• Journal of the Korean Data Analysis Society
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• 제20권6호
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• pp.2865-2872
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• 2018

데이터 마이닝 분야에서 개발된 기법에는 연관성 규칙, 군집분석, 의사결정나무, 신경망 등 여러 가지가 있는데 이들 중에서 연관성 규칙은 지지도, 신뢰도, 그리고 향상도 등 여러 가지 연관성 평가 기준을 이용하여 항목들 간에 특정한 연관성을 탐색하는 기법이다(Park, 2014). 이러한 연관성 규칙은 Agrawal et al.(1993)이 처음 제안하였으며, 그 이후로 여러 연구자들에 의해 연구가 진행되고 있으며, 최근에는 교차 엔트로피와 관련된 연구들이 발표되고 있다(Park, 2016b). 본 논문에서는 기존에 발표된 J 측도에 방향성과 순수성을 고려한 순수 대칭적 J 측도를 제안하고 예제를 활용하여 그 유용성에 대해 알아보았다. 그 결과, 동시발생빈도가 증가함에 따라 순수 대칭적 J 측도가 기존의 J 측도와 대칭적 J 측도, 순수 교차 엔트로피 측도보다 훨씬 분명하게 변하는 것을 알 수 있었으며, 불일치빈도의 크기에 따라서도 순수 대칭적 J 측도가 변화하는 폭이 더 커짐에 따라 연관성 유무를 더 분명하게 파악할 수 있었다. 따라서 순수 대칭적 J 측도는 데이터가 존재하는 어느 분야에서든지 연관성 규칙의 평가에 적용이 가능할 것으로 생각된다.

• 대한수학회지
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• 제60권3호
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• pp.537-564
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• 2023

In this paper, we are mainly concerned with two-sided estimates for transition probabilities of symmetric Markov chains on ℤ^d, whose one-step transition probability is comparable to |x - y|^-dϕ_j (|x - y|)^-1 with ϕ_j being a positive regularly varying function on [1, ∞) with index α ∈ [2, ∞). For upper bounds, we directly apply the comparison idea and the Davies method, which considerably improves the existing arguments in the literature; while for lower bounds the relation with the corresponding continuous time symmetric Markov chains are fully used. In particular, our results answer one open question mentioned in the paper by Murugan and Saloff-Coste (2015).

• 대한조선학회지
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• 제19권2호
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• pp.27-31
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• 1982

The practical utilization of the frequency and normal mode equations of uniform Timoshenko beams such as those presented by Huang is not simple due to their highly trancendental nature. In this note largely simplified equations obtained for the fixed-fixed and the free-free boundary conditions, the modes of which are separable into symmetric modes and antisymmetric ones, are given. Numerical results obtains for six common-type boundary conditions show that the quantitative measure of the effect of rotary inertia and shear deformation on the natural frequency is greatly dependent upon the boundary conditions as well as the order number.

• 한국항공운항학회지
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• 제12권3호
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• pp.25-39
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• 2004

An experimental study was quantitatively carried out in order to investigate the influence of flow conditions on a boundary layer in the near-wake of a flat plate. Tripping wires attached at various positions were selected to change flow conditions of a boundary layer in the vicinity of trailing edge. The flows such as laminar, transitional, and turbulent boundary layer at 0.98C from the leading edge are imposed to investigate the evolution of symmetric and asymmetric wake. Measurements were made at freestream velocity of 6.0m/s, and the corresponding Reynolds number is $2.8{\times}10^5$. An x-type hot-wire probe(55P61) was employed to measure at 8 stations in the near-wake region. Test results show that the near-wake of the flat plate for the case of a laminar and transitional boundary layer is sensitive to mean flow shear generated after separation but for the case of turbulent boundary layer is insensitive.