| 1. |
- Dawson, K. S., et al.
(författare)
-
An Intensive Hubble Space Telescope Survey for z>1 Type Ia Supernovae by Targeting Galaxy Clusters
- 2009
-
Ingår i: Astronomical Journal. - : American Astronomical Society. - 0004-6256 .- 1538-3881. ; 138, s. 1271-1283
-
Tidskriftsartikel (refereegranskat)abstract
- We present a new survey strategy to discover and study high-redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 < z < 1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of 3 improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides an SN sample that can be used to decouple the effects of host-galaxy extinction and intrinsic color in high-redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology. Based on observations made with the NASA/ESA Hubble Space Telescope and obtained from the data archive at the Space Telescope Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. The observations are associated with program 10496.
|
|
| 2. |
|
|
| 3. |
- Abrahamyan, Lilit, et al.
(författare)
-
A Problem Solving Environment for Image-Based Computational Hemodynamics
- 2005
-
Konferensbidrag (refereegranskat)abstract
- We introduce a complete problem solving environment designed for pulsatile flows in 3D complex geometries, especially arteries. Three-dimensional images from arteries, obtained from e.g. Magnetic Resonance Imaging, are segmented to obtain a geometrical description of the arteries of interest. This segmented artery is prepared for blood flow simulations in a 3D editing tool, allowing to define in- and outlets, to filter and crop part of the artery, to add certain structures ( e.g. a by-pass, or stents ), and to generate computational meshes as input to the blood flow simulators. Using dedicated fluid flow solvers the time dependent blood flow in the artery during one systole is computed. The resulting flow, pressure and shear stress fields are then analyzed using a number of visualization techniques. The whole environment can be operated from a desktop virtual reality system, and is embedded in a Grid computing environment.
|
|
| 4. |
|
|
| 5. |
- Axner, Lilit, et al.
(författare)
-
Performance evaluation of a Parallel Sparse Lattice Boltzmann Solver
- 2008
-
Ingår i: Journal of Computational Physics. - : Elsevier BV. - 0021-9991 .- 1090-2716. ; 227:10, s. 4895-4911
-
Tidskriftsartikel (refereegranskat)abstract
- We develop a performance prediction model for a parallelized sparse lattice Boltzmann solver and present performance results for simulations of flow in a variety of complex geometries. A special focus is on partitioning and memory/load balancing strategy for geometries with a high solid fraction and/or complex topology such as porous media, fissured rocks and geometries from medical applications. The topology of the lattice nodes representing the fluid fraction of the computational domain is mapped on a graph. Graph decomposition is performed with both multilevel recursive-bisection and multilevel k-way schemes based on modified Kernighan–Lin and Fiduccia–Mattheyses partitioning algorithms. Performance results and optimization strategies are presented for a variety of platforms, showing a parallel efficiency of almost 80% for the largest problem size. A good agreement between the performance model and experimental results is demonstrated.
|
|
| 6. |
- Axner, Lilit, et al.
(författare)
-
Simulating Time Harmonic Flows with the Regularized L-BGK Method
- 2007
-
Ingår i: International Journal of Modern Physics C. - 0129-1831. ; 18:4, s. 661-666
-
Tidskriftsartikel (refereegranskat)abstract
- A recent improvement of the lattice BGK model, based on a regularization of the precollision distribution function, is applied to three dimensional Womersley flow. The accuracy and the stability of the model are essentially improved by using this regularization. A good agreement with analytical Womersley solution is presented, as well as an improvement of the accuracy over standard L-BGK. Numerical stability of the scheme for a range of Reynolds and Womersley numbers is also presented, demonstrating an enhancement of the stability range of L-BGK for this type of flows.
|
|
| 7. |
- Axner, Lilit, et al.
(författare)
-
Simulations of time harmonic blood flow in the Mesenteric artery: comparing finite element and lattice Boltzmann methods
- 2009
-
Ingår i: Biomedical engineering online. - 1475-925X. ; 8:23, s. 28-
-
Tidskriftsartikel (refereegranskat)abstract
- Background: Systolic blood flow has been simulated in the abdominal aorta and the superior mesenteric artery. The simulations were carried out using two different computational hemodynamic methods: the finite element method to solve the Navier Stokes equations and the lattice Boltzmann method. Results: We have validated the lattice Boltzmann method for systolic flows by comparing the velocity and pressure profiles of simulated blood flow between methods. We have also analyzed flow-specific characteristics such as the formation of a vortex at curvatures and traces of flow. Conclusion: The lattice Boltzmann Method is as accurate as a Navier Stokes solver for computing complex blood flows. As such it is a good alternative for computational hemodynamics, certainly in situation where coupling to other models is required.
|
|
