| 1. |
- Bartholdsson, Åsa, 1963-, et al.
(författare)
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Cultivating the socially competent body : bodies and risk in Swedish programmes for social and emotional learning in preschools and schools
- 2014
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Ingår i: Critical Studies in Education. - : Taylor & Francis Group. - 1750-8495 .- 1750-8487. ; 55:2, s. 201-212
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Tidskriftsartikel (refereegranskat)abstract
- Social emotional learning (SEL) is common in preschools and schools both in Europe and North America today. Programmes for socio-emotional training and the rise of what is labelled therapeutic education have dramatically increased during the first decade of the millennium. In this article, a manual-based programme used for SEL in a Swedish school context is analysed from perspectives rooted in childhood sociology and post-structural studies. The aim of this study is to analyse the discursive constructions of a context of risk and the instilment of specific corporeal regimes. The main issue concerns the meaning and use of the body in the discursive construction of the social competent child within this context of risk. The analysis shows that the socially competent child is shaped and cultivated through self-regulating techniques aiming at creating a docile body, a body that will be a good citizen, a pliant member of the social order. Social emotional learning (SEL) is common in preschools and schools both in Europe and North America today. Programmes for socio-emotional learning and what is labelled therapeutic education (Ecclestone & Hayes, 2007; Furedi, 2009) have dramatically increased during the first decade of the millennium. In Sweden, schools often justify their use of these programmes as a way of organizing their value-based education (von Br mssen, 2011), that is, as a way of realizing the democratic ambitions expressed in educational policy documents, such as the national curriculum.
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| 2. |
- Gaborit, Mathieu, et al.
(författare)
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Controlled anisotropy materials and 3D printing: experimentations and analyses
- 2022
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Ingår i: Proceedings of ISMA 2022 - International Conference on Noise and Vibration Engineering and USD 2022 - International Conference on Uncertainty in Structural Dynamics. - : KU Leuven, Departement Werktuigkunde. ; , s. 477-481
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Konferensbidrag (refereegranskat)abstract
- Novel computational tools and optimisation strategies offer an unprecedented framework to explore large design spaces within a short time frame. In the scope of material design, these new possibilities have completely revolutionized the research horizon, leading amongst other things to controlled anisotropy media with a finer granularity than ever seen before. However, a question arises regarding the manufacturability of such media which most of the time relies on 3D printing and the agreement between modelled and printed geometry. In the recent years, the authors published several articles on the properties of Kelvin Cell packings and the possibility to control their anisotropy. In the last few months, an effort towards printing the designed media has been made in search for experimental validation of the numerical results. This contribution describes the printing process for kelvin cell packing samples with controlled anisotropy and analyses their agreement with the model both from a geometric and from a physical response standpoint. Depending on the advances of current research, information on the dynamic behaviour of such systems will be discussed.
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| 3. |
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| 4. |
- Lundberg, Eva, 1964-, et al.
(författare)
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Analytical method for predicting micro-geometry based flow resistivity in anisotropic foams to improve sound absorption of vehicle panels
- 2021
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Ingår i: Proceedings of the Resource Efficient Vehicles Conference - 2021 (rev2021). - Stockholm, Sweden.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Vehicle structures such as train floors or car roofs are usually built as multi-layer panels, where a foam is placed between a load-carrying structure and an interior panel. The foam adds acoustical and thermal performance, but very little weight. In most contributions introducing foams for acoustic treatment, these have been considered isotropic, with acoustic losses mainly dependingon properties in the thickness direction. Another mechanism investigated here is the possibilityfor the acoustic flow in the foam to change from acting only in the thickness direction but rather to be re-directed to also travel in-plane, where dimensions are substantially larger than in the thickness direction, permitting more losses as the wave travels through the material. That kind of effect would result in higher acoustic losses without increasing the thickness of the vehicle panel and better use of the allowable space to achieve acoustic and functional requirements, i.e. a better functional density. A first step is to investigate how the absorption properties of an anisotropic foam differs from an isotropic foam. The chosen approach is to use an analytical micro-modelto calculate the dynamic drag impedance (flow resistivity on micro-scale) for an anisotropic opencell foam material. Based on a simple micro-scale geometry of Kelvin cells, it has been shown that simple cell alterations to the micro-geometry, such as stretching, twisting and tilting results in an anisotropic foam structure. The anisotropic flow resistivity tensor is not diagonal and uniform, but different directions can have different magnitudes and it can display off-diagonal coupling terms. The influence of such micro-scale distortions on the flow resistivity, and on the resulting sound absorption is investigated with the purpose of improving the acoustic performance without adding volume. Future steps include to modify the functional density and tailor the sound transmission loss to a specific application.
