Adapting Conventional Tools to Analyse Ducted and Open Centre Tidal Stream Turbines

This is the author accepted manuscript. The final version is available from EWTEC via the link in this record.This paper details a hydrodynamic model based on Blade Element Momentum Theory (BEMT) developed to assess ’conventional’ 3-bladed tidal stream turbines (TSTs), adapted here to analyse an ’unconventional’ case of a ducted and open centre device. Validations against a more detailed coupled Reynolds averaged computational fluid dynamics (RANS-BEM) model shows excellent agreement, of within 2% up to the peak power condition, with associated computational times in the order of a few minutes on a single core. The paper demonstrates the application of hydrodynamic forces into a structural analysis tool, in order to assess blade stress distributions of a generic hubless turbine. Incorporation of parameters such as non-uniform inflows and blade weight forces are investigated, with their effects on stress profiles presented. Key findings include: i) the adapted BEMT model replicates the majority of turbine performance characteristics estimated through previous CFD assessments; ii) the proposed model reduces the computational effort by several orders of magnitude compared to the reference coupled CFD, making it suitable for engineering assessments iii) blade stress distribution profiles are quantified, detailing concentration zones and cyclic values for use in fatigue analyses. This work forms part of a greater project aimed to develop a suite of analytical tools to perform engineering assessments of bi-directional ducted TSTsThis research is carried out as part of the Industrial Doctoral centre for Offshore Renewable Energy (IDCORE), funded by the Energy Technology partnership and the RCUK Energy programme (Grant number EP/J500847/1), in collaboration with EDF R&D

On the log-local principle for the toric boundary

Let $X$ be a smooth projective complex variety and let $D=D_1+\cdots+D_l$ be a reduced normal crossing divisor on $X$ with each component $D_j$ smooth, irreducible, and nef. The log-local principle of van Garrel-Graber-Ruddat conjectures that the genus 0 log Gromov-Witten theory of maximal tangency of $(X,D)$ is equivalent to the genus 0 local Gromov-Witten theory of $X$ twisted by $\bigoplus_{j=1}^l\mathcal{O}(-D_j)$. We prove that an extension of the log-local principle holds for $X$ a (not necessarily smooth) $\mathbb{Q}$-factorial projective toric variety, $D$ the toric boundary, and descendent point insertions.Comment: 19 page

Gloss Perception in Painterly and Cartoon Rendering

International audienceDepictions with traditional media such as painting and drawing represent scene content in a stylized manner. It is unclear however how well stylized images depict scene properties like shape, material and lighting. In this paper, we describe the first study of material perception in stylized images (specifically painting and cartoon) and use non photorealistic rendering algorithms to evaluate how such stylization alters the perception of gloss. Our study reveals a compression of the range of representable gloss in stylized images so that shiny materials appear more diffuse in painterly rendering, while diffuse materials appear shinier in cartoon images. From our measurements we estimate the function that maps realistic gloss parameters to their perception in a stylized rendering. This mapping allows users of NPR algorithms to predict the perception of gloss in their images. The inverse of this function exaggerates gloss properties to make the contrast between materials in a stylized image more faithful. We have conducted our experiment both in a lab and on a crowdsourcing website. While crowdsourcing allows us to quickly design our pilot study, a lab experiment provides more control on how subjects perform the task. We provide a detailed comparison of the results obtained with the two approaches and discuss their advantages and drawbacks for studies like ours

CO-FREE Alternative Test Products for Copper Reduction in Agriculture

The project CO-FREE (2012-2016) aimed to develop strategies to replace/reduce copper use in organic, integrated and conventional farming. CO-FREE alternative test products (CTPs) were tested and integrated together with decision support systems, disease-tolerant varieties, and innovative breeding goals (ideotypes) into improved management strategies. CO-FREE focused on apple/apple scab (Venturia inaequalis), grape/downy mildew (Plasmopara viticola), and tomato and potato/late blight (Phytophthora infestans). Starting point of the project were ten CTPs with direct or indirect modes of action including Trichoderma atroviride SC1 and protein extract SCNB, Lysobacter spp., yeast-based derivatives, Cladosporium cladosporioides H39, the oligosaccharidic complex COS-OGA, Aneurinibacillus migulanus and Xenorhabdus bovienii, sage (Salvia officinalis) extract, liquorice (Glycyrrhiza glabra) extract, PLEX- and seaweed plant extracts. As the project progressed, further promising CTPs were included by the partners. Field trials were performed in different European countries in 2012-2015 following EPPO standards. In the first years, stand-alone applications of CTPs were tested. In the following years these were integrated into complete strategies. Effects on main and further diseases, on yield and on non-target organisms were assessed. Here, field trial results with CTPs are summarized

Perceptual quality of BRDF approximations: dataset and metrics

International audienceBidirectional Reflectance Distribution Functions (BRDFs) are pivotal to the perceived realism in image synthesis. While measured BRDF datasets are available, reflectance functions are most of the time approximated by analytical formulas for storage efficiency reasons. These approximations are often obtained by minimizing metrics such as L 2 —or weighted quadratic—distances, but these metrics do not usually correlate well with perceptual quality when the BRDF is used in a rendering context, which motivates a perceptual study. The contributions of this paper are threefold. First, we perform a large-scale user study to assess the perceptual quality of 2026 BRDF approximations, resulting in 84138 judgments across 1005 unique participants. We explore this dataset and analyze perceptual scores based on material type and illumination. Second, we assess nine analytical BRDF models in their ability to approximate tabulated BRDFs. Third, we assess several image-based and BRDF-based (Lp, optimal transport and kernel distance) metrics in their ability to approximate perceptual similarity judgments

Stable maps to Looijenga pairs: orbifold examples

In [15], we established a series of correspondences relating five enumerative theories of log Calabi–Yau surfaces, i.e. pairs (Y, D) with Y a smooth projective complex surface and D=D1+⋯+Dl an anticanonical divisor on Y with each Di smooth and nef. In this paper, we explore the generalisation to Y being a smooth Deligne–Mumford stack with projective coarse moduli space of dimension 2 and Di nef Q-Cartier divisors. We consider in particular three infinite families of orbifold log Calabi–Yau surfaces, and for each of them, we provide closed-form solutions of the maximal contact log Gromov–Witten theory of the pair (Y, D), the local Gromov–Witten theory of the total space of ⨁iOY(−Di), and the open Gromov–Witten of toric orbi-branes in a Calabi–Yau 3-orbifold associated with (Y, D). We also consider new examples of BPS integral structures underlying these invariants and relate them to the Donaldson–Thomas theory of a symmetric quiver specified by (Y, D) and to a class of open/closed BPS invariants