• Korean Journal of Optics and Photonics
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• v.24 no.6
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• pp.324-330
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• 2013

Phase-measuring deflectometry is a full-field gradient measuring technique that lends itself very well to testing specular optical surfaces. We have measured deformation of a large specular surface by deflectometry. In this work, we have used a Fourier-transform method to get the phase from a measured deformed fringe pattern, and we have used least squares method to obtain the height information of the specular surface from the calculated slope. Experimentally, we have confirmed that deflectometry can be used for deformation measurement of a specular surface like that of a wafer.

• Korean Journal of Optics and Photonics
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• v.26 no.3
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• pp.147-154
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• 2015

We propose a method for simultaneously measuring the front and back surface profiles of transparent optical components. The proposed method combines dual-wavelength transmission deflectometry with liquids to record distorted phases at different wavelengths, and then numerically reconstructs the three-dimensional phase information to image the front and back surfaces of the lens. We propose a theoretical model to determine the surface information, and a bifocal lens is experimentally investigated. Unlike conventional transmission deflectometry, our proposed method supports direct observation of the front and back surface profiles of the optical elements.

• Korean Journal of Optics and Photonics
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• v.27 no.2
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• pp.61-66
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• 2016

We used transmission deflectometry to measure the three-dimensional shapes of optical components, and we used the Hilbert transform to retrieve the phases from measured deformed fringe images. Deflectometry is useful for measuring large-scale samples, and specular samples. We have retrieved the phases from deformed fringe images and Hilbert-transformed images, and have used the least-squares method to find the height information. We have verified that phase retrieval using Hilbert transform is useful by computer simulation and experiment.

• Korean Journal of Optics and Photonics
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• v.25 no.6
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• pp.326-333
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• 2014

Phase-measuring deflectometry is a full-field gradient measuring technique that lends itself very well to testing specular optical surfaces. We have measured the deformation of the surface of a lens by transmission deflectometry with liquids. In this study, a method is proposed for measuring the refractive index distribution of a transparent object component. The proposed method combines transmission deflectometry with liquids. The deformed fringe patterns of a sample immersed in different fluids are recorded, and then the three-dimensional phase information of the sample is reconstructed numerically. We have used phase-shifting and temporal phase-unwrapping methods to retrieve the phase from the measured deformed fringe pattern, and we have used a least-squares method to find the height information of the specular surface from the calculated slope. In particular, we have proposed a theoretical model for determining the refractive index of sample and planar convex lens are demonstrated experimentally.

• The Korean Journal of Applied Statistics
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• v.33 no.4
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• pp.439-449
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• 2020

Meta-analysis provides a way of integrating several independent studies of interest. Since small studies with statistically significant results are more likely to be published, publication bias, which is a special case of selection bias, often occurs in meta analysis. Conditional likelihood and weighted estimating equation have been proposed to deal with publication bias, but they require to specify a correct selection probability model. In contrast, the pairwise pseudolikelihood approach can correct publication bias without fully specifying the correct selection probability model, but its performance in meta-analysis was not investigated. In this paper, we perform a numerical study about whether the pairwise pseudolikelihood approach is effective for solving publication bias arising from typical meta-analysis settings.

• Korean Journal of Forensic Psychology
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• v.11 no.1
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• pp.63-87
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• 2020

Judgment and decision-making studies have shown that people are easily influenced and biased by information irrelevant to the object of judgment. There is a great deal of research that indicates that bias exists in the legal judgment scene. One of them is a bias induced by defendants' character evidence. This study examined whether cognitive activities such as discussion, counterfactual thinking, and peer assessment could reduce the bias induced by the character evidece. In Experiment 1, 121 college students were asked to give the percentage they believed the defendant to be guilty. There was no cognitive activity for the control group. There were three different cognitive activities for the experimental group: discussion, counterfactual thinking and discussion, and counterfactual thinking and peer assessment. Results showed reduction in bias for all the experimental groups, and there was no difference between them. In Experiment 2, there were 125 participants from general population for the same procedure as in Experiment 1. Results showed reduction in bias only for the counterfactual thinking and discussion group. In general discussion, we speculated the implication of the results and the reason for the difference between the two experiments.

• Journal of Energy Engineering
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• v.10 no.1
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• pp.63-70
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• 2001

재료의 열확산계수를 비접촉적인 방법으로 구하기 위하여 광열편향법에 대한 3차원 모델을 해석하였다. 이 방법은 가열빔이 재료에 광학적으로 흡수될 때 검사빔의 초기궤적이 시편과 시편주의 매질의 온도상승으로 인하여 나타나는 굴절지수의 구배에 의하여 검사빔이 편향되는 원리를 이용하는 것이다. 기존의 연구에서는 주로 가열빔과 검사빔의 상대거리를 변화시키면서 편향의 위상각을 측정하여 열확산계수를 결정하였다. 하지만 본 연구에서는 고정된 상대거리에서 가열빔의 변조주파수를 변화시키면서 편향의 위상각을 계산하여 열확산계수를 구할 수 있는 관계식을 제시하였다. 본 연구에서 제시한 열확산계수 결정 방법은 다른 방법에 비하여 실험과 해석이 간단하고 비교적 측정하기가 어려운 상대거리에 영향을 받지 않는 방법이다.

• Proceedings of the KSEG Conference
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• 2003.04a
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• pp.27-35
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• 2003

시추공에서 측정된 절리자료의 샘플링 편향오류를 보정하는 절차를 기술하였다. 시추공에서 절리의 방향이 관측될 수 있는 확률은 시추공에 대한 절리의 상대적인 방향 이외에도 절리의 크기, 절리의 모양 및 시추공의 반경 과 길이와 같은 요인에 의하여 결정될 수 있으며, 이러한 요인들에 의하여 나타날 수 있는 절리자료의 방향편향을 보정할 수 있는 방법론을 제시하였다 유한 길이의 시추공으로부터 산정된 절리의 간격분포는 샘플링 영역인 시추공 길이의 영향에 의한 산정치의 오류를 내포하고 있으며, 이에 대한 보정법을 고찰하였다.

• Composites Research
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• v.23 no.5
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• pp.8-14
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• 2010

Three types of glass woven fabrics (plain, balanced twill, and unbalanced twill) having various sample sizes and aspect ratios were tested using the bias-extension tests. Real-time deformation images, force, and displacement data were collected. For the bias-extension test, the shear angle of the fabrics from the equation based on the crosshead displacement and fabric size was compared with direct manual measurements of the warp and weft angles as well as the optical measurement software. To determine the shear force, an analytical equation was introduced considering the kinematics of the bias-extension test. The obtained shear behaviors were further compared with the results by the trellis-frame test. The optical measurement methods showed that the mathematical method was reasonable before the shear angle of the fabrics reaches $30^{\circ}$ in the bias-extension tests. Also, the bias-extension test gave consistent behaviors with the trellis-frame test only for isotropic and homogeneous fabrics such as balanced plain and twill weaves.

• Survey Research
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• v.10 no.1
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• pp.169-186
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• 2009

The propensity score method is used to minimize the bias level in social survey, which comes from nonresponse. The theoretical concept and the background of the propensity score method is discussed first. The propensity score method was first applied in the epidemiology observational study. I have summarized the process of the three propensity score methods that were used to reduce estimation bias in this study. Matching by propensity score is applied to the relatively large control group. Subclassification has the advantage of using whole control group data and regression adjustment is applied to multiple covariates as well as propensity score of each unit is computable and usable. Lastly, the application procedures of propensity score method to reduce the nonresponse bias is suggested and its applicability to real situation is reviewed with the existing data.