• 한국데이터정보과학회:학술대회논문집
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• 한국데이터정보과학회 2003년도 춘계학술대회
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• pp.1-14
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• 2003

In man cases, the measurement error variances may be functions of the unknown true values or related covariate. In some cases, the measurement error variances increase in proportion to the value of predictor. This paper develops estimators of the parameters of a linear measurement error variance function under stratified multistage random sampling design and additional conditions. Also, this paper evaluates and compares the power of an asymptotically unbiased test with that of an asymptotically biased test. The proposed method are applied to blood sample measurements from the U.S. Third National Health and Nutrition Examination Survey(NHANES III)

• 한국공작기계학회논문집
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• 제12권4호
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• pp.77-84
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• 2003

The properties of a machine tool greatly affect machining quality since a machine tool has large variance in its features. Machine tool makers want to find best machining condition with the one that they have built. Machine builders need to develop test specimen since it helps finding characteristics of machine tools when the machining properties of the specimen are analyzed. This paper develops test specimen to identify features of the main spindle, the feeding device, and the frame of a machine tool. The specimen is machined with a high speed machine and the features of the machine are analyzed with test items. They are surface roughness, overshoot in axial movement, errors in circular movement, feeding with small movement and compensational error. This work can improve usability for a machine tool in machining practice.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.53-56
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• 2000

The performance of high-strength concrete is controlled by the fact, affecting the quality management, especially by revision error in water content of the ratio of surface moisture in fine aggregate. The difference in water content results from the revision error of the ratio of surface moisture and errors in sampled aggregate in the processing ready-mixed concrete plant. This study is to investigate the properties of flowing and hardening by investionally varying the revision error of the ratio of surface moisture in fine aggregate to compare and analyze the variance in quality.

• 제어로봇시스템학회논문지
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• 제17권12호
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• pp.1183-1187
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• 2011

In this paper, an optimal FIR (Finite-Impulse-Response) filter is proposed for discrete time-varying state-space models. The proposed filter estimates the current state using measured output samples on the recent time horizon so that the variance of the estimation error is minimized. It is designed to be linear, unbiased, with an FIR structure, and is independent of any state information. Due to its FIR structure, the proposed filter is believed to be robust for modeling uncertainty or numerical errors than other IIR filters, such as the Kalman filter. For a general system with system and measurement noise, the proposed filter is derived without any artificial assumptions such as the nonsingular assumption of the system matrix A and any infinite covariance of the initial state. A numerical example show that the proposed FIR filter has better performance than the Kalman filter based on the IIR (Infinite- Impulse-Response) structure when modeling uncertainties exist.

• 한국CDE학회논문집
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• 제15권5호
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• pp.325-332
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• 2010

A lens system for mobile phone cameras is comprised of various lenses and designed so as to satisfy design requirements for responses such as a modular transfer function (MTF). However, it is difficult to manufacture and assemble camera modules to maintain the same performance compared with the designed camera modules, because of uncertainty. We should always design a lens system by considering uncertainty that can be caused by errors in the manufacturing and assembly process of mobile phone cameras. The robust optimization offers tools of making robust decisions with the consideration of design parameters, uncontrollable parameters, and the variance of the system. Using an efficient reliability analysis method and an optimization algorithm, we obtained robust optimization results that maximize the mean of MTF and minimize the standard deviation and proposed a new robust design process for a lens system.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1858-1863
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• 2003

The properties of a machine tool greatly affect machining quality since a machine tool has large variance in its features. Machine tool makers want to find best machining condition with the one that they have built. Machine builders need to develop test specimen since it helps finding characteristics of machine tools when the machining properties of the specimen are analyzed. This paper develops test specimen to identify features of the main spindle, the feeding device, and the frame of a machine tool. The specimen is machined with a high speed machine and the features of the machine are analyzed with test items. They are surface roughness, overshoot in axial movement, errors in circular movement, feeding with small movement, and compensational error. This work can improve usability for a machine tool in machining practice.

• Communications for Statistical Applications and Methods
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• 제13권1호
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• pp.151-165
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• 2006

It is important to estimate the true misclassification rate of a given classifier when an independent set of test data is not available. Cross-validation and bootstrap are two possible approaches in this case. In related literature bootstrap estimators of the true misclassification rate were asserted to have better performance for small samples than cross-validation estimators. We compare the two estimators empirically when the classification rule is so adaptive to training data that its apparent misclassification rate is close to zero. We confirm that bootstrap estimators have better performance for small samples because of small variance, and we have found a new fact that their bias tends to be significant even for moderate to large samples, in which case cross-validation estimators have better performance with less computation.

• 전력전자학회논문지
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• 제22권5호
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• pp.382-389
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• 2017

The development of electronic technology has been rapidly achieved in the automotive industry. A trend that attaches electric equipment, including ECUs at vehicles, is observed. However, decrepit vehicles have several electrical noises and errors. The effect of electric noise on vehicles that are focused on smoke was investigated. Many researchers have argued that one of the reasons of the occurrence of smoke in vehicles is the inexact time of the occurrence of ignition. Moreover, various physical, chemical, and thermodynamic solutions were attempted to approach and many improvements were accomplished. However, in this study, the reduction of electrical and electronic noise is confirmed to improve the accuracy of the injection time on decrepit vehicles with electrical and electric technologies. Previous studies suggest that the distance between the pilot and main ignitions affect the occurrence of smoke and control the variance value of the distance between pilot and main ignitions with electric filter. Thus, the effect of reducing smoke occurred.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2010년도 학술발표회
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• pp.346-349
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• 2010

In this study several unit hydrographs by rainfall storms are derived and moving averaged unit hydrograph is extracted from them based on the rainfall-runoff data in a small basin 8.5 $km^2$ wide. And peak discharges and peak times of the unit hydrographs are investigated and reviewed. And then a representative unit hydrograph of the moving averaged one is applied to the linear convolution integration for obtaining the flood discharge hydrograph and peak discharge and time of its result are researched and inspected. Variance in application of the representative unit hydrograph in a basin on assumption of linearity is appeared and this is given as a counterevidence about that the runoff response from rainfall on a basin has nonlinear characteristics. And As a result of application of derived representative unit hydrograph the errors in peak discharge and time are investigated.

• 한국산업정보학회논문지
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• 제8권4호
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• pp.94-100
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• 2003

본 논문에서는k개 성분들이 지수분포를 따르는 병렬시스템에서 하나의 성분이 고장났을 때 나머지성분들의 수명분포에 영향을 줄 때 주어진 시각 t 에서 시스템의 신뢰도, 위험함수, 평균잔여수명, 신뢰도에 대한 최우추정량과 최소분산불편추정량을 제시하고 그리고 모의실험을 통하여 추정량들의 효율성을 연구한다.