| 1. |
- Coslovich, Francesco, 1990, et al.
(författare)
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Added resistance, heave and pitch for the KVLCC2 tanker using a fully nonlinear unsteady potential flow boundary element method
- 2021
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 229
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, a fully nonlinear unsteady potential flow method is used to predict added resistance, heave and pitch for the KVLCC2 hull in regular head waves at design speed. The method presents a nonlinear decomposition of the velocity potential and the wave field and an adaptive grid refinement. A formulation for the acceleration potential is used to obtain the pressure. To improve computational efficiency, a Barnes-Hut algorithm is introduced. A grid dependency study and a study on the impact of different time steps on the solution are performed. Numerical results have been compared with experimental data for the design speed. A general good agreement is found for added resistance, especially for longer waves. Heave and pitch are properly computed for all wave lengths in the range λ/Lpp=0.4 to 1.4. © 2021 The Author(s)
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| 2. |
- Jalkanen, Jukka-Pekka, et al.
(författare)
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Modeling of ships as a source of underwater noise
- 2017
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Shipping as a source of underwater noise is increasing. Underwater noise emission levels are seldom considered as a ship design parameter unless low vessel noise is specifically required, like in the case of warships and research vessels. Noise emissions are not regulated yet, but the awareness of possible impacts of noise on marine life is increasing. This paper describes the implementation of a noise source model for the Ship Traffic Emission Abatement Model (STEAM; Jalkanen et al. 2009; 2012; Johansson et al, 2017). The combination of vessel technical description and activity can be used to generate noise source maps which are based on actual ship traffic data. The generated noise source maps can ve used to describe the energy emitted as noise to the water, which facilitates regular annual updates of the noise emissions from ship traffic in the Baltic Sea area.
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| 3. |
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| 4. |
- Lindberg, Eskil, 1979-, et al.
(författare)
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A vibro-acoustic reduced order model using undeformed coupling interface substructuring - Application to rubber bushing isolation in vehicle suspension systems
- 2014
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 78, s. 43-50
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Tidskriftsartikel (refereegranskat)abstract
- A vibro-acoustic reduced order model (ROM) based on a substructuring method using undeformed coupling interfaces (UCI) is proposed. The method may be used to reduce the order of a global problem, this by subdividing the global system to substructures interacting through UCI's. The local dynamic stiffness of each substructure may then be modelled with a, for that particular problem, best suited description. The feasibility of the method is demonstrated by a sensitivity analysis of the vibro-acoustic power isolation in a vehicle suspension system, comprising of a link arm connected to a vehicle car body through two rubber bushings. The link arm ROM is a component mode synthesis (CMS)-UCI, the rubber bushing model is a UCI-ROM derived from a 2D axisymmetric model using a frequency dependent visco-elastic material model. Finally the car body model is a frequency dependent UCI-ROM from a full car body finite element model. It is shown that the UCI-ROM approach efficiently can be used for parametric studies on a substructure level. The results suggest that the performed reorientation of the rubber bushings can alter, with orders of magnitude, the energy flow into the car.
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| 5. |
- Lindberg, Olof, et al.
(författare)
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Hippocampal Shape Analysis in Alzheimer's Disease and Frontotemporal Lobar Degeneration Subtypes
- 2012
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Ingår i: Journal of Alzheimer's Disease. - 1387-2877 .- 1875-8908. ; 30:2, s. 355-365
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Tidskriftsartikel (refereegranskat)abstract
- Hippocampal pathology is central to Alzheimer's disease (AD) and other forms of dementia such as frontotemporal lobar degeneration (FTLD). Autopsy studies have shown that certain hippocampal subfields are more vulnerable than others to AD and FTLD pathology, in particular the subiculum and cornu ammonis 1 (CA1). We conducted shape analysis of hippocampi segmented from structural T1 MRI images on clinically diagnosed dementia patients and controls. The subjects included 19 AD and 35 FTLD patients [13 frontotemporal dementia (FTD), 13 semantic dementia (SD), and 9 progressive nonfluent aphasia (PNFA)] and 21 controls. Compared to controls, SD displayed severe atrophy of the whole left hippocampus. PNFA and FTD also displayed atrophy on the left side, restricted to the hippocampal head in FTD. Finally, AD displayed most atrophy in left hippocampal body with relative sparing of the hippocampal head. Consistent with neuropathological studies, most atrophic deformation was found in CA1 and subiculum areas in FTLD and AD.
