• 대한수학회지
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• 제36권1호
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• pp.159-171
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• 1999

We formulate and study a finite element method for a linearized steady state, compressible, viscous Navier-Stokes equations in 2D, based on the discontinuous Galerkin method. Dislike the standard discontinuous galerkin method, we do not assume that the triangle sides be bounded away from the characteristic direction. the unique stability follows from the inf-sup condition established on the finite dimensional spaces for the (incompressible) Stokes problem. An error analysis having a jump discontinuity for pressure is shown.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1995년도 가을 학술발표회 논문집
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• pp.153-160
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• 1995

Mixed finite element formulations for incompressible materials show pressure oscillations or pressure modes in four-node quadrilateral elements. The criterion for the stability in the pressure solution is the so-called Babufka-Brezzi stability condition, and the four-node elements based on mixed variational principles do not appear to satisfy this condition. In this study, a pressure continuity residual based on the pressure discontinuity at element edges is used to study the stabilization of pressure solutions in bilinear displacement-constant pressure four-node quadrilateral elements. It is shown that the pressure solutions, although stable, exhibit sensitivity to the stabilization parameters.

• 한국환경복원기술학회지
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• 제15권1호
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• pp.119-132
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• 2012

In order to connect eco-corridor and to harmonize with natural environment, it is necessary to construct small debris barrier. Therefore, we will evaluate applicability of small debris barrier which made of tetrapod utilized in construction of seashore protection facilities and breakwater. From result compared with the adaptation processes in fields, tetrapod were stabilized to critical tractive force. Stability evaluation method on sliding and overturn of tetrapod debris barrier was developed, and hereafter could be applied to similar debris barriers. According to results analyzed to continuity on sediment supply in debris barrier, boulders were deposited in upstream and gravels were deposited in downstream. Therefore, tetrapod debris barrier will be able to prevent in the long-term the erosion of river bed in down-stream, and the maintenance is easy because dredging is not necessary. Current were formed in between the tetrapod provided eco-corridors for fishes and shellfishes.

• International Journal of Control, Automation, and Systems
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• 제6권5호
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• pp.651-659
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• 2008

Autoreclosing techniques have been used in power systems to maintain system stability and continuity of supply. Environmental and economical issues have driven significant increases in the development of distributed generation (DG). DG connected to distribution systems, however, may impose negative influences with respect to power quality, protection, and stability, because DG can cause some challenges to protection, especially to reclosing. For this reason, in order to improve the reliability and safety of the distribution system, the rules and guidelines suggest that the DG system needs to be rapidly disconnected from the system before reclosing. We present, in this paper, an adaptive reclosing algorithm considering the DG. The algorithm consists of an angle oscillation's judgment, the emergency extended equal-area criterion (EEEAC), the calculation of an optimal reclosing time, and a reconnection algorithm. Our simulation results for three different DG technologies with Electromagnetic Transient Program (EMTP) indicate that we can maintain transient stability while the DG is protected against disturbances.

• 전기학회논문지
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• 제56권2호
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• pp.227-232
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• 2007

The autoreclosing is applied to power system for maintaining system stability and continuity of supply. Developments on distributed generation(DG) grows significantly by environmental issues and economical issues. If the DG is connected to distribution system, the DG influences the technical aspects such as power quality, protection and stability. It causes the challenges to protection, especially to reclosing. In order to achieve reliability and safety of the distribution system, the rules and guidelines suggest that the DG units should be rapidly disconnected from the network before the reclosing. If the DG is disconnected whenever the fault occurs, it cannot be utilized effectively. This paper presents the adaptive reclosing algorithm considering the DG. The algorithm consists of angle oscillation's judgment, EEEAC(Emergency Expanded Equal-Area Criterion), calculation of optimal reclosing time and re-connection algorithm. The simulation is implemented for the DG technology by using EMTP MODELS. The simulation results show that the transient stability is maintained and the DG is protected against disturbance.

