• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.235-238
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• 2001

Deformation phase can be obtained by using Least-Square Fitting. In extraction of phase values, Least-Square Fitting is superior to usual method like as 2, 3, 4-Bucket Algorithm. That can extract almost noise-free phase and retain 2$\pi$discontinuities. But more fringe in phase map, 2$\pi$ discontinuities is destroyed when that is filtered and reconstruction of deformation is not reliable. So, we adapted Least-Square Fitting using an isotropic window in dense fringe. using Sine-Cosine filter give us perfect 2$\pi$discontinuities information. We showed the process and result of extraction of phase map and filtering in this paper.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.1
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• pp.1-9
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• 2009

This paper presents stress distribution around a central crack tip in a tensile plate using phase-shifting photoelasticity and a power series stress function. Isochromatic data along the straight lines far from the crack tip were obtained by phase shifting photoelasticity and were used as input data of the hybrid experimental analysis. By using the complex-type power series stress equations, the photoelastic stress distribution fields in the vicinity of the crack and the mode I stress intensity factor were obtained. With the help of image processing software, accuracy and reliability was enhanced by twice multiplying and sharpening the measured isochromatics. Actual and reconstructed fringes were compared qualitatively. For quantitative comparison, percentage errors and standard deviations of the percentage errors were calculated for all measured input data by varying the number of terms in the stress function. The experimental results agreed with those predicted by finite element analysis and empirical equation within 2 percent error.

• Journal of the Korean Society for Precision Engineering
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• v.19 no.3
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• pp.66-72
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• 2002

Electronic Speckle Pattern Interferometry (ESPI) has been recently developed and widely used because it has advantage to be able to measure surface deformations of engineering components and materials in industrial areas with non-contact. The speckle patterns to be formed with interference and scattering phenomena can measure not only out-of-plane but also in-plane deformations, together with the use of digital image equipment to process the informations included in the speckle patterns and to display consequent interferogram on a computer monitor. In this study, the experimental results of a canti-levered plate using ESPI were compared with those obtained from the simple beam theory. The ESPI results of the canti-levered plate analyzed by 4-step phase shifting method are close to the theoretical expectation. Also, out-of-plane displacements of a spot welded cacti-levered plate were measured by ESPI with 4-step phase shifting technique. The phase map of the spot welded cacti-levered plate is quite different from that of the canti-levered plate without spot welding.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.11a
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• pp.839-840
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• 2010

• Proceedings of the Korea Water Resources Association Conference
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• 2016.05a
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• pp.214-214
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• 2016

이중편파 강우레이더는 차등반사도, 차등위상차, 비차등위상차 등 다양한 변수를 관측하여 호우의 공간적 규모, 호우를 구성하는 강수입자, 호우의 이동방향 등 종합적인 강우 정보를 제공한다. 이러한 이중편파레이더를 이용하면 단일편파레이더에 비해 보다 정량적인 강수 추정이 가능하다. 일반적으로 이중편파 강우레이더의 강우추정 관계식은 DSD 및 강우입자 모형을 기반으로 물리적으로 유도된다. 그러나 DSD는 호우 사상에 따라 그 양상이 다르며, 동일 호우 사상 내에서도 시공간적으로 변화가 크다. 이러한 DSD에 내포된 변동성은 결과적으로 레이더 강우에 큰 불확실성을 유발하게 된다. 이에 본 연구에서는 확률대응법을 이용하여 이중편파레이더의 강우추정 관계식을 추정하는 기법을 개발하고자 한다. 확률대응법은 실시간으로 강우추정 관계식의 매개변수를 추정하는 기법으로 단일편파레이더의 Z-R 관계식에 적용된 바 있다. 이러한 확률대응법을 이용하면 시공간적으로 변하는 DSD 등 호우사상의 개별적인 특징을 반영하여 호우사상별 강우추정 관계식의 매개변수를 실시간으로 결정할 수 있다. 따라서 본 연구에서는 이중편파레이더의 강우추정 관계식 중 R(KDP, Zdr), R(Zh, Zdr) 관계식을 위주로 매개변수를 이변량 확률대응법을 통해 추정하고, 기존의 강우추정 알고리즘 및 관계식의 레이더 강우 추정 결과와 비교를 통해 적용성을 평가하였다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.96-100
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• 1997

