• Journal of the Korean Data and Information Science Society
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• 제9권2호
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• pp.179-188
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• 1998

Local polynomial regression estimation is the most popular one among kernel type regression estimator. In local polynomial regression function esimation bandwidth selection is crucial problem like the kernel estimation. When the regression curve has complicated structure variable bandwidth selection will be appropriate. In this paper, we propose a variable bandwidth selection method fully data driven. We will choose the bandwdith by selecting minimising estiamted MSE which is estimated by the pilot bandwidth study via croos-validation method. Monte carlo simulation was conducted in order to show the superiority of proposed bandwidth selection method.

• Korea-Australia Rheology Journal
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• 제12권2호
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• pp.107-117
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• 2000

Prediction of the product shape in sheet casting process is performed from the numerical simulation. A three-dimensional finite element method is used to investigate the flow behavior and to examine the effects of processing conditions on the sheet produced. Effects of inertia, gravity, surface tension and non-Newtonian viscosity on the thickness profile of the sheet are considered since the edge bead and the flow patterns in the chill roll region have great influence on the quality of the products. In the numerical simulation with free surface flows, the spine method is adopted to update the free surface, and the force-free boundary condition is imposed along the take-up plane to avoid severe singularity problems existing at the take-up plane. From the numerical results of steady isothermal flows of a generalized Newtonian fluid, it is shown that the draw ratio plays a major role in predicting the shape of the final sheet produced and the surface tension has considerable effect on the bead thickness ratio and the bead width fraction, while shear-thinning and/or tension-thickening viscosity affect the degree of neck-in.

• Transactions of the Korean Society of Mechanical Engineers B
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• 제30권4호
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• pp.320-327
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• 2006

The computations of chemically reacting laminar and turbulent flows are performed using the preconditioned Navier-Stokes solver coupled with turbulent transport and multi-species equations. A low-Reynolds number $k-\varepsilon$ turbulence model proposed by Chien is used. The presence of the turbulent kinetic energy tenn in the momentum equation can materially affect the overall stability of the fluids-turbulence system. Because of this coupling effect, a fully coupled formulation is desirable and this approach is taken in the present study. Choi and Merkle's preconditioning technique is used to overcome the convergence difficulties occurred at low speed flows. The numerical scheme used for the present study is based on the implicit upwind ADI algorithm and is validated through the comparisons of computational and experimental results for laminar methane-air diffusion flame and $ H_2/O_2$ reacting turbulent shear flow. Preconditioning formulation shows better convergence characteristics than that of non-preconditioned system by approximately five times as much.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제22권1호
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• pp.117-124
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• 2009

The p-convergent boundary element method has been proposed to analyze two-dimensional potential problem on the basis of high order Legendre shape functions that have different property comparing with the shape functions in conventional boundary element method. The location of nodes corresponding to high order shape function are not defined along the boundary, called by nodeless node, similar to the p-convergent finite element method. As the order of shape function increases, the collocation point method is used to solve linear simultaneous equations. The collocation patterns of p-convergent boundary element method consist of non-symmetric hierarchial or symmetric non-hierarchical. As the order of shape function increases, the number of collocation point increases. The singular integral that appears in p-convergent boundary element has been calculated by special numeric quadrature technique and semi-analytical integration technique. The L-shape domain problem including singularity in the vicinity of reentrant comer is analyzed and the numerical results show that the relative error is smaller than $10^{-2}%$ range as compared with other results in literatures. In case of same condition, the symmetric p-collocation point pattern shows high accuracy of solution.

• Korean Institute of Interior Design Journal
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• 제23권6호
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• pp.51-59
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• 2014

Rem Koolhaas has pursued new architectural approaches breaking with conventional ones. Around the 1990s when large-scale projects occurred with the union of Europe ahead, Koolhaas recognized the limits to the existing methods for responding to such changes. Accordingly, he came to use design methods based on 'congestion' and 'void' as strategical alternatives, which became the moment for him to leap forward from the previous working sphere based in Europe to becoming an architect who would be commissioned a number of large-scale global projects. Therefore, this study intends to investigate his design methods which utilized congestion and void, and to derive spatial characteristics from the projects based on such methods. First of all, the study looked into the historical background, definition and process of congestion and the void as design methods, and analyzed his projects to which such methods were applied by classifying them into the following categories: 1) the void that removes a space of singularity; 2) the void that penetrates space while making a flow; and 3) the void that is formed by vertical extrusion. Then, the characteristics of architectural spaces made in this way were identified as 1)the single-body appearance made by congestion and the following types of space made by the void: 2) the non-uniformly shaped space that looks like floating; 3) the flexible space with various flows and directions; and 4) the space with virtual possibilities that embrace contingent events. This understanding of Rem Koolhaas's design methods which were attempted in various ways at his critical turning point will be the foundation to understand the overall world of his works.

