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Xia, M.,Tang, Z.,Kim, W.S.,Yu, T.,Park, B.J. North-Holland Pub. Co 2017 Journal of crystal growth Vol.469 No.-
In the synthesis of nanoparticles, the reaction rate is important to determine the morphology of nanoparticles. We investigated morphology evolution of Cu nanoparticles in this two different reactors, microemulsion reactor and batch reactor. In comparison with the batch reactor system, the enhanced mass and heat transfers in the emulsion system likely led to the relatively short nucleation time and the highly homogeneous environment in the reaction mixture, resulting in suppressing one or two dimensional growth of the nanoparticles. We believe that this work can offer a good model system to quantitatively understand the crystal growth mechanism that depends strongly on the local monomer concentration, the efficiency of heat transfer, and the relative contribution of the counter ions (Br<SUP>-</SUP> and Cl<SUP>-</SUP>) as capping agents.
A compact fourth-order finite difference scheme for the three-dimensional Cahn-Hilliard equation
Li, Y.,Lee, H.G.,Xia, B.,Kim, J. North-Holland Pub. Co 2016 Computer physics communications Vol.200 No.-
<P>This work extends the previous two-dimensional compact scheme for the Cahn-Hilliard equation (Lee et al., 2014) to three-dimensional space. The proposed scheme, derived by combining a compact formula and a linearly stabilized splitting scheme, has second-order accuracy in time and fourth-order accuracy in space. The discrete system is conservative and practically stable. We also implement the compact scheme in a three-dimensional adaptive mesh refinement framework. The resulting system of discrete equations is solved by using a multigrid. We demonstrate the performance of our proposed algorithm by several numerical experiments. (C) 2015 Elsevier B.V. All rights reserved.</P>
Development of the 3.7 GHz LHCD System on HL-2A
B. Lu,M. Huang,H. Zeng,X. Y. Bai,X. H. Mao,Z. H. Lu,J. Liang,Z. H. Kang,M. W. Wang,K. Feng,H. Wang,C. Wang,J. Q. Wang,S. Wei,T. Yao,Y. N. Bu,J. Feng,G. Y. Cheng,S. D. Song,D. H. Xia,J. Rao 한국물리학회 2014 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.65 No.8
A 2 MW-3.7 GHz lower hybrid current drive (LHCD) system is under development for physicsexperiments on the HL-2A device. The RF Power is generated by four TH2103A klystron amplifiersand propagates in the TE10 mode through WR284 waveguides. The transmission lines with a lengthof 20 m to 30 m are pressurized with 2 bars of nitrogen to decrease the possibility of arcing. Thelauncher, based on the passive-active multi-junction (PAM) concept, has been developed and iscurrently being realized. It was designed for a power spectrum peaked at Nk = 2.75 with goodcoupling properties over a wide range of plasma parameters. The four klystrons are fed by ahigh-voltage power supply (HVPS) based on the pulse step modulation (PSM) concept with a fastswitch-off time of less than ten μs. This system is expected to be in operation within 1 years and willexplore many international thermonuclear experimental reactor (ITER) related LH experiments inthe following years.
Hysteresis Loops, Critical Fields and Energy Products for Exchange-spring Hard/soft/hard Trilayers
B. Z. Chen,S. Yan,Y. Z. Ju,G. P. Zhao,X. C. Zhang,M. Yue,J. Xia 한국자기학회 2015 Journal of Magnetics Vol.20 No.1
Macroscopic hysteresis loops and microscopic magnetic moment distributions have been determined by a three-dimensional (3D) model for exchange-coupled Sm-Co/α-Fe/Sm-Co trilayers with in-plane collinear easy axes. These results are carefully compared with the popular one-dimensional (1D) micromagnetic models and recent experimental data. It is found that the results obtained from the two methods match very well, especially for the remanence and coercivity, justifying the calculations. Both nucleation and coercive fields decrease monotonically as the soft layer thickness L<SUP>s</SUP> increases while the largest maximum energy product (roughly 50 MGOe) occurs when the thicknesses of hard and soft layers are 5 ㎚ and 15 ㎚, respectively. Moreover, the calculated angular distributions in the thickness direction for the magnetic moments are similar. Nevertheless, the calculated nucleation and pinning fields as well as the energy products by 3D OOMMF are systematically smaller than those given by the 1D model, due mainly to the stray fields at the corners of the films. These demagnetization fields help the magnetic moments at the corners to deviate from the previous saturation state and facilitate the nucleation. Such an effect enhances as Ls increases. When the thicknesses of hard and soft layers are 10 ㎚ and 20 ㎚, respectively, the pinning field difference is as large as 30%, while the nucleation fields have opposite signs.
Plant leaf detection using modified active shape models
Xia, C.,Lee, J.M.,Li, Y.,Song, Y.H.,Chung, B.K.,Chon, T.S. Academic Press 2013 BIOSYSTEMS ENGINEERING Vol.116 No.1
We propose an in situ detection method of multiple leaves with overlapping and occlusion in greenhouse conditions. Initially a multilayer perceptron (MLP) is used to classify partial boundary images of pepper leaves. After the partial leaf boundary detection, active shape models (ASMs) are subsequently built to employ the images of entire leaves based on a priori knowledge using landmark. Two deformable models were developed with pepper leaves: Boundary-ASM and MLP-ASM. Matching processes are carried out by deforming the trained leaf models to fit real leaf images collected in the greenhouse. MLP-ASM detected 76.7 and 87.8% of overlapping and occluded pepper leaves respectively, while Boundary-ASM showed detection rates of 63.4 and 76.7%. The detection rates by the conventional ASM were 23.3 and 29.3%. The leaf models trained with pepper leaves were further tested with leaves of paprika, in the same family but with more complex shapes (e.g., holes and rolling). Although the overall detection rates were somewhat lower than those for pepper, the rates for the occluded and overlapping leaves of paprika were still higher with MLP-ASM (ranging from 60.4 to 76.7%) and Boundary-ASM (ranging from 50.5 to 63.3%) than using the conventional active shape model (from 21.6 to 30.0%). The modified active shape models with the boundary classifier could be an efficient means for detecting multiple leaves in field conditions.
Improved delay-dependent stability criteria for T-S fuzzy systems with time-varying delay
Zeng, H.B.,Park, J.H.,Xia, J.W.,Xiao, S.P. Elsevier [etc.] 2014 Applied Mathematics and Computation Vol.235 No.-
This paper is concerned with the robust stability of uncertain T-S fuzzy systems with time-varying delay. A novel Lyapunov-Krasovskii functional is established by employing the idea of combining delay-decomposition with state vector augmentation. Then, by employing some integral inequalities and the reciprocally convex approach, some less conservative delay-dependent stability criteria are obtained. The proposed stability conditions are formulated in the form of linear matrix inequalities (LMIs), which can be solved efficiently with Semi-Definite Programming (SDP) solvers. Finally, four numerical examples are provided to show that the proposed conditions are less conservative than existing ones.