• Title/Summary/Keyword: 4-Manifold

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SUBMAUFOLDS OF AN ALMOST QUATERNIONIC KAEHLER PRODUCT MANIFOLD

  • Kang, Tae-Ho;Nam, Hyo-Chang
    • Bulletin of the Korean Mathematical Society
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    • v.34 no.4
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    • pp.653-665
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    • 1997
  • We define an almost quaternionic Kaehler product manifold and study its submanifolds. Moreover we construct the curvature tensor of the product manifold of two quaternionic forms.

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CERTAIN INFINITESIMAL TRANSFORMATIONS ON QUATERNIONIC KAHLERIAN MANIFOLDS

  • JIN SUK PAK;DAE WON YOON
    • Communications of the Korean Mathematical Society
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    • v.13 no.4
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    • pp.817-823
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    • 1998
  • In the present paper, we study conformal and projective Killing vector fields and infinitesimal Q-transformations on a quaternionic Kahlerian manifold, and prove that an infinitesimal conformal or projective automorphism in a compact quaternionic Kahlerian manifold is necessarily infinitesimal automorphism.

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FlexDesigner:Object-Oriented Non-manifold Modeling Kernel with Hierarchically Modularized Structure (FlexDesigner:계층적으로 모듈화된 주초의 객체 지향 방식 비다양체 모델링 커널)

  • 이강수;이건우
    • Korean Journal of Computational Design and Engineering
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    • v.2 no.4
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    • pp.222-236
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    • 1997
  • Conventional solid or surface modeling systems cannot represent both the complete solid model and the abstract model in a unified framework. Recently, non-manifold modeling systems are proposed to solve this problem. This paper describes FlexDesigner, an open kernel system for modeling non-manifold models. It summarizes the data structure for non-manifold models, system design methodology, system modularization, and the typical characteristics of each module in the system. A data structure based on partial-topological elements is adopted to represent the relationship among topological elements. It is efficient in the usage of memory and has topological completeness compared with other published data structures. It can handle many non-manifold situations such as isolate vertices, dangling edges, dangling faces, a mixed dimensional model, and a cellular model. FlexDesigner is modularized hierarchically and designed by the object-oriented methodology for reusability. FlexDesigner is developed using the C++ and OpenGL on both SGI workstation and IBM PC.

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LOW CYCLE THERMAL FATIGUE OF THE ENGINE EXHAUST MANIFOLD

  • Choi, B.L.;Chang, H.;Park, K.H.
    • International Journal of Automotive Technology
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    • v.5 no.4
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    • pp.297-302
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    • 2004
  • This paper presents the low cycle thermal fatigue of the engine exhaust manifold subject to thermo-mechanical cyclic loading. As a failure of the exhaust manifold is mainly caused by geometric constraints of the less expanded inlet flange and cylinder head, the analysis is based on the exhaust system model with three-dimensional temperature distribution and temperature dependent material properties. The result show that large compressive plastic deformations are generated at an elevated temperature of the exhaust manifold and tensile stresses are remained in several critical zones at a cold condition. From the repetition of these thermal shock cycles, maximum plastic strain range (0.454%) could be estimated by the stabilized stress-strain hysteresis loops. It is used to predict the low cycle thermal fatigue life of the exhaust manifold for the thermal shock test.

On Semiparallel and Weyl-semiparallel Hypersurfaces of Kaehler Manifolds

  • Ozgur, Cihan;Murathan, Cengizhan;Arslan, Kadri
    • Kyungpook Mathematical Journal
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    • v.49 no.1
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    • pp.133-141
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    • 2009
  • We study on semiparallel and Weyl semiparallel Sasakian hypersurfaces of Kaehler manifolds. We prove that a (2n + 1)-dimensional Sasakian hypersurface M of a (2n+2)-dimensional Kaehler manifold $\widetilde{M}^{2n+2}$ is semiparallel if and only if it is totally umbilical with unit mean curvature, if dimM = 3 and $\widetilde{M}^4$ is a Calabi-Yau manifold, then $\widetilde{M}$ is flat at each point of M. We also prove that such a hypersurface M is Weyl-semiparallel if and only if it is either an ${\eta}$-Einstein manifold or semiparallel. We also investigate the extended classes of semiparallel and Weyl semiparallel Sasakian hypersurfaces of Kaehler manifolds.