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| 6. |
- Looi, Jefferey Chee Leong, et al.
(författare)
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Shape analysis of the neostriatum in frontotemporal lobar degeneration, Alzheimer's disease, and controls
- 2010
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Ingår i: NeuroImage. - : Elsevier BV. - 1053-8119 .- 1095-9572. ; 51:3, s. 970-986
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Tidskriftsartikel (refereegranskat)abstract
- Background and purpose: Frontostriatal circuit mediated cognitive dysfunction has been implicated in frontotemporal lobar degeneration (FTLD), but not Alzheimer's disease, or healthy aging. We measured the neostriatum (caudate nucleus and putamen) volume in FTLD (n=34), in comparison with controls (n=27) and Alzheimer's disease (AD, n=19) subjects. Methods: Diagnoses were based on international consensus criteria. Manual bilateral segmentation of the caudate nucleus and putamen was conducted blind to diagnosis by a single analyst, on MRI scans using a standardized protocol. Intra-cranial volume was calculated via a stereological point counting technique and was used for scaling the shape analysis. The manual segmentation binaries were analyzed using UNC Shape Analysis tools (University of North Carolina) to perform comparisons among FTLD, AD, and controls for global shape, local p-value significance maps, and mean magnitude of shape displacement. Results: Shape analysis revealed that there was significant shape difference between FTLD, AD, and controls, consistent with the predicted frontostriatal dysfunction and of significant magnitude, as measured by displacement maps. There was a lateralized difference in shape for the left caudate for FTLD compared to AD; non-specific global atrophy in AD compared to controls; while FTLD showed a more specific pattern in regions relaying fronto- and corticostriatal circuits. Conclusions: Shape analysis shows regional specificity of atrophy, manifest as shape deflation, with implications for frontostriatal and corticostriatal motoric circuits, in FTLD, AD, and controls.
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| 7. |
- Looi, Jeffrey Chee Leong, et al.
(författare)
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Shape analysis of the neostriatum in subtypes of frontotemporal lobar degeneration : neuroanatomically significant regional morphologic change
- 2011
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Ingår i: Psychiatry Research. - : Elsevier BV. - 0925-4927 .- 1872-7506 .- 0165-1781. ; 191:2, s. 98-111
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Tidskriftsartikel (refereegranskat)abstract
- Frontostriatal circuit mediated cognitive dysfunction has been implicated in frontotemporal lobar degeneration (FTLD) and may differ across subtypes of FTLD. We manually segmented the neostriatum (caudate nucleus and putamen) in FTLD subtypes: behavioral variant frontotemporal dementia, FTD, n=12; semantic dementia, SD, n=13; and progressive non-fluent aphasia, PNFA, n=9); in comparison with controls (n=27). Diagnoses were based on international consensus criteria. Manual bilateral segmentation of the caudate nucleus and putamen was conducted blind to diagnosis by a single analyst, on MRI scans using a standardized protocol. Intracranial volume was calculated via a stereological point counting technique and was used for normalizing the shape analysis. Segmented binaries were analyzed using the Spherical Harmonic (SPHARM) Shape Analysis tools (University of North Carolina) to perform comparisons between FTLD subtypes and controls for global shape difference, local significance maps and mean magnitude maps of shape displacement. Shape analysis revealed that there was significant shape difference between FTLD subtypes and controls, consistent with the predicted frontostriatal dysfunction and of significant magnitude, as measured by displacement maps. These differences were not significant for SD compared to controls; lesser for PNFA compared to controls; whilst FTD showed a more specific pattern in regions relaying fronto- and corticostriatal circuits. Shape analysis shows regional specificity of atrophy, manifest as shape deflation, with a differential between FTLD subtypes, compared to controls.
