On Love-type waves in a finitely deformed magnetoelastic layered half-space

In this paper, the propagation of Love-type waves in a homogeneously and finitely deformed layered half-space of an incompressible non-conducting magnetoelastic material in the presence of an initial uniform magnetic field is analyzed. The equations and boundary conditions governing linearized incremental motions superimposed on an underlying deformation and magnetic field for a magnetoelastic material are summarized and then specialized to a form appropriate for the study of Love-type waves in a layered half-space. The wave propagation problem is then analyzed for different directions of the initial magnetic field for two different magnetoelastic energy functions, which are generalizations of the standard neo-Hookean and Mooney–Rivlin elasticity models. The resulting wave speed characteristics in general depend significantly on the initial magnetic field as well as on the initial finite deformation, and the results are illustrated graphically for different combinations of these parameters. In the absence of a layer, shear horizontal surface waves do not exist in a purely elastic material, but the presence of a magnetic field normal to the sagittal plane makes such waves possible, these being analogous to Bleustein–Gulyaev waves in piezoelectric materials. Such waves are discussed briefly at the end of the paper

Magneto-sensitive elastomers in a homogeneous magnetic field: a regular rectangular lattice model

A theory of mechanical behaviour of the magneto-sensitive elastomers is developed in the framework of a linear elasticity approach. Using a regular rectangular lattice model, different spatial distributions of magnetic particles within a polymer matrix are considered: isotropic, chain-like and plane-like. It is shown that interaction between the magnetic particles results in the contraction of an elastomer along the homogeneous magnetic field. With increasing magnetic field the shear modulus for the shear deformation perpendicular to the magnetic field increases for all spatial distributions of magnetic particles. At the same time, with increasing magnetic field the Young's modulus for tensile deformation along the magnetic field decreases for both chain-like and isotropic distributions of magnetic particles and increases for the plane-like distribution of magnetic particles.Comment: 38 pages, 15 figure

Development of magnetorheological elastomers (MREs) for strength and fatigue resistance

Natural rubber (NR)-based magnetorheological elastomers (MREs) exhibiting a reasonable switching effect were fabricated and tested. They were strong enough for use in automotive applications but still needed protection against ageing. Ethylene–propylene–diene rubber (EPDM) is a cost-effective material that is frequently used in the automotive industry because of its advantageous range of properties. With these applications in mind, it was a logical progression to the development of EPDM-based MREs. Unlike strain-crystallising NR, EPDM requires reinforcement to render its tensile and fatigue strength suitable for use in most applications. While small amounts of carbon black were sufficient for the NR-based MREs, a trade-off between non-reinforcing carbonyl iron powder (CIP) and reinforcing carbon black fillers was necessary to imbue the EPDM-based MREs with reasonably good mechanical properties. With a limit on the quantities of fillers that could be added, attention was turned to the matrix material itself and the blend of polymers employed in EPDM2 and EPDM3 were chosen in order to strengthen the EPDM-based MREs by enhancing polymer molecular weight and reinforcement. However, an unwanted effect of the stronger polymer network was the high-viscosity matrix in these compounds which hindered the alignment of magnetic particles early in the vulcanisation process. This led to poorer magnetic particle orientation, resulting in a more homogenous dispersion of the CIP and consequently produced MRE specimens that were more isotropic than anisotropic. Subsequently the switching effect of these materials was lower than would be obtained in MREs with a low viscosity (say, 40 MU) matrix. It was not feasible to sacrifice reinforcing carbon black in these compounds, but there are other possibilities open to the rubber compounder. An alternative means of reducing the viscosity of EPDM3 is simply to double the content of softening oil. This would have a slight but minimal negative effect on the tensile properties of the material. The addition of a small amount of retardant to delay vulcanisation and extend the time available for orientation of the magnetic particles into chains would also be beneficial. This would also reduce the modulus of the compound, but the reduction would again be negligible. As in all material design, there is a trade-off to be made in choosing the right combination of properties, but both of these changes would result in the development of an effective magnetorheological compound

Dynamic Properties of Magnetorheological Elastomers Based on Iron Sand and Natural Rubber

