• Bulletin of the Korean Mathematical Society
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• v.26 no.1
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• pp.75-82
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• 1989

It is recently proved by Aiyama and the authors [2] that a complete space-like complex submanifold of a complex space form $M^{n+p}$$_{p}$ (c') (c'.geq.0) is to totally geodesic. This is a complex version of the Bernstein-type theorem in the Minkowski space due to Calabi [4] and Cheng and Yau [5], which is generalized by Nishikawa[7] in the Lorentz manifold satisfying the strong energy condition. The purpose of this paper is to consider his result in the complex Lorentz manifold and is to prove the following.e following.

• East Asian mathematical journal
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• v.32 no.3
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• pp.365-375
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• 2016

In this paper, we study some classes of spaces determined by closure-like operators $[{\cdot}]_s$, $[{\cdot}]_c$ and $[{\cdot}]_k$ etc. which are wider than the class of $Fr{\acute{e}}chet-Urysohn$ spaces or the class of sequential spaces and related spaces. We first introduce a WADS space which is a generalization of a sequential space. We show that X is a WADS and k-space iff X is sequential and every WADS space is C-closed and obtained that every WADS and countably compact space is sequential as a corollary. We also show that every WAP and countably compact space is countably sequential and obtain that every WACP and countably compact space is sequential as a corollary. And we show that every WAP and weakly k-space is countably sequential and obtain that X is a WACP and weakly k-space iff X is sequential as a corollary.

• The Journal of Korea Robotics Society
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• v.3 no.1
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• pp.1-8
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• 2008

Automatic parking assist system is one of the key technologies of the future automobiles. Control problem of a car-like vehicle is not easy due to the nonholonomic constraints. In this paper, a practical solution for planning a car-parking path is proposed according to the proposed motion space (M-space) approach. The M-space is the extension of the conventional configuration space (C-space). A collision-free, nonholonomic feasible path can be directly computed by the M-space conversion and a back-propagation of reachable regions from the goal. The proposed planning scheme provide not a single solution, but also a candidate solution set, therefore, optimization of the parking path can be easily carried out with respect to performance criteria such as safety, maneuvering, and so on. Presented simulation results clearly show that the proposed scheme provides various practical solutions.

• Journal of the Korean Society of Safety
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• v.31 no.6
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• pp.84-92
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• 2016

Since the mankind started its space mission, the number of artificial space objects has been increasing exponentially. It contains not just the space machines which are in use but the machines which are out of order. Meantime, those dead machines are being a serious danger, a real threat to human's lives and property because of it could re-enter into the earth's atmosphere and fall to the ground causing mega-disaster. As the number of space activities gets growing so far, the re-entry of the space objects will be a lot more happened in the future. Therefore, not just natural space object like asteroids but the artificial space object like artificial satellite and space station can cause the disaster by falling to the ground. To protect our nation and our property, the government has set up the space disaster management center in Korea astronomy and Space science Institute. In this study, we surveyed public's recognition of the space object's re-entry situation and analyzed it to contribute building national space disaster management policy.

• Journal of applied mathematics & informatics
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• v.5 no.2
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• pp.433-448
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• 1998

In this study we use inexact Newton-like methods to find solutions of nonlinear operator equations on Banach spaces with a convergence structure. Our technique involves the introduction of a generalized norm as an operator from a linear space into a par-tially ordered Banach space. In this way the metric properties of the examined problem can be analyzed more precisely. Moreover this approach allows us to derive from the same theorem on the one hand semi-local results of kantorovich-type and on the other hand 2global results based on monotonicity considerations. By imposing very general Lipschitz-like conditions on the operators involved on the other hand by choosing our operators appropriately we can find sharper error bounds on the distances involved than before. Furthermore we show that special cases of our results reduce to the corresponding ones already in the literature. Finally our results are used to solve integral equations that cannot be solved with existing methods.

• Korean Institute of Interior Design Journal
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• v.18 no.6
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• pp.115-123
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• 2009

The change of digital technology caused not only the whole human life but also the change of a thinking form and an expression method of human beings. Also, the interactive communication structure became to form in space structure, and space users also get changed to an active system. The interaction between a human being and space, which uses digital media as a medium, makes a human being experience sensitivity through a cognitive process of a human being. The present research aimed to find out characteristics and expression of emotional space applied with digital technology based on the relationship between media space and cognitive functioning and to realize new emotional space. The research method was to define on digital media and experience by cognition of a human being through a literature research and a precedent research and to consider on approach to emotional space through experience of a cognition process like this. Based on the theory like this, the present research progressed by focusing on dramatized characteristics of experience in the digital media space and emotional space expression by induced characteristics. Through the analysis like this, the space applied with digital media could appear as a field of communication that can experience by forming mutual relation through perception of a human being. Additionally, the space induces active participation of a human being through various productions of media and responds to movement, and thus, this suggested infinite possibility as emotional space that can try new experience by stimulating a sense as effect of a cognitive process of a human being.

• Journal of the Chungcheong Mathematical Society
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• v.25 no.4
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• pp.677-686
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• 2012

In this paper, we investigate the surfaces of revolution with light-like axis satisfying some equation in terms of a position vector field and the Laplacian with respect to the non-degenerate third fundamental form in Minkowski 3-space. As a result, we give some special example of the surfaces of revolution with light-like axis.

• East Asian mathematical journal
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• v.25 no.4
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• pp.425-431
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• 2009

We provide a local convergence analysis for Newton-like methods for the solution of generalized equations in a Banach space setting. Using some ideas of ours introduced in [2] for nonlinear equations we show that under weaker hypotheses and computational cost than in [7] a larger convergence radius and finer error bounds on the distances involved can be obtained.

• International Journal of Aeronautical and Space Sciences
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• v.14 no.1
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• pp.19-29
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• 2013

This paper deals with the study of buckling, vibration, and parametric instability characteristics in a damaged cross-ply and angle-ply laminated plate like beam under in-plane harmonic loading, using the finite element approach. Damage is modelled using an anisotropic damage formulation, based on the concept of reduction in stiffness. The effect of damage on free vibration and buckling characteristics of a thin plate like beam has been studied. It has been observed that damage shows a strong orthogonality and in general deteriorates the static and dynamic characteristics. For the harmonic type of loading, analysis was carried out on a thin plate like beam by solving the governing differential equation which is of Mathieu-Hill type, using the method of multiple scales (MMS). The effects of damage and its location on dynamic stability characteristics have been presented. The results indicate that, compared to the undamaged plate like beam, heavily damaged beams show steeper deviations in simple and combination resonance characteristics.

• Journal of the Korean Society of Systems Engineering
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• v.12 no.2
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• pp.19-27
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• 2016

Many countries concentrated on the space developments to enhance the national security and the people's quality of life. A space launch vehicle for accessing the space is a typical large complex system that is composed of the high-technology like high-performance, high-reliability, superhigh-pressure, etc. The project developing large complex system like space launcher is mostly conducted in the uncertain environment. To achieve a goal of the project, its success probability should be enhanced consistently by reducing its uncertainty during the life cycle: it's possible to reduce the project's uncertainty by performing the risk management (RM) that is a method for identifying and tracing potential risk factors in order to eliminate the risks of the project. In this paper, we introduce the risk management (RM) process applied for a Space Launch Vehicle R&D Project.