• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2005년도 Proceedings of ISRS 2005
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• pp.47-51
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• 2005

Using satellite images, an optimal solution to water motion has been presented in this study. Since temperature patterns are suitable tracers in water motion, Sea Surface Temperature (SST) images of Caspian Sea taken by MODIS sensor on board Terra satellite have been used in this study. Two daily SST images with 24 hours time interval are used as input data. Computation of templates correspondence between pairs of images is crucial within motion algorithms using non-rigid body objects. Image matching methods have been applied to estimate water body motion within the two SST images. The least squares matching technique, as a flexible technique for most data matching problems, offers an optimal spatial solution for the motion estimation. The algorithm allows for simultaneous local radiometric correction and local geometrical image orientation estimation. Actually, the correspondence between the two image templates is modeled both geometrically and radiometrically. Geometric component of the model includes six geometric transformation parameters and radiometric component of the model includes two radiometric transformation parameters. Using the algorithm, the parameters are automatically corrected, optimized and assessed iteratively by the least squares algorithm. The method used in this study, has presented more efficient and robust solution compared to the traditional motion estimation schemes.

• 한국정보통신학회논문지
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• 제24권3호
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• pp.448-458
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• 2020

공통현을 이용한 삼변측량 기반 실내 측위의 경우 각 AP로부터 이동체까지의 거리를 구하여, 각 AP별로 해당 거리를 반지름으로 하는 원을 이용하여 원들의 둘레가 교차 되는 접점들을 이용하여 이동체의 위치를 예상한다. 거리 오차로 인하여 원 간의 접점이 생성되지 않는 경우, 위치 예상에 실패하게 된다. 본 논문에서는 이를 개선하기 위한 알고리즘을 제안하였는데, 거리에 따라 반지름의 크기에 비례한 값을 임의로 추가하여 강제로 접점을 생성하여 예상 위치를 생성한 뒤, 해당 원의 반지름에 추가된 임의 값과 원점으로부터, 거리에 따른 보정을 하였다. 기존 삼변측량의 거리 오차로 인한 좌표 생성 실패 비율과 좌표 측위 오차를 최소화하는 발전된 알고리즘을 제안하고 시스템을 제작하여 성능을 분석하였다.

• Nuclear Engineering and Technology
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• 제53권9호
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• pp.2788-2802
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• 2021

Multigroup cross section (MG XS) generation by the UNIST in-house Monte Carlo (MC) code MCS for fast reactor analysis using nodal diffusion codes is reported. The feasibility of the approach is quantified for two sodium fast reactors (SFRs) specified in the OECD/NEA SFR benchmark: a 1000 MW_th metal-fueled SFR (MET-1000) and a 3600 MW_th oxide-fueled SFR (MOX-3600). The accuracy of a few-group XSs generated by MCS is verified using another MC code, Serpent 2. The neutronic steady-state whole-core problem is analyzed using MCS/RAST-K with a 24-group XS set. Various core parameters of interest (core k_eff, power profiles, and reactivity feedback coefficients) are obtained using both MCS/RAST-K and MCS. A code-to-code comparison indicates excellent agreement between the nodal diffusion solution and stochastic solution; the error in the core k_eff is less than 110 pcm, the root-mean-square error of the power profiles is within 1.0%, and the error of the reactivity feedback coefficients is within three standard deviations. Furthermore, using the super-homogenization-corrected XSs improves the prediction accuracy of the control rod worth and power profiles with all rods in. Therefore, the results demonstrate that employing the MCS MG XSs for the nodal diffusion code is feasible for high-fidelity analyses of fast reactors.

• Journal of electromagnetic engineering and science
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• 제19권1호
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• pp.6-12
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• 2019

An IE-FFT algorithm is implemented and applied to the electromagnetic (EM) solution of perfect electric conducting (PEC) scattering problems. The solution of the method of moments (MoM), based on the magnetic field integral equation (MFIE), is obtained for PEC objects with closed surfaces. The IE-FFT algorithm uses a uniform Cartesian grid to apply a global fast Fourier transform (FFT), which leads to significantly reduce memory requirement and speed up CPU with an iterative solver. The IE-FFT algorithm utilizes two discretizations, one for the unknown induced surface current on the planar triangular patches of 3D arbitrary geometries and the other on a uniform Cartesian grid for interpolating the free-space Green's function. The uniform interpolation of the Green's functions allows for a global FFT for far-field interaction terms, and the near-field interaction terms should be adequately corrected. A 3D block-Toeplitz structure for the Lagrangian interpolation of the Green's function is proposed. The MFIE formulation with the IE-FFT algorithm, without the help of a preconditioner, is converged in certain iterations with a generalized minimal residual (GMRES) method. The complexity of the IE-FFT is found to be approximately $O(N^{1.5})$and $O(N^{1.5}logN)$ for memory requirements and CPU time, respectively.

