Showing papers by "Donghua University published in 2006"

Some asymptotic methods for strongly nonlinear equations

Abstract: This paper features a survey of some recent developments in asymptotic techniques, which are valid not only for weakly nonlinear equations, but also for strongly ones. Further, the obtained approximate analytical solutions are valid for the whole solution domain. The limitations of traditional perturbation methods are illustrated, various modied perturbation techniques are proposed, and some mathematical tools such as variational theory, homotopy technology, and iteration technique are introduced to overcome the shortcomings. In this paper the following categories of asymptotic methods are emphasized: (1) variational approaches, (2) parameter-expanding methods, (3) parameterized perturbation method, (4) homotopy perturbation method (5) iteration perturbation method, and ancient Chinese methods. The emphasis of this article is put mainly on the developments in this eld in China so the references, therefore, are not exhaustive.

Exp-function method for nonlinear wave equations

Abstract: In this paper, a new method, called Exp-function method, is proposed to seek solitary solutions, periodic solutions and compacton-like solutions of nonlinear differential equations. The modified KdV equation and Dodd–Bullough–Mikhailov equation are chosen to illustrate the effectiveness and convenience of the suggested method.

Construction of solitary solution and compacton-like solution by variational iteration method

Abstract: Variational iteration method is used to construct solitary solutions and compacton-like solutions for nonlinear dispersive equations. The chosen initial solution (trial function) can be in compacton form or in soliton form with some unknown parameters which can be determined in the solution procedure. The compacton-like solution can be converted to solitary solution by suitable choice of a parameter, and vice versa.

Addendum:. New Interpretation of Homotopy Perturbation Method

Abstract: The present work constitutes a guided tour through the mathematics needed for a proper understanding of homotopy perturbation method as applied to various nonlinear problems. It gives a new interpretation of the concept of constant expansion in the homotopy perturbation method.

Filtration properties of electrospinning nanofibers

Abstract: Electrospinning is a relatively simple method to produce submicron fibers from solutions of dif- ferent polymers and polymer blends. The extensive applica- tion in future of electrospinning nanofibers is filtration. In this article, the filtration properties of electrospinning nano- fibers were investigated. During the experiments, nanofibers layers with different area weight were electrospun on the spunbonded or meltblown sublayers. Fiber diameter, pore diameter, filtration efficiency as well as filtration resistance of nanofibers web and sublayers were measured, respec- tively, through a series of experiments. The results show that the fiber diameter of nanofibers is much smaller than that of sublayers. It is also found that the pore diameter of nanofi- bers web is much smaller than sublayers and coefficient variation of the pore diameter of nanofibers web is much smaller than sublayers. Moreover, the filtration efficiency and filtration resistance of sublayers are lower than nanofi- bers webs. The balance between efficiency and press drop is also investigated in the article. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 1285-1290, 2006

Hamiltonian and quasi-Hamiltonian structures associated with semi-direct sums of Lie algebras

Abstract: The trace variational identity is generalized to zero curvature equations associated with non-semi-simple Lie algebras or, equivalently, Lie algebras possessing degenerate Killing forms. An application of the resulting generalized variational identity to a class of semi-direct sums of Lie algebras in the AKNS case furnishes Hamiltonian and quasi-Hamiltonian structures of the associated integrable couplings. Three examples of integrable couplings for the AKNS hierarchy are presented: one Hamiltonian and two quasi-Hamiltonian.

Dispersion and Rheological Aspects of SWNTs in Ultrahigh Molecular Weight Polyethylene

Abstract: A new method is developed to homogeneously disperse single-walled carbon nanotubes bundles (SWNTs) in an intractable polymer, for example, ultrahigh molecular weight polyethylene (Mw > 3 × 106 g/mol) (UHMWPE). The dispersion is obtained by spraying an aqueous solution of SWNTs onto a fine UHMWPE powder directly obtained from synthesis. The SWNTs are adsorbed on the surface of the polymer powder. A composite film is prepared from the solution of the polymer powder dissolved in xylene. The high viscosity of UHMWPE in solution prevents coagulation of the adsorbed SWNTs. Scanning electron microscopy (SEM) of the films reveals that SWNT bundles are randomly dispersed in the UHMWPE matrix. The observed “shish-kebab” morphology in the SEM pictures of the film shows that the polymer chains tend to crystallize from solution as chain-folded crystals (kebab). The nanotube surface can act as a nucleating site (shish). The orientation of the dispersed SWNTs in UHMWPE matrix is achieved on solid-state drawing the solut...

