| 1. |
- Hoffman, Johan, et al.
(författare)
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Towards a parameter-free method for high Reynolds number turbulent flow simulation based on adaptive finite element approximation
- 2015
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Ingår i: Computer Methods in Applied Mechanics and Engineering. - : Elsevier. - 0045-7825 .- 1879-2138. ; 288, s. 60-74
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Tidskriftsartikel (refereegranskat)abstract
- We present work towards a parameter-free method for turbulent flow simulation based on adaptive finite element approximation of the Navier-Stokes equations at high Reynolds numbers. In this model, viscous dissipation is assumed to be dominated by turbulent dissipation proportional to the residual of the equations, and skin friction at solid walls is assumed to be negligible compared to inertial effects. The result is a computational model without empirical data, where the only parameter is the local size of the finite element mesh. Under adaptive refinement of the mesh based on a posteriori error estimation, output quantities of interest in the form of functionals of the finite element solution converge to become independent of the mesh resolution, and thus the resulting method has no adjustable parameters. No ad hoc design of the mesh is needed, instead the mesh is optimised based on solution features, in particular no bounder layer mesh is needed. We connect the computational method to the mathematical concept of a dissipative weak solution of the Euler equations, as a model of high Reynolds number turbulent flow, and we highlight a number of benchmark problems for which the method is validated.
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| 2. |
- Spühler, Jeannette Hiromi, 1981-, et al.
(författare)
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A finite element framework for high performance computer simulation of blood flow in the left ventricle of the human heart
- 2015
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Progress in medical imaging, computational fluid dynamics and high performance computing (HPC) enables computer simulations to emerge as a significant tool to enhance our understanding of the relationship between cardiac diseases and hemodynamics. The field of cardiac modelling is diverse, covering different aspects on microscopic and macroscopic level. In our research, we develop a cardiac model which is embedded in a computational environment where specific properties of the heart such as fluid-structure interaction of the aortic valve can be modeled, or numerical and computational algorithms as parallel computing or adaptivity can be added in a modular way without extensive efforts. In this paper, we present a patient-specific Arbitrary Lagrangian-Eulerian (ALE) finite element framework for simulating the blood flow in the left ventricle of a human heart using HPC, which forms the core of our cardiac model. The mathematical model is described together with the discretization method, mesh smoothing algorithms, and the parallel implementation in Unicorn which is part of the open source software framework FEniCS-HPC. The parallel performance is demonstrated, a convergence study is conducted and intraventricular flow patterns are visualized. The results capture essential features observed with other computational models and imaging techniques, and thus indicate that our framework possesses the potential to provide relevant clinical information for diagnosis and medical treatment. Several studies have been conducted to simulate the three dimensional blood flow in the left ventricle of the human heart with prescribed wall movement. Our contribution to the field of cardiac research lies in establishing an open source framework modular both in modelling and numerical algorithms.
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| 3. |
- Jansson, Johan, et al.
(författare)
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Adaptive simulation of unsteady flow past the submerged part of a floating wind turbine platform
- 2015
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Ingår i: MARINE 2015 - Computational Methods in Marine Engineering VI. - : International Center for Numerical Methods in Engineering (CIMNE). - 9788494392863 ; , s. 35-46
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Konferensbidrag (refereegranskat)abstract
- Offshore floating platforms for wind turbines represent challenging concepts for designers trying to combine an optimal compromise between cost effectiveness and performance. Modelling of the hydrodynamic behaviour of the structure is still the subject of wide debate in the technical communities. The assessment of the hydrodynamics of the support structure is not an easy task as the floaters consist of an assembly of columns, braces and pontoons, commonly also with heave plates: Each of these components corresponds to a different hydrodynamic model and it further interacts with the other elements. This results in very complex non-linear modeling, which makes it necessary to resort to computational fluid dynamics (CFD) methods for the evaluation of the combined hydrodynamics. In the framework of the collaboration between the Basque Centre for Applied Mathematics (BCAM) and Tecnalia R&I, the interaction of the sea flow with a semisubmersible floating offshore wind platform have been calculated by using the open source solver Unicorn in the FEniCS-HPC framework when subject to a steady inflow. The prototype of the platform consists in a semi-submersible 4-columns column stabilized platform - NAUTILUS Floating Solutions concept-; columns are connected by a rigid ring pontoon provided with heave damping plates at the bottom. The novelty of the approach in FEniCS-HPC hinges upon an implicit formulation for the turbulence, a cheap free slip model of the boundary layer and goal-oriented mesh adaptivity [8, 6, 9, 20, 1]. We find that the results are consistent with experimental results for cylinders at high Reynolds number.
