• 대한원격탐사학회:학술대회논문집
• /
• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
• /
• pp.741-744
• /
• 2005

A numerical scattering model for artificial metal structure based on physical optics approximation is developed to identify the height of phase center, and the result is compared with interferometric SAR DEM. The interferometric SAR data were gathered by AIRSAR during PACRIM- II campaign on Jeju Island. Power transmission towers on piedmont pasture along the slopes of Mt. Halla look like elliptic risings in TOPSAR DEM. The heights of risings are quantitatively analyzed using a scattering model in the way of achieving the height of phase centers of power transmission towers. A numerical algorithm is developed on the basis of physical optics approximation. The structure of power transmission tower was decomposed into hundreds of rectangular metal plates, of which the scattering matrix is known in analytic form, and the calculated scattering fields were summed coherently. The effect of direct backscattering component, ground-scatterer component and scatterer-ground component are decomposed and computed individually for each rectangular metal plate. The $\Deltak-radar$ equivalent was used to calculate height of phase center of the scatterer. The heights of a selected power transmission tower and scattering algorithm results give existence and location of the transmission towers but not actual tower heights.

• 한국경영과학회지
• /
• 제27권4호
• /
• pp.41-65
• /
• 2002

We study a multi-component production/inventory system in which individual components are made to meet various demand types. We assume that the demands arrive according to a Poisson process, but there is a fixed probability that a demand requests a particular kit of different components. Each component is produced by a flow line with several stations in which the processing times of each station follow a two-stage Coxian distribution. The production of each component is operated by an independent base-stock policy with blocking. We assume that the time needed to assemble final products follows a general distribution and the capacity of an assembling facility is sufficiently large. The objective of this study is to obtain key performance measures such as the distribution of the number of each orders for each final product and the mean time of fulfilling a customer order. The basic principle of the proposed approximation method is to decompose the original system into a set of subsystems, each subsystem being associated with a flow line. Each subsystem is analyzed in isolation using a Marie's method. An iterative procedure is then used to determine the unknown parameters of each subsystem. Numerical results show that the accuracy of the approximation method is acceptable.

• 한국정보통신학회논문지
• /
• 제14권2호
• /
• pp.513-520
• /
• 2010

잡음에 의한 열화현상은 디지털화된 데이터의 인지도를 저하시킨다. 따라서 신호의 에지 성분을 보존함과 동시에 잡음을 제거하기 위한 시간영역과 주파수영역의 다양한 방법들이 사용되고 있다. 본 논문에서는 신호에 중첩된 복합적인 잡음을 감소시키기 위해, 웨이브렛 근사 계수를 이용한 새로운 잡음 제거 알고리즘을 제안하였다. 제안된 알고리즘에서는 신호의 에지와 잡음에 대한 구분 성능을 향상시키기 위해, 웨이브렛 근사계수의 누적으로부터 얻어지는 오차함수의 분포특성을 이용하였다.

• 산업공학
• /
• 제22권3호
• /
• pp.214-222
• /
• 2009

In the early design stage, system reliability must be estimated from life testing data at the component level. Previously, a point estimate of system reliability was obtained from the unbiased estimate of the component reliability after assuming that the number of failed components for a given time followed a binomial distribution. For deriving the confidence interval of system reliability, either the lognormal distribution or the normal approximation of the binomial distribution was assumed for the estimator of system reliability. In this paper, a new estimator is used for the component level reliability, which is biased but has a smaller mean square error than the previous one. We propose to use the beta distribution rather than the lognormal or approximated normal distribution for developing the confidence interval of the system reliability. A numerical example based on Monte Carlo simulation illustrates advantages of the proposed approach over the previous approach.

• Korean Journal of Mathematics
• /
• 제5권1호
• /
• pp.55-60
• /
• 1997

A continuum structure function(CSF) is a non-decreasing mapping from the unit hypercube to the unit interval. The reliability importance of component $i$ in a CSF at system level ${\alpha}$, $R_i({\alpha})$) say, is zero if and only if component $i$ is almost irrelevant to the system at level ${\alpha}$. A condition to check whether a component is almost irrelevant to the system is presented. It is shown that $R^{(m)}_i({\alpha}){\rightarrow}R_i({\alpha})$ uniformly as $m{\rightarrow}{\infty}$ where each $R^{(m)}_i({\alpha})$ is readily calculated.