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| 8. |
- Lucarelli, Andrea, 1982-
(författare)
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The Political Dimension of Place Branding
- 2015
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Place branding is commonly understood as the application of marketing and commercial ideas, strategies, measurements and logic to the realm of places such as cities, regions and nations. Nevertheless, place branding is also understood as the locus where political activities – imbued with political impact and political effects – appear and affect the soft and hard infrastructures of urban agglomeration and other spatial environments. In this regard, by performing an analysis that helps unpack the multiple characters and impacts of political structures and processes in relation to place branding activities, the present dissertation aims to offer a conceptualization of the political dimension of place branding. By drawing on the critical assessment of the academic literature on place branding and on a series of studies about the branding processes in the region of Romagna and in the Greater Stockholm, the present dissertation further specifies an alternative conceptual framework (i.e. ecological politics) that suggests how place branding should be seen an empirical and theoretical political apparatus that acts, in praxis, based on an emerging, multifaceted and spatio-temporal enfolding of politics. More specifically, the ecological politics of place branding is characterized by four main aspects: the unfolding of a biopolitical ecology around place-branding practices; the ideological appropriation of place-branding processes; the positioning through politicized actions between the interest groups; and finally place-branding as a process of policy-intervention. Finally, on more general level, the present dissertation, by recognizing the political activities and efforts of place branding as crucial elements to be analyzed, makes the case for a more explicit, complex and manifold political analysis of the political dimension of place branding, which allows attention to be given to the impact that branding processes, practices and activities have on cities, regions and nations
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| 9. |
- Martin, Cederlöf, 1980-, et al.
(författare)
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A longitudinal study of adolescent psychotic experiences and later development of substance use disorder and suicidal behavior
- 2017
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Ingår i: Schizophrenia Research. - Amsterdam, Netherlands : Elsevier. - 0920-9964 .- 1573-2509. ; 181, s. 13-16
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Psychotic experiences are associated with later substance use disorder and suicidal behavior, but individual psychotic experiences have not been examined in a longitudinal data set. Also, the potential dose-response relationship between these phenomena remains unknown.Method: Cohort study including 9242 adolescents who participated in The Child and Adolescent Twin Study in Sweden (CATSS). At ages 15 and/or 18, seven psychotic experiences (auditory and visual hallucinations, and five delusions) were assessed via questionnaires. Outcomes at follow-up were physician-assigned diagnoses of substance use disorder and suicide attempts ascertained from the Swedish Patient Register. Associations were estimated with Cox regressions and expressed as hazard ratios.Results: All psychotic experiences were associated with later substance use disorder and/or suicide attempts, with hazard ratios ranging from 1.6 to 3.0. A dose-response relationship was observed between psychotic experiences and later substance use disorder, and suicide attempt.Discussion: Auditory and visual hallucinations as well as delusions in adolescence are associated with later development of substance use disorder and suicide attempt, and there is a dose-response relationship between the load of psychotic experiences and these adverse outcomes. Clinicians should assess subclinical hallucinations as well as delusions in psychiatric evaluations of adolescents.
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| 10. |
- Martin, Cederlöf, 1980-, et al.
(författare)
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The association between childhood autistic traits and adolescent psychotic experiences is explained by general neuropsychiatric problems.
