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Cubic Convolution Scaler Optimized for Local Property of Image Data
Jin-Kee Chae,Jae-Yung Lee,Min-Ho Lee,Jong-Ki Han,Nguyen, Truong Q.,Woon-Young Yeo IEEE 2015 IEEE TRANSACTIONS ON IMAGE PROCESSING - Vol.24 No.12
<P>A scaler is one of the most important modules in various video applications, such as ultra-high definition TV and scalable video systems. A variety of scaling techniques have been used to increase the video quality when the resolution of the source image has to be up- and down-scaled. Some conventional schemes exploit the property of local block data. Others consider the edge information of the data to be scaled. In this paper, we formulate a scaling problem to minimize the information loss resulting from the resizing process. The loss is considered in both the spatial and the frequency domains, and then it is minimized to optimize the kernel of the scaler. The simulation results show that the proposed algorithm reduces the information loss more than conventional schemes. When compared with the conventional algorithms, the proposed method outperforms those with similar complexity.</P>
Magnetic Properties of Transition Metal-implanted ZnO Nanotips Grown on Sapphire and Quartz
Jeremy A. Raley,Yung Kee Yeo,Robert L. Hengehold,Mee-Yi Ryu,Yicheng Lu,Pan Wu 한국자기학회 2008 Journal of Magnetics Vol.13 No.1
ZnO nanotips, grown on c-Al₂O₃ and quartz, were implanted variously with 200 keV Fe or Mn ions to a dose level of 5 × 10<SUP>16</SUP> ㎝?². The magnetic properties of these samples were measured using a superconducting quantum interference device (SQUID) magnetometer. Fe-implanted ZnO nanotips grown on c-Al₂O₃ showed a coercive field width of 209 Oe and a remanent field of 12% of the saturation magnetization (2.3 × 10?? emu) at 300 K for a sample annealed at 700 ℃ for 20 minutes. The field-cooled and the zero-field-cooled magnetization measurements also showed evidence of ferromagnetism in this sample with an estimated Curie temperature of around 350 K. The Mn-implanted ZnO nanotips grown on c-Al₂O₃ showed superparamagnetism resulting from the dominance of a spin-glass phase. The ZnO nanotips grown on quartz and implanted with Fe or Mn showed signs of ferromagnetism, but neither was consistent.
류미이,Thomas R. Harris,Buguo Wang,Yung Kee Yeo,Michael R. Hogsed,이상조,김종수,John Kouvetakis 한국물리학회 2019 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.75 No.8
The temperature (T)-dependent photoluminescence (PL) from Ge1−ySny (y = 4.3%–9.0%) alloys grown on Ge-buffered Si substrates was studied as a function of the Sn content. The PL from Ge1−ySny alloys with high Sn contents (≥7.0%) exhibited the typical characteristics of direct bandgap semiconductors, such as an increase in the PL intensity with decreasing T and a single PL peak corresponding to a transition from the direct bandgap (Γ-valley) to the valence band at all temperatures from 10 to 300 K. For the Ge1−ySny alloys with low Sn contents (≤6.2%), the PL emission peaks corresponding to both the direct bandgap (ED) and the indirect bandgap (EID) PL appeared at most temperatures and as T was increased, the integrated PL intensities of ED initially increased, then decreased, and finally increased again. The unstrained ED and EID energies estimated from the PL spectra at 75 and 125 K were plotted as functions of the Sn concentration, and the cross-over point for unstrained Ge1−ySny was found to be about 6.4%–6.7% Sn by using linear fits to the data in the range of Sn contents from 0% to 9.0%. Based on the results at 75 and 125 K, the cross-over Sn concentration of unstrained Ge1−ySny should be about 6.4%–6.7% Sn content at room temperature. The ED energies of the Ge0.925Sn0.075 alloys were estimated from the T-dependent photoreflectance spectra, and the ED values was consistent with those obtained from PL spectra.
Magnetic and Electronic Properties of a Mn Delta-doping GaN Layer
H. C. Jeon,이승주,강태원,장기주,Yung Kee Yeo,T. F. George 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.58 No.51
The magnetization curve as a function of the magnetic field at 5 K showed that the magnetization of the Mn delta-doped (Ga_(0.995)Mn_(0.005))N thin films was significantly enhanced in comparison with that of the conventionally-doped (Ga_(0.995)Mn_(0.005))N thin films. The magnetization curve as a function of the temperature showed that the Curie temperature of the Mn delta-doped (Ga_(0.995)Mn_(0.005))N thin films was above room temperature. The theoretical electronic results showed that Ga vacancies near the Mn delta-doping layer were likely to cause p-type conductance, indicative of an enhancement of the magnetic properties in (Ga_(1−x)Mn_x)N thin films.
Harris, Thomas R.,Ryu, Mee-Yi,Yeo, Yung Kee,Beeler, Richard T.,Kouvetakis, John Elsevier 2014 Current Applied Physics Vol.14 No.1
The electrical properties of p-type Ge, Ge1-ySny, and Si0.09Ge0.882Sn0.028 samples grown on n-type Si substrates using ultra-high vacuum chemical vapor deposition have been investigated as a function of temperature. Degenerate parallel conducting layers were found in all Ge/Si, Ge1-ySny/Si, and Si0.09Ge0.882Sn0.028/Si samples, which are believed to be associated with dislocation defects at the interface produced by the lattice mismatch between the two materials. These degenerate conducting layers affect the electrical properties of all the thin epitaxial films. Additionally, temperature dependent Hall-effect measurements show that these materials exhibit a conductivity type change from p to n at around 370-435 K. The mobilities of these samples are generally lower than that of bulk Ge due to carrier scattering near the interface between the epitaxial layer and the Si substrate and also due to alloy scattering. Detailed behavior of temperature-dependent conductivity of these samples is also discussed. (C) 2013 Elsevier B.V. All rights reserved.
조현준,Geun-Hyeong Kim,김종수,류미이,Yung Kee Yeo,Thomas R. Harris,John Kouvetakis 한국물리학회 2016 Current Applied Physics Vol.16 No.1
Temperature- (T-) dependent photoreflectance (PR) measurements have been made for the tensilestrained, undoped Ge0.985Sn0.015 film grown on n-Si substrate by ultra-high vacuum chemical vapor deposition method. The PR spectra at room temperature consist of two signals at around 0.739 and 1.022 eV, which are assigned to the direct transitions from conduction G valley to valence and spin-orbit split-off bands, respectively. The T-dependent PR measurements show tensile-strain split direct bandgap transitions from the G valley to the light-hole (ELH) and heavy-hole (EHH) bands at energies of 0.772 and 0.803 eV at 12 K, respectively, which are not usually observable from the photoluminescence measurements for relatively high Sn content Ge1-ySny samples. The PR signals for both HH and LH bands are blue shifted and their intensities decrease with increasing temperature, but both LH and HH PR signals persist through 240 K and only one HH PR signal is observed at room temperature. It has been observed that the separation energy between the EHH and ELH increases as T decreases, which clearly indicates an increase in tensile strain as T decreases. From the analysis of the T-dependent separation energy between the ELH and EHH, the T-dependent tensile strain in the Ge0.985Sn0.015 film was obtained, which might not be easily measured using the X-ray diffraction method.