• 대한기계학회논문집A
• /
• 제22권2호
• /
• pp.458-466
• /
• 1998

In this work, a frequency domain method is tested numerically and experimentally to improve nonlinear model parameters using the frequency response function at the nonlinear element connected point of structure. This method extends the force-state mapping technique, which fits the nonlinear element forces with time domain response data, into frequency domain manipulations. The force-state mapping method in the time domain has limitations when applying to complex real structures because it needd a time domain lumped parameter model. On the other hand, the frequency domain method is relatively easily applicable to a complex real structure having nonlinear elements since it uses the frequency response function of each substurcture. Since this mehtod is performed in frequency domain, the number of equations required to identify the unknown parameters can be easily increased as many as it needed, just by not only varying excitation amplitude bot also selecting excitation frequency domain method has some advantages over the classical force-state mapping technique in the number of data points needed in curve fit and the sensitivity to response noise.

• 대한전기학회논문지:시스템및제어부문D
• /
• 제54권9호
• /
• pp.521-530
• /
• 2005

In this paper, a new high resolution reflectometry scheme, time-frequency domain reflectometry(TFDR), isproposed to detect and estimate a fault in a transmission line. Traditional reflectometry methodologies have been achieved either in the time domain or in the frequency domain only. However, the TFDR can jump over the performance limits of the traditional reflectometry methodologies because the acquired signal is analyzed in time and frequency domain simultaneously. In the TFDR, the new reference signal and the novel TFDR algorithm are proposed for analyzing the acquired signal in the time-frequency domain. Because the reference signal of Gaussian envelop chirp signal is localized in the time and frequency domain simultaneously, it is suitable to the analysis in the time-frequency domain. In the proposed TFDR algorithm, the time-frequency distribution function and the normalized time-frequency cross correlation function are used to detect and estimate a fault in a transmission line. That algorithm is verified for real-world coaxial cables which are typical transmission line with different types of faults by the TFDR system composed of real instruments. The performance of the TFDR methodology is compared with that o( the commercial time domain reflectomeoy(TDR) experiments, so that concludes the TFDR methodology can detect and estimate the fault with smaller error than TDR methodology.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• 제12권3호
• /
• pp.1205-1223
• /
• 2018

Image enhancement is an emerging method for analyzing the images clearer for interpretation and analysis in the spatial domain. The goal of image enhancement is to serve an input image so that the resultant image is more suited to the particular application. In this paper, a novel method is proposed based on Mamdani fuzzy inference system (FIS) using multiple fuzzy membership functions. It is observed that the shape of membership function while converting the input image into the fuzzy domain is the essential important selection. Then, a set of fuzzy If-Then rule base in fuzzy domain gives the best result in image contrast enhancement. Based on a different combination of membership function shapes, a best predictive solution can be determined which can be suitable for different types of the input image as per application requirements. Our result analysis shows that the quality attributes such as PSNR, Index of Fuzziness (IOF) parameters give different performances with a selection of numbers and different sized membership function in the fuzzy domain. To get more insight, an optimization algorithm is proposed to identify the best combination of the fuzzy membership function for best image contrast enhancement.

• International Journal of Control, Automation, and Systems
• /
• 제5권1호
• /
• pp.1-7
• /
• 2007

In this paper, the necessary and sufficient conditions for strict positive realness of the rational transfer functions directly from basic definitions in the frequency domain are studied. A new frequency domain approach is used to check if a rational transfer function is a strictly positive real or not. This approach is based on the Taylor expansion and the Maximum Modulus Principle which are the fundamental tools in the complex functions analysis. Four related common statements in the strict positive realness literature which is appeared in the control theory are discussed. The drawback of these common statements is analyzed through some counter examples. Moreover a new necessary condition for strict positive realness is obtained from high frequency behavior of the Nyquist diagram of the transfer function. Finally a more simplified and completed conditions for strict positive realness of single-input single-output linear time-invariant systems are presented based on the complex functions analysis approach.

• 한국수학교육학회지시리즈B:순수및응용수학
• /
• 제27권1호
• /
• pp.43-50
• /
• 2020

We investigate the domain of influence of the local volatility function on the solutions of the general Black-Scholes model. First, we generate the sample paths of underlying asset using the Monte Carlo simulation. Next, we define the inner and outer domains to find the effective volatility region. To confirm the effect of the inner domain, we use the root mean square error for the European call option prices, and then change the values of volatility in the proposed domain. The computational experiments confirm that there is an effective region which dominates the option pricing.