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| 5. |
- Lundberg, Eva, 1964-, et al.
(författare)
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Micro model for calculating flow resistivity for anisotropic open cell materials with high aspect ratio of struts
- 2016
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Micro-structure models for calculating flow resistivity for open cell materials with high aspect ratio of struts are presented. Two micro-geometries are analyzed and compared: the hexahedral model, with the solid frame in shape of a cube for the isotropic case, and the tetrakaidecahedron (Kelvin cell). For flow resistivity calculations the solid frame is assumed to be rigid. The models are elongated in one direction to study the influence of micro-structural anisotropy on the macro level flow resistivity. In order to evaluate how the redistribution of material affects the flow resistivity, the porosity of the material is kept constant. Since the porosity is defined as unity minus the ratio of strut volume of the cell to the total volume of the cell, there are different ways of linking the micro level properties to the macro level. The first approach presented here is to let strut thickness be uniform and adjust the volume of the cell to a constant ratio compared to the isotropic case. The second approach is to let the strut volume be constant, i.e. if a strut is elongated, it is also thinner. In this case the cell volume must equal the isotropic volume. For uniform strut thickness the flow resistivity increases substantially with increasing height to width ratio for the hexahedral model, and decreases for the Kelvin cell. For constant strut volume the flow resistivity perpendicular to the flow direction increases, and the other direction (where the strut thickness increases) will be reduced. The average flow resistivity will in this case be almost constant. The method of scaling the micro-cell properties has a high influence on the resulting average flow resistivity, as does the cell volume in relation to the isotropic volume. For open porous materials which are approximately isotropic, the choice of micro geometry is not so critical and can be determined by other considerations, such as elasticity.
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| 6. |
- Lundberg, Eva, 1964-
(författare)
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Micro-structural based acoustic modelling of anisotropic open cell materials
- 2022
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- A method for the calculation of the acoustic performance of open-cell foammaterials is discussed. From a known micro-structural geometry and theconstituent material, the relevant acoustic properties are computed using apreviously published analytical method for the calculation of the dynamicdrag impedance and a previously published method for the calculation of theelastic moduli. These have been combined and are here used to generate thenecessary inputs to a fully anisotropic state space formulation of a TransferMatrix Method (TMM) based solution where only geometry and materialproperties need to be known. From the TMM solution, the sound absorptionand sound transmission loss of multilayer panels including anisotropic opencell materials is estimated. It is shown that the proposed method may beused in an optimization of sound absorption in multi-layer porous materials, where the different layers can have different degrees of anisotropy in theiracoustic and elastic properties. In the current work, the micro-geometry is based on the Kelvin cellwhich then is modified to achieve a controlled degree of anisotropy. The method has been validated by comparing the absorption and sound transmission loss for isotropic porous materials have been compared to equivalent structures computed with a commercial TMM mode, including a porous material which has been fully characterized with regard to previously published Johnson-Champoux-Allard parameters. In addition the calculated dynamic drag impedance has been compared to measurements conductedon a series of small samples with a defined 3D printed micro geometry forwhich the static flow resistivity has been measured. The method in general underestimates the dynamic drag impedance compared to the static flowresistivity due to not including the contributions to the losses from the constrictions between the struts close to the cell vertices. All verification showa good degree of agreement, confirming that for open-cell porous materials with reasonably high porosity the method may be used for design of novel acoustic treatments.
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| 7. |
- Lundberg, Eva, 1964-
(författare)
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Micro-Structure Modelling of Acoustics of Open Porous Material
- 2016
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Transportation is a large and growing part of the world’s energy consumption. This drives a need for reduced weight of rail vehicles, just as it does for road vehicles. In spite of weight reductions, the vehicle still has to provide the same level of acoustic comfort for the passengers. Porous materials, with more than 90% air, are often included in multi-layer vehicle panels, contributing to acoustic performance without adding much weight. Here the acoustic performance of open cell porous materials, with focus on flow resistivity, is evaluated based on simplified micro-structure models to investigate the effect of anisotropy on the performance In order to evaluate how the redistribution of material affects the flow resistivity, the porosity of the material is kept constant. Two micro-geometries are analysed and compared: the hexahedral model and the tetrakaidecahedron (Kelvin cell). For flow resistivity calculations the solid frame is assumed to be rigid. The models are elongated in one direction to study the influence of micro-structural anisotropy on the macro level flow resistivity. To keep porosity constant, two different approaches are investigated. The first approach is to let strut thickness be uniform and adjust the volume of the cell to a constant ratio compared to the isotropic case. The second approach is to let the strut volume, and cell volume, be constant. For an anisotropic hexahedral cell with uniform strut thickness, the flow resistivity increases substantially with increasing height to width ratio for the hexahedral model, while the flow resistivity for the tetrakaidecahedron model with uniform strut thickness decreases with increasing height to width ratio. For both geometries and constant strut volume, the average flow resistivity is close to the same constant value. For uniform strut thickness the relative volume of anisotropic to isotropic volume is very important.
