• 천문학회지
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• 제33권3호
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• pp.159-163
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• 2000

We have investigated one dimensional steady flow model of a typical magnetic flux tube in the solar transition region constrained to observed Differential Emission Measure (DEM) for the average quiet-Sun deduced by Raymond & Doyle (1981) with a flux tube geometry conforming to Doppler shifts of UV lines measured by Chae, Yun & Poland (1998). Because local heating and filling factor in the transition region are not well known, we considered two extreme cases, one characterized by the filling factor= 1 ('filled-up model') and the other set by local heating=0 ('not-heated model'). We examined how much the heating is required for the flux tube by recomputing a model through adjustment of the filling factor in such a way that 'not-heated model' accounts for the observed DEM.

• 호남수학학술지
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• 제40권1호
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• pp.47-59
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• 2018

We define the $e^{\alpha}_1e^{\alpha}_3$-isotropic Smarandache curves of type-1 and type-2, the $e^{\alpha}_1e^{\alpha}_2e^{\alpha}_3$-isotropic Smarandache curve, and the $e^{\alpha}_1e^{\alpha}_2e^{\alpha}_4$-isotropic Smarandache curves of type-1 and type-2. Then we examine these kinds of isotropic Smarandache curve according to Cartan frame in the complex 4-space $\mathbb{C}^4$ and give some differential geometric properties of these Samarandache curves.

• 한국의학물리학회지:의학물리
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• 제8권2호
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• pp.77-85
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• 1997

방사선치료에 있어서 치료시 방사선영상을 획득하여 치료조사야를 확인하는 것은 매우 중요하다. 따라서 본 연구에서는 액체유전체를 이용하여 portal 영상을 획득할 수 있는 1차원 형태의 액체전리함을 제작하고 그 선형성을 조사하였다. 액체 유전체로는 isooetane (2,2,4-TetraMethyl Pentane)을 사용하였고, 측정기의 구조는 치료용방사선발생장치의 기하학적인 구조를 고려하여 설계하였으며 위치분해능이 2mm, 측정범위가 20 cm가 되도록 설계, 제작하였다. 이렇게 완성된 이온전리함을 사용하여 실제 방사선 조사야에 측정한 결과 4.7%의 미분선형성을 나타내었다.

• Interaction and multiscale mechanics
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• 제2권1호
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• pp.1-14
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• 2009

This paper proposes an interaction field concept based on the field theory of plasticity. Relative deformation between two arbitrary scales, e.g., macro and micro fields, is defined which can be implemented in the crystal plasticity-based constitutive framework. Differential geometrical quantities responsible for describing dislocations and defects in the interaction field are obtained, based on which dislocation density and incompatibility tensors are further derived. It is shown that the explicit interaction exists in the curvature or incompatibility tensor field, whereas no interaction in the torsion or dislocation density tensor field. General expressions of the interaction fields over multiple scales with more than three scale levels are derived and implemented into the present constitutive equation.

• 한국자동차공학회논문집
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• 제1권3호
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• pp.22-33
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• 1993

A theoretical analysis of predicting the detailed motion of a piston-crank mechanism within piston-guide clearance is presented, and the analysis is applied to the piston motion in a gasoline engine. A piston movement program is developed to calculate the piston attitude relative to the bore, the piston to bore impact velocity and kinetic energy loss and the net transverse force acting on the piston. This paper presents the formulation of a set of differential equations governing the transverse and rotational motion of a piston. These equations of motion were solved by well established Runge-Kutta method. As a result of this study, it is possible to predict the effects of piston geometry and piston pin offset on a piston motion and kinetic energy loss.

• Steel and Composite Structures
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• 제32권2호
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• pp.173-187
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• 2019

This study is concerned with the stability of laminated composite plates modelled using Eringen's nonlocal differential model (ENDM) and a novel refined-hyperbolic-shear-deformable plate theory. The plate is assumed to be lying on the Pasternak elastic foundation and is under the influence of an in-plane magnetic field. The governing equations and boundary conditions are obtained through Hamilton's principle. An analytical approach considering Navier series is used to fine the critical bucking load. After verifying with existing results for the reduced cases, the present model is then used to study buckling of the laminated composite plate. Numerical results demonstrate clearly for the first time the roles of size effects, magnetic field, foundation parameters, moduli ratio, geometry, lay-up numbers and sequences, fiber orientations, and boundary conditions. These results could be useful for designing better composites and can further serve as benchmarks for future studies on the laminated composite plates.

• 충청수학회지
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• 제28권1호
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• pp.65-72
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• 2015

The (affine) development of a smooth curve in a smooth manifold M with respect to an arbitrarily given affine connection in the bundle of affine frames over M is well known (cf. S.Kobayashi and K.Nomizu, Foundations of Differential Geometry, Vol.1). In this paper, we get the generalized affine development of a smooth curve $x_t$ ($t{\in}[0,1]$) in M into the affine tangent space at $x_0$ (${\in}M$) with respect to a given generalized affine connection in the bundle of affine frames over M.

• 대한수학회지
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• 제57권6호
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• pp.1335-1345
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• 2020

We will show a rigidity of a Kähler potential of the Poincaré metric with a constant length differential.

• Korean Journal of Mathematics
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• 제28권2호
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• pp.275-284
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• 2020

The aim of this paper is to study the invariant submanifolds of (LCS)_n-manifolds. We study pseudo parallel, generalized Ricci-pseudo parallel and 2-pseudo parallel invariant submanifolds of a (LCS)_n-manifold and get the necessary and sufficient conditions for an invariant submanifold to be totally geodesic and give some new results contribute to differential geometry.

• 대한수학회지
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• 제55권4호
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• pp.987-1004
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• 2018

In this paper, we get several centroaffine invariant properties for a ruled surface in ${\mathbb{R}}^4$ with centroaffine theories of codimension two. Then by solving certain partial differential equations and studying a centroaffine surface with some centroaffine invariant properties in ${\mathbb{R}}^4$, we obtain such a surface is centroaffinely equivalent to a ruled surface or one of the flat centered cyclic surfaces. Furthermore, some centroaffine invariant properties for centered cyclic surfaces are considered.