• 전자공학회논문지A
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• 제28A권11호
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• pp.855-865
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• 1991

A simple method for analysis of serial search burst-format direct-sequence spread-spectrum (DS-SS) code acquisition system had been recently proposed, and therein, the effect of the code autocorrelation sidelobes on the performance of DS-SS code acquisition system has been assessed [4],[5]. In this paper, a new hybrid scheme which combines the serial search with maximum likelihood search is proposed to eliminate the deleterious effect of code autocorrelation sidelobes, and the performance is analyzed for the additive withe Gaussian noise (AWGN) channels. To analyze the performance of this system, we have generalized the method used in [4],[5] to arbitrary burst-format DS-SS acquisition schemes. The results show that a new hybrid scheme has good immunity against the effect of code autocorrelation sidelobes. Thevalidity of the presented approach has been confirmed form the results of simulation.

• 대한전자공학회논문지TC
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• 제44권1호
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• pp.98-105
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• 2007

본 논문에서는 Maximum Likelihood(ML) 알고리즘을 변형한 Suboptimal ML 타이밍 검출기를 제안한다. 본 논문에서 제안하는 Suboptimal ML방식은 참조신호 생성과정이 Early-Late gate 또는 ML 방식에 비해 간단하면서도 타이밍 검출기의 이득은 거의 동일한 값을 얻을 수 있다. 또한, 타이밍 추적기는 데이터 판별을 이용하기 때문에 적은 타이밍 오차 범위만이 추적 가능하다. 즉, 펄스폭이 0.7ns인 4차 가우시안 모노사이클을 사용하였을 경우, 추적 가능한 타이밍 오차는 ${\pm}0.06ns$이다. 따라서 탐색기는 높은 정확도를 갖는 획득성능을 갖고 있어야 한다. 성능 분석은 잡음뿐만아니라 송신기와 수신기의 펄스 생성과정에서 사용되는 오실레이터 지터를 고려한다. 컴퓨터 모의 실험 결과는 타이밍 검출기의 평균과 분산 및 타이밍 추적기의 추적 성능을 보여준다. 그리고 이동성에 의해 타이밍 오차가 점차적으로 증가하는 경우를 가정하여 추적성능을 제시한다. 본 논문은 타이밍 추적기의 성능을 제시하기 위해 하나의 복조기인 단인 상관기만을 고려한다.

• 대한수학회논문집
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• 제34권4호
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• pp.1335-1352
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• 2019

In this article, a new family of lifetime distributions by adding two additional parameters is introduced. The new family is called, the logarithmic Kumaraswamy family of distributions. For the proposed family, explicit expressions for some mathematical properties are derived. Maximum likelihood estimates of the model parameters are also obtained. This method is applied to develop a new lifetime model, called the logarithmic Kumaraswamy Weibull distribution. The proposed model is very flexible and capable of modeling data with increasing, decreasing, unimodal or modified unimodal shaped hazard rates. To access the behavior of the model parameters, a simulation study has been carried out. Finally, the potentiality of the new method is proved via analyzing two real data sets.

• 한국지리정보학회지
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• 제3권4호
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• pp.73-86
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• 2000

본 연구에서는 다시기 위성영상과 GIS(geographic information system)를 이용하여 과수재배분포도 작성에 있어 다양한 분류기법을 적용하여 보다 효율적인 기법도출에 그 목적을 두고 있다. 이를 위해 다시기별 Landsat TM영상과 현지 조사자료 및 기존 과수재배 면적 통계자료를 활용하여 각 분류기법에 대한 시기별 및 과수별 분포 특성과 비교 분석함으로서 과수재배분포도 작성에 있어 효과적인 분류기법을 도출하였다. 다시기 Landsat TM 영상을 이용한 과수재배 분포도작성을 위해서는 초가을 영상으로 MLC(maximum likelihood classification)기법을 적용하는 것이 가장 효율적인 것으로 나타났다. 또한 GIS를 통한 공간분석으로 행정별 과수재배의 면적을 효과적으로 추출함과 동시에 과수재배분포의 형태를 효율적으로 파악 할 수 있음을 규명하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1997년도 한국자동제어학술회의논문집; 한국전력공사 서울연수원; 17-18 Oct. 1997
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• pp.1659-1662
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• 1997

