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| 2. |
- Alhulaimi, Bassemah, et al.
(författare)
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Anisotropic Einstein-aether cosmological models
- 2013
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Ingår i: Journal of Mathematical Physics. - Melville, USA : American Institute of Physics (AIP). - 0022-2488 .- 1089-7658. ; 54:4
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Tidskriftsartikel (refereegranskat)abstract
- We investigate a class of spatially anisotropic cosmological models in Einstein-aether theory with a scalar field in which the self-interaction potential depends on the timelike aether vector field through the expansion and shear scalars. We derive the evolution equations in terms of expansion-normalized variables, which reduce to a dynamical system. We study the local stability of the equilibrium points of the dynamical system corresponding to physically realistic solutions, and find that there are always ranges of values of the parameters of the models for which there exists an inflationary attractor. © 2013 AIP Publishing LLC.
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| 4. |
- Coley, Alan A., et al.
(författare)
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Spherically symmetric Einstein-aether perfect fluid models
- 2015
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Ingår i: Journal of Cosmology and Astroparticle Physics. - : Institute of Physics (IOP). - 1475-7516. ; :12
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Tidskriftsartikel (refereegranskat)abstract
- We investigate spherically symmetric cosmological models in Einstein-act her theory with a tilted (non-comoving) perfect fluid source. We use a 1+3 frame formalism and adopt the comoving aether gauge to derive the evolution equations, which form a well-posed system of first order partial differential equations in two variables. We then introduce normalized variables. The formalism is particularly well-suited for numerical computations and the study of the qualitative properties of the models, which are also solutions of Horava gravity. We study the local stability of the equilibrium points of the resulting dynamical system corresponding to physically realistic in homogeneous cosmological models and astrophysical objects with values for the parameters which are consistent. with current constraints. In particular, we consider dust models in (beta-) normalized variables and derive a reduced (closed) evolution system and we obtain the general evolution equations for the spatially homogeneous Kantowski-Sachs models using, appropriate bounded normalized variables. We then analyse these models, with special emphasis on the future asymptotic behaviour for different values of the parameters. Finally, we investigate static models for a mixture of a (necessarily non-tilted) perfect fluid with a barotropic equations of state and a scalar field.
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| 5. |
- Hansen, Johan Liseth, et al.
(författare)
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Problematic opioid use among osteoarthritis patients with chronic post-operative pain after joint replacement: analyses from the BISCUITS study
- 2023
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Ingår i: Scandinavian Journal of Pain. - : WALTER DE GRUYTER GMBH. - 1877-8860 .- 1877-8879. ; 23:2, s. 353-363
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Tidskriftsartikel (refereegranskat)abstract
- Objectives: Opioids are commonly used to manage pain, despite an increased risk of adverse events and complications when used against recommendations. This register study uses data of osteoarthritis (OA) patients with joint replacement surgery to identify and characterize problematic opioid use (POU) prescription patterns.Methods: The study population included adult patients diagnosed with OA in specialty care undergoing joint replacement surgery in Denmark, Finland, Norway, and Sweden during 1 January 2011 to 31 December 2014. Those with cancer or OA within three years before the first eligible OA diagnosis were excluded. Patients were allocated into six POU cohorts based on dose escalation, frequency, and dosing of prescription opioids post-surgery (definitions were based on guidelines, previous literature, and clinical experience), and matched on age and sex to patients with opioid use, but not in any of the six cohorts. Data on demographics, non-OA pain diagnoses, cardiovascular diseases, psychiatric disorders, and clinical characteristics were used to study patient characteristics and predictors of POU.Results: 13.7% of patients with OA and a hip/knee joint replacement were classified as problematic users and they had more comorbidities and higher pre-surgery doses of opioids than matches. Patients dispensing high doses of opioids pre-surgery dispensed increased doses post-surgery, a pattern not seen among patients prescribed lower doses pre-surgery. Being dispensed 1-4,500 oral morphine equivalents in the year pre-surgery or having a non-OA pain diagnosis was associated with post-surgery POU (OR: 1.44-1.50, and 1.11-1.20, respectively).Conclusions: Based on the discovered POU predictors, the study suggests that prescribers should carefully assess pain management strategies for patients with a history of comorbidities and pre-operative, long-term opioid use. Healthcare units should adopt risk assessment tools and ensure that these patients are followed up closely. The data also demonstrate potential areas for further exploration in improving patient outcomes and trajectories.
