Wu J.-S.,Zhanjiang Normal College
Rengong Jingti Xuebao/Journal of Synthetic Crystals | Year: 2013
In this paper, from the model of anion coordination polyhedron growth units, a according to the polarity surface structural features of the large dimensions of growth units, magnesium hydroxide whiskers were grown in an artificially controlled environment, and the methods of glycerol and magnesium supersaturation are introduced. The essence of method of polyols that is false incorporate (ie: adsorption) under certain conditions, it make a false incorporate of crystal face with polyols growth rate significantly reduce or even stop growing, while the other crystal faces remain the original rate of growth, it can be achieved manually controlled growth of magnesium hydroxide whisker. Method of supersaturation of magnesium solution is what makes the concentration of growth units [Mg-Ax](x-2)-(A≠OH-) great, and to be more than 4 times larger than the concentration of component [Mg-(OH)x](x-2)-, So to formation of basic magnesium whisker firstly, and then let it react with the appropriate alkali solution to prepare magnesium hydroxide whiskers.
Xue S.,Zhanjiang Normal College
Ceramics International | Year: 2013
Ar-ion-implantation to a dose of 1×1017 ions/cm 2 was performed on cubic ZnS thin films with (111) preferred orientation deposited on fused silica glass substrates by vacuum evaporation. After ion implantation, ZnS films were annealed in flowing argon at different temperatures from 400 to 800 °C. The effects of ion implantation and post-thermal annealing on the structural and optical properties of ZnS films were investigated by X-ray diffraction (XRD), photoluminescence (PL) and optical transmittance measurements. XRD reveals that the diffraction peaks recover at ∼500 °C. The optical transmittances show that the bandgap of ZnS films blueshifts when annealed below 500 °C, and redshifts when annealed above 500 °C. PL results show that the intrinsic defect related emissions decrease with increasing annealing temperature from 400 to 500 °C, and increase with increasing annealing temperature from 500 to 800 °C. The observed PL emissions at 414 and 439 nm are attributed to the transitions of Zn i→VZn and VS→VBM, respectively. © 2013 Elsevier Ltd and Techna Group S.r.l.
Li D.,Harbin Institute of Technology |
Li D.,Zhanjiang Normal College |
Wang Y.,Harbin Institute of Technology |
Zhang X.,Harbin Institute of Technology |
And 3 more authors.
Journal of Alloys and Compounds | Year: 2013
The SrMoO4:Yb3+/Tm3+/Ho3+ nanocrystals have been successfully synthesized via a sol-gel process. Under 976 nm laser diode excitation, the nanocrystals show the intense white upconversion (UC) emission, which is composed of the blue (1G4 → 3H6 of Tm3+), green (5F 4/5S2 → 5I8 of Ho3+), and red (5F5 → 5I 8 of Ho3+) UC emissions. The UC mechanisms based on spectral, kinetic, and pump power dependence analyses were discussed. It indicates that the white UC emission is attributed to the high excited state energy transfer from the sensitizer Yb3+-MoO42- dimer to the activators (Tm3+ and Ho3+), which can partly decrease the non-radiative processes at the lower energy levels of the activators. © 2012 Elsevier B.V. All rights reserved.
Xue S.,Zhanjiang Normal College
Physica Scripta | Year: 2013
Cubic zinc sulfide (ZnS) thin films with the (111) preferred orientation were prepared by sulfurization of radio frequency sputtered ZnO:Al films. The Al-doped ZnS films were annealed in argon to improve the film crystallinity and activate the dopant atoms. The surface morphology, and structural, optical and electrical properties were characterized by scanning electron microscopy, x-ray diffraction, optical transmittance and electrical measurements before and after the ZnO:Al samples were sulfurized and annealed. The results show that the hexagonal ZnO:Al films completely transform into cubic ZnS after being sulfurized in H2S at 550°C for 2 h. The crystallinity of the ZnS films is improved and the dopant atoms are electrically activated by the thermal annealing at higher temperatures. The resistivity of the ZnS films reaches as low as ∼0.4 Ω cm. This suggests the potential applications of ZnS in certain optoelectronic devices. © 2013 The Royal Swedish Academy of Sciences.
Sun S.,Zhanjiang Normal College |
Peng C.,Chongqing University |
Hou W.,Chongqing University |
Zheng J.,New Mexico Institute of Mining and Technology |
And 2 more authors.
Digital Signal Processing: A Review Journal | Year: 2012
This paper presents a variational Bayes expectation maximization algorithm for time series based on Attias variational Bayesian theory. The proposed algorithm is applied in the blind source separation (BSS) problem to estimate both the source signals and the mixing matrix for the optimal model structure. The distribution of the mixing matrix is assumed to be a matrix Gaussian distribution due to the correlation of its elements and the inverse covariance of the sensor noise is assumed to be Wishart distributed for the correlation between sensor noises. The mixture of Gaussian model is used to approximate the distribution of each independent source. The rules to update the posterior hyperparameters and the posterior of the model structure are obtained. The optimal model structure is selected as the one with largest posterior. The source signals and mixing matrix are estimated by applying LMS and MAP estimators to the posterior distributions of the hidden variables and the model parameters respectively for the optimal structure. The proposed algorithm is tested with synthetic data. The results show that: (1) the logarithm posterior of the model structure increases with the accuracy of the posterior mixing matrix; (2) the accuracies of the prior mixing matrix, the estimated mixing matrix, and the estimated source signals increase with the logarithm posterior of the model structure. This algorithm is applied to Magnetoencephalograph data to localize the source of the equivalent current dipoles. © 2010 Elsevier Inc. All Rights Reserved.