Inflation from R^2 gravity: a new approach using nonlinear electrodynamics

We discuss another approach regarding the inflation from the R^2 theory of gravity originally proposed by Starobinski. A non-singular early cosmology is proposed, where, adding a nonlinear electrodynamics Lagrangian to the high-order action, a bouncing is present and a power-law inflation is obtained. In the model the Ricci scalar works like an inflaton field.Comment: Definitive version to be published in Astroparticle Physics during 2011, 9 page

A spherically symmetric and stationary universe from a weak modification of general relativity

It is shown that a weak modification of general relativity, in the linearized approach, renders a spherically symmetric and stationary model of the universe. This is due to the presence of a third mode of polarization in the linearized gravity in which a "curvature" energy term is present. Such an energy can, in principle, be identified as the Dark Energy. The model can also help to a better understanding of the framework of the Einstein-Vlasov system.Comment: Accepted for publication by Europhysics Letter

Analytical optimisation of electromagnetic design of a linear (tubular) switched reluctance motor

The paper presents a method for optimising radial proportions of the magnetic circuit of a linear tubular switched reluctance motor in terms of maximising the developed thrust from a given machine volume at constant (rated) dissipation. The method is based on the use of analytically derived expressions for the machine’s phase inductance in the position of full misalignment between phase saliencies and mover teeth, and the flux-linkage vs. current relationship in the aligned position. The average thrust is calculated from a complete cycle of co-energy change

A non-geodesic motion in the R^-1 theory of gravity tuned with observations

In the general picture of high order theories of gravity, recently, the R^-1 theory has been analyzed in two different frameworks. In this letter a third context is added, considering an explicit coupling between the R^-1 function of the Ricci scalar and the matter Lagrangian. The result is a non-geodesic motion of test particles which, in principle, could be connected with Dark Matter and Pioneer anomaly problems.Comment: Accepted for Modern Physics Letters

Inclusion of eddy currents impact in the model of a switched reluctance machine based on the equivalent electric circuit

The paper outlines a method for inclusion of the impact of eddy-currents in the model for dynamic prediction of current waveform and force of a switched reluctance machine. The method is based on the equivalent electric circuit model which accounts for the impacts of magnetic saturation and eddy currents in the magnetic core. A linear tubular switched reluctance machine, which includes solid steel elements in the magnetic core, is selected for a case study

An application of multi-level DC-link converter for optimised permutation control of PV sources under partial shading

The paper describes application of a multi-level DC-link converter in overcoming the problem of partially shaded series-connected PV sources. The converter control engages a permutation algorithm which enables each PV source of the string to produce the maximum power. The main features of the system are: (i) a continual operation of all PV sources, shaded and non-shaded, at their maximum power points, (ii) delivery of all extracted power from PV sources to the load and (ii) generation of multi-level output voltage waveform with a low total harmonic distortion