49,294 research outputs found
The Metric-FF Planning System: Translating "Ignoring Delete Lists" to Numeric State Variables
Planning with numeric state variables has been a challenge for many years,
and was a part of the 3rd International Planning Competition (IPC-3). Currently
one of the most popular and successful algorithmic techniques in STRIPS
planning is to guide search by a heuristic function, where the heuristic is
based on relaxing the planning task by ignoring the delete lists of the
available actions. We present a natural extension of ``ignoring delete lists''
to numeric state variables, preserving the relevant theoretical properties of
the STRIPS relaxation under the condition that the numeric task at hand is
``monotonic''. We then identify a subset of the numeric IPC-3 competition
language, ``linear tasks'', where monotonicity can be achieved by
pre-processing. Based on that, we extend the algorithms used in the heuristic
planning system FF to linear tasks. The resulting system Metric-FF is,
according to the IPC-3 results which we discuss, one of the two currently most
efficient numeric planners
Many Particle Hardy-Inequalities
In this paper we prove three differenttypes of the so-called many-particle
Hardy inequalities. One of them is a "classical type" which is valid in any
dimesnion . The second type deals with two-dimensional magnetic
Dirichlet forms where every particle is supplied with a soplenoid. Finally we
show that Hardy inequalities for Fermions hold true in all dimensions.Comment: 20 page
Ordered Landmarks in Planning
Many known planning tasks have inherent constraints concerning the best order
in which to achieve the goals. A number of research efforts have been made to
detect such constraints and to use them for guiding search, in the hope of
speeding up the planning process. We go beyond the previous approaches by
considering ordering constraints not only over the (top-level) goals, but also
over the sub-goals that will necessarily arise during planning. Landmarks are
facts that must be true at some point in every valid solution plan. We extend
Koehler and Hoffmann's definition of reasonable orders between top level goals
to the more general case of landmarks. We show how landmarks can be found, how
their reasonable orders can be approximated, and how this information can be
used to decompose a given planning task into several smaller sub-tasks. Our
methodology is completely domain- and planner-independent. The implementation
demonstrates that the approach can yield significant runtime performance
improvements when used as a control loop around state-of-the-art sub-optimal
planning systems, as exemplified by FF and LPG
Multi-Lattice Kinetic Monte Carlo Simulations from First-Principles: Reduction of the Pd(100) Surface Oxide by CO
We present a multi-lattice kinetic Monte Carlo (kMC) approach that
efficiently describes the atomistic dynamics of morphological transitions
between commensurate structures at crystal surfaces. As an example we study the
reduction of a PdO(101) overlayer on
Pd(100) in a CO atmosphere. Extensive density-functional theory calculations
are used to establish an atomistic pathway for the oxide reduction process.
First-principles multi-lattice kMC simulations on the basis of this pathway
fully reproduce the experimental temperature dependence of the reduction rate
[Fernandes et al., Surf. Sci. 2014, 621, 31-39] and highlight the crucial role
of elementary processes special to the boundary between oxide and metal
domains.Comment: 19 pages, 10 figure
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