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| 4. |
- Lyth, Johan, 1980-, et al.
(författare)
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Trends in cutaneous malignant melanoma in Sweden 1997-2011: Thinner tumours and improved survival among men
- 2015
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Ingår i: British Journal of Dermatology. - : Wiley-Blackwell. - 0007-0963 .- 1365-2133. ; 172:3, s. 700-706
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Tidskriftsartikel (refereegranskat)abstract
- Background: Both patient survival and the proportion of patients diagnosed with thin cutaneous malignant melanoma (CMM) have been steadily rising in Sweden as in most western countries, though the rate of improvement in survival appears to have declined in Sweden at the end of last millennium.Objectives: To analyse the most recent trends in the distribution of tumour thickness (T-category) as well as CMM-specific survival in Swedish patients diagnosed 1997-2011.Methods: This nationwide population-based study included 30 590 patients registered in the Swedish Melanoma Register (SMR) and diagnosed with a first primary invasive CMM 1997-2011. The patients were followed through 2012 in the national Cause-of-Death Register.Results: Logistic and Cox regression analyses adjusting for age at diagnosis, tumour site, and health care region were carried out. The odds ratio for being diagnosed with thicker tumours was significantly reduced (P = 0·0008) and the CMM-specific survival significantly improved in men diagnosed 2007-2011 compared to men diagnosed 1997-2001 (hazard ratio=0·81; 95% CI 0·72-0·91, P = 0·0009) while the corresponding differences for women were not significant. Women were diagnosed with significantly thicker tumours during 2002-2006 and a tendency towards decreased survival was observed compared to those diagnosed earlier 1997-2001 and later 2007-2011.Conclusion: In Sweden, the CMMs of men are detected earlier over time and this seems to be followed by an improved CMM-specific survival for men. Women are still diagnosed with considerably thinner tumours and they experience a better survival than men.
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| 5. |
- Anderson, Johan, et al.
(författare)
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Fire dynamics in Façade fire tests : Measurement, modeling and repeatability
- 2015
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Ingår i: Applications of Structural Fire Engineering. - : Czech Technical University in Prague. - 2336-7318. - 9788001061947
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Konferensbidrag (refereegranskat)abstract
- Presented is a comparison between full-scale façade tests where SP Fire 105 and BS 8414-1 were used regarding repeatability and the use of modelling to discern changes in the set-ups. Results show that the air movements around the test set-up (the wind) may have a significant impact on the tests and that the heat exposure to the façade surface will among other depend on the thickness of the test specimen. Also demonstrated was that good results could be obtained by modelling of the façade fire tests giving us the opportunity to use these methods to determine the effect of a change in the experimental setup.
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| 6. |
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| 7. |
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| 8. |
- Bäck, Maria, 1978, et al.
(författare)
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How does kinesiophobia change over time in patients with acute coronary artery disease?