The shadow moire is one of the optical techniques which is able to give contour lines of an object with respect to a master grating plane. The moire patterns are issued from the superposition of a master grating and its shadow projected on the surface of an object. In case of the classical shadow moire method, the sensitivity was a few tenths millimeters. generally, it is difficult to use a phase shift method in shadow moire because it is impossible to obtain uniform phase shifts on the whole field. But in this study we use the fact that if the depth of object is much less than the distance between the observer and the master grating, and the object is displaced perpendicularly to the grating plane, phase shifts are almost uniform. Finally we obtained a better resolution by using a phase shift procedure and applied the phase shifting shadow moire to three dimensional shape measurement.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.12
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• pp.1387-1394
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• 2014

In a photoelastic experiment, it is necessary to know the material stress fringe constant of the photoelastic specimen to determine the stresses from the measured isochromatic fringe orders. The material stress fringe constant can be obtained using a simple tension specimen and/or a circular disk under diametric compression. In these methods, there is generally a need to apply numerous loads to the specimen in response to the relationship of the fringe order. Then, the least squares method is used to obtain the material constant. In this paper, the fringe orders that appear on a four-point bending specimen are used to determine the fringe constant. This method requires four photoelastic fringes obtained from a circular polariscope by rotating the analyzer to 0, ${\pi}/4$, ${\pi}/2$, and $3{\pi}/4$ radians. Using the four-point bending specimen to determine the material stress fringe constant has an advantage because measurements can be made at different locations by applying a constant load. The stress fringe constant measured with this method is within the range suggested by the manufacturer of the photoelastic material.

• Proceedings of the Korean Society of Applied Pharmacology
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• 1994.04a
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• pp.264-264
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• 1994

본 연구는 보리 씨앗에 존재하는 리보솜 불활성화 단백질(RIP) 의 삼차원 구조를 X-선 결정학 방법을 이용하여 밝히고, 그 결과로 분자 차원에서 기능을 이해하는 것을 목적으로 하고있다. 리보솜불활성화 단백질은 N-glucosidase 반응을 통하여 단백질 합성을 저해하기 때문에 세포를 죽일 수 있다. 따라서 암세포만을 특정적으로 인식하는 다른 물질과 결합시키면 암세포만을 특정적으로 죽일 수 있는 면역독소로 이용될 수 있다. 또, 최근에는 항바이러스의 작용을 함이 밝혀져 많은 연구가 진행되고 있다. 단백질 삼차원 구조 규명을 위해서는 여러가지 단계가 있는데 지난 번 과제까지 성공적으로 리보솜 불활성화 단백질의 대량 분리와 X-선 결정학의 필수 요건 좋은 결정을 길렀고, 이번에는 구조 해석을 위해 꼭 해결해야하는 위상문제를 극복하기 위하여 여러가지 실험을 진행하였다. 우선, 비슷한 구조인 피마자씨에서 분리한 Ricin의 A-체인과 미국자리공 잎에서 분리한 Pokeweed antiviral protein의 삼차원 분자좌표를 이용하여 분자치환법으로 위상문제 해결을 시도하였다. Ricin 의 A-체인을 이용하였을 때 분자의 위치가 정확히 찾아지지 않았고, 다른 모델인 Pokeweed antiviral protein을 이용하여 X-PLOR 프로그램내의 PC refinement법으로 분자치환을 시도하였다. Euler각도로 (187.37, 22.5, 311.94) 의 회전해 (Rotation solution) 를 가지고 있었고, 이러한 해에 맞추어서 분자를 돌려둔 후, 이동해 (Transaltion solution) 을 구해서 그 위치 (Orientation) 로 분자를 이동하였다. 이 때 R값은 53.9 % (8.0 - 3.5$\AA$) 이였고, 부분좌표 (Fractional coorcdinate) 에서는 0.102, 0.000, 0.261 이고, 직교좌표 (Orthogonal coorclinate) 에서는 4.616, 0.000, 13.167 의 결과를 얻었다.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.49-50
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• 2006

Photoelasticity is widely and conveniently used methods for whole field stress analysis. In this paper, 8-step photoelastic phase shifting method was performed by using a multi-purpose polariscope to measure the fringe orders along a specified line on the specimen containing a square hole. The material of the specimen is made of Polycarbonate. The measurement results by 8-step phase shifting method were compared with the those calculated by ABAQUS.

• Korean Journal of Optics and Photonics
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• v.8 no.4
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• pp.267-276
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• 1997

We set up a four-wave holographic interferometer using a symmetric dual-beam illumination which is to measure in-plane and out-of-plane displacement simultaneously. In order to acquire the displacement phase map we applied the phase-shifting method and removed the noise of the phase map with least-squares fitting. In this approach the access to information relative to both the difference and sum of phases existing in the two arms of four-wave holographic interferometer was allowed. As a result, in-plane and out-of-plane displacement was measured to the accuracy of λ/40 and λ/100, respectively at λ=632.8nm