- 2016
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Ingår i: American Journal of Medical Genetics Part B. - Hoboken, USA : Wiley-Blackwell. - 1552-4841 .- 1552-485X. ; 171:2, s. 153-159
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Tidskriftsartikel (refereegranskat)abstract
- Studies suggest associations between childhood autistic traits and adolescent psychotic experiences. However, recent research suggests that a general neuropsychiatric problems factor predicts adverse outcomes better than specific diagnostic entities. To examine if the alleged association between autistic traits and psychotic experiences could rather be explained by a general neuropsychiatric problems factor comprising symptoms of ADHD, tic disorder, developmental coordination disorder, and learning disorder, we conducted a prospective cohort study based on the Child and Adolescent Twin Study in Sweden. In addition, we examined the genetic and environmental influences on the associations. A total of 9,282 twins with data on childhood autistic traits and other neuropsychiatric problems, and follow-up data on psychotic experiences at ages 15 and/or 18 years were included. First, psychotic experiences were regressed on autistic traits and second, the general neuropsychiatric problems factor was added to the model. Auditory hallucinations were analyzed separately from the other psychotic experiences. Finally, twin analyses were employed to disentangle genetic from environmental influences in the observed associations. Replicating prior research, significant associations were found between autistic traits in childhood and auditory hallucinations at ages 15 and 18. However, after controlling for the general neuropsychiatric problems factor, the associations between autistic traits and auditory hallucinations disappeared, whereas the association between the general neuropsychiatric problems factor and auditory hallucinations persisted after controlling for autistic traits. Twin analyses revealed that the association between the general neuropsychiatric problems factor and auditory hallucinations was driven by shared genetic influences. .
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| 11. |
- Martin, Cederlöf, 1980-, et al.
(författare)
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The association between Darier disease, bipolar disorder, and schizophrenia revisited: a population-based family study.
- 2015
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Ingår i: Bipolar disorders. - Hoboken, USA : Wiley. - 1399-5618 .- 1398-5647. ; 17:3, s. 340-4
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Tidskriftsartikel (refereegranskat)abstract
- Darier disease is an autosomal dominant skin disorder caused by mutations in the ATPase, Ca++ transporting, cardiac muscle, slow twitch 2 (ATP2A2) gene and previously reported to cosegregate with bipolar disorder and schizophrenia in occasional pedigrees. It is, however, unknown whether these associations exist also in the general population, and the objective of this study was to examine this question.
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| 12. |
- Orych, Michal, 1979, et al.
(författare)
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Speed and delivered power in waves — Predictions with CFD simulations at full scale
- 2023
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Ingår i: Ocean Engineering. - : Elsevier Ltd. - 0029-8018 .- 1873-5258. ; 285
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Tidskriftsartikel (refereegranskat)abstract
- An efficient numerical method is proposed to estimate delivered power and speed loss for a ship in wind and waves. The added resistance in waves, obtained with an unsteady potential flow panel method, is added to the calm water resistance from a steady-state potential flow/RANS method coupled with a body force propeller model for self-propulsion. A comparison of numerical and experimental results is made for added resistance, calm water resistance and delivered power. A good agreement is obtained. As a practical application, the approach is used to calculate the weather factor, fw, of the Energy Efficiency Design Index (EEDI). The calculated weather factor is consistent with the values derived from full-scale measurements included in a database of similar ships. © 2023 The Author(s)
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| 13. |
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| 14. |
- Svendsen, Martin, et al.
(författare)
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Varning för Maslows bedrägliga tjuskraft! Behovshierarkin – en populär modell som saknar vetenskapliga belägg
- 2019
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Ingår i: Organisation & Samhälle. - 2001-9114 .- 2002-0287. ; :1
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- den här artikeln kommer vi att diskutera den så kallade behovshierarkin, en modell som gett avtryck i företagsekonomiska utbildningar och i förlängningen företagsekonomisk praktik. Modellen lanserades av psykologen Abraham Maslow på 1940-talet för att förklara mänskligt beteende. Ambitionen med modellen var att förklara alla mänskliga psykologiska drivkrafter.
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| 15. |
- Östberg, Kenneth, et al.
