• 한국광학회지
• /
• 제17권4호
• /
• pp.335-341
• /
• 2006

마이켈슨 간섭계 시스템에 두 개의 Convex Lens를 추가함으로서 평면파 참조광을 유지 시키며, 물체에 조사되는 물체광의 조사면적을 증대시킬 수 있는 변형된 마이켈슨 간섭계를 제작하였다. 변형된 마이켈슨 간섭계를 반사형 디지털 홀로그래피 현미경 시스템(Digital Holography Microscope System)에 적용한 결과 두 개의 Convex Lens를 추가하지 않은 고전 마이켈슨 간섭계를 사용한 디지털 홀로그래피 현미경 시스템 보다 넓은 영역에 대해 물체를 기록 할 수 있으며 또한 보다 넓은 영역을 재생 할 수가 있다.

• 한국전산유체공학회:학술대회논문집
• /
• 한국전산유체공학회 2010년 춘계학술대회논문집
• /
• pp.376-379
• /
• 2010

Bubble rising phenomenon is widely founded in many industrial applications such as a stream generator in power plant. Many experimental and numerical researches have been already performed to predict dynamic behavior of the bubble rising process. Recently numerical approaches are getting popular since it can offer much detailed information which is almost impossible to obtain from the experiments. Rising bubble could penetrate through the top free surface which makes the problem much more complicate in addition to the phase changing effect even with latest numerical techniques. In this paper, the top free surface effect on rising bubble has been investigated. The gas-liquid interface was explicitly tracked using high-order Level Contour Reconstruction Method(LCRM) which is a hybridization of Front-Tracking and Level-Set method. Break-up behavior of rising bubble at free surface showed different characteristics with initial diameter of bubble.

• Journal of the Korean Society for Industrial and Applied Mathematics
• /
• 제23권1호
• /
• pp.31-38
• /
• 2019

We present an explicit numerical algorithm for surface reconstruction from unorganized points using the Gaussian filter. We construct a surface from unorganized points and solve the modified heat equation coupled with a fidelity term which keeps the given points. We apply the operator splitting method. First, instead of solving the diffusion term, we use the Gaussian filter which has the effect of diffusion. Next, we solve the fidelity term by using the fully implicit scheme. To investigate the proposed algorithm, we perform computational experiments and observe good results.

• 한국멀티미디어학회논문지
• /
• 제19권8호
• /
• pp.1371-1376
• /
• 2016

In this paper, an iterative method is proposed to perform attenuation correction and image reconstruction simultaneously for positron emission tomography, by using the time-of-flight information. Numerical simulation results are presented to demonstrate an improved performance of the proposed method in attenuation correction and image reconstruction.

• 한국주조공학회지
• /
• 제31권3호
• /
• pp.124-129
• /
• 2011

We applied two numerical schemes to improve accuracy of the solution in the flow simulation of molten metal. One method is Piecewise Linear Interface Calculation (PLIC) method and the other is Donor-Acceptor (D-A) method. In the present work, we have tested simple problems to verify the module of the interface reconstruction algorithms. After validations, accuracy and efficiency of these two methods have compared by simulating various real products. On the numerical simulation of free surface flow, it is possible for PLIC method to track very accurately the interface between phases. PLIC method, however, has the weak point where a lot of computational time hangs, though it shows the more accurate interface reconstruction. Donor-Acceptor method has enough effectiveness in the macro observation of mold filling sequence though it shows the inferior accuracy.

