• 한국음향학회지
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• 제34권3호
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• pp.240-246
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• 2015

본 논문은 시간 연속성을 갖는 비음수 행렬 분해(Nonnegative Matrix Factorization, NMF)를 이용하여 잡음에 열화된 음성 신호의 음질을 개선하는 문제를 다룬다. 음성과 잡음 신호는 포아송 분포로 모델되며, NMF의 기본 벡터와 이득 벡터는 감마 분포로 모델된다. 이득 벡터의 시간 연속성은 음질 개선에 중요한 영향을 미치는 것으로 알려져 있다. 본 논문에서 시간의 연속성은 이득 벡터를 감마-마르코프 연쇄(Gamma-Markov chain, GMC) 사전 분포로 모델함으로써 이루어진다. 실험 결과는 제안된 알고리즘이 잡음 신호의 시간 연속성을 효과적으로 모델하는 것을 보여준다.

• 대한수학회보
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• 제50권3호
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• pp.839-865
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• 2013

We deal with the existence of positive radial solutions concentrating on spheres for the following class of elliptic system $$\large(S) \hfill{400} \{\array{-{\varepsilon}^2{\Delta}u+V_1(x)u=K(x)Q_u(u,v)\;in\;\mathbb{R}^N,\\-{\varepsilon}^2{\Delta}v+V_2(x)v=K(x)Q_v(u,v)\;in\;\mathbb{R}^N,\\u,v{\in}W^{1,2}(\mathbb{R}^N),\;u,v&gt;0\;in\;\mathbb{R}^N,}$$ where ${\varepsilon}$ is a small positive parameter; $V_1$, $V_2{\in}C^0(\mathbb{R}^N,[0,{\infty}))$ and $K{\in}C^0(\mathbb{R}^N,[0,{\infty}))$ are radially symmetric potentials; Q is a $(p+1)$-homogeneous function and p is subcritical, that is, 1 < $p$ < $2^*-1$, where $2^*=2N/(N-2)$ is the critical Sobolev exponent for $N{\geq}3$.

• 대한원격탐사학회:학술대회논문집
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• 대한원격탐사학회 2006년도 Proceedings of ISRS 2006 PORSEC Volume I
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• pp.126-129
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• 2006

The marine environment is under considerable threat from intentional or accidental oil spills, ballast water discharged, dredging and infilling for coastal development, and uncontrolled sewage and industrial wastewater discharges. Monitoring spills and illegal oil discharges is an important component in ensuring compliance with marine protection legislation and general protection of the coastal environments. For the monitoring task an image processing system is needed that can efficiently perform the detection and the tracking of oil spills and in this direction a significant amount of research work has taken place mainly with the use of radar (SAR) remote sensing data. In this paper the level set image segmentation technique was tested for the detection of oil spills. Level set allow the evolving curve to change topology (break and merge) and therefore boundaries of particularly intricate shapes can be extracted. Experimental results demonstrated that the level set segmentation can be used for the efficient detection and monitoring of oil spills, since the method coped with abrupt shape’s deformations and splits.

• Structural Engineering and Mechanics
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• 제52권1호
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• pp.115-136
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• 2014

In this study, an extended Kantorovich method, employing multi-term displacement functions, is applied to analyze the vibration problem of symmetrically laminated plates with arbitrary boundary conditions. The vibration behaviors of laminated plates are determined based on the variational principle of total energy minimization and the iterative Kantorovich method. The out-of-plane displacement is represented in the form of a series of a sum of products of functions in x and y directions. With a known function in the x or y directions, the formulation for the variation of total potential energy is transformed to a set of governing equations and a set of boundary conditions. The equations and boundary conditions are then numerically solved for the natural frequency and vibration mode shape. The solutions are verified with available solutions from the literature and solutions from the Ritz and finite element analysis. In most cases, the natural frequencies compare very well with the reference solutions. The vibration mode shapes are also very well modeled using the multi-term assumed displacement function in the terms of a power series. With the method used in this study, it is possible to solve the angle-ply plate problem, where the Kantorovich method with single-term displacement function is ineffective.

• 한국자기학회지
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• 제1권2호
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• pp.79-84
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• 1991

개 영역 교류자장 문제 해석을 위해 구부범함수를 사용한 변분법을 제시한다. 이 방법에 사용되는 국부범함수는 유한요소영역에 대한 영역적 분항과 유한요소영역과 무한요소영역 사이의 공유 경계면에 대한 경계적분항의 합으로써 이루어 진다. 경계적분항은 무한 계산영역에 대한 범함수의 무 한요소영역에 대한 영역적분항을 고유경계면에 대한 경계적분으로 치환시킴으로써 얻어진다. 본 논문 에서 제시한 방법을 이론해를 알고 있는 모델에 적요시켜 수치해석 결과를 얻고 그 결과를 이론해와 비교하여 보았다. 본 방법을 사용함으로써 이론해와 잘 일치하는 수치해석 결과를 덩었으며, 그리고 개 영역 교류자장 문제해석에 있어서 계산영역을 축소시킬 수 있기 때문에 컴퓨터 기억용량 감소 및 계산시간을 대폭 단축 시킬 수 있을 것이다.

