• 대한토목학회논문집
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• 제26권6D호
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• pp.1025-1032
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• 2006

고해상도 위성의 센서모형화는 도면화와 지형공간정보(Geo-spatial Information System)의 응용을 위해서는 필수적인 단계이다. 영상과 대상물과의 기하학적인 관계를 규정하는 센서모형은 크게 엄밀(rigorous)센서모형화와 간략(approximate)센서모형화의 두 가지로 나눌 수 있다. 엄밀센서모형화는 위성의 실제적인 촬영기하를 고려한 것으로 센서의 내외부적인 특성을 알고 있어야 하는 반면에 간략센서모형화 방법은 영상취득기하의 종합적인 이해나 센서의 내외부적인 특성정보를 필요로 하지 않기 때문에 사진측량 커뮤니티에서 많은 관심이 증대되고 있다. 본 연구에서는 고해상도 위성영상의 3차원 위치결정에 이용되고 있는 엄밀센서모형과 다양한 간략센서모형에 대해 비교연구를 수행하였으며 위성영상의 이용목적에 따른 적합한 모형화 방법을 제안하였다. IKONOS 위성영상을 이용한 사례연구를 통하여 엄밀센서모형과 간략센서모형에 대한 비교연구를 수행하였으며, 수집 가능한 지상기준점에 따른 위치정확도를 평가하였다. 간략센서모형화 방법 중에서 편의보정된 다항식비례모형(bias compensated RFM)이 가장 우수하였으며 개량평행투영모형(modified parallel projection)과 평행-중심투영모형(parallel-perspective model)은 적은 수의 기준점을 이용하여 센서모형화가 가능하였다. 또한 간략센서모형화 방법 중 부등각사상변환(affine transformation)은 고해상도 위성의 수평위치결정과 영상간의 등록에 활용가능하다.

• Journal of applied mathematics & informatics
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• 제33권5_6호
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• pp.699-721
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• 2015

This paper investigates the existence of mild solution for a fractional integro-differential equations with a deviating argument and nonlocal initial condition in an arbitrary separable Hilbert space H via technique of approximations. We obtain an associated integral equation and then consider a sequence of approximate integral equations obtained by the projection of considered associated nonlocal fractional integral equation onto finite dimensional space. The existence and uniqueness of solutions to each approximate integral equation is obtained by virtue of the analytic semigroup theory via Banach fixed point theorem. Next we demonstrate the convergence of the solutions of the approximate integral equations to the solution of the associated integral equation. We consider the Faedo-Galerkin approximation of the solution and demonstrate some convergenceresults. An example is also given to illustrate the abstract theory.

• 대한전자공학회논문지
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• 제17권1호
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• pp.23-30
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• 1980

C.T.(전산화 단층 영상 처리) 영상재구성의 경우, 투사되는 광양자(X-ray, positron 등)가 적을 때는 잡음에 의한 효과가 증폭되어 재구성된 화면은 거의 알아 볼 수 없게 된다. 그 경우 화질을 높이깅 nl해서는 재구성 필터를 사영 데이터(projection data)의 신호대잡음비에 따라 수정시켜야 할 필요성이 생긴다. 이 논문에서는 사영 데이터에서 얻은 정보를 사용하여 재구성 필터를 수정하는 방법에 관하여 고찰하고 그에 대한 시뮬레이션을 행하였다. 시뮬레이션의 결과, 이 방법은 재구성 화상에서의 잡음을 줄여, 그 분해능력을 크게 향상시킬 수 있음이 판명되었다. 또한 이 필터를 근사적으로 구현하는 방법에 관하여도 논하고, 그 근사 필터의 회귀적 구성(recursive implementation)의 가능성에 관하여도 언급하였다.

• 대한기계학회논문집A
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• 제27권10호
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• pp.1762-1771
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• 2003

In part of mechanical design analysis, quadrilateral mesh is usually used because it provides less approximate errors than triangular mesh. Over the decades, Paving method has been considered as the most robust method among existing automatic quadrilateral element mesh generation methods. However, it also has some problems such as unpredictable node projection and relatively large element generation. In this study, the aforementioned problems are corrected by updating the Paving method. In so doing, a part of node projection process is modified by classifying nodes based on the interior angles. The closure check process is also modified by adding more nodes while generating elements. The result shows well shaped element distribution in the final mesh without any aforementioned problems.