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| 6. |
- Heinzle, Mark, et al.
(författare)
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The Initial Singularity of Ultrastiff Perfect Fluid Spacetimes Without Symmetries
- 2012
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Ingår i: Communications in Mathematical Physics. - : Springer Science and Business Media LLC. - 0010-3616 .- 1432-0916. ; :313, s. 385-403
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Tidskriftsartikel (refereegranskat)abstract
- We consider the Einstein equations coupled to an ultrastiff perfect fluid and prove the existence of a family of solutions with an initial singularity whose structure is that of explicit isotropic models. This family of solutions is ‘generic’ in the sense that it depends on as many free functions as a general solution, i.e., without imposing any symmetry assumptions, of the Einstein-Euler equations. The method we use is a that of a Fuchsian reduction.
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| 8. |
- Lockby, Andreas, et al.
(författare)
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Finding Stationary Solutions of PDEs with Constraints using Damped Dynamical Systems
- 2016
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Ingår i: Comsol Conference 2016.
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Konferensbidrag (refereegranskat)abstract
- The dynamical functional particle method(DFPM) is a method for solving equations, e.g. PDEs, using a second order damped dynamical system. We show how the method can be extended to include constraints both explicitly as global constraints and adding the constraints as additional damped dynamical equations. These methods are implemented in Comsol and we show numerical tests for finding the stationary solution of a nonlinear heat equation with and without constraints (global and dynamical). The results show that DFPM is a very general and robust way of solving PDEs and it should be of interest to implement the approach more generally in Comsol.
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| 9. |
- Pathan, Risat, 1979, et al.
(författare)
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Overhead-Aware Temporal Partitioning on Multicore Processors
- 2014
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Ingår i: Real-Time Technology and Applications - Proceedings. - 1080-1812. ; 2014-October:October, s. 251-262
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Konferensbidrag (refereegranskat)abstract
- Many previously proposed interface models for composability analysis of hierarchical scheduling are overhead-unaware, which is unsafe for real systems. This paper proposes an overhead-aware schedulability analysis to guarantee temporal partitioning among real-time applications/components hosted on a multicore platform. First, a new interface model and the method to generate an interface for a given component is proposed. Each interface has a tunable parameter d (degree) that can balance between abstraction and accuracy in capturing each component's task-level timing constraints. Second, the problem of constructing an overhead-aware system-level schedule of all the components is addressed. The system designer has the flexibility to select parameters (e.g., allocated processor bandwidth) for each component such that overhead (e.g., preemptions across partitions) is minimized. Third, a slack distribution algorithm to reduce various overhead is proposed and its effectiveness is evaluated using randomly generated interface sets and also using workload of a real space-borne application provided by RUAG Space Sweden AB
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| 10. |
- Pathan, Risat, 1979, et al.
(författare)
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Temporal Partitioning on Multicore Platform
- 2014
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Ingår i: European Space Agency, (Special Publication) ESA SP. - 0379-6566. - 9789292212896 ; SP 725
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Konferensbidrag (refereegranskat)abstract
- This paper addresses the problem of ensuring temporal partitioning according to the ARINC-653 standard for integrating multiple applications on the same multicore platform. To employ temporal partitioning, we propose the design and analysis of a hierarchical scheduling framework (HSF) for multicore platform. In HSF, each application has a server task, which is mapped to one of the physical cores of the multicore platform. The HSF framework is based on scheduling at two-levels: (i) a system-level scheduler for each core schedules the server tasks that are mapped to that core, and (ii) a task-level scheduler for each application schedules the tasks of the application. This paper presents the design and analysis of this two-level HSF that can be used to ensure temporal partitioning and meeting all the deadlines of each application tasks. The effectiveness of our technique is demonstrated using real-world space applications provided by RUAG Space Sweden AB.
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