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Asymmetric tree-like branched networks are explored by geometric algorithms. Based on the network, an analysis of the thermal conductivity is presented. The relationship between effective thermal conductivity and geometric structures is obtained by using the thermal-electrical analogy technique. In all studied cases, a clear behaviour is observed, where angle (δ, θ) among parent branching extended lines, branches and parameter of the geometric structures have stronger effects on the effective thermal conductivity. When the angle δ is fixed, the optical diameter ratio β* is dependent on angle θ. Moreover, γ and m are not related to β*. The longer the branch is, the smaller the effective thermal conductivity will be. It is also found that when the angle θ 0.707, the optimal k decreases. In addition, the effective thermal conductivity is always less than that of single channel material. The present results also show that the effective thermal conductivity of the asymmetric tree-like branched networks does not obey Murray's law.

A realistic kinetic Monte Carlo (KMC) simulation model with physical parameters is developed, which well reproduces the heteroepitaxial growth of multilayered Ni thin film on Cu(100) surfaces at room temperature. The effects of mass transport between interlayers and edge diffusion of atoms along the islands are included in the simulation model, and the surface roughness and the layer distribution versus total coverage are calculated. Specially, the simulation model reveals the transition of growth mode with coverage and the difference between the Ni heteroepitaxy on Cu(100) and the Ni homoepitaxy on Ni(100). Through comparison of KMC simulation with the real scanning tunneling microscopy (STM) experiments, the Ehrlich–Schwoebel (ES) barrier Ees is estimated to be 0.18±0.02 eV for Ni/Cu(100) system while 0.28 eV for Ni/Ni(100). The simulation also shows that the growth mode depends strongly on the thickness of thin film and the surface temperature, and the critical thickness of growth mode transition is dependent on the growth condition such as surface temperature and deposition flux as well.

A tumour vascular network, characterized as an irregularly stochastic growth, is different from the normal vascular network. We systematically analyse the dependence of the branching. It is found that anastomosis of tumour on time is according to a number of tumour images, and both the fractal dimensions and multifractal spectra of the tumours are obtained. In the cases studied, the fractal dimensions of the tumour vascular network increase with time and the multifractal spectrum not only rises entirely but also shifts right. In addition, the best drug delivery stage is discussed according to the difference of the singularity exponent δα(δα = αmax — αmin), which shows some change in the growth process of the tumour vascular network. A common underlying principle is obtained from our analysis along with previous results.

The behaviour of water and small solutes in confined geometries is important to a variety of chemical and nanofluidic applications. Here we investigate the permeation and distribution of water and ions in electrically charged carbon cylindrical nanopore during the osmotic process using molecular dynamics simulations. In the simulations, charges are distributed uniformly on the pores with diameter of 0.9 nm. For nanopores with no charge or a low charge, ions are difficult to enter. With the increasing of charge densities on the pores, ions will appear inside the nanopores because of the large electronic forces between the ions and the charged pores. Different ion entries induce varying effects on osmotic water flow. Our simulations reveal that the osmotic water can flow through the negatively charged pore occupied by K+ ions, while water flux through the positively charged pores will be disrupted by Cl- ions inside the pores. This may be explained by the different radial distributions of K+ ions and Cl- ions inside the charged nanopores.

We study the response of water permeation properties through a carbon nanotube on the time-dependent mechanical signals. It is found that there is a critical frequency of vibrating f(c) (about 1333 GHz) which plays a significant role in the water permeation properties. The total water flow, the net flux, the number of hydrogen bonds and the dipole flipping frequency of the single-file water chain inside the nanotube are almost unchanged for the frequency of vibrating f < f(c). Simulation results show that the nanotube can be effectively resistant to the mechanical noise. Such excellent effect of noise screening is attributed to the exceptional property of water molecules connected by strong hydrogen bonds with each other and forming a one-dimensional water chain inside the nanotube. Our findings are important for the understanding of why biological systems can achieve accurate information transfer in an environment full of fluctuations.

The process of the multilayer growth of Pt on Pt (111) is studied by using a Monte Carlo model with realistic physical parameters. The effects of the substrate temperature, the ES barrier, and the deposition rate on the growth mode have been investigated. Gradual transitions of the surface roughness from oscillatory to non-oscillatory behavior and then back to oscillatory behavior are observed while increasing the substrate temperature from 270 K to 620 K. It is found that the growth mode depends strongly on ES barrier over the whole temperatures and the deposition rate of atoms effectively affects the growth mode. The simulation results are consistent with many experimental observations for homoexpitaxy on a Pt (111) substrate.

In this paper we present some simulation results about the behaviour of water molecules inside a single wall carbon nanotube (SWNT). We find that the confinement of water in an SWNT can induce a wave-like pattern distribution along the channel axis, similar phenomena are also observed in biological water channels. Carbon nanotubes(CNTs) can serve as simple nonpolar water channels. Molecular transport through narrow CNTs is highly collective because of tight hydrogen bonds in the protective environment of the pore. The hydrogen bond net is important for proton and other signal transports. The average dipoles of water molecules inside CNTs (7,7), (8,8) and (9,9) are discussed in detail. Simulation results indicate that the states of dipole are affected by the diameter of SWNT. The number of hydrogen bonds, the water–water interaction and water–CNT interaction are also studied in this paper.

By means of the Monte Carlo simulation, a fractal growth model is introduced to describe diffusion-limited aggregation (DLA) under rotation. Patterns which are different from the classical DLA model are observed and the fractal dimension of such clusters is calculated. It is found that the pattern of the clusters and their fractal dimension depend strongly on the rotation velocity of the diffusing particle. Our results indicate the transition from fractal to non-fractal behavior of growing cluster with increasing rotation velocity, i.e. for small enough angular velocity ω the fractal dimension decreases with increasing ω, but then, with increasing rotation velocity, the fractal dimension increases and the cluster becomes compact and tends to non-fractal.

Chessboard-like substrates are introduced in this paper, in order to study the diffusion-limited aggregation (DLA) and the motion of poly-atoms on heterogeneous surfaces. The effect of morphology of such substrates upon the cluster aggregation is investigated using the Monte Carlo simulation. It is found that the growth process and the cluster morphology are governed by the energetic topography of the substrates. Our simulation also indicate that the island density and the fractal dimension of the clusters depend strongly on the substrate topography and the activation energy.

The ON–OFF state transition of the water transport induced by the structural bending of a carbon nanotube is studied by molecule dynamics simulation. The water permeation through a bent carbon nanotube shows excellent gating property with a threshold bending angle of about 14.6°. We also investigate the water density distribution inside the nanochannel to illustrate the mechanism.

A kinetic Monte Carlo model describing the three-dimensional thin film growth on heterogeneous substrates is presented, in which the diffusion of adatoms on substrates, along the island edges and between various layers, as well as the heterogeneity of adsorptive energy, are taken into account. Three growth modes, namely the Layer-by-layer mode, Stranski-Krastanovs mode and 3D mode, and the morphology of multiple layer growth of thin films are simulated. The relationship between thin film growth modes and growth conditions is established by taking into account the distribution of deposited atoms on various layers and the surface roughness of thin films.