• 대한수학회논문집
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• 제25권2호
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• pp.161-165
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• 2010

Even though there is a formula for $h^0$(X, $\cal{O}_X(nK_X)$) for a canonical threefold X, it is not easy to compute $h^0$(X, $\cal{O}_X(nK_X)$) because the formula has a term due to singularities. In this paper, we find a way to control the term due to singularities. We show nonvanishing of plurigenus for the case when the index r in the singularity type $\frac{1}{r}$(1, -1, b) is sufficiently large.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1990년도 한국자동제어학술회의논문집(국내학술편); KOEX, Seoul; 26-27 Oct. 1990
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• pp.62-67
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• 1990

A number of performance measures have been proposed for the quantification of dexterity for kinematically redundant manipulators. The use of such measures is especially important for kinematically redundant manipulators since they can satisfy the subtasks such as singularity avoidance and obstacle avoidance in addition to satisfying a specification of end-effector motion. In this paper, the advantages and disadvantages of performance measures proposed up to date are compared through simulations under the same environment. Besides, a new dexterity index for manipulators with multiple degrees of redundancy is proposed and shown to be effective through the simulation.

• 대한수학회보
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• 제54권5호
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• pp.1627-1654
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• 2017

We prove that in the parameter space of M-dimensional Fano complete intersections of index one and codimension two the locus of varieties that are not birationally superrigid has codimension at least ${\frac{1}{2}}(M-9)(M-10)-1$.

• East Asian mathematical journal
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• 제39권1호
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• pp.29-36
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• 2023

In this paper, we consider φ-Laplacian nonlocal boundary value problems with singular weight function which may not be in L¹(0, 1). The existence and nonexistence of positive solutions to the given problem for parameter λ belonging to some open intervals are shown. Our approach is based on the fixed point index theory.

• 로봇학회논문지
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• 제12권2호
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• pp.194-205
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• 2017

A redundantly actuated planar 3-degree-of-freedom parallel mechanism is analyzed to show its high application potential as a haptic device. Its structure along with the closed form forward position solutions is briefly discussed. Then its geometric and kinematic characteristics via singularity analysis, the kinematic isotropy index, and the input-output force transmission ratio are investigated both for the redundantly actuated cases and for the non-redundantly actuated case. In addition, comparative joint torque simulations of the mechanism with different number of redundant actuations as well as without redundant actuation are conducted to confirm the improved joint torque distribution characteristics. Through these analyses it is shown that the geometric and kinematic characteristics of the redundantly actuated mechanism are superior to the ones of the mechanism without redundant actuation. Thus, it can be concluded that the suggested planar mechanism with redundant actuation has a very high potential for haptic device applications.

• 한국전산구조공학회논문집
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• 제15권1호
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• pp.127-136
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• 2002

본 논문은 교량 구조물의 손상위치 및 손상정도를 평가하기 위해 제한된 모드형상을 사용한 손상지수 방법에 기초한 실용적이며 개선된 손상평가 알고리즘을 제안한다. 손상평가 알고리즘에서 손상전 ·후의 구조물로부터 획득한 모드 벡터의 민감도 비에 근거한 손상지수를 사용하여 손상위치의 파악 및 손상정도를 평가한다. 그러나 모드형상의 진폭이 거의 영의 값을 가지는 요소에 손상이 존재하면 모드벡터 민감도 비는 무한대의 값을 가지게 되며, 이는 손상평가를 불가능하게 한다. 따라서 본 논문에서는 구조물의 모드형상과 비례하는 민감도 필터를 도입한 개선된 기법을 적용함으로써, 이러한 문제점을 극복하였으며 또한 기존의 방법보다 손상위치와 손상정도 평가에 있어 상당한 정확도의 향상을 구현하였다. 제안된 알고리즘을 검증하기 위해 단순보와 2경간 연속보에 대해 손상평가를 수행하였으며, 기존의 방법에 의한 결과와 비교하였다.

