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Chungju, South Korea

The Korea National University of Transportation is a public, national university in Chungju City, North Chungcheong province, South Korea. The university was established in 2012 by merging Chungju National University and Korea National Railroad College. It enrolls about 200 graduate and 8,000 undergraduate students, and employs about 295 professors. The president of the University is Dr. Kim Yeong Ho. Wikipedia.

Cho I.,Seoul National University of Science and Technology | Kim H.-C.,Korea National University of Transportation | Moon T.,Inje University
Physical Review Letters | Year: 2013

We investigate a nonsingular initial state of the Universe which leads to inflation naturally. The model is described by a scalar field with a quadratic potential in Eddington-inspired Born-Infeld gravity. The curvature of this initial state is given by the mass scale of the scalar field, which is much smaller than the Planck scale. Therefore, in this model, quantum gravity is not necessary in understanding this preinflationary stage, no matter how large the energy density becomes. The initial state in this model evolves eventually to a long inflationary period which is similar to the usual chaotic inflation. © 2013 American Physical Society.

Cho I.,Seoul National University of Science and Technology | Kim H.-C.,Korea National University of Transportation
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2013

We present a new manifestation of the nonlinearity of gravity-matter interactions. We show explicitly that there exists a nongravitating dynamical scalar field solution in Eddington-inspired Born-Infeld gravity. This kind of solution has not been found in previous literature based on general relativity or other modified gravity theories. The perturbation analysis shows that the solution is a late-time attractor if the scalar field rolls down the potential. This indicates that there are two weak-gravity regimes in the theory - one in the general relativity regime, and the other in the Eddington regime. © 2013 American Physical Society.

Kang J.W.,Korea National University of Transportation
Journal of Computational and Theoretical Nanoscience | Year: 2013

We investigate the translational and rotational motions of a nanoscale graphene flake with the retracting-motions by performing classical molecular dynamics simulations. While the translational motions of the graphene flake are quickly damped, the rotational motions of the graphene flake remain for a long time and its full rotations are found. This rapid damping of its translational motions shows that graphene-flake oscillators have a weakness to be stable translational-motion oscillators because of very low quality-factors in the translational motions. Graphene flakes have a great potential to be a core component in NEMSs by detecting their motions with ultrahigh sensitivity to facilitate the development of sensor, memory, and quantum computing. Copyright Copyright © 2013 American Scientific Publishers. All rights reserved All rights reserved.

Park J.-H.,Korea National University of Transportation
International Journal of Control and Automation | Year: 2014

For system analysis and design purposes, it is meaningful discussion to define control system pole status whether a pole is significant or not. If a pole is less important, it can be canceled from the transfer function of system and system order is reduced. In this paper a method for system order reduction of transfer function using Rationalized Haar functions based on approximation and transform algorithm is presented. The Haar function set forms a complete set of orthogonal rectangular functions such as Walsh and block pulse functions. But the Haar functions have some disadvantages of calculation because of including irrational numbers such as ± √ 2P, (p=1,2,..).The Rationalized Haar functions were introduced by M. Ohkita to overcome these disadvantages. The Rationalized Haar functions constitute of rational numbers only. The applied method to solve the system order reduction of transfer function problem is superior to conventional numerical methods. © 2014 SERSC.

Kim H.-C.,Korea National University of Transportation
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We study phenomena happening at the surface of a star in Eddington-inspired Born-Infeld (EiBI) gravity. The star is made of particles, which are effectively described by a polytropic fluid. The EiBI theory was known to have a pathology that singularities happen at a star surface. We suggest that the gravitational backreaction on the particles cures the problem. Strong tidal forces near the (surface) singularity modify the effective equation of state of the particles or make the surface be unstable depending on its matter contents. The geodesic deviation equations take after Hooke's law, where its frequency squared is proportional to the scalar curvature at the surface. For a positive curvature, a particle collides with a probing wall more often and increases the pressure. With the increased pressure, the surface is no longer singular. For a negative curvature, the matters around the surface experience repulsions with infinite accelerations. Therefore, the EiBI gravity is saved from the pathology of a surface singularity. © 2014 American Physical Society.

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