• Korean Journal of Optics and Photonics
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• v.17 no.4
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• pp.335-341
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• 2006

A modified Michelson interferometer type digital holography microscopy system is developed. There is a problem about recording and numerical reconstruction area at the microscopy application of Michelson type interferometer structure in the digital holography field. In this paper, to overcome this problem, we developed a new reflection type digital holography microscope system and increased recording and numerical reconstruction area of target object.

• 한국전산유체공학회:학술대회논문집
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• 2010.05a
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• pp.376-379
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• 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
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• v.23 no.1
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• pp.31-38
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• 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.

• Journal of Korea Multimedia Society
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• v.19 no.8
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• pp.1371-1376
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• 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.

• Journal of Korea Foundry Society
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• v.31 no.3
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• pp.124-129
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• 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
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• v.15 no.1
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• pp.15-40
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• 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.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.24 no.9
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• pp.1148-1156
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• 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.

• Journal of KSNVE
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• v.9 no.4
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• pp.687-692
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• 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.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.16 no.1
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• pp.9-15
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• 1998

Numerical cadastral surveying method has advantages of higher accuracy and less individual error than planetable surveying method if we consider the result of surveying at the same area. Now in the areas where they use numerical cadastral records, coordinate is the basis when the boundary location is registered in numerical cadastral re-cords or is reconstructed on land surface, and this coordinate represents simply the absolute locational relationship with respect to origin point. But when we register the cadastral boundary location in cadastral or reconstruct it on land, relative relationship with respect to traverse point is more advisable basis than absolute relationship with respect to orgin point. This study contributes to the numerical cadastral surveying by discussing the problems to be improved that the principle of coordinate based boundary location registration and reconstruction has.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.14 no.7
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• pp.3460-3467
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• 2013

The In this paper, we have made numerical experiments to compare 2D image reconstruction algorithm of earth model by electrical resistance tomograpy (ERT). Gauss-Newton, simultaneous iterative reconstruction technieque (SIRT) and truncated least squares (TLS) approaches for Wenner and Schlumberger electrode arrays are presented for the solution of the ERT image reconstruction. Computer simulations show that the Gauss-Newton and TLS approach in ERT are proper for 2D image reconstruction of an earth model.