Using cellular automata images and pseudo amino acid composition to predict protein subcellular location

Abstract: The avalanche of newly found protein sequences in the post-genomic era has motivated and challenged us to develop an automated method that can rapidly and accurately predict the localization of an uncharacterized protein in cells because the knowledge thus obtained can greatly speed up the process in finding its biological functions. However, it is very difficult to establish such a desired predictor by acquiring the key statistical information buried in a pile of extremely complicated and highly variable sequences. In this paper, based on the concept of the pseudo amino acid composition (Chou, K. C. PROTEINS: Structure, Function, and Genetics, 2001, 43: 246-255), the approach of cellular automata image is introduced to cope with this problem. Many important features, which are originally hidden in the long amino acid sequences, can be clearly displayed through their cellular automata images. One of the remarkable merits by doing so is that many image recognition tools can be straightforwardly applied to the target aimed here. High success rates were observed through the self-consistency, jackknife, and independent dataset tests, respectively.

Robust stability analysis of generalized neural networks with discrete and distributed time delays

Abstract: This paper is concerned with the problem of robust global stability analysis for generalized neural networks (GNNs) with both discrete and distributed delays. The parameter uncertainties are assumed to be time-invariant and bounded, and belong to given compact sets. The existence of the equilibrium point is first proved under mild conditions, assuming neither differentiability nor strict monotonicity for the activation function. Then, by employing a Lyapunov–Krasovskii functional, the addressed stability analysis problem is converted into a convex optimization problem, and a linear matrix inequality (LMI) approach is utilized to establish the sufficient conditions for the globally robust stability for the GNNs, with and without parameter uncertainties. These conditions can be readily checked by utilizing the Matlab LMI toolbox. A numerical example is provided to demonstrate the usefulness of the proposed global stability condition.

Robust stability for stochastic Hopfield neural networks with time delays

Abstract: In this paper, the asymptotic stability analysis problem is considered for a class of uncertain stochastic neural networks with time delays and parameter uncertainties. The delays are time-invariant, and the uncertainties are norm-bounded that enter into all the network parameters. The aim of this paper is to establish easily verifiable conditions under which the delayed neural network is robustly asymptotically stable in the mean square for all admissible parameter uncertainties. By employing a Lyapunov–Krasovskii functional and conducting the stochastic analysis, a linear matrix inequality (LMI) approach is developed to derive the stability criteria. The proposed criteria can be checked readily by using some standard numerical packages, and no tuning of parameters is required. Examples are provided to demonstrate the effectiveness and applicability of the proposed criteria.

The Physical Properties of Aqueous Solutions of the Ionic Liquid [BMIM][BF4]

Abstract: We report here the systematic study of the effect of concentration on the physical properties of aqueous solutions of the room-temperature ionic liquid [BMIM][BF4]. The measurements of density, ρ, refractive index △n, viscosity η, specific conductivity κ and surface tension, γ, were made over the whole concentration range. The equivalent conductance Λm was calculated. The observed linear variations of density and refractive index with the molar concentration are established as those of an ideal solution. The surface tension varied most rapidly in the dilute region whereas the viscosity changed much more rapidly in the concentrated region. Two regions with different composition dependences were found after the analyses of the relationship between the conductivity and the concentration of [BMIM][BF4]. A proposed model for a structural change in the mixtures was described. The physical origin of the observed concentration dependence of these properties is discussed. The physical properties of the solutions vary with changes of association between anions and cations and the interaction between [BMIM][BF4] and water.

Simulation of Gas Flow Pattern and Separation Efficiency in Cyclone with Conventional Single and Spiral Double Inlet Configuration

Abstract: The numerical simulation of the fluid flow and particle dynamics is presented by CFD technique to characterize the performance of two types of cyclones with the conventional single inlet (SI) and spiral double inlets (DI), respectively. The Reynolds-averaged Navier-Stokes equations with the Reynolds stress turbulence model (RSM) for fluid flow are solved by use of the finite volume method based on the SIMPLE pressure correction algorithm in the fluid computational domain. A Lagrangian method is employed to track the particle motion and calculate the gas–particle separation efficiency in the cyclones. According to the computational results, the differences of pressure, velocity and turbulence parameters of the gas flow are described to address the effects of the inlet geometry on the flow pattern of cyclones. Especially for the tangential velocity distribution, a key flow parameter in cyclones, are analysed using the classical Rankine vortex theories. Furthermore, the separation performances of cyclones are predicted, with the comparison of experimental data and theoretical model. The results indicate that the CFD method can effectively reveal the mechanism of gas–particle flow and separation in cyclone with different inlet configuration.

