First principles calculations of Hydrogen—Titanium vacancy complexes in SrTiO3

Hydrogen has been reported to serve exclusively as a donor in many oxides, including SrTiO₃. In a perfect crystal, a proton stays near an O atom, forming a strong O–H bond. In the presence of cation vacancies, i.e., Sr vacancy and Ti vacancy, protons prefer to electrically passivate the cation vacancies by forming strong bonds with the O atoms surrounding the vacancy. These result in the formation of nH–V_Sr and nH–V_Ti complexes. Based on first principles density functional calculations, local configurations and vibration signatures of nH–V_Sr complexes and their vibrational signatures have been previously reported [T-Thienprasert et al., Identification of hydrogen defects in SrTiO₃ by first-principles local vibration mode calculations, Physical Review B 85, 125205 (2012)]. Here, we report the computational results for nH–V_Ti complexes and compare the results with infrared measurements reported in the literatures.     

Chloroform hydrodechlorination behavior of alumina‐supported Pd and PdAu catalysts

Chloroform is a common groundwater contaminant that is very difficult to remove. Chemically converting it into a less toxic form through heterogeneous catalysis is an attractive approach over conventional physical removal methods if it can be done economically. In this study, we explore the efficacy of supported precious metal catalysts for chloroform hydrodechlorination. We find that Pd/Al₂O₃ is catalytically active for this reaction (6.4 L/g_Pd/min) at room temperature, atmospheric pressure, in buffered water, and in the presence of hydrogen gas, and that Pd deposited on commercial Au/Al₂O₃ shows activities as high as 22.4 L/g_Pd/min, suggestive of some Pd metal located on top of Au domains. The primary reaction product is methane, with selectivity values exceeding 90%. Surface‐enhanced Raman spectroscopy shows evidence of chloroform adsorption and dechlorination on the catalyst surface under aqueous conditions. The results highlight the potential of ambient‐condition reductive catalysis to remove chloroform from water. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4474–4482, 2013     

Lossy Image Compression Using Wavelets

In this paper, we report the results of the application of transform coding image data compression techniques using Daubechies and Coifman wavelets. More specifically, D2, D4, D8, D16, and C6, C12 wavelets were used. The results from these wavelets were compared with those of discrete cosine transform. They clearly demonstrated the superiority of the wavelet-based techniques both in compression ratios and image quality, as well as in computational speed. Two quantization methods were used: non-uniform scalar quantization and pseudo-quantization. Both produced satisfactory results (86–88% compression ratio, and acceptable image quality).     

Sound velocities and elastic properties of PbTiO3 and PbZrO3 under pressure: First principles study

The elastic constants and sound velocities as a function of pressure for perovskite materials PbTiO₃ (PTO) and PbZrO₃ (PZO) were investigated by first principles calculations. Under ambient pressure, the calculated structural parameters were calculated and found to be in good agreement with known values. To study properties under pressure, PTO and PZO were calculated at several reduced volumes, each of which corresponds to the system under pressure. The C₁₁, C₁₂ and C₄₄ elastic constants are all found to increase with pressure for the pressure range studied. Because the sound velocities are directly derived from the elastic constants, the relationships between the sound velocities and pressure also follow similar trends. The longitudinal modes are all larger than those of the transverse modes.     

Smart voice recognition based on deep learning for depression diagnosis

Artificial Life and Robotics - Depressive disorder is a kind of mental illness with a high incidence rate due to the stress from the environment or social impact. Depression affects mood and...