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HOMOCLINIC ORBITS IN TRANSITIONAL PLANE COUETTE FLOW
Julius Rhoan T. Lustro,Genta Kawahara,Lennaert van Veen,Masaki Shimizu 한국전산유체공학회 2015 한국전산유체공학회지 Vol.20 No.4
Recent studies on wall-bounded shear flow have emphasized the significance of the stable manifold of simple nonlinear invariant solutions to the Navier-Stokes equation in the formation of the boundary between the laminar and turbulent regions in state space. In this paper we present newly discovered homoclinic orbits of the Kawahara and Kida(2001) periodic solution in plane Couette flow. We show that as the Reynolds number decreases a pair of homoclinic orbits move closer to each other until they disappear to exhibit homoclinic tangency.
Homoclinic Orbits in Minimal Plane Couette Flow
Julius Rhoan T. Lustro,Genta Kawahara,Lennaert van Veen,Masaki Shimizu 한국전산유체공학회 2014 한국전산유체공학회 학술대회논문집 Vol.2014 No.10
In wall-bounded shear flow recent studies have pointed the significance of the stable manifold of nonlinear simple invariant solutions, referred to as edge states, to the Navier-Stokes equation in the formation of the laminar-turbulent boundary. Here we present homoclinic orbits of the periodic edge state found by Kawahara and Kida[1] in plane Couette flow. It is observed that these homoclinic orbits collide and disappear to exhibit homoclinic tangency as the Reynolds number decreases.
HOMOCLINIC ORBITS IN TRANSITIONAL PLANE COUETTE FLOW
Lustro, Julius Rhoan T.,Kawahara, Genta,van Veen, Lennaert,Shimizu, Masaki Korea Society of Computational Fluids Engineering 2015 한국전산유체공학회지 Vol.20 No.4
Recent studies on wall-bounded shear flow have emphasized the significance of the stable manifold of simple nonlinear invariant solutions to the Navier-Stokes equation in the formation of the boundary between the laminar and turbulent regions in state space. In this paper we present newly discovered homoclinic orbits of the Kawahara and Kida(2001) periodic solution in plane Couette flow. We show that as the Reynolds number decreases a pair of homoclinic orbits move closer to each other until they disappear to exhibit homoclinic tangency.
A Systematic study on the growth of GaN single crystals using the Na-based fluxmethod
M. Kawahara,Y. Yamada,H. Umeda,M. Morishita,F. Kawamura,M. Yoshimura,Y. Mori,T. Sasaki 한양대학교 세라믹연구소 2005 Journal of Ceramic Processing Research Vol.6 No.2
To obtain bulk gallium nitride (GaN) single crystals applicable as the substrate for GaN homoepitaxial growth, we have adopted the Na flux method with some modifications. Assuming that a key reaction of this method is nitrogen dissolution into a flux, we considered both the gas composition and the liquid phase composition. The use of ammonia gas had effects in lowering the threshold pressure for the GaN growth compared with the nitrogen gas which had been used in the original Na flux method. The composition change from pure Na to a mixture of Ca and Na for the flux also brought some favorable effects such as lowering the threshold pressure, and an improvement in the crystal transparency. Finally, the liquid phase epitaxy (LPE) technique along with the Na-based flux method led to the growth of bulk GaN single crystals with much lower dislocation densities than the seed crystals.
Electronic behavior of carbon clusters/hafnium oxide composite material
H. Matsui,T. Kuroda,T. Kawahara,S. Karuppuchamy,R. Kudoh,M. Yoshihara 한국물리학회 2009 Current Applied Physics Vol.9 No.1
An alternating hafnium-O-phenylene hybrid copolymer was calcined under the reduced pressure at 400–700 ℃ to obtain black-colored materials. XRD and TEM analyses showed that the calcined materials were composed of carbon clusters with the diameters of 20 nm and hafnium oxide particles with the diameters of a few nm. ESR spectral examinations revealed that the calcined materials formed a stable cation radical on the carbon clusters and exhibited an oxidation–reduction function. When Au particles were supported on the material, an efficient oxidation–reduction function was found to appear. An alternating hafnium-O-phenylene hybrid copolymer was calcined under the reduced pressure at 400–700 ℃ to obtain black-colored materials. XRD and TEM analyses showed that the calcined materials were composed of carbon clusters with the diameters of 20 nm and hafnium oxide particles with the diameters of a few nm. ESR spectral examinations revealed that the calcined materials formed a stable cation radical on the carbon clusters and exhibited an oxidation–reduction function. When Au particles were supported on the material, an efficient oxidation–reduction function was found to appear.
Microbial Transglutaminase Modifies Gel Properties of Porcine Collagen
Erwanto, Y.,Kawahara, S.,Katayama, K.,Takenoyama, S.,Fujino, H.,Yamauchi, K.,Morishita, T.,Kai, Y.,Watanabe, S.,Muguruma, M. Asian Australasian Association of Animal Productio 2003 Animal Bioscience Vol.16 No.2
We studied the gel properties of porcine collagen with microbial transglutaminase (MTGase) as a catalyst. A creep meter was used to measure the mechanical properties of gel. The results showed samples with high concentration of MTGase gelled faster than those with a low concentration of MTGase. The gel strength increased with incubation time and the peaks of breaking strength for 0.1, 0.2 and 0.5% MTGase were obtained at 40, 20 and 10 min incubation time, respectively. According to SDS-PAGE, the MTGase was successfully created a collagen polymer with an increase in molecular weight, whereas no change in formation was shown without MTGase. The sample with 0.5% MTGase began to polymerize after 10 or 20 min incubation at $50^{\circ}C$, and complete polymerization occurred after 40-60 min incubation. Scanning electron microscopic analysis revealed that the gel of porcine collagen in the presence of MTGase produced an extremely well cross-linked network. The differential scanning calorimetric analysis showed the peak thermal transition of porcine collagen gel was at $36^{\circ}C$, and that with MTGase no peak was detected during heating from 20 to $120^{\circ}C$. The melting point of porcine collagen gel could be controlled by MTGase concentration, incubation temperature and protein concentration. Knowledge of the structural and physicochemical properties of porcine collagen gel catalyzed with MTGase could facilitate their use in food products.
Effects of La Substitution for BiFeO<sub>3</sub> Epitaxial Thin Films
K. Wakazono,Y. Kawahara,K. Ujimoto,T. Yoshimura,N. Fujimura 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.7
The relationship between the Curie temperature and the piezoelectric properties for BiFeO<sub>3</sub> epitaxial thin films was investigated by using A-site substitution of La. BiFeO<sub>3</sub> and (Bi<sub>0.9</sub>La<sub>0.1</sub>)FeO<sub>3</sub> epitaxial thin films were deposited by using pulsed laser deposition. The crystallinities, ferroelectric domain structures and piezoelectric properties for the films were investigated. Although the crystallinity was improved by La substitution, the piezoelectric properties decreased. We suggest that La substitution for BiFeO<sub>3</sub> epitaxial thin films enlarges the domain size and decreases the 71˚ domain wall, which reduce the intrinsic contribution to the piezoelectric properties.