771 research outputs found
Dynamic Multilevel Graph Visualization
We adapt multilevel, force-directed graph layout techniques to visualizing
dynamic graphs in which vertices and edges are added and removed in an online
fashion (i.e., unpredictably). We maintain multiple levels of coarseness using
a dynamic, randomized coarsening algorithm. To ensure the vertices follow
smooth trajectories, we employ dynamics simulation techniques, treating the
vertices as point particles. We simulate fine and coarse levels of the graph
simultaneously, coupling the dynamics of adjacent levels. Projection from
coarser to finer levels is adaptive, with the projection determined by an
affine transformation that evolves alongside the graph layouts. The result is a
dynamic graph visualizer that quickly and smoothly adapts to changes in a
graph.Comment: 21 page
C++ Templates as Partial Evaluation
This paper explores the relationship between C++ templates and partial
evaluation. Templates were designed to support generic programming, but
unintentionally provided the ability to perform compile-time computations and
code generation. These features are completely accidental, and as a result
their syntax is awkward. By recasting these features in terms of partial
evaluation, a much simpler syntax can be achieved. C++ may be regarded as a
two-level language in which types are first-class values. Template
instantiation resembles an offline partial evaluator. This paper describes
preliminary work toward a single mechanism based on Partial Evaluation which
unifies generic programming, compile-time computation and code generation. The
language Catat is introduced to illustrate these ideas.Comment: 13 page
Streamers in air splitting into three branches
We investigate the branching of positive streamers in air and present the
first systematic investigation of splitting into more than two branches. We
study discharges in 100 mbar artificial air that is exposed to voltage pulses
of 10 kV applied to a needle electrode 160 mm above a grounded plate. By
imaging the discharge with two cameras from three angles, we establish that
about every 200th branching event is a branching into three. Branching into
three occurs more frequently for the relatively thicker streamers. In fact, we
find that the surface of the total streamer cross-sections before and after a
branching event is roughly the same.Comment: 6 pages, 7 figure
- …