(författare)
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Intelligent Transport Systems - The Role of a Safety Loop for Holistic Safety Management
- 2014
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Ingår i: Computer Safety, Reliability, and Security. - Cham : Springer. - 9783319105567 - 9783319105574
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Konferensbidrag (refereegranskat)abstract
- An ITS represents a Cyber-Physical System (CPS), which will involve information exchange at operational level as well as potential explicit collaboration between separate entities (systems of systems). Specific emphasis is required to manage the complexity and safety of such future CPS. In this paper we focus on model-based approaches for these purposes for analyzing and managing safety throughout the lifecycle of ITS. We argue that: (1) run-time risk assessment will be necessary for efficient ITS; (2) an information centric approach will be instrumental for future ITS to support all aspects of safety management – a “safety loop”; (3) a formal basis is required to deal with the large amounts of information present in an ITS. We elaborate these arguments and discuss what is required to support their realization.
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| 16. |
- Östberg, K., et al.
(författare)
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Intelligent transport systems - The role of a safety loop for holistic safety management
- 2014
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Ingår i: Computer Safety, Reliability, and Security. - Cham : Springer. - 1611-3349 .- 0302-9743. - 9783319105567 ; , s. 3-10, s. 3-10
-
Konferensbidrag (refereegranskat)abstract
- An ITS represents a Cyber-Physical System (CPS), which will involve information exchange at operational level as well as potential explicit collaboration between separate entities (systems of systems). Specific emphasis is required to manage the complexity and safety of such future CPS. In this paper we focus on model-based approaches for these purposes for analyzing and managing safety throughout the lifecycle of ITS. We argue that: (1) run-time risk assessment will be necessary for efficient ITS; (2) an information centric approach will be instrumental for future ITS to support all aspects of safety management - a "safety loop"; (3) a formal basis is required to deal with the large amounts of information present in an ITS. We elaborate these arguments and discuss what is required to support their realization.
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| 17. |
- Östberg, Martin, et al.
(författare)
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A study of the influence of rubber bushings on the audible frequency behaviour of a truck damper
- 2014
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Ingår i: International Journal of Heavy Vehicle Systems. - 1744-232X. ; 21:4, s. 281-294
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Tidskriftsartikel (refereegranskat)abstract
- The audible frequency range behaviour of a truck damper element, connected to surrounding structures by means of rubber bushings, is investigated, applying a mixed measurement/modelling procedure. The damper element properties are retrieved through an experimental procedure, while the rubber bushings are modelled using a finite element formulation including a realistic fractional derivative visco-elastic rubber model. Focus is on the influence of the subpart properties on the overall dynamic behaviour. It is found that, in the audible frequency range studied, similar to 100-1000 Hz, an accurate model of the rubber bushings plays an important role, while the level of detail in the description of the dynamical behaviour of the damper element itself is less crucial, contributing mainly with its lumped mass; these results aid in the development of new, quiet vehicles.
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| 18. |
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| 19. |
- Östberg, Martin, et al.
(författare)
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Dynamic stiffness of hollowed cylindrical rubber vibration isolators - The wave-guide solution
- 2013
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Ingår i: International Journal of Solids and Structures. - : Elsevier BV. - 0020-7683 .- 1879-2146. ; 50:10, s. 1791-1811
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Tidskriftsartikel (refereegranskat)abstract
- The dynamic stiffness of hollowed cylindrical vibration isolators using a wave-guide modelling approach is given. The isolators consist of rubber and metal elements in series. The boundary conditions at the lateral and radial surfaces of each rubber component are locally non-mixed and simultaneously satisfied by using the modes corresponding to the dispersion relation for axial waves in infinite hollow cylinders while the metal plates are assumed rigid, following Newton's second law. The modes of the rubber elements exactly satisfy the stress free boundary conditions at the curved radial boundaries, while the displacement conditions on the flat cylinder ends are satisfied in mean by a mode matching approach. The rubber is modelled as nearly incompressible with deviatoric visco-elasticity based on a fractional derivative, standard linear solid. The stiffness is found to depend strongly on frequency, displaying resonances and anti-resonances. Further, results indicate a great potential for optimising vibration isolators of the studied kind. By choosing appropriate combinations of metal plates and rubber elements, the dynamic transfer stiffness in higher frequency bands can be suppressed to be magnitudes lower than the static stiffness, a highly sought feature in vibration isolators. Finally, simplified models including mass-spring systems and the long rod theory are implemented and compared to the derived formulation.
