• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.26 no.5
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• pp.445-454
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• 2015

In this paper, we propose an optimal design method for a dual reflector antenna(DRA) using the Genetic algorithm. In order to reduce the computational burden during the optimal design, we exploit the iterative physical optics(IPO) to calculate the surface current distribution at each reflector antenna. To improve the accuracy, we consider the shadow effect by the structure and the coupling effect by the multi-reflection based on the iterative MFIE(Magnetic Field Integral Equation). To reduce the number of design variables and generate a smooth surface, we use the Bezier function with the control points, which become the design variables in this paper. We adopt the HPBW(Half Power Beam Width), the FNBW(First Null Beam Width), and the SLL(Side Lobe Level) as the objective or cost functions. To verify the results, we compare them with the those of the commercial tool.

• Journal of Korea Society of Industrial Information Systems
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• v.24 no.6
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• pp.55-65
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• 2019

With the advent of the Fourth Industrial Revolution and changes in the educational environment, team-based assignments are increasing in university classes. Effective team formation in team-based class is an important issue that affects students' satisfaction and the effectiveness of education. However, previous studies mostly focused on post analysis on the results of team formation, which makes it difficult to use them in actual classes. In this paper, we present a mathematical model of how to create a balanced team that reflects students' abilities and other characteristics. Characteristic values for assignment may be scores, such as students' proficiency, binary values such as gender, and multi-values, such as grade or department. This problem is a type of equitable partitioning problem, which takes the form of 0-1 integer programming, and the objective function is linear or nonlinear, depending on how balance is achieved. The basic model or the extended model presented can be applied to the situation where teams are balanced in consideration of various factors in actual class.

• The Korean Journal of Applied Statistics
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• v.35 no.3
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• pp.371-384
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• 2022

The fused LASSO signal approximator (FLSA) can be applied to find change points from the data having piecewise constant mean structure. It is well-known that the FLSA is inconsistent in change points detection. This inconsistency is due to a total-variation denoising penalty of the FLSA. ℓ₁ trend filter, one of the popular tools for finding an underlying trend from data, can be used to identify change points of piecewise linear trends. Since the ℓ₁ trend filter applies the sum of absolute values of slope differences, it can be inconsistent for change points recovery as the FLSA. However, there are few studies on the inconsistency of the ℓ₁ trend filtering. In this paper, we demonstrate the inconsistency of the ℓ₁ trend filtering with a numerical study.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.5 s.311
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• pp.80-88
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• 2006

In this paper we developed a novel system for automatic detection of mass type breast cancer on dense digital mammogram images. The new approaches presented in this paper are as follows: 1) we presented a method that stably decides the mass center and radius without being affected by image signal irregularity. 2) We developed a radial directional filter that is suitable to process mass image signal. 3) And we developed the multiple feature function based on mass shape spiculation, mass center homogeneity, and mass eccentricity, so as to determine mass-type breast cancer. When the proposed system is applied to dense mammographic images, the true 기arm rate is improved by 10% over a conventional system while the false alarm is increased by 1 per image.

• Korean Journal of Remote Sensing
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• v.27 no.2
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• pp.141-150
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• 2011

Precise image-to-image registration is required to process multi-sensor data together. The purpose of this paper is to develop an algorithm that register between high-resolution optical and SAR images using linear features. As a pre-processing step, initial alignment was fulfilled using manually selected tie points to remove any dislocations caused by scale difference, rotation, and translation of images. Canny edge operator was applied to both images to extract linear features. These features were used to design a cost function that finds matching points based on their similarity. Outliers having larger geometric differences than general matching points were eliminated. The remaining points were used to construct a new transformation model, which was combined the piecewise linear function with the global affine transformation, and applied to increase the accuracy of geometric correction.

• Journal of KIISE:Computing Practices and Letters
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• v.6 no.2
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• pp.206-215
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• 2000

This paper is concerned with the development of PCS(Platform for Collaborative System), which is a platform for development of remote collaborative experiment systems. Platform does not aim at the development of special-domain applications. This system implies the common development environments which can develop all-domain applications. PCS consists of collaborative experimental objects such as communication, session, user, application, media, message object and management objects that have management functions. Management objects are made up of collaborative experimental objects and operations which manipulate control information and data. It also supports application sharing for making single user interface of experimental applications to multi-user interface. Application sharing also supports instruments control on the remote site. PCS platform supports total environments for remote collaborative experiment and can be used as infrastructure to all kinds of collaboratory systems.

