• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.49-54
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• 1998

3-dimensional Euler solver is parallelized. The spatial discretization method is the 2nd order TVD scheme and DADI method with multigrid is used as a time integration. In order to parallelize this solver, the domain decomposition method with overlapped grid and message passing techniques are used. The informations on the each inter-processor bound-aries are communicated with MPI library. Finally, the parallel performance repsented by calculating the ONERA M6 wing at transonic flow condition using CRAY T3E and C90.

• Nuclear Engineering and Technology
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• v.48 no.3
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• pp.635-641
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• 2016

Because of prohibitive data storage requirements in large-scale simulations, the memory problem is an obstacle for Monte Carlo (MC) codes in accomplishing pin-wise three-dimensional (3D) full-core calculations, particularly for whole-core depletion analyses. Various kinds of data are evaluated and quantificational total memory requirements are analyzed based on the Reactor Monte Carlo (RMC) code, showing that tally data, material data, and isotope densities in depletion are three major parts of memory storage. The domain decomposition method is investigated as a means of saving memory, by dividing spatial geometry into domains that are simulated separately by parallel processors. For the validity of particle tracking during transport simulations, particles need to be communicated between domains. In consideration of efficiency, an asynchronous particle communication algorithm is designed and implemented. Furthermore, we couple the domain decomposition method with MC burnup process, under a strategy of utilizing consistent domain partition in both transport and depletion modules. A numerical test of 3D full-core burnup calculations is carried out, indicating that the RMC code, with the domain decomposition method, is capable of pin-wise full-core burnup calculations with millions of depletion regions.

• Journal of Korean Association for Spatial Structures
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• v.11 no.4
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• pp.49-59
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• 2011

This paper presents a new numerical method by using Singular Value Decomposition force method for form-finding of tensegrity structures with constraints. In order to maintain the tensegrity structures stable, state of self-equilibrium stress should be introduced. The existing force method has some advantages about form-finding of tensegrity structures. However, this method has complex formulation. In force density method, dummy members are required for form -finding of tensegrity structures with constraints. Therefore this study proposes new force method using Singular value decomposition. The proposed method is both having easy basic consept and simple computation than existing force method. A numerical example is presented to demonstrate the efficiency and robustness in searching initial single integral feasible self-stress mode for tensegrity structures with constraints.

• Journal of computational fluids engineering
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• v.5 no.2
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• pp.20-27
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• 2000

An unstructured implicit Euler solver is parallelized on a Cray T3E. Spatial discretization is accomplished by a cell-centered finite volume formulation using an upwind flux differencing. Time is advanced by the Gauss-Seidel implicit scheme. Domain decomposition is accomplished by using the k-way n-partitioning method developed by Karypis. In order to analyze the parallel performance of the solver, flows over a 2-D NACA 0012 airfoil and 3-D F-5 wing were investigated.

• 한국전산유체공학회:학술대회논문집
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• 1999.11a
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• pp.193-200
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• 1999

An unstructured implicit Euler solver is parallelized on a Cray T3E. Spatial discretization is accomplished by a cell-centered finite volume formulation using an unpwind flux differencing. Time is advanced by the Gauss-Seidel implicit scheme. Domain decomposition is accomplished by using the k-way N-partitioning method developed by Karypis. In order to analyze the parallel performance of the solver, flows over a 2-D NACA 0012 airfoil and a 3-D F-5 wing were investigated.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.34 no.2
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• pp.121-132
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• 2016

