• 한국콘텐츠학회논문지
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• 제9권9호
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• pp.68-79
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• 2009

분산맵은 텍스트 영역이 주변과의 색상 혹은 밝기 변화가 심하다는 특징을 이용하는 방법으로 특히 잦은 포맷 변환에 의하여 해상도가 낮거나 일정하지 않은 웹 이미지의 텍스트 영역을 추출하는 데 적용할 수 있다. 그러나 이전의 분산맵을 적용한 방법들은 입력 영상 전역에 고정된 마스크를 한 번만 적용하는 광역 분산맵을 사용하므로 텍스트 크기가 매우 작거나 큰 경우, 획의 색상에 gradation효과가 있는 경우, 각도, 위치, 색상 등이 복잡한 경우 텍스트 추출 성능이 안정 적이지 못하다. 본 논문은 2단계 분산맵을 사용하여 Web 이미지에서 텍스트 영역을 안정적으로 추출하는 방법을 제안한다. 제안된 방법은 광역 및 지역 분산맵이 각 단계에서 적용되며 서로 계층적 관계를 가진다. 1단계는 텍스트 영역 추출 재현율을 높일 수 있도록, 충분히 큰 글자 혹은 작은 글자도 추출할 수 있는 일정한 마스크 크기를 가진 광역의 수직 및 수평 색 분산맵을 적용하여 유사 텍스트 영역을 추출한다. 2단계에서는 1단계의 각 연결요소영역에 새로운 마스크 크기를 가진 명암 분산맵을 적용하여 최종적인 텍스트 영역을 추출한다. 2단계 분산맵 적용에 의하여 1단계에서 구한 유사 텍스트 영역에 남아 있는 배경 부분이 많이 사라지게 되어 추출 정확률이 높아진다. 제안한 방법을 400개의 Web 이미지에 적용한 결과 배경이 복잡해도 비교적 안정적으로 텍스트 영역을 추출하는 것을 확인할 수 있었다.

• 한국정보통신학회논문지
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• 제11권7호
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• pp.1341-1347
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• 2007

기존의 광류 (Optical flow)는 국소적 처리를 시작점으로 하는 bottom-up수법에 의해서 구하였다. 이에 반해, 본 논문은 영상유체보존식과 함수 전개법에 의해 영상 전체의 움직임을 차수가 낮은 모드로 부터 순차적으로 전개하는 bottom-down수법을 새로운 수법으로 제안한다. 의료 영상에 있어서 명도는 움직임이 있어도 불변으로 유지하려는 경우가 많다. 그러나 이 같은 영상계열에서의 움직임은 좌표 변환에 의해서 대응된다. 본 수법의 경우 광류는 선형모멘트방정식의 함수에 관한 도함수를 이용하는 투영법에 의해서 반복계산으로 구하여 진다. 본 논문에서는 심장의 영상계열을 이용하여 기존의 Horn and Schunck기법, Standard multigrid기법과 본 수법의 알고리즘을 비교 평가하여 유효성을 나타낸다.

• Structural Engineering and Mechanics
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• 제19권4호
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• pp.425-440
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• 2005

In this paper, the behavior of a crack between two half-planes of functionally graded materials subjected to arbitrary tractions is resolved using a somewhat different approach, named the Schmidt method. To make the analysis tractable, it is assumed that the Poisson's ratios of the mediums are constants and the shear modulus vary exponentially with coordinate parallel to the crack. By use of the Fourier transform, the problem can be solved with the help of two pairs of dual integral equations in which the unknown variables are the jumps of the displacements across the crack surfaces. To solve the dual integral equations, the jumps of the displacements across the crack surfaces are expanded in a series of Jacobi polynomials. This process is quite different from those adopted in previous works. Numerical examples are provided to show the effect of the crack length and the parameters describing the functionally graded materials upon the stress intensity factor of the crack. It can be shown that the results of the present paper are the same as ones of the same problem that was solved by the singular integral equation method. As a special case, when the material properties are not continuous through the crack line, an approximate solution of the interface crack problem is also given under the assumption that the effect of the crack surface interference very near the crack tips is negligible. It is found that the stress singularities of the present interface crack solution are the same as ones of the ordinary crack in homogenous materials.