• 한국소음진동공학회논문집
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• 제13권12호
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• pp.947-955
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• 2003

This research analyzes the dynamic stability of stiffened plates on elastic foundations using the finite element method. For analyzing the stiffened plates, both the Mindlin plate theory and Timoshenko beam-column theory were applied. In application of the finite element method, 8-nodes serendipity element system and 3-nodes finite element system were used for plate and beam elements, respectively Elastic foundations were modeled as the Pasternak foundations in which the continuity effect of foundation is considered. In order to verify the theory of this study, solutions obtained by this analysis were compared with the classical solutions in open literature and experimental solutions. The dynamic stability legions of stiffened plates on Pasternak foundations were determined according to changes of in-plane stresses, foundation parameters and dimensions of stiffener.

• 한국전자통신학회논문지
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• 제6권1호
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• pp.111-117
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• 2011

본 논문에서는 클라이언트 가상화 기술을 이용하여 로컬 컴퓨팅 환경의 성능 저하를 최소화 하고 가상화된 사용자 영역에서 사용자가 필요한 기능을 사용할 수 있도록 효율적으로 제공하며, 로컬 컴퓨팅 환경의 중요정보 보호와 성능의 안정성 및 지속성을 유지하였다. 또한 로컬 컴퓨팅 환경 뿐만 아니라 악성코드와 같은 공격으로부터 가상화된 영역을 보호하기 위한 방법을 제안함으로서 가상화된 영역에 있는 데이터들의 암호화를 통하여 가상화된 사용자 영역의 보안을 극대화시켰다. 가상화를 통해 로컬 컴퓨팅 자원을 그대로 사용하면서 효율적으로 로컬 컴퓨팅 시스템으로부터 하나의 사용자 컴퓨팅 리소스를 분리시키는 것과 같은 효과를 얻을 수 있다.

• 전산구조공학
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• 제8권4호
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• pp.189-198
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• 1995

비압축성 물체를 위한 일반적인 유한요소 공식화는 흔히 사용되는 사각형요소에서조차 압력해의 진동화(oscillations) 또는 pressure modes 현상을 나타낸다. 압력해의 안정화를 위한 규준은 소위 Babuska-Brezzi 안정조건이며, 위의 요소들은 이 조건을 만족시키지 못한다. 본 연구에서는 선형변위해와 상수값의 압력해를 갖는 사각형요소 사용시 압력해를 안정화시키기 위해 요소의 변에서 발생하는 불연속압에 근거한 압력연속여분치를 사용한다. 이 압력여분치를 비압축성 탄성론으로부터 유도되는 Q1P0요소에 적용하며 매개변수의 변화에 따른 수치해의 안정화의 정도를 연구한다. 압력해는 압력 여분치 사용시 안정화될 수 있으며, 해의 안정화는 매개변수에 민감성을 나타내었다.

• 대한수학회보
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• 제51권1호
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• pp.221-227
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• 2014

Our goal is to relax a sufficient condition for the exponential almost sure stability of a certain class of stochastic differential equations. Compared to the existing theory, we prove the almost sure stability, replacing Lipschitz continuity and linear growth conditions by the existence of a strong solution of the underlying stochastic differential equation. This result is extendable for the regime-switching system. An explicit example is provided for the illustration purpose.

• 한국도서관정보학회지
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• 제44권3호
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• pp.5-27
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• 2013

이 연구의 목적은 미국의 '한 책, 한 도시' 지역사회 독서운동 확산의 시기적 특성 및 지속성에 관하여 살펴보는 것이다. 2013년 6월까지 미국의회도서관 도서센터 웹사이트에 등록된 584개 '한 책' 프로젝트들의 확산 현황 및 특성을 태동기 (1998년-2001년), 성장기 (2002년-2006년) 및 재도약기 (2007년-현재)의 세 시기로 나누어 살펴보았다. 또한 주요한 '한 책' 프로젝트들의 웹사이트 등을 분석하여 적어도 50개(8.9%) 이상 '한 책' 프로젝트들의 지속성, 특히 초기에 시작된 '한 책' 프로젝트들의 안정성을 확인하였다. 지속적인 일부 '한 책' 프로젝트의 새로운 변화 모색 및 'The Big Read' 이니셔티브를 통한 '한 책' 독서운동 모형의 확산 추이는 향후 주목할 만하다.