• International Journal of Naval Architecture and Ocean Engineering
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• 제9권4호
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• pp.429-438
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• 2017

Cranke-Nicolson scheme in native OpenFOAM source libraries was not able to provide 2nd order temporal accuracy of velocity and pressure since the volume flux of convective nonlinear terms was 1st accurate in time. In the present study the simplest way of getting the volume flux with 2nd order accuracy was proposed by using old fluxes. A possible numerical instability originated from an explicit estimation of volume fluxes could be handled by introducing a weighting factor which was determined by observing the ratio of the finally corrected volume flux to the intermediate volume flux at the previous step. The new calculation of volume fluxes was able to provide temporally accurate velocity and pressure with 2nd order. The improvement of temporal accuracy was validated by performing numerical simulations of 2D Taylor-Green vortex of which an exact solution was known and 2D vortex shedding from a circular cylinder.

• 한국자기공명학회논문지
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• 제18권1호
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• pp.36-40
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• 2014

Predicting secondary structure of protein through assigned backbone chemical shifts has been used widely because of its convenience and flexibility. In spite of its usefulness, chemical shift based analysis has some defects including isotopic shifts and solvent interaction. Here, it is shown that corrected chemical shift analysis for secondary structure of protein. It is included chemical shift correction through consideration of deuterium isotopic effect and calculate chemical shift index using probability-based methods. Enhanced method was applied successfully to one of the proteins from Mycobacterium tuberculosis. It is suggested that correction of chemical shift analysis could increase accuracy of secondary structure prediction of protein and small molecule in solution.

• Current Optics and Photonics
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• 제4권1호
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• pp.23-30
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• 2020

This paper presents a new method for designing a lens system stable against chromatic variation at a specified wavelength. Conventional lenses are corrected for chromatic aberration, but the new method suppresses chromatic changes of the marginal ray in the image-side. By doing so, paraxial properties of the lens system are stabilized against chromatic variation. Since the new method is based on paraxial ray tracing, the stabilizing conditions against chromatic variation are given by recurrence formulas. However, there is an analytic solution for the case of a cemented doublet in the air. A stable doublet at 405 nm wavelength is designed and analyzed.

• 대한전자공학회논문지
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• 제25권8호
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• pp.884-892
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• 1988

An asymptotic solution of electromagnetic waves scattered by an arbitrary-angled dielectric wedge in the E-polarized plane wave incidence is obtained by adding a correction to the physical optical fields given in the previous paper of these companion papers, Part I. The source for the asymptotic correction field valid in the far-field region can be equivalent to the multipole line sources at the tip of the wedge, of which coefficients are evaluated numerically by solving a dual series equation. The corrected field patterns are plotted for the typical case treated in Part I.

• Journal of the Optical Society of Korea
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• 제14권4호
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• pp.424-430
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• 2010

In coherent anti-Stokes Raman scattering (CARS) microscopy reported until now, conventional microscope objectives are used, so that they are limited for introduction into a living body. Gradient-index (GRIN) rod lenses might be a solution for miniaturized microscope objectives for in-vivo CARS microscopy. However, due to the inherent large amount of chromatic aberration, GRIN rod lenses cannot be utilized for this purpose. CARS imaging catheter, composed of miniaturized microscope objective and fiber bundle, can be introduced into a living body for minimally invasive diagnosis. In order to design the catheter, we have to first investigate design requirements. And then, the optical design is processed with design strategies and intensive computing power to achieve the design requirements. We report the miniaturized objective lens system with diffraction-limited performance and completely corrected chromatic aberrations for an in-vivo CARS imaging catheter.

• 한국가정과교육학회지
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• 제7권1호
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• pp.1-10
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• 1995

This study was intended to provide an improved method for testing textiles in high school. Four kinds of test subjects were selected and applied to the classes. Problems of the methods in the textbooks were corrected as follows: 1)Burning test: The number of specimen is reduced to 3 kinds of fibers(cotton, wool, and polyester) and recommends are given to make result by comparing with the burning characteris-tics of paper and hair. 2) Absorbency test: Test Method is changed to drop test. The result is recorded by measuring time required for the water drops absorbed to the specimen. 3) Wrinkle recovery test: A glass is provided instead of metal weight. The method of measuring angle which is made by the specimen is shown in figure. 4) Effects of Detergent: 0.2% of detergent solution is provided before class. The amount of oil and carbon black is specified. Students have generally agreed that the improved methods were better than those in the text-books after they made the above 4 recommendable experiments(p<.001)