Performance enhancement of underwater propulsion motor using differential evolution optimization

1113-1119This paper describes the performance enhancement of underwater propulsion motor using differential evolution optimization (DEO). Usually during development stage, an analytical subdomain model (ASM) is often preferred to be used in the design of electric machines since ASM has faster computational time compared to the finite element method. differential evolution algorithm is deployed to provide the optimization process in searching the optimal motor parameters iteratively and intelligently with specific objective functions. For this purpose, a three-phase, 6-slot/4-pole permanent magnet synchronous motor (PMSM) intended for the underwater propulsion system is first designed by using ASM and then later optimized by differential evolution algorithm. Five main motor parameters, i.e., magnet pole arc, magnet thickness, air gap length, slot opening, and stator inner radius are varied and optimized to achieve the design objective functions, i.e., high motor efficiency, high output torque, low total harmonic distortion (THDv) in back-emf, and low cogging torque. Results from differential evolution optimization show an improved performance of the proposed PMSM where the efficiency of the motor is increased to 96.1% from its initial value of 94.2%, 13% increase in the output torque, and 4.1% reduction for total harmonic distortion in its back-emf. Therefore, DEO can be highly considered during initial design stage to optimize the motor parameters in developing a good underwater propulsion motor

Integration by parts identities in integer numbers of dimensions. A criterion for decoupling systems of differential equations

Integration by parts identities (IBPs) can be used to express large numbers of apparently different d-dimensional Feynman Integrals in terms of a small subset of so-called master integrals (MIs). Using the IBPs one can moreover show that the MIs fulfil linear systems of coupled differential equations in the external invariants. With the increase in number of loops and external legs, one is left in general with an increasing number of MIs and consequently also with an increasing number of coupled differential equations, which can turn out to be very difficult to solve. In this paper we show how studying the IBPs in fixed integer numbers of dimension d=n with $n \in \mathbb{N}$ one can extract the information useful to determine a new basis of MIs, whose differential equations decouple as $d \to n$ and can therefore be more easily solved as Laurent expansion in (d-n).Comment: 31 pages, minor typos corrected, references added, accepted for publication in Nuclear Physics

Poisson varieties from Riemann surfaces

Short survey based on talk at the Poisson 2012 conference. The main aim is to describe and give some examples of wild character varieties (naturally generalising the character varieties of Riemann surfaces by allowing more complicated behaviour at the boundary), their Poisson/symplectic structures (generalising both the Atiyah-Bott approach and the quasi-Hamiltonian approach), and the wild mapping class groups.Comment: 33 pages, 3 figure

Degenerations and limit Frobenius structures in rigid cohomology

We introduce a "limiting Frobenius structure" attached to any degeneration of projective varieties over a finite field of characteristic p which satisfies a p-adic lifting assumption. Our limiting Frobenius structure is shown to be effectively computable in an appropriate sense for a degeneration of projective hypersurfaces. We conjecture that the limiting Frobenius structure relates to the rigid cohomology of a semistable limit of the degeneration through an analogue of the Clemens-Schmidt exact sequence. Our construction is illustrated, and conjecture supported, by a selection of explicit examples.Comment: 41 page