| 21. |
- Jansson, Johan, et al.
(författare)
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Framework for adaptive fluid-structure interaction with industrial applications
- 2013
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Ingår i: International Journal of Materials Engineering Innovation. - 1757-2754. ; 4:2, s. 166-186
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Tidskriftsartikel (refereegranskat)abstract
- We present developments in the Unicorn-HPC framework for unified continuum mechanics, enabling adaptive finite element computation of fluid-structure interaction, and an overview of the larger FEniCS-HPC framework for automated solution of partial diffential equations of which Unicorn-HPC is a part. We formulate the basic model and finite element discretisation method and adaptive algorithms. We test the framework on a 2D model problem consisting of a flexible beam in channel flow, and to illustrate the capabilities of the computational framework, we show two application examples from industry and medicine. We simulate a flexible mixer plate in turbulent flow in an exhaust system where the target output is aeroacoustic quantities. The second example is a self-oscillating vocal fold configuration, where the ultimate goal is to predict how the voice is affected by physiological changes from aerodynamics. Here we give the displacement signal of a point on the folds.
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| 22. |
- Jansson, Johan, 1978-, et al.
(författare)
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Gestural 3D Interaction with a Beating Heart : Simulation Visualization and Interaction
- 2011
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Ingår i: Proceedings of SIGRAD 2011. - : Linköping University Electronic Press. - 9789173930086
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Konferensbidrag (refereegranskat)abstract
- The KTH School of Computer Science and Communication (CSC) established a strategic platform in Simulation-Visualization-Interaction (SimVisInt) in 2009, focused on the high potential in bringing together CSC core com-petences in simulation technology, visualization and interaction. The main part of the platform takes the form aset of new trans-disciplinary projects across established CSC research groups, within the theme of ComputationalHuman Modeling and Visualization: (i) interactive virtual biomedicine (HEART), (ii) simulation of human mo-tion (MOTION), and (iii) virtual prototyping of human hand prostheses (HAND). In this paper, we present recentresults from the HEART project that focused on gestural and haptic interaction with a heart simulation.
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| 23. |
- Jansson, Jan-Håkan, et al.
(författare)
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Snus (Swedish smokeless tobacco) use and risk of stroke: pooled analyses of incidence and survival
- 2014
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Ingår i: Journal of Internal Medicine. - : Wiley. - 1365-2796 .- 0954-6820. ; 276:1, s. 87-95
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Tidskriftsartikel (refereegranskat)abstract
- Background. Snus is a moist smokeless tobacco product with high nicotine content. Its use has a short-term effect on the cardiovascular system, but the relationship between snus use and stroke is unclear. Objective. The aim of this study was to assess the associations between use of snus and incidence of and survival after stroke, both overall and according to subtypes. Methods. Pooled analyses of eight Swedish prospective cohort studies were conducted, including 130 485 men who never smoked. We estimated hazard ratios (HRs) with 95% confidence intervals (CIs) of incidence and death after diagnosis using Cox proportional hazard regression models and case fatality and survival using logistic regression and Kaplan-Meier methods, respectively. Results. No associations were observed between the use of snus and the risk of overall stroke (HR 1.04, 95% CI 0.92-1.17) or of any of the stroke subtypes. The odds ratio (OR) of 28-day case fatality was 1.42 (95% CI 0.99-2.04) amongst users of snus who had experienced a stroke, and the HR of death during the follow-up period was 1.32 (95% CI 1.08-1.61). Conclusion. Use of snus was not associated with the risk of stroke. Hence, nicotine is unlikely to contribute importantly to the pathophysiology of stroke. However, case fatality was increased in snus users, compared with nonusers, but further studies are needed to determine any possible causal mechanisms.
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| 24. |
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| 25. |
- Sarwar, Nadeem, et al.
