• 한국멀티미디어학회논문지
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• 제18권12호
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• pp.1439-1444
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• 2015

Measuring spectral reflectance can be regarded as obtaining inherent color parameters, and spectral reflectance has been used in image processing. Model-based spectrum recovering, one of the method for obtaining spectral reflectance, uses ordinary camera with multiple illuminations. Conventional model-based methods allow to recover spectral reflectance efficiently by using only a few parameters, however it requires some parameters such as power spectrum of illuminations and spectrum sensitivity of camera. In this paper, we propose an enhanced model-based spectrum recovering method without pre-measured parameters: power spectrum of illuminations and spectrum sensitivity of camera. Instead of measuring each parameters, spectral reflectance can be efficiently recovered by estimating and using the spectrum characteristic matrix which contains spectrum parameters: basis function, power spectrum of illumination, and spectrum sensitivity of camera. The spectrum characteristic matrix can be easily estimated using captured images from scenes with color checker under multiple illuminations. Additionally, we suggest fast recovering method preserving positive constraint of spectrum by nonnegative basis function of spectral reflectance. Results of our method showed accurately reconstructed spectral reflectance and fast constrained estimation with unmeasured camera and illumination. As our method could be conducted conveniently, measuring spectral reflectance is expected to be widely used.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 1999년도 추계 학술대회논문집
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• pp.48-58
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• 1999

The Characteristic Flux Difference Splitting (CFDS) scheme designed to adapt the characteristic boundary conditions at the wall and inflow/outflow boundary planes satisfies Roe's property U, although the CFDS Jacobian matrix is decomposed by a product of elaborate transformation matrices and explicit eigenvalue matrix. When the CFDS algorithm, thus a variant of Roe's scheme, is applied straightforwardly to hypersonic flows over a blunt body, the strong bow shock gradually breaks down near the stagnation point. This numerical instability is widely observed by many researchers employing flux-difference method, known in the literature as the carbuncle phenomenon. Many remedies have been proposed and resulted in partial cures. When the idea of Sanders et al. which identifies the minimum eigenvalues near the discontinuity present is applied to CFDS method, it is shown that the instability problem can be controlled successfully. A few flux splitting methods have also been tested and results are compared against the Nakamori's Mach 8 blunt body flow.

• 대한수학회논문집
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• 제11권1호
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• pp.63-70
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• 1996

Let K be a field of characteristic 0 and G a Klein's four group. We find the idempotent elements and units of the group ring KG by using the basic group table matrix of G.

• 대한기계학회논문집A
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• 제25권10호
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• pp.1583-1589
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• 2001

Metal matrix composites with whisker reinforcements have significant potentials for demanding mechanical applications including defense, aerospace, and automotive industries. Especially metal matrix composites, which are reinforced with aluminum borate whisker, have been used leer the part of piston head in automobile because of good specific strength and wear resistance. In this study, AC4CH-based metal matrix composites with $Al_{18}$B$_{4}$ $O_{33}$ reinforcement have been produced using squeeze casting method, after T6 heat treatment, we evaluated fatigue life property of matrix and MMC composite and investigated fracture mechanism.m.

• Journal of Mechanical Science and Technology
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• 제19권spc1호
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• pp.283-291
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• 2005

Accurate seismic analyses of large deformable moving structures are still unsolved problems in the field of earthquake engineering. In order to analyze these problems, the nonlinear finite element method formulated by the absolute nodal coordinate approach is noticed. Because, this formulation has several advantages over the standard procedures on mass matrix, elastic forces and damping forces in the case of large displacement problems. But, it has not been fully studied to build frame structure models by using beam elements in the absolute nodal coordinate formulation. In this paper, we propose the connecting method of the beam elements formulated by the absolute nodal coordinate. The coordinate transformation matrix of this element is introduced into the frame structure. This beam element has the characteristic that the mass matrix and bending stiffiness matrix are constant even if in the case of large displacement problems, and this characteristic is being kept after the transformation. In order to verify the proposed method, we show the numerical simulation results of frame structures for a vibration problem and a large displacement problem.

