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Guo M.,Tianjin Chengjian University
RSC Advances | Year: 2014

The electronic structures and optical properties of C, Ag-codoped TiO2 were investigated within the GGA + U framework. Different doping concentration and different dopant distance (CsAgs (near and far), C2sAgs (near and far), and C3sAgs (near and far)) models were constructed. According to the formation energy results of these codoped systems, it was found that low concentration codoping was more stable than high concentration codoping. Therefore, we chose the CsAgs (near and far) codoped TiO2 to calculate further electronic structures and optical properties. It was found that near distance codoping could narrow the band gap to 2.81 eV, and far distance codoping decreased the band gap to 2.66 eV. Meanwhile, it was found that far distance codoping preferred to form more localized states near the top of the valence band, while near distance codoping could induce more significant hybrid states in the band gap. Optical property showed that C and Ag codoping could induce a synergistic effect compared with single C and single Ag doping. After codoping, the visible absorption was stronger for both the near and far distance codoped systems than those of the single doped systems, moreover, the far distance codoping configuration could induce both more significant band edge shift and stronger visible optical absorption than that of the near distance codoping configuration. This journal is © The Royal Society of Chemistry. Source

Pan L.,Tianjin Chengjian University
IEEE Transactions on Power Electronics | Year: 2014

On the basis of the classical Z-source inverter (ZSI), this paper presents a novel ZSI which only contains inductors and diodes in Z-source network. The inverter uses a unique inductor and diode network for boosting its output voltage, provides a common ground for the dc source and inverter, and avoids the disadvantage causing by capacitor in the classical ZSI and SL-ZSI, especially in prohibiting the inrush current at startup and the resonance of Z-source capacitors and inductors. The inverter can increase the boost factor through adjusting shoot-through duty ratio and increasing the number of inductor. The working principle of the proposed ZSI and comparison with the classical ZSI and SL-ZSI are analyzed in detail. Simulation and experimental results are given to demonstrate the operation features of the inverter. © 2014 IEEE. Source

Xu J.-J.,McGill University | Chen Y.-Q.,Tianjin Chengjian University
Acta Materialia | Year: 2014

The present paper investigates steady spatially periodic eutectic growth during directional solidification with isotropic surface tension in terms of analytical approach. We consider the case when the Péclet number ε is small and the segregation coefficient κ is close to unit, and obtain a family of the global, steady-state solutions with two free parameters: the tilt angle φ and the Péclet number ε. The corresponding interfacial patterns of the steady states are spatially periodic, and may be tilted or non-tilted. The results show that near the triple point, there is a boundary layer Oε12 thick, where the isotropic surface tension plays a significant role, the slope and curvature of interface may be very large and the undercooling temperatures of interface may have a noticeable non-uniformity. Quantitative comparisons between theoretical predictions and recent experimental data are made without making any adjustments to parameters, and show good agreement. © 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Source

Deng A.,University of Adelaide | Zhou Y.,Tianjin Chengjian University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2016

The results of numerical simulations for electroosmosis-surcharge preloading consolidation, obtained using the EC2 model, are presented. EC2 accounts for hydraulic and electroosmotic flows under the conditions of changing physical and geoelectrical properties of saturated compressible porous media. Verification checks for EC2 show excellent agreement of the pore pressure and degree of consolidation with analytical solutions for one- and two-dimensional small-strain consolidation. Similarly, excellent agreement is attained for twodimensional large-strain consolidation occurring to a kaolinite layer subjected to an experimental test. The EC2 model is then used to investigate consolidation optimization for soil layers in three example problems. The electroosmosis-surcharge preloading combined method outperformed single-process methods, particularly where hydraulic conductivity is on an order of magnitude of 10-8 m/s or lower. Applying voltage in steps optimizes electric power usage, as does cutting off the power supply when the degree of consolidation reaches approximately 80%. © 2015 American Society of Civil Engineers. Source

Deng A.,University of Adelaide | Zhou Y.,Tianjin Chengjian University
Journal of Geotechnical and Geoenvironmental Engineering | Year: 2016

A numerical model, EC2, is developed to simulate the consolidation of a soil layer subjected to combined electroosmosis and surcharge preloading. EC2 includes the capabilities of a previous model, EC1, in accounting for large-strain-induced nonlinear changes in the physical and geoelectrical properties that take place on a layer, with the additions of two-dimensional consolidation, coupled loading and electric fields, time-dependent loading and current density, and an external hydraulic gradient. A highlight of the EC2 model is the superposition of multiple streams between small elements, which improves the prediction accuracy of the rate of flow and the degree of consolidation. The consolidation algorithm of EC2 is one-dimensional and conducted using finite-difference and piecewise-linear methods. This paper presents the theoretical and numerical development of the EC2 model. A companion paper presents the validation of the model and the results of simulations that illustrate the optimization of the consolidating processes for some interesting design scenarios. © 2015 American Society of Civil Engineers. Source

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