ${\pm}13.62%$, respectively. With consideration of the entrance region, the heat transfer characteristics are expressed as a function of Re, Pr, and $z^*$ for both laminar and turbulent flows. The correlation for turbulent and laminar flows has errors of ${\pm}19.5$ and ${\pm}22.0%$, respectively.

• 한국광학회지
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• 제15권5호
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• pp.461-468
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• 2004

본 논문에서 연구된 정밀모형안은 정시안에서 1.2 시력의 적정한 수차를 가진 모형안임을 확인하였다. 망막의 특성을 생략한 안광학계에 광전달함수를 사용하여 망막에서의 광세기 분포를 조사하여 자각식으로 측정한 임상자료와 비교하였다. 망막의 광학적 특성을 나타내는 안구의 수차, 회절, 망막 대비감도, Stiles-Crawford 효과, 동공크기를 포함한 대비감도함수를 계산하였다. 모형안에 동공직경 1 mm와 8 mm의 범위에서 정시안과 비정시안에 대해 대비감도함수와 변조전달함수를 비교하여 시력을 예측하였다.

• 로봇학회논문지
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• 제18권4호
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• pp.403-408
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• 2023

In this paper, we introduce the results of the development of a care robot for the safe lifting and transportation of bedridden patients with difficulty moving by themselves, especially, in medical facilities. The purpose of the developed patient transfer robot is to improve the convenience of care givers and enhance the safety and comfort of care recipients by facilitating patient lifting and patient transfer tasks by applying robot technology. In order to implement the lifting function, a hoist was designed and developed, and a sway control and rollover warning system were included in the hoist module as product differentiators. In addition, in terms of implementing the transfer function, an omnidirectional movement mechanism to improve operability in confined spaces and an active safety system to prevent collisions were developed. The function of the developed patient transfer robot was verified through performance evaluation by an authorized testing agency.

• Journal of the Optical Society of Korea
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• 제20권3호
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• pp.381-388
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• 2016

The performance of a staring infrared imaging system can be characterized based on estimating the modulation transfer function (MTF). The slant edge method is a widely used MTF estimation method, which can effectively solve the aliasing problem caused by the discrete undersampling of the infrared focal plane array. However, the traditional slant edge method has some limitations such as the low precision of the edge angle extraction and using the approximate function to fit the edge spread function (ESF), which affects the accuracy of the MTF estimation. In this paper, we propose a modified slant edge method, including an edge angle extraction method that can improve the precision of the edge angle extraction and an ESF fitting algorithm which is based on the transfer function model of the imaging system, to enhance the accuracy of the MTF estimation. This modified slant edge method presents higher estimation accuracy and better immunity to noise and edge angle than other traditional methods, which is demonstrated by the simulation and application experiments operated in our study.

• 한국음향학회지
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• 제33권1호
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• pp.54-59
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• 2014

본 논문은 비정상 (nonstationary)특성을 가지는 잡음환경에서 마이크간 전달함수 비 (RTF, Relative Transfer Function) 추정 알고리즘을 제안한다. 음성을 이용한 다양한 기기에 다중 마이크를 이용한 잡음제거 기술은 널리 사용되며, 이때 각 마이크간의 입력 신호 사이의 관계는 필수적으로 추정되어야 한다. 본 논문에서는 기존의 OM-LSA(Optimally-Modified Log-Spectral Amplitude)기반의 추정 방식에 CASA (Computational Auditory Scene Analysis)를 접목시킨 방식을 제안한다. 제안한 방법의 성능 검증을 위하여 비정상 백색 잡음 (nonstationary white Gaussian noise) 환경에서 10명 화자 발음을 이용한 마이크간 전달함수 비 추정 성능 평가 실험을 수행하였다. 잡음 신호가 초당 8dB 증감하는 환경에서 SBF (Signal Blocking Factor)가 평균 2.65dB 개선됨을 확인하였다.