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| 20. |
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| 21. |
- Östberg, Martin, 1982-
(författare)
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Modelling tools for quieter vehicles : Waves in poro– and visco–elastic continua
- 2012
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- New modelling tools intended to contribute to the development of components for quieter vehicles are developed. The tools are based on continuum models for wave propagation in poro– and visco–elastic media. By using geometric attributes of the studied components, the computational cost may be radically decreased compared to traditional methods. By assigning known analytical functions for one or two of the spatial directions, the spatial dimension of the remaining numerical problem is reduced. This reduction of spatial dimensions is performed in two di↵erent ways. The first one treats wave propagation in infinitely extended homogeneous and hollowed cylindrical rods, or wave guides, consisting of visco–elastic media. The wave solutions obtained are then used to model rubber vibration isolators of finite length by mode–matching the fields to the radial boundary conditions of interest. The second one is a method for modelling rotationally symmetric multilayered structures consisting of poro–elastic, elastic and fluid domains. By using a harmonic expansion for the azimuthal spatial dependence, the original three–dimensional problem is split up into several, much smaller, two– dimensional ones, radically decreasing the computational load.Moreover, using a mixed measurement/modelling approach, the audible frequency range characteristics of a viscous damper from a truck is studied, illustrating the influence of the rubber bushings by which it is attached to surrounding structures.The modelling approaches presented in this thesis are intended as tools aiding the design process of new vehicles, enabling new technology striving for more sustainable vehicle concepts. More specifically, the tools aim to improve the modelling of sound and vibration properties which are often penalised when seeking new, more sustainable vehicle designs.
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| 22. |
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| 23. |
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| 24. |
- Östberg, Martin, et al.
(författare)
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Prediction of noise transmission through anisotropic multilayered aircraft fuselage, using finite element models including porous, elastic and fluid domains
- 2010
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Konferensbidrag (refereegranskat)abstract
- Prediction of noise transmission through anisotropic multilayered aircraft fuselage, using finite element models including porous, elastic and fluid domains is carried out. A passenger aircraft carrier is modelled using a novel finite element formulation, utilising the rotationally symmetric geometry in order to greatly reduce the computational cost. The model consists of anisotropic porous, elastic and fluid domains. The axi-symmetry of the structure allows for the use of analytical functions describing the wave propagation in the circumferential spatial directions, and thus reducing the number of required finite elements considerably. It is found that a fairly limited number of modes are required to satisfactorily describe the sound fields.
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| 25. |
- Östberg, Martin, et al.
(författare)
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Transverse, tilting and cross-coupling stiffness of cylindrical rubber isolators in the audible frequency range-The wave-guide solution
- 2011
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Ingår i: Journal of Sound and Vibration. - : Elsevier. - 0022-460X .- 1095-8568. ; 330:13, s. 3222-3244
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Tidskriftsartikel (refereegranskat)abstract
- Audio-frequency wave-guide models for antisymmetric dynamic stiffness of arbitrary long elastomer cylinders are presented. The locally non-mixed boundary conditions at the lateral and radial surfaces are simultaneously satisfied by using the modes corresponding to the dispersion relation for axial waves in cylinders satisfying the stress free boundary conditions at the curved radial boundaries, while the displacement conditions on the flat cylinder ends are satisfied by mode matching. The elastomer is modelled as nearly incompressible with deviatoric visco-elasticity based on a fractional derivative, standard linear solid embodying a Mittag-Leffler relaxation kernel, the main advantage being the minimum parameter number required to successfully model the material properties over a broad frequency band. The stiffness is found to depend strongly on frequency: displaying resonances and anti-resonances. The method is compared with and verified against finite element models. In addition, comparison to thin beam theories, i.e. Euler and Timoschenko theory and a simple shear model, is presented, illustrating the limitations of these models.