Using pseudo amino acid composition to predict protein structural classes: approached with complexity measure factor

Abstract: The structural class is an important feature widely used to characterize the overall folding type of a protein. How to improve the prediction quality for protein structural classification by effectively incorporating the sequence-order effects is an important and challenging problem. Based on the concept of the pseudo amino acid composition [Chou, K. C. Proteins Struct Funct Genet 2001, 43, 246; Erratum: Proteins Struct Funct Genet 2001, 44, 60], a novel approach for measuring the complexity of a protein sequence was introduced. The advantage by incorporating the complexity measure factor into the pseudo amino acid composition as one of its components is that it can catch the essence of the overall sequence pattern of a protein and hence more effectively reflect its sequence-order effects. It was demonstrated thru the jackknife crossvalidation test that the overall success rate by the new approach was significantly higher than those by the others. It has not escaped our notice that the introduction of the complexity measure factor can also be used to improve the prediction quality for, among many other protein attributes, subcellular localization, enzyme family class, membrane protein type, and G-protein couple receptor type.

Superhydrophobic surface directly created by electrospinning based on hydrophilic material

Abstract: We describe a method to form hydrophobic surfaces using PHBV (Poly (hydroxybutyrate-co-hydroxyvalerate))—a kind of intrinsically hydrophilic material. The concentration of polymer solutions was varied to control the surface morphology and resultant wetting property. The as-prepared films were characterized by micro-scale valley-and-hill structure, which was formed by aggregating of electrospun beads. The bead morphology changed from smooth to porous and popcorn-like with decreased concentrations. The shape of water droplet on these surfaces had contact angles ranging from 110.7 to 158.1°, with a maximum standard deviation of 2.5°. It was found that both the micro and nanostructure were important to create a superhydrophobic surface.

Study on mechanical properties, thermal stability and crystallization behavior of PET/MMT nanocomposites

Abstract: PET/montmorillonite (MMT) nanocomposites were prepared via melt-blending and its nano-dispersion morphology was confirmed by X-ray diffraction and transmission electron microscopy. Its non-isothermal crystallization behavior was studied by DSC. It is found that the crystallization rate of PET nanocomposite was increased significantly. The Avrami equation parameters related to crystallization, such as n , Z c and t 1/2 , were calculated and analyzed. The thermal property and mechanical property of the composite were studied. When the MMT content was 1%, the composite has a desired comprehensive property. At this composition, the thermal degradation onset temperature and the thermal deformation temperature of PET were increased by 12 and 35 °C, respectively, and the tensile strength of the PET was increased by 25% with slightly increase of the notched impact strength.

A Novel Highly Resilient Nanocomposite Hydrogel with Low Hysteresis and Ultrahigh Elongation

Abstract: A series of high clay content Laponite XLS/ polyacrylamide (PAAm) nanocomposite hydrogels (S-M gels) with excellent resilience, low elastic hysteresis, and ultrahigh elongation, have been successfully synthesized. Based on our results, it is concluded that the mechanical properties ofnanocomposite hydrogels probably depend to a great extent on the hydrophilicity and flexibility of the macromolecules. More, over, his found that the transparency during the in-situ polymrization of S-M gels does not change, which is quite different from clay/poly(N-isopropyl-acrylamide) nanocomposite hydrogels.

Study of the preparation and properties of UV‐blocking fabrics of a PET/TiO2 nanocomposite prepared by in situ polycondensation

Abstract: Poly(ethylene phthalate) (PET)/nano-TiO2 composites prepared via in situ polymerization were spun into fiber by the melt-spinning process. The dispersion of nanosized rutile TiO2 in the PET was studied using transmission electron microscopy (TEM) and scanning probe microscopy (SPM) techniques. The mechanical properties and the properties of ultraviolet (UV) protection were investigated. The results showed that rutile TiO2 can be dispersed uniformly by the in situ polycondensation process. The mechanical properties of PET/TiO2 fiber were slightly affected by adding nano-TiO2. The UV-ray transmittance of PET/nano-TiO2 fabrics was below 10% in the UV-A band and below 1% in the UV-B band. And the ultraviolet protection factor (UPF) of PET/nano-TiO2 fabrics was greater than 50. All these PET/TiO2 nanocomposite fabrics exhibited excellent UV-blocking properties. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 1588–1593, 2006