• Smart Structures and Systems
• /
• 제15권1호
• /
• pp.15-40
• /
• 2015

This paper proposes a structural damage identification approach based on the power spectral density transmissibility (PSDT), which is developed to formulate the relationship between two sets of auto-spectral density functions of output responses. The accuracy of response reconstruction with PSDT is investigated and the damage identification in structures is conducted with measured acceleration responses from the damaged state. Numerical studies on a seven-storey plane frame structure are conducted to investigate the performance of the proposed damage identification approach. The initial finite element model of the structure and measured acceleration measurements from the damaged structure are used for the identification with a dynamic response sensitivity-based model updating method. The simulated damages can be identified accurately without and with a 5% noise effect included in the simulated responses. Experimental studies on a steel plane frame structure in the laboratory are performed to further verify the accuracy of response reconstruction with PSDT and validate the proposed damage identification approach. The locations of the introduced damage are detected accurately and the stiffness reductions in the damaged elements are identified close to the true values. The identification results demonstrated the accuracy of response reconstruction as well as the correctness and efficiency of the proposed damage identification approach.

• 대한기계학회논문집B
• /
• 제24권9호
• /
• pp.1148-1156
• /
• 2000

The QUICK scheme for convection terms is modified for unstructured finite volume method by using linear reconstruction technique and validated through the computation of two well defined laminar flows. It uses two upstream grid points and one downstream grid point in approximating the convection terms. The most upstream grid point is generated by considering both the direction of flow and local grid line. Its value is calculated from surrounding grid points by using a linear construction method. Numerical error by the modified QUICK scheme is shown to decrease about 2.5 times faster than first order upwind scheme as grid size decreases. Computations are also carried out to see effects of the skewness and irregularity of grid on numerical solution. All numerical solutions show that the modified QUICK scheme is insensitive to both the skewness and irregularity of grid in terms of the accuracy of solution.

• 소음진동
• /
• 제9권4호
• /
• pp.687-692
• /
• 1999

Digital holographic reconstruction method [W. A. Veronesi, et al, 1989, JASA, Vol. 85, pp. 588∼598] reconstructs a whole sound field by using measured sound pressure. This paper reports numerical errors of the method that occur at specific frequencies. The errors occur due to the truncation errors included in the calculation of transfer matrixes. The frequencies of the errors depend on the size of boundary element surfaces. Moreover, a modified calculation technique is proposed in the paper. The technique prevents the truncation errors by employing an indirect calculation procedure.

• 한국측량학회지
• /
• 제16권1호
• /
• pp.9-15
• /
• 1998

수치지적측량방법은 평판측량방법보다 동일지역의 측량성과상에서 볼 때 측량의 정확도가 높고 개인오차가 적다는 장점을 가지고 있다. 현재 수치지적부 시행지역에서는 토지의 경계를 지적공부에 등록하거나 지표상에 복원할 때에는 좌표를 중심으로 하며, 이 좌표는 원점과의 절대적인 위치관계만을 아주 단순하게 나타내고 있다. 그러나 경계의 등록과 복원을 할 때 원점과의 절대적 위치관계를 중심으로 하는 것보다는 도근점과의 상대적인 위치관계를 중심으로 하는 것이 더 합리적이다. 본 연구는 수치지적시행지역에서 경계등록과 경계복원을 할 때 좌표에 의한다는 원칙이 가지는 문제점과 개선방안을 고찰하여 향후 수치지적측량시 기초자료로 활용할 수 있도록 하였다.

• 한국산학기술학회논문지
• /
• 제14권7호
• /
• pp.3460-3467
• /
• 2013

본 논문에서는 2차원 대지구조를 분석하기 위해 ERT(electrical resistance tomography) 방법을 사용하여 대지모델을 영상복원하는 방법들을 수치적인 실험방법들을 통해 비교분석한다. 영상복원을 위한 역산방법으로는 Gauss-Newton, TLS(truncated least squares), 그리고 SIRT(simultaneous iterative reconstruction technieque) 알고리즘들이 제시되고 대지저항을 측정하기 위한 전극법은 대표적인 웨너와 슐럼버거 측정방법을 사용한다. 컴퓨터 시뮬레이션을 통해 Gauss-Newton과 TLS 알고리즘이 대지모델의 2차원 영상복원에서 적합하다는 것을 보인다.