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| 26. |
- Östberg, Martin
(författare)
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Waves in elastic and poro-elastic cylinders with spatially varying anisotropy
- 2012
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Ingår i: Proceedings Of International Conference On Noise And Vibration Engineering (ISMA2012) / International Conference On Uncertainty In Structural Dynamics (USD2012). - 9789073802896 ; , s. 4193-4200
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Konferensbidrag (refereegranskat)abstract
- A modelling approach for studying waves in elastic and poro-elastic cylinders with spatially varying anisotropy is proposed. The formulation utilizes a spatial Fourier expansion for the azimuthal angle is used for the Hooke's tensor and the dependent variables. This causes the orthogonality of the modes to break down, and the modes will, sometimes to a very high degree, spread. The special case of anisotropic media having principal directions coinciding with a Cartesian coordinate system is studied, and the degree of mode spreading is discussed.
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| 27. |
- Östberg, Martin, et al.
(författare)
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Weak forms for modelling of rotationally symmetric, multilayered structures, including anisotropic poro-elastic media
- 2012
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Ingår i: International Journal for Numerical Methods in Engineering. - : John Wiley & Sons. - 0029-5981 .- 1097-0207. ; 90:8, s. 1035-1052
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Tidskriftsartikel (refereegranskat)abstract
- A weak form of the anisotropic Biot's equation represented in a cylindrical coordinate system using a spatial Fourier expansion in the circumferential direction is presented. The original three dimensional Cartesian anisotropic weak formulation is rewritten in an arbitrary orthogonal curvilinear basis. Introducing a cylindrical coordinate system and expanding the circumferential wave propagation in terms of orthogonal harmonic functions, the original, geometrically rotationally symmetric three dimensional boundary value problem, is decomposed into independent two-dimensional problems, one for each harmonic function. Using a minimum number of dependent variables, pore pressure and frame displacement, a computationally efficient procedure for vibro-acoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including anisotropic porous elastic materials is thus obtained. By numerical simulations, this method is compared with, and the correctness is verified against, a full three-dimensional Cartesian coordinate system finite element model.
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| 28. |
- Östberg, Martin, et al.
(författare)
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Weak formulation of Biot's equations in cylindrical coordinates with harmonic expansion in the circumferential direction
- 2010
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Ingår i: International Journal for Numerical Methods in Engineering. - : Wiley. - 0029-5981 .- 1097-0207. ; 81:11, s. 1439-1454
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Tidskriftsartikel (refereegranskat)abstract
- A weak symmetric form of Biot's equation in cylindrical coordinates with a spatial Fourier expansion in the circumferential direction is presented. The solid phase displacement and the pore pressure are used as the dependent variables. The original three-dimensional boundary value problem is here, due to the orthogonality of the harmonic functions and the rotationally symmetric geometry, decomposed into independent two-dimensional problems, one for each harmonic function. This formulation provides a computationally efficient procedure for vibroacoustic finite element modelling of rotationally symmetric three-dimensional multilayered structures including porous elastic materials. By numerical Simulations, this method is compared with, and verified against, full three-dimensional Cartesian coordinate system finite element models.
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| 29. |
- Østergaard, Per, et al.
(författare)
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Nordic Consumer Culture : Context and Concept
- 2014
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Ingår i: Research in Consumer Behavior. - : Emerald Group Publishing Limited. - 9781784411589 - 9781784411572 ; , s. 245-257
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Bokkapitel (refereegranskat)
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