Tan Zhen-Yu

A Novel Adaptive Observer-Based Control Scheme for Synchronization and Suppression of a Class of Uncertain Chaotic Systems

A novel adaptive observer-based control scheme is presented for synchronization and suppression of a class of uncertain chaotic system. First, an adaptive observer based on an orthogonal neural network is designed. Subsequently, the sliding mode controllers via the proposed adaptive observer are proposed for synchronization and suppression of the uncertain chaotic systems. Theoretical analysis and numerical simulation show the effectiveness of the proposed scheme.

A Monte Carlo Study of Low-Energy Electron Transport in Liquid Water: Influence of the Rutherford Formula and the Mott Model

Influence of the Rutherford formula and the Mott model on the Monte Carlo simulation of low-energy electron (< 10 keV) transport in liquid water is investigated. One of the features of the constructed Monte Carlo code is the implementation of the new optical-data model from Emfietzoglou et al. in inelastic cross section based on the dielectric response theory. In addition, a novel mean elastic cross section by means of the Mott model is proposed to calculate the electron elastic scattering for high simulation efficiency. The systematical calculations of both the distribution of energy depositions and penetration parameter for low-energy electrons in liquid water are performed by using the Rutherford formula and the Mott model, respectively, for the elastic collisions in the simulations. The calculated results show that the effect of the two models is evident at energies below about 1 keV.

Single-Walled Carbon Nanotubes Acting as Controllable Transport Channels

The motion and equilibrium distribution of water molecules adsorbed inside neutral and negatively charged single-walled carbon nanotubes (SWNTs) have been studied using molecular dynamics simulations (MDSs) at room temperature based on CHARMM (Chemistry at HARvard Molecular Mechanics) potential parameters. We find that water molecules have a conspicuous electropism phenomenon and regular tubule patterns inside and outside the charged tube wall. The analyses of the motion behaviour of water molecules in the radial and axial directions show that by charging the SWNT, the adsorption efficiency is greatly enhanced, and the electric field produced by the charged SWNTs prevents water molecules from flowing out of the nanotube. However, water molecules can travel through the neutral SWNT in a fluctuating manner. This indicates that by electrically charging and uncharging the SWNTs, one can control the adsorption and transport behaviour of polar molecules in SWNTs for using as a stable storage medium or long transport channels. The transport velocity can be tailored by changing the charge on the SWNTs, which may have a further application as modulatable transport channels.

Effects of Oxygen Concentration on Pulsed Dielectric Barrier Discharge in Helium-Oxygen Mixture at Atmospheric Pressure*

In this work the effects of O2 concentration on the pulsed dielectric barrier discharge in helium-oxygen mixture at atmospheric pressure have been numerically researched by using a one-dimensional fluid model in conjunction with the chosen key species and chemical reactions. The reliability of the used model has been examined by comparing the calculated discharge current with the reported experiments. The present work presents the following significant results. The dominative positive and negative particles are He2+ and O2−, respectively, the densities of the reactive oxygen species (ROS) get their maxima nearly at the central position of the gap, and the density of the ground state O is highest in the ROS. The increase of O2 concentration results in increasingly weak discharge and the time lag of the ignition. For O2 concentrations below 1.1%, the density of O is much higher than other species, the averaged dissipated power density presents an evident increase for small O2 concentration and then the increase becomes weak. In particular, the total density of the reactive oxygen species reaches its maximums at the O2 concentration of about 0.5%. This characteristic further convinces the experimental observation that the O2 concentration of 0.5% is an optimal O2/He ratio in the inactivation of bacteria and biomolecules when radiated by using the plasmas produced in a helium oxygen mixture.

