• 한국항만학회지
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• 제10권2호
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• pp.61-68
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• 1996

The main problems in structural analysis by Finite Eelement Method are difficulty in making data file and error estimation. For decreasing these problems' pays. have been suggesting the adaptive mesh refinement and error estimation method. Posteriory error estimation methods suggested by Jang[1], Babuska[2,3], Ohtsubo[8,9], and this paper. Comparing these methods and examine their properties. According this paper, In the problem supposed having singularity, the method suggested by this paper is good, But the problem supposed having no singularity, the method suggested by Jang[1] is good. For decreasing the effect of initial mesh in p-refinement, make application h-refinement at first and apply p-refinement, and confine polynomial's degree to two, for making program simply by plural mesh models are not needed.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2002년도 ICCAS
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• pp.76.5-76
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• 2002

In this paper, we provide a Nash solution to predictive control problem for nonminimum phase singular nonlinear systems. Until now, there is no result on predictive control problem for this class of nonlinear systems. Chen's recent work considered predictive control problem for a class of nonlinear systems with ill-defined relative degree. Since his work is not a result considered in the feedback linearization framework, there is no a result on singular probem in his paper. In contrast to the existing predictive control result, our work considers two main obstacles (singularity and nonminimum phase) in the feedback linearization framework. For a generally formu...

• 대한의용생체공학회:의공학회지
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• 제23권2호
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• pp.81-85
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• 2002

본 논문에서는 의료 영상에 대한 새로운 비견고 워터마킹 알고리듬을 제안한다. 이 알고리듬은 의료 영상의 보안 및 위조 문제를 해결 할 수 있다. 제안한 알고리듬에서는 영상의 고유한 특성을 나타내는 특이점 (singularity)을 추출하여 이를 워터마크로 사용한다. 이때 특이점 추출에는 영상의 에지 성분을 정확하게 추출하는 장점을 갖는 Mallat 웨이브릿 변환을 이용한다. 즉 Mallat 웨이브릿 변환을 통해 생성된 첫 번째 스케일의 수평 및 수직 상세 부대역 (detail subband)을 이용하여 상세 신호에 대한 크기 성분 및 위상 성분을 계산한 후, 이러한 정보들을 이용하여 입력 영상의 국부 계수 최대치 (local modulus maxima, LMM)를 추출한다. LMM은 영상의 고유한 특성을 갖는 특이전을 나타내므로, 어떠한 조작이 가해진 영상의 LMM은 원 영상의 LMM과의 차이를 나타낸다. 따라서 임의의 영상에 대하여 LMM을 구한 후 원 영상의 LMM과 비교함으로써 위조 여부를 판단할 수 있다. 제안한 알고리듬의 성능 평가를 위한 모의 실험을 통하여 제안한 워터마킹 알고리듬은 의료 영상의 위조된 부분을 정확하게 추출하는 것을 확인하였다.

• 대한기계학회논문집A
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• 제20권1호
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• pp.135-145
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• 1996

Order of stress singularities at bonded Edge Corners with two or three dissimilar isotropic Materials is analyzed. The problem is formulated by Mellin transform and characteristic equation is obtained as a determinant of matrix considering boundary conditions. Roots of characterictic equation are determinde by numerical calculations with ward method, from which the order of stress sigularities is obtained. Applying the results to the electronic packaging, the order of stress singularities is obtained. Applying the results to the electronic packaging, the order of stress singularities at bounded edge corners is calculated as a various bouned edge angle with given material combinations. Comparing the results, the optimal material combinaitons of bounded edge corners and bouned edge angle to reduce stress singularity could be determined. It suggests that the results are used to the basic design of electronic packaging reducing the stress singularity.

• 대한수학회지
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• 제37권6호
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• pp.1007-1019
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• 2000

In this paper, we discuss a uniqueness problem for the Cauchy problem of the Euler equation. W give a sufficient condition on the vorticity to show the uniqueness of a class of generalized solution in terms of the generalized solution in terms o the generalized Besov space. The condition allows the iterated logarithmic singularity to the vorticity of the solution. We also discuss the break down (or blow up) condition for a smooth solution to the Euler equation under the related assumption.

