• 대한수학회보
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• 제21권2호
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• pp.127-135
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• 1984

In this paper, we find the Fourier series of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$ and the Parseval relation of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$. In section 2, we investigate some basic properties of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$ In section 3, we show that the mean of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$ exists and in section 4, after showing the existence of Fourier exponents and Fourier coefficients of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$. we give the Parseval relation of X(t, .omega.).mem. $L^{2}$$_{s.a.p.}$. For convenience we will denote X(t, .omega.) as X(t) in what follows.hat follows.

• 대한수학회보
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• 제48권2호
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• pp.291-302
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• 2011

We first study the generalized Fourier-Gauss transforms of functionals defined on the complexification $\cal{B}_C$ of an abstract Wiener space ($\cal{H}$, $\cal{B}$, ${\nu}$). Secondly, we introduce a new class of convolution products of functionals defined on $\cal{B}_C$ and study several properties of the convolutions. Then we study various relations among the first variation the convolutions, and the generalized Fourier-Gauss transforms.

• 대한수학회보
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• 제48권2호
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• pp.223-245
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• 2011

In this paper, we de ne an $L_p$ analytic generalized Fourier Feynman transform and a convolution product of functionals in a Ba-nach algebra $\cal{F}$($C_{a,b}$[0, T]) which is called the Fresnel type class, and in more general class $\cal{F}_{A_1;A_2}$ of functionals de ned on general functio space $C_{a,b}$[0, T] rather than on classical Wiener space. Also we obtain some relationships between the $L_p$ analytic generalized Fourier-Feynman transform and convolution product for functionals in $\cal{F}$($C_{a,b}$[0, T]) and in $\cal{F}_{A_1,A_2}$.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.45-50
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• 1998

The coupled vibration occurs between traveling vehicle and bridge, when vehicle runs on it. The natural frequency of this coupled system is dependent on the contact position of vehicle and bridge, that is, time-varying system. The calculations of these natural frequencies are very complicated, and often carried out by using Green function theory, series. But, these methods have any limitations, such as, supporting condition, boundary condition. In this paper, on the coupled system constructed by the concentrated mass and elastically supported beam, an analytical method of natural frequency is proposed by using Fourier sine transformation. The results are compared and discussed with numerically calculated ones.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송공학회 2009년도 추계학술대회
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• pp.375-378
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• 2009

The Spectrum Sensing Technology is the core technology of the Cognitive Radio (CR) System that is one of the future wireless communication technologies. This is the technology that temporarily allocates the frequency bandwidth by scanning surrounding wireless environments to keep licensed terminals and search the unused frequency bandwidth. In this paper, we proposed the efficient Spectrum Sensing Method using the Short Time Fourier Transform (STFT). The Cosine and DVB-H signal with the 6MHz bandwidth is used as the Input Signal. And we confirm the Spectrum Sensing result using Modified Periodogram Method, Welch's Method for compared with Short Time Fourier Transform Algorithm.

• Journal of Astronomy and Space Sciences
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• 제28권1호
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• pp.71-77
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• 2011

Ionospheric error modeling is necessary to create reliable global navigation satellite system (GNSS) signals using a GNSS simulator. In this paper we developed algorithms to generate Klobuchar coefficients ${\alpha}_n$, ${\beta}_n$ (n = 1, 2, 3, 4) for a GNSS simulator and verified accuracy of the algorithm. The eight Klobuchar coefficients were extracted from three years of global positioning system broadcast (BRDC) messages provided by International GNSS service from 2006 through 2008 and were fitted with Fourier series. The generated coefficients from our developed algorithms are referred to as Fourier Klobuchar model (FOKM) coefficients, while those coefficients from BRDC massages are named as BRDC coefficients. The correlation coefficient values between FOKM and BRDC were higher than 0.97. We estimated total electron content using the Klobuchar model with FOKM coefficients and compared the result with that from the BRDC model. As a result, the maximum root mean square was 1.6 total electron content unit.

• 한국신뢰성학회지:신뢰성응용연구
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• 제16권2호
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• pp.110-117
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• 2016

Purpose: Biswas and Sarkar [11] found the availability of a system maintained through several imperfect repairs before a replacement is allowed. However they missed a part of coefficients in the integration. This paper corrects the erratum of Biswas and Sarkar [11] and performs the reliability analysis incorporating the optimal number of imperfect repairs. Methods: To find the singularities and residues of the suitable complex-valued function for the availability, the computer package Matlab is used. Also the performance measures are calculated by defining and assigning costs. Results: The accurate availability functions with respect to the numbers of imperfect repairs and the optimal number of imperfect repairs before a replacement are obtained. Conclusion: The reliability for a system under imperfect repair before a replacement is analyzed using Fourier transform technique.

• 대한수학회지
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• 제54권1호
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• pp.117-139
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• 2017

This paper presents a systematic study for theoretical aspects of a unified approach to the abstract relative Fourier transforms over canonical homogeneous spaces of semi-direct product groups with Abelian normal factor. Let H be a locally compact group, K be a locally compact Abelian (LCA) group, and ${\theta}:H{\rightarrow}Aut(K)$ be a continuous homomorphism. Let $G_{\theta}=H{\ltimes}_{\theta}K$ be the semi-direct product of H and K with respect to ${\theta}$ and $G_{\theta}/H$ be the canonical homogeneous space (left coset space) of $G_{\theta}$. We introduce the notions of relative dual homogeneous space and also abstract relative Fourier transform over $G_{\theta}/H$. Then we study theoretical properties of this approach.

• 대한수학회보
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• 제39권4호
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• pp.589-606
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• 2002

We introduce and analyze a frequency-domain method for parabolic partial differential equations. The method is naturally parallelizable. After taking the Fourier transformation of given equations in the space-time domain into the space-frequency domain, we propose to solve an indefinite, complex elliptic problem for each frequency. Fourier inversion will then recover the solution in the space-time domain. Existence and uniqueness as well as error estimates are given. Fourier invertibility is also examined. Numerical experiments are presented.

• Journal of Communications and Networks
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• 제8권1호
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• pp.38-48
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• 2006

A synchronous multicarrier (MC) code-division multiple access (CDMA) system using inverse fast Fourier transform (IFFT) and fast Fourier transform (FFT) for the downlink mobile communication system operating in a frequency selective Rayleigh fading channel is analyzed. Both carrier frequency offset and timing offset are considered in the analysis. Bit error rate performance of the system with both equal gain combining and maximum ratio combining are obtained. The performance is compared to that of the conventional system using correlation receiver. It is shown that when subcarrier number is large, the system using IFFT/FFT has nearly the same performance as the conventional one, while when the sub carrier number is small, the system using IFFT/FFT will suffer slightly worse performance in the presence of carrier frequency offset.