• 한국공작기계학회논문집
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• 제12권6호
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• pp.50-55
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• 2003

This study proposed the analysis of damage detection due to the change of the stiffness of structure by using the original and modified dynamic characteristics. The present approach allows the use of composite data which consist of eigenvalues and eigenvectors. The suggested method is applied to examples of a cantilever and 3 degree of freedom system by modifying the stiffness. The predicted damage detections are in good agreement with these from the structural reanalysis using the modified stiffness.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2003년도 춘계학술대회 논문집
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• pp.760-763
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• 2003

This study proposed the analysis of damage defection due to the change of the stiffness of structure by using the original and modified dynamic characteristics. The method is applied to examples of a cantilever and 3 degree of freedom by modifying the stiffness. The predicted damage detections are in good agreement with these from the structural reanalysis using the modified stiffness.

• Communications for Statistical Applications and Methods
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• 제2권1호
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• pp.89-98
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• 1995

This paper presents the interesting properties of a certain patterned matrix that plays an significant role in the multi-way balanced designs. The necessary and sufficient condition on the existence of the inverse of the patterned matrix and its determinant are described. In special cases of the pattermed matrix, explicit formulas for its inverse, determinant and the characteristic equation are obtained.

• 대한토목학회논문집
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• 제33권3호
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• pp.957-964
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• 2013

본 논문은 침수특성치를 이용한 도시유역의 침수위험성 평가방법을 제시하는 연구이다. 2010년 9월 21일 청계천상류의 효자배수분구(광화문 광장일대)에서 발생한 침수피해를 XP-SWMM 2010을 이용하여 모의하였다. 강우발생빈도별, 지속시간별로 관로첨두유출량 값을 구하여 침수상태를 분석한 결과 관로 내 첨두유출량만으로는 침수상태를 충분히 해석할 수 없음을 확인 할 수 있었다. 따라서 도시지역의 침수피해규모를 표현할 수 있는 침수특성치 6가지를 새롭게 정의하였으며 발생가능한 강우조합(강우량, 강우지속시간)을 침수특성치별로 산정하여 침수위험성 평가방법을 연구하였다. 모의 결과를 침수특성치별로 강우조합에 중첩하여 등치선도로 나타낸 "발생가능강우별 침수특성 등치선도"를 개발하여 이를 근거로 발생할 수 있는 모든 강우형태에 대한 침수위험성을 평가할 수 있음을 확인할 수 있었다. 또한 유역의 상태가 변하거나 치수계획규모를 변화시키는 것에 대한 침수특성치별 침수규모 해소정도를 쉽게 파악 할 수 있음을 확인하였다.

• 대한전자공학회논문지
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• 제12권6호
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• pp.14-20
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• 1975

일반적인 결합불균일선로에 대한 이론을 적용하여 결합삼각함수선로(CTTL)의 특성을 연구하였다. 우선 CTTL의 4-Port 전달메이트릭스 퍼래미터를 유도한 다음 이것을 사용하여 CTTL을 이용한 전역통과회로와 방향통합전압을 해석하였다. 선로에 연한 결합계수의 변화에 따라서 전역통도관로의 위상특성과 방향성결합기의 결합전압의 크기의 변화를 상세하게 연구하였다. 최후로 CTTL를 사용한 광대역 90° 차동위상추이기와 고역통과 방향성통합기의 설계예를 들고 그 실현방법을 고찰하였다. Characteristics of coupled trigonometric transmission lines (CTTL) are studies based on the theory of general coupled nonuniform transmission lines. First, the 4-port transmission matrix parameters of networks and directional couplers using CTTL. The phase slrift characteristic of the all-pass networks and the magnitude characteristic of the directional couplers are studied in detail for various coupling and a high-pass small ripple directional coupler using CTTL are given and their physical realization is considered.