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A novel lifetime-based phosphor thermography using three-gate scheme and a low frame-rate camera
Cai, T.,Peng, D.,Liu, Y.Z.,Zhao, X.F.,Kim, K.C. Elsevier 2017 Experimental thermal and fluid science Vol.80 No.-
<P>Lifetime-based method using multiple-frame technique and sophisticated high-speed cameras has been developed for two-dimensional phosphor thermography in recent years, which is however limited due to high cost and long time in data processing. In this study, a novel lifetime-based method using three-gate scheme and a low frame-rate camera was proposed, which is able to significantly reduce equipment cost, simplify data processing, and remarkably increase spatial resolution. Here, Mg4FGeO6:Mn was used as sensor material, which was excited by a pulsed UV LED. A low frame-rate CCD camera at 4 Hz was sufficient to conduct phosphor thermometry using a three-gate scheme: one in fully excited region, one in decay region and one for background subtraction. Calibration was performed with a temperature range from 200 degrees C to 550 degrees C, and the results agreed well with data obtained by a high-speed camera sampling at 40 kHz. The effect of exposure time was investigated to yield an optimum value of 2 ms in this study. Finally, this new method was demonstrated in temperature measurements of the steady and impulsively started impingement jet heat transfer. (C) 2016 Elsevier Inc. All rights reserved.</P>
Preparation, characterization and formation mechanism of gallium oxide nanowires
K.F. Cai,S. Shen,C. Yan,S. Bateman 한국물리학회 2008 Current Applied Physics Vol.8 No.3,4
Ga₂O₃ nanowires were fabricated via vaporsolid process in ambient atmosphere using Ga and Ga₂O₃ as starting materials withoutadding catalyst. The Ga₂2O₃ anism of the nanowires was analyzed by dierential scanning calorimeter and thermogravimetric analysis and found to be controlled bythe vaporsolid (VS) growth mechanism. This synthetic method is simple and low cost, and could be extended to synthesize ZnO and In₂O₃ nanowires.
Preparation and thermoelectric properties of AgPb18SbTe20−xSex (x = 1, 2, 4) materials
H. Li,K.F. Cai,Y. Du,H.F. Wang,S.Z. Shen,X.L. Li,C.W. Zhou,Y.Y. Wang 한국물리학회 2012 Current Applied Physics Vol.12 No.1
AgPb18SbTe20xSex (x ¼ 1, 2, 4) bulk materials were prepared by combining hydrothermal synthesis and melting. Thermoelectric properties were measured from room temperature up to 773K. The materials showed n-type conduction and exhibited degenerate semiconductor behavior. The power factors of the materials varied greatly with increase of Se content (x). Partial substitution of Se for Te in AgPb18SbTe20resulted in remarkable reduction of thermal conductivity in the whole temperature range and increase of power factor at lower temperatures; therefore, the dimensionless figure of merit, ZT, was enhanced below 600K. A maximum ZT value of w0.82 is obtained at 523K for the AgPb18SbTe18Se2 sample.
Flow characteristics around a row of circular and wavy cylinders
K. Lam,T. Cai,Y. F. Lin,Y. Liu 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.11
The near-wake and flow interference around a row of five circular cylinders, staggered wavy cylinders and nonstaggered wavy cylinders are investigated experimentally by using PIV and LIF techniques. The effects and characteristics of employing wavy cylinders instead of circular cylinders are discussed. The cylinders were arranged at T/d=1.5 with Re ranging from 125 to 40000. Results showed the staggered wavy cylinders give rise to a more stable flow pattern with less fluctuation and longer wake vortex closure length.
SYNTHESIS AND OPTICAL PROPERTIES OF CRYSTALLINE Si-1-xGexOy NANORODS
C.W. Zhou,K.F. Cai,D. H. YU,Y. Du 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2013 NANO Vol.8 No.6
Crystalline Si1-xGexOy nanorods were successfully synthesized by a chemical vapor deposition method using germanium as a starting material on Au-coated Si (111) substrate at ~ 1000°C in a flowing high-purity Ar atmosphere. Most of the nanorods have smooth surfaces, with diameters ranging from ~ 50 nm to 165 nm and lengths longer than several microns. Ultraviolet-visible absorption spectrum of the nanorods shows a maximum absorption wavelength at 203 nm. Photoluminescence spectrum of the nanorods exhibits an ultraviolet emission peak at 336 nm. The growth of the nanorods follows a vapor–liquid–solid mechanism.
H. M. Liang,K. Zhang,J. X. You,F. B. Luo,Z. W. Cai 한국자기학회 2017 Journal of Magnetics Vol.22 No.3
Leakage permeance of a permanent magnet (PM) is an important factor for improving the accuracy of electromagnetic device calculations based on a magnetic equivalent circuit (MEC). For PM leakage permeance calculations, the traditional simulation method of finite element analysis (FEA) and the lumped parameter analytical method (LPAM) have been considered; it was found that FEA has the disadvantage of a long calculation time and LPAM has low accuracy. The magnetic field lines distribution analytical method (MFLD) is proposed in this paper in order to raise computational efficiency and keep accuracy within a certain range. The electromagnetic features of open circuit fan-shaped PMs are presented by MFLD and finite element analysis (FEA) is adopted to match the MFLD results. In order to verify the validity of the proposed method in a magnetic system, the working points of PMs in an electromagnetic actuator are calculated, and the numerical results compared with the experimental results.