Analytical solution for the electric potential in arbitrary anisotropic layered media applying the set of Hankel transforms of integer order

2006 ◽  
Vol 54 (5) ◽  
pp. 651-661 ◽  
Author(s):  
E. Pervago ◽  
A. Mousatov ◽  
V. Shevnin
Author(s):  
Yongjun Shen ◽  
Jiangchuan Niu ◽  
Shaopu Yang ◽  
Sujuan Li

The classical mass-on-moving-belt model describing friction-induced vibration is studied. The primary resonance of dry-friction oscillator with fractional-order PID (FOPID) controller of velocity feedback is investigated by Krylov–Bogoliubov–Mitropolsky (KBM) asymptotic method, and the approximately analytical solution is obtained. The effects of the parameters in FOPID controller on dynamical properties are characterized by five equivalent parameters. Those equivalent parameters could distinctly illustrate the effects of the parameters in FOPID controller on the dynamical response. The effects of dry friction on the dynamical properties are characterized in the form of the equivalent linear damping and nonlinear damping. The amplitude-frequency equation for steady-state solution associated with the stability condition is also studied. A comparison of the analytical solution with the numerical results is fulfilled, and their satisfactory agreement verifies the correctness of the approximately analytical results. Finally, the effects of the coefficients and orders in FOPID controller on the amplitude-frequency curves are analyzed, and the control performances of FOPID and traditional integer-order proportional-integral-derivative (PID) controllers are compared. The comparison results show that FOPID controller is better than traditional integer-order PID controller for controlling the primary resonance of dry-friction oscillator, when the coefficients of the two controllers are the same. This presents theoretical basis for scholars and engineers to design similar fractional-order controlled system.


Author(s):  
Hongjun Song ◽  
Dawn J. Bennett

As a new technique, dielectrophoresis has been proven to be successful in the separation, transportation, entrapment and manipulation of cells, DNA molecules, and viruses. One typical design uses an array with interdigitated parallel electrodes to manipulate and separate particles using traveling wave and conventional dielectrophoresis. In order to obtain an analytical solution for the dielectrophoretic force or traveling wave dielectrophoretic force, the electric potential equation needs to be solved. Unfortunately, the mixed type of boundary condition (Dirichet and Neumann) for the electric potential equation poses a large challenge for obtaining an analytical solution. Although some analytical solutions have been achieved using an approximate single type of boundary condition instead of the exact boundary condition, this leads to inaccurate results especially in the zone near the electrodes which cannot be neglected. In this paper, we present an analytical method for solving the electric potential equation with the mixed type of boundary condition. We compare our analytical solution with the numerical results obtained using the Computational Fluid Dynamics Research Corporation, CFDRC, code which verifies our analytical method is correct for solving this problem. In addition, comparisons are made between the analytical solutions with approximate boundary conditions and those with exact boundary conditions. The comparison shows our analytical solution gives a more accurate analysis for the conventional and traveling wave dielectrophoretic forces.


2014 ◽  
Vol 136 (9) ◽  
Author(s):  
Ivor Dülk ◽  
Tamás Kovácsházy

The computation of the analytical solution of the steady temperature distribution in multilayered media can become numerically unstable if there are different longitudinal (i.e., the directions parallel to the layers) boundary conditions for each layer. In this study, we develop a method to resolve these computational difficulties by approximating the temperatures at the junctions step-by-step and solving for the thermal field separately in only the single layers. First, we solve a two-layer medium problem and then show that multilayered media can be represented as a hierarchy of two-layered media; thus, the developed method is generalized to an arbitrary number of layers. To improve the computational efficiency and speed, we use varying weighting coefficients during the iterations, and we present a method to decompose the multilayered media into two-layered media. The developed method involves the steady-state solution of the diffusion equation, which is illustrated for 2D slabs using separation of variables (SOV). A numerical example of four layers is also included, and the results are compared to a numerical solution.


2018 ◽  
Vol 6 (2) ◽  
Author(s):  
Afrah Sadiq Hasan

Numerical solution of the well-known Bagley-Torvik equation is considered. The fractional-order derivative in the equation is converted, approximately, to ordinary-order derivatives up to second order. Approximated Bagley-Torvik equation is obtained using finite number of terms from the infinite series of integer-order derivatives expansion for the Riemann–Liouville fractional derivative. The Bagley-Torvik equation is a second-order differential equation with constant coefficients. The derived equation, by considering only the first three terms from the infinite series to become a second-order ordinary differential equation with variable coefficients, is numerically solved after it is transformed into a system of first-order ordinary differential equations. The approximation of fractional-order derivative and the order of the truncated error are illustrated through some examples. Comparison between our result and exact analytical solution are made by considering an example with known analytical solution to show the preciseness of our proposed approach.


Sign in / Sign up

Export Citation Format

Share Document