• 한국해양공학회지
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• 제10권3호
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• pp.96-104
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• 1996

Hamilton's principle is used to derive Euler-Lagrange equations for free surface flow problems of incompressible ideal fluid. The velocity field is chosen to satisfy the continuity equation a priori. This approach results in a hierarchial set of governing equations consist of two evolution equations with respect to two canonical variables and corresponding boundary value problems. The free surface elevation and the Lagrange's multiplier are the canonical variables in Hamilton's sense. This Lagrange's multiplier is a velocity potential defined on the free surface. Energy is conserved as a consequence of the Hamiltonian structure. These equations can be applied to waves in water of finite depth including generalization of Hamilton's equations given by Miles and Salmon.

• 대한수학회지
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• 제36권5호
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• pp.959-1008
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• 1999

This paper considers foundational issues related to connections in the tangent bundle of a manifold. The approach makes use of second order tangent vectors, i.e., vectors tangent to the tangent bundle. The resulting second order tangent bundle has certain properties, above and beyond those of a typical tangent bundle. In particular, it has a natural secondary vector bundle structure and a canonical involution that interchanges the two structures. The involution provides a nice way to understand the torsion of a connection. The latter parts of the paper deal with the Levi-Civita connection of a Riemannian manifold. The idea is to get at the connection by first finding its.spary. This is a second order vector field that encodes the second order differential equation for geodesics. The paper also develops some machinery involving lifts of vector fields form a manifold to its tangent bundle and uses a variational approach to produce the Riemannian spray.

• 한국식품과학회지
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• 제34권6호
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• pp.1062-1066
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• 2002

참깨의 원산지를 판별하기 위하여 일반성분 및 low field NMR을 이용하여 relaxation time을 측정하였다. 일반성분으로는 한국산, 중국산 및 수단산간의 유의적인 차이는 없었으나 NMR 데이터 중 CPMG를 제외한 나머지 측정항목인 $T_1-IR,\;T_1-SR,\;T_2-SE,\;SFC$는 원산지별 유의적인 차이를 보였다. 가장 유의적인 차이가 높았던 SFC, IR, SR을 이용하여 정준 판별분석을 시행한 결과 수단산은 100% 판별이 가능하였고, 한국산 및 중국산은 각각 80%, 90%의 정확성을 나타내었으며, 5가지 NMR 측정항목을 모두 사용하여 판별한 결과 한국산, 중국산, 수단산이 각각 95%, 90%, 100%의 원산지 판별이 가능하였다.

• 대한수학회논문집
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• 제9권2호
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• pp.393-400
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• 1994

Let M(f,η,ξ,g) be a (2m ＋ 1)-dimensional Sasakian manifold with soldering form dp ∈ ΓHom(Λ/sup q/TM, TM) (dp: canonical vector-valued 1-form) where f,η,ξ and g are the (1,1)-tensor field, the structure 1-form, the structure vector field and the metric tensor of M, respectively.(omitted)

• Journal of Microbiology and Biotechnology
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• 제17권10호
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• pp.1645-1654
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• 2007

The total methylotrophic population associated with rice plants from different cultivars was enumerated at three different stages: vegetative, flowering, and harvesting. The bacterial population in the leaf, rhizosphere soil, endophytic in the stem and roots, and epiphytic in the florets and grains were determined from four rice cultivars, Il-mi, Nam-pyeoung, O-dae, and Dong-jin, sampled from three different field sites. The methylotrophic bacteria isolated on AMS media containing 0.5% methanol as the sole carbon source uniformly showed three distinct morphologies, which were recorded as separate groups and their distribution among the various samples was determined using the ecophysiological index. The growth stage at the time of sampling had a more significant effect on the methylotrophic population and their distribution than the field site or cultivar. A similar effect was also observed for the PPFMs, where their population in different plant parts increased from V10 to R4 and then decreased towards stage R9. A canonical discriminant analysis of the PPFM population from different parts of rice showed clear variations among the cultivars, sampled sites, and growth stages, although the variations were more prominent among the growth stages.

• Journal of Astronomy and Space Sciences
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• 제31권4호
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• pp.285-294
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• 2014

The uneven mass distribution of the Moon highly perturbs the lunar spacecrafts. This uneven mass distribution leads to peculiar dynamical features of the lunar orbiters. The critical inclination is the value of inclination which keeps the deviation of the argument of pericentre from the initial values to be zero. Considerable investigations have been performed for critical inclination when the gravity field is assumed to be symmetric around the equator, namely for oblate gravity field to which Earth's satellites are most likely to be subjected. But in the case of a lunar orbiter, the gravity field of mass distribution is rather asymmetric, that is, sectorial, and tesseral, harmonic coefficients are big enough so they can't be neglected. In the present work, the effects of the first sectorial and tesseral harmonic coefficients in addition to the first zonal harmonic coefficients on the critical inclination of a lunar artificial satellite are investigated. The study is carried out using the Hamiltonian framework. The Hamiltonian of the problem is cconstructed and the short periodic terms are eliminated using Delaunay canonical variables. Considering the above perturbations, numerical simulations for a hypothetical lunar orbiter are presented. Finally, this study reveals that the critical inclination is quite different from the critical inclination of traditional sense and/or even has multiple solutions. Consequently, different families of critical inclination are obtained and analyzed.

• 대한수학회보
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• 제45권2호
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• pp.269-271
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• 2008

We prove that a full jack field does not exist on the sum of a trivial bundle and the canonical bundle on $G_{2,4}$, the Grassmanian of 2-planes in 4-space.

• 대한수학회논문집
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• 제33권4호
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• pp.1097-1102
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• 2018

Let A and B be matrices which are polynomials in r pairwise commuting nilpotent matrices over a field. We give a sufficient condition for the null space of $A^i$ to equal that of $B^i$ for all i, in particular, for A and B to be similar.

• 대한전자공학회논문지TC
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• 제47권12호
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• pp.24-30
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• 2010

Super-RENS (Super-Resolution Near-field Structure) 디스크 시스템은 BD (Blu-ray Disc) 이후의 차세대 광 기록 저장 시스템의 유망한 후보이다. 따라서 super-RENS 시스템을 위한 등화기 개발과 성능 분석을 위해 정확하고 신뢰성 있는 채널 모델링은 매우 중요하다. 본 논문에서는 super-RENS 시스템의 모델링을 위해 SCPWL (Simplicial Canonical Piecewise-Linear) 모델을 적용하고자 한다. Super-RENS 디스크로부터 획득한 RF 신호 샘플들을 사용하여 모의실험을 수행한 결과, super-RENS 시스템의 비선형 모델링을 위해 SCPWL 모델이 효과적으로 활용될 수 있다는 것을 확인하였다.

• 한국지능시스템학회논문지
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• 제11권7호
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• pp.653-658
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• 2001

In this paper, we find the necessary and sufficient conditions for the discrete time nonlinear system to be transformed into observable canonical form by state coordinates change. Unlike the continuous time case, our theorems give the desired state coordinates change without solving partial differential equations. Also, our approach is applicable to both autonomous systems and control systems by slight change of the definition of the vector field.