Xian-Wu Zou

Growing networks with mixed attachment mechanisms

Networks grow and evolve when new nodes and links are added in. There are two methods to add the links: uniform attachment and preferential attachment. We take account of the addition of links with mixed attachment between uniform attachment and preferential attachment in proportion. By using numerical simulations and analysis based on a continuum theory, we obtain that the degree distribution P(k) has an extended power-law form P(k) ~ (k + k0)−γ. When the number of edges k of a node is much larger than a certain value k0, the degree distribution reduces to the power-law form P(k) ~ k−γ; and when k is much smaller than k0, the degree distribution degenerates into the exponential form . It has been found that degree distribution possesses this extended power-law form for many real networks, such as the movie actor network, the citation network of scientific papers and diverse protein interaction networks.

Influence of external field on diffusion-limited aggregation

Abstract The influence of external electric field on diffusion-limited aggregation (DLA) has been investigated by computer simulations. When the parameter λ increases from 0 to ∞, the morphology of aggregates changes from pure DLA to chain-like pattern gradually, where λ stands for the relative strength of field-induced dipolar interaction to thermal energy. The structure transition is the transition between a prototype disorder structure and a relative order one in essence. The reason of the transition is the interaction controlling systems changes from thermal force to field-induced dipolar interactions with λ rising.

Application of a probability model for relaxation to the dielectric and -relaxation of amorphous polyethylene terephthalate

A probability model (PM) developed recently, which is an alternative to the conventional Havriliak-Negami (HN) dispersion function for polymer systems, is applied for the first time to the study of the dielectric alpha- and beta-relaxation of amorphous polyethylene terephthalate (PET). It has been found that the temperature dependence of the maxima of the imaginary part of the dielectric function and of the half-width of the distribution in the PM of the alpha-relaxation exhibit Vogel-Fulcher-type temperature behaviour; the temperature dependence of the maxima of the imaginary part of the dielectric function of the beta ation is proportional to the ratio of the gauche content to the trans content of the ethylene glycol linkages in PET. Finally, the mechanisms of the alpha- and beta-relaxation are elucidated concisely.

Fabrication of a regular tripod Ni–P nanorod array and an AAO template with regular branched nanopores using a current-controlled branching method

We present a current-controlled branching method for the fabrication of anodic aluminum oxide (AAO) templates with a triply-branched nanopore structure. By controlling the current density in the branching process, a regular triply-branched nanopore array structure was obtained in the AAO template conveniently and precisely. Based on this template, a regular tripod Ni–P amorphous nanorod array was fabricated by electroless deposition. The present method is particularly advantageous for the fabrication of templates and materials with a complex and accurate multiply branched nanostructure.

Metal-nonmetal transition of fluid Cs along the liquid-vapour coexistence curve

Abstract The conductivity of expanded cesium along the liquid–vapour coexistence curve has been obtained by a three-component plasma model. The present work has concluded that the critical point of the liquid–vapour transition does not coincide with that of the metal–nonmetal transition of fluid Cs.

Calculated infrared and Raman spectra of P2O5 glass

Abstract The vibrational spectrum and structure of P 2 O 5 glass are calculated by the ab initio method with the STO-3G basis set. The cluster model PO 4 H 3 is used. The calculated results show that in P 2 O 5 glass each P atom is surrounded almost tetrahedrally by three bridging O atoms and one double-bonded O atom. The calculated frequencies are in good agreement with experimental data.

Computation and simulation of the structural characteristics of the kidney urea transporter and behaviors of urea transport.

Urea transporters are a family of membrane proteins that transport urea molecules across cell membranes and play important roles in a variety of physiological processes. Although the crystal structure of bacterial urea channel dvUT has been solved, there lacks an understanding of the dynamics of urea transport in dvUT. In this study, by using molecular dynamics simulations, Monte Carlo methods, and the adaptive biasing force approach, we built the equilibrium structure of dvUT, calculated the variation in the free energy of urea, determined the urea-binding sites of dvUT, gained insight into the microscopic process of urea transport, and studied the water permeability in dvUT including the analysis of a water chain in the pore. The strategy used in this work can be applied to studying transport behaviors of other membrane proteins.

Preparation of Fe-doped TiO{sub 2} nanotube arrays and their photocatalytic activities under visible light

Fe-doped TiO{sub 2} nanotube arrays have been prepared by the template-based liquid phase deposition method. Their morphologies, structures and optical properties were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and UV-vis absorption spectroscopy. Their photocatalytic activities were evaluated by the degradation of methylene blue under visible light. The UV-vis absorption spectra of the Fe-doped TiO{sub 2} nanotube arrays showed a red shift and an enhancement of the absorption in the visible region compared to the undoped sample. The Fe-doped TiO{sub 2} nanotube arrays exhibited good photocatalytic activities under visible light irradiation, and the optimum dopant amount was found to be 5.9 at% in our experiments.

Extended DDA model: deposition, diffusion and aggregation with a power-law adsorption

Abstract The deposition, diffusion and aggregation (DDA) on surfaces with a power-law adsorption has been studied by Monte Carlo simulations. The model incorporates four elementary processes including deposition, diffusion, adsorption, and aggregation. When the correlation parameter α increases from 0 to ∞, the patterns change from site percolations to DDA clusters. The fractal dimension increases too. It shows that there is a clustering transition from a weakly correlated distribution of particles to a strongly correlated one.

Synthesis and photoluminescence properties of the ZnO@SnO2 core–shell nanorod arrays

The ZnO@SnO2 core–shell nanorod arrays have been synthesized. As the cores, ZnO nanorod arrays were first prepared by aqueous chemical growth method. Then using a simple liquid-phase deposition method, SnO2 was deposited on the ZnO nanorod arrays. Scanning electron microscopy, transmission electron microscopy, and X-ray diffraction were used to characterize the morphologies and structures of the products. Photoluminescence properties were also investigated. It was found that the ZnO@SnO2 core–shell nanorod arrays showed enhanced UV and green emissions when compared with the bare ZnO nanorod arrays.