(författare)
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Interleukin-6 receptor pathways in coronary heart disease : a collaborative meta-analysis of 82 studies
- 2012
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Ingår i: The Lancet. - New York, NY, USA : Elsevier. - 0140-6736 .- 1474-547X. ; 379:9822, s. 1205-1213
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Tidskriftsartikel (refereegranskat)abstract
- Background: Persistent inflammation has been proposed to contribute to various stages in the pathogenesis of cardiovascular disease. Interleukin-6 receptor (IL6R) signalling propagates downstream inflammation cascades. To assess whether this pathway is causally relevant to coronary heart disease, we studied a functional genetic variant known to affect IL6R signalling. Methods: In a collaborative meta-analysis, we studied Asp358Ala (rs2228145) in IL6R in relation to a panel of conventional risk factors and inflammation biomarkers in 125 222 participants. We also compared the frequency of Asp358Ala in 51 441 patients with coronary heart disease and in 136 226 controls. To gain insight into possible mechanisms, we assessed Asp358Ala in relation to localised gene expression and to postlipopolysaccharide stimulation of interleukin 6. Findings: The minor allele frequency of Asp358Ala was 39%. Asp358Ala was not associated with lipid concentrations, blood pressure, adiposity, dysglycaemia, or smoking (p value for association per minor allele >= 0.04 for each). By contrast, for every copy of 358Ala inherited, mean concentration of IL6R increased by 34.3% (95% CI 30.4-38.2) and of interleukin 6 by 14.6% (10.7-18.4), and mean concentration of C-reactive protein was reduced by 7.5% (5.9-9.1) and of fibrinogen by 1.0% (0.7-1.3). For every copy of 358Ala inherited, risk of coronary heart disease was reduced by 3.4% (1.8-5.0). Asp358Ala was not related to IL6R mRNA levels or interleukin-6 production in monocytes. Interpretation: Large-scale human genetic and biomarker data are consistent with a causal association between IL6R-related pathways and coronary heart disease.
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| 26. |
- Vilela De Abreu, Rodrigo, et al.
(författare)
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Towards the development of adaptive finite element methods for internal flow aeroacoustics
- 2013
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Ingår i: 19th AIAA/CEAS Aeroacoustics Conference. - 9781624102134
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Konferensbidrag (refereegranskat)abstract
- We report the latest results obtained in the development of an adaptive finite element method for computational aeroacoustics (CAA). The new methodology is based on the General Galerkin (G2) method, which has been successfully used for the computation of incompressible, turbulent flow. Here, we simulate the flow past an in-duct mixer plate and compare the results with available experimental data. The comparisons include mean velocity profiles and frequency content of the turbulent signal. No direct simulation of sound or sound wave propagation has been performed; instead, simple analogy arguments have been used to extract acoustic results from incompressible simulations by assuming a direct correlation between the computed pressure drop signal and the sound at the far field. We were able to reproduce the sound signal from experiments with our incompressible simulation and our results compared well with both the level and the broadband frequency peak of the measured sound. We suggest that the methodology presented here is mainly suitable for the prediction of sound in low Mach number pipe flows.
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| 27. |
- Abreu, Rodrigo, et al.
(författare)
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Adaptive computation of aeroacoustic sources for a rudimentary landing gear using lighthill's analogy
- 2011
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Ingår i: 17th AIAA/CEAS AeroacousticsConference 2011.
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Konferensbidrag (refereegranskat)abstract
- We present our simulation results for the benchmark problem of the ow past a Rudimentary Landing Gear (RLG) using a General Galerkin (G2) nite element method, also referred to as Adaptive DNS/LES. In G2 no explicit subgrid model is used, instead the compuational mesh is adaptively re ned with respect to an a posteriori error es-timate of a quantity of interest in the computation, in this case the drag force on the RLG. Turbulent boundary layers are modeled using a simple wall layer model with the shear stress at walls proportional to the skin friction, which here is assumed to be small and, therefore, can be approximated by zero skin friction. We compare our results with experimental data and other state of the art computations, where we nd good agreement in sound pressure levels, surface velocities and ow separation. We also compare with detailed surface pressure experimental data where we nd largely good agreement, apart from some local dierences for which we discuss possible explanations.
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| 28. |
- Ahlström, Christine, et al.
