• Journal of applied mathematics & informatics
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• v.29 no.1_2
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• pp.497-504
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• 2011

In 1973, B. Y. Chen and K. Yano introduced the special conformally flat space for the generalization of a subprojective space. The typical example is a canal hypersurface of a Euclidean space. In this paper, we study the conditions for the base space B to be special conformally flat in the conharmonically flat warped product space $B^n{\times}_fR^1$. Moreover, we study the special conformally flat warped product space $B^n{\times}_fF^p$ and characterize the geometric structure of $B^n{\times}_fF^p$.

• Journal of applied mathematics & informatics
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• v.27 no.3_4
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• pp.857-864
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• 2009

The special conformally flatness is a generalization of a sub-projective space. B. Y. Chen and K. Yano ([4]) showed that every canal hypersurface of a Euclidean space is a special conformally flat space. In this paper, we study the conditions for the base space B is special conformally flat in the conharmonically flat warped product space $B^n{\times}f\;R^1$.

• Journal of applied mathematics & informatics
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• v.9 no.1
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• pp.441-447
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• 2002

We show that the conharmonical1y flat K-contact find cosymplectic manifolds are local1y Euclidean. Evidently non locally Euclidean conharmonically flat Sasakian manifold does not exist. Moreover we see that conharmonically flat Kenmotsu manifold does not exist and conharmonically flat fibred quasi quasi Sasakian space is locally Euclidean if and only if the scalar curvature of each fibre vanishes identically.

• Publications of The Korean Astronomical Society
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• v.23 no.2
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• pp.47-52
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• 2008

We have performed the flat-fielding correction for the $H{\alpha}$ full-disk monitoring system of KASI (Korea Astronomy and Space Science Institute), which is installed in the Solar Flare Telescope (SOFT) at the top of Bohyun Mountain. For this, we used a new method developed by Chae (2004), to determine the flat pattern from a set of relatively shifted images. Using this method, we successfully obtained the flat pattern for $H{\alpha}$ full-disk observations and compared our result with the image observed in Catania Astrophysical Observatory. The method that we used in this study seems to be quite powerful to obtain the flat image for solar observations. In near future, we will apply this method for the flat-fielding correction of all solar imaging instruments in KASI.

• Communications of the Korean Mathematical Society
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• v.21 no.4
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• pp.729-737
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• 2006

We study Ribaucour transformations on nondegenerate local isometric immersions of Riemannian space forms into Lorentzian space forms with flat normal bundles. They can be explained by dressing actions on the solution space of Lorentzian Grassmannian systems.

• Journal of the Korean Mathematical Society
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• v.45 no.6
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• pp.1577-1590
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• 2008

We study Ribaucour transformations on nondegenerate local isometric immersions of Lorentzian space forms into Lorentzian space forms with the same sectional curvatures which have flat normal bundles. They can be associated to dressing actions on the solution space of Lorentzian Grassmannian systems.

• Bulletin of the Korean Mathematical Society
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• v.40 no.4
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• pp.649-661
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• 2003

The ($\alpha,\;\beta$)-metric is a Finsler metric which is constructed from a Riemannian metric $\alpha$ and a differential 1-form $\beta$. In this paper, we discuss the projective flatness of Finsler spaces with certain ($\alpha,\;\beta$)-metrics ([5]) in a locally Minkowski space.

• Journal of applied mathematics & informatics
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• v.7 no.3
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• pp.1039-1044
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• 2000

We investigate the projectively flat warped product manifolds and study the geometric structure of the base space and its fibre. Specifically we find the conditions that the scalar curvature of the base space (B,g) vanishes if and only if f is harmonic on (B,g) and the fibre (F,$\bar{g}$) is a space of constant curvature.

• Journal for History of Mathematics
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• v.32 no.1
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• pp.17-25
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• 2019

This essay elucidates the way the geometries of space-time theories explain material bodies' motions. A conventional attempt to interpret the way that space-time geometry explains is to consider the geometrical structure of space-time as involving a causally efficient entity that directs material bodies to follow their trajectories corresponding to the laws of motion. Newtonian substantival space is interpreted as an entity that acts but is not acted on by the motions of material bodies. And Einstein's curved space-time is interpreted as an entity that causes the motions of bodies. This essay argues against this line of thought and provides an alternative understanding of the way space-time geometry explain the laws of motion. The workings of the way that Newton's flat and Einstein's curved space-time explains the law of motion is such that space-time geometry encodes the principle of inertia which specifies straight lines of moving bodies.

• Journal of applied mathematics & informatics
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• v.41 no.1
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• pp.193-203
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• 2023

In view of solution to the Hilbert fourth problem, the present study engages to investigate the projectively flat special (𝛼, 𝛽)-metric and the generalised first approximate Matsumoto (𝛼, 𝛽)-metric, where 𝛼 is a Riemannian metric and 𝛽 is a differential one-form. Further, we concluded that 𝛼 is locally Projectively flat and have 𝛽 is parallel with respect to 𝛼 for both the metrics. Also, we obtained necessary and sufficient conditions for the aforementioned metrics to be locally projectively flat.