49,471 research outputs found
Melting-induced stratification above the Earth's inner core due to convective translation
In addition to its global North-South anisotropy(1), there are two other
enigmatic seismological observations related to the Earth's inner core:
asymmetry between its eastern and western hemispheres(2-6) and the presence of
a layer of reduced seismic velocity at the base of the outer core(6-12). This
250-km-thick layer has been interpreted as a stably stratified region of
reduced composition in light elements(13). Here we show that this layer can be
generated by simultaneous crystallization and melting at the surface of the
inner core, and that a translational mode of thermal convection in the inner
core can produce enough melting and crystallization on each hemisphere
respectively for the dense layer to develop. The dynamical model we propose
introduces a clear asymmetry between a melting and a crystallizing hemisphere
which forms a basis for also explaining the East-West asymmetry. The present
translation rate is found to be typically 100 million years for the inner core
to be entirely renewed, which is one to two orders of magnitude faster than the
growth rate of the inner core's radius. The resulting strong asymmetry of
buoyancy flux caused by light elements is anticipated to have an impact on the
dynamics of the outer core and on the geodynamo
Multi-level Visualization of Concurrent and Distributed Computation in Erlang
This paper describes a prototype visualization system
for concurrent and distributed applications programmed
using Erlang, providing two levels of granularity of view. Both
visualizations are animated to show the dynamics of aspects of
the computation.
At the low level, we show the concurrent behaviour of the
Erlang schedulers on a single instance of the Erlang virtual
machine, which we call an Erlang node. Typically there will be
one scheduler per core on a multicore system. Each scheduler
maintains a run queue of processes to execute, and we visualize
the migration of Erlang concurrent processes from one run queue
to another as work is redistributed to fully exploit the hardware.
The schedulers are shown as a graph with a circular layout. Next
to each scheduler we draw a variable length bar indicating the
current size of the run queue for the scheduler.
At the high level, we visualize the distributed aspects of the
system, showing interactions between Erlang nodes as a dynamic
graph drawn with a force model. Speci?cally we show message
passing between nodes as edges and lay out nodes according to
their current connections. In addition, we also show the grouping
of nodes into “s_groups” using an Euler diagram drawn with
circles
CLPGUI: a generic graphical user interface for constraint logic programming over finite domains
CLPGUI is a graphical user interface for visualizing and interacting with
constraint logic programs over finite domains. In CLPGUI, the user can control
the execution of a CLP program through several views of constraints, of finite
domain variables and of the search tree. CLPGUI is intended to be used both for
teaching purposes, and for debugging and improving complex programs of
realworld scale. It is based on a client-server architecture for connecting the
CLP process to a Java-based GUI process. Communication by message passing
provides an open architecture which facilitates the reuse of graphical
components and the porting to different constraint programming systems.
Arbitrary constraints and goals can be posted incrementally from the GUI. We
propose several dynamic 2D and 3D visualizations of the search tree and of the
evolution of finite domain variables. We argue that the 3D representation of
search trees proposed in this paper provides the most appropriate visualization
of large search trees. We describe the current implementation of the
annotations and of the interactive execution model in GNU-Prolog, and report
some evaluation results.Comment: 16 pages; Alexandre Tessier, editor; WLPE 2002,
http://xxx.lanl.gov/abs/cs.SE/020705
eulerForce: Force-directed Layout for Euler Diagrams
Euler diagrams use closed curves to represent sets and their relationships. They facilitate set analysis, as humans tend to perceive distinct regions when closed curves are drawn on a plane. However, current automatic methods often produce diagrams with irregular, non-smooth curves that are not easily distinguishable. Other methods restrict the shape of the curve to for instance a circle, but such methods cannot draw an Euler diagram with exactly the required curve intersections for any set relations. In this paper, we present eulerForce, as the first method to adopt a force-directed approach to improve the layout and the curves of Euler diagrams generated by current methods. The layouts are improved in quick time. Our evaluation of eulerForce indicates the benefits of a force-directed approach to generate comprehensible Euler diagrams for any set relations in relatively fast time
Generalized parton distributions: Status and perspectives
We summarize recent developments in understanding the concept of generalized
parton distributions (GPDs), its relation to nucleon structure, and its
application to high-Q2 electroproduction processes. Following a brief review of
QCD factorization and transverse nucleon structure, we discuss (a) new
theoretical methods for the analysis of deeply-virtual Compton scattering
(t-channel-based GPD parametrizations, dispersion relations); (b) the
phenomenology of hard exclusive meson production (experimental tests of
dominance of small-size configurations, model-independent comparative studies);
(c) the role of GPDs in small-x physics and pp scattering (QCD dipole model,
central exclusive diffraction). We emphasize the usefulness of the transverse
spatial (or impact parameter) representation for both understanding the
reaction mechanism in hard exclusive processes and visualizing the physical
content of the GPDs.Comment: 10 pages, 6 figures. Proceedings of SPIN2008, University of Virginia,
October 6-11, 200
Flow visualization using momentum and energy transport tubes and applications to turbulent flow in wind farms
As a generalization of the mass-flux based classical stream-tube, the concept
of momentum and energy transport tubes is discussed as a flow visualization
tool. These transport tubes have the property, respectively, that no fluxes of
momentum or energy exist over their respective tube mantles. As an example
application using data from large-eddy simulation, such tubes are visualized
for the mean-flow structure of turbulent flow in large wind farms, in fully
developed wind-turbine-array boundary layers. The three-dimensional
organization of energy transport tubes changes considerably when turbine
spacings are varied, enabling the visualization of the path taken by the
kinetic energy flux that is ultimately available at any given turbine within
the array.Comment: Accepted for publication in Journal of Fluid Mechanic
- …