• Transactions of the Korean Society of Mechanical Engineers
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• 제16권10호
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• pp.1890-1899
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• 1992

In bonded structures, there are V-notched cracks in dissimilar materials and the stress concentration of these V-notched cracks causes to occur interface cracks in dissimilar materials Therefore the strength evaluation of V-notched cracks in dissimliar materials seems to be important. The stress fields of a V-notched cracks is known as .sigma.$_{ij}$ .var. K $r_{p-1}$,where K is the stress intensity factor and p-1 is the stress singularity. When the distance, r, approaches to 0 at the stress fields of V-notched cracks, the stresses become infinites by two more stress singularities of p-1 and p-1 is no more -0.5. Stress singularities and stress intensity factors for V-notched cracks in dissimilar materials are treated and discussed. The Newton-Raphson method which is an efficient numerical method for solving a non-linear equation is used for solving stress sigularities. And stress intensity factors are solved by the collocation method using the Newton-Raphson and least squares method. The effects of stress intensity factors and stress singularities on stress fields of V-notched cracks in dissimilar materials are studied by using photoelasic isochromatic frings patterns obtained from computer graphics.s.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.425-434
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• 2020

Practical non-synoptic fluctuating wind often exhibits nonstationary features and should be modeled as nonstationary random processes. Generally, the coherence function of the fluctuating wind field has time-varying characteristics. Some studies have shown that there is a big difference between the fluctuating wind field of the coherent function model with and without time variability. Therefore, it is of significance to simulate nonstationary fluctuating wind field with time-varying coherent function. However, current studies on the numerical simulation of nonstationary fluctuating wind field with time-varying coherence are very limited, and the proposed approaches are usually based on the traditional spectral representation method with low simulation efficiency. Especially, for the simulation of multi-variable wind field of large span structures such as transmission tower-line, not only the simulation is inefficient but also the matrix decomposition may have singularity problem. In this paper, it is proposed to conduct the numerical simulation of nonstationary fluctuating wind field in one-spatial dimension with time-varying coherence based on the wavenumber-frequency spectrum. The simulated multivariable nonstationary wind field with time-varying coherence is transformed into one-dimensional nonstationary random waves in the simulated spatial domain, and the simulation by wavenumber frequency spectrum is derived. So, the proposed simulation method can avoid the complicated Cholesky decomposition. Then, the proper orthogonal decomposition is employed to decompose the time-space dependent evolutionary power spectral density and the Fourier transform of time-varying coherent function, simultaneously, so that the two-dimensional Fast Fourier transform can be applied to further improve the simulation efficiency. Finally, the proposed method is applied to simulate the longitudinal nonstationary fluctuating wind velocity field along the transmission line to illustrate its performances.

• Journal of Korean Society of Coastal and Ocean Engineers
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• 제24권1호
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• pp.36-47
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• 2012

In this study, the control performance of resonator was reviewed through numerical analysis and 3-dimensional hydraulic model experiments by attaching the resonator suggested in the existing studies to the openings of rectangular harbor and breakwater placed in a straight line to reduce short-period waves. In the numerical analysis, linear analysis method of singularity distribution method based on vertical-line Green function and full non-linear analysis method by 3D-NIT model were applied, and the validity of the numerical analysis methods was verified through comparative analysis between results of hydraulic experiments and numerical analysis results. In addition, effectiveness of the resonator was confirmed by reviewing its control performance on the short-period waves through review on the comparison with the case in which the resonator is not attached.

• Korean Journal of Pharmacognosy
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• 제50권3호
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• pp.205-218
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• 2019

This study was conducted to investigate the toxicity symptoms and approximate lethal dose (ALD) of Oplopanax elatus (Nakai) Nakai hydrothermal extract powder by single oral dose toxicity and 4 weeks of repeated oral dose determination. The Sprague-Dawley (SD) male and female rats were treated with 1,250 (low- dosage group), 2,500 (medium- dosage group) and 5,000 (high- dosage group) mg/kg. In the single oral dose toxicity test, no dead animals and toxic symptoms were observed during the experiment. And there were no related with anomalies in normal weight changes and autopsy results. In the four-week repeated oral dose determination test, no death animals and toxicity symptoms were observed during the experiment, and there were no abnormal results in weight changes, feed and negative intake measurements. Results of eye examination, urinalysis, hematological values and serum biochemical values, gross findings and absolute organ were not of singularity. These result demonstrated that no toxic symptoms were observed by the test substance Oplopanax elatus (Nakai) Nakai hydrothermal extract powder under this test condition, and the non-toxic content is determined to be 5,000 mg/kg/day.

• Journal of Korea Entertainment Industry Association
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• 제13권8호
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• pp.209-221
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• 2019

A found-footage film La France est notre patrie is a documentary, in which archive images are juxtaposed with intertitles, non-diegetic music and foley, by borrowing an audiovisual strategy of silent films. The filmmaker Rithy Panh has excavated the images, which had been taken during the same period as the film history of the end of the 19^th and early 20^th centuries in Southeast Asia and Africa under French colonial rule. This paper examines the filmmaker's methods of historiography when utilizing archive images in order to represent the past by referring to Walter Benjamin's concept of historical montage and dialectical image. As the analysis illustrates the singularity of constructive methods, which include multi-layer viewpoints and montage styles of compilation and collage, it reveals how La France est notre patrie elicits the essay film modes through its self-reflexivity, leads audience to the threshold of critical thinking about time and history and creates a discourse of counter-memory.