• Journal of KIISE:Software and Applications
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• v.33 no.11
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• pp.942-952
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• 2006

We propose an automatic segmentation method for identifying pulmonary structures using gray-level information of chest CT images. Our method consists of following five steps. First, to segment pulmonary structures based on the difference of gray-level value, we select the threshold using optimal thresholding. Second, we separate the thorax from the background air and then the lungs and airways from the thorax by applying the inverse operation of 2D region growing in chest CT images. To eliminate non-pulmonary structures which has similar intensities with the lungs, we use 3D connected component labeling. Third, we segment the trachea and left and right mainstem bronchi using 3D branch-based region growing in chest CT images. Fourth, we can obtain accurate lung boundaries by subtracting the result of third step from the result of second step. Finally, we select the threshold in accordance with histogram analysis and then segment radio-dense pulmonary vessels by applying gray-level thresholding to the result of the second step. To evaluate the accuracy of proposed method, we make a visual inspection of segmentation result of lungs, airways and pulmonary vessels. We compare the result of the conventional region growing with the result of proposed 3D branch-based region growing. Experimental results show that our proposed method extracts lung boundaries, airways, and pulmonary vessels automatically and accurately.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.31 no.1
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• pp.47-52
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• 2018

In this study, a collimator composed of multi-dielectric structures is designed using the phase field design method, a kind of topology optimization methods. It is also purposed to improve the mechanical-structural performance of a collimator by replacing previously used air regions with another dielectric material. Polypropylene and paraffin are selected as the dielectric materials for the design process taking manufacturability into account. The design objective is formulated by integrating the intensity of the electromagnetic field in the pre-determined target area to realize the collimating performance. The model for accurate numerical analysis was derived from the final result obtained from the design process through the simple cut-off method and it shows the improved performance of 105% compared with the free space wave propagation. For the designed model, the possibility of reverse transformation, the mechanical durability evaluation under the compression load, and the electromagnetic performance in the X-band range were also evaluated.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.12
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• pp.2343-2348
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• 2006

Image magnification is among the basic image processing operations. The most commonly used technique for image magnification are based on interpolation method(such as nearest neighbor, bilinear and cubic interpolation). However, the magnified images produced by the techniques that often appear a variety of undesirable image artifacts such as 'blocking' and 'blurring' or too takes the processing time into the several processing for image magnification. In this paper, we propose image magnification method which uses input image's sub-band information such as edge information to enhance the image magnification method. We use the whole image and not use the one's neighborhood pixels to detect the edge information of the image that isn't occurred the blocking phenomenon. And then we emphasized edge information to remove the blurring phenomenon which incited of edge information. Our method, which improves the performance of the traditional image magnification methods in the processing time, is presented. Experiment results show that the proposed method solves the drawbacks of the image magnification such as blocking and blurring phenomenon, and has a higher PSNR and Correlation than the traditional methods.

• Journal of the Korea Computer Graphics Society
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• v.27 no.4
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• pp.11-24
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• 2021

In this paper, we propose an artificial neural network framework that can represent the foam effects expressed in liquid simulation in detail without noise. The position and advection of foam particles are calculated using the existing screen projection method, and the noise problem that appears in this process is solved through an proposed artificial neural network. The important thing in the screen projection approach is the projection map, but noise occurs in the projection map in the process of projecting momentum into the discretized screen space, and we efficiently solve this problem by using an artificial neural network-based denoising network. When the foam generating area is selected through the projection map, 2D is inversely transformed into 3D space to generate foam particles. We solve the existing denoising network problem in which small-scaled foam particles disappear. In addition, by integrating the proposed algorithm with the screen-space projection framework, all the advantages of this approach can be accommodated. As a result, it shows through various experiments whether it is possible to stably represent not only the clean foam effects but also the foam particles lost due to the denoising process.

