Kwangwoon University

About: Kwangwoon University is a education organization based out in Seoul, South Korea. It is known for research contribution in the topics: Thin film & Resonator. The organization has 4020 authors who have published 8217 publications receiving 104365 citations.

Data-driven Control of Flapping Flight

Abstract: We present a physically based controller that simulates the flapping behavior of a bird in flight. We recorded the motion of a dove using marker-based optical motion capture and high-speed video cameras. The bird flight data thus acquired allow us to parameterize natural wingbeat cycles and provide the simulated bird with reference trajectories to track in physics simulation. Our controller simulates articulated rigid bodies of a bird's skeleton and deformable feathers to reproduce the aerodynamics of bird flight. Motion capture from live birds is not as easy as human motion capture because of the lack of cooperation from subjects. Therefore, the flight data we could acquire were limited. We developed a new method to learn wingbeat controllers even from sparse, biased observations of real bird flight. Our simulated bird imitates life-like flapping of a flying bird while actively maintaining its balance. The bird flight is interactively controllable and resilient to external disturbances.

Umbral calculus associated with Frobenius-type Eulerian polynomials

Abstract: In this paper, we study some properties of several polynomials arising from umbral calculus. In particular, we investigate the properties of orthogonality type of the Frobeniustype Eulerian polynomials which are derived from umbral calculus. By using our properties, we can derive many interesting identities of special polynomials associated with Frobeniustype Eulerian polynomials. An application to normal ordering is presented.

Substrate hardness dependency on properties of Al2O3 thick films grown by aerosol deposition

Abstract: The effects of substrate hardness on the growth of Al 2 O 3 films using an aerosol deposition (AD) process were investigated. Substrates with different hardness, such as glass, Cu, Al 2 O 3 , and sapphire were used to examine the effects of the deposition rate, microstructure, and mechanical properties of Al 2 O 3 films. As the substrate hardness increased, the deposition rate and the hardness of the films rapidly decreased, but the surface roughness was increased. The adhesive properties of Al 2 O 3 films deposited on sapphire substrates deteriorated compared to those deposited on Cu substrates. To clarify the causes for this behavior, the relationship between the thickness of films and substrate hardness was investigated, and the microstructures of Al 2 O 3 particles at the initial stages were observed. It was revealed that it was difficult to make anchoring layers with Al 2 O 3 particles deposited on hard sapphire substrates. This is the main cause for the lower deposition rate and the more pronounced deterioration of the mechanical properties. In order to improve the deposition rate of Al 2 O 3 films when growing them on hard substrates, two methods were attempted to increase the kinetic energy of particles. The first method involved the use of larger Al 2 O 3 particles, and the second involved increasing the impact velocity of the particles by using specially designed nozzles. Consequently, dense and hard Al 2 O 3 thick films could be successfully fabricated on hard sapphire substrates at room temperature by the AD process through increasing the impact velocity using the acceleration nozzle.