Shear-induced particle diffusivities from numerical simulations

Using Stokesian dynamics simulations, we examine the flow of a monodisperse, neutrally buoyant, homogeneous suspension of non-Brownian solid spheres in simple shear, starting from a large number of independent hard-sphere distributions and ensemble averaging the results. We construct a novel method for computing the gradient diffusivity via simulations on a {\em homogeneous} suspension and, although our results are only approximate due to the small number of particles used in the simulations, we present here the first values of this important parameter, both along and normal to the plane of shear, which have ever been obtained directly either experimentally or numerically. We show furthermore that, although the system of equations describing the particle motions is deterministic, the particle displacements in the two directions normal to the bulk flow have Gaussian distributions with zero mean and, a variance which eventually grows linearly in time thereby establishing that the system of particles is diffusive. In addition we show that although the particle evolution equations are, in principle, reversible, the suspension has in fact a finite correlation time $T_c$ of the order of the inverse shear rate. For particle concentrations up to 45%, we compute the corresponding tracer diffusivities both from the slope of the mean square particle displacement as well as by integrating the corresponding velocity autocorrelations and find good agreement between the two sets of results.Comment: 51 pages ; 16 figures ; 5 tables; submitted to J.Fluid Mec

2-D constrained Navier-Stokes equation and intermediate asymptotics

We introduce a modified version of the two-dimensional Navier-Stokes equation, preserving energy and momentum of inertia, which is motivated by the occurrence of different dissipation time scales and related to the gradient flow structure of the 2-D Navier-Stokes equation. The hope is to understand intermediate asymptotics. The analysis we present here is purely formal. A rigorous study of this equation will be done in a forthcoming paper

Inductor based switching DC-DC converter for low voltage power distribution in SLHC

In view of a power distribution scheme compatible with the requirements of the SLHC environment, we are evaluating the feasibility of on-board inductor-based DC-DC step-down conversion. Such converter should be an integrated circuit and capable of operating in harsh radiation environments and in the high magnetic field of the experiments. In this paper we present results concerning the choice of the technology, the search for the magnetic components and the calculations of the expected efficiency

Implementing an interdisciplinary student centric approach to work-integrated learning

This paper describes the implementation of an innovative approach to work-integrated learning using interdisciplinary projects within a university Faculty of Business. Further, it discusses the implementation of integrated and authentic assessments involving academic units in the marketing, urban planning and business communication disciplines. The authors reflect on issues involved with the introduction of interdisciplinary teaching and learning strategies, representing a shift from traditional silo approaches in tertiary education. The paper considers how a student-centered learning approach can support innovation in higher education. It highlights the importance of providing students with an integrated, in situ approach to learning within the context of their own learning institution. The paper concludes by asserting that universities can provide business students with authentic and relevant business problems, the opportunity to access the resources of the university and engage with staff and students across a range of disciplines to facilitate a project-based learning environment on-campus

Integrating the academic experience: An inter-disciplinary approach to the authentic marketing research experience

This paper describes the evolution of an innovative inter–disciplinary approach to teaching and learning in a University Faculty of Business. Further, it reviews the implementation of a series of unique, integrated and authentic assessments involving units based in the marketing, urban planning and business communication disciplines. The project has used the production of Revitalization Plans for the University‘s campuses as the basis for integrating student teaching and learning. It has championed an approach which moves away from the traditional ‗silo‘ methods of academic assessment to integrated, contextualised learning which develops both generic and discipline-specific skills such as client/consultation roles, business communications and knowledge in marketing, urban planning, and management. The paper concludes by reflecting on the issues involved with the introduction of the inter-disciplinary approach to teaching and learning with the University

Evidence of the Most Stretchable Egg Sac Silk Stalk, of the European Spider of the Year Meta menardi

Spider silks display generally strong mechanical properties, even if differences between species and within the same species can be observed. While many different types of silks have been tested, the mechanical properties of stalks of silk taken from the egg sac of the cave spider Meta menardi have not yet been analyzed. Meta menardi has recently been chosen as the “European spider of the year 2012”, from the European Society of Arachnology. Here we report a study where silk stalks were collected directly from several caves in the north-west of Italy. Field emission scanning electron microscope (FESEM) images showed that stalks are made up of a large number of threads, each of them with diameter of 6.03±0.58 µm. The stalks were strained at the constant rate of 2 mm/min, using a tensile testing machine. The observed maximum stress, strain and toughness modulus, defined as the area under the stress-strain curve, are 0.64 GPa, 751% and 130.7 MJ/m(3), respectively. To the best of our knowledge, such an observed huge elongation has never been reported for egg sac silk stalks and suggests a huge unrolling microscopic mechanism of the macroscopic stalk that, as a continuation of the protective egg sac, is expected to be composed by fibres very densely and randomly packed. The Weibull statistics was used to analyze the results from mechanical testing, and an average value of Weibull modulus (m) is deduced to be in the range of 1.5–1.8 with a Weibull scale parameter (σ (0)) in the range of 0.33–0.41 GPa, showing a high coefficient of correlation (R(2) = 0.97)

New species and new records of exotic Scolytinae (Coleoptera, Curculionidae) in Europe

Background Bark and ambrosia beetles (Coleoptera, Scolytinae) are amongst the most important wood -boring insects introduced to Europe. During field investigations conducted between 2019 and 2021 in different countries and regions of Europe, many exotic species have been recorded providing new and relevant data. New information Dryoxylon onoharaense (Murayama, 1933) is recorded in Europe for the first time. Xyleborinus attenuatus (Blandford, 1894) is a species new to Italy, while Xylosandrus germanus (Blandford, 1894), Hypothenemus eruditus (Westwood, 1836) and Amasa sp. near A. truncata are new country records for Portugal. Cnestus mutilatus (Blandford, 1894), Phloeotribus liminaris (Harris, 1852) were collected in Italy and Amasa sp. near A. truncata was collected in France after the first discovery, confirming their establishment and their dispersal into new areas

Interaction of vortices in viscous planar flows

We consider the inviscid limit for the two-dimensional incompressible Navier-Stokes equation in the particular case where the initial flow is a finite collection of point vortices. We suppose that the initial positions and the circulations of the vortices do not depend on the viscosity parameter \nu, and we choose a time T > 0 such that the Helmholtz-Kirchhoff point vortex system is well-posed on the interval [0,T]. Under these assumptions, we prove that the solution of the Navier-Stokes equation converges, as \nu -> 0, to a superposition of Lamb-Oseen vortices whose centers evolve according to a viscous regularization of the point vortex system. Convergence holds uniformly in time, in a strong topology which allows to give an accurate description of the asymptotic profile of each individual vortex. In particular, we compute to leading order the deformations of the vortices due to mutual interactions. This allows to estimate the self-interactions, which play an important role in the convergence proof.Comment: 39 pages, 1 figur