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

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.47 no.11
• /
• pp.1-6
• /
• 2010

In Sensor Networks, the problem of finding the optimal routing path dynamically, which passes through all terminals or nodes once per each, may come up. Providing a generalized scheme of approximations that can be applied to the kind of problems, and formulating the bounds of the run time and the results of the algorithm made from the scheme, one may evaluate mathematically the routing path formed in a given network. This paper, dealing with Euclidean TSP(Euclidean Travelling Sales Person) that represents such problems, provides the scheme for constructing the approximated Euclidean TSP by parallel computing, and the ground for determining the difference between the approximated Euclidean TSP produced from the scheme and the optimal Euclidean TSP.

• Journal of the Computational Structural Engineering Institute of Korea
• /
• v.18 no.2
• /
• pp.123-131
• /
• 2005

According to ow previous study, we confirmed That the Petrov-Galerkin natural element method(PG-NEM) completely resolves the numerical integration inaccuracy in the conventional Bubnov-Galerkin natural element method(BG-NEM). This paper is an extension of PG-NEM to two-dimensional geometrically nonlinear problem. For the analysis, a linearized total Lagrangian formulation is approximated with the PS-NEM. At every load step, the grid points ate updated and the shape functions are reproduced from the relocated nodal distribution. This process enables the PG-NEM to provide more accurate and robust approximations. The representative numerical experiments performed by the test Fortran program, and the numerical results confirmed that the PG-NEM effectively and accurately approximates The large deformation problem.

• Journal of KIISE:Computing Practices and Letters
• /
• v.14 no.5
• /
• pp.527-531
• /
• 2008

For statistical modeling, the model parameters are usually estimated by maximizing a probability measure, such as the likelihood or the posterior. In contrast, a variational Bayesian method treats the parameters of a model as probability distributions and computes optimal distributions for them rather than values. It has been shown that this approach effectively avoids the overfitting problem, which is common with other parameter optimization methods. This paper applies a variational Bayesian technique to surface fitting for height field data. Then, we propose point cloud denoising based on the basic surface fitting technique. Validation experiments and further tests with scan data verify the robustness of the proposed method.

• Proceeding of EDISON Challenge
• /
• 2017.03a
• /
• pp.82-94
• /
• 2017

본 연구에서는 고분자의 해밀토니안을 Q-state Potts-Model로 근사하여, 2, 3차원 형태의 선형 고분자 시스템을 모사하고자 한다. 고분자 외부에서 힘이 작용하고 있는 경우와 아닌 경우에 대하여 전산모사 결과를 바탕으로 고분자의 크기의 경향성을 확인하였다. 그 결과, 흔히 사용되는 Flory's Theory와 달리 고분자의 대표적인 특성인 지수(exponent)에 대하여 더 유동적인 관계식을 얻어낼 수가 있었다. 이를 바탕으로, 고분자에서 흔히 사용되고 있는 scaling argument가 잘 적용되는지를 확인해보았으며, 그 결과 일부의 경우에서만 성립함을 확인할 수 있었다.

• The Korean Journal of Applied Statistics
• /
• v.15 no.2
• /
• pp.297-310
• /
• 2002

Liang and Zeger proposed generalized estimating equations(GEE) for analyzing repeated data which is discrete or continuous. GEE model can be extended to model for repeated categorical data and its estimator has asymptotic multivariate normal distribution in large sample sizes. But GEE is based on large sample asymptotic theory. In this paper, we study the properties of GEE estimators for repeated ordinal data in small sample sizes. We generate ordinal repeated measurements for two groups using two methods. Through Monte Carlo simulation studies we investigate the empirical type 1 error rates, powers, relative efficiencies of the GEE estimators, the effect of unequal sample size of two groups, and the performance of variance estimators for polytomous ordinal response variables, especially in small sample sizes.

• Journal of Korea Society of Industrial Information Systems
• /
• v.28 no.1
• /
• pp.27-34
• /
• 2023

The optimal assignment problem between agents and tasks is known as one of the representative problems of combinatorial optimization and an NP-hard problem. This paper covers multi agent-multi task assignment problems with uncertain completion probability. The completion probabilities are generally uncertain due to endogenous (agent or task) or exogenous factors in the system. Assignment decisions without considering uncertainty can be ineffective in a real situation that has volatility. To consider uncertain completion probability mathematically, a mathematical formulation with stochastic programming is illustrated. We also present an algorithm by using the sample average approximation method to solve the problem efficiently. The algorithm can obtain an assignment decision and the upper and lower bounds of the assignment problem. Through numerical experiments, we present the optimality gap and the variance of the gap to confirm the performances of the results. This shows the excellence and robustness of the assignment decisions obtained by the algorithm in the problem with uncertainty.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.28 no.1C
• /
• pp.47-55
• /
• 2003

This paper proposes a composition method of mosaic image from the compressed MPEG-2 video stream, in which the displacement between successive frames according to the camera operation is estimated directly from the information involved in the stream. In the proposed method. the approximated optical flow is constructed from motion vectors of macro blocks, and it is used to determine the parameters of the displacements according to the camera operation associated with pan and tilt. The extracted parameters are used to determine the geometric transform of successive video frames in order to construct a mosaic image. The construction of mosaic uses several blending techniques including the one proposed by Nichols in which an analytic weight is used to determine pixel values. Through the experiment, the blending technique based on analytic weights was superior to the others such as averaging and median-based techniques. It provided more smooth changes in background and made use of instantaneous frame information to construct a mosaic. The mosaic in the paper puts the emphasis on the reduction of computation because it is constructed from the motion vectors included in the compressed video without decoding and recalculating exact optical flows. The constructed mosaic can be used in the retrieval of the compressed video as the representative frame of a shot.

• Journal of KIISE:Software and Applications
• /
• v.36 no.11
• /
• pp.947-954
• /
• 2009

This paper proposes a novel method that reconstructs a surfel-based object by using visual hull from multiple images. The surfel is a point primitive that effectively approximates point-set surface. We create the surfel representation of an object from images by combining the LDC(Layered Depth Cube) surfel sampling with the concept of visual hull that represents the approximated shape from input images. Because the surfel representation requires relatively smaller memory resources than the polygonal one and its LDC resolution is freely changed, we can control the reconstruction quality of the target object and acquire the maximal quality on the given memory resource.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.16 no.3
• /
• pp.1630-1638
• /
• 2015

The finite element analysis has become an essential process to investigate the structural performance in many industry fields. In addition, the computer's performance is improving rapidly, but in large design problems, there is a limit to apply the optimal design techniques. For this, it is general to introduce a metamodel based optimization technique. The method to generate an approximate model can be classified into curve fitting and interpolation, and each representative one is response surface model and kriging interpolation method. This study proposes an ensemble model made of RSM and kriging to solve a structural design problem. The suggested method is applied to the designs of two bar and automobile outer tie rod.