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| 8. |
- Lundberg, Eva, 1964-
(författare)
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Reducing the environmental impact of rail transportation
- 2016
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Rapport (populärvet., debatt m.m.)abstract
- The environmental impact of the research project focussed on acoustic properties of lightweight structures for use in rail vehicles is investigated.The Environmental impact of rail transport is compared to that of road and air transport. The environmental impact of different trains are then compared using published data in the form of standardised Environmental Product Declarations (EPD), summarising Life Cycle Analysis (LCA) results.Since the EPDs are made for a certain train in a specified operation on a specified market, it is difficult to compare the environmental impact for trains in different types of operations. In spite of this it is clear that comfort requirements such as acoustics drives weight increase, and that a decrease of total train weight does have a significant impact on the energy consumption. Also the mode of electricity generation for the train operation has an impact. There is a large difference in environmental impact between markets with hydropower generated electricity and those who have to rely on electricity generated by fossil fuels.The conclusion is that research on how to improve acoustic properties, such as sound transmission loss, with a minimum increase of weight, does contribute to making an environmental friendly mode of transport more competitive compared to road and air transport
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| 9. |
- Lundberg, Eva, 1964-, et al.
(författare)
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Simplified acoustic model of an anisotropic foam using a micro-macro approach
- 2020
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Ingår i: Proceedings of ISMA 2020 - Internation Conference on Noise and Vibration Engineering and USD2020 - International Conference on Uncertainty in Structural Dynamics 2020. - Leuven, Belgium : KU Leuven, Departement Werktuigkunde, Heverlee, Belgium. ; , s. 437-450
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Konferensbidrag (refereegranskat)abstract
- Porous foam materials with high porosity are used as part of multi-layer panels for sound insulation andabsorption in transportation vehicles. The acoustic properties of the foam are highly dependant on the microgeometryof the foam cells. In this work, simplified analytical models for calculating the viscous dynamicdrag forces, and oscillatory heat transfer within fibrous materials have been adapted towards foam materialshaving micro-cell geometries composed primarily of cylindrical struts. The analytical results are comparedto full visco-thermal numerical models of an isotropic unit foam cell, For both high porosity foam and lowporosity foam examples with typical dimensions for 3D printed materials, the agreement between analyticaland thermoviscous numerical models is shown to be very good. This approach model can easily be extendedto anisotropic materials as well.
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| 10. |
- Lundberg, Eva, 1964-, et al.
(författare)
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Tunable absorption of micro-structure based anisotropic opencell materials
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- A simplified analytical model based on the Kelvin cell micro geometry has been developed for estimating the dynamic drag impedance of a periodic open cell material based on a Kelvincell based micro structure. The calculated dynamic drag impedance estimates similar properties as the static flow resistivity, but is based on dynamic micro scale estimates of the viscous losses neglecting interactions between struts. The Kelvin cell model can have a controlled degree ofanisotropy. Implementing the micro model in a state space transfer matrix method allows for absorption calculations of anisotropic micro material including stiffness to be calculated with limited input information. In addition to the solid constituent material parameters only cell height,strut thickness and twist angle, determining the degree of anisotropy, are required. The modelling allows for fast computations making optimization feasible, which is demonstrated by optimizing a two-layer porous material with the degree of anistropy as a design variable. An optimized design with enhanced absorption at lower frequencies, where the two layers have different anisotropic cell geoemetry, is discussed.
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| 11. |
- Lundberg, Eva, 1964-, et al.
