10,316 research outputs found
Building and Refining Abstract Planning Cases by Change of Representation Language
ion is one of the most promising approaches to improve the performance of
problem solvers. In several domains abstraction by dropping sentences of a
domain description -- as used in most hierarchical planners -- has proven
useful. In this paper we present examples which illustrate significant
drawbacks of abstraction by dropping sentences. To overcome these drawbacks, we
propose a more general view of abstraction involving the change of
representation language. We have developed a new abstraction methodology and a
related sound and complete learning algorithm that allows the complete change
of representation language of planning cases from concrete to abstract.
However, to achieve a powerful change of the representation language, the
abstract language itself as well as rules which describe admissible ways of
abstracting states must be provided in the domain model. This new abstraction
approach is the core of Paris (Plan Abstraction and Refinement in an Integrated
System), a system in which abstract planning cases are automatically learned
from given concrete cases. An empirical study in the domain of process planning
in mechanical engineering shows significant advantages of the proposed
reasoning from abstract cases over classical hierarchical planning.Comment: See http://www.jair.org/ for an online appendix and other files
accompanying this articl
Comparison of combustion efficiencies for ramjet engines
Four different combustion efficiencies commonly used for assessing ramjet engines are compared. The mixture ratios cover a range from stoichiometric to an equivalence ratio of 0.2, and the polyethylene/air propellant system is used. The ratio of effective to ideal temperature rise is taken as reference efficiency. As might be expected, major differences can be observed near stoichiometric and down to equilvalence ratios of 0.5. These are quantitatively demonstrated
Coherent population transfer beyond the adiabatic limit: generalized matched pulses and higher-order trapping states
We show that the physical mechanism of population transfer in a 3-level
system with a closed loop of coherent couplings (loop-STIRAP) is not equivalent
to an adiabatic rotation of the dark-state of the Hamiltonian but coresponds to
a rotation of a higher-order trapping state in a generalized adiabatic basis.
The concept of generalized adiabatic basis sets is used as a constructive tool
to design pulse sequences for stimulated Raman adiabatic passage (STIRAP) which
give maximum population transfer also under conditions when the usual condition
of adiabaticty is only poorly fulfilled. Under certain conditions for the
pulses (generalized matched pulses) there exists a higher-order trapping state,
which is an exact constant of motion and analytic solutions for the atomic
dynamics can be derived.Comment: 15 pages, 9 figure
Photoionization Suppression by Continuum Coherence: Experiment and Theory
We present experimental and theoretical results of a detailed study of
laser-induced continuum structures (LICS) in the photoionization continuum of
helium out of the metastable state 2s . The continuum dressing with a
1064 nm laser, couples the same region of the continuum to the {4s }
state. The experimental data, presented for a range of intensities, show
pronounced ionization suppression (by as much as 70% with respect to the
far-from-resonance value) as well as enhancement, in a Beutler-Fano resonance
profile. This ionization suppression is a clear indication of population
trapping mediated by coupling to a contiuum. We present experimental results
demonstrating the effect of pulse delay upon the LICS, and for the behavior of
LICS for both weak and strong probe pulses. Simulations based upon numerical
solution of the Schr\"{o}dinger equation model the experimental results. The
atomic parameters (Rabi frequencies and Stark shifts) are calculated using a
simple model-potential method for the computation of the needed wavefunctions.
The simulations of the LICS profiles are in excellent agreement with
experiment. We also present an analytic formulation of pulsed LICS. We show
that in the case of a probe pulse shorter than the dressing one the LICS
profile is the convolution of the power spectra of the probe pulse with the
usual Fano profile of stationary LICS. We discuss some consequences of
deviation from steady-state theory.Comment: 29 pages, 17 figures, accepted to PR
Interfacing requirements for MEMS components in system-on-chip methodologies
Modern VLSI design is moving towards a System-on-Chip design paradigm, where chip design involves the integration of separate macrocells from different manufacturers. This paper explores the obstacles to adopting this same methodology for systems incorporating MEMS components. These obstacles include the technology specific nature of most MEMS devices, interference between MEMS sensors, and the limited electronics device density of mixed MEMS/Microelectronics technologies. It is conjectured that one fruitful avenue for further work is the development of MEMS interface circuits which can be incorporated into a single SoC along with other electronics macrocells, and which men connect to discrete MEMS sensor chips
Ecological appropriation of Joel
Most modern ecological-hermeneutical approaches to biblical interpretation of prophetic texts have concentrated on identifying the ecological significance of the text in its original historical context. Given the urgency of concerns about the modern ecological crisis, there is also a need to use scripture to assist in development of contemporary environmental ethics within an industrialised society. This paper describes a technique called ecological appropriation which seeks to take a biblical text, in this case the book of Joel, and apply its message to modern ecological concerns, whilst still preserving its fundamental theological message. This technique yields new insights into an appropriate, biblically-inspired response to the ecological crisis which involves key steps of acknowledgement, mourning, repentance, judgement, return to God, and restoration
Large-order trend of the anomalous-dimensions spectrum of trilinear twist-3 quark operators
The anomalous dimensions of trilinear-quark operators are calculated at
leading twist by diagonalizing the one-gluon exchange kernel of the
renormalization-group type evolution equation for the nucleon distribution
amplitude. This is done within a symmetrized basis of Appell polynomials of
maximum degree for (up to order 400) by combining analytical and
numerical algorithms. The calculated anomalous dimensions form a degenerate
system, whose upper envelope shows asymptotically logarithmic behavior.Comment: 12 pages; 1 table; 4 figures as PS files; RevTex styl
Measuring a coherent superposition
We propose a simple method for measuring the populations and the relative
phase in a coherent superposition of two atomic states. The method is based on
coupling the two states to a third common (excited) state by means of two laser
pulses, and measuring the total fluorescence from the third state for several
choices of the excitation pulses.Comment: 7 pages, 1 figure, twocolumn REVTe
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