652 publications from this institution
Materials change their sizes when subjected to a temperature change. Generally the coefficient of thermal expansion is positive, however, a negative coefficient in nanoporous biomaterials from enteromorpha is observed.
In this paper, the general equations of equilibrium for axisymmetrical deformation including the torsional deformation of shells with general forms are derived as stationary conditions of a generalized variational principle, which is established by the semi-inverse method. It shows that they are different from the results obtained by Chien (1990) in case of revolutional shell, therefore Chien’s results can be further improved.
A facile strategy for preparing electrospun nanofibers by vibration technology is suggested. Under the influence of the vibration, the vibrorheological effects appear in dramatic reduction in viscosity, as a result moderate voltage is needed to produce fine nanofibers that is commonly observed during conventional electrospinning procedure at elevated voltage. The novel strategy produces finer nanofibers than those obtained without vibration.
No abstract is provided for this article.
An analytical method using Taylor series is proposed to solve a nonlinear two-point boundary problem arising in corneal shape. The solution process makes it extremely easy to obtain a relatively accurate solution. The pencil-and-paper solution procedure can be extended to other boundary value problems.
Variational iteration method has been favourably applied to various kinds of nonlinear problems. The main property of the method is in its flexibility and ability to solve nonlinear equations accurately and conveniently. In this paper recent trends and developments in the use of the method are reviewed. Major applications to nonlinear wave equation, nonlinear fractional differential equations, nonlinear oscillations and nonlinear problems arising in various engineering applications are surveyed. The confluence of modern mathematics and symbol computation has posed a challenge to developing technologies capable of handling strongly nonlinear equations which cannot be successfully dealt with by classical methods. Variational iteration method is uniquely qualified to address this challenge. The flexibility and adaptation provided by the method have made the method a strong candidate for approximate analytical solutions. This paper outlines the basic conceptual framework of variational iteration technique with application to nonlinear problems. Both achievements and limitations are discussed with direct reference to approximate solutions for nonlinear equations. A new iteration formulation is suggested to overcome the shortcoming. A very useful formulation for determining approximately the period of a nonlinear oscillator is suggested. Examples are given to illustrate the solution procedure.
A tendon shows excellent advantages in transmitting large loads efficiently and also in storing elastic energy during locomotion possibly due to its hierarchical structure. Its fractal dimension is calculated, which is quite close to the golden mean, 1·618. The present study might provide a new interpretation for the reason why the tendon has so many excellent properties. Based on this theory, a composite yarn with hierarchical structure is designed.
In this paper, a modified Lindstedt–Poincare method is proposed. In this technique, a constant, rather than the non-linear frequency, is expanded in powers of the expanding parameter to avoid the occurrence of secular terms in the perturbation series solution. Some examples are given here to illustrate its effectiveness and convenience. The results show that the obtained approximate solutions are uniformly valid on the whole solution domain, and they are suitable not only for weakly non-linear systems, but also for strongly non-linear systems.
No abstract is provided for this article.
various nanostructures. Electrospun nanofibres have a wide range of potential applications in many fields, such as air filtration, water filtration, biomedicine, catalyst supports, drug delivery, tissue engineering, nanowires, just say few. This experiment shows that operating parameters affect much morphology and mechanical character of electrospun nanofibres. This paper studies theoretically and experimentally the scaling relationship between two main operating parameters-current and applied voltage. Polyacrylonitrile (PAN) nanofibres are prepared by electrospinning of 12 wt% and 18 wt% PAN/DMF solution. In our experiment the volume flow rate keeps unchanged during the electrospinning process, and the voltage varies from 10 kV to 50 kV. The non-linear relationship between current and applied voltage is obtained by an allometrical approach. The theoretical prediction agrees very well with experimental data. Yu-Qin Wan, Ji-Huan He, and Jian-Yong Yu
In this work, we mainly focus on the fractal variant Boussinesq–Burgers equation which can well describe the motion of shallow water traveling along an unsmooth boundary. First, we construct its fractal variational principle and prove its strong minimum condition by the fractal Weierstrass theorem. Then two types of soliton solutions are acquired according to the constructed fractal variational principle. We find that the order of the fractal derivative hardly affects the whole shape of the solitary waves, but it remarkably affects its propagation process.
Triazole compounds are important organic systems with excellent electronic properties, which has diagnostic potential in the fields of organic electronics and organic photovoltaics. The important photophysical nature of these systems is the transformation between the enol and keto forms after excited-state proton transfer. In this work, the IR vibrational spectrum, ESIPT mechanism and excited-state decay dynamics of 2,2'-(1-Phenyl-1H-1,2,4-triazole-3,5-diyl)diphenol (ExPh) are explored by using electronic structure calculations and non-adiabatic dynamics simulations. Two S1/S0 conical intersections with distinct proton transfer (ESIPT-I and ESIPT-II) involved were obtained. The associated two-dimensional S1 minimum-energy potential energy surface indicates that the dynamical roles of these two S1/S0 conical intersections in the S1 excited-state decay are quite different. The ESIPT-I reaction is more favorable to occur than the ESIPT-II process. Our dynamics simulations support this suspect with the whole trajectories decay to the ground state via the S1S0-1 conical intersection which involves ESIPT-I process. The ESIPT-involved efficient deactivation pathway can be partially responsible for the decrease of fluorescence emission. These results and ESIPT mechanisms are helpful for understanding the decay pathways of similar systems.
The increase of global mean surface temperature leads to the increase of metabolic rate. This might lead to an unexpected threat from the small insect world. Global warming shrinks cell size, shorten lifespan, and accelerate evolution. The present note speculates on possible connections between allometry and E-infinity theory.
A Hamiltonian approach to nonlinear oscillators is suggested. A conservative oscillator always admits a Hamiltonian invariant, H, which keeps unchanged during oscillation. This property is used to obtain approximate frequency–amplitude relationship of a nonlinear oscillator with acceptable accuracy. Two illustrating examples are given to elucidate the solution procedure.
Bubble electrospinning technology inspired by the spinning a gift given by the nature of spiders has become a very important needleless electrospinning method for mass production of nanofibers. Firstly, the mechanism of bubble electrospinning is introduced herein. Secondly, the effect of bubble size and spinning parameters on nanofiber diameter is discussed. Thirdly, various bubble electrospinning apparatuses and their developments are systematically reviewed. Fourthly, various morphology nanofibers in the bubble electrospinning process by electronic force or airflow are presented. Lastly, we briefly introduce the polymers used in bubble spinning and the applications of bubble spinning nanofibers in recent years.