• Smart Structures and Systems
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• 제13권2호
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• pp.281-303
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• 2014

In order to suppress the wind-induced vibrations of the Canton Tower, a pair of active mass driver (AMD) systems has been installed on the top of the main structure. The structural principal directions in which the bending modes of the structure are uncoupled are proposed and verified based on the orthogonal projection approach. For the vibration control design in the principal X direction, the simplified model of the structure is developed based on the finite element model and modified according to the field measurements under wind excitations. The AMD system driven by permanent magnet synchronous linear motors are adopted. The dynamical models of the AMD subsystems are determined according to the open-loop test results by using nonlinear least square fitting method. The continuous variable gain feedback (VGF) control strategy is adopted to make the AMD system adaptive to the variation in the intensity of wind excitations. Finally, the field tests of free vibration control are carried out. The field test results of AMD control show that the damping ratio of the first vibration mode increases up to 11 times of the original value without control.

• Computers and Concrete
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• 제21권6호
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• pp.717-726
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• 2018

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that $SiO_2$ nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as $SiO_2$ nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of $SiO_2$ nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• 한국수자원학회논문집
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• 제54권10호
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• pp.759-768
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• 2021

이 연구는 스마트 미터 최종 사용자 수요 데이터의 특성을 조사하여 개별 가정용 물 사용량을 분류하는 새로운 접근방식을 도입한다. 여기서는 잘 알려진 비지도 기계학습법 중 하나인 K-means 알고리즘을 적용하여 각 가구별 물 사용 분류를 수행한다. 최종 사용자 수요의 물 사용강도와 지속 시간은 물 수요 패턴이 유사한 가구를 결정하는 주요한 특징으로 사용된다. 그 결과 21가구가 13개의 군집으로 분류되었고 각 군집은 1가구, 2가구, 3가구 또는 5가구로 구성된다. 수집된 데이터 및 최종 사용자의 물 수요 패턴과 관련하여 여러 가구가 동일한 클러스터로 분류되는 이유를 본 논문에서 소개한다.

• Nuclear Engineering and Technology
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• 제51권5호
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• pp.1373-1380
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• 2019

Besides promising implications as fertile nuclear materials, thorium carbonitrides are of great interest owing to their peculiar physical and chemical properties, such as high density, high melting point, good thermal conductivity. This paper reports first-principles simulation results on the structural, electronic and magnetic properties of cubic thorium carbonitrides $ThC_xN_{(1-x)}$ (X = 0.03125, 0.0625, 0.09375, 0.125, 0.15625) employing formalism of density-functional-theory. For the simulation of physical properties, we incorporated full-potential linearized augmented plane-wave (FPLAPW) method while the exchange-correlation potential terms in Kohn-Sham Equation (KSE) are treated within Generalized-Gradient-Approximation (GGA) in conjunction with Perdew-Bruke-Ernzerhof (PBE) correction. The structural parameters were calculated by fitting total energy into the Murnaghan's equation of state. The lattice constants, bulk moduli, total energy, electronic band structure and spin magnetic moments of the compounds show dependence on the C/N concentration ratio. The electronic and magnetic properties have revealed non-magnetic but metallic character of the compounds. The main contribution to density of states at the Fermi level stems from the comparable spectral intensity of Th (6d+5f) and (C+N) 2p states. In comparison with spin magnetic moments of ThSb and ThBi calculated earlier with LDA+U approach, we observed an enhancement in the spin magnetic moments after carbon-doping into ThN monopnictide.