Proton Inelastic Mean Free Path in a Group of Organic Materials in 0.05–10 MeV Range

Inelastic mean free paths (MFPs) of 0.05–10 MeV protons in a group of 10 organic compounds are systematically calculated. The calculations are based on the method newly derived from the Ashley optical-data model and from the higher-order correction terms in stopping power calculations. Especially, in this method the new and empirical Bloch correction for the inelastic MFP is given. An evaluation for the optical energy loss function is incorporated into the present calculations because of the lack of available experimental optical data for the considered organic compounds expect for kapton. The proton inelastic MFPs for these 10 organic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and the combination of these inelastic MFP data and our previous data of stopping power calculation for these bioorganic compounds may form a useful database for Monte Carlo track-structure studies of various radiation effects on these materials.

A Computational Study on the Discharge Characteristics of Atmospheric Dielectric Barrier Discharges at a Constant Power

The study on homogeneous DBDs at atmospheric pressure has attracted much attention for their advantages in applications. Tremendous work has been conducted both experimentally and numerically at a constant applied voltage or driving frequency. However the investigation of dielectric barrier discharges is still scarce for a constant power or power density. In this work, a new computational approach for DBDs is developed to explore atmospheric DBDs at a constant power based on a one-dimensional fluid model. The frequency and gap spacing effects on the atmospheric plasmas are systematically analyzed based on computational data. The computational results show that at a constant power both the current density and the amplitude of the applied voltage decrease, whereas the current pulse width increases, with increasing frequency. The simulation also indicates that as the gap spacing is raised with a fixed power and frequency, the current density and electron density increase initially, then reach their peak values, and then decrease, which means that there are maximum values for both of them. These results are significant for many industrial applications, as they can be used to optimize plasma devices of DBDs with the consideration of power consumption.

Electronic Stopping Power for 0.05?10 MeV Protons in a Group of Organic Materials

Electronic stopping powers for 0.05–10 MeV protons in a group of organic materials are systematically calculated. The calculations are based on Ashleys dielectric model, and an evaluation approach of optical energy loss function is incorporated into Ashleys model because no experimental optical data are available for most of the organic materials under consideration. The Barkas-effect correction and Bloch correction are included. The proton stopping powers for the considered organic materials except for mylar in the energy range from 0.05 to 10MeV are presented for the first time. The results may be useful for studies of various radiation effects in these materials and for space research.

Monte Carlo Simulation on Energy Deposition of Low-Energy Electrons in Liquid Water

A Monte Carlo approach to simulate the transport and energy deposition of low energy electrons (E0≤10 keV) in liquid water is presented. The elastic scattering of electrons is described by Mott cross section, which is derived from the relativistic wave equation of Dirac. The inelastic scattering model of electrons is based on the dielectric response theory with exchange effect included. A new method of sampling various inelastic scattering events is proposed in the simulation. Using the approach stated, the spatial distribution of inelastic scattering events and energy deposition of electrons in liquid water are computed and the results are compared with other theoretical studies.

Collisional Reactions of Energetic Methane Molecules with Single-Walled Carbon Nanotubes

We study the collisions of energetic methane molecules with single-walled carbon nanotubes in the incident energy range from 5 to 100 eV using classical molecular dynamics simulations combined with ab initio calculations. The methane molecules can be decomposed into different hydrocarbon radicals, e.g. CHn (n = 1–3), in the collisions depending on the incident energy. Chemical functionalization of the single-walled carbon nanotubes resulting from the chemical adsorption of these hydrocarbon radicals on the outside wall of single-walled carbon nanotubes can be achieved simultaneously. Some stable adsorption configurations of hydrocarbon-functionalized single-walled carbon nanotubes are also presented based on ab initio calculations.

Quasi-One-Dimensional Solid Lattice and Liquid Hydrogen in Single-Walled Carbon Nanotubes

We study the H2 molecules confined in single-walled carbon nanotubes by using molecular dynamics simulations and ab initio calculations. It is found that the H2 molecules at zero-temperature with low density tend to condense. When the linear density of the H2 molecules in the tube increases, various quasi-one-dimensional solid lattices can be observed at low temperature. When the lattices are heated above room temperature, molecular H2 liquids with different density can be observed. The quenching behaviour of the H2 fluids is also examined.