- 2015
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Ingår i: Physiotherapy, Oral presentation, World Confederation for Physical Therapy (WCPT), 1-4 May 2015Singapore. - : Elsevier BV. ; 101:Suppl. 1
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- The occurrence of kinesiophobia and the impact on kinesiophobia by clinical variables with influence on rehabilitation outcomes in exercise-based cardiac rehabilitation (CR) has by us been identified six months after acute coronary artery disease (CAD). However, the occurrence of kinesiophobia in the acute phase of CAD and how it changes over time has not previously been studied. Moreover, the gender perspective has not been highlighted. The primary purpose was to identify levels of kinesiophobia in the acute phase of CAD and to study changes over time and in relation to gender. Participants: In total, 105 patients with CAD (25 women), mean age 63.1±11.5 were included in the study at the cardiac intensive care, Sahlgrenska University Hospital, Sweden between October 2013 and June 2014. Design and statistics: The patients were asked to fill in a set of questionnaires including the Tampascale for Kinesiophobia Heart (TSK-SV Heart), the Hospital Anxiety and Depression Scale (HADS), Harm Avoidance (HA) and the Positive and Negative Affect Schedule (PANAS). The patients filled in the questionnaires at three different time points: At the cardiac intensive care (T1), after 2 weeks (T2) and after 4 months (T3). A linear mixed model (LMM) procedure was used to compare kinesiophobia across time points. The within-subjects-design factor was data collection time (T1-T3), and the between-subjects-design factor was gender. The dependent variable was kinesiophobia. The questionnaires reflecting personality traits and affective states (HADS, PANAS, HA) were used as covariates in order to discover any effects these might have on differences across groupings. Covariates were included in two steps: first all five, then only those that contributed significantly at p-level < 0.05. Thirty-five patients were excluded due to loss of follow-up or missing data. The mean value on the TSK-SV Heart was 32.1 at T1, 30.3 at T2 and 29.2 at T3. The presence of a high level of kinesiophobia was 24% at T1 and 19% at T2 and T3. Without covariates, there was an effect of gender (p=0.011), with a higher TSK-SV Heart mean score for women, and over time points (p=0.013), with lower TSK-SV Heart mean score at T3. No interaction effect was found. Inclusion of the covariates showed that the HADS variables had no impact on kinesiophobia. Although negative affect (p=0.016), positive affect (p=0.002), and HA (p=0.057) had impact on kinesiophobia, this did not influence the significane of gender (p=0.042) and over time points (p=0.004). Kinesiophobia decreased over time after acute CAD, independent of patients´ personality traits and affective states. Female gender had a significant influence on kinesiohobia. Still 19% of the patients were identified with a high level of kinesiophobia at T3. The further establishment of the impact of kinesiophobia in CR and the design of a treatment intervention should be prioritized in future studies. The results of this study suggest that it is desirable to screen for kinesiophobia in the acute phase of CAD, as recognition may facilitate the appropriate treatment for these patients with the overall target of enhancing attendance at CR.
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| 10. |
- Dicksved, Johan, et al.
(författare)
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Fecal microbiome of growing pigs fed a cereal based diet including chicory (Cichorium intybus L.) or ribwort (Plantago lanceolata L.) forage
- 2015
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Ingår i: Journal of Animal Science and Biotechnology. - : Springer Science and Business Media LLC. - 1674-9782 .- 2049-1891. ; 6
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Tidskriftsartikel (refereegranskat)abstract
- Background: The purpose of this study was to investigate how inclusion of chicory forage or ribwort forage in a cereal-based diet influenced the fecal microbial community (microbiome) in newly weaned (35 days of age) piglets. The piglets were fed a cereal-based diet without (B) and with inclusion (80 and 160 g/kg air-dry forage) of vegetative shoots of chicory (C) and leaves of ribwort (R) forage in a 35-day growth trial. Fecal samples were collected at the start (D0), 17 (D17) and 35 (D35) days after weaning and profiles of the microbial consortia were generated using terminal restriction fragment length polymorphism (T-RFLP). 454-FLX pyrosequencing of 16S rRNA gene amplicons was used to analyze the microbial composition in a subset of the samples already analyzed with T-RFLP.Results: The microbial clustering pattern was primarily dependent on age of the pigs, but diet effects could also be observed. Lactobacilli and enterobacteria were more abundant at D0, whereas the genera Streptococcus, Treponema, Clostridium, Clostridiaceae1 and Coprococcus were present in higher abundances at D35. Pigs fed ribwort had an increased abundance of sequences classified as Treponema and a reduction in lactobacilli. However, the abundance of Prevotellaceae increased with age in on both the chicory and the ribwort diet. Moreover, there were significant correlations between the abundance of Bacteroides and the digested amount of galactose, uronic acids and total non-starch polysaccharides, and between the abundance of Bacteroidales and the digested amount of xylose.Conclusion: This study demonstrated that both chicory and ribwort inclusion in the diet of newly weaned pigs influenced the composition of the fecal microbiota and that digestion of specific dietary components was correlated with species composition of the microbiota. Moreover, this study showed that the gut will be exposed to a dramatic shift in the microbial community structure several weeks after weaning.
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