• Journal of the Korean Society for Railway
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• v.17 no.5
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• pp.321-327
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• 2014

In this paper, linear dynamic equations are derived from nonlinear dynamic equations of constrained multibody systems using the QR decomposition method. The derived linear equations are applied to a railway vehicle bogie. The vibration characteristics of the railway vehicle are investigated by calculating the natural mode and transfer function of the bogie frame in relation to rail-roughness input. The main modes of the bogie were found below 35Hz, and the local modes above 198Hz. The magnitude of the vertical transfer function varied with the forward velocity due to vertical and pitch modes, which were influenced by the forward velocity. The magnitude of the lateral transfer function was negligibly small, and the mode in the longitudinal direction was excited for longitudinal transfer function regardless of the forward velocity.

• Transactions of the Korean Society of Automotive Engineers
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• v.6 no.4
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• pp.66-75
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• 1998

In many case of optimal design and sensitivity analysis, obtaining of transfer function between input and output variables is a difficult and time-consuming problem. The bond graph modeling is a method that is used for making it easy to analyze complex systems composed of mechanical and electrical parts. It gives us a simple and systematic tool to get state-space equations easily. And we can obtain the transfer function graphically using bond graph and Mason's rule. This paper shows how bond graphs are converted to block diagram and how Mason's rule is applied. And the simple direct method to obtain transfer function from bond graph is introduced. As a example, induction of transfer function of electric power steering composed of mechanical and electrical parts will be done.

• The Journal of the Acoustical Society of Korea
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• v.28 no.5
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• pp.409-415
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• 2009

The head-related transfer function (HRTF), which has an important role in virtual sound localization has different characteristics across the subjects. Measuring HRTF is very time-consuming and requires a set of specific apparatus. Accordingly, HRTF customization is often employed. In this paper, we propose a method to search an adequate HRTF from a set of the HRTFs. To achieve rapid and reliable customization of HRTF, all HRTFs in the database are partitioned, where a binary search tree was employed. The distortion measurement adopted in HRTF partitioning was determined in a heuristic way, which predicts the differences in perceived sound location well. The DC-Davis CIPIC HRTF database set was used to evaluate the effectiveness of the proposed method. In the listening test, where 10 subjects were participated, the stimuli filtered by the HRTF obtained by the proposed method were closer to those by the personalized HRTF in terms of sound localization. Moreover, performance of the proposed method was shown to be superior to the previous customization method, where the HRFT is selected by using anthropometric data.

• Journal of the Korean Society of Radiology
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• v.15 no.5
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• pp.705-713
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• 2021

The modulation transfer function (MTF) is calculated to analyze the resolution of the spatial frequency of the image acquired from the x-ray imaging system. In general, the response function of the detector acquires a line spread function (LSF) using a slit-camera, and derives a modulation transfer function through a Fourier transform. Because of the fact that the x-ray must always be incident on the center of the slit-camera, the tilt of the detector and slit-camera caused by the experimenter will affect the detector performance. In addition, if the tilt increases, the performance evaluation of the x-ray image system will be problematic. In this study, we analyzed the experimental and analytical models in the modulation transfer function, ie, the Fourier domain, based on the experimental error and analyzed the effect on the spatial frequency. Furthermore, performance evaluation is being carried out for various x-ray imaging systems, and experimental errors are indispensable, and the extent to which they can be tolerated should be reviewed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.16 no.12
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• pp.1219-1228
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• 1991

In the actual case, a model of noise canceller using adaptive filter has both a channel transfer function from noise source to main signal input and to noise canceller input. The previous models of noise canceller have been considered to be only one side channel transfer function. Therefore, it is proposed that a new model has two channel transfer functions and derives an optimal tranfer function of adaptive noise canceller. The adaptive filter is using the joint process lattice filter that has fast adaptive speed. The signal noise radio has been improved by a model of ANC-ALE and it is confirmed with computer simulation. Beside, a dc bias is very effective for noise cancelling, especially to the particular signal.

