• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2015년도 학술발표회
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• pp.488-488
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• 2015

Intermittent streamflow is common phenomenon in arid and semi-arid regions. To manage water resources of intermittent streamflows, stochactic simulation data is essential; however the seasonally stochastic modeling for intermittent streamflow is a difficult task. In this study, using the periodic Markov chain model, we simulate intermittent monthly streamflow for occurrence and the periodic gamma autoregressive and copula models for amount. The copula models were tested in a previous study for the simulation of yearly streamflow, resulting in successful replication of the key and operational statistics of historical data; however, the copula models have never been tested on a monthly time scale. The intermittent models were applied to the Colorado River system in the present study. A few drawbacks of the PGAR model were identified, such as significant underestimation of minimum values on an aggregated yearly time scale and restrictions of the parameter boundaries. Conversely, the copula models do not present such drawbacks but show feasible reproduction of key and operational statistics. We concluded that the periodic Markov chain based the copula models is a practicable method to simulate intermittent monthly streamflow time series.

• Journal of applied mathematics & informatics
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• 제7권3호
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• pp.1029-1038
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• 2000

In this paper, we show that if x is a positively Lyapunov stable point of an expansive homeomorphism with the pseudo-orbit-tracing-property, then x is a periodic point or its positive limit set consists of only one periodic orbit, and their periods are predictable. We give a necessary and sufficient condition that a basic set is to be a sink or source. Also, we consider some dynamical properties of basic sets.

• 대한수학회보
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• 제52권1호
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• pp.149-157
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• 2015

We show that $C^1$-generically, the shadowable chain component of a $C^1$-vector field containing a hyperbolic periodic orbit is hyperbolic if it is locally maximal.

• 충청수학회지
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• 제24권4호
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• pp.631-638
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• 2011

In this paper, we prove that for $C^1$ generically, if every hyperbolic periodic point in a chain component is uniformly far away from being nonhyperbolic, and it is $C^1$-robustly average shadowable, then the chain component is hyperbolic.

• 폴리머
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• 제34권4호
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• pp.289-293
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• 2010

비스트리에톡시시릴에탄(bis(triethoxy silyl) ethane)을 전구체로 도데실 트리메틸암모늄 브로마이드(dodecyl trimethyl ammonium bromide), 세틸 트리메틸암모늄 브로마이드(cetyl trimethyl ammonium bromide), 그리고 옥타데실 트리메틸암모늄 브로마이드(octadecyl trimethyl ammonium bromide)를 구조유도체로 사용하여 주기적인 메조포러스 유기실리카(periodic mesoporous organosilicas)(PMO)를 합성하였다. 합성된 PMO의 경우 구조유도 체로서 사용한 계면활성제의 알킬기가 증가할수록 PMO의 표면적과 기공부피가 감소하였으나 기공의 직경에는 영향 이 없었다. 그리고 합성된 PMO에 폴리에틸렌을 삽입한 결과 사용한 구조유도체의 알킬기의 크기에 따라서 폴리에 틸렌의 삽입과정에 많은 영향이 있었으나, 폴리(에틸렌 옥사이드)의 경우 합성된 PMO의 특성에 영향이 거의 없음을 XRD와 DSC로 확인하였다. 또한, 고분자의 열안정성을 확인한 결과 PMO에 삽입된 고분자의 열분해 온도가 증가함 을 알 수 있었다.

• 대한조선학회논문집
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• 제28권2호
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• pp.228-240
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• 1991

균열진전에 관한 많은 실험결과는 피로 균열진전 과정이 확률과정(stochastic process)임을 보여주고 있다. 따라서, 피로 균열진전에 관한 연구는 확률론적 기반에서 다루어져야 한다. 본 연구에서는 균열의 진전과정을 discrete Markov process로 가정하여, Bogdanoff가 제안한 Markov chain model(MCM)을 이용하여 구조물의 신뢰도를 평가할 수 있는 방법을 제시한다. 본 연구에서는 구조부재의 파괴형태로 누출, 소성붕괴 그리고 취성파괴를 취하였으며, 초기 균열크기의 변동성, 검사의 효과 등이 고려되었다. 또한, 불규칙 하중은 등가음력의 개념을 도입하여 처리하였다. 그리고, 구조물에의 계산례를 통하여 본 연구의 유용성을 보였다.

• Journal of the Korean Society for Industrial and Applied Mathematics
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• 제12권3호
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• pp.139-151
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• 2008

We investigate a three species food chain system with Lotka-Volterra type functional response and impulsive perturbations. We find a condition for the local stability of prey or predator free periodic solutions by applying the Floquet theory and the comparison theorems and show the boundedness of this system. Furthermore, we illustrate some examples.

• Kyungpook Mathematical Journal
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• 제48권3호
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• pp.515-527
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• 2008

We investigate a three species food chain system with a Holling type IV functional response and impulsive perturbations. We find conditions for local and global stabilities of prey(or predator) free periodic solutions by applying the Floquet theory and the comparison theorems.

• 대한수학회논문집
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• 제9권4호
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• pp.857-872
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• 1994

A PB-chain(Poincare-Birkhoff chain) is by definition a pair of elliptic and hyperbolic n-periodic orbits for a mapping and its existence has been well established numerically or analytically in many particular occasions such as in standard maps or twist maps [1, 8, 9] or Henon maps [1, 2, 12]. This paper gives focus on the investigaton of the appearance of such a PB-chain in a one-parameter family of general area-preserving maps and is in fact a generalization of the results given in [12] for a one-parameter family of specific area-preserving maps, so called Henon maps.

• 대한수학회논문집
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• 제24권2호
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• pp.215-226
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• 2009

For a class of Holling type II food chain systems with biological and chemical controls, we give conditions of the local stability of prey-free periodic solutions and of the permanence of the system. Further, we show the system is uniformly bounded.