• Proceedings of the Korea Water Resources Association Conference
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• 2015.05a
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• pp.159-159
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• 2015

상수관망시스템의 신뢰도를 정량화하기 위한 연구가 최근 활발히 진행되고 있다. 대부분의 연구는 절점의 공급가능수요량, 절점의 수두, 그리고 유량과 수두를 동시에 고려한 에너지(energy)를 이용하여 신뢰도 지수를 개발하였다. 이 중, Energy를 기반으로 하는 신뢰도지수로써 Resilience index(Todini, 2000), Network Resilience index(Prasad, 2004), Modified Resilience index(Jayaram, 2008)와 Entropy Resilience index(Raad, 2010) 등의 연구가 대표적이다. 상수관망시스템에 정상적인 상황을 넘어서는 부담이 가해졌을 때, 이를 완충하거나, 정상적인 용수공급 상황으로 빠르게 회복하는 능력인 복원력(Resilience)을 판단하기 위한 지표로써 제시된 Todini의 Resilience index를 기점으로, 상수관망의 신뢰도(Reliability)을 Energy 측면에서 판단할 수 있는 관련 지표에 대한 연구가 진행되어왔다. 특히, 상수관망의 최적설계 시, 상수관망의 기능적 요소로써 관련 지표들을 비용(Cost)과 함께 다중목적함수로 고려하는 연구까지 다수 진행되고 있으나, 이러한 지표들이 상수관망에서 핵심적인 몇 가지 요소들의 변화에 대하여 어떻게 반응하는지에 대한 분석은 제대로 이루어지지 않고 있다. 본 연구에서는 동일한 상수관망시스템에서 용수의 흐름상황을 크게 좌우할 수 있을 것으로 판단되는 몇 가지 변동상황을 고려하여 이러한 지표들이 각각의 변동상황에 어느정도 민감하게 반영하는지 분석하였다. 여기서, 상수관망시스템의 중요 변화요소로써 1) 수요량의 변화, 2) Loop 개수의 변화, 3) 수원지(Source) 개수의 변화, 4) 해당시스템의 최소 요구수압 변화 등을 고려하였다. 본 연구를 통해, 상수관망시스템의 신뢰도 산정에 활용되고 있는 기존의 지수들이 다양한 변동 상황을 얼마나 잘 반영할 수 있는지를 파악하고, 기존의 지수들을 보완한 개선된 신뢰도 지수의 개발가능성을 모색하도록 한다.

• Journal of Broadcast Engineering
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• v.25 no.6
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• pp.898-910
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• 2020

Single image-based super-resolution has been studied for a long time in computer vision because of various applications. Various deep learning-based super-resolution algorithms are introduced recently to improve the performance by reducing side effects like blurring and staircase effects. Most deep learning-based approaches have focused on how to implement the network architecture, loss function, and training strategy to improve performance. Meanwhile, Several approaches using Attention Module, which emphasizes the extracted features, are introduced to enhance the performance of the network without any additional layer. Attention module emphasizes or scales the feature map for the purpose of the network from various perspectives. In this paper, we propose the various channel attention and spatial attention in single image-based super-resolution and analyze the results and performance according to the architecture of the attention module. Also, we explore that designing multi-attention module to emphasize features efficiently from various perspectives.

• Journal of the Economic Geographical Society of Korea
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• v.10 no.4
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• pp.427-443
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• 2007

The purpose of this study is to investigate spacio-temporal structures of traffic flows on the subway network in the Metropolitan Seoul, and the relationships between topological structures of traffic flows and land use patterns. In particular we analyze in the topological structures of traffic flows on the subway network in time dimension as well as in spatial dimension. For the purpose, this study utilizes data mining techniques to the one day T-card transaction data of the last four years, which has developed for exploring the characteristics of traffic flows from large scale trip-transaction databases. The topological structures of traffic flows on the subway network has changed considerably during the last four years. The volumes of traffic flows, the travel time and stops per trip have increased until 2006 and decreased again in 2007. The results are visualized by utilizing GIS and analyzed, and thus the spatial patterns of traffic flows are analyzed. The spatial distribution patterns of trip origins and destinations show substantial differences among time zones during a day. We analyze the relationships between traffic flows at subway stops and the geographical variables reflecting land use around them. We obtain 6 log-linear functions from stepwise multiple regression analysis. We test multicollinearity among the variables and autocollelation for the residuals.

• Nuclear Engineering and Technology
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• v.3 no.3
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• pp.155-160
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• 1971

Average and effective energies for 239Pu-Be, 241Am-Li and 241Am-F neutron sources have been calculated from a number of published data for the neutron spectra and for the dose equivalent as a function of neutron energies by a numerical method. Also a calculation of the dose equivalent conversion factors, i. e., the first collision dose equivalent and the surface (or multicollision) dose equivalent that equals the product of surface-absorbed dose and a corresponding quality factor, per unit fluence of neutrons from these sources has been carried out in the same way as before. The results are as follows : 1. for average energies 4.07$\pm$0.33, 0.42 and 1.41 MeV； 2. for effective energies based on the concept of the first collision process in the human body 4.45$\pm$0.344, 0.51 and 1.47 MeV; 3. for effective energies based on the concept of the multi-collision process in the human body 4.50$\pm$0.36, 0.50 and 1.45 MeV； 4. for fluence-first collision dose equivalent conversion factors (2.74$\pm$0.07)10$^{-8}$ , 1.58$\times$ 10$^{-8}$ and 2.34$\times$10$^{-8}$ rems/(n/$\textrm{cm}^2$); and 5. for fluence-surface dose equivalent conversion factors (3.55$\pm$0.09)10$^{-8}$ , 2.19$\times$10$^{-8}$ and 2.82$\times$10$^{-8}$ rems/(n/$\textrm{cm}^2$) : respectively.