AC losses reduction in Hairpin Windings produced via Additive Manufacturing

One of the key challenges of hairpin windings is the reduction of their high losses at high-frequency operations. Hairpin layouts comprising conductors with variable cross sections have proven good loss performance in previous studies. However, they come at the cost of significant manufacturing complications. The aim of this work is to design hairpin layouts featuring reduced losses compared to classical configurations, exploiting the flexibility enabled by additive manufacturing. In this context, the choice of a proper material with relatively high conductivity and low ecological impact plays an important role. Hence, this article first presents an overview of materials that can be used for the winding additive manufacturing, aiming to select the most suitable one for the application at hand. Then, the loss performance is evaluated and compared against classical copper hairpins. The results demonstrate that opportunely selected alloys featuring asymmetric configurations can compete against classical hairpin windings. © 20XX IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other worksThis paper reflects only the author's view. JU is not responsible for any use that may be made of the information it contains

"Swiss-Cheese" Inhomogeneous Cosmology & the Dark Energy Problem

We study an exact swiss-cheese model of the Universe, where inhomogeneous LTB patches are embedded in a flat FLRW background, in order to see how observations of distant sources are affected. We find negligible integrated effect, suppressed by (L/R_{H})^3 (where L is the size of one patch, and R_{H} is the Hubble radius), both perturbatively and non-perturbatively. We disentangle this effect from the Doppler term (which is much larger and has been used recently \cite{BMN} to try to fit the SN curve without dark energy) by making contact with cosmological perturbation theory.Comment: 35 pages, 6 figure

Evaluation of hydraulic mixing performance in a full-scale anaerobic digester with an external liquid recirculation system using CFD and experimental validation

Anaerobic digestion (AD) has become an essential process for sludge treatment and its optimum performance is related to its mixing degree. In this study, a full-scale Anaerobic Digester (ADer) with an external recirculation mixing system was studied via single-phase 3D-CFD simulations to assess the influence of recirculation flow and a 3-blade propeller. The model was validated with inert tracer tests. The design and mixing parameters were studied to characterise the mixing efficiency in different scenarios. The design parameters were assessed first, but wide deviations from the recommended values were found. Local mixing parameters were found to be useful for defining the degree and type of mixing, and are highly recommended in the CFD studies of ADers. A second-order statistical moment was proposed as a global mixing parameter to describe geometrical and local mixing, and to state a reliable homogenisation time.Funding for open access charge: CRUE-Universitat Jaume

Light Propagation and Large-Scale Inhomogeneities

We consider the effect on the propagation of light of inhomogeneities with sizes of order 10 Mpc or larger. The Universe is approximated through a variation of the Swiss-cheese model. The spherical inhomogeneities are void-like, with central underdensities surrounded by compensating overdense shells. We study the propagation of light in this background, assuming that the source and the observer occupy random positions, so that each beam travels through several inhomogeneities at random angles. The distribution of luminosity distances for sources with the same redshift is asymmetric, with a peak at a value larger than the average one. The width of the distribution and the location of the maximum increase with increasing redshift and length scale of the inhomogeneities. We compute the induced dispersion and bias on cosmological parameters derived from the supernova data. They are too small to explain the perceived acceleration without dark energy, even when the length scale of the inhomogeneities is comparable to the horizon distance. Moreover, the dispersion and bias induced by gravitational lensing at the scales of galaxies or clusters of galaxies are larger by at least an order of magnitude.Comment: 27 pages, 9 figures, revised version to appear in JCAP, analytical estimate included, typos correcte

Design and analysis of fractional factorial experiments from the viewpoint of computational algebraic statistics

We give an expository review of applications of computational algebraic statistics to design and analysis of fractional factorial experiments based on our recent works. For the purpose of design, the techniques of Gr\"obner bases and indicator functions allow us to treat fractional factorial designs without distinction between regular designs and non-regular designs. For the purpose of analysis of data from fractional factorial designs, the techniques of Markov bases allow us to handle discrete observations. Thus the approach of computational algebraic statistics greatly enlarges the scope of fractional factorial designs.Comment: 16 page

Averaging anisotropic cosmologies

We examine the effects of spatial inhomogeneities on irrotational anisotropic cosmologies by looking at the average properties of anisotropic pressure-free models. Adopting the Buchert scheme, we recast the averaged scalar equations in Bianchi-type form and close the standard system by introducing a propagation formula for the average shear magnitude. We then investigate the evolution of anisotropic average vacuum models and those filled with pressureless matter. In the latter case we show that the backreaction effects can modify the familiar Kasner-like singularity and potentially remove Mixmaster-type oscillations. The presence of nonzero average shear in our equations also allows us to examine the constraints that a phase of backreaction-driven accelerated expansion might put on the anisotropy of the averaged domain. We close by assessing the status of these and other attempts to define and calculate `average' spacetime behaviour in general relativity.Comment: revised version, to appear in CQ

An inhomogeneous universe with thick shells and without cosmological constant

We build an exact inhomogeneous universe composed of a central flat Friedmann zone up to a small redshift $z_1$, a thick shell made of anisotropic matter, an hyperbolic Friedmann metric up to the scale where dimming galaxies are observed ($z\simeq 1.7$) that can be matched to a hyperbolic Lema\^{i}tre-Tolman-Bondi spacetime to best fit the WMAP data at early epochs. We construct a general framework which permits us to consider a non-uniform clock rate for the universe. As a result, both for a uniform time and a uniform Hubble flow, the deceleration parameter extrapolated by the central observer is always positive. Nevertheless, by taking a non-uniform Hubble flow, it is possible to obtain a negative central deceleration parameter, that, with certain parameter choices, can be made the one observed currently. Finally, it is conjectured a possible physical mechanism to justify a non-uniform time flow.Comment: Version published in Class. Quantum gra