652 publications from this institution
Using the semi-inverse method [He. Variational principles for some nonlinear partial differential equations with variable coefficients. Chaos Solitons & Fractals 2004;19(4):847–851], a generalized Poincaré-invariant action using the tetrad in any number of dimensions is obtained. The so-obtained generalized action with a free parameter might find potential applications in bosonic strings and E-infinity theory.
5G communication technology has been skyrocketing, and has changed everything in our daily lives, and its applications in various fields are also promising. However, the thermal conductivity/dissipation problems of highly integrated electronic devices and electrical equipment are becoming more and more prominent, and thermodynamics offers a solution, and fractal meta-surfaces provides an extremely efficient approach to transfer the generated waste heat, which can be used for thermal energy harvesting, and a fractal thermodynamic model is developed for thermal management.
In the paper, an heuristical example is given to illustrate the basic idea of the homotopy perturbation method, so that homotopy perturbation method has made all that is necessary simple, and all that is complex unnecessary.
A three-dimensional Hilbert cube has exactly three dimensions. It can mimic our spatial world on an ordinary observation scale. A four-dimensional Hilbert cube is equivalent to Elnaschie Cantorian spacetime. A very small distance in a very high observable resolution is equivalent to a very high energy spacetime which is inherently Cantorian, non-differentiable and discontinuous. This article concludes that spacetime is a fractal and hierarchical in nature. The spacetime could be modeled by a four-dimensional Hilbert cube. Gravity and electromagnetism are at different levels of the hierarchy. Starting from a simple picture of a four-dimensional cube, a series of higher dimensional polytops can be constructed in a self-similar manner. The resulting structure will resemble a Cantorian spacetime of which the expectation of the Hausdorff dimension equals to 4.23606799 provided that the number of hierarchical iterations is taken to infinity. In this connection, we note that Heisenberg Uncertainty Principle comes into play when we take measurement at different levels of the hierarchy.
This paper suggests a simple analytical method for Volterra-Fredholm integral equations, the solution process is similar to that by variational-based analytical method, e.g., Ritz method, however, the method requires no establishment of the variational principle for the discussed problem, making the method much attractive for practical applications. The examples show the method is straightforward and effective, and the method can also be extended to other nonlinear problems.
No abstract is provided for this article.
It is relatively easy to obtain a variational formulation for a self-adjoint equation, while it is difficult or impossible to do this for a non-self-adjoint one. This work suggests an alternative approach to the derivation of the Lagrangian for both cases. A trial-Lagrangian is constructed, and the exact variational formulation can be obtained after the identification of the unknown function involved in the trial-Lagrangian.
In this paper, we have bubble-electrospun PLA nanofibers to analyze and investigate the effect of different electrical conductivities by adding different amounts of LiCl into the PLA/DMF solutions on the morphology and diameter of the nanofibers. As a result, it is found that when the mass fraction of LiCl is 0.5%, we can obtain the smallest mean diameter of bubble-electrospun nanofibers with more smooth surface and uniform fineness. Moreover, both improving and reducing LiCl concentration brings on coarse nanofibers surface and poor diameter distribution.
Carbon materials are promising candidates for sensors to detect heavy metal ions. This paper reported an effective method of fabricating nanofiber membrane sensor for detection of heavy metal ions by electrospinning with the carbon nanoparticles and PANi (polyaniline) as additives. The results revealed that the PANi/C/PAN nanofiber membrane was the most economical approach to adsorbing and detecting metal ions with highly sensitive property. This paper sheds a light on an economic fabrication of nanofiber membrane sensor with well-defined characteristics in electrical sensors and adsorption applications.
Background: The patented bubble electrospinning, which is a simple and effective technique for mass-production of polymer nanofibers, has been studying extensively, but it is still under development. In the bubble electrospinning, multiple jets move from the positive electrode to the receptor, a long distance between the two electrodes is needed to guarantee complete solvent evaporation, as a result a relative high voltage is needed. Objective: The aim of the present study is to use an auxiliary electrode and an auxiliary air flow to improve bubble electrospinning with lower voltage and higher output than those by its traditional one. Methods: The modification of the bubble electrospinning with an auxiliary electrode and an auxiliary airflow is used to fabricate nanofibers. The auxiliary electrode is close to the positive electrode. The experiment was carried out at room temperature with 8%PVA solution. The result was analyzed with a S4800 cold field scanning electron microscope (SEM, Hitachi S-4800, Tokyo, Japan). Results: The auxiliary electrode can generate a strong induced electric field force. With the action of airflow, the jets will fly to the receptor instead of the auxiliary electrode. Conclusion: Both auxiliary electrode and auxiliary airflow are two important factors affecting the spinning process. It can reduce the spinning voltage and improve spinning efficiency.
No abstract is provided for this article.
Using the semi-inverse method [J.H. He, Chaos Solitons Fractals 19 (2004) 847], a variational principle for a one-dimensional warm-fluid model describing the longitudinal beam dynamics is established.
No abstract is provided for this article.
Purpose The purpose of this paper is to develop an effective numerical algorithm for a gas-melt two-phase flow and use it to simulate a polymer melt filling process. Moreover, the suggested algorithm can deal with the moving interface and discontinuities of unknowns across the interface. Design/methodology/approach The algebraic sub-grid scales-variational multi-scale (ASGS-VMS) finite element method is used to solve the polymer melt filling process. Meanwhile, the time is discretized using the Crank–Nicolson-based split fractional step algorithm to reduce the computational time. The improved level set method is used to capture the melt front interface, and the related equations are discretized by the second-order Taylor–Galerkin scheme in space and the third-order total variation diminishing Runge–Kutta scheme in time. Findings The numerical method is validated by the benchmark problem. Moreover, the viscoelastic polymer melt filling process is investigated in a rectangular cavity. The front interface, pressure field and flow-induced stresses of polymer melt during the filling process are predicted. Overall, this paper presents a VMS method for polymer injection molding. The present numerical method is extremely suitable for two free surface problems. Originality/value For the first time ever, the ASGS-VMS finite element method is performed for the two-phase flow of polymer melt filling process, and an effective numerical method is designed to catch the moving surface.
No abstract is provided for this article.
The present paper employs a numerical method based on the improved block–pulse basis functions (IBPFs). This was mainly performed to resolve the Volterra–Fredholm integral equations of the second kind. Those equations are often simplified into a linear system of algebraic equations through the use of IBPFs in addition to the operational matrix of integration. Typically, the classical alterations have enhanced the time taken by the computer program to solve the system of algebraic equations. The current modification works perfectly and has improved the efficiency over the regular block–pulse basis functions (BPF). Additionally, the paper handles the uniqueness plus the convergence theorems of the solution. Numerical examples have been presented to illustrate the efficiency as well as the accuracy of the method. Furthermore, tables and graphs are used to show and confirm how the method is highly efficient.
