• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.3
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• pp.223-230
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• 1999

A conventional sliding mode control approach is often impractical or difficult when it is applied to high order process b because the number of tuning parameters in the sliding mode controller increases with the order of the plant. C Camacho(l996) proposed a design method of a fixed structure sliding mode controller based on a first order plus dead t time approximation to the higher-order process. But, his method has such problems as chattering, over‘shoot, and c command following due to the Taylor the approximation en‘ors for the time delay term of the first order model. In this p paper, a new design technique for a sliding mode controller based on the modified Taylor approximation considered a w weight is developed to improve the Camacho's problems.

• Transactions on Electrical and Electronic Materials
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• v.13 no.1
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• pp.10-15
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• 2012

In conventional, skin detection methods using for skin color definitions is based on prior knowledge. By experimentation, the threshold value for dividing the background from the skin region is determined subjectively. A drawback of such techniques is that their performance is dependent on a threshold value which is estimated from repeated experiments. To overcome this, the present paper introduces a skin region detection method. This method uses a histogram approximation based on the mean shift algorithm. This proposed method applies the mean shift procedure to a histogram of a skin map of the input image. It is generated by comparing with the standard skin colors in the $C_bC_r$ color space. It divides the background from the skin region by selecting the maximum value according to the brightness level. As the histogram has the form of a discontinuous function. It is accumulated according to the brightness values of the pixels. It is then, approximated by a Gaussian mixture model (GMM) using the Bezier curve technique. Thus, the proposed method detects the skin region using the mean shift procedure to determine a maximum value. Rather than using a manually selected threshold value, as in existing techniques this becomes the dividing point. Experiments confirm that the new procedure effectively detects the skin region.

• Nuclear Engineering and Technology
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• v.23 no.1
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• pp.41-48
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• 1991

Many of the analyses of the transient radionuclide migration are approximated by an one-dimensional geometry and/or planar geometry. To validate these approximations, one should prove that these are reasonable and proper approximations. In this paper, the approximation which was in the study of the transport through backfill into a fissure is tried to validate. In that analysis, a cylindrical geometry was approximated by a planar geometry. The numerical illustrations show that the planar approximation agrees very well with the result of the cylindrical geometry for a ratio of the backfill outer radius to the waste form radius closed to unity. Even for a larger ratio of the two radii, the numerical difference is relatively small. Also the planar approximation which was used in the analysis gives conservative estimates.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.37 no.3
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• pp.17-30
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• 2000

In this paper, we propose an efficient algorithm to produce 3-D surface model from a set of range data, based on NURBS (Non-Uniform Rational B-Splines) surface fitting technique. It is assumed that the range data is initially unorganized and scattered 3-D points, while their connectivity is also unknown. The proposed algorithm consists of three steps: initial model approximation, hierarchical representation, and construction of the NURBS patch network. The mitral model is approximated by polyhedral and triangular model using K-means clustering technique Then, the initial model is represented by hierarchically decomposed tree structure. Based on this, $G^1$ continuous NURBS patch network is constructed efficiently. The computational complexity as well as the modeling error is much reduced by means of hierarchical decomposition and precise approximation of the NURBS control mesh Experimental results show that the initial model as well as the NURBS patch network are constructed automatically, while the modeling error is observed to be negligible.

• Composites Research
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• v.25 no.4
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• pp.117-125
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• 2012

Warpage of the film insert molded (FIM) part is caused by an asymmetric residual stress distribution. Asymmetric residual stress and temperature distribution is generated by the retarded heat transfer in the perpendicular direction to the attached film surface. Since warpage was not prevented by controlling injection molding conditions, glass fiber (GF) filled composites were employed as substrates for film insert molding to minimize the warpage. Distribution of short GFs was evaluated by using micro-CT equipment. Proper models for micro mechanics, anisotropic thermal expansion coefficients, and closure approximation should be selected in order to calculate fiber orientation tensor and warpage of the FIM part with the composite substrate. After six kinds of micro mechanics models, three models of the thermal expansion coefficient and five models of the closure approximation had been considered, the Mori-Tanaka model, the Rosen and Hashin model, and the third orthotropic closure approximation were selected in this study. The numerically predicted results on fiber orientation tensor and warpage were in good agreement with experimental results and effects of GF reinforcement on warpage of the FIM composite specimen were identified by the numerical results.

• Journal of the Korean Society for Nondestructive Testing
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• v.24 no.6
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• pp.559-565
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• 2004

Two different methods were used for the scattering analysis of side-drilled holes(SDH). The scattering models include an explicit model based on the Kirchhoff approximation and the solution of the exact separation of variables. The far-field scattering amplitude was calculated and their time-domain results were compared for the case of shear vertical wave. The exact solution predicts the existence of the creeping wave. The Kirchhoff approximation agreed to the exact solution, except the case of the creeping wave. Two measurement models were introduced to predict the response from the SDHs for the case of immersion, pulse-echo testing. The received voltage was calculated for the case of the shear vertical waves with the incident angle of $45^{\circ}$ to the SDH with the diameter of 1mm, and compared with the experimental results.

• The Journal of the Korea institute of electronic communication sciences
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• v.13 no.5
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• pp.917-922
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• 2018

In the conventional interchannel interference self-cancellation (ICI-SC) schemes, the length of sampling window is the same as the symbol length of orthogonal frequency division multiplexing (OFDM). Thus, the number of complex operations to compute the interference coefficient of each subchannel is significantly increased. To solve this problem, we present an approximated mathematical model for the coefficients of ICI-SC schemes. Based on the proposed approximation, we analyze mean squared error (MSE) and computational complexity of the ICI-SC schemes with the length of sampling window. As a result, the presented approximation has an error of less than 0.01% on the MSE compared to the original equation. When the number of subchannels is 1024, the number of complex computations for the interference coefficients is reduced by 98% or more. Since the computational complexity can be remarkably reduced without sacrificing the self-cancellation capability, it is considered that the proposed approximation is very useful to develop an algorithm for the ICI-SC scheme.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.13 no.2
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• pp.158-168
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• 2001

A numerical model based on the wide-angle parabolic approximation equation is developed for the accurate simulation of the directional spreading and partial breaking of irregular waves. This model disintegrates the irregular waves into a series of monochromatic wave components, and the simultaneous calculations are made for each wave component. Then, the computed wave components are superposed to get the wave height of irregular waves. To consider the partial breaking of irregular waves in the computation the amount of energy dissipation due to breaking is estimated using the superposed wave height. The accuracy of the developed model is tested by comparing the numerical results with the experimental measurements reported earlier. In the case of non-breaking waves a considerable accuracy of the model is observed for both regular and irregular waves. On the contrary it is found that the accuracy is significantly degenerated for the case of breaking waves. Some analyses for the accuracy degeneration are presented.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.33 no.2
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• pp.32-38
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• 2005

In this research, a procedure to improve the feasibility of design space is proposed by an approximation model. The Chebyshev Inequality is used as the criterion of modification of design space. This procedure is applied to the aero-elastic transonic wing design problem and the feasibility of the design space is greatly improved. Also the optimization results are improved by appling this procedure. That is, the probability to satisfy all imposed constraints is increased and the better design points are included in design space after this procedure. And the use of both a second-order response surface model and the Kriging model is investigated and compared in accuracy, efficiency, and robustness as approximation models in this procedure for different sampling methods. As a result, the second-order response surface model is more appropriate for our application than the Kriging model, because it is linear enough to be fitted well by the response surface model.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.331-332
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• 2007