• 한국콘텐츠학회논문지
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• 제19권7호
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• pp.166-175
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• 2019

전통의학의 체질론은 현대의학과는 구분되는 특성으로, 사상의학은 건강유지의 관점을 폐비간신(肺脾肝腎)의 기능적 강약(强弱)으로 구분하여 인체 장부(臟腑)의 체질에 따른 기능적 균형이 어떠한 조건에서 불균형이 되는 상태를 병의 주요한 요인으로 파악하였다. 아유르베다는 우리 몸에 존재하는 3개 "도샤(Dosha)'의 균형을 건강 유지의 기본으로 생각하고 질병이 생기는 이유를 체내 에너지 조절 기능을 하는 바따(Vata), 신진대사와 소화 기능을 담당하는 삣타(Pitha), 체온조절 기능을 담당하는 카파(Kapha)의 균형이 깨어졌기 때문으로 보았고 세가지 도샤(tridosha)가 균형을 맞추면 스스로 치유된다고 하였다. 체질에 따른 질병의 특징과 경향을 알아 치료에 접근하고 일상생활의 건강관리까지 포함하고 있는 두 이론은 각 개인의 특성과 독립적이고 자율적인 생활습관이 중시되는 현대사회에서 일상 생활 건강 유지 및 예방을 위해 다양한 예방 치료법의 융합영역으로 해석될 수 있다고 생각된다. 본 연구에서는 사상 의학과 아유르베다 이론을 체질 관점에서 비교 분석하여 환자의 치유력과 회복력에 도움이 되고, 환자의 만족도 증가를 위한 체질 기반 개념을 이해하고 예방 의료분야에 있어서의 활용의 다양성에 대해 도움이 되고자 한다.

• Computers and Concrete
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• 제24권2호
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• pp.125-135
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• 2019

Concrete pipelines are the most efficient and safe means for gas and oil transportation over a long distance. The use of nano materials and nono-engineering can be considered for enhancing concrete pipelines properties. the tests show that SiO2 nanoparticles can improve the mechanical behavior of concrete. Moreover, severe hazard for pipelines is seismic ground motion. Over the years, scientists have attempted to understand pipe behavior against earthquake most frequently via numerical modeling and simulation. Therefore, in this paper, the dynamic response of underwater nanocomposite submerged pipeline conveying fluid is studied. The structure is subjected to the dynamic loads caused by earthquake and the governing equations of the system are derived using mathematical model via Classic shell theory and Hamilton's principle. Navier-Stokes equation is employed to calculate the force due to the fluid in the pipe. As well, the effect of external fluid is modeled with an external force. Mori-Tanaka approach is used to estimate the equivalent material properties of the nanocomposite. 1978 Tabas earthquake in Iran is considered for modelling seismic load. The dynamic displacement of the structure is extracted using differential quadrature method (DQM) and Newmark method. The effects of different parameters such as SiO2 nanoparticles volume percent, boundary conditions, thickness to radius ratios, length to radius ratios, internal and external fluid pressure and earthquake intensity are discussed on the seismic response of the structure. From results obtained in this paper, it can be found that the dynamic response of the pipe is increased in the presence of internal and external fluid. Furthermore, the use of SiO2 nanoparticles in concrete pipeline reduces the displacement of the structure during an earthquake.

• Ocean Systems Engineering
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• 제9권2호
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• pp.191-218
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• 2019

The tower-platform interface and mooring system of floating offshore wind turbines (FOWTs) are some of the most critical components with significant influences on overall project costs. In addition to satisfying strength requirements, it is typical and vital to meet fatigue criteria for a service life of 25 years or more. Wind spectra characteristics considered in analysis can penalize fatigue designs, leading to unnecessary costs. The International Electrotechnical Commission (IEC, 2009) recommends the use of site-specific wind data (spectrum, turbulence intensity, etc.) in design of FOWTs, but for offshore sites it is often the case that such data is unavailable and land-based data are used as surrogates in design. For such scenarios, it is worth investigating whether such alternative approach is suitable and accurate, and understanding the consequence of the selection of wind spectral characteristics on fatigue design. This paper addresses the impact of the subsequent selection on fatigue responses of towerbase and mooring system in a FOWT, as a sequel to the paper by Udoh and Zou (2018) which focused on impacts on strength design. The 5 MW semi-submersible FOWT platform with six mooring lines implemented in the preceding study is applied in analysis. Results indicate significant variations in resulting fatigue life with considered wind parameters. Thus, it is critical to apply proper wind spectra characteristics for analysis and design of FOWTs to avoid unnecessary conservatism and costs. Based on the findings of this study, more explicit guidance on the application of turbulence intensities for IEC-recommended models in offshore sites could lead to more accurate load estimates in design of FOWTs.