137,079 research outputs found
An HPC-Based Approach to Study Living System Computational Model Parameter Dependency
High performance computing (HPC) allows one to run in parallel large amount of independent numerical experiments for computationally intensive simulations of a complex system. Results of such experiments can be used to derive dependencies between functional characteristics of simulated system and parameters of the computational model. In this paper, we implemented this HPC approach with using a computational model of the electrical activity in the left ventricle of human heart. To illustrate possibilities of the approach, we analyzed dependencies of electrophysiological characteristics of the left ventricle on the parameters of its geometry. Particularly, we identified a dependence of the dynamics of activated myocardium part during excitation on the model parameters of the myocardial fiber orientation in the ventricular wall
Dynamic model of elastoplastic contact interaction of smooth bodies
Dynamic model of introducing rigid smooth sphere into homogeneous elastoplastic hardenable solid body has been considered. On the basis of the model numerical-analytical dependencies describing the behaviour of solid body in elastoplastic region of contact interaction were suggested. The numerical-analytical dependencies allow us to take into consideration additional approach of contacting bodies owing to dynamic loading
The valuation of clean spread options: linking electricity, emissions and fuels
The purpose of the paper is to present a new pricing method for clean spread options, and to illustrate its main features on a set of numerical examples produced by a dedicated computer code. The novelty of the approach is embedded in the use of a structural model as opposed to reduced-form models which fail to capture properly the fundamental dependencies between the economic factors entering the production process
Microwave-induced thermal escape in Josephson junctions
We investigate, by experiments and numerical simulations, thermal activation
processes of Josephson tunnel junctions in the presence of microwave radiation.
When the applied signal resonates with the Josephson plasma frequency
oscillations, the switching current may become multi-valued in a temperature
range far exceeding the classical to quantum crossover temperature. Plots of
the switching currents traced as a function of the applied signal frequency
show very good agreement with the functional forms expected from Josephson
plasma frequency dependencies on the bias current. Throughout, numerical
simulations of the corresponding thermally driven classical Josephson junction
model show very good agreement with the experimental data.Comment: 10 pages and 4 figure
New Calculations of Stellar Wind Torques
Using numerical simulations of magnetized stellar winds, we carry out a
parameter study to find the dependence of the stellar wind torque on observable
parameters. We find that the power-law dependencies of the torque on parameters
is significantly different than what has been used in all spin evolution models
to date.Comment: To appear in the proceedings for the 15th Cambridge Workshop on Cool
Stars, Stellar Systems, and the Sun. 4 page poster contributio
Winds from clu\sters with non-uniform stellar distributions
We present analytic and numerical models of the `cluster wind' resulting from
the multiple interactions of the winds ejected by the stars of a dense cluster
of massive stars. We consider the case in which the distribution of stars
(i.e., the number of stars per unit volume) within the cluster is spherically
symmetric, has a power-law radial dependence, and drops discontinuously to zero
at the outer radius of the cluster. We carry out comparisons between an
analytic model (in which the stars are considered in terms of a spatially
continuous injection of mass and energy) and 3D gasdynamic simulations (in
which we include 100 stars with identical winds, located in 3D space by
statistically sampling the stellar distribution function). From the analytic
model, we find that for stellar distributions with steep enough radial
dependencies the cluster wind flow develops a very high central density and a
non-zero central velocity, and for steeper dependencies it becomes fully
supersonic throughout the volume of the cluster (these properties are partially
reproduced by the 3D numerical simulations). Therefore, the wind solutions
obtained for stratified clusters can differ dramatically from the case of a
homogeneous stellar distribution (which produces a cluster wind with zero
central velocity, and a fully subsonic flow within the cluster radius).
Finally, from our numerical simulations we compute predictions of X-ray
emission maps and luminosities, which can be directly compared with
observations of cluster wind flows.Comment: 10 pages, 11 figures. MNRAS - Accepted 2007 June 29. Received 2007
June 28; in original form 2007 May 2
Transport in the 3-dimensional Anderson model: an analysis of the dynamics on scales below the localization length
Single-particle transport in disordered potentials is investigated on scales
below the localization length. The dynamics on those scales is concretely
analyzed for the 3-dimensional Anderson model with Gaussian on-site disorder.
This analysis particularly includes the dependence of characteristic transport
quantities on the amount of disorder and the energy interval, e.g., the mean
free path which separates ballistic and diffusive transport regimes. For these
regimes mean velocities, respectively diffusion constants are quantitatively
given. By the use of the Boltzmann equation in the limit of weak disorder we
reveal the known energy-dependencies of transport quantities. By an application
of the time-convolutionless (TCL) projection operator technique in the limit of
strong disorder we find evidence for much less pronounced energy dependencies.
All our results are partially confirmed by the numerically exact solution of
the time-dependent Schroedinger equation or by approximative numerical
integrators. A comparison with other findings in the literature is additionally
provided.Comment: 23 pages, 10 figure
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