The objective of this paper is to estimate the aerodynamic derivatives of a single turbo-prop aircraft at a specified flight condition for the best deduction of the dynamic characteristics using modified maximum likelihood estimation method whcih is known to be unbiased, efficient, and consistent. The flight test data necessary to the estimation of aerodynamic derivatives is obtained by implementing the six degree of freedom nonlinear flight simulation to consider the effects of several control input types, control deflection amplitudes, and intensity of turbulence. The simulated data is added with the measurement noise, which is regarded as the actual flight test data.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제21권3호
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• pp.155-165
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• 2017

The Hansel-Spittel constitutive model requires a total of nine parameters for flow stress prediction. Typically, the parameters are estimated by least squares methods for given tensile test measurements from a deterministic perspective. In this research we took a different approach, a probabilistic viewpoint, to see through the development of the Hansel-Spittel constitutive model. This perspective change showed that deterministic least squares methods are closely related to statistical maximum likelihood methods via Gaussian noise assumption. More intriguingly, this perspective shift revealed that the Hansel-Spittel constitutive model may leave out deterministic trends in residuals despite nearly perfect agreement with measurements. With tensile test measurements of AA1070 aluminum alloy, we demonstrated this deficiency of the Hansel-Spittel constitutive model, suggesting room for improvement.

• 한국신뢰성학회지:신뢰성응용연구
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• 제13권2호
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• pp.99-107
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• 2013

One-shot device is required to successfully perform its function only once at the moment of use. The reliability of a one-shot device should be expressed as a probability of success. In this paper, we propose a bayesian approach for estimating reliability of one-shot devices with small sample size. We employ a gamma prior to obtain the posterior distribution. Finally, we compare the accuracy of the proposed method with general maximum likelihood method.

• Wind and Structures
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• 제22권4호
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• pp.393-408
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• 2016

Weibull distribution is a suitable distribution to use in modeling the life time data. It has been found to be a exact fit for the empirical distribution of the wind speed measurement samples. In brief this paper consist of important properties and characters of Weibull distribution. Also we discuss the application of Weibull distribution to wind speed measurements and derive an expression for the probability distribution of the power produced by a wind turbine at a fixed location, so that the modeling problem reduces to collecting data to estimate the three parameters of the Weibull distribution using Maximum likelihood Method.

• Journal of the Korean Data and Information Science Society
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• 제23권6호
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• pp.1271-1277
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• 2012

In this paper, we propose an estimation method of the parameter in an exponential distribution based on a progressive Type I interval censored sample with semi-missing observation. The maximum likelihood estimator (MLE) of the parameter in the exponential distribution cannot be obtained explicitly because the intervals are not equal in length under the progressive Type I interval censored sample with semi-missing data. To obtain the MLE of the parameter for the sampling scheme, we propose a method by which progressive Type I interval censored sample with semi-missing data is converted to the progressive Type II interval censored sample. Consequently, the estimation procedures in the progressive Type II interval censored sample can be applied and we obtain the MLE of the parameter and survival function. It will be shown that the obtained estimators have good performance in terms of the mean square error (MSE) and mean integrated square error (MISE).

• 산업공학
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• 제21권2호
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• pp.151-160
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• 2008

Defect size distribution is a probability density function for the defects that occur on wafers or glasses during semiconductor/LCD fabrication. It is one of the most important information to estimate manufacturing yield using well-known statistical estimation methods. The defects are detected by automatic optical inspection (AOI) facilities. However, the data that is provided from AOI is not accurate due to resolution of AOI and its defect detection mechanism. It causes distortion of defect size distribution and results in wrong estimation of the manufacturing yield. In this paper, I suggest a size conversion method and a maximum likelihood estimator to overcome the vague defect size information of AOI. The methods are verified by the Monte Carlo simulation that is constructed as similar as real situation.