• Journal of applied mathematics & informatics
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• 제8권1호
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• pp.97-109
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• 2001

This article is devoted to “forgotten” and rarely used technique of matrix analysis, introduced in 60-70th and enhanced by authors. We will study the matrix trace operator and it’s differentiability. This idea generalizes the notion of scalar derivative for matrix computations. The list of the most common derivatives is given at the end of the article. Additionally we point out a close connection of this technique with a least square problem in it’s classical and generalized case.

• Structural Engineering and Mechanics
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• 제66권5호
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• pp.557-568
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• 2018

An investigation is made in the present work on the post-buckling and geometrically nonlinear behaviors of moderately thick perfect and imperfect rectangular plates made-up of functionally graded materials. Spectral collocation approach based on Legendre basis functions is developed to analyze the functionally graded plates while they are subjected to end-shortening strain. The material properties in this study are varied through the thickness according to the simple power law distribution. The fundamental equations for moderately thick rectangular plates are derived using first order shear deformation plate theory and taking into account both geometric nonlinearity and initial geometric imperfections. In the current study, the domain of interest is discretized with Legendre-Gauss-Lobatto nodes. The equilibrium equations will be obtained by discretizing the Von-Karman's equilibrium equations and also boundary conditions with finite Legendre basis functions that are substituted into the displacement fields. Due to effect of geometric nonlinearity, the final set of equilibrium equations is nonlinear and therefore the quadratic extrapolation technique is used to solve them. Since the number of equations in this approach will always be more than the number of unknown coefficients, the least squares technique will be used. Finally, the effects of boundary conditions, initial geometric imperfection and material properties are investigated and discussed to demonstrate the validity and capability of proposed method.

• 한국항공우주학회지
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• 제31권4호
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• pp.26-34
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• 2003

본 논문에서는 이동최소자승 근사법 등의 무요소 근사법을 이용하여 유한요소모델 절점의 연결성과 무관하게 유한요소 절점을 자유로이 활성화시킬 수 있는 절점활성화 기법을 제안하고, 제안된 방법의 타당성을 고찰하기 위해 일관성 조건, 수치해의 유계성 등에 대한 이론적 고찰을 수행한다. 제안된 절점활성화 기법을 이용하면 많은 수의 유한요소 절점 중 관심이 있는 일부 절점만을 선택, 활성화시켜 이들만을 미지수로 이용하여 문제를 해석할 수 있기 때문에 설계 및 재해석을 효율적으로 수행할 수 있다.

• 한국방송∙미디어공학회:학술대회논문집
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• 한국방송∙미디어공학회 2016년도 하계학술대회
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• pp.260-263
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• 2016

Recently high dynamic range imaging technique is hot issue in computer graphic area. We present a progressive tone mapping algorithm, which is based on weighted least squares optimization framework. Our approach combines weighted leastsquaresfiltering with iCAM06, for showing more perceptual high dynamic range images in conventional display, while avoiding visual halo artifacts. We decompose high dynamic range image into base layer and detail layer. The base layer has large scale variation, it is obtained by using weighted least squares filtering, and then the base layer incorporates iCAM06 model. Then, adaptive compression on the base layer according to human visual system. Only the base layer reduces contrast, and preserving detail. The resultshows more perceptual color appearance and preserve fine detail, while avoiding common artifacts.

• Earthquakes and Structures
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• 제12권5호
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• pp.569-581
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• 2017

The Monte Carlo Simulation (MCS) based seismic fragility analysis (SFA) approach allows defining more realistic relationship between failure probability and seismic intensity. However, the approach requires simulating large number of nonlinear dynamic analyses of structure for reliable estimate of fragility. It makes the approach computationally challenging. The response surface method (RSM) based metamodeling approach which replaces computationally involve complex mechanical model of a structure is found to be a viable alternative in this regard. An adaptive moving least squares method (MLSM) based RSM in the MCS framework is explored in the present study for efficient SFA of existing structures. In doing so, the repetition of seismic intensity for complete generation of fragility curve is avoided by including this as one of the predictors in the response estimate model. The proposed procedure is elucidated by considering a non-linear SDOF system and an existing reinforced concrete frame considered to be located in the Guwahati City of the Northeast region of India. The fragility results are obtained by the usual least squares based and the proposed MLSM based RSM and compared with that of obtained by the direct MCS technique to study the effectiveness of the proposed approach.