In this study, magnetorheological elastomers (MREs) based on iron sand and natural rubber were prepared. The Taguchi method was employed to investigate the effect of a number of factors, namely, the iron sand content, iron sand particle size, and applied magnetic field during curing on the loss tangent (tan δ) and energy dissipated during cyclic loading. Tan δ was measured through dynamic mechanical analysis over a range of frequency (0.01–130 Hz), strain amplitude (0.1–4.5%), and temperature (−100 to 50°C). The energy dissipated was measured with a universal tester under cyclic tensile loading. The data were then statistically analyzed to predict the optimal combination of factors, and finally, experiments were conducted for verification. It was found that the iron sand content had the greatest influence on tan δ when measured over a range of frequency, and the energy dissipated during hysteresis tests. However, none of the factors showed a significant influence on tan δ when measured over a range of strain amplitude. Furthermore, the iron sand content and magnetic field were also found to influence the width of the peak in tan δ as a function of the temperature. The morphological characteristics of the MREs were also examined with scanning electron microscopy

Inkludering av elever i behov av särskilt stöd.

Elever i behov av särskilt stöd är ett begrepp som finns i alla skolor. Det kan vara elever som har specialundervisning eller får sina behov tillgodosedda i den egna klassrumsmiljön. Med inkludering av elever i behov av särskilt stöd menas att eleverna istället för särskild specialundervisning skall få den hjälp de behöver i den ordinarie klassrumsmiljön, men att undervisningen samtidigt skall anpassas efter elevens behov och förutsättningar. Vi anser att inkluderingsarbetet är viktigt då vi i vår framtida roll som lärare dagligen kommer att stöta på dessa elever. Att ha en kännedom om hur man som pedagog kan arbeta med inkludering av elever i behov av särskilt stöd bedömer vi som viktigt. Syftet med vårt arbete är att undersöka hur elever i behov av särskilt stöd inkluderas i den ordinarie klassrumsundervisningen. Arbetet avser att ta reda på hur fem lärare planerar inför och resonerar om arbetet med inkludering av elever i sina klassrum. För att precisera syftet har vi valt följande frågeställningar: 1. Hur kan inkluderingsarbete av elever i behov av särskilt stöd gå till i skolan? 2. Hur resonerar lärare om sitt undervisningssätt i relation till möjligheten att inkludera dessa elever? Vi har valt att titta på hur arbetet med inkludering kan gå till i skolorna. För att kunna svara på detta har vi valt att genomföra kvalitativa intervjuer med fem pedagoger som har olika syn på begreppet "barn i behov av särskilt stöd". Vårt resultat visar att arbetet med inkludering skiljer sig från skola till skola. För kunna genomföra ett bra arbete med inkludering krävs det, enligt våra respondenter, bra arbetsmaterial och tillgång på resurspersonal. Bristen på dessa kan göra att arbetet med inkludering försvåras. Det finns inget "recept" som pedagoger kan använda på alla sina elever, utan undervisningen måste individanpassas

Imagining Sustainable Futures : Framing of Energy Transition in Sweden

The concept of “energy transition” is often portrayed as a shift in the energy infrastructure and a transition toward renewable resources and technological innovation, with a prevalent focus on how to keep producing more and more energy to maintain economic growth. This study aims to analyse how key actors in the Swedish energy sector frame the energy transition, how their framing influences the discourse and how we can consider alternative framings to contribute to the ongoing debate and imagine more sustainable futures. Guided by environmental humanities, future-oriented frameworks, and infrastructure logics, texts from four key actors in the electricity sector in Sweden have been analysed. A multi-methodological approach incorporating discourse analysis, framework analysis and theme analysis have been employed to systematically examine how these key actors frame energy transition. The results show a significant focus on increased growth, where energy consumption is seen as constantly rising and where increased electrification is seen as a prerequisite for the transition. Key actors present a large number of solutions, all characterized by high-tech approaches, where the problem to be solved mainly revolves around meeting an increased demand for electricity. The future is depicted as largely predetermined with the transition seemingly only is matter of changing energy sources. It is argued that alternative framings are needed to address sustainability issues and societal values, acknowledging the interplay between technology and society. Additionally, the study highlights the need to reimagine energy transition beyond high-tech solutions, incorporating diverse actors and knowledge systems to foster more sustainable and equitable futures