• Journal of the Korean Institute of Gas
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• v.3 no.1
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• pp.64-74
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• 1999

Using the steady state gains, an appropriate criterion used for the interaction analysis among variables and the loop pairing is suggested. Based upon the suggested criterion derived from the derivative relation of implicit function, the SISO pairing which has minimum interaction among control system variables and good control performance can be determined. The relative effect among diagonal gains and off-diagona gains, which was not considered in other criteria, can be explained deterministically Also, the criterion can be easily applied to partial MIMO pairing. This criterion was applied to several examples to illustrate its usefulness in finding the feasible SISO pairing and MIMO pairing

• Steel and Composite Structures
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• v.47 no.5
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• pp.569-585
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• 2023

This paper proposes an efficient approach for the structural topology optimization of bi-directional functionally graded structures by incorporating popular radial basis functions (RBFs) into an implicit level set (ILS) method. Compared to traditional element density-based methods, a level set (LS) description of material boundaries produces a smoother boundary description of the design. The paper develops RBF implicit modeling with multiquadric (MQ) splines, thin-plate spline (TPS), exponential spline (ES), and Gaussians (GS) to define the ILS function with high accuracy and smoothness. The optimization problem is formulated by considering RBF-based nodal densities as design variables and minimizing the compliance objective function. A LS-RBF optimization method is proposed to transform a Hamilton-Jacobi partial differential equation (PDE) into a system of coupled non-linear ordinary differential equations (ODEs) over the entire design domain using a collocation formulation of the method of lines design variables. The paper presents detailed mathematical expressions for BiDFG beams topology optimization with two different material models: continuum functionally graded (CFG) and mechanical functionally graded (MFG). Several numerical examples are presented to verify the method's efficiency, reliability, and success in accuracy, convergence speed, and insensitivity to initial designs in the topology optimization of two-dimensional (2D) structures. Overall, the paper presents a novel and efficient approach to topology optimization that can handle bi-directional functionally graded structures with complex geometries.

• Journal of The Korean Association of Information Education
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• v.15 no.4
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• pp.635-644
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• 2011

This research analyzed the brainwave activities and brain hemispherity to find out any implications to design the connections between the activities of the brain function and the computerized arithmetic addition in two difficulty levels: easy: 1-5 vs. hard: 6-9. Thus, in developing the brain based math learning for the computer education by implicit association test(IAT) indicated the significant results for the exclusive brain location and the brain hemispherity on the theta, alpha, low alpha, beta brainwaves by QEEG analysis. The results of this study physiologically supported the theoretical background for the computerized math learning skills as well as the math learning material development. It shows the difficulty levels of math information education and the brain activities on cognitive process of the learner continued on the possible investigation of the brain science.

• Journal of Korean Society of Transportation
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• v.25 no.5
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• pp.209-231
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• 2007

This paper suggested an approach to characterize travel choice behaviors using the implicit price instead of the indirect utility. The choice criterion to compare the implicit prices of available trip options was developed from the utility maximization problem of a trip maker which is supposed to choose the best option from the available ones differentiated by only by the quantitative attributes such as travel cost and time but also by qualitative attributes such as comfort and safety. The utility maximization problem is constructed under household production theory, and is incorporated with a special kind of joint homogeneous production functions. The implicit price of a certain trip option is the sum of the monetary price and the multiple of travel time and the value-of-travel-time, and the value-of-travel-time refers to the portion of wage, which can be assignable to the trip-making activity. This choice criterion is statistically identifiable, and behaviorally plausible. Moreover, this criterion has the expression simpler than the indirect utility, and therefore could be an effective target of the statistical estimation for travel choice behaviors.

• International Journal of Control, Automation, and Systems
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• v.4 no.2
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• pp.146-154
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• 2006

In this paper, we propose direct and indirect adaptive fuzzy sliding mode control approaches for a class of nonaffine nonlinear systems. In the direct case, we use the implicit function theory to prove the existence of an ideal implicit feedback linearization controller, and hence approximate it to attain the desired performances. In the indirect case, we exploit the linear structure of a Takagi-Sugeno fuzzy system with constant conclusion to establish an affine-in-control model, and therefore design an indirect adaptive fuzzy controller. In both cases, the adaptation laws of the adjustable parameters are deduced from the stability analysis, in the sense of Lyapunov, to get a more accurate approximation level. In addition to their robustness, the design of the proposed approaches does not require the upper bounds of both external disturbances and approximation errors. To show the efficiency of the proposed controllers, a simulation example is presented.