• 한국전산구조공학회논문집
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• 제36권1호
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• pp.67-74
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• 2023

A meshless technique using the geometric conservation least-squares method (GC-LSM) was devised to discretize the governing equation of linear elasticity. Although the finite-element method is widely used for structural analysis, a meshless method was developed because of its advantages in a moving grid system. This work is the preliminary phase for developing a fully meshless-based fluid-structure interaction solver. In this study, Cauchy's momentum equation was discretized in strong form using GC-LSM for the structural domain, and the Newmark beta method was used for time integration. The solver was validated in 1D, 2D, and 3D benchmarking problems. Static and dynamic results were obtained. The results are more accurate than those of analytic solutions.

• 한국해안해양공학회지
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• 제4권3호
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• pp.139-145
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• 1992

본 논문에서는 2차원 수리모형실험시 인사파와 반사파를 분리할 수 있는 기법에 대해서 연구하였다. 계측오업의 제곱의 합을 최소화하는 방법을 이용하여 입, 반사파를 분리하는 기법을 체계적으로 수식화하였다. 이 분리기법은 규칙 및 불규칙 파낭조건에 대해서 적용이 가능하다. 본 방법의 타당성 및 적용성을 파악하기 위한 규칙 및 불규칙파에 대한 수치실험결과, 계측오차가 없는 경우는 거의 완벽하게 분리가 가능하며, 계측오차의 정도가 입사파고의 30% 정도일 경우에도 좋은 결과를 제시하는 것을 알 수 있었다. 또한 수리실험을 통한 실제상황으로의 적용성 검토도 수행하였다.

• 자원환경지질
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• 제14권3호
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• pp.193-201
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• 1981

수평다층(水平多層) 지질구조(地質構造)모델에 있어서 외견전기비저항곡선(外見電氣比抵抗曲線)의 자동해석(自動解析)에 최소자승법(最小自乘法)을 적용(適用)하여 보았다. 이 방법(方法)은 digital filtering 법(法)과 종합(綜合)된 damped least-squares algorithm으로 구성된 것으로서, 일반적(一般的)으로 사용(使用)되고 있는 curve-matching 법(法)보다 시간(時間)이 빠르고 정도(精度)도 높다는 것을 알게되었다. 이 반전법(反轉法)을 시험(試驗)하기 위해서 한개의 이론(理論)데이터와 3개의 현장탐사(現場探査) 결과(結果)를 선택(選擇)하여 해석(解析)하였다. 3층(層) 지질구조(地質構造)모델로부터 나오는 이론(理論)데이터의 해석(解析)을 통(通)하여 이 방법(方法)의 특징(特徵)을 파악(把握)할 수 있고, 또 종래(從來)의 Curve-matching법(法)에는 없는 명확(明確)한 특징(特徵)이 나타났다. 더우기 반전법(反轉法)의 유효성(有效性)은 현장탐사(現場探査) 결과(結果)의 해석(解析)에 의해서도 알 수 있었다. 그 때의 최적(最適) 지질구조(地質構造)모델은 시굴(試掘)로 확인(確認)된 지하구조(地下構造)와 일치(一致)함을 알 수 있었다.

• 전자공학회논문지B
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• 제29B권1호
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• pp.85-93
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• 1992

In this paper, we propose a parameter-free smoothing method for speckle images, i.e., an adaptive least squares image smoothing technique implemented in a multistep environment. The pertinent smoothing window size at a given pixel is determined by the discontinuity measure which is defined by the ratio of the local variance and mean squares of intensity values of pixels over the smoothing window centered there. The mode of the discontinuity measure at each step is estimated to replace the noise variance parameter that is required in the adaptive smoothing. Computer simulation shows that the proposed multistep technique can smooth homogeneous regions satisfactorily while preserving fine details near boundaries.

• 한국통신학회논문지
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• 제38C권3호
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• pp.288-295
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• 2013

본 논문에서는 4S (Ship to Ship, Ship to Shore) 해상통신을 위해 다른 채널 조건 하에서 기존의 채널 추정 기법을 비교하였다. 일반적으로 수신 신호는 다중경로나 부호 간 간섭에 의해 손상을 받게 된다. 시간 변화 다중 페이딩 채널의 추정은 수신기에서 어려운 작업이며, 적절한 채널 추정 필터를 사용함으로써 수신기의 성능을 향상시킬 수 있다. 모의실험은 MATLAB을 사용하여 AWGN (Additive White Gaussian Noise), Rician, Rayleigh 채널에서 채널 추정 알고리즘으로 주로 사용되어지는 LMS (Least Mean Square)와 RLS (Recursive Least-Squares) 알고리즘을 비교 하였다.