• 생명과학회지
• /
• 제14권6호
• /
• pp.997-1002
• /
• 2004

이 논문은 단백질의 기능분석을 위해 핵심적으로 요구되는 단백질 상호작용 관계정보 및 기능정보 등을 체계적으로 제공할 수 있는 WASPIFA (Web-based Assistant System for Protein-protein Interaction and function Analysis) 시스템에 대해서 다루고 있다. WASPIFA 시스템은 특정 분야에 국한해서 단편적 정보를 제공하는 기존의 단백질 기능 및 상호작용 분석 시스템과는 달리 분석하고자 하는 서열의 종합적인 정보 즉, 기능정보 및 주석정보, 도메인 정보, 상호작용 관계정보 등을 제공한다. 일반 검색 및 분석 시스템에서 제공하지 못하는 종합적인 정보들은 다양한 전처리 과정을 통해서 얻어진 데이터 및 정보 등을 시스템 내에 로컬 데이터베이스화해 놓은 것이다. 최종 사용자는 종합적인 정보를 통해서 올바른 평가와 판단을 통해서 효과적인 단백질 상호작용 분석과 기능분석을 행할 수 있다. 또한 자동관리 및 데이터 갱신 기능을 갖추고 있어 시스템 관리자가 효율적으로 시스템을 유지 및 관리할 수 있다.

• 한국수학교육학회지시리즈A:수학교육
• /
• 제58권2호
• /
• pp.239-262
• /
• 2019

본 연구에서는 특정한 학생의 질문에서 시작된 고민을 다루고 있으며, 교과서 분석을 통하여 해당 질문이 충분히 제기 가능한 질문임을 확인하였다. 또한 면담을 거쳐 두 대응관계가 연결된 새로운 대응관계에서 학생들이 합성함수 여부 판정과 역함수 존재 여부 판정에서 정의역에 대한 고민이 학생들에게서 어떻게 의미 있는 수학 지식으로 재구성 되어가는 지에 대한 사례를 관찰하였다. 본 연구에서 제시된 사례들은 제한된 상황에서의 특정한 사례라는 한계가 있기 때문에 곧바로 교수학습 상황에 적용될 수는 없으나 다른 연구자들에게 함수 학습 관련 연구에 대하여 통찰의 기회를 제공할 수 있을 것으로 기대된다.

• 대한조선학회논문집
• /
• 제47권3호
• /
• pp.291-305
• /
• 2010

A three-dimensional time-domain calculation method is of crucial importance in prediction of the motions and wave loads of a ship advancing in a severe irregular sea. The exact solution of the free surface wave-ship interaction problem is very complicated because of the essentially nonlinear boundary conditions. In this paper, an approximate body nonlinear approach based on the three-dimensional time-domain forward-speed free-surface Green function has been presented. The Froude-Krylov force and the hydrostatic restoring force are calculated over the instantaneous wetted surface of the ship while the forces due to the radiation and scattering potentials over the mean wetted surface. The time-domain radiation and scattering potentials have been obtained from a time invariant kernel of integral equations for the potentials which are discretized according to the second-order boundary element method (Hong and Hong 2008). The diffraction impulse-response functions of the Wigley seakeeping model advancing in transient head waves at various Froude numbers have been presented. A simulation of coupled heave-pitch motion of a long rectangular barge advancing in regular head waves of large amplitude has been carried out. Comparisons between the linear and the approximate body nonlinear numerical results of motions and wave loads of the barge at a nonzero Froude number have been made.

• 한국광학회지
• /
• 제22권2호
• /
• pp.72-76
• /
• 2011

반도체 광 증폭기와 파브리-페롯 가변 필터를 이용한 파장 훑음 레이저 기반 광 결맞음 단층 촬영을 구성하고, 이로부터 선명한 이미징을 얻기 위한 파수 영역 선형화를 구현하였다. 파수 영역 선형화는 5 개의 서로다른 공진 파장을 가진 광섬유 격자로 이루어진 어레이를 이용하여 보간법으로 수행하였다. 샘플단의 1 mm 깊이에서 파수 영역 선형화를 수행한 후 점 분포 함수(point spread function)로부터 측정한 SNR(signal-to-noise ratio)은 12 dB 향상된 값을 얻어냈다. 또한 파수 영역 선형화 전과 후에 대해 슬라이드 글라스를 이용하여 OCT 이미징을 얻어낸 결과 파수 영역 선형화가 매우 잘 되었음을 확인할 수 있었다.

• 대한수학회논문집
• /
• 제22권3호
• /
• pp.419-428
• /
• 2007

In this paper, we will investigate the Hessian geometry of the homogeneous domain over the hypersurface given by a function F : $\mathbb{R}^n{\rightarrow}\mathbb{R}$ with ${\mid}{\det}\;DdF\mid=1$.