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Xu G.,Aeronautical University | Deng J.,Shaanxi University of Technology
Physica E: Low-Dimensional Systems and Nanostructures | Year: 2015

The hierarchical branched ZnO nanoarrays (NAs) photoanode was prepared by a two-step hydrothermal method. Vertically aligned long ZnO NWs were first synthesized using as the backbone of hierarchical branched ZnO NAs structure and high quality ZnO NAs branches were grown on the surface of backbone ZnO NAs. The structured films enhance the optical path length through the light scatting effect of branched ZnO NAs and prove the larger internal surface area in NAs film to increase quantum dots (QDs) sensitizer loadings, so the light absorption has an optimization. Compared with the cell based conventional 1D ZnO NAs, the efficiency of the new cells has a great improvement due to the increase of the short circuit current density. © 2015 Published by Elsevier B.V. Source

Ren J.,Aeronautical University | Li G.,Tsinghua University
Proceedings - 2015 8th International Congress on Image and Signal Processing, CISP 2015 | Year: 2015

In this paper, we develop a new method to identify Wiener systems. Unlike previous techniques for Winer system identification, our method allows the linear dynamic subsystem to be infinite-impulse response (IIR) and the nonlinear function to be non-differentiable, discontinuous and non-invertible. Two input sequences are designed to estimate the nonlinear function as well as the parameters in the linear system. The convergence analysis is also discussed and the performance of the proposed method is illustrated by simulations. © 2015 IEEE. Source

Hu C.,Shaanxi Normal University | Hu C.,Aeronautical University | Liu P.,Shaanxi Normal University
Materials Research Bulletin | Year: 2015

Using a conventional solid-state reaction method SiO2 ceramics with addition of Li2TiO3 were synthesized and their phase evolution, chemical reactions, microstructure and microwave dielectric properties were studied. The microwave dielectric properties of SiO2 ceramics with addition of Li2TiO3 strongly depend on the formation and the decomposed of Li2(TiO)(SiO4) intermediate phase. The tridymite phase was formed for all samples sintered above 1150 °C and its microwave dielectric properties were reported for the first time (εr = 2.58, Q × f = 25,800 GHz, τf = -17.8 ppm/°C). The promising ceramics of 0.945SiO2-0.055Li2TiO3 sintered at 1050 °C were found to possess good microwave dielectric properties: εr = 3.21, Q × f = 10,180 GHz and τf ∼ 0.17 ppm/°C. © 2015 Elsevier Ltd. All rights reserved. Source

Liu S.,Northwestern Polytechnical University | Zhong C.,Northwestern Polytechnical University | Bai J.,Aeronautical University
Computers and Mathematics with Applications | Year: 2015

A Unified Gas-Kinetic Scheme (UGKS) is devised for micro and nano channel flow simulations. The principle underlying the scheme is a partial-differential-equation-based modeling in which the gas evolution is modeled with the help of kinetic equation, instead of solving the partial differential equation directly. Elastic collision and inelastic collision have both been taken into consideration in the presented scheme where the inelastic collision is modeled by a Landau-Teller-Jeans-type relaxation term. In this study, two dimensional channel flows are selected as our test cases. First, a thermal conduction case with a wide range of Knudsen number is carried out using the present scheme with different kinetic model equations in order to show the validity of the present scheme and to compare the accuracies of different model equations. Then, a series of pressure driven micro and nano channel flows whose working medium are nitrogen gas are used to validate the proposed scheme. In these cases, the results in both the stream direction and the radial direction agree well with the results predicted by the direct simulation Monte Carlo method, and UGKS results are smoother and without statistical fluctuation. When the density of working gas is high, the non-ideal effect should be taken into consideration. So, at the end of this paper, the presented scheme is also modified using the Enskog theory for non-ideal gas. Based on the gas evolution modeling process which automatically covers the whole scale mechanisms, the cell size and time step of UGKS are not limited by the molecular free path and collision time. Due to the advantages of cell size, time step, and accuracy (no statistical fluctuation), the UGKS is expected to be a practical method for the simulation of micro and nano channel flows. © 2014 Elsevier Ltd. Source

Guo W.,Aeronautical University
Chinese Control Conference, CCC | Year: 2014

Capacitive Micro-Accelerometer digital feedback system was developed using the theory of second-order Σ-Δ modulator. The second-order mechanical gauge outfit behaves as two integrators in second-order Σ-Δ modulator and the number of bits of the quantizer is 1 bit. Continuous-time model of the gauge outfit was transformed to discrete-time model based on the IIR theory and the quantizer linear model was established using the LMS arithmetic. Therefore the quasi-linear discrete model was derived. The simulation results shown that the micro-accelerometer system was a low pass system and it had linear phase characteristic approximately in the low frequency band. The simulation results also displayed that the second order noise shaping was performed in the system which made the noise transfer to higher frequency band. Finally the accelerometer system was simulated with the sine signal input, and the results validated that the output and the input are consistent. © 2014 TCCT, CAA. Source

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