• 한국콘텐츠학회논문지
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• 제16권2호
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• pp.666-672
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• 2016

좌심실비대는 심혈관계의 합병증을 유발함으로 임상적으로 문제가 되고 있으며 선별진단이 중요하다. 본 연구에서는 심장초음파상 좌심실비대로 판단된 30~80대의 환자 50명을 대상으로 심전도검사와 비교 분석하였다. 좌심실질량지수와 Sokolow-Lyon 공식에 의해 회귀분석을 하였으며, 두 검사 방법의 적정성을 평가하기 위해 ROC 분석을 이용하였다. 좌심실비대의 위험 요인인 나이와 체질량지수, 수축기 혈압, 확장기 혈압이 좌심실 비대 진단 검사의 기준치와 양의 상관성을 보였다. 심장초음파로 진단된 50명의 환자에서 심전도검사에서는 21명만이 진단되었다. 분석결과로 심장초음파에서는 AUC 99%, 민감도 96%, 특이도 95%, 정확도 95.5%였으며, 심전도검사에서 AUC 76%, 민감도 62%, 특이도 76%, 정확도 68% 인 것으로 나타났다. 좌심실비대 진단에 있어 심장초음파와 심전도검사의 정확도를 비교했을 때 심장초음파가 정확성 높은 검사란 것을 알 수 있었다. 따라서 1차 선별검사로 심전도검사에서 정상 판정을 받더라도, 나이와, 체질량지수, 수축기 혈압, 확장기 혈압에 대한 수치를 고려하여 심장초음파 검사를 고려해야할 필요성이 있다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1989년도 하계종합학술대회 논문집
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• pp.195-201
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• 1989

Voltage collapse is a serious concern to the electirc utility industry. It is common to associate steady-state stability with the ability of the transmission system to transport real power and to associate voltage collapse with the inability to provide reactive power at the necessary locations within the system. An algorithm to directly calculate the critical point of system voltage collapse was presented by the authors. The method (based on the ordinary power flow equations and explicit requirement of singularity of the Jacobian matrix) is basically one degree of freedom with proper load distribution factors. This paper suggests a modified algorithm to increase the degree of freedom, introducing the nonlinear programming technique. The objective function is a distance measure between the present operating point and the closest voltage collapse point. Knowledge of the distance and the most vulnarable bus from the voltage collapse point of view may be used as a useful index for the secure system operation.

• 대한전기학회논문지:전력기술부문A
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• 제48권3호
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• pp.190-196
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• 1999

Continuation power flow has been developed to remove the ill-condition problem caused by singularity of power flow Jacobian at and near at steady-state voltage instability point in conventional power flow. Continuation power flow consists of predictor and corrector. In prddictor, the direction vector at the resent solution is caluculated and the initial guess of next solution is determined at the distance of step length. The selection of step length is a very important part, since computational speed and convergence performance are both greatly affected by the choice of the step length. This paper presents the practical step length selection algorithm using the reactive power generation sensitivith. In numulation, the proposed algorithm is compared with step length selection algorithm using TVI(tangent vector index).

• Structural Engineering and Mechanics
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• 제24권6호
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• pp.665-682
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• 2006

A vibration-based nondestructive damage evaluation technique for a curved thin beam is introduced. The proposed method is capable of detecting, locating, and sizing structural damage simultaneously by using a few of the lower natural frequencies and their corresponding mode shapes before and after a small damage event. The proposed approach utilizes modal flexibilities reconstructed from measured modal parameters. A rigorous system of equations governing damage and curvature of modal flexibility is derived in the context of elasticity. To solve the resulting system of governing equations, an efficient pseudo-inverse technique is introduced. The direct inspection of the resulting solutions provides the location and severity of damage in a curved thin beam. This study confirms that there is a strong linear relationship between the curvature of modal flexibility and flexural damage in the selected class of structures. Several numerical case studies are provided to justify the performance of the proposed approach. The proposed method introduces a way to avoid the singularity and mode selection problems from earlier attempts.