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690 results on '"Li, R. K."'

221. Two New Barium Borate Fluorides ABa12(BO3)7F4 (A = Li and Na).

Author

Jing Zhao and Li, R. K.

Subjects
*BARIUM borate, *CRYSTALLIZATION, *FLUORIDES, *CRYSTAL structure, *LITHIUM ions, *IONIC mobility
Abstract

Two new barium borate fluorides LiBa12(BO3)7F4 and NaBa12(BO3)7F4 are obtained by spontaneous crystallization from high-temperature flux. The two compounds are isostructural and crystallized into the tetragonal system, I4/mcm space group, with unit cell parameters of a = 13.5709(6) Å, c = 14.9908(13) Å for LiBa12(BO3)7F4 and a = 13.6443(9) Å, c = 15.021(2) Å for NaBa12(BO3)7F4. Isolated Li/NaF4-BO3 units formed by Li/NaF4O square pyramids and B3O3 groups sharing the O5 atom are found occupying the octagonal tunnels built by Ba and BO3 groups along the c axis. High mobility of Li+ ion is observed in the LiBa12(BO3)7F4 single crystal by ac impedance measurements at different temperatures. [ABSTRACT FROM AUTHOR]

Published
2014
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222. Two new bismuth thiourea bromides: crystal structure, growth, and characterization.

Author

Ming Li and Li, R. K.

Subjects
*BISMUTH, *THIOUREA, *BROMIDES, *CRYSTAL structure, *X-ray diffraction
Abstract

Crystals of two new bismuth thiourea bromides, bismuth trithiourea bromide (Bi[CS(NH2)2]3Br3, BTB) and bismuth protonated-hexathiourea bromide (Bi[CS(NH2)2H]6Br9, BHB), have been successfully grown from hydrobromic acid solution with different pH values by slow evaporation. Single crystal X-ray diffraction reveals that BTB is isostructural to its Cl-analog crystallizing in a monoclinic space group Cc with unit cell dimensions of a = 8.6238(7) Å, b = 12.2506(11) Å, c = 15.5040(13) Å, β = 90.7810(10)° and Z = 4. In contrast, BHB crystallizes in a trigonal space group R3c with unit cell dimensions of a = b = 12.748(17) Å, c = 40.45(11) Å, and Z = 6. The protonation of the thiourea in BHB is confirmed by the structure solution, IR and Raman spectroscopy. The UV diffuse reflection spectra clearly indicate that both of the two crystals have good optical transparency in the range below 2000 nm. Both compounds decompose above 190 °C, and BHB melts at around 140 °C while BTB possesses a phase transition at 145 °C as indicated by thermogravimetric (TG) and differential thermal analysis (DTA). [ABSTRACT FROM AUTHOR]

Published
2014
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223. SVM-RFE Based Feature Selection and Taguchi Parameters Optimization for Multiclass SVM Classifier.

Author

Mei-Ling Huang, Yung-Hsiang Hung, Lee, W. M., Li, R. K., and Bo-Ru Jiang

Subjects
SUPPORT vector machines, FEATURE selection, TAGUCHI methods, PARAMETER estimation, MATHEMATICAL optimization, DERMATOLOGY
Abstract

Recently, support vector machine (SVM) has excellent performance on classification and prediction and is widely used on disease diagnosis or medical assistance. However, SVM only functions well on two-group classification problems. This study combines feature selection and SVMrecursive feature elimination (SVM-RFE) to investigate the classification accuracy ofmulticlass problems for Dermatology and Zoo databases. Dermatology dataset contains 33 feature variables, 1 class variable, and 366 testing instances; and the Zoo dataset contains 16 feature variables, 1 class variable, and 101 testing instances.The feature variables in the two datasets were sorted in descending order by explanatory power, and different feature sets were selected by SVM-RFE to explore classification accuracy.Meanwhile, Taguchimethodwas jointly combinedwith SVMclassifier in order to optimize parameters C and γ to increase classification accuracy formulticlass classification. The experimental results show that the classification accuracy can be more than 95% after SVM-RFE feature selection and Taguchi parameter optimization for Dermatology and Zoo databases. [ABSTRACT FROM AUTHOR]

Published
2014
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