• 제어로봇시스템학회논문지
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• 제19권11호
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• pp.998-1003
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• 2013

This study proposes an adaptive control algorithm for lateral motion of a UGV (Unmanned Ground Vehicle) using an NN (Neural Networks). The lateral motion of the UGV can be corrupted with various uncertainties such as side slip. In order to compensate the performance degradation of the UGV under various uncertainties, an NN-based adaptive control is designed by utilizing a virtual control concept. Since both the drift and input gain terms are uncertain, the proposed method adapts the whole terms related to the difference between the nominal and real systems. To avoid a singularity problem with the adaptive control, the affine property of the UGV dynamic model is utilized and the overall closed-loop stability is analyzed rigorously. Finally, numerical simulations using Carsim are performed to validate the effectiveness of the proposed scheme.

• 전산구조공학
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• 제6권3호
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• pp.89-97
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• 1993

지반위에 얹혀진 구형평판을 에너지 방법으로 해석하는 방법에 대한 일반적인 전개이다. 본 논문에서는 기본적으로 지표면과 평판사이의 접촉응력을 가정한 다음 Boussinesque의 식을 적분하여 지표면 혹은 평판의 처짐을 구하는 방법을 시도하였다. 임의의 차수를 갖는 다항식과 Chebychev다항식으로 접촉응력을 가정할 때 Boussinesque의 식을 적분하는 방법을 서술하고 그 결과를 에너지법에 이용하는 과정을 설명하였다. 해석결과 임의차수를 갖는 다항식을 접촉응력 함수로 적당하지 않고, Chebychev다항식이 합당한 것으로 나타났으나 평판 Boundary의 Stress Singularity를 고려한 함수를 선택하면 훨씬 효과적일 것으로 판단되었다.

• 대한수학회지
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• 제37권6호
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• pp.1071-1084
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• 2000

We show that a weak solution of the Cauchy problem for he nonlinear Schrodinger equation, {i∂(sub)t u + ∂$^2$(sub)x u = f(u,u), t∈(-T,T), x∈R, u(0,x) = ø(x).} in the negative solbolev space H(sup)s has a smoothing effect up to real analyticity if the initial data only have a single point singularity such as the Dirac delta measure. It is shown that for H(sup)s (R)(s>-3/4) data satisfying the condition (※Equations, See Full-text) the solution is analytic in both space and time variable. The argument is based on the recent progress on the well-posedness result by Bourgain [2] and Kenig-Ponce-Vega [18] and previous work by Kato-Ogawa [12]. We give an improved new argument in the regularity argument.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제22권2호
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• pp.101-113
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• 2018

The dual singular function method(DSFM) is a numerical algorithm to get optimal solution including corner singularities for Poisson and Helmholtz equations. In this paper, we apply DSFM to solve heat equation which is a time dependent problem. Since the DSFM for heat equation is based on DSFM for Helmholtz equation, it also need to use Sherman-Morrison formula. This formula requires linear solver n + 1 times for elliptic problems on a domain including n reentrant corners. However, the DSFM for heat equation needs to pay only linear solver once per each time iteration to standard numerical method and perform optimal numerical accuracy for corner singularity problems. Because the Sherman-Morrison formula is rather complicated to apply computation, we introduce a simplified formula by reanalyzing the Sherman-Morrison method.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.112-119
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• 2002

In this paper, an Extended Finite Element Method is proposed by adding discontinuity and singularity enrichment functions to the standard FEM approximation. In this method, the singularity and the discontinuity of the crack are efficiently modeled by using initial regular mesh without refining mesh near the crack tip, so that it enables express the asymptotic stress field near crack tip and crack surface successfully. The developed method was verified by evaluating crack tip stress profile and stress intensity factor of mode Ⅰ/mode Ⅱ fracture problems and the results showed the effectiveness and robustness for fracture problem.