Volume 4 Issue 3

Authors: J. O. Jonson

Abstract: It has been previously proved that the repulsive force between the two parts of Ampère’s bridge, measured in experiments performed by Pappas and Moyssides, can be explained by Coulomb’s law, if the effects of propagation delay are correctly taken into account. Special relativity theory is also necessary to estimate the extent to which it may affect the result. Otherwise it might be unnecessary to involve special relativity theory in the case of DC currents carried by electric conductors, because the velocities of conduction electrons are usually very small compared to the speed of light. However, in this paper, the force between the two parts of Ampère’s Bridge has been calculated, taking into account special relativity theory, particularly the Lorentz transformation which brings about a change in the lengths of moving bodies. The result is that the repulsive force between the two parts of Ampère’s bridge remains repulsive, displaying dependence on the thickness of the branches, decreasing with increasing thickness. This was also the case when analysis was conducted without taking into account the special relativity theory. In fact, the predictions are in complete agreement with physical measurements.

Keywords: Ampère’s Law; Coulomb’s Law; Propagation Delay; Electromagnets; Ampère’s Bridge; Lorentz Force; Retarded Action; Special Relativity Theory, Lorentz Transformation

Doi:10.5963/JBAP0403002

Authors: Guihua Zhang

Abstract: To accurately monitor the strain of a host with low strength, a new strain transfer model is proposed for the substrate FBG sensor. In the strain transfer model, the mechanical properties of the host are taken into consideration. The strain relationship between the fiber core and the host is obtained. The theoretical approach was verified by numerical simulation and experimental results. The influences of the mechanical parameters of the host on the strain transfer are analyzed. It is concluded that the strain transfer rate increases nonlinearly with the increase of the shear modulus of the host. The shear modulus of the host has different influence in different strain ranges; for the low strength host, the mechanical parameters of the host have great influence on the strain transfer rate. These results provide theoretical guidelines for the FBG sensor applications in low strength host.

Keywords: Fiber Bragg Grating; Strain Transfer; Similar Model; Mechanical Parameter

Doi:10.5963/JBAP0403001

Authors: Weiguo Yang; Michael A. Fiddy

Abstract: The widely accepted theoretical treatment of the electromagnetic boundary problem of evanescent wave refraction at an interface between a normal medium of and an ideal negative index medium of seems to predict that the negative index of refraction would result in perfect lenses. The treatment, however, disregards the effects of non-zero surface potentials due to the nonlocal nature of surface optics at the microscopic level, and is self-inconsistent. This paper proposed to capture the microscopic non-zero surface potentials by introducing the macroscopic electromagnetic description non-zero effective surface current and charge densities at the interface. This treatment provides a self-consistent solution to the aforementioned electromagnetic boundary problem by finding the effective surface current and charge distributions, and after which solving the refracted and reflected fields analytically using Green's function method. The self-consistent solution yielded a transmission coefficient of 1 and reflection coefficient of 0 for all evanescent waves at this special interface, making it impossible for resonant amplification of those waves to occur.

Keywords: Applied Classical Electromagnetism; Reflection and Refraction; Metamaterials; Surface Plasmon Polariton

Doi:10.5963/JBAP0403003