• 한국지구과학회지
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• 제36권5호
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• pp.460-475
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• 2015

A number of heavy rainfall events on the Korean Peninsula are indirectly influenced by tropical cyclones (TCs) when they are located in southeastern China. In this study, a heavy rainfall case in the middle Korean region is selected to examine the influence of typhoon simulation performance on predictability of remote rainfall over Korea as well as direct rainfall over Taiwan. Four different numerical experiments are conducted using Weather Research and Forecasting (WRF) model, toggling on and off two different improvements on typhoon in the model initial condition (IC), which are TC bogussing initialization and dropwindsonde observation data assimilation (DA). The Geophysical Fluid Dynamics Laboratory TC initialization algorithm is implemented to generate the bogused vortex instead of the initial typhoon, while the airborne observation obtained from dropwindsonde is applied by WRF Three-dimensional variational data assimilation. Results show that use of both TC initialization and DA improves predictability of TC track as well as rainfall over Korea and Taiwan. Without any of IC improvement usage, the intensity of TC is underestimated during the simulation. Using TC initialization alone improves simulation of direct rainfall but not of indirect rainfall, while using DA alone has a negative impact on the TC track forecast. This study confirms that the well-suited TC simulation over southeastern China improves remote rainfall predictability over Korea as well as TC direct rainfall over Taiwan.

• 천문학회지
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• 제29권1호
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• pp.43-51
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• 1996

We present test results of time-series CCD photometry to investigate the photometric precision of the BOAO (Bohyunsan Optical Astronomy Observatory) 1.8m telescope. A well-known field of the old open cluster M67, which includes two pulsating blue stragglers and two W UMa type binaries, was monitored for 3.5 hours on February 22, 1996. We have collected 148 V frames and 3 B frames. Photometric noises which consist mainly of photon noise and scintillation noise, were lowered down to about 1.9 mmag for stars of $10.\;^m5$ in M67 with exposure time of 20 seconds. From the C-M diagram for M67, a number of observational properties were derived; E(B-V) = 0.03, (V-Mv)o = 9.6, Age = 4 Gyr. We obtained light curves for four known variable stars and confirmed their variational characteristics. The pulsating blue stragglers show a low amplitude (about 0.01 mag) of light variation.

• 한국게임학회 논문지
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• 제17권1호
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• pp.89-98
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• 2017

본 논문에서는 물리기반 동적 변형을 실시간에 안정적으로 시뮬레이션하는 새로운 ARAP(as-rigid-as-possible) 방법을 제안한다. 1, 2, 3차원 물체의 변형을 안정적이며, 빠르고, 일관성 있게 다루기 위하여 방향성 입자로 이루어진 변형 그래프를 도입하고 그에 따른 ARAP 변형에너지를 공식화한다. 방향성 입자의 안정적인 시간 적분을 위해서는 변분 공식화에 기반을 둔 내재적 시간 적분 기법을 개발한다. 또한 국지적/전역적 최적화를 교대로 반복 적용하여 방향성 입자의 최적 위치 및 회전을 구한다. 제안된 방법은 구현이 쉽고 복잡한 변형을 실시간에 시뮬레이션할 수 있을 정도로 빠르다.

• 한국전자파학회지:전자파기술
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• 제6권2호
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• pp.35-44
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• 1995

본 논문에서는 우수한 양산성을 감안한 협대역 도파관형 대역통과 여파기를 제작하기 위하여 미리 제작된 판 재를 도파관 튜브의 내부에 파진 스롯에 끼워넣는 단일 E 평면구조를 제안하고, 이를 변분해석볍을 사용하여 해석하였다. 그리고 통과대역 보정법에 의한 여파기 합성설계방볍을 사용하여 마이크로파대 협대역 도파관형 대역통과 여파기를 설계하는 CAD 프로그램을 개발하였다. 개발된 프로그램으로 중심주파수 3.82GHz 5단 O.002dB equi-ripple Chebyshev형 28MHz의 대역폭을 갖는 대역통과 여파기를 설계하여 튜닝구조로 제작, 여파기 특성을 미세조정과정을 거쳐 실험하였다. 그 결과 이론치와 잘 일치하는 측정결과를 얻었다.

• 한국전기전자재료학회논문지
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• 제18권7호
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• pp.589-593
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• 2005

The electronic states of ZnO doped with Al, Ga and In, which belong to III family elements in periodic table, were calculated using the density functional theory. In this study, the calculation was performed by two Programs; the discrete variational Xa (DV-Xa) method, which is a sort of molecular orbital full potential method; Vienna Ab-initio Simulation Package (VASP), which is a sort of pseudo potential method. The fundamental mixed orbital structure in each energy level near the Fermi level was investigated with simple model using DV-Xa. The optimized crystal structures calculated by VASP were compared to the measured structures. The density of state and the energy levels of dopant elements were shown and discussed in association with properties.