• Journal of the Society of Naval Architects of Korea
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• v.31 no.4
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• pp.51-57
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• 1994

In this study, the method for calculation of the frequency transfer function of motions based on the multi-directional waves in the analysis of a full-scale seakeeping trials is presented. For calculation of the frequency transfer function in the directional waves, Takezawa's inverse estimation method was introduced and the frequency ranges were divided into three parts in order to consider following seas. To confirm the validity of this method, the numerical simulation was executed. Those results show that analysis method of the multi-directional waves is more reliable than that of one directional waves, and confirm the possibility of applying this method to the full-scathe seakeeping trials.

• Journal of ILASS-Korea
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• v.26 no.4
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• pp.182-188
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• 2021

In this paper, using a transfer function-based analytical model, major factors influencing the acoustics and combustion instability in a two-stage duct system composed of a nozzle and a combustor were derived and their quantitative effects were evaluated. From the acoustic analysis, it was confirmed that the change in reflection coefficient and mean flow could have a great influence on the instability growth rate, and the area ratio and speed of sound ratio between the nozzle and the combustor are also key parameters to determine combustion instability as well as flame transfer functions.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.1
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• pp.145-151
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• 1998

This paper addresses the results of an experimental and analytical research of cylindrical coil spring subjected to dynamic behavior. Transfer functions are presented for both deflection and transmitted force as the output with force as the input. Steady state sinusoidal magnitude ratio and transmittance are plotted along with experimental data. It is shown that dynamic characteristic of cylindrical coil spring must be used to enhance the reability of vibration system dynamic behavior analysis in actuating over some frequency.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.2
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• pp.168-175
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• 1996

The measured vibration on a machine or a structure is shaped by the excitation waveform and the path transfer function. Mechanism diagnostics tends to focus on retrieving source features by minimizing the effects of the structiral path, while in structural diagnostics we are more interested in minimizing source effects and retrieving path parameters. In structural diagnostics, therefore, there are experimental issues of gathering date that are independent source effects and finding a transfer function signature that reveals structural defects. This paper describes how the transfer function can be obtained more accurately by experiment using the compatibility relationship which is newly discovered.

• Journal of the Institute of Electronics and Information Engineers
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• v.54 no.6
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• pp.30-39
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• 2017

A digital calibration technique based on digital-domain averaging for cyclic ADC is proposed. The proposed calibration compensates for nonlinearity of ADC due to capacitance mismatch of capacitors in 1.5-bit/stage MDAC. A 1.5-bit/stage MDAC with non-matched capacitors has symmetric residue plots with respect to the ideal residue plot. This intrinsic characteristic of residue plot of MDAC is reflected as symmetric A/D transfer functions. A corrected A/D transfer function can be acquired by averaging two transfer functions with non-linearity, which are symmetric with respect to the ideal analog-digital transfer function. In order to implement the aforementioned averaging operation of analog-digital transfer functions, a 12-bit cyclic ADC of this work defines two operational modes of 1.5-bit/stage MDAC. By operating MDAC as the first operational mode, the cyclic ADC acquires 12.5-bits output code with nonlinearity. For the same sampled input analog voltage, the cyclic ADC acquires another 12.5-bits output code with nonlinearity by operating MDAC as the second operational mode. Since analog-digital transfer functions from each of operational mode of 1.5-bits/stage MDAC are symmetric with respect to the ideal analog-digital transfer function, a corrected 12-bits output code can be acquired by averaging two non-ideal 12.5-bits codes. The proposed digital calibration and 12-bit cyclic ADC are implemented by using a $0.18-{\mu}m$ CMOS process in the form of full custom. The measured SNDR(ENOB) and SFDR are 65.3dB (10.6bits) and 71.7dB, respectively. INL and DNL are measured to be -0.30/-0.33LSB and -0.63/+0.56LSB, respectively.