• Journal of Computational Design and Engineering
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• v.3 no.4
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• pp.370-384
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• 2016

Computer-aided materials design requires new modeling approaches to characterize and represent fine-grained geometric structures and material compositions at multiple scales. Recently, a dual-Rep approach was developed to model materials microstructures based on a new basis function, called surfacelet. As a combination of implicit surface and wavelets, surfacelets can efficiently identify and represent planar, cylindrical, and ellipsoidal geometries in material microstructures and describe the distribution of compositions and properties. In this paper, these primitive surfacelets are extended and composite surfacelets are proposed to model more complex geometries. Composite surfacelets are constructed by Boolean operations on the primitives. The surfacelet transform is applied to match geometric features in three-dimensional images. The composition of the material near the identified features can then be modeled. A cubic surfacelet and a v-joint surfacelet are developed to demonstrate the reverse engineering process of retrieving material compositions from material images.

• Journal of electromagnetic engineering and science
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• v.9 no.4
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• pp.211-217
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• 2009

A three-dimensional locally one-dimensional multiresolution time-domain(LOD-MRTD) method is introduced and unconditional stability is proved analytically. The updating formulations have fewer terms on the right-hand side than those of an alternating direction implicit MRTD(ADI-MRTD). The validation of the method is presented using the resonance frequency problem of an empty cavity. The reduction of the numerical dispersion technique is also combined with the proposed method. The numerical examples show that the combined method can improve the accuracy significantly.

• Journal of Mechanical Science and Technology
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• v.16 no.5
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• pp.720-731
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• 2002

Flow with moving free surfaces is analyzed with an the Eulerian coordinate system. This study proposes a semi-implicit filling algorithm using VOF in which the PLIC (Piecewise Linear Interface Calculation) -type interface reconstruction method and the donor-acceptor-type front advancing scheme are adopted. Also, a new scheme using extrapolation of the stream function is proposed to find the velocity of the node that newly enters the computational domain. The effect of wall boundary conditions on the flow field and temperature field is examined by numerically solving a two-dimensional casting process.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.12 no.11
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• pp.2077-2082
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• 2008

Recent the advanced technologies in medical imaging such as magnetic resonance imaging (MRI) and computed tomography (CT) make doctors improve the diagnostic skill with detailed anatomical information. In general, it is necessary to get a number of MRI images in order to obtain more detail information. However, the performance of MRI machines of privately run hospitals is not good and thus we may obtain only a few of MRI images. If 3D surface reconstruction is accomplished with a few slices, then it generates 3D surface of poor qualify. This paper propose a way to Set a 3D surface of high quality from a few of number of slices. First of all, our algorithm detects the boundary of tissues which we want to reconstruct as a 3D object and find out the set of vortices on the boundary. And then we generate a 3D implicit surface to interpolate the boundary points by using radial basis function. Lastly, we render the 3D implicit surface by using Marching cube algorithms.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.53 no.4
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• pp.210-215
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• 2004

This paper proposes an implicit method for computing the minimum cost feedback vertex set for a graph. For an arbitrary graph, a Boolean function is derived, whose satisfying assignments directly correspond to feedback vertex sets of the graph. Importantly, cycles in the graph are never explicitly enumerated, but rather, are captured implicitly in this Boolean function. This function is then used to determine the minimum cost feedback vertex set. Even though computing the minimum cost satisfying assignment for a Boolean function remains an NP-hard problem, it is possible to exploit the advances made in the area of Boolean function representation in logic synthesis to tackle this problem efficiently in practice for even reasonably large sized graphs. The algorithm has obvious application in flip-flop selection for partial scan. The algorithm proposed in this paper is the first to obtain the MFVS solutions for many benchmark circuits.