(författare)
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Tuning sound transmission loss for multi-layer panels with anisotropic foams
- 2022
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Multilayer panels consisting of a load carrying structure, a porous material for thermal and acoustic insulation and an interior trim panel is a very common type of design for vehicles. Weight as well as total build height are usually limiting constraints on the design. The idea of using an anisotropic porous material instead of an isotropic one to improve the sound transmission loss without adding a lot of weight or thickness is explored in the paper. By using a state space formulation of the transfer matrix method transmission loss it is possible to include anisotropic material properties in the calculation. The anisotropic material is modelled by a combination of a simplified analytical model for the acoustic losses and inverse estimation of the 21 independent elastic constants of the Hooke’s tensor. The porous material, which has typical dimensions possible to 3D print, is based on a Kelvin cell micro model that has a controlled degree of anisotropy.
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| 12. |
- Mao, Huina, et al.
(författare)
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Dynamic behaviour of low- to high-density anisotropic cellular materials
- 2022
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Ingår i: Journal of Sound and Vibration. - : Elsevier BV. - 0022-460X .- 1095-8568. ; 536
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic behaviour of a novel anisotropic cellular micro-structural geometry derived from the basic symmetric Kelvin cell is discussed for varying relative density. The cells are arranged in a cubic array and the dynamic response is studied in a classical seismic mass setup using beam elements to represent the ligaments of the cell. The eigenfrequencies and the eigenmodes of the cellular array are computed together with forced response simulations where a proportional damping model of the Young's modulus for the cell ligaments is assumed. The frequency dependence of the damping is based on a fractional derivative representation. Using a recently developed inversion method, equivalent, homogenised solid material models of the cellular array are discussed with the associated equivalent elastic properties given in terms of the 21 elastic constants of the Hooke's tensor. For the equivalent solid material models, the eigenfrequencies and eigenmodes are computed, and forced response simulations are performed assuming the same type of proportionality in the damping as the cellular array, for the same seismic mass setup. The correlation, between the eigenfrequencies and the eigenmodes, shows an overall interesting agreement between the cellular and the equivalent solid model for the quite complex deformation shapes observed. The forced response results indicate that the equivalent solid modelling accurately represents the global dynamics of the anisotropic cellular array, but needs to be further refined when local shearing deformation within the individual cells starts to be dominating.
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| 13. |
- Sannellappanavar, G., et al.
(författare)
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Towards real time automated early gear failure detection
- 2022
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Ingår i: Tribologia. - : The Finnish Society for Tribology. - 0780-2285 .- 1797-2531. ; 39:3-4, s. 42-44
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Tidskriftsartikel (refereegranskat)abstract
- The ability to stop a gear fatigue test before catastrophic failure has many advantages. However, today, a wide-ly accepted approach is not available. This case study applies a vibration-based condition monitoring methodologyto detect early gear failures. The gear studied takes part in an all-wheel-drive drivetrain system. Vibration signalsfrom four run-to-failure fatigue tests at two constant torque-speed combinations were used as input to time-synchronous averaging and autoregression model generation. The applied methodology shows promising resultsfor early failure detection, and the process is feasible for implementation in an automated environment. Real timeanalysis is also possible since the autoregression model generates a healthy state TSA signal during the early tes-ting stages. However, the time to failure detection varies with operating conditions, with low sensitivity at high-speed and low-torque conditions.
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| 14. |
- Semeniuk, Bradley, et al.
(författare)
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Acoustics modelling of open-cell foam materials from microstructure and constitutive properties
- 2021
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Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 149:3, s. 2016-2026
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic relations for highly porous fibrous materials, having analytical expressions for dynamic viscous drag forces and oscillatory solid-to-fluid heat transfer, are now extended towards open-cell foam materials where the struts of the foam are considered to be primarily cylindrical except in the region of the joints. By also including analytical expressions for the stiffness of the foam cell, an entirely analytically-based model is presented for the acoustics of highly-porous, open-celled foam materials. This approach is extremely efficient, requiring only the mean cell size, mean strut diameter, and constitutive properties of the solid foam material and the surrounding viscous fluid as input. The acoustic performance prediction of not only isotropic foam cell designs, but also anisotropic ones may be performed rapidly and virtually, without the need for the determination of poroelastic material properties from existing material samples. The steps required for the development of the analytical foam-cell model are presented, along with the acoustic performance prediction of a typical Melamine foam cell, yielding very promising results in comparison against measurements. In order to understand the suitability of the cylindrical foam strut assumption, a viscous drag force comparison with foam struts having square and triangular cross-sectional profiles is also presented.
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