(författare)
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Feedback modeling of non-esterified fatty acids in rats after nicotinic acid infusions
- 2011
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Ingår i: JOURNAL OF PHARMACOKINETICS AND PHARMACODYNAMICS. - 1567-567X. ; 38:1, s. 1-24
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Tidskriftsartikel (refereegranskat)abstract
- A feedback model was developed to describe the tolerance and oscillatory rebound seen in non-esterified fatty acid (NEFA) plasma concentrations following intravenous infusions of nicotinic acid (NiAc) to male Sprague-Dawley rats. NiAc was administered as an intravenous infusion over 30 min (0, 1, 5 or 20 μmol kg(-1) of body weight) or over 300 min (0, 5, 10 or 51 μmol kg(-1) of body weight), to healthy rats (n = 63), and serial arterial blood samples were taken for measurement of NiAc and NEFA plasma concentrations. Data were analyzed using nonlinear mixed effects modeling (NONMEM). The disposition of NiAc was described by a two-compartment model with endogenous turnover rate and two parallel capacity-limited elimination processes. The plasma concentration of NiAc was driving NEFA (R) turnover via an inhibitory drug-mechanism function acting on the formation of NEFA. The NEFA turnover was described by a feedback model with a moderator distributed over a series of transit compartments, where the first compartment (M (1)) inhibited the formation of R and the last compartment (M ( N )) stimulated the loss of R. All processes regulating plasma NEFA concentrations were assumed to be captured by the moderator function. The potency, IC (50), of NiAc was 45 nmol L(-1), the fractional turnover rate k ( out ) was 0.41 L mmol(-1) min(-1) and the turnover rate of moderator k ( tol ) was 0.027 min(-1). A lower physiological limit of NEFA was modeled as a NiAc-independent release (k ( cap )) of NEFA into plasma and was estimated to 0.032 mmol L(-1) min(-1). This model can be used to provide information about factors that determine the time-course of NEFA response following different modes, rates and routes of administration of NiAc. The proposed model may also serve as a preclinical tool for analyzing and simulating drug-induced changes in plasma NEFA concentrations after treatment with NiAc or NiAc analogues.
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| 29. |
- Albrektsson, Joakim, et al.
(författare)
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Assessment of fire exposed concrete structures
- 2012
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Ingår i: fib Symposium 2012: Concrete Structures for Sustainable Community. - 9789198009811 ; , s. 619-622, s. 619-622
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Konferensbidrag (refereegranskat)abstract
- Annually, several concrete structures, such as buildings, bridges, parking garages and tunnels are exposed to fires. An assessment is then necessary to decide whether the structure can be repaired or needs to be replaced. In a recent research project, recommendations for assessments of fire exposed concrete structures have been developed. The recommendations are based on a literature survey, results from an experimental study, where ultrasonic measurements, microscopy, Digital Image Correlation (DIC) measurement on loaded core samples were used and practical experience of real post-fire structural assessments. A refined assessment of the fire damage is obtained by combining these test methods.
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| 30. |
- Anderson, Johan, et al.
(författare)
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Façade fire tests : Measurements and modeling
- 2013
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Ingår i: 1st International Seminar for Fire Safety of Facades, FSF 2013. - : EDP Sciences. - 9782759811007
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Konferensbidrag (refereegranskat)abstract
- In two recent papers [1, 2] the fire dynamics in a test rig for façade constructions according to the test method SP Brand 105 [3, 4] was investigated both experimentally and numerically. The experimental setup simulates a three-story apartment building (height 6.7m, width 4m and depth 1.6m), with external wall-cladding and a "room fire" at the base. The numerical model was developed in the CFD program Fire Dynamics Simulator (FDS) [5] with analogous geometry and instrumentation. The general features of the fire test were well reproduced in the numerical model however temperatures close to the fire source could not be properly accounted for in the model. In this paper the bi-directional probe measurements are elaborated on and the test used in Ref. [1] is revisited using different heat release rates in the numerical model. The velocity of the hot gases along the façade was well reproduced by the simulations although some deviations were found.
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