• 한국음향학회지
• /
• 제38권2호
• /
• pp.177-183
• /
• 2019

본 논문에서는 수동 선배열 소나의 저주파 영역에서 수신된 표적 신호로부터 간섭신호를 분리해 내기 위해 독립성분분석 알고리즘을 적용하는 방안을 제안하고 기존 알고리즘들의 성능을 비교해 보았다. 저주파 대역 신호의 경우 비교적 넓은 방위로부터 수신되기 때문에 인접 빔 신호를 관측신호로 활용하여 독립성분분석을 수행할 수 있다. 신호분리에 사용한 독립성분분석 알고리즘은 FastICA(Fast Independent Component Analysis), NNMF (Non-negative Matrix Factorization), JADE (Joint Approximation Diagonalization of Eigen-matrices)이다. 실측 선배열 수동소나신호를 이용하여 독립성분분석을 수행한 결과 제안한 방법으로 간섭신호분리가 가능함을 확인하였으며, JADE 알고리즘의 신호 분리 성능이 가장 우수한 것으로 나타났다.

• 한국멀티미디어학회논문지
• /
• 제17권1호
• /
• pp.34-42
• /
• 2014

본 논문에서는 파형 신호와 이미지 등에서 패치를 추출하고 이를 패치 그래프로 구성한 다음, 이로부터 각 패치 간의 컴뮤트 타임을 구하여 이에 기반한 임베딩 기법을 구현하고, 가장 널리 이용되는 PCA(principal component analysis) 임베딩 결과와 비교 분석한다. 임베딩에서 차원을 줄일 경우 원 임베딩과 축소된 차원의 임베딩 간에는 오차가 크지 않도록 차원을 결정하는 것이 일반적이다. 하지만 본 논문에서 구현한 임베딩 방식은 삼차원 이하로 줄여 오차가 80~90%를 상회하여도 축소된 차원의 임베딩 공간에서 각 신호 고유의 기하 구조를 생성하므로 패턴 분류나 기계 학습 등의 응용 목적에 활용 가능함을 실험으로 확인한다.

• 대한수학회지
• /
• 제57권2호
• /
• pp.401-414
• /
• 2020

It is computationally expensive to compute principal components from scratch at every update or downdate when new data arrive and existing data are truncated from the data matrix frequently. To overcome this limitations, incremental principal component analysis is considered. Specifically, we present a sliding window based efficient incremental principal component computation from a covariance matrix which comprises of two procedures; simultaneous update and downdate of principal components, followed by the rank-one matrix update. Additionally we track the accurate decomposition error and the adaptive numerical rank. Experiments show that the proposed algorithm enables a faster execution speed and no-meaningful decomposition error differences compared to typical incremental principal component analysis algorithms, thereby maintaining a good approximation for the principal components.

• Progress in Superconductivity
• /
• 제1권2호
• /
• pp.99-104
• /
• 2000

The e.m.f. induced by a normal spot moving in a superconducting foil has been investigated by using the simulation and the experiment of a simple superconducting Power Supply. The induced e.m.f. has been derived theoretically from the magnetic field distribution within the spot. It is the sum of a DC component induced constantly by the Faraday's law during the spot's movement and a pulse component induced periodically by the flux conservation law at every electrical degrees 2$\pi$ radians. The DC component of the output voltage appears slightly nonlinear to the rotating speed, having values greater than the linear approximation values. The theoretical interpretation has been verified through experiment.

• 응용통계연구
• /
• 제7권2호
• /
• pp.113-130
• /
• 1994

본 논문에서는 Oh and Berger (1993)의 알고리즘을 확장하여, Oh and Berger의 알고리즘으로 효율적 처리가 어려웠던 복잡한 모양을 가진 다차원 함수의 적분에 보다 더 일반적으로 적용될 수 있는 알고리즘을 제시한다. 예를 들면 다봉함수이면서 동시에 기울어진 모양을 갖는 함수나 모든 극대점들이 다 파악되지 못한 경우 등이다. 제시된 알고리즘은 Oh and Berger의 알고리즘을 단계적으로 수행해 가면서 각 단계마다 새로운 부확률밀도 함수 (component density functin)를 함성 밀도 함수(mixture importance function) 형태인 중요함 수 (importance function에 더해 감으로써 중요함수를 적분 함수에 접근시킨다.