Generic submanifolds of a quaternionic kaehlerian manifold with nonvanishing parallel mean curvature vector

  • Jung, Seoung-Dal;Pak, Jin-Suk
    • Journal of the Korean Mathematical Society
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    • v.31 no.3
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    • pp.339-352
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    • 1994
  • A sumbanifold M of a quaternionic Kaehlerian manifold $\tilde{M}^m$ of real dimension 4m is called a generic submanifold if the normal space N(M) of M is always mapped into the tangent space T(M) under the action of the quaternionic Kaehlerian structure tensors of the ambient manifold at the same time.The purpose of the present paper is to study generic submanifold of quaternionic Kaehlerian manifold of constant Q-sectional curvature with nonvanishing parallel mean curvature vector. In section 1, we state general formulas on generic submanifolds of a quaternionic Kaehlerian manifold of constant Q-sectional curvature. Section 2 is devoted to the study generic submanifolds with nonvanishing parallel mean curvature vector and compute the restricted Laplacian for the second fundamental form in the direction of the mean curvature vector. As applications of those results, in section 3, we prove our main theorems. In this paper, the dimension of a manifold will always indicate its real dimension.

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Developing a computer program for simulation of 4 cycle diesel engine including intake & exhaust system (흡.배기계통을 포함한 4행정사이클 디젤기관의 성능시뮤레이션 프로그램의 개발)

  • 최재성
    • Journal of Advanced Marine Engineering and Technology
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    • v.13 no.3
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    • pp.64-71
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    • 1989
  • In this paper, a computer program for simulation of 4 cycle diesel engines including intake and exhaust manifold system is developed. The wave action theory is applied for optimization of the intake and exhaust manifold system. The calculation results of this computer program is finely accurate and agreed well with experimental results. Accordingly, it is recognized that the developed computer program can be utillized very usefully for the design of intake and manifold system. And then, influential factors of the engine performance in the design of intake manifold is numerically investigated by the calculation only. As the results it is concluded that the inertia one of the dynamic effects on the intake and exhaust maninfold affects mainly the engine performance and the pulsation one is a side effect.

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THE CURVATURE OF HALF LIGHTLIKE SUBMANIFOLDS OF A SEMI-RIEMANNIAN MANIFOLD OF QUASI-CONSTANT CURVATURE

  • Jin, Dae Ho
    • The Pure and Applied Mathematics
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    • v.19 no.4
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    • pp.327-335
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    • 2012
  • We study half lightlike submanifolds M of semi-Riemannian manifolds $\widetilde{M}$ of quasi-constant curvatures. The main result is a characterization theorem for screen homothetic Einstein half lightlike submanifolds of a Lorentzian manifold of quasi-constant curvature subject to the conditions; (1) the curvature vector field of $\widetilde{M}$ is tangent to M, and (2) the co-screen distribution is a conformal Killing one.

LIGHTLIKE HYPERSURFACES OF A SEMI-RIEMANNIAN MANIFOLD OF QUASI-CONSTANT CURVATURE

  • Jin, Dae-Ho
    • Communications of the Korean Mathematical Society
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    • v.27 no.4
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    • pp.763-770
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    • 2012
  • In this paper, we study the geometry lightlike hypersurfaces (M, $g$, S(TM)) of a semi-Riemannian manifold ($\tilde{M}$, $\tilde{g}$) of quasi-constant curvature subject to the conditions: (1) The curvature vector field of $\tilde{M}$ is tangent to M, and (2) the screen distribution S(TM) is either totally geodesic in M or totally umbilical in $\tilde{M}$.