• The Journal of the Acoustical Society of Korea
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• v.13 no.4
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• pp.60-68
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• 1994

In this paper we propose a new Hybrid learning rule applied to multilayer feedforward neural networks, which is constructed by combining Hebbian learning rule that is a good feature extractor and Back-Propagation(BP) learning rule that is an excellent classifier. Unlike the BP rule used in multi-layer perceptron(MLP), the proposed Hybrid learning rule is used for uptate of all connection weights except for output connection weigths becase the Hebbian learning in output layer does not guarantee learning convergence. To evaluate the performance, the proposed hybrid rule is applied to classifier problems in two dimensional space and shows better performance than the one applied only by the BP rule. In terms of learning speed the proposed rule converges faster than the conventional BP. For example, the learning of the proposed Hybrid can be done in 2/10 of the iterations that are required for BP, while the recognition rate of the proposed Hybrid is improved by about $0.778\%$ at the peak.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.48 no.9
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• pp.691-701
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• 2020

An actuator mixer design using convex optimization technique situation where the propulsion system of an electric VTOL UAV during vertical take-off and landing maneuvers is proposed. The attainable control set to analyze the impact from failure of each motor and propeller can be calculated and illustrated using the properties of the convex function. The control allocation can be defined as a convex function optimization problem to obtain an optimal solution in real time. The mixer is implemented using a convex optimization solver, and the performance of the control allocation methods is compared to the attainable control set. Finally, the proposed mixer is compared with other techniques with nonlinear sux degree-of-freedom simulation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.1
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• pp.1-8
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• 1992

A method analizing contact pressure between plate and elastic half space is presented by using F.E.M. With the method, the pressure intensities at surface nodes of half space cae be directly calculated by using flexibility matrix of half space. The method is originally presented by Y.K. Cheung et al.(3) Insted of Y.K. Cheung's method, which use a conception of equi-contact pressure area around each surface nodes of half space in the noded rectanqular element area. We use the equi-contact pressure area around the Gaussian integration points of half space surface in the noded isoparametric element area. Numarical examples are presented and compared with other's studies.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.41 no.3
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• pp.15-20
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• 2004

In this paper, a wideband two-layer H-shaped microstrip antenna for WLAN is designed. To increase the bandwidth of microstrip patch antenna a configuration of stacked type using parastic element is used. Furthermore, to reduce the size of microstrip patch antenna, two techniques are employed . the first one is H-shaped patch type and the second one is that the main radiator and parastic patch are shorted to the ground plane using ten shorting posts. The antenna bandwidth and radiation characteristics are calculated by ENSEMBLE ver. 5.0 simulation software, and compared with the experimental results. Experiment results show that the bandwidth of antenna in 740MHz centered at 5.46㎓(13.5%), which is close agreement with the calculations, 770MHz(13%). Also, the antenna size can be reduced by 71.5% compared with the half wavelength rectangular microstrip antenna using the same substrate at the same frequency.

• The Journal of the Acoustical Society of Korea
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• v.20 no.5
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• pp.83-91
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• 2001

This paper proposes the Focused beamforming to estimate the location of target residing near to the observation platform in the underwater environment. The Focused beamforming technique provides the location of target by the coherent summation of a series of incident spherical waveforms considering distinct propagation delay times at the sensor array. But due to the movement of the observation platform and the variation of the underwater environment, the shape of the sensor array is no longer to be linear but it becomes distorted as the platform moves. Thus the Focused beamforming should be peformed regarding to the geometric shape variation at each time. To estimate the target location, the artificial image plane comprised of cells is constructed, and the delays are calculated from each cell where the target could be proximity to sensors for the coherent summation. After the coherent combining, the beam pattern can be obtained through the Focused beamforming on the image plane. Futhermore to compensate the variation of the shape of the sensor array, the paper utilizes the Nth-order polynomial approximation to estimate the shape of the sensor array obeying the water pulley modeling. Simulation results show the performance of the Focused beamforming for different frequency bands of the radiated signal.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1231-1244
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• 2008

The objective of this study is to present a methodology for estimating runoff curve number(CN) using SWAT model which is capable of reflecting watershed heterogeneity such as climate condition, land use, soil type. The proposed CN estimation method is based on the asymptotic CN method and particularly, it uses surface flow data simulated by SWAT. This method has advantages to estimate spatial CN values according to subbasin division and to reflect watershed characteristics because the calibration process has been made by matching the measured and simulated streamflows. Furthermore, the method is not sensitive to rainfall-runoff data since CN estimation is on a daily basis. The SWAT based CN estimation method is applied to Chungju dam watershed. The regression equation of the estimated CN that exponentially decays with the increase of rainfall is presented.