This study proposes an approach for simulating high spatial resolution satellite images acquired under arbitrary sun-sensor geometry using existing images and 3D (three-dimensional) data. First, satellite images, having significant differences in spectral regions compared with those in the simulated image were transformed to the same spectral regions as those in simulated image by using the UPDM (Universal Pattern Decomposition Method). Simultaneously, shadows cast by buildings or high features under the new sun position were modeled. Then, pixels that changed from shadow into non-shadow areas and vice versa were simulated on the basis of existing images. Finally, buildings that were viewed under the new sensor position were modeled on the basis of open library-based 3D reconstruction program. An experiment was conducted to simulate WV-3 (WorldView-3) images acquired under two different sun-sensor geometries based on a Pleiades 1A image, an additional WV-3 image, a Landsat image, and 3D building models. The results show that the shapes of the buildings were modeled effectively, although some problems were noted in the simulation of pixels changing from shadows cast by buildings into non-shadow. Additionally, the mean reflectance of the simulated image was quite similar to that of actual images in vegetation and water areas. However, significant gaps between the mean reflectance of simulated and actual images in soil and road areas were noted, which could be attributed to differences in the moisture content.

• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1753-1762
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• 1996

Since the number of spatial objects go easily into millions, they are stored on a secondary storage. In order to speed up accessing the geometric objects, we investigate spatial database system. The spatial objects are organized and accessed by spatial access methods(SAMs). But, SAMs are not able to organize polygons directly The most popular approach for handing polygon in SAMs is to use MBR apporximaotion as a geometric key. MBR provides a fast but inaccurate answers to approximation-based query processing. The performance of approximation-based spatial query processing depends on which type of approximation is chosen for the spatial objects. A suitable approximation is crucial for reducing the size of the candidate set. The better the approxmation quality, the fewer accesses to the exact object are necessary. In this paper, I proposed a new multicontainer approximation named Slice decomposition. The performance of proposed method is compared with other method.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.8 no.3
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• pp.224-228
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• 2015

In this paper, we study the method for desired signals estimation that array antennas are received signals. We apply sub spatial method of direction of arrival algorithm and adaptive array antennas in order to remove interference and noise signal of received antenna signals. Array response vector of adaptive array antenna is probability, it is correctly estimation of direction of arrival of targets to update weight signal. Desired signals are estimated updating covariance matrix after moving interference and noise signals among received signals. We estimate signals using eigen decomposition and eigen value, high resolution direction of arrival estimation algorithm is devided signal sub spatial and noise sub spatial. Though simulation, we analyze to compare proposed method with general method.

• Smart Structures and Systems
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• v.1 no.1
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• pp.29-46
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• 2005

In this study, a wavelet packet based method is proposed for identifying damage occurrence and damage location for beam-like structures. This method assumes that the displacement or the acceleration response time histories at various locations along a beam-like structure both before and after damage are available for damage assessment. These responses are processed through a proper level of wavelet packet decomposition. The wavelet packet signature (WPS) that consists of wavelet packet component signal energies is calculated. The change of the WPS curvature between the baseline state and the current state is then used to identify the locations of possible damage in the structure. Two numerical studies, one on a 15-storey shear-beam building frame and another on a simply-supported steel beam, and an experimental study on a simply-supported reinforced concrete beam are performed to validate the proposed method. Results show the WPS curvature change can be used to locate both single and sparsely-distributed multiple damages that exist in the structure. Also the accuracy of assessment does not seem to be affected by the presence of 20-15dB measurement noise. One advantage of the proposed method is that it does not require any mathematical model for the structure being monitored and hence can potentially be used for practical application.

• Journal of Institute of Control, Robotics and Systems
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• v.20 no.6
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• pp.657-662
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• 2014

Usually, spatial information can be incorporated into histograms by taking histograms of a multiresolution image. For these reasons, many researchers are interested in multiresolution histogram processing. If the relation and sensitivity of the multiresolution images are well combined without loss of information, we can obtain satisfactory results in several fields of image processing including histogram equalization, specification and pattern matching. In this paper, we propose a multiresolution histogram specification method that improves the accuracy of histogram specification. The multiresolution decomposition technique is used in order to overcome the unique feature of a histogram specification affected by a quantization error of a digitalized image. The histogram specification is processed after the reduction of image resolution in order to enhance the accuracy of the results by histogram specification methods. The experimental results show that the proposed method enhances the accuracy of specification compared to conventional methods.