• East Asian mathematical journal
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• 제28권5호
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• pp.561-567
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• 2012

The approximate solvability of a generalized system for relaxed cocoercive extended general variational inequalities is studied by using the project operator technique. The results presented in this paper are more general and include many previously known results as special cases.

• 대한수학회보
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• 제49권4호
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• pp.829-850
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• 2012

In this paper, we adopt symmetric interior penalty discontinuous Galerkin (SIPG) methods to approximate the solution of nonlinear viscoelasticity-type equations. We construct finite element space which consists of piecewise continuous polynomials. We introduce an appropriate elliptic-type projection and prove its approximation properties. We construct semidiscrete discontinuous Galerkin approximations and prove the optimal convergence in $L^2$ normed space.

• Journal of applied mathematics & informatics
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• 제8권3호
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• pp.721-729
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• 2001

We consider finite element methods applied to a class of Sobolev equations in $R^d$($d{\geq}1$). Global strong superconvergence, which only requires that partitions are quais-uniform, is investigated for the error between the approximate solution and the Ritz-Sobolev projection of the exact solution. Two order superconvervgence results are demonstrated in $W^{1,p}({\Omega})$ and $L_p({\Omega})$ for $2{\leq}p$＜${\infty}$.

• 대한수학회지
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• 제34권3호
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• pp.515-531
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• 1997

In this paper, finite difference method is applied to approximate the generalized solutions of Sobolev equations. Using the Steklov mollifier and Bramble-Hilbert Lemma, a priori error estimates in discrete $L^2$ as well as in discrete $H^1$ norms are derived frist for the semidiscrete methods. For the fully discrete schemes, both backward Euler and Crank-Nicolson methods are discussed and related error analyses are also presented.

• Structural Engineering and Mechanics
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• 제74권5호
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• pp.635-655
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• 2020

The sag effect of long stay cables is one of the key factors restricting further increase in the span of cable-stayed bridges. Based on the formerly proposed concept of long stay cables lifted by an auxiliary suspension cable in cross-strait cable-stayed bridges, corresponding static approximate calculations and analytical theory based on catenary and parabolic cable configurations are established. Taking a main span 1400 m cable-stayed bridge as the research object, three typical lifting conditions and the whole process of auxiliary cable lifting are analyzed and discussed. The results show that the sag effect is effectively reduced. The support efficiency is only improved when the cables are lifted above the original cable chord. Reduction of the horizontal component force of the cable is limited. The equivalent elastic modulus and the vertical support stiffness of the lifted cables are significantly increased with increased horizontal projection length and not sensitive to the change of the lifting point position. The scheme of lifting the cable to the chord midpoint is more economical because of the less steel required for the auxiliary suspension cable, but its effect on improving the vertical support efficiency is limited. The support efficiency is better when the cable is lifted to the cable end tangential to the original cable chord, but the lifting force and the cross-sectional area of the auxiliary suspension cable are doubled. The approximate calculation results of the lifted cables are very close to the numerical analysis results, which verifies the applicability of the approximation method proposed in this study. The results of parabolic approximation calculations are approximately equal to that of catenary cable geometry. As the parabolic approximation analysis theory of lifted cables is more convenient in mathematical processing, it is feasible to use parabolic approximation analysis theory as the analytical method for the conceptual design of lifted cables of super-long span cable-stayed bridges.

• 한국지능시스템학회논문지
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• 제21권4호
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• pp.499-505
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• 2011

본 논문은 파라미터 투영 기법이 필요없는 비선형 계통에 대한 적응 퍼지 슬라이딩 모드 제어를 제안한다. 제어기의 구조를 약간 수정하여 추정된 입력 이득항이 영으로 되지 않도록 보장하고 온라인 동작중의 어떤 순간이라고 추정된 입력 이득항이 영이 되더라도 구현에 문제를 야기하지 않는다. 입력 이득 함수의 하한 추정치만이 필요한것을 제외하면 제안한 제어 기법은 바운딩 파라미터에 대한 정확한 값이 사전에 필요하지 않다. 리아프노프 합성기법을 기초로 전체 제어 시스템이 추종오차가 점근적으로 안정하고 제어기 내의 모든 신호가 유계임을 보장한다. 역진자 시스템의 적용하여 제안한 제어기의 유용성을 입증한다.